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  • Engineering (General)  (6)
  • PHYSICAL SCIENCES  (3)
  • Stackelberg games  (2)
  • 2020-2023
  • 1990-1994  (11)
  • 1950-1954
  • 1910-1914
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Time-axis decomposition of large-scale optimal control problems (1990)
    Springer
    Journal of optimization theory and applications 67 (1990), S. 259-277 
    Details
    ISSN: 1573-2878
    Keywords: Optimal control ; time-axis decomposition ; Stackelberg games ; bilevel programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Continuous-time optimal control problems can rarely be solved directly but have to be approximated with discrete analogues. Shorter time steps lead to more accurate approximations, but result in formulations that are often too big for computer memory. This paper presents a technique for decomposing the problem along the time axis and iterating toward a solution in a leader-follower framework. In the model, the leader controls a set of coordination parameters, which he passes to the followers, who then solve their individual subproblems. State and sensitivity information is returned to the leader, who attempts to minimize an unconstrained problem in the coordination space. Parameters are updated and the process continues until improvement ceases. Two advantages of this technique are that feasible solutions to the original problem are available at each iteration and that the optimal coordination parameters obtained provide some measure of feedback control. Computational results are presented for a comprehensive set of test problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940476
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Some properties of the bilevel programming problem (1991)
    Springer
    Journal of optimization theory and applications 68 (1991), S. 371-378 
    Details
    ISSN: 1573-2878
    Keywords: Bilevel programming ; Stackelberg games ; computational complexity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The purpose of this paper is to elaborate on the difficulties accompanying the development of efficient algorithms for solving the bilevel programming problem (BLPP). We begin with a pair of examples showing that, even under the best of circumstances, solutions may not exist. This is followed by a proof that the BLPP is NP-hard.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00941574
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  • 3
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    Dynamic Simulation of a Periodic 10 K Sorption Cryocooler (1994)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: A transient thermal simulation model has been developed to simulate the dynamic performance of a multiple-stage 10 K sorption cryocooler for spacecraft sensor cooling applications that require periodic quick-cooldown (under 2 minutes) , negligible vibration, low power consumption, and long life (5 to 10 years). The model was specifically designed to represent the Brilliant Eyes Ten-Kelvin Sorption Cryocooler Experiment (BETSCE), but it can be adapted to represent other sorption cryocooler systems as well. The model simulates the heat transfer, mass transfer, and thermodynamic processes in the cryostat and the sorbent beds for the entire refrigeration cycle, and includes the transient effects of variable hydrogen supply pressures due to expansion and overflow of hydrogen during the cooldown operation. The paper describes model limitations and simplifying assumptions, with estimates of errors induced by them, and presents comparisons of performance predictions with ground experiments. An important benefit of the model is its ability to predict performance sensitivities to variations of key design and operational parameters. The insights thus obtained are expected to lead to higher efficiencies and lower weights for future designs.
    Keywords: Engineering (General)
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Ground Testing of a 10 K Sorption Cryocooler Flight Experiment (BETSCE) (1994)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: The Brilliant Eyes Ten-Kelvin Sorption Cryocooler Experiment (BETSCE) is a Space Shuttle side-wall-mounted flight experiment designed to demonstrate 10 K sorption cryocooler technology in a space environment. The BETSCE objectives are to: (1) provide a thorough end-to-end characterization and space performance validation of a complete, multistage, automated, closed-cycle hydride sorption cryocooler in the 10 to 30 K temperature range, (2) acquire the quantitative microgravity database required to provide confident engineering design, scaling, and optimization, (3) advance the enabling technologies and resolve integration issues, and (4) provide hardware qualification and safety verification heritage. BETSCE ground tests were the first-ever demonstration of a complete closed-cycle 10 K sorption cryocooler. Test results exceeded functional requirements. This paper summarizes functional and environmental ground test results, planned characterization tests, important development challenges that were overcome, and valuable lessons-learned.
    Keywords: Engineering (General)
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  • 5
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    Component Reliability Testing of Long-Life Sorption Cryocoolers (1994)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: This paper summarizes ongoing experiments characterizing the ability of critical sorption cryocooler components to achieve highly reliable operation for long-life space missions. Test data obtained over the past several years at JPL are entirely consistent with achieving ten year life for sorption compressors, electrical heaters, container materials, valves, and various sorbent materials suitable for driving 8 to 180 K refrigeration stages. Test results for various compressor systems are reported. Planned future tests necessary to gain a detailed understanding of the sensitivity of cooler performance and component life to operating constraints, design configurations, and fabrication, assembly and handling techniques, are also discussed.
    Keywords: Engineering (General)
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  • 6
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    Component Reliabilty Testing of Long-Life Sorption (1994)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Engineering (General)
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  • 7
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    Dynamic Simulation of a Periodic 10 K Sorption Cryocooler (1994)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Keywords: Engineering (General)
    Format: text
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  • 8
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    Ground Testing for a 10 K Sorption Cryocooler Flight Expeiment (BETSCE) (1994)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Keywords: Engineering (General)
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Joule-Thomson Cooler Produces Nearly Constant Temperature (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Improved Joule-Thomson cooler maintains nearly constant temperature. Absolute-pressure relief valve helps stabilize temperature of cold head despite variations in atmospheric pressure. Feedback-controlled electrical heater provides additional stabilization. Demand-flow Joule-Thomson valve requires less nitrogen than fixed-orifice Joule-Thomson valve providing same amount of cooling. Provides stable low temperatures required for operation of such devices as tunable diode lasers in laboratory and balloon-borne instruments detecting contaminants in atmosphere.
    Keywords: PHYSICAL SCIENCES
    Type: NPO-18184 , NASA Tech Briefs (ISSN 0145-319X); 16; 1; P. 41
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  • 10
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    Mixed-Gas Sorption Joule-Thomson Refrigerator (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Proposed mixed-gas sorption Joule-Thomson refrigerator provides cooling down to temperature of 70 K. Includes only one stage and no mechanical compressor. Simpler, operates without vibrating, and consumes less power in producing same amount of cooling. Same sorption principle of operation applicable in compressor that chemisorbs oxygen or hydrogen from mixture with helium, neon, and/or other nonreactive gases.
    Keywords: PHYSICAL SCIENCES
    Type: NPO-17569 , NASA Tech Briefs (ISSN 0145-319X); 15; 5; P. 38
    Format: text
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