• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 동계학술발표회 논문집
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• pp.293-294
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• 2008

Using bi-direction SOA based Extension system, FTTH can enhance PON system by increasing both the upstream and downstream link budget. This increased link budget can be used to extend the distance, increase the split ratio or both. The bi-direction SOA regenerates signals using all-optical amplification, and is therefore transparent to data rate or protocol. The bi-direction SOA supports legacy as well as future FTTx standards. This is based on SOA's proprietary technology platform for the manufacturing of advanced discrete photonics and photonic integrated circuits (PICs). Because the bi-direction SOA uses the same InP semiconductor technology used in virtually all telecom lasers, it is able to amplify signals at 1310 and 1490 nm, wavelengths not accessible with commercial fiber-amplifier (EDFA) technology. Due to the extremely fast response time of the InP semiconductor optical amplifiers inside, the SOA can accommodate both continuous (downstream) and bursty (upstream) traffic.

• 한국전기전자재료학회논문지
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• 제18권1호
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• pp.89-95
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• 2005

We derived a formula which can calculate the space distribution of refractive index variation by an applied electric field about Bi$_{12}$ GeO$_{20}$ single crystal. Stereographic projection maps of refractive index variation by an applied electric field were made out using numerical value to be calculated by this formula. By the calculated results, since an electric field had applied to [(equation omitted) 1 1] direction and [1 (equation omitted) 1] direction of Bi$_{12}$ GeO$_{20}$ crystal, positive variation of the refractive index of [(equation omitted) 1 1] direction and [1 (equation omitted) 1] direction was the largest. The incremented refractive index per unit electric field was +3.2410${\times}$10$^{-11}$ V$^{-1}$ for the wavelength of 6328 $\AA$. Since an electric field had applied to [1 1 1] direction and [(equation omitted) 1] direction, negative variation of the refractive index of [1 1 1] direction and [(equation omitted) 1] direction was the largest. The decremented refractive index per unit electric field was -3.2410${\times}$10$^{-11}$ V$^{-1}$ for the wavelength of 6328 $\AA$.

• 한국재료학회지
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• 제5권2호
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• pp.251-258
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• 1995

$Bi_{2}Te_{3}$와 PbTe의 혼합물에서 $Bi_{2}Te_{3}-PbBi_{4}Te_{7}$의 공정조직이 형성됨을 이용, 제2상의 미세조직 제어로 열전도도의 감소에 따른 성능지수 향상을 목적하여 여러 조건에서 제조된 n-type(Bi, Pb)-Te계 공정조성 일방향 응고재의 열전특성을 조사하였다. 일방향응고시 공정상 PbBi_{4}Te_{7}$이 $Bi_{2}Te_{3}$의 벽개면(0001)을 따라 lamellar 형태로 성장하였으며, 성장속도가 1.4 \times 10^{-4}$cm/sec에서 $8.3 \times 10^{-4}$cm/sec로 증가됨에 따라 4PbBi_[4]Te_{7}$의 상간격은 10.4 $\mu \textrm{m}$에서 3.2$\mu \textrm{m}$로 감소되었다. Seeback계수는 성장방향 및 성장속도와 온도구배에는 관계없이 약 $\mid$$\alpha$$\mid$=29 $\mu$ V/K일정하였다. 전기전도도는 성장속도에 따라 약간 감소하는 경향을 보였고 성장방향에 평행한 경우가 수직한 경우보다 약 3배 정도 컸다. 성능지수는 성장방향과 성장속도 및 온도구배에 따라 약간씩 변화를 보였다. 수직한 경우가 평행한 경우에 비해 상대적으로 증가하는 경향을 나타내었는데 이는 lamellar 간격이 줄어듦에 따른 열전도도의 감속에서 비롯된 것으로 분석되었다.

• Bulletin of the Korean Chemical Society
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• 제34권3호
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• pp.773-776
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• 2013

We have prepared 1-D BiSI and 2-D BiOI nanostructures, and characterized them by scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction crystallography, thermogravimetric analysis/differential scanning calorimetry, and UV-visible absorption. Here, we first report clear HR-TEM image of BiSI. In addition, we first found that the growth direction of BiSI is [12-1] plane, with the neighboring distance of 0.30 nm. The crystal structures of BiSI and BiOI are found to be orthorhombic (Pnam) and tetragonal (P4/nmm), respectively. The absorption band gaps of BiSI and BiOI are measured to be 1.55 and 1.92 eV, respectively. Our study could further highlight the applications of V-VI-VII compounds.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1237-1239
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• 2005

In this study, we estimate the thermal conductivity of stainless steel reinforced Bi-2223/Ag tape which was made from American Superconductor. The equipments for thermal conductivity measurement was set up using conduction cooled cryocooler. Two direction of thermal conductivity was measured. The one is the direction of cut length, and the other is direction of transverse of wounded coil with insulation material. It was observed that the thermal conductivity of transverse direction of coil was extremely lower than that of cut length direction. It was mainly seems that superconducting filaments and insulation material were effected on thermal conductivity in thermal conductivity of transverse direction.

• 한국세라믹학회지
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• 제26권1호
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• pp.139-145
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• 1989

An eutectic melt in the system(Bi2O3)0.85·(Nb2O5)0.15-6Bi2O3·SiO2 was unidirectionally solidfield at a rate of 0.5mm/h under a thermal gradient of 100℃/cm. Double crucibles and seed crystal plate were used in order to botain the composite crystals which had uniform microstructure throughout the ingot. The obtained composite crystals showed uniform microstructure, in which needle-like δ-(Bi2O3)0.85·(Nb2O5)0.15 crystals were arrayed in parallel in a matrix of γ-6Bi2O3·SiO2 single crystal. It was found that the <110> direction of δ-(Bi2O3)0.85·(Nb2O5)0.15 crystal was essentially parallel to the <111> direction of γ-6Bi2O3·SiO2 crystal in the composite crystals. A transverse thin plate of the composite crystals showed a high resolution optical transmission like an optical fiber array, and sharp chatoyancy was observed in the cabochon shaped composite crystals. Then, this may be useful for applications such as screen of a cathode ray tube or artificial cat's eye gem stones.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.109-112
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• 1999

The normal zone propagation (NZP) velocity and V-I characteristics of two Bi-2223 pancake coils with different Ag/SC ratio were investigated by experiment. Non-uniformity of Ic and broad restive transition was oberserbed in two coils. The NZP velocity of azimuth direction is faster than radius direction, and the NZP velocity of coil with higher Ag/SC ratio is faster than another coil with lower Ag/SC ratio.

• Smart Structures and Systems
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• 제26권4호
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• pp.435-449
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• 2020

To effectively extract the vast wind resource, offshore wind turbines are designed with large rotor and slender tower, which makes them vulnerable to external vibration sources such as wind and wave loads. Substantial research efforts have been devoted to mitigate the unwanted vibrations of offshore wind turbines to ensure their serviceability and safety in the normal working condition. However, most previous studies investigated the vibration control of wind turbines in one direction only, i.e., either the out-of-plane or in-plane direction. In reality, wind turbines inevitably vibrate in both directions when they are subjected to the external excitations. The studies on both the in-plane and out-of-plane vibration control of wind turbines are, however, scarce. In the present study, the NREL 5 MW wind turbine is taken as an example, a detailed three-dimensional (3D) Finite Element (FE) model of the wind turbine is developed in ABAQUS. To simultaneously control the in-plane and out-of-plane vibrations induced by the combined wind and wave loads, another carefully designed (i.e., tuned) spring and dashpot are added to the perpendicular direction of each Tuned Mass Damper (TMD) system that is used to control the vibrations of the tower and blades in one particular direction. With this simple modification, a bi-directional TMD system is formed and the vibrations in both the out-of-plane and in-plane directions are simultaneously suppressed. To examine the control effectiveness, the responses of the wind turbine without control, with separate TMD system and the proposed bi-directional TMD system are calculated and compared. Numerical results show that the bi-directional TMD system can simultaneously control the out-of-plane and in-plane vibrations of the wind turbine without changing too much of the conventional design of the control system. The bi-directional control system therefore could be a cost-effective solution to mitigate the bi-directional vibrations of offshore wind turbines.

• 한국산학기술학회논문지
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• 제14권6호
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• pp.2971-2978
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• 2013

최근 배전계통은 정부의 녹색성장 정책으로 태양광, 풍력발전 등과 같은 분산전원의 보급률이 지속적으로 증가되고 있는 실정이다. 이러한 분산전원의 연계로 기존 배전계통의 조류흐름은 단방향(One-direction)에서 양방향(Bi-direction)으로 변화되고, 고장전류의 증 감이 발생하는 등, 다양한 변화가 생겨 배전계통의 운용상에 여러 가지 문제점들이 발생할 가능성이 커지고 있다. 따라서 본 논문에서는 분산전원의 배전계통 연계에 따른 보호기기의 정정 및 양방향 보호협조 검토가 가능한 보호협조 평가알고리즘과 실제의 사고전류 값을 이용한 개선된 T-C곡선 알고리즘을 제안하고, 이 알고리즘을 바탕으로 양방향 보호협조 평가시스템을 개선하였다. 또한 평가시스템을 이용하여 배전계통을 모델링하고, 분산전원 연계 시 보호기기들 간의 보호협조를 검토하여, 분산전원이 연계된 경우 배전계통에 발생할 수 있는 기술적인 문제점들을 분석하여 그 방안을 제시하였다.

• 한국재료학회지
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• 제4권1호
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• pp.97-106
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• 1994

전형적인 f-f 및 nf-f 공정합금계로 분류되는 Sb-InSb 및 Sn-Bi 합금계를 일방향 응고시켜서 성장속도에 따른 전기비저항값의 변화를 조사함으로써 미세조직의 이방성을 전기비저항의 특성으로 분석하고자 하였다. Sb-InSb 계의 경우 26-34wt.% In, Sn-Bi 계의 경우 53-65wt.% Bi의 조성을 갖는 공정합금을 진공봉합시켜 Bridgman형의수직관상로에서 일방향응고시켰다. 일방향응고 시편을 횡단면 및 종단면으로 절단 채취하여 미세조직을 관찰한 후 전기비저항을 측정하였다. Sb-InSb , Sn-Bi공정복합조직의 경우 모두 성장속도의 증가에 따라 성장방향에 수평한 방향의 비저항값($\rho$┴)은 감소하였으며, Sb InSb 공정복합조직의 경우 특히 성장 속도의 증가에 따르는 미세조직상의 두가지 변화 즉, 상경계면적(phase boundary area)의 증가와 fiber방향성의 감소는 공히 $\rho$ ll 값을 증가시키는 반면 $\rho$┴ 값에는 서로 상반된 영향을 끼쳤다. 또한 성장속도의 증가에 따라 점차 조직의 이방성이 상실되었다. 이와 같이 측정된 전기비저항은 미세조직특성과 잘 일치하는 바 전기비저항 측정은 조직 특성분석의 유효한 도구가 될 수 있다.