• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.3
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• pp.412-419
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• 2020

The strategic unit communication infrastructure for military command, communications requires a dualized network structure of various communication methods, considering the direction of development, strategic unit and line characteristic. It has been pointed out that MicroWave, which is typical of wireless systems, is inefficient because it operates only with existing technologies. Therefore, it is necessary to analyze the structure, efficiency of the MW transmission system and its effects. It is difficult to transfer efficiently considering wireless environment due to a fixed type of access structure in the existing MW transmission system. Adaptive modulation allows improvement, but with traditional access structures and fixed bandwidth, there is a limit. Following the transmission performance improvement technique considering availability and link distance in the previous study, this paper presented improved packetized MW transmission system structure and variable bandwidth transmission in consideration of adaptive modulation based variable transmission waveform, bandwidth and distance, and performed the analysis in view of the strategic unit and command control circuit.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.356-361
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• 2008

The conventional drive system of SRM has a current sensor per each phase. The torque demand signal generated by the outer control loop is translated into individual current reference signal for each phase. The torque is controlled by regulating these currents. Using the SRM in a variable-speed control, the phase currents are generally regulated to achieve a square wave. The simplest form of current regulation uses fixed frequency delta modulation of the phase voltages. The aim of this paper is to regulate 3-phases current of SRM by only single current sensor using delta modulation with digital chip. In this paper, the asymmetric bridge converter which is able to control independently phases and be excited simultaneously is used as the driver system for 6/4 poles SRM. And the current sensor is replaced 3 sensors of each phase with only one on bus line of converter so as to detect current of every phase. The proposed delta modulation technique has been implemented in a simple digital logic circuit using EPLD(Electrically Programmable Logic Device). This method is verified through simulation and experiment results.

• Current Optics and Photonics
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• v.4 no.4
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• pp.267-272
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• 2020

The propagation of a truncated Airy beam with spatial phase modulation (SPM) is investigated in Kerr nonlinearity with an optical lattice. Before the truncated Airy beam enters the optical lattice, a sinusoidal phase is introduced on the wave-front of the beam. The effect of the spatial phase modulation and optical lattice on propagation behavior is analyzed by direct numerical simulation. It is found that the propagation direction of a truncated Airy beam can be effectively controlled by adjusting the values of phase shift. The effects of optical amplitude, truncation factor, spatial modulation frequency, lattice period and lattice depth on the propagation are discussed in detail. By choosing a high modulation depth, the finite-energy Airy beam can be deflected with a large deflection angle in an optical lattice.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.1 s.145
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• pp.96-102
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• 2006

In this study, an optimization routine with genetic algorithms is coupled for the selection of free variables for the production of a control signal for the motion of wave board in the numerical wave tank. An excitation function for the controlling of the wave board is formulated on basis of amplitude modulation for the generation of nonlinear wave packets. The found variables by the optimization serve for the determination of wave board motion both with the computation and with the experiment. The breaking criterion of the water waves is implemented as boundary condition for the optimization procedure. With the analysis of the time registration on the local position in the wave tank the optimization routine is accomplished until the given design wave with defined surface elevation is found. Water surface elevation and associated fields of velocity and pressure are numerically computed.

• Journal of Biomedical Engineering Research
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• v.3 no.2
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• pp.105-112
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• 1982

Using electronic cochlear implant system, we studied in cats the difference in the response of the brain stem evoked response (BER) during the stimulation with the acoustic signals and the electric signals. These brain stem electric responses were analyzed using the integral pulse frequency modulation method of the auditory nervous system. Animal experimental results and the analysis show that the carrier wave hasimprored the frequency specificity. of the electronic auditory prosthesis.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1E
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• pp.43-47
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• 2000

The paper describes a theoretical study on the speed of torsional elastic waves propagating in a circular rod whose material properties vary periodically as harmonic functions of the axial coordinate. An approximate solution for the phase speed has been obtained by using the perturbation technique for sinusoidal modulation of small amplitude. This solution shows that the wave speed in the nonuniform rod is dependent on the wave frequency as well as the periodic variation of the material properties. It implies that the torsional waves considered in this paper are dispersive even in the fundamental mode.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1983.10a
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• pp.44-47
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• 1983

Through intensity modulation induced by micro bending of an optical fiber, a sensor detects the pressure and frequency of acoustic wave has been implemented. Axial slots on the cylinder suface with a period of 5.5 mm induce efficient microbending of the fiber, and a rubber sleeve covering the fiber enhances the fiber. Compared with a conventional hydrophone, it has a low minimum detectable pressure and can detect acoustic wave in 100Hz - 2KHz range.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.11
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• pp.896-904
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• 1989

PWM techniques which eliminate and reduce harmonics of output voltage in PWM Inverter driving System with fluctuating input volotage are described. First, harmonic factors are analyzed from harmonic equation of general PWM waveform and by examination of control possiblity of each factor, controllable factor is selected. Applying controllable factor to NPWM, PWM techniques using reference wave and carrier wave modulation are introduced. Actually, by the experiment applied with this strategy, the reduction of harmonics of output voltage is confirmed.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.651-658
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• 2012

This paper concentrates on the evaluation of microcracks in thermal damaged concrete on the basis of the nonlinear ultrasonic modulation technique. Since concrete structure exposed to high temperature accompanies the development of microcracks due to the physical and chemical changes from temperature and exposed time, the adoption of nonlinear approach is required. Instead of using the conventional ultrasonic nondestructive methods which have the limitation in evaluating excessive microcracks, accordingly, a nonlinear ultrasonic modulation method which shows better sensitivity in quantifying microcracks is introduced. Upon the analysis for the modulation of ultrasonic wave and low frequency impact to measure the nonlinearity parameter, which can be used as an indicator of thermal damage, the verification processes for the introduced technique are followed: SEM investigation and permeable pore space test are performed to characterize thermally induced microcracks in concrete, and ultrasonic pulse velocity tests are performed to confirm the outstanding sensitivity of nonlinear ultrasonic modulation technique. In advance, compressive strength of thermal damaged concrete is measured to represent the effect of microcracks on performance degradation. Correlation studies between experimental data and measured data show that nonlinear ultrasonic modulation technique can effectively be used to quantify thermally induced microcracks, and to estimate the compressive strength of thermally damaged concrete.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.3
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• pp.119-123
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• 2011

Carbon nanotilaments (CNFs) could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and$H_2$ as source gases under thermal chemical vapor deposition system. By the incorporation of $SF_6$ as a cyclic modulation manner, the geometries of carbon coils-related materials, such as nano-sized coil and wave-like nano-sized coil could be observed on the substrate. The characteristics (formation density and morphology) of as-grown CNFs with or without $SF_6$ incorporation were investigated. Diameter size reduction for the individual CNFs-related shape and the enhancement of the formation density of CNFs-related material could be achieved by the incorporation of $SF_6$ as a cyclic modulation manner. The cause for these results was discussed in association with the slightly increased etching ability by $SF_6$ addition and the sulfur role in SF 6 for the geometry change.