• Environmental Engineering Research
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• v.14 no.4
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• pp.200-210
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• 2009

The modern era of water quality modeling in the United States began in the 1960s. Pushed by advances in computer technology as well as environmental sciences, water quality modeling evolved through five broad periods: (1) initial model development with mainframe computers (1960s - mid 1970s), (2) model refinement and generalization with minicomputers (mid 1970s - mid 1980s), (3) model standardization and support with microcomputers (mid 1980s - mid 1990s), (4) better model access and performance with faster desktop computers running Windows and local area networks linked to the Internet (mid 1990s - early 2000s), and (5) model integration and widespread use of the Internet (early 2000s - present). Improved computer technology continues to drive improvements in water quality models, including more detailed environmental analysis (spatially and temporally), better user interfaces and GIS software, more accessibility to environmental data from on-line repositories, and more robust modeling frameworks linking hydrodynamics, water quality, watershed and atmospheric models. Driven by regulatory needs and advancing technology, water quality modeling will continue to improve to better address more complicated water bodies and pollutant types, and more complicated management questions. This manuscript describes historical trends in water quality model development in the United States, reviews current efforts, and projects promising future directions.

• Korea journal of population studies
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• v.6 no.1
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• pp.70-89
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• 1983

China's population and family planning program has heen successful. Women's fertility as measured by total fertility rate (TFR) has declined from 5.8 in 1970 to 2.3 in 1990, accordingly the annual crude birth rate(CBR) has declined from 34 per thousand in 1970 to 21 per thousand in 1989, and the annual natural growth rate from 2.6 percent in 1970 to 1.4 percent in 1989 (Coale and Chen, 1987; SSB, 1991; Gu, 1994). While this is indeed an astonishing achievement for a developing country to have its fertility down to replacement within a short period, some new issues emerging along with the rapid fertility decline require careful considerations. One of them is the uprising of the sex ratio at birth in China. The 1990 population census reported the sex ratio at birth in China of 113.8 in 1989, which is ohviously much higher than the acceptable level of normal ratio around 106. It has received since then a lot of tention in China and abroad, among demographic professionals and governmental agencies alike (Hull, 1990; Johansson and Nygren, 1991; Xuand Guo, 1991; Tu, 1993; Gu and Xu, 1994; among others). Based on the available demographic data and research results this paper will first have a review of the patterns and trends of sex ratio at birth in China, then turn to the immediate causes of abnormal sex ratio at birth and the determinants of the son preference, followed with a conceptual framework for understanding of the phenomenon, and finally the policy implications and recommendations will be discussed.

• Korea journal of population studies
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• v.17 no.2
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• pp.116-135
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• 1994

China's population and family planning program has heen successful. Women's fertility as measured by total fertility rate (TFR) has declined from 5.8 in 1970 to 2.3 in 1990, accordingly the annual crude birth rate(CBR) has declined from 34 per thousand in 1970 to 21 per thousand in 1989, and the annual natural growth rate from 2.6 percent in 1970 to 1.4 percent in 1989 (Coale and Chen, 1987; SSB, 1991; Gu, 1994). While this is indeed an astonishing achievement for a developing country to have its fertility down to replacement within a short period, some new issues emerging along with the rapid fertility decline require careful considerations. One of them is the uprising of the sex ratio at birth in China. The 1990 population census reported the sex ratio at birth in China of 113.8 in 1989, which is ohviously much higher than the acceptable level of normal ratio around 106. It has received since then a lot of tention in China and abroad, among demographic professionals and governmental agencies alike (Hull, 1990; Johansson and Nygren, 1991; Xuand Guo, 1991; Tu, 1993; Gu and Xu, 1994; among others). Based on the available demographic data and research results this paper will first have a review of the patterns and trends of sex ratio at birth in China, then turn to the immediate causes of abnormal sex ratio at birth and the determinants of the son preference, followed with a conceptual framework for understanding of the phenomenon, and finally the policy implications and recommendations will be discussed.

• Journal of Engineering Education Research
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• v.12 no.1
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• pp.82-94
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• 2009

This paper examines the roles, main contents, and writing guidelines of ethical codes, and analyses the developmental process and characteristics of ethical codes of scientific and technological communities in Korea. Korean communities occasionally tried for ethical codes from the 1970s to the 1990s, and have paid a serious attention to ethical codes in the 2000s. The forms of ethical codes became more sophisticated pursuing detailed commentary and ethical education. The focus of contents changed from professional dignity to social responsibility, and the importance of research integrity became embossed in the 2000s. Scientific and technological communities in Korea should make or revise ethical codes with self-imposed control considering realistic operation.

• Proceedings of the Korea Database Society Conference
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• 1994.09a
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• pp.9-16
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• 1994

Author outlines briefly developments of policies relating to telecommunication infrastructure and databases since latter half of 1970′s. There exist three phases. The first phase was from later 1970′s to 1985, which was an initial stage of electronic information service in Japan. In the second phase, 1985～1990, basic policy change made possible the privatization of telecommunication services and proliferation of database products and vendors, The third phase began in early 1990′s with downsizing in computer usage, wide-spreading information networks and rapid dissemination of personal computers. Then author describes offers on policy formation for "novel information infrastructure" and current situation concerning the "Internet" in Japan. Finally, tasks and problems for implementing new generation program for information infrastructure and database usage are pointed out, These are knowledge resource, cost, copyrights and cultural problems including language.

• Journal for History of Mathematics
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• v.25 no.2
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• pp.71-95
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• 2012

Nowadays, the big issues on mathematics education are mathematical modeling, mathematization, and problem solving. So, this paper looks about these issues. First, after 1990's, the researchers interested in mathematical model and mathematical modeling. So, this paper looks about mathematical model and mathematical modeling. Second, it looks about Freudenthal' mathematization after 1970's. And then, it compared with mathematical modeling. Also, it looks about that problem solving focused on mathematics education since 1980's. And it compared with mathematical modeling.

• KOMUNHWA
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• no.59
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• pp.3-34
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• 2002

The researches on the prehistoric sites in Jeonnam Province started in 1970s. During 1980s and 1990s, excavations increased and their results also became larger than before. For example, the paleolithic sites were excavated along the Yeongsan River basin

• Journal of the Korean Society for Library and Information Science
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• v.36 no.1
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• pp.111-125
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• 2002

The purpose of this study is to know the trends of research of reference service in Korea before 21th century from beginning. After analyzing of representative subject bibliographies , domestic research of this field can be devided into four chronical stages; the beginning stage in 1950’s, the changing stage in 1970’s, the developing stage in 1980’s and professional stage in 1990’s. And found out both domestic and internaional research seemed to have focused on the service theory, however there have been some differences in their lower subjects.

• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.1
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• pp.1-6
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• 2006

For the purpose of processing weather data for air conditioning equipment de sign in Busan area Korea, this study collected weather observations made by Busan weather Administration from 1970 to 2003, and then established external conditions for heating and air-conditioning design. For changes of temperature in external conditions for design, the highest temperature had little changed, whereas the lowest had been on the rise as the years went by through the 1970s, 1980s, 1990s, and 2000s, but insolation has a little lessened. Absolute humidity does not show a significant change but an incessant rise.

• Journal of the Korean association of regional geographers
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• v.14 no.6
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• pp.709-717
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• 2008

This study is to analyze environmental problems which have caused by changes of the population and agriculture in North Korea. Main results of the research are following. First, Population of the North Korea shows lower increase ratio less than 2% growth from 1970's to middle of 1990's. This is interpreted by food shortages. Second, population distribution by provinces represented that northern and eastern part of the North Korea were comparatively lower and other western areas were higher. Third, Food situation of the North Korea was relatively better in 1970's, but, 1990's was the worst in the way. Fourth, on the agricultural productivity according to each province, western areas possessing more plains were more higher than mountainous areas of the northern and eastern parts of North Korea. Fifth, Growth ratio of food production and population have grown very steadily until 1990's, but the increase ratio of population exceeded food productivity after 1990's. Sixth, Cropland reclamation for improving these situation have caused deforestation and environmental problems and especially eastern and northern areas became more serious. For the solving these problems of North Korea, it is necessary to get the help of South Korea and international societies with efforts by itself.