Use Of Process Models Research Articles

Long-term morphological modeling of a tidal inlet: the Arcachon Basin, France

The Arcachon Lagoon on the French Atlantic coast is a triangular shaped lagoon of 20 km on a side connected to the ocean by a 3-km wide inlet between the mainland and an elongated sand spit. This tidal inlet exhibits a particularly active morphology due to locally strong tidal currents and rough wave conditions. During the past 300 years, minimum and maximum spatial extents of the Cap Ferret sand spit have varied by 8 km while one or two channels have alternately allowed circulation between the lagoon and the ocean. These impressive morphological changes have never prevented regular flushing of the lagoon, eventhough the spit came as close as 300 m from the coast during the 18th century. According to Bruun's concept of tidal inlet stability [Theory and Engineering (1978), 510 pp.], the balance between longshore littoral transport and the tidal prism ensures the perpetuity of the inlet. Process modeling was believed to give better insight into the respective roles of tides and waves in driving the long-term morphological changes of the inlet. A two-dimensional horizontal morphodynamic model was therefore developed, combining modules for hydrodynamics, waves, sediment transport and bathymetry updates. The use of process models at a scale of decades requires a schematization of the input conditions. We defined representative mean annual wave and tide conditions with respect to sediment transport, i.e. conditions that induce the same annual transport as measured in the field. Driven by these representative conditions, simulations run from the 1993 bathymetry show that the tide is responsible for the opening of a new channel at the extremity of the sand spit (where tidal currents are the strongest), while waves induce a littoral transport responsible for the longshore drift of sand bodies across the inlet. One particular simulation consisted in running the model from a hypothetical initial topography where the channels are filled with sand and the entire inlet is set to a constant depth (3 m). The results show the reproduction of a channel and bar system comparable to historical observations, which supports the idea that the lagoon is unlikely to be disconnected from the ocean, provided tide and wave conditions remain fairly constant in the following decades.

Engineering analysis of crosslinking polymerization of diallyl lsophthalate

AbstractA kinetic model for crosslinking free radical polymerization of DAIM (monomer diallyl isophthalate) with initiator CHPC (dicyclohexyl peroxydicarbonate) is developed. An improved version of Batch and Macosko's model was used to describe the initiator efficiency (f) and the active radical fraction (Fact). The experimental data of allyl and carbonyl group consumption are used for the optimization of the model and calculating of f and Fact. From the developed kinetic model and experimental results, obtained by FT‐IR measurements of monomer conversion, the introduction of the Fact was proved. Application of this model may be of use in process modeling of DAIM and other crosslinking polymerizations with CHPC as initiator.

Model-based analysis of the health, safety and environment domain in the process industry

The chemical process industry needs well-defined, engineering-controlled operation procedures to insure the safety of their plant operations and to protect the people working with hazardous materials. Accidents may seriously harm the employees, destroy expensive factory equipment and contaminate and deteriorate the environment of the entire areas. The engineering control can be significantly enhanced through the use of process models for situation analysis. Process models will also provide effective decision support in the plant operation. The objective was to develop in Elf-Atochem a reference model for improving the complex process for implementing and tracking a work permit for people working in plant areas with health, safety and environmental risks. This permit documents all protection and formal authorisations required prior to any work in the hazardous areas of a chemical plant. The model consists of a process model and an information model. It further provides the identification of knowledge required to manage the work permit and to facilitate the automation of a number of activities. The model serves to analyse the process and to define the user requirements for a workflow application program. The methodology CimOsa/rg, which is based on CIMOSA, has been applied together with the modelling tool CimTool to document the requirements model.

Reducing CV Lifecycle Costs Through Process Modeling and Simulation

AbstractAn innovative methodology has been developed to achieve the objectives of carrier operation optimization programs using Integrated Definition (IDEF) modeling and associated Commercial Off the Shelf (COTS) tools. The primary objectives of the programs include manpower reduction, integrated automation, and support for new operational concepts. The methodology incorporates the use of process Modeling and Simulation (M&S) to establish the requirements for developing optimized carrier operations. This approach uses new techniques in performing analyses required, and replaces costly stovepipe approaches. Process M&S illustrates the impacts on operations if manpower is reduced, the impact to manpower if processes are modified, the areas where automation is most beneficial, and the capacity of existing and proposed processes in terms of meeting operational requirements.Process M&S is also used to assist in the evaluation of carrier re‐design proposals, the analysis of potential modifications to existing doctrine, and the analysis of human factors issues. The IDEF process modeling methodology, coupled with the interfacing requirements of the process, information, and product models identify opportunities for improvement. The methodology provides a basis upon which changes and specifications to the current system acquisition process as well as carrier operations can be made in a “total ship” evaluation framework.

Reducing CV Life Cycle Costs Through Process Modeling and Simulation

ABSTRACT An innovative methodology has been developed to achieve the objectives of carrier operation optimization programs utilizing Integrated Definition (IDEF) modeling and associated Commercial Off the Shelf (COTS) tools. The primary objectives of the programs include manpower reduction, integrated automation, and support for new operational concepts. The methodology incorporates the use of process Modeling and Simulation (M&S) to establish the requirements for developing optimized carrier operations. This approach uses new techniques in performing analyses required, and replaces costly stovepipe approaches. Process M&S illustrates the impacts on operations if manpower is reduced, the impact to manpower if processes are modified, the areas where automation is most beneficial, and the capacity of existing and proposed processes in terms of meeting operational requirements.Process M&S is also used to assist in the evaluation of carrier re‐design proposals, the analysis of potential modifications to existing doctrine, and the analysis of human factors issues. The IDEF process modeling methodology, coupled with the interfacing requirements of the process, information, and product models identify opportunities for improvement. The methodology provides a basis upon which changes and specifications to the current system acquisition process as well as carrier operations can be made in a “total ship” evaluation framework.Rob provided insight into the need for integrating process, product, and information M&S applications and has discussed approaches for achieving this integration with the authors. Rob has also provided information regarding the application of systems engineering to M&S efforts.

Process models of environmental systems: Simulation of forest development dynamics as an example

Successful management and stewardship of environmental systems requires reliable assessment of their development dynamics in response to changing environmental and management conditions. Descriptive (statistical) models cannot cope with this challenge since their development is based on historical time series with little or no reference to actual system structure. On the other hand, explanatory (process) models attempt to capture the essential eco-physiological processes determining dynamic behavior, and they are therefore much better suited for the computation of development dynamics under changing conditions, even when long-term empirical observations are not possible or feasible. As an example of the use of process models in environmental systems analysis, a forest simulation model describing growth, and carbon and nitrogen dynamics of a single-species, even-aged forest stand under silvicultural management and pollution influences is presented, together with some representative simulation results. Steps in obtaining valid but compact tree models for complex forest simulations are outlined, and recent software developments (object-oriented programming) are assessed with respect to their potential for environmental systems analysis.

Process models of decision making

Process-tracing approaches to the study of decision making usually involve analysis of verbal protocols or information board measures. This article draws a parallel between the decision-making research and the general field of problem solving with respect to the analysis of think-aloud protocols. A literature review is given of the types of analyses used in studies on decision making in which think-aloud protocols were collected. Results indicate that only four of the twenty-three decision studies involve the construction of process models such as are common in problem-solving research. Possible objections against think-aloud data are discussed and the construction and use of process models in decision-making research is illustrated by means of an information display board task in which subjects were asked to think aloud. Similarities and dissimilarities between decision making and general problem solving and their implications for the construction of process models are discussed.

A SURVEY AND ASSESSMENT OF SOFTWARE PROCESS REPRESENTATION FORMALISMS

Process modeling is a rather young and very active research area. During the last few years, new languages and methods have been proposed to describe software processes. In this paper we try to clarify the issues involved in software process modeling and identify the main approaches. We start by motivating the use of process modeling and its main objectives. We then propose a list of desirable features for process languages. The features are grouped as either already provided by languages from other fields or as specific features of the process domain. Finally, we review the main existing approaches and propose a classification scheme.

A Fundamental Approach to Resin Cure Kinetics

Thermoset polymer resins are an important class of materials, particularly when used as the matrix for advanced fiber composites. Because material performance is directly related to processing, it is useful to study the cure kinetics of these resins for use in process modeling, design and control. Several workers have attacked this problem using empirical rate laws. However, a fundamental approach can offer more flexibility without being cumbersome or impractical. In this work, amine-catalyzed epoxy reactions are studied. A kinetic model is developed and applied to experimental data from the literature, as well as from our laboratory. We show that this model is able to describe the cure reac tions of "real-world" systems, and unlike the empirical rate laws, can account for variations in the resin formulations.

Generating an Optimal Information System: PMAX-SDLC and the Redirection of MIS Research (or How to Help Joe Eat Salmon)

:It is argued that information systems should be treated as any other input into the firm’s production process and, as such, should be selected based on their contribution to the profit of the firm. It is argued that the present systems development life cycle (sdlc) heuristics lead to systems which are feasible and satisficing, but do not lead to a profit maximizing design. An alternative strategy—profit-maximizing systems development life cycle (PMAX-SDLC)—is proposed which is based on the use of process models. These models have their origin in the economics literature and were developed to accurately characterize engineering production processes. Although PMAX-SDLC is more complex than the current sdlc, several empirical conjectures are presented which would support the notion that the potential benefits of redirecting management information systems (mis) research toward optimal systems design could be large.

Process Fault Diagnosis with Parameter Estimation Methods

Fault detection and fault diagnosis of technical processe becomes more important in the course of progressive automation. Computer based fault supervision methods are developed which allow the early detection and localization of process faults during normal operation. The use of process models enables to estimate process state variables and parameters which directly are influenced by faults. The contribution concentrates or fault diagnosis based on process parameters.The general procedure is outlined, comprising parameter estimation, feature extraction, fault decision and classification. Recent experimental results are given for the detection of several faults in a d.c.moter and a centrifugal pump.

Statistical Cost Analysis Re-Revisited: Reply

The issues raised by Maddala and Roberts go well beyond the question of whether pseudo-data analysis is useful empirically. It is unfortunate that their paper was not written in response to the first translog application by Christensen, Jorgenson, and Lau. This would allow separation of questions unique to pseudo-data analysis from the questions aimed more generally at the translog and other generalized functional forms. In this reply I shall attempt to separate these two questions, showing that a major portion of Maddala and Roberts' concerns relates essentially to the approximation characteristics of generalized functional forms, irrespective of the type of data used for estimation. These issues are examined in Section II. In Section III we discuss Maddala and Roberts' raising of the important question of optimal sample design and functional form, noting that there is no necessity to use orthogonal price variation and the translog function. Finally, we address in Section IV the claim that direct use of process models in place of its statistical cost function approximation is to be preferred in policy and modeling exercises.