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Structural,electrical and optical characterization of InGaN layers grown by mOVPE

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Chinese Physics B 2009年第9期18卷 4007-4012页

作者： Yildiz A ztürk m Kemal Bosi m zelik S Kasap m Physics Department University of Ahi EvranAsikpasa Kampusu mineral Analysis and Technology Department MTA ImEm-CNR Institute Area delle Scienze 37/AI-43010 FontaniniParmaItaly Physics Department University of Gazi

We present a study on n-type ternary InGaN layers grown by atmospheric pressure metalorganic vapour phase epitaxy （mOVPE） on GaN template/（0001） sapphire substrate. An investigation of the different growth conditions on n-type InxGa1-xN （x = 0.06 -- 0.135） alloys was done for a series of five samples. The structural, electrical and optical properties were characterized by high resolution x-ray diffraction （HRXRD）, Hall effect and photolumineseence （PL）. Experimental results showed that different growth conditions, namely substrate rotation （SR） and change of total H2 flow （THF）, strongly affect the properties of InGaN layers. This case can be clearly observed from the analytical results. When the SR speed decreased, the HRXRD scan peak of the samples shifted along a higher angle. Therefore, increasing the SR speed changed important structural properties of InGaN alloys such as peak broadening, values of strain, lattice parameters and defects including tilt, twist and dislocation density. From PL results it is observed that the growth conditions can be changed to control the emission wavelength and it is possible to shift the emission wavelength towards the green. Hall effect measurement has shown that the resistivity of the samples changes dramatically when THF changes.

关键词： InGaN mOVPE substrate rotation total H2 flow

Reducing damage extent of epoxy coating on magnesium substrate by zr-enhanced PEO coating as an effective pretreatment

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Journal of magnesium and Alloys 2023年第2期11卷 641-656页

作者： z.Jamshidipour m.Toorani m.Aliofkhazraei m.mahdavian Department of materials Engineering Tarbiat Modares UniversityTehranIran Department of Surface Coatings and Corrosion Institute for Color Science and Technology(ICST)TehranIran

This research was undertaken to study the effect of zr-enhanced plasma electrolytic oxidation(PEO) as a pretreatment on the corrosion performance of epoxy coating applied on magnesium in 3.5 wt.% Na Cl solution. The parameters of delamination index along with coating damage index were extracted through electrochemical impedance spectroscopy(EIS) tests to determine how zr may affect the corrosion protection of duplex PEO/epoxy coated samples. Pull-off adhesion tests were also accomplished to form a better understanding of zr-enhanced PEO coating’ function. According to the obtained results, the presence of zr can reduce the damage to the coating system by almost twice.

关键词： magnesium EIS Pretreatment PEO Epoxy zirconyl nitrate

DNS in evolution of vorticity and sign relationship in wake transition of a circular cylinder:(pure)mode A

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Acta mechanica Sinica 2019年第6期35卷 1131-1149页

作者： L.m.Lin z.R.Tan Key Laboratory for mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Navigation Wuhan University of TechnologyWuhan 430063China Hubei Key Laboratory of Inland Shipping Technology Wuhan University of TechnologyWuhan 430063China

In the present paper,the spatio-temporal evolution of vorticity in the first wake instability,i.e.,(pure)mode A,is investigated in order to understand the wake vortex dynamics and sign relationships among vorticity *** numerical simulation(DNS)for the flow past a circular cylinder is performed,typically at a Reynolds number of 200,in the three-dimensional(3-D)wake *** to characteristics of time histories of fluid forces,three different stages are identified as the computational transition,the initial stage and fully developed *** the second initial stage,the original two-dimensional spanwise vortices become obviously three-dimensional associated with the streamwise or vertical vorticity intensified up to about *** a matter of fact,these additional vorticities,caused by the intrinsic 3-D instability,are already generated firstly on cylinder surfaces early in the computational transition,indicating that the three-dimensionality appeared early near the *** evolution of additional components of vorticity with features the same as mode A shows that(pure)mode A can be already formed in the late computational *** careful analysis of the vorticity field on the front surface,in the shear layers and near wake at typical times,two sign laws are *** illustrate intrinsic relationships among three vorticity components,irrelevant to the wavelength or Fourier mode and Reynolds number in(pure)mode *** importantly,the origin of streamwise vortices is found and explained by a new physical mechanism based on the theory of vortex-induced *** a result,the whole process of formation and shedding vortices with these vorticities is firstly and completely *** characteristics are presented in detail.

关键词： Wake transition Circular cylinder Vorticity mode A Sign law

Determination of volatile organic compounds in river water by solid phase extraction and gas chromatography

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Journal of Environmental Sciences 2004年第3期16卷 497-501页

作者： m.A.mottaleb m.z.Abedin m.S.Islam Department of Chemistry Department of Chemical Technology and Polymer SciencesDepartment of Chemical Technology and Polymer Sciences University of RajshahiRajshahi 6205 BangladeshDept.of Chemistry and BiochemistryBaylor UniversityWacoUSAShahjalal University of Science and TechnologySylhet 3114BangladeshShahjalal University of Science and TechnologySylhet 3114Bangladesh

A simple, rapid, and reproducible method is described employing solid phase extraction(SPE) using dichloromethane followed by gas chromatography(GC) with flame ionization detection(FID) for determination of volatile organic compound(VOC) from the Buriganga River water of Bangladesh. The method was applied to detect the benzene, toluene, ethylbenzene, xylene and cumene(BTEXC) in the sample collected from the surface or 15 cm depth of water. Two hundred ml of n hexane pretreated and filtered water samples were applied directly to a C 18 SPE column. BTEXC were extracted with dichloromethane and average concentrations were obtained as 0 104 to 0 372 μg/ml. The highest concentration of benzene was found as 0 372 μg/ml with a relative standard deviation(RSD) of 6 2%, and cumene was not detected. Factors influencing SPE e.g., adsorbent types, sample load volume, eluting solvent, headspace and temperatures, were investigated. A cartridge containing a C 18 adsorbent and using dichloromethane gave better performance for extraction of BTEXC from water. Average recoveries exceeding 90% could be achieved for cumene at 4℃ with a 2 7% RSD.

关键词： solid phase extraction river water environmental analysis VOC recoveries

Evaluating instrumented Charpy impact strain signals using curve fitting equations

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Journal of Central South University 2014年第2期21卷 600-609页

作者： m.B.Ali S.Abdullah m.z.Nuawi A.K.Ariffin z.m.Nopiah Department of mechanical and materials Engineering Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia Department of Structure and material Faculty of Mechanical EngineeringUniversiti Teknikal Malaysia Melaka

An effective and simple way to develop equations from impact strain signals was *** research has been performed in this area,but this equation is very important for evaluating input signals in finite element analysis impact tests and for obtaining additional information on material deformation and fracture processes under impact *** this purpose,dynamic impact responses were examined through signals obtained from a strain gauge installed on an impact striker connected to a data acquisition *** 6061-T6 was used to extract strain responses on the striker during Charpy impact *** analysis was performed using the I-kaz method,and curve fitting equations based on the equation for vibration response under a non-periodic force were used to evaluate the Charpy impact *** I-kaz coefficients and curve fitting equations were then compared and discussed with related parameters,such as velocities and *** and thickness were found to be related to the strain signal patterns,curve fitting equations and I-kaz *** equations developed using this method had R2 values greater than 97.7%.Finally,the constructed equations were determined to be suitable for evaluating Charpy impact strain signal patterns and obtaining additional information on fracture processes under impact loading.

关键词： charpy impact curve fitting I-kaz signal and strain

HIGHLY ACTIVE CATALYSTS FOR CYCLOPROPANATION OF TETRAmETHYLETHYLENE

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Chinese Chemical Letters 1996年第8期7卷 739-740页

作者： zheng, z Han, m Chen, HL CHINESE ACAD SCI DALIAN INST CHEM PHYSDALIAN 116023PEOPLES R CHINA

Copper(II) Schiff base complexes derived from aromatic amine and salicylaldehyde were found to be highly active catalysts for the cyclopropanation of tetramethylethylene with ethyl diazoacetate. 82% yield of cycloprop...

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A new model for the expansion tube considering the stress coupling:Theory,experiments and simulations

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Defence Technology（防务技术） 2022年第7期18卷 1190-1204页

作者： m.z.Wu X.W.zhang Q.m.zhang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyHaidian DistrictBeijing10081China

Based on the two-arc profile assumption,the expansion deformation and energy absorption of circular tubes compressed by conical-cylindrical dies were ***,the deformation of the two arcs was analyzed independently and an improved model denoted as model-I was ***,by further involving the coupling between the bending moment and membrane forces,a more elaborate model,i.e.,model-II was ***,experiments and simulations were conducted to verify the models,which show that,compared with previous theoretical models,model-II could not only capture the prominent features of the deformation,but also improve the prediction accuracy of the steady driving force *** means of this model,it was found that the critical semi-conical angle,which makes the driving force minimum,increases with the increase of the friction coefficient,expansion ratio as well as the radius/thickness ratio of the ***,the energy dissipation due to stretching is always greater than that of bending,while the friction dissipation can account for the largest proportion at small semi-conical angle or large friction *** a certain friction and die conditions,the specific energy absorption of expanded tubes can be much higher than that under progressive collapse mode.

关键词： Expansion Circular tube Stress coupling Strain hardening Energy absorption

Infrared, Diffuse Reflectance and Dielectric Studies ofAntimony Trisulphide

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Journal of materials Science & Technology 1998年第4期14卷 344-348页

作者： Hanafi, z.m. Ismail, F.m. Khalil, m.Sh. Inorganic Chemistry Dept. National Research Centre Dokki Cairo Egypt

Infrared absorption spectra of orange, black and transferred Sb//2S//3 samples have been studied in the spectral range 200-4000 cm** minus **1. The pronounced difference between the different samples is the appearance of excess sulphur present in the orange and transferred samples except those of transferred at 543 K and the black Sb//2S//3. The change of sharpness of some IR peaks reveals the amorphous/crystalline change. The effect of the degree of crystallinity and stoichiometry on the energy gap values was investigated by using optical method. The obtained dielectric parameters epsilon prime and epsilon double prime of the different samples are thoroughly affected by the degree of crystallinity and smoothly affected by either the frequency or the temperature or both, except at lower frequencies. (Edited author abstract) 26 Refs.

关键词： Antimony compounds

Antimonene-based saturable absorber for a soliton mode-locked and Q-switched fiber laser in the 2 μm wavelength region

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Chinese Physics B 2023年第6期32卷 259-269页

作者： H Ahmad B Nizamani m z Samion N Yusoff m F Ismail Photonics Research Centre Universiti Malaya50603 Kuala LumpurMalaysia Physics Department Faculty of ScienceUniversiti Malaya50603 Kuala LumpurMalaysia Distinguished Visiting Professor Universiti Kuala Lumpur British Malaysian Institute(UniKL BMI)Batu 8Jln Sungai Pusu53100SelangorMalaysia

We demonstrate antimonene as a saturable absorber(SA) to generate an ultrafast mode-locked and Q-switched laser in the 2 μm wavelength region. The two antimonene-based SAs were prepared and inserted separately in a thulium–holmiumdoped fiber laser to produce the pulsed laser. Antimonene was coated onto a tapered fiber to generate soliton mode-locked pulses and used in thin-film form for the generation of Q-switched pulses. The mode-locking was stable within a pump power of 267 m W–511 m W, and the laser operated at a central wavelength of 1897.4 nm. The mode-locked laser had a pulse width of 1.3 ps and a repetition rate of 12.6 mHz, with a signal-to-noise ratio of 64 d B. Q-switched laser operation was stable at a wavelength of 1890.1 nm within a pump power of 312 m W–381 m W. With the increase in pump power from 312 m W to 381 m W, the repetition rate increased to a maximum of 56.63 k Hz and the pulse width decreased to a minimum value of 2.85 μs. Wide-range tunability of the Q-switched laser was also realized within the wavelength range of1882 nm–1936 nm.

关键词： mode-locking Q-switched fiber laser optical saturable absorber