• The Journal of Engineering Geology
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• v.31 no.1
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• pp.83-101
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• 2021

The high-density polyurethane method uses the instantaneous expansion pressure of injected material to stabilize soft ground, allowing reinforcement, restoration, and construction to be carried out in suboptimal ground conditions. Under normal and, even poor conditions, the method is easily applied because the working time is very short. The method is environmentally friendly and results have excellent durability. The purpose of this study was to verify the physical and mechanical properties of high-density polyurethane in the ground. Initial testing of strength, direct shear, and soil environment stability was followed by testing for permeability in order to address environmental concerns. The results of the experiments showed that the internal friction angle was about twice as high and the adhesion was about 2.5 to 3.5 times higher than for dense and hard clay, and that the permeability factor was significantly lower compared with the existing grouting method, within the range of 1.0 × 10-5.

• Journal of Software Assessment and Valuation
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• v.16 no.2
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• pp.163-172
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• 2020

Recently, concepts of the Fourth Industrial Revolution technologies such as artificial intelligence, big data, and cloud computing have been introduced and the limits of individual or team development policies are being reviewed. Also, a lot of latest technology source codes have been opened to the public, and related studies are being conducted based on them. Meanwhile, the company is applying the strengths of the open source software development methodology to proprietary software development, and publicly announcing support for open source development methodology. In this paper, we introduced several software development methodology such as open source model, inner source model, and the similar DevOps model, which have been actively discussed recently, and compared their characteristics and components. Rather than claiming the excellence of a specific model, we argue that if the software development policy of an individual or affiliated organization is established according to each benefit, they will be able to achieve software quality improvement while satisfying customer requirements.

• Journal of the Korean Society for Library and Information Science
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• v.57 no.1
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• pp.233-261
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• 2023

Drawing on Bronfenbrenner's ecological system, the study explored the effect of the ecological variables affecting library satisfaction for mothers of early school-age children. The study used the eighth wave(2015) of Panel Study on Korean Children and conducted correlation analysis, multiple regression analysis, hierarchical regression analysis, and stepwise regression analysis. Researchers selected ecological variables for each ecological system based on previous studies. Results showed that mothers had moderate satisfaction with libraries, and their satisfaction with libraries was affected by library accessibility, satisfaction with public services, type of residence, children's reading time, and supportiveness of parenting policy. The study showed that external factors such as family, community, and policies could affect library satisfaction along with internal factors in the sociocultural context. The study suggested a possible practical implication for library policy.

• Journal of the Korean Geotechnical Society
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• v.26 no.4
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• pp.59-68
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• 2010

Piping, a common form of internal embankment erosion, is caused by progressive movement of soil particles through an embankment. The phenomenon commonly occurs with precursory signs of development of fractures in dam structures, but also occurs without any noticeable signs in dams that showed satisfactory dam performance for several years, due to dissolution of soluble material in an embankment. While piping accounts for nearly 50% of the causes for dam failure, few studies have been made for systematic evaluation of the phenomenon. In this study, we attempted to monitor the changes in electrical resistivities of fill-dam material while a saddle dam is dismantled for the construction of emergency spillways of Daechung dam. Two artificial subhorizontal boreholes were drilled into the embankment structure to simulate piping along the two artificial flow channels. Monitoring of changes in electrical resistivity showed an increase in resistivity values during piping. Thus, the investigation of resistivity over time could be an effective method for piping prediction.

• Composites Research
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• v.22 no.3
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• pp.1-8
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• 2009

In this paper, we present the results of experimental and analytical investigations on the structural behavior of GFRP pipes used in the water supply pipeline system. Cross-section of the pipe is consisted with two GFRP tubes and polymer mortar between the tubes. Due to the advantages such as light-weight, corrosion resistance, smooth surface, flexibility, etc., use of GFRP pipe in the water supply pipeline system is ever increasing trend. Therefore, more optimized structural design methodology should be developed. In the investigation, we conducted theoretical and analytical studies on the load versus radial deformation characteristics of GFRP pipes. In addition, ring stiffness test is also performed. Test results are compared with theoretical and analytical results and it was found that the results are agreed well within 5% of radial deformation. Finally, it was also found that the GFRP pipes used in the water supply pipeline system are strong enough to satisfy the industrial requirements.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.3
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• pp.223-228
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• 2023

According to the Korea Information Society Development Institute, OTT services grew at a rate of 33.4% in four yearsfrom 2017, when they were first launched.TheKorea Export-Import Bank announced in 2020 that the domestic OTT market was worth 780.1 billionKRW. This growth of the OTT market is expected to stimulate competition among OTT service platforms, and user satisfactionwithconvenience features, such as video recommendations, seems to be acting as an important factor in the competition.Currently, the OTT market uses a variety ofdata for customized recommendations, but the limitationis that it only uses datacollected within the app. Thereby we have proposed the use ofpersonal data collected outside the app for personalized recommendations, and the survey results showed that user satisfaction was 23.72% higher for recommended content based on the proposedmethod thanNetflix recommended content.

• Analytical Science and Technology
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• v.21 no.5
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• pp.403-411
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• 2008

Dimethyldibutyltetradecylmalonamide (DMDBTDMA) extractant was used in a solvent extraction process for a radioactive liquid waste treatment. For the study of radiolysis phenomena, DMDBTDMA was synthesized and the degradation compounds (n-methylbutylamine, tetradecane, 1-tetradecanol) in the DMDBTDMA extractant, irradiated with $^{60}Co$ gamma ray, were identified and determined as radiolysis products by a Fourier transform infrared (FT-IR), gas chromatograph/mass spectrometer (GC/MS) analysis and GC/MS with selected ion monitoring (SIM) mode. Retention behavior of n-methylbutylamine, n-dodecane, tetradecane and 1-tetradecanol in the total ion chromatogram with the standard materials and n-dodecane as the internal standard (ISTD) were 2.35 min., 8.83 min., 10.68 min. and 12.75 min., respectively. In the case of tetradecane, there was a linear relationship between the concentration of the tetradecane and the absorbed dose of the ${\gamma}$-ray irradiated DMDBTDMA.

• Journal of the Korea Institute of Building Construction
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• v.23 no.5
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• pp.527-536
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• 2023

This research embarked on a comprehensive examination of the engineering characteristics of lightweight concrete intended for implementation in rhamen-type modular building walls. The concrete was formulated utilizing bottom ash and coated EPS beads, in accordance with the Korea Construction Standards Center(KCS) 14 20 20 "Lightweight Aggregate Concrete". Our findings articulate that while EPS beads tend to diminish the compressive strength of the lightweight concrete, they concurrently contribute to a notable reduction in unit mass. The porous nature of the bottom ash endows the material with diminished thermal conductivity. Significantly, a mixture containing 50% EPS beads and 50% BA20 aggregates, replacing half of the coarse aggregates, was found to meet the standard specifications.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.1
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• pp.83-102
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• 2024

Recently, as the use of the cloud increases year by year and remote work within the enterprise has become one of the new types of work, the security of the cloud-based remote work environment has become important. The introduction of zero trust is required due to the limitations of the existing perimeter security model that assumes that everything in the internal network is safe. Accordingly, NIST and DoD published standards related to zero trust architecture, but the security requirements of that standard describe only logical architecture at the abstract level. Therefore, this paper intends to present more detailed security requirements compared to NIST and DoD standards by performing threat modeling for OpenStack clouds. After that, this research team performed a security analysis of commercial cloud services to verify the requirements. As a result of the security analysis, we identified security requirements that each cloud service was not satisfied with. We proposed potential threats and countermeasures for cloud services with zero trust, which aims to help build a secure zero trust-based remote working environment.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.41-44
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• 2010

Purpose: Along with recent advances in PET/CT instrumentation and imaging technology, the number of patients has also been steadily increasing. This resulted in the increased radiation exposure to radiation workers in PET/CT rooms. In this study, we installed a radiation shield and investigated whether it could reduce radiation exposure to the workers and thus enhance job satisfaction. Materials and Methods: A radiation shield is composed of 5 cm thick lead and has a structure in which a radiation worker sits and watches a patient through lead glass while injecting radiopharmaceutical to the patient. Quarterly absorbed dose of radiation workers was measured using thermoluminescence dosimeters (TLD) and the results were compared for six months each before and after installation of the radiation shield. Exposure dose was also measured using a pocket dosimeter placed at the same location in the front and the back of the radiation shield. In addition, frequency of use of the shield and job satisfaction of radiation workers were investigated using a survey. Results: Quarterly absorbed dose of radiation workers was 2.70 mSv on average before installation of new radiation shield, whereas that dropped to 2.13 mSv after installation of radiation shield, reducing radiation exposure dose by 21%. Exposure dose on the front side of the shield was 61.2 R, whereas that on the back side of shield was 2.8 R. According to the survey, 85% of workers used the shield and were satisfied with the outcome: each radiation worker made injections to patients average of 6.5 times/day and preferred sitting to standing while injecting radiopharmaceutical to patients. Conclusion: Use of radiation shield reduced the exposure dose of radiation workers, which is the ultimate goal of radiation protection to minimize radiation exposure and is an appropriate method for the improvement of hospital working environment. Furthermore, we found that use of radiation shield not only relieves physical and psychological burden of radiation workers but also enhances job satisfaction. This result indicates that use of radiation shield is important for improvement of the radiation workers' job environment in terms of radiation protection.