• Journal of the Korean Geosynthetics Society
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• v.23 no.2
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• pp.53-62
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• 2024

Recently, development of non-traditional energy such as oil sands has been actively conducted in the cold region such as Canada. Frozen soil has different thermal and mechanical characteristics from general soil due to its high organic contents. This study evaluated the impact of organic matter content on the thermal and mechanical behavior of frozen soil samples collected from Alberta, Canada, and Gangwon Province, South Korea. As the organic content increases, the maximum dry unit weight decreases and the optimum moisture content increases in compaction tests. In uniaxial compression tests under frozen conditions, the strength of the frozen specimens increased as the temperature decreased. The strength of Canada soil sample increased with higher organic matter content at low temperatures. However, the strength of frozen soil was not significantly affected by organic matter content due to the complex behavior and unfrozen water content. Thermal conductivity tests showed higher thermal conductivity in frozen conditions compared to unfrozen conditions, due to the higher thermal conductivity of ice compared to water. These findings provide essential data for geotechnical design and construction in large-scale projects such as oil sands development in cold regions. Further research is needed to explore the impact of organic matter content on different types of frozen soils.

• Journal of The Korean Association For Science Education
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• v.27 no.1
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• pp.50-58
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• 2007

In this study, students' thoughts were searched according to the types of experiments related to the "law of definite proportions" in 9th grade science textbooks. The most common four types of experiments in textbooks were selected and analyzed for this study. It was found that the experiments needed various preconceptions and complex inferring process by students. But most of the students could not catch the concept understanding desired from the experiments. They just perceived simple observation from their senses. These phenomena were common regardless of types of experiments. These means that the level of preconceptions and inferring process for the interpretation of the experimental data did not match with students' level of thoughts. The goals of the experiments in science textbooks are to increase students' inquiry ability, and to acquire science concepts by themselves from the experiment results. But if the contents of experiments are not suitable to students' understanding level, the educational effects of the performance of these experiments were not positive. Therefore, these experiments need contents revisions for students to acquire the concept related to the "law of definite proportions" by themselves.

• Journal of Korean society of Dental Hygiene
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• v.24 no.2
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• pp.109-119
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• 2024

Objectives: This study aimed to confirm the correlation between oral frailty and health-related quality of life (HINT-8) among older adults in Korea. Methods: The data of 1,318 individuals aged ≥65 years who participated in the eighth Korean National Health and Nutrition Examination Survey (2019) were analyzed using complex sample statistical analysis. Results: Chewing discomfort was found to decrease the HINT-8 scores by 1.246, 1.324, and 1.089 times in the physical, social, and mental domains, respectively. Speech discomfort was found to decrease the HINT-8 scores by 1.275, 1.449, and 1.175 times in the physical, social, and mental domains, respectively. The HINT-8 scores of participants with ≤19 natural teeth were lower in the physical and social domains. Similarly, the HINT-8 scores of participants with brushing frequency of ≤2 were lower in the positive health domain. Non-use of oral hygiene products led to a reduction in the HINT-8 score in the social health domain. Conclusions: Oral frailty in older adults reduces the health-related quality of life. Thus, it is necessary to formulate policies to manage oral frailty in this population and develop specialized programs for the management of oral frailty.

• Korean Journal of Construction Engineering and Management
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• v.25 no.1
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• pp.32-41
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• 2024

In the construction industry, not only safety accidents, but also various complex risks such as construction delays, cost increases, and environmental pollution occur, and management technologies are needed to solve them. Among them, process risk management, which directly affects the project, lacks related information compared to its importance. This study tried to develop a MATM tunnel process risk classification system to solve the difficulty of risk information retrieval due to the use of different classification systems for each project. Risk collection used existing literature review and experience mining techniques, and DB construction utilized the concept of natural language processing. For the structure of the classification system, the existing WBS structure was adopted in consideration of compatibility of data, and an RBS linked to the work species of the WBS was established. As a result of the research, a risk classification system was completed that easily identifies risks by work type and intuitively reveals risk characteristics and risk factors linked to risks. As a result of verifying the usability of the established classification system, it was found that the classification system was effective as risks and risk factors for each work type were easily identified by user input of keywords. Through this study, it is expected to contribute to preventing an increase in cost and construction period by identifying risks according to work types in advance when planning and designing NATM tunnels and establishing countermeasures suitable for those factors.

• Journal of Navigation and Port Research
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• v.48 no.3
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• pp.181-191
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• 2024

Ports play a crucial role in the complex global supply chain. While many researchers have used social network analysis (SNA) to study active networks, there is a lack of SNA cohesion analysis specifically related to logistics and trade. Therefore, this study aims to identify time-series structural changes in all domestic import and export logistics networks, including regions, ports, and airports, by utilizing techniques such as k-core and community analysis. To carry out this analysis, we rely on data from the Korea Customs Service's Import and Export Logistics Statistical Yearbook spanning from 2004 to 2022. The findings from the k-core and community analysis indicate that the cohesion of the domestic import and export logistics network has continuously strengthened over time. Moreover, it reveals that regions, ports, and airports are becoming more cohesive and homogeneous, with Busan Port emerging as the central hub of a large community. These insights are expected to enhance our understanding of global logistics dynamics and contribute to the development of policies and sustainable import and export logistics processes.

• Korean Journal of Radiology
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• v.23 no.2
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• pp.271-279
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• 2022

Objective: To compare the clinical and radiologic findings between perforated and non-perforated choledochal cysts in children. Materials and Methods: Fourteen patients (mean age ± standard deviation, 1.7 ± 1.2 years) with perforated choledochal cysts (perforated group) and 204 patients (3.6 ± 3.8 years) with non-perforated choledochal cysts (non-perforated group) were included between 2000 and 2019. All patients underwent choledochal cyst excision after ultrasound, CT, or MR cholangiopancreatography. Relevant data including demographics, clinical symptoms, laboratory findings, imaging findings, and outcomes were analyzed. Statistical differences were compared using the Mann-Whitney U test and Fisher's exact test. Results: Choledochal cyst perforation occurred only in children under the age of 4 years. Acute symptoms, including fever (p < 0.001), were more common in the perforated group than in the non-perforated group. High levels of white blood cells (p = 0.004), C-reactive protein (p < 0.001), and serum amylase (p = 0.002), and low levels of albumin (p < 0.001) were significantly associated with the perforated group. All 14 patients with perforated choledochal cysts had ascites, whereas only 16% (33/204) of patients in the non-perforated group had ascites (p < 0.001). In the subgroup of patients who had ascites, a large amount of ascites (p = 0.001), increase in the amount of ascites in a short time (p < 0.001), complex ascites (p < 0.001), and perihepatic pseudocysts (p < 0.001) were more common in the perforated group than in the non-perforated group. Conclusion: Children with perforated choledochal cysts have characteristic clinical and radiologic findings compared to those with non-perforated choledochal cysts. In young children with choledochal cysts, perforation should be differentiated in cases with acute symptoms, laboratory abnormalities, and characteristic ascites findings.

• Journal of the Korean Society of Radiology
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• v.81 no.6
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• pp.1523-1528
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• 2020

Partial anomalous pulmonary venous return (PAPVR) is a rare congenital cardiac anomaly that can be difficult to detect and often remains undiagnosed. PAPVR is diagnosed using non-invasive imaging techniques such as echocardiography, CT, and MRI. Image data are reviewed on a 2-dimensional (D) monitor, which may not facilitate a good understanding of the complex 3D heart structure. In recent years, 3D printing technology, which allows the creation of physical cardiac models using source image datasets obtained from cardiac CT or MRI, has been increasingly used in the medical field. We report a case involving a 3D-printed model of PAPVR with a biatrial connection. This model demonstrated separate drainages of the right upper and middle pulmonary veins into the lower superior vena cava (SVC) and the junction between the SVC and the right atrium, respectively, with biatrial communication through the right middle pulmonary vein.

• Information Systems Review
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• v.20 no.4
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• pp.59-78
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• 2018

With the advent of the various device types and marketing communication, customer's search and purchase behavior have become more complex and segmented. However, extant research on multichannel marketing effects of the purchase funnel has not reflected the specific features of device User Interface (UI) and User Experience (UX). In this study, we analyzed the marketing channel effects of multi-device shoppers using a unique click stream dataset from global online retailers. We examined device types that activate online shopping and compared the differences between marketing channels that promote visits. In addition, we estimated the direct and indirect effects on visits and purchase revenue through customer's accumulated experience and channel conversions. The findings indicate that the same customer selects a different marketing channel according to the device selection. These results can help retailers gain a better understanding of customers' decision-making process in multi-marketing channel environment and devise the optimal strategy taking into account various device types. Our empirical analyses yield business implications based on the significant results from global big data analytics and contribute academically meaningful theoretical framework using an economic model. We also provide strategic insights attributed to the practical value of an online marketing manager.

• Korean Journal of Radiology
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• v.20 no.5
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• pp.759-772
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• 2019

Objective: To investigate the value of ultrasound (US) microflow assessment in distinguishing malignant from benign solid breast masses as well as the association between US parameters and histologic microvessel density (MVD). Materials and Methods: Ninety-eight breast masses (57 benign and 41 malignant) were examined using Superb Microvascular Imaging (SMI) and contrast-enhanced US (CEUS) before biopsy. Two radiologists evaluated the quantitative and qualitative vascular parameters on SMI (vascular index, morphology, distribution, and penetration) and CEUS (time-intensity curve analysis and enhancement characteristics). US parameters were compared between benign and malignant masses and the diagnostic performance was compared between SMI and CEUS. Subgroup analysis was performed according to lesion size. The effect of vascular parameters on downgrading Breast Imaging Reporting and Data System (BI-RADS) category 4A masses was evaluated. The association between histologic MVD and US parameters was analyzed. Results: Malignant masses were associated with a higher vascular index (15.1 ± 7.3 vs. 5.9 ± 5.6), complex vessel morphology (82.9% vs. 42.1%), central vascularity (95.1% vs. 59.6%), penetrating vessels (80.5% vs. 31.6%) on SMI (all, p < 0.001), as well as higher peak intensity (37.1 ± 25.7 vs. 17.0 ± 15.8, p < 0.001), slope (10.6 ± 11.2 vs. 3.9 ± 4.2, p = 0.001), area (1035.7 ± 726.9 vs. 458.2 ± 410.2, p < 0.001), hyperenhancement (95.1% vs. 70.2%, p = 0.005), centripetal enhancement (70.7% vs. 45.6%, p = 0.023), penetrating vessels (65.9% vs. 22.8%, p < 0.001), and perfusion defects (31.7% vs. 3.5%, p < 0.001) on CEUS (p ≤ 0.023). The areas under the receiver operating characteristic curve (AUCs) of SMI and CEUS were 0.853 and 0.841, respectively (p = 0.803). In 19 masses measuring < 10 mm, central vascularity on SMI was associated with malignancy (100% vs. 38.5%, p = 0.018). Considering all benign SMI parameters on the BI-RADS assessment, unnecessary biopsies could be avoided in 12 category 4A masses with improved AUCs (0.500 vs. 0.605, p < 0.001). US vascular parameters associated with malignancy showed higher MVD (p ≤ 0.016). MVD was higher in malignant masses than in benign masses, and malignant masses negative for estrogen receptor or positive for Ki67 had higher MVD (p < 0.05). Conclusion: US microflow assessment using SMI and CEUS is valuable in distinguishing malignant from benign solid breast masses, and US vascular parameters are associated with histologic MVD.

• Journal of Cardiovascular Imaging
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• v.31 no.1
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• pp.18-23
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• 2023

BACKGROUND: Three-dimensional (3D) transesophageal echocardiogram (TEE) is the gold standard for the diagnosis of degenerative mitral regurgitation (dMR) and preoperative planning for transcatheter mitral valve repair (TMVr). TEE is an invasive modality requiring anesthesia and esophageal intubation. The severe acute respiratory syndrome coronavirus 2 pandemic has limited the number of elective invasive procedures. Multi-detector computed tomographic angiography (MDCT) provides high-resolution images and 3D reconstructions to assess complex mitral anatomy. We hypothesized that MDCT would reveal similar information to TEE relevant to TMVr, thus deferring the need for a preoperative TEE in certain situations like during a pandemic. METHODS: We retrospectively analyzed data on patients who underwent or were evaluated for TMVr for dMR with preoperative MDCT and TEE between 2017 and 2019. Two TEE and 2 MDCT readers, blinded to patient outcome, analyzed: leaflet pathology (flail, degenerative, mixed), leaflet location, mitral valve area (MVA), flail width/gap, anterior-posterior (AP) and commissural diameters, posterior leaflet length, leaflet thickness, presence of mitral valve cleft and degree of mitral annular calcification (MAC). RESULTS: A total of 22 (out of 87) patients had preoperative MDCT. MDCT correctly identified the leaflet pathology in 77% (17/22), flail leaflet in 91% (10/11), MAC degree in 91% (10/11) and the dysfunctional leaflet location in 95% (21/22) of patients. There were no differences in the measurements for MVA, flail width, commissural or AP diameter, posterior leaflet length, and leaflet thickness. MDCT overestimated the measurements of flail gap. CONCLUSIONS: For preoperative TMVr planning, MDCT provided similar measurements to TEE in our study.