• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.100-100
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• 2022

일반적으로 유체와 구조물간 상호작용의 수리동역학적 모의에서는 벽경계조건을 통하여 유동에 대한 구조물의 영향이 반영된다. 하지만 도심지에서 발생한 홍수를 예측하려는 경우 이러한 방법으로는 밀집한 구조물들 사이에 형성된 좁은 길들로 인하여 세밀한 격자망을 요하여 큰 계산량을 유발하고 빠른 예측 속도를 기대할 수 없게 한다. 최근 이러한 문제를 극복하기 위해 성긴 격자망에서도 구조물의 유체에 대한 영향을 반영할 수 있도록 하는 방법들이 큰 관심을 받고 있다. 그 중에서도 다공성 천수방정식은 벽경계조건 대신 다공도(posority)의 개념을 이용한 모형으로 도시범람모의에 있어 계산량과 정확도를 가장 적절하게 타협한 모형으로 보고되고 있다. 이러한 흐름에 맞추어 본 연구는 다공도 천수방정식을 해석하는 수치 기법을 개발하였고, 여기에 최근 쌍곡선계 방정식의 수치적 연구들에서 소개된 주요 특징들이 반영되도록 설계하였다. 우선, WENO 기법과 Runge-Kutaa 기법을 통하여 공간과 시간에 대한 고차 정확도를 만족시켰다. 이 때, 재구성 변수와 알고리즘를 새롭게 제시하여 정상흐름조건에 대한 플럭스항과 생성·소멸항간 절단오차에 의한 비물리적인 흐름생성을 억제하였다. 또한, 수치모의 중 음수심의 발생으로 인하여 수치모형이 불안정해지는 현상을 막기 위해, 양-보존성 제한자를 구축하였다. 마지막으로 도심지에서 즐비한 인위적인 구조물에 의해 나타나는 지형적인 불연속의 효과를 적절하게 반영할수 있도록 정상파 재구축의 단계를 구축하여 수치 기법에 반영하였다. 이렇게 구성된 수치기법은 리만문제의 해석해에 기반하여 기존의 주요 연구들의 결과와 비교되었고, 그 결과 본 연구의 방법이 정확성, 수렴성, 안전성의 측면에서 가장 우수함을 수치적으로 증명하였다.

• 한국벤처창업학회:학술대회논문집
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• 2023.04a
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• pp.7-10
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• 2023

IT기술의 발전과 스마트기기의 대중화로 인한 정보통신기술의 눈부신 발전으로 온라인 플랫폼을 통한 식품구매 비중이 급격히 증가하여 온·오프라인의 경계를 없어지고 있다. 더군다나 COVID-19 팬데믹은 반조리식품, 밀키트 등 홈쿡(Home-cook) 온라인시장을 급격히 확산시키며 소비자 구매추세를 오프라인에서 온라인으로 완전히 바꿔놓는 전환점이 되었다. 이런 트랜드를 반영하듯 다양한 온라인 식자재 이커머스 플랫폼의 출현하면서 브랜드마다 각각의 차별점을 내세우고 있으나 경쟁은 치열해지고 차별화는 더욱 어려운 게 현실이다. 이는 기업이 소비자에게 일방향으로 정보 또는 상품 및 서비스를 제공 하는 수직적 관계가 아닌, 수평적 쌍방향 관계로의 발전으로 이어져 브랜드가 가지고 있는 가치에 대해 보다 정직하게 보여주어야 소비자의 신뢰를 얻을 수 있게 되었다(Kotler, 2017). 또한, 과거에 소비자들의 만족도가 높았던 서비스도 현재 환경에서는 소비자의 니즈를 충족시키지 못하는 경우가 증가하고 있다(조윤오, 2018). 이는 서비스에 대한 소비자의 기대와 니즈가 지속적으로 변화하고 있다는 것을 의미하며, 이에 따라 기업은 소비자들의 새로운 요구를 만족시키기 위하여 다양한 서비스를 개발 및 제공하는 것이 중요하다고 사료된다(김광재 등, 2011). 이미 높은 인지도를 가진 플랫폼일지라도 지속가능한 우위를 선점하기 어려운 상황에서 온라인 플랫폼에 대한 소비자의 긍정적인 태도와 재구매를 유도하기 위해 제품 본질 뿐 아니라 서비스 차별화를 꾀하고 있고 차별화된 포지션을 차지하기 위해 온라인 플랫폼에 대한 소비자 인식과 서비스 품질 요인을 측정하여 고객이 중시하는 요인에 집중하는 것이 필요하다. 이에 본 연구는 온라인 플랫폼을 통해 식자재를 구매하는 소비자의 꾸준한 방문과 구매를 유인하기 위해 어떤 변수의 영향력을 높여야 소비자 재구매의도를 증가시킬 수 있는지 방법을 모색하고 온라인 플랫폼 기업 및 스타트업의 경영전략 마련에 목적이 있다. 이를 위해 식자재 구매 플랫폼 품질속성, 서비스품질 정도,, 충성도의 전반적인 영향관계를 파악하는 연구 과제를 설정하고, 식자재 이커머스 온라인 플랫폼 이용 전반에 대한 평가를 실시할 예정이다. 이러한 과정을 통해 도출된 결과는 식자재 이커머스 플랫폼 운영 전략을 세우는데 유용한 자료가 될 것이라 기대하며, 기존의 온라인 식품구매 플랫폼의 서비스품질 요인과 소비자 행동 간의 관계를 설명하는 것과는 다른 새로운 시사점을 제공할 수 있다는 측면에서 의미 있는 연구가 될 것이다. 또한, 다양한 산업에서의 플랫폼 비지니스 모델 적용을 위한 전략 수립을 하는 데에 필요한 기초자료를 마련하고자 한다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.476-483
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• 2023

The present study concerns modelling the structural behaviour for concrete structure into the crack initiation at corrosion of steels. The degradation source included the axial load and steel corrosion. A development of the rust formed on the steel surface was considered with the interfacial gap between steel and concrete. As a result, the tensile damage could occur on the surface of concrete into the cracking with no steel corrosion, which could be further developed by the increasing rust formation, while the cracking at the steel-concrete interface was mainly attributed to the compressive deformation, being restricted within the interfacial zone.

• Journal of the Korean GEO-environmental Society
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• v.18 no.5
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• pp.45-53
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• 2017

IPM bridge was developed to revise the problems of IAB bridge by Nam et al, (2016). This research conducted the p-y analysis to examine the parameter traits among the protruded length (H), penetrated length (L) of pile bent and soil conditions. From the results, the maximum bending moment happened in the top segment of pile bent, because it is integrated to the upper structure. Also, the maximum shear force was shown in the boundary of the sand and weathered soil zones according to the analysis soil conditions. The maximum member force and unbraced length is converged when the ratio (L/H) of protruded length (H) and penetrated length (L) is 1.0. The larger material force is happened, if the pile bent is penetrated shallowly compared to the protruded length. The definite inflection points were shown in the horizontal displacement curve from the p-y analysis, also the smaller penetrated length made the curve grade slower.

• Journal of the Korean Society of Radiology
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• v.18 no.1
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• pp.21-26
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• 2024

The one of the famous deep learning models for object detection task is you only look once version 5 (YOLOv5) framework based on the one stage architecture. In addition, YOLOv5 model indicated high performance for accurate lesion detection using the bottleneck CSP layer and skip connection function. The purpose of this study was to evaluate the performance of YOLOv5 framework according to various hyperparameters in position emission tomogrpahy (PET) phantom images. The dataset was obtained from QIN PET segmentation challenge in 500 slices. We set the bounding box to generate ground truth dataset using labelImg software. The hyperparameters for network train were applied by changing optimization function (SDG, Adam, and AdamW), activation function (SiLU, LeakyRelu, Mish, and Hardwish), and YOLOv5 model size (nano, small, large, and xlarge). The intersection over union (IOU) method was used for performance evaluation. As a results, the condition of outstanding performance is to apply AdamW, Hardwish, and nano size for optimization function, activation function and model version, respectively. In conclusion, we confirmed the usefulness of YOLOv5 network for object detection performance in nuclear medicine images.

• Journal of Hospice and Palliative Care
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• v.2 no.2
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• pp.114-124
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• 1999

Purpose : To clarify the relation between psychosocial variables and cancer in Korea. Methods : Case-control study. Participants: 239 subjects in 2 university hospitals in Seoul completed a series of psychometric instruments(the Olson's FACES III and the Lee's 98-items life event scale). Results : In bivariable analysis, there were statistically significant difference in age and economic status(income): marginal significance in education status and marital status between the cases and controls. The family function type and stress score were not significantly different. The result of multivariable logistic regression, analysis showed that the risk of cancer was associated with economic status and marital status, but neither the family function nor the life event stress. Conclusion : In this study, we cannot prove the statistical association between the family function, life event stress and cancer. It is necessary to persevere in our efforts to clarify the relation between stress and disease and to develop the useful tools to measure the Korean family function and life event stress.

• The Journal of Engineering Geology
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• v.33 no.1
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• pp.105-119
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• 2023

Water supply is decreasing due to climate change, and coastal and island regions are highly dependent on groundwater, reducing the amount of available water. For sustainable water supply in coastal and island regions, it is necessary to accurately diagnose the current condition and efficiently distribute and manage water. For a precise analysis of the groundwater flow in the coastal island region, submarine fresh groundwater discharge was calculated for the Seongsan basin in the eastern part of Jeju Island. Two methods were used to estimate the thickness of the fresh groundwater. One method employed vertical interpolation of measured electrical conductivity in a multi depth monitoring well; the other used theoretical Ghyben-Herzberg ratio. The value using the Ghyben-Herzberg ratio makes it impossible to accurately estimate the changing salt-saltwater interface, and the value analyzed by electrical conductivity can represent the current state of the freshwater-saltwater interface. Observed parameter was distributed on a virtual grid. The average of submarine fresh groundwater discharge fluxes for the virtual grid was determined as the watershed's representative flux. The submarine fresh groundwater discharge and flux distribution by year were also calculated at the basin scale. The method using electrical conductivity estimated the submarine fresh groundwater discharge from 2018 to 2020 to be 6.27 × 10⁶ m³/year; the method using the Ghyben-Herzberg ratio estimated a discharge of 10.87 × 10⁶ m³/year. The results presented in this study can be used as basis data for policies that determine sustainable water supply by using precise water budget analysis in coastal and island areas.

• The Korean Journal of Petroleum Geology
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• v.5 no.1_2 s.6
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• pp.36-47
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• 1997

This study presents multi-variable sequence model for a broader application of sequence concept proposed by Exxon group. The concept of the multi-variable model is based on the fact that internal organization and boundary type of the sequences are determined by three varying factors including 3rd-order cycles of eustasy, and tectonic movement and sediment influx with 2nd-order changes. Instead of Exxon group's systems tracts, this model adopts parasequence sets as the fundamental building blocks of the sequence, because they are descriptive stratigraphic units simply defined by internal stacking pattern, reflecting interactions of accommodation and sediment influx. Seven sequence types which vary in number and type of internal parasequence sets are formulated as associations of four types of accommodation development and three grades of sediment influx. In the southwestern margin of Ulleung Basin, the multi-variable sequence analysis of shelf-slope sequence shows systematic changes in stratal patterns and the numbs, of constituent parasequence sets (i.e. sequence type). These changes are interpreted to reflect temporal and spatial changes in type and rate of tectonic movement and sediment influx, as a result of back-arc opening and closing. During the back-arc opening, rapid subsidence, continuous rise of relative sea level, and high sediment influx gave rise to sequences dominantly of single progradational parasequence set. In the early stage of back-arc closing accompanied by local contractional deformation, different types of sequences contemporaneously formed depending on the spatial changes in tectonically-controlled accommodation and influx rates. During the subsequent slow back-arc subsidence, rise-dominated relative sea-level cycle was coupled with moderate to high sedimentation rate to have resulted in sequences consisting of $2~3$ parasequence sets.

• Atmosphere
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• v.23 no.1
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• pp.85-92
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• 2013

We estimate atmospheric radiative heating effect of aerosols, based on AErosol RObotic NETwork (AERONET) and lidar observations and radiative transfer calculations. The column radiation model (CRM) is modified to ingest the AERONET measured variables (aerosol optical depth, single scattering albedo, and asymmetric parameter) and subsequently calculate the optical parameters at the 19 bands from the data obtained at four wavelengths. The aerosol radiative forcing at the surface and the top of the atmosphere, and atmospheric absorption on pollution (April 15, 2001) and dust (April 17~18, 2001) days are 3~4 times greater than those on clear-sky days (April 14 and 16, 2001). The atmospheric radiative heating rate (${\Delta}H$) and heating rate by aerosols (${\Delta}H_{aerosol}$) are estimated to be about $3\;K\;day^{-1}$ and $1{\sim}3\;K\;day^{-1}$ for pollution and dust aerosol layers. The sensitivity test showed that a 10% uncertainty in the single scattering albedo results in 30% uncertainties in aerosol radiative forcing at the surface and at the top of the atmosphere and 60% uncertainties in atmospheric forcing, thereby translated to about 35% uncertainties in ${\Delta}H$. This result suggests that atmospheric radiative heating is largely determined by the amount of light-absorbing aerosols.

• Journal of Preventive Medicine and Public Health
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• v.29 no.1 s.52
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• pp.79-90
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• 1996

The purpose of the study was to determine factors influencing compliance with anti-tuberculosis therapy. The study subjects were 104 tuberculosis patients who have received the initial treatment in 3 health centers of Kyongju-City, Dalseong-Gun in Teagu and Kumi-City. Data were collected between September and October 1995. The patients were classified into the improved group and the non-improved group according to outcomes of 3 month treatment with short-term therapeutic regimen. To find factors influencing compliance with anti-tuberculosis therapy, multiple logistic regression was made. There was no significant differences between the improved group and the non-improved group in sex, age, education level, occupation, family pattern, and habitual change regarding smoking and drinking. The level of knowledge about anti-tuberculosis therapy in the improved group was significantly higher than the non-improved group(p<0.01). Multiple logistic regression analysis revealed that family support for not forgetting medication (p<0.05) wis a predictor of improvement and knowledge about anti-tuberculosis therapy(p=0.054), regularity of medication(p=0.062), and consultation to family, doctor and nurse(p=0.075) were marginal predictors of improvement. Treatment must be given to every patient confirmed as having tuberculosis and must be given free of charge to the patients. The requirements for adequate chemotherapy are prescribed in the correct dosage and taken regularly by the patient for a sufficient period to prevent relapse of the disease after cure. It is suggested that education to the patients should be reinforced and connectedness between patients and tuberculosis control workers and family should be solidated.