• 대한수학회보
• /
• 제52권1호
• /
• pp.183-200
• /
• 2015

In this paper, we define the directional associated curve and the self-associated curve of a null curve in Minkowski 3-space. We study the properties and relations between the null curve, its directional associated curve and its self-associated curve. At the same time, by solving certain differential equations, we get the explicit representations of some null curves.

• 사회복지연구
• /
• 제45권2호
• /
• pp.233-261
• /
• 2014

본 연구에서는 국내 성인의 자아존중감과 우울의 인과관계를 살펴보는데 목적을 두고, 한국복지패널 1~4차 데이터를 활용하여 인과관계를 설명할 수 있는 인지취약모델과 상처모델을 검증하였다. 또한 우울과 자아존중감의 변화궤적에 영향을 미치는 인구사회학적 변인을 파악함으로써 우울과 자아존중감 손상에 취약한 인구집단을 밝히고자 하였다. 분석결과 우울의 초기값이 자아존중감 변화율에 미치는 영향과 자아존중감 초기값이 우울 수준 변화율에 미치는 영향이 모두 유의하게 나타나 외국 연구와는 달리 국내 성인집단에서는 인지취약모델과 상처모델이 모두 지지되는 것으로 밝혀졌다. 또한 이 상호관계는 인구사회학적 요인을 통제한 상태에서도 지지되었으며, 우울의 변화궤적과 자아존중감의 변화궤적 모두에 유의한 영향을 미치는 요인으로는 교육수준, 빈곤여부, 만성질환 여부 및 사회적 관계 만족도로 나타났다. 본 연구는 아직까지 연구되지 않은 성인기 집단의 우울과 자아존중감 관계의 매커니즘을 밝혔다는데 의의가 있으며, 논의를 통해 우울 예방 및 치료에 대한 실천적 함의를 제안하였다.

• 보건의료산업학회지
• /
• 제11권2호
• /
• pp.105-115
• /
• 2017

Objectives : The aim of this study was to suggest the optimal cut off for best, very good, good, slightly bad, and bad grades. Methods : The subjects were recruited from 4 areas of South Korea and 487 questionnaires were analyzed. The nominal and continuous self-rated health questions were used to reveal the optimal cut off and the Short Form-12 Health Survey questionnaire (SF-12) was additionally used. Frequency, Pearson's correlation coefficient, and ROC-curve analysis were used; the significance level was <.05. Results : Subjects assigned 15(3.1%), 90(18.5%), 237(48.7%), 130(26.7%), and 15(3.1%) to best, very good, good, slightly bad and bad groups respectively. The self-rated health score was associated with total Component (r=.563, p<.001), Physical Component (r=.520, p<.001) and Mental Component of SF-12 (r=.303, p<.001). The optimal cut off was 80.5, 70.5, 53.5, and 40.5 for best, very good or more, good or more, and under slightly bad respectively and area under curve was 0.898, 0.908, 0.945, and 0.908 accordingly. Conclusions : This study suggests that the self-rated health score and grade could be integrated with the optimal cut off.

• 한국아동복지학
• /
• 제59호
• /
• pp.25-58
• /
• 2017

본 연구는 우리나라 중학교 1학년 코호트 청소년의 긍정적 자아존중감과 부정적 자아존중감 각각의 변화궤적을 확인하고, 이러한 변화궤적 및 예측요인의 관계가 긍정적, 부정적 자아존중감에 따라서 다르게 나타나는지 살펴보았다. 이를 위해서 한국청소년정책연구원에서 수집하는 한국아동 청소년 패널조사 자료 중 중학교 1학년 코호트의 1차 년도(2010년), 3차 년도(2012년), 5차 년도(2014년), 6차 년도(2015년) 자료를 이용하였고, 최종분석대상은 2,350명이다. 주요 결과는 다음과 같다. (1) 우리나라 중학교 1학년 코호트 청소년의 긍정적 자아존중감과 부정적 자아존중감은 증가하는 경향을 보였지만 점차 그 증가속도가 감소하는 이차함수의 모형으로 변화하였다. (2) 긍정적 자아존중감과 부정적 자아존중감에 영향을 주는 예측요인의 종류가 달랐다. 구체적으로, 긍정적 자아존중감에만 영향을 미치는 요인은 교사관계와 소득이 있고, 부정적 자아존중감에만 영향을 미치는 요인은 질병유무와 부모의 과잉간섭 요인이 있었다. 긍정적 자아존중감과 부정적 자아존중감에 동시에 영향을 미치는 요인은 성별, 부모의 애정, 또래신뢰와 또래소외가 있었다. 이러한 결과는 긍정적 부정적 자아존중감에 대한 독립적인 개입이 필요하고, 청소년의 긍정적 부정적 자아존중감 각각에 개입할 수 있는 세분화된 개입의 전략을 세우는 데 있어서 중요한 근거기반이 될 수 있다.

• 한국환경보건학회지
• /
• 제40권6호
• /
• pp.492-501
• /
• 2014

Objectives: The purpose of this study was to assess the validity of self-reported cigarette smoking status and investigate factors associated with the accuracy self-reported and measured urinary cotinine in Korean adults. Methods: We used data from the $1^{st}$ Korean National Environmental Health Survey (2009-2011) among adults aged ${\geq}19$ years (N=6,246). The survey examined self-reported smoking status, and urinary cotinine was regarded as the biomarker of exposure to tobacco smoke. Urinary cotinine was analyzed using a gas chromatography-mass spectrometry (GC/MS) and data analysis was conducted using IBM SPSS version 20.0, which uses the sample weight and calculates variance estimates to adjust for the unequal probability of selection into the survey. Results: We calculated a cut-off point (53.3 ug/L) by using a ROC (Receiver Operating Characteristic) curve. The smoking prevalence was 24.6% based on self-reported data and 28.2% based on urinary cotinine concentrations. When we assessed the agreement between self-reported and urinary cotinine, we found an average agreement of 97.7% among self-reported smokers and 94.5% among self-reported non-smokers. Among self-reported smokers, factors affected the discrepancy were age, household economic status and average number of cigarettes smoked per day. On the other hand, gender, former smoking experience, and exposure to SHS (second hand smoke) were associated with discrepancies among self-reported non-smokers. Conclusion: These results suggest that self-reported data on smoking status provide a valid estimate of actual smoking status. In future research, we will conduct a continuous monitoring study for reliability verification of the data to reduce potential interpretation errors.

• 한국노년학
• /
• 제29권4호
• /
• pp.1611-1628
• /
• 2009

건강상태와 심리사회적 요인이 우울증상과 밀접한 관련이 있다는 것은 기존연구를 통하여 널리 알려진 사실이다. 하지만 기존의 종단데이터 부족과 분석방법의 한계로 이러한 변수들과 우울증상 궤적과의 관계에 대해서는 알려진 바가 많지 않다. 이러한 기존 연구의 한계를 염두에 두고, 본 연구는 건강상태 및 심리사회적 요인과 우울증상의 궤적간의 관계를 살펴보는 것을 주 목적으로 한다. 본 연구는 전국 대표샘플인 한국복지패널데이터 1, 2, 3차 자료를 이용하여 60세 이상의 노인들(N=4,919)의 우울궤적 예측요인을 잠재성장모형을 이용하여 분석하였다. 사회경제적 변수를 통제한 상태에서 건강변수와 심리사회적 변수들이 우울궤적에 미치는 영향은 기존연구와 유사한 점도 있지만 다른 점도 있는 것으로 나타났다. 구체적으로 건강변수는 우울증상의 수준에는 영향을 미치지만 우울증상의 변화속도에는 영향을 미치지 않는 것으로 나타났다. 반면 심리사회적 변수는 기존 연구와 동일하게 모두 우울수준에 영향을 미치지만, 기존 연구와는 다르게 변수에 따라서 우울증상의 변화속도에 미치는 영향은 상이한 것으로 나타났다. 즉, 자아존중감과 가족관계 변수는 우울증상 변화속도에 긍정적 영향을 미치는 반면, 사회적 관계는 우울증상 변화속도에 부정적 영향을 미치는 것으로 나타났다. 이러한 연구결과를 토대로 실천 및 향후 연구를 위한 함의를 논의하였다.

• Wind and Structures
• /
• 제8권2호
• /
• pp.79-88
• /
• 2005

This paper deals with a unified way for calculating vortex-induced vibrations (Aeolian vibrations in transmission line parlance) of undamped single overhead conductors. The main objective of the paper is to identify reduced parameters which would unify the predicted vibration response to the largest possible extent. This is actually done by means of a simple mathematical transformation resulting, for a given terrain (associated to a given wind turbulence intensity), into a single, unified response curve that is applicable to any single multi-layered aluminium conductor. In order to further validate the above process, the predicted, unified response curve is compared with measured response curves drawn from tests run on a full-scale test line using several aluminium-conductor-steel-reinforced (ACSR), all-alloy-aluminium-conductor (AAAC) and aluminium-conductor-alloy-reinforced (ACAR) conductors strung at different tensions. On account of the expected scatter in the results from such field tests, the agreement is shown to be good. The final results are expressed by means of only four different curves pertaining to four different terrain characteristics. These curves may then be used to assess the vibration response of any undamped single, multi-layer aluminium conductor of any diameter, strung at any practical tension.

• 한국전기전자재료학회논문지
• /
• 제31권6호
• /
• pp.427-432
• /
• 2018

High-capacity secondary batteries can cause explosion hazards owing to microcurrent variations or current surges that occur in short circuits. Consequently, complete safety cannot be achieved with general protection that is limited to a mere current fuse. Hence, in the case of secondary batteries, it is necessary for the protector to limit the inrush current in a short circuit, and to detect the current during microcurrent variations. To serve this purpose, a fuse can be employed for the secondary battery protection circuit with current detection. This study aims at designing a protection device that can stably operate in the hazardous circumstances associated with high-capacity secondary batteries. To achieve the said objective, a detecting fuse was designed from an alloy of low melting point elements for securing stability in abnormal current states. Experimental results show that the operating I-T and V-T characteristic constraints can be satisfied by employing the proposed current detecting self-contained low melting point fuse, and through the resistance of the heating resistor. These results thus verify that the proposed protection device can prevent the hazards of short circuit current surges and microcurrent variations of secondary batteries.

• Journal of Periodontal and Implant Science
• /
• 제46권1호
• /
• pp.10-21
• /
• 2016

Purpose: This study evaluated the predictive performance of a combination of self-report questionnaires, salivary hemoglobin levels, and age as a non-invasive screening method for periodontitis. Methods: The periodontitis status of 202 adults was examined using salivary hemoglobin levels, responses to 10 questions on a self-report questionnaire, and the Community Periodontal Index (CPI). The ability of those two variables and the combination thereof with age to predict the presence of CPI scores of 3-4 and 4 was assessed using logistic regression and receiver operating characteristic (ROC) curve analysis. Results: CPI scores of 3-4 and 4 were present among 79.7% and 46.5% of the sample, respectively. The area under the ROC curves (AUROCs) of salivary hemoglobin levels for predicting prevalence of CPI scores of 3-4 and 4 were 0.63 and 0.67, respectively (with sensitivity values of 71% and 60% and specificity values of 56% and 72%, respectively). Two distinct sets of five questions were associated with CPI scores of 3-4 and 4, with AUROCs of 0.73 and 0.71, sensitivity values of 76% and 66%, and specificity values of 63% and 69%. The combined model incorporating both variables and age showed the best predictive performance, with AUROCs of 0.78 and 0.76, sensitivity values of 71% and 65%, and specificity values of 68% and 77% for CPI scores of 3-4 and 4, respectively. Conclusions: The combination of salivary hemoglobin levels and self-report questionnaires was shown to be a valuable screening method for detecting periodontitis.

• 대한임상독성학회지
• /
• 제18권2호
• /
• pp.102-109
• /
• 2020

Purpose: This study examined factors associated with the hospitalization of patients who visited the emergency department (ED) after deliberate self-poisoning. Methods: The medical records of the patients, who visited the ED at a tertiary teaching hospital after deliberate self-poisoning between March 2017 and December 2019, were reviewed retrospectively. Results: Fifty-seven in the hospitalization and 236 in the discharge group patients were included. The mean age in the hospitalization and discharge group was 48.8±20.4 and 41.8±19.1, respectively (p=0.020). Univariate analysis revealed statistically significant differences in age (p=0.020), mental status (p<0.001), request for help (p=0.046), chronic disease (p=0.036), substance ingested (p<0.001), and risk rescue-rating scale (p<0.001) between the two groups (hospitalization group and discharge group). In multiple logistic regression analysis for predicting the hospitalization of patients after deliberate self-poisoning, the Risk-Rescue Rating Scale (RRRS) was identified (OR=1.493, 95% confidential interval=1.330-1.675, p<0.001). Receiver operating characteristics analysis of RRRS for the decision to hospitalize showed a cut-off value of 38.9, with a sensitivity, specificity, and area under the curve of 96.4%, 77.0%, and 0.949, respectively. Conclusion: The RRRS can be used to determine the hospitalization for patients who visited the ED after deliberate self-poisoning. Nevertheless, multicenter prospective studies will be needed to determine the generalisability of these results.