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RISS 인기검색어
- 검색키워드
- 저자 : Yan-Gang Zhao (검색결과 31 건)
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Cubic normal distribution and its significance in structural reliability
Yan-Gang Zhao,Zhao-Hui Lu 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.3
Information on the distribution of the basic random variable is essential for the accurate analysis of structural reliability. The usual method for determining the distributions is to fit a candidate distribution to the histogram of available statistical data of the variable and perform approximate goodness-of-fit tests. Generally, such candidate distribution would have parameters that may be evaluated from the statistical moments of the statistical data. In the present paper, a cubic normal distribution, whose parameters are determined using the first four moments of available sample data, is investigated. A parameter table based on the first four moments, which simplifies parameter estimation, is given. The simplicity, generality, flexibility and advantages of this distribution in statistical data analysis and its significance in structural reliability evaluation are discussed. Numerical examples are presented to demonstrate these advantages.
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Cubic normal distribution and its significance in structural reliability
Zhao, Yan-Gang,Lu, Zhao-Hui Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.28 No.3
Information on the distribution of the basic random variable is essential for the accurate analysis of structural reliability. The usual method for determining the distributions is to fit a candidate distribution to the histogram of available statistical data of the variable and perform approximate goodness-of-fit tests. Generally, such candidate distribution would have parameters that may be evaluated from the statistical moments of the statistical data. In the present paper, a cubic normal distribution, whose parameters are determined using the first four moments of available sample data, is investigated. A parameter table based on the first four moments, which simplifies parameter estimation, is given. The simplicity, generality, flexibility and advantages of this distribution in statistical data analysis and its significance in structural reliability evaluation are discussed. Numerical examples are presented to demonstrate these advantages.
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Comparative Study of Electromyographic Signal in Stroke Patients
Yan Zhao,Chi Zhang,Gang Hao 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.5
Stroke is a common condition among the elderly in high latitude and cold area. Its high occurrence, recurrence and disability rate makes it a serious threat for the health and life of middle to old age population, and a heavy burden for patient’s family and the society as a whole. Surface electromyogram signal is a bio-electricity signal recorded from electrodes on muscle surface with controlled neuromuscular actions. It is a direct signal revealing muscle activity and function, and it can reflect neuromuscular activity to certain extent. This study focuses on the accumulated data of electromyographic signal recorded from human upper limb, using Matlab tool to analyze and compare neuromuscular signals between healthy population and stroke patients, finding characters of surface neuromuscular signals with mathematical methods such as Fourier transformation, Hilbert transformation and AR modelling, and then induce the changing pattern of neuromuscular signals with various physiological indicators and make prediction of muscular pathological tendency.
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Reliability-based assessment of American and European specifications for square CFT stub columns
Zhao-Hui Lu,Yan-gang Zhao,Zhi-wu Yu,Cheng Chen 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.4
This paper presents a probabilistic investigation of American and European specifications (i.e., AISC and Eurocode 4) for square concrete-filled steel tubular (CFT) stub columns. The study is based on experimental results of 100 axially loaded square CFT stub columns from the literature. By comparing experimental results for ultimate loads with code-predicted column resistances, the uncertainty of resistance models is analyzed and it is found that the modeling uncertainty parameter can be described using random variables of lognormal distribution. Reliability analyses were then performed with/without considering the modeling uncertainty parameter and the safety level of the specifications is evaluated in terms of sufficient and uniform reliability criteria. Results show that: (1) The AISC design code provided slightly conservative results of square CFT stub columns with reliability indices larger than 3.25 and the uniformness of reliability indices is no better because of the quality of the resistance model; (2) The uniformness of reliability indices for the Eurocode 4 was better than that of AISC, but the reliability indices of columns designed following the Eurocode 4 were found to be quite below the target reliability level of Eurocode 4.
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Estimation of load and resistance factors based on the fourth moment method
Zhao-Hui Lu,Yan-gang Zhao,Alfredo H-S. Ang 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.1
The load and resistance factors are generally obtained using the First Order Reliability Method (FORM), in which the design point should be determined and derivative-based iterations have to be used. In this paper, a simple method for estimating the load and resistance factors using the first four moments of the basic random variables is proposed and a simple formula for the target mean resistance is also proposed to avoid iteration computation. Unlike the currently used method, the load and resistance factors can be determined using the proposed method even when the probability density functions (PDFs) of the basic random variables are not available. Moreover, the proposed method does not need either the iterative computation of derivatives or any design points. Thus, the present method provides a more convenient and effective way to estimate the load and resistance factors in practical engineering. Numerical examples are presented to demonstrate the advantages of the proposed fourth moment method for determining the load and resistance factors.
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Comparison of Deformation Behavior of Saturated Sand under Constant and Variable Deviatoric Stress
Zhiyi Zhao,Gang Deng,Yunshan Han,Zhaopeng Zhang,Yanli Dong,Ying Gao 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.3
The cyclic triaxial tests were carried out on Fujian standard sand under two stress paths, the constant deviatoric stress path (CDS) and constant stress-ratio path (variable deviatoric stress, VDS), and the influence of cyclic deviatoric stress on the development characteristics of saturated sand was preliminarily discussed. Under the condition of the same consolidation stress state and amplitude of cyclic spherical stress, the amplitude of deviatoric stress under the two stress paths was different. The test results indicated that cyclic deviatoric stress had significant effect on the volumetric and shear strain in soil. When the consolidation deviatoric stress was relatively small, the volumetric and shear strain curves under these two stress paths almost coincided. However, the cyclic deviatoric stress had a stronger effect with an increase in the consolidation deviatoric stress. During the loading and unloading stages, the slope of the volumetric strain curve under the VDS path was smaller than that under the CDS path. The accumulated volumetric strain under the VDS path was greater than that under the CDS path. In the loading stage, the growth rate of shear strain under the VDS path was greater than that under the CDS path, but the opposite relationship was observed in the unloading stage. The presence of cyclic deviatoric stress accelerated or slowed down the accumulation of shear strain. These phenomena were related to the positional relationship between the stress state of soil and the critical state line.
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Estimation of load and resistance factors based on the fourth moment method
Lu, Zhao-Hui,Zhao, Yan-Gang,Ang, Alfredo H.S. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.1
The load and resistance factors are generally obtained using the First Order Reliability Method (FORM), in which the design point should be determined and derivative-based iterations have to be used. In this paper, a simple method for estimating the load and resistance factors using the first four moments of the basic random variables is proposed and a simple formula for the target mean resistance is also proposed to avoid iteration computation. Unlike the currently used method, the load and resistance factors can be determined using the proposed method even when the probability density functions (PDFs) of the basic random variables are not available. Moreover, the proposed method does not need either the iterative computation of derivatives or any design points. Thus, the present method provides a more convenient and effective way to estimate the load and resistance factors in practical engineering. Numerical examples are presented to demonstrate the advantages of the proposed fourth moment method for determining the load and resistance factors.
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Pan, Yan,Zhao, Lei,Chen, Xing-Miao,Gu, Yong,Shen, Jian-Gang,Liu, Lu-Ming Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.10
The potential correlation of X-ray repair cross-complementing group 1 (XRCC1) Arg399Gln polymorphism with hepatocellular carcinoma (HCC) susceptibility is ambiguous. Taking account of inconsistent results of previous meta-analyses and new emerging literatures, we conducted a meta-analysis covering 15 case-control datasets to evaluate the relationship. Relevant studies from Medline, Embase and CNKI were retrieved. A fixed-effect model or a random-effect model, depending on between-study heterogeneity, were applied to estimate the association between XRCC1 polymorphism Arg399Gln and HCC risk with the results presented as odds ratios (ORs) and 95% confidence intervals (95% CIs). In accordance with Hardy-Weinberg equilibrium, 15 studies with data for 6,556 individuals were enrolled in this systematic review. For overall HCC,thr XRCC1 polymorphism Arg399Gln was significantly associated with HCC susceptibility in a homozygote model as well as in a dominant model (G/G vs. A/A, OR=1.253, p=0.028; G/G+A/G vs. A/A, OR= 1.281, p=0.047, respectively), but not in a heterozygote model (A/G vs. A/A, OR=1.271, p=0.066) or a recessive model (G/G vs. A/G + A/A, OR= 1.049, p=0.542). Similar results were also observed on stratification analysis by ethnicity (A/G vs. A/A, OR=1.357, p=0.025; G/G vs. A/A, OR=1.310, p=0.011; G/G+A/G vs. A/A, OR= 1.371, p=0.013). However, no potential contribution of XRCC1 Arg399Gln polymorphism to HCC susceptibility in HBV/HCV subgroups was identified. No publication bias was found in this study. In conclusion, the XRCC1 Arg399Gln polymorphism contributes to HCC susceptibility. Due to the lack of studies in Western countries, further large-sample and rigorous studies are needed to validate the findings.
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