• Title/Summary/Keyword: Three Cavities

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Crystal Structure of a Benzene Sorption Complex of Dehydrated Fully $Cd^{2+}$-Exchanged Zeolite X

  • 김양;염영훈;최은영;김안나;한영욱
    • Bulletin of the Korean Chemical Society
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    • v.19 no.11
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    • pp.1222-1227
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    • 1998
  • The crystal structure of a benzene sorption complex of fully dehydrated Cd2+-exchanged zeolite X, Cd46Si100Al92O384·43C6H6 (a=24.880(6) Å), has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21 ℃. The crystal was prepared by ion exchange in a flowing stream of 0.05 M aqueous Cd(NO3)2 for 3 d, followed by dehydration at 400 ℃ and 2 x 10-6 Torr for 2 d, followed by exposure to about 92 Torr of benzene vapor at 22 ℃. The structure was determined in this atmosphere and refined to the final error indices R1=0.054 and Rw=0.066 with 561 reflections for which I > 3σ(I). In this structure, Cd2+ ions are found at four crystallographic sites: eleven Cd2+ ions are at site 1, at the centers of the double six-oxygen rings; six Cd2+ ions lie at site I', in the sodalite cavity opposite to the double six-oxygen rings; and the remaining 29 Cd2+ ions are found at two nonequivalent threefold axes of unit cell, sites Ⅱ' (in the sodalite cavity ) and site Ⅱ (in the supercage) with occupancies of 2 and 27 ions, respectively. Each of these Cd2+ ions coordinates to three framework oxylkens, either at 2.173(13) or 2.224(10) Å, respectively, and extends 0.37 Å into the sodalite unit or 0.60 Å into the supercage from the plane of the three oxygens to which it is bound. The benzene molecules are found at two distinct sites within the supercages. Twenty-seven benzenes lie on threefold axes in the large cavities where they interact facially with the latter 27 site-Ⅱ Cd2+ ions (Cd2+-benzene center=2.72 Å; occupancy=27 molecules/32 sites). The remaining sixteen benzene molecules are found in 12ring planes; occupancy=16 molecules/16 sites. Each hydrogen of these sixteen benzenes is ca. 2.8/3.0 Å from three 12-ring oxygens where each is stabilized by multiple weak electrostatic and van der Waals interactions with framework oxygens.

Color Stability and Surface Roughness of Single-Shade Composite Resin after Finishing and Polishing

  • Hyewon Shin;Haeni Kim;Minho Hong;Juhyun Lee
    • Journal of the korean academy of Pediatric Dentistry
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    • v.51 no.3
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    • pp.197-207
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    • 2024
  • This study aims to evaluate the color stability and surface roughness of the single-shade composite resin after finishing and polishing for primary molars. A single-shade composite resin (OM, OMNICHROMA) and two multi-shade composite resins (FT, FiltekTM Z350XT; ES, ESTELITE® SIGMA QUICK) were included. The specimens were divided into three subgroups using different polishing methods: control, Sof-Lex XT, and Sof-Lex Diamond. For color stability tests, cavities were prepared on extracted primary second molars and restored with experimental composite resins. Each specimen was immersed in the coffee solution for 48 hours. The color difference of each specimen was calculated. For surface roughness tests, cylindrical specimens were crafted with experimental composite resins. Surface roughness was analyzed using an atomic force microscope and a scanning electron microscope. In the color stability tests, FT demonstrated a significantly lower ΔEab than ES among the control groups, but no significant differences were observed between the ΔEab values of OM and FT or OM and ES. Additionally, no significant differences were found between the Sof-Lex XT and Sof-Lex Diamond subgroups in the three composite groups. Moreover, no significant differences in the surface roughness were found between the three composite groups, regardless of the polishing methods. The single-shade composite resin demonstrated comparable color stability and surface roughness to that of the multi-shade composite resins regardless of the polishing methods used in restoring primary molars. The single-shade composite resin is expected to be applicable in clinical pediatric dentistry reducing chair time due to the easy shade matching procedures.

Estimation of Creep Cavities Using Neural Network and Progressive Damage Modeling (신경회로망과 점진적 손상 모델링을 이용한 크리프 기공의 평가)

  • Jo, Seok-Je;Jeong, Hyeon-Jo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.2 s.173
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    • pp.455-463
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    • 2000
  • In order to develop nondestructive techniques for the quantitative estimation of creep damage a series of crept copper samples were prepared and their ultrasonic velocities were measured. Velocities measured in three directions with respect to the loading axis decreased nonlinearly and their anisotropy increased as a function of creep-induced porosity. A progressive damage model was described to explain the void-velocity relationship, including the anisotropy. The comparison of modeling study showed that the creep voids evolved from sphere toward flat oblate spheroid with its minor axis aligned along the stress direction. This model allowed us to determine the average aspect ratio of voids for a given porosity content. A novel technique, the back propagation neural network (BPNN), was applied for estimating the porosity content due to the creep damage. The measured velocities were used to train the BP classifier, and its accuracy was tested on another set of creep samples containing 0 to 0.7 % void content. When the void aspect ratio was used as input parameter together with the velocity data, the NN algorithm provided much better estimation of void content.

AN EXPERIMENTAL STUDY ON THE MEASUREMENT OF MARGINAL LEAKAGE USING A NEUTRON ACTIVATION ANALYSIS (Neutron Activation Analysis를 이용한 Composite Resin의 변연누출 측정에 관한 실험적 연구)

  • Kim, Mi-Ja;Lee, Myung-Jong
    • Restorative Dentistry and Endodontics
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    • v.13 no.1
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    • pp.185-190
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    • 1988
  • The study was designed to establish quantitative method for assessing the marginal leakage of dental restorations. 18 Class V cavities with $45^{\circ}$ bevel joint were prepared and replicas of these teeth were made with polyethylene wax. and classified with three groups. First group was filled with Scotch bond and silux. Second group was filled with glass ionomer cement:scotchbond/silux. Third group was filled with Dentin-Adhesit/Heliosit. After finishing, all specimens were subjected manually to 100 thermal cycles at $0^{\circ}C$ and $100^{\circ}C$ Samarium nitrate solution, irradiated with flux of $6{\times}12^{12}$ neutrons/$cm^2$/sec for 11 hours, woled for 200 hours, counted with the HpGe detector and the tracer uptake was determined by comparison with a standard of samarium ($10{\mu}g$). The following results were obtained. 1) The group filled with glass ionomer cement base showed least marginal leakage. 2) The group filled with Dentin-Adhesit/Heliosit showed less marginal leakage than the group filled with scotchbond/silux.

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Cavity and Interface effect of PI-Film on Charge Accumulation and PD Activity under Bipolar Pulse Voltage

  • Akram, Shakeel;Wu, Guangning;Gao, GuoQiang;Liu, Yang
    • Journal of Electrical Engineering and Technology
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    • v.10 no.5
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    • pp.2089-2098
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    • 2015
  • With the continuous development in insulation of electrical equipment design, the reliability of the system has been enhanced. However, in the manufacturing process and during operation under continues stresses introduce local defects, such as voids between interfaces that can responsible to occurrence of partial discharge (PD), electric field distortion and accumulation of charges. These defects may lead to localize corrosion and material degradation of insulation system, and a serious threat to the equipment. A model of three layers of PI film with air gap is presented to understand the influence of interface and voids on exploitation conditions such as strong electrical field, PD activity and charge movement. The analytical analysis, and experimental results are good agreement and show that the lose contact between interfaces accumulate more residual charges and in consequences increase the electric field intensity and accelerates internal discharges. These residual charges are trapped charges, injected by the electrodes has often same polarity, so the electric field in cavities increases significantly and thus partial discharge inception voltage (PDIV) decreases. Contrary, number of PD discharge quantity increases due to interface. Interfacial polarization effect has opposite impact on electric field and PDIV as compare to void.

Case Stories of Microgravity Survey for Shallow Subsurface Investigation (고정밀 중력탐사를 이용한 천부 지질구조 조사 사례)

  • Park Yeong-Sue;Rim Hyoungrae;Lim Mutaek;Koo Sung Bon;Kim Hag Soo;Oh Seok Hoon
    • 한국지구물리탐사학회:학술대회논문집
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    • 2005.05a
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    • pp.181-186
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    • 2005
  • Gravity method produces subsurface density distribution, which is direct information of soundness of basement. Therefore, microgravity is one of the most effective method for detections of limestone cavities, abandoned mine-shafts and other tunnels, The paper show the effectiveness of microgravity by three different field cases.

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Numerical Simulation of Micro-Fluidic Flows of the Inkjet Printing Deposition Process for Microfabrication

  • Chau S.W.;Chen S.C.;Liou T.M.;Hsu K.L.;Shih K.C.;Lin Y.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2003.10a
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    • pp.113-115
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    • 2003
  • Droplet impinging into a cavity at micro-scale is one of important fluidic issues for microfabrications, e.g. bio-chip applications and inkjet deposition processes in the PLED panel manufacturing. The droplets generally dispensing from an inkjet head, which contains an array of nozzles, have a volume in several picoliters, while each nozzle jets the droplets into cavities with micron-meter size located on substrates. Due to measurement difficulties at micro-scale, the numerical simulation could serve as an efficient and preliminary way to evaluate the micro-sized droplet impinging behavior into a cavity. The micro-fluidic flow is computed by solving the three-dimensional Navier-Stokes equations through a finite volume discretization. The droplet front is predicted by a volume-of-fluid approach, in which the surface tension is modeled as a function of the fluid concentration. This paper discusses the influence of fluid properties, such as surface tension and fluid viscosity, on micro-fluidic characteristics at different jetting speeds in the deposition process via the proposed numerical approach.

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An Optimal Restoration Method of Noncarious Cervical Lesions Using Three-Dimensional Finite Element Analysis (3차원 유한요소해석을 이용한 비우식성 치아의 수복 방법)

  • Woo, Sung-Gwan;Kim, Kwang-Hoon;Park, Jeong-Kil;Hur, Bock;Son, Kwon
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.7 s.196
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    • pp.112-119
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    • 2007
  • Cavities of Class V are caused by heavy occlusal loads due to bruxism and clenching habit. It is general to restore abfraction lesions with dental filler materials to reduce stress concentration. A material should be selected from various dental products based on long term clinical experiences or personal preference concerning filler methods. A quantitative criterion is necessary to make an evaluation of the results as dentists decide treatment methods and dental materials relying on their clinical experiences. The purpose of this study is to find an optimal restoration method and material for noncarious cervical lesions using the finite element method. An objective function was defined to minimize the sum of tensile and compressive stresses. Several models with different combinations of resins were suggested and compared in terms of the values of objective function. An optimal solution was to fill TetricFlow inside the lesion and Z100 in the remaining region with a thickness ratio of 0.125.

A Case Study of Developing a Subsurface Information and Visualization System Using ArcView (ArcView를 이용한 지하 정보 및 시각화 시스템 구축 사례 연구)

  • Kim, Hyeon-Gyu;Lee, Doo-Sung
    • Geophysics and Geophysical Exploration
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    • v.4 no.4
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    • pp.101-109
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    • 2001
  • In order to develop a spatial information system that can efficiently manage various subsurface data and produce information in a proper form for a user, we established a database of the well cores and built 3-D shapes that visualize the subsurface objects such as wells, ore bodies, tunnels, and mine cavities. We also made analysis tools available for three-dimensional ore bodies constructed here, such as vertical cross-section generator and mass computing tool. This system was developed by coding Avenue, a scripting language incorporated in ArcView, which is a commercial GIS software. Using the system, it is expected that users can make fast and accurate analysis and interpretation through real-time queries and by contemplating various objects in 3-D perspective.

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Microstructure of Cured Urea-Formaldehyde Resins Modified by Rubber Latex Emulsion after Hydrolytic Degradation

  • Nuryawan, Arif;Park, Byung-Dae
    • Journal of the Korean Wood Science and Technology
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    • v.42 no.5
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    • pp.605-614
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    • 2014
  • This study investigated microstructural changes of cured urea-formaldehyde (UF) resins mixed with aqueous rubber latex emulsion after intentional acid etching. Transmission electron microscopy (TEM) was used in order to better understand a hydrolytic degradation process of cured UF resins responsible for the formaldehyde emission from wood-based composite panels. A liquid UF resin with a formaldehyde to urea (F/U) molar ratio 1.0 was mixed with a rubber latex emulsion at three different mixing mass ratios (UF resin to latex = 30:70, 50:50, and 70:30). The rate of curing of the liquid modified UF resins decreased with an increase of the rubber latex proportion as determined by differential scanning calorimetry (DSC) measurement. Ultrathin sections of modified and cured UF resin films were exposed to hydrochloric acid etching in order to mimic a certain hydrolytic degradation. TEM observation showed spherical particles and various cavities in the cured UF resins after the acid etching, indicating that the acid etching had hydrolytically degraded some part of the cured UF resin by acid hydrolysis, also showing spherical particles of cured UF resin dispersed in the latex matrix. These results suggested that spherical structures of cured UF resin might play an important role in hindering the hydrolysis degradation of cured UF resin.