• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
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• pp.123-124
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• 2009

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 하계학술발표회 논문집
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• pp.177-178
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• 2008

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 하계학술발표회 논문집
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• pp.367-368
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• 2006

• 한국생산제조학회지
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• 제21권2호
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• pp.252-258
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• 2012

A study of terahertz waves was made for the nondestructive evaluation of FRP (Fiber reinforced plastics) composite materials. The terahertz systems were consisted of time domain spectroscopy (TDS) and continuous wave (CW). The composite materials investigated include both non-conducting polymeric composites and conducting carbon fiber composites. Terahertz signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, a terahertz pulse was not able to detect a material with conductivity. The CFRP (Carbon fiber reinforced plastics) laminates were utilized for confirming the experimentation in the terahertz NDE. In carbon composites the penetration of terahertz waves is quite limited and the detection of flaws is strongly affected by the angle between the electric field direction of the terahertz waves and the intervening fiber directions. A refractive index (n) was defined as one of mechanical properties; so a method was obtained in order solve the "n" in the material with non-conductivity. The usefulness and limitations of terahertz radiation are investigated for the NDE of FRP composites.

• 한국전기전자재료학회논문지
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• 제30권11호
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• pp.745-750
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• 2017

Terahertz time-domain spectroscopy has been used to study the optical properties of $Pr^{3+}-doped$ selenide glasses. The complex refractive indexes of $Pr^{3+}-selenide$ glasses were measured in a frequency range from 0.3 to 1.5 THz. The real and imaginary refractive indexes increased with increasing frequency and $Pr^{3+}$ ion concentration. The obtained result indicated that the phonon modes of the $Pr^{3+}-doped$ selenide glasses shift to lower frequencies with the concentration of $Pr^{3+}$ ions. The theory of far-infrared absorption in amorphous materials was used to analyze the results. The measured data showed that the disorder-induced terahertz absorption increased with increasing $Pr^{3+}$ ion concentration.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 춘계종합학술대회
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• pp.303-306
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• 2001

본 연구는 테라헤르츠 시간영역 분광법 (THz time-domain spectroscopy : THz-TDS)을 이용하여 광학 및 전기 전자 재료로 널리 사용되는 이산화규소의 흡수율과 도전율을 각각 테라헤르츠 주파수 영역에서 측정하였다. 입자 형태로 구성된 이산화규소의 재료는 기존의 접촉식인 Hall 측정이나 4-point probe 측정으로는 그 전기적 특성 분석이 불가능하지만, THz-TDS 방법은 비접촉식 방법으로 전기적 특성뿐만 아니라 광학적 특성 분석도 가능하다. 또한 기존의 전기적 폭정 장치는 DC 영역에서만 가능하지만, 본 방법은 테라헤르츠 주파수 영역에 따른 그 특성을 분석 할 수 있다. 특히 도전율은 금속 및 반도체와 달리 테라헤르츠 주파수가 증가함에 따라 증가하였는데, 이러한 결과는 Drude 이론을 따르지 않음을 확인하였다.

• 한국생산제조학회지
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• 제21권1호
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• pp.102-108
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• 2012

A study of terahertz waves (T-ray) was made for the nondestructive evaluation of FRP (Fiber reinforced plastics) composite materials. The to-be-used systems were time domain spectroscopy (TDS) and continuous wave (CW). The composite materials investigated include both turbine blades of wind energy (non-conducting polymeric composites) and conducting carbon fiber composites. Terahertz signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, a terahertz pulse was not able to detect a material with conductivity. This was demonstrated in CFRP (Carbon fiber reinforced plastics) laminates. Refractive index (n) was defined as one of mechanical properties; so a method was solved in order solve the "n" in the material with the cut parts of the turbine blades of wind energy. The defects and anomalies investigated by terahertz radiation were foreign material inclusions and simulated disband. Especially, it is found that the T-ray went through the turbine blade with greater thickness (about 90mm).

• 공학기술논문지
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• 제11권4호
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• pp.245-251
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• 2018

Terahertz waves (T-ray) was extensively studied for the NDE (nondestructive evaluation) of characterization of trailing edges for a use of turbines composed with composite materials. The used NDE system were consisted of both CW(Continuous wave) and TDS (Time domain spectroscopy). The FRP composites were utilized for two kinds of both trailing edges of wind energy (non-conducting polymeric composites) and carbon fiber composites with conducting properties. The signals of T-ray in the TDS (Time domain spectroscopy) mode resembles almost that of ultrasound waves; however, a terahertz pulse could not penetrate a material with conductivity unlike ultrasound. Also, a method was suggested to obtain the "n" in the materials, which is called the refractive index (n). The data of refractive index (n) could be solved for the trailing edges. The trailing edges were scanned for characterization and inspection. C-scan and B-scan images were obtained and best optimal NDE techniques were suggested for complicated geometry samples by terahertz radiation. Especially, it is found that the defect image of T-ray corresponded with defect locations for the trailing edges of wind mill.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3312-3316
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• 2013

Single crystals of hexagonal graphenes were successfully grown on Cu foils using the atmospheric pressure chemical vapor deposition (CVD) method. We investigated the effects of reaction parameters, such as the growth temperature and annealing time, on the size, coverage, and density of graphene domains grown over Cu foil. The mean size of the graphene domains increased significantly with increases in both the growth temperature and annealing time, and similar phenomena were observed in graphene domains grown by low pressure CVD over Cu foil. From the comparison of micro Raman spectroscopy in the graphene films grown with different annealing times, we found that the nucleation and growth of the domains were strongly dependent on the annealing time and growth temperature. Therefore, we confirmed that when reaction time was same, the number of layers and the degree of defects in the synthesized graphene films both decreased as the annealing time increased.

• Journal of Electrochemical Science and Technology
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• 제8권2호
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• pp.115-123
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• 2017

Electrochemical noise signals in many cases exhibit a DC drift that should be removed prior to further data analysis. Polynomial fitting and moving average removal method have been used to remove trends of electrochemical noise (EN) in time domain. The corrosion inhibition of synthesized schiff base N,N'-bis(3,5-dihydroxyacetophenone)-2,2-dimethylpropandiimine on API-5L-X70 steel in hydrochloric acid solutions were used to study the effects of drifts removal methods on noise resistance calculation. Also, electrochemical impedance spectroscopy (EIS) was used to study the corrosion inhibition property of the inhibitor. The results showed that for the calculation of $R_n$, both methods were effective in trend removal and the polynomial with m=4 and MAR with p=40 were in agreement.