• 지질공학
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• 제24권1호
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• pp.53-67
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• 2014

댐붕괴로 인하여 빚어지는 홍수위험지도 작성에서 물리적 현상을 재현해내기 위하여 수치모형이 사용되는 것이 일반적이다. 이때 모형의 정확도는 저수지의 수량과 댐붕괴 형성 및 진행을 포함한 모형의 물리적 구조, 입력인자 및 매개변수의 신뢰도에 의하여 결정되기 마련이다. 특히 입력인자 및 매개변수는 모형을 이용하기 이전에 미리 결정하여 입력하게 되며 사용자의 판단과 주관에 의지하므로 주의가 요구된다. 이 연구에서는 댐붕괴 모형을 FLO-2D와 연동하여 홍수 침수모의를 실시할 때에 댐붕괴 모형에서 세 개의 매개변수(붕괴각도 ${\theta}$, 저수지 형상계수 P, 붕괴율 k가 FLO-2D의 침수모의(침수범위, 침수깊이 등)에 어떻게 영향을 미치는 가를 살펴보았다. 붕괴각도 ${\theta}$는 FLO-2D의 침수모의에 있어 낮은 영향을 미치나 저수지 형상계수 P와 붕괴율 k는 중대한 영향을 미치는 것으로 나타났다. 이 연구는 향후 댐붕괴에 의한 홍수 위험의 피해를 저감하는데 기여할 것이다.

• 수산경영론집
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• 제51권2호
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• pp.51-69
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• 2020

The purpose of this study is to construct an outlook model that is consistent with the "Fisheries Outlook" monthly published by the Fisheries Outlook Center of the Korea Maritime Institute(KMI). In particular, it was designed as a partial equilibrium model limited to abalone items, but a model was constructed with a dynamic ecological equation model(DEEM) system taking into account biological breeding and shipping time. The results of this study are significant in that they can be used as basic data for model development of various items in the future. In this study, due to the limitation of monthly data, the market equilibrium price was calculated by using the recursive model construction method to be calculated directly as an inverse demand. A model was built in the form of a structural equation model that can explain economic causality rather than a conventional time series analysis model. The research results and implications are as follows. As a result of the estimation of the amount of young seashells planting, it was estimated that the coefficient of the amount of young seashells planting from the previous year was estimated to be 0.82 so that there was no significant difference in the amount of young seashells planting this year and last year. It is also meant to be nurtured for a long time after aquaculture license and limited aquaculture area(edge style) and implantation. The economic factor, the coefficient of price from last year was estimated at 0.47. In the case of breeding quantity, it was estimated that the longer the breeding period, the larger the coefficient of breeding quantity in the previous period. It was analyzed that the impact of shipments on the breeding volume increased. In the case of shipments, the coefficient of production price was estimated unelastically. As the period of rearing increased, the estimation coefficient decreased. Such result indicates that the expected price, which is an economic factor variable and that had less influence on the intention to shipments. In addition, the elasticity of the breeding quantity was estimated more unelastically as the breeding period increased. This is also correlated with the relative coefficient size of the expected price. The abalone supply and demand forecast model developed in this study is significant in that it reduces the prediction error than the existing model using the ecological equation modeling system and the economic causal model. However, there are limitations in establishing a system of simultaneous equations that can be linked to production and consumption between industries and items. This is left as a future research project.

• 콘크리트학회논문집
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• 제24권6호
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• pp.659-666
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• 2012

최근 대형 매스콘크리트 구조물의 온도균열 저감을 위해 저열 포틀랜드시멘트(LPC), 삼성분계 저발열시멘트(TBC) 및 조강형저발열시멘트(EBC)에 대한 다양한 연구와 현장적용이 이루어지고 있다. 콘크리트 구조물의 온도균열검토를 위해서는 단열온도 예측모델이 필수적이지만, 아직 많은 종류의 배합에 대한 자료가 축적되어 있지 않으며, 단열온도 상승 시험체의 용적에 따른 결과 차이가 보고되고 있다. 따라서 이 연구에서는 결합재 종류 및 단열 시험체 용적에 따른 단열온도 상승시험을 수행하고 배합별 최대 단열온도 상승양과 반응계수를 분석 제시하였다. 실험 결과, TBC 배합의 최대 단열온도 상승양($Q_{\infty}$) 및 반응계수(r)가 가장 작은 것으로 나타났다. 또한 단열 시험체 용적에 따라 $Q_{\infty}$과 r가 다르게 나타났으며, 50 l 시험체에 의한 측정 결과가 60 l보다 일정하게 높은 상관관계를 나타냈다. 이상의 상관관계를 이용하면, 6 l 시험체에 의한 결과로 50 l 시험체의 단열온도 상승양을 예측할 수 있어 현장 콘크리트 품질관리 및 기초연구단계에서 활용할 수 있을 것으로 판단된다.

• 문화기술의 융합
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• 제8권5호
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• pp.577-582
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• 2022

외상 거래는 고객의 수요를 증대시킬 목적으로 공급자가 경쟁 업체와의 가격 차별화 수단의 하나로 활용되어진다. 특히 공급자(Supplier), 중간유통자(Retailer) 그리고 고객(Customer)으로 구성되는 2 단계 공급사슬의 경우 공급자로부터 허용되는 상품 대금의 지불 유예는 중간유통자의 재고투자비용을 줄이는 수단이 되고, 중간유통자는 줄어든 재고 투자비용의 절감으로부터 최종 고객의 수요 증대를 기대하면서 판매 가격을 할인 할 수 있는 여지를 갖게 된다. 이와 같이 외상을 통한 지불 유예가 고객의 수요 증대를 목적으로 경쟁 기업과의 차별화 방안으로 제공되어 진다는 면에서 보면 외상 거래 기간은 거래량에 따라 차등적으로 허용되는 것이 좀 더 일반적일 수 있다. 퇴화성 제품의 경우 주문량에 따라 주어지는 외상 거래 기간은 중간유통자의 주문량에 긍정적인 요인이 되지만 제품의 퇴화는 주문량의 증가에 부정적인 요인이 될 수 있어 중간유통자의 재고정책 결정에는 두 요인의 절충이 필요하고, 특히 퇴화율은 중간유통자의 재고정책 결정에 중요한 역할을 하게 된다. 본 연구에서는 주문량에 따라 종속적으로 외상 거래기간이 허용되는 상황 하에서 퇴화율이 중간유통자의 재고정책에 미치는 영향을 분석하고자 한다.

• International Journal of Fluid Machinery and Systems
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• 제10권2호
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• pp.119-137
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• 2017

Although the stall stagnation phenomena have often been experienced in site and also analytically in numerical experiments in surges in systems of compressors and flow paths, the fundamental causes have not been identified yet. In order to clarify the situations, behaviours of infinitesimal disturbance waves superposed on a main flow were studied in a simplified one-dimensional flow model. A ratio of the amplifying rate of the system instability to the characteristic slope of the compressor element was surveyed as the instability enhancement factor. Numerical calculations have shown the following tendency of the factor. In the situation where both the sectional area ratio and the length ratio of the delivery flow-path to the suction duct are sufficiently large, the enhancement factors are greater in magnitude, which means occurrence of ordinary deep surges. However, in the situation where the area ratio and/or the length ratio is relatively smaller, the enhancement factor tends to lessen significantly, which situation tends to suppress deep surges for the same value of the characteristic slope. It could result in the stall stagnation condition. In the domain of area ratio vs. length ratio of the delivery duct to the suction duct, contour-lines of the enhancement factor behave qualitatively similar to those of the stall stagnation boundaries of a fan analytically obtained, suggesting that a certain range of the enhancement factor values could specify the stagnation occurrence. The significant decreases in the factors are observed to accompany appearances of phase lags and travelling waves in the wave motions, which macroscopically suggests breaking down of the complete surge actions of filling and emptying of the air in the delivery duct. The strength of the action is deeply related with acoustic interferences and is evaluated in terms of the volume-modified reduced resonance frequency proposed by the author. These observations have shown the fundamental cause and the sequence of the stall stagnation in principle.

• 대한디지털의료영상학회논문지
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• 제12권1호
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• pp.51-58
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• 2010

Ionization chambers often exhibit a stem effect, caused by interactions of radiation with air near the chamber end, or with dielectric in the chamber stem or cable. In this study measured stem effect correction factor for length of ionization chamber from medical linear accelerator recommend to with the use of stem correction method. For a model of the Farmer-type chamber, were used to calculate the beam quality correction factor. These interactions contribute to the apparent measured exposure. Additionally, it needs to consider ionization chamber use of small volume and stem effect of cable by a large field. Linear accelerator generated photons energy and increased dose repeatedly measured by using stem correction method. Stem effect was dependence of the energy and increases with photon energy conditions improved of beam quality. In conclusion, stem effect correction factor was measured within 0.4% calculated according to the exposures stem length and also supposed to determined below 1% of another stem correction method.

• Computers and Concrete
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• 제21권5호
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• pp.513-523
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• 2018

Time dependent strain due to creep is a significant factor in structural design. Multi-gene genetic programming (MGGP) and artificial neural network (ANN) are used to develop two models for prediction of creep compliance in concrete. The first model was developed by MGGP technique and the second model by hybridized MGGP-ANN. In the MGGP-ANN, the ANN is working in parallel with MGGP to predict errors in MGGP model. A total of 187 experimental data sets that contain 4242 data points are filtered from the NU-ITI database. These data are used in developing the MGGP and MGGP-ANN models. These models contain six input variables which are: average compressive strength at 28 days, relative humidity, volume to surface ratio, cement type, age at start of loading and age at the creep measurement. Practical equation based on MGGP was developed. A parametric study carried out with a group of hypothetical data generated among the range of data used to check the generalization ability of MGGP and MGGP-ANN models. To confirm validity of MGGP and MGGP-ANN models; two creep prediction code models (ACI209 and CEB), two empirical models (B3 and GL 2000) are used to compare their results with NU-ITI database.

• 한국초등과학교육학회지:초등과학교육
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• 제31권1호
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• pp.13-24
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• 2012

This purpose of this study was to analyze the characteristics of elementary students' argumentation in science problem solving process. For this study, the two argumentation topics were developed on the basis of Williams and Colomb's argumentation model. The topics of argumentation were the weight of the air and the change of volume according to state of water. The participants of this study were 6th grade students (n=51). Data were analyzed by Williams and Colomb's argumentation model and Kienpointner's argumentation style. The results of this study were as follows: In the argumentation model, most of students had the factors of claim, reason, evidence/data in their statements. But low-achievement students had difficulty in warrant and acknowledge & response. In argumentation style, the frequency of the cause-effect and explanation of example style were higher than other argumentation styles. Some implications were suggested, such as understanding the characteristics of elementary students' argumentation activities and need of educational programs including scientific argumentation.

• Journal of Korean Neurosurgical Society
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• 제55권3호
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• pp.125-130
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• 2014

Objective : This study was conducted to elucidate neuroprotective effect of carnosine in early stage of stroke. Methods : Early stage of rodent stroke model and neuroblastoma chemical hypoxia model was established by middle cerebral artery occlusion and antimycin A. Neuroprotective effect of carnosine was investigated with 100, 250, and 500 mg of carnosine treatment. And antioxidant expression was analyzed by enzyme linked immunosorbent assay (ELISA) and western blot in brain and blood. Results : Intraperitoneal injection of 500 mg carnosine induced significant decrease of infarct volume and expansion of penumbra (p<0.05). The expression of superoxide dismutase (SOD) showed significant increase than in saline group in blood and brain (p<0.05). In the analysis of chemical hypoxia, carnosine induced increase of neuronal cell viability and decrease of reactive oxygen species (ROS) production. Conclusion : Carnosine has neuroprotective property which was related to antioxidant capacity in early stage of stroke. And, the oxidative stress should be considered one of major factor in early ischemic stroke.

• Tribology and Lubricants
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• 제39권2호
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• pp.61-71
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• 2023

This study proposes a procedure for designing a labyrinth seal that meets both leakage flow rate and rotordynamic performance criteria (effective damping, amplification factor, separation margin, logarithmic decrement, and vibration amplitude). The seal is modeled using a one control volume (1CV) bulk flow approach to predict the leakage flow rate and rotordynamic coefficients. The rotating shaft is modeled with the finite element (FE) method and is assumed to be supported by two linearized bearings. Geometry, material and operating conditions of the rotating shaft, and the supporting characteristics of the bearings were fixed. A single labyrinth seal is placed at the center of the rotor, and the linearized dynamic coefficients predicted by the seal numerical model are inserted as linear springs and dampers at the seal position. Seal designs that satisfy both leakage and rotordynamic performance are searched by modifying five seal design parameters using the multi-grid method. The five design parameters include pre-swirl ratio, number of teeth, tooth pitch, tooth height and tooth tip width. In total, 12500 seal models are examined and the optimal seal design is selected. Finally, normalization was performed to select the optimal labyrinth seal designs that satisfy the system performance requirements.