排序方式: 共有12条查询结果,搜索用时 31 毫秒
1.
Garenaux K. Merlet T. Alouini M. Lopez J. Vodjdani N. Boula-Picard R. Fourdin C. Chazelas J. 《Aerospace and Electronic Systems Magazine, IEEE》2007,22(2):3-8
Radar systems require transmission of very high purity signals. Photonics is now mature enough to achieve analog transmission with very low noise, strong immunity, and wide-bandwidth even in harsh environments. We present our recent developments of optimized optical links dedicated to radar and multifunction systems 相似文献
2.
A mission template for exploration and damage mitigation of potential hazard of Near Earth Asteroids
D. C. Hyland H. A. Altwaijry R. Margulieux J. Doyle J. Sandberg B. Young N. Satak J. Lopez S. Ge X. Bai 《Cosmic Research》2010,48(5):437-442
The Apophis Exploratory and Mitigation Platform (AEMP) concept was developed as a prototype mission to explore and potentially
deflect the Near Earth Asteroid (NEA) 99942 Apophis. Deflection of the asteroid from the potential 2036 impact will be achieved
using a gravity tractor technique, while a permanent deflection, eliminating future threats, will be imparted using a novel
albedo manipulation technique. This mission will serve as an archetypal template for future missions to small NEAs and could
be adapted to mitigate the threat of collision with other potential Earth-crossing objects. 相似文献
3.
The subject paper (July 1993) has raised some issues regarding the probability of the Instrument Landing System (ILS) radiating out-of-tolerance vertical guidance signals. An independent study has substantiated the findings of that paper and adds further concern regarding some FAA ILS snow procedures. The principal conclusions of this paper are: 1) an analysis, based on Walton's discovery of rare snow conditions that cause the null-reference ILS antenna image to disappear, indicates that these conditions can cause out-of-tolerance guidance signals, 2) operation without a monitor of the image radiation can result in signal-in-space guidance signal errors that are significantly beyond the intended limit values, and 3) the integrity of image glide path equipment in snow environments does not satisfy the ILS integrity requirements 相似文献
4.
Duarte C.C. Dorta Naranjo B.P. Lopez A.A. del Campo A.B. 《Aerospace and Electronic Systems Magazine, IEEE》2007,22(2):22-26
Continuous wave lineal frequency modulated (CWLFM) radar presents some interesting advantages for coast surveillance and control as well as low probability of interception (LPI). This paper presents real results obtained with a radar prototype and processed with ISAR techniques. Also, results of an automatic ship identification system applied to simulated ISAR images are exposed. Moreover, radar behavior with unfavorable meteorological conditions is discussed 相似文献
5.
R.E. Lopez 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Space physics is not a subject typically found in the undergraduate curriculum, and it is rare even at the graduate level. On the other hand, the basis of space physics is electromagnetism and the motion of charged particles, which are common topics in both the introductory and advanced undergraduate physics curriculum, and examples from space physics can be used to enliven instruction. In this paper, I will discuss various topics commonly found in both introductory and upper-division electricity and magnetism classes where examples from space physics may facilitate student understanding or provide interesting, real-life examples of electromagnetism in action. 相似文献
6.
R.E. Lopez N.A. Gross 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
In recent years there has been considerable research in undergraduate physics education regarding the application to classroom instruction of techniques that are generally referred to as active engagement techniques. However, in very few cases have such pedagogical strategies been applied to graduate-level instruction. In this paper we describe an innovative application of a variety of active engagement techniques at the graduate summer school conducted by the Center for Integrated Space Weather Modeling, a Science and Technology Center funded by the National Science Foundation. We believe that the model presented here can serve as a valuable guide to other group contemplating space physics education at all levels, as well as graduate education generally. 相似文献
7.
We review the major advances in understanding the morphologies and kinematics of supernova remnants (SNRs). Simulations of SN explosions have improved dramatically over the last few years, and SNRs can be used to test models through comparison of predictions with SNRs’ observed large-scale compositional and morphological properties as well as the three-dimensional kinematics of ejecta material. In particular, Cassiopeia A—the youngest known core-collapse SNR in the Milky Way—offers an up-close view of the complexity of these explosive events that cannot be resolved in distant, extragalactic sources. We summarize the progress in tying SNRs to their progenitors’ explosions through imaging and spectroscopic observations, and we discuss exciting future prospects for SNR studies, such as X-ray microcalorimeters. 相似文献
8.
It is pointed out that fully automatic hands-off landing (autoland) capability for commercial aircraft, using the Global Positioning System (GPS), has not been demonstrated, and that ground multipath errors limit vertical positioning accuracy. An evolving integrated-sensor-based architecture for approach and landing, called the tunnel concept, is examined. The precise velocity information available could substantially reduce the vertical accuracy requirement for autoland 相似文献
9.
D. C. Hyland H. A. Altwaijry S. Ge R. Margulieux J. Doyle J. Sandberg B. Young X. Bai J. Lopez N. Satak 《Cosmic Research》2010,48(5):430-436
In the later stages of a combined mission of exploration and damage mitigation of a hazardous Near Earth Asteroid (NEA), sufficiently
detailed tracking, orbit prediction, mass distribution, and physical properties data have been accumulated. It may be desirable
to implement a “slow push” damage mitigation technique that is capable of altering the NEA orbit continuously and permanently.
This possibility was suggested in a companion paper that outlined an archetypal exploration/mitigation mission to the NEA
99942 Apophis, which is achieved using a novel albedo change approach. The details and apparatus used in the albedo modification
technique are described in the paper. We describe the design details and the constraints on particle size (to prevent electrostatic
levitation and escape) and on the dispensing speed (to achieve the desired coverage zone and prevent particles from orbiting
or escaping). 相似文献
10.
This paper presents a comprehensive review of uncertainties involved in flight vehicle structural damage monitoring, diagnosis, prognosis and control. Uncertainties can cause infeasibilities, false diagnosis and very imprecise prognosis if not correctly taken into account. The purpose of this paper is to review existing methods that have been developed to address the problem of uncertainty in the area of damage sensing, diagnosis, prognosis and control in flight vehicles. The mathematical and statistical methods in analyzing uncertainty are first presented and compared. Then, the different sources and perspectives of uncertainties in the damage assessment process are presented and classified. Following this, diagnosis and prognosis methods are reviewed. Final review section covers the control of damaged structure under uncertainty. In each section and in the concluding remarks section the research challenges in the field of flight vehicle structural damage sensing, diagnosis and prognosis methods as well as control under uncertainty are identified and promising new ideas are discussed. 相似文献