• 설비공학논문집
• /
• 제7권3호
• /
• pp.435-449
• /
• 1995

In this paper, pressure drop through a capillary tube is modeled to determine the length of a capillary tube for a given set of conditions. HCFC-22 and its alternatives, HFC-134a, R407B, and R410A are used as working fluids. The conditions on which the model is tested are as follows : condensing temperature; 40.0, 45.0, 50.0, $55.0^{\circ}C$, degree of subcooling;0.0, 2.5, $5.0^{\circ}C$, capillary tube exit condition;choked flow, capillary tube diameter;1.2~2.4mm, mass flow rate;5.0~50.0g/sec. The results justify the use of Stoecker's model which yields the results very close to the values in ASHRAE handbook. While McAdams' method yields much better results than Duckler's in calculating the viscosity of the fluid in 2-phase, the friction factor suggested by Stoecker seems to be the best for capillary tubes of large diameter used in residential air conditioners. For each refrigerant, 372 data with various variables are calculated by the model. The results show that capillary tube length varies very uniformly with changes in condensing temperature and degree of subcooling. Based on this fact, regression analysis is performed to determine the dependence of mass flow rate on the length and diameter of a capillary tube, condensing temperature, and degree of subcooling. Thus determined correlation yields a mean deviation of 2.36% for 1,488 data, showing an excellent agreement.

• The Korean Journal of Physiology
• /
• 제11권1호
• /
• pp.37-44
• /
• 1977

In the previous study of the release, excretion, and plasma concentration of aldosterone in normal Koreans, the author found that urinary aldosterone excretion and aldosterone secretion rate of the Korean who usually take high amount of salt are significantly lower, in compared to Americans, although the plasma concentration is only tended to be low. The control of plasma aldosterone level depends on the secretion rate and the metabolic clearance of the hormone. In this experiments, the metabolic clearance rate of aldosterone was determined in normotensive korean and the effects of adrenal stimulations on the rates were also studied in the same subjects. The metabolic clearance rate of the normal Korean was not significantly different from those of the American, and shown a little increase in response to sodium restriction. These results indicate that the decrease in secretion rate rather than the increase in metabolic clearance Tate is the major factor maintaining lower plasma aldosterone level. After furosemide diuresis, on the contrary, the removal of aldosterone showed significant the decrease despite slight increase of secretion rate. This suggest that the reduction in metabolic clearance rate of the hormone during volume depletion found to be major cause of high plasma concentration. Additional potassium supply produced detectable decrease of metabolic clearance rate, but the changes were smaller than that of secretion rate, which suggested that the higher secretion rate could account for elevated plasma concentration of aldosterone rather than metabolic clearance. Above results also support author's previous evidences that the normal Korean who already adapted to a high sodium diet have ability to produce adequate aldosterone activity without producing detectable changes on the metabolic clearance rate under the condition of sodium restriction with approp riate potassium intake.

• 한국식품영양과학회지
• /
• 제27권1호
• /
• pp.191-199
• /
• 1998

This paper has studied the nutritional iron status of adults in the city of Taegu. The subjects of the experiment were twenty six men and women living in the city of Taegu. The iron intake was 26.1mg for men and 17.1mg for women, which were respectively 217.5% and 95% of RDA. For men heme iron was 5% and nonheme iron, 95% for women heme iron was 5.8% and nonheme iron, 94.2%. The absorption rate of dietary iron was 6.2% for men and 9.1% for women. The hemoglobin was 14.5g/dl for men and 11.9g/dl for women, and the rate of developing anemia was 8.3% in men and 57.1% in women. The serum ferritin was 57.8ng/ml with men, which was found to be normal, and 14.7ng/ml with women, which showed that 57.1% of women were in the condition of iron depletion or iron deficiency anemia. The rate of developing anemia resulting from the deficiency of serum ferritin was as high as that from the deficiency of hemoglobin. The correlation between iron intake based on the dietary record, and energy intake, vegetable protein intake and dietary fiber intake was found to be positive. So was the correlation between the iron intake, and hemoglobin, serum ferritin and urinary iron excretion. There was also a positive correlation between hemoglobin, and hematocrit and serum ferritin. The correlation between fecal iron excretion and serum ferritin was positive. Fecal iron excretion and urinary iron excretion can be complemented by iron intake but the fact should be considered that 95% of iron intake is nonheme iron, which is difficult to absorb. Based on the above-mentioned things, serum ferritin and hemoglobin can be used as the standards of measuring anemia. As women in their child bearing years show the high rate of 57.1% of developing anemia, the more thorough nutritional education of iron is required.

• 사상체질의학회지
• /
• 제23권2호
• /
• pp.240-253
• /
• 2011

1. Objectives: The purpose of this study was to survey the Original symptoms(素證) of Soyangin's and to compare the tendency of their symptoms between Soyangin Heat-related diarrhea accompanied by headache(身熱頭痛亡陰證) and Soyangin Cold-related diarrhea accompanied by abdominal pain(身寒腹痛亡陰證). 2. Methods: We recruited 56 Soyangin subjects in the Korean Medicine clinic and researched their original symptoms. Subjects were diagnosed by the Sasang Constitutional specialists and Sasang Constitutional Medication. Subjects were two groups, confirmed to Soyangin Heat-related diarrhea accompanied by headache and Soyangin Cold-related diarrhea accompanied by abdominal pain. All subjects answered the questionnaire about their Original symptoms. We found the differences between 2 groups using the Independent-Samples T-test. Analysis was conducted using SPSS 12.0 for Korean. 3. Results and Conclusions: In Original symptoms, Tendency of overeating(p=0.01), Condition of digestion(p=0.04), Perspiration after exercise (p=0.02), Usual perspiration(p=0.00), Tiredness after perspiration(p=0.05) Cold intolerance on extremities(p=0.04), General edema(p=0.01) etc. are different between 2 groups. We found the differences of heat and cold in symptoms between two Soyangin syndromes.

• Journal of Ecology and Environment
• /
• 제30권2호
• /
• pp.109-119
• /
• 2007

The effect of water flow on the growth of Gafrarium tumidum was studied in the field using open cages constructed with stainless steel net and perspex in which holes were drilled. Cages with different flows (25, 50 and 75% of the control) were made by varying the area of perspex being drilled. Reduction in flow rate was directly proportional to the undrilled area, and the mean flow rate of the different treatment groups varied from 3.12 cm/s for the 25% exposure to 12.48 cm/s for the control cages. At the end of the 3-month experiment, no significant differences in sediment characteristics were found among the treatments. Growth in shell length, shell weight and tissue dry weight was, however, positively correlated with flow rate. Percentage increases ranged from $3.0{\sim}8.3%$ for shell length, $9.9{\sim}23.1%$ for shell weight and $17.2{\sim}53.3%$ for tissue dry weight. Condition index of the clam was not significantly different among the treatments. Seston depletion effect could reduce growth in G. tumidum only when water flow was reduced to 25% of the control. G. tumidum also exhibited different responses in shell and tissue growth at low flow rates, in which shell growth continued to decrease as flow rate decreased whereas tissue growth was relatively independent of low flows at 25 and 50% of the control. It was suggested that when seston flux was reduced at slow flows, it would be a better strategy for G. tumidum to channel energy for gonad development instead of shell growth during the reproductive stage.

• 한국표면공학회지
• /
• 제49권2호
• /
• pp.159-165
• /
• 2016

The hydrogen has been recognized as a clean, nonpolluting and unlimited energy source that can solve fossil fuel depletion and environmental pollution problems at the same time. Water electrolysis has been the most attractive technology in a way to produce hydrogen because it does not emit any pollutants compared to other method such as natural gas steam reforming and coal gasification etc. In order to improve efficiency and durability of the water electrolysis, comprehensive studies for highly active and stable electrocatalysts have been performed. The platinum group metal (PGM; Pt, Ru, Pd, Rh, etc.) electrocatalysts indicated a higher activity and stability compared with other transition metals in harsh condition such as acid solution. It is necessary to develop inexpensive non-noble metal catalysts such as transition metal oxides because the PGM catalysts is expensive materials with insufficient it's reserves. The optimization of operating parameter and the components is also important factor to develop an efficient water electrolysis cell. In this study, we optimized the operating parameter and components such as the type of AEM and density of gas diffusion layer (GDL) and the temperature/concentration of the electrolyte solution for the anion exchange membrane water electrolysis cell (AEMWEC) with the transition metal oxide alloy anode and cathode electrocatalysts. The maximum current density was $345.8mA/cm^2$ with parameter and component optimization.

• 한국광물학회지
• /
• 제18권1호
• /
• pp.61-72
• /
• 2005

백령도와 보은 지역의 마이오세 알칼리현무암에 상부맨틀암석인 스피넬 페리도타이트가 포획되어 있다. 이들 포획체 내의 단사휘석의 모드 조성과 주성분원소, 미량원소, 희토류원소 조성은 백령도와 보은 지역의 상부맨틀의 평형 온도와 맨틀결핍, 맨틀부화와 같은 지화학적 과정들을 규명하는 매우 중요하다. 원생입상조직과 반상쇄설조직 사이의 전이 조직을 보이는 백령도와 보은 스피넬 페리도타이트의 평형온도는 15 kb 압력에서 각각 773∼1188℃와 705∼1106℃이다. 단사휘석의 Y, Yb 성분은 백령도와 보은 스피넬 페리도타이트가 각각 1~10%와 1∼4%의 부분용융을 받았고, 단사휘석의 LREE 부화 패턴은 이들 지역 상부맨틀이 은폐 맨틀교대작용을 받았음을 지시한다.

• The Korean Journal of Physiology and Pharmacology
• /
• 제23권2호
• /
• pp.121-130
• /
• 2019

Glutamate toxicity-mediated mitochondrial dysfunction and neuronal cell death are involved in the pathogenesis of several neurodegenerative diseases as well as acute brain ischemia/stroke. In this study, we investigated the neuroprotective mechanism of dieckol (DEK), one of the phlorotannins isolated from the marine brown alga Ecklonia cava, against glutamate toxicity. Primary cortical neurons ($100{\mu}M$, 24 h) and HT22 neurons (5 mM, 12 h) were stimulated with glutamate to induce glutamate toxic condition. The results demonstrated that DEK treatment significantly increased cell viability in a dose-dependent manner ($1-50{\mu}M$) and recovered morphological deterioration in glutamate-stimulated neurons. In addition, DEK strongly attenuated intracellular reactive oxygen species (ROS) levels, mitochondrial overload of $Ca^{2+}$ and ROS, mitochondrial membrane potential (${\Delta}{\Psi}_m$) disruption, adenine triphosphate depletion. DEK showed free radical scavenging activity in the cell-free system. Furthermore, DEK enhanced protein expression of heme oxygenase-1 (HO-1), an important anti-oxidant enzyme, via the nuclear translocation of nuclear factor-like 2 (Nrf2). Taken together, we conclude that DEK exerts neuroprotective activities against glutamate toxicity through its direct free radical scavenging property and the Nrf-2/HO-1 pathway activation.

• Nuclear Engineering and Technology
• /
• 제51권6호
• /
• pp.1708-1714
• /
• 2019

The purpose of the critical evaluation of the spent fuel pool (SFP) is to verify that the maximum effective multiplication factor ($K_{eff}$) is less than the critical safety limit at 100% stored condition of the spent fuel with the maximum reactivity. At nuclear power plants, the storage standard of spent fuel, ie, the loading curve, is established to prevent criticality from being generated in SFP. Here, the loading curve refers to a graph showing the minimum discharged burnup versus the initial enrichment of spent fuel. Recently, US NRC proposed the new critical safety assessment guideline (DSS-ISG-2010-01, Revision 0) of PWR SFPs and most of utilities in US is following it. Of course, the licensed criterion of the maximum effective multiplication factor of SFP remains unchanged and it should be less than 0.95 from the 95% probability and the 95% confidence level. However, the new guideline is including the new evaluation methodologies like the application of the axial burnup profile, the validation of depletion and criticality code, and trend analysis. Among the new evaluation methodologies, the most important factor that affects $K_{eff}$ is the axial burnup profile of spent fuel. US NRC recommends to consider the axial burnup profiles presented in NUREG-6801 in criticality analysis. In this paper, criticality effect was evaluated considering three profiles, respectively: i) Axial burnup profiles presented in NUREG-6801. ii) Representative PWR axial burnup profile. iii) Uniform axial burnup profile. As the result, the case applying the axial burnup profiles presented in NUREG-6801 showed the highest $K_{eff}$ among three cases. Therefore, we need to introduce a new methodology because it can be issued if the axial burnup profiles presented in NUREG/CR-6801 are applied to the domestic nuclear power plants without any other consideration.

• Nuclear Engineering and Technology
• /
• 제54권6호
• /
• pp.2107-2119
• /
• 2022

Accurate remaining useful life (RUL) prediction for critical components of nuclear power equipment is an important way to realize aging management of nuclear power equipment. The electric gate valve is one of the most safety-critical and widely distributed mechanical equipment in nuclear power installations. However, the electric gate valve's extended service in nuclear installations causes aging and degradation induced by crack propagation and leakages. Hence, it is necessary to develop a robust RUL prediction method to evaluate its operating state. Although the particle filter(PF) algorithm and its variants can deal with this nonlinear problem effectively, they suffer from severe particle degeneracy and depletion, which leads to its sub-optimal performance. In this study, we combined the whale algorithm with regularized particle filtering(RPF) to rationalize the particle distribution before resampling, so as to solve the problem of particle degradation, and for valve RUL prediction. The valve's crack propagation is studied using the RPF approach, which takes the Paris Law as a condition function. The crack growth is observed and updated using the root-mean-square (RMS) signal collected from the acoustic emission sensor. At the same time, the proposed method is compared with other optimization algorithms, such as particle swarm optimization algorithm, and verified by the realistic valve aging experimental data. The conclusion shows that the proposed method can effectively predict and analyze the typical valve degradation patterns.