Adaptive Mesh Refinement for Computational Aeroacoustics-University of Southampton Southampton, UK

合集下载

基于提前终止策略改进的运动估计算法

第 22卷第 7期2023年 7月Vol.22 No.7Jul.2023软件导刊Software Guide基于提前终止策略改进的运动估计算法朱鑫磊，汪伟（上海理工大学光电信息与计算机工程学院，上海 200093）摘要：针对HM-16.14中TZSearch标准算法存在的计算复杂度高、耗时相对较长等问题，提出一种基于提前终止策略的改进TZSearch算法。

首先，根据编码产生的率失真代价对编码单元、变换单元和预测单元的深度进行划分，有效避免了额外的划分深度；然后，在TZSearch初始网格搜索过程中，采用钻石搜索和六边形搜索两种搜索方式，根据运动矢量分布位置选择一种更为有效的方式，精确找出最佳匹配点；最后，使用OARP栅格搜索和精细搜索完成运动估计。

由实验结果可知，该方法与标准算法相比，平均降低了60％以上的TZSearch运动估计耗时，且基本不影响视频质量。

关键词：TZSearch算法；提前终止策略；栅格搜索；精细搜索；运动估计DOI：10.11907/rjdk.221887开放科学（资源服务）标识码（OSID）：中图分类号：TP391.1 文献标识码：A文章编号：1672-7800（2023）007-0051-08A Modified Motion Estimation Algorithm Based on Early Termination StrategyZHU Xinlei， WANG Wei（School of Optical-Electrical and Computer Engineering， University of Shanghai for Science and Technology，Shanghai 200093， China）Abstract：Considering the high computational complexity and relatively long time consumption of the TZSearch standard algorithm within HM-16.14， an improved TZSearch algorithm based on early termination strategy is proposed to improve the efficiency of video coding. Firstly，the depth sorting of the coding unit， transform unit and prediction unit is calculated according to the performance of rate distortion， which can effectively decrease additional division depths. Secondly， two search methods， i.e. diamond search and hexagonal search， are employed within the initial grid search step of TZSearch in order to precisely find the best matching point according to the motion vector distribution. Finally，OARP raster search and fine search are used to acquire the motion estimation results. Compared with the standard algorithm， experimental re‐sults show that the proposed method reduces more than 60% motion estimation time consumption on average， yet keeps the similar video quali‐ty .Key Words：TZSearch algorithm； early termination strategy； raster search； fine search； motion estimation0 引言随着视频技术的快速发展，依靠视频传递信息变得越来越普及，这使得视频流数据在互联网传输中的占比越来越大。

基于遗传算法的递归MTI自适应滤波器的设计

信息疼术2018卑第7期文章编号：1009 -2552(2018)07 -0090 -04 DOI：10. 13274/j. cn k i. h d z j. 2018. 07. 021基于遗传算法的递归M T I自适应滤波器的设计殷万君\金炜东2(1.四川信息职业技术学院，四川广元628040; 2.西南交通大学，成都610031)摘要：针对自适应滤波器在F P G A上实现结构灵活性的特点，文中提出了一种基于遗传算法的递归M T I自适应滤波器的设计方法。

根据遗传算法的特点，结合滤波器的性能指标，阐述了设计思想，通过遗传算法实现了自适应滤波器的权系数寻优，在系数寻优中采用了创新的适应度函数和惩罚函数，通过场景仿真，验证了文中所提算法的实用性和有效性。

关键词：遗传算法；递归M T I;自适应滤波器；设计中图分类号：T N957.52 文献标识码：ADesign of recursive MTI adaptive filter based on genetic algorithmYIN Wan-jun1，JIN Wei-dong2(1. Sichuan Inform ation Technology College，Guangyuan 628040，Sichuan Province，China；2. Southwest Jiaotong University，Chengdu 610031，China)Abstract ：In order to realize the fle x ib ility o f adaptive filte r in F P G A，a design m ethod o f recursive M T I adaptive filte r based on genetic a lgo rithm is proposed in th is p a p e r.A c co rd in g to the cha racteristics o f genetic a lg o rith m，com bined w ith the perform ance o f the f ilt e r，it expounds the design id e a s，through the genetic a lgo rithm to achieve the rig h t of the adaptive filte r co e fficie n t o p tim iz a tio n，op tim iza tio n of the coe fficien ts in the in no vation o f the fitness fu n c tio n and pe na lty fu n c tio n.Through s im u la tio n，it verifies the p ra c tic a lity and effectiveness o f the proposed a lg o rith m.Key words：genetic a lg o rith m；recursive M T I；adaptive f ilt e r；design0引言自适应滤波器使用广泛，可以由训练样本根据某种算法去调节加权系数，使实际输出与理想输出的均方差达到最小。

自适应拉曼光谱成像数据去噪及其在植物细胞壁光谱分析中的应用

自适应拉曼光谱成像数据去噪及其在植物细胞壁光谱分析中的应用张逊;陈胜;吴博士;杨桂花;许凤【摘要】Two inevitable noise signals, baseline drifts and cosmic spikes in Raman spectral imaging data should be eliminated before data analysis. However, current denoising methods for a single spectrum often lead to unstable results with bad reproducible properties. In this study, a novel adaptive method for denoising Raman spectral imaging data was proposed to address this issue. Adaptive iteratively reweighted penalized least-squares (airPLS) and principal component analysis (PCA) based despiking algorithm were applied to correct drifting baselines and cosmic spikes, respectively. The method offers a variety of advantages such as less parameter to be set, no spectral distortion, fast computation speed, and stable results, etc. We utilized the method to eliminate the noise signals in Raman spectral imaging data of Miscanthus sinensis ( involving 9010 spectra) , and then employed PCA and cluster analysis ( CA) to distinguish plant spectra from non-plant spectra. Theoretically, this method could be used to denoise other spectral imaging data and provide reliable foundation for achieving stable analysis results.%拉曼光谱成像数据存在基线漂移与宇宙射线干扰峰两类噪声信号,无法直接用于光谱分析研究,必须去除。

信息存储技术课堂报告-忆阻器交叉点阵列的非理想特性与解决方案

互联电阻压降会导致交叉
and
互联电阻压降会损害读裕
阵列中每个单元上的有效
度并使感应电路的设计变
电压分布不均匀、写入延
得复杂。
迟不均匀、潜电流不均匀。
1.C. Wang, D. Feng, J. Liu, W. Tong, B. Wu, and Y. Zhang. 2017. DAWS: Exploiting crossbar characteristics for improving write performance of high density resistive memory. In Proceedings of the IEEE International Conference on Computer Design (ICCD’17). 281–288. 2. M. A. Zidan, A. M. Eltawil, F. Kurdahi, H. A. H. Fahmy, and K. N. Salama. 2014. Memristor multiport readout: A closed-form solution for sneak paths. IEEE Trans. Nanotechnol. 13, 2 (2014), 274–282.
Flip-N-Write的伪代码 Flip-N-Write实例
1.W. Wen, L. Zhao, Y. Zhang and J. Yang, "Speeding up crossbar resistive memory by exploiting in-memory data patterns," 2017 IEEE/ACM International Conferenceon Computer-Aided Design (ICCAD), Irvine, CA, 261-267. 2.Y. Zhang, D. Feng, W. Tong, Y. Hua, J. Liu, Z. Tan, C. Wang, B. Wu, Z. Li, and G. Xu. 2018. CACF: A novel circuit architecture co-optimization framework for improving performance, reliability and energy of ReR main memory system. ACM Trans. Archit. Code Optim. 15, 2 (2018). 3.W. Wen, L. Zhao, Y. Zhang and J. Yang, "Exploiting In-memory Data Patterns for Performance Improvement on Crossbar Resistive Memory," in IEEE Transactions on Computer-Aided Design of Integrated Circuits a Systems.

惠普彩色激光打印机 Pro M454 和惠普彩色激光多功能一体机 Pro M479 维修手册说明书

Table -1 Revision history Revision number 1
Revision date 6/2019
Revision notes HP LaserJet Pro M454 HP LaserJet Pro MFP M479 Repair manual initial release
Additional service and support for HP internal personnel HP internal personnel, go to one of the following Web-based Interactive Search Engine (WISE) sites: Americas (AMS) – https:///wise/home/ams-enWISE - English – https:///wise/home/ams-esWISE - Spanish – https:///wise/home/ams-ptWISE - Portuguese – https:///wise/home/ams-frWISE - French Asia Pacific / Japan (APJ) ○ https:///wise/home/apj-enWISE - English ○ https:///wise/home/apj-jaWISE - Japanese ○ https:///wise/home/apj-koWISE - Korean ○ https:///wise/home/apj-zh-HansWISE - Chinese (simplified)
Find information about the following topics ● Service manuals ● Service advisories ● Up-to-date control panel message (CPMD) troubleshooting ● Install and configure ● Printer specifications ● Solutions for printer issues and emerging issues ● Remove and replace part instructions and videos ● Warranty and regulatory information

纳米纤维掺杂自增强策略开发增强型质子交换膜

纳米纤维掺杂自增强策略开发增强型质子交换膜下载提示：该文档是本店铺精心编制而成的，希望大家下载后，能够帮助大家解决实际问题。

文档下载后可定制修改，请根据实际需要进行调整和使用，谢谢！本店铺为大家提供各种类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，想了解不同资料格式和写法，敬请关注！Download tips: This document is carefully compiled by this editor. I hope that after you download it, it can help you solve practical problems. The document can be customized and modified after downloading, please adjust and use it according to actual needs, thank you! In addition, this shop provides you with various types of practical materials, such as educational essays, diary appreciation, sentence excerpts, ancient poems, classic articles, topic composition, work summary, word parsing, copy excerpts, other materials and so on, want to know different data formats and writing methods, please pay attention!基于纳米纤维的自增强策略开发增强型质子交换膜质子交换膜燃料电池因其高效、清洁等特点,在清洁能源领域受到广泛关注。

山东大学学报(工学版)总目次

第6期第50卷总目次山东大学学报(工学版）第50卷2020 年总目次机器学习与数据挖掘基于域对抗网络和B E R T 的跨领域文本情感分析...............基于V i B e 算法运动特征的关键帧提取算法......................自适应属性选择的实体对齐方法.............................基于门控循环单元与主动学习的协同过滤推荐算法...........基于异质集成学习的虚假评论检测..........................一种使用并行交错采样进行超分辨的方法....................基于校正神经网络的视频追踪算法...........................基于改进Y O L O v 3的复杂场景车辆分类与跟踪..................基于混合决策的改进鸟群算法..............................一种基于深度神经网络的句法要素识别方法..................基于多维相似度和情感词扩充的相同产品特征识别...........符号序列的L D A 主题特征表示方法 .........................基于元图归一化相似性度量的实体推荐.......................基于Laplacian 支持向量机和序列信息的m i c r o R N A -结合残基预测基于三维剪切波变换和B M 4D 的图像去噪方法................................蔡国永，林强，任凯琪（1-1)……李秋玲，邵宝民，赵磊，王振，姜雪（1-8)……苏佳林，王元卓，靳小龙，程学旗（1-14)......陈德蕾，王成，陈建伟，吴以茵（1-21)…张大鹏，刘雅军，张伟，沈芬，杨建盛（2-1)........................朱安，徐初（2-10)...........陈宁宁，赵建伟，周正华（2-17).............宋士奇，朴燕，蒋泽新（2-27)闫威，张达敏，张绘娟，辛梓芸，陈忠云（2-34)......陈艳平，冯丽，秦永彬，黄瑞章（2-44)...................胡龙茂，胡学钢（2-50).............冯超，徐鲲鹏，陈黎飞（2-60).............张文凯，禹可，吴晓非（2-66).....................马昕，王雪（2-76)......张胜男，王雷，常春红，郝本利（2-83)基于预测数据特征的空气质量预测方法...................................................................................................高铭壑，张莹，张蓉蓉,黄子豪，黄琳焱，李繁菀，张昕，王彦浩（2-91)基于轻型卷积神经网络的火焰检测方法..........................严云洋，杜晨锡，刘以安，高尚兵（2-100)基于深度学习的洗衣机异常音检测..........................李春阳，李楠，冯涛，王朱贺，马靖凯（2-108)语义分析及向量化大数据跨站脚本攻击智检.....................................张海军，陈映辉（2-118)自然语言问答中的语义关系识别.....................一种Chirplet 神经网络自动目标识别算法..............基于G a b o r 特征的乳腺肿瘤M R 图像分类识别模型......基于U A R T 串口的多机通讯.............................基于多模态子空间学习的语义标签生成方法.........基于背景复杂度自适应距离阈值修正的S u B S E N S E 算法基于双重启发式信息求解影响最大化问题的蚁群算法…联合检测的自适应融合目标跟踪.....................基于核极限学习机自编码器的标记分布学习.........基于集成学习〇,的质量浓度预测模型................基于空间注意力和卷积神经网络的视觉情感分析..............................段江丽，胡新（3-1)......................李怡霏，郭尊华（3-8).........袁高腾，刘毅慧，黄伟，胡兵（3-15).............................马金平（3-24)田楓，李欣，刘芳，李闯，孙小强，杜睿山（3-31)...............成科扬，孙爽，詹永照（3-38)•…覃俊，李蔚栋，易金莉，刘晶，马懋德（3-45)...............刘保成，朴燕，宋雪梅（3-51).......王一宾，李田力，程玉胜，钱坤（3-58)..................彭岩，冯婷婷，王洁（4-1)............蔡国永，贺歆灏，储阳阳（4-8)• 2 ■山东大学学报（工学版)第50卷一种基于多目标的容器云任务调度算法...............基于卷积神经网络的深度线段分类算法................基于类激活映射-注意力机制的图像描述方法...........基于Bi -LSTM 的脑电情绪识别.........................带特征指标约束描述的设计模式分类挖掘..............基于NRC 和多模态残差神经网络的肺部肿瘤良恶性分类中文对话理解中基于预训练的意图分类和槽填充联合模型融合残差块注意力机制和生成对抗网络的海马体分割••…........................谢晓兰，王琦（4-14)..............赵宁宁，唐雪嵩，赵鸣博（4-22).....廖南星，周世斌，张国鹏，程德强（4-28)..................刘帅，王磊，丁旭涛（4-35).....肖卓宇，何锫，陈果,徐运标，郭杰（6-48)■•…霍兵强，周涛，陆惠玲，董雅丽，刘珊（6-59)........................马常霞，张晨（6-68)张月芳，邓红霞，呼春香，钱冠宇，李海芳（6-76)控制科学与工程基于空间隐患分布与运动意图解析的危险评估方法........一类非仿射非线性大系统的结构在线扩展.................GPRS 监管的多协议异构现场总线控制系统................基于新型趋近律的参数未知分数阶Rucklidge 系统的滑模同步分数阶Brussel 系统混沌同步的三种控制方案...............一类非线性混沌系统的自适应滑模同步...................含对数项分数阶T 混沌系统的滑模同步...................赵越男，陈桂友，孙琛，卢宁，譽立伟（1 -28)............曹小洁，李小华，刘辉（1-35)……侯鹏飞，孙竹梅，王琦，白建云（1-49).........王春彦，邸金红，毛北行（4-40).........................程春蕊（4-46)..................程春蕊，毛北行（5-1)..................孟晓玲，毛北行（5-7)土木工程含层状节理岩体力学性质数值模拟研究.......................................徐子瑶，虞松，付强（3-66)水泥土搅拌桩沿海软基处理..............................................吕国仁，葛建东，肖海涛（3-73)高地应力下砂岩力学参数和波速变化规律试验研究..............................宫嘉辰，陈士海（3-82)饱和地基中单排孔近场隔振的现场试验与数值分析智慧公路关键技术发展综述...................双节理岩体T B M 滚刀破岩过程数值模拟......基于熵值法的水利施工企业绩效考核K P I 设计方法偏压大跨小净距公路隧道施工力学行为..........基于B P 神经网络算法的结构振动模态模糊控制••砂土介质中颗粒浆液扩散距离变化规律........预应力中空棒构件设计与力学特性..............隐伏溶洞对隧道围岩稳定性影响规律及处治技术硬岩隧道纯钢纤维混凝土管片应用..............喷扩锥台压灌桩最优构造.......................松散地层隧道进洞段管棚注浆加固效应分析……孙连勇，时刚，崔新壮，周明祥，王永军，纪方，闫小东（3-88)................................吴建清，宋修广（4-52)施雪松，管清正，王文扬，许振浩，林鹏，王孝特，刘洁（4-70).........................................程森(4-80)........................................王春国（4-85)...........................王志伟，葛楠，李春伟（5-13)........................冯啸，夏冲，王凤刚，张兵（5-20).............................林超，张程林，王勇（5-26).....................陈禹成，王朝阳，郭明，林鹏（5-33)..............徐振，李德明，王彬，詹谷益，张世杰（5-44)...........李连祥，邢宏侠，李金良，黄亨利，王雷（6-82)...................余俊，翁贤杰，樊文胜，张连震（6-92)机械与能动工程柔性Rushton 桨的振动特性.........................................................刘欣，杨锋茶（5-50)湿法脱硫塔一维传热传质性能模型理论与试验.....................陈保奎，孙奉仲，高明，史月涛（5-56)波浪能发电装置浮体形状参数对俘能性能影响............刘延俊，王伟，陈志，王冬海,王登帅，薛钢（6-1)深拖地震线列阵的动力学建模与位置预报...................朱向前,魏峥嵘，裴彦良，于凯本，宗乐（6-9)淹没深度对三自由度波能浮子获能的影响........................黄淑亭，翟晓宇，刘延俊，史宏达（6-17)尾缘襟翼振荡水翼的水动力特性.................................孙光，王勇，谢玉东，陈晨，张玉兵（6-23)深海带电插拔连接器力学特性分析…韩家桢，王勇，谢玉东，王启先，张新标，高文彬，李荣兰，张传军（6-30) 振荡翼改进运动模型的能量捕获性能分析............................乔凯，王启先，王勇，谢玉东（6-40)第6期第50卷总目次电气工程能源消费发展及预测方法综述..............................杨明，杜萍静，刘凤全，郝旭鹏，孛一凡（1-56)基于物理不可克隆函数的电网NB-IoT端到端安全加密方案............................................................................................刘冬兰，刘新，陈剑飞，王文婷，张昊，马雷，李冬（丨-63)中央空调紧急控制应对受端电网直流闭锁故障研究.................................................................................................刘萌，程定一，张文，张恒旭，李宽，张国辉，苏建军U-72)风电爬坡事件的非精确条件概率预测..........................王勃，汪步惟，杨明，赵元春，朱文立（丨-82)考虑同步调相机无功特性的多馈入直流同时换相失败风险评估方法............................................................................................麻常辉，王亮，谭邵卿，卢奕，马欢，赵康（3-98)考虑路灯充电桩接入的城市配电网电压控制方法............宋士瞻，陈浩宇，张健，王坤，郝庆水（3-104)基于分时电价的含光伏的智慧家庭能量调度方法…潘志远，刘超男，李宏伟，王婧，王威，刘静，郑鑫（3-111)基于弹性梯度下降算法的B P神经网络降雨径流预报模型..........金保明，卢光毅，王伟，杜伦阅（3-117)基于学习理论的含光储联合系统的输电网双层规划……孙东磊，赵龙，秦敬涛，韩学山，杨明，王明强（4-90) 考虑内部动态约束的MMC功率运行区间的确定及控制方法……张锋,杨桂兴，岳晨晶，郝全睿，李东（4 - 9 8)虾米腰弯管内置导流板优化...................................祁金胜，曹洪振，石岩，杜文静，王湛（5-64)基于B P神经网络的短期光伏集群功率区间预测........孙东磊，王艳，于一潇，韩学山，杨明，闰芳晴（5-70)偏心方圆节扩散管数值模拟.................................曹洪振,祁金胜，袁宝强，杜文静，王湛（5-77)烟气成分对湿式电除尘器电晕放电特性的影响.................王磊，张玉磊，李兆东，张金峰，王翔（5-83)含电极式电锅炉的地区电网电源侧综合效益分析......葛维春，李昭，赵东，李振宇，叶青，傅予，于娜（5-90)基于特征频带相电流提取的故障选相和选线方法........................张贺军，王鹏，徐凯，石访（5-99)电动汽车虚拟储能可用容量建模.......................................李蓓，赵松，谢志佳，牛萌（6-101)基于RTDS的配电网一二次融合仿真技术...............李志，余绍峰，苏毅方，王蔚，蒋宏图，张伟（6-112)芒刺参数对电晕放电及细颗粒物脱除特性的影响............................王磊，李明臻，王翔（6-118)含不凝气蒸汽在锯齿形表面的凝结传热特性............................闫吉庆，王效嘉，田茂诚（6-129)化学与环境济南城区大气PM2.5、PM,。

高通量计算集成机器学习催化描述符设计新型二维MXenes析氢催化剂

高通量计算集成机器学习催化描述符设计新型二维MXenes析氢催化剂摘要：二维MXenes作为一种具有优异催化性能的材料，其析氢性能的研究显得尤为重要。

然而，传统的试错方法耗费时间和资源，难以大规模筛选出性能优异的MXenes。

因此，我们提出了一种基于高通量计算和机器学习的催化描述符设计方法，以加速和优化MXenes的析氢性能预测和发现过程。

本文首先通过大量密度泛函理论计算筛选出112种可能的析氢MXenes，并通过Fe原子掺杂进一步优化其析氢性能，得到7种性能优异的Fe doped MXenes。

接着，我们基于多项式回归、随机森林和支持向量回归等机器学习算法构建了基于17种物理和化学性质的催化描述符，并通过训练集和测试集的误差分析，选择了随机森林作为最佳预测模型。

最后，我们使用该模型预测了所有112种MXenes的析氢性能，并发现了15种前所未有的性能优异MXenes，其中析氢活性高于Ni和Pd催化剂，且可能具有实际应用价值。

关键词：MXenes；催化描述符；高通量计算；机器学习；析氢。

Abstract:As a kind of material with excellent catalytic performance, the study of hydrogen evolution performance of two-dimensional MXenes is particularly important. However, traditional trial-and-errormethods are time-consuming and resource-consuming, making it difficult to screen MXenes with excellent performance on a large scale. Therefore, we propose a catalytic descriptor design method based on high-throughput computing and machine learning to accelerate and optimize the prediction and discovery process of MXenes' hydrogen evolution performance. In this paper, 112 possible hydrogen evolution MXenes were screened through a large number of density functional theory calculations, and 7 performance-excellent Fe-doped MXenes were further optimized by Fe doping. Then, based on machine learning algorithms such as polynomial regression, random forest, and support vector regression, we constructed catalytic descriptors based on 17 physical and chemical properties, and selected random forest as the best prediction model through the error analysis of the training set and test set. Finally, we used this model to predict the hydrogen evolution performance of all 112 MXenes, and discovered 15 performance-excellent MXenes that have not been seen before, among which hydrogen evolution activity is higher than that of Ni and Pd catalysts, and may have practical application value.Keywords: MXenes; catalytic descriptors; high-throughput computing; machine learning; hydrogen evolution。

Hierarchical Finite Element Mesh Refinement有限元网格分层细化-PPT精选文档

( 0)
(1)
M M (1) ( 2) M (3) M
( 0)
M ( n)
Strict nesting of
Refinement Equation Refinement relation
N ( x )
( n ) k ( n 1 ) ( n 1 ) kj k ( n ) j s upp[ N k ]
Algorithms Field transfer: prolongation, restriction operators. Integration: single level vs. multiple-level. Algorithms:
refinement equation has a big advantage: genericity.
CHARMS
Refinement equation: Multiresolution:
Naturally conforming, dimension and order independent.
Adapted basis 1 Quasi-hierarchical basis:
Some basis functions are removed:
M M (1) ( 2) M (3) M
Nodes associated with active basis functions
( 0)
Adapted basis 2 True hierarchical basis
Subdivision surface: overlap of two basis functions.
Conceptual Hierarchy Infinite globally-refined

表面增强拉曼散射活性基底

表面增强拉曼散射活性基底高书燕　张树霞　杨恕霞　张洪杰#(河南师范大学化学与环境科学学院,新乡　453007;#中国科学院长春应用化学研究所,长春　130022)摘　要　表面增强拉曼散射(SERS)是人们将激光拉曼光谱应用到表面科学研究中所发现的异常表面光学现象。

它可以将吸附在材料表面的分子的拉曼信号放大106到1014倍,这使其在探测器的应用和单分子检测方面有着巨大的发展潜力。

由于分子所吸附的基底表面形态是SERS效应能否发生和SERS信号强弱的重要影响因素,所以分子的承载基体是很关键的,因而SERS活性基底的研究一直是该领域的研究热点之一。

本文总结了形态各异的表面增强拉曼散射活性基底,分析了最新发展并对其未来作一展望。

关键词　表面增强拉曼散射　活性基底Surface2enhanced R aman Scattering Active SubstratesG ao Shuyan,Zhang Shuxia,Y ang Shuxia,Zhang H ongjie#(C ollege of Chemistry and Environmental Science,Henan N ormal University,X inxiang453007;#Changchun Institute of Applied Chemistry,Chinese Academy of Sciences,Changchun130022)Abstract　Sur face2enhanced Raman scattering(SERS)is a special optical phenomenon originating from the application of laser Raman into sur face science.SERS can greatly magnify the Raman signals of the ads orbed m olecules106 to1014times,which makes SERS have potentials in detectors and single2m olecule analysis.Because the sur face m orphologies and structures of the substrates determines the generation and intensity of Raman signals,the substrates play a vital role in SERS and the research on the SERS active substrates remains a hot topic.In this paper,SERS active substrates are reviewed.In addition,the newly developments and futures of this area are ananlyzed and outlooked,respectively.K eyw ords　Sur face2enhanced Raman scattering,Active substrate表面增强拉曼散射(Surface2enhanced Raman Scattering,SERS)主要是纳米尺度的粗糙表面或颗粒体系所具有的异常光学增强现象,它可以将吸附在材料表面的分子的拉曼信号放大约106倍,对于特殊的纳米量级粒子形态分布的基底表面,信号的增强甚至可以高达1014倍,因此在探测器的应用和单分子检测方面有着巨大的发展潜力。

双频激电及其数据处理

工程实例证明时间域与频率域的等效性
甘肃某金银矿点金银矿受断裂带产于绿泥石角闪片岩、绢云母石英片岩内的挤压带中，金、银与铅、锌、黄铁矿化共生，且有正相关关系。黄铁矿化较强处可呈稠密浸染至半块状。图为该矿体IV号剖面综合图。Fs 与 ηs 相似性也是一目了然。
时间域与频率域的差异
频率域电法的主要优点 a.轻便; b.抗干扰能力强。传统频率域电法的主要缺点任何一种频率域电法都是要在不同的频率进行测量，传统的主动源电法勘探（包括激发极化法和电磁法）的工作方式都是“变频法”,变频法是一个频率、一个频率地逐个改变频率进行测量,以致带来了它两大致命弱点. a.变频法的工作效率低(“扫面”的速度更低); b.变频法的相对精度低。 (1)在激电法中区分矿异常性质能力低, (2)在电磁法(CSAMT)中发现深部异常能力低。 (3)不能（像TEM那样）进行近区的频率域电磁测深。
电流脉冲宽度 T（即充电时间长度）对极化强度的影响
ΔV0
电位差ΔV
ΔV0
时间 (t)
T大，二次电位大
电位差ΔV
ΔV0
ΔV0
T小，二次电位小
T
T
二次电位差 ΔVIP
频率域与时间域的等效性
脉冲宽度 (T)
电位差 ΔV
二次电位差 ΔVIP
ΔVIP
时间域
时间域
频率域
二次电位差 ΔVIP
频率域IP与时间域IP的物理实质是一样的，对于寻找金属矿来说它们的能力是等效的。
01
对于线性时不变系统，在理论上二者是可以相互转换的。
02
在实际条件下，一般电流密度都非常小（小于0.01μA/cm2），实际上可以看作线性系统，如果能测量到相当完整的时间响应和频率响应，则它们在一定精度内也是可以相互转换的。

自适应网格交互多模型不敏粒子滤波算法

的缺陷，同时各模型滤波算法采用不敏粒子滤波（Ｐ）法，使重要性密度函数融合了最新量测信息，更好地逼近ＵＦ算真实状态的后验概率分布。通过计算机仿真证明，出的算法可以有效提高Ｉ提ＭＭＰＦ的费效比。
摘要：将一种变结构多模型算法—— 自适应网格交互多模型（ＧＭＭ）ＡＩ算法和不敏粒子滤波（Ｐ）法相ＵＦ算
结合，出了自适应网格交互多模型不敏粒子滤波算法（ＧＭＭＵＦ。该算法通过自适应网格实现了模型自适应，提ＡＩＰ）从而以较小的模型集合覆盖了目标大范围的机动，以此来克服固定结构交互多模型粒子滤波（ＭＦ算法存在并１ＭＰ）
，
ｌｔｔｎｏｘｄｓｃｕｅｉｔｒｃｉｇｍｕｔｌｄｌｐｒｃｅｆｔｒＩｉａｉｆｆｅｔｔｒｎｅａｔｌｐｅｍｏｅａｔｌｌ（ＭＭＰｉｏｅｃｍｅ．ｈｎｃｎｅｍｉｏｉｕｒｎｉｉｉｅＦ）ｓｖｒｏｄＴｅｕｓｅｔｄ
关键词：自适应网格；变结构多模型算法；不敏粒子滤波中图分类号：Ｔ９７Ｎ５文献标识码：Ａ
文章编号：１７－６９２１）８０１～５ｄｉ１．４４ｊｉｎ１７ — ６９２１．８０４６２７４（０２０～０８０ｏ：０３０／．ｓ．６２７４．０２０．０ｓ

Adaptive pyramid mean shift for global real-time visual tracking

order approximation and real-time performance on personal computer (PC), but it does not meet the sparse tracking need for onboard surveillances. The particle ﬁlter (PF), also known as the Condensation algorithm, constructs the probability density function in terms of a set of weighted particles through sequential importance sampling [7]. The main disadvantage of PF is the high computational complexity. A Markov chain Monte Carlo (MCMC) sampling step is developed by Khan et al. [8,9] to reduce the number of required particles to speed up PF for tracking multiple targets. Another trick for PF is to marginalize out the linear dynamics in the models to further accelerate it and this results in Rao-Blackwellized PF (RBPF) [10]. However, few PF meets the sparse tracking needs even under PC conditions.

Parallel and Distributed Computing and Systems

Proceedings of the IASTED International ConferenceParallel and Distributed Computing and SystemsNovember3-6,1999,MIT,Boston,USAParallel Reﬁnement of Unstructured MeshesJos´e G.Casta˜n os and John E.SavageDepartment of Computer ScienceBrown UniversityE-mail:jgc,jes@AbstractIn this paper we describe a parallel-reﬁnement al-gorithm for unstructuredﬁnite element meshes based on the longest-edge bisection of triangles and tetrahedrons. This algorithm is implemented in P ARED,a system that supports the parallel adaptive solution of PDEs.We dis-cuss the design of such an algorithm for distributed mem-ory machines including the problem of propagating reﬁne-ment across processor boundaries to obtain meshes that are conforming and non-degenerate.We also demonstrate that the meshes obtained by this algorithm are equivalent to the ones obtained using the serial longest-edge reﬁne-ment method.Weﬁnally report on the performance of this reﬁnement algorithm on a network of workstations.Keywords:mesh reﬁnement,unstructured meshes,ﬁnite element methods,adaptation.1.IntroductionTheﬁnite element method(FEM)is a powerful and successful technique for the numerical solution of partial differential equations.When applied to problems that ex-hibit highly localized or moving physical phenomena,such as occurs on the study of turbulence inﬂuidﬂows,it is de-sirable to compute their solutions adaptively.In such cases, adaptive computation has the potential to signiﬁcantly im-prove the quality of the numerical simulations by focusing the available computational resources on regions of high relative error.Unfortunately,the complexity of algorithms and soft-ware for mesh adaptation in a parallel or distributed en-vironment is signiﬁcantly greater than that it is for non-adaptive computations.Because a portion of the given mesh and its corresponding equations and unknowns is as-signed to each processor,the reﬁnement(coarsening)of a mesh element might cause the reﬁnement(coarsening)of adjacent elements some of which might be in neighboring processors.To maintain approximately the same number of elements and vertices on every processor a mesh must be dynamically repartitioned after it is reﬁned and portions of the mesh migrated between processors to balance the work.In this paper we discuss a method for the paral-lel reﬁnement of two-and three-dimensional unstructured meshes.Our reﬁnement method is based on Rivara’s serial bisection algorithm[1,2,3]in which a triangle or tetrahe-dron is bisected by its longest edge.Alternative efforts to parallelize this algorithm for two-dimensional meshes by Jones and Plassman[4]use randomized heuristics to reﬁne adjacent elements located in different processors.The parallel mesh reﬁnement algorithm discussed in this paper has been implemented as part of P ARED[5,6,7], an object oriented system for the parallel adaptive solu-tion of partial differential equations that we have devel-oped.P ARED provides a variety of solvers,handles selec-tive mesh reﬁnement and coarsening,mesh repartitioning for load balancing,and interprocessor mesh migration.2.Adaptive Mesh ReﬁnementIn theﬁnite element method a given domain is di-vided into a set of non-overlapping elements such as tri-angles or quadrilaterals in2D and tetrahedrons or hexahe-drons in3D.The set of elements and its as-sociated vertices form a mesh.With theaddition of boundary conditions,a set of linear equations is then constructed and solved.In this paper we concentrate on the reﬁnement of conforming unstructured meshes com-posed of triangles or tetrahedrons.On unstructured meshes, a vertex can have a varying number of elements adjacent to it.Unstructured meshes are well suited to modeling do-mains that have complex geometry.A mesh is said to be conforming if the triangles and tetrahedrons intersect only at their shared vertices,edges or faces.The FEM can also be applied to non-conforming meshes,but conformality is a property that greatly simpliﬁes the method.It is also as-sumed to be a requirement in this paper.The rate of convergence and quality of the solutions provided by the FEM depends heavily on the number,size and shape of the mesh elements.The condition number(a)(b)(c)Figure1:The reﬁnement of the mesh in using a nested reﬁnement algorithm creates a forest of trees as shown in and.The dotted lines identify the leaf triangles.of the matrices used in the FEM and the approximation error are related to the minimum and maximum angle of all the elements in the mesh[8].In three dimensions,the solid angle of all tetrahedrons and their ratio of the radius of the circumsphere to the inscribed sphere(which implies a bounded minimum angle)are usually used as measures of the quality of the mesh[9,10].A mesh is non-degenerate if its interior angles are never too small or too large.For a given shape,the approximation error increases with ele-ment size(),which is usually measured by the length of the longest edge of an element.The goal of adaptive computation is to optimize the computational resources used in the simulation.This goal can be achieved by reﬁning a mesh to increase its resolution on regions of high relative error in static problems or by re-ﬁning and coarsening the mesh to follow physical anoma-lies in transient problems[11].The adaptation of the mesh can be performed by changing the order of the polynomi-als used in the approximation(-reﬁnement),by modifying the structure of the mesh(-reﬁnement),or a combination of both(-reﬁnement).Although it is possible to replace an old mesh with a new one with smaller elements,most -reﬁnement algorithms divide each element in a selected set of elements from the current mesh into two or more nested subelements.In P ARED,when an element is reﬁned,it does not get destroyed.Instead,the reﬁned element inserts itself into a tree,where the root of each tree is an element in the initial mesh and the leaves of the trees are the unreﬁned elements as illustrated in Figure1.Therefore,the reﬁned mesh forms a forest of reﬁnement trees.These trees are used in many of our algorithms.Error estimates are used to determine regions where adaptation is necessary.These estimates are obtained from previously computed solutions of the system of equations. After adaptation imbalances may result in the work as-signed to processors in a parallel or distributed environ-ment.Efﬁcient use of resources may require that elements and vertices be reassigned to processors at runtime.There-fore,any such system for the parallel adaptive solution of PDEs must integrate subsystems for solving equations,adapting a mesh,ﬁnding a good assignment of work to processors,migrating portions of a mesh according to anew assignment,and handling interprocessor communica-tion efﬁciently.3.P ARED:An OverviewP ARED is a system of the kind described in the lastparagraph.It provides a number of standard iterativesolvers such as Conjugate Gradient and GMRES and pre-conditioned versions thereof.It also provides both-and -reﬁnement of meshes,algorithms for adaptation,graph repartitioning using standard techniques[12]and our ownParallel Nested Repartitioning(PNR)[7,13],and work mi-gration.P ARED runs on distributed memory parallel comput-ers such as the IBM SP-2and networks of workstations.These machines consist of coarse-grained nodes connectedthrough a high to moderate latency network.Each nodecannot directly address a memory location in another node. In P ARED nodes exchange messages using MPI(Message Passing Interface)[14,15,16].Because each message has a high startup cost,efﬁcient message passing algorithms must minimize the number of messages delivered.Thus, it is better to send a few large messages rather than many small ones.This is a very important constraint and has a signiﬁcant impact on the design of message passing algo-rithms.P ARED can be run interactively(so that the user canvisualize the changes in the mesh that results from meshadaptation,partitioning and migration)or without directintervention from the user.The user controls the systemthrough a GUI in a distinguished node called the coordina-tor,.This node collects information from all the other processors(such as its elements and vertices).This tool uses OpenGL[17]to permit the user to view3D meshes from different angles.Through the coordinator,the user can also give instructions to all processors such as specify-ing when and how to adapt the mesh or which strategy to use when repartitioning the mesh.In our computation,we assume that an initial coarse mesh is given and that it is loaded into the coordinator.The initial mesh can then be partitioned using one of a num-ber of serial graph partitioning algorithms and distributed between the processors.P ARED then starts the simulation. Based on some adaptation criterion[18],P ARED adapts the mesh using the algorithms explained in Section5.Af-ter the adaptation phase,P ARED determines if a workload imbalance exists due to increases and decreases in the num-ber of mesh elements on individual processors.If so,it invokes a procedure to decide how to repartition mesh el-ements between processors;and then moves the elements and vertices.We have found that PNR gives partitions with a quality comparable to those provided by standard meth-ods such as Recursive Spectral Bisection[19]but which(b)(a)Figure2:Mesh representation in a distributed memory ma-chine using remote references.handles much larger problems than can be handled by stan-dard methods.3.1.Object-Oriented Mesh RepresentationsIn P ARED every element of the mesh is assigned to a unique processor.V ertices are shared between two or more processors if they lie on a boundary between parti-tions.Each of these processors has a copy of the shared vertices and vertices refer to each other using remote ref-erences,a concept used in object-oriented programming. This is illustrated in Figure2on which the remote refer-ences(marked with dashed arrows)are used to maintain the consistency of multiple copies of the same vertex in differ-ent processors.Remote references are functionally similar to standard C pointers but they address objects in a different address space.A processor can use remote references to invoke meth-ods on objects located in a different processor.In this case, the method invocations and arguments destined to remote processors are marshalled into messages that contain the memory addresses of the remote objects.In the destina-tion processors these addresses are converted to pointers to objects of the corresponding type through which the meth-ods are invoked.Because the different nodes are inher-ently trusted and MPI guarantees reliable communication, P ARED does not incur the overhead traditionally associated with distributed object systems.Another idea commonly found in object oriented pro-gramming and which is used in P ARED is that of smart pointers.An object can be destroyed when there are no more references to it.In P ARED vertices are shared be-tween several elements and each vertex counts the number of elements referring to it.When an element is created, the reference count of its vertices is incremented.Simi-larly,when the element is destroyed,the reference count of its vertices is decremented.When the reference count of a vertex reaches zero,the vertex is no longer attached to any element located in the processor and can be destroyed.If a vertex is shared,then some other processor might have a re-mote reference to it.In that case,before a copy of a shared vertex is destroyed,it informs the copies in other processors to delete their references to itself.This procedure insures that the shared vertex can then be safely destroyed without leaving dangerous dangling pointers referring to it in other processors.Smart pointers and remote references provide a simple replication mechanism that is tightly integrated with our mesh data structures.In adaptive computation,the struc-ture of the mesh evolves during the computation.During the adaptation phase,elements and vertices are created and destroyed.They may also be assigned to a different pro-cessor to rebalance the work.As explained above,remote references and smart pointers greatly simplify the task of creating dynamic meshes.4.Adaptation Using the Longest Edge Bisec-tion AlgorithmMany-reﬁnement techniques[20,21,22]have been proposed to serially reﬁne triangular and tetrahedral meshes.One widely used method is the longest-edge bisec-tion algorithm proposed by Rivara[1,2].This is a recursive procedure(see Figure3)that in two dimensions splits each triangle from a selected set of triangles by adding an edge between the midpoint of its longest side to the opposite vertex.In the case that makes a neighboring triangle,,non-conforming,then is reﬁned using the same algorithm.This may cause the reﬁnement to prop-agate throughout the mesh.Nevertheless,this procedure is guaranteed to terminate because the edges it bisects in-crease in length.Building on the work of Rosenberg and Stenger[23]on bisection of triangles,Rivara[1,2]shows that this reﬁnement procedure provably produces two di-mensional meshes in which the smallest angle of the re-ﬁned mesh is no less than half of the smallest angle of the original mesh.The longest-edge bisection algorithm can be general-ized to three dimensions[3]where a tetrahedron is bisected into two tetrahedrons by inserting a triangle between the midpoint of its longest edge and the two vertices not in-cluded in this edge.The reﬁnement propagates to neigh-boring tetrahedrons in a similar way.This procedure is also guaranteed to terminate,but unlike the two dimensional case,there is no known bound on the size of the small-est angle.Nevertheless,experiments conducted by Rivara [3]suggest that this method does not produce degenerate meshes.In two dimensions there are several variations on the algorithm.For example a triangle can initially be bisected by the longest edge,but then its children are bisected by the non-conforming edge,even if it is that is not their longest edge[1].In three dimensions,the bisection is always per-formed by the longest edge so that matching faces in neigh-boring tetrahedrons are always bisected by the same com-mon edge.Bisect()let,and be vertices of the trianglelet be the longest side of and let be the midpoint ofbisect by the edge,generating two new triangles andwhile is a non-conforming vertex doﬁnd the non-conforming triangle adjacent to the edgeBisect()end whileFigure3:Longest edge(Rivara)bisection algorithm for triangular meshes.Because in P ARED reﬁned elements are not destroyed in the reﬁnement tree,the mesh can be coarsened by replac-ing all the children of an element by their parent.If a parent element is selected for coarsening,it is important that all the elements that are adjacent to the longest edge of are also selected for coarsening.If neighbors are located in different processors then only a simple message exchange is necessary.This algorithm generates conforming meshes: a vertex is removed only if all the elements that contain that vertex are all coarsened.It does not propagate like the re-ﬁnement algorithm and it is much simpler to implement in parallel.For this reason,in the rest of the paper we will focus on the reﬁnement of meshes.5.Parallel Longest-Edge ReﬁnementThe longest-edge bisection algorithm and many other mesh reﬁnement algorithms that propagate the reﬁnement to guarantee conformality of the mesh are not local.The reﬁnement of one particular triangle or tetrahedron can propagate through the mesh and potentially cause changes in regions far removed from.If neighboring elements are located in different processors,it is necessary to prop-agate this reﬁnement across processor boundaries to main-tain the conformality of the mesh.In our parallel longest edge bisection algorithm each processor iterates between a serial phase,in which there is no communication,and a parallel phase,in which each processor sends and receives messages from other proces-sors.In the serial phase,processor selects a setof its elements for reﬁnement and reﬁnes them using the serial longest edge bisection algorithms outlined earlier. The reﬁnement often creates shared vertices in the bound-ary between adjacent processors.To minimize the number of messages exchanged between and,delays the propagation of reﬁnement to until has reﬁned all the elements in.The serial phase terminates when has no more elements to reﬁne.A processor informs an adjacent processor that some of its elements need to be reﬁned by sending a mes-sage from to containing the non-conforming edges and the vertices to be inserted at their midpoint.Each edge is identiﬁed by its endpoints and and its remote ref-erences(see Figure4).If and are sharedvertices,(a)(c)(b)Figure4:In the parallel longest edge bisection algo-rithm some elements(shaded)are initially selected for re-ﬁnement.If the reﬁnement creates a new(black)ver-tex on a processor boundary,the reﬁnement propagates to neighbors.Finally the references are updated accord-ingly.then has a remote reference to copies of and lo-cated in processor.These references are included in the message,so that can identify the non-conforming edge and insert the new vertex.A similar strategy can be used when the edge is reﬁned several times during the re-ﬁnement phase,but in this case,the vertex is not located at the midpoint of.Different processors can be in different phases during the reﬁnement.For example,at any given time a processor can be reﬁning some of its elements(serial phase)while neighboring processors have reﬁned all their elements and are waiting for propagation messages(parallel phase)from adjacent processors.waits until it has no elements to reﬁne before receiving a message from.For every non-conforming edge included in a message to,creates its shared copy of the midpoint(unless it already exists) and inserts the new non-conforming elements adjacent to into a new set of elements to be reﬁned.The copy of in must also have a remote reference to the copy of in.For this reason,when propagates the reﬁne-ment to it also includes in the message a reference to its copies of shared vertices.These steps are illustrated in Figure4.then enters the serial phase again,where the elements in are reﬁned.(c)(b)(a)Figure5:Both processors select(shaded)mesh el-ements for reﬁnement.The reﬁnement propagates to a neighboring processor resulting in more elements be-ing reﬁned.5.1.The Challenge of Reﬁning in ParallelThe description of the parallel reﬁnement algorithm is not complete because reﬁnement propagation across pro-cessor boundaries can create two synchronization prob-lems.Theﬁrst problem,adaptation collision,occurs when two(or more)processors decide to reﬁne adjacent elements (one in each processor)during the serial phase,creating two(or more)vertex copies over a shared edge,one in each processor.It is important that all copies refer to the same logical vertex because in a numerical simulation each ver-tex must include the contribution of all the elements around it(see Figure5).The second problem that arises,termination detection, is the determination that a reﬁnement phase is complete. The serial reﬁnement algorithm terminates when the pro-cessor has no more elements to reﬁne.In the parallel ver-sion termination is a global decision that cannot be deter-mined by an individual processor and requires a collabora-tive effort of all the processors involved in the reﬁnement. Although a processor may have adapted all of its mesh elements in,it cannot determine whether this condition holds for all other processors.For example,at any given time,no processor might have any more elements to re-ﬁne.Nevertheless,the reﬁnement cannot terminate because there might be some propagation messages in transit.The algorithm for detecting the termination of parallel reﬁnement is based on Dijkstra’s general distributed termi-nation algorithm[24,25].A global termination condition is reached when no element is selected for reﬁnement.Hence if is the set of all elements in the mesh currently marked for reﬁnement,then the algorithmﬁnishes when.The termination detection procedure uses message ac-knowledgments.For every propagation message that receives,it maintains the identity of its source()and to which processors it propagated reﬁnements.Each prop-agation message is acknowledged.acknowledges to after it has reﬁned all the non-conforming elements created by’s message and has also received acknowledgments from all the processors to which it propagated reﬁnements.A processor can be in two states:an inactive state is one in which has no elements to reﬁne(it cannot send new propagation messages to other processors)but can re-ceive messages.If receives a propagation message from a neighboring processor,it moves from an inactive state to an active state,selects the elements for reﬁnement as spec-iﬁed in the message and proceeds to reﬁne them.Let be the set of elements in needing reﬁnement.A processor becomes inactive when:has received an acknowledgment for every propa-gation message it has sent.has acknowledged every propagation message it has received..Using this deﬁnition,a processor might have no more elements to reﬁne()but it might still be in an active state waiting for acknowledgments from adjacent processors.When a processor becomes inactive,sends an acknowledgment to the processors whose propagation message caused to move from an inactive state to an active state.We assume that the reﬁnement is started by the coordi-nator processor,.At this stage,is in the active state while all the processors are in the inactive state.ini-tiates the reﬁnement by sending the appropriate messages to other processors.This message also speciﬁes the adapta-tion criterion to use to select the elements for reﬁnement in.When a processor receives a message from,it changes to an active state,selects some elements for reﬁne-ment either explicitly or by using the speciﬁed adaptation criterion,and then reﬁnes them using the serial bisection algorithm,keeping track of the vertices created over shared edges as described earlier.When itﬁnishes reﬁning its ele-ments,sends a message to each processor on whose shared edges created a shared vertex.then listens for messages.Only when has reﬁned all the elements speciﬁed by and is not waiting for any acknowledgment message from other processors does it sends an acknowledgment to .Global termination is detected when the coordinator becomes inactive.When receives an acknowledgment from every processor this implies that no processor is re-ﬁning an element and that no processor is waiting for an acknowledgment.Hence it is safe to terminate the reﬁne-ment.then broadcasts this fact to all the other proces-sors.6.Properties of Meshes Reﬁned in ParallelOur parallel reﬁnement algorithm is guaranteed to ter-minate.In every serial phase the longest edge bisectionLet be a set of elements to be reﬁnedwhile there is an element dobisect by its longest edgeinsert any non-conforming element intoend whileFigure6:General longest-edge bisection(GLB)algorithm.algorithm is used.In this algorithm the reﬁnement prop-agates towards progressively longer edges and will even-tually reach the longest edge in each processor.Between processors the reﬁnement also propagates towards longer edges.Global termination is detected by using the global termination detection procedure described in the previous section.The resulting mesh is conforming.Every time a new vertex is created over a shared edge,the reﬁnement propagates to adjacent processors.Because every element is always bisected by its longest edge,for triangular meshes the results by Rosenberg and Stenger on the size of the min-imum angle of two-dimensional meshes also hold.It is not immediately obvious if the resulting meshes obtained by the serial and parallel longest edge bisection al-gorithms are the same or if different partitions of the mesh generate the same reﬁned mesh.As we mentioned earlier, messages can arrive from different sources in different or-ders and elements may be selected for reﬁnement in differ-ent sequences.We now show that the meshes that result from reﬁning a set of elements from a given mesh using the serial and parallel algorithms described in Sections4and5,re-spectively,are the same.In this proof we use the general longest-edge bisection(GLB)algorithm outlined in Figure 6where the order in which elements are reﬁned is not spec-iﬁed.In a parallel environment,this order depends on the partition of the mesh between processors.After showing that the resulting reﬁned mesh is independent of the order in which the elements are reﬁned using the serial GLB al-gorithm,we show that every possible distribution of ele-ments between processors and every order of parallel re-ﬁnement yields the same mesh as would be produced by the serial algorithm.Theorem6.1The mesh that results from the reﬁnement of a selected set of elements of a given mesh using the GLB algorithm is independent of the order in which the elements are reﬁned.Proof:An element is reﬁned using the GLBalgorithm if it is in the initial set or reﬁnementpropagates to it.An element is reﬁnedif one of its neighbors creates a non-conformingvertex at the midpoint of one of its edges.Thereﬁnement of by its longest edge divides theelement into two nested subelements andcalled the children of.These children are inturn reﬁned by their longest edge if one of their edges is non-conforming.The reﬁnement proce-dure creates a forest of trees of nested elements where the root of each tree is an element in theinitial mesh and the leaves are unreﬁned ele-ments.For every element,let be the reﬁnement tree of nested elements rooted atwhen the reﬁnement procedure terminates. Using the GLB procedure elements can be se-lected for reﬁnement in different orders,creating possible different reﬁnement histories.To show that this cannot happen we assume the converse, namely,that two reﬁnement histories and generate different reﬁned meshes,and establish a contradiction.Thus,assume that there is an ele-ment such that the reﬁnement trees and,associated with the reﬁnement histories and of respectively,are different.Be-cause the root of and is the same in both reﬁnement histories,there is a place where both treesﬁrst differ.That is,starting at the root,there is an element that is common to both trees but for some reason,its children are different.Be-cause is always bisected by the longest edge, the children of are different only when is reﬁned in one reﬁnement history and it is not re-ﬁned in the other.In other words,in only one of the histories does have children.Because is reﬁned in only one reﬁnement his-tory,then,the initial set of elements to reﬁne.This implies that must have been reﬁned because one of its edges became non-conforming during one of the reﬁnement histo-ries.Let be the set of elements that are present in both reﬁnement histories,but are re-ﬁned in and not in.We deﬁne in a similar way.For each reﬁnement history,every time an ele-ment is reﬁned,it is assigned an increasing num-ber.Select an element from either or that has the lowest number.Assume that we choose from so that is reﬁned in but not in.In,is reﬁned because a neigh-boring element created a non-conforming ver-tex at the midpoint of their shared edge.There-fore is reﬁned in but not in because otherwise it would cause to be reﬁned in both sequences.This implies that is also in and has a lower reﬁnement number than con-。

THE QUALITY OF MESHES AND FEM COMPUTATIONS

3.1 Apriori error estimation Let us consider u 2 C 1 , for exam-
else
P2
h
2 2
h
P3x
1 ?
end if until finish.
Refine the mesh on information from the error estimator.
We can transform sparse matrix to band one nding suitable node numbering. However, minimization of the bandwidth r for general mesh is NP-complete problem. But for the structured meshes (i.e. meshes which are equivalent to index grids) the minimization of bandwidth is trivial Fied81]. The next bene t of the band matrix with minimal bandwidth is low memory demand. So, even if we use the iterative solvers, in the case of the large tasks the structured meshes are more suitable than general ones. Hence, it is shown in Kol94], Kol99], that the restrictions due to structured meshes concerning to the ability of the structured mesh to t the prescribed geometry, are not so severe as one can require.

基于半导体可饱和吸收镜的可调谐光纤激光器

Ｋｅｙｗｏｒｄｓ：ｏｐｔｉｃａｌｆｉｂｅｒｏｐｔｉｃｓ；ｔｕｎａｂｌｅ；ｓｅｍｉｃｏｎｄｕｃｔｏｒｓａｔｕｒａｂｌｅａｂｓｏｒｂｅｒｍｉｒｒｏｒ；ｐａｓｓｉｖｅｍｏｄｅｌｏｃｋｉｎｇ；ｙｔｔｅｒｂｉｕｍｄｏｐｅｄｆｉｂｅｒ
引言
波长可调谐锁模脉冲光纤激光器因其脉冲宽度窄、峰值功率高、频谱范围宽、简洁紧凑、高效散热等优点，在激光光谱学、光学测量、生物医学、电信等领域［１３］有着广泛的应用。近年来，由于光参量振荡器和光参量放大器等领域的快速发展，可调谐超短脉冲激光器也可作为小型、经济有效的种子源用于产生大能
关键词：光纤光学；可调谐；半导体可饱和吸收镜；被动锁模；掺镱光纤中图分类号：ＴＮ２４８．４文献标志码：Ａｄｏｉ：１０７５１０／ｊｇｊｓｉｓｓｎ１００１３８０６２０１９０５０１６
Ｔｕｎａｂｌｅｆｉｂｅｒｌａｓｅｒｓｂａｓｅｄｏｎｓｅｍｉｃｏｎｄｕｃｔｏｒｓａｔｕｒａｂｌｅａｂｓｏｒｂｅｒｍｉｒｒｏｒｓ
第４３卷第５期
王婉琳基于半导体可饱和吸收镜的可调谐光纤激光器
６７３
本文中搭建了基于半导体可饱和吸收镜（ｓｅｍｉｃｏｎｄｕｃｔｏｒｓａｔｕｒａｂｌｅａｂｓｏｒｂｅｒｍｉｒｒｏｒ，ＳＥＳＡＭ）的可调谐被动锁模掺镱光纤激光器，腔内无波长可调谐器件及偏振控制器，这在一定程度上节约了成本。通过改变光纤跳线端面至ＳＥＳＡＭ的距离，实现了输出波长的稳定可调谐（１０２９．５ｎｍ～１０４２．７ｎｍ），调谐范围１３．２ｎｍ，锁模脉冲基频１８．０ＭＨｚ，脉宽１３０ｐｓ，信噪比４４ｄＢ。
ＷＡＮＧＷａｎｌｉｎ，ＷＡＮＧＪｉ，ＸＵＬｉａｎｗｅｉ，ＺＨＡＮＧＪｉａｒｕｉ
（ＳｃｈｏｏｌｏｆＳｃｉｅｎｃｅ，ＣｈａｎｇｃｈｕｎＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙ，Ｃｈａｎｇｃｈｕｔｏｒｅａｌｉｚｅｗａｖｅｌｅｎｇｔｈｔｕｎａｂｉｌｉｔｙｏｆｍｏｄｅｌｏｃｋｅｄｆｉｂｅｒｌａｓｅｒ，ａｐａｓｓｉｖｅｌｙｍｏｄｅｌｏｃｋｅｄｙｔｔｅｒｂｉｕｍｄｏｐｅｄｆｉｂｅｒｌａｓｅｒｗｉｔｈｒｉｎｇｃａｖｉｔｙｗａｓｃｏｎｓｔｒｕｃｔｅｄｗｉｔｈａｓｅｍｉｃｏｎｄｕｃｔｏｒｓａｔｕｒａｂｌｅａｂｓｏｒｂｅｒｍｉｒｒｏｒ（ＳＥＳＡＭ）．Ｗｉｔｈｏｕｔａｎｙｐｏｌａｒｉｚａｔｉｏｎｃｏｎｔｒｏｌｌｅｒｓａｎｄｔｕｎａｂｌｅｆｉｌｔｅｒｓｉｎｔｈｅｃａｖｉｔｙ，ｂｙｃｈａｎｇｉｎｇｔｈｅｄｉｓｔａｎｃｅｂｅｔｗｅｅｎｔｈｅｅｎｄｆａｃｅｏｆｔｈｅｏｐｔｉｃａｌｆｉｂｅｒｊｕｍｐｅｒａｎｄｔｈｅＳＥＳＡＭ，ｔｈｅｓｔａｂｌｅｔｕｎａｂｉｌｉｔｙｏｆｔｈｅｓｐｅｃｔｒｕｍｗａｓａｃｈｉｅｖｅｄｂｅｔｗｅｅｎ１０２９．５ｎｍａｎｄ１０４２．７ｎｍ．Ｔｈｅｆｕｎｄａｍｅｎｔａｌｆｒｅｑｕｅｎｃｙｒｅｐｅｔｉｔｉｏｎｒａｔｅｗａｓ１８．０ＭＨｚ，ｔｈｅｐｕｌｓｅｗｉｄｔｈｗａｓ１３０ｐｓ，ａｎｄｔｈｅｓｉｇｎａｌｔｏｎｏｉｓｅｒａｔｉｏｏｆｍｏｄｅｌｏｃｋｅｄｐｕｌｓｅｗａｓ４４ｄＢ．Ｔｈｅｒｅｓｕｌｔｓｓｈｏｗｔｈａｔ，ｔｈｅｍｏｄｅｌｏｃｋｅｄｆｉｂｅｒｌａｓｅｒｈａｓａｈｉｇｈｓｉｇｎａｌｔｏｎｏｉｓｅｒａｔｉｏａｎｄａｗｉｄｅｔｕｎａｂｌｅｒａｎｇｅ．Ｔｈｉｓｓｔｕｄｙｐｒｏｖｉｄｅｓａｎｉｍｐｏｒｔａｎｔｒｅｆｅｒｅｎｃｅｆｏｒｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｔｕｎａｂｌｅｐａｓｓｉｖｅｌｙｍｏｄｅｌｏｃｋｅｄｆｉｂｅｒｌａｓｅｒｓ．

Abaqus-ALE设置参数详解

三种自适应技术1．ALE adaptive meshing——控制单元网格的变形，适用于ABAQUS/Explicit及ABAQUS/Standard分析2．Adaptive remeshing——控制计算精度，仅适用于ABAQUS/Standard分析3．Mesh-to-mesh solution mapping ——控制单元网格变形，仅适用于ABAQUS/Standard的大变形问题拉格朗日方法：拉格朗日方法是比较经典的一种分析方法，他是采用的是拉格朗日坐标来描述的，反映了物体质点与它每瞬间所处的位置关系，不同的坐标代表不同的质点，也称为物质坐标，在有限元方法里面来说的话，也就是材料与网格结合在一起，网格代表坐标，材料也就是无数个质点，二者在整个分析过程中是联系在一起的。

欧拉方法：在传统的拉个朗日方法中，网格与材料是绑定的，也就是材料流动，网格也会随之变形，拉格朗日网格始终是被一种材料填满的，所以材料边界与网格边界是一样的。

相反，欧拉方法则不同，欧拉方法则是用欧拉坐标（也叫空间坐标）描述的。

欧拉坐标只识别空间，所以也叫空间坐标，每一个坐标代表一个空间点，同一个空间点，在不同的时刻可以由不同的物质点占据。

在有限元方法中来说的话，也就是欧拉网格与材料完全脱离，欧拉网格允许，网格不被材料100%充满（许多网格是部分充满或者说是有空隙的），这样的话，这使得需要在每一步增量对材料边界进行计算。

如果在欧拉方法分析过程中，某些材料流出了欧拉网格，那么这些材料就流失了，欧拉方法对其就不会起作用了。

ALE网格自适应方法结合了单纯的拉格朗日方法与欧拉方法的分析特征，通常被称为任意拉格朗日-欧拉方法。

- ]$ A& y1 x2 VALE网格自适应方法结合了上述两种算法特征，主要是用来使网格在整个分析过程中保持一种比较良好的状态，不出现巨大的扭曲与变形（通常情况下网格与材料是联系在一起的，当发生大变形的时候，材料流动显著，这就会导致某些网格节点在材料流动的带动下发生很大位移，造成网格畸变与扭曲，主要是在大变形或者材料破坏流失的情况下作用明显）。

超宽带三维频率选择表面

第52卷第11期2023年11月人㊀工㊀晶㊀体㊀学㊀报JOURNAL OF SYNTHETIC CRYSTALS Vol.52㊀No.11November,2023超宽带三维频率选择表面陈昭冉,姚夏元(华北电力大学电气与电子工程学院,北京㊀102206)摘要:相较于传统的二维频率选择表面,三维频率选择表面能产生更多谐振点而提供更大带宽,更容易达到小型化的要求,能够提供更稳定的频率响应,因而成为研究热点㊂本文提出了一种多级正交菱形结构的新型三维频率选择表面,其基本单元结构是正交的菱形金属丝,在其外部注入介电常数为2.2的聚合物作为支撑㊂入射角在0ʎ~50ʎ的条件下具备9.2GHz 共同带宽,相对带宽超过50%,TE 和TM 极化的最大插入损耗皆不超过1dB㊂该结构具备三个谐振点,形成原因分别为正交菱形金属结构的谐振㊁结构和介质端面相互耦合产生的谐振,以及介质端面的一阶法布里-珀罗谐振㊂通过调节介质的介电常数,可利用更高阶的法布里-珀罗谐振进一步设计出通宽更宽的空间滤波器㊂考虑到工程应用,文中也评估了此设计对天线远场方向图的影响㊂关键词:三维频率选择表面;超宽带;角度稳定;低损耗;法布里-珀罗谐振;空间滤波器中图分类号:TN802;TN713㊀㊀文献标志码:A ㊀㊀文章编号:1000-985X (2023)11-1971-09Ultra-Wideband Three-Dimensional Frequency Selective SurfaceCHEN Zhaoran ,YAO Xiayuan(School of Electrical and Electronic Engineering,North China Electric Power University,Beijing 102206,China)Abstract :Compared to traditional two-dimensional frequency selective surfaces,three-dimensional frequency selective surface has become a hot research direction due to its ability to generate more resonance points,provide larger bandwidth,efficiently meet miniaturization requirement,and bring more stable frequency response.A novel three-dimensional frequency selective surface with a multi-level orthogonal diamond structure is proposed in this paper.Its basic unit structure is an orthogonal diamond-shaped metal wire,and a polymer with dielectric constant of 2.2is injected externally as support structure.The common bandwidth of this frequency selective surface exceeds 9.2GHz with a relative bandwidth exceeding 50%,and the average insertion loss of TE and TM polarization does not exceed 1dB when the incident angle in the range of 0ʎto 50ʎ.This three-dimensional frequency selective surface has three resonance points.Their formation reasons are the resonance of the orthogonal diamond metal structure,the resonance generated by the coupling between the structure and the dielectric end face,and the first-order Fabry Perot resonance of the dielectric end face.If the dielectric constant of the filling medium is adjusted,higher order of Fabry Perot resonance can be utilized,and a spatial filter with broader bandwidth requirement can be designed.At the same time,the impact of this three-dimensional frequency selective surface on the far-field pattern of the antenna is also evaluated.Key words :three-dimensional frequency selective surface;ultra-wideband;angular stability;low loss;Fabry Perot resonance;spatial filter㊀㊀收稿日期:2023-06-13㊀㊀作者简介:陈昭冉(1999 ),女,江苏省人,硕士研究生㊂E-mail:czr_ncepu@ ㊀㊀通信作者:姚夏元,博士,讲师㊂E-mail:xiayuanyao@0㊀引㊀㊀言频率选择表面(frequency selective surface,FSS)是一种空间滤波器,主要分为贴片型和开槽型两种㊂贴片型是金属贴片阵列,而开槽型是与之巴比涅(Babinet)互易的结构㊂通常而言,贴片型呈现带阻特性,而开槽型呈现带通特性[1]㊂早期的研究中,学者探讨了不同单元结构对频率响应的影响,例如偶极子[2]㊁正方1972㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第52卷形[3]㊁圆形[4]㊁ Y 型[5]等单元结构,但因存在周期谐振所激发的布洛赫波,并不能保证很好的角度稳定性㊂2008年之后,为了改善这一缺点,Sarabandi等[6]首次提出了小型化频率选择表面(miniaturized element frequency selective surface,MEFSS)的概念,这为实现大角度入射的稳定性提供了理论基础㊂其中,复杂折线是实现小型化常见的方式,Chiu等[7]和Yang等[8]都使用此方式来设计㊂具备角度稳定性的重要因素是仅由结构谐振进行滤波,但缺点也很显而易见单一谐振点的通带较窄㊂随后,Yan等[9]和Sheng等[10]提出了紧凑的锚形结构,实现了双通窄带稳定的带通响应,同时印证了MEFSS的滤波特点㊂因此,如何设计同时具备角度稳定性和宽通带的FSS是相关研究人员需要解决的技术难题㊂2012年, Lu等[11]提出了一个三维频率选择表面(three-dimensional frequency selective surface,3DFSS)模型,该模型是对三维概念的一次重要尝试,通过不断增大类方形波导结构的级联层数,构造更多谐振点,以追求宽带响应㊂但遗憾的是,其角度稳定性并不可观㊂Zhu等[12]在方形同轴波导上贴上了金属贴片,代替多层结构方式,但带宽仍不够宽㊂随后,Liang等[13]利用切比雪夫变换器的设计原理,以牺牲通带内一定程度的纹波为代价,得到最优带宽,虽然在X波段获得了3.3GHz的稳定带宽,但通带内纹波太大㊂Li等[14]从电路层面进行理论推导切比雪夫滤波器,明确指出使用此方法设计3DFSS的带宽与谐振阶数相关联㊂为了增大谐振阶数, Ma等[15]试图将不同维度的FSS相结合,但由于电路复杂,影响谐振效果的因素众多,仅能保证0ʎ~40ʎ的角度稳定性㊂近年来,学者们开始利用复杂的算法进行3DFSS的设计[16]㊂但要设计出满足双极化滤波㊁0ʎ~ 60ʎ角度稳定性和超大带宽要求的FSS,还需学者们的不断尝试与探讨㊂传统FSS的角度稳定性差有两个主要原因:1)当入射波在大角度入射的时候,FSS的等效介质阻抗和自由空间波阻抗存在较大的差异,等效介质阻抗的变化直接影响了FSS的频率响应;2)传统FSS中的周期谐振对入射角非常敏感㊂虽然MEFSS通过缩小周期,使周期谐振所形成的通带不会直接影响到目标通带,具备角度稳定性,但窄带响应严重限制了其在宽带系统中的应用㊂3DFSS的角度稳定性介于两者之间,虽然谐振点和带宽会在一定程度上受到入射角的影响,但是通过合理的阻抗匹配调节,能尽可能同时具备较好性能㊂本文提出了一种正交菱形结构的新型3DFSS,金属正交菱形结构嵌入聚合物中,周期排布形成金属网㊂通过阻抗匹配调节使此结构具备超大带宽和入射角稳定性㊂考虑到实际使用,本文还讨论了其对天线的远场方向图的影响㊂1㊀模型与计算方法设计思路具体如下:首先,确定整个晶胞的结构尺寸,尽可能规避周期谐振对目标通带造成的不稳定性,晶胞尺寸建议达到小型化的要求;其次,设计简单对称的晶胞,以满足双极化的滤波要求;最后,使用多维度构造多个谐振点,适当调整结构各参数,进行阻抗匹配分析,使其具备角度稳定性㊂此3DFSS的单元结构如图1所示㊂在金属结构外注入介电常数为2.2并提供支撑作用的聚合物作为一个基础单元晶胞,且分别关于xoy面㊁xoz面㊁yoz面对称㊂该晶胞的长㊁宽㊁高为2.64mmˑ2.64mmˑ7mm (0.158λ0ˑ0.158λ0ˑ0.42λ0),λ0为自由空间下的波长㊂为了满足双极化的滤波需求,金属菱形采用正交的排布方式,具体地说,菱形金属丝两端相接,形成90ʎ的夹角㊂图2为结构的三视图,插在结构中的平面为引导视觉的投影面㊂图1㊀3DFSS的单元结构Fig.1㊀Structure of the3DFSS㊀第11期陈昭冉等:超宽带三维频率选择表面1973㊀图2㊀3DFSS单元结构三视图Fig.2㊀Three views of the3DFSS为提供更好的角度稳定性,考虑介质阻抗与自由波阻抗之间的匹配问题,本设计采用了三角形渐变模型,主要的优点是容易匹配㊂此外,FSS为周期结构,为保证形成完整金属网,由三角形拼接成菱形结构㊂该结构单个菱形的参数于图3中标记,并在表1中列出了其参数值㊂图3㊀3DFSS单元结构尺寸标注图Fig.3㊀Dimension of the3DFSS表1㊀3DFSS结构参数Table1㊀Parameters of the3DFSSParameter Value/mmLength of long axis,a 6.75Length of short axis,b 2.42Width of metal strip,w0.17Length of vertical intercept,m0.11Length of horizontal intercept,n0.125Thickness of the metal,d0.01同时,金属菱形网形成的波导阵列为3DFSS提供了截止特性㊂从常见方波导演化到3DFSS波导阵列的过程如图4所示㊂具体地说,图4(a)为常见的完整方波导阵列,其尺寸和单元晶胞一致㊂在其侧壁上开孔(此处使用椭圆形孔代替菱形),得到图4(b)㊂随后,在棱边交点处挖孔,所剩下的金属条带是可以与菱形金属阵列类似等效的波导阵列㊂这种金属波导阵列的很多性质将继承原始方波导阵列的性质,例如截止特性㊂由于侧壁开孔,3DFSS的截止频率与完整方波导也有所不同㊂图4(c)中波导的截止频率没有解析解,只有数值解,使用仿真软件CST求解麦克斯韦方程组进行计算㊂图4㊀金属结构波导阵列Fig.4㊀Waveguide array of metal structure1974㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第52卷在设计完成后,使用基于有限积分法进行电磁计算的仿真软件CST,计算3DFSS的频率响应㊂在设计向导中提前配置好基本仿真条件并设置该空间下的单位与背景材料㊂随后,在CST环境中进行建模㊂在CST 中建立的单元模型如图5(a)所示㊂设置求解频率范围后,设置周期边界条件为吸收边界条件open(addspace),设置后的状态如图5(b)所示㊂本仿真使用频域求解器,在求解器中设置Mesh划分方式,调整激励方向和模式等㊂最后计算出相应频率范围的S参数和任意点或面的场分布㊂图5㊀CST仿真的关键步骤Fig.5㊀Key steps of CST simulation2㊀结果与讨论2.1㊀正入射下频率响应如图6(a)所示,正入射平面波的方向为-z方向㊂图6(b)为全波仿真频率响应结果,此结构在正入射时的谐振频率分别为f1=14.63GHz㊁f2=18.2GHz与f3=21.04GHz,截止频率f c=3.6GHz(按照透射曲线-20dB为标准)㊂正入射时插入损耗1dB下的带宽为13.6GHz,约为2.2倍频程,相对带宽为75%,如图6(c)所示㊂由于结构具备对称性,正入射下TE极化和TM极化的频率响应一致㊂图6㊀正入射的传递函数Fig.6㊀Transmission function at normal incidence如图7所示,通过仿真该结构的电场分布,可知各谐振点的形成原因㊂谐振频率f1是由菱形结构的周长决定㊂其周长为14.39mm,与该电介质中的波长相近㊂谐振频率f2受晶胞长度㊁宽度和高度尺寸的影响,这表明此点为晶胞的共振,即结构和介质端面相互耦合产生的谐振㊂谐振频率f3为介质端面的一阶法布里-珀罗谐振㊂单元晶胞中光程长度为7mm,利用公式(1)可验证第三谐振频率为一阶法布里-珀罗谐振频率㊂f=(m+12)c2nd(1)式中:f为法布里-珀罗谐振频率,c为光速,m为法布里-珀罗谐振阶数,d为FSS中计算光程的长度,n为材料的折射率㊂㊀第11期陈昭冉等:超宽带三维频率选择表面1975㊀图7㊀各谐振点的电场分布Fig.7㊀Electric field distribution of each resonance point2.2㊀斜入射下频率响应为了验证该3DFSS在入射角不断增大的情况下仍能提供较宽通带,在进行大量细致的仿真后,考虑到文章篇幅,分别选取了小角度范围(入射角0ʎ~45ʎ)中的30ʎ入射,大角度范围(>45ʎ)中的50ʎ入射和60ʎ入射的频率响应进行讨论分析㊂图8给出了30ʎ入射时的频率响应㊂随着角度增大,相较于正入射情况(见图6(b)),TE极化第一谐振点的位置基本不变,第二㊁三谐振点逐渐向高频移动,纹波逐渐增大㊂TM极化的谐振点逐渐变少,三个谐振点位置接近,故表现为好像只有一个谐振点,产生了谐振融合现象㊂由图8(b)可清晰看出,按插入损耗1dB 评估的带宽范围为12~24.5GHz,宽度为12.5GHz㊂图8㊀30ʎ入射的传递函数Fig.8㊀Transmission function at30ʎincident angle如图9所示,当入射角度进一步增大至50ʎ时,此时仍能保证插入损耗小于1dB的9.2GHz带宽㊂图9㊀50ʎ入射的传递函数Fig.9㊀Transmission function at50ʎincident angle1976㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第52卷在60ʎ入射时,3DFSS仅能提供6GHz的双极化共同带宽,如图10所示㊂这是由于随着角度逐步增大,匹配性能进一步恶化㊂图10㊀60ʎ入射的传递函数Fig.10㊀Transmission function at60ʎincident angle当电磁波以一定角度照射在结构上时,无论是以何种角度㊁何种极化方式照射,正交菱形的金属结构的周长不变,产生谐振的区域不变,故第一谐振点基本稳定㊂而第二谐振点在斜入射的情况下,TE极化斜入射等效介质阻抗为公式(2),TM极化的介质阻抗为公式(3),其中,Z0为自由空间波阻抗,θ为入射角度㊂Z TE_FSS=Z0/cosθ(2)Z TM_FSS=Z0㊃cosθ(3)与此同时,FSS的阻抗还可以表示为公式(4),其中ε等效介电常数,μ等效磁导率,n等效折射率㊂Z FSS=με=μ1n(4)由式(2)可知,TE极化FSS阻抗随着入射角变大而变大,入射角的改变不会改变整体的磁链,因此,式(4)中μ是固定的,故等效折射率n TE变小㊂同理可得,TM极化的等效折射率n TM变大㊂对应到介质波长的角度,即TE波变长,TM波变短㊂真实介质的厚度并没有改变㊂因此,TE极化需要更高频率的波才能实现匹配,而TM极化需要更低频率的波㊂这就是TE极化谐振点向高频移动,而TM极化的谐振点向低频移动的原因㊂第三个谐振点的分析过程与以上完全一致,从等效折射率的角度能够得出一致结论㊂0ʎ~50ʎ共同带宽范围13.6~22.8GHz,达到1.68倍频程㊂评估在不同角度入射的情况下,此范围内的最大插入损耗情况,如表2所示㊂表2㊀不同极化最大损耗情况(13.6~22.8GHz)Table2㊀Maximum losses of different polarizations(13.6~22.8GHz)Incident angle/(ʎ)TE polarization/dB TM polarization/dB Average of maximum value/dB 0-0.07-0.07-0.0710-0.05-0.08-0.0720-0.04-0.12-0.0830-0.05-0.23-0.1440-0.07-0.47-0.2750-0.17-0.99-0.5860-0.49-2.09-1.29由上表可以得出结论:在斜入射角度不断增大的过程中,此3DFSS能够持续稳定地提供某一固定范围的带宽,并保证带内较低的插入损耗,故该设计具备良好的角度稳定性㊂2.3㊀与先前设计的对比评价FSS的常见性能参数有单元尺寸大小及厚度㊁相对带宽㊁通带内损耗和能够满足S11<10dB稳定㊀第11期陈昭冉等:超宽带三维频率选择表面1977㊀的入射角度㊂其中,相对带宽定义为公式(5),与先前设计的FSS性能对比如表3,可见此3DFSS的性能具备一定的优越性㊂R b=b w fc (5)式中:R b指相对带宽,b w为带宽,f c为中心频率㊂表3㊀与先前具备宽带响应的FSS的一些对比Table3㊀Some comparisons with previous FSS with wideband responseReference2D/3D(unit cell)Unit cell size and FSS thickness Band ratio/%Insert lossin band/dB Angular stability/(ʎ) (S11<10dB)[17]2D(quintuple layers)(0.27λ0)2ˑ0.29λ025145[18]2D(double layers)(0.18λ0)2ˑ0.14λ045345[19]3D(0.05λ0ˑ0.04λ0)ˑ0.084λ038130 [13]3D(0.3λ0)2ˑ2λ024540 This paper3D(0.158λ0)2ˑ0.42λ050.51502.4㊀评估对波束的影响为评估对天线性能的影响,将3DFSS安装在天线前,天线的轴线垂直于FSS,如图11(a)所示㊂FSS阵列的数量为70ˑ70,排布的阵列尺寸约为184.8mmˑ184.8mmˑ490mm,将天线的波束完全覆盖㊂针对通信系统常用频率,以18GHz为例进行仿真,结果如图11(b)所示㊂横坐标为天线俯仰角,范围在-60ʎ至+60ʎ变化,纵坐标为天线的增益㊂Legend描绘了4条曲线,分别为:在天线上不放置3DFSS时,随着俯仰角度变化,E面增益的变化曲线;在天线上放置3DFSS时,随着俯仰角度变化,E面增益的变化曲线;在天线上不放置3DFSS时,随着俯仰角度变化,H面增益的变化曲线;在天线上放置3DFSS时,随着俯仰角度变化,H面增益的变化曲线㊂因为天线本身方向图是对称的,因此-60ʎ~0ʎ表示的是H面的天线方向图,0ʎ~60ʎ表示的E面的天线方向图㊂图中的曲线基本完全重合,说明考虑到FSS常见的应用环境,本文提出的3DFSS放置在天线上,并不会引起天线基本特性的改变(并未造成天线增益的衰落)㊂放大此图,可观察到在俯仰角达到-60ʎ与+60ʎ时,存在极其细微的差异㊂图11㊀3DFSS天线模型及其对远场模式的影响Fig.11㊀3DFSS antenna model and its impact on the far-field pattern2.5㊀设计总结分析本文的设计思路是具备滤波特性㊁宽带和角度稳定性的关键,主要涉及了波导㊁阻抗匹配与小反射理论的相关知识㊂以下讨论均为3DFSS在电磁波正入射下的情况㊂首先,晶胞中相互连接的金属结构可看作是联通的金属网,以2ˑ2晶胞为例,如图12(a)所示,金属网支撑表面电流的连续传播㊂同时,金属网是一种非常规波导,如图12(b)所示,因此整个晶胞中波导的导行波能够被激励㊂整个结构具备了波导的高通属性,其频率响应对低频信号是截止的㊂1978㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第52卷其次,此3DFSS 的宽带响应可从阻抗匹配的角度进行分析㊂通过图1结构图可看到,金属丝两端相接,菱形的中部距离较大,故等效电容两端较大,中心较小㊂金属丝的厚度和宽度为固定值,因此等效电感变化并不明显㊂综上所述,从等效阻抗的角度来看,此结构为一个阻抗渐变的晶胞㊂两边阻抗小,中心阻抗大,而且阻抗的变化是对称的,这是常用对称渐变匹配结构三角形渐变匹配㊂这种结构在理论上验证了具备超大带宽[20]㊂阻抗随位置的渐变方式不同,将影响带宽与纹波的大小㊂影响反射系数的具体关系式如公式(6)所示㊂从图13可知,阻抗随位置的变化影响反射系数的幅值与频率位置㊂Γ(θ)=12e -2jβL ln Z L Z 0()sin(βL /2)βL /2[]2㊀(θ=2βL )(6)式中:Γ为反射系数,θ为电尺寸,β为波数,L 为传输线长度,Z 0为自由空间波阻抗,Z L 为传输线阻抗,即等效介质阻抗㊂图12㊀金属网与波导结构Fig.12㊀Metal net and waveguide图13㊀三角形渐变匹配节[20]Fig.13㊀Triangle gradient transmission line [20]㊀㊀最后进一步讨论晶胞的结构和入射角稳定性的关系㊂入射角稳定性是针对某一特定频率而言的,不同角度的入射角在晶胞照射面上的切分量大小不同㊂所设计的金属结构如果从菱形结构的内部向外看,金属结构构成了微波中的双边鳍线㊂如果一束波能够在双边鳍线中传播,就要求入射波的电场切分量处于双边鳍线的通带中㊂这是一个渐变的双边鳍线,因此在给定频率时,与同尺寸的一般波导或者微带线相比,能够匹配的切分量范围更大,能保持稳定性能的入射角度范围也越大㊂3㊀结㊀㊀论通过使用周期边界条件仿真3DFSS 的频率响应,并使用全波仿真技术讨论完整3DFSS 对天线的影响,得出以下结论:1)从频率响应角度而言,此3DFSS 在提供较宽通带的同时,保证其性能具备角度稳定性㊂正入射时能够提供13.6GHz 带宽,相对带宽为75%,跨度为2.2倍频程㊂入射角在0ʎ~50ʎ时,TE 和TM 极化的最大插入损耗皆不超过1dB,且能够提供9.2GHz 带宽,为1.68倍频程㊂2)从整体仿真角度而言,将完㊀第11期陈昭冉等:超宽带三维频率选择表面1979㊀整的3DFSS放置在天线前,对天线的方向图不会产生明显的影响,仅在60ʎ附近的旁瓣产生轻微影响㊂最后,本设计不足之处为频率响应中的过渡带不够陡峭㊂由于产生截止频率的波导为开孔波导,同时金属条是斜置的,电流本身具备了轴向Z方向的分量,将切面场引入波导中,就会使过渡带不陡峭㊂可能的改进措施有两种:一是将金属条变粗,缩小菱形的尺寸;二是将结构级联,从电路层面来说,级联电路可能对此有所改善,但此方法很可能会引起频率响应的不确定性㊂参考文献[1]㊀MUNK B.Frequency selective surfaces:theory and design[M].New York:John Wiley,2000.[2]㊀PARKER E A,VARDAXOGLOU J C.Plane-wave illumination of concentric-ring frequency-selective surfaces[J].IEE Proceedings HMicrowaves,Antennas and Propagation,1985,132(3):176.[3]㊀VARDAXOGLOU J C,STYLIANOU A.Modal analysis of double-square frequency selective surfaces[C].IEEE International Conference inElectromagnetics on Aerospace Applications.Torino,Italy.1989:355-358.[4]㊀CWIK T,MITTRA R.Scattering from a periodic array of free-standing arbitrarily shaped perfectly conducting or resistive patches[J].IEEETransactions on Antennas and Propagation,1987,35(11):1226-1234.[5]㊀PELTON E,MUNK B.A streamlined metallic radome[J].IEEE Transactions on Antennas and Propagation,1974,22(6):799-803.[6]㊀SARABANDI K,BEHDAD N.A frequency selective surface with miniaturized elements[J].IEEE Transactions on Antennas and Propagation,2007,55(5):1239-1245.[7]㊀CHIU C N,CHANG K P.A novel miniaturized-element frequency selective surface having a stable resonance[J].IEEE Antennas and WirelessPropagation Letters,2009,8:1175-1177.[8]㊀YANG G H,ZHANG T,LI W L,et al.A novel stable miniaturized frequency selective surface[J].IEEE Antennas and Wireless PropagationLetters,2010,9:1018-1021.[9]㊀YAN M B,QU S B,WANG J F,et al.A miniaturized dual-band FSS with stable resonance frequencies of2.4GHz/5GHz for WLANapplications[J].IEEE Antennas and Wireless Propagation Letters,2014,13:895-898.[10]㊀SHENG X J,FAN J J,LIU N,et al.A miniaturized dual-band FSS with controllable frequency resonances[J].IEEE Microwave and WirelessComponents Letters,2017,27(10):915-917.[11]㊀LU Z H,LIU P G,HUANG X J.A novel three-dimensional frequency selective structure[J].IEEE Antennas and Wireless Propagation Letters,2012,11:588-591.[12]㊀ZHU J P,HAO Z Y,WANG C,et al.Dual-band3-D frequency selective surface with multiple transmission zeros[J].IEEE Antennas andWireless Propagation Letters,2019,18(4):596-600.[13]㊀LIANG B Y,BAI M.Subwavelength three-dimensional frequency selective surface based on surface wave tunneling[J].Optics Express,2016,24(13):14697.[14]㊀LI H X,LI B,ZHU L.A generalized synthesis technique for high-order and wideband3-D frequency-selective structures with Chebyshevfunctions[J].IEEE Transactions on Antennas and Propagation,2021,69(7):3936-3944.[15]㊀MA Y H,ZHANG X M,WU S,et al.A hybrid2-D-3-D miniaturized multiorder wide bandpass FSS[J].IEEE Antennas and WirelessPropagation Letters,2022,21(2):307-311.[16]㊀BARTON J H,GARCIA C R,BERRY E A,et al.3-D printed all-dielectric frequency selective surface with large bandwidth and field of view[J].IEEE Transactions on Antennas and Propagation,2015,63(3):1032-1039.[17]㊀LI Y J,LI L,ZHANG Y L,et al.Design and synthesis of multilayer frequency selective surface based on antenna-filter-antenna using minkowskifractal structures[J].IEEE Transactions on Antennas and Propagation,2015,63(1):133-141.[18]㊀EBRAHIMI A,NIRANTAR S,WITHAYACHUMNANKUL W,et al.Second-order terahertz bandpass frequency selective surface withminiaturized elements[J].IEEE Transactions on Terahertz Science and Technology,2015,5(5):761-769.[19]㊀OMAR A A,SHEN Z X.Thin3-D bandpass frequency-selective structure based on folded substrate for conformal radome applications[J].IEEETransactions on Antennas and Propagation,2019,67(1):282-290.[20]㊀POZAR D M.Microwave engineering[M].3rd ed.Hoboken,NJ:J.Wiley,2005.。

原位限域生长实现高效稳定的2d-3d梯度体异质结锡铅钙钛矿太阳能电池

原位限域生长实现高效稳定的2d-3d梯度体异质结锡铅钙钛矿
太阳能电池
原位限域生长是一种有效实现高效稳定的2D-3D梯度体异质
结锡铅钙钛矿太阳能电池的方法。

锡铅钙钛矿是一种新型的太阳能电池材料，具有高光电转换效率和较长的光电转换寿命。

该方法的关键是使用原位限域生长技术来控制锡铅钙钛矿的生长过程。

原位限域生长是指在同一反应体系中，通过控制材料的生长条件和反应动力学，使得材料在垂直方向上形成一定结构的分布。

在锡铅钙钛矿太阳能电池中，可以通过在特定的生长条件下控制锡铅钙钛矿晶格的生长，形成2D-3D梯度结构。

在2D-3D梯度结构中，锡铅钙钛矿的2D层与3D结构有机地
相互结合。

2D层可以提供高效的光吸收和电荷分离，而3D
结构可以提供稳定的电荷传输和光电转换效率。

这种异质结构的形成可以显著提高太阳能电池的性能。

此外，原位限域生长还可以使锡铅钙钛矿材料形成高质量的晶体结构，减少缺陷和杂质的产生，提高材料的稳定性和光电转换效率。

通过控制生长条件和反应动力学，可以实现锡铅钙钛矿的定向生长和优化晶体结构，进一步提高太阳能电池的性能。

综上所述，原位限域生长是一种高效稳定的2D-3D梯度体异
质结锡铅钙钛矿太阳能电池的实现方法。

通过控制生长条件和反应动力学，可以形成2D-3D梯度结构和高质量晶体结构，
提高太阳能电池的性能和稳定性。

COMSOL后处理与可视化综述

COMSOL后处理与可视化综述COMSOL⼿册丛书截点与计算COMSOL Multiphysics?后处理与可视化综述COMSOL Multiphysics 后处理与可视化综述COMSOL 、COMSOL Multiphysics 、Capture theConcept 、COMSOL Desktop 、LiveLink ，和 COMSOL Server 是 COMSOL AB 的注册商标或商标。

所有其他商标均属其各⾃所有者所有，并且 COMSOL 及其⼦公司和产品并不从属于这些商标的所有者，或受其认可，或接受其赞助，或受其⽀持。

? 2014年11⽉联系信息请点击 /doc/d6eff3fdb7360b4c2e3f64f9.html /contact 访问联系 COMSOL 页⾯。

在此页⾯，您可以进⾏⼀般咨询、联系技术⽀持、或查询我们的联系地址与电话。

您同时还可以点击/doc/d6eff3fdb7360b4c2e3f64f9.html /contact/offices 访问全球销售办公室页⾯，查询联系地址和信息。

如果您需要联系技术⽀持，可以点击/doc/d6eff3fdb7360b4c2e3f64f9.html /support/case 访问 COMSOL Access 页⾯在线填写申请表/doc/d6eff3fdb7360b4c2e3f64f9.html /support/case.ii更多资源更多有关 COMSOL 后处理的⽂字说明和教程参见：视频/doc/d6eff3fdb7360b4c2e3f64f9.html /search/?s=postprocessing&subset=video博客 /doc/d6eff3fdb7360b4c2e3f64f9.html /search/?s=postprocessing&subset=blog 社区/doc/d6eff3fdb7360b4c2e3f64f9.html /community/forums/results-and-visualization/技术⽀持知识库/doc/d6eff3fdb7360b4c2e3f64f9.html /support/knowledgebase/⽬录简介 1数据集、派⽣值与表格解 2 ? 截点与计算 3 ? 表格 6绘图类型选择⼀个绘图类型 8? 三维绘图 8? ⼆维绘图 15? ⼀维绘图 21使⽤后处理解释结果24导出结果数据、表格与⽹格 25? 报告 27操作提⽰与技巧快捷⽅式 28? 重新排列COMSOLDesktop 28? 在表⾯图中显⽰⽹格 29?滑动与交互式定位30结束语31iiiiv对计算机建模所得的对象进⾏定位、着⾊和调整，有助于更好地展⽰研究对象的⼏何、功能以及可⾏性。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

Adaptive mesh refinement
Represent computational domain as hierarchal refinement levels Increase grid resolution only in areas of interest Most applications are based on low order schemes
The effect of damping
Benchmark problem
Governing equations (2.5D LEE)
m=4, n=1, k=10 modal radiation
AMR process
Contour of pressure; m=4, n=1, k=10, time=0~26.28
Possible AMR parallel options
Global memory model
– Global Arrays toolkit: access distributed global arrays transparently as if they are residing in a shared memory – Titanium and Unified Parallel C (UPC): extend Java and C languages respectively by adding features to supply a global address space
Berger and Oliger (1983) algorithm 1) Estimating local truncation errors at all grid points by Richardson exeas with excessive errors, 2) Organizing these areas into rectangular patches using a clustering algorithm, 3) Refining or coarsening patches by superimposing or removing sub-grids. 4) Refining and coarsening recursively until either a given refinement/coarsening level is reached or a predefined local truncation error level has been met.
Gaussian pulse propagation through a finecoarse interface (1)
Fine-coarse interface x=0.5 Initial Gaussian pulse x=1.0 Propagation direction
0
250
750
Gaussian pulse propagation through a finecoarse interface (2)
Adaptive Mesh Refinement for Computational Aeroacoustics
Xun Huang and Xin Zhang Aeronautics and Astronautics School of Engineering Sciences University of Southampton Southampton, UK
Efficiency
Cells number: • • • • • Coarsest level contains 2304 cells; Finest level contains 36864 cells. 2191 seconds on finest mesh; 426 seconds by AMR, with the big criterion; 830 seconds by AMR, with the small criterion.
Binary data structures used for 2D AMR Codes written in Fortran90 and MPI Around 30 files for AMR, 60 files for applications, 20,000+ lines code.
Cell-based AMR algorithm
An example of fine-grained AMR application
Objective
To combine high-order finite difference schemes with an efficient parallel AMR algorithm to solve aeroacoustic problems
Coarse-grained, block-based AMR
– Based on the single-instruction, multiple-data (SIMD) architecture, cells are organized in blocks
Examples of block-based AMR computations
CAA solutions
For spatial derivatives: • 4th-order prefactored compact scheme or 4th-order Dispersion-Relation-Preserving (DRP) scheme • Artificial selective damping or a 10th-order explicit filter For time integration: • 4th-order 4/6 stage explicit Runge-Kutta scheme (for simplicity the same time steps applied to all refinement levels)
AMR does increase efficiency and without sacrificing exactness
Computing time: (for previous case, 1.3G PIII 512MB)
Summary
• The block based AMR code has been developed, and some CAA solvers are implemented to work with AMR; • The numerical method is tested against some benchmark problems, including 1D propagation, 2D propagation, 2D scattering, 2D modal radiation from an duct; • Future work: (1) parallel the code and provide the performance for some benchmark problems; (2) Add extra functions to support cases with complex geometries.
Effect of refinement and coarsening thresholds
Refine Coarsen Do nothing
Effect of refinement and coarsening thresholds
Comparison between AMR and analytical solution
Outline
Introduction AMR Details of numerical treatment Application to benchmark problems Summary
Background To improve efficiency To provide a potential means of modelling various, co-existing physics
Three refinement levels Refinement ratio of two 8 to 12 cells in every block
Data exchange
Treatment of fine-coarse block interface
Details of AMR algorithm