Pancreatic carcinoma coexisting with chronic pancreatitis versus tumor-forming pancreatitis:Diagnostic utility of the time-signal intensity curve from dynamic contrast-enhanced MR imaging

AIM: To evaluate the ability of the time-signal intensity curve (TIC) of the pancreas obtained from dynamic contrast-enhanced magnetic resonance imaging (MRI) for differentiation of focal pancreatic masses, especially pancreatic carcinoma coexisting with chronic pancreatitis and tumor-forming pancreatitis. METHODS: Forty-eight consecutive patients who underwent surgery for a focal pancreatic mass, including pancreatic ductal carcinoma (n = 33), tumor-forming pancreatitis (n = 8), and islet cell tumor (n = 7), were reviewed. Five pancreatic carcinomas coexisted with longstanding chronic pancreatitis. The pancreatic TICs were obtained from the pancreatic mass and the pancreatic parenchyma both proximal and distal to the mass lesion in each patient, prior to surgery, and were classified into 4 types according to the time to a peak: 25 s and 1, 2, and 3 min after the bolus injection of contrast material, namely, type-Ⅰ, Ⅱ, Ⅲ, and Ⅳ, respectively, and were then compared to the corresponding histological pancreatic conditions. RESULTS: Pancreatic carcinomas demonstrated type-Ⅲ (n = 13) or Ⅳ (n = 20) TIC. Tumor-forming pancreatitis showed type-Ⅱ (n = 5) or Ⅲ (n = 3) TIC. All islet cell tumors revealed type-Ⅰ. The type-Ⅳ TIC was only recognized in pancreatic carcinoma, and the TIC of carcinoma always depicted the slowest rise to a peak among the 3 pancreatic TICs measured in each patient, even in patients with chronic pancreatitis.CONCLUSION: Pancreatic TIC from dynamic MRI provides reliable information for distinguishing pancreatic carcinoma from other pancreatic masses, and may enable us to avoid unnecessary pancreatic surgery and delays in making a correct diagnosis of pancreatic carcinoma, especially, in patients with longstanding chronic pancreatitis.

The effect of different intensity measures and earthquake directions on the seismic assessment of skewed highway bridges

In this study the probable seismic behavior of skewed bridges with continuous decks under earthquake excitations from different directions is investigated. A 45° skewed bridge is studied. A suite of 20 records is used to perform an Incremental Dynamic Analysis （IDA） for fragility curves. Four different earthquake directions have been considered： -45°, 0°, 22.5, 45°. A sensitivity analysis on different spectral intensity measures is presented; efficiency and practicality of different intensity measures have been studied. The fragility curves obtained indicate that the critical direction for skewed bridges is the skew direction as well as the longitudinal direction. The study shows the importance of finding the most critical earthquake in understanding and predicting the behavior of skewed bridges.

Quantitative Assessment of Coronary Flow Reserve by the Variables of Time-Intensity Curve with Myocardial Contrast Echocardiography

The reliability and reliable indexes of q ua ntitative assessment of coronary flow reserve (CFR) by using time intensity cur ve (TIC) via myocardial contrast echocardiography were investigated. The TIC var iables were obtained by employing acoustic densitometry (AD) technique before an d after acetylcholine (Ach) injection in 12 dogs. Meanwhile, the correlation be tween these variables and CFR was analyzed. Among the variables derived from TIC , peak intensity (PI), area under the curve (AUC) and descending slope (DS) were increased significantly ( P <0.05) with the increase of coronary blood flow a fter Ach injection. Conversely, time to peak (TP), half time of descent (HT) , and mean transit time (MTT) were decreased remarkably ( P <0.0001). Th e P I and AUC ratios from post to pre Ach injection were strongly associated with CFR with the correlation coefficient (r) being 0.8366 and 0.8824, respectively. It is reliable by using the variables derived from TIC with myocardial contrast echocardiography to quantitatively evaluate regional myocardial CFR. The PI an d AUC ratios from post to pre Ach injection are the reliable indexes for quan titative assessment of CFR.

Quantitative Assessment of Right Ventricular Systolic Function by the Analysis of Right Ventricular Contrast Time-intensity Curve

Summary: To study reliability and reliable indices of quantitative assessment of right ventricular systolic function by time-intensity curve (TIC) with right ventricular contrast, 5 % sonicated human albumin was injected intravenously at a does of 0.08 ml/kg into 10 dogs at baseline status and cardiac insufficiency. Apical four-chamber view was observed for washin and washout of contrast agent from right ventricle. The parameters of TIC were obtained by curve fitting. The differences of parameters were analyzed in different states of cardiac functions. Among the parameters derived from TIC, the time constant (k) was decreased significantly with decline of cardiac function (P<0.001). But half-time of decent of peak intensity (HT) and mean-transit-time (MTT) of washout were increased significantly (P<0.001). The k was strongly related to cardiac output of right ventricle (CO) and ejection fraction (EF) of left ventricle and fractional shortening (FS) of left ventricle. Right ventricular systolic function could be assessed reliably by the parameters derived from TIC with right ventricular contrast echocardiography. The k, HT and MTT are reliable indices for quantitative assessment of right ventricular systolic function.

Usefulness of dynamic contrast-enhanced MR imaging in the evaluation of pulmonary isolated lesions

Objective： The aim of our study was to investigate the value of dynamic contrast-enhanced MRI for evaluating differential diagnosis of pulmonary isolated lesions. Methods： Twenty-nine consecutive patients enrolled in this study, all of whom underwent DCE-MRI examinations and received a histologic and clinical diagnosis. Among these, lung tuberculoma 7 cases, harmatoma 3 cases, peripheral lung cancer 19 cases. DCE-MRI was acquired with 3D LAVA technique, total 18 phases were acquired, scanner time of per phase was 5-7″. After contrasting agent, twice successive scanning was acquired at 10″ and 50″. Then 1′30″, 2′, 2′30″, 3′, 3′30″, 4′, 5′, 6′, 7′, 8′, 9′, 10′, 11′, 12′ performed scanning. Region of interest was placed on the Maximum level in the tumors. According to Schaefer＇s standard, four types of time signal intensity curve （TIC） were classified, which were A, B, C and D. Compared the dynamic parameters between benign and malignant nodules. Results： Lung tuberculoma may display three curves： A type 1 case, ring-shaped enhancement 4 cases （periphery ring A type, central region D type）, D type 2 cases. Harmatoma may display three curves： A type 1 case, C type 2 case. Peripheral lung cancer may display A type. Except 2 cases D type lung tuberculoma, we compared curve data of 8 cases benign nodules （including tuberculoma Atype and periphery ring Atype, harmatoma Atype and C type） and lung cancer. SlEP%： benign nodules 0.7885 ±0.5543, lung cancer 1.2623 ±0.3059, P 〈 0.05; MER： benign nodules 1.0007 ± 0.4251, lung cancer 1.3694 ±0.2740, P 〈 0.05; washout： P 〉 0.05. Conclusion： Lung MR imaging is helpful to diagnosis and differential diagnosis of isolated benign and malignant nodules. SIEP% and MER could offer valuable information. The evolution of global tuberculosis may be from A type to ring-shaped ennoblement to D type. It was easy to do right diagnosis to lung tuberculoma with ring-shaped ennoblement and D type. Peripheral lung cancer commonly displayed A type and needed identification with acute inflammation. So, it is important to anti-inflammatory follow-up for a few A type nodules.

Development of Rainfall Intensity Duration Frequency Curves for Mumbai City, India

The change in rainfall pattern and intensity is becoming a great concern for hydrologic engineers and planners. Many parts of the world are experiencing extreme rainfall events such as experienced on 26th July 2005 in Mumbai, India. For the appropriate design and planning of urban drainage system in an area, Intensity Duration Frequency (IDF) curves for given rainfall conditions are required. The aim of the present study is to derive the IDF curves for the rainfall in the Mumbai city, Maharashtra, India. Observed rainfall data from 1901 pertaining to Colaba and from 1951 of the Santacruz rain gauge stations in Mumbai are used in the present study to derive the IDF curves. Initially, the proposed IDF curves are derived using an empirical equation (Kothyari and Garde), by using probability distribution for annual maximum rainfall and then IDF curves are derived by modifying the equation. IDF curves developed by the modified equation gives good results in the changing hydrologic conditions and are compatible even with the extreme rainfall of 26th July 2005 in Mumbai.

Can semi-quantitative evaluation of uncertain (type II) time-intensity curves improve diagnosis in breast DCE-MRI?

Objective/Background: Qualitative assessment of uncertain (type II) time-intensity curves (TICs) in breast DCE-MRI is problematic and operator dependent. The aim of this work is to evaluate if a semi-quantitative assessment of uncertain TICs could improve overall diagnostic performance. Methods: In this study 49 lesions from 44 patients were retrospectively analysed. Per each lesion one region-of-interest (ROI)- averaged TIC was qualitatively evaluated by two radiologists in consensus: all the ROIs resulted in type II (uncertain) TIC. The same TICs were semi-quantitatively re-classified on the basis of the difference between the signal intensities of the last-time-point and of the peak: this difference was classified according to two different cut-off ranges (±5% and ±3%). All patients were cytological or histological biopsy proven. Fisher test and McNemar test were performed to evaluate if results were statistically significant (p < 0.05). Results: Using ±5% cut-off 16 TICs were reclassified as type III and 12 as type I while 21 were reclassified again as type II. Using ±3% 22 TICs were reclassified as type III and 16 as type I while 11 were reclassified again as type II. The semi-quantitative classification was compared to the histological-cytological results: the sensitivity, specificity, positive and negative predictive values obtained with ±3% were 77%, 91%, 91% and 78% respectively while using ±5% were 58%, 96%, 94% and 68% respectively. Using the ±5% cut-off 26/28 (93%) TICs were correctly reclassified while using the ±3% cut-off 34/38 (90%) TICs were correctly reclassified (p < 0.05). Conclusions: Semi-quantitative methods in kinetic curve assessment on DCE-MRI could improve classification of qualitatively uncertain TICs, leading to a more accurate classification of suspicious breast lesions.

Diagnosis of bowel diseases:The role of imaging and ultrasonography

Examinations with a visualisation of the anatomy and pathology of the gastrointestinal(GI) tract are often necessary for the diagnosis of GI diseases.Traditional radiology played a crucial role for many years.Endoscopy,despite some limitations,remains the main technique in the differential diagnosis and treatment of GI diseases.In the last decades,the introduction of,and advances in,non-invasive cross-sectional imaging modalities,including ultrasound(US),computed tomography(CT),positron-emission tomography(PET),and magnetic resonance imaging,as well as improvements in the resolution of imaging data,the acquisition of 3D images,and the introduction of contrast-enhancement,have modified the approach to the examination of the GI tract.Moreover,additional co-registration techniques,such as PET-CT and PET-MRI,allow multimodal data acquisition with better sensitivity and specificity in the study of tissue pathology.US has had a growing role in the development and application of the techniques for diagnosis and management of GI diseases because it is inexpensive,non-invasive,and more comfortable for the patient,and it has sufficient diagnostic accuracy toprovide the clinician with image data of high temporal and spatial resolution.Moreover,Doppler and contrastenhanced ultrasound(CEUS) add important information about blood flow.This article provides a general review of the current literature regarding imaging modalities used for the evaluation of bowel diseases,highlighting the role of US and recent developments in CEUS.

Gravitational Perturbation of Hydrogen Spectrum in the Space Curved by Intense Laser Pulses

The energy level shifts of hydrogen in the space curved by the intense short laser pulses are studied. It shows that for present power level of laser pulses, the magnitude of the energy level shifts in a highly excited hydrogen atom is detectable.

New Formulation for Arbitrary Cracks Problem and Its Stress Intensity Factor of Plane Elasticity

Aim The general arbitrary cracked problem in an elastic plane was discussed. Methods For the purpose of acquiring the solution of the problem, a new formulation on the problem was proposed. Compared with the classical plane elastic crack model, only the known conditions were revised in the new formulation, which are greatly convenient to solve the problem, and no other new condition was given. Results and Conclusion The general exact analytic solution is given here based on the formulation though the problem is very complicated. Furthermore, the stress intensity factors K Ⅰ, K Ⅱ of the problem are also given.

ANTIPLANE CIRCULAR INCLUSION WITH A CURVED CRACK CROSSING THE BOUNDARY

The weakly singular integral equation sued to solve the problem ofthe curved crack crossing the boundary of the antiplane circularinclusion is presented. Using the principal part analysis method ofthe Cauchy type integral equation, the singular stress index at theintersection and the singular stress of angular Regions near theintersection are obtained. By using the singular stress obtained, thestress intensity factor at The intersection is defined. After thenumerical solution of the integral equation, the stress intensityfactors at The end points of the crack and intersection areobtainable.

The analysis of the optimal scalar and vector intensity measurements for seismic performance assessment of deep-buried hydraulic arched tunnels

The selection of optimal intensity measures(IMs)has been recommended for generating the seismic demand models with different probabilities by researchers since the seismic IMs are closely associated with earthquake risks and structural safety.However,the seismic design code(mainly for aboveground structures)and dynamic analysis of underground structures conventionally employ the peak ground acceleration(PGA)as an optimal IM.In this paper,the research is to identify the optimal scalar and vector IMs in the fragility investigation of deep-buried hydraulic arched tunnels using the finite element method.A refinement process was performed to determine the optimal scalar IMs by comprehensively comparing their correlation,efficiency,practicality,proficiency,and sufficiency among the examined IMs.Furtherly,the optimum vector IMs were also developed,followed by the three different scalar IMs.Eventually,the dif-ferences between the fragility curves of the tunnel produced using the optimal scalar and vector IM were compared.The generated vector fragility surface can be used to estimate the seismic fragility of identical hydraulic tunnels in an approximative manner.

Flume Experiment Investigation on Propagation Characteristics of Tidal Bore in A Curved Channel

Tidal bore is a special and intensive form of flow movement induced by tidal effect in estuary areas, which has complex characteristics of profile, propagation and flow velocity. Although it has been widely studied for the generation mechanism, propagation features and influencing factors, the curved channel will complicate the characteristics of tidal bore propagation, which need further investigation compared with straight channel. In this study, the flume experiments for both undular and breaking bores’ propagation in curved channel are performed to measure the freesurface elevation and flow velocity by ultrasonic sensors and ADV respectively. The propagation characteristics,including tidal bore height, cross-section surface gradient, tidal bore propagation celerity, and flow velocity are obtained for both sides of the curved channel. And three bore intensities are set for each type of tidal bores. The freesurface gradients are consistently enlarged in high-curvature section for undular and breaking bores, but have distinct behaviors in low-curvature section. The spatial distributions of tidal bore propagation celerity and flow velocity are compared between concave and convex banks. This work will provide experimental reference for engineering design of beach and seawall protection, erosion reduction and siltation promotion in estuary areas with the existence of tidal bores.

葡萄叶绿素荧光参数测量方法的优化与日变化特征分析

【目的】确定葡萄叶绿素荧光参数测量最适的暗适应时间、测量光强度,分析葡萄叶绿素荧光参数日变化特征并确定最适测量时间,提出优化测量方法的建议,为进一步研究葡萄光合特性提供理论依据,以提高研究数据的准确性和可靠性。【方法】选择阳光玫瑰葡萄和巨峰葡萄叶龄为40~50 d的健康成熟叶片,利用JIP测定(JIP-test)和主成分分析(PCA)研究葡萄叶片在不同暗适应时间(5、10、15、20、25、30、35和40 min)、不同测量光强度[500、1000、1500、2000、2500、3000和3500μmol/(m^(2)·s)]和一天中不同时间点(8:00、10:00、12:00、14:00、16:00、18:00和20:00)的快速叶绿素荧光诱导动力学(OJIP)曲线特征,分析不同测量条件对葡萄叶片叶绿素荧光参数的影响。【结果】暗适应时间和测量光强度均明显影响葡萄叶片叶绿素荧光参数,较长的暗适应时间和较高的测量光强度能获得更稳定和可靠的测量结果。OJIP曲线特征显示,在较短的暗适应时间(5~15 min)内,各暗适应时间与暗适应5 min间的特征区间(OJ相、JI相和IP相)相对可变荧光差值(ΔWOJ、ΔWJI和ΔWIP)曲线变化幅度较大,初始荧光(F_(o))、最大荧光(F_(m))和最大光化学效率(F_(v)/F_(m))等参数波动较大,当暗适应时间达30 min以上时,各参数再无显著变化(P>0.05,下同),趋于稳定。随着测量光强度的增加,F_(m)、F_(v)/F_(m)、OJIP曲线的初始斜率(M_o)和单位面积反应中心数量(RC/CSm)等参数呈上升趋势,各测量光强度与500μmol/(m^(2)·s)测量光强度间的ΔWOJ、ΔWJI和ΔWIP曲线呈正K峰、负H峰和正G峰,当光强度达3000μmol/(m^(2)·s)以上时,各参数均无显著变化。葡萄叶片的多数叶绿素荧光参数随着一天中时间点的推移而变化,光系统II(PSII)光化学效率在12:00之前较高,14:00时光化学效率下降,16:00之后PSII逐渐恢复至最佳状态。【结论】针对葡萄叶片进行OJIP曲线测定时,暗适应时间应为30 min以上,最小测量光强度为3000μmol/(m^(2)·s),测量时间宜选择在12:00之前和16:00之后,以确保结果的准确性和可靠性。

基于低温-雨雪-冻雨综合强度指数的湖北省冰冻事件分型及灾损评估

低温雨雪冰冻是一种复合型气候事件,极端低温雨雪冰冻事件发生频率低,但造成的影响往往十分严重,开展低温雨雪冰冻事件演变特征研究对有效防御和减轻灾害影响具有重要意义。利用湖北省1981-2024年逐日气象观测资料,从低温、雨雪、冻雨等3个方面遴选指标,构建大范围持续低温雨雪冰冻事件综合评估模型;依据致灾因子类型、承灾体受灾特征对事件分型并排序;结合历史灾损数据分析了湖北省1981年以来大范围持续低温雨雪冰冻事件的致灾特征。结果表明:(1)近44 a湖北省共出现64次大范围持续低温雨雪冰冻事件,平均每年出现1.5次,1月出现频率最高,约占42%,其次是2月,约占34%。(2)湖北省大范围持续低温雨雪冰冻事件判别为六大分型,其中雨雪为主型占40%,低温雨雪冻雨型占31%,低温雨雪型占16%,其他类型共占13%,最强10次事件均属于低温雨雪冻雨型。(3)湖北省因低温雨雪冰冻灾害造成的直接经济损失总体呈增加趋势,但直接经济损失占GDP比重呈下降趋势。(4)湖北省大范围持续低温雨雪冰冻事件“综合强度指数-直接经济损失”相关关系呈幂指数分布,当事件综合强度指数超过1.85时,直接经济损失迅速增加。

郑州市暴雨强度公式计算与对比分析

为真实客观地反映郑州市近年来暴雨特征变化,进一步优化郑州市暴雨强度公式,选取2000~2022年11个降雨历时的年最大暴雨量,采用最小二乘法、遗传算法、拟牛顿法优化了郑州市暴雨强度公式参数,并与郑州市2002年暴雨强度公式以及2023年暴雨强度公式进行对比分析。结果表明,郑州市暴雨强度公式在指数分布中采用拟牛顿法拟合误差最小,最终确定的优化参数A1为11.312、C为2.968、b为19.8、n为0.900;在不同重现期暴雨条件下,优化公式相对于2002年公式呈现出完全不同的极值分布情况,即“大的更大、小的更小”,而与2023年公式的雨强相差较小;在不同降雨情景管网水力运行特征中,优化公式与2023年公式的模拟结果高度一致,两者在预测郑州市内涝情况整体上具有相似的准确性和可靠性,对城市排水防涝具有一定的指导作用。

经直肠超声造影评估前列腺癌新辅助内分泌治疗反应的价值

目的:探讨经直肠超声造影(contrast-enhanced transrectal ultrasound)时间-强度曲线(time-intensity curve,TIC)参数评估前列腺癌(prostate cancer,PCa)患者对新辅助内分泌治疗(neoadjuvant hormonal therapy,NHT)的反应程度。方法:纳入27例接受NHT的PCa患者的临床资料,根据术后病理学检查结果分为有效组(n=16)和无效组(n=11)。对比两组患者临床病理学特征、治疗前后血清前列腺特异性抗原(prostate-specific antigen,PSA)和CETRUS检查指标及其变化率,以筛选与NHT反应性有关的潜在指标。进一步采用相关性分析评价其在评估患者对NHT反应方面的价值。结果:有效组和无效组在临床病理学特征、治疗前的血清PSA和C E T R U S检查指标方面的差异无统计学意义(均P>0.05)。治疗后,仅有效组的TIC曲线下面积(area under curve,AUC)低于无效组(560 dB·s vs 710 dB·s),其变化率大于无效组(-27.1%vs-5.3%)(均P<0.05)。相关性分析显示AUC变化率与组织学反应评分之间的相关性略高于治疗后AUC(r为-0.690 vs-0.630)。结论:CETRUS TIC参数中,NHT后的AUC及其变化率在评估PCa患者对NHT反应方面具有较好的价值。其中,AUC变化率可能与治疗反应程度更相关。

超声造影时间-强度曲线相关参数鉴别诊断肝细胞癌与转移性肝癌价值研究

目的探讨超声造影(CEUS)时间-强度曲线(TIC)相关参数鉴别诊断肝细胞癌(HCC)与转移性肝癌的价值。方法2021年3月~2023年3月我院诊治的106例肝癌患者,均接受CEUS检查,记录造影剂到达时间(AT)、达峰时间(TTP)、峰值强度(PI)和上升斜率(RS)等TIC相关参数,均进行肝穿刺组织病理学检查。绘制受试者工作特征(ROC)曲线,以曲线下面积(AUC)评估TIC参数的鉴别诊断效能。结果在106例肝癌患者中,经病理学检查诊断为HCC者44例(41.5%)和转移性肝癌者62例(58.5%);HCC病灶AT和PI分别为(9.1±2.2)s和(41.7±5.1)dB,均显著低于转移性肝癌病灶【分别为(13.4±2.6)s和(45.8±5.5)dB,P<0.05】,而TTP为(24.8±4.7)s,显著慢于转移性肝癌病灶【(18.9±3.4)s,P<0.05】;HCC患者血清AFP水平为(226.7±37.5)ng/mL,显著高于转移性肝癌患者【(73.1±14.6)ng/mL,P<0.05】;ROC曲线分析显示,采用AT、TTP和PI联合诊断HCC的AUC为0.89(95%CI:0.83~0.96),其敏感度(Se)和特异度(Sp)分别为70.5%和95.2%,显著优于血清AFP诊断【其AUC为0.78(95%CI:0.68~0.79),其Se和Sp分别为56.8%和78.8%,P<0.05】。结论使用CEUS检测的TIC相关参数鉴别诊断HCC与转移性肝癌有一定的临床应用价值,值得进一步研究。

DCE-MRI联合DWI扫描在肝脏局灶性病变(直径≤3cm)定性诊断中的应用

目的分析磁共振动态增强扫描(DCE-MRI)联合弥散加权成像(DWI)扫描在肝脏局灶性病变(FLLs)(直径≤3cm)定性诊断中的应用价值。方法选择我院2021年4月至2024年4月收治的50例FLLs患者,均接受DCE-MRI和DWI检查,以穿刺或手术等病理结果为标准,比较不同病理类型动态增强扫描曲线分布情况、在不同弥散敏感系数(b值)下的表观弥散系数(ADC)值,并分析DCE-MRI联合DWI扫描对FLLs定性诊断的价值。结果病理结果显示,50例FLLs患者中13例为肝血管瘤,21例为原发性肝癌,16例为肝脏转移瘤。不同b值下,不同病理类型间ADC值比较均有明显差异(P<0.05),且肝血管瘤组ADC值均明显高于原发性肝癌组和肝脏转移瘤组(P<0.05)。DCE-MRI结果显示,肝血管瘤组曲线以Ⅲ型为主(占比76.92%),原发性肝癌组曲线以Ⅰ型为主(占比66.67%),肝脏转移瘤组曲线以Ⅱ型为主(占比75.00%);三组曲线类型分布情况比较有明显差异(P<0.05),且肝血管瘤组与其他两组间曲线类型分布情况比较均有明显差异(P<0.05)。检查结果显示,DCE-MRI联合DWI扫描对良性、恶性病灶诊断准确率最高,分别是92.31%(12/13)、97.30%(36/37);其次是DCE-MRI扫描,分别是69.23%(9/13)、75.68%(28/37);最低是DWI扫描,分别是61.54%(8/13)、54.05%(20/37)。不同检查方法定性诊断FLLs的灵敏度、准确度比较均有明显差异(P<0.05),且DCE-MRI联合DWI扫描诊断的灵敏度和准确度均明显高于DWI及DCE-MRI单独扫描(P<0.05)。结论在FLLs(直径≤3cm)定性诊断中应用DCE-MRI联合DWI扫描有更高的灵敏度和准确度,利于明确其良恶性质,为临床诊治提供更精确指导。

隧道纵向地震易损性分析

为研究隧道纵向抗震性能,使用改进的地基梁-弹簧非线性分析模型计算隧道纵向地震响应,其中采用PQ-Fiber纤维梁模型模拟隧道纵向的非线性行为,并施加弯矩来考虑隧道与场地之间的切向相互作用。随后,将基于增量动力分析(IDA)方法的结构地震易损性分析方法应用于隧道结构,探究适用于隧道结构的地震动强度指标(IM)。选取12条近场地震记录,用于IDA分析隧道纵向的抗震性能水平。将概率地震需求模型与工程需求参数相结合,建立结构的地震易损性曲线。结果表明,峰值速度(PGV)是适用于隧道纵向抗震性能的地震动强度指标;场地类型对隧道纵向损伤程度的影响最为深远,其中Ⅰ类场地在地震作用下损伤概率最大。此外,将计算所得易损性曲线与经验易损性曲线和横向易损性曲线进行对比分析,验证了模型的可行性,为隧道结构的抗震设计提供了一定的参考。