Consistency of Markov chain quasi-Monte Carlo on continuous state spaces

The random numbers driving Markov chain Monte Carlo (MCMC) simulation are usually modeled as independent U(0,1) random variables. Tribble [Markov chain Monte Carlo algorithms using completely uniformly distributed driving sequences (2007) Stanford Univ.] reports substantial improvements when those random numbers are replaced by carefully balanced inputs from completely uniformly distributed sequences. The previous theoretical justification for using anything other than i.i.d. U(0,1) points shows consistency for estimated means, but only applies for discrete stationary distributions. We extend those results to some MCMC algorithms for continuous stationary distributions. The main motivation is the search for quasi-Monte Carlo versions of MCMC. As a side benefit, the results also establish consistency for the usual method of using pseudo-random numbers in place of random ones.Comment: Published in at http://dx.doi.org/10.1214/10-AOS831 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Results from the Scottish report card on physical activity for children and youth

The Active Healthy Kids Scotland Report Card aims to consolidate existing evidence, facilitate international comparisons, encourage more evidence-informed physical activity and health policy, and improve surveillance of physical activity. Application of the Active Healthy Kids Canada Report Card process and methodology to Scotland, adapted to Scottish circumstances and availability of data. The Active Healthy Kids Scotland Report Card 2013 consists of indicators of 7 Health Behaviors and Outcomes and 3 Influences on Health Behaviors and Outcomes. Grades of F were assigned to Overall Physical Activity, Sedentary Behavior (recreational screen time), and Obesity Prevalence. A C was assigned to Active Transportation and a D- was assigned to Diet. Two indicators, Active and Outdoor Play and Organized Sport Participation, could not be graded. Among the Influences, Family Influence received a D, while Perceived Safety, Access, and Availability of Spaces for Physical Activity and the National Policy Environment graded more favorably with a B. The Active Healthy Kids Canada process and methodology was readily generalizable to Scotland. The report card illustrated low habitual physical activity and extremely high levels of screen-based sedentary behavior, and highlighted several opportunities for improved physical activity surveillance and promotion strategies

Gold-free GaAs/GaAsSb heterostructure nanowires grown on silicon

Growth of GaAs/GaAsSb heterostructurenanowires on silicon without the need for gold seed particles is presented. A high vertical yield of GaAsnanowires is first obtained, and then GaAsₓSb₁ˍₓ segments are successfully grown axially in these nanowires. GaAsSb can also be integrated as a shell around the GaAs core. Finally, two GaAsSb segments are grown inside a GaAsnanowire and passivated using an AlₓGa₁ˍₓAs shell. It is found that no stacking faults or twin planes occur in the GaAsSb segments.Part of this work was funded by the Swedish Foundation for Strategic Research SSF, the Swedish Research Council VR, and the Knut and Alice Wallenberg Foundation

Noise emission corrections at intersections based on microscopic traffic simulation

One of the goals of the European IMAGINE project, is to formulate strategies to improve traffic modelling for application in noise mapping. It is well known that the specific deceleration and acceleration dynamics of traffic at junctions can influence local noise emission. However, macroscopic traffic models do not always model intersections, and if they do, only the influence of intersections on travel time is incorporated. In these cases, it would be useful to know what increase or decrease in noise production can be expected at or near intersections. A correction factor for road crossings has been suggested in several national noise emission standards. The question is open whether such a correction factor should be included in future harmonized methods. In this paper, a case study is presented, consisting of a large set of microscopic traffic simulations and associated noise emission calculations, which provides some insight into the specific dynamics of the noise emission near different types of intersections. A spatial approach is used, in which inbound and outbound lanes are divided into deceleration, queuing and acceleration zones. Results from regression analysis on the numerical simulations indicate that meaningful relations between noise corrections and traffic flow parameters such as traffic intensity and composition can be deduced

Effects of pH on Growth of Salvinia molesta Mitchell

Growth of giant salvinia ( Salvinia molesta Mitchell) under different pH regimes was examined at the Lewisville Aquatic Ecosystem Research Facility (LAERF) in Lewisville, Texas.(PDF has 5 pages.

Spatial low-discrepancy sequences, spherical cone discrepancy, and applications in financial modeling

In this paper we introduce a reproducing kernel Hilbert space defined on $\mathbb{R}^{d+1}$ as the tensor product of a reproducing kernel defined on the unit sphere $\mathbb{S}^{d}$ in $\mathbb{R}^{d+1}$ and a reproducing kernel defined on $[0,\infty)$. We extend Stolarsky's invariance principle to this case and prove upper and lower bounds for numerical integration in the corresponding reproducing kernel Hilbert space. The idea of separating the direction from the distance from the origin can also be applied to the construction of quadrature methods. An extension of the area-preserving Lambert transform is used to generate points on $\mathbb{S}^{d-1}$ via lifting Sobol' points in $[0,1)^{d}$ to the sphere. The $d$-th component of each Sobol' point, suitably transformed, provides the distance information so that the resulting point set is normally distributed in $\mathbb{R}^{d}$. Numerical tests provide evidence of the usefulness of constructing Quasi-Monte Carlo type methods for integration in such spaces. We also test this method on examples from financial applications (option pricing problems) and compare the results with traditional methods for numerical integration in $\mathbb{R}^{d}$.Comment: 37 pages, 6 table

Distribution of human waste samples in relation to sizing waste processing in space

Human waste processing for closed ecological life support systems (CELSS) in space requires that there be an accurate knowledge of the quantity of wastes produced. Because initial CELSS will be handling relatively few individuals, it is important to know the variation that exists in the production of wastes rather than relying upon mean values that could result in undersizing equipment for a specific crew. On the other hand, because of the costs of orbiting equipment, it is important to design the equipment with a minimum of excess capacity because of the weight that extra capacity represents. A considerable quantity of information that had been independently gathered on waste production was examined in order to obtain estimates of equipment sizing requirements for handling waste loads from crews of 2 to 20 individuals. The recommended design for a crew of 8 should hold 34.5 liters per day (4315 ml/person/day) for urine and stool water and a little more than 1.25 kg per day (154 g/person/day) of human waste solids and sanitary supplies

Linking theory and practice in using action-oriented methods

We felt that there is a great opportunity for PM researchers to use dialectical approaches such as action research, action learning and action science to link theory and practice. The aim of this chapter to provide doctoral students a practical way to use action-oriented methods – action research, action learning and action science – to carry out research in and about projects while making a theoretical contribution to the field. After briefly explaining each of these methods the chapter discusses ways in which these methods can be combined to provide synergy. The chapter discusses some common data collection strategies used with these methods, also pointing out that other methods of data collection are welcome if the research project requires such data. Action research is often criticised for not being scientific and therefore a discussion on how it can be made rigorous and valid at both data collection and data analysis stages is discussed. Action researchers often do not write up their research using the conventions used in conventional quantitative and qualitative research theses or dissertations. A section is therefore devoted to discussing how to write up action research in novel ways. The chapter includes several reflective exercises to guide the reader (student or researcher) as well as some tips for supervisors of action research projects. At the end of this chapter, the reader can: • understand the basics of action-oriented methods and how they can be used in a research project; • justify adequately why action-oriented methods are applicable to your research project; • establish a model/process to carry out your research applying action-oriented methods