• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.425-431
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• 2011

The harmonic distortion level may be significant in electric propulsion systems, as the main loads usually are variable speed propulsion/thruster drives. Distortion of currents and supply voltage waveforms may lead to: Increased power dissipation(losses) in equipment connected to the network, such as generators, motors, transformers, cables, etc., from the harmonic currents, may cause overheating and deterioration of the insulation, and reduced life time of the equipment. In this paper introduced the canceling method of harmonic currents by a multipulse drive with phase shifting transformer. The simulation results indicated a good speed response to the middle speed range of electric propulsion motor. And also, THD(total harmonic distortion) and torque ripple could be reduced in comparing the 12-pulse drive with 6-pulse drive.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2121-2128
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• 2009

The application range of IEEE 802.11 wireless LAN has rapidly expanding from campus, enterprise to the public network of Hot Spot area due to the advantages of easiness of construction, mobility of wireless client station, convenience of usage and so on. However the security of WLAN(Wireless LAN) is vulnerable inherently because of using RF as a medium, and so the dangers of infringement of personal information and inside data of enterprises have increased and wardriving attack searching for security vulnerability in wireless LAN has become more serious especially. In this paper, we find out the overview of various procedures and preparatory stages for wardriving attack against wireless LAN, and propose complementary methods to prevent information infringement accidents from wardriving attack in wireless LAN. For this purpose, we make an equipment which is suitable for wardriving in wireless LAN and show security vulnerability of AP(Access Point) operation in WLAN around Yangjae-Dong in Seoul as a result of using the equipment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1948-1954
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• 2014

Advances in IT technology and modernization of AtoN(Aids to Navigation) facility has increased the unmanned operation of AtoN. However, in AtoN facilities, accessibility is low and it is not able to perform maintenance on the bad weather at the time. In connection with this, in this paper, by applying the protocol of the enhanced dual LED marine lantern, we implemented the short-range monitoring system for a mobile terminal. System implemented in this paper can be carried out confirm the operation status, inspection or control of the dual LED marine lantern at a short distance. Also, it is possible to reduce maintenance costs and prevent accidents during inspection of AtoN. At the same time, it enables the operation test easily without disassembling the product, effective AtoN operation is possible. We tested the system that has been implemented using prototype of the LED marine lantern and confirmed state informations and controlled the behavior of the system in real time.

• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.45-50
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• 2008

Mobile ad hoc networks (MANETs) allow mobile nodes to communicate among themselves via wireless multiple hops without the help of the wired infrastructure. Therefore, in the MANET, a route setup mechanism that makes nodes not within each other's transmission range communicate is required and, for this, the Ad-hoc On-demand Distance Vector (AODV) was proposed as one of the reactive routing protocols well suited for the characteristics of the MANET. AODV uses the hop count as the routing metric and, as a result, a node selects the farthest neighbor node as its next hop on a route, which results in a problem of deteriorating the overall network throughput because of selecting a relatively low data rate route. In this paper, we propose an efficient reactive routing protocol based on the multi-rate aware MAC. Through the simulations, we analyze the performance of our proposed mechanism and, from the simulation results, we show that our proposed mechanism outperforms the existing mechanism.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.481-481
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• 2007

This work describes the effect of the number of roll pressing and the composition of carbon black on the electric and mechanical properties of carbon-PTFE electrode, in which composition is MSP 20 : carbon black: PTFE = 95-x : x : 5 wt.%. It was found that the best electric and mechanical properties were obtained in sheet electrode roll-pressed for about 15 times and in sheet electrode, in which composition is MSP 20 : carbon black: PTFE = 80 : 15 : 5 wt.%. These behaviors could be explained by the network structure of PTFE fibrils and conducting paths linked with carbon blacks, respectively. On the other hand, cell capacitor using the sheet electrode with 15 wt.% of carbon black attached on aluminum current collector with the electric conductive adhesive, in composition is carbon black : CMC = 70 : 30 wt.%, has exhibited the best rate capability in the current range of $0.5mA/cm^2$ $100mA/cm^2$ and the lowest equivalent series resistance.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.170-170
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• 2000

Synthetic polymers such as polyimide, polycarbonate, and poly(methyl methacrylate) are long chain molecules which consist of carbon, hydrogen, and heteroatom linked together chemically. Recently, polymer surface can be modified by using a high energy ion beam process. High energy ions are introduced into polymer structure with high velocity and provide a high degree of chemical bonding between molecular chains. In high energy beam process the modified polymers have the highly crosslinked three-dimensionally connected rigid network structure and they showed significant improvements in electrical conductivity, in hardness and in resistance to wear and chemicals. Polyimide films (Kapton, types HN) with thickness of 50~100${\mu}{\textrm}{m}$ were used for investigations. They were treated with two different surface modification techniques: Plasma Source Ion Implantation (PSII) and conventional Ion Implantation. Polyimide films were implanted with different ion species such as Ar+, N+, C+, He+, and O+ with dose from 1 x 1015 to 1 x 1017 ions/cm2. Ion energy was varied from 10keV to 60keV for PSII experiment. Polyimide samples were also implanted with 1 MeV hydrogen, oxygen, nitrogen ions with a dose of 1x1015ions/cm2. This work provides the possibility for inducing conductivity in polyimide films by ion beam bombardment in the keloelectronvolt to megaelectronvolt energy range. The electrical properties of implanted polyimide were determined by four-point probe measurement. Depending on ion energy, doses, and ion type, the surface resistivity of the film is reduced by several orders of magnitude. Ion bombarded layers were characterized by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS), XPS, and SEM.

• Molecules and Cells
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• v.39 no.1
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• pp.65-71
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• 2016

A challenge in the redox field is the elucidation of the molecular mechanisms, by which $H_2O_2$ mediates signal transduction in cells. This is relevant since redox pathways are disturbed in some pathologies. The transcription factor OxyR is the $H_2O_2$ sensor in bacteria, whereas Cys-based peroxidases are involved in the perception of this oxidant in eukaryotic cells. Three possible mechanisms may be involved in $H_2O_2$ signaling that are not mutually exclusive. In the simplest pathway, $H_2O_2$ signals through direct oxidation of the signaling protein, such as a phosphatase or a transcription factor. Although signaling proteins are frequently observed in the oxidized state in biological systems, in most cases their direct oxidation by $H_2O_2$ is too slow ($10^1M^{-1}s^{-1}$ range) to outcompete Cys-based peroxidases and glutathione. In some particular cellular compartments (such as vicinity of NADPH oxidases), it is possible that a signaling protein faces extremely high $H_2O_2$ concentrations, making the direct oxidation feasible. Alternatively, high $H_2O_2$ levels can hyperoxidize peroxiredoxins leading to local building up of $H_2O_2$ that then could oxidize a signaling protein (floodgate hypothesis). In a second model, $H_2O_2$ oxidizes Cys-based peroxidases that then through thiol-disulfide reshuffling would transmit the oxidized equivalents to the signaling protein. The third model of signaling is centered on the reducing substrate of Cys-based peroxidases that in most cases is thioredoxin. Is this model, peroxiredoxins would signal by modulating the thioredoxin redox status. More kinetic data is required to allow the identification of the complex network of thiol switches.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.1
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• pp.24-51
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• 2011

When supporting both voice and TCP in a wireless multihop network, there are two conflicting goals: to protect the VoIP traffic, and to completely utilize the remaining capacity for TCP. We investigate the interaction between these two popular categories of traffic and find that conventional solution approaches, such as enhanced TCP variants, priority queues, bandwidth limitation, and traffic shaping do not always achieve the goals. TCP and VoIP traffic do not easily coexist because of TCP aggressiveness and data burstiness, and the (self-) interference nature of multihop traffic. We found that enhanced TCP variants fail to coexist with VoIP in the wireless multihop scenarios. Surprisingly, even priority schemes, including those built into the MAC such as RTS/CTS or 802.11e generally cannot protect voice, as they do not account for the interference outside communication range. We present VAGP (Voice Adaptive Gateway Pacer) - an adaptive bandwidth control algorithm at the access gateway that dynamically paces wired-to-wireless TCP data flows based on VoIP traffic status. VAGP continuously monitors the quality of VoIP flows at the gateway and controls the bandwidth used by TCP flows before entering the wireless multihop. To also maintain utilization and TCP performance, VAGP employs TCP specific mechanisms that suppress certain retransmissions across the wireless multihop. Compared to previous proposals for improving TCP over wireless multihop, we show that VAGP retains the end-to-end semantics of TCP, does not require modifications of endpoints, and works in a variety of conditions: different TCP variants, multiple flows, and internet delays, different patterns of interference, different multihop topologies, and different traffic patterns.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.621-627
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• 2008

This paper presents a compact and miniaturized power detector utilizing low temperature co-fired ceramics(LTCC) technology for the application in wireless handset system to monitor the transmitting power at the frequency of 824-849MHz. The proposed power detector is composed of detector diode, lumped components for matching network, and LTCC stripline coupler based on LTCC substrate technology. A 20dB LTCC stripline direction coupler is designed and implemented with many bending section in order to reduce the practically occupied area for miniaturization. A zero bias schottky diode is adopted for detector design because of its high speed operation with minimized loss. The measured performances of fabricated detector agree well with the predicted results with a good linearity within the effective input RF power range.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.5
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• pp.97-105
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• 2008

The micro capacitors are passive elements necessary to electronic circuits and wireless portable PAN(personal area network) and Mobile Communications device modules in the baseband circuits in combination with another passive and active devices. As capacitance is proportionally increased with dielectric constant and electrode areas, in addition, inversely decreased the thickness of the dielectric material, thus thin film capacitors are generally seen as a preferable means to achieve high performance and thin film capacitors are used in a variety of functional circuit devices. In this paper, propose dielectric material as AIN(Aluminium nitride) to make micro thin film capacitor, and this capacitor has the MIM(metal-insulator-metal) structure. AIN thin films are widespread applied because they had more excellent properties such as chemical stability, high thermal conductivity, electrical isolation and so on. In addition, AIN films show low frequency response for baseband signal ranges, I-V and C-V electrical characterization of a thin film micro capacitor. The above experimental test and estimated results demonstrate that the thin film capacitor has sufficient and efficient functional performance to be the baseband range frequency of general electronics circuit and passive device applications.