• Nuclear Engineering and Technology
• /
• v.55 no.10
• /
• pp.3775-3786
• /
• 2023

Mixing Vane Grid (MVG) is one of the most important structures in fuel assembly due to its high performance in mixing the coolant and ultimately increasing Critical Heat Flux (CHF), which avoids the temperature rising suddenly of fuel rods. To evaluate the mixing performance of the MVG, a Total Diffusion Coefficient (TDC) mixing coefficient is defined in the subchannel analysis code. Conventionally, the TDC of the spacer grid is obtained from the combination of experiments and subchannel analysis. However, the processing of obtaining and determine a reasonable TDC is much challenging, it is affected by boundary conditions and MVG geometries. In is difficult to perform all the large and costing rod bundle tests. In this paper, the CFD method was applied in TDC analysis. A typical 5 × 5 MVG was simulated and validated to estimate the mixing performance of the MVG. The subchannel code was used to calculate the TDC. Firstly, the CFD method was validated from the aspect of pressure drop and lateral temperature distribution in the subchannels. Then the effect of boundary conditions including the inlet temperature, inlet velocities, heat flux ratio between hot and cold rods and the arrangement of hot and cold rods on MVG mixing and TDC were studied. The geometric effects on mixing are also carried out in this paper. The effect of vane pattern on mixing was investigated to determine which one is the best to represent the grid's mixing performance.

• Atmosphere
• /
• v.29 no.4
• /
• pp.451-461
• /
• 2019

Medium-range forecast is highly dependent on ensemble forecast data. However, operational weather forecasters have not enough time to digest all of detailed features revealed in ensemble forecast data. To utilize the ensemble data effectively in medium-range forecasting, representative weather patterns in East Asia in this study are defined. The k-means clustering analysis is applied for the objectivity of weather patterns. Input data used daily Mean Sea Level Pressure (MSLP) anomaly of the ECMWF ReAnalysis-Interim (ERA-Interim) during 1981~2010 (30 years) provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Using the Explained Variance (EV), the optimal study area is defined by 20~60°N, 100~150°E. The number of clusters defined by Explained Cluster Variance (ECV) is thirty (k = 30). 30 representative weather patterns with their frequencies are summarized. Weather pattern #1 occurred all seasons, but it was about 56% in summer (June~September). The relatively rare occurrence of weather pattern (#30) occurred mainly in winter. Additionally, we investigate the relationship between weather patterns and extreme weather events such as heat wave, cold wave, and heavy rainfall as well as snowfall. The weather patterns associated with heavy rainfall exceeding 110 mm day^-1 were #1, #4, and #9 with days (%) of more than 10%. Heavy snowfall events exceeding 24 cm day^-1 mainly occurred in weather pattern #28 (4%) and #29 (6%). High and low temperature events (> 34℃ and < -14℃) were associated with weather pattern #1~4 (14~18%) and #28~29 (27~29%), respectively. These results suggest that the classification of various weather patterns will be used as a reference for grouping all ensemble forecast data, which will be useful for the scenario-based medium-range ensemble forecast in the future.

• The Journal of the Society of Korean Medicine Diagnostics
• /
• v.16 no.1
• /
• pp.27-34
• /
• 2012

Objectives The purpose of this study was to find out whether if there is correlation between the pattern differentiation questionnaire and edema index of body composition analysis. Methods The authors obtained results of pattern differentiation Questionnaires and body composition analysis tests from 195 female patients who visited the Oriental gynecology department in Kyung Hee university Oriental medicine hospital at Gang-dong. The authors conducted correlation analysis between indicators of Body composition analysis and each part of the pattern differentiation Questionnaire. Pearson correlation analysis was performed on SPSS version 13.0 for windows. Results There was negative correlation between the Phlegm Questionnaire and right arm ECF, left arm ECF, and left arm ECW of the Body composition index. There was no correlation between Yin-deficiency Questionnaire and Body composition index. There was no correlation between Heat pattern Questionnaire and Body composition index. There was positive correlation between the Cold pattern Questionnaire and right leg ECF, and right leg ECW of the body composition index. There was no correlation between degree of edema self-awareness and Body composition index. Conclusions The result showed that each Questionnaire score has different correlation or even no correlation with Body composition index and degree of edema self-awareness. Further studies are needed for a better understanding and interpretation of the relationship between edema index on Body composition analysis and Questionnaires.

• Journal of Energy Engineering
• /
• v.7 no.1
• /
• pp.44-56
• /
• 1998

Separate heat pipe exchanger is considered as the high thermal transportation equipment, because evaporator and condenser are separately positioned in the long distance. Its characteristics are that the working fluid is circulated naturally by the position height of two exchangers. But the operating characteristics are restricted by the temperature of hot and cold fluid, flow pattern and diameter of vapor line, etc. in this study, the vapor pressure and the minimum height of two exchangers are studied about the factors restricting the operating characteristics.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.2 s.233
• /
• pp.189-196
• /
• 2005

The physical model considered here is a horizontal layer of fluid heated below and cold above with a conducting body placed at the center of the layer. The body has dimensionless thermal conductivities to the fluid of 0.1, 1 and 50. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for different Rayleigh numbers. Multi-domain technique is used to handle a square-shaped conducting body. The results for the case of a conducting body are also compared to those of adiabatic and neutral isothermal bodies. When the dimensionless thermal conductivity is 0.1, a pattern of fluid flow and isotherms and the corresponding time-averaged surface Nusselt number are almost the same as the case of an adiabatic body. When the dimensionless thermal conductivity is 50, a pattern of flow and isotherm and the corresponding surface and time-averaged Nusselt number are similar to those of neutral body. The results for the case of dimensionless thermal conductivity of unity are also compared to those of pure natural convection.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.425-428
• /
• 2006

A semi-solid forming technology has some advantages compared with conventional forming processes such as die casting, squeeze casting and hot/cold forging. In this study, the numerical analysis of semi-solid filling has been studied with solid fraction fs = 30% of A356 aluminum alloys. The finite difference program of two-phase flow model of Navier Stokes' equation coupled with heat transfer and solidification has been developed to predict a filling pattern, liquid segregation and temperature distribution of semi-solid metals. It gives die filling patterns and final solidification area. It can predict mechanical properties of semi-solid forming processes.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.3
• /
• pp.541-550
• /
• 1988

Natural convection in a square enclosure was investigated numerically for low prandtl number fluids using Finite Element Method. In case of Ra=10$^{4}$, 10$^{5}$ and 10$^{6}$ the temperature gradient decreases gradually at the lower end of the hot wall(or at the upper end of the cold wall) as prandtl number decreases in the range of 0.01 .leq. Pr .leq. 10. Maximum heat transfer occurs at a somewhat higher point from the lower end of hot wall(or at somewhat lower point from the upper end of the cold wall) and it draws near to the lower end of the hot wall(or draws near to the upper end of the cold wall) with increasing prandtl number. The flow in the enclosure appears as an Unicell Pattern for Ra .leq. 10$^{4}$ and secondarily flows(or tertiary flows) appears in the core region for Ra .geq. 10$^{5}$ . The line joining the center of secondary cells skewes in a clockwise direction as the Prandtl number decreases.

• Fashion & Textile Research Journal
• /
• v.18 no.4
• /
• pp.457-467
• /
• 2016

This study aimed to develop functional underwear for elderly women in their sixties in terms of good fit, wear comfort and body temperature regulation. To satisfy elderly women's physical and metabolical needs, an automatic temperature control system via PCM treatment was applied. Underwear pattern was produced by producing body surface replica, which was derived from 3D body parametric model. Differential ratios of outline length and area between 3D surface and 2D plane were 1.4% and 0.5%, respectively. The reduction rate was determined as 10% through the expert's evaluation. PCM treated fabric showed higher Q-max, meaning that it can facilitate the thermal transition in hot situation. Moreover, it also showed higher insulation to preserve heat and keep warm microclimate in a cold weather. Heat distribution measurements on various body parts revealed that the temperature after PCM treatment was significantly higher. The clothing pressure after 10% pattern reduction showed higher before reduction, at the same time, even lower than the comfort clothing pressure range of $5{\sim}10gf/cm^2$, implying that experimental garment of this research is acceptable in terms of clothing pressure. Evaluation results on the comfort to move in various motions proved that adequate clothing pressure improved the wear comfort in various motions.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
• /
• v.34 no.3
• /
• pp.13-26
• /
• 2021

Objectives : This study was planned to help clinical treatment by examining the efficacy and frequency of use of medicines with removing nebula and improving vision action, centering on historical literature. Methods : Chinese literature centered on CNKI published after 2000 and ophthalmic books of the Beijing University of Chinese Medicine Library, regardless of the publication period. Domestic literature was searched using NDSL and OASIS, and literature published after 2000 was referenced. Results : According to traditional medical classics, as medicine with removing nebula and improving vision action, medicine with dispelling wind and clearing heat action accounted for the majority. However, it is desirable to use these medicine in the early stages of the disease. Conclusions : 1. Among the external contacts that induce corneal opacity, the wind-heat pattern was the most common. Among the visceral manifestation patterns that induce corneal opacity, liver or spleen was the most common. Cold-tempered medicine which is dispelling wind, clearing heat and bottling up the liver were most commonly used as therapeutic medicine. 2. As removing nebula and improving vision medicine, Cassiae Semen, Chrysanthmi Flos, Eriocauli Flos, and Buddlejae Flos have been widely used. 3. It has been investigated that removing nebula and improving vision medicine can be effectively used in the early stages of various diseases that cause corneal opacity.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.22 no.5
• /
• pp.1125-1131
• /
• 2008

The purpose of this study is to evaluate the clinical implication of Eight Principle Pattern Identification, EPPI in Sasang Typology. Although EPPI is considered as the most basic differential diagnosis in Oriental Medical Science, it has not been used actively enough in clinical practice owing to the presumption that EPPI is not sufficient for the analysis of complex clinical symptoms. In Zhang Jiebin's Jingyuequanshu, he separates Yin-Yang with Six-identification in EPPI when explaining them. This implies that it is difficult to talk about each of EPPI in same perspective. Thus, for the active clinical usage of EPPI it is necessary to study in hierarchical perspective. Lee Je-ma's Sasang typology could be a good example that uses the hierarchical perspective of EPPI. In the book Dongeuisoosebowon Lee Je-ma talks about differentiating Yin with Yang by constitution, Exterior with Interior and Cold with Heat accordingly, to apply in prescriptions. After differentiation, Yin and Yang are placed in higher level from the rest of EPPI, thus Yin and Yang can influence the rest of EPPI. This study showed the importance of EPPI in understanding the differential diagnosis system of Sasang typology in clinical perspectives.