• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.783-786
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• 2003

Thin films of vanadium oxide(VOx) have been deposited by r.f. magnetron sputtering from $V_2O_5$ target in gas mixture of argon and oxygen. The oxygen/(oxygen+argon) partial pressure ratio of 0% and 8% is adopted. Crystal structure and optical properties of films sputter-deposited under different oxygen gas pressures and in situ annealed in vacuum at $400^{\circ}C$ for 1h and 4h are characterized through XRD and optical absorption measurements. The films as-deposited are amorphous, but $0%O_2$ films annealed for time longer than 4h and $8%O_2$ films annealed for time longer than 1h are polycrystalline. The optical transmission of the films annealed in vacuum decreases considerably than the as-deposited films and the optical absorption of all the films increases rapidly at wavelength shorter than about 550nm. Indirect and direct optical band gaps were decreased with increasing the annealing time.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.175-175
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• 2011

인체감지 적외선 센서로 사용되는 마이크로볼로미터 센서 감지재료인 $V_{2-x}W_xO_5$를 증착하고 단위소자를 제작하여 저항 및 센서성능을 측정 조사하였다. 감지재료는 $V_2O_5$에 W을 첨가하여 $V_{2-n}W_nO_5$ 타겟을 제작하였으며 RF sputtering 장비를 이용하여 $V_{1.85}W_{0.15}O_5$ 박막을 증착하였다. 증착온도 $400^{\circ}C$, $Ar/O_2$ 가스비율 50/20, 두께 200nm로 증착된 센서 재료의 특성을 조사한 결과 저항은 약 $20{\sim}70k{\Omega}$이었으며, TCR 값은 -3%/$^{\circ}C$ 이상으로 매우 우수한 박막특성을 얻었다. 볼로미터소자는 $40{\times}40{\sim}140{\times}140um^2$의 셀면적으로 설계하여 전극패턴과 습식식각공정으로 센서 구조체를 제작하였다. 소자의 성능평가는 검출기 측정장비를 이용하여 반응도 및 탐지도 특성을 조사하였다.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.30 no.1
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• pp.48-52
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• 2019

Background and Objectives : Functional aphonia is characterized by incomplete closure of the vocal folds. Semi-occluded vocal tract exercise (SOVTE) allows smoothly vocal folds collision without damage to the vocal folds tissues to produce normal vocal intensity. The purpose of this study is to report the effect of SOVTE in patients with functional aphonia. Materials and Method : Seven patients diagnosed with functional aphonia were treated with 1-3 voice therapy sessions using voiced lip-trill, humming, Lax Vox in SOVTE. To assess the effectiveness of semi-occluded vocal tract exercise, cepstral analysis and auditory perceptual assessment were performed before and after voice therapy. Results : F0 (fundamental frequency), CPP (cepstral peak prominence) and L/H ratio (low/high spectral ratio) were significantly increased, while CPP Standard deviation, L/H ratio Standard deviation were decreased. In addition, 'Grade', 'Breathiness' and 'Asthenia' were significantly decreased in the GRBAS scale after SOVTE (p<0.05). Conclusion : In our study, SOVTE seemed to be effective to elicit voice quickly and promote vocal folds vibration without muscular effort in patients with functional aphonia.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.131-131
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• 2003

Surface micromachined uncooled IR detector with the optimized VOx bolometric layer was fabricated based on sandwich structure of the V$_2$O$_{5}$V/V$_2$O$_{5}$. In order to improve the detectivity of the IR detector, we optimized a few factors in the viewpoint of bolometric material. Vanadium oxide thin film is a promising material for uncooled microbolometers due to its high temperature coefficient of resistance at room temperature. It is, however, very difficult to deposit vanadium oxide thin films having high temperature coefficient of resistance and low resistance because of process limits in microbolometer fabrication. In order to increase the responsivity and decrease noise, we increase TCR of bolometric material and decrease room temperature resistance based on the sandwich structure of the V$_2$O$_{5}$V/V$_2$O$_{5}$ by conventional sputter. By oxygen diffusion through low temperature annealing of V$_2$O$_{5}$V/V$_2$O$_{5}$ in oxygen ambient, various mixed phase vanadium oxide was formed and we obtained TCR in range of-1.2 ~-2.6%/$^{\circ}C$ at room temperature resistance of 5~100k$\Omega$.mega$.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.311-316
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• 2018

An antenna-coupled bolometer-type terahertz sensor was designed, fabricated, evaluated, and utilized to obtain terahertz transmission images. The sensor consists of a thin film bowtie antenna that resonates accordingly in response to an incident terahertz beam, a heater that converts the applied current in the antenna into heat, and a microbolometer that converts the rise in temperature into a change in resistance. The device is fabricated by a bulk micromachining process on a 4-inch silicon wafer. The fabricated sensor chip has a size of $2{\times}2mm$ and an active area of $0.1{\times}0.1mm^2$. The temperature coefficient of resistance (TCR) of the bolometer film (VOx) is 2.0%, which is acceptable for bolometer applications. The output sensor signal is proportional to the power of the incident terahertz beam. Transmission images were obtained with a 2-axis scanning imaging system that contained the sensor. The small active area of the sensor will enable the development of highly sensitive focal plane array sensors in terahertz imaging cameras in the future.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.1002-1010
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• 2013

Intercom System(ICS) of Korean Utility Helicopter(KUH) is an essential equipment for pilot to perform flight mission and it consists of communication system of KUH with VHF-FM radio set and U/VHF-AM radio set. It provides pilots and crews with internal communication, external communication and audible alarm. It has function of controlling volume and selecting two communication modes, normal mode and backup mode. This paper summarizes pilot comments in flight test which are classified by cause of occurrence and the troubleshooting process about each comment. It also describes design improvements which was derived from troubleshooting and suggests verification results of flight test.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.109-110
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• 2006

In bio applications, high temperature coefficient of resistance (TCR) at $30^{\circ}C{\sim}40^{\circ}C$ is especially important for a temperature sensor. In this work, single phase-vanadium dioxide ($VO_2$) thin films for temperature sensor were fabricated by reactive DC magnetron sputtering and post-annealing method. VOx thin films deposited by reactive sputtering in a controlled $Ar/O_2$ atmosphere can be transformed into single phase-$VO_2$ films by post-annealing in $N_2$ atmosphere. The grown $VO_2$ thin films have a moderate resistance at room temperature and very high TCR at room temperature and transition temperature, respectively 2.88%/K and 15.8%/K. A detailed structural characterization is performed by SEM, XRD and RBS. SEM morphology image indicates that grains of fabricated $VO_2$films are homogeneous and ball-like in shape. A fact that the films contain only single phase-$VO_2$ is obtained by XRD and RBS analysis. After deposition, the sensors were fabricated by micromachining technology. Silicon nitride membrane and black nickel were used for a thermal isolation structure and absorption layer. In the vicinity of room temperature, the TCR of sensors was enough high to apply for bio sensors.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.12
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• pp.1321-1328
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• 2015

A radio is a half-duplex voice communication method using the PTT(: Push To Talk), occupy a single line calls during transmission. As an interface between the telephone and the radio, UHF and VHF, for voice communication between the different heterogeneous devices, A device automatically switches between the two devices is required. Therefore, in accordance with the performance of the voice switching apparatus for detecting a voice to be transmitted from an input signal, loss of the audio signal to be transmitted is subjected to Significant influence. Conventional method has the problem responding to noise by setting the level through simple means of amplitude of input signal, in other words, the energy level of the input signal. This paper, by using the audio signal processing techniques, this discriminated what the voice is among the input signal and substantiated a device for the automatic voice transmission between heterogeneous devices. With this proposal, I was confirmed of improvement of performance in the automatic voice switching device, could perform loss-less transmission of voice between heterogeneous devices.

• Convergence Security Journal
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• v.23 no.1
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• pp.27-33
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• 2023

Digitalization due to COVID-19 has rapidly developed artificial intelligence-based voice recognition technology. However, this technology causes unfair social problems, such as race and gender discrimination if datasets are biased against some groups, and degrades the reliability and security of artificial intelligence services. In this work, we compare and analyze accuracy-based unfairness in biased data environments using VGGNet (Visual Geometry Group Network), ResNet (Residual Neural Network), and MobileNet, which are representative CNN (Convolutional Neural Network) models of artificial intelligence. Experimental results show that ResNet34 showed the highest accuracy for women and men at 91% and 89.9%in Top1-accuracy, while ResNet18 showed the slightest accuracy difference between genders at 1.8%. The difference in accuracy between genders by model causes differences in service quality and unfair results between men and women when using the service.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.361-361
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• 2013

비냉각 적외선 검출소자는 빛이 전혀 없는 환경에서도 사물을 감지하는 열상장비의 핵심소자이다. 마이크로볼로미터 적외선 검출기는 상온에서 동작하며, 온도안정화를 위해 TEC를 장착하여 진공패키지로 조립된다. 패키지는 진공을 유지할 수 있도록 일반적으로 메탈로 제작되며, 단가 감소 및 생산성 증대를 위해 wafer level packaging 방법을 이용한다. 마이크로볼로미터의 특성은 패키지의 진공 변화에 매우 민감하다. 센서의 감도를 증가시키기 위해서는 진공환경을 유지해야 한다. 볼로미터 소자의 특성은 상압에서 열전도는 기판과 멤브레인 사이의 에어갭을 통해 열손실을 야기하므로 센서의 반응도가 현저히 줄어든다. 에어갭이 1 um 정도 되더라도 그 사이에 존재하는 열전도가 가능하므로 진공을 유지하여 열고립 상태를 증대시킬 수 있다. 이에 본 연구에서는 소자의 동작시 압력, 즉 진공도가 볼로미터 소자의 반응도 특성에 미치는 영향을 조사하였다. 마이크로볼로미터 소자는 $2{\times}8$ 어레이 형태로 제작하였으며, metal pad를 각 단위셀에 배치하였으며, 공통전극으로 한 개의 metal pad를 넣어 설계하였다. 흡수체로써 VOx를 사용하였으며, 열 고립구조를 위해 2.5 um 공명 흡수층의 floating 구조로 멤브레인을 형성하였다. 진공패키지는 메탈패키지를 제작하여 볼로미터 칩을 TEC 위에 장착하였으며, 신호의 감지를 위해 가변저항을 매칭시켰다. 반응도는 신호 대 잡음 값을 획득하여 소자에 도달하는 적외선 에너지에 대해 반응하는 값을 계산에 의해 얻어내는 것이다. 픽셀 크기는 $50{\times}50$ um이며, 패키지 조립 공정 후 온도변화에 따른 저항 측정을 통해 TCR 값을 얻었다. 이때 TCR은 약 -2.5%/K으로 나타났다. $2{\times}8$의 4개 단위소자에 대해 측정한 값은 균일하게 TCR 값이 나타났다. 광반응 특성은 볼로미터 단위소자에 대해서 먼저 고진공(5e-6 torr) 하에서 측정하였으며, 반응도는 25,000 V/W의 값을 나타내었고, 탐지도는 약 2e+8 $cmHz_{1/2}$/W로 나타났다. 패키지의 압력 조절을 위해 TMP 및 로터리 펌프를 이용하여 100 torr에서 1e-4 torr의 범위에서 압력조절 밸브를 이용하여 질소가스의 압력으로 진공도를 변화시켰다. 적외선 반응신호는 압력이 증가함에 따라 감소하였으며, 2e-1 torr의 압력에서 신호의 크기가 감소하기 시작하여 5 torr에서 반응도의 1/2 값을 나타냄을 알 수 있었다. 30 torr 이상에서는 신호가 잡음값 과거의 동일하여 신호대 잡음비가 1로 나타남을 알 수 있었다. 또한 진공도 변화에 대해, 흑체온도에 따른 반응도 및 탐지도의 특성을 조사한 결과를 발표한다. 반응도의 증가를 위해 진공도는 진공도는 1e-2 torr 이하의 압력을 유지해야 함을 본 실험을 통해 알 수 있었다.