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Aluminium and cerium co-doped ZnO nanoparticles:Facile and inexpensive synthesis and visible light photocatalytic performances

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Journal of Rare Earths 2021年第2期39卷 151-159页

作者： Irshad ahmad Muhammad Shoaib Akhtar Ejaz Ahmed Mukhtar ahmad Department of Physics Bahauddin Zakariya UniversityMultan60800Pakistan School of Computer and Communication Lanzhou University of TechnologyLanzhou 730000China

Facile combustion route synthesized Al and Ce co-doped ZnO nanoparticles photocatalysts were characterized using XRD,SEM,BET,EDS,UV-visible DRS,PL,photocurrent and EIS *** and SEM analyses identify that crystallite and particle size is reduced from 13.26 to 11.88 nm with introduction of Al and Ce into ZnO which assists inhibiting the recombination of photo generated charge *** DRS spectra indicate that optical assimilation of ZnO is significantly increased to visible region(-406 nm)and band gap reduces from 3.18 to 3.06 eV with introduction of Al and Ce *** impedance spectroscopy analysis under visible light illumination confirms the enhancement in visible light activity of Al and Ce co-doped ZnO nanoparticles as *** enhanced activity of Al and Ce co-doped ZnO photocatalyst can be ascribed to enhanced light assimilation,high surface area and efficient charge transfer *** results reveal that by incorporating precise amount of Al(~2%)and Ce(~2%)into ZnO,a highly efficient catalyst can be synthesized that have degraded almost 95%methyl orange(MO)dye in just 45 ***,the influence of various operational parameters such as solution pH,catalyst dose,dye concentration,airflow rate and light intensity on photodecomposition of MO was *** rmore,a possible mechanism for Al and Ce modified ZnO was proposed and designed photocatalysts demonstrates good stability in aqueous medium.

关键词： Nanoparticles ZnO Combustion MO decomposition PL Rare earths

Modeling and Backstepping-based Nonlinear Control Strategy for a 6 DOF Quadrotor Helicopter

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Chinese Journal of Aeronautics 2008年第3期21卷 261-268页

作者： Ashfaq ahmad Mian China Nanjing 210016 College of Automation Engineering Nanjing University of Aeronautics and Astronautics

In this article,a nonlinear model of an underactuated six degrees of freedom (6 DOF) quadrotor helicopter is derived on the basis of the Newton-Euler formalism. The derivation comprises determining equations of the motion of the quadrotor in three dimensions and approximating the actuation forces through the modeling of aerodynamic coefficients and electric motor dynamics. The derived model composed of translational and rotational subsystems is dynamically unstable,so a sequential nonlinear control strategy is used. The con-trol strategy includes feedback linearization coupled with a PD controller for the translational subsystem and a backstepping-based PID nonlinear controller for the rotational subsystem of the quadrotor. The performances of the nonlinear control method are evaluated by nonlinear simulation and the results demonstrate the effectiveness of the proposed control strategy for the quadrotor helicopter in quasi-stationary flights.

关键词： underactuated systems quadrotor helicopter backstepping control

Landsat based distribution mapping of high-altitude peatlands in Hindu Kush Himalayas–a case study of Broghil Valley, Pakistan

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Journal of Mountain Science 2020年第1期17卷 42-49页

作者： ahmad KHAN ahmad SAID Imran ULLAH Department of Geographical Sciences University of MarylandCollege ParkMD20770USA True Green Office 20 Raffaele RoadPlymouthMA 02360USA Departments of Paediatrics and Biochemistry University of TexasSouthwestern Medical CenterDallasTexas 75235USA

In the alpine regions of Hindu Kush,Himalayas and Karakorum, climatic and topographic conditions can support the formation of peat,important for the livelihood of the local communities,and ecological services alike. These peatlands are a source of fuel for the local community, habitat for nesting birds, and water regulation at source for ***-based surveys of high-altitude peatlands are not only difficult, but also expensive and time consuming. Therefore, a method using cost-effective remote sensing technology is required. In this article we assessed the distribution and extent of highaltitude peatlands in a 2000 ha area of Broghil Valley using Landsat 8 data. The composite image was trained using a priori knowledge of the area, and classified into peatland and non-peatland land covers using a supervised decision tree algorithm. The Landsat-based classification map was compared with field data collected with a differential GPS. This comparison suggests 82% overall accuracy, which is fairly high for high altitude areas. The method was successfully applied and has the potential to be replicated for other areas in Pakistan and the highaltitude regions of the neighbouring Asian countries.

关键词： Peatland distribution Chitral Qurumbar Wakhi Hindu Kush Yarkhun

Dynamic modeling and nonlinear control strategy for an underactuated quad rotor rotorcraft

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第4期9卷 539-545页

作者： Ashfaq ahmad MIAN College of Automation Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

In this paper, a nonlinear dynamic MIMO model of a 6-DOF underactuated quad rotor rotorcraft is derived based on Newton-Euler formalism. The derivation comprises determining equations of motion of the quad rotor in three dimensions and seeking to approximate the actuation forces through modeling of the aerodynamic coefficients and electric motor dynamics. The derived model is dynamically unstable, so a sequential nonlinear control strategy is implemented for the quad rotor. The control strategy includes exact feedback linearization technique, using the geometric methods of nonlinear control. The performance of the nonlinear control algorithm is evaluated using simulation and the results show the effectiveness of the proposed control strategy for the quad rotor rotorcraft near quasi-stationary flight.

关键词： Quad rotor rotorcraft MIMO model Underactuated systems

Order selection in fractional Fourier transform based beamforming

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Journal of Systems Engineering and Electronics 2010年第3期21卷 361-369页

作者： Muhammad Ishtiaq ahmad School of Information and Electronics Beijing Institute of Technology

Traditionally,beamforming using fractional Fourier transform（FrFT） involves a trial-and-error based FrFT order selection which is impractical.A new numerical order selection scheme is presented based on fractional power spectra（FrFT moment） of the linear chirp *** method can adaptively determine the optimum FrFT order by maximizing the second-order central FrFT *** makes the desired chirp signal substantially concentrated whereas the noise is rejected *** improves the mean square error minimization beamformer by reducing effectively the signal-noise cross terms due to the finite data length de-correlation *** results show that the new method works well under a wide range of signal to noise ratio and signal to interference ratio.

关键词： adaptive beamforming fractional Fourier transform (FrFT) fractional moments chirp signal.

ALLOCATING REPAIRABLE SYSTEM'S RELIABILITY SUBJECT TO MINIMAL TOTAL COST-AN INTEGER PROGRAMMING APPROACH

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Journal of Systems Science and Systems Engineering 2007年第4期16卷 499-506页

作者： ahmad A.Moreb Department of Industrial Engineering King Abdul Aziz University JeddahSaudi Arabia

Reliability allocation problem is commonly treated using a closed-form expression relating the cost to reliability. A recent approach has introduced the use of discrete integer technique for un-repairable systems. This research addresses the allocation problem for repairable systems. It presents an integer formulation for finding the optimum selection of components based on the integer values of their Mean Time to Failure （MTTF） and Mean Time to Repair （MTTR）. The objective is to minimize the total cost under a system reliability constraint, in addition to other physical constraints. Although, a closed-form expression relating the cost to reliability may not be a linear; however, in this research, the objective function will always be linear regardless of the shape of the equivalent continuous closed-form function. An example is solved using the proposed method and compared with the solution of the continuous closed-form version. The formulation for all possible system configurations, components and subsystems are also considered.

关键词： Reliability allocation cost minimization integer programming

Finite element model updating for structural damage detection using transmissibility data

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Earthquake Engineering and Engineering Vibration 2024年第1期23卷 87-101页

作者： ahmad Izadi Akbar Esfandiari Department of Maritime Engineering Amirkabir University of TechnologyTehran 15875-4413Iran

This paper presents a new finite element model updating method for estimating structural parameters and detecting structural damage location and severity based on the structural responses(output-only data).The method uses the sensitivity relation of transmissibility data through a least-squares algorithm and appropriate normalization of the extracted *** proposed transmissibility-based sensitivity equation produces a more significant number of equations than the sensitivity equations based on the frequency response function(FRF),which can estimate the structural parameters with higher *** abilities of the proposed method are assessed by using numerical data of a two-story two-bay frame model and a plate structure *** evaluating different damage cases,the number,location,and stiffness reduction of the damaged elements and the severity of the simulated damage have been accurately *** reliability and stability of the presented method against measurement and modeling errors are examined using error-contaminated *** parameter estimation results prove the method’s capabilities as an accurate model updating algorithm.

关键词： damage detection model updating output-only transmissibility sensitivity equation

Correlation between structural phase transition and physical properties of Co^(2+)/Gd^(3+)co-substituted copper ferrite

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Journal of Rare Earths 2024年第7期42卷 1344-1353,I0006页

作者： Mohsen Choupani ahmad Gholizadeh School of Physics Damghan UniversityDamghan36716-45667Iran

The doping of the spinel ferrites with selective cations usually improves the properties of the parent *** effect of Co^(2+)/Gd^(3+)co-substitution on the microstructure,optical,and magnetic properties of Cu1-xCoxFe2-xGdxO4 prepared by the citrate-nitrate auto-combustion synthesis was *** of the samples was performed with powder X-ray diffraction(XRD),Raman and Fouriertransform infrared(FTIR)spectroscopy,field-emission scanning electron microscopy,X-ray energydispersive spectroscopy,UV-Vis spectroscopy,and a vibrating sample *** results of XRD,Raman,and FTIR analysis show a gradual structural phase transition from a tetragonal(I41/amd)structure to a cubic(Fd3m)*** bandgap energy of the studied samples is in a range of 1.57-1.75 eV with a minimum in sample x=0.06 and then *** investigations show that the presence of Co^(2+)/Gd^(3+)cations in an octahedral site of the copper ferrite structure could increase saturation magnetization and coercive field from 567.9 Oe and 23.62 emu/g to 929.4 Oe and 28.27 emu/g,respectively.

关键词： Spinel copper ferrite Citrate-nitrate method Structure phase transition Microstructure properties Magnetic properties Rare earths

Class Imbalanced Problem:Taxonomy,Open Challenges,Applications and State-of-the-Art Solutions

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China Communications 2024年第11期21卷 216-242页

作者： Khursheed ahmad Bhat Shabir ahmad Sofi Department of Information Technology National Institute of TechnologyHazratbal Srinagar 190006Jammu and KashmirIndia

The study of machine learning has revealed that it can unleash new applications in a variety of *** limitations limit their expressiveness,and researchers are working to overcome them to fully exploit the power of data-driven machine learning(ML)and deep learning(DL)*** data imbalance presents major hurdles for classification and prediction problems in machine learning,restricting data analytics and acquiring relevant insights in practically all real-world research *** visual learning,network information security,failure prediction,digital marketing,healthcare,and a variety of other domains,raw data suffers from a biased data distribution of one class over the *** article aims to present a taxonomy of the approaches for handling imbalanced data problems and their comparative study on the classification metrics and their application *** have explored very recent trends of techniques employed for solutions to class imbalance problems in datasets and have also discussed their *** article has also identified open challenges for further research in the direction of class data imbalance.

关键词： class imbalance classification deep learning GANs sampling