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由煤岩变形冲击破坏所产生的电磁辐射 被引量:78
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作者 窦林名 何学秋 +1 位作者 王恩元 谷德钟 《清华大学学报(自然科学版)》 EI CAS CSCD 北大核心 2001年第12期86-88,共3页
对岩石破裂所产生的电磁辐射现象的观测和研究 ,对于研究地震规律和矿山冲击矿压及其预报具有重要的意义。在实验室和现场条件下 ,采用 EAE- 0 4声电测试系统和KBD5电磁辐射监测仪对煤岩变形破裂过程中的电磁辐射进行了测定。试验和测... 对岩石破裂所产生的电磁辐射现象的观测和研究 ,对于研究地震规律和矿山冲击矿压及其预报具有重要的意义。在实验室和现场条件下 ,采用 EAE- 0 4声电测试系统和KBD5电磁辐射监测仪对煤岩变形破裂过程中的电磁辐射进行了测定。试验和测试结果表明 ,煤岩体在变形、破坏过程中均产生电磁辐射现象 ;煤岩在冲击破坏前 ,电磁辐射强度一般在某个值以下 ,而在冲击破坏时 ,电磁辐射强度突然增加 ;而电磁辐射的脉冲数则随载荷的增加及变形破裂过程的发展而增大。依此规律 ,可以对冲击矿压危险性进行评价和预测预报。 展开更多
关键词 煤岩冲击破坏 冲击矿压 电磁辐射辐射 强度 辐射脉冲 岩体变形
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具有不依赖于状态脉冲的双曲型偏微分方程的振动准则 被引量:37
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作者 张立琴 《数学学报(中文版)》 SCIE CSCD 北大核心 2000年第1期17-26,共10页
本文研究脉冲双曲型偏微分方程解的振动性质.得到了两类具有不依赖于状态脉冲的双曲边值问题的若干振动准则.
关键词 振动准则 双曲型方程 状态脉冲 边值问题
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基于ICP传感器的存储式冲击波超压测试系统 被引量:38
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作者 王代华 宋林丽 张志杰 《传感技术学报》 CAS CSCD 北大核心 2012年第4期478-482,共5页
针对冲击波超压测试方法不足的现状,采用存储测试原理进行了冲击波超压测试系统设计。对比了不同类型压力传感器的优缺点,选用性能优良的ICP压力传感器并配套设计了驱动电路和信号调理电路。采用单片机和CPLD进行数字逻辑电路的集成设计... 针对冲击波超压测试方法不足的现状,采用存储测试原理进行了冲击波超压测试系统设计。对比了不同类型压力传感器的优缺点,选用性能优良的ICP压力传感器并配套设计了驱动电路和信号调理电路。采用单片机和CPLD进行数字逻辑电路的集成设计,提高测试系统的智能化和可靠性并减小系统体积。系统标定后参加了多次实弹测试试验,验证了其可靠性和有效性。文中给出了某型弹的冲击波超压测试曲线、正压持续时间和冲量数据。 展开更多
关键词 存储测试 冲击波 超压 冲量 ICP传感器
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基于小波变换的电能质量扰动信号的检测 被引量:35
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作者 储珺 马建伟 《电力系统保护与控制》 EI CSCD 北大核心 2009年第5期34-36,64,共4页
为对电能质量进行有效的治理,提高用电效率,有必要对扰动信号进行实时检测和定位。针对当前电力系统存在的电能质量扰动信号中持续时间短、发生随机性大及不容易检测的特点,采用小波变换对电力系统的高频扰动、瞬时脉冲、电压切痕信号... 为对电能质量进行有效的治理,提高用电效率,有必要对扰动信号进行实时检测和定位。针对当前电力系统存在的电能质量扰动信号中持续时间短、发生随机性大及不容易检测的特点,采用小波变换对电力系统的高频扰动、瞬时脉冲、电压切痕信号进行检测。研究表明,该方法能够精确定位扰动信号产生的时刻和持续的时间,证实了该法的准确性和优越性。 展开更多
关键词 小波变换 瞬时脉冲 电压切痕 电能质量 检测
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冲量法谷物流量测量系统的试验研究 被引量:29
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作者 孙宇瑞 汪懋华 +1 位作者 马道坤 黄季平 《农业机械学报》 EI CAS CSCD 北大核心 2001年第4期48-50,共3页
根据精细农业研究的实际要求 ,首先在不考虑外部振动的情况下设计了一种基于冲量原理的谷物流量测量试验装置。该装置由自行研制的冲量传感器、数据采集器和谷物流动模拟箱体组成。试验结果表明 ,这种装置测量误差的绝对值小于 5 %。在... 根据精细农业研究的实际要求 ,首先在不考虑外部振动的情况下设计了一种基于冲量原理的谷物流量测量试验装置。该装置由自行研制的冲量传感器、数据采集器和谷物流动模拟箱体组成。试验结果表明 ,这种装置测量误差的绝对值小于 5 %。在此基础上又进行了谷物产量实时监测系统的试验研究 ,试验结果表明 ,在引入外部机械振动的情况下 ,经过滤波处理系统测量误差的绝对值小于 8%。 展开更多
关键词 冲量法 固体流量 测量系统 试验装置 谷物流量 在线测量 田间收获
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基于PWM的逆变电路分析 被引量:27
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作者 汤才刚 朱红涛 +1 位作者 李莉 陈国桥 《现代电子技术》 2008年第1期159-160,163,共3页
PWM控制技术是逆变电路中应用最广泛的技术。为了对PWM型逆变电路进行分析,从PWM控制的基本原理出发,首先建立了逆变器控制所需的电路模型,采用IGBT作为开关器件,并对单相桥式电压型逆变电路和PWM控制电路的工作原理进行了分析。使用双... PWM控制技术是逆变电路中应用最广泛的技术。为了对PWM型逆变电路进行分析,从PWM控制的基本原理出发,首先建立了逆变器控制所需的电路模型,采用IGBT作为开关器件,并对单相桥式电压型逆变电路和PWM控制电路的工作原理进行了分析。使用双踪示波器对电路的输出波形进行分析,给出了仿真波形。实践表明:运用PWM控制技术能够很好地实现逆变电路的运行要求。 展开更多
关键词 脉宽调制 逆变电路 IGBT 脉冲
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Shear wave velocity is a useful marker for managing nonalcoholic steatohepatitis 被引量:30
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作者 Akihiko Osaki Tomoyuki Kubota +11 位作者 Takeshi Suda Masato Igarashi Keisuke Nagasaki Atsunori Tsuchiya Masahiko Yano Yasushi Tamura Masaaki Takamura Hirokazu Kawai Satoshi Yamagiwa Toru Kikuchi Minoru Nomoto Yutaka Aoyagi 《World Journal of Gastroenterology》 SCIE CAS CSCD 2010年第23期2918-2925,共8页
AIM:To investigate whether a noninvasive measurement of tissue strain has a potential usefulness for management of nonalcoholic steatohepatitis(NASH).METHODS:In total 26 patients,23 NASHs and 3 normal controls were en... AIM:To investigate whether a noninvasive measurement of tissue strain has a potential usefulness for management of nonalcoholic steatohepatitis(NASH).METHODS:In total 26 patients,23 NASHs and 3 normal controls were enrolled in this study.NASH was staged based on Brunt criterion.At a region of interest(ROI),a shear wave was evoked by implementing an acoustic radiation force impulse(ARFI),and the propagation velocity was quantif ied.RESULTS:Shear wave velocity(SWV) could be reproducibly quantified at all ROIs in all subjects except for 4 NASH cases,in which a reliable SWV value was not calculated at several ROIs.An average SWV of 1.34 ± 0.26 m/s in fibrous stage 0-1 was significantly slower than 2.20 ± 0.74 m/s and 2.90 ± 1.01 m/s in stages 3 and 4,respectively,but was not significantly different from 1.79 ± 0.78 m/s in stage 2.When a cutoff value was set at 1.47 m/s,receiver operating characteristic analysis showed significance to dissociate stages 3 and 4 from stage 0-1(P=0.0092) with sensitivity,specificity and area under curve of 100%,75% and 94.2%,respectively.In addition,the correlation between SWV and hyaluronic acid was significant(P<0.0001),while a tendency toward negative correlation was observed with serum albumin(P=0.053).CONCLUSION:The clinical implementation of ARFI provides noninvasive repeated evaluations of liver stiffness at an arbitrary position,which has the potential to shed new light on NASH management. 展开更多
关键词 Nonalcoholic steatohepatitis ULTRASOUND Liver stiffness measurement Shear wave velocity Acoustic radiation force impulse
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约束大医院无限扩张的冲动——建立和谐医患关系的重中之重 被引量:29
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作者 杜治政 《医学与哲学》 北大核心 2005年第11S期1-5,共5页
医患关系紧张的原因首先是来自看病贵,而看病贵则主要源于大医院的无限急速扩张。约束大医院的无限扩张冲动,是建立和谐医患关系的重中之重。
关键词 约束 无限扩张 冲动 大医院
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Evaluation of acoustic radiation force impulse imaging for determination of liver stiffness using transient elastography as a reference 被引量:30
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作者 Gerald Kircheis Abdurrahman Sagir +3 位作者 Christoph Vogt Stephan vom Dahl Ralf Kubitz Dieter Hussinger 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第10期1077-1084,共8页
AIM: To evaluate cut-off values and performance of acoustic radiation force impulse imaging (ARFI) using transient elastography [FibroScan■ (FS)] as a reference. METHODS: Six hundred and six patients were enrolled in... AIM: To evaluate cut-off values and performance of acoustic radiation force impulse imaging (ARFI) using transient elastography [FibroScan■ (FS)] as a reference. METHODS: Six hundred and six patients were enrolled in this study.All patients underwent liver stiffness measurement with FS (FS-LS) and ARFI (with shear wave velocity quantification; ARFI-SWV) and the performance of ARFI in comparison to FS was determined. Sixtyeight patients underwent liver biopsy. RESULTS: Significantly higher success rates for the determination of liver stiffness were found using ARFI as compared to FS [604/606 (99.7%) vs 482/606 (79.5%); P < 0.001]. ARFI-SWV correlated significantly with FS-LS (r = 0.920, P < 0.001). ARFI-SWV increased significantly with the stage of fibrosis (1.09 ± 0.13 m/s for patients with no significant fibrosis (FS-LS < 7.6 kPa); 1.46 ± 0.27 m/s for patients with significant liver fibrosis (7.6 < FS-LS ≤ 13.0 kPa); and 2.55 ± 0.77 m/s for patients with liver cirrhosis (FS-LS > 13.0 kPa)). ARFI-SWV cut-off values were identified for no significant fibrosis (1.29 m/s; sensitivity 91.4% and specificity 92.6%) and for liver cirrhosis (1.60 m/s; sensitivity 92.3% and specificity 96.5%). The optimal cut-off value for predicting liver fibrosis (F ≥ 2) was 1.32 m/s (sensitivity 87.0% and specificity 80.0%) and for liver cirrhosis (F4) 1.62 m/s (sensitivity 100% and specificity 85.7%), for patients who underwent liver biopsy. An excellent inter-and intraobserver reproducibility was observed for ARFI-SWV determinations. CONCLUSION: An ARFI-SWV cut-off value of 1.29 m/s seems to be optimal for patients with no significant liver fibrosis and 1.60 m/s for patients with liver cirrhosis. 展开更多
关键词 Acoustic radiation force impulse imaging ELASTOGRAPHY FIBROSCAN LIVER
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Non-invasive diagnosis of hepatitis B virus-related cirrhosis 被引量:29
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作者 Sangheun Lee Do Young Kim 《World Journal of Gastroenterology》 SCIE CAS 2014年第2期445-459,共15页
Chronic hepatitis B(CHB)infection is a major public health problem associated with significant morbidity and mortality worldwide.Twenty-three percent of patients with CHB progress naturally to liver cirrhosis,which wa... Chronic hepatitis B(CHB)infection is a major public health problem associated with significant morbidity and mortality worldwide.Twenty-three percent of patients with CHB progress naturally to liver cirrhosis,which was earlier thought to be irreversible.However,it is now known that cirrhosis can in fact be reversed by treatment with oral anti-nucleotide drugs.Thus,early and accurate diagnosis of cirrhosis is important to allow an appropriate treatment strategy to be chosen and to predict the prognosis of patients with CHB.Liver biopsy is the reference standard for assessment of liver fibrosis.However,the method is invasive,and is associated with pain and complications that can be fatal.In addition,intra-and inter-observer variability compromises the accuracy of liver biopsy data.Only small tissue samples are obtained and fibrosis is heterogeneous in such samples.This confounds the two types of observer variability mentioned above.Such limitations have encouraged development of non-invasive methods for assessment of fibrosis.These include measurements of serum biomarkers of fibrosis;and assessment of liver stiffness via transient elastography,acoustic radiation force impulse imaging,real-time elastography,or magnetic resonance elastography.Although significant advances have been made,most work to date has addressed the diagnostic utility of these techniques in the context of cirrhosis caused by chronic hepatitis C infection.In the present review,we examine the advantages afforded by use of non-invasive methods to diagnose cirrhosis in patients with CHB infections and the utility of such methods in clinical practice. 展开更多
关键词 Chronic liver disease Chronic hepatitis B Hepatitis B virus CIRRHOSIS Liver stiffness measurement Transient elastography Acoustic radiation force impulse imaging Real-time elastography Magnetic resonance elastography FibroTest Aspartate aminotransferase to platelet ratio index
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检测变压器绕组变形的低压脉冲法的研究 被引量:19
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作者 秦少臻 王钰 +1 位作者 李彦明 张成良 《变压器》 北大核心 1997年第7期24-29,共6页
对变压器绕组变形的低压脉冲检测法进行了研究。简要介绍了低压脉冲法检测绕组变形的基本原理,对影响低压脉冲法检测变压器绕组变形测试结果的因素进行了考察,并利用测试系统对模拟不同部位、不同种类变形故障的模型变压器进行了测试... 对变压器绕组变形的低压脉冲检测法进行了研究。简要介绍了低压脉冲法检测绕组变形的基本原理,对影响低压脉冲法检测变压器绕组变形测试结果的因素进行了考察,并利用测试系统对模拟不同部位、不同种类变形故障的模型变压器进行了测试,提出可根据变压器绕组时域响应波形的畸变及变压器传递函数频谱图的变化来判断变压器绕组是否发生变形故障。 展开更多
关键词 变压器 绕组 变形 检测 低压 脉冲
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美国经济周期稳定化研究述评 被引量:25
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作者 曹永福 《经济研究》 CSSCI 北大核心 2007年第7期152-158,共7页
近50年来美国经济周期出现了稳定化的趋势,其中二战之后经济周期的波动性比二战之前有明显下降,20世纪80年代中期之后比80年代之前亦有显著下降。引起这种经济周期稳定化的原因是多方面的,美国宏观经济学界对这一现象展开了热烈的讨论... 近50年来美国经济周期出现了稳定化的趋势,其中二战之后经济周期的波动性比二战之前有明显下降,20世纪80年代中期之后比80年代之前亦有显著下降。引起这种经济周期稳定化的原因是多方面的,美国宏观经济学界对这一现象展开了热烈的讨论。本文对该领域的主要文献进行了梳理,对不同的观点进行了比较,并从美国的争论中得出了对中国有借鉴意义的启示。 展开更多
关键词 经济周期 稳定化 外部冲击 传导机制
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水下爆炸冲击波数值模拟的网格尺寸确定方法 被引量:27
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作者 张社荣 李宏璧 +1 位作者 王高辉 孔源 《振动与冲击》 EI CSCD 北大核心 2015年第8期93-100,共8页
网格尺寸对水下爆炸冲击波传播过程的数值模拟精度有较大影响,且不同当量下可接受的网格尺寸也有较大区别。通过研究不同比例爆炸距离处水下爆炸冲击波峰值、比冲量对有限元网格尺寸的依赖性,以"炸药半径与网格尺寸之比"作为... 网格尺寸对水下爆炸冲击波传播过程的数值模拟精度有较大影响,且不同当量下可接受的网格尺寸也有较大区别。通过研究不同比例爆炸距离处水下爆炸冲击波峰值、比冲量对有限元网格尺寸的依赖性,以"炸药半径与网格尺寸之比"作为网格尺寸划分依据,提出了一种对不同当量均具有较强适用性的网格尺寸确定方法;对数值结果的误差分析表明,采用炸药半径的1/3作为数值模型的网格尺寸,其计算精度可满足工程要求;同时通过对数值计算误差进行非线性拟合,得到了不同网格尺寸下冲击波峰值压力、比冲量的误差估计式,可为研究人员根据可接受的误差范围确定任意当量下合适的网格尺寸或估计数值计算的整体误差提供参考。 展开更多
关键词 网格尺寸效应 峰值压力 比冲量 炸药量 比例爆炸距离
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TNT、PBX和Hexel空中爆炸冲击波参数的实验研究 被引量:26
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作者 王建灵 郭炜 冯晓军 《火炸药学报》 EI CAS CSCD 2008年第6期42-44,68,共4页
利用空中爆炸测试系统,对相同质量不同密度不同装药的TNT、PBX和Hexel进行了空中爆炸参数测试。比较了3种炸药在相同测点处的冲击波峰值超压和冲量的大小。研究了冲击波峰值超压和冲量与比例距离的关系。结果显示,TNT的冲击波峰值超压... 利用空中爆炸测试系统,对相同质量不同密度不同装药的TNT、PBX和Hexel进行了空中爆炸参数测试。比较了3种炸药在相同测点处的冲击波峰值超压和冲量的大小。研究了冲击波峰值超压和冲量与比例距离的关系。结果显示,TNT的冲击波峰值超压和冲量明显低于PBX和Hexel;在比例距离(1.8~4.9)m/kg1/3范围内,Hexel的冲击波峰值超压和冲量高于PBX。当比例距离为6.1m/kg1/3时,Hexel的冲击波峰值超压和冲量与PBX相当。 展开更多
关键词 爆炸力学 冲击波 冲击波峰值超压 TNT PBX Hexel 冲量
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航空重力数据窗函数法FIR低通数字滤波试验 被引量:25
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作者 郭志宏 罗锋 安战锋 《物探与化探》 CAS CSCD 2007年第6期568-571,576,共5页
采用窗函数法FIR低通数字滤波方法,对GT-1A型航空重力系统的测量数据进行了滤波试验研究,获得了一些有意义的结果。试验结果表明,通过选择合适窗形、窗口长度和滤波参数,窗函数法FIR低通数字滤波器是可以在航空重力数据的低通数字滤波... 采用窗函数法FIR低通数字滤波方法,对GT-1A型航空重力系统的测量数据进行了滤波试验研究,获得了一些有意义的结果。试验结果表明,通过选择合适窗形、窗口长度和滤波参数,窗函数法FIR低通数字滤波器是可以在航空重力数据的低通数字滤波处理中发挥应有的作用,获得满意的效果。 展开更多
关键词 航空重力 窗函数法 FIR(Finite impulse Response) 低通数字滤波
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Is ARFI elastography reliable for predicting fibrosis severity in chronic HCV hepatitis? 被引量:24
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作者 Ioan Sporea Roxana Sirli +6 位作者 Simona Bota Carmen Fierbinteanu-Braticevici Alina Popescu Radu Badea Monica Lupsor Ana Petrisor Mirela Dnil 《World Journal of Radiology》 CAS 2011年第7期188-193,共6页
AIM:To determine whether acoustic radiation force impulse(ARFI) elastography is a reliable method for predicting fibrosis severity in patients with chronic hepatitis C virus(HCV) hepatitis.METHODS:We performed a multi... AIM:To determine whether acoustic radiation force impulse(ARFI) elastography is a reliable method for predicting fibrosis severity in patients with chronic hepatitis C virus(HCV) hepatitis.METHODS:We performed a multicenter study including 274 subjects with HCV chronic hepatitis in which we compared ARFI with liver biopsy(LB).In each patient we performed LB(evaluated according to the Metavir score) and ARFI measurements(using a Siemens Acuson S2000TM ultrasound system:10 valid measurements were performed and median values were calculated and expressed in meters/second(m/s).RESULTS:A direct,strong,correlation(Spearman r = 0.707) was found between ARFI measurements and fibrosis(P < 0.0001).For predicting the presence of fibrosis(F ≥ 1 Metavir),significant fibrosis(F ≥ 2),severe fibrosis(F ≥ 3) and cirrhosis(F = 4),the cutoff values of 1.19,1.21,1.58 and 1.82 m/s were determined,respectively,liver stiffness measurements had 73%,84%,84% and 91% Se respectively;93%,91%,94%,90% Sp,respectively;with AUROCs of 0.880,0.893,0.908 and 0.937,respectively.CONCLUSION:ARFI measurement is a reliable method for predicting the severity of fibrosis in HCV 展开更多
关键词 Acoustic radiation force impulse ELASTOGRAPHY CHRONIC HCV HEPATITIS Cirrhosis LIVER FIBROSIS LIVER stiffness
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ARFI elastography for the evaluation of diffuse thyroid gland pathology:Preliminary results 被引量:25
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作者 Ioan Sporea Roxana Sirli +3 位作者 Simona Bota Mihaela Vlad Alina Popescu Ioana Zosin 《World Journal of Radiology》 CAS 2012年第4期174-178,共5页
AIM: To assess whether acoustic radiation force impulse (ARFI) elastography can differentiate normal from pathological thyroid parenchyma. METHODS: We evaluated 136 subjects (mean age 45.8 ± 15.6 years, 106 women... AIM: To assess whether acoustic radiation force impulse (ARFI) elastography can differentiate normal from pathological thyroid parenchyma. METHODS: We evaluated 136 subjects (mean age 45.8 ± 15.6 years, 106 women and 30 men): 44 (32.3%) without thyroid pathology, 48 (35.3%) with Basedow-Graves’ disease (GD), 37 (27.2%) with chronic autoimmune thyroiditis (CAT; diagnosed by specific tests), 4 (2.9%) with diffuse thyroid goiter and 3 (2.2%) cases with thyroid pathology induced by amiodarone. In all patients, 10 elastographic measurements were made in the right thyroid lobe and 10 in the left thyroid lobe, using a 1-4.5 MHZ convex probe and a 4-9 MHz linear probe, respectively. Median values were calculated for thyroid stiffness and expressed in meters/second (m/s). RESULTS: Thyroid stiffness (TS) assessed by means of ARFI in healthy subjects (2 ± 0.40 m/s) was significantly lower than in GD (2.67 ± 0.53 m/s) (P < 0.0001) and CAT patients (2.43 ± 0.58 m/s) (P = 0.0002), but the differences were not significant between GD vs CAT patients (P = 0.053). The optimal cut-off value for the prediction of diffuse thyroid pathology was 2.36 m/s. For this cut-off value, TS had 62.5% sensitivity, 79.5% specificity, 87.6% predictive positive value, 55.5% negative predictive value and 72.7% accuracy for the presence of diffuse thyroid gland pathology (AUROC = 0.804). There were no significant differences between the TS values obtained with linear vs convex probes and when 5 vs 10 measurements were taken in each lobe (median values). CONCLUSION: ARFI seems to be a useful method for the assessment of diffuse thyroid gland pathology. 展开更多
关键词 Acoustic radiation force impulse elastography Thyroid stiffness Thyroid pathology
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Characterization of focal liver masses using acoustic radiation force impulse elastography 被引量:23
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作者 Hana Park Jun Yong Park +4 位作者 Do Young Kim Sang Hoon Ahn Chae Yoon Chon Kwang-Hyub Han Seung Up Kim 《World Journal of Gastroenterology》 SCIE CAS 2013年第2期219-226,共8页
AIM:To investigate the diagnostic performance of acoustic radiation force impulse(ARFI) elastography for characterizing focal liver mass by quantifying their stiffness.METHODS:This prospective study included 62 patien... AIM:To investigate the diagnostic performance of acoustic radiation force impulse(ARFI) elastography for characterizing focal liver mass by quantifying their stiffness.METHODS:This prospective study included 62 patients with a focal liver mass that was well visualized on conventional ultrasonography performed in our institution from February 2011 to November 2011.Among them,12 patients were excluded for ARFI measurement failure due to a lesion that was smaller than the region of the interest and at an inaccessible location(deeper than 8 cm)(n = 7) or poor compliance to hold their breath as required(n = 5).Finally,50 patients with valid ARFI measurements were enrolled.If a patient had multiple liver masses,only one mass of interest was chosen.The masses were diagnosed by histological examination or clinical diagnostic criteria.During ultrasonographic evaluation,stiffness,expressed as velocity,was checked 10 times per focal liver mass and the surrounding liver parenchyma.RESULTS:After further excluding three masses that were non-diagnostic on biopsy,a total of 47 focal mass lesions were tested,including 39(83.0%) malignant masses [24 hepatocellular carcinomas(HCC),seven cholangiocellular carcinomas(CCC),and eight liver metastases] and eight(17.0%) benign masses(five hemangiomas and three focal nodular hyperplasias,FNH).Thirty-seven(74.0%) masses were confirmed by histological examination.The mean velocity was 2.48 m/s in HCCs,1.65 m/s in CCCs,2.35 m/s in metastases,1.83 m/s in hemangiomas,and 0.97 m/s in FNHs.Although considerable overlap was still noted between malignant and benign masses,significant differences in ARFI values were observed between malignant and benign masses(mean 2.31 m/s vs 1.51 m/s,P = 0.047),as well as between HCCs and benign masses(mean 2.48 m/s vs 1.51 m/s,P = 0.006).The areas under the receiver operating characteristics curves(AUROC) for discriminating the malignant masses from benign masses was 0.724(95%CI,0.566-0.883,P = 0.048),and the AUROC for discriminating HCCs from benign masses was 展开更多
关键词 Acoustic radiation force impulse FOCAL LIVER mass Hepatocellular CARCINOMA HEMANGIOMA FOCAL NODULAR HYPERPLASIA Cholangiocellular CARCINOMA LIVER metastasis
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Kagome点阵夹芯板的抗冲击性能研究 被引量:21
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作者 郑华勇 吴林志 +1 位作者 马力 王新筑 《工程力学》 EI CSCD 北大核心 2007年第8期86-92,共7页
Kagome点阵夹芯结构是近年来提出的一种力学性能十分优异的新型点阵夹芯结构。建立了3D-Kagome点阵夹芯板在理想冲击载荷作用下的分析模型,将含有大量周期性单胞的芯子等效为实体板,得到了Kagome芯子的等效本构关系,给出了芯子的等效强... Kagome点阵夹芯结构是近年来提出的一种力学性能十分优异的新型点阵夹芯结构。建立了3D-Kagome点阵夹芯板在理想冲击载荷作用下的分析模型,将含有大量周期性单胞的芯子等效为实体板,得到了Kagome芯子的等效本构关系,给出了芯子的等效强度和刚度。采用有限元方法模拟3D-Kagome夹芯板在理想冲击载荷作用下的响应,研究了板的最大挠度随芯子相对密度、芯子的厚度参数和冲击载荷大小的变化规律,得出了该结构抗冲击的最优化设计方案。与相同重量的实体板比较发现,3D-Kagome点阵夹芯板在抵抗冲击、能量吸收和耗散等方面具有很大的优势。 展开更多
关键词 工程力学 轻结构 点阵夹芯 KAGOME 冲击 优化设计
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OSCILLATION OF NONLINEAR IMPULSIVE PARABOLIC DIFFERENTIAL EQUATIONS WITH SEVERAL DELAYS 被引量:20
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作者 CuiChenpei ZouMin +1 位作者 LiuAnping XiaoLi 《Annals of Differential Equations》 2005年第1期1-7,共7页
In this paper, oscillatory properties for solutions of certain nonlinear impulsive parabolic equations with several delays are investigated and a series of new sufficient conditions for oscillations of the equation ar... In this paper, oscillatory properties for solutions of certain nonlinear impulsive parabolic equations with several delays are investigated and a series of new sufficient conditions for oscillations of the equation are established. 展开更多
关键词 impulse DELAY parabolic differential equation OSCILLATION NONLINEAR
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