• Korean Journal of Optics and Photonics
• /
• v.15 no.4
• /
• pp.361-368
• /
• 2004

We separated the multilayer structure of CD-R(compact disk-recordable) and investigated optimal spot marking conditions and physical and chemical transitions in response to various laser beam energh levels. Spot marking(80 ${\mu}{\textrm}{m}$ spot size) was produced on the surface of each layer using a Q-switched Nd:YAG laser between 27 mJ and 373mJ. By investigating resulting pit formation with Optical Microscopy(OM) and Optical Coherence Tomography(OCT), we analyzed the formation process of spot marking in the multilayer structure of different chemical composition. The localized heating of the substrate in the multilayer thin film caused the short temporal thermal expansion, and absorbed optical energy between reflective and dye interfaces melted dye and increased the volume. During the cooling phase, formation of pit and surrounding rim can be explained by three distinct processes; effect of surface tension, evaporation by spontaneous temperature increase due to laser energy, and mass flow from the recoil pressure. Our results shows that the spot marking formation process in the multilayer thin film is closely related to the layers' physical, chemical, and optical properties, such as surface tension, melt viscosity, layer thickness, and chemical composition.

• Fire Science and Engineering
• /
• v.28 no.6
• /
• pp.52-57
• /
• 2014

The present study suggests the fundamental method for the prediction time of the fire origin by analyzing the combustion phenomenon of inflammable material in the building structure. The heat release rate (HRR) with time variant is evaluated for the interphone as a inflammable material, which is opted from the fire incidents in the stairwell. the fire dynamics simulator (FDS ver. 6.1) is applied in order to analyze the difference of the smoke inflow time to the downstair from the fire event area with various fire pattern. The results show that the maximum inflow time difference for the case of the interphone made from ABS materials is about 4.93 times with the input conditions of heat flux values and the environment in the FDS for the fixed stairwell which composed of total volume $291.3m^3$, floorage $23.3m^2$ and the height of each floor 2.5 m. This research can be practical information for the application method of simulation scheme with experimental data to the fire Identification.

• Journal of Korea Water Resources Association
• /
• v.55 no.6
• /
• pp.461-469
• /
• 2022

It is very important to ensure the reliability of dam inflow data, which is critical in planning and managing the supply and demand of water resources in a basin. However, the simple water balance model sometimes results in negative inflows and does not consider the actual inflow characteristics. In this study, to address these issues, the existing water balance formula was modified by considering evaporation which is available for calculation among other outflows. The modified water balance formula was applied to the Soyang Dam. The results showed that the rate of negative inflows decreased in the re-evaluated dam inflow data and it was possible to secure consistency for the total inflow volume. In addition, investigating the water availability in the Soyang Dam watershed based on the water balance concept considering evaporation, it was found that direct water use in the human aspect was about 60%, and the indirect water use in the natural aspect was about 40%. In drought years, it was also confirmed that the proportion of indirect use of water resources increased.

• Fire Science and Engineering
• /
• v.22 no.1
• /
• pp.1-9
• /
• 2008

Carbon dioxide($CO_2$) agent, which has more safely extinguished fire than any other gaseous fire extinguishing agents, has been widely used in various protected enclosures and types of fires. According to the concept of performance-based design(PBD). $CO_2$ extinguishing system to be designed is needed to be evaluated for the performance of fire suppression with possible fire scenarios in an enclosure. In this paper, CFD simulations were carried out to study the effects of opening area on the performance of $CO_2$ extinguishing system and the flow characteristics in the machine room of $100m^3$ in which kerosene spill fire happened. This study showed that time of fire suppression increased linearly in proportion to the size of opening area, and fires for each model were completely suppressed prior to the end of discharge of $CO_2$ agent. It was shown that mass flow rate through opening was influenced by the combined effects of heat release rate of fire and discharge of $CO_2$ agent. After $CO_2$ agent was completely discharged, oxygen concentrations in enclosures for each model were lower than the limit concentration of combustion.

• Journal of the Korea Concrete Institute
• /
• v.20 no.4
• /
• pp.415-421
• /
• 2008

Reinforced concrete starts to corrode when the chloride ion concentration which is the sum of included in concrete and penetrated from environments exceeds a certain level of critical chloride concentration. Therefore each country regulates the upper bounds of chloride amount in concrete and the regulations are different for each country due to its circumstances. In this study, the critical threshold chloride content according to unit cement amount is empirically calculated to propose a reasonable regulation method on the chloride amount. As a result, the critical threshold chloride content increases considerably according to cement content and it agrees with the established theories. The present regulations on total chloride amount 0.3 or 0.6 kg chloride ions per $1\;m^3$ of concrete does not reflect the influences of mix design, environmental conditions and etc. So it can be said that it is more reasonable to regulate the critical threshold chloride content by the ratio of chloride amount per unit cement content than by the total chloride content in $1\;m^3$ of concrete.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.34 no.3
• /
• pp.254-259
• /
• 2014

A pressurized heavy water reactor (PHWR) core has 380 fuel channels contained and supported by a horizontal cylindrical vessel known as the calandria, whereas a pressurized water reactor (PWR) has only a single reactor vessel. The pressure tube, which is a pressure-retaining component, has a 103.4 mm inside diameter ${\times}$ 4.19 mm wall thickness, and is 6.36 m long, made of a zirconium alloy (Zr-2.5 wt% Nb). This provides support for the fuel while transporting the $D_2O$ heat-transfer fluid. The simple tubular geometry invites highly automated inspection, and good approach for all inspection. Similar to all nuclear heat-transfer pressure boundaries, the PHWR pressure tube requires a rigorous, periodic inspection to assess the reactor integrity in accordance with the Korea Nuclear Safety Committee law. Volumetric-based nondestructive evaluation (NDE) techniques utilizing ultrasonic and eddy current testing have been adopted for use in the periodic inspection of the fuel channel. The eddy current testing, as a supplemental NDE method to ultrasonic testing, is used to confirm the flaws primarily detected through ultrasonic testing, however, eddy current testing offers a significant advantage in that its ability to detect surface flaws is superior to that of ultrasonic testing. In this paper, effectiveness of flaw detection and the depth sizing capability by eddy current testing for the inside surface of a pressure tube, will be introduced. As a result of this examination, the ET technique is found to be useful only as a detection technique for defects because it can detect fine defects on the surface with high resolution. However, the ET technique is not recommended for use as a depth sizing method because it has a large degree of error for depth sizing.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.3
• /
• pp.21-29
• /
• 2023

In this study, the stress characteristics of temporary fixed steel rods were analyzed in the "temporary fixing system using internal prestressing tension", which is mainly applied to the construction of superstructures by FCM. It was difficult to confirm the changes in initial tensile force in this system because the steel rod was internally connected to the pier and the PSC BOX. Therefore, measurement was performed before and after the completion of each segment using an FBG sensor to measure the change in the micro length of the steel rod. The results of the analysis showed that 75% to 90% of the maximum vertical contraction of the steel rod that occurred until the completion of the cantilever segment occurred in the fixing ~ 1segment, and the maximum loss of initial prestressing force was 39%. Such excessive loss of tension force to 1 segment means that tension is needed to improve the precision of construction during the fixation, and re-tension is needed to secure stability for conduction of cantilever segments after the completion of 1segment. In the 2 ~ last segment, the stress of the steel rod decreased gradually, and in the summer, the decrease in stress tended to partially recover due to the increase in the length of the steel rod corresponding to the increase in the vertical volume of PSC BOX. The dominant factor in the stress change in 2~ last segment in this phenomenon is judged to be the change in the length of the steel rod according to the temperature. Unlike the change in length, the relaxation was 1.2-2.7%, which was mostly offset by the opposite stress corresponding to the temperature stress. Therefore, a plan was proposed to improve the internal stress, such as adjusting the fixation time.

• The Journal of Korean Society for Radiation Therapy
• /
• v.24 no.2
• /
• pp.157-165
• /
• 2012

Purpose: We evaluated usefulness of abdominal compressor for stereotactic body radiotherapy (SBRT) with unresectable hepatocellular carcinoma (HCC) patients and hepato-biliary cancer and metastatic liver cancer patients. Materials and Methods: From November 2011 to March 2012, we selected HCC patients who gained reduction of diaphragm movement >1 cm through abdominal compressor (diaphragm control, elekta, sweden) for HT (Hi-Art Tomotherapy, USA). We got planning computed tomography (CT) images and 4 dimensional (4D) images through 4D CT (somatom sensation, siemens, germany). The gross tumor volume (GTV) included a gross tumor and margins considering tumor movement. The planning target volume (PTV) included a 5 to 7 mm safety margin around GTV. We classified patients into two groups according to distance between tumor and organs at risk (OAR, stomach, duodenum, bowel). Patients with the distance more than 1 cm are classified as the 1st group and they received SBRT of 4 or 5 fractions. Patients with the distance less than 1 cm are classified as the 2nd group and they received tomotherapy of 20 fractions. Megavoltage computed tomography (MVCT) were performed 4 or 10 fractions. When we verify a MVCT fusion considering priority to liver than bone-technique. We sent MVCT images to Mim_vista (Mimsoftware, ver .5.4. USA) and we re-delineated stomach, duodenum and bowel to bowel_organ and delineated liver. First, we analyzed MVCT images to check the setup variation. Second we compared dose difference between tumor and OAR based on adaptive dose through adaptive planning station and Mim_vista. Results: Average setup variation from MVCT was $-0.66{\pm}1.53$ mm (left-right) $0.39{\pm}4.17$ mm (superior-inferior), $0.71{\pm}1.74$ mm (anterior-posterior), $-0.18{\pm}0.30$ degrees (roll). 1st group ($d{\geq}1$) and 2nd group (d<1) were similar to setup variation. 1st group ($d{\geq}1$) of $V_{diff3%}$ (volume of 3% difference of dose) of GTV through adaptive planing station was $0.78{\pm}0.05%$, PTV was $9.97{\pm}3.62%$, $V_{diff5%}$ was GTV 0.0%, PTV was $2.9{\pm}0.95%$, maximum dose difference rate of bowel_organ was $-6.85{\pm}1.11%$. 2nd Group (d<1) GTV of $V_{diff3%}$ was $1.62{\pm}0.55%$, PTV was $8.61{\pm}2.01%$, $V_{diff5%}$ of GTV was 0.0%, PTV was $5.33{\pm}2.32%$, maximum dose difference rate of bowel_organ was $28.33{\pm}24.41%$. Conclusion: Despite we saw diaphragm movement more than 5 mm with flouroscopy after use an abdominal compressor, average setup_variation from MVCT was less than 5 mm. Therefore, we could estimate the range of setup_error within a 5 mm. Target's dose difference rate of 1st group ($d{\geq}1$) and 2nd group (d<1) were similar, while 1st group ($d{\geq}1$) and 2nd group (d<1)'s bowel_organ's maximum dose difference rate's maximum difference was more than 35%, 1st group ($d{\geq}1$)'s bowel_organ's maximum dose difference rate was smaller than 2nd group (d<1). When applicating SBRT to HCC, abdominal compressor is useful to control diaphragm movement in selected patients with more than 1 cm bowel_organ distance.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.33 no.3
• /
• pp.1-15
• /
• 2015

Based on the analysis and interpretation of the headwords and poetic words of a group of eleven collecting sceneries of Jeonju, the origin and transformations of the Jeonju-Palkyung(Eight sceneries of Jeonju) investigated by a time-series analysis are as follows. As there is no collection of landscape with a formal structure similar to that of the current Jeonju-Palkyung, prior to the Palkyung by Chujae(秋齋) Cho Soo-Sam(趙秀三, 1762~1849), there is no significant problem in assuming the eight poems in Chujaejib(秋齋集) are the origins of the Jeonju-Palkyung, and it is estimated to have been produced in 1829. In the late-19th century poem 'Wansanseunggyeong(完山勝景)', 'the Palkyung in Yeollyeo Chunhyang Sujeolga', and 'the Palkyung delivered by poet Shin Seokjeong in the Japanese colonial era', only the 'Dongpogwibeom(東浦歸帆)' changed from Dongjipo to Dongchon of Bongdong as for 'Landscape Setting There($L_{ST}$)' according to changes in district administration; despite this change, the fact that they are not too different from the Palkyung of Cho Soo-Sam, also supports this. Moreover, according to the headword concordance analysis, it is proven that the Jeonju-Palkyung was established in the late-19th century and continued to be the region's representative sceneries even during the Japanese colonial era, and later 'Namcheonpyomo(南川漂母)' and 'Gonjimangwol(坤止望月)' were added to expand to the Jeonju-Sipkyung(ten sceneries of Jeonju). But when we see there are famous spots that are the origins of the Jeonju-Sipkyung, including Gyeonggijeon, Geonjisan, Jogyeongdan, Omokdae, and Girinbong, Deokjinyeon, and Mangyeongdae, all of which have great representational significance as the capital of Jeolla Provincial Office as well as of the place of origin for Joseon Dynasty in the grouping of sceneries during the early Joseon Dynasty, including "Paehyangsipyeong (沛鄕十詠)", "Gyeondosipyeong (甄都十詠)", and "Binilheonsipyeong(賓日軒十詠)", the beginnings of the semantic Jeonju-Palkyung should be considered up to the first half of Joseon Dynasty. During this period, not only the fine sceneries with high retrospective merit as the capital of Hubaekje, like Gyeonhwondo(甄萱都), but also the sceneries like Mangyeongdae that reminds people of Jeong Mongju(鄭夢周) and Yi Seonggye(李成桂) in the late period of Goryeo appeared, elevating the status of Jeonju as the capital of Hubaekje and shortening the historical gaps as the place of origin of the Joseon Dynasty. The Jeonju-Palkyung is an organic item that carries the history of the Joseon Dynasty after Hubaekje and has gone through many cycles of disappearing and reappearing, but it has continued to change and transform as the region's representative sceneries. The Jeonju-Palkyung is a cultural genealogy that helps one understand the 'Jeonju Hanpunggyeong(韓風景: the sceneries of Korea in Jeonju)', and the efforts to preserve and pass it down to the next generation would be the responsibility of the people of Jeonju.

• Korean Journal of Environmental Agriculture
• /
• v.37 no.4
• /
• pp.268-276
• /
• 2018

BACKGROUND: In the month of January 2018, fine dust alerts and warnings were issued 36 times for $PM_{10}$ and 81 times for PM2.5. Air quality is becoming a serious issue nation-wide. Although interest in air-purifying plants is growing due to the controversy over the risk of chemical substances of regular air-purifying solutions, industrial spread of the plants has been limited due to their efficiency in air-conditioning perspective. METHODS AND RESULTS: This study aims to propose a vegetation-based bio-filter system that can assure total indoor air volume for the efficient application of air-purifying plants. In order to evaluate the quantitative performance of the system, time-series analysis was conducted on air-conditioning performance, indoor air quality, and comfort index improvement effects in a lecture room-style laboratory with 16 persons present in the room. The system provided 4.24 ACH ventilation rate and reduced indoor temperature by $1.6^{\circ}C$ and black bulb temperature by $1.0^{\circ}C$. Relative humidity increased by 24.4% and deteriorated comfort index. However, this seemed to be offset by turbulent flow created from the operation of air blowers. While $PM_{10}$ was reduced by 39.5% to $22.11{\mu}g/m^3$, $CO_2$ increased up to 1,329ppm. It is interpreted that released $CO_2$ could not be processed because light compensation point was not reached. As for the indoor comfort index, PMV was reduced by 83.6 % and PPD was reduced by 47.0% on average, indicating that indoor space in a comfort range could be created by operating vegetation-based bio-filters. CONCLUSION: The study confirmed that the vegetation-based bio-filter system is effective in lowering indoor temperature and $PM_{10}$ and has positive effects on creating comfortable indoor space in terms of PMV and PPD.