Optical Flash of GRB 990123: Constraints on the Physical Parameters of the Reverse Shock

The optical flash accompanying GRB 990123 is believed to be powered by the reverse shock of a thin shell. With the best-fit physical parameters for GRB 990123 and the assumption that the parameters in the optical flash are the same as in the afterglow, we show that: 1) the shell is thick rather than thin, and we have provided the light curve for the thick shell case which coincides with the observation; 2) the theoretical peak flux of the optical flash accounts for only 3×10~-4 of the observed. In order to remove this discrepancy, the physical parameters, the electron energy and magnetic ratios, εe and εB, should be 0.61 and 0.39, which are very different from their values for the late afterglow.     

A micromechanical finite element model for linear and damage‐coupled viscoelastic behaviour of asphalt mixture

This study presents a finite element (FE) micromechanical modelling approach for the simulation of linear and damage‐coupled viscoelastic behaviour of asphalt mixture. Asphalt mixture is a composite material of graded aggregates bound with mastic (asphalt and fine aggregates). The microstructural model of asphalt mixture incorporates an equivalent lattice network structure whereby intergranular load transfer is simulated through an effective asphalt mastic zone. The finite element model integrates the ABAQUS user material subroutine with continuum elements for the effective asphalt mastic and rigid body elements for each aggregate. A unified approach is proposed using Schapery non‐linear viscoelastic model for the rate‐independent and rate‐dependent damage behaviour. A finite element incremental algorithm with a recursive relationship for three‐dimensional (3D) linear and damage‐coupled viscoelastic behaviour is developed. This algorithm is used in a 3D user‐defined material model for the asphalt mastic to predict global linear and damage‐coupled viscoelastic behaviour of asphalt mixture. For linear viscoelastic study, the creep stiffnesses of mastic and asphalt mixture at different temperatures are measured in laboratory. A regression‐fitting method is employed to calibrate generalized Maxwell models with Prony series and generate master stiffness curves for mastic and asphalt mixture. A computational model is developed with image analysis of sectioned surface of a test specimen. The viscoelastic prediction of mixture creep stiffness with the calibrated mastic material parameters is compared with mixture master stiffness curve over a reduced time period. In regard to damage‐coupled viscoelastic behaviour, cyclic loading responses of linear and rate‐independent damage‐coupled viscoelastic materials are compared. Effects of particular microstructure parameters on the rate‐independent damage‐coupled viscoelastic behaviour are also investigated with finite element simulations of asphalt numerical samples. Further study describes loading rate effects on the asphalt viscoelastic properties and rate‐dependent damage behaviour. Copyright © 2006 John Wiley & Sons, Ltd.     

罗氏沼虾育苗用水中Mg2+与Ca2+含量及Mg2+/Ca2+对出苗率的影响

１９９１年３－６月和１９９２年３－６月在南汇县东海水产养殖公司对罗氏沼虾育苗用水调配原则与不同基础水的调配方法进行试验研究。结果表明，育苗用水中Ｍｇ＾２＋与Ｃａ＾２＋含量及Ｍｇ＾２＋／Ｃａ＾２＋必须达到一定的范围，这是调配的基本原则。以鱼塘水作基础水时，需添加６种化学药品，其中Ｍｇ＾２＋与Ｃａ＾２＋含量可适范围分别为３００．０－４４０．０ｍｇ／Ｌ与１７０．０－２４４．０ｍｇ／Ｌ，Ｍｇ＾２＋／Ｃａ＾     

中国岩溶洞穴数据库建设研究

为了有效地保护和利用洞穴这一具有多方面价值的、不可再生的国土资源而建立了中 国岩溶洞穴数据库,首期完成900个洞穴数据建库工作。数据库中含有图、文、声、 像等方面的数字化信息,数据容量2500MB,作为非商业数据,可通过授权共享,为 科研机构、旅游行业和公众提供服务。     

科学计算可视化技术的研究与应用

本文介绍了科学计算可视化技术的发展和应用情况，论述了这一新技术的特点及其在油气藏描述，工程设计ＣＡＤ等学科的应用和发展趋势。阐述了目前国际国内计算机图形学领域具体的研究方向和方法及图形软件、图形硬件的发展概况。     

The ACPI Climate Change Simulations

The Parallel Climate Model (PCM) has been used in the Accelerated ClimatePrediction Initiative (ACPI) Program to simulate the global climateresponse to projected CO₂, sulfate, and other greenhouse gasforcingunder a business-as-usual emissions scenario during the 21st century. In these runs, the oceans were initialized to 1995 conditions by a group from the Scripps Institution of Oceanography and other institutions. An ensemble of three model runs was then carried out to the year 2099 using the projected forcing. Atmospheric data fromthese runs were saved at 6-hourly intervals (hourly for certain criticalfields) to support the ACPI objective of accurately modeling hydrologicalcycles over the western U.S. It is shown that the initialization to1995 conditions partly removes the un-forced oceanic temperature and salinity drifts that occurred in the standard 20th century integration. The ACPI runs show a global surface temperature increase of 3–8 °C over northern high-latitudes by the end of the 21st century, and 1–2 °C over the oceans. This is generally within ±0.1°Cof model runs without the 1995 ocean initialization. The exception is in theAntarctic circumpolar ocean where surface air temperature is cooler in theACPI run; however the ensemble scatter is large in this region. Althoughthe difference in climate at the end of the 21st century is minimalbetween the ACPI runs and traditionally spun up runs, it might be largerfor CGCMs with higher climate sensitivity or larger ocean drifts. Ourresults suggest that the effect of small errors in the oceans (such asthose associated with climate drifts) on CGCM-simulated climate changesfor the next 50–100 years may be negligible.     

Geochemistry and occurrence of inorganic gas accumulations in Chinese sedimentary basins

Inorganic gases are commonly seen in eastern China and occasionally in southern China from the shallow water columns above hot and cold springs. The gases contain 68% to nearly 100% CO₂, with δ¹³C_CO2 and δ¹³C₁ values in the range of −1.18‰ to −6.00‰ and −19.48‰ to −24.94‰, respectively. All of the 34 large inorganic CO₂ and one inorganic methane accumulations discovered in China are distributed in eastern parts of the country, from both onshore and continental shelf basins. No commercial inorganic gas accumulation has been found in central and western China. This is a review of the occurrence and geochemical characteristics of inorganic gas accumulations in Chinese sedimentary basins. A detailed study of gas samples collected from four representative inorganic CO₂ pools and one possible inorganic methane pool indicates that inorganic alkane gases typically show δ¹³C₁ values greater than −10‰ versus PDB (mostly −30‰), with a positive stable carbon isotope sequence of δ¹³C₁ < δ ¹³C₂ < δ¹³C₃ < δ ¹³C₄. In contrast, the δ¹³C₁ values of biogenic alkane gases are lighter than −30‰, with a negative isotope sequence (i.e. δ¹³C₁ > δ¹³C₂ > δ ¹³C₃ > δ¹³C₄). Inorganic gases also tend to show less negative δ¹³C_CO2 values (−10‰) than biogenic gases (<−10‰).     

华宁盘溪金山-大石山泥盆纪珊瑚礁的基本特征

滇东华宁盘溪火车站以北的金山—大石山地区发育中、晚泥盆世的丘状珊瑚礁。以Ａｌｖｅｏｌｉｔｅｓ和Ｔｈａｍｎｏｐｏｒａ为代表的床板珊瑚为造礁生物。纵剖面上岩相变化的记录清楚地表明，该礁体经历了定殖、繁殖和衰亡三个阶段。海水变浅及其盐化是导致礁体衰亡的直接原因     

三峡工程大江截流水文泥沙监测规划

鉴于三峡工程大江截流是一项复杂的系统工程,具有水深大,流量大,抛投量大和截流期不断航等显著特点。水文泥沙监测作为其重要的组成部分,监测导流与截流过程中水流泥沙和水下地形的变化,为截流设计优化,调整施工方案与措施等提供科学的决策依据,同时也为导流明渠分流与通航,围堰度汛,截流水力学试验研究及水文预报,水文分析计算等提供水文原型观测资料。本文介绍了水文泥沙监测的目的、任务和水文数据采集,传输,处理与信