分类： 物理学 >> 核物理学 提交时间： 2024-06-02
摘要： The Circular Electron Positron Collider (CEPC) is designed to precisely measure the properties of the Higgs boson, study electroweak interactions at the Z-boson peak, and search for new physics beyond the Standard Model. As a component of the 4th Conceptual CEPC detector, the drift chamber facilitates the measurement of charged particles. This study implemented a Geant4-based simulation and track reconstruction for the drift chamber. For the simulation, detector construction and response were implemented and added to the CEPC simulation chain. The development of track reconstruction involved track finding using the Combinatorial Kalman Filter method and track fitting using the tool of GenFit. Using the simulated data, the tracking performance was studied. The results showed that both the reconstruction resolution and tracking efficiency satisfied the requirements of the CEPC experiment.
分类： 核科学技术 >> 核科学与技术 提交时间： 2024-06-02
摘要： 氢化物是锆合金包壳管在核电厂正常运行过程中与一回路冷却剂发生锆水反应而产生的常见缺陷。本文利用分子动力学方法，采用COMB3势函数，构建含氢化物的锆基模型进行单轴拉伸模拟，探究了氢化物密度对锆力学性能的影响。研究结果表明，当氢化物密度在0~1078 µg/g时，随着氢化物密度的增加，屈服强度、应变和杨氏模量降低。在弹性阶段，氢化物密度的增加使应力集中区域增大，有利于位错形核；在塑性变形阶段，随着氢化物密度的增大，初始位错更倾向于在氢化物周围扩展。当氢化物密度在1078 ~ 2311 µg/g时，随氢化物密度的增加，屈服强度、应变和杨氏模量升高，这是由于氢化物密度较高时产生了大量位错并造成位错塞积。
分类： 核科学技术 >> 核科学技术其他学科 提交时间： 2024-05-31
摘要： Neutron-sensitive microchannel plates (nMCPs) have applications in neutron detection, including energy spectrum measurements, neutron-induced cross-sections, and neutron imaging. 10B-doped MCPs (B-MCPs) have attracted significant attention owing to their potential for exhibiting a high neutron detection efficiency over a large neutron energy range. Good spatial and temporal resolutions are useful for neutron energy-resolved imaging. However, their practical applications still face many technical challenges. In this study, a B-MCP with 10 mol% 10B was tested for its response to wide-energy neutrons from eV to MeV at the Back-n white neutron source at the China Spallation Neutron Source. The neutron detection efficiency was calibrated at 1 eV, which is approximately 300 times that of an ordinary MCP and indicates the success of 10B doping. The factors that caused the reduction in the detection efficiency were simulated and discussed. The neutron energy spectrum obtained using B-MCP was compared with that obtained by other measurement methods, and showed very good consistency for neutron energies below tens of keV. The response is more complicated at higher neutron energy, at which point the elastic and non-elastic reactions of all nuclides of B-MCP gradually become dominant. This is beneficial for the detection of neutrons, as it compensates for the detection efficiency of B-MCP for high-energy neutrons.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-05-31
摘要： Neutron resonance imaging (NRI) has recently emerged as an appealing technique for neutron radiography. Its complexity surpasses that of conventional transmission imaging, as it requires a high demand for both a neutron source and detector. Consequently, the progression of NRI technology has been sluggish since its inception in the 1980s, particularly considering the limited studies analyzing the neutron energy range above keV. The white neutron source (Back-n) at the China Spallation Neutron Source (CSNS) provides favorable beam conditions for the development of the NRI technique over a wide neutron energy range from eV to MeV. Neutron-sensitive microchannel plates (MCP) have emerged as a cutting-edge tool in the field of neutron detection owing to their high temporal and spatial resolutions, high detection efficiency, and low noise. In this study, we report the development of a 10B-doped MCP detector, along with its associated electronics, data processing system, and NRI experiments at the Back-n. Individual heavy elements such as gold, silver, tungsten, and indium can be easily identified in the transmission images by their characteristic resonance peaks in the 1-100 eV energy range; the more difficult medium-weight elements such as iron, copper, and aluminum with resonance peaks in the 1-100 keV energy range can also be identified. In particular, results in the neutron energy range of dozens of keV (Aluminum) are reported here for the first time.
分类： 核科学技术 >> 核科学技术其他学科 提交时间： 2024-05-31
摘要： 随着机器学习在中子-伽马（n-γ）甄别中的广泛应用，脉冲波形甄别中的特征子集选择成为一个值得关注的问题。经验方法、Random Forest分类和Logistic回归特征选择算法较为全面地完善了特征子集选择方法，核主成分分析（KPCA）则将特征子集进一步降维。实验结果表明，特征选择算法在微弱的核信号中表现不佳，错误率均达30%以上。经验方法中的特征子集选取范围则至关重要，特征子集“1-62”的错误率达到49.096%，远高于来自脉冲尾部的特征子集约1%的错误率。最优特征子集与尾积分对应的采样点不完全重合，但差异不大，尾积分对应的采样点可近似为最优特征子集。通过研究目前具有代表性的Random Forest分类、Logistic回归等特征选择算法和细致的经验方法，论文结果具有普适性，为特征子集的选择提供了进一步的理论支持。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-05-31
摘要： To further research on high-parameter plasma, we plan to develop a two-dimensional hard X-ray (HXR) imag#2;ing system at the HL-3 tokamak to measure HXRs with energies ranging from 20 to 300 keV. The application of an array-structured detector ensures that this system can measure HXR-radiation spectra from the entire plasma cross section. Therefore, it is suitable for the study of fast-electron physics, such as radio-frequency wave current drives, fast electrons driving instabilities, and plasma disruptions in fusion research. In this study, we develop a simulation for calculating fast-electron bremsstrahlung in the HL-3 tokamak based on the Monte Carlo simulation code Geant4, in which the plasma geometry and forward scattering of fast-electron bremsstrahlung are considered. The preliminary calculation results indicate that the HXR energy deposition on the detector is symmetrically distributed, even though the plasma distribution is asymmetric owing to the toroidal effect. These simulation results are helpful in constructing the relationship between the energy deposition on the de#2;tector and parameter distribution on the plasma cross section during HL-3 experiments. This is beneficial for the reconstruction of the fast-electron distribution function and for optimizing the design of the HXR-imaging system.
分类： 核科学技术 >> 核科学与技术 提交时间： 2024-05-29
摘要： CF系列燃料组件是中核集团自主研发的先进三代核电反应堆核心部件，为分析CF2燃料组件在多对中值工况下，驱动线运动部件在水和空气中的摩擦力与落棒性能，采用1：1的CF2模拟燃料组件配合自主设计研发的可调节旋转式顶盖首次实现了多个错对中值的集成，能够对多个错对中值进行科学准确的调节。优化了驱动机构性能研究的方法，获取了驱动机构在水和空气两种介质中全行程、多错对中值工况下的摩擦力与落棒性能数据。落棒总时间和棒到缓冲口时间均随着对中值增加而增大，但缓冲时间基本保持一致。燃料组件与控制棒在最大对中值工况下运行良好，摩擦力没有超过允许极限值，也未发生在大对中值工况下的卡棒现象。该研究结果为CF系列燃料组件的设计定型、安全评定与软件开发提供了重要的试验依据，其方法可推广至后续CF3等燃料组件的科研项目中。
分类： 管理学 >> 企业管理 提交时间： 2024-06-05
摘要： This paper aims to leverage the advancements in General Computer Control (GCC) to improve the efficiency and effectiveness of risk management operations in financial institutions. Specifically, we introduce an LLM-based Robotic Process Automation (RPA) framework designed to enhance front-line employee work, adapt to the specific needs of financial institutions, and automate tasks requiring minimal cognitive effort. To demonstrate the effectiveness of our proposed framework, stress testing, a common task for risk management department, is used as a case study. The results show that the RPA system can improve efficiency, reduce costs, and minimize errors, all without significantly altering the existing workflow. Moreover, to address customer information security and prompts copyright protection issues, a storage method that separates the server from the client is used. Finally, empirical evidence implies that even models with weaker capabilities can achieve the desired work objectives when guided by detailed prompts.
提交时间： 2024-06-02 合作期刊: 《广西植物》
摘要： 报道了中国苦苣苔科（Gesneriaceae）一新记录属——四轮苣苔属（Tetraphyllum Griff. ex C. B. Clarke）。四轮苣苔属仅有3 种，其中密花四轮苣苔［T. confertiflorum (Drake) B. L. Burtt］在我国首次记录，该研究提供该属的形态描述和分种区别特征，并提供了该种的详 细的形态描述及彩色照片，凭证标本藏于广西植物研究所标本馆（IBK）和上海辰山植物标 本馆（CSH）。
分类： 图书馆学、情报学 >> 图书馆学 提交时间： 2024-06-05
摘要： 目的 分析Hindawi期刊批量撤销的论文的部分特征，以期为中国科技期刊处理对出版流程的系统性操纵提供参考； 方法 从Hindawi XML文集获取撤稿声明与被撤销论文。基于Web of Science核心合集分析被撤销论文的作者所属机构与被引用情况； 结果 Hindawi期刊在2022年11月16日至2024年3月20日共撤销11371篇论文。被撤销论文74.7%发表于2022年，从投稿到接收平均46日，从投稿到发表平均77日，从发表到被撤销平均526日。同期发文量最多的50所中国内地机构参与发表18.6%的被撤销论文； 结论 批量撤销牵涉到对出版流程的系统性操纵的论文，是出版商打击“论文工厂”的实践。尽管被批量撤销的论文绝大部分有来自中国内地的作者，但不能认为被撤销论文的作者对中国科研人员具有代表性。中国科技期刊应避免由编辑工作失能导致出版流程被操纵，科研机构应加强科研诚信教育以避免中国作者涉入类似事件。
分类： 图书馆学、情报学 >> 图书馆学 提交时间： 2024-06-03
摘要： 深入研究中华体育精神有助于赓续红色体育基因，凝聚中华民族伟大复兴的精神力量，对加快实现体育强国的战略目标具有重要的时代价值和现实意义。运用文献计量法与Cite Space软件，通过对CNKI文献数据解析、整理，系统阐释学界关于中华体育精神研究的现状、热点、路径及发展态势。中华体育精神研究已形成基本范式，具有连续性和持久性、导向性和实践性、多样性和高被引率，但也有一定的局限性和分散性，需要从多元主体、多维视角协同推进中华体育精神的系统性研究。
分类： 护理学 >> 护理学 分类： 医学、药学 >> 中医学与中药学 提交时间： 2024-06-05
摘要： 总结分析1例巨细胞感染继发颅内静脉窦血栓形成案例，本例患者以头痛为主要临床表现，伴呕吐、冷汗等表现，无发热、咳嗽症状。入院后完善相关检查，予以降低颅内压、抗凝、抗病毒等治疗，并完善腰椎穿刺和颅内血管造影，密切监测患者生命体征，通过卧位、饮食及大小便等基础护理来预防脑疝形成，监测用药及术后体征，多方面治疗及护理，促进患者康复。
提交时间： 2024-06-02 合作期刊: 《古脊椎动物学报》
摘要： 裂齿鱼科是新鳍鱼类干群的一支，只生活于三叠纪。根据江苏句容和安徽巢湖早三 叠世奥伦尼克期晚史密斯亚期海相地层中发现的6块保存较好的化石，命名了裂齿鱼科一 新种，吴氏三叠鱼(Teffichthys wui sp. nov.)。它代表了三叠鱼属的第三个种，时代上略晚于 非洲马达加斯加早史密斯亚期的马达加斯加三叠鱼和贵州印度期晚第纳尔亚期的优雅三叠 鱼，是该属迄今已知最年轻的种。新种具有三叠鱼属的共近裔特征(一块喷水骨，38–41列 侧线鳞，尾鳍轴上鳍条不超过3条), 但同时它以一些自近裔特征与马达加斯加三叠鱼和优雅 三叠鱼相区别，如主鳃盖骨和下鳃盖骨水平接触，鳞片光滑并且后缘无锯齿。根据新种与 其他裂齿鱼科鱼类的详细比较，修订了三叠鱼属及裂齿鱼科的鉴定特征。在分支系统学研 究的基础上，讨论了裂齿鱼科与其他新鳍鱼类干群的系统发育关系。研究结果为了解新鳍 鱼类干群的系统发育和分类提供了新的信息。
分类： 语言学及应用语言学 >> 语言学及应用语言学 分类： 计算机科学 >> 自然语言理解与机器翻译 提交时间： 2024-06-05
摘要： 目的 量化低资源语言平行语料的句对齐评分，获取高质量平行语料，提升机器翻译的性能。 方法 提出基于神经网络的无监督句嵌入双语平行语料句对齐评分方法 NeuroAlign：将平行句对嵌入至同一向量空间，计算平行语料中给定候选句对的对齐评分，然后根据评分排序过滤分值较低的平行句对，获得高质量的低资源语言双语平行语料。 结果 BUCC2018 平行文本挖掘任务中 F1 值可提升 0.5-0.8；CCMT2021 低资源语言神经机器翻译中 BLEU 值可提升 0.1-10.9；句对齐评分可接近人工评分。 局限 限于低资源双语平行语料的资源匮乏，未在藏汉、维汉、蒙汉以外的语言对上进行探索研究。 结论 可以有效应用至低资源语言平行语料的句对齐评分，从数据源端提升语料质量，进而改进机器翻译的效果。
分类： 管理学 >> 科学学与科技管理 提交时间： 2024-06-05
摘要： 目的 检验主要科技论文数据库的作者识别号的覆盖范围与准确性，并验证其能否直接用于科学学与科技政策的实证研究。方法 以825位华人科学家的发表论文为标准数据集，通过检索和收集科技论文数据库中科学家识别号及其论文信息，计算数据的覆盖率、准确性和稳健性，并运用双重差分法进行实验复现检验数据库的适用性。结果 第一，WOS、Scopus、AMiner和OpenAlex四个数据库可检索到90%以上的华人科学家识别符，ORCID覆盖率不足50%。第二，Scopus的准确性最高为85.2%，OpenAlex最低仅为51.2%；第三，直接使用数据库作者识别号的数据用于实证研究会引入不可忽视的误差。局限 准确集主要由青年科学家组成，学科层面未覆盖社会科学与人文科学，具有一定的局限性。结论 当前主要数据库的作者识别号还不能直接应用于大规模数据的实证研究，可通过建立标准化的科学家成果认证信息平台来提高中国作者姓名识别准确性。
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Electromagnetic spins, including longitudinal and transverse ones, have been playing important roles in light-matter interactions. Here, we formulate a unified equation to uncover the physical origins and topological properties of longitudinal and transverse spins in a generic electromagnetic field. The equation reveals universally that the transverse spin is locked with the kinetic momentum and originated from the transverse inhomogeneities of field, whereas the helix-dependent longitudinal spin orients parallel to the local wavevector. Remarkably, a hidden extraordinary helix-dependent transverse spin possessing helix-dependent spin-momentum locking is discovered and the number of locking states consistent with the nontrivial topological spin Chern number. Furthermore, this spin which determines the inverted helical components is related to the Berry curvature closely. The findings, which are demonstrated experimentally by measuring the three-dimensional spin components in the focusing configuration, will deepen the understanding the underlying physics of spins and open an avenue for chiral quantum optical applications.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Polarization vectors of light traveling in a coiled optical fiber rotate around its propagating axis even in the absence of birefringence. This rotation was usually explained due to the Pancharatnam-Berry phase of spin-1 photons. Here, we use a purely geometric method to understand this rotation. We show that similar geometric rotations also exist for twisted light carrying orbital angular momentum (OAM). The corresponding geometric phase can be applied in photonic OAM-state-based quantum computation and quantum sensing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Optical forces in the near fields have important applications in on-chip optical manipulations of small particles and molecules. Here, we report a study of optical force and torque on small particles induced by the optical polarization singularities of a gold cylinder. We show that the scattering of the cylinder generates both electric and magnetic C lines (i.e., lines of polarization singularities) in the near fields, and the C lines can induce complex force and torque on a dielectric/magnetic particle. The force and torque manifest dramatic spatial variations with interesting symmetry properties, providing rich degrees of freedom for near-field optical manipulations. The study, for the first time to our knowledge, uncovers the effect of optical polarization singularities on light-induced force and torque on small particles. The results contribute to the understanding of chiral light-matter interactions and can find applications in on-chip optical manipulations and optical sensing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： How migratory birds can find the right way in navigating over thousand miles is an intriguing question, which much interested researchers in both fields of biology and physics for centuries. There several putative proposals that sound intuitively plausible all remain contested so far because those hypothesis-models of magnetoreceptor to sense geomagnetic field need either extremely high sensitivity or humankind-like intelligence to guide. Here we explore theoretically that the birds can navigate to their destination through an entirely new scenario to sense the geomagnetic field. Our proposal is based on separate peaks of the resonance-fluorescence spectrum of a four-level system derived from the ferric sulfide cluster which exists in a protein complex (Drosophila CG8198) of migratory birds. As the separation of spectral peaks contains information about geomagnetic field at both current location and birthland, the change of such separation cues the bird to choose a right direction to move and double-resonance emerges once arrived the destination. Our theoretical mechanism can explain previous experiments on the disorientation of migratory birds caused by oscillating magnetic field naturally and more precisely. This work provides insight to explain migratory navigation and motivates possible manmade practical devices.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Conventional coherent absorption occurs only when two incident beams exhibit mirror symmetry with respect to the absorbing surface, i.e., the two beams have the same incident angles, phases, and amplitudes. In this work, we propose a more general metasurface paradigm for coherent perfect absorption, with impinging waves from arbitrary asymmetric directions. By exploiting excitation of unidirectional evanescent waves, the output can be fixed at one reflection direction for any amplitude and phase of the control wave. We show theoretically and confirm experimentally that the relative amplitude of the reflected wave can be tuned continuously from zero to unity by changing the phase difference between the two beams, i.e. switching from coherent perfect absorption to full reflection. We hope that this work will open up promising possibilities for wave manipulation via evanescent waves engineering with applications in optical switches, one-side sensing, and radar cross section control.
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