• Geosystem Engineering
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• 제21권6호
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• pp.297-308
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• 2018

In this paper, we investigate the differences between LNG price of South Korea and Japan. Although S. Korean and Japanese LNG markets have similar structures, there are some differences in the price formation. From DCC-MGARCH, we confirm that Japan LNG price have less persistence of disturbance on time than S. Korean LNG price. The conditional correlation also shows linkage effects between LNG prices and impacts of S-curve and DS-curve. Moreover, ARDL estimation result shows that there is co-integration in all models and that impacts of Fukushima accident and LNG volumes are responsible for the increase in Japanese LNG price. Also, adjustment speed of error correction term shows that Japan's deviation from long-run equilibrium disappears faster than S. Korea does, indicating relatively strong Japanese linkage between LNG price and oil price.

• Journal of Preventive Medicine and Public Health
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• 제47권4호
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• pp.206-215
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• 2014

Objectives: The hospital standardized mortality ratio (HSMR) has been widely used because it allows for robust risk adjustment using administrative data and is important for improving the quality of patient care. Methods: All inpatients discharged from hospitals with more than 700 beds (66 hospitals) in 2008 were eligible for inclusion. Using the claims data, 29 most responsible diagnosis (MRDx), accounting for 80% of all inpatient deaths among these hospitals, were identified, and inpatients with those MRDx were selected. The final study population included 703 571 inpatients including 27 718 (3.9% of all inpatients) in-hospital deaths. Using logistic regression, risk-adjusted models for predicting in-hospital mortality were created for each MRDx. The HSMR of individual hospitals was calculated for each MRDx using the model coefficients. The models included age, gender, income level, urgency of admission, diagnosis codes, disease-specific risk factors, and comorbidities. The Elixhauser comorbidity index was used to adjust for comorbidities. Results: For 26 out of 29 MRDx, the c-statistics of these mortality prediction models were higher than 0.8 indicating excellent discriminative power. The HSMR greatly varied across hospitals and disease groups. The academic status of the hospital was the only factor significantly associated with the HSMR. Conclusions: We found a large variation in HSMR among hospitals; therefore, efforts to reduce these variations including continuous monitoring and regular disclosure of the HSMR are required.

• Journal of Korean Neurosurgical Society
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• 제49권1호
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• pp.8-12
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• 2011

Objective: Ossification of the posterior longitudinal ligament (OPLL) has a strong genetic component. Specific gene polymorphisms may be associated with OPLL in several genes which regulate calcification in chondrocytes, change of extracellular collagen matrix and secretions of many growth factors and cytokines controlling bone morphogenesis. Toll-like receptor 5 (TLR5) may playa role in the pathogenesis of OPLL by intermediate nuclear factor-kappa B (NF-${\kappa}B$). The current study focused on coding single nucleotide polymorphisms (SNPs) of TLR5 for a case-control study investigating the relationship between TLR5 and OPLL in a Korean population. Methods: A total of 166 patients with OPLL and 231 controls were recruited for a case-control association study investigating the relationship between SNPs of TLR5 gene and OPLL. Four SNPs were genotyped by direct sequencing (rs5744168, rs5744169, rs2072493, and rs5744174). SNP data were analyzed using the SNPStats, SNPAnalyzer, Haploview, and Helixtree programs. Multiple logistic regression analysis with adjustment for age and gender was performed to calculate an odds ratio (OR). Results: None of SNPs were associated with OPLL in three alternative models (codominant, dominant, and recessive models; p> 0.05). A strong linkage disequilibrium block, including all 4 SNPs, was constructed using the Gabriel method. No haplotype was significantly associated with OPLL in three alternative models. Conclusion: These results suggest that Toll-like receptor 5 gene may not be associated with ossification of the posterior longitudinal ligament risk in Korean population.

• 한국도로학회논문집
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• 제13권1호
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• pp.69-77
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• 2011

본 연구는 신호교차로 교통사고예측모형 구축 과정 중 일반적으로 제한된 변수의 선정 및 모형의 구축에만 주로 초점이 맞추어진 기존 방법론의 문제점을 개선하고, 자료조사 및 수집 과정에서 발생하는 자료의 불확실한 상태를 인정하면서 자료의 불확실성을 최소화하여 이용할 수 있는 방법론을 개발하는데 연구의 주안점을 두었다. 퍼지추론이론과 신경망이론을 이용한 모형을 구축하였고, 마지막으로 구축된 퍼지추론이론 모형 및 신경망이론 모형과 기존 회귀모형인 포아송 회귀모형간의 통계적인 검증과 실제 Data를 이용한 모형의 적정성을 검토하였다. 모형의 통계적인 검증시 기존모형에 비해 퍼지추론모형과 신경망이론모형이 더 설명력이 높은 것으로 나타났고, 검증에서도 퍼지추론이론과 신경망이론이 적절한 것으로 나타났으며 기존모형보다 사고건수를 예측하는 설명력이 높은 것으로 입증되었다. 본 연구에서 개발된 모형은 계획 및 운영단계에서 신호교차로의 안전성을 측정하는데 활용될 수 있으며, 궁극적으로는 신호교차로에서 교통사고를 줄이는데 기여할 수 있을 것으로 판단된다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권6호
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• pp.716-722
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• 2014

DC 모터 시스템의 속도 제어기를 설계하기 위해서는 먼저 시스템의 파라미터 추정이 선행되어야 한다. 본 논문에서는 유전알고리즘을 이용하여 DC 모터 시스템의 파라미터를 추정하는 기법에 대해 다룬다. 이때 사용되는 추정 모델은 1차 및 2차 모델을 고려하며, 유전알고리즘의 3가지 평가함수를 고려하여 최적화한다. 또한, 유전알고리즘이 해공간에서 최적해를 탐색하는 능력의 우수함을 보여주기 위해 수치적 해석 방법을 통한 추정 결과도 함께 비교한다. 이때 파라미터 추정에 사용되는 데이터는 실제 실험장치의 입출력데이터를 이용하며, 신호의 잡음 제거를 위해 Butterworth 필터도 함께 설계한다. 마지막으로 제안한 기법을 통해 얻어진 모델과 실제 실험장치의 데이터와 비교하여 그 유효성과 정확성을 확인한다.

• 한국측량학회지
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• 제25권6_1호
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• pp.545-555
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• 2007

3D buildings are the most prominent feature comprising urban scene. A few of mega-cities in the globe are virtually reconstructed in photo-realistic 3D models, which becomes accessible by the public through the state-of-the-art online mapping services. A lot of research efforts have been made to develop automatic reconstruction technique of large-scale 3D building models from remotely sensed data. However, existing methods still produce irregular building polygons due to errors induced partly by uncalibrated sensor system, scene complexity and partly inappropriate sensor resolution to observed object scales. Thus, a geometric regularization technique is urgently required to rectify such irregular building polygons that are quickly captured from low sensory data. This paper aims to develop a new method for regularizing noise building outlines extracted from airborne LiDAR data, and to evaluate its performance in comparison with existing methods. These include Douglas-Peucker's polyline simplication, total least-squared adjustment, model hypothesis-verification, and rule-based rectification. Based on Minimum Description Length (MDL) principal, a new objective function, Geometric Minimum Description Length (GMDL), to regularize geometric noises is introduced to enhance the repetition of identical line directionality, regular angle transition and to minimize the number of vertices used. After generating hypothetical regularized models, a global optimum of the geometric regularity is achieved by verifying the entire solution space. A comparative evaluation of the proposed geometric regulator is conducted using both simulated and real building vectors with various levels of noise. The results show that the GMDL outperforms the selected existing algorithms at the most of noise levels.

• 한국치위생학회지
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• 제16권6호
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• pp.931-941
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• 2016

Objectives: The purpose of this study was to examine the association between depression and poor oral health in Korean elderly using Korean version of the Patient Health Questionnaire-9 (PHQ-9) for assessment of depressive symptoms. Methods: This study used the data from Korean National Health and Nutrition Examination Survey (KNHANES VI-2). The study included 1,454 elderly Korean aged over 65. Variables included demographic characteristics (gender, age), socioeconomic factor (income, education), systemic diseases, oral health related factor (tooth brush, dental products), health related factor (alcohol drinking, smoking), and depression. Logistic regression analysis was used as sequential models. Effects were quantified as odds ratios (OR) and 95% confidence intervals (CI). Results: From frequency analysis, being female, primary school or less, non-alcohol drinking, poor oral health were significantly related to depression. In the multiple logistic regression model, depression was significantly associated with poor oral health (OR=1.96, CI=1.15-3.53) after adjustment for other covariates including demographic characteristics, socioeconomic factor, systemic diseases, oral health related factor, and health related factor (OR=1.91, CI=1.13-3.27). Conclusions: Depression had an influence on the poor oral health after adjustment as confounding variable in the elderly. It should be focused on the health promotion for the elderly vulnerable to depression and poor oral health. The development of the mental health and oral health should be established.

• Journal of Preventive Medicine and Public Health
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• 제53권5호
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• pp.342-352
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• 2020

Objectives: The aim of this retrospective cohort study was to investigate whether non-alcoholic fatty liver disease (NAFLD) was associated with incident bone mineral density (BMD) decrease. Methods: This study included 4536 subjects with normal BMD at baseline. NAFLD was defined as the presence of fatty liver on abdominal ultrasonography without significant alcohol consumption or other causes. Decreased BMD was defined as a diagnosis of osteopenia, osteoporosis, or BMD below the expected range for the patient's age based on dual-energy X-ray absorptiometry. Cox proportional hazards models were used to estimate the hazard ratio of incident BMD decrease in subjects with or without NAFLD. Subgroup analyses were conducted according to the relevant factors. Results: Across 13 354 person-years of total follow-up, decreased BMD was observed in 606 subjects, corresponding to an incidence of 45.4 cases per 1000 person-years (median follow-up duration, 2.1 years). In the model adjusted for age and sex, the hazard ratio was 0.65 (95% confidence interval, 0.51 to 0.82), and statistical significance disappeared after adjustment for body mass index (BMI) and cardiometabolic factors. In the subgroup analyses, NAFLD was associated with a lower risk of incident BMD decrease in females even after adjustment for confounders. The direction of the effect of NAFLD on the risk of BMD decrease changed depending on BMI category and body fat percentage, although the impact was statistically insignificant. Conclusions: NAFLD had a significant protective effect on BMD in females. However, the effects may vary depending on BMI category or body fat percentage.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.293-296
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• 2008

콘크리트의 크리프와 건조수축은 재료 자체의 변동성과 모델의 불확실성 때문에 매우 복잡한 현상이다. 콘크리트 구조물의 장기거동을 예측할 수 있는 크리프와 건조수축 모델은 여러 가지 환경요인을 고려한 설계기준(Design Code)으로부터 얻을 수 있다. 하지만 같은 환경하에서 설계기준으로부터 구한 모델은 각기 다르기도 하다. 실제 콘크리트의 특성을 구하기 위해 장기간 실험을 통하기도 하지만 이는 실제 건설 현장에서는 쉬운 일이 아니고 이 또한 실구조물에서 다를 수 있다. 설계과정에서의 가정한 물성과 실제 물성의 차이가 있다면, 실제 구조물의 장기 거동을 정확히 예측하지 못하게 된다. 따라서 시공중이나 공용중 시간거동 예측을 정확히 하기 위해서는 실제 교량에서 시간의존거동에 미치는 요소 중 크리프 특성이 적절하게 주어졌는지에 대한 검토가 필요하다. 본 논문에서는 교량의 시간에 따른 거동을 측정한 자료가 주어졌을 때크 리프 민감도 해석을 수행하여 콘크리트의 크리프 계수를 예측하였다.

• Journal of Preventive Medicine and Public Health
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• 제42권1호
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• pp.29-34
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• 2009

Objectives : This study was performed to evaluate the relationship between C-reactive protein(CRP) and carotid intima-media thickness(carotid IMT) in a population of middle-aged Koreans. Methods : A total of 1,054 men and 1,595 women(aged 40-70 years) from Kanghwa County, Korea, were chosen for the present study between 2006 and 2007. We measured high-sensitivity CRP and other major cardiovascular risk factors including anthropometrics, blood pressure, blood chemistry, and carotid ultrasonography. Health related questionnaires were also completed by each study participant. Carotid IMT value was determined by the maximal IMT at each common carotid artery. The relationship between CRP level and carotid IMT was assessed using multiple linear and logistic regression models after adjustment for age, body mass index, menopause(women), systolic blood pressure, total/HDL cholesterol ratio, triglyceride level, fasting glucose, smoking, and alcohol consumption. Results : Mean carotid IMT values from the lowest to highest quartile of CRP were 0.828, 0.873, 0.898, and 0.926 mm for women(p for trend<0.001), and 0.929, 0.938, 0.949, and 0.979 mm for men(p for trend=0.032), respectively. After adjustment for major cardiovascular risk factors, the relationship between CRP and carotid IMT was significant in women(p for trend=0.017), but not in men(p for trend=0.798). Similarly, adjusted odds ratio of increased IMT, defined as the sex-specific top quartile, for the highest versus lowest CRP quartiles was 1.55(95% CI=1.06-2.26) in women, but only 1.05(95% CI=0.69-1.62) in men. Conclusions : CRP and carotid IMT levels appear to be directly related in women, but not in men.