On the stability of compact supermassive objects

Proceeded from the gravitation equations proposed by one of authors it was argued in a previous paper that there can exist supermassive compact configurations of degenerated Fermi‐gas without events horizon. In the present paper we consider the stability of these objects by a method like the one used in the theory of stellar structure. It is shown that the configurations are stable.     

用正交多项式进行平面磁场拟合的一种新方法

提高现代舰艇磁隐身能力的前提是准确地了解和掌握舰艇空间磁场分布,和舰艇所处地区的地磁场分布情况.针对目前磁场插值或拟合中存在的精度不够高,需要网格化等问题,本文提出了一种基于正交多项式的平面磁场拟合方法.不同于一维正交多项式的拟合方法,此方法首先从一般的完备二维多项式族出发,然后用Gram-Schmidt正交化过程将此完备二维多项式族正交化,得到数值正交基底,然后以此正交基进行平面磁场拟合.为了解决分块拟合问题,又提出了紧支的概念,通过与拉格朗日二维插值的船模试验及仿真比较,发现此方法拟合精度比较高,能够较准确的反映平面磁场的分布,有一定的工程实用价值.     

Quad and compact multitemporal C-band PolSAR observations for crop characterization and monitoring

Monitoring crop condition using optical satellite indices has a legacy of several decades. Early warning of variances in crop production is vital in mitigating regional and global food insecurity. Adoption of optical vegetation indices for this purpose is widespread, yet cloud cover impedes the acquisition of these data. Although early research using scatterometers and aircraft hinted at the sensitivity of Synthetic Aperture Radar (SAR) responses to crop development, the implementation of satellite SAR observations in operational crop condition monitoring is limited. In the research presented here, volume-to-surface (V/S) scattering ratios derived from C-band RADARSAT-2 quad and simulated compact polarimetric (QP and CP) imagery are assessed for their potential to monitor crop growth. Both V/S ratios were strongly correlated with optical vegetation indices, including the widely adopted Normalized Difference and Soil Adjusted Vegetation Indices. The changes in the ratio of volume to surface scattering were correlated with variations in crop biomass. The results support the potential of a SAR scattering ratio for crop condition monitoring. In particular, encouraging results were reported for compact polarimetry, a mode that can be implemented to deliver broader swath coverage conducive to regional and national monitoring.     

致密星系群SCGG223的ASCA观测

光学观测表明,致密星系群ＳＣＧＧ ２２３中成员星系的速度弥散高达１１０６ｋｍ／ｓ,并且 整个星系群处于平衡状态．星系群的数值模拟也显示, ＳＣＧＧ ２２３是维里化的．这些光学 波段上的研究结果暗示, ＳＣＧＧ ２２３可能具有星系团量级的大引力质量,其星系际气体则 很可能处在极高温的状态．为了证实这些推测,作者在 １９９９年 ２月利用 ＡＳＣＡ卫星对 ＳＣＧＧ ２２３进行了 Ｘ射线观测．通过光谱分析,获得了它的气体温度和 ０．５～１０ ｋｅＶ波段 上的光度分别为ｋＴ＝１．４_（－０．４）~（＋．６）： ｋｅＶ和９．８５_（－２．０４）~（６．１１）× １０３６Ｊ Ｓ－１．与光学观测所作出的预计相 反,这些数值显示 ＳＣＧＧ ２２３是一个正常的低温星系群．由于 ＳＣＧＧ ２２３在 ０．５～１０ ｋｅＶ 波段上很暗,无法从ＡＳＣＡ获得的Ｘ射线表面亮度分布推算其总引力质量,因此,尚不 能直接判断它的质量是否真的像光学维里质量那样大．     

The youngest lobe-dominated radio sources

We present an analysis of multi-epoch global VLBI observations of the Compact Symmetric Objects: 2352+495 and 0710+439 at 5 GHz. Analysis of data spread over almost two decades shows strong evidence for an increase in separation of the outer components of both sources at a rate of 0.2h⁻¹c (for q=0.5 and H=100h km s⁻¹Mpc⁻¹). Dividing the overall sizes of the sources by their separation rates implies that these Compact Symmetric Objects have a kinematic age 10⁴ years. These results (and those for other CSOs) strongly argue that CSOs are indeed very young sources that probably evolve into much larger classical doubles.     

挤压成孔的研究

挤压成孔方法经常用于地基基础工程及非开挖铺设管线的施工中,作者简便介绍了几种挤压成孔方法及其应用,对挤压成孔的机理进行了研究,对挤压成孔方法对地层的适用范围进行了初步探讨。     

四川盆地西部致密碎屑岩含气领域勘探实践

四川盆地自１９７１ 年发现了中坝气田后,系统地对致密碎屑岩含气领域进行了研究,并做到理论与实践相结合,从而不断取得突破。在成都平原发现和有效开发了大中型致密砂岩气田,使储产量大幅度增长。加强对致密碎屑岩含气的基础地质研究、探讨天然气的富集规律、紧密结合勘探开发、认真解决科技创新和工艺方法,这样在川西气田的开发中将会获得良好的经济效益和社会效益。     

Stability and Grid Dispersion of the P-SV 4th-Order Staggered-Grid Finite-Difference Schemes

Stability and grid dispersion in the P-SV 4th-order in space, 2nd-order in time, displacement-stress staggered-grid finite-difference scheme is investigated in the case of a homogeneous unbounded medium. All results, however, also apply to the velocity-stress and displacement- velocity-stress finite-difference schemes. Independent stability conditions for the P and S waves are obtained by exact separation of equations for the two types of waves. Since the S-wave group velocity can differ from the actual velocity as much as 5% for the sampling ratio 1/5, commonly used in numerical modelling, the sampling of the minimum S wavelength by 6 grid spacings (with the velocity difference not larger than 2.5%) is recommended. Grid dispersion is strongest for a wave propagating in a direction of a coordinate axis and weakest for a wave propagating along a plane diagonal. Grid dispersion in the 4 ^th -order scheme for the sampling ratios s = 1/5 and s = 1/6 is smaller than grid dispersion in the 2 ^nd -order scheme for s = 1/10 and s = 1/12, respectively.     

坚硬致密岩层钻进用热压金刚石钻头的研究

针对坚硬致密岩石钻进中遇到的钻头打滑、钻进效率低的问题，通过改变弱包镶材料，加入强化的石墨颗粒，进行试验与研究，获得了颗粒状石墨能提高金刚石出刃的初步效果。随后对石墨颗粒的粒度和强化程度进行反复试验，得到石墨颗粒的粒度、含量和强化程度对金刚石出刃的影响关系；在此基础上研制成新型的热压金刚石钻头，生产试验表明能明显提高金刚石钻头的出刃效果，达到了提高钻进效果的目的。     

Genetic algorithms for determining the parameters of cellular automata in urban simulation

This paper demonstrates that cellular automata(CA) can be a useful tool for analyzing the process of many geographical phenomena.There are many studies on using CA to simulate the evolution of cites.Urban dynamics is determined by many spatial variables.The contribution of each spatial variable to the simulation is quantified by its parameter or weight.Calibration procedures are usually required for obtaining a suitable set of parameters so that the realistic urban forms can be simulated.Each pa-rameter has a unique role in controlling urban morphology in the simulation.In this paper,these pa-rameters for urban simulation are determined by using empirical data.Genetic algorithms are used to search for the optimal combination of these parameters.There are spatial variations for urban dynam-ics in a large region.Distinct sets of parameters can be used to represent the unique features of urban dynamics for various subregions.A further experiment is to evaluate each set of parameters based on the theories of compact cities.It is considered that the better set of parameters can be identified ac-cording to the utility function in terms of compact development.This set of parameters can be cloned to other regions to improve overall urban morphology.The original parameters can be also modified to produce more compact urban forms for planning purposes.This approach can provide a useful ex-ploratory tool for testing various planning scenarios for urban development.