Use of jump process to model mobility in massive multiplayer on-line games

This paper proposes a methodology to model the mobility of characters in Massively Multiplayer On-line (MMO) Games. We propose to model the mobility of characters in the map of an MMO game as a jump process using two approaches to model the times spent in the states of the process: parametric and non-parametric. Furthermore, a simulator for the mobility is presented. We analyze geographic position data of the characters in the map of the game World of Warcraft and compare the observed and simulated data. The proposed methodology and the simulator can be used to optimize computing load allocation of servers, which is extremely important for game performance, service quality and cost.     

Social Justice and the Research Curriculum

This article presents a study of justice as a concept and value in the research curriculum. Twelve researchers and research instructors were asked to define justice, discuss how it informed their work, and indicate whether a justice focus required special topics, theories, or methods. The conceptual literature on justice, research textbooks, and syllabi were reviewed. Most respondents defined justice broadly, and did not perceive certain topics, theories, or methods as more relevant to justice than others. Further, justice was not systematically discussed in classes, syllabi, and textbooks. Questions for future investigation and implications for social work educators are discussed.     

Comparison to control in logistic regression

We are interested in comparing logistic regressions for several test treatments or populations with a logistic regression for a standard treatment or population. The research was motivated by some real life problems, which are discussed as data examples. We propose a step-down likelihood ratio method for declaring differences between the test treatments or populations and the standard treatment or population. Competitors based on the sequentially rejective Bonferroni Wald statistic, sequentially rejective exact Wald statistic and Reiers?l's statistic are also discussed. It is shown that the proposed method asymptotically controls the probability of type I error. A Monte Carlo simulation shows that the proposed method performs well for relatively small sample sizes, outperforming its competitors.     

Inference on high-dimensional implicit dynamic models using a guided intermediate resampling filter

Statistics and Computing - We propose a method for inference on moderately high-dimensional, nonlinear, non-Gaussian, partially observed Markov process models for which the transition density is...     

The effect of earthworms on roadway-derived Zn deposited as a surface layer in storm water retention basin soils

Increased urban development, including an increase in impervious surfaces has the potential to alter the biogeochemistry of surface systems due to storm water runoff contaminated with potentially toxic trace metals (e.g. Zn, Cu and Pb). A major source for urban metals is dust that accumulates on roadways. This roadway dust is derived from vehicle wear sources and tends to be enriched in trace metals such as Pb, Zn, Cu, Cd, Ni and Cr. This continuous source is then being transported via storm water runoff to receiving systems, such as storm water retention systems, which become important focusing environments for trace metal deposition. The fate of these roadway derived metals and their bioavailability once deposited in these urban ecosystems is not well understood. In this investigation we tested the hypothesis that the distribution and form of surface deposited roadway-derived Zn is a function of earthworm processes and is species dependent. The results of this investigation indicate that roadway dust derived Zn deposited as a surface layer on urban soils is readily removed from the surface in less than 30 days whether earthworms are present or not. However, after 90 days, the presence of earthworms and the life habit of the earthworm species present was found to have a significant impact on the physical and chemical cycling of roadway derived trace metals in storm water retention basin soils.     

A modified approximate method for analysis of degradation data

Estimation of the lifetime distribution of industrial components and systems yields very important information for manufacturers and consumers. However, obtaining reliability data is time consuming and costly. In this context, degradation tests are a useful alternative approach to lifetime and accelerated life tests in reliability studies. The approximate method is one of the most used techniques for degradation data analysis. It is very simple to understand and easy to implement numerically in any statistical software package. This paper uses time series techniques in order to propose a modified approximate method (MAM). The MAM improves the standard one in two aspects: (1) it uses previous observations in the degradation path as a Markov process for future prediction and (2) it is not necessary to specify a parametric form for the degradation path. Characteristics of interest such as mean or median time to failure and percentiles, among others, are obtained by using the modified method. A simulation study is performed in order to show the improved properties of the modified method over the standard one. Both methods are also used to estimate the failure time distribution of the fatigue-crack-growth data set.     

Exercise and executive functioning in older women

Research suggests that exercise can slow the rate of decline in cognitive functioning in older adults. The effects of aerobic and resistance exercise on executive functioning was examined in 68 women over 50 years of age. Participants completed the Tower of London and Benton Controlled Oral Word Association tests. Findings indicated that individuals participating in both aerobic and resistance exercises performed significantly better than individuals not participating in exercise. Individuals who were participating in both aerobic and resistance exercises did not perform disproportionately better. Thus the form of exercise appears to be less important than engaging in some form of exercise.     

Narratives about Work and Family Life among Portuguese Academics

A qualitative study conducted with Portuguese academics of both genders was devised to better understand the interface between work and family life. The academics seemed to position themselves along two different narratives. The first pointed to work and family as complementary, while the second described the subordination of one dimension to the other. The family life cycle, particularly parenthood experiences, illustrates the different narratives. Gender differences were more visible in the case of academics who were parents of young children, with women presenting a diverse set of micro‐narratives on motherhood. The findings also showed the need to design less standardized career models.