• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.401-401
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• 2014

In this study, graphene, the most attractive material today, has been applied to the wavelength-modulated surface plasmon resonance (SPR) sensor. The optical fiber sensor technology is the most fascinating topic because of its several benefits. In addition to this, the SPR phenomenon enables the detection of biomaterials to be label-free, highly sensitive, and accurate. Therefore, the optical fiber SPR sensor has powerful advantages to detect biomaterials. Meanwhile, Graphene shows superior mechanical, electrical, and optical characteristics, so that it has tremendous potential to be applied to any applications. Especially, grapheme has tighter confinement plasmon and relatively long propagation distances, so that it can enhance the light-matter interactions (F. H. L. Koppens, et al., Nano Lett., 2011). Accordingly, we coated graphene on the optical fiber probe which we fabricated to compose the wavelength-modulated SPR sensor (Figure 1.). The graphene film was synthesized via thermal chemical vapor deposition (CVD) process. Synthesized graphene was transferred on the core exposed region of fiber optic by lift-off method. Detected analytes were biotinylated double cross-over DNA structure (DXB) and Streptavidin (SA) as the ligand-receptor binding model. The preliminary results showed the SPR signal shifts for the DXB and SA binding rather than the concentration change.

• 대한전자공학회논문지SD
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• 제41권8호
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• pp.45-50
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• 2004

전류집속을 위하여 Vertical Cavity Surface Emitting Laser(VCSEL)에 임플랜트 공정으로 만들어지는 반 절연층의 깊이는 VCSEL의 특성 및 신뢰도에 많은 영향을 준다. 이 연구에서는 낮은 문턱전류와 높은 신뢰도의 관점에서 최적화된 임플랜트 깊이를 정하고, 전기적 미분특성을 사용하여 최적화된 임플랜트 깊이를 판정하는 간단한 방법을 제시하였다. 최적화된 임플랜트 깊이는 임플랜트 선단을 1 - λ cavity에서 p-DBR mirror 약 2 주기 위에 위치시키는 것이다. 이 최적화된 임플랜트 깊이는 임플랜트 영역 밑을 옆 방향으로 흐르는 누설전류의 크기로부터 구할 수 있다. 전기적 미분특성은 이 누설전류를 찾아내는 좋은 방법인데, 이 전기적 미분특성을 이용하면 임플랜트 깊이를 간단하고 빠르게 알아낼 수 있기 때문이다.

• 한국재료학회지
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• 제16권11호
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• pp.663-667
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• 2006

CTAB(cetyltrimethylammonium bromide)-capped CdSe nanoparticles were prepared by using a 4 : 1(v/v) distilled water-isopropyl alcohol mixture. The cadmium chloride and sodium selenosulfate were used as the cadmium and selenium source. By the analysis of XRD and XPS, the resultant particle was confirmed to be cubic CdSe phase. TEM image showed CdSe nanoparticles with empty core. The CTAB-capped sample showed an maximum absorption at 418nm, blue-shifting compared with bulk CdSe, which indicated stronger quantum confinement effect compared with uncapped sample. From FT-IR analysis, it was found that the presence of the new peaks in the $850{\sim}1250cm^{-1}$ range indicated the existence of chemical bonding between CTAB and surface of CdSe nanoparticles. Also TG analysis indicated that there were two weight-loss steps for the CTAB-capped CdSe nanoparticles. It was suggested that CTAB played a significant role in protecting CdSe nanoparticles.

• Computers and Concrete
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• 제27권5호
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• pp.437-445
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• 2021

Retrofitting of structures has gained importance over the recent years. Particularly, Reinforced Cement Concrete (RCC) column strengthening has become a challenge to the structural engineers, owing to the risks and complexities involved in it. There are several methods of RCC column strengthening viz. RCC jacketing, steel jacketing and Fiber Reinforced Polymer (FRP) wrapping etc., FRP wrapping is the most promising alternative when compared to the others. The large research database shows FRP wrapping, through lateral confinement, improves the axial load carrying capacity of the columns under concentric loading. However, its confining efficiency reduces under eccentric loading. Hence a relative newer technique called Near Surface Mounting (NSM), in which Carbon FRP (CFRP) strips are epoxy grouted to the precut grooves in the cover concrete of the columns, has been thrust domain of research. NSM technique strengthens the column nominally under concentric load case while significantly under eccentric case. A novel configuration of NSM in which the vertical NSM (VNSM) strips are being connected by horizontal NSM (HNSM) strips was numerically investigated under both concentric and eccentric loading. It was found that the configuration with 6 HNSM strips performed better under eccentric loading than under concentric loading, while the configuration with 3 HNSM strips performed better under concentric loading than under eccentric loading. Hence an optimum of 4 HNSM strips is recommended as strengthening measure for the given column specifications. It was also found that Aluminum alloy cannot be used instead of CFRP in NSM applications owing to its lower mechanical properties.

• Bulletin of the Korean Chemical Society
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• 제25권4호
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• pp.525-528
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• 2004

The photoluminescence (PL) emission of Si nanocrystals synthesized by 400 keV Si ion implanted in $SiO_2$ is studied as a function of ion dose and annealing time. The formation of nanocrystals at around 600 nm from the surface was confirmed by RBS and HRTEM, and the Si nanocrystals showed a wide and very intense PL emission at 700-900 nm. The intensity of this emission showed a typical behaviour with a fast transitory increase to reach a saturation with the annealing time, however, the red shift increased continuously because of the Ostwald ripening. The oversaturation of dose derived a decrease of PL intensity because of the diminishment of quantum confinement. A strong enhancement of PL intensity by H passivation was confirmed also, and the possible mechanism is discussed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.185-190
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• 1992

ACI318-89 Recommended that when the specified compressive strength of concrete in a column is greater than1.4 times that specified for a floor system, top surface of the column concrete shall extend 2ft(600mm)into the slab from the face of column to avoid unexpected brittle failure. The major variables are extension distance, flexural strength ratio(Mr), and shear reinforcement ratio(Vs). Test results are as follows ; (1) The failure modes of specimens under cyclic loading were concentrated at critical region from beam-column joint face. (2) Ductility index($\mu$f) were increased with increasing of shear confinement ratio and flexural strength ratio. (3)The specimens with 2ft extension distance showed more ductility than the specimens with 1ft extension distance.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.111-111
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• 2003

반도체 나노결정은 양자구속효과(quantum confinement effect)에 의한 광학적인 특성을 갖기 때문에 광전자공학(optoelectronic), 광전지(photovoltaic)분야에 응용하려는 연구가 활발히 진행되고 있다. 본 연구에서는 고순도의 CdTe 나노결정을 1-thioglycerol 표면 완화제(surface stabilizer)로 사용하여 수용액 상태로 합성하였다. 모든 실험은 $N_2$ 분위기의 삼각플라스크에서 실험하였다. Cadmium 소오스로는 Cd(CIO$_4$)$_2$.6$H_2O$(Cadmium perchlorate hydrate-Aldrich)를 사용하였고 Tellurium 소오스로는 A1$_2$Te$_3$(Aluminum telluride-CERAC)와 H$_2$SO$_4$가 반응하여 H$_2$Te gas가 주입되도록 하였다. 합성된 CdTe 나노결정은 core-shell 형태로 존재하며 결정크기에 따른 특성분석을 위해서 High Resolution Transmission Electron Microscope (HRTEM), Photoluminescence spectroscopy, X-ray diffraction(XRD), UV-vis absorption spectra 분석을 하였다 또한 CdTe 나노결정을 나노와이어로 제작하여 CdTe 나노결정을 이용한 태양전지 제작에 응용하고자 한다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.510-513
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• 2004

The objectives of this research are to evaluate the effect of the compressive strength of concrete, reinforcing bar size, spacing of column transverse bars related to the concrete confinement effects on anchorage bond strength and bond behavior of beam-column joints subjected to cyclic loading and to predict the bond behavior of beam-column joints according to the variables by Finite Element Analysis appling the interface element between concrete and reinforced bar surface in a three-dimensional configuration. This paper shows that to verify the results by three-dimensional nonlinear finite element analysis appling a interface element, the test results that were already conducted are compared with analytic results. The behavior of bond and anchorage of beam bar is expressed by a local bond stress-slip relationship and the failure mode of bond is predicted by principal stress contour.

• 통합자연과학논문집
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• 제8권3호
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• pp.147-152
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• 2015

Photoluminescent porous silicon (PSi) were prepared by an electrochemical etch of n-type silicon under the illumination with a 300 W tungsten filament bulb for the duration of etch. The red photoluminescence emitting at 620 nm with an excitation wavelength of 450 nm is due to the quantum confinement of silicon nanocrystal in porous silicon. As-prepared PSi was sonicated, fractured, and centrifuged in toluene to obtain photoluminescence silicon quantum dots. BET and BHJ methods were employed to study the specific surface area of as-prepared PSi. Optical characterization of red photoluminescent silicon nanocrystal was investigated by UV-vis and fluorescence spectrometer. Also SEM and TEM images of porous silicon and nanoparticles were investigated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.488.1-488.1
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• 2014

As the society demands the high performance energy storage devices, development of efficient and renewable energy storage materials has been a topic of interest. Here, we report pseudocapacitive behaviors of biopolymer (lignin) that was confined onto reduced graphene oxides (RGOs) for a renewable energy storage system. The strong surface confinement of quinone groups onto the electroconductive RGOs created the renewable hybrid electrodes for supercapacitors (SCs) with fast and reversible redox charge transfer. As a result, the pseudocapacitors fabricated with the hybrid electrodes of lignin and RGO presented the outstanding electrochemical performances of remarkable rate and cyclic performances:~4% capacitance drop after 3000 cycles and a maximum capacitance of 432 F g-1.