检索结果-南通市图书馆

Acta Metallurgica Sinica(English Letters) 2015年第2期28卷 159-163页

作者： Hassan Waqas Ammad Hussain Qureshi Muhammad Shahzad Materials Division Directorate of Technology PINSTECH

Current investigation deals with the effect of grain growth process as a function of sintering temperature on the electromagnetic properties （initial permeability, impedance, and gain） of Mn-Zn ferrite （MZF） cores （toroids）. By employing auto combustion process, nanosized [（20 ± 5） nm] MZF powders were synthesized and toroid shape cores were obtained after subsequent calcination and firing （sintering） process. It was observed that the submicron structure （0.5 μm） achieved in the ferrite core sintered at 1,000 ℃ was gradually transformed into micron size grains by increasing the firing temperature i.e., 1,100, 1,200, and 1,350 ℃. The results reveal that MZF core sintered at low temperature （1,000 ℃） showed high impedance, low initial permeability, and narrow working frequency range i.e., 3-15 MHz. However, the improvement in initial permeability, sintered density, and operational frequency range （100 kHz-17 MHz） was observed at high temperature （1,350 ℃） firing in the inert environment. This synthesized MZF core is more suitable for miniaturized switch mode power supply applications.

关键词： Mn-Zn ferrites Nanosized powders Impedance Sintering

The Use of High-Performance Fatigue Mechanics and the Extended Kalman/Particle Filters,for Diagnostics and Prognostics of Aircraft Structures

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2015年第5期105卷 1-24页

作者： Hai-Kun Wang Robert Haynes Hong-Zhong Huang Leiting Dong Satya N.Atluri School of Mechanical Electronicand Industrial EngineeringUniversity of Electronic Science and Technology of China Center for Aerospace Research&Education University of CaliforniaIrvine vehicle technology directorate US Army Research Laboratory Department of Hohai University China

In this paper,we propose an approach for diagnostics and prognostics of damaged aircraft structures,by combing high-performance fatigue mechanics with filtering ***&accurate deterministic analyses of fatigue crack propagations are carried out,by using the Finite Element Alternating Method(FEAM)for computing SIFs,and by using the newly developed Moving Least Squares(MLS)law for computing fatigue crack growth *** algorithms for simulating fatigue crack propagations are embedded in the computer program Safe-Flaw,which is called upon as a subroutine within the probabilistic framework of filter *** the extended Kalman as well as particle filters are applied in this study,to obtain the statistically optimal and semi-optimal estimates of crack lengths,from a series of noisy measurements of crack-lengths over *** the specific problem,a simple modification to the particle filter,which can drastically reduce the computational burden,is also *** on the results of such diagnostic analyses,the prognostics of aerospace structures are thereafter achieved,to estimate the probabilistic distribution of the remaining useful *** using a simple example of a single-crack near a fastener hole,we demonstrate the concept and effectiveness of the proposed *** paper thus forms the scientific foundation for the recently proposed concepts of VRAMS(Virtual Risk-Informed Agile Maneuver Sustainment)and Digital Twins of aerospace vehicles.

关键词： Diagnostics and prognostics fatigue mechanics extended Kalmanfilter particle filter

Resilient Fault Diagnosis Under Imperfect Observations–A Need for Industry 4.0 Era

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

IEEE/CAA Journal of Automatica Sinica 2020年第5期7卷 1279-1288页

作者： Alejandro White Ali Karimoddini Mohammad Karimadini IEEE vehicle technology directorate CCDC Army Research LaboratoryAberdeen Proving GroundMD 21005 USA Department of Electrical and Computer Engineering North Carolina Agricultural and Technical State UniversityGreensboroNC 27411 USA Department of Electrical Engineering Arak University of TechnologyArak ***Iran

In smart industrial systems,in many cases,a fault can be captured as an event to represent the distinct nature of subsequent ***-based fault diagnosis techniques are capable model-based methods for diagnosing faults from a sequence of observable events executed by the system under *** event-based diagnosis techniques rely on perfect observations of observable ***,in practice,it is common to miss an observable event due to a problem in sensorreadings or communication/transmission *** paper develops a fault diagnosis tool,referred to as diagnoser,which can robustly detect,locate,and isolate occurred *** developed diagnoser is resilient against missed observations.A missed observation is detected from its successive sequence of *** detecting a missed observation,the developed diagnoser automatically resets and then,asynchronously resumes the diagnosis *** is achieved solely based on postreset/activation observations and without interrupting the performance of the system under *** concepts of asynchronous detectability and asynchronous diagnosability are *** is shown that if asynchronous detectability and asynchronous diagnosability hold,the proposed diagnoser is capable of diagnosing occurred faults under imperfect *** proposed technique is applied to diagnose faults in a manufacturing *** examples are provided to explain the details of the proposed *** result paves the way towards fostering resilient cyber-physical systems in Industry4.0 context.

关键词： Cyber-physical systems discrete event systems fault diagnosis imperfect communication imperfect observation Industry 4.0 resilience

Nonlinear Bayesian Estimation： From Kalman Filtering to a Broader Horizon

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2018年第2期5卷 401-417页

作者： Huazhen Fang Ning Tian Yebin Wang Meng Chu Zhou Mulugeta A. Haile IEEE Department of Mechanical Engineering University of Kansas Lawrence KS 66045 USA Mitsubishi Electric Research Laboratories Cambridge MA 02139 USA the Helen and John C. Hartmann Department of Electrical and Computer Engineering New Jersey Institute of Technology Newark NJ 07102 USA the vehicle technology directorate US Army Research Laboratory Aberdeen MD 21005 USA

This article presents an up-to-date tutorial review of nonlinear Bayesian estimation. State estimation for nonlinear systems has been a challenge encountered in a wide range of engineering fields, attracting decades of research effort. To date,one of the most promising and popular approaches is to view and address the problem from a Bayesian probabilistic perspective,which enables estimation of the unknown state variables by tracking their probabilistic distribution or statistics(e.g., mean and covariance) conditioned on a system's measurement *** article offers a systematic introduction to the Bayesian state estimation framework and reviews various Kalman filtering(KF)techniques, progressively from the standard KF for linear systems to extended KF, unscented KF and ensemble KF for nonlinear systems. It also overviews other prominent or emerging Bayesian estimation methods including Gaussian filtering, Gaussian-sum filtering, particle filtering and moving horizon estimation and extends the discussion of state estimation to more complicated problems such as simultaneous state and parameter/input estimation.

关键词： Index Terms-Kalman filtering (KF) nonlinear Bayesian esti-mation state estimation stochastic estimation.

A possible approach to reduce the emittance of HLS- storage ring using a Robinson wiggler

在线全文

学校读者我要写书评

暂无评论

Chinese Physics C 2013年第10期37卷 99-104页

作者：李京祎刘功发徐卫李为民李永军 National Synchrotron Radiation Laboratory University of Science and Technology of China Photon Science directorate Brookhaven National Laboratory

In this paper, we present some preliminary studies on using a Robinson wiggler to reduce the horizontal beam emittance in the Hefei Light Source II （HLS-II） storage ring. A proof-of-principle lattice demonstrates that it is possible to reduce its emittance by 50% with a 2-meter long wiggler. This encouraging result suggests a feasible option to significantly improve the machine performance at a relatively low cost.

关键词： storage ring emittance Robinson wiggler

Prediction of Vibration Characteristics in Beam Structure Using Sub-Scale Modeling with Experimental Validation

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2015年第5期28卷 928-934页

作者： ZAI Behzad Ahmed SAMI Saad KHAN M Amir AHMAD Furqan PARK Myung Kyun Structure Design and Development directorate Institute of Space Technology Department of Civil and Environmental Engineering KAIST Department of Mechanical Engineering Myongji University

Geometric or sub-scale modeling techniques are used for the evaluation of large and complex dynamic structures to ensure accurate reproduction of load path and thus leading to true dynamic characteristics of such structures. The sub-scale modeling technique is very effective in the prediction of vibration characteristics of original large structure when the experimental testing is not feasible due to the absence of a large testing facility. Previous researches were more focused on free and harmonic vibration case with little or no consideration for readily encountered random vibration. A sub-scale modeling technique is proposed for estimating the vibration characteristics of any large scale structure such as Launch vehicles, Mega structures, etc., under various vibration load cases by utilizing precise scaled-down model of that dynamic structure. In order to establish an analytical correlation between the original structure and its scaled models, different scale models of isotropic cantilever beam are selected and analyzed under various vibration conditions（ i.e. free, harmonic and random） using finite element package ANSYS. The developed correlations are also validated through experimental testing The prediction made from the vibratory response of the scaled-down beam through the established sets of correlation are found similar to the response measured from the testing of original beam structure. The established correlations are equally applicable in the prediction of dynamic characteristics of any complex structure through its scaled-down models. This paper presents modified sub-scale modeling technique that enables accurate prediction of vibration characteristics of large and complex structure under not only sinusoidal but also for random vibrations.

关键词： sub-scale modeling resonance frequency vibration characteristics scale factors power spectral density

Green synthesis of bentonite-supported iron nanoparticles as a heterogeneous Fenton-like catalyst:Kinetics of decolorization of reactive blue 238 dye

在线全文

学校读者我要写书评

暂无评论

Water Science and Engineering 2020年第4期13卷 286-298页

作者： Ahmed Khudhair Hassan Ghayda Yaseen Al-Kindi Dalal Ghanim Environment and Water directorate Ministry of Science and TechnologyBaghdad 10070Iraq Sanitary and Environmental Branch Civil Engineering DepartmentUniversity of TechnologyBaghdad 10009Iraq

This study aimed to synthesize green tea nano zero-valent iron(GT-NZVI)and bentonite-supported green tea nano zero-valent iron(BGT-NZVI)nanoparticles using green tea extracts in an environmentally sustainable *** was used as a support material because it disperses and stabilizes GT-NZVI,and it helps to reduce the cost,increase the adsorption capacity of GT-NZVI,and decrease the optimum amount of GT-NZVI used in Fenton-like oxidation.A scanning electron microscope,an atomic force microscope,and a Fourier transform infrared spectroscope were used to characterize GT-NZVI and B-GT-NZVI,while the zeta potential was measured to evaluate the stability of iron *** decolorization kinetics of reactive blue 238(RB 238)dye in the aqueous phase in the Fenton-like oxidation process were investigated as *** effects of various experimental conditions such as reaction time,dosages of catalysts,concentration of H2O2,temperature,addition of inorganic salts,and other parameters were *** results show that the oxidative degradation efficiencies of RB 238 dye catalyzed by GT-NZVI and B-GT-NZVI were 93.5%and 96.2%,respectively,at the optimum reaction conditions as follows:c(H2O2)¼5 mmol/L,r(GT-NZVI)¼0.5 g/L or r(B-GT-NZVI)¼0.5 g/L,c(RB 238 dye)¼0.05 mmol/L,and pH¼2.5 at 180 *** best catalytic performance was exhibited when B-GT-NZVI was *** kinetic models were employed,and the second-order model was found to be the best model representing the experimental kinetic data of RB 238 *** value of activation energy decreased from 38.22 kJ/mol for GT-NZVI to 14.13 kJ/mol for *** indicates that the effect of B-GT-NZVI in decreasing the energy barrier is more pronounced than that of the GT-NZVI catalyst,leading to improved Fenton-like oxidation processes.©2020 Hohai *** and hosting by Elsevier *** is an open access article under the CC BY-NC-ND license(http://***/licenses/by-nc-nd/4.0/).

关键词： Green synthesis Bentonite-supported iron nanoparticles Azo dye Fenton-like process Kinetics

Machine Learning-based Stable P2P IPTV Overlay

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2022年第6期71卷 5381-5397页

作者： Muhammad Javid Iqbal Ihsan Ullah Muhammad Ali Atiq Ahmed Waheed Noor Abdul Basit directorate of Information technology Sardar Bahadur Khan Women’s UniversityQuettaPakistan Department of Computer Science and Information technology University of BalochistanQuettaPakistan

Live video streaming is one of the newly emerged services over the Internet that has attracted immense interest of the service *** Internet was not designed for such services during its inception,such a service poses some serious challenges including cost and ***-to-Peer(P2P)Internet Protocol Television(IPTV)is an application-level distributed paradigm to offer live video *** terms of ease of deployment,it has emerged as a serious alternative to client server,Content Delivery Network(CDN)and IP multicast ***,P2P approach has struggled to provide the desired streaming quality due to a number of *** of peers in a network is one of themajor issues among *** of the existing approaches address this issue through older-stable *** paper first extensively investigates the older-stable principle to observe its validity in different *** is observed that the older-stable principle does not hold in several of ***,it utilizes machine learning approach to predict the stability of *** work evaluates the accuracy of severalmachine learning algorithms over the prediction of stability,where the Gradient Boosting Regressor(GBR)out-performs other ***,this work presents a proof-of-concept simulation to compare the effectiveness of older-stable rule and machine learning-based predictions for the stabilization of the *** results indicate that machine learning-based stability estimation significantly improves the system.

关键词： P2P IPTV live video streaming user behavior overlay networks stable peers machine learning

Ab initio prediction of fast non-equilibrium transport of nascent polarons in SrI2: a key to high-performance scintillation

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

npj Computational Materials 2016年第1期2卷 77-83页

作者： Fei Zhou Babak Sadigh Paul Erhart Daniel Åberg Physical and Life Sciences directorate Lawrence Livermore National LaboratoryLivermoreCAUSA Department of Physics Chalmers University of TechnologyGothenburgSweden

The excellent light yield proportionality of europium-doped strontium iodide(SrI2:Eu)has resulted in state-of-the-artγ-ray detectors with remarkably high-energy resolution,far exceeding that of most halide *** this class of materials,the formation of self-trapped hole polarons is very ***,polaron formation is usually expected to limit carrier mobilities and has been associated with poor scintillator light-yield proportionality and *** using a recently developed first-principles method,we perform an unprecedented study of polaron transport in SrI2,both for equilibrium polarons,as well as nascent polarons immediately following a self-trapping *** propose a rationale for the unexpected high-energy resolution of *** identify nine stable hole polaron configurations,which consist of dimerised iodine pairs with polaron-binding energies of up to 0.5 *** are connected by a complex potential energy landscape that comprises 66 unique nearest-neighbour migration *** initio molecular dynamics simulations reveal that a large fraction of polarons is born into configurations that migrate practically barrier free at room ***,carriers created duringγ-irradiation can quickly diffuse away reducing the chance for nonlinear recombination,the primary culprit for non-proportionality and resolution *** conclude that the flat,albeit complex,landscape for polaron migration in SrI2 is a key for understanding its outstanding *** insight provides important guidance not only for the future development of high-performance scintillators but also of other materials,for which large polaron mobilities are crucial such as batteries and solid-state ionic conductors.

关键词： polaron equilibrium iodine

Assessing Lateral Continuity within the Yammama Reservoir in the Foroozan Oilfield, Offshore Iran: An Integrated Study

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

Acta Geologica Sinica(English Edition) 2018年第6期92卷 2405-2415页

作者： Payam HASSANZADEH Ahmad Reza RABBANI Ardeshir HEZARKHANI Saeed KHAJOOIE Department of Petroleum Engineering Amirkabir University of Technology Department of Mining and Metallurgy Engineering Amirkabir University of Technology Department of Reservoir Engineering Exploration Directorate of National Iranian Oil Company (NIOC-EXP)

Located in Iranian sector of the Persian Gulf, Foroozan Oilfield has been producing hydrocarbons via seven different reservoirs since the 1970 s. However, understanding fluid interactions and horizontal continuity within each reservoir has proved complicated in this field. This study aims to determine the degree of intra-reservoir compartmentalization using gas geochemistry, light hydrocarbon components, and petroleum bulk properties, comparing the results with those obtained from reservoir engineering indicators. For this purpose, a total of 11 samples of oil and associated gas taken from different producing wells in from the Yammama Reservoir were selected. Clear distinctions, in terms of gas isotopic signature and composition, between the wells located in northern and southern parts of the reservoir(i.e. lighter δ13 C1, lower methane concentration, and negative sulfur isotope in the southern part) and light hydrocarbon ratios(e.g. nC 7/toluene, 2,6-dmC7/1,1,3-tmcyC5 and m-xylene/4-mC8) in different oil samples indicated two separate compartments. Gradual variations in a number of petroleum bulk properties(API gravity, V/Ni ratios and asphaltene concentration) provided additional evidence on the reservoir-filling direction, signifying that a horizontal equilibrium between reservoir fluids across the Yammama Reservoir is yet to be achieved. Finally, differences in water-oil contacts and reservoir types further confirmed the compartmentalization of the reservoir into two separate compartments.

关键词： reservoir compartmentalization gas geochemistry light hydrocarbons reservoir engineering Yammama Reservoir Foroozan Oilfield Iran