• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.4
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• pp.196-200
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• 2004

This paper presents a method to reduce the commutation torque ripple in a position sensorless brushless DC motor drive. To compensate the commutation torque ripple considerably, the duration of commutation must be known. The proposed method measures the duration of commutation from the terminal voltage of the motor, calculates a PWM duty ratio using the measured commutation interval to suppress the commutation torque ripple, and applies it to the calculated PWM duty ratio only during the next commutation. Experimental results show that pulsating currents and vibrations are considerably reduced when the proposed method is applied to a position sensorless brushless DC motor drive for the air-conditioner compressor.

• Journal of the Korean Mathematical Society
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• v.38 no.6
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• pp.1191-1204
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• 2001

The paper is devoted to the study of fractional integration and differentiation on a finite interval [a, b] of the real axis in the frame of Hadamard setting. The constructions under consideration generalize the modified integration $\int_{a}^{x}(t/x)^{\mu}f(t)dt/t$ and the modified differentiation ${\delta}+{\mu}({\delta}=xD,D=d/dx)$ with real $\mu$, being taken n times. Conditions are given for such a Hadamard-type fractional integration operator to be bounded in the space $X^{p}_{c}$(a, b) of Lebesgue measurable functions f on $R_{+}=(0,{\infty})$ such that for c${\in}R=(-{\infty}{\infty})$, in particular in the space $L^{p}(0,{\infty})\;(1{\le}{\le}{\infty})$. The existence almost every where is established for the coorresponding Hadamard-type fractional derivative for a function g(x) such that $x^{p}$g(x) have $\delta$ derivatives up to order n-1 on [a, b] and ${\delta}^{n-1}[x^{\mu}$g(x)] is absolutely continuous on [a, b]. Semigroup and reciprocal properties for the above operators are proved.

• Proceedings of the ESK Conference
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• 1998.04a
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• pp.194-199
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• 1998

The purpose of this study is conducted to evaluate the psycho-physiological effects of the dynamic lighting on VDT workers and to establish the dynamic lighting design guides. The main experimental factors are changes of illuminance. There were five conditions including 1) ripid change, 2) slow change at 300lx .approx. 500lx, 3) a static illuminance level at 300lx, and 4) rapid chante, 5) slow change at 200lx .approx. 300lx. The ranges of change were set typical illuminance level for the simple visual task requirement and reasonable to a VDT task ; 200-300-500lx. The psycho-physiological measurements used were EEG, R-R interval, CFF, near point accommodation, feeling perceived fatigue, and work performance. Analysis of psycho-physiological factors shows that higher illumination level conditions are more affirmative effects than lower on VDT workers under 500lx except for the results of feeling perceived fatigue. And about the speed of changes of illuminance level. The conditions of slow change were better than the others in terms of the work performance as well as psycho-physiological results.

• Progress in Medical Physics
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• v.11 no.2
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• pp.141-146
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• 2000

Power spectrum analysis is a powerful noninvasive tool for quantifying autonomic nervous system activity. In this paper, We developed a measuring system for Autonomic Nervous Activity by using power spectrum analysis method to obtain the activities of autonomic nervous system. This system adopt a isolated power for patient's safety. In this system, Two output signal is obtained - R-R interval time variability and Respiration time variability. Time variability is use to find out some disease related to Autonomic Nervous System. Experimental tested range is 30 ～ 240 BPM for ECG and 15～80 BPM for Respiration.

• Journal of the Korean Statistical Society
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• v.23 no.2
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• pp.403-420
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• 1994

An economic design of the $\bar{X}-R$ chart using variable sample size (VSS) scheme is proposed in this paper. In this design the sample size at each sampling time changes according to the values of the previous two sample statistics, sample mean and range. The VSS scheme uses large sample if the sample statistics appear near inside the control limits and smaller sample otherwise. The set of process parameters, such as the sampling interval, control limits and the sample sizes, are chosen to minimize the expected cost per hour. The efficiency of the VSS scheme is compared to the fixed sample size one for cases where there is multiple of assignable causes. Percent reductions of the expected cost in the VSS design are calculated for some given sets of cost parameters. It is shown that the VSS scheme improves the confidence of the procedure and performs statistically better in terms of the number of false alarms and the average time to signal, respectively.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.57
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• pp.1-10
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• 2000

The purpose of this paper is to propose a method of rest to reduce work load of night shift workers for night shift work. The experiment was carried out 10minutes preparing time, 45minutes first work, 10minutes first rest, 45minutes second work, 10minutes second rest between 2 and 4 o'clock that the lowest physiological function of workers. The methods of rest set up as four patterns (1) non-action rest (2) non-action rest + listening music (3) action rest + non-action rest, (4) action rest + non-action rest + listening music. For the measurements of experiment, heart rates(R-R interval), critical flicker fusion frequency(CFF), blood pressure, oral temperature, reaction time and error rates were considered as criteria for work performance. As a result, action rest + non-action rest and action rest + non-action rest + listening music were more effective to reduce work load additional work than non-action rest and non-action rest + listening music.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.162-165
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• 1989

This paper describes an algorithm of P-wave detection by significant point extraction method with digital differentiation. P-waves are detected by pattern matching algorithm with significant points. By means of defecting onset and offset points of P-waves, this algorithm can measure the PR intervals exactly which is important to diagnosis the atrial arrhythmia. Because P-wave duration is changed according to heart-rates, we calculate the R-R interval prior to the determination of P-wave duration threshold values in order to actively adapt to the change of P duration The results obtained from the proposed algorithm have defected successfully P-wave almost more than 90%.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.261-262
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• 2010

The Reaction structure in POSCO Global R&D center has to be investigated to minimize the crack especially by the hydration heat. In this study, several methods to control the hydration heat are suggested and the computational analysis of hydration heat is performed. The main variables are kinds of concrete, the interval of placement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.565-566
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• 2006

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2001-2004
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• 2008

모든 심전도 압축에서는 압축율과 신호왜곡간의 관계를 다루며 이는 매우 중요하다. 특별히 임상적인 의미를 가진다고 평가되는 5%의 Percent Root mean square Difference(PRD)값을 만족 시키면서 높은 압축율을 얻기 위한 연구는 필수적이다. 본 논문에서는 DCT를 사용하여 심전도 압축을 수행하였을 때, 심전도의 주요한 파라미터인 파형과 RRI(R-R Interval)가 압축율에 따라 어떻게 변화하는지를 평가하고 심전도의 두 가지 주요 파라미터를 진단정보의 왜곡 없이 압축할 수 있는 DCT계수 및 압축율을 도출해 내었다. 실험에는 MIT-BIH ECG Compression Test Database를 사용하였으며 DCT압축을 수행하였을 때 5 % 이하의 PRD를 확보하기 위해서는 81개 샘플에 대하여 평균 4.496 : 1, 최하 3.422 : 1 의 CR을 가지는 것을 확인할 수 있었으며, QRS를 올바르게 검출하는 범위에서의 78개의 샘플에 대하여 평균 CR은 17.3 : 1 최저 CR은 4.6512 : 1 로 나타났다. QRS 검출 한계에서의 RRI 시간왜곡은 평균 3.7149 $\pm$ 4.3147 ms로 나타났으며, 최대 시간왜곡은 13.0256 $\pm$ 14.2035 ms 로 조사되었다.