• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.191-196
• /
• 2000

본 논문에서는 공조용 소음기에 대한 삽입손실 및 압력손실과 같은 음향성능 평가를 위해 필요한 제반 사항을 ISO 7235에 근거하여 소개하였다. 이를 위해 시험설비의 종류 및 구비조건, 측정방법, 측정시 유의사항 등을 기술하였고, 이로서 공조용 소음기의 보다 정확한 음향성능평가가 이루어지도록 검토 하였다.

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.02a
• /
• pp.192-193
• /
• 2003

광학박막은 유리, 플라스틱, 실리콘, 금속 기판 등에서 표면의 반사율, 투과율, 흡수율과 편광상태 등의 광학적 특성을 변화시키기 위해 광학표면에 코팅을 하여 많이 사용하고 있으며, 파장영역으로는 수 nm의 연x선부터 자외선, 가시광선과 수십 $\mu$m의 적외선까지 적용할 수 있고, 광학기기에서는 대부분의 광학부품이 광학적 특성을 증진시키기 위하여 각각의 목적에 맞도록 코팅되어 있다. 광학코팅의 종류로는 단순한 무반사코팅으로부터 고반사코팅, 칼라필터, 간섭필터, 편광분리기코팅, 마이너스필터 등까지 매우 다양하다. (중략)

• Journal of the Korean Solar Energy Society
• /
• v.23 no.3
• /
• pp.81-91
• /
• 2003

본 연구에서는 복층으로 구성된 $WSio_2Al$ 금속절연체의 상세를 보여주고 있는데, 금속과 절연체의 합성물질은 태양 흡수율의 설계와 열적인 현상을 보여주기 위해 종종 사용된다. 금속의 접착기면 위에 얇은 복층 코팅으로 구성되는 디자인은 태양 스펙트럼의 파장권역에서 선택적 흡수를 위함이다. 본 연구는 태양 복사의 열성능 평가를 위해 금속과 절연체 필름의 방사율, 태양흡수율, 코팅순서, 미 반사층(AR)의 두께, 코팅 두께와 코팅 면수, 전체 코팅 두께 등에 대해 시뮬레이션 하였다. 그 결과 네 겹의 코팅설계에서 $Sio_2AR$ 75 nm 두께와 각각의 층에서 $0.5\sim0.7$의 가변 금속부분 구성이 가장 우수한 성능을 갖는 것으로 나타났다. 또한 시뮬레이션으로 금속과 절연체 합성물의 최적의 구성과 각각의 코팅 두께에 대한 예측이 가능했으며, 최대 태양흡수율은 0.94, 방사율은 0.115의 금속과 절연체의 합성물을 구성할 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.11
• /
• pp.1285-1294
• /
• 2010

This study describes the design and verification of short range UWB(Ultra Wideband) imaging radar that is able to display high resolution radar image for front area of a UGV(Unmanned Ground Vehicle). This radar can help a UGV to navigate autonomously as it detects and avoids obstacles through foliage. We describe the relationship between bandwidth of transmitting signal and range resolution. A vivaldi antenna is designed and it's radiation pattern and reflection are measured. It is easy to make array antenna because of small size and thin shape. Aperture size of receiving array antenna is determined by azimuth resolution of radar image. The relation of interval of receiving antenna array, image resolution and aliasing of target on a radar image is analyzed. A vector network analyzer is used to obtain the reflected signal and corner reflectors as targets are positioned at grass field. Applicability of the proposed radar to UGV is proved by analysis of image resolution and penetrating capability for grass in the experiment.

• The Journal of the Convergence on Culture Technology
• /
• v.8 no.5
• /
• pp.483-488
• /
• 2022

In this paper, when a gain grating and a refractive index grating exist simultaneously in a DFB laser diode having a wavelength of 1.55 ㎛, an anti-reflection coating is applied to the right mirror surface so that ρ_r=0. In case of δL<0, the characteristics of the oscillation frequency and oscillation gain have been analyzed. Whenever the phase of the grating on the left side of the mirror continuously decreases by π/2, the δL value of each oscillation mode decreases by about 0.6 to the left of the graph lines of each oscillation mode. The case of the oscillation mode having the lowest threshold gain is the case of κL=10, and in this case, the mode selectivity is relatively low compared to the case of other values of κL. From κL=0.1 to κL=6, the mode selectivity and the frequency stability are excellent. As the mode selectivity is excellent, the frequency stability is excellent. Compared to the case with two cleaved mirrors, the DFB laser diode with anti-reflection coating increases the threshold gain of the oscillation mode by about 2 times, but the mode selectivity becomes about 2 times better.

• Journal of Software Assessment and Valuation
• /
• v.16 no.1
• /
• pp.55-63
• /
• 2020

Lasers for optical broadband communication systems should have excellent frequency selectivity and modal stability. DFB lasers have low lasing frequency shift during high speed current modulation. In this paper, when a refractive index grating and a gain grating are simultaneously present in a DFB laser having a wavelength of 1.55 ㎛, the dielectric film is coated so that reflection does not occur on the right mirror surface, so that ρ_r=0. For the first mode, which requires a minimum gain at the threshold, the beam distribution of the oscillation mode in the longitudinal direction and the radiated power ratio P_l/P_r were analyzed and compared for the cases of the phase of ρ_l=π and π/2. If the phase of ρ_l=π, in order to obtain a low threshold current and high frequency stability, κL should be greater than 8. In the case of the phase of ρ_l=π/2, for low threshold current, κL is necessary to be 1.0, where the oscillation frequency coincides with the lattice frequency. DFB lasers with an anti-reflection coated mirror have excellent mode selectivity than 1.55um DFB lasers with two mirror facets

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.19 no.3
• /
• pp.173-178
• /
• 2019

To analyze the diffraction properties of optical signals by periodic blazed 2D diffraction gratings, Toeplitz dielectric tensor is first defined and formulated by 2D spatial Fourier expansions associated with asymmetric blazed grating profile. The characteristic modes in each layer is then based on eigenvalue problem, and the complete solution is found rigorously in terms of modal transmission-line theory (MTLT) to address the pertinent boundary-value problems. Toeplitz matrix of symmetric and sawtooth profiles is derived from that of asymmetric blazed grating profile, and the diffraction properties for each profile are numerically simulated. The numerical results reveal that the asymmetric and symmetric profiles behave as anti-reflection GMR filter while the sawtooth profile works better as anti-transmission one rather than anti-reflection filter.

• Journal of the Korean Society of Radiology
• /
• v.12 no.1
• /
• pp.17-22
• /
• 2018

Multilayer mirrors are optical elements that can replace single crystal optical elements such as silicon or germanium, and they have artificial diffraction plane of a thickness of several nanometers. We examined the first Bragg angle and the reduction of reflectivity by variation of layer thickness in a W/Si multilayer mirror of small d-spacing. A W/Si multilayer mirror for an incidence angle of $0.55^{\circ}$ and an energy of 17.5 keV was designed and showed a maximum reflectivity of 72.67%. When the thickness of tungsten or silicon layer was simultaneously changed, the first Bragg angle was shifted and the reflectivity was reduced. When there was a change in thickness for one layer of W/Si multilayer, no change in the reflectivity was showed but the unevenness of the envelope was observed. Reduction of reflectivity was also observed at random Gaussian thickness variations. It is possible to predict the tolerance of multilayer mirror by examining the reflectivity degradation according to the thickness change in the W/Si multilayer mirror of small d-spacing.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.23 no.10
• /
• pp.1261-1268
• /
• 2019

In this paper, we present the analysis of a novel monopole antenna with a reflector. The proposed monopole antenna is printed on a TRF-45 substrate, and the reflector, which is positioned near the base of the antenna, is printed on the FR-4 substrate. Positioning the reflector near the base of the antenna was found to suppress current radiation toward the back of the monopole antenna. Comparative analysis of the proposed monopole antenna and a conventional monopole antenna without a reflector revealed that the bandwidths of the antenna with and without a reflector were 2.65 GHz and 2.88 GHz, respectively. Additionally, the antenna without a reflector was observed to have a bi-directional radiation pattern in the E-plane, and an omni-directional radiation pattern in the H-plane. However, only the antenna with a reflector was found to suppress back radiation, and provide non-uniform directional radiation in the E-plane and H-plane.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.387-387
• /
• 2012

결정 Si 및 비정질 Si 태양전지는 환경친화적이며 안정적인 물질로 전력변환 및 에너지 저장 장치에 중요하기 때문에 연구가 활발하게 진행되고 있다. 고효율 Si 태양전지를 제작하여 상용화하기에는 여러 가지 문제점이 있다. 공기와 비교하여 높은 굴절률을 갖고 있기 때문에 발생하는 반사를 줄이기 위해서 필요한 무반사 코팅층(Anti-reflective coating; ARC)은 주로 SiO2 와 SiNx 와 같은 유전체를 이용하여 사용하지만 이들 ARC 증착은 PECVD와 같은 진공장비를 사용하므로 제작 비용이 높아지는 단점이 있다. 나노선 또는 나노 팁과 같은 sub-wavelength 구조를 표면에 만들어 반사율을 줄이는 작업을 통해 ARC 공정비용을 감소하고 효율을 증진하는 연구가 활발히 진행되고 있다. CdS 양자점을 태양전지 표면에 형성함으로 ARC로 해결할 수 없는 단파장영역에 해당하는 부분을 줄이는 연구가 진행되었으며, 비정질의 경우 원기둥 형태의 태양전지 형태와 더불어 지름 방향으로의 PN 접합 나노로드 배열을 만들어 흡수면을 증가하여 효율을 증가한 연구도 진행되었다. 태양전지 표면의 형태를 V-groove 형태로 형성하여 입사하는 태양전지의 광밀도를 증가하는 이론적 결과도 발표되었다. 본 연구에서는 Si 태양전지의 표면변형에 따른 태양전지의 전력변환효율의 변화를 관찰하기 위하여 태양전지 표면의 texture 지름을 $3{\sim}15{\mu}m$, 간격을 $5{\sim}20{\mu}m$로 변화하고, 태양전지 표면의 나노 패턴을 2~10 nm 로 변화하여 반사율과 전력변환효율을 비교하였다. 나노와 마이크로 패턴은 각각 polystyrene nanosphere 와 photo mask를 이용하여 제작하였으며 PN junction Si 태양전지는 spin on dopant 방식으로 제작하여 성능을 조사하였다.