检索结果-南通市图书馆

Journal of Forestry Research 2015年第4期26卷 905-917页

作者： Chang-bae Lee Jung-Hwa Chun Korea Green Promotion Agency 121 DunsanbukroSeoguDaejeon 302-831Republic of Korea Division of Forest Ecology Korea Forest Research Institute57 HoegiroDongdaemunguSeoul 130-712Republic of Korea

We examined patterns of plant species richness on an elevation gradient and evaluated the effects of cli- matic variables including mean annual temperature and precipitation, area, the mid-domain effect and productivity on species richness along two transects on Mt. Seorak, South Korea. A total of 235 plant species of 72 families and 161 genera were recorded from 130 plots along the two transects. two different patterns, monotonic decline and a unimodal shape, were observed for woody plants with the change in elevation along the two transects, whereas multimodal patterns were observed for all plant species considered together and for herbaceous plants. Area and productivity showed significant relationships with total plant richness. Climatic variables were better predictors than other variables for variation by elevation in woody plant richness, whereas productivity was a more important variable for herbaceous plant richness. Although area was an important variable for predicting species richness pat- terns, the effects differed by transect and plant group. No empirical evidence was linked to the mid-domain *** elevational patterns may characterize different groups in the same taxon and there might be fundamental differences in the mechanisms underlying these richness patterns.

关键词： Area Climatic variables Elevationalpatterns Plant richness Productivity

three-Dimensional Lattice Kinetic Scheme and its Application to Simulate Incompressible Viscous thermal Flows

在线全文

学校读者我要写书评

暂无评论

Communications in Computational Physics 2007年第2期2卷 239-254页

作者： y.Peng C.Shu y.t.Chew Department of Mechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260.

In this paper,the three-dimensional lattice kinetic scheme is presented to simulate incompressible viscous thermal *** compared with the standard LBM,the present scheme has the following good *** can save the computer memory since there is no need to store the density *** the conventional NS solvers,the implementation of boundary conditions is straightforward since the dependent variables are the macroscopic flow *** easy implementation of boundary conditions is a good property for solving three-dimensional flow *** present scheme is validated by simulating the three-dimensional natural convection in an air-filled cubical enclosure,which is heated differentially at two vertical side *** obtained numerical results compare very well with available data in the literature.

关键词： Lattice kinetic scheme lattice Boltzmann method three-dimensional incompressible flow natural convection thermal flow.

PREDICtION OF CARBON CONCENtRAtION AND FERRItE VOLUME FRACtION OF HOt-ROLLED StEEL StRIP DURING LAMINAR COOLING

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2007年第4期20卷 251-257页

作者： y.t. Zhang C.Z. Wang D.Z. Li y.y. Li School of Material Science and Engineering Shenyang Ligong University Shenyang 110168 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

A phase transformation model was presented for predicting the phase fraction transformed and the carbon concentration in austenite for austenite to ferrite transformation during laminar cooling on run-out table in hot rolling strip mill. In this model, the parameter k in Avrami equation was developed for carbon steels. the wide range of chemical composition, the primary austenite grain size, and the retained strain were taken into account. It can be used to predict the ferrite volume fraction and the carbon concentration in austenite of hot-rolled steel strip during laminar cooling on run-out table. the coiling temperature controlling model was also presented to calculate the temperature of steel strip. the transformation kinetics of austenite to ferrite and the evolution of carbon concentration in austenite at different temperatures during cooling were investigated in the hot rolled Q235B strip for thickness of 9.35, 6.4, and 3.2mm. the ferrite volume fraction along the length of the strip was also calculated. the calculated ferrite volume fraction was compared with the log data from hot strip mill and the calculated results were in agreement with the experimental ones. the present study is a part of the prediction of the mechanical properties of hot-rolled steel strip, and it has already been used on-line and off-line in the hot strip mill.

关键词： carbon concentration ferrite volume fraction laminar cooling hot rolling

the Effect of Reflector with Sound-Absorbing Material on Supersonic Jet Noise

在线全文

学校读者我要写书评

暂无评论

Journal of thermal Science 2005年第1期14卷 22-27页

作者： y.-H.KWEON M.tSUCHIDA y.MIyAZAtO t.AOKI H.-D.KIM t.SEtOGUCHI Department of Energy and Environmental Engineering Kyushu University Kasuga 816-8580Japan School of Mechanical Engineering Andong National University Andong 760-749Korea Department of Mechanical Engineering Saga University Saga 840-8502Japan

this paper describes an experimental work to investigate the effect of a reflector on supersonic jet noise radiated from a convergent-divergent nozzle with a design Mach number *** the present study,a metal reflector and reflectors made of three different sound-absorbing materials(grass wool and polyurethane foam)were employed,and the reflector size was *** measurement is carried out to obtain the acoustic characteristics such as frequency,amplitude of screech tone and overall sound pressure level(OASPL).A high-quality schlieren optical system is used to visualize the detailed structure of supersonic *** results obtained show that the acoustic characteristics of supersonic jet noise are strongly dependent upon the jet pressure ratio and the reflector *** is also found that the reflector with sound-absorbing material reduces the screech tone amplitude by about 5-13dB and the overall sound pressure levels by about 2-5dB,compared with those of the metal reflector.

关键词： supersonic jet supersonic jet noise screech tone OASPL reflector sound-absorbing material.

X-ray Peak-Shift Determination of Deformation Fault Probability in Fe-Mn-Si Alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & technology 2002年第5期18卷 459-461页

作者： yonghuaRONG GangHE ZhenghongGUO ShipuCHEN t.y.Hsu(XUZuyao) School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai 200030 China

the X-ray diffraction peak-shift method was introduced into the determination of deformation fault probability (a) of Fe-Mn-Si alloys with various Mn contents and thermomechanical cycling numbers. the precise lattice constants required were obtained by numerical calculation instead of using standard sample without any fault. the influence of internal stress on the determined a has been evaluated, and the caused relative error was determined as about 4% and thus negligible. the results show that the deformation fault probability increases with decreasing Mn-content and increasing cycle number, which are qualitatively consistent with those results of Psf determined by peak-broadening method.

关键词： X-ray diffraction Peak-shift method Deformation fault probability Fe-Mn-Si alloy

A GCM-Based Forecasting Model for the Landfall of tropical Cyclones in China

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2011年第5期28卷 1049-1055页

作者：孙建奇 Joong bae AHN Nansen-Zhu International Research Centre Institute of Atmospheric PhysicsChinese Academy of Sciences Beijing 100029 Division of Earth Environmental System Atmospheric SciencesPusan National University Pusan 609735 Korea Division of Earth Environmental System Atmospheric SciencesPusan National UniversityPusan 609735Korea

A statistical dynamic model for forecasting Chinese landfall of tropical cyclones （CLtCs） was developed based on the empirical relationship between the observed CLtC variability and the hindcast atmospheric circulations from the Pusan National University coupled general circulation model （PNU-CGCM）.In the last 31 years,CLtCs have shown strong year-to-year variability,with a maximum frequency in 1994 and a minimum frequency in *** features were well forecasted by the model.A cross-validation test showed that the correlation between the observed index and the forecasted CLtC index was high,with a coefficient of *** relative error percentage （16.3%） and root-mean-square error （1.07） were *** the coupled model performs well in terms of forecasting CLtCs;the model has potential for dynamic forecasting of landfall of tropical cyclones.

关键词： statistical-dynamical model cyclone forecast tropical cyclone coupled model cross validation

Closed-form solutions for free vibration of rectangular FGM thin plates resting on elastic foundation

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2016年第6期32卷 1088-1103页

作者： t. F. Xu y. F. Xing Institute of Solid Mechanics Beihang UniversityBeijing 100191 China China Academy of Launch Vehicle technology R&D Center Beijing 100076 China

this article presents closed-form solutions for the frequency analysis of rectangular functionally graded material (FGM) thin plates subjected to initially in-plane loads and with an elastic foundation. Based on classical thin plate theory, the governing differential equations are derived using Hamilton's principle. A neutral surface is used to eliminate stretching-bending coupling in FGM plates on the basis of the assumption of constant Poisson's ratio. the resulting governing equation of FGM thin plates has the same form as homogeneous thin plates. the separation-of-variables method is adopted to obtain solutions for the free vibration problems of rectangular FGM thin plates with separable boundary conditions, including, for example, clamped plates. the obtained normal modes and frequencies are in elegant closed forms, and present formulations and solutions are validated by comparing present results with those in the literature and finite element method results obtained by the authors. A parameter study reveals the effects of the power law index n and aspect ratio a/b on frequencies.

关键词： Functionally graded material Free vibration Rectangular plate Close form solutions Neutral surface

Dynamic stabilization of plasma instability

在线全文

学校读者我要写书评

暂无评论

High Power Laser Science and Engineering 2019年第1期7卷 17-26页

作者： S.Kawata t.Karino y.J.Gu Graduate School of Engineering Utsunomiya University Institute of Physics of the ASCR ELI-Beamlines Institute of Plasma Physics of the CAS

the paper presents a review of dynamic stabilization mechanisms for plasma instabilities. One of the dynamic stabilization mechanisms for plasma instability was proposed in the paper [Kawata, Phys. Plasmas 19, 024503(2012)],based on a perturbation phase control. In general, instabilities emerge from the perturbations. Normally the perturbation phase is unknown, and so the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superimposition of perturbations imposed actively. Based on this mechanism we present the application results of the dynamic stabilization mechanism to the Rayleigh–taylor instability(RtI) and to the filamentation instability as typical examples in this paper. On the other hand, in the paper [Boris, Comments Plasma Phys. Control. Fusion 3, 1(1977)] another mechanism was proposed to stabilize RtI, and was realized by the pulse train or the laser intensity modulation in laser inertial fusion [Betti et al., Phys. Rev. Lett. 71, 3131(1993)]. In this latter mechanism, an oscillating strong force is applied to modify the basic equation, and consequently the new stabilization window is created. Originally the latter was proposed by Kapitza. We review the two stabilization mechanisms, and present the application results of the former dynamic stabilization mechanism.

关键词： dynamic instability stabilization filamentation instability plasma instability Rayleigh-taylor instability stabilization of instability

Gradient Structured Copper by Rotationally Accelerated Shot Peening

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & technology 2017年第7期33卷 758-761页

作者： X.Wang y.S.Li Q.Z.ang y.H.Zhao y.t.Zhu Nano Structural Materials Center School of Materials Science and Engineering Nanjing University of Science and Technology Nanjing 210094 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing 210094 China Department of Materials Science and Engineering North Carolina State University Raleigh NC 27695 USA

A new technology-rotationally accelerated shot peening（RASP）, was developed to prepare gradient structured materials. By using centrifugal acceleration principle and large steel balls, the RASP technology can produce much higher impact energy compared to conventional shot peening. As a proof-of-concept demonstration, the RASP was utilized to refine the surface layer in pure copper（Cu） with an average grain size of 85 nm. the grain size increases largely from surface downwards the bulk, forming an800 ？m thick gradient-structured surface layer and consequently a micro-hardness gradient. the difference between the RASP technology and other established techniques in preparing gradient structured materials is discussed. the RASP technology exhibits a promoting future for large-scale manufacturing of gradient materials.

关键词： Microstructure Rotationally accelerated shot peening Gradient structure Hardness Copper

Combined approach for analysing evolutionary power spectra of a track-soil system under moving random loads

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2019年第3期35卷 674-690页

作者： y.Zhao L.t.Si H.Ouyang State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsInternational Center for Computational MechanicsDalian University of TechnologyDalian 116023Chin School of Engineering University of LiverpoolLiverpool L69 3GHUK

the pseudo-excitation method combined with the integral transform method (PEM-ItM) is presented to investigate the ground vibration of a coupled track-soil system induced by moving random loads. Commonly in the track model, the rail, sleepers, rail pads, and ballast are modelled as an infinite Euler beam, discretely distributed masses, discretely distributed vertical springs, and a viscoelastic layer, respectively. the soil is regarded as a homogenous isotropic half-space coupled with the track using the boundary condition at the surface of the ground. By introducing a pseudo-excitation, the random vibration analysis of the coupled system is converted into a harmonic analysis. the analytical form of evolutionary power spectral density responses of the simplified coupled track-soil system under a random moving load is derived in the frequency/wavenumber domain by PEM-ItM. In the numerical examples, the effects of different parameters, such as the moving speed, the soil properties, and the coherence of moving loads, on the ground response are investigated.

关键词： track-soil system Moving random loads Evolutionary power spectrum Pseudo-excitation method Integral transform method Vibration transmission