检索结果-南通市图书馆

Hydrodynamics of the interceptor on a 2-D flat plate by cFD and experiments

Journal of Hydrodynamics 2015年第6期27卷 919-933页

作者： mANSOORI m. FERNANDES A.c. Department of Naval and Ocean Engineering Federal University of Rio de Janeiro

Nowadays, the use of interceptor by both partial and total dynamic lift crafts is quite common. In this article, a lot of evidence is given regarding the effectiveness of interceptor. The interceptor, when placed at the stern region, changes the pressure distribution around the craft. Its presence affects drag force, lifting force and the position of pressure＇s center leading to a new trim. This study focuses on hydrodynamic effects of interceptors on a 2-D fiat plate based on both computational fluid dynamic （cFD） and experimental approaches. The Reynolds average Navier-Stokes （RANS） equations are used to model the flow around a fixed flat plate with an interceptor at different heights and attack angles. Based on finite volume method and SImPLE algorithm which uses static structures, this model can be analyzed and the RANS results can be compared with the experimental data obtained in the current channel of the laboratory of waves and current of cOPPE/UFRJ （LOc in Portuguese acronym）. According to the results, the increase of pressure at the end of the flat plate was proportional to the interceptor height. In addition, the existence of interceptors can significantly increase the lift force coefficient at high angles of attack also proportional to the interceptor height. The presence of interceptor at the end of the fiat plate increased both the lift coefficient and the drag coefficient but hydrodynamic drag did not grow as fast as the lift coefficient did. The lift coefficient increased much more. Furthermore, the results showed that the interceptor effectiveness is proportional to the boundary layer thickness at the end of the fiat plate. As the interceptor was inside the boundary layer alterations of flow speed led to changes in boundary layer thickness, directly affecting interceptor＇s efficiency. Optimum choice of interceptor height had a great effect on its efficiency, and in choosing it the flow speed and length of the boat must be taken into consideration.

关键词： interceptor craft 2-D fiat plate lifting coefficient Reynolds average Navier-Stokes (RANS) pressure distribution,computational fluid dynamic drag

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A code-independent technique for computational verification of fluid mechanics and heat transfer problems

引用

Acta mechanica Sinica 2008年第4期24卷 387-397页

作者： m.Garbey c.Picard Department of computer Science University of Houston Houston TX 77204 USA

The goal of this paper is to present a versatile framework for solution verification of PDE＇s. We first generalize the Richardson Extrapolation technique to an optimized extrapolation solution procedure that constructs the best consistent solution from a set of two or three coarse grid solution in the discrete norm of choice. This technique generalizes the Least Square Extrapolation method introduced by one of the author and W. Shyy. We second establish the conditioning number of the problem in a reduced space that approximates the main feature of the numerical solution thanks to a sensitivity analysis. Overall our method produces an a posteriori error estimation in this reduced space of approximation. The key feature of our method is that our construction does not require an internal knowledge of the software neither the source code that produces the solution to be verified. It can be applied in principle as a postprocessing procedure to off the shelf commercial code. We demonstrate the robustness of our method with two steady problems that are separately an incompressible back step flow test case and a heat transfer problem for a battery. Our error estimate might be ultimately verified with a near by manufactured solution. While our pro- cedure is systematic and requires numerous computation of residuals, one can take advantage of distributed computing to get quickly the error estimate.

关键词： Solution verification PDE's Navier Stokes ·Heat transfer. Aposteriori estimate·Distributed computing

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

How do greenhouse gas emissions vary with biofertilizer type and soil temperature and moisture in a tropical grassland?

引用

Pedosphere 2020年第5期30卷 607-617页

作者： Abmael da Silva cARDOSO Juliana Bega JUNQUEIRA Ricardo Andrade reis Ana claudia RUGGIERIAnimal Science Departament College of Agricultural and Veterinarian SciencesSao Paulo State UniversityJaboticabal 14884-900(Brazil) Kenji Agricultural and Environmental consultancy Ribeirdo Preto 14010-079(Brazil)

Greenhouse gases are known to play an important role in global *** this study,we determined the effects of selected soil and climate variables on nitrous oxide(N2O),methane(cH4),and carbon dioxide(cO2)emissions from a tropical grassland fertilized with chicken slurry,swine slurry,cattle slurry,and cattle *** N2O emissions did not differ between treatments and varied from 29.26 to 32.85 mg N m^-***,cumulative cH4 emissions were not significantly different among the treatments and ranged from 6.34 to 57.73 mg cH4 m^-*** and compost application induced cO2 emissions that were significantly different from those in the control *** cH4 conversion factors measured were 0.21%,1.39%,4.39%,and 5.07%for cattle compost,chicken slurry,swine slurry,and cattle slurry,respectively,differing from the recommendations of the Intergovernmental Panel on climate change(IPcc).The fraction of added Nemitted as N2O was 0.39%,which was lower than the IPcc default value of 2%.Our findings suggest that N2O emissions could be mitigated by replacing synthetic fertilizer sources with either biofertilizer or *** results indicate the following:N2O emission was mainly controlled by soil temperature,followed by soil moisture and then soil NH^"content;cH4 fluxes were mainly controlled by soil moisture and chamber headspace temperature;and cO2 fluxes were mainly controlled by chamber headspace temperature and soil moisture.

关键词： emission factor methane conversion factor methane oxidation methane production capacity slurry fertilizer soil moisture

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

modelling mechanical Properties in Native and Biomimetically Formed Vascular Grafts

引用

Journal of Bionic Engineering 2009年第4期6卷 371-377页

作者： m.mandru c.Ionescu m.chirita University of medicine and Pharmacy Faculty of Biomedical EngineeringUniversity street 16700115 IasiRomania Ghent University Department of Electrical energySystems and AutomationTechnologiepark 913B9052GentBelgium

The paper presents a detailed analysis of experimental data in order to characterize the elastic properties of *** analysis would provide a good basis for evaluation of biomimetic vascular *** the latter needs to exhibit similar properties of native tissue,it is important to accurately characterize the biomimetic sample in a large range of applied stresses. The stress-strain properties vary according to the specific pathology(***,aneurism)and the tissue graft must be chosen *** models are proposed in this paper on the stress-strain *** extension for frequency-domain analysis is provided for one of the *** comparison between vascular grafts and native tissue for carotid and thoracic arteries in pigs are in good agreement with results from *** proposed experimental method offers suitable parameters for identifying models which characterize both elasticity and stiffness properties of the analyzed tissues(stress-strain).The proposed models show good performance in characterizing the intrinsic material properties.

关键词： biomimetic biomaterials vascular graft native and artificial tissues stress-strain modeling

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Analysis of Differences in Productivity,Profitability and Soil Fertility Between Organic and conventional cropping Systems in the Tropics and Sub-tropics

引用

Journal of Integrative Agriculture 2014年第10期13卷 2299-2310页

作者： Te Pas c m Rees R m School of GeoSciences University of Edinburgh carbon management centre Scotland's Rural College

Organic farming aims to stimulate soil fertility by avoiding the use of synthetic fertiliser inputs, relying instead on locally available natural resources. It is regarded by many as a sustainable alternative to conventional fanning because it ensures higher biodiversity, restricts environmental pollution, prevents land degradation and is easy to apply for smallholder and subsistence farmers. Although widely practiced and studied in temperate regions, little is known about the potential overall benefits of organic farming in the tropics and subtropics. This paper addresses this gap by undertaking an analysis of the differences between organic and conventional agriculture in the tropics and sub-tropics based on an extensive literature review including 88 papers with 458 data pairs. The comparison is based on three main indicators： yield, gross margin and soil organic carbon （SOc）. The differences between the organic and conventional systems for each of these main indicators is represented by the ratio of the value of the indicator in the organic system divided by the corresponding value in the conventional system. This was initially calculated for each data pair individually, and grouped by a variety of explanatory factors, such as precipitation, human development level, soil texture, crop type, organic input type, time after conversion and certification. The results demonstrate that under organic management, yields were on average 26% higher, gross margins 51% higher and soil organic carbon 53% higher than under conventional management. The highest yield increases in organic cropping systems were achieved in the least developed countries, in arid regions and on coarse soils. For gross margins, certification was the main reason for differences between organic and conventional systems. certified farmers, mostly located in developed countries, receive significantly higher prices. Furthermore, organic farming in the driest regions results in higher profits than in other

关键词： organic farming conventional fanning tropics subtropics carbon sequestration yield soil quality soil organic carbon

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Role of Ag microalloying on glass forming ability and crystallization kinetics of ZrcoAgAlNi amorphous alloy

引用

chinese Physics B 2021年第1期30卷 471-476页

作者： A Surendar K Geetha c Rajan m Alaazim Department of Pharmacology Saveetha Dental College and HospitalSaveetha Institute of Medical and Technical SciencesChennaiIndia cSE Excel Engineering CollegePallakapalayamKomarapalayam637303India IT K S Rangasamy College of Technology TiruchengodeNamakkalTamil Nadu 637215India Faculty of Engineering Universitas Muhammadiyah Surakarta(UMS)Indonesia

Bulk metallic glasses(BmGs) with new chemical compositions(ZrcoAgAlNi) were fabricated and the effects of Ag minor addition on the glass forming ability(GFA) and crystallization kinetics were studied. The x-ray diffraction(XRD) test was applied to identify the amorphousness of BmGs or possible crystalline phases. Using differential scanning calorimeter(DSc), the thermal stability and crystallization kinetics under a non-isothermal condition at the different heating rates were studied. considering the heating rate dependency of glass transition and crystallization kinetics, the activation energy was evaluated and measured for the mentioned processes. It was revealed that the rise in Ag content led to the decrease in activation energy for glass transition, while the activation energy for crystallization increased. The thermal stability and GFA were also studied and it was found that the Ag addition strongly affected the inherent features of BmGs. With the increase in Ag content, the atomic mobility and structural rearrangement changed in the material and consequently, the GFA and thermal stability were significantly improved.

关键词： bulk metallic glass materials design crystallization kinetics glass forming ability

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

combining material characterization with single and multi-oxyanion adsorption for mechanistic study of chromate removal by cationic hydrogel

引用

Journal of Environmental Sciences 2011年第6期23卷 1004-1010页

作者： Irene m.c.Lo Samuel c.N.Tang Department of civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong KongChina

cationic hydrogel with magnetic property was synthesized via radical polymerization and its removal capacity of chromate from contaminated water was found to be 200 mg/*** Fourier transform infrared spectroscopy（FT-IR） study,the mechanism of chromate removal by hydrogel was found to be non-specific adsorption,mainly due to ion exchange,as evidenced by the positively charged functional group,trimethyl ammonium-N＋（cH3）3,in the *** were accordingly determined by testing di？erent oxyanion adsorption onto the *** results of the chromate adsorption experiments illustrated that the amount of chromate adsorbed was nearly equal to that of the chloride released from the hydrogel,which is part of the evidence for ion *** and multi-oxyanion adsorption experiments were also performed,and it was demonstrated that ion removal was species independent,but charge dependent,another characteristic of the ion exchange *** was found that the same Langmuir model can be applied to best fit the findings of single and multi-oxyanion adsorption,which further indicates the mechanism of chromate removal is attributed to ion *** view of the above,the background anions compete for adsorption sites with chromate,evidenced by inhibitive chromate removal in the presence of background electrolytes in the batch studies,further echoing the ion exchange mechanism.

关键词： adsorption magnetic hydrogel mechanism ion exchange oxyanion

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Preliminary performance analysis and optimization based on 1D neutronics model for Indian DEmO HccB blanket

引用

Plasma Science and Technology 2020年第8期22卷 184-191页

作者： D AGGARWAL c DANANI m Z YOUSSEF Institute for Plasma Research GandhinagarGujarat 382428India Homi Bhabha National Institute(HBNI) AnushaktinagarMumbai 400094India University of california-Los Angeles Los AngelesCA 90095United States of America

India,under its breeding blanket R&D program for DEmO,is focusing on the development of two tritium breeding blanket concepts;namely the lead-lithium-cooled ceramic breeder and the helium-cooled ceramic breeder(HccB).The study presented in this paper focuses on the neutronic design analysis and optimization from the tritium breeding perspective of the HccB *** Indian concept has an edge-on configuration and is one of the variants of the helium-cooled solid breeder blanket concepts proposed by several partner countries in *** Indian HccB blanket having lithium titanate(Li2TiO3)as the tritium breeder and beryllium(Be)as the neutron multiplier with reduced-activation ferritic/martensitic steel structure aims at utilizing the low-energy neutrons at the rear part of the *** aim of the optimization study is to minimize the radial blanket thickness while ensuring tritium self-sufficiency and provide data for further neutronic design and thermal-hydraulic layout of the HccB *** is found that inboard and outboard blanket thicknesses of 40 cm and 60 cm,respectively,can give a tritium breeding ratio(TBR)>1.3,with 60%6Li enrichment,which is assumed to be sufficient to cover potential tritium losses and associated *** results also demonstrated that the Be packing fraction(PF)has a more profound impact on the TBR as compared to 6Li enrichment and the PF of Li2TiO3.

关键词： DEmO helium-cooled ceramic breeder blanket neutronic optimization study tritium breeding ratio

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Interplay of parallel electric field and trapped electrons in kappa-maxwellian auroral plasma for EmEc instability

引用

communications in Theoretical Physics 2021年第1期73卷 78-86页

作者： m Nazeer m N S Qureshi c Shen Department of Physics GC UniversityLahore(54000)Pakistan Shenzhen Graduate School HIT CampusUniversity Town of ShenzhenShenzhen 518055China

In this paper,propagation characteristics of electromagnetic electron cyclotron(EmEc)waves based on kappa-maxwellian distribution have been investigated to invoke the interplay of the electric field parallel to the Earth’s magnetic field and auroral trapped *** dispersion relation for EmEc waves in kappa-maxwellian distributed plasma has been derived using the contribution of the parallel electric field and trapped electron *** results show that the presence of the electric field has a stimulating effect on growth rate,which is more pronounced at low values of wave *** is also observed that as the threshold value of trapped electron speed is surpassed,it dominates the effect of the parallel electric field and EmEc instability is enhanced *** electric field acts as another source of free energy,and growth can be obtained even in the absence of trapped electron drift speed and for very small values of temperature *** the present study reveals the interplay of the parallel electric field and trapped electron speed on the excitation of EmEc waves in the auroral region.

关键词： EmEc waves kappa-maxwellian distribution trapped electrons parallel electric field in aurora

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

TRANSIENT ANALYSIS OF cOmPOSITE PLATES BY A LOcAL RADIAL BASIS FUNcTIONS-FINITE DIFFERENcE TEcHIQUE

引用

Acta mechanica Solida Sinica 2012年第1期25卷 22-36页

作者： c.m.c.Roque D.cunha A.J.m.Ferreira INEGI Faculdade de Engenharia da Universidade do PortoRua Dr.Roberto Frias Departamento de Engenharia mecnica Faculdade de Engenharia da Universidade do PortoRua Dr.Roberto Frias

The use of local numerical schemes,such as finite differences produces much better conditioned matrices than global collocation radial basis functions ***,finite differ-ence schemes are limited to special *** scattered points,a combination of finite differences and radial basis functions would be a possible *** this paper,we use a higher-order shear deformation plate theory and a radial basis function-finite difference technique for predicting the transient behavior of thin and thick composite *** numerical experiments on beams and composite plates,the accuracy and efficiency of this collocation technique is demonstrated.

关键词： meshless beam composite plate

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：