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Oxide perovskite crystals type ABCO4:application and growth

  • Pajaczkowska, A.
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • 1996.06a
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    • pp.258-292
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    • 1996
  • In the last year great interest appears to YBCO thin films preparation on different substrate materials. Preparation of epitaxial film is a very difficult problem. There are many requirements to substrate materials that must be fullfilled. Main problems are lattice mismatch (misfit) and similarity of structure. From paper [1] or follows that difference in interatomic distances and angles of substrate and film is mire important problem than similarity of structure. In this work we present interatomic distances and angle relations between substrate materials belonging to ABCO4 group (where A-Sr or Ca, B-rare earth element, C-Al or Ga) of different orientations and YBCO thin films. There are many materials used as substrates for HTsC thin films. ABCO4 group of compounds is characterized by small dielectric constants (it is necessary for microwave applications of HTsC films), absence of twins and small misfit [2]. There most interesting compounds CaNdAlO4, SrLaAlO4 and SrLaGaO4 were investigated. All these compounds are of pseudo-perovskite structure with space group 14/mmm. This structure is very similar to structure of YBCO. SLG substrate has the lowest misfit (0.3%) and dielectric constant. For preparation of then films of substrates of this group of compound plane of <100> orientation are mainly used. Good quality films of <001> orientations are obtained [3]. In this case not only a-a misfit play role, but c-3b misfit is very important too. Sometimes, for preparation of thin films substrates of <001> and <110> orientations were manufactured [3]. Different misfits for different YBCO faces have been analyzed. It has been found that the mismatching factor for (100) face is very similar to that for (001) face so there is possibility of preparation of thin films on both orientations. SrLaAlO4(SLA) and SrLaGaO4(SLG) crystals of general formula ABCO4 have been grown by the Czochralski method. The quality of SLA and SLG crystals strongly depends on axial gradient of temperature and growth and rotation rates. High quality crystals were obtained at axial gradient of temperature near crystal-melt interface lower than 50℃/cm, growth rate 1-3 mm/h and the rotation rate changing from 10-20pm[4]. Strong anisotropy in morphology of SLA and SLG single crystals grown by the Czochralski method is clearly visible. On the basics of our considerations for ABCO4 type of the tetragonal crystals there can appear {001}, {101}, and {110} faces for ionic type model [5]. Morphology of these crystals depend on ionic-covalent character of bonding and crystal growth parameters. Point defects are observed in crystals and they are reflected in color changes (colorless, yellow, green). Point defects are detected in directions perpendicular to oxide planes and are connected with instability of oxygen position in lattice. To investigate facets formations crystals were doped with Cr3+, Er3+, Pr3+, Ba2+. Chromium greater size ion which is substituted for Al3+ clearly induces faceting. There appear easy {110} faces and SLA crystals crack even then the amount of Cr is below 0.3at.% SLG single crystals are not so sensitive to the content of chromium ions. It was also found that if {110} face appears at the beginning of growth process the crystal changes its color on the plane {110} but it happens only on the shoulder part. The projection of {110} face has a great amount of oxygen positions which can be easy defected. Pure and doped SLA and SLG crystals measured by EPR in the<110> direction show more intensive lines than in other directions which allows to suggest that the amount of oxygen defects on the {110} plane is higher. In order to find the origin of colors and their relation with the crystal stability, a set of SLA and SLG crystals were investigated using optical spectroscopy. The colored samples exhibit an absorption band stretching from the UV absorption edge of the crystal, from about 240 nm to about 550 m. In the case of colorless sample, the absorption spectrum consists of a relatively weak band in the UV region. The spectral position and intensities of absorption bands of SLA are typical for imperfection similar to color centers which may be created in most of oxide crystals by UV and X-radiation. It is pointed out that crystal growth process of polycomponent oxide crystals by Czochralski method depends on the preparation of melt and its stoichiometry, orientation of seed, gradient of temperature at crystal-melt interface, parameters of growth (rotation and pulling rate) and control of red-ox atmosphere during seeding and growth (rotation and pulling rate) and control of red-ox atmosphere during seeding and growth. Growth parameters have an influence on the morphology of crystal-melt interface, type and concentration of defects.

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A Study on the Governance of U.S. Global Positioning System (미국 글로벌위성항법시스템(GPS)의 거버넌스에 관한 연구 - 한국형위성항법시스템 거버넌스를 위한 제언 -)

  • Jung, Yung-Jin
    • The Korean Journal of Air & Space Law and Policy
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    • v.35 no.3
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    • pp.127-150
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    • 2020
  • A Basic Plan for the Promotion of Space Development (hereinafter referred to as "basic plan"), which prescribes mid- and long-term policy objectives and basic direction-setting on space development every five years, is one of the matters to be deliberated by the National Space Committee. Confirmed February 2018 by the Committee, the 3rd Basic Plan has a unique matter, compared to the 2nd Basic Plan. It is to construct "Korean Positioning System(KPS)". Almost every country in the world including Korea has been relying on GPS. On the occasion of the shooting down of a Korean Air flight 007 by Soviet Russia, GPS Standard Positioning Service has been open to the world. Due to technical errors of GPS or conflict of interests between countries in international relations, however, the above Service can be interrupted at any time. Such cessation might bring extensive damage to the social, economic and security domains of every country. This is why some countries has been constructing an independent global or regional satellite navigation system: EU(Galileo), Russia(Glonass), India(NaVic), Japan(QZSS), and China(Beidou). So does South Korea. Once KPS is built, it is expected to make use of the system in various areas such as transportation, aviation, disaster, construction, defense, ocean, distribution, telecommunication, etc. For this, a pan-governmental governance is needed to be established. And this governance must be based on the law. Korea is richly experienced in developing and operating individually satellite itself, but it has little experience in the simultaneous development and operation of the satellites, ground, and users systems, such as KPS. Therefore we need to review overseas cases, in order to minimize trial and error. U.S. GPS is a classic example.

Perceptions of Clothing Norms Clothing Behavior and their Relations to Psychological Variables of College Student (남녀 대학생의 의복규범에 대한 의식과 복식행동 및 심리적변인에 관한 연구)

  • 박찬부
    • Journal of the Korean Society of Costume
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    • v.31
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    • pp.165-188
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    • 1997
  • This study aims at 1) examining the perceived importance of clothing norms 2) examining relationship between perceptions of clothing norms clothing behavior and psycho-logical variables-ego identity(uniqueness and self acceptance) and sex role identity and 3) ascertaining any significant differences in the level of the perceived importance of clothing norms among variables-sex role identity and the uniqueness in psychological variables-and which variables are influencingon perception of clothing norms. The perception of cloth in norms inventory clothing norms inventory clothin behavior inventory ego identity in-ventory and the Bem Sex Role Inventory were administered to 620 college students. Sex role identity was classified into androgynous mas-culine feminine and undifferentiated type. Subjects were asked to rate each statement on the clothing norms under two kinds of instructions: their attitudes(TATT) and their beliefs about the expectations of others toward clothing norms(TBEO). 1) The scores of 3 TBEO of the students were higher than the scores of TATT. But the scores of TBEO concerning modesty of students were lower than the scores of TATT. Discrepancy scores of TATT and TBEO of the students were revealed significances differently according to clothing norms. males lower and higher class students had more free attitudes to the norms concerning genaral clothing attitudes. Females and higher class students had less free attitudes to the clothing norms concerning modesty. Females and lower and higher class students had more free attitudes to the norms concening sex-role related clothing attitudes but male students had less free to the sex-role related clothing norms. 2) Significant negative correlations between each variable of clothing norms and conform-ity-individuality were found. But negative correlations between those variables of the males and lower class students were higher than the correlations of the female and higher class students and the former had more posi-tive relationships with clothing norms and con-formity as compared with the latter. And sig-nificant positive correlations between each variable of clothing norms and modesty were found. But positive correlations between those variables of the males females and higher class students were higher than the correlations of the lower class students and the latter had less positive relationship with clothing norms and modesty as compared with the former. 3) Significant negative correlations between clothing norms and uniqueness were found in the subjects groups. The females and lower class students had more negative relationships with clothing norms and uniqueness as compared with the male and higher class students. Significant positive correlations be-tween uniqueness and conformity-individuality were found in all subjects groups, Therefore the higher uniqueness the student have the less they perceive theimportance of clothing norms and the more they have individuality. Significant positive correlations between sex-role related(higher class) general(female) clothing norms and self acceptance were found. but significant negative correlations be-tween campus style(higher class) general(female) clothing norms and self acceptance were found. But significant negative correlations be-tween campus style(males lower class, higher class) clothing norms and self acceptance were found. Clothing norms therfore related posi-tively or negatively with self acceptance ac-cording to the subjects groups. And significant negative correlations between conformity in-dividuality and self acceptance was found in higher class students. 4) The female masculine groups and the masculine groups of lower class revealed high scores than the scores of andrgynous group and undifferentiated group in clothing norms concerning modesty. And the feminine group revealed high scores in conformity-individu-ality than the scores of the masculine group. Male masculine and feminine group revealed high scores in clothing norms concerning cam-pus style than the scores of the androgynous group. The masculine group and feminine group of the lower classes revealed high scores in general clothing norms than the scores of the androgynous group. 5) The most influencing variables on the clothing norms were sex conformity-individu-altiy and masculine-feminine variables in the right order. The general clothing norms and clothing norms concerning modesty were influened by the sex role identity but the sex role related clothing norms and clothing norms concerning campus style were influenced by the ego identity. 6) Based on the sum scores of the uniqueness each group of the subjects was separately segmened into "high medium and low" groups. By the analysis of variances sig-nificant differences in discrepancy scores of TBEO and TATT among 3 uniqueness level groups were found on all clothing norms variables in all students three clothing norms variables in male and female students and one clothing norms variable in lower and higher students and in each clothing norms variable the mean discrepancy scores of the high uniqueness group were higher than those of the other groups. The findings indicated that the differences in the discrepancy score mainly contributed to the results of correla-tions described above.bed above.

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Performance of Collaboration Activities upon SME's Idiosyncrasy (중소기업 특성에 따른 외부 협업 활동이 혁신성과에 미치는 영향)

  • Lee, Hye Sun;Oh, Junseok;Lee, Jaeki;Lee, Bong Gyou
    • Journal of Internet Computing and Services
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    • v.14 no.6
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    • pp.95-105
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    • 2013
  • Recently, SME's Collaboration activities have become one of a vital factor for sustaining competitive edge. This is because of the rapidly changing and competitive market environment, and also to leverage performance by overcoming obstacles of having limited internal resources. Discussing about the effects and relationships of the firm's collaboration activities and its outputs are not new. However, as ICT and various technologies have been diffused into the traditional industries, boundaries and practice capabilities within the industries are becoming ambiguous. Thus contents of the products/services and their development methods are also go and come over the industries. Although many researchers suggested the relations of SME's collaboration activities and innovation performances, most of the previous literatures are focusing on broad perspectives of firm's environmental factors rather than considering various SME's idiosyncrasy factors such as their major product and customer types at once. Therefore, the purpose of this paper is to analyze how SME(Small Medium Enterprise)'s external collaboration activities by their idiosyncrasy act as an input to types of innovation performance. In order to analyze collaboration effects in detail, we defined factors that can represent the SME's business environment - Perceived importance of using external resources, Perceived importance of external partnership, Collaboration and Collaboration levels of Major Product types, Customer types and lastly the Firm Sizes. We have also specifically divided the performance of innovation types as product innovation and process innovation based on existing research. In this study, the empirical analysis is based on Probit Regression Model to observe the correlations with the impact of each SME's business environment and their activities. For the empirical data, 497 samples were collected which, this sample data was extracted from the 'Korean Open Innovation Survey' performed by ETRI(Korean Electronics Telecommunications Research Institute) in 2010. As a result, empirical test results indicated that the impact of collaboration varies depend on the innovation types (Product and Process Innovation). The Impact of the collaboration level for the product innovation tend to be more effective when SMEs are developing for a final product, targeting on for individual customers (B2C). But on the other hand, the analysis result of the Process innovation tend to be higher than the product innovation, when SMEs are developing raw materials for their partners or to other firms targeting on for manufacturing industries(B2B). Also perceived importance of using external resources has effected to both product and process innovation performance. But Perceived importance of external partnership was statistically insignificant. Interesting finding was that the service product has negative effects on for the process innovation performance. And Relationship between size of the firms and their external collaboration activities with their performance of the innovations indicated that the bigger firms(over 100 of employees) tend to have better for both product and process innovations. Finally, implications of the results can be suggested as performance of innovation can be varied depends on firm's unique business idiosyncrasy as well as levels of external collaboration activities. The Implication of this research can be considered for firms in selecting an appropriate strategy as well as for policy makers.

An Analysis of the National Suicide Rate in Korea during 2005 (2005년 전국 자살실태 분석)

  • Kim, Gi-Jeong;Kwak, Jyung-Sik
    • Journal of forensic and investigative science
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    • v.2 no.1
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    • pp.5-22
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    • 2007
  • From the numerous social problems generated by the unbalanced social development and the social trend of belittling life overall, we found the causes of suicide getting worse in its seriousness day by day. In reality, the problem has been approached in a collateral level in contrast with other social problems. There have been an active involvement in studying the definition, causes and ways of prevention of suicide theoretically until now. However, different from other social problems, it is almost impossible to treat or fix the problem of suicide. Only ways to treat or fix the problem is when the suicide has ended in failure. Thus, this study intends to examine the suicide rate among the total accidents during the year 2005, perform the analyses on the actual causes according to the relations such as the means of suicide, occupation, age group, educational background, etc. In order to present a solution to the issue of suicide becoming serious each day. Among the total accidents in 2005, the suicide rate came out to be approximately 52.4%. Among the result, 52.4%, male with 69% resulted higher than female with 31%, which appears to be related to the social functions. While men tends to take more active(80%) means of suicide like jumping off, poison, hanging, etc., women tends to take more passive(60%) means of suicide like sleeping pills, slitting wrist, etc. In terms of the cause, pessimism, illness, denial, mental disorder, etc resulted more than 75%, and there were many cases of suicide after exhibiting the signs of depression. Also there were higher suicide rate of the unemployed engaged in direct labor with educational background lower than college level related to the pessimism regarding the family living cost. We were able to determine the recent increase in the suicidal tendency of the educated people higher than the college level and the retired people with depression caused by the sudden change in social status. Overall there are several reasons for suicide, however, in most cases the signs of depression were exhibited until the final suicide, which tells us the serious psychological problem of suicide. Assuming that the current development of suicide will continue in future, the result of this study will guide the corresponding social policies, be utilized in preparing the insurance or management at the national level dealing with the real social problems that are not just a conflict of an individual, but could spread like a fad and become much bigger than the present by the continuous support at the environmental, social and political levels, and be utilized as the basic data to establish the research plan.

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Type and Dependency of R&D Cooperation Partners and Innovation Performance: An Empirical Study with Korean Venture Firms (R&D 협력 파트너 유형 및 의존도와 혁신의 성과: 한국 벤처기업들을 대상으로 한 실증연구)

  • Kim, Nami;Kim, Eonsoo
    • The Journal of Small Business Innovation
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    • v.19 no.4
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    • pp.1-17
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    • 2016
  • The purpose of this study is to suggest an efficient way for ventures to achieve innovation performance through R&D cooperative arrangements. Achieving innovation is one of the critical factors for the survival of ventures. Unlike established firms, ventures often do not have the specialized assets necessary to take technological developments to the product and market stages. Young and resource-constrained firms can achieve innovation by finding and accessing to the complementary resources from R&D cooperation. In the current business environment, many firms are likely to engage in multiple simultaneous R&D cooperations with different partners. Recent research stream addresses the importance of efficient cooperation management from the holistic portfolio perspective. Since maintaining the multiple cooperative relations require substantial amount of time and effort, managing cooperative relationships play a more important role to resource-constrained firms. In order to find an efficient composition of R&D cooperative partners, we mainly focus on the diversity of partner type and dependence level in partnership. We analyze the data on Korean manufacturing ventures collected in the Korean Innovation Survey (KIS) which was conducted by the Science and Technology Policy Institute (STEPI). The KIS questionnaire assesses the existence of cooperative relationships with different types of partners respectively. The types of cooperating partners are affiliated companies, suppliers, clients & customers, competitors or other firms in the same industry, consulting firms, universities, and research institutes. We confirm that ventures obtain relatively higher benefits from R&D cooperation compared with established firms in terms of innovation performance. The results show that a moderate level of diversity in cooperative partner type composition increases innovation. Moreover, diversity of cooperation dependency among the partners enhances innovation performance. Likewise, concentrating on the quality aspects of cooperative composition, such as diversity of partners and degree of dependencies, this study offers some implications for ventures in managing partners from an integrative perspective.

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A Diagnostic Study on High School Students' Health and Quality of Life - Based on the PRECEDE model - (고등학생의 건강 및 삶의 질에 대한 진단적 연구 - PRECEDE 모형을 근간으로 -)

  • Yoo Jae-Soon;Hong Yeo-Shin
    • The Journal of Korean Academic Society of Nursing Education
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    • v.3
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    • pp.78-98
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    • 1997
  • Health education, as the most fundamental concept for national health promotion, alms for developing the self-care ability of the general public. High school days are regarded as the period when most important physical, mental and social developments occur, and most health-related behaviors are formed. School health education is one of the major learning resources influencing health potential in the home and community as well as for the individual student. High school health education in Korea has a fundamental systemic flaw in that health-related subjects are divided and taught under various subjects areas at school. In order to achieve the goal of school health education, it is essential to make a systematic assessment of the learner's concerns connected with his health and life, and the factors affecting them. So far, most of the research projects that had been carried out for improving high school health education were limited in their concerns to a particular aspect of health. Even though some had been done in view of comprehensive school health education, they failed to Include a health assessment of the learner. Therefore, in this study the high school students' concerns related to health and life were investigated in the first place on the basis of the PRECEDE model, developed by Green and others for the purpose of a comprehensive diagnostic research on high school health education. This study was done in two steps : one was the basic study for developing research instrument and the other was the main one. The former was conducted at five high schools in Seoul and Cheongju for 2 months-beginning in March, 1996. The students were asked to respond to questions related to their health and lives in unstructured open-ended question forms. On the basis of analysis of the basic study, the diagnostic instruments for the quality of life, health problems, health behavior and educational factors were constructed to be used for the collection of data for main study. An expert panel and the pilot study were used to improve content validity and reliability of the instruments. The reliability of the instruments was measured at between .7697 and .9611 by the Cronbach $\alpha$. The data for this study were collected from the sample consisted of the junior and senior classes of twenty general and vocational high schools in Seoul and Cheongju for two months period beginning in July, 1996. In analyzing the data, both t-test and $X^2$-test were done by using SAS-$PC^+$ Program to compare data between the sexes of the high school students and the types of high school. A canonical correlation analysis was carried out to determine the relationships among the diagnostic variables, and a multivariate multiple regression analysis was conducted by using LISREL 8.03 to ascertain the influences of variables on the high school students' health and quality of life. The results were as follows : 1) The findings of the hypothesis tests (1) The canonical correlation between the educational diagnosis variables and behavioral, epidemiological, social diagnosis variables was .7221, which was significant at the level of p<.001. (2) The canonical correlation between the educational diagnosis variables and the behavior variables was .6851, which also was significant (p<.001). (3) The canonical correlation between the behavioral diagnosis variables and the epidemiological variables was 4295, which was significant (p<.001). (4) The canonical correlation between the epidemiological diagnosis variables and the social variables was .6005, which was also significant (p<.001). Therefore, the relationship between each diagnosis variable suggested by the PRECEDE model had been experimentally proven to be valid, supporting the conceptual framework of the study as appropriate for assessing the multi-dimensional factors affecting high school students' health and quality of life. Health behavior self-efficacy, the level of parents' interest and knowledge of health, and the level of the perception of school health education, all of which are the educational diagnostic variables, are the most influential variables in students' health and quality of life. In particular, health behavior self-efficacy, a causative factor, was one of the main influential variables in their health and quality of life. Other diagnostic variables suggested in the steps of the PRECEDE model were found to have reciprocal relations rather than a unidirectional causative relationship. The significance of this research is that it has diagnosed the needs of high school health education by the learner-centered assessment of variety of factors related to the health and the life of the students. This research findings suggest an integrated system of school health education to be contrived to enhance the effectiveness of the education by strengthening the influential factors such as self-efficacy to improve the health and quality of the lives of high school students.

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A Study on the Current Status of Health Screening and the Health Type(Physical Activity, and etc) of the Disabled by Using the Statistics of Health Insurance Corporation (건강보험공단 통계를 이용한 장애인의 건강검진 현황 및 건강형태(신체활동 등)에 대한 소고)

  • Kim, Seck-Jin;Jung, Jin-Sung
    • Journal of the Korean Applied Science and Technology
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    • v.35 no.2
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    • pp.433-444
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    • 2018
  • This study aims to examine the screening rate of health screening of the disabled by screening the data of disability and health statistics of the National Health Insurance Corporation, to suggest the problems of health examination and the future improvement measures, and also to review the type of health management of the disabled based on the results of health examination interview. As people with limited daily life or social life for a long time because of their physical/psychological disabilities in accordance with the Article2 of , out of 2,479,080 registered people with disabilities on the basis of December 31st 2015, the research subjects were limited to people with disabilities who participated in the health screening and health type for presenting the opinions about policies. In conclusion, regarding the health screening for the disabled, first, it would be necessary to collect the opinions from people with disabilities in order to prepare the health screening service suitable for them. Second, it would be needed to develop the health screening items for each type of disability and severity. Third, it would be necessary to consider the medical equipments and amenities of health examination for the disabled. Fourth, there should be the securement of manpower and education for service providers. Fifth, the mobility right of the disabled should be secured. Regarding the health type of the disabled, first, the expert consultative group in each area should be composed for the health enhancement of the disabled. Second, it would be necessary to screening the current status of health enhancement programs for the disabled and operating facilities. Third, the Central Health Medical Center for the Disabled, shown in the law on the securement of health rights & medical accessibility of the disabled should develop the standardized health enhancement programs for each disability type and severity. After examining the contents of health examination and health type of the disabled, the opinions about policies were suggested. Thus, in the future, there should be more detailed researches based on the tasks suggested by this study, and also the causal relations between health of the disabled and relevant programs should be continuously revealed.

Product Liability and Causation in Criminal Law (형법상 제조물책임과 인과관계의 확정)

  • Lee, Seok-Bae
    • The Korean Society of Law and Medicine
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    • v.17 no.2
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    • pp.3-28
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    • 2016
  • While product liability has been settled as a technical term in civil law, criminal law does not commonly accept technical term for it. Not like civil law, product liability in criminal law point outs individual responsibility and disability of normative order. Meaning that causation between individual's action of violation of duty and the result of danger of legal interest or infringement of legal interest must be proved. In criminal law excluding "non-result-constituted crimes (Unternehmensdelikt)", charge of injuring, accidental infliction of injury, homicide or involuntary manslaughter is problematic in product liability. Of course, it is necessary to distinguish whether the action related to the outcome is act or ommission. Also the causal relationship between the action and the result must be proved, and the intention or negligence should be recognized. In this paper, it analyzes cases that were problematic in Korea, Germany, Spain, etc. Mainly focusing on the problems revealed in the determination of causal relationship, especially recognizing criminal liability related to products. Furthermore it is followed by the view of reviewing the cause-and-effect relationship by 2 steps, dividing natural scientific causation and the normative causal relationship. In this process, to acknowledge criminal product liability in accordance with recognizing cause-and-effect relationship, there should be general risk of specific substance causing the outcome. This only premise can be meaningful to examine the casual relationship from specific cases. As it shows in some cases and theories, it is not contradicting general law of cause and effect by determining specific causal relationship by free evaluation of evidence if a general causal relationship does not exist. Also since judge's testimony does not hold a dominant position from rule of thumb, it is possible to recognize specific causal relationship. However this paper takes position that if there is no objective and reasonably undeniable cause and effect law. If there is no objective and reasonably undeniable causal law, which is the premise for recognizing concrete causal relations, judge should sentence guilty according to "in dubio pro reo" principle. In addition, it is not allowed for the defendant to burden unproven fact by free evaluation of evidence which has an effect of shift of burden of proof.

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Mineralogy and Genesis of Bentonites from the Tertiary Formations in Geumgwangdong Area, Korea (제(第)3기층(紀層)에 부존(賦存)하는 점토광물(粘土鑛物)에 대(對)한 광물학적(鑛物學的) 및 성인적(成因的) 연구(硏究))

  • Kim, Soo Jin;Noh, Jin Hwan;Yu, Jae Young
    • Economic and Environmental Geology
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    • v.18 no.4
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    • pp.399-410
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    • 1985
  • Bentonites from the Janggi Group of the Lower Miocene age from the Geumgwangdong area, Korea, have been studied for mineralogical and genetic characterization. The Janggi Group is subdivided, in ascending order, into the Janggi Conglomerate, the Nuldaeri Tuff, the Geumgwangdong Shale, the Lower Coal-bearing Formation, the Basaltic Tuff, and the Upper Coalbearing Formation. Bentonites occur as thin or thick beds in all sedimentary units of the Janggi Group, except for the Janggi Conglomerate. Significant bentonite deposits are found in the Nuldaeri Tuff, the Lower Coal-bearing Formation and the Basaltic Tuff. Bentonites consist mainly of smectite (mainly montmorillonite), with minor quartz, cristobalite, opal-CT and feldspar. Occasionally, kaolinite, clinoptilolite or gypsum is associated with bentonites. Bentonites were studied by the methods of petrographic microscopy, X-ray diffraction, thermal analysis (DT A and TG), infrared absorption spectroscopic analysis, SEM, intercalation reaction, and chemical analysis. Smectites commonly occur as irregular boxwork-like masses with characteristic curled thin edges, but occasionally as smoothly curved to nearly flat thin flakes. Most of smectites have layer charge of 0.25-0.42, indicating typical montmorillonite. Crystal-chemical relations suggest that Fe is the dominant substituent for Al in the octahedral layer and there are generally no significant substituents for Si in the tetrahedral layer. Ca is the dominant interlayer cation in montmorillonite. Therefore, montmorillonite from the study area is dioctahedral Ca-montmorillonite. Occurrence and fabrics of bentonites suggest that smectites as well as cristobalite, opal-CT and zeolites have been formed diagenetically from tuffaceous materials. The precursor of smectites is trachytic or basaltic tuff. Smectites derived from the former contain relatively more $Al_2O$ a and less $Fe_2O_3$ than those from the latter.

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