Migration decisions under ambiguity: Migration distance effects revisited

There is ample evidence that distance has a strong negative effect on migration. Despite its significance in migration decisions, scholars rarely explore the migration distance effect deeper than the first level of interpretation derived from the simple neoclassical theory of migration. This study revisits the migration distance effect in the spirit of Knightian distinction between risk and uncertainty. To this end, this study attempts to construct estimates of the risk premium migrants are willing to pay to avoid the risk associated with migration distance. The results show that the magnitude of the distance effect is not rationalized by risk aversion in the Arrow–Pratt sense (Arrow, 1965, The theory of risk aversion, Yrjo Jahnssonin Saatio, Helsinki, Finland, 90; Pratt, 1964, Econometrica, 32, 122). In particular, the risk premium demanded by distant rural residents is unjustifiably higher compared with that of those living closer to urban areas in their migration decisions. The results suggest that the migration distance effect is analogous to the equity home bias puzzle and the Ellsberg paradox in that the assumption of subjective expected utility can lead to seemingly irrational human behaviors. Some of the findings in this study shed light on the role of subjective aspects such as perception, confidence, and pessimism in migration decisions, which have been neglected in the literature.     

Impact assessment of reservoir desiltation measures for downstream riverbed migration in climate change: A case study in northern Taiwan

Typhoon Aere in 2004 induced severe sedimentation and loss of storage capacity of the Shihmen Reservoir in northern Taiwan. The resulting dramatic increase in the turbidity of the water seriously affected the water supply. To effectively maintain the stability of the water supply and maintain the reservoir’s storage capacity, the government of Taiwan began to plan and construct a series of improvement measures, such as a sediment flushing tunnel, the JhongJhuang Bank-Side Reservoir, and the Amuping Desilting Tunnel. However, previous studies only focused on the impact of the sediment flushing tunnel and the Amuping Desilting Tunnel on the downstream riverbed, and did not consider the possibility of increasing sediment discharge after the completion of the JhongJhuang Bank-Side Reservoir. In addition, climate change will cause the intensity of extreme rainfall to increase enormously in the future. That rainfall and extra sediment flushing will challenge the existing flood prevention facilities. Therefore, this study considered that the JhongJhuang Bank-Side Reservoir will increase sediment discharge of the Shihmen Reservoir, and used dynamical downscaling extreme typhoon data of climate change under the RCP 8.5 scenario to explore the flood prevention and riverbed migration of the main channels of the Dahan and Tamsui Rivers in the future. We used the rainfall–runoff model of Hydrologic Modeling System to simulate rainfall and runoff, and used the hydraulic and sediment transport model of CCHE1D to holistically simulate flood events and consequent river scouring and deposition behaviors. Our results showed that the projected peak discharge during the late 21st century (2075 to 2099) will be at least 50% higher than that during the baseline (1979 to 2003) period. In terms of flood prevention, the potential of overbank flooding will increase in the downstream area, and the trend of long-term change in the riverbed will be dominated by degradation (-0.489 ± 0.743 m) in the future. The improvement measures will have a limited impact on riverbed migration (0.011 ± 0.094 m) in the Dahan and Tamsui Rivers. After the operation of the JhongJhuang Bank-Side Reservoir, the Shihmen Reservoir is expected to increase the sediment discharge ratio by 70% during floods, and it will not cause excessive water turbidity that may affect downstream water supply.     

高坝洲电站碾压混凝土纵向围堰拆除爆破设计与实践

介绍了高坝洲电站碾压混凝土下游纵向围堰现场爆破试验成果,在分析爆破试验效果的基础上进行碾压混凝土围堰拆除爆破设计,详细分析了拆除爆破实施效果及主要影响因素.     

Demographic and Economic Pressure on Emigration out of Africa*

Two of the main forces driving European emigration in the late nineteenth century were real wage gaps between sending and receiving regions and demographic booms in the low‐wage sending regions. Our new estimates of net migration for the countries of sub‐Saharan Africa show that exactly the same forces driving African across‐border migration are at work today. The results suggest that rapid growth in the cohort of potential young emigrants, population pressure on the resource base, and slow economic growth are likely to intensify the pressure for migration out of Africa and into high‐wage OECD countries over the next two decades.     

节理岩体的代表单元集合体模型及弹性参数预测

本文明确提出了节理岩体“代表单元集合体”的概念和模型，通过对节理岩体的“代表单元集合体”进行数值模拟，研究了节理岩体的“代表单元集合体”的变形特性，建立了节理岩体的弹性模型，提出了预测节理岩体宏观等效弹性参数的计算机模拟方法，并将其应用于岩体工程稳定性分析中。     

铜街子工程坝基预裂控制爆破

本文介绍了在复杂地质条件下,通过反复试验、采用预裂爆破技术在玄武岩坝基进行各种坡面角度的全方位、大面积的生产性实践,并对预裂控制爆破提出了一些意见和具体施工方法.     

Rural Population Growth, 1950–1990: The Roles of Human Capital, Industry Structure, and Government Policy

Human capital raises rural incomes, but this effect is swamped by higher returns to human capital in urban markets. This leads to "brain drain" from rural areas. Populations grow more rapidly in rural counties that have a diversified employment base. Farm population grows faster (or declines more slowly) in counties with relatively high farm income, and nonfarm populations grow faster in counties with relatively high nonfarm income. However, higher farm incomes lead to slower nonfarm population growth and vice versa. Rural county government services financed by local taxes or debt have neutral or negative effects on population growth.     

Model-based control charts in phase 1 statistical process control

In this paper, a general method of constructing control charts for preliminary analysis of individual observations is presented, which is based on recursive score residuals. A simulation study shows that certain implementations of these charts are highly effective in detecting assignable causes.     

Public and Private Education in an Integrated Europe: Studying to Migrate and Teaching to Stay?

This paper investigates public and private choices between internationally applicable and country‐specific education when graduates are mobile. Human capital depends on innate skills and study effort with either type of education. It is shown that national governments provide too few students with internationally applicable education, and too many with country‐specific education. This effect is mitigated, but not entirely eliminated, by the introduction of a graduate tax, according to which graduates are required to pay part of their taxes to the country where they received their education, regardless of residence. However, private educational choices are socially optimal with suitably differentiated tuition fees.     

Analytical investigations of transitional operating modes of the second circuit of units at NPP with water-moderated reactors with consideration of control systems

A mathematical model for analysis of process parameters of equipment in the second circuit of nuclear power plants is presented, and the structure of the program and principles used for analysis of the equipment are described. A mathematical model for analysis of the deaerator and steam generator is described in detail. A computational analysis of several transitional modes, which is made possible on the basis of the mathematical model in question, is also presented in this paper, and a comparison is made with test data. __________ Translated from élektricheskie Stantsii, No. 3, March 2007, pp. 16–22.