Computer Simula Research Articles

Methyl Benzoylformate Derivative Norrish Type I Photoinitiators for Deep-Layer Photocuring under Near-UV or Visible LED

We designed and prepared a series of methyl benzoylformate (MBF) derivatives Norrish type I photoinitiators (MBFs) for light-emitting diode (LED)-induced photopolymerization through computer simula...

Morphological Transformation Network of Nanoparticles via DFT Simulations

The development and advancement of nanomaterials engineering have become essential points in the goal of designing new materials with applications of particular interest. Therefore, computer simula...

New Algorithm for Color Image Encryption Using Improved 1D Logistic Chaotic Map

This paper introduces a simple and effective improved one-dimension (1D) Logistic chaotic map. Simulations and performance evaluations show that the improved 1D Logistic chaotic map is able to get larger chaotic range and better chaotic behaviors compared with its prototype map. To investigate its applications in multimedia security, I propose an ef- ficient encryption algorithm for color image. Firstly, used an improved 1D Logistic chaotic map to confuse the addresses of a color image pixels. Secondly, decomposed the resultant image into 24-bits planes to get a bit-matrix containing a mixture of the red, green and blue elements. Finally, utilized global diffusion to permute the bit-matrix which makes the three elements influence each other effectively without neglecting the relativity between R, G and B. Computer simula- tions indicate that the proposed algorithm has some good properties such as easy to implement, large key space, and ex- cellent encryption effect with just one round of iteration. Hence, it has application in secure communication to enhance the security of transmitting color image.

ANALYSIS OF DEFLECTED MODE IN THE DEFORMATION ZONE DURING THE ROD ROLLING IN VARIOUS CALIBER SYSTEMS BASED ON THE MODELING BY FINITE ELEMENT METHOD

In the article the stressed state of metal in the deformation zone during hot rolling of rod using the finite element method for computer simula- tion in program system DEFORM-3D are analyzed. The methodology for evaluation of the stressed state during the high-speed hot rolling of rod is presented. The known systems of calibers are analyzed. The factors of roll pass design, which influence the magnitude and distribu-tion of the longitudinal tensile stresses in the deformation zone, are determined.

An efficient receiver scheme for downlink ZP-CDMA

A signal transmitted through a wireless channel may be severely distorted by intersymbol interference (ISI) and multiple access interference (MAI). In this paper, we propose an efficient CDMA receiver based on frequency domain equalization (FDE) with a regularized zero forcing (RZF) equalizer and parallel interference cancellation with a unit clipper decision function (CPIC) to combat both the ISI and the MAI. We call this receiver the FDE-RZF-CPIC receiver. This receiver is suitable for downlink zero padding CDMA cellular systems. The effects of the decision function, the channel estimation, the number of cancelled users, and the user loading on the performance of the proposed receiver are discussed in the paper. The bit error rate (BER) of the data received by the proposed receiver is evaluated by computer simula- tions. The experimental results show that the proposed receiver provides a good performance, even with a large number of interfering users. At a BER of 10 −3 ,t he performance gain of the proposed receiver is about 2 dB over the RAKE receiver with a clipper decision function and PIC in the half-loaded case (eight users) and is much larger in the full-loaded case (16 users).

Reading sensitivity of a new thermomechanical data-storage technique: The effect of reducing probe dimensions

Heat transfer in a thermomechanical probe operated in a noble gas is studied by computer simula- tion in the collisionless approximation. The study is motivated by the fact that heat transfer in the gaseous envi- ronment becomes the main factor affecting the data-reading sensitivity as the feature sizes of thermomechanical probes used in data-storage systems approach the mean free path in the gas at room temperature and atmo- spheric pressure. A mathematical model is constructed and implemented in software. This is employed to run a computer simulation with the aim of evaluating the data-reading sensitivity in the case of helium. The behav- ior of the sensitivity with decreasing probe size is examined.

The Fluctuation Theorem

The question of how reversible microscopic equations of motion can lead to irreversible macroscopic behaviour has been one of the central issues in statistical mechanics for more than a century. The basic issues were known to Gibbs. Boltzmann conducted a very public debate with Loschmidt and others without a satisfactory resolution. In recent decades there has been no real change in the situation. In1993 we discovered a relation, subsequently known as the Fluctuation Theorem (FT), which gives an analytical expression for the probability of observing Second Law violating dynamicaluctuations in thermostatted dissipa- tive non-equilibrium systems. The relation was derived heuristically and applied to the special case of dissipative non-equilibrium systems subject to constant energy `thermostatting'. These restrictions meant that the full importance of the Theorem was not immediately apparent. Within a few years, derivations of the Theorem were improved but it has only been inthe last few of years that the generality ofthe Theorem has been appreciated. We now know that the Second Law of Thermo- dynamics can be derived assuming ergodicity at equilibrium, and causality. We take the assumption of causality to be axiomatic. It is causality which ultimately is responsible for breaking time reversal symmetry and which leads to the possibility of irreversible macroscopic behaviour. The Fluctuation Theorem does much more than merely prove that in large systems observed for long periods of time, the Second Law is overwhelmingly likely to be valid. The Fluctuation Theorem quanti®es the probability of observing Second Law violations in small systems observed for a short time. Unlike the Boltzmann equation, the FT is completely consistent with Loschmidt's observa- tion that for time reversible dynamics, every dynamical phase space trajectory and its conjugate time reversedanti-trajectory', are both solutions of the underlying equations of motion. Indeed the standard proofs of the FT explicitly consider conjugate pairs of phase space trajectories. Quantitative predictions made by the Fluctuation Theorem regarding the probability of Second Law violations have been con®rmed experimentally, both using molecular dynamics computer simula- tion and very recently in laboratory experiments.

The Simulation Education Homepage

Both novice and experienced educators across dif ferent disciplines have expressed the need for a tool to help orient them to teach computer simula tion. This paper presents the Simulation Educa tion Homepage (http://www.acs.ilstu.edu/faculty/ dldoss/yurcik/nsfteachsim/indexnew.html) which was initiated as a result of an US National Sci ence Foundation sponsored Simulation Education Workshop held in August 1998 in Washington D.C. With input from leading simulation educa tors, web-based simulation education resources have been linked and cross-referenced in this one "virtual " location which serves as a meeting place for discussion about teaching simulation. After introducing the different categories of resources (software/courses/textbooks/people/etc.), data about categorization and use of the resources is presented. We found clear trends within categories and common characteristics between requests for information and recommendations for new links from all over the world. We also include discus sion of a future project to enhance the interactivity of this website using XML integrated with database processing.

Schwarzschild objective for soft x-rays

The geometrical aberrations theory of a centered system is applied to calculate the third order aberrations of the optical system based on two spherical mirrors (the so-called Schwarzschild objective). The role of each of the third order field aberrations in the formation of the view field is analyzed. The scaling effect (i.e., the relationship between the optics' geometrical dimensions and the spatial resolution) is studied. The performance of a 213 Schwarzschild objective (including the non- concentric scheme) is investigated using a ray-tracing computer simula- tion. The tolerances of the axial and lateral alignments of the Schwarzs- child objective are found and the results are used to design a soft x-ray optical system based on multilayer mirrors to provide low geometrical aberrations (spatial resolution about 0.05 mm) and a view field up to 300 mm. Soft x-ray imaging microscope experiments demonstrate good ac- cordance with the predicted performance of the optics. High resolution optics such as these can be a good basis for the optical instrumentation in soft x-ray microscopy, extreme ultraviolet lithography (EUVL), mi- croanalysis, etc. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)02307-2)

Modeling and Simulation of Computerized Tomography Systems

The field of Computerized Tomography (CT) has revolutionized medical imaging and has been ap plied to the diverse fields of radio astronomy, elec tron microscopy, geophysics, stress analysis, radar, and nondestructive testing. Computer simula tion has played an integral role in the development of CT systems and algorithms. This article pro vides an overview of CT and the tools used to model and simulate CT systems, and demon strates the evaluation of a novel Localized CT (LCT) technique through simulation. The key features of the discrete wavelet transform are reviewed as they relate to the development of LCT algorithms. The Shepp-Logan head phantom is presented and utilized in the simulation and evalu ation of the proposed LCT technique.

Integration of the Genetic Algorithm and Discrete-Event Computer Simulation for Decision Support

The genetic algorithm, a search algorithm based on the mechanics of natural selection and popula tion genetics, is implemented using a discrete- event computer simulation language. The impe tus behind this study is to integrate a tool typi cally used in the development of descriptive stud ies with a potentially powerful method of optimi zation. The facilities needed to implement a genetic algorithm using a traditional computer language are remarkably similar to a set of functions already existing in most discrete-event computer simula tion languages. Three methods of integrating the genetic algorithm and computer simulation are discussed, then a two-phase study is conducted to assess the feasibility of the theoretical discussion. A free-ranging automated guided vehicle example illustrates the results. Computational experience suggests the genetic algorithm is relatively adapt able for use in a discrete-event computer simula tion environment. Within this environment, ad ditional support for the decision maker is pro vided by combining the power of representational modeling with optimization capability.

A Calibration Method Free of Optimum Factor Number Selection for Automated Multivariate Analysis. Experimental and Theoretical Study

Several analytical applications of multivariate calibration methods require human decisions, the most difficult being the number of factors involved. Thus, eliminating the optimum factor number may contribute to the improvement of automatic calibration processes. We propose a factor analysis method that does not need the factor number. It is particularly suitable for indirect calibration of a system under indirect observation. The algorithm is based on composing a subspace excluding the contribution from the component of interest and calculating its net analyte signal through an orthogonal projection to an orthogonal space. This method is applicable as long as the spectral vector dimension (i.e., the number of data points) is larger than the calibration set size. This condition readily satisfied in spectroscopic analysis. The relevant effects, including the effect of the spectral vector dimension and of the calibration set size upon prediction errors, have been investigated using extensive computer simula...

Shock-shock collisions in the interstellar medium

We show that the nonlinear structure produced by the collision of two spherical shock fronts develops into binary self-collimating outflows behind the accelerating reflected shocks. Computer simula...

An Interactive Simulation Model for the Logistics Planning of Container Operations in Seaports

Today, more than 90 percent of international cargo moves through seaports, and 80 percent of seaborne cargo moves in containers. It has thus become imperative for major seaports to manage their container operations both effec tively and efficiently. We have designed and developed an interactive computer simula tion model to support the logistics planning of container operations. Logistics planning of container operations deals with the assign ment and coordination of port equipments such as quay cranes, prime movers, and yard cranes in the transportation of containers between the ship's bay and the container storage yards. This model provides estimates for port performance indicators such as berth occupancy, ship outputs, and ship turnaround time for various operating strategies in the logistics planning of container operations. The main objective of port management is to reduce the ship turnaround time by optimally utilizing the port resources. Reduced turn around time encourages trade and improves the competitiveness of the port to provide efficient and effective services at low cost.

Computer Simulation and Library Management

In 1975 Bommer said that computer simulation models had remained on the fringes of library science because too much attention has been devoted to the construction and solution of complex mathematical models, and too little attention to the implementation aspect. Nine years later, in 1984, Simonton makes the same point, substantially reflecting the lack of progress in this field.This paper surveys the relevant literature, and attempts to isolate key issues which might explain why computer simula tion models are not implemented to any extent in libraries.

The entity - connection approach to modelling and simulation

To cope with the huge complexity of many simulation programs, a series of description, implementation and documentation tools have been invented to support the whole software development process. The tools range from simulation model specification and documenta tion languages, through program generators, to knowledge-based advanced simulation environ ments or model management systems. Most of these tools transform meta-information about the model into a code in an existing simulation language. Little attention is, however, paid to the question which concepts of a computer simula tion language are appropriate to support meta- programming (i.e. module combination, alteration, replication etc.). In this paper a modular concept for a discrete event simulation language is presented. This language contains abstraction mechanisms, namely the entity and the connection module, which are at the same time data and control abstractions. To each such module there corresponds a graphically displayable icon. The graphic representation is such that the consistency of the model is equivalent to a correctly assembled representa tion graph. The aims of this new concept are to present a new structure for simulation program ming, to create an appropriate software engineering tool and to provide a graphical representation technique for simulation models, which enhances modularity and decomposition for parallelization.

PRE-PRIM as a pre-processor to simulations: a cohesive unit

Large scale computer simula tions are in widespread and growing use in government, business and science. Large numbers of parameters may initially appear to be needed in simulations; the user needs the flexibility to evaluate as many parameters as possible. Mathe matical and statistical tools can reduce the final set of parame ters to an efficient minimum. This paper describes the con cepts underlying PRE-PRIM, a preprocessor to simulations integrated by the present author. PRE-PRIM assures that (a) a wide number of parameters can be analyzed with a minimum number of simulation runs, (b) efficiency and replicability in the coefficients of these parameters is established, and (c) a protocol for the sequence of simulation runs is determined.

Software Reviews : SOCIOLOGY LABORATORY: COMPUTER SIMULA TIONS FOR LEARNING SOCIOLOGY Reviewed by William F. Bengston, St. Joseph's College Publisher: Wadsworth Publishing Co., Belmont, CA 94002 (telephone: 415-595-2350) Year of Publication: 1987 Materials: One diskette, 106-page manual, data forms Price: $16.75 Machine Specificity: IBM and compatibles System Requirements: 128K memory, one disk drive Effectiveness: Fair to good User-Friendliness: Excellent Documentation:

The SOCIOLOGY LABORATORY diskette provides 12 simulations for use by introductory sociology students as computer lab assignments. Eleven of the simulations emphasize exchange theory in the teaching of a wide variety of theories and concepts. The programs are remarkably user-friendly, and the manual is clearly and concisely written. Criticisms of the effectiveness of the program concern the uneven quality of the simulations, their tendency to be like recreational computer games, and the overreliance on exchange theory.

Computer simulation and library management

In 1975 Bommer said that computer simulation models had remained on the fringes of library science because too much attention has been devoted to the construction and solution of complex mathematical models, and too little attention to the implementation aspect. Nine years later, in 1984, Simonton makes the same point, substantially reflecting the lack of progress in this field. This paper surveys the relevant literature, and attempts to isolate key issues which might explain why computer simula tion models are not implemented to any extent in libraries.

3RD THIRD PLACE WINNER Simulation of the signalized intersection

Simulation is commonly used to model vehicular behavior at intersections in urban grid networks. In recent years traffic volume in suburban areas has increased to the point where it rivals urban congestion. This shift in traffic concentrations has placed increased emphasis on the need for understanding traf fic flows at non-grid or isolated intersections. A computer simula tion model of a prototypical isolated intersection was developed. The model was used to test preliminary hypothesis regarding ef ficient isolated intersection design and signal operation policy.