• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.79-80
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• 2009

The local oxidation using an atomic force microscopy (AFM) is useful for Si-base fabrication of nanoscale structures and devices. SiC is a wide band-gap material that has advantages such as high-power, high-temperature and high-frequency in applications, and among several SiC poly types, 4H-SiC is the most attractive poly type due to the high electron mobility. However, the AFM local oxidation of 4H-SiC for fabrication is still difficult, mainly due to the physical hardness and chemical inactivity of SiC. In this paper, we investigated the local oxidation of 4H-SiC surface using an AFM. We fabricated oxide patterns using a contact mode AFM with a Pt/Ir-coated Si tip (N-type, $0.01{\sim}0.025\;{\Omega}cm$) at room temperature, and the relative humidity ranged from 40 to 50%. The height of the fabricated oxide pattern ($1{\sim}3\;nm$) on SiC is similar to that of typically obtained on Si ($10^{15}{\sim}10^{17}\;cm^{-3}$). We perform the 2-D simulation to further analyze the electric field between the tip and the surface. Whereas the simulated electric field on Si surface is constant ($5\;{\times}\;10^7\;V/m$), the electric field on SiC surface increases with increasing the doping concentration from ${\sim}10^{15}$ to ${\sim}10^{17}\;cm^{-3}$. We demonstrated that a specific electric field ($4\;{\times}\;10^7\;V/m$) and a doping concentration (${\sim}10^{17}\;cm^{-3}$) is sufficient to switch on/off the growth of the local oxide on SiC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.439-444
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• 2012

For the application of photo-detector as active layer, we have studied how to deposit SiGe thin film using an independent Si target and Ge target, respectively. Both targets were synthesized by purity of 99.999%. Plasma generators were generated by radio frequency (rf, 13.56 MHz) and direct current (dc) power. When Ge and Si targets were sputtered by dc and rf power, respectively, we could observe the growth of highly crystalline Ge thin film at the temperature of $400^{\circ}C$ from the result of raman spectroscopy and X-ray diffraction method. However, SiGe thin film did not deposit above method. Inversely, we changed target position like that Ge and Si targets were sputtered by rf and dc power, respectively. Although Ge crystalline growth without Si target sputtering deteriorated considerably, the growth of SiGe thin film was observed with increase of Si dc power. SiGe thin film was evaluated as microcrystalline phase which included (111) and (220) plane by X-ray diffraction method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.409-415
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• 2011

A gimbal system in observation reconnaissance aircraft was fabricated by assembling many parts and bearings. This system consists of a camera module and a stabilization gimbal that supports the camera module. During the flight for recording images, the gimbal system experiences various accelerations with wide frequencies. Although base excitation of stabilization gimbal results in vibration of the camera module, the camera module must be able to capture the correct and clear image even while vibrating. Hence, it is important to know the natural frequencies and vibration modes of the gimbal system with the camera module. Considering bearings as spring elements, the vibration characteristic of the gimbal system was analyzed by finite element method. In addition, harmonic response analysis was performed to determine the correct transmissibility of acceleration for the camera module in the frequency range of 0-500 Hz.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.459-459
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• 2012

Recently, the discharge of global warming gases in dry etching process of TFT-LCD display industry is a serious issue because perfluorocarbon compound (PFC) gas causes global warming effects. PFCs including CF4, C2F6, C3F8, CHF3, NF3 and SF6 are widely used as etching and cleaning gases. In particular, the SF6 gas is chemically stable compounds. However, these gases have large global warming potential (GWP100 = 24,900) and lifetime (3,200). In this work, we chose C3F6O gas which has a very low GWP (GWP100 = <100) and lifetime (< 1) as a replacement gas. This study investigated the effects of the gas flow ratio of C3F6O/O2 and process pressure in dual-frequency capacitively coupled plasma (CCP) etcher on global warming effects. Also, we compared global warming effects of C3F6O gas with those of SF6 gas during dry etching of a patterned positive type photo-resist/silicon nitride/glass substrate. The etch rate measurements and emission of by-products were analyzed by scanning electron Microscopy (SEM; HITACI, S-3500H) and Fourier transform infrared spectroscopy (FT-IR; MIDAC, I2000), respectively. Calculation of MMTCE (million metric ton carbon equivalents) based on the emitted by-products were performed during etching by controlling various process parameters. The evaluation procedure and results will be discussed in detail.

• Korean Journal of Materials Research
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• v.30 no.9
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• pp.489-494
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• 2020

SiC is a material with excellent strength, heat resistance, and corrosion resistance. It is generally used as a material for SiC invertors, semiconductor susceptors, edge rings, MOCVD susceptors, and mechanical bearings. Recently, SiC single crystals for LED are expected to be a new market application. In addition, SiC is also used as a heating element applied directly to electrical energy. Research in this study has focused on the manufacture of heating elements that can raise the temperature in a short time by irradiating SiC-I₂ with microwaves with polarization difference, instead of applying electric energy directly to increase the convenience and efficiency. In this experiment, Polydimethylsilane (PDMS) with 1,2 wt% of iodine is synthesized under high temperature and pressure using an autoclave. The synthesized Polycarbosilane (PCS) is heat treated in an argon gas atmosphere after curing process. The experimental results obtain resonance peaks using FT-IR and UV-Visible, and the crystal structure is measured by XRD. Also, the heat-generating characteristics are determined in the frequency band of 2.45 GHz after heat treatment in an air atmosphere furnace.

• Journal of Sasang Constitutional Medicine
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• v.21 no.1
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• pp.197-216
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• 2009

1. Objectives This study is to investigate the relationship between type A behavior pattern(TABP) and diabetes according to Sasang Constitution. 2. Methods 162 persons(81 IGM persons vs 81 normal persons) out of 666 persons, more than 40 years old, who participated the community based cohort in Wonju City of South Korea from July 2nd to August 30th in 2006, were randomly selected and analyzed. Framingham Type A score, Social Support index, glucose related laboratory results were measured and analyzed according to Sasang Constitution. 3. Results Soeumin in IGM group had significantly high scores in FTA scales compared with Soyangin and Taeeumin, bur in female IGM group and normal group there was no significant difference in FTA scales and TABP frequency by Sasang Constitution. There was no significant difference in social support index in IGM and normal group by Sasang Constitution. There was no significant difference in glucose-related values between TABP/TBBP in IGM group and normal group. Soyangin in female IGM group had significantly high values in insulin(fasting) and HOMA-IR in TABP group, Soeumin group had significantly high values in FBS in TABP group. According to binary logistic regression analysis for IGM, Sasang Constitution was a significant risk factor and the ORs of Taeeumin and Soyangin were significantly higher than that of Soeumin. Social Support index was significantly higher only in female group. 4. Conclusions Adequate questionnaire of TABP for our country or a research of another subjects are needed. And Sasang Constitution is thought to be the reasonable intervention to control diabetes in terms of prevention, treatment and regimen.

• Journal of the Korean Chemical Society
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• v.39 no.9
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• pp.692-697
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• 1995

The chemical compositions and possible structure for the complex of B15C5 with Nd(Ⅲ) have been determined by NMR spectrophotometry in acetone-d6. On the stepwise additions of Nd(Ⅲ) to B15C5 solution of constant concentration, all the resonances shifted to downfield and the mole ratio of B15C5 to Nd(Ⅲ) was found to be 1 : 1. From the line broadening of proton peaks of NMR spectra, it was found that oxygen atoms in B15C5 interact with Nd(Ⅲ) ion. And in IR spectra of Nd(Ⅲ)-B15C5 complex, the band of asymmetric C-C-O stretching vibration shifted to a lower frequency region upon complexation. We have proposed the possible structure of the Nd(Ⅲ)-B15C5 coordinated with the five ether oxygen atoms and with the three bidentate nitrato groups.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.12
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• pp.1097-1104
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• 2016

The infrared camera is difficult to satisfy the RE-102 specification of Mil-Std-461. Especially, in the case of UAV electronics, shielded cable is not used, so it is difficult to meet the electromagnetic compatibility standard. In the RE-102 test of the IR camera for UAV, radiated noise exceeding 30 dBuV/m was observed in the range of 50 MHz to 200 MHz. As a result of pcb em scan, peak noise which caused by the harmonic frequency of the digital control signal clock was observed. Radiated noise was reduced by up to 22.9 dBuV/m by applying the spread spectrum clock generator(SSCG) with 3 % down spreading method to the camera control clock.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.140-145
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• 2008

The purpose of this paper is to discuss the fabrication of $\beta$-PVDF($\beta$-Polyvinylidene fluoride, ${\beta}-PVF_2$) organic thin films using the vapor deposition method. Vapor deposition was performed under the following conditions: the temperature of evaporator, the applied electric field, and the pressure of reaction chamber were $270^{\circ}C$, 142.4 kV/cm, and $2.0{\times}10^{-5}\;Torr$, respectively. The molecular structure of the evaporated organic thin films were evaluated by a FT-IR. The results showed that the characteristic absorption peaks of $\beta$-form crystal increase from 72% to 95.5% with an increase in the substrate temperature. In the analysis of the electric characteristics, the abnormal increases in the relative dielectric constant and the dielectric loss factor in the regions of low frequency and high temperature are known to be caused by inclusion of impurity carriers in the PVDF organic thin films. In order to analyze quantitatively the abnormalities in the conductivity mechanism caused by ionic impurities, the product of the ion density and the mobility that affect the electrical property in polymeric insulators is analyzed. In the case of a specimen produced by varying the substrate temperature from $30^{\circ}C$ to $105^{\circ}C$, the product of mobility and the ion density decreased from $4.626{\times}10^8$ to $8.47{\times}10^7/V{\cdot}cm{\cdot}s$. This result suggests that the higher the substrate temperature is maintained, the better excluded the impurities are, and the more electrically stable material can be obtained.

• Journal of Communications and Networks
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• v.17 no.6
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• pp.622-633
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• 2015

The coexistence among different systems is a major problem in communications. Mutual interference between different systems should be analyzed and mitigated before their deployment. The paper focuses on two aspects that have an impact on the system performance. First, the coexistence analysis, i.e. evaluating the mutual interference. Second aspect is the coexistence techniques, i.e. appropriate system modifications that guarantee the simultaneous use of the spectrum by different technologies. In particular, the coexistence problem is analyzed between ultra-wide bandwidth (UWB) and narrow bandwidth (NB) systems emphasizing the role of spectrum sensing to identify and classify the NB interferers that mostly affect the performance of UWB system. A direct sequence (DS)-time hopping (TH) code design technique is used to mitigate the identified NB interference. Due to the severe effect of Narrowband Interference on UWB communications, we propose an UWB transceiver that utilizes spectrum-sensing techniques together with mitigation techniques. The proposed transceiver improves both the UWB and NB systems performance by adaptively reducing the mutual interference. Detection and avoidance method is used where spectrum is sensed every time duration to detect the NB interferer's frequency location and power avoiding it's effect by using the appropriate mitigation technique. Two scenarios are presented to identify, classify, and mitigate NB interferers.