• The Journal of Engineering Geology
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• v.30 no.4
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• pp.603-615
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• 2020

The design factors of artificial recharge are determined by considering the hydrogeological characteristics of the aquifer. The optimal design factors for artificial recharge were derived after performing the injection tests step by step for each injection type (vertical well, ditch and mixed type), which were built in the test site of the study area. It was analyzed that the difference in the injection effect according to the diameter of the injection well was not large, and the 100 mm well was evaluated as appropriate in consideration of the availability and economy of land use. Since the injection effect was well maintained even in the upper rock, the depth of the injection well was proposed for the alluvial layer and the upper rock layer. On the other hand, in four cases of filter media in the ditch, it was analyzed that the penetration efficiency and the hydraulic interference effect indicated excellent injection performance when a filter medium of 10 to 30 mm diameter was filled in the ditch. In addition, the proper spacing of the injection wells was analyzed as 9~12 m considering the interference efficiency. The interference efficiency attenuation coefficient per 1 m of hole spacing was calculated to be 1.75% in this area. In the future study, the artificial recharge design factors obtained in this stage are applied and verified on site construction and operation. Also it is expected to contribute to securing water in areas where there is always a lack of water.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.53-65
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• 2021

While the hydrogen refueling station is rapidly expanded and installed, the safety inspection of the hydrogen pressure vessel in the station should be very important. Of these, according to ASME, hydrogen embrittlement tests must be performed for hydrogen vessel that store hydrogen above a certain pressure. The main test method for hydrogen embrittlement inspection is to carry out fracture tests and fatigue fracture tests in a high pressure hydrogen atmosphere, which allows the durability limit of the pressure vessel to be measured and the endurable limit to be determined in the hydrogen atmosphere. In detail, the critical crack depth can be calculated by the stress intensity factor(K), and the service life can be determined by da/dN (fatigue growth rate). API579-1/ ASME FFS-1 part 9 exemplifies the calculation method according to the mode of crack-like flaws, but for various shapes such as plates and cylinders, there are about 55 modes according to the shape and location of the crack. Due to the fairly complex formula, it is not easily accessible. In this study, we will show you how to calculate fracture mechanics numerically via Excel and VBA. In addition, this was applied to analyze the effects of the thickness and inner diameter of the pressure vessel on the service life.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.469-479
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• 2021

As a material for preventing spalling of concrete, the effectiveness of PP fiber has already been confirmed. However, it is necessary to consider the maximum temperature that occurs during a fire, and to solve the mixing problem and the strength reduction problem that occur depending on the mixing amount. In this study, the fire resistance performance of tunnel segment linings according to the PP fiber content and air volume under the RABT fire scenario was investigated. As a result, no spalling or cross-sectional loss occurred in all test specimens, and when the PP fiber content was small, the maximum temperature was relatively high and the maximum temperature arrival time was also fast. On the other hand, no trend was found for the maximum temperature and arrival time according to the difference in air volume. In the internal temperature distribution results for the PP fiber mixing amount of 0.75, 1.0, 1.5, and 2.0 kg/m³, the results of 0.75 and 1.0 kg/m³ showed similar temperature distribution, and the results of 1.5 and 2.0 kg/m³ were similar. It was confirmed that the internal temperature distribution tends to decrease at the same depth when the amount of PP fiber mixed is large, and it was confirmed that a remarkable difference occurred from the results of 1.0 kg/m³ and 1.5 kg/m³ of PP fiber mixed amounts.

• Journal of Environmental Health Sciences
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• v.48 no.5
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• pp.282-289
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• 2022

Background: Airborne fungi are ubiquitous in the air and exposure to an airborne fungus can be a significant risk factor. The composition of fungi has been potentially important for human health, especially for respiratory diseases like asthma and atopic dermatitis. Therefore, we attempted to ascertain what kind of airborne fungi affect human health at a nationwide level. Objectives: This study was carried out to provide information on indoor fungi distribution at multi-use facilities throughout South Korea. Methods: We classified our data by region and public facility after collection, cultivation, and identification via the sequencing of the ITS (internal transcribed spacer) region. We investigated whether or not the proliferation of HaCaT cells was affected by the identified airborne fungi. Results: In our data, the most isolated airborne fungi by region were Penicillium spp (Seoul, Daegu), Periconia sp (Gyeonggi-do), Iprex sp (Gangwon-do), Phanerochaete sp (Busan), Bjerkandera sp (Gwangju), and Aspergillus sp (Jeju-do). In the public facilities, the most detected fungi were Cladosporium sp (public transport), Penicillium sp (apartment house, retail market, financial institution, karaoke room), Bjerokandera sp (underground parking lot, public toilet, medical institution), Periconia sp (retail store), and Fusarium sp (general restaurant). Next, we selected twenty airborne fungi to examine their cytotoxicity and proliferation of human skin cells. In this experiment, the proliferation of the cells was influenced by most of the identified fungi. In case of the cytotoxicity test, most genera except for Rhodotorula sp and Moesziomyces sp showed cytotoxicity in HaCaT cells. Conclusions: The distribution of mold in the indoor air in multi-use facilities in South Korea differs from region to region, and this is an indicator that should be considered in future health impact studies. In addition, as a result of culturing about 20 types of bacteria dominant in indoor air, it was found that most (90%) inhibit the growth of skin cells, which can be harmful to health. An in-depth study of the health effects of floating fungi is needed.

• Resources Recycling
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• v.31 no.4
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• pp.3-11
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• 2022

Owing to the increasing demand for electric vehicles (EVs), appropriate management of their waste batteries is required urgently for scrapped vehicles or for addressing battery aging. With respect to technological developments, data-driven diagnosis of waste EV batteries and management technologies have drawn increasing attention. Moreover, robot-based automatic dismantling technologies, which are seemingly interesting, require industrial verifications and linkages with future battery-related database systems. Among these, it is critical to develop and disseminate various advanced battery diagnosis and assessment techniques to improve the efficiency and safety/environment of the recirculation of waste batteries. Incorporation of lithium-related chemical substances in the public pollutant release and transfer register (PRTR) database as well as in-depth risk assessment of gas emissions in waste EV battery combustion and their relevant fire safety are some of the necessary steps. Further research and development thus are needed for optimizing the lifecycle management of waste batteries from various aspects related to data-based diagnosis/classification/disassembly processes as well as reuse/recycling and final disposal. The idea here is that the data should contribute to clean design and manufacturing to reduce the environmental burden and facilitate reuse/recycling in future production of EV batteries. Such optimization should also consider the future technological and market trends.

• Journal of the Korea Institute of Building Construction
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• v.22 no.1
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• pp.11-21
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• 2022

Currently, in the domestic construction industry, the free web method has been emerging as a potential solution to the shortage of skilled workers due to the prolonged COVID-19 crisis, as it helps in securing economic feasibility through shortening the construction period and reducing labor costs. To consider one part of the construction method, in this study, the bending behavior according to the load was evaluated for the SY slope-type beam formwork, which was manufactured at a factory, assembled with rebar, brought into the site, and then poured into the site. For the SY Beam standard cross-sectional shape, a cross-sectional dimensional width of 400mm and depth 600mm determined through structural modeling using the MIDAS GEN program were applied. A total of 6 specimens were made with a member length of 5,000mm, 5 specimens and one RC specimen in the comparison group were manufactured in real-size format using the thickness of the steel plate(0.8, 1.0, 1.2mm) as a variable, and bending experiments were performed. In the bending test, the steel plate deck showed high initial stiffness and maximum strength as it yielded, which showed that it sufficiently contributed to the flexural strength. It is judged that additional analysis and experimental studies for 1.05, 1.1, and 1.15mm are needed to derive the appropriate steel plate thickness and the method for calculating the tensile force contribution of the steel plate to secure the manufacturing, construction and economic feasibility of SY Beam in the future.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.3
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• pp.63-82
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• 2022

The purpose of this study is to compare growth condition of landscape woody plants growing on the different ground structures in apartment complex. I chose Manseok Beach Town Complex 2, in Manseok-dong, Seo-gu, Incheon which has both natural and artificial ground as a subject site. Analysis of three phases of soil showed that artificial ground had average liquid phase of 30.89%, artificial ground mounding 33.88% and natural ground 24.40%. It means that artificial ground has higher water content than natural ground despite having same earthiness. It is believed that artificial ground is not as well drained as natural ground even though it is connected to the natural ground and has a deep soil depth because of mounding. Comparative study between woody plants on natural ground and those on artificial ground demonstrated that trees on natural ground grew 40.4% compared to those on artificial ground(0.875mm more) in terms of diameter growth. Average diameter growth of trees on natural ground was 3.040mm against 2.165mm for those on artificial ground. All 19 tree species which were measured for root diameter growth showed similar or higher growth on natural ground than on artificial ground. When it comes to growth of height, arborvitae showed highest growth on natural ground, followed by Thuja occidentalis, Pinus strobus, Magnolia denudata, Diospyros kaki and Aesculus turbinata. I measured branch growth and rate of leaf adherence of Pinus strobus. Average annual rate of branch growth of woody plants on natural ground was twice as high as those on artificial ground. I could conclude that ground structure influences branch growth of Pinus strobus. Statistics analysis of tree damage demonstrated significant result, meaning that there is a difference in the average damage rate depending on structure of ground. In order to validate growth difference by planting ground, I conducted T-Test of growth of diameter, root diameter, branch and height on woody plants growing on natural and artificial ground. As a result, it is believed that there is a difference in the growth of trees depending on the ground structure. Putting all these results together demonstrates that woody plants on natural ground generally grow better than those on artificial ground, which means ground structure does have an influence on the environment of growth of trees.

• Journal of Korea Entertainment Industry Association
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• v.15 no.7
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• pp.87-96
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• 2021

The purpose of this study is to analyze the problems of the Physical Activity Promotion System(PAPS) implemented in elementary, middle, and high schools in Korea and to prepare improvement measures. The data of the study was obtained through in-depth interviews, related papers, and press releases. The research participants of this study were 5 incumbent physical education teachers who directly instruct and measure PAPS at school and 5 college students who directly experienced PAPS. The results of the study are as follows. First, the problems that occurred in the educational environment of PAPS were students' indifference, teachers' passive guidance, and decreased physical education hours replaced by PAPS measurement days. Second, the problems occurring in the measurement environment of PAPS were errors due to measurement equipment, deviations due to different measurement locations, and differences in grades according to measurement items. Third, the problems that occur in the measurement process of PAPS are the lack of measurement personnel, the expedient physical fitness measurement, and the non-standardized measurement method. In order to improve these problems and successfully apply PAPS, the following improvement measures should be attempted. Details on this are as follows. First, teachers should inspire students' interest and interest in PAPS. Second, it is necessary to secure the reliability of the measurement result value of PAPS. Third, it is necessary to systematically supplement the school education system for PAPS measurement.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.48 no.4
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• pp.225-231
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• 2022

Objectives: This study aims to evaluate the efficacy and safety of two types of sandblasted with large-grit and acid-etched (SLA) surface implants with different surface roughness. Patients and Methods: This study was conducted based on a clinical record review of 55 patients (mean age, 53.00 years). A total of 80 SLA surface implants was placed. Among the 80 implants, 38 implants placed in 29 subjects had surface roughness (Ra) of 3.09 ㎛ (test group, TG), while the other 42 implants placed in 31 subjects had a surface roughness (Ra) of 2.50 ㎛ (control group, CG). A comparison was made of implant primary/secondary stability; success and survival rates; marginal bone loss; and soft tissue assessment including probing pocket depth (PPD), plaque index (PI), gingival index (GI), and bleeding on probing (BOP) between the groups at 1 year after implant placement. Results: Among the implants that were initially registered, 1 from the TG and 4 from the CG dropped out, leaving 37 implants in the TG and 38 implants in the CG to be traced and analyzed. Although 1 TG case showed unstable primary stability, all cases showed stable secondary stability. Success and survival rates at 1 year after implant placement were 100% in both groups. Marginal bone loss was 0.07 mm and 0.00 mm for the TG and CG, respectively, but the difference was not significant. Among the several parameters for evaluation of soft tissue, the TG showed lower PI at 1 year after implant placement (TG=0.00, CG=0.29; P=0.0004), while the remaining categories showed no significant difference between the groups. Conclusion: This study shows that the two types of SLA implants with different surface roughness have no difference in efficacy or safety. Therefore, both of the implants can be used safely and with promising outcomes.

• Journal of Korean Elementary Science Education
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• v.41 no.2
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• pp.325-337
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• 2022

This study aims to determine the implications of the efficient and effective implementation of science core competency (ScC) education by examining the state of science core competencies derived from the 2015 revised elementary school science curriculum and analyzing teachers' and students' perceptions. To this end, this paper investigated the reality of reflecting the science core competencies of science textbooks in a group of third and fourth graders from seven elementary schools who passed the test. In addition, in-depth interviews were conducted with four elementary school teachers who participated in qualification textbook selection, and 156 elementary school students were surveyed to determine their perceptions of science core competencies. Findings showed that, first, 1,586 science core competencies were reflected throughout the textbooks, with an average of 227 per textbook and biology being the most salient area. Second, teachers did not understand the difference between previous inquiry activities in textbooks and ScC education. Third, no statistically significant differences were observed in the perceptions of male and female students on science core competencies, the highest average of perceptions being those of scientific thinking ability. From these results, this study concluded that for ScC education to be realized as a curriculum, textbooks must be organized according to the purpose of core competency education, implementing practical changes, and efforts must be directed toward changing the perceptions of individuals who deliver education.