• Journal of Ocean Engineering and Technology
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• v.34 no.6
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• pp.442-453
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• 2020

Underwater color images suffer from low visibility and color cast effects caused by light attenuation by water and floating particles. This study applied single image enhancement techniques to enhance the quality of underwater images and compared their performance with real underwater images taken in Korean waters. Dark channel prior (DCP), gradient transform, image fusion, and generative adversarial networks (GAN), such as cycleGAN and underwater GAN (UGAN), were considered for single image enhancement. Their performance was evaluated in terms of underwater image quality measure, underwater color image quality evaluation, gray-world assumption, and blur metric. The DCP saturated the underwater images to a specific greenish or bluish color tone and reduced the brightness of the background signal. The gradient transform method with two transmission maps were sensitive to the light source and highlighted the region exposed to light. Although image fusion enabled reasonable color correction, the object details were lost due to the last fusion step. CycleGAN corrected overall color tone relatively well but generated artifacts in the background. UGAN showed good visual quality and obtained the highest scores against all figures of merit (FOMs) by compensating for the colors and visibility compared to the other single enhancement methods.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3754-3767
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• 2023

Turbulent jet discharges in subcooled water pools are essential for safety systems in nuclear power plants, specifically in the pressure suppression pool of boiling water reactors and In-containment Refueling Water Storage Tank of advanced pressurized water reactors. The gas and liquid flow in these systems is investigated using multiphase flow analysis. This field has been extensively examined using a combination of experiments, theoretical models, and Computational Fluid Dynamics (CFD) simulations. ANSYS CFX offers two approaches to model multiphase flow behavior. The non-homogeneous Eulerian-Eulerian Model has been used in this work; it computes global information and is more convenient to study interpenetrated fluids. This study utilized the Large Eddy Simulation Model as the turbulence model, as it is better suited for non-stationary and buoyant flows. The CFD results of this study were validated with experimental data and theoretical results previously obtained. The figures of merit dimensionless penetration length and the dimensionless buoyancy length show good agreement with the experimental measurements. Correlations for these variables were obtained as a function of dimensionless numbers to give generality using only initial boundary conditions. CFD numerical model developed in this research has the capability to simulate the behavior of non-condensable gases discharged in water.

• The Transactions of the Korea Information Processing Society
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• v.5 no.6
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• pp.1639-1651
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• 1998

In this paper, we present analytical and simulation models for evaluating the operation of a uniprocessor computer which utilizes a time redundant approach (such as recomputation by shilted operands) for lault-tolerant computing. In the proposed approach, all incoming jobs to the uniprocessor are duplicated, thus two versions 01 each job must be processed. Three methods for appropriately scheduling the primary and sL'Condary versions of the jobs are proposed and analyzed. The proposed scheduling methods take into account the load and the fault rate of the uniprocessor to evaluate two figures of merit for cost and profit with respect to a delay in response time due to faults and fault tolerance. Our model utilizes a fault-tolerant schedule according to which it is possible to find an optimal delay (given by $\kappa$) based on empiric parameters such as cost, the load and the fault rate of the uniprocessor.

• Korean Journal of Materials Research
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• v.5 no.2
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• pp.251-258
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• 1995

In an effort to increase the thermoelectric figure of merit by reducing the thermal conductivity, the unidirectionally solidified n-type (Bi, Pb)-Te based alloys which form a $Bi_{2}Te_{3}-PbBi_{4}Te_{7}$eutectic lamellar structure were investigated with the microstructural control at various solidification conditions. PbBi_{4}Te_{7}$ lamellae were grown on cleavage plane(0001) of $Bi_{2}Te_{3}$ and the interlamellar spacing decreased from 10.4 $\mu \textrm{m}$to 3.2$\mu \textrm{m}$ with growth velocity variation from 1.4 \times 10^{-4}$cm/sec to $8.3 \times 10^{-4}$cm/sec. Seebeck coefficient was constant, $\mid$$\alpha$$\mid$=29 $\mu$ V/K regardless of growth direction, growth velocity and temperature gradient. Electrical conductivity showed a tendency to decrease slightly with growth velocity and it parallel to growth direction was about three times as large as perpendicular direction. The figures of merit were varied differently from Seebeck coefficients and electrical conductivities depending on the growth direction, growth velocity and temperature gradients. They showed the relative increase in case of perpendicular direction compared with parallel to growth direction. It is believed to be due to the reduction of the thermal conductivity according to decrease of the interlamellar spacing.

• The Journal of Korean Philosophical History
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• no.32
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• pp.43-78
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• 2011

The two schools which eventually came to form the "Northerners party" in the middle period of the Joseon dynasty, were Nam'myeong school and Hwadam school. Nam'myeong's philosophy, which emphasized the importance and merit of acting upon respect and righteousness(敬義), encouraged many people to organize righteous militias during the war with the Japanese in the 1590s, and when Jeong In-hong established himself as the leader of the Northerners party during the reign of King Gwang'hae-gun, the philosophy of the party and the school continued to thrive. Also, Hwadam's philosophy, which tried to understand Neo-Confucianism from a flexible point of view and demonstrated a level of openness toward it, had a considerable influence upon the Northerners school as well. It seems Nam'myeong Jo Shik and Hwadam Seo Gyeong-deok were the ones who ultimately enabled the Northerners party to be more active in their operations of the government and also to approach more freely toward the ideology of Neo-Confucianism. Prime examples of the party's stance and attitude, and also of the school's philosophy and perception of the world, were figures like Jeong In-hong and Heo Gyun from the 'Majority Northerners(大北) party,' and Kim Shin-guk and Nam I-gong from the 'Minority Northerners(小北) party.'Since the time of King Injo's ascension to the throne in 1623, the philosophical society of Joseon came to be occupied by schools who were deeply committed and dedicated to the teachings of Ju Hi and his Neo-Confucianism, such as the Twe'gye and Yulgok schools, and as a result the Northerners' philosophy was pushed away from its former formidable status. Their political philosophy was also partially responsible for their fall, as they believed only them were the ideal Confucian figures(君子黨), and never appreciated the stances of other political factions. In the middle of the 17th century, passing through a war with the Manchurian Qing dynasty as well, they further became a mere undercurrent. Yet their thinking and philosophy partially survived, as it managed to affect and influence the Southerner school scholars who were living in the vicinity of the capital in the mid and late 17th century, as well as the "Shilhak" scholars such as Yi Ik/李瀷 in the 18th century, on a certain level. The Northerners faction was a party and a school which led the political and philosophical societies of Joseon, alongside the Westerners and Southerners, in the middle period of the Joseon dynasty. Recently, studies of Jo Shik and Seo Gyeong-deok, figures who were the roots of the Northerners faction, and studies of how the Northerners' political philosophy was inherited to the following generations, have been published and announced. All these efforts will enrich future studies dealing with the political history and philosophical history of the middle and latter periods of the Joseon dynasty.

• Korean Journal of Agricultural Science
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• v.46 no.1
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• pp.183-194
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• 2019

Adulteration of argan oil with some other cheaper oils with similar chemical compositions has resulted in increasing demands for authenticity assurance and quality control. Fast and simple analytical techniques are thus needed for authenticity analysis of high-priced argan oil. Raman spectroscopy is a potent technique and has been extensively used for quality control and safety determination for food products In this study, Raman spectroscopy in combination with a net analyte signal (NAS)-based methodology, i.e., hybrid linear analysis method developed by Goicoechea and Olivieri in 1999 (HLA/GO), was used to predict the different concentrations of olive oil (0 - 20%) added to argan oil. Raman spectra of 90 samples were collected in a spectral range of $400-400cm^{-1}$, and calibration and validation sets were designed to evaluate the performance of the multivariate method. The results revealed a high coefficient of determination ($R^2$) value of 0.98 and a low root-mean-square error (RMSE) value of 0.41% for the calibration set, and an $R^2$ of 0.97 and RMSE of 0.36% for the validation set. Additionally, the figures of merit such as sensitivity, selectivity, limit of detection, and limit of quantification were used for further validation. The high $R^2$ and low RMSE values validate the detection ability and accuracy of the developed method and demonstrate its potential for quantitative determination of oil adulteration.

• Korean Journal of Radiology
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• v.23 no.4
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• pp.402-412
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• 2022

Objective: To evaluate the image quality and lesion detectability of lower-dose CT (LDCT) of the abdomen and pelvis obtained using a deep learning image reconstruction (DLIR) algorithm compared with those of standard-dose CT (SDCT) images. Materials and Methods: This retrospective study included 123 patients (mean age ± standard deviation, 63 ± 11 years; male:female, 70:53) who underwent contrast-enhanced abdominopelvic LDCT between May and August 2020 and had prior SDCT obtained using the same CT scanner within a year. LDCT images were reconstructed with hybrid iterative reconstruction (h-IR) and DLIR at medium and high strengths (DLIR-M and DLIR-H), while SDCT images were reconstructed with h-IR. For quantitative image quality analysis, image noise, signal-to-noise ratio, and contrast-to-noise ratio were measured in the liver, muscle, and aorta. Among the three different LDCT reconstruction algorithms, the one showing the smallest difference in quantitative parameters from those of SDCT images was selected for qualitative image quality analysis and lesion detectability evaluation. For qualitative analysis, overall image quality, image noise, image sharpness, image texture, and lesion conspicuity were graded using a 5-point scale by two radiologists. Observer performance in focal liver lesion detection was evaluated by comparing the jackknife free-response receiver operating characteristic figures-of-merit (FOM). Results: LDCT (35.1% dose reduction compared with SDCT) images obtained using DLIR-M showed similar quantitative measures to those of SDCT with h-IR images. All qualitative parameters of LDCT with DLIR-M images but image texture were similar to or significantly better than those of SDCT with h-IR images. The lesion detectability on LDCT with DLIR-M images was not significantly different from that of SDCT with h-IR images (reader-averaged FOM, 0.887 vs. 0.874, respectively; p = 0.581). Conclusion: Overall image quality and detectability of focal liver lesions is preserved in contrast-enhanced abdominopelvic LDCT obtained with DLIR-M relative to those in SDCT with h-IR.

• Current Optics and Photonics
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• v.6 no.5
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• pp.497-505
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• 2022

Topological photonic nanocavities are considered to possess outstanding optical performance, and provide new platforms for realizing strong interaction between light and matter, due to their robustness to impurities and defects. Here hybrid plasmonic topological photonic nanocavities are proposed, by embedding various plasmon nanoantennas such as gold nanospheres, cylinders, and rectangles in a topological photonic crystal corner-state nanocavity. The maximum quality factor Q and minimum effective mode volume V_eff of these hybrid nanocavities can reach the order of 10⁴ and 10^-4 (𝜆/n)³ respectively, and the high figures of merit Q/V_eff for all of these hybrid nanocavites are stable and on the order of 10⁵ (𝜆/n)^-3. The relative positions of the plasmon nanoantennas will influence the coupling strength between the plasmon structures and the topological nanocavity. The hybrid nanocavity with gold nanospheres possesses much higher Q, but relatively large V_eff. The presence of a gold rectangular structure can confine more electromagnetic energy within a smaller space, since its V_eff is smallest, although Q is lowest among these structures. This work provides an outstanding platform for cavity quantum electrodynamics and has a wide range of applications in topological quantum light sources, such as single-photon sources and nanolasers.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.760-770
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• 2016

A 12-bit 750 kS/s Dual-Sampling Successive Approximation Register Analog-to-Digital Converter (SAR ADC) technique with reduced Capacitive DAC (CDAC) is presented in this paper. By adopting the Adaptive Power Control (APC) technique for the two-stage latched type comparator and using bootstrap switch, power consumption can be reduced and overall system efficiency can be optimized. Bootstrapped switches also are used to enhance the sampling linearity at a high input frequency. The proposed SAR ADC reduces the average switching energy compared with conventional SAR ADC by adopting reduced the Most Significant Bit (MSB) cycling step with Dual-Sampling of the analog signal. This technique holds the signal at both comparator input asymmetrically in sample mode. Therefore, the MSB can be calculated without consuming any switching energy. The prototype SAR ADC was implemented in $0.18-{\mu}m$ CMOS technology and occupies $0.728mm^2$. The measurement results show the proposed ADC achieves an Effective Number-of-Bits (ENOB) of 10.73 at a sampling frequency of 750 kS/s and clock frequency of 25 MHz. It consumes only 0.13 mW from a 5.0-V supply and achieves the INL and DNL of +2.78/-2.45 LSB and +0.36/-0.73 LSB respectively, SINAD of 66.35 dB, and a Figures-of-Merit (FoM) of a 102 fJ/conversion-step.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.283-292
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• 2008

The foremost criterion in the design of a Satellite Launch Vehicle(SLV) is its performance capability to boost the designated payload to the desired mission orbit; it starts from focusing on the SLV configuration to achieve the velocity requirements($}\Delta}V$) for the mission. In this paper we review an analytical approach which is suitable enough for preliminary conceptual design and is used previously to optimize stage configurations for Two Stage to Orbit SLV for Low Earth Orbit(LEO) Missions; we have extended this approach to Three Stage to Orbit SLV and compared different propellant options for the mission. The objective is to minimize the Gross Lift off Weight(GLOW). The primary performance figures of merit were the total inert weight of the SLV and the payload weight that the SLV could lift into LEO, given candidate propulsion systems. The optimization is achieved by configuring the $}\Delta}V$ between stages. A comparison of configurations of single-stage and multi-stage SLVs is made for different propellants. Based upon the optimized stage configurations a comparative performance analysis is made between Liquid and Solid fueled SLV. A 3 degree of freedom trajectory-analysis program is modeled in SIMULINK and used to conduct the performance analysis. Furthermore, a cost analysis is performed on our stage optimized SLVs. The cost estimation relationships(CER) used give us a comparison of development and fabrication costs for the Liquid vs. Solid fueled SLV in man years. The pros and cons of the production, operation ability, performance, responsiveness, logistics, price, shelf life, storage etc of both Solid and Liquid fueled SLVs are discussed. The statistics and data are used from existing or historical(real) SLV stages.