期刊文献+
共找到48,731篇文章
< 1 2 250 >
每页显示 20 50 100
Moho反射波噪声干涉方法及其在青藏高原东北缘地壳结构成像的应用初探 被引量:1
1
作者 马小军 吴庆举 《地球与行星物理论评(中英文)》 2025年第2期167-181,共15页
基于南北地震带北段布设的密集流动地震台阵的连续波形记录,采用台阵噪声干涉技术获得了青藏高原东北缘Moho面PmP反射波,利用已有的区域三维地壳速度模型,采用沉积层校正方法建立研究区域的三维地壳初始模型,进而对噪声互相关函数进行... 基于南北地震带北段布设的密集流动地震台阵的连续波形记录,采用台阵噪声干涉技术获得了青藏高原东北缘Moho面PmP反射波,利用已有的区域三维地壳速度模型,采用沉积层校正方法建立研究区域的三维地壳初始模型,进而对噪声互相关函数进行基准面校正,然后采用共中心点叠加方法获得了研究区的地壳厚度分布.结果显示,青藏高原东北缘及周边不同块体地壳厚度差异显著,沿青藏高原北东向的扩展方向,地壳厚度逐渐变薄.祁连造山带中、西段地壳厚度约55~65 km,西秦岭造山带地壳厚度从西至东从53 km左右减小至42 km上下,阿拉善块体地壳厚度约50 km,鄂尔多斯块体西缘地壳厚度约40~45 km.六盘山断裂、海原断裂与天景山断裂附近呈现局部的地壳增厚,并且出现脉冲状Moho面反射震相,表明断裂带附近可能存在速度跃变较大的Moho面结构.祁连山北缘断裂出现叠置的反射震相,推测下地壳的逆冲形成了此类Moho结构. 展开更多
关键词 青藏高原东北缘 噪声干涉技术 Moho面反射波 基准面校正 地壳厚度
下载PDF
地震宽角反射/折射方法发展述评
2
作者 王夫运 田晓峰 刘汉奇 《地球与行星物理论评(中英文)》 2025年第2期118-130,共13页
本文从地震宽角反射/折射方法的仪器装备、观测系统、观测实验、震相识别、数据分析等主要技术环节的出现、改进、发展、完善,回顾了该方法的百年发展历史.按照我们的见解,将其发展过程分为萌芽期、诞生期、成长期和发展期.对于早期的追... 本文从地震宽角反射/折射方法的仪器装备、观测系统、观测实验、震相识别、数据分析等主要技术环节的出现、改进、发展、完善,回顾了该方法的百年发展历史.按照我们的见解,将其发展过程分为萌芽期、诞生期、成长期和发展期.对于早期的追溯,重点放在方法的孕育和诞生起到关键作用的人物和事件上,并且尽可能详细;对后期的回顾,聚焦在方法的技术内容的萌发、出现、改进、应用和重点文献等方面,如,何时出现了剖面方法、相遇和追逐观测、地震宽角反射/折射剖面数据的完备性等,成果表述不作为重点,而且叙述简略.述及了天然地震学、地震折射勘探、地震反射勘探、电子技术、通讯技术、测量技术、计算机技术、计算数学等相关学科的进步,对地震宽角反射/折射方法发展的促进作用.展望未来,宽角反射/折射方法在我国深部探测与矿产资源勘查领域大有可为.以此文致敬追寻科学真理的地学前辈. 展开更多
关键词 地震宽角反射/折射方法 轻便地震仪 观测系统 观测实验 资料分析
下载PDF
基于物联网和弱反射光栅阵列的地质灾害监测系统设计与应用
3
作者 张晓飞 吕中虎 +1 位作者 孟庆佳 王晨辉 《现代电子技术》 北大核心 2025年第1期144-150,共7页
我国是世界上地质灾害类型最多、地质灾害最严重的国家之一,而雨量监测和形变监测在地质灾害监测中发挥着越来越重要的作用,因此确保地质灾害监测系统的长期运行以及在降雨期间的稳定运行尤为重要。文中基于STM32微控制器、LORA模块、4... 我国是世界上地质灾害类型最多、地质灾害最严重的国家之一,而雨量监测和形变监测在地质灾害监测中发挥着越来越重要的作用,因此确保地质灾害监测系统的长期运行以及在降雨期间的稳定运行尤为重要。文中基于STM32微控制器、LORA模块、4G模块设计了一款物联网数据采集控制板,并结合压电式雨量传感器、拉绳位移传感器研制了雨量智能监测仪、裂缝位移智能监测仪;结合物联网数据采集控制板和弱反射光栅阵列传感技术构建了基于物联网的弱反射光栅地质灾害监测系统,实现了对地质灾害体的定时监测和降雨期间的自动监测;最后将雨量智能监测仪、裂缝位移智能监测仪和弱反射光栅地质灾害监测系统应用于桐梓县大河镇新场火车站新场滑坡、崩塌的监测实验中。监测数据表明,弱反射光栅监测系统测得传感光缆41#弱反射光栅传感段的位移变化达5 mm,在其附近的位移监测仪也测到有位移变化,可有效实现对地质灾害的定时监测和降雨期间的自动监测。 展开更多
关键词 弱反射光栅 地质灾害 物联网 雨量监测 位移监测 光纤传感 光栅传感器 滑坡监测
下载PDF
Deghosting towed streamer data in τ/p domain based on rough sea surface reflectivity 被引量:11
4
作者 张兴岩 潘冬明 +3 位作者 史文英 方中于 但志伟 张立霞 《Applied Geophysics》 SCIE CSCD 2015年第4期573-584,629,共13页
Currently, the deghosting of towed streamer seismic data assumes a flat sea level and a sea-surface reflection coefficient of-1; this decreases the precision of deghosting. A new method that considers the rough sea su... Currently, the deghosting of towed streamer seismic data assumes a flat sea level and a sea-surface reflection coefficient of-1; this decreases the precision of deghosting. A new method that considers the rough sea surface is proposed to suppress ghost reflections. The proposed deghosting method obtains the rough sea surface reflection coefficient using Gaussian statistics, and calculates the optimized deghosting operator in the r/p domain. The proposed method is closer to the actual sea conditions, offers an improved deghosting operator, removes the ghost reflections from marine towed seismic data, widens the bandwidth and restores the low-frequency information, and finally improves the signal-to- noise ratio and resolution of the seismic data. 展开更多
关键词 deghosting τ/p transform submarine tow cable sea surface reflection coefficient
下载PDF
Passively Mode Locked Diode-End-Pumped Yb∶YAB Laser with High Reflectivity Type Semiconductor Saturable Absorption Mirror 被引量:1
5
作者 王勇刚 马骁宇 +3 位作者 薛迎红 孙虹 张志刚 王清月 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2005年第2期250-253,共4页
A novel high reflectivity type of semiconductor saturable absorption mirror grown by metal organic chemical vapor deposition is presented.Using the mirror as well as an end mirror,passively mode locked Yb∶YAB laser i... A novel high reflectivity type of semiconductor saturable absorption mirror grown by metal organic chemical vapor deposition is presented.Using the mirror as well as an end mirror,passively mode locked Yb∶YAB laser is realized,which produces a pulse as short as 3 05ps at 1 044μm.The pulse frequency is 375MHz;the output power is 45mW. 展开更多
关键词 Yd∶YAB high reflectivity SESAM
下载PDF
液晶智能超表面辅助的室内可见光通信系统优化设计
6
作者 余礼苏 吕欣欣 +3 位作者 钟润 张鸣莉 王正海 王玉皞 《工程科学学报》 EI 北大核心 2025年第2期307-314,共8页
可见光通信(VLC)作为6G的候选技术,具备广阔的免许可频谱、更高的安全级别、避免射频干扰等诸多优势,这些特点使得VLC成为射频通信的有效补充方案.本文设计并优化了一种基于功率域非正交多址(PD-NOMA)技术的室内VLC下行链路通信系统,该... 可见光通信(VLC)作为6G的候选技术,具备广阔的免许可频谱、更高的安全级别、避免射频干扰等诸多优势,这些特点使得VLC成为射频通信的有效补充方案.本文设计并优化了一种基于功率域非正交多址(PD-NOMA)技术的室内VLC下行链路通信系统,该系统中包括一块位于信道中间的同时透射和反射智能超表面(STAR-RIS)和一个基于液晶智能超表面(LC-RIS)的接收器.为了评估所设计的系统性能,本文提出了一个和速率最大化问题,并考虑了实际情况下发射机和接收机之间的视距(LoS)路径存在非用户遮挡因素.由于所提出优化问题的非凸性,首先使用二次变换将目标函数转化为一个分式规划(FP)问题,其次采用分步优化算法和凸优化(CVX)工具来获得可行解.此外,本文分析了发光二极管(LED)的数量、入射光波长以及液晶折射率对室内可见光通信系统和速率的影响.数值仿真结果表明,在能量分裂(ES)操作协议下,STAR-RIS和LC-RIS联合辅助的室内VLC系统的和速率明显高于仅有反射智能超表面(RIS)和无LC-RIS的VLC系统.LED灯数量、入射光波长以及液晶(LC)折射率均会在一定程度上对系统性能产生影响.这些研究结果为室内可见光通信系统的设计和优化提供了重要参考. 展开更多
关键词 可见光通信 同时透射和反射智能超表面 液晶智能超表面 功率域非正交多址 分式规划
下载PDF
改进暗通道原理下视觉图像光晕消除算法
7
作者 任晓楠 李广 《现代电子技术》 北大核心 2025年第1期60-64,共5页
在光晕区域附近进行光晕消除操作可能会降低图像的对比度、清晰度和细节。因此,需要开发有效的方法来恢复和增强光晕消除后的图像细节,以确保整体图像质量的提高,为此设计一种改进暗通道原理下视觉图像光晕消除算法。建立大气散射模型... 在光晕区域附近进行光晕消除操作可能会降低图像的对比度、清晰度和细节。因此,需要开发有效的方法来恢复和增强光晕消除后的图像细节,以确保整体图像质量的提高,为此设计一种改进暗通道原理下视觉图像光晕消除算法。建立大气散射模型深度分析光晕产生条件,根据图像中的像素强度值计算成像环境中的透射率,按照大气光照的散射系数建立光照条件研究模型。在较高的像素颜色通道条件下,根据图像中高亮度和强反射部分搭建无光晕图像亮通道定义,聚类图像亮通道特征,利用快速双边滤波器细化透射率,建立光晕图像的成像模型。在改进暗通道原理的过程中通过调整多个计算参数,包括改变权重函数,设置光晕消除的恢复指令,完成对视觉图像的光晕消除处理。经过实验分析可以证明,所提方法具备良好的光晕消除性能,光晕消除效果较好。 展开更多
关键词 改进暗通道 视觉图像 光晕消除 透射率 多尺度算法 大气散射模型
下载PDF
智能超表面辅助的通感一体化性能优化
8
作者 庄宏成 卢浩宇 +2 位作者 钭奕煊 陈曾平 庞高昆 《中山大学学报(自然科学版)(中英文)》 CAS 北大核心 2025年第1期83-92,共10页
为了解决因障碍物等遮挡导致的覆盖空洞和探测精度下降问题,提出了一种基于栅格化的智能超表面辅助的通感一体化优化方法。首先,建模了最小化均方位置误差问题,将弱通感区域和RIS可能部署区域栅格化以降低计算难度,并采用粒子群优化算... 为了解决因障碍物等遮挡导致的覆盖空洞和探测精度下降问题,提出了一种基于栅格化的智能超表面辅助的通感一体化优化方法。首先,建模了最小化均方位置误差问题,将弱通感区域和RIS可能部署区域栅格化以降低计算难度,并采用粒子群优化算法和交替优化算法联合优化智能超表面期望反射角角度和部署位置。最后,引入探测需求因子,建模通感性能联合优化问题,并分析了探测需求因子对系统通感性能的影响。仿真结果显示:(1)相较于仅优化期望反射角,联合优化智能超表面的期望反射角和部署位置的方案,在平均信噪比仅有略微下降的情况下,可显著降低平均均方位置误差,平均均方位置误差降低10倍左右;(2)不同尺寸大小的智能超表面会对其最佳部署位置有影响;(3)联合优化智能超表面的期望反射角和部署位置提高了探测精度,最大化了通感整体性能。 展开更多
关键词 智能超表面 通感一体化 6G 期望反射角 部署位置
下载PDF
五星教学模式在方剂学中的运用
9
作者 柳琳 张智华 +4 位作者 李德顺 吕银娟 王世友 曹秋实 刘哲 《中国中医药现代远程教育》 2025年第2期41-44,共4页
针对学生学习方剂学主动性不高、兴趣不强、学习方法不当等问题,作者尝试将“五星教学模式”融入现有的教学中,以期改变这一现状。实践表明,通过五星教学模式的聚焦问题、激活旧知、示证新知、应用新知、融会贯通五个环节,有助于激发学... 针对学生学习方剂学主动性不高、兴趣不强、学习方法不当等问题,作者尝试将“五星教学模式”融入现有的教学中,以期改变这一现状。实践表明,通过五星教学模式的聚焦问题、激活旧知、示证新知、应用新知、融会贯通五个环节,有助于激发学生学习兴趣、改善学习方法、提升学习能力及“主动学习”意识,亦能发挥教师的“有效教学”,提升教学质量,对方剂学教学改革发展具有重要意义。 展开更多
关键词 五星教学模式 方剂学 教学改革 教学反思
下载PDF
Reflectivity Measurement of Weak Fiber Bragg Grating (FBG) 被引量:3
10
作者 郭会勇 ZHENG Yu +4 位作者 TANG Jianguan LI Xiaofu YU Haihu WEN Hongqiao JIANG Deshcng 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2012年第6期1177-1179,共3页
One method based on the end-face reflection as a reference was used to measure weak grating reflectivity of 0.01%-1%. For measuring ultra-weak grating reflectivity, the grating group with an identical wavelength was u... One method based on the end-face reflection as a reference was used to measure weak grating reflectivity of 0.01%-1%. For measuring ultra-weak grating reflectivity, the grating group with an identical wavelength was used. By using anhydrous alcohol and deionized water as the reflecting medium, the single- pulse FBG reflectivity of a highly doped-Ge photosensitive fiber was calculated to be about 0.747% and 0.739%, respectively; and the single-pulse FBG reflectivity of ordinary SMF fiber was about 0.016% and 0.015%, respectively. The consistent results by the two different reflecting media showed that the end-face reflection method on the grating group was feasible. 展开更多
关键词 reflectivity measurement weak FBG end-face reflection
下载PDF
Study on the Electromagnetic Interference of CFRC Composites by Reflectivity 被引量:3
11
作者 Kezhi LI Chuang WANG Hejun LI Gengsheng JIAO Jian WEI 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2008年第2期265-271,共7页
The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites (CFRC) on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the ... The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites (CFRC) on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the CFRC samples was observed with a scanning electron microscope (SEM). The electromagnetic interference (EMI) was evaluated indirectly by reflectivity in the Naval Research Laboratory (NRL) testing system. The reflectivity of the electromagnetic radiation by the composites was measured in the frequency range of 8.0- 18.2 GHz for different carbon fiber contents of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% (in wt pct), respectively. The results showed that the reflectivity decreased with the growing fiber content till the percentage of 0.6%. The minimum reflectivity was -23 dB, far less than -10 dB, and the composites were strong wave absorbers. After this percentage, the curve increased abruptly as the fiber content proceeded. The electromagnetic waves were gradually reflected. When the fiber content reached 1.0% finally, the maximum reflectivity -7.5 dB appeared and there was stronger reflection. The shielding mechanism includes mainly reflection, absorption, and multiple reflections. 展开更多
关键词 Carbon fibers CEMENT-BASED Electromagnetic interference reflectivity
下载PDF
Relationship between Cloud Characteristics and Radar Reflectivity Based on Aircraft and Cloud Radar Co-observations 被引量:3
12
作者 宗蓉 刘黎平 银燕 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2013年第5期1275-1286,共12页
Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the... Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the millimeter-wavelength cloud radar vertically scanned the same cloud that the aircraft penetrated. The reflectivity factor calculated from aircraft measurements was compared in detail with sinmltaneous radar observations. The results showed that the two reflectivities were comparable in warm clouds, but in ice cloud there were more differences, which were probably associated with the occurrence of liquid water. The acceptable agreement between reflectivities obtained in water cloud confirmed that it is feasible to derive cloud properties by using aircraft data, and hence for cloud radar to remotely sense cloud properties. Based on the dataset collected in warm clouds, the threshold of reflectivity to diagnose drizzle and cloud particles was studied by analyses of the probability distribution function of reflectivity from cloud particles and drizzle drops. The relationship between refiectivity factor (Z) and cloud liquid water content (LWC) was also derived from data on both cloud particles and drizzle. In comparison with cloud droplets, the relationship for drizzle was blurred by many scatter points and thus was less evident. However, these scatters could be partly removed by filtering out the drop size distribution with a large ratio of reflectivity and large extinction coefficient but small effective radius. Empirical relationships of Z-LWC for both cloud particles and drizzle could then be derived. 展开更多
关键词 AIRCRAFT millimeter wavelength cloud radar droplet size distribution reflectivity liquid water content
下载PDF
Reflectivity forward modeling and a CSSI method seismic inversion study of igneous intrusive area,coked area,and gas-enriched area located within a coal seam 被引量:18
13
作者 XU Yong-zhong CUI Ruo-fei +3 位作者 HUANG Wei-chuan CHEN Tong-jun CHEN Shi-zhong DONG Shou-hua 《Mining Science and Technology》 EI CAS 2009年第4期457-462,共6页
We applied the reflectivity method and the constrained sparse spike inverse modeling(CSSI) method to the interpretation of coal field lithologic seismic data.After introducing the principles of these two methods we di... We applied the reflectivity method and the constrained sparse spike inverse modeling(CSSI) method to the interpretation of coal field lithologic seismic data.After introducing the principles of these two methods we discuss some parameters of a geological model involving possible gas enriched areas or intruded igneous rock.The geological model was constructed and a 60 Hz seismic response profile was obtained looking for igneous rock intrusion and coked areas of the coal seam using the reflectivity method.Starting from synthesized logging data from two wells and a synthesized seismic wavelet we calibrated the model to show accurate strata.Finally,we predicted the lithology within a 10 m igneous rock area,a 3 m coal seam area,and a coked area using the CSSI technique.The results show that the CSSI technique can identify hard to recognize lithologic features that normal profil-ing methods might miss.It can quantitatively analyze and evaluate the intrusive area,the coked area,and the gas-enriched area. 展开更多
关键词 CSSI reflectivity method igneous rock coal seam coked area gas-enriched area
下载PDF
Measurement of inner surface roughness of capillary by an x-ray reflectivity method 被引量:1
14
作者 李玉德 林晓燕 +2 位作者 谭植元 孙天希 刘志国 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第4期217-221,共5页
The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope (AFM). The roughness ... The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope (AFM). The roughness measured by this new method can reach the order of angstroms with high quality capillaries. 展开更多
关键词 inner surface roughness reflectivity method CAPILLARY
下载PDF
Influence of Silica Fume on the Reflectivity and Transmission Efficiency of Cement-Based Materials 被引量:2
15
作者 Xiuzhi Zhang Guodong Zhang +1 位作者 Yu Zhang Zonghui Zhou 《Journal of Applied Mathematics and Physics》 2014年第9期843-847,共5页
As a kind of mineral admixture, silica fume has low permittivity, which will affect the electromagnetic properties of cement-based materials. To study the effect of silica fume on the properties of cement-based materi... As a kind of mineral admixture, silica fume has low permittivity, which will affect the electromagnetic properties of cement-based materials. To study the effect of silica fume on the properties of cement-based materials, the reflectivity, transmission efficiency and pore structure were analyzed by using the vector network analyzer and mercury injection apparatus. Results show that silica fume can make the mortar more compact and the porosity of sample with 9% silica fume is only 17.8%, which is far lower than the control sample;With the increase of the silica fume content, the peak of reflectivity curve increases from -23.2 dB to -16.0 dB, and then decreases from -16.04 dB to -28.7 dB in the frequency range of 6 – 18 GHz. Reflectivity of sample with 3% content of silica fume is lower than other samples within 26.5 - 40 GHz;Transmission efficiency of samples shows the trend of increase with silica fume content increases from 0% to 6% within 8.2 - 12.4 GHz, 12 - 18 GHz and 26.5 - 40 GHz, but when the content increases from 6% to 9%, the transmission efficiency of samples reduces. 展开更多
关键词 SILICA Fume CEMENT-BASED MATERIALS reflectivity TRANSMISSION EFFICIENCY
下载PDF
Prestack AVA joint inversion of PP and PS waves using the vectorized reflectivity method 被引量:1
16
作者 Liu Wei Wang Yan-Chun +2 位作者 Li Jing-Ye Liu Xue-Qing Xie Wei 《Applied Geophysics》 SCIE CSCD 2018年第3期448-465,共18页
Most current prestack AVA joint inversion methods are based on the exact Zoeppritz equation and its various approximations. However, these equations only reflect the relation between reflection coefficients, incidence... Most current prestack AVA joint inversion methods are based on the exact Zoeppritz equation and its various approximations. However, these equations only reflect the relation between reflection coefficients, incidence angles, and elastic parameters on either side of the interface, which means that wave-propagation effects, such as spherical spreading, attenuation, transmission loss, multiples, and event mismatching of P-and S-waves, are not considered and cannot accurately describe the true propagation characteristics of seismic waves. Conventional AVA inversion methods require that these wave-propagation effects have been fully corrected or attenuated before inversion but these requirements can hardly be satisfied in practice. Using a one-dimensional(1 D) earth model, the reflectivity method can simulate the full wavefield response of seismic waves. Therefore, we propose a nonlinear multicomponent prestack AVA joint inversion method based on the vectorized reflectivity method, which uses a fast nondominated sorting genetic algorithm(NSGA II) to optimize the nonlinear multiobjective function to estimate multiple parameters, such as P-wave velocity, S-wave velocity, and density. This approach is robust because it can simultaneously cope with more than one objective function without introducing weight coefficients. Model tests prove the effectiveness of the proposed inversion method. Based on the inversion results, we find that the nonlinear prestack AVA joint inversion using the reflectivity method yields more accurate inversion results than the inversion by using the exact Zoeppritz equation when the wave-propagation effects of transmission loss and internal multiples are not completely corrected. 展开更多
关键词 reflectivity METHOD fast nondominated SORTING GENETIC algorithm multiple parameters PRESTACK AVA joint INVERSION
下载PDF
Study on the Relation Between the Reflectivity and Frequency in Dusty Plasma of the Polar Summer Mesopause 被引量:1
17
作者 李海龙 吴健 +1 位作者 黄际英 王茂琰 《Plasma Science and Technology》 SCIE EI CAS CSCD 2009年第3期279-282,共4页
Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes (PMSE) is studied using the small-scale structure of electron density caused by charged dust particles. A theoreti... Relation between the volume reflectivity and frequency in view of the polar mesosphere summer echoes (PMSE) is studied using the small-scale structure of electron density caused by charged dust particles. A theoretical expression for the radar volume reflectivity is derived, which agrees with the statistical result. Both the theoretical and statistical results are confirmed with the data obtained from simultaneous observations at three frequencies. Hence the small-scale structure caused by charged dust particles may be a useful tool for the study on the generation mechanism of PMSE. 展开更多
关键词 polar mesosphere summer echoes reflectivity dusty plasma DUST
下载PDF
Spectral dispersion of cloud droplet size distributions and radar threshold reflectivity for drizzle 被引量:1
18
作者 解小宁 刘晓东 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第10期659-662,共4页
From first principles, we find that the radar threshold reflectivity between nonprecipitating clouds and precipitating clouds is strongly related to not only the cloud droplet number concentration but also the spectra... From first principles, we find that the radar threshold reflectivity between nonprecipitating clouds and precipitating clouds is strongly related to not only the cloud droplet number concentration but also the spectral dispersion of cloud droplet size distributions. The further investigation indicates that the threshold value is an increasing function of spectral dispersion and cloud droplet number concentration. These results may improve our understanding of the cloud-precipitation interaction and the aerosol indirect effect. 展开更多
关键词 radar threshold reflectivity spectral dispersion cloud droplet number concentration
下载PDF
In-situ wafer bowing measurements of GaN grown on Si(111) substrate by reflectivity mapping in metal organic chemical vapor deposition system 被引量:1
19
作者 杨亿斌 柳铭岗 +12 位作者 陈伟杰 韩小标 陈杰 林秀其 林佳利 罗慧 廖强 臧文杰 陈崟松 邱运灵 吴志盛 刘扬 张佰君 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第9期362-366,共5页
In this work, the wafer bowing during growth can be in-situ measured by a reflectivity mapping method in the 3×2 Thomas Swan close coupled showerhead metal organic chemical vapor deposition(MOCVD) system. The r... In this work, the wafer bowing during growth can be in-situ measured by a reflectivity mapping method in the 3×2 Thomas Swan close coupled showerhead metal organic chemical vapor deposition(MOCVD) system. The reflectivity mapping method is usually used to measure the film thickness and growth rate. The wafer bowing caused by stresses(tensile and compressive) during the epitaxial growth leads to a temperature variation at different positions on the wafer, and the lower growth temperature leads to a faster growth rate and vice versa. Therefore, the wafer bowing can be measured by analyzing the discrepancy of growth rates at different positions on the wafer. Furthermore, the wafer bowings were confirmed by the ex-situ wafer bowing measurement. High-resistivity and low-resistivity Si substrates were used for epitaxial growth. In comparison with low-resistivity Si substrate, Ga N grown on high-resistivity substrate shows a larger wafer bowing caused by the highly compressive stress introduced by compositionally graded Al Ga N buffer layer. This transition of wafer bowing can be clearly in-situ measured by using the reflectivity mapping method. 展开更多
关键词 stresses metal organic chemical vapor deposition wafer bowing in-situ reflectivity mapping
下载PDF
Short-duration transient visual evoked potentials and color reflectivity discretization analysis in glaucoma patients and suspects 被引量:1
20
作者 Michael Waisbourd Rebekah H.Gensure +7 位作者 Ardalan Aminlari Sonya B.Shah Nitasha Khanna Neil Sood Jeanne Molineaux Alberto Gonzalez Jonathan S.Myers L.Jay Katz 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2017年第2期254-261,共8页
AIM: To evaluate the use of short-duration transient visual evoked potentials(VEP) and color reflectivity discretization analysis(CORDA) in glaucomatous eyes,eyes suspected of having glaucoma,and healthy eyes.MET... AIM: To evaluate the use of short-duration transient visual evoked potentials(VEP) and color reflectivity discretization analysis(CORDA) in glaucomatous eyes,eyes suspected of having glaucoma,and healthy eyes.METHODS: The study included 136 eyes from 136 subjects: 49 eyes with glaucoma,45 glaucoma suspect eyes,and 42 healthy eyes.Subjects underwent Humphrey visual field(VF) testing,VEP testing,as well as peripapillary retinal nerve fiber layer optical coherence tomography imaging studies with post-acquisition CORDA applied.Statistical analysis was performed using means and ranges,ANOVA,post-hoc comparisons using Turkey's adjustment,Fisher's Exact test,area under the curve,and Spearman correlation coefficients.RESULTS: Parameters from VEP and CORDA correlated significantly with VF mean deviation(MD)(P〈0.05).In distinguishing glaucomatous eyes from controls,VEP demonstrated area under the curve(AUC) values of 0.64-0.75 for amplitude and 0.67-0.81 for latency.The CORDA HR1 parameter was highly discriminative for glaucomatous eyes vs controls(AUC=0.94).CONCLUSION: Significant correlations are found between MD and parameters of short-duration transient VEP and CORDA,diagnostic modalities which warrant further consideration in identifying glaucoma characteristics. 展开更多
关键词 short-duration transient visual evoked potentials optical coherence tomography color reflectivity discretization analysis GLAUCOMA
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部