利用电子磁谱仪测量超热电子能谱和注量

为了测量超热电子能谱和注量,利用磁感应强度为1200 Gs和600 Gs,对应的量程分别为258 keV～3 MeV、70 keV～1200 keV的电子磁谱仪,测量靶前法线方向和靶后激光传输方向超热电子能谱.用LiF热释光探测器(TLD)记录超热电子的总剂量,然后根据得到的TLD剂量就可推出电子注量,从而得到超热电子的能谱.     

飞秒激光与固体靶相互作用中产生表面电子的实验研究

在近相对论光强下, 对p偏振超强激光脉冲与固体靶相互作用过程中产生的超热电子的角分布和能谱进行了研究. 实验发现, 超热电子的发射主要集中在三个方向: 靠近靶面方向、法线方向和激光的背向. 结果分析表明: 导致超热电子沿着靶面发射的原因是它受到靶前的鞘层电场与表面磁场的共同作用; 而沿着法线方向发射的超热电子的主要加速机制是共振吸收机制.     

激光功率密度对超热电子发射方向的影响

超短脉冲强激光与固体靶相互作用后会产生高能超热电子, 就超热电子对激光功率密度的依赖关系进行了研究. 实验结果发现, 在非相对论光强下超热电子的发射方向主要在激光的偏振面内, 并且在较低光强时超热电子的发射方向接近激光的偏振方向, 随着光强的增加, 在接近激光光轴的方向上的超热电子数目逐渐增多; 在相对论光强时超热电子的发射方向偏离偏振面而转向激光的反射方向.     

激光偏振态对飞秒激光等离子体中产生的超热电子喷射方向的影响

采用2×10 16 W/cm 2 的超短激光脉冲辐照铝靶,研究了激光偏振态对超热电珑子发射的影响.对s偏振光,向外传播的超热电子射流沿激光偏振方向发射,而对于p偏振光,超热电子射流方向靠近靶面法线方向.文中还通过观测靶背面的X射线韧致辐射,对p,s偏振光产生的向内传播的超热电子行为进行了研究.     

强流中子发生器n—γ辐射场参数的测量

为满足强流中子发生器１４ＭｅＶ中子的辐照实验要求，已建立了基本配套的中子注量测量装置和两个环境剂量监测站。在样品待辐照的近靶区，测量了中子能谱、中子和γ剂量的空间分布。ｎ－γ辐射场参数的测量将为中子物理实验和加速器的安全运行提供有用数据。     

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。     

飞秒激光与双层靶相互作用靶背质子加速实验研究

研究了飞秒激光与10μm的Cu和5μm的C8H8构成的双层薄膜靶相互作用中在靶背法线方向质子的能量分布.采用CR39固体核径迹探测器和Thomson磁谱仪相结合测量质子能谱.实验结果表明:质子沿着靶背法线方向发射;随着质子能量的增加,质子数减少;质子在一定能量处出现截断,截止能是1179 keV.     

注银热解碳的抗菌机理研究

使用革兰氏阳性菌--金黄色葡萄球菌,对注银热解碳的抗菌机理作了探讨分析.银离子的注入能量为70 keV,注入剂量分别为 5×1014, 1×1016, 5×1017 ion/cm2.用俄歇电子能谱(AES)和X射线光电子能谱(XPS)对样品表面进行了微观分析.结果表明:材料表面形成了富银层;对注银剂量相同的热解碳,直接接触的抗菌效果比其滤液的抗菌效果好.说明注银热解碳的抗菌作用是溶出的银离子和未溶出的材料表面络合状银离子的共同抗菌结果,且杀菌以银离子溶出为主.     

电子碰撞Ag的L壳层电离截面的测量

作者用Si(Li)探测器测量了能量为5～2keV的电子碰撞Ag的L壳总平均电离截面；用Monte Carlo方法计算的电子反射能谱，修正了来自衬底的反射电子对测量结果的影响．作者对实验结果与Cryzinski的理论计算结果进了比较．     

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。     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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