Three-dimensional cellular automaton simulation of tumour growth in inhomogeneous oxygen environment

Cellular automaton theory has previously been used to study cell growth. In this study, we present a three-dimensional cellular automaton model performing the growth simulation of normal and cancerous cells. The necessary nutrient supply is provided by an artificial arterial tree which is generated by constrained constructive optimization. Spatial oxygen diffusion is approximated again by a cellular automaton model. All results could be illustrated dynamically by three-dimensional volume visualization. Because of the chosen modelling approach, an extension of the model to simulate angiogenic processes is possible.     

Electric field assisted annealing effects on microstructure and ionic conductivity in ceria/YSZ oxide heterostructures

The effect of electric field assisted annealing on the microstructure, composition and ionic conductivity properties in CeO₂/YSZ oxide heterostructures have been investigated using molecular dynamics simulations. Amorphization–recrystallization steps were performed with and without external electric field of strength 10?MV/cm along three different orientations: in-plane (YZ), normal (X) and 45° resultant (XY) with respect to the oxide heterointerfaces. The microstructural and compositional differences at the interfaces and in the interior of the oxide heterolayers were evaluated and were found to show a clear correlation with the orientations of the applied field. In particular, the XY configuration displayed a compressive lattice strain of ～9% along with a reduced oxygen vacancy concentration when compared to the others. Ionic density profiles suggest pronounced segregation (～60% higher compared to the average value in the interior) of yttrium ions closer to the YSZ/CeO₂ interface for the XY configuration. Other configurations exhibit minimal to no such variations. These microstructural differences are found to affect the number of mobile charge carriers and the activation barriers associated with ionic migration through the oxide lattice and consequently, influence the ionic conductivity.     

Multiscale Lagrangian fluid dynamics simulation for polymeric fluid

We have developed a simulation technique of multiscale Lagrangian fluid dynamics to tackle hierarchical problems relating to historical dependency of polymeric fluid. We investigate flow dynamics of dilute polymeric fluid by using the multiscale simulation approach incorporating Lagrangian particle fluid dynamics technique (the modified smoothed particle hydrodynamics) with stochastic coarse‐grained polymer simulators (the dumbbell model). We have confirmed that our approach is well in agreement with the macroscopic results obtained by a constitutive equation corresponding to the dumbbell model, and observed that microscopic thermal fluctuation appears in macroscopic fluid dynamics as dispersion phenomena. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 886–893, 2010     

Models and people: An alternative view of the emergent properties of computational models

Computer models can help humans gain insight into the functioning of complex systems. Used for training, they can also help gain insight into the cognitive processes humans use to understand these systems. By influencing humans understanding (and consequent actions) computer models can thus generate an impact on both these actors and the very systems they are designed to simulate. When these systems also include humans, a number of self‐referential relations thus emerge which can lead to very complex dynamics. This is particularly true when we explicitly acknowledge and model the existence of multiple conflicting representations of reality among different individuals. Given the increasing availability of computational devices, the use of computer models to support individual and shared decision making could potentially have implications far wider than the ones often discussed within the Information and Communication Technologies community in terms of computational power and network communication. We discuss some theoretical implications and describe some initial numerical simulations. © 2015 Wiley Periodicals, Inc. Complexity 21: 202–213, 2016     

Two‐dimensional replica‐exchange method for predicting protein–ligand binding structures

We have developed a two‐dimensional replica‐exchange method for the prediction of protein–ligand binding structures. The first dimension is the umbrella sampling along the reaction coordinate, which is the distance between a protein binding pocket and a ligand. The second dimension is the solute tempering, in which the interaction between a ligand and a protein and water is weakened. The second dimension is introduced to make a ligand follow the umbrella potential more easily and enhance the binding events, which should improve the sampling efficiency. As test cases, we applied our method to two protein‐ligand complex systems (MDM2 and HSP 90‐alpha). Starting from the configuration in which the protein and the ligand are far away from each other in each system, our method predicted the ligand binding structures in excellent agreement with the experimental data from Protein Data Bank much faster with the improved sampling efficiency than the replica‐exchange umbrella sampling method that we have previously developed. © 2013 Wiley Periodicals, Inc.     

On the Statistical Nonliving Nature of the Cationic Ring‐Opening Copolymerization of Oxetane with Tetrahydropyran

The copolymerization system of oxetane and tetrahydropyran is reinterpreted with the aid of computer simulations. The original claim that this system is a “living” and/or controlled pseudoperiodic copolymerization 1 is not confirmed by the simulation results. It is suggested that the formation of branched oxonium cations and the statistical nature of THP incorporation are the reasons for the observed discrepancies between the simulation results and experimental data.

     

Modeling of Low Concentrations of Reactive Species in Kinetic Monte Carlo Simulations

A new method for determination of contributions of species present in low concentration in kinetic Monte Carlo (MC) simulations of chemical processes is proposed. It allows, for instance, to calculate of exact concentrations when species being of interest appear in MC experiments only for short time intervals. The method is based on monitoring of the cumulative life‐time of the investigated species under consideration as a function of the reaction time and subsequent differentiation of the resulting curve. It is especially useful for determination of distributions of low‐concentration active propagation species in radical polymerizations, both free and controlled ones. The method enables to reduce significantly a simulation scale required for determination of the concentrations of investigated species.

     

近场宽带电场耦合天线的高频结构模拟器软件仿真及性能分析

近场宽带电场耦合天线是一种新型的短距离、高速无线通信天线,它是索尼公司力推的近距离高速无线通信技术——.Transferjet^TM的工作天线.使用高频结构模拟器软件,对一种典型的近场宽带电场耦合天线进行了参数化的结构设计;通过仿真模拟,分析短截线的线长和线宽,以及耦合电极的面积对天线中心频率和工作带宽的影响;分析了天线间的距离和夹角,以及耦合电极的面积,对天线传输损耗和性能的影响.设计了一个满足Transferjet^TM技术指标的小尺寸天线,给出了性能仿真结果.     

计算全息检测离轴非球面的离散相位拟合

为了计算补偿用计算全息图的刻线位置,需要对光线追迹得到的离散相位数据进行拟合。为此详细推导了均匀三次B样条和非均匀三次B样条的基函数,介绍了各自对应的曲面拟合方法。以一块抛物型离轴非球面数据为例,对其非对称的离散相位分布进行了三次B样条曲面拟合。拟合结果表明,三次B样条曲面拟合能使拟合面经过所有数据点,保证拟合精度,且得到的连续的相位补偿函数表达式结构简单（最高次数只有3次）, 还能根据实际情况优化采样点数量,控制计算量。     

基于LabVIEW激光引信回波模拟装置设计

激光引信回波模拟装置是激光引信测试设备的重要组成部分。介绍了激光引信回波模拟装置的组成,设计了用于该装置的硬件电路和软件控制系统。硬件电路采用单片机完成控制指令的接收和控制信号的产生,使用串行扩展芯片GM8125将单片机AT89S52的串行口扩展成5个,满足了激光引信回波模拟装置串口资源要求。软件控制系统基于LabVlFⅣ设计,主要包括串口通信程序和控制指令的产生程序,控制指令经串口通信传送给硬件电路。实验结果表明,该装置满足激光引信测试设备的要求。