A general quantity discount and supplier selection mixed integer programming model

Recently, new models and heuristics for exploiting quantity discounts have been proposed that are applicable in classical purchasing as well as in an e-business environment and can be implemented as part of an advanced planning system. These models can now handle both the single- and multi-item case with fixed cost to be shared among several products ordered at the same point in time from a single supplier. Furthermore, the supplier selection problem is addressed, i.e., how to best exploit quantity discounts over time offered by several suppliers. Last but not least, additional constraints on the buyer’s or on the supplier’s side may be included. While so far only purpose-built heuristics have been proposed for this generalized problem, we present a linear mixed integer programming (MIP) model, which not only represents the all-units discount but also the incremental discount case. Furthermore, the objective function chosen resolves (former) conflicts among proponents of a purely cost oriented and a cash flow oriented modeling approach. Computational tests show that our model yields near optimal solutions within a given CPU time limit by making use of a standard MIP solver.     

Improving Flood Forecasting in a Developing Country: A Comparative Study of Stepwise Multiple Linear Regression and Artificial Neural Network

Due to limited data sources, practical situations in most developing countries favor black-box models in real time operations. In a simple and robust approach, this study examines performances of stepwise multiple linear regression (SMLR) and artificial neural network (ANN) models, as tools for multi-step forecasting Chindwin River floods in northern Myanmar. Future river stages are modeled using past water levels and rainfall at the forecasting station as well as at the hydrologically connected upstream station. The developed models are calibrated with flood season data from 1990 to 2007 and validated with data from 2008 to 2011. Model performances are compared for 1- to 5-day ahead forecasts. With a high accuracy, both candidate models performed well for forecasting the full range of flood levels. The ANN models were superior to the SMLR models, particularly in predicting the extreme floods. Correlation analysis was found to be useful for determining the initial input variables. Contribution of upstream data to both models could improve the forecasting performance with higher R ² values and lower errors. Considering the commonly available data in the region as primary predictors, the results would be useful for real time flood forecasting, avoiding the complexity of physical processes.     

A multi-sensor climatological view of double ITCZs over the Indian Ocean

We characterize the climatological features of the double inter-tropical convergence zones (DITCZs) over the western Indian Ocean during November–December by a synergistic analysis of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite (HOAPS III) data (1988–2005) and the National Aeronautics and Space Administration's (NASA's) A-Train data (2002–2009). We investigate rainfall, freshwater flux and cloud liquid water, cloud fraction and relative humidity over the DITCZs. In addition, the daily rainfall data from the Global Precipitation Climatology Project (GPCP) are used to document the DITCZs during the El Niño southern oscillation (ENSO) events. An analysis of the GPCP data shows that the DITCZs are clearly discernible during strong ENSO events (1997, 2002 and 2006), in sharp contrast to the DITCZs in the eastern Pacific Ocean, where they are absent during ENSOs. Further, these convergence zones on either side of the equator are of short duration, approximately 3–6 pentads during November and December. All satellite sensor data sets consistently capture the major features of DITCZs. As an accurate simulation of DITCZs in coupled global climate models remains a challenge, the results from the present study would provide a platform for evaluating these models.     

Beschreibung von Ver- und Entfestigungsvorgängen am Beispiel austenitformgehärteter Stähle mit Hilfe von Fließkurven

Fließkurven beschreiben das Formänderungsvermögen von Werkstoffen. Gleichzeitig liefern sie Informationen über die Wechselwirkung zwischen der Ver- und Entfestigung, wobei diese beiden Eigenschaften temperaturabhängig sind. Fließkurven wurden an Stählen aufgenommen, die sich im wesentlichen in ihrem Kohlenstoffgehalt unterscheiden. Die Bestimmung der Formänderungsfähigkeit erfolgte bei Temperaturen, die denen entsprechen, bei denen eine Austenitformhärtung vorgenommen wird. Die mathematische Beschreibung der Fließkurven läßt erkennen, daß zunächst mit steigender Umformtemperatur die Verfestigungsrate abnimmt. Der Kohlenstoffgehalt erhöht dagegen die Verfestigungsrate. Die dynamische Erholung wird mit wachsender Umformtemperatur beschleunigt, ebenso mit steigendem Kohlenstoffgehalt.     

Internal and external algorithms for the points-in-regions problem—the inside join of geo-relational algebra

We consider the problem of collectively locating a set of points within a set of disjoint polygonal regions when neither for points nor for regions preprocessing is allowed. This problem arises in geometric database systems. More specifically it is equivalent to computing theinside join of geo-relational algebra, a conceptual model for geo-data management. We describe efficient algorithms for solving this problem based on plane-sweep and divide-and-conquer, requiringO(n(logn) +t) andO(n(log² n) +t) time, respectively, andO(n) space, wheren is the total number of points and edges, and (is the number of reported (point, region) pairs. Since the algorithms are meant to be practically useful we consider as well as the internal versions-running completely in main memory-versions that run internally but use much less than linear space and versions that run externally, that is, require only a constant amount of internal memory regardless of the amount of data to be processed. Comparing plane-sweep and divide-and-conquer, it turns out that divide-and-conquer can be expected to perform much better in the external case even though it has a higher internal asymptotic worst-case complexity. An interesting theoretical by-product is a new general technique for handling arbitrarily large sets of objects clustered on a singlex-coordinate within a planar divide-and-conquer algorithm and a proof that the resulting “unbalanced” dividing does not lead to a more than logarithmic height of the tree of recursive calls.     

Auf dem Weg zu idealen Programmierwerkzeugen – Bestandsaufnahme und Ausblick

Zusammenfassung  Angeregt durch Robert W. Floyds Turing-Award-Lecture ,,The Paradigms of Programming“ von 1979 [6] und motiviert durch die Unzufriedenheit des Praktikers mit dem Stand der Softwaretechnik aus vielen Industrieprojekten, versucht dieser Beitrag eine Bestandsaufnahme der Programmiertechnik und identifiziert die Defizite aus Sicht der Grundprinzipien des Konstruktionsprozesses. Mit der Objektorientierung sind, besonders in den letzten Jahren, viele neue Programmiersprachen entstanden, die sowohl Wert auf schnelle Entwicklungszyklen als auch auf Erweiterbarkeit legen. Die heute haupts?chlich verwendeten Sprachen und Umgebungen sind von diesen Zielen weit entfernt. Das Entwickeln von Software ist zum einen zu kompliziert und zum anderen schmerzt die ,,semantische Lücke“ zwischen den ausdrückbaren und den erforderlichen Konzepten. Neue, viel versprechende Programmiersprachen, die sich durchweg auf Metaprogrammierung stützen, um die erforderliche semantische Erweiterbarkeit der Sprachen zu erreichen, deuten die Richtung zukünftiger Entwicklungen an.     

Ziele und Methoden der elektrochemischen Verfahrens- und Reaktionstechnik

Objectives and methods of electrochemical process and reaction engineering . Electrolysis processes are distinguished from ?normal”? chemical processes in several respects: (1) The electrical energy consumed is expensive and assumed the role of an expensive raw material. (2) Mass transfer in electrolytes is sluggish and limits space time yield to relative low values. (3) The rate of reaction is dictated by the applied electrode potential and this determines the cell voltage and energy efficiency of electrolysis processes. Effective electrocatalysts diminish energy consumption per unit mass of product. (4) The relatively poor electrical conductivity of electrolytes leads to construction of special closely spaced cells with narrow cell gaps. It is important to select the operation conditions of, e. g. organo-electrosyntheses to minimise the efforts involved in isolation and purification of the product.     

Composition and quality attributes of conventionally and organically farmed Pangasius fillets (Pangasius hypophthalmus) on the German market

A range of conventionally and organically farmed Pangasius or sutchi catfish fillets available on the German market were analysed to compare both composition and quality. Differentiation of Pangasius hypophthalmus from Pangasius bocourti was achieved by RFLP-SSCP analysis. The protein content of conventionally farmed fillets ranged between 13.3 and 15.7%, whereas organically produced fillets had significantly higher protein contents of between 17.0 and 17.4%. No difference in the fat content between farming methods was observed, which varied between 1.4 and 3.2%. Polyunsaturated fatty acids represented about 24% of the total fatty acids with a high level of linoleic acid. The comparison of the proximate composition indicated that water was added to most of the conventionally farmed products, in different amounts, as well as water-binding capacity enhancing additives. Differential scanning calorimetry was used to demonstrate the presence of polyphosphate on muscle proteins. Differences in texture, water-binding capacity and colour are discussed.