• Membrane Journal
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• v.33 no.4
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• pp.222-232
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• 2023

In this study, a hollow fiber support membrane was prepared by a non-solvent induced phase separation (NIPS) method using a polysulfone (PSf). The prepared hollow fiber support membrane was coated with PDMS and Pebax to prepare a hollow fiber composite membrane. The prepared composite membrane was measured for permeance and selectivity for pure CO₂, H₂, O₂ and N₂. Gas separation performance of the module having the highest selectivity (CO₂/H₂) among the prepared composite membrane modules was measured according to the change in stage cut using simulated gas. The composition of the simulated gas used at this time was 70% CO₂ and 30% H₂. In the 1 stage experiment, it was possible to obtain values of about 60% of H₂ concentration and 12% of H₂ recovery. In order to overcome the low H₂ concentration and recovery, 2 stage serial test was performed, and through this, it was possible to achieve 70% H₂ concentration and 70% recovery. Through this, it was possible to derive a separation process configuration for CO₂/H₂ separation.

• Journal of Life Science
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• v.33 no.8
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• pp.680-691
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• 2023

Peak oil, climate change, and microplastics caused by the production and usage of petroleum-based plastics have threatened the sustainability of our daily life, and this has emerged as a recent global issue. To solve this global issue, the production and usage of biodegradable eco-friendly bioplastics such as polyhydroxyalkanoates (PHAs) has been suggested as an alternative. Therefore, in this review, the present status of global PHA manufacturers, the advantages of the production of PHAs using marine-origin microorganisms (with their productivity potential) and further required research and development strategies for cost-competitive production of PHAs using marine-based microorganisms were investigated. In this review, PHAs produced from marine microorganisms were found to have similar physical properties to petroleum-based plastics but with several advantages that can reduce the costs of PHA production. Those advantages include, seawater used in the medium preparation step, and osmotic-based cell lysis technology used in the separation and purification steps. However, the PHA productivities from marine microorganisms showed somewhat lower efficiencies than those from the commercial strains isolated from terrestrial environments. In order to solve the problem, further research strategies using synthetic microbiology-based technology, the development of long-term continuous culture technology, and solutions to improve PHA efficiency are required to meet future market demands for alternative bioplastics.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.15-23
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• 2023

The grouting method is a method of construction for the purpose of waterproofing and reinforcing soft ground. When grout is injected into the ground, there are various types of penetration and diffusion of grout depending on the shape of the ground, the size of soil, the porosity, and the presence or absence of groundwater. the current situation. Therefore, in this study, to investigate the penetration performance of the grouting to conductive material, laboratory tests were performed on the addition of the conductive material. In the injection test, 0%, 3%, and 5% of the mixed water were added as conductive materials to the grout, and the original ground condition was composed of various types of ground composed of gravel and silica sand. Conductive grout is injected by pressure into the model ground using a dedicated injection device, and the injection time (t), pressure (p), flow rate (v) and injection amount (q) are measured, and the hardened body injected in the model ground is collected. Penetration performance was evaluated. In the results of the grout injection experiment, the amount of conductive material used and the grout injection rate showed an inverse relationship, and it was confirmed that the penetration pattern was changed according to the size of the soil particles in the model ground. The grout containing the conductive material has relatively good penetration into the ground and excellent strength and durability of the hardened body, so it was judged that it could be used as an additive for measuring the penetration range of the grout.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.3
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• pp.1-19
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• 2023

Bikes have recently emerged as an alternative to carbon neutrality. To understand the demand for public bikes, we endeavored to estimate travel frequency of public bike by considering the intermediate stops. Using the GPS trajectory data of 'Ttareungyi', a public bike service in Seoul, we identified a stay point and estimated travel frequency reflecting population, land use, and physical characteristics. Application of map matching and a stay point detection algorithm revealed that stay point appeared in about 12.1% of the total trips. Compared to a trip without stay point, the trip with stay point has a longer average travel distance and travel time and a higher occurrence rate during off-peak hours. According to visualization analysis, the stay points are mainly found in parks, leisure facilities, and business facilities. To consider the stay point, the unit of analysis was set as a hexagonal grid rather than the existing rental station base. Travel frequency considering the stay point were analyzed using the Zero-Inflated Negative Binomial (ZINB) model. Results of our analysis revealed that the travel frequency were higher in bike infrastructure where the safety of bike users was secured, such as 'Bikepath' and 'Bike and pedestrian path'. Also, public bikes play a role as first & last mile means of access to public transportation. The measure of travel frequency was also observed to increase in life and employment centers. Considering the results of this analysis, securing safety facilities and space for users should be given priority when planning any additional expansion of bike infrastructure. Moreover, there is a necessity to establish a plan to supply bike infrastructure facilities linked to public transportation, especially the subway.

• Journal of Practical Engineering Education
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• v.14 no.3
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• pp.479-489
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• 2022

In order to understand how to increase the use of virtual training content at K University's online lifelong education institute, this study examined the use experience, content recognition, field practice replacement, and requirements, focusing on the examples of operating institutions. To this end, 12 institutions that operated virtual training contents distributed by the K University Online Lifelong Education Center in 2020 were selected for in-depth interviews and qualitative analysis was conducted on the interviews of 11 institutions. As a result of the analysis, first, the experience of using the contents of the virtual training operating institution was aimed at changing the educational environment, supplementing theoretical learning, and improving the sense of practice. Second, according to a survey on the recognition of virtual training content, if the importance and utilization of the content are high, it can be replaced by on-site practice in non-face-to-face classes, such as experiences of facilities and equipment, attracting interest and attention. Third, in many cases, the perception of replacement for field practice is not unreasonable to use as a pre-training material for field practice, but it is difficult to replace field practice. Fourth, content quality improvements can be summarized as content quality improvement, content access and manipulation improvement, dedicated device development, training for instructors, and curriculum systematization. Fifth, institutional requirements include improving the quality of virtual training content itself, equipment support, curriculum systemization and characterization, systematic curriculum and detailed content sharing, detailed guidance on using virtual training content, introducing how to use content, and recruiting instructors. This study is meaningful in that it sought ways to improve the utilization of virtual training content based on the perception of virtual training content operating institutions.

• Clean Technology
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• v.29 no.4
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• pp.305-312
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• 2023

Due to the strengthening of environmental requirements, aging denitrification facilities need to improve their performance. The present study aims to suggest the possibility of improving performance using computational analysis techniques. This involved modifying both the geometric design and the operating conditions, including the flow path shape of the equipment such as the inlet guide vane and the curved diffusing part, and the flow control of the ammonia injection nozzle. The conditions presented in this study were compared with existing operating conditions in terms of the flow uniformity, the NH₃/NO molar ratio of the mixed gas flowing into the catalyst layer, and the total pressure drop of the facility. The flow field applied in the computational analysis ranged from the outlet of the economizer in the combustion furnace to the inlet of the air preheater, the full domain of the denitrification facility. The performances were derived by solving the flow fields using ANSYS-Fluent and the injection amount of ammonia was adjusted for each nozzle using Design Xplorer. Compared to the denitrification performances of the equipment currently in operation, the conditions proposed in this study showed an improvement in the flow uniformity and NH₃/NO composition ratio by 45.1% and 8.7%, respectively, but the total pressure drop increased by 1.24%.

• Journal of the Institute of Convergence Signal Processing
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• v.24 no.1
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• pp.27-33
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• 2023

Recently, water shortages have occurred due to climate change, and the need for water management of agricultural water has increased due to the occurrence of algal blooms in reservoirs. Existing algae prevention is operated by putting many people on site and misses the optimal spraying time due to movement through boats. In order to solve this problem, it is necessary to block contamination in advance and move within time to uniformly spray complex microorganisms uniformly. Control drones are used for pesticide spraying and can be applied to algae prevention work by utilizing control drones. In this paper, basic research for the establishment of a marine control system was conducted for application to the reservoir environment, and as one of the results, the characteristics of a drone nozzle, a core technology that can be used for control drones, were calculated. In particular, it was found that the existing agricultural control drones had a disadvantage that the concentration was non-uniform within the suggested spraying interval, and to compensate for this, nozzle positioning and nozzle spraying uniformity were calculated. Based on the experimental results, we develop a core algorithm for establishing an algal bloom monitoring system in the reservoir environment and propose a precision control technology that can be used for marine control work in the future.

• Journal of the Korean Society of Radiology
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• v.82 no.1
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• pp.116-127
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• 2021

Purpose To evaluate the feasibility of texture analysis of gray-scale ultrasound (US) images for staging of hepatic fibrosis. Materials and Methods Altogether, 167 patients who had undergone routine US and laboratory tests for a fibrosis-4 (FIB-4) index were included. Texture parameters were measured using a dedicated in-house software. Regions of interest were placed in five different segments (3, 5, 6, 7, 8) for each patient. The FIB-4 index was used as the reference standard for hepatic fibrosis grade. Comparisons of the texture parameters between different fibrosis groups were performed with the Student's t-test or Mann-Whitney U-test. Diagnostic performance was evaluated by receiver operating curve analysis. Results The study population comprised of patients with no fibrosis (FIB-4 < 1.45, n = 50), mild fibrosis (1.45 ≤ FIB-4 ≤ 2.35, n = 37), moderate fibrosis (2.35 < FIB-4 ≤ 3.25, n = 27), and severe fibrosis (FIB-4 > 3.25, n = 53). Skewness in hepatic segment 5 showed a difference between patients with no fibrosis and mild fibrosis (0.2392 ± 0.3361, 0.4134 ± 0.3004, respectively, p = 0.0109). The area under the curve of skewness for discriminating patients with no fibrosis from those with mild fibrosis was 0.660 (95% confidence interval, 0.551-0.758), with an estimated accuracy, sensitivity, specificity of 64%, 87%, 48%, respectively. Conclusion A significant difference was observed regarding skewness in segment 5 between patients with no fibrosis and patients with mild fibrosis.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.23 no.2
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• pp.157-172
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• 2024

Autonomous driving technology, when commercialized, has the potential to improve the safety, mobility, and environmental performance of transportation networks. However, safe autonomous driving may be hindered by poor sensor performance and limitations in long-distance detection. Therefore, cooperative autonomous driving that can supplement information collected from surrounding vehicles and infrastructure is essential. In addition, since HDVs, AVs, and CAVs have different ranges of perceivable information and different response protocols, countermeasures are needed for mixed traffic that occur during the transition period of autonomous driving technology. There is a lack of research on traffic flow optimization that considers the penetration rate of autonomous vehicles and the different characteristics of each road segment. The objective of this study is to develop weights based on safety, operational, and environmental factors for each infrastructure control use case and autonomous vehicle MPR. To develop an integrated evaluation index, infra-guidance AHP and hybrid AHP weights were combined. Based on the results of this study, it can be used to give right of way to each vehicle to optimize mixed traffic.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.23 no.2
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• pp.119-131
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• 2024

Understanding accurate traffic performance is crucial for ensuring efficient highway operation and providing a sustainable mobility environment. On the other hand, an immediate and precise estimation of highway traffic performance faces challenges because of infrastructure and technological constraints, data processing complexities, and limitations in using integrated big data. This paper introduces a framework for estimating traffic performance by analyzing real-time data sourced from toll collection systems and dedicated short-range communications used on highways. In particular, this study addresses the data errors arising from segmented information in data, influencing the individual travel trajectories of vehicles and establishing a more reliable Origin-Destination (OD) framework. The study revealed the necessity of trip linkage for accurate estimations when consecutive segments of individual vehicle travel within the OD occur within a 20-minute window. By linking these trip ODs, the daily average highway traffic performance for South Korea was estimated to be248,624 thousand vehicle kilometers per day. This value shows an increase of approximately 458 thousand vehicle kilometers per day compared to the 248,166 thousand vehicle kilometers per day reported in the highway operations manual. This outcome highlights the potential for supplementing previously omitted traffic performance data through the methodology proposed in this study.