• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.77-83
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• 2023

Energy consumption is increased by rapid industrialization. As a result, climate change is accelerating due to the increase in CO₂ concentration in the atmosphere. Therefore, a shift in the energy paradigm is required. Hydrogen is in the spotlight as a part of that. Currently 95% of hydrogen is fossil fuel-based reforming hydrogen which is accompanied by CO₂ emissions. This is called gray hydrogen, if the CO₂ is captured and emission of CO₂ is reduced, it can be converted into blue hydrogen. There are 3 technologies to capture CO₂: absorption, adsorption and membrane technology. In order to select CO₂ capture technology, the analysis of the exhaust gas should be carried out. The concentration of CO₂ in the flue gas from the hydrogen production process is higher than 20%if water is removed as well as the emission scale is classified as small and medium. So, the application of the membrane technology is more advantageous than the absorption. In addition, if LNG cold energy can be used for low temperature CO₂ capture system, the CO₂/N₂ selectivity of the membrane is higher than room temperature CO₂ capture and enabling an efficient CO₂ capture process. In this study, we will analyze the flue gas from hydrogen production process and discuss suitable CO₂ capture technology for it.

• Journal of Internet Computing and Services
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• v.24 no.6
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• pp.161-169
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• 2023

Due to the Fourth Industrial Revolution, innovation in various technologies such as artificial intelligence (AI), big data (Big Data), and cloud (Cloud) is accelerating, and data is considered an important asset. With the innovation of these technologies, various efforts are being made to lead technological innovation in the field of defense science and technology. In Korea, the government also announced the "Defense Innovation 4.0 Plan," which consists of five key points and 16 tasks to foster advanced science and technology forces in March 2023. The plan also includes the establishment of a Condition-Based Maintenance system (CBM+) to improve the operability and availability of weapons systems and reduce defense costs. Condition Based Maintenance (CBM) aims to secure the reliability and availability of the weapon system and analyze changes in equipment's state information to identify them as signs of failure and defects, and CBM+ is a concept that adds Remaining Useful Life prediction technology to the existing CBM concept [1]. In order to establish a CBM+ system for the weapon system, sensors are installed and sensor data are required to obtain condition information of the weapon system. In this paper, we propose a sensor data metadata schema to efficiently and effectively manage sensor data collected from sensors installed in various weapons systems.

• Land and Housing Review
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• v.14 no.4
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• pp.121-129
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• 2023

In this study, we attempted to reduce CO₂ generated during manufacturing by replacing limestone (CaCO₃), a carbonate mineral used to produce cement clinker, with a decarbonated raw material to which CO₂ is not bound. The raw material for decarbonization was cement paste attached to waste concrete, among various industrial by-products. Waste concrete has cement paste adhered to the aggregate, which cannot be separated efficiently by general crushing and grinding methods. Peeling and grinding methods effectively remove only the cement paste without damaging the original aggregate. The abrasion time, steel ball type, and steel ball ratio were selected as effective factors for Abrasion. An optimal abrasion experiment was conducted to produce waste concrete fine powder containing decarbonated CaO as a cement clinker raw material through an experimental design method. The experiment revealed that the optimal conditions for producing waste concrete fine powder were an abrasion time of 7 minutes, a steel ball size for pulverization of 8 mm, and a steel ball ratio for pulverization of 0.6.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.118-126
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• 2009

Benthic diatoms are very important primary producers in understanding estuary ecosystems and their productions are largely varied by their photo-physiological characteristics. The short-term effects of increased temperature on the photosynthetic and photo-physiological characteristics of cultured different species of benthic diatoms (Navicula sp., Nitzschia sp., Cylindrotheca closterium, and Pleurosigma elongatum) were investigated by measuring their PSII-fluorescence kinetics using a Diving-PAM. Photosynthesis versus irradiance curves were measured every two hours at six different temperatures (10, 15, 20, 25, 30, and $35^{\circ}C$) for twenty-four hour. The effective quantum yield of PSII ($\Phi_{PSII}$) for most of the species showed a decreasing trend with increased temperature. The relative maximum electron transport rate (rETRmax) was significantly increased up to the optimum temperature level and then sharply decreased. Relative to the values of other parameters, the maximum light use coefficient ($\alpha$) was not substantially changed at lower temperature levels (<$30^{\circ}C$) but significantly decreased only at higher temperatures (30 and $35^{\circ}C$). The light saturation coefficient ($E_K$) mirrored the rETRmax temperature response. In regards to the temperature acclimation abilities of the four species with time, Navicula sp. and C. closterium acclimated to short-term changes in temperature through their photo-physiological adjustments.

• Journal of the Korean Society of Radiology
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• v.18 no.1
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• pp.27-36
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• 2024

In this study, When acquisition thyroid scintigraphy images, a parallel hole collimator was applied, and the difference from the pinhole collimator was quantitatively analyzed under each image acquisition condition. Visual size, resolution, sensitivity, signal to noise ratio (SNR), and contrast to noise ratio (CNR) were evaluated using thyroid phantom and point source. When comparing visual size, it was confirmed that an image similar to the size of the pinhole collimator could be obtained only when a magnification ratio of about 2.00 to 2.09 times when applying a parallel hole collimator. There was no tendency in FWHM(mm) measurement using a point source, and sensitivity was high in the parallel hole collimator. SNR and CNR were high when using a low magnification ratio, matrix size of 128×128, and a parallel hole collimator. In images of similar size to the naked eye, when the matrix size was the same, both SNR and CNR were high in the pinhole collimator. Therefore, when performing a thyroid scintigraphy test, if appropriate conditions are set according to the situation of each hospital and a parallel hole collimator is applied, it can be a good option in terms of equipment utilization and work efficiency.

• Journal of Navigation and Port Research
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• v.47 no.6
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• pp.367-375
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• 2023

This study developed a new distance metric for vessel trajectories, applicable to marine traffic control services in the Korean coastal waters. The proposed metric is designed through the weighted summation of the traditional Hausdorff distance, which measures the similarity between spatiotemporal data and incorporates the differences in the average Speed Over Ground (SOG) and the variance in Course Over Ground (COG) between two trajectories. To validate the effectiveness of this new metric, a comparative analysis was conducted using the actual Automatic Identification System (AIS) trajectory data, in conjunction with an agglomerative clustering algorithm. Data visualizations were used to confirm that the results of trajectory clustering, with the new metric, reflect geographical distances and the distribution of vessel behavioral characteristics more accurately, than conventional metrics such as the Hausdorff distance and Dynamic Time Warping distance. Quantitatively, based on the Davies-Bouldin index, the clustering results were found to be superior or comparable and demonstrated exceptional efficiency in computational distance calculation.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.103-111
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• 2024

Axial-flow fans are used to transport fluids in relatively low-pressure flow regimes, and a variety of design variables are employed. The tip geometry of an axial fan plays a dominant role in its flow and noise performance, and two of the most prominent flow phenomena are the tip vortex and the tip leakage vortex that occur at the tip of the blade. Various studies have been conducted to control these three-dimensional flow structures, and winglet geometries have been developed in the aircraft field to suppress wingtip vortices and increase efficiency. In this study, a numerical and experimental study was conducted to analyze the effect of winglet geometry applied to an axial fan blade for an air conditioner outdoor unit. The unsteady Reynolds-Averaged Navier-Stokes (RANS) equation and the FfocwsWilliams and Hawkings (FW-H) equation were numerically solved based on computational fluid dynamics techniques to analyze the three-dimensional flow structure and flow noise numerically, and the validity of the numerical method was verified by comparison with experimental results. The differences in the formation of tip vortex and tip leakage vortex depending on the winglet geometry were compared through a three-dimensional flow field, and the resulting aerodynamic performance was quantitatively compared. In addition, the effect of winglet geometry on flow noise was evaluated by numerically simulating noise based on the predicted flow field. A prototype of the target fan model was built, and flow and noise experiments were conducted to evaluate the actual performance quantitatively.

• The Journal of the Convergence on Culture Technology
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• v.10 no.6
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• pp.759-764
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• 2024

An agricultural drones are the increasing demand for the use of multicopters in spraying operations, there is a growing emphasis on high operational efficiency, convenience, and applicability. In agricultural spraying tasks, efforts to address the issue of spraying drift have led to experimental validation of various nozzle designs aimed at reducing drift through comparative analysis with prior research. This study aims to experimentally validate the characteristics of drift associated with different nozzles and predict application performance by evaluating the target areas post-spraying. The results showed that the DG nozzle achieved a relatively higher coverage rate. As flight speed increased, coverage rate decreased relatively. This was due to reduced downward wind resulting from changes in the aircraft's tilt and increased rotor thrust, which enhanced drift and reduced the number of droplets reaching the target area. This was because higher flight altitude resulted in a wider effective spraying distance, which reduced the droplet deposition per unit area. Similarly, as flight altitude increased, the coverage rate also decreased relatively. This decrease in coverage was due to the wider effective spraying distance at higher altitudes, resulting in reduced droplet deposition per unit area. These findings allow for the derivation of optimal spraying conditions(flight altitude and speed) and aim to minimize drift in pest control operations, thereby applying these optimal conditions to improve the spraying process.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.4
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• pp.45-55
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• 2024

This study aims to distinguish between utilitarian walking and leisure walking activities and analyze the correlation between these types of walking and the walking environment. To measure the walking environment, we utilized Google Street View (GSV) and employed semantic segmentation deep learning techniques to quantitatively assess urban walking environment elements as perceived by pedestrians. A survey was conducted to measure utilitarian walking, leisure walking, and perceived walking environment satisfaction, collecting valid responses from 192 participants. Using the survey data, we visualized utilitarian walking, leisure walking, and perceived walking environment satisfaction, and analyzed the correlation between these variables and the walkability scores. The results indicated that leisure walking had a significant positive correlation with walkability (Pearson's r = 0.121, p-value = 0.012), while there was no significant correlation between utilitarian walking and walkability (Pearson's r = 0.093, p-value = 0.055). These findings suggest that people prioritize mobility efficiency over the walking environment for utilitarian walking, whereas the quality of the walking environment significantly influences the frequency of leisure walking. Based on these results, the study proposes specific strategies to improve the walking environment around residential areas to promote leisure walking. These strategies include creating vertical gardens or various forms of three-dimensional gardens on narrow walkways and improving sidewalk design. The findings of this study can contribute to promoting leisure walking by creating walk-friendly environments, ultimately enhancing urban sustainability and the quality of life for residents.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.5
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• pp.353-359
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• 2024

Lattice structures exhibit good thermal performance due to the high surface-to-volume ratio. Previous studies have investigated the thermal conductivity to improve the performance of lattice structures. However, the conventional approach simplifies the geometry of lattice structures using limited design parameters due to the high computational or experimental costs. This study introduces a lattice structure with optimal thermal conductivity. We propose a lattice beam shape that overcomes the existing design limitations through shape optimization using artificial intelligence. First, the beam shape of the body-centered (BC) lattice structure is modeled as a smooth Bézier curve. Second, the coordinates of the control points of the Bézier curve are randomly set to obtain training data. Finally, the optimal beam shape is designed by generating a beam shape with excellent effective thermal conductivity through a neural network combined with a genetic algorithm. A mechanism of optimized thermal conductivity is suggested and the optimal beam shape is compared with a lattice structure with optimal elastic stiffness. The results of this study are expected to provide an appropriate structural solution for lattice structures under various thermal conditions in the future.