• 지질공학
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• 제17권4호
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• pp.633-642
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• 2007

터널탐사의 탄성파 자료처리 기법에는 주시 토모그램 방법이 많이 이용되어 왔다. 현장자료는 이론 자료와는 달리 파동원과 수신기의 거리 증가에 따른 도착 시간의 차이가 작기 때문에, 피킹과 같은 작은 오차에도 계산 결과는 큰 오류를 범할 수 있다. 본 연구에서는 이러한 문제점을 극복할 수 있는 진폭법과 오차 토모그램 방법을 시도하였으며, 앞으로 현장 자료 처리에 많은 도움을 줄 수 있을 것이다.

• 대한안전경영과학회지
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• 제1권1호
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• pp.55-60
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• 1999

Presses are very widely used in industrial and commercial companies and are often the source of serious accidents occurring during operation. In Korea, the press holds the first place in the industrial hazard machines for frequency of accidents. Most of the press accidents are due to the human error. Continuous recordings of eye and hand movements that included operating errors of five experienced subjects were made during the press operation. The results showed that significant differences were observed on eye fixation time, hand fixation time, and lead departure time between the operations that has errors and no errors. The result could be used as basic data to establish a guideline for preventing the accidents.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.77-79
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• 1997

An induction watthour meter was designed for use on circuits in which the voltage and current are essentially sinusoidal. As the application of switching devices has been increased, the waveforms of voltage and current have involved the harmonics. Therefore, power energy involving voltage and current with the harmonics is supplied to the system and the registration error of watthour meter is existed. In this paper, we experimented on the error of watthour mesurement under the sinusoidal and nonsinusoidal input source.

• 한국경영과학회지
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• 제16권1호
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• pp.120-134
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• 1991

Various technological forecasting models have been proposed to represent the time pattern of technological growths. Of six such models studied, some models do significantly better than others, especially at low penetration levels, in predicting future levels of growth. Criteria for selecting an appropriate model for technological growth model are examined in this study. Two major characteristics were selected which differentiate the various models ; the skew of the curve and the underlying assumptions regarding the variance of the error structure of the model. Although the use of statistical techniques stil requires some subjective input and interpretations, this study provides some practical procedures in the selection of technological growth models and helps to reduce or control the potential source of judgmental error inconsistencies in the analyst's decision.

• Journal of electromagnetic engineering and science
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• 제12권3호
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• pp.189-195
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• 2012

In this paper, we propose a novel protocol called a Multi-hop Diversity Transmission protocol in which the retransmission is realized by a relay that is Nearest to a current Source (MDTNS). We derive the mathematical expressions of the packet error rate (PER) and the average number of transmissions over Nakagami-m fading channels, and verify them by Monte Carlo simulations. The simulation results show that the MDTNS protocol improves the performance of the network in terms of PER when compared to the Multi-hop Diversity Transmission protocol in which the retransmission is done by a relay that is Nearest to Destination (MDTND) and to the conventional multi-hop transmission (CMT) protocol.

• Journal of Communications and Networks
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• 제18권1호
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• pp.19-26
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• 2016

In this paper, the performance of dual-hop multi-relay maximum ratio transmission (MRT) over Rayleigh flat fading channels is studied with both conventional (all relays participate the transmission) and opportunistic (best relay is selected to maximize the received signal-to-noise ratio (SNR)) relaying. Performance analysis starts with the derivation of the probability density function, cumulative distribution function and moment generating function of the SNR. Then, both approximate and asymptotic expressions of symbol error rate (SER) and outage probability are derived for arbitrary numbers of antennas and relays. With the help of asymptotic SER and outage probability, diversity and array gains are obtained. In addition, impact of imperfect channel estimations is investigated and optimum power allocation factors for source and relay are calculated. Our analytical findings are validated by numerical examples which indicate that multi-relay MRT can be a low complexity and reliable option in cooperative networks.

• 한국군사과학기술학회지
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• 제19권2호
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• pp.163-170
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• 2016

Tropospheric delay is one of the largest error source in pseudolite navigation system. Because a pseudolite is installed on the ground and transmits its signal to a user in the air or on the ground, the conventional tropospheric delay model developed for a satellite navigation doesn't work properly. In this paper, performance analysis of several pseudolite tropospheric delay models has been done using meteorological data. Based on the result, a new compensation method for Hopfield model has been proposed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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• pp.103-105
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• 2002

Instantaneous following PWM control technique is pulsed nonlinear dynamic control method. This new control technique using analog integrator is proposed to control the duty ratio D of Cuk converter. In this control method, the duty ratio of a switch is exactly equal to or proportional to the control reference in the steady state or in a transient. Proposed control method compensates power source perturbation in one switching cycle, and the average value of the dynamic reference in one switching cycle. There is no steady state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with Cuk converter have demonstrated the robustness of the control method and verified theoretical prediction. The control method is very general and applicable to all type PWM.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.72-73
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• 2006

The error function can be calculated based on the Simpson method through a subroutine program. An integration program by FORTRAN language was made for diffusion equations of extended source with infinite extent and limited extent. The results on some alloying elements such as C, Co, Cr, Mn, Mo, Ni and V's diffusion in iron, showed the diffusion distance for Ni and Mo can only be $1{\sim}3\;{\mu}m$ and more distance for Co at common sintering temperature of $1120^{\circ}C$. To refine the particle size of the added elements down to a scale of micrometers is an effective way to get homogeneous distribution.

• Journal of the Optical Society of Korea
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• 제9권3호
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• pp.107-110
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• 2005

An optical method of measuring hematocrit noninvasively is presented. An LED Light with multiple wavelengths was irradiated on fingernail and transmitted light from the finger was measured to predict hematocrit. A finger probe contained an LED array and detector. Our previous experience showed that prediction accuracy was sensitive to reliability of the finger probe hardware and we optimized the finger probe parameters such as the internal color, detector area and the emission area of a light source based on Design of Experiment. Using the optimized finger probe, we developed a hematocrit monitoring system and tested with 549 persons. For the calibration model with 368 persons, a regression coefficient of 0.74 and a standard deviation of 3.67 and the mean percent error of $8\%$ were obtained. Hematocrits for 181 persons were predicted. We achieved a mean percent error of $8.2\%$ where the regression coefficient was 0.68 and the standard deviation was 3.69.