• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.423-429
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• 2019

Recently, a variety of methods for the performance improvement of ultra-high speed wideband wireless transmission systems have been suggested. This paper proposes a space-frequency (SF) block coded single side band (SSB) single carrier (SC)-frequency division multiple access (FDMA) transmission system. In the proposed SSB SC-FDMA system, SF block code is implemented with the complex conjugates, which are formed from discrete Fourier transform (DFT) spreading of pulse amplitude modulation (PAM) signals. As a result, transmit diversity gain can be obtained in the proposed SF block coded SSB SC-FDMA system without any significant increase of the system computational complexity. The simulation result shows that the signal-to-noise power ratio (SNR) performance of the proposed SF block coded SSB SC-FDMA system is approximately 4 dB better than the SNR performance of the conventional SSB SC-FDMA system with single transmit antenna at a symbol error rate (SER) of $10^{-2}$.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.93-99
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• 2021

In order to decrease the weight of stretchable energy storage devices, interest in developing lightweight materials to replace metal current collectors is increasing. In this study, nanofibers prepared by electrospinning a conductive polymer, PEDOT:PSS, were used as current collectors for lithium ion batteries. The nanofiber showed improved electrical conductivity by using DMSO, a dopant, and indicated a stretch rate of 30% or more from the elasticity evaluation result. In addition, the use of the nanofiber current collector facilitates penetration of the liquid electrolyte and exhibits the effect of increasing the electronic conductivity through the nanofiber network. The lithium-ion battery using the DMSO-doped PEDOT:PSS@PAM nanofiber current collector indicated a high discharge capacity of 135mAh g^-1, and indicated a high capacity retention rate of 73.5% after 1000 cycles. Thus, the excellent electrochemical stability and mechanical properties of conductive nanofibers showed that they can be used as lightweight current collectors for stretchable energy storage devices.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.118-126
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• 2009

Benthic diatoms are very important primary producers in understanding estuary ecosystems and their productions are largely varied by their photo-physiological characteristics. The short-term effects of increased temperature on the photosynthetic and photo-physiological characteristics of cultured different species of benthic diatoms (Navicula sp., Nitzschia sp., Cylindrotheca closterium, and Pleurosigma elongatum) were investigated by measuring their PSII-fluorescence kinetics using a Diving-PAM. Photosynthesis versus irradiance curves were measured every two hours at six different temperatures (10, 15, 20, 25, 30, and $35^{\circ}C$) for twenty-four hour. The effective quantum yield of PSII ($\Phi_{PSII}$) for most of the species showed a decreasing trend with increased temperature. The relative maximum electron transport rate (rETRmax) was significantly increased up to the optimum temperature level and then sharply decreased. Relative to the values of other parameters, the maximum light use coefficient ($\alpha$) was not substantially changed at lower temperature levels (<$30^{\circ}C$) but significantly decreased only at higher temperatures (30 and $35^{\circ}C$). The light saturation coefficient ($E_K$) mirrored the rETRmax temperature response. In regards to the temperature acclimation abilities of the four species with time, Navicula sp. and C. closterium acclimated to short-term changes in temperature through their photo-physiological adjustments.

• Journal of the Korean Applied Science and Technology
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• v.27 no.2
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• pp.196-201
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• 2010

The influence of red lead($Pb_3O_4$) to curing and formation reaction properties when it was added in positive material of lead acid battery for vehicle use has been investigated. At the results, it was confirmed that the addition of red lead led 4BS crystal size to be smaller and increased the rates of 4BS formation and Pb consumption. Consequently the curing time was shortened to half compared with that of red lead-free one. In addition to this, the lead acid battery prepared by adding red lead showed 14% higher efficiency at the life cycle test than that without red lead.

• Current Optics and Photonics
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• v.5 no.2
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• pp.121-128
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• 2021

We propose a novel, tiny optical receiver engine utilizing an all-in-one package based on embedded optics technology. The package's best transmission S21 and reflection S22 opto-electric (OE) bandwidths are 49.8 GHz and 34.9 GHz, respectively, and the reflectance of the optical engine is below -31.7 dB for all channels. The engine satisfies the MIL-STD-883G standard for reliability tests, such as mechanical and thermal shock, and vibration resistance. The sensitivity after 10 km single-mode fiber (SMF) transmission is below -8 dBm. The optical receiver engine is cost-competitive and applicable for 400G coarse wavelength division multiplexing 4 (CWDM4) 10 km optical transceivers.

• Current Optics and Photonics
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• v.6 no.1
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• pp.39-43
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• 2022

Underwater optical wireless communication (UOWC) is a good candidate for high-speed underwater wireless communication. In this work, we compare the performance of several modulation techniques for a UOWC system consisting of a light-emitting diode (LED) with an operating wavelength of 405 nm and a Si avalanche photodiode (APD). In this work, we consider six modulation schemes: 4-quadrature amplitude modulation (QAM), 8-QAM, quadrature phase shift keying (QPSK), binary phase shift keying (BPSK), on-off keying (OOK), and 4-pulse amplitude modulation (PAM). We also consider the cases of pure water and seawater for the working conditions. Our results show that 4-QAM and 8-QAM perform the best, in terms of communication distance and transmission power efficiency, for all water types considered.

• Toxicological Research
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• v.13 no.1_2
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• pp.87-94
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• 1997

This study was carried out to investigate toxicity of insecticide carbofuran and compensatory effects of phenobarbital sodium (PB) in vivo and in vitro. Sprague Dawley male rats were used as experimental animals and divided into carbofuran only administered group and simultaneous application group of carbofuran and PB. At 30 rain and 1, 3, 6, 12, 24, 48 and 96 hrs after each treatment, the animals were sacrificed by decapitation. Kidney were immediately removed, immersed in fixatives, and processed with routine method for light microscopic study. Paraffin sections were stained with H-E, PAM and PAS. $5.0\times 10^4$ cell/ml of NIH 3T3 fibroblast in each well of 24 multidish were cultured: After 24 hours, the cells were treated with solution of six groups; control group cultured in media only, carbofuran $MTT_50$ or $NR_50$ group cultured in the media containing carbofuran $MTT_50$ or $NR_50$ and four experimental groups cultured in the media containing carbofuran $NR_50$ plus various concentratins of PB. After the NIH 3T3 fibroblast of all groups were cultured in same condition for 48 hours, Tetrazolium MTT (MTT) and NR (neutral red) assay were performed to evaluate the cytotoxicity of cell organelles. Under the light microscope, atrophic change of renal corpuscles were frequently observed in 1 and 2 days after carbofuran treatment. The increase of the mesangium was apparent in 1 and 2 days after carbofuran treatment. Necrotic changes of the epithelium and loss of brush border of proximal tubules were most severe at 2 and 3 days after carbofuran treatment, respectively. In contrast, there were no evidences of the toxic effects on renal tissues at 48hrs in carbofuran-PB treated groups. Carbofuran $MTT_50$ and $NR_50$ were 78$\mu M$, 82.5$\mu M$ respectively. MTT and NR quantities were significantly increased in carbofuran-PB 100$\mu M$ treatment group and carbofuran-PB 100$\mu M$ treatment group. On the basis of these results, it is obvious that PB has compensatory effects against carbofuran toxicity.

• Journal of Korea Foresty Energy
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• v.23 no.1
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• pp.38-44
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• 2004

The application of the dispersant is indispensable to the manufacture of Korean traditional paper (Hanji). However the mucilage of which extracted from Abelmoschus manihot root has viscosity drop problem in summertime and synthetic dispersant such as polyacrylamide (PAM) and polyethyleneoxide (PEO) have some problems that under the influence of the quality of. water, cohesion, and bad solubility. This study was carried out not only to develop new natural dispersant that can solve such problems but also to investigate the viscosity and papermaking characteristics of Hydrangea paniculata mucilage. There were no viscosity changes between control and treated mucilage that adjusted to pH 9, heated 6 hours at 40 $^{\circ}C$, and stored heating treatment one for a week at 5 $^{\circ}C$. The treatment of mucilage that adjusted to pH 9 and aged for 120 hours at 4$0^{\circ}C$ resulted in viscosity drop. In the hydrolysis of mucilage, galacturonic acid and glucuronic acid contents were decreased by heating and pH adjusting treatments. Wet web stripping quality and physical properties of Korean traditional paper, which used Hydrangea paniculatamucilage were same or superior to the Abelmoschus manihot root.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.744-751
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• 2004

This paper presents the implementation of the low cost and high speed RF ATE(Automatic Test Equipment) system, which can be a reasonable solution for reducing the test cost of RF devices. This paper suggests high speed and precise measurement capabilities which are realized by the 16 independent RF ports with high speed switching time and high accuracy digitizer using the industry standard Versus module eXtensions for Instrument(VXI) General Purpose Interface Bus(GPIB) interfaces. Also, the system has the capabilities of quad-site test which can dramatically increase the device throughput. This paper concludes with the demonstration of the implemented ATE system through the setup of RF Power Amplifier Module(PAM), which is under the most competitive market situation.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.220-225
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• 2000

This paper develops a finite element model for studying occupant behavior of a mid-size truck equipped with a driver side airbag. The developed model simulates an occupant behavior using PAM-CRASH/PAM-SAFE in super computer SP2. The model is developed based on a sled test. A 50% hybrid dummy III is used for measuring head and chest accelerations and femur loads, and major injury coefficients such as HIC, CA and femur load. Inferior components such as foot rest, seat, kneebolster, crash pad, etc. are roughly modeled and defined by a rigid material model. And contact type II is used for detecting a contact with dummy. Contact type II definition uses force-deflection relationship of each body Such components as steering column which directly affect on the occupant injuy are modeled in detail and defined by an elastic-plastic material model. Airbag cushion is modeled using rivet elements. Airbag cover groove is modeled using rivet elements. Airbag tether is modeled as nonlinear bar elements. Airbag model has two vent holes to ventilating the exploded gas. Airbag is folded close to the real airbag folding procedure, and folded cautiously in order not to have initial penetration. A vehicle pulse acquired from 31mph frontal barrier test is used as input signal for the simulation. The simulation conditions are tuned to the sled test ones. The measured dummy accelerations and major injury coefficients, and filmed dummy behavior and airbag inflation process using high speed camera are compared to the simulation results to verify the developed finite element model.