Contact process with temporal disorder

We investigate the influence of time-varying environmental noise, i.e., temporal disorder, on the nonequilibrium phase transition of the contact process. Combining a real-time renormalization group, scaling theory, and large scale Monte-Carlo simulations in one and two dimensions, we show that the temporal disorder gives rise to an exotic critical point. At criticality, the effective noise amplitude diverges with increasing time scale, and the probability distribution of the density becomes infinitely broad, even on a logarithmic scale. Moreover, the average density and survival probability decay only logarithmically with time. This infinite-noise critical behavior can be understood as the temporal counterpart of infinite-randomness critical behavior in spatially disordered systems, but with exchanged roles of space and time. We also analyze the generality of our results, and we discuss potential experiments.Comment: 14 pages, 16 eps figures included. Final version as publishe

Analytical approach to the transition to thermal hopping in the thin- and thick-wall approximations

The nature of the transition from the quantum tunneling regime at low temperatures to the thermal hopping regime at high temperatures is investigated analytically in scalar field theory. An analytical bounce solution is presented, which reproduces the action in the thin-wall as well as thick-wall limits. The transition is first order for the case of a thin wall while for the thick wall case it is second order.Comment: Latex file, 22 pages, 4 Postscript figure

A New Monte Carlo Based Algorithm for the Gaussian Process Classification Problem

Gaussian process is a very promising novel technology that has been applied to both the regression problem and the classification problem. While for the regression problem it yields simple exact solutions, this is not the case for the classification problem, because we encounter intractable integrals. In this paper we develop a new derivation that transforms the problem into that of evaluating the ratio of multivariate Gaussian orthant integrals. Moreover, we develop a new Monte Carlo procedure that evaluates these integrals. It is based on some aspects of bootstrap sampling and acceptancerejection. The proposed approach has beneficial properties compared to the existing Markov Chain Monte Carlo approach, such as simplicity, reliability, and speed

OPTIMAL CONTROL FOR DISTRIBUTED CONTROL SYSTEMS

In modern cities, factories and high technology operations are run using distributed control. Distributed control involves the use of computer networks. Computer networks consist of computers on both ends, sensors, actuators, and communication links. However, control over computer networks faces many problems such as the delay and loss of control message and the delay or loss of sensor data. This paper proposes a new method such that the control system can handle the network delays and at the same time find an optimal controller. The method uses the modified zero-order hold to account for the delays and uses the linear matrix inequality optimization method to find the controller. This method also takes advantage of the polynomial representation of systems and constraints and places norm constraints on the problem

A PROPOSED SCHEME FOR AN ARAB QUALITY ASSURANCE AGENCY IN THE FIELD OF COMPUTING & INFORMATION TECHNOLOGY

Over the past few years scientists, researchers and experts form the Arab world and distinguished experts from all over the world in the field of information technology have been meeting annually at the Arab International Conference on Information Technology. Some of those experts had been trained in the field of quality assurance in higher education. This group was trained to perform external reviews and evaluations at the subject level and program level. Evaluations also could take place at the module level

An Automated Irrigation System for Greenhouses

Gaza Strip is a small region with limited agriculture land and water resources. Greenhouse technology allows farmers to optimize the use of this land. In this paper a computer-based control and monitoring system is designed and tested to automate drip irrigation. The model greenhouse can be used as a prototype where several sensors are connected to an acquisition and control system using a PC and a data acquisition card. The designed system can be used as a stand-alone system by lay farmers with no technical background where they can command full control through a screen command. The system is set up to handle several crops by using a user screen to adjust certain parameters on the front panel. A web server enables users to remotely monitor and control the greenhouse through VI's from any place in the world with internet access. Moreover, the system periodically generates alarms and automatically sends emails to notify users of the conditions inside greenhouse

Topological Defects in the Left-Right Symmetric Model and their Relevance to Cosmology

It is shown that the minimal left-right symmetric model admits cosmic string and domain wall solutions. The cosmic strings arise when the SU(2)_R is broken and can either be destabilized at the electroweak scale or remain stable through the subsequent breakdown to U(1)_{EM}. The strings carry zero modes of the neutrino fields. Two distinct domain wall configurations exist above the electroweak phase transition and disappear after that. Thier destablization provides new sources of non-equilibrium effects below the electroweak scale which is relevant to baryogenesis.Comment: 29 pages, LaTex file with 6 postscript figure