检索结果-南通市图书馆

Development and preliminary results of a large-pixel two-layer LaBr_(3) Compton camera prototype

Nuclear Science and Techniques 2023年第8期34卷 100-114页

作者： Ming-Hao Dong zhi-yang Yao Yong-Shun Xiao Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

Lanthanum bromide(LaBr_(3))crystal has a high energy resolution and time resolution and has been used in Compton cameras(CCs)over the past few ***,LaBr_(3) crystal arrays are difficult to process because LaBr_(3) is easy to crack and break;thus,few LaBr_(3)-based CC prototypes have been *** this study,we designed and fabricated a large-pixel LaBr_(3) CC prototype and evaluated its performance with regard to position,energy,and angular *** used two 10×10 LaBr_(3) crystal arrays with a pixel size of 5 mm×5 mm,silicon photomultipliers(SiPMs),and corresponding decoding circuits to construct our ***,a framework based on a Voronoi diagram and a lookup table was developed for list-mode projection data *** Carlo(MC)simulations based on Geant4 and experiments were conducted to evaluate the performance of our CC *** lateral position resolution was 5 mm,and the maximum deviation in the depth direction was 2.5 and 5 mm for the scatterer and absorber,*** corresponding measured energy resolu-tions were 7.65%and 8.44%,respectively,at 511 *** experimental results of ^(137)Cs point-like sources were consistent with the MC simulation results with regard to the spatial positions and full widths at half maximum(FWHMs).The angular resolution of the fabricated prototype was approximately 6°when a point-like ^(137)Cs source was centrally placed at a distance of 5 cm from the *** proposed and investigated a large-pixel LaBr_(3) CC for the first time and verified its feasibility for use in accurate spatial positioning of radiative sources with a high angular *** proposed CC can satisfy the requirements of radiative source imaging and positioning in the nuclear industry and medical applications.

关键词： Compton camera Large pixel Gamma camera LaBr_(3)detector Prototype evaluation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Environmental impact of radionuclide migration in groundwater from a low intermediate level radioactive waste repository

引用

Journal of Environmental Sciences 2001年第2期13卷 180-184页

作者： Wang, Jin-sheng yang, zhi-feng Li, Shu-shen Wang, zhi-ming Institute of Environmental Sciences Beijing Normal UniversityState Key Joint Laboratory of Environmental Simulation and Pollution Control Beijing 100875 China China Institute for Radiation Protection Taiyuan 030006 China

The radionuclide migration from a certain Chinese repository with low-intermediate level radioactive solid waste is studied. The migration in groundwater is analyzed and computed in detail. Under presumption of normal releasing, or the bottom of the repository has been marinated for one month with precipitation reaching 600 mm once and a 6 m aerated zone exists, a prediction for 7 radionuclides is conducted. It shows that the aerated zone is the primary barrier for migration. The migration for radionuclides 60Co, 137Cs, 90Sr, 63Ni, etc. will be retarded in it within 500 years. The concentration of 239Pu will be decreased by amount of 6 order. Only 3H and 14C can migrate through the aerated zone. The radionuclides that go through the aerated zone and enter the aquifer will exist in spring, stream and sea. Based on this, the intake dose by residents in different age group resulting from drinking contaminated spring water, eating seafood is calculated. The results showed that the impact of the repository to the key resident group is lower than the limit in national repository regulation standard. This complies with the repository management target.

关键词： intermediate level radioactive waste repository Environmental impact of radionuclide migration in groundwater from a low

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Luminescence and Site Occupancy of Eu2＋ in Ba2 Ca（BO3）2

引用

Chinese Physics Letters 2011年第1期28卷 190-192页

作者： LI Pan-Lai WANG zhi-Jun yang zhi-Ping GUO Qing-Lin Colleg-e of Physics Science and Technology Hebei University Baoding 071002

A green phosphor Ba2Ca（BOa）2：Eu2＋ was syntheMzed by a high temperature solid-state reaction method under a reductive amosphere,, The luminescence and site occupancy of Eu2＋ in Ba2Ca（BOa）2 are investigated. Ba2Ca（BO3）2：Eu2＋ shows one green band （537nzn） under 400nln near ultraviolet excitation which is suitable for UV LED. Ca2＋ and Ba2＋ ions in Ba2Ca（BO3）2 are replaced by Eu2＋ ions, the Ba2Ca（BO3）2：Eu2＋ shows a dissymmetrical emission band. The influence of Eu2＋ doping concentrations on the emission intensity of Ba2Ca（BOa）2：Eu2＋ is studied. It is found that the emission intensity is influenced by the Eu2＋ concentration and reaches the maxinmm value at 2% Eu2＋, According to the Dexter theory, the concentration quenching mechanisms of Eu2＋ in Ba2 Ca（B03）2 are the d - d interaction,

关键词： Greening Calcium Ions Concentrates Concentrating

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Coupled Bending-Bending-Axial-Torsional Vibrations of Rotating Blades

引用

Acta Mechanica Solida Sinica 2019年第3期32卷 326-338页

作者： Feng Liang Zhen Li Xiao-Dong yang Wei Zhang Tian-zhi yang College of Mechanical Engineering Yangzhou University Yangzhou 225127 China Beijing Key Laboratory of Nonlinear Vibrations and Strength of Mechanical Engineering College of Mechanical Engineering and Applied Electronics Beijing University of Technology Beijing 100124 China Department of Engineering Mechanics Shenyang Aerospace University Shenyang 110136 China

In this paper, the coupled bending-bending-axial-torsional free vibrations of rotating blades are investigated based on the Euler-Bernoulli beam model. The coupled partial differential equations governing flapwisc, edgewise, axial and torsional motions are derived by the Hamilton's principle, wherein three types of velocity-dependent terms, namely static centrifugal terms, dynamic centrifugal terms and gyroscopic coupling terms, are focused. The ordinary di& ferential equations are acquired by the Galerkin truncation, and the natural frequencies in all directions and complex mode shapes of the rotating blades are analyzed in detail. It is revealed that the three types of velocity-dependent terms have different effects on the natural frequencies. The natural frequencies are noticeably dependent on the rotating speed and preset angle, except for the axial vibration, which is almost immune to the preset angle. The complex modal motions are displayed by a series of positions of the central line and free-end cross section for different time instants, showing the coupled vibrations among different directions.

关键词： Rotating blades Coupled vibrations Gyroscopic coupling Complex modes Preset angle

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Free vibration analysis of a spinning piezoelectric beam with geometric nonlinearities

引用

Acta Mechanica Sinica 2019年第4期35卷 879-893页

作者： Wei Li Xiao-Dong yang Wei Zhang Yuan Ren Tian-zhi yang Beijing Key Laboratory of Non-linear Vibrations and Strength of Mechanical Engineering College of Mechanical Engineering Beijing University of Technology Beijing100124 China Department of Aerospace Science and Technology Space Engineering University Beijing 101416 China Department of Mechanics Tianjin University Tianjin 300072 China

The linear and non-linear free vibrations of a spinning piezoelectric beam are studied by considering geometric nonlinearities and electromechanical coupling effect. The non-linear differential equations of the spinning piezoelectric beam governing two transverse vibrations are derived by using two Euler angles transformation and extended Hamilton principle, wherein an additional piezoelectric coupling term and different linear terms are present in contrast to the traditional shaft model. Linear frequencies are obtained by solving the standard eigenvalues of the linearized system directly, and the non-linear frequencies and non-linear complex modes are achieved by using the method of multiple scales. For free vibrations analysis of a spinning piezoelectric beam, the non-linear modal motions are investigated as forward and backward precession with different spinning speeds. The responses to the initial conditions for such a gyroscopic system are studied,and a beat phenomenon is found, which are then validated by numerical simulation. The influences of some parameters such as electrical resistance, rotary inertia and spinning speeds to the non-linear dynamics of a spinning piezoelectric beam are investigated.

关键词： Spinning piezoelectric beam Free vibrations Non-linear frequencies Complex modes

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Exploring the entanglement of free spin-(1/2), spin-1 and spin-2 fields

引用

Chinese Physics C 2019年第5期43卷 12-22页

作者： zhi yang Ling-Yan Hung Department of Physics & Center for Field Theory and Particle Physics Fudan University State Key Laboratory of Surface Physics & Department of Physics Fudan University

In this study, we explore the entanglement of free spin-(1/2), spin-1, and spin-2 fields. We start with an example involving Majorana fields in 1+1 and 2+1 dimensions. Subsequently, we perform the Bogoliubov transformation and express the vacuum state with a particle pair state in the configuration space, which is used to calculate the entropy. This clearly demonstrates that the entanglement entropy originates from the particles across the ***, we generalize this method to free spin-1 and spin-2 fields. These higher free massless spin fields have wellknown complications owing to gauge redundancy. We deal with the redundancy by gauge-fixing in the light-cone gauge. We show that this gauge provides a natural tensor product structure in the Hilbert space, while surrendering explicit Lorentz invariance. We also use the Bogoliubov transformation to calculate the entropy. The area law emerges naturally by this method.

关键词： entanglement Bogoliubov transformation tensor product structure

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Innate immunity against malaria parasites in Anopheles gambiae

引用

Insect Science 2008年第1期15卷 45-52页

作者： yang Chen zhi-Hui Weng Liangbiao Zheng Shanghai Institute of Plant Physiology and Ecology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences 300 Fenglin Road ShanghaL China

Malaria continues to exert a huge toll in the world today, causing approximately 400 million cases and killing between 1-2 million people annually. Most of the malaria burden is borne by countries in Africa. For this reason, the major vector for malaria in this continent, Anopheles gambiae, is under intense study. With the completion of the draft sequence of this important vector, efforts are underway to develop novel control strategies. One promising area is to harness the power of the innate immunity of this mosquito species to block the transmission of the malaria parasites. Recent studies have demonstrated that Toll and Imd signaling pathways and other immunity-related genes （encoding proteins possibly function in recognition or as effector molecules） play significant roles in two different arms of innate immunity： level of infection intensity and melanization of Plasmodium oocysts. The challenges in the future are to understand how the functions of these different genes are coordinated in defense against malaria parasites, and if different arms of innate immunity are cross-regulated or coordinated.

关键词： Anopheles immunity infection intensity malaria melanization

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

A possible explanation for the electron/positron excess of ATIC/PAMELA

引用

Research in Astronomy and Astrophysics 2010年第1期10卷 39-46页

作者： Rui-zhi yang Jin Chang Jian Wu Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

Results from PAMELA and ATIC indicate that the Kaluza-Klein type dark matter particles could be the annihilation source of the observed excess of electrons and positrons. Assuming the existence of a nearby black hole with 10000-100000 solar masses and a point source boost algorithm, we apply the standard propagation model and find that the results fit the data well.

关键词： dark matter - black hole physics - cosmic rays

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

与图像内容无关的聚焦程度评价方法

引用

西安交通大学学报 2025年第1期59卷 116-124页

作者：夏晓华柴玉琳岳鹏举杨治秦绪芳长安大学道路施工技术与装备教育部重点实验室西安710000

针对现有的聚焦程度评价方法在图像场景内容改变时不能正确评价图像聚焦程度的问题,基于“分类+拟合”的思想,提出了一种与高斯模糊标准差完全等价的图像聚焦程度评价方法。首先,建立了以有限高斯模糊标准差为标记的图像聚焦程度分类数... 详细信息

针对现有的聚焦程度评价方法在图像场景内容改变时不能正确评价图像聚焦程度的问题,基于“分类+拟合”的思想,提出了一种与高斯模糊标准差完全等价的图像聚焦程度评价方法。首先,建立了以有限高斯模糊标准差为标记的图像聚焦程度分类数据集;然后,构建了用于提取图像高斯模糊标准差分类分数的非对称核卷积神经网络(AKC-net);最后,采用三次样条插值函数拟合AKC-net全连接层输出的分类分数以及对应的高斯模糊标准差,以最大分数对应的标准差作为图像的聚焦程度评价结果,并在Waterloo数据集和实际拍摄图像上分别进行仿真实验和实拍实验。结果表明:所提方法在不同聚焦图像上分类的平均准确率可达到97.7%,得到的评价结果与高斯模糊标准差真值的均方根误差和平均绝对误差均小于0.07,且实际拍摄图像的聚焦测度值与图像内容无关,实现了图像聚焦程度的绝对评价。

关键词：聚焦程度评价高斯模糊标准差非对称核卷积神经网络三次样条插值

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effect of Dissolved Organic Matter on Chlorotoluron Sorption and Desorption in Soils

引用

Pedosphere 2005年第4期15卷 432-439页

作者： yang Hong WU Xin ZHOU Li-Xiang yang zhi-Min Department of Chemistry College of Science Nanjing Agricultural University Nanjing 210095 （China） College of Resources and Environmental Sciences Nanjing Agricultural University Nanjing 210095 （China） College of Life Science Nanjing Agricultural University Nanjing 210095 （China）

A batch equilibrium techniques was used to examine the effect of dissolved organic matter （DOM） extracted from both non-treated sludge （NTS） and heat-expanded sludge （HES） on the sorption and desorption of chlorotoluron （3-（3-chloro-p-tolyl）-1,1-dimethylurea） in two types of soils, a yellow fluvo-aquic and a red soil from China. Without DOM,sorption of chlorotoluron was significantly greater （P 〈 0.05） in the red soil than in the yellow fluvo-aquic soil. However,with DOM the effect was dependent on the soil type and nature of DOM. Chlorotoluron sorption was lower in the yellow fluvo-aquic soil than in the red soil, suggesting that with the same DOM levels the yellow fluvo-aquic soil had a lower sorption capacity for this herbicide. Application of DOM from both NTS and HES led to a general decrease in sorption to the soils and an increase in desorption from the soils. Desorption of chlorotoluron also significantly increased （P 〈 0.05） with an increase in the DOM concentration. Additionally, for sorption and desorption, at each DOM treatment level the NTS treatments were significantly lower （P 〈 0.05） than the HES treatments. This implied that non-treated sludge had a greater effect on the sorption and desorption of chlorotoluron than heat-expanded sludge.

关键词： chlorotoluron desorption dissolved organic matter sludge sorption

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：