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干旱环境对哀牢山中山湿性常绿阔叶林土壤呼吸的影响

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西部林业科学 2020年第3期49卷 109-116页

作者：徐刚郭子豪袁朝祥巩合德西南林业大学地理与生态旅游学院云南昆明655024

长期的干旱会对土壤呼吸造成十分显著的影响。为了解2010年初西南地区特大干旱对云南哀牢山中山湿性常绿阔叶林土壤呼吸的影响,通过人工控制降雨时间的长短来模拟不同的干旱环境,利用红外CO2分析法收集和测算3个试验组土壤呼吸速率的数... 详细信息

长期的干旱会对土壤呼吸造成十分显著的影响。为了解2010年初西南地区特大干旱对云南哀牢山中山湿性常绿阔叶林土壤呼吸的影响,通过人工控制降雨时间的长短来模拟不同的干旱环境,利用红外CO2分析法收集和测算3个试验组土壤呼吸速率的数据,并分析了不同干旱环境下,土壤呼吸的变化规律及其主要的影响因素。结果表明:(1)哀牢山中山湿性常绿阔叶林土壤呼吸表现出明显的干季低、雨季高的季节性变化特点[CK组干季土壤呼吸速率平均值1.51μmol/(m^2·s)、雨季5.03μmol/(m^2·s)],土壤呼吸呈单峰曲线;(2)不同干旱环境中,土壤呼吸速率与土壤含水量和土壤温度的变化,均呈正相关,将单因素关系模型(Rs=aebT或Rs=aW+b)和双因素关系模型(Rs=aebTWc)。的拟合结果对比表明,单因子土壤含水量对土壤呼吸的变化存在极其显著影响(P<0.01)。干旱环境对哀牢山中山湿性常绿阔叶林土壤呼吸存在影响,土壤含水量处于较低水平时,水分成为影响土壤呼吸最主要的因素。对比CK组,模拟轻度干旱环境(DL组)的年度平均土壤呼吸速率减少了35.4%,模拟重度干旱环境(DH组)减少了62.08%,且截雨设施拆除后的DL组仍明显少于CK组。

关键词：土壤呼吸土壤温度温度敏感性干旱

Dielectric Function of Silicon Nanoclusters: Role of Hydrogen

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Chinese Physics Letters 2011年第9期28卷 241-244页

作者： SIB KRISHNA Ghoshal m.R.Sahar m.S.Rohani Advanced Optical material Research Group Department of PhysicsFaculty of ScienceUniversiti Teknologi Malaysia81310 UTM SkudaiJohorMalaysia

Electronic and optical properties of small silicon quantum dots having 3 to 44 atoms per dot with and without surface passivation are investigated by computer simulation using the pseudo-potential *** empirical pseudo-potential Hamiltonian,a plane-wave basis expansion and a basic tetrahedral structure with undistorted local bonding configurations are *** structures of the quantum dots are relaxed and optimized before and after hydrogen *** is found that the gap increases more for a hydrogenated surface than the unpassivated ***,both quantum confinement and surface passivation determine the optical and electronic properties of Si quantum *** luminescence is probably due to the radiative recombination of electrons and holes in the quantum-confined *** effect of passivation of the surface dangling bonds by hydrogen atoms and the role of surface states on the gap energy is also *** results for the density of states,the dielectric function,the frequency dependent optical absorption cross section,the extinction coefficient and the static dielectric constants of the size are *** importance of the confinement and the role of surface passivation on the optical effects are discussed.

关键词： quantum dielectric extinction

The changing landscape of mangroves in Bangladesh compared to four other countries in tropical regions

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Journal of Forestry Research 2014年第3期25卷 605-611页

作者： S.m.mijan Uddin A.T.m.Rafiqul Hoque Saiful Arif Abdullah Institute of Forestry and Environmental Sciences University of Chittagong Institute for Environment and Development (LESTARI) National University of Malaysia (UKM)

Loss of mangroves and consequent habitat fragmentation is a major concern throughout the world’s tropical countries. Conversion of mangrove habitat due to aquaculture, agriculture, urbanization and industrialization, ecotourism, overlapping bureaucracy and conflicting policies is occurring at a striking rate. This paper reviews the trends of mangrove area changes in Bangladesh and compares them with four other countries in tropical regions that have significant mangrove areas. The rate of mangrove loss from the 1980 to 2005 was calculated using the compound interest rate formula for its explicit biological implication. In Bangladesh, the area of mangroves was found to have increased due to its higher accretion rate. In India the rate of mangrove loss had fallen. The rate of mangrove loss in malaysia in the 1990s （-0.008 ha＆#183;a-1） was higher than the 1980s （-0.004 ha＆#183;a-1）. In Indonesia, the rate decreased, from the 1980s （-0.018 ha＆#183;a-1） to the 1990s （-0.010 ha＆#183;a-1）. Finally in myanmar the rate of mangrove loss gradually accelerated. Aquaculture was found to be the common cause of mangrove conversion in the regions. Loss of mangroves is now a prominent global issue, associated with the loss of biodiversity, deterioration of habitat integrity, climatic changes, the amount of carbon sequestration, and resulting sea-level rise. Therefore, a systematic evaluation of these environmental impacts is prerequisite to realize sustainable mangrove management.

关键词： mangrove loss accretion aquaculture mangrove landscape land-use change.

mixed convection stagnation-point flow on vertical stretching sheet with external magnetic field

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Applied mathematics and mechanics(English Edition) 2014年第2期35卷 155-166页

作者： F.m.ALI R.NAZAR N.m.ARIFIN I.POP Department of mathematics & Institute for mathematical Research Universiti Putra Malaysia UPM School of mathematical Sciences Faculty of Science & TechnologyUniversitiKebangsaan Malaysia UKM Department of mathematics Babes-Bolyai University

The problem of steady laminar magnetohydrodynamic （mHD） mixed con- vection stagnation-point flow of an incompressible viscous fluid over a vertical stretch- ing sheet is studied. The effect of an externally magnetic field is taken into account. The transformed boundary layer equations are solved numerically by using an implicit finite-difference scheme. Numerical results are obtained for various values of the mixed convection parameter, Hartmann number, and Prandtl number. The effects of an exter- nally magnetic field on the skin friction coefficient, local Nusselt number, velocity, and temperature profiles for both A 〉 1 and A ~ 1, where A is the velocity ratio parameter, are presented graphically and discussed in detail. Both assisting and opposing flows are considered, and it is found that dual solutions exist for the opposing flow.

关键词： boundary layer mixed convection magnetohydrodynamic (mHD) numer-ical result stagnation-point stretching sheet

Comparison Study of Two Commercial Spectrometers for Heavy metal Analysis of Laser Induced Breakdown Spectroscopy （LIBS）

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Photonic Sensors 2014年第1期4卷 63-69页

作者： m.Arab N.Bidin Z.H.Rizvi S.Safie m.A.Alsaedi Advance Photonics Science Institute Faculty of ScienceUniversiti Teknologi Malaysia81310Johor BahruJohorMalaysia

The purpose of this paper is to compare the performance of two spectrometers that are manufactured from the same company. In this work, heavy metals like lead Pb and copper Cu in the KBr matrix were analyzed using the laser induced breakdown spectroscopic technique. A Q-switched Nd：YAG laser with 90mJ per pulse operating at the fundamental wavelength of 1064nm and pulse duration of 10 ns was used to generate plasma at the focal region. The important experimental parameters such as the laser energy, integration time, distance between the lens and sample, distance and angle of the optical fiber from the target were optimized. Two spectrometers manufactured by Ocean Optics namely as maya2000Pro and USB 4000 were employed for anlyzing the spectral lines. The experimental setup and conditions were remained the same for both experiments. The production of spectral lines from each of the interested elements was analyzed and compared with the NIST （National Institute of Standards and Technology） database. The sensitivity, repeatability and limit of detection for each of the systems are discussed in detail.

关键词： Heavy metal spectrometer LIBS LOD

Optical Investigation of Sm^(3+) Doped Zinc-Lead-Phosphate Glass

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Chinese Physics Letters 2012年第8期29卷 233-236页

作者： Raja J.Amjad m.R.Sahar S.K.Ghoshal m.R.Dousti S.Riaz B.A.Tahir Advanced Optical material Research Group Faculty of ScienceUniversiti Teknologi Malaysia81310 SkudaiJohorMalaysia Centre for Solid State Physics University of the PunjabQACLahore-54590Pakistan

Samarium doped lead-zinc-phosphate glasses having composition(60-x)P_(2)O_(5)-20PbO-20ZnO-xSm_(2)O_(3) where x=0,0.5,1.0,3.0mol%were prepared by using the melt quenching *** Archimedes method was used to measure their densities,which are used to calculate the molar *** values of densities lie in the range 3.698–4.090 gm/cm^(3) whereas those of molar volume lie in the range of 37.24–40.00 cm^(-3).UV-vis-NIR absorption spectroscopy in the wavelength range 200–2000 nm was carried *** spectra consist of seven absorption peaks corresponding to the transitions from the 6H5/2 ground state to various excited energy *** energy band gap measured from the optical absorbance is found to be in the range of 3.88–4.43 eV and 3.68–4.33 eV for direct and indirect transitions,*** addition,the photoluminescence spectrum shows four prominent emission bands centered at 560,597,642 and 700 nm corresponding to the 4G5/2–6HJ(J=5/2,7/2,9/2,11/2)transitions respectively and the intensity of all the bands are enhanced as the concentration of Sm3+ions increases.

关键词： technique transitions bands

Influence of Cu content on microstructure and mechanical properties of thixoformed Al-Si-Cu-mg alloys

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Transactions of Nonferrous metals Society of China 2015年第11期25卷 3523-3538页

作者： m.S.SALLEH m.Z.OmAR Department of mechanical and materials Engineering Faculty of Engineering and Built Environment Universiti Kebangsaan Malaysia Department of manufacturing Process Faculty of Manufacturing Engineering Universiti Teknikal Malaysia Melaka

The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3mg(x= 3,4,5and 6,mass fraction,%) alloys were *** samples were thixoformed at 50%liquid content and several of the samples were treated with the T6 heat *** samples were then examined by optical microscopy(Om),scanning electron microscopy(SEm),energy dispersive X-ray(EDX) spectroscopy and X-ray diffraction(XRD) analysis,as well as hardness and tensile *** results show that the cooling slope casting and thixoforming process promote the formation of very fine and well distributed intermetallic compounds in the aluminium matrix and the mechanical properties of the alloys increase considerably compared with the permanent mould *** results also reveal that as the Cu content in the alloy increases,the hardness and tensile strength of the thixoformed alloys also *** ultimate tensile strength,yield strength and elongation to fracture of the thixoformed heat-treated Al-6Si-3Cu-0.3mg alloy are 298 mPa,201 mPa and 4.5%,respectively,whereas the values of the thixoformed heat-treated alloy with high Cu content(6%) are 361 mPa,274 mPa and 1.1%,*** fracture of the thixoformed Al-6Si-3Cu-0.3mg alloy shows a dimple rupture,whereas in the alloy that contains the highest Cu content(6%),a cleavage fracture is observed.

关键词： Al-Si-Cu-mg alloy Cu content thixoforming T6 heat treatment mechanical properties

microstructural evolution and mechanical properties of thixoformed A319 alloys containing variable amounts of magnesium

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Transactions of Nonferrous metals Society of China 2016年第8期26卷 2029-2042页

作者： m.S.SALLEH m.Z.OmAR K.S.ALHAWARI m.N.mOHAmmED m.A.mAD ALI E.mOHAmAD Department of manufacturing Process Faculty of Manufacturing Engineering Universiti Teknikal Malaysia Melaka Department of mechanical and materials Engineering Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia Department of Engineering and Technology Faculty of Information Sciences and EngineeringManagement and Science University

The effects of mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (Om), scanning electron microscopy (SEm), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9Femg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 mPa, 201 mPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% mg content were 325 mPa, 251 mPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.

关键词： aluminium alloy thixoforming T6 heat treatment mechanical properties

From pollutant to solution of wastewater pollution: Synthesis of activated carbon from textile sludge for dye adsorption

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Chinese Journal of Chemical Engineering 2018年第4期26卷 870-878页

作者： Syieluing Wong Nurul Atiqah Najlaa Yac'cob Norzita Ngadi Onn Hassan Ibrahim m.Inuwa Faculty of Chemical and Energy Engineering Universiti Teknologi Malaysia Department of Industrial Chemistry Kaduna State University

Adsorption is an important process in wastewater treatment,and conversion of waste materials to adsorbent offers a solution to high material cost related to the use of commercial activated *** study investigated the adsorption behaviour of Reactive Black 5（RB5）and methylene blue（mB）onto activated carbon produced from textile sludge（TSAC）.The activated carbon was synthesized through chemical activation of precursor followed with carbonization at 650℃ under nitrogen *** of time（0–200 min）,pH（2–10）,temperature（25–60℃）,initial dye concentration（0–200 mg·L^-1）,and adsorbent dosage（0.01–0.15 g）on dye removal efficiency were *** screening revealed that TSAC synthesized via H2SO4activation showed higher adsorption behaviour than TSAC activated by KCl and *** adsorption capacity of TSAC was found to be 11.98 mg·g^-1（RB5）and 13.27 mg·g^-1（mB）,and is dependent on adsorption time and initial dye *** adsorption data for both dyes were well fitted to Freundlich isotherm model which explains the heterogeneous nature of TSAC *** dye adsorption obeyed pseudo-second order kinetic model,thus chemisorption was the controlling *** study reveals potential of textile sludge in removal of dyes from aqueous solution,and further studies are required to establish the applicability of the synthesized adsorbent for the treatment of waste water containing toxic dyes from textile industry.

关键词： Activated carbon Textile sludge Reactive Black 5 methylene blue Adsorption