检索结果-南通市图书馆

Study of the Bulk Magnetic and Electrical Properties of MgFe<sub>2</sub>O<sub>4</sub>Synthesized by Chemical Method

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Materials Sciences and Applications 2011年第11期2卷 1564-1571页

作者： Sheikh Manjura Hoque M. Abdul Hakim Al Mamun Shireen Akhter md. tanvir hasan Deba Prasad Paul Kamanio Chattopadhayay 不详

Nanocrystalline Magnesium ferrite has been prepared by chemical co-precipitation technique. Structural characterization has been performed by X-ray diffraction. Formation of ferrites has also been studied by using FTIR. Frequency dependence of real and imaginary part of initial permeability has been presented for the samples sintered at different temperatures. Real part of initial permeability, increases with the increase of grain growth. The loss component repre- sented by imaginary part of initial permeability decreases with frequency up to the measured frequency of this study of 13 MHz. Curie temperatures have been determined from the temperature dependence of permeability. Curie temperatures for the samples of this composition do not vary significantly with the variation of sintering temperatures. B-H loop measurements have been carried out by B-H loop tracer. Transport property measurements haven been carried out by electrometer and impedance analyzer.

关键词： MgFe2O4 Nanograins Complex Initial Permeability B-H Curves Transport Properties

Nitrogen-doped graphene quantum dots: Optical properties modification and photovoltaic applications

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2019年第5期12卷 1041-1047页

作者： md.tanvir hasan Roberto Gonzalez-Rodriguez Conor Ryan Kristof Pota Kayla Green Jeffery L.Coffer Anton V.Naumov Department of Physics and Astronomy Texas Christian UniversityTCU Box 298840Fort WorthTexas 76129USA Department cf Chemistry and Eiochemistry Texas Christian UniversityTCU Box 298860Fort WorthTexas 76129USA

In this work,we utilize a bottom-up approach to synthesize nitrogen self-doped graphene quantum dots (NGQDs) from a single glucosamine precursor via an eco-friendly microwave-assisted hydrothermal *** and optical properties of as-produced NGQDs are further modified using controlled ozone ***-treated NGQDs (Oz-NGQDs) are reduced in size to 5.5 nm with clear changes in the lattice structure and/D//G Raman ratios due to the introduction/alteration of oxygen-containing functional groups detected by Fourier-transform infrared (FTIR) spectrometer and further verified by energy dispersive X-ray spectroscopy (EDX) showing increased atomic/weight percentage of oxygen *** with structural modifications,GQDs experience decrease in ultraviolet-visible (UV-vis) absorption coupled with progressive enhancement of visible (up to 16 min treatment) and near-infrared (NIR)(up to 45 min treatment) *** allows fine-tuning optical properties of NGQDs for solar cell applications yielding controlled emission increase,while controlled emission quenching was achieved by either blue laser or thermal *** Oz-NGQDs were further used to form a photoactive layer of solar calls with a maximum efficiency of 2.64% providing a 6-fold enhancement over untreated NGQD devices and a 3-fold increase in fill factor/current *** study suggests simple routes to alter and optimize optical properties of scalably produced NGQDs to boost the photovoltaic performance of solar cells.

关键词： nitrogen-doped graphene quantum dots ozone treatment optical properties photovoltaics solar cells

A critical review of ash slagging mechanisms and viscosity measurement for low-rank coal and bio-slags

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers in Energy 2021年第1期15卷 46-67页

作者： md.tanvir ALAM Baiqian DAI Xiaojiang WU Andrew HOADLEY Lian ZHANG Department of Chemical Engineering Monash UniversityClaytonVictoria 3800Australia R&D Division Shanghai Boiler Works Co.Ltd.Shanghai 200245China

Gasification or combustion of coal and biomass is the most important form of power generation ***,the use of coal/biomass at high temperatures has an inherent problem related to the ash *** formation of ash leads to a problematic phenomenon called *** is the accumulation of molten ash on the walls of the furnace,gasifier,or boiler and is detrimental as it reduces the heat transfer rate,and the combustion/gasification rate of unburnt carbon,causes mechanical failure,high-temperature corrosion and on occasions,superheater *** improve the gasifier/combustor facility,it is very important to understand the key ash properties,slag characteristics,viscosity and critical viscosity *** paper reviews the content,compositions,and melting characteristics of ashes in differently ranked coal and biomass,and discusses the formation mechanism,characteristics,and structure of *** particular,this paper focuses on low-rank coal and biomass that have been receiving increased attention ***,it reviews the available methodologies and formulae for slag viscosity measurement/prediction and summarizes the current limitations and potential ***,it discusses the slagging behavior of different ranks of coal and biomass by examining the applicability of the current viscosity measurement methods to these fuels,and the viscosity prediction models and factors that affect the slag *** review shows that the existing viscosity models and slagging indices can only satisfactorily predict the viscosity and slagging propensity of high-rank coals but cannot predict the slagging propensity and slag viscosity of low-rank coal,and especially biomass ashes,even if they are limited to a particular composition ***,there is a critical need for the development of an index,or a model or even a measurement method,which can predict/measure the slagging propensity and slag viscosity correctly for all low-rank co

关键词： slag viscosity biomass low-rank coal combustion gasification

Improved voltage tracking of autonomous microgrid technology using a combined resonant controller with lead-lag compensator adopting negative imaginary theorem

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Protection and Control of Modern Power Systems 2022年第1期7卷 149-164页

作者： md.Yah-Ya Ul Haque md.Rashidul Islam tanvir Ahmed md.Rafiqul Islam Sheikh Department of Electrical and Electronic Engineering Varendra UniversityRajshahi 6204Bangladesh Department of Electrical and Electronic Engineering Rajshahi University of Engineering&TechnologyRajshahi 6204Bangladesh

Growing application of distributed generation units at remote places has led to the evolution of microgrid(MG)*** an MG system functions independently,i.e.,in autonomous mode,unpredictable loads and uncertainties emerge throughout the *** obtain stable and flexible operation of an autonomous MG,a rigid control mechanism is *** this paper,a robust high-performance controller is introduced to improve the performance of voltage tracking of an MG system and to eliminate stability problems.A combination of a resonant controller and a lead-lag compensator in a positive position feedback path is designed,one which obeys the negative imaginary(NI)theorem,for both single-phase and three-phase autonomous MG *** controller has excellent tracking *** is investigated through considering various uncertainties with different load *** feasibility and effectiveness of the controller are also determined with a comparative analysis with some well-known controllers,such as linear quadratic regulator,model predictive and NI approached resonant *** confirms the superi-ority of the designed controller.

关键词： Negative imaginary theorem Resonant controller Lead-lag compensator Autonomous microgrid Voltage tracking

A Photonic Crystal Fiber Based Asymmetric Slotted Structured Highly Sensitive Refractive Index Plasmonic Biosensor

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 Sensor Technology 2022年第1期12卷 1-17页

作者： md. Arafat Rahman tanvir Ahmed md. Ismail Haque md. Shamim Anower Department of Electrical and Electronic Engineering Rajshahi University of Engineering and Technology Rajshahi Bangladesh Department of Electrical and Electronic Engineering International Islamic University Chittagong Chittagong Bangladesh

Surface plasmon resonance (SPR) sensors have grown in popularity owing to their sensitivity, precision, and capacity for a variety of applications, including detection, monitoring, and sensing, among others. Sensitivity and resolution are two areas where this technology has room for development. A plasmonic biosensor based on an asymmetric slotted PCF structure with extremely high sensitivity has been described and theoretically investigated. This high performance sensor is constructed and completely characterized using finite element method in COMSOL Multiphysics software environment. Sensitivity and resolution are analyzed as performance parameters for the proposed sensor. Numerical simulation exhibits the maximum wavelength-sensitivity of 1100 nm/RIU with 9.09 × 10-6 RIU resolution in the broad measurement range of refractive index from 1.30 to 1.44. A polarization controller can be used to fine-tune this extremely sensitive and wide-ranging refractive index sensor to fulfil a variety of practical needs. This is performed with the consideration of the variation in the refractive index (RI) of the analyte channels. In comparison with earlier PCF-based sensors, the fiber design structure is basic, symmetrical, simple to produce, and cost-effective. Because of the asymmetric air holes and higher sensitivities of the refractive index detector, it is possible to identify biomolecules, biochemicals and other analytes.

关键词： Surface Plasmon Resonance (SPR) Sensor High Sensitivity Photonic Crystal Fiber (PCF) Optical Fiber Sensor

Comparative Analysis between Single Diode and Double Diode Model of PV Cell: Concentrate Different Parameters Effect on Its Efficiency

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 Power and Energy Engineering 2016年第3期4卷 31-46页

作者： tanvir Ahmad Sharmin Sobhan md. Faysal Nayan Department of Electrical and Electronic Engineering Ahsanullah University of Science and Technology Dhaka Bangladesh

This research appraises comparative analysis between single diode and double diode model of photovoltaic (PV) solar cells to enhance the conversion efficiency of power engendering PV solar systems. Single diode model is simple and easy to implement, whereas double diode model has better accuracy which acquiesces for more precise forecast of PV systems performance. Exploration is done on the basis of simulation results and MATLAB tool is used to serve this purpose. Simulations are performed by varying distinct model parameters such as solar irradiance, temperature, value of parasitic resistances, ideality factor of diode and number of series and parallel connected solar cells used to assemble PV array. Conspicuous demonstration is executed to analyze effects of these specifications on the efficiency curve and power vs. voltage output characteristics of PV cell for specified models.

关键词： Photovoltaic Cell Single Diode Model Double Diode Model Efficiency Simulation

Pattern of Presentation of Iatrogenic Biliary Injury Following Laparoscopic Cholecystectomy

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Clinical Diagnostics 2022年第4期12卷 55-62页

作者： Fahmid-Uz-Zaman Mohammad Aminul Islam md. Saba Al Galib md. Mashkurul Alam md. Shamsuddoha Khan Muhammad tanvir Alam Akhanda Sania Hossain Laila Siddika Mohammad Emrul hasan Khan Abul Bashar md. Jamal Department of Surgery Dhaka Medical College Hospital Dhaka Bangladesh Department of Surgery Shaheed M. Monsur Ali Medical College Hospital Shirajgonj Bangladesh Department of Pediatric Surgery Dhaka Medical College Hospital Dhaka Bangladesh Department of Surgery Shaheed Suhrawardy Medical College Hospital Dhaka Bangladesh National Institute of Cancer Research and Hospital Dhaka Bangladesh Department of Laboratory Medicine Sheikh Russel National Gastroliver Institute and Hospital Dhaka Bangladesh Mugda Medical College and Hospital Dhaka Bangladesh

Background: Cholecystectomy is one of the most now common abdominal surgeries performed every day. The incidence of bile duct injury (BDI) following open cholecystectomy is only 0.1% - 0.2%. After the introduction of laparoscopic cholecystectomy, the incidence has gone up to 0.4% - 0.7%. The present study is a prospective analysis of all patients with bile duct injury who were admitted to Dhaka Medical College Hospital during or at a variable period following cholecystectomy. Methods: To determine the pattern of presentation of iatrogenic biliary injury following cholecystectomy in the department of surgery of Dhaka Medical College Hospital, a total of 30 patients were purposively selected from May 2018 to November 2018. Patient particulars, records of physical and clinical evaluation, and operative details were collected by individual researchers. Data analysis was done by SPSS for windows version 21. Results: BDI was found very common among the age group 21 - 30 yrs (36%) and female dominant (60%). Majority of the patients presented with abdominal pain (96%), intra-abdominal collection (88%), biliary peritonitis (68%), cholangitis (60%), and obstructive jaundice (40%), and biliary fistula (40%). Laparoscopic cholecystectomy (84%) was the principal cause of biliary injury in our study. 48% of patients experienced clinical features within 7 days post-cholecystectomy. Per-operative diagnosis was done in only 12% of cases. 44% of patients in this study were recognized as Bismuth grade-3, followed by 36%, grade-2 patients. Management outcomes included wound infection (41.66%), minor bile leak (25%), peritonitis (8.33%), and renal impairment (8.33%). Conclusion: The effect of BDI is an extremely distressful clinical condition for the patients and their family members, hence proper care and management protocol should be followed.

关键词： Bile Duct Injury Laparoscopic Cholecystectomy Post-Operative Complications Bangladesh

Short-Term Financial Time Series Forecasting Integrating Principal Component Analysis and Independent Component Analysis with Support Vector Regression

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 Computer and Communications 2018年第3期6卷 51-67页

作者： Utpala Nanda Chowdhury Sanjoy Kumar Chakravarty md. tanvir Hossain Department of Computer Science and Engineering University of Rajshahi Rajshahi Bangladesh

Financial time series forecasting could be beneficial for individual as well as institutional investors. But, the high noise and complexity residing in the financial data make this job extremely challenging. Over the years, many researchers have used support vector regression (SVR) quite successfully to conquer this challenge. In this paper, an SVR based forecasting model is proposed which first uses the principal component analysis (PCA) to extract the low-dimensional and efficient feature information, and then uses the independent component analysis (ICA) to preprocess the extracted features to nullify the influence of noise in the features. Experiments were carried out based on 16 years’ historical data of three prominent stocks from three different sectors listed in Dhaka Stock Exchange (DSE), Bangladesh. The predictions were made for 1 to 4 days in advance targeting the short term prediction. For comparison, the integration of PCA with SVR (PCA-SVR), ICA with SVR (ICA-SVR) and single SVR approaches were applied to evaluate the prediction accuracy of the proposed approach. Experimental results show that the proposed model (PCA-ICA-SVR) outperforms the PCA-SVR, ICA-SVR and single SVR methods.

关键词： Financial Time Series Forecasting Support Vector Regression Principal Component Analysis Independent Component Analysis Dhaka Stock Exchange

Experimental evaluation of asphalt mixtures with emerging additives against cracking and moisture damage

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 Road Engineering 2023年第4期3卷 336-349页

作者： md.tanvir A.Sarkar Mostafa A.Elseifi Department of Civil and Environmental Engineering Louisiana State UniversityBaton RougeLA 70803USA

The objective of this study was to evaluate and recommend an asphalt mixture design with emerging additive technologies that would provide superior performance against asphalt concrete(AC)stripping and *** achieve this objective,a laboratory test program was developed to evaluate the use of nanomaterials(nanoclay and graphene nanoplatelet),an emerging anti-stripping agent(adhere),and warm-mix asphalt technologies(ZycoTherm,Sasobit,and EvoTherm).Two mix types were evaluated,which were a stone-matrix asphalt(SMA)and a dense-graded binder *** addition,the modified Lottman test(AASHTO T 283)and the indirect tensile asphalt cracking test(IDEAL-CT)test were used as performance indicators of moisture damage resistance and cracking *** were analyzed statistically to identify and quantify the effects of the design variables and selected additives on the performance,moisture damage resistance,and durability of asphalt *** on the cracking test results,a superior cracking resistance performance was observed with ZycoTherm,irrespective of the mix *** had the lowest average cracking indices for both mix types,which suggest that it would not perform as well as the other additives in terms of cracking ***,SMA mixes displayed greater cracking resistance than the dense-graded mixtures,which may have been the result of the reclaimed asphalt pavement(RAP)material used in the dense-graded mix and its lower asphalt binder *** terms of moisture resistance,both nanomaterials(graphene nanoplatelet and nanoclay)did not perform well as they did not meet the minimum required tensile strength ratio(TSR)criterion(>0.80).In addition,nanomaterials showed the lowest TSR values in both mix types suggesting that their effectiveness against moisture-induced damage may not be as good as warm-mix *** the other hand,warm-mix additives were expected to show enhanced performance in terms of moisture resistance as compared to the o

关键词： Pavement Asphalt concrete Moisture damage Cracking Laboratory testing Nanomaterials