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Agricultural Sciences in China 2009年第10期8卷 1270-1275页

作者： M Najiah S w Lee w wendy L w Tee M Nadirah S H Faizah Department of Fisheries Science and Aquaculture Faculty of Agrotechnology and Food Science Universiti Malaysia Terengganu Institute of Tropical Aquaculture Universiti Malaysia Terengganu Faculty of Agro Industry and Natural Resources Universiti Malaysia Kelantan

A total of 140 bacterial isolates have been successfully isolated from various organs of diseased American bullfrog （Rana catesbeiana） cultured in Malaysia. The most frequently isolated bacteria was Edwardsiella spp. （46 isolates） followed by Aeromonas spp. （33 isolates）, Flavobacterium spp. （31 isolates）, and Vibrio spp. （30 isolates）. Majority of the bacterial isolates were found sensitive to furazolidone （85.0%）, chloramphenicol （85.0%）, oxolinic acid （90.0%）, florfenicol （95.0%）, and flumequine （97.5%）. On the other hand, most of the bacterial isolates were resistant to oleandomycin （77.5%） and lincomycin （87.5%）. Nitrofurantoin and flumequine can be inhibited the growth of all of Vibrio spp. whereas all isolates of Edwardsiella spp. were found sensitive to florfenicol and flumequine. Multiple antibiotic resistance （MAR） index were in range of 0.30-0.40, indicating that bacterial isolates from cultured bullfrogs may have received high risk exposure to the tested antibiotics. In addition, 90-100% of the isolates were resistant to copper, cadmium, and chromium. These results provided insight information on tolerance level of bacterial isolates from cultured bullfrogs to 21 antibiotics as well as heavy metals.

关键词： Rana catesbeiana MAR index Edwardsiella Aeromonas Flavobaeterium Vibrio antibiotic resistance,heavy metal tolerance

Effects of longwall-induced stress and deformation on the stability and mechanical integrity of shale gas wells drilled through a longwall abutment pillar

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International Journal of Mining Science and Technology 2017年第1期27卷 115-120页

作者： Daniel w.H.Su National Institute for Occupational Safety and Health Bruceton 15236PAUSA

This paper presents the results of a comprehensive study conducted by CONSOL Energy, Marcellus Shale Coalition, and Pennsylvania Coal Association to evaluate the effects of longwall-induced subsurface deformations on the mechanical integrity of shale gas wells drilled over a longwall abutment *** primary objective is to demonstrate that a properly constructed gas well in a standard longwall abutment pillar can maintain mechanical integrity during and after mining operations. A study site was selected over a southwestern Pennsylvania coal mine, which extracts 457-m-wide longwall faces under about 183 m of cover. Four test wells and four monitoring wells were drilled and installed over a 38-m by84-m centers abutment pillar. In addition to the test wells and monitoring wells, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457-m-wide longwall panels on the south and north sides of the abutment pillar were mined by. To evaluate the resulting coal protection casing profile and lateral displacement, three separate 60-arm caliper surveys were conducted. This research represents a very important step and initiative to utilize the knowledge and science obtained from mining research to improve miner and public safety as well as the safety and health of the oil and gas industries.

关键词： Gas well Casing Abutment pillar Stability Safety and health Instrumentation Numerical simulation

Particle size effect on ammonium perchlorate decomposition kinetics

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航空动力学报 2012年第5期27卷 1179-1184页

作者： Abdel-wareth w XU Xu School of Astronautics Beijing University of Aeronautics and AstonauticeBeijing 100191China

The decomposition kinetic parameters of ammonium perchlorate(AP) having different grain size(10-390 μ m) were investigated through simultaneous DSC / TGA(differential scanning calorimetry / thermal gravimetric analysis) analyzer in a dynamic nitrogen atmosphere under heating rate of 40K / *** kinetic parameters such as activation energy and pre-exponential factor were determined by the modified isoconversional *** Brurzauer-Emmett-Teller(BET)-method was applied to measure AP specific surface *** results show that the higher the AP particle size the lower the determined kinetic parameters and are matched with some important literatures.

关键词： ammonium perchlorate particle size specific surface area thermal decomposition thermogravimetry

Spin switching in antiferromagnets using Néel-order spin-orbit torques

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Chinese Physics B 2018年第10期27卷 88-95页

作者： P wadley K w Edmonds School of Physics and Astronomy University of Nottingham

Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to spin–orbit coupling in environments with particular crystalline or structural symmetries, the electric current can induce an effective magnetic field with a sign that alternates on the lengthscale of the unit cell. The staggered effective field provides an efficient mechanism for switching antiferromagnetic domains and moving antiferromagnetic domain walls, with writing speeds in the terahertz regime.

关键词： spintronics antiferromagnetic current-induced torques magnetic domains

Stability and nonlinear vibrations of a flexible pipe parametrically excited by an internal varying flow density

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Acta Mechanica Sinica 2020年第1期36卷 206-219页

作者： w.D.Xie X.F.Gao w.H.Xu State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin30072China

Pipes are often used to transport multiphase flows in many engineering *** total fluid flow density inside a pipe may vary with time and *** this paper,a simply supported pipe conveying a variable density flow is modeled theoretically,and its stability and nonlinear vibrations are investigated in *** variation of the flow density is simulated using a mathematical *** equation governing the vibration of the pipe is derived according to Euler-Bernoulli beam *** the internal flow density varies with time,the pipe is excited *** stability of the pipe is determined by Floquet *** simple parametric and combination resonances are *** a higher mass ratio(mean flow mass/pipe structural mass),higher flow velocity,or smaller end axial tension,the pipe becomes unstable more easily due to wider parametric resonance *** the subcritical flow velocity regime,the vibrations of the pipe are periodic and quasiperiodic for simple and combination resonances,***,in the supercritical regime,the vibrations of the pipe exhibit much richer dynamics including periodic,multiperiodic,quasiperiodic,and chaotic behaviors.

关键词： Pipe Varying flow density Parametric excitation Stability Nonlinear vibrations

Effect of different water supply on morphology, growth and physiological characteristics of Salix psammophila seedlings in Maowusu sandland, China

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Journal of Environmental Sciences 2001年第4期13卷 411-417页

作者： Xiao, C.-w. Lab. Quantitative Vegetation Ecol. Institute of Botany Chinese Academy of Sciences Beijing 100093 China

Response pattern was investigated for seedlings of Salix psammophila, a dominant shrub in Maowusu sandland, to the simulated precipitation change by artificially controlling water supply at four levels. The growth characters, in terms of plant height, stem diameter, total branch number, total leaf number and area, total bifurcation ratio, total branch lenght and branch number, branch lenght, leaf number and leaf area of each branch order, and leaf, branch and root biomass significantly increased when water supply increased. That water supply had significant effect on biomass allocation showed different investment pattern of biomass resource of the seedlings grown under different water supply treatments. Stomatal density of abaxial leaf surface decreased, and stomatal apparatus length and width of adaxial and abaxial leaf surface increased with the increase of water supply, while Stomatal density of adaxial leaf surface was not affected by water supply. water supply obviously affected the diumal changes of photosynthetic rate, and the photosynthetic rate of the seedlings showed strongly midday depression grown under the 157.5 mm water supply, but not grown under higher water supply. Additionally the assimilation-light response curves and flourescence efficiency more showed that water supply improve photosynthesis capacity. Finally, S. psammophila seedlings stood out by their slow growth and relatively high investments in root growth in order to reduce tissue losing rate and consumption of water resource for keeping water balance under water stress. The seedlings that grown under rich water supply did by their fast growth and relatively high investments in branch and leaf growth in order to improve the power of capturing light energy for higher photosynthesis.

关键词： Biomass Fluorescence Morphology Photosynthesis Physiology Plants (botany) Precipitation (chemical) Seed Tissue

Do increasing respiratory costs explain the decline with age of forest growth rate?

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Journal of Forestry Research 2020年第3期31卷 693-712页

作者： P.w.west Forest research centre southern cross universitylismorensw 2480australia

Once forests have achieved a full canopy, their growth rate declines progressively with age. This work used a global data set with estimates from a wide range of forest types, aged 20-795 years, of their annual photosynthetic production(gross primary production, GPP) and subsequent above-plus below-ground biomass production(net primary production, NPP). Both GPP and NPP increased with increasing mean annual temperature and precipitation. GPP was then unrelated to forest age whilst NPP declined progressively with increasing age. These results implied that autotrophic respiration increases with age. It has been proposed that GPP should decline in response to increasing water stress in leaves as water is raised to greater heights as trees grow taller with age. However, trees may make substantial plastic adjustment in mor phology and anatomy of newly developing leaves, xylem and fi ne roots to compensate for this stress and maintain GPP with age. This work reviews the possibilities that NPP declines with age as respiratory costsincrease progressively in, any or all of, the construction and maintenance of more complex tissues, the maintenance of increasing amounts of live tissue within the sapwood of stems and coarse roots, the conversion of sapwood to hear twood, the increasing distance of phloem transport, increased turnover rates of fine roots, cost of supporting very tall trees that are unable to compensate fully for increased water stress in their canopies or maintaining alive competitively unsuccessful small trees.

关键词： Primary production Photosynthesis Respiration Biomass growth Ageing

Enhancement of Gain in L-Band Bismuth-Based Erbium-Doped Fibre Amplifier Using an Un-pumped EDF and Midway Isolator

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Chinese Physics Letters 2004年第12期21卷 2452-2453页

作者： w.Y.Chong S.w.Harun H.Ahmad PhotonicsLaboratory DepartmentofPhysicsUniversityofMalaya50603KualaLumpur FacultyofEngineering MultimediaUniversityJalanMultimedia63100CyberjayaSelangorMalaysia

A hybrid L-band erbium-doped fibre amplifier (EDFA) with enhanced gain characteristic is demonstrated without a significant noise figure penalty. It uses a backward C-band amplified stimulated emission from both the ends of a bismuth-based EDFA system to pump an unpumped erbium-doped fibre (EDF) for gain enhancing. The maximum gain enhancement of 4.0dB is obtained at wavelength 1604nm with EDF length of 20m. The gain spectrum is reasonably flat in this amplifier compared with the amplifier without an EDF. The gain varies from 27.4dB to 30.2dB at wavelength region 1564--1608nm with incorporation of 20m EDF. Noise figure also varies from 6.0 to 7.7dB at this wavelength region.

关键词： Condensed matter: electrical magnetic and optical Optics quantum optics and lasers

Secondary steady-state and time-periodic flows from a basic flow with square array of odd number of vortices

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Applied Mathematics and Mechanics(English Edition) 2023年第3期44卷 447-458页

作者： Zhimin CHEN w.G.PRICE School of Mathematics and Statistics Shenzhen UniversityShenzhen 518060Guangdong ProvinceChina Ship Science University of SouthamptonSouthampton SO171BJU.K.

In a magnetohydrodynamic(MHD)driven fluid cell,a plane non-parallel flow in a square domain satisfying a free-slip boundary condition is *** energy dissipation of the flow is controlled by the viscosity and linear *** latter arises from the influence of the Hartmann bottom boundary layer in a three-dimensional(3D)MHD experiment in a square bottomed *** basic flow in this fluid system is a square eddy flow exhibiting a network of N~2 vortices rotating alternately in clockwise and anticlockwise *** N is odd,the instability of the flow gives rise to secondary steady-state flows and secondary time-periodic flows,exhibiting similar characteristics to those observed when N=*** this reason,this study focuses on the instability of the square eddy flow of nine *** is shown that there exist eight bi-critical values corresponding to the existence of eight neutral eigenfunction ***,there exist non-real neutral eigenfunctions,which produce secondary time-periodic flows exhibiting vortices merging in an oscillatory *** Hopf bifurcation phenomenon has not been observed in earlier investigations.

关键词： two-dimensional(2D)Navier-Stokes equation non-parallel square vortex flow primary bifurcation secondary steady-state flow secondary time-periodic flow

Feasibility Study of Using DLC Coating in Conjunction with Laser Ablation process to Improve the Tribological Performance of an Engineering Surface

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稀有金属材料与工程 2012年第S1期41卷 52-56页

作者： Shum P w Department of Manufacturing Engineering and Engineering Management(MEEM) City University of Hong KongHong KongChina

Increasing demands such as low friction,low wear rate,and long life-time have reached the limits of single DLC *** order to meet the requirements,we propose to use an integrated approach to improve the wear property of an engineering ***,dimples are introduced perpendicular to an engineering surface by a Nd:YAG laser emitting at 1064 ***,solid lubricant DLC is prepared on the patterned surface by magnetron sputtering *** effect of dimple densities from 7%to 45 %on tribological properties of the coating surface was *** wear performance of the textured DLC surfaces was studied by a pin-on-disk reciprocating sliding wear tester under boundary lubrication and dry *** results showed that the DLC coatings with appropriate dimple densities have an obvious improvement on wear performance in term of friction coefficient,wear rate and wear life,as compared to un-textured DLC *** boundary lubrication conditions,the improved wear performance can be explained by the promotion of reservoirs to enhance lubricant retention during *** dry condition,the dimples trap wear particles and leave a free interface between pin and sliding contact surface,and avoid the surface worn by abrasive manner,thereby improving the wear performance of the DLC coating.

关键词： laser wear DLC