基于GATE仿真的分光法探测器优化设计

基于分光法的晶体阵列解码技术是正电子发射成像系统最为高效的探测器设计方案之一,但目前基于分光法的晶体阵列解码设计依赖于经验和实验迭代,晶体解码和分光层设计缺少有效的仿真方法。该文采用了GATE仿真软件,对分光法的探测器进行建模仿真,提出了逐列逼近的优化算法对分光层反光片进行长度优化设计,且对优化仿真中主要参数进行了分析,并组装4mm×4mm×25mm、12×12阵列实验模块对所提方法进行验证。实验结果表明:该基于GATE仿真的优化设计方法能有效实现分光法探测器晶体阵列解码的仿真以及解码斑点均匀分布的反光片长度优化设计。     

闪烁薄膜中子探测器灵敏度Monte Carlo计算

闪烁薄膜探测器的灵敏度和中子/γ分辨能力与闪烁晶体厚度密切相关,合理选择闪烁晶体厚度是探测器设计的关键。该文应用Monte Carlo方法模拟了中子和γ射线与闪烁晶体的相互作用过程,计算研究了晶体厚度对探测器灵敏度及中子/γ分辨能力的影响,给出了0.1~16.0MeV中子和γ射线照射下探测器的相对灵敏度,并结合部分能点的实验室标定数据,得到了探测器灵敏度能量响应曲线和中子/γ分辨率。理论计算的灵敏度能量响应曲线与实验标定趋势基本一致。     

相对永久密封真空康普顿探测器伽马灵敏度研究

针对强流脉冲γ射线探测,研制了厚入射窗结构真空康普顿探测器,并在60Co辐照装置上,准直孔径为40 mm的条件下,对2套样品探测器灵敏度进行了测量,得到了1.25 MeV的γ射线灵敏度,实验值分别为4.65×10-22 C/MeV和4.59×10-22 C/MeV.该实验值与蒙特卡罗程序MCNP的计算值(4.70×10-22 C/MeV)相比,误差范围一致,在0.5～3.0 MeV能量区间,探测灵敏度的能量响应变化小于20%.实验证明:该探测器比薄窗结构真空康普顿探测器的灵敏度提高了60%,克服了薄窗探测器封装加工和静态真空保持的困难;保存使用期可达2年以上,达到了相对永久密封的目的,可应用于粒子注量率为1020 cm-2·s-1以上的强流脉冲γ射线测量.     

具有间隙反射膜的稀疏SiPM阵列PET探测器性能评估

正电子发射断层成像仪(positron emission tomography,PET)通常采用模块化闪烁探测器,由闪烁晶体阵列耦合光电传感器阵列构成。近年来硅光电倍增管(silicon photomultiplier,SiPM)广泛应用于PET。虽然SiPM紧密排列可以获得较好性能,但是稀疏排列可以有效降低成本,获得较高性价比。该文采用SensL公司MicroFB-30035-SMT芯片自主拼接了一款8×8的稀疏SiPM阵列,阵列面积为33.7mm×33.7mm,SiPM芯片尺寸为3.16mm×3.16mm,即阵列间隙面积比例为44%。基于该稀疏SiPM阵列,开发了一款具有作用深度信息的双层错位LYSO晶体PET探测器模块。SiPM间隙为探测死区,将造成光损失。该文评估了在SiPM间隙粘贴增强型镜面反射膜(enhanced specular reflector,ESR)后对探测器性能的影响。在室温下采集了有无间隙反射膜2种情况下的泛场图像。开发了定量评估方法,评估了探测器的光电峰、能量分辨率和晶体响应均方根误差。结果表明:SiPM间隙粘贴反射膜提高光收集量25.5%,将探测器的能量分辨率由13.48%优化到12.80%;泛场图像质量也有了提升,即改善了探测器固有空间分辨率。     

籽晶保护条件下铈掺杂溴化镧晶体生长及其性能

为定向生长出铈掺杂溴化镧（LaBr3:Ce）晶体,改进了坩埚下降法,并在籽晶接种过程引进冷却气体的保护装置。生长出的LaBr3:Ce晶体在137Cs放射源辐照下,其能量分辨率为3.08%,衰减时间为20.1 ns。采用多通道DRS4采集系统,以XP20D0型光电倍增管耦合 Ф 20 mm×5 mm 溴化镧器件作为开始道探测器,H8500型光电倍增管耦合LaBr3:Ce阵列作为被测停止道探测器,放射源为22Na（511 keV）。制备了6×6的LaBr3:Ce阵列,单根晶体条的尺寸为2 mm×2 mm×15 mm。利用数字化波形分析法,获得阵列的清晰二维散点图和一维位置谱,阵列x和y方向的位置分辨率分别为1.01 mm和0.89 mm。制备出的LaBr3:Ce晶体具有优异的能量分辨率和位置分辨率,可以应用于PET等医学成像技术领域。     

电子加速器X射线发射率的MCNP分析

为满足现代X射线应用和设计电子加速器的靶结构和束流参数的需要,采用MCNP4B程序对2～20MeV能量范围内的电子束入射不同厚度钨靶的X射线发射率进行了系统的模拟计算和研究.结果表明在电子能量小于10MeV时,MCNP4B的结果与NCRP-51报告一致,但在10MeV以上,它们间的差别增大.该文结果对早期NCRP-51报告的结果有重要的改进,对于现代产生X射线的电子加速器靶的设计具有参数作用.     

用于激光等离子体X射线诊断的谱仪

为了诊断波长为0.5～0.8 nm的激光等离子体X射线,研制了一种新型的高空间和光谱分辨率的晶体谱仪.采用2个不同分光计材料、不同形状且相互垂直分布的通道可以同时获得谱线的空间和光谱分辨率.利用成像板接收光谱信号,其有效接收面积为30 mm×80 mm.讨论晶体基本参数和给出了谱仪设计参数.在中国工程物理研究院激光聚变研究中心的20 J激光器装置进行实验,两个方向的成像板同时获取得到了Al激光等离子体X射线光谱,其中水平通道的PET平面晶体获取的空间分辨率为1.73～6.88 mm,而垂直通道的Mica球面弯晶得到的光谱分辨率达到1 000～1 500.实验结果表明该谱仪适合于激光等离子体X射线的光谱学研究.     

钢纤维高强混凝土的配合比设计

结合钢纤维高强混凝土的工作特点,对钢纤维高强混凝土的原材料选择要求与配合比设计进行了阐述.根据设计的钢纤维高强混凝土配合比,浇筑了168个150 mm×150 mm×150 mm立方体、30个100 mm×100 mm×400 mm和60个150 mm×150 mm×450 mm棱柱体钢纤维高强混凝土试件,并测试了其基本力学指标.结果表明,通过材料优选和适宜的配合比设计,采用常规制备工艺可以配制出拌和性能良好及满足强度要求的钢纤维高强混凝土.     

用Monte Carlo方法设计X射线均整器

在以电子直线加速器为X射线源的工业CT和辐射治疗中,需要较均匀的X射线剂量率空间分布。利用MonteCarlo方法,设计了6MeV和9MeV的X射线均整器。对9MeV的X射线均整器进行了实验。实验结果表明:在距靶1m处测得均整后0°处的剂量率约为均整前的74%,7.5°处的剂量率约为0°处的69%。满足Varian标准。该均整器在满足平坦度要求的同时提高X射线剂量利用率,不经过打磨便可得到较好的均整结果。     

Xe~(30+)在Au下表面退激辐射的X射线谱

报导了1.0~3.0MeV的Xe~(30+)离子与1.0MeV的Xe~(26+)离子入射Au表面发射的X射线谱,考虑到探测器Be窗对射线的非均匀衰减,还原了1.0MeV的Xe~(30+)离子产生X射线谱。通过用经典过垒模型及两体碰撞模型的分析表明:动能1.0~3.0MeV的Xe~(30+)离子入射Au靶,下表面空心原子M壳层空穴退激发射了能量0.7~1.75keV的Xe M X射线,下表面空心原子N壳层空穴退激发射了能量0.5~0.7keV的Xe N X射线。     

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.     

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.     

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.     

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.     

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.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

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。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

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.     

The Analects and the Moment in Peking——The influence of a Confucian education system on the personality formation,the way of thinking and the fate of the main characters

0.Preface China has long been boasting of its colorful and immense culture which comprises of Taoism,Confucianism and Buddhism.The interwoven influence among the religions on Chinese way of thinking,on the nation＇s behavior in their social life throughout the long history is beyond list.