The beginning of immigrant settlement in the Helsinki metropolitan area and the role of social housing

Finland has experienced a rapid increase inimmigration since the beginning of the 1990s.Almost half of the foreign population isconcentrated in the metropolitan area of thecapital, Helsinki. The development andexplanations of their settlement patterns havenot yet been thoroughly studied. It ishypothesised in this study that social housingcan explain the settlement patterns. Indices ofdissimilarity were calculated to study thelevel and development of spatial segregation ofimmigrant groups in the Helsinki metropolitanarea in 1995–99, and the association betweenthe settlement patterns of immigrants andsocial housing was studied by regressionanalysis. Neighbourhood-level data were used.The results indicate that the Helsinkimetropolitan area has avoided extreme ethnicsegregation so far and that segregation isdecreasing. Especially immigrants from poorcountries are clearly associated with socialhousing in their settlement patterns, evenafter adjustment for socio-economic anddemographic differentiation. Also newconstruction of social housing seems to haveaffected the spatial distribution of thisgroup. Despite this dependence, the group isnot extremely segregated, which is probablybecause the social housing sector is nottotally marginalised.     

高温和低张应力引起的非平衡晶界偏聚动力学(Ⅱ)--实验结果的动力学模拟

以文献[1]建立的张应力引起的非平衡晶界偏聚动力学方程模拟了Shinoda T等的磷在钢中的应力时效实验结果和Misra R D K的硫在钢中的应力时效实验结果，模拟结果与实验结果互相吻合。通过模拟发现，张应力使磷-空位复合体以及硫-空位复合体在钢中的扩散系数均增加3个数量级，且磷原子和硫原子的扩散系数分别降低3个和5个数量级。     

Structure of rapidly solidified aluminum alloys

This paper is a summary of an extensive research program carried out by the authors on the structure of rapidly solidified aluminum alloys; and a comparison with the work of others also involved in this field. The paper discusses the changes in the dendritic and non-dendritic structure of the matrix at cooling rates from 10^–3 to 10¹⁰ K/s and discusses the hetergeneity of the structure caused by interdendritic-segretion during solidification.     

Tree-shaped flow structures designed by minimizing path lengths

This paper outlines a direct route to the construction of effective tree-shaped flow structures. Dendritic flow structures dominate the design of natural and engineered flow systems, especially in thermal and fluid systems. The starting point is the optimization of the shape of each elemental area or volume, such that the length of the flow path housed by the element is minimized. Proceeding toward larger and more complex structures - from elements, to first constructs, second constructs, etc. - the paper develops tree-shaped flow structures between one point and a straight line, one point and a plane, a circle and its center, and a point and many points distributed uniformly over an area. In the latter, the construction method is applied to a fluid flow configuration with laminar fully developed flow. The constructions reveal several features that are supported by empirical observations of natural tree-shaped flows: asymmetry, flow rate imbalance, pairing or bifurcation, angles between branches, and Y-shaped constructs that lie in a plane. It is shown that these basic features are necessary because of “packing”, i.e., assembling optimized elements into a fixed space, and filling the space completely. For the flow between an area and one point, the best elemental shape is the regular hexagon. It is shown that the emergence of string-shaped links that connect two or more elements are necessary features, which are also required by packing. Strings cover some of the inner zones of the tree network, particularly the inner zones of large and complex trees. Dichotomous Y-shaped constructs dominate the tree structure, especially the peripheral zones of the tree canopy. The practical importance of the simplified design method is discussed.     

复合射孔枪枪身材料动态本构关系的试验研究

为确定复合射孔枪枪身材料32CrMo4钢在井下高温、高加载率工作环境下的动态性能,利用MTS试验机和分离式Hopkinson冲击压杆装置做了应变率为0.001、1000和3000/s,温度为294、373、473和573K的单轴动态压缩试验,得到32CrMo4钢各组温度及应变率下的流动应力-应变曲线。拟合得到该钢Johnson-Cook本构关系模型所需的5个参数,模型拟合曲线与试验曲线吻合。     

Low surface energy films based on partially fluorinated isocyanates: the effects of curing temperature

Self-stratification strategy can be used to prepare films in which both bulk and surface properties can be optimized. By using this approach, only a very small quantity of fluorinated species is needed to generate a surface with low surface energy. When cross-linking is involved during film formation, we are dealing with a competition behavior between the diffusion of fluorinated species and the formation of cross-linked network. In this study low surface energy polymeric films were prepared on the basis of partially fluorinated polyisocyanates, in combination with hydroxyl-end-capped three-armed solventless liquid oligoesters and modified hyperbranched polyesters. At a fluorine concentration of only 0.5 wt.%, contact angles of water and hexadecane can reach 120° and 80°, respectively. A surface energy as low as 10–15 mN/m can be obtained upon the addition of less than 1 wt.% of fluorine in the films. It was shown, from real time ATR-FTIR and contact angle measurements, that the curing temperatures demonstrated significant effects on the cross-linking rate as well as on the wettability of the films.     

溶质原子在再结晶运动晶界上偏聚的研究

Ｂ~（１０）（ｎ，α）Ｌｉ~７裂变反应的径迹显微照相技术被用来研究含硼Ｆｅ－３０％Ｎｉ合金高温热变形再结晶过程中硼在晶界上的偏聚行为，实验表明，含硼Ｆｅ－３０％Ｎｉ合金１０００℃热变形２０％再结晶过程中，运动晶界前方发生硼偏聚而后方发生贫硼现象，而在静止晶界上看不到硼偏聚，随着再结晶新晶粒的长大，运动晶界上的硼偏聚变弱。本文提出，可以用晶界对溶质原子热运动散射的量子理论来解释溶质原子在运动晶界上的偏聚现象。     

含RE铝阳极中析出相的电化学行为研究

用电子探针和能谱分析技术，观察了Al-5Zn-0．05In-0．1Sn-1Mg-0．3RE阳极中主要析出相的成分，并熔炼了析出相合金．电位测量和腐蚀后铝阳极表面的电子探针面扫描分析表明：富Sn相为阳极相，富Fe相、富RE相为阴极相；Fe相是铝阳极自腐蚀微电池中的主要阴极相，温度对析出相的电化学行为有影响．     

P，Zr，B对定向凝固IN738合金组织和偏析的影响SCIEI

用不同凝固速度下定向凝固和定向凝固加快淬的方法研究了Ｐ，Ｚｒ，Ｂ对定向凝固ＩＮ７３８合金组织和偏析的影响发现随磷含量的增加，合金固液两相区宽度及温度区间显著增加；凝固前沿低熔点液相区增大；树枝晶组织发达，二次晶变细、变多；固液界面表面积增加。发现只加Ｐ与同时加Ｐ，Ｚｒ合金的溶质原子偏析规律有差异。Ｐ，Ｚｒ，Ｂ促进合金中（γ＋γ′）共晶形成，在其前沿有（γ＋硼化物）共晶析出。     

机械振动对Sn-Sb合金β相的影响

初步探讨了机械振动对Sn-Sb合金β相在基体中分布的影响,重点讨论了在不同振击力作用下对Sn-Sb11合金中β相(SnSb)偏析和细化的影响效果.试验表明,在不同振击力作用下,合金晶粒以及组织明显得到改善,而且随着振击力的增大,组织均匀化程度的改善效果呈明显上升趋势.分析结果表明,这是由于强烈的振动对金属液体的搅拌以及促使合金液晶粒(或晶团)的游离作用的缘故.