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Articles by Jun Hu
Total Records ( 5 ) for Jun Hu
  Jun Hu , Zhuoxian Zhang , Jingwen Luo and Xiaojun Sheng
  A three-dimensional axial symmetrical model of laser cutting is established by adopting N–S equation and RNG kε onflow model in the paper, and numerical simulation is put up to analyze the flow field of shield gas in cutting slot. The investigation reveals the law about how standoff distance affects the dynamic characteristic of gas jet in cutting process, and the distribution of pressure and velocity of gas jet with different standoff distances are shown in the study. Two typical subsonic nozzles are designed for the laser cutting experiment. At the end of the paper experimental results are compared with the numerical simulation results.
  Jun Hu , Yong Liang , Minjie Chen and Xiaorong Wang
  This study was conducted to examine the adverse biological effects of two veterinary pharmaceuticals (Amprolium and tylosin) on aquatic organisms. The zebrafish embryo toxicity assays were performed in combination with three biomarkers, including superoxide dismutase (SOD), lipid peroxidation (LPO) and heat shock protein 70(Hsp70). The LPO extent was expressed by malondialdehyde (MDA) in this paper. Logit Loglinear analysis was used to study the effect of exposure concentration and time on survival rate and percent hatched in embryo toxicity tests. The data on SOD, MDA and Hsp70 were analyzed by one-way ANOVA followed by Dunnett's test. The results showed that both pharmaceuticals had no effect on Hsp70 levels in zebrafish. Amprolium and tylosin had significant effect on the survival rate, the percent hatched, SOD and MDA in the range of the experimental concentrations. Furthermore, there was a sharp increase, followed by a decrease in the survival rate, as the exposure concentrations of amprolium or tylosin increased; while SOD and MDA indicated a sharp decrease followed by an increase in survival rates. These results indicated that both pharmaceuticals can be useful to the embryos at low concentrations, while causing acute toxicity at high concentrations. However, two pharmaceuticals cause an acute toxicity effect at concentrations several orders of magnitude higher than detected in the aquatic environments. Both do not result in acute toxicity to zebrafish, but it is recommended that the proper strategy and approach be found to perform chronic low-dose exposure studies.
  Jun Hu , Zhen Ning , Xinzhou Lu and Shuai Hao
  The existence of “Online Water Army” makes the mode of depending on regarding customer comments as the criteria of judging sellers become less and less reliable in E-commerce. Based on this fact, from the buyer’s social network, authors set up a trust model for effective selection of sellers based on the social network and take the advantage of the node of social network on the evaluation feedback result of the seller to assist the customer to make a decision. The model, according to the theory of structural holes of social relations, evaluates the weight of every recommended route formed in the social network and finally gets a trust value which shows the seller’s reliability. In this paper, finally, authors take an example and show how to calculate the trust value.
  Jun Hu , Chun Guan and Bocheng Liu
  With the fast development of information on the web, relevant web pages can be discovered by analyzing web server log files and user access database. Based on the granular computing theory, a method of clustering web pages is proposed in this study. Firstly, according to the users accessing the website URL, the method can coarse grain the universal set gradually by granular operation and processing similar grains technology. Then, it can adjust the threshold value to make the division of the universal set be a relatively reasonable status. Finally it can implement the optimal adjustment of websites.
  Jun Hu , Kaifeng Hu , David C. Williams, Jr. , Michal E. Komlosh , Mengli Cai and G. Marius Clore
  Solution structures of complexes between the isolated A (IIAMan) and B (IIBMan) domains of the cytoplasmic component of the mannose transporter of Escherichia coli have been solved by NMR. The complex of wild-type IIAMan and IIBMan is a mixture of two species comprising a productive, phosphoryl transfer competent complex and a non-productive complex with the two active site histidines, His-10 of IIAMan and His-175 of IIBMan, separated by ∼25Å. Mutation of the active site histidine, His-10, of IIAMan to a glutamate, to mimic phosphorylation, results in the formation of a single productive complex. The apparent equilibrium dissociation constants for the binding of both wild-type and H10E IIAMan to IIBMan are approximately the same (KD ∼ 0.5 mM). The productive complex can readily accommodate a transition state involving a pentacoordinate phosphoryl group with trigonal bipyramidal geometry bonded to the Nε2 atom of His-10 of IIAMan and the Nδ1 atom of His-175 of IIBMan with negligible (<0.2Å) local backbone conformational changes in the immediate vicinity of the active site. The non-productive complex is related to the productive one by a ∼90° rotation and ∼37Å translation of IIBMan relative to IIAMan, leaving the active site His-175 of IIBMan fully exposed to solvent in the non-productive complex. The interaction surface on IIAMan for the non-productive complex comprises a subset of residues used in the productive complex and in both cases involves both subunits of IIAMan. The selection of the productive complex by IIAMan(H10E) can be attributed to neutralization of the positively charged Arg-172 of IIBMan at the center of the interface. The non-productive IIAMan-IIBMan complex may possibly be relevant to subsequent phosphoryl transfer from His-175 of IIBMan to the incoming sugar located on the transmembrane IICMan-IIDMan complex.
 
 
 
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