• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.2
• /
• pp.63-68
• /
• 2005

This paper describes the characteristics of effective impulse ground impedance of deeply driven ground rods combined with grounding grid or counterpoises with needles. The potential rises of the test ground electrodes were measured as a function of the rise time of applied impulse currents and the effective impulse ground impedances were calculated The impulse ground impedances of deeply driven ground rods strongly depend on the rise time of impulse currents and significantly reduced by the connection of grounding grids in parallel.

• International Journal of Fluid Machinery and Systems
• /
• v.9 no.4
• /
• pp.300-306
• /
• 2016

A twin unidirectional impulse turbine for wave energy conversion has been suggested in our previous study, and the performance under unsteady flow has been investigated by quasi-steady analysis. In the present study, the performance of twin impulse turbine under unsteady flow condition has been investigated by unsteady analysis of Computational fluid dynamics. As a result, the mean efficiency of twin unidirectional impulse turbine under unsteady flow is lower than the maximum efficiency of unidirectional impulse turbine. Moreover, it is verified that airflow goes backward in the reverse turbine in low flow rates.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.2
• /
• pp.363-369
• /
• 2017

This paper presents the experimental results related to soil ionization and electrical breakdown in a concentric hemispherical electrode system under lightning impulse voltages. Dynamic voltage-current and impedance-time characteristics of soil ionization were measured and analyzed. Also the electrical breakdowns of the soil gap were investigated. The time-lag to the peak current corresponds to the soil ionization propagation. The time of ionization propagation in wet sand is found to decrease with increasing the impulse currents. A drastic decrease in ground resistance was observed during the impulse current spreading in sand. The electrical breakdown appears at the wave tail of impulse voltage and results in a wide scatter in V-t curves. The voltage-current curves have a fan-like shape attributed to ionization processes which result in increasing current and decreasing voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.484-485
• /
• 2007

This paper describes the series-gap characteristics of transmission line arrester with switching and lightning impulse flashover test. The transmission line arrester exhibited external gap because it is must not flashover with switching impulse on the other hand it is must flashover with lightning impulse. In accordance, minimum and maximum length of series-gap was determinated with these tests. As gap length is increased flashover voltage was increased in the range of 315.4 kV~496.3 kV and negative polarity exhibited a high voltage. As a result, It was thought tat the series-gap length of transmission line arrester exhibited in the range of 580 mm~1100 mm.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.828-832
• /
• 1995

This paper describes the efficient design, analysis method and experimental verification of capacitor discharge impulse magnetizer system. A capacitor discharge magnetizer system is used to produce a high current impulse of short duration in this magnetizing fixture. The parasitic resistance and parasitic inductance of the capacitor discharge impulse magnetizer system have been estimated using known air-core test coil. Finite element analysis (using MAXWELL 2-D field simulator) and magnetizing circuit analysis (using SPICE) are also used as part of the design and analysis process of the capacitor discharge impulse magnetizer system. Application study for a magnetizing fixture design is shown. 8-pole magnetizing fixture has been designed and analyzed using finite element analysis. The fixture design for 8-pole magnet are presented along with the experimental results. The experimental results have been achieved using a high-voltage, high-energy capacitor discharge impulse magnetizer and 8-pole iron core fixtures (charging voltage : 2000[V], capacitor bank : 4000[$\mu\textrm{F}$]).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2019.05a
• /
• pp.597-599
• /
• 2019

When frequency domain high amplitude impulse is inserted before IFFT in OFDM transmitter, the PAPR of OFDM signal in tme domain can be effectively reduced. In this paper, the degree of PAPR improvement of OFDM communication system with CQAM subcarrier modulation is analysed by adopting impulse insertion technique before IFFT of transmitter. Furthermore, it is verified that additional PAPR performance improvement can be obtained by finding optimum position of impulse insertion for maximizing PAPR reduction.

• Asia-Pacific Journal of Business
• /
• v.15 no.1
• /
• pp.15-31
• /
• 2024

Purpose - This study explores the causes behind the high rate of impulse purchases in live streaming e-commerce. Design/methodology/approach - The research model is empirically validated with survey data collected from 324 respondents in China, using the Partial Least Squares (PLS) methodology. Findings - We found that the interactivity and visibility of live streaming are key in creating para-social relationships and perceived presence, leading to customers' impulse purchases. Research implications or Originality - This study deepens the understanding of consumers' impulse purchases in live-streaming e-commerce, revealing that para-social relationships and perceived presence developed through real-time interactions can increase impulse buying. It also highlights the differences between relationship-oriented and task-oriented interactions in fostering customers' perceived presence and para-social relationships in live streaming.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.38 no.1
• /
• pp.87-96
• /
• 2014

E-shopping is traditional method to purchase products in a modern society. Fashion products are one of the most popular product categories sold and impulsively bought online. This study examined the causal relationship of shopping value, positive emotion, urge to buy impulsively, and e-impulse buying in the context of shopping for apparel products. A self-administered questionnaire developed from the literature was administered in class to 501 female college students in Busan. AMOS 21.0 estimated the structural equation model of e-impulse buying using a correlation matrix with a maximum likelihood. The analysis of the data supported most of the predictions. The results suggested that consumer shopping values (hedonic shopping value and utilitarian shopping value) had a positive effect on positive emotion; in addition, positive emotion urge to buy impulsively directly affected the e-impulse buying of apparel products. In the structural model, e-impulse buying of consumers can be predicted by the attitudinal component (e.g., shopping values), emotional factors (e.g., enthusiastic or proud), and the urge to buy impulsively felt by young consumers. There are implications that both positive emotion and impulsive buying are important predictors for the e-impulse buying of apparel products by consumers. Moreover, the urge to buy impulsively was an important mediator to determine the e-impulse buying of apparel products. This study provides insight to retailers and researchers to understand the structural relationship of consumer characteristics and the e-impulse buying of apparel products.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.25 no.3
• /
• pp.24-32
• /
• 2011

[ $SF_6$ ]gas, which has an excellent dielectric strength and interruption performance, is used in various applications such as gas insulated switchgear (GIS) in substations. However, since $SF_6$ has a high global warming potential (GWP), it is necessary to find an eco-friendly alternative insulation gas. In order to examine the possibility of using alternative insulation gases for $SF_6$ in power distribution system equipment, the dielectric strength and physical phenomena of dry air in a quasi-uniform electric field are investigated experimentally in this paper. As a result, the breakdown voltages for positive polarity are higher than those for negative polarity under impulse voltage applications. The negative 50[%] flashover voltage, $V_{50}$ of dry air under conditions above 0.4[MPa] gas pressure, is higher than 150[kV], that is the basic impulse insulation level of distribution equipment. The $V_{50}$ increases linearly with increasing the gas pressure, regardless of the waveform and polarity of the applied impulse voltages. The voltage-time curves are dependent on the rise time of the impulse voltage and gas pressure. Furthermore, streamer discharge was observed through light emission images by an ICCD camera under impulse voltage applications.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.42 no.6 s.336
• /
• pp.61-66
• /
• 2005

In this paper, we implemented a impulse generator, the one of the part in UWB(Ultra Wide Band) system using step recovery diode(SRD) and gain-switced semiconductor laser. The impulse generator was consisted of four stages; The first stage used SRD to generate the first impulse for gain switching. The second stage controled current for the suitable gain switching condition. The third was the second impulse generator to generate gaussian pulse. For gain switching, the first impulse was applied to semiconductor laser. In the last stage the gain switched impulse was converted into mono-gaussian pulse. The measured mono-gaussian pulse was 360 psec pulse-width and $-70mV \~ +50mV$ amplitude in time domain. In frequency domain its magnitude and bandwidth was, respectively, -41dBm and 3.6GHz. Accordingly, the impulse generator that we suggested was suitable for UWB systems.