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841.
Lignell K. Sievers R. Mattes B. Pantolin J. 《Aerospace and Electronic Systems Magazine, IEEE》2001,16(3):33-36
There are several terrestrial applications for energy conversion systems with electrical outputs of a few volts in the power range from hundreds of milliwatts to a few watts. Potential applications include: power for instrumentation, communication and device actuation in severe or harsh environments, as well as a variety of low duty cycle monitoring tasks for the military. For cost and/or packaging reasons, some of these applications are severely heat source limited. In this paper we describe the development and performance of AMTEC systems capable of producing 0.3 to 0.5 watts from a radioisotope heat source limited to a total thermal output of less than 4 watts, The approach utilizes a new “chimney cell” design and a thermal insulation system consisting of a specialized multi-layer insulation (MLI) package in combination with fibrous insulation. The cell operates at 0.4 Wc to over 0.5 Wc with an input surface temperature of 700°C. Measurements of the thermal performance of a readily manufactured MLI package indicate that operation at these temperatures will be achievable with a total heat input of ~4 Wth 相似文献
842.
Gallacher B.J. Burdess J.S. Harris A.J. 《IEEE transactions on aerospace and electronic systems》2001,37(4):1333-1343
The principal features of a three-axis ring gyroscope are described. The equations of motion, the response to constant rates of turn, and the relationships between the modes of vibration are derived. Tuned and untuned cases are considered 相似文献
843.
S Philosoph-Hadas H Friedman S Meir R Berkovitz-SimanTov I Rosenberger A H Halevy P B Kaufman P Balk E J Woltering 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(5):921-932
The negative gravitropic response of cut flower stalks is a complex multistep process that requires the participation of various cellular components acting in succession or in parallel. The process was particularly characterized in snapdragon (Antirrhinum majus L.) spikes with regard to (1) gravity stimulus perception associated with amyloplast reorientation; (2) stimulus transduction mediated through differential changes in the level, action and related genes of auxin and ethylene and their possible interaction; (3) stimulus response associated with differential growth leading to stalk curvature; (4) involvement of cytosolic calcium and actin cytoskeleton. Results show that the gravity-induced amyloplast reorientation, differential over-expression of two early auxin responsive genes and asymmetrical distribution of free IAA are early events in the bending process. These precede the asymmetrical ethylene production and differential stem growth, which was derived from initial shrinkage of the upper stem side and a subsequent elongation of the lower stem side. Results obtained with various calcium- and cytoskeleton-related agents indicate that cytosolic calcium and actin filaments may play essential roles in gravitropism-related processes of cut flower stalks. Therefore, modulators of these two physiological mediators may serve as means for controlling any undesired gravitropic bending. 相似文献
844.
B Konig M Dunne K Slenzka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(9):1523-1528
The importance of the research on Bioregenerative Life Support has increased dramatically in the last decade not only with regard to possible space flight application but also as a way to obtain a better understanding of our Earth's ecology. A major goal was to reach long-term stability of artificial model systems. Preliminary data are presented on the development of an improved aquatic system, currently dedicated for ground-based research. Closed aquatic ecosystems require reliability of the key parameters of pH, O2 and CO2 concentration and stability of sensors for monitoring. Besides the integration of an artificial lung (holofiber system and air pump with valves, allowing controlled oxygen uptake of air), in parallel to the oxygen producing water plants. Our new approach is to implement opto-chemical sensors, for such environmental monitoring. One major advantage of the new sensor technique is their better long-term reliability as compared to the electrochemical sensors. Our experiment with the new sensor technique has demonstrated satisfactory performance in closed aquatic ecosystems. 相似文献
845.
846.
Perturbation theory is applied to the Vinti problem—motion about an oblate spheroid—to include the gravitational effects of the sun and moon. The problem is formulated using the extended phase space method which introduces a new independent variable similar to the true anomaly. The disturbing Hamiltonian H1 for third bodies is of order J22 (second order) and the final goal is a theory including second order short and long period terms and third order secular terms. The current paper however carries the development only to the second order in the secular terms and the first order in the periodic terms. Problems of including the higher orders are discussed. Therefore, in the development of H1 all terms of order 10?9 or larger are retained. The lunar emphemeris retains terms to e′2 in the lunar eccentricity. The perturbation analysis is carried out by means of Lie series and is developed through the first order only which is consistent with the final accuracy desired. The generating function W1 is obtained and separated into the long period, short period and secular terms. From W1 the coordinates are defined from the Lie series by means of a transformation equation. These coordinates are non-singular for small eccentricity and inclination. Because of the complexity of the equations all algebraic computations were accomplished by means of a computerized Poisson series manipulator developed at the Naval Research Laboratory. 相似文献
847.
B.G. Taylor M.R. Sims J. Davelaar A. Peacock 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(4):225-228
The development of an imaging gas scintillation proportional counter which utilises a channel multiplier array as the readout element is discussed. Preliminary experimental results and theoretical considerations indicate that spatial and energy resolutions of below 500 μm and 8% respectively should be achievable at an X-ray energy of 6 keV. 相似文献
848.
B. Higel 《Space Science Reviews》1978,22(5):611-631
The plasma resonance phenomena observed at f
pe, nf
ce, and f
qn by the GEOS-1 S-301 relaxation sounder are identified through a pattern recognition software process implemented in a mini-computer which receives on-line the compressed data. First, this processing system distributes in real time f
pe and f
ce measurements to the ground media. Second, it drives and controls automatically the S-301 on-board experiment by sending appropriate telecommands: the tracking of resonances is performed by shortening the frequency sweeps to a narrow range centered on the resonance location. Examples of such tracking sequences are presented, exhibiting sampling rates of the electron density measurements from once every 22 s (slowest rate) to once every 86 ms (highest rate available). The results give evidence of the existence of very small scale structures in the magnetospheric density, having characteristic sizes of the order of a few 102 m or/and a few 10-1 s. The relative amplitude of these density fluctuations is typically 1%. Because of satellite spinning, fixed frequency sounding sequences allow to measure in a few seconds the directivity features of the plasma resonance signals. Examples of directional patterns in the plane perpendicular to the geomagnetic field are presented: the electrostatic nature of the waves received at f
pe, nf
ce, and f
qe being consistent with these patterns, the corresponding k vector orientations become available. The Bernstein modes properties are used to interpret the cf
ce and f
qe results. 相似文献
849.
Krishnamoorthy B.M. Krishnamurthy M.R. 《IEEE transactions on aerospace and electronic systems》1982,(1):58-75
The asynchronous performance of a polyphase reluctance machine with rotor provided with axial slits is investigated for the first time on the basis of conductor boundary treated as a flux line. Theoretical and experimental investigations are presented for rotors with 1) many values of pole arc/pole pitch ratio, 2) varying slot depths, 3) slots on either pole faces or slot portions or both of them, and 4) with and without terminating end rings. Their comparison with predictions leads to interesting conclusions. 相似文献
850.
The use of linearized error equations in the design of model-reference adaptive systems developed by Part I is illustrated. Using standard control specifications on the system error (e.g., percent overshoot, rise time, etc.), a set of desired root locations on the root loci can be obtained. Then constants in the adaptive scheme can be chosen to obtain the desired root locations. Simulation results are given to illustrate the validity of the linearized error characteristic equation design procedure. 相似文献