• Journal of Electrical Engineering and Technology
• /
• v.7 no.3
• /
• pp.320-329
• /
• 2012

The Load Tap Changing (LTC) transformer and Shunt Capacitor (SC) bank are major devices for voltage and reactive power control in a distribution substation. Thus, the coordination operation of a LTC transformer and a SC bank is required to achieve better voltage and reactive power compensation at a distribution substation in the same time. This paper proposes coordinate control method of LTC transformer and SC bank to achieve better voltage and reactive power compensation and operation times of these two devices in the same time. The mathematical formulations of the proposed coordinate control method are introduced. Sample case studies are shown to verify the effectiveness of the proposed coordinate control method.

• Journal of Magnetics
• /
• v.16 no.3
• /
• pp.234-239
• /
• 2011

Transcranial magnetic stimulation utilizes the method of controlling applied time and changing pulse by output pulse through power density control for diagnosis purposes. Transcranial magnetic stimulation can also be used in cases where diagnosis and treatment are difficult since output pulse shape can be changed. As intensity, pulse range, and pulse shape of the stimulation pulse must be changed according to lesion, the existing sine wave-shaped stimulation treatment pulse poses limitations in achieving various treatments and diagnosis. This study actualized a new method of transcranial magnetic stimulation that applies a 3 Stage 2 Switch( power semiconductor 2EA) for controlling pulse repetition rate by achieving numerous switching control of stimulation coil. Intensity, pulse range, and pulse shape of output can be freely changed to transform various treatment pulses in order to overcome limitations in stimulation treatment presented by the previous sine wave pulse shape. The method of freely changing pulse range by using 3 Stage 2 Switch discharge method is proposed. Pulse shape, composed of various pulse ranges, was created by grafting PFN (Pulsed Forming Network) through AVR AT80S8535 one-chip microprocessor technology, and application in transcranial magnetic stimulation was achieved to study the output characteristics of stimulation treatment pulse according to delaying time of the trigger signal applied in section switch.

• Journal of the Ergonomics Society of Korea
• /
• v.4 no.2
• /
• pp.17-24
• /
• 1985

To compare heart rate, $O_2$ uptake, $Vo_2$ ($O_2$ consumption), blood pressure (systolic, diastolic), reaction time, stability, flicker fusion value during 4 load levels with Rs (self-paced respiration) and Rp (paced respiration), 4 subjects participated in this experiment 1 hour/day, 6 days/week for 9 weeks. The cycle of Rp is 6 sec. (inspiration: 3 sec. & expiration: 3 sec.) Implications of the results are discussed in terms of the change in the physiological responses and human performance by the respiratory pattern. The results are as follows, 1. The changing magnitude of heart rate with Rp was larger than with Rs and the variance during load level 4 was significant. 2. The $Vo_2$ with Rp was smaller than with Rs and maximal $O_2$ uptake given load levels with Rp occurred and for two subjects, it significantly moved from low load level to high load level. 3. The changing magnitude of blood pressure was not consistent but the systolic pressure with Rp was smaller at rest than with Rs. 4. The score of reaction time test and stability test with Rp was better than with Rs.

• Journal of the Korean Society for information Management
• /
• v.9 no.1
• /
• pp.55-82
• /
• 1992

It can be assumed that exciting improvements of technology concerning the ways in which information is stored and processed have significantly affected information science and may lead to a dramatic change of research in the field. Author co-citation analysis was used to investigate changes in research patterns of information retrieval over two time periods, 1980-1982, and 1988-1990. Nonmetric multidimensional scaling and clustering techiqes were used to create two dimensional maps displaying the changing research patterns among 22 authors as perceived by scholars citing their work over the two time periods. The co-cited author clusters and the placement of authors on the two maps both appear to correspond well with characterizations of the author's work obtained in texts and social relationships.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.148-148
• /
• 2019

The 2006 Millennium Ecosystem Assessment (MA) defines ecosystem services (ES) as "the benefits people obtain from ecosystems". Identifying where ES originates, whom it benefits and how it is changing over a period of time is critical in rapidly developing country like Nepal, where the risk of ES loss is high. In the context of various ecosystem services provided by watershed, this study, particularly deals with water yield, Soil loss and Carbon sequestration computation and evaluation in Bagmati Basin of Nepal. As Bagmati Basin incorporates capital city Kathmandu of nepal, land use change is significant over decades and mapping of ES is crucial for sustainable development of Basin in future. In this regard, the objectives of this study are 1) To compute the total and sub-watershed scale water yield of the basin, 2) Computation of soil loss and sediment retention in the basin, and 3) Computation of carbon sequestration in the basin. Integrated Valuation of Environmental Services and Tradeoffs (InVEST), a popular model for ecosystem service assessment based on Budyko hydrological method is used to compute Ecosystem services. The scenario of ES in two periods of time can be referenced for various approaches of prioritization and incorporation of their value into local and regional decision making for management of basin.

• Proceedings of the Korean Information Science Society Conference
• /
• 2012.06a
• /
• pp.305-307
• /
• 2012

World Wide Web (WWW)의 지속적인 성장으로 인해 Web Service의 Response Time을 수집하는 방식에 관한 연구가 진행되고 있다. 현재 Client Response Time을 수집하는 방식은 sniffer[1] 를 이용한 Agent 방식을 사용하고 있다. 하지만, 기존의 방식은 클라이언트 PC에 설치되어 수집하게 되므로 Agent의 설치가 쉽지 않고, 관리 또한 어려운 문제점을 갖고 있다. 이러한 문제점을 개선하기 위하여, 본 논문에서는 Web Application Server (WAS)[2] 에서의 Dynamic HTML 변경을 통해 Client에 추가적인 Application을 설치하지 않고도 Client의 Response Time을 Collection하는 방식에 대하여 제안하였다. 이를 통해, 사용자 (End-User)에게 추가적인 응용 프로그램을 설치하지 않고도 Dynamic HTML 을 이용하여 Client Response Time을 수집함과 동시에 Server에 Feedback할 수 있다.

• Journal of Mechanical Science and Technology
• /
• v.18 no.11
• /
• pp.2058-2065
• /
• 2004

A light collecting probe named Multi-color Integrated Cassegrain Receiving Optics (MICRO) is applied to spark-ignited spherical spray flames to obtain the flame propagation speed in freely falling droplet suspension produced by an ultrasonic atomizer. Two MICRO probes are used to monitor time-series signals of OH chemiluminescence from two different locations in the flame. By detecting the arrival time difference of the propagating flame front, the flame propagation speed is calculated with a two-point delay-time method. In addition, time-series images of OH chemiluminescence are simultaneously obtained by a high-speed digital CCD camera to ensure the validity of the two-point delay-time method by the MICRO system. Furthermore, the relationship between the spray properties measured by phase Doppler anemometer (PDA) and the flame propagation speed are discussed with three different experimental conditions by changing the fuel injection rate. It was confirmed that the two-point delay-time method with two MICRO probes is useful and convenient to obtain the flame propagation speed and that the flame propagation speed depends on the spray properties.

• Current Optics and Photonics
• /
• v.2 no.1
• /
• pp.34-38
• /
• 2018

An X-band microwave photonic (MWP) filter using switch-based fiber-optic delay lines has been proposed and experimentally demonstrated. It is composed of two electro-optic modulators (EOMs) and $2{\times}2$ optical MEMS-switch-based fiber-optic delay lines. By changing time-delay difference and coefficients of each wavelength signal by using fiber-optic delay lines and an electro-optic modulator, respectively, a bandpass filter or a notch filter can be implemented. For an X-band MWP filter with four channel elements, fiber-optic delay lines with the unit time-delay of 50 ps have been experimentally realized and the frequency responses corresponding to the time-delays has been measured. The measured frequency response error at center frequency and the time-delay difference error were 180 MHz at 10 GHz and 3.2 ps, respectively, when the fiber-optic delay line has the time-delay difference of 50 ps.

• Proceedings of the KIEE Conference
• /
• 1999.07f
• /
• pp.2715-2720
• /
• 1999

To prevent the short circuit of upper and lower arms of bridge type PWM converters as like a voltage source inverter and PWM AC/DC converter, the dead time is inserted in between two switching signals. As a result, unexpected errors are occurred. In this paper, a new dead time minimization method is proposed. According to the proposed method, very short time which is equal to the applied dead time or more short than it, is adopted at the time of current polarity is changing. Moreover, it can be operated with the polarity information of reference current in case of current control. With the experimental results. the varidity of proposed method is verified.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.66 no.1
• /
• pp.48-52
• /
• 2017

This paper proposes a hybrid algorithm of space-time block coding and space-frequency block coding using alternate time switch. The traditional alternate time-switched space-time or space-frequency block coding technique for orthogonal frequency division multiplexing system does not provide a good performance with a variety of communication environments. This hybrid algorithm has searched good performance ranges in various environments in view points of mobile speed and doppler frequency. In this paper, we investigate better performance ranges for two algorithms, suggest a hybrid algorithm for dynamically changing communication environments, propose a structure for transmitter and receiver, and show that its performance is better than the traditional algorithm by simulations.