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Phase change materials as quenching media for heat treatment of 42CrMo4 steels

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Journal of Central South University 2020年第3期27卷 752-761页

作者： Milad SAKKAKI Farhad SADEGH MOGHANLOU Soroush PARVIZI Haniyeh BAGHBANIJAVID Aziz BABAPOOR mehdi shahedi asl Department of Mechanical Engineering University of Mohaghegh ArdabiliArdabilIran Department of Materials Engineering Shahid Rajaee Teacher Training UniversityLavizanTehranIran Department of Chemical Engineering University of Mohaghegh ArdabiliArdabilIran

In the present work,paraffin phase change material is used as quenchant for the heat treatment of 42CrMo4 alloy and compared with water,air,and CuO doped *** samples were prepared based on ASTM E 8M-98 standard for tensile test and then heated up to 830°C,kept for 4 h in an electric resistance furnace and then quenched in the mentioned *** modulus,yield strength,ultimate tensile strength,elongation,and modulus of toughness were determined according to the obtained stress?strain ***,the hardness and microstructural evolution were investigated after the heat treatment at different *** samples quenched in paraffin and CuO-doped paraffin are higher in ultimate tensile strength(1439 and 1306 MPa,respectively)than those quenched in water(1190 MPa)and air(1010 MPa).The highest hardness,with a value of HV 552,belonged to the sample quenched in CuO-doped *** microstructural studies revealed that the non-tempered steel had a ferrite/pearlite microstructure,while by quenching in water,paraffin and CuO-doped paraffin,ferrite/martensite microstructures were *** is also observed that using the air as quenchant resulted in a three-phase bainite/martensite/ferrite microstructure.

关键词： phase change materials heat treatment quenchant 42CrMo4 steel microstructure mechanical property

Limb Lengthening and Reconstruction Society orthopedic surgeons in the United States:An analysis of geographical distribution,academic,leadership,and demographic characteristics

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World Journal of Orthopedics 2024年第2期15卷 147-155页

作者： Amir Human Hoveidaei Reza Niakan Seyed Hossein Hosseini-asl Abijith Annasamudram Janet D Conway International Center for Limb Lengthening Rubin Institute for Advanced OrthopedicsSinai Hospital of BaltimoreBaltimoreMD 21215United States Student Research Committee Shiraz University of Medical SciencesShiraz 73Iran Students’Scientific Research Center Tehran University of Medical SciencesTehran ***Iran

BACKGROUND The Limb Lengthening and Reconstruction Society(LLRS)is a premier orthopedic specialty organization that promotes limb reconstruction for all *** membership characteristics,however,are poorly *** study delineates orthopedic surgeon LLRS members’demographic traits,academic achievement,leadership attainment,and geographical distribution across the United *** To inform aspiring orthopedic professionals,as well as to promote growth and diversity in both the LLRS organization and overarching *** This cross-sectional study examined United States LLRS members’academic,leadership,demographic,and geographical *** reviewing the 2023 LLRS member directory,Google search results were matched to the listings and appended to the compiled *** and ethnicity were evaluated visually utilizing retrieved *** Hirsch index(H-index)of academic activity,residency and fellowship training,other graduate degrees,leadership positions,practice type(academic or non-academic),and spoken languages were *** members per state and capita determined geographic *** Mann Whitney U test was applied to compare H-index between males and females,as well as to assess member differences pertaining to affiliation with academic vs non-academic practice *** The study included 101 orthopedic surgeons,78(77.23%)Caucasian and 23(22.77%)non-Caucasian,79(78.22%)male and 22(21.78%)*** with DO degrees comprised only 3.96%(4)of the cohort,while the vast majority held MDs[96.04%(97)].Mean H-index was 10.55,with male surgeons having a significantly higher score(P=0.002).Most orthopedic surgeons(88.12%,)practiced in academic *** those professionals who occupied leadership positions,14%were women,while 86%were ***,19(37.25%)United States regions and the District of Columbia lacked an LLRS-member orthopedic *** per capita rate across the United States was 0.30 LLRS orthopedic

关键词： Limb lengthening and reconstruction Orthopedic surgeon demographics Orthopedic surgeon societal membership Orthopedic fellowships

QUANTITATIVE EVALUATION OF ARRANGEMENT OF MONOMERS IN LINEAR BINARY COPOLYMERS USING A MONTE CARLO SIMULATION METHOD

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Chinese Journal of Polymer Science 2009年第2期27卷 195-208页

作者： Mohammad Najafi mehdi Salami-Kalajahi Vahid Haddadi-asl Polymer Engineering Department Amirkabir University of TechnologyP.O.Box 15875-4413TehranIran National Petrochemical Company Petrochemical Research and Technology Company14358TehranIran

A Monte Carlo method was used to take thorough account of the influences of different reactivity ratios and initial feed compositions on copolymer *** model proves the lack of azeotropic behavior in systems in which r_A>1 and r_B<1 or vice versa;it is also able to calculate the drift in the copolymer properties:copolymer composition,and randomness ***,for each reactivity ratio pair given,there is a unique reaction conversion,at which macromolecules produced inherit their ...

关键词： Radical copolymerization Copolymer microstructure Copolymer composition Monte Carlo simulation Randomness parameter Copolymer heterogeneity Azeotrope point.

A COMPREHENSIVE MONTE CARLO SIMULATION OF STYRENE ATOM TRANSFER RADICAL POLYMERIZATION

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Chinese Journal of Polymer Science 2010年第4期28卷 483-497页

作者： Mohammad Najafi Hossein Roghani-Mamaqani mehdi Salami-Kalajahi Vahid Haddadi-asl International Affairs Research Institute of Petroleum Industry(RIPI)***TehranIran Polymer Engineering Department Amirkabir University of TechnologyP.O.Box 15875-4413TehranIran

An optimized and high-performance Monte Carlo simulation is developed to take thorough account of four different cases of termination in styrene ATRP. According to the simulation results, the bimolecular termination rate constant sharply drops throughout the polymerization when either chain-length dependency of termination rate constant, gel effect, or both together is applied to the simulation. In addition, as expected, the initiator is quickly decomposed at the early stages of the polymerization. The concentration of the catalyst in lower oxidation state decreases at first and then plateaus at higher conversion; furthermore, the steady concentration of Ml^nY/L in the polymerization is the highest when the chain-lengthdependent diffusion-controlled termination rate constant is employed in the simulation. The rates of deactivation and chain end degradation reactions are also smaller in this case. Therefore, the fraction of dormant chains is higher throughout the reaction and consequently the portion of dead polymers decreases. Besides, molecular weight increases linearly with conversion; however, when neither gel effect nor chain-length dependency of termination rate constant is considered, the molecular weight deviates from linearity at the end of the reaction. The peak of chain length distribution shifts toward higher molecular weight too during the reaction. Finally, the molecular weight distribution broadens at higher conversion; however, the chain length distribution of polymers produced under conditions of applying chain-length-dependent diffusion-controlled termination rate constant is narrower.

关键词： Styrene ATRP Monte Carlo simulation Chain length distribution Gel effect Chain-length-dependent termination.

Corrigendum to ‘Exploring multidimensional aspects of walkability: An innovative analysis approach in Besiktas, Istanbul’ [Frontiers of Architectural Research Volume 12, Issue 6, (2023) Pages 1097–1126]

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Frontiers of Architectural Research 2024年第2期13卷 284-284页

作者： Ozge Ceylin Yildirim asl Sungur Derya Gulec Ozer Department of Architecture Yildiz Technical UniversityIstanbul 34349Turkey Department of Architecture Istanbul Technical UniversityIstanbul 34367Turkey

We thank architecture students who participated in the MIM3142 Barrier-Free Architecture course at Yildiz Technical University in 2021-2022 Spring Semester and 2022-2023Fall *** also sincerely thank Besiktas Municipality for sharing the relevant *** paper is part of a study supported by the Scientific Research Project(5159 ID)at Yildiz Technical University,*** authors would like to acknowledge that this paper is submitted in partial fulfilment of the requirements for PhD degree at YildizTechnical University.

关键词： Spring thank Pages

Effects of nitric oxide on the prefrontal cortex in stressed rats

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Neural Regeneration Research 2010年第14期5卷 1096-1099页

作者： Batoul Ebadi mehdi mehdizadeh Arezoo Nahavandi Tabandeh Shariati Sara Soleimani asl Hamdolah Delaviz Department of Radiology Iran University of Medical Sciences Cellular and Molecular Research Center Department of AnatomyIran University of Medical Sciences Department of Physiology Iran University of Medical Sciences Department of Anatomy Hammedan University of Medical Sciences Department of Anatomy Yasuj University of Medical Sciences

BACKGROUND： Nitric oxide （NO） exhibits both protective and detrimental effects in the central nervous system. OBJECTIVE： To investigate the effect of NO on the prefrontal cortex in neonatal stressed rats. DESIGN, TIME AND SETTING： A randomized, controlled, animal study was performed at the Anatomical Department of Iran University of Medical Sciences from May 2007 to August 2008. MATERIALS; Forty-eight male, Wistar rats were obtained from Pasteur＇s Institute, Tehran, Iran. METHODS： Rat stress models were established by immobilization and randomly received intraperitoneal injection of 2 mL physiological saline, L-arginine （200 mg/kg） as a NO precursor, N（G）-nitro-L-arginine methyl ester （20 mg/kg）, or subcutaneous injection of 7-nitroindazole （25 mg/kg） as a NO synthase inhibitor. MAIN OUTCOME MEASURES： After the rats were treated for 4 weeks, the frontal cortex was harvested for histological observation and NO detection. RESULTS： Subcutaneous administration of N（G）-nitro-L-arginine methyl ester or 7-nitroindazole resulted in significantly lower prefrontal cortex thickness and NO production compared with subcutaneous administration of L-arginine （P 〈 0.05）. Prefrontal cortex thickness significantly increased in rats following L-arginine treatment, compared with physiological saline intervention （P 〈 0.05）. CONCLUSION： NO exhibited protective effects on the prefrontal cortex of stressed rats.

关键词： nitric oxide prefrontal cortex thickness nerve cell stress rats neural regeneration

EFFECTS OF REACTION AND PROCESSING PARAMETERS ON ETHYLENE POLYMERIZATION USING DIFFERENT ZIEGLER-NATTA CATALYSTS:EMPLOYMENT OF TAGUCHI EXPERIMENTAL DESIGN AND RESPONSE SURFACE METHOD

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Chinese Journal of Polymer Science 2007年第2期25卷 153-162页

作者： Mohammad Najafi Vahid Haddadi-asl Polymer Engineering Department Amirkabir University of TechnologyP.O.Box 15875-4413TehranIran

Different Ziegler-Natta catalysts were employed to polymerize ethylene. To investigate the influences of reaction parameters, namely Al/Ti molar ratio, hydrogen and processing parameters, i.e. ethylene pressure and temperature, a Taguchi experimental design was worked out. An L27 orthogonal array was chosen to take the above-mentioned parameters and relevant interactions into account. Response surface method was the tool used to analyze the experimental design results. Al/Ti, ethylene pressure and temperature were selected as experimental design factors, and catalyst activity and polymerization yield were the response parameters. Increasing pressure, due to an increment in monomer accessibility, and rising Al/Ti, because of higher reduction in the catalysts, cause an increase in both polymerization yield and catalyst activity. Nonetheless, a higher temperature, thanks to reducing ethylene solubility in the slurry medium and partially catalyst destruction, lead to a reduction in both response parameters. A synergistic effect was also observed between temperature and pressure. All catalyst activities will reduce in the presence of hydrogen. Molecular weight also shows a decline in the presence of hydrogen as a transfer agent. However, the polydispersity index remains approximately intact. Using SEM, various morphologies, owing to different catalyst morphologies, were seen for the polyethylene.

关键词： L27 Taguchi experimental design Response surface method Polyethylene polymerization Ziegler-Natta catalysts.

An Efficient Randomized Fixed-Precision Algorithm for Tensor Singular Value Decomposition

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Communications on Applied Mathematics and Computation 2023年第4期5卷 1564-1583页

作者： Salman Ahmadi-asl Skolkovo Institute of Science and Technology(SKOLTECH) Center for Artificial Intelligence TechnologyMoscowRussia

The existing randomized algorithms need an initial estimation of the tubal rank to compute a tensor singular value *** paper proposes a new randomized fixed-precision algorithm which for a given third-order tensor and a prescribed approximation error bound,it automatically finds the tubal rank and corresponding low tubal rank *** algorithm is based on the random projection technique and equipped with the power iteration method for achieving better *** conduct simulations on synthetic and real-world datasets to show the efficiency and performance of the proposed algorithm.

关键词： Tubal tensor decomposition Randomization Fixed-precision algorithm

Magnetic polyacrylonitrile/ZIF-8/Fe_(3)O_(4) nanocomposite bead as an efficient iodine adsorbent and antibacterial agent

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Chinese Journal of Chemical Engineering 2023年第9期61卷 210-220页

作者： Reza Sacourbaravi Zeinab Ansari-asl Esmaeil Darabpour Department of Chemistry Faculty of ScienceShahid Chamran University of AhvazAhvazIran Department of Biology Faculty of ScienceShahid Chamran University of AhvazAhvazIran

The efficient adsorption of radioactive iodine(^(129)I and^(131)I)as nuclear waste is of great *** nanocomposites consist of metal-organic frameworks(MOFs)developing for various pollutions sorption and separation have attracted much *** study reports the fabrication of magnetic polyacrylonitrile(PAN)/zeolitic imidazolate frameworks(ZIF-8)nanocomposites,PAN/ZIF-8(x%)/Fe_(3)O_(4),x=30 and 50,as iodine capture *** PAN/ZIF-8(x%)/Fe_(3)O_(4)nanocomposite beads were fabricated via the phase inversion method,and their potential for iodine capture and separation in solution and vapor was investigated through UV-vis and weighing methods,***,antibacterial activity of the as-prepared beads was assessed against *** and *** as-fabricated compounds were studied by various techniques such as Fourier-transform infrared,X-ray diffraction,scanning electron microscope,energy-dispersive X-ray spectroscopy mapping,transmission electron microscope,N_(2)adsorption isotherm,and vibrating sample *** iodine capture results showed that the efficiency of nanocomposites is remarkably higher than the pure PAN ***,the asprepared nanocomposite adsorbents displayed higher capture capacities for iodine vapor(1524-4345mg·g^(-1))than iodine solution(187-295 mg·g^(-1)).The as-obtained magnetic nanocomposites can be successfully separated from polluted media by simple filtration or an external magnet,regenerated through washing with ethanol,and *** capturing,high sorption capacity,rapid separation,and good reusability make the PAN/ZIF-8(x%)/Fe_(3)O_(4)nanocomposites highly effective adsorbents for the separation of iodine from ***,PAN/ZIF-8(50%)/Fe_(3)O_(4)bead can be considered as a potential new antibacterial agent for water and wastewater treatment.

关键词： ZIF-8 Polyacrylonitrile Composites Adsorption Waste treatment Antibacterial agent