저밀도 폴리에틸렌의 전기전도에 미치는 실리콘유의 영향

서광석,이창용,강창균 고려대학교 공학기술연구소 1991 고려대학교 생산기술연구소 생기연논문집 Vol.27 No.1

Electrical conduction characteristics of low density polyethylene with a silicon-oil layer at the surface have been investigated at medium fields ranging from about 75 to 650 ㎸/㎝ over the temperature range of 20 to 100℃. The conduction current of polyethylene increases exponentially with the electric field and gets higher as the temperature increases. The observed conduction behavior was explained in term of the SCLC and tunneling effect. Activation energy ranges from 0.54 to 0.44 eV over the field range of 90∼450 ㎸/㎝ and the charge mobility was estimated from a Child law to be in the order of 10^(-16)∼10^(-14)㎡/V·s. Silicone oil layer modifies the conduction behaviors in polyethylene. Major changes are (1) an increase in conduction currents, (2) a suppression in a rate of change of conduction currents, and (3) a decrease in activation energy.

대학생의 성교육 효과측정을 위한 기초 연구

장순복,최연순,강희선,박소미,Chang, Soon-Bok,Choi, Yun-Soon,Kang, Hee-Sun,Park, So-Mi 대한간호협회 1997 대한간호 Vol.36 No.2

This study was performed to provide preliminary data for the development of a useful instrument to measure the effect of sex education. The study was conducted with the voluntary participation of 155 college students enrolled in the course "Sexuality and Relationship" at Y university in Seoul. At the end of that course, they were asked to write freely about the change they had experienced on sexuality. All meaningful statements were elicited and classified into 7 categories; "Change of Knowledge", "Enlightenment", "Change of Attitude on Sexuality", "Buildup of Ability", "Buildup of. Identity", "Change of Emotion", "Change of Behavior:' There were significant changes in the areas of knowledge(28. 6%), enlightenment(27.4%), and attitudes(20.3%) about sexuality among these 7 categories. The Change of Knowledge category consists of 3 areas: "concretion of knowledge", "increase of information", and "correction of misunderstanding." In the category of Enlightenment, total 12 areas are included: "sex role", "erception of lack of knowledge", "importance of family", "life plan", "parent role", "value of life", "equality", "sexual autonomy", "importance of sexuality", "freedom of sexuality", "perception of sexual problem", and "meaning of love." The Attitude Change category consists of 8 areas. These are "being natural", "being progressive", "being sensitive", "being truthful", "being expressive", "being cautious", "being responsible", and "being confident". The category of Buildup of Ability includes 4 areas: "problem solving", "sex education", "relationship", and "communication". The category of Buildup of Identity includes "sexual identity", and "value of sexuality". The Emotional Change category includes 3 areas: "positive feeling", "negative feeling", and "breaking from negative feeling on sexuality". The Behavior Change category includes "sex-related behavioral change". In conclusion, up to now most researches on sex education effect measures only changes of knowledge, attitude, and behavior. But we believe the changes in "Enlightenment", "Buildup of Ability", "Buildup of Identity", "Change of Emotion", should be included in addition to knowledge, attitude, and behavior in the development of an instrument to measure the sex education effects. And the effect of sex education should measure the degree of learning of autonomy, enlightenment, and ability of behavior and so on rather than studying the simple changes in sexuality.enment", "Buildup of Ability", "Buildup of Identity", "Change of Emotion", should be included in addition to knowledge, attitude, and behavior in the development of an instrument to measure the sex education effects. And the effect of sex education should measure the degree of learning of autonomy, enlightenment, and ability of behavior and so on rather than studying the simple changes in sexuality.ng the simple changes in sexuality.

논문 : 배당의 미래이익 예측력과 외국인투자자

강태구 ( Tae Goo Kang ),이창우 ( Chang Woo Lee ),남혜정 ( Hye Jeong Nam ) 명지대학교 금융지식연구소 2013 금융지식연구 Vol.11 No.3

본 연구는 배당의 미래이익 예측력이 외국인 투자자들의 지분율에 따라 어떻게 달라지는지 검증하였다. 일반적으로 배당지급은 기업의 미래이익을 예측하는 데 유용한 정보로 여겨지고 있으나, 이에 대한 실증연구결과들은 혼재되어 있다. 또한 배당의사결정과 관련된 연구들은 투자자들의 배당선호현상에 따라 기업의 배당의사결정이 영향을 받고 있음을 제시하고 있으며, 특히 우리나라의 경우, 배당의사결정에 외국인투자자가 미치는 영향이 매우 높게 나타나고 있다. 이는 특정투자자집단의 배당요구가 높은 경우, 기업의 배당의사결정이 미래이익에 대한 사적정보의 전달수단이기 보다는 단기적으로 배당에 대한 투자자들의 요구를 반영한 결과로 나타날 수 있음을 보여준다. 나아가 이러한 배당의사결정은 배당의 미래이익 예측력을 낮게 만들 것으로 예측된다. 본 연구는 배당의 미래이익 예측력을 재검증하고, 나아가 외국인지분율에 따라 배당의 미래이익예측력이 달라지는지 검증하였다. 먼저, 배당의 미래이익 예측연구들은 자기자본이익률(ROE)의 평균회귀(mean reverting)현상과 배당증가 또는 배당감소가 이익변화에 미치는 비대칭적 영향을 고려하고 있으나, 이익변화에 영향을 미치는 여러 가지 변수들을 통제하지 않고 있다. 따라서 본 연구는 선행연구에서 제시되고 있는 기업규모(SIZE), 성장성(SGR), 부채비율(LEV), 그리고 연도더미를 추가하여, 이를 통제하고 난 후에도 배당의 미래이익예측력이 여전히 존재하는지 검증하였다. 둘째, 배당의 미래이익 예측력이 기업의 배당의사결정에 영향을 미치는 특정집단에 의하여 달라지는지 검증하였다. 2000년부터 2007년까지 배당지급을 한 6,720 기업-년 표본을 대상으로 분석한 결과, 기본 모형뿐만 아니라 여러 통제변수를 포함한 모형에서도 우리나라 기업들의 배당변화는 미래 1년 뒤의 이익변화와 유의한 양의 관계를 나타냈으나, 미래 2년 뒤의 이익변화와는 유의하지 않았다. 또한 이익변화에 영향을 미치는 변수들을 추가한 모형의 설명력(R2=0.46)이 기본모형의 설명력(R2=0.28)보다 급격히 증가함을 알 수 있었다. 그러나 이러한 관계는 외국인지분율을 통제할 경우, 유의하지 않게 나타났다. 이는 기업의 배당의사결정이 미래전망에 근거하여 이루어지기보다는 특정투자자집단의 배당요구를 반영하는 수단으로 사용되고 있음을 보여준다. 즉 우리나라의 경우, 배당의사결정이 외국인투자자들의 배당요구를 반영하여 이루어짐을 알 수 있다. 본 연구는 대부분의 선행연구들이 외국인투자자와 배당성향간의 동시적인 관계에 대한 결과들을 제시한 반면에, 외국인투자자가 우리나라 기업들의 배당의사결정에 미치는 영향과 함께 배당의 미래이익예측력의 관점에서 살펴보았다는 점에 의의가 있다. This paper investigates whether the dividend payout predicts future earnings and the predictability varies depending on the proportion of investors. Specifically, this paper examines the effect of foreign investors on the relationship between dividend change and the predictability of future earnings in Korean firms. Reasoning from the hypothesis that dividend changes convey new information about a firm`s future profitability, a dividend increase is seen as a positive signal about the firm`s future earnings and profitability. However, the results from prior studies are controversial. Some papers have suggested that dividend changes would mean different things depending on a firm`s dividend policy and the motives behind its managers` decision to pay dividends. In addition, a firm`s governance is considered as one of important factors that affects dividend policy. In the Korean security market, foreign investors owned about 38% of the stock in 2007. As the percentage of foreign ownership had grown, many researchers have analyzed the effect of this ownership on dividend policy. However, prior studies found mixed results and have focused on the association between foreign investors and the level of the dividend or dividend change. They also suggest that predictability of dividend on future earnings is influenced by applied assumption on earnings and other factors like governance as well. We revisit the dividend signaling issue in the light of the catering theory of dividends suggested by Baker and Wurgler (2004). Lintner (1956) argued that managers unwilling to change payout ratio without any important change on the firm`s future performance. Won and Kim (1992) report that managers are more likely to be concerned about the internal factors such as net income, divisible surplus, predicted future performance, and the shareholders` preference for dividend policy. More importantly, several studies suggest that the foreign investors have a significant effect on the Korean market. Park (2004) reports that foreign investors` participation in firms generally pushes up the dividend payments while pulling down investments made in facilities no matter which industry a company is in. Sul and Kim (2006) show that those companies whose majority shareholders are foreign investors tend to pay higher dividends than others whose majority shareholders are domestic investors. In contrast to negative effect of foreign investor, there are empirical studies claiming positive impact of foreign investor in Korean market. Ahn, Shin, and Chang (2005) suggest that foreign investors prefer firms with lower information asymmetry. The study also shows that foreign investors can effectively monitor the management of firm in lessening information asymmetry. Similarly, Park and Lee (2006) suggest that foreign investors` participation in investment of domestic firms can help them make more efficient management decision by improving their corporate governance. Thus, Park and Lee claim that it is problematic to generalize the negative role of foreign investors in the Korean market. Based on this argument, we predict that if foreign investors play an effective monitoring role in a dividend policy, dividend change for firms with higher level of foreign investors is a good indicator in predicting future earnings than for firms with lower level of foreign investors. However, if foreign investors play a negative role in dividend decision process, predictability of dividend decreases. We test this prediction by using the modified model with several control variables that can affect earnings changes. Using 6,720 observations from 1993 to 2007, we find that the dividend change predicts future earnings for next one year relative to the dividend change year. Specifically, the coefficient on RDIV is 0.045 (t=6.85) and this indicates the dividend increases is a good indicator in predicting future earnings. When it comes to model specification, adjusted R2 of modified model is greater than that of the basic model, which means that the modified model is well specified in explaining earnings changes. The result of the effect of foreign investors on predictability of dividend is not significant. This finding implies that managers, on average, decide to pay dividend as a response to demand from foreign investors.

Causes and Predictive Factors Associated with "Diagnosis Changed" Outcomes in Patients Notified as Tuberculosis Cases in a Private Tertiary Hospital

Kang, Byung Ju,Jo, Kyung-Wook,Park, Tai Sun,Yoo, Jung-Wan,Lee, Sei Won,Choi, Chang-Min,Oh, Yeon-Mok,Lee, Sang-Do,Kim, Woo Sung,Kim, Dong Soon,Shim, Tae Sun The Korean Academy of Tuberculosis and Respiratory 2013 Tuberculosis and Respiratory Diseases Vol.75 No.6

Background: The aim of our study was to evaluate the "diagnosis changed" rate in patients notified as tuberculosis (TB) on the Korean TB surveillance system (KTBS). Methods: A total of 1,273 patients notified as TB cases on the KTBS in one private tertiary hospital in 2011 were enrolled in the present study. Patients were classified into three groups: "diagnosis maintained", "diagnosis changed" (initially notified as TB, but ultimately diagnosed as non-TB), and "administrative error" (notified as TB due to administrative errors). Results: Excluding 17 patients in the "administrative error" group, the "diagnosis maintained" and "diagnosis changed" groups included 1,097 (87.3%) and 159 patients (12.7%), respectively. Common causes of "diagnosis changed" were nontuberculous mycobacterial (NTM) disease (51.7%, 61/118), and pneumonia (17.8%) in cases notified as pulmonary TB, and meningitis (19.5%, 8/41) and Crohn's disease (12.2%) in cases notified as extrapulmonary TB. Being older than 35 years of age (odds ratio [OR], 2.18) and a positive acid-fast bacilli stain (OR, 1.58) were positive predictors and a TB-related radiological finding (OR, 0.42) was a negative predictor for a "diagnosis changed" result via multivariate logistic regression analysis in pulmonary TB cases. Conclusion: Because of a high "diagnosis changed" rate in TB notifications to the KTBS, the TB incidence rate measured by the KTBS may be overestimated. Considering the worldwide trend toward increased NTM disease, the "diagnosis changed" rate may increase over time. Thus, when reporting the annual TB notification rate in Korea, the exclusion of "diagnosis changed" cases is desirable.

텍스트마이닝을 활용한 우리나라 기후변화 리스크 평가 및 적응 대책 논의

강영은(Kang, Youngeun),신지영(Shin, Jiyoung),박창석(Park, Chang Sug) 한국도시설계학회 2016 도시설계 : 한국도시설계학회지 Vol.17 No.2

기후변화 연구는 광범위한 영향 범위와 불확실성 때문에, 장기적인 관점에서 기후변화 리스크를 평가하고 예측하여 효율적으로 대비하는 것이 필수적이다. 본 연구는 텍스트마이닝 기법을 활용하여 1990년대 이후 기후변화 영향 관련 신문기사 4,150건에 대해 연관되는 기후변화 리스크 항목을 매칭하고, 리스크 항목별 매칭 빈도 및 피해 크기(피해액)를 분석하였다. 연구 결과, 주요 리스크 항목들의 기후 동인들은 태풍/호우에 의한 영향이 많았으며, 피해 유형에서는 인명 피해, 인프라 시설 파괴 및 훼손, 농경지 피해 등의 비중이 높은 것으로 나타났다. 기 수행된 리스크 평가의 주요 리스크 항목과 비교에서는 42.4%의 중복 비율이 도출되었으며, 중복되지 않은 항목분석 결과, 본 연구의 결과가 직접적인 피해(1차적인 리스크)에 보다 집중되고 있는 경향을 파악할 수 있었다. 본 연구에서는 기존 연구에서 한계점으로 제기되었던 리스크의 ‘발생가능성’과 ‘결과의 크기’ 의 과학적 증거 부족을 보완했다는 측면에서 충분한 의의가 있다. 향후 기후변화 적응 대책 반영을 위한 바람직한 리스크 평가를 위해서는 본 연구에서 도출한 내용과 전문가 평가결과가 절충되어 리스크 평가의 신뢰성과 타당성을 동시에 확보할 수 있어야 할 것이다. Climate change adaptation plans and related studies have played a major role in reducing the risks of climate change. The studies, associated with climate change in particular, assess and predict the long run influence of climate change risk on society, the economy, and the environment in the long run, due to its extensive impact and uncertainty. This study evaluates the consequences and probability of climate change risk based on 4,150 newspapers articles after the 1990s related to climate change impact through text-mining. This study revealed that the climate drivers causing high recorded climate change risks include typhoons, heavy rains, and others. In addition, risk consequence categories were focused on casualties, damages to infrastructure and agricultural land. The percentage of risk overlapping between this study and the previous studies was 42.4%. The risks, that did not overlap, illustrate that this study has a tendency to focus on direct rather than indirect risks like social group vulnerability, social disparities, and so on. This study’s originality is illustrated through its supplementary concrete evidence for climate change risk assessment. From this step forward, climate change adaptation plans have to reflect not only the result of observed climate change risks like those identified in this study but also experts’ survey based risk for minimizing uncertainty.

Causes and Predictive Factors Associated with “Diagnosis Changed” Outcomes in Patients Notified as Tuberculosis Cases in a Private Tertiary Hospital

( Byung Ju Kang ),( Kyung Wook Jo ),( Tai Sun Park ),( Jung Wan Yoo ),( Sei Won Lee ),( Chang Min Choi ),( Yeon Mok Oh ),( Sang Do Lee ),( Woo Sung Kim ),( Dong Soon Kim ),( Tae Sun Shim ) 대한결핵 및 호흡기학회 2013 Tuberculosis and Respiratory Diseases Vol.75 No.6

Background: The aim of our study was to evaluate the “diagnosis changed” rate in patients notified as tuberculosis (TB) on the Korean TB surveillance system (KTBS). Methods: A total of 1,273 patients notified as TB cases on the KTBS in one private tertiary hospital in 2011 were enrolled in the present study. Patients were classified into three groups: “diagnosis maintained”, “diagnosis changed” (initially notified as TB, but ultimately diagnosed as non-TB), and “administrative error” (notified as TB due to administrative errors). Results: Excluding 17 patients in the “administrative error” group, the “diagnosis maintained” and “diagnosis changed” groups included 1,097 (87.3%) and 159 patients (12.7%), respectively. Common causes of “diagnosis changed” were nontuberculous mycobacterial (NTM) disease (51.7%, 61/118), and pneumonia (17.8%) in cases notified as pulmonary TB, and meningitis (19.5%, 8/41) and Crohn`s disease (12.2%) in cases notified as extrapulmonary TB. Being older than 35 years of age (odds ratio [OR], 2.18) and a positive acid-fast bacilli stain (OR, 1.58) were positive predictors and a TB-related radiological finding (OR, 0.42) was a negative predictor for a “diagnosis changed” result via multivariate logistic regression analysis in pulmonary TB cases. Conclusion: Because of a high “diagnosis changed” rate in TB notifications to the KTBS, the TB incidence rate measured by the KTBS may be overestimated. Considering the worldwide trend toward increased NTM disease, the “diagnosis changed” rate may increase over time. Thus, when reporting the annual TB notification rate in Korea, the exclusion of “diagnosis changed” cases is desirable.

Effect of Total Hip Arthroplasty on Ipsilateral Lower Limb Alignment and Knee Joint Space Width: Minimum 5-Year Follow-up

Choi Yun Seong,Park Jung-Wee,Kim Tae Woo,Kang Kee Soo,Lee Young-Kyun,Koo Kyung-Hoi,Chang Chong Bum 대한의학회 2023 Journal of Korean medical science Vol.38 No.20

Background: This study aimed to 1) assess the effect of total hip arthroplasty (THA) on coronal limb alignment, namely, the hip–knee–ankle angle (HKA), 2) identify factors that determine changes in the HKA, and 3) determine whether alignment changes influence the knee joint space width. Methods: We retrospectively evaluated 266 limbs of patients who underwent THA. Three types of prostheses with neck shaft angles (NSAs) of 132°, 135°, and 138° were used. Several radiographic parameters were measured in the preoperative and final radiographs (at least 5 years after THA). A paired t-test was used to confirm the effect of THA on HKA change. Multiple regression analysis was performed to identify radiographic parameters related to HKA changes following THA and changes in knee joint space width. Subgroup analyses were performed to reveal the effect of NSA change on the HKA change, and the proportion of total knee arthroplasty usage and changes in radiographic parameters between maintained joint space and narrowed joint space groups were compared. Results: The preoperative mean HKA was 1.4° varus and increased to 2.7° varus after THA. This change was related to changes in the NSA, lateral distal femoral angle, and femoral bowing angle. In particular, in the group with a decrease in NSA of > 5°, the preoperative mean HKA was largely changed from 1.4° varus to 4.6° varus after THA. The prostheses with NSA of 132° and 135° also led to greater varus HKA changes than those with an NSA of 138°. Narrowing of the medial knee joint space was related to changes in the varus direction of the HKA, decrease in NSA, increase in femoral offset. Conclusion: A large reduction in NSA can lead to considerable varus limb alignment after THA, which can have adverse effects on the medial compartment of the ipsilateral knee.

Design of a shape memory composite(SMC) using 4D printing technology

Kang, Minkyu,Pyo, Youngjun,Jang, Joon young,Park, Yunchan,Son, Yeon-Ho,Choi, MyungChan,Ha, Joo wan,Chang, Young-Wook,Lee, Caroline Sunyong Elsevier 2018 Sensors and actuators. A Physical Vol.283 No.-

<P><B>Abstract</B></P> <P>A fused deposition modeling (FDM) tool was used to fabricate a shape memory composite (SMC) that combined a shape memory alloy (SMA) with a shape memory polymer (SMP). The SMA caused a shape memory effect due to a phase change between martensite and austenite phases, in turn due to a temperature change. Also, the SMP had a shape memory effect caused by changes in the proportions of hard and soft segments near the glass transition temperature (T<SUB>g</SUB>). Usually, common SMAs and SMPs are not reversible, so these materials do not go back to their original shapes once they are deformed. In this study, we fabricated 4D printing actuator via reversible SMC actuations using 3D printing technology. Nylon 12 was used as the 3D printing material in filament form. Moreover, the volume fraction of SMA to SMP was varied to find the optimum ratio for good operation cycles. A volume fraction of SMA:SMP of 1:5 showed the largest length change, of 8 mm, and the most rapid response time, of 4 s in overall dimension of 140mm×10mm×1mm (length×width×thickness).Thus, the SMC showed promising results for the application of stents and valve controllers that could be manufactured by 3D printing technology.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An 4D printed SMC actuator was fabricated using SMA and SMP with a FDM 3D printer. </LI> <LI> A volume fraction of SMA:SMP of 1:5 showed the largest length change of 8 mm, and the most rapid response time of 4 s. </LI> <LI> The reversible actuator mechanism explains the SMC actuation via each shape memory effect. </LI> <LI> SMC showed potential application for stents and valve controllers via 3D printing technology to achieve customized designs. </LI> </UL> </P>

Changes in Spatiotemporal Parameters and Lower Limb Coordination During Prosthetic Gait Training in Unilateral Transfemoral Amputees

Yunhee Chang,Chang-Yong Ko,Bo Ra Jeong,Jung Sun Kang,Hyuk-Jae Choi,Gyoosuk Kim,Hyunjun Shin,Sehoon Park 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.3

When applying prosthetic gait training to patients with lower limb amputation, monitoring the gait change process is crucial for establishing and modifying rehabilitation training plans. In addition, since human gait involves complex movement of several joints, it is necessary to analyze the organic movement of adjacent joints rather than a single joint in the lower extremities for understanding the process of gait change. Therefore, this study aimed to analyze changes in spatiotemporal parameters and lower limb coordination during prosthetic gait training in unilateral transfemoral amputees (TFAs). This retrospective case–control study included 10 unilateral TFAs and 10 healthy individuals as controls. TFAs received prosthetic gait training for 12 weeks and gait changes were analyzed every 2 weeks using a 3D motion analysis system. The measured variables were spatiotemporal parameters and the continuous relative phase between hip and knee joints. The highest improvement in walking speed was seen at week 4 of training, and the continuous relative phase was most symmetric at week 8. The lower limb coordination pattern was more in-phase in the TFAs than in the controls, and the coordination variability was also lower for the TFAs than for the controls. In addition, the rate of change in lower limb coordination of TFAs was lower than that of spatiotemporal parameters and was significantly different from that of the controls even after training. Considering that the decrease in lower limb coordination is related to gait efficiency, balance, and risk of fall, there is a need to develop therapeutic strategies that can further improve the coordination of TFAs.

Step Free Energy Change and Microstructural Development in BaTiO₃-SiO₂

Chang, Jaem Yung,Kang, Suk Joong L. Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.352 No.-

<P>The effect of step free energy on the grain growth behavior in a liquid matrix is studied in a model system BaTiO3-SiO2. BaTiO3-10SiO2 (mole %) powder compacts were sintered at 1280°C under various oxygen partial pressures (PO2), 0.2, ~ 10-17 and ~ 10-24 atm. As the step free energy decreases with the reduction of PO2, it was possible to observe the change in growth behavior with the reduction of the step free energy. At PO2 = 0.2 atm, essentially no grain growth (stagnant grain growth) occurred during sintering up to 50 h. At PO2 ≈ 10-17 atm, abnormal grain growth followed stagnant grain growth during extended sintering (incubation of abnormal grain growth). At PO2 ≈ 10-24 atm, normal grain growth occurred. These changes in growth behavior with PO2 and the step free energy reduction are explained in terms of the change in the critical driving force for appreciable growth relative to the maximum driving force for grain growth. The present experimental results provide an example of microstructure control in solid-liquid two- phase systems via step free energy change.</P>