• Horticultural Science & Technology
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• v.17 no.5
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• pp.572-577
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• 1999

Research was initiated to evaluate plant growth regulator effects on the vertical shoot growth of Korean lawngrass and to determine desirable growth regulator and its rate. The experiments were conducted twice at different sites in 1995. All the tested growth regulators inhibited the growth, but the inhibition period was variable among the product in Experiments I and II. During the first week after treatment, there was approximately 10 to 20% growth reduction in most of the treated plots. In the amidochlor-treated plots, growth suppression was effective for 3 to 4 weeks at low to medium rates ($0.60mL{\cdot}m^{-2}$). A Type II growth regulator, trinexapac-ethyl exceeding the medium rate of $0.08mL{\cdot}m^{-2}$ consistently tended to suppress vertical shoot growth for 8 weeks, being above 35% reduction in both experiments. In the plots applied with mefluidide, growth suppression appeared with foliar discoloration 3 or 4 days earlier than the other growth regulators and continued to work till the 8 weeks after treatment. Suppression intensity on vertical shoot growth increased with time after treatment up to a certain period of time, depending on growth regulators. Generally, the higher the application rate, the greater the suppression intensity. Seasonal variation of activity and effectiveness of growth regulators was observed, resulting in lower suppression intensity in July than in June. It is expected to reduce mowing requirements by 30 to up to 60% for a certain period with a specific growth regulator. In low to medium maintenance of Korean lawngrass turf, a long-term suppression may be more effectively accomplished with trinexapac-ethyl rather than mefluidide and amidochlor in terms of vertical shoot growth inhibition. Therefore, turf managers will need to select proper growth regulator and determine optimum rate of application for turfgrass management, based on a defined period of mowing reduction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.3
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• pp.567-577
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• 2015

Climate and land use changes have impact on availability water resource by hydrologic cycle change. The purpose of this study is to evaluate the hydrologic behavior by the future potential climate and land use changes in Anseongcheon watershed ($371.1km^2$) using SWAT model. For climate change scenario, the HadGEM-RA (the Hadley Centre Global Environment Model version 3-Regional Atmosphere model) RCP (Representative Concentration Pathway) 4.5 and 8.5 emission scenarios from Korea Meteorological Administration (KMA) were used. The mean temperature increased up to $4.2^{\circ}C$ and the precipitation showed maximum 21.2% increase for 2080s RCP 8.5 scenario comparing with the baseline (1990-2010). For the land use change scenario, the Conservation of Land Use its Effects at Small regional extent (CLUE-s) model was applied for 3 scenarios (logarithmic, linear, exponential) according to urban growth. The 2100 urban area of the watershed was predicted by 9.4%, 20.7%, and 35% respectively for each scenario. As the climate change impact, the evapotranspiration (ET) and streamflow (ST) showed maximum change of 20.6% in 2080s RCP 8.5 and 25.7% in 2080s RCP 4.5 respectively. As the land use change impact, the ET and ST showed maximum change of 3.7% in 2080s logarithmic and 2.9% in 2080s linear urban growth respectively. By the both climate and land use change impacts, the ET and ST changed 19.2% in 2040s RCP 8.5 and exponential scenarios and 36.1% in 2080s RCP 4.5 and linear scenarios respectively. The results of the research are expected to understand the changing water resources of watershed quantitatively by hydrological environment condition change in the future.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.3 s.8
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• pp.33-43
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• 2005

Traffic condition monitoring system serves as the foundation for all intelligent transportation system operation. Loop detectors and Video Image Processing are the most widely common technology approach to condition monitoring in korea Highways. Lane Usage is defined as the proportion of total link volume served by each lane. In this research, the lane Usage(LU) of two lane link for one day. Interval is 56% : 44%. The LU of three lane link is 39% : 37% : 24%. The LU of four lane link is 25% : 29% : 26% : 21%. These analysis reveal that each lane distributions of link are not same. This research investigates the general concept of lane usage by using collected loop detector data and the investigated that lane distribution is different by traffic lane and lane usage is consistent by time of day.

• Information Systems Review
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• v.21 no.4
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• pp.99-123
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• 2019

The software industry is a high value-added industry in the knowledge information age, and its importance is growing as it not only plays a key role in knowledge creation and utilization, but also secures global competitiveness. Among various SW available in today's business environment, Open Source Software(OSS) is rapidly expanding its activity area by not only leading software development, but also integrating with new information technology. Therefore, the purpose of this research is to empirically examine and analyze the effect of factors on the switching behavior to OSS. To accomplish the study's purpose, we suggest the research model based on "Push-Pull-Mooring" framework. This study empirically examines the two categories of antecedents for switching behavior toward OSS. The survey was conducted to employees at various firms that already switched OSS. A total of 268 responses were collected and analyzed by using the structural equational modeling. The results of this study are as follows; first, continuous maintenance cost, vender dependency, functional indifference, and SW resource inefficiency are significantly related to switch to OSS. Second, network-oriented support, testability and strategic flexibility are significantly related to switch to OSS. Finally, the results show that willingness to secures SW competitiveness has a moderating effect on the relationships between push factors and pull factor with exception of improved knowledge, and switch to OSS. The results of this study will contribute to fields related to OSS both theoretically and practically.

• Journal of Information Management
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• v.9 no.1
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• pp.21-25
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• 1976

1975년(年) 3월(月), 4년반(年半) 동안의 Chemical Abstracts 색인(索引)과 온-라인이 가능(可能)한 CA Condensates를 비교(比較)하였다. 두가지 데이터 베이스를 함께 이용(利用)하여 검색(檢索)하는 방법(方法)이 가장 효율적(效率的)이지만 실예(實例)에서 보는 바와 같이 CA Condensates를 검색(檢索)하는 것이 보다 실용적(實用的)이다. System Development Corp 사(社) (SDC)에 설치(設置)되어 있는 온-라인 형태(形態)인 CHEMCON과 CHEM7071을 Chemical Abstracts 색인(索引)과 비교(比較)하였다. 대부분(大部分)의 Chemical Abstracts 이용자(理容者)들은 Chemical Abstracts 책자나 우가색인(累加索引)에는 친숙(親熟)하지만 CA Condensates는 아마도 그리 친숙(親熟)하지 못할 것이다. CA Condensates는 서지적 사항을 기계(機械)로 읽을 수 있는 형태(形態)로 되어 있고 Chemical Abstracts에 따라서 색인(索引)되므로 매주 발행되는 Chemical Abstracts 책자의 뒷 부분이 있는 색인(索引)과 같이 우리에게 가장 친숙(親熟)한 형태(形態)로 되어 있다. Chemical Abstracts가 현재(現在) 사용(使用)하고 있는 데이터 데이스이지만 본고(本稿)에서는 Index와 Condensates를 둘 다 데이터 베이스로 정의(定義)한다. Condensates가 미국(美國)의 Chemical Abstracts Service 기관으로부터 상업적(商業的)으로 이용(利用)할 수 있게 되자 여러 정보(情報)센터에서는 이용자(利用者)들의 프로 파일을 뱃취방식(方式)으로 처리(處理)하여 매주 나오는 자기(磁氣)테이프에서 최신정보(最新情報)를 검색(檢索)하여 제공(提供)하는 서어비스 (SDI)를 시작하였다. 어떤 정보(情報)센터들은 지나간 자기(磁氣)테이프들을 모아서 역시 뱃취방식(方式)으로 소급(遡及) 문헌검색(文獻檢索) 서어비스를 한다. 자기(磁氣)테이프를 직접 취급(取扱)하는 사람들을 제외(除外)하고는 대부분(大部分) Condensates를 아직 잘 모르고 있다. 소급(遡及) 문헌검색(文獻檢索)은 비용이 다소 비싸고 두서없이 이것 저것 문헌(文獻)을 검색(檢索)하는 방법(方法)은 실용적(實用的)이 못된다. 매주 나오는 색인(索引)에 대해서 두 개나 그 이상의 개념(槪念)이나 물질(物質)을 조합(組合)하여 검색(檢索)하는 방법(方法)은 어렵고 실용적(實用的)이 못된다. 오히려 주어진 용어(用語) 아래에 있는 모든 인용어(引用語)들을 보고 초록(抄錄)과의 관련성(關連性)을 결정(決定)하는 것이 때때로 더 쉽다. 상호(相互) 작용(作用)하는 온-라인 검색(檢索)을 위한 Condensates의 유용성(有用性)은 많은 변화를 가져 왔다. 필요(必要)한 문헌(文獻)만을 검색(檢索)해 보는 것이 이제 가능(可能)하고 어떤 항목(項目)에 대해서도 완전(完全)히 색인(索引)할 수 있게 되었다. 뱃취 시스팀으로는 검색(檢索)을 시작해서 그 결과(結果)를 받아 볼 때 까지 수시간(數時間)에서 며칠까지 걸리는 번거로운 시간차(時間差)를 이제는 보통 단 몇 분으로 줄일 수 있다. 그리고 뱃취 시스팀과는 달리 부정확하거나 불충분한 검색방법(檢索方法)은 즉시 고칠 수가 있다. 연속적인 뱃취 형태의 검색방법(檢索方法)에 비해서 순서(順序)없이 온-라인으로 검색(檢索)하는 방법(方法)이 분명(分明)하고 정확(正確)한 장점(長點)이 있다. CA Condensates를 자주 이용(移用)하게 되자 그의 진정한 가치(價値)에, 대해 논의(論義)가 있었다. CA Condensates의 색인방법(索引方法)은 CA Abstract 책자나 우가색인(累加索引)의 방법(方法)보다 확실히 덜 체계적(體系的)이고 철저(徹底)하지 못하다. 더우기 두 데이터 베이스는 중복(重複)것이 많으므로, 중복(重複)해서 검색(檢索)할 가치(價値)가 없는지를 결정(決定)해야 한다. 다른 몇 개의 데이터 베이스와 CA Condensates를 비교(比較)한 논문(論文)들이 여러 번 발표(發表)되어 왔는데 일반적(一般的)으로 CA Condensates는 하위(下位)의 데이터 베이스로 나타났다. Buckley는 Chemical Abstracts의 색인(索引)이 CA Condensates 보다 더 좋은 문헌 (데라마이신의 제법에 관해서)을 제공(提供)한 실례(實例)를 인용(引用)하였다. 죠오지대학(大學)의 Search Center는 CA Condensates가 CA Integrated Subject File 보다 기능(機能)이 못하다는 것을 알았다. CA Condensates의 다른 여러 가지 형태(形態)들을 또한 비교(比較)하였다. Michaels은 CA Condensates를 온-라인으로 검색(檢索)한 것과 매주 나오는 Chemical Abstracts 책자의 색인(索引)은 수작업(手作業)으로 검색(檢索)한 것을 비교(比較)한 논문(論文)을 발표(發表)하였다. 그리고 Prewitt는 온-라인으로 축적(蓄積)한 두 개의 상업용(商業用) CA Condensates를 비교(比較)하였다. Amoco Research Center에서도 CA Condensates와 Chemical Abstracts 색인(索引)의 검색결과(檢索結果)를 비교(比較)하고 CA Condensates의 장점(長點)과 색인(索引)의 장점(長點), 그리고 사실상(事實上) 서로 동등(同等)하다는 실례(實例)를 발견(發見)하였다. 1975년(年) 3월(月), 적어도 4년분(年分)의 CA Condensates와 색인(索引)(Vols 72-79, 1970-1973)을 비교(比較)하였다. 저자(著者)와 일반(一般) 주제(主題) 대한 검색(檢索)은 Vol 80 (Jan-June, 1974)을 사용(使用)하여 비교(比較)하였다. CA Condensates는 보통 세분화(細分化)된 복합물(複合物)을 검색(檢索)하는 데 불편(不便)하다. Buckly가 제시(提示)한 실례(實例)가 그 대표적(代表的)인 예(例)이다. 그러나, 다른 형태(形態)의 검색실예(檢索實例)(단체저자(團?著者), 특허수탁저(特許受託著), 개인저자(個人著者), 일반적(一般的)인/세분화(細分化)된 화합물(化合物) 그리고 반응종류(反應種類)로 실제적(實際的)인 검색(檢索)을 위한 CA Condensates의 이점(利點)을 예시(例示)하였다. 다음 실례(實例)에서 CHEMCON과 CHEM7071은 CA Condensates를 온-라인으로 입력(入力)시킨 것이다.

• Journal of Intelligence and Information Systems
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• v.27 no.2
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• pp.55-78
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• 2021

Tosolve complex and diverse social problems and ensure the quality of life of individuals, social robots that can interact with humans are attracting attention. In the past, robots were recognized as beings that provide labor force as they put into industrial sites on behalf of humans. However, the concept of today's robot has been extended to social robots that coexist with humans and enable social interaction with the advent of Smart technology, which is considered an important driver in most industries. Specifically, there are service robots that respond to customers, the robots that have the purpose of edutainment, and the emotionalrobots that can interact with humans intimately. However, popularization of robots is not felt despite the current information environment in the modern ICT service environment and the 4th industrial revolution. Considering social interaction with users which is an important function of social robots, not only the technology of the robots but also other factors should be considered. The design elements of the robot are more important than other factors tomake consumers purchase essentially a social robot. In fact, existing studies on social robots are at the level of proposing "robot development methodology" or testing the effects provided by social robots to users in pieces. On the other hand, consumer emotions felt from the robot's appearance has an important influence in the process of forming user's perception, reasoning, evaluation and expectation. Furthermore, it can affect attitude toward robots and good feeling and performance reasoning, etc. Therefore, this study aims to verify the effect of appearance of social robot and consumer emotions on consumer's attitude toward social robot. At this time, a social robot design evaluation model is constructed by combining heterogeneous data from different sources. Specifically, the three quantitative indicator data for the appearance of social robots from the ABOT Database is included in the model. The consumer emotions of social robot design has been collected through (1) the existing design evaluation literature and (2) online buzzsuch as product reviews and blogs, (3) qualitative interviews for social robot design. Later, we collected the score of consumer emotions and attitudes toward various social robots through a large-scale consumer survey. First, we have derived the six major dimensions of consumer emotions for 23 pieces of detailed emotions through dimension reduction methodology. Then, statistical analysis was performed to verify the effect of derived consumer emotionson attitude toward social robots. Finally, the moderated regression analysis was performed to verify the effect of quantitatively collected indicators of social robot appearance on the relationship between consumer emotions and attitudes toward social robots. Interestingly, several significant moderation effects were identified, these effects are visualized with two-way interaction effect to interpret them from multidisciplinary perspectives. This study has theoretical contributions from the perspective of empirically verifying all stages from technical properties to consumer's emotion and attitudes toward social robots by linking the data from heterogeneous sources. It has practical significance that the result helps to develop the design guidelines based on consumer emotions in the design stage of social robot development.

• KDI Journal of Economic Policy
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• v.13 no.4
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• pp.91-116
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• 1991

Market liberalization progressing simultaneously with high and rapidly rising domestic wages has created an adverse business environment for domestic firms. Korean firms are losing their international competitiveness in comparison to firms from LDC(Less Developed Countries) in low-tech industries. In high-tech industries, domestic firms without government protection (which is impossible due to the liberalization policy and the current international status of the Korean economy) are in a disadvantaged position relative to firms from advanced countries. This paper examines the division of roles between the private sector and the government in order to achieve a successful structural adjustment, which has become the impending industrial policy issue caused by high domestic wages, on the one hand, and the opening of domestic markets, on the other. The micro foundation of the economy-wide structural adjustment is actually the restructuring of business portfolios at the firm level. The firm-level business restructuring means that firms in low-value-added businesses or with declining market niches establish new major businesses in higher value-added segments or growing market niches. The adjustment of the business structure at the firm level can only be accomplished by accumulating firm-specific managerial assets necessary to establish a new business structure. This can be done through learning-by-doing in the whole system of management, including research and development, manufacturing, and marketing. Therefore, the voluntary cooperation among the people in the company is essential for making the cost of the learning process lower than that at the competing companies. Hence, firms that attempt to restructure their major businesses need to induce corporate-wide participation through innovations in organization and management, encourage innovative corporate culture, and maintain cooperative labor unions. Policy discussions on structural adjustments usually regard firms as a black box behind a few macro variables. But in reality, firm activities are not flows of materials but relationships among human resources. The growth potential of companies are embodied in the human resources of the firm; the balance of interest among stockholders, managers, and workers of the company' brings the accumulation of the company's core competencies. Therefore, policymakers and economists shoud change their old concept of the firm as a technological black box which produces a marketable commodities. Firms should be regarded as coalitions of interest groups such as stockholders, managers, and workers. Consequently the discussion on the structural adjustment both at the macroeconomic level and the firm level should be based on this new paradigm of understanding firms. The government's role in reducing the cost of structural adjustment and supporting should the creation of new industries emphasize the following: First, government must promote the competition in domestic markets by revising laws related to antitrust policy, bankruptcy, and the promotion of small and medium-sized companies. General consensus on the limitations of government intervention and the merit of deregulation should be sought among policymakers and people in the business world. In the age of internationalization, nation-specific competitive advantages cannot be exclusively in favor of domestic firms. The international competitiveness of a domestic firm derives from the firm-specific core competencies which can be accumulated by internal investment and organization of the firm. Second, government must build up a solid infrastructure of production factors including capital, technology, manpower, and information. Structural adjustment often entails bankruptcies and partial waste of resources. However, it is desirable for the government not to try to sustain marginal businesses, but to support the diversification or restructuring of businesses by assisting in factor creation. Institutional support for venture businesses needs to be improved, especially in the financing system since many investment projects in venture businesses are highly risky, even though they are very promising. The proportion of low-value added production processes and declining industries should be reduced by promoting foreign direct investment and factory automation. Moreover, one cannot over-emphasize the importance of future-oriented labor policies to be based on the new paradigm of understanding firm activities. The old laws and instititutions related to labor unions need to be reformed. Third, government must improve the regimes related to money, banking, and the tax system to change business practices dependent on government protection or undesirable in view of the evolution of the Korean economy as a whole. To prevent rational business decisions from contradicting to the interest of the economy as a whole, government should influence the business environment, not the business itself.

• Journal of Intelligence and Information Systems
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• v.23 no.3
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• pp.45-67
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• 2017

According to the Internet Usage Research performed in 2016, the number of internet users and the internet usage have been increasing. Smartphone, compared to the computer, is taking a more dominant role as an internet access device. As the number of smart devices have been increasing, some views that the demand on high-speed internet will decrease; however, Despite the increase in smart devices, the high-speed Internet market is expected to slightly increase for a while due to the speedup of Giga Internet and the growth of the IoT market. As the broadband Internet market saturates, telecom operators are over-competing to win new customers, but if they know the cause of customer exit, it is expected to reduce marketing costs by more effective marketing. In this study, we analyzed the relationship between the cancellation rates of telecommunication products and the factors affecting them by combining the data of 3 cities, Anyang, Gunpo, and Uiwang owned by a telecommunication company with the regional data from KOSIS(Korean Statistical Information Service). Especially, we focused on the assumption that the neighboring areas affect the distribution of the cancellation rates by coupling type, so we conducted spatial cluster analysis on the 3 types of cancellation rates of each region using the spatial analysis tool, SatScan, and analyzed the various relationships between the cancellation rates and the regional data. In the analysis phase, we first summarized the characteristics of the clusters derived by combining spatial information and the cancellation data. Next, based on the results of the cluster analysis, Variance analysis, Correlation analysis, and regression analysis were used to analyze the relationship between the cancellation rates data and regional data. Based on the results of analysis, we proposed appropriate marketing methods according to the region. Unlike previous studies on regional characteristics analysis, In this study has academic differentiation in that it performs clustering based on spatial information so that the regions with similar cancellation types on adjacent regions. In addition, there have been few studies considering the regional characteristics in the previous study on the determinants of subscription to high-speed Internet services, In this study, we tried to analyze the relationship between the clusters and the regional characteristics data, assuming that there are different factors depending on the region. In this study, we tried to get more efficient marketing method considering the characteristics of each region in the new subscription and customer management in high-speed internet. As a result of analysis of variance, it was confirmed that there were significant differences in regional characteristics among the clusters, Correlation analysis shows that there is a stronger correlation the clusters than all region. and Regression analysis was used to analyze the relationship between the cancellation rate and the regional characteristics. As a result, we found that there is a difference in the cancellation rate depending on the regional characteristics, and it is possible to target differentiated marketing each region. As the biggest limitation of this study and it was difficult to obtain enough data to carry out the analyze. In particular, it is difficult to find the variables that represent the regional characteristics in the Dong unit. In other words, most of the data was disclosed to the city rather than the Dong unit, so it was limited to analyze it in detail. The data such as income, card usage information and telecommunications company policies or characteristics that could affect its cause are not available at that time. The most urgent part for a more sophisticated analysis is to obtain the Dong unit data for the regional characteristics. Direction of the next studies be target marketing based on the results. It is also meaningful to analyze the effect of marketing by comparing and analyzing the difference of results before and after target marketing. It is also effective to use clusters based on new subscription data as well as cancellation data.

• Dementia and Neurocognitive Disorders
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• v.23 no.1
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• pp.54-66
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• 2024

Background and Purpose: Dementia subtypes, including Alzheimer's dementia (AD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD), pose diagnostic challenges. This review examines the effectiveness of ¹⁸F-Fluorodeoxyglucose Positron Emission Tomography (¹⁸F-FDG PET) in differentiating these subtypes for precise treatment and management. Methods: A systematic review following Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines was conducted using databases like PubMed and Embase to identify studies on the diagnostic utility of ¹⁸F-FDG PET in dementia. The search included studies up to November 16, 2022, focusing on peer-reviewed journals and applying the goldstandard clinical diagnosis for dementia subtypes. Results: From 12,815 articles, 14 were selected for final analysis. For AD versus FTD, the sensitivity was 0.96 (95% confidence interval [CI], 0.88-0.98) and specificity was 0.84 (95% CI, 0.70-0.92). In the case of AD versus DLB, ¹⁸F-FDG PET showed a sensitivity of 0.93 (95% CI 0.88-0.98) and specificity of 0.92 (95% CI, 0.70-0.92). Lastly, when differentiating AD from non-AD dementias, the sensitivity was 0.86 (95% CI, 0.80-0.91) and the specificity was 0.88 (95% CI, 0.80-0.91). The studies mostly used case-control designs with visual and quantitative assessments. Conclusions: ¹⁸F-FDG PET exhibits high sensitivity and specificity in differentiating dementia subtypes, particularly AD, FTD, and DLB. This method, while not a standalone diagnostic tool, significantly enhances diagnostic accuracy in uncertain cases, complementing clinical assessments and structural imaging.

• Current Research on Agriculture and Life Sciences
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• v.7
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• pp.201-219
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• 1989

Rice culture in Korea has a long history ranging over two thousand years. In the agriculture economy of pre-mordern Korea, however, its importantce was not as great as generally assumed. In fact, rice culture reached full development only after the 1920s when the Japanese colonial government carried out its drive to increase rice production in the Korea peninsula. It was not until the mid-1930s that rice became the staple in Korean diet. This can be attributed to two factors : (1) a mountainous topography that provides little irrigated fields and (2) a climate characterized by droughts in spring and heavy precipitation in summer. The present paper attempts to answer some of these questions. Specifically it will focus on these : Did the development of rice culture actually result in population growth? What are the salient features of agricultural develdpment and population grow in traditional Korea? Does the case of Korea conform the prevailing generalization about the agriculture in East Asia? I have discussed the development of rice culture and population growth in the Chos$\breve{o}$n dynasty, focusing on the relation between the rapid spread of transplanting and the rapid growth of population from the seventeenth to the nineteenth century. Here are my conclusions. (1) The spread of transplanting and other technological innovationsc contributed to the rapid growth of population in this period. However, we should also note that the impact of rice culture on population growth was rather limited, for rice culture was not the mainstay of agricultural economy in pre-modern Korea. Indeed we should consider the influence of dry field cropsn population growth. Nevertheless, it is obvious that the proliferation of rice culture was a factor crucial to population growth and regional concentration. (2) How should we characterize the spread of rice culture in the whole period? Evidently rice culture spread from less then 20% of cultivated fields in the fifteenth century to about 36% of them in the early twentieth century. Although rice as a single crop outweighed other crops, rice culture was more then counter-balanced by dry field crops as a whole, due to Korea's unique climate and geography. Thus what we have here in not a typical case of competition between rice culture and day field culture. Besides, the spread of rice culture in the seventeenth and eighteenth centuries accomplished by technological innovations that overcame severe springtime drought, rather than extensive irrigation. Althougt irrigarion facilities did proliferate to some extent, this was achieved by local landlords and peasants rather than the state. This fact contradicts the classical thesis that the productivity of rice culture increased through the state management of irrigation and that this in turn determined the type of society. (3) We should further study other aspects of the transition from the stable population and production struture in the fifteenth and sixteenth centuries to the rapid population growth and excessive density of population thereafter. We should note that there were continuing efforts to reclaim the land in order to solve the severe shortage of land. Changes also took place in the agricultural production relations. The increase in land producrivity developed tenancy based on rent in kind, and this in turn increased the independence of tenants from their landlords. There were changes in family relations-such as the shift to primogeniture as an effort to prevent progressive division of property among multiplying offspring. The rapid population growth also produced a great mass of propertyless farm laborers. These changes had much to do with the disintegration of traditional social institutions and political structure toward the end of the Chos$\breve{o}$n dynasty.