• Advances in aircraft and spacecraft science
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• v.4 no.6
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• pp.679-699
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• 2017

The aim of this study is to perform a finite element analysis of the Von Mises stresses distribution in the adhesive layer and of the J-Integral for a damaged plate repaired by a composite patch. Firstly, we study the effect of the fiber orientation, especially the position of the layers that have orientation angle different of $0^{\circ}$ from the first layer which is in all cases of our study oriented at ($0^{\circ}$) on the J-Integral. Secondly, we evaluate the effects of the mechanical properties of the patch and the use of a hybrid patch on the reduction of stresses distribution and J-Integral. The results show clearly that the stacking sequence for the composite patch must be selected to absorb optimally the stresses from the damaged area and to position the various layers of the composite under the first layer whose fibers orientation will remain in all cases equal to $0^{\circ}$. The use of a hybrid composite reduces significantly the J-Integral and the stresses in both damaged plate and the adhesive layer.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.51.2-51.2
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• 2011

A novel electrospun nanofiber membrane was fabricated using combined poly (vinylphosphonic acid) (PVPA) and polyvinyl alcohol (PVA) intended for bone tissue engineering applications. PVPA is a proton-conducting polymer used as primer for bone implants and dental cements to prevent corrosion and brush abrasion. The phosphonate groups of PVPA have the ability to crosslink and attach itself to the hydroxyapatite surface facilitating faster integration of the biomaterial to the bone matrix. PVA was combined with PVPA to provide hydrophilicity, biocompatibility and improve its spinnability. To improve its mechanical strength, PVPA/PVA and neat PVA mixtures were combined to produce a multilayer scaffold. The physical and chemical properties of the of the fabricated matrix was investigated by SEM and TEM morphological analyses, tensile strength test, XRD, FT-IR spectra, swelling behavior and biodegradation rates, porosity and contact angle measurements. Biocompatibility was also examined in vitro by cytotoxicity and cell proliferation studies with MTT assay and cell adhesion behavior by SEM and confocal microscopy.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.233-240
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• 1994

We have investigated how the magneto-optical and recording properties of Pt/Co modulated films vary with sample preparation conditions : sputtering at various gas pressures, sputtering with Xe instead of Ar, and etching the buffer layers, etc. The magneto-optical characteristics of Pt/Co multilayers was comparable with those of currently prevailing rare-earth transition-metal alloys(Tb-Fe-Co amorphous films). On a disk of $12{\times}[Pt10.7\;{\AA}/Co2.8{\;}{\AA}]$ multilayer enhanced with 70nm silicon nitride, we have achieved a CNR of 36dB with a reading laser(${\lambda}\;=\;780nm$) power of 2.5-4.5mW for 720KHz carrier at 1.4m/s and the enhanced kerr rotation angle of $1.23^{\circ}$ at 780nm. It is suggested that Pt/Co modulated films clearly are very promising magneto-optical materials for a commercially use.

• Journal of information and communication convergence engineering
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• v.2 no.2
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• pp.110-115
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• 2004

The prosthesis of current commercialized apparatus has considerable problems, requiring improvement. Especially, LLP(Lower Limb Prosthesis)-related problems have improved, but it cannot provide normal walking because, mainly, the gait control of the LLP does not fit with patient's gait manner. To solve this problem, HCI((Human Computer Interaction) that adapts and controls LLP postures according to patient's gait manner more effectively is studied in this research. The proposed control technique has 2 steps： 1) the multilayer neural network forecasts angles of gait of LLP by using the angle of normal side of lower limbs； and 2) the adaptive neural controller manages the postures of the LLP based on the predicted joint angles. According to the experiment data, the prediction error of hip angles was 0.32［deg.］, and the predicted error of knee angles was 0.12［deg.] for the estimated posture angles for the LLP. The performance data was obtained by applying the reference inputs of the LLP controller while walking. Accordingly, the control performance of the hip prosthesis improved by 80% due to the control postures of the LLP using the reference input when comparing with LQR controller.

• Macromolecular Research
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• v.10 no.1
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• pp.2-12
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• 2002

The small-angle X-ray scattering (SAXS) beamline BL4C1 at the 2.5 GeV storage ring of the Pohang Accelerator Laboratory (PAL) has been in its first you of operation since August 2000. During this first stage it could meet the basic requirements of the rapidly growing domestic SAXS user community, which has been carrying out measurements mainly on various polymer systems. The X-ray source is a bending magnet which produces white radiation with a critical energy of 5.5 keV. A synthetic double multilayer monochromator selects quasi-monochromatic radiation with a bandwidth of ca. 1.5%. This relatively low degree of monochromatization is sufficient for most SAXS measurements and allows a considerably higher flux at the sample as compared to monochromators using single crystals. Higher harmonics from the monochromator are rejected by reflection from a flat mirror, and a slit system is installed for collimation. A charge-coupled device (CCD) system, two one-dimensional photodiode arrays (PDA) and imaging plates (IP) are available its detectors. The overall performance of the beamline optics and of the detector systems has been checked using various standard samples. While the CCD and PDA detectors are well-suited for diffraction measurements, they give unsatisfactory data from weakly scattering samples, due to their high intrinsic noise. By using the IP system smooth scattering curves could be obtained in a wide dynamic range. In the second stage, stating from August 2001, the beamline will be upgraded with additional slits, focusing optics and gas-filled proportional detectors.

• Macromolecular Research
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• v.16 no.7
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• pp.575-585
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• 2008

There are two beamlines (BLs), 4C1 and 4C2, at the Pohang Accelerator Laboratory that are dedicated to small angle X-ray scattering (SAXS). The 4C1 BL was constructed in early 2000 and is open to public users, including both domestic and foreign researchers. In 2003, construction of the second SAXS BL, 4C2, was complete and commissioning and user support were started. The 4C2 BL uses the same bending magnet as its light source as the 4C1 BL. The 4C1 BL uses a synthetic double multilayer monochromator, whereas the 4C2 BL uses a Si(111) double crystal monochromator for both small angle and wide angle X-ray scattering. In the 4C2 BL, the collimating mirror is positioned behind the monochromator in order to enhance the beam flux and energy resolution. A toroidal focusing mirror is positioned in front of the monochromator to increase the beam flux and eliminate higher harmonics. The 4C2 BL also contains a digital cooled charge coupled detector, which has a wide dynamic range and good sensitivity to weak scattering, thereby making it suitable for a range of SAXS and wide angle X-ray scattering experiments. The general performance of the 4C2 BL was initially tested using standard samples and further confirmed by the experience of users during three years of operation. In addition, several grazing incidence X-ray scattering measurements were carried out at the 4C2 BL.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.03a
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• pp.61-61
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• 2011

지구 온난화로 인해 환경파괴, 병원성 세균 감염 등에 의한 각종 질병과 아토피 피부염 등 수없이 많은 요소들에서 우리 몸을 보호하기 위하여 친환경 소재의 용품들이 각광 받고 있다. 이중에서도 키토산과 칼슘알지네이트는 천연재료로써 이미 다른 분야에서 응용되어 사용되고 있으며, 이 두 가지 천연재료를 두 층으로 면섬유에 코팅시킨 CCAC섬유를 제조하였다. CCAC섬유와 키토산이 코팅된 면섬유, 칼슘알지네이트가 코팅된 면섬유, 미처리 면섬유의 총 4가지 섬유에 체액, 증류수, 생리식염수의 각각의 조건에서 흡습량, 흡습시간을 측정하여 비교하고, 수분율과 함수율을 측정하고, 접촉각을 Contact angle system OCA20을 이용하여 측정하였다. CCAC섬유의 키토산 부착 함량을 알아보기 위하여 정량적인 방법으로 add-on율을 이용하여 확인하고, 정성적인 방법으로 원소분석기(Elemental Analyzer, FLASH 1112)를 이용하여 측정하였다. 칼슘알지네이트의 함량 분석은 EDS(EX-250, HORIBA, Japan)를 이용하여 측정하고, 직물의 표면과 단면의 형태는 주사전자현미경(S-4100, Hitachi Co., Japan)으로 ${\times}100$, ${\times}1000$ 배율로 측정하여 단면과 표면 상태를 확인하고, 물리적인 특성은 KES-FB system 을 통하여 확인 하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1323-1329
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• 2015

The WO₃/Ag/WO₃ transparent thin films are fabricated by the RF magnetron sputtering. This has a transmittance of front and rear about 90% in the visible light range and surface resistance of 6.41Ω/□. In this paper, we analyzed the surface characteristics caused by the working pressure and O₂ plasma surface treatment to apply a transparent electrode that was prepared to the laminated structure with other materials. The working pressure was changed in the WO₃ film to 10mTorr, 7mTorr, and 5mTorr, it showed a lower than roughness of conventional ITO. In addition, by 55.5774 J/m² at 5mTorr, it shows the hydrophobic property with lower process pressure. O₂ plasma surface treatment was changed at the condisions of the RF power to 150W, 100W, and 50W and the process time to 240s, 180s, 120s, and 60s. The surface roughness are the maximum roughness(Rmax) 6.437nm and the average roughness(Rq) 0.827nm at RF power 150W, and the maximum roughness (Rmax) 6.880nm and the average roughness (Rq) 0.839nm at process time 240sec. It showed a lower value than the surface treatment. also about working pressure and process time is increased, it showed the hydrophobic.

• Journal of the Korean Magnetics Society
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• v.6 no.4
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• pp.235-241
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• 1996

Co/Pd and Co/Pt multilayered thin films for perpendicular magnetic recording media were fabricated by sput¬tering method and the effects of the sputtering pressure during the formation of Pd or Pt underlayers on the magnetization behavior and coercivity of the multilayers were investigated. It was found that the coercivity of Co/Pd multilayers was strongly dependent on the sputtering pressure of underlayer and could be enhanced to a large extent merely by increasing the sputtering pressure of underlayer, while in case of Co/Pt films, the degree of coercivity enhancement by controlling the sputtering pressure of underlayer was almost negligible. Coercivity variation of Co/Pd and Co/Pt multilayers with the underlayer material and deposition pressure of underlayer could be well explained in terms of the interface roughness of multilayer films induced by underlayer topology, which could also be correlated to the change of perpendicular anisotropy energy and magnetic reversal feature with the sputtering pressure of underlayer. Kerr rotation angle was hardly affected by the preparation conditions of underlayers.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.531-538
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• 2004

Studies of adsorption isotherms with sharp step-wise layer condensation help us to better understanding of two dimensional layers. For this, an adsorption isotherm apparatus, using a phase modulated ellipsometric technique, has been constructed and an adsorption experiment has been performed. With subatomic scale resolution(∼0.3 $\AA$), the adsorption processes could be observed by ellipsometric signals. On measurement of multilayer adsorption of argon on highly oriented pyrolytic graphite(HOPG), thousands of adsorbed layers were observed at 34.04 K, which suggests that the adsorption is completely wet. On the contrary nine sharp layers of steps for adsorptions and desorptions were observed at 67.05 K. These isotherms obtained can provide a lot of information about thermodynamic states, bonding energies between adsobate and substrate, and structure transitions in the adsorbed film.