• Clinical and Experimental Pediatrics
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• v.55 no.10
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• pp.377-382
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• 2012

Purpose: This single-center study aimed to assess the clinical features and surgical approaches and outcomes of complete transposition of the great arteries (TGA). Methods: TGA patients who had undergone surgical correction at the Kyungpook National University Hospital from January 2000 to December 2010, were retrospectively evaluated for patient characteristics, clinical manifestation, preoperative management, intraoperative findings, postoperative progress, and follow-up status. Results: Twenty-eight patients (17 boys and 11 girls, mean age=$10.6{\pm}21.5$ days) were included and were categorized as follows: group I, TGA with intact ventricular septum (n=13); group II, TGA with ventricular septal defect (VSD, n=12); and group III, TGA/VSD with pulmonary stenosis (n=3). Group I underwent the most intensive preoperative management (balloon atrial septostomy and prostaglandin E1 medication). Group II showed the highest incidence of heart failure (P<0.05). Usual and unusual coronary anatomy patterns were observed in 20 (71%) and 8 patients, respectively. Arterial and half-turned truncal switch operations were performed in 25 and 3 patients (Group III), respectively. Postoperative complications included cardiac arrhythmias (8 patients), central nervous system complications (3 patients), acute renal failure (1 patient), infections (3 patients), and cardiac tamponade (1 patient), and no statistically significant difference was observed between the groups. Group II showed the mildest aortic regurgitation on follow-up echocardiograms (P<0.05). One patient underwent reoperation, and 1 died. The overall mortality rate was 4%. Conclusion: Our study showed favorable results in all the groups and no significant difference in postoperative complication, reoperation, and mortality among the groups. However, our results were inadequate to evaluate the risk factors for reoperation and mortality owing to the small number of patients and short follow-up duration.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.4
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• pp.867-886
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• 1996

The purpose of this study was to evaluate the shearbond strength and resin-dentin interface of three different dentinal bonding systems in primary and permanent teeth. Thirty extracted human primary molars and premolars, which were non-carious and free of obvious defect, were selected for this study. All specimens were divided into six groups with two groups allocated for each of the three dentinal bonding system(All-bond 2, Scotchbond Multi-Purpose, Gluma bonding system). After completion of bonding composite to dentin using each tested dentin bonding system, bond strength measurement and histological observation were performed. The results are as follows: 1. All-bond 2 and Scotchbond Multi-Purpose, A good quality hybrid layer was identified, the morphology of which could be equated with the zone of H-E and Brown-Brenn staining. In Gluma bonding system, hybrid layer was very thin, and separated from the solid polymer. 2. All-bond 2 had the highest mean shearbond strength, followed by Scotchbond Multi-Purpose and Gluma bonding system in both primary and permanent teeth. There was no statistically significant difference between All-bond 2 and Scotchbond Multi-Purpose. Statistically significant difference could be found between Gluma bonding system and the other two groups(p<0.05). 3. The fracture patterns observed were mainly the mixture of adhesive failure and dentin dettachment pattern in All-bond 2 and Scotchbond Multi-Purpose while adhesive failure prevailed in Gluma bonding system.

• Geotechnical Engineering
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• v.6 no.2
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• pp.55-66
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• 1990

Many landslides have been taken place during the wet season in Korea. Rainfall in one of the most significant factors relevant to the landsildes, which cause a great loss of lived and properties every year, However, forecast systems for landslides have not been sufficiently established in Korea. In order to minimize a disaster due to landslides, the relationship between landslides and rainfall was investigated based on meteorological records and landslides occrrence ranging from 1977 to 1987. According to rainfall patterns which cause landslides, such as the daily rainfall on failure day or the cumulative rainfalls before failure day, the area in which landslides were taken place, could be divided into three groups of Middl area, Young- Ho Nam area, and Young-Dong Area. And the frequency of landslides was also dependent on the hourly rainfall intensity. It shows from the analyses that prediction of landslides can be made based on both the cumulative rainfall and the hourly rainfall intensity.

• Earthquakes and Structures
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• v.7 no.3
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• pp.317-331
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• 2014

An experimental study was performed to investigate the seismic performance of solid steel reinforced concrete (SRC) frames with special-shaped columns that are composed of SRC special-shaped columns and reinforced concrete beams. For this purpose, two models of two-bay and three-story frame, including an edge frame and a middle frame, were designed and tested. The failure process and patterns were observed. The mechanical behaviors such as load-displacement hysteretic loops and skeleton curves, load bearing capacity, drift ratio, ductility, energy dissipation and stiffness degradation of test specimens were analyzed. Test results show that the failure mechanism of solid SRC frame with special-shaped columns is the beam-hinged mechanism, satisfying the seismic design principle of "strong column and weak beam". The hysteretic loops are plump, the ductility is good and the capacity of energy dissipation is strong, indicating that the solid SRC frame with special-shaped columns has excellent seismic performance, which is better than that of the lattice SRC frame with special-shaped columns. The ultimate elastic-plastic drift ratio is larger than the limit value specified by seismic code, showing the high capacity of collapse resistance. Compared with the edge frame, the middle frame has higher carrying capacity and stronger energy dissipation, but the ductility and speed of stiffness degradation are similar. All these can be helpful to the designation of solid SRC frame with special-shaped columns.

• Smart Structures and Systems
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• v.29 no.3
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• pp.445-455
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• 2022

Steel anchor bolts are installed in concrete using a variety of methods. One of the most common methods of anchor bolt installation is using epoxy resin as an infill material injected into the drilled hole to act as a bonding material between the steel bolt and the surrounding concrete. Typical design standards assume uniform stress distribution along the length of the anchor bolt accompanied with single crack leading to pull-out failure. Experimental evidence has shown that the steel anchor bolts fail owing to the multiple failure patterns, hence these design assumptions are not realistic. In this regard, the presented research work details the analytical model that takes into consideration multiple micro cracks in the infill material induced via impact loading. The impact loading from the Schmidt hammer is used to evaluate the bond condition bond condition of anchor bolt and the epoxy material. The added advantage of the presented analytical model is that it is able to take into account the various type of end conditions of the anchor bolts such as bent or U-shaped anchors. Through sensitivity analysis the optimum stiffness and shear strength properties of the epoxy infill material is achieved, which have shown to achieve lower displacement coupled with reduced damage to the surrounding concrete. The accuracy of the presented model is confirmed by comparing the simulated deformational responses with the experimental evidence. From the comparison it was found that the model was successful in simulating the experimental results. The proposed model can be adopted by professionals interested in predicting and controlling the deformational response of anchor bolts.

• Steel and Composite Structures
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• v.46 no.4
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• pp.539-551
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• 2023

In order to study the fire resistance of castellated composite beams with ortho-hexagonal holes and different beam-end restraints, temperature rise tests with constant load were conducted on full-scale castellated composite beams with ortho-hexagonal holes and hinge or rigid joint constraints to investigate the temperature distribution, displacement changes and failure patterns of castellated composite beams with two different beam-end constraints during the whole course of fire. The results show that (1) During the fire, the axial pressure and horizontal expansion deformation generated in the rigid joint constrained composite beam were larger than those in the hinge joint constrained castellated composite beam, and their maximum horizontal expansion displacements were 30.2 mm and 17.8 mm, respectively. (2) After the fire, the cracks on the slab surface of the castellated composite beam with rigid joint constraint were more complicated than hinge restraint, and the failure more serious; the lower flange and web at the ends of the castellated steal beams with hinge and rigid joint constraint produced serious local buckling, and the angles of the ortho-hexagonal holes at the support cracked; the welds at both ends of the castellated composite beam with rigid joint constraint cracked. (3) Based on the simplified calculation method of solid-web composite beam, considering the effect of holes on the web, this paper calculated the axial force and displacement of the beam-end constrained castellated composite beams under fire. The calculation results agreed well with the test results.

• Journal of the Korean Geosynthetics Society
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• v.22 no.1
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• pp.67-74
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• 2023

In order to monitor the stability of slopes, research on data-based slope failure prediction and early warning is increasing. However, most papers overlook the quality of data. Poor data quality can cause problems such as false alarms. Therefore, this paper proposes a two-step hybrid approach consisting of rules and machine learning models for quality control of data collected from slopes. The rule-based has the advantage of high accuracy and intuitive interpretation, and the machine learning model has the advantage of being able to derive patterns that cannot be explicitly expressed. The hybrid approach was able to take both of these advantages. Through a case study, the performance of using the two methods alone and the case of using the hybrid approach was compared, and the hybrid method was judged to have high performance. Therefore, it is judged that using a hybrid method is more appropriate than using the two methods alone for data quality control.

• Journal of Korean Critical Care Nursing
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• v.16 no.2
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• pp.15-27
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• 2023

Purpose : This study aimed to examine the relationship between sleep quality and its influencing factors in patients with coronary artery disease (CAD). Methods : This descriptive correlational study included 130 patients with CAD admitted to the cardiology department of a general hospital in B City between September 2019 and February 2020. Data were collected using structured questionnaires and research instruments to measure sleep quality, anxiety, depression, chronotype, and daytime sleepiness. Results : The mean scores for sleep quality, daytime sleepiness, anxiety, and depression were 7.59±3.45, 6.45±3.46, 6.58±3.88, and 7.74±4.05, respectively. In terms of chronotypes, 10.8%, 48.5%, and 40.7% of the participants had evening-, intermediate-, and morning-type patterns, respectively. Sleep quality was significantly correlated with anxiety (r=0.38, p<.001), depression (r=.37, p<.001), and daytime sleepiness (r=.26, p =.002). Factors associated with sleep quality in patients with CAD included anxiety (β=.29), heart failure (β=.22), daytime sleepiness(β=.21), and sleeping alone (β=.19). Collectively, these factors had an explanatory power of 23.1% for sleep quality variance. Conclusion: Patients with CAD often experience poor sleep quality owing to various factors such as anxiety, daytime sleepiness, heart failure, and sleeping alone. It is recommended that healthcare providers objectively evaluate sleep and identify factors that influence sleep quality. This will enable the development of effective methods for sleep management as part of nursing care.

• Journal of Technologic Dentistry
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• v.46 no.2
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• pp.21-27
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• 2024

Purpose: This study aimed to analyze the stress distribution and deformation in implant abutments made from titanium (Ti-6Al-4V), zirconia, and polyetheretherketone (PEEK), including their screws and fixtures, under various loading conditions using finite element analysis (FEA). Methods: Three-dimensional models of the mandible with implant abutments were created using Siemens NX software (NX10.0.0.24, Siemens). FEA was conducted using Abaqus to simulate occlusal loads and assess stress distribution and deformation. Material properties such as Young's modulus and Poisson's ratio were assigned to each component based on literature and experimental data. Results: The FEA results revealed distinct stress distribution patterns among the materials. Titanium alloy abutments exhibited the highest stress resistance and the most uniform stress distribution, making them highly suitable for long-term stability. Zirconia abutments showed strong mechanical properties with higher stress concentration, indicating potential vulnerability to fracture despite their aesthetic advantages. PEEK abutments demonstrated the least stress resistance and higher deformation compared to other abutment materials, but offered superior shock absorption, though they posed a higher risk of mechanical failure under high load conditions. Conclusion: The study emphasizes the importance of selecting appropriate materials for dental implants. Titanium offers durability and uniform stress distribution, making it highly suitable for long-term stability. Zirconia provides aesthetic benefits but has a higher risk of fracture compared to titanium. PEEK excels in shock absorption but has a higher risk of mechanical failure compared to both titanium and zirconia. These insights can guide improved implant designs and material choices for various clinical needs.

• Geomechanics and Engineering
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• v.39 no.2
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• pp.157-170
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• 2024

In the present study, the acoustic emission characteristics of hard sedimentary sandstone with varying bedding dip angles were examined through uniaxial compression tests using a rock mechanics creep apparatus combined with an acoustic emission system. The deformation and failure behavior of the sandstone was analyzed by correlating acoustic emission parameters with stress over time. A damage constitutive model was developed, incorporating cumulative acoustic emission ringing counts as a key parameter, with time acting as the intermediary. The findings indicate that, despite the differences in bedding dip angles, the stress-strain curves of the samples follow a similar pattern throughout the loading process, passing through four distinct phases: compaction, elastic deformation, yielding, and post-peak failure. The fracture patterns of the sandstone are influenced by the dip angle of the bedding. Acoustic emission parameters, including the ringing count, cumulative ringing count, and energy, align with these four stages of the stress-strain curve. During the compaction and elastic deformation phases, acoustic emissions remain in a quite state, with only brief spikes at points of rapid stress change. In the unstable fracture stage, acoustic emissions become highly active, while they return to a quite state in the post-fracture stage. The RA value of the acoustic emission displays a banded pattern as time progresses, with areas of dense clustering. When the stress curve declines, RA values enter an active period, mainly associated with the generation of shear cracks. Conversely, during periods of smooth stress progression, RA values remain in a quiet state, primarily linked to the formation of tensile cracks. The time-based damage constitutive model for layered sandstone effectively captures the entire process of rock fracture development.