曙光4000A上三维叠前深度偏移并行计算的应用设计

波动方程叠前深度偏移在地震勘探成像处理方面起着不可替代的作用。随着高性能大规模并行计算机技术的发展,波动方程叠前深度偏移计算在地震勘探中的应用有了很大进步。在波动方程叠前深度偏移处理中,庞大的数据规模与海量计算对计算性能提出了很高的要求。曙光4000A超级计算机系统是我国目前峰值速度最快的商用超级计算机系统,无论是硬件平台建设还是应用软件的配置方面,都具有良好的应用性能。基于该系统设计的三维波动方程叠前深度偏移(炮域)PSDM软件,采用动态负载平衡并行计算模式,具有较高的计算效率,高度的可扩展性和可靠性。     

线性矩法估计参数的保证修正值系数B的推求

在设计洪水的抽样误差估计中,采用保证修正值系数B方法估计均方差简单易用。应用线性矩法估计频率分布曲线的参数,有较好的无偏性和有效性,具有一定的应用前景。目前线性矩法的B值诺模图尚未确定,给用线性矩法确定参数时估计抽样误差带来了难度与不便。采用统计试验,分析了离差系数、偏态系数和样本长度对B值的影响,结果表明线性矩法估计参数时仍可采用保证修正值系数B值诺模图方法来估计抽样误差,并推求了不同偏态系数、设计频率情形下的B值,制成了线性矩法的B值诺模图备用。     

基于B/S结构的网上考试系统

介绍了基于B／S结构的网上考试系统应用于气象部门的理论研究，并分析了系统总体结构，提供了一种应用SQL数据库以及ASP编程实现的网络考试系统，详细阐述了科目管理、随机生成试卷等模块的设计与实现，以及相关数据库表的结构。     

The complex gravitational lens system B1933+503

We report the discovery of the most complex arcsec-scale radio gravitational lens system yet known. B1933+503 was found during the course of the CLASS survey and MERLIN and VLA radio maps reveal up to 10 components. Four of these are compact and have flat spectra; the rest are more extended and have steep spectra. The background lensed object appears to consist of a flat-spectrum core (quadruply imaged) and two compact 'lobes' symmetrically disposed relative to the core. One of the lobes is quadruply imaged while the other is doubly imaged. An HST observation of the system with the WFPC2 shows a galaxy with an axial ratio of 0.5, but none of the images of the background object is detected. A redshift of 0.755 has been measured for the lens galaxy.     

Modelling the 10-image lensed system B1933+503

A gravitational lens model is presented for the newly discovered 10-image system B1933+503. The underlying object, revealed by modelling, is a triple radio source on the scale of a couple of hundred mas that is well-aligned along the line of sight with a foreground and somewhat flattened lensing galaxy, the orientation and location of which match those of an observed galaxy, known to be at a redshift of 0.755. Uncertainties in the modelling are obtained by a Monte Carlo exercise. Observational tests of the lens model are proposed, and the time delays between various pairs of images are determined, as the core of the source is known to be significantly variable. Future observations of the lens hold the key to using B1933+503 to constrain Hubble's constant. Despite the absence of a source redshift, the utility of the system as a probe of the structure of the lens galaxy is unparalleled as it provides a surfeit of easily identifiable constraints for modelling the system.     

Cygnus A: stars, dust and cones

We present new Hubble Space Telescope ( HST  ) continuum and spectral line images of the radio galaxy Cygnus A. The images show much complex structure in the central kpc². Continuum images show the central dust lane in detail, allowing detailed maps of E ( B  −  V ) to be constructed; the dust appears to follow a roughly Galactic extinction law. The emission-line components are resolved in the line images and investigated in detail. A clear 'opening cone' morphology is found, especially in the lines of Hα and [O  i ]. Blue condensations are seen in the south-eastern emission component and surrounding the central region. These are almost certainly due to star formation, which began <1 Gyr ago as deduced from the colour of the regions. More extended blue continuum is also seen and corresponds to the blue polarized component detected by other recent spectropolarimetric observations.     

A timing formula for main-sequence star binary pulsars

In binary radio pulsars with a main-sequence star companion, the spin-induced quadrupole moment of the companion gives rise to a precession of the binary orbit. As a first approximation one can model the secular evolution caused by this classical spin-orbit coupling by linear-in-time changes of the longitude of periastron and the projected semi-major axis of the pulsar orbit. This simple representation of the precession of the orbit neglects two important aspects of the orbital dynamics of a binary pulsar with an oblate companion. First, the quasiperiodic effects along the orbit, owing to the anisotropic 1/ r ³ nature of the quadrupole potential. Secondly, the long-term secular evolution of the binary orbit, which leads to an evolution of the longitude of periastron and the projected semi-major axis, which is non-linear in time.   In this paper a simple timing formula for binary radio pulsars with a main-sequence star companion is presented which models the short-term secular and most of the short-term periodic effects caused by the classical spin-orbit coupling. I also give extensions of the timing formula that account for long-term secular changes in the binary pulsar motion. It is shown that the short-term periodic effects are important for the timing observations of the binary pulsar PSR B1259–63. The long-term secular effects are likely to become important in the next few years of timing observations of the binary pulsar PSR J0045–7319. They could help to restrict or even determine the moments of inertia of the companion star and thus probe its internal structure.   Finally, I reinvestigate the spin-orbit precession of the binary pulsar PSR J0045–7319 since the analysis given in the literature is based on an incorrect expression for the precession of the longitude of periastron. A lower limit of 20° for the inclination of the B star with respect to the orbital plane is derived.     

Survey on PCDDs and PCDFs in sediments and soils in Ya-Er Lake area, China

INTRODUCTIONOverthepastseveralycars,considerableinteffethasbocenteIdontheenvir0nmentalbehaviouroftoxicandpersistritcomP0undssuchashalogenatalaromat-ies,inparticularthepolychiorinataldibopdioxins(PCDDe)andpolydil0rinateddi~fUtansrpCDFs).ManyofthesecomPounds,espedllythosewithahighdegere0fchiorinesubstitution,arehighlylipophiliccontawhnantSwithlowWhtersolubility,highre-sistancet0chdricaltransformationsandlowwhcrobiologhaldegradatfonpeatnnann,l988,Bromanetal.,l989,Hites,l990)whichexplain…     

参数调整对气象预测的B-P网络模型性能的影响

为了探索ＢＰ网络的参数调整特性,进行了参数α、β的选取对ＢＰ算法的收敛速度和模型的稳定性的影响研究。通过ＢＰ网络用于气象预测建模的参数调整个例分析表明：参数α、β的取值对ＢＰ模型的稳定性无显著影响,但参数值的调整尤其是β值的调整对建模的收敛速度有明显的影响。     

Mathematical Modelling and Accuracy Testing of Spot Level 1B Stereopairs

During a project concerned with DEM generation using SPOT stereoscopic imagery, difficulties were experienced when using Level 1B stereopairs for the task. This paper presents a mathematical solution to overcome this problem which has been implemented at the University of Glasgow. Results are included from experimental tests which were carried out over a test field in Jordan using this solution. These tests used five SPOT Level 1B stereopairs together with a single SPOT Level 1A stereopair for comparative purposes. The residual errors at the ground control points and independent check points are given and show that a satisfactory solution was achieved.