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At least 19 recordsLinked to original sources
PubMed1997

Relationship between microstructure and ductility of investment cast ASTM F-75 implant alloy.

Hip replacement implants fabricated using the ASTM F-75 alloy sometimes fail in a sudden catastrophic way. In general, fractures start at microstructural defects subjected to stress-corrosion under chemical attack by body fluids. In this paper the results of a study on the effect of casting parameters on the microstructure of ASTM F-75 are presented. The preheating mold temperature and the liquid temperature were varied between 900 and 1000 degrees C, and 1410 and 1470 degrees C, respectively. Optimum static strength and ductility were obtained when shrinkage microporosity and the volume fraction of M23C6 "eutectic" carbides precipitated at grain boundaries were minimized by increasing the preheating mold temperature to 1000 degrees C and by using intermediate pouring temperatures of 1455 degrees C. Under these casting conditions, however, the solidification rates are low, leading to large grain sizes, which, in turn, reduce the strength of the material under dynamic loading conditions. The volume fraction of the M23C6 "blocky" carbides appears to be independent of the casting conditions; however, their size and spatial distributions determine the strength of the as-cast alloys.

Alloys↗
PubMedDate not supplied

Settlement network development policy and urbanisation in Hungary in the 20th century.

"The paper brings out the role of political economy in influencing the process of urbanisation and [the] structure of settlement network. This is demonstrated through an empirical study of Hungary during the twentieth century. Three phases get easily distinguished: pre-1949 or the period of changes in the state boundaries; 1949-89 or the period of state socialism; and post-1989 or the period of institutional reform. An interesting finding is that there was a bias in favour of large cities and county seats in allocation of development funds under all the regimes."

Demography↗
PubMed1997

Political unification and regional consequences of German East-West migration.

"The purpose of this paper is to evaluate the impact of the post-unification East to West transfer of the German population on levels of spatial concentration and deconcentration in Eastern and Western Germany. Using 1991 internal migration data, it was found that German East-to-West migration served to deconcentrate regional population in the West, but concentrate population in the East. Regional variations in German East-to-West migration during 1991 can be explained by the availability of employment and housing, a distance-minimisation effect, and the location of relatives and friends."

Demography↗
PubMed1998

The geography of Bangladeshi migration to Rome.

"With reference to the Bangladeshi community in Rome, this paper provides some answers to three key geographical questions: what is the migrants' regional pattern of origin in their home country; what are the mechanisms and routes of their migration to Italy; how are they spatially distributed in Rome?... Chain migration links specific origins in Bangladesh with spatial clusters and economic activities in Rome; the key here is the role of Bangladeshi community leaders in Rome who act both as migration sponsors and entrepreneurs."

Asia↗
PubMed1996

Urbanization and economic development: a bias toward large cities?

"We find that a nation's urban population percentage increases with GDP per capita; industrialization; export orientation; and possibly, foreign assistance. It decreases with the importance of agriculture. Industrialization and agricultural importance have the same implications for the concentration of urban population in cities with 100,000+ population as for the urban percentage. Greater export orientation reduces such concentration. Finally, GDP per capita, population, and export orientation reduce primacy. Political factors, such as whether a country's largest city is also its capital, affect primacy. Our results do not seem to imply that developing-country urbanization today differs fundamentally from urbanization in the past."

Agriculture↗
PubMed1998

The effect of housing on migrations in Israel: 1988-1994.

"The analysis of 1988-1994 statistical data indicates that the population of Israel simultaneously moves in two opposite directions: while the initial distribution of new immigrants is primarily focused on the areas where jobs are available, the existing population of these areas tends to move outward, to the less populated districts where housing is more available and affordable. The paper thus argues that the heterogeneity of the population is indeed a crucial consideration for the proper modeling of migration behavior."

Asia↗
PubMed1998

Estimation of megacity growth: simple rules versus complex phenomena.

"The growth of large urban aggregates (megacities) is analogous to the development of self-organized structures known in physics. Using empirical data about changes in the built-up areas of different cities as input, the self-organizing model employed here suggests that megacities evolve towards a hierarchical form of spatial organization, and provides estimates of the size of subclusters that compose the urban aggregate.... The model has been validated by reproducing the evolution of the Berlin area over a period of 35 years (1910-45). Using the same assumptions, the evolution of the built-up area of Daegu (Korea) is simulated up to the year 2010."

Asia↗
PubMed1997

A place in the sun: international retirement migration from northern to southern Europe.

"This article considers four aspects of IRM [international retirement migration]. The first considers the limited literature on this... topic and identifies the distinctiveness of both its international and European features. The second reviews the existing statistical data for north-south IRM in Europe, particularly from the UK to Italy, Malta, Portugal and Spain; it establishes both the scale and the geography of these migrations. In the third section we investigate some of the major influences on both the volume and the spatial pattern of IRM. Finally, in the fourth section, a brief review is presented of the economic, social and cultural implications of IRM for both the emigrants and their host communities."

Data Collection↗
PubMed1987

Population growth of small towns in Libyan Arab Jamahiriya.

The rapid population growth of small towns in Libya is examined, and future prospects are considered. "Their growth can be attributed to natural increase, internal migration and the influx of foreigners, all of which factors have been stimulated by the State. The paper provides detailed data on the growth and development of small towns and the changes occurring in the overall distribution and density of the Libyan population. The reasons behind the growth and sometimes the demise of individual towns are examined."

Africa↗
PubMed1999

The resurgence of marvellous Melbourne--trends in population distribution in Victoria, 1991 to 1996.

"Between 1991 and 1996 the population of Melbourne [Australia] grew faster than that of Regional Victoria. During the same period the population of Sydney grew faster than that of Regional New South Wales. Both these developments were unexpected. They occurred during a period of declining net overseas migration. Both developments can be partly explained by fewer people leaving Melbourne and Sydney and moving to the regional areas of their respective states. In Victoria, this development can also be partly explained by an increase in the number of people migrating interstate from Regional Victoria."

Australia↗
PubMed1999

The internal migration patterns of the foreign-born and native-born populations in the United States: 1975-80 and 1985-90.

"The focus of this article is on an examination of the influence of birthplace on the internal migration and spatial redistribution patterns of the foreign-born and native-born populations in the United States during the 1975-80 and 1985-90 periods. The analyses presented here consider the following principal questions: (1) What are the internal migration patterns of the foreign-born population in the United States, and how do they differ from those of the native-born population? (2) How do the relocation choices of various birthplace-specific foreign-born and native-born subpopulations differ from each other? (3) Are the internal migration patterns generating an increased or a decreased geographical concentration of such birthplace-specific subgroups?"

Americas↗
PubMed1995

[Trend analysis for interprefectural migration in Japan, 1954-1993].

"In this paper, our main aim is to examine long-term trends of Japanese interprefectural migration after the War by using a Markov migration model.... We observed dependence of in- and out-migration on the size of populations by prefecture.... Major findings based on the time-series observation of stationary distributions by year are as follows: First from [the 1950s] to 1970 migrants tended to concentrate [on] densely populated industrialized prefectures (Tokyo, Osaka and Aichi), but after that during [the 1970s] populations have redistributed to provincial prefectures. Reconcentration of population to [the] Tokyo area again occurred around [the mid-1980s, but] it ceased at the beginning of the [1990s] in accordance with economic recession.... It can be concluded that [the] recent Japanese interprefectural migration system has lost its potential power to redistribute populations." (SUMMARY IN ENG)

Asia↗