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美国Circularity Fuels公司在紧凑型装置中将沼气成功转化为合成气
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作者 汤玮健(摘译) 《石油炼制与化工》 北大核心 2025年第12期60-60,共1页
美国Circularity Fuels公司利用加州中央谷地一家奶牛场的沼气,通过一个紧凑型的电动处理装置,成功将其转化为合成气,这是可持续航空燃料(SAF)的关键前体。该装置的成本仅为传统蒸汽甲烷或自热重整器的1%。此次示范项目的成功标志着可... 美国Circularity Fuels公司利用加州中央谷地一家奶牛场的沼气,通过一个紧凑型的电动处理装置,成功将其转化为合成气,这是可持续航空燃料(SAF)的关键前体。该装置的成本仅为传统蒸汽甲烷或自热重整器的1%。此次示范项目的成功标志着可再生燃料的生产在经济性方面迈出了重要一步,Circularity公司认为这将有助于航空公司满足可持续燃料替代品的相关规定,同时为农民开辟数十亿美元的新收入来源。 展开更多
关键词 circularity Fuels 奶牛场 沼气 加州中央谷地
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基于时域同步平均的Circular图分析方法及齿轮故障智能诊断研究
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作者 胥永刚 张翼飞 +1 位作者 孙国栋 张坤 《机械强度》 北大核心 2025年第6期11-16,共6页
齿轮Circular图是用于与时域同步平均(Time Synchronous Averaging,TSA)相结合的一种结果呈现方法,可以将TSA提取到的齿轮啮合振动波形直观、清晰地展现出来。针对齿轮Circular图绘制参数设置和其缺少量化指标的问题,提出了用于波形边... 齿轮Circular图是用于与时域同步平均(Time Synchronous Averaging,TSA)相结合的一种结果呈现方法,可以将TSA提取到的齿轮啮合振动波形直观、清晰地展现出来。针对齿轮Circular图绘制参数设置和其缺少量化指标的问题,提出了用于波形边缘识别的F_(i)指标和基于Hu氏不变矩的Y_(i)指标。首先,使用TSA算法提取出齿轮啮合振动信号,通过计算最小F_(i)指标确定振动信号波形的上、下边缘;其次,利用上、下边缘参数绘制齿轮Circular图;再次,将齿轮Circular图分割为4个部分,通过计算分割后图片的Hu氏不变矩得到齿轮Circular图的Y_(i)指标;最后,基于从齿轮Circular图中提取出的Y_(i)和F_(i)指标,使用K最近邻(K-Nearest Neighbor,KNN)分类器对齿轮振动信号进行分类。仿真信号及齿轮断齿、裂纹故障信号的处理结果表明了该方法的有效性。 展开更多
关键词 齿轮箱 齿轮Circular图 特征指标 智能故障诊断
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Tunable reflective spin-decoupled encoding metasurface based on Dirac semimetals
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作者 HAO Xiao-yu ZHENG Si-yu +6 位作者 WANG Yu LIU Yang LIU Meng ZHANG Yu-ping ZHANG Jin-juan ZHAN Yi ZHANG Hui-yun 《中国光学(中英文)》 北大核心 2025年第4期968-978,共11页
Multiple functional metasurfaces with high information capacity have attracted considerable attention from researchers.This study proposes a 2-bit tunable spin-decoupled coded metasurface designed for the terahertz ba... Multiple functional metasurfaces with high information capacity have attracted considerable attention from researchers.This study proposes a 2-bit tunable spin-decoupled coded metasurface designed for the terahertz band,which utilizes the tunable properties of Dirac semimetals(DSM)to create a novel multilayer structure.By incorporating both geometric and propagating phases into the metasurface design,we can effectively control the electromagnetic wave.When the Fermi level(EF)of the DSM is set at 6 meV,the electromagnetic wave is manipulated by the gold patch embedded in the DSM film,operating at a frequency of 1.3 THz.When the EF of the DSM is set at 80 meV,the electromagnetic wave is manipulated by the DSM patch,operating at a frequency of 1.4 THz.Both modes enable independent control of beam splitting under left-rotating circularly polarized(LCP)and rightrotating circularly polarized(RCP)wave excitation,resulting in the generation of vortex beams with distinct orbital angular momentum(OAM)modes.The findings of this study hold significant potential for enhancing information capacity and polarization multiplexing techniques in wireless communications. 展开更多
关键词 coding metasurface dirac semimetal spin decoupling circular polarization TUNABLE
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Experimental study on the buckling of composite cylinders with reinforced circular hole under hydrostatic pressure
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作者 Zhun Li Xinhu Zhang +3 位作者 Kechun Shen Jing Liu Jian Zhang Guang Pan 《Defence Technology(防务技术)》 2025年第2期231-247,共17页
In this paper,a type of reinforcing structure for composite shell with single and through hole is presented.The experimental tests for the composite shells without hole,with single hole and reinforced structure,with t... In this paper,a type of reinforcing structure for composite shell with single and through hole is presented.The experimental tests for the composite shells without hole,with single hole and reinforced structure,with through hole and reinforced structure subjected to hydrostatic pressure were carried out by the designed experimental test system.The mechanical responses of the composite shells under hydrostatic pressure are obtained by the high-speed camera and strain measurement.The results show that the entire deformation process of the shell can be divided into three:uniform compression,"buckling mode formation"and buckling.The"buckling mode formation"process is captured and reported for the first time.For the composite shell with single hole,the proposed reinforcing structure has a significant reinforcement effect on the shell and the buckling capacity of the shell is not weaker than the complete composite shell.For the composite shell with through hole,sealing effect can be achieved by the proposed reinforcing structure,but the buckling capacity of the shell after reinforcement can only reach 77%of the original buckling capacity. 展开更多
关键词 Composite cylindrical shell Circular hole Reinforcing structure BUCKLING Hydrostatic pressure
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A new dimensionless number for dynamic plastic deformation analysis of clamped circular plates subjected to underwater blast loading
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作者 Weizheng Xu Yu Huang +4 位作者 Tong Li Hao Tang Yexun Li Hua Fu Xianxu Zheng 《Defence Technology(防务技术)》 2025年第9期294-302,共9页
A new dimensionless number is proposed for dynamic plastic deformation analysis of clamped circular plates under underwater explosion loads by introducing dimensional analysis method to the basic dynamical governing e... A new dimensionless number is proposed for dynamic plastic deformation analysis of clamped circular plates under underwater explosion loads by introducing dimensional analysis method to the basic dynamical governing equations of circular plates.The relation between dimensionless final plastic deformation of circular plates and the new dimensionless number is established based on massive underwater explosion test data.Meanwhile,comparative analysis was discussed with two other published dimensionless parameters which indicated the new dimensionless number proposed in this paper is more effective and extensive to predict the dynamic plastic response of circular plates under underwater explosion condition. 展开更多
关键词 Dimensionless number Underwater blast loading Clamped circular plate Dynamic plastic deformation
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基于熵和局部邻域信息的高斯约束CV模型 被引量:8
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作者 卢振泰 郑倩 +3 位作者 冯衍秋 刘燕杰 冯前进 陈武凡 《计算机学报》 EI CSCD 北大核心 2013年第5期1076-1085,共10页
基于曲线演化的Chan-Vese(CV)模型常常不能准确分割非均匀性且结构复杂的医学图像.针对此缺点,文中提出了一种基于熵和局部邻域信息的高斯约束CV模型,作者利用熵构造内部和外部区域能量的权值系数,加强了对曲线演化的控制;同时将曲线上... 基于曲线演化的Chan-Vese(CV)模型常常不能准确分割非均匀性且结构复杂的医学图像.针对此缺点,文中提出了一种基于熵和局部邻域信息的高斯约束CV模型,作者利用熵构造内部和外部区域能量的权值系数,加强了对曲线演化的控制;同时将曲线上各点的局部邻域信息引入到曲线演化过程中,提高了分割的准确性,并降低了区域内灰度不均匀等因素对曲线演化的影响;高斯约束保证了曲线演化过程中的稳定性、光滑性,同时不需要曲线周长约束项和重复初始化.利用Circular Hough变换对左心室壁内、外膜进行初始定位,避免了人工设置初始轮廓,减少了曲线向目标轮廓演化时间和初始轮廓位置敏感性对分割结果的影响.作者对心脏MR图像的左心室内、外膜进行了分割.结果表明文中方法能够快速准确地分割左心室壁内、外膜,抗干扰能力强,鲁棒性好. 展开更多
关键词 Chan-Vese(CV)模型 Circular HOUGH变换 邻域信息 高斯核函数
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基于机器视觉技术的新能源汽车零部件表面缺陷检测 被引量:8
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作者 黄爱维 钱辉 牛华 《激光杂志》 CAS 北大核心 2024年第6期253-258,共6页
新能源汽车零部件表面缺陷种类繁多,依靠人工检测存在错检、漏检等问题。为了提高新能源汽车零部件表面缺陷精度,提出基于机器视觉技术的新能源汽车零部件表面缺陷检测方法。结合Ridegelet变换与小波变换,在不破坏图像细节前提下,对基... 新能源汽车零部件表面缺陷种类繁多,依靠人工检测存在错检、漏检等问题。为了提高新能源汽车零部件表面缺陷精度,提出基于机器视觉技术的新能源汽车零部件表面缺陷检测方法。结合Ridegelet变换与小波变换,在不破坏图像细节前提下,对基于机器视觉技术采集的新能源汽车零部件表面缺陷图像展开去噪处理。引入MSR算法,通过信息熵占比权值的自适应计算,实现图像的快速增强。利用数学形态学计算方法,对新能源汽车零部件图像中的缺陷主体展开边缘提取,进而实现新能源汽车零部件表面缺陷的检测。实验结果表明,所提方法检测耗时低于10 ms、缺陷位置分析准确,面对多类型新能源汽车零部件表面缺陷,能够做到精准识别,提高了新能源汽车零部件的缺陷检测效率。 展开更多
关键词 Ridegelet变换 小波变换 机器视觉技术 MSR算法 circularity算子
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圆二色谱研究胶原模拟多肽三螺旋结构及其热稳定性 被引量:18
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作者 张之宝 王静洁 +3 位作者 陈晖娟 熊青青 刘玲蓉 张其清 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2014年第4期1050-1055,共6页
胶原是广泛研究和应用的生物材料,具有独特的三螺旋结构,此结构与其生物学性能密切相关。以胶原模拟多肽(collagen mimetic peptide,CMP)作为胶原的模型分子,通过圆二色谱研究了CMP的三螺旋结构、热稳定性等随序列或长度的改变所发生的... 胶原是广泛研究和应用的生物材料,具有独特的三螺旋结构,此结构与其生物学性能密切相关。以胶原模拟多肽(collagen mimetic peptide,CMP)作为胶原的模型分子,通过圆二色谱研究了CMP的三螺旋结构、热稳定性等随序列或长度的改变所发生的规律性变化。根据形成胶原三螺旋结构的重复序列(POG)_n及胶原上α_2β_1整合素识别位点序列GFOGER设计五种不同序列或长度的CMP,采用圆二色谱表征了CMP的三螺旋结构,并通过检测CMP的程序升温变性和程序降温复性过程中圆二色谱的变化,研究了CMP三螺旋结构的热变性过程、解链温度以及复性过程。实验结果显示,五种CMP室温下均以三螺旋结构的形式存在,CMP三螺旋结构的热稳定性随POG的个数增加而增强;不同于胶原,CMP三螺旋结构的热变性是可逆的,升温过程中三螺旋解聚(变性),降温过程又可重新组装(复性),复性过程有明显的'磁滞'现象。研究结果可为进一步研究胶原与CMP分子特征性的三螺旋结构形成规律以及基于CMP的人工类胶原生物材料的研究提供依据。 展开更多
关键词 胶原模拟多肽(CMP) 圆二色谱(CD) 三螺旋结构 热稳定性 Collagen MIMETIC peptide(CMP) Circular dichroism(CD)
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平面三次代数曲线
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作者 陈谷新 《图学学报》 CSCD 1989年第2期67-73,共7页
从本讲起,将陆续介绍各种特殊的三阶曲线,如狄克雷斯蔓叶线(The cissoid ofDiocles),笛卡尔叶形线(The folium of Descartes),马克劳林三等分角线(The trisectfix ofMaclsulin),环索线(The strophoid),蚌线(The conchoid),虚圆点曲线(Th... 从本讲起,将陆续介绍各种特殊的三阶曲线,如狄克雷斯蔓叶线(The cissoid ofDiocles),笛卡尔叶形线(The folium of Descartes),马克劳林三等分角线(The trisectfix ofMaclsulin),环索线(The strophoid),蚌线(The conchoid),虚圆点曲线(The circular cubic)等。文中将着重说这些曲线的方程、基本性质及作图方法。由于这些曲线的形状规则,作图简便,具有某些特殊的性质,因而在工程技术中占有重要的地位。 展开更多
关键词 代数曲线 蔓叶线 叶形线 虚圆点 环索线 蚌线 形状规则 三等分角 CIRCULAR 克雷斯
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基于Circular模型的大剪应变率点接触弹流界面滑移数值分析 被引量:5
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作者 刘奕壕 黄柏林 +2 位作者 付忠学 郭峰 胡松钰 《摩擦学学报》 EI CAS CSCD 北大核心 2018年第2期129-137,共9页
采用Circular流变模型,将假定的流体的极限剪应力特性模型拟合入Reynolds方程,编写Fortran语言程序,数值模拟界面滑移效应.计算从弹流润滑(EHL)延展到动压润滑(HL)区域.随着速度增加,摩擦系数曲线出现反常波动,表现为两个异常拐点.在中... 采用Circular流变模型,将假定的流体的极限剪应力特性模型拟合入Reynolds方程,编写Fortran语言程序,数值模拟界面滑移效应.计算从弹流润滑(EHL)延展到动压润滑(HL)区域.随着速度增加,摩擦系数曲线出现反常波动,表现为两个异常拐点.在中、高速度下,模拟获得的接触轮廓等值线图中观测到入口凹陷及中心区下凸.进一步讨论了载荷、速度、综合弹性模量、滑滚比等因素对滑移的影响.界面滑移效应被认为是产生反常接触轮廓和摩擦力波动的主因,与试验结果互为验证. 展开更多
关键词 弹流 STRIBECK曲线 摩擦系数 界面滑移 circular模型
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环状非编码RNA hsa_circ_001842对肾癌细胞增殖、凋亡、侵袭和成瘤能力的影响 被引量:1
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作者 冯倩 李园梦 +4 位作者 曾家伟 王耀东 谢刚 杨渝伟 俸家富 《重庆医科大学学报》 CAS CSCD 北大核心 2021年第1期49-56,共8页
目的:探究环状非编码RNA hsa_circ_001842作为癌基因在肾细胞癌(renal cell carcinoma,RCC)患者肾癌组织及细胞中的表达情况,以及其对肾癌细胞增殖、凋亡、侵袭与成瘤能力的影响。方法:收集2018年9月至2019年10月绵阳市中心医院泌尿外... 目的:探究环状非编码RNA hsa_circ_001842作为癌基因在肾细胞癌(renal cell carcinoma,RCC)患者肾癌组织及细胞中的表达情况,以及其对肾癌细胞增殖、凋亡、侵袭与成瘤能力的影响。方法:收集2018年9月至2019年10月绵阳市中心医院泌尿外科进行手术切除的肾癌标本及癌旁组织标本各64例。利用qRT-PCR检测所有RCC组织与癌旁正常组织中hsa_circ_001842的表达情况。将Caki-1肾癌细胞分别转染hsa_circ_001842基因过表达质粒(ox-circ_001842)、沉默质粒(shcirc_001842)和空质粒(ox-NC和sh-NC),采用细胞克隆形成实验、流式细胞术、细胞划痕实验和细胞侵袭实验,检测hsa_circ_001842对肾癌细胞增殖凋亡和迁移侵袭能力的影响。使用Western blot检测各组肾癌细胞上皮间充质转化(epithelial mesenchymal transition,EMT)相关蛋白与MMP-9蛋白表达水平。将转染sh-NC和sh-circ_001842的Caki-1肾癌细胞分别接种于裸鼠皮下,每7天测量一次肿瘤体积及体质量,4周后处死各组小鼠,并使用免疫组化技术和qRT-PCR检测肿瘤组织中EMT相关蛋白的表达情况。结果:RCC患者肾癌组织中hsa_circ_001842的表达量明显高于癌旁正常组织(P<0.05)。体外实验表明,与ox-NC组和sh-circ_001842组相比,ox-circ_001842组和sh-NC组Caki-1肾癌细胞的集落形成率、划痕愈合比率、细胞侵袭能力和E-cadherin蛋白的表达均明显增加(P<0.05),而细胞凋亡率、N-cadherin和MMP-9蛋白的表达明显降低(P<0.05)。裸鼠成瘤实验表明,与sh-NC组相比,sh-circ_001842组裸鼠形成的肿瘤体积和体质量均小于sh-NC组形成的肿瘤(P<0.05),并且E-cadherin蛋白表达水平明显上升,N-cadherin蛋白表达水平明显下降(P<0.05)。结论:hsa_circ_001842在肾癌组织及细胞中表达上调,抑制hsa_circ_001842的表达可以抑制癌细胞的增殖、迁移、侵袭和成瘤能力。 展开更多
关键词 肾细胞癌 circular RNA hsa_circ_001842 增殖 迁移 侵袭
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Experimental simulation investigation of influence of depth on spalling characteristics in circular hard rock tunnel 被引量:31
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作者 LUO Yong GONG Feng-qiang +1 位作者 LI Xi-bing WANG Shan-yong 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第3期891-910,共20页
A series of true-triaxial compression tests were performed on red sandstone cubic specimens with a circular hole to investigate the influence of depth on induced spalling in tunnels.The failure process of the hole sid... A series of true-triaxial compression tests were performed on red sandstone cubic specimens with a circular hole to investigate the influence of depth on induced spalling in tunnels.The failure process of the hole sidewalls was monitored and recorded in real-time by a micro-video monitoring equipment.The general failure evolution processes of the hole sidewall at different initial depths(500 m,1000 m and 1500 m)during the adjustment of vertical stress were obtained.The results show that the hole sidewall all formed spalling before resulting in strain rockburst,and ultimately forming a V-shaped notch.The far-field principal stress for the initial failure of the tunnel shows a good positive linear correlation with the depth.As the depth increases,the stress required for the initial failure of the tunnels clearly increased,the spalling became more intense;the size and mass of the rock fragments and depth and width of the V-shaped notches increased,and the range of the failure zone extends along the hole sidewall from the local area to the entire area.Therefore,as the depth increases,the support area around the tunnel should be increased accordingly to prevent spalling. 展开更多
关键词 deep underground engineering circular tunnels SPALLING strain rockburst true-triaxial loading V-shaped notch
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Engagement of circular RNA HECW2 in non-autophagic role of ATG5 implicated in endothelial-mesenchymal transition 被引量:12
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作者 YANG Li HAN Bing +4 位作者 ZHANG Yuan BAI Ying CHAO Jie HU Gang YAO Hong-hong 《中国药理学与毒理学杂志》 CAS CSCD 北大核心 2018年第9期736-737,共2页
Endothelial-mesenchymal transition(EndoMT)is associated with damage to blood-brain barrier(BBB)integrity.Circular RNAs(circRNAs)are highly expressed in the brain and are involved in brain diseases;however,whether circ... Endothelial-mesenchymal transition(EndoMT)is associated with damage to blood-brain barrier(BBB)integrity.Circular RNAs(circRNAs)are highly expressed in the brain and are involved in brain diseases;however,whether circR NAs regulate the EndoM T in the brain remains unknown.Our study demonstrated that circH ECW2 regulated the EndoM T by directly binding to MIR30 D,a significantly downregulated miR NA from miR NA profiling,which subsequently caused an increased expression of ATG5.These findings shed new light on the understanding of the noncanonical role of ATG5 in the EndoMT induced by methamphetamine or lipopolysaccharide.The in vivo relevance was confirmed as microinjection of circHecw2 siRNA lentivirus into the mouse hippocampus suppressed the EndoMT induced by LPS.These findings provide novel insights regarding the contribution of circHECW2 to the nonautophagic role of ATG5 in the EndoMT process in the context of drug abuse and the broad range of neuroinflammatory disorders. 展开更多
关键词 ATG5 circular RNA HECW2 EndoMT MIR30D nonautophagy
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Experimental investigation on influence of loading rate on rockburst in deep circular tunnel under true-triaxial stress condition 被引量:11
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作者 SI Xue-feng HUANG Lin-qi +2 位作者 GONG Feng-qiang LIU Xi-ling LI Xi-bing 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第10期2914-2929,共16页
To investigate the influence of loading rate on rockburst in a circular tunnel under three-dimensional stress conditions,the true-triaxial tests were conducted on 100 mm×100 mm×100 mm cubic sandstone specime... To investigate the influence of loading rate on rockburst in a circular tunnel under three-dimensional stress conditions,the true-triaxial tests were conducted on 100 mm×100 mm×100 mm cubic sandstone specimens with d50 mm circular perforated holes,and the failure process of hole sidewall was monitored and recorded in real-time by the microcamera.The loading rates were 0.02,0.10,and 0.50 MPa/s.The test results show that the rockburst process of hole sidewall experienced calm period,pellet ejection period,rock fragment exfoliation period and finally formed the V-shaped notch.The rockburst has a time lag and vertical stress is high when the rockburst occurs.The vertical stress at the initial failure of the hole sidewall increases with loading rate.During the same period after initial failure,the rockburst severity of hole sidewalls increased significantly with increasing loading rate.When the vertical stress is constant and maintains a high stress level,the rockburst of hole sidewall under low loading rate is more serious than that under high loading rate.With increasing loading rate,the quality of rock fragments produced by the rockburst decreases,and the fractal dimension of rock fragments increases. 展开更多
关键词 ROCKBURST loading rate deep circular tunnel true-triaxial test V-shaped notch
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Tooth surface geometry optimization of spiral bevel and hypoid gears generated by duplex helical method with circular profile blade 被引量:12
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作者 张宇 严宏志 +1 位作者 曾韬 曾亦愚 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第3期544-554,共11页
In order to effectively improve meshing performance of spiral bevel and hypoid gears generated by the duplex helical method, the effects of straight lined and circular cutting edges profile on meshing and contact of s... In order to effectively improve meshing performance of spiral bevel and hypoid gears generated by the duplex helical method, the effects of straight lined and circular cutting edges profile on meshing and contact of spiral bevel and hypoid gears were investigated analytically. Firstly, a mathematical model of spiral bevel and hypoid gears with circular blade profile was established according to the cutting characteristics of the duplex helical method. Based on a hypoid gear drive, the tooth bearings and the functions of transmission errors of four design cases were analyzed respectively by the use of the tooth contact analysis(TCA), and the contact stresses of the four design cases were analyzed and compared using simulation software. Finally, the curvature radius of the circular profile blade was optimized. The results show that the contact stresses are availably reduced, and the areas of edge contact and severe contact stresses can be avoided by selecting appropriate circular blade profile. In addition, the convex and concave sides are separately modified by the use of different curvature radii of inside and outside blades, which can increase the flexibility of the duplex helical method. 展开更多
关键词 circular blade profile duplex helical method spiral bevel and hypoid gears modification contact stress
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Chaotic system and QR factorization based robust digital image watermarking algorithm 被引量:9
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作者 宋伟 侯建军 +1 位作者 李赵红 黄亮 《Journal of Central South University》 SCIE EI CAS 2011年第1期116-124,共9页
In order to protect copyright of digital images,a new robust digital image watermarking algorithm based on chaotic system and QR factorization was proposed.The host images were firstly divided into blocks with same si... In order to protect copyright of digital images,a new robust digital image watermarking algorithm based on chaotic system and QR factorization was proposed.The host images were firstly divided into blocks with same size,then QR factorization was performed on each block.Pseudorandom circular chain(PCC) generated by logistic mapping(LM) was applied to select the embedding blocks for enhancing the security of the scheme.The first column coefficients in Q matrix of chosen blocks were modified to embed watermarks without causing noticeable artifacts.Watermark extraction procedure was performed without the original cover image.The experimental results demonstrate that the watermarked images have good visual quality and this scheme is better than the existing techniques,especially when the image is attacked by cropping,noise pollution and so on.Analysis and discussion on robustness and security issues were also presented. 展开更多
关键词 digital watermarking QR factorization pseudorandom circular chain logistic mapping
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Joint estimation of DOA, frequency, and polarization based on cumulants and UCA 被引量:7
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作者 Huang Jiacai Shi Yaowu Tao Jianwu 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2007年第4期704-709,共6页
A joint estimation algorithm of direction of arrival (DOA), frequency, and polarization, based on fourth-order cumulants and uniform circular array (UCA) of trimmed vector sensors is presented for narrowband non-G... A joint estimation algorithm of direction of arrival (DOA), frequency, and polarization, based on fourth-order cumulants and uniform circular array (UCA) of trimmed vector sensors is presented for narrowband non-Gaussian signals. The proposed approach, which is suitable for applications in arbitrary Gaussian noise environments, gives a closed-form representation of the estimated parameters, without spectral peak searching. An efficient method is also provided for elimination of cyclic phase ambiguities. Simulations are presented to show the performance of the algorithm. 展开更多
关键词 POLARIZATION direction of arrival FREQUENCY fourth-order cumulant uniform circular array vector sensor
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Upper bound analysis of ultimate pullout capacity of shallow 3-D circular plate anchors based on nonlinear Mohr-Coulomb failure criterion 被引量:8
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作者 ZHAO Lian-heng TAN Yi-gao +2 位作者 HU Shi-hong DENG Dong-ping YANG Xin-ping 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第9期2272-2288,共17页
Based on the nonlinear Mohr-Coulomb failure criterion and the associated flow rules,the three-dimensional(3-D)axisymmetric failure mechanism of shallow horizontal circular plate anchors that are subjected to the ultim... Based on the nonlinear Mohr-Coulomb failure criterion and the associated flow rules,the three-dimensional(3-D)axisymmetric failure mechanism of shallow horizontal circular plate anchors that are subjected to the ultimate pullout capacity(UPC)is determined.A derivative function of the projection function for projecting the 3-D axisymmetric failure surface on plane is deduced using the variation theory.By using difference principle,the primitive function of failure surface satisfying boundary condition and numerical solution to its corresponding ultimate pullout capacity function are obtained.The influences of nonlinear Mohr-Coulomb parameters on UPC and failure mechanism are studied.The result shows that UPC decreases with dimensionless parameter m and uniaxial tensile strength increases but increases when depth and radius of plate anchor,surface overload,initial cohesion,geomaterial density and friction angle increase.The failure surface is similar to a symmetrical spatial funnel,and its shape is mainly determined by dimensionless parameter m;the surface damage range expands with the increase of radius and depth of the plate anchor as well as initial cohesion but decreases with the increase of dimensionless parameter m and uniaxial tensile strength as well as geomaterial density.As the dimensionless parameter m=2.0,the numerical solution of UPC based on the difference principle is proved to be feasible and effective through the comparison with the exact solution.In addition,the comparison between solutions of UPC computed by variation method and those computed by upper bound method indicate that variation method outperforms upper bound method. 展开更多
关键词 shallow circular plate anchors ultimate pullout capacity variation analysis nonlinear Mohr-Coulomb failure criterion upper bound limit analysis
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Failure of circular shaft subjected to hydraulic uplift: Field and numerical investigation 被引量:5
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作者 ZHAO Guo-qing YANG Yu-you MENG Su-yun 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第1期256-266,共11页
A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft fo... A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft for its efficiency, safety and sustainability. Full-scale field tests and numerical analysis were conducted to analyze the base failure of the circular shaft with confined water. The failure process of the shaft was observed on site. The construction process of step-by-step excavation of shaft and layer-by-layer assembly of pre-stressed structure was simulated in detail. Simulation results agree well with the phenomenon on site. The base failure modes present that tensile damage generates at the center of the base due to non-uniform uplift and shear failure occurs along the soil-structure interface. The effects of shaft size and confined water head were also discussed. As a result, a critical ratio of diameter to shaft depth is put forward to assess the size effect of circular shaft. A conclusion that the soil strength should be partially considered in anti-inrushing safety factor calculation is drawn by analysis and comparison of various calculation methods. This research provides a reference for the base stability evaluation of similar shaft subjected to hydraulic uplift. 展开更多
关键词 circular shaft field test finite element analysis base stability water inrush
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Circular SAR processing using an improved omega-k type algorithm 被引量:7
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作者 Leilei KOU Xiaoqing Wang +2 位作者 Jinsong Chong Maosheng Xiang Minhui Zhu 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2010年第4期572-579,共8页
An improved circular synthetic aperture radar(CSAR) imaging algorithm of omega-k(ω-k) type mainly for reconstructing an image on a cylindrical surface is proposed.In the typical CSAR ω-k algorithm,the rage traje... An improved circular synthetic aperture radar(CSAR) imaging algorithm of omega-k(ω-k) type mainly for reconstructing an image on a cylindrical surface is proposed.In the typical CSAR ω-k algorithm,the rage trajectory is approximated by Taylor series expansion to the quadratic terms,which limits the valid synthetic aperture length and the angular reconstruction range severely.Based on the model of the CSAR echo signal,the proposed algorithm directly transforms the signal to the two-dimensional(2D) wavenumber domain,not using approximation processing to the range trajectory.Based on form of the signal spectrum in the wavenumber domain,the formula for the wavenumber domain interpolation of the w-k algorithm is deduced,and the wavenumber spectrum of the reference point used for bulk compression is obtained from numerical method.The improved CSAR ω-k imaging algorithm increases the valid synthetic aperture length and the angular area greatly and hence improves the angular resolution of the cylindrical imaging.Additionally,the proposed algorithm can be repeated on different cylindrical surfaces to achieve three dimensional(3D) image reconstruction.The 3D spatial resolution of the CSAR system is discussed,and the simulation results validate the correctness of the analysis and the feasibility of the algorithm. 展开更多
关键词 circular synthetic aperture radar omega-k algorithm wavenumber domain three-dimensional spatial resolution.
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