• The Korean Journal of Pain
• /
• v.20 no.2
• /
• pp.116-122
• /
• 2007

Background: Lumbar zygapophysial joints are a common source of chronic lower back pain and radiofrequency thermocoagulation (RF) of the medial branches (MB) has been shown to be effective at providing substantial pain relief for chronic low back pain. Therefore, we carried out this study to determine the short term outcomes and prognostic factors of RF on the MB of patients with lumbar facet syndrome. Methods: We performed RF in fourteen patients who showed greater than 80% pain relief up to three times after a diagnostic MB block was conducted using 0.3 ml of 0.5% bupivacaine. Using 10 cm curved electrodes with 10-mm active tip, a 60 second, $80^{\circ}C$ lesion was made after electrical stimulation at 50 Hz for sensory and 2 Hz for motor nerve testing. The degree of pain relief was then assessed after 2 weeks, and again after 3 months using a visual analog scale (VAS) and a four point Likert scale. The outcome was regarded as 'success' if at least a 50% reduction in the VAS was observed. Possible prognostic factors between the two groups were also evaluated Results: The success rate was 71.4% (10/14) after three months of follow-up. However, there were transient complications, such as neuritis like syndrome, in 4 patients. In addition, short symptom duration and low minimal voltage (< 0.4 V) for sensory stimulation were shown to be the relevant prognostic factors for a successful outcome. Conclusions: RF may be an alternative to repeated MB block or intraarticular injection for palliation of lumbar facet syndrome. For better outcomes, early diagnosis and strict patient selection should be coupled with efforts to avoid anatomically incorrect RF.

• Journal of Technologic Dentistry
• /
• v.30 no.1
• /
• pp.25-31
• /
• 2008

Cp-Ti and Ti-6Al-4V alloys commonly used dental implant materials, particularly for orthopaedic and osteosynthesis because of its suitable mechanical properties and excellent biocompatibility. This alloys have excellent corrosion behavior in the clinical environment. The first factor to decide the success of dental implantation is sufficient osseointegration and high corrosion resistance between on implant fixture and its surrounding bone tissue. In this study, in order to increase corrosion resistance and biocompatibility of Cp-Ti and Ti-6Al-4V alloy that surface of manufactured alloy was coated with TiN by RF-magnetron sputtering method. The electrochemical behavior of TiN coated Cp-Ti and Ti-6Al-4V alloy were investigated using potentiodynamic (EG&G Co, PARSTAT 2273. USA) and potentiostatic test (250mV) in 0.9% NaCl solution at 36.5 $\pm$ 1$^{\circ}C$. These results are as follows : 1. From the microstructure analysis, Cp-Ti showed the acicular structure of $\alpha$-phase and Ti-6Al-4V showed the micro-acicular structure of ${\alpha}+{\beta}$ phase. 2. From the potentiodynamic test, Ecorr value of Cp-Ti and Ti-6Al-4V alloys showed -702.48mV and -319.87mV, respectively. Ti-6Al-4V alloy value was higher than Cp-Ti alloy. 3. From the analysis of TiN and coated layer, TIN coated surface showed columnar structure with 800 nm thickness. 4. The corrosion resistance of TiN coated Cp-Ti and Ti-6Al-4V alloys were higher than those of the non-coated Ti alloys in 0.9% NaCl solution from potentiodynamic test, indicating better protective effect. 5. The passivation current density of TiN coated Cp-Ti and Ti-6Al-4V alloys were smaller than that of the noncoated implant fixture in 0.9% NaCl solution, indicating the good protective effect resulting from more compact and homogeneous layer formation.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.78.2-78.2
• /
• 2010

Cu(In,Ga)Se2 (CIGS)박막태양전지는 간단한구조와 가격경쟁력 및 고효율화 가능성에 대한 기대감에 의해 많은 연구가 수행되어오고 있다. 특히 높은 흡수계수와 적절한 밴드갭, 큰 결정크기와 같은 물질의 특성들이 장점으로 작용하고 있기 때문이다. 또한 CIGS박막태양전지는 다른 태양전지에 비해 광열화가 적다는 장점도 가지고 있다. CIGS 박막은 CuInSe2내의 In 사이트에 Ga을 도핑함으로서 형성이 되는데 그때의 밴드갭은 약 1.4eV이며 이를 형성하기 위해 많은 방법들이 제안되고 있는데, CIGS박막 형성 시 가장 중요시 여겨야 될 인자는 구성원소로부터 최적화된 조성비를 찾는 것이다. 이러한 관점에서 볼때 evaporation법이나 sputtering법같은 진공방식의 공정법이 비진공방식에 비해 최적의 조성비를 찾는 것이 수월할 것으로 생각된다. selenization을 하기전에, 동시증착이나 다층박막형성을 통해 Cu-In-Se의 조합이 일반적으로 이루어진다. 어떤방법이든 Se의 부가적인 공급이 이루어지는데 시작 전구체의 조합에서 그 해법을 제시하는 것에 대한 논의가 많이 부족한 현실로서, CuInSe2의 단일전구체에 의한 박막형성과 특성평가에 대해 구체적인 논의가 필요하다. 본 실험에서는 Cu-In-Se 전구체를 CuInSe2 단일 타겟에서부터 RF 마그네트론 스퍼터링법을 이용하여 박막증착을 하여 Se의 Rapid Thermal Process(RTA)법을 통해 Se이 순차적으로 공급되었다. 이때 형성되는 박막의 태양전지 흡수층 적용을 위한 광학적, 전기적 및 구조적에 대한 논의된다. Soda lime glass(SLG)와 Corning 1737 유리를 기판으로 하여 아세톤-에탄올을 이용, 초음파세척을 실시하였다. 스퍼터 공정을 하기전에 흡착된 물분자를 제거하기 위하여 약 30분간 $120^{\circ}C$로 열을 가해주었으며, 공정을 위한 총 아르곤 가스의 양은 약 50sccm이며 이때의 공정압력은 20mtorr로 고정하였다. 우선 RF power와 기판온도에 따른 단일전구체 형성을 관찰하기 위하여 각각 30~80W, RT~$400^{\circ}C$로 변화를 주어 박막을 형성한 후 모든 sample에 대하여 $500^{\circ}C$분위기에 effusion cell을 이용하여 Se 분위기에서 결정화를 실시하였다. 샘플의 두께는 Surface profiler로 측정하였고 단면은 전자주사현미경으로 관찰되었다. 동시에 SEM이미지를 통하여 morphology와 grain size 및 EDX를 통하여 조성분석을 하였다. 밴드갭, 투과율 및 흡수계수는 UV-VIS-NIR분광분석법을 통하여 수행되었으며, 전기적 특성분석을 위해 4-point-probe와 Hall effect측정을 수행하였다. 공정변수에 따른 단일타겟으로 얻어 결정화된 CuInSe2박막의 자세한 결과와 논의에 대하여 발표한다.

• Journal of electromagnetic engineering and science
• /
• v.6 no.2
• /
• pp.110-116
• /
• 2006

A reflective array type surface acoustic wave(SAW) dispersive delay line(DDL) with high time-bandwidth at the V/UHF-band is designed and fabricated for compressive receiver applications. This type of the SAW DDL has the properties of the relative bandwidth of 20 %, the time delay of 49.89 usec, the insertion loss of 38.5 dB and the side lobe rejection of 39 dB. In comparison with a commercial SAW DDL, the insertion loss, amplitude ripple and side lobe rejection are improved by $1.5dB{\pm}0.6dB$ and 4 dB respectively. Using the fabricated SAW DDL, the prototype of the compressive receiver is developed. It is composed of RF converter, fast tunable LO, chirp LO, A/D converter, signal processing unit and control unit. This prototype system shows a fine frequency resolution of below 30 kHz with high scan rate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.301-302
• /
• 2009

The Green emitting OLED was fabricated with the structure of ITO(plasm treatment)/TPD($400\;{\AA}$)/$Alq_3(600\;{\AA})$/LiF($5\;{\AA}$)/Al($1200\;{\AA}$). Turn-on voltage of PMOLED was 7 V and luminance was 7,371 cd/$m^2$ at the RF power of 25W. O2 plasma treatment of ITO surface was result in lowering the operating voltage and improving luminance of green OLED.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.04b
• /
• pp.52-55
• /
• 2000

In this study, (Ba,Sr)$TiO_3$(BST) thin films were etched with a magnetically enhanced inductively coupled plasma(MEICP) as a function Ar/$CF_4$ gas mixing ratio. Experiment was done by varying the etching parameters such as rf power, dc bias voltage and chamber pressure. The maximum etch rate of the BST films was 1700 ${\AA}/min$ under $CF_4/(CF_4+Ar)$ of 0.1, 600 W/350 V and 5 mTorr. The selectivity of BST to Pt and PR was 0.6, 0.7, respectively. X -ray photoelectron spectroscopy(XPS) studies shows that there are surface reaction between Ba, Sr, Ti and C, F radicals during the etching. To analyze the composition of surface residue remaining after the etching, films etched with different $CF_4$/Ar gas mixing ratio were investigated using XPS.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.10
• /
• pp.850-854
• /
• 2001

In this study, carbon nanotubes was vertically grown pm Ni/Cr-deposited glass substrates by Inductively Coupled Plasma Chemical Vapor Deposition. Using Radio-Frequence(RF) plasma below temperature of 600$^{\circ}C$. The grown CNTs shows field emission properties and high quality materials. Turn-on fields and current density showed 5V/${\mu}$m and 1.06${\times}$10$\^$-6/ A/$\textrm{cm}^2$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.866-869
• /
• 2001

In this study, (Ba,Sr)TiO$_3$(BST) thin films were etched with a magnetically enhanced inductively coupled plasma(MEICP). Etching characteristics of BST thin films including etch rate and selectivity were evaluated as a function of the etching parameters such as gas mixing ratio, rf power, dc bias voltage and chamber pressure. The maximum etch rate of the BST films was 1700 $\AA$/min at Ar(90)/CF$_4$(10), 600 W/350 V and 5 mTorr. The selectivity of BST to PR was 0.6, 0.7, respectively. To analyze the composition of surface residue remaining after the etching, samples etched with different CF$_4$/Ar gas mixing ratio were investigated with X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). From the results of XPS and SIMS, there are chemical reaction between Ba, Sr, Ti and C, F radicals during the etching and remained on the surface.

• Proceedings of the KIEE Conference
• /
• 2006.10c
• /
• pp.482-484
• /
• 2006

This paper describes fast-hopping frequency synthesizers for multi-band OFDM(MB-OFDM) ultra-wide band(UWB) systems. Three different structures in generating 3 center frequencies(3432MHz, 3960MHz, 4488MHz) are designed and compared. The first structure generates 3 center frequencies using only one PLL operating at 4224MHz. The second uses three PLLs operating at corresponding center frequencies. The third employes two PLLs operating at 3960MHz and 528MHz. Simulation results using a 0.18um RF CMOS process parameters show that the third structure exhibit the best characteristics. The band switching time of the proposed synthesizer is less than 1.3ns and the spur is less than -36dBc. The synthesizer consumes 22mA from a 1.8V supply.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.529-530
• /
• 2008

The proposed CMOS Quadrature VCO for WLAN application was designed in TSMC $0.18\;{\mu}m$ RF CMOS technology. The QVCO based on NMOS back-gate as a coupling transistor and switched capacitors array without tail transistors is designed to generate quadrature output signals. The simulated results show that the QVCO core consumed 3.67 mA and 6.6 mW from a 1.8 V supply. The QVCO is tunable between $4.76\;GHz\;{\sim}\;6.35\;GHz$ and has a phase noise lower than -116.8 ㏈c/Hz at 1 MHz offset over the entire tuning range