Experimental and analytical behavior of a prestressed U-shaped girder bridge

Xun Wu,Hui Li 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.61 No.3

This paper presents an experimental and analytical investigation on the behavior of a U-shaped girder subjected to operation, cracking and ultimate loads. A full-scale destructive test was conducted on a U-shaped girder to study the cracking process, load-carrying capacity, failure mechanism and load-deformation relationships. Accordingly, the tested U-shaped girder was modeled using ANSYS and a non-linear element analysis was conducted. The investigation shows that the U-shaped girder meets the specified requirements of vertical stiffness, cracking and ultimate load capacity. Unfavorable torsional effect is tolerable during operation. However, compared with box girders, the U-shaped girder has a more transverse mechanical effect and longitudinal cracks are apt to occur in the bottom slab.

A Fuzzy Algorithm of Peer Selection for P2P Streaming Media System Based on Gossip Transmission Protocol

Xunli Fan,Weiwei Zhang,Lin Guan 보안공학연구지원센터 2009 International Journal of Multimedia and Ubiquitous Vol.4 No.1

The traditional Gossip protocol selects the neighbor nodes randomly. It does not consider the factors, such as the capacities of network transmission and node storage, which affect the network performance. It further causes the drawback of successful search ratio relatively lower, and also network transmission payloads have the characteristics of randomness. In this paper, to overcome those drawbacks of traditional Gossip protocol, a neighbor node selection algorithm has been studied, and various factors that may affect the neighbor node selection have been analyzed in P2P networks. A new neighbor node selection policy has been proposed, which is a reliable Gossip message transmission Protocol based on fuzzy theory. Empirical simulation experiments with various data analysis have demonstrated the improvement of efficiency of the proposed strategy on node selection and correctness of the proposed algorithm in P2P networks.

Numerical investigation of the effect of surface roughness on the flow coefficient of an eccentric butterfly valve

Xun Sun,김현수,양승덕,김철규,윤준용 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6

Butterfly valves are used widely as flow controllers in many industrial applications. In order to design and select an appropriate valvefor a particular application, it is important to predict correctly its flow coefficient. The flow coefficient of a valve can be affected by anumber of factors. This study presents a numerical investigation of the effect of friction on the flow coefficient of a triple eccentric butterflyvalve with various valve opening degrees. Since the Reynolds number and cavitation can affect the flow coefficient under certainconditions, these effects are discussed and analyzed based on previously reported experimental data before studying the effects of friction. Under the test conditions recommended in IEC 60534-2-3, it is found that the effects of the Reynolds number and cavitation are quitesmall and can be ignored. The flow coefficients obtained from numerical simulations that take into account friction are found to be ingood agreement with the experimentally determined ones. The differences in the flow coefficients obtained from numerical simulationsthat consider friction and those that ignore it are discussed. There is a maximum difference of 17 % for a fully open valve. The resultsshow that increases in the roughness height significantly increase the frictional pressure drop. The effect of the roughness height on thefrictional pressure drop and total pressure drop can be fitted well using fitting functions for fixed opening degree. It is found that the effectof the roughness can cause the determined flow coefficient to be different from the actual value. Thus, the measured flow coefficientsand pressure drops for such valves can be determined with accuracy through experimental techniques and numerical simulationsthat account for the effect of roughness.

A Model For Fractured Well Performance Coupled WithComplex Seepage Mechanism in Shale Gas

Xun Yan,Jing Sun,Dehua Liu 한국자원공학회 2020 Geosystem engineering Vol.23 No.3

Hydraulic fracture is a key technology for high-efficiency development of shale gas, and the flow mechanism of fractured well with Stimulated Reservoir Volume (SRV) is complex in shale gas. In this paper, an apparent permeability model is proposed, which can not only reflect the multi-scale flow characteristics in shale gas but also characterize the variation of permeability with effective stress. In addition, a composite model for a fractured well with SRV is established, which comprises multiscale, geomechanics and adsorption phenomenon. The object of this paper is to investigate some important impacts on a fractured well with SRV. The results reveal that the cumulative gas production will decrease sharply when the shale gas reservoir stress-sensitive coefficient increases. Additionally, the gas production rate and cumulative gas production will increase with the increase of SRV permeability. And, the adsorption phenomenon has an influence on shale gas seepage and sorption capacity, the larger Langmuir volume, the richer adsorption gas content in shale gas. And, more adsorbed gas will be exploited into free gas, which slows down the production decline of gas wells. The production of gas well will increase with the increase of perforation thickness of gas reservoir.

Negative regulation of aryl hydrocarbon receptor by its lysine mutations and exposure to nickel

Xun Che,Wei Dai 대한독성 유전단백체 학회 2019 Molecular & cellular toxicology Vol.15 No.4

Backgrounds: Aryl Hydrocarbon Receptor (AhR) is a nuclear receptor for many environmental toxicants including TCDD. It mediates the induction of many metabolic enzymes of the cytochrome P450 family after engaging with its ligands. Meanwhile, nickel, also an environmental toxicant, induces a hypoxic response, leading to stabilization of HIF-1α. Lysine residues known for posttranslational modifications are important for subcellular localization, stability, and/or activity of gene products. Methods: In this study, we have determined nickel’s suppressive effect on TCDD-induced expression of CYP1A1 and CYP1A2, two members of the cytochrome P450 super-family. We have also analyzed CYP1A1 and CYP1A2 levels after expression of AhR with various lysine mutations. Results: We have shown that induction of CYP1A1 and CYP1A2 by TCDD and other AhR ligands is significantly suppressed by hypoxia-mimetics including nickel. This effect is likely due to a competition for β-subunit shared by AhR and HIF-1 transcription factors. We have also found that substitutions of lysines 14, 17, and 21 with arginines suppress the ability of AhR to transactivate P450 genes after treatment with TCDD. Conclusion: Ligand-mediated AhR activation can be significantly modulated by co-exposure to other environmental toxicant (s) or by its lysine mutations.

Decolorization and Biodegradation of the Azo Dye Congo Red by an Isolated Acinetobacter baumannii YNWH 226

Xun-an Ning,Chongyang Yang,Yujie Wang,Zuoyi Yang,Jingyu Wang,Ruijing Li 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.4

A strict aerobic Acinetobacter baumanniiYNWH 226, isolated from an activated sludge reactortreating textile wastewater, was able to grow on Congo redas the sole carbon source under aerobic conditions. Thedecolorization and TOC reduction efficiency were 99.1 and93.72%, respectively. The effects of the Congo redconcentration were studied. The environmental factors (i.e.,pH, temperature and agitation speed) on the biodegradationof Congo red in aqueous phase were studied and evaluatedusing response surface methodology. The results indicatedthat when the Congo red concentration was 100 mg/L, theoptimal decolorization conditions were as follows: 37°C,pH 7.0 and 180 rpm. The single A. baumannii YNWH 226was able to form aromatic amines by reductive breakage ofthe azo bond and then oxidize them into non-toxicmetabolites.

Design and Implementation of an ONS Test-bed

Xun, Lu,Piao, Chunjie,Hongryul Yoon,Park, Sangwee,Choung, Jaeuk 대구대학교 정보통신연구소 2004 情報通信硏究 Vol.3 No.1

This paper presents a design and implementation of an ONS test-bed. It provides EPC naming and Web services with respect to EPCTM code currently under standardization. The goal of this research is to investigate the feasibility and complexity of the EPC network. The prototype can be used to verify the concept of the EPC network by providing experimental setup for domestic researchers and engineers.

A Practical Video Fragment Identification System

Xun Jin,Jongweon Kim 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.6

In this paper, we present a practical identification approach of video fragment for digital video files. Before analyzing the video content, we must decode it based on its encoding format first. In order to effectively identify the format of a fragment, a format classification is performed before the format identification. The methods of format classification and identification are discriminative subspace clustering (DiSC) and the K-nearest neighbor (KNN).Because of losing the meta-information, we add a maximum similar header (MSH) to the front of the fragment to recover the video content. We adopt a simple key frame detection method using standard deviation and mean value. Motion vectors of macro blocks are utilized to classify the video features for effectively identifying the video. Several edges of frames are accumulated and compose a video feature. The experimental results show the evaluations of the video format classification and identification, fragment recovery, and content identification.

Background Removing for Digital image self-adaptive acquisition in medical X-ray imaging

Xun Li,Young Ju Kim,Young Jun Song 한국콘텐츠학회 2008 International Journal of Contents Vol.4 No.1

Optimizing the Novel Formulation of Liposome-Polycation-DNA Complexes (LPD) by Central Composite Design

Xun Sun,Zhirong Zhang 대한약학회 2004 Archives of Pharmacal Research Vol.27 No.7

LPD vectors are non-viral vehicles for gene delivery comprised of polycation-condensed plasmid DNA and liposomes. Here, we described a novel anionic LPD formulation containing protamine- DNA complexes and pH sensitive liposomes composed of DOPE and cholesteryl hemisuccinate (Chems). Central composite design (CCD) was employed to optimize stable LPD formulation with small particle size. A three factor, five-level CCD design was used for the optimization procedure, with the weight ratio of protamine/DNA (X1), the weight ratio of Chems/ DNA (X2) and the molar ratio of Chems/DOPE in the anionic liposomes (X3) as the independent variables. LPD size (Y1) and LPD protection efficiency against nuclease (Y2) were response variables. Zeta potential determination was utilized to define the experimental design region. Based on experimental design, responses for the 15 formulations were obtained. Mathematical equations and response surface plots were used to relate the dependent and independent variables. The mathematical model predicted optimized X1-X3 levels that achieve the desired particle size and the protection efficiency against nuclease. According to these levels, an optimized LPD formulation was prepared, resulting in a particle size of 185.3 nm and protection efficiency of 80.22%.