• Polymer(Korea)
• /
• v.38 no.5
• /
• pp.632-639
• /
• 2014

2,7-Dihydroxynaphthalene bis(trimellitate anhydride) (2,7-TA) was synthesized from trimellitic anhydride chloride and 2,7-dihydroxynaphthalene. Copolyimides (Co-PI) containing ester group were synthesized from 2,7-TA, pxylylenediamine, and 2,2'-bis(trifluoromethyl)benzidine (TFB). The Co-PI films were obtained from poly(amic acid) by solution casting through thermal imidization on a glass plate. The thermal property, gas permeation, and optical transparency of the Co-PI films with various TFB monomer contents were investigated. These Co-PIs could be solution-cast into a flexible and tough film. The cast Co-PI films exhibited high optical transparency with a cut-off wavelength of 370~395 nm in UV-vis. absorption and a low yellow index value of 3.55~7.63. The thermal property of Co-PI films increased linearly with increasing TFB content. However, the oxygen permeation and optical transparency of the Co-PI films was found to worsen with increasing TFB content.

• Journal of the Korean Chemical Society
• /
• v.31 no.1
• /
• pp.102-109
• /
• 1987

Some characteristics of $SnO_2$ film which was deposited on a slide glass substrate, using dibutyl tin diacetate and oxygen, by the chemical vapor deposition were observed. The optimum condition for the preparation of the film was found to be at 420$^{\circ}C$ of substrate temperature for 20 min of deposition. Important optical, electrical, and structural features of the film were examined. It was found that the typical $SnO_2$ film on the untreated substrate was 4000${\AA}$ in thickness, transmitted 90% of the visible liglit, and provided 5800 ohms/${\square}$ of the sheet resistance. It was also found that the surface treatments of the slide glass by acid leaching were beneficial. The film structure was found to be a mixture of polycrystalline tetragonal stannic oxide confirmed by the X-ray diffraction and to be spherical fine grains concluded by the scanning electron microscopy.

• Polymer(Korea)
• /
• v.33 no.4
• /
• pp.313-318
• /
• 2009

Copolyimides were synthesized from bis (3-aminophenyl) sulfone (APS) and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) containing a fluorine substituent ($-CF_3$) with different mole ratios of 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA) containing a sulfone group (-$SO_2$-). The PI films were obtained from poly (amic acid) (PAA) by solution casting through thermal imidization on a glass plate. Wide-angle X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), universal tensile machine (UTM) measurements, and UV-Vis spectrometry were used to assess thermo-mechanical properties, morphology, and optical transparency. Thermal properties and optical transparency decreased with increasing DSDA mole fraction. In contrast, mechanical properties increased with increasing DSDA mole fraction. As compared to conventional PI films, however, the PI copolymer films in this work were found to exhibit better optical transparency.

• Journal of Korea Water Resources Association
• /
• v.43 no.9
• /
• pp.781-787
• /
• 2010

A new method for water level measurement method and its verification results are described. In this method, water surface in motion can be detected by temporal variation of pixel arrangement in successive digital images including the boundary between the staff gauge and the water surface. Laboratory and field tests were conducted for the two cases in which the staff gauge was contaminated by dirt or transparent due to clear water. The result shows water level can be accurately measure by this method for these two cases. It is expected that the accuracy of previous image stage gauge will be improved by the new method.

• Journal of Korean Society for Geospatial Information Science
• /
• v.24 no.1
• /
• pp.99-107
• /
• 2016

Korea has been known as volcanic disaster free area. However, recent surveying result shows that Baekdu mountain located in northernmost in the Korean peninsula is not a dormant volcano anymore. When Baekdu mountain is erupting, various damages due to the volcanic ash are expected in South Korea area. Especially, volcanic ash in the air may cause big aviation accident because it can hurt engine or gauges in the airplane. Therefore, it is a crucial issue to interrupt airplane navigation, whose route is overlapped with volcanic ash, after predicting three dimensional dispersion of volcanic ash. In this paper, we deals with 3D visualization techniques for volcanic ash dispersion prediction results. First, we introduce the data acquisition of the volcanic ash dispersion prediction. Dispersion prediction data is obtained from Fall3D model, which is volcanic ash dispersion simulation program. Next, three 3D visualization techniques for volcanic ash dispersion prediction are proposed. Firstly proposed technique is so called 'Cube in the Air', which locates the semitransparent cubes having different color depends on its particle concentration. Second technique is a 'Cube in the Cube' which divide the cube in proportion to particle concentration and locates the small cubes. Last technique is 'Semitransparent Volcanic Ash Plane', which laminates the layer, whose grids present the particle concentration, and apply the semitransparent effect. Based on the proposed techniques, the user could 3D visualize the volcanic ash dispersion prediction results upon his own purposes.

• 한국해양학회지
• /
• v.23 no.1
• /
• pp.24-40
• /
• 1988

In the Korea Ocean Nodule Development (KONOD)-1 area between the Clarion and Clipperton fracture zones of the northeastern equatorial Pacific, the pelagic sediment layer can be divided into two or three units on air-gun seismic profile. The acoustic units can be also correlated with those in the DSDP site 163 core. The topmost unit (unit I) is acoustically transparent and consists of zeolitic clay and radiolarian ooze of late Oligocene to middle Eocene age. Unit IIA is well-stratified and transparent in the lower part. consisting of the radiolarian ooze intercalated with chert beds and zeolitic clay of early Eocene to Paleocene age. Unit IIB is stratified with layers of silicified and compacted flinty-cherty nannofossil chalk (late Cretaceous) on top of the acoustic basement. Units I and IIA form the Line Islands Formation that overlies an unnamed formation of unit lIB. The entire layers and the unit I layer propressively thin northward, except near the Line Islands Ridge. The distribution of sediment layer has been controlled by the equatorial Cenozoic CCD and the northward spreading of the Pacific plate. The change of CCD corresponding to the subsidence and migration of the plate has determined the sediment composition of the DSDP 163 core passed across the equator of high sedimentation suite. The late Cretaceous sedimentary layer (unit IIB) in the 163 core was formed above the CCD south of the equator. The unit IIA resulted from rapid subsidence of the Pacific plate below the CCD in the Paleocene. The unit IIA is seen only in the west of 149 W. Both the units IIA and I were probably formed during the Pacific plate passing and after leaving the equatorial region respectively since early Eocene. In the south of the KONOD-l area, the unit I was redistributed by bottom current, a branch of the Antarctic Bottom Water flowing eastward guided by the Clipperton fracture zone. The activities of bottom currents were prolonged for a long geological time. Turbidite layers occur more than 350 km from the Hawaiian Ridge to near the Clarion fracture zone. They originated directly from the Hawaiian Ridge, filling the topographic lows.

• Restorative Dentistry and Endodontics
• /
• v.30 no.3
• /
• pp.178-183
• /
• 2005

This study was done to evaluate whether vital bleaching agents could influence on the translucency of the bovine enamel. The anterior bovine teeth that were extracted one day before and without any gross discoloration were obtained and then were preserved in physiologic saline. 6 mm cylindrical tooth specimens were fabricated with diamond puncher perpendicularly on labial surface of bovine tooth. After embedded in transparent acrylic resin with labial surface being exposed, they were cut to a thickness of 1.2 mm with low speed diamond saw (Isomat, Buehler Co., Lake Bluff, IL, USA). They were smoothly ground to 1 mm thickness of enamel with sandpaper. 24 specimens were randomly divided into 3 groups and control group respectively. Opalescence (10% carbamide peroxide, Ultradent, South Jordan, USA), Rembrandt (10% carbamide peroxide, DenMat, USA) and Opalescence F (15% carbamide peroxide with fluoride, Ultradent, USA) were applied on labial sides of the bovine enamel for 7 days (bleaching agents were reapplied every 24 hours) and the opposite surface was contacted to cotton that soaked in distilled water. The control group was soaked in distilled water. Three stimulus value X, Y and Z were evaluated with colorimeter (Color ' Color Differencerneter, Model TC-6FX, Tokyo Denshoku Co., Japan) on the labial surface of all specimen three times on white and black background plate before the bleaching agents were applied and on 3rd, 5th and 7th day after applied. The degree of translucency was normally assessed by measuring the inverse property, opacity (contrast ratio). 10% Opalescence, 15% Opalescence-F, and control group showed no significant variation in the translucency of bovine enamel, However Rembrandt decreased the translucency of it (p < 0.01).

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.3
• /
• pp.213-220
• /
• 2000

The method of photoelasticity allows one to obtain principal stress differences and principal stress directions in a photoelastic model. In the classical approach, the photoelastic parameters are measured manually point by point. The previous methods require much time and skill in the identification and measurement of photoelastic data. Fringe phase shifting method has been recently developed and widely used to measure and analyze fringe data in photo-mechanics. This paper presents the test results of photoelastic fringe phase shifting technique for the stress analysis of a circular disk under compression and an edge-cracked plate subjected to tensile load. The technique used here requires four phase stepped photoelastic images obtained from a circular polariscope by rotating the analyzer at $0^{\circ}$, $45^{\circ}$, $90^{\circ}$ and $135^{\circ}$. Experimental results are compared with those or FEM. Good agreement between the results can be observed. However, some error may be included if the technique is used to general direction which is not parallel to isoclinic fringe.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.7
• /
• pp.25-36
• /
• 2008

The plane strain test can reproduce the real field condition and failure behavior precisely over other laboratory shear tests. Accordingly, this test has been utilized to investigate the shearing behaviors associated with overall failure behavior and local deformation of soils. However, most plane strain tests have been carried out with restrained end plates due to difficulties in manufacturing the equipment and also performing it. This restraint induces different results with real field because of shear stress on end plates. In this study, plane strain tests with/without bottom plate restraint were performed on Jumunjin-sand. The measurement of overall and local deformation was accomplished by digital image correlation technique as well as external LVDT. By applying digital image correlation method using two consecutive images captured through the transparent wall, local deformation behavior of various parts inside the specimen was estimated. And the formation and development of shear band caused by the restrained effect of end plate and the deformation mechanism of sand under plane strain condition were examined.

• Journal of Environmental Impact Assessment
• /
• v.28 no.4
• /
• pp.387-399
• /
• 2019

This research aimed to prepare the classification of the damage types and the damage rating system of noise barriers for expressway noise barriers and to develop deterioration evaluation method of noise barriers by reflecting them. The noise barrier consists of soundproof panels, foundations and posts and the soundproof panels with 10 different types of materials are used in a single or mixed form.In this paper, damage of soundproof panel shows a single or composite damage, and thus a evaluation model of deterioration has been developed for noise barriers that can reflect the characteristic of noise barriers. Materials used mainly for soundproof walls were divided into material types for metal, plastic, timber, transparent and concrete. And damage types for noise barrier were classified into corrosion, discoloration, deformation, spalling and dislocation and damage types were subdivided according to the noise barrier's components and materials. Damage rating was divided into good, minor, normal and severe for each major part of noise barrier to assess damage rating of soundproof panel, foundation and post. The deterioration degree of noise barrier was evaluated comprehensively by using the deterioration evaluation method of whole noise barrier using weighted average. Deterioration evaluation method that can be systematically assessed has been developed for noise barrier using single or mixed soundproof panel and noise barrier with single or complex damage types. Through such an evaluation system, it is deemed that the deterioration status of noise barrier installed can be systematically understood and utilized for efficient maintenance planning and implementation for repair and improvement of noise barriers.