• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.657-667
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• 2012

In the MPR selection algorithm of Optimized Link State Routing (OLSR), each node selects own MPRs independently, so most of nodes are selected to MPR at least once. To cope with this problem, the MPR candidate selection algorithm was proposed. The MPR candidate selection algorithm can reduce the number of MPRs, but the efficiencies of route and connectivity decline due to decreased number of MPRs. So, in this paper, we propose the Significant Multi-Point Relay (S-MPR) selection algorithm which can enhance the performance of ad hoc network by improving the MPR selection algorithm of OLSR. In proposed S-MPR selection algorithm, each node selects the most important node to S-MPR to guarantee the connectivity then selects remaining MPRs in MPR candidates. So proposed S-MPR selection algorithm can reduce the overhead of many MPRs without decline of routing performance. To show the performance gain of proposed S-MPR selection algorithm, we simulate the proposed S-MPR selection algorithm by using OPNET.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8B
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• pp.797-804
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• 2009

Recently, SIP(Session Initiation Protocol) is used to set up and manage sessions for multimedia applications such as VoIP(Voice over IP) and IMS(IP Multimedia Subsystem). However, because SIP operates over the Internet, it is exposed to pre-existed internet security threats such as service degradation or service disruptions. Multimedia applications which are delay sensitive even suffers more from the threats mentioned above. The proposed methods so far to detect SIP INVITE flooding are CUSUM(Cumulative Sum), Hellinger distance and adaptive threshold, but among methods only take normal state into consideration. So, it is not capable of adapting the condition of the network congestion which are dynamically changing. In this paper, SIP INVITE flooding detection algorithm considering network congestion which enables efficient detections of such attacks is proposed. The proposed algorithm is expected to detect other types of attacks such as BYE and CANCEL more precisely compared to other methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.239-246
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• 2014

In the context of wireless sensor networks, one of major issues is energy conservation. For low power communication, by utilizing our experimental results for the relation between clock drift and synchronization interval, we designed a new protocol which can support a wide range of duty cycles for applications with very low traffic rate and insensitive delay. The transmission (TX) node in the protocol synchronizes with the reception (RX) node very before transmitting a packet, and it can adaptively estimate the synchronization error size according to the synchronization interval from minutes to hours. We conducted simulations and a testbed implementation to show the efficacy of the proposed protocol. We found that our protocol substantially outperforms other state-of-the-art protocols, resulting in order-of-magnitude increase in network lifetime over a variety of duty cycles.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.2
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• pp.45-49
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• 1999

A flammable gas sensor based on the $SnO_2$thin film deposited by the reactive ion assisted deposition was fabricated and ultra-thin Pd layer as catalyst was adsorbed at surface by ion beam sputtering. The initial oxidation states of Pd catalyst were controlled to investigate the role of Pd in the sensing process of inflammale gas sensor through annealing in air and vacuum respectively. The Pd catalyst existing in pure metallic state showed the sensitivity higher than that of PdO. The result might be closely related to the fact that PdO as a surface acceptor would receive electrons via Pd sub-channel from $SnO_2$, and thus which reduces the sensitivity and delay the response time.

• Tuberculosis and Respiratory Diseases
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• v.42 no.5
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• pp.777-780
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• 1995

Salmonellosis is one of communicable disease and still occur in sporadic in Korea frequently. They are four main clinical manifestations in salmonellosis. They are gastrocnteritis, typhoidal or septisemia syndrome, focal manifestation and carrier state. Among them, focal manifestation is rarely seen. Saphra, et al. reported that localized salmonella infection is about 5%. Localized salmonella infection frequently occur during salmonella bacteremia, but may also occur with enteric fever or gastroenteritis. Gray, et al reported 3390 cases of minor gunshot wound infection that bacterial isolates from infected wounds consisted of Staphylococcus aureus(90%), Streptococcus sp.(6%), and mixed organisms(4%). Incresed host susceptibility to infection secondary to lowered resistance due to debilitating disease is an important determinant of Salmonella infection. Since salmonella is seldom suspected as a cause of soft tissue infections, there is usually a dangerous delay in the institution of appropriate antimicrobial therapy and isolation procedure. We experienced one case of subcutaneous salmonella abscess developed on gunshot wound area in lung cancer patient, which was confirmed by pus culture.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12B
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• pp.1058-1065
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• 2008

In the Internet, as computer resource is developed, multimedia data request being increase more and more. It is effective way that process both high capacity-data and real-time data. Overlay Multicast is an effective method for efficient utilization of system resources and network bandwidth without using hardware customization. Overlay Multicast is an effective method for multimedia data service to multi-users. Multicast tree reconstruction is required when a non-leaf host leaves or fails. In this paper, relay-frame interval is selected as revealed network-state with jitter. In our proposal, multi-user service control algorithm gives a delay effect in multimedia request time. The simulation results show that our proposal takes shorter period of time than the other algorithms to reconstruct a similar tree and that it is a more effective way to deal with a lot of nodes that have lost their multi-user nodes.

• Journal of Power Electronics
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• v.16 no.1
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• pp.297-309
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• 2016

Grid-connected inverters (GCIs) with an LCL output filter have the ability of attenuating high-frequency (HF) switching ripples. However, by using only grid-current control, the system is prone to resonances if it is not properly damped, and the current distortion is amplified significantly under highly distorted grid conditions. This paper proposes a synchronous reference frame equivalent proportional-integral (SRF-EPI) controller in the αβ stationary frame using the parallel virtual resistance-based active damping (PVR-AD) strategy for grid-interfaced distributed generation (DG) systems to suppress LCL resonance. Although both a proportional-resonant (PR) controller in the αβ stationary frame and a PI controller in the dq synchronous frame achieve zero steady-state error, the amplitude- and phase-frequency characteristics differ greatly from each other except for the reference tracking at the fundamental frequency. Therefore, an accurate SRF-EPI controller in the αβ stationary frame is established to achieve precise tracking accuracy. Moreover, the robustness, the harmonic rejection capability, and the influence of the control delay are investigated by the Nyquist stability criterion when the PVR-based AD method is adopted. Furthermore, grid voltage feed-forward and multiple PR controllers are integrated into the current loop to mitigate the current distortion introduced by the grid background distortion. In addition, the parameters design guidelines are presented to show the effectiveness of the proposed strategy. Finally, simulation and experimental results are provided to validate the feasibility of the proposed control approach.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.65-74
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• 2012

The QoS guarantee for the forward link in satellite communication networks is very important because there are a variety of packets with multiplexing. Especially, the packets are processed depending on the available bandwidth in satellite network changing the wireless channel state in accordance with weather condition. The DVB-S2 increases the transmission efficiency by applying the adaptive coding and modulation (ACM) techniques as a countermeasure of rain attenuations. However, the channel estimation algorithm is required to support the ACM techniques that select the MODCOD values depending on the feedback data transmitted by RCSTs(Return Channel via Satellite Terminal) because satellite communication networks have a long propagation delay. In this paper, we proposed the channel estimation algorithm using rain attenuation values and reference data and the packet scheduling scheme to support the QoS and fairness. As a result of performance evaluation, we showed that proposed algorithm exactly predicts the channel conditions and supports bandwidth fairness to the individual RCST and guarantees QoS for user traffics.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1585-1592
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• 2015

Currently, the existing schedule management of ship repair has depended on hand-written notes of engineering manager in the repair ship yard. Simple management based on the hand-written notes is inefficient because current states of equipments and staff are not graspable in real-time. To solve this problem, the ICT based scheduling method is required in ship repair industry. In this paper, we propose a system based on ICT which manages schedules for repairing ships. The proposed system solves the problem occurred by the management to use the hand-written notes. Because the system has a function to report the current state of ship repair, it is able to cope with various problems, such as delay, wrong repair and so on. Moreover, the system is able to maximize the efficiency of ship repair process due to efficient management to staff and equipment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.7
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• pp.1411-1421
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• 2009

As the wireless internet grows exponentially, the recent trend has an increasing demand for wireless network and multimedia services. RTP is used to support the multimedia communication over the Internet and it supports the flexibility and adaptability over a wide range. However, RTP has a limitation that it cannot support end-to-end QoS guarantee in a wireless home network which has low throughput and high delay. In this paper, we propose the architecture of a real-time multimedia communication and design and implement the hybrid flow control in the architecture. The hybrid flow control mechanism is based on modified AIMD using metrics such as the network state information and the user properties. We implement the porposed flow control using JMF to evaluate the performance of the proposed flow control. The experimental results show that the proposed flow control has better performance than the AIMD.