• The korean journal of orthodontics
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• 제48권5호
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• pp.304-315
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• 2018

Objective: The purpose of this study was to analyze initial displacement and stress distribution of the maxillofacial complex during dentoskeletal maxillary protraction with various appliance designs placed on the palatal region by using three-dimensional finite element analysis. Methods: Six models of maxillary protraction were developed: conventional facemask (Type A), facemask with dentoskeletal hybrid anchorage (Type B), facemask with a palatal plate (Type C), intraoral traction using a Class III palatal plate (Type D), facemask with a palatal plate combined with rapid maxillary expansion (RME; Type E), and Class III palatal plate intraoral traction with RME (Type F). In Types A, B, C, and D, maxillary protraction alone was performed, whereas in Types E and F, transverse expansion was performed simultaneously with maxillary protraction. Results: Type C displayed the greatest amount of anterior dentoskeletal displacement in the sagittal plane. Types A and B resulted in similar amounts of anterior displacement of all the maxillofacial landmarks. Type D showed little movement, but Type E with expansion and the palatal plate displayed a larger range of movement of the maxillofacial landmarks in all directions. Conclusions: The palatal plate served as an effective skeletal anchor for use with the facemask in maxillary protraction. In contrast, the intraoral use of Class III palatal plates showed minimal skeletal and dental effects in maxillary protraction. In addition, palatal expansion with the protraction force showed minimal effect on the forward movement of the maxillary complex.

• Elastomers and Composites
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• 제42권4호
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• pp.201-208
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• 2007

In this study, the thermal shrinkage and expansion stresses of filled NR and SBR vulcanizates were measured to investigate the dimensional stability at an elevated temperature. When a rubber sample was held at constant pre-strain, a thermal stress developed upon heating due to the entropic consideration. The peak shrinkage stress of carbon black or silica filled NR decreased with increasing filler content. In SBR compounds, however, the peak shrinkage stress of SBR with 30 phr filler content was higher than that of unfilled compounds. The expansion stress of carbon black filled NR was changed little, but that of filled SBR increased with increasing the filler content. The peak expansion stress of silica filled NR and SBR vulcanizates increased with increasing silica content.

• Journal of Technologic Dentistry
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• 제43권3호
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• pp.71-76
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• 2021

Purpose: In this study, thermal properties were observed by measuring the extent of thermal expansion and the amount of thermal residue that appears upon burnout on a workpiece made by using a dental digital light processing (DLP) three-dimensional (3D) printer. Methods: Thermal properties of workpieces manufactured by using two 3D printers were observed. The specimens were designed in cylindrical form with dimensions 10 mm in diameter and 10 mm in height. The control specimen was made of wax, and the experimental specimen was made of resin. The thermal expansion rate was measured by applying heat to three types of specimens, and burnout residue was measured. Results: The thermal expansion rate of the wax pattern (WP) specimen was 0.93%±0.05%, of the RP1 specimen was 1.30%±0.08%, and of the RP2 specimen was 1.20%±0.09%. Measuring the recovered residue yielded residual amounts of 0.2% for the WP specimen, 1.1% for the RP2 specimen, and 1.8% for the RP1 specimen. Conclusion: 1. From measurements of the workpieces manufactured by dental DLP 3D printing, the thermal expansion rate was found to be higher than that of wax. 2. As a result of measuring burnout residues on the workpieces manufactured by dental DLP 3D printing, the required summoning temperature to obtain suitable castings was determined to >750℃.

• Journal of the Korean Geotechnical Society
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• 제38권9호
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• pp.53-67
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• 2022

Micropiles are cast-in-place-type piles with small diameters. They are widely used for the foundation reinforcement of existing buildings and structures because this technique is easy to construct and economic. A base expansion structure is developed following the mechanism of radial expansion at the pile tip under compression. Numerical analysis, durability tests, and centrifuge tests have been conducted using the base expansion structure. In this study, three-dimensional numerical modeling was performed to describe the behavioral mechanism of the base expansion structure using steel bar penetration under compressive loading, and numerical analyses using centrifuge test conditions were performed for the comparative studies. Additionally, the base structure was modified based on the results of lab-scale analyses, and the bearing capacities of micropiles were compared using field-scale numerical analyses under various ground conditions.

• Journal of Korean Neurosurgical Society
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• 제48권5호
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• pp.399-405
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• 2010

Objective : Patients with spontaneous intracerebral hemorrhage (ICH) presenting within 24 hours of symptom onset are known to be increased risk of hematoma expansion which is closely correlated with morbidity and mortality. We investigated whether tiny enhancing foci ('Spot sign') on axial view of 3-dimensional computed tomography angiography (3D-CTA) source images can predict subsequent hematoma expansion in spontaneous ICH. Methods : During a 2-year period (March 2007-March 2009), we prospectively evaluated 3D-CTA of 110 patients with spontaneous ICH. Based on source images of 3D-CTA, patients were classified according to presence or absence of 'Spot sign'; 'Spot sign' (+) group, 'Spot sign' (-) group. Radiological factors and clinical outcomes were compared between two groups. Results : Hematoma expansion occurred in 16 patients (15%). Mean Glasgow Coma Scale (GCS) score of patients with hematoma expansion was significantly different compared to score of patients without hematoma expansion (5 vs. 9, P < 0.001). Nineteen patients (16%) of 110 ICH patients demonstrated 'spot sign' on 3D-CTA. Among the 'spot sign' (+) group, 53% of patients developed hematoma expansion. Conversely 7% of patients without 'spot sign' demonstrated the hematoma expansion (p < 0.001). Initial volume and location of hematoma were significantly not associated with hematoma expansion except shape of hematoma. Conclusion : Our study showed that patients with hematoma expansion of spontaneous ICH had significant clinical deterioration. And the fact that 'spot sign' (+) group have higher risk of hematoma expansion suggests the presence of 'spot sign' on source images of 3D-CTA can give a clue to predict hematoma expansion in spontaneous ICH.

• Journal of Korea Water Resources Association
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• 제42권12호
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• pp.1125-1133
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• 2009

Evanescent modes which are the other solutions of the Laplace equation for the linear dispersion equation may affect the wave transformation especially when a water depth varies abruptly. In this study, the effects of evanescent modes for a three-dimensional depression of seabed are investigated by using the eigenfunction expansion method. A convergence test is first carried out by changing numbers of domains and evanescent modes. The wave transformation for various depressions of seabed is then calculated under condition that the solution of the eigenfunction expansion method is converged.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.830-836
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• 2012

Dead times appear often in describing process dynamics and raise some difficulties in simulating process dynamics or analyzing process control systems. To relieve these difficulties, it is needed to approximate the infinite dimensional dead time by the finite dimensional transfer function and, for this, the Pade approximation method is often used. For the accurate approximation of the dead time, high order Pade approximation is needed and the high order Pade approximation is not easy to memorize and is not stable numerically. We propose a method based on the continued fraction expansion that provides the same transfer functions. The method is excellent numerically as well as systematic to be memorized easily. It can be used conveniently for the process control lecture and computations.

• The Journal of Korean Physical Therapy
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• 제30권6호
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• pp.229-233
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• 2018

Purpose: This study aims to verify the effects of Pilates exercise using the three-dimensional (3D) Schroth breathing technique on scoliosis patients in comparison with the existing Pilates exercise technique, which uses lateral breathing. Methods: The subjects were 16 scoliosis patients who went to S fitness center in Daegu, Korea. They were randomly and equally divided into a Schroth Pilates exercise group (SPEG), who performed Pilates exercise using 3D Schroth breathing, and a Pilates exercise group (PEG) who performed Pilates exercise using lateral breathing. The subjects conducted the Pilates exercise three times per week for 12 weeks. Changes in their Cobb's angle, angle of trunk rotation, and chest expansion ability were measured before and after the exercise. Results: Both groups experienced significant improvement in their Cobb's angle, angle of trunk rotation, and chest expansion ability after the exercise (p<0.05). Between-group comparison after the exercise showed that SPEG's improvement in Cobb's angle, angle of trunk rotation, and chest expansion ability were more significant than those of the PEG (p<0.05). Conclusion: This study verified that Pilates exercise using 3D Schroth breathing was more effective in improving scoliosis patients'physical condition than existing Pilates exercise. The researcher anticipates that the 3D Schroth breathing technique will be effectively utilized in other diverse intervention exercises besides Pilates exercise.

• Journal of Ocean Engineering and Technology
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• 제15권3호
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• pp.107-113
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• 2001

This study is focused on the wave control by economical multi-rowed impermeable submerged breakwaters which need less materials than a one-rowed submerged breakwater. A boundary element method and eigenfunction expansion method based on the Green\`s theorem are appled to analyze the characteristics of wave transformation. Submerged breakwaters are consisted of one and two-row with rectangular section. Wave transformation characteristics are investigated by the various combinations of placement distance and crown water depth.

• Journal of the Korean Wood Science and Technology
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• 제34권5호
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• pp.52-58
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• 2006

Coffee chaff for manufacturing of the 6 mm thick cement-bonded boards was obtained from a coffee processing industry at Omuo-Ekiti, in Ekiti State, Nigeria. Boards were produced with three levels of cement to coffee chaff ratio of 1.5:1, 2.5:1 and 3.5:1; and at three levels of mixing curing reagent of 2.0%, 2.5% and 3.0%. Three dimensional properties of thickness swelling (TS), water absorption (WA) and linear expansion (LE) were investigated after 48 hours immersion in water. The mean values obtained for TS, WA and LE ranged from 0.46% to 1.47%, from 11.52% to 24.00%, from 0.19% to 0.35%, respectively. The most dimensionally stable boards were produced at the highest mixing levels of curing reagent and cement to coffee chaff ratio of 3.0% and 3.5:1, respectively. The coffee chaff is suitable as raw material for the manufacture of cement-bonded composites and it would be able to stimulate and activate the use of other agro-byproducts for the manufacture of value-added panels.