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  • Inorganic Chemistry  (1,343)
  • Cell & Developmental Biology  (1,326)
  • Aerodynamics
  • 2005-2009  (60)
  • 1980-1984  (2,673)
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  • 2008  (60)
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  • 1980-1984  (2,673)
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  • 1
    Publication Date: 2018-06-06
    Description: Much of technology needed for analysis of HALE nonlinear aeroelastic problems is available from rotorcraft methodologies. Consequence of similarities in operating environment and aerodynamic surface configuration. Technology available - theory developed, validated by comparison with test data, incorporated into rotorcraft codes. High subsonic to transonic rotor speed, low to moderate Reynolds number. Structural and aerodynamic models for high aspect-ratio wings and propeller blades. Dynamic and aerodynamic interaction of wing/airframe and propellers. Large deflections, arbitrary planform. Steady state flight, maneuvers and response to turbulence. Linearized state space models. This technology has not been extensively applied to HALE configurations. Correlation with measured HALE performance and behavior required before can rely on tools.
    Keywords: Aerodynamics
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  • 2
    Publication Date: 2018-06-11
    Description: Following the completion of NASA s Exploration Systems Architecture Study in August 2004 for the NASA Exploration Systems Mission Directorate (ESMD), the Ares Projects Office at the NASA Marshall Space Flight Center was assigned project management responsibilities for the design and development of the first vehicle in the architecture, the Ares I Crew Launch Vehicle (CLV), which will be used to launch astronauts to low earth orbit and rendezvous with either the International Space Station or the ESMD s earth departure stage for lunar or other future missions beyond low Earth orbit. The primary elements of the Ares I CLV project are the first stage, the upper stage, the upper stage engine, and vehicle integration. Within vehicle integration is an effort in integrated design and analysis which is comprised of a number of technical disciplines needed to support vehicle design and development. One of the important disciplines throughout the life of the project is aerodynamics. This paper will present the status, plans, and initial results of Ares I CLV aerodynamics as the project was preparing for the Ares I CLV Systems Requirements Review. Following a discussion of the specific interactions with other technical panels and a status of the current activities, the plans for aerodynamic support of the Ares I CLV until the initial crewed flights will be presented. Keywords: Ares I Crew Launch Vehicle, aerodynamics, wind tunnel testing, computational fluid dynamics
    Keywords: Aerodynamics
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  • 3
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    In:  CASI
    Publication Date: 2019-08-26
    Description: During the 1970s and 1980s, researchers at Dryden Flight Research Center conducted numerous tests to refine the shape of trucks to reduce aerodynamic drag and improved efficiency. During the 1980s and 1990s, a team based at Langley Research Center explored controlling drag and the flow of air around a moving body. Aeroserve Technologies Ltd., of Ottawa, Canada, with its subsidiary, Airtab LLC, in Loveland, Colorado, applied the research from Dryden and Langley to the development of the Airtab vortex generator. Airtabs create two counter-rotating vortices to reduce wind resistance and aerodynamic drag of trucks, trailers, recreational vehicles, and many other vehicles.
    Keywords: Aerodynamics
    Type: Spinoff 2008: 50 Years of NASA-Derived Technologies (1958-2008); 70-73; NASA/NP-2008-OL-527-HQ
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  • 4
    Publication Date: 2019-07-12
    Description: Equations are developed with which to calculate lift and drag coefficients along the spans of torsionally-stiff rotating airfoils of the type used in wind turbine rotors and wind tunnel fans, at angles of attack in both the unstalled and stalled aerodynamic regimes. Explicit adjustments are made for the effects of aspect ratio (length to chord width) and airfoil thickness ratio. Calculated lift and drag parameters are compared to measured parameters for 55 airfoil data sets including 585 test points. Mean deviation was found to be -0.4 percent and standard deviation was 4.8 percent. When the proposed equations were applied to the calculation of power from a stall-controlled wind turbine tested in a NASA wind tunnel, mean deviation from 54 data points was -1.3 percent and standard deviation was 4.0 percent. Pressure-rise calculations for a large wind tunnel fan deviated by 2.7 percent (mean) and 4.4 percent (standard). The assumption that a single set of lift and drag coefficient equations can represent the stalled aerodynamic behavior of a wide variety of airfoils was found to be satisfactory.
    Keywords: Aerodynamics
    Type: NASA/CR-2008-215434 , E-16599
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  • 5
    Publication Date: 2019-07-12
    Description: A bypass transition model has been implemented in the Wind-US Reynolds Averaged Navier-Stokes (RANS) solver. The model is based on the Shear Stress Transport (SST) turbulence model and was built starting from a previous SST-based transition model. Several modifications were made to enable (1) consistent solutions regardless of flow field initialization procedure and (2) fully turbulent flow beyond the transition region. This model is intended for flows where bypass transition, in which the transition process is dominated by large freestream disturbances, is the key transition mechanism as opposed to transition dictated by modal growth. Validation of the new transition model is performed for flows ranging from incompressible to hypersonic conditions.
    Keywords: Aerodynamics
    Type: NASA/TM-2008-215451 , E-16671
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  • 6
    Publication Date: 2019-07-12
    Description: Computational fluid dynamics (CFD) analysis has been performed to study the plume effects on sonic boom signature for isolated nozzle configurations. The objectives of these analyses were to provide comparison to past work using modern CFD analysis tools, to investigate the differences of high aspect ratio nozzles to circular (axisymmetric) nozzles, and to report the effects of underexpanded nozzle operation on boom signature. CFD analysis was used to address the plume effects on sonic boom signature from a baseline exhaust nozzle. Near-field pressure signatures were collected for nozzle pressure ratios (NPRs) between 6 and 10. A computer code was used to extrapolate these signatures to a ground-observed sonic boom N-wave. Trends show that there is a reduction in sonic boom N-wave signature as NPR is increased from 6 to 10. The performance curve for this supersonic nozzle is flat, so there is not a significant loss in thrust coefficient as the NPR is increased. As a result, this benefit could be realized without significant loss of performance. Analyses were also collected for a high aspect ratio nozzle based on the baseline design for comparison. Pressure signatures were collected for nozzle pressure ratios from 8 to 12. Signatures were nearly twice as strong for the two-dimensional case, and trends also show a reduction in sonic boom signature as NPR is increased from 8 to 12. As low boom designs are developed and improved, there will be a need for understanding the interaction between the aircraft boat tail shocks and the exhaust nozzle plume. These CFD analyses will provide a baseline study for future analysis efforts.
    Keywords: Aerodynamics
    Type: AIAA Paper-2008-3729 , E-16535
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  • 7
    Publication Date: 2019-07-12
    Description: Active flow control efficacy was investigated by means of leading-edge and flap-shoulder zero mass-flux blowing slots on a semispan wing model that was tested in unswept (standard) and swept configurations. On the standard configuration, stall commenced inboard, but with sweep the wing stalled initially near the tip. On both configurations, leading-edge perturbations increased CL,max and post stall lift, both with and without deflected flaps. Without sweep, the effect of control was approximately uniform across the wing span but remained effective to high angles of attack near the tip; when sweep was introduced a significant effect was noted inboard, but this effect degraded along the span and produced virtually no meaningful lift enhancement near the tip, irrespective of the tip configuration. In the former case, control strengthened the wingtip vortex; in the latter case, a simple semi-empirical model, based on the trajectory or "streamline" of the evolving perturbation, served to explain the observations. In the absence of sweep, control on finite-span flaps did not differ significantly from their nominally twodimensional counterpart. Control from the flap produced expected lift enhancement and CL,max improvements in the absence of sweep, but these improvements degraded with the introduction of sweep.
    Keywords: Aerodynamics
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  • 8
    Publication Date: 2019-07-12
    Description: Examples of the design and flight test of three true X-planes are described, particularly X-plane design techniques that relied heavily on computational fluid dynamics(CFD) analysis. Three examples are presented: the X-36 Tailless Fighter Agility Research Aircraft, the X-45A Unmanned Combat Air Vehicle, and the X-48B Blended Wing Body Demonstrator Aircraft. An overview is presented of the uses of CFD analysis, comparison and contrast with wind tunnel testing, and information derived from CFD analysis that directly related to successful flight test. Lessons learned on the proper and improper application of CFD analysis are presented. Highlights of the flight-test results of the three example X-planes are presented. This report discusses developing an aircraft shape from early concept and three-dimensional modeling through CFD analysis, wind tunnel testing, further refined CFD analysis, and, finally, flight. An overview of the areas in which CFD analysis does and does not perform well during this process is presented. How wind tunnel testing complements, calibrates, and verifies CFD analysis is discussed. Lessons learned revealing circumstances under which CFD analysis results can be misleading are given. Strengths and weaknesses of the various flow solvers, including panel methods, Euler, and Navier-Stokes techniques, are discussed.
    Keywords: Aerodynamics
    Type: NASA/TM-2008-214636 , H-2838
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  • 9
    Publication Date: 2019-08-13
    Description: A forebody and inlet have been designed for the HIFiRE 2 scramjet flight test. The test will explore the operating, performance, and stability characteristics of a simple hydrocarbon-fueled scramjet combustor as it transitions from dual-mode to scramjet-mode operation and during supersonic combustion at Mach 8+ flight conditions. Requirements for the compression system were derived from inlet starting and combustor inflow requirements as well as physical size constraints. The design process is described. A planar, fixed geometry, mixed compression concept was used to produce laterally uniform flow at the inlet entrance and a conservative amount of internal contraction with respect to inlet starting. A grid sensitivity study was performed so that important flow physics caused by three-dimensional shock boundary layer interactions could be captured with confidence. Results from low Mach number operability studies, nominal trajectory cases, and high dynamic pressure heat load cases are discussed. The forebody and inlet solutions provide information for on-going combustor calculations, mass capture across the trajectory for fuel system design, and surface heating rates for thermal/structural analysis. The design has a one freestream Mach number margin for inlet starting, exceeds the high Mach number combustor entrance pressure requirement, produces high quality flow at the inlet exit for all Mach numbers and vehicle attitudes in the design space, and fits inside the booster shroud.
    Keywords: Aerodynamics
    Type: JANNAF Airbreathing Propulsion Subcommittee Meeting; May 12, 2008 - May 16, 2008; Boston, MA; United States
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  • 10
    Publication Date: 2019-08-13
    Description: Historically, testing in the 10x10 Supersonic Wind Tunnel involved aeronautics type testing including testing of Supersonic Propulsion Components such as inlets and nozzles, Propulsion System Integration, Full-scale Jet and Rocket Engines, Aerodynamic Force and Moment testing, Sonic Boom Mitigation and the investigation of Advanced Aircraft Models. The New Space Directive(s) called for new areas of testing. Two interesting and challenging tests were proposed for the 10x10 SWT, the Inflatable Aerodynamic Decelerator (IAD) and the Mars Science Lab (MSL) Flexible Parachute. This presentation highlights those tests and plans for future testing in the 10x10 SWT.
    Keywords: Aerodynamics
    Type: E-16911 , 110th STAI Meeting; Oct 26, 2008 - Oct 28, 2008; Tel Aviv; Israel
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  • 11
    Publication Date: 2019-07-13
    Description: Theoretical studies on the dissipation and dispersion of sound in two-phase suspensions have been briefly reviewed. Previous studies on the sound attenuation in particle-laden flows under Stokesian drag and conduction-controlled heat transfer have been extended to accommodate the nonlinear drag and heat transfer. It has been shown that for large particle-to-fluid density ratio, the particle Reynolds number bears a cubic relationship with Omega Tau(sub d) (where Omega is the circular frequency and Tau(sub d) the Stokesian particle relaxation time). This dependence leads to the existence of a peak value in the linear absorption coefficient occurring at a finite value Omega Tau (sub d). Comparison of the predictions with the test data for the spectral attenuation of sound with water injection in a perfectly expanded supersonic air jet shows a satisfactory trend of the theory accounting for nonlinear particle relaxation processes.
    Keywords: Aerodynamics
    Type: KSC-2008-101 , Acoustics ''08, Acoustical Society of America/The French Acoustical Society; Jun 29, 2008 - Jul 04, 2008; Paris; France
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  • 12
    Publication Date: 2019-07-13
    Description: A collection of statistical and mathematical techniques referred to as response surface methodology was used to estimate the longitudinal stage separation aerodynamic characteristics of a generic, bimese, winged multi-stage launch vehicle configuration using data obtained on small-scale models at supersonic speeds in the NASA Langley Research Center Unitary Plan Wind Tunnel. The simulated Mach 3 staging was dominated by multiple shock wave interactions between the orbiter and booster vehicles throughout the relative spatial locations of interest. This motivated a partitioning of the overall inference space into several contiguous regions within which the separation aerodynamics were presumed to be well-behaved and estimable using cuboidal and spherical central composite designs capable of fitting full second-order response functions. The primary goal was to approximate the underlying overall aerodynamic response surfaces of the booster vehicle in belly-to-belly proximity to the orbiter vehicle using relatively simple, lower-order polynomial functions that were piecewise-continuous across the full independent variable ranges of interest. The quality of fit and prediction capabilities of the empirical models were assessed in detail, and the issue of subspace boundary discontinuities was addressed. The potential benefits of augmenting the central composite designs to full third order using computer-generated D-optimality criteria were also evaluated. The usefulness of central composite designs, the subspace sizing, and the practicality of fitting low-order response functions over a partitioned inference space dominated by highly nonlinear and possibly discontinuous shock-induced aerodynamics are discussed.
    Keywords: Aerodynamics
    Type: 26th Congress of International Council of the Aeronautical Sciences (ICAS 2008); Sep 14, 2008 - Sep 19, 2008; Anchorage, AK; United States
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  • 13
    Publication Date: 2019-07-13
    Description: LaCETS baseline flight study include: 29 high-quality nearfield shock structure probings at three Mach numbers; Shocks in exhaust plume measured; ! CFD study of simplified nozzle shows similar plume structures as flight data; ! Phase II flights scheduled for October 2008; and ! US Industry and Academia invited to participate in analysis, review, and assessment of LaNCETS data.
    Keywords: Aerodynamics
    Type: Fundamental Aeronautics 2008 Annual Meeting; Oct 07, 2008 - Oct 09, 2008; Atlanta, GA; United States
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  • 14
    Publication Date: 2019-07-13
    Description: A wind tunnel investigation was conducted to measure the aerodynamic effects of damage to lifting and stability/control surfaces of a commercial transport aircraft configuration. The modeling of such effects is necessary for the development of flight control systems to recover aircraft from adverse, damage-related loss-of-control events, as well as for the estimation of aerodynamic characteristics from flight data under such conditions. Damage in the form of partial or total loss of area was applied to the wing, horizontal tail, and vertical tail. Aerodynamic stability and control implications of damage to each surface are presented, to aid in the identification of potential boundaries in recoverable stability or control degradation. The aerodynamic modeling issues raised by the wind tunnel results are discussed, particularly the additional modeling requirements necessitated by asymmetries due to damage, and the potential benefits of such expanded modeling.
    Keywords: Aerodynamics
    Type: AIAA-2008-6203 , AIAA Atmospheric Flight Mechanics Conference; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 15
    Publication Date: 2019-07-13
    Description: Recently acquired experimental data for the DLR-F6 wing-body transonic transport con figuration from the National Transonic Facility (NTF) are compared with the database of computational fluid dynamics (CFD) predictions generated for the Third AIAA CFD Drag Prediction Workshop (DPW-III). The NTF data were collected after the DPW-III, which was conducted with blind test cases. These data include both absolute drag levels and increments associated with this wing-body geometry. The baseline DLR-F6 wing-body geometry is also augmented with a side-of-body fairing which eliminates the flow separation in this juncture region. A comparison between computed and experimentally observed sizes of the side-of-body flow-separation bubble is included. The CFD results for the drag polars and separation bubble sizes are computed on grids which represent current engineering best practices for drag predictions. In addition to these data, a more rigorous attempt to predict absolute drag at the design point is provided. Here, a series of three grid densities are utilized to establish an asymptotic trend of computed drag with respect to grid convergence. This trend is then extrapolated to estimate a grid-converged absolute drag level.
    Keywords: Aerodynamics
    Type: AIAA Paper 2008-6918 , 26th AIAA Applied Aerodynamics Conference; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 16
    Publication Date: 2019-07-13
    Description: The development of a wing/body/nacelle/pylon/horizontal-tail configuration for a common research model is presented, with focus on the aerodynamic design of the wing. Here, a contemporary transonic supercritical wing design is developed with aerodynamic characteristics that are well behaved and of high performance for configurations with and without the nacelle/pylon group. The horizontal tail is robustly designed for dive Mach number conditions and is suitably sized for typical stability and control requirements. The fuselage is representative of a wide/body commercial transport aircraft; it includes a wing-body fairing, as well as a scrubbing seal for the horizontal tail. The nacelle is a single-cowl, high by-pass-ratio, flow-through design with an exit area sized to achieve a natural unforced mass-flow-ratio typical of commercial aircraft engines at cruise. The simplicity of this un-bifurcated nacelle geometry will facilitate grid generation efforts of subsequent CFD validation exercises. Detailed aerodynamic performance data has been generated for this model; however, this information is presented in such a manner as to not bias CFD predictions planned for the fourth AIAA CFD Drag Prediction Workshop, which incorporates this common research model into its blind test cases. The CFD results presented include wing pressure distributions with and without the nacelle/pylon, ML/D trend lines, and drag-divergence curves; the design point for the wing/body configuration is within 1% of its max-ML/D. Plans to test the common research model in the National Transonic Facility and the Ames 11-ft wind tunnels are also discussed.
    Keywords: Aerodynamics
    Type: AIAA Paper 2008-6919 , 26th AIAA Applied Aerodynamics Conference; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 17
    Publication Date: 2019-07-13
    Description: This paper discusses the verification of the Constraint Force Equation (CFE) methodology and its implementation in the Program to Optimize Simulated Trajectories II (POST2) for multibody separation problems using three specially designed test cases. The first test case involves two rigid bodies connected by a fixed joint; the second case involves two rigid bodies connected with a universal joint; and the third test case is that of Mach 7 separation of the Hyper-X vehicle. For the first two cases, the POST2/CFE solutions compared well with those obtained using industry standard benchmark codes, namely AUTOLEV and ADAMS. For the Hyper-X case, the POST2/CFE solutions were in reasonable agreement with the flight test data. The CFE implementation in POST2 facilitates the analysis and simulation of stage separation as an integral part of POST2 for seamless end-to-end simulations of launch vehicle trajectories.
    Keywords: Aerodynamics
    Type: AIAA Modeling and Simulation Technologies Conference; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 18
    Publication Date: 2019-07-13
    Description: A new approach for distribution of grid points on the surface and in the volume has been developed and implemented in the NASA unstructured grid generation code VGRID. In addition to the point and line sources of prior work, the new approach utilizes surface and volume sources for automatic curvature-based grid sizing and convenient point distribution in the volume. A new exponential growth function produces smoother and more efficient grids and provides superior control over distribution of grid points in the field. All types of sources support anisotropic grid stretching which not only improves the grid economy but also provides more accurate solutions for certain aerodynamic applications. The new approach does not require a three-dimensional background grid as in the previous methods. Instead, it makes use of an efficient bounding-box auxiliary medium for storing grid parameters defined by surface sources. The new approach is less memory-intensive and more efficient computationally. The grids generated with the new method either eliminate the need for adaptive grid refinement for certain class of problems or provide high quality initial grids that would enhance the performance of many adaptation methods.
    Keywords: Aerodynamics
    Type: 26th AIAA Applied Aerodynamics Conference; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 19
    Publication Date: 2019-07-13
    Description: An experimental aerodynamic investigation of the DLR (German Aerospace Center) F6 generic transport configuration has been conducted in the NASA NTF (National Transonic Facility) for CFD validation within the framework of the AIAA Drag Prediction Workshop. Force and moment, surface pressure, model deformation, and surface flow visualization data have been obtained at Reynolds numbers of both 3 million and 5 million. Flow-through nacelles and a side-of-body fairing were also investigated on this wing-body configuration. Reynolds number effects on trailing edge separation have been assessed, and the effectiveness of the side-of-body fairing in eliminating a known region of separated flow has been determined. Data obtained at a Reynolds number of 3 million are presented together for comparison with data from a previous wind tunnel investigation in the ONERA S2MA facility. New surface flow visualization capabilities have also been successfully explored and demonstrated in the NTF for the high pressure and moderately low temperature conditions required in this investigation. Images detailing wing surface flow characteristics are presented.
    Keywords: Aerodynamics
    Type: 26th AIAA Applied Aerodynamics Conference; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 20
    Publication Date: 2019-07-13
    Description: In this paper we describe flow-field measurements obtained in the wake of a full-span Hybrid Wing Body model with internally blown flaps. The test was performed at the NASA Langley 14 x 22 Foot Subsonic Tunnel at low speeds. Off-body measurements were obtained with a 7-hole probe rake survey system. Three model configurations were investigated. At 0deg angle of attack the surveys were completed with 0deg and 60deg flap deflections. At 10deg angle of attack the wake surveys were completed with a slat and a 60deg flap deflection. The 7-hole probe results further quantified two known swirling regions (downstream of the outboard flap edge and the inboard/outboard flap juncture) for the 60deg flap cases with blowing. Flow-field results and the general trends are very similar for the two blowing cases at nozzle pressure ratios of 1.37 and 1.56. High downwash velocities correlated with the enhanced lift for the 60deg flap cases with blowing. Jet-induced effects are the largest at the most inboard station for all (three) velocity components due in part to the larger inboard slot height. The experimental data are being used to improve computational tools for high-lift wings with integrated powered-lift technologies.
    Keywords: Aerodynamics
    Type: 26th AIAA Applied Aerodynamics Conference; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 21
    Publication Date: 2019-07-13
    Description: As part of the Airborne Subscale Transport Aircraft Research (AirSTAR) project, NASA Langley Research Center (LaRC) has developed a subscaled flying testbed in order to conduct research experiments in support of the goals of NASA s Aviation Safety Program. This research capability consists of three distinct components. The first of these is the research aircraft, of which there are several in the AirSTAR stable. These aircraft range from a dynamically-scaled, twin turbine vehicle to a propeller driven, off-the-shelf airframe. Each of these airframes carves out its own niche in the research test program. All of the airplanes have sophisticated on-board data acquisition and actuation systems, recording, telemetering, processing, and/or receiving data from research control systems. The second piece of the testbed is the ground facilities, which encompass the hardware and software infrastructure necessary to provide comprehensive support services for conducting flight research using the subscale aircraft, including: subsystem development, integrated testing, remote piloting of the subscale aircraft, telemetry processing, experimental flight control law implementation and evaluation, flight simulation, data recording/archiving, and communications. The ground facilities are comprised of two major components: (1) The Base Research Station (BRS), a LaRC laboratory facility for system development, testing and data analysis, and (2) The Mobile Operations Station (MOS), a self-contained, motorized vehicle serving as a mobile research command/operations center, functionally equivalent to the BRS, capable of deployment to remote sites for supporting flight tests. The third piece of the testbed is the test facility itself. Research flights carried out by the AirSTAR team are conducted at NASA Wallops Flight Facility (WFF) on the Eastern Shore of Virginia. The UAV Island runway is a 50 x 1500 paved runway that lies within restricted airspace at Wallops Flight Facility. The facility provides all the necessary infrastructure to conduct the research flights in a safe and efficient manner. This paper gives a comprehensive overview of the development of the AirSTAR testbed.
    Keywords: Aerodynamics
    Type: AIAA-2008-6660 , AIAA Guidance, Navigation and Control Conference and Exhibit; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 22
    Publication Date: 2019-07-13
    Description: A multi-body flight simulation for the Phoenix Mars Lander has been developed that includes high fidelity six degree-of-freedom rigid-body models for the parachute and lander system. The simulation provides attitude and rate history predictions of all bodies throughout the flight, as well as loads on each of the connecting lines. In so doing, a realistic behavior of the descending parachute/lander system dynamics can be simulated that allows assessment of the Phoenix descent performance and identification of potential sensitivities for landing. This simulation provides a complete end-to-end capability of modeling the entire entry, descent, and landing sequence for the mission. Time histories of the parachute and lander aerodynamic angles are presented. The response of the lander system to various wind models and wind shears is shown to be acceptable. Monte Carlo simulation results are also presented.
    Keywords: Aerodynamics
    Type: AIAA Atmospheric Flight Mechanics Conference; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 23
    Publication Date: 2019-07-13
    Description: This paper describes two attitude control laws suitable for atmospheric flight vehicles with a steady angular momentum bias in the vehicle yaw axis. This bias is assumed to be provided by an internal flywheel, and is introduced to enhance roll and pitch stiffness. The first control law is based on Lyapunov stability theory, and stability proofs are given. The second control law, which assumes that the angular momentum bias is large, is based on a classical PID control. It is shown that the large yaw-axis bias requires that the PI feedback component on the roll and pitch angle errors be cross-fed. Both control laws are applied to a vehicle simulation in the presence of disturbances for several values of yaw-axis angular momentum bias. It is seen that both control laws provide a significant improvement in attitude performance when the bias is sufficiently large, but the nonlinear control law is also able to provide improved performance for a small value of bias. This is important because the smaller bias corresponds to a smaller requirement for mass to be dedicated to the flywheel.
    Keywords: Aerodynamics
    Type: AIAA Guidance, Navigation and Control Conference and Exhibit; Aug 18, 2008 - Aug 21, 2008; Honolulu, HI; United States
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  • 24
    Publication Date: 2019-07-13
    Description: The effect of the upstream wake on the blade heat transfer has been numerically examined. The geometry and the flow conditions of the first stage turbine blade of GE s E3 engine with a tip clearance equal to 2 percent of the span was utilized. Based on numerical calculations of the vane, a set of wake boundary conditions were approximated, which were subsequently imposed upon the downstream blade. This set consisted of the momentum and thermal wakes as well as the variation in modeled turbulence quantities of turbulence intensity and the length scale. Using a one-blade periodic domain, the distributions of unsteady heat transfer rate on the turbine blade and its tip, as affected by the wake, were determined. Such heat transfer coefficient distribution was computed using the wall heat flux and the adiabatic wall temperature to desensitize the heat transfer coefficient to the wall temperature. For the determination of the wall heat flux and the adiabatic wall temperatures, two sets of computations were required. The results were used in a phase-locked manner to compute the unsteady or steady heat transfer coefficients. It has been found that the unsteady wake has some effect on the distribution of the time averaged heat transfer coefficient on the blade and that this distribution is different from the distribution that is obtainable from a steady computation. This difference was found to be as large as 20 percent of the average heat transfer on the blade surface. On the tip surface, this difference is comparatively smaller and can be as large as four percent of the average.
    Keywords: Aerodynamics
    Type: NASA/TM-2008-215257 , GT2008-51242 , E-16520 , 2008 Expo 2008 Gas Turbine Technical Congress and Exposition; Jun 01, 2008; Berlin; Germany
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  • 25
    Publication Date: 2019-07-13
    Description: This paper describes development of high frequency pulse detonation tubes similar to a small pulse detonation engine (PDE). A high-speed valve injects a charge of a mixture of fuel and air at rates of up to 1000 Hz into a constant area tube closed at one end. The reactants detonate in the tube and the products exit as a pulsed jet. High frequency pressure transducers are used to monitor the pressure fluctuations in the device and thrust is measured with a balance. The effects of injection frequency, fuel and air flow rates, tube length, and injection location are considered. Both H2 and C2H4 fuels are considered. Optimum (maximum specific thrust) fuel-air compositions and resonant frequencies are identified. Results are compared to PDE calculations. Design rules are postulated and applications to aerodynamic flow control and propulsion are discussed.
    Keywords: Aerodynamics
    Type: 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit; Jul 20, 2008 - Jul 23, 2008; Hartford, CT; United States
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  • 26
    Publication Date: 2019-07-13
    Description: Circulation control is a viable active flow control approach that can be used to meet the NASA Subsonic Fixed Wing project s Cruise Efficient Short Take Off and Landing goals. Currently, circulation control systems are primarily designed using empirical methods. However, large uncertainty in our ability to predict circulation control performance has led to the development of advanced CFD methods. This paper provides an overview of a systematic approach to developing CFD tools for basic and advanced circulation control applications. This four-step approach includes "Unit", "Benchmar", "Subsystem", and "Complete System" experiments. The paper emphasizes the ongoing and planned 2-D and 3-D physics orientated experiments with corresponding CFD efforts. Sample data are used to highlight the challenges involved in conducting circulation control computations and experiments.
    Keywords: Aerodynamics
    Type: 2008 International Powered Lift Conference; Jul 22, 2008 - Jul 24, 2008; London; United Kingdom
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  • 27
    Publication Date: 2019-07-13
    Description: Short take-off and landing (STOL) systems can offer significant capabilities to warfighters and, for civil operators thriving on maximizing efficiencies they can improve airspace use while containing noise within airport environments. In order to provide data for next generation systems, a wind tunnel test of an all-wing cruise efficient, short take-off and landing (CE STOL) configuration was conducted in the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) 14- by 22-foot Subsonic Wind Tunnel. The test s purpose was to mature the aerodynamic aspects of an integrated powered lift system within an advanced mobility configuration capable of CE STOL. The full-span model made use of steady flap blowing and a lifting centerbody to achieve high lift coefficients. The test occurred during April through June of 2007 and included objectives for advancing the state-of-the-art of powered lift testing through gathering force and moment data, on-body pressure data, and off-body flow field measurements during automatically controlled blowing conditions. Data were obtained for variations in model configuration, angles of attack and sideslip, blowing coefficient, and height above ground. The database produced by this effort is being used to advance design techniques and computational tools for developing systems with integrated powered lift technologies.
    Keywords: Aerodynamics
    Type: 2008 International Powered Lift Conference; Jul 22, 2008 - Jul 24, 2008; London; United Kingdom
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  • 28
    Publication Date: 2019-07-13
    Description: Infrared thermography is a powerful tool for investigating fluid mechanics on flight vehicles. (Can be used to visualize and characterize transition, shock impingement, separation etc.). Updated onboard F-15 based system was used to visualize supersonic boundary layer transition test article. (Tollmien-Schlichting and cross-flow dominant flow fields). Digital Recording improves image quality and analysis capability. (Allows accurate quantitative (temperature) measurements, Greater enhancement through image processing allows analysis of smaller scale phenomena).
    Keywords: Aerodynamics
    Type: 13th International Symposium on Flow Visualization; Jul 01, 2008 - Jul 04, 2008; Nice; France
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  • 29
    Publication Date: 2019-07-13
    Description: Under the NASA Fundamental Aeronautics Program, the Supersonics Project is working to overcome the obstacles to supersonic commercial flight. The proposed vehicles are long slim body aircraft with pronounced aero-servo-elastic modes. These modes can potentially couple with propulsion system dynamics; leading to performance challenges such as aircraft ride quality and stability. Other disturbances upstream of the engine generated from atmospheric wind gusts, angle of attack, and yaw can have similar effects. In addition, for optimal propulsion system performance, normal inlet-engine operations are required to be closer to compressor stall and inlet unstart. To study these phenomena an integrated model is needed that includes both airframe structural dynamics as well as the propulsion system dynamics. This paper covers the propulsion system component volume dynamics modeling of a turbojet engine that will be used for an integrated vehicle Aero-Propulso-Servo-Elastic model and for propulsion efficiency studies.
    Keywords: Aerodynamics
    Type: NASA/TM--2008-215172 , E-16415 , GT2008-50524 , ASME Turbo Expo; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
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  • 30
    Publication Date: 2019-07-13
    Description: A simple matrix polynomial approach is introduced for approximating unsteady aerodynamics in the s-plane and ultimately, after combining matrix polynomial coefficients with matrices defining the structure, a matrix polynomial of the flutter equations of motion (EOM) is formed. A technique of recasting the matrix-polynomial form of the flutter EOM into a first order form is also presented that can be used to determine the eigenvalues near the origin and everywhere on the complex plane. An aeroservoelastic (ASE) EOM have been generalized to include the gust terms on the right-hand side. The reasons for developing the new matrix polynomial approach are also presented, which are the following: first, the "workhorse" methods such as the NASTRAN flutter analysis lack the capability to consistently find roots near the origin, along the real axis or accurately find roots farther away from the imaginary axis of the complex plane; and, second, the existing s-plane methods, such as the Roger s s-plane approximation method as implemented in ISAC, do not always give suitable fits of some tabular data of the unsteady aerodynamics. A method available in MATLAB is introduced that will accurately fit generalized aerodynamic force (GAF) coefficients in a tabular data form into the coefficients of a matrix polynomial form. The root-locus results from the NASTRAN pknl flutter analysis, the ISAC-Roger's s-plane method and the present matrix polynomial method are presented and compared for accuracy and for the number and locations of roots.
    Keywords: Aerodynamics
    Type: RTO-AVT-154 , NATO RTO Specialists Meeting AVT-154 on Advanced Methods in Aeroelasticity; May 05, 2008 - May 07, 2008; Norway; Norway
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  • 31
    Publication Date: 2019-07-13
    Description: NASA Langley Research Center has continued to develop its long standing computational tools to address new challenges in aircraft and launch vehicle design. This paper discusses the application and development of those computational aeroelastic tools. Four topic areas will be discussed: 1) Modeling structural and flow field nonlinearities; 2) Integrated and modular approaches to nonlinear multidisciplinary analysis; 3) Simulating flight dynamics of flexible vehicles; and 4) Applications that support both aeronautics and space exploration.
    Keywords: Aerodynamics
    Type: AVT-154-003 , NATO RTO Specialists'' Meeting AVT-154 on Advanced Methods in Aeroelasticity; May 05, 2008 - May 07, 2008; Norway; Norway
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  • 32
    Publication Date: 2019-07-13
    Description: Tandem cylinders are being studied because they model a variety of component level interactions of landing gear. The present effort is directed at the case of two identical cylinders with their centroids separated in the streamwise direction by 1.435 diameters. Experiments in the Basic Aerodynamic Research Tunnel and Quiet Flow Facility at NASA Langley Research Center have provided an extensive experimental database of the nearfield flow and radiated noise. The measurements were conducted at a Mach number of 0.1285 and Reynolds number of 1.66x10(exp 5) based on the cylinder diameter. A trip was used on the upstream cylinder to insure a fully turbulent flow separation and, hence, to simulate a major aspect of high Reynolds number flow. The parallel computational effort uses the three-dimensional Navier-Stokes solver CFL3D with a hybrid, zonal turbulence model that turns off the turbulence production term everywhere except in a narrow ring surrounding solid surfaces. The experiments exhibited an asymmetry in the surface pressure that was persistent despite attempts to eliminate it through small changes in the configuration. To model the asymmetry, the simulations were run with the cylinder configuration at a nonzero but small angle of attack. The computed results and experiments are in general agreement that vortex shedding for the spacing studied herein is weak relative to that observed at supercritical spacings. Although the shedding was subdued in the simulations, it was still more prominent than in the experiments. Overall, the simulation comparisons with measured near-field data and the radiated acoustics are reasonable, especially if one is concerned with capturing the trends relative to larger cylinder spacings. However, the flow details of the 1.435 diameter spacing have not been captured in full even though very fine grid computations have been performed. Some of the discrepancy may be associated with the simulation s inexact representation of the experimental configuration, but numerical and flow modeling errors are also likely contributors to the observed differences.
    Keywords: Aerodynamics
    Type: AIAA Paper 2008-2862 , 14th AIAA/CEAS Aeroacoustics Conference; May 05, 2008 - May 07, 2008; Vancouver; Canada
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  • 33
    Publication Date: 2019-07-13
    Description: The second flight of the Hyper-X program afforded a unique opportunity to determine the aerodynamic force and moment characteristics of an airframe-integrated scramjet-powered aircraft in hypersonic flight. These data were gathered via a repeated series of pitch, yaw, and roll doublets, frequency sweeps, and pushover-pullup maneuvers performed throughout the X-43A cowl-closed descent. Maneuvers were conducted at Mach numbers of 6.80-0.95 and at altitudes from 92,000 ft mean sea level to sea level. The dynamic pressure varied from 1300 to 400 psf with the angle of attack ranging from 0 to 14 deg. The flight-extracted aerodynamics were compared with preflight predictions based on wind-tunnel test data. The X-43A flight-derived axial force was found to be 10-15%higher than prediction. Underpredictions of similar magnitude were observed for the normal force. For Mach numbers above 4.0, the flight-derived stability and control characteristics resulted in larger-than-predicted static margins, with the largest discrepancy approximately 5 in. forward along the x-axis center of gravity at Mach 6.0. This condition would result in less static margin in pitch. The predicted lateral-directional stability and control characteristics matched well with flight data when allowance was made for the high uncertainty in angle of sideslip.
    Keywords: Aerodynamics
    Type: AIAA Paper-2006-8028 , 14th AIAA/AHI Space Planes and Hypersonic Systems and Technologies Conference; Nov 06, 2006 - Nov 09, 2006; Canberra; Australia|Journal of Spacecraft and Rockets; 45; 3; 472-484
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  • 34
    Publication Date: 2019-07-13
    Description: A review is presented of the initial experimental results and analysis that formed the basis the Vortex Flow Experiment 2 (VFE-2). The focus of this work was to distinguish the basic effects of Reynolds number, Mach number, angle of attack, and leading edge bluntness on separation-induced leading-edge vortex flows that are common to slender wings. Primary analysis is focused on detailed static surface pressure distributions, and the results demonstrate significant effects regarding the onset and progression of leading-edge vortex separation.
    Keywords: Aerodynamics
    Type: AIAA Paper-2008-0378 , 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 35
    Publication Date: 2019-07-13
    Description: In the present paper the main results of the new experiments from Vortex Flow Experiment (VFE-2) are summarized. These include some force and moment results, surface and off-body measurements, as well as steady and fluctuating quantities. Some critical remarks are added, and an outlook for future investigations is given.
    Keywords: Aerodynamics
    Type: AIAA Paper-2008-0383 , 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 36
    Publication Date: 2019-07-13
    Description: An experiment was designed to create a simplified simulation of the flow through a hole in the surface of a hypersonic aerospace vehicle and the subsequent impingement of the flow on internal structures. In addition to planar laser-induced fluorescence (PLIF) flow visualization, pressure measurements were recorded on the surface of an impingement target. The PLIF images themselves provide quantitative spatial information about structure of the impinging jets. The images also help in the interpretation of impingement surface pressure profiles by highlighting the flow structures corresponding to distinctive features of these pressure profiles. The shape of the pressure distribution along the impingement surface was found to be double-peaked in cases with a sufficiently high jet-exit-to-ambient pressure ratio so as to have a Mach disk, as well as in cases where a flow feature called a recirculation bubble formed at the impingement surface. The formation of a recirculation bubble was in turn found to depend very sensitively upon the jet-exit-to-ambient pressure ratio. The pressure measured at the surface was typically less than half the nozzle plenum pressure at low jet pressure ratios and decreased with increasing jet pressure ratios. Angled impingement cases showed that impingement at a 60deg angle resulted in up to a factor of three increase in maximum pressure at the plate compared to normal incidence.
    Keywords: Aerodynamics
    Type: 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 37
    Publication Date: 2019-07-13
    Description: Over the past three years, the National Aeronautics and Space Administration (NASA) has initiated design, development, and testing of a new human-rated space exploration system under the Constellation Program. Initial designs within the Constellation Program are scheduled to replace the present Space Shuttle, which is slated for retirement within the next three years. The development of vehicles for the Constellation system has encountered several unsteady aerodynamics challenges that have bearing on more traditional unsteady aerodynamic and aeroelastic analysis. This paper focuses on the synergy between the present NASA challenges and the ongoing challenges that have historically been the subject of research and method development. There are specific similarities in the flows required to be analyzed for the space exploration problems and those required for some of the more nonlinear unsteady aerodynamic and aeroelastic problems encountered on aircraft. The aggressive schedule, significant technical challenge, and high-priority status of the exploration system development is forcing engineers to implement existing tools and techniques in a design and application environment that is significantly stretching the capability of their methods. While these methods afford the users with the ability to rapidly turn around designs and analyses, their aggressive implementation comes at a price. The relative immaturity of the techniques for specific flow problems and the inexperience with their broad application to them, particularly on manned spacecraft flight system, has resulted in the implementation of an extensive wind tunnel and flight test program to reduce uncertainty and improve the experience base in the application of these methods. This provides a unique opportunity for unsteady aerodynamics and aeroelastic method developers to test and evaluate new analysis techniques on problems with high potential for acquisition of test and even flight data against which they can be evaluated. However, researchers may be required to alter the geometries typically used in their analyses, the types of flows analyzed, and even the techniques by which computational tools are verified and validated. This paper discusses these issues and provides some perspective on the potential for new and innovative approaches to the development of methods to attack problems in nonlinear unsteady aerodynamics.
    Keywords: Aerodynamics
    Type: AVT-154-002 , NATO/RTO AVT-154 Advanced Methods in Aeroelasticity; May 05, 2008 - May 08, 2008; Oslo; Norway
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  • 38
    Publication Date: 2019-07-13
    Description: This paper presents comparisons of seven propagation codes for predicting liner attenuation in ducts with flow. The selected codes span the spectrum of methods available (finite element, parabolic approximation, and pseudo-time domain) and are collectively representative of the state-of-art in the liner industry. These codes are included because they have two-dimensional and three-dimensional versions and can be exported to NASA's Columbia Supercomputer. The basic assumptions, governing differential equations, boundary conditions, and numerical methods underlying each code are briefly reviewed and an assessment is performed based on two predefined metrics. The two metrics used in the assessment are the accuracy of the predicted attenuation and the amount of wall clock time to predict the attenuation. The assessment is performed over a range of frequencies, mean flow rates, and grazing flow liner impedances commonly used in the liner industry. The primary conclusions of the study are (1) predicted attenuations are in good agreement for rigid wall ducts, (2) the majority of codes compare well to each other and to approximate results from mode theory for soft wall ducts, (3) most codes compare well to measured data on a statistical basis, (4) only the finite element codes with cubic Hermite polynomials capture extremely large attenuations, and (5) wall clock time increases by an order of magnitude or more are observed for a three-dimensional code relative to the corresponding two-dimensional version of the same code.
    Keywords: Aerodynamics
    Type: 14th AIAA/CEAS Aeroacoustics Conference; May 05, 2008 - May 08, 2008; Vancouver, BC; Canada
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  • 39
    Publication Date: 2019-07-13
    Description: The Hypersonic Thermodynamic Infrared Measurement (HYTHIRM) project is presently focused on near term support to the Shuttle program through the development of an infrared imaging capability of sufficient spatial and temporal resolution to augment existing on-board Orbiter instrumentation. Significant progress has been made with the identification and inventory of relevant existing optical imaging assets and the development, maturation, and validation of simulation and modeling tools for assessment and mission planning purposes, which were intended to lead to the best strategies and assets for successful acquisition of quantitative global surface temperature data on the Shuttle during entry. However, there are longer-term goals of providing global infrared imaging support to other flight projects as well. A status of HYTHIRM from the perspective of how two NASA-sponsored boundary layer transition flight experiments could benefit by infrared measurements is provided. Those two flight projects are the Hypersonic Boundary layer Transition (HyBoLT) flight experiment and the Shuttle Boundary Layer Transition Flight Experiment (BLT FE), which are both intended for reducing uncertainties associated with the extrapolation of wind tunnel derived transition correlations for flight application. Thus, the criticality of obtaining high quality flight data along with the impact it would provide to the Shuttle program damage assessment process are discussed. Two recent wind tunnel efforts that were intended as risk mitigation in terms of quantifying the transition process and resulting turbulent wedge locations are briefly reviewed. Progress is being made towards finalizing an imaging strategy in support of the Shuttle BLT FE, however there are no plans currently to image HyBoLT.
    Keywords: Aerodynamics
    Type: AIAA 2008-4027 , 40th AIAA Thermophysics Conference; Jun 23, 2008 - Jun 26, 2008; Seattle, WA; United States
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  • 40
    Publication Date: 2019-07-13
    Description: High resolution calibrated infrared imagery of vehicles during hypervelocity atmospheric entry or sustained hypersonic cruise has the potential to provide flight data on the distribution of surface temperature and the state of the airflow over the vehicle. In the early 1980 s NASA sought to obtain high spatial resolution infrared imagery of the Shuttle during entry. Despite mission execution with a technically rigorous pre-planning capability, the single airborne optical system for this attempt was considered developmental and the scientific return was marginal. In 2005 the Space Shuttle Program again sponsored an effort to obtain imagery of the Orbiter. Imaging requirements were targeted towards Shuttle ascent; companion requirements for entry did not exist. The engineering community was allowed to define observation goals and incrementally demonstrate key elements of a quantitative spatially resolved measurement capability over a series of flights. These imaging opportunities were extremely beneficial and clearly demonstrated capability to capture infrared imagery with mature and operational assets of the US Navy and the Missile Defense Agency. While successful, the usefulness of the imagery was, from an engineering perspective, limited. These limitations were mainly associated with uncertainties regarding operational aspects of data acquisition. These uncertainties, in turn, came about because of limited pre-flight mission planning capability, a poor understanding of several factors including the infrared signature of the Shuttle, optical hardware limitations, atmospheric effects and detector response characteristics. Operational details of sensor configuration such as detector integration time and tracking system algorithms were carried out ad hoc (best practices) which led to low probability of target acquisition and detector saturation. Leveraging from the qualified success during Return-to-Flight, the NASA Engineering and Safety Center sponsored an assessment study focused on increasing the probability of returning spatially resolved scientific/engineering thermal imagery. This paper provides an overview of the assessment task and the systematic approach designed to establish confidence in the ability of existing assets to reliably acquire, track and return global quantitative surface temperatures of the Shuttle during entry. A discussion of capability demonstration in support of a potential Shuttle boundary layer transition flight test is presented. Successful demonstration of a quantitative, spatially resolved, global temperature measurement on the proposed Shuttle boundary layer transition flight test could lead to potential future applications with hypersonic flight test programs within the USAF and DARPA along with flight test opportunities supporting NASA s project Constellation.
    Keywords: Aerodynamics
    Type: AIAA 2008-4022 , 40th AIAA Thermophysics Conference; Jun 23, 2008 - Jun 26, 2008; Seattle, WA; United States
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  • 41
    Publication Date: 2019-07-13
    Description: The successful Mach 7 and 10 flights of the first fully integrated scramjet propulsion systems by the Hyper-X (X-43A) program have provided the means with which to verify the original design methodologies and assumptions. As part of Hyper-X s propulsion-airframe integration, the forebody was designed to include a spanwise array of vortex generators to promote boundary layer transition ahead of the engine. Turbulence at the inlet is thought to provide the most reliable engine design and allows direct scaling of flight results to groundbased data. Pre-flight estimations of boundary layer transition, for both Mach 7 and 10 flight conditions, suggested that forebody boundary layer trips were required to ensure fully turbulent conditions upstream of the inlet. This paper presents the results of an analysis of the thermocouple measurements used to infer the dynamics of the transition process during the trajectories for both flights, on both the lower surface (to assess trip performance) and the upper surface (to assess natural transition). The approach used in the analysis of the thermocouple data is outlined, along with a discussion of the calculated local flow properties that correspond to the transition events as identified in the flight data. The present analysis has confirmed that the boundary layer trips performed as expected for both flights, providing turbulent flow ahead of the inlet during critical portions of the trajectory, while the upper surface was laminar as predicted by the pre-flight analysis.
    Keywords: Aerodynamics
    Type: AIAA-2008-3736 , L-6068 , 40th AIAA Thermophysics Conference; Jun 23, 2008 - Jun 26, 2008; Seattle, WA; United States
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  • 42
    Publication Date: 2019-07-13
    Description: The drag prediction workshop series (DPW), held over the last six years, and sponsored by the AIAA Applied Aerodynamics Committee, has been extremely useful in providing an assessment of the state-of-the-art in computationally based aerodynamic drag prediction. An emerging consensus from the three workshop series has been the identification of spatial discretization errors as a dominant error source in absolute as well as incremental drag prediction. This paper provides an overview of the collective experience from the workshop series regarding the effect of grid-related issues on overall drag prediction accuracy. Examples based on workshop results are used to illustrate the effect of grid resolution and grid quality on drag prediction, and grid convergence behavior is examined in detail. For fully attached flows, various accurate and successful workshop results are demonstrated, while anomalous behavior is identified for a number of cases involving substantial regions of separated flow. Based on collective workshop experiences, recommendations for improvements in mesh generation technology which have the potential to impact the state-of-the-art of aerodynamic drag prediction are given.
    Keywords: Aerodynamics
    Type: 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 43
    Publication Date: 2019-07-13
    Description: Computational fluid dynamics (CFD) was used to evaluate a promising concept for reducing the noise at take-off of dual-stream, turbofan nozzles. The concept, offset stream technology, reduces the jet noise observed on the ground by diverting (offsetting) the majority of the fan flow below the core flow, thickening this layer between the high velocity core flow and the ground observers. In this study a wedge placed in the internal fan stream is used as the diverter. Wind, a Reynolds Averaged Navier-Stokes (RANS) code, was used to analyze the flowfield of the exhaust plume and to calculate nozzle performance. Results showed that the wedge effectively diverts the fan flow and the turbulent kinetic energy on the observer side of the nozzle is reduced. The reduction in turbulent kinetic energy should correspond to a reduction in noise. The blockage due to the wedge reduces the fan massflow proportional to its blockage and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental data. This noise reduction concept shows promise for reduced jet noise at a small reduction in thrust. It has been demonstrated that RANS CFD can be used to optimize this concept.
    Keywords: Aerodynamics
    Type: 46th AIAA Aerospace Sciences Meeting; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 44
    Publication Date: 2019-07-13
    Description: Far-field noise sound power level (PWL) spectra and overall sound pressure level (OASPL) directivities were compared for three significantly different model fan stages which were tested in the NASA Glenn 9x15 Low Speed Wind Tunnel. The test fans included the Advanced Ducted Propulsor (ADP) Fan1, the baseline Source Diagnostic Test (SDT) fan, and the Quiet High Speed Fan2 (QHSF2) These fans had design rotor tangential tip speeds from 840 to 1474 ft/s and stage pressure ratios from 1.29 to 1.82. Additional parameters included rotor-stator spacing, stator sweep, and downstream support struts. Acoustic comparison points were selected on the basis of stage thrust. Acoustic results for the low tip speed/low pressure ratio fan (ADP Fan1) were thrust-adjusted to show how a geometrically-scaled version of this fan might compare at the higher design thrust levels of the other two fans. Lowest noise levels were typically observed for ADP Fan1 (which had a radial stator) and for the intermediate tip speed fan (Source Diagnostics Test, SDT, R4 rotor) with a swept stator. Projected noise levels for the ADP fan to the SDT swept stator configuration at design point conditions showed the fans to have similar noise levels. However, it is possible that the ADP fan could be 2 to 3 dB quieter with incorporation of a swept stator. Benefits of a scaled ADP fan include avoidance of multiple pure tones associated with transonic and higher blade tip speeds. Penalties of a larger size ADP fan would include increased nacelle size and drag.
    Keywords: Aerodynamics
    Type: 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 45
    Publication Date: 2019-07-13
    Description: A detailed uncertainty analysis for the Ares I ascent aero 6-DOF wind tunnel database is described. While the database itself is determined using only the test results for the latest configuration, the data used for the uncertainty analysis comes from four tests on two different configurations at the Boeing Polysonic Wind Tunnel in St. Louis and the Unitary Plan Wind Tunnel at NASA Langley Research Center. Four major error sources are considered: (1) systematic errors from the balance calibration curve fits and model + balance installation, (2) run-to-run repeatability, (3) boundary-layer transition fixing, and (4) tunnel-to-tunnel reproducibility.
    Keywords: Aerodynamics
    Type: AIAA Paper-2008-4259 , 26th AIAA Aerodynamic Measurement Technology & Ground Testing Conference; Jun 23, 2008 - Jun 26, 2008; Seattle, WA; United States
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  • 46
    Publication Date: 2019-07-13
    Description: An experimental wind tunnel program is being conducted in support of a NASA wide effort to develop a Space Shuttle replacement and to support the Agency s long term objective of returning to the Moon and Mars. This report documents experimental measurements made on several scaled ceramic heat transfer models of the proposed Crew Exploration Vehicle Crew Module. The experimental data highlighted in this test report are to be used to assess numerical tools that will be used to generate the flight aerothermodynamic database. Global heat transfer images and heat transfer distributions were obtained over a range of freestream Reynolds numbers and angles of attack with the phosphor thermography technique. Heat transfer data were measured on the forebody and afterbody and were used to infer the heating on the vehicle as well as the boundary layer state on the forebody surface. Several model support configurations were assessed to minimize potential support interference. In addition, the ability of the global phosphor thermography method to provide quantitative heating measurements in the low temperature environment of the capsule base region was assessed. While naturally fully developed turbulent levels were not obtained on the forebody, the use of boundary layer trips generated fully developed turbulent flow. Laminar and turbulent computational results were shown to be in good agreement with the data. Backshell testing demonstrated the ability to obtain data in the low temperature region as well as demonstrating the lack of significant model support hardware influence on heating.
    Keywords: Aerodynamics
    Type: 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 47
    Publication Date: 2019-07-13
    Description: The aerodynamic effects of the recession of the ablative thermal protection system for the Orion Command Module of the Crew Exploration Vehicle are important for the vehicle guidance. At the present time, the aerodynamic effects of recession being handled within the Orion aerodynamic database indirectly with an additional safety factor placed on the uncertainty bounds. This study is an initial attempt to quantify the effects for a particular set of recessed geometry shapes, in order to provide more rigorous analysis for managing recession effects within the aerodynamic database. The aerodynamic forces and moments for the baseline and recessed geometries were computed at several trajectory points using multiple CFD codes, both viscous and inviscid. The resulting aerodynamics for the baseline and recessed geometries were compared. The forces (lift, drag) show negligible differences between baseline and recessed geometries. Generally, the moments show a difference between baseline and recessed geometries that correlates with the maximum amount of recession of the geometry. The difference between the pitching moments for the baseline and recessed geometries increases as Mach number decreases (and the recession is greater), and reach a value of -0.0026 for the lowest Mach number. The change in trim angle of attack increases from approx. 0.5deg at M = 28.7 to approx. 1.3deg at M = 6, and is consistent with a previous analysis with a lower fidelity engineering tool. This correlation of the present results with the engineering tool results supports the continued use of the engineering tool for future work. The present analysis suggests there does not need to be an uncertainty due to recession in the Orion aerodynamic database for the force quantities. The magnitude of the change in pitching moment due to recession is large enough to warrant inclusion in the aerodynamic database. An increment in the uncertainty for pitching moment could be calculated from these results and included in the development of the aerodynamic database uncertainty for pitching moment.
    Keywords: Aerodynamics
    Type: 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, Nevada; United States
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  • 48
    Publication Date: 2019-07-12
    Description: Wind turbines are immense, flexible structures with aerodynamic forces acting on the rotating blades at harmonics of the turbine rotational frequency, which are comparable to the modal frequencies of the structure. Predicting and experimentally measuring the modal frequencies of wind turbines has been important to their successful design and operation. Performing modal tests on wind turbine structures over 100 meters tall is a substantial challenge, which has inspired innovative developments in modal test technology. For wind turbines, a further complication is that the modal frequencies are dependent on the turbine rotation speed. The history and development of a new technique for acquiring the modal parameters using output-only response data, called the Natural Excitation Technique (NExT), will be reviewed, showing historical tests and techniques. The initial attempts at output-only modal testing began in the late 1980's with the development of NExT in the 1990's. NExT was a predecessor to OMA, developed to overcome these challenges of testing immense structures excited with environmental inputs. We will trace the difficulties and successes of wind turbine modal testing from 1982 to the present. Keywords: OMA, Modal Analysis, NExT, Wind Turbines, Wind Excitation
    Keywords: Aerodynamics
    Type: JSC-CN-16440 , To be published in Mechanical Systems and Signal Processing, August 2008
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  • 49
    Publication Date: 2019-07-12
    Description: Flow control using synthetic jet injection has been applied in a low speed axial compressor. The synthetic jets were applied from the suction surface of a stator vane via a span-wise row of slots pitched in the streamwise direction. Actuation was provided externally from acoustic drivers coupled to the vane tip via flexible tubing. The acoustic resonance characteristics of the system, and the resultant jet velocities were obtained. The effects on the separated flow field for various jet velocities and frequencies were explored. Total pressure loss reductions across the vane passage were measured. The effect of synthetic jet injection was shown to be comparable to that of pulsatory injection with mass addition for stator vanes which had separated flow. While only a weak dependence of the beneficial effect was noted based on the excitation frequency, a strong dependence on the amplitude was observed at all frequencies.
    Keywords: Aerodynamics
    Type: NASA/TM-2008-215145 , AIAA Paper-2008-0602 , E-16308
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  • 50
    Publication Date: 2019-07-12
    Description: An experimental wind tunnel test was conducted in the NASA Langley Research Center s 20-Inch Mach 6 Air Tunnel in support of the Hypersonic International Flight Research Experimentation Program. The information in this article is focused on the Flight 1 configuration, the first in a series of flight experiments. The article documents experimental measurements made over a Reynolds numbers range of 2.1x10(exp 6)/ft to 5.6x10(exp 6)/ft and angles of attack of -5 to +5 deg on several scaled ceramic heat transfer models of the Flight 1 configuration. Global heat transfer was measured using phosphor thermography and the resulting images and heat transfer distributions were used to infer the state of the boundary layer on the vehicle windside and leeside surfaces. Boundary layer trips were used to force the boundary layer turbulent and the experimental data highlighted in this article were used to size and place the boundary layer trip for the flight vehicle. The required height of the flight boundary layer trip was determined to be 0.079 in and the trip was moved from the design location of 7.87 in to 20.47 in to ensure that augmented heating would not impact the laminar side of the vehicle. Allowable roughness was selected to be 3.2x10(exp -3) in.
    Keywords: Aerodynamics
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  • 51
    Publication Date: 2019-07-12
    Description: Reentry models for use in hypersonic wind tunnel tests were fabricated using a stereolithography apparatus. These models were produced in one day or less, which is a significant time savings compared to the manufacture of ceramic or metal models. The models were tested in the NASA Langley Research Center 31-Inch Mach 10 Air Tunnel. Only a few of the models survived repeated tests in the tunnel, and several failure modes of the models were identified. Planar laser-induced fluorescence (PLIF) of nitric oxide (NO) was used to visualize the flowfields in the wakes of these models. Pure NO was either seeded through tubes plumbed into the model or via a tube attached to the strut holding the model, which provided localized addition of NO into the model s wake through a porous metal cylinder attached to the end of the tube. Models included several 2- inch diameter Inflatable Reentry Vehicle Experiment (IRVE) models and 5-inch diameter Crew Exploration Vehicle (CEV) models. Various model configurations and NO seeding methods were used, including a new streamwise visualization method based on PLIF. Virtual Diagnostics Interface (ViDI) technology, developed at NASA Langley Research Center, was used to visualize the data sets in post processing. The use of calibration "dotcards" was investigated to correct for camera perspective and lens distortions in the PLIF images.
    Keywords: Aerodynamics
    Type: LF99-5899
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  • 52
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2019-07-12
    Description: Constrained fitting for airfoil curvature smoothing (CFACS) is a splinebased method of interpolating airfoil surface coordinates (and, concomitantly, airfoil thicknesses) between specified discrete design points so as to obtain smoothing of surface-curvature profiles in addition to basic smoothing of surfaces. CFACS was developed in recognition of the fact that the performance of a transonic airfoil is directly related to both the curvature profile and the smoothness of the airfoil surface. Older methods of interpolation of airfoil surfaces involve various compromises between smoothing of surfaces and exact fitting of surfaces to specified discrete design points. While some of the older methods take curvature profiles into account, they nevertheless sometimes yield unfavorable results, including curvature oscillations near end points and substantial deviations from desired leading-edge shapes. In CFACS as in most of the older methods, one seeks a compromise between smoothing and exact fitting. Unlike in the older methods, the airfoil surface is modified as little as possible from its original specified form and, instead, is smoothed in such a way that the curvature profile becomes a smooth fit of the curvature profile of the original airfoil specification. CFACS involves a combination of rigorous mathematical modeling and knowledge-based heuristics. Rigorous mathematical formulation provides assurance of removal of undesirable curvature oscillations with minimum modification of the airfoil geometry. Knowledge-based heuristics bridge the gap between theory and designers best practices. In CFACS, one of the measures of the deviation of an airfoil surface from smoothness is the sum of squares of the jumps in the third derivatives of a cubicspline interpolation of the airfoil data. This measure is incorporated into a formulation for minimizing an overall deviation- from-smoothness measure of the airfoil data within a specified fitting error tolerance. CFACS has been extensively tested on a number of supercritical airfoil data sets generated by inverse design and optimization computer programs. All of the smoothing results show that CFACS is able to generate unbiased smooth fits of curvature profiles, trading small modifications of geometry for increasing curvature smoothness by eliminating curvature oscillations and bumps (see figure).
    Keywords: Aerodynamics
    Type: LAR-17227-1 , NASA Tech Briefs, September 2008; 40-41
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  • 53
    Publication Date: 2019-07-12
    Description: An experimental multisegmented telescoping nose boom has been installed on an F-15B airplane to be tested in a flight environment. The experimental nose boom is representative of one that could be used to tailor the sonic boom signature of an airplane such as a supersonic business jet. The nose boom consists of multiple sections and could be extended during flight to a length of 24 ft. The preliminary analyses indicate that the addition of the experimental nose boom could adversely affect vehicle flight characteristics and air data systems. Before the boom was added, a series of flights was conducted to update the aerodynamic model and characterize the air data systems of the baseline airplane. The baseline results have been used in conjunction with estimates of the nose boom's influence to prepare for a series of research flights conducted with the nose boom installed. Data from these flights indicate that the presence of the experimental boom reduced the static pitch and yaw stability of the airplane. The boom also adversely affected the static-position error of the airplane but did not significantly affect angle-of-attack or angle-of-sideslip measurements. The research flight series has been successfully completed.
    Keywords: Aerodynamics
    Type: NASA/TM-2008-214634 , H-2809
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  • 54
    Publication Date: 2019-07-12
    Description: An investigation of distortions of the rotor exit flow field caused by an aerodynamic probe mounted in the rotor is described in this paper. A rotor total pressure Kiel probe, mounted on the rotor hub and extending up to the mid-span radius of a rotor blade channel, generates a wake that forms additional flow blockage. Three types of high-response aerodynamic probes were used to investigate the distorted flow field behind the rotor. These probes were: a split-fiber thermo-anemometric probe to measure velocity and flow direction, a total pressure probe, and a disk probe for in-flow static pressure measurement. The signals acquired from these high-response probes were reduced using an ensemble averaging method based on a once per rotor revolution signal. The rotor ensemble averages were combined to construct contour plots for each rotor channel of the rotor tested. In order to quantify the rotor probe effects, the contour plots for each individual rotor blade passage were averaged into a single value. The distribution of these average values along the rotor circumference is a measure of changes in the rotor exit flow field due to the presence of a probe in the rotor. These distributions were generated for axial flow velocity and for static pressure.
    Keywords: Aerodynamics
    Type: NASA/CR-2008-215215 , E-16503
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  • 55
    Publication Date: 2019-07-12
    Description: The data contained on this CD are a supplement to NASA/TP-2001-210629 published in February 2001. This CD replaces a web-site database search and retrieval system - noted as reference 36 in the NASA/TP - that was to supply the aeronautical community with access to the flight data. Unfortunately, this web-site was only available for a short time after the publication of NASA/TP-2001-21068 due to software and support issues. The contents of this CD are organized into five folders containing data from the flight test and reference 1. In particular, the following are provided: (1) tabular data of the Flight Conditions from Table 5; (2) boundary layer data from Table 12 for three flights in multiple formats; (3) skin-friction data - xmgr format (ref. 3) - used to generate Figure 26; (4) surface pressure data with a listing of the parameters; and (5) tuft-images from three cameras in two formats.
    Keywords: Aerodynamics
    Type: NASA/TP-2001-210629/SUPPL , L19482
    Format: text
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  • 56
    Publication Date: 2019-07-12
    Description: A survey is made of recent computations published for synthetic jet flow control cases from a CFD workshop held in 2004. The three workshop cases were originally chosen to represent different aspects of flow control physics: nominally 2-D synthetic jet into quiescent air, 3-D circular synthetic jet into turbulent boundary-layer crossflow, and nominally 2-D flow-control (both steady suction and oscillatory zero-net-mass-flow) for separation control on a simple wall-mounted aerodynamic hump shape. The purpose of this survey is to summarize the progress as related to these workshop cases, particularly noting successes and remaining challenges for computational methods. It is hoped that this summary will also by extension serve as an overview of the state-of-the-art of CFD for these types of flow-controlled flow fields in general.
    Keywords: Aerodynamics
    Type: LF99-7374
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  • 57
    Publication Date: 2019-07-13
    Description: The potential for energy savings by reducing the aerodynamic drag of rail cars is significant. A previous study of aerodynamic drag of coal cars suggests that a 25% reduction in drag of empty cars would correspond to a 5% fuel savings for a round trip [1]. Rail statistics for the United States [2] report that approximately 5.7 billion liters of diesel fuel were consumed for coal transportation in 2002, so a 5% fuel savings would total 284 million liters. This corresponds to 2% of Class I railroad fuel consumption nationwide. As part of a DOE-sponsored study, the aerodynamic drag of scale rail cars was measured in a wind tunnel. The goal of the study was to measure the drag reduction of various rail-car cover designs. The cover designs tested yielded an average drag reduction of 43% relative to empty cars corresponding to an estimated round-trip fuel savings of 9%.
    Keywords: Aerodynamics
    Type: ARC-E-DAA-TN112 , AfricaRail 2008; Jun 02, 2008 - Jun 06, 2008; Johannesburg; South Africa
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  • 58
    Publication Date: 2019-07-13
    Description: This presentation focuses on nearfield airborne pressure signatures from the Lift and Nozzle Change Effect on Tail Shocks (LaNCETS) flight test experiment. The primary motivation for nearfield probing in the supersonic regime is to measure the shock structure of aircraft in an ongoing effort to overcome the overland sonic boom barrier for commercial supersonic transportation. LaNCETS provides the opportunity to investigate lift distribution and engine plume effects. During Phase 1 flight testing an F-15B was used to probe the F-15 LaNCETS aircraft in order to validate CFD and pre-flight prediction tools. A total of 29 probings were taken at 40,000 ft. altitude at Machs 1.2, 1.4 and 1.6. LaNCETS Phase 1 flight data are presented as a detailed pressure signature superimposed over a picture of the LaNCETS aircraft. The attenuation of the Inlet-Canard shocks with distance as well as its forward propagation and the coalescence of the noseboom shock are illustrated. A detailed CFD study on a simplified LaNCETS aircraft jet nozzle was performed providing the ability to more accurately capture the shocks from the propulsion system and emphasizing how under- and over-expanding the nozzle affects the existence of shock trains inside the jet plume. With Phase 1 being a success preparations are being made to move forward to Phase 2. Phase 2 will fly similar flight conditions, but this time changing the aircraft's lift distribution by biasing the canard positions, and changing the plume shape by under- and over-expanding the nozzle. Nearfield probing will again be completed in the same manner as in Phase 1. An additional presentation focuses on LaNCETS CFD solution methodology. Discussions highlight grid preprocessing, grid shearing and stretching, flow solving and contour plots. Efforts are underway to better capture the flow features via grid modification and flow solution methodology, which will help to achieve better agreement with flight data. An included CD-ROM provides animations of the nearfield probing procedure and of real data from one of the probings integrated with GPS positional and velocity data. An additional in-flight video from the rear seat of the probing aircraft is also provided.
    Keywords: Aerodynamics
    Type: Industry Panel Presentation at the University of Southern California; Nov 03, 2017; Los Angeles, CA; United States|Fundamental Aeronautics 2008 Annual Meeting; Oct 07, 2008 - Oct 09, 2008; Atlanta, GA; United States
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  • 59
    Publication Date: 2019-07-13
    Description: The OVERFLOW code was used to calculate the flow field for a family of five relaxed compression inlets, which were part of a screening study to determine a configuration most suited to the application of microscale flow control technology as a replacement for bleed. Comparisons are made to experimental data collected for each of the inlets in the 1- by 1-Foot Supersonic Wind Tunnel at the NASA Glenn Research Center (GRC) to help determine the suitability of computational fluid dynamics (CFD) as a tool for future studies of these inlets with flow control devices. Effects on the wind tunnel results of the struts present in a high subsonic flow region accounted for most of the inconsistency between the results. Based on the level of agreement in the present study, it is expected that CFD can be used as a tool to aid in the design of a study of this class of inlets with flow control.
    Keywords: Aerodynamics
    Type: NASA/TM-2008-215416 , AIAA Paper-2008-0092 , E-16580 , 46th AIAA Aerospace Sciences Meeting; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 60
    Publication Date: 2019-07-13
    Description: This paper presents a discrete adjoint method for a broad class of time-dependent optimization problems. The time-dependent adjoint equations are derived in terms of the discrete residual of an arbitrary finite volume scheme which approximates unsteady conservation law equations. Although only the 2-D unsteady Euler equations are considered in the present analysis, this time-dependent adjoint method is applicable to the 3-D unsteady Reynolds-averaged Navier-Stokes equations with minor modifications. The discrete adjoint operators involving the derivatives of the discrete residual and the cost functional with respect to the flow variables are computed using a complex-variable approach, which provides discrete consistency and drastically reduces the implementation and debugging cycle. The implementation of the time-dependent adjoint method is validated by comparing the sensitivity derivative with that obtained by forward mode differentiation. Our numerical results show that O(10) optimization iterations of the steepest descent method are needed to reduce the objective functional by 3-6 orders of magnitude for test problems considered.
    Keywords: Aerodynamics
    Type: 12th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference; Sep 10, 2008 - Sep 12, 2008; Victoria; Canada
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  • 61
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1940-1953 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Charge-Transfer Complexes of Tetrathiafulvalene (TTF) with 1,2,5-Thiadiazolequinones1)The syntheses and the X-ray structure analyses of the charge-transfer complexes of tetrathiafulvalene (TTF) with naphtho[2,3-c][1,2,5]thiadiazole-4,9-dione (1 : 2) (2) and benzol[1,2-c: 4,5-c′]-bis[1,2,5]thiadiazole-4,8-dione (1 : 1) (4) are reported. In their crystal structures both compounds are built up by mixed columnar stacks of donors and acceptors, forming a characteristic packing motive for organic D-A complexes with properties of an electrical insulator.
    Notes: Es wird über die Synthese und die Einkristallröntgenstrukturanalysen der Charge-Transfer-Komplexe von Tetrathiafulvalen mit Naphtho[2,3-c][1,2,5]thiadiazol-4,9-dion (1 : 2) (2) und Benzo-[1,2-c: 4,5-c′]bis[1,2,5]thiadiazol-4,8-dion (1 : 1) (4) berichtet. Beide Verbindungen weisen in ihrer Kristallstruktur aus Donoren und Acceptoren gemischte kolumnare Stapel auf, ein charakteristisches Packungsmotiv organischer D-A-Komplexe mit elektrischen Isolatoreigenschaften.
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  • 62
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1973-1976 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Generation of Nitrosyl Salts in Dry Organic MediaTrimethylsilyl halides (CH3)3SiX (2a - c, X = Cl, Br, I) are sufficiently electrophilic to cleave, in an equilibrium reaction, alkyl nitrites O = NOR (1a, b, R = i-C5H11, C2H5) with formation of O = NX (3a - c) and (CH3)3SiOR (4a, b). This reaction serves as a convenient in-situ-method to generate nitrosyl compounds NOX in chlorinated hydrocarbons as inert organic media.
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  • 63
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1954-1964 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Iminoboranes from the Thermal Decomposition of DialkylazidoboranesIminoboranes RB = NR (1a - f) are formed by the thermal decomposition of azidoboranes R2BN3 (5a - f) in the gas phase or in solution. At low temperature, the iminoboranes 1b, d, e (R = iPr, iBu, sBu) can be trapped from the gas phase. They are characterized and brought to reaction as isolated species. Without other reactands, the iminoboranes dimerize or trimerize to form the cyclic products 2 or 3, respectively, or polymerize to the wax-like solids 4. Produced in solution below 100 °C, the iminoboranes are azidoborated by the educts 5 to give the (azidoboryl)amines 6 which are transformed into the borazines 3 at 160 - 180 °C. Iminoboranes undergo an ethyloboration with BEt3, a cycloaddition with PhN3, and in the absence of the strongly reactive R2BN3 a concurring cycloaddition and azidosilation with Me3SiN3 with formation of 7 - 10, respectively.
    Notes: Iminoborane RB = NR (1a - f) entstehen beim thermischen Zerfall von Azidoboranen R2BN3 (5a - f) in der Gasphase oder in Lösung. Die aus der Gasphase abgeschiedenen Produkte 1b, d, e (R = iPr, iBu, sBu) lassen sich bei tiefer Temperatur isolieren, charakterisieren und isoliert umsetzen. Mit sich selbst reagieren die in der Gasphase ergzeugten Iminoborane 1a - f unter Cyclodi-oder -trimerisierung oder unter Polymerisierung zu Produkten von Typ 2, 3 bzw. 4. In Lösung unterhalb 100 °C erzeugt, werden die Iminoborane von den Edukten 5 zu Produkten 6 azidoboriert; diese lassen sich bei 160 - 180 °C in Borazine 3 überführen. Iminoborane erfahren durch BEt3 eine Ethyloborierung zu 7, mit PhN3 eine Cycloaddition zu 8 und mit Me3SiN3 nebeneinander eine Cycloaddition zu 9 und eine Azidosilierung zu 10, sofern nicht das Edukt R2BN3 zugegen ist, das dem Azid Me3SiN3 in der Reaktivität gegenüber 1 überlegen ist.
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  • 64
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1965-1972 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azodesilylation - a Novel Aprotic Diazotization TechniqueNitrosyl compounds NOA (4a - e, A = Cl, Br, BF4, CF3SO3, I) - generated partially in situ from O = N - OR/(CH3)3SiA (7a, b, R = i-C5H11, C2H5/8a, b, e, A = Cl, Br, I) - react in aprotic organic media with N,N-bissilylated organylamines RN[Si(CH3)3]2 (3b, R = C6H5; 15, R = CH3) under generation of diazonium systems R - N2+ A- and formation of non-nucleophilic hexamethyldisiloxane (6b). This method represents the first nucleophile excluding diazotization technique on the basis of three-coordinated nitrogen and is termed „azodesilylation“.
    Notes: Nitrosylverbindungen NOA (4a - e, A = Cl, Br, BF4, CF3SO3, I) - teilweise in situ hergestellt aus O = N - OR/(CH3)3SiA (7a, b, R = i-C5H11, C2H5/8a, b, e, A = Cl, Br, I) - reagieren mit N,N-bissilylierten Organylaminen RN[Si(CH3)3]2 (3b, R = C6H5; 15, R = CH3) in aprotischen organischen Medien unter Bildung von Diazonium-Systemen R - N2+ A- und nicht-nucleophilem Hexamethyldisiloxan (6b). Diese Methode repräsentiert die erste, Nucleophile ausschließende Diazotierungstechnik auf der Basis von 3fach koordiniertem Stickstoff und wird als „Azodesilylierung“ bezeichnet.
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  • 65
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1977-1979 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Säurekatalysierte Cyclisierung des En-Produkts aus α-Pinen und PTADAluminiumchlorid-katalysierte Reaktion des En-Produkts 2 aus 4-Phenyl-4H-1,2,4-triazol-3,5-dion (PTAD) und α-Pinen (1), des 1-(6,6-Dimelthyl-2-methylenbicyclo[3.1.1]hept-3-yl)-4-phenyl-1,2,4-triazolidin-3,5-dions, ergab 3,8,8-Trimelthyl-N-phenyl-4,5-diazatricyclo[4.2.1.03,7]nonan-4,5-dicarboxamid (6) in 78% Ausbeute. Auch Bortrifluorid-etherat, trockener Chlorwasserstoff und p-Toluolsulfonsäure katalysieren die Cyclisierung von 2 zu 6, aber nicht in diesem Maße. Der Mechanismus der Cyclisierung wird über eine Gerüstumlagerung der Carbenium-Ionen-Zwischenstufen gedeutet.
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  • 66
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1980-1981 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chain Lengthening of Tetrafluoro-1,2-ethanedisulfenyl Dichloride by the Reaction with Hydrogen PeroxideThe reaction of the little compound ClSCF2CF2SCl (1) with aqueous H2O2 results in the formation of ClS2CF2CF2SSCF2CF2SO2Cl(2), which is characterized on the basis of 19F NMR, mass, IR, and Raman spectroscopy.
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  • 67
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1982-1986 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fluorination of Adamantane Derivatives with Oxygen DifluorideFluorination of adamantane and adamantane derivatives 1 with OF2 in the absence of an HF-trap gives fluoroadamantanes 2 and adamantanols 3 in varying amounts. Increasing yields of 2 are obtained in the presence of Na2CO3 as an HF-trap. In addition, the fluorooxahomoadamantanes 4b and e are formed in this reaction. The fluorination of adamantanone (5) with OF2 leads to analogous products.
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  • 68
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1987-1990 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photoelektronenspektren einiger Reduktionsprodukte von [2.2]ParacyclophanAnhand des He(I)-Photoelektronen(PE)-Spektrums von 2,3′,5,6′-Tetrahydro[2.2]paracyclophan (2) wird gezeigt, daß die Through-Bond-Wechselwirkung zwischen den Sechsringen klein, innerhalb der Cyclohexadienringe aber groß ist. Über die PE-Spektren der weiteren Hydrierungsprodukte 3 und 4 wird berichtet.
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  • 69
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1991-1993 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses with Cyclobutadienes, 51). 5,5,6,6-Tetracyano-5,6-dihydro-Dewar benzene/3,3,4,4-Tetracyano-3,4-dihydrobenzvalene - a Novel Equilibrating SystemThe cyclobutadiene 3 reacts with tetracyanoethylene to give a 1 : 1-mixture of the dihydro-Dewar benzene 5 and the dihydrobenzvalene 6, which can be separated by crystallisation. In deuteriochloroform solution 5 and 6 are in a 1 : 1 equilibrium.
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  • 70
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 71
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 2275-2286 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Electron Rich Heterocycles as Donor Groups in Fluorescent DyesThe synthesis of N-methylphthalimides substituted with the donor groups pyrazole, triazole, benzotriazole, and naphthotriazole in position 4 is described (17, 18, 14, 12). The substituent constants of these groups are obtained by alkaline hydrolysis of the corresponding phthalimide dyes. Their solvatochromism in absorption and fluorescence gives information about charge distribution in ground- and excited state.
    Notes: Die Darstellung von N-Methylphtalimiden wird beschrieben, die in 4-Stellung die Donorgruppen Pyrazol, Triazol, Benzotriazol und Naphthotriazol tragen (17, 18, 14, 12). über die alkalische Hydrolyse des Imids werden die Substituentenkonstanten der Reste bestimmt. Die Solvatochromie in Absorption und Fluoreszenz gibt Information über die Ladungsverteilung in Grund- und angeregtem Zustand.
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  • 72
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Arene(phosphane)metal Complexes, IV1). Synthesis of (6-Phosphonio-η5-cyclohexadienyl)ruthenium(II) Compounds and their Conversion into Dicationic (Benzene)ruthenium(II) Complexes[C6H6Ru(PR3)(PR3′)PR3″]2+The complexes [C6H6RuCl(PR3)PR3′]PF6 (1 - 4) and [C6H6RuCl2(PR3)] (9, 10) react with phosphanes PR3″ in the presence of NH4PF6 to give the (6-phosphonio-η5-cyclohexadienyl)ruthenium(II) compounds [(6-R3″P-η5-C6H6)Ru(PR3)(PR3′)PR3″](PF6)2 (5 - 8 11). Similarly, from [C6H6Ru(CH3CN)3](PF6)2 (12) and PMe3 the complex [(6-Me3P-η5-C6H6)Ru(PMe3)2CH3CN](PF6)2 (13) is formed. The IR and NMR spectra of 5 - 8, 11, and 13 indicate that the phosphonio group is in the exo-position at the sp3 carbon atom of the cyclohexadienyl ligand. Below - 30°C, rotation around the metal-ring bond is so hindered that rigid conformers are detected. Compounds 5 - 8 react with trifluoroacetic acid with elimination of the phosphonio group to yield the PF6 salts of the half-sandwich type complexes [C6H6Ru(PR3)(PR3′)PR3″]2+ (14 - 17).
    Notes: Die Komplexe [C6H6RuCl(PR3)PR3)]PF6 (1 - 4) und [C6H6RuCl2(PR3)] (9, 10) reagieren mit Phosphanen PR3″ in Gegenwart von NH4PF4 zu den (6-Phosphonio-η5-cyclohexadienyl)-ruthenium(II)-Verbindungen [(6-R3″P-η5-C6H6)Ru(PR3)(PR3″](PF6)2 (5 - 8, 11). Aus [C6H6Ru(CH3CN)3](PF6)2 (12) und PMe3 erhält man analog den Komplex (6-Me3P-η5-C6H6)Ru(PMe3)2CH3CN](PF6)2 (13). Die IR- und NMR-Spektren von 5 - 8, 11 und 13 weisen darauf hin, daß sich die Phosphoniogruppierung in der exo-Position am sp3-C-Atom des Cyclohexadienylliganden befindet. Unterhalb - 30°C ist die Rotation um die Metall-Ring-Bindung so stark behindert, daß starre Konformere nachweisbar sind. Die Verbindungen 5 - 8 reagieren mit Trifluoressigsäure unter Abspaltung der Phosphoniogruppe zu den PF6-Salzen der Halbsandwich-Komplexe [C6H6Ru(PR3)(PR3′)PR3″]2+ (14 - 17).
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  • 73
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Arene(phosphane)metal Complexes, VI1). Synthesis of [(RC6H5)OsI(PMe3)2]PF6 from (exo-6-RC6H6)OsI(PMe3)2: A contribution to the Mechanism of Aromatization of Substituted Cyclohexadienyl Ligands by „endo-H Abstraction“The compounds (exo-6-RC6H6)OsI(PMe3)2 (2 - 5, 7) react smoothly with [CPh3]PF6 in acetone to give the (arene)osmium(II) complexes [(RC6H5)OsI(PMe3)2]PF6 (8 - 12) in quantitative yield. The hydride elimination proceeds via two (cyclohexadienyl)hydridoosmium(IV) intermediates (13 and 14, 15, respectively) which can be prepared from 2, 5, 6 (R = CH3, n-C4H9, t-C4H9) and CF3CO2H/NH4PF6. The (cyclohexadienyl)hydrido complexes [(RC6H6)Os(H)I(PMe3)2]+ undergo an intramolecular isomerization which leads to a cation possessing a CH2 group in the six-membered ring. This cationic complex or (more probably) the neutral compound (2- or 3-RC6H6)OsI(PMe3)2 formed on deprotonation reacts with [CPh3]+ by abstraction of an exo-hydrogen atom.
    Notes: Die Verbindungen (exo-6-RC6H6)OsI(PMe3)2 (2 - 5, 7) reagieren mit [CPh3]PF6 in Aceton rasch und quantitativ zu den (Aromaten)osmium(II)-Komplexen [(RC6H5)OsI(PMe3)2]PF6 (8 - 12). Die Hydrid-Eliminierung verläuft über zwei (Cyclohexadienyl)hydridoosmium(IV)-Zwischenstufen (13 bzw. 14, 15), die aus 2, 5, 6 (R = CH3, n-C4H9, t-C4H9) und CF3CO2H/NH4PF6 synthetisiert werden können. Die (Cyclohexadienyl)hydrido-Komplexe [(RC6H6)Os(H)I(PMe3)2]+ gehen eine intramolekulare Isomerisierung ein, wobei ein Kation mit einer CH2-Gruppe im Sechsring entsteht. Dieses Komplexkation oder (wahrscheinlicher) die nach Deprotonierung erhaltene Neutralverbindung (2- bzw. 3-RC6H6)OsI(PMe3)2 reagiert mit [CPh3]+ unter Abstraktion eines exo-H-Atoms.
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  • 74
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Arene(phosphane)metal Complexes, V1). On the Addition of Carbanions to (Benzene)ruthenium(II) and -osmium(II) Complexes. The Crystal and Molecular Structure of (exo-6-n-C4H9-η5-C6H6)OsI(PMe3)2The complex [C6H6RuCl(PMe3)2]PF6 (1) reacts with methyllithium to give a mixture of products that contains (η5-C6H6CH3)RuCH3(PMe3)2 (2) as the main component. From 1 and LiC6H5/LiBr the bromide 3 is primarily formed but the final product is (η5-C6H6C6)H5RuC6H5(PMe3)2 (4). Reaction of [C6H6OsI(PMe3)2]PF6 (5) with organyllithium compounds LiR (R = CH3, C2H5, n-C3H7, n-C4H9, t-C4H9, C6H5) yields the complexes (η5-C6H6R)OsI(PMe3)2 (6 - 11). 31P NMR spectra of 6 - 11 indicate restricted rotation at low temperatures around the metal-ring axis. According to X-ray structure analysis of 9 (R = n-C4H9) the cyclohexadienyl ring possesses an envelope conformation. The n-butyl group occupies the exo-position at the sp3-C atom.
    Notes: Der Komplex [C6H6RuCl(PMe3)2]PF6 (1) reagiert mit Methyllithium zu einem Produktgemisch, welches (η5-C6H6CH3)RuCH3(PMe3)2 (2) als Hauptkomponente enthält. Aus 1 und LiC6H5/LiBr entsteht über 3 bei längeren Reaktionszeiten (η5-C6H6C6H5)RuC6H5(PMe3)2 (4). Die Umsetzung von [C6H6OsI(PMe3)2]PF6 (5) mit Organyllithium-Verbindungen LiR (R = CH3, C2H5, n-C3H7, n-C4H9, t-C4H9, C6H5 ergibt die Komplexe (η5-C6H6R)OsI(PMe3)2 (6 - 11), in denen nach den 31P-NMR-Spektren die Rotation um die Metall-Ring-Bindung bei tiefen Temperaturen stark eingeschränkt ist. Die Röntgenstrukturanalyse von 9 (R = n-C4H9) beweist die „Envelope“-Konformation des Cyclohexadienylrings. Die n-Butylgruppe befindet sich in der exo-Position am sp3-C-Atom.
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  • 75
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 172-186 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Radical Ions, 55. The One-Electron Oxidation of Tetrahedrane to Cyclobutadiene Radical CationTetra-tert-butyltetrahedrane, on one-electron oxidation using AlCl3 in CH2Cl2, opens to form tetra-tert-butylcyclobutadiene radical cation, which can also be generated under identical reaction conditions from tetra-tert-butylcyclobutadiene itself. The assignments of the ESR and ENDOR spectra are supported by deutero substitution of one tert-butyl group and by MNDO hypersurfaces for the thermal and for the oxidative structural changes of both C4 skeletons. The feasible formation of a valence isomeric tert-butyl(tri-tert-butylcyclopropenyl)carbene radical cation is discussed.
    Notes: Tetra-tert-butyltetrahedran öffnet sich bei Einelektronen-Oxidation mit AlCl3 in CH2Cl2 zum Tetra-tert-butylcyclobutadien-Radikalkation, das unter gleichen Reaktionsbedingungen auch aus Tetra-tert-butylcyclobutadien erzeugt werden kann. Die Zuordnungen der ESR- und ENDOR-Spektren werden durch Deutero-Substitution einer tert-Butyl-Gruppe sowie durch MNDO-Hyperflächen für die thermischen und oxidativen Strukturänderungen der beiden C4-Gerüste gestützt. Die mögliche Bildung eines valenzisomeren tert-Butyl(tri-tert-butylcyclopropenyl)carben-Radikalkations wird diskutiert.
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  • 76
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 948-954 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Acidic Complexones Bearing Donor-enhancing Pyridine Anchour GroupsThe synthesis, complex stability and -selectivity for alkaline earth metal ions of 2,6-pyridinebis-(methylamine)-N, N, N′, N′-tetraacetic acid (3a) and of their donor-enforced analogues 3b, c are described. The acid dissociation constants and the stability constants of the metal complexes have been measured potentiometrically at 25°C in water of constants ionic strength (μ = 0.1). The stability order is Ca 〉 Mg 〉 Sr 〉 Ba which is analogues to the selectivity of EDTA and comparable aliphatic complexones. The magnitudes of the stability constants of 3a are comparable to those of EDTA, while the donor-enforced analogues 3b, c form less stable complexes with alkaline earth metal ions.
    Notes: Synthese, Komplexstabilität und -selektivität gegenüber Erdalkalimetall-Ionen von 2,6-Pyridinbis(methylamin)-N, N, N′, N′-tetraessigsäure (3a) und ihren Donor-verstäkten Analoga 3b, c werden beschrieben. Die Bestimmung der Dissoziations- und Komplexbildungskonstanten erfolgt potentionmetrisch bei 25°C in Wasser konstanter ionaler Stärke (μ = 0.1). Die Bildungskonstanten der Metallkomplexe nehmen in der Reihenfolge Ca 〉 Mg 〉 Sr 〉 Ba ab und folgen damit der bei EDTA und vergleichbaren aliphatischen Komplexonen vorgefundenen Selektivität. 3a weist mit EDTA vergleichbare hohe Komplexbildungskonstanten auf, während die Donor-verstärkten Analoga 3b, c schwächere Erdalkalimetallkomplexe bilden.
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  • 77
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 959-965 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and X-Ray Structure Analysis of the Diels-Alder Adduct of 4-Phenyl-4H-1,2,4-triazole-3,5-dione with OctavaleneIn the reaction of 4-phenyl-4H-1,2,4-triazole-3,5-dione with octavalene (1) the Diels-Alder adduct 2 is formed. From its X-ray structure analysis the dihedral angle for the bicyclo[1.1.0]butane group, the 2- and 4-positions of which are spanned by four atoms, has been determined to be 122.7°. The bridging bond C1 - C3 has a length of 1.487 Å.
    Notes: Aus Octavalen (1) und 4-Phenyl-4H-1,2,4-triazol-3,5-dion bildet sich das Diels-Alder-Addukt 2. Seine Röntgenstrukturanalyse ergab für das Bicyclo[1.1.0]butan-Gerüst, dessen 2- und 4-Stellung durch vier Atome überbrückt sind, einen Interplanarwinkel von 122.7°. Die Brückenbindung C1 - C3 hat eine Länge von 1.487 Å.
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  • 78
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Condensed Ring Systems, XV. About the Reaction of α-Chloro Sulfoxides with Potassium tert-Butoxide by the Example of the Synthesis of OxapropellenesThe synthesis of dithia- 1a - 3a and oxathiapropellenes 1b - 3b is described. From 1b - 3b the α-chloro sulfoxides 4 - 6 and α-chloro sulfones 4a - 6a are prepared, or which in most cases several stereoisomeric racemates are obtained. The constitution, configuration, and conformation of the α-chloro sulfoxide 4, the main product obtained from 1b, was elucidated by X-ray structure analysis. Only in that way it was possible to deduce the constitutions and configurations of the other stereoisomeric α-chloro sulfoxides 4 - 6 and α-chloro sulfones 4a - 6a, respectively, using 13C NMR spectroscopy. By the reaction of the α-chloro sulfones 4a - 6a with potassium tert-butoxide (Ramberg-Bäcklund reaction) the corresponding oxapropellenes 7 - 9 are obtained only in low yields (〈 10%). Contrary, the α-chloro sulfoxides 4 - 6, und analogous conditions give yields of 80 - 90% (from 4, 6) and 25% (from 5).
    Notes: Es wird die Synthese der Dithia- 1a - 3a und Oxathiapropellene 1b - 3b beschrieben. Aus 1b - 3b werden die α-Chlorsulfoxide 4 - 6 und α-Chlorsulfone 4a - 6a hergestellt, von denen meist mehrere stereoisomere Racemate erhalten werden. Konstitution, Konfiguration und Konformation des Hauptprodukts der aus 1b erhaltenen α-Chlorsulfoxide 4 wurden durch Röntgenstrukturanalyse ermittelt. Erst dadurch wurde es möglich, mit Hilfe der 13C-NMR-Spektroskopie die Konstitutionen und Konfigurationen der anderen stereoisomeren α-Chlorsulfoxide 4 - 6 und α-Chlorsulfone 4a - 6a aufzuklären. Bei der Reaktion der α-Chlorsulfone 4a - 6a mit Kalium-tert-butylat (Ramberg-Bäcklund-Reaktion) erhält man die entsprechenden Oxapropellene 7 - 9 nur in geringer Ausbeute (〈 10%), während die α-Chlorsulfoxide 4 - 6 unter analogen Bedingungen Ausbeuten von 80 - 90% (aus 4, 6) und 25% (aus 5) ergeben.
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 982-989 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Selectivity of the Reaction of Carbocations with NucleophilesThe problem of the selectivity of the nucleophilic attack on carbocations according to the HSAB-principle is discussed in relation to the solvolysis in ether of 7,7-bis(trifluoromethylsulfonyloxy)-norbornane (2) and 7,7-bis(trifluoromethylsulfonyloxy)-2-norbornene (4) in presence of dimethyl-magnesium, magnesium iodide and methylmagnesium iodide. The nucleophiles and carbocations are arranged according to the hard-soft-scale, so our results can be explained.
    Notes: Das Problem der Selektivität beim nucleophilen Angriff an Carbokationen wird im Rahmen des HSAB-Prinzips am Beispiel der Solvolysen in Ether von 7,7-Bis(trifluormethylsulfonyloxy)norbornan (2) und 7,7-Bis(trifluormethylsulfonyloxy)-2-norbornen (4) in Anwesenheit von Dimethylmagnesium, Magnesiumiodid und Methylmagnesiumiodid erörtert. Die Nucleophile und die als Zwischenstufen auftretenden Carbokationen werden auf der Hart-weich-Skala eingeordnet, wobei die Ergebnisse erklärt werden können.
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  • 80
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1003-1012 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Dichloropalladium(II) Complexes with α-Amino Acids, α-Amino Acid Esters, Dipeptides, and Dipeptide EstersA series of trans-dichloropalladium(II) complexes Cl2PdL2 (L = α-amino acid, α-amino acid ester, dipeptide, dipeptide esters) and cis-Cl2Pd(histidine) has been prepared and spectroscopically characterized. The X-ray structure of trans-Cl2Pd(GlyOEt)2 (3b) has been determined.
    Notes: Eine Reihe von trans-Dichloropalladium(II)-Komplexen Cl2PdL2 mit (L = α-Aminosäure, α-Aminosäureester, Dipeptid, Dipeptidester) sowie cis-Cl2Pd(Histidin) wurde dargestellt und spektroskopisch charakterisiert. Die Röntgenstruktur von trans-Cl2Pd(GlyOEt)2 (3b) wurde bestimmt.
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  • 81
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1436-1454 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Evidence for a Radical Chain Mechanism for the Knabe Reaction of 1,2-Dihydro-2-methylpapaverineA free radical chain mechanism is proposed for the Knabe reaction and the accompanying elimination reaction on account of their nonintegral reaction order and of successful inhibition experiments. 3,4-Dimethoxybenzyl radicals are the chain carrying species. Battersby's synthesis of N-methylpavine (19) from 1,2-dihydro-2-methylpapaverine (9) is dependent on the presence of formic acid as radical chain inhibitor. In the presence of inhibitors 1-benzyl-1,4-dihydro-2-methyl-isoquinolinium ions like 10 are persistent species whose chemistry can now be investigated.
    Notes: Die Knabe-Reaktion von 1,2-Dihydro-2-methylpapaverin (9) und die begleitende Eliminierungsreaktion wurden durch ihre gebrochene Reaktionsordnung und durch die Möglichkeit der Inhibition als Radikalkettenreaktionen erkannt, deren kettentragendes Radikal das 3,4-Dimethoxybenzylradikal ist. Die Synthese von N-Methylpavin (19) aus 1,2-Dihydro-2-methylpapaverin (9) ist an die Anwesenheit von Ameisensäure als Inhibitor der Radikalketten gebunden. Durch Zusatz von Inhibitoren können nun Immoniumionen 10 und analoge Verbindungen stabilisiert und ihre Chemie untersucht werden.
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  • 82
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1455-1464 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azo Bridges from Azines, III. Unexpected Formation of a Compounds with Parallel C=C and N=N Bonds2)Dialdehyde 5 reacts with hydrazine at pH 〉 7 to form the trimeric azine 6Tr, at pH 〈 4, however, to yield unexpectedly 8, which contains parallel C=C and N=N bonds in close proximity. The complex reaction is clarified. 8 is characterized by structure proving reactions and its spectroscopic data.
    Notes: Der Dialdehyd 5 reagiert mit Hydrazin bei pH 〉 7 zu dem trimeren Azin 6Tr, bei pH 〈 4 unerwartet zu 8, das parallel benachbarte C=C- und N=N-Bindungen besitzt. Der komplexe Reaktionsverlauf wird aufgeklärt. 8 wird durch struktursichernde Reaktionen und spektroskopische Daten charakterisiert.
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  • 83
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1465-1475 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azo Bridges from Azines, IV1). Intramolecular [2 + 2] Photocycloaddition of Parallel C=C and N=N BondsThe parallel C=C and N=N bonds in the rigid molecules 1 - 10 photocyclize nearly quantitatively, forming 1,2-diazetidines 11 - 20. Their structure is confirmed by spectroscopic methods and for 13 by X-ray analysis. Radiation induced denitrogenation, the normal reaction for similar compounds without neighbouring C=C bonds, is suppressed even with the sensitive derivatives of 2,3-diazabicyclo[2.2.1]heptene. Photocyclization of 6, carrying two neighbouring C=C bonds, includes only the norbornene bond.
    Notes: In den starren Molekülen 1 - 10 reagieren die benachbarten parallelen C=C- und N=N-Bindungen nahezu quantitativ unter Photocyclisierung zu den 1,2-Diazetidinen 11 - 20, deren Struktur spektroskopisch und für 13 durch Kristallstrukturanalyse bewiesen wird. Die in Abwesenheit der C=C-Bindung beobachtete Photo-Denitrogenierung unterbleibt selbst bei den empfindlichen Derivaten des 2,3-Diazabicyclo[2.2.1]heptens. Photocyclisierung von 6 mit zwei zur N=N-Bindung benachbarten C=C-Bindungen tritt nur mit der Norbornendoppelbindung ein.
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  • 84
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1497-1512 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Amino Acids, 21,2). N-Acetyl α,β-Didehydro α-Amino Acid Esters from α-Azidocarboxylic Acid Esters and Acetic Anhydride by Nitrogen Elimination with Rhenium Catalystsα-Azidocarboxylic acid esters 2 react with acetic anhydride in presence of catalytic amounts of rhenium heptasulfide and - if necessary - by addition of hydrochloric acid to give N-acetyl 3 or/and N,N-diacetyl-α,β-didehydro-α-amino acids esters 4 in very good yields. Exclusively monoacetylated products 3 are formed if water ist added before work up.
    Notes: Beim Erwärmen von α-Azidocarbonsäureestern 2 in Acetanhydrid/Essigsäure in Gegenwart katalytischer Mengen Rheniumheptasulfid und gegebenenfalls unter Zugabe von Chlorwasserstoff entstehen in sehr guten Ausbeuten N-Acetyl- 3 und/oder N,N-Diacetyl-α-β-didehydro-α-amino-säureester 4. Durch Zugabe von Wasser vor der Aufarbeitung erfolgt partielle Deacetylierung unter ausschließlicher Bildung der N-Monoacetylverbindungen 3.
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  • 85
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Amino Acids, 31). N-Acetylated α-β-Didehydro α-Amino Acid Derivatives by Nitrogen Elimination from α-Azido-carboxylic Acid Amides and α-Azido-ω-aminocarboxylic Acid Lactams with Rhenium Catalystsα-Azidocarboxylic acid amides 2 and α-azido-ω-aminocarboxylic acid lactams 6, respectively, react with acetic anhydride in the presence of rhenium catalysts by nitrogen eliminations to give N-acetyl- 7 and N,N-diacetyl-α,β-didehydro-α-amino acid amides 8, α-acetylamino- 11 and α-diacetylamino-α,β-didehydro-ω-aminocarboxylic acid lactams 12, respectively. Reactions of the educts 6c, d - with a ring size 7 or 8 - additionally lead to the oxazoloazepine 14c and the oxazoloazocine 14d, respectively.
    Notes: Bei der Umsetzung von α-Azidocarbonsäureamiden 2 mit Acetanhydrid in Gegenwart von Rheniumkatalysatoren entstehen unter Stickstoffabspaltung N-Acetyl- 7 und N,N-Diacetyl-α,β-didehydro-α-aminosäureamide 8, bei der von α-Azido-ω-aminocarbonsäurelactamen 6 α-Acetyl-amino- 11 und α-Diacetylamino-α,β-didehydro-ω-aminocarbonsäurelactamen 12, wobei sich aus den Verbindungen 6c, d, mit der Ringgliederzahl 7 bzw. 8 außerdem noch das Oxazoloazepin 14c bzw. das Oxazoloazocin 14d bilden.
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  • 86
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    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Phosphorus, 131. Synthesis and Properties of the Methylenediphosphiranes (t-BuP)2)C = CR2 (R = H, Me, 4-ClC6H4)The first methylenediphosphiranes (diphosphamethylenecyclopropanes) (t-BuP)2C = CH2 (1), (t-BuP)2C = CMe2 (2), and (t-BuP)2C = C(4-ClC6H4)2 (3) were synthesized by [2 + 1] cyclocondensation of K(t-Bu)P - P(t-Bu)K with the corresponding 1,1-dichloroolefins. The homocyclophosphanes (t-BuP)n (n = 4,3) and in the case of 1 mainly H(t-Bu)P - P(t-Bu)H are formed as by-products. The three-membered heterocycles 2 and 3 could be purely isolated as surprisingly stable compounds. According to an X-ray single-crystal analysis 3 possesses approximately C2 symmetry and exhibits one of the smallest bonding angles ψ (P - P - C) = 52.4° on a phosphorus atom experimentally proved so far. Along [100] there are canals filled with disordered n-pentane molecules.
    Notes: Die ersten Methylendiphosphirane (Diphosphamethylencyclopropane) (t-BuP)2C = CH2 (1), (t-BuP)2C = CMe2 (2) und (t-BuP)2C = C(4-ClC6H4)2 (3) wurden durch [2 + 1]-Cyclokondensation von K(t-Bu)P - P(t-Bu)K mit den entsprechenden 1,1-Dichlorolefinen synthetisiert. Als Nebenprodukte entstehen die Homocyclophosphane (t-BuP)n (n = 4,3) und im Fall von 1 vor allem H(t-Bu)P - P(t-Bu)H. Die Dreiringheterocyclen 2 und 3 konnten als thermisch überraschend beständige Verbindungen in reiner Form isoliert werden. 3 besitzt nach der Röntgenstrukturanalyse annähernd die Symmetrie C2 und enthält mit ψ (P - P - C) = 52.4° einen der kleinsten experimentell gesicherten Bindungswinkel am Phosphor. Längs [100] liegen fehlgeordnet mit n-Pentan gefüllte Kanäle vor.
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  • 87
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1523-1541 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Aminierung, III. Trimethylsilanol als austretende Gruppe, V. Silylierung-Aminierung von Hydroxy-N-heterocyclenDurch Silylierung-Aminierung lassen sich Hydroxy-N-heterocyclen (z. B. 18, 21, 26 u. a.) bequem in einer Einstufen-Eintopfreaktion aminieren (→ 20, 23 - 25 etc.). Aromatische Hydroxy-N-heterocyclen werden durch Silylierung in aktivierte und lipophile Zwischenprodukte vom Typ 3, 8 umgewandelt, die sich in situ mit Ammoniak, primären oder sekundären Aminen zu den entsprechenden mono-, bis- und tris-aminierten Produkten (5, 10) umsetzen. Die Additions-Eliminierungsreaktion von Aminen an O-silylierte Heterocyclen ist Lewissäure-katalysiert und verläuft gewöhnlich in hohen Ausbeuten, falls die austretende Gruppe Trimethylsilanol in situ durch überschüssiges Silylierungsmittel in Hexamethyldisiloxan umgewandelt wird. Anwendungsbreite und Grenzen dieser einfachen Methode werden diskutiert.
    Notes: Hydroxy N-heterocycles such as 18, 21, 26, and others are efficiently aminated in a one-step/one-pot procedure by silylation-amination to give 20, 23 - 25 etc. Silylation converts aromatic hydroxy N-heterocycles into activated and lipophilic intermediates of type 3, 8 which react in situ with ammonia, primary or secondary amines to form the corresponding mono-, bis- or tris-aminated products (5, 10). This addition-elimination of amines to O-silylated heterocycles in Lewis acid-catalyzed and proceeds usually in high yields if the leaving group trimethylsilanol is converted in situ by excess silylated agent into hexamethyldisiloxane. Scope and limitations of this simple procedure are discussed.
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  • 88
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1572-1582 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Benzonitrile as a 6-Electron Donor Ligand: The Clusters Fe3(CO)9(μ3(η2)-NCC6H5) and Fe4(CO)12(μ4(η2)-NCC6H5)The reaction of Fe3(CO)12 with benzonitrile in the presence of hydrogen leads to the benzonitrile complexes Fe3(CO)9(μ3(η2)-NCC6H5) (1a) and Fe4(CO)12(μ4(η2)-NCC6H5) (2). Their structures were determined crystallographically. The benzonitrile ligand is coordinated to the iron atoms formally via on „s̰-bond“ and two „π-bonds“ in 1a, and via three s̰-bonds and one π-bond in 2.
    Notes: Die Reaktion von Fe3(CO)12 mit Benzonitril in Anwesenheit von Wasserstoff führt zu den beiden Benzonitril-Komplexen Fe3(CO)9(μ3(μ2)-NCC6H5) (1a) und Fe4(CO)12(μ4(η2)-NCC6H5) (2). Ihre Strukturen wurden kristallographisch aufgeklärt. Der Benzonitril-Ligand ist in 1a formal über eine „s̰-Bindung“ und zwei „π-Bindungen“, in 2 über drei s̰-Bindungen und eine π-Bindung an die Eisenatome koordiniert.
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  • 89
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Spin-Spin Coupling Constants by Platinium-195 as Criteria for a Configuration Determination in Platinum Organic CompoundsThe platinum organic compounds [Pt(η4-1,5-cyclooctadiene)(XC6H4)2] and cis-[Pt(P(n-Bu)3)2-(XC6H4)2] (X = H, 4-CH3, 4-(CH3)3C, 4-(CH3)2N, 3-F, 4-F, 4-CH3O, 4-CF3; 3a - 4, cis-4a - h) as well as trans-[Pt(P(n-Bu)3)2(4-CH3OC6H4)2] (trans-4g) and trans-[Pt(P(n-Bu)3)2(4-CF3C6H4)2] (trans-4h) have been studied by 31P-, 13C-, and 1H NMR spectroscopy. The coupling constants 1J[195Pt, 31P], nJ[195Pt, 13C], nJ[195Pt, H], and 2J[31P, 13C] show a clear correlation to the ligand configuration at the dsp2-hybridized platinum and can therefore be used as basis for configuration determination.
    Notes: Die platin-organischen Verbindungen [Pt(η4-1,5-cyclooctadien)(XC6H4)2] und cis-[Pt(P(n-Bu)3)2-(XC6H4)] (X = H, 4-CH3, 4-(CH3)3C, 4-(CH3)2N, 3-F, 4-F, 4-CH3O, 4-CF3; 3a - h, cis-4a - h) sowie trans-[Pt(P(n-Bu)3)2(4-CH3OC6H4)2] (trans-4g) und trans-[Pt(P(n-Bu)3)2(4-CF3C6H4)2] (trans-4h) wurden 31P-, 13C- und 1-NMR-spektroskopisch untersucht. Die Kopplungskonstanten 1J[195Pt, 31P], nJ[195Pt, 13C], nJ[195Pt, H] und 2J[31P, 13C] zeigen eine eindeutige Abhängigkeit von der Konfiguration der Liganden am dsp2-hybridisierten Platin; sie können daher zur sicheren Konfigurations-Bestimmung verwendet werden.
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  • 90
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1597-1605 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Structure of N-Methylenecarboxamides: X-Ray Data, Spectroscopy, and Quantum Mechanical CalculationsN-(Diphenylmethylene)acetamide (1) has been studied by X-ray crystallography as an example for the polyfunctional, highly reactive N-methyleneamides. The dihedral angle (C = N - C = O = 73°) and the bond lengths indicate that there is only little interaction between the C = O and the C = N groups. Extensive ab initio 3-21G calculations for the parent molecule H2C = N - CH = O (2) predict a C - N rotational barrier of ca. 4 kcal/mol with a cisoid form (C = N - C = O = 23°) as the most stable structure. MNDO data as well as spectroscopic properties (IR, 13C NMR) suggest high molecular flexibility due to the many electronic interactions possible for the nitrogen atom.
    Notes: Als Beispiel für die polyfunktionellen N-Methylencarbonsäureamide wurde N-(Diphenylmethylen)acetamid (1) röntgenographisch untersucht. C = N - C = O-Torsionswinkel (73°) und Bindungslängen deuten auf nur geringe Wechselwirkungen zwischen C = O- und C = N-Molekülteil. Ausführliche ab initio-3-21G-Berechnungen am Grundsystem H2C = N - CH = O (2) sagen eine C - N-Rotationsbarriere von ca. 4 kcal/mol voraus, wobei als stabilste Struktur eine cisoide Form (C = N - C = O-Winkel = 23°) gefunden wurde. MNDO-Daten und spektroskopische Untersuchungen (IR, 13C-NMR) deuten ebenfalls auf hohe molekulare Beweglichkeit, die vor allem durch die vielfältigen elektronischen Wechselwirkungsmöglichkeiten des Stickstoffatoms verursacht wird.
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  • 91
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1659-1670 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reduction of β-Lactams, I. Reduction of 3,3,3′,3′-Tetramethyl[1,1′-biazetidine]-2,2′-dione with Complex HydridesReduction of the title compound 7 with lithium aluminium hydride leads to four products 8 to 11 in yields depending on the reaction conditions. Compounds 8 to 10 are also obtained from the bicyclic hydrazide 12, isomeric with 7. Therefore, the reduction of 7 and 12 is likely to proceed in part via common intermediates. A reaction scheme is proposed to account for the generation of the products. With other hydride reagents complex reaction mixtures are obtained from 7. The reduction of 7 to 3,3,3′,3′-tetramethyl-1,1′-biazetidine (13) failed.
    Notes: Die Reduktion der Titelverbindung 7 mit Lithiumaluminiumhydrid liefert die vier Produkte 8 - 11 in von den Reaktionsbedingungen abhängigen Mengenverhältnissen. Da die Verbindungen 8 - 10 auch aus dem mit 7 isomeren bicyclischen Hydrazid 12 erhalten werden, muß die Reduktion von 7 und 12 z. T. einheitlich ablaufen. Hierfür wird ein Reaktionsschema vorgeschlagen. Mit anderen Hydridübertragungsreagenizen entstehen aus 7 komplexe Produktgemische. Die Reduktion von 7 zu 3,3,3′,3′-Tetramethyl-1,1′-biazetidin (13) gelang nicht.
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  • 92
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 565-574 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of (Trimethylstannyl)adamantane DerivativesReaction of brominated adamantane compounds with (trimethylstannyl)lithium afforded a series of (trimethylstannyl)adamantane derivatives. Additionally, we found products from fragmentation and reduction reactions which allowed conclusions concerning the mechanisms. Surprisingly high stereoselectivities were observed in most instances. By Wurtz synthesis we obtained 2-adamantyltriphenylstannane.
    Notes: Die Umsetzung bromierter Adamantanverbindungen mit (Trimethylstannyl)lithium lieferte eine Reihe von (Trimethylstannyl)adamantan-Derivaten. Wir fanden zusätzlich Fragmentierungs- und Reduktionsprodukte, die Rückschlüsse auf den Mechanismus zuließen. Überraschend ist die hohe Stereoselektivität der meisten Reaktionen. Durch Wurtz-Synthese wurde auch 2-Adamantyltriphenylstannan erhalten.
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  • 93
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 575-584 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Influence of Substituents on the Valence-tautomeric Equilibrium of 4,8-Substituted HomotropilidenesThe valence-tautomeric equilibrium of 4,8-substituted homotropilidenes 2 - 4 is governed by electronic (preference of a substituent for attachment to a cyclopropyl or an aliphatic carbon atom) and steric factors. The conformational change chair → boat, which precedes the Cope rearrangement of a homotropilidene, cannot take place when both endo-8- and cis-4-substituents are present.
    Notes: Das Valenzgleichgewicht 4,8-substituierter Homotropilidene 2 - 4 wird durch elektronische (Präferenz eines Substituenten für Cyclopropyl- oder aliphatische Verknüpfung) und sterische Faktoren bestimmt. Die der Cope-Umlagerung vorgeschaltete Konformationsänderung Sessel → Boot wird verhindert, wenn das Homotropiliden sowohl in endo-8- wie in cis-4-Stellung substituiert ist.
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  • 94
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Heterocyclic β-Enamino Esters, 311). Novel 6:7-, 6:8, and 5:6:7-Combinations of Heterocondensed Pyrimidines from Iminophosphoranes of Heterocyclic β-Enamino Esters. - Stable Heterocyclic YlidesWith acetylenic esters the (5-azolylimino)triphenylphosphoranes 10a - d do not show any cyclo-addition tendency, while the (2-thienylimino)triphenylphosphoranes 8a, b yield the stable ylids 13a, b. By treatment with phenyl isocyanate the iminophosphoranes 16a - m, 17, and 18a, b afford the carbodiimides 19a - m, 20, and 21a, b; however, 10b - d give the O-ethylisoureas 24b - d. 19a, b, e, f, h are transformed in aqueous ethanol into 6:7-bicycles, namely into oxepino[2,3-d]pyrimidines 25a, b, e, f, h. With isopropylamine the 2-isopropylamino-6:7-bicycles 31a - c, e - h are formed analogously, while in the case of thiocin 21a the 6:8-bicycle 34 is obtained. The salts 33f, g are formed by treating 19f, g or 25f with aqueous diethylamine. Accordingly, 2-aminoethanol, 3-aminopropanol, and ethylenediamine react with 19a, b, f, l to afford the 2-hydroxy- and 2-aminoalkyl-6:7-bicycles 36a - f; by treatment with hydrazine the 2-hydrazinooxepino- and -thiepino[2,3-d]pyrimidines 38a - h and 39 are obtained, which are converted with functional C1-units into 5:6:7-tricycles 43a - d, 45'a, b.
    Notes: Die (5-Azolylimino)triphenylphosphorane 10a - d zeigen mit Acetylendicarbonsäureestern keine Tendenz zur Cycloaddition, während die (2-Thienylimino)triphenylphosphorane 8a, b, zu den stabilen Yliden 13a, b reagieren. Mit Phenylisocyanat ergeben die Iminophosphorane 16a - m, 17 und 18a, b die Carbodiimide 19a - m, 20 und 21a, b; 10b - d liefern statt dessen die O-Ethylisoharnstoffe 24b - d. In wäßrigem Ethanol werden 19a, b, e, f, h in 6:7-Bicyclen, nämlich in die Oxepino[2,3-d]pyrimidine 25a, b, e, f, h umgewandelt. Mit Isopropylamin bilden sich die 2-Isopropylamino-6:7-Bicyclen 31a - c, e - h und im Fall des Thiocins 21a der 6:8-Bicyclus 34. Die Salze 33f, g entstehen durch Einwirkung von wäßrigem Diethylamin auf 19f, g bzw. auf 25f. 2-Aminoethanol, 3-Aminopropanol und Ethylendiamin ergeben mit 19a, b, f. l analog die 2-Hydroxy- und 2-Aminoalkyl-6:7-Bicyclen 36a - f; mit Hydrazin werden die 2-Hydrazinooxepino- und -thiepino[2,3-d]pyrimidine 38a - h und 39 erhalten, die mit funktionellen C1-Bausteinen zu den 5:6:7-Tricyclen 43a - d, 45'a, b führen.
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  • 95
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 682-693 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Addition of Aldehydes to Activated Double Bonds, XXXIV1). Addition of Aldehydes to Cyclic α-Methylene KetonesThe thiazolium salt-catalyzed addition of aldehydes to the cyclic α-methylene ketones 3, 4, 7, 8, 48, and 49 leads to γ-diketones 9 - 22, 50 - 53; some of them were converted into unsaturated ketones 23 - 28, pyrroles 29 - 34, 37 - 43, and furans 35, 36, 44 - 46. The α-methylene ketones were synthesized by retro Diels-Alder reaction of the corresponding norbornene compounds 1, 2, 5, 6, 47.
    Notes: Die Thiazoliumsalz-katalysierte Addition von Aldehyden an die cyclischen α-Methylenketone 3, 4, 7, 8, 48 und 49 führt zu γ-Diketonen 9 - 22, 50 - 53, aus denen einige ungesättigte Ketone 23 - 28, Pyrrol- 29 - 34, 37 - 43 und Furanderivate 35, 36, 44 - 46 synthetisiert wurden. Die Darstellung der α-Methylenketone erfolgte durch Retrospaltung entsprechender Norbornenderivate 1, 2, 5, 6 und 47.
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  • 96
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 694-701 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Diazadiene als Steuerliganden in der Katalyse, 51). Synthese chiraler Diazadiene R* - N = CR' - CR' = N - R*Die im Prinzip einfache Kondensationsreaktion von Glyoxal (als Hydrat) und 2,3-Butandion mit primären Aminen führt leider bei aliphatischen Aminen mit tertiärem bzw. sekundärem α-Kohlenstoff oftmals zu unerwünschten Additionsprodukten. Unter speziellen Synthesebedingungen können mit (R)-1-Phenylethylamin (1) und (1S,2S,3S,5R)-3-(Aminomethyl)pinan die gewünschten Diimine (Diazadiene (dad): R* - N = CR' - CR' = N - R*, R' = H, CH3) 4, 6 - 8 erhalten werden. Aus (S)-2-Amino-1-butanol (3) werden je nach Dion-Komponente ein Morpholinomorpholin 9 bzw. ein Bioxazolidin 10 gebildet, die von elektronenreichen Metallen in ihrer isomeren Form als Diazadiene gebunden werden ((dad)Mo(CO)4 11 und 12). Die offenkettige dad-Form ist durch O-Silylierung (14, 15) stabilisierbar. Die (dad)Eisen(0)-katalysierte Dimerisierung von Butadien zu 4-Vinyl-1-cyclohexen mit diesen dad-Liganden ergibt Enantiomerenüberschüsse e.e. bis zu 16%.
    Notes: The condensation of glyoxal (as hydrate) or 2,3-butanedione with primary amines is, in principle, a simple reaction. Unfortunately, aliphatic amines with secondary or tertiary α-carbons often give unwanted addition products. Under special reaction conditions the desired diimines (diazadienes (dad): R* - N = CR' - CR' = N - R*, R' = H, CH3) 4, and 6 - 8 are obtained from (R-1-phenyl-ethylamine (1) and (1S,2S,3S,5R)-3-(aminomethyl)pinane (2). Depending on the dione, a morpholinomorpholine 9 and a bioxazolidine 10 are formed from (S)-2-amino-1-butanol (3), which are bound by electron-rich metals in their isomeric dad form ((dad)Mo(CO)4 11 and 12). The acyclic dad structure is stabilized by O-silylation (14, 15). The (dad)iron(0) catalyzed dimerization of butadiene with these controlling ligands to 4-vinyl-1-cyclohexene occurs with an enantiomeric excess up to 16%.
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  • 97
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Application of High-Resolution Solid State NMR Spectroscopy for the Determination of the Ring-Chain TautomerismThe structure of the benzaldehyde derivatives 1 and 2 showing ring-chain tautomerism was investigated by NMR spectroscopy in the solid state and in solution. Difficulties in preparing single crystals, low solubility, and the presence of solvent in the crystal prevent an X-ray analysis and other spectroscopic methods. The structural problem was solved by C-13 CP-MAS NMR spectroscopy. 2-[2-(Methylamino)ethyl]-3-nitrobenzaldoxime (1) exists in the chain form in the crystal but is in equilibrium with the cyclic isomer in solution. Two different types of crystals were obtained from the aminoethenylbenzaldehyde derivative 2, one of them containing the chain the other the cyclic form of 2. Signal assignments in the solid state result from comparison with the spectra in solution, which have been partially assigned by 2D 1H 13C NMR shift correlation.
    Notes: Die Struktur der Benzaldehyd-Derivate 1 und 2, die Ring-Ketten-Tautomerie zeigen, wird durch NMR-Spektroskopie im festen und gelösten Zustand untersucht. Schwierigkeiten beim Züchten von Einkristallen sowie die Schwerlöslichkeit bzw. die Anwesenheit von Kristallösungsmittel verhinderten die Anwendung der Röntgenstrukturanalyse und anderer spektroskopischer Methoden. Mit Hilfe von C-13-CP-MAS-NMR-Spektren wird das Strukturproblem lösbar. In 2-[2-(Methyl-amino)ethyl]-3-nitrobenzaldoxim (1) liegt im Kristall die offene Form vor, die in Lösung mit dem cyclischen Tautomeren 1b im Gleichgewicht steht. Vom Aminoethenylbenzaldehyd-Derivat 2 lassen sich zwei verschiedene Kristalle gewinnen, in denen alternativ die offene und die cyclische Struktur vorliegt. Zur Signalzuordnung werden die Festkörper-NMR-Spektren mit den z. T. durch 2D-1H-13C-NMR-Verschiebungskorrelation zugeordneten C-13-Spektren verglichen.
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  • 98
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 710-724 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Asymmetric Catalyses, 121). New Optically Active P,N Ligands and Their Use in Rh-Catalyzed Asymmetric Hydrogenation and HydrosilylationNew P,N-ligands 2, 4 and 5 were prepared by Schiff base condensation of (2-formylphenyl)diphenyl- and tris(2-formylphenyl)phosphane with (R)-(+)-1-phenylethylamine and ethylenediamine. (R)-(+)-aminphos (6) was obtained by hydrogenation of the C = N bond in (R)-(+)-iminphos (2). The new imine ligands form stable chelate complexes. The pseudotetrahedral CpFe(CO)[R)-(+)-iminphos]PF6 was separated into the diastereoisomes with respect to the Fe configuration. The square planar Rh[(R)-(+)-iminphos]2X is obtained as a cis/trans mixture. The isolated Rh complexes and the combinations [Rh(COD)Cl]2/2, 4, and 6, respectively, were used as catalysts for the homogeneous hydrogenation of (Z)-α-(acetylamino)cinnamic acid and for the hydrosilylation of acetophenone with diphenysilane. The optical yield of 1-phenyl-ethanol, the product of hydrolysis of the hydrosilylation, increases with increasing ligand excess, decreasing catalyst concentration, and decreasing temperature.
    Notes: Neue P,N-Liganden 2, 4 und 5 wurden durch Schiffbasenkondensation von (2-Formylphenyl)diphenyl- und Tris(2-formylphenyl)phosphan mit (R)-(+)-1-Phenylethylamin und Ethylendiamin dargestellt. (R)-(+)-aminphos (6) wurde durch Hydrierung der C = N-Bindung in (R)-(+)-iminphos (2) erhalten. Die neuen Imin-Liganden bilden stabile Chelatkomplexe. Das pseudotetraedrische CpFe(CO)[(R)-(+)-iminphos]PF6 wurde in die Diastereomeren bezüglich der Fe-Konfiguration getrennt. Das quadratisch-planare Rh[(R)-(+)-iminphos]2X fällt als cis/trans-Gemisch an. Die isolierten Rh-Komplexe und die Kombinationen [Rh(COD)Cl]2/ 2, 4 bzw. 6 wurden als Katalysatoren für die homogene Hydrierung von (Z)-α-(Acetylamino)zimtsäure und für die Hydrosilylierung von Acetophenon mit Diphenylsilan eingesetzt. Die optische Ausbeute an 1-Phenylethanol, dem Hydrolyseprodukt der Hydrosilylierung, steigt mit zunehmendem Ligandenüberschuß, mit abnehmender Katalysatorkonzentration und mit abnehmender Temperatur.
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    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 3021-3033 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Solvolysis of (Z)/(E)-1-Methyl-2-[2-(1-propyn-1-yl)phenyl]vinyl Triflate and 1-Methylene-2-[2-(1-propyn-1-yl)phenyl]ethyl TriflateThe synthesis and solvolysis of the triflates (Z)/(E)-8 and 20 in various solvents are described. The (E)-triflate 8 reacts in trifluoroethanol by rearrangement via the intermediate naphthyl cation 9 to give the naphthyl ether 22 and the naphthyl triflate 24. The identification of 1-bromo-2,3-dimethylnaphthalene (26) after addition of bromide ions to the solvolysis confirms 9 as a reactive intermediate. The (Z)-triflate 8 solvolyses preferably to the elimination product 28, the formation of [(3-methyl-2-naphthyl)methyl] (trifluoroethyl) ether (23), however, can not be explained via the cation 9 as an intermediate. The solvolysis of the triflate 20 leads also to the rearranged products 22 and 23.
    Notes: Die Synthese und Solvolyse der Triflate (Z)/(E)-8 und 20 in verschiedenen Lösungsmitteln wird beschrieben. Das (E)-Triflat 8 reagiert in Trifluorethanol bevorzugt unter Umlagerung über das intermediäre Naphthylkation 9 zum Naphthylether 22 und zum Naphthyltriflat 24. Der Nachweis von 1-Brom-2,3-dimethylnaphthalin (26) nach Bromidionenzusatz zur Solvolyse bestätigt 9 als reaktive Zwischenstufe. Das (Z)-Triflat 8 solvolysiert bevorzugt zum Eliminierungsprodukt 28, die Bildung des [(3-Methyl-2-naphthyl)methyl]-(trifluorethyl)-ethers (23) kann jedoch nicht über das Kation 9 als Zwischenstufe erklärt werden. Die Solvolyse des Triflates 20 führt ebenfalls zu den Umlagerungsprodukten 22 und 23.
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  • 100
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 3160-3164 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurement of Absolute Rates of Radical Additions to Alkenes by the “Mercury Method”Using the 5-hexenyl radical (2) as “radical clock” the rates of radical additions to methyl acrylate (5a) and acrylonitrile (5b) are measured by the “mercury method” (Table 1). Alkyl radicals are trapped by the alkylmercury hydride 1 with rate constants of at least 107 1 · mol-1 · s-1.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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