• Korean Journal of Materials Research
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• v.13 no.8
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• pp.519-523
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• 2003

We report the synthesis of cubic spinel $ZnCo_2$$O_4$thin films and the tunability of the conduction type by control of the oxygen partial pressure ratio. Zinc cobalt oxide films were grown on$ SiO_2$(200 nm)/Si substrates by reactive magnetron sputtering method using Zn and Co metal targets in a mixed Ar/$O_2$atmosphere. We found from X-ray diffraction measurements that the crystal structure of the zinc cobalt oxide films grown under an oxygen-rich condition (the $O_2$/Ar partial pressure ratio of 9/1) changes from wurtzite-type $Zn_{1-x}$ $Co_{X}$O to spinel-type $ZnCo_2$$O_4$with the increase of the Co/Zn sputtering ratio,$ D_{co}$ $D_{zn}$ . We noted that the above structural change accompanied by the variation of the majority electrical conduction type from n-type (electrons) to p-type (holes). For a fixed $D_{co}$ $D_{zn}$ / of 2.0 yielding homogeneous spinel-type $_2$O$ZnCo_4$films, the type of the majority carriers also varied, depending on the$ O_2$/Ar partial pressure ratio: p-type for an $O_2$-rich and n-type for an Ar-rich atmosphere. The maximum electron and hole concentrations for the Zn $Co_2$ $O_4$films were found to be 1.37${\times}$10$^{20}$ c $m^{-3}$ and 2.41${\times}$10$^{20}$ c $m^{-3}$ , respectively, with a mobility of about 0.2 $\textrm{cm}^2$/Vs and a high conductivity of about 1.8 Ω/$cm^{-1}$ /.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6C
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• pp.544-561
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• 2002

In this paper, we propose a new hybrid type of the routing protocol (Virtual Cluster-based Routing Protocol: VCRP) for mobile ad-hoc networks, based on a virtual cluster, which is defined as a narrow-sense network to exchange the basic information related to the routing among the adjacent nodes. This particular approach combines advantage of proactive routing protocol (PRP), which immediately provides the route collecting the network-wide topological and metric information, with that of reactive routing protocol, which relies on the route query packet to collect the route information on its way to the destination without exchanging any information between nodes. Furthermore, it also provides the back-up route as a byproduct, along with the optimal route, which leads to the VCBRP (Virtual Cluster-based Routing Protocol with Backup Route) establishing the alternative route immediately after a network topology is changed due to degradation of link quality and terminal mobility, Our simulation studies have shown that the proposed routing protocols are robust against dynamics of network topology while improving the performances of packet transfer delay, link failure ratio, and throughput over those of the existing routing protocols without much compromising the control overhead efficiency.

• The KIPS Transactions:PartD
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• v.11D no.6
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• pp.1247-1258
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• 2004

The LBS(Location-Based Service), which is based on individual's mobility, is required increasingly as mobile telecommunication and various infrastructures have developed rapidly. The technologies for LBS are location determination technology, service platform technology, contents provider technology and moving object database technology generally. Among these, service platform must be interoperable with location gate-way server and provide common function of billing, authentification, protect location information, privacy control, location trigger and intelligent acquisition and so on. The TTA(Telecommunications Technology Association) published specification that defines a standard protocol for safe and simple interface between LBS client and LBS platform and the OpenLS(Open Location Service) in OGC (Open GIS Consortium) released implementation specifications for providing Location based core services. In this paper, we implemented service platform for LBS which is able to interoperable with location gateway server and contents provider and is caracterized as follows. First, it could require and response location information from different types of location gateway server with same interface. Second, it complies with the standard interfaces with OpenLS 4 contents providers for core LBS. Third, it could provide location of wired phone as well as wireless mobile terminal compling with the standard protocol. Last, it could provide trajectorH information based past location as well as current location, because it is able to interoperable with moving object DBMS. This paper contributes to the construction and practical use of LBS by providing the method of implementation of service platform for LBS.

• Archives of design research
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• v.17 no.3
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• pp.353-362
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• 2004

This research has been done to evaluate the interior environmental factors in Gyungro-dang to suggest the advanced recommendations for them. For this research, the essential interior elements influencing on elderly's behavior were examined with the developed checklist, the lighting and color conditions of main hall at 14 facilities in Seoul area were analysed, and 124 subjects staying at Gyungro-dang were participated in questionaire survey for color preferences. Results showed that 1.The average installation rate of 39 items in checklist was 59%, the mandatory items such as accessible dimension were considered, but several items related to mobility and safety were not properly installed. Therefore not only guiding handrail and floor block to destination but also elimination of obstacles should be reconsidered. 2.The average of illuminances was 289 Lux dose to standard 300 Lux, but lighting quality was too low to support the activities of elderly users. The lighting control devices, combined lighting sources, and suitable lighting techniques should be applied for those facilities. 3.Most facilities were predominantly in warm colors in hue, medium or high value, low saturation, and natural atmosphere with similarity harmony. The color applications in those facilities were not functional, but similar as color preferences for the elderly except overall atmosphere. It is recommendable to include contrast harmony with classic or romantic mood.

• Journal of KIISE:Information Networking
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• v.30 no.4
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• pp.545-558
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• 2003

It is expected that per-user customized services are widely used in next generation Personal Communication Network. The ultimate goal for personalized service is the Virtual home Environment (VHE) providing ´same-look-and-feel´ services for the subscriber wherever he roams to. To provide personalized services for each call, per-user service profiles are frequently referenced, so efficient service profile management is essentially required. To realized the VHE, typically two schemes, can be employed; One is Intelligent Network based service control and the other is a full replication scheme that always replicates profile in user´s current zone. The first scheme is referred as Central scheme and th second scheme is the modified replication scheme of IMT-2000, we refer to as Follow-Me Replication Unconditional (FMRU). Since the Central scheme only depends on the service cal rate and the FMRU is merely dependent on the movement rate, it is apparent that FMRU scheme outperforms the Central scheme if the call to mobility ratio (CMR) is large, and vice versa. In this paper, we propose a new service profile replication schemes, Adaptive Follow-Me Replication (AFMR) that determine replication automatically according to the user´s CMR. We compared the performance of the AFMR with the non-adaptive Follow-Me Replication unconditional on Demand (FMRUD) scheme. Performance results indicate that as the CMR of a user changes AFMR adapts well compared to the existing schemes.

• The KIPS Transactions:PartC
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• v.15C no.4
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• pp.297-302
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• 2008

In case of display a lot of information from mobile devices, those systems are being developed that display the information from mobile devices on remote devices such as TV using the mobile devices as remote controllers because it is difficult to display a lot of information on mobile devices due to their limited bandwidth and small screen sizes. A lot of cost is required to design and develop interfaces for these systems corresponding to each of remote display devices. In this paper, a mobile environment based remote display system for displays at real times is proposed for continuous monitoring of status data for unique 'Mote IDs'. Also, remote data are collected and monitored through sensor network devices such as ZigbeX by applying status perception based remote displays at real times through processing ubiquitous computing environment data, and remote display applications at real times are implemented through PDA wireless mobiles. The system proposed in this paper consists of a PDA for remote display and control, mote embedded applications programming for data collections and radio frequency, server modules to analyze and process collected data and virtual prototyping for monitoring and controls by virtual machines. The result of the implementations indicates that this system not only provides a good mobility from a human oriented viewpoint and a good usability of accesses to information but also transmits data efficiently.

• Polymer(Korea)
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• v.28 no.3
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• pp.239-244
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• 2004

Effect of lubricants on the rheological and thermal properties of poly(butylene terephthalate) [PBT] were investigated. Calcium stearate and adipic acid glycol polyester (AhGP) were used as processing lubricants for PBT. Decrease of melt viscosity was accomplished by the addition of 1 wt％ of lubricants. It was understood that melt viscosity was affected by the enhancement of chain mobility of PBT with AhGP as an internal lubricant as well as the lubricity on processing equipment developed by calcium stearate as an external lubricant. Lubricants also influenced chain scission of PBT which caused the viscosity drop as well. In addition, lubricant is resulted in the lowering of thermal stability, however, this might be minimized by adding less than 3 wt％ of calcium stearate as a lubricant. As a consequence, calcium stearate as an external lubricant is more effective to control the melt viscosity of PBT with minimizing of chain scission and thermal instability in PBT.

• Journal of Internet Computing and Services
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• v.17 no.6
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• pp.81-91
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• 2016

VANET is one of the most developed technologies many people have considered a technology for the next generation. It basically utilizes the wireless technology and it can be used for measuring the speed of the vehicle, the location and even traffic control. With sharing those information, VANET can offer Cooperative ITS which can make a solution for a variety of traffic issues. In this way, safety for drivers, efficiency and mobility can be increased with VANET but data between vehicles or between vehicle and infrastructure are included with private information. Therefore alternatives are necessary to secure privacy. If there is no alternative for privacy, it can not only cause some problems about identification information but also it allows attackers to get location tracking and makes a target. Besides, people's lives or property can be dangerous because of sending wrong information or forgery. In addition to this, it is possible to be information stealing by attacker's impersonation or private information exposure through eavesdropping in communication environment. Therefore, in this paper we propose Privacy Assurance Architecture for VANET to ensure privacy from these threats.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.4
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• pp.412-420
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• 1999

A controlled column study using elution development and miscible displacement was conducted to assess heavy metal transport characteristics in sludge-untreated soil ("Control"), soil treated with an equivalent of sludge 50 and 100 dry ton $ha^{-1}$ ("Soil-Sludge mixtures"), and sewage sludge ("Sludge"). The elution curves (ECs) and the breakthrough curves (BTCs) for Cd, Cu and Zn in sludge 50 and 100 dry ton $ha^{-1}$ treated soils are not different from the sludge-untreated soil, The ECs for Cd, Cu and Zn in soil column which received a pulse of 10 mg of each Cd, Cu and Zn were similar to those of Cd, Cu and Zn in soil column which had no Cd, Cu and Zn added, but were very different with the ECs for Cd, Cu and Zn in soil column which received a pulse of Cd, Cu and Zn containing 50 mg of each metal. On the other hand, the BTCs for Cd, Cu and Zn in soil columns that were eluted with 500 and $1000mg\;L^{-1}$ of mixed solution of Cd, Cu and Zn were similar to each other, but were distinctly different with the BTCs for Cd, Cu and Zn in soil column that was eluted with $100mg\;L^{-1}$ mixed solution of Cd, Cu and Zn. Sewage sludge applied at rates of 50 and 100 dry ton $ha^{-1}$ did not affect the transport characteristics of this calcareous soil. The apparent mobility for this sludge treated soil and sludge is: Cd >Zn>Cu. The transport characteristics of Cd and Zn are similar to each other, but are different from those of Cu.

• Journal of Life Science
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• v.29 no.4
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• pp.455-460
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• 2019

In previous studies, we confirmed the effective antimicrobial activity of fermented Dendropanax morbifera leaf/branch extracts with Lactobacillus plantarum ilchiwhangchil 1785 and Lactobacillus plantarum ilchiwhangchil 2020. In this study, we investigated the hair growth effect of D. morbifera leaf/branch extracts fermented with L. plantarum ilchiwhangchil 1785 and L. plantarum ilchiwhangchil 2020 on human hair dermal papilla cells. The growth rate of human hair dermal papilla cells treated with fermented extracts in the range of 1 to $10{\mu}g/ml$ significantly increased in a concentration-dependent manner, without increasing cell death. Double staining studies showed that the growth of cells treated with fermented D. morbifera leaf/branch extracts was more active than that of control cells. Moreover, the cells treated with the fermented D. morbifera leaf/branch extracts exhibited a 18.84% and 23.31% increase in cell mobility, respectively, as compared with that of the untreated cells. High-performance liquid chromatography (HPLC) was used to determine the active agents responsible for hair growth. The results showed that the content of ${\beta}$-sitosterol, which is known to affect hair growth, increased about 10 times in the fermentation process of D. morbifera leaf/branch extracts. Taken together, the findings confirm that fermented Dendropanax morbifera leaf/branch extracts promote hair growth.