检索结果-南通市图书馆

Acta Mechanica Sinica 2014年第3期30卷 361-369页

作者： zhe-yan Jin Sylvio Pasqualini Bo Qin School of Aerospace Engineering and Applied Mechanics Tongji University Institute of Unmanned Aircraft System Beihang University

In the present study, an experimental study was conducted to characterize the effect of Reynolds number on flow structures in the turbulent wake of a circular parachute canopy by utilizing stereoscopic particle image velocime- try （Stereo-PIV） technique. The parachute model tested in the present study was attached by 28 nylon suspension lines and placed horizontally at the test section center of the wind tunnel. The obtained results showed that with the in- crease of Reynolds number, the intensities of the vortices near the downstream region of the canopy skirt were found to increase accordingly. However, the increase of Reynolds number did not result in a significant change in ensemble- averaged normalized x-component of the velocity, ensembleaveraged normalized vorticity, normalized Reynolds stress, and normalized turbulent kinetic energy distributions in the turbulent wake of the circular parachute canopy. The obtained results are very useful to further our understanding about the unsteady aerodynamics in the wake of flexible circular parachute canopies and to constitute a reference for CFD computation.

关键词： Stereo-PIV Circular parachute - Canopy Flexible Turbulent wake

Estimation of solid concentration in solid-liquid two-phase flow in horizontal pipeline using inverse-problem approach

在线全文

学校读者我要写书评

暂无评论

Particuology 2022年第3期20卷 1-13页

作者： Ji Zhang Han Yuan Ning Mei zhe yan Marine Engineering College of EngineeringOcean University of ChinaQingdao 266100China Offshore Engineering Department of CivilEnvironmental and MiningUniversity of Western Australia35 Stirling HwyCrawleyWA 6009Australia Power Engineering and Engineering Thermophysics School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

In this study,an inverse-problem method was applied to estimate the solid concentration in a solid-liquid two-phase *** algebraic slip mixture model was introduced to solve the forward problem of solid-liquid convective heat *** time-average conservation equations of mass,momentum,energy,as well as the volume fraction equation were computed in a computational fluid dynamics(CFD)*** solid concentration in the CFD model was controlled using an external program that included the inversion iteration,and an optimal estimation was performed via experimental *** using a fly-ash-water mixture and sand-water mixture with different solid concentrations in a horizontal pipeline were conducted to verify the accuracy of the inverse-problem *** estimated results were rectified using a method based on the relationship between the estimated results and estimation error;consequently,the accuracy of the corrected inversion results improved *** a verification through experiments,the inverse-problem method was concluded to be feasible for predicting the solid concentration,as the estimation error of the corrected results was within 7%for all experimental samples for a solid concentration of less than 50%.The inverse-problem method is expected to provide accurate predictions of the solid concentration in solid-liquid two-phase flow systems.

关键词： Solid-liquid two-phase flow Solid concentration estimation Coupling calculation Inverse heat transfer problem Algebraic slip mixture model

The effect of single-horn glaze ice on the vortex structures in the wake of a horizontal axis wind turbine

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2015年第1期31卷 62-72页

作者： zhe-yan Jin Qiao-Tian Dong Zhi-Gang yang School of Aerospace Engineering and Applied Mechanics Tongji University School of Automotive Studies Tongji University Shanghai Automotive Wind Tunnel Center

The present study experimentally investigated the effect of a simulated single-horn glaze ice accreted on ro- tor blades on the vortex structures in the wake of a hori- zontal axis wind turbine by using the stereoscopic particle image velocimetry （Stereo-PIV） technique. During the ex- periments, four horizontal axis wind turbine models were tested, and both ＂free-run＂ and ＂phase-locked＂ Stereo-PIV measurements were carried out. Based on the ＂free-run＂ measurements, it was found that because of the simulated single-horn glaze ice, the shape, vorticity, and trajectory of tip vortices were changed significantly, and less kinetic en- ergy of the airflow could be harvested by the wind turbine. In addition, the ＂phase-locked＂ results indicated that the pres- ence of simulated single-horn glaze ice resulted in a dramatic reduction of the vorticity peak of the tip vortices. Moreover, as the length of the glaze ice increased, both root and tip vortex gaps were found to increase accordingly.

关键词： Stereo-PIV Single-horn glaze ice. Tip vorticesRoot vortices Wind turbine icing

Development and application of a life cycle energy consumption and CO2emissions analysis model for high-speed railway transport in China

在线全文

学校读者我要写书评

暂无评论

Advances in Climate Change Research 2021年第2期12卷 270-280页

作者： WANG yan-zhe ZHOU Sheng OU Xun-Min Tsinghua University-Zhang Jiagang Joint Institute for Hydrogen Energy and Lithium-Ion Battery Technology Tsinghua UniversityBeijing100084China Institute of Energy Environment and EconomyTsinghua UniversityBeijing100084China Tsinghua-Rio Tinto Joint Research Centre for Resources Energy and Sustainable DevelopmentLaboratory for Low Carbon EnergyTsinghua UniversityBeijing100084China China Automotive Energy Research Center Tsinghua UniversityBeijing100084China

China's high-speed railway(HSR)is booming recently,the HSR's performance of energy conservation and carbon reduction has attractedmuch *** study developed a new life cycle model of energy consumption and greenhouse gas(GHG)emissions on China's HSR bylife cycle analysis(LCA),covering the stages of infrastructure,HSR train,and operation,based on the TLCAM(Tsinghua-LCA Model).A caseof the BeijingeShanghai HSR has been studied to show that the full life cycle energy consumption and GHG emissions of HSR transportationare 0.4 MJ km1per capita and 0.04 kg CO2ekm1per capita,respectively,which are far less than aviation,gasoline vehicles,diesel vehicles,electric vehicles and public *** the cleaner power structure and the progress of HSR train technology,the energy consumption andcarbon emissions of HSR in 2020 could be reduced by 20%compared to *** study indicates that electricity generation mix structure andfull load rate are important factors influencing the life-cycle energy consumption and GHG emissions of HSR *** is recommendedto improve the coverage of HSR network,accelerate train upgrades,improve the full load rate of HSR trains,and promote the low-carbondevelopment of electricity supply to strengthen and realize the low-carbon advantage of HSR transport mode in *** transportationcan be used to achieve the low carbon transformation of China's transportation sector and improve oil supply safety situation.

关键词： High-speed railway transport Life cycle analysis Energy consumption Greenhouse gas emissions China

Association of glycosylated hemoglobin level with lipid ratio and individual lipids in type 2 diabetic patients

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Asian Pacific Journal of Tropical Medicine 2012年第6期5卷 469-471页

作者： zhe yan yang Liu Hui Huang Department of Endocrine and Metabolism Sichuan University Westchina Hospital

Objective:To study the correlation of lipid ratios and individual lipid indexes of patients with type 2 diabetes with glycosylated hemoglobin(HbA_(1c)).Methods:Samples were collected from 128 type 2 diabetic patients(aged 19-90 years;male 72,female 56).The sera were analyzed for HbA_(1c),total cholesterol(TC),triglycerides(TG),high-density lipoprotein cholesterol(HDL-C) and low-density lipoprotein cholesterol(LDL-C).According to the HbA_(1e) level,the patients were divided into three groups,group A(HbA_(?)10%,n=49).The correlation of HbA_(1c)with lipid ratios & individual lipid indexes were ***:With the increased level of HbA(1c),LDL-C had a significantly increasing trend(P<0.05);whereas TC went up with the increased HbA(1c),without any significant differences between three *** was no significant correlation between HbA_(1c) and TG or HDL-C. With the increased level of HbA_(1c),TC/HDL-C,LDL-C/HDL-C ratios were gradually increased, with significant differences among groups(P<0.05).The lipid ratios,especially LDL-C/HDL-C ratio was more susceptible to impaired lipid metabolism in T2DM patients than individual lipid. Conclusions:LDL-C/HDL-C ratio is helpful in assessing and reducing the risk of cardiovascular disease caused by impaired lipid metabolism in type 2 diabetic patients.

关键词： Type 2 diabetes HbA_(1c) Lipid ratio Cardiovascular disease

EDA: an enhanced dual-active algorithm for location privacy preservation in mobile P2P networks

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of zhejiang University-Science C(Computers and Electronics) 2013年第5期14卷 356-373页

作者： yan-zhe CHE Kevin CHIEW Xiao-yan HONG Qiang yanG Qin-ming HE College of Computer Science and Technology Zhejiang University School of Engineering Tan Tao University Department of Computer Science University of Alabama College of Electrical Engineering Zhejiang University

Various solutions have been proposed to enable mobile users to access location-based services while preserving their location privacy. Some of these solutions are based on a centralized architecture with the participation of a trustworthy third party, whereas some other approaches are based on a mobile peer-to-peer (P2P) architecture. The former approaches suffer from the scalability problem when networks grow large, while the latter have to endure either low anonymization success rates or high communication overheads. To address these issues, this paper deals with an enhanced dual-active spatial cloaking algorithm (EDA) for preserving location privacy in mobile P2P networks. The proposed EDA allows mobile users to collect and actively disseminate their location information to other users. Moreover, to deal with the challenging characteristics of mobile P2P networks, e.g., constrained network resources and user mobility, EDA enables users (1) to perform a negotiation process to minimize the number of duplicate locations to be shared so as to significantly reduce the communication overhead among users, (2) to predict user locations based on the latest available information so as to eliminate the inaccuracy problem introduced by using some out-of-date locations, and (3) to use a latest-record-highest-priority (LRHP) strategy to reduce the probability of broadcasting fewer useful locations. Extensive simulations are conducted for a range of P2P network scenarios to evaluate the performance of EDA in comparison with the existing solutions. Experimental results demonstrate that the proposed EDA can improve the performance in terms of anonymity and service time with minimized communication overhead.

关键词： Location-based service Privacy preservation Spatial cloaking Mobile peer-to-peer networks

Efficient synthesis of 2-arylquinazolines via copper-catalyzed dual oxidative benzylic C–H aminations of methylarenes

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2015年第10期26卷 1216-1220页

作者： Li-yan Liu Yi-zhe yan Ya-Jie Bao Zhi-Yong Wang Hefei National Laboratory for Physical Sciences at Microscale CAS Key Laboratory of Soft Matter Chemistry & Collaborative Innovation Center of Suzhou Nano Science and Technology University of Science and Technology of China

A novel copper-catalyzed dual oxidative benzylic C–H aminations of methylarenes with 2-aminobenzoketones in the presence of ammonium acetate was developed. This reaction represents a new avenue for 2-arylquinazolines with good yields. A key intermediate was detected and the kinetics isotope effect（KIE） indicated that C–H bond cleavage was the rate-determining step.

关键词： Quinazolines Copper C–H aminations Methylarenes

理论研究IIB族金属二氢化物分子的基态性质

在线全文

学校读者我要写书评

暂无评论

原子与分子物理学报 2025年第3期42卷 1-7页

作者：张志鹏杨培龙涂喆研李仁忠西安工程大学理学院西安710048 西安工程大学环境与化学工程学院西安710048

基于小核能量一致性相对论赝势,采用密度泛函理论和耦合簇理论,分别在标量和二分量水平上计算研究了MH_(2)(M=Zn,Cd,Hg,Cn)分子的平衡键长和振动频率.计算结果显示,HgH_(2)和CnH_(2)的自旋轨道耦合效应较为明显.采用的8种泛函总体较好... 详细信息

基于小核能量一致性相对论赝势,采用密度泛函理论和耦合簇理论,分别在标量和二分量水平上计算研究了MH_(2)(M=Zn,Cd,Hg,Cn)分子的平衡键长和振动频率.计算结果显示,HgH_(2)和CnH_(2)的自旋轨道耦合效应较为明显.采用的8种泛函总体较好地评估了自旋轨道耦合效应.耦合簇理论计算的ZnH_(2)、CdH_(2)、HgH_(2)的键长和Σ_(u)振动频率与实验值偏差略大,这可能是由于其多参考态特性较明显.二分量PBE泛函计算的键长和Σ_(u)振动频率与实验值最接近.目前最重的CnH_(2)相关研究未见报道,研究给出了其键长和振动频率的理论值.

关键词：金属二氢化物密度泛函理论耦合簇理论标量相对论自旋轨道耦合

维普期刊数据库博看期刊

同方期刊数据库

Gene therapy for type 1 diabetes mellitus in rats by gastrointestinal administration of chitosan nanoparticles containing human insulin gene

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2008年第26期14卷 4209-4215页

作者： Li Niu yan-Cheng Xu zhe Dai Hui-Qin Tang Department of Endocrinology Zhongnan Hospital of Wuhan UniversityWuhan 430071 Hubei Province China

AIM:To study the expression of human insulin gene in gastrointestinal tracts of diabetic rats. METHODS: ***, an expression plasmid of the human insulin gene, wrapped with chitosan nanoparticles, was transfected to the diabetic rats through lavage and coloclysis, respectively. Fasting blood glucose and plasma insulin levels were measured for 7 d. Reverse transcription polymerase chain reaction (RT-PCR) analysis and Western blot analysis were performed to confirm the expression of human insulin gene. RESULTS: Compared with the control group, the fasting blood glucose levels in the lavage and coloclysis groups were decreased significantly in 4 d (5.63 ± 0.48 mmol/L and 5.07 ± 0.37 mmol/L vs 22.12 ± 1.31 mmol/L, respectively, P < 0.01), while the plasma insulin levels were much higher (32.26 ± 1.81 μIU/mL and 32.79 ± 1.84 μIU/mL vs 14.23 ± 1.38 μIU/mL, respectively, P < 0.01). The human insulin gene mRNA and human insulin were only detected in the lavage and coloclysis groups. CONCLUSION: Human insulin gene wrapped with chitosan nanoparticles can be successfully transfected to rats through gastrointestinal tract, indicating that chitosan is a promising non-viral vector.

关键词： Gastrointestinal tract Human insulin gene Gene expression Diabetes mellitus Chitosan nanoparticle

Multiple Unmanned Underwater Vehicles Consensus Control with Unmeasurable Velocity Information and Environmental Disturbances Under Switching Directed Topologies

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China Ocean Engineering 2020年第5期34卷 631-640页

作者： yan zhe-ping WU Yi LIU Yi-bo REN Hong-liang DU Xue College of Automation Harbin Engineering UniversityHarbin 150000China Department of Biomedical Engineering National University of Singapore119007Singapore Systems Engineering Research Institute Beijing 100094China

A consensus algorithm proposed in the paper is applied to tackle remarkable problems of unmeasurable velocities,the environmental disturbances, and the limited communication environment for the multiple unmanned underwater vehicles(multi-UUVs). Firstly, for a complex nonlinear and coupled model of the unmanned underwater vehicle(UUV), a technique of feedback linearization is developed to transform the nonlinear UUV model into a secondorder integral UUV model. Secondly, to address the problem of the unavailable velocity information and environmental disturbances for the multi-UUVs system, we design a distributed extended state observer(DESO) to estimate the unmeasurable velocities and environmental disturbances using the relative position information. Finally,we propose a protocol based on the estimation information from the DESO and demonstrate that the multi-UUVs system with the switching directed topologies under the protocol can reach consensus asymptotically. The theoretical result proposed in the literature is verified by one numerical example.

关键词： multiple unmanned underwater vehicles feedback linearization distributed extended state observe switching directed topologies