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Effect of reinforcement amount, mold temperature, superheat, and mold thickness on fluidity of in-situ Al-Mg_2Si composites

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China Foundry 2018年第1期15卷 66-74页

作者： reza Vatankhah Barenji Department of lndustrial Engineering Hacettepe University Beytepe Campus Ankara 06800 Turkey

In the present study, the effects of mold temperature, superheat, mold thickness, and Mg_2Si amount on the fluidity of the Al-Mg_2Si as-cast in-situ composites were investigated using the mathematical models. Composites with different amounts of Mg_2Si were fabricated, and the fluidity and microstructure of each were then analyzed. For this purpose, the experiments were designed using a central composite rotatable design, and the relationship between parameters and fluidity were developed using the response surface method. In addition, optical and scanning electron microscopes were used for microstructural observation. The ANOVA shows that the mathematical models can predict the fluidity accurately. The results show that by increasing the mold temperature from 25℃ to 200℃, superheat from 50℃ to 250℃, and thickness from 3 mm to 12 mm, the fluidity of the composites decreases, where the mold thickness is more effective than other factors. In addition, the higher amounts of Mg_2Si in the range from 15 wt.% to 25 wt.% lead to the lower fluidity of the composites. For example, when the mold temperature, superheat, and thickness are respectively 100℃, 150℃, and 7 mm, the fluidity length is changed in the range of 11.9 cm to 15.3 cm. By increasing the amount of Mg_2Si, the morphology of the primary Mg_2Si becomes irregular and the size of primary Mg_2Si is increased. Moreover, the change of solidification mode from skin to pasty mode is the most noticeable microstructural effect on the fluidity.

关键词： Al-Mg2Si composites microstructure fluidity

Influences of adsorptions of some inorganic molecules on electronic, optical, and thermodynamic properties of Mg_(12)O_(12) nanocage: A computational approach

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Chinese Physics B 2018年第8期27卷 280-289页

作者： Asghar Mohammadi Hesari Hamid reza Shamlouei Chemistry Department Lorestan UniversityI(horram AbadLorestanIraa

According to density functional theory, we investigate the effects of BF3, BF4, BCI3, A1F3, AICI3, A1Br3, 13eF3, GaF3, GaC13, GaBr3, NO3, BS2, BSO, BO2, F2, PFs, PC15, and ASF5 molecules on the geometric, electronic, linear, and nonlinear optical properties of an Mg12012 nanocage. The thermodynamic stability and feasibility of the adsorption process are investigated by analyzing the free energy. It is shown that the adsorptions of almost all molecules on the Mg12OI2 surface are exothermic. The calculations of the polarizability of these nanoclusters show that among the studied molecules, BeF3 has the largest influence on the polarizability value （a≈315 a.u., the unit a.u. is short for atomic unit）. The static first hyperpolarizability （β0） value is increased in the presence of these superhalogens. This increase is greatest for BeF3 and BF4 of which the highest value of the first hyperpolarizability （βO≈ 5775 a.u.） is related to a BeF3_c（e@Mgl2Ol2） nanocluster. The adsorption position is a key to estimating the value of increasing the first hyperpolarizability.

关键词： Mg1201 polarizability hyperpolarizability binding energy nanocage DFT calculation

Photocatalytic degradation of the acetaminophen by nanocrystal-engineered TiO_(2)thin film in batch and continuous system

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Frontiers of Environmental Science & Engineering 2021年第2期15卷 15-18页

作者： reza Katal Mohammad Tanhaei Jiangyong Hu Department of Civil&Environmental Engineering National University of SingaporeSingapore 117576Singapore Institute of Materials Research and Engineering Agency for ScienceTechnologyand ResearchSingapore 138634Singapore

Un-biodegradable pharmaceuticals are one of the major growing threats in the *** the current study,TiO_(2)thin film photocatalysts were designed by nanocrystal engineering and fabricated for degradation of the acetaminophen(ACE)in a photocatalytic reaction under UV light irradiation in batch and continuous *** photocatalyst was prepared by sputtering and then engineered by thermal treatment(annealing at 300℃(T300)and 650℃(T650)).The annealing effects on the crystallinity and photocatalytic activity of the TiO_(2)film were completely studied;it was found that annealing at higher temperatures increases the surface roughness and grain size which are favorable for photocatalytic activity due to the reduction in the recombination rate of photo-generated electron-hole *** the continuous system,a flat plate reactor(FPR)was designed and *** photocatalytic performance was decreased with the increase of flow rate because the higher flow rate caused to form the thicker film of the liquid in the reactor and reduced the UV light received by *** reusability and durability of the samples after 6 h of photocatalytic reaction showed promising performance for the T650 sample(annealed samples in higher temperatures).

关键词： Acetaminophen TiO2 Thin film Batch Continuous

A Comparative Study of the Application of Electronic Data Interchange and Internet Technology to Business Process Reengineering

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Tsinghua Science and Technology 2004年第4期9卷 489-496页

作者： Hamid reza Ahadi School of Economics and Management Tsinghua University Beijing 100084 China

This study investigates the role of information technology in business process reengineering (BPR) implementation. To increase the prospects of successful BPR implementation, the role of information technology in BPR should be thoroughly investigated to find the logical relationships between information technology and BPR. This study used a survey methodology to gather information from 72 BPR programs. The results show that different information technologies, such as those examined in this study, electronic data interchange (EDI) and Internet, provide different capabilities and can be useful in different ways and for different purposes. Lack of attention to these relationships may be due to the unacceptable high implemen-tation failure rate in the previous BPR efforts.

关键词： business process reengineering organizational enablers information technology

Improvement in the protective performance and adhesion of polypyrrole coating on AZ31 Mg alloys

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Progress in Natural Science:Materials International 2015年第5期25卷 478-485页

作者： Maryam Hatami Mohsen Saremi reza Naderi School of Metallurgy and Materials Engineering Faculty of Engineering University of Tehran

The electrochemical synthesis of polypyrrole(Ppy) coating on AZ31 magnesium alloy was successfully achieved in a solution containing sodium salicylate and monomer of pyrrole through cyclic voltammetry *** effect of potential range,passivation pretreatment and number of cycles of polymerization on the quality and protective performance of the coatings was evaluated using surface analysis and electrochemical *** taking the advantage of charge transfer resistance,current density,corrosion potential,optical microscopy images and SEM micrographs,the optimum condition of synthesis of a Ppy coating with the best adhesion and corrosion protection was *** optimal PPy coating synthesized over AZ31 increases the polarization resistance and decreases the corrosion current more than one order of magnitude and shift the corrosion potential about 200 mV toward nobler *** SEM studies showed that Ppy coating have cauliflower morphology of Ppy grains with a diameter ranging from 20 nm to 60 nm.

关键词： PolyPyrrole AZ31 Mg Cyclic voltammetry Electropolymerization Corrosion protection

A novel nest-based scheduling method for mobile wireless body area networks

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Digital Communications and Networks 2020年第4期6卷 514-523页

作者： Zhijun Xie Guangyan Huang Roozbeh zarei Zhenyan Ji Hongwu Ye Jing He Department of Information Science and Engineering Ningbo UniversityNingboChina School of Information Technology Deakin UniversityMelbourneAustralia Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingboChina School of Software Engineering Beijing Jiaotong UniversityBeijingChina Zhejiang Fashion Institute of Technology NingboChina Institute of Information Technology Nanjing University of Finance and EconomicsJiangsuNanjingChina Swinburne Data Science Research Institute Swinburne University of TechnologyMelbourneAustralia

Wireless Body Area Networks(WBANs)comprise various sensors to monitor and collect various vital signals,such as blood pressure,pulse,heartbeat,body temperature,and blood sugar.A dense and mobile WBAN often suffers from interference,which causes serious problems,such as wasting energy and degrading *** reality,not all of the sensors in WBAN need to be active at the same ***,they can be divided into different groups so that each group works in turn to avoid *** this paper,a Nest-Based WBAN Scheduling(NBWS)algorithm is proposed to cluster sensors of the same types in a single or multiple WBANs into different groups to avoid ***,we borrow the graph coloring theory to schedule all groups to work using a Time Division for Multimodal Sensor(TDMS)group scheduling *** theoretical analysis and experimental results demonstrate that the proposed NBWS algorithm performs better in terms of frequency of collisions,transmission delay,system throughput,and energy consumption compared to the counterpart methods.

关键词： Interference elimination Nest Sensors Scheduling Wireless body area networks Graph coloring theory

Adaptive H_∞ Synchronization of Master-slave Systems with Mixed Time-varying Delays and Nonlinear Perturbations: An LMI Approach

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International Journal of Automation and computing 2011年第4期8卷 381-390页

作者： Hamid reza Karimi Department of Engineering Faculty of Engineering and Science University of Agder N-4898 Grimstad Norway

This paper proposes an adaptive synchronization problem for the master and slave structure of linear systems with nonlinear perturbations and mixed time-varying delays comprising different discrete and distributed time delays. Using an appropriate Lyapunov-Krasovskii functional, some delay-dependent sufficient conditions and an adaptation law including the master-slave parame- ters are established for designing a delayed synchronization law in terms of linear matrix inequalities（LMIs）. The time-varying controller guarantees the H ∞ synchronization of the two coupled master and slave systems regardless of their initial states. Particularly, it is shown that the synchronization speed can be controlled by adjusting the updated gain of the synchronization signal. Two numerical examples are given to demonstrate the effectiveness of the method.

关键词： Adaptive synchronization master-slave systems delay H ∞ performance nonlinear perturbations.

Modeling the oxidative coupling of methane: Heterogeneous chemistry coupled with 3D flow field simulation

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Journal of Natural Gas Chemistry 2009年第1期18卷 39-44页

作者： Yaghobi Nakisa Ghoreishy Mir Hamid reza Iran Polymer and Petrochemical Institute P. O. Box 14965/115 Tehran Iran

The oxidative coupling of methane （OCM） over titanate perovskite catalyst has been developed by three-dimensional numerical simulations of flow field coupled with heat transfer as well as heterogeneous kinetic model. The reaction was assumed to take place both in the gas phase and on the catalytic surface. Kinetic rate constants were experimentally obtained using a ten step kinetic model. The simulation results agree quite well with the data of OCM experiments, which were used to investigate the effect of temperature on the selectivity and conversion obtained in the methane oxidative coupling process. The conversion of methane linearly increased with temperature and the selectivity of C2 was practically constant in the temperature range of 973-1073 K. The study shows that CFD tools make it possible to implement the heterogeneous kinetic model even for high exothermic reaction such as OCM.

关键词： OCM simulation kinetics fixed bed catalytic reactor ethylene

A note on the surface motion of a semi-cylindrical canyon for incident cylindrical SH waves radiated by a finite fault

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Earthquake Engineering and Engineering Vibration 2016年第3期15卷 445-455页

作者： reza S.Jalali Zaniar Tokmechi Department of Civil Engineering Faculty of Engineering University of Guilan

The plane-wave assumption for incident SH waves can be a good approximation for cylindrical and spherical waves radiated from finite sources, even when the source is as close as twice the size of the inhomogeneity, and when the source and the inhomogeneity are described within the same coordinate system. However, in a more general setting, and when the fault＇s radiation pattern must be considered, the plane-wave approximation may not yield satisfactory answers for arbitrary orientation of the fault. Jalali et al. （2015） demonstrated this for a semi-cylindrical, sedimentary valley, and in this study we extend their results to a case in which the semi-circular, sedimentary valley is replaced by a canyon. We describe the effects of incident cylindrical waves on the amplitudes of surface motion in and near the semi-cylindrical canyon when the causative faults are at different distances and have different curvatures and orientations.

关键词： plane SH waves cylindrical SH waves effects of arbitrary fault orientation on amplification of surfacemotions