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A Study on the Construction Cost Risk through Analyzing the Actual Cost of Public Apartment (공공주택 실적공사비 분석을 통한 공사비 리스크에 관한 연구)

  • Yoon, Woo-Sung;Go, Seong-Seok
    • Korean Journal of Construction Engineering and Management
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    • v.12 no.6
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    • pp.65-78
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    • 2011
  • Construction business, which is complex and long-term business, requires accurate estimation and verification in construction costs and payment procedure from project planning to the completion of construction phase. And more importantly, it is necessary to investigate and determine the risk factors related to construction costs during the entire process including design planning, construction drawings, and quantity calculating. But, currently, it is not seem to be adequate to cope with the risk and increased construction costs against the operational budget in terms of actual costs when screening and estimating the bidding cost of public apartment. Therefore, this study selected and analyzed 40 sites' report of construction completion account from 2004 to 2010 focused on the adequacy on the modification of contract and design planning and on the complication of the budget in the beginning of the project. This study deducted various risk causes and results by analyzing actual costs according to year, architectural area, region, construction cost and sale/lease classification. We could find out construction risk according to annual variation of government policy and economy, and also deducted risk items by construction characteristic according to region and architectural area. Study result, we first found out the problems of lowest price award system according to the construction costs. The weight of the cost increase risk was analyzed that subcontract and material costs are very high. Roof and tile work were analyzed highly in subcontract cost risk and reinforcing bar and cement were analyzed highly in material cost risk, among direct construction cost. Finally, this study results could be used in comparing the categories of the construction costs made by specific construction process, belonging to the construction costs, with the operational budget made in the beginning of the project that can enable to grasp unpredictable risks over the construction costs and making quantitative analysis for it through analyzing the range of fluctuation and variations led by the fluctuations in the actual construction costs.

Effect of Panax ginseng on the Graft-versus-Host Reaction, Production of Leucocyte Migration Inhibitory Factor and Expulsion of Adult Trichinella spiralis in Mice (인삼이 이식편대숙주반응, 대식세포유주저지반응 및 Trichinella spiralis의 expulsion에 미치는 영향)

  • Ha, Tai-You;Lee, Jeong-Ho;Kim, Sang-Hyung
    • The Journal of the Korean Society for Microbiology
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    • v.21 no.1
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    • pp.133-144
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    • 1986
  • This study was undertaken to assess the effect of ginseng administration on T lymphocyte induced local xenogenic graft-versus-host(GVM) reactions which were induced with thymocyte, spleen cell and lymph node cell of ICR mice. Mice received daily 10mg of 70% alcohol ginseng extract oral1y for 100days and control mice remained untreated for the same period of time. The cells from donor mice were injected intradermally into the closely shaven abdominal skin of Sprague-Dawley rats for GVH tests. The thymocyte from control(ginseng-untreated) mice showed a negative local GVH reaction, whereas thymocyte from experimental(ginseng-treated) mice showed a positive reaction with the rate of 17.4%. When spleen cells were injected, the incidence of positive local GVH reaction was 66.7% among ginseng-treated mice, as opposed to incidence of 45.5% of positive local GVH reaction among control mice. The incidence of positive local GVH reaction of the lymph node cells when injected into a recipient was 71.4% among ginseng-treated mice as compared with that of 18.9% among control mice. The relationship between spleen cell inoculum and intensity of the local GVH reaction was assessed in ginseng-untreated mice. The intensity of GVH reaction clearly appears to be dose related. In ginseng-treated mice, a minimum of $1{\times}10^7$ spleen cell was required for production of positive local GVH reaction with almost linear relationship up to an inoculum of $5{\times}10^8$ cells. In control mice, however, a minimum of $1{\times}10^8$ spleen cells was required for positive GVH reaction. These results strongly suggest that the ginseng administration augments significantly the local xenogenic GVH reaction which was used to assess T lymphocyte function and immunocompetence of mice and in addition to this, these results appear to support previous suggestions that the local GVH reaction consitutes a qualitative test of the functional activity of T lymphocytes. These results may be the first to induce local GVH reaction, employing rats as recipient and mice as donor. This study was also desingned to investigate some of the effects of ginseng extract on lymphocyte-macrophage interactions. This was accomplished by in vitro quantification of 1) migratory inhibitory factor(MIF) synthetic capacity of splenic lymphocytes in mice previously primed with ginseng 2) MIF responsiveness of mouse peritoneal macrophages or chicken peripheral leucocytes under the presence of ginseng extract 3) migration ability of chicken peripheral leucocytes by direct stimulation of ginseng extract or ginseng saponin and 4) immunosuppressive effects of immunosuppressants such as cyclophosphamide, cyclosporin A or dexamethasone. Mice divided equally into the ginseng and the saline groups, which received intraperitoneally daily 0.2ml of ginseng absolute alcohol-extract(5mg/ml) and same amount of saline for 15 days, respectively. The cellular immune responsiveness of these mice was assayed 15 days after ginseng pretreatment. Splenic lymphocytes of mice treated with ginseng, when stimulated with sensitized specific-antigen such as sheep red blood cells or toxoplasmin, or with polyclonal activator concanavalin A, produced significantly more MIF than those of control saline group. MIF responsiveness of normal mouse macrophages was significantly augmented when assayed under the presence of ginseng extract (1mg/ml). The migratory ability of normal chicken leucocytes in the absence of MIF was significantly decreased by the stimulation of ginseng extract alone. MIF response was significantly decreased by immunosuppressants and this impaired response was not restored by ginseng pretreatment. This study was additionally performed to evaluate the effect of ginseng on the expulsion of adult Trichinella spiralis in mice. ICR mice were infected experimentally by esophageal incubation of 300 T. spiralis infective muscle larvae prepared by acid-pepsin digestion of infected mice. and received oral administration of 70% alcohol ginseng extract(10mg/mouse/day) for the indicated days plus 4 days before infection. At various times after infection, the number of adult T. spiralis worms in small intestines was determined. Interestingly, ginseng-treatment was accompanied by accelerated expulson of T. spiralis. These results led to the conclusion that Panax ginseng caused some enhancing effect on GVH reaction, macrophage migration inhibition reaction and expulsion of T. spiralis. In addition these results suggested that the mechanisms responsible for this enhancement of ginseng may be chiefly or partially due to nonspecific stimulation of cell-mediated immune response.

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A Study on the Characteristics of Humic Materials Extracted from Decomposing Plant Residues -I. Chemical Properties of Humic Acids from Plant Residues Characterized by IR Spectra (식물성(植物性) 유기물질(有機物質)의 부숙과정중(腐熟過程中) 부식특성(腐植特性)에 관(關)한 연구(硏究) -1. 분광분석(分光分析)에 의(依)한 식물잔해(植物殘骸) 부식산(腐植酸)의 화학적(化學的) 성질규명(性質糾明))

  • Kim, Jeong-Je;Shin, Young-Oh
    • Korean Journal of Soil Science and Fertilizer
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    • v.20 no.3
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    • pp.251-259
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    • 1987
  • Humic acids extracted from decomposing plant residues were characterized by infrared(IR) spectra. The IR spectra were further interpreted by chemical analyses for oxygen-containing functional groups such as carboxyl, phenolic, alcoholic, carbonyl, and quinionic groups. 1. The IR spectra obtained in this study were divied into three categories: spectra of humic acids from grain crop straws of rice, barley, wheat and rye produced Type I, while that from wild grass hay yielded Type II, and those from forest tree litter of the deciduous and conifers were led to give Type III. 2. There were no significant changes in the absorption bands observed among humic acids extracted at various stages of decomposition of a given Plant material. 3. The absorption band at about $3,430cm^{-1}$ represents the presence of hydrogen-bonded hydroxyl groups, phenolic-OH groups being the major component. 4. A close relationship was found between the total acidity and the content of phenolic-OH groups of humic acids. The content of carboxyl groups maintains a direct relationship with the content of total hydroxyl groups, and such a close relationship also exists between the content of alcoholic hydroxyls and that of total hydroxyl groups. 5. Overlapping of the absorption bands of carbonyl groups and quinones renders it difficult to make differentiation between the two. 6. A variety of non-armoatic cyclic hydrocarbons appears to be a structural component as evidenced by a sharp absorption peak near $995-1000cm^{-1}$.

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A Case Study on Characteristics of the Mathematics Gifted Children (수학영재의 특성에 관한 사례연구)

  • Kim, Min-Jung;Ryu, Sung-Rim
    • Education of Primary School Mathematics
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    • v.10 no.1 s.19
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    • pp.41-56
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    • 2007
  • Related with the mathematics gifted children the situation of different case studies is the research which is limited in mathematics problem solving process of the most mathematics gifted children. The research which it sees hereupon observes from the scope which is wider the quality of the mathematics gifted children, before the hazard mathematics gifted children whom it sees enter into the mathematics gifted children education center unit life and life after studying living and dismissal of a class from the general school, namely for their general life it leads compared to attitude it observes the reporter it does a quality. For a what kind of interest in the mathematics gifted children, the research leads the family or general class, from the gifted children education center it has it considers encouragement, map and to give a help to good mathematics gifted children education activation, it does. It will reach and to respect with afterwards it set a same three research problem. First, before entering into the mathematics gifted children education center, are the mathematics gifted children what kind of quality? Second, Are the mathematics gifted children what kind of quality for general school hour? Third, Are the mathematics gifted children what kind of quality after dismissal of a class after hour? Being selected in the hazard gifted children education center which solves an up research problem, simple characteristic and approach ease characteristic, by the condition of the permission possibility back it selected 2 person gifted children school boxes which are coming and going. And, before entering into these mathematics gifted children education center, studying life from the general school, life after dismissal of a class it will extend at 1 years, various recording it will ask and it collected direct observation and interview it led against their quality it analyzed. It shared the result which it analyzes with emotional quality, studying conduct qualities, general qualities of the mathematics gifted children and qualities of mathematics gifted children parents. Studies level of the mathematics gifted children parents high facility when them are young from, the interest and helping out which it has were considerable, to advance with the direction where in order for always with great disaster them are proper the map it did. In general quality of the mathematics gifted children from young age the ability which finds a language and a possibility concept superiorly the ability which expresses the thought of oneself logically was superior, the competitive spirit was high, it liked it came reading, a leader role, to reveal a deepening school with the fact that it comes and goes. Also it will burn with their studying conduct quality and it will roll and it did deeply and it arranged knot eagerly, accomplishing which is superior from the field which is various it showed, the originality was superior, the subject attachment power was high quite, oneself it studies it has a devotion the possibility of knowing it was. And, the social characteristic of the friends and is good with their emotional quality and it does there is own reflection and an encouragement at any time and also a confidence, but just as good as the stress also it receives the possibility of knowing it was to him.

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The Effects of Internal Competence and Growth Stages on the Performance of Venture Business : the Moderating Effect in Connection with Government Funding Utilization (벤처기업의 내부역량과 성장단계가 경영성과에 미치는 영향 : 정부 지원자금 활용의 조절효과를 중심으로)

  • Kim, Yoonjung;Suh, Yoonkyo;Hong, Jungim
    • Journal of Korea Technology Innovation Society
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    • v.21 no.2
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    • pp.636-662
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    • 2018
  • Recently, the Moon administration established the Ministry of Small and Medium-sized Enterprises (SMEs) and Startups, as part of its national strategy for start-up and innovation growth led by small and medium-sized venture companies. In a slowing economy, as venture companies with excellent internal competencies are seen to be favorable to growth, the government funding for technology development is becoming increasingly important. Previous studies examine the internal competence factors that can strengthen competitiveness through self-efforts and the influence structure of growth stage, which is an important factor in industrial environment, on business performance. As the government support for venture firms has been strengthened, the effect of government funding on the management performance and technological innovation performance of venture firms have been recently discussed in various ways. However, there is a lack of precedent research on the moderating effect of the utilization of government funding on the existing influence structure in which firm's internal competence and growth stages affects business performance. Therefore, this study examined whether the internal competencies of the venture firms and the stage of growth have direct effects on business performance and analyzed the moderating effect in connection with government funding utilization under these influence structures. The results of the study are as follows. First, the utilization of government funding in the venture firms whose R&D personnel ratio is relatively low, not to have own brands and showed an increase of employees has a significantly positive influence on business performance. Second, the moderating effects of the government funding utilization at the high growth stage of the venture firms are shown significantly. These results suggest that the venture policy linked to the job creation of the present government requires not only the support considering R&D personnel but also the necessity of supporting human resources policy to a greater extent and further study on the effectiveness of venture firms in the high growth stage.

Recent Developments in Space Law (우주법(宇宙法)의 최근동향(最近動向))

  • Choi, June-Sun
    • The Korean Journal of Air & Space Law and Policy
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    • v.1
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    • pp.223-243
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    • 1989
  • The practical application of modern space science and technology have resulted in many actual and potential gains of mankind. These successes have conditioned and increased the need for a viable space law regime and the challenge of space has ultimately led to the formation of an international legal regime for space. Space law is no longer a primitive law. It is a modern law. Yet, in its stages of growth, it has not reached the condition of perfection. Therefore, under the existing state of thing, we could carefully say that the space law is one of the most newest fields of jurisprudence despite the fact that no one has so far defined it perfectly. However, if space law can be a true jurisprudential entity, it must be definable. In defining the space law, first of all, the grasp of it's nature iis inevitable. Although space law encompasses many tenets and facets of other legal discriplines, its principal nature is public international law, because space law affects and effects law relating intercourse among nations. Since early 1960s when mankind was first able to flight and stay in outer space, the necessity to control and administrate the space activities of human beings has growingly increased. The leading law-formulating agency to this purpose is the United Nation's ad hoc Committee on Peaceful Uses of Outer Space("COPUOS"). COPUOS gave direction to public international space law by establishing the 1963 Declaration of Legal Principles Governing the Activities of the States in the Exploration and Use of Outer Space("1963 Declaration"). The 1963 Declaration is very foundation of the five international multilateral treaties that were established successively after the 1963 Declaration. The five treaties are as follows: 1) The Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space including Moon and other Celestial Bodies, 1967. 2) The Agreement on the Rescue of Astronauts, the Return of Astronauts, and the Return of Objects Launched into Outer Space, 1968. 3) The Convention on International Liability for Damage Caused by Space Objects, 1972. 4) The Convention on Registration of Objects Launched into Outer Space, 1974. 5) The Agreement Governing Activities of States on the Moon and Other Celestial Bodies: Moon Treaty, 1979. The other face of space law is it's commercial aspect. Space is no longer the sole domination of governments. Many private enterprise have already moved directly or indirectly into space activities in the parts such as telecommunications and space manufacturing. Since space law as the public international law has already advanced in accordance with the developments of space science and technology, there left only a few areas untouched in this field of law. Therefore the possibility of rapid growth of space law is expected in the parts of commerical space law, as it is, at this time, in a nascent state. The resources of the space environment are also commercially both valuable and important since the resources include the tangible natural resources to be found on the moon and other celestial bodies. Other space-based resources are solar energy, geostationary and geosynchronous orbital positions, radio frequencies, area possibly suited to human habitations, all areas and materials lending themselves to scientific research and inquiry. Remote sensing, space manufacturing and space transportation services are also another potential areas in which commercial. endeavors of Mankind can be carried out. In this regard, space insurance is also one of the most important devices allowing mankind to proceed with commercial space venture. Thus, knowlege of how space insurance came into existence and what it covers is necessary to understand the legal issues peculiar to space law. As a conclusion the writer emphasized the international cooperation of all nations in space activities of mankind, because space commerce, by its nature, will give rise many legal issues of international scope and concern. Important national and world-community interests would be served over time through the acceptance of new international agreements relating to remote sencing, direct television broadcasting, the use of nuclear power sources in space, the regularization of the activities of space transportation systems. standards respecting contamination and pollution, and a practical boundary between outer space and air space. If space activity regulation does not move beyond the national level, the peaceful exploration of space for all mankind will not be realized. For the efficient regulation on private and governmental space activities, the creation of an international space agency, similar to the International Civil Aviation Organization but modified to meet the needs of space technology, will be required. But prior to creation of an international organization, it will be necessary to establish, at national level, the Office of Air and Space Bureau, which will administrate liscence liscence application process, safety review and sale of launch equipment, and will carry out launch service.

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A Methodology for Extracting Shopping-Related Keywords by Analyzing Internet Navigation Patterns (인터넷 검색기록 분석을 통한 쇼핑의도 포함 키워드 자동 추출 기법)

  • Kim, Mingyu;Kim, Namgyu;Jung, Inhwan
    • Journal of Intelligence and Information Systems
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    • v.20 no.2
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    • pp.123-136
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    • 2014
  • Recently, online shopping has further developed as the use of the Internet and a variety of smart mobile devices becomes more prevalent. The increase in the scale of such shopping has led to the creation of many Internet shopping malls. Consequently, there is a tendency for increasingly fierce competition among online retailers, and as a result, many Internet shopping malls are making significant attempts to attract online users to their sites. One such attempt is keyword marketing, whereby a retail site pays a fee to expose its link to potential customers when they insert a specific keyword on an Internet portal site. The price related to each keyword is generally estimated by the keyword's frequency of appearance. However, it is widely accepted that the price of keywords cannot be based solely on their frequency because many keywords may appear frequently but have little relationship to shopping. This implies that it is unreasonable for an online shopping mall to spend a great deal on some keywords simply because people frequently use them. Therefore, from the perspective of shopping malls, a specialized process is required to extract meaningful keywords. Further, the demand for automating this extraction process is increasing because of the drive to improve online sales performance. In this study, we propose a methodology that can automatically extract only shopping-related keywords from the entire set of search keywords used on portal sites. We define a shopping-related keyword as a keyword that is used directly before shopping behaviors. In other words, only search keywords that direct the search results page to shopping-related pages are extracted from among the entire set of search keywords. A comparison is then made between the extracted keywords' rankings and the rankings of the entire set of search keywords. Two types of data are used in our study's experiment: web browsing history from July 1, 2012 to June 30, 2013, and site information. The experimental dataset was from a web site ranking site, and the biggest portal site in Korea. The original sample dataset contains 150 million transaction logs. First, portal sites are selected, and search keywords in those sites are extracted. Search keywords can be easily extracted by simple parsing. The extracted keywords are ranked according to their frequency. The experiment uses approximately 3.9 million search results from Korea's largest search portal site. As a result, a total of 344,822 search keywords were extracted. Next, by using web browsing history and site information, the shopping-related keywords were taken from the entire set of search keywords. As a result, we obtained 4,709 shopping-related keywords. For performance evaluation, we compared the hit ratios of all the search keywords with the shopping-related keywords. To achieve this, we extracted 80,298 search keywords from several Internet shopping malls and then chose the top 1,000 keywords as a set of true shopping keywords. We measured precision, recall, and F-scores of the entire amount of keywords and the shopping-related keywords. The F-Score was formulated by calculating the harmonic mean of precision and recall. The precision, recall, and F-score of shopping-related keywords derived by the proposed methodology were revealed to be higher than those of the entire number of keywords. This study proposes a scheme that is able to obtain shopping-related keywords in a relatively simple manner. We could easily extract shopping-related keywords simply by examining transactions whose next visit is a shopping mall. The resultant shopping-related keyword set is expected to be a useful asset for many shopping malls that participate in keyword marketing. Moreover, the proposed methodology can be easily applied to the construction of special area-related keywords as well as shopping-related ones.

Mapping Categories of Heterogeneous Sources Using Text Analytics (텍스트 분석을 통한 이종 매체 카테고리 다중 매핑 방법론)

  • Kim, Dasom;Kim, Namgyu
    • Journal of Intelligence and Information Systems
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    • v.22 no.4
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    • pp.193-215
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    • 2016
  • In recent years, the proliferation of diverse social networking services has led users to use many mediums simultaneously depending on their individual purpose and taste. Besides, while collecting information about particular themes, they usually employ various mediums such as social networking services, Internet news, and blogs. However, in terms of management, each document circulated through diverse mediums is placed in different categories on the basis of each source's policy and standards, hindering any attempt to conduct research on a specific category across different kinds of sources. For example, documents containing content on "Application for a foreign travel" can be classified into "Information Technology," "Travel," or "Life and Culture" according to the peculiar standard of each source. Likewise, with different viewpoints of definition and levels of specification for each source, similar categories can be named and structured differently in accordance with each source. To overcome these limitations, this study proposes a plan for conducting category mapping between different sources with various mediums while maintaining the existing category system of the medium as it is. Specifically, by re-classifying individual documents from the viewpoint of diverse sources and storing the result of such a classification as extra attributes, this study proposes a logical layer by which users can search for a specific document from multiple heterogeneous sources with different category names as if they belong to the same source. Besides, by collecting 6,000 articles of news from two Internet news portals, experiments were conducted to compare accuracy among sources, supervised learning and semi-supervised learning, and homogeneous and heterogeneous learning data. It is particularly interesting that in some categories, classifying accuracy of semi-supervised learning using heterogeneous learning data proved to be higher than that of supervised learning and semi-supervised learning, which used homogeneous learning data. This study has the following significances. First, it proposes a logical plan for establishing a system to integrate and manage all the heterogeneous mediums in different classifying systems while maintaining the existing physical classifying system as it is. This study's results particularly exhibit very different classifying accuracies in accordance with the heterogeneity of learning data; this is expected to spur further studies for enhancing the performance of the proposed methodology through the analysis of characteristics by category. In addition, with an increasing demand for search, collection, and analysis of documents from diverse mediums, the scope of the Internet search is not restricted to one medium. However, since each medium has a different categorical structure and name, it is actually very difficult to search for a specific category insofar as encompassing heterogeneous mediums. The proposed methodology is also significant for presenting a plan that enquires into all the documents regarding the standards of the relevant sites' categorical classification when the users select the desired site, while maintaining the existing site's characteristics and structure as it is. This study's proposed methodology needs to be further complemented in the following aspects. First, though only an indirect comparison and evaluation was made on the performance of this proposed methodology, future studies would need to conduct more direct tests on its accuracy. That is, after re-classifying documents of the object source on the basis of the categorical system of the existing source, the extent to which the classification was accurate needs to be verified through evaluation by actual users. In addition, the accuracy in classification needs to be increased by making the methodology more sophisticated. Furthermore, an understanding is required that the characteristics of some categories that showed a rather higher classifying accuracy of heterogeneous semi-supervised learning than that of supervised learning might assist in obtaining heterogeneous documents from diverse mediums and seeking plans that enhance the accuracy of document classification through its usage.

Relationship between Innovation Performance and R&D Investment: The Mediating Role of Entrepreneurial Orientation (과거 혁신성과와 R&D 투자 간의 관계와 기업가 지향성의 매개효과에 대한 연구)

  • Han, Su-Kyeong;Yoo, Jae-Wook;Kim, Choo-Yeon
    • Management & Information Systems Review
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    • v.36 no.3
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    • pp.219-237
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    • 2017
  • Looking into the top-five innovative sectors in Korea's manufacturing and service industries, this study empirically analyzes the effect of innovation performance on R&D investment, which is one of the most important strategic decisions for corporate management. In the midst of an uncertain business environment, R&D investment has been regarded as the most important strategic decision making in corporate management related to innovation. Corporate management, however, tend to be reluctant to make sufficient R&D investment due to the risk of an investment failure. Therefore, having R&D investment by offsetting this risk has been deemed as a key task for corporate management. However, prior studies have failed to identify which factors affect companies' strategic decision making on R&D investment. This study is to remedy this weakness of prior study. Relying on path dependency theory at organization-level and dominant logic at individual-level, this study empirically examines the multiple regression model, which sees entrepreneurial orientation as a positive mediator between innovation performance and R&D investment. The results found in the analysis of 242 local companies in the manufacturing and service sectors represent that innovation performance has a direct and positive effect on R&D investment, while it indirectly affects R&D investment through the mediating roles of entrepreneurial orientation. They also revealed that innovation performance had a meaningful impact on entrepreneurial orientation, which is an inclination to seek innovation, led to R&D investment. The founding of this study imply that innovation performance in the past affects innovation strategies in the future, and such a relationship could be strengthened by entrepreneurial orientation as the dominant logic of corporate management.

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Relationships of Physiological Activity and Anatomical Structure to the Wilting Phenomena in Rice Plant 2. Relationships between the anatomical structure and wilting phenomena of rice variety "Yushin" (수도품종의 위조현상과 생리 및 형태해부학적 구조와의 관련성에 관한 연구 제2보 유신벼의 위조현상발생과 형태해부학적 구조와의 관계)

  • Jong-Hoon Lee
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.25 no.2
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    • pp.6-14
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    • 1980
  • One of the physiological disease, sudden wiliting of Yushin variety suggested that low sunlight, excessive nitrogen application, and highly reduced soil condions either singly or combined, might be possible causes of the disorder. Some visual symptom of sudden wilting are discoloration of leaves, development of nodal roots above the soil surface, total root rot, and lodging. Those observations led to the hypothesis that suffocation of root tissues was a direct cause of the wilting. The oxygen transport characteristics of Yushin, IR262 and Tongil were examined by two methods. First, Soil-cultured plants of the three varieties were subjected to paraffin treatment to decrease the oxygen supply from the air to root tissues through the soil-water system, liquid paraffin was applied to the water surface in the pots at panicle formation stage. In this experiment, sudden wilting was observed of Yushin and IR262 at about a week after the treatment, but Tongil remained green and healthy. Wilting-resistant variety Tongil had higher oxygen release, whereas the susceptible Yushin and IR262 had lower oxygen release. Second, the number and size of the air spaces in each internode were investigated in the 5th internode from the top, all three varieties have a similar number of air spaces, although the air spaces of Thongil were larger. In the 4th internode, Tongil had plenty air spaces, Yushin and one of the Yushin's parents IR262 had scanty or none. The observations indicated that the ability of Yushin and IR262 for oxygen transport is very limited compared with that of Tongil. The limited oxygen supply due to poor development of air space in internode of rice plants may cause suffocation of root tissues, weaken metabolic activity of the tissues, and induce root rot, subsequently inducing sudden wilting and lodging under unfavorable weather, soil and cultural conditions.

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