Coordinated replenishment systems with discount opportunities

In many practical situations, coordination of replenishment orders for a family of items can lead to considerable cost savings. A well-known class of strategies for the case where cost savings are due to reduced joint ordering costs is the class of can-order strategies. However, these strategies, which are simple to implement in practice, do not take discount possibilities into account. We propose a method to incorporate discounts in the framework of can-order strategies. A continuous review multi-item inventory system is considered with independent compound Poisson demand processes for each of the individual items. Discounts are offered by the supplier as a percentage of the total dollar value whenever this value exceeds a given threshold. Starting from the can-order strategy as a basic decision rule, we develop a simple heuristic to evaluate these discount opportunities. The performance of the can-order strategy with discount evaluation is compared with that of another class of discount evaluation rules as proposed by Miltenburg and Silver.     

NEW DEVELOPMENTS IN STRUCTURAL OPTIMIZATION USING ADAPTIVE MESH REFINEMENT AND MULTIPOINT APPROXIMATIONS

Combining Shape Optimization (SO) with Adaptive Mesh Refinement (AMR) potentially offers a higher accuracy and higher computational efficiency, especially if the applied target error for AMR is reduced in the course of the optimization process. The disadvantage of that approach is that the rate of convergence of the corresponding optimization processes can be significantly lower as compared to processes which apply a fixed target error for AMR. In the present paper the so-called Multipoint Approximation Method (MAM) is used as a basis for SO in conjunction with AMR. Several techniques for improvement of the rates of convergence are presented and investigated. Firstly, alternative algorithms for determining the approximation functions using a weighted least squares method are investigated. The focus is on weights which depend on the discretization errors. Secondly, different strategies for moving and resizing the search sub-regions in the space of design variables are presented. The proposed methods are illustrated by means of several optimization problems in which the effect of AMR with changing discretization errors is modelled by artificially introduced numerical noise.     

Investigation of Generalized SIFs of cracks in 3D piezoelectric media under various crack-face conditions

This paper investigates the influence of crack geometry, crack-face and loading conditions, and the permittivity of a medium inside the crack gap on intensity factors of planar and non-planar cracks in linear piezoelectric media. A weakly singular boundary integral equation method together with the near-front approximation is adopted to accurately determine the intensity factors. Obtained results indicate that the non-flat crack surface, the electric field, and the permittivity of a medium inside the crack gap play a crucial role on the behavior of intensity factors. The mode-I stress intensity factors (K_{\mathrm{I}}) for two representative non-planar cracks under different crack-face conditions are found significantly different and they possess both upper and lower bounds. In addition, K_{\mathrm{I}} for impermeable and semi-permeable non-planar cracks treated depends strongly on the electric field whereas those of impermeable, permeable, and semi-permeable penny-shaped cracks are identical and independent of the electric field. The stress/electric intensity factors predicted by permeable and energetically consistent models are, respectively, independent of and dependent on the electric field for the penny-shaped crack and the two representative non-planar cracks. Also, the permittivity of a medium inside the crack gap strongly affects the intensity factors for all crack configurations considered except for K_{\mathrm{I}} of the semi-permeable penny-shaped crack.     

Pulse NMR of Casein Dispersions

The spin-spin relaxation time, T₂, of skimmilk, sodium caseinate dispersions and milk ultrafiltrate was measured as a function of pH and temperature using pulse proton NMR. The T₂ shows a maximum around pH = 5.2 for skimmilk, decreases with decreasing pH for sodium caseinate dispersions and is independent of pH for milk ultrafiltrate. For all systems studied T₂ increases with temperature, but, the extent of increase depends on the system. It is concluded that the T₂ of casein dispersions is mainly determined by factors determining the state of aggregation of the caseins. Apart from affecting the extent of aggregation of the casein particles, micellar calcium phosphate probably contributes also directly to the measured T₂.     

Particle Size Distribution in Tomato Concentrate and Effects on Rheological Properties

The particle size distribution of a tomato concentrate was determined by wet sieving. Wet sieve fractions were then investigated by microscopy and a method based on laser diffraction. Both methods showed that the size of many particles was considerably larger (up to two to three times) than the diameter of the pores through which they have passed during wet sieving. This was explained by the deformability of the tomato cell wall. Effects of particle size distribution on rheological properties were studied by standardizing wet sieve fractions (dry matter, pH). Highest values for yield stress and apparent viscosity were found for the 90–125 and 125–180 μm wet sieve fractions.     

Some Volatile Components of Vitis Vinifera Variety White Riesling. 2. Organic Acids Extracted from Wine

SUMMARY— The acids of a table wine from Vitis vinifera var. White Riesling were recovered by basic extraction from a methylene chloride extract of the wine. The acids were identified by gas chromatographic retention times and by infrared spectroscopy, in most cases both on the free acids and on the methyl, ethyl or hexyl esters. The major acids identified in the wine are: acetic, n-butyric, n-caproic, n-caprylic, n-capric, 9-decenoic, succinic, and ethyl acid succinate. Acids present in smaller amounts are: formic, propionic, isobutyric, 2-methylbutyric, isovaleric, lactic, 2-hydroxyisocaproic, n-pelargonic, and malic.     

Evaluation of Performance Measurement Instruments on Their Use for Food Quality Systems

Due to regular challenges of food safety, consumers put high demands on the performance of food quality systems. To deal with these requirements, food manufacturers need effective quality management. Performance of food quality systems can be partly realized by quality assurance systems, such as HACCP (hazard analysis and critical control point), ISO (international organization for standardization), and BRC (british retail consortium). However, it is still unknown to what extent these systems factually contribute to the realization of quality in the wider sense. Therefore, an instrument is needed that measures the effectiveness of quality systems.

This article describes the evaluation of instruments on their suitability for the development of a diagnostic instrument that measures the effectiveness of food quality systems. For this evaluation, perspectives of quality, typical characteristics of agrifood production, quantification, and performance measurement of quality management were studied.

Instruments that measure the performance of both quality management and production quality were identified and evaluated on the basis of the defined criteria. The criteria for the performance of production quality were 6 quality dimensions, i.e., product quality, availability, costs, flexibility, reliability, and service. The criteria for performance of quality management were analyses of the relationships between quality management, context of the organization, and production quality, a normative procedure, validation, applicability, classification, and a process approach. Finally, for the final instrument, the evaluation resulted in an integrated approach i.e., a technomanagerial approach, and 3 suitable instruments i.e., Wageningen Management Approach, Extended Quality Triangle, and the quality concept of Noori and Radford.     

A Collaborative Study to Develop a Standardized Food Protein Solubility Procedure

A colaborative study was conducted to develop a rapid, simple and reliable procedure for determining the solubility of food protein products, e.g., spray-dried whey protein concentrate, sodium caseinate, egg white protein and soy protein isolate. The procedure was developed by modifying the nitrogen solubility index (NSI) procedure. Protein content and soluble protein were determined by micro-Kjeldahl or biuret procedures with standard deviations of 0.83-4.12 for all proteins except caseinate which had a value of 13.95. Although the biuret and micro-Kjeldahl procedures generally provided comparable accuracy and precision for protein content and solubility of certain proteins, the biuret procedure exhibited considerable error and variability for other proteins.