• 전기학회논문지P
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• 제56권2호
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• pp.90-98
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• 2007

More and All-Electric Aircraft (AEA) carry many loads with varied functions. In particular, there may be large pulsed loads with short duty ratio, which can affect the normal operation of other loads. In this paper, a bi-directional converter with inductive storage is used as a voltage bus conditioner (VBC) to mitigate voltage transients on the bus. In addition, the constant frequency hysteresis control technique for a VBC is presented. A simple and fast prediction of the hysteresis band-width is implemented by the phase-lock loop control, keeping constant switching frequency. This technique offers the excellent dynamic response in load or parameter variation. The control performance is illustrated by simulated results with the SABER package, The proposed hysteresis control results in the shortest and the smallest excursions.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.51-54
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• 1996

We deal with a design problem of assembly/disassembly (AD) systems with finite buffer capacities where the times between failures, the times to repair, and the processing times are exponentially distributed with different parameter values. We present a solution procedure for finding the minimum cost configuration which achieves a desired throughput rate for an AD system. The configuration is defined by the types of machines to be used and capacities of buffers in the AD system. Results of computational experiments on randomly generated test problems show that the proposed heuristics give relatively good configurations in a reasonable amount of time.

• 전기학회논문지P
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• 제54권4호
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• pp.163-170
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• 2005

This paper deals with an improved fault location algorithm with compensation ground capacitance through distributed parameter for a long parallel T/L. For the purpose of fault locating algorithm non-influenced by source impedance and fault resistance, the loop method was used in the system modeling analysis. This algorithm uses a positive and negative sequence of the fault current for high accuracy of fault locating calculation. Power system model of 160km and 300km long parallel T/L was simulated using EMTP software. To evaluate of the proposed algorithm, we used the several different cases 64 sampled data per cycle. The test results show that the proposed algorithm was minimized the error factor and speed of fault location estimation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.145-147
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• 2002

In this paper, the improved fault locating method using distributed parameter which calculating the reduced voltage and current according to the ground capacitance in long transmission line was proposed. For the purpose of the fault locating algorithm non influenced source impedance, the loop method was used in the system modeling analysis. To enhance the fault locating, zero sequence of the fault current which is variable according to ground capacitance was not used but positive and negative sequence. System model was simulated using EMTP software. To verify the accuracy of proposed method, in different cases 64 sampled data per cycle was used and 160km and 300km long transmission line has fault resistance $0{\Omega}\;and\;100{\Omega}$ respectively was compared.

• International journal of advanced smart convergence
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• 제5권4호
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• pp.10-14
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• 2016

Among the methods of treating tinnitus, the transcutaneous clectrical nerve stimulation (TENS) method of treating by electrical stimulation is common. However, there is a problem that surgical operation is required to stimulate the vagus nerve (VN) main trunk near most of the bronchus. Alternatively, we found that the same effect could be achieved by electrically stimulating the vagus nerve VN branch (Arnold's nerve) distributed in the outer ear. The TENS system for stimulation of vagus nerve has been developed, but it has not been able to implement to stimulate as a parameter optimized for the patient by simultaneously playing the sound of eliminating the tinnitus frequency. Therefore, in this paper, it is important to develop a safe and practical TENS device for tinnitus treatment based on a 32-bit microprocessor that simultaneously applies non-invasive and notched sounds and to develop optimal treatment methods for treating tinnitus.

• 대한원격탐사학회지
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• 제7권1호
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• pp.45-67
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• 1991

An overview is given on stochastic techniques with which remotely sensed data may be used together with ground measurements for purposes of state estimation and prediction. They can explicitly account for spatiotemporal differences in measurement characteristics between ground measurements and remotely sensed data, and are suitable for highly variant space or space-time processes, such as atmosperic processes, which may be viewed as (containing) a random process. For state estimation of static ststems, optimal linear estimation is described. As alternatives, various co-kriging estimation techniques are also described, including simple, ordinary, universal, lognormal, disjunctive, indicator, and Bayesian extersion to simple and lognormal. For illustrative purposes, very simple examples of optimal linear estimation and simple co-kriging are given. For state estimation and prediction of dynamic system, distributed-parameter kalman filter is described. Issues concerning actual implemention are given, and with application potential are described.

• 한국농공학회지
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• 제38권3호
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• pp.50-57
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• 1996

A numerical method is presented to obtain the natural frequencies and mode shapes of the arbitrary tapered beams with static deflection due to arbitrary distributed dead loads. The differential equation governing free vibration of such beams is derived and solved numerically. The double integration method using the trapezoidal rule is used to solve the static behaviour of beams loaded arbitrary distributed dead load. Also, the Improved Euler method and the determinant search method are used to integrate the differential equation subjected to the boundary conditions and to determine the natural frequencies of the beams, respectively. In the numerical examples, the various geometries of the beams are considered : (1) linearly tapered beams as the arbitrary variable cross-section, (2) the triangular, sinusoidal and uniform loads as the arbitrary distributed dead loads and (3) the hinged-hinged, clamped-clamped and hinged-clamped ends as the end constraints. All numerical results are shown as the non-dimensional forms of the system parameters. The lowest three natural frequencies versus load parameter, slenderness ratio and section ratio are reported in figures. And for the comparison purpose, the typical mode shapes with and without the effects of static deflection are presented in the figure. According to the numerical results obtained in this analysis, the following conclusions may be drawn : (1) the natural frequencies increase when the effects of static deflections are included, (2) the effects are larger at the lower modes than the higher ones and (3) it should be betteF to include the effect of static deflection for calculating the frequencies when the beams are supported by both hinged ends or one hinged end.

• Journal of Communications and Networks
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• 제14권2호
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• pp.188-194
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• 2012

Cognitive networks (CNs) are capable of enabling dynamic spectrum allocation, and thus constitute a promising technology for future wireless communication. Whereas, the implementation of CN will lead to the requirement of an increased energy-arrival rate, which is a significant parameter in energy harvesting design of a cognitive user (CU) device. A well-designed spectrum-sensing scheme will lower the energy-arrival rate that is required and enable CNs to self-sustain, which will also help alleviate global warming. In this paper, spectrum sensing in a multi-user cognitive ad hoc network with a wide-band spectrum is considered. Based on the prospective spectrum sensing, we classify CN operation into two modes: Distributed and centralized. In a distributed network, each CU conducts spectrum sensing for its own data transmission, while in a centralized network, there is only one cognitive cluster header which performs spectrum sensing and broadcasts its sensing results to other CUs. Thus, a wide-band spectrum that is divided into multiple sub-channels can be sensed simultaneously in a distributed manner or sequentially in a centralized manner. We consider the energy consumption for spectrum sensing only of an analog-to-digital convertor (ADC). By formulating energy consumption for spectrum sensing in terms of the sub-channel sampling rate and whole-band sensing time, the sampling rate and whole-band sensing time that are optimal for minimizing the total energy consumption within sensing reliability constraints are obtained. A power dissipation model of an ADC, which plays an important role in formulating the energy efficiency problem, is presented. Using AD9051 as an ADC example, our numerical results show that the optimal sensing parameters will achieve a reduction in the energy-arrival rate of up to 97.7% and 50% in a distributed and a centralized network, respectively, when comparing the optimal and worst-case energy consumption for given system settings.

• 설비공학논문집
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• 제25권7호
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• pp.398-405
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• 2013

Small and medium-size buildings employ a multi-distributed individual air-conditioning system that utilizes package air conditioners instead of centralized cooling systems, which can allow easier building management and maintenance, along with a diversification of facility use. Inverter driven system heat pumps have been developed to achieve not only an easy distribution control, allowing free combination of indoor units with different models and different capacities, but also wide applications to intelligent air conditioning. However, the control algorithms of the system heat pump are limited in the open literature, due to complicated operating conditions. In this paper, an inverter-driven system heat pump having two indoor units with electronic expansion valves (EEV) was simulated in the cooling mode. An integral optimum regulating controller employing the state space control method was also simulated, and applied to the system-heat pump system, to obtain efficient control of the MIMO (multi input multi output) system. The simulation model for the controller yielded satisfactory prediction results. The new control model can be successfully utilized as a basic tool in controller design.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4528-4535
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• 2014

본 논문은 승객 위치정보 기반의 지하철 분산대피 안내 시스템을 제안하고자 한다. 최근 지하철 역사는 지하철 승강장 역할 뿐만 아니라, 환승, 쇼핑몰, 영화관 등의 다양한 편의 시설과 결합하여 대형화, 복잡화 되어 가고 있다. 이러한 지하철 역사의 복잡도 증가에 비해서 비상시를 대비한 대피경로, 대피안내 등의 대비체계는 부족한 실정이다. 이를 해결하기 위하여 현재 지하철에 설치되어 있는 Access Point(AP)와 실제 통계 자료를 이용하여 지하철 각 객차의 전체 승객 수를 추정하고, 추정된 승객 수와 지하철 역사의 출구 정보를 기반으로 각 객차의 승객 대피 경로를 방향 지시등과 스마트폰의 Push 알람을 통해 제공함으로써, 비상 시 가장 위험한 지하철 승객의 신속하고 안전한 대피시스템을 제안하였다. OpenWrt 임베디드 OS가 설치된 AP를 이용하여 접속자 수를 추정하는 실험을 수행하였으며, 시뮬레이션을 통해 승객 수를 추정한 결과 신뢰구간 파라미터 $1{\sigma}$, $2{\sigma}$, $3{\sigma}$에서 15%, 17% 그리고 23%의 평균 에러율을 갖는 것을 확인하였다. 이를 통해 본 시스템의 가능성을 확인하였다.