Bias evaluation and reduction in linear least squares procedures for the synthesis of transfer functions

Following Whitfield's (1987) discovery that established linear least squares procedures used in the synthesis of transfer functions generally lead to biased parameter estimates, the present work analyses in detail how such bias arises from imperfections in the frequency response data. Procedures are classified according to their order accuracy. A simple improvement to the well-known Sanathanan and Koerner procedure is given.     

The Problem of the Experimental Confirmation of Landau Damping†

The experimental confirmation of Landau damping in a one-dimensional plasma or electron beam requires the measurement of the velocity distribution, the wave amplitude as a function of time or space, and the numerical solution of the Volterra integral equation through which these data are theoretically related. It is shown that the errors inherent in the two measurements are, under the best of circumstances, of such magnitude that it is not possible to adduce a damping law. The analysis is devoted for the most part to the spatial damping on an electron beam, and a typical numerical example is given     

Revisiting the mixed-model multi-level just-in-time scheduling problem

Morabito and Kraus (1994) propose a modification to the mathematical model of the mixed-model, multi-level just-in-time (JIT) scheduling problem introduced in Miltenburg and Sinnamon (1989). In this note we relate their proposal to the goals of JIT production and emphasize the importance of using the weights in the original formulation to express management priorities.     

Percutaneous absorption of urea

The effect of several variables on the in vitro permeation of urea through hairless mouse skin has been studied in order to determine the causes of an increasing permeability phenomenon found in studies with a range of hydrophilic compounds.
The permeation of urea increased for a period of approximately 100 h after which a steady state permeation pattern was observed for approximately 25 h. Urea did not effect its own permeation in concentrations between 0.01 M and 1.67 M, and the same pattern of increasing permeation was followed in the presence of ( N -morpholine)propanesulphonic acid and tris(hydroxyme)amino-methane buffers, as in the presence of normal saline. Urea did not affect the permeation of tritiated water. Methanol and water exhibited the same pattern of increasing permeation as urea.
The continuously increasing permeation rate of urea up to 100 h is believed to be due to penetration and extensive association of water with the components of the stratum corneum, altering the ultra-structure of the stratum corneum and leading to the formation of large and extensive hydrophilic diffusion channels which do not exist in fresh, untreated skin. These presumed channels open the stratum corneum to facile permeation of highly polar substances such as urea. The physical events leading up to the ultra structural changes within the tissue at the microscopic level remain obscure and are the subject of ongoing research.
L'absorption percutanée de l'urée     

ACCEPTABILITY OF BEEF PATTIES EXTENDED WITH PORK AND/OR TEXTURED SOY PROTEIN1

Four beef or beef/pork ground meat blends were extended with textured soy protein (TSP) at 0, 10, 20 and 30% levels. Ground beef/pork/textured soy protein (TSP) patties with 30% TSP were rated lowest by consumers for raw color and appearance and overall cooked appearance. A beef (50%) and pork (30%) blend containing no TSP was rated highest by consumers for tenderness, flavor and overall desirability and higher by a trained sensory panel for flavor and overall desirability than blends containing TSP. Overall desirability ratings for visual and palatability characteristics of beef/pork meat patties were higher than for beef/pork/TSP blends. Results indicated a distinct advantage for palatability of the beef/pork blend as compared to beef/pork/TSP combinations.     

Mathematical Modeling of Microwave Thawing by the Modified Isotherm Migration Method

A mathematical model of microwave thawing of homogeneous food products is developed and solved numerically using the Modified Isotherm Migration Method. The model is used to predict thawing time and temperature profiles for microwave thawed meat cylinders at three frequencies (2450 MHz, 915 MHz, 300 MHz) and different power levels. Model and experimental results for thawing a lean beef cylinder heated at low microwave power using 2450 MHz frequency compare well. The advantage of using 915 or 300 MHz power over 2450 MHz power is shown by calculations. The results show that microwaves significantly accelerate the thawing rate. The mathematical model is explored as a tool for designing optimal microwave/convective heating protocols for rapidly thawing foods in desired temperature ranges.     

Microcomputer-Based Optimization of Steel Structures in Professional Practice

The paper concerns the computer-automated design of least-weight structural steel frameworks, where members are automatically sized using commercial standard steel sections in full conformance with steel design code provisions for strength/stability and stiffness. The necessary features and functions of such a design system are first identified. Two alternative approaches to the optimal design of steel frameworks are then discussed. Finally, a microcomputer software system is applied for the least-weight design of a steel framework comprised of a variety of member types and subject to a number of load effects. A number of alternative designs of the framework are conducted to illustrate differing optimization strategies and corresponding outcomes.     

The future for milk products in the EEC

The future of milk products must be set against a static European population of increasing age, already generally overfed, and a greater public emphasis on health aspects of foods. Patterns of consumption in the main countries of the EEC are examined with particular reference to the German market. It is suggested that dairy products can expand their share of the market only by replacing other foods, and that this might best be done not by the marketing of mass products but by introducing variety and segmentation of products.     

Release of Iron from Phosvitin by Heat and Food Additives

Most of the iron in egg yolk is bound by phosvitin. Heating whole egg or yolk in a double boiler does not release this iron. Also, heating a 0.125 mg/ml solution of phosvitin in distilled water for 20 and 40 min at 110°C did not free iron. A second phosvitin solution mixed equally with 0.04M citric acid, 2 M NaCl and 0.03M Na₂ EDTA. Only EDTA released (ca) iron from phosvitin without heating.     

Adjustment of Thermal Expansion of Cone 8 Glazes

Shivering of cone 8 zirconium-opacifled glazes for use on one-fire pyrophyllite wall tile and warping of the tile body were corrected by increasing the thermal expansion of the glazes. This was accomplished by (1) increasing the alkali content, (2) substituting strontium oxide for zinc oxide, (3) substituting calcium oxide for magnesium oxide, and (4) decreasing the silica-alumina ratio. The last method appeared to be the most effective. It is shown that the calculated coefficient of cubic thermal expansion is often unreliable as a value for the actual expansion. Expansions were obtained with a quartz-rod dilatometer.