• Elastomers and Composites
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• v.50 no.3
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• pp.210-216
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• 2015

Polyurethane modified silicone (PUMS) was synthesized from various molecular weights of polydimethylsiloxane (PDMS 2000, PDMS 6000, PDMS 20000), polypropyleneglycol with molecular weight of 3000 g/mol (PPG 3000) and 2,4-toluenediisocyanate (TDI) under tin catalyst. Their structures were confirmed by the measurement of FT-IR and $^1H-NMR$, and the thermal properties were studied from DSC and TGA. Glass transition temperature of PUMS exhibited exothermic peak at $-63{\sim}-69^{\circ}C$, and residual weight was 19~35% at $800^{\circ}C$.

• Journal of the Economic Geographical Society of Korea
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• v.15 no.3
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• pp.376-389
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• 2012

Ethnic entrepreneurship, an important means by which immigrants improve economic status, is widely believed to be facilitated by their residential concentration, i.e. ethnic enclaves. However, the recent immigrants' residential dispersion and re-clustering in some selected well-to-do suburbs portend changes in the role of ethnic enclave as a nest of immigrant entrepreneurship. This paper investigates the impacts of the residential dispersal on ethnic entrepreneurship with a case study of Korean small businessmen in Chicago, Illinois PMSA. The research utilizes the Public Use Microdata Sample (PUMS) to know the overall changes in Korean entrepreneurship through 1990s and conducts a survey to understand reactions and surviving strategies of Korean enclave businessmen to the residential shifts. Relevant to those analyses is the enclave-economy hypothesis which argues benefit from spatial clustering of co-ethnic entrepreneurs by yielding more business opportunities and higher returns.

• Journal of the Korean Association of Geographic Information Studies
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• v.1 no.1
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• pp.39-51
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• 1998

The purpose of this study is to find out the ways to supplement the Census, the digital maps, and their integration in comparison with the U.S. Census and the TIGER file and in light of their usefulness for urban and environmental analysis in Korea. Recommendations in this study are: (1) to include questions on household income and housing price in the Census, (2) to implement a 1~5% sampling survey similar to PUMS in the U.S. Census, (3) to make the Census Tract as a minimum size unit of analysis through subdivision of current Eup, Myon, and Dong into 5~10 smaller units, and (4) to utilize the 1:5,000 scale digital maps completed by the Korea National Geographic Institute for the fast and efficient activation of digital maps instead of producing 1:1,000 or 1:1,200 scale digital maps through each city's effort.

• Korea journal of population studies
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• v.24 no.2
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• pp.255-286
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• 2001

The development of language skills among immigrants is important for their economic adjustment in their host societies since language is an important dimension of the skill levels of immigrants relevant for the labor markets of the host countries. Moreover, language plays a key role in the social adjustment of immigrants and in the social and political cohesion particularly in the society like the US that has diverse racial and ethnic groups. The main purposes of the present study are to analyze the determinants of English abilities of Korean and other Asian immigrants in the US. The present study utilizes the Public Use Microdata Sample (PUMS, S, 5%) in the US. We adopted the ordered probit technique to analyze qualitative differences of English ability. The study found that English fluency increases with a longer duration in the US, the presence of children in the household, living in an area in which a smaller proportion speak ones mother tongue, a younger age at immigration, a higher level of schooling. However, there are marked variations in levels of English proficiency among Asian immigrants.

• Korea journal of population studies
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• v.25 no.2
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• pp.163-192
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• 2002

Residential overcrowding, also called density, measured as more than one person per room, is a important variable as a principal indicator of inadequate housing. We investigated how immigrants in the US are assimilated to the host society through a lens of housing density. We estimated the probability of living in overcrowded housing of Korean, Chinese and Japanese immigrants armored with the 1980 and 1990 Public Use Microdata Sample(PUMS, A, 5%) in the US. Along with economic effects, we also consider life-cycle effects on the indicator. We applied "double cohort" method that enables duration of immigration effects to be separated from aging effects, which captures family size fluctuations due to life-cycle effects. The study found that cohort trends sharply changed during 10years. The 1970's immigrants are more likely to live in overcrowded housing than the pre-1970 immigrants. The pre-1970 immigrants are more likely to live in overcrowded housing than native-born persons. This may be explained by different assimilation processes driven by the disparities of individual human capitals or cultural differences among the ethnic groups. Especially, Korean experienced a sharp decline in overcrowding between 1980 and 1990. We also found that the major determinants that affect the level of housing density are years since migration, income, and gender. The present study concluded with some future studies related to the Korean immigrants abroad.ts abroad.

• Korea journal of population studies
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• v.10 no.2
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• pp.58-81
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• 1987

The purpose of this study is to examine major factors that affect patterns of living arrangements of older Korean noncitizens in the United States using the 1990 8% Public Use Microdata Sample(PUMS). In order to do so, I analyzed the effects of four factors including acculturation(English proficiency and Age at migration), economic circumstances(Personal Income and Supplemental Security Income: SSI receipt), health status(Mobility and Personal care limitation), and the ethnic community. The results show that acculturation and economic circumstances play an important role in determining the patterns of living arrangements among older Korean aliens, whereas the health status and the ethnic community do not show consistent effects. Regardless of marital status, the impact of age at migration is positively associated with solitary living of older Korean noncitizens, though, the effect of English proficiency show the opposite direction in accordance with marital status. That is, among nonmarried elders, those who cannot speak English are more likely to live alone. The case is reverse for married elders. The impact of economic feasibility is also positively associated with independent living arrangements. Those who receive SSI are much more likely to live apart from family, and elders whose annual personal income between $5,001 and $10,000 have the greatest propensity of solitary living-a large proportion of their income source is SSI. Individuals who receive SSI are also qualified to collect Medicaid, food stamps, rent subsidies, and other welfare benefits. In a sense, the economic feasibility provided by welfare benefits is the key determinant of independent living of older Korean noncitizens. Therefore, the recent welfare reform which denies legal aliens welfare benefits such as SSI and food stamps will severly affect the present living arrangements of older Korean aliens, and give economic burden to their family member The findings also show that there are significant differences within the elderly Korean Americans in terms of demographics, income, fertility, health status, and patterns of living arrangements by U.S. citizenship status. In particular, after controlling for age at migration as a proxy for acculturation, there is a statistically significant variation in living arrangements between elderly Korean noncitizens and naturalized citizens. For both theoretical and methodological reasons, future research on minority aging needs to investigate the concept of U.S. citizenship status for its impact on patterns of living arrangements among the minority elderly.

• Korea journal of population studies
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• v.20 no.2
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• pp.99-134
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• 1997

The purpose of this study is to examine major factors that affect patterns of living arrangements of older Korean noncitizens in the United States using the 1990 8% Public Use Microdata Sample(PUMS). In order to do so, I analyzed the effects of four factors including acculturation(English proficiency and Age at migration), economic circumstances(Personal Income and Supplemental Security Income: SSI receipt), health status(Mobility and Personal care limitation), and the ethnic community. The results show that acculturation and economic circumstances play an important role in determining the patterns of living arrangements among older Korean aliens, whereas the health status and the ethnic community do not show consistent effects. Regardless of marital status, the impact of age at migration is positively associated with solitary living of older Korean noncitizens, though, the effect of English proficiency show the opposite direction in accordance with marital status. That is, among nonmarried elders, those who cannot speak English are more likely to live alone. The case is reverse for married elders. The impact of economic feasibility is also positively associated with independent living arrangements. Those who receive SSI are much more likely to live apart from family, and elders whose annual personal income between $5, 001 and $10, 000 have the greatest propensity of solitary living-a large proportion of their income source is SSI. Individuals who receive SSI are also qualified to collect Medicaid, food stamps, rent subsidies, and other welfare benefits. In a sense, the economic feasibility provided by welfare benefits is the key determinant of independent living of older Korean noncitizens. Therefore, the recent welfare reform which denies legal aliens welfare benefits such as SSI and food stamps will severly affect the present living arrangements of older Korean aliens, and give economic burden to their family member The findings also show that there are significant differences within the elderly Korean Americans in terms of demographics, income, fertility, health status, and patterns of living arrangements by U.S. citizenship status. In particular, after controlling for age at migration as a proxy for acculturation, there is a statistically significant variation in living arrangements between elderly Korean noncitizens and naturalized citizens. For both theoretical and methodological reasons, future research on minority aging needs to investigate the concept of U.S. citizenship status for its impact on patterns of living arrangements among the minority elderly.