The traveling salesman problem on grids with forbidden neighborhoods

We introduce the traveling salesman problem with forbidden neighborhoods (TSPFN). This is an extension of the Euclidean TSP in the plane where direct connections between points that are too close are forbidden. The TSPFN is motivated by an application in laser beam melting. In the production of a workpiece in several layers using this method one hopes to reduce the internal stresses of the workpiece by excluding the heating of positions that are too close. The points in this application are often arranged in some regular (grid) structure. In this paper we study optimal solutions of TSPFN instances where the points in the Euclidean plane are the points of a regular grid. Indeed, we explicitly determine the optimal values for the TSPFN and its associated path version on rectangular regular grids for different minimal distances of the points visited consecutively. For establishing lower bounds on the optimal values we use combinatorial counting arguments depending on the parities of the grid dimensions. Furthermore we provide construction schemes for optimal TSPFN tours for the considered cases.     

Individual Wealth and Subjective Financial Well‐being in Marriage: Resource Integration or Separation?

Economic wealth is mostly assumed to be a household‐level resource that is pooled by spouses in married couples. Using comprehensive data on the individual wealth of both spouses in married couples from the German Socio‐Economic Panel Study (N = 13,623 individuals), the author tests this assumption. To this end, the associations between individuals' wealth and their spouses' wealth with individuals' subjective financial well‐being are examined. Results show that women's financial well‐being is equally associated with their own individual wealth and their spouses' wealth in older birth cohorts. In younger birth cohorts, women's financial well‐being is more strongly associated with their own individual wealth than with their spouses' wealth. For men from all birth cohorts, their own individual wealth is more strongly related to their financial well‐being than is their spouses' wealth. These findings suggest that wealth is not generally and fully pooled and that individual ownership matters within married couples in Germany.     

Verbot von Leerverkäufen in der Krise

During the recent financial and economic crisis political and corporate representatives demanded for stricter regulations of short sales to limit the risks of price manipulation and potential stock price crashes. In autumn 2008 regulators of most industrial countries decided to implement temporary short sale restrictions to prevent a further collapse of the capital market. While some countries restricted only naked short sales and increased their disclosure requirements, other markets like the USA and Great Britain implemented a full ban on short selling. The analysis of these two markets supports the hypothesis that temporary bans are unlikely to prevent or limit large price drops in the affected stocks. Instead the results suggest that the implemented emergency measures led to a temporary overvaluation of stock prices and to a deterioration of market efficiency. These results become even more prominent for stocks with high dispersion of investor opinion.     

Drivers of internationalization success: a conjoint choice experiment on German SME managers

Internationalization is a common growth strategy for small and medium-sized enterprises (SMEs). However, SMEs face several challenges within the internationalization process. As SMEs are characterized by limited resources, managers are constantly involved in a decision-making process concerning the allocation of the SMEs’ resources. Therefore, internationalization can be understood as a complex, multidimensional decision process. Based on a set of 2244 internationalization decisions made by German SME managers, the present study examines how eight strategic and structural factors drive the perceived international success of SMEs. When applying conjoint choice analysis, the results suggest that especially equity financing in the internationalization process, an appropriate market selection as well as proactive motives, and a long-term scope can drive SMEs’ international success. Moreover, it becomes evident that strategic factors are more relevant for successful internationalization than structural factors.     

Effects of habitat and landscape quality on amphibian assemblages of urban stormwater ponds

Urbanisation is one of the most severe drivers of current global biodiversity loss and has contributed to severe declines in many amphibian species. The aim of this study was to determine whether artificial stormwater ponds, designed to control water flow, can act as refuges for amphibians in urban areas. Moreover, we analysed the influence of habitat and landscape quality on amphibian species richness of 46 stormwater ponds (STOPON) in comparison to 46 control ponds (CONTROL).Our study revealed that environmental conditions clearly varied between STOPON and CONTROL. The most pronounced differences were that STOPON were larger, shallower, sunnier, more isolated by streets and had a greater cover of built-up area and lower cover of arable land surrounding them. Nevertheless, the amphibian assemblages of STOPON and CONTROL were very similar. All nine amphibian species (including three threatened species) detected in this study were found in both pond types. Moreover, species richness (2.8 ± 0.2 vs. 2.3 ± 0.2) and the frequency of each species did not differ between STOPON and CONTROL. The only exception was Pelophylax spp., which occurred more regularly in STOPON. Both habitat and landscape quality affected amphibian species richness; however, the explanatory power of the habitat models was about twice as high as those of the landscape models.In conclusion, stormwater ponds play an important role for amphibians in urban areas. In comparison to CONTROL, the low landscape quality in the surroundings of STOPON seemed to be compensated by a higher habitat quality due to regular management.     

How Journalists Think about Media Effects—And Why We Should Care

Research suggests that journalists’ beliefs about media effects are influenced by unsystematically gathered knowledge and subjective-intuitive judgments. However, it has also been shown that these presumptions must be considered important factors for the formation of journalistic coverage. Against this background, this article synthesizes existing research on dimensions, determinants, and consequences of journalists’ presumptions of media effects. The resulting framework offers researchers in the field of journalistic content production a comprehensive overview of the possible role that presumptions of media effects could play for journalistic content creation. In a second step, we summarize the implications that the current state of research points at. We discuss why journalism scholars should integrate presumed media effects into their research agendas and what communication researchers, as well as journalists themselves, could do to promote more realistic beliefs about media effects among journalists.     

K?nnen Studienbeitr?ge die Lehre in der BWL verbessern?

The introduction of tuition fees by some German universities raised fears about possible negative effects, which scientific research has not substantiated, though. Meanwhile, little attention has been paid to positive effects tuition fees might entail. This is surprising as universities are obliged to use tuition fees to improve study conditions. Business programs are highly frequented with limited academic staff. More assistance would therefore improve study conditions substantially. Tutorials funded by fees can be introduced quickly and, unlike faculty positions, do not tie up money in the long run. This makes them ideal to cope with the one-time enrollment peak due to the shortening of secondary education. We show that tutorials improve both satisfaction and study outcomes. We use data from an introductory course characteristic of business programs, where tutorials have been introduced. This course is attended by about 750 students per term and the data cover several terms. We control for a number of effects, including general academic ability. Increased satisfaction and improved study outcomes show that tutorials enhance both the objective and perceived study conditions. This makes tutorials an example of how tuition fees can be used to produce positive effects.     

Supervision der Geschäftsführung kleiner freier Träger der Sozialen Arbeit

The economic pressure weighting on social organizations is ever increasing. Leadership coaching supports smaller operating agencies in implementing social management, in integrating an appropriate leadership strategy and in taking measures allowing them to survive in times of scarce resources. The introduction of patterns of economic thinking and action is often perceived as a threat and is considered to be incompatible with the traditional values of social work. Two detailed case studies reflect problems in the coaching practice and ways of a successful restructuring.