• Title/Summary/Keyword: Congestion

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Safety of Ductility Demand Based Seismic Design for Circular RC Bridge Columns (원형 철근콘크리트 교각에 대한 연성도 내진설계법의 안전성)

  • Lee, Jae-Hoon;Hwang, Jung-Kil;Choi, Jin-Ho
    • Journal of the Korea Concrete Institute
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    • v.20 no.2
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    • pp.193-202
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    • 2008
  • Seismic design for bridge columns of the current Korea Highway Bridge Design Specifications which adopt full ductility design concept results in reinforcement congestion problems in construction site. It is due to large amount of confining steel is required even for small ductility demand which is a normal case in low and moderate seismicity regions like Korean peninsular. Therefore a new seismic design method based on limited ductility concept was proposed, which is called ductility demand based design method. It uses the new confining steel design equation considering ductility demand and aspect ratio of the column as well as material strength. The purpose of this study is to verify safety of the ductility demand based design method by the confining steel design equation. Eighty nine circular column test results are selected and investigated in terms of ductility factor and its safety. The safety factor for the circular column test results ranges between 1.11 and 3.98, and the average is 1.90. In this paper, the basic concept and detailed design procedure of the ductility demand based design method are also introduced as well as the investigation of the safety with respect to the major variables in confining steel design.

Hepatoprotective Effects of Semisulcospira libertina and Garlic on the Liver Damage Induced by Carbon Tetrachloride in Rats (다슬기와 마늘이 사염화탄소로 유발된 랫드의 간손상에 미치는 보호효과)

  • 김효정;김광중;전태원;이은실;이영선;한옥경;박무현
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.31 no.3
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    • pp.516-520
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    • 2002
  • This study was designed to investigate the hepatoprotective effects of Semisulcospira libertina and garlic on the acute hepatotoxicity induced by carbon tetrachloride (CCl$_4$) of rats. Male Sprague-Dawley rats weighing 200∼220g were pretreated with dehydrated powder of Semisulcospira libertina (2.1 g/kg, po; SL) and dehydrated powder mixture of Semisulcospira libertina and garlic (3g/kg, 7:3 ratio, po; SG) once daily for 3 consecutive days, and then given a single dose of CCl$_4$(1g/kg in 5ml/kg corn oil, po) and liver function was determined 24 hrs later. Liver damage was assessed by quantitating activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), sorbitol dehydrogenase (SDH) and alkaline phosphatase (ALP) as well as by histopathological examination. Pretreatments with SL and SG significantly decleased CCl$_4$-elevated ALT (48% and 61% respectively), AST (32% and 47%) and SDH (51% and 76%), but had no effect on ALP. SL and SG had revealed hepatoprotective effects against CCl$_4$-induced histopathological changes such as severe necrosis, inflammatory cell infiltration and congestion in the central gene of hepatic lobule. These findings demonstrate that SL and SG may haute the hepatoprotective effect on CCl$_4$-induced liver damage.

A Study on the User's Motivation and Satisfaction for Civic Garden (시민농원의 이용동기와 만족도에 관한 연구)

  • 노경아;김유일
    • Journal of the Korean Institute of Landscape Architecture
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    • v.22 no.4
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    • pp.133-148
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    • 1995
  • This study was carried out to provide behavioral data for its planning and management of civic garden through the evaluation of user's motivation & satisfaction. The civic gardens around Seoul were surveyed. The site are located in Kwangtan-myeon, Sudong-myeon, Wonsam-myeon, Nam-myeon, Buknae-myeon, and Jumdong-myeon, A total of 244 questionnaires were completed by mail questionnaires. The results are as follows: 1. 82 percentage of users are in thirties or fourties most of them have children who go to the elementary school. 50 percentage of users are just typical house wifes. 74 percentage of users graduated form university. 60 percentage of users live in lofty apartment buildings. 2. As a result from factor analysis, their motivations are categorized into four fator groups.: 'to experience nature', 'weekend recreation', 'nostalgia', 'to provide their old parent's sparetime'. And their satisfactions are categorized into eleven fator groups.: 'psychological/intellectual component', 'recreational components', 'instruction/management', 'facility'. 'vegetable cultivation', 'social contact', 'crowing', 'aesthetic component', 'family contact', 'the terms of lease', 'visition time'. 3. The user of civic garden can be divided into four user groups by their motivation. CLUSTER1 can represent the user group who have motivations for 'leisure, relaxation'. They are considerably satisfied with all other factor 'opportunity of meeting new person'. CLUSTER2 at the age of 41 to 50 have motivation for 'health, nostalgia'. CLUSTER3 at the age of 31 to 40 have motivation for 'harvest, experiencing nature'. CLUSTER4 at the age of more than 51 want to let their parents enjoy their sparetime. They are dissatisfied with accessibility, amount of cultivation area, crowding and overall farm management. 4. The regression analysis was employed with predicting the overall satisfaction. The results of regression analysis showed that 69% of total variances was explained by six variables: The most effective variable is 'whether visiting on weekend or weekdays', the visitors on weekdays are far more satisfied than weekend visitors because of traffic congestion, and crowding. The second source of satisfactions are 'psychological/intellectual components', they are satisfied with 'family contact', 'the terms of lease' and 'instruction in farming' are sources of satisfaction or dissatisfaction, and finally 'aesthetic landscape' is the source of satisfaction. The second most important variable is psychological one. Even though the civic gardens were not well equipped, they liked the atmosphere of rural life, refreshness, nostalgia, satisfaction from cultivation plants, and sense of achievement.

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A Priority Packet Forwarding for TCP Performance Improvement in Mobile W based Networks with Packet Buffering (모바일 IP 패킷 버퍼링 방식에서 TCP 성능향상을 위한 패킷 포워딩 우선권 보장 방안)

  • Hur, Kyeong;Roh, Young-Sup;Eom, Doo-Seop;Tchah, Kyun-Hyon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.8B
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    • pp.661-673
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    • 2003
  • To prevent performance degradation of TCP due to packet losses in the smooth handoff by the route optimization extension of Mobile IP protocol, a buffering of packets at a base station is needed. A buffering of packets at a base station recovers those packets dropped during handoff by forwarding buffered packets at the old base station to the mobile user. But, when the mobile user moves to a congested base station in a new foreign subnetwork, those buffered packets forwarded by the old base station are dropped and TCP transmission performance of a mobile user in the congested base station degrades due to increased congestion by those forwarded burst packets. In this paper, considering the general case that a mobile user moves to a congested base station, we propose a Priority Packet Forwarding to improve TCP performance in mobile networks. In the proposed scheme, without modification to Mobile IP protocol, the old base station marks a buffered packet as a priority packet during handoff. And priority queue at the new congested base station schedules the priority packet firstly. Simulation results show that proposed Priority Packet Forwarding can improve TCP transmission performance more than Implicit Priority Packet Forwarding and RED (Random Early Detection) schemes.

Slotted ALOHA Random Access with Multiple Coverage Classes for IoT Applications (사물인터넷 응용을 위한 다중 커버리지 클래스를 지원하는 슬롯화된 알로하 랜덤 접속)

  • Kim, Sujin;Chae, Seungyeob;Cho, Sangjin;Rim, Minjoong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.42 no.3
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    • pp.554-561
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    • 2017
  • IoT (Internet of Things) devices are often located in environments where indoor or underground, signals are difficult to reach. In addition, the transmission power is low, the base station should be designed to be able to receive signals even at low reception sensitivity. For this reason, a device having a poor channel condition can be transmitted at a low data rate using a low coding rate or repetition. When the coverage class is divided according to the channel condition and the data rate, the packet length may vary from one coverage class to another, and the performance of the slotted aloha random access may be degraded. We will focus on two methods of using shared-resource and seperate resources among multiple slotted aloha methods. In particular, when devices with different coverage classes use shared resources, performance of a device with a bad channel condition may deteriorate. Conversely, when using separate resources for each coverage class, there is a problem that congestion may occur which increases the number of devices that perform random access to one resource area. In this paper, we propose some methods to overcome this problem. This study is mainly focused on MTC devices, and is considered to be a high possibility of future development.

The Gravity Separation of Speiss and Limestone Granules Using Vibrating Zirconia Ball Bed (지르코니아볼층 진동을 이용한 스파이스와 석회석 입자의 비중선별)

  • Yoo, Jae Kyoung;Lee, Minji;Kim, Gyeong Hwan;Yoo, Kyoungkeun
    • Resources Recycling
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    • v.29 no.3
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    • pp.36-42
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    • 2020
  • In the present study, gravity separation of speiss (6.74 g/㎤) and limestone (2.7 g/㎤) was investigated using a vibrating 1 mm-zirconia ball (5.6 g/㎤) bed as a medium. The floating ratio and separation efficiency with increasing the number of spiess and limestone granules were examined by changing the vibration frequency from 18 Hz to 26 Hz. During the vibration, the zirconia balls circulate inside the vessel, and the spiess granules sink with the zirconia balls, but limestone granules remain on the surface of the zirconia ball bed. As the number of particles of spiess and limestone granules increased, it was observed that the granules were congested in the path of the granule sinking, so the rate of particle sinking decreased, and that limestone granules overlapping with the spiess granule also sunk. Therefore, the separation efficiency decreases with increasing the number of granules, but when the vibrational frequency increases, there is no more congestion and the separation efficiency increases. When each of the three particles was added, a separation efficiency of 100% was acheived at 22 Hz, which indicates that a dry gravity separation process that does not require a drying process is possible.

An Efficient Route Discovery using Adaptive Expanding Ring Search in AODV-based MANETs (AODV 기반의 MANET에서 적응적인 확장 링 검색을 이용한 효율적인 경로 탐색)

  • Han, Seung-Jin
    • The KIPS Transactions:PartC
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    • v.14C no.5
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    • pp.425-430
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    • 2007
  • Without the aid of stationary infrastructure, maintaining routing information for all nodes is inefficient in the Mobile Ad hoc Networks(MANET). It is more efficient when every time routing information is necessary that the source node broadcasts a query message to neighbour nodes. The source node using Ad hoc On-Demand distance Vector(AODV), which is one of the routing protocols of MANET, uses the Expanding Ring Search(ERS) algorithm which finds a destination node efficiently. In order to reduce the congestion of the network, ERS algorithm does not broadcast Route REQuest(RREQ) messages in the whole network. When the timer expires, if source node does not receive Route REPly(RREP) messages from the destination node, it gradually increases TTL value and broadcasts RREQ messages. Existing AODV cost a great deal to find a destination node because it uses a fixed NODE_TRAVERSAL_TIME value. Without the message which is added in existing AODV protocols, this paper measures delay time among the neighbours' nodes by making use of HELLO messages. We propose Adaptive ERS(AERS) algorithm that makes NET_TRAVERSAL_TIME optimum which apply to the measured delay time to NODE_TRAVERSAL_TIME. AERS suppresses the unnecessary messages, making NET_TRAVERSAL_TIME optimum in this paper. So we will be able to improve a network performance. We prove the effectiveness of the proposed method through simulation.

Load Balancing of Unidirectional Dual-link CC-NUMA System Using Dynamic Routing Method (단방향 이중연결 CC-NUMA 시스템의 동적 부하 대응 경로 설정 기법)

  • Suh Hyo-Joon
    • The KIPS Transactions:PartA
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    • v.12A no.6 s.96
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    • pp.557-562
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    • 2005
  • Throughput and latency of interconnection network are important factors of the performance of multiprocessor systems. The dual-link CC-NUMA architecture using point-to-point unidirectional link is one of the popular structures in high-end commercial systems. In terms of optimal path between nodes, several paths exist with the optimal hop count by its native multi-path structure. Furthermore, transaction latency between nodes is affected by congestion of links on the transaction path. Hence the transaction latency may get worse if the transactions make a hot spot on some links. In this paper, I propose a dynamic transaction routing algorithm that maintains the balanced link utilization with the optimal path length, and I compare the performance with the fixed path method on the dual-link CC-NUMA systems. By the proposed method, the link competition is alleviated by the real-time path selection, and consequently, dynamic transaction algorithm shows a better performance. The program-driven simulation results show $1{\~}10\%$ improved fluctuation of link utilization, $1{\~}3\%$ enhanced acquirement of link, and $1{\~}6\%$ improved system performance.

Improvement of F-GCRA Algorithm for ATM-GFR Service (ATM-GFR 서비스를 위한 F-GCRA 알고리즘 개선)

  • Park, In-Yong
    • The KIPS Transactions:PartC
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    • v.13C no.7 s.110
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    • pp.889-896
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    • 2006
  • ATM Forum has defined a guaranteed frame rate (GFR) service to serve Internet traffic efficiently. The GFR service provides virtual connections (VCs) for minimum cell rate (MCR) guarantees and allows them to fairly share the residual bandwidth. And ATM Forum has recommended a frame-based generic cell rate algorithm (F-GCRA) as a frame classifier, which determines whether an Am cell is eligible to use the guaranteed bandwidth in a frame level. An ATM switch accommodates cells in its buffer or drops them in a frame level according to current buffer occupancy. A FIFO shared buffer has so simple structure as to be feasibly implemented in switches, but has not been able to provide an MCR guarantee for each VC without buffer management based on per-VC accounting. In this paper, we enhance the F-GCRA frame classifier to guarantee an MCR of each VC without buffer management based on per-VC accounting. The enhanced frame classifier considers burstness of TCP traffic caused by congestion control algorithm so as to enable each VC to use its reserved bandwidth sufficiently. In addition, it is able to alleviate the unfairness problem in usage of the residual bandwidth. Simulation results show that the enhanced frame classifier satisfies quality of services (QoSs) of the GFR service for the TCP traffic.

A Study on the Traffic Flow and Navigational Characteristics for the Ship's Routing of Po-hang Port (포항항 항로지정을 위한 주요 통항로 및 통항 특성에 관한 연구)

  • Song Chae-Uk;Lee Yun-Sok;Park Young-Soo;Kim Jin-Kwon;Lee Yun-Chul;Kang Jeong-Gu
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2005.10a
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    • pp.111-116
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    • 2005
  • The approaching waters of Po-hang port will be increased the traffic volume and passage of larger vessel according to the opening of Young-il new port in 2006. But the adjacent area of Po-hang port still exist the danger elements of safe navigation, the disordered navigation and traffic congestion. Therefore the safety of traffic must be improved in Po-hang vicinity area. This paper describes the status of marine traffic flow and navigational characteristics based on the marine traffic survey using the exclusive software, and the results of marine traffic survey classify into the ship's types and tonnage and track history of passing ships through the statistical method. Finally the examinations of main traffic route, traffic flow and navigational characteristics are discussed, and these results can be utilized the best design of ship's routing at the Po-hang approaching water.

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