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Primordial black holes and curvature perturbations from false vacuum islands

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Science China(Physics,Mechanics & Astronomy) 2024年第9期67卷 58-72页

作者： Rong-Gen Cai Yu-Shi Hao Shao-Jiang wang School of Physical Science and Technology Ningbo UniversityNingbo 315211China CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Asia Pacific Center for Theoretical Physics Pohang 37673Republic of Korea

Recently,much attention has been focused on the false vacuum islands that are flooded by an expanding ocean of true-vacuum bubbles slightly later than most of the other parts of the *** delayed decay regions will accumulate locally larger vacuum energy density by staying in the false vacuum longer than those already transited into the true vacuum.A false vacuum island with thus acquired density contrast of a super-horizon size will evolve locally from radiation dominance to vacuum dominance,creating a local baby Universe that can be regarded effectively as a local closed *** such density contrasts of super-horizon sizes can ever grow large enough to exceed the threshold of gravitational collapse,primordial black holes will form similar to those collapsing curvature perturbations on super-horizon scales induced by small-scale enhancements during *** not,such density contrasts can still induce curvature perturbations potentially observable *** this paper,we revisit and elaborate on the generations of primordial black holes and curvature perturbations from delayed-decayed false vacuum islands during asynchronous first-order phase transitions with fitting formulas convenient for future model-independent studies.

关键词： first-order phase transitions primordial black holes curvature perturbations

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材料基因工程技术在电工材料研发中的应用与展望

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材料导报 2024年第13期38卷 208-224页

作者：王博盛鹏徐丽李圣驿白会涛李慧薛晴国网智能电网研究院有限公司北京102209

电工材料是电气装备的基础,其材料特性直接决定电气装备的极限电磁参数。随着科学技术的进步,生产、生活水平的不断提高,人们对电气装备具有的功能和性能的需求日益增加。理论研究和工程实践表明,以传统电工材料为基础生产的电气装备在... 详细信息

电工材料是电气装备的基础,其材料特性直接决定电气装备的极限电磁参数。随着科学技术的进步,生产、生活水平的不断提高,人们对电气装备具有的功能和性能的需求日益增加。理论研究和工程实践表明,以传统电工材料为基础生产的电气装备在功能和性能方面不能完全满足人类社会对先进电气装备快速增长的需求。电工新材料及其应用研究应使未来的电工装备具有挑战更高电磁参数极限的能力。材料基因工程为电工材料设计筛选提供了新的技术手段,通过利用高通量的方式设计与筛选材料,大幅缩短了材料的研发周期,显著降低了研发成本。本文综述了近几年材料基因工程先进理念与前沿技术在电工材料开发中的应用案例,这些案例表明了材料基因工程技术在电工材料研发中的适用性。本文还重点分析了以机器学习为代表的大数据技术在电工材料研发中的应用现状。

关键词：电工材料材料基因工程机器学习高通量计算高通量实验

平板电极下微米级粉尘弥散浓度探测方法与时空演化特性分析

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电工技术学报 2024年第7期39卷 2132-2142页

作者：薛乃凡魏来李庆民王媛杨睿成北京市高电压与电磁兼容重点实验室(华北电力大学) 北京102206 新能源电力系统全国重点实验室(华北电力大学) 北京102206

气体绝缘全封闭组合电器/气体绝缘金属封闭输电线路(GIS/GIL)在生产、运行和维护过程中会不可避免地产生微米级粉尘,可能是诱发工程现场不明放电的根本原因。为检测微米级粉尘弥散浓度并研究浓度的时空演化特性,该文分析了10000目、200... 详细信息

气体绝缘全封闭组合电器/气体绝缘金属封闭输电线路(GIS/GIL)在生产、运行和维护过程中会不可避免地产生微米级粉尘,可能是诱发工程现场不明放电的根本原因。为检测微米级粉尘弥散浓度并研究浓度的时空演化特性,该文分析了10000目、2000目和1000目粉尘的光散射特性,在此基础上设计并搭建了基于平板电极的粉尘浓度探测平台,实现了粉尘弥散浓度的定量探测。通过实验研究,获得了在升压过程和持续加压下,不同粒径、不同初始质量微米级粉尘的弥散浓度演化规律。研究表明,随着电压作用时间的增加,粉尘浓度快速出现最大值,然后逐渐下降。微米级粉尘弥散浓度在升压过程中会出现峰值现象,当粉尘粒径减小或初始质量增大时,均出现更大的浓度峰值。在粉尘运动过程中,存在团聚启举的特殊现象,造成严重的电场畸变,威胁气隙绝缘安全。该文结果阐释了微米级金属粉尘弥散浓度的时空演化规律,可为GIS/GIL等电气设备中微米级金属污染物的监测和危险程度评估提供支撑。

关键词：微米级粉尘光散射法浓度检测弥散特性时空演化

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Precipitates Generation Mechanism and Surface Quality Improvement for Aluminum Alloy 6061 in Diamond Cutting

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Journal of Wuhan University of Technology(Materials Science) 2024年第1期39卷 150-159页

作者：王海龙 DENG Wenping 王素娟 State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment Guangdong University of TechnologyGuangzhou 510006China Guangdong Provincial Key Laboratory of Micro-Nano Manufacturing Technology and Equipment School of Electromechanical EngineeringGuangdong University of TechnologyGuangzhou 510006China

To improve the surface quality for aluminum alloy 6061(Al6061) in ultra-precision machining, we investigated the factors affecting the surface finish in single point diamond turning(SPDT)by studying influence of the precipitates generation of Al6061 on surface integrity and surface *** on the Johnson-Mehl-Avrami solid phase transformation kinetics equation, theoretical and experimental studies were conducted to build the relationship between the aging condition and the type, size and number of the precipitates for Al6061. Diamond cutting experiments were conducted to machine Al6061 samples under different aging conditions. The experimental results show that, the protruding on the chip surface is mainly Mg_(2)Si and the scratches on the machined surface mostly come from the iron-containing phase(α-, β-AlFeSi).Moreover, the generated Mg_(2)Si and α-, β-AlFeSi affect the surface integrity and the diamond turned surface roughness. Especially, the achieved surface roughness in SPDT is consistent with the variation of the number of AlFeSi and Mg_(2)Si with the medium size(more than 1 μm and less than 2 μm) in Al6061.

关键词： Al6061 precipitates aging treatment diamond cutting surface roughness

Carbonation of Pure Minerals in Portland Cement:Evolution in Products as a Function of Water-to-solid Ratio

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Journal of Wuhan University of Technology(Materials Science) 2024年第5期39卷 1214-1222页

作者： XIONG Kun SHANG Xiaopeng LI Hongyan wang Dan Zhengzhou Lutong Highway Construction Co. Ltd.Zhengzhou 450052China (Special Glass Key Lab of Hainan Province)&(State Key Laboratory of Marine Resource Utilization in South China Sea) Hainan UniversityHaikou 570228China Department of Architectural Engineering Shandong Urban Construction Vocational CollegeJinan 250103China (State Key Laboratory of High Performance Civil Engineering Materials Jiangsu Sobute New Materials Co.Ltd.)&(School of Material Science and EngineeringSoutheast UniversityNanjing 211189China)

Minerals in Portland cement including tricalcium silicate(C_(3)S),β-dicalcium silicate(β-C_(2)S),tricalcium aluminate(C_(3)A),and tetracalcium ferroaluminate(C_(4)AF),show a significantly different activity and product evolution for CO_(2)curing at various water-to-solid *** pure minerals were synthesized and subject to CO_(2)curing in this study to make an in-depth understanding for the carbonation properties of cement-based *** showed that the optimum water-to-solid ratios of C_(3)S,β-C_(2)S,C_(3)A and C_(4)AF were 0.25,0.15,0.30 and 0.40 for carbonation,corresponding to 2 h carbonation degree of 38.5%,38.5%,24.2%,and 21.9%,*** produced calcite duringβ-C_(2)S carbonation decreased as the water-to-solid ratio increased,with an increase in content of metastable CaCO_(3)of vaterite and *** thermodynamic stability of CaCO_(3)produced during carbonation was C_(3)A>C_(4)AF>β-C_(2)S>C_(3)*** carbonation degree of Portland cement was predicted based on the results of pure minerals and the composition of cement,and the error of predicted production of CaCO_(3)was only 1.1%,which provides a potential method to predict carbonation properties of systems with a complex mineral composition.

关键词： accelerated carbonation portland cement calcium carbonate water-to-solid ratio

Structured trajectory planning of collision-free lane change using the vehicle-driver integration data

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Science China(Technological Sciences) 2016年第5期59卷 825-831页

作者： wang Jiang feng ZHANG Qian ZHANG Zhi Qi YAN xue Dong MOE Key Laboratory for Urban Transportation Complex Systems Theory and Technology Beijing Jiaotong University

In this paper, the structured trajectory planning of lane change in collision-free road environment is studied and validated using the vehicle-driver integration data, and a new trajectory planning model for lane change is proposed based on linear offset and sine function to balance driver comfort and vehicle dynamics. The trajectory curvature of the proposed model is continuous without mutation, and the zero-based curvature at the starting and end points during lane change assures the motion direction of end points in parallel with the lane line. The field experiment are designed to collect the vehicle-driver integration data, such as steering angle, brake pedal angel and accelerator pedal angel. The correction Correlation analysis of lane-changing maneuver and influencing variables is conducted to obtain the significant variables that can be used to calibrate and test the proposed model. The results demonstrate that vehicle velocity and Y-axis acceleration have significant effects on the lane-changing maneuver, so that the model recalibrated by the samples of different velocity ranges and Y-axis accelerations has better fitted performance compared with the model calibrated by the sample trajectory. In addition, the proposed model presents a decreasing tendency of the lane change trajectory fitted MAE with the increase of time span of calibrating samples at the starting stage.

关键词： intelligent vehicle lane change trajectory planning vehicle-driver integration

Multi-scale detector optimized for small target

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Optoelectronics Letters 2024年第4期20卷 243-248页

作者： ZHU Yongchang YANG Sen TONG Jigang wang Zenghui School of Electrical Engineering and Automation Tianjin University of TechnologyTianjin 300384China Center of Artificial Intelligence and Data Science University of South AfricaFlorida 1709South Africa Department of Electrical Engineering University of South AfricaFlorida 1709South Africa

The effectiveness of deep learning networks in detecting small objects is limited,thereby posing challenges in addressing practical object detection *** this research,we propose a small object detection model that operates at multiple *** model incorporates a multi-level bidirectional pyramid structure,which integrates deep and shallow networks to simultaneously preserve intricate local details and augment global ***,a dedicated multi-scale detection head is integrated into the model,specifically designed to capture crucial information pertaining to small *** comprehensive experimentation,we have achieved promising results,wherein our proposed model exhibits a mean average precision(mAP)that surpasses that of the well-established you only look once version 7(YOLOv7)model by 1.1%.These findings validate the improved performance of our model in both conventional and small object detection scenarios.

关键词： networks details thereby

不确定性环境下维纳模型的随机变分贝叶斯学习

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自动化学报 2024年第6期50卷 1185-1198页

作者：刘切李俊豪王浩曾建学柴毅重庆大学自动化学院重庆400044

多重不确定性环境下的非线性系统辨识是一个开放问题.贝叶斯学习在描述、处理不确定性方面具有显著优势,已在线性系统辨识方面得到广泛应用,但在非线性系统辨识的应用较少,且面临概率估计复杂、计算量大等难题.针对上述问题,以典型维纳(... 详细信息

多重不确定性环境下的非线性系统辨识是一个开放问题.贝叶斯学习在描述、处理不确定性方面具有显著优势,已在线性系统辨识方面得到广泛应用,但在非线性系统辨识的应用较少,且面临概率估计复杂、计算量大等难题.针对上述问题,以典型维纳(Wiener)非线性过程为对象,提出基于随机变分贝叶斯的非线性系统辨识方法.首先对过程噪声、测量噪声以及参数不确定性进行概率描述;然后利用随机变分贝叶斯方法对模型参数进行后验估计.在估计过程中,利用随机优化思想,仅利用部分中间变量概率信息估计模型参数分布的自然梯度期望,与利用所有中间变量概率信息估计模型参数比较,显著降低了计算复杂性.该方法是首次在系统辨识领域中的应用.最后,利用一个仿真实例和一个维纳模型的Benchmark问题,证明了该方法在对大规模数据下非线性系统辨识的有效性.

关键词：非线性系统辨识随机优化变分贝叶斯维纳模型

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Probing the Bardeen-Kiselev black hole with the cosmological constant caused by Einstein equations coupled with nonlinear electrodynamics using quasinormal modes and greybody bounds

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Communications in Theoretical Physics 2024年第6期76卷 102-119页

作者： S R Wu B Q wang Z W Long College of Physics Guizhou UniversityGuiyang 550025China College Pharmacy Guizhou University of Traditional Chinese MedicineGuiyang 550025China

In this work,we investigate a static and spherically symmetric Bardeen-Kiselev black hole(BH)with the cosmological constant,which is a solution of the Einstein-non-linear Maxwell field *** compute the quasinormal frequencies for the Bardeen-Kiselev BH with the cosmological constant due to electromagnetic and gravitational *** varying the BH parameters,we discuss the behavior of both real and imaginary parts of the BH quasinormal frequencies and compare these frequencies with the Reissner-Nordström-de Sitter BH surrounded by quintessence(RN-dSQ).Interestingly,it is shown that the responses of the Bardeen-Kiselev BH with the cosmological constant and the RN-dSQ under electromagnetic perturbations are different when the charge parameter q,the state parameter w and the normalization factor c are varied;however,for the gravitational perturbations,the responses of the Bardeen-Kiselev BH with the cosmological constant and the RN-dSQ are different only when the charge parameter q is ***,compared with the gravitational perturbations,the electromagnetic perturbations can be used to understand nonlinear and linear electromagnetic fields in curved spacetime *** interesting observation is that,due to the presence of Kiselev quintessence,the electromagnetic perturbations around the Bardeen-Kiselev BH with the cosmological constant damps faster and oscillates slowly;for the gravitational perturbations,the quasinormal mode decays slowly and oscillates *** also study the reflection and transmission coefficients along with the absorption cross section in the Bardeen-Kiselev BH with the cosmological constant;it is shown that the transmission coefficients will increase due to the presence of Kiselev quintessence.

关键词： quasinormal modes greybody factors Bardeen-Kiselev black hole with cosmological constant