• Title/Summary/Keyword: 통신량

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Compensation of Instantaneous Voltage Drop at AC Railroad System with Single-Phase Distributed STATCOM (전기철도 급전시스템의 순시전압강하 보상을 위한 단상 배전 STATCOM의 적용)

  • Kim, Jun-Sang;Lee, Seung-Hyuk;Kim, Jin-O;Lee, Jun-Kyung;Jung, Hyun-Soo
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.21 no.1
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    • pp.42-51
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    • 2007
  • An AC electrical railroad system has rapidly changing dynamic single-phase load, and at a feeding substation, three-phase electric power is transformed to the paired directional single-phase electric power. There is a great difference in electrical phenomenon between the load of AC electrical railroad system and that of general power system. Electric characteristics of AC electrical railroad's trainload are changed continuously according to the traction, operating characteristic, operating schedule, track slope, etc. Because of the long feeding distance of the dynamic trainload, power quality problems such as voltage drop, voltage imbalance and harmonic distortion my also occur to AC electrical railroad system. These problems affect not only power system stability, but also power quality deterioration in AC electrical railroad system. The dynamic simulation model of AC electrical railroad system presented by PSCAD/EMTDC is modeled in this paper, andthen, it is analyzed voltage drop for AC electrical railroad system both with single-phase distributed STATCOM(Static Synchronous Compensator) installed at SP(Sectioning Post) and without.

The QoS Filtering and Scalable Transmission Scheme of MPEG Data to Adapt Network Bandwidth Variation (통신망 대역폭 변화에 적응하는 MPEG 데이터의 QoS 필터링 기법과 스케일러블 전송 기법)

  • 유우종;김두현;유관종
    • Journal of Korea Multimedia Society
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    • v.3 no.5
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    • pp.479-494
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    • 2000
  • Although the proliferation of real-time multimedia services over the Internet might indicate its successfulness in dealing with heterogeneous environments, it is obvious, on the other hand, that the internet now has to cope with a flood of multimedia data which consumes most of network communication channels due to a great deal of video or audio streams. Therefore, for the purpose of an efficient and appropriate utilization of network resources, it requires to develop and deploy a new scalable transmission technique n consideration of respective network environment and individual clients computing power. Also, we can eliminate the waste effects of storage device and data transmission overhead in that the same video stream duplicated according to QoS. The purpose of this paper is to develop a technology that can adjust the amount of data transmitted as an MPEG video stream according to its given communication bandwidth, and technique that can reflect dynamic bandwidth while playing a video stream. For this purpose, we introduce a media scalable media decomposer working on server side, and a scalable media composer working o n a client side, and then propose a scalable transmission method and a media sender and a media receiver in consideration of dynamic QoS. Those methods proposed her can facilitate an effective use of network resources, and provide multimedia MPEG video services in real-time with respect to individual client computing environment.

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Energy-Efficient Routing Protocol based on Interference Awareness for Transmission of Delay-Sensitive Data in Multi-Hop RF Energy Harvesting Networks (다중 홉 RF 에너지 하베스팅 네트워크에서 지연에 민감한 데이터 전송을 위한 간섭 인지 기반 에너지 효율적인 라우팅 프로토콜)

  • Kim, Hyun-Tae;Ra, In-Ho
    • The Journal of the Korea Contents Association
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    • v.18 no.3
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    • pp.611-625
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    • 2018
  • With innovative advances in wireless communication technology, many researches for extending network lifetime in maximum by using energy harvesting have been actively performed on the area of network resource optimization, QoS-guaranteed transmission, energy-intelligent routing and etc. As known well, it is very hard to guarantee end-to-end network delay due to uncertainty of the amount of harvested energy in multi-hop RF(radio frequency) energy harvesting wireless networks. To minimize end-to-end delay in multi-hop RF energy harvesting networks, this paper proposes an energy efficient routing metric based on interference aware and protocol which takes account of various delays caused by co-channel interference, energy harvesting time and queuing in a relay node. The proposed method maximizes end-to-end throughput by performing avoidance of packet congestion causing load unbalance, reduction of waiting time due to exhaustion of energy and restraint of delay time from co-channel interference. Finally simulation results using ns-3 simulator show that the proposed method outperforms existing methods in respect of throughput, end-to-end delay and energy consumption.

An Efficient TCP Buffer Tuning Algorithm based on Packet Loss Ratio(TBT-PLR) (패킷 손실률에 기반한 효율적인 TCP Buffer Tuning 알고리즘)

  • Yoo Gi-Chul;Kim Dong-kyun
    • The KIPS Transactions:PartC
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    • v.12C no.1 s.97
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    • pp.121-128
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    • 2005
  • Tho existing TCP(Transmission Control Protocol) is known to be unsuitable for a network with the characteristics of high RDP(Bandwidth-Delay Product) because of the fixed small or large buffer size at the TCP sender and receiver. Thus, some trial cases of adjusting the buffer sizes automatically with respect to network condition have been proposed to improve the end-to-end TCP throughput. ATBT(Automatic TCP fluffer Tuning) attempts to assure the buffer size of TCP sender according to its current congestion window size but the ATBT assumes that the buffer size of TCP receiver is maximum value that operating system defines. In DRS(Dynamic Right Sizing), by estimating the TCP arrival data of two times the amount TCP data received previously, the TCP receiver simply reserves the buffer size for the next arrival, accordingly. However, we do not need to reserve exactly two times of buffer size because of the possibility of TCP segment loss. We propose an efficient TCP buffer tuning technique(called TBT-PLR: TCP buffer tuning algorithm based on packet loss ratio) since we adopt the ATBT mechanism and the TBT-PLR mechanism for the TCP sender and the TCP receiver, respectively. For the purpose of testing the actual TCP performance, we implemented our TBT-PLR by modifying the linux kernel version 2.4.18 and evaluated the TCP performance by comparing TBT-PLR with the TCP schemes of the fixed buffer size. As a result, more balanced usage among TCP connections was obtained.

Digital Forensic Investigation of HBase (HBase에 대한 디지털 포렌식 조사 기법 연구)

  • Park, Aran;Jeong, Doowon;Lee, Sang Jin
    • KIPS Transactions on Computer and Communication Systems
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    • v.6 no.2
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    • pp.95-104
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    • 2017
  • As the technology in smart device is growing and Social Network Services(SNS) are becoming more common, the data which is difficult to be processed by existing RDBMS are increasing. As a result of this, NoSQL databases are getting popular as an alternative for processing massive and unstructured data generated in real time. The demand for the technique of digital investigation of NoSQL databases is increasing as the businesses introducing NoSQL database in their system are increasing, although the technique of digital investigation of databases has been researched centered on RDMBS. New techniques of digital forensic investigation are needed as NoSQL Database has no schema to normalize and the storage method differs depending on the type of database and operation environment. Research on document-based database of NoSQL has been done but it is not applicable as itself to other types of NoSQL Database. Therefore, the way of operation and data model, grasp of operation environment, collection and analysis of artifacts and recovery technique of deleted data in HBase which is a NoSQL column-based database are presented in this paper. Also the proposed technique of digital forensic investigation to HBase is verified by an experimental scenario.

Progressive Iterative Forward and Backward (PIFAB) Search Method to Estimate Path-Travel Time on Freeways Using Toll Collection System Data (고속도로 경로통행시간 산출을 위한 전진반복 전후방탐색법(PIFAB)의 개발)

  • NamKoong, Seong
    • Journal of Korean Society of Transportation
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    • v.23 no.5 s.83
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    • pp.147-155
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    • 2005
  • The purpose of this paper is to develop a method for estimation of reliable path-travel time using data obtained from the toll collection system on freeways. The toll collection system records departure and arrival time stamps as well as the identification numbers of arrival and destination tollgates for all the individual vehicles traveling between tollgates on freeways. Two major issues reduce accuracy when estimating path-travel time between an origin and destination tollgate using transaction data collected by the toll collection system. First, travel time calculated by subtracting departure time from arrival time does not explain path-travel time from origin tollgate to destination tollgate when a variety of available paths exist between tollgates. Second, travel time may include extra time spent in service and/or rest areas. Moreover. ramp driving time is included because tollgates are installed before on-ramps and after off-ramps. This paper describes an algorithm that searches for arrival time when departure time is given between tollgates by a Progressive Iterative Forward and Backward (PIFAB) search method. The algorithm eventually produces actual path-travel times that exclude any time spent in service and/or rest areas as well as ramp driving time based on a link-based procedure.

Exploring the Impacts of Autonomous Vehicle Implementation through Microscopic and Macroscopic Approaches (자율주행차량 도입에 따른 교통 네트워크의 효율성 변화 분석연구)

  • Yook, Dong-Hyung;Lee, Baeck-Jin;Park, Jun-Tae
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.17 no.5
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    • pp.14-28
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    • 2018
  • Thanks to technical improvement on the vehicle to vehicle communication and the intelligent transportation system, gradual introduction of the autonomous vehicles is expected soon in the market. The study analyzes the autonomous vehicles' impacts on the network efficiencies. In order to measure the network efficiencies, the study applies the sequential procedures that combines the microscopic and macroscopic simulations. The microscopic simulation attends to the capacity changes due to the autonomous vehicles' proportions on the roadway while the macroscopic simulation utilizes the simulation results in order to identify the network-wide improvement. As expected, the autonomous vehicles efficiently utilizes the existing capacity of the roadway than the human driving does. Particularly, the maximum capacity improvements are expected by the 190.5% on the expressway. The significant capacity change is observed when the autonomous vehicles' proportions are about 80% or more. These improvements are translated into the macroscopic model, which also yields overall network efficiency improvement by the autonomous vehicles' penetration. However, the study identifies that the market debut of the autonomous vehicles does not promise the free flow condition, which implies the possible needs of the system optimal routing scheme for the era of the autonomous vehicles.

(2)건강기능식품법의 하위법 제정에 즈음한 방향 제안

  • Son, Dong-Hwa
    • Bulletin of Food Technology
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    • v.15 no.4
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    • pp.73-101
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    • 2002
  • 21세기는 과학기술의 비약적인 발전으로 정보통신기술, 환경기술, 나노기술 그리고 생명과학에 의한 바이오기술이 고부가가치 지식산업으로서 국가경쟁력 강회를 위한 국가전략 핵심산업으로 대두되고 있습니다. 특히 바이오기술의 응용산업인 건강기능식품은 국민의 질병예방과 건강증진을 통한 삶의 질 향상에 이바지하고, 21세기 미래 고부가가치산업으로 발전할 것으로 기대하고 있습니다. 이러한 시기에 국민보건과 건강기능식품산업의 발전을 위한 건강기능식품에 관한 법률(건강기능식품법) 이 의원입법으로 국회에 상정되어 1년 이상의 검토를 거쳐 지난 7월 31일에 국회 본회의를 통과하였습니다. 그후 8월 26일자로 이 법을 정부에서 공포하였으며 내년 8월 26일부터는 발효할 예정입니다. 그러나, 건강기능식품법의 제정은 건강기능식품관련 제도의 완성이 아니라 시작입니다. 즉, 건강기능식품법의 기초는 마련하였지만, 그 하위법인 시행령, 시행규칙, 고시등이 제대로 된 모습을 갖추어야 비로소 국민이 만족하고, 산학연의 동반 발전을 이룰 수 있는 이 분야의 산업발전을 기할 수 있습니다. 그리고, 건강기능식품담당 정부부처인 식품의약품안전청은 현실적으로 그 하위법을 금년 말(2002년)이나 내년 초(2003년)에 준비한 후 입법 예고하여야하는 시간적 제약을 안고 있습니다. 이러한 연유로 단기간 내에 하위법을 준비하다 보면 자칫 애초에 정부와 산학연이 바라던 바와는 다른 엉뚱한결과를 초래할 우려가 있는 만큼, 법 제도의 명확한 방향설정이 매우 중요합니다. 그래서, 한국식품과학회 건강기능식품분과위원회는 이 문제의 중요성을 깊이 인식하고 산학연 전문가그룹(식품과학자, 영양과학자, 학계, 연구계, 기업계: 16인)을 구성하였습니다. 전문가그룹은 지난 7 - 8월, 2달 동안에 수 차례 회의를 통하여, 건강기능식품법 하위법 준비 중 핵심사항은 건강기능식품의 기능성 표시와 평가 라는 점에 착안하고, 이에 대하여 중점적으로 검토하였습니다. 그 이외에도 섭취량 설정 , 심사자료의 인증요건 , 기능성분의 표시 등에 대하여도 부수적으로 검토하였습니다. 그 결과, 동물실험을 이용한 기능성평가 방향 (이미 본지의 전호에서 게재한 바 있어생략)을 제외한 주요사항을 다음의 별도 기사로 각각 소개합니다. 또한, 이 내용은 지난 9월 13일, COEX에서 제1회 건강기능식품 전시회 및 학술세미나 행사의 일환으로서 개최된 학술세미나에서 발표하고 토론회를 거쳤습니다. 또한, 지난 10월 26일, 무주리조트에서 식품과학회 추계학술대회 행사의 일환으로 개최된 건강기능식품분과위원회의 토론회에서도 좋은 의견을 교환한 바 있습니다. 두 차례의 토론회를 통하여 건강기능식품분과위원회가 제안한 초안이 대체적으로 매우 바람직한 것으로 평가받았으며 많은 동의를 얻었습니다. 이어서 토론회의 내용을 반영한 식품과학회의 안을 최종적으로 준비하고 이를 11월초에 식품의약품안전청에게 정책 건의하였습니다. 다음의 별도기사에 덧붙여서, 토론회를 통하여 수정(또는 강조)하고자 하는 부분은 아래와 같습니다. 1) 동물실험 등에서 흡수, 대사 등으로 표기한 서술 용어는 흡수, 분포, 대사, 배설 로 대체합니다. 2) 기능성 평가방법의 표준화와 관련하여 분과위원회에서 제시한 안은 평가방법은 심의위원회가 사안에 따라 기능성 평가시에 그 평가방법의 적합성을 검토함이 바람직하다 라고 하였습니다. 그러나, 이를 부분적으로는 평가방법을 표준화할 필요가있다 로 수정하고자 합니다. 즉, 평가방법이 전혀 제시되지 않으면 막막함으로, 기본적인 방법이면서 여러사람들이 참고로 할만한 방법에 대하여는 표준화를 병행함이 더욱 좋겠다고 생각합니다. 또한, 표준방법으로 제시된 것만이 유일한 방법은 아니므로 다른 방법으로 평가하는 것도 가능함으로 제시합니다. 3) (가칭)건강기능식품 인체시험 관리지침과 관련하여 이는 식약청장이 정할 사안이지만, 그것은 국내 의약품 임상시험 관리지침 과는 뚜렷이 차별화되는 것으로 실제로는 의사의 도움없이도 인체시험을 시행할 수 있음을 명확히 할 필요가 있습니다.

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Noise Analysis and Measurement for a CW Bio-Radar System for Non-Contact Measurement of Heart and Respiration Rate (호흡 및 심박수 측정을 위한 비접촉 방식의 CW 바이오 레이더 시스템의 잡음 분석 및 측정)

  • Jang, Byung-Jun;Yook, Jong-Gwan;Na, Won;Lee, Moon-Que
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.9
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    • pp.1010-1019
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    • 2008
  • In this paper, we present a noise analysis and measurement results of a bio-radar system that can detect human heartbeat and respiration signals. The noise analysis including various phase noise effects is very important in designing the bio-radar system, since the frequency difference between the received signal and local oscillator is very small and the received power is very low. All of the noise components in a bio-radar system are considered from the point of view of SNR. From this analysis, it can be concluded that the phase noise due to antenna leakage is a dominant factor and is a function of range correlation. Therefore, the phase noise component with range correlation effect, which is the most important noise contribution, is measured using the measurement setup and compared with the calculated results. From the measurement results, our measurement setup can measure a closed-in phase noise of a free-running oscillator. Based on these results, it is possible to design a 2.4 GHz bio-radar system quantitatively which has a detection range of 50 cm and low power of 1 mW without additional PLL circuits.

Properties of Strength and Stress-Strain of Recycled-Plastic Polymer Concrete (폐플라스틱 재활용 폴리머콘크리트의 강도와 응력-변형률 특성)

  • Jo Byung-Wan;Koo Jakap;Park Seung-Kook
    • Journal of the Korea Concrete Institute
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    • v.17 no.3 s.87
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    • pp.329-334
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    • 2005
  • The use of Polymer Concrete (PC) is growing very rapidly in many structural and construction applications such as box culverts, hazardous waste containers, trench lines, floor drains and the repair and overlay of damaged cement concrete surfaces in pavements, bridges, etc. However, PC has a defect economically because resin which be used for binder is expensive. Therefore the latest research is being progressed to replace existing resin with new resin which can reduce the high cost. Here, Polymer concrete using the recycled PET(polyethylene terephthalate) has some merits such as decrease of environmental destruction, decrease of environmental pollution and development of new construction materials. The variables of this study are amount of resin, curing condition and maximum size of coarse aggregate to find out mechanic properties of this. Stress-strain curve was obtained using MTS equipment by strain control. The results indicated that modulus of elasticity was increased gradually in an ascending branch of curve, as an increase of resin content. Compressive strength was the highest for resin content of $13\%$. And Compressive strength was increased as maximum size of coarse aggregate increases. The strain at maximum stress increases with an increase of resin content and size of coarse aggregate. For the descending branch of stress-strain curve the brittle fracture was decreased when it was cured at the room temperature compared to high temperature.