• Polymer(Korea)
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• v.28 no.3
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• pp.239-244
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• 2004

Effect of lubricants on the rheological and thermal properties of poly(butylene terephthalate) [PBT] were investigated. Calcium stearate and adipic acid glycol polyester (AhGP) were used as processing lubricants for PBT. Decrease of melt viscosity was accomplished by the addition of 1 wt％ of lubricants. It was understood that melt viscosity was affected by the enhancement of chain mobility of PBT with AhGP as an internal lubricant as well as the lubricity on processing equipment developed by calcium stearate as an external lubricant. Lubricants also influenced chain scission of PBT which caused the viscosity drop as well. In addition, lubricant is resulted in the lowering of thermal stability, however, this might be minimized by adding less than 3 wt％ of calcium stearate as a lubricant. As a consequence, calcium stearate as an external lubricant is more effective to control the melt viscosity of PBT with minimizing of chain scission and thermal instability in PBT.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.3
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• pp.207-214
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• 2017

The problem of trunk stability is a major factor in back pain.. Abdominal draw in maneuver(ADIM), One of the trunk stabilization exercises to relieve lumbar instability, is a method of inducing selective contraction of the transverse abdominis associated with anticipatory posture control among the abdominal stabilization muscles. ADIM is usually performed with a visual feedback by applying a pressure biofeedback unit(PBU) under the lumbar at the supine position, which is not functional compared to the sitting position. This study was conducted to investigate the effect of ADIM applied in supine and sitting position on 31 healthy men and women. In each posture, muscle activity was measured by rectal abdominis (RA), external oblique (EO), transverse abdominis (TrA)/internal obilique (IO) and erector spinae (ES) using wireless EMG. In the result, there was no significant difference between RA and EO between the two postures and there was a significant difference between TrA / IO and ES. In both postures, the activity of TrA/IO was higher than that of RA, and the effect of ADIM was shown to be the same, whereas TrA/IO and ES showed higher activity in sitting position. This means that the activity of the muscles involved in the postural stability and lumbar stability is increased further in the sitting position. Therefore, ADIM in sitting, which can be applied more easily in daily life, is useful for improving lumbar stability.

• Archives of Craniofacial Surgery
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• v.12 no.2
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• pp.93-96
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• 2011

Purpose: In most cases of nasal bone fracture, closed reduction with internal or external splint fixation approach is selected. However, because of indiscriminate insertion of the internal splint without considering of anatomical difference or deformity, insufficient fixation happens frequently that need additional fixation. Therefore, we suggest a new method for providing adequate support in reduced nasal bone by carving $Merocel^{(R)}$ that is fixed for the anatomical structure. Method: Closed reduction and internal fixation with carved $Merocel^{(R)}$ was performed in 15 nasal bone fracture patients from March, 2010 to July, 2010. Each patient was evaluated by physical examination, facial photographic check, simple X-ray, and computerized tomography. On the first day post-operation, location of packing and amount of reduction were checked by follow up X-ray and computerized tomography. In addition, patients' symptoms were evaluated. During the 3-month post-op follow up at out-patient clinic, operator, 2 doctors in training and one assistant performed the objective evaluations by physical examination on nasal dorsal hump, nasal deviation, nasal depression, nasal breath difficulty, and nasal airway obstruction. A survey of subjective patients' satisfaction in 4-stages was also performed. Results: The results of follow-up computerized tomography of the 15 patients revealed that 11 patients had good reduced state. Three patients with combined maxillary frontal process fracture had over reductions. A survey performed on the first day post-operation showed that 14 of 15 patients answered that their current symptoms were more than tolerable. At the 3-month follow-up physical exam, one case had a dorsal hump. However, there were no nasal deviations, nasal depressions, nasal breath difficulties, or nasal airway obstructions. Twelve of the 15 patients answered more than moderate on the 3-month survey. Conclusion: Intranasal packing after carving the $Merocel^{(R)}$ considering anatomical structure is a new effective method to promote proper-reduction, maintain stability, and minimize patients' symptoms by addition of a simple procedure.

• Journal of Korean Orthopaedic Sports Medicine
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• v.12 no.1
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• pp.29-36
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• 2013

Purpose: Proprioceptive function has been known to be important to shoulder stability. However, the function in rotator cuff tear patients is rarely investigated. The purpose of current study is to report the proprioceptive function in rotator cuff tear patients and to analyze the proprioceptive function regarding the tear size and the presence of subscapularis tear. Materials and Methods: Between 2011 and 2012, total 76 patients (male 28 and female 48) were recruited and average age was 61.7 years old (range, 38~76). Preoperatively, joint position senses in internal and external rotation were measured for proprioceptive function testing by method of active re-positioning technique. The absolute difference from set point was measured. Proprioceptive function was further analyzed according to tear size of rotator cuff, the presence of subscapularis tear, visual analogue scale of pain, shoulder functional score (American society of elbow and shoulder score), and ranges of motion in shoulder. Results: The absolute difference for external rotation was $4.9^{\circ}{\pm}2.9^{\circ}$, in normal joint and $4.9^{\circ}{\pm}3.0^{\circ}$for involved joint in rotator cuff tear patients. This difference was not significant statistically (p=0.87). The absolute difference for internal rotation was $4.0^{\circ}{\pm}2.7^{\circ}$in normal joint whereas $4.8^{\circ}{\pm}3.7^{\circ}$ for involved joint showing statistically significant difference (p=0.043). There was some trend that the proprioceptive function of internal rotation was more impaired in the bigger tear size group (more than medium tear) compared to the smaller tear size group (partial thickness and small tear, 5.0 vs. 4.0, p=0.061). The impairment of internal rotation proprioception was also accentuated in patients with subscapularis tear (4.8 vs. 4.0, p=0.065). The proprioceptive function of internal rotation was decreased when the pain visual analogue scale was increased (5.2 vs. 4.0 p=0.04), shoulder functional score was decreased (6.1 vs. 4.2, p=0.005), or range of motion in shoulder joint was restricted (5.3 vs. 3.7, p=0.041). Conclusion: The deficit of proprioceptive function was observed in rotator cuff tear patients. Proprioception for internal rotation was impaired in patients with the bigger tear size and subscapularis tear. Pain, shoulder function score, and range of motion were also shown to be related with the deficit in proprioceptive function.

• Communications for Statistical Applications and Methods
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• v.15 no.5
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• pp.697-708
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• 2008

Operational risk is defined as the risk of loss resulting from inadequate or failed internal processes, people and systems, or external events. The advanced measurement approach proposed by Basel committee uses loss distribution approach(LDA) which quantifies operational loss based on bank's own historical data and measurement system. LDA involves two distribution fittings(frequency and severity) and then generates aggregate loss distribution by employing mathematical convolution. An objective validation for the operational risk measurement is essential because the operational risk measurement allows flexibility and subjective judgement to calculate regulatory capital. However, the methodology to verify the soundness of the operational risk measurement was not fully developed because the internal operational loss data had been extremely sparse and the modeling of extreme tail was very difficult. In this paper, we propose a methodology for the validation of operational risk measurement based on bootstrap confidence intervals of operational VaR(value at risk). We derived two methods to generate confidence intervals of operational VaR.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.164-173
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• 2009

Purpose: The purpose of this study was to evaluate the effect of abutment material on screw-loosening before and after cyclic loading. Among the different materials of abutments, zirconia and metal abutment were used. Material and methods: Two types of implant systems: external butt joint(US II, Osstem Implant, Korea) and internal conical joint(GS II, Osstem Implant, Korea) were used. In each type, specimens were divided into two different kinds of abutments: zirconia and metal(n=5). The implant was rigidly held in a special holding to device ensure fixation. Abutment was connected to 30 Ncm with digital torque gauge, and was retightened in 30 Ncm after 10 minutes. The initial removal torque values were measured. The same specimens were tightened in 30 Ncm again and held in the cycling loading simulator(Instron, USA) according to ISO/FPIS 1480. Cycling loading tests were performed at loads 10 to 250 N, for 1 million cycles, at 14 Hz,(by subjecting sinusoidal wave from 10 to 250 N at a frequency of 14 Hz for 1 million cycles,) and then postload removal torque values were evaluated. Results: 1. In all samples, the removal values of abutment screw were lower than tightening torque values(30 Ncm), but the phenomenon of the screw loosening was not observed. 2. In both of the implant systems, initial and postload removal torque of zirconia abutment were significantly higher than those of metal abutment(P<.05). 3. In both of the implant systems, the difference in removal torque ratio between zirconia abutment and metal abutment was not significant(P>.05). 4. In metal abutments, the removal torque ratio of GS II system(internal conical joint system) was lower than that of US II system(external butt joint system)(P<.05). 5. In zirconia abutments, the difference in removal torque ratio between the two implant systems was not significant(P>.05). Conclusion: Zirconia abutment had a good screw joint stability in the condition of one million cycling loading.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.72-77
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• 2010

The Incheon Bridge, which was opened to the traffic in October 2009, is an 18.4 km long sea-crossing bridge connecting the Incheon International Airport with the expressway networks around the Seoul metropolitan area by way of Songdo District of Incheon City. This bridge is an integration of several special featured bridges and the major part of the bridge consists of cable-stayed spans. This marine cable-stayed bridge has a main span of 800 m wide to cross the vessel navigation channel in and out of the Incheon Port. In waterways where ship collision is anticipated, bridges shall be designed to resist ship impact forces, and/or, adequately protected by ship impact protection (SIP) systems. For the Incheon Bridge, large diameter circular dolphins as SIP were made at 44 locations of the both side of the main span around the piers of the cable-stayed bridge span. This world's largest dolphin-type SIP system protects the bridge against the collision with 100,000 DWT tanker navigating the channel with speed of 10 knots. Diameter of the dolphin is up to 25 m. Vessel collision risk was assessed by probability based analysis with AASHTO Method-II. The annual frequency of bridge collapse through the risk analysis for 71,370 cases of the impact scenario was less than $0.5{\times}10^{-4}$ and satisfies design requirements. The dolphin is the circular sheet pile structure filled with crushed rock and closed at the top with a robust concrete cap. The structural design was performed with numerical analyses of which constitutional model was verified by the physical model experiment using the geo-centrifugal testing equipment. 3D non-linear finite element models were used to analyze the structural response and energy-dissipating capability of dolphins which were deeply embedded in the seabed. The dolphin structure secures external stability and internal stability for ordinary loads such as wave and current pressure. Considering failure mechanism, stability assessment was performed for the strength limit state and service limit state of the dolphins. The friction angle of the crushed stone as a filling material was reduced to $38^{\circ}$ considering the possibility of contracting behavior as the impact.

• Journal of the Korean Geotechnical Society
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• v.36 no.6
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• pp.5-15
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• 2020

This study deals with the use of porewater pressure transducers to evaluate the stability of a fill dam through the correlation between the porewater pressure and water level. As a result of performing principal component analysis on a total of eight porewater pressure transducers installed in the fill dam, they were distributed into three groups. It was found to be distributed as internal, external, and top based on seepage line in the dam body. The correlation coefficient between porewater pressures and water level in group A located inside the seepage line indicated 0.94 to 1.00 and they are showing a strong positive linear relationships. It indicates that maintenance of the dam is required by the porewater pressure transducers of the group A. In addition, a linear regression analysis was performed with the determination coefficients of the group A of 0.89 to 0.99. It was found that the pore water pressure can be predicted and the stability of the dam can be evaluated by comparing it with the currently measured values when the water level is fixed as an explanatory variable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.207-215
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• 2019

This study was conducted to identify key success factors of the Agricultural Cooperative Federation. We classified the divisions of regional agricultural cooperatives into high performers and low performers to investigate differences in environmental stability, resource capacity, resource flexibility, differentiation strategy, and low-cost strategies between high and low performers. Empirical analyses revealed that high performers are superior to low performers in resource capacity, resource flexibility, differentiation, and low-cost, but there was no difference in environmental stability between high performers and low performers. Internal factors including resource and strategy attributes affect business performance, but external factors such as environmental attributes do not. Moreover, resource flexibility generates the broadest gap between high performers and low performers. These results indicate that resource flexibility is the key factor leading to success of organizations with greater competitors because it enables them to overcome their disadvantageous competitive position in size and resources through complete exploitation of resources across divergent business areas owing to its flexibility. Our contribution is that we draw the key success factors of the Agricultural Cooperative Federation through an empirical approach.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.65-76
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• 2024

With the recent activation of the offshore wind power industry, there has been a development of power plants with a scale exceeding 400MW, comparable to traditional thermal power plants. Renewable energy, characterized by intermittency depending on the energy source, is a prominent feature of modern renewable power generation facilities, which are structured based on controllable inverter technology. As the integration of renewable energy sources into the grid expands, the grid codes for power system connection are progressively becoming more defined, leading to active discussions and evaluations in this area. In this paper, we propose a method for selecting optimal reactive power compensation capacity when multiple offshore wind farms are integrated and connected through a shared interconnection facility to comply with grid codes. Based on the requirements of the grid code, we analyze the reactive power compensation and excessive stability of the 400MW wind power generation site under development in the southwest sea of Jeonbuk. This analysis involves constructing a generation site database using PSS/E (Power System Simulation for Engineering), incorporating turbine layouts and cable data. The study calculates reactive power due to charging current in internal and external network cables and determines the reactive power compensation capacity at the interconnection point. Additionally, static and dynamic stability assessments are conducted by integrating with the power system database.