Enhanced Process Model Research Articles

Enhanced problem solving through redefined 8D step completion criteria

This research aims to review the fundamentals of problem solving by evaluating alternative processes and proposing an enhanced process model named Defined 8D. The enhanced model guides the problem solver through a defined step completion process to enable complex problems to be broken down into manageable and defined segments. Existing processes present challenges in defining the problem and can lead to continuously testing preconceived theories in a revolving loop without eventually confirming the root cause. The defined step completion criteria support product specialists to quickly acquire problem solving skills and reduce the cost and duration of resolving product related issues.

A novel approach for understanding laser sintering of polymers

Selective laser sintering (LS) of thermoplastic powders allows for the construction of complex parts with higher mechanical properties and durability compared to other additive manufacturing methods. According to the current model of isothermal laser sintering, semi-crystalline thermoplastics need to be processed within a certain temperature range, resulting in the simultaneous presence of the material both in a molten and solid state, which is present during part building. Based on this process model, high cycle times ranging from hours to days are a thought to be a necessity to avoid warpage.In this paper, the limited validity of the model of isothermal laser sintering is shown by various experiments, as ongoing solidification could be detected a few layers below the powder bed surface. The results indicate that crystallization and material solidification is initiated at high temperatures and further progresses throughout part build-up in z-direction. Therefore, a process-adapted material characterization was performed to identify the isothermal crystallization kinetics at processing temperature and to track changes of the material state over time. A dual approach on measuring surface temperatures by infrared thermography and additional thermocouple measurements in z-direction was performed to identify further influences on the material solidification. A model experiment revealed that a few millimeters below the surface, components produced by LS are already solidified. Based on these results, the authors present an enhanced process model of isothermal laser sintering, which considers material solidification in z-direction during part build-up. In addition, a new processing strategy is derived to increase the efficiency of LS processes significantly.

Model-Based Integration of Test and Evaluation Process and System Safety Process for Development of Safety-Critical Weapon Systems

In weapon system development, the necessity of adopting unestablished advanced technology is continuously increasing to address the competitive acquisition environment. Thus, an effective test and evaluation (TE this can potentially result in a variety of accidents. Therefore, an effective safety process is necessary. A systematic integration of T&E process and system safety process is required for the development of safety-critical weapon systems. To achieve this integration, a model-based approach is adopted in this study. Specifically, T&E and system safety processes are first studied with their constituent tasks. The identified tasks are then analyzed with a focus on the artifacts they produce. The result is used to obtain an initial model that represents the intended integrated process. Based on the process model, a design structure matrix (DSM) is constructed. Thereafter, the constructed DSM is sequenced and torn to obtain an enhanced process model, which effectively integrates the T&E and system safety processes. The resultant integrated process is evaluated through a case study, which revealed reduced complexity that can be transformed into reduced time and cost in the development of safety-critical weapon systems.

Modelling of Nitric and Nitrous Acid Chemistry for Solvent Extraction Purposes

Nitric acid plays an integral role in the reprocessing of irradiated fuel. It is well known that nitric acid degrades; its often yellow hue signifies the presence of decomposition products. The decomposition of nitric acid is accelerated by temperature and radiolysis; therefore it is an important consideration in the reprocessing of nuclear fuels.Thermal and radiolytic reactions of nitric acid result in the formation of redox active nitrogen species, of which nitrous acid is of particular concern, largely due to its redox reactions with plutonium and neptunium. Such reactions are important to understand as plutonium and neptunium can exist in a number of oxidation states; the oxidation state has a direct effect on the species extractability. The effect of nitrous acid is exacerbated as it catalyzes its own production and its reactions with actinides are typically autocatalytic; thus even micromolar quantities can have a large effect. A full understanding of solvent extraction requires us to understand actinide valence states which in turn require us to understand what nitrogen species are present and their concentrations.As a first step in the overall objective of enhancing process models, the kinetic data for nitric acid decomposition reactions has been investigated in order to produce an initial dynamic model of decomposition under aqueous conditions. The identification of a set of kinetic reactions suitable for modelling has been the primary focus of this work. A model of nitric acid thermal decomposition will help develop a better understanding of nitric acid decomposition chemistry and enable better prediction of the oxidation states of species in solution. It is intended to later extend the model to include radiolytic reactions and then further to incorporate an organic phase in order to have a model which covers all decomposition routes for nitric acid within a nuclear fuel reprocessing scheme. The model will be used as a sub model for process models relating to nuclear fuel reprocessing to allow the nitric acid decomposition to be included and the effect of this on operations to be predicted. This is particularly relevant for models of maloperations where different fault scenarios can be investigated and the results of these predicted, as for example unusually high acidity could increase the yields of redox active species significantly altering actinide oxidation states.

Bootstrapping New Organizational Forms: The Legitimation of the Travel Agency in Victorian England

Although institutional theory has strongly advanced our understanding of organizational form emergence, it is unclear how resource-poor entrepreneurs create novel forms. Based on an inductive study of how the entrepreneur Thomas Cook legitimated the travel agency in Victorian England, we propose a process model of Form Bootstrapping. This approach achieves resource-poor form creation by using publicly available resources. We contribute to the literature by reorienting the role of resources for form creation, enhancing process models of form emergence and showing a new approach to venture creation under resource constraints.

Differences in GHG and Nitric Oxide Emissions for Activated Sludge and Biofilm ENR processes based on Aeration, MCRT, Mixing and Media, and Control of Emissions and Nutrients by Enhancing Process Models in an ENR Operations Simulator (Aquifas)

Differences in GHG and Nitric Oxide Emissions for Activated Sludge and Biofilm ENR processes based on Aeration, MCRT, Mixing and Media, and Control of Emissions and Nutrients by Enhancing Process Models in an ENR Operations Simulator (Aquifas)

Local fossil identification in time warp simulations

This paper presents an enhanced process model in an optimistic distributed simulation to develop a method for tracking causality and safe-time and its application in the design of a local fossil identification technique. The fossil identification process is reduced to a local operation that operates without requiring a GVT estimation method. The information needed for fossil identification is captured during normal event processing from the enhanced process model. This technique assumes FIFO communication channels and simulation model with static communication topology. A proof of correctness of the fossil identification technique using this enhanced process model is presented.

Small net carbon dioxide uptake by Russian forests during 1981–1999

A permafrost‐enhanced biogeochemical process model using observed climate and CO2 data, and satellite‐observed maps of forest composition and density predicts a moderate biomass increment and carbon sink of 74 and 131 Tg carbon per year (TgC/a) in the Russian forests during 1981–1999. The enhanced process model realistically represents ecosystem state in terms of river runoff, area burned by fires, vegetation productivity and biomass, in comparison to monitoring and inventory data. Rising atmospheric CO2 content is found to have been the main cause of the carbon sink. Amounting to 7% of carbon emissions from fossil fuel emissions in Eurasia, our results demonstrate a limited capability of the Russian boreal forest in its current state to compensate anthropogenic carbon emissions.

The Proposed Yucca Mountain Repository from a Corrosion Perspective

ABSTRACTIn this paper, the proposed Yucca Mountain Repository is viewed from a corrosion perspective. A major component of the long-term strategy for safe disposal of nuclear waste at the Yucca Mountain Repository is first to completely isolate the radionuclides in the waste packages for long times and to greatly retard the egress and transport of radionuclides from penetrated packages. Therefore, long-lived waste packages are important. The corrosion resistance of the waste package outer canister is reviewed, and a framework for the analysis of localized corrosion processes is presented. An overview is presented of the Materials Performance targeted thrust of the U.S. Department of Energy/Office of Civilian Radioactive Waste Management's Office of Science and Technology and International. The thrust program strives for increased scientific understanding, enhanced process models and advanced technologies for corrosion control.

Implementation, study and calibration of a modified ASM2d for the simulation of SBR processes

An enhanced process model for SBRs has been developed. Though the basic mechanism largely draws on the Activated Sludge Model n. 2d, its new features are the splitting of the nitrification stage in a two-step process, according to the well known Nitrosomonas-Nitrobacter oxidation sequence, and an improved XPAO dynamics, involved in the anaerobic/aerobic phosphorus removal process. The model was implemented through the DLL technique allowing complied C++ modules to be linked to an ordinary Simulink block diagram. The static sensitivity study revealed that if the parameter vector is partitioned into subsets of biologically related parameters and calibrated separately, the calibration procedure does not present particularly difficult aspects. Trajectory sensitivity showed also to which extent data collection could be optimised in order to improve calibration accuracy. The study of the shape of the error functional generated by parameters couples allows a much more effective calibration strategy.