Error estimate of a finite element method using stress intensity factor

Cai, Zhiqiang,Kim, Seokchan,Lee, Hyung-Chun Elsevier 2018 COMPUTERS & MATHEMATICS WITH APPLICATIONS - Vol.76 No.10

<P><B>Abstract</B></P> <P>An algorithm on computing accurate finite element approximation to the Poisson equation on a polygonal domain with corner singularities was studied in Kim and Lee (2016, 2017) numerically. The algorithm requires several iterations depending on singularities of the solution. Each iteration requires a solution of the standard finite element approximation to the Poisson equation with possible different Dirichlet data and the corresponding stress intensity factors. This paper provides an error estimate of the finite element approximation given by the algorithm, and, hence, determine the number of iterations needed to achieve full rates of convergence in both the energy and the <SUP> L 2 </SUP> norms.</P>

Revitalization and Re-cultivation of Vegetation in Karst Region Through Animal

Zhiqiang Lai,Xian-feng Yi,Na Yao,Xiao-Yan Cai,Yongliang Liang,Shize Qin,Yuanrong Chen,Shangmin Qin,M. Pogaonik 한국초지조사료학회 2009 한국초지조사료학회 학술대회논문집 Vol.2009 No.08

From 2002 to 2007, two different systems (shrubs and grasses) were established to raise appropriate ruminants for the purpose of improving biological diversity and fragile ecological environment in the karst-areas through grazing. The objective was to find out a novel way to promote the application of ecological restoration and reconstruction, and the agricultural economy could develop in sustainable way in the karst areas in Guangxi and similar areas in Southwest China.

Anti-corrosion impact of green synthesis of Silica nanoparticles for the sports structures in physical exercise activities

Zhixin Zhang,Zhiqiang Cai,Khidhair Jasim Mohammed,H. Elhosiny Ali Techno-Press 2023 Advances in concrete construction Vol.15 No.1

Sport has no age limit and can be done anywhere and in any condition with minimal equipment. The existence of sports spaces in all parts of the world is considered a citizen's right. One of the activities carried out in this field is installing sports equipment and structures in parks and encouraging citizens to use this equipment for physical health with the least cost and facilities. Installing sports structures in open spaces such as parks is a practical step for developing citizens' sports. Although using devices in parks is acceptable, it is more critical to meet scientific and technical standards. The components of these structures must have high strength and endurance against changes in environmental conditions such as humidity, temperature difference, and corrosion. Among the various causes of material degradation, corrosion has always been one of several fundamental causes of metal equipment failure. Sports structures in open spaces are not safe from corrosion. Uniform corrosion is the most common type of corrosion. This corrosion usually occurs uniformly through a chemical or electrochemical reaction across the surface exposed to the corrosive environment. Rust and corrosion of outdoor sports structures are examples of this corrosion. For this reason, in this research, with the green synthesis of silica nanoparticles and its application in outdoor sports structures, the life span of these structures can be increased for the use of physical exercises as well as their quality.

THE FINITE ELEMENT METHOD DEALING WITH CORNER SINGULARITIES : DIV-CURL SYSTEM

Seok Chan KIM,Zhiqiang CAI 한국산업응용수학회 2005 한국산업응용수학회 학술대회 논문집 Vol.- No.-

In [1-3] we give a new finite element method to control the domain singularity of the solution of Poisson equation. Years ago we reported that the singular decomposition of the solution of Div-curl system is computed. Now we find the dual singular functions and applied our method to control the domain singularity of the Div-curl system and get the expected results.

Intelligent Matching Assembly: System Design Based on Reuse of Ultra-Difference Parts

Yongjie Zhang,Kang Cao,Zhiqiang Cai,Xinwen Wang,Wei Jin 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.7

As the industrial digitalization has been recently leaping forward, high-efficiency production processes emerge, and assembly integration technologies are being progressively developed. For high-tech industries (e.g., aerospace manufacturing), however, unprecedented challenges are imposed on the conventional assembly manufacturing process technology. To be specific, the shallow digitizing and intelligent technologies fail to satisfy the rising requirements for efficiency, pass rates and cost; in particular, the way to down-regulate the unqualified rate and assembly cost of parts production remains unclear. In the present study, an intelligent matching assembly system was designed for reapplying out-of-tolerance parts. In addition, the concept of the mating base is proposed. Next, the fi t relation between parts is quantified by employing the functional expression of dimension data, and such a relation is characterized as a function constraint with a variable of dimension. Moreover, the designed intelligent matching system was introduced into the existing assembly process to reemploy a number of unqualified parts and determine the matching parts most suitable for the original unqualified parts. On that basis, the most suitable parts are enabled to be involved in the assembly activities, as an attempt to satisfy the design requirements. To efficiently find the optimal matching scheme in the database of the unqualified parts and most effectively employ the unqualified parts, a set of optimal matching algorithms are proposed, thereby significantly down-regulating the production cost. Lastly, Monte Carlo method was adopted to simulate the actual production data, and the optimal matching scheme determined by the intelligent matching system was analyzed and assessed, which verified the effectiveness and practicability of the system.

FINITE ELEMENT METHODS FOR DEALING WITH POISSON PROBLEM WITH DISCONTINUOUS COEFFICIENTS

Seok Chan KIM,Zhiqiang Cai,Jae-Hong Pyo,Sooryoun Kong 한국산업응용수학회 2006 한국산업응용수학회 학술대회 논문집 Vol.1 No.1

We study an accurate numerical method on quasi-uniform grids for two-dimensional interface problems. The method makes use of the singular function representation of the solution, the dual singular functions, and the extraction formula for the stress intensity factors. It is shown that our finite element approximation using continuous piecewise linear element on quasi-uniform grids has O(h) accuracy in H¹ norm. This is confirmed by a numerical experiment for an interface problem whose solution is even not in H<SUP>l.l</SUP>.

Blood lipids and all-cause mortality among old people: the Chinese Longitudinal Healthy Longevity Survey 2008-2018

Wang Rongxi,Yu Xiaoyue,Wang Zhiqiang,Liu Yujie,Chen Hui,Liu Shangbin,XU CHENG,Chen Yingjie,Xia Danni,Ge Xin,Chang Ruijie,Xu Gang,Xiang Mi,Wang Ying,Shen Tian,Hu Fan,Cai Yong 한국역학회 2022 Epidemiology and Health Vol.44 No.-

OBJECTIVES: Proper blood lipid levels are essential for survival in older adults, but inconsistent relationships have been reported between blood lipids and all-cause mortality in the elderly. METHODS: This retrospective longitudinal study analyzed data from 1,067 Chinese older adults enrolled in the Chinese Longitudinal Healthy Longevity Survey collected in 2008 and followed up until death or December 31, 2018. The outcome was allcause mortality. Multivariate Cox regression analyses were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with stratification by age (60-80, 80-100, or ≥ 100 years) for further analysis. The survival probability according to lipid profile quartiles was calculated using Kaplan-Meier curves and the log-rank test. RESULTS: The participants’ mean age was 84.84 years, and 57.0% were female. In total, 578 individuals died, and 277 were lost to follow-up. The mean total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) levels were higher among those who died than among those who survived. Participants in the second HDL-C quartile and the highest LDL-C and triglyceride (TG) quartiles had 28% higher, 23% lower, and 49% lower risks of all-cause mortality, respectively. After further adjustment, the associations remained except for HDL-C, and additional associations were observed between all-cause mortality and the third TC and LDL-C quartiles and the second TG quartile (HR, 1.44; 95% CI, 1.01 to 2.06; HR, 0.68; 95% CI, 0.49 to 0.94; HR, 0.79; 95% CI, 0.62 to 0.99, respectively). CONCLUSIONS: Older adults should maintain an LDL-C level of 1.91-2.47 mmol/L and a TG level of no less than 1.66 mmol/L.