• Proceedings of the Korean Information Science Society Conference
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• 2003.04c
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• pp.205-207
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• 2003

본 논문에서는 카메라 렌즈에서 흔히 발견할 수 있는 렌즈계 왜곡에 의한 영상 품질 저하 현상을 소개하고 이를 보정하는 방법을 제시한다. 렌즈계 왜곡은 크게 두 가지로 나눌 수 있는데 기하학적 왜곡과 광도 왜곡이 그것이다. 이상적인 렌즈계가 아닌 경우 이러한 왜곡 현상은 필연적으로 발생을 하게 되는데 왜곡 보정을 위해서 기존의 카메라 캘리브레이션과는 다른 방식의 접근이 필요하게 된다. 본 논문에서는 기하학적 왜곡 보정을 위한 이미지 워핑 방법을 제시하며 아울러 광도 왜곡 보정을 위한 보정 방법을 다루고자 한다.

• Journal of Korean Society of Forest Science
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• v.90 no.4
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• pp.476-487
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• 2001

In this study, three tree species (Populus euramericana, Kalopanax pictus and Quercus serrata) exhibiting different levels of shade tolerance were employed to investigate photosynthetic responses to the lower light condition on forest floors. Chlorophyll contents, spectral properties and photosynthetic characteristics were examined by using the tree species grown under high light intensity (PPFD $920{\mu}mol\;m^{-2}s^{-1}$) or low light intensity (PPFD $80{\mu}mol\;m^{-2}s^{-1}$). Plants grown under the low light intensity tended to have reduced leaf area, chlorophyll content per unit leaf area, light absorption and respiration in the shade intolerant tree species of P. euramericana. However, the shade tolerant species K. pictus and Q. serrata showed increased leaf area, chlorophyll content and net apparent quantum yield. Therefore, light absorption and light utilization efficiency were improved under the low light intensity. Also shade tolerant species maintained activities of photosystems and $CO_2$ fixation systems with little changes in low light intensity condition.

• Journal of the Korean Society of Radiology
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• v.9 no.2
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• pp.67-72
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• 2015

In diagnostic radiology, the use of automatic exposure control device is internationally recommended for diagnosis and optimization. However, if exposed to prolonged radiation is a complicated manufacturing process, there is a problem that occurs decrease of various performance overall brightness sensor, which is commercially available conventional. Therefore, in this study, absorption of X-ray is high, and I want to evaluate the AEC applicability of the sensor of the photoconductor-based production has an easy advantage. Experimental results confirms the possibility of fabrication of the sensor through an increase in the SNR, with the detection efficiency superior, accurate turn-off. In addition, it is confirmed that the experimental results of the transmittance and the latent image, Ghost effect by the light conductor does not appear, in the case of a photoconductor with the exception of the PbO, 80% - and it was confirmed good transmittance of 90%. Therefore, excellent mechanical stability and poor performance due to a change of the doping concentration than the existing products that have been put to practical use, the sensor easy photoconductor based, fabrication and can be applied as AEC sensor is expected.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1271-1276
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• 2008

This study has explained about LED for BLU which is widely used in the kinds of display devices or lighting. It was shown that the open due to delamination were the dominant LED for BLU failure mode and mechanisms from failure analysis of LED samples. Then, we have defined failure as yellowing and 100% reduction of light output intensity of LED for BLU and acceleration factors as temperature and current in Accelerated Life Test(ALT). Finally, we have estimated the Weibull distribution, life-stress relationship, and accelerating factor is used by ALTA Software.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.149-154
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• 2007

Bragg reflecting waveguide devices have been fabricated on a flexible polymer substrate utilizing a post lift-off process which could Provide excellent uniformity of grating Patterns on Plastic film. The 510 m Period Bragg grating pattern is made by two methods. In the first sample the grating is fabricated by exposing the laser interference pattern on a photoresist, and then it is inscribed by $O_2$ plasma etching. The grating pattern of the second sample is formed by a PDMS soft mold imprinting process. The selective adhesion property of SU-8 material for Au and Si surfaces is utilized to prepare a 100-mm thick plastic substrate. Single mode waveguide is fabricated on the plastic substrate using polymer materials with refractive indices of 1.540 and 1.430 for the core and the cladding layers, respectively. The Bragg grating on Plastic substrate does not show any degradation in its spectral response compared to the reference sample made on a silicon wafer.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.60-67
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• 2011

Visible light communication system transmits data by controlling light emission of LED and receives data through photo detecter, which is considered as one of strong candidates of next generation wireless communication systems. The transmission capacity of visible light communication system depends on light intensity emitted from LED, sensitivity of PD, distance between transmitter and receiver, angle of incidence at the receiver. In particular, the receiver's vertical and horizontal movement changes distance between transmitter and receiver and angle of incidence, which may degrades transmission capacity of system. In this paper, we propose an estimation algorithm of receiver's position and angle based on tracking of received light intensity for indoor visible light communication systems. The performance evaluation of proposed algorithm confirms that the estimation algorithm of receiver's position and angle is quite important for visible light communication system to improve its transmission capacity.

• FLOWER RESEARCH JOURNAL
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• v.16 no.4
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• pp.284-290
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• 2008

In order to elucidate growth characteristics, physiological responses and leaf color changes of leaf-variegated Arundinaria munsuensis and Carex ciliato-marginata for variegata, These experiments were performed under four different light ragimes control(full sun), 40%, 70% and 85%. Plant height and leaf area became promoted as shading level increases in leaf-variegated Arundinaria munsuensis. Photosynthetic effect was the highest in 85% shading of the full sun. Thus, this plant could be growing in the deep shade condition. Plant growth and the leaf color changes were most obviously shown in the 40% shading level. In the Carex ciliatomarginata for. variegata growth status was the best and green or strong greenish yellow leaf color turned out to be much clearer in the 40% shading treatment. And photosynthetic activity was enhanced as the light intensity decreases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6221-6226
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• 2015

In this paper, waveguide analysis was interpreted as an optical waveguide using the feedback perturbation method simple and easy to apply compared to the analysis method, while the other almost identical to the numerical calculation method. In addition, efficient coupling with an optical transmission line of optical fiber and the waveguide form the thin film of different functional elements is required in order to achieve the full optical communication system. However, problems arise, such as the light field (field) and the decrease of the access efficiency due to inconsistency in the distribution characteristics of the connection surface by the difference in size of the cross section thereof when connecting the optical fiber and the waveguide directly to the combination of a thin film. Therefore propose a new type of connector structure to increase the efficiency of the connection when connecting the optical fiber waveguide and the thin film was analyzed by applying a coupled mode theory, the binding efficiency of the modified contactor. And by diffusing Ti on the $LiNbO_3$ substrate and a wide range of applications in the manufacture of integrated optical material made of a current low-loss Ti: $LiNbO_3$ optical waveguide and making the Y-branch waveguide, and the properties were confirmed.

• Journal of Korean Society of Forest Science
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• v.97 no.6
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• pp.680-689
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• 2008

This present study was conducted to investigate photosynthetic responses and chlorophyll fluorescence performances of Cornus controversa, Fraxinus rhynchophylla, Betula schmidtii, Prunus leveilleana, and Acer mono seedlings growing under four different light intensity regimes (full sun, and 65~72%, 29~40%, 7~12% of full sun). As result, Cornus controversa, Fraxinus rhynchophylla, and Betula schmidtii showed outstanding photosynthetic capacities in full sun and showed low shade tolerance. Prunus leveilleana showed good photosynthetic capacity in three treatment levels except for 7~12% of full sun and showed common shade tolerance. While, Acer mono showed good photosynthetic capacity and chlorophyll fluorescence in 29~40% of full sun. Acer mono showed the highest shade tolerance compared to the other four species.

• Journal of Astronomy and Space Sciences
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• v.19 no.1
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• pp.39-46
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• 2002

BV observations for V523 Cas were performed with 1.8m telescope and 2K CCD camera at Bohyunsan Optical Astronomy Observatory, Korea, on October 27, 1999. ${\Delta}m$ light curves for 11 comparison objects were made. It was found that their light curve slopes are different each other. Factor analysis for items of slope, (b-v) , magnitude, X pixel, and Y pixel results that there is strong correlation between the slope and the location (X,Y). It might be due to problems of CCD cooling system.