There is considerable pressure on the U.K. clothing industry to remain competitive in the face of foreign competition. Market forces and the trend of decreasing contract sizes have produced perceived problems with current methods of production which, coupled with the inertia to radical change, justify research. Computer simulation is an established production management tool but its potential in clothing manufacture could not be inferred. Concentrating on progressive bundle systems as the dominant method of production, this research considers the capacity of simulation in this context. Factory-based studies identified factors affecting system performance which allowed a conceptual model with high face validity to be defined. The requirement to handle complex supervisory control strategies led to the identification of visual interactive simulation as an experimental route. A computerised model, with an appropriate user interface and reporting facilities, was developed in the ~Siman si@ulat~£~~Dguage __ This was supported by animated graphics which played a substantial role in the attainment of face validity. Replication was considered to be essential for sound estimates of system performance to be obtained from this stochastic model but, as interactive control works against replication, steps were taken to reduce compromise. Software development facilitated an experimental technique that employed interaction to develop a control strategy, which then became embedded in the model for replication. By providing control consistency between replications, a more reliable assessment of system sensitivity to stochastic variability was possible. Pilot runs and single factor analysis enabled the effect of controllable factors on system performance to be quantified. Supervisory control was found to have a major effect on system performance so that the need for consistency in interaction was amplified. Considering alternative experimental methods and the practical use of the model, application areas for simulation in the absence of real time data capture were identified and demonstrated. Each application offered significant advantage over currently available planning methods and the use of simulation was supported. Information from the model can be gained about the design and control of progressive bundle lines at the pre-production phase, and the output of performance indicators can be useful in assessing real production lines. The evidence presented by this research illustrates that animated simulation can provide insight that is otherwise unobtainable.

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

published_or_final_version / Business Administration / Master / Master of Business Administration

Typescript (photocopy). / Digitized by Kansas Correctional Industries

No description available.

Fruit producers in Northern Utah face several challenges to their production, urbanization, decreased availability of agricultural land, and competition from domestic producers and imports. As consumers are willing to pay premiums for foods differentiated by production method, such as eco-friendly and organic, conversion to these methods may increase the profitability of fruit growing operations. This study found that consumers in Northern Utah are willing to pay a premium for peaches grown using organic and eco-friendly production practices over conventionally grown peaches. The study also found that of the three methods of peach production examined (conventional, eco-friendly, and organic), organic had the highest average grower net returns and had the lowest associated risk, while conventional peach production had the potential for the highest net returns. These results may guide producers when making orchard management decisions and in the profitability assessment of alternative production methods.

This work addresses the poroelastic effect on the processes involved in hydraulic fracturing and post-fracture production using a finite element based fully coupled poroelastic model which includes a triple system of wellbore-fracture-reservoir. A novel numerical procedure for modeling hydraulic fracture propagation in a poroelastic medium is introduced. The model directly takes into account the interaction of wellbore, hydraulic fracture and reservoir in a fully coupled manner. This allows realistic simulation of near fracture phenomena such as back stress and leak-off. In addition, fluid leak-off is numerically modeled based on the concept of fluid flow in porous media using a new technique for evaluating local pressure gradient. Besides, the model is capable of accommodating the zone of reduced pressure (including intermediate and fluid lag zones) at the fracture front so as to capture the behavior of fracture tip region more realistically. A fully coupled poroelastic model for gas reservoirs has been also developed using an innovative numerical technique. From the results of this study it has been found that fracture propagation pressure is higher in poroelastic media compared to that of elastic media. Also high formation permeability (in the direction normal to the hydraulic fracture) and large difference between minimum horizontal stress (in case of it being the smallest principal stress) and reservoir pressure reduce the rate of fracture growth. Besides, high pumping rate is more beneficial in elongating a hydraulic fracture whereas high viscous fracturing fluid is advantageous in widening a hydraulic fracture. It has been also shown that rock deformation, permeability anisotropy and modulus of elasticity can have a significant effect on fluid flow in a hydraulically fractured reservoir. Furthermore, it has been shown that long stress reversal time window and large size of stress reversal region can be caused by high initial pressure differential (i.e. the difference between flowing bottomhole pressure and reservoir pressure), low initial differential stress (i.e. the difference between maximum and minimum horizontal stresses) and low formation permeability in tight gas reservoirs. By taking advantage of production induced change in stress state of a reservoir, this study has also shown that a refracture treatment, if carried out in an optimal time window, can lead to higher economic gain. Besides, analysis of stress reversal region has depicted that a small region with high stress concentration in the vicinity of the wellbore could impede refracture from initiating at the desired place. Moreover, re-pressurization of the wellbore can result in further propagation of the initial fracture before initiation or during propagation of the secondary fracture.

This work addresses the poroelastic effect on the processes involved in hydraulic fracturing and post-fracture production using a finite element based fully coupled poroelastic model which includes a triple system of wellbore-fracture-reservoir. A novel numerical procedure for modeling hydraulic fracture propagation in a poroelastic medium is introduced. The model directly takes into account the interaction of wellbore, hydraulic fracture and reservoir in a fully coupled manner. This allows realistic simulation of near fracture phenomena such as back stress and leak-off. In addition, fluid leak-off is numerically modeled based on the concept of fluid flow in porous media using a new technique for evaluating local pressure gradient. Besides, the model is capable of accommodating the zone of reduced pressure (including intermediate and fluid lag zones) at the fracture front so as to capture the behavior of fracture tip region more realistically. A fully coupled poroelastic model for gas reservoirs has been also developed using an innovative numerical technique. From the results of this study it has been found that fracture propagation pressure is higher in poroelastic media compared to that of elastic media. Also high formation permeability (in the direction normal to the hydraulic fracture) and large difference between minimum horizontal stress (in case of it being the smallest principal stress) and reservoir pressure reduce the rate of fracture growth. Besides, high pumping rate is more beneficial in elongating a hydraulic fracture whereas high viscous fracturing fluid is advantageous in widening a hydraulic fracture. It has been also shown that rock deformation, permeability anisotropy and modulus of elasticity can have a significant effect on fluid flow in a hydraulically fractured reservoir. Furthermore, it has been shown that long stress reversal time window and large size of stress reversal region can be caused by high initial pressure differential (i.e. the difference between flowing bottomhole pressure and reservoir pressure), low initial differential stress (i.e. the difference between maximum and minimum horizontal stresses) and low formation permeability in tight gas reservoirs. By taking advantage of production induced change in stress state of a reservoir, this study has also shown that a refracture treatment, if carried out in an optimal time window, can lead to higher economic gain. Besides, analysis of stress reversal region has depicted that a small region with high stress concentration in the vicinity of the wellbore could impede refracture from initiating at the desired place. Moreover, re-pressurization of the wellbore can result in further propagation of the initial fracture before initiation or during propagation of the secondary fracture.