期刊文献+
共找到776篇文章
< 1 2 39 >
每页显示 20 50 100
Measurement of T wave in magnetocardiography using tunnel magnetoresistance sensor
1
作者 陆知宏 纪帅 杨建中 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第2期5-10,共6页
Several critical clinical applications of magnetocardiography(MCG)involve its T wave.The T wave’s accuracy directly affects the diagnostic accuracy of MCG for ischemic heart disease and arrhythmogenic.Tunnel magnetor... Several critical clinical applications of magnetocardiography(MCG)involve its T wave.The T wave’s accuracy directly affects the diagnostic accuracy of MCG for ischemic heart disease and arrhythmogenic.Tunnel magnetoresistance(TMR)attracts attention as a new MCG measurement technique.However,the T waves measured by TMR are often drowned in noise.The accuracy of T waves needs to be discussed to determine the clinical value of MCG measured by TMR.This study uses an improved empirical mode decomposition(EMD)algorithm and averaging to eliminate the noise in the MCG measured by TMR.The MCG signals measured by TMR are compared with MCG measured by the optically pumped magnetometer(OPM)to judge its accuracy.Using the MCG measured by OPM as a reference,the relative errors in time and amplitude of the T wave measured by TMR are 3.4%and 1.8%,respectively.This is the first demonstration that TMR can accurately measure the time and amplitude of MCG T waves.The ability to provide reliable T wave data illustrates the significant clinical application value of TMR in MCG measurement. 展开更多
关键词 MAGNEtOCARDIOGRAPHY tunnel magnetoresistance optically pumped magnetometer t wave detection
下载PDF
T Wave Amplitude Deviation as a Participation Marker of Glycolysis in Myocardial Repolarization 被引量:1
2
作者 Mikhail U. Alekseev Aleksandr M. Alekseev 《World Journal of Cardiovascular Diseases》 2019年第5期343-353,共11页
Glucose metabolism is essential for heart physiology, especially in ischemic conditions. Anaerobic glycolysis participates along with aerobic fatty acid oxidation in generating energy supply, and the balance is shifte... Glucose metabolism is essential for heart physiology, especially in ischemic conditions. Anaerobic glycolysis participates along with aerobic fatty acid oxidation in generating energy supply, and the balance is shifted towards fatty acids. In the case of aerobic path restriction due to coronary artery disease (CAD), this ratio changes. The aim of the present research was to discover the aspects of glycolysis in cardiac electrophysiology.?We utilized the normalized (by average value) T wave amplitude deviation values, named the G criterion,?from high-resolution, 12-channel, 120-seconds-long electrocardiograms,?which were obtained using DACG technology. The calculated G criterion allows a quantitative assessment of the ischemic process and corresponds to the functional class (FC) according to the Canadian cardiovascular classification. We examined 22 healthy people and 79 proven CAD patients: 24 II FC, 40 III FC and 15 IV FC by original ECG and fasting blood sugar tests. A strong correlation was found between the average G criterion from all 12 channels and the level of fasting blood sugar (r = +0.88). In the control group, blood sugar levels were 91 ± 6.5 mg/dl, II FC 103 ± 14.8 mg/dl (p < 0.01), III FC 113 ± 23.4 mg/dl (p < 0.001), and IV FC 152 ± 42.4 (p < 0.001). Moreover, the correlation factor (average G criterion and blood sugar) was strong and positive in each group: control +0.72, II FC +0.83, III FC +0.76, and IV FC +0.89. For the first time, heart electrical activity from the ECG curve was associated with high glucose level as one of the main CAD risk factors. The presence of such dependence of increased blood sugar level from the severity of the ischemic process in the myocardium indicates that hyperglycemic reaction is adaptive and can accelerate the anaerobic glycolysis for energy demand compensation in heart muscle. 展开更多
关键词 ELECtROCARDIOGRAM t wave Deviation Blood SUGAR HYPERGLYCEMIA GLYCOLYSIS
下载PDF
A METHOD FOR EPICENTER LOCATNG BY USING T WAVES
3
作者 陈佐林 杨作升 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 1994年第3期255-261,共7页
Two OBS arrays were deployed in the southern Okinawa Trough.Some of the OBS records revealedmany earthquakes with intensive T waves but ambiguous body waves.A new method using T waves for epicenter locating was develo... Two OBS arrays were deployed in the southern Okinawa Trough.Some of the OBS records revealedmany earthquakes with intensive T waves but ambiguous body waves.A new method using T waves for epicenter locating was developed that was found to be as precise as the body wave method for locatingepicenters when T waves are clearly recorded. 展开更多
关键词 OBS t waveS EARtHQUAKE epicenter locating
下载PDF
THE APPLICATION OF EVOLUTIONARY ALGORITHM IN DETERMINING T WAVE-END
4
作者 Luo Jianhua Li Gaoping Zhuang Tiange(Department of Biomedical Engineering, Shanghai Jiaotong University, Shanghai 200030) (ECG Department of Zhongshan Hospital, Shanghai Medical University, Shanghai 200030) 《Journal of Electronics(China)》 2001年第1期32-37,共6页
There have been several methods for determining T wave-end. But none of them can overcome the difficulty from multiformity of ECG signal pattern. In this paper, a method for determining T wave-end using evolutionary a... There have been several methods for determining T wave-end. But none of them can overcome the difficulty from multiformity of ECG signal pattern. In this paper, a method for determining T wave-end using evolutionary algorithm (EA) is proposed. In this way, first, every characteristic parameter related to T wave-end is encoded to a string of codes, and adaptation function is constructed with the string of codes. Then choose the individual according to the adaptation function value and do genetic operation (reproduction, crossover and mutation), so as to produce offspring with more adaptation function value. Because of EA's autoadaptation and autoorganization character, it can trace ECG signal type and find the T wave-end automatically.Experiment results show that the error ratio of recognizing T wave-end using this method is much smaller than that using existing method. 展开更多
关键词 t wave-end ADAPtAtION FUNCtION GENEtIC operation
下载PDF
Analysis of the Q-T Dispersion and T Wave Alternans in Patients with Epilepsy
5
作者 Dan Sheng Xianglin Cheng 《Yangtze Medicine》 2017年第2期109-116,共8页
Objectives: There is a high rate of sudden death in epilepsy patients, part of which is sudden cardiac death. By investigating ECG T wave alternans and Q-T dispersion changes of epilepsy patients, we may predict the p... Objectives: There is a high rate of sudden death in epilepsy patients, part of which is sudden cardiac death. By investigating ECG T wave alternans and Q-T dispersion changes of epilepsy patients, we may predict the possibility of the occurrence of sudden death and provide basis for clinical prevention. Methods: Selecting 587 cases of epilepsy patients as the study group, 672 same period cases of healthy persons as the control group;Analyzing the effect of epilepsy on ECG T wave alternans and Q-T dispersion with the standard 12 lead ECG. Results: The study group had a significantly prolonged Q-T dispersion and an increased incidence of T wave alternans than that of the control group;Compared with other seizure types, tonic clonic seizure and absence seizure had a significantly prolonged Q-T dispersion and an increased occurrence rate of T wave alternans. Conclusions: Epilepsy patients ECG T wave alternans and Q-T dispersion has higher abnormal rate, and are prone to sudden cardiac death;Routine ECG(RECG) T wave alternans and Q-T dispersion changes can provide guidance for clinical prevention of sudden unexpected death in epilepsy (SUDEP). 展开更多
关键词 EPILEPSY t wave ALtERNANS Q-t DISPERSION
下载PDF
The Relationship between Changes of Polarity of the T Waves and Left Ventricular Function after Acute Anterior Myocardial Infarction
6
作者 朱建国 崔长琮 朱参战 《South China Journal of Cardiology》 CAS 2001年第1期52-54,共3页
Objective To explore therelation between changes of T waves and left ventricular function in patients with Q - wave anterior wall MI. Methods 105 consecutive patients with Q-wave anterior wall MI were enrolled in this... Objective To explore therelation between changes of T waves and left ventricular function in patients with Q - wave anterior wall MI. Methods 105 consecutive patients with Q-wave anterior wall MI were enrolled in this study. These patients were divided into two groups according to the polarity of T wave at 6 months: negative T - wave group (n=45) and positive T-wave group (n = 60) . Electrocardiograms were recorded and echocardiogra-phy was performed on admission and at 6 months after anterior MI. Results The peak serum creatine ki-nase activity of negative T - wave group and positive T -wave group was (4158 ±2478) IU/L and (2868±2358) IU/L, respectively (P < 0. 05). Left ventricular function was better in positive T - wave group than negative T - wave group. Conclusion Earlier normalization of the precordial T waves was associated with greater improvement in LV function. The early presence of inverted T waves in leads with abnormal Q waves can be used to assess the degree of LV dysfunction. 展开更多
关键词 t - wave inversion Anterior wall MI
下载PDF
Isolated Hyperacute T-Waves in West Nile Encephalitis Indicating Atypical Variant of Stress-Induced Cardiomyopathy
7
作者 Soomal Rafique Nadeem Khan Momin Siddique 《Journal of Biosciences and Medicines》 2024年第2期303-310,共8页
Several cardiac outcomes have been reported with West Nile-encephalitis;however, the underlying pathophysiology remains complex. We present a 42-year-old female, with multiple sclerosis, whose neurological symptoms an... Several cardiac outcomes have been reported with West Nile-encephalitis;however, the underlying pathophysiology remains complex. We present a 42-year-old female, with multiple sclerosis, whose neurological symptoms and respiratory decline were finally explained by the diagnosis of West Nile-encephalitis. During her admission, the isolated peaked T-waves indicated the underlying stress-induced cardiomyopathy. The absence of all other causes of hyperacute T-waves, their subsequent resolution with the resolution of infection and improvement in wall motion abnormalities, further supported the association. This case highlights the importance of considering hyperacute T-waves in an approach towards the diagnosis of WNV-encephalitis related atypical variant of stress-induced cardiomyopathy. 展开更多
关键词 West Nile Virus encephalitis WNV Hyperacute t-waves takotsubo Cardiomyopathy Atypical/Inverted Variant of Stress-Induced Cardiomyopathy CMP
下载PDF
Defective T wave combined with incomplete right bundle branch block: a new electrocardiographic index for diagnosing atrial septal defect 被引量:4
8
作者 WANG Mu-xuan WU Gui-fu +8 位作者 GU Jing-li LI Li LU Kun YANG Da CHEN Long ZHANG Xi LUO Fu-tian Andrew D. Michaels MA Hong 《Chinese Medical Journal》 SCIE CAS CSCD 2012年第6期1057-1062,共6页
Background Incomplete right bundle branch block (ICRBBB) is commonly associated with atrial septal defect (ASD), but lacks sufficient diagnostic test characteristics. An abnormal T wave is also often observed in A... Background Incomplete right bundle branch block (ICRBBB) is commonly associated with atrial septal defect (ASD), but lacks sufficient diagnostic test characteristics. An abnormal T wave is also often observed in ASD, with horizontal or inverted displacement of the proximal T wave limb in the right precordial leads, termed "defective T wave" (DTW). Methods We examined the diagnostic test characteristics of combining ICRBBB with DTW as a new index to diagnose ASD. A total of 132 consecutive patients with ASD and 132 cases of age/gender-matched controls without ASD were enrolled. Results Sensitivities of DTW, ICRBBB, and both were 87.1%-87.9%. Specificities were 97.0%, 96.2%, and 100%, respectively. Positive predictive values were 1.3%, 1.1%, and 100.0% respectively, while negative predictive values were 99.9% for each. Conclusion Combining ICRBBB with DTW in electrocardiogram (ECG) as a new index significantly increased the specificity and positive predictive values while maintaining a high sensitivity in diagnosing ASD. 展开更多
关键词 bundle branch block ELECtROCARDIOGRAPHY atrial septal defect t wave diagnosis
原文传递
Predicting apical hypertrophic cardiomyopathy using T-wave inversion:Three case reports 被引量:2
9
作者 Liang Kang Yi-Hua Li +1 位作者 Rong Li Qing-Min Chu 《World Journal of Clinical Cases》 SCIE 2023年第25期5970-5976,共7页
BACKGROUND Apical hypertrophic cardiomyopathy(AHCM)is a subtype of hypertrophic cardiomyopathy.Due to its location,the thickening of the left ventricular apex can be missed on echocardiography.Giant negative T waves(G... BACKGROUND Apical hypertrophic cardiomyopathy(AHCM)is a subtype of hypertrophic cardiomyopathy.Due to its location,the thickening of the left ventricular apex can be missed on echocardiography.Giant negative T waves(GNTs)in left-sided chest leads are the hallmark electrocardiogram(ECG)change of AHCM.CASE SUMMARY The first patient was a 68-year-old woman complaining of recurrent chest tightness persisting for more than 3 years.The second was a 59-year-old man complaining of spasmodic chest tightness persisting for more than 2 years.The third was a 55-year-old woman complaining of recurrent chest pain persisting for 4 mo.In all three cases,GNTs were observed several years prior to apical cardiac hypertrophy after other causes of T-wave inversion were ruled out.CONCLUSION Electrophysiological abnormalities of AHCM appear earlier than structural abnormalities,confirming the early predictive value of ECG for AHCM. 展开更多
关键词 ELECtROCARDIOGRAM Negative t waves Hypertrophic cardiomyopathy Apical hypertrophic cardiomyopathy ECHOCARDIOGRAPHY Case report
下载PDF
Preoperative Atrial Fibrillation and T-Wave Inversion Associated with Postoperative Pulmonary Edema
10
作者 Thomas Hong Benson George +1 位作者 Mohamad Hashim Dennis E. Feierman 《Open Journal of Anesthesiology》 2016年第10期181-185,共5页
Background: Atrial fibrillation (AF) and T wave inversion (TWI) are occasionally found on pre-operative electrocardiograms (EKG) of patients with long standing hy-pertension (HTN) associated with left ventricular hype... Background: Atrial fibrillation (AF) and T wave inversion (TWI) are occasionally found on pre-operative electrocardiograms (EKG) of patients with long standing hy-pertension (HTN) associated with left ventricular hypertrophy (LVH). Each of these two pathologies, AF and LVH, can impose negative hemodynamic effects on the car-diac function. Case: We present a case of a patient with AF, TWI and long standing HTN that went into post-operative pulmonary edema. Conclusion: Even returning to base line poorly controlled hypertension, and even more so during a hypertensive cri-sis, their concurrent presence may inflict even more detrimental effect manifested by elevation of pulmonary venous pressure and pulmonary edema. 展开更多
关键词 Pulmonary Edema Atrial Fibrillation t wave Inversion
下载PDF
MTWA技术联合血清miR-130a对心脏再同步化治疗后CHF患者室性心律失常的预测价值
11
作者 李培培 邵莹莹 +1 位作者 王莉 陈利红 《海南医学》 CAS 2024年第23期3345-3349,共5页
目的探讨微伏级T波电交替(MTWA)技术联合血清微小RNA-130a(miR-130a)对心脏再同步化治疗(CRT)后慢性心力衰竭(CHF)患者室性心律失常的预测价值。方法前瞻性选取2021年3月至2022年1月郑州大学第一附属医院收治的130例经CRT治疗的CHF患者... 目的探讨微伏级T波电交替(MTWA)技术联合血清微小RNA-130a(miR-130a)对心脏再同步化治疗(CRT)后慢性心力衰竭(CHF)患者室性心律失常的预测价值。方法前瞻性选取2021年3月至2022年1月郑州大学第一附属医院收治的130例经CRT治疗的CHF患者,均于CRT前、CRT 6个月后进行MTWA检查和血清miR-130a检测。所有患者均随访12个月,失访7例,根据随访期间是否发生室性心律失常分为发生组26例和未发生组97例,比较两组患者CRT前和CRT 6个月后的MTWA参数、血清miR-130a水平;采用Spearman相关系数法分析MTWA参数、血清miR-130a与CHF患者室性心律失常的相关性;采用受试者工作特征(ROC)曲线及曲线下面积(AUC)分析MTWA、血清miR-130a预测CHF患者室性心律失常的价值。结果CRT前、CRT 6个月后发生组V1导联MTWA_(max)、V1导联8:00 am MTWA、V5导联MTWA_(max)、V5导联8:00 am MTWA、miR-130a均高于未发生组,差异均有统计学意义(P<0.05);Spearman相关系数法分析结果显示,CRT前、CRT 6个月后V1导联MTWA_(max)、V1导联8:00 am MTWA、V5导联MTWA_(max)、V5导联8:00 am MTWA及miR-130a均与CHF患者室性心律失常发生呈正相关(P<0.05);ROC曲线分析结果显示,CRT前、CRT 6个月后V1导联MTWA_(max)、V1导联8:00 am MTWA、V5导联MTWA_(max)、V5导联8:00 am MTWA及血清miR-130a联合预测的AUC分别为0.912、0.933(P<0.05)。结论MTWA参数、血清miR-130a与CHF患者室性心律失常存在一定线性关系,CRT治疗前后MTWA参数和血清miR-130a联合预测CHF患者发生室性心律失常具有一定的价值。 展开更多
关键词 慢性心力衰竭 微伏级t波电交替 微小RNA-130a 心脏再同步化治疗 室性心律失常 预测价值
下载PDF
T/R双模微波功率模块技术及其应用
12
作者 李建兵 邱立 +2 位作者 王斌 郭静坤 董雪雨 《强激光与粒子束》 CAS CSCD 北大核心 2024年第1期12-17,共6页
微波功率模块(MPM)是真空电子器件和固态电子器件组合而成的一种新型微波功率器件,具有频率高、频带宽、功率大、体积重量小等特点,它使常规行波管的应用变得更加便利和广泛。现代战争向雷达、电子战综合一体化方向发展,这就要求功放既... 微波功率模块(MPM)是真空电子器件和固态电子器件组合而成的一种新型微波功率器件,具有频率高、频带宽、功率大、体积重量小等特点,它使常规行波管的应用变得更加便利和广泛。现代战争向雷达、电子战综合一体化方向发展,这就要求功放既能工作在高峰值功率、低占空比的高模工作方式,也能工作在低峰值功率、准连续波的低模工作方式,针对这一需求,结合电子系统收发共孔径的要求,提出了T/R双模MPM技术。T/R双模MPM技术的核心是T/R双模行波管,基于三端口双向T/R行波管,通过在慢波系统的衰减器附近设置一个耦合口,实现行波管的信号反向接收功能;通过T/R双模行波管设计、双模放大均衡组件、双调制栅极电源等技术实现MPM的双模双向功能。T/R双模MPM应用前景广阔,特别是在基于无人机平台的作战应用中的具有明显优势。 展开更多
关键词 微波功率模块 t/R行波管 收发共孔径 功放 均衡器
下载PDF
Cardiac and non-cardiac causes of T-wave inversion in the precordial leads in adult subjects: A Dutch case series and review of the literature 被引量:7
13
作者 Salah AM Said Rene Bloo +1 位作者 Ramon de Nooijer Andries Slootweg 《World Journal of Cardiology》 CAS 2015年第2期86-100,共15页
AIM: To describe the electrocardiographic(ECG) phenomena characterized by T-wave inversion in the precordial leads in adults and to highlight its differential diagnosis. METHODS: A retrospective chart review of 8 adul... AIM: To describe the electrocardiographic(ECG) phenomena characterized by T-wave inversion in the precordial leads in adults and to highlight its differential diagnosis. METHODS: A retrospective chart review of 8 adult patients who were admitted with ECG T-wave inversion in the anterior chest leads with or without prolongation of corrected QT(QTc) interval. They had different clinical conditions. Each patient underwent appropriate clinical assessment including investigation for myocardial involvement. Single and multimodality noninvasive, semi-invasive and invasive diagnostic approach were used to ascertain the diagnosis. The diagnostic assessment included biochemical investigation, cardiac and abdominal ultrasound, cerebral and chest computed tomography, nuclear medicine and coronary angiography.RESULTS: Eight adult subjects(5 females) with a mean age of 66 years(range 51 to 82) are analyzed. The etiology of T-wave inversion in the precordial leads were diverse. On admission, all patients had normal blood pressure and the ECG showed sinus rhythm. Five patients showed marked prolongation of the QTc interval. The longest QTc interval(639 ms) was found in the patient with pheochromocytoma. Giant T-wave inversion(≥ 10 mm) was found in pheochromocytoma followed by electroconvulsive therapy and finally ischemic heart disease. The deepest T-wave was measured in lead V3(5 ×). In 3 patients presented with mild T-wave inversion(patients 1, 5 and 4 mm), the QTc interval was not prolonged(432, 409 and 424 msec), respectively.CONCLUSION: T-wave inversion associated with or without QTc prolongation requires meticulous history taking, physical examination and tailored diagnostic modalities to reach rapid and correct diagnosis to establish appropriate therapeutic intervention. 展开更多
关键词 t-wave INVERSION Coronary ANGIOGRAPHY Pulmonary computed tomography ANGIOGRAPHY Mag-netic resonance imaging Differential diagnosis
下载PDF
Scattering of Tollmien-Schlichting waves as they pass over forward-/backward-facing steps 被引量:3
14
作者 Ming DONG Anyong ZHANG 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第10期1411-1424,共14页
Forward-/backward-facing steps in boundary-layer flows are often seen in engineering applications, and they have potential impacts on laminar-turbulent transition through scattering of the oncoming instability modes(e... Forward-/backward-facing steps in boundary-layer flows are often seen in engineering applications, and they have potential impacts on laminar-turbulent transition through scattering of the oncoming instability modes(e.g., Tollmien-Schlichting(T-S) waves). This issue is studied in the present paper by applying a local scattering framework, which is a rather generic mathematical framework on describing the mode scattering process. In this framework, a high-Reynolds-number triple-deck formalism is employed, and a transmission coefficient, defined as the ratio of the asymptotic amplitude of the instability mode downstream of the step to that upstream, is introduced. Through the systematical study, it has been found that both the forward-and backward-facing steps have a destabilizing effect on the oncoming T-S waves in subsonic boundary layers, this effect increases with the height of the step and/or the frequency of the T-S wave, and a backward-facing step(BFS) always has a greater impact than a forward-facing step(FFS). These facts agree with most of the previous investigations.However, one numerical study(WORNER, A., RIST, U., and WAGNER, S. Humps/steps influence on stability characteristics of two-dimensional laminar boundary layer. AIAA Journal, 41, 192–197(2003)), which was based on an ad-hoc configuration, showed an opposite impact of an FFS. Through the investigation on the specific configuration, it is revealed that the wrong conclusion was drawn by misinterpreting the numerical results. 展开更多
关键词 boundary layer SCAttERING instability tollmien-Schlichting(t-S) wave triple deck
下载PDF
基于慢性心肌缺血小鼠模型探究心电图T波低平的电生理机制
15
作者 王兆博 潘熠 +1 位作者 林谦 钟菊迎 《中国比较医学杂志》 CAS 北大核心 2024年第6期54-62,共9页
目的 建立通过稳定的冠心病慢性心肌缺血小鼠模型,初步阐述缺血状态下T波低平的电生理原理。方法 将APOE-/-小鼠随机分为模型组和降脂药(lipid-lowering drug, LLD)组,高脂饮食喂养3个月,同时设立C57BL/6J小鼠作为空白组。检测造模前后... 目的 建立通过稳定的冠心病慢性心肌缺血小鼠模型,初步阐述缺血状态下T波低平的电生理原理。方法 将APOE-/-小鼠随机分为模型组和降脂药(lipid-lowering drug, LLD)组,高脂饮食喂养3个月,同时设立C57BL/6J小鼠作为空白组。检测造模前后小鼠心电图变化,通过核素PET/CT扫描评估心脏血流灌注情况,使用主动脉苏木伊红(hematoxylin-eosin, HE)染色和油红染色评估斑块动脉粥样硬化(atherosclerosis, AS)病理。同时,分离小鼠心肌细胞并记录心肌细胞动作电位。结果 高脂喂养3个月后模型组小鼠的胆固醇(cholesterol, CHO)和低密度脂蛋白(low-density lipoprotein, LDL-C)显著升高,同时主动脉出现脂质斑块。LLD组病变减少,空白组无斑块。心肌核素扫描显示模型组小鼠的心肌血流灌注显著低于LLD组和空白组。小鼠心电图显示模型组和LLD组的T/QRS显著降低,空白组无明显改变。记录心肌细胞动作电位发现,缺血的内层心肌细胞复极速率增加,内外电位差减小是T波低平的主要电生理机制。结论 APOE-/-小鼠可用于慢性心肌缺血小鼠模型,缺血状态下内层心肌复极速率的增加可能是心电图中T波降低的主要原因。 展开更多
关键词 冠心病 慢性心肌缺血 小鼠心电图 t波低平
下载PDF
Crack Detection in Pipes with Different Bend Angles Based on Ultrasonic Guided Wave 被引量:3
16
作者 Qi Minxin Chen Shaojie +2 位作者 Zhou Shaoping Li Yong Jia Jiuhong 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2017年第3期318-325,共8页
Pipeline plays an indispensable role in process industries,because the progressing crack-like defects of in it may result in serious accidents and significant economic losses.Therefore,it is essential to detect the cr... Pipeline plays an indispensable role in process industries,because the progressing crack-like defects of in it may result in serious accidents and significant economic losses.Therefore,it is essential to detect the cracks occurred in pipelines.The axial crack-like defects in elbows with different angle are inspected by using the T(0,1)mode guided waves,in which different configurations including 45°,90°,135°and 180°(straight pipe)are considered respectively.Firstly,the detection sensitivity for different defect location is experimentally investigated.After that,finite element simulation is used to explore the propagation behaviors of T(0,1)mode in different bend structures.Simulation and experiment results show that the crack in different areas of the elbow can affect the detection sensitivity.It can be found that the detection sensitivity of crack in the middle area of the elbow is higher compared to the extrados and intrados of the elbow.Finally,the mode conversion is also investigated when the T(0,1)crosses the bend,and the results show that bend is a key factor to the mode conversion phenomenon which presents between the T(0,1)mode and F(1,2)mode. 展开更多
关键词 guided straight indispensable Pipeline pipe defects waveform distinguished axial longitudinal
下载PDF
Seismic Wave Propagation and Excitation in Multi-layered Media with Irregular Interfaces Part (Ⅰ): SH Case 被引量:3
17
作者 Chen XiaofeiDepartment of Geophysics, Peking University, Beijing 100871, China 《Earthquake Research in China》 1999年第2期79-97,共19页
Study of seismic wave excitation and propagation in laterally heterogeneous media was an active and important subject in seismology in the past two decades, numerous analytical and numerical efforts have been made in ... Study of seismic wave excitation and propagation in laterally heterogeneous media was an active and important subject in seismology in the past two decades, numerous analytical and numerical efforts have been made in this research field. In this article, I have, first, made a brief review on those developments and then introduced and summarized a unified and efficient method, global generalized reflection-transmission (abbreviated to R/T thereafter) matrices method, for synthetic seismograms in multi-layered media with irregular interfaces developed by the author [24~26]. As demonstrated in this article, this method could be regarded as an extension of the generalized R/T coefficients method for the horizontally layered case [2,5] to the layered media with irregularly shaped interfaces by incorporating the T matrices technique [27,28]. Because of the use of a recursive scheme in computing the global generalized R/T matrices, this method is efficient, particularly for the case with a large number of 展开更多
关键词 SYNtHEtIC seismogram Laterally HEtEROGENEOUS MEDIA SEISMIC waveS R/t matrix
下载PDF
心电图avL导联T波变化对老年冠心病病人冠脉狭窄程度的诊断价值
18
作者 向超 罗彩东 《实用老年医学》 CAS 2024年第8期788-791,807,共5页
目的分析心电图avL导联T波变化对老年冠心病(CHD)病人冠脉狭窄程度的诊断价值。方法选择2019年7月至2022年10月就诊于本院的124例老年CHD病人,冠状动脉狭窄程度按照Gensini积分法分为重度组(36例,Gensini评分>40分)、中度组(40例,Gen... 目的分析心电图avL导联T波变化对老年冠心病(CHD)病人冠脉狭窄程度的诊断价值。方法选择2019年7月至2022年10月就诊于本院的124例老年CHD病人,冠状动脉狭窄程度按照Gensini积分法分为重度组(36例,Gensini评分>40分)、中度组(40例,Gensini评分为21~40分)、轻度组(48例,Gensini评分为1~20分)。所有病人均接受心电图检测。比较3组病人一般资料、实验室指标、avL导联T波改变与其他心电图特征,采用Logistic回归分析老年CHD病人冠脉狭窄程度的危险因素,绘制ROC曲线分析avL导联T波改变对老年CHD病人冠脉狭窄程度的诊断价值。结果左心室舒张末期内径(LVEDD)和血清N末端脑钠肽前体(NT-proBNP)水平在轻度组、中度组和重度组中逐步升高,且3组间差异有统计学意义(P<0.01);3组间avL导联T波改变、ST段抬高、ST段压低、病理性Q波比例相比,差异有统计学意义(P<0.01)。Logistic回归分析显示,NT-proBNP、LVEDD、avL导联T波改变、ST段抬高、ST段压低、病理性Q波是影响老年CHD病人冠脉狭窄程度的独立危险因素;ROC曲线分析表明,avL导联T波改变诊断老年CHD冠脉狭窄程度的AUC为0.701(95%CI:0.603~0.798)。结论心电图avL导联T波改变是老年CHD病人冠脉狭窄程度的独立危险因素,在冠脉狭窄程度诊断中具有一定价值。 展开更多
关键词 老年人 冠心病 心电图 avL导联t 冠脉狭窄程度
下载PDF
Adaptive Match-Filtering: A Biomedical Application to Identify T-Wave Alternans
19
作者 Laura Burattini Giovanni Ottaviano +1 位作者 Francesco Di Nardo Sandro Fioretti 《Natural Science》 2014年第10期709-718,共10页
T-wave alternans (TWA), consisting in an alternation of the electrocardiographic (ECG) repolarization segment (T-wave), is a promising index of the risk of sudden cardiac death. By definition, it is characterized by a... T-wave alternans (TWA), consisting in an alternation of the electrocardiographic (ECG) repolarization segment (T-wave), is a promising index of the risk of sudden cardiac death. By definition, it is characterized by a frequency component, termed fTWA, that matches half heart rate. The heart-rate adaptive match filter (AMF) based method is a technique for automatic TWA identification from the digital ECG. Aim of the present study was to provide a complete technical description of the filter able to explain its methodological principles. The AMF is usually realized as a 6th order Butterworth filter with a narrow (0.12 Hz) passing band centered in fTWA. It is applied in a bidirectional fashion, so that final filtering order is 12. While extracting the TWA component, the AMF simultaneously filters out every ECG component including noise and artefacts, and thus results are very robust. Goodness of the technique was tested using 8 synthetic ECG tracings corrupted by typical noisy factors, such as white random noise, baseline wanderings, heart-rate variability, and others. Six ECG tracings were affected by 100 μV TWA, whereas two were not. Results indicate that the AMF-based method is able to prevent false-positive and false-negative detections and, thus, represents a useful tool for a reliable TWA identification. 展开更多
关键词 ADAPtIVE FILtERING Digital ECG t-wave ALtERNANS SUDDEN Cardiac DEAtH
下载PDF
On the basis of the morphology of the T-wave alternans: A Poincare mapping method research
20
作者 Hui Guo Jie Zhao +1 位作者 Fei Li Tiantian Li 《Journal of Biomedical Science and Engineering》 2013年第4期504-507,共4页
Presently T-wave alternans (TWA) has become a clinical index of non-invasive diagnosis for heart sudden death prediction, and detecting T-wave alternate accurately is particularly important. This paper introduces an a... Presently T-wave alternans (TWA) has become a clinical index of non-invasive diagnosis for heart sudden death prediction, and detecting T-wave alternate accurately is particularly important. This paper introduces an algorithm for detecting TWA using Poincare mapping method which is a technique for nonlinear dynamic systems to display periodic behavior. Sample series of beat to beat cycles were selected to prepare Poincare mapping method. Vector Angle Index (VAI), which is the mean of the difference between θi (the angle between the line connecting the i point to the origin and the X axis) and 45 degrees was used to present the presence or absence of TWA. The value of 0.9 rad ≤ VAI ≤ 1.03 rad is accepted as a level determinative for presence of TWA. VAI via Poincare mapping method (PM) is used for correlation analysis with T-wave alternans voltage (Vtwa) by way of the spectral method (SM). The cross-correlation coefficient between Vtwa and VAI is γ = 0.8601. The algorithm can identify the absence and presence of TWA accurately and provide idea for further study of TWA-PM. 展开更多
关键词 t-wave ALtERNANS POINCARE Mapping MEtHOD Spectral MEtHOD Vector Angle Index (VAI)
下载PDF
上一页 1 2 39 下一页 到第
使用帮助 返回顶部