• Restorative Dentistry and Endodontics
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• v.44 no.1
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• pp.5.1-5.9
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• 2019

Objectives: The aim of this in vitro study was to evaluate the push-out bond strength of a novel calcium silicate-based root repair material-BIOfactor MTA to root canal dentin in comparison with white MTA-Angelus (Angelus) and Biodentine (Septodont). Materials and Methods: The coronal parts of 12 central incisors were removed and the roots were embedded in acrylic resin blocks. Midroot dentin of each sample was horizontally sectioned into 1.1 mm slices and 3 slices were obtained from each root. Three canal-like standardized holes having 1 mm in diameter were created parallel to the root canal on each dentin slice with a diamond bur. The holes were filled with MTA-Angelus, Biodentine, or BIOfactor MTA. Wet gauze was placed over the specimens and samples were stored in an incubator at $37^{\circ}C$ for 7 days to allow complete setting. Then samples were subjected to the push-out test method using a universal test machine with the loading speed of 1 mm/min. Data was statistically analyzed using Friedman test and post hoc Wilcoxon signed rank test with Bonferroni correction. Results: There were no significant differences among the push-out bond strength values of MTA-Angelus, Biodentine, and BIOfactor MTA (p > 0.017). Most of the specimens exhibited cohesive failure in all groups, with the highest rate found in Biodentine group. Conclusions: Based on the results of this study, MTA-Angelus, Biodentine, and BIOfactor MTA showed similar resistances to the push-out testing.

• The Journal of Advanced Prosthodontics
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• v.11 no.3
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• pp.187-192
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• 2019

PURPOSE. The purpose of this in vitro study was to investigate the fracture loads and modes of failure for the full range of natural teeth under simulated occlusal loading. MATERIALS AND METHODS. One hundred and forty natural teeth were taken from mandibles and maxillas of patients. There were 14 groups of teeth with 10 teeth in each group (5 males and 5 females). Each specimen was embedded in resin and mounted on a positioning jig, with the long axis of the tooth at an inclined angle of 30 degrees. A universal testing machine was used to measure the compression load at which fracture of the tooth specimen occurred; loads were applied on the incisal edge and/or functional cusp. RESULTS. The mean fracture load for the mandibular first premolar was the highest (2002 N) of all the types of teeth, while the mean fracture load for the maxillary first premolar was the lowest (525 N). Mean fracture loads for the mandibular and maxillary incisors, and the first and second maxillary premolars, had significantly lower values compared to the other types of teeth. The mean fracture load for the teeth from males was significantly greater than that for the teeth from females. There was an inverse relationship between age and mean fracture load, in which older teeth had lower fracture loads compared to younger teeth. CONCLUSION. The mean fracture loads for natural teeth were significantly different, with dependence on tooth position and the sex and age of the individual.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.87-93
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• 2021

As the portion of modern weapons systems equipped with electronic components increases, the presence of embedded software has also increased, subsequently drawing interest in quality management and development methods. Unlike mechanical systems, software is logically intangible, hard to troubleshoot, and hard to reuse, making it hard to utilize limited resources when exposed to failures. The United States had successful results in establishing the Capability Maturity Model (CMM) by studying and applying separate processes for development and quality management of defense software. South Korea has also established, and utilizes, a standard of development and quality management for defense software based on international standards. However, some say those standards still remain at a basic level, and should be modified along with the progress in software. If the standard stays at a basic level, compared to software progression, the cost to reuse and restore resources will increase exponentially. This paper discusses improvement in the test processes for defense software through the Test Maturity Model-integration (TMMi)-derived from the CMM-and presents a blueprint for defense software quality management.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.12
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• pp.997-1004
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• 2020

A synchropter is a type of rotorcraft in which a pair of blades inclined with each other rotates in synchronization. Removing the tail rotor enables an efficient and compact configuration similar to a coaxial-rotor helicopter. This paper describes the design and flight test results of a small synchropter to examine the suitability of a drone system for the army. The synchropter in this paper is a small vehicle with a rotor diameter of 1.4m and a weight of 7kg and was assembled based on commercial parts to examine flight characteristics effectively. The flight control system adopted Pixhawk, which is designed based on an open-architecture. The model-based design technique is applied to develop the control law of the synchropter and a new firmware embedded on the Pixhawk. Through qualitative flight tests, we analyzed the flight characteristics. As a result of the analysis, we confirmed the possibility of application as a drone system of the synchropter.

• Smart Structures and Systems
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• v.29 no.2
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• pp.267-278
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• 2022

Pre-stressed concrete circular spun piles are widely used in various infrastructure projects around the world and offer an economical deep foundation system with consistent and superior quality compared to cast in-situ and other concrete piles. Conventional methods for measuring the lateral response of piles have been limited to conventional instrumentation, such as electrical based gauges and pressure transducers. The problem with existing technology is that the sensors are not able to assist in recording the lateral stiffness changes of the pile which varies along the length depending on the distribution of the flexural moments and appearance of tensile cracks. This paper describes a full-scale bending test of a 1-m diameter spun pile of 30 m long and instrumented using advanced fibre optic distributed sensor, known as Brillouin Optical Time Domain Analysis (BOTDA). Optical fibre sensors were embedded inside the concrete during the manufacturing stage and attached on the concrete surface in order to measure the pile's full-length flexural behaviour under the prescribed serviceability and ultimate limit state. The relationship between moments-deflections and bending moments-curvatures are examined with respect to the lateral forces. Tensile cracks were measured and compared with the peak strains observed from BOTDA data which corroborated very well. By analysing the moment-curvature response of the pile, the structure can be represented by two bending stiffness parameters, namely the pre-yield (EI) and post-yield (EI_cr), where the cracks reduce the stiffness property by 89%. The pile deflection profile can be attained from optical fibre data through closed-form solutions, which generally matched with the displacements recorded by Linear Voltage Displacement Transducers (LVDTs).

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.228-234
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• 2023

As the increasing demand for high-quality software, there is huge requiring for quality certification of international standards, industrial functional safety (IEC 61508), automotive (ISO 26262), embedded software guidelines for weapon systems, etc., in the industry. Software companies are very difficult to systematically acquire the quality certification in terms of cost and manpower of Startup, venture small-sized companies. For their companies one test case automatic generation is considered as a core technique to evaluate or improve software quality. This paper proposes a test case automatic generation method based on the design decision table for system and software design verification. We apply the proposed method with OMG's standard techniques of metamodel and model transformation for automatically generating test cases. To do this, we design the metamodels of design decision table (Model) and test case document (Text) and define model transformation to automatically generate test cases, which will expect to easily work MC/DC coverage.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.113-127
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• 2008

The purpose of this study was to evaluate effect of application of $ZirLiner^{(R)}$ and blasting treatments on shear bond strength of zirconia-veneered porcelain interface. 60 uncolored zirconia plates and 30 colored zirconia plates were fabricated and divided into nine groups of 10 according to blasting treatment such as as-ground, glass blasting and alumina blasting and zirliner application. Veneering porcelains were built up over the center of the treated zirconia ceramic surface using jig and fired according to the manufacturers' instructions. Each specimen was completely embedded in acrylic resin. The specimens were placed in a mounting jig and subjected to shear force by a universal testing machine. Load was applied at a crosshead speed of 0.5㎜/min until failure. Average shear strengths were analyzed with two-way analysis of variance and one-way analysis of variance and the Duncan's post-hoc test. The fracture surfaces of the failed specimens were examined by SEM. The obtained results were as follows: 1. Depending on surface treatment by blasting, the degree of roughness is revealed in the order of Glass-blasted, As-ground, and Alumnia-blasted. The roughness average of uncolored and colored zirconia ceramic were not significantly different from blasting treatments. 2. In uncolored zirconia ceramic, the shear bond strength were not significantly different from blasting treatments. However, the shear bond strength were significantly different from Zirliner application. 3. Used ZirLiner, mean shear bond strength of colored zirconia was lower than uncolored zirconia. Especially, mean shear bond strength of colored zirconia was quite low with alumina-blasting treatment. 4. SEM analysis showed that veneered porcelain failed in zirconia ceramic interface and there was no cohesive failure.

• Journal of IKEEE
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• v.18 no.3
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• pp.383-391
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• 2014

In this paper, temperature, pressure and flow analysis system for testing a fuel filter of a diesel engine at the low-temperature environment in winter, is proposed. The light oil of diesel engine below a specific temperature is changed to the waxing materials like paraffin, and it prevents engine to start easily because of reducing fluidity. Thus, built-in block heater should be installed with fuel filter in order to solve this problem. And it is necessary to design evaluation system that can analyze the performance according to temperature, pressure and flow characteristics near fuel filter at a very low temperature. In this paper, we measured a physical quantity related to the performance of around the fuel filter using the proposed system, and analyzed their characteristics. Also the measured data is transferred to remote user by using a web server of embedded systems, and analyzed their conditions in remote place via web browser in order to know the operating status of fuel filter. We installed the proposed system in a small test chamber to verify the performance and took an experiment in normal temperature and very low temperature, and could obtain temperature, pressure and flow of near the fuel filter. As a result, the fuel flow could be improved during operation of the fuel heater.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.95-102
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• 2012

The serious issue of tall building is to ensure the fire resistance of high strength concrete. Therefore, Solving methods are required to control the explosive spalling. The fire resistant finishing method is installed by applying a fire resistant material as a light-weight material to structural steel and concrete surface. This method can reduce the temperature increase of the reinforcement embedded in structural steel and concrete at high temperature due to the installation thickness control. This study is interested in identifying the effectiveness of light-weight fire protection material compounds including the inorganic admixture such as fly ash, meta-kaolin and light-weight aggregate as the fire resistant finishing materials through the analysis of fire resistance and components properties at high temperature. Also, this paper is concerned with change in microstructure and dehydration of the light-weight fire protection materials at high temperatures. The testing methods of fire protection materials in high temperature properties are make use of SEM and XRD. The study results show that the light-weight fire resistant finishing material composed of fly ash, meta-kaolin and light-weight aggregate has the thermal stability of the slight decrease of compressive strength at high temperature. These thermal stability is caused by the ceramic binding capacity induced by alkali activation reaction by the reason of the thermal analysis result not showing the decomposition of calcium hydrate. Developed light-weight fire protection materials showed good stability in high Temperatures. Thus, the results indicate that it is possible to fireproof panels, fire protection of materials.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.347-353
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• 2016

The purpose of this study was to evaluate shear bond strength and microleakage of a new self-etch fissure sealant containing S-PRG filler (BeautiSealant). Fourty-five premolars were randomly divided into three groups: SEPBS group (Self-etching primer + BeautiSealant), AEBS group (Phosphoric acid etching + BeautiSealant), AECP group (Phosphoric acid etching + $Clinpro^{TM}$ sealant). For the shear bond strength test, microcylinders of fissure sealant were bonded to prepared buccal surfaces of teeth and shear bond strengths were measured by a universal testing machine. For the microleakage test, sealants were applicated on each occlusal fissure of teeth. All teeth surface were coated with finger nail varnish, with the exception of a 1.0 mm window around the sealant margins. The teeth were immersed in 2% methylene blue solution for 24 hours and then rinsed in water. The teeth were then embedded in resin and cut buccolingually along the tooth axis and observed with a stereomicroscope to determine the degree of microleakage. SEPBS group demonstrated lower bond strength in comparison with that of AEBS and AECP groups (p < 0.05). However, no significant differences were observed between AEBS and AECP groups. There was no statistically significant difference in degree of microleakage among three groups.