• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3220-3226
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• 2011

In order to monitor internal risk factors such as fire, terror, etc. on the subway station, the surveillance systems using CCTV and various kinds of sensors have been implemented and recently, introduction of surveillance systems using an advanced IT technology, sensor network technology is tried on several areas. Since 2007, Korean government has made an effort to develop the intelligent surveillance and monitoring system, which can monitor fire, intrusion, passenger congestion, health-state of structure, etc., by using wireless sensor network technology and intelligent video analytic technique. For that purpose, this study carried out field wireless communication environment test on Chungmuro Station of Seoul Metro on the basis of ZigBee that is considered as a representative wireless sensor network before field application of the intelligent integrated surveillance system being developed, arranged and analyzed and ZigBee based wireless communication environment test results on the platform and waiting room of Chungmuro Station on this paper. Results of wireless spectrum analysis on the platform and waiting room showed that there is no radio frequency overlapped with that of ZigBee based sensor network and no frequency interference with adjacent frequencies separated 10MHz or more. As results of wireless data transmission test using ZigBee showed that data transmission is influenced by multi-path fading effect from the number and flow rate of passengers on the platform or the waiting room rather than effects from entrance and exit of the train to/from the platform, it should be considered when implementing the intelligent integrated surveillance system on the station.

• Applied Microscopy
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• v.23 no.2
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• pp.27-40
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• 1993

This study was taken to examine the light microscopic and ultrastructural changes of gill and kidney of female tilapia{Oreochromis niloticus) adapted in 0%o, 10%o, 20%o, and 30%o salt concentrations, respectively, by light, scanning and transmission electron microscope. The results obtained in these experiments were summarized as follows: Gill chloride cell hyperplasia, gill lamellar epithelial separation, kidney glomerular shrinkage, blood congestion in kidneys and deposition of hyalin droplets in kidney glomeruli, tubules were the histological alterations in Oreochromis niloticus. Incidence and severity of gill chloride cell hyperplasia rapidly increased together with increase of salinity, and the number of chloride cells in gill lamellae rapidly increased in response to high external NaCl concentrations. The ultrastructure by scanning electron microscope(SEM) indicated that the gill secondary lamella of tilapia(Oreochromis niloticus) exposed to seawater, were characterized by rough convoluted surfaces during the adaptation. Transmission electron microscopy(TEM) indicated that mitochondria in chloride cells exposed to seawater, were both large and elongate and contained well-developed cristae. TEM also showed the increased chloride cells exposed to seawater. The presence of two mitochondria-rich cell types is discussed with regard to their possible role in the hypoosmoregulatory changes which occur during seawater-adaptation. Most Oreochromis niloticus adapted in seawater had an occasional glomerulus completely filling Bowman's capsule in kidney, and glomerular shrinkage was occurred higher in kidney tissues of individuals living in 10%o, 20%o, 30%o of seawater than in those living in 0%o of freshwater, and blood congestion was occurred severer in kidney tissues of individuals living 20%o, 30%o of seawater than in those living in 10%o of seawater. There were decreases in the glomerular area and the nuclear area in the main segments of the nephron, and that the nuclear areas of the nephron cells in seawater-adapted tilapia were of smaller size than those from freshwater-adapted fish. Our findings demonstrated that Oreochromis niloticus tolerated moderately saline environment and the increased body weight living in 30%o was relatively higher than that living in 10%o in spite of histopathological changes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.149-158
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• 2006

We proposed a method for improving a performance of TCP downstream between a desktop PC as a fixed host and a PDA as a mobile host in a wired and wireless network based on IEEE 802.11x wireless LAN. With data transmission between these heterogeneous terminals a receiving time during downstream is slower than that during upstream by 20% at maximum. The reason is that their congestion window size will be oscillated due to a significantly lower packet processing rate at receiver compared to a packet sending rate at sender. Thus it will cause to increase the number of control packets to negotiate their window size. To mitigate these allergies, we proposed two distinct methods. First, by increasing a buffer size of a PDA at application layer an internal processing speed of a socket receive buffer of TCP becomes faster and then the window size is more stable. However, a file access time in a PDA is kept nearly constant as the buffer size increases. With the buffer size of 32,768bytes the receiving time is faster by 32% than with that of 512bytes. Second, a delay between packets to be transmitted at sender should be given. With an inter-packet delay of 5ms at sender a resulting receiving time is faster by 7% than without such a delay.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2394-2402
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• 2017

The frequency selective fading by multipaths determines a performance of underwater acoustic communication system in shallow littoral ocean. In this study, a characteristics of underwater acoustic channel and performance of multi-carrier system is evaluated in littoral ocean with a 50m deep water, an effective wave height of 0.5m and sandy mud bottom near Busan city. A multipath delay spread and time and frequency domain are presented as a function of a transmitter-to-receiver range. A bit-error-rate of a 5 channel 4FSK(Frequency Shift Keying) with a transmission rate of 1kbps, is examined and RS(Reed-Solomon) code is also adopted to remove a burst error due to time domain fading. A number of multipath are less than four and a bit-error-rate is decreased as an increase of a transmitter-to-receiver range which gives a congestion of multi-paths resulting in a decrease of time and frequency domain fading. The measured bit-error-rate is about 10-4 at greater than 600m of transmitter-to-receiver range.

• 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.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.1
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• pp.12-21
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• 2012

IEEE 802.11 MAC protocol standard, DCF(CSMA/CA), is originally designed to ensure the fair channel access between mobile nodes sharing the local wireless channel. It has been, however, revealed that some misbehavior nodes transmit more data than other nodes through artificial means in hot spot area spreaded rapidly. The misbehavior nodes may modify the internal process of their MAC protocol or interrupt the MAC procedure of normal nodes to achieve more data transmission. This problem has been referred to as a selfish node problem and almost literatures has proposed methods of analyzing the MAC procedures of all mobile nodes to detect the selfish nodes. However, these kinds of protocol analysis methods is not effective at detecting all kinds of selfish nodes enough. This paper address this problem of detecting selfish node using Tsallis-Entropy which is a kind of statistical method. Tsallis-Entropy is a criteria which can show how much is the density or deviation of a probability distribution. The proposed algorithm which operates at a AP node of wireless LAN extracts the probability distribution of data interval time for each node, then compares the one with a threshold value to detect the selfish nodes. To evaluate the performance of proposed algorithm, simulation experiments are performed in various wireless LAN environments (congestion level, how selfish node behaviors, threshold level) using ns2. The simulation results show that the proposed algorithm achieves higher successful detection rate.

• Journal of Veterinary Clinics
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• v.26 no.6
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• pp.591-594
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• 2009

Acute and massive death was noted in 10-week-old chickens, broiler breeder, housed in the floor pens. The number of dead chickens exceeded 20 birds each day. Grossly, fibrinous peritonitis with adhesion of mesenteries and intestinal organs was noted. The ceca were enlarged, expanded, and thickened with congestion. Cecal lumen was distended with a caseous core composed of serous, fibrinopurulent, and hemorrhagic exudates with desquamated masses of epithelial cells. The liver had multifocal white irregular necrotic foci surrounded by a raised ring. Light and electron microscope revealed Histomonas meleagridis in the liver with its characteristic structures and not in the intestinal mucoca and submucosa. In this case, the examination of parasite, larvae and egg was conducted more carefully; however, we could not find eggs or worms of Heterakis gallinarum in the dead or live chickens and earthworms in the soils of floor pens. Therefore, we concluded that an outbreak of blackhead disease probably occurred by direct transmission of histomonads from chickens to chickens in this case.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.28-37
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• 2017

Multipath TCP (MPTCP), which is a layer 4 protocol that can get the reliability and the efficiency of the transmission by using multipath transfer, was standardized by the IETF. MPTCP provides superior performance when compared to a single TCP when used in a homogeneous network with similar network characteristics. However, MPTCP degrades performance when used in heterogeneous networks with different network characteristics. In this paper, we propose 'Delay-alerted path-blocking scheduler'. It measures the delay of each path and blocks the path with a long delay to reduce the order of packets in the receive buffer. If the duplicated packet is sent to the blocked path to measure the delay and the congestion on the blocking path is reduced, the blocked path is unblocked. For performance analysis, the proposed scheduler was implemented in the Linux kernel and improved performance was obtained in the test bed. We also confirmed that the proposed scheduler reduces the degradation of MPTCP performance in real wireless networks with heterogeneous path characteristics.

• 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.

• International Journal of Highway Engineering
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• v.7 no.4 s.26
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• pp.151-162
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• 2005

Variable Message Sign (VMS), which provides drivers with direct information about state of traffic congestion and for prevent an accident, is the most effective method among the methods of providing information in Advanced Transportation Management System. Currently establishment and the VMS which is operated foundation lets in Guidelines on the use of Variable message sign (a book of the VMS) of 1999 November the Ministry Construction & Transportation, these contents mean main viewpoint on physical part such as message special quality variable (font, character size and line space, word interval) and position mainly among standard about establishment in general. But, it is true that using without effect verification on the character of VMS display and that using mode of stationary-centered. In this paper, it executed significance test to effort verification on the character of VMS display for more practical and effective information transmission based on the driver viewpoint For the researches; develop 3D-Simulation, select characteristics of driver's visual cognition behavior (the conspicuity, the legibility and the comprehensibility), evaluation each issue (day or night, 80km/h or 100km/h). Especially, that used the Eye Marker Recorder to measure of reading-time (legibility) thus, confirmed objectivity and reduce an observational error. The results showed that the conspicuity is Flashing> Stationary>Scroll. The legibility is not deference that Flashing between stationary form. Also the comprehensibility result showed that Flashing> Stationary>Stroll form.