• 제목/요약/키워드: Scanning Electron Microscope

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유한요소법을 사용한 주사전자 현미경의 전자렌즈 설계 및 해석에 관한 연구 (A Study on Design and Analysis for Magnetic Lenses of a Scanning Electron Microscope using Finite Element Method)

  • 박근;정현우;박만진;김동환;장동영
    • 한국정밀공학회지
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    • 제24권9호
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    • pp.95-102
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    • 2007
  • The scanning electron microscope (SEM) is one of the most popular instruments available for the measurement and analysis of the micro/nano structures. It is equipped with an electron optical system that consists of an electron beam source, magnetic lenses, apertures, deflection coils, and a detector. The magnetic lenses playa role in refracting electron beams to obtain a focused spot using the magnetic field driven by an electric current from a coil. A SEM column usually contains two condenser lenses and an objective lens. The condenser lenses generate a magnetic field that forces the electron beams to form crossovers at desired locations. The objective lens then focuses the electron beams on the specimen. The present work concerns finite element analysis for the electron magnetic lenses so as to analyze their magnetic characteristics. To improve the performance of the magnetic lenses, the effect of the excitation current and pole-piece design on the amount of resulting magnetic fields and their peak locations are analyzed through the finite element analysis.

수치해석을 통한 SEM 챔버내의 이차전자 거동해석 및 이차전자 검출기의 최적 장착 위치 선정 (The Behavior of Secondary Electrons and Optimal Mounting Position of a Secondary Electron Detector in SEM with a Numerical Analysis)

  • 부경석;전종업
    • 한국공작기계학회논문집
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    • 제17권4호
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    • pp.15-21
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    • 2008
  • Secondary electron detectors used in scanning electron microscope accept secondary electrons emitted from the specimen and convert them to an electrical signal that, after amplification, is used to modulate the gray-level intensities on a cathode ray tube, producing an image of the specimen. In order to acquire images with good qualities, as many secondary electrons as possible should be reached to the detector. To realize this it is very important to select an appropriate mounting position and angle of the detector inside the chamber of scanning electron microscope. In this paper, a number of numerical simulations are performed to explore the relationships between detection rates of secondary electrons and the values of some parameters, such as distances between the detector and sample, relative mounting positions of scintillator positioned inside the detector with respect to detector cover, two types of mounting angles of the detector. The relationships between detection rates and applied voltages to corona ring and faraday cage, and energies of secondary electrons are investigated as well.

Performance evaluation of METAMIC neutron absorber in spent fuel storage rack

  • Kim, Kiyoung;Chung, Sunghwan;Hong, Junhee
    • Nuclear Engineering and Technology
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    • 제50권5호
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    • pp.788-793
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    • 2018
  • High-density spent fuel (SF) storage racks have been installed to increase SF pool capacity. In these SF racks, neutron absorber materials were placed between fuel assemblies allowing the storage of fuel assemblies in close proximity to one another. The purpose of the neutron absorber materials is to preclude neutronic coupling between adjacent fuel assemblies and to maintain the fuel in a subcritical storage condition. METAMIC neutron absorber has been used in high-density storage racks. But, neutron absorber materials can be subject to severe conditions including long-term exposure to gamma radiation and neutron radiation. Recently, some of them have experienced degradation, such as white spots on the surface. Under these conditions, the material must continue to serve its intended function of absorbing neutrons. For the first time in Korea, this article uses a neutron attenuation test to examine the performance of METAMIC surveillance coupons. Also, scanning electron microscope analysis was carried out to verify the white spots that were detected on the surface of METAMIC. In the neutron attenuation test, there was no significant sign of boron loss in most of the METAMIC coupons, but the coupon with white spots had relatively less B-10 content than the others. In the scanning electron microscope analysis, corrosion material was detected in all METAMIC coupons. Especially, it was confirmed that the coupon with white spots contains much more corrosion material than the others.

유한요소해석과 광선추적을 연계한 주사전자 현미경 대물렌즈의 설계 및 해석 (Design and Analysis of an Objective Lens for a Scanning Electron Microscope by Coupling FE Analysis and Ray Tracing)

  • 박근;이재진;박만진;김동환;장동영
    • 한국정밀공학회지
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    • 제26권11호
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    • pp.92-98
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    • 2009
  • The scanning electron microscope (SEM) contains an electron optical system in which electrons are emitted and moved to form a focused beam, and generates secondary electrons from the specimen surfaces, eventually making an image. The electron optical system usually contains two condenser lenses and an objective lens. The condenser lenses generate a magnetic field that forces the electron beams to form crossovers at desired locations. The objective lens then focuses the electron beams on the specimen. The present study covers the design and analysis of an objective lens for a thermionic SEM. A finite element (FE) analysis for the objective lens is performed to analyze its magnetic characteristics for various lens designs. Relevant beam trajectories are also investigated by tracing the ray path of the electron beams under the magnetic fields inside the objective lens.

Comparative scanning electron microscope analysis of the enamel of permanent human, bovine and porcine teeth

  • Olek, Aneta;Klimek, Leszek;Boltacz-Rzepkowska, Elzbieta
    • Journal of Veterinary Science
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    • 제21권6호
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    • pp.83.1-83.14
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    • 2020
  • Background: Bovine and porcine teeth are often used in in vitro experiments as substitutes of human teeth. Objectives: The aim of the present study was to perform a comparative analysis of enamel morphology of permanent human, bovine and porcine teeth under the scanning electron microscope. Methods: As many as 10 human, 10 bovine, and 10 porcine teeth were studied. All the teeth were sectioned and the halves were randomly divided into 2 groups according to the examined tissue (vestibular enamel at the mid-height of the dental crown and in the cervical area). Human and bovine enamel was etched for 15 sec and porcine enamel for 30 sec. The scanning electron microscope analysis was performed. The length and width of enamel prisms were determined with the "Met-Ilo" 1.1 computer program. Results: All enamel samples revealed the same etching pattern-Silverstone's type 2. Bovine enamel showed a similar porosity and the amount of interprismatic enamel compared to human enamel while the amount and width of interprismatic enamel bands in porcine enamel were evidently greater. The shape of the porcine prisms was visually similar to human prisms, although dimensions were significantly different. However, bovine prisms differed in form and appeared to be distinctly elongated. Conclusions: Reported findings indicate that the results of experimental studies carried out on bovine and porcine enamel should not be compared with the results obtained on human enamel.

Suppression of Melanose Caused by Diaporthe citri on Citrus Leaves Pretreated with Bio-sulfur

  • Shin, Yong Ho;Ko, Eun Ju;Kim, Su Jeong;Hyun, He Nam;Jeun, Yong Chull
    • The Plant Pathology Journal
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    • 제35권5호
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    • pp.417-424
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    • 2019
  • Melanose, caused by Diaporthe citri, is one of severe diseases in citrus, a major economic resource in Jeju island. To reduce the usage amount of organic synthetic fungicide, bio-sulfur was tested as an alternative chemical to control citrus melanose in the present study. Direct antifungal activity of bio-sulfur against D. citri was determined through in vitro experiment using artificial nutrient media. Disease severity of melanose on bio-sulfur pretreated citrus leaves was lower than that on untreated ones. To illustrate the mechanism of disease suppression by bio-sulfur, infection structures were observed with a fluorescent microscope and a scanning electron microscope. In fluorescent microscopic observation, most conidia rarely germinated. In addition, hyphal growth on leaves pretreated with bio-sulfur was inhibited compared to that on untreated ones. In scanning electron microscope images of bio-sulfur pretreated leaves, surfaces of most conidia were shrunk while hyphae were morphologically changed and frequently branched. Such microscopic observations were also found for leaves pretreated with a commercial fungicide Dithianon. These results suggest that bio-sulfur may be used to control citrus melanose as an environment friendly alternative to organic synthetic fungicides

엘라스토머 TPV의 사출성형조건에 따른 기계적 물성 (Mechanical Properties of Elastomer TPVs due to Injection Molding Conditions)

  • 한성렬;정영득
    • 한국기계가공학회지
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    • 제5권1호
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    • pp.27-32
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    • 2006
  • Thermoplastic elastomer(TPE) has many advantages such as high flexibility, high elasticity and high elongation, etc. TPE is easily molded as plastic materials, therefore, many TPE parts are applied as home appliances and mechanical parts. However, its mechanical properties would be changed by injection molding conditions such as melt temperature, mold temperature, injection pressure and holding pressure, etc. In this study, the influences of the injection molding condition on the mechanical properties as tensile strength, hardness of thermoplastic vulcanizates(TPVs), which is one of the TPE, were investigated. By the injection molding experiment, the molding's tensile strength and hardness was influenced on the melt temperature and composition ratio of PP and EPDM. The morphology of moldings were shown by the scanning electron microscope.

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