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Search Results: 1 - 10 of 8346 matches for " Hejun Kang "
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Social integration: How is it related to self-rated health?  [PDF]
Hejun Kang, Yvonne L. Michael
Advances in Aging Research (AAR) , 2013, DOI: 10.4236/aar.2013.21002

Social integration has well-established health benefits among older adults in observational studies. However, interventions designed to increase social integration have not improved health suggesting important knowledge gaps on how social integration influences health outcomes. This study developed a new measure of social integration, daily social contact, capturing the interpersonal nature of social integration and mobility of individuals, and providing a direct assessment of individuals’ real-time access to companionship and social support. The data used is the 2006-2007 American Time Use Survey (ATUS), which surveyed 25,191 individuals aged 15 years and older (n = 4378 aged 65 years and older). Generalized ordinal logistic regression analyses revealed positive, but non-parallel relationships between daily social contacts and the ordinal categories of self-rated health among older adults. This study may be used to identify populations that experience social exclusion, such that future research can determine more precisely how to intervene to improve health outcomes.

Relative accuracy of spatial predictive models for lynx Lynx canadensis derived using logistic regression-AIC, multiple criteria evaluation and Bayesian approaches
Current Zoology , 2009,
Abstract: We compared probability surfaces derived using one set of environmental variables in three Geographic Information Systems (GIS)-based approaches: logistic regression and Akaike’s Information Criterion (AIC), Multiple Criteria Evaluation (MCE), and Bayesian Analysis (specifically Dempster-Shafer theory). We used lynx Lynx canadensis as our focal species, and developed our environment relationship model using track data collected in Banff National Park, Alberta, Canada, during winters from 1997 to 2000. The accuracy of the three spatial models were compared using a contingency table method. We determined the percentage of cases in which both presence and absence points were correctly classified (overall accuracy), the failure to predict a species where it occurred (omission error) and the prediction of presence where there was absence (commission error). Our overall accuracy showed the logistic regression approach was the most accurate (74.51%). The multiple criteria evaluation was intermediate (39.22%), while the Dempster-Shafer (D-S) theory model was the poorest (29.90%). However, omission and commission error tell us a different story: logistic regression had the lowest commission error, while D-S theory produced the lowest omission error. Our results provide evidence that habitat modellers should evaluate all three error measures when ascribing confidence in their model. We suggest that for our study area at least, the logistic regression model is optimal. However, where sample size is small or the species is very rare, it may also be useful to explore and/or use a more ecologically cautious modelling approach (e.g. Dempster-Shafer) that would over-predict, protect more sites, and thereby minimize the risk of missing critical habitat in conservation plans[Current Zoology 55(1): 28 – 40, 2009].
Prediction of Properties in Thermomechanically Treated Cu-Cr-Zr Alloy by an Artificial Neural Network
Juanhua SU,Qiming DONG,Ping LIU,Hejun LI,Buxi KANG,

材料科学技术学报 , 2003,
Abstract: A supervised artificial neural network (ANN) to model the nonlinear relationship between parameters of thermomechanical treatment processes with respect to hardness and conductivity properties was proposed for Cu-Cr-Zr alloy. The improved model was developed by the Levenberg-Marquardt training algorithm. A basic repository on the domain knowledge of thermomechanical treatment processes is established via sufficient data acquisition by the network. The results showed that the ANN system is an effective way and can be successfully used to predict and analyze the properties of Cu-Cr-Zr alloy.

Shi Rong,Li Hejun,Yang Zhang,Kang Mokuang,

光子学报 , 1997,
Abstract: There have been several advanced deposition models for pyrocarbons up to now,but all the models are suitable only for a narrow limit and can not give sufficient explanation for the three main textures,namely smooth laminar (SL),rough lamlnar (RL)and lsotropic carbons (ISO). Based on the droplet model for pyrocarbons that was raised early,in this paper a droplet model in broad sence is given by studying the textures,growth features and the binding of carbon atoms of pyrocarbons on graphite substrate and matrix of unidirectional carbon/carbon composites (ID-C/C) prepared by chemical vapor deposition (CVD). Droplets in broad sense refer to all kinds of sphenoids that are more or less viscous. This model can explain the mechanism of the formation of SL,RL and ISO satisfactorily.

LUO Ruiying,LI Hejun,YANG Zheng,KANG Mokuang,

材料研究学报 , 1996,
Abstract: The process prepared of high tribological properties (HTP) C/C composites was explored,the mode of microstructure of HTP C/ C composites was designed, C/C composites that possess microstructure with spherical deposition carbon on carbon fibre were developed. Experiments showed that the HTP C/C composites have better tribological properties: the variation of brake moment with velocity is stable, the peak value of starting moment is low, friction coefficient is moderate, specific wear is small, friction surface is smooth, samples are not delaminded and fractured.
Rapid Concentration of Nanoparticles with DC Dielectrophoresis in Focused Electric Fields
Chen Dafeng,Du Hejun,Tay CheeYong
Nanoscale Research Letters , 2009,
Abstract: We report a microfluidic device for rapid and efficient concentration of micro/nanoparticles with direct current dielectrophoresis (DC DEP). The concentrator is composed of a series of microchannels constructed with PDMS-insulating microstructures for efficiently focusing the electric field in the flow direction to provide high field strength and gradient. The location of the trapped and concentrated particles depends on the strength of the electric field applied. Both ‘streaming DEP’ and ‘trapping DEP’ simultaneously take place within the concentrator at different regions. The former occurs upstream and is responsible for continuous transport of the particles, whereas the latter occurs downstream and rapidly traps the particles delivered from upstream. The performance of the device is demonstrated by successfully concentrating fluorescent nanoparticles. The described microfluidic concentrator can be implemented in applications where rapid concentration of targets is needed such as concentrating cells for sample preparation and concentrating molecular biomarkers for detection.
Intrusion Detection Method Using Protocol Classification and Rough
Xunyi Ren,Ruchuan Wang,Hejun Zhou
Computer and Information Science , 2009, DOI: 10.5539/cis.v2n4p100
Abstract: In order to improve the efficiency of support vector intrusion detection, we first do protocol Classification for the intrusion data, then refine its characteristic by rough set reduction. By using these procedures, we propose an intrusion detection method using protocol classification and rough set based support vector machine. The method is divided into training and testing processes. In the process of training, we first do protocol classification for the training data, and then do rough set refinement. The refined characteristics are stored as the pre-defined process, and finally the usage of support vector machine for data reduction training, the training model will be stored in accordance with the agreement. In the testing process, the data is classified according to protocol classification and then start the characteristics reduction procedure according to protocol classification. Finally, make a decision using the Support Vector Machines that corresponding to the agreement. The experimental results based on KDDCUP'99 data show that the method is the method is faster and the detection accuracy is comparable compared with the SVM without using protocol classification and using all characteristic.
An All-E-Beam Lithography Process for the Patterningof 2D Photonic Crystal Waveguide Devices
Yu Hejun,Yu Jinzhong,Chen Shaowu,
Yu Hejun
,Yu Jinzhong,Chen Shaowu

半导体学报 , 2006,
Abstract: We present an all-e-beam lithography (EBL) process for the patterning of photonic crystal waveguides.The whole device structures are exposed in two steps.Holes constituting the photonic crystal lattice and defects are first exposed with a small exposure step size (less than 10nm).With the introduction of the additional proximity effect to compensate the original proximity effect,the shape,size,and position of the holes can be well controlled.The second step is the exposure of the access waveguides at a larger step size (about 30nm) to improve the scan speed of the EBL.The influence of write-field stitching error can be alleviated by replacing the original waveguides with tapered waveguides at the joint of adjacent write-fields.It is found experimentally that a higher exposure efficiency is achieved with a larger step size;however,a larger step size requires a higher dose.
Rapeseed Oil Monoester of Ethylene Glycol Monomethyl Ether as a New Biodiesel
Jiang Dayong,Wang Xuanjun,Liu Shuguang,Guo Hejun
Journal of Biomedicine and Biotechnology , 2011, DOI: 10.1155/2011/293161
Abstract: A novel biodiesel named rapeseed oil monoester of ethylene glycol monomethyl ether is developed. This fuel has one more ester group than the traditional biodiesel. The fuel was synthesized and structurally identified through FT-IR and P1PH NMR analyses. Engine test results show that when a tested diesel engine is fueled with this biodiesel in place of 0# diesel fuel, engine-out smoke emissions can be decreased by 25.0%–75.0%, CO emissions can be reduced by 50.0%, and unburned HC emissions are lessened significantly. However, NOx emissions generally do not change noticeably. In the area of combustion performance, both engine in-cylinder pressure and its changing rate with crankshaft angle are increased to some extent. Rapeseed oil monoester of ethylene glycol monomethyl ether has a much higher cetane number and shorter ignition delay, leading to autoignition 1.1°CA earlier than diesel fuel during engine operation. Because of certain amount of oxygen contained in the new biodiesel, the engine thermal efficiency is improved 13.5%–20.4% when fueled with the biodiesel compared with diesel fuel.

REN Xiangqian,LI Hejun,

金属学报 , 1996,
Abstract: A numerical simulation technique based on the stable alternating direction implicit(SADI) method and the upper bound element technique(UBET) is presented and applied to simulations of the direct extrusion process of liquid metal during solidification (the process is hereafter called "liquid extrusion" for short) which involves solidification and large plastic deformation in one process. The computer-generated animation displays the forming process of workpiece lively. The simulative results are helpful to a better understanding of the technology of liquid extrusion
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