• Proceedings of the KIPE Conference
• /
• 2019.07a
• /
• pp.293-294
• /
• 2019

본 논문은 입출력 전력품질이 우수하고 전압별 시리즈화가 용이한 고전압 대용량 전동기 구동용 H-브릿지 멀티레벨 컨버터의 직류 전압 변동 억제를 위한 전압변조 방법에 관하여 기술하였다. H-브릿지 멀티레벨 컨버터의 Phase-shifted PWM에 의해서 전동기 무부하 구동 조건에서 유효전력이 Negative로 전이해서 전력이 전동기에서 컨버터로 유입되어 특정 파워 셀 직류 전압이 상승하는 현상이 발생한다. 따라서, 개발 파워 셀 위상 전이량을 일정 주기마다 변경하여 회생된 에너지를 H-브릿지 멀티레벨 컨버터의 모든 파워 셀에 분산시켜 파워 셀 직류 전압 상승을 억제하였다. 제안된 방법의 타당성과 실용성은 실용량 제품의 현장 적용 시험을 통하여 입증하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.11
• /
• pp.941-944
• /
• 2021

PCM/FM with a modulation index of 0.7 is widely used in the telemetry field. If the modulation index is slightly changed to 2/3, it can be interpreted as 3-PSK with a state number of 3 in phase transition trellis and can be received with a simple Viterbi decoder. As a result of computer simulation, the Eb/No performance in the AWGN channel is about 8.3 dB when the BER is 10^-5, which is close to the theoretical limit.

• Proceedings of the KIPE Conference
• /
• 2020.08a
• /
• pp.245-247
• /
• 2020

본 논문에서는 DUT(Device Under Test) 및 PHIL(Power Hardware-in-the-Loop) 시뮬레이터의 스위칭 주파수 비 및 PWM 위상차에 의하여 발생할 수 있는 문제를 분석하였다. 또한, DUT 인버터의 PWM 특성을 고려한 디지털 필터를 적용하여 PHIL 시뮬레이터의 운전 영역을 확대하였다. 디지털 필터는 DUT 스위칭 주파수의 고조파 성분만을 선택적으로 제거하여 PHIL 스위칭 주파수에 무관하게 일정한 시뮬레이션 결과를 생성할 수 있다. 분석한 내용과 디지털 필터의 변경으로 인한 PHIL 시뮬레이터의 특성은 다양한 조건에서 시행된 실험을 통하여 검증하였다.

• Korean Journal of Legislative Studies
• /
• v.17 no.3
• /
• pp.83-116
• /
• 2011

선거운동에 있어서 자유와 공정은 선거과정의 민주적 품질을 가늠하는 핵심적 가치이다. 선거과정에서 자유와 공정이 충분히 보장될 때, 유권자와 후보자 간의 역동적이며 설득적인 커뮤니케이션이 가능하다. 이 점에서 한국 선거운동의 민주적 품질은 아직 낮은 상태에 머무르고 있다. 한국의 선거법은 대단히 규제 중심적이며, 이는 과거 부정선거 및 타락선거의 경험에서 비롯된다. 하지만 선거환경은 빠르게 변화하여 왔다. 유권자의 선거문화 및 의식수준이 크게 개선되었으며, 인터넷의 확산은 더욱 능동적이고 참여적인 유권자를 탄생시키고 있다. 선거환경의 변화는 규제 중심적 선거규칙의 변경을 요구하고 있다. 하지만 선거운동의 민주적 품질은 법제도적 개선만으로 향상되는 것은 아니다. 선거경쟁의 장에서 공명정대한 관리자로서 선관위의 위상정립과 더불어, 유권자들의 건전한 선거문화의 형성을 위한 끊임없는 노력이 함께 병행될 때 비로소 선거운동을 둘러싼 민주적 품질의 실질적 향상이 성취될 수 있을 것이다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2008.05a
• /
• pp.13-15
• /
• 2008

유비쿼터스 컴퓨팅 환경에서 상황 인지는 지능형 서비스의 필수 요소로 인식되어 왔다. 현재 상황을 인식함에 있어 위치 인식이 주를 이루고 있다. 그러나 기존의 연구들이 제안하는 2차원 공간에서의 위치 관계만으로는 지능형 서비스가 필요로 하는 상황 모델 구축에 부족하다. 이에 본 연구에서는 3차원 공간에서의 위치 관계 인식 및 추론과정을 통한 3차원 상황 모델을 구축하기 위한 방법을 제안한다. 3차원 공간 상황은 서비스가 제공되는 환경에 대한 입체적 상황을 제공함으로써, 보다 상세한 상황에 대한 정보를 제공하고 이에 준한 상황에 민감한 서비스를 제공할 수 있다. 3차원 상황 모델은 공간을 수평/수직의 격자로 분할하여 연속된 평면의 집합으로 분류하여, 각 평면들 사이의 연계 정보에 근거하여 만들어진다. 각 평면은 방향 정보와 위상 정보의 조합으로 구성되고 이들 정보는 추론 규칙에 의해 서로 변경될 수 있다.

• Journal of Satellite, Information and Communications
• /
• v.5 no.1
• /
• pp.58-62
• /
• 2010

This paper presents the effects of RF performance parameters on the Galileo receiver design via simulation after reviewing the requirements of the Galileo receiver structure. At first, we considered the general requirements, structure and characteristics of the Galileo system. Then we designed the Galileo receiver focused on performance requirement of 16 dB C/N which is equal to 15 % Error Vector Magnitude(EVM) by using Advanced Design System(ADS) simulation program. In order to verify the function of Automatic Gain Control(AGC)), we measured the IF output power level by changing the input power level at the front - end of the receiver. We analyzed the performance degradation due to phase noise variations of Local Oscillator(LO) in the Galileo receiver through EVM when the minimum sensitivity level of -127 dBm is applied at the receiver. We also analyzed the performance degradation according to variable Analog-to-Digital Converter(ADC) bits within the Dynamic range, -92 ~ -139 dBm, which has been defined by gain range (-2.5 ~ +42.5 dB) in the AGC operation. The results clearly show that the performance of the Galileo receiver can be improved by increasing ADC bits and reducing Phase Noise of LO.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.6C
• /
• pp.834-841
• /
• 2004

There can be lips transformed geometrically in the lip images according to the location or the pose of camera and speaker. This transformation of the lip images changes geometric information of original lip phases. Therefore, for enhancing global lip information by using partial information of lips to correct lip phases transformed geometrically, in this paper we propose a method that can geometrically correct lips. The method is composed of two steps - the feature-deciding step and the correcting step. In the former, it is for us to extract key points and features of source image according to the its lip model and to create that of target image according to the its lip model. In the latter, we decide mapping relation after partition a source and target image based on information extracted in the previous step into each 4 regions. and then, after mapping, we unite corrected sub-images to a result image. As experiment image, we use fames that contain pronunciation on short vowels of the Korean language and use lip symmetry for evaluating the proposed algorithm. In experiment result, the correcting rate of the lower lip than the upper lip and that of lips moving largely than little was highly enhanced.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.1
• /
• pp.63-69
• /
• 2015

In this paper, infrared reflector design targeting infrared stealth effect is presented using structural optimization based on the phase field method. The analysis model was determined to accomplish the design that an incident infrared wave was reflected to a desired direction. The design process was to maximize the objective value at the measuring domain located in a target region and the design objective was set to the Poynting vector value which represents the energy flux. Optimization results were obtained according to the variation of some parameter values related to the phase field method. The model with a maximum objective value was selected as the final optimal model. The optimal model was modified to eliminate the gray scale using the cut-off method and it confirmed improved performance. In addition, to check the desired effect in the middle wave infrared range(MWIR), the analysis was performed by changing the input wavelength. The finite element analysis and optimization process were performed by using the commercial package COMSOL combined with the Matlab programming.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.1
• /
• pp.121-126
• /
• 2013

Cycloconverter used as a power conversion device in the speed and torque control system of AC machines has the advantage of a simple control and a large torque at low speed. In addition, because a rectifier, a DC link, and an inverter are not installed, this system is simple and suitable for large power system. If a power conversion device, which is currently used as a propulsion motor of large vessel, is changed into cycloconverter, the system is simplified and then the installation costs can be significantly reduced. However, conventional cycloconverter has the increased harmonics because the power loss is large and the waveform of output voltage is distorted, due to the high-speed switching of power semiconductor devices. In order to improve these shortcomings, this paper describes a phase shifting filter which is composed of two inputs with different phases in the primary side and one output in the secondary one. As the voltage waveforms with two different phases are added and transformed into the secondary side, these outputs are close to sinusoidal waves. Thereby the voltage waveforms, which are applied to the propulsion motors, are improved and total harmonic distortions (THDs) are significantly reduced.

• Land and Housing Review
• /
• v.7 no.4
• /
• pp.251-259
• /
• 2016

As the spatial structure of a region is evolving into a decentralized multi-nucli model, networked connection among cities in a region is emerging as an important issue to strengthen regional competitiveness. This paper focused on the limitation of current new town planning criteria which just suggest a uniform standard for economic self-sufficiency by new-town size, without representing the network characteristics of new town. If a new town is planned as a economic strongpoint within a region, it needs to secure appropriate industrial functions. This study classified the characteristics of new towns by network analysis and reviewed the economic self-sufficiency criteria by new town types. Using various network connectedness indices, the 1st and 2nd round new towns in the capital region were analyzed, and land-use distribution of new-towns in other countries were also examined comparatively. The network characteristics of new towns are classified as three types: mono-nucleus, distributed center, and dependent. Based on this classification, planning criteria for self-sufficiency were compared among 6 new towns. This study provides implications for the amendment of "the sustainable new town planning criteria" or the revision of development plans.