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Robust Controller synthesis and Analysis in Inverter-Dominant Droop-Controlled Islanded Microgrids

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IEEE/CAA Journal of Automatica sinica 2021年第8期8卷 1401-1415页

作者： s.Mohsen Azizi school of Applied Engineering and Technology and the Department of Electrical and Computer EngineeringNew Jersey Institute of TechnologyNJ 07102 USA

This work investigates the problem of controller design for the inverters in an islanded ***-synthesis controllers and local droop controllers are designed to regulate the output voltages of inverters and share power among them,*** designed controllers alleviate the need for additional sensors to measure the states of the system by relying only on output *** is shown that the designed-synthesis controller properly damps resonant oscillations,and its performance is robust to the control-loop time delay and parameter *** stability of a droop-controlled islanded microgrid including multiple distributed generation(DG)units is analyzed by linearizing the nonlinear power flow model around the nominal operating point and applying theorems from linear *** is indicated that the droop controller stabilizes the microgrid system with dominantly inductive tie-line impedances for all values of resistive-inductive loads,while for the case of resistive-capacitive loads the stability is conditioned on an upper bound on the load *** robust performance of the designed-synthesis controller is studied analytically,compared with the similar analysis in an control(benchmark)framework,and verified by simulations for a four DG benchmark ***,the robustness of the droop controllers is analyzed by Monte Carlo simulations in the presence of local voltage fluctuations and phase differences among neighboring DGs.

关键词： Droop control inverter microgrid Monte Carlo simulation robust control μ-synthesis

study of Radially Varying Magnetic Field on Blood Flow through Catheterized Tapered Elastic Artery with Overlapping stenosis

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Communications in Theoretical Physics 2015年第11期64卷 537-546页

作者： s.Nadeem s.Ijaz Department of Mathematics Quaid-i-Azam University

A precise model has been developed for studying the inBuence of metallic nanoparticles on blood Row through catheterized tapered elastic arteries with radially varying magnetic *** model is solved under the mild stenosis approximation by considering blood as viscous *** influence of different Bow parameters associated with this problem such as Hartmann number,nanoparticle volume fraction,Grashof number and heat source or sink parameter is analyzed by plotting the graphs of the wall shear stress,resistance impedance to blood flow and stream *** inEuence of the radially varying magnetic field on resistance impedance to Bow is analyzed and it is observed that the signiBcantly strong magnetic force tends to increase in resistance.

关键词： blood flow overlapping stenosis radially varying m

setpoint Feasibility and stability of Wind Park Control Interactions at Weak Grids

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Journal of Modern Power systems and Clean Energy 2022年第6期10卷 1790-1796页

作者： Argüello Andrés IEEE the school of Electrical Engi‐neering and Computation University of CampinasCampinasBrazil

The controllers of wind parks that are connected to weak grids can induce unstable oscillations near the fundamental *** phenomenon can be studied with equivalent impedances of the wind generators,which depend on their operational setpoints at the fundamental *** feasibility of such setpoint,i.e.,solution to the power flow,does not depend on the control ***,oscillations from unfeasible setpoints and control instabilities both occur at weak grids and near the fundamental *** letter presents an exploratory study to map the conditions where both phenomena occur,using sensitivity studies comprising multiple setpoints and control parameter *** results are visually presented as the regions which inform the configurations leading to unfeasible setpoints,and unstable control interaction *** the results,it can be observed that the trajectory of the eigenvalues in the Nyquist plots towards an unfeasible setpoint approaches a fundamental frequency instability.

关键词： Control interaction impedance power quality resonance stability wind generator

Quality of service support in RPL Networks:standing state and Future Prospects

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Journal of Computer science & Technology 2022年第2期37卷 344-368页

作者： Ibrahim s.Alsukayti Department of Computer science College of ComputerQassim UniversityBuraydah 51452Saudi Arabia

The development of IP-based Internet of Things(IoT)networks would facilitate more effective end-to-end IP network architectures,but it remains a *** routing needs to be effectively addressed in the IoT environments of scarce computational and energy ***,the Internet Engineering Task Force(IETF)has specified the IPv6 Routing Protocol for Low Power and Lossy Network(RPL)to provide a bespoke IPv6-based routing framework for IoT ***,RPL comes with no Quality of service(Qos)support which is an essential requirement for many IoT *** network research community has introduced a number of research proposals enhancing RPL with different Qos *** paper presents a review of these proposed solutions and aims to establish a firm understanding of recent Qos developments for RPL and possible areas for future IoT routing *** focus is on comprehending the protocol and networking properties that can affect Qos performance in RPL *** is also given to different objective functions developed for addressing varying Qos aspects such as throughput,delay,and packet *** is also extended in a number of Qos solutions following different approaches at the MAC,network,and application ***,there is still a need for further developments to address effective Qos support,particularly for dynamic RPL networks.

关键词： Internet of Things low power and lossy network quality of service routing protocol

A chemical perspective on high pressure crystal structures and properties

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National science Review 2020年第1期7卷 149-169页

作者： John s.Tse Department of Physics and Engineering Physics University of Saskatchewan Saskatoon

The general availability of third generation synchrotron sources has ushered in a new era of high pressure research. The crystal structure of materials under compression can now be determined by X-ray diffraction using powder samples and, more recently, from multi-nano single crystal diffraction. Concurrently, these experimental advancements are accompanied by a rapid increase in computational capacity and capability,enabling the application of sophisticated quantum calculations to explore a variety of material *** of the early surprises is the finding that simple metallic elements do not conform to the general expectation of adopting 3D close-pack structures at high pressure. Instead, many novel open structures have been identified with no known analogues at ambient pressure. The occurrence of these structural types appears to be random with no rules governing their formation. The adoption of an open structure at high pressure suggested the presence of directional bonds. Therefore, a localized atomic hybrid orbital description of the chemical bonding may be appropriate. Here, the theoretical foundation and experimental evidence supporting this approach to the elucidation of the high pressure crystal structures of group Ⅰ and Ⅱ elements and polyhydrides are reviewed. It is desirable and advantageous to extend and apply established chemical principles to the study of the chemistry and chemical bonding of materials at high pressure.

关键词： high pressure crystal structure chemical bonding superconductivity

Nanosized complex fluorides based on Eu^(3+) doped sr_2LnF_7(Ln=La, Gd)

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Journal of Rare Earths 2014年第3期32卷 242-247页

作者： M.Runowski s.Balabhadra s.Lis Department of Rare Earths Faculty of Chemistry Adam Mickiewicz University

A simple co-precipitation approach taking place between Ln3＋, sr2＋ cations and F anions, led to the formation of nanocrystalline Eu3＋ doped sr2LnF7 （Ln-La and Gd） complex fluorides. The reaction was carried out in the presence of polyeth- ylene glycol, PEG 6000 as a surfactant/surface modifier, providing small size and homogeneity of the products. The synthesized compounds were composed of small nanoparticles with an average size of 15 nm. All obtained Eu3＋ doped compounds exhibited an intensive red luminescence. In the case of gadolinium based compounds, the energy transfer phenomena could be observed from Gd3＋ ions to Eu3＋ ions. In order to study the structure and morphology of the synthesized fluorides, powder X-ray diffraction （XRD） and transmission electron microscopy （TEM） measurements were performed. Also FT-IR spectra of the products were re- corded, revealing the presence of PEG molecules on the nanoparticles suN＇ace. A spectrofluorometry technique was applied to examine optical properties of the synthesized nanoparticles. Excitation and emission spectra as well as luminescence decay curves were measured and analysed. The performed analysis revealed a red luminescence, typical for the Eu3＋ ion situated in the inorganic, highly symmetric matrix. Concentration quenching phenomena and lifetimes shortening, together with an increasing of the Eu3＋ doping level, were observed and discussed. Judd-Ofelt analysis was also performed for all doped samples, in order to support the registered spectroscopic data and examine in details structural and optoelectronic properties of the synthesized nanomaterials.

关键词： luminescence Eu3+ doping complex strontium lanthanide fluorides nanoparticles sr2LnF7 sr0.69La0.31F2.31 rare earths

Condition assessment of structures under unknown support excitation

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Earthquake Engineering and Engineering Vibration 2009年第1期8卷 103-114页

作者： Zhang Kun s. s. Law Duan Zhongdong school of Civil Engineering Harbin Institute of Technology Harbin 150090 China Civil and structural Engineering Department Hong Kong Polytechnic University Hung Hom Kowloon Hong Kong China

A new method is proposed to assess the condition of structures under unknown support excitation by simultaneously detecting local damage and identifying the support excitation from several structural dynamic responses. The support excitation acting on a structure is modeled by orthogonal polynomial approximations, and the sensitivities of structural dynamic response with respect to its physical parameters and orthogonal coefficients are derived. The identification equation is based on Taylor＇s first order approximation, and is solved with the damped least-squares method in an iterative procedure. A fifteen-story shear building model and a five-story three-dimensional steel frame structure are studied to validate the proposed method. Numerical simulations with noisy measured accelerations show that the proposed method can accurately detect local damage and identify unknown support excitation from only several responses of the structure. This method provides a new approach for detecting structural damage and updating models with unknown input and incomplete measured output information.

关键词： condition assessment damage detection support excitation identification dynamic response sensitivity

Hidden periodicity in stripe 82 with saraswati supercluster—a fractal analysis

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Communications in Theoretical Physics 2021年第1期73卷 71-77页

作者： Vimal Raj M s swapna s sankararaman Department of Optoelectronics University of KeralaTrivandrumKerala695581-India

The manuscript attempts to explore the periodicity in the distribution of galaxies in the recently reported saraswati supercluster and the stripe 82 region containing it as an *** report of 120 Mpc periodicity in the Abell galaxy clusters by power spectrum analysis is the motivation behind the *** power spectral analysis across the central part of the stripe 82 region shows a periodic variation of 3.09°or 71 Mpc in fractal dimension whereas an average angular periodicity of 3.45°or 94 Mpc is observed across the stripe 82 *** refers to the periodicity of complexity or cluster density of galaxy *** texture of the distribution pattern understood through lacunarity analysis indicates a near symmetric *** dimensions like box-counting dimension,information dimension and correlation dimension are also found through multifractal *** the information dimension tells about the distribution density of galactic points,the correlation dimension details the distribution of galaxies in the neighbourhood.

关键词： galaxy distribution fractal analysis multifractals lacunarity saraswati supercluster stripe 82

strip Casting of High Performance structural Alloys

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Journal of Rare Earths 2004年第z2期22卷 78-84页

作者： s s Park J G Lee Nack J Kim Center for Advanced Aerospace Materials Pohang University of Science and TechnologyPohang 790-784Korea Center for Advanced Aerospace MaterialsPohang University of Science and TechnologyPohang 790-784Korea Center for Advanced Aerospace MaterialsPohang University of Science and TechnologyPohang 790-784Korea

There exists a great need for the development of high performance alloys due to increasing demands for energy conservation and environmental protection. Application of strip casting shows a strong potential for the improvement of properties of existing alloys and also for the development of novel alloy systems with superior properties. The present paper reviews our Center's activities in the development of high performance alloys by strip casting. Examples include (1) Al alloys, (2) wrought Mg alloys, and (3) bulk metallic glass (BMG) alloys.

关键词： strip casting 6061 Al alloy AZ Mg alloy bulk metallic glass (BMG) alloy dispersion hardening