• Journal of Integrative Natural Science
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• v.11 no.4
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• pp.197-203
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• 2018

Long Term Evolution-Advanced (LTE-A) is the next drive in the broadband mobile communication, which allows operators to improve networks performance and service capabilities. LTE-A targets the peak data rates of 1Gbps in the downlink and 500Mbps in the uplink. This requirement is only fulfilled by a transmission bandwidth of up to 100MHz. However the accessibility of such large part of the contiguous spectrum is uncommon in practice. Therefore LTE-A uses some new features on top of the existing LTE standards to provide very high data rate transmission. Some of the most significant features introduced in LTE-A are carrier aggregation, heterogeneous network enhancement, coordinated multipoint transmission and reception, enhanced multiple input and multiple output, and development relay nodes with universal frequency reuse. This review paper presents an overview of the above mentioned LTE-A key features and functionalities. Based on this review, in the conclusion we discuss the current technical challenges for future broadband mobile communication systems.

• Korean Journal of Medicinal Crop Science
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• v.24 no.4
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• pp.309-316
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• 2016

Background: This study represents the first report that the anti-obesity activity of ethanol extracts of Aronia melanocarpa can be enhanced through ultrasonification at a frequency of 120 kHz at $60^{\circ}C$ (UE). Methods and Results: The amounts of cyanidin-3-O-galactose (cya-gal), a major anthocyanin in A. melanocarpa were higher by up to 402.4 mg/100 g, as compared with 221.4 mg/100 g and 322.1 mg/100 g, for hot water at $100^{\circ}C$ and 70% ethanol at $80^{\circ}C$ respectively. This result should cause the higher antioxidant activities of the UE than extract of hot water and ethanol in DPPH free radical scavenging. It was confirmed that the high antioxidant activity of UE could play an important role in inhibiting the production of proteins related to adipocyte differentiation, such as peroxisome proliferator activated receptor-${\gamma}$ (PPAR-${\gamma}$) and sterol regulatory element binding protein 1 (SREBP1). Conclusions: Ultrasonification at a frequency of 120 kHz at $60^{\circ}C$ should result in better anti-obesity activity than that observed using other processes. It was also observed for the first time that the anti-obesity activity of A. melanocarpa was associated with its antioxidant activity, possibly due to the higher elution of intact cya-gal, owing to efficient low temperature ultrasonification extraction. These results could also be applied to improve other biological activities of medicinal herbs that contain many types of heat-labile bioactive substances.

• Journal of KIISE:Software and Applications
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• v.41 no.7
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• pp.492-500
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• 2014

This paper presents the performance enhancement of automatic bilingual lexicon extraction by using refinement of pivot-context vectors under the standard pivot-based approach, which is very effective method for less-resource language pairs. In this paper, we gradually improve the performance through two different refinements of pivot-context vectors: One is to filter out unhelpful elements of the pivot-context vectors and to revise the values of the vectors through bidirectional translation probabilities estimated by Anymalign and another one is to remove non-noun elements from the original vectors. In this paper, experiments have been conducted on two different language pairs that are bi-directional Korean-Spanish and Korean-French, respectively. The experimental results have demonstrated that our method for high-frequency words shows at least 48.5% at the top 1 and up to 88.5% at the top 20 and for the low-frequency words at least 43.3% at the top 1 and up to 48.9% at the top 20.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.1 s.307
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• pp.39-44
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• 2006

In this paper, search result list synthesis method is proposed using borda count method for still image retrieval based on MPEG-7 descriptors. MPEG-7 standardizes descriptors that extract feature information from media data. In many cases, using a single descriptor lacks of correctness, it is suggested to use multiple descriptors to enhance retrieval efficiency. In this paper, retrieval efficiency enhancement is achieved by combining multiple search results which are from each descriptor. In combining search result, newly calculated borda count method is proposed. Comparing current frequency compensated calculation, rank considered frequency compensation is used to score animage in database. This combining method is considered in Content based image retrieval system with relevance feedback algorithm which uses high level information from system user. In each relevance iteration step, adoptive borda count method is used to calculate score of images.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.3 s.333
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• pp.1-8
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• 2005

In this paper, design and implement 60W Doherty power amplifiers for 3GPP repeater and base station transceiver system. Efficiency improvement and high power property of Doherty power amplifier is distinguishable; however implementation of assistance amplifer is difficult, though. To solve the problem, therefore, GCHD (Gate Control Hybrid Doherty) power amplifier is embodied to gate bias adjusament circuit of assistance amplifier to General Doherty power amplifier. Experiment result shows that $2.11\~2.17GHz$, 3GPP operating frequency band, with 62.55 dB gain, PEP output is 50,76 dBm, W-CDMA average power is 47.81 dBm, and -40.05 dBc ACLR characteristic in 5MHz offset frequency band. Each of the parameter satisfied amplifier specification which we want to design. Especially, GCHD power amplifier shows proper efficiency performance improvement in uniformity ACLR than general power amplifier.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1344-1349
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• 2012

The Korean DGPS station transmits the 200 bps GPS enhancement signal using the MSK modulation in frequency range of 283.5 kHz to 325 kHz. The land-based stations of 6 sites provide the service area of 80 km with the output power of 500 W. The ocean-based stations of 11 sites provide the output power of 300 W, which provide the DGPS service to 185 kM. Some places are serviced from two or three DGPS stations. The interferences among the DGPS stations using the high power can be occurred. Also, the performances of the user terminasl in dual service area can be degraded. In this paper, the protection ratios for the DGPS service are defined. Using the MF wave propagation model, the interferences among the DGPS stations and the adjacent wireless ground stations are analyzed. Also, the performances of DGPS user terminals are analyzed in the viewpoint of interference.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.12-16
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• 2005

The $Fe_{87}Zr_{7}B_{6}$ amorphous alloy after neutron irradiation are studied hysteresis loop and complex permeability measurements. The total integration fluence of fast neutrons is varied from $1.92{\times}10^{14}$ to $4.85{\times}10^{16}n_{f1}cm^{-2}$. After neutron irradiation, the imaginary part of complex permeability in low frequency region decreased due to the decrease of wall motion, but the permeability in high frequency region increased due to the enhancement of rotational magnetization. The measurement of hysteresis loop showed the increase of magnetic softness, related to rotational magnetization, but saturation magnetization was decreased in neutron irradiation sample.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.359-364
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• 2016

As cable TV networks have a media feature that is a broadband wire network, they can provide not only TV broadcasting services but also communication services. Accordingly, the cable TV network is mentioned as the optimal network for convergence of broadcasting and communication services. Recently, Available frequencies of the cable TV network have become insufficient as enhancement of video quality, increment of VoD service, and growth of high-speed internet service. This paper presents a new implementation method of switched digital video (SDV) technology that is introduced for obtaining additional frequency band. In the SDV system, only TV channels requested from viewer are sent and non-requested channels are dropped. The presented SDV uses a sharing method of TV broadcasting and communication service in a same frequency band. This method shows increase of spectrum efficient from switching of TV service channels without building a complex system.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.255-260
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• 1998

Fabrication condition and magnetic properties of ultrathin Co-based amorphous alloy have been investigated. When the ejection gas pressure was lower than 0.05 kgf/$\textrm{cm}^2$ at the roll speed of 55 m/s, ultrathin ribbons with the thickness less than 10 ${\mu}{\textrm}{m}$ were successfully obtained. The ribbon thickness decreased linearly with the decrease in ejection pressure. Moreover the significant decrease in ribbon width was accompanied with the decrease of thickness in the range of ejection pressure to form an ultrathin ribbon. This behavior was attributed to the decrease of effective ejection pressure in the both end-sides of rectangular nozzle due to the larger friction between molten metal and nozzle wall. The effective permeability at low frequency (1 kHz) decreased largely with the decrease in ribbon thickness, while the coercive force increased with the thickness decrease. It was considered that these behaviors were due to the enhancement of surface effect leading to the suppression of wall motion. However effective permeability at high frequency (1 MHz) increased with the decrease in ribbon thickness, and this was ascribed to the easier magnetization rotation owing to the reduction of eddy current.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.2
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• pp.252-258
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• 2017

In this paper, the bandwidth and gain enhancement of a double-dipole quasi-Yagi antenna (DDQYA) using a modified balun and two directors is studied. The proposed DDQYA consists of two strip dipoles with different lengths, a ground reflector, which are connected through a coplanar strip line, and two directors. The modified balun is used to increase the bandwidth, whereas two directors are appended to the DDQYA to enhance the gain in the middle and high frequency band. The effects of the length and width of the first director on the antenna performance are analyzed, and final design parameters to obtain a gain over 7 dBi at 1.60-2.90 GHz band are obtained. A prototype of the proposed DDQYA is fabricated on an FR4 substrate, and the experimental results show that the antenna has a frequency band of 1.57-3.00 GHz for a VSWR < 2, and measured gain ranges 7.1-7.8 dBi at 1.60-2.90 GHz band.