A nearly optimal randomized algorithm for explorable heap selection

Explorable heap selection is the problem of selecting the nth smallest value in a binary heap. The key values can only be accessed by traversing through the underlying infinite binary tree, and the complexity of the algorithm is measured by the total distance traveled in the tree (each edge has unit cost). This problem was originally proposed as a model to study search strategies for the branch-and-bound algorithm with storage restrictions by Karp, Saks and Widgerson (FOCS '86), who gave deterministic and randomized n⋅exp(O(logn−−−−√)) time algorithms using O(log(n)2.5) and O(logn−−−−√) space respectively. We present a new randomized algorithm with running time O(nlog(n)3) using O(logn) space, substantially improving the previous best randomized running time at the expense of slightly increased space usage. We also show an Ω(log(n)n/log(log(n))) for any algorithm that solves the problem in the same amount of space, indicating that our algorithm is nearly optimal

Youth life skills training: Exploring outcomes and mediating mechanisms of a group-randomized trial in physical education

This exploratory group-randomized study aimed at verifying (a) if a life skills program in physical education (PE) had a positive impact on physical fitness, sport skills, and executive cognitive function, and (b) if eventual physical and sport outcomes were mediated by gains in life skills and executive function. Ninety students aged 14-15 years participated in either an experimental life skills program integrated in a multisport PE setting, or traditional PE. Prior to and after the intervention, they were administered tests assessing physical fitness (aerobic and muscular), sport skills (passing and dribbling), and executive functions (inhibition and working memory updating). Furthermore, they were evaluated in goal setting knowledge, self-efficacy in sport-relevant life skills (problem solving, selfregulation, communication, and social skills), and decision making and tactical cooperation skills in sport game situations. The results showed that (a) the life skills program induced improvements in aerobic fitness, sport passing skill, and inhibitory executive function compared with the control group, and (b) fitness and sport skill outcomes were mediated by gains in life skills operationalized as behavioral change in decision making skill. Thus, life skills training in a designed sport education context seems beneficial to the fitness dimension of physical health and the cognitive dimension of mental health. Mechanisms underlying the physical and sport outcomes of the life skills training program may be cognitive in nature. © 2016 American Psychological Association

Negative buoyant plume model for solar domestic hot water tank systems incorporating a vertical inlet

Thermal stratification in solar energy storage tanks plays an important role in enhancing the performance of solar domestic hot water systems. The mixing that occurs when hot fluid from the solar collector enters the top of the tank is detrimental to the stratification. Mathematical models that are used for system analysis must therefore be able to capture the effects of this inlet jet mixing in order to accurately predict system performance. This paper presents a computational study of the heat transfer and fluid flow in a thermal storage tank of a solar domestic hot water system with a vertical inlet under negative buoyant plume conditions. The effects of parameters such as the fluid inlet velocity and temperature as well as inlet pipe diameter on the thermal mixing were considered. The work culminated in the development of a one-dimensional empirical model capable of predicting the transient axial temperature distribution inside the thermal storage tank. Predictions from the new model were in good agreement with both experimental data and detailed computational fluid dynamics predictions