Modular nonblocking verification using conflict equivalence

This paper proposes a modular approach to verifying whether a large discrete event system is nonconflicting. The new approach avoids computing the synchronous product of a large set of finite-state machines. Instead, the synchronous product is computed gradually, and intermediate results are simplified using conflict-preserving abstractions based on process-algebraic results about fair testing. Heuristics are used to choose between different possible abstractions. Experimental results show that the method is applicable to finite-state machine models of industrial scale and brings considerable improvements in performance over other methods

Modular control-loop detection

This paper presents an efficient algorithm to detect control-loops in large finite-state systems. The proposed algorithm exploits the modular structure present in many models of practical relevance, and often successfully avoids the explicit synchronous composition of subsystems and thereby the state explosion problem. Experimental results show that the method can be used to verify industrial applications of considerable complexity

The physicochemical and antioxidant properties of double-boiled kelulut honey

Kelulut honey is a unique Malaysian food that has beneficial components and high potential in many health aspects. In commercial processing plant, honey is usually subjected to thermal treatment, where its quality is compromised due to unstable and thermolabile components. Therefore, double boiling was chosen as it does not exert significant heat, thus minimizes damage done. The quality was determined after treated by double boiling technique at optimized condition. Three different sources of Kelulut honey based on the main types of foods consumed by the bees (Coconut, Multifloral and Wild Flowers) were tested. Kelulut honey samples were subjected to an optimized condition at 60 °C for 35 minutes. Thermal treatment at the same condition was conducted for comparison purpose. The results showed that double boiling treatment increased the total phenolic content of Kelulut-C honey significantly, from 2430.78 ± 12.24 to 2711.10 ± 23.00 mg GAE/100 g. The treatment also significantly increased the brown pigment for both Kelulut-C and Kelulut-W honey by 11.11 ± 0.00% and 27.27 ± 0.00%, respectively. Whereas, the pH and moisture content of all samples remain unchanged with no formation of hydroxymethylfurfural (HMF) was observed. A preliminary four-week storage study showed that double boiling treatment improves physicochemical properties of Kelulut honey as compared to the untreated samples for all three types of Kelulut honey tested. Meanwhile, a room temperature (27 °C) condition leads to an improvement of antioxidant properties as compared to cold temperature (4 °C). In conclusion, double boiling treatment has established itself as a good alternative processing method for Kelulut honey, hence increasing the possibility to bring forward Kelulut honey as a unique source for the application in food and beverages industries

Operating Point Optimization of a Hydrogen Fueled Hybrid Solid Oxide Fuel Cell-Steam Turbine (SOFC-ST) Plant

This paper presents a hydrogen powered hybrid solid oxide fuel cell-steam turbine (SOFC-ST) system and studies its optimal operating conditions. This type of installation can be very appropriate to complement the intermittent generation of renewable energies, such as wind generation. A dynamic model of an alternative hybrid SOFC-ST configuration that is especially suited to work with hydrogen is developed. The proposed system recuperates the waste heat of the high temperature fuel cell, to feed a bottoming cycle (BC) based on a steam turbine (ST). In order to optimize the behavior and performance of the system, a two-level control structure is proposed. Two controllers have been implemented for the stack temperature and fuel utilization factor. An upper supervisor generates optimal set-points in order to reach a maximal hydrogen efficiency. The simulation results obtained show that the proposed system allows one to reach high efficiencies at rated power levels.This work has been carried out in the Intelligent Systems and Energy research group of the University of the Basque Country (UPV/EHU) and has been supported by the UFI11/28 research grant of the UPV/EHU and by the IT677-13 research grant of the Basque Government (Spain) and by DPI2012-37363-CO2-01 research grant of the Spanish Ministry of Economy and Competitiveness

Ecological Interface Design for Flexible Manufacturing Systems: An Empirical Assessment of Direct Perception and Direct Manipulation in the Interface

Four interfaces were developed to factorially apply two principles of ecological interface design (EID; direct perception and direct manipulation) to a flexible manufacturing system (FMS). The theoretical foundation and concepts employed during their development, with findings related to more significant issues regarding interface design for complex socio-technical systems, are discussed. Key aspects of cognitive systems engineering (CSE) and EID are also discussed. An FMS synthetic task environment was developed, and an experiment was conducted to evaluate real-time decision support during supervisory operations. Participants used all four interfaces to supervise and maintain daily part production at systematically varied levels of difficulty across sessions. Significant results provide evidence that the incorporation of direct perception and direct manipulation in interface design produced an additive effect, allowing for greater support for the supervisory agents

Incremental verification and synthesis of discrete-event systems guided by counter-examples

This article presents new approaches to system verification and synthesis based on subsystem verification and the novel combined use of counterexamples and heuristics to identify suitable subsystems incrementally. The scope of safety properties considered is limited to behavioral inclusion and controllability. The verification examples considered provide a comparison of the approaches presented with straightforward state exploration and an understanding of their applicability in an industrial context

Understanding Behavioral Sources of Process Variation Following Enterprise System Deployment

This paper extends the current understanding of the time-sensitivity of intent and usage following large-scale IT implementation. Our study focuses on perceived system misfit with organizational processes in tandem with the availability of system circumvention opportunities. Case study comparisons and controlled experiments are used to support the theoretical unpacking of organizational and technical contingencies and their relationship to shifts in user intentions and variation in work-processing tactics over time. Findings suggest that managers and users may retain strong intentions to circumvent systems in the presence of perceived task-technology misfit. The perceived ease with which this circumvention is attainable factors significantly into the timeframe within which it is attempted, and subsequently impacts the onset of deviation from prescribed practice and anticipated dynamics

Supervisory Control based Fuzzy Interval Arithmetic Applied for Discrete Scheduling of Manufacturing Systems

6 pagesInternational audienceThis paper considers the modelling and designing of a production-flow scheduler based on fuzzy interval system. Particularly, the supervisory control is built according to the satisfaction degree of conflicting objectives which are quantified by fuzzy intervals. The control system aims at adjusting the machine's production rates in such a way that satisfies the demand while maintaining the overall performances within acceptable limits. At the shop-floor level, the actual dispatching times are determined from the continuous production rates through a sampling procedure. A decision for the actual part to be processed is taken using some criterions which represent a measure of the job's priority. A case study demonstrates the efficiency of the proposed control approach

Hierarchical Control of Production Flow based on Capacity Allocation for Real-Time Scheduling of Manufacturing System

8International audienceThis paper considers the modelling and simulation of a hierarchical production-flow control system. It uses a continuous control approach for machine capacity allocation at the design level and real time scheduling at the shop-floor level. Particularly, at the design level, the control of machine throughput has been addressed by a set of distributed and supervised fuzzy controllers. The objective is to adjust the machine's production rates in such a way that satisfies the demand while maintaining the overall performances within acceptable limits. At the shop-floor level, the problem of scheduling of jobs is considered. In this case, the priority of jobs (actual dispatching times) is determined from the continuous production rates through a discretization procedure. A case study demonstrates the efficiency of the proposed methodology through a simulation case study

Synthesis equivalence of triples

This working paper describes a framework for compositional supervisor synthesis, which is applicable to all discrete event systems modelled as a set of deterministic automata. Compositional synthesis exploits the modular structure of the input model, and therefore works best for models consisting of a large number of small automata. State-space explosion is mitigated by the use of abstraction to simplify individual components, and the property of synthesis equivalence guarantees that the final synthesis result is the same as it would have been for the non-abstracted model. The working paper describes synthesis equivalent abstractions and shows their use in an algorithm to compute supervisors efficiently. The algorithm has been implemented in the DES software tool Supremica and successfully computes modular supervisors, even for systems with more than 1014 reachable states, in less than 30 seconds