Measure of Asymmetry for Square Contingency Tables Having Ordered Categories

For the analysis of square contingency tables with nominal categories, Tomizawa and coworkers have considered measures that represent the degree of departure from symmetry. This paper proposes a measure that represents the degree of asymmetry for square contingency tables with ordered categories (instead of those with nominal categories). The measure proposed is expressed using the Cressie–Read power-divergence or Patil–Taillie diversity index, defined for the cumulative probabilities that an observation falls in row (column) category i or below and column (row) category j (> i ) or above. The measure depends on the order of listing the categories. It should be useful for comparing the degree of asymmetry in several tables with ordered categories. The relationship between the measure and the normal distribution is shown.     

Maternal employment and food produced at home: evidence from Japanese data

This paper examines whether mothers’ labor supply discourages home production, focusing on food preparation at home in Japanese families. Although empirical studies on home production are usually conducted using time use data, we use data collected by scanners, which cover daily goods purchased by over 10,000 households over 3 years. Based on the composition of daily food expenditures for foods consumed, we measure how many products are made using time-consuming processes at home, and examine if time-consuming home production is discouraged by mothers’ employment away from home. Controlling for unobserved heterogeneity among households using the panel structure of our scanner data, we first show that mothers’ out-of-home employment has a negative effect on home cooking. This effect is shared across economic classes, particularly when mothers work part-time, as compared with non-working mothers. Second, we show that this negative effect is more apparent in the low economic class. Households in this class show a particular decrease in time-consuming home cooking, especially when the mothers work part-time. Third, the smaller negative effect among the higher class can be explained by stronger health-consciousness and aversion to less-healthy products in this class.     

The minimum vulnerability problem on specific graph classes

Suppose that each edge e of an undirected graph G is associated with three nonnegative integers \(\mathsf{cost}(e)\), \(\mathsf{vul}(e)\) and \(\mathsf{cap}(e)\), called the cost, vulnerability and capacity of e, respectively. Then, we consider the problem of finding \(k\) paths in G between two prescribed vertices with the minimum total cost; each edge e can be shared without any cost by at most \(\mathsf{vul}(e)\) paths, and can be shared by more than \(\mathsf{vul}(e)\) paths if we pay \(\mathsf{cost}(e)\), but cannot be shared by more than \(\mathsf{cap}(e)\) paths even if we pay the cost for e. This problem generalizes the disjoint path problem, the minimum shared edges problem and the minimum edge cost flow problem for undirected graphs, and it is known to be NP-hard. In this paper, we study the problem from the viewpoint of specific graph classes, and give three results. We first show that the problem is NP-hard even for bipartite outerplanar graphs, 2-trees, graphs with pathwidth two, complete bipartite graphs, and complete graphs. We then give a pseudo-polynomial-time algorithm for bounded treewidth graphs. Finally, we give a fixed-parameter algorithm for chordal graphs when parameterized by the number \(k\) of required paths.     

Rapid Socio-Economic Transition and Material Flows in Japan

Material Flow Accounting (MFA) is a useful tool to describe interactions between the environment and human activities. An international comparison of economy-wide material flows over the past 25 years was undertaken for five industrialized countries and successfully described the similarities and dissimilarities of the studied countries. This paper shows the relevance of MFA to Japanese environmental policy issues and summarizes the characteristics of recent Japanese material flows based on the outcomes of the international comparison study. In addition, it attempts to analyze longer-term trends in demographic changes and economic growth, as well as changes in material and energy production/consumption. An attempt is also made to offer some insights on the upcoming matured and aging society.     

Biomechanical analysis of loading/unloading a ladder on a truck

Loading/unloading a ladder on vehicles are frequent tasks and involve overhead handling that may expose workers to risk factors of shoulder musculoskeletal disorders. The objective of the present study was to evaluate posture, forces required and perceived exertion when loading and unloading the ladder on a utility truck. Thirteen male overhead line workers from an electric utility in Brazil participated in this study. Shoulder elevation angle was measured using inclinometers. The required force to load/unload the ladder was measured by dynamometer. Subjective assessment of the perceived exertion was recorded to compare the exertion reported during the test conditions to the field conditions. The task of loading/unloading the ladder presented risks of shoulder musculoskeletal disorders (MSDs) to workers because it requires high levels of force (approximately 60% of the maximal force) combined with overhead posture of the shoulders (more than 100° from the neutral posture). Age and height presented to interfere in biomechanical risks presented in load/unload task. There was no significant difference between the subjective exertion during the test conditions and handling the ladder in the field. Ergonomic intervention is recommended to reduce these risks for shoulder MSDs.     

Looking represents choosing in toddlers: Exploring the equivalence between multimodal measures in forced-choice tasks

In the two-alternative forced-choice (2AFC) paradigm, manual responses such as pointing have been widely used as measures to estimate cognitive abilities. While pointing measurements can be easily collected, coded, analyzed, and interpreted, absent responses are often observed particularly when adopting these measures for toddler studies, which leads to an increase of missing data. Although looking responses such as preferential looking can be available as alternative measures in such cases, it is unknown how well looking measurements can be interpreted as equivalent to manual ones. This study aimed to answer this question by investigating how accurately pointing responses (i.e., left or right) could be predicted from concurrent preferential looking. Using pre-existing videos of toddlers aged 18–23 months engaged in an intermodal word comprehension task, we developed models predicting manual from looking responses. Results showed substantial prediction accuracy for both the Simple Majority Vote and Machine Learning-Based classifiers, which indicates that looking responses would be reasonable alternative measures of manual ones. However, the further exploratory analysis revealed that when applying the created models for data of toddlers who did not produce clear pointing responses, the estimation agreement of missing pointing between the models and the human coders slightly dropped. This indicates that looking responses without pointing were qualitatively different from those with pointing. Bridging two measurements in forced-choice tasks would help researchers avoid wasting collected data due to the absence of manual responses and interpret results from different modalities comprehensively.     

Gender Differences in the Effect of Job Characteristics on Work‐to‐Family Conflict in Japan: Application of the Job Demands‐Resources Model into Japanese Population1

This article uses the job demand‐resources (JD‐R) model to analyze the Japanese population and gender differences in work‐to‐family conflict in Japan. Using data from the International Social Survey Programme in 2015, the study addresses four main questions: (i) does the JD‐R model apply to the Japanese population? (ii) which gender is more likely to experience work‐to‐family conflict? (iii) does gender moderate the relationship between work‐related factors and work‐to‐family conflict? and (iv) do different factors predict work‐to‐family conflict between men and women? The findings show that the JD‐R model applies in part to the Japanese population, and women are more likely to experience a higher level of work‐to‐family conflict than men. There are also different factors predicting work‐to‐family conflict by gender, even though gender does not moderate the relationship between work‐related factors and work‐to‐family conflict. This article points out the peculiar Japanese social and cultural contexts that lead to gender differences in work‐to‐family conflict. It offers two solutions: (i) legal regulations to reduce working hours and the frequency of working on weekends to prevent work from intruding on family life; and (ii) changes to the work environment to make women workers more comfortable at work because of the male‐dominated workplace and Japanese culture on family gender roles in Japan.     

Furniture dimensions and postural overload for schoolchildren's head, upper back and upper limbs

The aim of this study was to evaluate how the fixed furniture dimensions match with students' anthropometry and to describe head, upper back and upper limbs postures and movements. Evaluation was performed in 48 students from a Brazilian state school. Furniture dimensions were measured with metric tape, movements and postures by inclinometers (Logger Tecknologi, ?karp, Sweden). Seat height was high for 21% and low for 36% of the students; seat length was short for 45% and long for 9% and table height was high for 53% and low for 28%. Regression analysis showed that seat/popliteal height quotient is explained by 90th percentile of upper back inclination (β=0.410) and 90th percentile of right upper arm elevation (β=-0.293). For seat/thigh length quotient the significant variables were 90th percentile of upper back velocity (β=-0.282) and 90th percentile of right upper arm elevation (β=0.410). This study showed a relationship between furniture mismatch and postural overload. When the seat height is low students increase upper back left inclination and right upper arm elevation; when the seat is short students decrease the upper back flexion velocity and increase right upper arm elevation.     

Effects of a school based exercise program on children's resistance and flexibility

The aim of this study was to evaluate the short term effects of an exercise program on abdominal and back muscles resistance and hamstring flexibility among schoolchildren. Fifty eight healthy schoolchildren were divided into two groups: experimental (15 males and 14 females; mean age 12.2(1.8 years) and control (14 males and 15 females; mean age 11.9(2.1 years). The intervention was performed twice a week, on nonconsecutive days, during six weeks. The duration of each session was fifty minutes and they were composed by warming up aerobic exercises, isotonic and isometric abdominal and back muscle exercises and hamstring stretching. The intervention effects were evaluated through Kraus-Weber test (abdominal resistance), modified Biering-S?rensen test (back muscle resistance) and sit and reach test (hamstring flexibility). Data were analyzed by mixed-design two-way ANOVA, with one between-subjects and one within-subject (time) factors. The alpha level was set at P≤0.05. The experimental group improved back muscles resistance and hamstring flexibility, but not abdominal muscles resistance. There was a significant interaction between groups and time for back muscles resistance (P=0.018) and for hamstring flexibility (P=0.017). The 6-week training period showed positive results in improving back muscles resistance and hamstring flexibility of schoolchildren.