Estimation of hazard of death in vertically transmitted HIV-1-infected children for doubly censored failure times and fixed covariates

This work estimates the effect of covariates on survival data when times of both originating and failure events are interval-censored. Proportional hazards model [16] along with log-linear models was applied on a data of 130 vertically infected HIV-1 children visiting the paediatrics clinic. The covariates considered for the analysis were antiretroviral (ARV) therapy, age at diagnosis, and change in CD4+T cell count. Change in CD4+T cell count was the difference in the last and first count in non-ARV therapy group, while in the ARV therapy group the same was considered after the start of the treatment. Our findings suggest that children on ARV therapy had significantly lower risk of death (p<0.001). We further investigated the effect of age and change in CD4+T cell count on risk of death. These covariates exhibited a possible association with risk of death by both the procedures (p<0.0001). The effect of number of years under ARV therapy with diagnosis year as a confounding factor was directly related to longevity. The results obtained by the two procedures gave reasonable estimates. We conclude that when the lengths of intervals are narrow, we can opt for parametric modeling which is less computationally intensive.     

Economic analysis of demand uncertainty and delayed information sharing in a third-party managed supply chain

Designers and retailers in consumer products industry are faced with high demand volatility and potential loss of profit from design piracy. Many retailers rely on third-party supply chain managers (SCMs) to manage global supply chains. A SCM starts raw materials procurement and production process based on expected demand and takes financial risks associated with demand uncertainty. But a retailer often delays sharing product design information with SCM forcing it to expedite production and distribution processes incurring additional financial penalties. To analyse economic impact of delayed information sharing under uncertain demand, we develop a mathematical model. Our model indicates that higher demand volatility lessens the effect of penalty associated with delayed information sharing for retailers. The model also shows that for a given demand volatility, per-unit premium increases asymptotically for a retailer compared to marginal production cost increase for SCM. Such findings are not intuitive for SCMs or retailers.     

Fuzzy preferences and Arrow-type problems in social choice

There are alternative ways of decomposing a given fuzzy weak preference relation into its antisymmetric and symmetric components. In this paper I have provided support to one among these alternative specifications. It is shown that on this specification the fuzzy analogue of the General Possibility Theorem is valid even when the transitivity restrictions on the individual and the social preference relations are relatively weak. In the special case where the individual preference relations are exact but the social preference relation is permitted to be fuzzy it is possible to distinguish between different degrees of power of the dictator. This power increases with the strength of the transitivity requirement.For comments on an earlier version of the paper I am indebted to an anonymous referee, an anonymous member of the Board of Editors and to participants in the 1991 Annual Conference of the Indian Econometric Society at North Bengal University, India. However, I retain sole responsibility for any error(s) that the paper may contain.     

Probabilistic Modeling of Flood Hazard and its Risk Assessment for Eastern Region of India

This article models flood occurrence probabilistically and its risk assessment. It incorporates atmospheric parameters to forecast rainfall in an area. This measure of precipitation, together with river and ground parameters, serve as parameters in the model to predict runoff and subsequently inundation depth of an area. The inundation depth acts as a guide for predicting flood proneness and associated hazard. The vulnerability owing to flood has been analyzed as social vulnerability $(V_S)$, vulnerability to property $(V_P)$, and vulnerability to the location in terms of awareness $(V_A)$. The associated risk has been estimated for each area. The distribution of risk values can be used to classify every area into one of the six risk zones—namely, very low risk, low risk, moderately low risk, medium risk, high risk, and very high risk. The prioritization regarding preparedness, evacuation planning, or distribution of relief items should be guided by the range on the risk scale within which the area under study falls. The flood risk assessment model framework has been tested on a real‐life case study. The flood risk indices for each of the municipalities in the area under study have been calculated. The risk indices and hence the flood risk zone under which a municipality is expected to lie would alter every day. The appropriate authorities can then plan ahead in terms of preparedness to combat the impending flood situation in the most critical and vulnerable areas.     

A decision support system for a third-party coordinator managing supply chain with demand uncertainty

Global supply chains reduce cost but increase lead times, complexities and uncertainties. Retailers in consumer products industry are getting shorter lead time to respond to market demand. To meet this challenge, many rely on third party supply chain managers (SCMs) for economically supplying required quantities of finished products quickly. However, due to shorter ‘time to market’, the SCM has to procure raw materials and start production process based on expected demand. Since SCM absorbs financial penalties associated with under- and over-estimation of demand from retailer, finding an optimal production lot size and product customisation strategy are essential to an SCM's operation. We develop a profit maximisation model and provide a close-form solution that allows an SCM to calculate optimal production lot size. The model is used to examine profitability of postponing product customisation. Finally, the effect of demand variation on SCM's profitability is explored.     

Multi-product lot scheduling with backordering and shelf-life constraints

In this paper, we revisit the economic lot scheduling problem (ELSP), where a family of products is produced on a single machine, or facility, on a continual basis. Our focus is on the determination of a feasible production schedule, including the manufacturing batch size of each item. We assume that total backordering is permissible and that each of the products has a limited post-production shelf life. Several studies examining this problem have suggested a rotational common cycle approach, where each item is produced exactly once every cycle. To ensure schedule feasibility, we resort to the technique of reducing individual production rates and allow the flexibility of producing any item more than once in every cycle, in conjunction with appropriate timing adjustments. In order to solve this more generalized model, which is NP hard, we suggest a two-stage heuristic algorithm. A numerical example demonstrates our solution approach.     

Mind Engineering for Value-Based Order

This paper tries to trace the background of the modern business paradigm. A business mind dominating the social mind has been the root cause of unethicality in an order, according to this paper. The solution could come from the liberation of the social mind through a process of mind engineering at the individual level. The paper suggests an active mechanism to inculcate values through a systematic process of mind engineering.     

Adolescent egocentrism and indoor tanning: is the relationship direct or mediated?

This paper explored how imaginary audience and personal fable ideations contribute to adolescent indoor tanning intentions directly and indirectly through the way they shape pro-tanning attitude and association with peers who use tanning beds. Five hundred and ninety-five male (n = 207) and female (n = 387) adolescents, ranging in age from 11 to 19 (M = 16.87; SD = 1.34) years completed a cross-sectional survey. Measures included imaginary audience, personal fable (three dimensions: invulnerability, uniqueness, and omnipotence), pro-tanning attitude, association with peers who use tanning beds, and tanning bed use intentions. Bootstrapping analyses documented that imaginary audience ideations are indirectly associated with indoor tanning intentions through the mediation of pro-tanning attitude and association with peers who use tanning beds. Of the personal fable ideations, only invulnerability ideation is indirectly associated with indoor tanning intentions through the mediation of association with peers who use tanning beds. Design and evaluation of interventions and campaigns to reduce indoor tanning must be targeted to adolescents varying in imaginary audience ideations differently.     

Decreasing the Recent Immigrant Earnings Gap: The Impact of Canadian Credential Attainment

It is well documented that newly arrived immigrants face a significant earnings gap relative to native‐born workers. One way for new immigrants to improve their relative labour market position upon arrival in a host country is to improve their educational credentials. According to signalling theory, a host‐country credential should provide employers with a proxy for true productivity on the job, leading to higher earnings. Using data from a Canadian longitudinal survey, we employ longitudinal growth‐curve techniques to estimate the effect of receiving a Canadian educational credential on the income growth of racial‐minority recent immigrants compared to native‐born Canadians. The results indicate that the earnings gap between recent immigrants and native‐born Canadians is significantly reduced with the attainment of a Canadian educational credential.