• ETRI Journal
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• v.38 no.5
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• pp.799-806
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• 2016

In this paper, we propose an emergency wake-up alert system (EWAS) for providing accurate and rapid emergency information. The proposed system can provide an emergency wake-up alert service without an additional frequency allotment by utilizing the guard band of the Advanced Television Systems Committee (ATSC) Terrestrial Digital Television (DTV) system. The design target of the proposed system is to match the indoor reception coverage of EWAS with the outdoor reception coverage of the ATSC DTV system. To achieve this, the proposed system should be about 35.65 dB more robust than the ATSC DTV system. The simulation results show that the proposed system offers an emergency wake-up alert service supporting a data rate of up to 23 bps.

• Journal of Korea Multimedia Society
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• v.25 no.8
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• pp.1097-1108
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• 2022

This paper aimed to design and implement an EMS for real-time power generation control based on wake effect optimization of wind farm, and then to test it in commercial operating wind farm. For real-time control, we proposed the wake band-based optimization and setting the wake effect distance limit, and when the wake effect distance limit was set to 7D in the actual wind farm layout, the calculation time was improved by about 93.94%. In addition, we designed and implemented the script-based EMS for flexible operation logic management in preparation for unexpected issues during testing, and it was installed and tested on a wind farm in commercial operation. However, three issues arose during the testing process. These are the communication interface problem of meteorological tower, the problem of an abnormal wake effect, and the problem of wind turbine yaw control. These issues were solved by modifying the operation logic using EMS's script editor, and the test was successfully completed in the wind farm in commercial operation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1210-1218
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• 2004

Experimental study was performed to investigate the flow behavior in boundary layer on the blade suction surface of a multi-stage axial flow compressor, which was focused on the third stage of the 4-stage Low Speed Research Compressor. Flow measurements in the boundary layer were obtained using a boundary layer hot wire probe, which was traversed normal to the blade suction surface at small increments by the probe traverse specially designed. Detailed boundary layer flow measurements covering most of the stator suction surface were taken and are described using time mean and ensemble averaged velocity profiles. Amplitude of the velocity fluctuation and turbulence intensity in the boundary layer flow are also discussed. At midspan, narrow but strong wake zone due to passing wake disturbances is generated in the boundary layer near the blade leading edge for the rotor blade passing period. Corner separation is observed at the tip region near the trailing edge, which causes to increase steeply the boundary layer thickness.

• Journal of Broadcast Engineering
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• v.19 no.4
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• pp.491-501
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• 2014

Recently, the need for disaster-preventing broadcast has increased gradually to cope with natural disaster like earthquake and tsunami causing enormous losses of both life and property. In disaster-preventing broadcast system, the wake-up signal is used to alert user terminal and switch the current state of channel to the emergency channel, which is for the fast and efficient delivery of emergency information. In this paper, we propose the detection method of wake-up signal for disaster-preventing broadcast systems. The wake-up signals for disaster-preventing broadcast should have a good auto-correlation property in low power and narrow-band conditions that does not affect the existing digital television (DTV) system. The suitability of the m-sequence and complementary code (CC) is analyzed for wake-up signals according to signal to noise ratio. A wake-up signal is proposed by combining the direct sequence spread spectrum (DSSS) technique and pseudo noise (PN) sequences such as Barker and Walsh-Hadamard codes. By using the proposed method, a higher detecting performance can be achieved by the spreading gain compared to the single long m-sequence and the Golay code.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.20-25
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• 2005

The thickness, loading, and broadband noise generated from the trailing edge of the UH-1H main rotor are numerically compared each other. The Kocureck and Tangler's prescribed wake model is adopted to represent the wake geometry during the hovering motion. Three tip Mach numbers of $M_{T}$ = 0.2, 0.4, and 0.8, are selected to analyze the effects of different tip Mach numbers. At $M_{T}$ = 0.8, in considering the A-weighting and audible frequency band, the random noise is smaller than the tonal noises such as the thickness and the loading noise which have the low frequency characteristics. Especially most of the random noise frequency spread on the ultrasound region. On the other hand, below $M_{T}$ = 0.4, the band of random noise moves to the audible frequency region, and the random noise becomes larger than the tonal noise. It turns out that the random noise analysis of the rotor should be necessary at low speed operating condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.2
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• pp.75-82
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• 2015

Noises from the large scale marine propeller are calculated numerically on non-cavitation condition. The hydrodynamic analysis is carried out by potential based panel method with time marching free wake approach. The distribution of hydrodynamic loads on the propeller surface and noise signals are obtained using the unsteady Bernoulli's equation and the Farasssat's formula respectively. It turns out that the noise signal at the narrow band shows strong peak at the blade passage frequency, and the peak value at the 1/3 octave band also shows the same trend. Noise signals and directivity patterns for both the thickness and the loading noise are compared with each other. The directivity pattern for the loading noise shows minor lobe at the backward side of the rotating disc plane.

• Asian Journal for Public Opinion Research
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• v.8 no.2
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• pp.105-125
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• 2020

The purpose of this paper is to analyze 1) who created and distributed fake news, 2) the distribution channels of fake news, 3) who fake news has targeted, and 4) the effects on voting and the impact of fake news on Korean politics. In South Korea, fake news was mainly created by candidates or election campaigns. The reason is that in the wake of the impeachment of President Park Guen Hye, all the political parties in Korea used fake news as a means of mobilizing supporters for each of their candidates or parties to gain an advantage in situations involving political divisions and confrontations between the pro-impeachment, progressive young generation and anti-impeachment, conservative senior generation. Voters' media usage patterns were polarized through social network services (SNS) media and television. Fake news was mostly received through these two media outlets. According to the spreading structure of fake news in Korea, the younger generation generally uses SNS posts intended for unspecified individuals, and the older generation uses closed SNS like KakaoTalk or Naver's BAND. In the end, it is typically characteristic of the older generation to spread fake news through existing offline human networks. In the 2017 presidential election, fake news has been confirmed to have the effect of mobilizing supporters for each political party. In the presidential election, an increase in voter turnout was confirmed among those in their 20s and those in their 60s or older. Evidently, fake news influenced the election of Moon Jae-In. The influence of fake news is expected to grow further as ideological polarization and consequent political polarization continues to intensify in South Korea.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.6 no.2
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• pp.102-115
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• 2020

In the state of Positronium (Ps), which is an unstable material created by the temporary combination of electrons and positrons, the imaging technology through photo-conversion methodology is emerging as a new research theme under resonance conditions through terahertz electromagnetic waves. Normally, Positronium can be observed in the positron emission computed tomography (PET) process when an unstable, separate state that remains after the pair annihilation of an electron and a positron remains. In this study, terahertz (THz) waves and Cherenkov radiation (CR) are generated using the principle of ponderomotive force in the plasma wake-field acceleration, and electrons and positrons are simultaneously generated by using a relativistic electron beam without using a PET device. We confirm the possibility of Positronium photoconversion technology in terahertz electromagnetic resonance conditions through experimental studies that generate an unstable state. Here, a relativistic electron beam (REB) energy of 0.5 MeV (γ=2) was used, and the terahertz wave frequencies is G-band. Meanwhile, a THz wave mode converting three-stepped axicon lens was used to apply the photoconversion technology. Through this, light emission in the form of a luminescence-converted Bessel beam can be verified. In the future, it can be used complementarily with PET in nuclear medicine in the field of medical imaging.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.407-410
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• 2018

As the operating frequency of an electromagnetic wave increases, the maximum output and wavelength of the wave decreases, so that the size of the circuit cannot be reduced. As a result, the fabrication of a circuit with high power (of the order of or greater than kW range) and terahertz wave frequency band is limited, due to the problem of circuit size, to the order of ${\mu}m$ to mm. In order to overcome these limitations, we propose a source design technique for 0.1 THz~0.3 GW level with cylindrical shape (diameter ~2.4 cm). Modeling and computational simulations were performed to optimize the design of the high-power electromagnetic sources based on Cherenkov radiation generation technology using the principle of plasma wakefield acceleration with ponderomotive force and artificial dielectrics. An effective design guideline has been proposed to facilitate the fabrication of high-power terahertz wave vacuum devices of large diameter that are less restricted in circuit size through objective verification.

• 한국환경농학회:학술대회논문집
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• 2009.07a
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• pp.273-282
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• 2009

The transmissible spongiform encephalopathies (TSEs) disease group are fatal neurodegenerative disorders affecting a wide range of hosts. The group includes kuru and Creutzfeldt-Jakob disease (CJD) in humans, scrapie in sheep and goats and Bovine spongiform encephalopathy (BSE) in cattle. The exact nature of the infectious agent involved in the transmission of these diseases remains controversial. However, a central event in their pathogenesis is the accumulation in infected tissues of an abnormal form of a host-encoded protein, the prion protein (PrP). Whereas the normal cellular protein is fully sensitive to protease ($PrP^{sen}$), the disease-associated prion protein ($PrP^d$) is only partly degraded ($PrP^{res}$), its amino-terminal end being removed. BSE was first reported in the mid-80s in the UK. Ten years later, a new form of human prion disease, variant CJD (vCJD) developed in the wake of the BSE epidemic, and there is now strong scientific evidence that vCJD was initiated by the exposure of humans to BSE-infected tissues, thus indicating a zoonotic disease. However, the ban on the feeding of animal-derived proteins to ruminants, and the apparent lack of vertical transmission of BSE, have led to a decline in the incidence of the disease within cattle herd and therefore, an assumed decreased risk for human contacting vCJD. The origin of the original case(s) of BSE still remains an enigma even though three hypotheses have been raised. Hypotheses are i) sheep- or goat-derived scrapie-infected tissues included in meat and bone meal fed to cattle, ii) a previously undetected sporadic or genetic bovine TSE contaminating cattle feed or iii) originating from a human TSE through animal feed contaminated with human remains. A host cellular membrane protein ($PrP^C$), which is abundant in central nervous system tissue, appear to be conformationally altered in the diseased host into a prion protein ($PrP^{Sc}$). This $PrP^{Sc}$ is detergent insoluble and partially protease-resistant ($PrP^{res}$). The term $PrP^{res}$ is normally used to describe the protein detected after protease treatment, in techniques such as Western immunoblotting, and enzyme-linked immunosorbant assay using fresh/frozen tissue. Immunohistochemistry may performed with formalin-fixed tissues. Also, clinical signs of the BSE are one of the major diagnostic indicators. Recently, atypical forms (known as H- and L-type) of BSE have appeared in several European countries, Japan, Canada and the United States. An unusual case was also reported in a miniature zebu. The atypical BSE fall into two groups based on the relative molecular mass (Mm) of the unglycosylated $PrP^{res}$ band relative to that of classical BSE, one of the higher Mm (H-type) and the other lower (L-type). Both types have been detected worldwide as rare cases in older animals, at a low prevalence consistent with the possibility of sporadic forms of prion diseases in cattle. This raises the unwelcome possibility that vCJD could increase in the human population. Now, active surveillance program against BSE is going on in Korea. In regional veterinary service lab, ELISA is applied to screen the BSE in slaughter and confirmatory tests by Western immunoblotting and immunohistochemisty are carried out if there are positive or suspect in the screening test. Also, the ruminant feed ban is rigorously enforced. Removal of specified risk materials such as brain and spinal cord from cattle is mandatory process at slaughter to prevent the infected material from entering the human food chain.