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基于体素模型的优化体绘制技术 被引量:10
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作者 洪歧 张树生 徐夏刚 《计算机应用》 CSCD 北大核心 2004年第10期82-85,共4页
直接体绘制技术因可绘制数据场中包含的内部结构形成较高图像质量而倍受青睐,但大量计算导致的绘制速度慢严重制约着其在大规模数据场交互绘制方面的应用。对现有算法进行优化是其发展方向之一。对目前基于体素模型的体绘制关键环节优... 直接体绘制技术因可绘制数据场中包含的内部结构形成较高图像质量而倍受青睐,但大量计算导致的绘制速度慢严重制约着其在大规模数据场交互绘制方面的应用。对现有算法进行优化是其发展方向之一。对目前基于体素模型的体绘制关键环节优化技术进行了概括,并分析了进行优化的主要思路,为进一步应用、改进这些技术提供参考。 展开更多
关键词 相关性 影响域 空间跳越 模板 存在加速 同质区域
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动态光散射中光子相关谱测量系统的空间相干性问题 被引量:8
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作者 王少清 娄本浊 +1 位作者 陶冶薇 任中京 《应用激光》 CSCD 北大核心 2004年第5期279-281,共3页
利用光干涉的简化模型讨论了动态光散射中光子相关谱测量系统的空间相干性要求的物理本质。利用相干面积概念对光子相关谱测量系统空间相干性判据的几种常见表述进行了规范。提出一种具有普遍意义的简明判据。
关键词 光子 空间相干性 物理本质 动态光散射 光干涉 判据 面积 性问题 常见 性要求
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裂缝预测技术在清溪场地区的应用 被引量:8
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作者 胡伟光 蒲勇 +2 位作者 肖伟 赵卓男 肖继林 《中国石油勘探》 CAS 2010年第6期52-58,共7页
通过对川东北清溪场地区的钻井资料及试气情况进行研究,发现飞仙关组裂缝型含气储层横向上呈不均匀分布。QX1井及XQX1井钻遇高压裂缝气藏,而QX2井、QX3井却落空了,所以有必要对该区的裂缝分布进行研究。对此,首先利用QX2井测井资料进行... 通过对川东北清溪场地区的钻井资料及试气情况进行研究,发现飞仙关组裂缝型含气储层横向上呈不均匀分布。QX1井及XQX1井钻遇高压裂缝气藏,而QX2井、QX3井却落空了,所以有必要对该区的裂缝分布进行研究。对此,首先利用QX2井测井资料进行岩石物理正演模型研究,得到了飞仙关组裂缝型含气储层具有AVO响应;其次基于地下介质在地震波传播中表现的各向异性理论,利用叠前地震资料,对地震资料进行方位属性和不同入射角的叠前道集研究,从叠前地震属性随方位角和入射角的变化关系分析入手来表征和描述清溪场构造飞仙关组顶部裂缝储层的分布特征;再次,利用叠后相干体属性切片对该区的裂缝型储层进行分析,并采用地质经验分析方法——构造应力场数值模拟来对该区裂缝系统进行验证。结果表明,飞仙关组顶部储层裂缝发育,各向异性特征检测对该区的裂缝预测效果很好,在平面上FVO梯度低值异常也与各向异性检测较一致。而相干体属性切片和构造应力场数值模拟效果则较差。预测结果和研究区内已有的钻井在飞仙关组顶部钻遇的裂缝型储层进行对比研究,各向异性检测结果和井上的资料对应较好,钻井部位预测的裂缝走向与测井资料解释的裂缝走向相吻合。 展开更多
关键词 相干体 FVO梯度 飞仙关组 纵波各向异性 裂缝预测 应力场数值模拟 清溪场地区
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山东日照地区不同类型含水层地下水位多年动态变化特征及其影响因素 被引量:2
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作者 杨鹏 张寿川 +4 位作者 郭本力 杨崇敬 冯启原 吕有成 解露茜 《吉林大学学报(地球科学版)》 CAS CSCD 北大核心 2024年第3期967-979,共13页
自然条件下沿海地区地下水与海水呈现动态平衡,但地下水超采会破坏二者间平衡关系,进而引发一系列地质环境问题。地下水动态变化受多种因素影响呈现非平稳信号变化特征,传统时间序列分析方法无法从多角度准确描述时间序列动态变化特征,... 自然条件下沿海地区地下水与海水呈现动态平衡,但地下水超采会破坏二者间平衡关系,进而引发一系列地质环境问题。地下水动态变化受多种因素影响呈现非平稳信号变化特征,传统时间序列分析方法无法从多角度准确描述时间序列动态变化特征,基于时间域和频率域分解的小波分析方法为探究地下水动态变化特征及影响因素提供了便利条件。利用山东日照地区不同类型含水层3口监测井1996—2015年间地下水位和降雨量监测数据,应用连续小波变换法和小波相干分析法开展研究,结果表明:不同类型含水层地下水位动态变化周期特征存在差异,荻水监测井(第四系松散岩类孔隙水含水层)地下水位呈现年际、4~5 a和11 a周期变化,莒县地震办监测井(基岩裂隙含水层)和东莞中学监测井(碳酸盐岩类裂隙岩溶水含水层)地下水位均呈现11 a周期和14 a强趋势项变化,总体而言,该地区降雨量呈现年际周期、4~5 a周期、11 a周期变化以及14 a强趋势项变化;降雨量周期变化是导致不同类型含水层地下水位呈现年际周期变化和多年周期变化的主要因素;不同含水层地下水位对降雨量响应时间存在差异是造成其呈现不同周期变化特征的主要原因。 展开更多
关键词 地下水动态 连续小波变换 小波相干 时滞性 日照地区
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年龄相关性白内障手术前后黄斑厚度观察 被引量:5
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作者 付颖 于璐 +2 位作者 相义会 伍腾飞 郭秀华 《中华眼外伤职业眼病杂志》 2014年第11期806-809,共4页
目的应用光学相干断层扫描(OCT)技术检测单纯年龄相关性白内障超声乳化并人工晶状体植入手术前后黄斑区视网膜厚度。方法对行超声乳化吸出术,且术前无合并症、术中无并发症的单纯年龄相关性白内障86例(104只眼)于术前及术后1周、1... 目的应用光学相干断层扫描(OCT)技术检测单纯年龄相关性白内障超声乳化并人工晶状体植入手术前后黄斑区视网膜厚度。方法对行超声乳化吸出术,且术前无合并症、术中无并发症的单纯年龄相关性白内障86例(104只眼)于术前及术后1周、1个月、3个月分别以OCT观察黄斑中心凹及黄斑区视网膜平均厚度的变化情况。结果所有术眼术后最佳矫正视力0.3~1.0,均较术前提高,OCT检查结果显示与术前比较术后1周黄斑中心凹厚度无增加,差异无统计学意义(t=-1.554,P=0.122),而黄斑区视网膜厚度增加,差异有统计学意义(t=-2.557,P=0.011);手术后1个月黄斑中心凹厚度和黄斑区视网膜厚度与术前比较均有增加,差异有统计学意义(t=-3.975,P=0.000;t=-2.862,P=0.005);术后3个月两区域厚度与术前比较差异均无统计学意义(t=-1.568,P=0.118;t=-0.197,P=0.844)。结论黄斑区视网膜平均厚度的检测可能比单纯黄斑中心凹厚度的检测更早、更全面地反映出患者白内障术后视网膜厚度增加的情况,为白内障术后黄斑水肿的诊治提供更多可靠依据。 展开更多
关键词 白内障 光学相干断层扫描(OCT) 厚度 黄斑中心凹 厚度 黄斑区
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应用OCTA分析不同分期原发性开角型青光眼患者视网膜的血流密度变化
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作者 贾飞 刘舒静 +1 位作者 任家平 曹靖 《中华眼外伤职业眼病杂志》 2024年第1期27-32,共6页
目的分析应用光学相干断层扫描血管成像(OCTA)评价不同分期原发性开角型青光眼患者(POAG)视网膜血流密度的变化。方法横断面研究。纳入2023年1月至7月郑州市第二人民医院收治的POAG者94例(122眼), 根据视野平均缺损(MD)将患者分为早期组... 目的分析应用光学相干断层扫描血管成像(OCTA)评价不同分期原发性开角型青光眼患者(POAG)视网膜血流密度的变化。方法横断面研究。纳入2023年1月至7月郑州市第二人民医院收治的POAG者94例(122眼), 根据视野平均缺损(MD)将患者分为早期组(MD≥-6 dB)30例(44眼)、中期组(-12 dB≤MD<-6 dB)35例(40眼)和晚期组(MD<-12 dB)29例(38眼)。另选取健康志愿者31名(36眼)为对照组。采用OCTA检查比较各组视盘整体血流密度(VD)、视盘旁VD及黄斑浅层VD、黄斑深层VD。采用Pearson单因素相关性分析法检验视网膜血流与视野损害的相关性。绘制视盘整体VD、视盘周围VD及黄斑浅层VD、黄斑深层VD的受试工作者曲线(ROC), 计算曲线下面积(AUC)判断诊断效能。结果 POAG早期组、中期组及晚期组视盘区整体VD及周围VD、黄斑浅层VD及深层VD均低于对照组(均P<0.05), 且从早期组至晚期组视盘区整体VD、周围VD、黄斑区浅层VD及深层VD均逐渐降低(均P<0.05)。Pearson相关性分析显示, 视盘整体VD、视盘周围VD及黄斑浅层VD、黄斑深层VD均与视野指数(VFI)呈正相关(均P<0.05)。比较AUC发现, 由高到低分别为黄斑浅层VD(AUC=0.956)、黄斑深层VD(AUC=0.912)、视盘周围VD(AUC=0.901)及视盘整体VD(AUC=0.884)。结论应用OCTA分析, 随着POAG程度加重, 视盘整体VD、视盘周围VD及黄斑浅层VD、黄斑深层VD均逐渐降低;黄斑浅层VD和深层VD可能有助于判断POAG的病情进展。 展开更多
关键词 青光眼 开角型 原发性 血管成像 光学相干断层扫描 密度 血流 视盘 黄斑
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一种利用InSAR相干图的干旱地区采空区检测方法
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作者 郑希望 李振今 +1 位作者 朱野 王志勇 《遥感信息》 CSCD 北大核心 2024年第2期36-42,共7页
针对采空区快速检测的需要,探讨利用雷达干涉测量(InSAR)技术生成的相干图检测地下采矿活动造成的采空区的可行性。基于InSAR技术,重点分析InSAR相干图在干旱地区的相干性特征及低相干区与煤矿采空区的相关性。在此基础上,构建了一种基... 针对采空区快速检测的需要,探讨利用雷达干涉测量(InSAR)技术生成的相干图检测地下采矿活动造成的采空区的可行性。基于InSAR技术,重点分析InSAR相干图在干旱地区的相干性特征及低相干区与煤矿采空区的相关性。在此基础上,构建了一种基于InSAR低相干区的煤矿采空区快速识别方法,利用InSAR相干图和自然断点分级法对大范围内可能发生的采空区进行广域识别与快速检测。以哈密市某煤矿为实验区,利用2020—2023年的28景Sentinel-1雷达数据,检测出InSAR相干图中的低相干区范围,获取了煤矿采空区的位置及范围。通过光学影像辅助验证,该方法对采空区识别的IoU和precision分别达到72.40%和96.40%。该方法为干旱地区的煤矿采空区的广域识别与检测提供了一条新的技术途径。 展开更多
关键词 INSAR 相干性 地面沉陷 采空区 干旱地区 自然断点分级法
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相干技术及其在西沙周缘深水区油气勘探中的应用 被引量:3
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作者 杨涛涛 王彬 +3 位作者 吕福亮 范国章 杨志力 吴敬武 《热带海洋学报》 CAS CSCD 北大核心 2013年第3期16-21,共6页
近年来珠江口盆地南部深水区油气勘探不断取得重大突破,证实了该区油气地质条件优越。西沙周缘深水区与其同处于一个构造带上,具有相似的构造沉积演化史,类比推测西沙周缘深水区可能具有良好的油气勘探前景。文章在介绍相干技术的基础上... 近年来珠江口盆地南部深水区油气勘探不断取得重大突破,证实了该区油气地质条件优越。西沙周缘深水区与其同处于一个构造带上,具有相似的构造沉积演化史,类比推测西沙周缘深水区可能具有良好的油气勘探前景。文章在介绍相干技术的基础上,采用近年来西沙海域新采集的高分辨率地震资料对比各代相干算法的计算效果,并将相干技术应用于该区深水油气勘探工作中。1)相干技术对地震数据的不连续性十分敏感,可有效精确地识别断层。在相干切片上,断层走向清晰,相互切割关系明确。2)相干技术强调振幅加强和边缘检测,可用于深水水道的识别刻画。在相干切片上,水道的整体形态、曲流特征和侧向侵蚀特征清晰,水道边缘为不连续性条带。3)由于生物礁核部岩性较均一,地震响应特征相似,而礁体边缘部位的地震反射杂乱,因此可以利用相干技术突出不连续性的特点识别生物礁。4)火山岩内部与围岩地震响应特征差别明显,因此可利用相干技术识别火山岩体。在相干切片上火山岩发育区为明显的弱相干,且会出现以火山岩为中心向四周发散的放射状断层。 展开更多
关键词 相干技术 西沙周缘 深水区 油气勘探
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光波的空间相干性分析与研究 被引量:2
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作者 周杰 徐满平 +1 位作者 范明星 杨齐民 《新疆师范大学学报(自然科学版)》 2005年第4期28-31,共4页
文章从杨氏干涉实验出发,揭示了光波空间相干性的物理本质。同时指出平面波在自然界根本不存在,存在的是具有一定空间频率和一个有限空间频谱宽度的准平面波。分析了空间频谱具有有限宽度的原因。进一步指出空间频谱宽度与相干面积成反... 文章从杨氏干涉实验出发,揭示了光波空间相干性的物理本质。同时指出平面波在自然界根本不存在,存在的是具有一定空间频率和一个有限空间频谱宽度的准平面波。分析了空间频谱具有有限宽度的原因。进一步指出空间频谱宽度与相干面积成反比,空间频率越高的光波偏离光轴的角度越大,空间频谱宽度越大的光波,其衍射发散角越大。 展开更多
关键词 杨氏干涉实验 准平面波 空间相干性 相干面积
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Comparison of measurements of anterior chamber angle via anterior segment optical coherence tomography and ultrasound biomicroscopy 被引量:2
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作者 Zi-Yan Yu Ting Huang +1 位作者 Lu Lu Bo Qu 《World Journal of Clinical Cases》 SCIE 2020年第15期3249-3258,共10页
BACKGROUND Glaucoma is an irreversible optic neuropathy with the loss of visual field and decrease of vision.The variable clinical manifestations may result in differential diagnostic difficulties.The early screening ... BACKGROUND Glaucoma is an irreversible optic neuropathy with the loss of visual field and decrease of vision.The variable clinical manifestations may result in differential diagnostic difficulties.The early screening and diagnosis of glaucoma are currently experiencing a demand for anterior segment analysis tools that can gather more information with one short measurement.Therefore,we analyzed the agreement,difference,and correlation of chamber angle parameters such as angel opening distance at 500μm(AOD500)and trabeculo-iris space area at 500μm^2(TISA500)measured by anterior segment optical coherence tomography(ASOCT)and ultrasound biomicroscopy(UBM).AIM To compare the differences,correlation,and agreement in measuring AOD500 and TISA500 by AS-OCT and UBM.METHODS Both AS-OCT and UBM were performed to measure AOD500 and TISA500 in 45 subjects(72 eyes).All subjects without glaucoma were collected from October 2015 to August 2016 at the Ophthalmology Department of the Fourth Affiliated Hospital of China Medical University.Data of the two groups(AOD500 and TISA500)were compared by nonparametric tests.Pearson correlative analysis and Bland-Altman analysis were used to compare the correlation and agreement.RESULTS There were no significant differences between AS-OCT and UBM in measuring AOD500(P1=0.110,P2=0.633,P3=0.078,and P4=0.474)and TISA500(P1=0.584,P2=0.889,P3=0.297,and P4=0.550)of the four quadrants of the anterior chamber angle.There was a high correlation in measuring AOD500(r1=0.562,r2=0.671,r3=0.635,and r4=0.720;P<0.001)and TISA500(r1=0.584,r2=0.889,r3=0.297,and r4=0.550;P<0.001).There was a good agreement in measuring AOD500 and TISA500 by the two modalities.CONCLUSION There is a high correlation and agreement between AOD500 and TISA500 measurements by AS-OCT and UBM.They are interchangeable under some circumstances.AS-OCT proves to be a better early screening tool for glaucoma. 展开更多
关键词 Anterior segment-optical coherence tomography Primary angle closure glaucoma Anterior chamber angle Angel opening distance at 500 m Trabeculo-iris space area at 500 m^2
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动态光散射颗粒测量区大小对测量结果的影响 被引量:1
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作者 杨晖 郑刚 +2 位作者 李孟超 郁飞龙 边岱泉 《激光技术》 CAS CSCD 北大核心 2009年第4期384-386,共3页
为了研究动态光散射颗粒测量中测量区域大小对测量结果的影响,采用50nm,100nm,500nm3种标准颗粒与过滤的蒸馏水制作不同体积分数的溶液作为测量颗粒样品进行了测试,得到不同测量区大小下颗粒粒径的测量数据,并通过计算测量平均值... 为了研究动态光散射颗粒测量中测量区域大小对测量结果的影响,采用50nm,100nm,500nm3种标准颗粒与过滤的蒸馏水制作不同体积分数的溶液作为测量颗粒样品进行了测试,得到不同测量区大小下颗粒粒径的测量数据,并通过计算测量平均值和重复性对数据进行了分析。结果表明,当体积分数较低时,测量区过小会导致测量值的方差过大;当体积分数较高时,测量区过大会导致测量平均值偏小。 展开更多
关键词 散射 颗粒测量 测量区 相干面积
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Choroidal vascularity index in thyroidassociated ophthalmopathy:a crosssectional study
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作者 Pasquale Loiudice Marco Pellegrini +6 位作者 Michele Marino Barbara Mazzi Ilaria Ionni Giuseppe Covello Michele Figus Marco Nardi Giamberto Casini 《Eye and Vision》 SCIE CSCD 2023年第4期21-28,共8页
Background:Hemodynamic changes have been observed in patients with Graves'disease.The aim of our study was to evaluate choroidal vascular change using the choroidal vascularity index(CVi)in patients with thyroid-a... Background:Hemodynamic changes have been observed in patients with Graves'disease.The aim of our study was to evaluate choroidal vascular change using the choroidal vascularity index(CVi)in patients with thyroid-associated ophthalmopathy(TAO).Methods:In this cross-sectional observational study,40 patients affected by TAO were recruited.Forty healthy individuals,matched for age and sex,served as controls.Foveal enhanced-depth imaging optical coherence tomography scans were obtained from all participants.Images were binarized using the ImageJ software and luminal area(LA)and total choroidal area(TCA)were measured.CVI was calculated as the proportion of LA to TCA.The relation between CVI or subfoveal choroidal thickness(SFCT)and clinical activity score,exophthalmometric value,diplopia status,gender,and age was evaluated.Results:CVI was significantly higher in patients with TAO(P=0.004).No significant difference was observed in SFCT(P=0.200)and TCA(P=0.153)comparing TAO patients and healthy controls.LA was significantly higher in TAO group(P=0.045).On multiple regression analysis,CVI was associated with TCA(P=0.043).No association Was found between SFCT or CVI and TCA,clinical activity score,exophthalmometric value,Inami value,diplopia status,genderorage(P>0.05).Conclusions:This is the first study that has demonstrated an increase in CVI in eyes with TAO compared with healthy controls and has assessed its association with clinical features. 展开更多
关键词 Choroidal vascularity index Choroidal vasculature Enhanced depth optical coherence tomography Image binarization Luminal area Subfoveal choroidal thickness Thyroid-associate ophthalmopathy
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Influence of vegetation type and topographic position on volumetric soil water content dynamics and similarity among surface and deep soil layers
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作者 Muxing Liu Qiuyue Wang +3 位作者 Jun Yi Hailin Zhang Ji Liu Wei Hu 《International Soil and Water Conservation Research》 SCIE CSCD 2023年第1期183-196,共14页
Clarifying the mechanisms governing volumetric soil water content(VSWC)dynamics in soil profiles is essential,as it can help to elucidate soil water transport processes and improve the prediction accuracy of soil hydr... Clarifying the mechanisms governing volumetric soil water content(VSWC)dynamics in soil profiles is essential,as it can help to elucidate soil water transport processes and improve the prediction accuracy of soil hydrological processes.Using Spearman's rank correlation and wavelet coherence analysis methods,similarity in soil profile VSWC dynamics and factors governing VSWC soil profile dynamics in upslopes and downslopes under three vegetation types(evergreen forest[EG],secondary deciduous forest mixed with shrubs[SDFS],and deforested pasture[DP])at different time scales(hourly,daily,weekly,and monthly)and in different seasons were analyzed.The results revealed significant similarity in the VSWC of different soil depths(P<0.01),with the similarity decreasing in accordance with the increment in soil depth.Greater VSWC similarity was found in EG than SDFS and DP sites and in upslope than downslope areas at both forest sites.The average significant coherence area(SCA)of VSWC similarity among surface and deep soil layers varied with the time scale,which was in the order of monthly(58.6%)>weekly(42.8%)>daily(21.8%).The effects of soil properties(e.g.,texture,saturated hydraulic conductivity),rainfall,and potential evapotranspiration(ET_(p))on VSWC similarity were related to the time scale and season in which VSWC monitoring took place.Soil properties had apparent effects on VSWC similarity at longer time scales(i.e.,monthly),with a high SCA.In contrast,the effects of rainfall and ET_(p) on VSWC similarity were concentrated at weekly and daily scales,with a relatively low SCA.Rainfall and ET_(p) dominated VSWC dynamics in the summer and fall,respectively.These results imply the use of measured VSWC at one soil depth to predict the VSWC at other soil depths was a reliable method.While the in-fluence of time scale effects and seasonal variations on prediction accuracy of VSWC should be considered. 展开更多
关键词 Volumetric soil water content Wavelet analysis Significant coherence area Time scale Vegetation type Slope postion
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Evaluation of macular choroidal and microvascular network changes by activity scores and serum antibodies in thyroid eye patients and healthy subjects
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作者 Mehmet Erkan Dogan Ibrahim Basol +2 位作者 Hatice Deniz Ilhan Yusuf Ayaz Olgar Ocal 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2023年第12期2089-2094,共6页
AIM:To investigate the choroidal thickness and the microvascular network changes around the macula in thyroid eye disease(TED)patients at different stages and the relationship of those changes with risk factors,serum ... AIM:To investigate the choroidal thickness and the microvascular network changes around the macula in thyroid eye disease(TED)patients at different stages and the relationship of those changes with risk factors,serum antibodies and the severity of TED.METHODS:A total of 85 participants were enrolled.All participants underwent ophthalmology and endocrinology examinations.Subfoveal choroidal thickness(SFCT),superficial(s)and deep(d)foveal avascular zone(FAZ)area,mean(m)and central(c)superficial vascular density(SVD),deep vascular density(DVD)measurements of the enrolled cases were performed with Topcon swept source optical coherence tomography(OCT)/OCT angiography(OCTA)DRI OCT Triton.Multiple linear regression analysis was used to explore the associations between SFCT,FAZ area,SVD,DVD and the relevant factors of TED.RESULTS:Those with active TED patients had higher c-DVD and m-DVD levels(P<0.05),however there is no statistically significant difference in SFCT between active and stable TED patients.Among the serum antibodies,it was observed that s-FAZ and d-FAZ increased,c-SVD and m-SVD decreased in patients with high thyroid stimulating hormone-receptor autoantibodies(TRAB)level,whereas SFCT thickened in patients with high levels of both TRAB and human thyroglobulin(hTG).There was no significant difference in SFCT,FAZ,SVD and DVD measurement at gender,between hyperthyroid and euthyroid patients and among those with or without thyroid papillary carcinoma.CONCLUSION:The results show that both disease activation and serum antibodies differentially affect both superficial and deep retinal vascular density.It has also been shown that high serum antibody levels affect choroidal thickness independent of clinical activity. 展开更多
关键词 thyroid eye disease optic coherence tomography angiography vascular density choroidal thickness foveal avascular zone area
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基于延时自动同步的调频同步广播 被引量:1
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作者 周场如 《广播与电视技术》 2018年第10期100-105,共6页
各地早年规划建设的单点大功率调频广播发射台,其覆盖范围内由于受地形或高大建筑物的阻挡容易产生阴影区。本文通过珠海船底山和唐家909台的调频同步广播工程,采用小功率的补点发射,较好解决了该问题。文中介绍了该工程整体概况,详细... 各地早年规划建设的单点大功率调频广播发射台,其覆盖范围内由于受地形或高大建筑物的阻挡容易产生阴影区。本文通过珠海船底山和唐家909台的调频同步广播工程,采用小功率的补点发射,较好解决了该问题。文中介绍了该工程整体概况,详细分析了两发射台的设备和FM射频信号的固定延时,微波传输信号源的链路延时,介绍了同步设备的参数设置并收测了工程结果数据。该工程的建设可为其他补点同步广播提供参考。 展开更多
关键词 补点 同步广播 相干区 延时 自动同步
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Evaluation of childhood developing via optical coherence tomography-angiography in Qamdo,Tibet,China:A prospective cross-sectional,school-based study
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作者 Ke-Xin Sun Yong-Guo Xiang +7 位作者 Tong Zhang Sheng-Lan Yi Jiu-Yi Xia Xin Yang Shi-Jie Zheng Yan Ji Wen-Juan Wan Ke Hu 《World Journal of Clinical Cases》 SCIE 2023年第23期5479-5493,共15页
BACKGROUND Optical coherence tomography angiography(OCTA)is a new and reliable machine used to evaluate retinal structure and macular perfusion in children.The use of OCTA under bad condition such as high altitude,low... BACKGROUND Optical coherence tomography angiography(OCTA)is a new and reliable machine used to evaluate retinal structure and macular perfusion in children.The use of OCTA under bad condition such as high altitude,low atmospheric oxygen,and low humidity,in children is rarely.AIM To quantify the macular micro-vasculature in healthy children of various ages using OCTA in Qamdo.METHODS Design:Prospective cross-sectional,school-based study.Three hundred and fortyseven normal students from 9 schools in 4 different areas in Qamdo were included.OCTA was performed on a 3 mm×3 mm area centered on the macular region and macular cube 512×128 showed details in macular.Early treatment of diabetic retinopathy study Vessel Flow Density(VD)of the macular central vascular plexus density(CVD),inner vascular plexus density(IVD),full vascular plexus density(FVD),and the size of the foveal avascular zone(FAZ)were measured.All these results corrected by t/s=3.382×0.01306×(axial length-1.82).The differences were compared among various ages,sexes and living environments.RESULTS The mean FAZ area in all eyes was 0.27 mm^(2)±0.12 mm^(2).The mean foveal thickness(MFT)in the macular cube was 227.64μm±23.51μm.Compared with girls,boys had a lager FAZ(P=0.0029).Among the different age groups,MFT(P<0.001)and FVD(P<0.0001),IVD(P<0.0001),and CVD(P=0.0050)increased with age.FAZ areas were not correlated with age(P=0.8853)or others(MFT,area).CONCLUSION OCTA can use to evaluate macular perfusion in children.Our data bridge the gap between structural OCT and perfusion density in children in high altitude.Even though these were not a longitudinal study,it may provide us with hints about retina development during puberty and clinical implications of OCTA in children. 展开更多
关键词 Optical coherence tomography-angiography Qamdo Foveal avascular zone area Vessel flow density TEENAGER
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Choroidal vascularity index in thyroidassociated ophthalmopathy:a crosssectional study 被引量:1
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作者 Pasquale Loiudice Marco Pellegrini +6 位作者 Michele Marinò Barbara Mazzi Ilaria Ionni Giuseppe Covello Michele Figus Marco Nardi Giamberto Casini 《Eye and Vision》 SCIE CSCD 2021年第1期175-182,共8页
Background:Hemodynamic changes have been observed in patients with Graves’disease.The aim of our study was to evaluate choroidal vascular change using the choroidal vascularity index(CVI)in patients with thyroidassoc... Background:Hemodynamic changes have been observed in patients with Graves’disease.The aim of our study was to evaluate choroidal vascular change using the choroidal vascularity index(CVI)in patients with thyroidassociated ophthalmopathy(TAO).Methods:In this cross-sectional observational study,40 patients affected by TAO were recruited.Forty healthy individuals,matched for age and sex,served as controls.Foveal enhanced-depth imaging optical coherence tomography scans were obtained from all participants.Images were binarized using the ImageJ software and luminal area(LA)and total choroidal area(TCA)were measured.CVI was calculated as the proportion of LA to TCA.The relation between CVI or subfoveal choroidal thickness(SFCT)and clinical activity score,exophthalmometric value,diplopia status,gender,and age was evaluated.Results:CVI was significantly higher in patients with TAO(P=0.004).No significant difference was observed in SFCT(P=0.200)and TCA(P=0.153)comparing TAO patients and healthy controls.LA was significantly higher in TAO group(P=0.045).On multiple regression analysis,CVI was associated with TCA(P=0.043).No association was found between SFCT or CVI and TCA,clinical activity score,exophthalmometric value,Inami value,diplopia status,gender or age(P>0.05).Conclusions:This is the first study that has demonstrated an increase in CVI in eyes with TAO compared with healthy controls and has assessed its association with clinical features. 展开更多
关键词 Choroidal vascularity index Choroidal vasculature Enhanced depth optical coherence tomography Image binarization Luminal area Subfoveal choroidal thickness Thyroid-associate ophthalmopathy
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Microvascular changes after conbercept therapy in central retinal vein occlusion analyzed by optical coherence tomography angiography 被引量:21
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作者 Yang Deng Qi-Wen Zhong +11 位作者 Ai-Qi Zhang Xiao-Juan Cai Ming-Zhi Lu Shao-Chong Zhang Li-Shi Su Hui Chen Ying Lin Li-Mei Sun Guan-Di Chen Li-Ting Zhong Chen-Jin Jin Wei Chi 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2019年第5期802-808,共7页
AIM: To investigate microvascular changes in eyes with central retinal vein occlusion(CRVO) complicated by macular edema before and after intravitreal conbercept injection and evaluate correlations between these chang... AIM: To investigate microvascular changes in eyes with central retinal vein occlusion(CRVO) complicated by macular edema before and after intravitreal conbercept injection and evaluate correlations between these changes and best-corrected visual acuity(BCVA) and retinal thickness. METHODS: Twenty-eight eyes of 28 patients with macular edema caused by CRVO were included in this retrospective study. All patients received a single intravitreal conbercept injection to treat macular edema. BCVA and the results of optical coherence tomography angiography(OCTA) automatic measurements of the vessel density in the superficial(SCP) and deep retinal capillary plexus(DCP), the foveal avascular zone(FAZ) area, the FAZ perimeter(PERIM), the vessel density within a 300-μm wide ring surrounding the FAZ(FD-300), the acircularity index(AI), the choriocapillaris flow area, and retinal thickness were recorded before and at one month after treatment and compared with the results observed in age-and sexmatched healthy subjects. RESULTS: The vessel density in the SCP and DCP, the FD-300, and the flow area of the choriocapillaris were allsignificantly lower in CRVO eyes than in healthy eyes, while the AI and retinal thickness were significantly higher(all P<0.05). After treatment, retinal thickness was significantly decreased, and the mean BCVA had markedly improved from 20/167 to 20/65(P=0.0092). The flow area of the choriocapillaris was also significantly improved, which may result from the reduction of shadowing effect caused by the attenuation of macular edema. However, there were no significant changes in SCP and DCP vessel density after treatment. The flow area of the choriocapillaris at baseline was negatively correlated with retinal thickness.CONCLUSION: OCTA enables the non-invasive, layerspecific and quantitative assessment of microvascular changes both before and after treatment, and can therefore be used as a valuable imaging tool for the evaluation of the follow-up in CRVO patients. 展开更多
关键词 central retinal VEIN OCCLUSION optical coherence tomography ANGIOGRAPHY MACULAR EDEMA conbercept vessel density flow area foveal AVASCULAR zone
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基于多变量AR模型的脑电相干性分析及其在脑区协作机制研究中的应用 被引量:10
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作者 洪波 杨福生 +1 位作者 岳小敏 陈天祥 《生物物理学报》 CAS CSCD 北大核心 2001年第1期105-113,共9页
研究脑皮层不同区域之间功能协作的机制一直是认知和神经科学关注的重要问题之一。基于多变量自回归模型的动态相干性分析方法 ,被用于观察不同脑区在认知过程中的同步化 ,结果显示 ,人在感知和识别物体时 ,相关的脑区自动地发生了同步... 研究脑皮层不同区域之间功能协作的机制一直是认知和神经科学关注的重要问题之一。基于多变量自回归模型的动态相干性分析方法 ,被用于观察不同脑区在认知过程中的同步化 ,结果显示 ,人在感知和识别物体时 ,相关的脑区自动地发生了同步化的神经活动 ,这种同步化被证实是不受干扰刺激影响的 ,但被干扰的注意力确实影响了与判断和主动运动有关的脑区的同步化 ,而且这种影响的趋势与反应时间的分析结果一致。 展开更多
关键词 脑电 相干性 多变量自回归模型 同步化 脑区协作 神经生理
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糖尿病视网膜病变激光面积与疗效的分析 被引量:14
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作者 李朝晖 孟丽珠 +2 位作者 崔治华 胡晓英 张敬维 《眼科新进展》 CAS 北大核心 2013年第2期165-168,共4页
目的通过自行设计的计算机软件量化激光斑面积,计算糖尿病视网膜病变(diabetic retinopathy,DR)患者全视网膜光凝(panretinal photocoagulation,PRP)后激光斑所占眼底图总面积百分比,探讨激光斑面积与视力及黄斑厚度、黄斑容积之间的关... 目的通过自行设计的计算机软件量化激光斑面积,计算糖尿病视网膜病变(diabetic retinopathy,DR)患者全视网膜光凝(panretinal photocoagulation,PRP)后激光斑所占眼底图总面积百分比,探讨激光斑面积与视力及黄斑厚度、黄斑容积之间的关系。方法选择重度非增生性DR患者30例60眼行PRP治疗。将不伴有黄斑水肿的患者分为A、B两组,每组24眼;将伴有黄斑水肿的患者分为C、D两组,每组6眼。其中A、B两组行PRP,C、D两组先行黄斑格栅样光凝,1周后再行PRP;A组、C组PRP间隔1个激光斑;B组、D组PRP间隔2个激光斑。记录PRP前、PRP后3个月各组视力及黄斑厚度、黄斑容积,并测量4组眼底激光斑面积占眼底图总面积的百分比,比较激光斑面积比值与激光治疗效果的关系。结果 PRP间隔1个激光斑时,激光斑面积(像素)为20000~50000(34398.27±8808.51),激光斑面积与眼底图总面积的百分比为(32.64±4.43)%(25%~40%)。PRP间隔2个激光斑时,激光斑面积为10000~20000(15442.33±2737.77),激光斑面积与眼底图总面积的百分比为(18.35±3.43)%(10%~25%)。A组与B组比较,PRP后视力、黄斑厚度及黄斑容积差异均无统计学意义(均为P>0.05);C组与D组比较,PRP后视力恢复更好,黄斑厚度及黄斑容积均有显著降低(均为P<0.05)。结论有效的激光斑面积是PRP治疗成功的关键,对于伴有黄斑水肿的重度非增生性DR患者,激光斑所占视网膜总面积为25%~40%时,术后视力及黄斑厚度、黄斑容积恢复较好。 展开更多
关键词 糖尿病视网膜病变 全视网膜光凝 光学相干断层扫描 激光斑面积
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