Rockburst hazard determination by using computed tomography technology in deep workface

The rockburst in mines results from the dynamic load coupled with static one in coal seams around workface zones, so it is essential to learn the stress distribution of the coal and surrounding rock for determination of rockburst risk areas. The relationship between the elastic wave velocity and stress applied on coal sample was investigated systematically by laboratory testing, theoretically analysis, as well as on-site observation, and a positive correlation between them under uniaxial compression was put forward. Furthermore, it is drawn that the anomaly of elastic wave velocity reflects the stress changes: the positive anomaly ascertains the stress concentration while the negative anomaly estimates the mining destress and weaken degree, and corresponding assessment criterions and parameters were established respectively. The hazard areas and degree of an island longwall face 16302C were forecasted before coal winning based on the elastic wave anomaly distribution rules using active tremor velocity inversion, monitoring results of mining shocks during exploitation indicate that the consistency between locations of big tremors and where forecasted by computed tomography (CT) exceed 80%. The successful application of this technology achieved remarkable economic and social benefits for disaster control in rockburst mines.     

A comparative study of prenatal ultrasound findings and post-mortem examination in a tertiary referral centre

This retrospective study compares the findings of prenatal ultrasound, performed in a tertiary fetal medicine centre, with the results of post-mortem examination in pregnancies complicated by suspected fetal abnormality that results in fetal loss. The study was carried out over a year at a teaching hospital, Fetal Medicine Centre and Regional Centre for Perinatal Pathology. Results were directly compared and the level of agreement between the ultrasound and post-mortem findings described. These were classified as having complete agreement; major agreement or major disagreement. The group of cases with major agreement between findings was further divided into those with significant, or minor, additional findings at post-mortem examination. Over the 12-month period, 153 ultrasound cases were identified, of which 47 were also examined by autopsy and were thus suitable for comparison in this study (30.7%). Complete agreement between ultrasound and post-mortem findings was found in 22 cases (46.8%). In 24 cases (51.1%), major agreement between ultrasound and post-mortem findings was seen. Of these, 11 had minor additional findings at post-mortem examination and 13 were found to have significant additional findings at post-mortem (27.7%), adding to the eventual diagnosis. In 12.8% of cases, post-mortem examination provided a definitive diagnosis. Only in one case was there complete discordance in the findings of the ultrasound examination and the autopsy (2.1%). No major disagreement between ultrasound and post-mortem findings was seen in 98% of cases. This study confirms the accuracy of prenatal ultrasound diagnosis in specialist centres, whilst emphasising the continuing importance of post-mortem examination in cases of fetal malformation to refine and, in some cases, define the diagnosis. Copyright © 2004 John Wiley & Sons, Ltd.     

南黄海6.1级地震的地磁异常特征

研究认为：虽然此次南黄海６．１级地震距江苏地磁台网较远，但南通台的Ｆ２１测值在震前仍有历时约２２个月的信度较高的异常，同时存在幅相法异常，然而希望据此做出准确的地震三要素的预报难度仍是较大的     

华北中部早涝成因的分析研究

本文对北京等华北中部5站1956至1985年旱涝成因进行了分析讨论.结果表明,区域性旱涝主要是在海洋和局地土壤热状况异常作用下产生的.对华北中部而言,冬季黑潮海温与局地地温变化是引起汛期旱涝变异最重要的原因.前期下垫面热源异常对后期旱涝影响往往是通过累积的异常加热造成环流形势和系统的异常而实现的.海温与地温影响降水的机制不同,前者的影响是大尺度的,而后者的影响只是区域性的.当海温异常造成的大尺度环流变化与局地热状况都有利于降水时.洪涝更容易发生,反之易旱.     

苍山5．2级地震前安徽省观测到的地震前兆

汇集了１９９５年９月２０日山东苍山５．２级地震前安徽省所属各观测项目记录到的地震前兆数据变化，并初步分析了震前难以做出预报的原因     

利用负离子的油烟多级净化装置的研究探讨

针对目前餐饮油烟净化技术去除细小颗粒物的不足,在总结现阶段油烟净化技术的研究应用现状的基础上,分析湿式+过滤的复合式油烟净化装置基础上应用空气负离子除污技术的可能性,提出了基于空气负离子技术的新型多级油烟净化装置设想及其发展途径与研究方向。     

Small sample estimation for Taylor's power law

An analysis of counts of sample size N=2 arising from a survey of the grass Bromus commutatus identified several factors which might seriously affect the estimation of parameters of Taylor's power law for such small sample sizes. The small sample estimation of Taylor's power law was studied by simulation. For each of five small sample sizes, N=2, 3, 5, 15 and 30, samples were simulated from populations for which the underlying known relationship between variance and mean was given by ² = c^d. One thousand samples generated from the negative binomial distribution were simulated for each of the six combinations of c=1,2 and 11, and d=1, 2, at each of four mean densities, =0.5, 1, 10 and 100, giving 4000 samples for each combination. Estimates of Taylor's power law parameters were obtained for each combination by regressing log₁₀ s ² on log₁₀ m, where s ² and m are the sample variance and mean, respectively. Bias in the parameter estimates, b and log₁₀ a, reduced as N increased and increased with c for both values of d and these relationships were described well by quadratic response surfaces. The factors which affect small-sample estimation are: (i) exclusion of samples for which m = s ² = 0; (ii) exclusion of samples for which s ² = 0, but m > 0; (iii) correlation between log₁₀ s ² and log₁₀ m; (iv) restriction on the maximum variance expressible in a sample; (v) restriction on the minimum variance expressible in a sample; (vi) underestimation of log₁₀ s ² for skew distributions; and (vii) the limited set of possible values of m and s ². These factors and their effect on the parameter estimates are discussed in relation to the simulated samples. The effects of maximum variance restriction and underestimation of log₁₀ s ² were found to be the most severe. We conclude that Taylor's power law should be used with caution if the majority of samples from which s ² and m are calculated have size, N, less than 15. An example is given of the estimated effect of bias when Taylor's power law is used to derive an efficient sampling scheme.     

豫西南地区河南庄金矿埋藏矿体的地表标志

在第四系总厚度为 1 7m以上 ,由 1m左右直径的巨砾石层、亚砂土、黄粘土组成的巨厚冲洪积物之上发现有清晰的后生Au、Hg异常带 ,经工程验证 ,发现了其下埋藏的厚1 .6～ 8m ,Au品位最高达 1 0 3 .1 3×1 0 -6,一般为 (4～ 8)× 1 0 -6的金矿体。后生异常在找矿工作中不能忽视     

一起"宏观异常"落实事件引发的思考

通过介绍发生在台站附近一次"宏观异常"落实事件,结合当前防震减灾工作的重点,就今后地震台站所面临的新形势,如何贯彻防震减灾总体发展战略和部署,发挥地震监测一线的重要作用作一探讨.本文提出了台站要转变思想,拓展职能,不断增强其基层窗口作用,向现代化、多功能、综合型的模式发展的新思路.     

三江中段Dupal同位素异常的识别及其意义

玄武岩的Sr Pb同位素示踪表明 ,古特提斯时期 (D -T)三江中段普遍存在Dupal异常 ,其同位素指标为 :△2 0 7Pb/2 0 4 Pb>7,最高可达 3 4 ;△2 0 8Pb/2 0 4 Pb >5 2 ,最高可达 87;△Sr>3 9,最高可达 79。Nd Sr Pb同位素体系示踪表明 ,三江中段Dupal异常源于EM2地幔源区。Dupal异常的存在说明 ,自古特提斯时期以来 ,三江中段已向北发生了几千公里的漂移