INTEGRATION, RISK, AND SUPPLY RESPONSE: A SIMULATION AND LINEAR PROGRAMMING ANALYSIS OF AN EAST TEXAS COW-CALF PRODUCER

Livestock Production/Industries,

Thermal conductivity of refractory glass fibres

In the present study, the current international standards and corresponding apparatus for measuring the thermal conductivity of refractory glass fibre products have been reviewed. Refractory glass fibres are normally produced in the form of low-density needled mats. A major issue with thermal conductivity measurements of these materials is lack of reproducibility in the test results due to transformation of the test material during the test. Also needled mats are inherently inhomogeneous, and this poses additional problems. To be able to compare the various methods of thermal conductivity measurement, a refractory reference material was designed which is capable of withstanding maximum test temperatures (1673 K) with minimum transformation. The thermal conductivity of this reference material was then measured using various methods according to the different standards surveyed. In order to compare different materials, samples have been acquired from major refractory glass fibre manufacturers and the results have been compared against the newly introduced reference material. Materials manufactured by melt spinning, melt blowing and sol–gel have been studied, and results compared with literature values

Optimisation of Metallic FibreNetwork Materials for Compact Heat Exchangers

This paper describes an experimental and analytical study of conductive and convective heat transport in metallic fibre network materials. Thermal profiles were measured while gas flowed through such networks. The lateral heat flow rate was found to be proportional to the logarithm of the mean temperature difference between the inlet gas and the wall. Such behaviour is expected when transverse heat flow is a dominant process. An analytical model is developed to simulate the performance of compact heat exchangers based on fibre networks. A study is presented of the inter-relationships between heat transfer performance, fibre network properties, system dimensions and pump characteristics. Some guidelines are presented for controlling the architecture of such fibre network materials, so as to optimise their performance as heat exchangers

Firm level beef supply : a simulation and linear programming application in East Texas

Vita.Beef production is the foremost agricultural activity in East Texas. Although production practices vary, the cow-calf enterprise dominates. Much of the land is used for production of forages that vary from native grasses to tame pastures. But high production costs are causing producers to search for more profitable combinations of forage and livestock systems. To achieve this goal, they need better and more accurate information on forage and livestock production relationships. The overall objective of this study is to identify the most profitable forage and beef systems, both under certainty and uncertainty, for an experimental cow-calf farm in East Texas. Specific objectives addressed are: (a) to generate reliable input-output coefficients for beef calves, stockers, and slaughter cattle for this farm, (b) to determine the effects on beef production of simultaneous changes in quality and quantity of forages, of different calving seasons, and of different cattle enterprises, (c) to analyze effects of changes in product and factor prices on the firm's supply of beef in the short and long run, and (d) to develop expected profit-risk frontiers. Three models, a biological beef cattle simulation model (the TAMU model) and two linear programming models (the acreage model and the economic model), are interfaced to achieve the objectives of this study. Given four livestock enterprises (cow-calf, Stocker, drylot-finishing, and forage-finishing), three alternative forage systems (Coastal bermudagrass, Coastal bermudagrass overseaaed with rye-ryegrass, and common bermudagrass overseeded with crimson clover-ryegrass), and four levels of winter feeding (ad lib and 80 percent, 60 percent, and 40 percent of ad lib), the TAMU model is used to simulate beef cattle production. Using the simulated results as model inputs, the acreage model is applied to determine for each of the above the least cost acreage of a particular forage, purchased hay and supplements required to support the simulated herd. Then the results generated by these two models are used as data in the economic model. The economic model is used (a) to solve for the optimal livestock enterprises, forage systems, and winter feed stress level, (b) to derive firm-level beef supply response under certainty, and (c) to develop expected E-A frontiers under uncertainty..

Forced Convective Heat Transfer in Metallic Fibrous Materials

A numerical study is reported for high Reynolds number forced convection in a channel filled with rigid metallic fibrous materials of high porosity. The effects of convective and form inertia, viscous shear, and thermal dispersion are all considered together. Inertia and thermal dispersion are modeled. The numerical results suggest that heat transfer rate increases with increasing Reynolds number within a range, but not significantly beyond that range. The heat transfer rate also increases with stagnant thermal conductivity, and decreases with Darcy number. The fiber thickness was found to have significant influence on thermal dispersion. The range of applicability of the local volume averaging in terms of the significant parameters is discussed.</jats:p

Firm level beef supply : a simulation and linear programming application in East Texas

Vita.Beef production is the foremost agricultural activity in East Texas. Although production practices vary, the cow-calf enterprise dominates. Much of the land is used for production of forages that vary from native grasses to tame pastures. But high production costs are causing producers to search for more profitable combinations of forage and livestock systems. To achieve this goal, they need better and more accurate information on forage and livestock production relationships. The overall objective of this study is to identify the most profitable forage and beef systems, both under certainty and uncertainty, for an experimental cow-calf farm in East Texas. Specific objectives addressed are: (a) to generate reliable input-output coefficients for beef calves, stockers, and slaughter cattle for this farm, (b) to determine the effects on beef production of simultaneous changes in quality and quantity of forages, of different calving seasons, and of different cattle enterprises, (c) to analyze effects of changes in product and factor prices on the firm's supply of beef in the short and long run, and (d) to develop expected profit-risk frontiers. Three models, a biological beef cattle simulation model (the TAMU model) and two linear programming models (the acreage model and the economic model), are interfaced to achieve the objectives of this study. Given four livestock enterprises (cow-calf, Stocker, drylot-finishing, and forage-finishing), three alternative forage systems (Coastal bermudagrass, Coastal bermudagrass overseaaed with rye-ryegrass, and common bermudagrass overseeded with crimson clover-ryegrass), and four levels of winter feeding (ad lib and 80 percent, 60 percent, and 40 percent of ad lib), the TAMU model is used to simulate beef cattle production. Using the simulated results as model inputs, the acreage model is applied to determine for each of the above the least cost acreage of a particular forage, purchased hay and supplements required to support the simulated herd. Then the results generated by these two models are used as data in the economic model. The economic model is used (a) to solve for the optimal livestock enterprises, forage systems, and winter feed stress level, (b) to derive firm-level beef supply response under certainty, and (c) to develop expected E-A frontiers under uncertainty..