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Search Results: 1 - 10 of 23348 matches for " Wenjie Yuan "
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The Statistical Analysis and Evaluation of Examination Results of Materials Research Methods Course  [PDF]
Wenjie Yuan, Chengji Deng, Hongxi Zhu, Jun Li
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.37B042
Abstract: The statistical analysis and evaluation of examination results provide the theoretical basis for teaching quality and management. Materials research methods course is the key course for the undergraduates major in materials science and engineering. Based on the examination results of inorganic nonmetal materials engineering specialty students in the first term of 2011-2012 school year of Wuhan University of Science and Technology, the quantitative analysis for several parameters including difficulty, discrimination and reliability were investigated. The results indicate that the distribution of examination scores approximate to normal distribution. Difficulty of the exam paper belongs to median level, and discrimination of this is qualified as well as reliability. Thus it was concluded that the design of the examination paper was good and dependable.
Effects of SnO2 Addition on the Properties of Alumina-Magnesia Refractory Castables  [PDF]
Wenjie Yuan, Qingyou Zhu, Chengji Deng, Hongxi Zhu
New Journal of Glass and Ceramics (NJGC) , 2015, DOI: 10.4236/njgc.2015.51001
Abstract: Alumina-magnesia refractory castables have been widely used in the wall and bottom impact pad of steel ladles. The properties of alumina-magnesia refractory castables with SnO2 additive in 0 - 5 wt% range were investigated. The phase composition, microstructure, physical and mechanical properties of these refractories were studied. The results showed that the addition of SnO2 could have a great influence on the properties of alumina-magnesia refractory castables. The expansion, apparent porosity and strength of refractories with SnO2 were all more prominent than those of reference samples, which were attributed to the formation of CA6 and enhanced bonding. Meanwhile SnO2 could react with spinel and CA6 to form solid solution.
Effects of carbon sources, oxygenation and ethanol on the production of inulinase by Kluyveromyces marxianus YX01
JIAOQI GAO,LIJIE CHEN,WENJIE YUAN
Journal of BioScience and Biotechnology , 2012,
Abstract: Inulinase is one of the most important factors in consolidated bioprocessing, which combines enzyme production, inulin saccharification, and ethanol fermentation into a single process. In our study, inulinase production and cell growth of Kluyveromyces marxianus YX01 under different conditions were studied. Carbon source was shown to be significant on the production of inulinase, because the activity of inulinase was higher using inulin as a carbon source compared with glucose or fructose. The concentration of the carbon source had a repressive effect on the activity of inulinase. When the concentration was increased to 60 g/L, inulinase activity was only 50% compared with carbon source concentration of 20 g/L. Enzyme activity was also strongly influenced by aeration rate. It has been shown that the activity of inulinase and cell growth under anaerobic conditions were maintained at low levels, but aeration at 1.0 vvm (air volume/broth volume minute) led to higher activity. Inulinase activity per unit biomass was not significantly different under different aeration rates. Ethanol had a repressive effect on the cell growth. Cells ceased growing when the level of ethanol was greater than 9% (v/v), but ethanol did not affect the activity of secreted inulinase and the enzyme was stable at ethanol concentration up to 15%.
Numerical Analysis of Three-Dimensional Unsteady Turbulent Flow in Circular Casing of a High Power Centrifugal Diffuser Pump
Ji Pei,Shouqi Yuan,Wenjie Wang
Advances in Mechanical Engineering , 2013, DOI: 10.1155/2013/204521
Abstract: For high power centrifugal pump which is usually used in high risk applications, circular casing structure has been adopted to increase the reliability of the pump. This special casing structure can make the flow more complex and cause huge hydraulic losses. In this paper, the periodically unsteady turbulent flow in the circular casing of a high power centrifugal diffuser pump has been investigated numerically by CFD calculation. The velocity distributions in different positions were analyzed, and the pressure fluctuation results in time and frequency domains were considered. Finally, the pressure fluctuation intensity coefficient (PFIC) and peak pressure coefficient (PPC) based on statistical thinking were defined on each grid node and the results were analyzed quantitatively to check the time accumulation effect of the unsteady flow phenomenon. The results show that strong flow unsteadiness can be found near diffuser outlet positions of the circular channel and in discharge tube. In addition, the PPC and PFIC results can supply a new angle of view to evaluate the pressure variation, and it is a good supplement to the traditional unsteady pressure analysis method in time and frequency domains. 1. Introduction Centrifugal pump is one of the most important energy conversion devices widely used in almost all industrial and agricultural applications: nuclear industry, petroleum, agri-business, chemistry, as well as cryogenic propellant pumping, and so forth. The complex inner flow phenomenon of centrifugal pump, such as strong rotor-stator interaction, can generate hydraulic excitation forces and give rise to pressure pulsations. These dynamic pressure components then will lead to mechanical vibrations and alternate stresses in various pump components, called flow-induced vibration problem [1]. The vibrations transmitted to the foundations can spread as solid-borne noise throughout the building, and the vibrating pump structures can also radiate airborne and fluid-borne noise [2]. When the power of centrifugal pump becomes higher and higher, the severer stability problems of centrifugal pump caused by unsteady turbulent flow should be noticed, especially in the application field of high risk industry. Obvious unsteady turbulent flow phenomenon is mainly caused by rotor-stator interaction of a rotating impeller and stationary diffuser under conventional operating conditions and can spread into the whole flow passage. This periodic rotor-stator interaction has two kinds of effects, discussed by Feng et al. [3]. The first is the down-stream effect of the
Evolution with Reinforcement Learning in Negotiation
Yi Zou, Wenjie Zhan, Yuan Shao
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0102840
Abstract: Adaptive behavior depends less on the details of the negotiation process and makes more robust predictions in the long term as compared to in the short term. However, the extant literature on population dynamics for behavior adjustment has only examined the current situation. To offset this limitation, we propose a synergy of evolutionary algorithm and reinforcement learning to investigate long-term collective performance and strategy evolution. The model adopts reinforcement learning with a tradeoff between historical and current information to make decisions when the strategies of agents evolve through repeated interactions. The results demonstrate that the strategies in populations converge to stable states, and the agents gradually form steady negotiation habits. Agents that adopt reinforcement learning perform better in payoff, fairness, and stableness than their counterparts using classic evolutionary algorithm.
Design and demonstration of a 0.22 THz gyrotron oscillator
Yang Yan,ShengGang Liu,XiaoYun Li,WenJie Fu,XueSong Yuan
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0172-9
Abstract: Gyrotrons are the most powerful terahertz sources and have potential applications in many areas. A terahertz gyrotron oscillator with a pulsed solenoid producing up to an 8 T magnetic field has been designed, constructed and tested. In a 7.96 T magnetic field, 3 kW output power radiations at 0.22 THz frequency have been generated.
Generating 0.42 THz radiation from a second harmonic gyrotron
WenJie Fu,Yang Yan,XiaoYun Li,XueSong Yuan,ShengGang Liu
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4709-3
Abstract: Gyrotrons are high powered coherent electromagnetic radiation sources, and are considered to be available powerful sources that have the potential to bridge the so-called terahertz gap. In the University of Electronic Science and Technology of China, a second harmonic gyrotron has been designed, manufactured, and tested. The gyrotron generated radiation at a 0.423 THz frequency in 5 μs pulses with an 8.1 Tesla magnetic field, with a power per pulse of about 4.4 kW. To date this is the highest frequency recorded for vacuum electronic devices in China. The gyrotron design, operation and measurements are presented.
Responses of grassland and forest to temperature and precipitation changes in Northeast China

Jing Peng ,Wenjie Dong,Wenping Yuan,Yong Zhang ,

大气科学进展 , 2012,
Abstract: Using the Normalized Difference Vegetation Index (NDVI) as an indicator of vegetation growth, we explored the characteristics and differences in the response to drought of five vegetation biomes in Northeast China, including typical steppe, desert steppe, meadow steppe, deciduous coniferous forest and deciduous broad-leaved forest during the period 1982--2009. The results indicate that growing season precipitation may be the primary vegetation growth-limiting factor in grasslands. More than 70% of the temporal variations in NDVI can be explained by the amount of precipitation during the growing season in typical and desert steppes. During the same period, the mean temperature in the growing season could explain nearly 43% of the variations in the mean growing season NDVI and is therefore a dominant growth-limiting factor for forest ecosystems. Therefore, the NDVI trends differ largely due to differences in the vegetation growth-limiting factors of the different vegetation biomes. The NDVI responses to droughts vary in magnitude and direction and depend on the drought-affected areas of the five vegetation types. Specifically, the changes in NDVI are consistent with the variations in precipitation for grassland ecosystems. A lack of precipitation resulted in decreases in NDVI, thereby reducing vegetation growth in these regions. Conversely, increasing precipitation decreased the NDVI of forest ecosystems. The results also suggest that grasslands under arid and semi-arid environments may be more sensitive to drought than forests under humid environments. Among grassland ecosystems, desert steppe was most sensitive to drought, followed by typical steppe; meadow steppe was the least sensitive.
Associations between TNF-α Polymorphisms and Pneumonia: A Meta-Analysis
Li Li, Wei Nie, Weifeng Li, Weifeng Yuan, Wenjie Huang
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0061039
Abstract: Background Several studies evaluated the associations of tumor necrosis factor-α (TNF-α) polymorphisms with pneumonia in different populations. However, the results were conflicting and controversial. Methods Databases including PubMed, Embase, Web of Science, and China National Knowledge Infrastructure (CNKI) were searched to find relevant studies. Data were extracted independently by two investigators. Crude odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated. Results Twelve case-control studies and one cohort study were included. Overall, no association between TNF-α ?308A/G polymorphism and pneumonia risk was observed for AA +AG vs. GG (OR = 1.13; 95% CI 0.99–1.30; P = 0.07). In addition, TNF-α ?308A/G polymorphism was not associated with pneumonia mortality (OR = 1.96; 95% CI 0.94–4.09; P = 0.07). Furthermore, there was no association of TNF-α ?238A/G polymorphism with the risk of pneumonia (OR = 1.38; 95% CI 0.84–2.28; P = 0.20). Conclusions TNF-α ?308A/G, ?238A/G polymorphisms were not associated with pneumonia risk. Moreover, TNF-α ?308A/G polymorphism did not play a role in the pneumonia mortality risk.
飞机结构疲劳可靠度贝叶斯组合预测
袁修开, 刘文杰
YUAN Xiukai
, LIU Wenjie

- , 2018, DOI: 10.11887/j.cn.201804016
Abstract: 在实际工程中,常常需要利用模型去描述和分析问题。然而模型亦存在不确定性,即可能存在多个描述同一现象的模型,例如多个疲劳分析的模型。针对飞机结构的疲劳可靠性问题,提出在考虑三种裂纹扩展模型下基于贝叶斯公式的疲劳可靠度组合预测方法。针对不同应力水平下飞机结构试件的裂纹扩展数据建立了三种随机裂纹扩展模型;在考虑模型参数不确定性条件下,采用贝叶斯模型平均方法对三种模型进行组合;基于组合模型分析结构的可靠度。所提方法在分析飞机结构疲劳可靠度上,采用了组合模型,能够最大限度保障结果的稳定性。此外,考虑了模型参数的不确定性,能够得到更为合理的裂纹扩展预测分布和可靠度预测值。给出的实例及分析结果表明所提方法可行。
In practical engineering, it is often necessary to use models to describe and analyze problems. However, uncertainty exists in the models. There are many models that can describe the same phenomenon, such as the multiple fatigue analysis models. In order to solve the problem of fatigue reliability of aircraft structures, a combination forecasting method based on Bayesian model averaging was proposed by considering three kinds of crack propagation models. Three random crack propagation models were established by using the crack propagation data of aircraft structures under three stress levels. Considering the uncertainty of the model parameters, the Bayesian model averaging method was used to combine the three models. The reliability of the structure was analyzed based on the combined model. The combined model was used to analyze the fatigue reliability of aircraft structure, which can improve the robustness of the results. In addition, considering the uncertainty of the model parameters, more reasonable predictive distribution of crack propagation as well as the reliability can be obtained. Examples and analysis results are given to show the feasibility of this method. 
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