• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.19-24
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• 2020

In this work, the electrical property of Si-doped β-Ga2O3 was investigated via a post-growth annealing process. The Ga2O3 samples were annealed under air (O-rich) or N2 (O-deficient) ambient at 800~1,200℃ for 30 mins. There was no correlation between the crystalline quality and the electrical conductivity of the films within the experimental conditions explored in this work. However, it was observed the air ambient led to severe degradation of the film's electrical conductivity while N2-annealed samples exhibited improvement in both the carrier concentration and Hall mobility measured at room temperature. Interestingly, the x-ray photoemission spectroscopy (XPS) revealed that both annealing conditions resulted in higher concentration of oxygen vacancy (VO). Although it was a slight increase for the air-annealed sample, high resistivity of the film strongly suggests that VO cannot be a shallow donor in β-Ga2O3. Therefore, the enhancement of the electrical conductivity of N2-annealed samples must be originated from something other than VO. One possibility is the activation of Si. The XPS analysis of N2-annealed samples showed increasing relative peak area of Si 2p associated with SiOx with increasing annealing temperature from 800 to 1,200℃. However, it was unclear whether or not this SiOx was responsible for the improvement as the electrical conductivity quickly degraded above 1,000℃ even under N2 ambient. Furthermore, XPS suggested the concentration of Si actually increased near the surface as opposed to the shift of the binding energy of Si from its initial chemical state to SiOx state. This study illustrates the electrical changes induced by a post-growth thermal annealing process can be utilized to probe the chemical and electrical states of vacancies and dopants for better understanding of the electrical property of Si-doped β-Ga2O3.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.2
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• pp.135-144
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• 2001

This study was performed to measure airborne dimethylformamide(DMF), methyl ethyl ketone(MEK) and toluene and their urinary metabolites concentrations and to determine the relationship between airborne and urinary concentration. Airborne samples and their urinary metabolites were measured 98 male workers who work for 8 synthetic leather factories in a portion of Kyoung-In area. Urine samples were collected at end-of-shift to estimate the exposure levels. 1. The concentration of airborne DMF by process was 8.81 ppm for wet-mixing, 15.05 ppm for wet-coating, 6.03 ppm for dry-mixing, 5.58 ppm for dry-coating, 5.37 ppm for printing, and 9.03 ppm for total. There was statistically significant difference by process. Urinary NMF concentrations of wet-mixing, wet-coating, dry-mixing, dry-coating and printing were $90.55mg/{\ell}$, $79.80mg/{\ell}$, $39.86mg/{\ell}$, $25.23mg/{\ell}$, and $38.15mg/{\ell}$, respectively, and total geometric mean was $56.24mg/{\ell}$. There was significant difference by process. 2. The concentration of airborne MEK by process was 1.89 ppm for wet-mixing, 1.96 ppm for wet-coating, 10.33 ppm for dry-mixing, 29.24 ppm for dry-coating, 14.98 ppm for printing, and 4.87 ppm for total. There was statistically significant difference by process. Urinary MEK concentrations of wetmixing, wet-coating, dry-mixing, dry-coating and printing were $0.93mg/{\ell}$, $0.70mg/{\ell}$, $3.29mg/{\ell}$, $3.29mg/{\ell}$, and $1.06mg/{\ell}$, respectively, and total geometric mean was $1.25mg/{\ell}$. There was statistically significant difference by process. Urinary MEK 3. The concentration of airborne toluene by process was 0.35ppm for wet-mixing, 0.42ppm for wet-coating, 2.95ppm for dry-mixing, 11.67ppm for dry-coating, 4.88ppm for printing, 1.24ppm for total. There was statistically significant difference by process. Urinary hippuric acid concentrations of wet-mixing, wet-coating, dry-mixing, dry-coating and printing were 0.24g/g creatinine, 0.21g/g creatinine, 0.34g/g creatinine, 0.52g/g creatinine, and 0.29g/g creatinine, respctively and total geometric mean was 0.28g/g creatinine. There was statistically significant difference by process. 4. No. of exceeded KPEL was 40 workers(40.8%) for DMF(10ppm), 1 worker(1.0%) for MEK(200ppm), and no worker for toluene(100ppm). No. of exceeded KBEI was 62 workers(63.3%) for urinary NMF($40mg/{\ell}$), 29 workers(29.6%) for urinary MEK, 1 worker(1.0%) for urinary hippuric acid. 5. The regression equations were Log(NMF)=0.4094*Log(DMF)+1.3587(r=0.4516) for DMF, Log(MEKU)=0.1859*Log(MEK)-0.0324(r=0.3303) for MEK, Log(HA)=0.2106*Log(Toluene)-0.5685(r=0.4497) for toluene. Synthetic leather factory workers expose to 3 kinds of organic solvents which are DMF, MEK and toluene. Their urinary NMF and MEK levels were higher than their concentration levels through respiratory. It seems that the urinary levels were affected skin absorption for working habit and alcohol intake.

• Journal of The Korean Association For Science Education
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• v.36 no.1
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• pp.45-61
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• 2016

The purpose of this study is to explore students' epistemic goals and considerations in designing an experiment task and to investigate how a shift in the students' epistemology affected their argumentation. Four 7th grade students were selected as a focus group. According to the results, when they designed their own experiment, their epistemic goal was 'scientific sense-making' and their epistemic considerations - the perception of the nature of the knowledge product was 'this experiment should explain how something happened', the perception of the justification was 'we need to use our interpretation of the data' and the perception of the audience was 'constructor' - contributed to designing their experiment actively. When students tried to select one argument, their epistemic goal shifted to 'winning a debate', showing 'my experiment is better than the others' with the perception of the audience, 'competitor'. Consequently, students only deprecated the limits of different experiment so that they did not explore the meaning of each experiment design deeply. Eventually, student A's experiment design was selected due to time restrictions. When they elaborated upon their result, their epistemic goal shifted to 'scientific sensemaking', reviewing 'how this experiment design is scientifically valid' through scientific justification - we need justification to make members accept it - acting as 'cooperator'. Consequently, all members engaged in a productive argumentation that led to the development of the group result. This study lays the foundation for future work on understanding students' epistemic goals and considerations to prompt productive argumentation in science classrooms.

• Journal of Preventive Medicine and Public Health
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• v.22 no.2 s.26
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• pp.290-301
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• 1989

This is preliminary report on anthrax epidemic occurred in an island with about 100 residents. Since 1982 there had been sudden deaths among all kinds of domestic animals including cattle, dogs, ducks, chicken and goat but only a few among cats in an isolated island about three hours distance away by ferry boat from Mokpo city. From 1986 through 1988 nine human deaths and four patients occurred, which made the government intervene for investigation on June 25 1988. The epidemiological investigation consisted of interview survey and medical examination, medical record analysis, laboratory work to isolate the pathogens under the direction of hypothesis derived from the study and further confirmation of the pathogens by international institute. The summarized results are as followings: 1. According to the interview survey there were many deaths among domestic animals usually in cold and dry season such as January through March and September through November; 36 heads of cattle leaving one head, more than 40 hogs(all), hundreds of chicken leaving few alive, goats that had taken home from mountain and two or three cats out of around 40 had sudden deaths from 1982 till 1985, when the residents stopped to purchase and take them into the island anymore. Also there were eleven persons who had experienced the similar syndrome complex to those of admitted and expired patients and four of them revealed typical chest X-ray findings; from one of these four patients(Rho) B. anthracis is isolated. 2. Medical record on patients who had been admitted, showed common characteristics of the disease course. On admission they had either gastrointestinal or upper respiratory infection symptoms which invariably progressed to septicemic nature with pulmonary interstitial infiltration and mediastinal widening/bulging, and then to deadly acute respiratory distress syndrome. At the end stage chest X-ray revealed multiple bullous emphysema. One of another characteristics was oral ulceration with bleeding occurred in about 50% of the patients. Laboratory test results in common were leukocytosis with left shift and abnormal liver and kidney functions, particularly at the later stage of the illness. 3. Epidemiological characteristics was striking in that both mortality and incidence rates were high: the mortality rate was 8.7% average, male being three times higher than females but there was no distictive clustering by age group. The incidence rate for both sexes was 28.2% and there was no sex difference although a tendency of higher incidence among older ages was noticed. The highest mortality and incidence were observed in Won village where the first death of animal occurred and with the highest frequency among three villages of the island. 4. Among twelve bacilli species isolated from various specimens, two strains, one from patient and the other from soil where the recently died cow is hurried, were confirmed as B. anthracis by Pasteur Institute and CDC of USA(strain from soil). CDC reported that the strain did not produce capsule in bicarbonate media but reacted with the bacteriophage and one of five sera taken from the patients. Mode of transmission as well as incubation period of the agent has not been established yet, which needs further investigation in relation to the antigenic structure of the variant when it is confirmed.

• Investigative Magnetic Resonance Imaging
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• v.10 no.2
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• pp.98-107
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• 2006

Magnetization Transfer (MT) imaging generates contrast dependent on the phenomenon of magnetization exchange between free water proton and restricted proton in macromolecules. In biological materials in knee, MT or cross-relaxation is commonly modeled using two spin pools identified by their different T2 relaxation times. Two models for cross-relaxation emphasize the role of proton chemical exchange between protons of water and exchangeable protons on macromolecules, as well as through dipole-dipole interaction between the water and macromolecule protons. The most essential tool in medical image manipulation is the ability to adjust the contrast and intensity. Thus, it is desirable to adjust the contrast and intensity of an image interactively in the real time. The proton density (PD) and T2-weighted SE MR images allow the depiction of knee structures and can demonstrate defects and gross morphologic changes. The PD- and T2-weighted images also show the cartilage internal pathology due to the more intermediate signal of the knee joint in these sequences. Suppression of fat extends the dynamic range of tissue contrast, removes chemical shift artifacts, and decreases motion-related ghost artifacts. Like fat saturation, phase sensitive methods are also based on the difference in precession frequencies of water and fat. In this study, phase sensitive methods look at the phase difference that is accumulated in time as a result of Larmor frequency differences rather than using this difference directly. Although how MT work was given with clinical evidence that leads to quantitative model for MT in tissues, the mathematical formalism used to describe the MT effect applies to explaining to evaluate knee disorder, such as anterior cruciate ligament (ACL) tear and meniscal tear. Calculation of the effect of the effect of the MT saturation is given in the magnetization transfer ratio (MTR) which is a quantitative measure of the relative decrease in signal intensity due to the MT pulse.

• Sleep Medicine and Psychophysiology
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• v.10 no.2
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• pp.93-99
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• 2003

Objectives：Sleep loss and excessive daytime sleepiness may have serious consequences, including traffic and industrial accidents, decreased productivity, learning disabilities and interpersonal problems. Yet despite these adverse effects, there are few epidemiological studies on sleep loss and daytime sleepiness in the general population of Korea. This study investigates the number of people who suffer from sleep insufficiency, how much recovery sleep occurs on weekends, and the relationship between the amount of recovery sleep and daytime sleepiness. Methods：A total 164 volunteers, aged 20 and over, were recruited by advertisement. The subjects were workers and college students living in Seoul, Korea. Subjects were excluded if they were aged over 60；if they had medical, neurological, psychiatric or sleep disorders that could cause insomnia or daytime sleepiness；if they were not following a regular sleep schedule；if they traveled abroad during the study；or if they did not leave home to work or were shift workers. They were interviewed and given a sleep log to complete on each of 14 consecutive mornings. They also completed the Epworth Sleepiness Scale (ESS) at noontime on the last day of the second week. All statistical data were analyzed by t-test, $X^2$-test or ANOVA, using SPSS/PC+. Results：The results showed that the subjects woke up at 6：50 (${\pm}1$：16) on weekdays, 7：09 (${\pm}1$：29) on Saturdays, and 8：12 (${\pm}1$：39) on Sundays and holidays. They took more frequent and longer naps on Sundays than on weekdays and Saturdays. The mean sleep duration was 6h 35 min. on week nights, with a mean increase of about 1h on weekends. Only 9.1% of the subjects spent more than 8h in bed on week nights, with 67% spending less than 7h, and 49.4% reported recovery sleep of more than 1h on Sundays. The subjects who reported recovery sleep of more than 2h on Sundays, showed significantly more excessive daytime sleepiness than those who reported less than 30 min (F=2.62, p<.05). Conclusions：These findings suggest that sleep insufficiency and excessive daytime sleepiness are relatively common in Korea, and that the people who get insufficient sleep on weekdays try to compensate for sleep loss with oversleeping and daytime napping on Sundays and holidays. It appeared that daily sleep insufficiency had a cumulative effect and increased daytime sleepiness.

• The Korean Society of Law and Medicine
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• v.20 no.1
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• pp.133-162
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• 2019

Due to the nature of medical malpractice lawsuits, it is difficult for medical consumers, who are weak in getting information when it comes to health care problem, to secure all information inside the hospital. Even if you are confident about the hospital infection, it is true that people have difficult to obtain medical testimony by expert. It is seen as no easy task to testify to the malpractice of colleagues who work in the same field not only in our country but also abroad, when a doctor gives negative testimony to another doctor in a medical malpractice lawsuit. Although few health care providers will be motivated to take medical care from the outset, testimony or statements from a medical practitioner can have a significant impact on the outcome of a lawsuit, as it is impossible for the patient to control or be aware of the whole process of medical conduct, especially in the event of a hospital infection and the victim. If the hospital can prove the causality of damages caused by negligence of the employees or supervision of the hospital itself in a medical suit caused by the infection, the level of protection of the victim could be raised further. We sought to find a solution to these problems by looking at the provisions of other laws related to hospital infection. In particular, as the comparative legal review regarding hospital infection, Germany's legislative precedent sets a medical contract as a typical civil law contract, so it is thought that looking at German civil law regulations also has implications for Korean law. We also tried to improve the French Special Act 'rights of patients' and we can look at the consequent changes in court cases. Finally, the content of the U.S. case's and the theory of 'the doctrine of res ipsa loquitur' in relation to it show that doctors and hospitals have been forced to shift the burden of proof through this theory. This paper tried to find out the implications of mitigating the burden of proof by reviewing various issues that might be related to medical litigation of hospital infection from a comparative point of view.

• The Journal of Art Theory & Practice
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• no.14
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• pp.125-158
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• 2012

After liberation from Japanese colonial rule in 1945, there was the three-year period of United States Army Military Government in Korea. In 1948, Democratic People's Republic of Korea, and Republic of Korea were established in the north and south of the Korean Peninsula. The Republic of Korea is now a modern state set in the southern part of the Korean. We usually refer to Koreans as people who belong to the Republic of Korea. Can we say that is true exactly? Why make of this an obsolete question? The period from 1945 when Korea was emancipated from Japanese colonial rule to 1948 when the Republic of Korea was established has not been a focus of modern Korean history. This three years remains empty in Korean history and makes the concept of 'Korean' we usually consider ambiguous, and prompts careful attention to the silence of 'some Koreans' forced to live against their will in the blurred boundaries between nation and people. This dissertation regards 'Koreans' who came to live in the border of nations, especially 'Korean-Japanese third generation women artists'who are marginalized both Japan and Korea. It questions the category of 'Korean women's art' that has so far been considered, based on the concept of territory, and presents a new perspective for viewing 'Korean women's art'. Almost no study on Korean-Japanese women's art has been conducted, based on research on Korean diaspora, and no systematic historical records exist. Even data-collection is limited due to the political situation of South and North in confrontation. Representation of the Mother Country on the Artworks by First and Second-Generation Korean-Japanese(Zainich) Women Artists after Liberation since 1945 was published in 2011 is the only dissertation in which Korean-Japanese women artists, and early artistic activities. That research is based on press releases and interviews obtained through Japan. This thesis concentrates on the world of Korean-Japanese third generation women artists such as Kim Jung-sook, Kim Ae-soon, and Han Sung-nam, permanent residents in Japan who still have Korean nationality. The three Korean-Japanese third generation women artists whose art world is reviewed in this thesis would like to reveal their voices as minorities in Japan and Korea, resisting power and the universal concepts of nation, people and identity. Questioning the general notions of 'Korean women' and 'Korean women's art'considered within the Korean Peninsula, they explore their identity as Korean women outside the Korean territory from a post-territorial perspective and have a new understanding of the minority's diversity and difference through their eyes as marginal women living outside the mainstream of Korean and Japanese society. This is associated with recent post-colonial critical viewpoints reconsidering myths of universalism and transcendental aesthetic measures. In the 1980s and 1990s art museums and galleries in New York tried a critical shift in aesthetic discourse on contemporary art history, analyzed how power relationships among such elements as gender, sexuality, race, nationalism. Ghost of Ethnicity: Rethinking Art Discourses of the 1940s and 1980s by Lisa Bloom is an obvious presentation about the post-colonial discourse. Lisa Bloom rethinks the diversity of race, ethnicity, sexuality, and gender each artist and critic has, she began a new discussion on artists who were anti-establishment artists alienated by mainstream society. As migration rapidly increased through globalism lead by the United States the aspects of diaspora experience emerges as critical issues in interpreting contemporary culture. As a new concept of art with hybrid cultural backgrounds exists, each artist's cultural identity and specificity should be viewed and interpreted in a sociopolitical context. A criticism started considering the distinct characteristics of each individual's historical experience and cultural identity, and paying attention to experience of the third world artist, especially women artists, confronting the power of modernist discourses from a perspective of the white male subject. Considering recent international contemporary art, the Korean-Japanese third generation women artists who clarify their cultural identity as minority living in the border between Korea and Japan may present a new direction for contemporary Korean art. Their art world derives from their diaspora experience on colonial trauma historically. Their works made us to see that it is also associated with postcolonial critical perspective in the recent contemporary art stream. And it reminds us of rethinking the diversity of the minority living outside mainstream society. Thus, this should be considered as one of the features in the context of Korean women's art.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.3
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• pp.121-132
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• 2020

University Students go through the development process of expertise in a single field based on theoretical knowledge they have learned in the university. Their plans to develop their careers could lead to a shift in business as they choose to find jobs and start businesses throughout their lives. The attitude of career decision making process has been changed from learning in the form of receiving and memorizing existing knowledge to learning in a more proactive and autonomous manner, and there is a growing need for informal learning. In this study, the informal learning is investigated to clarify the impact on the employment competency and entrepreneurial intention. New implications are deduced by the introduction of start-up business to the traditional approach based on the employment ability. In addition, the importance of team-work has been increased in the field of eduction and business. The impact on the employment competency and entrepreneurial intention is studied based on the satisfaction level of team-based learning. Survey was conducted on 163 university students in North Chungcheong Province from March to June 2019 and the results of the study were summarized as follows. First, it has been confirmed that the informal learning of university students has a significant impact on their employment competency, but not on their entrepreneurial intention. Second, the employment competencies have perfect mediating effect on the informal learning and the entrepreneurial intention. Third, the satisfaction on the team-based learning did not have a significant impact on the employment competency of university students by informal learning, but it had a positive effect on the dependency between employment competency and entrepreneurial intention. In these days, start-up education at universities has been strengthened. Throughout this research, the need for informal learning is confirmed to enhance the employment competency and entrepreneurial intention of the university education program. In addition, team-based learning is introduced actively to utilize a variety of information from the university students.

• Korean Journal of Psychosomatic Medicine
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• v.11 no.2
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• pp.196-204
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• 2003

Objectives: It is known that sedative hypnotics would make cross tolerance with alcohol and deteriorate quality of sleep in alcoholics. Light therapy is effective non-pharmacological intervention for sleep disturbance in circadian phase disorders, jet-lag, shift-work and age-related sleep disorders. Authors would investigate the effects of morning light therapy on sleep of patients with alcohol dependence during recovery state without withdrawal symptoms. Methods: 13 patients with alcohol dependence who have not any alcohol withdrawal symptom were recruited. Light therapy during 1 hour in the morning had been administered by 2500 Lux light box through serial 3 days. Sleep state of subjects were assessed by sleep log and the subjective satisfaction at sleep was by 100 mm visual analogue scale. Sleepiness, depressive mood, anxiety were evaluated by 100mm visual analogue scale at 8 AM, 2 PM and 8 PM. For assessment of performance ability that would be associated with sleepiness and vigilance, trail making test A, B and digit symbol substitution test were performed by two times on base line and 4th day. Univariate repeated-measures ANOVAs were performed for each measures except performance tests which were analysed by paired t-test. Results: Sleep latency and sleep efficiency were significantly improved with light therapy and satisfaction at sleep was. There was no significant difference in sleepiness at 2 PM with light therapy but sleepiness at 8 AM significantly decreased and at 8 PM increased. The time to complete Trail making test and digit symbol substitution test were significantly shortened at 4th day compared with baseline. Fatigue at 8 AM were not significantly changed with light therapy but at 2 PM and 8 PM significantly decreased. Depressive mood and anxiety were not significantly changed with light therapy. Conclusion: Although this study had some limitations, it showed that light therapy would be effective modality on sleep disturbance of patients with alcohol dependence who have recovered from alcohol withdrawal symptoms. It is proposed that short term light therapy could be used clinically for alcoholics with insomnia. In the future, long term controlled studies using more objective tools for sleep are required to further investigate the effect of light therapy in alcoholics.