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氢氟酸处理InP/GaP/ZnS量子点的光学性能及其发光二极管应用
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作者 陈晓丽 陈佩丽 +3 位作者 卢思 朱艳青 徐雪青 苏秋成 《发光学报》 EI CAS CSCD 北大核心 2024年第1期69-77,共9页
采用氢氟酸(HF)原位注入法制备了InP/GaP/ZnS量子点。通过紫外/可见/近红外光谱、光致发光光谱、透射电镜、球差校正透射电镜、X射线衍射、X射线光电子能谱等测试手段分析了HF对InP量子点的发光性能影响。实验结果表明,HF刻蚀减少了量... 采用氢氟酸(HF)原位注入法制备了InP/GaP/ZnS量子点。通过紫外/可见/近红外光谱、光致发光光谱、透射电镜、球差校正透射电镜、X射线衍射、X射线光电子能谱等测试手段分析了HF对InP量子点的发光性能影响。实验结果表明,HF刻蚀减少了量子点表面氧化缺陷状态,有效控制了InP核表面的氧化,并且原子配体形式的F-钝化了量子点表面的悬挂键,显著提升了量子点的光学性能。HF处理的InP/GaP/ZnS量子点具有最佳的发光性能,PLQY高达96%。此外,用HF处理InP/GaP/ZnS量子点制备的发光二极管,其发光的电流效率为6.63 cd/A,最佳外量子效率(EQE)为3.83%。 展开更多
关键词 HF InP/gap/ZnS量子点 光学性能 发光二极管
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道地药材云木香GAP研究与规范化种植基地建设实践与展望
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作者 杨丽云 陈翠 +4 位作者 康平德 戚淑威 程远辉 徐天才 杨少华 《安徽农业科学》 CAS 2024年第19期11-15,共5页
云木香原产印度,20世纪30年代初在云南丽江引进种植,并逐渐推广扩展至全省多地,1959年首次出口,誉为“云木香”,为云南省重要道地药材之一,药用历史悠久。为规范云南道地药材云木香的栽培措施,以保证其产品质量,参照国家药品监督管理局... 云木香原产印度,20世纪30年代初在云南丽江引进种植,并逐渐推广扩展至全省多地,1959年首次出口,誉为“云木香”,为云南省重要道地药材之一,药用历史悠久。为规范云南道地药材云木香的栽培措施,以保证其产品质量,参照国家药品监督管理局颁布实施的《中药材生产质量管理规范》相关要求,综述云木香的道地沿革与种植历史、规范化种植技术研究、传统初加工方法的继承与创新、标准化生产质量管理体系的建立以及规范化种植试验示范基地建设5个方面的研究,以期为云南西北高寒山区该道地药材品种产业化生产提供科学依据。 展开更多
关键词 云木香 道地药材 gap研究 质量 可追溯
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基于5GAP模型的高校食堂服务质量差距分析与对策探讨 被引量:1
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作者 陈森 《中国食品工业》 2024年第8期62-64,58,共4页
食堂服务是高校后勤服务体系中最重要的环节之一,高校食堂管理必须要有的放矢地改进工作。5GAP模型是一种直接有效的服务环节分析工具,更注重找出内部的服务缺陷。在以往的高校食堂研究中,多以顾客满意度的外部视角分析服务质量问题,本... 食堂服务是高校后勤服务体系中最重要的环节之一,高校食堂管理必须要有的放矢地改进工作。5GAP模型是一种直接有效的服务环节分析工具,更注重找出内部的服务缺陷。在以往的高校食堂研究中,多以顾客满意度的外部视角分析服务质量问题,本文通过5GAP模型以内部视角分析发现引发高校食堂服务质量问题的根源,以期能对高校食堂服务质量的改进和提升起到一定作用。 展开更多
关键词 服务质量 5gap模型 高校食堂
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青年职场“Gap day”现象探究
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作者 张良驯 付成梅 《中国青年社会科学》 北大核心 2024年第4期11-22,共12页
青年职场“Gap day”现象引起了社会的广泛关注和热烈讨论。青年职场“Gap day”现象的典型特征是:通过语言上的拼贴与再造,表达部分职业青年的困顿疲倦情绪;通过行为上的放空与逃离,排解青年在工作中积攒的情绪和压力;通过价值上的戏... 青年职场“Gap day”现象引起了社会的广泛关注和热烈讨论。青年职场“Gap day”现象的典型特征是:通过语言上的拼贴与再造,表达部分职业青年的困顿疲倦情绪;通过行为上的放空与逃离,排解青年在工作中积攒的情绪和压力;通过价值上的戏谑与自嘲,赋予青年的短暂休息以正向意义。青年职场“Gap day”现象的深层原因是:青年在高压生存环境中的“弹性姿态”、在加速社会运行中的“精神逃离”和在社会时钟齿轮下的“自我审视”。对青年职场“Gap day”现象的有效治理,既要着眼于青年发展,运用公共政策实现青年发展的普遍性诉求,又要立足于青年就业,采取切实措施促进青年实现高质量充分就业。 展开更多
关键词 gap day 青年现象 青年就业 青年职业发展
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共混GAP基含能热塑性弹性体的氢键行为与力学性能
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作者 郑梦泽 张宁 +4 位作者 刘双 靳鹏 张锡铭 刘文皓 罗运军 《火炸药学报》 EI CAS CSCD 北大核心 2024年第4期365-371,共7页
为了改善GAP热塑性弹性体的力学性能,采用了DSC、低场核磁测试、静态力学测试和动态力学测试的方法对两种异氰酸酯固化的弹性体共混体系的氢键行为和力学性能进行分析,建立微观结构与宏观性能的关系。结果表明,由于分子结构原因,HMDI固... 为了改善GAP热塑性弹性体的力学性能,采用了DSC、低场核磁测试、静态力学测试和动态力学测试的方法对两种异氰酸酯固化的弹性体共混体系的氢键行为和力学性能进行分析,建立微观结构与宏观性能的关系。结果表明,由于分子结构原因,HMDI固化的GAP热塑性弹性体和IPDI固化的弹性体显示出不同的氢键行为和力学性能,通过物理共混得到了兼具抗拉强度及断裂延伸率的弹性体,50℃下抗拉强度高于1.5MPa,-40℃下延伸率不低于300%,相较于纯HMDI固化的弹性体,低温延伸率提升了约150%,IPDI固化的弹性体高温抗拉强度提升了约1.4MPa,说明通过共混可得到性能更为均衡的含能热塑性弹性体。 展开更多
关键词 材料力学 聚叠氮缩水甘油醚 gap 热塑性弹性体 氢键行为 高分子物理共混 高低温力学性能
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基于Roussouly分型的脊柱形态和GAP评分对成人脊柱畸形术后临床疗效的影响
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作者 李嘉鑫 陈振 +3 位作者 杨万忠 范嘉旺 郑任春 戈朝晖 《宁夏医科大学学报》 2024年第5期507-514,共8页
目的评估成人脊柱畸形(ASD)手术前后的Roussouly矢状面脊柱形态及全脊柱序列比例(GAP)评分对术后临床疗效的影响。方法回顾性分析2016年1月至2021年12月在宁夏医科大学总医院行手术治疗的72例ASD患者临床资料,其中男性20例,女性52例,年... 目的评估成人脊柱畸形(ASD)手术前后的Roussouly矢状面脊柱形态及全脊柱序列比例(GAP)评分对术后临床疗效的影响。方法回顾性分析2016年1月至2021年12月在宁夏医科大学总医院行手术治疗的72例ASD患者临床资料,其中男性20例,女性52例,年龄(46.9±19.0)岁。将纳入患者按照“当前”[依据骶骨倾斜角(SS)]和“理论”[依据骨盆入射角(PI)]Roussouly分型脊柱形态进行划分。根据一个恒定参数(PI)判断出患者“理论”形态,然后将此种类型的理想形态参数与实际参数作对比,若术后3个月患者的“当前”Roussouly脊柱形态与其“理论”Roussouly脊柱形态各项参数均符合则归入匹配组,否则归入非匹配组。根据相关参数计算两组患者手术前后GAP评分,并收集术前、术后3个月和末次随访时的疼痛视觉模拟评分(VAS)、Oswestry功能障碍指数(ODI)及术前和末次随访时SRS-22评分(包括总分、疼痛、功能、自我形象、心理健康和治疗满意度),同时记录患者随访时机械并发症发生情况。比较两组患者的影像学参数、GAP评分、临床疗效评分及机械并发症中的差异。结果72例ASD患者术前以RoussoulyⅠ型和Ⅱ型脊柱形态为主,术后以RoussoulyⅡ型和Ⅲ型为主。所有患者术后影像学参数和临床疗效评分较术前均得到改善(P均<0.05)。组间比较,非匹配组末次随访骨盆倾斜角和躯干整体倾斜角大于匹配组(P均<0.05),术后3个月及末次随访,匹配组GAP评分均低于非匹配组(P均<0.05),匹配组较非匹配组在术后3个月和末次随访有更好的VAS评分、ODI评分及SRS-22评分(包括总分、疼痛、功能和治疗满意度)(P均<0.05)。匹配组术后机械并发症发生率更低(P<0.05),腰椎前凸顶点位于理想位置可降低机械并发症发生率。结论ASD术后脊柱矢状面匹配理想Roussouly分型的患者临床疗效和GAP评分更好、机械并发症发生率更低,PI术中应尽可能矫正至理想Roussouly分型脊柱形态。 展开更多
关键词 成人脊柱畸形 Roussouly分型 gap评分 临床疗效 机械并发症
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基于GIS的漳州市松岭村乡村旅游适宜性评价及GAP分析
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作者 康丽婷 罗紫薇 +2 位作者 胡希军 韦宝婧 周冬梅 《生态科学》 CSCD 北大核心 2024年第2期123-131,共9页
以“全国乡村旅游扶贫重点村”漳州市松岭村为研究对象,借助地理信息系统(GIS),从资源禀赋潜力出发,构建乡村旅游适宜性评价体系,利用地理探测器计算各旅游适宜性影响因子的权重,基于乡村旅游适宜性评价结果对旅游空间进行开发空缺(GAP... 以“全国乡村旅游扶贫重点村”漳州市松岭村为研究对象,借助地理信息系统(GIS),从资源禀赋潜力出发,构建乡村旅游适宜性评价体系,利用地理探测器计算各旅游适宜性影响因子的权重,基于乡村旅游适宜性评价结果对旅游空间进行开发空缺(GAP)分析,并提出旅游规划优化策略。旨在优化景观资源在空间整体布局中的合理利用,为乡村旅游规划提供新思路。研究结果表明:(1)松岭村旅游适宜性受基础设施因子影响最大,受坡向因子影响最小;(2)松岭村旅游适宜等级可分为高适宜、较高适宜、中适宜、较低适宜、低适宜区5类,其中高适宜区面积最小,仅占松岭村总面积的4.64%,低适宜区面积最大,占总面积的58.00%;(3)借鉴GAP分析思路,识别松岭村景观资源点开发潜力分级区块,各适宜等级区均存在较多景观资源点未开发。建议结合现有特色景观资源点,优先开发较高及高潜力区块、积极开发中潜力区、适度开发较低及低潜力区,以期在保留旅游资源特色的同时最大化利用其景观资源。 展开更多
关键词 旅游适宜性评价 地理探测器 gap分析 乡村旅游 松岭村
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LiF/GAP协同作用改善硼粉的燃烧性能
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作者 伍双艳 王吉权 +4 位作者 邵建 刘俊 陈九玉 朱宝忠 孙运兰 《火炸药学报》 EI CAS CSCD 北大核心 2024年第3期279-286,I0006,共9页
以氟化锂/缩水甘油叠氮化物聚合物(LiF/GAP)为界面层对微米硼进行改性,研究LiF/GAP协同作用对硼粉热行为、燃烧性能和凝聚相燃烧产物的影响。结果表明,通过硅烷偶联剂处理后,硼粉表面黏结性得以提高,LiF能够较好地包覆在硼粉表面;GAP在... 以氟化锂/缩水甘油叠氮化物聚合物(LiF/GAP)为界面层对微米硼进行改性,研究LiF/GAP协同作用对硼粉热行为、燃烧性能和凝聚相燃烧产物的影响。结果表明,通过硅烷偶联剂处理后,硼粉表面黏结性得以提高,LiF能够较好地包覆在硼粉表面;GAP在400℃之前抑制了LiF与硼表面氧化膜的反应,使LiF的除膜效应延后至硼粉氧化增重阶段,从而将更多的活性硼暴露在空气中发生氧化,促进了硼粉的燃烧;LiF和GAP协同作用显著改善了硼粉的燃烧性能,尤其当LiF和GAP质量分数均为10%时,作用效果最为明显。此外,LiF和GAP协同作用有效抑制了燃烧过程中硼粉团聚,使其凝聚相燃烧产物粒径降低。 展开更多
关键词 物理化学 硼颗粒 LiF/gap协同作用 燃烧特性 团聚抑制 燃烧机理
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固化剂对GAP固化反应的影响研究
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作者 杜永安 王敦举 《现代工程科技》 2024年第15期57-60,共4页
针对含能黏结剂GAP应用时固化剂的选择问题,采用红外、凝胶测试仪、非等温差示扫描量热法(Differential Scanning Calorimetry,DSC),研究了氰酸酯固化剂和丁二酸二丙炔醇酯固化剂对GAP固化反应的影响。实验表明,GAP分子结构中的羟基和... 针对含能黏结剂GAP应用时固化剂的选择问题,采用红外、凝胶测试仪、非等温差示扫描量热法(Differential Scanning Calorimetry,DSC),研究了氰酸酯固化剂和丁二酸二丙炔醇酯固化剂对GAP固化反应的影响。实验表明,GAP分子结构中的羟基和叠氮基团都能参与反应,氰酸酯类固化剂与GAP的固化速率小于丁二酸二丙炔醇酯固化剂与GAP的固化速率,采用非等温DSC进行测试可以获得丁二酸二丙炔醇酯固化剂与GAP的固化放热峰,无法获得氰酸酯与GAP的固化放热峰。丁二酸二丙炔醇酯/GAP固化物的拉伸强度小于N-100/GAP固化物,延伸率大于N-100/GAP固化物。该研究为含能黏结剂GAP应用时固化剂的确定提供了试验基础数据。 展开更多
关键词 gap 氰酸酯固化剂 丁二酸二丙炔醇酯固化剂
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GAP/N-100交联体系力学和热解机理的MD模拟
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作者 黄肖勇 周添 +2 位作者 王梓霖 王江涛 付一政 《兵器装备工程学报》 CAS CSCD 北大核心 2024年第5期8-14,共7页
为探究聚叠氮缩水甘油醚(GAP)与多异氰酸酯(N-100)交联形成三维网状聚合物的力学性能、热分解机理和主要产物信息,采用perl语言结合分子动力学模拟软件编写了能实现GAP与N-100交联的脚本,建立了不同交联度的GAP/N-100分子模型,并预测了... 为探究聚叠氮缩水甘油醚(GAP)与多异氰酸酯(N-100)交联形成三维网状聚合物的力学性能、热分解机理和主要产物信息,采用perl语言结合分子动力学模拟软件编写了能实现GAP与N-100交联的脚本,建立了不同交联度的GAP/N-100分子模型,并预测了不同交联体系的力学性能,采用反应分子动力学对热解机理和产物进行了模拟。结果表明:通过自编脚本可以得到一系列不同交联度的交联模型,最终交联度为96.7%;随着交联度的增大,GAP/N-100体系的杨氏模量、剪切模量和体积模量均逐渐提高。GAP/N-100交联体系热解的初始分解机理为叠氮基团的脱落以及碳骨架的分解,热解反应的活化能Ea为13.411 kJ/mol,指前因子A为0.099 1/ps-1,热解的主要产物有N2、H_(2)、H_(2)O以及NH3,主要的中间产物为CH_(2)O。 展开更多
关键词 聚叠氮缩水甘油醚(gap) 多异氰酸酯(N-100) 交联 分子动力学 力学性能 热解机理
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Behavior of exciton in direct−indirect band gap Al_(x)Ga_(1−x)As crystal lattice quantum wells
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作者 Yong Sun Wei Zhang +10 位作者 Shuang Han Ran An Xin-Sheng Tang Xin-Lei Yu Xiu-Juan Miao Xin-Jun Ma Xianglian Pei-Fang Li Cui-Lan Zhao Zhao-Hua Ding Jing-Lin Xiao 《Journal of Semiconductors》 EI CAS CSCD 2024年第3期64-70,共7页
Excitons have significant impacts on the properties of semiconductors.They exhibit significantly different properties when a direct semiconductor turns in to an indirect one by doping.Huybrecht variational method is a... Excitons have significant impacts on the properties of semiconductors.They exhibit significantly different properties when a direct semiconductor turns in to an indirect one by doping.Huybrecht variational method is also found to influence the study of exciton ground state energy and ground state binding energy in Al_(x)Ga_(1−x)As semiconductor spherical quantum dots.The Al_(x)Ga_(1−x)As is considered to be a direct semiconductor at AI concentration below 0.45,and an indirect one at the concentration above 0.45.With regards to the former,the ground state binding energy increases and decreases with AI concentration and eigenfrequency,respectively;however,while the ground state energy increases with AI concentration,it is marginally influenced by eigenfrequency.On the other hand,considering the latter,while the ground state binding energy increases with AI concentration,it decreases with eigenfrequency;nevertheless,the ground state energy increases both with AI concentration and eigenfrequency.Hence,for the better practical performance of the semiconductors,the properties of the excitons are suggested to vary by adjusting AI concentration and eigenfrequency. 展开更多
关键词 exciton effects aluminum gallium arsenide crystal direct band gap semiconductor indirect band gap semiconductor
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Spin gap in quasi-one-dimensional S=3/2 antiferromagnet CoTi2O5
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作者 徐浩航 刘庆元 +10 位作者 辛潮 申沁鑫 罗军 周睿 程金光 刘健 陶玲玲 刘志国 霍明学 王先杰 隋郁 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第3期609-617,共9页
Quasi-one-dimensional(1D)antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectra.Here we demonstrate that a spin gap exists in the quasi-1D Heise... Quasi-one-dimensional(1D)antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectra.Here we demonstrate that a spin gap exists in the quasi-1D Heisenberg antiferromagnet CoTi2O5 with highly ordered Co2+/Ti4+occupation,in which the Co2+ions with S=3/2 form a 1D spin chain along the a-axis.CoTi2O5 undergoes an antiferromagnetic transition at TN~24 K and exhibits obvious anisotropic magnetic susceptibility even in the paramagnetic region.Although a gapless magnetic ground state is usually expected in a quasi-1D Heisenberg antiferromagnet with half-integer spins,by analyzing the specific heat,the thermal conductivity,and the spin-lattice relaxation rate(1/T1)as a function of temperature,we found that a spin gap is opened in the spin-excitation spectrum of CoTi2O5 around TN,manifested by the rapid decrease of magnetic specific heat to zero,the double-peak characteristic in thermal conductivity,and the exponential decay of 1/T1 below TN.Both the magnetic measurements and the first-principles calculations results indicate that there is spin-orbit coupling in CoTi2O5,which induces the magnetic anisotropy in CoTi2O5,and then opens the spin gap at low temperature. 展开更多
关键词 quasi-one-dimensional antiferromagnet magnetic anisotropy spin gap
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Experimental Study of Local Scour Around Four Piles Under Different Attack Angles and Gap Ratios
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作者 LIU Ming-ming TANG Guo-qiang +1 位作者 JIN Xin GENG Shao-yang 《China Ocean Engineering》 SCIE EI CSCD 2024年第4期612-624,共13页
In an effort to investigate and quantify the patterns of local scour,researchers embarked on an in-depth study using a systematic experimental approach.The research focused on the effects of local scour around a set o... In an effort to investigate and quantify the patterns of local scour,researchers embarked on an in-depth study using a systematic experimental approach.The research focused on the effects of local scour around a set of four piles,each subjected to different hydromechanical conditions.In particular,this study aimed to determine how different attack angles—the angles at which the water flow impinges on the piles,and gap ratios—the ratios of the spacing between the piles to their diameters,influence the extent and nature of scour.A comprehensive series of 35 carefully designed experiments were orchestrated,each designed to dissect the nuances in how the gap ratio and attack angle might contribute to changes in the local scour observed at the base of pile groups.During these experimental trials,a wealth of local scour data were collected to support the analysis.These data included precise topographic profiles of the sediment bed around the pile groups,as well as detailed scour time histories showing the evolution of scour at strategic feature points throughout the test procedure.The analysis of the experimental data provided interesting insights.The study revealed that the interplay between the gap ratio and the attack angle had a pronounced influence on the scouring dynamics of the pile groups.One of the key observations was that the initial phases of scour,particularly within the first hour of water flow exposure,were characterized by a sharp increase in the scour depth occurring immediately in front of the piles.After this initial rapid development,the scour depth transitioned to a more gradual change rate.In contrast,the scour topography around the piles continuously evolved.This suggests that sediment displacement and the associated sculpting of the seabed around pile foundations are sustained and progressive processes,altering the underwater landscape over time.The results of this empirical investigation have significant implications for the design and construction of offshore multi-pile foundations,providing a critical reference for engineers and designers to estimate the expected scour depth around such structures,which is an integral part of decisions regarding foundation design,selection of structural materials,and implementation of scour protection measures. 展开更多
关键词 local scour PILES gap ratio attack angle
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Ultra-wide band gap and wave attenuation mechanism of a novel star-shaped chiral metamaterial
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作者 Shuo WANG Anshuai WANG +7 位作者 Yansen WU Xiaofeng LI Yongtao SUN Zhaozhan ZHANG Qian DING G.D.AYALEW Yunxiang MA Qingyu LIN 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2024年第7期1261-1278,共18页
A novel hollow star-shaped chiral metamaterial(SCM)is proposed by incorporating chiral structural properties into the standard hollow star-shaped metamaterial,exhibiting a wide band gap over 1500 Hz.To broaden the ban... A novel hollow star-shaped chiral metamaterial(SCM)is proposed by incorporating chiral structural properties into the standard hollow star-shaped metamaterial,exhibiting a wide band gap over 1500 Hz.To broaden the band gap,solid single-phase and two-phase SCMs are designed and simulated,which produce two ultra-wide band gaps(approximately 5116 Hz and 6027 Hz,respectively).The main reason for the formation of the ultra-wide band gap is that the rotational vibration of the concave star of two novel SCMs drains the energy of an elastic wave.The impacts of the concave angle of a single-phase SCM and the resonator radius of a two-phase SCM on the band gaps are studied.Decreasing the concave angle leads to an increase in the width of the widest band gap,and the width of the widest band gap increases as the resonator radius of the two-phase SCM increases.Additionally,the study on elastic wave propagation characteristics involves analyzing frequency dispersion surfaces,wave propagation directions,group velocities,and phase velocities.Ultimately,the analysis focuses on the transmission properties of finite periodic structures.The solid single-phase SCM achieves a maximum vibration attenuation over 800,while the width of the band gap is smaller than that of the two-phase SCM.Both metamaterials exhibit high vibration attenuation capabilities,which can be used in wideband vibration reduction to satisfy the requirement of ultra-wide frequencies. 展开更多
关键词 METAMATERIAL ultra-wide band gap wave propagation vibration suppression
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Differential modulation of crown allometry and stem growth at gap edges in five European tree species by drought conditions
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作者 Luke Bohnhorst Peter Biber +2 位作者 Torben Hilmers Enno Uhl Hans Pretzsch 《Forest Ecosystems》 SCIE CSCD 2024年第5期618-631,共14页
Background In Central Europe,forests are increasingly affected by various disturbances,resulting in an increasing gap formation in the canopy.In order to support goal-oriented management,more knowledge is required abo... Background In Central Europe,forests are increasingly affected by various disturbances,resulting in an increasing gap formation in the canopy.In order to support goal-oriented management,more knowledge is required about the acclimation of the crown and its effects on the basal area growth of trees at the edge of a gap.Methods This work compared trees'growth and crown structure at the edge of a transient gap,with a gap size of more than 80m^(2),with trees in the stand that were at least 30m away from the gap.A total of 249 European beeches(Fagus sylvatica L.),Norway spruces(Picea abies L.Karst),Scots pines(Pinus sylvestris L.),oaks(Quercus spp.;Quercus petraea(Matt.)Liebl.,Quercus robur L.),and silver firs(Abies alba Mill.)were examined on long-term experimental plots in southern Germany.Various crown measures were developed and calculated using high-resolution terrestrial laser scanning(TLiDAR)to capture the three-dimensional crown structures.Growth responses to edge conditions were measured based on tree rings.Using linear mixed models,we predict the basal area increment of edge trees relative to trees in the stand under wet and dry soil moisture conditions after the gap formation.Results We identified i)species-specific acclimation of the crown of edge trees after the gap formation,ii)under wet soil moisture conditions a growth increase of 25%–45%for beech,pine,and oak edge trees and growth losses of 5%–60%for spruce and fir and iii)coniferous tree species benefited from the edge position regarding their basal area increment under dry soil moisture conditions and deciduous tree species grew regardless of the soil moisture conditions at the edge of a gap.Conclusion Gaps have a species-specific effect on the habitus and growth of edge trees and can have both positive and negative impacts on silviculture. 展开更多
关键词 Canopy gaps Disturbance Growth TLiDAR Drought stress Crown structure ACCLIMATION
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Optimal design for rubber concrete layered periodic foundations based on the analytical approximations of band gaps and mapping relations
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作者 Wu Qiaoyun Xu Zhifeng +2 位作者 Xu Peishan Zeng Wenxuan Chen Xuyong 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2024年第3期593-608,共16页
The seismic performance of rubber concrete-layered periodic foundations are significantly influenced by their design,in which the band gaps play a paramount role.Aiming at providing better designs for these foundation... The seismic performance of rubber concrete-layered periodic foundations are significantly influenced by their design,in which the band gaps play a paramount role.Aiming at providing better designs for these foundations,this study first proposes and validates the analytical formulas to approximate the bounds of the first few band gaps.In addition,the mapping relations linking the frequencies of different band gaps are presented.Furthermore,an optimal design method for these foundations is developed,which is validated through an engineering example.It is demonstrated that ensuring the superstructure’s resonance zones are completely covered by the corresponding periodic foundation’s band gaps can achieve satisfactory vibration attenuation effects,which is a good strategy for the design of rubber concrete layered periodic foundations. 展开更多
关键词 periodic foundation band gap vibration attenuation seismic isolation optimal design
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Analysis of the Digital Skill Gap of Agricultural Extension Personnel in South-East, Nigeria
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作者 Ogbonnaya Okoro Aja Chigozie Cyril Asiabaka +1 位作者 Anthony Okorie Ani Edna Chioma Matthews-Njoku 《Agricultural Sciences》 2024年第9期1057-1070,共14页
The study analysed the digital skill gap of agricultural extension personnel on the use of digital technologies for extension services delivery in South-East, Nigeria. The specific objectives were to describe the soci... The study analysed the digital skill gap of agricultural extension personnel on the use of digital technologies for extension services delivery in South-East, Nigeria. The specific objectives were to describe the socioeconomic characteristics of agricultural extension personnel in South-East Nigeria and identify the digital skill gaps among agricultural extension personnel in the area of study. Purposive sampling technique was used to select 364 Agricultural Extension personnel for the study. Data were collected through the use of structured questionnaire and were analysed using simple descriptive statistical tools such as percentages, mean score, and standard deviation. Findings indicated that most of the personnel were male (57.8%), within the age bracket of 38 - 47 years (62.9%), had B.Sc./HND as their highest educational qualification (74.7%), married (86.3%), and had a household size of 6 - 10 Persons (57.7%). It was further revealed that the majority (70.1%) were members of professional organization, earned a monthly income of N50,001.00 - N100,000.00 (65.7%), had a work experience of 11 - 15 years (51.1%), and owned a smartphone/ iPad/laptop (91.5%). Findings further indicated that they had moderate skill gap in Basic Computer skills (Mean = 4.32), and digital communication and collaboration skills (Mean = 4.26). Findings also showed that they had a high skill gap in digital technical skills (Mean = 2.46), digital data analysis skills (Mean = 2.09), digital content creation skills (Mean = 2.43), digital ethical skills (Mean = 2.79), multimedia production skills (Mean = 2.81), and video library management skills (Mean = 2.39). The study concluded that though there exists a high digital skill gap among agricultural extension personnel in South-East, Nigeria, their socioeconomic characteristics are capable of supporting the implementation of digital extension services in the area. The study recommended that the management of Agricultural Development Programs in South-East, Nigeria, should provide digital training for extension personnel to close the digital skill gap that currently exists among the personnel. 展开更多
关键词 Agricultural Extension Personnel Socioeconomic Characteristics Digital Skill gap South-East NIGERIA
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Numerical Study on the Effect of Gap Diffraction on the Hydrodynamic Performance of A Floating Breakwater
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作者 BIAN Xiang-qian JI Chun-yan +2 位作者 XU Sheng GUO Jian-ting HUO Fa-li 《China Ocean Engineering》 SCIE EI CSCD 2024年第4期663-675,共13页
Two-dimensional(2D)flume experiments are useful in investigating the performances of floating breakwaters(FBs),including hydrodynamic performances,motion responses,and mooring forces.Designing a reasonable gap between... Two-dimensional(2D)flume experiments are useful in investigating the performances of floating breakwaters(FBs),including hydrodynamic performances,motion responses,and mooring forces.Designing a reasonable gap between the flume wall and the FBs is a critical step in 2D flume tests.However,research on the effect of the gap on the accuracy of 2D FB experimental results is scarce.To address this issue,a numerical wave tank is developed using CFD to estimate the wave-FB interaction of a moored dual-cylindrical FB,and the results are compared to experimental data from a previously published work.There is good agreement between them,indicating that the numerical model is sufficiently accurate.The numerical model is then applied to explore the effect of gap diffraction on the performance of FBs in2D experiments.It was discovered that the nondimensional gap length L_(Gap)/W_(Pool)should be smaller than 7.5%to ensure that the relative error of the transmission coefficient is smaller than 3%.The influence of the gap is also related to the entering wave properties,such as the wave height and period. 展开更多
关键词 floating breakwater diffraction effect gap hydrodynamic performance model experiments CFD numerical simulation
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A CombustionModel for Explosive Charge Affected by a Bottom Gap in the Launch Environment
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作者 ShiboWu Weidong Chen +4 位作者 Jingxin Ma Lan Liu Shengzhuo Lu Honglin Meng Xiquan Song 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第2期1207-1236,共30页
Launch safety of explosive charges has become an urgent problem to be solved by all countries in the world aslaunch situation of ammunition becomes consistentlyworse.However, the existing numericalmodels have differen... Launch safety of explosive charges has become an urgent problem to be solved by all countries in the world aslaunch situation of ammunition becomes consistentlyworse.However, the existing numericalmodels have differentdefects. This paper formulates an efficient computational model of the combustion of an explosive charge affectedby a bottom gap in the launch environment in the context of the material point method. The current temperatureis computed accurately from the heat balance equation, and different physical states of the explosive charges areconsidered through various equations of state. Microcracks in the explosive charges are described with respectto the viscoelastic statistical crackmechanics (Visco–SCRAM) model. Themethod for calculating the temperatureat the bottomof the explosive charge with respect to the bottomgap is described. Based on this combustionmodel,the temperature history of a Composition B (COMB) explosive charge in the presence of a bottom gap is obtainedduring the launch process of a 155-mm artillery. The simulation results show that the bottom gap thickness shouldbe no greater than 0.039 cm to ensure the safety of the COM B explosive charge in the launch environment. Thisconclusion is consistent with previous results and verifies the correctness of the proposed model. Ultimately, thispaper derives amathematical expression for themaximumtemperature of the COMB explosive chargewith respectto the bottomgap thickness (over the range of 0.00–0.039 cm), and establishes a quantitative evaluationmethod forthe launch safety of explosive charges.The research results provide some guidance for the assessment and detectionof explosive charge safety in complex launch environments. 展开更多
关键词 Combustion model explosive charge safety launch environment bottom gap TEMPERATURE
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Observation and analysis of positive leader re-illumination in a 10 m ultra-high voltage transmission line gap under switching impulse voltages
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作者 Biao HUANG Xuan ZHOU +3 位作者 She WANG Chijie ZHUANG Rong ZENG Le DENG 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第10期93-100,共8页
The leader propagation is one of the most important stages in long air gap discharge.The mechanism behind leader re-illumination remains unclear.In high humidity conditions(20.0–30.1 g/m^(3)),we have conducted experi... The leader propagation is one of the most important stages in long air gap discharge.The mechanism behind leader re-illumination remains unclear.In high humidity conditions(20.0–30.1 g/m^(3)),we have conducted experiments of long sparks in a 10 m ultra-high voltage(UHV)transmission line gap under switching impulse voltages.The positive leaders predominantly propagate discontinuously,with almost no significantly continuous propagation occurring.The leader channels are intensely luminous and each elongation segment is straight,with streamers resembling the“branch type”which differs from the“diffuse type”streamers at the front of continuous propagation leaders.The distribution of the propagation velocities is highly random(3.7–18.4 cm/μs),and the average velocity(9.2 cm/μs)significantly exceeds that of continuous propagation(1.5–2.0 cm/μs).Analysis suggests that the current-velocity models suitable for continuous leader propagation do not align well with the experimental data in re-illumination mode.Based on the discharge current waveforms and optical images,it is speculated that the newly elongated leader in re-illumination mode does not evolve gradually from the stem(about 1 cm)but rather evolves overall from a thermal channel much longer than stem. 展开更多
关键词 long air gap discharge positive leader re-illumination discontinuous leader propagation
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