• Korean Journal of Computational Design and Engineering
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• v.17 no.1
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• pp.54-61
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• 2012

In this paper, we performed numerical analysis to improve the heat exchange efficiency of wasted heat recovery ventilator which has a delivery and a exhaustion fan. One of the most important design factors that affect the efficiency of heat exchange is uniform counter-flow between inbound and outbound air flows. We had simulated several types of porous plates which were installed at air intake area. With plate having 45 degrees of installation angle and 15 mm diameter holes which are uniformly arranged, we can generate a uniform air flows at the area of porous media where inbound and outbound air flows are cross over. In addition, we installed a duct to reduce vortex flows at the outlet and to discharge exhaust airs rapidly. By using the proposed numerical assessment, we expect the improvement of the heat exchange efficiency of ventilator.

• The Journal of Bigdata
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• v.6 no.2
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• pp.17-28
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• 2021

Current development of technologies related to 4^th industrial revolution and the pandemic of COVID-19 lead the rapid expansion of e-marketplace. The level of competition among several companies gets increased by introducing different strategies. To cope with the current change in the market and satisfy the customers who request the better delivery service, the new concept, fulfillment, has been introduced. It makes the leadtime of process from order picking to delivery reduced and the efficiency improved. Still, the efficiency of operation in fulfillment centers constrains the service level of the entire delivery process. In order to solve this problem, several different approaches for demand forecasting and coordinating supplies using Bigdata, IoT and AI, which there exists the trivial limitations. Because it requires the most lead time for operation and leads the inefficiency the process from picking to packing the ordered items, the logistics service providers should try to automate this procedure. In this research, it has been proposed to develop the efficient plans to automate the process to move the ordered items from the location where it stores to stage for packing using AGV and AMR. The efficiency of automated devices depends on the number of items and total number of devices based on the demand. Therefore, the result of simulation based on several different scenarios has been analyzed. From the result of simulation, it is possible to identify the several factors which should be concerned for introducing the automated devices in the fulfillment centers. Also, it can be referred to make the optimal decisions based on the efficiency metrics.

• Broadcasting and Media Magazine
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• v.19 no.2
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• pp.36-45
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• 2014

With major sports events such as FIFA World Cup and The Olympic Games coming up, UHDTV technology has been given a major push by broadcasters, test and measurement (T&M), and consumer electronics (TV and set-top box) manufacturers. The increase in picture resolution ($3840{\times}2160$) for 4K and ($7680{\times}4320$) for 8K compared to current HDTV ($1920{\times}1080$), as well as the need to deliver these services in higher frame rates (50/60 up to 100/120fps) translate to a big challenge in UHDTV content delivery to households over terrestrial transmission due to higher data rates. DVB-T2 has been favored by many countries across the world as it is proven to give the best spectral efficiency for terrestrial broadcasting. On the other hand MPEG-4 appears to be the bottleneck for UHDTV since a much higher data rate is needed to deliver such services. Therefore HEVC becomes mandatory for UHDTV delivery over DVB-T2. In this paper, we will give an overview about a complete end-to-end solution for UHDTV delivery over DVB-T2 based on a realistic SFN scenario in Seoul metropolitan area.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.38.2-38.2
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• 2009

Regeration of natural tissuesor to create biological substitutes for defective or lost tissues and organs through the use of cells. In addition to cells and their porous, drugs are required to promote tissue regeneration. Therefore, the present studies were prepared using simvastatim loaded porous poly(lactide-co-glycolide) (PLGA) by double emulsion solvent evaporation water-in-oil-in-water technique (W/O/W) as drug delivery system strategies for injuring tissue. The resulting microspheres were evaluated for morphology, particle size, encapsulation efficiency, degradation of PLGA microspheres in vitro drug release and in vitro cell viability. Scanning electronic microscopic (SEM) showed that the porosities of the particles was changed by experimental conditions and cultured cells were attached well on porous microspheres surface. The X-ray diffraction (XRD) and differential scanning calometry (DSC) analysis indicate thatsimvastatim was highly dipersed in the microsphere at amorphousstate.

• Journal of Pharmaceutical Investigation
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• v.27 no.1
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• pp.71-77
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• 1997

With the aim of improving periodontal regeneration efficacy, as a biodegradable local drug delivery device, drug releasing chitosan beads were prepared. Chitosan beads were prepared through the formation of intermolecular or intramolecular ionic interaction bewteen chitosan and sodium tripolyphosphate and were loaded with flurbiprofen. The mean diameter of the beads was $250\;{\mu}m$. Drug loading efficiency was improved by regulating the pH of tripolyphosphate solution. The drug release kinetics mainly depended upon the hydrophobic properties of the flurbiprofen, that is, the release of flurbiprofen showed initial burst with rapid release for the first day followed by a levelling off of the release rate. However, the release rate could be controlled by the formulation factor including the pH, concentration of the tripolyphosphate solution, gelation time, drug contents. From these results, flurbiprofen loaded chitosan beads were anticipated as biodegradable local drug delivery devices for periodontal regeneneration.

• Journal of Pharmaceutical Investigation
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• v.38 no.5
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• pp.325-329
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• 2008

To enhance the skin delivery of genistein (GT), a soybean isoflavone having anti oxidative activity, comparative formulation studies including liposomes were carried out. GT-loaded conventional and elastic liposomal gel showed the enhanced skin deposition and photoprotection effect as well, in comparison to GT suspension. Elastic liposomes composed of soybean phosphatidylcholine and sodium deoxycholate (85:15, w/w%) were superior to conventional liposomes and were of characteristics as follows: about 130 nm in size; 85% encapsulation efficiency of GT; 5.8% skin deposition of applied dose; 40% inhibition effect on UVB-induced $H_2O_2$ production. Photoprotection effect was closely related to skin deposition of GT. In conclusion, it is possible to suggest that elastic liposomes could be a promising nanocarrier system for efficient skin delivery.

• Journal of Pharmaceutical Investigation
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• v.36 no.2
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• pp.115-121
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• 2006

The aim of this study was to develop new protein/peptide depot system instead of poly(DL-lactic acid-coglycolic acid) (PLGA) microspheres. Pullulan was chemically modified by the addition of acetic anhydride (pullulan acetate; PA) and then investigated as new depot system for protein/peptide delivery. PA microspheres (PAM) with lysozyme as a model protein were prepared by w/o/w double emulsion method. The microspheres had a mean size of 10-50 mm with a spherical shape. The size distributions reduced with increasing the degree of acetylation. The loading efficiency of lysozyme was also increased. Lysozyme aggregation behavior in the microsphere was monitored to estimate the change of protein stability during preparation step. The ratios of protein aggregation in PAMs are lower than that of PLGA microsphere, in particular, PA 5 showed lowest as about 16%. The result indicated that the increase of acetylation suppressed the aggregation of protein. The release profiles of lysozyme from PAMs were significantly different. High acetylation effectively improved lysozyme release kinetics by reducing initial burst release and extending continuous release over a period of time. To check the effect of preservation for structural stability of lysozyme, the activity of lysozyme released from PA 5 was also observed. The activity of lysozyme was maintained almost 100% for 25 day. Therefore, PAM may become to a useful carrier for delivery of protein/peptide drugs, if it will be supported by biocompatibility and biodegradability results.

• Journal of Distribution Science
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• v.18 no.9
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• pp.45-53
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• 2020

Purpose: This study aims at investigating consumers' choice in online food purchasing behavior and the impact on repurchase for fresh food delivery which has recently shown rapid growth in Korea. The study focuses on the user experience factors af fecting satisfaction and intention to continuously use the online food market. Research design, data and methodology: The survey was conducted by 309 people who had purchased fresh food online, and the analysis was conducted using SPSS and AMOS. Structural Equation Modeling was used for the analysis for the verification of hypotheses. The factors that consumers value when ordering fresh food delivery services were defined as system quality, service quality, commodity quality, brand characteristics, and economics from the preceding study and the relationship between satisfaction and willingness to repurchase was verified. Results: When consumers purchase fresh food online, system quality, product quality, brand characteristics, and economics have had a significant impact on satisfaction. Meanwhile, of the five optional attributes of consumers, only economic efficiency has been verified to have a statistically significant impact on repurchase intentions. Conclusions: The results of the study suggested factors that consumers consider important when ordering fresh food online, providing basic data for companies to develop related strategies.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.377-380
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• 2001

A recent trend in flexible manufacturing systems(FMS) is to compose of the identical versatile-machines and to use dynamic tool allocation strategy, sharing tools between machines with fast tool delivery system. Unlike a conventional FMS where parts are fed to the machines with the required tools, tools are acquired from other machines using a tool delivery system and parts can be finished on the same machine in these FMS. Therefore it is more important problem to plan tool flow using tool delivery system in these FMS rather than part flow in conventional FMS. According to existing study, in FMS 20~30 percent of the total management cost is the cost related with tools and it is possible to reduce the tool inventory by 40 percent using efficient tool allocation. In this study, in FMS under dynamic tool allocation strategy, a new method of part release considering tool flow at the stage of part release is proposed. In order to prove the efficiency of the proposed part release it is compared with other part release through simulation experiments. Performance measures in these experiments are the throughput and the number of tardy parts.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.45-51
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• 2008

As noted in the various USN service implementations including those in U-City, the reliable data transmission has become the essential component as the USN services are getting more various. The assurance of the reliability is needed sometimes prior to other QoS specifications of the USN services. The efficiency would become more important as well in USNs because the efficient and reliable delivery of a packet could be consequently linked to the energy saving. This paper is intended to provide the performance comparisons of data delivery schemes in USNs.