Multi-phase Algorithms for Throughput Maximization for Real-Time Scheduling

We consider the problem of off-line throughput maximization for job scheduling on one or more machines, where each job has a release time, a deadline and a profit. Most of the versions of the problem discussed here were already treated by Bar-Noy et al. (Proc. 31st ACM STOC, 1999, pp. 622–631; http://www.eng.tau.ac.il/amotz/). Our main contribution is to provide algorithms that do not use linear programming, are simple and much faster than the corresponding ones proposed in Bar-Noy et al. (ibid., 1999), while either having the same quality of approximation or improving it. More precisely, compared to the results of in Bar-Noy et al. (ibid., 1999), our pseudo-polynomial algorithm for multiple unrelated machines and all of our strongly-polynomial algorithms have better performance ratios, all of our algorithms run much faster, are combinatorial in nature and avoid linear programming. Finally, we show that algorithms with better performance ratios than 2 are possible if the stretch factors of the jobs are bounded; a straightforward consequence of this result is an improvement of the ratio of an optimal solution of the integer programming formulation of the JISP2 problem (see Spieksma, Journal of Scheduling, vol. 2, pp. 215–227, 1999) to its linear programming relaxation.     

Inventory placement problems in dynamic supply chains

Summary  In this paper a basic model for analyzing the inventory placement problem in a supply chain is developed. The problem will be studied for a capacitated, multi-stage supply chain facing a continuous, stochastic demand for a single period for a single product — a specialty item with a very short selling season. The objective is to maximize the probability of achieving a set profit level. We prove that finding an optimal stock investment at the stages entails solving a mixed binary integer linear program. We characterize properties of the stock investment, examine two interesting cases where the stock investments have a simple structure, and develop a branch and bound approach for solving the more general case.

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Zusammenfassung  In diesem Beitrag wird ein Grundmodell entwickelt, um das Problem der Lagerplatzierung in einer Lieferkette analysieren zu k?nnen. Das Problem wird für eine kapazitierte mehrstufige Lieferkette untersucht, wobei unterstellt wird, dass es um die Nachfrage nach einem einzigen Produkt für eine einzige Periode (einen Sonderartikel mit sehr kurzer Verkaufszeit) geht und diese Nachfrage stetig und stochastisch ist. Unter diesen Bedingungen soll die Wahrscheinlichkeit maximiert werden, ein vorgegebenes Gewinnniveau zu erreichen. Die Suche nach der optimalen Vorratsinvestition auf den Stufen der Lieferkette führt zur Formulierung eines gemischten ganzzahligen linearen Programmierungsproblems mit Bin?rvariablen. Die Eigenschaften der Bevorratungsinvestition werden charakterisiert, zwei interessante F?lle mit einer einfachen Struktur der Bevorratungsinvestition untersucht und ein Branch-and-Bound-Ansatz zur L?sung eines allgemeineren Problemfalls entwickelt.

     

Effects of human-related disturbance on breeding success of urban and non-urban blue tits (<Emphasis Type="Italic">Cyanistes caeruleus</Emphasis>)

There is a need to study the effects of urbanization on wildlife in order to understand the ecological implications of increasing urbanization and find out how to reduce its threats to biodiversity. The blue tit evolved as a forest species and prefers deciduous and mixed forests, whereas its nesting in urban habitats is a more recent phenomenon. Our long-term study of blue tit populations has been conducted in two habitats: an urban parkland (frequently visited by people) and a deciduous forest outside of the city. Using linear mixed modeling, we revealed that a relationship of blue tit breeding success (and the number of fledglings) with thermal conditions in May differed between the urban parkland and the forest. While the relationship was positive in the forest, it was negative in the parkland. In addition, breeding success in the parkland increased with increasing number of rainy days in May. We argue that the main possible reason for such patterns is human activity in the parkland, which interferes with tit parental care, especially the regular feeding of nestlings, whereas it is evidently associated with weather conditions. Human disturbance in the forest is likely to be negligible.     

The Index of Household Financial Condition,Combining Subjective and Objective Indicators: An Appraisal of Italian Households

With data from the Italian Survey of Household Income and Wealth, we present an Index of Household Financial Condition and quantify with it the position of households between 2004 and 2010. The Index of Household Financial Condition is composed of subjective and objective indicators, which enable to capture differently the existing uncertainty concerning the future development of a household’s financial situation. We show with a measurement model based on multi-group confirmatory factor analysis (MGCFA) that the proposed Index is two-dimensional and comprises financial position and financial prudence. Through application of the MGCFA, we show that the interrelations between the indicators had not changed at four measurement occasions (2004–2010), and thus the proposed set comprises a coherent and time-invariant framework for measuring two dimensions of the latent concept: financial condition. Established measurement invariance in the MGCFA framework allows an assessment of trend in financial position and financial prudence of Italian households. We show that the financial position of Italian households improved in the period 2004–2006 and later declined. Improvement of the financial prudence was observed, however, till 2008. Finally, we incorporate a set of socioeconomic features of Italian households into a structural equation model. With the provided set of indicators, we find positive relation between age and both financial position and prudence, but also we show the positive impact of white-collar jobs on scores in each of the dimensions of the financial condition.     

On interrelations between internal and international migration

International migration represents just one type of spatial population mobility, along with inter‐regional, rural‐urban, or intra‐urban migration. The possible connections among various forms of migration are, however, only rarely traced in the professional literature on the political and social determinants as well as consequences of international migration. Against this background, an attempt is made in the present paper to identify possible associations between internal and international migration in the case of Poland.     

On a new type of sufficiency in undominated models

If a family of measures is dominated by a σ-finite measure, then the classical Fisher formulation of sufficiency and the pairwise sufficiency coincide. However, in undominated models, these definitions are essentially different. In particular, the Fisher formulation lacks the basic property: if a σ-algebra is sufficient, then also any larger σ-algebra ? is sufficient. We introduce a new definition of sufficiency, based on the concept of randomization, which has the property described above. We show that in the undominated case, our definition implies pairwise sufficiency and that the converse does not hold. If we assume that the underlying measurable space is a standard Borel space, then Fisher sufficiency implies our new formulation, and the converse implication does not hold.