• The Journal of the Korea Contents Association
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• v.3 no.3
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• pp.11-18
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• 2003

Error diffusion is a procedure for generating high quality bilevel images from continuous-tone images but blurs the edge information. To solve this problem, we propose the improved method appling edge enhanced weights based on local characteristic of the original images. We consider edge information as local characteristic. First, we produce edges by appling 3$\times$3 sobel operator to the original image. The edge is normalized from 0 to 1. Edge information weights are computed by using sinusoidal function and the normalized edge information. The edge enhanced weights are computed by using edge information weights multiplied input pixels. The proposed method is compared with conventional methods by measuring the edge correlation and quality of the recovered images from the halftoned images. The proposed method provides better quality than the conventional method due to the enhanced edge and represents efficiently the detail edge. Also, the proposed method is improved in edge representation than the conventional method.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.1
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• pp.139-149
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• 1999

In this paper, we estimate the scale factor error and random walk characteristics of the ring laser gyro which has the body dither for Lock-in compensation. And then, we compared those results with the static test results for 28cm square ring laser gyro which has about 0.5 deg/sec static Lock-in. In the case of sinusoidal body dither, dynamic Lock-in occurs periodically at the points where the gyro output pulse becomes the integer multiples of body dither frequency. The width of dynamic Lock-in is changed by variation of dither amplitude, and, between the width of dynamic Lock-in which occurs at the even multiple points of body dither frequency and that at the odd muliple points of body dither frequency, it has 180o phase difference. Generally random body dither is adopted to compensate for dynamic Lock-in. Then if the irregularity is not large enough, the scale factor error by dynamic Lock-in is not vanished. And if the irregularity is large enough, the scale factor error decreases, but random walk becomes larger relatively. And we confirmed that the larger body dither amplitude, the smaller random walk.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2157-2163
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• 2010

This paper includes the study of DOA(Direction of Arrival). CVDF(Correlative Vector Direction Finding) algorithm using at the phase difference each antenna needs to obtain ideal sinusoidal phase difference patterns. However, the phase difference patterns of circular array antennas may be interfered on a specific frequency band and to particular angle. The effect of installing each array antenna circularly and the effect of the interference by center pole (located in the center of a circular array antennas) may distort the phase difference patterns. This paper propose how to change the combination of antennas to measure phase difference patterns in real-time and how to use antenna beam patterns for minimizing the degradation phenomena with old CVDF algorithm. According to the test result, the capability of direction finding is improved.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.6
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• pp.465-471
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• 2007

The system efficiency of the proposed Buck-Boost AC-DC converter is increased by soft switching method. The converter includes to merit of power factor correction (PFC) from sinusoidal control of input current. The switching behavior of control switches operates with soft switching by partial resonance, and then the proposed converter has high system efficiency with decrement of switching power loss. The input current waveform in proposed converter is got to be a sinusoidal form of discontinuous quasi-pulse row in proportion to magnitude of AC input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity. The output voltage of the converter is regulated by PWM control technique. The discontinuous mode action of current flowing into inductor makes to simplify control method and control components. The proposed PFC Buck-Boost converter is analyzed to compare with the conventional PFC Buck-Boost converter. Some computer simulative results and experimental results confirm to the validity of the analytical results.

• Korean Journal of Remote Sensing
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• v.29 no.4
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• pp.351-360
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• 2013

Harmonic analysis enables to characterize patterns of variation in MODIS NDVI time series data and track changes in ground vegetation cover. In harmonic analysis, a periodic phenomenon of time series data is decomposed into the sum of a series of sinusoidal waves and an additive term. Each wave is defined by an amplitude and a phase angle and accounts for the portion of variance of complex curve. In this study, harmonic analysis was explored to tract ground vegetation variation through time for land-cover vegetation change detection. The process also enables to reconstruct observed time series data including various noise components. Harmonic model was tested with simulation data to validate its performance. Then, the suggested change detection method was applied to MODIS NDVI time series data over the study period (2006-2012) for a selected test area located in the northern plateau of Korean peninsula. The results show that the proposed approach is potentially an effective way to understand the pattern of NDVI variation and detect the change for long-term monitoring of land cover.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.8 s.350
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• pp.6-12
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• 2006

Recently, according to the rapid development of mobile system, the development of relative mobile components has been required, and especially, with the miniaturization of mobile component, the complex with nearby components has been progressed. In this paper, multi-output VC-TCXO (Voltage Controlled-Temperature Compensated Crystal Oscillator) for WCDMA integrates the additional CMOS inverter, so it can be the normal clipped sinewave output and additional CMOS output, and also it can be satisfied the VC-TCXO's requirements for WCDMA system. And the important characteristics of reference oscillator, like phase noise and frequency short term stability, are satisfied with WCDMA(UMTS) system's requirement In this paper, however, 25MHz is used for reference frequency, similarly and practically, we think that it can be used from 10MHz to 40MHz.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.254-260
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• 2013

This paper deals with electromagnetic characteristics of IPMSM (Interior Permanent Magnet Synchronous motor) caused by field weakening current control. In order to extend operation speed, field weakening current control is generally used in IPMSM operation. During field weakening, distorted linkage fluxes are resulted by saturation of core material. Therefore, distorted input voltage waveform is required for sinusoidal current input. As the current vector angle increases for field weakening, distortion of linkage flux and back-emf becomes significant. This situation is analyzed by 2-dimensional finite element analysis and verified by experiment. With the results, it is concluded that motor parameters, such as linkage flux by permanent magnet, phase resistance, d-q axis inductance, are insufficient for estimating required voltage for given speed especially in field weakening and additional considerations for increased harmonics of voltage are required.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.4
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• pp.38-46
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• 1999

This paper discusses the repetitive tracking control method for a coarse-fine actuator. The proposed system is composed of a magnetic linear drive as a coarse actuator and a piezoelectric linear positioner as a fine actuator. In particular, nonlinear friction in a magnetic linear drive and hysteresis characteristic of a piezoelectric linear positioner are modeled first. The feedback linearization loop uses these models in tracking position control. The control strategy is then further extended to include a repetitive control algorithm in tracking periodic reference inputs. This repetitive controller is implemented on the existing PID controller augmented with feedback linearization loop. The experimental results show that performance in tracking sinusoidal waveforms is noticeably improved by augmenting a PID controller with feedback linearization loop and a repetitive controller together.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.1-14
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• 1996

The purpose of this paper is to analyze the performance of M-ary PSK communication system according to the types of electromagnetic interference in an impulsive noise environment. We have introduced Gaussian, sinusoidal and rectangular waves as a electromagnetic interference. Using the derived equations, we evaluated the error performance of the BPSK and QPSK system in the presence of electromagnetic interference and impulsive noise. From results, we have obtained that the Gaussian wave produced the most significant performance degradation and that sinusoidal wave produced more performance degradation than rectangular wave. Therefore, without knowing the types of electromagnetic interference, it is best to regard it as Gaussian wave when designing a communication system. In addition, we could found out that the error performance degrades as impulsive noise becomes strong and the error performance can not be improved significantly even the electromagnetic interference becomes weak. Therefore, this describes that the impulsive noise affects dominantly to the performance degradation.

• Composites Research
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• v.31 no.5
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• pp.276-281
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• 2018

In this paper, elastic behavior of woven fabric composites with various fiber yarn structure were predicted through a theoretical calculation model. A representative volume elements (RVE) that can represent the mechanical properties of the woven composites were selected and crimp angle of the weave yarn was defined by several sinusoidal functions. The effective material properties of the woven composite such as young's modulus, shear modulus and poisson's ratio was predicted by classical laminate theory (CLT). The fiber volume fractions were calculated according to the shape and pattern (plain, twill weave) of the fiber yarn, and the elastic behavior of each woven composite was obtained through a theoretical calculation model. Also, to verify the theoretical predictions, woven composite specimens of plain and twill weave were fabricated by vacuum assisted resin transfer molding (VARTM) process and then mechanical test was conducted. As a results, a good correlation between theoretical and experimental results for the elastic behavior of woven composites could be achieved.