检索结果-南通市图书馆

Fabrication method and microstructural characteristics of coal-tar-pitchbased 2D carbon/carbon composites

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2015年第2期22卷 210-216页

作者： Mohammad Esmaeeli Hamed Khosravi alireza Mirhabibi School of Metallurgy and Materials Engineering Iran University of Science and Technology Faculty of Materials Science and Engineering K. N. Toosi University of Technology

The lignin-cellulosic texture of wood was used to produce two-dimensional （2D） carbon/carbon （C/C） composites using coal tar pitch. Ash content tests were conducted to select two samples among the different kinds of woods present in lran, including walnut, white poplar, cherry, willow, buttonwood, apricots, berry, and blue wood. Walnut and white poplar with ash contents of 1.994wt% and 0.35 lwt%, respectively, were selected. The behavior of these woods during pyrolysis was investigated by differential thermal analysis （DTA） and thermo gravimetric （TG） analysis. The bulk density and open porosity were measured after carbonization and densification. The mierostruc- tural characteristics of samples were investigated by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and Fourier-transform infrared （FT-IR） spectroscopy. The results indicate that the density of both the walnut and white poplar is increased, and the open porosity is decreased with the increasing number of carbonization cycles. The XRD patterns of the wood charcoal change gradually with increasing py- rolysis temperature, possibly as a result of the ultra-structural changes in the charcoal or the presence of carbonized coal tar pitch in the composite＇s body.

关键词： carbon/carbon composites microstructure porosity density densification carbonization

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

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

Power system flexibility: an overview of emergence to evolution

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

Inhibition Behaviour of 2-butinel,4diol and Tartrate Salt,and Their Synergistic Effects on Corrosion of AA3003 Aluminium Alloy in 0.5% NaCl Solution

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2008年第3期24卷 427-432页

作者： Taghi Shahrabi alireza Yazdzad Mirghasem Hosseini Department of Materials Engineering Faculty of EngineeringTarbiat Modares University Department of Physical chemistry Faculty of ChemistryTabriz University

This work intends to investigate the inhibition behaviour of 2-butine 1, 4diol and potassium sodium tartrate and their synergistic effects on 3003 aluminium alloy corrosion in 0.5% NaCl solution. Experiments were carried out by electrochemical impedance spectroscopy （EIS） and Tafel polarization method in a three-electrode cell. It was concluded that the inhibition efficiencies increased with an increase in the concentrations of inhibitors. For 2-butinel, 4diol and tartrate salt, the optimum in the inhibition efficiency, at room temperature and neutral pH, was observed for concentrations close to 10-3 mol/L and 1.5×10^-3mol/L, respectively. The electrochemical results illustrated that 2-butinel, 4diol and tartrate salt, have significant synergistic inhibition effects on corrosion of 3003 aluminium alloy in 0.5% NaCl solution. The optimum ratio of concentrations for tartrate to alcohol was 2：1.

关键词： Inhibitor 3003 aluminium alloy 2-butinel 4diol Tartrate salt

Effect of Active Gas on Weld Shape and Microstructure of Advanced A-TIG-Welded Stainless Steel

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2016年第3期29卷 295-300页

作者： Reza Nakhaei alireza Khodabandeh Hamidreza Najafi Department of Materials Engineering Tehran Science and Research BranchIslamic Azad University

Advanced A-TIG method was conducted to increase the weld penetration and compared with the conventional TIG welding process.A two-pipeline setup was designed to apply Ar ＋ CO_2 mixed gas as the outer layer,while pure argon was applied as the inner layer to prevent any consumption of the tungsten *** results indicate that the presence of active gas in the molten pool led to the change in the temperature coefficient of surface tension so that the Marangoni convection turns inward and forms a deep weld *** increase in gas flow rate causes a decrease in the weld efficiency which is attributed to the increase in oxygen content in the weld pool and the formation o f a thicker oxide layer on the weld ***,the stir and the temperature fluctuation,led by double shielding gas,create more homogeneous nucleation sites in the molten pool so that a fine grain micros true ture was obtained.

关键词： Advanced A-TIG welding Weld metal Active gas Microstructure Marangoni convection