Fuzzy K-means clustering models for triangular fuzzy time trajectories

We focus our attention on the classification of fuzzy time trajectories with triangular membership function, described by a given set of individuals. To this purpose, we adopt a fullyinformational approach, explicitly recognizing the informational nature shared by the ingredients of the classification procedure: the observed data (Empirical Information) and the classification model (Theoretical Information). In particular, by supposing that the informational paradigm has a fuzzy nature, we suggest three fuzzy clustering models allowing the classification of the triangular fuzzy time trajectories, based on the analysis of the cross sectional and/or longitudinal characteristics of their components (centers and spreads). Two applicative examples are illustrated.     

Administrative rationality and coping strategies in shift work

Shift work (SW) can affect worker health and productivity. Working at night, workers often accumulate fatigue and are less productive. In Brazil, laws have been drafted aiming to reduce night work and rotating shift hours. In order to slash costs, companies have been looking for new arrangements to improve productivity under these conditions. The purpose of this study was to examine management changes and their outcomes in a large glass factory located in an industrial region of Brazil. The results show that the management, seeking equal productivity among shifts, focused its efforts mainly on distributing employee expertise. The arrangement resulted in 12 different groups that combine to serve three fixed shifts. A same shift can be served by more than one group, and the members of a same group share days off on different days. There was no statistically significant productivity difference among the three shifts. The on-site examination showed that part of the production was held by the workers and transferred to the next shift in order for them to be able to meet the management's performance rate requirements. The finding shows how a Brazilian cultural trait (resistance without conflict) is used to drive coping in SW.     

COWORDS: a probabilistic model for multiple word clouds

Word clouds constitute one of the most popular statistical tools for the visual analysis of text documents because they provide users with a quick and intuitive understanding of the content. Despite their popularity for visualizing single documents, word clouds are not appropriate to compare different text documents. Independently generating word clouds for each document leads to configurations where the same word is typically located in widely different positions. This makes it very difficult to compare two or more word clouds. This paper introduces COWORDS, a new stochastic algorithm to create multiple word clouds, including one for each document. The shared words in multiple documents are placed in the same position in all clouds. Similar documents produce similar and compact clouds, making it easier to simultaneously compare and interpret several word clouds. The algorithm is based on a probability distribution in which the most probable configurations are those with a desirable visual aspect, such as a low value for the total distance between the words in all clouds. The algorithm output is a set of word clouds that are randomly selected from this probability distribution. The selection procedure uses a Markov chain Monte Carlo simulation method. We present several examples that illustrate the performance and visual results that can be obtained by our algorithm.     

Very Preterm and Full‐Term Infants’ Response to Socio‐Emotional Stress: The Role of Postnatal Maternal Bonding

Very preterm (VPT) infants are at risk for altered socio‐emotional stress regulation, even in the absence of perinatal complications. Moreover, becoming a mother of a VPT infant is a traumatic event, which might affect the establishment of a bonding relationship toward the infant during the postnatal period. The main aim of the present study was to assess the association between maternal postnatal bonding and socio‐emotional stress response in 3‐month‐old VPT infants, compared to full‐term (FT) controls. Thirty‐three VPT and 28 FT infant‐mother dyads underwent the maternal Face‐to‐Face Still‐Face (FFSF) procedure to assess socio‐emotional stress regulation. Maternal postnatal bonding was measured through the Maternal Post‐Natal Attachment Scale (MPAS), which includes three scales: Quality of attachment, Absence of hostility, and Pleasure in interaction. The VPT infants exhibited less self‐directed and other‐directed regulatory behaviors during the Still‐Face episode. Mothers of VPT infants reported lower Quality of attachment compared to FT counterparts. Importantly, higher levels of Quality of attachment were associated with more other‐directed behaviors during the Still‐Face episode in FT dyads, whereas this was not observed in VPT dyads. In conclusion, VPT infants might be exposed to a double‐risk condition for socio‐emotional development, encompassing both difficulties in stress response and the exposure to a less‐than‐optimal maternal bonding.     

Knox meets Cox: Adapting epidemiological space-time statistics to demographic studies

Many important questions and theories in demography focus on changes over time, and on how those changes differ over geographic and social space. Space-time analysis has always been important in studying fertility transitions, for example. However, demographers have seldom used formal statistical methods to describe and analyze time series of maps. One formal method, used widely in epidemiology, criminology, and public health, is Knox’s space-time interaction test. In this article, we discuss the potential of the Knox test in demographic research and note some possible pitfalls. We demonstrate how to use familiar proportional hazards models to adapt the Knox test for demographic applications. These adaptations allow for nonrepeatable events and for the incorporation of structural variables that change in space and time. We apply the modified test to data on the onset of fertility decline in Brazil over 1960–2000 and show how the modified method can produce maps indicating where and when diffusion effects seem strongest, net of covariate effects.     

Determinants of voluntary executive stock option disclosure in Brazil

This study investigates whether the governance attributes of Brazilian companies are associated with voluntary executive stock option (ESO) disclosure. Results show that Brazilian companies voluntarily disclose very little about their ESO plans, and that board size, presence of a compensation committee, and auditing by a Big 4 firm are significantly related to the degree of voluntary ESO disclosure. We also show that family-controlled companies in Brazil are associated with low voluntary ESO disclosure. Results are robust to a number of specification tests, dependent and explanatory variable measurements, and sample composition. This study has professional and regulatory implications for Brazil and other emerging capital markets. The results underscore the need for stricter rules for executive compensation reporting in Brazil, and they invite policy makers and regulators in emerging markets to consider the effects of company-level governance factors on disclosure incentives.