• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.583-603
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• 2023

Recently, the advancement of mechanical tunnel boring machine (TBM) technology and the characteristics of subsea railway tunnels subjected to hydrostatic pressure have led to the widespread application of shield TBM methods in the design and construction of subsea railway tunnels. Subsea railway tunnels are exposed in a constant pore water pressure and are influenced by the amplification of seismic waves during earthquake. In particular, seismic loads acting on subsea railway tunnels under various ground conditions such as soft ground, soft soil-rock composite ground, and fractured zones can cause significant changes in tunnel displacement and stress, thereby affecting tunnel safety. Additionally, the dynamic response of the ground and tunnel varies based on seismic load parameters such as frequency characteristics, seismic waveform, and peak acceleration, adding complexity to the behavior of the ground-tunnel structure system. In this study, a finite difference method is employed to model the entire ground-tunnel structure system, considering hydrostatic pressure, for the investigation of dynamic behavior of subsea railway tunnel during earthquake. Since the key factors influencing the dynamic behavior during seismic events are ground conditions and seismic waves, six analysis cases are established based on virtual ground conditions: Case-1 with weathered soil, Case-2 with hard rock, Case-3 with a composite ground of soil and hard rock in the tunnel longitudinal direction, Case-4 with the tunnel passing through a narrow fault zone, Case-5 with a composite ground of soft soil and hard rock in the tunnel longitudinal direction, and Case-6 with the tunnel passing through a wide fractured zone. As a result, horizontal displacements due to earthquakes tend to increase with an increase in ground stiffness, however, the displacements tend to be restrained due to the confining effects of the ground and the rigid shield segments. On the contrary, peak compressive stress of segment significantly increases with weaker ground stiffness and the effects of displacement restrain contribute the increase of peak compressive stress of segment.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.30-36
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• 2006

Japan's first pilot-scale $CO_2$ sequestration experiment has been conducted in Nagaoka, where 10400 t of $CO_2$ have been injected in an onshore aquifer at a depth of about 1100 m. Among various measurements conducted at the site for monitoring the injected $CO_2$, we conducted time-lapse crosswell seismic tomography between two observation wells to determine the distribution of $CO_2$ in the aquifer by the change of P-wave velocities. This paper reports the results of the crosswell seismic tomography conducted at the site. The crosswell seismic tomography measurements were carried out three times; once before the injection as a baseline survey, and twice during the injection as monitoring surveys. The velocity tomograms resulting from the monitoring surveys were compared to the baseline survey tomogram, and velocity difference tomograms were generated. The velocity difference tomograms showed that velocity had decreased in a part of the aquifer around the injection well, where the injected $CO_2$ was supposed to be distributed. We also found that the area in which velocity had decreased was expanding in the formation up-dip direction, as increasing amounts of $CO_2$ were injected. The maximum velocity reductions observed were 3.0% after 3200 t of $CO_2$ had been injected, and 3.5% after injection of 6200 t of $CO_2$. Although seismic tomography could map the area of velocity decrease due to $CO_2$ injection, we observed some contradictions with the results of time-lapse sonic logging, and with the geological condition of the cap rock. To investigate these contradictions, we conducted numerical experiments simulating the test site. As a result, we found that part of the velocity distribution displayed in the tomograms was affected by artefacts or ghosts caused by the source-receiver geometry for the crosswell tomography in this particular site. The maximum velocity decrease obtained by tomography (3.5%) was much smaller than that observed by sonic logging (more than 20%). The numerical experiment results showed that only 5.5% velocity reduction might be observed, although the model was given a 20% velocity reduction zone. Judging from this result, the actual velocity reduction can be more than 3.5%, the value we obtained from the field data reconstruction. Further studies are needed to obtain more accurate velocity values that are comparable to those obtained by sonic logging.

• Tuberculosis and Respiratory Diseases
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• v.50 no.3
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• pp.293-299
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• 2001

Background : Sustained-release theophylline, which is generally prescribed as a twice-daily equal-dose regimen, is one of the more common asthma treatments. The development of a sustained-release drug delivery technology that enables improved control of the theophylline blood levels represents a significant advancement in both the efficacy and safety of dosing. Method : A crossover study was conducted with 25 adult chronic asthmatic patients requiring daily bronchodilator therapy. The study group included thirteen males and twelve females with ages ranging from 19 to 71 years. The overall approach was to place the patients first on the twice-daily preparation($Etheophyl^{(R)}$) for 28 days at 8 AM and 8 PM, and measure the pulmonary function and theophylline level on the 28th day. The patients were subsequently switched to the once-daily preparation($Uniphyl^{(R)}$) in the same daily dose at 8 PM on the 29th day and the same parameters were measured on the 56th day. Results : The mean serum levels of theophylline were $8.18{\pm}1.66\;{\mu}g/ml$ in the $Etheophyl^{(R)}$-treated period and $8.00{\pm}1.75\;{\mu}g/ml$ in the $Uniphyl^{(R)}$-treated period. ln addition, the $FEV_1$ showed $71.40{\pm}7.48$ percent in the $Etheophyl^{(R)}$-treated and $69.18{\pm}9.00$ percent in the $Uniphyl^{(R)}$-treated period. Thus there were no significant differences between the once-daily and twice-daily preparation. Conclusion : The results indicated little clinical differences between the two medications. The two drugs are equally effective in controlling asthma over the four weeks of treatment.

• Korean Journal of Remote Sensing
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• v.40 no.2
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• pp.229-241
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• 2024

With the advancement of big data processing technology using cloud platforms, access, processing, and analysis of large-volume data such as satellite imagery have recently been significantly improved. In this study, the Change Detection Method, a relatively simple technique for retrieving soil moisture, was applied to the backscattering coefficient values of pre-processed Sentinel-1 synthetic aperture radar (SAR) satellite imagery product based on Google Earth Engine (GEE), one of those platforms, to estimate the surface soil moisture for six observatories within the Yongdam Dam watershed in South Korea for the period of 2015 to 2023, as well as the watershed average. Subsequently, a correlation analysis was conducted between the estimated values and actual measurements, along with an examination of the applicability of GEE. The results revealed that the surface soil moisture estimated for small areas within the soil moisture observatories of the watershed exhibited low correlations ranging from 0.1 to 0.3 for both VH and VV polarizations, likely due to the inherent measurement accuracy of the SAR satellite imagery and variations in data characteristics. However, the surface soil moisture average, which was derived by extracting the average SAR backscattering coefficient values for the entire watershed area and applying moving averages to mitigate data uncertainties and variability, exhibited significantly improved results at the level of 0.5. The results obtained from estimating soil moisture using GEE demonstrate its utility despite limitations in directly conducting desired analyses due to preprocessed SAR data. However, the efficient processing of extensive satellite imagery data allows for the estimation and evaluation of soil moisture over broad ranges, such as long-term watershed averages. This highlights the effectiveness of GEE in handling vast satellite imagery datasets to assess soil moisture. Based on this, it is anticipated that GEE can be effectively utilized to assess long-term variations of soil moisture average in major dam watersheds, in conjunction with soil moisture observation data from various locations across the country in the future.

• Journal of Venture Innovation
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• v.7 no.3
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• pp.25-43
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• 2024

The rapid advancement of the 4th Industrial Revolution and the ongoing effects of COVID-19 significantly accelerated the adoption of smart work practices, especially in the financial sector. This study aimed to empirically investigate the impact of smart work on job satisfaction among employees in this industry. Specifically, the study examined the effects of time flexibility and workplace flexibility (as quantitative elements of smart work) and work autonomy (as a qualitative element) on job satisfaction. Additionally, the study explored the impact of technostress factors, including techno-overload, techno-invasion, and techno-complexity. Using data from 250 valid survey responses collected from financial sector employees, the study employed structural equation modeling (SEM) with AMOS to analyze the relationships. The findings revealed that time flexibility and work autonomy positively influenced job satisfaction, with work autonomy being the most significant predictor. Conversely, techno-overload and techno-invasion negatively affected job satisfaction. However, workplace flexibility and techno-complexity did not show a significant relationship with job satisfaction, possibly due to the already established norms in the financial sector, where remote work and high-level technology usage were standard practices. A critical aspect of the study was the examination of work-life balance as a mediating factor. The analysis confirmed that work-life balance mediated the relationship between work autonomy, techno-overload, techno-invasion, and job satisfaction. This suggested that maintaining a balance between work and personal life was crucial for enhancing job satisfaction in smart work environments, particularly in the financial sector. Effective management of technostress was essential to preserving this balance and improving overall employee satisfaction. These findings contributed to the academic understanding of how smart work practices and technostress impacted job satisfaction. They offered practical insights for financial sector organizations seeking to optimize smart work environments by emphasizing the importance of work-life balance and carefully managing technostress factors.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.19-29
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• 2006

The first Japanese pilot-scale $CO_2$ sequestration project has been undertaken in an onshore saline aquifer, near Nagaoka in Niigata prefecture, and time-lapse well logs were carried out in observation wells to detect the arrival of injected $CO_2$ and to evaluate $CO_2$ saturation in the reservoir. $CO_2$ was injected into a thin permeable zone at the depth of 1110m at a rate of 20-40 tonnes per day. The total amount of injected $CO_2$ was 10400 tonnes, during the injection period from July 2003 to January 2005. The pilot-scale demonstration allowed an improved understanding of the $CO_2$ movement in a porous sandstone reservoir, by conducting time-lapse geophysical well logs at three observation wells. Comparison between neutron well logging before and after the insertion of fibreglass casing in observation well OB-2 showed good agreement within the target formation, and the higher concentration of shale volume in the reservoir results in a bigger difference between the two well logging results. $CO_2$ breakthrough was identified by induction, sonic, and neutron logs. By sonic logging, we confirmed P-wave velocity reduction that agreed fairly well with a laboratory measurement on drilled core samples from the Nagaoka site. We successfully matched the history changes of sonic P-wave velocity and estimated $CO_2$ saturation a(ter breakthrough in two observation wells out of three. The sonic-velocity history matching result suggested that the sweep efficiency was about 40%. Small effects of $CO_2$ saturation on resistivity resulted in small changes in induction logs when the reservoir was partially saturated. We also found that $CO_2$ saturation in the $CO_2$-bearing zone responded to suspension of $CO_2$ injection.

• The Korean Journal of Air & Space Law and Policy
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• v.35 no.3
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• pp.95-126
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• 2020

In 2017, the world's first WIG ship (WIG: Wing In-Ground) pilot's license written test was conducted in Korea. The WIG ship is a ship that combines the characteristics of ships and airplanes. Therefore, the pilot of the WIG ship was allowed to apply only for those who had the aircraft pilot's license and the 6th class marine nautical license. The WIG ship pilot's license system was first introduced by Korea, so there are no international standards for the license system, and the introduction of a domestic qualification system also requires institutional arrangements due to various restrictions such as pilot training. However, in order to become a valuable industry as a future growth engine for the ocean, several urgent problems need to be solved, and that is the training of manpower for WIG ships. Therefore, I reviewed the institutional issues related to pilot training as this subject. Since 2001, various countries around the world have been discussing this issue, centering on IMO, and Korea has continued to participate and cooperate in IMO meetings. And the national qualification test for surface flying ships was conducted in Korea from 2011. However, there are still problems to be solved, and I pointed out the advancement of the manpower training system, the education and training system, and the designated national educational institution system. As a solution to this, it was suggested through the improvement of the license system and the operation of designated educational institutions. Among these solutions, I believe that the best way is to entrust the operation of designated national educational institutions to private educational institutions. However, I propose a plan that the government entrusts to private educational institutions, but the government is responsible for licensing and supervision. WIG ship will be a new market for the aviation industry and aviation workers.

• Journal of Internet Computing and Services
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• v.17 no.1
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• pp.101-107
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• 2016

Due to the recent advancement in digital imaging technology, development of intervention equipment has become generalize. Video arbitration procedure is a process to insert a tiny catheter and a guide wire in the body, so in order to enhance the effectiveness and safety of this treatment, the high-quality of x-ray of image should be used. However, the increasing of radiation has become the problem. Therefore, the studies to improve the performance of x-ray detectors are being actively processed. Moreover, this intervention is based on the reference of the angiographic imaging and 3D medical image processing. In this paper, we propose a guidance system to support this intervention. Through this intervention, it can solve the problem of the existing 2D medical images based vessel that has a formation of cerebrovascular disease, and guide the real-time tracking and optimal route to the target lesion by intervention catheter and guide wire tool. As a result, the system was completely composed for medical image acquisition unit and image processing unit as well as a display device. The experimental environment, guide services which are provided by the proposed system Brain Phantom (complete intracranial model with aneurysms, ref H+N-S-A-010) was taken with x-ray and testing. To generate a reference image based on the Laplacian algorithm for the image processing which derived from the cerebral blood vessel model was applied to DICOM by Volume ray casting technique. $A^*$ algorithm was used to provide the catheter with a guide wire tracking path. Finally, the result does show the location of the catheter and guide wire providing in the proposed system especially, it is expected to provide a useful guide for future intervention service.

• Journal of The Korean Association For Science Education
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• v.44 no.5
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• pp.433-451
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• 2024

Modern society has become a "digital risk society" with the rapid advancement of digital technologies. The growing use of digital tools in education has led to discussions on managing digital risks that arise in teaching and learning contexts. Among all subjects, science education has experienced significant digital transformation, emphasizing the need for strategies to address digital risks within the subject. This study explores digital literacy education as a possible approach to addressing digital risks in science education. To achieve this, the study analyzes the types of digital risks prevalent in modern society and examines the trends of research on digital risks within the context of digital literacy education. This was done by collecting 415 SSCI articles published over the past decade (2014-2023) with the keyword "Digital Risk" and conducting topic modeling and hierarchical clustering to identify types of digital risks. Additionally, 110 KCI articles published with the keyword "Digital Literacy Education" were collected and classified according to the identified digital risk types. These articles were then compared and analyzed based on publication year, school level, and subject to understand the characteristics of digital risks within science education. The findings are as follows: First, the identified digital risk types include intellectual property infringement, spreading fake news, privacy infringement, cyber financial crimes, gaps in digital literacy, digital technology overdependence, and social structural risks. Second, an analysis of publication trends over the years revealed that discussions on digital risks increased significantly during the COVID-19 pandemic, with research on the digital literacy gap being the most prominent. Third, in terms of school level, digital literacy education addressing digital risks was more actively researched in primary education than in secondary education. Finally, subject-area analysis indicated that science education had the lowest proportion of research on digital risks relative to overall digital literacy studies. In science education, discussions primarily focused on intellectual property infringement, spreading fake news, and gaps in digital literacy. This study emphasizes the importance of addressing digital risks in science education and provides foundational data for further discussions on this topic.

• Journal of the Korean Society of International Agriculture
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• v.30 no.4
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• pp.328-338
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• 2018

Central Asia (Uzbekistan, Kazakhstan, Kyrgyzstan) is a hot and arid continental climate, with most areas (68%) consisting of barren vegetation, desert, and meadows. The main agricultural areas for crop production include irrigated farmland, non-irrigated farmland, grassland, prairie and mountain. We are experiencing climate change with recent climate variability increasing. Agriculture is one of major economic sectors and provides a means of livings for the rural population of Central Asia, especially the poor. In the past two decades, Central Asia has experienced a high population growth rate, with Kazakhstan at 16.8%, Uzbekistan at 34.5% and Kyrgyzstan at 28.4%. As a major industry, Kazakhstan has the largest share of exports of agricultural products followed by petroleum, mineral resources, steel, and chemicals. Uzbekistan is the fifth largest cotton exporter as well as the sixth largest cotton producer in the world. Kyrgyzstan exports ores, stones, cultured pearls, and minerals. These three countries are rich in mineral resources, agricultural products, and energy resources. However, not only do they have difficulties in economic development due to the weakness of logistics and industrial infrastructure, but they also have imperceptible cooperation and investment among countries due to insufficient research and development. Through this study, we will investigate national outlook, economic indicators, major agricultural products, import and export status, and agricultural technology cooperation status, and study how Korean agricultural industry advances into these countries through SWOT analysis. Through this, we hope to contribute to the basic data of Central Asian studies and cooperation and investment in agriculture in each country. In addition, in order to increase cooperative exchange and investment in these countries, we will prepare a Central Asia logistics hub for the rapidly changing interKorean railroad era.