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311.
The advantages of a constant volume combustion cycle as compared to constant pressure combustion in terms of thermodynamic efficiency has focused the search for advanced propulsion on detonation engines. Detonation of acetylene mixed with oxygen in various proportions is studied using mathematical modeling. Simplified kinetics of acetylene burning includes 11 reactions with 9 components. Deflagration to detonation transition (DDT) is obtained in a cylindrical tube with a section of obstacles modeling a Shchelkin spiral; the DDT takes place in this section for a wide range of initial mixture compositions. A modified ka-omega turbulence model is used to simulate flame acceleration in the Shchelkin spiral section of the system. The results of numerical simulations were compared with experiments, which had been performed in the same size detonation chamber and turbulent spiral ring section, and with theoretical data on the Chapman–Jouguet detonation parameters. 相似文献
312.
The Ultra Low Maintenance (ULM) battery technology and its historical performance validation programs are reviewed. Recent military flight test programs are discussed and the growing lists of both military and commercial aircraft flying ULM batteries are presented 相似文献
313.
In this paper, the results of calculating the processes of two fuel mixture combustion in different proportions are presented.
The values of temperature, thermal capacity, specific gas constant and isentropic expansion ratio of combustion products are
given. Also shown is the distinction of thermodynamic properties from the additivity law. 相似文献
314.
T. Blöcker H. Holweger B. Freytag F. Herwig H.-G. Ludwig M. Steffen 《Space Science Reviews》1998,85(1-2):105-112
Based on radiation hydrodynamics modeling of stellar convection zones, a diffusion scheme has been devised describing the
downward penetration of convective motions beyond the Schwarzschild boundary (overshoot) into the radiative interior. This
scheme of exponential diffusive overshoot has already been successfully applied to AGB stars. Here we present an application
to the Sun in order to determine the time scale and depth extent of this additional mixing, i.e. diffusive overshoot at the
base of the convective envelope. We calculated the associated destruction of lithium during the evolution towards and on the
main-sequence. We found that the slow-mixing processes induced by the diffusive overshoot may lead to a substantial depletion
of lithium during the Sun's main-sequence evolution.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
315.
Walker Gene B. Castles M. Pike Travers Douglas N. 《IEEE transactions on aerospace and electronic systems》1968,(5):752-755
A previously reported HF loop antenna array for multipolarization direction finding consisting of two spaced loops is described. The method is compatible with twin channel Watson-Watt operation as an Adcock so that the direction finding process is independent of polarization characteristics of the element pattern. Experimentally measured direction finder (DF) bearings were compared with near simultaneous polarimeter data and conventional crossed loops bearings. A major reduction in polarization error was obtained at the expense of full 360° azimuth response. It is theoretically possible to cover 360° with two similar arrays of the type investigated or with crossed loops elements with quadrature phase shifters. 相似文献
316.
Abdul-Baki B. Baldwin J. Rudel M.-P. 《Aerospace and Electronic Systems Magazine, IEEE》2000,15(8):3-21
This paper describes the specification-based testing, analysis tools, and associated processes used to independently validate, verify, and ultimately, provide for certifying safety-critical software developed for the Traffic Alert and Collision Avoidance System (TCAS II) program. These tools and processes comprise an effective and Independent Validation and Verification (IV and V) activity applied to the Collision Avoidance Subsystem (GAS) software development process. A requirements specification language called the Requirements State Machine Language (RSML), originally developed by the University of California, Irvine (UCI), was employed for the specification of GAS. The end result is the next generation of TCAS II collision avoidance logic, referred to as Version 7, that is of a higher quality than its predecessors, meets the certification requirements of DO-178B Level B (Ref. 1), and can be shown to satisfy the new operational requirements it was developed to address 相似文献
317.
318.
Pulsone N.B. Raghavan R.S. 《IEEE transactions on aerospace and electronic systems》1999,35(3):903-916
Coherent signal detection in non-Gaussian interference is presently of interest in adaptive array applications. Conventional array detection algorithms inherently model the interference with a multivariate Gaussian random vector. However, non-Gaussian interference models are also under investigation for applications where the Gaussian assumption may not be appropriate. We analyze the performance of an adaptive array receiver for signal detection in interference modeled with a non-Gaussian distribution referred to as a spherically invariant random vector (SIRV). We first motivate this interference model with results from radar clutter measurements collected in the Mountain Top Program. Then we develop analytical expressions for the probability of false alarm and the probability of detection for the adaptive array receiver. Our analysis shows that the receiver has constant false alarm rate (CFAR) performance with respect to all the interference parameters. Some illustrative examples are included that compare the detection performance of this CFAR receiver with a receiver that has prior knowledge of the interference parameters 相似文献
319.
D. B. Dobritsa 《Cosmic Research》2014,52(3):229-234
In this paper, the problems of the application and development of models of space debris when designing means of the anti-meteorite spacecraft protection are considered. The developed method enables us to calculate the resistance of design elements based on the conjugation of a modified spatial model of the distribution of space-debris particles and ballistic limit dependences for a calculated element. 相似文献
320.
Ceres appears likely to be differentiated and to have experienced planetary evolution processes. This conclusion is based on current geophysical observations and thermodynamic modeling of Ceres?? evolution. This makes Ceres similar to a small planet, and in fact it is thought to represent a class of objects from which the inner planets formed. Verification of Ceres?? state and understanding of the many steps in achieving it remains a major goal. The Dawn spacecraft and its instrument package are on a mission to observe Ceres from orbit. Observations and potential results are suggested here, based on number of science questions. 相似文献