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Events and reaction mechanisms during the synthesis of an AI2O3-TiB2 nanocomposite via high energy ball milling

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Frontiers of Chemical Science and Engineering 2013年第2期7卷 123-129页

作者： M. ABDELLAHI M. ZAKERI H. bahmanpour Materials Engineering Department Islamic Azad University Saveh Branch Saveh Iran Ceramic Department Materials and Energy Research Center Tehran 31787/316 Iran Chemical engineering and Materials Science Department University of California Davis CA 95616 USA

An AI2O3-TiB2 nanocomposite was success- fully synthesized by the high energy ball milling of A1, B2O3 and TiO2. The structures of the powdered particles formed at different milling times were evaluated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Thermo- dynamic calculations showed that the composite formed in two steps via highly exothermic mechanically induced self-sustaining reactions （MSRs）. The composite started to form at milling times of 9-10 h but the reaction was not complete. The remaining starting materials were consumed by increasing the milling time to 15 h. The XRD patterns of the annealed powders showed that aluminum borate is one of the intermediate products and that it is consumed at higher temperatures. Heat treatment of the 6-h milled sample at l l00℃ led to a complete formation of the composite. Increasing the milling time to 15 h led to a refining of the crystallite sizes. A nanocomposite powder with a mean crystallite size of 35-40 nm was obtained after milling for 15 h.

关键词： ball milling nanocomposite AI2O3 TiB2

GPIO-Based Continuous Sliding Mode Control for Networked Control Systems Under Communication Delays With Experiments on Servo Motors

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IEEE/CAA Journal of Automatica Sinica 2025年第1期 99-113页

作者： kamal Rsetam Zhenwei Cao Zhihong Man Xian-Ming Zhang the School of Software and Electrical Engineering Swinburne University of Technology the Department of Automated Manufacturing Al Khwarizmi College of Engineering University of Baghdad IEEE

To handle input and output time delays that commonly exist in many networked control systems(NCSs), a new robust continuous sliding mode control(CSMC) scheme is proposed for the output tracking in uncertain single input-single-output(SISO) networked control systems. This scheme consists of three consecutive steps. First, although the network-induced delay in those systems can be effectively handled by using Pade approximation(PA), the unmatched disturbance cames out as another difficulty in the control design. Second, to actively estimate this unmatched disturbance, a generalized proportional integral observer(GPIO) technique is utilized based on only one measured state. Third, by constructing a new sliding manifold with the aid of the estimated unmatched disturbance and states, a GPIO-based CSMC is synthesized, which is employed to cope with not only matched and unmatched disturbances, but also networkinduced delays. The stability of the entire closed-loop system under the proposed GPIO-based CSMC is detailedly *** promising tracking efficiency and feasibility of the proposed control methodology are verified through simulations and experiments on Quanser's servo module for motion control under various test conditions.

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Performance enhancement of water bath heater at natural gas city gate station using twisted tubes

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Chinese Journal of Chemical Engineering 2020年第1期28卷 165-179页

作者： P.Soleimani M.Khoshvaght-Aliabadi H.Rashidi H.bahmanpour Department of Chemical Engineering Shahrood BranchIslamic Azad UniversityShahroodIran Department of Environment Shahrood BranchIslamic Azad UniversityShahroodIran

Natural gas is transported from producing regions to consumption regions by using transmission pipelines at high pressures. At consumption regions, the pressure of natural gas is reduced in city gate stations(CGSs). Before the pressure reduction process, the temperature of natural gas is increased usually by using a water bath heater,which burns natural gas as fuel, to protect against freezing of natural gas. These types of heat exchangers have a low efficiency and consume a lot of fuel to generate the required heat. In the current study, the twisted configuration of the heating coil is proposed and investigated to enhance the heat transfer through a water bath heater with a nominal capacity of 1000 m^3·h^-1. Firstly, the implementation procedure is validated with data collected from the CGS of Qaleh-Jiq(located in Golestan province of Iran). A very good agreement is achieved between the obtained results and the real data. Then, three different twist ratios are considered to examine the twisting effects. The proposed technique is evaluated in the terms of velocity, temperature, and pressure variations, and the results are compared with the conventional case, i.e. straight configuration. It is found that both the heat transfer rate and the pressure drop augment as the twist ratio is raised. Finally, it is concluded that the twisted tubes can reduce the length of the gas coil by about 12.5% for the model with low twist ratio, 18.75% for the model with medium twist ratio, and 25% for the model with high twist ratio as compared to the straight configuration.

关键词： Natural gas city gate station Water bath heater Heat transfer enhancement Twisted tube

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Parameter Estimation Based on Censored Data under Partially Accelerated Life Testing for Hybrid Systems due to Unknown Failure Causes

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Computer Modeling in Engineering & Sciences 2022年第3期130卷 1239-1269页

作者： Mustafa kamal Department of Basic Sciences College of Science and Theoretical StudiesSaudi Electronic UniversityDammam32256Saudi Arabia

In general,simple subsystems like series or parallel are integrated to produce a complex hybrid *** reliability of a system is determined by the reliability of its constituent *** is often extremely difficult or impossible to get specific information about the component that caused the system to *** failure causes are instances in which the actual cause of systemfailure is *** the other side,thanks to current advanced technology based on computers,automation,and simulation,products have become incredibly dependable and trustworthy,and as a result,obtaining failure data for testing such exceptionally reliable items have become a very costly and time-consuming ***,because of its capacity to produce rapid and adequate failure data in a short period of time,accelerated life testing(ALT)is the most utilized approach in the field of product reliability and life *** on progressively hybrid censored(PrHC)data froma three-component parallel series hybrid system that failed to owe to unknown causes,this paper investigates a challenging problem of parameter estimation and reliability assessment under a step stress partially accelerated life-test(SSPALT).Failures of components are considered to follow a power linear hazard rate(PLHR),which can be used when the failure rate displays linear,decreasing,increasing or bathtub failure *** Tempered random variable(TRV)model is considered to reflect the effect of the high stress level used to induce early failure *** maximum likelihood estimation(MLE)approach is used to estimate the parameters of the PLHR distribution and the acceleration factor.A variance covariance matrix(VCM)is then obtained to construct the approximate confidence intervals(ACIs).In addition,studentized bootstrap confidence intervals(ST-B CIs)are also constructed and compared with ACIs in terms of their respective interval lengths(ILs).Moreover,a simulation study is conducted to demonstrate the

关键词： Step stress partially accelerated life test progressive hybrid censoring data masking power linear hazard rate distribution hybrid system

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Journal of Systems Science & Complexity 2019年第3期32卷 737-758页

作者： BERAHMAND kamal BOUYER Asgarali Department of Information Technology and Communications Azarbaijan Shahid Madani University

Community structure is one of the most best-known proper ties of complex networks. Finding communities help us analyze networks from a mesoscopic viewpoints instead of microscopic or macroscopic one. It helps to understand behavior grouping. Various community detection algorithms have been proposed with some shortcomings in time and space complexity, accuracy, or stability. Label Propagation Algorithm (LPA) is a popular method used for finding communities in an almost-linear time-consuming process. However, its performance is not satisfactory in some metrics such as accuracy and stability. In this paper, a new modified version of LPA is proposed to improve the stability and accuracy of the LPA by defining two concepts -nodes and link strength based on semi-local similarity-, while preserving its simplicity. In the proposed method a new initial node selection strategy, namely the tiebreak strategy, updating order and rule update are presented to solve the random behavior problem of original LPA. The proposed algorithm is evaluated on artificial and real networks. The experiments show that the proposed algorithm is close to linear time complexity with better accuracy than the original LPA and other compared met hods. Furthermore, the proposed algorithm has the robustness and stability advantages while the original LPA does not have these features.

关键词： Community detection complex networks LPA similarity measure

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Atomistic Line Graph Neural Network for improved materials property predictions

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npj Computational Materials 2021年第1期7卷 1691-1698页

作者： kamal Choudhary Brian DeCost Materials Measurement Laboratory National Institute of Standards and TechnologyGaithersburgMD 20899USA Theiss ResearchLa Jolla California 92037USA DeepMaterials LLC Silver SpringMD 20906USA

Graph neural networks(GNN)have been shown to provide substantial performance improvements for atomistic material representation and modeling compared with descriptor-based machine learning *** most existing GNN models for atomistic predictions are based on atomic distance information,they do not explicitly incorporate bond angles,which are critical for distinguishing many atomic ***,many material properties are known to be sensitive to slight changes in bond *** present an Atomistic Line Graph Neural Network(ALIGNN),a GNN architecture that performs message passing on both the interatomic bond graph and its line graph corresponding to bond *** demonstrate that angle information can be explicitly and efficiently included,leading to improved performance on multiple atomistic prediction *** ALIGNN models for predicting 52 solid-state and molecular properties available in the JARVIS-DFT,Materials project,and QM9 *** can outperform some previously reported GNN models on atomistic prediction tasks by up to 85%in accuracy with better or comparable model training speed.

关键词： explicitly property passing

Designing high-TC superconductors with BCS-inspired screening,density functional theory,and deep-learning

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npj Computational Materials 2022年第1期8卷 2331-2342页

作者： kamal Choudhary Kevin Garrity Material Measurement Laboratory GaithersburgMD20899USA National Institute of Standards and Technology GaithersburgMD20899USA Theiss Research La JollaCA92037USA

We develop a multi-step workflow for the discovery of conventional superconductors,starting with a Bardeen–Cooper–Schrieffer inspired pre-screening of 1736 materials with high Debye temperature and electronic density of ***,we perform electron-phonon coupling calculations for 1058 of them to establish a large and systematic database of BCS superconducting *** the McMillan-Allen-Dynes formula,we identify 105 dynamically stable materials with transition temperatures,TC≥5 ***,we analyze trends in our dataset and individual materials including MoN,VC,VTe,KB_(6),Ru_(3)NbC,V_(3)Pt,ScN,LaN_(2),RuO_(2),and *** demonstrate that deep-learning(DL)models can predict superconductor properties faster than direct first-principles ***,we find that by predicting the Eliashberg function as an intermediate quantity,we can improve model performance versus a direct DL prediction of *** apply the trained models on the crystallographic open database and pre-screen candidates for further DFT calculations.

关键词： database BCS faster

EXISTENCE AND NONEXISTENCE OF SOLUTIONS FOR A HARMONIC EQUATION WITH CRITICAL NONLINEARITY

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Acta Mathematica Scientia 2016年第5期36卷 1305-1316页

作者： kamal OULD BOUH Department of Mathematics College of Sciences Taibah University

This paper is concerned with the harmonic equation(P;) : ?u = 0, u > 0 in B;and ?u/?ν+(（n-2）/2)u =(（n-2）/2) Ku;on S;where B;is the unit ball in R;, n ≥ 4 with Euclidean metric g;, ?B;= S;is its boundary, K is a function on S;and ε is a small positive parameter. We construct solutions of the subcritical equation(P;) which blow up at one critical point of K. We give also a sufficient condition on the function K to ensure the nonexistence of solutions for(P;) which blow up at one point. Finally, we prove a nonexistence result of single peaked solutions for the supercritical equation(P;).

关键词： variational problem critical points harmonic equation mean curvature critical exponent

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Profile based routing in vehicular ad-hoc networks

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Science China(Information Sciences) 2014年第6期57卷 154-164页

作者： BOHLOOLI Ali JAMSHIDI kamal Department of Computer Engineering Faculty of EngineeringUniversity of Isfahan

One of the main problems in the VANET(vehicular ad-hoc network)routing algorithms is how to establish the stable *** link duration in these networks is often very short because of the frequent changes in the network *** link duration reduce the network *** speeds of the vehicles and choosing different directions by the vehicles in the junctions are the two reasons that lead to link breakage and a reduction in link *** routing protocols have been proposed for VANET in order to improve the link duration,while none of them avoids the link breakages caused by the second *** this paper,a new method for routing algorithms is proposed based on the vehicles trips ***,each vehicle has a profile containing its movement patterns extracted from its trips *** next direction which each vehicle may choose at the next junction is predicted using this profile and is sent to other *** each vehicle selects a node the future direction of which is the same as its predicted *** case study indicates that applying our proposed method to ROMSGP(receive on most stable group-path)routing protocol reduces the links breakages and increases the link duration time.

关键词： vehicle communication VANET stable routing