MRP lot sizing with variable production/purchasing costs: formulation and solution

The research on lot sizing is extensive; however, no author in the literature reviewed to date provides an optimal solution algorithm to a prevalent problem which is found in manufacturing. A multi-level, general product-structure, variable-cost model is presented which follows the procedure of a closed-loop material requirements planning (MRP) system, and incorporates many conditions that production and material managers find in practice. A branch and bound (B&B7) algorithm is developed. The efficiency of B&B is derived from effective lower bounds and solution procedures which are determined on the basis of the space-time structure of the MRP lot-sizing problem and its non-convex total-cost function. This path-dependent lower bound is computationally efficient and guarantees an optimal solution. The B&B algorithm is tested on problems and compared to heuristics in the literature.     

The effects of market power on the stocks and prices of world coffee

The objective of this study is to explore the consequences of market power for optimal stockholding and price variations in the world coffee economy. Optimal storage decision rules which incorporate risk aversion under several market scenarios are considered. These generate a set of price and quantity series that can be compared with the historical data and to test the hypothesis proposed by Newbery that a monopolistic producer tends to undertake more storage than a competitive producer and hence price stability may increase in proportion to the dominant role played by the monopolist. Our study reveals that the world coffee market has been rather close to the competitive regime since the 1960s. As far as price variations are concerned, results are not always consistent with the Newbery hypothesis.     

Aldehydes, Ketones and Esters in Valencia Orange Peel Oil

SUMMARY: The aldehydes, ketones and esters in the volatile portion of Valencia orange oil have been isolated and identified. Seventeen aldehydes and ketones and three esters are included, 10 of which have never been identified as constituents of Valencia oil. Cis- and trans-limonene oxide have also been found to occur in the same fraction. This is the first time that these compounds have been identified in cold-pressed orange oil. A series of five homologous α,β-unsaturated aldehydes were isolated and partially characterized.     

Note on the pole assignment of q-dimensional linear systems

The method in Chu (1986) for the solution of the pole assignment problem of separable 2-D linear discrete systems with state feedback is improved and extended to q-D linear discrete systems and systems with output feedback.     

Use of Ultrasound to Determine Cod Fillet Composition

The relationships between the composition and ultrasonic properties of Atlantic cod (Gadus morhua) fillets were examined. The lipid, protein, moisture and ash contents of cod fillets were determined by official methods. The ultrasonic velocity and attenuation coefficient of the fillets were measured using a pulse-echo technique. The ultrasonic velocity of the fillets varied between 1575 and 1595 m s^?1, decreasing linearly with increasing moisture content (r² > 0.8 for 26 samples). No systematic relationship was observed between the attenuation coefficient and moisture content. Our experiments highlight the potential of using ultrasonic velocity measurements to rapidly and nondestructively determine the moisture content of cod fillets (and possibly their protein content by deduction).     

National Defense Migration and the Transformations of American Urbanism, 1940–1942

This article examines how a shift toward decentralized and automobile-based patterns of American metropolitan development was a major aspect of the national defense buildup that took place just before Pearl Harbor. It suggests that the continuing and seemingly permanent clash between what are now standard contemporary suburban development practices and the ideas of architects about the design of cities and metropolitan areas can be traced back to that pivotal time.     

Conjugated Linoleic Acid Concentrations in Dairy Products as Affected by Processing and Storage

Total conjugated linoleic acid (CLA) concentrations increased 1.32 fold in salted and 1.27 in unsalted butter but did not alter the ratio of 9-cis 11-trans to total CLA. Nonfat yogurt showed an increase in CLA content with processing (5.25 mg total CLA/g fat) compared to unprocessed raw material (4.40 mg CLA/g fat). No changes in CLA content was observed in processed dairy products such as lowfat yogurt, regular yogurt, lowfat and regular ice cream, sour cream or cheeses such as Mozzarella, Gouda and Cheddar. Storage did not affect CLA concentration in any products suggesting that CLA is a stable component.     

Influence of a grass layer on vineyard soil temperature

Vineyard grass cover can modify soil variables such as temperature and water content, which in turn influence berry quality at harvest. Such effects require further documentation and this study was conducted to determine how a grass layer could change soil thermal behaviour compared to bare soil. Soil temperature, soil water content and net radiation were measured in a Médoc vineyard, Château Talbot (France). The field used for the experiment was divided into two parts, one with a bare ploughed soil and the other with a partial grass cover. The same measurements were taken on both parts. Bare soil temperatures were generally higher, and the difference between the two treatments was greater in the middle of the inter-row, just under the grass layer. Nevertheless, net radiation above the vegetation, which represents the radiative available energy, was the same for the two plots. Soil conduction heat flux (G) was calculated from temperature measurements. Under the grass layer, the horizontal component of G was barely detectable, whereas under bare soil, G was essentially vertical. The grass layer was therefore acting as an insulating layer, preventing exchanges between soil and atmosphere. Soil temperature and thermal behaviour are heavily influenced by soil surface management practices. The field experiment provided a large data set of measurements which will be used to calibrate a heat and mass transfer model.     

A pole-assignment problem for 2-dimensional linear discrete systems

In Kaczorek (1983) the pole-assignment problem of a class of 2-dimensional linear discrete systems is solved. In this paper, an algorithm for a larger class of systems is presented. If degrees of freedom permit, the most 'robust' feedback gain matrix can be found. Numerical examples are included.