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  • 1
    Publication Date: 2005-11-27
    Description: Using finite element method in analysis and design of optical space telescopes
    Keywords: STRUCTURAL MECHANICS
    Type: OPT. TELESCOPE TECHNOL. 1970; P 401-415
    Format: text
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  • 2
    Publication Date: 2006-01-12
    Description: The lunar quarantine program was designed to ensure that return of lunar material represented no threat to the public health, to agriculture, or to other living resources. It established definitely that no life exists on the moon. The crews of the three lunar quarantine missions, Apollo 11, 12, and 14, experienced no health problems as a result of their exposure to lunar samples. Plants and animals also showed no adverse effects. Stringent quarantine was terminated after Apollo 14, but lunar samples continued to be protected to guarantee that scientists would receive uncontaminated materials for study.
    Keywords: AEROSPACE MEDICINE
    Type: Biomedical Results of Apollo; p 407-424
    Format: text
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  • 3
    Publication Date: 2011-08-18
    Description: The motion of two and four rectilinear vortices inside a cylindrical pipe is studied under the restriction that the total circulation be zero. In the two-vortex case, it is shown that the motion is always periodic and an expression for the period is derived. In the four-vortex case, the motion is determined not to be periodic in general. However, a class of solutions where the motion is periodic is found. Several sample calculations of the vortex motion are included.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 27; 1583-158
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  • 4
    Publication Date: 2011-08-12
    Description: NASA Lunar Receiving Laboratory functional areas and physical, chemical, biological and quarantine activities for crew and lunar samples
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: ; VUE TECHNIQUE CECLES
    Format: text
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  • 5
    Publication Date: 2011-08-16
    Description: Eigenvalue equations of the form D(lambda) = 0 are studied for acoustic modes in circular and annular ducts without flow. The ducts have locally reacting walls with arbitrary wall admittance. It is shown that circular ducts may have double eigenvalues, or wall admittances where both D(lambda) and D prime (lambda) are zero. These double eigenvalues are formed by the coalescence of the lowest-order eigenfunction with some higher-order eigenfunction. The eigenfunctions, or acoustic modes, associated with the double eigenvalues are found to be orthogonal to themselves so that the standard expansion formula for the acoustic field, which is obtained from a separation-of-variables analysis, is invalid. An alternate expansion formula for the acoustic field is derived. This alternate formula shows that the coalesced acoustic mode is linearly amplified by the transmission distance and exponentially attenuated at the expected rate. The expansion formula also reveals a new eigenfunction, or acoustic mode, which is exponentially attenuated at the same rate as the coalesced eigenfunction.
    Keywords: PHYSICS, GENERAL
    Type: Acoustical Society of America; vol. 55
    Format: text
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  • 6
    Publication Date: 2016-06-07
    Description: NASTRAN solution techniques are shown for a numerical analysis of a class of coupled vector flow processes described by simultaneous parabolic differential equations. To define one physical problem type where equations of this form arise, the differential equations describing the coupled transfers of heat and mass in mechanical equilibrium with negligible mass average velocity are presented and discussed. Also shown are the equations describing seepage when both electrokinetic and hydrodynamic forces occur. Based on a variational statement of the general problem type, the concepts of scalar transfer elements and parallel element systems are introduced. It is shown that adoptation of these concepts allows the direct use of NASTRAN's existing Laplace type elements for uncoupled flow (the heat transfer elements) for treating multicomponent coupled transfer. Sample problems are included which demonstrate the application of these techniques for both steady-state and transient problems.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: Users' Experiences; p 65-90
    Format: application/pdf
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  • 7
    Publication Date: 2016-06-07
    Description: The program not only can render temperature distributions in solids subjected to various thermal boundary conditions, including effects of diffuse-gray thermal radiation, but is fully compatible in capacity and in the finite-element model representation with that of its structural counterpart in the NASTRAN system. The development history of the finite-element approach for determining temperatures is summarized. The scope of analysis capability, program structure, features, and limitations are given with the objective of providing NASTRAN users with an overall veiw of the NASTRAN thermal analyzer.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASTRAN: Users' Experiences; p 443-454
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  • 8
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    In:  Other Sources
    Publication Date: 2016-06-07
    Description: The investigation of the effects of variations of mesh refinement and mesh pattern were conducted using a basic rectangular mesh pattern. When employing the constant strain TRMEM element, the basic rectangular pattern was subdivided into triangles. This subdivision employs two different triangular patterns and allows results to be obtained which demonstrate the effect of modelling bias. Errors in tip deflection, direct stress, and shearing stress as a function of mesh size and element aspect ratio were obtained as well as mid-span stress distributions. All problems were solved on an IBM 360/95 computer using MacNeal-Schwendler Version MSC-38 Rigid Format-1 of the NASTRAN computer program. While NASTRAN uses double precision arithmetic for the solution of the global equations for displacements, subsequent computations to obtain element stresses are carried out in single precision. This suggests that some improvement in stress recovery might be expected when using the higher precision DCD machines.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Washington 6th NASTRAN (R) Users' Colloq.; p 383-403
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  • 9
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    In:  CASI
    Publication Date: 2016-06-07
    Description: During the 1980's, some 200 Spacelab missions will be flown on space shuttle in earth-orbit. Within these 200 missions, it is planned that at least 20 will be dedicated to life sciences research, projects which are yet to be outlined by the life sciences community. Objectives of the Life Sciences Shuttle/Spacelab Payloads Program are presented. Also discussed are major space life sciences programs including space medicine and physiology, clinical medicine, life support technology, and a variety of space biology topics. The shuttle, spacelab, and other life sciences payload carriers are described. Concepts for carry-on experiment packages, mini-labs, shared and dedicated spacelabs, as well as common operational research equipment (CORE) are reviewed. Current NASA planning and development includes Spacelab Mission Simulations, an Announcement of Planning Opportunity for Life Sciences, and a forthcoming Announcement of Opportunity for Flight Experiments which will together assist in forging a Life Science Program in space.
    Keywords: SPACE TRANSPORTATION
    Type: Bioprocessing in Space; p 5-27
    Format: application/pdf
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  • 10
    Publication Date: 2019-06-28
    Description: A simulation system, ROCETS, was designed and developed to allow cost-effective computer predictions of liquid rocket engine transient performance. The system allows a user to generate a simulation of any rocket engine configuration using component modules stored in a library through high-level input commands. The system library currently contains 24 component modules, 57 sub-modules and maps, and 33 system routines and utilities. FORTRAN models from other sources can be operated in the system upon inclusion of interface information on comment cards. Operation of the simulation is simplified for the user by run, execution, and output processors. The simulation system makes available steady-state trim balance, transient operation, and linear partial generation. The system utilizes a modern equation solver for efficient operation of the simulations. Transient integration methods include integral and differential forms for the trapezoidal, first order Gear, and second order Gear corrector equations. A detailed technology test bed engine (TTBE) model was generated to be used as the acceptance test of the simulation system. The general level of model detail was that reflected in the Space Shuttle Main Engine DTM. The model successfully obtained steady-state balance in main stage operation and simulated throttle transients, including engine starts and shutdown. A NASA FORTRAN control model was obtained, ROCETS interface installed in comment cards, and operated with the TTBE model in closed-loop transient mode.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-184099 , NAS 1.26:184099
    Format: application/pdf
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