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Dark count rate and band to band tunneling optimization for single photon avalanche diode topologies

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Chinese Physics B 2019年第6期28卷 458-464页

作者： Taha Haddadifam mohammad Azim karami Iran University of Science and Technology

This paper proposes two optimal designs of single photon avalanche diodes(SPADs) minimizing dark count rate(DCR). The first structure is introduced as p^+/pwell/nwell, in which a specific shallow pwell layer is added between p^+and nwell layers to decrease the electric field below a certain threshold. The simulation results show on average 19.7%and 8.5% reduction of p^+/nwell structure’s DCR comparing with similar previous structures in different operational excess bias and temperatures respectively. Moreover, a new structure is introduced as n+/nwell/pwell, in which a specific shallow nwell layer is added between n+and pwell layers to lower the electric field below a certain threshold. The simulation results show on average 29.2% and 5.5% decrement of p^+/nwell structure’s DCR comparing with similar previous structures in different operational excess bias and temperatures respectively. It is shown that in higher excess biases(about 6 volts), the n+/nwell/pwell structure is proper to be integrated as digital silicon photomultiplier(dSiPM) due to low DCR. On the other hand, the p^+/pwell/nwell structure is appropriate to be utilized in dSiPM in high temperatures(above 50?C) due to lower DCR value.

关键词： single-photon avalanche diode digital silicon photomultiplier dark count rate

Improvement in IBC-silicon solar cell performance by insertion of highly doped crystalline layer at heterojunction interfaces

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Chinese Physics B 2017年第10期26卷 508-514页

作者： Hadi Bashiri mohammad Azim karami Shahramm mohammadnejad School of Electrical Engineering Iran University of Science &Technology (IUST)

By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact （IBC） silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters （doping concentration and thickness） is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of 2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si：H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density.

关键词： IBC silicon solar cells interface layer recombination interface defect density

Astragalus adscendens extract shows antidiabetic effects through controlling oxidative stress,inflammation and apoptosis in streptozotocin-induced diabetic rats

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Asian Pacific Journal of Tropical Biomedicine 2023年第6期13卷 242-249页

作者： Yosra Raziani Kimia karami Hamid reza mohammadi Hossein Mahmoudvand mohammad Nabi Moradi Javad Ghasemian Yadegari Nursing Department Al-Mustaqbal University College51001 HillahBabylonIraq Razi Herbal Medicines Research Center Lorestan University of Medical SciencesKhorramabadIran Molecular and Cellular Laboratory School of Allied MedicineLorestan University of Medical SciencesKhorramabadIran

Objective:To assess the effect of oral treatment of methanolic extract of the aerial parts of Astragalus adscendens in streptozotocin-induced diabetic ***:In order to induce diabetes,rats intraperitoneally received streptozotocin at 65 mg/*** adult male Wistar rats were allocated into six groups(10 rats per each)including the healthy control group,the diabetic group as well as the diabetic group treated with Astragalus adscendens methanolic extract at 50,100,and 200 mg/kg per day or glibenclamide(0.6 mg/kg/day)for 28 *** effects of Astragalus adscendens methanolic extract on the levels of glucose,insulin,alanine aminotransferase,alkaline phosphatase,aspartate aminotransferase,bilirubin,creatinine,urea,uric acid,total protein,albumin,triglyceride,cholesterol,α-amylase,oxidant/antioxidant enzymes,and inflammatory cytokines were *** time-PCR was also used for measuring the gene expression of caspase-3,Bcl2,and ***:The levels of glucose,cholesterol,triglyceride,creatinine,urea,uric acid,alanine aminotransferase,aspartate aminotransferase,alkaline phosphatase,bilirubin,and malondialdehyde considerably declined(P<0.001)in diabetic rats after treatment with Astragalus adscendens methanolic extract especially at a dose of 200 mg/*** addition,treatment with Astragalus adscendens methanolic extract noticeably increased the level of insulin,total protein,and albumin as well as improved the activities of catalase,glutathione peroxidase,and superoxide dismutase,as well as the expression levels of TNF-α,IL-1β,caspase-3,Bcl2 and Bax(P<0.001)compared to the diabetic control *** extract also inhibitedα-amylase in a dose-dependent manner with an IC_(50)value of 19.6μg/***:Astragalus adscendens methanolic extract shows potent antidiabetic,anti-inflammatory,anti-apoptotic,and antioxidant effects in diabetic ***,more studies are needed to verify the underlying mechanism of the effect of this plant extract and test its effica

关键词： Herbal medicines Astragalus adscendens Diabetes Antioxidant Antidiabetes Streptozotocin Antiinflammation

Evaluation of the stability of terraced slopes in clayey gravel soil using a novel numerical technique

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Frontiers of Structural and Civil Engineering 2023年第5期17卷 796-811页

作者： Mehrdad karami mohammad NAZARI-SHARABIAN James BRISTOW Moses KARAKOUZIAN Department of Civil and Environmental Engineering and Construction University of NevadaLas VegasLas VegasNV 89154USA Department of Mathematics Engineeringand Computer ScienceWest Virginia State UniversityInstituteWV 25112USA R&D Department Universal Engineering SciencesLas VegasNV 89118USA

Conventional geotechnical software limits the use of the strength reduction method(SRM)based on the Mohr–Coulomb failure criterion to analyze the slope safety factor(SF).The use of this constitutive model is impractical for predicting the behavior of all soil *** the present study,an innovative numerical technique based on SRM was developed to determine SF using the finite element method and considering the extended Cam–clay constitutive model for clayey gravel soil as opposed to the Mohr–Coulomb *** this regard,a novel user subroutine code was employed in ABAQUS to reduce the stabilizing forces to determine the failure surfaces and resist and drive shear stresses on a *** validating the proposed technique,it was employed to investigate the performance of terraced slopes in the context of a case *** impacts of geometric parameters and different water table elevations on the SF were *** results indicated that an increase in the upper and lower slope heights led to a decrease in SF,and a slight increase in the horizontal offset led to an increase in the ***,when the water table elevation was lower than the toe of the terraced slope,the SF increased because of the increase in the uplift force as a resistant component.

关键词： terraced slope safety factor finite element method ABAQUS extended Camclay

Performance of fixed beam without interacting bars

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Frontiers of Structural and Civil Engineering 2020年第5期14卷 1180-1195页

作者： Aydin SHISHEGARAN Behnam karami Timon RABCZUK Arshia SHISHEGARAN mohammad Ali NAGHSH Mohammreza mohammad KHANI School of Civil Engineering Iran University of Science and TechnologyTehran 13114-16846Iran International Institute of Earthquake Engineering and Seismology Tehran 19537-14453Iran Division of Computational Mechanics Ton Duc Thang UniversityHo Chi Minh CityVietnam Faculty of Civil Engineering Ton Duc Thang UniversityHo Chi Minh CityVietnam School of Civil engineering Islamic Azad UniversityTehran ***Iran School of Civil Engineering Isfahan University of TechnologyIsfahan ***Iran

Increasing the bending capacity of reinforced concrete(RC)elements is one of important topics in structure *** goal of this study is to develop a transferred stress system(TSS)on longitudinal reinforcement bars for increasing the bending capacity of RC *** study is divided into two parts,i.e.,experimental tests and nonlinear FE *** experiments were carried out to determine the load-deflection curves and crack patterns of the ordinary and TSS fixed *** FE models were developed for simulating the fixed *** obtained load-deflection results and the observed cracks from the FE analysis and experimental tests are compared to evaluate the validation of the FE nonlinear *** on the validated FE models,the stress distribution on the ordinary and TSS bars were *** found the load carrying capacity and ductility of TSS fixed beam are 29.39%and 23.69%higher compared to those of the ordinary fixed *** crack expansion occurs on the ordinary fixed beam,although there are several crack openings at mid-span of the TSS fixed *** crack distribution was changed in the TSS fixed *** TSS fixed beam is proposed to employ in RC frame instead of ordinary RC beam for improving the performance of RC frame.

关键词： transferred stress system bending capacity crack opening crack propagation FE nonlinear model stress distribution

Experimental investigation and flow analysis of clear-water scour around pier and abutment in proximity

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Water Science and Engineering 2023年第1期16卷 94-105页

作者： mohammad Saeed Fakhimjoo Abdollah Ardeshir Kourosh Behzadian Hojat karami Department of Civil and Environmental Engineering Amirkabir University of TechnologyTehran 15875-4413Iran School of Computing and Engineering University of West LondonLondon W55RFUK Department of Civil Engineering Semnan UniversitySemnan 35131-19111Iran

Local scour around bridge piers and abutments is one of the most significant causes of bridge *** a plethora of studies on scour around individual bridge piers or abutments,few studies have focused on the joint impact of a pier and an abutment in proximity to one another on *** study conducted laboratory experiments and flow analyses to examine the interaction of piers and abutments and their effect on clear-water *** experiments were conducted in a rectangular laboratory *** included 18 main tests(with a combination of different types of piers and abutments)and five control tests(with individual piers or abutments).Three pier types(a rectangular pier with a rounded edge,a group of three cylindrical piers,and a single cylindrical pier)and two abutment types(a wingewall abutment and a semicircular abutment)were *** acoustic Doppler velocimeter was used to measure the three-dimensional flow velocity for analyses of streamline,velocity magnitude,vertical velocity,and bed shear *** results showed that the velocity near the pier and abutment increased by up to 80%.The maximum scour depth around the abutment increased by up to 19%.In contrast,the maximum scour depth around the pier increased significantly by up to l71%.The presence of the pier in the vicinity of the abutment led to an increase in the scour hole volume by up to 87%relative to the case with a solitary *** equations were also derived to accurately estimate the maximum scour depth at the pier adjacent to the abutment.

关键词： Abutment ADV Bridge scour Laboratory experiment Maximum scour depth Pier

Simulation of flow pattern at rectangular lateral intake with different dike and submerged vane scenarios

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Water Science and Engineering 2017年第3期10卷 246-255页

作者： Hojat karami Saeed Farzin mohammad Tavakol Sadrabadi Hasan Moazeni Faculty of Civil Engineering Semnan University School of Water Sciences Engineering Shahid Chamran University of Ahvaz

A comprehensive understanding of the sediment behavior at the entrance of diversion channels requires complete knowledge of threedimensional(3 D) flow behavior around such structures. Dikes and submerged vanes are typical structures used to control sediment entrainment in the diversion channel. In this study, a 3 D computational fluid dynamic(CFD) code was calibrated with experimental data and used to evaluate flow patterns, the diversion ratio of discharge, the strength of secondary flow, and dimensions of the vortex inside the channel in various dike and submerged vane installation scenarios. Results show that the diversion ratio of discharge in the diversion channel is dependent on the width of the flow separation plate in the main channel. A dike perpendicular to the flow with a narrowing ratio of 0.20 doubles the ratio of diverted discharge in addition to reducing suspended sediment input to the basin, compared with a no-dike situation, by creating the outer arch conditions. A further increase in the narrowing ratio decreases the diverted discharge. In addition, increasing the longitudinal distance between consecutive vanes(Ls) increases the velocity gradient between the vanes and leads to a more severe erosion of the bed, near the vanes.

关键词： Three-dimensional simulation Computational fluid dynamics Submerged vanes Dike Side and vortex flow

Prediction of the load-carrying capacity of reinforced concrete connections under post-earthquake fire

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2021年第6期22卷 441-466页

作者： Aydin SHISHEGARAN Mehdi MORADI mohammad Ali NAGHSH Behnam karami Arshia SHISHEGARAN School of Civil Engineering Iran University of Science and TechnologyTehranIran Institute of Structural Mechanics Bauhaus-Universitat WeimarWeimar 99423Germany School of Civil Engineering Isfahan UniversityIsfahanIran School of Civil Engineering Isfahan University of TechnologyIsfahanIran International Institute of Earthquake Engineering and Seismology TehranIran 不详

Finding out the most effective parameters relating to the resistance of reinforced concrete connections(RCCs)is an important topic in structural *** this study,first,a finite element(FE)model is developed for simulating the performance of RCCs under post-earthquake fire(PEF).Then surrogate models,including multiple linear regression(MLR),multiple natural logarithm(Ln)equation regression(MLn ER),gene expression programming(GEP),and an ensemble model,are used to predict the remaining load-carrying capacity of an RCC under *** statistical parameters,error terms,and a novel statistical table are used to evaluate and compare the accuracy of each surrogate *** to the results,the ratio of the longitudinal reinforcement bars of the column(RLC)has a significant effect on the resistance of an RCC under *** the value of this parameter from 1%to 8%can increase the residual load-carrying capacity of an RCC under PEF by 492.2%when the RCC is exposed to fire at a temperature of 1000°***,based on the results,the ensemble model can predict the residual load-carrying capacity with suitable accuracy.A safety factor of 1.55 should be applied to the results obtained from the ensemble model.

关键词： Reinforced concrete connection(RCC) Post-earthquake fire(PEF) Surrogate models Load-carrying capacity Gene expression programming(GEP) Ensemble model

An innovative model for predicting the displacement and rotation of column-tree moment connection under fire

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Frontiers of Structural and Civil Engineering 2021年第1期15卷 194-212页

作者： mohammad Ali NAGHSH Aydin SHISHEGARAN Behnam karami Timon RABCZUK Arshia SHISHEGARAN Hamed TAGHAVIZADEH Mehdi MORADI Department of Civil Engineering Isfahan University of TechnologyIsfahan 84156-83111Iran School of Civil Engineering School of Civil EngineeringIran University of Science and TechnologyTehran 13114-16846Iran Department of Civil Engineering International Institute of Earthquake Engineering and SeismologyTehran 19539-14453Iran Division of Computational Mechanics Ton Duc Thang UniversityHo Chi Minh CityVietnam Faculty of Civil Engineering Ton Duc Thang UniversityHo Chi Minh CityVietnam Department of Civil Engineering Islamic Azad UniversityTehran 16511-53311Iran Department of Civil Engineering Isfahan UniversityIsfahan 81746-73441Iran

In this study,we carried out nonlinear finite element simulations to predict the performance of a columntree moment connection(CTMC)under fire and static *** also conducted a detailed parameter study based on five input variables,including the applied temperature,number of flange bolts,number of web bolts,length of the beam,and applied static *** first variable is changed among seven levels,whereas the other variables are changed among three *** the Taguchi method for variables 2-5 and their levels,9 samples were designed for the parameter study,where each sample was exposed to 7 different temperatures yielding 63 *** related variables for each output are imported for the training and testing of different surrogate *** surrogate models include a multiple linear regression(MLR),multiple Ln equation regression(MLnER),an adaptive network-based fuzzy inference system(ANFIS),and gene expression programming(GEP).44 samples were used for training randomly while the remaining samples were employed for *** show that GEP outperforms MLR,MLnER,and *** results indicate that the rotation and deflection of the CTMC depend on the *** addition,the fire resistance increases with a decrease in the beam length;thus,a shorter beam can increase the fire resistance of the *** numbers of flanges and web bolts slightly affect the rotation and displacement of the CTMCs at temperatures of above 400℃.

关键词： column-tree moment connection Finite element model parametric study fire regression models gene expression programming