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Deep learning-based evaluation of factor of safety with confidence interval for tunnel deformation in spatially variable soil

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Journal of rock Mechanics and Geotechnical Engineering 2021年第6期13卷 1358-1367页

作者： Jinzhang Zhang kok kwang phoon Dongming Zhang Hongwei Huang Chong Tang key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai200092China Department of Geotechnical Engineering Tongji UniversityShanghai200092China Department of Civil and Environmental Engineering National University of Singapore117576Singapore singapore University of Technology and Design 487372Singapore

The random finite difference method(rFDM) is a popular approach to quantitatively evaluate the influence of inherent spatial variability of soil on the deformation of embedded ***,the high computational cost is an ongoing challenge for its application in complex *** address this limitation,a deep learning-based method for efficient prediction of tunnel deformation in spatially variable soil is *** proposed method uses one-dimensional convolutional neural network(CNN) to identify the pattern between random field input and factor of safety of tunnel deformation *** mean squared error and correlation coefficient of the CNN model applied to the newly untrained dataset was less than 0.02 and larger than 0.96,*** means that the trained CNN model can replace rFDM analysis for Monte Carlo simulations with a small but sufficient number of random field samples(about 40 samples for each case in this study).It is well known that the machine learning or deep learning model has a common limitation that the confidence of predicted result is unknown and only a deterministic outcome is *** calls for an approach to gauge the model’s confidence *** is achieved by applying dropout to all layers of the original model to retrain the model and using the dropout technique when performing *** excellent agreement between the CNN model prediction and the rFDM calculated results demonstrated that the proposed deep learning-based method has potential for tunnel performance analysis in spatially variable soils.

关键词： Deep learning Convolutional neural network(CNN) Tunnel safety Confidence interval random field

Determination of site-specific soil-water characteristic curve from a limited number of test data-A Bayesian perspective

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Geoscience Frontiers 2018年第6期9卷 1665-1677页

作者： Lin Wang Zi-Jun Cao Dian-Qing Li kok-kwang phoon siu-kui Au state key Laboratory of Water resources and Hydropower Engineering science Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering(Ministry of Education)Wuhan University8 Donghu South RoadWuhan 430072China Department of Civil and Environmental Engineering National University of SingaporeBlk E1A#07-031 Engineering Drive 2Singapore 117576Singapore Institute for risk and Uncertainty University of LiverpoolHarrison Hughes BuildingBrownlow HillLiverpoolL69 3GHUnited Kingdom

Determining soilewater characteristic curve(sWCC) at a site is an essential step for implementing unsaturated soil mechanics in geotechnical engineering practice, which can be measured directly through various in-situ and/or laboratory tests. such direct measurements are, however, costly and timeconsuming due to high standards for equipment and procedural control and limits in testing apparatus. As a result, only a limited number of data points(e.g., volumetric water content vs. matric suction)on sWCC at some values of matric suction are obtained in practice. How to use a limited number of data points to estimate the site-specific sWCC and to quantify the uncertainty(or degrees-of-belief) in the estimated sWCC remains a challenging task. This paper proposes a Bayesian approach to determine a site-specific sWCC based on a limited number of test data and prior knowledge(e.g., engineering experience and judgment). The proposed Bayesian approach quantifies the degrees-of-belief on the estimated sWCC according to site-specific test data and prior knowledge, and simultaneously selects a suitable sWCC model from a number of candidates based on the probability logic. To address computational issues involved in Bayesian analyses, Markov Chain Monte Carlo simulation(MCMCs), specifically Metropolis-Hastings(M-H) algorithm, is used to solve the posterior distribution of sWCC model parameters, and Gaussian copula is applied to evaluating model evidence based on MCMCs samples for selecting the most probable sWCC model from a pool of candidates. This removes one key limitation of the M-H algorithm, making it feasible in Bayesian model selection problems. The proposed approach is illustrated using real data in Unsaturated soil Database(UNsODA) developed by U.s. Department of Agriculture. It is shown that the proposed approach properly estimates the sWCC based on a limited number of site-specific test data and prior knowledge, and reflects the degrees-of-belief on the estimated sWCC

关键词： soilewater characteristic curve Bayesian approach Unsaturated soils Degrees-of-belief UNsODA

Estimating pressure gradients by auscultation:How technology(echocardiography)can help improve clinical skills

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World Journal of Cardiology 2017年第8期9卷 693-701页

作者： rohini L kadle Colin kL phoon Division of Pediatric Cardiology Hassenfeld Children’s Hospital of New York at NYU LangoneFink Children’s CenterNew YorkNY 10016United States

AIM To extend our previously-published experience in estimating pressure gradients(PG) via physical examination in a large patient cohort. METHODs From January 1, 1997 through December 31, 2009, an attending pediatric cardiologist compared clinical examination(EXAM) with Doppler-echo(ECHO), in 1193 patients with pulmonic stenosis(Ps, including tetralogy of Fallot), aortic stenosis(As), and ventricular septal defect(VsD). EXAM PG estimates were based primarily on a murmur's pitch, grade, and length. ECHO peak instantaneous PG was derived from the modified Bernoulli equation. Patients were 0-38.4 years old(median 4.8).rEsULTs For all patients, EXAM correlated highly with ECHO: ECHO = 0.99(EXAM) + 3.2 mm Hg; r = +0.89; P reement was excellent(mean difference =-2.9 ± 16.1 mm Hg). In 78% of all patients, agreement between EXAM and ECHO was within 15 mm Hg and within 5 mm Hg in 45%. Clinical estimates of Ps PG were more accurate than of As and VsD. A palpable precordial thrill and increasing loudness of the murmur predicted highergradients(P racy. A learning curve was evident, such that the most recent quartile of patients showed ECHO = 1.01(EXAM) + 1.9, r = +0.92, P ring this time, the attending pediatric cardiologist had been > 10 years in *** Clinical examination can accurately estimate PG in Ps, As, or VsD. Continual correlation of clinical findings with echocardiography can lead to highly accurate diagnostic skills.

关键词： Physical examination Ventricular septal defect Clinical skills Echocardiography Aortic stenosis Pulmonary stenosis

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希望联盟执政时期的马中关系

东南亚研究 2020年第4期 124-138,157页

作者：潘永强马来西亚南方大学学院

在2018年举行的马来西亚第14届大选中,长期执政的国民阵线败选,希望联盟赢得选举,组成新政府。希望联盟政府上台后,马来西亚的外交政策既有延续,也有局部的变迁,一方面继续强调发展面向东亚和伊斯兰国家的传统关系,另一方面重回马哈蒂... 详细信息

在2018年举行的马来西亚第14届大选中,长期执政的国民阵线败选,希望联盟赢得选举,组成新政府。希望联盟政府上台后,马来西亚的外交政策既有延续,也有局部的变迁,一方面继续强调发展面向东亚和伊斯兰国家的传统关系,另一方面重回马哈蒂尔首度担任首相时期的外交方针,即在大国强权之间保持中立,在中美之间则确保自主和对冲空间。因此,希望联盟政府局部修正了国民阵线时期的对华政策,其主要焦点就是检讨中资项目,特别是东海岸铁路计划,同时确立安全战略与经贸分离的原则,试图塑造政党轮替后的新型马中关系。当马中关系重回正轨之际,希望联盟的短暂执政就宣告结束。虽然马中关系既有的格局在短期内不会改变,但鉴于马来西亚政治转型走向不明确,马中关系也将面临新的变数和前景。

关键词：希望联盟马中关系马哈蒂尔东海岸铁路

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缺血导致终末期肾病轴突兴奋性的异常改变

世界核心医学期刊文摘(神经病学分册) 2006年第11期 13-14页

作者： krishnan A.V phoon r.k.s.Pussell B.A M.C.kiernan 高中宝 Prince of Wales Medical research Institute Barker Street Sydney NSW 2031 Australia Prof.

Peripheral neuropathy is present in 65%of patients with end stage kidney disease (EskD). No cause is yet established: nerve excitability studies have shown that axons are chronically depolarized, primarily owing to hyperkalaemia, but in vitro studies have suggested a role for axonal Na+/k +pump dysfunction. To investigate Na+/k+pump activity in vivo, lower limb ischaemia was induced in five EskD patients and six healthy controls by a sphygmomanometer cuff, inflated to 200 mm Hg and maintained for 13 min. The peroneal nerve was stimulated at the fibular neck and excitability parameters were recorded from tibialis anterior (TA) and extensor digitorum brevis (EDB) before, during and after the ischaemic period. Baseline excitability studies in EskD patients demonstrated reductions in threshold electrotonus and superexcitability and increased refractoriness, consistent with membrane depolarization. During ischaemia, threshold increased in EskD patients [by +23.6 ±5.0%(TA); +32.1 ±7.3%(EDB)] in contrast to the persistent threshold reduction observed in normal controls [-2.4 ±5.2%(TA); -13.0 ±8.2%(EDB); P se changes were accompanied by increased refractoriness and reduced superexcitability in both EskD and control groups, consistent with ischaemic depolarization. Conversely, there was reduction in strength-duration time constant towards the end of ischaemia. Following release of ischaemia, the marked increase in threshold observed in normal controls was not evident in EskD patients, but the rapid return of threshold to baseline argues against significant Na+/k+pump dysfunction. The abnormal pattern of response to ischaemia in the EskD patients was not fully explained by the hyperkalaemic membrane depolarization and suggests that another dialysable factor affects nerve excitability in EskD patients, most likely H+ions, but that this factor only becomes evident during ischaemia. Blockade of persistent Na+conductances by H+would also explain the reduction in stren

关键词：终末期肾病患者 EskD 兴奋性应激性轴突轴索神经纤维

考虑参数空间变异性的隧道结构变形分析简化方法

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岩土工程学报 2022年第1期44卷 134-143,I0007页

作者：张晋彰黄宏伟张东明方国光唐冲同济大学土木工程学院上海200092 新加坡国立大学土木及环境工程系新加坡117576

土体参数具有空间变异性是被广泛接受的,而这种变异性对岩土中结构性能有着重要的影响。随机场理论是一种常用的用来模拟土体参数空间变异性的方法。基于随机场理论,以土体弹性模量的空间变异性为切入点,采用蒙特卡罗方法和有限差分模... 详细信息

土体参数具有空间变异性是被广泛接受的,而这种变异性对岩土中结构性能有着重要的影响。随机场理论是一种常用的用来模拟土体参数空间变异性的方法。基于随机场理论,以土体弹性模量的空间变异性为切入点,采用蒙特卡罗方法和有限差分模拟计算相结合的方法,开展隧道水平收敛的随机分析。在大量蒙特卡罗计算基础上,提出了3种简单易用的简化考虑空间变异性的方法,分别为参数折减法、放大系数法和可靠度分项系数标定法。经过对计算结果的统计分析,给出了在土体弹性模量的水平、竖向相关距离及其变异系数的不同组合下3种简化考虑方法的建议值。提出的简化方法可以为空间变异性研究应用到实际工程提供一定的参考。

关键词：隧道空间变异性随机场相关距离简化方法

二维联合概率分布函数构造方法对结构串联系统可靠度影响分析

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计算力学学报 2013年第6期30卷 777-782页

作者：李典庆蒋水华周创兵方国光武汉大学水资源与水电工程科学国家重点实验室武汉430072 武汉大学水工岩石力学教育部重点实验室武汉430072 新加坡国立大学土木与环境工程系

简要介绍了两种构造联合分布函数近似方法:基于Pearson相关系数的近似方法P和基于spearman相关系数的近似方法s。推导了基于直接积分方法的串联系统失效概率计算公式,提出了两构件功能函数间负相关时串联结构系统失效概率上限值的计算... 详细信息

简要介绍了两种构造联合分布函数近似方法:基于Pearson相关系数的近似方法P和基于spearman相关系数的近似方法s。推导了基于直接积分方法的串联系统失效概率计算公式,提出了两构件功能函数间负相关时串联结构系统失效概率上限值的计算公式。以理论联合概率分布函数是二维极值分布为例研究了两种近似方法在串联系统可靠度计算中的精度。结果表明,两种近似方法能够有效地计算串联结构系统可靠度,且精度很高,为不完备概率信息条件下串联结构系统可靠度分析提供了一条有效的途径。当两构件的功能函数正相关时,两种近似方法误差随串联系统失效概率的减小而增加,但近似方法与精确方法系统失效概率的差别最大也不会超过2倍;当两构件的功能函数负相关时,两种近似方法误差随系统失效概率的减小而减小,但两种近似方法的失效概率几乎与精确解一样。此外,两种近似方法误差不是随构件间相关性的增加而单调增加,而是存在一极大值。

关键词：联合概率密度函数 Pearson相关系数 spearman相关系数串联系统失效概率