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Search Results: 1 - 10 of 25606 matches for " Cheng Yikang "
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The attenuation of retinal nerve fiber layer thickness and cognitive deterioration
Yuan Shen,Zhongyong Shi,Renbao Jia,Yikang Zhu,Yan Cheng,Wei Feng,Chunbo Li
Frontiers in Cellular Neuroscience , 2013, DOI: 10.3389/fncel.2013.00142
Abstract: Thinner retinal nerve fiber layer (RNFL) has been reported in Alzheimer’s disease (AD) patient. However, whether changes in RNFL thickness can predict the cognitive deterioration remains unknown. We therefore set out a prospective clinical investigation to determine the potential association between the attenuation of RNFL thickness and the deterioration of cognitive function over a period of 25 months. We assessed cognitive function using the Repeatable Battery for the Assessment of Neuropsychological Status and measured RNFL thickness employing optical coherence tomography in 78 participants (mean age 72.31 ± 3.98 years, 52% men). The participants were categorized as stable participants whose cognitive status remained no change (N = 60) and converted participants whose cognitive status deteriorated (N = 18). We found that there was an association between the attenuation of superior quadrant RNFL thickness and the deterioration of cognitive function in the stable participants. In the converted participants, however, there was an inverse association between the reduction of inferior quadrant RNFL thickness and decline of cognitive functions [scores of list recall (R = -0.670, P = 0.002), adjusted (R = -0.493, P = 0.031)]. These data showed that less reduction in the inferior quadrant of RNFL thickness might indicate a higher risk for the patients to develop cognitive deterioration. These findings have established a system to embark a larger scale study to further test whether changes in RNFL thickness can serve as a biomarker of AD, and would lead to mechanistic studies to determine the cellular mechanisms of cognitive deterioration.
Predicting the Arrival Time of Coronal Mass Ejections with the Graduated Cylindrical Shell and Drag Force Model
Tong Shi,Yikang Wang,Linfeng Wan,Xin Cheng,Mingde Ding,Jie Zhang
Physics , 2015,
Abstract: Accurately predicting the arrival of coronal mass ejections (CMEs) at the Earth based on remote images is of critical significance in the study of space weather. In this paper, we make a statistical study of 21 Earth directed CMEs, exploring in particular the relationship between CME initial speeds and transit times. The initial speed of a CME is obtained by fitting the CME with the Graduated Cylindrical Shell model and is thus free of projection effects. We then use the drag force model to fit results of the transit time versus the initial speed. By adopting different drag regimes, i.e., the viscous, aerodynamics, and hybrid regimes, we get similar results, with the least mean estimation error of the hybrid model of 12.9 hours. CMEs with a propagation angle (the angle between the propagation direction and the Sun-Earth line) larger than its half angular width arrive at the Earth with an angular deviation caused by factors other than the radial solar wind drag. The drag force model cannot be well applied to such events. If we exclude these events in the sample, the prediction accuracy can be improved, i.e., the estimation error reduces to 6.8 hours. This work suggests that it is viable to predict the arrival time of CMEs at the Earth based on the initial parameters with a fairly good accuracy. Thus, it provides a method of space weather forecast of 1--5 days following the occurrence of CMEs.
TESTING STUDY ON PERMEABILITY OF NON-DARCY FLOW IN POST-PEAK SANDSTONE
峰后砂岩非Darcy流渗透特性的试验研究

Cheng Yikang,Chen Zhanqing,Miao Xiexing,Mao Xianbiao,
程宜康
,陈占清 缪协兴 茅献彪

岩石力学与工程学报 , 2004,
Abstract: It is of practical importance to investigate the permeability of rock under high stress,especially under post-peak stress with low confining pressure. A patented device,combined with MTS815.02 Rock Mechanics System,makes the measurement of non-Darcy permeability possible. The configuration of test system of permeability measurement of non-Darcy flow in post-failure rock,test principle and plan,and the processing method for test data are presented. The permeability of non-Darcy flow in post-peak rock is carefully measured by using steady seepage method. Sandstone specimens are divided into five groups. Every group consists of ten specimens,which undergo same axial strain before permeability measurement. The permeability of each specimen is obtained by fitting the seepage velocity-pressure gradient curve. The statistical indexes of every group of specimens are calculated. The relation between the indexes and axial strain are established by linear regression. It is shown that the permeability of post-peak rock is remarkably larger than that of pre-peak rock. The permeability of post-peak rock varies parabolically with axial strain. This study provides the method and technique for measuring permeability of non-Darcy flow in post-peak rock,which can be employed in mining,civil and other engineerings.
Spatial and Temporal Variations in Available Soil Nitrogen—A Case Study in Kobresia Alpine Meadow in the Qinghai-Tibetan Plateau, China  [PDF]
Li Lin, Guangmin Cao, Fawei Zhang, Xun Ke, Yikang Li, Xingliang Xu, Qian Li, Xiaowei Guo, Bo Fan, Yangong Du
Journal of Geoscience and Environment Protection (GEP) , 2019, DOI: 10.4236/gep.2019.73010
Abstract: Elucidating the factors that determine the effects of temporal and spatial variation of nutrients is important for analyzing the characteristics of an ecosystem. The goal of this paper was to estimate how values obtained using a particular sampling approach correlated with the actual data for an entire plot. The mesh partition method was employed to divide an integrated observing field (IOF) located at the Haibei National Field Research Station of an alpine grassland ecosystem, China, into 25 subplots. Five of the 25 subplots were randomly selected for soil sampling and to determine the source of variations in soil nutrient content from 2001 to 2012. The results showed that, contributions of temporal and spatial variation in available nitrogen in the 0 - 10 cm soil layer accounted for 47.3% and 52.7%, respectively. The contribution of spatial variance was higher than that of temporal variance especially in the surface soil layers. The available soil nitrogen content in the alpine meadow was not obviously affected by fluctuations in rainfall and temperature. Increasing the number of samples could reduce calculation errors in measuring available soil nitrogen content, while collecting a reasonable number of samples can save time and labor.
Competition between Replicative and Translesion Polymerases during Homologous Recombination Repair in Drosophila
Daniel P. Kane,Michael Shusterman,Yikang Rong,Mitch McVey
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002659
Abstract: In metazoans, the mechanism by which DNA is synthesized during homologous recombination repair of double-strand breaks is poorly understood. Specifically, the identities of the polymerase(s) that carry out repair synthesis and how they are recruited to repair sites are unclear. Here, we have investigated the roles of several different polymerases during homologous recombination repair in Drosophila melanogaster. Using a gap repair assay, we found that homologous recombination is impaired in Drosophila lacking DNA polymerase zeta and, to a lesser extent, polymerase eta. In addition, the Pol32 protein, part of the polymerase delta complex, is needed for repair requiring extensive synthesis. Loss of Rev1, which interacts with multiple translesion polymerases, results in increased synthesis during gap repair. Together, our findings support a model in which translesion polymerases and the polymerase delta complex compete during homologous recombination repair. In addition, they establish Rev1 as a crucial factor that regulates the extent of repair synthesis.
Practice and Realization in the Examination (and Reading)of the Scientific and Technical Periodical
开展科技期刊审读工作的实践与体会

Dan Ping,Ma YiKang,
丹萍
,马益康

中国科技期刊研究 , 2000,
Abstract: 为了不断地提高期刊的总体质量,三年来,江苏省科委每年组织30余位专家对本省100余种省属科技期刊全面开展了审读工作。文章总结并阐述了开展科技期刊审读工作的必要性、工作方法,以及审读工作取得的初步成效。
Design of Adaptive Pole Placement Controller for Plants Having Unknown Deterministic Disturbances
抑制未知确定性扰动的极点配置自适应控制

Liu Heping,Sun Yikang,
刘贺平
,孙一康

自动化学报 , 1996,
Abstract: This paper deals with a design method of adaptive pole placement controller which can eliminate unknown deterministic disturbances, such as sine wave with unknown frenqency and/or bonded t polynomial etc. In the algorithm, the calculation of disturbance model is reformed, which is applicable to the case of many frequencies. The proposed scheme is simple and control performance is improved compared with other methods concerned. The effectiveness of proposed methods is shown through simulations.
A Mathematical Model for Forecasting Distortion of Workpieces with Phase Transformation on Cooling Process
Jiansong YE,Yikang LIU,Yuanjun ZHOU,
JiansongYE
,YikangLIU,YuanjunZHOU

材料科学技术学报 , 2003,
Abstract: A temperature phase transformation stress coupled 3D nonlinear mathematical model has been proposed for forecasting distortion of workpieces on the cooling processes in this paper. Moreover, a series of subroutines were developed on the MARC (analysis research corporation) software platform and the simulation result is basically identical with the experimental one that measured on the workpiece shape with LEITZ equipment. This verifies that the mathematical model and method are feasible.
Caustic Failure of Thermal Insulated Tubing in Steam Flooding
Aiping XIAN,Yiyin SAN,Dun ZHANG,Yikang WANGHeping SUN,

材料科学技术学报 , 1997,
Abstract: The coupling of the pre-stressed thermal insulated tubing string broke down inside the steam flooding wells, after the tubing were used in high temperature and high pressure steam for about two years. With further check, it was found that most of the weld joints between the inner and outer tubing also cracked. The failure analysis for the accidents has been carried out by the analysis of chemical composition for the steels, microstructure observation, mechanical property tests, and the investigation of the service environment etc.. The results show that the early damage of the pre-stressed thermal insulated tubing string is mainly induced by the caustic stress corrosion, which can be strengthened by an unstable microstructure of the coupling serviced at high temperature for a long time. Moreover, the high pre-stress design on the thermal insulated pipe for the cyclic steam injection may be not suitable to the situation of steam flooding, which would result in the weld joint cracking.
TRAPPING OF HYDROGEN BY PRECIPITATE TiC IN LOW CARBON STEEL

by XIAN Aiping,LI Peiji,WANG Yikang,LI Xun,

金属学报 , 1986,
Abstract:
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