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Shortening the Duration of heat Treatment in the Lower Bainitic Range

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材料热处理学报 2004年第5期25卷 555-560页

作者： h. Vetters h.-W. Zoch Foundation Institute for Materials Science Bremen GermanyFoundation Institute for Materials Science Bremen Germany

In many cases an isothermal treatment of throughhardening bearing grades in the lower bainitic range allows to adjust the mechanical properties of machine components to the later application, similar to those of martensitic hardening. The achieved microstructure contains only a negligible amount of retained austenite, so a dimensional change of components during application can be reduced. One disadvantage of the isothermal bainitic treatment in salt bath is that the duration of the treatment is much longer than that of the martensitic hardening and this causes higher costs. Therefore it would be desirable to be able to shorten the transformation duration in the lower bainitic range. The aim of the present work is to determine the parameters, by which the process could be greatly shortened in comparison with the conventional transformation process in the lower bainitic range. Therefore the bainitic transformation behavior of the steel 100 Cr6 (SAE 52100) and the relevant influence factors were investigated by means of dilatometry, in which the heat treatments were carried out with different process variants including pre-quenching or post-quenching. The amount of retained austenite in the microstructure and the hardness of the steel after the shortened heat treatments were measured. Finally the possibility to use these processes in industrial production is discussed.

关键词：贝氏体轴承钢膨胀测定法热处理

hot Forging and hot Pressing of AlSi Powder Compared to Conventional Powder Metallurgy Route

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Materials Sciences and Applications 2011年第8期2卷 1127-1133页

作者： Sayed Moustafa Walid Daoush Ahmed Ibrahim erich Neubaur 不详

Aluminum silicon alloy of composition (Al-25%Si-3%Ni-1%Fe-2%Cu) was atomized using water atomization. The powders were cold compacted in a die to produce green cylinder compacts. Four consolidation processes were applied, namely;conventional sintering at 500℃, sintering followed by hot forging to obtain pistons, one step hot forging into pistons, and hot pressing. The microstructure of the sintered specimens showed inter-granular pores and oxide layers on particle interfaces of 84% relative density. When the sintered specimens were hot forged, both the inter-granular pores and oxide layers on particle interfaces almost disappeared and the relative densities increased up to about 95%. The same microstructure is also obtained for the one step forged specimens, but the relative densities increased to about 97%. however, the hot pressing specimens showed the presence of oxide layers on particle surfaces as well as few isolated pores. The relative density of the hot pressed specimens was about 90%. hardness and ultimate compression strength were measured. It is noted that the strongest bulk materials are those made by hot forging, followed by those made by hot pressing and the weakest bulk materials are those made by conventional sintering.

关键词： Aluminum-Silicon Alloy Powder Metallurgy hot Forging hot Pressing hardness Compression Test

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爱情的故事英语读物

Structural and dielectric properties of giant dielectric Na1/2Sm1/2Cu3Ti4O12 ceramics prepared by reactive sintering methods

丛书名：大学英语阶梯阅读系列教程

2001年

作者： erich Segal原李凤华选编

《爱情的故事》是美国畅销小说，书中描写了年轻人的热恋与奋斗，以及美国学生的生活及美国社会家庭、婚姻、父子关系等方面一些矛盾，本书对原文重点有注释，并附有针对性的练习及其参考答案。

ISBN: (数字)7810770322

ISBN: (纸本)7810770322

关键词：长篇小说地点:美国年代:现代英语学科:高等学校

来源：汇雅图书（南通市图书馆... 评论

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Chinese Physics B 2019年第9期28卷 359-366页

作者： h Mahfoz Kotb Department of Physics College of Science King Faisal University Department of Physics Faculty of Science Assiut University

Na0.5Sm0.5Cu3Ti4O12(NSCTO) ceramics have been prepared by reactive sintering of amorphous *** plasma sintering(SPS) for 10 min at 1025℃ and conventional sintering(CS) for 10 h at 1090℃ have been employed.X-ray diffraction measurements confirmed the pure CCTO-like phase for SPS and CS NSCTO *** SPS ceramic showed an average grain size of 500 nm, which is much smaller than that of the CS(~ 5 μm) *** impedance spectroscopy measurements revealed an electrically inhomogeneous structure in the prepared *** the resistivities of grains of both ceramic samples were in the same order of magnitude, the resistivity of grain-boundaries of the CS ceramic was three orders of magnitude greater than that of the SPS *** of the samples showed giant dielectric constant(> 10^3) over wide ranges of temperatures and ***, the room-temperature dielectric loss of the SPS NSCTO(3.2 at 1.1 khz) ceramic sample was higher than that of the CS NSCTO(0.08 at 1.1 khz) ceramic sample due to the reduced grain-boundary resistivity of the *** dielectric relaxations were detected for each sample and attributed to the relaxations in grains and *** dielectric behavior of the SPS and CS NSCTO ceramics could be interpreted in terms of the internal barrier layer capacitor(IBLC) model.

关键词： ceramics sintering dielectric loss and relaxation

A Lyapunov-based three-axis attitude intelligent control approach for unmanned aerial vehicle

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Journal of Central South University 2015年第12期22卷 4669-4678页

作者： A.h.Mazinan Department of Control Engineering Faculty of Electrical EngineeringSouth Tehran BranchIslamic Azad University (IAU)

A novel Lyapunov-based three-axis attitude intelligent control approach via allocation scheme is considered in the proposed research to deal with kinematics and dynamics regarding the unmanned aerial vehicle *** is a consensus among experts of this field that the new outcomes in the present complicated systems modeling and control are highly appreciated with respect to *** control scheme presented here is organized in line with a new integration of the linear-nonlinear control approaches,as long as the angular velocities in the three axes of the system are accurately dealt with in the inner closed loop *** the corresponding rotation angles are dealt with in the outer closed loop *** should be noted that the linear control in the present outer loop is first designed through proportional based linear quadratic regulator(PD based LQR) approach under optimum coefficients,while the nonlinear control in the corresponding inner loop is then realized through Lyapunov-based approach in the presence of uncertainties and *** order to complete the inner closed loop control,there is a pulse-width pulse-frequency(PWPF) modulator to be able to handle on-off ***,the number of these on-off thrusters may be increased with respect to the investigated control efforts to provide the overall accurate performance of the system,where the control allocation scheme is realized in the proposed *** may be shown that the dynamics and kinematics of the unmanned aerial vehicle systems have to be investigated through the quaternion matrix and its corresponding vector to avoid presenting singularity of the *** the end,the investigated outcomes are presented in comparison with a number of potential benchmarks to verify the approach performance.

关键词： Lyapunov based control approach PD based LQR approach control allocation scheme kinematics and dynamics unmanned aerial vehicle system on-off thrusters PWPF modulator

Compressible closure models for turbulent multifluid mixing

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Applied Mathematics and Mechanics(English Edition) 2016年第1期37卷 97-106页

作者： h.JIN Department of Mathematics Jeju National University

This paper studies governing equations describing the turbulent fluid mixing behavior effectively. The goal is to propose a closure for compressible multiphase flow models with transport and surface tension, which satisfy the boundary conditions at the mixing zone edges, the conservation requirements, and an entropy inequality constraint. Implicitness of positivity for the entropy of averaging requires entropy inequality as op- posed to conservation of entropy for microphysically adiabatic processes.

关键词： multiphase flow closure constitutive law averaged equation

Application of hybrid robust three-axis attitude control approach to overactuated spacecraft——A quaternion based model

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Journal of Central South University 2016年第7期23卷 1740-1753页

作者： A.h.Mazinan Department of Control Engineering Faculty of Electrical Engineering South Tehran BranchIslamic Azad University(IAU)

A novel hybrid robust three-axis attitude control approach, namely hRTAC, is considered along with the well-known developments in the area of space systems, since there is a consensus among the related experts that the new insights may be taken into account as decision points to outperform the available materials. It is to note that the traditional control approaches may generally be upgraded, as long as a number of modifications are made with respect to state-of-the-art, in order to propose high-precision outcomes. Regarding the investigated issues, the robust sliding mode finite-time control approach is first designed to handle three-axis angular rates in the inner control loop, which consists of the pulse width pulse frequency modulations in line with the control allocation scheme and the system dynamics. The main subject to employ these modulations that is realizing in association with the control allocation scheme is to be able to handle a class of overactuated systems, in particular. The proportional derivative based linear quadratic regulator approach is then designed to handle three-axis rotational angles in the outer control loop, which consists of the system kinematics that is correspondingly concentrated to deal with the quaternion based model. The utilization of the linear and its nonlinear terms, simultaneously, are taken into real consideration as the research motivation, while the performance results are of the significance as the improved version in comparison with the recent investigated outcomes. Subsequently, there is a stability analysis to verify and guarantee the closed loop system performance in coping with the whole of nominal referenced commands. At the end, the effectiveness of the approach considered here is highlighted in line with a number of potential recent benchmarks.

关键词： three-axis angular rates and rotations sliding mode finite-time control approach proportional derivative based linearquadratic regulator approach dynamics and kinematics of overactuated spacecraft

Bio-fluid flow analysis based on heat transfer and variable viscosity

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Applied Mathematics and Mechanics(English Edition) 2019年第7期40卷 1029-1040页

作者： h.SADAF Department of Basic Sciences and humanities College of Electrical and Mechanical EngineeringNational University of Sciences and TechnologyIslamabad

This study investigates the cilia transport phenomenon from the perspectives of the heat transfer and variable viscosity in a bending channel. The rightward wall is maintained at a temperature of T0, and the leftward wall has a temperature of T1. Each wall has a metachronal wave that travels along its wall. The structures of the ciliary assemblies are calculated by the well-known simplifying suppositions of the large wavelength and the small Reynolds number approximation. The flow phenomenon for the Newtonian fluid is described as a function of cilia and a metachronal wave velocity. The pressure rise is calculated with MAThEMATICA. The theme of the cilia beating flow is inspected with scheming plots, and its features are discussed at the end of the article.

关键词： cilia-driven flow curved channel temperature dependent viscosity metachronal wave heat transfer exact solution

Comparison of the Groundwater Quality in the West Tahta Area, Upper Egypt in 1989 and 2011

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Journal of Environmental Protection 2012年第11期3卷 1442-1457页

作者： Ismail Esam Faid Abdalla Niesner erich Mauritsch hermann Department of Applied Geoscience and Geophysics Montan University Leoben Austria National Authority for Remote Sensing and Space Sciences (NARSS) Cairo Egypt

Egypt is characterized by arid climate with rare rainfall that means surface water. The River Nile is the main source of water supply. The study area is located in Upper Egypt in the western desert. The area under investigation is subjected to intensive development in the last twenty years, clearly seen in the change of the agriculture and urban areas. The rapid increase of the population in Egypt especially in the upper part leads to an increasing demand for houses on the old cultivated land lead to the migration towards the desert and reclaimed new areas. These new reclaimed areas are depending on the ground water. The extensive use of groundwater and increasing fertilizing system leads to the change of the water table, characterization and quality. In this study we use the analysis of 30 groundwater samples collected and analyzed in 1989 and 28 groundwater samples collected and analyzed in 2011 from the same area to identify the change in the quality of the ground water. According the hydrogeologic data which were collected from the study area in 1989 and 2011 we found a changing water table decreasing, from 1 to 48 m in 1989 and 5 to 60 m in 2011. The water level is decreasing in the same direction towards the River Nile. The sufficient recharge and leaching and dissolution of the aquifer materials due to extensive use lead to increase in TDS which reaching to 4453 ppm in 2011. The water type in the 1989 samples is mainly NahCO3 and in 2011 samples Na2SO4. Grid classification shows that the water samples collected in 1989 are mainly sodium bicarbonate and sodium chloride extending to sodium sulphate while the water samples collected in 2011 are mainly sodium sulphate and sodium chloride. Most of the 1989 groundwater samples are suitable for drinking purposes while majority of the 2011 groundwater samples are not suitable due to high salinity.

关键词： Under Groundwater Withdrawal West Tahta Evaluation of Groundwater