21世纪中国大陆第一个大震活动幕的预测

基于对 2 0世纪中国大陆 7.0级以上大地震与月亮白赤交角的变化和太阳活动的研究结果 ,根据对未来 50a (年 )月亮白赤交角的值与目前太阳活动的形势 ,提出 2 1世纪中国大陆第一个大地震活动幕可能是 2 0 0 6或 2 0 0 7～ 2 0 1 5年     

Direct method of image and spectrum recovery in high-energy astronomy

In this paper we propose to use the method of iterative calculation to solve directly the imaging equation for image recovery. The same method can be applied to the recovery of one-dimensional spectra. During the iteration suitable constraints are applied to effect nonlinear control over the process. The use of fitting technique in the treatment of the imaging equation suppresses noise and raises sensitivity. Analyses of both Monte Carlo samples and actual high-energy astronomical data showed that the direct method is more sensitive and having greater resolving power than the traditional method, is capable of revealing simultaneously both diffuse and discrete structures in the target object and can be used on data of lower statistical quality. In principle, the direct method can be used in all types of image and spectrum recovery in other fields.     

确定剩余油分布技术

目前，国内外确定剩余油饱和度及其分布技术归纳起来可分为四类：单井分析技术、井间测试技术、室内模拟技术和油藏动态分析技术。每种技术都有其优点和局限，在实际应用中通常采用多种技术的综合。相对稀油而言，稠油剩余油饱和度及其分布的研究起步较晚。辽河油田稠油的多数主力区块都进入吞吐开采中后期，通过油蒇精细描述，应用测井、室内模拟和油藏动态分析等技术研究稠油剩余油的分布，对油田的长期高产稳产起着十分关键的作用。     

The effects of artificial ammonium enhancement on riverine periphytic diatom communities

An experiment to ascertain the influence of artificially enhanced ammonium concentrations on riverine periphytic diatom communities was conducted during an 80 day period in winter 1988/89 (temperature: 5°C). During an initial 47 day enrichment phase, ammonium chloride at different concentrations was added to O₂-saturated river water in experimental channels. Compared to a control, the addition of 1.2 mg NH ₄ ⁺ -N·l^–1 resulted in only slight changes in the species composition of the diatom community. The addition of 5.1 mg NH ₄ ⁺ -N·l^–1 and more (60 µg NH₃-N·l^–1) resulted in a decrease in the biomass and a drastic change in the species composition. After the 42 day enrichment period, the diatom speciesFragilaria capucina var.vaucheriae, Navicula saprophila, Navicula atomus andGomphonema parvulum, all of which are known to be tolerant to organic pollution, were found with relative abundances of 44.8%, 35.6%, 2.3% and 1.5%, respectively. Changes in species composition of the periphytic diatom communities occurred within the first two weeks of the subsequent recovery phase. After a month of recovery, all periphytic diatom communities exhibited a high degree of structural similarity with the control.     

华北地区地震活动的月相效应及其预测意义

对华北地区1970年以来ML4．0以上地震的月相效应进行了分析。结果表明,华北地区Ms5．0以上地震活动的月相效应并不明显,而是呈现较强的随机性。但在7级以上强震发生前,中等地震的发生具有较为明显的月相效应,这对7级以上强震的发生具有中期（1～3年）预测意义。未来强震可能发生在“朔望地震”分布的地区。目前,华北地区中等地震发生没有显示明显的月相效应,因此未来1～2年内华北地区发生7级以上地震的可能性较小。     

稻田砂金开采生物复田技术研究

从生物复田方面对稻田下砂金船采后的复田技术进行了系统的试验和分析研究。认为稻田下采矿金,复田后种植的农作物以大豆类作物为宜;生物复田全过程采用大豆—绿肥—杂交中稻—绿肥—杂交中稻种植模式,两年后稻田肥力可望达到或接近正常稻田肥力水平。     

煤层气藏可采性

本文提出吸附定律的判断方法,根据煤层气藏状态,提出了欠饱和煤层气藏、饱和煤层气藏、过饱和煤层气藏的采收率计算方法,为煤层气藏可采储量计算奠定了基础。     

Experiences of vulnerable households in low-attention disasters: Marshalltown,Iowa (United States) after the EF3 Tornado

Tornados are among natural hazards that many towns in the Midwest region of the United States (US) experience frequently, sometimes with relatively overwhelming impacts and little attention and resources from media or government entities. Low-attention disasters that affect vulnerable populations create unique recovery challenges that are rarely addressed in the disaster literature. This paper presents a qualitative case study of impacts and recovery of housing in Marshalltown, Iowa, US after an EF3 Tornado in 2018 which affected a large portion of the town, in particular neighborhoods with high concentration of immigrant, low-income households in old and poorly maintained housing. Our analyses highlight the long-term challenges created by delayed and unsuccessful recovery of housing as a result of the intersection of pre-disaster social and physical vulnerability and inadequate housing recovery policy.     

Scientific objectives and payloads of Chang’E-1 lunar satellite

China plans to implement its first lunar exploration mission Chang’E-1 by 2007. The mission objectives are