Towards high-accuracy data modelling, uncertainty quantification and correlation analysis for SHM measurements during typhoon events using an improved most likely heteroscedastic Gaussian process

Qi’ang Wang,Zhi-Jun Liu,Hao-Bo Wang,Zhanguo Ma,Yi-Qing Ni,Jian Jiang,Rui Sun,Hao-Wei Zhu 국제구조공학회 2023 Smart Structures and Systems, An International Jou Vol.32 No.4

Data modelling and interpretation for structural health monitoring (SHM) field data are critical for evaluating structural performance and quantifying the vulnerability of infrastructure systems. In order to improve the data modelling accuracy, and extend the application range from data regression analysis to out-of-sample forecasting analysis, an improved most likely heteroscedastic Gaussian process (iMLHGP) methodology is proposed in this study by the incorporation of the outof- sample forecasting algorithm. The proposed iMLHGP method overcomes this limitation of constant variance of Gaussian process (GP), and can be used for estimating non-stationary typhoon-induced response statistics with high volatility. The first attempt at performing data regression and forecasting analysis on structural responses using the proposed iMLHGP method has been presented by applying it to real-world filed SHM data from an instrumented cable-stay bridge during typhoon events. Uncertainty quantification and correlation analysis were also carried out to investigate the influence of typhoons on bridge strain data. Results show that the iMLHGP method has high accuracy in both regression and out-of-sample forecasting. The iMLHGP framework takes both data heteroscedasticity and accurate analytical processing of noise variance (replace with a point estimation on the most likely value) into account to avoid the intensive computational effort. According to uncertainty quantification and correlation analysis results, the uncertainties of strain measurements are affected by both traffic and wind speed. The overall change of bridge strain is affected by temperature, and the local fluctuation is greatly affected by wind speed in typhoon conditions.

Efficacy and dosimetry analysis of image-guided radioactive 125I seed implantation as salvage treatment for pelvic recurrent cervical cancer after external beam radiotherapy

Ang Qu,Ping Jiang,Haitao Sun,Weijuan Jiang,Yuliang Jiang,Suqing Tian,Junjie Wang 대한부인종양학회 2019 Journal of Gynecologic Oncology Vol.30 No.1

Objective: To investigate the efficacy of image-guided radioactive 125I seed (IGRIS) implantation for pelvic recurrent cervical cancer (PRCC) after external beam radiotherapy (EBRT), and analyze the influence of clinical and dosimetric factors on efficacy. Methods: From July 2005 to October 2015, 36 patients with PRCC received IGRIS. We evaluated local progression-free survival (LPFS) and overall survival (OS). Results: The median follow up was 11.5 months. The 1- and 2-year LPFS rate was 34.9% and 20%, respectively. The multivariate analysis indicated recurrence site (central or pelvic wall) (hazard ratio [HR]=0.294; 95% confidence interval [CI]=0.121–0.718), lesion volume (HR=2.898; 95% CI=1.139–7.372), D 90 (HR=0.332; 95% CI=0.130–0.850) were the independent factors affecting LPFS. The 1- and 2-year OS rate was 52.0% and 19.6%, respectively. The multivariate analysis suggested pathological type (HR=9.713; 95% CI=2.136–44.176) and recurrence site (HR=0.358; 95% CI=0.136–0.940) were the independent factors affecting OS. The dosimetric parameters of 33 patients mainly included D 90 (128.5±47.4 Gy), D 100 (50.4±23.7 Gy) and V 100 (86.7%±12.9%). When D 90 ≥105 Gy or D 100 ≥55 Gy or V 100 ≥91%, LPFS was extended significantly, but no significant difference for OS. The 79.2% of 24 patients with local pain were suffering from pain downgraded after radioactive 125I seed implantation. Conclusion: IGRIS implantation could be a safe and effective salvage treatment for PRCC after EBRT, which could markedly release the pain. Recurrence site, tumor volume and dose were the main factors affected efficacy. Compared with central recurrence, it was more suitable for patients with pelvic wall recurrent cervical cancer after EBRT.

A Comparison of Friction Force Calibration in Lateral Force Microscope

Wang Yuli-Ang,Kim Hong-Joon,Kong Ho-Sung,Zhao Xu-Zheng,Yoon Eui-Sung Korean Tribology Society 2006 KSTLE International Journal Vol.7 No.1

The main principle of two widely used methods which were proposed by Ruan and Bhushan, and by Ogletree and Carpick are introduced. Experiments were conducted using the two methods to measure friction force between AFM probe and silicon sample quantitatively. To characterize the frictional properties, the conversion factors of the two methods by which lateral electronic signal is converted into actual friction force were calculated. The experimental results show that that the conversion factors were extraordinarily different from each other. Further research should be done to identity the reasons for these differences.

Cervical Cancer Screening and Analysis of Potential Risk Factors in 43,567 Women in Zhongshan, China

Wang, Ying,Yu, Yan-Hong,Shen, Keng,Xiao, Lin,Luan, Feng,Mi, Xian-Jun,Zhang, Xiao-Min,Fu, Li-Hua,Chen, Ang,Huang, Xiang Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.2

Objective: The objective of this study was to establish a program model for use in wide-spread cervical cancer screening. :Methods: Cervical cancer screening was conducted in Zhongshan city in Guangdong province, China through a coordinated network of multiple institutes and hospitals. A total of 43,567 women, 35 to 59 years of age, were screened during regular gynecological examinations using the liquid-based ThinPrep cytology test (TCT). Patients who tested positive were recalled for further treatment. Results: The TCT-positive rate was 3.17%, and 63.4% of these patients returned for follow-up. Pathology results were positive for 30.5% of the recalled women. Women who were younger than 50 years of age, urban dwelling, low-income, had a history of cervical disease, began having sex before 20 years of age, or had sex during menstruation, were at elevated risk for a positive TCT test. The recall rate was lower in women older than 50 years of age, urban dwelling, poorly educated, and who began having sex early. Ahigher recall rate was found in women 35 years of age and younger, urban dwelling, women who first had sex after 24 years of age, and women who had sex during menstruation. The positive pathology rate was higher in urban women 50 years of age and younger and women who tested positive for human papillomavirus. Conclusion: An effective model for large-scale cervical cancer screening was successfully established. These results suggest that improvements are needed in basic education regarding cervical cancer screening for young and poorly educated women. Improved outreach for follow-up is also necessary to effectively control cervical cancer.

Adaptive kernel method for evaluating structural system reliability

Wang, G.S.,Ang, A.H.S.,Lee, J.C. Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.2

Importance sampling methods have been developed with the aim of reducing the computational costs inherent in Monte Carlo methods. This study proposes a new algorithm called the adaptive kernel method which combines and modifies some of the concepts from adaptive sampling and the simple kernel method to evaluate the structural reliability of time variant problems. The essence of the resulting algorithm is to select an appropriate starting point from which the importance sampling density can be generated efficiently. Numerical results show that the method is unbiased and substantially increases the efficiency over other methods.

Numerical Simulation on Energy Concentration and Release Process of Strain Rockburst

Ang Lu,Peng Yan,Wenbo Lu,Ming Chen,Gaohui Wang,Sheng Luo,Xiao Liu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.10

Rockburst mechanism has been a hot topic in the stability analysis of underground carven excavation, and the accurate description of energy evolution process is very critical to rockburst prediction. To study the evolution process of rockburst, such as V-shaped rockburst pit, theoretical formula derivation and numerical simulation are adopted to research the dynamic response characteristics during the formation process of rockburst pits quantitatively. The results show that rockburst intensity distribution varies with failure depth. It can be divided into three zone: slow-increase, rapid-increase and slow-decrease. For a circular tunnel with radius R, the strain energy release rate and vibration response of surrounding rock increases gradually within (0 − 0.06) R; reaches the peak value around (0.06 − 0.1) R and drops to a balance beyond 0.1R. Due to the same law of them, the rockburst risk can be conveniently predicted by monitoring vibration of surrounding rock with a certain depth. This work is beneficial to provide a good reference for rockburst prediction.

Deformation Mechanism of 5052 Aluminum Alloy Using Electrically Assisted Electromagnetic Forming

Ang Xiao,Changqing Huang,HongSheng Liu,Xiaohui Cui,Shipeng Wang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10

A technology named as electrically assisted electromagnetic forming (EAEMF) was used to improve the plastic deformationability of 5052 aluminum alloy at room temperature. The ANSYS software is used to study the force and deformation ofworkpiece based on sequential coupling method. The simulation results show that the pulse current can increase the currentdensity, improve the uniformity of current distribution, and increase the forming height of the sample. The primary strainand secondary strain are increased by 53.8% and 27.4% respectively. Under the same deformation condition, the elongationof EAEMF sample increases by 160%, while the strength decreases slightly. From the perspective of microstructure evolution,the dislocation density of EAEMF sample is lower than that of EMF sample, and the pinning effect of the second phaseparticles on the dislocation is weakened. Under the action of the pulse current, the dislocations continue to move around thesecond phase particles with higher energy, and the dislocations appear directional arrangement.

Multivariate Probabilistic Seismic Demand Model for the Bridge Multidimensional Fragility Analysis

Qi’ang Wang,Ziyan Wu,Shukui Liu 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.9

Seismic fragility analysis for bridges is an essential issue for risk assessment of transportation networks exposed to seismic hazards. Considering multiple Performance Limit States (PLSs) and seismic demand parameters, the study proposes a multidimensional fragility evaluation methodology for engineering structures, and the objective of the paper is to show that the uncertainty and dependence between seismic demand parameters should be considered for fragility analysis. Thus, a new Probabilistic Seismic Demand Model (PSDM) following multivariate logarithmic normal distribution is addressed. Taking PLS correlation into consideration, multidimensional PLS formula is constructed to identify the structural failure domain. A RC bridge is studied to show the proposed theory. To consider bridge column plastic deformation and bearing nonlinear characteristic, nonlinear dynamic analyses are carried out. The bridge multidimensional fragility curves are derived and compared with fragility curves for an individual component. Results indicate that uncertainty and dependence of demand parameters can be properly dealt with by the multivariate PSDM. The multidimensional fragility is higher than fragility of any individual component, and the bridge as a system is more fragile. The ignorance of multiple components contribution to the system will generate an overestimation for the whole structural performance, which is adverse to engineering structural safety.

Mechanical Properties and Microstructure Evolution of Pre-stretched Aluminum Alloy After Induced Electro-Pulsing Treatment

Shipeng Wang,Xiaohui Cui,Ang Xiao,Lei Zhang,Peng Zhao 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.3

In this study, the effect of induced electro-pulsing treatment (IEPT) on the microstructure evolution and correspondingchanges in the mechanical properties of pre-stretched 5052-O aluminum alloy was investigated. Microstructural changesin the alloy were observed using electron backscatter diffraction, transmission electron microscopy, and scanning electronmicroscopy. The application of induced current significantly reduced the yield strength of pre-stretched specimens whilethe elongation increased. In terms of microstructure, more uniformly distributed dimples were observed after induced currentapplication, which indicate the increased plasticity of the alloy. The average grain size and number of low angle grainboundaries increased with application of induced current. The texture types did not change, however, the cube-type texturebecame less pronounced, whereas brass-type and copper-type textures were enhanced. Furthermore, the dislocation densitydecreased and dislocation rearrangement occurred. Thus, IEPT provides a new way to alter the microstructure and mechanicalproperties of the deformed components.

certainty and Dependence Analysis of Performance Limit State for Structural Multidimensional Fragility Evaluation

Qi’ang Wang,Ziyan Wu,Lu Liu 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.4

Considering uncertainty and dependence of performance limit states (PLSs), the study addresses a methodology to evaluate multidimensional fragility. The purpose is to identify the PLS uncertainty quantitatively. The dependence between each PLS parameters is also investigated. The limit state band is firstly proposed to describe the bi-dimensional case. Through interval estimation, the band area with a certain confidence level is determined. A reinforcement concrete bridge is used as example to illustrate the proposed approach for developing fragility curves. PLS threshold samples are obtained to formulate limit state function using incremental dynamic analysis. The study investigates the sensitivity of the method for fragility assessment when different confidence levels are considered. In addition, influence of correlation coefficient between PLSs is evaluated. Results show that a fragility interval is obtained with the introduction of limit state band. The interval length decreases as with the reduction of the confidence level. The probability of failure becomes smaller when the dependence between PLSs is ignored, which will result in overestimation of the structural seismic performance