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Numerical Analysis of a Wells turbine at Different Non-dimensional Piston Frequencies

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journal of thermal Science 2015年第6期24卷 535-543页

作者： t.Ghisu P.Puddu F.Cambuli Department of Mechanical Chemical and Materials Engineering University of Cagliari

Wave energy is one of the renewable energy sources with the highest *** pilot plants have been built based on the principle of the Oscillating Water Column(OWC).Among the different solutions that have been suggested,the Wells turbine has gained particular attention due to its simplicity and *** majority of available studies concentrate on the steady operation of the Wells turbine,while only few analyze its performance under an unsteady and bi-directional air flow,as determined by the presence of the OWC *** this work,experimental and numerical performance of a high-solidity Wells turbine with NACA0015 profiles have been compared,at different non-dimensional piston *** numerical simulations have been conducted using commercial CFD software and focus on unsteady predictions,with particular attention to the behavior of the flow upstream and downstream of the rotor,flow hysteresis between acceleration and deceleration phases and differences between intake and exhaust strokes due to the non-symmetrical configuration of the machine.

关键词： Wells turbine unsteady flow CFD OWC systems experimental investigation

Embracing revenge and Logical Consequence

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学术界 2017年第2期 257-272页

作者： roy t Cook University of Minnesota-twin Cities

Ⅰ.A philosophical sketch of embracing revenge We begin on familiar ground,with the Liar paradox,which arises when we consider the Liar sentence:

关键词：逻辑哲学发展现状社会学

INNOVAtIVE APPrOACHES tO ENHANCE WAtEr QUALItY AND ECOSYStEM FUNCtION OF CHANNELIZED StrEAMS AND DrAINAGE CANALS

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INNOVATIVE APPROACHES TO ENHANCE WATER QUALITY AND ECOSYSTEM...

Optimal dynamic emergency reserve activation using spinning, hydro and demand-side reserves

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作者： r.O.Evans r.D.Hinson M.Doxey r.johnson K.L Bass j.t.Smith Professor Extension Associate and Extension AssistantDepartment of Biological and Agricultural EngineeringNorth Carolina State UniversityBox 7625RaleighNC 27695-7625 District Conservation USDA Natural resources Conservation Service District technician Currituck Soil and Water Conservation District Albemarle rC ＆ D Coordinator USDA-NrCS Professor Extension Associate and Extension AssistantDepartment of Biological and Agricultural EngineeringNorth Carolina State UniversityBox 7625RaleighNC 27695-7625 Professor Extension Associate and Extension AssistantDepartment of Biological and Agricultural EngineeringNorth Carolina State UniversityBox 7625RaleighNC 27695-7625

＜正＞More than 50 percent of fields in eastern North Carolina require improved drainage for efficient production and other land uses. Historically, drainage practices focused on straightening and deepening natural channels to increase their hydraulic capacity and minimize upstream flooding. there are few un-channelized streams remaining in the region. traditional channel improvements disassociated the channel from the natural floodplain thereby degrading riparian floodplain ecological functions. Intensive drainage systems that are necessary to provide adequate flood protection during wet periods tend to remove more water than necessary during drier periods. However, wetness continues to be a major concern to many landowners. Pilot studies were begun in 1994 to investigate, evaluate, and demonstrate alternative channel design geometries and management to enhance water conservation, water quality, and ecological functions while maintaining the necessary drainage function. Channel alternatives included : establishment of in-stream wetlands, lowering of the floodplain to reconnect the channel with a new floodplain, redesign of channels using natural channel design principles, and establishment of conservation easements to encourage establishment of perennial riparian vegetation. this paper discusses several recent projects that have been implemented to provide better management of drainage water and to restore or enhance ecological functions of large drainage canals. Nitrogen and sediment transport was reduced by 20 to 30 percent on a mass balance basis by incorporation of riparian vegetation and wetland systems within the drainage networks.

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Frontiers in Energy 2016年第4期10卷 409-423页

作者： S. Surender rEDDY P. r. BIjWE A. r. ABHYANKAr Department of railroad and Electrical Engineering Woosong University Republic of Korea Department of Electrical Engineering Indian Institute of TechnologyDelhi India

this paper proposes an optimal dynamic reserve activation plan after the occurrence of an emergency situation （generator/transmission line outage, load increase or both）. An optimal plan is developed to handle the emergency, using the coordinated action of fast and slow reserves, for secure operation with minimum overall cost. It considers the reserves supplied by the conventional thermal generators （spinning reserves）, hydro power units and load demands （demand-side reserves）. the optimal backing down of costly/fast reserves and bringing up of slow reserves in each sub-interval in an integrated manner is proposed. the proposed reserve activation approaches are solved using the genetic algorithm, and some of the simulation results are also compared using the Matlab optimization toolbox and the general algebraic modeling system （GAMS） software. the simulation studies are performed on the IEEE 30, 57 and 300 bus test systems. these results demonstrate the advantage of the proposed integrated/dynamic reserve activation plan over the conventional/sequential approach.

关键词： demand-side reserves dynamic reserve acti-vation approach hydro power units post contingency,sequential reserve activation approach spinning reserves

Electrical properties of Na_(2)Pb_(2)r_(2)W_(2)ti_(4)V_(4)O_(30)(r=Dy,Pr)ceramics

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journal of Advanced Ceramics 2013年第2期2卷 112-118页

作者： Piyush r.DAS B.N.PArIDA r.PADHEE r.N.P.CHOUDHArY Department of Physics Institute of Technical Education&ResearchSiksha‘O’Anusandahan UniversityKhandagiriBhubaneswar 751030OdishaIndia

the polycrystalline samples of complex tungsten bronze(tB)Na_(2)Pb_(2)r_(2)W_(2)ti_(4)V_(4)O_(30)(r=Dy,Pr)compounds were prepared by solid-state reaction ***-temperature preliminary structural studies confirm the formation of the compounds in the orthorhombic crystal *** studies of electrical properties of the materials using complex impedance spectroscopy technique exhibit that the impedance and related parameters are strongly dependent upon temperature and microstructure(bulk,grain boundary,etc).An observation of negative temperature coefficient of resistance(NtCr)suggests the materials have semiconducting *** variation of AC conductivity with temperature shows a typical Arrhenius behavior of the *** the samples obey jonscher’s universal power *** existence of hopping mechanism in the electrical transport processes in the system with non-exponential type of conductivity relaxation is confirmed by electrical modulus analysis.

关键词： ceramics impedance spectroscopy electrical properties ferroelectricity microstructure

MHD free convective flow past semi-infinite vertical permeable wall

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Applied Mathematics and Mechanics(English Edition) 2012年第9期33卷 1207-1222页

作者： r.K.SINGH A.K.SINGH Department of Mathematics Banaras Hindu University

In this paper, the basic equations governing the flow and heat transfer of an incompressible viscous and electrically conducting fluid past a semi-infinite vertical per- meable plate in the form of partial differential equations are reduced to a set of non-linear ordinary differential equations by applying a suitable similarity transformation. Approx- imate solutions of the transformed equations are obtained by employing the perturbation method for two cases, i.e., small and large values of the suction parameter. From the numerical evaluations of the solution, it can be seen that the velocity field at any point decreases as the values of the magnetic and suction parameters increase. the effect of the magnetic parameter is to increase the thermM boundary layer. It is also found that the velocity and temperature fields decrease with the increase in the sink parameter.

关键词： magnetohydrodynamics (MHD) suction source/sink Prandtl number permeability boundary layer

Impedance spectroscopy study on Mn_(1+x)Fe_(2-2x)ti_xO_4(0≤x≤0.5) ferrites

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journal of Central South University 2010年第6期17卷 1133-1138页

作者： KUMAr S BAtOO K M PrAKASH r CHOI H K KOO B H SONG j I CHUNG H jEONG H LEE C G School of Nano and Advanced Materials Engineering Changwon National UniversityChangwon 641773Korea King Abdullah Institute for Nanotechnology King Saud UniversityRiyadh 11451Saudi Arabia Department of Mechanical Engineering Changwon National UniversityChangwon 641773Korea Department of Precision & Mechanical Engineering and BK21 Eco-Friendly Heat & Cold Energy Mechanical research team Gyeongsang National U niversityTongyeong 650160Korea

the complex impedance spectroscopy and surface morphology of Mn1+xFe2-2xtixO4(0≤x≤0.5) system,prepared using a conventional solid state reaction technique,were *** impedance spectroscopy measurements were carried out at room temperature in the frequency range of 42-5 *** electrical processes in the samples were modeled in the form of an equivalent circuit made up of a combination of two parallel rC circuits attributed to grain and grain *** DC conductivity obtained by extrapolation of AC data using impedance spectroscopy and four-probe method increases at 10% doping of ti *** energy-dispersive X-ray(EDX) pattern confirmed the homogeneous mixing of the Mn,Fe,ti and O atoms in pure and doped ferrite samples.

关键词： spinel ferrite magnetic properties impedance spectroscopy ti4+ ions doping

Climate change and groundwater resources in Mekong Delta, Vietnam

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journal of Groundwater Science and Engineering 2017年第1期5卷 76-90页

作者： Duong D Bui Nghia C Nguyen Nuong t Bui Anh t t Le Dao t Le National Center for Water resources Planning and Investigation MONRE Vietnam tokyo Metropolitan University Japan Center for Environmental Fluid Dynamics Hanoi University of Science Vietnam

Groundwater resources have considerable influences on the human population and socioeconomic development of Vietnam and the Mekong river Delta(MrD). this paper presents an overview of the relationship between climate change and groundwater in the MrD, including the challenges, strategies and technical measures. Our results showed that groundwater levels are related to other climate and hydrological variables(i.e., rainfall, river levels, etc.); therefore, the impacts of climate change on the groundwater resources of the Mekong delta are significant, especially on groundwater recharge. Based on the results of this study, it is recommended that groundwater development in the future should focus on reducing groundwater harvesting, enhancing groundwater quantity by establishing artificial works and exploiting surface water. this study suggests that the Artificial Neural Network(ANN) model is an effective tool for forecasting groundwater levels in periods of 1 month and 3 months for aquifers in the natural and tidal regime areas of the delta.

关键词： Groundwater management Climate change ANN model Mekong river Delta

地壳浅部S波速度结构的多频接收函数两步反演法及其在中国东北盆-山构造区的应用

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中国科学：地球科学 2024年第3期54卷 708-724页

作者：杨睿豪王旭陈凌冯铭业陈棋福中国科学院地质与地球物理研究所岩石圈演化国家重点实验室北京100029 中国科学院大学地球与行星科学学院北京100049 中国科学院地质与地球物理研究所中国科学院地球与行星物理重点实验室北京100029

地壳浅部(<10km)速度模型既是地壳结构与变形研究和资源勘探前景评估的基础,又可为壳幔深部结构成像等研究提供先验信息.针对区域尺度结构,被动源方法相比主动源方法具有明显优势.被动源方法中,基于接收函数和/或体波振幅比的成像方法... 详细信息

地壳浅部(<10km)速度模型既是地壳结构与变形研究和资源勘探前景评估的基础,又可为壳幔深部结构成像等研究提供先验信息.针对区域尺度结构,被动源方法相比主动源方法具有明显优势.被动源方法中,基于接收函数和/或体波振幅比的成像方法由于具有较高空间分辨率,近年来受到广泛关注.然而,盆地松散沉积层内部的反射混响常导致此类方法表现出较强的多解性及不确定性,限制了其应用.因此,本文提出一种基于多频径向接收函数波形及其与垂向接收函数振幅比的两步反演法,以约束地壳浅部S波速度结构.理论测试表明,两步反演策略能有效降低反演多解性、提高结果稳定性.将该方法应用于一条横跨中国东北沉积盆地的线性地震台阵数据,获得了地壳浅部S波速度精细结构图像.结果显示,盆地与山地地壳浅部结构差异显著:二连盆地浅部(<1.0km)和松辽盆地浅部(<2.5km)速度较低(<2.8km s^(-1)),反映低速沉积层;松辽盆地7km以深地壳速度较高(3.4~3.8km s^(-1)),可能反映早白垩世镁铁质岩浆侵入体.此外,成像结果中速度异常分布与盆地内大型断裂、隆起及沉积凹陷等构造的地表位置吻合,速度异常延深深度也与已有地震勘探结果相吻合.这些观测表明,两步反演法能有效约束松散沉积盆地S波速度随深度变化特征,并实现区域尺度地壳浅部结构高精度成像.

关键词：接收函数频率依赖性两步反演地壳浅部S波速度结构松散沉积盆地

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