• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.910-913
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• 2001

Rapid Prototyping(RP) techniques have unique characteristics according to their working principle: the stair-stepped surface of a part due to layer-by-layer stacking, low building speed, and additional post-processing to improve surface roughness. A new RP process, Variable Lamination Manufacturing by using expandable polystyrene foam(VLM-S), has been developed to overcome the unfavorable characteristics. The objective of this study is to investigate the thermal characteristics and skeleton size effects as the hotwire cuts EPS foam sheet in order to improve dimensional accuracy of the parts, which is produced by VLM-S. Empirical and analytical approaches are performed to find the relationship between cutting speed and heat input, and the relationship between maximum available cutting speed and heat input. In addition, empirical approaches are carried out to find the relationship between cutting error and skeleton size, and cutting deviation and skeleton size. Based on these results, the optimal hotwire cutting condition and available minimum skeleton size are derived. The outcomes of this study are reflecting in the enhancement of VLM-S input data generation S/W.

• 대한전자공학회논문지
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• 제16권5호
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• pp.1-11
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• 1979

1960년대 후반 이후 전세계적으로 정보 산업의 가장 중요하고 미개척된 분야의 하나로서 data 통신/컴퓨터 통신이 급격히 대두되어 그 영향력을 광범위하게 확산시키기 시작하였다. 이의 구현을 위하여서는 먼저 통신 채널의 여러가지 고유한 특성이 구명되고 그 신뢰도가 확인되어야 하는 것이 선결 문제이다. 본 논문은 1973년도 이후부터 현재까지 이 분야에 축적된 데이타를 집대성하고 조직적으로 분석하여 몇가지 기본적인 근거를 제시하고 발전적 제안을 하였다. 전용선과 공중선, 통신 속도, 통신 형태, block의 크기, 측정 구간의 지역적 특성등에 따른 통신채널의 최종적 외부 특성인 error rate, 주파수 특성, 직류 특성등을 분석하고 논하였으며 block의 크기가 performance에 미치는 영향을 해석하여 보았다. 또한 9300BPS급의 고속도 통신의 가능성 크기가 performance에 미치는 영향을 해석하여 보았다. 또한 9600BPS급의 고속도 통신의 가능성을 검토하였다.

• Communications for Statistical Applications and Methods
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• 제14권1호
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• pp.121-131
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• 2007

In this paper, we examine the problem of estimating the sensitive characteristics and behaviors in a multinomial randomized response model using Bayesian approach. We derived a posterior distribution for parameter of interest for multinomial randomized response model. Based on the posterior distribution, we also calculated a credible intervals and mean squared error (MSE). We finally compare the maximum likelihood estimator and the Bayes estimator in terms of MSE.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.283-286
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• 2002

In fiber optic sensor, the error of the measurement is influenced by the surface roughness of the target and surroundings, especially the outside light. To reduce or modify this error, the sensitivity of the fiber optic sensor and the noise change by the surface roughness of the target should be known. The purpose of this paper is to observe the sensitivity of the fiber optic sensor and the noise according to the surface roughness of the target.

• Journal of Information Processing Systems
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• 제5권4호
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• pp.221-228
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• 2009

Due to low cost, low-power, and scalability, ZigBee is considered an efficient wireless AMR infrastructure. However, these characteristics of ZigBee can make the devices more vulnerable to unexpected error environments. In this paper, a fault-tolerant wireless AMR network (FWAMR) is proposed, which is designed to improve the robustness of the conventional ZigBee-based AMR systems by coping well with dynamic error environments. The experimental results demonstrate that the FWAMR is considerably fault-tolerant compared with the conventional ZigBee-based AMR network.

• 한국통신학회논문지
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• 제29권5C호
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• pp.611-617
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• 2004

The optimum convolutional error correction codes for recently standardized Feher-patented quadrature phase-shift keying (FQPSK-B) modulation are proposed. We utilize the continuous phase modulation characteristics of FQPSK-B signals for calculating the minimum Euclidean distance of convolutional coded FQPSK-B signal. It is shown that the Euclidean distance between two FQPSK-B signals is proportional to the Hamming distance between two binary data sequence. Utilizing this characteristic, we show that the convolutional codes with optimum free Hamming distance is the optimum convolutional codes for FQPSK-B signals.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.311.2-311
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• 2002

Even through the problem of misalignment is of great importance, not much work has been reported in the literature on the effect of misalignment on the vibrations of the gear-bearing systems. Therefore, the nonlinear dynamic characteristics of the gear driving system due to misalignment are investigated in this work. Transmission error for helical gear and bearing nonlinear stiffness is calculated. (omitted)

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.5-8
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• 2001

SSB(Single Sideband) modulation scheme is high bandwidth efficient method in the mobile communication system compared with present DSB(Double Sideband) modulation scheme. Using the othogonality between inphase PN code and Hilbert transformed quadrature PN code, we propose phase estimation structure that enables coherent demodulation in the reverse link basestation receiver Several system characteristics, bit error rate and phase error variance, are simulated and compared with balanced QPSK DS/CDMA system. To verify system performance, SSB/BPSK-DS/CDMA test board is implemented using FPGA chips.

• Journal of the Korean Data and Information Science Society
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• 제12권2호
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• pp.35-45
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• 2001

We introduce a new percentile envelope for diagnosing supernormality in regression analysis. Furthermore, we compare this percentile envelope, which is much simpler and easier, with Atkinson's and Flack and Flores' envelopes. Using percentile envelope, we investigate characteristics of normal probability plots with envelope for error distributions when supernormality is occurred. We give cautions that test result for normality assumption of errors can be reached the wrong conclusion by supernormality.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 추계학술대회 논문집
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• pp.85-89
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• 2004

This paper presents Power Control and Distribution Unit development of GEO satellite with 3kW power output. The sensing error of bus voltage produce control signal of the shunt switch assembly and battery power converter, and the tolerance of error signals generated decide the stability of proposed system. The dynamic characteristics of main bus according to the load changing and the control logic of FPGA are simulated. In order to verify the proposed design, the simulation and experimental results for solar array shunt switch, battery power converter and bus controller are shown.