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  • Space Sciences (General)  (2)
  • assignment  (2)
  • Aerodynamics; Spacecraft Design, Testing and Performance  (1)
  • Electronics and Electrical Engineering  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The singly constrained assignment problem: An AP basis algorithm (1995)
    Springer
    Computational optimization and applications 4 (1995), S. 347-374 
    Details
    ISSN: 1573-2894
    Keywords: mathematical programming ; assignment ; networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This manuscript presents a specialized primal simplex algorithm to obtain near optimal integer solutions for the singly constrained assignment problem. An optimal solution for the continuous relaxation of the problem is obtained by generalizing the alternating basis algorithm of Barr, Glover, and Klingman for the pure assignment problem. Near optimal integer solutions are obtained by pivoting into the optimal basis the slack variable associated with the side constraint. Our empirical analysis indicated that for our test problems the soft-ware implementation of this algorithm was six times faster than CPLEX and four times faster than NETSIDE (a specialized code for network problems with side constraints). The integer solutions obtained in our tests were typically within 2% of the optimum of the continuous relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01300862
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The singly constrained assignment problem: A Lagrangian relaxation heuristic algorithm (1994)
    Springer
    Computational optimization and applications 3 (1994), S. 7-26 
    Details
    ISSN: 1573-2894
    Keywords: network programming ; assignment ; integer programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This manuscript presents a new heuristic algorithm to find near optimal integer solutions for the singly constrained assignment problem. The method is based on Lagrangian duality theory and involves solving a series of pure assignment problems. The software implementation of this heuristic, ASSIGN+1, successfully solved problems having one-half million binary variables (assignment arcs) in less than 17 minutes of wall clock time on a Sequent Symmetry S81 using a single processor. In computational comparisons with MPSX and OSL on an IBM 3081D, the specialized software was from 100 to 1,000 times faster. In computational comparisons with the specialized code of Mazzola and Neebe, we found that ASSIGN+1 was 40 times faster. In computational comparisons with our best alternating path specialized code, we found that ASSIGN+1 was more than three times faster than that code. This new software proved to be very robust as well as fast. The robustness is due to an elaborate scheme used to update the Lagrangean multipliers and the speed is due to the fine code used to solve the pure assignment problems. We also present a modification of the algorithm for the case in which the number of jobs exceeds the number of men along with an empirical analysis of the modified software.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01299389
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    Paper (German National Licenses)
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  • 3
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    Mars Balloon Flight Test Results (2009)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper describes a set of four Earth atmosphere flight test experiments on prototype helium superpressure balloons designed for Mars. Three of the experiments explored the problem of aerial deployment and inflation, using the cold, low density environment of the Earth's stratosphere at an altitude of 30-32 km as a proxy for the Martian atmosphere. Auxiliary carrier balloons were used in three of these test flights to lift the Mars balloon prototype and its supporting system from the ground to the stratosphere where the experiment was conducted. In each case, deployment and helium inflation was initiated after starting a parachute descent of the payload at 5 Pa dynamic pressure, thereby mimicking the conditions expected at Mars after atmospheric entry and high speed parachute deceleration. Upward and downward looking video cameras provided real time images from the flights, with additional data provided by onboard temperature, pressure and GPS sensors. One test of a 660 cc pumpkin balloon was highly successful, achieving deployment, inflation and separation of the balloon from the flight train at the end of inflation; however, some damage was incurred on the balloon during this process. Two flight tests of 12 m diameter spherical Mylar balloons were not successful, although some lessons were learned based on the failure analyses. The final flight experiment consisted of a ground-launched 12 m diameter spherical Mylar balloon that ascended to the designed 30.3 km altitude and successfully floated for 9.5 hours through full noontime daylight and into darkness, after which the telemetry system ran out of electrical power and tracking was lost. The altitude excursions for this last flight were +/-75 m peak to peak, indicating that the balloon was essentially leak free and functioning correctly. This provides substantial confidence that this balloon design will fly for days or weeks at Mars if it can be deployed and inflated without damage.
    Keywords: Space Sciences (General)
    Type: AIAA Paper 2009- 2809 , AIAA Balloon Systems Conference; May 05, 2009 - May 07, 2009; Seattle, WA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Flow Energy Piezoelectric Bimorph Nozzle Harvester (2014)
    In:  Other Sources
    Details
    Publication Date: 2019-08-26
    Description: There is a need for a long-life power generation scheme that could be used downhole in an oil well to produce 1 Watt average power. There are a variety of existing or proposed energy harvesting schemes that could be used in this environment but each of these has its own limitations. The vibrating piezoelectric structure is in principle capable of operating for very long lifetimes (decades) thereby possibly overcoming a principle limitation of existing technology based on rotating turbo-machinery. In order to determine the feasibility of using piezoelectrics to produce suitable flow energy harvesting, we surveyed experimentally a variety of nozzle configurations that could be used to excite a vibrating piezoelectric structure in such a way as to enable conversion of flow energy into useful amounts of electrical power. These included reed structures, spring mass-structures, drag and lift bluff bodies and a variety of nozzles with varying flow profiles. Although not an exhaustive survey we identified a spline nozzle/piezoelectric bimorph system that experimentally produced up to 3.4 mW per bimorph. This paper will discuss these results and present our initial analyses of the device using dimensional analysis and constitutive electromechanical modeling. The analysis suggests that an order-of-magnitude improvement in power generation from the current design is possible.
    Keywords: Electronics and Electrical Engineering
    Type: SPIE Smart Structures and Non-Destructive Evaluation; Mar 09, 2014 - Mar 13, 2014; San Diego, CA; United States
    Format: text
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  • 5
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    Large-Scale Extratropical Weather Systems in Mars' Atmosphere (2013)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: During late autumn through early spring, extratropical regions on Mars exhibit profound mean zonal equator-to-pole thermal contrasts. The imposition of this strong meridional temperature variation supports intense eastward-traveling, synoptic weather systems (i.e., transient baroclinic/barotropic waves) within Mars' extratropical atmosphere. Such disturbances grow, mature and decay within the east-west varying seasonal-mean midlatitude jet stream (i.e., the polar vortex) on the planet. Near the surface, the weather disturbances indicated large-scale spiraling "comma"-shaped dust cloud structures and scimitar-shaped dust fronts, indicative of processes associated with cyclo-/fronto-genesis. The weather systems occur during specific seasons on Mars, and in both hemispheres. The northern hemisphere (NH) disturbances are significantly more intense than their counterparts in the southern hemisphere (SH). Further, the NH weather systems and accompanying frontal waves appear to have significant impacts on the transport of tracer fields (e.g., particularly dust and to some extent water species (vapor/ice) as well). And regarding dust, frontal waves appear to be key agents in the lifting, lofting, organization and transport of this particular atmospheric aerosol. In this paper, a brief background and supporting observations of Mars' extratropical weather systems is presented. This is followed by a short review of the theory and various modeling studies (i.e., ranging from highly simplified, mechanistic and full global circulation modeling investigations) which have been pursued. Finally, a discussion of outstanding issues and questions regarding the character and nature of Mars' extratropical traveling weather systems is offered.
    Keywords: Space Sciences (General)
    Type: ARC-E-DAA-TN7413 , American Meteorological Society annual meeting (AMS); Jan 06, 2013; Austin, TX; United States
    Format: text
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  • 6
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    A Survey of Titan Balloon Concepts and Technology Status (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper surveys the options for, and technology status of, balloon vehicles to explore Saturn's moon Titan. A significant amount of Titan balloon concept thinking and technology development has been performed in recent years, particularly following the spectacular results from the descent and landing of the Huygens probe and remote sensing observations by the Cassini spacecraft. There is widespread recognition that a balloon vehicle on the next Titan mission could provide an outstanding and unmatched capability for in situ exploration on a global scale. The rich variety of revealed science targets has combined with a highly favorable Titan flight environment to yield a wide diversity of proposed balloon concepts. The paper presents a conceptual framework for thinking about balloon vehicle design choices and uses it to analyze various Titan options. The result is a list of recommended Titan balloon vehicle concepts that could perform a variety of science missions, along with their projected performance metrics. Recent technology developments for these balloon concepts are discussed to provide context for an assessment of outstanding risk areas and technological maturity. The paper concludes with suggestions for technology investments needed to achieve flight readiness.
    Keywords: Aerodynamics; Spacecraft Design, Testing and Performance
    Type: AIAA Balloon Systems Conference; Sep 20, 2011 - Sep 22, 2011; Virginia Beach, VA; United States
    Format: text
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