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Effects of loading rate and hydraulic residence time on anoxic sulfide biooxidation

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第7期8卷 1149-1156页

作者： mahmood Qaisar ISLAM Ejazul Department of Environmental Engineering Zhejiang University

The optimal operation conditions in an anoxic sulfide oxidizing (ASO) bioreactor were investigated. The maximal removal rates for sulfide and nitrate were found to be 4.18 kg/(m3·d) and 1.73 kg/(m3·d), respectively. The volumetrical volumetric loading rates (Lrs) observed through decreasing hydraulic retention time (HrT) at fixed substrate concentration are higher than those by increasing substrate concentration at fixed HrT. The sulfide oxidation in ASO reactor was partially producing both sulfate and sulfur; but the amount of sulfate produced was approximately one third that of sulfur. The process was able to tolerate high sulfide concentration, as the sulfide removal percentage always remained near 99% when influent concentration was up to 580 mg/L. It tolerated relatively lower nitrate concentration because the removal percentage dropped to 85% when influent con- centration was increased above 110 mg/L. The process can tolerate shorter HrT but careful operation is needed. Nitrate conversion was more sensitive to HrT than sulfide conversion since the process performance deteriorated abruptly when HrT was decreased from 3.12 h to 2.88 h. In order to avoid nitrite accumulation in the reactor, the influent sulfide and nitrate concentrations should be kept at 280 mg/L and 67.5 mg/L respectively. Present biotechnology is useful for removing sulfides from sewers and crude oil.

关键词： Anaerobic processes Anoxic nitrate removal Biodesulfurization Biotransformation Fluidized bed bioreactors Hydraulic residence time (HrT)

Data driven models for compressive strength prediction of concrete at high temperatures

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Frontiers of Structural and Civil Engineering 2020年第2期14卷 311-321页

作者： mahmood AKBArI Vahid JAFArI DELIGANI Department of Civil Engineering Faculty of EngineeringUniversity of KashanKashan ***Iran

The use of data driven models has been shown to be useful for simulating complex engineering processes,when the only information available consists of the data of the *** this study,four data-driven models,namely multiple linear regression,artificial neural network,adaptive neural fuzzy inference system,and K nearest neighbor models based on collection of 207 laboratory tests,are investigated for compressive strength prediction of concrete at high *** addition for each model,two different sets of input variables are examined:a complete set and a parsimonious set of involved *** results obtained are compared with each other and also to the equations of NIST Technical Note standard and demonstrate the suitability of using the data driven models to predict the compressive strength at high *** addition,the results show employing the parsimonious set of input variables is sufficient for the data driven models to make satisfactory results.

关键词： data driven model compressive strength oncrete high temperature

CuCrW(Al2O3) nanocomposite: mechanical alloying, microstructure, and tribological properties

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International Journal of Minerals,Metallurgy and Materials 2017年第11期24卷 1321-1334页

作者： Mohammad Baghani mahmood Aliofkhazraei Department of Materials Science Faculty of Engineering Tarbiat Modares University Tehran Iran P.O. Box: 14115-143

The effect of alumina nanoparticle addition on the microstructure and tribological properties of a CuCrW alloy was investigated in this work. Mechanical alloying was carried out in a satellite ball mill. The tribological properties of the samples were evaluated using pin-on-disk wear tests with different pins(alumina, tungsten carbide, and steel pins). The results indicated that the tungsten carbide pin had a lower coefficient of friction than the alumina and steel pins because of its high hardness and low surface roughness. In addition, when the sliding rate was decreased, the weight-loss rate increased. The existence of alumina nanoparticles in the nanocomposite led to a lower weight-loss rate and to a change in the wear mechanism from adhesive to abrasive.

关键词： wear mechanicalalloying nanocomposite tribologicalproperties metalmatrix

Defocus Blur Segmentation Using Genetic Programming and Adaptive Threshold

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Computers, Materials & Continua 2022年第3期70卷 4867-4882页

作者： Muhammad Tariq mahmood Future Convergence Engineering School of Computer Science and EngineeringKorea University of Technology and EducationCheonan31253Byeongcheon-myeonKorea

Detection and classification of the blurred and the non-blurred regions in images is a challenging task due to the limited available information about blur type,scenarios and level of *** this paper,we propose an effective method for blur detection and segmentation based on transfer learning *** proposed method consists of two separate *** the first step,genetic programming(GP)model is developed that quantify the amount of blur for each pixel in the *** GP model method uses the multiresolution features of the image and it provides an improved blur *** the second phase,the blur map is segmented into blurred and non-blurred regions by using an adaptive threshold.A model based on support vector machine(SVM)is developed to compute adaptive threshold for the input blur *** performance of the proposed method is evaluated using two different datasets and compared with various state-of-the-art *** comparative analysis reveals that the proposed method performs better against the state-of-the-art techniques.

关键词： Blur measure blur segmentation sharpness measure genetic programming support vector machine

Theoretical investigation of optical properties and band gap engineering for Zn1-xTMxTe(TM=Fe,Co)alloys by modified Becke-Johnson potential

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Chinese Physics B 2017年第8期26卷 491-498页

作者： Q mahmood M Yaseen M Hassan Shahid M ramay Asif mahmood Materials Growth and Simulation Laboratory Department of PhysicsUniversity of the PunjabQuaid-i-Azam Campus54590LahorePakistan Department Of Physlcs University of Agriculture UniversityFaisalabad 38040Pakistan Physics and Astronomy Department College of ScienceKing Sand UniversityRiyadhSaudi Arabia Chemical Engineering Department College of EngineeringKing Saud UniversityRiyadhSaudi Arabia

The direct band gap ZnTe with transition metal （TM） impurities plays a vital role in optoelectronic and spintronic applications. In the present study, we use the advanced modified Becke-Johnson （mBJ） functional for performing the structural computations and detailed investigations of the optical characters in Zn1_xTMxTe （TM = Fe, Co） alloys with 0 ≤ x ≤1. By employing the FP-LAPW method, we determine various optical parameters for the ternary alloys and for the end binaries. The calculated static dielectric constants and optical band gaps for Zn1_xTMxTe （TM = Fe, Co） have an inverse relation that verifies the Penn model. We find that the static dielectric constant is nearly equal to the square of the static refractive index, and both increase with TM content. Furthermore, we also find a slight shift of peaks to a higher energy region with increasing TM concentration. The decreasing band gap and high value of the absorption in the visible region of electromagnetic spectrum make these alloys suitable for photonic and solar cell applications.

关键词： amorphous semiconductors transition metal-doped ZnTe structural computation optical property

Performance improvement of complementary feeders using static transfer switch system

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第2期10卷 189-200页

作者： Tahir mahmood Mohammad Ahmad CHOUDHrY Department of Electrical Engineering University of Engineering and Technology

The performance of complementary feeders, running in parallel, can be significantly improved by installing static transfer switches （STSs） at critical locations. We develop the STS control logic, which transfers the critical load from the preferred feeder to the alternate feeder when a voltage sag or a fault occurs on the preferred feeder. A forced commutation technique is proposed and implemented to turn off the preferred feeders＇ thyristor, thus avoiding cross current to flow and minimizing the transfer time. Simulation results show that the forced commutation technique is more effective as compared to the recently proposed time delay technique for STS operation. Two different feeders, namely New Exchange, the preferred feeder, and Sector 1-10/2, the alternate feeder of Islamabad Electric Supply COmpany （IESCO）, Pakistan, have been selected for case studies. The software PSCAD/EMTDC professional package has been used for simulation.

关键词： Complementary feeder Cross current Static transfer switch (STS) Sensitive load Voltage sag PSCAD/EMTDC

Insight into generation of induced mesenchymal stem cells from induced pluripotent cells

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World Journal of Stem Cells 2022年第1期14卷 142-145页

作者： mahmood S Choudhery ruhma mahmood Department of Biomedical Sciences King Edward Medical UniversityLahore 54000PunjabPakistan Department of Genetics and Molecular Biology University of Health SciencesLahore 54600PunjabPakistan Stem Cells Laboratory Allama Iqbal Medical CollegeLahore 54000PunjabPakistan

Mesenchymal stem cells(MSCs)have the potential for use in cell-based regenerative ***,hundreds of clinical trials are using MSCs for the treatment of various ***,MSCs are low in number in adult tissues;they show heterogeneity depending upon the cell source and exhibit limited proliferative potential and early senescence in in vitro *** factors negatively impact the regenerative potential of MSCs and therefore restrict their use for clinical *** a result,novel methods to generate induced MSCs(iMSCs)from induced pluripotent stem cells have been *** development and optimization of protocols for generation of iMSCs from induced pluripotent stem cells is necessary to evaluate their regenerative potential in vivo and in *** addition,it is important to compare iMSCs with primary MSCs(isolated from adult tissues)in terms of their safety and *** investigation of the properties of iMSCs in vitro and their long term behavior in animals is important for their translation from bench to bedside.

关键词： Induced mesenchymal stem cells Induced pluripotent stem cells regenerative potential Pluripotent Multipotent Clinical studies

Electronic and thermoelectric properties of alkali metal-based perovskites CsYbF3 and rbYbF3

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Chinese Physics B 2020年第11期29卷 473-478页

作者： Q mahmood N A Noor T Ghrib Nessrin A Kattan Asif mahmood Shahid M ramay Basic and Applied Scientific research Center Imam Abdulrahman Bin Faisal UniversityP.O.Box 198231441DammamSaudi Arabia Department of Physics College of ScienceImam Abdulrahman Bin Faisal UniversityP.O.Box 198231441DammamSaudi Arabia Department of Physics Riphah International UniversityLahorePakistan Department of Physics Faculty of ScienceTaibah UniversityMedinaSaudi Arabia Chemical Engineering Department College of EngineeringKing Saud UniversityRiyadhSaudi Arabia Physics and Astronomy Department College of ScienceKing Saud University RiyadhRiyadhSaudi Arabia

The electronic and thermoelectric properties of alkali metal-based fluorides CsYbF3 and rbYbF3 are studied by using Wien2k and BoltzTraP *** structural and thermodynamic stability of these materials are confirmed by tolerance factor(0.94 and 0.99 for rbYbF3 and CsYbF3)and negative formation *** optimized lattice constants and bulk moduli are consistent with the results reported in the *** reported band gap for rbYbF3 is 0.86 eV which decreases to 0.83 eV by the replacement of Cs with *** electrical and thermal conductivities along with Seebeck coefficients decrease with temperature rising from 0 K to 800 *** large values of thermoelectric parameters for positive chemical potentials show that the character is dominated by *** studied materials have figures of merit 0.82 and 0.81 at room temperature respectively,for rbYbF3 and CsYbF3 and increase with temperature ***,the materials under study may have potential application values in thermoelectric generators and refrigerators.

关键词： density functional theory thermodynamic stability electrical conductivity figure of merit

Dynamic replication of web contents

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Science in China(Series F) 2007年第6期50卷 811-830页

作者： Amjad mahmood Department of Computer Science University of Bahrain Kingdom of Bahrain

The phenomenal growth of the World Wide Web has brought huge increase in the traffic to the popular web sites. Long delays and denial of service experienced by the end-users, especially during the peak hours, continues to be the common problem while accessing popular sites. replicating some of the objects at multiple sites in a distributed web-server environment is one of the possible solutions to improve the response time/latency. The decision of what and where to replicate requires solving a constraint optimization problem, which is NP-complete in gen- eral. In this paper, we consider the problem of placing copies of objects in a dis- tributed web server system to minimize the cost of serving read and write requests when the web servers have limited storage capacity. We formulate the problem as a 0-1 optimization problem and present a polynomial time greedy algorithm with backtracking to dynamically replicate objects at the appropriate sites to minimize a cost function. To reduce the solution search space, we present necessary condi- tions for a site to have a replica of an object in order to minimize the cost function. We present simulation results for a variety of problems to illustrate the accuracy and efficiency of the proposed algorithms and compare them with those of some well-known algorithms. The simulation results demonstrate the superiority of the proposed algorithms.

关键词： object replication Web distributed web-server system data placement Internet