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Search Results: 1 - 10 of 103870 matches for " Chaoqun Zhang "
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Influence of Wettability and Mechanical Properties on Tribological Performance of DLC Coatings under Water Lubrication  [PDF]
Chaoqun Zhang, Masahiro Fujii
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2015, DOI: 10.4236/jsemat.2015.53013
Abstract: DLC coatings are currently used in a wide variety of industrial fields because of their outstanding properties such as high hardness, high wear resistance, low friction and so on under oil lubrication as well as no lubrication. In order to evaluate the tribological performance of DLC coatings under water lubrication, eight types of DLC coatings were evaluated by water-lubricated sliding tests at sliding velocities of 0.02 m/s and 0.1 m/s. The different DLC coating types comprised both hydrogenated and hydrogen-free DLC films that were deposited using different techniques: amorphous hydrogenated DLC (a-C:H), that doped with tungsten (a-C:H:W), that doped with silicon (a-C:H:Si) and hydrogen-free DLC (ta-C). DLC coatings showed low friction coefficient and excellent wear resistance. Friction coefficient and wear rate decreased with increasing sliding velocity. The effect of surface wettability and mechanical properties on tribological characteristics was investigated. Friction coefficient decreased as the contact angle increased. Hydrogen-free DLC coating with the highest hardness showed the highest friction and a larger wear rate. Furthermore, DLC coatings deposited with interlayer showed longer lifetimes.
Tribological Behavior of Thermally Sprayed WC Coatings under Water Lubrication  [PDF]
Chaoqun Zhang, Masahiro Fujii
Materials Sciences and Applications (MSA) , 2016, DOI: 10.4236/msa.2016.79045
Abstract: Thermally sprayed coatings have been used in various fields of industry for enhancing surface characteristics of materials and extending their service life. The contact surface of some mechanical equipment such as the fine pulverization equipment which is used in the woody biomass production process is required to have wear resistance in the water environment. Thermally sprayed coatings would be a good candidate to improve surface wear resistance under water lubrication. The objective of this study was to evaluate the tribological performance of thermally sprayed coatings under water lubrication. Thermally sprayed coatings which were classified into WC, WB and Ni spraying of three categories were compared with water-lubricated sliding test at a sliding velocity of 0.02 m/s and mean pressure of p0 = 10 MPa with a ring-on-disk apparatus. Thermally sprayed coatings showed comparatively high friction coefficient and well wear resistance under water lubrication. WC contained coatings showed better wear resistance than WB and Ni coatings. Thermally sprayed coatings showed obviously different mechanical properties and tribological behaviors, and the effect of wettability and hardness on tribological characteristics was discussed under water lubrication. Friction coefficient increased as the surface contact angle of thermally sprayed coatings increased. The wear rate decreased as the surface hardness of thermally sprayed coatings increased. Wear resistance of thermally sprayed coatings was excellent under water lubrication. WC contained coatings showed lower wear rate than WB and Ni coatings. WC-14CoCr coating showed the lowest wear rate.
The impact of dynamic change of cropland on grain production in Jilin

HE Yanfen,ZHANG Bai,MA Chaoqun,

地理学报 , 2004,
Abstract: The quantity and quality changes of cropland in Jilin province are analyzed by combining the statistics from 1949 to 1999 and land-use maps interpreted from TM images in 1986 and in 2000. In general, the decreasing trend of the cropland in Jilin province was derived from the statistic data in 1949-1999. While since 1983, the cropland area has increased slightly, because of the conversion from other land-use types to cropland. It is showed that the net increase of cropland was about 43.40×104 ha. While the quality change of the cropland can be seen from that mainly caused by the conversion from forestland, grassland to cropland and the change mainly took place in the west, where it is ecologically fragile. According to the spatial distribution model, the centroids' move of the cropland and the grain production are calculated, whose directions are not consistent. The impact of the dynamic change of the cropland on food security is further analyzed.
Asymptotic Behavior of a Chemostat Model with Stochastic Perturbation on the Dilution Rate
Chaoqun Xu,Sanling Yuan,Tonghua Zhang
Abstract and Applied Analysis , 2013, DOI: 10.1155/2013/423154
Abstract:
Efficacy and Safety of Using Antifibrinolytic Agents in Spine Surgery: a Meta-Analysis
Chaoqun Yuan, Hailong Zhang, Shisheng He
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0082063
Abstract: Purpose Spine surgery, particularly reconstructive surgery, can be associated with significant blood loss, and blood transfusion. Antifibrinolytic agents are used routinely to reduce bleeding in cardiac, orthopaedic, and hepatic surgery. The purpose of this study was to assess the efficacy and safety of using antifibrinolytic agents in reducing blood loss and blood transfusions in spine surgery. Methods A systematic search of all related studies written in English published by October 2012 was conducted using the MEDLINE, EMBASE and the Cochrane Library databases. Randomized controlled trials that reported the drug dosage, total blood loss, blood transfusion and incidence of deep vein thrombosis as the primary outcome were included. Results Nine studies involving 482 patients were identified. Patients receiving antifibrinolytic agents had reduced blood loss (WMD =-288.8, 95 % CI – 46.49, - 110.19; P = 0.002), reduced blood transfusion (WMD =-242.7, 95 % CI – 422.57, - 62.95; P = 0.008), reduced blood transfusion rate (RR 0.73, 95% CI 0.58, 0.93; p = 0.010) and no increase (RR 0.25, 95 % CI 0.03, 2.22; P = 0.21) in the risk of deep vein thrombosis. Conclusions: We conclude that antifibrinolytic agents significantly decrease blood loss, blood transfusion, and there is no increase in the risk of deep vein thrombosisfor transfusion requirements in spine surgery.
Characterization of mitochondrial genome of sea cucumber Stichopus horrens: A novel gene arrangement in Holothuroidea
SiGang Fan,ChaoQun Hu,Jing Wen,LvPing Zhang
Science China Life Sciences , 2011, DOI: 10.1007/s11427-011-4168-8
Abstract: The complete mitochondrial DNA sequence contains useful information for phylogenetic analyses of metazoa. In this study, the complete mitochondrial DNA sequence of sea cucumber Stichopus horrens (Holothuroidea: Stichopodidae: Stichopus) is presented. The complete sequence was determined using normal and long PCRs. The mitochondrial genome of Stichopus horrens is a circular molecule 16257 bps long, composed of 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes. Most of these genes are coded on the heavy strand except for one protein-coding gene (nad6) and five tRNA genes (tRNA Ser(UCN) , tRNA Gln , tRNA Ala , tRNA Val , tRNA Asp ) which are coded on the light strand. The composition of the heavy strand is 30.8% A, 23.7% C, 16.2% G, and 29.3% T bases (AT skew=0.025; GC skew= 0.188). A non-coding region of 675 bp was identified as a putative control region because of its location and AT richness. The intergenic spacers range from 1 to 50 bp in size, totaling 227 bp. A total of 25 overlapping nucleotides, ranging from 1 to 10 bp in size, exist among 11 genes. All 13 protein-coding genes are initiated with an ATG. The TAA codon is used as the stop codon in all the protein coding genes except nad3 and nad4 that use TAG as their termination codon. The most frequently used amino acids are Leu (16.29%), Ser (10.34%) and Phe (8.37%). All of the tRNA genes have the potential to fold into typical cloverleaf secondary structures. We also compared the order of the genes in the mitochondrial DNA from the five holothurians that are now available and found a novel gene arrangement in the mitochondrial DNA of Stichopus horrens.
Analysis of Strain Clamp Failure on 500 kV Transmission Line  [PDF]
Mingcheng Sun, Che Tan, Chaoqun Zhang, Chao Yang, Hongqiang Li
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.64007
Abstract:
In this work, the main reasons for the breakage of 500 kV transmission line are studied. Under low temperature condition, the coverage of the ice results in the disconnection between the aluminum tube and the steel anchor of strain clamp. Using macroscopic analysis, structure stress analysis, force analysis and mechanical property test, the fractured strain clamps are investigated. The crimping of the aluminum tube on the polished rod not on the grooves of the steel anchor leads to the damage of the strain clamps, which is defined as improper crimping. When improper crimping emerges, there will be only friction force between the aluminum tube and the steel anchor without shear force, and the tension of the conductor will be mainly supported by the steel strands which should be supported by both the aluminum tube and steel stands. Therefore, the breaking force of the strain clamp will greatly decrease. The failure analysis helps to promote the proper hydraulic crimping process and the safe operation of the transmission line.
Three-Dimensional Finite Element Numerical Simulation and Physical Experiment for Magnetism-Stress Detecting in Oil Casing Three-Dimensional Finite Element Numerical Simulation and Physical Experiment for Magnetism-Stress Detecting in Oil Casing
MENG Fanshun,ZHANG Jie,YANG Chaoqun,YU Weizhe,CHEN Yuxi
- , 2015,
Abstract: The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil industry, the number of offshore oil wells is becoming larger and larger. Because the cost of offshore oil well is very high, the casing damage will cause huge economic losses. What's more, it can also bring serious pollution to marine environment. So the effective methods of detecting casing damage are required badly. The accumulation of stress is the main reason for the casing damage. Magnetic anisotropy technique based on counter magnetostriction effect can detect the stress of casing in real time and help us to find out the hidden dangers in time. It is essential for us to prevent the casing damage from occurring. However, such technique is still in the development stage. Previous studies mostly got the relationship between stress and magnetic signals by physical experiment, and the study of physical mechanism in relative magnetic permeability connecting the stress and magnetic signals is rarely reported. The present paper uses the ANSYS to do the three-dimensional finite element numerical simulation to study how the relative magnetic permeability works for the oil casing model. We find that the quantitative relationship between the stress' s variation and magnetic induction intensity's variation is: Δδ =K* ΔB, K = 8.04×109, which is proved correct by physical experiment
The Impact of Anti-Corruption on Macau’s Gaming Industry: An Externality Analysis  [PDF]
Chaoqun Chen
Chinese Studies (ChnStd) , 2018, DOI: 10.4236/chnstd.2018.72012
Abstract: This study identifies and decomposes the impact of China’s central anti-corruption on Macau’s gaming industry by examining the quarter revenue data of six gaming companies from 2010 to the third quarter of 2017. The analysis results show that the negative impact of the anti-corruption campaign on the revenue of Macau’s gaming industry is lagging behind, and the strengthening of anti-corruption efforts since the establishment of the 18th Central Committee of the Communist Party of China has caused clear externality. The effect remains significant after excluding the influences of macroeconomic factors, the Brazilian World Cup, and the Asia gaming industry competition. For the impact mechanism, the effect is mainly determined through the per capita gaming of Macau visitors instead of the number of gamers. This study provides empirical support for research on the externality of anti-corruption.
Nanostructured transition metal nitride composites as energy storage material
YanHua Yue,PengXian Han,ShanMu Dong,KeJun Zhang,ChuanJian Zhang,ChaoQun Shang,GuangLei Cui
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-012-5301-1
Abstract: There are growing demands for the next generation lithium ion batteries with high energy density as well as high power performance for renewable energy storage and electric vehicles application. Recently, nanoscale materials with outstanding energy storage capability have received considerable attention due to their unique effect caused by the reduced dimensions. This review describes some recent developments of our group in research of transition metal nitride nanocomposites in application of energy storage, especially for lithium ion battery and supercapacitor. The strategies of mixed conduction (electron and ion) network with a favorable charge transportation interface in the design of the nanocomposites for such devices are highlighted.
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