检索结果-南通市图书馆

Bonding of compound casted Ti/Al bimetal by heat treatment

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2021年第9期28卷 1515-1524页

作者： M.Fadaeinia ramin Raiszadeh Department of Metallurgy and Materials Science School of EngineeringShahid Bahonar University of KermanKerman ***Iran

The formation mechanism of the bonding between compound cast Al/Ti bimetal during a heat treatment regime was *** pure Al was cast and melt on a Ti bar in a steel tube,followed by heat treatment on the compound cast Ti/Al bimetal for different periods of time once the Al melt was *** bonding was observed between the two metals after the initial casting,which can be attributed to the presence of oxide films on the liquid Al and solid Ti alloys and the trapped atmosphere between *** effect of these layers in preventing the formation of bonding was eliminated after heat treating the cast part at~973 K(~700℃)for at least 15 min,and the metals started to bond with each other.A detailed description of this bonding mechanism is presented in this paper.

关键词： compound casting titanium/aluminium bimetal bonding

Numerical evaluation of passive control of shock wave/boundary layer interaction on NACA0012 airfoil using jagged wall

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2016年第5期32卷 792-804页

作者： Mojtaba Dehghan Manshadi ramin Rabani Mechanical and Aerospace Engineering Department Malek-Ashtar University of TechnologyEsfahan Iran Department of Mechanical Engineering Yazd University

Shock formation due to flow compressibility and its interaction with boundary layers has adverse effects on aerodynamic characteristics, such as drag increase and flow separation. The objective of this paper is to appraise the practicability of weakening shock waves and, hence, reducing the wave drag in transonic flight regime using a two-dimensional jagged wall and thereby to gain an appropriate jagged wall shape for future empirical study. Different shapes of the jagged wall, including rectangular, circular, and triangular shapes, were employed. The numerical method was validated by experimental and numerical studies involving transonic flow over the NACA0012 airfoil, and the results presented here closely match previous experimental and numerical results. The impact of parameters, including shape and the length-to-spacing ratio of a jagged wall, was studied on aerodynamic forces and flow field. The results revealed that applying a jagged wall method on the upper surface of an airfoil changes the shock structure significantly and disintegrates it, which in turn leads to a decrease in wave drag. It was also found that the maximum drag coefficient decrease of around 17 % occurs with a triangular shape, while the maximum increase in aerodynamic efficiency（lift-to-drag ratio）of around 10 % happens with a rectangular shape at an angle of attack of 2.26？.

关键词： Jagged wall Passive flow control Shock wave/boundary layer interaction Aerodynamic efficiency

Undrained seismic bearing capacity of strip footing adjacent to a heterogeneous excavation

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2023年第4期17卷 566-583页

作者： ramin VALI Saeed KHOSRAVI Majid BEYGI Department of Civil Engineering Technical and Vocational UniversityTehran ***Iran Department of Mining Engineering Shahid Bahonar University of KermanKerman ***Iran Department of Civil Engineering Yazd UniversityYazd ***Iran

The analysis of the bearing capacity of strip footings sited near an excavation is critical in *** this study,the effects of the geometrical features of the excavation and the soil strength properties on the seismic bearing capacity of a strip footing resting on an excavation were evaluated using the lower and upper bounds of the finite element limit analysis *** effects of the setback distance ratio(L/B),excavation height ratio(H/B),soil strength heterogeneity(kB/cu),and horizontal earthquake coefficient(kh)were *** charts and tables were produced to clarify the relationship between the undrained seismic bearing capacity and the selected parameters.

关键词： excavation finite element limit analysis heterogeneous soil strip footing undrained bearing capacity

State of the Art in Alcohol Sensing with 2D Materials

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano-Micro Letters 2020年第3期12卷 22-54页

作者： ramin boroujerd. Amr Abdelkader Richard Paul Faculty of Science and Technology Bournemouth UniversityTalbot CampusFern BarrowPoole BH125BBUK Department of Engineering University of CambridgeCambridge CB30FSUK

Since the discovery of graphene,the star among new materials,there has been a surge of attention focused on the monatomic and monomolecular sheets which can be obtained by exfoliation of layered *** materials are known as two-dimensional(2D)materials and offer enormous versatility and *** ultimate single atom,or molecule,thickness of the 2D materials sheets provides the highest surface to weight ratio of all the nanomaterials,which opens the door to the design of more sensitive and reliable chemical *** variety of properties and the possibility of tuning the chemical and surface properties of the 2D materials increase their potential as selective sensors,targeting chemical species that were previously difficult to *** planar structure and the mechanical flexibility of the sheets allow new sensor designs and put 2D materials at the forefront of all the candidates for wearable *** developing sensors for alcohol,the response time is an essential factor for many industrial and forensic applications,particularly when it comes to hand-held ***,we review recent developments in the applications of 2D materials in sensing alcohols along with a study on parameters that affect the sensing *** review also discusses the strategies used to develop the sensor along with their mechanisms of sensing and provides a critique of the current limitations of 2D materials-based alcohol sensors and an outlook for the future research required to overcome the challenges.

关键词： Sensors and biosensors Alcohol probes Electrochemical detectors Ethanol metabolites 2D materials

Multi-objective optimization of molten carbonate fuel cell system for reducing CO2 emission from exhaust gases

在线全文

学校读者我要写书评

暂无评论

Frontiers in Energy 2015年第1期9卷 106-114页

作者： ramin ROSHANDEL Majid ASTANEHI Farzin GOLZAR Department of Energy Engineering Sharif University of TechnologyTehran 14565114 Iran

The aim of this paper is to investigate the implementation of a molten carbonate fuel cell （MCFC） as a CO2 separator. By applying multi-objective optimization （MOO） using the genetic algorithm, the optimal values of operating load and the corresponding values of objective functions are obtained. Objective functions are minimiza- tion of the cost of electricity （COE） and minimization of CO2 emission rate. CO2 tax that is accounted as the pollution-related cost, transforming the environmental objective to the cost function. The results show that the MCFC stack which is fed by the syngas and gas turbine exhaust, not only reduces CO2 emission rate, but also produces electricity and reduces environmental cost of the system.

关键词： molten carbonate fuel cell (MCFC) multi-objective optimization (MOO) Pareto curve geneticalgorithm CO2 separation

Optimum blade loading for a powered rotor in descent

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2016年第3期29卷 580-584页

作者： ramin Modarres David A.Peters Department of Mechanical Engineering & Materials Science Washington University in St.Louis

The optimum loading for rotors has previously been found for hover, climb and wind turbine conditions; but, up to now, no one has determined the optimum rotor loading in descent. This could be an important design consideration for rotary-wing parachutes and low-speed des- cents. In this paper, the optimal loading for a powered rotor in descent is found from momentum theory based on a variational principle. This loading is compared with the optimal loading for a rotor in hover or climb and with the Betz rotor loading （which is optimum for a lightly-loaded rotor）. Wake contraction for each of the various loadings is also presented.

关键词： Descent HelicopterInflow Loading Optimum

Estimating seismic demand parameters using the endurance time method

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第8期12卷 616-626页

作者： ramin MADARSHAHIAN Homayoon ESTEKANCHI Akbar MAHVASHMOHAMMADI Department of Civil Engineering Sharif University of Technology ATLSS Center Department of Civil and Environmental EngineeringLehigh University

The endurance time (ET) method is a time history based dynamic analysis in which structures are subjected to gradually intensifying excitations and their performances are judged based on their responses at various excitation levels. Using this method, the computational effort required for estimating probable seismic demand parameters can be reduced by an order of magnitude. Calculation of the maximum displacement or target displacement is a basic requirement for estimating performance based on structural design. The purpose of this paper is to compare the results of the nonlinear ET method with the nonlinear static pushover (NSP) method of FEMA 356 by evaluating performances and target displacements of steel frames. This study will lead to a deeper insight into the capabilities and limitations of the ET method. The results are further compared with those of the standard nonlinear response history analysis. We conclude that results from the ET analysis are in proper agreement with those from standard procedures.

关键词： Endurance time(ET) method Nonlinear static pushover(NSP) Nonlinear dynamic analysis(NDA) Target displacement

Propane catalytic cracking on pretreated La-ZSM-5 zeolite during calcination for light olefins production

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2017年第6期35卷 542-550页

作者： Roya Pouria Leyla Vafi ramin Karimzadeh Department of Chemical Engineering Tarbiat Modares University Jalal AlAhmad Highway P.O. Box 14155-4838 Tehran Iran

The purpose of this study was to increase light olefins yield and selectivity in catalytic cracking of propane. Pretreatment of ZSM-5 zeolite was performed during calcination. First, lanthanum was loaded on the catalyst by wet impregnation method and then the effect of parameters, such as temperature（400–800 oC）, time（120–480 min） and type of stream, on La-ZSM-5 zeolite was examined during calcination using central composite design（CCD） method. Based on the proposed models, the optimized condition for maximizing selectivity of light olefins for air stream was 680 oC and 310 min and for the nitrogen stream was 735 oC and 173 min that under these conditions, selectivity amount increased 24% for nitrogen stream and 19% for air stream as compared with H-ZSM-5 catalyst. The synthesized catalysts were characterized by X-ray diffraction（XRD） and temperature-programmed desorption（TPD） techniques. According to the results of NH3-TPD, as the temperature increased, the number of strong acid sites（specially Bronsted acid sites） reduced and resulted in increased production of light olefins as well as catalyst stability. Accordingly, stability of the samples calcined with nitrogen stream was higher than the samples calcined with the air stream.

关键词： calcination cracking selectivity zeolite calcined impregnation programmed lanthanum loaded propane

Microwave promoted rapid dehydration of aldoximes to nitriles using melamine-formaldehyde resin supported sulphuric acid in dry media

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2011年第7期22卷 815-818页

作者： ramin Rezaei Marzeih Karami Department of Chemistry Islamic Azad UniversityFirouzabad BranchP.O.Box 74715-117FirouzabadIran

A simple and convenient procedure for the synthesis of nitriles by dehydration of aldoxime using supported sulphuric acid on melamine-formaldehyde resin （MFR） under solvent-free condition has been developed. A variety of aromatic and aliphatic aldoximes were converted to the corresponding nitriles. The resin was recovered and reused for subsequent reactions. ~ 2011 ramin Rezaei. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

关键词： Aldoximes Nitriles Melamine-formaldehyde resin Sulphuric acid Solvent-free