室内环境中子能谱及剂量率的多球谱仪测量

利用自主研发的多球中子谱仪对北京市某室内环境中子能谱及剂量率进行了测量。从中子能谱获得了能量低于20MeV的环境中子注量率为2.83×10~(-3)cm~(-2)·s~(-1),估算出环境中子总注量率为3.54×10~(-3)cm-2·s~(-1);利用中子注量与周围剂量当量转换系数计算出了能量低于20MeV中子周围剂量当量率为(1.5±0.1)nSv/h,总中子周围剂量当量率为(2.1±0.1)nSv/h,与中子剂量仪测量值(2.3±0.2)nSv/h基本一致。该文测量结果与相近纬度比较相差不多,可以为评估北京室内环境中子剂量提供参考。     

光子注量到周围剂量当量转换系数的Monte-Carlo模拟

本文采用蒙特卡罗程序EGS5计算了10 keV～10 MeV光子注量到周围剂量当量的转换系数.模拟计算中考虑了两种情况：1）不带次级电子模拟;2）带次级电子模拟.把两种情况下的计算值与前研究者的计算值及ICRP 74号报告中的建议值进行了比较.并给出了用于计算光子注量与周围剂量当量间的转换系数的拟合公式。     

蒙特卡罗方法在中子测井屏蔽中的应用

利用蒙卡罗方法模拟研究了在套管中子测井条件下，铜、银、含硼聚乙烯（含10％B4C聚乙烯）、钨、镉、铝不同厚度对中子的屏蔽效果．以及中子源到屏蔽层距离对屏蔽效果的影响。结果表明：用不同屏蔽材料对中子进行屏蔽，得到的中子能量分布相差很大。相同厚度下，银做屏蔽材料时．总中子和小于0．1MeV能量范围内的中予计数最小，钨在14MeV～0．1MeV中子能量区的计数最小.     

氘-氘和氘-氚随钻中子孔隙度测井探测特性对比

为考察在随钻中子孔隙度测井中用氘-氘(D-D)脉冲源替代氘氚(D-T)源的可行性,利用蒙特卡罗模拟方法,对比分析使用两种脉冲源时测井仪器的热中子空间分布、零源距区域、地层孔隙度灵敏度以及探测深度等探测特性.研究结果表明,D-D与D-T源相比,虽然在水平或大斜度井段对地层界面的分辨能力稍低一点,但是两者的零源距区的上限值、近源距和探测深度都大致相等,且D-D源对地层孔隙度的灵敏度更高、使用时更安全,在随钻脉冲中子孔隙度测井中可以得到更好的使用.     

基于MCNP安全作业舱辐射屏蔽特性研究

采用蒙特卡罗软件MCNP5程序建立挖掘机安全作业舱及内部驾驶人员实验模型,研究在辐射源(钴-60)类型不同和源距不同的情况下,不同材料及不同结构的安全作业舱屏蔽γ射线的能力.分析讨论人体各部位剂量率值以评价安全作业舱的屏蔽效果,并依据电离辐射防护与辐射源安全基本标准(GB18871—2002)规定的工作人员的照射水平应低于0.01 m Sv/h的剂量限值,确定安全作业舱结构的设计方案.此次研究为挖掘机驾驶舱屏蔽设计提供必要的研究数据和设计依据,使驾驶舱在野外高放射环境下能够有效地屏蔽γ射线,保护驾驶人员的辐射屏蔽安全.     

煤质检测装置屏蔽体的优化设计

为满足南京大陆煤质检测装置辐射防护优化设计的需求,利用Monte Carlo方法模拟了中子、光子在复合屏蔽体中的输运过程,计算了14MeV脉冲中子在使用不同屏蔽材料下的透射剂量率,通过剂量率的比较优化设计了最经济实用的屏蔽体方案,为屏蔽体的设计提供了可靠的科学依据。研究结果表明:以石蜡作屏蔽体主材料为最佳的选择,通过几何优化,有效地降低了防护体的重量,提高了防护体的性价比。     

2.8 MeV中子引起的~(232)Th(n,γ)~(233)Th反应截面的测量

用中子活化法和离线γ能谱测量技术对2.8MeV中子引起的~(232)Th(n,γ)~(233)Th反应截面进行了测量.2.8 MeV强流中子由D-D中子发生器获得,中子注量率的波动通过测量伴随~3He粒子得到;中子的平均能量通过~(64)Zn(n,p)~(64)Cu和~(115)In(n,n′)~(115m)In的反应截面比得到.γ能谱采用低本底高分辨率高纯锗伽马谱仪进行测量.实验结果与已发布的截面数据及评价核数据库ENDF/B-Ⅷ.b4、JENDL-4.0u+和CENDL-3.1的数据进行了比较.利用模型程序TALYS-1.8对~(232)Th的中子俘获反应激发函数曲线进行理论计算,并与实验数据和评价数据进行了对比分析.     

30万居里~(60)Co辐照装置贮源井屏蔽计算

使用MCNP计算30万居里60Co辐照装置贮源井铅屏蔽盖中心轴不同点处的光子注量率,通过拟合得出光子注量率的衰减系数,外推出铅屏蔽盖上表面中心点处的剂量.结果表明,铅屏蔽盖表面最大剂量率为5.91×10-9Sv/s,检修时工作人员受到的年最大剂量水平为0.55 mSv,低于20 mSv每年的职业照射限值.     

快中子发生器屏蔽的Monte－Carlo估计

本文介绍的是一个在微机上实现的计算快中子屏蔽的Ｍｏｎｔｅ－Ｃａｒｌｏ程序．采用历次飞行法对结果进行统计估计，对中子发生器周围的屏蔽作了简单模拟，结果表明采用的物理模型是正确的．该程序改进后也可用于多次散射的计算，或模拟其他中子源的屏蔽，故有一定的实用价值．     

桶型3He中子探测器探测效率标定装置设计分析研究

基于后处理生产的³He中子探测器,开展了桶型中子探测效率标定装置的材料选择及功能结构设计分析,使用MCNP程序构建了装置及³He探测器的相关计算模型,根据生产过程及设计需求,分别分析了桶型中子探测效率标定装置慢化层的慢化效果,及不同位置多根³He管中子探测器的探测效率,并计算了源管、探测器上方及屏蔽体周围的剂量,结果表明该装置的慢化能力及屏蔽效果良好,放射性剂量水平满足辐射防护要求。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the