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LAMINAR DEVELOPING FLOW IN THE ENTRANCE REGION OF ROTATING CURVED PIPES

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Journal of Hydrodynamics 2006年第4期18卷 418-423页

作者： MA Jian-feng SHEN xin-rong zhang Ming-kan zhang Ben-Zhao Department of Mechanics Zhejiang University Hangzhou 310027 China

Three-dimensional laminar flow in the entrance region of rotating curved pipes was investigated. The governing equations were written in an orthogonal curvilinear coordinate system and solved with a fully three-dimensional numerical method. The development of secondary flow, axial velocity, local and average friction factors for different cases of rotation were given and discussed in detail. The results show that rotation influences the flow structure and friction factor greatly and that the secondary flow is sink-type in the early stage of development and then turns to vortex structure. The average friction factor and the intensity of secondary flow have drastic decrease near the entrance. At some proper rotation, the average friction factor can be noticeably reduced.

关键词： developing flow secondary flow rotating curved pipe

Impact of ventilation design on the precooling effectiveness of horticultural produce-a review

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Food Quality and Safety 2020年第1期4卷 29-40页

作者： Yuhui Cao Ya-Fang Gong xin-rong zhang College of Engineering Sciences University of Chinese Academy of SciencesBeijingChina Department of Energy and Resource Engineering College of EngineeringPeking UniversityBeijingChina

Optimizing the ventilation design of packaging system is of crucial importance for improving the efficiency of the forced-air precooling process to maintain the quality of horticultural produce and extend the shelf life in food cold *** efforts had been devoted to the study about the impact of ventilation design on airflow and temperature distribution inside ventilated *** paper reviews relevant research methods,commonly used quantities for the measurement of precooling effectiveness,attractive design parameters,and their impact on precooling *** allow us to know exactly the characteristic and deficiency of each research method,identify dominant design parameters,and seek a promising way for the future improvement of the ventilated packaging system.

关键词： horticultural produce precooling effectiveness ventilation design forced-air precooling technique packaging system

FLOW AND HEAT TRANSFER OF OLDROYD-B FLUIDS IN A ROTATING CURVED PIPE

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Journal of Hydrodynamics 2008年第1期20卷 39-46页

作者： SHEN xin-rong zhang Ming-kan MA Jian-feng zhang Ben-zhao Institute of Fluid Engineering Zhejiang University Hangzhou 310027 China

The flow and convected heat transfer of the Oldroyd-B fluids in a rotating curved pipe with circular cross-section were investigated by employing a perturbation method. A perturbation solution up to the second order was obtained for a small curvature ratio, κ. The variations of axial velocity distribution and secondary flow structure with F, Re and We were discussed in detail in order to investigate the combined effects of the three parameters on flow structure. The combined effects of the Coriolis force, inertia force and elastic force on the temperature distribution were also analyzed, which are greater than the adding independent effects of the three forces. The variations of the flow rate and Nusselt number with the rotation, inertia and elasticity were examined as well. The results show the characteristics of the heat and mass transfer of the Oldroyd-B fluids in a rotating curved pipe.

关键词： Oldroyd-B fluids flow structure convected heat transfer rotating curved pipe

Underwater video transceiver designs based on channel state information and video content

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Frontiers of Information Technology & Electronic Engineering 2018年第8期19卷 984-998页

作者： rong-xin zhang Xiao-li MA De-qing WANG Fei YUAN En CHENG MOE Key Laboratory of Underwater Acoustic Communication and Marine Information Technology Xiamen University Department of Communication Engineering Xiamen University School of Electrical and Computer Engineering Georgia Institute of Technology

Underwater hostile channel conditions challenge video transmission designs. The current designs often treat video coding and transmission schemes as individual modules. In this study, we develop an adaptive transceiver with channel state information(CSI) by taking into account the importance of video components and channel conditions. The design is more effective than the traditional ones. However, in practical systems, perfect CSI may not be available. Therefore, we compare the imperfect CSI case with existing schemes, and validate the effectiveness of our design through simulations and measured channels in terms of a better peak signal-to-noise ratio and a higher video structural similarity index.

关键词： Underwater video transmission Transceiver design Imperfect channel state information

Numerical study of Natural Convection of Magnetic Fluids in a Cubic Cavity with a Heat Generating Object Inside by the Lattice Boltzmann Method

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Advances in Applied Mathematics and Mechanics 2010年第1期2卷 76-85页

作者： Xiao-Dong Niu Hiroshi Yamaguchi xin-rong zhang Keisuke Yoshikawa Energy Conversion Research Center Department of Mechanical EngineeringDoshisha UniversityKyoto 630-0321Japan Department of Energy and Resources Engineering College of EngineeringPeking University100871P.R.China

In this article,natural convection of a magnetic fluid in a cubic cavity with a heat generating object inside and under a uniform magnetic field is simulated by the lattice Boltzmann *** obtained from the present simulations are shown to be agreed well with our experimental measurements,and reveal more of effects of the magnetic field on the flow and heat transfer of the magnetic fluids.

关键词： Magnetic fluids natural convection Lattice Boltzmann method

THE FLOW IN ROTATING CURVED CIRCULAR PIPE

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Journal of Hydrodynamics 2000年第1期12卷 108-116页

作者： zhang Jin suo, Shen xin rong, zhang Ben zhao Department of Mechanics, Zhejiang University, Hangzhou 310027, P.R.China Zhejiang Univ Hangzhou China

The combined effects of the system rotation (Coriolis force) and curvature (centrifugal force) on the flow in rotating curved circular pipe with small curvature are examined by perturbation method. A second order perturbation solution is presented. The secondary flow structure and the primary axial velocity distributions are studied in detail. The loops of the secondary flow are more complex than those in a curved pipe without rotation or a rotating straight pipe. Its numbers depend on the body force ratio F which represents the ratio of the Coriolis to the centrifugal force. The maximum of the axial velocity is pushed to either outer bend or inner bend, which is also determined by F. The results are confirmed by the results of other authors who studied the same problem by different methods.

关键词： secondary flow curved pipe perturbation method

Evaluation of coal pillar loads during longwall extraction using the numerical method and its application

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Journal of Coal Science & Engineering(China) 2013年第3期19卷 269-275页

作者： Jin-He JIA Hong-Pu KANG xin-rong zhang Department of Coal Mining and Mine Design Tiandi Science & Technology Co. Ltd. Beijing 100013 China State Key Laboratory of Coal Mining and Clean Utilization China Coal Research Institute Beijing 100013 China Inner Mongolia Yitai Coal Co. Ltd. Erdos 017000 China

It is very difficult to reasonably evaluate the loads acting on coal pillars in longwall panels during the planning of a new pillar system. The application of empirical equations is a common practice in calculating coal pillar loads while designing a new pillar. This paper proposes numerical models for evaluating coal pillar loads. The key of building a successful numerical model for calculating coal pillar loads lies in the fact that the model should represent the redistribution of stress all over the longwall panels and the surrounding areas, and it is especially important to include the characteristics of the stress rebuilding process in the gob areas, which are crucial for the building process of coal pillar loads. Based on the geo-mechanical background of the Baoshan Coal Mine, this paper details the procedures of applying numerical models to the evaluation of coal pillar loads and their local practices. The study results show it is feasible and reasonable to use numerical models to evaluate coal pillar loads.

关键词： numerical simulation longwall panel longwall face coal pillar load gob area strain-hardening

Microbial Activity in a Temperate Forest Soil as Affected by Elevated Atmospheric CO_2

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Pedosphere 2010年第4期20卷 427-435页

作者： ZHENG Jun-Qiang HAN Shi-Jie ZHOU Yu-Mei REN Fei-rong xin Li-Hua zhang Yan Forestry Center Institute of Applied Ecology Chinese Academy of Sciences 72 Wenhua Road Shenyang 110016 （China）

Microorganisms play a key role in the response of soil ecosystems to the rising atmospheric carbon dioxide （CO2） as they mineralize organic matter and drive nutrient cycling. To assess the effects of elevated CO2 on soil microbial C and N immobilization and on soil enzyme activities, in years 8 （2006） and 9 （2007） of an open-top chamber experiment that begun in spring of 1999, soil was sampled in summer, and microbial biomass and enzyme activity related to the carbon （C）, nitrogen （N） and phosphorus （P） cycling were measured. Although no effects on microbial biomass C were detected, changes in microbial biomass N and metabolic activity involving C, N and P were observed under elevated CO2. Invertase and .dehydrogenase activities were significantly enhanced by different degrees of elevated CO2. Nitrifying enzyme activity was significantly （P 〈 0.01） increased in the August 2006 samples that received the elevated COs treatment, as compared to the samples that received the ambient treatment. Denitrifying enzyme activity was significantly （P 〈 0.04） decreased by elevated COs treatments in the August 2006 and June 2007 （P 〈 0.09） samples, β-N-acetylglucosaminidase activity was increased under elevated CO2 by 7% and 25% in June and August 2006, respectively, compared to those under ambient CO2. The results of June 2006 samples showed that acid phosphatase activity was significantly enhanced under elevated CO2. Overall, these results suggested that elevated CO2 might cause changes in the belowground C, N and P cycling in temperate forest soils.

关键词： CO2 enrichment microbial biomass soil carbon cycling soil nitrogen cycling

Machine Learning Models in Type 2 Diabetes Risk Prediction:Results from a Cross-sectional Retrospective Study in Chinese Adults

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Current Medical Science 2019年第4期39卷 582-588页

作者： Xiao-lu XIONG rong-xin zhang Yan BI Wei-hong ZHOU Yun YU Da-long ZHU Department of Endocrinology Nanjing Drum Tower Hospital Clinical College of Nanjing Medical UniversityNanjing 210008China School of Biomedical Engineering and Informatics Nanjing Medical UniversityNanjing 211166China

Type 2 diabetes mellitus (T2DM) has become a prevalent health problem in China,especially in urban *** prevention strategies are needed to reduce the associated mortality and *** applied the combination of rules and different machine learning techniques to assess the risk of development of T2DM in an urban Chinese adult population.A retrospective analysis was performed on 8000 people with non-diabetes and 3845 people with T2DM in *** Perceptron (MLP),AdaBoost (AD),Trees Random Forest (TRF),Support Vector Machine (SVM),and Gradient Tree Boosting (GTB) machine learning techniques with 10 cross validation methods were used with the proposed model for the prediction of the risk of development of *** performance of these models was evaluated with accuracy,precision,sensitivity,specificity,and area under receiver operating characteristic (ROC) curve (AUC).After comparison,the prediction accuracy of the different five machine models was 0.87,0.86,0.86,0.86 and 0.86 *** combination model using the same voting weight of each component was built on T2DM,which was performed better than individual *** findings indicate that,combining machine learning models could provide an accurate assessment model for T2DM risk prediction.

关键词： type 2 diabetes risk prediction machine learning