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311.
Cross regulation performance of multioutput series resonant converter (SRC) topologies using capacitive or inductive filters is analyzed. The steady state cross regulation characteristics are derived using the state-plane techniques and are illustrated by the examples of two-output SRCs with capacitive and inductive filters. The characteristic curves show that over some range of output currents, the cross regulation performance of an SRC with an inductive filter is much improved over the SRC with capacitance filter and less dependent on the tolerances in leakage inductances and the loading on unregulated outputs. It is shown that the converter control characteristics of an SRC with an inductive filter are relatively unaffected by the addition of the second output. The theoretical results are verified by simulation 相似文献
312.
Wilson T.G. Lee F.C.Y. Burns W.W. Owen H.A. 《IEEE transactions on aerospace and electronic systems》1975,(2):238-244
It recently has been shown in the literature that many dc-to-squarewave parallel inverters which are widely used in power-conditioning applications can be grouped into one of two families. Each family is characterized by an equivalent RLC network. Based on this approach, a classification procedure is presented for self-oscillating parallel inverters which makes evident natural relationships which exist between various inverter configurations. By utilizing concepts from the basic theory of negative resistance oscillators and the principle of duality as applied to nonlinear networks, a chain of relationships is established which enables a methodical transfer of knowledge gained about one family of inverters to any of the other families in the classification array. 相似文献
313.
The AE-C spacecraft skimmed through the southern polar cusp at a 400 km altitude during a large geomagnetic storm on September 21, 1977. This period has been designated as a special IMS period, and the AE-C data were acquired close to the times that data were acquired by the DMSP satellite at nearly the same location over the southern polar cap, and by the GEOS satellite located near the noon-meridian in the northern hemisphere. Low energy electrons (1-500 eV) were measured with the photoelectron spectrometer experiment experiment onboard AE-C. This instrument was operated in the mode which measured precipitating electron fluxes and backscattered electron fluxes in alternating 4s intervals with two sensors. A region of intense precipitating electron fluxes was observed near 0924 UT on September 21, 1977 extending from 69 degree invariant latitude at 1100 MLT to 72 degree invariant latitude at 1152 MLT. From the spectra of the precipitating electrons, this region is identified as the southern polar cusp. Since the K
p equals 7- during this time, the displacement of the cusp down to these low latitudes is not unreasonable. Particle data obtained from the DMSP satellite on orbits close to AE-C, confirm that the position of the cusp was rapidly changing during this period, and was displaced to latitudes equatorward of the quiet time position. A second region of intense fluxes of precipitating electron was observed by AE-C at approximately 0933 UT from 69 degree invariant latitude near 1700 MLT to 66 degree invariant latitude near 1730 MLT. This region of low energy electron fluxes is characterized by slightly harder energy spectra and is interpreted as being the afternoon auroral zone. The remarkable and fortunate location of the AE-C, DMSP, and GEOS spacecraft during this special IMS period will allow future correlative studies aimed at the determination of the shape of the magnetosphere during very disturbed conditions. 相似文献
314.
Lee Seegmiller H. Bader Jan B. Cooney John P. DeYoung Anemarie Donaldson Ralph W. Gunter William D. Harrison Dean R. 《Aerospace and Electronic Systems Magazine, IEEE》1986,1(5):16-20
A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. II is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to psoition the laser beams in the channel flow. Techniques used to seed the flow with 0.5-?-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy. 相似文献
315.
Jen King Jao Lee C.E. Ayasli S. 《IEEE transactions on aerospace and electronic systems》1999,35(2):614-626
Analysis of UHF synthetic aperture radar (SAR) images has revealed a spatially correlated phase structure over a resolved target such as a long wire or a large truck. This phase variation, approximated by a simple, range-dependent factor 4πr/λ, results in a line-shaped image spatial spectrum. Such image phase and spectral features can be exploited by coherent spatial filtering to improve target-to-clutter ratios of large targets and stationary target detectability in a strong clutter environment 相似文献
316.
不同矢量偏角下二元喷管内流特性的数值研究 总被引:1,自引:1,他引:0
应用多重网格MacCormack显式格式对不同矢量角下二元喷管的内部流动进行了模拟分析。计算时, 在细网格上采用了雷诺平均N-S方程与k-ε湍流模型方程;在粗网格上则采用Euler方程。数值计算给出了较清晰的流谱, 壁面压力分布的计算也与实验结果相吻合。通过计算结果分析了矢量喷管几何参数对流场的影响, 并对矢量喷管的推力特性进行了数值研究。 相似文献
317.
318.
1 INTRODUCTION
Today's machine tool industries are facing unprecedented challenges brought about by development of outsourcing and low cost manufac-turing in Asia. Manufacturing outsourcing provided many opportu-nities but also added challenges to produce and deliver products with improved productivity, quality, service and costs. Lead times must be cut short to their extreme extend to meet need the changing demands of customers in different regions of the world. Products are required to be make-to-order, which requires a tight control and near-zero downtime of the plant floor, equipment and devices. 相似文献