• 전력전자학회논문지
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• 제6권2호
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• pp.132-140
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• 2001

유니버셜모터는 소형의 직류 직권전동기와 같은 기계적 구조를 가지며 교류.직류 전원을 양용할 수 있는 장점으로 동급의 일반전동기에 비해 높은 속도로 구동이 가능하므로 핸드드릴이나 진공청소기, 세탁기 등의 가정용 기기 등에 일반적으로 사용된다. 위상각제어기를 이용하여 모터로 입력되는 전압을 제어하는 방법은 간단한 구조 때문에 위상지연으로 인해 입력 역률 및 저차 고조파 전류특성이 좋지 않음에도 불구하고 널리 사용되고 있다. 브리지 정류기를 사용하여 교류 전원을 맥동하는 직류 전원으로 변환한 후 DC 초퍼로써 유니버셜모터에 입력되는 평균전압을 제어하는 방법은 제어기의 효율을 높일 수 있고 저차 고조파전류를 감소시킬 뿐만 아니라 저전력값에 대해서도 부하역률의 저하를 막을 수 있다. 본 논문에서는 기존의 제어기의 방법으로 저가의 위상각 제어기를 구서하고 EH한 저가의 마이크로 컨트롤러를 이용한 DC 초퍼시스템을 각각 구성하여 저차 고조파전류 특성을 비교 분석하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권5호
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• pp.2338-2356
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• 2019

Vehicular ad-hoc network (VANET) is the name of technology, which uses 'mobile internet' to facilitate communication between vehicles. The aim is to ensure road safety and achieve secure communication. Therefore, the reliability of this type of networks is a serious concern. The reliability of VANET is dependent upon proper communication between vehicles within a given amount of time. Therefore a new formula is introduced, the terms of the new formula correspond 1 by 1 to a class special ST route (SRORT). The new formula terms are much lesser than the Inclusion-Exclusion principle. An algorithm for the Source-to-Terminal reliability was presented, the algorithm produced Source-to-Terminal reliability or computed a Source-to-Terminal reliability expression by calculating a class of special networks of the given network. Since the architecture of this class of networks which need to be computed was comparatively trivial, the performance of the new algorithm was superior to the Inclusion-Exclusion principle. Also, we introduce a mobility metric called universal speed factor (USF) which is the extension of the existing speed factor, that suppose same speed of all vehicles at every time. The USF describes an exact relation between the relative speed of consecutive vehicles and the headway distance. The connectivity of vehicles in different mobile situations is analyzed using USF i.e., slow mobility connectivity, static connectivity, and high mobility connectivity. It is observed that $p_c$ probability of connectivity is directly proportional to the mean speed ${\mu}_{\nu}$ till specified threshold ${\mu}_{\tau}$, and decreases after ${\mu}_{\tau}$. Finally, the congested network is connected strongly as compared to the sparse network as shown in the simulation results.

• 한국음향학회지
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• 제33권3호
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• pp.216-224
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• 2014

본 논문은 Gaussian Mixture Model (GMM) 기반의 화자식별에서 급격한 계산 복잡도 감소를 위한 새로운 방법을 제안한다. 일반적으로 GMM 기반의 화자식별 시스템은 테스트 발성의 길이, 등록 화자의 수, GMM의 크기 등 크게 세 가지 요인에 비례하는 많은 계산 복잡도를 가진다. 이러한 점은 화자식별 시스템이 다양한 응용분야에 적용되는 것을 막는 큰 요인이기에 계산 복잡도와 식별 성능 사이의 trade-off 관계는 실제 적용을 위해 가장 중요한 고려요소이다. 식별 성능을 거의 그대로 유지하면서 최대한 계산 복잡도를 감소시키기 위해 우리는 Universal Background Model (UBM) 클러스터링 접근 방법을 제시하고, 또한 이 방법은 실시간 구조의 화자식별에 적용할 수 있다는 것을 보여준다. 제안한 방법의 실험을 통해 미미한 정도의 식별 성능 저하에서 speed-up factor 6의 결과를 얻을 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1151-1154
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• 2000

Phase angle control ac drives system gains a high popularity due to their simple implementation despite the disadvantage of their poor input power factor especially for large values of phase delay angle. Furthermore it generates subharmononic current at specific phase angle. As input current of do drive systems are sinusoidal, the power factor and subharmonic current characteristics are improve. This paper presents the application of a PWM control technique of do chopper system to reduce the subharmonic current and its characteristics using single-phase dc chopper drive system of universal motor.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권3호
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• pp.116-123
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• 2003

This paper deals with an experimental study for on-line monitoring the performance of a universal motor for vacuum cleaner. Performance tests are conducted on the PC-based virtual instrumentation system designed using the graphical programming language LabVIEW. The proposed monitoring system is capable of performing real time measurement functions, including data acquisition, display, and analyses in the time and frequency domains, as well as data archiving. The measured mechanical and iron loss, voltage, current, input power, power factor, torque, and efficiency characteristics are presented as function of speed.

• 대한인간공학회지
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• 제26권3호
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• pp.117-124
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• 2007

A few people are frequently using Korean text entry function in the mobile phone. To make matters worse, too many kinds of Korean text entry methods exist in the market, compelling mobile phone users to learn how to input texts all over again, whenever they purchase a new mobile phone. The purpose of this study is to propose a universal design of Korean text entry method for mobile phones. Several experiments and several questionnaire surveys were conducted in order to induce design factors for the universal design. Participants were mobile phone users with the diverse levels of text entry expertise and with the diverse ages. The results of this investigation were identical, irrespective of participants' age and expertise. The efficiency of the text entry method was not more important factor than memorability. The layout of vowels to keypad was preferred to map just 3 strokes to the 3 buttons so that users can make for themselves vowels that they want to input. The preference on the consonants layout was different according to investigation methods. According to the survey, it was preferred that consonants were arranged by alphabet order. However, the result of text entry speed measurement was that the arrangement by alphabet order was not superior to the typical arrangement. Such results may be used to design mobile phones for diverse users.

• Journal of Power Electronics
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• 제15권3호
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• pp.644-651
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• 2015

This paper introduces a novel digital one cycle control (DOCC) boost power factor correction (PFC) converter. The proposed PFC converter realizes the FPGA-based DOCC control approach for single-phase PFC rectifiers without input voltage sensing or a complicated two-loop compensation design. It can also achieve a high power factor and the operation of low harmonic input current ingredients over universal loads in continuous conduction mode. The trailing triangle modulation adopted in this approach makes the acquisition of the average input current an easy process. The controller implementation is based on a boost topology power circuit with low speed, low-resolution A/D converters, and economical FPGA development board. Experimental results demonstrate that the proposed PFC rectifier can obtain a PF value of up to 0.999 and a minimum THD of at least 1.9% using a 120W prototype.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.154-158
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• 2009

The vortex ventilation system (VV) which uses a rotating finned swirler installed coaxially with the exhaust duct is a very effective local ventilator. VV can enhance the capture depth by a factor of 3-5 compared to the conventional exhaust hood, in the absence of any solid walls nearby. In real situations there may exist ceiling, side wall and floor, all of which can affect the flow field and suction performance by way of the no-slip condition on the walls. 3D CFD simulation was performed in order to see the effect of the floor on the capture performance of the VV. The presence of floor reduced suction flow velocity, and increased the critical rotational speed which is the rotational speed required for stable vortex formation. Flow velocity profile along the axis could be well approximated by a universal functional form when the distance from the exhaust inlet is non-dimensionalized by the distance to the floor. Capture depth, define by the distance from the exhaust inlet to a point of velocity decreased to 10% of that at the inlet, is reduced by about 10% when the floor distance is 6 times the exhaust hood diameter.

• JSTS:Journal of Semiconductor Technology and Science
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• 제2권3호
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• pp.197-204
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• 2002

DRAM, SRAM, and FLASH memory are three major memory devices currently used in most electronic applications. But, they have very distinct attributes, therefore, each memory could be used only for limited applications. MRAM (Magneto-resistive Random Access Memory) is a promising candidate for a universal memory that meets all application needs with non-volatile, fast operational speed, and low power consumption. The simplest architecture of MRAM cell is a series of MTJ (Magnetic Tunnel Junction) as a data storage part and MOS transistor as a data selection part. To be a commercially competitive memory device, scalability is an important factor as well. This paper is testing the actual electrical parameters and the scaling factors to limit MRAM technology in the semiconductor based memory device by an actual integration of MRAM core cell. Electrical tuning of MOS/MTJ, and control of resistance are important factors for data sensing, and control of magnetic switching for data writing.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.337-338
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• 2013

Combination the several type of single phase power conversion utilized simply topology are proposed in this paper. Totally four kind of converter are investigated, they are Boost AC/AC Converter, Buck AC/AC Converter, Boost AC/DC Converter, and Buck DC/AC Converter. Two types action mode are presented to determine the functional of circuit. First is AC chopper action mode, representation of the AC/AC converter. AC chopper action mode offered the sinusoidal current waveform, better power factor, faster dynamics, and smaller input/output filter. They present high robustness, offer safe commutation and have high efficiency. The second is full bridge action mode, determined the transformation AC to DC power and otherwise. Four switching devices and one magnetic contactor will establish the mode operation of circuit and manage the flow of power proceed in proper. The correction and advance of the kind of converter are verified by simulation.