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911.
912.
The leading cause of worldwide aviation fatalities comes from inadvertently flying a perfectly operating aircraft into the ground or water. This type of accident is referred to as Controlled Flight Into Terrain (CFIT). Statistics show that introduction of the Ground Proximity Warning System (GPWS) into the scheduled air carrier turbojet fleet has been accompanied by a dramatic drop in the frequency of CFIT accidents. Training aids, videos, checklists, and procedural recommendations have also been produced to aid in CFIT risk reduction. Despite these actions, CFIT worldwide losses continue. Common characteristics of these continued accidents are a lack of installed GPWS or shortcomings of the current GPWS detection algorithms. The Enhanced Ground Proximity Warning Systems have been developed to address these shortcomings, and to provide enhanced situational awareness to the pilots such that CFIT accidents can become a thing of the past 相似文献
913.
Transmitter model for the design of communication satellites 总被引:1,自引:0,他引:1
914.
High resolution radar clutter statistics 总被引:6,自引:0,他引:6
Anastassopoulos Lampropoulos G.A. Drosopoulos A. Rey N. 《IEEE transactions on aerospace and electronic systems》1999,35(1):43-60
The generalized compound probability density function (GC-pdf) is presented for modeling high resolution radar clutter. In particular, the model is used to describe deviation of the speckle component from the Rayleigh to Weibull or other pdfs with longer tails. The GC-pdf is formed using the generalized gamma (GΓ) pdf to describe both the speckle and the modulation component of the radar clutter. The proposed model is analyzed and thermal noise is incorporated into it. The validation of the GC-pdf with real data is carried out employing the statistical moments as well as goodness-of-fit tests. A large variety of experimental data is used for this purpose. The GC-pdf outperforms the K-pdf in modeling high resolution radar clutter and reveals its structural characteristics 相似文献
915.
Napolitano M.R. Cnsanova J.J. Windon D.A. II. Seanor B. Martinelli D. 《IEEE transactions on aerospace and electronic systems》1999,35(1):61-71
The results are presented of a comparative study evaluating the performance of neural network (NN) and fuzzy logic reconstructors (FLRs) for the development of a virtual flight data recorder (VFDK). Typical flight data recorders (FDRS) on commercial airliners do not record the aircraft control surface deflections. These dynamic parameters are critical in the investigation of an accident or an uncommanded maneuver. The results are shown relative to a VFDR based on a neural network simulator (NNS) along with a neural network reconstructor (NNR) or a FLR The NNS is trained off-line, using available flight data for the particular aircraft, for the purpose of simulating any desired dynamic output recorded in current FDRs. The NNS is then interfaced with the NNR or with the FLR. The output of the two reconstructors are the control surface deflections which minimize a performance index based on the differences between the available data from the FDR and the output from the NNS. The study tested with night data from a B737-300 shows that both schemes, the one with the NNR and the one with the FLR, provide accurate reconstructions of the control surface deflections time histories 相似文献
916.
A regulated peak-power tracking (RPPT) system for space power application is proposed. Large-signal stability analysis is provided to understand the main four different modes of operations of the system, as well as the mode transitions. A simple and effective control scheme for the system is also proposed. Small-signal analysis is performed thereafter to provide design optimization, and the predictions are verified by computer simulations 相似文献
917.
Adaptive control and stabilization of elastic spacecraft 总被引:1,自引:0,他引:1
This work treats the question of large angle rotational maneuver and stabilization of an elastic spacecraft (spacecraft-beam-tip body configuration). It is assumed that the parameters of the system are completely unknown. An adaptive control law is derived for the rotational maneuver of the spacecraft. Using the adaptive controller, asymptotically decoupled control of the pitch angle of the space vehicle is accomplished, however this maneuver causes elastic deformation of the beam connecting the orbiter and tip body. For the stabilization of the zero dynamics (flexible dynamics), a stabilizer is designed using elastic mode velocity feedback. In the closed-loop system including the adaptive controller and the stabilizer, reference pitch angle trajectory tracking and vibration suppression are accomplished. Simulation results are presented to show the maneuver capability of the control system 相似文献
918.
The performances of the importance sampling (IS) techniques are improved by using multiparametric distortions of the input random processes. The analysis of different constant false-alarm rate (CFAR) algorithms confirms the usefulness of this method. The potential of this new approach is fully exploited if optimization techniques are used to obtain the optimum distortions and to avoid bias in the estimates 相似文献
919.
A theoretical analysis of the sequential lobing technique for target angle tracking is presented. The signal power received by each antenna beam is assumed to pass through a logarithmic amplifier. A rigorous statistical approach is adopted in the analysis for both non-fluctuating and fluctuating targets. Closed form expressions are derived for the normalized mean error and rms error of the angle estimate for Swerling 0, I, II, and III targets. Results are compared with those obtained using a simplified approach for the non-fluctuating target 相似文献
920.
One of the more significant errors in the history of science occurred during the “marginal revolution” in economics near the end of the nineteenth century. Rather than explicitly recognize in basic theory that the happiness we seek to maximize in life originates within oneself, the early theorists formulated their equations as though human satisfaction resided in external things-as in so much utility (economist's term for satisfaction) per pound of sugar. Over the past 125 years, economists have developed mainstream mathematical economics on this incorrect basis resulting in the ill-founded neoclassical Equilibrium Theory. Because of this error economic theory is fundamentally timeless. The present theory, in its canonical form, corrects the early marginalist's error by identifying utility (time-integrated pleasure) exclusively with the stream-of-consciousness attending (expected) mental and physical activity. Time is now explicit in basic theory, thereby allowing, for the first time, the substantive computer-modeling of time-dependent, small- and large-scale economic systems. Furthermore, this new approach is methodologically compatible with mainstream sociology and institutional economics, allowing increased interdisciplinary cooperation that may influence policy and thereby affect industry and markets. And safety engineering stands to benefit from the accommodation of neuropsychology in understanding human error in the supervision and control of technology 相似文献