Intransitivity,the spatial interaction model,and U.S. migration streams

"The flows predicted by a large class of spatial interaction models are transitive, yet US migration tables have been shown to contain large numbers of intransitivities. This paper investigates a number of possible conditions under which flows regulated by the spatial interaction model might be observed to be intransitive. A singly constrained gravity model is calibrated for a number of flow tables, and distorted by sampling error, by aggregation over strata, and by an independently distributed error term.... The results of the calibration of the spatial interaction using US interstate migration flows, 1935-1970, are given and compared with others previously published."     

Hierarchically organized migration fields: The application of higher order factor analysis to population migration tables

The structure of human geographical systems is often of a hierarchical nature. Population migration systems can usefully be conceptualized as a series of hierarchically related levels of migration fields: the fields at one level nesting within the fields at the next higher level. Such migration fields and the relationships between different levels can be extracted from large population migration origin-destination matrices with the aid of higher order factor analysis.     

The importance of place of birth in migration and population redistribution analysis

"In this paper, U.S. Census data is used to examine further the importance of place of birth on migration streams and to trace the impacts of such 'native dependence' on age patterns of migration, multiregional life expectancies, and spatial population projections."     

Design and analysis of Coanda effect nozzle with two independent streams

ABSTRACT

This project aims at presenting a method of making use of the ACHEON Coanda effect based on velocity. The main component of the model is HOMER nozzle. It consists of two inlets, in which streams of different velocity can be made to flow. It is made possible by using the PEACE concept. This project is an analysis work of six different 2D models varying in their geometry. Deflection at various angles is produced. From the base design, five designs are made by varying their domain and they are analysed at different conditions. Higher deflection angle is produced in either direction. The graphs are plotted for pressure and also in terms of velocity. The concept of thrust vectoring is used here. This project helps in creating more flexibility of thrust vectoring nozzle. It overcomes the limitations of traditional systems related to jet deflection exhausts.     

An economic analysis of migration in Mexico

This paper analyzes internal migration in Mexico over the 1960–1970 period. A model of the determinants of migration is specified and estimated for aggregated interstate migration flows. The results show that distance serves as a significant deterrent to migration, that higher destination earlings levels are attractive to migrants, and that regions with high unemployment rates experience lower rates of in-migration. An unanticipated finding is that regions with higher earnings levels have greater rates of out-migration.The data are disaggregated to examine separate migration relationships for each state. The results are that distance is a lesser deterrent for those migrants with more accessible alternatives, that higher earnings levels reduce the deterring effects of distance, and that regions with higher earnings levels have lower associated elasticities of migration.It is concluded that economic factors have played a crucial role in internal migration and thus in the changing occupational and geographic structure of the Mexican labor force.This research was supported by Grant Number 1-RO-1-HD08567-01 from the Population and Reproduction Grants Branch, Center for Population Research, National Institute of Child Health and Human Development, United States Department of Health, Education, and Welfare. Part of this study was completed at the Food Research Institute, Stanford University, where J. R. Ladman was a Visiting Scholar. We are grateful to Barry Edmonston and Dudley Kirk for their helpful comments on an earlier draft of the paper. Responsibility for remaining shortcomings remains ours.     

Models for the analysis of interregional migration

"Asymmetric square tables, such as those arising from interregional migration, can be analysed by separating the skew-symmetric and symmetric components. A least-squares analysis of the skew-symmetric part can indicate the degree of complexity of model that is consistent with data and this can be combined with some suitable model for the symmetric part. The joint model may then be fitted by maximum likelihood based on suitable distributional assumptions. This approach is used for an analysis of Australian interstate migration for l960-l966 and indicates a model with independent in-migration and out-migration rates proportional to a symmetric function of population sizes and interstate distance."     

A multiregional population-projection framework that incorporates both migration and residential mobility streams: application to metropolitan city-suburb redistribution

"In this paper the author introduces a population-projection framework that incorporates interregional migration and intraregional residential mobility streams to project future population sizes both across and within regions in a manner that is consistent with existing migration theory. The author presents a general matrix model of the framework, shows how its parameters can be estimated from fixed-interval census migration data, and discusses how the framework can be employed to 'update' population projections when recent, more limited data sets become available. These features of the framework are demonstrated with intrametropolitan central-city-suburb projections for selected US Standard Metropolitan Statistical Areas over the period, 1970-2020."     

日用陶瓷制品元素迁移及铜、锰迁移量风险分析

日用陶瓷制品被广泛使用,其使用安全问题和人的健康息息相关。陶瓷制品在使用时的元素迁移日益受到关注。本文概述了日用陶瓷制品中铜、锰元素来源及其迁移量检测结果,以期促进对铜、锰迁移的相关研究。     

Stream productivity analysis with dorm—III: Productivity of experimental streams

Thirty-two two-station diel dissolved oxygen surveys were made in the experimental streams of the U.S. EPA Monticello Ecological Research Station. The data were analyzed by a numerical Dissolved Oxygen Routing Model (DORM) to determine total community respiratory and photosynthetic rates. The artificial channels consisted of pools and riffles and had pH of 8.0, 6.3 and 5.4. Community photosynthetic production and respiration ranged from highs of 14.8 and 10.7gm⁻² day⁻¹ to lows of 1.5 and 2.6gm⁻² day⁻¹ between June and September 1979. P/R ratios varied from 2.1 in May to 0.6 in August. Seasonal trends were affected by pH and/or age of the channel. The channels also exhibited large diel variations in photosynthetic efficiency, where dependence of photosynthetic production upon light was nonlinear and had a strong hysteresis. This hysteresis cannot be explained by physical processes and is attributed to several biological processes.     

Approaches to modelling overdispersion in the analysis of migration

"In this paper the modelling of overdispersion in generalised Poisson and multinomial models of migration flows and rates is considered, and its importance within the wider question of substantive model specification is shown. It is argued that substantive specification and the modelling of overdispersion are closely interrelated. Simplified ways of estimating the form of overdispersion--moments methods and pseudo-likelihood--are considered wherever possible. Overdispersion is set within the broader context of correlation effects which relate to migration--correlation across different destinations, between spatially adjacent origins and destinations, and between different time periods. The data used to illustrate the modelling development [concern England and Wales and] are drawn from the Office of Population Censuses and Surveys Longitudinal Study, the decennial Census, and the National Health Service Central Register."     

基于多离子运移模型的混凝土电迁移试验数值分析研究

电迁移试验目前已经被广泛用来测试氯离子在混凝土中的扩散系数.离子在混凝土中的运移过程是个涉及离子与电场以及离子之间相互藕合作用的复杂过程,目前其具体运移过程仍不清楚.基于扩展Nernst-Plank方程和电中性条件建立多离子运移模型,通过计算预测电流和实测电流的最小误差确定离子扩散系数.该模型的主要优点是仅通过测试电流即可计算每个离子的扩散系数,且电流指标稳定,简单易测.数值分析详细给出了试样中电势分布、每个离子浓度、流量分布和其对电流的贡献情况,有助于深入理解电迁移试验中离子运移机理.     

Calibration, validation and sensitivity analysis of an ecosystem model applied to artificial streams

There is a growing interest for the use of ecological models to improve the Ecological Risk Assessment (ERA) of toxic pollutants. However, although several models have been proposed, there is little information available on their relevance (i.e., validation through comparison with original data) and on their sensitivity to the input parameters. In this study, the Aquatox Model was used to simulate biomass dynamics of various biological compartments in artificial streams designed for measuring the effects of pollutants on aquatic communities. Calibration and validation of the model were performed using data from control streams. Multi-variate sensitivity analysis was implemented to identify those parameters that exert a prominent role in the outputs of the model. The calibrated model was able to adequately describe the dynamics of most of the simulated biological compartments of a stream. Using data from other streams, it was shown that between-streams natural variability was a source of discrepancy between observed and simulated data. Sensitivity analysis showed that the model was highly sensitive to the parameters related to the temperature limitation, maximum rate of photosynthesis of producers and consumption by consumers. This strongly suggests that particular attention should be devoted to the estimation of these parameters if this model has to be used for ERA of toxicants in aquatic ecosystems.     

A note on opportunity costs and migration analysis

The hypothesis that opportunity costs associated with foregone alternatives in moving from region i to region j significantly affect the migration decision has been proposed by Levy and Wadycki in the context of a regression model of migration. Their results for Venezuela were highly successful and additional evidence reported by Wadycki with United States data for 1955–60 also substantiated the basic hypothesis.These previous attempts at including the concept of intervening opportunities into the regression model of migration employed definitions similar to Stouffer's seminal 1940 article on the subject of intervening opportunities. The present paper presents two alternative formulations for intervening opportunities and tests them with 1955–60 United States interstate migration data. In all cases we find that both the explanatory power of distance and its estimated elasticity fall substantially when we include the proxy variables for intervening opportunities. Furthermore, including these proxies increases the explanatory power of the migration model substantially. Proxy variables which employ Stouffer's 1960 reformulation of the concept of intervening opportunities prove superior in our empirical tests.     

The effect of income taxes on interstate migration: an analysis by age and race

The topic of interstate migration and the effects of taxes on migration have been extensively studied. Prior research has examined not only many possible determinants of migration but also the migrations of various populations, including the elderly, African-Americans, and the college educated. The present study will attempt to differentiate itself from this prior research by looking at the effect of income taxes on the interstate migration of both whites and African-Americans at various ages. Another distinguishing feature of the present study is that it will use data from the NLSY-Geocode, a data set not used previously for this type of study. Results of the present study are similar to the results of prior works; income taxes have an effect on migration for most races and age groups. Individuals move from states with high income taxes to states with low income taxes; these results corroborate the results obtained from the use of aggregate, state-level data. In addition, results of the present study suggest that non-economic factors, such as ties to a particular state and changes in employment status, are also important factors in an individual’s migration decision.