We present a syntax-based statistical translation model. Our model transforms a source-language parse tree into a target-language string by applying stochastic operations at each node. These operations capture linguistic differences such as word order and case marking. Model parameters are estimated in polynomial time using an EM algorithm. The model produces word alignments that are better tha...

Contrary to popular belief, we show that the optimal parameters for IBM Model 1 are not unique. We demonstrate that, for a large class of words, IBM Model 1 is indifferent among a continuum of ways to allocate probability mass to their translations. We study the magnitude of the variance in optimal model parameters using a linear programming approach as well as multiple random trials, and demon...

An individual-based model (IBM) was developed to examine the effects of intraspecific competition and spatial structuring of food on life history traits of grasshoppers inhabiting temperate-zone grasslands. Each individual carried real-valued genes which determined size of offspring and size at maturity, and which were passed on to its offspring. Size at maturity was a plastic trait, depending ...

Based on a simple overlapping generations model with endogenous fertility, we show that the effectiveness of childcare support and social security reform depends much on the openness of the economy, altruism, and initial fertility. For example, introducing a child allowance, which is often expected to mitigate demographic pressures, might be ineffective in a closed economy. Downsizing a social ...

D. F. Ferguson M. L. Stockton IBM products increasingly implement a service-oriented architecture (SOA), in which programmers build services, use services, and develop solutions that aggregate services. IBM Software Group middleware products and tools support the development and deployment of SOA solutions, and increasingly make functional interfaces between components and products visible thro...

Soil fertility is a comprehensive reflection of soil properties, and its variation has been a central issue in the field of soil science. Most of current research on Variation of the soil fertility are most for a single time and place, and using expertise, simple mathematical model approach that can not effectively simulate the temporal and spatial variation of soil nutrients law. Therefore, th...

Fisheries models have tradi­ tionally focused on patterns of growth, fecundity, and survival of fish. However, reproductive rates are the outcome of a variety of interconnected factors such as life-history strategies, mating patterns, population sex ratio, social interactions, and individual fecundity and fertility. Behaviorally appropriate models are necessary to understand stock dynamics and ...

How great an effect does self-generated spatial structure have on logistic population growth? Results are described from an individual based model (IBM) with spatially localised dispersal and competition, and from a deterministic approximation to the IBM describing the dynamics of the first and second spatial moments. The dynamical system incorporates a novel closure that gives a close approxim...

We examine the effects of population aging due to declining fertility and rising elderly life expectancy on consumption possibilities in the presence of intergenerational transfers. Our analysis is based on a highly tractable continuous-time overlapping generations model in which the population is divided into three groups (youth dependents, workers, and elderly dependents) and lifecourse trans...