• 한국통신학회논문지
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• 제30권7C호
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• pp.687-695
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• 2005

차세대 통신기술인 Software-Defined Radio (SDR)시스템은 단일 하드웨어 플랫폼에 소프트웨어 변경만으로 다양한 통신표준을 수용할 수 있는 시스템이다. 시스템의 융통성(flexibility)과 적응성(adaptability)을 위하여 RF와 관련된 하드웨어의 최소화가 필요하며, 이를 위해 ADC를 사용으로 기저대역(baseband) 또는 낮은 IF단으로 직접하향 변환(downconversion)을 할 수 있는 bandpass sampling 기법이 필수적이다. 이 논문에서는 complex bandpass sampling 방식을 이용하여 두 가지의 통신 표준이 한 시스템에서 동시에 직접 하향 변환하는 새로운 방법을 제안하였다. 이에 따른 sampling 가능 영역, 보호대역(guard-band)을 고려한 sampling 가능 최소 주파수 그리고 이동된 신호의 위치를 구하는 수식들을 유도한 뒤 그래프를 통해 비교 분석하였다. 또한 제안한 sampling방식이 모의실험을 통해 기존에 제안되었던 real bandpass sampling방식보다 SDR시스템에 더욱 적합하다는 것을 입증하였다.

• 대한안전경영과학회지
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• 제22권1호
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• pp.23-32
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• 2020

There has been a significant decline in the number of rail accidents in Korea since system safety management activities were introduced. Nonetheless, analyzing and preventing human error-related accidents is still an important issue in railway industry. As a railway system is increasingly automated and intelligent, the mechanism and process of an accident occurrence are more and more complicated. It is now essential to consider a variety of factors and their intricate interactions in the analysis of rail accidents. However, it has proved that traditional accident models and methods based on a linear cause-effect relationship are inadequate to analyze and to assess accidents in complex systems such as railway systems. In order to supplement the limitations of traditional safety methods, recently some systemic safety models and methods have been developed. Of those, FRAM(Functional Resonance Analysis Method) has been recognized as one of the most useful methods for analyzing accidents in complex systems. It reflects the concepts of performance adjustment and performance variability in a system, which are fundamental to understanding the processes of an accident in complex systems. This study aims to apply FRAM to the analysis of a rail accident involving human errors, which occurred recently in South Korea. Through the application of FRAM, we found that it can be a useful alternative to traditional methods in the analysis and assessment of accidents in complex systems. In addition, it was also found that FRAM can help analysts understand the interactions between functional elements of a system in a systematic manner.

• 한국수학사학회지
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• 제21권4호
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• pp.141-152
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• 2008

본 연구는 복소수의 교수학적 분석인데 주로 문제해결에 필요한 지식의 연결성에 초점을 맞추고 있으며 복소수 개념이 학교수학에서 핵심적 역할을 한다는 것을 보이고 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1863-1866
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• 2002

This paper describes synthesis of a complex R$^{i}$ CR filter with a finite transmission zero except zero frequency. First, a new kernel function is proposed. Secondly, how to determine the element values included in the R$^{i}$ CR filter is described. A fifth-order R$^{i}$ CR filter is designed. Finally, the sensitivity property of the proposed filter is evaluated through computer simulation.

• 한국통신학회논문지
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• 제21권10호
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• pp.2579-2585
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• 1996

In this paper, a complex fuzzy adaptive decision feedback equalizer(CFADFE) based on the LMS algorithm is proposed. The propoed equalizer is based on the complex fuzzy adaptive equalizer. The CFADFE isconstructed from a set of changeable complex fuzzy IF-THEN rules, where the 'IF' part of the rule is characterized by the state from a set of changealble complex fuzzy IF-THEN rules, where the 'IF' part of the rule is characterized by the state of the desision feedback. the role of decision feedback is to reduce the computational complexity. Computer simulation of the decision feedback. The role of decision feedback is to reduce the computational complexity. Computer simulation shosw that the CFADFE notonly reduces the computational complexity but also improves the performance compared with the conventional complex fuzzy adaptive equalizers. We also show that the adaptation speed is greatly improved by incorporating some linguistic information about the channel into the equalzer. It is applied to M-ary QAM digital communication system with linear and nonlinear complex channel characteristics.

• 조명전기설비학회논문지
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• 제18권1호
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• pp.15-20
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• 2004

복소홀로그램을 광학적으로 구현할 수 있는 시스템을 제안하고, 제안된 시스템이 복소홀로그램을 표현할 수 있다는 것을 이론적으로 입증하였다. 그리고, 변형 삼각간섭계를 이용하여 3차원 영상의 복소홀로그램을 생성하고, 이를 수치적 및 광학적으로 복원한 3차원 영상을 제시하고 분석하였다.

• 제어로봇시스템학회논문지
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• 제16권4호
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• pp.313-318
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• 2010

This paper deals with the relationship between zeros and step response of the second and third order LTI (Linear Time Invariant) SISO (Single-Input and Single-Output) systems with complex poles. Although it has been known that the maximum number of local extrema is less than the number of zeros in the system with only real poles[8], some cases with complex poles are shown in this paper to have many local extrema. This paper proposes monotone nondecreasing conditions and describes the relationship between the transient response and the number of local extrema in step response with each region of zeros.

• 한국환경보건학회지
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• 제35권1호
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• pp.53-57
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• 2009

In order to treat the complex wastewater containing organic compound and solids, pre-treatment system associated with molecular separation process were investigated. The reductions of COD and turbidity were obtained after coagulation processes using Alum (Aluminium sulfate, $Al_2(SO_4)_2{\cdot}18H_{2}O$) and PACl (poly aluminium chloride as 17% $Al_{2}O_{3}$). The results of study were as follows: using variable dosage of Alum, COD removal was highest at 4,000 mg/l, and the reduction of COD and turbidity was 42% and 92%, respectively. The optimum coagulation would be effective at pH 7.3 than pH 9.0 by the addition of alum at a concentration of 6,000 mg/l and PACl was add at 4.25% in raw complex wastewater with 2,000 mg/l alum at pH 7.3, the reduction of COD was reduced by 32%. But coagulation aid experiments indicated that PACl would be more effective in sludge separation ability than COD removal efficiency.

• Current Research on Agriculture and Life Sciences
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• 제14권
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• pp.37-47
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• 1996

The main objectives of this studies are to present the most desirable rice processing complex model system in a given our situations by comparision and analyzing the major factors and, also recommend the future prospect of the rice processing complex in Korea. There are 3 different rice processing complex models in Korea. Those are concrete bin, flat type steel bin and square bin. These systems have a lot of differences and have their own characteristics such as capital requirement, efficiency, storage capacity and quality controls. The major problems of the existing rice processing centers in Korea are high fixed cost and the unbalnced systems. Following is summary to solve this problems: 1. Development of the large scale harvester and high speed continuous dryer. 2. Quality inspective system of bulk grain and large scale temporary storage facilities. 3. Large size readjustment of arable land. 4. Select the convenient location of rice processing center and formulation of well equipment facilities.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.824-829
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• 1994

High-frequency and complex vibration ultrasonic wire bonding systems are propsed and their welding characteristic are studied. Ultrasonic wire bonding is used widely for joining thin connecting wire of various electronic devices including IC or LSI. Conventional bonding systems use vibration frequency of 40 or 60 kHz and linear vibration welding tips. Complex vibration welding tip which vibrates in elliptical to circular or rectangular to square in the same or different frequency is effective to join welding specimens in shorter welding time and under smaller vibration amplitude, and furthermore high-frequency systems such as 90, 120, 190 kHz are also significantly effective. High-frequency and complex vibration welding system of 90, 120 and 190 kHz are designed. Welding characteristics of these systems are found very superior than a conventional system. Welding specimens of aluminum wire of 0.1mm diameter are successfully.