Investigation of the behavior of a crack between two half-planes of functionally graded materials by using the Schmidt method

Zhen-Gong Zhou,Biao Wang,Lin-Zhi Wu 국제구조공학회 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.4

In this paper, the behavior of a crack between two half-planes of functionally graded materials subjected to arbitrary tractions is resolved using a somewhat different approach, named the Schmidt method. To make the analysis tractable, it is assumed that the Poisson’s ratios of the mediums are constants and the shear modulus vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations in which the unknown variables are the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the jumps of the displacements across the crack surfaces are expanded in a series of Jacobi polynomials. This process is quite different from those adopted in previous works. Numerical examples are provided to show the effect of the crack length and the parameters describing the functionally graded materials upon the stress intensity factor of the crack. It can be shown that the results of the present paper are the same as ones of the same problem that was solved by the singular integral equation method. As a special case, when the material properties are not continuous through the crack line, an approximate solution of the interface crack problem is also given under the assumption that the effect of the crack surface interference very near the crack tips is negligible. It is found that the stress singularities of the present interface crack solution are the same as ones of the ordinary crack in homogenous materials.

Investigation of the behavior of a crack between two half-planes of functionally graded materials by using the Schmidt method

Zhou, Zhen-Gong,Wang, Biao,Wu, Lin-Zhi Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.19 No.4

In this paper, the behavior of a crack between two half-planes of functionally graded materials subjected to arbitrary tractions is resolved using a somewhat different approach, named the Schmidt method. To make the analysis tractable, it is assumed that the Poisson's ratios of the mediums are constants and the shear modulus vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations in which the unknown variables are the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the jumps of the displacements across the crack surfaces are expanded in a series of Jacobi polynomials. This process is quite different from those adopted in previous works. Numerical examples are provided to show the effect of the crack length and the parameters describing the functionally graded materials upon the stress intensity factor of the crack. It can be shown that the results of the present paper are the same as ones of the same problem that was solved by the singular integral equation method. As a special case, when the material properties are not continuous through the crack line, an approximate solution of the interface crack problem is also given under the assumption that the effect of the crack surface interference very near the crack tips is negligible. It is found that the stress singularities of the present interface crack solution are the same as ones of the ordinary crack in homogenous materials.

The nonlocal theory solution for two collinear cracks in functionally graded materials subjected to the harmonic elastic anti-plane shear waves

Zhou, Zhen-Gong,Wang, Biao Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.23 No.1

In this paper, the scattering of harmonic elastic anti-plane shear waves by two collinear cracks in functionally graded materials is investigated by means of nonlocal theory. The traditional concepts of the non-local theory are extended to solve the fracture problem of functionally graded materials. To overcome the mathematical difficulties, a one-dimensional non-local kernel is used instead of a two-dimensional one for the anti-plane dynamic problem to obtain the stress field near the crack tips. To make the analysis tractable, it is assumed that the shear modulus and the material density vary exponentially with coordinate vertical to the crack. By use of the Fourier transform, the problem can be solved with the help of a pair of triple integral equations, in which the unknown variable is the displacement on the crack surfaces. To solve the triple integral equations, the displacement on the crack surfaces is expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips.

ORiginal Article : Endoscopic Intervention through Endoscopic Retrograde Cholangiopancreatography in the Management of Symptomatic Pancreas Divisum: A Long-Term Follow-Up Study

( Yi Lu ),( Bin Xu ),( Lu Chen ),( Li Ke Bie ),( Biao Gong ) 대한간학회 2016 Gut and Liver Vol.10 No.3

Background/Aims: To evaluate the efficacy and safety of endoscopic retrograde cholangiopancreatography (ERCP) for the treatment of symptomatic pancreas divisum (PD) and to discuss whether ERCP procedures and outcomes in younger patients differ from those of adults. Methods: Symptomatic patients with PD were included in the study and divided into underaged (age ≤17 years) and adult (age ≥18 years) group. The clinical information of each patient was reviewed, and then the patients were contacted by telephone or their medical records were reviewed to determine their long-term followup outcomes. Results: A total of 141 procedures were performed in 82 patients (17 underaged and 65 adult patients). The ERCP indications included abdominal pain (39.02%), pancreatitis (12.20%), recurrent pancreatitis (36.59%), and other discomfort (12.20%). The endoscopic interventions included endoscopic pancreatic sphincterotomy in 44.68% of the patients, bouginage in 26.95%, pancreatic ductal stone extraction in 19.15%, endoscopic nasopancreatic drainage in 21.99%, and endoscopic retrograde pancreatic drainage in 56.74%. After a median follow-up of 41 months, the overall response rate was 62.32%. Between the underaged group and the adult group, significant differences were not observed in the ERCP procedures, complications and longterm follow-up results. Conclusions: ERCP is a safe and effective treatment for symptomatic PD. Based on the details, complications, and follow-up results, the ERCP procedure did not present differences between the underaged and adult groups. (Gut Liver 2016;10:476-482)

Association of MDR1 Gene Polymorphisms with Susceptibility to Hepatocellular Carcinoma in the Chinese Population

Ren, Yong-Qiang,Han, Ju-Qiang,Cao, Jian-Biao,Li, Shao-Xiang,Fan, Gong-Ren Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.11

Objective: The objective of this study was to evaluate the association of MDR1 gene polymorphisms with susceptibility to hepatocellular carcinoma (HCC). Methods: A total of 689 HCC patients and 680 cancer-free subjects were enrolled. Human MDR1 gene polymorphisms were investigated by created restriction site-polymerase chain reaction (CRS-PCR) and DNA sequencing methods. Multiple logistic regression models were applied to estimate the association between MDR1 gene polymorphisms and susceptibility to HCC. Results: We detected a novel c.4125A>C polymorphism and our findings suggested that this variant was significantly associated with susceptibility to HCC. A significantly increased susceptibility to HCC was noted in the homozygote comparison (CC versus AA: OR=1.621, 95% CI 1.143-2.300, ${\chi}^2$=7.4095, P=0.0065), recessive model (CC versus AC+AA: OR=1.625, 95% CI 1.167-2.264, ${\chi}^2$=8.3544, P=0.0039) and allele contrast (C versus A: OR=1.185, 95% CI 1.011-1.389, ${\chi}^2$=4.4046, P=0.0358). However, no significant increase was observed in the heterozygote comparison (AC versus AA: OR=0.995, 95% CI 0.794-1.248, ${\chi}^2$=0.0017, P=0.9672) and dominant model (CC+AC versus AA: OR=1.106, 95% CI 0.894-1.369, ${\chi}^2$=0.8560, P=0.3549). Conclusions: These findings suggest that the c.4125A>C polymorphism of the MDR1 gene might contribute to susceptibility to HCC in the Chinese population. Further work will be necessary to clarify the relationship between the c.4125A>C polymorphism and susceptibility to HCC on larger populations of diverse ethnicity.