• Journal of Korean Society on Water Environment
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• v.35 no.4
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• pp.299-307
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• 2019

The purpose of this study was to investigate the effect of low temperature thermal pre-treatment on biodegradation of waste activated sludge for anaerobic digestion as a countermeasure for increasing sludge generation. The experimental condition was accomplished in 2 %, 4 %, and 6 % TS concentration, and $70^{\circ}C$, $80^{\circ}C$, $90^{\circ}C$ of temperature for a maximum of 120 minutes retention time. Then, it was followed by analysis of physical/chemical properties, BMP test and composition of biogas. The biogas characteristic was evaluated by applying the modified Gomperz model. As a result, solubility of dissolved substrate, such as $SCOD_{Cr}$, soluble carbohydrate, and soluble protein, and biogas production increased as temperature increased. Solubilization efficiency at $90^{\circ}C$ was 18.4 %, 17.03 % and 16.88% in 2 %, 4 %, and 6 % TS concentration respectively. Also, solubilization rates of carbohydrate and protein similarly increased. BMP test results also showed that methane production in excess sludge increased to 0.194, 0.187 and $0.182m^3/kg$ VS. respectively, and lag phase decreased to 0.145, 0.220, 0.351 day due to acceleration of the hydrolysis step. Consequently, low-temperature thermal pre-treatment could increase biodegradability of sludge, positively affecting biogas production and sludge reduction.

• Environmental and Resource Economics Review
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• v.28 no.2
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• pp.177-200
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• 2019

Energy demand forecast which serves as an essential input in energy policy is exposed to multiple factors of uncertainty such as GDP and weather forecast uncertainty. The Master Plan of Electricity Market in Korea which is biennially prepared is critically based on fluctuating energy demand forecast whereas its resulting proposal on electricity generation mix is substantially irreversible. The paper provides a real options model to evaluate energy transition policy by considering Knightian uncertainty as a measure to study multiple uncertainties with multiple set of probability distributions. Our finding is that the current energy transition policy under the master plan is not robust in terms of securing stable management of electricity demand and supply system.

• Tribology and Lubricants
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• v.34 no.6
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• pp.247-253
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• 2018

Temperature rise due to viscous shear of the lubricating oil generates hydrodynamic pressure, even if the lubricating surfaces are parallel. This effect, known as the thermal wedge effect, varies significantly with film-temperature boundary conditions. The bearing conducts a part of the heat generated; hence, the oil temperature varies with the thermal conductivity of the bearing. In this study, we analyze the effect of thermal conductivity on the thermohydrodynamic (THD) lubrication of parallel slider bearings. We numerically analyze the continuity equation, Navier-Stokes equation, energy equation including the temperature-viscosity and temperature-density relations for lubricants, and the heat conduction equation for bearing by creating a 2D model of the micro-bearing using the commercial computational fluid dynamics (CFD) code FLUENT. We then compare the variation in temperature, viscosity, and pressure distributions with the thermal conductivity. The results demonstrate that the thermal conductivity has a significant influence on THD lubrication characteristics of parallel slider bearings. The lower the thermal conductivity, the greater the pressure generation due to the thermal wedge effect resulting in a higher load-carrying capacity and smaller frictional force. The present results can function as the basic data for optimum bearing design; however, the applicability requires further studies on various operating conditions.

• Journal of the Korea Convergence Society
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• v.10 no.3
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• pp.395-400
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• 2019

The Web environment of the frontend domain is increasingly competitive to preempt the new standard of presentation layer. N-Screen, a service that enables users to seamlessly use one content in various devices in Korea, is competing for market preemption by recognizing it as a core service of the future. In the cloud computing, N-screen is a typical service type. However, most of the frontend research required for groupware in enterprise environments has been limited to responsive web design for the web and native apps for mobile. Gradually, the need for MVC design patterns is increasingly widening in enterprise environments to overcome the cultural differences of companies and to support one source multi-use strategy supporting multiple devices and development productivity. Therefore, in this study, we will analyze and design JPetStore with hybrid application design based on Spring MVC, e-government standard framework environment of next generation web standard, and provide reference model of frontend hybrid apps design in future enterprise environment.

• Journal of Ocean Engineering and Technology
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• v.33 no.1
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• pp.76-84
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• 2019

For decades, solitary waves have commonly been used to simulate tsunami conditions in numerical studies. However, the main component of a tsunami waveform acts at completely different spatial and temporal distributions than a solitary waveform. Thus, this study applied a 2-D numerical wave tank that included a non-reflected tsunami generation system based on Navier-Stokes equations (LES-WASS-2D) to directly simulate the run-up of a tsunami-like solitary wave on a slope. First, the waveform and velocity due to the virtual depth factor were applied to the numerical wave tank to generate a tsunami, which made it possible to generate the wide waveform of a tsunami, which was not reproduced with the existing solitary wave approximation theory. Then, to validate the applied numerical model, the validity and effectiveness of the numerical wave tank were verified by comparing the results with the results of a laboratory experiment on a tsunami run-up on a smooth impermeable 1:19.85 slope. Using the numerical results, the run-up characteristics due to a tsunami-like solitary wave on an impermeable slope were also discussed in relation to the volume ratio. The maximum run-up heights increased with the ratio of the tsunami waveform. Therefore, the tsunami run-up is highly likely to be underestimated compared to a real tsunami if the solitary wave of the approximation theory is applied in a tsunami simulation in a coastal region.

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.648-653
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• 2018

Analysis of a specific wavelength band of a video signal is an old research field. However, studies on the analysis of signals having the characteristics of a specific wavelength band or the generation of samples have been conducted actively in recent years. In this paper, we analyze the signal of digital halftoned image. The interpretation of halftoning in terms of signals was first made by Ulichney. We have come to the view that the signal characteristics between pixels used for half toning are good for blue noise. Lau has developed a halftoning method that uses green-noise characteristics by using output-dependent feedback as an error diffusion method. Jho has developed a method for producing halftoned images using a reaction diffusion model. In this paper, we analyze reaction diffusion halftoning in terms of signal to show green noise and compare it with existing green noise half tone.

• Journal of Hydrogen and New Energy
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• v.30 no.4
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• pp.303-311
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• 2019

Reversible solid oxide fuel cell (RSOFC) has become a prospective device for energy storage and hydrogen production. Many studies have been conducted around the world focusing on system efficiency improvement and realization. The system should have not only high efficiency but also a certain level of simplicity for stable operation. External waste steam utilization was proved to remarkably increase the efficiency at solid oxide electrolysis system. In this study, RSOFC system coupled with waste steam was proposed and optimized in term of simplicity and efficiency. Ejector for fuel recirculation is selected due to its simple design and high stability. Three system configurations using ejector for fuel recirculation were investigated for performance of design condition. In parametric study, the system efficiencies at different current density were analyzed. The system configurations were simulated using validated lumped model in EBSILON(R) program. The system components, balance of plants, were designed to work in both electrolysis and fuel cell modes, and their off-design characteristics were taken into account. The base case calculation shows that, the system with suction pump results in slightly lower efficiency but stack can be operated more stable with same inlet pressure of fuel and air electrode.

• Journal of Microbiology and Biotechnology
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• v.29 no.8
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• pp.1193-1203
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• 2019

We investigated the protective effects of 3-bromo-4,5-dihydroxybenzaldehyde (BDB) from Polysiphonia morrowii Harvey against hydrogen peroxide ($H_2O_2$)-induced apoptosis in Vero cells. BDB exhibited scavenging activity for DPPH, hydroxyl, and alkyl radicals. BDB also inhibited $H_2O_2$-induced lipid peroxidation, cell death, and apoptosis in Vero cells by inhibiting the production of ROS. To evaluate the molecular mechanisms of apoptosis inhibition, the expression of Bax/Bcl-xL and $NF-{\kappa}B$ was assessed by western blot assay. BDB significantly suppressed the cleavage of caspase-9 and PARP and reduced Bax levels in $H_2O_2$-induced Vero cells. Besides, BDB suppressed the phosphorylation of $NF-{\kappa}$B and the translocation of p65 in $H_2O_2$-induced cells. Furthermore, we evaluated the effect of BDB on ROS production, cell death, and lipid peroxidation in an $H_2O_2$-stimulated zebrafish embryo model. Taken together, these results indicated that ROS generation and cell death were significantly inhibited by BDB in zebrafish embryos, thereby proving that BDB exerts excellent antioxidant activity in vitro and in vivo.

• The Journal of Information Systems
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• v.28 no.2
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• pp.53-72
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• 2019

Purpose The purpose of this study is to examine the impact of tie strength in the network of industrial clustering on the knowledge acquisition, integration and innovation performance of small and medium sized enterprises. We test the positive relationship of weak tie and knowledge acquisition, strong tie and knowledge integration, and the interaction effect of two tie strengths on both processes of knowledge acquisition and integration. By identifying these relationships, we can better understand how to manage the attributes of social networks in terms of tie strength in order to improve the performance of innovation for the small and medium sized enterprises. Design/methodology/approach We collect 200 survey data from 2 industrial cluster respectively: Pankyo and Guroo. In Pankyo, the proportion of IT industry is the highest (35%) while the proportion of manufacturing is highest (35%) in Guroo. Pooling the data from two industrial cluster, we check the reliability and validity of our research model and test the hypotheses. Findings First, we find the positive relationship of weak tie and knowledge acquisition from both industrial clustering. Weak tie is composed of heterogeneous organizations with various background and expertise. The communication and information sharing of organizations in the weak tie network helps the idea generation for organization's innovation, which is the knowledge acquisition process. Second, the relationship of strong tie and knowledge integration is insignificant. Typically the strong tie from long-lasting partnership is expected to be beneficial in the action stage of innovation, which is the knowledge integration process. However it is not identified in our industry cluster. Finally, the interaction effect of weak and strong tie is identified to be effective on both knowledge acquisition and integration processes.

• The Research Journal of the Costume Culture
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• v.27 no.5
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• pp.449-460
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• 2019

Today, the fashion business environment of the 4.0 generation is changing based on fashion technology combined with advanced digital technologies such as AI (Artificial Intelligence), big data and IoT (Internet of Things). "Digital Transformation" means a fundamental change and innovation in a digital paradigm including corporate strategy, organization, communication, and business model, based on the utilization of digital technology. Thus, this study examines digital transformation strategies through the fashion brand Burberry. The study contents are as follows. First, it examines the theoretical concept of digital transformation and its utilization status. Second, it analyzes the characteristics of Burberry's digital transformation based on its strategies. For the research methodology, a literature review was performed on books and papers, aligning with case studies through websites, social media, and news articles. The result showed that first, Burberry has reset their main target to Millennials who actively use mobile and social media, and continues to communicate with them by utilizing digital strategy in the entire management. Second, Burberry is quickly delivering consistent brand identity to consumers by internally creating and providing social media-friendly content. Third, they have started real-time product sales and services by using IT to enhance access to brands and to lead consumers towards more active participation. In this study, Burberry's case shows that digital transformation can contribute to increased brand value and sales, keeping up with the changes in the digital paradigm. Therefore, the study suggests that digital transformation will serve as an important business strategy for fashion brands in the future.