• Imaging Science in Dentistry
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• v.31 no.2
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• pp.85-91
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• 2001

Purpose: To evaluate the effect of the slice thickness and the size of region of interest (ROI) on CT number using quantitative CT phantom Materials and Methods: The phantom containing 150 mg/cc, 75 mg/cc and 0 mg/cc calcium hydroxyapatite was scanned with 1, 3, 5 and 10 mm slice thicknesses by single energy quantitative computed tomography (QCT). CT numbers were measured on center position of the phantom. Shape of ROI was circular and sizes were 1, 3, 5, 11, 16, 21, 26 and 33 mm². ANOVA and Tukey's multiple comparison method were performed for statistical comparison of CT numbers according to different slice thicknesses. Coefficient of variation of CT number measured in each size of ROI was evaluated in same slice thickness. Results : CT numbers had statistically significant difference according to slice thicknesses (p<0.05). As the slice thickness increased, CT number also increased. As the density of phantom became lower and the size of ROI became smaller, the coefficient of variation of CT number increased. When the size of ROI was more than 11 mm² in 1 mm slice thickness, 5 mm² in 3 mm slice thickness and 3 mm² in 5 mm slice thickness, the coefficient of variation became consistent. In 10 mm slice thickness, the size of ROI had little effect on the coefficient of variation. Conclusion: CT number had variation according to the slice thickness and the size of ROI although the object was homogeneous. The slice thickness and the size of ROI are critical factors in precision of the CT number measurements.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.281-281
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• 2015

Shallow landslide often occurs in areas of this topography where subsurface soil water flow paths give rise to excess pore-water pressures downslope. Recent hillslope hydrology studies have shown that subsurface topography has a strong impact in controlling the connectivity of saturated areas at the soil-bedrock interface. In this study, the physically based SHALSTAB model was used to evaluate the effects of three soil thicknesses (i.e. average soil layer, soil thickness to weathered soil and soil thickness to bedrock soil layer) and subsurface flow reflecting three soil thicknesses on shallow landslide prediction accuracy. Three digital elevation models (DEMs; i.e. ground surface, weathered surface and bedrock surface) and three soil thicknesses (average soil thickness, soil thickness to weathered rock and soil thickness to bedrock) at a small hillslope site in Jinbu, Kangwon Prefecture, eastern part of the Korean Peninsula, were considered. Each prediction result simulated with the SHALSTAB model was evaluated by receiver operating characteristic (ROC) analysis for modelling accuracy. The results of the ROC analysis for shallow landslide prediction using the ground surface DEM (GSTO), the weathered surface DEM and the bedrock surface DEM (BSTO) indicated that the prediction accuracy was higher using flow accumulation by the BSTO and weathered soil thickness compared to results. These results imply that 1) the effect of subsurface flow by BSTO on shallow landslide prediction especially could be larger than the effects of topography by GSTO, and 2) the effect of weathered soil thickness could be larger than the effects of average soil thickness and bedrock soil thickness on shallow landslide prediction. Therefore, we suggest that using BSTO dem and weathered soil layer can improve the accuracy of shallow landslide prediction, which should contribute to more accurately predicting shallow landslides.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.3
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• pp.131-140
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• 2022

Purpose : Although many studies have explored the effect of seating side angles on the spinal curve and surrounding muscles during seating, only a few studies have investigated the effect of different seating face angles on different lower limb and deep trunk muscles. Therefore, this study investigated the effects of seating surface angles (0 degrees, 10 degree anterior, and 10 degree rear) on lower extremity and deep trunk muscles in healthy adults. Methods : Thirty people were asked to sit once on each seating surface three times during the day, and their muscle thicknesses were measured by ultrasound while sitting. The method of sitting was the same when sitting on the three seating surfaces. Results : From the comparison results of the muscle thicknesses according to the seating surface angles, a significant difference existed in the muscle thicknesses of the vastus medialis, vastus medialis oblique, vastus intermedius, soleus and gastrocnemius (p<.05). However, no significant difference was found in the transversus abdominis, internal obliques, rectus femoris and vastus lateralis (p>.05). Conclusion : Our findings revealed that the lower back load decreases, the leg load increases, and the legs specific muscles are affected as the body tilts forward when sitting on the seating surface inclined forward. Therefore, it is possible to suggest a forwardly inclined seating surface that reduces lower back loads and utilizes the posture-maintaining muscles of the legs when sitting in a person with a poor sitting posture or lower back pain at ordinary times.

• Journal of The Korean Society of Integrative Medicine
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• v.6 no.3
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• pp.25-32
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• 2018

Purpose : This study investigated the effects of different types of plank exercise on abdominal muscle thickness in subjects with asymmetric pelvic anterior tilt. Methods : Participants with a diagnosis of pelvic anterior tilt were divided into an experimental group (n=12) and a control group (n=13). The thicknesses of the transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles were measured using an ultrasound diagnostic apparatus. The data were analyzed using an SPSS (Ver. 21) program. Results : In the experimental group, there was a significant difference in the thicknesses of the left and right muscles in the standing and elbow plank exercises (p<.05). All the muscle thicknesses increased significantly during the plank exercises(elbow plank, right-side plank, and left-side plank) as compared with those in the standing position (p<.05). In addition, the side-plank exercise resulted in significantly higher muscle thickness of the supported side (p<.01, p<.001). Conclusion : These findings suggest that asymmetric exercise should be applied to the change of the left and right muscles of the abdominal when applying plank exercise according to pelvic anterior tilt.

• The Journal of Advanced Prosthodontics
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• v.12 no.2
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• pp.61-66
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• 2020

PURPOSE. The aim of the present study was to determine the degree of conversion of light- and dual-cured resin cements used in the cementation of all-ceramic restorations under different thicknesses of translucent (T) and high-translucent (HT) polymer-infiltrated ceramic-network (PICN) material. MATERIALS AND METHODS. T and HT PICN blocks were prepared at 0.5, 1.0, 1.5, and 2.0 mm thicknesses (n=80). Resin cement samples were prepared with a diameter of 6 mm and a thickness of 100 ㎛. Light-cured resin cement was polymerized for 30 seconds, and dual-cure resin cement was polymerized for 20 seconds (n=180). Fourier transform infrared spectroscopy (FTIR) was used for degree of conversion measurements. The obtained data were analyzed with ANOVA and Tukey HSD, and independent t-test. RESULTS. As a result of FTIR analysis, the degree of conversion of the light-cured resin cement prepared under 1.5- and 2.0-mm-thick T and HT ceramics was found to be lower than that of the control group. Regarding the degree of conversion of the dual-cured resin cement group, there was no significant difference from the control group. CONCLUSION. Within the limitation of present study, it can be concluded that using of dual cure resin cement can be suggested for cementation of PICN material, especially for thicknesses of 1.5 mm and above.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.7
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• pp.475-480
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• 2018

We investigated the tribological properties of amorphous carbon (a-C) films deposited with CrC interlayers of various thicknesses as the adhesive layer. A-C and CrC thin films were deposited using the unbalanced magnetron (UBM) sputtering method with graphite and chromium as the targets. CrC films as the interlayer were fabricated under a-C films, and various structural, surface, and tribological properties of a-C films deposited with various CrC interlayer thicknesses were investigated. With various CrC interlayer thicknesses under a-C films, the tribological properties of CrC/a-C films were improved; the increased film thickness exhibited a maximum high hardness of over 27.5 GPa, high elastic modulus of over 242 GPa, critical load of 31 N, residual stress of 1.85 GPa, and a smooth surface below 0.09 nm at the condition of 30-nm CrC thickness.

• The Journal of the Korean dental association
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• v.49 no.4
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• pp.203-210
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• 2011

The aims of this study were to evaluate the adequate thickness of opaque resins for situations such as an oral black cavity and discolored tooth structure, as well as the translucency of each opaque material at various thicknesses. Six opaque-shade composite resins (Z-350 OA3, Amelogen Universal A2O, Esthet-X A2O, Esthet-X A4O, Charmfil UO and Aelite Universal OA3) were prepared in metal molds with a hole of 8 mm in diameter and various thicknesses (0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0 mm and 4.0mm). Four backgrounds (white tile, black tile, C4 shade porcelain and opaque resin itself) were used to determine the translucency parameter (between black and white backgrounds). and to mimic a black oral cavity (between black and opaque resin backgrounds) and a discolored tooth structure (between C4 and opaque resin backgrounds). Color measurements were made by a colorimeter to determine the CIELAB values of each specimen with each background and to calculate the translucency parameter and ${\Delta}E^*$ value difference among the specimens on the backgrounds. The translucency parameter and ${\Delta}E^*$ obtained between black and opaque resin backgrounds decreased in similar pattern as thickness increased. A C4 background was masked by resin thicknesses of 0.5-1.0mm, while a black background required thicknesses of 1.0-2.0mm. Adequate knowledge about differences in the optical character like translucency of the materials used is essential, together with the accumulated experience of the individual clinician.

• The Journal of Advanced Prosthodontics
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• v.6 no.1
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• pp.8-13
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• 2014

PURPOSE. The purpose of this study was to evaluate whether surface treatments affect the translucency of laminate veneers with different shades and thicknesses. MATERIALS AND METHODS. A total of 224 disc-shaped ceramic veneers were prepared from A1, A3, HT (High Translucent) and HO (High Opaque) shades of IPS e.max Press (Ivoclar Vivadent) with 0.5 mm and 1.0 mm thicknesses. The ceramics were divided into four groups for surface treatments. Group C: no surface treatments; Group HF: etched with hydrofluoric acid; Group SB: sandblasted with 50-${\mu}m$ $Al_2O_3$; and Group L; irradiated with an Er;YAG laser. A translucent shade of resin cement (Rely X Veneer, 3M ESPE) was chosen for cementation. The color values of the veneers were measured with a colorimeter and translucency parameter (TP) values were calculated. A three-way ANOVA with interactions for TP values was performed and Bonferroni tests were used when appropriate (${\alpha}=0.05$). RESULTS. There were significant interactions between the surface treatments, ceramic shades and thicknesses (P=.001). For the 0.5-mm-thick specimens there were significant differences after the SB and L treatments. There was no significant difference between the HF and C treatments for any shades or thicknesses (P>.05). For the 1-mm-thick ceramics, there was only a significant difference between the L and C treatments for the HT shade ceramics (P=.01). There were also significant differences between the SB and C treatments except not for the HO shades (P=.768). CONCLUSION. The SB and L treatments caused laminate veneers to become more opaque; however, HF treatment did not affect the TP values. When the laminate veneers were thinner, both the shade of the ceramic and the SB and laser treatments had a greater effect on the TP values.

• Smart Structures and Systems
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• v.16 no.5
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• pp.759-780
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• 2015

Based on the theory of piezoelasticity, the static performance of a piezoelectric bilayer cantilever fully covered with electrodes on the upper and lower surfaces is studied. Three models are considered, i.e., the sensor model, the driving displacement model and the blocking force model. By establishing suitable boundary conditions and proposing an appropriate Airy stress function, the exact solutions for piezoelectric bilayer cantilevers are obtained, and the effect of ambient thermal excitation is taken into account. Since the layer thicknesses and material parameters are distinguished in different layers, this paper gives unified solutions for composite piezoelectric bilayer cantilevers including piezoelectric bimorph and piezoelectric heterogeneous bimorph, etc. For some special cases, the simplifications of the present results are compared with other solutions given by other researches based on one-dimensional constitutive equations, and some amendments have been found. The present investigation shows: (1) for a PZT-4 piezoelectric bimorph, the amendments of tip deflections induced by an end shear force, an end moment or an external voltage are about 19.59%, 23.72% and 7.21%, respectively; (2) for a PZT-4-Al piezoelectric heterogeneous bimorph with constant layer thicknesses, the amendments of tip deflections induced by an end shear force, an end moment or an external voltage are 9.85%, 11.78% and 4.07%, respectively, and the amendments of the electrode charges induced by an end shear force or an end moment are both 1.04%; (3) for a PZT-4-Al piezoelectric heterogeneous bimorph with different layer thicknesses, the maximum amendment of tip deflection approaches 23.72%, and the maximum amendment of electrode charge approaches 31.09%. The present solutions can be used to optimize bilayer devices, and the Airy stress function can be used to study other piezoelectric cantilevers including multi-layered piezoelectric cantilevers under corresponding loads.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.259-262
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• 2008

This paper introduces a simplified method to consider forming effects in a car crash analysis. Representative value was used to consider forming effects simply. Four representative values, which are the mean value of thicknesses and effective plastic strains at nodes, the median of thicknesses and effective plastic strains at nodes, were evaluated. A crash analysis of a front side member shows that analysis results from the suggested methods are similar to those from the conventional method to consider forming effects. Use of the mean effective plastic strain shows the best results. A car crash analysis for a ULSAB/AVC model under the condition of US SINCAP were carried out to demonstrate the validity of the suggested method. Analysis results show that the error of suggested method is less than 1.5%.