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Broadrange tunable slow and fast light in quantum dot photonic crystal structure

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Chinese Physics B 2017年第12期26卷 283-289页

作者： alireza Lotfian Reza Yadipour Hamed Baghban Department of Electrical and Computer Engineering University of Tabriz Tabriz *** Iran School of Engineering-Emerging Technologies University of Tabriz Tabriz *** Iran

Slow and fast light processes, based on both structural and material dispersions, are realized in a wide tuning range in this article. Coherent population oscillations （CPO） in electrically tunable quantum dot semiconductor optical amplifiers lead to a variable group index ranging from the background index （nbgd） to^30. A photonic crystal waveguide is then dispersion engineered and a group index of 260 with the normalized delay-bandwidth product （NDBP） of 0.65 is achieved in the proposed waveguide. Using comprehensive numerical simulations, we show that a considerable enhancement of slow light effect can be achieved by combining both the material and the structural dispersions in the proposed active QDPCW structure. We compare our developed FDTD results with analytical results and show that there is good agreement between the results, which demonstrates that the proposed electrically-tunable slow light idea is obtainable in the QDPCW structure. We achieve a total group index in a wide tuning range from nbgd to^1500 at the operation bandwidth, which shows a significant enhancement compared with the schemes based only on material or structural dispersions. The tuning range and also NDBP of the slow light scheme are much larger than those of the electrically tunable CPO process.

关键词： photonic crystal quantum dot slow light semiconductor optical amplifier

Intracavity configuration for tuning and obtaining simultaneous dual-wavelength operation from CW Nd:YAG laser

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Chinese Optics Letters 2011年第7期9卷 55-58页

作者： alireza Khorsandi Saeed Ghavami Sabouri Department of Physics Isfahan University

In this letter, a thin slab of glass is used as Fabry-Perot etalon inside a cavity of a continuous wave （CW） Nd：YAG laser to change the behavior of its output longitudinal modes. The slab etalon is used as tuning element when it turns around the laser cavity axis. Two simultaneous longitudinal modes with a relatively wide tuning range from 5.83 MHz to 0,02 THz are obtained when the Nd：YAG laser is operated at moderate output power of about 120 roW. The mode structure of this configuration is modeled and simulated. Computer-generated diagrams are also presented schematically and compared with the experimental results.

关键词： YAG Intracavity configuration for tuning and obtaining simultaneous dual-wavelength operation from CW Nd Nd CW

The influence of environmental variables on distribution patterns of Irano-Turanian forests in Alborz Mountains, Iran

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Journal of Mountain Science 2016年第8期13卷 1375-1386页

作者： Hooman RAVANBAKHSH alireza MOSHKI Faculty of Desert Studies Semnan University

Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topographic parameters can affect the tree and shrub communities. Initially, 27 forest stands were identified and the homogeneous units were separated regarding physiognomy. In each single homogeneous unit, one random sample plot （1000 m^2） and totally 43 plots were established. In each plot, the presence and abundance of all trees and shrubs were recorded and four soil samples were taken from depths of 0-5 and 5-20 cm. Concerning classification results, eight different forest communities were identified. The lowest and highest soil pH values were observed in Malus orientalis and pistacia-Amygdalus communities, respectively. The water saturation percent of pure- and mixed Juniperus excelsa and Rhus coriaria was the highest amongst communities. The clay content was the highest in pure ***. The 0-5 organic matter and Nitrogen content in mixed J. excelsa were significantly higher than pure J. excelsa and other communities. The CCA （Canonical Correspondence Analysis） altitude, precipitation, pH, results indicated that the EC, SP, clay and CaCO3 are the most important factors determine the distribution of trees and shrub in central Alborz.

关键词： Irano-Turanian Mountainouswoodlands Multivariate analysis Species-environment relationship

Power system flexibility: an overview of emergence to evolution

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Journal of Modern Power Systems and Clean Energy 2019年第5期7卷 987-1007页

作者： alireza AKRAMI Meysam DOOSTIZADEH Farrokh AMINIFAR School of Electrical and Computer Engineering College of EngineeringUniversity of TehranTehranIran Faculty of Engineering Lorestan UniversityKhorramabadIran

Power systems are evolving to the networks with proliferated penetration of renewable energy resources to leverage their environmental and economic advantages However,due to the stochastic nature of renewables,the management of the rapidly increasing uncertainty and variability in power system planning and operation is of crucial *** paper represents a comprehensive overview of power system flexibility as an effective way to maintain the power balance at every *** of power system flexibility from various aspects are explained to reach the reliable and economic planning and operation of the power *** effects of the high penetration of variable energy resources on power systems and the evolution of flexibility in response to renewables are studied.A variety of resources during the flexibility evolutionary transition are introduced and *** an influential flexibility solution in current power systems integrated with renewable resources,market design improvement is widely reviewed in this paper,and required modifications in market design mechanisms are investigated pertaining to various time horizons.

关键词： Power system flexibility Renewable energy resources Ancillary services Electricity market design

Effect of Deep Cryogenic Heat Treatment on the Wear Behavior of Carburized DIN 1.7131 Grade Steel

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Acta Metallurgica Sinica(English Letters) 2015年第3期28卷 348-353页

作者： Kamran Amini alireza Araghi Amin Akhbarizadeh Department of Materials Science Majlesi BranchIslamic Azad University Department of Materials Science and Engineering Shiraz BranchIslamic Azad University

The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were *** show that cryogenic heat treatment reduced the retained austenite and increased the carbide *** addition,after the cryogenic heat treatment,carbide shows a more uniform distribution,as compared to the conventionally treated *** was also clarified that the hardness of the cryogenically treated samples was improved,but the relative improvement decreases with the distance as the surface *** has been shown that the wear resistance improves due to the cryogenic heat treatment,and the predominant wear mechanism is a combination of the adhesive and tribo-chemical wear.

关键词： DIN 1.7131 grade steel Carburized steel Hardness Deep cryogenic heat treatment Tribo-chemical wear

Proposing a novel geo-structural model for Torbat-e-Jam-Fariman plain(Northeast of Iran),based on Geomorphic indices calculation,conjugating the field evidences

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Journal of Mountain Science 2023年第5期20卷 1385-1401页

作者： Mohsen JAMI alireza DOCHESHMEH GORGIJ Mining Engineering Group Industry and Mining Faculty(khash)University of Sistan and Baluchesan+009854IRAN

There are various faults in northern and southern margins of Torbat-e-Jam-Fariman plain which show the probability of enormous earthquake in the *** present study the geomorphic indices contain Asymmetry Function(Af),Sinuosity of mountain front(Smf),Valley floor index(Vf),Hypsometric index(Hi),Mean Axial slope of channel index(MASC)and Drainage Basin Shape(Bs),have been utilized to determine the relative tectonic activity index(IAT)to recognize,eventually,the geo-structural model of the study *** and folds control the geo-structural activities of the study area,and the geomorphic indices are being affected in consequence of their *** intensity of these activities is different throughout the *** are many geomorphic evidences,related to active transform fault which are detectable all over the study area such as deviated rivers,quaternary sediments transformation,fault ***,recognition of geo-structural model of the study area is extremely *** study,then,approved the results of geomorphic indices calculation in determining the geo-structural model of the study *** depicted that the geostructural model of the study area is a kind of Horsetail splay form which is in accordance to the relative tectonic activity of the study *** on the above mentioned results it can be predicted that the splays are the trail of Neyshabour fault.

关键词： Fault Geo-structural Model Relative tectonic activity Geomorphic indices Horsetail Splay

Optimization of total harmonic current distortion and torque pulsation reduction in high-power induction motors using genetic algorithms

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第12期9卷 1741-1752页

作者： Arash SAYYAH Mitra AFLAKI alireza REZAZADEH Department of Electrical and Computer Engineering University of Illinois at Urbana-ChampaignUrbanaIL 61801USA Graduate School of Management and Economics Sharif University of TechnologyTehranIran Department of Electrical and Computer Engineering Shahid Beheshti UniversityTehranIran

This paper presents a powerful application of genetic algorithm （GA） for the minimization of the total harmonic current distortion （THCD） in high-power induction motors fed by voltage source inverters, based on an approximate harmonic model. That is, having defined a desired fundamental output voltage, optimal pulse patterns （switching angles） are determined to produce the fundamental output voltage while minimizing the THCD. The complete results for the two cases of three and five switching instants in the first quarter period of pulse width modulation （PWM） waveform are presented. Presence of harmonics in the stator excitation leads to a pulsing-torque component. Considering the fact that if the pulsing-torques are at low frequencies, they can cause troublesome speed fluctuations, shaft fatigue, and unsatisfactory performance in the feedback control system, the 5th, 7th, 1 lth, and 13th current harmonics （in the case of five switching angles） are constrained at some pre-specified values, to mitigate the detrimental effects of low-frequency harmonics. At the same time, the THCD is optimized while the required fundamental output voltage is maintained.

关键词： Induction motor Genetic algorithm (GA) Optimization Pulse width modulation (PWM) Torque pulsation Totalharmonic current distortion (THCD)

Monitoring the security of audio biomedical signals communications in wearable IoT healthcare

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Digital Communications and Networks 2023年第2期9卷 393-399页

作者： Saeid Yazdanpanah Saman Shojae Chaeikar alireza Jolfaei Department of Computer Engineering Khorramabad BranchIslamic Azad UniversityKhorramabadIran Australian Institute of Higher Education SydneyAustralia College of Science and Engineering Flinders UniversityAdelaideAustralia

Smart home devices are vulnerable to a variety of *** matter gets more complicated when a number of devices collaborate to launch a colluding attack(e.g.,Distributed-Denial-of-Service(DDoS))in a network(e.g.,Smart home).To handle these attacks,most studies have hitherto proposed authentication protocols that cannot necessarily be implemented in devices,especially during Device-to-Device(D2D)*** into the potential of Ethereum blockchain and smart contracts,this work proposes a lightweight authentication mechanism that enables safe D2D interactions in a smart *** Ethereum blockchain enables the implementation of a decentralized prototype as well as a peer-to-peer distributed ledger *** work also uses a single server queuing system model and the authentication mechanism to curtail DDoS attacks by controlling the number of service requests in the *** simulation was conducted twenty times,each with varying number of devices chosen at random(ranging from 1 to 30).Each requester device sends an arbitrary request with a unique resource requirement at a *** is done to measure the system's consistency across a variety of device *** experimental results show that the proposed protocol not only prevents colluding attacks,but also outperforms the benchmark protocols in terms of computational cost,message processing,and response times.

关键词： DDoS attack Device-to-device Smart homes Blockchain Authentication Ethereum smart contract

H_∞ Consensus Control of Discrete-Time Multi-Agent Systems Under Network Imperfections and External Disturbance

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IEEE/CAA Journal of Automatica Sinica 2019年第3期6卷 667-675页

作者： Arezou Elahi alireza Alfi Hamidreza Modares IEEE the Faculty of Electrical and Robotic Engineering Shahrood University of Technology the Department of Mechanical Engineering at Michigan State University

This paper presents a distributed control protocol for consensus control of multi-agent systems(MASs) under external disturbances and network imperfections, including communication delay and random packet dropout. To comply with the discrete nature of networked systems, in contrast to most of the existing work for MASs under network imperfections,the agents are modeled by discrete-time dynamics. The communication network is considered to be undirected, its delay is considered to be time-varying but bounded, and its packet dropout is modeled by a Bernoulli distributed white *** conditions in terms of linear matrix inequalities(LMIs)for asymptotic mean-square consensus stability are derived under network imperfections without considering external disturbances.A desired disturbance attenuation level in the presence of both external disturbances and network imperfections is also provided.A simulation example is given to verify the effectiveness of the proposed approach in coping with network imperfection and disturbances.

关键词： Consensus distributed control H∞ control packet dropout stability time delay