Networks of Polarized Evolutionary Processors as Problem Solvers.

In this paper, we propose a solution to an NP-complete problem, namely the "3-colorability problem", based on a network of polarized processors. Our solution is uniform and time efficient.

An Integrated Approach to Strategic Asset Management

This paper focuses on identifying and analysing the elements of Strategic Management for infrastructure and engineering assets. These elements are contended to involve an understanding of governance, corporate policy, corporate objectives, corporate strategy and interagency collaboration and will in turn, allow the ability determine a broader and more comprehensive framework for engineering asset management, ie a ‘staged approach’ to understanding how assets are managed within organisations. While the assets themselves have often been the sole concern for good management practices, other social and contextual elements have come into the mix in order to promote strategic asset management. The development of an integrated approach to asset management is at the base of the research question. What are the considerations and implications for adopting and implementing an integrated strategic asset management (ISAM) framework? While operational matters have been given prominence, a subset of corporate governance, Asset Governance, details the policies and processes needed to acquire, utilise, maintain and account for an organisation’s assets. Asset governance stems from the organisation’s overarching corporate governance principles; as a result it defines the management context in which engineering asset management is implemented. This aspect will be examined to determine the appropriate relationship between organisational strategic management and strategic asset management to further the theoretical engagement with the maturity of strategy,policy and governance for infrastructure and engineered assets. Asset governance stems from the organisation’s overarching corporate governance principles; as a result it defines the management context in which engineering asset management is implemented. The research proceeds by a document analysis of corporate reports and policy recommendations in terms of infrastructure and engineered assets. The paper concludes that incorporating an integrated asset management framework can promote a more robust conceptualisation of public assets and how they combine to provide a comprehensive system of service outcomes.

Using Electronic Documents for Knowledge Acquisition and Model Maintenance

Knowledge acquisition and model maintenance are key problems in knowledge engineering to improve the productivity in the development of intelligent systems. Although historically a number of technical solutions have been proposed in this area, the recent experience shows that there is still an important gap between the way end-users describe their expertise and the way intelligent systems represent knowledge. In this paper we propose an original way to cope with this problem based on electronic documents. We propose the concept of intelligent document processor as a tool that allows the end-user to read/write a document explaining how an intelligent system operates in such a way that, if the user changes the content of the document, the intelligent system will react to these changes. The paper presents the structure of such a document based on knowledge categories derived from the modern knowledge modeling methodologies together with a number of requirements to be understandable by end-users and problem solvers.

Extensiones a los métodos de planificación de sistemas de tiempo real críticos basados en prioridades

Los sistemas de tiempo real tienen un papel cada vez más importante en nuestra sociedad. Constituyen un componente fundamental de los sistemas de control, que a su vez forman parte de diversos sistemas de ingeniería básicos en actividades industriales, militares, de comunicaciones, espaciales y médicas. La planificación de recursos es un problema fundamental en la realización de sistemas de tiempo real. Su objetivo es asignar los recursos disponibles a las tareas de forma que éstas cumplan sus restricciones temporales. Durante bastante tiempo, el estado de la técnica en relación con los métodos de planificación ha sido rudimentario. En la actualidad, los métodos de planificación basados en prioridades han alcanzado un nivel de madurez suficiente para su aplicación en entornos industriales. Sin embargo, hay cuestiones abiertas que pueden dificultar su utilización. El objetivo principal de esta tesis es estudiar los métodos de planificación basados en prioridades, detectar las cuestiones abiertas y desarrollar protocolos, directrices y esquemas de realización práctica que faciliten su empleo en sistemas industriales. Una cuestión abierta es la carencia de esquemas de realización de algunos protocolos con núcleos normalizados. El resultado ha sido el desarrollo de esquemas de realización de tareas periódicas y esporádicas de tiempo real, con detección de fallos de temporización, comunicación entre tareas, cambio de modo de ejecución del sistema y tratamiento de fallos mediante grupos de recuperación. Los esquemas se han codificado en Ada 9X y se proporcionan directrices para analizar la planificabilidad de un sistema desarrollado con esta base. Un resultado adicional ha sido la identificación de la funcionalidad mínima necesaria para desarrollar sistemas de tiempo real con las características enumeradas. La capacidad de adaptación a los cambios del entorno es una característica deseable de los sistemas de tiempo real. Si estos cambios no estaban previstos en la fase de diseño o si hay módulos erróneos, es necesario modificar o incluir algunas tareas. La actualización del sistema se suele realizar estáticamente y su instalación se lleva a cabo después de parar su ejecución. Sin embargo, hay sistemas cuyo funcionamiento no se puede detener sin producir daños materiales o económicos. Una alternativa es diseñar el sistema como un conjunto de unidades que se pueden reemplazar, sin interferir con la ejecución de otras unidades. Para tal fin, se ha desarrollado un protocolo de reemplazamiento dinámico para sistemas de tiempo real crítico y se ha comprobado su compatibilidad con los métodos de planificación basados en prioridades. Finalmente se ha desarrollado un esquema de realización práctica del protocolo.---ABSTRACT---Real-time systems are very important now a days. They have become a relevant issue in the design of control systems, which are a basic component of several engineering systems in industrial, telecommunications, military, spatial and medical applications. Resource scheduling is a central issue in the development of real-time systems. Its purpose is to assign the available resources to the tasks, in such a way that their deadlines are met. Historically, hand-crafted techniques were used to develop real-time systems. Recently, the priority-based scheduling methods have reached a sufficient maturity level to be feasible its extensive use in industrial applications. However, there are some open questions that may decrease its potential usefulness. The main goal of this thesis is to study the priority-based scheduling methods, to identify the remaining open questions and to develop protocols, implementation templates and guidelines that will make more feasible its use in industrial applications. One open question is the lack of implementation schemes, based on commercial realtime kernels, of some of the protocols. POSIX and Ada 9X has served to identify the services usually available. A set of implementation templates for periodic and sporadic tasks have been developed with provisión for timing failure detection, intertask coraraunication, change of the execution mode and failure handling based on recovery groups. Those templates have been coded in Ada 9X. A set of guidelines for checking the schedulability of a system based on them are also provided. An additional result of this work is the identification of the minimal functionality required to develop real-time systems based on priority scheduling methods, with the above characteristics. A desirable feature of real-time systems is their capacity to adapt to changes in the environment, that cannot be entirely predicted during the design, or to misbehaving software modules. The traditional maintenance techniques are performed by stopping the whole system, installing the new application and finally resuming the system execution. However this approach cannot be applied to non-stop systems. An alternative is to design the system as a set of software units that can be dynamically replaced within its operative environment. With this goal in mind, a dynamic replacement protocol for hard real-time systems has been defined. Its compatibility with priority-based scheduling methods has been proved. Finally, a execution témplate of the protocol has been implemented.

A conceptual framework for evaluating traffic safety system measures.

National Highway Safety Bureau, Washington, D.C.

Development of additional Federal Outdoor Impact Laboratory (FOIL) facilities.

"June 1990."

Conceptual design of a lunar colony.

"NASA grant NGT 44-005-114."

Design and implementation of a windows-based parallel computing environment for large scale optimization

A parallel computing environment to support optimization of large-scale engineering systems is designed and implemented on Windows-based personal computer networks, using the master-worker model and the Parallel Virtual Machine (PVM). It is involved in decomposition of a large engineering system into a number of smaller subsystems optimized in parallel on worker nodes and coordination of subsystem optimization results on the master node. The environment consists of six functional modules, i.e. the master control, the optimization model generator, the optimizer, the data manager, the monitor, and the post processor. Object-oriented design of these modules is presented. The environment supports steps from the generation of optimization models to the solution and the visualization on networks of computers. User-friendly graphical interfaces make it easy to define the problem, and monitor and steer the optimization process. It has been verified by an example of a large space truss optimization. (C) 2004 Elsevier Ltd. All rights reserved.

Interference between propagating changes and its effect on system failure

Computer-based, socio-technical systems projects are frequently failures. In particular, computer-based information systems often fail to live up to their promise. Part of the problem lies in the uncertainty of the effect of combining the subsystems that comprise the complete system; i.e. the system's emergent behaviour cannot be predicted from a knowledge of the subsystems. This paper suggests uncertainty management is a fundamental unifying concept in analysis and design of complex systems and goes on to indicate that this is due to the co-evolutionary nature of the requirements and implementation of socio-technical systems. The paper shows a model of the propagation of a system change that indicates that the introduction of two or more changes over time can cause chaotic emergent behaviour.

Developing a probabilistic graphical structure from a model of mental-health clinical risk expertise

This paper explores the process of developing a principled approach for translating a model of mental-health risk expertise into a probabilistic graphical structure. The Galatean Risk Screening Tool [1] is a psychological model for mental health risk assessment based on fuzzy sets. This paper details how the knowledge encapsulated in the psychological model was used to develop the structure of the probability graph by exploiting the semantics of the clinical expertise. These semantics are formalised by a detailed specification for an XML structure used to represent the expertise. The component parts were then mapped to equivalent probabilistic graphical structures such as Bayesian Belief Nets and Markov Random Fields to produce a composite chain graph that provides a probabilistic classification of risk expertise to complement the expert clinical judgements. © Springer-Verlag 2010.

Power-controlled phase-matching and instability of CW propagation in multicore optical fibers with a central core

We present modulation instability analysis including azimuthal perturbations of steady-state continuous wave (CW) propagation in multicore-fiber configurations with a central core. In systems with a central core, a steady CW evolution regime requires power-controlled phase matching, which offers interesting spatial-division applications. Our results have general applicability and are relevant to a range of physical and engineering systems, including high-power fiber lasers, optical transmission in multicore fiber, and systems of coupled nonlinear waveguides. © 2013 Optical Society of America.

On-off and multistate intermittencies in cascaded random distributed feedback fibre laser

A range of physical and engineering systems exhibit an irregular complex dynamics featuring alternation of quiet and burst time intervals called the intermittency. The intermittent dynamics most popular in laser science is the on-off intermittency [1]. The on-off intermittency can be understood as a conversion of the noise in a system close to an instability threshold into effective time-dependent fluctuations which result in the alternation of stable and unstable periods. The on-off intermittency has been recently demonstrated in semiconductor, Erbium doped and Raman lasers [2-5]. Recently demonstrated random distributed feedback (random DFB) fiber laser has an irregular dynamics near the generation threshold [6,7]. Here we show the intermittency in the cascaded random DFB fiber laser. We study intensity fluctuations in a random DFB fiber laser based on nitrogen doped fiber. The laser generates first and second Stokes components 1120 nm and 1180 nm respectively under an appropriate pumping. We study the intermittency in the radiation of the second Stokes wave. The typical time trace near the generation threshold of the second Stokes wave (Pth) is shown at Fig. 1a. From the number of long enough time-traces we calculate statistical distribution between major spikes in time dynamics, Fig. 1b. To eliminate contribution of high frequency components of spikes we use a low pass filter along with the reference value of the output power. Experimental data is fitted by power law, ~(P-Pth)y, where is a mean time between pikes. There are two different intermittency regimes. Just above Pth, the mean time is approximated by the -3/2 power law. The -3/2 power law is typical to the on-off intermittency with hopping between two states (first and second Stokes waves in our case) [7]. At higher power, the mean time is approximated by -4 power law, that indicates a change in intermittency type to multistate. Multistable dynamics is observed in erbium-doped fiber lasers [8]. The origin of multiples states in our system could be probably connected with polarization hopping or other reasons and should be further investigated. We have presented a first experimental statistical characterisation of the on-off and multistate intermittencies that occur in the generation of the second Stokes wave in nitrogen doped random DFB fiber laser. References [1] H. Fujisaka and T. Yamada, “A New Intermittency in Coupled Dynamical Systems,” Prog. Theor. Phys. 74, 918 (1985). [2] S. Osborne, A. Amann, D. Bitauld, and S. O’Brien, “On-off intermittency in an optically injected semiconductor laser,” Phys. Rev. E 85, 056204 (2012). [3] S. Sergeyev, K. O'Mahoney, S. Popov, and A. T. Friberg, “Coherence and anticoherence resonance in high-concentration erbium-doped fiber laser,” Opt. Lett. 35, 3736 (2010). [4] A.E. El-Taher, S.V. Sergeyev, E.G. Turitsyna, P. Harper, and S. K. Turitsyn, “Intermittent Self-Pulsing in a Fiber Raman Laser”, In proc. Conf. Nonlin. Photon., paper ID 1367139, Colorado Springs, USA, 2012 [5] S.K. Turitsyn, S.A. Babin, A.E. El-Taher, P. Harper, D.V. Churkin, S.I. Kablukov, J.D. Ania-Castañón, V. Karalekas, and E.V. Podivilov, “Random distributed feedback fibre laser”, Nat. Photon..4, 231 (2010). [6] I. D. Vatnik, D. V. Churkin, S. A. Babin, and S. K. Turitsyn, "Cascaded random distributed feedback Raman fiber laser operating at 1.2 μm," Opt. Express 19, 18486 (2011). [7] W. Feller, An introduction to probability theory and its applications, Vol. 1, 3rd ed. (Wiley, New-York, 1968). [8] G. Huerta-Cuellar, A.N. Pisarchik, and Y.O. Barmenkov, “Experimental characterization of hopping dynamics in a multistable fiber laser,” Phys. Rev. E 78, 035202(R) (2008).

Minimizing makespan for hybrid flowshops with batch, discrete processing machines and arbitrary job sizes

This research aims at a study of the hybrid flow shop problem which has parallel batch-processing machines in one stage and discrete-processing machines in other stages to process jobs of arbitrary sizes. The objective is to minimize the makespan for a set of jobs. The problem is denoted as: FF: batch1,sj:Cmax. The problem is formulated as a mixed-integer linear program. The commercial solver, AMPL/CPLEX, is used to solve problem instances to their optimality. Experimental results show that AMPL/CPLEX requires considerable time to find the optimal solution for even a small size problem, i.e., a 6-job instance requires 2 hours in average. A bottleneck-first-decomposition heuristic (BFD) is proposed in this study to overcome the computational (time) problem encountered while using the commercial solver. The proposed BFD heuristic is inspired by the shifting bottleneck heuristic. It decomposes the entire problem into three sub-problems, and schedules the sub-problems one by one. The proposed BFD heuristic consists of four major steps: formulating sub-problems, prioritizing sub-problems, solving sub-problems and re-scheduling. For solving the sub-problems, two heuristic algorithms are proposed; one for scheduling a hybrid flow shop with discrete processing machines, and the other for scheduling parallel batching machines (single stage). Both consider job arrival and delivery times. An experiment design is conducted to evaluate the effectiveness of the proposed BFD, which is further evaluated against a set of common heuristics including a randomized greedy heuristic and five dispatching rules. The results show that the proposed BFD heuristic outperforms all these algorithms. To evaluate the quality of the heuristic solution, a procedure is developed to calculate a lower bound of makespan for the problem under study. The lower bound obtained is tighter than other bounds developed for related problems in literature. A meta-search approach based on the Genetic Algorithm concept is developed to evaluate the significance of further improving the solution obtained from the proposed BFD heuristic. The experiment indicates that it reduces the makespan by 1.93 % in average within a negligible time when problem size is less than 50 jobs.

Novel online data cleaning protocols for data streams in trajectory, Wireless Sensor Networks

The promise of Wireless Sensor Networks (WSNs) is the autonomous collaboration of a collection of sensors to accomplish some specific goals which a single sensor cannot offer. Basically, sensor networking serves a range of applications by providing the raw data as fundamentals for further analyses and actions. The imprecision of the collected data could tremendously mislead the decision-making process of sensor-based applications, resulting in an ineffectiveness or failure of the application objectives. Due to inherent WSN characteristics normally spoiling the raw sensor readings, many research efforts attempt to improve the accuracy of the corrupted or "dirty" sensor data. The dirty data need to be cleaned or corrected. However, the developed data cleaning solutions restrict themselves to the scope of static WSNs where deployed sensors would rarely move during the operation. Nowadays, many emerging applications relying on WSNs need the sensor mobility to enhance the application efficiency and usage flexibility. The location of deployed sensors needs to be dynamic. Also, each sensor would independently function and contribute its resources. Sensors equipped with vehicles for monitoring the traffic condition could be depicted as one of the prospective examples. The sensor mobility causes a transient in network topology and correlation among sensor streams. Based on static relationships among sensors, the existing methods for cleaning sensor data in static WSNs are invalid in such mobile scenarios. Therefore, a solution of data cleaning that considers the sensor movements is actively needed. This dissertation aims to improve the quality of sensor data by considering the consequences of various trajectory relationships of autonomous mobile sensors in the system. First of all, we address the dynamic network topology due to sensor mobility. The concept of virtual sensor is presented and used for spatio-temporal selection of neighboring sensors to help in cleaning sensor data streams. This method is one of the first methods to clean data in mobile sensor environments. We also study the mobility pattern of moving sensors relative to boundaries of sub-areas of interest. We developed a belief-based analysis to determine the reliable sets of neighboring sensors to improve the cleaning performance, especially when node density is relatively low. Finally, we design a novel sketch-based technique to clean data from internal sensors where spatio-temporal relationships among sensors cannot lead to the data correlations among sensor streams.

Mode-locking via dissipative Faraday instability

Emergence of coherent structures and patterns at the nonlinear stage of modulation instability of a uniform state is an inherent feature of many biological, physical and engineering systems. There are several well-studied classical modulation instabilities, such as Benjamin-Feir, Turing and Faraday instability, which play a critical role in the self-organization of energy and matter in non-equilibrium physical, chemical and biological systems. Here we experimentally demonstrate the dissipative Faraday instability induced by spatially periodic zig-zag modulation of a dissipative parameter of the system - spectrally dependent losses - achieving generation of temporal patterns and high-harmonic mode-locking in a fibre laser. We demonstrate features of this instability that distinguish it from both the Benjamin-Feir and the purely dispersive Faraday instability. Our results open the possibilities for new designs of mode-locked lasers and can be extended to other fields of physics and engineering.