Sampling from spatial databases

This paper deals with techniques for obtaining random point samples from spatial databases. We seek random points from a continuous domain (usually ²) which satisfy a spatial predicate that is represented in the database as a collection of polygons. Several applications of spatial sampling (e.g. environmental monitoring, agronomy, forestry, etc) are described. Sampling problems are characterized in terms of two key parameters: coverage (selectivity), and expected stabbing number (overlap). We discuss two fundamental approaches to sampling with spatial predicates, depending on whether we sample first or evaluate the predicate first. The approaches are described in the context of both quadtrees and R-trees, detailing the sample first, acceptance/rejection tree, and partial area tree algorithms. A sequential algorithm, the one-pass spatial reservoir algorithm is also described. The relative performance of the various sampling algorithms is compared and choice of preferred algorithms is suggested. We conclude with a short discussion of possible extensions.     

Who owns the trauma? A Kleinian perspective on the dialogue between child protection social workers and the media

The present paper makes use of the developmental model of movement between mental positions that was formulated by psychoanalyst Melanie Klein, aimed at understanding the dialogue that takes place between the media and social workers in the field of child welfare, centring around incidents of murder within the family. The basic concept in the paper is that when working with children who are victims of abuse and with their parents, and when reporting on them as well, the feeling of personal control is severely undermined, being associated with the loss of the hallowed social value known as ‘unconditional love of a parent for his child’. The paper illustrates these theoretical ideas by describing two cases that took place in Israel and recommendations are made regarding ways of promoting the dialogue between the professions.     

The Association Between Adolescent Life Satisfaction, Family Structure, Family Affluence and Gender Differences in Parent–Child Communication

The study sought to examine young people’s life satisfaction in the context of the family environment, using data from the 2006 HBSC: WHO-collaborative Study in Scotland (N = 5,126). Multilevel linear regression analyses were carried out for 11-, 13- and 15-year old boys and girls, with outcome measure ridit-transformed life satisfaction. The study found there to be a relationship between family structure and life satisfaction for boys and girls aged 13 and 15 years. Family affluence mediated this relationship, however the extent of this mediation depended both on age and gender. For both boys and girls at all ages, life satisfaction was more strongly associated with parent–child communication than with family structure or family affluence. After adjustment for risk/health behaviours and attitudes towards peers and school, family structure remained significant for boys aged 13 years only. Whereas difficult parent–child communication acted as a risk factor of low life satisfaction for boys and girls, easy communication acted as protective factor among girls only.     

MANAGED COMPETITION IN HEALTH INSURANCE

Rising healthcare costs have sparked debate about the best way to provide high‐quality affordable health insurance. We discuss the potential for regulated insurance markets to outperform single‐payer public insurance. We use as an example the private Medicare plans that now provide insurance to almost a third of seniors in the United States. The evidence suggests that private plans can limit costs and potentially appeal to enrollees, and that well‐designed risk adjustment can mitigate market failures due to adverse selection. However, fostering competition between insurers, especially in smaller markets, is difficult. We discuss how future research might illuminate the relative advantages of public and private health insurance.     

Nah der Wissenschaft und fern der Führung in einer Fach‑/Expertenlaufbahn?

In order to motivate and retain technical employees, representatives of strategic career management face the challenge of establishing alternative career paths in addition to the common leadership/management career. Surveying a sample of 629 doctorate holders from the STEM fields, we differentiated between five career paths within and beyond structured career models. Structured career ladders were predominantly present in major enterprises. Female participants less frequently reported to be part of a structured career path. Entering a leadership/management career seems to occur at a later stage compared to other paths. Generally, advancement on a leadership/management path was related to stronger increases in incentives than climbing up the technical/expert or project management ladders. Contrary to our expectations, we did not find members of a technical/expert career to work closer to basic research and their initial qualification than their colleagues on other career paths. Members of leadership/management paths reported to have significantly more leadership responsibility than those working on alternative paths.     

On nonlinear multi-covering problems

In this paper we define the exact k-coverage problem, and study it for the special cases of intervals and circular-arcs. Given a set system consisting of a ground set of n points with integer demands \(\{d_0,\dots ,d_{n-1}\}\) and integer rewards, subsets of points, and an integer k, select up to k subsets such that the sum of rewards of the covered points is maximized, where point i is covered if exactly \(d_i\) subsets containing it are selected. Here we study this problem and some related optimization problems. We prove that the exact k-coverage problem with unbounded demands is NP-hard even for intervals on the real line and unit rewards. Our NP-hardness proof uses instances where some of the natural parameters of the problem are unbounded (each of these parameters is linear in the number of points). We show that this property is essential, as if we restrict (at least) one of these parameters to be a constant, then the problem is polynomial time solvable. Our polynomial time algorithms are given for various generalizations of the problem (in the setting where one of the parameters is a constant).