• Tunnel and Underground Space
• /
• v.32 no.6
• /
• pp.491-501
• /
• 2022

Bentonite has been proposed as a buffer and backfill material for high-level radioactive waste repository. Under such repository environment conditions, bentonite is subjected to combined thermal, hydrological, mechanical, and chemical processes. This study evaluates the feasibility of applying X-ray CT technology on the characterization of bentonite under hydration conditions using a newly developed testing cell. The cylindrical cell is made of platic material, with a removable cap to place the sample, enabling to apply vertical pressure on the sample and to measure swelling pressure. The hydration test was carried out with a sample made of Gyeonju bentonite, with a dry density of 1.4 g/cm³, and a water content of 20%. The sample had a diameter of 27.5 mm and a height of 34 mm. During the test, water was injected at a constant pressure of 0.207 MPa, and lasted for 7 days. After one day of hydration, bentonite swelled and filled out the space inside the cell. Moreover, CT histograms showed how the hydration process induced an initial increase and later progressive decrease on the density of the sample. Detailed profiles of the mean CT value, CT standard deviation, and CT gradient provided more details on the hydration process of the sample and showed how the bottom and top regions exhibited a decrease on density while the middle region showed an increase, especially during the first two days of hydration. Later, the differences in CT values with respect to the initial state decreased, and were small at the end of testing. The formation and later reduction of cracks was also characterized through CT scanning.

• Korean Journal of Heritage: History & Science
• /
• v.55 no.4
• /
• pp.138-164
• /
• 2022

The Neolithic shell midden in Daejuk-ri, Seosan, is distributed on the gentle slope of a low hill close to the west coast. The bedrock of the area consists mainly of schist with various mafic minerals, but shows a partial gneiss pattern. The site consists of loamy topsoil and clay loam subsoil, and the degree of siallization is relatively low. Although the pottery excavated from the shell midden shares mostly similar features, a variety of shapes and patterns coexist. The surface colors, thickness and physical properties are slightly different. The pottery can be subdivided into three types (IA, IB and II) according to the composition of the body clay, the temper and the existence of a black core. Types IA and IB are colorless mineral pottery with a non-black or black core respectively. TypeII is colored mineral pottery with a non-black core. Type I pottery also contains non-plastic colored minerals, but type II contains a large amount of biotite, chlorite, talc, amphibole, diopside and tremolite, which include a large amount of Mg and Fe. The studied pottery contains a small amount of organic matter. Considering the grain size and relatively poor sorting and roundness of the non-plastic particles, the pottery appears to be made by adding coarse non-plastic tempers for special purposes to the untreated weathered soil around the site. The three types of pottery seem to have been incompletely fired in general. While type IB has the lowest degree of oxidation, typeII shows the highest degree of redness and oxidation. It can be interpreted that these differences depend on the firing temperature and the ratio of non-plastic particles. Through a synthesis of the minerals, geochemical data and thermal history, it can be determined that the firing temperature ranged from 600 to 700℃. The pottery types of the Daejuk-ri Shell Midden have slightly different production conditions, mineral compositions, and physical properties, but have undergone similar production processes with basically the same clay materials. The clay is almost identical to the composition of the bedrock and weathered soil distributed in the Daejuk-ri area. Currently, there is an industrial complex in the area, so it is difficult to confirm the soil and geological distribution of the site. However, it is highly probable that the area around the site was self-sufficient for the clay and tempers required for the production of the Neolithic pottery. Therefore, it can be interpreted that the group that left the shell midden in Daejuk-ri lived near the site, visited the site for the purpose of collecting and processing shellfish, and discarded the broken pottery along with shells.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5D
• /
• pp.885-894
• /
• 2006

The purpose of this study is focused on the development of the effective classification technique using ultra multiband of hyperspectral image. This study suggests the classification technique using canonical correlation analysis, one of multivariate statistical analysis in hyperspectral image classification. High accuracy of classification result is expected for this classification technique as the number of bands increase. This technique is compared with Maximum Likelihood Classification(MLC). The hyperspectral image is the EO1-hyperion image acquired on September 2, 2001, and the number of bands for the experiment were chosen at 30, considering the band scope except the thermal band of Landsat TM. We chose the comparing base map as Ground Truth Data. We evaluate the accuracy by comparing this base map with the classification result image and performing overlay analysis visually. The result showed us that in MLC's case, it can't classify except water, and in case of water, it only classifies big lakes. But Canonical Correlation Classification (CCC) classifies the golf lawn exactly, and it classifies the highway line in the urban area well. In case of water, the ponds that are in golf ground area, the ponds in university, and pools are also classified well. As a result, although the training areas are selected without any trial and error, it was possible to get the exact classification result. Also, the ability to distinguish golf lawn from other vegetations in classification classes, and the ability to classify water was better than MLC technique. Conclusively, this CCC technique for hyperspectral image will be very useful for estimating harvest and detecting surface water. In advance, it will do an important role in the construction of GIS database using the spectral high resolution image, hyperspectral data.

• Korean Journal of Remote Sensing
• /
• v.39 no.5_3
• /
• pp.979-995
• /
• 2023

As wildfires are difficult to predict, real-time monitoring is crucial for a timely response. Geostationary satellite images are very useful for active fire detection because they can monitor a vast area with high temporal resolution (e.g., 2 min). Existing satellite-based active fire detection algorithms detect thermal outliers using threshold values based on the statistical analysis of brightness temperature. However, the difficulty in establishing suitable thresholds for such threshold-based methods hinders their ability to detect fires with low intensity and achieve generalized performance. In light of these challenges, machine learning has emerged as a potential-solution. Until now, relatively simple techniques such as random forest, Vanilla convolutional neural network (CNN), and U-net have been applied for active fire detection. Therefore, this study proposed an active fire detection algorithm using state-of-the-art (SOTA) deep learning techniques using data from the Advanced Himawari Imager and evaluated it over East Asia and Australia. The SOTA model was developed by applying EfficientNet and lion optimizer, and the results were compared with the model using the Vanilla CNN structure. EfficientNet outperformed CNN with F1-scores of 0.88 and 0.83 in East Asia and Australia, respectively. The performance was better after using weighted loss, equal sampling, and image augmentation techniques to fix data imbalance issues compared to before the techniques were used, resulting in F1-scores of 0.92 in East Asia and 0.84 in Australia. It is anticipated that timely responses facilitated by the SOTA deep learning-based approach for active fire detection will effectively mitigate the damage caused by wildfires.

• Clean Technology
• /
• v.29 no.4
• /
• pp.255-261
• /
• 2023

Power semiconductors are semiconductors used for power conversion, transformation, distribution, and control. Recently, the global demand for high-voltage power semiconductors is increasing across various industrial fields, and optimization research on high-voltage IGBT components is urgently needed in these industries. For high-voltage IGBT development, setting the resistance value of the wafer and optimizing key unit processes are major variables in the electrical characteristics of the finished chip. Furthermore, the securing process and optimization of the technology to support high breakdown voltage is also important. Etching is a process of transferring the pattern of the mask circuit in the photolithography process to the wafer and removing unnecessary parts at the bottom of the photoresist film. Ion implantation is a process of injecting impurities along with thermal diffusion technology into the wafer substrate during the semiconductor manufacturing process. This process helps achieve a certain conductivity. In this study, dry etching and wet etching were controlled during field ring etching, which is an important process for forming a ring structure that supports the 3.3 kV breakdown voltage of IGBT, in order to analyze four conditions and form a stable body junction depth to secure the breakdown voltage. The field ring ion implantation process was optimized based on the TEG design by dividing it into four conditions. The wet etching 1-step method was advantageous in terms of process and work efficiency, and the ring pattern ion implantation conditions showed a doping concentration of 9.0E13 and an energy of 120 keV. The p-ion implantation conditions were optimized at a doping concentration of 6.5E13 and an energy of 80 keV, and the p+ ion implantation conditions were optimized at a doping concentration of 3.0E15 and an energy of 160 keV.

• Korean journal of applied entomology
• /
• v.62 no.4
• /
• pp.315-323
• /
• 2023

The brassica leaf beetle, Phaedon brassicae Baly (Coleoptera: Chrysomelidae), is one of the important pests infesting cruciferous vegetables. In order to understand the biological characteristics of the insect, we investigated the effects of temperature on development of each life stage, adult longevity and fecundity of P. brassicae at four constant temperatures of 15, 20, 25 and 27.5℃ for immature life stage and five constant different temperatures of 10, 15, 20, 25 and 27.5℃ for adult stage. Eggs and larvae successfully developed next life stage at temperature tested. The development period of egg, larva, and pupa decreased as temperature increased. Lower developmental threshold (LDT) and thermal constant (K) were calculated using linear regression as 8.7℃ and 344.73DD, respectively. Lower and higher threshold temperature (TL and TH) from egg to adult emergence were estimated by Briere function as 5.3℃ and 40.4℃, respectively. Adults produced eggs at the temperature range between 10℃ and 27.5℃, and showed an estimated maximum number, ca. 627.5 eggs at 21.7℃. Adult oviposition models including aging rate, age-specific survival rate, age-specific cumulative oviposition, and temperature-dependent fecundity were constructed. Temperature-dependent development models and adult oviposition models would be useful components to understand the population dynamics of P. brassicae and to establish the strategy of integrated pest management in cruciferous crops.

• Korean Journal of Heritage: History & Science
• /
• v.56 no.3
• /
• pp.158-171
• /
• 2023

Pottery filled with organic materials was excavated from the G-2 building site of Yongjangseong Fortress, Jingo, a relic of the Goryeo Dynasty. In this study, the characteristics of organic material were confirmed by a scientific analysis of organic material in pottery found at the palace in Yongjangseong, Jindo. In addition, it was intended to review the analysis method to identify the natural resin and to secure characteristic components(biomarkers) for each natural resin and use them as basic data in the future. The organic materials in the pottery were analyzed using attenuated total reflectance Fourier-transformed infrared spectroscopy(ATR-FTIR) and gas chromatography mass spectrometry(GC-MS). The infrared spectral characteristics were estimated to be natural resin, and biomarkers of organic materials were identified as sesquiterpene-based compounds(C₁₅H₂₄, MW 204) and derivatives. The lacquer(T.vemicifluum) is composed mainly of alkenes, alkanes, and catechol. Pine resin(P.densiflora), on the other hand, is primarily composed of diterpenoid(abietic acid, pimaric acid) and Whangchil(yellow lacquer) is identified to have sesquiterpenes(such as selinene, muurolene, calamenene) as its main components. So, the organic material in the pottery can be identified as Whangchil by comparing their compounds with modern resin materials from Dendropanax. morbifera that correspond with the results. Whangchil, which is exuded from the Dendropanax. morbifera, has been used as a natural coating materials since ancient times, and it has been confirmed that the characteristic components are well preserved even 700 years later. It can be assumed that the interior Whangchil was stored not for use as a coating, but rather for ritual purposes when the building was constructed, because the pottery was found near the cornerstone. Furthermore, based on simplified sample preparation using pyrolysis-gas chromatography mass spectrometry(Py-GC-MS), the thermal decomposition products were found to be similar to the characteristic components, suggesting that this method can be applied to the identification of natural resins used in historic artifacts.

• Journal of the Korean Institute of Gas
• /
• v.27 no.3
• /
• pp.52-58
• /
• 2023

With the increasing awareness of the importance of carbon neutrality in response to global climate change, the utilization of hydrogen as a carbon-free fuel source is also growing. Hydrogen is commonly used in fuel cells (FC), but it can also be utilized in internal combustion engines (ICE) that are based on combustion. Particularly, ICEs that already have established infrastructure for production and supply can greatly contribute to the expansion of hydrogen energy utilization when it becomes difficult to rely solely on fuel cells or expand their infrastructure. However, a disadvantage of utilizing hydrogen through combustion is the potential generation of nitrogen oxides (NOx), which are harmful emissions formed when nitrogen in the air reacts with oxygen at high temperatures. In particular, for the EURO-7 exhaust regulation, which includes cold start operation, efforts to reduce exhaust emissions during the warm-up process are required. Therefore, in this study, the characteristics of nitrogen oxides and fuel consumption were investigated during the warm-up process of cooling water from room temperature to 88℃ using a 2-liter direct injection spark ignition (SI) engine fueled with hydrogen. One advantage of hydrogen, compared to conventional fuels like gasoline, natural gas, and liquefied petroleum gas (LPG), is its wide flammable range, which allows for sparser control of the excessive air ratio. In this study, the excessive air ratio was varied as 1.6/1.8/2.0 during the warm-up process, and the results were analyzed. The experimental results show that as the excessive air ratio becomes sparser during warm-up, the emission of nitrogen oxides per unit time decreases, and the thermal efficiency relatively increases. However, as the time required to reach the final temperature becomes longer, the cumulative emissions and fuel consumption may worsen.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.13 no.1
• /
• pp.27-41
• /
• 2008

Distribution characteristics of phytoplankton community were investigated by HPLC and flow cytometry in Jeju Strait and the Northern East China Sea (NECS) in May 2004, in order to understand the relationship between physical environmental factors and distribution pattern of phytoplankton communities. Based on temperature and salinity data, three distinct water masses were identified; warm and saline Tsushima Warm Current (TWC), which is flowing from northwest of Jeju Island, warm and low saline water at the center of Jeju Strait, which is originated from China Coastal Water (CCW) and relatively cold and high saline water originated from Yellow Sea at the bottom of the Jeju Strait. At Jeju Strait, less saline water (<33 psu) of 15 km width occupied surface layer up to 20 m which located at 20 km offshore and strong thermal front between warm and saline water and cold and less saline water was found in the middle of the Jeju Strait. Vertical transect of temperature and salinity at the NECS also showed that low saline (<33 psu) water occupied the upper 20 m layer and cold and saline water was present at the eastern part. Chl a was measured as $0.06{\sim}3.07\;{\mu}g/L$. Spring bloom of phytoplankton was recognized by the high concentrations of Chl a at the low saline water masses influenced by the CCW and subsurface chlorophyll maximum layer appeared between $20{\sim}30\;m$ depth, which was at thermocline depth or below. Abundances of Synechococcus and picoeukaryote were $0.2{\sim}9.5{\times}10^4\;cells/mL$ and $0.43{\sim}4.3{\times}10^4\;cells/mL$, respectively. Dinoflagellate, diatom and prymnesiophyte were major groups and minor groups were chlorophyte+prasinophyte, chrysophyte, cryptophyte and cyanophyte. Especially high abundance of dinoflagellate was identified by high concentration (>1\;{\mu}g/L$) of peridinin at the bottom of the thermocline, which showed an outbreak of red tide by high density of dinoflagellates. Abundances of picoeukaryote in Jeju Strait were about $5{\sim}10$ times higher than abundance measured in Kuroshio water and showed a good correlation with Chl b (Pras+Viola), which implies the most of population of picoeukaryote was composed of prasinophytes. Prochlorococcus was not detected at all, which suggests that Kuroshio Current did not directly influenced on the study area. Based on the strong negative correlations between biomass of phytoplankton (Chl a) and temperature+salinity, the primary production and biomass of phytoplankton in the study area were controlled by the nutrients supply from CCW.

• Korean Journal of Heritage: History & Science
• /
• v.57 no.1
• /
• pp.146-159
• /
• 2024

In this study, a study on the production technology of the Buddha statue and the production of raw material origin was conducted through scientific analysis on the Bronze seated Bodhisattva Statue of Goseongsa Temple, a treasure. As a result of microstructure analysis through a metal microscope, it was confirmed that the microstructure of the Bronze seated Bodhisattva Statue of Goseongsa Temple was a process-type dendritic structure, and the casting structure of bronze was well represented, so it was manufactured through casting. Subsequently, as a result of analyzing the alloy composition ratio through SEM-EDS, it was identified as a ternary alloy with 81.26 wt% of copper (Cu) and 16.42 wt% of tin (Sn) and 1.72 wt% of lead (Pb). The results of the analysis of lead isotope ratios using a thermal ionization mass spectrometer (TIMS) were substituted into the distribution of lead isotope ratios on the Korean Peninsula, it was shown in corresponding to Jeolla-do and Chungcheong-do regions and North and South Gyeongsang Province. This suggests that the raw materials used in their production were likely sourced from the mines around Goseong Temple in Gangjin. Despite the fact that the statue is a medium and large Buddha with a total height of 51 centimeters, 1.72 wt% of lead (Pb) was found as a result of alloy composition ratio analysis, which showed a similar composition to the lead content ratio of small bronze and gilt-bronze Buddha statues. Therefore, we compared and analyzed the results of the analysis of the composition ratio of the alloys of bronze and gilt bronze statues, which has been scientifically analyzed with a compositional age similar to that of the Bronze seated Bodhisattva Statue of Goseongsa Temple. Comparison results, Various factors, such as the size of the Buddha statue as well as its stylistic characteristics and the age of composition, may exist in determining the alloy composition ratio of the bronze and gilt bronze Buddha statues, and it was confirmed that the alloy composition ratio or casting technology was properly adjusted when the Buddha statue was created. In other words, it is judged that a more comprehensive system of Buddha statue production technology should be investigated by conducting archaeological and art history studies on stylistic characteristics and age of composition, as well as scientific analysis results such as observation of internal structure, microstructure observation, and analysis of alloy composition ratio using radiation transmission irradiation.