• Journal of the Korean Wood Science and Technology
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• v.26 no.2
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• pp.16-23
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• 1998

This paper examines the effects of specimen length and grade on the strength and stiffness properties of structural timber of radiata pine. The tensile strength and modulus of elasticity of 1,902 machine-graded boards with 3.15- and 1.62-m clear span lengths, were determined using a horizontal tension test machine. The mean failure and characteristic stress values for tensile strength show an extremely high dependency on test specimen length. The mean and characteristic values of both modulus of elasticity and tensile strength show significant dependency on machine stress grades.

• Journal of Periodontal and Implant Science
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• v.51 no.3
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• pp.163-178
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• 2021

Purpose: The aim of this study was to evaluate clinical factors affecting the longevity of fixed retainers and the influence of fixed retainers on periodontal health in periodontitis patients. Methods: In total, 52 patients with at least 2 years of follow-up after periodontal and orthodontic treatment were included in this study. After scaling and root planing, orthodontic treatment with fixed appliances or clear aligners was performed. Fixed retainers with twist-flex stainless steel wires were bonded to the palatal or lingual sides of anterior teeth. Changes in clinical parameters, including the plaque index, gingival index, calculus index (CI), probing pocket depth, and radiographic bone levels, were evaluated before bonding of fixed retainers and at a 12-month follow-up. Cumulative survival rates (CSRs) for retainer failure were evaluated according to sex, site, CI, stage of periodontitis, and the severity of the irregularity with the log-rank test and hazard ratios (HRs). Results: Twelve months after bonding of fixed retainers, improvements were observed in all clinical parameters except CI and radiographic bone gain. The overall CSR of the retainers with a CI <1 at the 12-month follow-up after bonding of fixed retainers was significantly higher than that of the retainers with a CI ≥1 at the 12-month follow-up (log-rank test; P<0.001). Patients with stage III (grade B or C) periodontitis had a higher multivariate HR for retainer failure (5.4; 95% confidence interval, 1.22-23.91; P=0.026) than patients with stage I (grade A or B) periodontitis. Conclusions: Although fixed retainers were bonded in periodontitis patients, periodontal health was well maintained if supportive periodontal treatment with repeated oral hygiene education was provided. Nonetheless, fixed retainer failure occurred more frequently in patients who had stage III (grade B or C) periodontitis or a CI ≥1 at 12-month follow-up after bonding of fixed retainers.

• Journal of the Korean Wood Science and Technology
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• v.51 no.4
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• pp.239-252
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• 2023

In this study, bending and compression strength tests were performed to investigate effect of composition of layer layout of Larix cross-laminated timber (CLT) on mechanical properties. The Larix CLT consists of five laminae, and specimens were classified into four types according to grade and composition of layer. The layer's layout were composited as follows 1) cross-laminating layers in major and minor direction (Type A), and 2) cross-laminating external layer in major direction and internal layer applied grade of layer in minor direction (Type B). E12 and E16 were used as grades of lamina for major direction layer of Type A and external layer of Type B according to KS F 3020. In results of the bending test of CLT using same grade layer according to layer composition, the modulus of elasticity (MOE) of Type B was higher than Type A. In case of prediction of bending MOE of Larix CLT, the experimental MOE was higher than 1.00 to 1.09 times for Shear analogy method and 1.14 to 1.25 times for Gamma method. Therefore, it is recommended to predict the bending MOE for Larix CLT by shear analogy method. Compression strength of CLT in accordance with layer composition was measured to be 2% and 9% higher for Type A using E12 and E16 layers than Type B, respectively. In failure mode of Type A, progress direction of failure generated under compression load was confirmed to transfer from major layer to minor layer by rolling shear or bonding line failure due to the middle lamina in major direction.

• Journal of Korean Society for Quality Management
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• v.46 no.3
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• pp.441-452
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• 2018

Purpose: The purpose of this paper is to study quantitative risk grade assessment for objective government quality assurance activities based on risk management in initial mass production for weapon systems. Methods: The Defense quality management regulations and foreign risk assessment documents are referred to analyze problems performing quality assurance actives. The failure rate data, maintainability and cost of products have been studied to quantify the risk Likelihood and impact. The analyzed data were classified as risk grade assessment through K-means Cluster Analysis method. Results: Results show that a proposed method can objectively evaluate risk grade. The analyzed results are clustered into three levels such as high, middle and low. Two products are allocated high, eleven low and seven middle. Conclusion: In this paper, quantitative risk grade assessment methods were presented by analyzing risk ratings based on objective data. The findings showed that the methods would be effective for initial mass production for weapon systems.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.4
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• pp.394-400
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• 2016

The b-type natriuretic peptide (BNP) values and increase on functional disorder in the ventricle, and are used as an index to diagnose heart failure and predict the prognosis. BNP values is known to be relevant to dyssystole in congestive heart failure. This study aimed to identify correlation between the BNP values and the items that indicate the diastolic function in echocardiography. The research divided 188 patients who went through the BNP test and echocardiography in the hospital into the groups with the BNP values; <100, 100-300, 301-600, 601-900, and >901 pg/mL. As the BNP values increase, there was relevance with the echocardiography items of ejection fraction, size of left atrium, E velocity, A velocity, Deceleration time, E/A ratio, E', A', S' and E/E'. In comparison on the groups divided based on the BNP values, E/E' had the highest relevance. The research also categorized 67 patients who diagnosed with heart failure. In comparison on the groups of the heart failure patients, the BNP values of the three groups of Grade I: $623.0{\pm}459.7pg/mL$, Grade II: $1013.2{\pm}1155.1pg/mL$ and Grade III: $1693.4{\pm}1544.0pg/mL$, respectively (p<0.01). As the grade was higher, there was a higher relevance with the echocardiography items of ejection fraction, size of left atrium, E velocity, A velocity, Deceleration time, E/A ratio, E', A', S' and E/E' (p<0.001). Higher BNP values had a higher relevance with the items that indicate the diastolic function in echocardiography and the BNP values of the Restrictive physiology group were the highest in echocardiography. So the BNP values was thought to be valuable to predict diastolic function of heart.

• Tunnel and Underground Space
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• v.17 no.4
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• pp.311-321
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• 2007

Failure of underground structures in hard rocks is a function of the in-situ stress, the intact rock strength and the distribution of fractures in the rock mass. At highly stressed regime, brittle failure is often observed due to excavation-induced stress. The characteristics of brittle failure are classified as failure grade, failure initiation stress, extent of failure and depth of failure. For safety construction of underground structures, these characteristics of brittle failure with stress conditions should be understood. In this study we evaluated the relationship between the extent and depth of failure with stress conditions for failure happened model specimens through true triaxial model experiments. The extent and depth of failure were determined using visual observation and computed tomography (CT). The results indicate that the depth of failure was affected by differential stress perpendicular to the axis of tunnel. However the extent of failure was irrelevant to the stress conditions.

• Journal of Korean Neurosurgical Society
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• v.60 no.6
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• pp.627-634
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• 2017

Objective : Few studies have reported the outcome of mechanical thrombectomy with Solitaire stent retrival (MTSR) in subtypes of acute ischemic stroke. The purpose of this study was to evaluate the efficacy and result of MTSR in acute cardioembolic stroke. Methods : Twenty consecutive patients with acute cardioembolic stroke were treated by MTSR. The angiographic outcome was assessed by thrombolysis in cerebral infarction (TICI) grade. TICI grade 2a, 2b, or 3 with a measurable thrombus that was retrieved was considered as a success when MTSR was performed in the site of primary vessel occlusion, and TICI grade 2b or 3 was considered as a success when final result was reported. Clinical and radiological results were compared between two groups divided on the basis of final results of MTSR. Persistent thrombus compression sign on angiogram was defined as a stenotic, tapered arterial lumen whenever temporary stenting was performed. The clinical outcomes were assessed by the modified Rankin Scale (mRS) at 3 months. Results : The failure rate of MTSR was 20% (4/20) and other modalities, such as permanent stenting, were needed. Final successful recanalization (TICI grade 2b or 3) was 80% when other treatments were included. The rate of good outcome ($mRS{\leq}2$) was 35% at the 3-month follow-up. Failure of MTSR was significantly correlated with persistent thrombus compression sign (p=0.001). Conclusion : Some cases of cardioembolic stroke are resistant to MTSR and may need other treatment modalities. Careful interpretation of angiogram may be helpful to the decision.

• Radiation Oncology Journal
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• v.11 no.1
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• pp.159-166
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• 1993

A retrospective analysis was done for 69 patients with Stage I and II non-Hodgkin's lymphoma who were treated from May 1981 to December 1990, in the Department of Radiadtion Oncology, Korea University Hospital. We used Ann Arbor Staging system and Working Formulation for histological classification. Forty-three patients (43/69, $62.3{\%}$) were Stage I and 26 patients (26/69, $37.7{\%}$) were Stage II, and B symptom was found in $10.1{\%}$ (7/69). Nodal lymphoma was $21.7{\%}$ (15/69); 14 patients with supradiaphragmatic disease and 1 patient with infradiaphragmatic disease. Extranodal lymphoma was $78.3{\%}$ (54/69): $64.8{\%}$ (35/54) for head and neck, $25.9{\%}$ (14/54) for gastrointestinal tract. Histologically, low grade consists of $8.7{\%}$ (6/69), intermediate grade $84.2{\%}$ (56/69), high grade $10.1{\%}$ (7/69), and diffuse large cell type was the most frequent form with 36 patients (36/69, $52.2{\%}$). Eighteen patients ($26.1{\%}$) were treated with radiation therapy alone,20 patients ($29.0{\%}$) with radiation therapy combined with chemotherapy, 15 patients ($21.7{\%}$) with radiation therapy combined with surgery and chemotherapy, Median survival duration was 28 months, and the range of survival time was from 1 month to 134 months. Overall five-year survival rate for Stage I and II disease was $54.2{\%}$, with $64.5{\%}$ for Stage I and $37.1{\%}$ for Stage II. For nodal lymphoma,5-year survival rate was $45.9{\%}$, and $56.5{\%}$ for extranodal lymphoma; $60.6{\%}$ for head and neck, $52.9{\%}$ for GI tract primary disease. Local control rate for all patients was $88.4{\%}$ (61/69), with $80{\%}$ (12/15) for nodal lymphoma and $90.7{\%}$ (49/54) for extranodal lymphoma. The total failure rate was $34.8{\%}$ (24/69). Five of 24 ($20.8{\%}$) patients who were failed developed local failure only, $12.5{\%}$ (3/24) local failure with distant failure, and distant failure only were found in $66.7{\%}$ (16/24). Between nodal lymphoma and extranodal lymphoma, there was no significant survival difference, but extranodal lymphoma showed higher incidence.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.31 no.1
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• pp.19-26
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• 2020

Background and Objective Endoscopic airway dilation is the primary treatment for pediatric subglottic stenosis (SGS) due to its feasibility and non-invasiveness. The aim of this study is to evaluate the risk factors for the failure of endoscopic airway dilation in pediatric patients with SGS. Materials and Methods This study reviewed medical records of 38 pediatric patients had endoscopic dilation from a single and tertiary referral center, retrospectively. The success of the endoscopic dilation procedure was defined as no dyspneic symptom without tracheostomy or laryngotracheal reconstruction. Demographic profiles, underlying disease, and Myer-Cotton SGS severity grade were recorded. Success rates and risk factors for the failure of treatment were analyzed. Results The SGS patients with severity grade I was most common. After mean 1.8 numbers of procedures, there were 23 patients (60.5%) in the success group and 15 patients (39.5%) in the failure group. Age, sex, underlying diseases, and SGS severity grade were not significantly different between two groups. In patients who had multiple endoscopic procedures, the failure group showed SGS deteriorated after procedures in 66.7%, compared to 11.1% of the success group. In multivariable analysis, a long-term intubation (≥1 month) was identified as an independent risk factor for failure of endoscopic dilation procedure. Conclusion Although endoscopic dilation procedure is safe and effective for the management, repetitive endoscopic dilation may not give clinical benefit in patient with long-term intubation. Other airway procedures must be considered in those group of patients.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.28-34
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• 2016

Galvannealed(GA) steels are now generally used in car body manufacturing for corrosion resistance. In this study, the weldability and joint mechanical behavior of a newly developed 1.2GPa grade GA ultra high strength TRIP(transformation induced plasticity) steel was investigated for three joining processes, such as adhesive bonding, resistance spot welding and weldbonding. Under both shear and peel stress conditions, the failure mode of the adhesive joints were the mixture of the adhesive cohesive failure, adhesive interface failure and coating layer failure. It means that the adhesion strength of GA coating onto the base metal was similar to that of adhesive bonding onto the GA coating. Under the shear stress condition, the weldbonding exerted to expand the optimal spot welding condition of 1.2GPa GA TRIP steel because the strength of adhesive bond overwhelmed that of the resistance spot weld. Under the peel stress condition, the weldbonding also exerted to expand the optimal spot welding condition of 1.2GPa GA TRIP steel by inducing the tear fracture mode rather than the partial plug fracture mode.