• Journal of Power Electronics
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• 제16권3호
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• pp.1209-1217
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• 2016

This paper presents a novel charge pump scheme that combines the advantages of Fibonacci and Dickson charge pumps to obtain 30 V voltage for display driver integrated circuit application. This design only requires four external capacitors, which is suitable for a small-package application, such as smart card displays. High-amplitude (<6.6 V) clocks are produced to enhance the gate drive of a Dickson charge pump and improve the system's current drivability by using a voltage-doubler charge pump with a pulse skip regulator. This regulation engages many middle-voltage devices, and approximately 30% of chip size is saved. Further optimization of flying capacitors tends to decrease the total chip size by 2.1%. A precise and simple model for a one-stage Fibonacci charge pump with current load is also proposed for further efficiency optimization. In a practical design, its voltage error is within 0.12% for 1 mA of current load, and it maintains a 2.83% error even for 10 mA of current load. This charge pump is fabricated through a 0.11 μm 1.5 V/6 V/32 V process, and two regulators, namely, a pulse skip one and a linear one, are operated to maintain the output of the charge pump at 30 V. The performances of the two regulators in terms of ripple, efficiency, line regulation, and load regulation are investigated.

• 한국추진공학회지
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• 제19권5호
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• pp.84-90
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• 2015

티타늄 합금은 고온 추진체의 부품에 사용될 경우, 고온의 화염에서 순간적으로 노출될 수 있음으로, 고온의 화염하에서의 내산화특성을 평가할 필요가 있다. 본 연구에서는 Ti64 합금 (Ti-6%Al-4%V) 및 코팅된 Ti64 합금을 고온화염하에서 산화손상 및 내산화 특성을 평가하고자 하였다. Ti64 합금의 코팅은 알루미늄 확산코팅법을 사용하여 코팅을 수행하였다. 표면에 알루미나이드층이 코팅되지 않은 Ti64 합금은 고온의 화염 노출시에 표면 박리현상이 발생하였으나, 코팅된 시험편은 표면박리현상이 나타나지 않았고 알루미나이드 층의 산화물 생성으로 인하여 표면이 보호됨을 관찰할 수 있었다. 화염노출시 코팅층의 역할을 고찰하기 위하여 코팅층을 분석하였으며, 조직의 변화를 고찰하고 논의하였다.

• 한국환경과학회지
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• 제24권3호
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• pp.353-358
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• 2015

In this study, we analyzed two types of echolocation calls used by the parti-coloured bat, Vespertilio sinensis. Bats were captured in the Naejangsan National Park in October 2013. Call sounds of hand-released bats were recorded at the location of capture within the National Park. We analyzed pulse duration (PD), pulse interval (PI), peak frequency (PF), maximum frequency ($F_{MAX}$), minimum frequency ($F_{MIN}$), and bandwidth (BW). V. sinensis emitted the different types of the echolocation calls depending on the surrounding environment. Frequency modulated-constant frequency (FM-CF) signal of audible range was emitted when they flew in the uncluttered space over the canopy. However, when flying in the cluttered space below the canopy, they only emitted FM signal. FM-CF signal is in the audible range (e.g., low frequency), and FM signal has a harmonic broadband frequency range of two. There were significant differences in PD, PI, PF, FMAX, FMIN, and BW between the calls emitted over and below the canopy. Considering the functional characteristics of FM and CF signals, we conclude that the foraging activity of V. sinensis was observed below the canopy, and recommend the use of FM signal and broadband as echolocation signals.

• Journal of Power Electronics
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• 제16권5호
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• pp.1725-1734
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• 2016

This paper presents a novel seven-level (7L) voltage source converter for high-power medium-voltage applications. The proposed topology is an H-bridge connection of two nested neutral-point clamped (NNPC) converters and is referred to as an HNNPC converter. This converter exhibits advantageous features, such as operating over a wide range of output voltages, particularly for 10-15 kV applications, without the need to connect power semiconductors in series; high-quality output voltage; and fewer components relative to other classic seven-level topologies. A novel sinusoidal pulse width modulation technique is also developed for the proposed 7L-HNNPC converter to control flying capacitor voltages. One of the main features of the control strategy is the independent application of control to each arm of the converter to significantly reduce the complexity of the controller. The performance of the proposed converter is studied under different operating conditions via MATLAB/Simulink simulation, and its feasibility is evaluated experimentally on a scaled-down prototype converter.

• 대한의용생체공학회:의공학회지
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• 제23권1호
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• pp.73-79
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• 2002

최근 들어 컴퓨터와 디스플레이 기술의 발달로 실제 공포 상황에서의 자극과 거의 유사한 자극을 유발할 수 있는 가상환경의 창조가 가능하게 되었으며 이러한 실제 상황에서의 노출치료 대안으로 가상현실을 이용한 공포증의 치료방법이 사용되어져 왔다. 하지만 가상환경이 공포증 환자 에게 심리적이나 생리적으로 어떠한 영향을 미치는지에 대한 연구는 거의 전무한 실정이다. 따라서 본 논문에서는 가상환경 하에서 공포증환자와 정상인의 생리적 반응에 대한 평가를 함으로써 가상환경이 미치는 영향에 대하여 분석하고. 또한 가상현실 치료 시에 공포증환자의 생리적 반응의 변화를 측정함으로써 치료의 성공유무를 판단할 수 있는 지표를 제시하고자 한다. 본 실험은 스물 두 명의 정상인 (평균 32.74세)과 서른여섯 명의 비행공포증 환자를 대상으로 두 그룹으로 나누어 진행되었다. 생리적 반응으로는 심박동수, 피부저항. 그리고 피부 온도를 측정하였다. 실험결과. 두 그룹에서의 피부저항은 유의한 차이(T(56)=2.978, p〈0.01)를 보였으며, 공포증 환자 그룹 중 가상현실로 공포증이 치료가 된 서른세 명의 피부저항은 치료가 진행됨에 따라 점차 정상인의 특성 쪽으로 가까워짐을 보였다. 본 연구를 통해 생리적 반응. 특히 피부저항은 가상환경에서 피험자의 상태를 이해하거나, 가상환경을 이용한 치료의 결과를 검증하는데 유용하게 사용될 수 있을 것이라 사려된다.

• 항공우주기술
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• 제12권1호
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• pp.22-31
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• 2013

틸트로터 항공기인 스마트무인기의 회전익모드, 천이모드, 고정익 모드 비행시험을 수행하여 전체 비행영역에 대한 비행제어법칙 검증을 완료하였다. 회전익모드에서는 자동이륙과 자동착륙, 자동호버 비행 및 자동회귀모드 비행을 수행하였다. 천이모드에서는 틸트각 10도 간격으로 속도, 고도, 롤/방위 유지명령을 이용하여 상승, 하강, 좌선회 및 우선회 비행을 수행하고, 자율천이비행을 수행하였다. 회전익모드와 천이모드에서의 로터속도는 98%를 유지하였고, 고정익 모드 비행은 260 km/h 속도에서 로터 회전수를 82%로 감속하여 최대속도까지 점진적으로 영역확장비행을 수행하였다. 최종적으로 대기고도 3 km에서 최고속도 440 km/h까지 도달하였다. 본 논문에서는 스마트무인기의 전체 비행영역에 대해 비행영역 확장시험을 수행하는 동안 획득된 데이터의 분석결과를 제시하고, 규격서의 비행제어 요구조건과 비교하여 비행성이 요구성능을 만족함을 검증하였다.

• 전기학회논문지
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• 제57권6호
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• pp.972-981
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• 2008

A New ZVS(Zero Voltage Switching) and ZVZCS(Zero Voltage and Zero Current Switching) Three-Level Converter is proposed. The proposed converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the all switch. A primary auxiliary circuit, which consists of one coupled inductor, is added in the primary to provide ZVZCS conditions to primary switches. Many advantages including simple circuit topology high efficiency, and low cost make this converter attractive for high power applications. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 2kW(27V, 74A) 40 kHz IGBT based experimental circuit.

• KSTLE International Journal
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• 제5권2호
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• pp.52-56
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• 2004

The hard disk drive performance depends strongly on air bearing characterisitcs of the head slider. The objective of the slider design is to provide accurate positioning of the magnetic read/write element at the very small height above the disk. Application of the numerical methods is required due to complexity of the air bearing surface of the slider. The Boundary-Fitted Coordinate System Divergence Formulation method can be used for calculation of pressure distribution in the case of steep film thickness gradients. In the present work, the interpolating functions used in the expression for the Couette flow are modified in order to improve the solution characteristics in the extremely high compressibility number region. The advantages of the modified method are demonstrated on example of the flat skewed slider. Finally, the modi.ed method is applied to analysis of the static characteristics of the femto-slider. The analysis results indicate the effect of the silder's air bearing surface crown on the flying height and the pitching angle in steady state position.

• 한국항행학회논문지
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• 제27권5호
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• pp.685-689
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• 2023

The proposed system in the study aims to detect forest fires in real-time stream data received from the drone-camera. Recently, the number of wildfires has been increasing, and also the large scaled wildfires are frequent more and more. In order to prevent forest fire damage, many experiments using the drone camera and vision analysis are actively conducted, however there were many challenges, such as network speed, pre-processing, and model performance, to detect forest fires from real-time streaming data of the flying drone. Therefore, this study applied image data processing works to capture five good image frames for vision analysis from whole streaming data and then developed the object detection model based on YOLO_v2. As the result, the classification model performance of forest fire images reached upto 93% of accuracy, and the field test for the model verification detected the forest fire with about 70% accuracy.

• 수산해양기술연구
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• 제43권1호
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• pp.1-11
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• 2007

It is the basic studies for productivity improvement and laborsaving of purse seine fishery. Because the seine shape is apt to be transformed in seine shooting process due to the effect of tide, this study is intended to establish 4 steps, whose flow velocity are 0, 2, 4 and 6cm/sec, in flume tank and perform the experiment to review the character. We used two model seines designed on the scale of 1 to 180 based on the power block seine, which is the mackerel purse seine generally used in the near sea of Jeju Island and triplex seine, which is the mackerel purse seine of one boat system fishing expected in the future, for the experiment, analyzed of the sinking movements on the two seines and its results are as follows. In the setting over the flow velocity 6cm/sec, experiment was impossible because of flying and transformation of seine were severe. The sinking movements of P seine and T seine generally showed linear phenomenon and the sinking speed showed gentle curve shape. Sinking tendency was distinguished by existence of flow velocity. When there is flow velocity, it showed the phenomenon that it sinking by similar type. Although sinking depth and sinking speed did not show distinguished classification, P seine shows bigger than T seine. When there was in flow velocity, the elapsed time(Et) and sinking depth (PDp, TDp) of P seine and T seine can be shown such experimental equations as PDp=(0.21V+4.96)Et-(0.62V-0.10) and TDp=(0.19V+4.95)Et-(0.72V+0.34). When there was in flow velocity, the elapsed time and siking speed (PSp, TSp) of P seine and T seine can be shown such experimental equations as $PSp=-0.11Et^2+1.42Et+1.75\;and\;TSp=-0.11Et^2+1.41Et+1.37$.