Lower bounds on bayes factors for a linear regression model

This paper develops a Bayesian analysis of testing linear parameter restictions in a normal regression model. Instead of searching for a suitable "objective" prior for such a test, several interesting classes of informative priors are postulated, and the lower bounds on the Bayes factors are derived.     

Correction to: contrasting effects of urbanization on arboreal and ground-dwelling land snails: role of trophic interactions and habitat fragmentation

Urban Ecosystems - The original version of the article unfortunately contained mistakes in the legends of Fig. 3. The legends (1) Blue square: Euhadra brandtii sapporo, ground is changed...     

Lattice population dynamics for plants with dispersing seeds and Vegetative propagation

The population dynamics of plants in a lattice structured habitat are studied theoretically. Plants are assumed to propagate both by producing seeds that scatter over the population and by vegetative reproduction by extending runners, rhizomes, or roots, to neighboring vacant sites. In addtion, the seed production rate may be dependent on the local density in the neighborhood, indicating beneficial or harmful crowding effects. Two sets of population dynamical equation(s) are derived: one based onmean-field approximation and the other based onpair approximation (tracing both global and local densities simultaneously). We examine the accuracy of these approximate dynamics by comparing them with direct computer simulation of the stochastic lattice model. Pair approximation is much more accurate than mean-field approximation. Mean-field approximation overestimates the parameter range for persistence if crowding effects on seed production are harmful or weakly beneficial, but underestimates it if crowding effects are highly beneficial. Dynamics may show bistability (both population persistence and extinction) if the effect of crowding is strongly beneficial. If there is a linear trade-off between seed production and vegetative reproduction, the equilibrium abundance of the population may be maximised by a mixture of seed production and vegetative reproduction, rather than by pure seed production or by pure vegetative reproduction. This result is correctly predicted by pair approximation but not by mean-field approximation.     

The Opportunity Cost of Pro-Environmental Activities: Spending Time to Promote the Environment

This study examines how working hours and the opportunity cost of time affect an individual’s decision to participate in a time-consuming pro-environmental activity—namely, the purchase of refillable products—while using data from the Japanese General Social Survey 2002. By purchasing refillable products, an individual can reduce the amount of waste that needs to be disposed; however, she or he must spend time refilling bottles (i.e., a pro-environmental activity). Our empirical results demonstrate that individuals who work long hours and those with high wage rates tend to purchase nonrefillable products. Therefore, both time constraints and the opportunity cost of time are important factors in the decision to undertake pro-environmental activities.     

Evolution of litter size

Summary Theories on the evolution of litter size among organisms were reexamined. The competition theories, including that based on ther−K-selection hypothesis, could not explain well why low-fecundity strategies have often evolved in stressful environments such as mountain streams, deep sea and the antarctic, where interspecies competition is considered to be lax. The theory, based on It?'s (1980) concept of theprocurability of food by the young, was considered to have greater generality because it could explain not only the above-mentioned cases but also those where small litter size is observed in habitats with high species diversity (where interspecific competition may be keen), such as tropical rain forest. Examination of the process of selection of high-fecundity and low-fecundity genotypes also suggested that the procurability of food by the young can best explain the evolution of low-fecundity. The concept of density-induced dispersal and a distinction between density-dependent and density-independent predation pressures should be incorporated into our discussions on the evolution of reproductive rates. This work was supported in part by Grant-in-Aid No. 439017 from the Ministry of Education, Science and Culture.     

Inventory Positioning/Partitioning for Backorders Optimization for a Class of Multi-Echelon Inventory Problems*

Inventory management has undergone significant philosophical changes in recent decades such as the advent of the zero inventory concept. However, as attractive as the concept of minimal inventories may be, it is often unrealistic in application. Attention to basic features of inventory control systems such as order quantities, base stock levels, and reorder points remain crucial to ensure customer service at minimal cost. A nonlinear optimization model for determining base stock levels in a multi-echelon inventory network is presented. Lagrangian relaxation results in (1) newsboy-style relations that provide the optimal solutions, and (2) instantaneous shadow prices for the budget constraint. Sensitivity analysis of this model will facilitate making decisions concerning the desired investment in inventory for the entire system. This model may be solved on standard nonlinear programming software and is generalizable to problems in both production and distribution settings.