• Journal of KIISE:Information Networking
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• v.32 no.3
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• pp.382-390
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• 2005

As today's networks evolve towards an If-based integrated network, the role of transmission control protocol(TCP) has been increasing as well. As a well-known issue, the performance of TCP is affected by its loss recovery mechanism that is comprised of two algorithms; fast retransmit and fast recovery. Although retransmission timeout(RTO) caused by multiple packet losses can be avoided by using selective acknowledgement(SACK) option, RTO cannot be avoided if a retransmitted packet is lost. Therefore, we propose a simple modification to make it possible for a TCP sender using SACK option to detect a lost retransmission. In order to evaluate the proposed algorithm, simulations have been performed for two scenarios where packet losses are random and correlated. Simulation results show that the proposed algorithm can improve TCP performance significantly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2B
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• pp.124-132
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• 2007

Where a wireless LAN and a cellular network coexist, a mobile node has to experience vertical handoffs to move between them. Immediately after the vertical handoffs, TCP must need adaptation latency to adjust its congestion window to the proper size at a newly arrived network to use full of a new end-to-end available bandwidth. Even though SACK TCP has the best performance among other regular TCPs in the previous studies, it still cannot use full of the new available bandwidth quickly due to its inefficient increasing way of congestion window. BIC TCP, that becomes a popular TCP in long fat networks, has great feature working well against vertical handoffs by increasing congestion window exponentially with TCP connection sustained. In this paper, we derive adaptation latency of SACK TCP and BIC TCP numerically, and verify them by simulations. We also find that the shorter adaptation latency of BIC TCP produces higher throughput than SACK TCP on vertical handoffs. Consequently, to get higher performance on vertical handoff situations, we propose to use BIC TCP.

• The KIPS Transactions:PartC
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• v.9C no.5
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• pp.647-654
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• 2002

Ad-hoc networks consist of a set of mobile hosts that communicate using wireless links, without the use of other supporting communication facilities (such as base stations, etc.). Therefore, the topology of an Ad-hoc network frequently changes due to the movement of mobile host, which nay lead to sudden packet loss. Recently, the large amount of research has focused on the routing protocols needed in such an environment. In this paper, TCP Reno, Sack, and Tahoe versions are analysed using DSR protocol which is the representative On-Demand routing protocol in Ad-hoc wireless network. As the result of this simulation, we know that TCP Reno relatively has higher throughput than that of Sack and Tahoe, and TCP Reno has more stable performance than that of TCP Tahoe and Sack, regardless of the speed of mobile node and the size of topology.

• The KIPS Transactions:PartC
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• v.11C no.2
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• pp.245-252
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• 2004

Stream Control Transmission Protocol(SCTP) is a new connection-oriented, reliable delivery transport protocol operating on top of an unreliable connectionless packet service such as IP. It inherits many of the functions developed for TCP, including flow control and packet loss recovery functions. In addition, it also supports transport layer multihoming and multistreaming In this paper, we study the impact of multi-homing on the performance of SCTP. We first compare performance of single-homed SCTP. multi-homed SCTP, TCP Reno and TCP SACK. We, then describe potential flaw in the current SCTP retransmission policy, when SCTP host is multihomed. Our Results show that SCTP performs better than TCP Reno and TCP SACK due to several changes from TCP in its congestion control mechanism. In particular. multi-homed SCTP shows the best result among the compared schemes. Through experimentation for multi-homed SCTP, we found that the current SCTP retransmission policy nay deteriorate the perfomance when the retransmission path it worse than the original path. Therefore, the condition of retransmission path is a very important factor In SCTP performance and a proper mechanism would be required to measure the condition of the retransmission path.

• Journal of the Korea Society of Computer and Information
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• v.4 no.4
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• pp.148-154
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• 1999

TCP has improved by many papers which suggest the new algorithms and modify the previous algorithms. This paper compares Tahoe, Reno, New-Reno, Vegas, and SACK. The first version is Tahoe and is globally used. Reno has optimal performance during occurring one packet loss within a window of data, but can suffer from performance when multiple packets are dropped from a window of data. New-Reno avoids some of the performance problems of Reno TCP when multiple packets are dropped from a window of data. but is occurring the problem of the necessary retransmission. SACK resolves the all above problems and is used in bandwidth delay product environment. Vegas uses network bandwidth more efficiently and is a new implementation of TCP that achieves between 40 and 70 better throughput, with one-fifth to one-half the losses, as compared to the implementation of Reno TCP.

• The Journal of the Convergence on Culture Technology
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• v.6 no.1
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• pp.1-6
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• 2020

This study is about the safe arm posture in case of emergency escape using the vertical dive rescue sack at the fire site. The experimental results are as follows. First, the arms extended upward contact with the endothelium and narrowing part of the rescue sack minimized the scratches did not occur. Second, the bent position with both arms open was subject to light abrasions of on the elbows due to friction between the elbows and the scapula and the endothelium. Third, in the posture where both arms were gathered in the chest, the body passed through the narrowing part and friction between the bag's narrowing part, All subjects had light abrasions on their elbows. Fourth, because the arms are lowered, the legs are extended to the width of the shoulders when descending, so that the back of the hand has friction with the narrowing part of the bag and the endothelial skin. Finally, posture with both arms below the front increased the volume of the front of the body, resulting in a slight back injury. As a future research task, it is necessary to study the proper posture of legs and the posture of landing on the ground.

• Journal of Korean Society of Forest Science
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• v.47 no.1
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• pp.44-51
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• 1980

In order to find out the suitable methods that can omit the earth healing and increase the survival through improving the seedling-healing and transportable methods. Several trials with plastic vinyl have been done and its results are as follows: 1. Though P. rigitaeda seedling have been stored in the black and white vinyl sack for 35 days in the storehouse. This seedling have survived with very high percentage as Table 1. This means that the earth healing work at the nursery or planting area can be omitted if seedling sould be stored in the storehouse by using the vinyl sack. The possibilities of long-period storage in the black and white vinyl sack seem to be come from the reasons that air humidity in the sack is nearly 100% and its air temperature is only around $15^{\circ}C$ with very little difference between day and night time. This sack also can be utilized in place of the planting sack, and though this sack with seedling have been laid under direct sunshine for 1 to 2 days. Any difference between the sack stored in the storehouse has not been observed on the survival specially Table 2. 2. When the bundled seedling have been covered with the black and white vinyl instead of earth healing, even if these seedling have been laid for 18 days under the vinyl. This seedling show us high survival as Table 3. High humidity with nearly 95%, very little difference of air temperature between day and night time under the vinyl and not so big difference between out-and inside temperature could be reasons of high survival to be considered. So through covering by the black and white vinyl. The labour power for earth healing works can be saved also. 3. In order to protect the healed seedling from the direct sunshine and the eva-transpiration. Black vinyl net and reed mat could be effective for this purpose. Because vinyl net could intercept around one to third, reed mat two to third of total solar energy and also suppress more than 50% of total water loss by the transpiration.

• Journal of Biosystems Engineering
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• v.24 no.5
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• pp.399-406
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• 1999

This study was conducted to investigate the labor requirements and transportation cost of paddy for the different harvest and transportation systems for obtaining a basic reference to the improvement of present harvest-transportation systems. One hundred and eighty five farm households with sack type combine harvester and thirty farm households with bulk type combine harvester were surveyed for thirty counties from eight provinces except jeju and also eleven Rice Processing Complex were covered for this survey. This survey was carried from 8th. October 1997 to 5th. November 1997. For the labor requirements, bulk trailer system require 6.8th/ha, 10.3/ha for sack harvest-tractor trailer, and 8.8h/ha for bulk harvest-container bag. The machinery utilization cost for the different paddy harvest-transportation systems, combine sack harvest-tractor trailer system is 282 thousand won/ha, and most economical compared with other systems. Combine bulk harvest with tractor system was 416 thousands won/ha and combine bulk harvest with container bag system was 446 thousands won/ha. In order to propagate bulk harvest-transportation system, a proper bulk transportation means with considering road condition in the paddy field and paddy size should be developed, and considering cycle time it appeared that the proper capacity of bulk container was 3.5ton at the present.

• Journal of Internet Computing and Services
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• v.2 no.3
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• pp.9-17
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• 2001

Ad-Hoc networks consist of a set of mobile hosts that communicate using wireless links, without the use of other communicate support facilities (such as base stations). The topology of an Ad-Hoc network changes due to the movement of mobile host. which may lead to sudden packet loss. Recently, a large amount of research has focused on the routing protocols needed in such an environment. but researches about Internet traffic performance analysis were unexhausted. Accordingly, we have simulated Ad-Hoc mobile network that using AODV routing protocol and Ad-Hoc mobile network topology size and node speed as simulation estimation-factor to analysis traffic performance. As the result of the simulation, we identify that TCP /Reno was more sensitive than TCP/Sack about node speed and a number of the node.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.509-512
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• 2007

The fire area need management to prevent enlargement of collapes and sinkage. and it need that repair Vegetation sack work, Soil arresting structure, Terrace-sodding works, Direct seeding works in greening works and Water cushion in erosion control dam. The whole of the Concrete stream grade stabilization structures were broken, it need to be repair. As pass the time, a lot of structures were abandoned. Therefore, it need to reorganize erosion control structures and the method of construction in the fire area