• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2221-2231
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• 2017

In this paper, we surveyed previous cases, network protocols (such as Wi-Fi, Zigbee, Z-wave, and WirelessHart) and propagation characteristics on the application of maintaining equipments for instrumentation and control (I&C) using wireless communication techniques inside the nuclear power plant (NPP). In addition, we compared and analyzed the difference of detailed regulations with respect to the electromagnetic interference (EMI) and radio frequency interference (RFI) in the Regulatory Guide 1.180 rev. 1 (RG. 1.180) for adopting the wireless communication techniques inside the NPP, and other regulations, such as MIL-STD 461E and IEC 61000-4, that are recognized in the KINS/RG-N03.09 (Rev. 2). Furthermore, we investigated evaluating factors about electromagnetic properties by considering indoor environments, wave scattering, shielding effectiveness, and the indoor wave attenuation model that were not included in the current electromagnetic compatibility regulation.

• Korean Journal of Optics and Photonics
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• v.31 no.5
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• pp.218-222
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• 2020

In this paper, we have experimentally demonstrated a 2-kW-class spectrally-beam-combined laser with high beam quality, using narrow-linewidth ytterbium-doped polarization-maintaining fiber amplifiers. Five fiber amplifiers with different center wavelengths were implemented for the spectrally-beam-combined laser. The center wavelengths of the five amplifiers were 1062, 1063, 1064, 1065, and 1066 nm, respectively. A phase-modulated laser diode was used as a seed source for each amplifier. The seed sources were modulated by filtered pseudorandom-bit-sequence (PRBS) signals 5 GHz in linewidth. The polarization-maintaining large-mode-area fiber with a core size of 30 ㎛ was used as a delivery fiber to mitigate the stimulated Brillouin scattering (SBS) effect. The laser beams from five amplifiers were spectrally combined by a multilayer dielectric diffraction grating. The maximum output power and beam quality M² of the combined laser were measured to be 2.3 kW and 1.74, respectively.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.5
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• pp.43-51
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• 2010

Attenuation coefficients of medical ultrasound not only reflect the pathological information of tissues scanned but also provide the quantitative information to compensate the decay of backscattered signals for other medical ultrasound parameters. Based on the frequency-selective attenuation property of human tissues, attenuation estimation methods in spectral domain have difficulties for real-time implementation due to the complexicity while estimation methods in time domain do not achieve the compensation for the diffraction effect effectively. In this paper, we propose the modified VSA method, which compensates the diffraction with reference phantom in time domain, using adaptive bandpass filters with decreasing center frequencies along depths. The adaptive bandpass filtering technique minimizes the distortion of relative echogenicity of wideband transmit pulses and maximizes the signal-to-noise ratio due to the random scattering, especially at deeper depths. Since the filtering center frequencies change according to the accumulated attenuation, the proposed algorithm improves estimation accuracy and precision comparing to the fixed filtering method. Computer simulation and experimental results using tissue-mimicking phantoms demonstrate that the distortion of relative echogenicity is decreased at deeper depths, and the accuracy of attenuation estimation is improved by 5.1% and the standard deviation is decreased by 46.9% for the entire scan depth.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.291-298
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• 2020

ZITO/Ag/ZITO multilayer transparent electrodes at room temperature on glass substrates were prepared using RF/DC magnetron sputtering. Transparent conductive films with a sheet resistance of 9.4 Ω/㎡ and a transmittance of 83.2% at 550 nm were obtained for the multilayer structure comprising ZITO/Ag/ZITO (100/8/42 nm). The sheet resistance and transmittance of ZITO/Ag/ZITO multilayer films meant that they would be highly applicable for use in polymer-dispersed liquid crystal (PDLC)-based smart windows due to the ability to effectively block infrared rays (heat rays) and thereby act as an energy-saving smart glass. Effects of the thickness of the PDLC layer and the intensity of ultraviolet light (UV) on electro-optical properties, photopolymerization kinetics, and morphologies of difunctional urethane acrylate-based PDLC systems were investigated using new transparent conducting electrodes. A PDLC cell photo-cured using UV at an intensity of 2.0 mW/c㎡ with a 15 ㎛-thick PDLC layer showed outstanding off-state opacity, good on-state transmittance, and favorable driving voltage. Also, the PDLC-based smart window optimized in this study formed liquid crystal droplets with a favorable microstructure, having an average size range of 2~5 ㎛ for scattering light efficiently, which could contribute to its superior final performance.

• Journal of radiological science and technology
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• v.25 no.1
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• pp.63-71
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• 2002

The aim of this study Is to develop a simple and fast method which computes in-vivo doses from transmission doses measured doting patient treatment using an ionization chamber. Energy fluence and the dose that reach the chamber positioned behind the patient is modified by three factors: patient attenuation, inverse square attenuation. and scattering. We adopted a straightforward empirical approach using a phantom transmission factor (PTF) which accounts for the contribution from all three factors. It was done as follows. First of all, the phantom transmission factor was measured as a simple ratio of the chamber reading measured with and without a homogeneous phantom in the radiation beam according to various field sizes($r_p$), phantom to chamber distance($d_g$) and phantom thickness($T_p$). Secondly, we used the concept of effective field to the cases with inhomogeneous phantom (patients) and irregular fields. The effective field size is calculated by finding the field size that produces the same value of PTF to that for the irregular field and/or inhomogeneous phantom. The hypothesis is that the presence of inhomogeneity and irregular field can be accommodated to a certain extent by altering the field size. Thirdly, the center dose at the prescription depth can be computed using the new TMR($r_{p,eff}$) and Sp($r_{p,eff}$) from the effective field size. After that, when TMR(d, $r_{p,eff}$) and SP($r_{p,eff}$) are acquired. the tumor dose is as follows. $$D_{center}=D_t/PTF(d_g,\;T_p){\times}(\frac{SCD}{SAD})^2{\times}BSF(r_o){\times}S_p(r_{p,eff}){\times}TMR(d,\;r_{p,eff})$$ To make certain the accuracy of this method, we checked the accuracy for the following four cases; in cases of regular or irregular field size, inhomogeneous material included, any errors made and clinical situation. The errors were within 2.3% for regular field size, 3.0% irregular field size, 2.4% when inhomogeneous material was included in the phantom, 3.8% for 6 MV when the error was made purposely, 4.7% for 10 MV and 1.8% for the measurement of a patient in clinic. It is considered that this methode can make the quality control for dose at the time of radiation therapy because it is non-invasive that makes possible to measure the doses whenever a patient is given a therapy as well as eliminates the problem for entrance or exit dose measurement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.777-784
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• 2017

Energy harvesting through a thermoelectric module normally makes use of the temperature gradient in the system's operational environment. Therefore, it is difficult to obtain the desired output power when the system is subjected to an environment in which a low temperature gradient is generated across the module, because the power generation efficiency of the thermoelectric device is not optimized. The utilization of solar energy, which is a form of renewable energy abundant in nature, has mostly been limited to photovoltaic solar cells and solar thermal energy generation. However, photovoltaic power generation is capable of utilizing only a narrow wavelength band from the sunlight and, thus, the power generation efficiency might be lowered by light scattering. In the case of solar thermal energy generation, the system usually requires large-scale facilities. In this study, a simple and small size thermoelectric power generation system with a solar concentrator was designed to create a large temperature gradient for enhanced performance. A solar tracking system was used to concentrate the solar thermal energy during the experiments and a liquid circulating chiller was installed to maintain a large temperature gradient in order to avoid heat transfer to the bottom of the thermoelectric module. Then, the setup was tested through a series of experiments and the performance of the system was analyzed for the purpose of evaluating its feasibility and validity.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.443-450
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• 2016

In this study, we propose a novel fiber optic sensor to show the measurement feasibility of distributed temperature and strains in a single sensing fiber line. Distributed temperature can be measured using optical time domain reflectometry (OTDR) with a Raman anti-Stokes light in the sensing fiber line. Moreover, the strain can be measured by fiber Bragg gratings (FBGs) in the same sensing fiber line. The anti-Stokes Raman back-scattering lights from both ends of the sensing fiber, which consists of a 4 km single mode optical fiber, are acquired and inserted into a newly formulated equation to calculate the temperature. Furthermore, the center wavelengths from the FBGs in the sensing fiber are detected by an optical spectrum analyzer; these are converted to strain values. The initial wavelengths of the FBGs are selected to avoid a cross-talk with the wavelength of the Raman pulsed pump light. Wavelength shifts from a tension test were found to be 0.1 nm, 0.17 nm, 0.29 nm, and 0.00 nm, with corresponding strain values of $85.76{\mu}{\epsilon}$, $145.55{\mu}{\epsilon}$, $247.86{\mu}{\epsilon}$, and $0.00{\mu}{\epsilon}$, respectively. In addition, a 50 m portion of the sensing fiber from $30^{\circ}C$ to $70^{\circ}C$ at $10^{\circ}C$ intervals was used to measure the distributed temperature. In all tests, the temperature measurement accuracy of the proposed sensor was less than $0.50^{\circ}C$.

• Atmosphere
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• v.27 no.2
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• pp.225-233
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• 2017

Korea has recently suffered from severe hazes, largely being long-range transported from China but frequently mixed with domestic pollution. It is important to identify the origin of the frequently-occurring hazes, which is however hard to clearly determine in a quantitative term. In this regard, we suggest a possible classification procedure of various hazes into long-range transported haze (LH), Yellow Sand (YS), and urban haze (UH), based on mass loading of fine particles, time lag of PM mass concentrations between two sites aligned with dominant wind direction, backward trajectory of air mass, and the mass ratio of PM2.5 to PM10. The analysis sites are Seoul (SL) and Baengnyeongdo (BN), which are distant about 200 km from each other in the west to east direction. Aerosol concentrations at BN are overall lower than those of SL, indicative of BN being a background site for SL. We found distinct time lag of PM2.5 and PM10 concentrations between BN and SL in case of both LH and YS, but the intensity of YS being stronger than LH. Time scale (e-folding time scale) of LH appears to be longer and more variable than YS, which implies that LH covers much larger spatial scale. In addition, we found linear and significant correlations between ${\tau}_a$ obtained from sunphotometer and ${\tau}_{cal}$ calculated from surface aerosol scattering coefficient for LH episodes, relative to few correlation between those for YS, which might be associated with transported height of YS being much higher than LH. Therefore surface PM concentrations for the YS period are thought to be not representative for vertical integrated amount of aerosol loadings, probably by virtue of decoupled structure of aerosol vertical distribution. Improvement of various hazes classification based on the current result would provide the public as well as researchers with more accurate information of LH, UH, and YS, in terms of temporal scale, size, vertical distribution of aerosols, etc.

• Journal of Korean Society of Forest Science
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• v.110 no.3
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• pp.295-307
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• 2021

This study proposed a field-applicable natural regeneration method using natural seeding to afforest a secondary growth forest after felling in Larix kaempferi plantations. In 2016, an experimental site was established usingseed-tree and clear-cutting methods in Gapyeong, Gyeonggi-do, South Korea. Characteristics of seed fructification and inflow in the natural regeneration site were analyzed along with an experimental site in Bonghwa, Gyeongsangbuk-do, which was established in 2014. As a result, the number of seeds per individual tree of V age class L. kaempferi was 690,340 seeds in a good year, with an estimated 13.8 million seeds per ha fruited in natural regeneration sites of L. kaempferi with 25 seed-trees per ha. Seed dispersal began in September and germination rates of seeds dispersed until November were greater than 40%. Reserved seed-tree sites showed the highest amount of seed inflow, followed by the seed-tree site and clear-cut site in descending order. The reserved seed-tree method performed better than other methods for evenly scattering seeds. Therefore, the timing of logging and seedbed generation for natural regeneration of L. kaempferi is estimated to be most effective before September when seeds are purposefully scattered using the reserved seed-tree method as an effective method for uniform seed supply.

• Korean Journal of Remote Sensing
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• v.37 no.2
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• pp.305-319
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• 2021

The overseas calibration sites such as Mongolia used for Korea Multi-purpose Satellite (KOMPSAT-5 or K5), have a disadvantage in that maintenance and repair costs are high and immediate response is difficult when an unexpected problem occurs. Accordingly, the necessity of establishing a domestic SAR calibration site was suggested, but the progress of related research is insignificant. In this paper, we investigated what conditions should be satisfied in terms of backscattering characteristics to construct a site for SAR satellite image quality evaluation and calibration. First of all, it was selected first by applying general indicators such as accessibility and availability among places recommended as satellite image calibration candidate sitesin Korea. Next, three places, site A (Goheung-gun, Jeollanam-do), site B (Jeonju-si, Jeollabuk-do), and site C (Daedeok Research Complex, Daejeon), were selected as the final candidates because they are relatively wide and easy to install AT or CR. Site A, located in Goheung-gun, Jeollanam-do, was best considered in terms of slope measurements, minimum site area to obtain ISLR, uniformity of DN values and backscatter coefficients, interference by strong reflectors, and backscatter clutter level.