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Feng Z.-G.,UTSA | Michaelides E.E.,TCU | Mao S.,Los Alamos National Laboratory
Fluid Dynamics Research

We investigate the hydrodynamic drag force on a viscous sphere in a fluid of different viscosities at small but finite Reynolds numbers when interfacial slip is present at the surface of the sphere. The sphere is small enough for it to retain its spherical shape, as is the case with most small droplets. By using a singular perturbation method, the exterior flow field of the droplet is decomposed into an inner region, where the viscous effects dominate, and an outer region, where the inertia is important. The interior flow of the viscous sphere is also solved analytically. By applying appropriate boundary conditions to the surface of the viscous sphere and matching the conditions between the inner and outer flow fields, stream functions up to the order of Re 2 log Re for both the exterior and the interior flow are obtained. Thus, an analytical expression for the drag force coefficient of the viscous droplet is derived. This general expression yields, as special cases, several other expressions that are applicable to spheres that translate rectilinearly under more restrictive conditions. One of the practical conclusions from this study is that the presence of interfacial slip can significantly reduce the drag force on a droplet. © 2012 The Japan Society of Fluid Mechanics and IOP Publishing Ltd. Source

Michaelides E.E.,Texas Christian University | Feng Z.,UTSA
Proceedings of the 25th International Conference on Efficiency, Cost, Optimization and Simulation of Energy Conversion Systems and Processes, ECOS 2012

Coal gasification is becoming a common method of producing synthetic gas to be used subsequently with reduced pollution products. The coal gasifiers are essentially chemical reactors where the coal particles are fluidized and react chemically with the gas. The modelling of the gasifiers involves both particle flow and heat transfer processes. Direct Numerical Simulation (DNS) methods for particulate flows have been welldeveloped in the last decade. Following the significant advances in computational power, DNS methods may now be employed to solve relatively complex particulate flow problems and provide us with scientific, reliable and validated information on fluid-particle interactions that will lead to the design optimization of gasifiers. While most of the DNS methods that have been developed pertain to isothermal flows, the effects of heat and mass transfer on the momentum and energy exchanges are very important in all practical applications. This because, for most practical applications of particulate flow-e.g. fluidized bed reactors, gasifiers, coal burners and chemical reactor columns-the heat and mass transfer processes influence significantly the flow and, in addition, are of primary interest to engineers. We have developed a new DNS method, which uses an extension of the Immersed Boundary Method (IBM) to track individual particles and calculate the Lagrangian motion as well as the heat transfer from them. The model enables us to examine the lift of hotter particles due to the buoyancy their temperature field creates; the temperature field around the particles; and the effect of the Reynolds and Grashof numbers on the flow and heat transfer of suspensions. This model is also of use in the determination of the boundary conditions of particles at solid boundaries, conditions that are essential to all two-fluid models. The simulations show that a significant slip exists along the longitudinal direction at the walls of the gasifiers and that the size of the particles is the primary parameter that determines this velocity slip. Source

Araujo P.R.,Greehey Childrens Cancer Research Institute | Yoon K.,Greehey Childrens Cancer Research Institute | Ko D.,UTSA | Smith A.D.,University of Southern California | And 4 more authors.
Comparative and Functional Genomics

Translation regulation plays important roles in both normal physiological conditions and diseases states. This regulation requires cis-regulatory elements located mostly in 5′; and 3′; UTRs and trans-regulatory factors (e.g., RNA binding proteins (RBPs)) which recognize specific RNA features and interact with the translation machinery to modulate its activity. In this paper, we discuss important aspects of 5′; UTR-mediated regulation by providing an overview of the characteristics and the function of the main elements present in this region, like uORF (upstream open reading frame), secondary structures, and RBPs binding motifs and different mechanisms of translation regulation and the impact they have on gene expression and human health when deregulated. Copyright © 2012 Patricia R. Araujo et al. Source

Manjili Y.S.,UTSA | Vega R.,The Texas Institute | Jamshidi M.,ACE Inc
Intelligent Automation and Soft Computing

A smart decision-making framework based on genetic algorithms (GA) and fuzzy logic is proposed for control and energy management of micro-grids. Objectives are to meet the demand profile, minimize electricity consumption cost, and to modify air pollution under a dynamic electricity pricing policy. The energy demand in the micro-grid network is provided by distributed renewable energy generation (coupling solar and wind), battery storage and balancing power from the electric utility. The fuzzy intelligent approach allows the calculation of the energy exchange rate of the micro-grid storage unit as a function of time. Such exchange rate (or decision-making capability) is based on (1) the electrical energy price per kilowatt-hour (kWh), (2) local demand (load), (3) electricity generation rate of renewable resources (supply), and (4) air pollution measure, all of which are sampled at predefined rates. Then, a cost function is defined as the net dollar amount corresponding to electricity flow between micro-grid and the utility grid. To define the cost function one must consider the cost incurred by the owner of the micro-grid associated to its distribution losses, in addition to its demand and supply costs, in such a way that a positive cost translates to owner losses and a negative cost is a gain. Six likely scenarios were defined to consider different micro-grid configurations accounting for the conditions seen in micro-grids today and also the conditions to be seen in the future. GA is implemented as a heuristic (DNA-based) search algorithm to determine the sub-optimal settings of the fuzzy controller. The aforementioned net cost (which includes pricing, demand and supply measures) and air pollution measures are then compared in every scenario with the objective to identify best-practices for energy control and management of micro-grids. Performance of the proposed GA-fuzzy intelligent approach is illustrated by numerical examples, and the capabilities and flexibility of the proposed framework as a tool for solving intermittent multi-objective function problems are presented in detail. Micro-grid owners looking into adopting a smart decision-making tool for energy storage management may see an ROI between 5 and 10. © 2013 TSI® Press. Source

News Article
Site: http://phys.org/technology-news/

"I've spent a fair amount of time trying to get people to understand that the human component of cybersecurity is very important," Kilger said. "Understanding the motivations of cyberterrorists was a foreign concept until very recently and still is to many information security professionals." Kilger recently represented UTSA, which is home to the nation's top cybersecurity program, at a North Atlantic Treaty Organization (NATO) training facility in Ankara, Turkey. There, he stressed the importance of understanding that cyberterrorists are different from traditional terrorists. There are several motivations for the attacks they carry out. Kilger said that while some are driven by ego, politics or entertainment, the most common reason is money. "You can basically rob a bank without actually robbing a bank," he said. "The risk of getting caught is fairly low and the chance of success is pretty high." Kilger is among the UTSA faculty leading the charge in studying the human component of cyberterrorism. He has unique expertise in cybersecurity and social psychology. The reason why this topic is lesser known, he said, is that security professionals become very focused on the technological side of responding to attacks and lack the social psychology background to analyze and understand the human being on the other side of that attack. "Being able to project future scenarios is one of the most important aspects of cybersecurity," he said. "A lot of information security efforts are defense-based and reactive. We need a more proactive approach." According to Kilger, a new approach is needed because now a single person can effectively attack a nation-state. In his study, published in Availability, Reliability and Security, he explains that the dramatic shift in power between a country and an individual is very enticing and it's one sign that a cyber terrorism community could be on the rise. "As a social psychologist, you look at markers and clues. You analyze what's happened before and how that informs what's going on now," he said. "Losses are adding up significantly. They're recruiting all the time and they're very organized." As societies become more reliant on the Internet the threat of cyber terrorism looms larger. It's something Kilger said needs to be kept in mind moving forward in a world where cars and airplanes are connected to the Internet. "There's no easy solution," he said. "We need more understanding of why these attacks occur and why people do them. Then we can start figuring out what their targets will be and what they're likely to do. With that, we can stop them from happening." More information: "Integrating Human Behavior into the Development of Future Cyberterrorism Scenarios." ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7299981

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