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81.
Lorraine Young 《Geoforum》2004,35(4):471-488
Children have generally been afforded little attention in migration research or unsatisfactorily included within family migration. Although they are an important consideration in family decisions to move, children also engage in autonomous, independent migration. Further, researchers now argue for the need to situate migration within political, economic and social conditions to obtain a full understanding of why people migrate. Through the use of children-centred research methods, and in-depth interviews with key informants, this paper considers children's journeys to the street in Uganda. By integrating an analysis of Ugandan street children's spatial origins with the familial and societal contexts of their migration decisions, this research highlights the complexity of their migration. In addition, an exploration of the impact of changing social, spatial and temporal conditions on street children's movements illustrates that their journeys are far more than just single processes. 相似文献
82.
The Tertiary Mineoka ophiolite occurs in a fault zone at the intersection of the Honshu and Izu forearcs in central Japan and displays structural evidence for three major phases of deformation: normal and oblique-slip faults and hydrothermal veins formed during the seafloor spreading evolution of the ophiolite at a ridge-transform fault intersection. These structures may represent repeated changes in differential stress and pore-fluid pressures during their formation. The second series of deformation is characterized by oblique thrust faults with Riedel shears and no significant mineral veining, and is interpreted to have resulted from transpressional dextral faulting during the obduction of the ophiolite through oblique convergence and tectonic accretion. This deformation occurred at the NW corner of a TTT-type (trench–trench–trench) triple junction in the NW Pacific rim before the middle Miocene. The third series of deformation of the ophiolite is marked by contractional and oblique shear zones, Riedel shears, and thrust faults that crosscut and offset earlier structures, and that give the Mineoka fault zone its lenticular (phacoidal) fabric at all scales. This deformation phase was associated with the establishment and the southward migration of the TTT Boso triple junction and with the kinematics of oblique subduction and forearc sliver fault development. The composite Mineoka ophiolite hence displays rocks and structures that evolved during its complex geodynamic history involving seafloor spreading, tectonic accretion, and triple junction evolution in the NW Pacific Rim. 相似文献
83.
Àngels Pascual-de-Sans 《Area》2004,36(4):348-357
The aim of this article is to explore a methodological approach relevant to the study of population mobility. The approach considers not only the whole migratory process and the sequence of connected movements, but also what happens between each of them. The study of mobility is considered inseparable from the study of passage, permanence and settlement. This paper establishes the interest in elaborating concepts that express the interaction between people and places, and how these interactions contribute to an understanding of migratory processes and of 'place histories'. In this sense, geographical identification (idiotopy) and place identification (idiotope) are put forward as useful concepts. 相似文献
84.
Maruja Milagros B. Asis Shirlena Huang Brenda S.A. Yeoh 《Singapore journal of tropical geography》2004,25(2):198-215
The migration of women engaged in transnational domestic work reveals how the uneven impacts of globalisation have intruded into the micro‐world of families and households. In this age of globalisation and migration, family membership has become multisited or transnational, with members dispersed in space. The migration of workers and the separation this entails has raised challenges to notions and ideals of “being family”. Unlike other workers on the move, the migration of domestic workers has some distinctive characteristics. It can be framed in terms of women moving between families and households; workers whose departure from their family of origin and insertion into their family of employment reconstitute the structure and content of family relationships in both material and imagined ways. Drawing on in‐depth interviews conducted in the Philippines and Singapore, we explore how migrant women and their family members define and negotiate family ideals, gender identities and family relationships, given the family's transnational configuration. Our findings provide some support to the notion that individual members in transnational families resort to “relativising” in fashioning responses to their situation. 相似文献
85.
86.
Imaging the Dead Sea Transform with scattered seismic waves 总被引:2,自引:0,他引:2
87.
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89.
The dynamic characteristics and migration of a pyramid dune 总被引:6,自引:0,他引:6
TAO WANG WEIMIN ZHANG ZHIBAO DONG JIANJUN QU ZHEFAN JING WANFU WANG JIANMIN FENG 《Sedimentology》2005,52(3):429-440
The results of wind tunnel experiments and field observations show that when the intersection angle between airflow direction and dune crest (ridge) line is > 30°, a reverse vortex is formed. Because of the convergence of sand streams from the windward and lee slopes at the crest, sand accumulates in the crestal region, causing vertical growth. Nevertheless, studies also show that the common asymmetry of the two slopes of a dune may significantly influence the evolution of arms of a pyramid dune. The migration rates of pyramid dunes are mediated by the interplay of their arms moving transversely and the vertical growth in response to the variations in wind regimes. Comparing the effects of airflow transverse to a given arm with longitudinal airflow, it is indicated that the transverse airflow is more significant in controlling the arms of pyramid dunes. The whole body of the studied pyramid dune, particularly the upper quarter section, migrated SE direction during the monitoring period. The patterns of wind erosion and deposition change alternately with seasonal variations in wind directions. The W, NE and SE sides undergo constant erosion, deposition and both erosion and deposition, respectively. The results of long-term monitoring of a pyramid dune show that southerly winds, resulting from a local circulation, markedly affect the transverse migration of the whole pyramid dune. 相似文献
90.
The effect of fluids on recrystallization behaviour is well known; however, the detailed microscale distribution of fluid in grain boundaries and the influence of fluid on grain boundary migration are still unresolved. In this study, in‐situ deformation experiments in transmitted light microscopy were undertaken, as this allows continuous and direct observation of the whole range of processes involved in fluid‐assisted grain boundary migration. A new see‐through deformation apparatus was developed to enable the control of fluid pressure. Bischofite containing small amounts of aqueous fluid was deformed at temperatures between 50 and 90 °C, over a range of fluid pressure from 0.5 to 1 MPa, and strain rates of 5 × 10?6 to 1 × 10?4 s?1. The rates of grain boundary migration were measured at different temperatures and strain rates. Detailed observations during and after the deformation illustrate the evolution of migrating fluid‐filled grain boundaries and show that the incorporation of fluids from inclusions as well as their pinch‐off is dependent on the grain boundary velocity, the thickness of the grain boundary and the size and shape of the inclusions. Direct evidence is presented for the contraction of the grain boundary fluids into isolated inclusions after equilibrium conditions are attained. 相似文献