• Title/Summary/Keyword: Aluminum and polymethyl methacrylate (PMMA)

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Composition Dependence and Optical Properties of Polymethyl Methacrylate/Alumina Nanocomposite in the IR Region Determined by Kramers-Kronig Relation

  • Ghamari, Misagh;Ghasemifard, Mahdi
    • Journal of the Korean Ceramic Society
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    • v.54 no.2
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    • pp.102-107
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    • 2017
  • The dependence of the IR optical properties of PMMA/$Al_2O_3$ nanocomposite on the alumina content was investigated in the wavelength range of $3500-2800cm^{-1}$. The samples were prepared via emulsion polymerization technique using oleic acid as a coupling agent. Grafting density calculations were carried out by means of elemental analysis CHN to yield the best coupling agent content. FTIR analysis confirmed the existence of a chemical bond between aluminum oxide and oleic acid. The outcomes of XRD analyses showed the presence of cubic gamma aluminum oxide in the nanocomposite, in contrast to the amorphous nature of PMMA. TEM images showed the core-shell morphology of the particles other than pristine PMMA. Optical constants of the nanocomposite were calculated based on FTIR spectra and the Kramers-Kronig equations. The presence of nano alumina modified some of the optical indexes in IR region.

Optimization Study of Digital X-ray Imaging with Dual Energy Subtraction Method (듀얼 에너지 감산기법을 이용한 디지털 X-ray 영상 최적화에 관한 연구)

  • Kim, Dae Ho;Lee, Yong-Gu;Lee, Youngjin
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.10
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    • pp.138-142
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    • 2016
  • Dual-energy digital radiography (DEDR) has been used for detecting lesions within the body using energy subtraction methods. The purpose of this study was to acquire optimal bone and tissue image by changing physical factors such as Tube voltage (kVp) and add filters, and then we compared with the predicted values using SRS-78 program and experimental results. For that purpose, we acquired images according to changes in physical parameters of various materials since we had to acquire the optimal bone and tissue image using energy subtraction. Used phantom consists of aluminum and polymethyl methacrylate (PMMA) and a comparison of image optimization was measured by contrast-to-noise ratio (CNR). In results, first of all, we confirmed that a subtraction image from 50 kVp image and 120 kVp image is optimal bone and tissue image. Also when we added a 10 mm Aluminum add filter, we expected it is a result of the optimal bone and tissue image. Besides, we confirmed these results are consistent with the predicted optimized condition by SRS-78 program.. In conclusion, we indicated that we can acquire optimal bone and tissue image by controling physical factors such as kVp, add filters through this study. Also we expected that DEDR will contribute to the field of medical imaging technology.

Comparative evaluation of shear bond strength of orthodontic brackets bonded to three-dimensionally-printed and milled materials after surface treatment and artificial aging

  • Ameer Biadsee;Ofir Rosner;Carol Khalil;Vanina Atanasova;Joel Blushtein;Shifra Levartovsky
    • The korean journal of orthodontics
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    • v.53 no.1
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    • pp.45-53
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    • 2023
  • Objective: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensionally (3D)-printed materials after various surface treatments and artificial aging compared with that bonded to computer-aided design/computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA)-milled materials. Methods: Eighty cylindrical specimens were 3D printed and divided into the following four subgroups (n = 20 each) according to the surface treatment and artificial aging procedure. Group A, sandblasted with 50 ㎛ aluminum oxide particles (SA) and aging; group B, sandblasted with 30 ㎛ silica-coated alumina particles (CO) and aging; group C, SA without aging; and group D, CO without aging. For the control group, 20 CAD-CAM PMMA-milled cylindrical specimens were sandblasted with SA and aged. The SBS was measured using a universal testing machine (0.25 mm/min), examined at ×2.5 magnification for failure mode classification, and statistically analyzed (p = 0.05). Results: The retention obtained with the 3D-printed materials (groups A-D) was higher than that obtained with the PMMA-milled materials (control group). However, no significant difference was found between the study and control groups, except for group C (SA without aging), which showed significantly higher retention than the control group (PMMA-SA and thermocycling) (p = 0.037). Study groups A-D predominantly exhibited a cohesive specimen mode, indicating specimen fracture. Conclusions: Orthodontic brackets bonded to 3D-printed materials exhibit acceptable bonding strengths. However, 3D-printed materials are prone to cohesive failure, which may result in crown fractures.

A Study on the Material Decomposition of Dual-Energy Iodine Image by Using the Multilayer X-ray Detector (다층구조 엑스선 검출기를 이용한 이중에너지 조영제 영상의 물질 구분에 관한 연구)

  • Kim, Jun-Woo
    • Journal of radiological science and technology
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    • v.44 no.5
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    • pp.465-471
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    • 2021
  • Dual-energy X-ray imaging (DEI) techniques can provide X-ray images that a certain material is suppressed or emphasized by combining two X-ray images obtained from two different x-ray spectrum. In this paper, a single-shot DEI, which uses stacked two detectors (i.e., multilayer detector), is proposed to reduce the patient dose and increase throughput in angiography. The polymethyl methacrylate (PMMA) and aluminum (Al) were selected as two basis materials for material decomposition, and material-specific images are reconstructed as a vector combination of these two materials. We investigate the contrast and noise performance of material-decomposed images using iodine phantoms with various concentrations and diameters. The single-shot DEI shows comparable performances to the conventional dual-shot DEI. In particular, the single-shot DEI shows edge enhancement in material-decomposed images due to the different spatial-resolution characteristics of upper and lower detectors. This study could be useful for designing the multilayer detector including scintillators and energy-separation filter for angiography purposes.

Effect of scattered x-rays on subject contrast and image sharpness

  • Arimura, Hidetaka;Date, Takuji;Morikawa, Kaoru;Kubota, Hideaki;Matsumoto, Masao;Kanamori, Hitoshi
    • Proceedings of the Korean Society of Medical Physics Conference
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    • 1999.11a
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    • pp.278-281
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    • 1999
  • The purpose of this study is to investigate the effect of the scattered x-rays on the subject contrast and image sharpness for various tube voltages. For the purpose, we measured the scatter-to-primary ratio(SPR) for the tube voltages f 50 to 100kV and obtained the tube voltage dependence of the subject contrast of an aluminum plate in a polymethyl methacrylate(PMMA) phantom. Furthermore, the overall modulation transfer functions(MTFs), which consist of MTFs of a screen-film system and scatter FTMs, were obtained for tube voltages of 50 to 100 kV. The subject contrast decreased with the tube voltage due to that the SPR increased with the tube voltage and that the difference in effective linear attenuation coefficients between the object and its surroundings decreased with the tube voltage. The maximum frequency of the overall MTF decreased from about 2 mm$\^$-1/ to 1 mm$\^$-1/ with the tube voltage increasing from 50 to 100 kV.

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