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841.
Metallic resonator Q-factor is very sensitive to the resonator's material, its thermal and chemical treatment, design, and environment; i.e., pressure and temperature. In order to obtain higher accuracy for CVG it is necessary to use resonator evacuation. Resonator mass plays a very important role in sensitivity to angle rate, in stability of vibration, in response to environmental condition changes, and also to external vibration and shock resistance. tnnalabs Holding Inc. uses a cylindrical resonator with increased rim thickness of up to 2 mmn and more. This concerns resonator material and design parameters selection, material thermal treatment to increase resonator Q-factor, and improved control algorithms in order to increase metallic CVG accuracy. As a result, CVG bias instability of 0.025 degth and random walk of 0.008 degvh for the resonator diameter 43 mmn, and 0.2 deg/h for the resonator diameter 25 mm were obtained. Future opportunities for Innalabs CVG is also discussed herein. Test results are presented for CVG43 and CVG25. Three-axis CVG unit under control of one DSP "Sharc" and IMU parameters are forecasted.  相似文献   
842.
A novel thin line detection algorithm for use in low-altitude aerial vehicles is presented. This algorithm is able to detect thin obstacles such as cables, power lines, and wires. The system is intended to be used during urban search and rescue operations, capable of dealing with low-quality images, robust to image clutter, bad weather, and sensor artifacts. The detection process uses motion estimation at the pixel level, combined with edge detection, followed by a windowed Hough transform. The evidence of lines is tracked over time in the resulting parameter spaces using a dynamic line movement model. The algorithm's receiver operating characteristic curve (ROC) is shown, based on a multi-site dataset with 86 videos with 10160 wires spanning in 5576 frames.  相似文献   
843.
A technique for selecting a rational variant of a multifunctional aircraft system using the analytic hierarchy process is proposed and a solution of a practical problem is presented.  相似文献   
844.
845.
Investigation of the infrared characteristics of a rocket nozzle is very important for the study of infrared initiating technology. The Narrow-Band Zone model is developed for that purpose. The spectral transmission and absorption factors are introduced, and the equations between radiative heat flux and the temperature of waill surfaces and gas are developed. The radiative heat transfer in one axisymmetric cylindrical enclosure filled with homogeneous radiative participating medium is computed with the Narrow-Band Zone model and compared with those in the reference documents. The comparison shows good agreement. The radiative heat transfer to the nozzle of one rocket engine is also calculated with the Narrow-Band Zone model, and the outgoing radiative energy flux and energy rate integrated in a mid-wave infrared band 2-6 pm, a long-wave infrared band 8-14 pm and the full wave band are analyzed. The following conclusions can be derived: the spectral radiation from the inlet and outlet of the nozzle show apparent spectral discontinuity, which appears greater in the 2.7-2.95 pm than in the neighboring wave band. The spectral outgoing radiative energy flux of nozzle wail is similar to that of gray body, which decreases with wavelength in 2-14 pm. The outgoing radiative energy flux on the nozzle wall is greater in the cylindrical and contracting section of nozzle, but smaller in the divergent section, which is determined by temperature. The nozzle of the rocket engine radiates most energy in the mid-wave surfaces by absorption. The most important feature of gas radiation is the strong selection of the waveband, so the detailed study of the infrared characteristics of nozzle of the rocket engine should be carried out on narrow-band computation.  相似文献   
846.
The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as “central tenets”, for example, the importance of radio science in establishing the conducting upper layer. The central tenets are distinguished from additional findings that merely corroborate, or are explained by, the global circuit model. Using this analysis it is possible to specify which observations are preferable for detecting global circuits in extraterrestrial atmospheres. Schumann resonances, the extremely low frequency signals generated by excitation of the surface-ionosphere cavity by electrical discharges, are identified as the most useful single measurement of electrical activity in a planetary atmosphere.  相似文献   
847.
Congress authorized NASA's Prometheus Project in February 2003, with the first Prometheus mission slated to explore the icy moons of Jupiter. The project had two major objectives: 1) to develop a nuclear reactor that would provide unprecedented levels of power and show that it could be processed safely and operated reliably in space for long-duration, deep-space exploration; and 2) to explore the three icy moons of Jupiter - Callisto, Ganymede, and Europa - and return science data that would meet the scientific goals as set forth in the Decadal Survey Report of the National Academy of Sciences. Early in project planning, it was determined that the development of the Prometheus nuclear-powered spaceship would be complex and require the intellectual knowledge residing at numerous organizations across the country. In addition, because of the complex nature of the project and the multiple partners, approaches beyond those successfully used to manage a typical JPL project would be needed. This describes the key experiences in managing Prometheus, which should prove useful for future projects of similar scope and magnitude.  相似文献   
848.
Waveform Design for Multistatic Radar Detection   总被引:1,自引:0,他引:1  
We derive the optimal Neyman-Pearson (NP) detector and its performance, and then present a methodology for the design of the transmit signal for a multistatic radar receiver. The detector assumes a Swerling I extended target model as well as signal-dependent noise, i.e., clutter. It is shown that the NP detection performance does not immediately lead to an obvious signal design criterion so that as an alternative, a divergence criterion is proposed for signal design. A simple method for maximizing the divergence, termed the maximum marginal allocation algorithm, is presented and is guaranteed to find the global maximum. The overall approach is a generalization of previous work that determined the optimal detector and transmit signal for a monostatic radar.  相似文献   
849.
The telecommunications market is reaching new types of customers who require their applications anywhere and anyway. Therefore, the DVB-RCS standard, which had great success in the fixed version is changing in this direction. The main objective of this work is to give an overview of architectures and technologies that can be used for implementation of a first-generation of advanced mobile satellite systems for the provision of broadband multimedia services.  相似文献   
850.
The Polar Balloon Atmospheric Composition Experiment (P-BACE) is a new generation of neutral gas mass spectrometer based on the time-of-flight principle. P-BACE is the scientific experiment on the Mars Environment Analog Platform (MEAP) flown successfully on a balloon mission in summer 2008. The MEAP mission was flown with a 334,000 m3 helium balloon in the stratosphere on a semicircular trajectory from northern Sweden around the North Pole to Canada using the summer northern hemispheric wind current. The atmospheric conditions at an atmospheric altitude of 35–40 km are remarkably similar to those on the surface of Mars and thus the balloon mission was an ideal testbed for our mass spectrometer P-BACE. Originally this instrument was designed for in situ measurements of the chemical composition of the Martian atmosphere.P-BACE has a unique mass range from 0 to 1000 amu/q with a mass resolution mm (FWHM) > 1000, and the dynamic range is at least six orders of magnitude. During this experiment, the acquisition of one mass spectrum is a sum of 65,535 single spectra, recorded in a time frame of 66 s.The balloon mission lasted 5 days and had successfully demonstrated the functionality of the P-BACE instrument during flight conditions. We had recorded more than 4500 mass spectra. With little modifications, P-BACE can be used on a planetary mission for Mars, but for example also for Venus or Mercury, if placed on a satellite.  相似文献   
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