共查询到20条相似文献，搜索用时 78 毫秒
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根据１５００年以来的地震资料,应用数理统计、灰色预测、干支６０周期分析等多种方法,对江苏—南黄海地区未来３～５年地震形势进行分析和预测,结果表明：该区目前处于本世纪第２活跃幕中后期,未来几年内依然存在５～６级地震的危险性,至２０００年７月,累积发震概率将达到０．７～０．８,１９９９—２０００年、２００２—２００３年均有可能发生５级以上中强地震。 相似文献
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Tang Mengxing 《CT理论与应用研究》2001,10(2)
本刊《ＣＴ理论与应用研究》杂志从２０００－２月起，即开始在北京民营科技网上，开辟了“ＣＴ科技进展与科技咨询的网页／ｗｗｗ．Ｍｙｓｔａｒ．ｃｏｍ．ｃｎ／３ＤＣＴ／”登载千禧之年“第七届 １９９９年度亚洲 ＣＴ科技十大进展与中国ＣＴ科技新进展信息交流会”的有关信息和评述．从２０００－０５月起，陆续登载“首届２０００年国际ＣＴ和三维成像会议”的组委会和征文及发奖事项。 本刊从１９９４年起，即向清华大学“国家学学术期刊光盘中心”和“ＣＮＫＩ中国期刊网”提供每期的杂志和相应的文章软磁盘，从２００ｉＮ１０日起… 相似文献
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继海震５．６级地震以后,于２０００年元月１２日灾海城、岫岩交界处发生了５．１级地震,震中烈度为ＶＩＩ度。本文就这次地震的特点和震灾损失作了阐述,这次地震所造成的损失为２６５１．８４万元。 相似文献
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利用门限自回归原理对山西地区未来地震活动进行了预测。结果表明，山西地区至２０００年可能发生的最大地震的震级为ＭＬ５．３，而１９９７年可能发生的最大地震震级为ＭＬ４．１。认为，在该区未来几年内发生ＭＳ≥６．０地震的可能性不大。 相似文献
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内蒙古湖相沉积14C年代测定中“硬水”影响的发现 总被引：17，自引：3，他引：14
对内蒙古科尔沁沙地巴克窑泡子湖相沉积物分别做了＾２１０Ｐｂ和＾１４Ｃ测年,比较这两种方法测定结果发现,＾１４Ｃ年龄比＾２１０Ｐｂ估计年龄偏老约２０００年,内蒙古其它湖泊的沉积物＾１４Ｃ测年资料一般也都存在年龄偏老问题,作者认为,这一现象主要是由干燥和半干燥地区湖泊“硬水”影响引起的。 相似文献
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利用自激励门限自回归建模的原理和方法,对广东地区陆地和珠江口外以及台湾海峡部分地区２０００年前后的最大地震强度进行了预测。结果表明,该区至２００１年可能发生地震的最大震级为ＭＬ５．２级,未来几年内发生Ｍ≥６．０级地震的可能性较小。 相似文献
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１９９８年２月４日阿富汗北部地区发生里氏６．１级破坏性地震,造成重大人员伤亡和财产损失,至少２０几个村庄被毁,４４５０人死亡,２０００多人受伤,数万人无家可归。本文综合介绍了这次地震的破坏和人员伤亡,地震参数,发震背景,地质构造的历史地震记录及抗震救灾情况等。 相似文献
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K.-G. Malle 《洁净——土壤、空气、水》1992,20(4):196-204
Zinc in the Environment. In 1990 the world production of zinc ammounted to 7 Mio. metric tons. The main areas of application were: galvanization, alloys like brass and zinc metal. The content in the earth crust varies between 10–300 ppm zinc with a mean of 70 ppm. Uncontaminated surface waters contain less than 10 mg/m3 zinc. Apart from civilization air contains 1–10 ng zinc per m3. These background concentrations are exceeded by orders of magnitude in zinc deposit areas and where anthropogenic influences predominate. Accumulation can occur in sediments and sewage sludge. Molluscs and Algae also accumulate zinc. Zinc is essential for live. With normal food the zinc supply of man is just sufficient. Bioaccumulation of zinc towards man or chronic oversupply of man is not known. Zinc has no teratogenic or mutagenic effects, a suspicion on a carcinogenic effect proved wrong. In stockbreeding and plant cultivation a minimum supply of zinc is necessary. Plants are relatively less sensitive against higher soil contents of zinc. Considering the toxicological and ecotoxicological effects of zinc in the environment, the critical organismens are marine invertebratae like tubifex, daphnia, gammarus and algae. But normally only a minor part of the total zinc contest is biologically available, depending on salt content and pH of the waters. 相似文献
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Richard D. Hey 《地球表面变化过程与地形》1979,4(1):59-72
Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape. 相似文献
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M. N. French R. L. Bras W. F. Krajewski 《Stochastic Environmental Research and Risk Assessment (SERRA)》1992,6(1):27-45
A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities. 相似文献
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Wastewater with high ammonia concentrations is produced by many industries, e.g. in the production of fertilizer and explosives and in the agricultural and food industry. A direct discharge into rivers and lakes has to be avoided: Oxidation of ammonia requires 4.56 g DO/g NH+4-N and results in a decrease of dissolved oxygen concentration. Moreover, nitrate stimulates the proliferation of algae, with regard to the eutrophication of natural waters. For municipal wastewater with an ammonia concentration less than 50 mg/L NH+4-N nitrification is a standard process. However, the removal of higher loaded industrial effluents still poses many questions. Recently, lab-scale and pilot-scale investigations show remarkable advances in the increase in nitrification efficiency and in the stabilization of the process. But because of changing flowrates and concentrations, the aid of advanced control algorithms is necessary. Some of the most important variables of biochemical reactors can be determined only with difficulty, at times only with off-line measurements. Model-aided measurement approaches try to determine these variables indirectly from easily measured variables. An experimentally-proved reactor model is required. Therefore, a dynamic model of nitrification in ideally mixed reactors is proposed based on mass balances for the components ammonia. nitrite, nitrate. dissolved oxygen DO, carbon dioxide, pH. nitrosomonas and nitrobacter. The biological reaction rates consider oxygen limitation and substrate inhibition. The process model presented is tested by lab scale experiments using an aerated stirred tank reactor and a fluidized bed reactor. Conformity between the predictions of the model and the observed data was positive. It has been shown that the nitrite oxidation by nitrobacter is the most sensible step in nitrification. 相似文献
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Depositional ages and characteristics of Middle–Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia 
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下载免费PDF全文 Hitoshi Hasegawa Hisao Ando Noriko Hasebe Niiden Ichinnorov Tohru Ohta Takashi Hasegawa Masanobu Yamamoto Gang Li Bat‐Orshikh Erdenetsogt Ulrich Heimhofer Takayuki Murata Hironori Shinya G. Enerel G. Oyunjargal O. Munkhtsetseg Noriyuki Suzuki Tomohisa Irino Koshi Yamamoto 《Island Arc》2018,27(3)
Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250 m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150 m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8 ±2.0 Ma and 118.5 ±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165–158 Ma of Callovian–Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7 ±2.6 cm/ky and 10.0 ±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer‐scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro‐laminae and calculated sedimentation rate, the micro‐lamination is most likely of varve origin. Both Middle–Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo‐Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian–Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia. 相似文献
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Community Structures of Different Groundwater Habitats Investigated Using Methods of Molecular Biology The degradation of pollutants in groundwater and aquifers depends on microbiological and hydrogeochemical processes. To understand the transport and fate of anthropogenic compounds during bank filtration and artificial recharge of groundwater it is necessary to gain more information about the structure of microbial populations in these systems. The population structure of aerobic, anaerobic groundwater habitats and of water samples during artificial groundwater recharge was examined by 16S rDNA based analysis. Water and sediment samples were collected from a groundwater catchment area with artificial groundwater recharge near the river Ruhr in NW-Germany. 16S rRNA genes of mixed bacterial DNA from different samples were amplified by PCR (polymerase chain reaction) with eubacterial primer sequences. To reveal eubacterial population structure amplified PCR-products were separated by DGGE (denaturing gradient gel electrophoresis) on the basis of melting domain structure and nucleotide composition. DGGE patterns of groundwater enrichment cultures and groundwater samples were compared to demonstrate differences between the use of cultivation dependent and molecularbiological approaches. The DGGE pattern of groundwater is very complex and differs significantly from DGGE patterns of groundwater enrichment cultures characterized by a small number of distinct bands. This shows the small quantity of culturable microorganisms in groundwater eco-systems. Aerobic and anaerobic groundwater and sediment samples differ markedly in their DGGE profiles. Different hydrogeochemical zones of this groundwater catchment area are mirrowed by distinct DGGE patterns indicating changes in microbial community structure.Analysis of bacterial population structure in the course of artificial groundwater recharge shows identical DGGE patterns comparing surface water samples to samples taken be-fore gravel prefiltration and before sand filtration. In contrast the DGGE pattern of artificial recharged groundwater differs markedly, indicating significant changes in microbial population during underground passage. 相似文献
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Richard D. Hey 《地球表面变化过程与地形》1979,4(2):179-182
The concept of causality has been a fundamental principle of scientific investigation for many centuries. Recently, however, there has been a significant reappraisal of the philosophical basis of the concept of causality and this has important implications for future geomorphological research. It is now recognized that there are two approaches to the study of relations between variables. Conventionally knowledge was divided into classes and, on the basis of time precedence, causal relations were defined. While this approach enables static systems to be analysed it does not apply to dynamic systems which exhibit mutual causality. This traditional view of knowledge became obsolete with the introduction of the concept of the continuum. Algebraic techniques now enable the solution of systems of simultaneous equations, provided that there are as many equations as unknowns. Significantly this approach applies to dynamic as well as static systems. Further advances in fluvial geomorphological research are dependent on the adoption of mathematical reasoning. This will concentrate research on the mode and rate of operation of channel processes and feedback mechanisms. Given this information it will be possible to develop a static process-response model to explain and predict channel response to a set of input conditions, and a dynamic model to simulate channel development through time and space. 相似文献
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In water treatment calcium hydroxide is used in softening and decarbonization techniques as well as in stabilization processes. Due to its slight solubility calcium hydroxide is applied as suspension. The dissolution kinetics plays a major role in these processes. For the characterization of calcium hydroxide dissolution empirical methods exist. These methods allow relative comparison of different calcium hydroxide products. Thus in this study a dissolution rate model is presented that is based on the chemical reactions determining the dissolution. This model allows to predict the dissolution with respect to particle diameter and temperature. However, the most important factor is the particle diameter i.e. the total surface of particles in solution. Furthermore an effect of the dosed amount of calcium hydroxide particles on the solubility was found. 相似文献