元胞自动机方法在MEMS工艺模拟中的应用

随着计算机技术的发展和MEMS(micro-electro-mechanical system)自身发展的需要,应用元胞自动机方法模拟MEMS加工工艺的研究发展迅速.首先,简要介绍了元胞自动机原理,然后,综述了元胞自动机方法在MEMS工艺模拟中的应用现状,分析了应用元胞自动机方法模拟MEMS加工工艺的前景和方向.     

Retina simulation using cellular automata and GPU programming

This article shows how the architectural modelization of biological retina allows real-time performances, on standard widespread computing systems. First, we describe the biological retina with regard to its pipeline architecture, detailing its layer behaviours and properties. Then we propose a corresponding pipelined model of artificial retina based on cellular automata. In this work, the main innovation is the computing method based on the programming of a personal computer graphical card using OpenGL shading language. The last section demonstrates the efficiency of our model through numerical and graphical results. We lay particular emphasis on the fact that our direct implementation of the Graphical Processor Unit (GPU) provides computation power about 20 times as fast as conventional programming.     

Design and simulation of nano-arbiters using quantum-dot cellular automata

Arbiters are the essential components of the Network-On-Chip (NOC) systems and are used to resolve the contention problem where multiple requests must be handled for shared resources. On the other hand, with the ever-increasing downsizing trend in the fabrication technology, Quantum-dot Cellular Automata (QCA) with its nano scales and very low power consumption is a promising candidate for implementing future NOCs. In the current work, we design and simulate nano-arbiters using QCA with the following contributions: i) The 2-bit Basic Round Robin Arbiter (RRA) and the 2-bit Ping Pong Arbiter (PPA) are designed and simulated; ii) A solution for an erroneous condition found in the original circuit of RRA is reported and fixed; iii) We use Cartesian Genetic Programming (CGP) approach to simplify the RRA and PPA designs; iv) In order to leverage our QCA designs, we apply a more realistic clock distribution (2-DW clocking) and report the results. At the end, a one-to-one comparison of the two arbiters designed with QCA will be presented using such benchmarks as area, latency, etc. Our results show that in the 2-bit input mode, the PPA arbiter has the best overall performance.     

污水处理净化过程的三维细胞自动机动态模拟

针对污水处理过程的复杂性、不可重复性和不可再现性等特点,根据活性污泥的净化机理与动力学特性,在Mckinney等人建立的经典活性污泥法动力学模型的基础上,提出了一种模拟活性污泥净化过程的三维格子气细胞自动机模型.该模型的演化规则根据微生物的增殖规律和经典的动力学模型设计,模型通过模拟有机物和微生物的扩散、反应和沉降过程,反应了活性污泥的整个净化过程.对模型进行的仿真实验结果表明:该模型不仅可以复现污水净化过程,而且更直观地刻画了活性污泥法污水处理过程的动态演化行为,直接反映出活性污泥法系统的表观特征.     

Corrosion-passivation processes in a cellular automata based simulation study

A short survey of cellular automata based models for corrosion and passivation phenomena is given. Results of simulations based on the model of spatially separated anodic and cathodic reactions are presented for a cavity development from a point-like damage of a protective layer and from an initially flat unprotected surface. We show some new peculiar examples of the symmetry breaking in the cavity development. The results for the initially flat surface show roughening of the surface at the beginning of the corrosion process. After that, pit merging causes a resmoothing of the surface. An oscillatory behavior of the surface roughness is observed caused by a peninsula formation with subsequent island detachment. These results are obtained in 2D because of computational limitations. We plan simulations in 3D and point out the problems we encounter in their realization.     

Quadratic programming method in numerical simulation of metal forming process

In this paper, a quadratic programming (QP) model based on a parametric variational principle is proposed for elastic–plastic (EP) finite element analysis of metal forming processes. The contact problem with friction between blank and tools is treated in the same way as in plastic analysis. The penalty factors, which are normally introduced into the algorithm for contact analysis, have a direct influence on accuracy of solution. There is no available rule for choosing a reasonable value of these factors for simulation of metal forming, and they are therefore cancelled through a special technique so that the numerical results can be of high accuracy. The algorithms for contact analysis and plastic analysis are established in one frame and consistent with each other. Compared with the conventional EP FEM, the newly developed method requires no tedious iterative procedures, and has no convergence problems. To apply this method easily to simulation of metal forming, detailed forms of some key matrices or vectors for 2D FEM and 3D FEM are presented, and a parametric loading algorithm for the QP model is developed, which is suitable for QP problem with free variables, and can decrease memory cost by avoiding the introduction of additional slack variables and improve the solution efficiency to some extent. Finally the proposed QP model is validated by two examples, analysis of V-notched tension test and analysis of the drawing of a square box––one of the benchmarks proposed at NUMISHEET93. It can be seen that the accuracy of solution of the new EP FEM based on QP is better than that of the conventional EP FEM based on iteration. To make the new EP FEM more applicable to metal forming industries, It is necessary to develop a more efficient QP algorithm that is suitable for large-scale problems.     

Micromachining process simulation using a continuous cellularautomata method

In this paper, we present results on the development of an anisotropic crystalline etching simulation (AGES) program based on a continuous cellular automata (CA) model. The program provides improved spatial resolution and accuracy compared with the conventional and stochastic CA methods. Implementation of a three-dimensional (3-D) dynamic CA technique provides increased simulation speed and reduced memory requirement. The first AGES software based on common personal computer platforms has been realized for simulation of micromachining processes and visualizing results in 3-D space. The software is uniquely capable of simulating the resultant profile following a series of micromachining steps, including surface passivation, reactive ion etching, as well as wet chemical bulk etching. A novel method for accurately obtaining the etch-rate diagram of anisotropic etching using both experimental and numerical techniques has been developed     

Epidemiological modeling with a population density map-based cellular automata simulation system

We present a new numerical, two-dimensional cellular automata framework for simulation of the spread of an infectious disease in a region with non-homogenous spatial population distribution. For the simulation the real map of the population density in Poland is used, where the sources of the infection are located. Presented model is a combination of SEIR and IBM models complemented with additional factors like variable population density, death, birth and some stochastic parameters to reflect the more realistic population dynamics. In proposed model the states of individuals are tracked through time like in IBM model and the evolution of the whole system is described by SEIR transition function which determines how cells interact with their neighbours, influencing global behavior of the system. Presented model requires less complicated input than IBM models and is less expensive computationally. We explore influenza as the contagious disease in our map-based simulation. The results of the simulation show the spreading-rate of the disease and can be used to describe possible actions for preventing pandemic.     

Design of materials using hybrid cellular automata

This paper presents a new approach for the topological design of materials with extreme properties. The method is based on hybrid cellular automaton (HCA), which is an implicit optimization technique that uses local rules to update design variables iteratively until meeting the described optimality conditions. By means of an energy-based homogenization approach, the effective properties of the considered material are calculated in terms of element mutual energies. By this method, no sensitivity information is required to find the optimal topology for the considered design objectives: bulk modulus, shear modulus, and negative Poisson’s ratio. The proposed method is validated by a series of numerical examples.     

Data compression and encryption using cellular automata transforms

A family of basis functions, generated from the evolving states of Cellular Automata (CA), is used to compress and encrypt data. The operations required in encoding and decoding the data are described under the umbrella Cellular Automata Transforms (CAT). There is a huge number of these transform bases. CAT can be used in the way other mathematical transforms (e.g., Fourier, Discrete Cosine, Laplace, Wavelet, etc.) are utilized. In data-compression applications, the rules and pertinent keys used to generate the CA are selected to favor those that yield basis functions with the best information-packing characteristics. On the other hand, for encryption the selection is biased towards those with the tendency to yield an avalanche effect. In the latter case the transform process must be error-free.     

基于元胞自动机和模糊理论的人群疏散仿真

基于元胞自动机和模糊理论建立了人群疏散模型,对教学楼内的人群疏散过程进行了模拟。该模型根据人员对建筑物的熟悉程度、周围人员的吸引力设计元胞行为准则,并且采用模糊隶属度定义人员的体能状态及人员对环境的熟悉程度。实验结果表明,该仿真模型能够较好地模拟紧急状况下的人群疏散过程。     

Construction of living cellular automata using the Physarum plasmodium

The plasmodium of Physarum polycephalum is a unicellular and multinuclear giant amoeba that has an amorphous cell body. To clearly observe how the plasmodium makes decisions in its motile and exploratory behaviours, we developed a new experimental system to pseudo-discretize the motility of the organism. In our experimental space that has agar surfaces arranged in a two-dimensional lattice, the continuous and omnidirectional movement of the plasmodium was limited to the stepwise one, and the direction of the locomotion was also limited to four neighbours. In such an experimental system, a cellular automata-like system was constructed using the living cell. We further analysed the exploratory behaviours of the plasmodium by duplicating the experimental results in the simulation models of cellular automata. As a result, it was revealed that the behaviours of the plasmodium are not reproduced by only local state transition rules; and for the reproduction, a kind of historical rule setting is needed.     

Review on cellular automata simulations of microstructure evolution during metal forming process: Grain coarsening, recrystallization and phase transformation

Cellular automata (CA) algorithm has become an effective tool to simulate microstructure evolution. This paper presents a review on CA modeling of microstructural evolution, such as grain coarsening, recrystallization and phase transformation during metal forming process which significantly affects mechanical properties of final products. CA modeling of grain boundary motion is illustrated and several aspects of recrystallization are described, e.g. nucleation and growth, the development of static and dynam...     

Assessing cellular automata model behaviour using a sensitivity analysis approach

Rapid advances in computer and geospatial technology have made it increasingly possible to design and develop urban models to efficiently simulate spatial growth patterns. An approach commonly used in geography and urban growth modelling is based on cellular automata theory and the GIS framework. However, the behaviour of cellular automaton (CA) models is affected by uncertainties arising from the interaction between model elements, structures, and the quality of data sources used as model input. The uncertainty of CA models has not been sufficiently addressed in the research literature. The objective of this study is to analyze the behaviour of a GIS-based CA urban growth model using sensitivity analysis (SA). The proposed SA approach has both qualitative and quantitative components. These components were operationalized using the cross-tabulation map, KAPPA index with coincidence matrices, and spatial metrics. The research focus was on the impacts of CA neighbourhood size and type on the model outcomes. A total of 432 simulations were generated and the results suggest that CA neighbourhood size and type configurations have a significant influence on the CA model output. This study provides insights about the limitations of CA model behaviour and contributes to enhancing existing spatial urban growth modelling procedures.     

Implementing a one-bit reversible full adder using quantum-dot cellular automata

Quantum-dot cellular automata (QCA) technique is one of the emerging and promising nanotechnologies. It has considerable advantages versus CMOS technology in various aspects such as extremely low power dissipation, high operating frequency and small size. In this paper, designing of a one-bit full adder is investigated using a QCA implementation of Toffoli and Fredkin gates. Then, a full adder design with reversible QCA1 gates is proposed regarding to overhead and power savings. Our proposed full adder design is more preferable when considering both circuit area and speed. The proposed design uses only two QCA1 gates and maximizes the circuit density and focuses on a layout of the circuit which is minimal in using QCA cells.     

Simulation of forest fire fronts using cellular automata

In this work a new model for fire front spreading based on two-dimensional cellular automata is proposed. It is a more realistic modification of the model introduced by Karafyllidis and Thanailakis (see [Karafyllidis I, Thanailakis A. A model for predicting forest fire spreading using cellular automata. Ecol Model 1997;99:87–97]), which is based on the transfer of fractional burned area. Specifically, the model proposed in this work introduces a more accurate factor of propagation from a diagonal neighbor cell and includes, in a detailed form, the rate of fire spread. Moreover, the model is useful for both homogeneous and inhomogeneous environments. Some tests have been passed in order to determine the goodness of the method.     

基于元胞自动机的肿瘤生长形态动态模拟

为了模拟肿瘤生长和附近组织发生机械作用过程以及自身所发生形变,研究了肿瘤生长过程形态的连续性,穿透深度的计算以及肿瘤的真实感绘制。用元胞自动机模拟肿瘤动态生长过程,并在模型每次发生形变后对元胞状态进行更新,以增强肿瘤生长形态的连续性;模型顶点穿透深度的准确性直接影响力学模型计算形变结果的合理性、准确性,采用基于隐式曲面的方法计算穿透深度的大小和方向;为了增强肿瘤模型的真实感,采用隐式曲面的方法渲染每个生长时刻的肿瘤形态。实验结果表明：该方法能得到形态较连续的生长过程;改进后的穿透深度计算方法能得到一致性较好的深度矢量;基于模型表面点集隐式曲面绘制的肿瘤模型具有平滑表面,有较好的仿真效果。     

Acceleration of cellular automata algorithms using genetic algorithms

The following problem is solved: Given a Cellular Automaton with continuous state space which simulates a physical system or process, use a Genetic Algorithm in order to find a Cellular Automaton with discrete state space, having the smallest possible lattice size and the smallest possible number of discrete states, the results of which are as close as possible to the results of the Cellular Automaton with continuous state space. The Cellular Automaton with discrete state space evolves much faster than the Cellular Automaton with continuous state space. The state spaces of two Cellular Automata have been discretized using a Genetic Algorithm. The first Cellular Automaton simulates the two-dimensional photoresist etching process in integrated circuit fabrication and the second is used to predict forest fire spreading. A general method for the discretization of the state space of Cellular Automata using a Genetic Algorithm is also presented. The aim of this work is to provide a method for accelerating the execution of algorithms based on Cellular Automata (Cellular Automata algorithms) and to build a bridge between Cellular Automata as models for physical systems and processes and Cellular Automata as a VLSI architecture.     

Directional multi-scale analysis and simulation of urban expansion in Auckland,New Zealand using logistic cellular automata

In characterising urban expansion, existing landscape indices lack consideration for directional changes. This limitation is overcome with the proposed directional perspective (urban expansion vector) in this study, which can identify both the urban expansion mode and local changes at the patch and sectorial levels, and reveal the varying importance of the same urbanisation factors at multi-scales. Landscape (expansion) indices (LEI) and directional characteristics of newly grown urban patches were derived / extracted from time-series (1975–2016) satellite images in the Auckland metropolitan area, based on which urban expansion was simulated using logistic regression cellular automata at both the global and sectorial levels. The results show that Auckland urban development was mostly compact with “organic” being the dominant mode of expansion throughout the last 40 years. Most urban development took place in the southeast (270° - 360°) and northwest (90° - 180°) sectors, within which urban expansion occurred mostly in places that had favourable transportation infrastructures and are close to the CBD. The influence of the nine factors of urbanisation studied varies with scale and sector. In general, accessibility (e.g., proximity to roads and the CBD) and amenity (e.g., distance to transportation and schools) are more important than physical variables (e.g., terrain) in affecting urban development. The localised sectorial simulation result is in a closer agreement with the observed urbanisation than the global, sectorless result. The directional perspective, in conjunction with the LEI and other landscape indices, can effectively characterise the spatiotemporal patterns of urban expansion. More importantly, it improves the simulation accuracy of urban expansion (e.g., simulation kappa rising from 0.024 to 0.161 in the northwest sector, and from 0.31 to 0.40 in the southeast sector) for a monocentric city whose urbanisation is strongly sectorial.