• Journal of Digital Contents Society
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• v.7 no.3
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• pp.139-145
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• 2006

Short-range wireless transmission and networking technologies are becoming increasingly important in enabling useful mobile applications. Bluetooth and IEEE 802.11b standards are the most commonly deployed technologies for WPAN and WLAN. This paper investigates the effect of short range wireless channel on the performance of MC-CDMA/BPSK system and Bluetooth GFSK signal transmission in AWGN and Rician fading environments. And we investigate performance degradation due to interference effects in short range wireless channel. We firstly derive a equation for the bit error probability in additive white Gaussian noise depending on MC-CDMA/BPSK signal and GFSK modulation signal parameters according to the Bluetooth RF standard. Then, from this error rate expression we calculate the mean error probability for MC-CDMA/BPSK signal and Bluetooth GFSK signal in Rician fading and interference channel. In particular, the impacts of the Rician fading depth and interference level on the error probability is shown in BER performance figures.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.15-22
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• 2011

Integrated-optic symmetric/asymmetric Mach-Zehnder interferometers at $1.3{\mu}m$ wavelength were studied as sensing part for electric-field measurement system. The devices were simulated based on the BPM software and fabricated utilizing Ti-diffused $LiNbO_3$ channel optical waveguides and lumped-type electrodes. A half-wave voltage of $V_{\pi}$=6.6V and modulation depth of 100% and 75% for a symmetric structure were measured for 200Hz and 1kHz electrical signal bandwidth, respectively. By the way, almost half-maximum power transmission was observed for asymmetric interferometers with ${\pi}$/2 intrinsic phase difference. Expected experimental measurements were observed for 1kHz electrical signal bandwidth.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.145-152
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• 1989

Volume phase diffraction grating is formed in 5${mu}m$ Agfa 8E75 photographic emulsion film using He-Ne laser. It is dependent on the chemical processing rather than materials themselves that high diffraction efficiency can obtained in silver halide emulsions. With potassium dichromate bleach and alcohol drying, overall efficiency of 71% (81% after allowing for reflection at the two surfaces) has been achieved at an exposure of 180${mu}J/cm^2.$ Dichromate cross-linkage and air void by rapid dehydration increase refractive index modulation depth. The grating is swollen, which is newly identified by Scanning Electronic Microscope(SEM) photography, and it causes on-Bragg at larger angle than the recording angle. It is pointed out that controlling the emulsion thickness has an important role as a potential source for high diffraction efficiency.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.258-264
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• 1997

$YBa_{2}Cu_{3}O_{7}$ single layer dc SQUID magnetometers, prepared on $1\;cm^{2}\;SrTiO_{3}$ substrates, have been fabricated and characterized. Based on the analytical description, a SQUID magnetometer design having a 8.5 mm pickup coil with 2.6 mm linewidth, and a SQUID inductance Ls = 50 pH with $3\;{\mu}m$ Josephson junctions is presented. The devices showed a maximum modulation voltage depth of $65\;{\mu}V$ and a magnetic field noise of 0.6 pT /$\sqrt{Hz}$ at 1 Hz. Clear traces of human magnetocardiogram could be obtained with the SQUID magnetometer operating at 77 K.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.154-160
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• 1996

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tighter and desired surface cnotours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated dapth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in additn to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamoneter. Based on the parameter estimation of cutting dynamics and the admitance model-based nanodynamic control scheme, simulation results are shown.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.557-560
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• 2020

최근, 광소자에서 공간 변조되는 wavefront profile 특성을 광소자의 표면 단차 변화 없이 단일 두께 박막 상에서 자유로이 구현할 수 있는 기하위상 홀로그램 (geometric phase hologram) 기반의 optical component에 대한 관심이 증대되고 있다. 특히 이를 이용해 제작된 기하위상 렌즈 (geometric phase lens)는 dynamic phase의 공간적 차이에 의해 구현되던 기존 bulk optics 기반의 lens 대비 초박형으로 제작이 가능한 파장 선택적 flat optics 기술로써, 다초점 및 경량화를 요구하는 차세대 디스플레이 기술 (augmented reality 또는 AR, mixed reality 또는 MR) 및 광파변조 및 제어를 요구하는 홀로그래픽 카메라 분야에 대한 응용처로 많은 주목을 받고 있다. 이에 본 논문에서는 해당 기하 위상렌즈에 대한 원리 및 이에 따른 개발이슈 및 해결법에 대해 연구 하였으며, 이에 대한 응용처로 기하위상 렌즈의 편광에 따른 이중초점특성을 이용해, 기존 단일 초점 형성이 가능한 AR기기 대비, 다초점 형성이 가능한 switchable dual-depth 3D AR device를 compact한 모듈과 함께 구현하였다. 또한, 기하위상렌즈의 광파 변조 및 분리특성을 이용한 기하위상 렌즈기반의 자가간섭 홀로그래픽 시스템(GP-self-interference incoherent digital holographic, GP-SIDH)에 편광 이미지센서 적용과 함께 맞춤형 설계/제작된 기하 위상렌즈를 적용함으로써, 기존 GP-SIDH 시스템대비 안정적으로 실시간 복소 홀로그램 획득이 가능한 실시간 공간영상정보 획득용 GP-SIDH을 동영상 프레임으로 구현하였다.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.68-78
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• 2021

A subminiature catadioptric omnidirectional optical system (SCOOS) with 2 mirrors, 6 plastic aspherical lenses, and an illumination system of 6 light emitting diodes, to observe the 360° panoramic image of the inner intestine, is optically designed and evaluated for a capsule endoscope. The total length, overall length, half field of view (HFOV), and F-number of the SCOOS are 14.3 mm, 8.93 mm, 51°~120°, and 3.5, respectively. The optical system has a complementary metal-oxide-semiconductor sensor with 0.1 megapixels, and an illumination system of 6 light-emitting diodes (LEDs) with 0.25 lm to illuminate on the 360° side view of the intestine along the optical axis. As a result, the spatial frequency at the modulation transfer function (MTF) of 0.3, the depth of focus, and the cumulative probability of tolerance at the Nyquist frequency of 44 lp/mm and MTF of 0.3 of the optimized optical system are obtained as 130 lp/mm, -0.097 mm to +0.076 mm, and 90.5%, respectively. Additionally, the simulated illuminance of the LED illumination system at the inner surface of the intestine within HFOV, at a distance of 15.0 mm from the optical axis, is from a minimum of 315 lx to a maximum of 725 lx, which is a sufficient illumination and visibility.

• Korean Journal of Optics and Photonics
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• v.32 no.6
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• pp.286-295
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• 2021

A modified catadioptric omnidirectional optical system (MCOOS) using an RGB/NIR CMOS sensor is optically designed for a capsule endoscope with the front field of view (FOV) in visible light (RGB) and side FOV in visible and near-infrared (NIR) light. The front image is captured by the front imaging lens system of the MCOOS, which consists of an additional three lenses arranged behind the secondary mirror of the catadioptric omnidirectional optical system (COOS) and the imaging lens system of the COOS. The side image is properly formed by the COOS. The Nyquist frequencies of the sensor in the RGB and NIR spectra are 90 lp/mm and 180 lp/mm, respectively. The overall length of 12 mm, F-number of 3.5, and two half-angles of front and side half FOV of 70° and 50°-120° of the MCOOS are determined by the design specifications. As a result, a spatial frequency of 154 lp/mm at a modulation transfer function (MTF) of 0.3, a depth of focus (DOF) of -0.051-+0.052 mm, and a cumulative probability of tolerance (CPT) of 99% are obtained from the COOS. Also, the spatial frequency at MTF of 170 lp/mm, DOF of -0.035-0.051 mm, and CPT of 99.9% are attained from the front-imaging lens system of the optimized MCOOS.

• International Journal of Oncology
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• v.54 no.6
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• pp.2169-2178
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• 2019

Forkhead box A1 (FOXA1) functions as a tumor suppressor gene or an oncogene in various types of cancer; however, the distinct function of FOXA1 in colorectal cancer is unclear. The present study aimed to evaluate whether FOXA1 affects the oncogenic behavior of colorectal cancer cells, and to investigate its prognostic value in colorectal cancer. The impact of FOXA1 on tumor cell behavior was investigated using small interfering RNA and the pcDNA6-myc vector in human colorectal cancer cell lines. To investigate the role of FOXA1 in the progression of human colorectal cancer, an immunohistochemical technique was used to localize FOXA1 protein in paraffin-embedded tissue blocks obtained from 403 patients with colorectal cancer. Tumor cell apoptosis and proliferation were evaluated using a terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and Ki-67 immunohistochemical staining, respectively. FOXA1 knockdown inhibited tumor cell invasion in colorectal cancer cells, and induced apoptosis and cell cycle arrest. FOXA1 knockdown activated cleaved caspase-poly (ADP-ribose) polymerase, upregulated the expression of p53 upregulated modulator of apoptosis, and downregulated BH3 interacting domain death agonist and myeloid cell leukemia-1, leading to the induction of apoptosis. FOXA1 knockdown increased the phosphorylation level of signal transducer and activator of transcription-3. By contrast, these results were reversed following the overexpression of FOXA1. The overexpression of FOXA1 was associated with differentiation, lymphovascular invasion, advanced tumor stage, depth of invasion, lymph node metastasis and poor survival rate. The mean Ki-67 labeling index value of FOXA1-positive tumors was significantly higher than that of FOXA1-negative tumors. However, no significant association was observed between the expression of FOXA1 and the mean apoptotic index value. These results indicate that FOXA1 is associated with tumor progression via the modulation of tumor cell survival in human colorectal cancer.

• Progress in Medical Physics
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• v.26 no.4
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• pp.250-257
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• 2015

Multi-leaf collimator (MLC) systems are frequently used to deliver photon-based radiation, and allow conformal shaping of treatment beams. Many proton beam centers currently make use of aperture and snout systems, which involve use of a snout to shape and focus the proton beam, a brass aperture to modify field shape, and an acrylic compensator to modulate depth. However, it needs a lot of time and cost of preparing treatment, therefore, we developed the manual MLC for solving this problem. This study was carried out with the intent of designing an MLC system as an alternative to an aperture block system. Radio-activation and dose due to primary proton beam leakage and the presence of secondary neutrons were taken into account during these iterations. Analytical calculations were used to study the effects of leaf material on activation. We have fabricated tray model for adoption with a wobbling snout ($30{\times}40cm^2$) system which used uniform scanning beam. We designed the manual MLC and tray and can reduce the cost and time for treatment. After leakage test of new tray, we upgrade the tray with brass and made the safety tool. First, we have tested the radio-activation with usually brass and new brass for new manual MLC. It shows similar behavior and decay trend. In addition, we have measured the leakage test of a gantry with new tray and MLC tray, while we exposed the high energy with full modulation process on film dosimetry. The radiation leakage is less than 1%. From these results, we have developed the design of the tray and upgrade for safety. Through the radio-activation behavior, we figure out the proton beam leakage level of safety, where there detects the secondary particle, including neutron. After developing new design of the tray, it will be able to reduce the time and cost of proton treatment. Finally, we have applied in clinic test with original brass aperture and manual MLC and calculated the gamma index, 99.74% between them.