• Journal of Convergence Society for SMB
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• v.4 no.4
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• pp.37-42
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• 2014

In this paper, we analyzed the main factors that affect the performance in Visible Light Communication (VLC) system. Generally, published papers of VLC system have been studies to focus on increased data rates, transmission distance and modulation scheme. Therefore, in order to analyze detailed environment for VLC system, we was performed to analyze the performance of a major impact on the VLC system according to communication distance and the angle of incidence. The computer simulation results show that the performance attenuation was confirmed.

• Journal of the Korean Solar Energy Society
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• v.24 no.3
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• pp.55-63
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• 2004

빛이 입사각별로 태양투과율이 제어되어지는 첨단 창과 같은 물체를 통과할 때 투과되는 성분은 직달투과와 산란투과성분으로 볼 수 있다. 직달투과는 물체를 통과하면서 일정한 방향으로 굴절되어 투과되는 성질을 말하고, 산란투과는 직달투과를 제외한 나머지 방향의 성분들의 형태를 말한다. 이러한 첨단 창의 냉난방부하에 미치는 에너지성능을 평가하기 위해서는 산란투과에 대한 정보가 필요하고, 이에 대한 물리적 변수는 입사각, 출력각, 양방향 투과율 분산함수인 BTDF로 정의된다. 본 논문에서는 3개의 서로 나른 첨단 창 (1) $42^{\circ}/5^{\circ}$ 프리즘 창 판넬, (2) 레이저 컷 판넬 (3) $45^{\circ}$ 프리즘 3M 필름의 BTDF 데이터 획득을 위한 실험 방안을 소개하고, 실험을 통해 획득한 정보를 이용하여 계산식과 비교 검증을 하였다. 따라서 이 검증된 방안을 이용하여 지역별 냉난방 부하를 최소화 할 수 있는 입사각별로 태양 투과율 제어 판넬을 선정할 수 있게 되었다.

• Korean Journal of Optics and Photonics
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• v.26 no.2
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• pp.110-114
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• 2015

We propose a reflective cholesteric liquid crystal cell with reduced color shift, using dichroic dyes. Color-shifted light is absorbed by dye molecules in the proposed dye-doped cholesteric liquid crystal (DDCLC) cell. We have shown that the color shift can be reduced by increasing the concentration of dye molecules in the proposed DDCLC cell.

• The Journal of the Acoustical Society of Korea
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• v.22 no.1
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• pp.61-68
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• 2003

The guided wave has been widely employed to characterize thin plates and layered media. The dispersion curves of phase and group velocities are essential for the quantitative application of guided waves. In the present work, a fully automated system for the measurement of backward radiation of LLW has been developed. The specimen moves in two dimensional plane as well as in angular rotation. The signals of backward radiation of LLW were measured from an elastic plate in which specific modes of Lamb wave were strongly generated. Phase velocity of the corresponding modes was determined from the incident angle. The generated Lamb waves propagated forward and backward with the leakage of energy into water. Backward radiated LLW was detected by the same transducer and its frequency components were analyzed to extract the related information to the dispersion curves. The dispersion curves of phase velocity were measured by varying the incident angle. Moving the specimen in the linear direction of LLW propagation, group velocity was determined by measuring the transit time shift in the ultrasonic waveform.

• Journal of the Korean Magnetics Society
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• v.4 no.4
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• pp.313-318
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• 1994

We have investigated the effects of deposition angle on magnetic and magneto-optic properties in Co/Pt multilayer thin films. which were prepared bye-beam evaporation on tilted substrates. with varying tilt angle from $0^{\circ}$ to $60^{\circ}$. The structure of the specimens was examined by x-ray diffractometer and scanning electron microscope. and the magnetic and magneto-optical properties were measured by VSM, torque magnetometer, and Kerr loop tracer. X-ray diffractometry revealed that all of the specimens had multilayer structure and growth orientation of column followed the tangent rule but the crystallograpic orientation, <111>, was slightly deviated from the substrate normal even though the deposition angle was increased up to $60^{\circ}$. A decrement of the magnetization and Kerr angle with the deposition angle was related with that of the film density due to increasing porosity. The perpendicular mag¬netic anisotropy was also decreased with increasing the deposition angle.

• The Journal of Engineering Geology
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• v.6 no.2
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• pp.53-58
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• 1996

In order to investigate the source mechanism of micro cracks through acoustic emission measurement induced by rock fracture, careful calibration of the entire linkage of the detecting system, from the transducers to transient recorder, is an essential requirement prior to testing. Transducers and digitiging system are generally the weakest links in the measurement system because they must translate mechanical motions into digital electric signals. In this study, PAC piezoelectric pressure transducers are calibrated with a standard NBS conical shaped displacement transducer and a DG piezoelectric displacement transducer. The NBS and PAC transducers are insensitive to changes in horizontal impingement angle but sensitive to changes in incident angle. The ray path along the logitudinal axis of the tranducer produced a maximum response while the ray path perpendicular to the transducer axis gave a minimum. And a difference in individual transducers factor for a peak-to-peak amplitude of PAC transducers was within 40%. An average PAC transducer coefficient was determined as 77mv/pm by an absolute calibration test using NBS transducer.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.26-35
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• 2012

Until now, study on the hydraulic resistance characteristics of the ground at the river and the ocean current has been focused on the behavior under uni-directional flow without the direction change of flow. However, recent research result shows that scour rate which were measured under the bi-directional flow was much higher than those measured under uni-directional flow for both fine grained and coarse soil. Since the direction of inflow and return flow at the shore, where the structure will be constructed, is not always $180^{\circ}$, effect of the incidence angle on the hydraulic resistance capacity of the ground should be examined. Using the improved EFA which can consider the direction change of flow, hydraulic resistance capacities of the artificially composed clayey fine grained soil and clayey sandy soil under $0^{\circ}$, $90^{\circ}$, $135^{\circ}$, $180^{\circ}$ flow angle of incidence were assessed. Test result shows that hydraulic resistance capacity decreases and scour rate increase with the increase of the incidence angle between inflow and return flow. For the low consolidation pressure condition, hydraulic resistance capacity of the fine grained soil decreases rapidly. While the hydraulic resistance capacity of the coarse grained soil decreases more rapidly than fine grained soil under high consolidation pressure. Eventually since the larger the incidence angle between inflow and return flow, the larger the scour rate. Hydraulic resistance capacity under bi-directional flow($0^{\circ}{\longleftrightarrow}180^{\circ}$) should be examined for the design purpose.

• Korean Journal of Remote Sensing
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• v.14 no.4
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• pp.325-342
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• 1998

Two RADARSAT SAR images with different modes acquired by Canadian Space Agency to test the effectiveness of geological lineament extraction and spring water detection over the Cheju Island. Geological lineaments are poorly developed this basalt dominant volcanic island, but more linear features can be extracted when SAR and TM images are simultaneously analyzed than when TM image alone is used. This results mainly owe to the facts that RADARSAT SAR systems are able to provide data with different frequencies, azimuth, and incidence angles. Distribution of spring water along coast is poorly correlated with geological lineaments or drainage pattern, but those in middle range of mountain region are developed along geological lineaments. Detection of spring water using remotely sensed images are turned out to be very difficult to achieve. Radial shaped sea surface temperature anomaly derived from TM thermal band should be the best candidate for spring water, but the resolution is not high enough. We also investigate the normalized radar cross section (or sigma naught) converted from RADARSAT and ERS-1 SAR data but to discriminate the spring water effectively except where relatively large water mass is observed on land side. Speckle noise and irregularity in physical sea surface condition are the serious obstacles for this application. ERS-1 SAR image acquired in low incidence angle was more useful for geological lineament estimation and water body study than RADARSAT SAR images with high incidence angles. Therefore the selection of incidence angle is critical in geological and spring water applications of SAR images, and low incidence angles less than about 30$^{\circ}$ are recommended to monitor the Cheju volcanic island.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.9
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• pp.31-37
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• 2000

An angular selectivity through the focused readout beam is geometrically analyzed and experimental results are presented. Based on the analysis of geometrical results, we derive a new relation that the angular selectivity depends on incident conditions of the readout beam and independent on the writing conditions. In order to demonstrate our theory, we investigate angular selectivity as functions of following factors: writing beam incident angle, readout beam width and lens focal length. From the experimental results, it is shown that the angular selectivities are 2.632$^{\circ}$, 2.618$^{\circ}$, 2.604$^{\circ}$ when the external half-crossing angles of writing beam are 8$^{\circ}$, 10$^{\circ}$, 14$^{\circ}$, respectively. Applying the same incident angle of the recording beam, angular selectivity is changed by the control of readout beam width and then their properties are 2.632$^{\circ}$, 0.588$^{\circ}$. From these results, we have known that the angular selectivity is very critical to incident conditions of readout beam.

• Korean Journal of Optics and Photonics
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• v.34 no.1
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• pp.13-21
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• 2023

We have investigated the acceptance angle and imaging performance of a curved artificial compound eye (ACE), depending on the sag height of the microlens array to maximize its sensitivity to light. When the h/r values increased from 0.22 to 0.37, the acceptance angle of the curved ACE was expanded from 28.70° to 49.02°, which is an enhancement by 70.8%. With the designed optical system, it was demonstrated that a microlens located at the 23rd position from the center of the main lens could still focus an incident beam tilted at 56.35°, so that the letter F was clearly observed.