• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2541-2546
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• 2009

In the anti-collision scheme proposed by EPCglobal Class-1 Gen-2 standard, the frame size for a query round is determined by Q-algorithm. In the Q-algorithm, the reader calculates a frame size without estimating the number of tags in it's identification range. It uses only the slot status. Therefore, the Q-algorithm has advantage that the reader's algorithm is simpler than other DFSA algorithms. However, the standard does not define an optimized parameter value for adjusting the frame size. In this paper, we propose the optimized parameter values for minimizing the identification time by various computer simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.756-758
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• 2010

Fixed frame size is used in the RFID system with the frame-based slot ALOHA algorithm. Therefore, it is anticipated that the tag identification performances will highly depend on the number of tags within the reader's identification range and the frame size. In this paper, we propose a tag number estimation scheme and analyze the performance with the computer simulations. The proposed scheme is based on the status of slots that the tags respond during a query round as well as the probabilistic calculations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.806-811
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• 2006

In RFID system, when multiple tags respond simultaneously, a collision can occur. A method that solves this collision is referred to as anti-collision algorithm. Among the existing anti-collision algorithms, SFSA, though simple, has a disadvantage that when the number of tags is variable, the system performance degrades because of the fixed frame size. This paper proposes a new anti-collision algorithm called DFSA which determines the optimal frame size using the number of collided slots at every frame. According to the simulation results, the tag identification time of the proposed algorithm is faster than that of SFSA.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.194-198
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• 2004

This paper presents a broadband compact microstrip antenna design with four U slots on the ground plane by using of genetic algorithm. FDTD method is used as fitness function for antenna analysis, and length of rectangular patch, length of ground plane slot, distance from center point to feed point is used as optimization parameter for maximum bandwidth and minimum size. The measurement result of implemented antenna present 10 dB bandwidth of 15.63 ％ and peak gain of 3.61 dBi in the 2.445 GHz, and antenna has a reduced patch size of 54.8 ％ compare with normal microstrip antenna.

• The korean journal of orthodontics
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• v.18 no.1 s.25
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• pp.155-163
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• 1988

The purpose of this study was to evaluate and compare frictional forces generated between orthodontic brackets and arch wires. Independent variables were chosen for study: arch wire size and shape, arch wire material, bracket width, and second-order angulation between bracket and arch wire. Kinetic frictional forces of stainless steel (0.014', 0.016', 0.018', 0.016' ${\times}$ 0.022', 0.018' ${\times}$ 0.022'), $\beta-titanium$ (0.016' ${\times}}$ 0.022') arch wires were measured on wide and junior edgewise twin brackets (0.018' ${\times}$ 0.022' slot). Instron was used to pull arch wires while $0^{\circ},\;3^{\circ},\;6^{\circ},\;or\;9^{\circ}$ angulation between and wire and bracket was given. The results were as follows: 1. The frictional force of $\beta-titanium$ wire was larger than that of stainless steel wire. 2. The frictional force was generally increased as the size of wire is increased. 3. The frictional force of rectangular wire was larger than that of round wire. 4. As second order angulation was increased, the frictional force was also increased. 5. The frictional force was larger on a wide bracket than on a junior bracket.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.9
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• pp.1883-1890
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• 2009

Existing MAC protocol can not show good performance in WMN environment. New MAC protocols is proposed because of Mobile Point's mobility, entire distributed environment, heavy traffic problems. This thesis proposes new channel contention method fur Mesh DCF. Mesh DCF uses ACH phase in TDMA frame to perform selection and elimination. Prioritized phases's count m and Fair Elimination phases's count n is determine contention level and make string probability to only one win the contention. Contention Number group's count K to determine the contention level in Fair Elimination Phase gives Fairness but make low probability to only one win the contention. It is sure that enough size of n and K can improve entire performance as result.

• Journal of Advanced Navigation Technology
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• v.20 no.5
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• pp.490-495
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• 2016

In the present study, a microstrip-fed monopole antenna is proposed for wireless local area network (WLAN) operations which cover dual band of 2.4 GHz (2.4 ~ 2.484 GHz) and 5 GHz (5.15 ~ 5.825 GHz). In order to obtain its compact structure and good omnidirectional radiation patterns, a modified inverted L-shaped slot separated from ground for impedance matching in 5 GHz band is etched on 2.4 GHz printed monopole antenna. The proposed antenna is designed and fabricated on a FR4 substrate with dielectric constant 4.3, thickness of 1.6 mm, and size of $30{\times}45mm^2$. The measured impedance bandwidths (${\mid}S_{11}{\mid}{\leq}-10dB$) of fabricated antenna are 270 MHz (2.22 ~ 2.48 GHz) in 2.4 GHz band and 890 MHz (5.08 ~ 5.97 GHz) in 5 GHz band respectively. In particular, high gain of more than about 4 dBi and good omnidirectional radiation patterns have been observed over the entire frequency band of interest.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.10-15
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• 2007

Small size and low profile antenna for mobile vehicular-top-mounted is needed in satellite communication services such as DBS, Satellite Internet and VSAT. In middle latitudes, the development of an array antenna which has the conformal, low profile and 45 degree beam tilted configuration, and has the high gain with sharp beamwidth, low sidelobe and low loss is required for Ku-band satellite communication. In this paper, in order to meet with these performances, an array antenna consisting of the vertical polarized waveguide longitudinal slots based on the leaky-wave mode of traveling wave antenna is proposed. An array antenna consisting of 16 leaky-wave elements is showing 30 dBi of gain, 4.9 degree of beamwidth, below than -20 dB of sidelobe level, 45 degree of beam tilt angle in center frequency. Feed network designed by waveguide cooperated feed shows good performance of wideband and low loss.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.7
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• pp.261-272
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• 2003

An Ethernet PON(Passive Optical Network) is an economical and efficient access network that has received significant research attention in recent years. A MAC(Media Access Control) protocol of PON , the next generation access network, is based on TDMA(Time Division Multiple Access) basically and can classify this protocol into a fixed length slot assignment method suitable for leased line supporting QoS(Quality of Service) and a variable length slot assignment method suitable for LAN/MAN with the best effort. For analyzing the performance of these protocols, we design an Ethernet PON model using OPNET tool. To establish the maximum efficiency of a network, we verify a MAC protocol and determine the optimal number of ONUs(Optical Network Unit) that can be accepted by one OLT(Optical Line Terminal) and propose the suitable buffer size of ONU based on analyzing the end-to-end Ethernet delay, queuing delay, throughput, and utilization.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.22-30
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• 2006

In this paper, a systematic design method on an IPMC(ionic polymer-metal composite)-driven ZNMF(zero-net-mass-flux) pump is introduced for the flow control of an MAV's (micro air vehicle) wing. Since the IPMC is able to generate a large deformation under a low input voltage along with its ability to operate in air, and is easier to be manufactured in a small size, it is considered to be an ideal material of the actuating diaphragm. Through the numerical methods, an optimal shape of the IPMC　diaphragm was found for maximizing the stroke volume. Based on the optimal IPMC diaphragm, a proto-type ZNMF pump with a slot, was designed. By using the flight speed of the MAV considered in this work, the driving frequencies(~ 40 Hz) of IPMC diaphragm, and the flow velocity through the pump's slot, the calculated non-dimensional frequency and the momentum coefficient ensure the feasibility of the designed ZNMF pump as a flow control device.