检索结果-南通市图书馆

A novel control strategy for load converter of DC isolated distribution system under unbalanced loading conditions

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第6期10卷 890-899页

作者： R.NOROOZIAN m.abedi G.B.GHAREHPETIAN S.H.HOSSEINI Department of Electrical Engineering Amirkabir University of Technology Department of Electrical and Computer Engineering Tabriz University

A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanced AC loading. The unbalanced load is characterized in the d-q-0 rotating coordinate based on symmetrical sequence components. Also, the mathematical model of the load converter in both a-b-c and d-q-0 coordinates is derived by using the average large signal model. Then, two control strategies for the load converter are presented. The first one uses the conventional d-q-0 controller to ensure the voltage and current regulation. The second one is a newly proposed control strategy based on the decomposition of the voltage and current into in-stantaneous positive, negative, and zero sequences. These three sequences are controlled independently in their own reference frames as DC signals. The performance of the load converter using these two control strategies is compared. Simulation results show the validity and capability of the newly proposed control strategy.

关键词： Unbalanced load Power quality Symmetrical components Control strategy

Axisymmetric and three-dimensional flow simulation of a mixed compression supersonic air inlet

在线全文

学校读者我要写书评

暂无评论

Propulsion and Power Research 2020年第1期9卷 51-61页

作者： m.abedi R.Askari J.Sepahi-Younsi m.R.Soltani Department of Aerospace Engineering Sharif University of TechnologyTehranIran mechanical Engineering Department Faculty of EngineeringFerdowsi University of MashhadMashhadIran Visiting Professor William E.Boeing Department of Aeronautics and AstronauticsUniversity of WashingtonWashingtonU.S.A.

The flow through an axisymmetric supersonic mixed-compression air inlet has been simulated numerically to investigate the effects and the necessity of the three-dimensional(3D)modeling in comparison with the axisymmetric *** this purpose,a supersonic inlet has been simulated numerically via axisymmetric and 3D CFD solvers,using the steady state Reynolds-averaged Navier-Stokes equations along with the SST k-ωturbulence model,for a free-stream mach number of 2.0 and at zero degrees angle of *** grid for the 3D cases was a 14.4-degree sector,instead of a 360-degree domain one,with rotational periodic boundary condition for the side *** results show that both static and total pressure distributions match well with the experimental data for both the axisymmetric and the 3D *** the prediction of performance parameters is the main goal of simulations,it seems that the axisymmetric simulation provides adequate accuracy,and the 3D simulation one is not the best *** 3D numerical simulation results in an in-depth study on the supersonic inlets,including the shock wave-boundary layer interaction,the location of the terminal normal shock wave,and consequently the separation *** an axisymmetric supersonic inlet in an axisymmetric flow condition,3D effects are not strong enough to have a significant influence on the inlet performance for all operational ***,it seems that 3D effects play an important role in both critical and supercritical operating conditions during the steady state operation.

关键词： Supersonic inlet Axisymmetric simulation Three-dimensional simulation Inlet performance Shock-boundary layer interaction

The dark side of cyclooctatetraene(COT):Photophysics in the singlet states of“self-healing”dyes

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2024年第8期35卷 225-228页

作者： Supphachok Chanmungkalakul Syed Ali Abbas abedi Federico J.Hernández Jianwei Xu Xiaogang Liu Fluorescence Research Group Singapore University of Technology and DesignSingapore 487372Singapore Department of Chemistry University College LondonLondon WC1H 0AJUnited Kingdom Institute of Sustainability for Chemicals Energy and Environment(ISCE2)Agency for ScienceTechnology and Research(A^(∗)STAR)Jurong Island 627833Singapore

Cyclooctatetraene(COT)attachment to fluorophores(“self-healing”dyes)is known for quenching reac-tive triplet states via triplet-state energy transfer(TET),enhancing ***,COT’s impact on singlet states remains *** calculations reveal that COT induces energy transfer to dark states in deep blue dyes while promoting photoinduced electron transfer(PET)and intersystem crossing(ISC)in visible dyes,potentially compromising brightness and/or *** address this,we pro-pose the use of △E descriptor to optimize COT’s *** findings uncover COT’s multifaceted *** insights will guide the development of superior triplet state quenchers and photostable dyes.

关键词： Cyclooctatetraene Photostability Triplet state quencher Energy transfer Electron transfer

Prevalence and Factors Associated with Anemia among People Living with Human Immunodeficiency Virus Followed at the Outpatient Treatment Centre of Panzi General Referral Hospital in Eastern Democratic Republic of Congo

在线全文

学校读者我要写书评

暂无评论

Journal of Biosciences and medicines 2024年第3期12卷 259-274页

作者： marlene abedi Zalufa Jean-Paulin mbo mukonkole Aline Byabene Kusinza Nicolas Vignier Dieudonné Bihehe masemo David Willy Shamputi Omari mukanga Lampard marie Hatem Department of Internal medicine Panzi General Referral Hospital Bukavu Democratic Republic of Congo Evangelical University in Africa Bukavu Democratic Republic of Congo Statistics Department Panzi General Referral Hospital Bukavu Democratic Republic of Congo International Centre for The Advanced Research and Training-ICART Panzi Foundation Bukavu Democratic Republic of Congo Faculty of medicine University of Kisangani Kisangani Democratic Republic of Congo Service des maladies Infectieuses et Tropicales CHU Avicenne Bobigny France Sorbonne University Paris France School of Public Health Department of Social and Preventive medicine Université de Montréal Montréal Canada

Introduction: Anemia in people living with human immunodeficiency virus (PLHIV) is a major health problem. Although anemia often responds to combination antiretroviral therapy, many patients remain anemic despite treatment, and such persistent anemia continues to adversely affect prognosis, regardless of drug response. Scientists have identified some of the factors involved. However, the mechanisms put in place have not been effective in overcoming them. Examples include the withdrawal of zidovudine from antiretroviral treatment lines, iron and folate supplementation, etc. Anemia is still a major concern in HIV-positive patients. The aim of this study is to assess the prevalence of anemia and its associated factors among PLHIV followed up at the outpatient treatment centre (CTA) of the Panzi General Reference Hospital (HGR) in South Kivu, Democratic Republic of Congo (DRC). method: We conducted a cross-sectional, comparative study of 276 HIV-infected adults on antiretroviral therapy (ART) followed up at the CTA of Panzi HGR. Socio-demographic and nutritional parameters were collected using a survey questionnaire, and clinical assessment and nutritional status were performed at the centre. Hemoglobin, seric albumin and viral load determinations were performed at the HGRP laboratory. We constructed univariate and multivariate logistic regression models to assess factors associated with anemia in people living with HIV/AIDS. Results: We found a prevalence of anemia of 39.4%, including 4.1% severe anemia, 17.7% moderate anemia and 17.5% mild anemia. After multivariate adjustment, the factors associated with anemia in our PLHIV were: moderate undernutrition (aOR = 1.26;95% CI: 1.50 - 4.20;p = 0.001), severe undernutrition (aOR = 115.4;95% CI: 2.04 - 164.52;p = 0.021), hypoalbuminemia (aOR = 2.11;95% CI: 1.87 - 5.10;p = 0.004) and the lower degree of dietary diversity (aOR = 1.56;95% CI: 1.10 - 4.32;p = 0.034). Conclusion: The prevalence of anemia in PLHIV on ART is high.

关键词： Anemia HIV/AIDS Undernutrition PANZI Hospital

Some non-linear height–diameter models performance for mixed stand in forests in Northwest Iran

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of mountain Science 2020年第5期17卷 1084-1095页

作者： Roya abedi Tooba abedi Department of Forestry Ahar Faculty of Agriculture and Natural ResourcesUniversity of TabrizAhar ***Iran Environmental Research Institute Academic Center for EducationCulture and ResearchRasht 41635-3114Iran

This study evaluated the total height of trees based on diameter at breast height by using 23 widely used height-diameter non-linear regression models for mixed-species forest stands consisting of Caucasian oak,field maple,and hornbeam from forests in Northwest Iran.1920 trees were measured in 6 sampling plots(every sampling plot has 1 ha area).The fit of the best height–diameter models for each species were compared based on R2,Root mean Square Error(RmSE),Akaike information criterion(AIC),standard error,and relative ranking performance *** the final step,verification of results was performed by paired sample t-test to compare the observed height and estimated *** showed that among 23 height-diameter models,the best models were obtained from the top five ones including modified-logistic,Prodan,Sibbesen,Burkhart,and *** between the actual observed height and estimated height for Caucasian oak showed that modified–Logistic,Prodan,Sibbesen,Burkhart,and Exponential performed better than the others,respectively(There were no statistically significant differences between observed heights and predicted height(p≥0.05)).Prodan,modified-Logistic,Burkhart,and Loetch evaluated field maple tree height correctly,and modified-Logistic,Burkhart,and Loetch had better fitness compared to the others for hornbeam,*** other models were introduced as appropriate criteria,they could not reliably predict the height of *** the Rank analysis,the modified-Logistic model for the Caucasian oak and Prodan model for field maple and hornbeam had the best ***,to complement the results of this study,it is suggested to assess how environmental factors such as elevation,climate parameters,forest protection policy and forest structure will modify height-diameter allometry models and will enhance the prediction accuracy of tree heights prediction in mixed stands.

关键词： Arasbaran Forest inventory Height prediction model validation Non-linear modeling Rank analysis

Frequency-dependent viscoelasticity effects on the wave attenuation performance of multi-layered periodic foundations

在线全文

学校读者我要写书评

暂无评论

Applied mathematics and mechanics(English Edition) 2024年第3期45卷 407-424页

作者： m.SAFI m.VAKILIFARD m.J.mAHmOODI Faculty of Civil Water&Environmental EngineeringShahid Beheshti UniversityTehran ***Iran Faculty of mechanical and Energy Engineering Shahid Beheshti UniversityTehran ***Iran

In this paper,layered periodic foundations(LPFs)are numerically examined for their responses to longitudinal and transverse modes in the time and frequency *** different unit-cells,i.e.,2-layer,4-layer,and 6-layer unit-cells,comprising concrete/rubber,concrete/rubber/steel/rubber,and concrete/rubber/steel/rubber/lead/rubber materials,respectively,are taken into ***,the viscoelasticity behavior of the rubber is modeled with two factors,i.e.,a frequency-independent(FI)loss factor and a linear frequency-dependent(FD)loss *** the extraction of the complex dispersion curves and the identification of the band gaps(BGs),the simulations of wave transmission in the time and frequency domains are performed using the COmSOL *** parametric studies evaluate the effects of the rubber viscoelasticity models on the dispersion curves and the wave transmission for the longitudinal and transverse *** results show that considering the rubber viscoelasticity enhances the wave attenuation ***,the transverse-mode damping is more sensitive to the viscoelasticity model than its longitudinal *** 6-layer unit-cell LPF exhibits the lowest BG,ranging from 4.8 Hz to 6.5 Hz.

关键词： layered metamaterial periodic foundation complex dispersion curve wave transmission diagram

Engineering of efficient visible light photocatalysts:Ti_(1-x+y)Cu_(x)La_(y)O_(2)(x=0.03;y=0,0.005,0.01) compositions

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第3期42卷 497-505,I0003页

作者： S.m.Yakout A.m.Youssef Inorganic Chemistry Department National Research Centre(NRC)El Buhouth StDokkiCairo12622Egypt

In dye-photocatalysis, widening the wavelengths absorption range of catalysts as well as aborting the recombination of the photoexcited charge carriers(electrons-holes pairs) are of paramount *** the current study, we report the photocatalytic characteristics of four compositions composed of TiO_(2),Ti_(0.97)Cu_(0.03)O_(2), Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders for two harmful dyes(Congo red and methylene blue). The X-ray diffraction technique verified the configuration of mixed anatase and rutile phases in pure TiO_(2)and Ti_(0.97)Cu_(0.03)O_(2)powders while Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders possess anatase phase only. The changes of the band gap structure and dimensions of the unit cell volume of TiO_(2)confirm the substitution of Ti^(4+)sites by Cu^(2+)and La^(3+)ions. Remarkable widening of wavelengths absorption with formation of long absorption tails were found in TiO_(2)(3.13 e V) through insertion of La^(3+)plus Cu^(2+)ions. Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)samples exhibit a visible light band gap of 2.3 and 2.7 e V, respectively. Based on SEm images, incorporation of Cu^(2+)and La^(3+)ions influences the surface morphology of TiO_(2). The resulting Ti_(0.97)Cu_(0.03)O_(2), Ti_(0.965)Cu_(0.03)La_(0.005)O_(2)and Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)powders present enhanced photocatalytic activity towards Congo red dye degradation compared to pure one under natural solar spectrum. The best Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)catalyst exhibits superior photocatalytic activity of 96% for 10 ppm CR dye in 20 min as well as above average photocatalytic efficiency of 63% for 30 ppm CR dye in 120 min. As well, it showed acceptable photodegradation activity of 52% for 30 ppm mB solution in 140 min of sunlight irradiation. The heightened photodegradation efficiency of Ti_(0.96)Cu_(0.03)La_(0.01)O_(2)catalyst can be clarified in terms of higher ch

关键词： Semiconductor TiO_(2) Rare earths Congo red methylene blue Solar spectrum Photodegradation

Parametric study of hexagonal castellated beams in post-tensioned self-centering steel connections

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2019年第5期13卷 1020-1035页

作者： Hassan abedi SARVESTANI Faculty of Water and Environmental Engineering Shahid Beheshti UniversityTehran 16589-53571Iran

The effects o f important parameters (beam reinforcing plates, initial post-tensioning, and material properties o f steel angles) on the behavior o f hexagonal castellated beams in post-tensioned self-centering (PTSC) connections undergone cyclic loading up to 4% lateral drift have been investigated by finite element (FE) analysis using ABAQUS. The PTSC connection is comprised o f bolted top and bottom angles as energy dissipaters and steel strands to provide self-centering capacity. The FE analysis has also been validated against the experimental test. The new formulations derived from analytical method has been proposed to predict bending moment o f PTSC connections. The web-post buckling in hexagonal castellated beams has been identified as the dominant failure mode when excessive initial post-tensioning force is applied to reach greater bending moment resistance, so it is required to limit the highest initial post-tensioning force to prevent this failure. Furthermore, properties o f steel material has been simulated using bilinear elastoplastic modeling with 1.5% strain-hardening which has perfectly matched with the real material of steel angles. It is recommended to avoid using steel angles with high yielding strength since they lead to the yielding o f bolt shank. The necessity o f reinforcing plates to prevent beam flange from local buckling has been reaffirmed.

关键词： finite element analysis hexagonal castellated beam parametric study post-tensioned self-centering steel connection steel moment-resisting frame

Nonlinear dynamic modeling of planar moving Timoshenko beam considering non-rigid non-elastic axial effects

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied mathematics and mechanics(English Edition) 2024年第3期45卷 479-496页

作者： m.ABBASI GAVARI m.R.HOmAEINEZHAD Faculty of mechanical Engineering K.N.Toosi University of TechnologyTehran 19991-43344Iran

Due to the importance of vibration effects on the functional accuracy of mechanical systems,this research aims to develop a precise model of a nonlinearly vibrating single-link mobile flexible *** manipulator consists of an elastic arm,a rotary motor,and a rigid carrier,and undergoes general in-plane rigid body motion along with elastic transverse *** accurately model the elastic behavior,Timoshenko’s beam theory is used to describe the flexible arm,which accounts for rotary inertia and shear deformation *** applying Newton’s second law,the nonlinear governing equations of motion for the manipulator are derived as a coupled system of ordinary differential equations(ODEs)and partial differential equations(PDEs).Then,the assumed mode method(Amm)is used to solve this nonlinear system of governing equations with appropriate shape *** assumed modes can be obtained after solving the characteristic equation of a Timoshenko beam with clamped boundary conditions at one end and an attached mass/inertia at the *** addition,the effect of the transverse vibration of the inextensible arm on its axial behavior is *** the axial rigidity,the effect makes the rigid body dynamics invalid for the axial behavior of the ***,numerical simulations are conducted to evaluate the performance of the developed model,and the results are compared with those obtained by the finite element *** comparison confirms the validity of the proposed dynamic model for the *** to the mentioned features,this model can be reliable for investigating the system’s vibrational behavior and implementing vibration control algorithms.

关键词： planar moving Timoshenko beam non-rigid non-elastic axial effect as-sumed mode method(Amm) nonlinear motion analysis