Cellular Automata

Modelling and simulation are disciplines of major importance for science and engineering. There is no science without models, and simulation has nowadays become a very useful tool, sometimes unavoidable, for development of both science and engineering. The main attractive feature of cellular automata is that, in spite of their conceptual simplicity which allows an easiness of implementation for computer simulation, as a detailed and complete mathematical analysis in principle, they are able to exhibit a wide variety of amazingly complex behaviour. This feature of cellular automata has attracted the researchers' attention from a wide variety of divergent fields of the exact disciplines of science and engineering, but also of the social sciences, and sometimes beyond. The collective complex behaviour of numerous systems, which emerge from the interaction of a multitude of simple individuals, is being conveniently modelled and simulated with cellular automata for very different purposes. In this book, a number of innovative applications of cellular automata models in the fields of Quantum Computing, Materials Science, Cryptography and Coding, and Robotics and Image Processing are presented

AFCI Quarterly Input – UNLV April 1 through June 30, 2007

Quarterly report highlighting research projects, activities and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center. The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support

University of Nevada, Las Vegas Transmutation Research Program Annual Progress Report Academic Year 2007-2008

It is my pleasure to present the UNLV Transmutation Research Program’s seventh annual report that highlights the academic year 2007-2008. Supporting this document are the many technical reports and theses that have been generated over the past seven years. In the seventh year of our program, we continued to see growth in the Radiochemistry Ph.D. program with a total of 20 students in the fourth year of the program (we anticipated twelve in the program proposal). Since our inception, the program has sponsored to their conclusion 48 M.S. and 6 Ph.D. degrees. The program supported 53 graduate students, 11 undergraduates, and eight post-doctoral scholars in eight academic departments across the UNLV scientific and engineering communities in the academic year 2007-2008. Our research tasks span the range of technology areas for transmutation, including separation of actinides from spent nuclear fuel, methods of fuel fabrication, reactoraccelerator coupled experiments, corrosion of materials exposed to lead-bismuth eutectic, and special nuclear materials protection and accountability. We continued our emphasis on molten metal technology and actinide chemistry in our enhancements to UNLV this year to build a foundation in areas that are in line with UNLV’s strategic growth and our ability to address student-appropriate research in the transmutation program

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Modeling of the protective oxide layer growth in non-isothermal lead-alloys coolant systems

Lead alloys have been determined to be potential coolant candidates in advanced reactors and accelerator driven systems (ADS) because of their favorable thermal-physical and chemical properties. However, the corrosiveness of the lead-alloys is a critical obstacle and challenge for safe applications in reactors and ADS. Furthermore, the selective dissolution of materials into lead alloys would destroy the structure and contaminate the coolant rapidly, and the deposition of corrosion product may lead to severe flow-path restrictions. One of the effective ways to protect the material is to form and maintain a protective oxide film along the structural material surface by active oxygen control technology; The goal of this research is to provide basic understanding of the protective oxide layer behaviors and to develop oxide layer growth models of steels in non-isothermal lead-alloys coolant systems in order to provide useful information for active oxygen control technique; First, a theoretical kinetic model based on the boundary layer theory was developed to investigate the corrosion/precipitation in non-isothermal lead alloy coolant systems. The analytical expressions of the local corrosion/precipitation rate and the bulk concentration of the corrosion products were obtained by considering a turbulent core region and a laminar sub-layer. Numerical solutions were also accomplished together with considering the effect of the eddy mass diffusivity in lead alloy systems. Second, a diffusion controlling oxide layer growth model with scale removal was built in oxygen containing lead alloys. Scale removal effect was considered and the formation mechanism of duplex oxide layer structure was investigated in the model. Finally, the oxide layer growth process, together with the transport of oxygen and ionic metal, was studied at a mesoscopic level based on an improved stochastic cellular automaton (CA) model; Results from the developed models were compared with the available experimental data and previous work, and good agreement was attained. Moreover, the extended applications of the developed models were analyzed

Modelling the localized corrosion effects experienced by electroplated zinc and zinc - 4.5 wt.% aluminium steel coatings.

A general modelling approach is described for the numerical simulation of localized corrosion phenomena. The model is demonstrated using several simple cases and compared both to analytical solutions and experimental measurements. The model is intended to operate at the microscopic-mesoscopic length scales and involves two- or three-dimensional field calculations performed in a finite difference computational framework. Limitations and possible extensions to the algorithm are discussed. Experimental work has been reported that demonstrates the effects of microstructural variations within Zn-Al Galfan type coatings on the corrosion behaviour of cut-edge material, i.e. those cases where both the underlying steel and the organic coated Galfan layer are simultaneously exposed to a corrosive environment. An attempt to model the localized corrosion effects in electroplated zinc and hot-dip Galfan coatings has been made. The model combines both diffusive and electrochemical phenomena and describes corrosion effects on micro scale coating layers in NaCl electrolyte. The model predicts the 3D form of electrical potential, localized current densities and concentrations and also the time-dependent degradation of the micro scale coating layer. Results of the prototype model are quantitatively compared with measured current densities obtained from Scanning Vibrating Electrode Technique (SVET) studies. Simulations have been performed to predict the microstructural influence on the corrosion of Galfan coatings cooled at different rates. The model is in good agreement with experimental findings with respect to the cut-edge behaviour of these coatings, although contradicts those SVET measurements made in respect of the surface corrosion performance