检索结果-南通市图书馆

Er^(3+)/Yb^(3+)/Li^+/Zn^(2+):Gd_2(MoO_4)_3 upconverting nanophosphors in optical thermometry

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2019年第3期37卷 242-247页

作者： Anita kumari Lakshmi Mukhopadhyay vineet kumar Rai Laser and Spectroscopy Laboratory Department of Applied Physics Indian Institute of Technology (Indian School of Mines)

Er^(3+)-Yb^(3+)-Li^+:Gd_2(MoO_4)_3 and Er^(3+)-Yb^(3+)-Zn^(2+):Gd_2(MoO_4)_3 nanophosphors, synthesized by chemical co-precipitation technique were characterized through XRD,FESEM,dynamic light scattering(DLS),diffuse reflectance, photoluminescence, photometric and decay time analysis. The enhancement of about～28, ～149 and ～351 times in the green upconversion emission band is observed for the optimized Er^(3+)-Yb^(3+),Er^(3+)-Yb^(3+)-Li^+ and Er^(3+)-Yb^(3+)-Zn^(2+):Gd_2(MoO_4)_3 nanophosphors in comparison to the singly Er^(3+) doped nanophosphors. The electric dipole-dipole interaction is found to be responsible for the concentration quenching. The temperature dependent behaviour of the two green thermally coupled levels of the Er^(3+) ions based on the fluorescence intensity ratio technique was studied. The maximum sensor sensitivity ～38.7 × 10^(-3) K^(-1) at 473 K for optimized Er^(3+)-Yb^(3+)-Zn^(2+) codoped Gd_2(MoO_4)_3 nanophosphors is reported with maximum population redistribution ability～88% among the ~2H_(11/2) and ~4S_(3/2) levels.

关键词： Upconversion Phosphors Dynamic light scattering Non-lanthanide ions Optical thermometry Rare earths

Parallel Fuzzy P+Fuzzy I+Fuzzy D Controller:Design and Performance Evaluation

在线全文

学校读者我要写书评

暂无评论

International Journal of Automation and computing 2010年第4期7卷 463-471页

作者： vineet kumar A.P.Mittal Department of Instrumentation and Control Engineering Netaji Subhash Institute of TechnologySector-3

In this paper, a parallel fuzzy proportional plus fuzzy integral plus fuzzy derivative （FP＋FI＋FD） controller is proposed. It is derived from the conventional parallel proportional-integral-derivative （PID） controller. It preserves the linear structure of a conventional parallel PID controller, with analytical formulas. The final shape of the controller is a discrete-time fuzzy version of a conventional parallel PID controller. Computer simulations are performed to evaluate the performance of the FP＋FI＋FD controller for setpoint tracking and load-disturbance rejection for some complex processes, such as first- and second-order processes with delay, inverse response process with and without delay and higher order processes. Also, the performance of the proposed fuzzy controller is evaluated experimentally on highly nonlinear liquid-flow process with a hysteresis characteristic due to a pneumatic control valve. The simulation and real time control is done using National InstrumentTM hardware and software （LabVIEWTM）. The response of the FP＋FI＋FD controller is compared with the conventional parallel PID controller, tuned with the Ziegler-Nichols （Z-H） and /~strSm- H^gglund （A-H） tuning technique. It is observed that the FP＋FI＋FD controller performed much better than the conventional PI/PID controller. Simulation and experimental results demonstrate the effectiveness of the proposed parallel FP＋FI＋FD controller.

关键词： Proportional-integral-derivative (PID) fuzzy proportional plus fuzzy integral plus fuzzy derivative (FP+FI+FD) controller liquid-flow process inverse response process dead time.

Er^(3+)-Yb^(3+)-Na^(+):ZnWO_(4) phosphors for enhanced visible upconversion and temperature sensing applications

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2021年第3期39卷 291-296,I0002页

作者： Sonali Biswas Lakshmi Mukhopadhyay Manisha Mondal vineet kumar Rai Laser and Spectroscopy Laboratory Department of PhysicsIndian Institute of Technology(Indian School of Mines)Dhanbad-826004JharkhandIndia

The crystal structure and surface morphology of the Er^(3+)/Yb^(3+)/Na+:ZnWO_(4) phosphors synthesized by solid state reaction method were analyzed by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM) *** frequency upconversion(UC) emission study in the developed phosphors was investigated by using 980 nm laser diode *** effect of codoping in the Er^(3+):ZnWO_(4) phosphors on the UC emission intensity was *** UC emission bands that are exhibited in the blue(490 nm),green(530,552 nm),red(668 nm) and NIR(800 nm) region correspond to the ^(4)F_(7/2)→^(4)I_(15/2).^(2)H_(11/2),^(4)S_(3/2)→^(4)I_(15/2),^(4)F_(9/2)→^(4)I_(15/2) and ^(4)I9/2→^(4)I_(15/2) transitions,*** temperature sensing performance of the Er^(3+)-Yb^(3+)-Na+:ZnWO_(4) phosphors was investigated based on the 2 H_(11/2)→^(4)I_(15/2) and ^(4)S_(3/2)→^(4)I_(15/2) thermally coupled transitions of the Er^(3+)*** photometric study was also carried out for the developed phosphors.

关键词： Upconversion Non-lanthanides Temperature sensing Fluorescence intensity ratio Rare earths

RTV silicone rubber composites reinforced with carbon nanotubes,titanium-di-oxide and their hybrid:Mechanical and piezoelectric actuation performance

在线全文

学校读者我要写书评

暂无评论

Nano Materials Science 2021年第3期3卷 233-240页

作者： vineet kumar Anuj kumar Sung Soo Han Sang-Shin Park School of Mechanical Engineering Yeungnam UniversitySouth Korea School of Chemical Engineering Yeungnam UniversitySouth Korea

The use of nanofillers with high surface area and extreme purity in polymer composite is an effective strategy to obtain high performance polymeric ***,the effect of nanofillers such as carbon nanotubes(CNT),titanium dioxide(TiO_(2)),and their hybrid on rubber-based composites was *** this study,rubber nanocomposites were fabricated by using room temperature vulcanized(RTV)silicone rubber matrix and nanofillers(***,TiO_(2),and CNT-TiO_(2))through solution casting ***,the purity and surface area of CNT(purity:>96%and BET surface area:300 m2/g)and TiO_(2)(purity:>98%and BET surface area:165 m2/g)were estimated by field emission scanning electron microscopy/energy dispersive X-ray(FESEM-EDX)and adsorption *** mechanical properties of the rubber nanocomposites were enhanced by incorporating *** compressive modulus was 2.18 MPa for unfilled composites and increased to 6.8 MPa(CNT),3.95 MPa(CNT-TiO_(2)),and 2.44 MPa(TiO_(2))at 5 phr,***,the tensile strength was 0.54 MPa for unfilled composites and increased to 1.37 MPa(CNT),1.33 MPa(CNT-TiO_(2))and 0.61 MPa(TiO_(2))at 5 phr,***,the actuation displacement was improved with increasing input voltage and it was 2 mm for CNT,1.6 mm for CNT-TiO_(2) hybrid and 0.5 mm for TiO_(2) at 10 ***,a series of experiments show the potential application in piezoelectric actuation.

关键词： Multi-walled carbon nanotubes Titanium dioxide Hybrid Mechanical properties Piezoeletric actuation

Some Investigations on Hybrid Fuzzy IPD Controllers for Proportional and Derivative Kick Suppression

在线全文

学校读者我要写书评

暂无评论

International Journal of Automation and computing 2016年第5期13卷 516-528页

作者： vineet kumar K.P.S.Rana Division of Instrumentation and Control Engineering Netaji Subhas Institute of Technology(NSIT)

Proportional and derivative kick i.e., a large change in control action of a proportional plus integral plus derivative （PID） controller due to a sudden change in reference set-point is generally undesired in process industry. Therefore, the structure of conventional parallel PID controller is modified to integral minus proportional derivative （I-PD） controller. In this paper, three hybrid fuzzy IPD controllers such as a fuzzy I-fuzzy PD （FI-FPD） controller and its hybrid combinations with its conventional counterpart such as fuzzy I-PD （FI-PD） and I-fuzzy PD （I-FPD） are presented in view of above industrial problem. These controllers are based upon the counterpart conventional I-PD controller and contains analytical formulae. Computer simulations are carried out to evaluate the performance of hybrid fuzzy controllers along with conventional I-PD and PID controllers for set-point tracking and disturbance rejection for an induction motor in closed loop using LabVIEWTM environment. The gains of conventional and hybrid fuzzy controllers are tuned using genetic algorithm （GA） for minimum overshoot and settling time. It has been observed that hybrid fuzzy controllers along with the conventional I-PD controller significantly remove the kick from the control action in reference set-point tracking. However, in disturbance rejection, I-PD and FI-PD controllers fail to eliminate the kick from the control signal. In contrast, FI-FPD and I-FPD controllers considerably reduced spikes from the control action in disturbance rejection. Among the conventional and hybrid fuzzy IPD controllers, FI--FPD demonstrates much better set-point tracking and disturbance rejection response with spike free control action.

关键词： Proportional plus integral plus derivative (PID) integral minus proportional derivative (I-PD) hybrid fuzzy IPD con- troller proportional kick derivative kick.

Stability Analysis of Parallel Fuzzy P + Fuzzy I + Fuzzy D Control Systems

在线全文

学校读者我要写书评

暂无评论

International Journal of Automation and computing 2013年第2期10卷 91-98页

作者： vineet kumar A. P. Mittal R. Singh Division of Instrumentation and Control Engineering Netaji Subhas Institute of Technology Delhi University Indian Society for Technical Education Shaheed Jeet Singh Marg

The study presented in this paper is in continuation with the paper published by the authors on parallel fuzzy proportional plus fuzzy integral plus fuzzy derivative （FP ＋ FI ＋ FD） controller. It addresses the stability analysis of parallel FP ＋ FI ＋ FD controller. The famous＂small gain theorem＂ is used to study the bounded-input and bounded-output （BIBO） stability of the fuzzy controller. Sufficient BIBO-stability conditions are developed for parallel FP ＋ FI ＋ FD controller. FP ＋ FI ＋ FD controller is derived from the conventional parallel proportional plus integral plus derivative （PID） controller. The parallel FP ＋ FI ＋ FD controller is actually a nonlinear controller with variable gains. It shows much better set-point tracking, disturbance rejection and noise suppression for nonlinear processes as compared to conventional PID controller.

关键词： Proportional plus integral plus derivative (PID) fuzzy proportional plus fuzzy integral plus fuzzy derivative (FP + FI + FD) controller fuzzy control bounded-input and bounded-output (BIBO) stability nonlinear process.

Improved Fracture Toughness of Cryorolled and Room Temperature Rolled 6082 Al Alloys

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2014年第2期27卷 359-367页

作者： vineet kumar I.V.Singh B.K.Mishra R.Jayaganthan Department of Mechanical and Industrial Engineering Indian Institute of Technology Department of Metallurgical and Materials Engineering Indian Institute of Technology

In the present work, 6082 Al alloy has been rolled to 40% and 70% thickness reductions at the cryogenic and room temperatures for the improvement in mechanical and fracture toughness properties. All cryorolled samples are subjected to aging at different temperatures, i.e., 140, 160, and 190 ℃ to improve the strength, ductility, and fracture toughness. The microstructures of the cryorolled （CR） and room temperature rolled （RTR） alloy after 40% and 70% thickness reductions are characterized by FE-SEM to reveal the modes of failure. The results show that the starting bulk Al alloy specimen is fractured in total ductile manner, consisting of well-developed dimples over the entire surface. The mechanical properties and fracture toughness of the 70% CR alloy are found better than 70% RTR alloy due to higher dislocations density and formation of sub-grain structures in the CR alloy.

关键词： 6082 Al alloy Rolling Mechanical properties Fracture toughness J-Integral Material characterization

Indian stock market prediction using artificial neural networks on tick data

在线全文

学校读者我要写书评

暂无评论

Financial Innovation 2019年第1期5卷 267-278页

作者： Dharmaraja Selvamuthu vineet kumar Abhishek Mishra Department of Mathematics Indian Institute of Technology DelhiHauz KhasNew Delhi 110016India

Introduction:Nowadays,the most significant challenges in the stock market is to predict the stock *** stock price data represents a financial time series data which becomes more difficult to predict due to its characteristics and dynamic *** description:Support Vector Machines(SVM)and Artificial Neural Networks(ANN)are widely used for prediction of stock prices and its *** algorithm has its way of learning patterns and then *** Neural Network(ANN)is a popular method which also incorporate technical analysis for making predictions in financial *** and evaluation:Most common techniques used in the forecasting of financial time series are Support Vector Machine(SVM),Support Vector Regression(SVR)and Back Propagation Neural Network(BPNN).In this article,we use neural networks based on three different learning algorithms,i.e.,Levenberg-Marquardt,Scaled Conjugate Gradient and Bayesian Regularization for stock market prediction based on tick data as well as 15-min data of an Indian company and their results ***:All three algorithms provide an accuracy of 99.9%using tick *** accuracy over 15-min dataset drops to 96.2%,97.0%and 98.9%for LM,SCG and Bayesian Regularization respectively which is significantly poor in comparison with that of results obtained using tick data.

关键词： Neural Networks Indian Stock Market Prediction Levenberg-Marquardt Scale Conjugate Gradient Bayesian Regularization Tick by tick data

A Robust Fractional Order Fuzzy P ＋ Fuzzy I ＋ Fuzzy D Controller for Nonlinear and Uncertain System

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

International Journal of Automation and computing 2017年第4期14卷 474-488页

作者： vineet kumar K. P. S. Rana Jitendra kumar Puneet Mishra Sreejith S Nair Division of Instrumentation and Control Engineering Netaji Subhas Institute of Technology (NSIT) University of Delhi New Delhi 110078 India

In this paper, a robust fractional order fuzzy P ＋ fuzzy I ＋ fuzzy D （FOFP ＋ FOFI ＋ FOFD） controller is presented for a nonlinear and uncertain 2-1ink planar rigid manipulator. It is a nonlinear fuzzy controller with variable gains that makes it self- adjustable or adaptive in nature. The fractional order operators further make it more robust by providing additional degrees of freedom to the design engineer. The integer order counterpart, fuzzy P ＋ fuzzy I ＋ fuzzy D （FP ＋ FI ＋ FD） controller, for a comparative study, was realized by taking the integer value for the fractional order operators in FOFP ＋ FOFI ＋ FOFD controller. The performances of both the fuzzy controllers are evaluated for reference trajectory tracking and disturbance rejection with and without model uncertainty and measurement noise. Genetic algorithm was used to optimize the parameters of controller under study for minimum integral of absolute error. Simulation results demonstrated that FOFP ＋ FOFI ＋ FOFD controller show much better performance as compared to its counterpart FP ＋ FI ＋ FD controller in servo as well as the regulatory problem and in model uncertainty and noisy environment FOFP ＋ FOFI ＋ FOFD controller demonstrated more robust behavior as compared to the FP ＋ FI ＋ FD controller. For the developed controller bounded-input and bounded-output stability conditions are also developed using Small Gain Theorem.

关键词： Fuzzy P + fuzzy I + fuzzy D (FP + FI + FD) controller fractional order fuzzy P + fuzzy I + fuzzy D (FOFP + FOFI+ FOFD) controller fractional order operator robust control model uncertainty noise suppression.