分类： 物理学 >> 核物理学 提交时间： 2024-04-12
摘要： 奇$A$核$^{53-65}$Co负宇称晕态能级结构的系统性比较表明，$^{55}$Co存在能级$9/2^-$与$11/2^-$反转，且$^{53,57}$Co可能存在较强的集体效应。基于GXPF1A有效相互作用的壳模型计算较好地再现这些核的晕态能级，及相应的磁矩和电四极矩实验值。壳模型计算结果展示$^{53-65}$Co基态$7/2^-$波函数中质子主要组态成分均为$ pi left(1f_{7/2} right)^7$。$^{55}$Co中激发态$9/2^-$与$11/2^-$中$1f_{7/2}$质子激发和$1f_{7/2}$中子激发之间存在竞争，从而导致两能级反转。此外，利用Constrained Hartree-Fock（CHF）方法研究了$^{53,55,57}$Co四极形变特征，结合壳模型计算得到的平均占据数和组态，分析了$^{55}$Co激发态能量相较于其他Co同位素更高的原因。
分类： 信息科学与系统科学 >> 信息科学与系统科学基础学科 分类： 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 分类： 天文学 >> 天文学 提交时间： 2024-04-11
摘要： The electromagnetic fields of point sources with time varying charges moving in the vacuum are derived using the Liénard-Wiechert potentials. The properties of the propagation velocities and the Doppler effect are discussed based on their far fields. The results show that the velocity of the electromagnetic waves and the velocity of the sources cannot be added like vectors; the velocity of electromagnetic waves of moving sources are anisotropic in the vacuum; the transverse Doppler shift is intrinsically included in the fields of the moving sources and is not a pure relativity effect caused by time dilation. Since the fields are rigorous solutions of the Maxwell’s equations, the findings can help us to abort the long-standing misinterpretations concerning about the classic mechanics and the classic electromagnetic theory. Although it may violate the theory of the special relativity, we show mathematically that, when the sources move faster than the light in the vacuum, the electromagnetic barriers and the electromagnetic shock waves can be clearly predicted using the exact solutions. Since they cannot be detected by observers in the region outside their shock wave zones, an intuitive and reasonable hypothesis can be made that the superluminal sources may be considered as a kind of electromagnetic blackholes.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2024-04-10
摘要： 本文考虑一种量子化的参考系理论，考虑这种时空参考系在量子二阶矩涨落下的Ricci流理论及其蕴含的引力理论。由于该理论中非平凡的时空二阶量子涨落，我们讨论了宇宙加速膨胀(宇宙学常数)问题、星系尺度的径向加速度反常问题，极早期暴涨等问题，及其时空熵的起源问题。最后我们也给出该理论的一些可能预言。
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2024-04-10
摘要： Artificial Neural Network (ANN) has become a powerful tool in the field of scientific research with its powerful information encapsulation ability and convenient variational optimization method. In particular, there have been many recent advances in computational physics to solve variational problems. Deep neural network (DNN) is used to represent the wave function to solve quantum many-body problems using variational optimization. In this work we used a new Physics-Informed Neural Network (PINN) to represent the Cumulative Distribution Function (CDF) of some classical problems in quantum mechanics and to obtain their ground state wave function and ground state energy through the CDF. By benchmarking against the exact solution, the error of the results can be controlled at a very low level. This new network architecture and optimization method can provide a new choice for solving quantum many- body problems.
分类： 信息科学与系统科学 >> 信息科学与系统科学基础学科 分类： 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 分类： 电子与通信技术 >> 光电子学与激光技术 分类： 物理学 >> 地球物理学、天文学和天体物理学 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2024-04-08
摘要： The Einstein’s theory of special relativity is based on his two postulates. The first is that the laws of physics are the same in all inertial reference frames. The second is that the velocity of light in the vacuum is the same in all inertial frames. The theory of special relativity is considered to be supported by a large number of experiments. This paper revisits the two postulates according to the new interpretations to the exact solutions of moving sources in the laboratory frame. The exact solutions are obtained using the classic Maxwell’s theory, which clearly show that the propagation velocity of the electromagnetic waves of moving sources in the vacuum is not isotropic; the propagation velocity of the electromagnetic waves and the moving velocity of the sources cannot be added like vectors; the transverse Doppler effect is intrinsically included in the fields of the moving sources. The electromagnetic sources are subject to the Newtonian mechanics, while the electromagnetic fields are subject to the Maxwell’s theory. We argue that since their behaviors are quite different, it is not a best choice to try to bind them together and force them to undergo the same coordinate transformations as a whole, like that in the Lorentz transformations. Furthermore, the Maxwell’s theory does not impose any limitations on the velocity of the electromagnetic waves. To assume that all objects cannot move faster than the light in the vacuum need more examinations. We have carefully checked the main experiment results that were considered as supporting the special relativity. Unfortunately, we found that the experimental results may have been misinterpreted. We here propose a Galilean-Newtonian-Maxwellian relativity, which can give the same or even better explanations to those experimental results.
分类： 物理学 >> 核物理学 提交时间： 2024-04-08
摘要： 原子核同位旋标量巨单极共振的研究是约束核物质不可压缩系数 $K_ infty$ 的重要途径，对理解核天体物理现象提供了重要的信息。目前巨单极共振研究中存在的主要问题是 Pb 和 Sn 中巨单极共振不能够同时描述的矛盾，它阻碍了核物质不可压缩系数的精确约束。本文综述了准粒子无规相位近似理论和准粒子振动耦合理论对该问题的研究进展。
分类： 物理学 >> 核物理学 提交时间： 2024-04-01
摘要： Using two nuclear models, i) the relativistic continuum Hartree-Bogoliubov (RCHB) theoryand ii) the Weizs acker-Skyrme (WS) model WS$^ ast$,the performances of nine kinds of kernel functions in the kernel ridge regression (KRR) methodare investigated by comparing the accuracies of describing the experimental nuclear chargeradii and the extrapolation abilities.It is found that, except the inverse power kernel, other kernels can reach the same levelaround 0.015-0.016~fm for these two models with KRR method.The extrapolation ability for the neutron rich region of each kernel depends on the trainning data.Our investigation shows that the performances of the power kernel and Multiquadric kernel arebetter in the RCHB+KRR calculation, and the Gaussian kernel is better in the WS$^ ast$+KRR calculation.In addition, the performance of different basis functions inthe radial basis function method is also investigated for comparison.The results are similar to the KRR method.The influence of different kernels on the KRR reconstruct function is discussedby investigating the whole nuclear chart.At last, the charge radii of some specific isotopic chains have been investigatedby the RCHB+KRR with power kernel and the WS$^ ast$+KRR with Gaussian kernel.The charge radii and most of the specific features in these isotopic chainscan be reproduced after considering the KRR method.
分类： 物理学 >> 核物理学 提交时间： 2024-03-28
摘要： 中能区电荷交换反应可以从自旋-同位旋激发的角度研究原子核复杂结构。利用中国科学院近代物理研究所的放射性束流线，利用逆运动学方法进行电荷交换反应实验，可以将研究的对象核素拓展至丰中子核乃至不稳定核。基于此，设计了用于电荷交换反应实验的探测器系统，该系统主要包括了3He气体靶、TPC和CsI(Tl) 阵列，其中TPC和CsI(Tl) 阵列构成ΔE-E系统。利用Geant4、Garfield++等模拟软件，优化了TPC的工作条件，确定了实验研究的运动学区间和探测器的基本设计，考察了探测系统的粒子鉴别能力。基于模拟优化，搭建了探测系统。
分类： 物理学 >> 核物理学 提交时间： 2024-03-27
摘要： 采用有限元法和热介电张量模拟研究了非一次吸收假设，以及一次吸收假设对EAST四电流带天线少数离子加热波传播和功率沉积的影响。模拟结果显示：在其他参数相同的条件下，当天线电流相位为(0 0 π π)和(0 π π 0)时，两种模型计算的天线附近电场分布基本一致；当天线电流相位为(0 π 0 π)时，两个模型的电场模拟结果出现显著差别。环向传播多圈的离子回旋波是导致结果差异的主要原因。环形聚变装置中，当波的平行波数较大时，一次吸收假设的模拟结果偏小。对于环形聚变装置，一次吸收假设的适用性需要进一步系统的研究。
分类： 物理学 >> 凝聚态:结构、力学和热性能 提交时间： 2024-03-27
摘要： Electron-diffraction patterns with5-fold rotational symmetry of experimental alloy phases are assumedto be produced by periodic structures. Two three-dimensionalperiodic structures are presented based on regular pentagonaldodecahedrons. These structures can be used as atomic models todescribe the alloy phases. The Fourier-transform patterns of themodels are found to be similar to the correspondingelectron-diffraction patterns of these alloy phases. Details of themotivations and approaches that lead to thesemodels are also discussed.
分类： 物理学 >> 凝聚态:电子结构、电、磁和光学性质 提交时间： 2024-03-26
摘要： Under typical circumstances, it is commonly believed that solutions carrying a single type of charge are either non-existent or unstable. We have investigated the principles of high-concentration charged solution preparation techniques, employing methods such as electrostatic attraction, gravity separation, positive feedback, and self-powered mechanisms to effectively separate anions and cations in solution. Through electrostatic repulsion and the use of electrostatic separation networks, the partition of homoelectric ions has been achieved. Through water and electric separation, the capability for sustained accumulation of single-charge species has been attained, thus overcoming application bottlenecks and establishing evidence for the existence of charged solutions. We have proposed voltage limits and predicted phenomena such as electrostatic boiling, topological ice crystals, and strange ice crystals, thereby opening new perspectives and possibilities for enriching the understanding and research of electrostatics and electrochemistry. The introduction of the high-concentration charged solution and its controllable preparation are expected to facilitate or pioneer research in various fields including seawater desalination, wastewater treatment, hydrovoltaic power generation, and topological ice crystals, etc. This advancement holds the potential to rectify relevant discussions in textbooks. Implementing the dual electrostatic method for self-powered desalination and purification, coupled with wind, solar, and pumped hydro storage technologies, can aid in mitigating the intermittency and waste of wind and solar power, thus advancing the cause of seawater for land.
分类： 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间： 2024-03-23
摘要： To predict the fractal decoded image quality more efficiently, an accumulated collage error coefficient (ACEC) based method was proposed in this study. Firstly, the definition of ACEC was introduced to describe the relationship among the upper bound, lower bound, and actual value of theaccumulated collage error of all range blocks. Moreover, the definition and monotonicity of the relative error of ACEC were also defined and discussed. While the relative error of ACEC reaches a relatively small value, the average collage error (ACER) can be estimated approximately, and then the encoding process can be terminated to directly predict the peak signal-to-noise ratio (PSNR) quality of decoded images. Experimental results show that compared with the previous method, the proposed method can predict the decoded image quality more accurately with fewer computations.
分类： 物理学 >> 核物理学 提交时间： 2024-03-22
摘要： 介子束流与原子核碰撞实验在中高能核物理和粒子物理研究领域发挥了重要推动作用，特别是在强子谱研究方面取得了一系列重要实验测量结果。本文对目前国际上几个比较典型的介子束流实验进行了梳理与总结，这包括了位于日本的 J-PARC 实验；欧洲核子中心的 COMPASS 实验、AMBER 实验以及计划中的 HIKE实验；美国 JLab 的 GlueX 实验和 EIC 项目。进一步，我们基于国内的 HIAF 装置对可能产生的次级介子束流的参数指标进行了分析估算，并讨论了可以开展的相关物理测量。通过对这些实验项目的调研分析，旨在为进一步规划和建造我国的介子束流实验装置并开展强子物理方面的研究有所启发和借鉴。
分类： 物理学 >> 交叉学科物理及相关领域的科学与技术 分类： 材料科学 >> 陶瓷学 提交时间： 2024-03-20
摘要： 高放废物固化体的长期辐照稳定性是评价其深地质处置安全性的关键指标之一。本文利用 500 keV He2+离子束辐照 2M、 3O 和 4M 型钙钛锆石陶瓷固化体， 研究高放核素长期α 衰变辐照对陶瓷结构的损伤行为。三种钙钛锆石样品通过传统高温固相法（1400 ℃， 48h两次烧结）合成。掠入射 X 射线衍射（GIXRD） 、 Raman 光谱和 XPS 研究结果发现在 α 粒子辐照下， zirconolite-2M 固化体在辐照非晶化的过程中经历了 zirconolite-2M 到 zirconolite-4M 到 pyrochlore 的结构演变； zirconolite-3O 在 5×1015 ions/cm2 剂量下部分晶体结构转变为钙钛矿，在 1×1016 ions/cm2 以上剂量快速转变为无序烧绿石； zirconolite-4M 样品在 1×1017 ions/cm2 剂量时依旧保留 zirconolite-4M 主相，次生无序烧绿石/缺陷萤石晶相。综上， 从维持晶体结构稳定性来看 zirconolite-2M 和 zirconolite-3O 的抗 α 粒子辐照能力相似，略弱于zirconolite-4M 固化体。
分类： 物理学 >> 核物理学 提交时间： 2024-03-19
摘要： The exploration of exotic shapes and properties of atomic nuclei, e.g., α cluster and toroidal shape, is afascinating field in nuclear physics. To study the decay of these nuclei, a novel detector aimed at detectingmultiple alpha-particle events was designed and constructed. The detector comprises two layers of double-sidedsilicon strip detectors (DSSD) and a cesium iodide scintillator array coupled with silicon photomultipliers arrayas light sensors, which has the advantages of their small size, fast response, and large dynamic range. DSSDscouple with cesium iodide crystal arrays are used to distinguish multiple alpha hits. The detector array has acompact and integrated design that can be adapted to different experimental conditions. The detector array wassimulated using Geant4, and the excitation energy spectra of some alpha-clustering nuclei were reconstructedto demonstrate the performance. The simulation results show that the detector array has excellent angularand energy resolutions, enabling effective reconstruction of the nuclear excited state by multiple alpha particleevents. This detector offers a new and powerful tool for nuclear physics experiments and has the potential todiscover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms
分类： 物理学 >> 核物理学 提交时间： 2024-03-19
摘要： In recent years, the gap between the supply and demand of medical radioisotopes has increased, necessitating new methods for producing medical radioisotopes. Photonuclear reactions based on gamma sources have unique advantages in terms of producing high specific activity and innovative medical radioisotopes. However, the lack of experimental data on reaction cross sections for photonuclear reactions of medical radioisotopes of interest has severely limited the development and production of photonuclear transmutation medical radioisotopes. In this study, the entire process of the generation, decay, and measurement of medical radioisotopes was simulated using online gamma activation and offline gamma measurements combined with a shielding gammaray spectrometer. Based on a quasi-monochromatic gamma beam from the Shanghai Laser Electron Gamma Source (SLEGS), the feasibility of the measurement of production cross section for surveyed medical isotopes was simulated, and specific solutions for measuring medical radioisotopes with low production cross sections were provided. The feasibility of this method for high precision measurements of the reaction cross section of medical radioisotopes was demonstrated.
分类： 物理学 >> 核物理学 提交时间： 2024-03-19
摘要： 重离子碰撞过程中轻粒子的产生对于提取核物质状态方程的信息有着重要的作用。基于极端相对论量子分子动力学（UrQMD）模型，利用统计衰变模型GEMINI++处理预激发碎片的衰变，研究了预碎片的衰变对中能区Au+Au碰撞过程中轻粒子的集体流和核阻止本领的影响。研究发现，由于记忆效应，重离子碰撞过程中的预碎片的衰变产生的子核继承了母核的部分动力学性质，在考虑预碎片的衰变后可以更好地描述实验数据，并且这种效应对观测量的影响随碰撞能量的升高而减弱。结果表明，重离子碰撞过程中预碎片的衰变以及轻粒子的产生对敏感于核物质状态方程的观测量有着一定的影响。在利用这些观测量提取核物质状态方程的信息时应当仔细处理。
分类： 物理学 >> 核物理学 提交时间： 2024-03-18
摘要： 通过在Nilsson势中引入八极关联相互作用，基于推转壳模型（CSM）下的粒子数守恒方法（PNC）处理包含单极和四极对力的哈密顿量，研究了反射不对称（RA）原子核的基态转动带。基于此，PNC-CSM的计算结果重现了轻锕系区偶偶核236,238U和238,240Pu的交替宇称带，以及奇-𝐴核237U和239Pu的宇称带双重带的转动惯量实验值。与相邻偶偶核236,238U和238,240Pu相比，奇-𝐴核237U和239Pu的𝑠=−𝑖内禀转动带的转动惯量增加了50%∼60%。这些增加的转动惯量主要是由费米面附近中子轨道的泡利堵塞效应减弱了中子体系的对关联导致。U和Pu同位素中，转动惯量随着转动频率缓慢增加则可以解释为转动使得体系的对关联减弱。在低频率区，反射不对称原子核的转动惯量明显高于相对应的反射对称（RS）原子核的转动惯量。并且，与反射对称原子核相比，较大的八极形变将导致反射不对称原子核体系的对关联减弱更加明显。
分类： 物理学 >> 核物理学 提交时间： 2024-03-13
摘要： Prompt radiation emitted during accelerator operation poses a significant health risk, necessitating a thorough search and securing of hazardous areas prior to initiation. Currently, manual sweep methods are employed. However, the limitations of manual sweeps have become increasingly evident with the implementation of large-scale accelerators. By leveraging advancements in machine vision technology, the automatic identification of stranded personnel in controlled areas through camera imagery presents a viable solution for efficient search and security. Given the criticality of personal safety for stranded individuals, search and security processes must be sufficiently reliable. To ensure comprehensive coverage, 180° camera groups were strategically positioned on both sides of the accelerator tunnel to eliminate blind spots within the monitoring range. The YOLOV8 network model was modified to enable the detection of small targets, such as hands and feet, as well as larger targets formed by individuals near the cameras. Furthermore, the system incorporates a pedestrian recognition model that detects human body parts, and an information fusion strategy is used to integrate the detected head, hands, and feet with the identified pedestrians as a cohesive unit. This strategy enhanced the capability of the model to identify pedestrians obstructed by equipment, resulting in a notable improvement in the recall rate. Specifically, recall rates of 0.915 and 0.82 were obtained for Datasets 1 and 2, respectively. Although there was a slight decrease in accuracy, it aligned with the intended purpose of the search-and-secure software design. Experimental tests conducted within an accelerator tunnel demonstrated the effectiveness of this approach in achieving reliable recognition outcomes.
分类： 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 提交时间： 2024-03-13
摘要： 工程中必须处理的以及人们在自然中碰到的流体，其流动在绝大多数情况下是湍动的，对这些流动的描述需要一种统计性的方法。容易描述的层流（Laminar flow）异常少见。我们相信，流体力学不能只局限于这些很少碰到的特殊情形，并且个别层流的经典描述虽然无疑重要而有价值，但是只能作为真正湍流理论的导引章节。在湍流理论中，研究的目标是宏观上相同外界条件下的流动系综的性质。
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