乙炔法氯乙烯转化器的定态模拟设计

建立了描述乙炔法生产聚氯乙烯生产过程中的关键设备氯乙烯转化器的反应与传热联立微分方程组,据此数学模型编制运算程序.计算结果表明与实际情况吻合,并可在变更多种工艺参数下描述反应过程特征。为氯乙烯转化器的最佳设计与操作调优提供了可靠的依据.

连续搅拌釜式丙烯聚合反应器的模拟（Ⅱ）反应器的动态模拟

建立了丙烯液相本体聚合连续搅拌釜式反应器的动态数学模型，通过计算机模拟，研究了进夹套冷却水流量、丙烯蒸汽冷凝量、催比剂浓度及进料温度４个变量在矩形波和阶跃两种干扰方式下反应器的动态行为，为反应器控制系统的设计提供了定量依据。

苯与十二烯烷基化悬浮床催化精馏塔的模拟

建立了苯与十二烯烷基化悬浮床催化精馏过程的动态平衡级模型,模型对过渡过程达到定态时的系统性能预测与定态实验数据和定态模拟结果吻合良好.利用模型模拟,就苯的进料位置、苯和混合烃进料流量的正向扰动对系统性能的影响进行了研究.结果表明:在给定条件下系统仅存在一个定态;反应段最后一块塔板是苯的最优进料位置;系统对于所施加量级的扰动是稳定的,其抗干扰能力很强.

Simulation and Analysis on Multiple Steady States of an Industrial Acetic Acid Dehydration System

In this work, an industrial acetic acid dehydration system via heterogeneous azeotropic distillation is simulated by Aspen Plus software. Residue curves are used to analyze the distillating behavior, and appropriate operating region of the system is determined. Based on steady states simulation, a sensitivity analysis is carried out to detect the output multiple steady states in the system. Different solution branches are observered when the flow rates of the feed stream and the organic reflux stream are selected as manipulated variables. The performance of the column under different steady states is different. A method is oroposed to achieve the desired steady state.

Transient Stability Assessment of Synchronous Generator in Power System with High-Penetration Photovoltaics

As photovoltaic （PV） capacity in power system increases, the capacity of synchronous generator needs to be reduced relatively. This leads to the lower system inertia and the higher generator reactance, and hence the generator transient stability may negatively be affected. In particular, the impact on the transient stability may become more serious when the considerable amounts of PV systems are disconnected simultaneously during voltage sag. In this work, the generator transient stability in the power system with significant PV penetration is assessed by a numerical simulation. In order to assess the impact from various angles, simulation parameters such as levels of PV penetration, variety of power sources （inverter or rotational machine）, and existence of LVRT capability are considered. The simulation is performed by using PSCAD/EMTDC software.

Dynamic Scaling of Ramified Clusters Formed on Liquid Surfaces

A comprehensive simulation model -- deposition, diffusion, rotation, reaction and aggregation model is presented to simulate the formation processes of ramified clusters on liquid surfaces, where clusters can disuse and rotate easily. The mobility （including diffusion and rotation） of clusters is related to its mass, which is given by Dm = Dos^-γD and θm = θos^-γθ, respectively. The influence of the reaction probability on the kinetics and structure formation is included in the simulation model. We concentrate on revealing dynamic scaling during ramified cluster formation. For this purpose, the time evolution of the cluster density and the weight-average cluster size as well as the cluster-size distribution scaling function at different time are determined for various conditions. The dependence of the cluster density on the deposition flux and time-dependence of fractal dimension are also investigated. The obtained results are helpful in understanding the formation of clusters or thin film growth on liquid surfaces.

Identification and Modeling of Froth to Spray Transition on Sieve Trays

The transition from froth to spray regime on sieve trays was experimentally studied in an air/water simulator with 300mm diameter. It has been found that the regime transition occurs as the clear liquid height is equal to the residual pressure drop on the trays. A convenient and accurate technique was proposed for determination of the regime transition point. Based on analysis of the transition process at a sieve hole, a new formula which can be used to correlate the experimental results was provided.

A Macro Model for Traffic Flow with Consideration of Static Bottleneck

In this paper, we develop a macro model for traffic flow with consideration of static bottleneck to explore the impacts of static bottleneck on traffic flow. The analytical and numerical results show that the proposed model can qualitatively describe the equilibrium flux, uniform flow and small perturbation under the action of a static bottleneck.

On ferroelectric domain polarization switching mechanism subject to an external electric field by simulations with the phase-field method

The ferroelectric domain formation(FDF) and polarization switching(FDPS) subjected to an external electric field are simulated using the phase-field(PF) method,and the FDPS mechanism under different external electric fields is discussed.The results show that the FDF is a process of nucleation and growth in ferroelectric without applying any external stress.Four kinds of parallelogram shaped ferroelectric domains are formed at the steady state,in which the 180° anti-phase domains regularly align along the 45° direction and the 90° anti-phase domains regularly distribute like a stepladder.Steady electric fields can rotate domain polarization by 90° and 180°,and force the orientation-favorite domains and the average polarization to grow into larger ones.The greater the steady electric field,the larger the average polarization at the steady state.In ferroelectrics subject to an alternating electric field,domain polarization switches to cause a hysteresis loop and an associated butterfly loop with the alternating electric field.The coercive field and remnant field are enhanced with the increase of the electric field frequency or strength,or with the decrease of temperature.

Two-dimensional finite element model to study unsteady state Ca^2＋ diffusion in neuron involving ER LEAK and SERCA

In this paper, finite element approach using two-dimensional unsteady state problem has been developed to study radial and angular calcium diffusion problem in neurons. Calcium is responsible messenger for transmitting information in communication process between neurons. The most important Ca^2＋ binding proteins for the dynamics of Ca^2＋ is itself buffer and other physiological parameters are located in Ca^2＋ stores. In this study, the model incorporates the physiological parameters like diffusion coefficient, receptors, exogenous buffers etc. Appropriate boundary conditions have been framed in view of the physiological conditions. Computer simulations in MATLAB 7.11 are employed to investigate mathematical models of reaction-diffusion equation, the details of the implementation can heavily affect the numerical solutions and, thus, the outcome simulated on Core（TM） i3 CPU M 330 @ 2.13GHz processing speed and 3GB memory.

Variation of Sediment Concentration and Its Drivers Under Different Soil Management Systems

In order to prevent soil erosion in southern China,a study was performed to determine the drivers of sediment concentration variation using simulated rainfall and four soil management systems under field condition.Four soil management systems,i.e.,forest and grass coverage(FG),forest coverage with disturbed soil surface(FD),contour tillage(CT) and downslope tillage(DT),were exposed to two rainfall intensities(40 and 54 mm h-1) using a portable rainfall simulator.The drivers of sediment concentration variation were determined by the variations of runoff rate and sediment concentration as well as their relationships.The effects of the four soil management systems in preventing water and soil losses were compared using runoff rates and sediment concentrations at steady state.At runoff initial stage,sediment concentration variation was mainly driven by rainfall and management.The degree of sediment concentration variation driven by flow varied with different soil management systems.Three best relationships between runoff rate and sediment concentration were identified,i.e.,reciprocal(CT),quadratic(FG and FD) and exponential(DT).At steady state,runoff rates of the four soil management systems varied slightly,whereas their sediment concentrations varied greatly.FG and CT were recommended as the best soil management systems for preventing water and soil losses.

PREPARATION OF ENTANGLEMENT STATES IN A TWO-SPIN SYSTEM BY LYAPUNOV-BASED METHOD

A stable Lyapunov-based control law is proposed for entanglement states preparation in this paper. Tbe mathematical model of a two-spin system is constructed in interaction picture. An average value of observable operator is selected as the Lyapunov fllnction. This paper designs the observable operator to make sure that the target state is stable in Lyapunov sense. Then the authors analyze the convergence of the control system, and demonstrate that the Bell states are asymptotically stable under the control law designed. Compared with other methods, the control method proposed in this paper has the advantages of easy design and convergence to the target states. Numerical simulation experiments for the preparation of Bell states are implemented.

Spatial patterns created by cross-diffusion for a three-species food chain model

This paper deals with the stability analysis to a three-species food chain model with crossdiffusion, the results of which show that there is no Turing instability but crossdiffusion makes the model instability possible. We then show that the spatial patterns are spotted patterns by using numerical simulations. In order to understand why the spatial patterns happen, the existence of the nonhomogeneous steady states is investigated. Finally, using the Leray-Schauder theory, we demonstrate that cross-diffusion creates nonhomogeneous stationary patterns.

Research on Modern Nonlinear Dynamic Model of Five-Elements Theory

This article studied on five elements system and set general and strict model expectations combining with Traditional Chinese Medicine Zang-fu organs theory,in which absolute stable state,conditional stable state or transient stability and instability in mathematical models were corresponding to human healthy state,sub-healthy state(pathological plateau phase) and health deterioration state respectively.Model parameters were set up according to the mutual generation and restriction relations among five elements.The dynamic model of Five-Elements System was built,of which impulse responses were corresponding to human response under TCM treatment.Analyses of initial value and excitation response were conducted by numerical simulation and results turned out to meet the requirements of general model expectation:five elements system dynamic model had self-organization function;there existed only one non-global stable point and instability region in the five-dimensional space consisting of variables,in which instability was corresponding to pathological deterioration;system stable region was an unbounded domain and it included the stable sub-regions of special straight line-type,ray-type and line segment-type.Among those ray-types,some contained "Regression Peak" were classed as conditional stable regions while others as absolute ones.The existence of this peak indicates that our body must exceed a "Regression Threshold" when transiting from sub-healthy state(pathological plateau phase) to healthy state through self-regulation mechanism.Impulse excitation can reduce certain threshold and then increase the system health level,which is complied with the operating principle of Five-Elements System and the empirical rule of TCM clinical practice.This model has revealed qualitatively the inherent movement law of Five-Elements System and thus provides a new analysis tool for basic theoretical study on TCM.