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Dynamics of loose granular flow and its subsequent deposition in a narrow mountainous river
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作者 LEI Ming XU Ze-xing +1 位作者 ZHAO Tao WANG Xie-kang 《山地科学学报:英文版》 SCIE CSCD 2019年第6期1367-1380,共14页
A large amount of loose debris materials were deposited on the slope of mountainous areas after the 2008 Ms 8.0 Wenchuan earthquake. During and after the earthquake, these loose debris deposits collapsed and slide int... A large amount of loose debris materials were deposited on the slope of mountainous areas after the 2008 Ms 8.0 Wenchuan earthquake. During and after the earthquake, these loose debris deposits collapsed and slide into valleys or rivers, changing river sediment supply condition and channel morphology. To investigate the mechanisms of granular flow and deposition, the dynamics of slope failure and sediment transportation in typical mountainous rivers of different intersection angles were analyzed with a coupling model of Computational Fluid Dynamics and Discrete Element Method(CFD-DEM). The numerical results show that the change of intersection angle between the granular flow flume and the river channel can affect the deposit geometry and the fluid flow field significantly. As the intersection angle increases, the granular velocity perpendicular to the river channel increases, while the granular velocity parallel to the river channel decreases gradually. Compared to the test of dry granular flow, the CFD-DEM coupling tests show much higher granular velocity and larger volume of sediments entrained in the river. Due to the river flow, particles located at the edge of the deposition will move downstream gradually and the main section of sediments deposition moves from the center to the edge of the river channel. As a result, sediment supply in the downstream river will distribute unevenly. Under the erosion of fluid flow, the proportion of fine particles increases, while the proportion of coarse particles decreases gradually in the sediment deposition. The build-up of accumulated sediment mass will cause a significant increase in water level in the river channel, thus creating serious flooding hazard in mountainous rivers. 展开更多
关键词 LOOSE DEBRIS materials SEDIMENT supply CFD-DEM coupling method NUMERICAL simulations
A combined application of micro-vortex generator and boundary layer suction in a high-load compressor cascade
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作者 Shan MA Wuli CHU +2 位作者 Haoguang ZHANG Xiangjun LI Haiyang KUANG 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第5期1171-1183,共13页
In the current study, the effects of a combined application between micro-vortex generator and boundary layer suction on the flow characteristics of a high-load compressor cascade are investigated. The micro-vortex ge... In the current study, the effects of a combined application between micro-vortex generator and boundary layer suction on the flow characteristics of a high-load compressor cascade are investigated. The micro-vortex generator with a special configuration and the longitudinal suction slot are adopted. The calculated results show that a reverse flow region, which is considered the main reason for occurring stall at 7.9° incidence, grows and collapses rapidly near the leading edge and leads to two critical points occurring on the end-wall with the increasing incidence in the baseline. As the micro-vortex generator is introduced in the baseline cascade, the corner separation is switched to a trailing edge separation by the thrust from the induced vortex. Meanwhile, the occurrence of failure is delayed due to the mixed low energy fluid and main flow. The synergistic effects between the micro-vortex generator and the boundary layer suction on the performance of the cascade are superior to the baseline at all the incidence conditions before the occurrence of failure, and the sudden deterioration of the cascade occurs at 10.3° incidence. The optimal results show that the farther upstream suction position, the lower total pressure loss of the cascade with vortex generator at the near stall condition. Moreover, the induced vortex with a leg can migrate the accumulated low energy fluid backward to delay the occurrence of stall. 展开更多
关键词 Boundary layer SUCTION Flow control strategies High-load COMPRESSOR CASCADE Numerical simulations VORTEX generators
Alkyl group functionalization-induced phonon thermal conductivity attenuation in graphene nanoribbons
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作者 王彩云 鲁爽 +1 位作者 于晓东 李海鹏 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第1期522-526,共5页
We calculated the room-temperature phonon thermal conductivity and phonon spectrum of alkyl group-functionalized zigzag graphene nanoribbons(ZGNRs) with molecular dynamics simulations. The increase in both chain lengt... We calculated the room-temperature phonon thermal conductivity and phonon spectrum of alkyl group-functionalized zigzag graphene nanoribbons(ZGNRs) with molecular dynamics simulations. The increase in both chain length and concentration of alkyl groups caused remarkable reduction of phonon thermal conductivity in functionalized ZGNRs. Phonon spectra analysis showed that functionalization of ZGNR with alkyl functional groups induced phonon–structural defect scattering, thus leading to the reduction of phonon thermal conductivity of ZGNR. Our study showed that surface functionalization is an effective routine to tune the phonon thermal conductivity of GNRs, which is useful in graphene thermal-related applications. 展开更多
关键词 graphene nanoribbons(GNRs) thermal CONDUCTIVITY PHONON spectrum surface FUNCTIONALIZATION molecular dynamics simulations
Drawdown mechanism of light particles in baffled stirred tank for the KR desulphurization process
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作者 Meng Li Yangbo Tan +2 位作者 Jianglong Sun De Xie Zeng Liu 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2019年第2期247-256,共10页
To improve the efficiency of the desulfurization process, the drawdown mechanism of light particles in stirred tank is studied in this paper. For both up and down pumping modes, the just drawdown speeds(Njd) of floati... To improve the efficiency of the desulfurization process, the drawdown mechanism of light particles in stirred tank is studied in this paper. For both up and down pumping modes, the just drawdown speeds(Njd) of floating particles in transformative Kanbara Reactor(KR) are measured in one and four baffled stirred tanks experimentally. Then numerical simulations with standard k-ε model coupled with volume of fluid model(VOF) and discrete phase model(DPM) are conducted to analyze the flow field at the just drawdown speed Njd. The torques on the impeller obtained from experiments and simulations agree well with each other, which indicates the validity of our numerical simulations. Based on the simulations, three main drawdown mechanisms for floating particles, the axial circulation, turbulent fluctuation and largescale eddies, are analyzed. It’s found that the axial circulation dominates the drawdown process at small submergence(S = 1/4 T and 1/3 T) and the large-scale eddies play a major role at large submergence(S= 2/3 T and 3/4 T). Besides, the turbulent fluctuation affects the drawdown process significantly for up pumping mode at small submergence(S = 1/4 T and 1/3 T) and for down pumping mode at large submergence(S= 2/3 T and 3/4 T). This paper helps to provide a more comprehensive understanding of the KR desulphurizer drawdown process in the baffled stirred tank. 展开更多
关键词 LIGHT PARTICLES DRAWDOWN MECHANISM Baffled stirred tank SUBMERGENCE Numerical simulations KR impeller
A Software-in-the-Loop Implementation of Adaptive Formation Control for Fixed-Wing UAVs 预览
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作者 Jun Yang Ximan Wang +2 位作者 Simone Baldi Satish Singh Stefano Fari 《自动化学报:英文版》 CSCD 2019年第5期1230-1239,共10页
This paper discusses the design and software-in-theloop implementation of adaptive formation controllers for fixedwing unmanned aerial vehicles(UAVs) with parametric uncertainty in their structure, namely uncertain ma... This paper discusses the design and software-in-theloop implementation of adaptive formation controllers for fixedwing unmanned aerial vehicles(UAVs) with parametric uncertainty in their structure, namely uncertain mass and inertia. In fact, when aiming at autonomous flight, such parameters cannot assumed to be known as they might vary during the mission(e.g.depending on the payload). Modeling and autopilot design for such autonomous fixed-wing UAVs are presented. The modeling is implemented in Matlab, while the autopilot is based on ArduPilot, a popular open-source autopilot suite. Specifically, the ArduP ilot functionalities are emulated in Matlab according to the Ardupilot documentation and code, which allows us to perform software-in-the-loop simulations of teams of UAVs embedded with actual autopilot protocols. An overview of realtime path planning, trajectory tracking and formation control resulting from the proposed platform is given. The software-inthe-loop simulations show the capability of achieving different UAV formations while handling uncertain mass and inertia. 展开更多
关键词 ArduPilot ADAPTIVE formation control FIXED-WING UAVs software-in-the-loop simulations
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Low temperature annealing of metals with electrical wind force effects
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作者 Daudi Waryoba Zahabul Islam +1 位作者 Baoming Wang Aman Haque 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第4期465-472,共8页
Conventional annealing is a slow, high temperature process that involves heating atoms uniformly, i.e., in both defective and crystalline regions. This study explores an electrical alternative for energy efficiency,wh... Conventional annealing is a slow, high temperature process that involves heating atoms uniformly, i.e., in both defective and crystalline regions. This study explores an electrical alternative for energy efficiency,where moderate current density is used to generate electron wind force that produces the same outcome as the thermal annealing process. We demonstrate this on a zirconium alloy using in-situ electron back scattered diffraction(EBSD) inside a scanning electron microscope(SEM) and juxtaposing the results with that from thermal annealing. Contrary to common belief that resistive heating is the dominant factor, we show that 5 × 10~4 A/cm~2 current density can anneal the material in less than 15 min at only135?C. The resulting microstructure is essentially the same as that obtained with 600?C processing for360 min. We propose that unlike temperature, the electron wind force specifically targets the defective regions, which leads to unprecedented time and energy efficiency. This hypothesis was investigated with molecular dynamics simulation that implements mechanical equivalent of electron wind force to provide the atomistic insights on defect annihilation and grain growth. 展开更多
关键词 ANNEALING Grain-growt ELECTRON backscattered diffraction(EBSD) Molecular dynamics simulations ELECTRON WIND FORCE
THE IMPACT OF MOUNTAIN TO BASIN WINDS ON THE DIURNAL VARIATION IN FOG OVER THE SICHUAN BASIN, CHINA
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作者 张福颖 刘海文 +3 位作者 朱玉祥 赵亮 段伯隆 傅宁 《热带气象学报:英文版》 SCIE 2019年第2期257-268,共12页
There is an increased demand for the accurate prediction of fog events in the Sichuan Basin(SCB) using numerical methods. A dense fog event that occurred over the SCB on 22 December 2016 was investigated. The results ... There is an increased demand for the accurate prediction of fog events in the Sichuan Basin(SCB) using numerical methods. A dense fog event that occurred over the SCB on 22 December 2016 was investigated. The results show that this dense fog event was influenced by the southwest of a low pressure with a weak horizontal pressure gradient and high relative humidity. This fog event showed typical diurnal variations. The fog began to form at 1800 UTC on 21 December 2016(0200 local standard time on 22 December 2016) and dissipated at 0600 UTC on 22 December 2016(1400 local standard time on 22 December 2016). The Weather Research and Forecasting model was able to partially reproduce the main features of this fog event and the diurnal variation in the local mountain to basin winds. The simulated horizontal visibility and liquid water content were used to characterize the fog. The mountain to basin winds had an important role in the diurnal variation of the fog event. The positive feedback mechanism between the fog and mountain to basin winds was good for the formation and maintain of the fog during the night. During the day, the mountain to basin wind displayed a transition from downslope flows to upslope flows. Water vapor evaporated easily from the warm, strong upslope winds, which resulted in the dissipation of fog during the day. The topography surrounding the SCB favored the lifting and condensation of air parcels in the lower troposphere as a result of the low height of the lifting condensation level. 展开更多
关键词 MOUNTAIN to BASIN winds FOG events WEATHER research and forecasting simulations TIBETAN PLATEAU
Phase diagrams, mechanisms and unique characteristics of alternating-structured polymer self-assembly via simulations
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作者 Shanlong Li Chunyang Yu Yongfeng Zhou 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第2期226-237,共12页
Alternating-structured polymers(ASPs), like alternating copolymers, regular multiblock copolymers and polycondensates, are very important polymer structures with broad applications in photoelectric materials. However,... Alternating-structured polymers(ASPs), like alternating copolymers, regular multiblock copolymers and polycondensates, are very important polymer structures with broad applications in photoelectric materials. However, their self-assembly behaviors,especially the self-assembly of alternating copolymers, have not been clearly studied up to now. Meanwhile, the unique characteristics therein have not been systematically disclosed yet by both experiments and theories. Herein, we have performed a systematic simulation study on the self-assembly of ASPs with two coil alternating segments in solution through dissipative particle dynamics(DPD) simulations. Several morphological phase diagrams were constructed as functions of different impact parameters. Diverse self-assemblies were observed, including spherical micelles, micelle networks, worm-like micelles, disklike micelles, multimicelle aggregates, bicontinuous micelles, vesicles, nanotubes and channelized micelles. Furthermore, a morphological evolutionary roadmap for all these self-assemblies was constructed, along with which the detailed molecular packing models and self-assembly mechanisms for each aggregate were disclosed. The ASPs were found to adopt a folded-chain mechanism in the self-assemblies. Finally, the unique characteristics for the self-assembly of alternating copolymers were revealed especially, including(1) ultra-fine and uniform feature sizes of the aggregates;(2) independence of self-assembled structures from molecular weight and molecular weight distribution;(3) ultra-small unimolecular aggregates. We believe the current work is beneficial for understanding the self-assembly of alternating structured polymers in solution and can serve as a guide for the further experiments. 展开更多
关键词 alternating-structured POLYMER SELF-ASSEMBLY DISSIPATIVE particle dynamics simulations phase diagram
Preliminary investigation on electrothermal instabilities in early phases of cylindrical foil implosions on primary test stand facility
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作者 王冠琼 肖德龙 +7 位作者 但家坤 张扬 丁宁 黄显宾 王小光 孙顺凯 薛创 束小建 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第2期352-357,共6页
Recent experiments on the implosions of 15-mm long and 2-μm thick aluminum liners having a diameter of 12.8 mm have been performed on the primary test stand(PTS) facility. The stratified structures are observed as al... Recent experiments on the implosions of 15-mm long and 2-μm thick aluminum liners having a diameter of 12.8 mm have been performed on the primary test stand(PTS) facility. The stratified structures are observed as alternating dark and light transverse stripes in the laser shadowgraph images. These striations perpendicular to the current flow are formed early in the implosion, i.e., at the stage when the bulk of the material mass was almost at rest. A two-dimensional(2 D)magnetohydrodynamics(MHD) code is employed to simulate the behavior of liner dynamics in the early phases. It is found that the striations may be produced by the electrothermal instability(ETI) that results from non-uniform Joule heating due to the characteristic relation between the resistivity and the temperature. In 2 D simulations, the stratified structures can be seen obviously in both density and temperature contours as the liner expands rapidly. By analyzing instability spectrum, the dominant wavelengths of the perturbations are 8.33 μm–20.0 μm, which agree qualitatively with the theoretical predictions.It is also interesting to show that ETI provides a significant seed to the subsequent magneto Rayleigh–Taylor(MRT)instability. 展开更多
关键词 Z-PINCH ELECTROTHERMAL instability magnetohydrodynamics(MHD) simulations
Polarized proton beams from laser-induced plasmas
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作者 Anna Hützen Johannes Thomas +7 位作者 Jürgen Boker Ralf Engels Ralf Gebel Andreas Lehrach Alexander Pukhov T.Peter Rakitzis Dimitris Sofikitis Markus Büscher 《高功率激光科学与工程:英文版》 CAS CSCD 2019年第1期114-119,共6页
We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the par... We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the particle-in-cell(PIC) simulation code VLPL(Virtual Laser Plasma Lab) to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circularly polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms. Subsequently, their degree of polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM, Shanghai. 展开更多
关键词 LASER-DRIVEN plasma ACCELERATOR PARTICLE-IN-CELL simulations POLARIZED gas-jet target POLARIZED PROTON BEAMS
SE2IR Invest Market Rumor Spreading Model Considering Hesitating Mechanism 预览
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作者 Hongxing YAO Xiangyang GAO 《系统科学与信息学报:英文版》 CSCD 2019年第1期54-69,共16页
According to the actual situation of investor network, a SE2IR rumor spreading model with hesitating mechanism is proposed, and the corresponding mean-?eld equations is obtained on scale-free network. In this paper, w... According to the actual situation of investor network, a SE2IR rumor spreading model with hesitating mechanism is proposed, and the corresponding mean-?eld equations is obtained on scale-free network. In this paper, we ?rst combine the theory of spreading dynamics and ?nd out the basic reproductive number R0. And then analyzes the stability of the rumor-free equilibrium and the?nal rumor size. Finally, we discuss random immune strategies and target immune strategies for the rumor spreading, respectively. Through numerical simulation, we can draw the following conclusions:Reducing the fuzziness and attractiveness of invest market rumor can effectively reduce the impact of rumor. And the target immunization strategy is more effective than the random immunization strategy for the communicators in the invest investor network. 展开更多
关键词 RUMOR SPREADING SCALE-FREE network immune strategy basic REPRODUCTIVE NUMBERS numerical simulations
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Residue-Specialized Membrane Poration Kinetics of Melittin and Its Variants:Insight from Mechanistic Landscapes
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作者 邓智雄 李景亮 +1 位作者 元冰 杨恺 《理论物理通讯:英文版》 SCIE CAS CSCD 2019年第7期887-902,共16页
Pore-forming peptides have promising potentials for biomedical uses due to their ability to permeabilize cell membranes.However,to molecularly engineer them for practical applications is still blocked by the poor unde... Pore-forming peptides have promising potentials for biomedical uses due to their ability to permeabilize cell membranes.However,to molecularly engineer them for practical applications is still blocked by the poor understanding of the specific roles of individual residues in peptides’activity.Herein,using an advanced computational approach that combines Coarse-Grained molecular dynamics and well-tempered metadynamics,the membrane activities of melittin,a representative pore-forming peptide,and its gain-of-function variants,are characterized from the kinetics and thermodynamics perspectives.Unbiased simulations elucidate the molecular details of peptide-induced membrane poration;during which,some vital intermediate states,including the aggregation and U-shape configuration formation of peptides in the membrane,are observed and further applied as collective variables to construct the multi-dimensional free energy landscapes of the peptide-membrane interactions.Such a combination of kinetic and thermodynamic descriptions of the interaction process provides crucial information of residue-specialized contribution in chain conformation and consequently membrane perforation ability of the peptide.It is found that residues at the kink part(e.g.Thr)determine the chain flexibility and U-shape bending of the peptide,while residues near the C-terminus(e.g.Arg and Lys)are responsible for recruiting neighboring peptides for inter-molecular cooperation;the probable reaction pathway and the poration efficiency are consequently regulated.These results are helpful for a comprehensive understanding of the complicated molecular mechanism of pore-forming peptides and pave the way to rationally design and/or engineer the peptides for practical applications. 展开更多
关键词 PORE-FORMING peptide LIPID MEMBRANE MELITTIN molecular dynamics simulations free energy landscape
大跨度半铺盖深大基坑工程开挖及支护方案研究
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作者 孟庆军 刘东双 刘朋飞 《施工技术》 CAS 2019年第13期13-18,共6页
针对大跨度基坑施工问题,依托南宁市轨道交通1号线埌东地铁站基坑工程,对大跨度半铺盖深大基坑工程开挖及支护进行了研究。研究表明:从施工工期与土方开挖效率角度考虑,选择直接装土与后期台阶接力结合的施工方案更有利于缩短工期;通过... 针对大跨度基坑施工问题,依托南宁市轨道交通1号线埌东地铁站基坑工程,对大跨度半铺盖深大基坑工程开挖及支护进行了研究。研究表明:从施工工期与土方开挖效率角度考虑,选择直接装土与后期台阶接力结合的施工方案更有利于缩短工期;通过有限元数值模拟,得到在钻孔灌注桩+内支撑支护下,内支撑的存在有效地减少了岩土体及桩体的侧向位移,桩体弯矩明显降低,最终确定了钻孔灌注桩+内支撑的支护形式。实践证明优选的技术方案确保了土方开挖工程的安全顺利施工。 展开更多
关键词 地铁车站 基坑 大跨度 半铺盖 支护 数值模拟
Experimental study and simulation of a three-phase flow stirred bioreactor
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作者 Chenghui Zheng Jiashun Guo +4 位作者 Chengkai Wang Yuanfeng Chen Huidong Zheng Zuoyi Yan Qinggen Chen 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2019年第3期649-659,共11页
In order to obtain the reasonable operating conditions and minimize the power consumption in the stirred bioreactor,the hydrodynamic experiments in the stirred bioreactor have been taken to obtain the basic data.Subse... In order to obtain the reasonable operating conditions and minimize the power consumption in the stirred bioreactor,the hydrodynamic experiments in the stirred bioreactor have been taken to obtain the basic data.Subsequently,an Eulerian model for the gas–liquid–solid three phase flow in the stirred bioreactor has been proposed and the CFD simulation has been conducted.By comparing the results of experiment and simulation,it can be concluded that the simulation results were consistent with the experimental data.The inner relationship between operating variables and indicators could be obtained by comparing the results of just suspension speed,gas holdup,power consumption and operational maps,further the reasonable operating conditions could be also determined under the minimum power consumption.The operational maps could provide the theoretical foundation for industrial application of the gas–liquid–solid stirred bioreactors under the low solid concentration(no more than 20 wt%). 展开更多
关键词 Stirred BIOREACTOR HYDRODYNAMICS EXPERIMENT Simulations OPERATIONAL MAPS
Research on the Glass Transition Temperature and Mechanical Properties of Poly(vinyl chloride)/Dioctyl Phthalate (PVC/DOP) Blends by Molecular Dynamics Simulations
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作者 Jing Li Shao-Hua Jin +4 位作者 Guan-Chao Lan Zi-Shuai Xu Lu-Ting Wang Na Wang Li-Jie Li 《高分子科学:英文版》 SCIE CAS CSCD 2019年第8期834-840,共7页
To effectively improve the performance and expand the applications of polymers, molecular dynamics(MD) simulations with the COMPASS force field have been applied to predict the miscibility, glass transition temperatur... To effectively improve the performance and expand the applications of polymers, molecular dynamics(MD) simulations with the COMPASS force field have been applied to predict the miscibility, glass transition temperature(Tg), and mechanical properties of poly(vinyl chloride)/dioctyl phthalate(PVC/DOP) blends. The solubility parameter values obtained are in good agreement with the reference data and the little difference(|Δδ|< 2.0 MPa0.5) between two components indicates that PVC/DOP is a miscible system. Tg is predicted by the slope of the free volume and density versus temperature simulation data based on density and free volume theory which is agree well with the experimental data. In addition, the analyses of mechanical properties results indicate that the values of Young’s modulus(E), bulk modulus(K), and shear modulus(G) decrease with the addition of DOP, demonstrating that the rigidity of material is weakened and the ductility is improved. The mechanical properties can also be effectively improved by increasing the temperature, which may provide a more flexible mixture, with lower E, K, G but an increased ductility. 展开更多
关键词 Poly(vinyl chloride)(PVC) Dioctyl PHTHALATE (DOP) MD simulations Glass transition temperature MECHANICAL properties
Representation of the Madden–Julian Oscillation in CAMS-CSM
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作者 Pengfei REN Li GAO +2 位作者 Hong-Li REN Xinyao RONG Jian LI 《气象学报:英文版》 SCIE CSCD 2019年第4期627-650,共24页
The Madden–Julian Oscillation(MJO)has a significant impact on global weather and climate and can be used as a predictability resource in extended-term forecasting.We evaluate the ability of the Chinese Academy of Met... The Madden–Julian Oscillation(MJO)has a significant impact on global weather and climate and can be used as a predictability resource in extended-term forecasting.We evaluate the ability of the Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM)to represent the MJO by using the diagnostic method proposed by the US Climate Variability and Predictability Program(CLIVAR)MJO Working Group(MJOWG).In general,the model simulates some major characteristics of MJO well,such as the seasonality characteristics and geographical dependence,the intensity of intraseasonal variability(ISV),dominant periodicity,propagation characteristics,coherence between outgoing longwave radiation(OLR)and wind,and life cycle of MJO signals.However,there are a few biases in the model when compared with observational/reanalyzed data.These include an overestimate of precipitation in the convergence zone of the North and South Pacific,a slightly weaker eastward propagation,and a shift in the dominant periodicity toward lower frequencies with slower speeds of eastward propagation.The model gives a poor simulation of the northward propagation of MJO in summer and shows less coherence between the MJO convection and wind.The role of moistening in the planetary boundary layer(PBL)in the eastward/northward propagation of MJO was also explored.An accurate representation of the vertical titling structure of moisture anomalies in CAMS-CSM leads to moistening of the PBL ahead of convection,which accounts for the eastward/northward propagation of MJO.Poor simulation of the vertical structure of the wind and moisture anomalies in the western Pacific leads to a poor simulation of the northward propagation of MJO in this area.Budget analysis of the PBL integral moisture anomalies shows that the model gives a good simulation of the moisture charging process ahead of MJO convection and that the zonal advection of moisture convergence term has a primary role in the detour of MJO over the Maritime Continent. 展开更多
关键词 Madden-Julian Oscillation CAMS-CSM simulations budget analysis
地铁穿越工程管幕支护参数优化与工程实践
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作者 陈城 彭丽云 范磊 《施工技术》 CAS 2019年第1期104-109,共6页
以北京某穿越既有盾构隧道工程为背景,采用FLAC3D对管幕支护进行模拟,重点对钢管直径、钢管环向间距和环向布置角度进行优化,以穿越工程隧道结构的沉降控制值为标准,得出各参数的合理取值范围。并对上述3种参数进行了显著性分析,发现3... 以北京某穿越既有盾构隧道工程为背景,采用FLAC3D对管幕支护进行模拟,重点对钢管直径、钢管环向间距和环向布置角度进行优化,以穿越工程隧道结构的沉降控制值为标准,得出各参数的合理取值范围。并对上述3种参数进行了显著性分析,发现3种参数中钢管直径的影响最不显著。基于该结论,仅对钢管环向间距和环向布置角度进行综合优化,给出满足穿越工程隧道结构沉降控制值时二者之间的关系表达式。 展开更多
关键词 地铁 盾构 管幕法 支护 数值模拟 参数 优化
Reaction mechanism of hydrogen activation by frustrated Lewis pairs 预览
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作者 Lei Liu Binit Lukose +1 位作者 Pablo Jaque Bernd Ensing 《绿色能源与环境:英文版》 CSCD 2019年第1期20-28,共9页
Typically, a Lewis acid and a Lewis base can react with each other and form a classical Lewis adduct. The neutralization reaction can however be prevented by ligating the acid and base with bulky substituents and the ... Typically, a Lewis acid and a Lewis base can react with each other and form a classical Lewis adduct. The neutralization reaction can however be prevented by ligating the acid and base with bulky substituents and the resulting complex is known as a 'frustrated Lewis pair'(FLP). Since the Lewis acid and base reactivity remains in the formed complex, FLPs can display interesting chemical activities, with promising applications in catalysis. For example, FLPs were shown to function as the first metal-free catalyst for molecular hydrogen activation. This, and other recent applications of FLPs, have opened a new thriving research field. In this short-review, we recapitulate the computational and experimental studies of the H2 activation by FLPs. We discuss the thus-far uncovered mechanistic aspects, including pre-organization of FLPs,the reaction paths for the activation, the polarization of He H bond and other factors affecting the reactivity. We aim to provide a rather complete mechanistic picture of the H2 activation by FLPs, which has been under debate for decades since the first discovery of FLPs. This review is meant as a starting point for future studies and a guideline for industrial applications. 展开更多
关键词 Frustrated LEWIS PAIRS HYDROGEN ACTIVATION Reaction MECHANISMS Density functional theory Molecular dynamics simulations
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Effects of Offset Blade on Aerodynamic Characteristics of Small-Scale Vertical Axis Wind Turbine
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作者 LI Yan ZHAO Shouyang +2 位作者 QU Chunming FENG Fang KOTARO Tagawa 《热科学学报:英文版》 SCIE EI CAS CSCD 2019年第2期326-339,共14页
A new way of connecting blade to rotor shaft named offset blade method was proposed for straightbladed vertical axis wind turbine(SB-VAWT) in this study. In order to invest the efficiency of this method and effects of... A new way of connecting blade to rotor shaft named offset blade method was proposed for straightbladed vertical axis wind turbine(SB-VAWT) in this study. In order to invest the efficiency of this method and effects of main parameters including offset length and blade airfoil on improving the output power performance and static starting characteristics, numerical simulations and wind tunnel tests were carried out. Four kinds of blade airfoil including NACA0012, NACA0018, NACA0024 and S809 were selected to analyze the influence of blade thickness and symmetry on SB-VAWT with offset blade. Numerical simulations were firstly carried out on output power for the rotor with 6 kinds of offset length for each airfoil. Wind tunnel tests were also carried out to compare with the results of simulations. The flow fields of rotor with different offset lengths were simulated and the effects of offset blade were analyzed. The optimum offset length among all studied for output power performance was found. Furthermore, the static starting torque and aerodynamic force characteristics of the rotor with optimum offset length were researched. According to the results, appropriate offset length can improve the output power characteristics and smooth the fluctuations of the static torque during one rotational period. The best offset length varies with the airfoil. 展开更多
关键词 vertical axis WIND turbine(VAWT) OFFSET BLADE AIRFOIL numerical simulations WIND tunnel tests
大断面小净距隧道水力耦合围岩稳定性数值模拟
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作者 许梦飞 姜谙男 韩朝 《施工技术》 CAS 2019年第7期89-93,97共6页
以在建富水区大断面小净距公路隧道为工程依托,通过自主开发的弹塑性应力-渗流-损伤耦合有限元计算模型对水力耦合作用下大断面小净距隧道围岩稳定性进行计算。采用差异进化算法进行损伤参数反演,在所得反演参数的基础上,对不同净距下,... 以在建富水区大断面小净距公路隧道为工程依托,通过自主开发的弹塑性应力-渗流-损伤耦合有限元计算模型对水力耦合作用下大断面小净距隧道围岩稳定性进行计算。采用差异进化算法进行损伤参数反演,在所得反演参数的基础上,对不同净距下,所选开挖断面处围岩的塑性区分布、损伤场演化规律和不同注浆圈参数对隧道周边损伤值及洞内涌水量的影响规律进行计算结果分析。 展开更多
关键词 隧道 水力耦合 稳定性 损伤演化 注浆圈参数 数值模拟
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