Solving Steiner Tree Problems in Graphs with Lagrangian Relaxation

This paper presents an algorithm to obtain near optimal solutions for the Steiner tree problem in graphs. It is based on a Lagrangian relaxation of a multi-commodity flow formulation of the problem. An extension of the subgradient algorithm, the volume algorithm, has been used to obtain lower bounds and to estimate primal solutions. It was possible to solve several difficult instances from the literature to proven optimality without branching. Computational results are reported for problems drawn from the SteinLib library.     

Operations research from the viewpoint of general systems theory

This paper examines the operations research process from the viewpoint of General Systems Theory. The components of the OR process and the relations between them are critically examined. The five components are: (1) the “reality” of the problem situation, (2) the conceptual model of the problem situation, (3) the scientific model of the conceptual model, (4) the solution to the scientific model, and (5) the implementation of the solution. The paper argues that we have sub-optimized both our knowledge (study) and our application of the OR process. That is, there have been extremely few studies and applications of OR which have concerned themselves with OR from a whole systems point of view. The paper argues that without a whole systems perspective OR can neither be understood nor effectively applied.     

Ethnic pride, biculturalism, and drug use norms of urban American Indian adolescents

This study examines how strength of ethnic identity, multiethnic identity, and other indicators of biculturalism relate to the drug use norms of urban American Indian middle school students. The article distinguishes categories of norms that may affect drug use. Regression analysis of self-reports by 434 American Indian seventh graders attending middle schools in a large southwestern U.S. city indicated that students who had a more intense sense of ethnic pride adhered more strongly to certain antidrug norms than those who did not. Whereas American Indian students with better grades in school held consistently stronger antidrug norms, there were few differences by gender, socioeconomic status, or age. These results have implications in social work practice for better understanding and strengthening the protective aspects of American Indian culture in drug prevention efforts.     

Not ‘women's burden’: how washing clothes and grinding corn became issues of social justice and development

Women's heavy and unequal responsibilities for care, long considered ordinary or insignificant by development workers as well as the wider public, are being reframed as issues of social justice through new methodologies for communities to analyse care work and advocate for change. Oxfam and local partners in the Philippines, Honduras, and Bangladesh are piloting two approaches. The first, Rapid Care-Analysis, uses focus groups to assess the local provision of care, identify problems, and propose solutions, reframing care as a compelling issue for both women and men. The second, the Household Care Survey, can be used to gather evidence to persuade governments and aid donors to invest in infrastructure to lessen the practical load of care work. This article shares the experience so far of evolving and piloting these innovative methods.     

The Poisson–exponential distribution: a Bayesian approach

In this paper, we proposed a new two-parameter lifetime distribution with increasing failure rate. The new distribution arises on a latent complementary risk scenario. The properties of the proposed distribution are discussed, including a formal proof of its density function and an explicit algebraic formulae for its quantiles and survival and hazard functions. Also, we have discussed inference aspects of the model proposed via Bayesian inference by using Markov chain Monte Carlo simulation. A simulation study investigates the frequentist properties of the proposed estimators obtained under the assumptions of non-informative priors. Further, some discussions on models selection criteria are given. The developed methodology is illustrated on a real data set.     

Bayesian Estimation of the Log–linear Exponential Regression Model with Censorship and Collinearity

In this work, a simulation study is conducted to evaluate the performance of Bayesian estimators for the log–linear exponential regression model under different levels of censoring and degrees of collinearity for two covariates. The diffuse normal, independent Student-t and multivariate Student-t distributions are considered as prior distributions and to draw from the posterior distributions, the Metropolis algorithm is implemented. Also, the results are compared with the maximum likelihood estimators in terms of the mean squared error, coverages and length of the credibility and confidence intervals.     

The Effect of Rainfall on Migration from Mexico to the United States

There has been very little work on the impact of rainfall on migration from Mexico or even elsewhere. We use satellite data from NASA to examine the effect of the lagged level of rainfall relative to an area's historical average, on migration from small Mexican communities to the United States. Controlling for the level of education, proportion married, and historic migration levels, we find higher levels of rainfall significantly reduce Mexican migration to the United States and a 20 percentage point higher‐than‐normal level of rainfall leads to a predicted 10.3 percent decrease in migration.     

Re-Placing Objects

This essay contemplates the importance of things and places for psychoanalysis. In contrast to the more common psychoanalytic category of space, it celebrates the density and specificity of place. In contrast to relational and internal objects, it examines material objects, with a special emphasis on the materiality of the transitional object. Materiality, it proposes, is a reservoir of innovation.     

A new destructive Poisson odd log-logistic generalized half-normal cure rate model

We propose a new cure rate survival model by assuming that the initial number of competing causes of the event of interest follows a Poisson distribution and the time to event has the odd log-logistic generalized half-normal distribution. This survival model describes a realistic interpretation for the biological mechanism of the event of interest. We estimate the model parameters using maximum likelihood. For different sample sizes, various simulation scenarios are performed. We propose the diagnostics and residual analysis to verify the model assumptions. The potentiality of the new cure rate model is illustrated by means of a real data.