Stochastic Systems: Modeling, Optimization, and Applications

The special issue of Mathematical Problems in Engineering deals with the issues of modeling, optimization, and applications associated with stochastic systems. This special issue provides a forum for researchers and practitioners to publish quality research work on modeling, optimization approaches, and their applications in the context of theory analysis and engineering developments. The accepted papers in this special issue include stochastic stability, stabilization and control optimization, stochastic optimization, particle swarm optimization, modeling and identification methods, signal processing, and robust filtering. The issue includes thirty-nine papers out of which six consider the stability and stabilization problems of stochastic systems. Twelve papers cover the problems of the controller design and relevant optimization algorithms

Fidelity of optimally controlled quantum gates with randomly coupled multiparticle environments

This work studies the feasibility of optimal control of high-fidelity quantum gates in a model of interacting two-level particles. One particle (the qubit) serves as the quantum information processor, whose evolution is controlled by a time-dependent external field. The other particles are not directly controlled and serve as an effective environment, coupling to which is the source of decoherence. The control objective is to generate target one-qubit gates in the presence of strong environmentally-induced decoherence and under physically motivated restrictions on the control field. It is found that interactions among the environmental particles have a negligible effect on the gate fidelity and require no additional adjustment of the control field. Another interesting result is that optimally controlled quantum gates are remarkably robust to random variations in qubit-environment and inter-environment coupling strengths. These findings demonstrate the utility of optimal control for management of quantum-information systems in a very precise and specific manner, especially when the dynamics complexity is exacerbated by inherently uncertain environmental coupling.Comment: tMOP LaTeX, 9 pages, 3 figures; Special issue of the Journal of Modern Optics: 37th Winter Colloquium on the Physics of Quantum Electronics, 2-6 January 200

Real-time motion planning and decision-making for a group of differential drive robots under connectivity constraints using robust MPC and mixed-integer programming

This work is concerned with the problem of planning trajectories and assigning tasks for a Multi-Agent System (MAS) comprised of differential drive robots. We propose a multirate hierarchical control structure that employs a planner based on robust Model Predictive Control (MPC) with mixed-integer programming (MIP) encoding. The planner computes trajectories and assigns tasks for each element of the group in real-time, while also guaranteeing the communication network of the MAS to be robustly connected at all times. Additionally, we provide a data-based methodology to estimate the disturbances sets required by the robust MPC formulation. The results are demonstrated with experiments in two obstacle-filled scenariosComment: Submitted to Advanced Robotics special issue on Online Motion Planning and Model Predictive Contro

Current and Evolving Practices in the Quality Control of Cosmetics

Cosmetic products undergo nowadays rigorous Quality Control testing to ensure that they are safe and stable and that their claims are substantiated by scientifically robust data. Quality Control tests used in the pharmaceutical industry can be applicable also for cosmetic formulations. However, claim substantiation testing is unique to cosmetic products. To enable time- and cost-effective quality control testing, assessment methodologies constantly keep evolving. This Special Issue includes manuscripts that explore all stages of Quality Control testing for cosmetic products, i.e., (1) physicochemical stability testing; (2) microbial stability testing; (3) efficacy testing including objective/subjective claim substantiation testing and the evaluation of sensorial properties; (4) toxicological/safety testing with emphasis on current and evolving methodologies that replace animal testing

Effects of motion in cavity QED

We consider effects of motion in cavity quantum electrodynamics experiments where single cold atoms can now be observed inside the cavity for many Rabi cycles. We discuss the timescales involved in the problem and the need for good control of the atomic motion, particularly the heating due to exchange of excitation between the atom and the cavity, in order to realize nearly unitary dynamics of the internal atomic states and the cavity mode which is required for several schemes of current interest such as quantum computing. Using a simple model we establish ultimate effects of the external atomic degrees of freedom on the action of quantum gates. The perfomance of the gate is characterized by a measure based on the entanglement fidelity and the motional excitation caused by the action of the gate is calculated. We find that schemes which rely on adiabatic passage, and are not therefore critically dependent on laser pulse areas, are very much more robust against interaction with the external degrees of freedom of atoms in the quantum gate.Comment: 10 pages, 5 figures, REVTeX, to be published in Walls Symposium Special Issue of Journal of Optics

Governance and Private Investment in the Middle East and North Africa

This paper addresses the issue of the low level of private investment in the Middle East and North Africa (MENA) region, with special emphasis on the role of governance. Based on the existing literature, we have categorized what types of governance institutions are more detrimental to entrepreneurial investments. We have then estimated a simultaneous model of private investment and governance quality where economic policies concurrently explain both variables. Our empirical results show that governance plays a significant role in private investment decisions. This result is particularly true in the case of “Administrative Quality” in the form of control of corruption, bureaucratic quality, investment-friendly profile of administration, and law and order, as well as for “Political Stability”. Evidence in favor of “Public Accountability” seems, however, less robust. Our estimations also stress that structural reforms -- such as financial development and trade openness – and human development affect private investment decisions directly, and/or through their positive impact on governance. These findings bring new empirical evidence on the subject of private investment in the developing world and in MENA countries in particular.governance, private investment, institutions, Middle East and North Africa.

Governance and private investment in the Middle East and North Africa

This paper addresses the issue of the low level of private investment in the Middle East and North Africa (MENA) region, with special emphasis on the role of governance. Based on the existing literature, the authors categorize what types of governance institutions are more detrimental to entrepreneurial investments. They then estimate a simultaneous model of private investment and governance quality where economic policies concurrently explain both variables. The empirical results show that governance plays a significant role in private investment decisions. This result is particularly true in the case of"administrative quality"in the form of control of corruption, bureaucratic quality, investment-friendly profile of administration, and law and order, as well as for"political stability."Evidence in favor of"public accountability"seems, however, less robust. The estimations also stress that structural reforms-such as financial development and trade openness-and human development affect private investment decisions directly, and/or through their positive impact on governance. These findings bring new empirical evidence on the subject of private investment in the developing world and in MENA countries in particular.Governance Indicators,Investment and Investment Climate,Economic Theory&Research,National Governance,Trade and Regional Integration

Sensors for ultrasonic nondestructive testing (NDT) in harsh environments

In this special issue of Sensors, seven peer-reviewed manuscripts appear on the topic of ultrasonic transducer design and operation in harsh environments: elevated temperature, high gamma and neutron fields, or the presence of chemically aggressive species. Motivations for these research and development projects are strongly focused on nuclear power plant inspections (particularly liquid-sodium cooled reactors), and nondestructive testing of high-temperature piping installations. It is anticipated that we may eventually see extensive use of permanently mounted robust transducers for in-service monitoring of petrochemical plants and power generations stations; quality control in manufacturing plants; and primary and secondary process monitoring in the fabrication of engineering materials