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Modeling of environmental influence in structural health assessment for reinforced concrete buildings

Earthquake Engineering and Engineering Vibration 2010年第2期9卷 295-306页

作者： Ka-Veng yuen Sin-Chi Kuok Department of Civil and Environmental Engineering Univeristy of Macao

One branch of structural health monitoring (SHM) utilizes dynamic response measurements to assess the structural integrity of civil infrastructures. In particular,modal frequency is a widely adopted indicator for structural damage since its square is proportional to structural stiffness. However,it has been demonstrated in various SHM projects that this indicator is substantially affected by fluctuating environmental conditions. In order to provide reliable and consistent information on the health status of the monitored structures,it is necessary to develop a method to filter this interference. This study attempts to model and quantify the environmental influence on the modal frequencies of reinforced concrete buildings. Daily structural response measurements of a twenty-two story reinforced concrete building were collected and analyzed over a one-year period. The Bayesian spectral density approach was utilized to identify the modal frequencies of this building and it was clearly seen that the temperature and humidity fluctuation induced notable variations. A mathematical model was developed to quantify the environmental effects and model complexity was taken into consideration. Based on a Timoshenko beam model,the full model class was constructed and other reduced-order model class candidates were obtained. Then,the Bayesian modal class selection approach was employed to select the one with the most suitable complexity. The proposed model successfully characterizes the environmental influence on the modal frequencies. Furthermore,the estimated uncertainty of the model parameters allows for assessment of the reliability of the prediction. This study not only improves the understanding about the monitored structure,but also establishes a systematic approach for reliable health assessment of reinforced concrete buildings.

关键词： Bayesian inference model selection reinforced concrete building structural health monitoring temperature and humidity effects Timoshenko beam

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Mechanical stretching of 3D hydrogels for neural stem cell differentiation

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Bio-Design and Manufacturing 2022年第4期5卷 714-728页

作者： Quanjing Mei Ho-Yin yuen Xin Zhao Department of Biomedical Engineering The Hong Kong Polytechnic UniversityHung HomHong KongChina

While it is known that mechanical dynamics are influential in neural differentiation for critical processes like neurogenesis or neurodegeneration, studies on neural stem cell therapies usually focus on biochemical interactions rather than mechanical aspects, frequently resulting in low efficacy and unfulfilled potential. Therefore, current studies are attempting to elucidate the effect of mechanical stimulus on neural performance using conventional two-dimensional(2D) planar substrates. Yet, these2D substrates fail to capture the defining three-dimensional(3D) characteristics of the in vivo neural stem cell *** complete this research gap, we synthesized a series of soft and elastic 3D hydrogels to mimic the neural tissue mechanical environment for 3D cell culture, using long-chain polyethylene glycol diacrylate(PEGDA) and gelatin-methacryloyl(Gel MA).By varying the concentration of the polymer, we obtained biomimicking hydrogels with a tensile modulus as low as 10 k Pa and a compressive modulus as low as 0.8 k Pa. The in vitro results demonstrated that Gel MA-PEGDA hydrogels have the high biocompatibility required to support neural cell growth, proliferation, and differentiation, as well as neurite outgrowth. We then studied the effect of mechanical stretching on the behaviors of neural cells and observed that mechanical stretching could significantly enhance neurite extension and axon elongation. In addition, the neurites were more directionally oriented to the stretching direction. Immunocytochemistry and relative gene expression data also suggested that mechanical tension could upregulate the expression of neural differentiation protein and genes, including GFAP and βIII-Tubulin. Overall, this study shows that in addition to the specific mechanical properties of Gel MA-PEGDA that improve neural differentiation towards specific lineages, hydrogel stretching is also a potentially attractive strategy to improve the therapeutic outcomes of neural stem cel

关键词： Mechanical property Tensile stretching Hydrogels Neural differentiation 3D cell culture

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Additive Schwarz Preconditioners with Minimal Overlap for Triangular Spectral Elements

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Communications in Computational Physics 2013年第2期13卷 411-427页

作者： yuen-Yick Kwan Center for Computational Science Tulane UniversityNewOrleansLA 70118USA

The additive Schwarz preconditioner with minimal overlap is extended to triangular spectral elements(TSEM).Themethod is a generalization of the corresponding method in tensorial quadrilateral spectral elements(QSEM).The proposed preconditioners are based on partitioning the domain into overlapping subdomains,solving local problems on these subdomains and solving an additional coarse problem associated with the subdomain *** results of numerical experiments show that the proposed preconditioner are robust with respect to the number of elements and are more efficient than the preconditioners with generous overlaps.

关键词： Spectral elements additive Schwarz

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Effects of SARS-CoV-2 infection on incidence and treatment strategies of hepatocellular carcinoma in people with chronic liver disease

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World Journal of Hepatology 2024年第2期16卷 211-228页

作者： Lung-Yi Mak Matthew Shing Hin Chung Xue Li Francisco Tsz Tsun Lai Eric Yuk Fai Wan Celine Sze Ling Chui Franco Wing Tak Cheng Esther Wai Yin Chan Ching Lung Cheung Ivan Chi Ho Au Xi Xiong Wai-Kay Seto Man-Fung yuen Carlos King Ho Wong Ian Chi Kei Wong Department of Medicine The University of Hong KongHong KongChina State Key Laboratory of Liver Research The University of Hong KongHong KongChina Department of Pharmacology and Pharmacy The University of Hong KongHong KongChina Laboratory of Data Discovery for Health(D24H) Hong Kong Science and Technology ParkHong KongChina Department of Family Medicine and Primary Care The University of Hong KongHong KongChina School of Nursing The University of Hong KongHong KongChina School of Public Health The University of Hong KongHong KongChina Research Department of Practice and Policy University College LondonLondon WC1E 6BTUnited Kingdom Aston School of Pharmacy Aston UniversityBirmingham B47ETUnited Kingdom

BACKGROUND Chronic liver disease(CLD)was associated with adverse clinical outcomes among people with severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)*** To determine the effects of SARS-CoV-2 infection on the incidence and treatment strategy of hepatocellular carcinoma(HCC)among patients with *** A retrospective,territory-wide cohort of CLD patients was identified from an electronic health database in Hong *** with confirmed SARS-CoV-2 infection[coronavirus disease 2019(COVID-19)+CLD]between January 1,2020 and October 25,2022 were identified and matched 1:1 by propensity-score with those without(COVID-19-CLD).Each patient was followed up until death,outcome event,or November 15,*** outcome was incidence of *** outcomes included all-cause mortality,adverse hepatic outcomes,and different treatment strategies to HCC(curative,non-curative treatment,and palliative care).Analyses were further stratified by acute(within 20 d)and post-acute(21 d or beyond)phases of SARS-CoV-2 *** rate ratios(IRRs)were estimated by Poisson regression *** Of 193589 CLD patients(>95%non-cirrhotic)in the cohort,55163 patients with COVID-19+CLD and 55163 patients with COVID-19-CLD were included after 1:1 propensity-score *** 249-d median follow-up,COVID-19+CLD was not associated with increased risk of incident HCC(IRR:1.19,95%CI:0.99-1.42,P=0.06),but higher risks of receiving palliative care for HCC(IRR:1.60,95%CI:1.46-1.75,P<0.001),compared to *** both acute and post-acute phases of infection,COVID-19+CLD were associated with increased risks of allcause mortality(acute:IRR:7.06,95%CI:5.78-8.63,P<0.001;post-acute:IRR:1.24,95%CI:1.14-1.36,P<0.001)and adverse hepatic outcomes(acute:IRR:1.98,95%CI:1.79-2.18,P<0.001;post-acute:IRR:1.24,95%CI:1.13-1.35,P<0.001),compared to *** Although CLD patients with SARS-CoV-2 infection were not associated with increased risk of HCC,they

关键词： SARS-CoV-2 infection Chronic liver disease Long COVID Post-COVID-19 syndrome Cirrhosis Hepatocellular carcinoma

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Frequency dependence in the emission from subpulse drifting pulsars

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Research in Astronomy and Astrophysics 2021年第9期21卷 153-162页

作者： Xiao-Hong Han Rai yuen Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China Key Laboratory of Radio Astronomy Chinese Academy of SciencesUrumqi 830011China SIfA School of PhysicsUniversity of SydneySydneyNSW 2006Australia

We investigate relations in the emission properties as revealed by drifting subpulses detected at different observing frequencies based on the method that incorporates the rotating carousels in pulsar magnetospheres of multiple emission *** emission state is associated with particular emission properties as determined by the drifting subpulses at a particular frequency,and different emission states obtained at different frequencies reveal the variation of emission properties across the emission *** method allows the determination of the essential radio emission properties such as the relative emission height,subpulse number,charge density and the plasma flow relative to corotation in an emission region for a particular *** apply the method to seven pulsars that exhibit subpulse drifting along single drift-band at 326 MHz and 1429 *** results show that drifting subpulses observed at different frequencies correspond to particular emission states suggesting that the pulsar emission properties are frequency *** show that emission follows the frequency-to-radius mapping for pulsars with obliquity angle?30°regardless of the sign and magnitude of the *** pulsars with long rotation periods in our sample,the circulation time for the plasma to revolve once around the magnetosphere relative to corotation increases as the rotation period increases at both frequencies,but exhibits irregularity for pulsars with short rotation *** results suggest that evolution of the obliquity angles in subpulse drifting pulsars is from large to small,and the emission region tends to be’thicker’in younger pulsars.

关键词： radiation mechanisms:non-thermal pulsar:general

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Updatable timed automata with one updatable clock

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Science China(Information Sciences) 2018年第1期61卷 99-112页

作者： Guoqiang LI Yunqing WEN Shoji yuen BASICS School of Software Shanghai Jiao Tong University Graduate School of Information Science Nagoya University

Updatable timed automata(UTAs) proposed by Bouyer ***., is an extension of timed automata(TAs) having the extra ability to update clocks in a more elaborate way than simply reset them to *** reachability of UTAs is generally undecidable, which can be easily gained by regarding a pair of clocks as updatable counters. This paper investigates a subclass of UTAs by restricting the number of updatable clocks to be one. We will show that(1) the reachability of general UTAs with one updatable clock(UTA1 s)is still undecidable, and(2) that of UTA1 s under diagonal-free constraints is decidable, and the complexity is Pspace-complete. The former is achieved by encoding Minsky machines to the general UTA1 s, where two counters are simulated by the updatable clock. The latter is gained by regarding a region of a UTA1 to be an unbounded digiword, and encoding sets of digiwords that are accepted by a one counter automaton where regions are generated as the value of the counter.

关键词： updatable timed automata one counter automata digiword reachability problem

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Asymptotic Results for Tail Probabilities of Sums of Dependent and Heavy-Tailed Random Variables

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Chinese Annals of Mathematics,Series B 2012年第4期33卷 557-568页

作者： Kam Chuen yuen Chuancun YIN Department of Statistics and Actuarial Science The University of Hong Kong Pokfulam Road HongKong China. Corresponding author. School of Mathematical Sciences Qufu Normal University Qufu 273165 Shan- dong China

Abstract Let X1, X2,... be a sequence of dependent and heavy-tailed random variables with distributions F1, F2,.. on （-∞,∞）, and let T be a nonnegative integer-valued random variable independent of the sequence {Xk, k 〉 1}. In this framework, the asymptotic behavior of the tail probabilities of the quantities Sn = fi Xk and S（n） =∑ k=1 n 〉 1, and their randomized versions ST and S（τ） are studied. Some risk theory are presented. max Sk for 1〈k〈n applications to the

关键词： Asymptotic tail probability Copula Heavy-tailed distribution Partialsum Risk process

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Single-atom Catalysts for Polymer Electrolyte Membrane Fuel Cells

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Chemical Research in Chinese Universities 2020年第3期36卷 320-328页

作者： ZHU Mengzhao WANG Jing WU yuen Department of Chemistry iChEM(Collaborative Innovation Center of Chemistryfor Energy Materials)University of Science and Technology of ChinaHefei 230026P.R.China

Searching for high-activity,stabilily and highly casbellective electrocalalysts for acid oxygen reaction rolutioo(ORR)has always been a urgent problem in polymer ectrolyte menbrane fuel ells(PEMFC).Nonetheless,the electrochemical poperties of various systems have their intrinsic limits and tremendous eforts have been paid oul to search for highly eficient electocatalysts by more raional control over the size,morphology,compoition,and *** particular,single-atom catalysts(SACs)have atrascted extensive intenest due to theirs cxcellant activity,stability,slctivity and the highest metal tiliztion In rceat yeurs,the number of papers in the field of SACs has incressed rapidly,indicating that SACs have made great *** review foouses on SACs electo-echemical applications in the acid ORR and introduces immovative syntheses,fiuel cell performance and long-time durabilily.

关键词： Singe-aton catalyst Oxygen reactio reduction Polymer electrolyte membrane fuel cell

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Preliminary estimation of rock-fall lateral dispersion by laboratory test

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第12期15卷 3343-3351页

作者： Louis Ngai yuen Wong Zhicheng Tang Department of Earth Sciences The University of Hong KongHong KongChina Faculty of Engineering China University of GeosciencesWuhan430074China

Lateral dispersion significantly directs the assessment of rockfall hazard and design of countermeasures. In the present study, the dependence of lateral dispersion on different controlling factors has been systematically evaluated by performing laboratory tests using three different rock block types, namely circular block, and two types of elliptical block. The three types of rock block are released onto an inclined surface with the identical initial status. Parallel, anti-parallel, and oblique impact tests set at slope angles of 22.5° and 45°are conducted to study the block-slope interaction of rockfall. Lateral dispersion of rockfall is less influenced by the block shape for the oblique impact, while the post-impact behaviors are greatly affected by the block shape. The key factors influencing the deviation of the post-impact trajectory direction are the slope angle (θ) and direction difference (Δφ). An empirical model is then developed to characterize the deviation distribution of lateral dispersion by 5th and 95th percentile values with the inclusion of the two key factors. Linear function can be used to describe the 5th percentile boundary, while hyperbolic function is good for the 95th percentile boundary, which need to be validated by field tests in the subsequent research.

关键词： Rockfall Block shape Slope angle Oblique impact Lateral dispersion

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每人支付5欧元！这是威尼斯的入城费还是逐客令？

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环球人文地理 2024年第1期 46-55页

作者：蒋雨宁 Edmond yuen 张鹏 Luca Bravo canmandawe Tao Qi Daniil Markus Nikhg Nataliia Mark Alena scaliger

想去威尼斯旅行吗？进城请先支付5欧元！据路透社消息，意大利威尼斯市长路易吉·布鲁尼亚罗宣布，将在2024年4月25日开始，对进入威尼斯的游客收费。市长表示，这项措施将会让城市变得“可预约”，既能控制客流，又能保障游客的出行体...

想去威尼斯旅行吗？进城请先支付5欧元！据路透社消息，意大利威尼斯市长路易吉·布鲁尼亚罗宣布，将在2024年4月25日开始，对进入威尼斯的游客收费。市长表示，这项措施将会让城市变得“可预约”，既能控制客流，又能保障游客的出行体验。意大利时间2023年11月27日，威尼斯市长宣布，从2024年4月起，游客进入威尼斯将不再免费。

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