Variability of Travel Time,Congestion, and the Cost of Travel

The variability of travel time modifies the rush hour traffic and the cost of commuting. The bottleneck model of road congestion with fixed peak-load demand is augmented of an additive random delay. When individuals have (α-β-γ) preferences, there exists a unique Nash equilibrium. The variability of travel time leads to departure rates that are spread more evenly over the rush hour than when travel times are deterministic. This equilibrium mechanism mitigates both congestion and the cost of unreliability. This implies that “single-traveler models,” which treat congestion as an exogenous phenomenon, overestimate the value of reliability for the rush hour. The application with the uniform or with the exponential distribution helps appraise the overestimation.     

Model-based Clustering of Sequential Data with an Application to Contraceptive Use Dynamics

ABSTRACT

Multi-state models describe the transitions people experience as life unfolds. The transition probabilities depend on sex, age, and attributes of the person and the context. Empirical evidence suggests that attributes that cannot be measured directly may at most be inferred from a long list of observable characteristics. A cluster-based, discrete-time multi-state model is presented, where transition probabilities are estimated simultaneously for several subpopulations of a heterogeneous population. The subpopulations are not defined a priori but are determined on the basis of similarities in behavior in order to determine which women exhibit similar characteristics with respect to method choice, method switch, discontinuation and subsequent resumption of contraceptive use. The data are from the life history calendar based on the Brazilian Demographic and Health Survey 1996. The parameters of the model are estimated using the EM algorithm. Seven subpopulations with heterogeneous transition probabilities are identified.     

An approximation algorithm for the maximum spectral subgraph problem

Journal of Combinatorial Optimization - Modifying the topology of a network to mitigate the spread of an epidemic with epidemiological constant $$\lambda $$ amounts to the NP-hard problem of...     

Getting tuned in to those who are different: The role of empathy as mediator between diversity and performance

We present a theoretical model on the processes that mediate and moderate the diversity-performance relationship. Past research on this topic—for example the categorization elaboration model (van Knippenberg et al. 2004)—has often focused on information elaboration as mediator. Complementing this cognitive perspective, we propose that group diversity can also stimulate group members to engage with each other emotionally, resulting in higher levels of empathy—an emotional state which arises from the comprehension and apprehension of fellow group members’ emotional state. Empathy, in turn, is likely to enhance performance through processes within a single group member and through processes between group members. At the core of the model lies the proposition that group- as well as individual-level empathy mediate the relationship between diversity of organizational units and the performance of individual members and groups at large (multilevel mediation). Furthermore, we specify moderating conditions for the relationship between diversity and empathy. Diversity beliefs and diversity climates are introduced as second-order moderators.     

Cognitive and organizational ergonomics in the transition of the new integrated center of control of an oil refinery: human reliability and administration of changes

The conception of a product is closely tied to its adaptation level to the users. In this view, designers are increasingly oriented to survey the needs and features of the users. This paper aims at developing a diagnosis of employees working in high-complexity activities in a petrochemical company, in light of the physical and operating changes in the Integrated Center of Control; assessing the reception sensibility to changes; assessing the cognitive pattern of the group; and making suggestions that might eliminate or minimize the difficulties in the transition process of the change, in order to reduce the adaptation period. The field of study comprised 111 production, transfer and storage operators, forming 5 groups of desktop activities. The stages of the study followed the following flow: survey of the prescribed tasks and organizational structure; Concentrated Attention test; application of the Work and Disease Risks Inventory (ITRA, Portuguese acronym); and structured psychological interview. The ITRA results pointed to a serious cognitive cost (3.83) for all five groups, this being the largest intervention focus. The items: division of task contents (3.52), social professional relationships (2.93), quality of the physical environment (2.91), physical cost (3.24), emotional cost (2.71), freedom of expression (3.77), professional fulfillment (3.41); experience and suffering (2.75), lack of recognition (2.18) and physical injuries (2.07) were considered critical. Meanwhile, social damages (1.64) and psychological injuries (1.35) are bearable. As to the Concentrated Attention test, most workers registered average level. In the individual interviews, workers showed that larger involvement in the process of physical, organizational and operational change in the desktops and on field works was required, as well as the follow up of implementations, so as to reduce the adaptation process and prevent rework (furniture, equipment, noise, form of communication with the area and training for the changes). As a result of the findings handed to the management and returned to the workers, several actions were implemented on ergonomic non-conformities found in the analysis. It is possible to prove the importance of the insertion of cognitive and organizational ergonomics in the building projects of new facilities for high-complexity activities in petrochemical plants.     

The impact of remittances from Canada's seasonal workers programme on Mexican farms

Based on a survey of participants in Canada's Seasonal Agricultural Workers Program, the authors’ three‐stage least squares estimation of a simultaneous equation model finds that migrants’ remittances enhance on‐farm investments in Mexico, which, in turn, increase farm income. Remittances are also found to have a positive influence on non‐farm income in Mexico, by giving respondents the possibility of starting a new business and diversifying their investments. These results support the hypothesis underlying the “new economics of labour migration” that remittances contribute to economic development by relaxing the credit constraint on the investment function of family farms.     

Public Administration and Organizational Theory: Prescribing the Proper Dose

Public Organization Review - Since the founding of the field of public administration, scholars have struggled with questions related to the “publicness” of public organizations...     

THE DURATION OF FIRM‐DESTINATION EXPORT RELATIONSHIPS: EVIDENCE FROM SPAIN, 1997–2006

This article uses survival analysis to investigate the duration of Spanish firms' trade relationships by destination over 1997–2006. Whereas firm export status is highly persistent, firms' destination portfolio is very dynamic: a typical firm‐country exporting relationship has a median duration of 2 years. Yet, if a firm manages to export to a country beyond 2 years the risk of exiting that market sharply falls afterwards. The results indicate that not only firm heterogeneity but also destination heterogeneity are crucial to explain survival in export markets. In particular, country (political) risk heavily shapes the effect of firm, product, and other destination characteristics on the length of trade relationships. Whereas firm productivity, comparative advantage, partners' GDP, and proximity enhance duration of trade with low‐risk countries, they have no effect on trade survival with high‐risk countries. On the contrary, information spillovers are particularly relevant to enhance survival of trade relationships with high‐risk countries. (JEL C41, F10, F14)     

An Age-Structured Model for Childhood Obesity

An age-structured model for childhood obesity at population level is fitted to empirical data in order to predict the proportion of overweighted and obese children in the 6–8 and 9–12 year old classes in the region of Valencia, Spain.