We present approximation algorithms with O(n) processing time for the minimum vertex and edge guard problems in simple polygons. It is improved from previous O(n) time algorithms of Ghosh. For simple polygon, there are O(n) visibility regions, thus any approximation algorithm for the set covering problem with approximation ratio of log(n) can be used for the approximation of n vertex and edge g...

INTRODUCTION The adjustment difficulties of college students have been an emerging issue. Many studies have proved that the adjustment difficulties like appetite disturbance, concentration problems and depression are most evident in freshmen. To help college students in resolving their adjustment issues, we made efforts in the form of establishing a counselling system to provide intervention to...

Let G be a finite Abelian group and D(G) its Davenport constant, which is defined as the maximal length of a minimal zero-sum sequence in G. We show that various problems on zero-sum sequences in G may be interpreted as certain covering problems. Using this approach we study the Davenport constant of groups of the form (Z/nZ)r , with n ≥ 2 and r ∈ N. For elementary p-groups G, we derive a resul...

The paper addresses the problem of locating sensors with a circular field of view so that a given line segment is under full surveillance, which is termed as the Disc Covering Problem on a Line. The cost of each sensor includes a fixed component f , and a variable component b that is proportional to the field-of-view area. When only one type of sensor or, in general, one type of disc, is availa...

The present study examined predictors of emotional problems amongst a nationally representative cohort of recent immigrants in Canada. Specifically, the effects of parenting status were examined given the association between parenting stress and mental health. Data came from the Longitudinal Survey of Immigrants to Canada (N = 7055). Participants were recruited 6-months post landing (2001-2002)...

Variation in attention problems in children and adolescents from non-clinical samples is highly heritable. It is unknown how attention problems develop later in life and whether the heritability in the general adult population is the same as in children and adolescents. We assessed the heritability and stability of individual differences in attention problems in the general young adult populati...

Although insomnia or excessive tiredness are familiar to most who live with schizophrenia they are not unique to it. At least 70% of people suffer from some sleep abnormalities at some point in their lives for various reasons. Sleep problems can be the result of either a physical, mental or emotional issue that disturbs the normal rhythm of our bodies which then creates a vicious circle, as lac...

BACKGROUND Although childhood hyperactivity and conduct problems are associated with difficulties in adulthood, little is known about later service use or public expenditure costs in the UK. AIMS To describe the use of services and calculate recent (past 6 months) and early adulthood (since the age of 18 years) public expenditure costs incurred by young adults who had hyperactivity and/or con...

Individual heterogeneity exists in the onset and development of conduct problems, but theoretical claims about predictors and prognosis are often not consistent with the empirical findings. This study examined shape and outcomes of conduct problem trajectories in a Belgian population-based sample (N = 682; 49.5 % boys). Mothers reported on children's conduct problems across six waves (age 4-17)...