Practice-centred approach to research in design

This paper gives an overview of practice-centred research programmes at Sheffield Hallam University and discusses the principles behind practice-centred research, its place in the Design School, its effect on the regional economy and the community and the resources and methods employed. Implications for research degrees are discussed and developments in the form of the PhD are described.</p

Gas core reactors for actinide transmutation and breeder applications

This work consists of design power plant studies for four types of reactor systems: uranium plasma core breeder, uranium plasma core actinide transmuter, UF6 breeder and UF6 actinide transmuter. The plasma core systems can be coupled to MHD generators to obtain high efficiency electrical power generation. A 1074 MWt UF6 breeder reactor was designed with a breeding ratio of 1.002 to guard against diversion of fuel. Using molten salt technology and a superheated steam cycle, an efficiency of 39.2% was obtained for the plant and the U233 inventory in the core and heat exchangers was limited to 105 Kg. It was found that the UF6 reactor can produce high fluxes (10 to the 14th power n/sq cm-sec) necessary for efficient burnup of actinide. However, the buildup of fissile isotopes posed severe heat transfer problems. Therefore, the flux in the actinide region must be decreased with time. Consequently, only beginning-of-life conditions were considered for the power plant design. A 577 MWt UF6 actinide transmutation reactor power plant was designed to operate with 39.3% efficiency and 102 Kg of U233 in the core and heat exchanger for beginning-of-life conditions

Analysis of the Gas Core Actinide Transmutation Reactor (GCATR)

Design power plant studies were carried out for two applications of the plasma core reactor: (1) As a breeder reactor, (2) As a reactor able to transmute actinides effectively. In addition to the above applications the reactor produced electrical power with a high efficiency. A reactor subsystem was designed for each of the two applications. For the breeder reactor, neutronics calculations were carried out for a U-233 plasma core with a molten salt breeding blanket. A reactor was designed with a low critical mass (less than a few hundred kilograms U-233) and a breeding ratio of 1.01. The plasma core actinide transmutation reactor was designed to transmute the nuclear waste from conventional LWR's. The spent fuel is reprocessed during which 100% of Np, Am, Cm, and higher actinides are separated from the other components. These actinides are then manufactured as oxides into zirconium clad fuel rods and charged as fuel assemblies in the reflector region of the plasma core actinide transmutation reactor. In the equilibrium cycle, about 7% of the actinides are directly fissioned away, while about 31% are removed by reprocessing

An Empirical Model of Inventory Investment by Durable Commodity Intermediaries

This paper introduces a new detailed data set of high-frequency observations on inventory investment by a U.S. steel wholesaler. Our analysis of these data leads to six main conclusions: orders and sales are made infrequently; orders are more volatile than sales; order sizes vary considerably; there is substantial high-frequency variation in the firm's sales prices; inventory/sales ratios are unstable; and there are occasional stockouts. We model the firm generically as a durable commodity intermediary that engages in commodity price speculation. We demonstrate that the firm's inventory investment behavior at the product level is well approximated by an optimal trading strategy from the solution to a nonlinear dynamic programming problem with two continuous state variables and one continuous control variable that is subject to frequently binding inequality constraints. We show that the optimal trading strategy is a generalized (S,s) rule. That is, whenever the firm's inventory level q falls below the order threshold s(p) the firm places an order of size S(p) - q in order to attain a target inventory level S(p) satisfying S(p) >= s(p), where p is the current spot price at which the firm can purchase unlimited amounts of the commodity after incurring a fixed order cost K. We show that the (S,s) bands are decreasing functions of p, capturing the basic intuition of commodity price speculation, namely, that it is optimal for the firm to hold higher inventories when the spot price is low than when it is high in order to profit from "buying low and selling high." We simulate a calibrated version of this model and show that the simulated data exhibit the key features of inventory investment we observe in the data.Commodities, inventories, dynamic programming

Solar vector magnetograph for Max 1991 programs

An instrument for measuring solar magnetic fields is under construction. Key requirements for any solar vector magnetograph are high spatial resolution, high optical throughput, fine spectral selectivity, and ultralow instrumental polarization. An available 25 cm Cassegrain telescope will provide 0.5 arcsec spatial resolution. Spectral selection will be accomplished with a 150 mA filter based on electrically tunable solid Fabry-Perot etalon. Filter and polarization analyzer design concepts for the magnetograph are described in detail. The instrument will be tested at JHU/APL, and then moved to the National Solar Observatory in late 1988. It will be available to support the Max 1991 program

Is the ’Linkage Principle’ Valid?: Evidence from the Field

revenue comparison, auction choice, linkage principle, used-car auctions

Knowledge and the artefact

This paper discusses ways that knowledge may be found in or through artefacts. One purpose is to suggest situations where artefacts might be central to a narrative, rather than secondary to a text. A second purpose is to suggest ways that design and production of artefacts might be instrumental in eliciting knowledge. Four general situations are proposed: (1) Simple Forms - an artefact demonstrates or describes a principle or technique. (2) Communication of Process - artefacts arising from a process make the process explicit. (3) Artefacts Within the Research - artefacts are instrumental in advancing the research by communicating ideas or information. (4) Knowledge Elicited by Artefacts - artefacts provide a stimulus or context which enables information to be uncovered. .</p

ECONOMICS OF ALTERNATIVE STOCKING DENSITIES FOR DIRECT-SEEDED CENTRAL MICHIGAN ALFALFA PASTURES

A framework which permits estimation of economically optimal stocking rates for alternative economic parameters and alfalfa forage availability was developed and applied to a controlled grazing experiment conducted with Holstein steers (243 kg) placed on direct seeded alfalfa pastures in Central Michigan. Responses of ADG to alternative levels of forage availability per standard livestock unit (FA) were summarized by a quadratic function and the associated gains/ha were calculated. The ADG decreased as standard stocking rate (SSR; SLU/ha) increased except for the combination of the lowest observed SSR and highest FA, where ADG was curvilinear as SSR increased. The trend for gain/ha was curvilinear for all FA. The SSR which maximized gain/ha increased with FA and was greater than that which maximized ADG. Net returns to fixed resources(NRFR)/ha ($/ha)were calculated for alternative SSR and the economically optimal SSR were identified under various levels of herbage mass (kg/d). The SSR's which maximized NRFR were between the SSR's which maximized ADG and gain/ha. The magnitude of the sale price discount for heavier weight calves (slide) influenced the economically optimal SSR and the sensitivity of net return to SSR. The economically optimal SSR increased as slide increased because animals stocked under higher SSR weighed less off pasture and therefore received less price discount.Crop Production/Industries,