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“稳流”教学探讨
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作者 张爱国 郑爱萍 《技术物理教学》 2003年第1期22-23,共2页
在中等卫校物理教学中,液体的流动是一个比较重要的内容.而学生对这部分内容又较难理解和掌握.因此,从书本上的概念出发,建立抽象的物理模型十分重要.在实际教学中,笔者采用了以下方法,效果较好.在此,与大家共同探讨.
关键词 中等专业学校 卫校 物理教学 教学研究 “稳流”
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Singular Points, Closed Orbits, Stable Manifolds and Unstable Manifolds of Second Order Autonomous Birkhoff Systems 被引量:1
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作者 陈向炜 梅凤翔 《Journal of Beijing Institute of Technology》 EI CAS 1998年第4期330-336,共7页
Aim To study singular points, closed orbits, stable manifolds and unstable manifolds of a second order autonomous Birkhoff system. Methods Qualitative methods of ordinary differential equation were used. Results and ... Aim To study singular points, closed orbits, stable manifolds and unstable manifolds of a second order autonomous Birkhoff system. Methods Qualitative methods of ordinary differential equation were used. Results and Conclusion The criteria for singular points, closed orbits and hyperbolic equilibrium points of a second order autonomous Birkhoff system are given. Moreover the stability of equilibria, stable manifolds and unstable manifolds are obtained. 展开更多
关键词 Birkhoff system singular point closed orbit stable manifold unstable manifold
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Fluidization characteristics of magnetic particles and determination of stable fluidization zone in magnetically fluidized bed 被引量:1
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作者 王迎慧 归柯庭 施明恒 《Journal of Southeast University(English Edition)》 EI CAS 2006年第4期523-527,共5页
To determine and calculate the stable fluidization zone in a magnetically fluidized bed, the fluidization characteristics of magnetic particles are investigated. Four kinds of magnetic particles with different average... To determine and calculate the stable fluidization zone in a magnetically fluidized bed, the fluidization characteristics of magnetic particles are investigated. Four kinds of magnetic particles with different average diameters, ranging from 231 to 512 μm, are fluidized in the presence of magnetic fields with specified values of the intensity in the range of zero to 7330 A/m, and the particle fluidization curves are plotted. For marking the stable fluidization zone in the curves, the minimum bubbling velocities of particles are measured by the pressure-drop fluctuation. Based on the fluidization curves, the influences of the average particle diameter and magnetic field intensity on the zone are analyzed and discussed. A correlation to determine the stable fluidization zone is derived from the experimental data, using three dimensionless numbers, i. e., the ratio of magnetic potential to gravity potential, the Reynolds number and the Archimedes number. Compared with available data reported, it is shown that the correlation is more simplified to predict relative parameters for the bed operating in the state of stable fluidization under reasonable conditions. 展开更多
关键词 magnetically fluidized bed fluidization characteristics stable fluidization minimum bubbling gas velocity pressure-drop fluctuation
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Influence of regenerator flow resistance on stability of pulse tube cooler 被引量:1
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作者 蒋彦龙 陈国邦 《Journal of Southeast University(English Edition)》 EI CAS 2005年第3期277-281,共5页
Based on the fluid network theory,the possibility of utilizing regenerator flow resistance to suppress the direct current (DC) flow induced by the introduction of a double-inlet in a pulse tube cooler is investigate... Based on the fluid network theory,the possibility of utilizing regenerator flow resistance to suppress the direct current (DC) flow induced by the introduction of a double-inlet in a pulse tube cooler is investigated theoretically. The calculation results show that increasing regenerator flow resistance can lead to a smaller extent of DC flow.Therefore,a better stability performance of the cooler can be realized.On this basis,the stability characteristics of the cooler with various regenerator matrix arrangements are studied by experiments.By replacing 30% space of 247 screens of stainless steel mesh at the cold part of the regenerator by lead balls of 0.25 mm diameter,a long-time stable temperature output at 80 K region is achieved. This achievement provides a new way to obtain stable performance for pulse tube coolers at high temperature and is helpful for its application. 展开更多
关键词 pulse tube cooler flow resistance STABILITY
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Flow instability criteria in processing map of superalloy GH79 被引量:4
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作者 周舸 丁桦 +2 位作者 曹富荣 韩寅奔 张北江 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2012年第7期1575-1581,共7页
Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GE... Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GEGEL,MALAS,MURTY and SEMIATIN were compared,and the physical significance of parameters was analyzed.Meanwhile,the processing maps with different instability criteria were obtained.It is shown that instability did not occur when average power dissipation rate was larger than 60%in the temperature range of 900-930°C and 960-1080°C,corresponding to the strain rate range of 5×10 -4 -1.8×10 -1 s -1 and 5×10 -4 -1.5×10 -1 s -1 ,respectively.The two domains are appropriate for the processing deformation of superalloy GH79. 展开更多
关键词 nickel-based superalloy hot compression flow instability criterion processing map
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Turbulence regime near the forest floor of a mixed broad leaved/Korean pine forest in Changbai Mountains 被引量:5
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作者 张军辉 丁之慧 +2 位作者 韩士杰 邹春静 周玉梅 《Journal of Forestry Research》 SCIE CAS CSCD 2002年第2期119-122,164,共4页
The measurement and observation for this study were carried out by using a three-dimensional (u, v, w) Sonic anemometer (IAP-SA 485), at Forest Ecosystem Opened Research Station of Changbai Mountains (12828扙 and 4224... The measurement and observation for this study were carried out by using a three-dimensional (u, v, w) Sonic anemometer (IAP-SA 485), at Forest Ecosystem Opened Research Station of Changbai Mountains (12828扙 and 4224?N, Jilin Province, P. R. China) in August 2001. The basic characteristics of turbulence, such as turbulence intensity, atmospheric stability, time scales, and convection state, near the forest floor were analyzed. It is concluded that the airflow near forest floor is characterized by high intermittence and asymmetry, and the active and upward movement takes the leading position. Near forest floor, the vertical turbulence is retained and its time scale and length scale are much less than that of u, v components. The eddy near forest floor shows a flat structure and look like a ’Disk’. Buoyancy plays a leading role in the generation and maintenance of local turbulence 展开更多
关键词 Forest floor Velocity statistics Atmospheric stability Convection states
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Dynamical analysis for a malware propagation model in wireless sensor network 被引量:4
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作者 宋礼鹏 张蓉萍 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2016年第2期136-144,共9页
The threat of malware in wireless sensor network has stimulated some activities to model and analyze the malware prevalence.To understand the dynamics of malware propagation in wireless sensor network,we propose a nov... The threat of malware in wireless sensor network has stimulated some activities to model and analyze the malware prevalence.To understand the dynamics of malware propagation in wireless sensor network,we propose a novel epidemic model named as e-SEIR(susceptible-exposed-infectious-recovered)model,which is a set of delayed differential equations,in this paper.The model has taken into account the following two factors:1 Multi-state antivirus measures;2 Temporary immune period.Then,the stability and Hopf bifurcation at the equilibria of linearized model are carefully analyzed by considering the distribution of eigenvalues of characteristic equations.Both mathematical analysis and numerical simulations show that the dynamical features of the proposed model rely on the basic reproduction number R0 and time delayτ.This novel model can help us to better understand and predict the propagation behaviors of malware in wireless sensor networks. 展开更多
关键词 wireless sensor network STABILITY Hopf bifurcation epidemic model time delay
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Preparation and stability of zinc ferrite nano-particle suspension of ammonia-water solution
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作者 杨柳 杜垲 +1 位作者 张小松 牛晓峰 《Journal of Southeast University(English Edition)》 EI CAS 2010年第2期368-371,共4页
In order to apply nano-particles to the ammonia-water absorption refrigeration, the zinc ferrite nano-particles suspension of ammonia-water solution with the mixed surfactants of sodium dodecyl benzene sulfonate (SDB... In order to apply nano-particles to the ammonia-water absorption refrigeration, the zinc ferrite nano-particles suspension of ammonia-water solution with the mixed surfactants of sodium dodecyl benzene sulfonate (SDBS) and cetyl trimethyl ammonium bromide (CTAB) is prepared. A series of experiments is performed to investigate the stability of the prepared nanofluid with different contents and proportions of surfactants, different durations of ultrasonic wave vibration and different durations of illumination. The optimal dispersion conditions are 1.5% SDBS, 0. 015% CTAB(mass fraction), 30 min of ultrasonic vibration and over 72 h of illumination. Finally, based on double electrode layer theory, the influences of the content of the surfactants on the stability of nanofluid are analyzed. The existence of the optimal surfactant content is proved, which is in accordance with the experimental results. 展开更多
关键词 NANOFLUID STABILITY SURFACTANT ammonia water
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The Effect of pH on the Permeation of Lidocaine Hydrochloride Across Excised Rat Skin
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作者 贾士聪 丁平田 +2 位作者 郑俊民 吴翠栓 华士元 《Journal of Chinese Pharmaceutical Sciences》 CAS 2001年第3期133-135,共3页
The effect of pH on the permeation of Lidocaine hydrochloride (LH) across excised rat skin was studied, the steady state flux (JSS) at different pH being determined using improved Valia-Chien diffusion cells. JSS incr... The effect of pH on the permeation of Lidocaine hydrochloride (LH) across excised rat skin was studied, the steady state flux (JSS) at different pH being determined using improved Valia-Chien diffusion cells. JSS increased substantially when pH was close to the pKa of LH. The profile of JSS versus pH showed an 慡?shaped curve. JSS of Lidocaine free base (LFB) was fourteen times that of LH. The pH of vehicle influences the permeation of LH significantly and should be considered as an important factor when a formulation is developed. 展开更多
关键词 PH PKA LIDOCAINE PERMEATION
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FURTHER OBSERVATIONS OF LATE TRANSITION PROCESSES IN CROSSFLOW INSTABILITY EXPERIMENT
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作者 吴永健 明晓 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2000年第1期26-30,共5页
The experiments of primary and secondary instabilities with controlled excitation are carried out on a swept flat plate to study the process leading to the final breakdown of laminar flow. Two types of high frequency ... The experiments of primary and secondary instabilities with controlled excitation are carried out on a swept flat plate to study the process leading to the final breakdown of laminar flow. Two types of high frequency secondary instabilities are identified. The most amplified mode is centered about the inflection point of the crosswise profile of the boundary layer and is interpreted as inflectional instability, the other occurs in the one third of the boundary layer from the wall. The high frequency disturbances are highly amplified but they also saturate similarly to the primary and nonlinearly generated disturbances. Their main effect in the final breakdown seems interact with the disturbances is developed and thus widens the frequency spectrum to turbulent state. 展开更多
关键词 three dimensional boundary layer cross flow instability secondary instability final onset of transition BREAKDOWN
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MULTI-BODY AEROELASTIC STABILITY ANALYSIS OF TILTROTOR AIRCRAFT IN HELICOPTER MODE 被引量:4
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作者 董凌华 杨卫东 夏品奇 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2006年第3期161-167,共7页
The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish th... The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode. 展开更多
关键词 TILTROTOR HELICOPTER aeroelastic stability multi body dynamics dynamic inflow
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Study on Leaching Loss of Nitrogen in Ricefields by Using Large Undisturbed Monolith Lysimeters 被引量:17
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作者 WANGJIA-YU WANGSHENG-JIA 《Pedosphere》 SCIE CAS CSCD 1994年第1期87-92,共6页
StudyonLeachingLossofNitrogeninRicefieldsbyUs-ingLargeUndisturbedMonolithLysimetersWANGJIA-YU,WANGSHENG-JIAa... StudyonLeachingLossofNitrogeninRicefieldsbyUs-ingLargeUndisturbedMonolithLysimetersWANGJIA-YU,WANGSHENG-JIAandCHENYI(Institut... 展开更多
关键词 LEACHING lysimeter. nitrate NITROGEN ricefields
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Study on the instability of airflow in mine hoisting-shaf 被引量:7
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作者 王海桥 田峰 黄俊歆 《Journal of Coal Science & Engineering(China)》 2007年第1期69-73,共5页
In order to discover the airflow pattern in mine shaft which outfitted with hoist equipment (HE), this paper set up the physical model and anatomized the piston-wind caused by hoist equipment, and researched the flo... In order to discover the airflow pattern in mine shaft which outfitted with hoist equipment (HE), this paper set up the physical model and anatomized the piston-wind caused by hoist equipment, and researched the flow field and velocity field around the hoist equipment during its moving process, and analyzed the airflow around single and couple hoist equipment as well as decisive range of piston effect and additional effect of hoist equipment to ventilation system. Research conclusion indicate that during hoist equipment movement, airflow pattern changes repeatedly because of the influence of pis-ton effect from hoist equipment, and the study of airflow stability in shaft is the foundation for the stability of ventilation in mine. 展开更多
关键词 mine shaft hoist equipment (HE) piston effect ventilation system unsteady flow
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Flow field simulation and establishment for mathematical models of flow area of spool valve with sloping U-shape notch machined by different methods 被引量:10
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作者 王兆强 顾临怡 +2 位作者 冀宏 陈家旺 李林 《Journal of Central South University》 SCIE EI CAS 2014年第1期140-150,共11页
Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape not... Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, effiux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch (ABU) should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch (PBU) is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character. 展开更多
关键词 spool valve flow field simulation flow area steady state flow force mathematical model sloping U-shape notch
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Direct Numerical Simulation of Particle Dispersion in Gas-Solid Compressible Turbulent Jets 被引量:4
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作者 罗坤 金军 +1 位作者 郑友取 岑可法 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2005年第2期161-166,共6页
A numerical method was developed to directly simulate the compressible, particle-laden turbulent jets.The fourth order compact finite difference schemes were used to discretize the space derivatives. The Lagrangian me... A numerical method was developed to directly simulate the compressible, particle-laden turbulent jets.The fourth order compact finite difference schemes were used to discretize the space derivatives. The Lagrangian method was adopted to simulate the particle motion based on one-way coupling. It is found that the turbulent intensity profiles attain self-similar status in the jet downstream regions. At the Stokes number of 1, particles are concentrated largely in the outer boundaries of the large-scale vortex structures with the most uneven distribution and the widest dispersion in the lateral direction. Particles at the much smaller Stokes numbers are distributed evenly in the flow field, and the lateral dispersion is also considerable. Distribution of particles at much larger Stokes numbers is more uniform and the lateral dispersion becomes small. In addition, the inflow conditions have different effects on the particle dispersion. The direct numerical simulation (DNS) results accord with the previous experiments and numerical studies. 展开更多
关键词 direct numerical simulation compressible turbulent jet coherent structure particle dispersion
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ANALYSIS OF FORWARD-FLYBACK CONVERTER EMPLOYING TWO SWITCHES AND TWO TRANSFORMERS 被引量:1
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作者 HONGFeng SHIdian-jiang YANYang-guang 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2004年第4期311-316,共6页
A novel forward-flyback converter employing two switches and two transformers is presented. Two diodes of the primary side enable the voltage stress of two switches to be clamped at the input voltage ,which is lower t... A novel forward-flyback converter employing two switches and two transformers is presented. Two diodes of the primary side enable the voltage stress of two switches to be clamped at the input voltage ,which is lower than that of a conventional forward-flyback converter. Two transformers offer the following advantages. Firstly, the turns of primary transformer winding are reduced to half of that of a conventional forward-flyback converter with a single transformer; Secondly, the use of two transformers enables the smaller low-profile cores to be utilized, thus facilitating a low-profile design. The unequal condition of turn ratios is compared with the equal condition of turn ratios. When two turn ratios are unequal, the power distribution between the two transformers can be easily designed. Finally, experimental results verify the above analyses. 展开更多
关键词 power supply CONVERTER design
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A method for numerical calculation of propeller hydrodynamics in unsteady inflow 被引量:2
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作者 HUANG Sheng WANG Pei-sheng HU Jian 《Journal of Marine Science and Application》 2007年第2期6-11,共6页
The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with consta... The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with constant source and doublet distribution. Each panel's comer coordinates were calculated by spline interpolation between the main parameter and the blade geometry of the propeller. The integral equation was derived using the Green Formula. The influence coefficient of the matrix was calculated by the Morino analytic formula. The tangential velocity distribution was calculated with the Yanagizawa method, and the pressure coefficient was calculated using the Bonuli equation. The pressure Kutta condition was satisfied at the trailing edge of the propeller blade using the Newton-Raphson iterative procedure, so as to make the pressure coefficients of the suction and pressure faces of the blade equal at the trailing edge. Calculated results for the propeller in steady inflow were taken as initialization values for the unsteady inflow calculation process. Calculations were carried out from the moment the propeller achieved steady rotation. At each time interval, a linear algebraic equation combined with Kutta condition was established on a key blade and solved numerically. Comparison between calculated results and experimental results indicates that this method is correct and effective. 展开更多
关键词 unsteady hydrodynamics PROPELLER surface panel method
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Large Eddy Simulations of Flow Instabilities in a Stirred Tank Gen-erated by a Rushton Turbine 被引量:4
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作者 樊建华 王运东 费维扬 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2007年第2期200-208,共9页
The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation (LES). The sliding mesh method was used for the coupli... The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation (LES). The sliding mesh method was used for the coupling between the rotating and the stationary frame of references. The calculations were carried out on the "Shengcao-21C" supercomputer using a computational fluid dynamics (CFD) code CFX5. The flow fields predicted by the LES simulation and the simulation using standard κ-ε model were compared to the results from particle image velocimetry (PIV) measurements. It is shown that the CFD simulations using the LES approach and the standard κ-ε model agree well with the PIV measurements. Fluctuations of the radial and axial velocity are predicted at different frequencies by the LES simulation. Velocity fluctuations of high frequencies are seen in the impeller region, while low frequencies velocity fluctuations are observed in the bulk flow. A low frequency velocity fluctuation with a nondimensional frequency of 0.027Hz is predicted by the LES simulation, which agrees with experimental investigations in the literature. Flow circulation patterns predicted by the LES simulation are asymmetric, stochastic and complex, spanning a large portion of the tanks and varying with time, while circulation patterns calculated by the simulation using the standard κ-ε model are symmetric. The results of the present work give better understanding to the flow instabilities in the mechanically agitated tank. However, further analysis of the LES calculated velocity series by means of fast Fourier transform (FFT) and/or spectra analysis are recommended in future work in order to gain more knowledge of the complicated flow phenomena. 展开更多
关键词 stirred tank flow instabilities computational fluid dynamics large eddy simulation κ-ε model particle image velocimetry
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Thermal Fission Rate Calculated Numerically by Particles Multi-passing over SaddlePoint 被引量:3
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作者 LIULing BAOJing-Dong 《Communications in Theoretical Physics》 SCIE CAS CSCD 2004年第2期273-278,共6页
Langevin simulation of the particles multi-passing over the saddle point is proposed to calculate thermal fission rate. Due to finite friction and the corresponding thermal fluctuation, a backstreaming exists in the p... Langevin simulation of the particles multi-passing over the saddle point is proposed to calculate thermal fission rate. Due to finite friction and the corresponding thermal fluctuation, a backstreaming exists in the process of the particle descent from the saddle to the scission. This leads to that the diffusion behind the saddle point has influence upon the stationary flow across the saddle point. A dynamical correction factor, as a ratio of the flows of multi- and first-overpassing the saddle point, is evaluated analytically. The results show that the fission rate calculated by the particles multi-passing over the saddle point is lower than the one calculated by the particle firstly passing over the saddle point, and the former approaches the results at the scission point. 展开更多
关键词 Langevin simulation backstreaming effect multi-passing oven saddle point dynamical correction factor
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Motion behavior of particles in air-solid magnetically stabilized fluidized beds for separation 被引量:13
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作者 Song Shulei a,,Zhao Yuemin a,Luo Zhenfu a,Tang Ligang b a School of Chemical Engineering and Technology,China University of Mining & Technology,Xuzhou 221116,China b Coal Mining and Designing Department,Tiandi Science & Technology Company Co.Ltd.,Beijing 100013,China 《International Journal of Mining Science and Technology》 SCIE EI 2012年第5期725-729,共5页
In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed(MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The ... In order to study the settling mechanism of particles in an air-solid magnetically stabilized fluidized bed(MSFB) for separation,we carried out free settling and quasi-zero settling tests on the tracing particles.The results show that the main resistance forces as the tracing particles settled in an air-solid MSFB were motion resistance force and yield force.The motion resistance and yield forces greatly hindered the free settling of the particles by greatly decreasing the acceleration for settling process of the particles.The acceleration decreased from 3022.62 cm/s 2 to zero in 0.1 s,and in the end,the particles stopped in the air-solid MSFB.The yield force on particles increased with increasing the magnetic field intensity,resulting in decrease of the quasi-zero settling displacement.However,the yield force on particles decreased with increasing the fluidized air velocity,leading to increase of the quasi-zero settling displacement.When the structure and operating parameters of the air-solid MSFB were set up,the yield stress on particles stopped in an air-solid MSFB was a function of diameter and density of particles.The settling displacements of equal diameter particles increased with increasing their densities,and the settling displacements of equal density particles increased with increasing their diameters. 展开更多
关键词 Air-solid MSFB Free settling Quasi-zero velocity settling Motion of particles
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