• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.471-480
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• 2000

With the limited wireless resources, various traffic in the cellular system is served based on micro-cell or pico-cell structure. The rapid increase in the number of mobile users results in the frequent handoff which is becoming a critical issue. In this paper, we propose a channel allocation scheme to reduce the probability of handoff failure. In this scheme, we provide a guard channel for each service to handle the handoff processes. It maintains the low probability of failure in handoff calls. To prevent the performance degradation due to the traffic variation, we use a channel arbitration method that adaptively manages the number of channels based on the call density. We evaluated the performance in terms of the initial call blocking probability and the handoff call blocking probability for various traffic and motility. We found that the proposed scheme keeps the lower probability of call blocking through the efficient channel arbitration than other suggested methods even for the irregular traffic conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.417-425
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• 2005

KOINONIA is high-rate Wireless Personal Area Network (WPAN) technology, and is developed for multimedia traffic transmission in personal area. A KOINONIA piconet is a collection of one or more associated slaves under a single master. Efficient scheduling of a master for the traffic of slaves is essential to use channel effectively and to guarantee QoS of multimedia traffic. We propose a new scheduling algorithm to allocate channel time at desired intervals regardless of superframe length, and a Connection Admission Control(CAC) algorithm to regulate the number of traffics in a piconet. Our proposed algorithms have been shown to save channel time and to meet QoS requirements compared to the conventional weighted round-robin algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.770-777
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• 2007

Smaller cell size in the micro-cell or pico-cell structure brings about more frequent hand-overs between cells, and higher speed movement of the mobile terminal makes short the permissible time interval for executing these hand-over procedures. In this situation the hand-over failure may occur or some packets may be lost during the hand-over. Moreover a rapid degradation of throughput is triggered by packet re-transmission for compensating such errors. The QoS (Quality of Services) of mobile multimedia applications with higher bits rate requirements and higher speed mobility are severely affected by even shot service interruption. This paper proposes a new hand-over scheme to provide seamless services in the next generation mobile communication systems. Simulation is done to evaluate the performance of the proposed scheme based on its hand-over failure rate and packet loss rate.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.83.1-83.1
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• 2015

세계전파통신회의 (WRC; World Radiocommunication Conference)회의는 국제전기통신연합 (ITU)에서 규정하는 국제 전파법 제개정을 위해, 3-4년 간격으로 개최되는 전파통신 관련 최고회의이다. 2015년 11월 2일-27일에 개최되는 WRC-15 본회의에서 다루는 28개 의제에 대해서는 의제별 주파수대역별로 공유/양립성/보호 연구결과가 제시되어야 한다. 따라서 2015년 3월 23일-4월 2일에는 스위스 제네바에서 190여개 ITU회원국의 국가대표 1,000여명이 모여서 의제별 최종연구결과보고서를 작성하며(CPM-15 2차회의, Conference Preparatory Meeting), 그 결과는 11월의 WRC회의에서 중요한 잣대 역할을 하게 된다. 동 회의에서 다루는 의제 가운데, 과학업무 연구반에서 다루는 주요 의제들은 다음과 같다. 1) 7145-7250 MHz 대역의 지구탐사위성(지구대우주)업무의 1순위 분배연구, 2) 8,700~10,500MHz대역의 지구탐사위성업무의 신규 SAR용대역(연속 1.2GHz) 분배방안 연구, 3) 우주선 근거리통신용 410-420MHz 대역 규제 철폐 관련 검토, 4) 윤초 삭제 또는 개정 방안 연구가 있다. 그리고 모바일 광대역 응용 실현을 위한 이동통신업무 추가 분배 및 IMT 추가 지정 연구, 나노 위성 및 피코 위성 규제 관련 연구들이 있다. 따라서 본 발표에서는 3월에 개최된 CPM-15 2차회의의 과학업무 의제 관련 최종결과를 소개하고, WRC-15회의에 대비하여 국내 전파천문업무 보호를 위해 준비가 필요한 주요 이슈에 대해 소개를 하고자 한다.

• Journal of the Korean Chemical Society
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• v.48 no.4
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• pp.339-350
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• 2004

The simplified cumulant method was applied to diffraction data of $CClF_3$ to study the equilibrium molecular parameters over a range of temperatures. The molecular parameters of $CClF_3$ by the simplified cumulant method were compared with those from the traditional method. Also the instrumentation of picosecond time resolved electron diffraction (TRED) and the experimental details are described. The total experimental temporal resolution was discussed in terms of the electron pulse width. The TRED system was applied to study the molecular structures for $CClF_3$ at room temperature. The molecular structural parameters $CClF_3$ from TRED are compared with those from GED/RT. The molecular parameters ($r_e$)of bonded C-F and C-Cl for $CClF_3$ by simplified CA are 132.00(2) pm and 175.20(3) pm, respectively, by using GED/RT. From the results of TRED experiments $r_a$ for bonded C-F and C-Cl are 132.23(13) pm and 177.23(19) pm.

• Journal of the Korean Chemical Society
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• v.26 no.6
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• pp.378-382
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• 1982

Green crystalline salts of substituted pyridinium oxopentachloromolybdates(V) were obtained from concentrated hydrochloric acid solution of molybdenum(V)-thiocyanate extract. $MoOCl_3(X-py)_2$ (X-py were 4-and 3-cyanopyridine, 2-amino-4-picoline and 4-acetylpyridine) were obtained by reflux of the corresponding substituted pyridinium salts of oxopentachloromolybdates(Ⅴ) in absolute ethanol. ($X-pyH_2$)[$MoOCl_5$]$H_2$O containing the $MoO^{3+}$ group are dissolved and hydrolysed in water but $MoOCl_3(X-py)_2$ are insoluble in water, alcohol and acetone. The complexes are paramagnetic compounds.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1262-1268
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• 2016

Bluetooth has been developed to be applied over the course of several versions in different environments. Especially low is moving to address the constraints, it gives a high utilization rate is faster than the Zigbee wireless LAN communication. To gather information on children's environmental copper transition to multiple versions. There is one limitation of Bluetooth requirements to effectively apply the information collected by Bluetooth. At the same time need to collect several information actions, Bluetooth can not connect to one of only seven Slave Master. In this paper, in order to take advantage of the many benefits of Bluetooth to gather the information by operating the Bluetooth operates in Beacon deliver packets of 168 bits, and the pairing between the master and slave unnecessarily generate a regular signal a large number of connections simultaneously Information We consider how to apply the effective policy that can be collected.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.11
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• pp.57-66
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• 2004

It is widely accepted that the coverage with high user densities in mobile multimedia environments can only be achieved with small cell such as micro- and pico-cell. The smaller cell size causes frequent handovers between cells and a decrease in the permissible handover processing delay. This may result in the handover failure, in addition to the loss of some packets during the handover. In these cases, re-transmission is needed in order to compensate errors, which triggers a rapid degradation of throughput. In this paper, we propose a new handover scheme in the next generation mobile communication systems, in which the handover setup process is done in advance before a handover request by predicting the handover cell based on mobile terminal's current position and moving direction. Simulation is focused on the handover failure rate and packet loss rate. The simulation results show that our proposed method provides a better performance than the conventional method.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.54.3-55
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• 2015

국제전기통신연합 (ITU)에서 주관하여 2015년 11월 2일-27일 스위스 제네바에서 개최되는 WRC-15(세계전파 통신회의, World Radiocommunication Conference)회의에서는 28개 의제에 대해서는 의제별 주파수대역별로 국제전파규칙(Radio Regulations)을 개정하게 된다. WRC-15 본회의에는 200여개 ITU회원국의 국가대표 3,000여명이 모여서 회의를 진행하게 되며, 원활한 회의진행과 의견 결정을 위하여 각 국가별 제안서 제출은 지양하고, 해당 지역별 국가들의 공동제안서를 중심으로 논의하게 된다. ITU에는 현재 6개의 지역(유럽, 러시아, 아랍, 북남미, 아프리카 및 아태지역) 공동체가 등록되어 있으며, 아태지역은 아태지역 전파통신협의체(Asia-Pacipic Telecommunity)를 구성하여 WRC 의제에 대응하고 있다. 지난 2015년 7월 27일-8월 1일에는 WRC의제에 대한 아태지역의 공동제안서(PACP)를 작성하기 위한 최종 회의(APG-15 5차회의)가 서울 힐튼호텔에서 개최되었다. 과학업무 의제의 경우, 5개 의제에 대한 공동제안서가 작성되었으며, 그 결과는 다음과 같다. 1) 7145-7250 MHz 대역의 지구탐사위성(지구대우주)업무의 1순위 분배 지지, 2) 9,200~9,300MHz 및 9,900~10,400MHz대역의 지구탐사위성업무의 신규 SAR용 1순위 분배 지지, 3) 우주선 근거리통신용 410-420MHz 대역 관련 거리제한 규정 삭제 지지, 4) 윤초 삭제 지지, 5) 나노 위성 및 피코 위성의 규정개정 연구를 위한 차기 WRC회의 의제 수행 지지를 들 수 있다. 따라서 본 발표에서는 7월에 개최된 APG-15 5차회의의 주요 결과를 소개하고, WRC-15회의에 대비하여 국내 전파천문업무 보호를 위한 주요 이슈에 대해 소개를 하고자 한다.

• Korean Journal of Food Science and Technology
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• v.52 no.5
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• pp.487-494
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• 2020

This study was performed to evaluate the quality characteristics and antioxidant activities of rice crispy cereal supplemented with dried laver powder. Reducing sugar content decreased in the dried laver-supplemented group. According to the Hunter color system, the L, a, and b values of rice crispy cereal decreased with an increase in the amount of dried laver. The LP5 (rice crispy cereal added with 5% dried laver) group showed the highest phycocyanin and chlorophyll contents, which tended to increase with increased amounts of added dried laver. Total phenolic and flavonoid contents increased with the amount of dried laver, as did 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical-scavenging activities. Intensity test results showed that the color, flavor, and taste of rice crispy cereal improved with the addition of dried laver. The LP5 group scored the highest on overall satisfaction. These results suggest that the addition of dried laver to rice crispy cereal improves sensory properties by increasing antioxidant activities.