巴基斯坦恰希玛核电站用P300工程核级冷冻机组抗震力学 …

核电站中的结构、设备的安全可靠性是公众所关注的焦点,国内外的研究人员对此做了大量的工作。对于各种不同的荷载组合,针对某一类结构进行细致的分析研究是必要的。本文采用有限元法对巴基斯坦恰希玛核电站中采用核级冷冻机组在地震动、结构内压及自重等多种荷载组合作用下的结构抗震性能进行了计算分析。     

核电站用冷热交换器抗震性能研究

核电站中的结构、设备的安全可靠性是公众所关注的焦点，国内外的研究人员对此作了大量的工作，因而，对于不同的荷载组合，针对某一类结构进行细致的分析研究是必要的。本文采用有限元法对核电站中采有的核级冷势交换器在地震动或其它荷载作用下的抗震力学性能进行了计算分析。     

巴基斯坦恰希玛核电站用 P300 工程核级离心通风机抗震性能计算及试验研究

核电中的结构、设备的安全可靠性是公众所关注的焦点，国内外的研究人员对此做了大量的工作。然而，对于多种不同的荷载组合，针对某一类结构进行细致的分析研究是必要的。本文对巴基斯坦恰希玛核电站中采用的离心通风机在地震动、转子离心力、结构内压及自重等多种荷载组合作用下对结构进行如下几项分析：（１）对结构建立有限元计算模型，并通过大型振动台试验验证模型的合理性与准确性；（２）减振后结构的动力特性研究。     

巴基斯坦恰希玛核电站用P300工程核级离心通风要抗震性能…

核电中的结构，设备的安全可靠性是公众所关注的焦点，国内外的研究人员对此做了大量的工作。然而对于多种不同的荷载组合，针对某一类结构进行细致的分析研究是必要的。本文对巴基斯坦恰希玛核电站中采用的离心通风机在地震动，转了离心力，结构内压及自重等多种荷载组合作用下的对结构进行如下几项分析：１．对结构建立有限元计算模型，并通过大型振动台试验验证模型的合理性与准确性；２．减振遑结构的动力特性研究。     

山东海阳核电一期取水沟道进出口部位抗震分析

以山东海阳核电一期取水沟道工程为背景,采用动力时程反应分析方法,利用非线性有限差分软件FLAC3D建立三维土体-结构模型,分析该核电站取水沟道进、出口部位在自重、外水压力、土压力、温度、水锤压力、地震等荷载效应组合下的内力变化情况。通过编制FLAC3D程序并结合五点公式计算衬砌结构的内力,对该核电取水沟道进、出水口部位进行抗震分析。计算结果表明温度荷载、水锤压力以及地震荷载对沟道进出口部位内力影响显著,设计施工时应对薄弱截面进行加密配筋处理。本文的计算方法和分析成果可为核电厂取水沟道地震反应分析以及其他类似结构设计提供参考。     

GFRP套管钢筋混凝土柱恢复力模型的试验研究

GFRP(Glass Fiber Reinforced Polymer)套管钢筋混凝土柱是一种新型的组合结构形式,为研究其抗震性能,对8根GFRP套管钢筋混凝土柱进行低周反复荷载作用下的试验研究。主要研究了轴压力大小、混凝土强度及FRP管与基础的连接方式对GFRP套管钢筋混凝土组合柱的变形能力和滞回特征的影响,根据GFRP套管钢筋混凝土组合柱在低周反复荷载作用下滞回曲线的特点,采用截面层纤维模型法对试件截面进行全过程分析获得骨架曲线。通过试验数据回归分析确定加卸载规则,提出了适合于GFRP套管钢筋混凝土组合柱的恢复力模型,并与试验结果进行了比较,计算模型与试验结果吻合良好。     

基于桥梁多灾害设计的典型桥梁实证分析

目前美国的桥梁设计规范在考虑重力荷载和卡车荷载组合时分别采用1.25和1.75的系数,但是当考虑地震荷载作用时,取地震系数1.0,一般不考虑卡车荷载,特殊情况需要考虑时卡车荷载系数为0.5。这说明地震与卡车组合时候,其概率理论的不完备性。基于此,参考文献[16,17]不仅给出了地震和重卡车作用下的组合理论,还给出其共同作用下荷载系数的计算方法。本文的主要目的是用一个典型桥梁实例对求解的荷载系数进行检验。通过有限元软件对采用新的荷载系数的桥墩截面配筋进行重新设计,然后,对新桥进行地震作用下的pushover分析,并与现行LRFD规范的规定值进行对比。结果表明,新的荷载系数能够保证桥梁结构的安全,可以按其设计。     

偏心水平荷载下内藏钢桁架混凝土核心筒抗震试验研究

对两个1／6缩尺的核心筒结构模型进行了偏心水平荷载作用下的低周反复荷载试验研究，其中包括一个普通混凝土核心筒和一个内藏钢桁架混凝土组合核心筒。在试验的基础上，分析了两个试件的承载力、刚度、延性、滞回特性、耗能能力、破坏特征以及抗震机理。试验研究表明：偏心水平荷载作用下，内藏钢桁架混凝土组合核心筒比普通混凝土核心筒抗震能力显著提高。     

偏心水平荷载下内藏钢桁架开洞混凝土核心筒抗震研究

对两个1/6缩尺的开洞核心筒结构模型进行了偏心水平荷载作用下的低周反复荷载试验研究,其中包括一个普通开洞混凝土核心筒和一个内藏钢桁架开洞混凝土组合核心筒。在试验的基础上,对比分析了两个试件的承载力、刚度、延性、滞回特性、耗能能力、破坏特征以及抗震机理。试验研究表明,在偏心水平荷载作用下,内藏钢桁架开洞混凝土组合核心筒比普通开洞混凝土核心筒抗震能力显著提高。     

桅杆结构抗震、抗风和裹冰研究现状与展望

概述了国内外桅杆结构的工程应用与理论研究现状,介绍了桅杆结构的分类及其特点,分析了桅杆结构在地震荷载、风荷载、裹冰荷载的破坏机理与破坏工程实例,总结了钢管混凝土桅杆与网壳结构的组合形式及其特点,最后归纳了桅杆结构的研究方向和发展趋势。     

A discussion of the validity of hydrodynamical equations of motions

Summary Starting from the eqts. (1) and (4) resp. (19) which are valuable for the streaming of an ideal gas in the space, where the plane resp. spheric wave is propagated adiabatically, it follows that for such a motion instead of the Euler's equation the eqts. (11) resp. (20) are valid. In the discussed cases the eqts. (1), (4) and (19) are the fundamental equations and reflect the Newton's principles of dynamics. In our two special cases the one dimensional Euler's equation follows from the fundamental eqts. (1), (4) and (19) only approximately.

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Zusammenfassung In zwei Beispielen wird gezeigt, dass die Gültigkeit der Eulerschen Bewegungsgleichungen nicht allgemein ist.

     

The Precision Estimate of Multi-Fractal Methods of Time Sequence of Earthquakes

At present,there are many methods of calculating seismic time-fractal.However,there isn’t aquantitative result about the precision of every method.So,in this Paper,we use the digitalimitation of theoretic model to solve precision estimate problems of calculating the precision ofone dimension distribution of theoretic models with Cantor multi-fractal set,we obtained someresults as follows:(1)There exists many problems such as rules,numbers of samples,basicpoint selection,the diffence resulted from different methods and so on.(2)The fixed-massmethod(MAS)and the minimal spanning tree method(MST)can give good structure charac-teristics with different q value,while the counting-boxes method can’t.And the error of thefixed-radius method(RAD)in the range of-q is too big.(3)There are scale problems of rulesfor multi-fractal,it is objective reflection for non-rule area.(4)MST has the boundary prob-lem,while MAS and RAD don’t.(5)With increasing sample number,the precision of allfractal-dimension values becomes     

Performance comparison of two biotic indices measuring the ecological status of water bodies in the Southern Baltic and Gulf of Lions

Two biotic indices, ATZI Marine Biotic Index (AMBI) and Benthic Quality Index (BQI) have been recently introduced within the EC Water Framework Directive to assess the quality of marine habitats: both are based on sensitivity/tolerance classification and quantitative information on the composition of soft-bottom macrofauna. Their performance, especially with regard to sampling effort was assessed based on two data sets collected in Southern Baltic and one from the Gulf of Lions Mediterranean. AMBI was not affected by sampling effort but BQI was. Two modifications were proposed for BQI (i.e., BQI) (1) the removal of the scaling term (i.e., BQI(W)), and (2) the replacement of the scaling term by different scaling term (i.e., BQI(ES)). Both modified BQIs were largely independent of sampling effort. Variability was slightly lower for BQI(W) than for BQI(ES). BQI was highly correlated with BQI(W) and with BQI(ES) both in the Southern Baltic and in the Gulf of Lions. However, the proportions of stations, which were not attributed the same ecological quality status (EcoQ) when using BQI and its two modified forms were always high. Differences in ecological classification were mostly due to the scales used to infer EcoQ. Based on this study we recommend to use BQI(ES) in future studies because it apparently constitutes the best compromise in (1) being independent of sampling effort, (2) limiting the variability in computation in relation with sampling effort, (3) being correlated with BQI and corresponding EcoQ.     

Peroxymonosulfate Improves the Activity and Stability of Manganese Oxide for Oxidation of Arsenite to Arsenate

Manganese oxide has been widely investigated for oxidation of arsenite (As(III)) to arsenate (As(V)) due to its high redox potential; however, it becomes extremely unstable after reuse. Here, As(III) oxidation activity and stability of manganese oxide in the presence of peroxymonosulfate (PMS) is investigated. Batch experimental results reveal that manganese oxide/PMS exhibits high catalytic activity for As(III) oxidation compared to manganese oxide or PMS alone. Addition of PMS to manganese oxide not only reveals long‐term stability for As(III) oxidation, but also shows high As(III) oxidation activity in the presence of coexisting ions such as As(V) and phosphate. Quenching tests reveal that As(III) oxidation in the manganese oxide/PMS system is attributed to activation of PMS by manganese oxide at different oxidation states (Mn(III) and Mn(IV)), and the generation of sulfate radicals that are responsible for As(III) oxidation.     

Comparative effects of herbicides on photosynthesis and growth of tropical estuarine microalgae

Pulse amplitude modulation (PAM) fluorometry is ideally suited to measure the sub-lethal impacts of photosystem II (PSII)-inhibiting herbicides on microalgae, but key relationships between effective quantum yield [Y(II)] and the traditional endpoints growth rate (mu) and biomass increase are unknown. The effects of three PSII-inhibiting herbicides; diuron, hexazinone and atrazine, were examined on two tropical benthic microalgae; Navicula sp. (Heterokontophyta) and Nephroselmis pyriformis (Chlorophyta). The relationships between Y(II), mu and biomass increase were consistent (r(2)0.90) and linear (1:1), validating the utility of PAM fluorometry as a rapid and reliable technique to measure sub-lethal toxicity thresholds of PSII-inhibiting herbicides in these microalgae. The order of toxicity (EC(50) range) was: diuron (16-33nM)>hexazinone (25-110nM)>atrazine (130-620nm) for both algal species. Growth rate and photosynthesis were affected at diuron concentrations that have been detected in coastal areas of the Great Barrier Reef.     

Determination of arsenic(III) for the investigation of the microbial oxidation of arsenic(III) to arsenic(V)

Recent evaluations of acute and chronical toxicity of arsenic resulted in a reduction of the standard value for total arsenic from 40 μg/L to 10 μg/L in drinking water which will be valid in Germany after a transition period as from January 1996. Arsenic is well known as substance of deep groundwaters, mainly of geogenic origin and normally found as As(III) or As(V). As(V) is well removable by flocculation and filtration after adding iron salts. As(III), however, has to be oxidized first to As(V). Therefore, it is important for treatment techniques to be able to distinguish between As(III) and As(V). A modified determination of As(III) using flow injection analysis was installed and optimized in order to investigate whether As(III) may be oxidized to As(V) by bacteria in natural waters. The results showed that at 4°C, no As(III)-oxidation was observed within 14 days. At room temperature, however, in the bacteria-containing samples, an As(III)-oxidation was found starting after 3 to 7 days. After 14 days, no As(III) was left over. In contrast, in the sterile samples, no As(III)-oxidation could be observed within 14 days. These results demonstrated that microbial processes influence the oxidation of As(III) to As(V) in natural waters.     

Simulation of the time-space evolution of an extratropical cyclonic precipitation field over USA

The time-space evolution of an extratropical cyclonic precipitation field over U S A is simulated in a stochastic setting as outlined in Kavvas et al. (1988). The birth of a cyclonic storm is characterized by the simultaneous birth of a cyclone center and births of subsynoptic precipitation areas (SPA) at preferred locations around the cyclone center. The precipitation cores and cells which are used as the fundamental building blocks of the SPAs are approximated by circular precipitation areas (CPA) of different sizes. The time space evolution of the precipitation field after the birth is governed by (1) the movement of the synoptic cyclone described by the cyclone center trajectory, (2) independent nonidentically distributed random velocities of the individual CPAs relative to the cyclone center, (3) the births of new CPAs in time and space relative to the cyclone center, (4) the independent evolution in time of the individual spatially uniform intensities of the existing CPAs, (5) the expansion and shrinkage of the existing CPAs in the course of movement and (6) the dissipation (death) of a random number of existing CPAs within the cyclonic system. The computer simulation, the results of which are presented in this paper, successfully reproduced the general mesoscale and synoptic scale features of the radar detected cyclonic rain fields as observed by Austin and Houze (1972), Houze et al. (1976), Hobbs (1978), Hobbs and Locatelli (1978), Houze (1981), Houze and Hobbs (1982) and others.     

Soil organic carbon and nitrogen content of density fractions and effect of meadow degradation to soil carbon and nitrogen of fractions in alpine Kobresia meadow

This research was conducted on the non-disturbed native alpine Kobresia meadow(YF) and the severely degraded meadow(SDL) of Dari County of Qinghai Province.By a density fractionation approach,each soil sample was divided into two fractions:light fraction(LF) and heavy fraction(HF).The obtained fractions were analyzed for organic carbon(OC) and nitrogen(N) concentrations.The results showed:(1) the OC concentration in HF and LF was 3.84% and 28.63% respectively while the nitrogen concentration in HF and LF wa...     

64层螺旋CT螺距的不同设置在新型冠状病毒感染肺炎中筛查应用探讨

目的:探讨通过64层螺旋CT螺距参数的设置,降低新型冠状病毒肺炎患者筛查的辐射剂量和扫描时间的可行性。方法:前瞻性选择需进行新型冠状病毒肺炎筛查患者,按扫描时间随机分为大螺距组和对照组,每组各16例。大螺距组选择1.375∶1螺距,对照组选择0.984∶1螺距。对肺纹理、支气管、纵膈结构的图像质量;胸主动脉、竖脊肌、双肺肺实质;辐射剂量的客观数据进行评价和分析。结果:32例图像均符合影像诊断要求。伪影、肺纹理评分差异有统计学意义（P<0.05）。两组右肺CT值分别是（-804.62±45.43） HU和（-852.12±28.13） HU、左肺CT值分别是（-808.13±37.74） HU和（-858.77±19.95） HU,均具有统计学意义（P<0.05）。两组的扫描时间分别为（2.14±0.15） s和（3.14±0.28） s,具有统计学意义（P<0.05）。两组记录所得的容积CT剂量指数（CTDIvol）是（7.88±0.89） HU和（11.17±1.08） HU、剂量长度乘积（DLP）是（279.14±36.33） HU和（387.25±47.86） HU均具有统计学意义（是P<0.05）,有效剂量（ED）分别是（3.91±0.51） HU和（5.42±0.67） HU具有统计学意义（P<0.05）。结论:新型冠状病毒肺炎患者CT筛查检查中,使用大螺距扫描,能够减少辐射剂量、显著缩短了扫描时间,在不影响病灶诊断的前提下,降低病人接受到的辐射剂量和放射技师感染的风险,具有实际工作意义,有待进一步推广验证。      

Subsurface hydrology of tile-drained headwater catchments: Compatibility of concepts and hydrochemistry

Concepts and terms used in previous multidisciplinary studies of tile-drained aquitard-dominated catchments (TDADC) are inconsistent and confusing. We provide a well-defined, comprehensive conceptual model of the subsurface hydrology of TDADC by selecting seven mutually compatible and consistent concepts. These concepts are: (1) groundwater as the main source of baseflow in headwater streams, (2) dominance of ‘pre-event’ water in stormflow, (3) importance of both macropores and matrix, (4) changes in flowpaths with rate of stream discharge, (5) dominance of shallow, lateral subsurface flow, (6) interactive nature of subsurface water, (7) transpiration of groundwater. This conceptual model was successfully ‘field-tested’ by examining data collected in a TDADC in a rural area of southern Ontario, Canada. The data consist mainly of chemical and isotopes tracers in water samples (headwater streams, groundwater, precipitation, tile water, soil-surface water), supplemented by water levels and meteorological data.