• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.43-54
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• 1999

The divergence connection between steel circular tubes is widely used in such structures as factory facilities, steel circular hollow section truss, and off-shore tower. Steel circular hollow section (SCHS) have close section, and it makes their per-unit production expense higher than open sectioned products like L-shape, H-shape steels, but the sectional resistance of SCHS against vertical compression and torsion is very high. Despite the structural merits of SCHS, however, many engineers dislike to use them in their design because of uncertainty regarding the stress distribution and deformation behavior at their connections. Therefore, this thesis dealt with X-type connections, the most common forms of connection, and studied their load-deformation relationship. It observed how to show the load-deformation relationship at steel circular tube connections according to the diameter-thickness ratio (D/T) of the chord and diameter of branch-diameter of chord ratio (d/D) and suggested prediction yield load using by ring analysis method.

• The Korean Journal of Applied Statistics
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• v.30 no.3
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• pp.487-501
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• 2017

A machine vision system (MVS) is a computer system that utilizes one or more image-capturing devices to provide image data for analysis and interpretation. Recently there have been a number of industrial- and medical-device applications where control charts have been proposed for use with image data. The use of image-based control charting is somewhat different from traditional control charting applications, and these differences can be attributed to several factors, such as the type of data monitored and how the control charts are applied. In this paper, we investigate the adjustment effect of image size and region of interest (ROI) size, when we use control charts to monitor grayscale image data in industry.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.49-49
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• 1999

리튬 이차 전지를 박막화함으로써 개발된 고상의 마이크로 박막전지는 임의의 크기 및 형태로의 제작이 가능하며 액체전해질을 사용하지 않기 때문에 작동 중 열 또는 기체 생성물이 생기지 않아 높은 안정성을 갖으며 광범위한 사용 온도 범위를 가진다. 위와 같은 장점으로 인하여 충전 가능한 고상의 박막형 리튬 이차 전지는 점진적으로 그 사용 범위가 크게 확대될 것으로 판단된다. 즉, 초소형 전자, 전기 소자는 물론이며 조만간 실현될 스마트 카드, 셀루러폰 및 PCS와 같은 개인용 휴대 통신장비의 전력 공급계로의 응용이 가능할 것이다. 특히 장수명, 고에너지 밀도를 갖는 초소형의 전지를 필요로 하는 microelectronics, MEMS등에 이용될 수 있는 이차전지에 대한 요구가 점점 가시화 됨에 따라 박막공정을 이용한 이차전지개발기술이 요구되고 있으며, 박막제조기술을 이용한 고상의 박막형 및 전지에 관한 연구가 증가하고 있다. 본 연구에서는 박막형 리튬 이차전지의 Cathode 물질로써 비정질의 산화바나듐 박막을 반응성 스퍼터링에 의하여 상온에서 증착하였다. 박막형 이차전지의 여러 가지 Cathode 물질중 산화바나듐은 다른 물질들과는 달리 비정질 형태로 매우 우수한 충방전 특성을 나타낸다. 이런 특성으로 인해 다소 전지자체의 성능은 낮지만 저전력 저전압을 필요로 하는 초소형 전자 소자와 혼성되어 이용할 수 있는 잠재성이 매우 높은 물질이다. 바나듐 타겟의 경우 타겟 표면의 ageing에 따라 증착되는 박막의 특성이 매우 달라지게 되므로 presputtering의 시간을 변화시키면서 실험하였다. 또한 스퍼터링 중의 산소의 분압도 타겟의 ageing에 많은 영향을 주므로 실험 변수로 산소분압을 변화시키면서 실험하였다. 증착된 산화바나듐 박막의 표면은 scanning electron microscopy로 분석하였으며 구조 분석은 X-선 회절분석, X-ray photoelectron spectroscopy 그리고Auger electron spectroscope로 하였다. 증착된 산화바나듐 박막의 전기화학적 특성을 분석하기 위하여 리튬 메탈을 anode로 하고 EC:DMC=1:1, 1M LiPF6 액체 전해질을 사용한 Half-Cell를 구성하여 200회 이상의 정전류 충 방전 시험을 행하였다. Half-Cell test 결과 박막의 결정성과 표면상태에 따라 매우 다른 전지 특성을 나타내었다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1573-1578
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• 2011

In this study, a novel electromagnetic microrobot system with locomotion and drilling functions in threedimensional space was developed. Because of size limitations, the microrobot does not have actuator, battery, and controller. Therefore, an electromagnetic actuation (EMA) system was used to drive the robot. The proposed EMA system consists of three rectangular Helmholtz coil pairs in x-, y- and z-axes and a Maxwell coil pair in the z-axis. The magnetic field generated in the EMA coil system could be controlled by the input current of the EMA coil. Finally, through various experiments, the locomotion and drilling performances of the proposed EMA microrobot system were verified.

• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.377-383
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• 2009

Aluminum-doped zinc oxide (AZO) thin films were deposited on sapphire substrate by using radio-frequency magnetron sputtering and were performed in the temperature range of $600-900^{\circ}C$ by rapid thermal annealing (RTA). The crystallographic structure and the surface morphology were investigated by using X-ray diffraction and scanning electron microscopy, respectively. The crystallinity of the films was improved with increasing the annealing temperature and the average size of crystalline grains was found to be 50 nm. All the thin films showed an average transmittance of 92% in the wavelength range of 400-1100 nm. As the annealing temperature was increased, the bandgap energy was decreased and the violet photoluminescence (PL) signal at 400 nm replaced the ultraviolet PL signal. The electrical properties of the thin films showed a significant dependence on the annealing temperature.

• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.267-272
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• 2007

Al-doped ZnO (AZO) thin films were grown on glass substrates by radio-frequency magnetron sputtering. The effects of oxygen flow ratio, which was used for a sputtering gas, on the AZO thin films were investigated by using the X-ray diffraction (XRD), atomic force microscopy (AFM), and Hall effects measurement. The AZO thin film, deposited with oxygen flow ratio of 0% at the growth temperature of $400^{\circ}C$, showed a strongly c-axis preferred orientation and the lowest resistivity of $6.9{\times}10^{-4}{\Omega}cm$. The ZnO (002) diffraction peak indicated a tendency to decrease substantially with increasing the oxygen flow ratio. Furthermore, as the oxygen flow ratio was decreased, the carrier concentration and the hall mobility were increased, but the electrical resistivity was decreased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.157-162
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• 2011

High temperature and stress are encounted in power plants and vehicle engines. Therefore, determination of the creep-fatigue life of a material is necessary prior to fabricating equipments. In this study, life design was determined on the basis of the lethargy coefficient for different temperatures, stress and rupture times. SP-Creep test data was compared with computed data. The SP-Creep test was performed to obtain the rupture time for X20CrMoV121 steel. The integration life equation was considered for three cases with various load, temperature and load-temperature. First, the lethargy coefficient was calculated by using the obtained rupture stress and the rupture time that were determined by carrying out the SP-Creep test. Next, life was predicted on the basis of the temperature condition. Finally, it was observed that life decreases considerably due to the coupling effect that results when fatigue and creep occur simultaneously.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.233-240
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• 2021

For the production of neodymium-doped zinc sulfide thin films in various amounts, zinc sulfide and neodymium were simultaneously deposited using an RF magnetron sputtering equipment to form a thin films, and rapid thermal annealing was performed at 400℃ for 30 minutes as a post-treatment process. The structure, shape, and optical properties of ZnS thin films having various neodymium doping contents (0.35at.%, 1.31at.%, 1.82at.% and 1.90at.%) were studied. The X-ray diffraction pattern was grown to a (111) cubic structure in all thin films. The surface and structural morphology of the thin films due to the neodymium doping content was explained through SEM and AFM images. Only elements of Zn, S, and Nd that do not contain other impurities were identified through EDAX. The transmittance and band gap of the prepared thin films were confirmed using the UV-vis spectrum.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.6
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• pp.329-334
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• 2003

Microstructure and mechanical properties of $(Ti_{1-x}Alx)N$ films, Produced by the the Ion Beam Sputtering(IBS) method, were studied by changing the Ti, Al contents. The compositions of films determined by RBS were $(Ti_{0.75}Al_{0.25})N$, $(Ti_{0.61}Al_{0.39})N$ and $(Ti_{0.5}Al_{0.5})N$, and XPS binding energies of Ti2P, A12p and N1s shifted to higher energies than those of pure Ti, Al and N, which indicated that nitrides were formed. XRD results indicated that the NaCl structure for $$x{\leq_-}0.39$$ changed into amorphous structure at x=0.5. For films with $$x{\leq_-}0.39$$, the lattice parameter decreased in proportion to the Al content. Nanoindentation hardness value were above HV=3300 at Al content up to x=0.39. However, the hardness of films with x=0.5 abruptly decreased to HV=1800, and this lower hardness values were attributed to different crystal structure. Critical load(Lc) in scratch test showed 23N at x=0.25, 22N at x=0.39 and 22N at x=0.5, which indicated that films with different Al contents showed similar adhesion behavior.

• Journal of the Korean Geotechnical Society
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• v.27 no.11
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• pp.93-101
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• 2011

High quality X-ray computed microtomography (micro-CT) imaging of internal microstructures and pore space in geomaterials is often hampered by some inherent noises embedded in the images. In this paper, we introduce image calibration techniques for removing the most common noises in X-ray micro-CT, cupping (brightness difference between the periphery and central regions) and ring artifacts (consecutive concentric circles emanating from the origin). The artifacts removal sequentially applies coordinate transformation, normalization, and low-pass filtering in 2D Fourier spectrum to raw CT-images. The applicability and performance of the techniques are showcased by describing extraction of 3D pore structures from micro-CT images of porous basalt using artifacts reductions, binarization, and volume stacking. Comparisions between calibrated and raw images indicate that the artifacts removal allows us to avoid the overestimation of porosity of imaged materials, and proper calibration of the artifacts plays a crucial role in using X-ray CT for geomaterials.