• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.559-562
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• 2003

In this paper, we introduce a new method detecting thyristor faults of the power converter module in Control Rod Control System. When we control the currents in each coil of Control Rod Drive Mechanism by using the current control method, the current value can follow the current reference despite the faults like the missing phase or the diode acting. Comparing the fault current values with the normal current values, the bad transient characteristics of the abnormal current can make the operations of control rods incorrect. In this case, the information from the current trends cannot be enough to detect the fault occurrence in thyristors. Instead of the coil currents, the state of thyristors can be watched by measuring the coil voltages. In the existing system of Westinghouse type, the ripple detector takes charge of this task. But this detector has some shortcomings in the point of time for fault detection, we come to devise a new fault detection method solving the problems which belong to the ripple detector.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.12-18
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• 2006

A three-degree of freedom model of intake system was contrived and investigated in various ways for the purpose of the amelioration of the volumetric efficiency in a low and transient engine speed for a multi cylinder diesel engine. The basic concept beyond this model started from the theory that each degree of freedom model has volumetric efficiency peak as many as its number of the degree of freedom. The volumetric efficiency affects significantly to the engine performance; torque characteristics, fuel economy and emission level. For commercial vehicles and stationary engines, the engine is designed so as to produce their best performance near the normal engine speeds, thus the low engine speed area has a tendency of poor volumetric efficiency. The aim of this study was highlighted on the amelioration of volumetric efficiency of low engine speed area in a multi cylinder diesel engine matched with an additional Helmholtz resonator. By the use of VIS(variable induction system) volumetric efficiency at low engine speed range was significantly improved. The availability of control by combination of VIS and CIS(conventional induction system) will be proposed as a variable induction system that would be an appropriate model for amelioration of the volumetric efficiency at low engine speed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.3
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• pp.296-305
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• 1995

A numerical study was undertaken to clarify the mechanisms of heat transfer in fluid-particle suspension flows. Such flows, including fluidization, are of considerable industrial importance. The present study uses 2-D numerical computations of collisions of normal incidence between a particle and a wall. By comparing the results using (a) adiabatic boundary conditions on the particle and (b) uniform, elevated temperature conditions on the particle, the contributions of fluid-mediated conduction and particle induced convection were successfully separated. Computational expedience led to the use of a transient conduction thermal layer as the background thermal field for the analysis. The results shows that the effect of particle movement is very small until the particle reaches a distance of one to one half diameter away from the wall. The gas-mediated conduction effect is dominant over the induced gas convection effect when Pe is small and the induced gas convection effect becomes significant as Pe increases.

• Annals of dermatology
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• v.30 no.6
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• pp.653-661
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• 2018

Background: Citron is well known for an abundance of antioxidative and anti-inflammatory ingredients such as vitamin C, polyphenol compounds, flavonoids, and limonoids. Objective: In this study, we aimed to evaluate the effects of citron essential oils on rosacea mediators in activated keratinocytes in vitro. Methods: Normal human epidermal keratinocytes (NHEKs) were stimulated with $1{\alpha}$, 25-dihydroxyvitamin $D_3$ ($VD_3$) and interleukin 33 (IL-33) with LL-37 to induce rosacea mediators such as kallikrein 5 (KLK5), cathelicidin, vascular endothelial growth factor (VEGF), and transient receptor potential vanilloid 1 (TRPV1). These mediators were analyzed by performing reverse-transcription polymerase chain reaction (PCR), quantitative real-time PCR, immunocytofluorescence and enzyme-linked immunosorbent assay after NHEKs were treated with citron seed and unripe citron essential oils. Results: The messenger RNA (mRNA) and protein levels of KLK5 and LL-37 induced by $VD_3$ were suppressed by citron seed and unripe citron essential oils. Furthermore, the mRNA and protein levels of VEGF and TRPV1 induced by IL-33 with LL-37 were also suppressed by citron essential oils. Conclusion: These results show that citron essential oils have suppressive effects on rosacea mediators in activated epidermal keratinocytes, which indicates that the citron essential oils may be valuable adjuvant therapeutic agents for rosacea.

• The korean journal of orthodontics
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• v.49 no.6
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• pp.372-380
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• 2019

Objective: To determine the effects of a local injection of leukocyte-platelet-rich plasma (L-PRP) on orthodontic tooth movement in rabbits. Methods: Twenty-three male New Zealand white rabbits were included in a split-mouth design. Tooth movement with a 100-g nickel-titanium closed-coil spring was performed on the maxillary first premolars. L-PRP was injected submucosally at the buccal and lingual areas of the first premolar in one random side of the maxilla and the other side served as the control and received normal saline. The amount of tooth movement was assessed on three-dimensional digital models on days 0, 3, 7, 14, 21, and 28. Histological findings and osteoclast numbers were examined on day 0 as the baseline and on days 7, 14, and 28. Results: The L-PRP group showed significantly greater cumulative tooth movement at all observed periods. However, a significantly higher rate of tooth movement was observed only on days 0-7 and 7-14. The osteoclast numbers were significantly increased in the L-PRP group on days 7 and 14. Conclusions: Local injection of L-PRP resulted in a transient increase in the rate of tooth movement and higher osteoclast numbers.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2757-2772
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• 2023

The fluid retention effect of the Volume Control Tank (VCT) leads to a long time delay in Reactor Coolant System (RCS) concentration during the boration process. A coupled model combining a lumped-parameter sub-model and a computational fluid dynamics sub-model is currently used to investigate the concentration dynamic characteristic of RCS during the boration process. This model is validated by comparison with experimental data, and the predicted results show excellent agreement with experimental data. We provide detailed fields in VCT and concentration variations of RCS to study the interaction between mixing in VCT and the transient responses of RCS. Moreover, the impacts of the inlet flow rate, inlet nozzle diameter, original concentration, and replenishing temperature of VCT on the RCS concentration characteristic are studied. The inlet flow rate and nozzle diameter of VCT remarkably affect the RCS concentration characteristic. Too-large or too-small inlet flow rates and nozzle diameters will lead to unacceptable long delays. In this work, the optimal inlet flow rate and nozzle diameter of VCT are 5 m³/h and 58.8 mm, respectively. Besides, the impacts of the original concentration and replenishing temperature of VCT are negligible under normal operating conditions.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1052-1065
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• 2024

Advanced Pressurized Water Reactors (APWRs) and Boiling Water Reactors (BWRs) employ a suppression pool as a heat sink to prevent containment overpressure. Steam can be discharged into the pool through multi-hole spargers or blowdown pipes in both normal and accident conditions. Direct Contact Condensation (DCC) creates sources of momentum and heat. The competition between these two sources determines the development of thermal stratification or mixing of the pool. Thermal stratification is of safety concern as it reduces the cooling capability compared to a completely mixed pool condition. In this work we develop a scaling approach to prediction of the thermal stratification in a water pool induced by steam injection through spargers. Experimental data obtained from large-scale pool tests conducted in the PPOOLEX and PANDA facilities, as well as simulation results obtained using validated codes are used to develop the scaling. Two injection orientations, namely radial injection through multi-hole Sparger Head (SH) and vertical injection through Load Reduction Ring (LRR), are considered. We show that the erosion rate of the cold layer can be estimated using the Richardson number. In this work, scaling laws are proposed to estimate both the (i) transient erosion velocity and (ii) the stable position of the thermocline. These scaling laws are then implemented into a 1D model to simulate the thermal behavior of the pool during steam injection through the sparger.

• The Journal of Korean Medicine
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• v.26 no.2 s.62
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• pp.217-230
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• 2005

Objectives: Chungpaesagan-tang (CPSGT), which is frequently used for treating patients of cerebrovascular disease, has not been reported by clinical doctors concerning the effect of neuronal aptosis caused by brain ischemia. To study the effect of CPSGT on focal cerebral ischemia in normal and diabetic rats and SHR, focal cerebral ischemia was induced by transient MCAO, and after onset CPSGT was administrated. Methods: Rats (Sprague-Dawley) were divided into four groups: sham-operated group, MCA-occluded group, CPSGT­administrated group after MCA occlusion, and normal group. The MCA was occluded by intraluminal method. CPSGT was administrated orally twice (l and 4 hours) after middle cerebral artery occlusion. All groups were sacrificed at 24 hours after the surgery. The brain tissue Was stained with $2\%$ triphenyl tetrazolium chloride (TTC) or $1\%$ cresyl violet solution, to examine effect of CPSGT on ischemic brain tissue. The blood samples were obtained from the heart.~. Tumor necrosis $factor-\alpha$ level and interleukin-6 level of serum was measured from sera using enzyme-linked immunoabsorbent assay (ELISA). Then changes of immunohistochemical expression of $TNF-\alpha$ in ischemic damaged areas were observed. Results: In NC+MCAO+CP and DM+MCAO+CP, CPSGT significantly (p<0.01) decreased the number of neuron cells compared to the control group. CPSGT markedly reduced (p<0.01) the infarct size of the forebrain in distance from the interaural line on cerebral ischemia in diabetic rats. CPSGT significantly reduced the $TNF-\alpha$ expression in penumbra region of damaged hemisphere in diabetic rats. Conclusions: CPSGT had a protective effect on cerebral ischemia in SD rats, especially in diabetic rats compared with normal SD rats.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.131-135
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• 2008

Purpose: To measure and quantify the factors of intraocular pressure (IOP) variation for normal Korean youth. Methods: The IOP of normal youth 805 persons (male: 367, female: 438) were measured as a function of time and quantity for fixation, reclining posture, hard blinking, drinking water, drinking hard liquor, tobacco and coffee by using non-contact tonometer (AT555, Reichert Co.). In the case of fixation, reclining posture and hard blinking, the intraocular pressure of right and left eye were measured for 6 males and 6 females every 10 minutes during 30 minute. In the case of water, liquor, tobacco and coffee, the measurement for 4 or 5 groups (6 persons/ group) having similar IOP were done for the IOP variation of right eye. Results: The mean IOP was 15.2 mmHg for males and 15.8 mmHg for females (slightly higher than male's), respectively and the 99% of those were in the range of the normal IOP. The measured IOP was increased by fixation, reclining posture and hard blinking with males and females. The gradient of increasing slope was 0.15/0.13/0.07/0.08, 0.09/0.08/0.08/0.08 and 0.19/0.08/0.26/0.31, respectively. The IOP variation was elevated by drinking water (especially in the case of 1000 ml) and lowered in proportion to the amount of drinking by hard liquor. Cigarette smoking was associated with rise in intra ocular pressure, but was not shown a definite relation. And coffee had virtually no effect. Conclusions: Fixation, reclining posture, hard blinking and Tobacco caused a transient increase in IOP, but alcohol elicited a slight reduction in IOP overall.

• Journal of Korean Biological Nursing Science
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• v.4 no.2
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• pp.19-40
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• 2002

The purpose of this study was to determine the effect of DHEA on Type I(soleus) and II muscles(plantaris, gastrocnemius) in a focal brain ischemia model rat. Thirty-seven male Sprague-Dawley rats with $200{\sim}250g$ body weights were randomly divided into four groups : CINS(cerebral ischemia + normal saline), CIDH(cerebral ischemia + DHEA), SHNS(sham + normal saline), SHDH (sham + DHEA). Both the CINS and CIDH groups were undergone a transient right middle cerebral artery occlusion operation. In the SHNS and SHDH groups, a sham operation was done. DHEA was administered daily at a dose of 0.34mmol/kg, and normal saline was administered daily at the same dose by intraperitoneal injection for 7days after operation. Cerebral infarction in the CINS and CIDH groups was identified by staining with 2% triphenyltetrazolium chloride solution for 60 minutes. The data were analyzed by Kruskal-Wallis test and Mann-Whitney U test using the SPSSWIN 9.0 program. The results were summarized as follows: 1) The muscle weights of soleus(Type I), plantaris and gastrocnemius(Type II) in CINS group were significantly less than those of the SHNS group(p<.01). The muscle fiber cross-sectional area of the CINS group was significantly less than that of the SHNS group in Type I muscle fiber of the soleus and Type II muscle fiber of the plantaris and gastrocnemius(p<.05). The myofibrillar protein content of the CINS group was significantly less than that of the SHNS group in the left gastrocnemius and right soleus(p<.05). 2) The muscle weights of the soleus, plantaris and gastrocnemius except the unaffected side of the plantaris in the CIDH significantly increased compared to those of the CINS group(p<.05). The muscle fiber cross-sectional area of the CIDH group significantly increased compared to that of the CINS group in Type II muscle fiber of the plantaris and gastrocnemius(p<.05). The myofibrillar protein content of the CIDH group significantly increased compared to that of the CINS group in the left soleus(p<.05). 3) On the post-op 8 day, the body weight of the CINS group was significantly less than that of the CIDH, SHNS and SHDH groups(p<.01). Total diet intake of the CINS and CIDH groups was significantly less than that of the SHNS and SHDH groups(p<.01). Based on these results, it was identified that muscle atrophy could be induced during the 7 days after cerebral infarction, and DHEA administration during the early stage of cerebral infarction might attenuate muscle atrophy.