GaN基带电粒子探测器能谱测量的改进研究

分析了GaN和Si两种不同探测器的电荷灵敏前置放大器增益,修正了GaN基带电粒子探测器能谱的放大倍数。利用~(241)Am和~(239)Pu两种α粒子源标定了能量与道指的关系,获得了能量刻度曲线方程。根据标定的曲线方程,测量了修正前后的GaN基pin探测器~(241)Am源的能谱。修正后的测量结果表明,当反向偏压为-10 V时,5.48 MeV的~(241)Am源在GaN基pin探测器里沉积的能量约为620 keV。     

第3代双源CT虚拟单能量成像去除腰椎金属 内固定伪影的效果评估

目的:评估双源CT虚拟单能量成像对腰椎椎弓根螺钉内固定术后腰椎金属伪影的去除效果.方法:对40例腰椎椎弓根螺钉内固定术后患者使用Force双源CT行双能量扫描复查,并将图像进行标准线性融合(M_0.6)、FAST DE、虚拟单能量图像重建6组(虚拟能级为40～190 keV,间隔为30 keV)共8组.分别对8组图像的主观质量按照4分法评分.使用Friedman(M)检验评价8组图像的主观质量评分之间差异;用Kappa检验评价主观评分的一致性;客观评分为有、无伪影层面腰大肌CT值,并对其进行配对t检验.结果:130 keV及160 keV图像主观评分明显优于其他组重建图像(P0.01),其中130 keV图像评分均值显著高于160 keV图像(P0.01);130 keV图像中腰大肌CT值,在有、无伪影层面无统计学差异(P0.05).结论:双源CT虚拟单能量重建技术可以减少腰椎内固定金属伪影,得到高质量的重建图像,最佳成像条件为130 keV单能量重建.     

Hf同位素新衰变γ射线的观测

利用14MeV中子轰击天然钨靶,通过^180,182,183,184,186W（n,2pxn）反应,产生铪的放射性同位素,以γ（X）谱学方法鉴别出铪,观测到了能量为75．2keV和88．7keV的2条新1射线,测定其半衰期为（3．6±0．6）min。     

能量转换器件参数对氚和~(147)Pm辐射伏特同位素电池性能影响

采用理论模拟和实验方法,开展单晶硅PN结能量转换器件的结构参数和性能对氚源和147Pm源加载下的同位素电池输出性能影响研究.结果显示:同样的能量转换器件参数(包括表面钝化层厚度、顶层掺杂浓度和厚度、基层掺杂浓度和厚度、器件的漏电流等)对不同加载放射源的辐伏同位素电池输出性能影响相差较大.该结果对选择不同加载源的辐伏同位素电池能量转换器件设计具有较大指导和参考作用.     

延长PET轴向视野的马赛克物理设计方案

该文提出一种马赛克式正电子发射断层成像(PET)探测器设计方案,通过改变晶体的排布方式,并基于GATE(Geant4Application for Emission Tomography)软件模拟,对3种马赛克PET的设计方案和传统的PET设计方案进行了多方面的对比,对比的内容包括:轴向探测效率、体源探测效率以及空间分辨率。并且进一步考虑能量下阈的影响,比较能量下阈为0keV、250keV和350keV时各个方案测得的结果的变化。结果表明:马赛克PET方案在不考虑能量下域时,轴向探测效率提高24%~50%,而体源探测效率更是可以提高47%~62%。当能量下阈为250keV时,方案4的轴向探测效率和体源探测效率可分别提升12%和8%,于此同时其重建图像空间分辨率较传统方案相比接近。     

椭球单毛细管高能X射线微焦斑透镜模拟表征

为了使单毛细管透镜在X射线微区分析中获得高能X射线微焦斑,设计并模拟了基于椭球单毛细管的高能X射线微焦斑透镜,并模拟透镜内表面镀金属氧化膜,氧化膜主要成分为HfO₂.结果表明：镀膜透镜和普通玻璃透镜都可以将能量为100 keV的X射线会聚成<10.0μm的焦斑;与普通玻璃透镜相比,透镜镀膜后X射线聚焦能量上限提高了约2倍.为增加镀膜透镜光通量,重新设计了镀膜透镜,该新透镜相比于最初设计的普通玻璃透镜,在相同的实验室光源条件下聚焦能量为100 keV的X射线,在焦斑处光通量提高了3.8倍,功率密度增益提高了1个数量级,这表明透镜镀膜对聚焦高能X射线有一定的应用价值.模拟结果对椭球单毛细管高能X射线透镜的研制和应用具有指导意义.     

不同放射源在同位素电池换能单元肖特基结金属中的能量沉积

辐射伏特效应同位素微电池具有体积小、能量密度高、寿命长、安全稳定等优点,逐渐成为微能源研究的重要方向。采用基于蒙特卡罗数值计算法的Geant 4软件,对基于宽禁带半导体金刚石/金属肖特基结的辐伏电池换能单元中使用不同放射源在不同肖特基金属内的能量沉积进行了模拟计算,结果表明,Ni-63,H-3,Pm-147放射源对应Cu,Au,Ni肖特基金属,不同β辐射源通过金属的能量损失主体方式不同,Ni-63放射源以能量反散射和金属内能量沉积两种主体形式损失能量,而H-3放射源和Pm-147放射源主要以反散射形式损失能量,入射能量在金属层内的能量沉积占比很小。要使反射和沉积的能量低于设定的阈值(10%),相应的金属厚度要求各有不同:对于Ni-63源,对应金属Cu,Au,Ni最大厚度分别为30,20,30 nm;对于H-3源,3种金属Cu,Au,Ni临界厚度均为100 nm;对于Pm-147源,对应的厚度分别为20,10,10 nm。计算结果可为金刚石/金属肖特基结同位素电池换能单元中金属层的优化设计提供理论参考。     

纤锌矿GaN/AlN无限量子阱中激子能量

利用改进的LLP变分法计算了纤锌矿GaN/AlN无限量子阱中激子的基态能量和结合能,并对闪锌矿GaN/AlN量子阱和纤锌矿GaN/AlN量子阱中激子的基态能量和结合能进行了对比.结果表明:纤锌矿GaN/AlN无限量子阱材料中激子基态能量和结合能随着量子阱宽度增大而降低,当阱宽较小时急剧下降,阱宽较大时缓慢下降,最后趋近GaN体材料的三维值;考虑极化子效应时激子的基态能量和结合能明显低于裸激子的基态能量和结合能,电子-声子相互作用对激子能量的贡献较大;纤锌矿GaN/AlN量子阱中激子基态能量小于闪锌矿GaN/AlN量子阱中激子的基态能量,纤锌矿GaN/AlN量子阱中激子的结合能大于闪锌矿GaN/AlN量子阱中激子的结合能,且随着阱宽的增大,两种阱中基态能量和结合能的差距越来越小.     

强流脉冲离子束与钛靶相互作用数值研究

简要讨论了强脉冲离子束与钛靶相互作用的理论模型,选取特定参数,应用数值计算的方法模拟计算离子能量为100 keV、300 keV和450 keV的H 、C 离子束与钛靶相互作用,给出了钛靶在辐照后离子浓度-深度分布、能量梯度分布等模拟计算结果.H 与钛靶相互作用过程中的能量损失在钛靶内部出现峰值,然后迅速减少为零,而C 在钛靶表面沉积较多的能量.     

新型射频能量收集系统设计与分析

随着无线传感器网络等电子微系统的发展,作为能量源的电池满足不了长久供电的需求.利用周围环境中的射频能量为自身提供电能已经越来越受到科研工作者的关注.针对目前常用射频能量收集系统转换效率较低的不足,提出了一种由超宽带天线、匹配网络、整流升压电路等组成的新型能量收集系统.利用HFSS软件对超宽带天线进行仿真优化,使得该天线在宽频带下具有较好的特性;通过整流升压电路在不同负载下的整流效率分析,确定了整流器转换效率较高的负载取值范围.新型射频能量收集系统的效率为13.5%,比常用的其他射频能量收集系统的效率提高了将近6%.     

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