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951.
The towfish location and orientation problems that arise in using side-scan sonar to detect objects on the sea bottom are treated separately. Data which locate the towfish relative to the ship are usually deteriorated by multipath receptions and other effects. In order to overcome this serious degradation in the location measurements, a modified Kalman filter is proposed. An estimate of the state transition matrix for this filter is derived, and a means of switching between two Kalman gains is suggested. The feasibility of the proposed filter is justified by a case study. Improved estimates of towfish pitch and heading measurements are obtained by a separate system employing model identification and subsequent Kalman filtering. Application of these methods to data from similar towed side-scan sonar systems should yield significant gains in object location accuracy 相似文献
952.
本文介绍一种无线数据传接口及控制装置。装置中采用计算机软件实现串—并、并—串变换及频率调制、其硬件成本低廉,工作可靠,可用于速率为50、300、600或1200bps的数传通信。 相似文献
953.
This study on the environmental quality of the Qingdao Cove intertidal zone sewage discharge area is based on data obtained
from the December of 1989 and 1990 macrobenthos investigations there, and uses pollution indicator species and computer aided
cladistic analysis to divide the area into a polluted area and a semipolluted area. The study showed the environmental quality
in 1990 improved over that in 1989.
Project supported by the National Natural Science Fonndation of China 相似文献
954.
Gamma—Ray Bursts:Afterglows and Central Engines 总被引:5,自引:0,他引:5
K.S.Cheng T.Lu 《中国天文和天体物理学报》2001,1(1):1-20
Gamma-ray bursts (GRBs) are the most intense transient gamma-ray events in the sky; this, together with the strong evidence (the isotropic and inhomogeneous distribution of GRBs detected by BASTE) that they are located at cosmological distances, makes them the most energetic events ever known. For example, the observed radiation energies of some GRBs are equivalent to the total convertion into radiation of the mass energy of more than one solar mass. This is thousand times stronger than the energy of a supernova explosion. Some unconventional energy mechanism and extremely high conversion efficiency for these mysterious events are required. The discovery of host galaxies and association with supernovae at cosmoligical distances by the recently launched satellite of BeppoSAX and ground based radio and optical telescopes in GRB afterglow provides further support to the cosmological origin of GRBs and put strong constraints on their central engine. It is the aim of this article to review the possible central engines, energy mechanisms, dynamical and spectral evolution of GRBs, especially focusing on the afterglows in multi-wavebands. 相似文献
955.
Xinxian Lu 《中国地理科学(英文版)》1992,2(3):256-265
The developed regions are faced with the problems of regional comprehensive development, and the research on regional comprehensive
development has become a trend in the world. To optimize regional industrial structure and to select and determine scientifically
the spatial development strategy of regional industries are the central themes to be solved for the research on regional comprehensive
development in the developed regions. This paper proposed the basis for optimizing regional industrial structure, and the
main factors of selecting and determining the regional leading industries. Based on this, the paper puts forward the leading
industries and the spatial development strategy in Shanghai-Nanjing-Hangzhou area in the future ten or more years. Combined
with the situation of Shanghai-Nanjing-Hangzhou area, the paper also discusses some problems of locating superior developing
axis to benefit the rational distribution of regional productive forces. 相似文献
956.
在8000至8670的波长范围内,利用一个由144颗恒星光谱组成的光谱厍,我们对57个巨椭圆和S0星系(M_B<-21)的光谱和它们的平均光谱进行了光谱合成.这个光谐库包括了光谱型为G,K和M的巨星和矮星,它具有的金属丰度[Fe/H]覆盖了-0.1到-0.5的范围,表面重力log g为1.0至5.0.光谱合成的结果表明:巨椭圆和S0星系的金属丰度约为太阳的一倍半;有效表面重力分布在3.2—4.1的范围内;矮星在8400附近光的贡献可与巨星相比较. 相似文献
957.
腾冲火山区地表垂直形变分析 总被引:11,自引:3,他引:8
对腾冲火山区1998~2000年的3期垂直形变资料进行了分析,进而利用相关资料得出与计算有关的参数,再用多元Mogi模型反演了岩浆房的位置和大小,所得出的结果与地震层析反演结果基本相似。分析反演结果,认为火山区可能存在多个岩浆房,并有岩脉相通。 相似文献
958.
在Li&Yang (2 0 0 1 )所给出的局部对流理论的基础上 ,我们进一步采用梯度型方案给出了非局部对流理论 ,并将它用于太阳模型中。这一理论考虑了恒星对流区内的非局部效应 ,它得到了一个与原来用混合长理论或局部理论给出的结果有所区别的对流区 ,扩散效应很明显。但是 ,目前我们的理论还不能处理时间相关的对流以及对流超射等问题。这些问题将在后续工作中加以考虑。当把这一理论应用于太阳模型中时 ,我们发现它对标准太阳模型的改正非常微小。我们讨论了这一现象 ,并对其加以解释 相似文献
959.
In this paper, a new index is proposed for the selection of the best regional frequency analysis method. First, based on the theory of reliability, the new selective index is developed. The variances of three regional T‐year event estimators are then derived. The proposed methodology is applied to an actual watershed. For each regional method, the reliability of various T‐year regional estimates is computed. Finally, the reliability‐based selective index graph is constructed from which the best regional method can be determined. In addition, the selection result is compared with that based on the traditional index, root mean square error. The proposed new index is recommended as an alternative to the existing indices such as root mean square error, because the influence of uncertainty and the accuracy of estimates are considered. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
960.
Results from an ionoipheric founding rocket of the “mother-daugther” type, equipped with an 8 keV electron accelerator, is reported. The emphasis is on the results obtained from the three plasma probes which monitored both the electron- and the ion-population. It is shown that no significant increase of the electron density was observed during the beam injections. However, the electron temperature varied rapidly during these pulses. The influence of the vehicle charging on the measurements is also discussed. 相似文献