• Nuclear Engineering and Technology
• /
• v.49 no.1
• /
• pp.54-70
• /
• 2017

The accumulator is a passive safety injection device for emergency core cooling systems. As an important safety feature for providing a high-speed injection flow to the core by compressed nitrogen gas pressure during a loss-of-coolant accident (LOCA), the accumulator injects its precharged nitrogen into the system after its coolant has been emptied. Attention has been drawn to the possible negative effects caused by such a nitrogen injection in passive safety nuclear power plants. Although some experimental work on the nitrogen injection has been done, there have been no comparative tests in which the effects on the system responses and the core safety have been clearly assessed. In this study, a new thermal hydraulic integral test facility-the advanced core-cooling mechanism experiment (ACME)-was designed and constructed to support the CAP1400 safety review. The ACME test facility was used to study the nitrogen injection effects on the system responses to the small break loss-of-coolant accident LOCA (SBLOCA) transient. Two comparison test groups-a 2-inch cold leg break and a double-ended direct-vessel-injection (DEDVI) line break-were conducted. Each group consists of a nitrogen injection test and a nitrogen isolation comparison test with the same break conditions. To assess the nitrogen injection effects, the experimental data that are representative of the system responses and the core safety were compared and analyzed. The results of the comparison show that the effects of nitrogen injection on system responses and core safety are significantly different between the 2-inch and DEDVI breaks. The mechanisms of the different effects on the transient were also investigated. The amount of nitrogen injected, along with its heat absorption, was likewise evaluated in order to assess its effect on the system depressurization process. The results of the comparison and analyses in this study are important for recognizing and understanding the potential negative effects on the passive core cooling performance caused by nitrogen injection during the SBLOCA transient.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.1
• /
• pp.11-23
• /
• 1997

This paper contains a new approach to blade section design method for marine propellers. The hydrodynamic characteristics of 2-D section are highly influenced by its geometrical parameters i.e., thickness and camber distributions and leading edge radius etc. To consider fully turbulent flow field near 2-D section. the finite volume method with k-${\varepsilon}$ turbulent model which solve Reynolds time averaged Navier-Stokes(RANS) equation is applied. In this study, O-type grid system that can provide many calculation points on blade surface is used. The results were compared with those of the experiment of NACA0012 to confirm the accuracy of the developed codes. The goal of this study is the development of a blade section with high efficiency and low drag. To achieve this, we carried out the tests of lift, drag and cavitation characteristics in cavitation tunnel. The results of experiment were compared with numerical results in order to validate the proposed blades design method. By comparing the numerical results with the experiments, we found that the new blade section, KH28 allows superior performance in efficiency and cavitation avoidance characteristics. We further investigated the blade section design method and an application study of this section, KH28 to apply to the marine propeller. In order to improve the accuracy of numerical results on prediction of lift and drag, we conclude here that the 2-layer boundary model must be used.

• Tuberculosis and Respiratory Diseases
• /
• v.63 no.1
• /
• pp.52-58
• /
• 2007

Background: Photodynamic therapy is a viable option for lung cancer treatment, and many studies have shown that it is capable of inducing cell death in lung cancer cells. However, the precise mechanism of this cell death has not been fully elucidated. To investigate the early changes in cancer cell transcription, we treated A549 cells with the photosensitizer DH-I-180-3 and then we illuminated the cells. Methods: We investigated the gene expression profiles of the the A549 lung cancer cell line, using a DEG kit, following photodynamic therapy and we evaluated the cell viability by performing flow cytometry. We identified the genes that were significantly changed following photodynamic therapy by performing DNA sequencing. Results: The FACS data showed that the cell death of the lung cancer cells was mainly caused by necrosis. We found nine genes that were significantly changed and we identified eight of these genes. We evaluated the expression of two genes, 3-phosphoglycerate dehydrogenase and ribosomal protein S29. The expressed level of carbonic anhydrase XII, clusterin, MRP3s1 protein, complement 3, membrane cofactor protein and integrin beta 1 were decreased. Conclusion: Many of the gene products are membrane-associated proteins. The main mechanism of photodynamic therapy with using the photosensitizing agent DH-I-180-3 appears to be necrosis and this may be associated with the altered production of membrane proteins.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.12
• /
• pp.1327-1336
• /
• 2012

In this paper, the dual-faced monopole antenna, which is arranged by numerous rectangular ring patches in sequence for the multi-bands is proposed. The ring type structure of the patch can be increased the bandwidth. Therefore the bandwidth and beam width are improved by using multiple arrayed patches. When the ring type patches are inserted serially, the resonance frequencies are occurred by the current flow from the first ring patch. It is possible because the gap between the patches is very narrow. In addition, if the patches are composed on the same plane as the feed-line, fabrication could be very difficult because the gap between the patches is extremely narrow. The thickness and permittivity of the antenna, moreover, are very important parameters because both sides of the substrate are used. We finally found the optimal thickness and permittivity to generate the coupling effect by simulation. All patches are consisted of 4-steps which the patch size was decreased 85 % by each step. In conclusion, the resonant frequency bands are 1.75~2.6 GHz(850 MHz), 3.24~3.46 GHz(220 MHz), 3.8~4.0 GHz(200 MHz), and 4.4~4.9 GHz(500 MHz).

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.6
• /
• pp.1726-1732
• /
• 2008

Injection molding is one of plastic forming technology which can easily mass-produce plastic parts with various and even complex shape. The technology has lots of difficulties in making a good part due to phase change of material, high applied pressure, and fast melt flow speed in the cavity. To overcome the problems, they had to make trial and error method until the CAE(Computer Aided Engineering) could be a tool for concurrent engineering. In this paper, we investigate the optimal design for a plastic DVD tray part by systematic approach of the commercial CAE program. In design, we should consider two objectives which are both dimensional stability and cost-down. The dimension of the part is crucial because the tray should carry a DVD correctly, but the part is too thin to injection-mold easily. In order to improve the moldability, the mold is designed in the form of stack mold which is a kind of 4 hot runner system. In first, we changed the stack-mold system with one hot-runner to cost down, and decided the optimal position of the gate. After that, we investigate the effect of both the layout of cooling channels and the cooling temperature on the shrinkage of the DVD tray. A optimal simulation approach, the gate design is 2Gate#3 and the layout is Case2 cooling line as the optimal temperature of $70^{\circ}C$. The Moldflow and PC+ABS are used for the CAE program and material respectively.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.32 no.1
• /
• pp.55-68
• /
• 2020

In order to investigate the hydraulic characteristics of a boundary layer streaming over the beach cusps appeared in swells prevailing mild seas, we numerically simulated the shoaling process of Edge waves over the beach cusp. Synchronous Edge waves known to sustain the beach cusps could successfully be duplicated by generating two obliquely colliding Edge waves in front of beach cusps. The amplitude A_B and length L_B of Beach Cusp were elected to be 1.25 m and 18 m, respectively based on the measured data along the Mang-Bang beach. Numerical results show that boundary layer streaming was formed at every phase of shoaling process without exception, and the maximum boundary layer streaming was observed to occur at the crest of sand bar. In RUN 1 where the shortest waves were deployed, the maximum boundary layer streaming was observed to be around 0.32 m/s, which far exceeds the amplitude of free stream by two times. It is also noted that the maximum boundary layer streaming mentioned above greatly differs from the analytical solution by Longuet-Higgins (1957) based on wave Reynolds stress. In doing so, we also identify the recovery procedure of natural beaches in swells prevailing mild seas, which can be summarized such as: as the infra-gravity waves formed in swells by the resonance wave-wave interaction arrives near the breaking line, the sediments ascending near the free surface by the Phase II waves orbital motion were carried toward the pinnacle of foreshore by the shoreward flow commenced at the steep front of breaking waves, and were deposited near the pinnacle of foreshore due to the infiltration.

• Archives of design research
• /
• v.12 no.4
• /
• pp.294-303
• /
• 1999

With the breakthrough development of computing environment, the design phases have been changed a lot nowadays. In the case of prior phases of transportation design such as cars and forklift-trucks design, designers have depended on surveys and 2D line drawings for fixing a product layout and extracting ergonomic data. In this method, designers don't meet only the problem of reliability of measuring data but also, the problems of unknown situation of operators' fatigue and comfort in work situation. In these methods, it has much less creditability to have a 2D human model to check the real world motion due to the limitation of the 3 Dimension. Even though with a 2D human model, perfect layout is determined, it is still difficult to measure about comfort and fatigue for a user because it measuring an analysing method is static. The development of computer hardware and software have not only changed the flow in the social-wide range but also immerged design into Virtual Environment. In conventional design method, visualization and data transferring have been the main issues but, in virtual environment, determining of design layout and analysing ergonomic data with sophisticated feeling about comfort and fatigue are possible by using 3D virtual human. In this study, the general characteristics of virtual environment was discussed and the possibility of digital process of design was treated. For these studies, layout design for forklift-trucks was tested. Eventually, the merits of each design phase applied virtual environment are discussed.

• Analytical Science and Technology
• /
• v.13 no.4
• /
• pp.504-510
• /
• 2000

The impurity profiles from the raw materials of glycyrrhizin were performed by the high performance liquid chromatography (HPLC)/electrospray ionization (ESI)- mass spectrometry (MS). For the HPLC experiment, a $C_{18}$($3.9{\times}300mm$, $10{\mu}m$) column was used and the mobile phase was acetic acid/$H_2O$ (1:10):acetonitrile=3:2 with a flow rate of 0.8 ml/min. The effluent was splitted into the ratio of 50:1 and went into the ESI-MS. Three to six impurities were found and informed of the identification of the structure of the impurities by ESI-MS. And the structures of impurities were suggested to a hydroxy-glycyrrhizin which is added with hydroxy group (-OH) in the glycyrrhetic acid moiety and a reduced-glycyrrhizin which the position of 12 of the glycyrrhetic acid moiety is reduced. The purities of the standard materials were about 90%.

• The Korean Journal of Physiology and Pharmacology
• /
• v.16 no.6
• /
• pp.393-398
• /
• 2012

Mast cells are involved in allergic responses, protection against pathogens and autoimmune diseases. Dexamethasone (Dex) and other glucocorticoids suppress $Fc{\varepsilon}RI$-mediated release of inflammatory mediators from mast cells. The inhibition mechanisms were mainly investigated on the downstream signaling of Fc receptor activations. Here, we addressed the effects of Dex on Fc receptor expressions in rat mast cell line RBL-2H3. We measured mRNA levels of Fc receptors by real-time PCR. As expected, Dex decreased the mRNA levels of activating Fc receptor for IgE ($Fc{\varepsilon}R$) I and increased the mRNA levels of the inhibitory Fc receptor for IgG $Fc{\gamma}RIIb$. Interestingly, Dex stimulated transcriptions of other activating receptors such as Fc receptors for IgG ($Fc{\gamma}R$) I and $Fc{\gamma}RIII$. To investigate the mechanisms underlying transcriptional regulation, we employed a transcription inhibitor actinomycin D and a translation inhibitor cycloheximide. The inhibition of protein synthesis without Dex treatment enhanced $Fc{\gamma}RI$ and $Fc{\gamma}RIII$ mRNA levels potently, while $Fc{\varepsilon}RI$ and $Fc{\gamma}RIIb$ were minimally affected. Next, we examined expressions of the Fc receptors on cell surfaces by the flow cytometric method. Only $Fc{\gamma}RIIb$ protein expression was significantly enhanced by Dex treatment, while $Fc{\gamma}RI$, $Fc{\gamma}RIII$ and $Fc{\varepsilon}RI$ expression levels were marginally changed. Our data showed, for the first time, that Dex regulates Fc receptor expressions resulting in augmentation of the inhibitory receptor $Fc{\gamma}RIIb$.

• Journal of the Korean Institute of Gas
• /
• v.14 no.6
• /
• pp.15-20
• /
• 2010

Compressed Natural Gas (CNG) buses have been supplied since the year 2000 in order to resolve severe atmospheric pollution in metropolitan area and contributed on the improvement of urban atmospheric environment. However, it is indispensible to take an adequate measure to guarantee the safety of CNG vehicles because of the possibility of huge fire accident. A receptacle, connecting device between high pressure fuel supply tank and fuel line, plays an important role in CNG supply system. In recent, leakage of CNG from receptacles has been reported. So, the concern about the security and reliability of receptacles has been arisen. Therefore, a lot of efforts to prevent leakage are invested among researchers and the durability of this component should be guaranteed despite repeated operation. This research has performed durability tests of a CNG receptacle regarding the repeated usage, extreme chattering, and continuous full flow test. Although a receptacle used for CNG vehicle satisfies validation requirements in the test results, it has been found that failure in the function of leakage prevention in a receptacle could take place in the case of prolonged exposure to high supply pressure in common quick charging environment on site.