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.     

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.     

Probabilistic automata and simulation

Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 20–31, May–June, 1993.     

Dynamical properties of hybrid automata

Hybrid automata provide a language for modeling and analyzing digital and analogue computations in real-time systems. Hybrid automata are studied here from a dynamical systems perspective. Necessary and sufficient conditions for existence and uniqueness of solutions are derived and a class of hybrid automata whose solutions depend continuously on the initial state is characterized. The results on existence, uniqueness, and continuity serve as a starting point for stability analysis. Lyapunov's theorem on stability via linearization and LaSalle's invariance principle are generalized to hybrid automata.     

Reducing I/O variability using dynamic I/O path characterization in petascale storage systems

In petascale systems with a million CPU cores, scalable and consistent I/O performance is becoming increasingly difficult to sustain mainly because of I/O variability. The I/O variability is caused by concurrently running processes/jobs competing for I/O or a RAID rebuild when a disk drive fails. We present a mechanism that stripes across a selected subset of I/O nodes with the lightest workload at runtime to achieve the highest I/O bandwidth available in the system. In this paper, we propose a probing mechanism to enable application-level dynamic file striping to mitigate I/O variability. We implement the proposed mechanism in the high-level I/O library that enables memory-to-file data layout transformation and allows transparent file partitioning using subfiling. Subfiling is a technique that partitions data into a set of files of smaller size and manages file access to them, making data to be treated as a single, normal file to users. We demonstrate that our bandwidth probing mechanism can successfully identify temporally slower I/O nodes without noticeable runtime overhead. Experimental results on NERSC’s systems also show that our approach isolates I/O variability effectively on shared systems and improves overall collective I/O performance with less variation.     

通用分布式仿真I/O体系结构设计及其应用

分析了几种典型仿真I/O体系结构的优缺点,设计并实现了一种软硬件可伸缩的分布式 仿真二级I/O体系结构,该结构不仅直接支持了共享的时分多路通道存取型数字设备(如7段数码管 显示器),将硬联逻辑复杂度从O(n)降低到O(logn)的水平,而且具有实时性、可伸缩性、容错性、可 维护性和通用性等良好特征,较好地满足了半实物仿真系统的需要。     

NAND flash memory-based hybrid file system for high I/O performance

As the performance potentials of SSD (Solid State Device) have been recognized, adopting SSD to IT products as HDD replacements is rapidly increasing. Since SSD is organized into multiple flash memory packages, it deploys peculiar device characteristics that do not occur in HDD, such as block-unit erasure overhead. Also, its high cost per capacity is the main obstacle to building a large-scale storage subsystem with only SSDs. An alternative is to build a hybrid storage subsystem where a small portion of SSDs are integrated with HDDs so as to utilize SSD’s performance advantages in a cost-effective way. This study introduces a new form of file system, called N-hybrid (New-Form of hybrid file system), that enables us to support the hybrid device structure combined with both HDD and SSD. Our primary objectives in developing N-hybrid are to provide better I/O bandwidth by exploiting the characteristics of HDD and SSD and to provide a flexible data layout maximizing the usage of tight SSD storage resources. Several experiments were conducted to verify the effectiveness and suitability of N-hybrid.     

Design, analysis, and simulation of I/O architectures for hypercubemultiprocessors

Several issues concerning the design of an I/O (input/output) system for a multiprocessor such as a hypercube are examined. A methodology is proposed for connecting the I/O processors to such a system for efficient I/O access. The effect of I/O communication on the multiprocessor network is analyzed. Different disk organizations that can be employed within such a system are evaluated to see which organization has a better performance. It is observed that parallelism in serving an I/O request plays a dominant role in the scientific workload. The problem of mapping specific data structures such as matrices onto the disks so that the data can be accessed efficiently is considered     

Spatial Networks of Hybrid I/O Automata for Modeling Excitable Tissue

We propose a new biological framework, spatial networks of hybrid input/output automata (SNHIOA), for the efficient modeling and simulation of excitable-cell tissue. Within this framework, we view an excitable tissue as a network of interacting cells disposed according to a 2D spatial lattice, with the electrical behavior of a single cell modeled as a hybrid input/ouput automaton. To capture the phenomenon that the strength of communication between automata depends on their relative positions within the lattice, we introduce a new, weighted parallel composition operator to specify the influence of one automata over another.The purpose of the SNHIOA model is to efficiently capture the spatiotemporal behavior of wave propagation in 2D excitable media. To validate this claim, we show how SNHIOA can be used to model and capture different spatiotemporal behavior of wave propagation in 2D isotropic cardiac tissue, including normal planar wave propagation, spiral creation, the breakup of spirals into more complex (potentially lethal) spatiotemporal patterns, and the recovery of the tissue to the rest via defibrillation.     

IEEE-488 interface using parallel I/O ports

A single-board computer system and a selfdesigned interface card are used along with a monitor in ROM to interface a frequency spectrum analyser and a remote computer system using an IEEE-488 interface. Various settings on the analyser can be controlled as well as the collection of data. The monitor also has the ability to act as a terminal on a remote computer system and to transfer spectra between the microsystem and the remote host.     

基于OPNET的Link 16建模与仿真

基于对Link16的研究,建立符合OSI分层标准的JTIDS端机模型和毁伤加载节点模型,仿真平台实现Link16基本功能,并重点解决:功能端机退出带来的网络拓扑结构变化问题;链路仿真和网络仿真跨平台间的接口问题;基于数据库的快速构建大型网络仿真场景的问题。针对不同设置,仿真实验将获得各种情况下的网络和端机性能指标,有效指导Link16网络设计和优化。     

Flexible multibody simulation using hybrid integration scheme

One issue in the dynamic simulation of flexible multibody system is poor computation efficiency, which is due to high frequency components in the solution associated with a deformable body. Standard explicit numerical methods should take very small time steps in order to satisfy the absolute stability condition for the high frequency components and, in turn, the computational efficiency deteriorates. In this study, a hybrid integration scheme is applied to solve the equations of motion of a flexible multibody system for achieving better computational efficiency. The computation times and simulation results are compared between the hybrid scheme and conventional methods. The results demonstrate that the efficiency of a flexible multibody simulation can be improved by using the hybrid scheme.     

Modeling the aging process of flash storage by leveraging semantic I/O

The major advantages of flash memory such as small physical size, no mechanical components, low power consumption, and high performance have made it likely to replace the magnetic disk drives in more and more systems. Many research efforts have been invested in employing flash memory to build high performance and large-scale storage systems for data-intensive applications. However, the endurance cycle of flash memory has become one of the most important challenges in further facilitating the flash memory based systems. This paper proposes to model the aging process of flash memory based storage systems constructed as a Redundant Array of Independent Disks (RAID) by leveraging the semantic I/O. The model attempts to strike a balance between the program/erase cycles and the rebuilding process of RAID. The analysis results demonstrate that a highly skewed data access pattern ages the flash memory based RAID with an arbitrary aging rate, and a properly chosen threshold of aging rate can prevent the system from aging with a uniform data access pattern. The analysis results in this paper provide useful insights for understanding and designing effective flash memory based storage systems.     

Lifting motion simulation using a hybrid approach

In this study, a hybrid dynamic model for lifting motion simulation is presented. The human body is represented by a two-dimensional (2D) five-segment model. The lifting motions are predicted by solving a nonlinear optimisation problem, the objective function of which is defined based on a minimal-effort performance criterion. In the optimisation procedure, the joint angular velocities are bounded by time-functional constraints that are determined by actual motions. Symmetric lifting motions performed by younger and older adults under varied task conditions were simulated. Comparisons between the simulation results and actual motion data were made for model evaluation. The results showed that the mean and median joint angle errors were less than 10°, which suggests the proposed model is able to accurately simulate 2D lifting motions. The proposed model is also comparable with the existing motion simulation models in terms of the prediction accuracy. Strengths and limitations of this hybrid model are discussed.     

与线性混杂自动机等价的状态依赖空间模型

混杂系统可以由多种等价系统进行描述,本文研究用状态依赖空间模型对线性混杂自动机进行描述,线性混杂自动机是一类自治的不确定性系统,而状态依赖空间模型是含有输入的确定性系统.在状态依赖空间模型中,通过增加输入变量可以描述线性混杂自动机转换过程中的不确定性,进而将其转换成等价的状态依赖空间模型.本文所提到的等价性是指两个系统产生的轨迹是相同的.