• Title/Summary/Keyword: Power Station

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Compensation Method of eLoran Signal's Propagation Delay and Performance Assessment in the Field Experiment

  • Son, Pyo-Woong;Fang, Tae Hyun;Park, Sul Gee;Han, Younghoon;Seo, Kiyeol
    • Journal of Positioning, Navigation, and Timing
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    • v.11 no.1
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    • pp.23-28
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    • 2022
  • The eLoran system is a high-power terrestrial navigation system that is recognized as the most appropriate alternative to complement the GNSS's vulnerability to radio frequency interference. Accordingly, Korea has conducted eLoran technology development projects since 2016. The eLoran system developed in Korea provides 20 m positioning accuracy to maritime user in Incheon and Pyeongtaek harbor. To accurately calculate the position with the eLoran signal, it is necessary to apply a compensation method that mitigates the propagation delay. In this paper, we develop the compensation method to mitigate the eLoran signal propagation delay and evaluate the positioning performance in Incheon harbor. The propagation delay due to the terrain characteristics is pre-surveyed and stored in the user receiver. Real-time fluctuations in propagation delay compared to the pre-stored data are mitigated by the temporal correction generated at a nearby differential Loran station. Finally, two performance evaluation tests were performed to verify the positioning accuracy of the Korean eLoran system. The first test took place in December 2020 and the second in April 2021. As a result, the Korean eLoran service has been confirmed to provide 20 m location accuracy without GPS.

[Retracted]Effects of emotional labor and job stress on turnover intention among firefighters ([논문철회]소방공무원의 직무스트레스와 감정노동이 이직의도에 미치는 영향)

  • Hyo-Cheol, Lee
    • The Korean Journal of Emergency Medical Services
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    • v.26 no.3
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    • pp.21-35
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    • 2022
  • Purpose: The purpose of this study was to investigate the effects of firefighters' job stress and emotional labor on their turnover intention, and analyze the main factors impacting turnover intention in this context. Methods: Based on a descriptive survey study design, we administered a structured questionnaire among 231 firefighters at one fire station in G metropolitan city from November 13 to 27, 2020. Results: Regarding job stress, participants showed differences based on marital status (p<.05), health status (p<.001), total service period (p<.05), and assignment (p<.05). For emotional labor, a significantly higher rate was observed for female than male firefighters (p<.05), with differences also observed in age (p<.001), health status (p<.001), total service period (p<.05), rank (p<.001), and assignment (p<.05). Further, for turnover intention, significant differences were noted with respect to age (p<.001), education (p<.01), health status (p<.001), total service period (p<.01), work unit (p<.05), rank (p<.001), and assignment (p<.05). A significant correlation was found between job stress and emotional labor and turnover intention. Regarding the factors affecting turnover intention, significant differences were noted based on education, rank, job stress, and emotional labor; the explanatory power was 53.9% (F=13.806, p<.001). Conclusion: Tailored support programs must be developed to ease firefighters' job stress and reduce their emotional labor to facilitate effective manpower management and reduce firefighters' turnover intention.

A Study of Vibration Analysis of 100 MPa Class Fitting Thread for Mobile Hydrogen Charging Station (이동식 수소 충전 장비용 100 MPa급 고압 피팅의 진동 해석)

  • JUNYEONG KWON;SEUNGJUN OH;JUNGHWAN YOON;JEONGJU CHOI
    • Journal of Hydrogen and New Energy
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    • v.35 no.1
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    • pp.83-89
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    • 2024
  • In order to confirm the safety against vibration of high-pressure fittings for mobile hydrogen charging devices, the natural frequency was confirmed through ANSYS, and vibration data occurring during driving was applied to utilize the vehicle's operating power spectral density data specified in MIL-STD-810H regulations. Fatigue analysis and resonance were confirmed, and as a result, it was confirmed that the sum of the pure phase ratios was less than 1 for the driving history presented in the standard, and there was no risk of resonance.

Design and transient analysis of a compact and long-term-operable passive residual heat removal system

  • Wooseong Park;Yong Hwan Yoo;Kyung Jun Kang;Yong Hoon Jeong
    • Nuclear Engineering and Technology
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    • v.55 no.12
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    • pp.4335-4349
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    • 2023
  • Nuclear marine propulsion has been emerging as a next generation carbon-free power source, for which proper passive residual heat removal systems (PRHRSs) are needed for long-term safety. In particular, the characteristics of unlimited operation time and compact design are crucial in maritime applications due to the difficulties of safety aids and limited space. Accordingly, a compact and long-term-operable PRHRS has been proposed with the key design concept of using both air cooling and seawater cooling in tandem. To confirm its feasibility, this study conducted system design and a transient analysis in an accident scenario. Design results indicate that seawater cooling can considerably reduce the overall system size, and thus the compact and long-term-operable PRHRS can be realized. Regarding the transient analysis, the Multi-dimensional Analysis of Reactor Safety (MARS-KS) code was used to analyze the system behavior under a station blackout condition. Results show that the proposed design can satisfy the design requirements with a sufficient margin: the coolant temperature reached the safe shutdown condition within 36 h, and the maximum cooling rate did not exceed 40 ℃/h. Lastly, it was assessed that both air cooling and seawater cooling are necessary for achieving long-term operation and compact design.

Wind turbulence characteristics over an industrial landscape in neutral atmospheric conditions

  • Petr Michalek;Stanislav Pospisil;Pavel Sedlak
    • Wind and Structures
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    • v.39 no.2
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    • pp.111-123
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    • 2024
  • The atmospheric turbulence characteristics measured at a meteorological station in northwest part of the Czech Republic are presented for selected time periods in the year 2017. The terrain of this region is influenced by surface coal mining and the related industry. The datasets used in this study were measured using four ultrasonic anemometers installed on an 80 m high meteorological mast at heights of 20, 40, 60 and 80 m, respective. From the primary high-frequency datasets, time intervals in order of hours were selected and integral turbulence characteristics (ITCs), turbulence intensities and turbulence spectra were analyzed. The time intervals were selected with respect to atmospheric stability parameter, known as Obukhov number. We concentrated on the days with higher wind velocity and neutral atmospheric stratification. The wind characteristics investigated in this study include the wind speed, wind direction and its histograms, turbulence intensity, friction velocity and wind power spectra. The ITCs and spectral characteristics were compared with the theoretical models and values from the literature. The resulting ITCs showed the values for urban locations similar to those found in other studies and can be used in practical design. The computed turbulence spectra followed the shape of theoretical spectra of turbulence for both horizontal and vertical velocity components. The computed integral length scales have shown to be unsuitable for further use due to their highly scattered values.

Estimation of Fire Emissions Using Fire Radiative Power (FRP) Retrieved from Himawari-8 Satellite (히마와리 위성의 산불방사열에너지 자료를 이용한 산불배출가스 추정: 2017년 삼척 및 강릉 산불을 사례로)

  • Kim, Deasun;Won, Myoungsoo;Lee, Yangwon
    • Korean Journal of Remote Sensing
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    • v.33 no.6_1
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    • pp.1029-1040
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    • 2017
  • Wildfires release a large amount of greenhouse gases (GHGs) into the atmosphere. Fire radiative power (FRP) data obtained from geostationary satellites can play an important role for tracing the GHGs. This paper describes an estimation of the Himawari-8 FRP and fire emissions for Samcheock and Gangnueng wildfire in 6 May 2017. The FRP estimated using Himawari-8 well represented the temporal variability of the fire intensity, which cannot be captured by MODIS (Moderate Resolution Imaging Spectroradiometer) because of its limited temporal resolution. Fire emissions calculated from the Himwari-8 FRP showed a very similar time-series pattern compared with the AirKorea observations, but 1 to 3 hour's time-lag existed because of the distance between the station and the wildfire location. The estimated emissions were also compared with those of a previous study which analyzed fire damages using high-resolution images. They almost coincided with 12% difference for Samcheock and 2% difference for Gangneung, demonstrating a reliability of the estimation of fire emissions using our Himawari-8 FRP without high-resolution images. This study can be a reference for estimating fire emissions using the current and forthcoming geostationary satellites in East Asia and can contribute to improving accuracy of meteorological products such as AOD (aerosol optical depth).

Korean Paddy Soil Microbial Community Analysis Method Using Denaturing Gradient Gel Electrophoresis (Denaturing gradient gel electrophoresis를 이용한 한국의 논 토양 미생물 다양성 분석 방법)

  • Choe, Myeongeun;Hong, Sung-Jun;Lim, Jong-Hui;Kwak, Yunyoung;Back, Chang-Gi;Jung, Hee-Young;Lee, In-Jung;Shin, Jae-Ho
    • Journal of Applied Biological Chemistry
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    • v.56 no.2
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    • pp.95-100
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    • 2013
  • Soil microbes are important integral components of soil ecosystem which have significant and diverse role in organic matter decomposition, nitrogen cycling, and nitrogen fixation. In this study an effective denaturing gradient gel electrophoresis (DGGE) method was employed for paddy soil microbial diversity survey. For optimum paddy soil microbial DNA extraction, different methods such as Lysis buffer, skim milk bead, sodium phosphate buffer, Epicentre Soil Master DNA extraction kit (Epicentre, USA) and Mo Bio Power Soil DNA kit (MO BIO, USA) methods were utilized. Among all the method, using Mo Bio Power Soil kit was most effective. DGGE analysis of Bacteria was carried out at 6% polyacylamide gel and 45-60% denaturing gradient in the optimal conditions. Whereas DGGE analysis of fungi was done at 6% polyacrylamide gel and 45-80% denaturing gradient in the optimal conditions. By applying the above assay, it was found that variation within the microbial community of paddy soil occurs by a factor of time. DGGE assay used in this study through for a variety of soil microbial analysis suggests the potential use of this method.

Design of Sedimentary Rock Slopes in River Diversion Works (가배수로 터널공사의 퇴적암 사면 안정화 설계)

  • Jee, Wang-Ruel
    • Geotechnical Engineering
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    • v.14 no.6
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    • pp.17-32
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    • 1998
  • The Bakun hydroelectric project includes the construction of a hydroelectric power plant with an installed capacity of 2,520MW and a power transmission system connecting to the existing transmission networks in Sarawak and Western Malaysia, The power station will consist of a 210m height concrete faced rockfill dam. During the construction of the dam and the power facilities the Balui river has to be diverted by three diversion tunnels with a length of some 1,400m each. The inner diameter of the tunnels is 12m and the tunnel width is 16m at the portal area. This paper describes the stability analysis and design methods for the open cut rock slopes in the inlet and outlet area of the diversion tunnels. The geotechnical parameters employed in stability calculations were given as a function of four. defined Rock Mass Types (RMT) which were based on RMR system from Bieniawski. The stability calculations procedure of the rock slopes are divided into two stages. In the first stage, it is calculated for the stability of each 'global' slope without any rock support and shotcrete system. In the second stage, it is calculated for each 'local'slope stability with berms and supported with rock bolts and shotcrete. The monitoring instrumentation was performed continuously and some of the design modification was carried out in order to increase the safety of failed area based on the unforeseen geological risks during the open cut excavation.

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A UHF-band Passive Temperature Sensor Tag Chip Fabricated in $0.18-{\mu}m$ CMOS Process ($0.18-{\mu}m$ CMOS 공정으로 제작된 UHF 대역 수동형 온도 센서 태그 칩)

  • Pham, Duy-Dong;Hwang, Sang-Kyun;Chung, Jin-Yong;Lee, Jong-Wook
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.45 no.10
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    • pp.45-52
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    • 2008
  • We investigated the design of an RF-powered, wireless temperature sensor tag chip using $0.18-{\mu}m$ CMOS technology. The transponder generates its own power supply from small incident RF signal using Schottky diodes in voltage multiplier. Ambient temperature is measured using a new low-power temperature-to-voltage converter, and an 8-bit single-slope ADC converts the measured voltage to digital data. ASK demodulator and digital control are combined to identify unique transponder (ID) sent by base station for multi-transponder applications. The measurement of the temperature sensor tag chip showed a resolution of $0.64^{\circ}C/LSB$ in the range from $20^{\circ}C$ to $100^{\circ}C$, which is suitable for environmental temperature monitoring. The chip size is $1.1{\times}0.34mm^2$, and operates at clock frequency of 100 kHz while consuming $64{\mu}W$ power. The temperature sensor required a -11 dBm RF input power, supported a conversion rate of 12.5 k-samples/sec, and a maximum error of $0.5^{\circ}C$.

Optimized Cell ID Codes for SSDT Power Control in W-CDMA System (W-CDMA 시스템의 최적의 SSDT 전력 제어용 셀 식별 부호)

  • Young-Joon Song;Bong-Hoe Kim;Hae Chung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.13 no.8
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    • pp.804-810
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    • 2002
  • The code division multiple access(CDMA) system capacity is limited by the amount of interference of the system. To reduce the unnecessary interference, this paper proposes optimized cell identification codes for site selection diversity transmission(SSDT) power control in wideband code division multiple access system of third generation partnership project(3GPP). The main objective of SSDT power control is to transmit on the downlink from the primary cell, and thus reducing the interference caused by the multiple transmission. In order to select a primary cell, each cell is assigned a temporary identification(ID) and user equipment(UE) periodically informs a primary cell ID to the connecting cells during soft handover. The non-primary cells selected by UE do not transmit the dedicated physical data channel(DPDCH) to reduce the interference. A major issue with the SSDT technology is the impact of uplink symbol errors on its performance. These errors can corrupt the primary ID code and this may lead to wrong decoding in the base station receivers. The proposed SSDT cell ID codes are designed to minimize the problem and to be easily decoded using simple fast Hadamard transformation(FHT) decoder.