• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.14 no.2
• /
• pp.113-122
• /
• 2016

In this study, the dispersion process of pollutant substances in a port under wave and current environments was evaluated by a hydraulic experiment. Once the contaminants washed ashore into the port of Wolseong nuclear power plant, transport processes of pollutants were investigated by tracking the tracer according to the variations of experimental condition through a hydraulic experiment. Several hydraulic experiments were performed to analyze the pollutant discharge rate of the surface coming from the different coastal environments. From the hydraulic experiment results, the tracer concentration decreased exponentially. These results suggested that, after the tracer was transported to the open sea, a different gradient was shown under different conditions. For the case of a diluted condition, the half-life of flow rate was 2.70, 10.40, and 26.39 days for 30, 20 and 10 rpm in the left-side, respectively. The decrease of the tracer concentration under conditions of 30 rpm was much faster than that under conditions of 10 rpm. For the wave condition, the half-life of flow rate was 4.59 and 15.35 days for the right and left side of the port in a hydraulic scale prototype, respectively.

• Smart Structures and Systems
• /
• v.8 no.3
• /
• pp.303-320
• /
• 2011

Comparing to active damage monitoring, impact localization on composite by using time reversal focusing method has several difficulties. First, the transfer function of the actuator-sensor path is difficult to be obtained because of the limitation that no impact experiment is permitted to perform on the real structure and the difficulty to model it because the performance of real aircraft composite is much more complicated comparing to metal structure. Second, the position of impact is unknown and can not be controlled as the excitation signal used in the active monitoring. This makes it not applicable to compare the difference between the excitation and the focused signal. Another difficulty is that impact signal is frequency broadband, giving rise to the difficulty to process virtual synthesis because of the highly dispersion nature of frequency broadband Lamb wave in plate-like structure. Aiming at developing a practical method for on-line localization of impact on aircraft composite structure which can take advantage of time reversal focusing and does not rely on the transfer function, a PZT sensor array based phase synthesis time reversal impact imaging method is proposed. The complex Shannon wavelet transform is presented to extract the frequency narrow-band signals from the impact responded signals of PZT sensors. A phase synthesis process of the frequency narrow-band signals is implemented to search the time reversal focusing position on the structure which represents the impact position. Evaluation experiments on a carbon fiber composite structure show that the proposed method realizes the impact imaging and localization with an error less than 1.5 cm. Discussion of the influence of velocity errors and measurement noise is also given in detail.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.1
• /
• pp.261-267
• /
• 2015

The eigenvalue problems involving the diffraction of waves by multi-layered grating configurations can be explained by rigorous modal expansion terms. Such a modal solution can be represented by equivalent transmission-line networks, which are generalized forms of simple conventional circuits. This approach brings considerable physical insight into the grating diffraction process of the fields everywhere. In particular, the transmission-line representation can serve as a template for computational algorithms that systematically evaluate dispersion properties, radiation effects and other optical characteristics that are not readily obtained by other methods. To illustrate the validity of the present rigorous approach, the previous research works are numerically confirmed and the results agree well each other.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.5
• /
• pp.362-367
• /
• 2005

Ultrasonic backward radiation profile is frequency-dependent when the incident region has deptional gradient of acoustical properties or multi-layers. Until now, we have measured the profiles of principal frequencies of an used transducers so that it was not easy to characterize the frequency dependence of the SAW(surface acoustic wave) from the backward radiation profile. We tried to measure the spectral backward radiation profiles using DFP(digital filer package) in a Lecroy DSO(digital storage oscilloscope). The measured spectral profiles showed that the steel specimen of #1200 surface treatment have 2% SAW velocity dispersion of the loaded case and the severly rusty steel specimen have the very big changes in the shape and pattern of the spectral profile. It is concluded that the spectral backward radiation profiles could be very effective tool to evaluate the frequency dependence of surface area.

• Journal of Advanced Navigation Technology
• /
• v.15 no.5
• /
• pp.714-721
• /
• 2011

In this paper, developing management programs for EMI tracking can navigate the site quickly and solve EMI tracking cause and location to use materials such as analysis of air accidents, EMI site location data of 1000 RF companys, radio wave spectrum analysis and audio data. these data are databased and used comparable data. Also, EMI has been prevented by establishing continuous monitoring system through a 24-hour surveillance. Therefore we were able to provide high quality air waves in order to prevent aircraft accidents. In addition, radar control staff of Korea Airports Corporation against passenger aircraft that will prevent the worst aircraft accident have been established based to continue periodic aviation frequency protection and Portable Electronic Devices(PED) on board aircraft to prevent the culture of safety campaign.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.8C
• /
• pp.637-644
• /
• 2012

In this paper, a new compact power divider is suggested. Instead of the quarter wavelength transmission line(TX-line)s for the branches of the conventional Wilkinson's power divider design method, we use our composite right- and left-handed(CRLH) TX-line zeroth order resonator(ZOR) bandpass filters of one twelfth wavelength and reduce the physical length of the power divider. Besides, the filters in the branches can secure the passband for power-division. To validate the proposed power divider, we take an L-band for millitary satellaite transponder as the test case and the performances of the circuit and full-wave simulation results with the CRLH properties of the structure are shown with the dispersion curve and E-field at the ZOR. The measurement is compared with the simulation results. Also, the size reduction effect by the proposed scheme is addressed

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.3
• /
• pp.1-9
• /
• 1995

In the B-ISDN using satellite between geo-satellites and earth stations, the laser having high security and broad band width has to be used as a carrier for transmitting massive information of visual, vocal, and high rate data. In this paper, by computer simulation we analyzed the number of optical detector array of optical satellite communication downlink in case of using channel coding and no channel coding for BISDN between geo-satelites and earth stations under clear weather condition. It was supposed that 1 watt semiconductor laser was used and as modulation method, the binary FSK was used. The data rate of 10Gbps was used for B-ISDN. Also, hardly affected by atmospheric absorption 1.55$\mu$m wave-length was used to reduce influence of dispersion and chirp generated at a high speed transmission. We analyzed the received power, SNR and BER. The number of optical detector array was determined to satisfy for the BER less than 10$^{-7}$. Also, we ananlyzed the possibility of reducting the number of optical detector array in case of using channel coding. the number of optical detector array is one in the region where the elevation nangle is between 38$^{\circ}$ and 90$^{\circ}$ and two where the elevation angle is between 33$^{\circ}$ and 37$^{\circ}$ and three where the elevation angle is between 30$^{\circ}$ and 32$^{\circ}$ and increases per one as the elevation angle decreases per 1.deg.. So in the region where the elevation angle is 25$^{\circ}$, the number of optical detector arrays is eight. In case of using channel coding, the number of optical detector arrays decreases to five in the region where the elevation angle is 25$^{\circ}$. Therefore, we remaark the advantage of the channelcoding to decrease the size of received antenna and the number ob optical detector arrays.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.4
• /
• pp.269-277
• /
• 2009

The current paper focuses on the analysis of transient cavitating flow in pressurised polyethylene pipes, which are characterized by viscoelastic rheological behaviour. A hydraulic transient solver that describes fluid transients in plastic pipes has been developed. This solver incorporates the description of dynamic effects related to the energy dissipation (unsteady friction), the rheological mechanical behaviour of the viscoelastic pipe and the cavitating pipe flow. The Discrete Vapour Cavity Model (DVCM) and the Discrete Gas Cavity Model (DGCM) have been used to describe transient cavitating flow. Such models assume that discrete air cavities are formed in fixed sections of the pipeline and consider a constant wave speed in pipe reaches between these cavities. The cavity dimension (and pressure) is allowed to grow and collapse according to the mass conservation principle. An extensive experimental programme has been carried out in an experimental set-up composed of high-density polyethylene (HDPE) pipes, assembled at Instituto Superior T$\acute{e}$cnico of Lisbon, Portugal. The experimental facility is composed of a single pipeline with a total length of 203 m and inner diameter of 44 mm. The creep function of HDPE pipes was determined by using an inverse model based on transient pressure data collected during experimental runs without cavitating flow. Transient tests were carried out by the fast closure of the ball valves located at downstream end of the pipeline for the non-cavitating flow and at upstream for the cavitating flow. Once the rheological behaviour of HDPE pipes were known, computational simulations have been run in order to describe the hydraulic behaviour of the system for the cavitating pipe flow. The calibrated transient solver is capable of accurately describing the attenuation, dispersion and shape of observed transient pressures. The effects related to the viscoelasticity of HDPE pipes and to the occurrence of vapour pressures during the transient event are discussed.

• Journal of Powder Materials
• /
• v.22 no.4
• /
• pp.234-239
• /
• 2015

Electronic products are a major part of evolving industry and human life style; however most of them are known to emit electromagnetic waves that have severe health hazards. Therefore, different materials and fabrication techniques are understudy to control or limit transfer of such waves to human body. In this study, nanocomposite powder is dispersed into epoxy resin and shielding effects such as absorption, reflection, penetration and multiple reflections are investigated. In addition, nano size powder (Ni, $Fe_2O_3$, Fe-85Ni, C-Ni) is fabricated by pulsed wire evaporation method and dispersed manually into epoxy. Characterization techniques such as X-ray diffraction, Scanning electron microscopy and Transmission electron microscopy are used to investigate the phase analysis, size and shape as well as dispersion trend of a nano powder on epoxy matrix. Shielding effect is measured by standard test method to investigate the electromagnetic shielding effectiveness of planar materials, ASTM D4935. At lower frequency, sample consisting nano-powder of Fe-85%Wt Ni shows better electromagnetic shielding effect compared to only epoxy, only Ni, $Fe_2O_3$ and C-Ni samples.

• Proceedings of the KSRS Conference
• /
• 2007.10a
• /
• pp.397-400
• /
• 2007

For mapping the distribution of heavy metals in the mining area, field spectroscopy and hyperspectral remote sensing were used in this study. Although heavy metals are spectrally featureless from the visible to the short wave infrared range, possible variations in spectral signal due to heavy metals bound onto minerals can be explained with the metal binding reaction onto the mineral surface. Variations in the spectral absorption shapes of lattice OH and oxygen on the mineral surface due to the combination of heavy metals were surveyed over the range from 420 to 2400 nm. Spectral parameters such as peak ratio and peak area were derived and statistically linked to metal concentration levels in the streambed samples collected from the dry stream channels. The spatial relationships between spectral parameters and concentrations of heavy metals were yielded as well. Based on the observation at a ground level for the relationship between spectral signal and metal concentration levels, the spectral parameters were classified in a hyperspectral image and the spatial distribution patterns of classified pixels were compared with the product of analysis at the ground level. The degree of similarity between ground dataset and image dataset was statistically validated. These techniques are expected to support assessment of dispersion of heavy metal contamination and decision on optimal sampling point.