• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.116.1-116.1
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• 2011

L1448-MM, known as a class 0 YSO with a prominent outflow, was observed with the Photodetector Array Camera and Spectrometer (PACS) aboard Herschel Space Observatory by the key program, DIGIT (Dust, Ice, Gas in Time, PI: Neal Evans). The PACS covers various molecular and atomic line transitions such as CO, OH, $H_2O$, [OI], and [CII] at wavelengths from 55 to 210 ${\mu}m$. The line emission of $H_2O$, [OI], mid-J CO, and the OH fundamental transition distributes along the outflow direction although high-J CO and other OH emission peaks at the central spatial pixel. According to our excitation analysis, the CO gas has two temperature components: 300 K and 750 K, which are attributed to PDR and shock, respectively. However, the $H_2O$ gas with the rotation temperature ($T_{rot}$) of 200 K seems only affected by shock. Interestingly, the relative strength of OH transitions suggests the IR pumping process in L1448-MM. We also mapped L1448-MM in CO J=2-1 with the SRAO 6m telescope to compare with the FIR line transition maps.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1824-1827
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• 1998

A Laser Doppler Vibrometer(LDV) was developed using He-Ne laser as a light source. The heterodyne method was employed and its output signal was digitally processed with a $\mu$-processor and the result was displayed with LCD. The frequency shifted object beam(40 MHz) by a Bragg cell was focused on the surface of the moving target and the Doppler shifted reflected beam was recombined with reference beam at the fast photodetector to produce frequency modulated signal centered at 40 MHz. The signal from the detector was amplified and downconverted to intermediate frequency centered at 1 MHz after mixing process. The voltage output that was proportional to the velocity of the moving surface was obtained using PLL. With the same method, the fringe pattern signal of the moving surface is obtained. This fringe pattern signal is converted to TTL signal with ZCD(zero-crossing detector) and then counted to calculate the displacement due to the vibration, which is displayed with LCD. This LDV can be used to measure the resonant frequency of the electric equipments such as circuit breakers and transformers, of which resonant frequencies are changed when they are damaged.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.573-577
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• 2015

In this paper, we propose a signal processing board suitable for a semi-active laser tracking to detect an optical signal generated from the laser target designator by applying an analog trigger signal, the quadrant photodetector and a high speed ADC(analog-digital converter) sampling technique. We improved the stability by applying the averaging method to minimize the measurement error of a gaussian pulse. To evaluate the performances of the proposed methods, we implemented a prototype board and performed experiments. As a result, we implemented a frequency counter with an error 14.9ns in 50ms. PRF error code has a stability of less than 1.5% compared to the NATO standard. Applying the three point averaging method to ADC sampling, the stability of 28% in X-axis and 22% in Y-axis than one point sampling was improved.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.943-952
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• 2018

This paper presents a new type of absolute rotary encoder system based on the affine n-digit N-ary gray code. A brief comparison of the existing encoder systems is carried out in terms of resolution, encoding and decoding principles and number of sensor heads needed. Using the proposed method, two different types of encoder disks are designed, namely, color-coded disk and grayscale coded disk. The designed coded disk pattern is used to manufacture 3 digit 3 ary and 2 digit 5 ary grayscale coded disks respectively. The manufactured disk is used with the light emitter and photodetector assembly to design the entire encode system. Experimental analysis is done on the designed prototype with LabVIEW platform for data acquisition. A comparison of the designed system is done with the traditional binary gray code encoder system in terms of resolution, disk diameter, number of tracks and data acquisition system. The resolution of the manufactured system is 3 times higher than the conventional system. Also, for a 5 digit 5 ary coded encoder system, a resolution approximately 100 times better than the conventional binary system can be achieved. In general, the proposed encoder system gives $(N/2)^n$ times better resolution compared with the traditional gray coded disk. The miniaturization in diameter of the coded disk can be achieved compared to the conventional binary systems.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.85-90
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• 2002

$RuO_2$/GaN and related contacts were investigated for Schottky contacts in GaN-Based optical and electronic devices. We demonstrated that an $RuO_2$ film forms a stable Schottky contact on a GaN layer with a barrier height (${\Phi}_B$) of 1.46 eV and transmittance of 70% in the visible and near UV region. $RuO_2$/GaN Schottky diode showed a breakdown at over -50V and leakage current of only 0.3 nA at -5V. The $RuO_2$/GaN Schottky type photodetector had the UV/Visible rejection ratio of over $10^5$ and the responsivity of 0.23 A/W at 330 nm. The $RuO_2$ gate AlGaN/GaN EFET exhibited high drain current ($I_d$) of 689.3 mA/mm and high transconductance ($g_m$) of 197.4 mS/mm. Cut-Off frequency ($f_t$) and maximum operating frequency ($f_{max}$) were measured as 27.0 GHz and 45.5 GHz, respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.2
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• pp.130-137
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• 2005

LCD needs a backlight that is a light source as a photodetector that has a light modulation function and CCFL is used usually. Inverter that composes using existent winding transformer operates multi lamps, however, this efficiency falls by losses of core or winding and volume or weight increases or there is danger of fire by overheating. In order to solve these problems, a multi lamp driving Inverter using PT is composed according to the design guideline in this paper. We conformed whether the multi lamp drive method using EEFL that a current burden is less in applicable to piezoelectric inverter, and used the method that connect two piezoelectric transformers by parallel to an inverter.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.6
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• pp.359-364
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• 2016

NiO serves as a window layer for Si photoelectric devices. Due to the wide energy bandgap of NiO, high optical transparency (over 80%) was achieved and applied for Si photoelectric devices. Due to the high the high mobility, the heterojunction device (Al/n-Si/$SiO_2$/p-NiO/ITO) provide ultimately fast photoresponses of rising time of $38.33{\mu}s$ and falling time of $39.25{\mu}s$, respectively. This functional NiO layer would provide benefits for high-performing photoelectric devices, including photodetectors and solar cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.8
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• pp.508-513
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• 2017

Ultraviolet (UV) photodetectors are used in various industries and fields of research, including optical communication, flame sensing, missile plume detection, astronomical studies, biological sensors, and environmental research. However, general UV detectors that employ Schottky junction diodes and p-n junctions have high fabrication cost and low quantum efficiency. In this study, we investigated the characteristics of materials used to manufacture UV photodetectors in a low-cost solution process that requires easy fabrication of flexible substrates. We fabricated p-type NiO and n-type ZnO substrates with wide band gap by the sol-gel method and compared the characteristics of substrates prepared under different spin-coating and heat-treatment conditions.

• Journal of Sensor Science and Technology
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• v.24 no.2
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• pp.79-82
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• 2015

This paper proposes a novel complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) and presents its performance characteristics. The proposed APS exhibits a linear-logarithmic response, which is simulated using a standard $0.35-{\mu}m$ CMOS process. To maintain high sensitivity and improve the dynamic range (DR) of the proposed APS at low and high-intensity light, respectively, two additional nMOSFETs are integrated into the structure of the proposed APS, along with a photogate. The applied photogate voltage reduces the sensitivity of the proposed APS in the linear response regime. Thus, the conversion gain of the proposed APS changes from high to low owing to the addition of the capacitance of the photogate to that of the sensing node. Under high-intensity light, the integrated MOSFETs serve as voltage-light dependent active loads and are responsible for logarithmic compression. The DR of the proposed APS can be improved on the basis of the logarithmic response. Furthermore, the reference voltages enable the tuning of the sensitivity of the photodetector, as well as the DR of the APS.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.116-116
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• 2000

질화물 반도체는 LED, LD, Transistor, 그리고 Photodetector 등 광소자 및 전자소자를 실현할 수 있는 소재로써 최근에 각광 받고 있으며, 또한 국·내외적으로 연구가 활발히 진행되고 잇다. 질화물 발광 다이오드 제작에는 소자의 효율과 수명시간의 향상을 위하여 질화물 반도체와 금속과의 접합시 고 품질의 오믹 접합이 필수적이다. 특히 p-형 GaN의 경우에는 높은 정공 농도를 갖는 p-형 GaN를 얻기가 어렵고 GaN의 일함수에 비하여 높은 일함수를 갖는 금속이 없기 때문에 매우 낮은 접합 저항을 가지며 안정성이 매우 우수한 금 접합을 얻기가 어렵다고 알려져 있다. 또한, GaN 계열의 발광 다이오드는 일반적으로 표면 발광 다이오드 형태로 제작되기 때문에 p-형 GaN 층의 오믹 접촉으로 사용되는 금속의 전기적 특성뿐만 아니라 발광 다이오드의 활성층에서 발광되어 나오는 빛에 대한 투과도 또한 우수하여야 발광 다이오드의 효율이 우수해진다. 본 연구에서는 p-형 GaN층의 접합 금속으로 Pt(80nm)과 Ni(5nm)/Au(7nm)를 사용하여 InGaN/GaN 다중양자우물 구조의 발광 다이오드를 제작하여 전기적 특성 및 발광효율을 측정하였다. 그리고, Pt(80nm)과 p-형 GaN와의 접합시 온도 변화에 따른 전기적 특성을 TLM 방법으로 조사하고, 가시광선 영역에서의 빛에 대한 투과도를 UV/VIS spectrometer, X-ray reflectivity, 그리고 Atomic Force Microscopy 등을 이용하여 분석하였다.