Effect of residual stress on the hydrogen diffusion near the crack tip in the weldment

Jianjun Chen,Yong Wha Ma,Doo Il Won,Kwan-Ju Lee,Kee Bong Yoon 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

In this paper the hydrogen diffusion in the weld structure containing defect was analyzed by the finite element method. The effect of the welding residual stress on the hydrogen distribution has been studied using a coupling analysis procedure conducted by Abaqus code. The hydrogen diffusion without the residual stress was also simulated for comparison. The results show that the hydrogen distribution changed significantly due to the existence of the residual stress. It is found that the residual stress not only increases the hydrogen concentration but also reduces the hydrogen concentration at different regions ahead of the crack tip.

A method of optimum design based on reliability for antenna structures

Chen, Jianjun,Wang, Fanglin,Sun, Huaian,Zhang, Chijiang Techno-Press 1999 Structural Engineering and Mechanics, An Int'l Jou Vol.8 No.4

A method of optimum design based on reliability for antenna structures is presented in this paper. By constructing the equivalent event, the formula is derived for calculating the reliability of reflector accuracy of antenna under the action of random wind load. The optimal model is developed, in which the cross sectional areas of member are treated as design variables, the structure weight as objective function, the reliability of reflector accuracy and the strength or stability of structural elements as constraints. The improved accelerated convergence gradient algorithm developed by the author is used. The design results show that the method in this paper is feasible and effective.

Finite element study for determination of material's creep parameters from small punch test

Chen, Jianjun,Ma, Young-Wha,Yoon, Kee-Bong 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.6

Compared with the conventional tensile creep test, it is much more difficult to obtain the creep properties of a material by the small punch creep test due to the complex deformation response and stress distribution in the miniature specimen of the material. Although creep behavior has been investigated by the small punch test, most studies have been limited to a specimen geometry and therefore, cannot be extended to other conditions conveniently. In this study, a new developed analysis routine is presented to derive the creep parameters of a material using data obtained from the small punch creep test. With the aid of the finite element method, the displacement and the displacement rate of the small punch are obtained for different load levels. The relationship between the stress and creep strain of the specimen and the applied load and the punch displacement is obtained by a dimensional analysis and the membrane stretching model. The creep properties obtained from small punch tests and the conventional creep tests are also compared. The values of the creep properties between the two types of tests agree well with each other within an acceptable accuracy range. This indicates that it is possible to obtain the creep parameters of a material from the small punch creep test instead of the conventional creep test by the analysis routines proposed in this study. Some suggestions for data reduction of the small punch creep tests are also presented to obtain more accurate material creep parameters.

Study on stress intensity factor of a finite width laminate

Jianjun Chen,Kee Bong Yoon 한국가스학회 2008 한국가스학회 학술대회논문집 Vol.2008 No.11

Individualized Treatment of Allergic Rhinitis According to Nasal Cytology

Jianjun Chen,Yue Zhou,Li Zhang,Yanjun Wang,Amber N. Pepper,Seong H. Cho,Weijia Kong 대한천식알레르기학회 2017 Allergy, Asthma & Immunology Research Vol.9 No.5

Purpose: Nasal cytology is important in the diagnosis and treatment of nasal inflammatory diseases. Treatment of allergic rhinitis (AR) according to nasal cytology has not been fully studied. We plan to explore the individualized treatment of AR according to nasal cytology. Methods: Nasal cytology from 468 AR patients was examined for inflammatory cell quantity (grade 0-5) and the percentage of neutrophils and eosinophils. Results were subdivided into the following categories: AR(Eos), eosinophil ≥50% of the whole inflammatory cells; AR(Neu), neutrophils ≥90%; AR(Eos/Neu), 10%≤ eosinophil <50%; AR(Low), grade 0/1 inflammatory cell quantity. Nasal cytology-guided treatment was implemented: all AR(Eos) patients (n=22) and half of the AR(Neu) patients (AR[Neu1], n=22) were treated with mometasone furoate spray and oral loratadine. Another half of the AR(Neu) patients (AR[Neu2], n=22) were treated with oral clarithromycin. Visual analog scale (VAS), symptom scores, and nasal cytology were evaluated 2 weeks before and after treatment. Results: There were 224/468 (47.86%) AR(Eos), 67/468 (14.32%) AR(Neu), 112/468 (23.93%) AR(Eos/Neu), and 65/468 (13.89%) AR(Low) of the AR patients studied. There were no significant differences in clinical characteristics among these subgroups, except that the nasal blockage score was higher in AR(Eos) patients than in AR(Neu) patients (1.99 vs 1.50, P=0.02). Comparing AR(Eos) patients with AR(Neu1) patients 2 weeks after treatment, nasal symptoms and VAS were significantly lower in AR(Eos) patients, except for nasal blockage symptoms (P<0.05 of nasal itching and sneezing; P<0.01 for nasal secretion, total scores, and VAS). Comparing AR(Neu1) with AR(Neu2) patients, nasal symptoms, and VAS were significantly lower in AR(Neu2), except for nasal blockage and nasal itching symptoms (P<0.05 for nasal secretions, sneezing, total score, and VAS). Conclusions: Nasal cytology may have important value in subtyping AR and optimizing AR treatment. Treating neutrophils is very important in AR patients with locally predominant neutrophils.

An Optimized CLBP Descriptor Based on a Scalable Block Size for Texture Classification

( Jianjun Li ),( Susu Fan ),( Zhihui Wang ),( Haojie Li ),( Chin-chen Chang ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.1

In this paper, we propose an optimized algorithm for texture classification by computing a completed modeling of the local binary pattern (CLBP) instead of the traditional LBP of a scalable block size in an image. First, we show that the CLBP descriptor is a better representative than LBP by extracting more information from an image. Second, the CLBP features of scalable block size of an image has an adaptive capability in representing both gross and detailed features of an image and thus it is suitable for image texture classification. This paper successfully implements a machine learning scheme by applying the CLBP features of a scalable size to the Support Vector Machine (SVM) classifier. The proposed scheme has been evaluated on Outex and CUReT databases, and the evaluation result shows that the proposed approach achieves an improved recognition rate compared to the previous research results.

Selected microRNA-192 mutant indicates association with several function genes in bovine cells

Chen Zi,Dexin Zeng,Jiyong Zhou,Jianjun Dai,Luyan Jiang,Feng Xue,Yuan Jiang,Baoguang Li 한국유전학회 2018 Genes & Genomics Vol.40 No.4

MicroRNAs are implicated in many cellular processes such as cell differentiation and development, tumorigenesis, and immune regulation. In this study, miR192 was detected using quantitative real-time polymerase chain reaction (qRT-PCR) when MDBK cells were exposed to Escherichia coli. Cells with malfunction of bta-miR-192 were established using transcription activator-like effector nuclease (TALEN) technology. Finally, bta-miR-192 mutant cells were screened for differentially expressed genes using RNA-sequencing (RNA-seq). The results showed that miR192 significantly decreased in cells exposed to E. coli F18ac and E. coli K88ac. The RNA-seq results showed that 1673 differentially expressed transcripts were identified; 890 genes were upregulated and 775 genes were downregulated. With the gene ontology enrichment analysis, 431 differentially expressed genes (DEGs) were classified into 937 gene ontology terms. The pathway enrichment analysis showed that 535 genes were involved in 254 pathway terms. Interestingly, most of these DEGs were associated with the pathways in cancers or infectious diseases. When the selected DEGs (n = 162) in these pathways were intersected with 120 differential transcripts, 11 DEGs were identified. Subsequently, several genes associated with regulation, cancers, or viral infections, such as LEF1, AXIN2, MX1, and FCGR2B, were identified among the DEGs using functional analysis. Furthermore, associations between bta-miR-192 and DEGs were detected by intersecting the bta-miR-192’s target genes with the DEGs, indicating that three genes including CBL, DICER1 and TRERF1 were involved in this relationship. These findings provided useful guidance for investigating the role played by bta-miR-192 in cellular functionality in bovine cells.

Experimental and numerical study on the oblique water-entry impact of a cavitating vehicle with a disk cavitator

Chen, Cheng,Yuan, Xulong,Liu, Xiyan,Dang, Jianjun The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

In this paper, the oblique water-entry impact of a vehicle with a disk cavitator is studied experimentally and numerically. The effectiveness and accuracy of the numerical simulation are verified quantitatively by the experiments in this paper and the data available in the literature. Then, the numerical model is used to simulate the hydrodynamic characteristics and flow patterns of the vehicle under different entry conditions, and the axial force is found to be an important parameter. The influences of entry angle, entry speed and cavitator area on the axial force are studied. The variation law of the force coefficient and the dimensionless penetration distance at the peak of the axial force are revealed. The research conclusions are beneficial to engineering calculations on the impact force of a vehicle with a disk cavitator over a wide range of water-entry parameters.

THE EXISTENCE AND MULTIPLICITY OF SOLUTIONS TO p-LAPLACE EQUATION WITH PERIODIC BOUNDARY CONDITIONS

Chen, Taiyong,Liu, Wenbin,Zhang, Jianjun,Zhang, Huixing The Korean Society for Computational and Applied M 2009 Journal of applied mathematics & informatics Vol.27 No.3

In this paper, we consider p-Laplace equation which models the turbulent flow in a porous medium. Using a continuation principle (cf. [R. $Man{\acute{a}}sevich$ and J. Mawhin, Periodic solutions for nonlinear systems with p-Lplacian-like operators, J. Diff. Equa. 145(1998), 367-393]), we prove the existence of solutions for p-Laplace equation subject to periodic boundary conditions, under some sign and growth conditions for f. With the help of Leray-Schauder degree theory, the multiplicity of periodic solutions for p-Laplace equation is obtained under the similar conditions above and some known results are improved.

A new method of synthesis on high-quality AgGaS2 polycrystalline

Jianjun Zhang,Shifu Zhu,Beijun Zhao,Baojun Chen,Zhiyu He 한국물리학회 2010 Current Applied Physics Vol.10 No.2

High-pure, single-phase, free of voids and high mass density AgGaS2 polycrystalline was synthesized by a new method, i.e. two-temperature zone vapor-transporting together with the mechanical and melt temperature oscillation method (TVMMTOM), directly from high-purity (6 N) elements silver, gallium and sulfur with excess sulfur. The mechanism and advantages of the new method for synthesizing high-quality AgGaS2 were discussed. It is found that the polycrystalline material synthesized by the new method is superior to that synthesized by the conventional method, what is more the new method can avoid the explosion of the synthetic quartz ampoule. Adopting the modified Bridgman method an integral and crack-free AgGaS2 single crystal with diameter of 14 mm and length of 63 mm has been obtained. It was found that there was a (1 0 1) cleavage face and the four order X-ray spectrum of the {1 0 1} faces was observed. By the method of DSC analysis the melting and freezing points of the AgGaS2 single crystal were about 995 and 955 ℃. The transmission spectra of the AgGaS2 sample of 10 × 8 ×2㎣ were obtained by means of UV and IR spectrophotometer. The limiting wavelength was 470 nm and the band gap was 2.64 eV. It can be found in the infrared spectrum that the infrared transmission was above 55%from 4000 to 800 cm-1, and the infrared transmittance of the crystal is up to 63% at 10.6 lm, which is higher than that of the crystal grown using polycrystalline materials synthesized by the conventional method. The value of a in 10.6 lm was 0.267 cm-1. Above mentioned results showed that the crystal was of good quality and TVMMTOM is preferable for synthesizing high-quality AgGaS2 polycrystalline materials.