• Restorative Dentistry and Endodontics
• /
• 제23권1호
• /
• pp.1-19
• /
• 1998

After polymerizing composite resin with argon laser and visible light, four test, to be concretely, measurement of compressive strength using Instron testing machine, surface microhardness using Rockwell hardness tester, quantitative analysis of residual monomer using HPLC and analysis of degree of conversion using FTIR, were accomplished. Test groups were a sort of specimen with 3mm diameter, 4mm thickness for measuring compressive strength, two sort of specimen with 7mm diameter, 2mm and 3mm thickness for measuring surface microhardness, quantitative analysing of residual monomer after curing and measuring the degree of conversion, each were divided by six groups according to the condition of light exposure. In case of argon laser, in 1.0W and 0.5W output, the exposure time for specimen were 5 sec, 10 sec respectiyely. In case of visible light, the exposure time for specimen were 20 sec, 40 sec respectively. The test were accomplished and following results were obtained. 1. Compressive strength of composite resin was the highest in the group of 1 W output, exposing for 10 sec with argon laser, followed by the group of 0.5W, exposing for 10 sec with argon laser, the group of exposing for 40 sec with visible light. But there were statistically no significant difference between these three groups(p>0.05). 2. Surface microhardness of composite resin wasn't significantly affected by light curing conditions. 3. BIS-GMA within residual monomer was least detected in the group of exposing for 40 sec. TEGDMA was least detected in the group of 1 W output, exposing for 10 sec with argon laseboth 2mm and 3mm thickness specimen. 4. The degree of conversion of all groups in the 2mm thickness specimen were more than 50%, similar to each other but in the group of 1W, exposing 10 sec with argon laser the degree of conversion was highest in the 3mm thickness specimen. 5. Argon laser could make composite resin to has similar properties with 25% lesser exposure time than visible light.

• Journal of Mechanical Science and Technology
• /
• 제17권11호
• /
• pp.1704-1713
• /
• 2003

Point contact film thickness in elastohydrodynamic lubrication (EHL) is analyzed by image processing method for the images from an optical interferometer with monochromatic incident light. Interference between the reflected lights both on half mirror Cr coating of glass disk and on super finished ball makes circular fringes depending on the contact conditions such as sliding velocity, applied load, viscosity-pressure characteristics and viscosity of lubricant under ambient pressure. In this situation the film thickness is regarded as the difference of optical paths between those reflected lights, which make dark and bright fringes with monochromatic incident light. The film thickness is computed by numbering the dark and bright fringe orders and the intensity (gray scale image) in each fringe regime is mapped to the corresponding film thickness. In this work, we developed a measuring technique for EHL film thickness by dividing the image patterns into two typical types under the condition of monochromatic incident light. During the image processing, the captured image is converted into digitally formatted data over the contact area without any loss of the image information of interferogram and it is also interpreted with consistency regardless of the observer's experimental experience. It is expected that the developed image processing method will provide a valuable basis to develop the image processing technique for color fringes, which is generally used for the measurement of relatively thin films in higher resolution.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2003년도 학술대회지
• /
• pp.368-376
• /
• 2003

In this research, DLC thin films are produced as several hundred nm thickness by PE-CVD method. And then these thin films are estimated tribological characteristics to find out useful possibilities as a protecting film for high-quality function and life extension at MEMs by mechanical properties observation . These are measured thickness and residual stress of DLC coating. Compared after measuring friction coefficient, adhesion force, hardness, cohesive force of coating films. As results all test, we can decide several conclusions. First, friction coefficient decreased, as the load increased. otherwise, friction coefficient increased, as thickness of coating film increased under low load$(1\~50mN)$. Secod, adhesion force increased as thickness of coating films. Third, hardness of coating film is affected by substrate coating film when it is less than thickness of 300nm and it has general hardness of DLC coating film when it is more than thickness of 500nm. Fourth, cohesive force of coating film is complexly affected by hardness, adhesion force, residual stress, etc.

• 한국재료학회지
• /
• 제17권8호
• /
• pp.402-407
• /
• 2007

In electronics manufacturing processes, soldering process has generally been used in surface mounting technology. Because of environmental restriction, lead free solders as like a SnAgCu ternary system are being used widely. After soldering process, the formation and growth of intermetalic compounds(IMCs) are formed in the interface between solder and Cu substrate as follows isothermal temperature and time. In this studies, therefore, we investigated the effects of the Cu substrate thickness on the IMC formation and growth of Sn-40Pb/Cu and Sn-3.0Ag-0.5Cu/Cu solder joints, respectively. The effect of the Cu thickness in PCB Cu pad and pure Cu plate was analyzed as measuring of thickness of each IMC. After solder was soldered on PCB and Cu plate which have different Cu thickness, we measured the IMC thickness in solder joints respectively. Also we compared with the effectiveness of Cu thickness on the IMC growth. From these results, we calculated the activation energy.

• PNF and Movement
• /
• 제14권1호
• /
• pp.53-57
• /
• 2016

Purpose: This study aimed to examine the correlation between the asymmetric ratio of occlusal force of the temporomandibular joint and the thickness of the middle scalene muscle. Methods: The study measured the occlusal force of the right and left temporomandibular joints in 30 subjects (12 males and 18 females). Pearson's correlation analysis was performed to examine the effect of occlusal force on the asymmetric ratio of the thickness of their middle scalene muscles by measuring the force using ultrasound after the break. Results: The correlation between the asymmetric ratio of occlusal force and muscle thickness is 0.41, according to Pearson's correlation coefficient. Therefore, the result shows a moderate correlation with the asymmetric ratio of the temporomandibular joint depending on differences in the thickness of the middle scalene muscle. Conclusion: Based on the above results, the asymmetric ratio of occlusal force was found to correlate with the thickness of the middle scalene muscle. Thus, therapeutic intervention is required for the middle scalene muscle in the case of temporomandibular joint disorder.

• 한국해양공학회지
• /
• 제27권5호
• /
• pp.82-87
• /
• 2013

The icebreaking research vessel ARAON conducted her second ice trial in the Arctic Ocean during the summer season of 2010. During this voyage, the local ice loads acting on the bow of the port side were measured using 14 strain gauges. The measurement was carried out during icebreaking while measuring the thickness of the ice every 10 m. The obtained strain data were converted to the equivalent stress values, and the effects of the ship speed and ice thickness on the ice load were investigated. As a result, it was found that a faster speed produced a larger stress, according to the variation in the peak values below an ice thickness condition of 1.5 m. Meanwhile, the effect of the ice thickness on the ice load was not clear.

• 대한물리의학회지
• /
• 제16권1호
• /
• pp.73-81
• /
• 2021

PURPOSE: This study examined effects of the untact trunk stabilization exercise program on muscle thickness, trunk strength, maximal expiratory flow, and static balance. METHODS: The subjects were 20 normal adults divided into 10 in the contact exercise group and 10 in the untact exercise group. The trunk stabilization exercise program was conducted for four weeks. The muscle thickness was measured using ultrasound. The maximal expiratory flow was measured using Personal Best Full Range Peak Flow Meter. The static balance was measured through Bio-rescue; and the trunk muscle strength was measured by bending the upper body forward and measuring the time for maintaining the posture. RESULTS: Both contact and untact exercise groups showed significant differences in muscle thickness, muscle strength, maximal expiratory flow, and static balance (p < .05). A significant difference in muscle thickness on ultrasound was observed between the contact and untact exercise groups (p < .05). CONCLUSION: Activation of the transverse abdominal muscle requires accurate instructions of the contact exercise, but despite environmental constraints, the untact exercise program is as effective as the contact exercise for improving muscle strength, maximum expiratory flow, and static balance.

• Physical Therapy Rehabilitation Science
• /
• 제5권3호
• /
• pp.155-161
• /
• 2016

Objective: This study aimed to investigate the reliability and validity of a personal computer-based muscle viewer (PC-BMW) compared with that of a portable ultrasound (P-US) for measuring upper trapezius (UT) and transversus abdominis (TrA) muscle thickness at rest and during contraction. Design: Observational inter-rater reliability study. Methods: Fifty-five healthy participants (25 men, 30 women) participated in this study. PC-BMW and P-US were randomly measured at the UT and TrA muscles. Two examiners randomly obtained the images of all participants in 3 test sessions lasting 2 days. Intra-class correlation coefficients (ICCs), standard error of measurement, contraction ratio, and correlation were used to estimate reliability and validity. Pearson's correlation coefficients were used to analyze the relationship between muscle thickness measures taken from PC-BMW and P-US. Results: The intra-rater reliability ICCs of UT and TrA muscle thickness for the PC-BMW were >0.995, indicating excellent reliability. Inter-rater reliability ICCs for the PC-BMW ranged from 0.963 to 0.987. The P-US also exhibited high reliability. A high correlation was found between the measurements of the two muscles in PC-BMW and P-US (p<0.01). Conclusions: PC-BMW provides clear and excellent images, is pocket-sized and less expensive than a conventional ultrasound imaging system. PC-BMW can be utilized variously and has the advantage of rehabilitative ultrasound imaging. More research is needed to evaluate the utility of PC-BMW for rehabilitation.

• Corrosion Science and Technology
• /
• 제13권1호
• /
• pp.20-27
• /
• 2014

The structures of reinforced concrete has been extensively increased with rapid development of industrial society. Futhermore, these reinforced concretes are easy to expose to severe corrosive environments such as sea water, contaminated water, acid rain and seashore etc.. Thus, corrosion problem of inner steel bar embedded in concrete is very important in terms of safety and economical point of view. In this study, multiple mortar test specimen(W/C:0.4) with six types having different cover thickness each other was prepared and was immerged in seawater solution for five years to evaluate the effect of cover thickness and immersion years to corrosion property of embedded steel bar. And the polarization characteristics of these embedded steel bars was investigated using electrochemical methods such as measuring corrosion potential, cathodic polarization curve, and cyclic voltammogram. At the beginning of immersion, the corrosion potentials exhibited increasingly nobler values with increasing cover thickness. However, after immersed for 5 years, the thicker cover of thickness, the corrosion potentials shifted in the negative direction, and the relationship between corrosion potential and cover thickness was not in good agreement with each other. Therefore, it is considered that the thinner cover of thickness, corrosive products deposited on the surface of the embedded steel bar plays the role as a resistance polarization which is resulted in decreasing the corrosion rate as well as shifting the corrosion potential in the positive direction. As a result, it seemed that the evaluation which corrosion possibility of the reinforced steel would be estimated by only measuring the corrosion potential may not be a completely desirable method. Therefore, it is suggested that we should take into account various parameters, including cover thickness, passed aged years as well as corrosion potential for more accurate assessment of corrosion possibility of reinforced steel which is exposed to partially or fully in marine environment for long years.

• Nuclear Engineering and Technology
• /
• 제54권9호
• /
• pp.3272-3282
• /
• 2022

To improve the safety and life extension qualities of nuclear fuel rods which is currently made of zirconium (Zr) alloy, research on the application of chromium (Cr) coating was conducted. Cr coating has advantages such as increased corrosion resistance and reduced oxidation rate, but non-destructive thickness evaluation studies are needed to ensure the reliability of the steps taken to provide uniform coating thickness. Eddy current testing (ECT) is a representative non-destructive technique for such as thickness evaluation and surface defect inspection. To inspect changes in thickness at micron scale, the Swept Frequency Eddy Current Testing (SFECT) method was applied to select a frequency range sensitive to changes in thickness. The coating thickness was evaluated using changes in signals, such as that for impedance. In this study, basic research was performed to evaluate the thickness of the Cr coating on a rod using an encircling sensor and the SFECT technique. The sensor design parameters were determined through simulation, after which the new sensor was manufactured. A sensor capable of measuring the thickness of a non-uniformly Cr-coating rod was selected through an experiment evaluating the performance of the manufactured sensor. This was done using the impedance-difference of a Cr-coating rod and a Zr alloy rod. The possibility of evaluation of the Cr coating thickness was confirmed by comparing the experimental results with the selected sensor and the signals of the measured Cr-coating rod. All simulation results were verified experimentally.