• International Journal of Automotive Technology
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• v.7 no.3
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• pp.245-249
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• 2006

Accelerated aging of engine exhaust system components such as catalytic converters are traditionally performed using an engine/dynamometer test stand. $SwRI^{(R)}'s\;FOCAS^{(R)}$ system reduces or eliminates many of the engine based aging limitations. This paper will describe several studies. These include: 1) replication of engine based catalyst aging cycles with added precision and dependability; 2) catalyst aging with and without lubricating oil effects; 3) effects of lubricant phosphorus on catalyst performance; and 4) the potential to thermally age components beyond the capabilities of engine based systems. The first study includes the development of the SwRI FOCAS system to run programmed aging conditions with or without lubricating oil. A description of the subsystems is given. The second two studies used the SwRI FOCAS system to age catalysts. One study compared thermal-only aging using of the SwRI FOCAS system with equivalent aging on a traditional engine/dynamometer test stand. The other study examined the effect on catalyst performance of two lubricating oils containing different levels of phosphorus, and compared the results to field data generated using the same oils in a fleet of vehicles.

• KIEE International Transactions on Power Engineering
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• v.3A no.3
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• pp.168-176
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• 2003

The Korea Electric Power Corporation (KEPCO) has installed an 80 MY A Unified Power Flow Controller (UPFC) at its 154㎸ 'Kang-Jin Substation in South Korea. The device, manufactured by Siemens & Hyusung, has been operational since October 2002. The Korea Electric Power Research Institute (KEPRI), a division of KEPCO was tasked to study operational strategies that could be employed for the UPFC and surrounding reactive support devices concerning problems of low voltages and overloads in the Mokpo & Gwangju areas. Particular apprehension surrounded the possibility of delay in the installation of a new 345㎸ transmission line from 2005 to beyond 2010. The studies were to specifically determine whether these problems could be eliminated by application of a UPFC. The analysis included determining the UPFC operating point under various conditions, investigations of the coordination between the UPFC and a HYDC line terminating in this area, and the design of a supplementary damping controller for the UFPC. This paper summarizes the results of those studies, demonstrating the dynamic characteristics of the operation of this UPFC operation in the Korean power system.

• International journal of advanced smart convergence
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• v.9 no.3
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• pp.49-58
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• 2020

Non-orthogonal multiple access (NOMA) has been recognized as a significant technology in the fifth generation (5G) and beyond mobile communication, which encompasses the advanced smart convergence of the artificial intelligence (AI) and the internet of things (IoT). In NOMA, since the channel resources are shared by many users, it is essential to establish the user fairness. Such fairness is achieved by the power allocation among the users, and in turn, the less power is allocated to the stronger channel users. Especially, the first and second strong channel users have to share the extremely small amount of power. In this paper, we consider the power optimization for the two users with the small power. First, the closed-form expression for the power allocation is derived and then the results are validated by the numerical results. Furthermore, with the derived analytical expression, for the various channel environments, the optimal power allocation is investigated and the impact of the channel gain difference on the power allocation is analyzed.

• Journal of Industrial Convergence
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• v.21 no.3
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• pp.1-15
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• 2023

Expectations for wireless communication technology are rising as a base technology that promotes innovation in various industries in line with the paradigm of digital transformation in the 21st century beyond the stage of being used only for communication service itself. In this study, in order to compare 6G technological competitiveness between Korea and leading countries, technological competitiveness was confirmed through PFS, CPP, and network analysis based on GaN Integrated Circuit patent data. Korea's 6G technological competitiveness was 0.62 in PFS and 3.93 in CPP, which were 32.8% and 19.9%, respectively, compared to leading countries. In addition, as a result of network analysis, the collaboration rate in the 6G field was 7.2%, and the collaboration ecosystem was very insufficient in most countries. In contrast, it was confirmed that Korea, unlike leading countries, has established a small-scale collaboration ecosystem linked by industry and academia. Thus, it is necessary to establish a strategy for 6G communication technology at the national level so that communication technology can be advanced based on a relatively well-established collaborative ecosystem.

• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.271-280
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• 2010

For the next generation mobile communication system, diverse wireless network techniques such as beyond 3G LTE, WiMAX/WiBro, and next generation WLAN etc. are proceeding to the form integrated into the All-IP core network. According to this development, Beyond 3G integrated into heterogeneous wireless access technologies must support the vertical handover and network to be used of several radio networks. However, unified management of each network is demanded since it is individually serviced. Therefore, in order to solve this problem this study is introducing the theory of Common Radio Resource Management (CRRM) based on Generic Link Layer (GLL). This study designs the structure and functions to support the vertical handover and propose the vertical handover algorithm of which policy-based and MCDM are composed between LTE and WLAN systems using GLL. Finally, simulation results are presented to show the improved performance over the data throughput, handover success rate, the system service cost and handover attempt number.

• Journal of Digital Contents Society
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• v.8 no.3
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• pp.323-328
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• 2007

Communication systems beyond 3G should provide more than 100 Mbps for wireless access. In addition to smart antennas, wireless multi-hop networks are proposed to increase the cell size and throughput. For example, Zigbee technology is expected to provide low cost and low power connectivity and can be implemented in wireless mesh networks larger than is possible with Bluetooth. Also, home embedded system using wireless mesh network is one of the key market areas for Zigbee applications. If the line-of-sight path is shadowed by home obstacles, a direct connection between the access point (AP) and the node is not possible at high frequencies. Therefore, by using multi-hop relay scheme the end node can be reached to AP. In this paper, the relaying of data between the AP and the end node is investigated and the throughput and PER(Packet Error Rate) are evaluated in multi-hop wireless mesh networks by using DSSS/BPSK system.

• Journal of Internet Computing and Services
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• v.11 no.1
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• pp.35-48
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• 2010

For the next generation mobile communication system, diverse wireless network techniques such as beyond 3G LTE, WiMAX/WiBro, and next generation WLAN etc. are proceeding to the form integrated into the All-IP core network. According to this development, Beyond 3G integrated into heterogeneous wireless access technologies must support the vertical handover and network to be used of several radio networks. However, unified management of each network is demanded since it is individually serviced. Therefore, in order to solve this problem this study is introducing the theory of Common Radio Resource Management (CRRM) based on Generic Link Layer (GLL). This study designs the structure and functions to support the vertical handover and propose the vertical handover algorithm of which policy-based and MCDM are composed between LTE and WLAN systems using GLL and CRRM. Finally, simulation results are presented to show the improved performance over the data throughput, handover success rate and the system service cost.

• Journal of Information Technology Services
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• v.11 no.2
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• pp.339-353
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• 2012

Mobile communication technology is advancing forward to deliver more connected devices and richer content and applications. The number of subscriptions continues to grow along with an explosive increase in the mobile data traffic demand. Thereby, it creates a significant network capacity shortage concerns for mobile network operators. In order to address this problem, it is essential to increase the network capacity at a low additional cost. The device-to-device (D2D) communication based proximity service is believed to have a promising future mobile communication technology that is capable to create new mobile service opportunities and offload traffic to the eNB. In addition, it is also required to develop new mobile communication services and its business models not only to accommodate the increasing mobile traffic demand but also to foster profitability of mobile business service providers such as the network providers, contents providers and platform providers. In this article, we first analyze current mobile business eco-system in the context of CPNT based value chain. Then, propose service development framework and business model creation methodologies for the device-to-device communication based services in the beyond LTE/LTE-Advanced systems.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.6
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• pp.503-511
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• 2009

VOC mixture was fed to a trickle bed air biofilter (TBAB) with step-change in influent mixture concentrations from 50 ppmv to 1,000 ppmv, corresponding to loadings of $5.7\;g/m^3/hr$ to $114.1\;g/m^3/hr$. VOC mixture was an equimolar ratio of two aromatic VOCs, i.e., toluene and styrene, and two oxygenated VOCs, i.e., methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK). The TBAB system employed backwashing as biomass control. The experimental results showed that a critical loading rate for VOC mixture removal was determined to be about $60\;g/m^3/hr$, and critical loading rates for individual VOCs in the mixture were different. Specifically, toluene content in the mixture played a major role in the biofilter overall performance. As VOC mixture was fed beyond the critical loading rate, reacclimation of the biofilter to reach the 99% removal efficiency following backwashing was delayed, which was a critical factor in the biofilter performance. In the mass balance analysis, 63.8% of the carbon equivalent in VOCs removal was used for $CO_2$ production during the experimental runs. The 82.6% nitrogen utilized in the biofilter was contributed to microbial cell synthesis. The obtained results were compared against consistently high efficient performance of TBAB for VOC mixture by employing backwashing as biomass control.

• Reproductive and Developmental Biology
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• v.28 no.2
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• pp.77-82
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• 2004

The purpose of this study was performed to establish the in vitro culture system of porcine in vitro maturation and in vitro fertilization(IVM/IVF) embryo. These studies was to determine the effects of antioxidants(aesculetin, taurine and melatonin) in porcine IVM/IVF embryos. In routine porcine IVM/IVF procedure, oocytes were cultured for 40∼44h incubation in NCSU 23 mediumand matured oocytes were inseminated with frozen semen. Then 2 to 8 cell embryos were removed cumulus cell and were allotted randomly to NCSU 23 containing different concentration of antioxidants in 5% $O_2$ and 5% $CO_2$ at 38.5$^{\circ}C$. Cell numbers of blastocyst were also counted using double fluorescence stain method. Aesculetin were added to NCSU 23 medium at concentration of 1 ug, 5 ug, and 10 ug, when treated with 10 ug(35.7%) of aesucletin at the rate of embryos of the morula plus blatocsyts were higher than those of any other groups (30.2%, 29.5% and 29.2%)(P<0.05). The developmental rates beyond morula stage of porcine embryos in NCSU 23 medium supplemented with taurine 0, 2.5 and 5.0 mM were 26.1%, 26.9% and 31.7%, respectively. The addition of 5.0 mM taurine was higher the developmental rate beyond morula stage than in any other groups. In NCSU 23 medium treated with melatonin 0, 1, 5 and 10 nM, the developmental rate of morula plus blastocysts were 33.3%, 39.1%, 33.3% and 27.9%, respectively. The developmental rate of morula and blascytocys treated with 1nM melatonin was higher than in any other groups(P<0.05). Cell numbers of blastocyst in NCSU 23 treated with melatonin 0, 1, 5 and 10nM were 41.0, 42.6, 39.6 and 33.0, respectively. These results indicate that aesculetin, taurine and melation can increase the developmental rate beyond the morulae and blastocysts in porcine embryos.