• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.130-134
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• 1999

In this paper, we introduce a modified interference cancellation scheme for multiuser detection in CDMA. This detector uses successive interference canceller(SIC) and the divided received signal concepts. The active users are splits into two groups large signal power group and small signal power group- throughout ranking, matched filter, decision, regeneration. And each group is subtracted from the received signal respectively to obtain good BER performance. Each of the resulting signal is become respectively SICs input signal The computer simulation and analysis of structure demonstrate that the proposed SIC keeps the SICs BER performance, complexity and reduces SICs delay time.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.86-90
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• 2014

A DC-DC Converter operates in CCM(Continuous Coundcution Mode), DCM(Discontinuous Conduction Mode), CRM(Critical Conduction Mode). The CRM is boundary between CCM and DCM. If a DC-DC converter is designed to operate in CRM, its inductor volume can decrease and power loss which caused by switch and diode can decrease. In this paper, the DC-DC converter which operates in CRM is applied to a solar array regulator(SAR) for the satellite. The switching frequency of the CRM boost SAR changes according to input and output condition. The switching frequency limit logic is applied to limit the maximum switching frequency. Meanwhile, the small signal transfer function of the CRM boost SAR is simple, so the controller design is also simple. In this paper, the small signal transfer function from control reference to solar array voltage is induced. And the voltage controller is designed based on the small signal transfer function. Finally, the CRM boost SAR is verified by simulation.

• Journal of the Korean Vacuum Society
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• v.20 no.5
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• pp.345-355
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• 2011

GaAs-based metamorphic high electron mobility transistors (MHEMTs) and InP-based high electron mobility transistors (HEMTs) have good microwave and millimeter-wave frequency performance with lower minimum noise figure. MHEMTs have some advantages, especially for cost, compared with InP-based ones. In this paper, InAlAs/InxGa1-xAs/GaAs MHEMTs are simulated for DC/RF small-signal analysis. The hydrodynamic simulation parameters are calibrated to a fabricated 0.1-${\mu}m$ ${\Gamma}$-gate MHEMT device having the modulation-doped $In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}As$ heterostructure on the GaAs substrate, and the simulations for RF small-signal characteristics are performed, compared with the measured data, and analyzed for the devices. In addition, the simulations for the DC/RF characteristics of the MHEMTs with different gate-recess structures are performed, compared and analyzed.

• Journal of Korea Multimedia Society
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• v.8 no.1
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• pp.46-55
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• 2005

In this paper, we realize the panoramic infrared warning system to detect the small threaten object and propose the infrared image enhancement method to improve the warning ability of this system. This system composes of the sense head unit, the signal processing unit, and so on. In the proposed system, the sense head unit acquires the panoramic IR image with 360 degree field of view(FOV) by rotating the thermal sensor. The signal processing unit divides panoramic image into four sub-images with 90 degree FOV and computes the adaptive plateau value by using statistical characteristics of each subimage. Then the histogram equalization is performed for each subimage by using the adaptive plateau value. We realize the signal Processing unit by using the DSP and FPGA to perform the proposed method in real time. Experimental results show that the proposed method has better discrimination and lower false alarm rate than the conventional methods in this warning system.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.231-239
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• 1998

This paper presents the dynamic analysis and control loop design of a zero voltage switching full bridge (ZVS-FB) PWM DC/DC converter. The small-signal model is derived incorporating the effects of phase shift control and the utilization of transformer leakage inductance and power FET junction capacitance to achieve zero voltage resonant switching. These effects are modeled by introducing additional feedforward and feedback terms for duty cycle modulation. Based on the results of the small-signal analysis, the control loop is designed using a simple two-pole one-zero compensation circuit. To show the validity of the design procedures, the small signal analysis of the closed loop system is carried out and the potential of the zero voltage switching and the superiority of the dynamic characteristics are verified through the experiment with a 2 kW prototype converter.

• Journal of Plant Biology
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• v.33 no.3
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• pp.211-215
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• 1990

There is a family of homologous proteins known to small GTP-inding proteins which have a GTP binding domains and GTPase activity with molecular weight of about 20000 in mammalian tissues. Recently at least 20 different small GTP-binding proteins including three rasproto-oncogene, smg25, rho, and ral gene products were identified. These proteins play a central role in cellular prolifration, neoplasia, signal transduction, terminal differentiation, and secretory process of the cells. In this review, I have briefly compiled current information on the different areas of research in the small GTP-binding proteins in an attempt to convey an overall view of the fundamental role that this family of protein in normal cellular processes. Moreover, furture goals of research in the small GTP-binding proteins as well as the possible existence of this family of proteins in plant cells were discussed.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.410-417
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• 2012

Currently domestic thermal and nuclear power plants are comprised of many type's condenser and steam generator tubes to produce the electricity of good quality. There are some methods to inspect these tubes in the event that several defects were discovered in these facilities. Among many non-destructive methods, we used guided wave to inspect the soundness of tubes, because this method is very fast to detect the defect and very simple to install the equipment and also, can inspect up to the long range at a fixed point. Also, this method has a drawback that does not detect a very small size defect. So, we made an effort to overcome this drawback through the experimentation and signal analysis according to the size and shape of the defect through the manufacture of various artificial cracks capable to generate within the small size tube in the study and we anticipate that these detect limits can be overcome along with the development of the signal processing and manufacturing technology of the sensor for the inspection.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.1
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• pp.129-139
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• 1989

During a signal is being transmitted, an interference signal can be introduced through an unknown channel. In these cases, an adaptive system, so called adaptive noise canceller, can restore the original signal from the corrupted signal by first identifying the unknown interference channel on the minimum mean square error criteron, and then by cancelling the interference signal using the identified interference channel. Whereas this method is quite effective when the a priori knowledges about the characteristics of the interference signal and of the intrference channel are unknown or time-varyng, but has a drawback that the presence of the original signal has a severe effect on the optimum value of the interference channel to be identified on the miniumum mean square eror criterion In this paper an adaptive noise canceller and its algorithms are introduced that can restore the original signal more accurately especially when the correlatedness between the original signal and the interference signal is small.

• Journal of Convergence for Information Technology
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• v.11 no.6
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• pp.1-6
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• 2021

In the field of speech recognition, as the DNN is applied, the use of speech recognition is increasing, but the amount of calculation for parallel training needs to be larger than that of the conventional GMM, and if the amount of data is small, overfitting occurs. To solve this problem, we propose an efficient method for robust voice feature extraction and voice signal noise removal even when the amount of data is small. Speech feature extraction efficiently extracts speech energy by applying the difference in frame energy for speech and the zero-crossing ratio and level-crossing ratio that are affected by the speech signal. In addition, in order to remove noise, the noise of the speech signal is removed by removing the noise of the speech signal with an average predictive improved LMS filter with little loss of speech information while maintaining the intrinsic characteristics of speech in detection of the speech signal. The improved LMS filter uses a method of processing noise on the input speech signal by adjusting the active parameter threshold for the input signal. As a result of comparing the method proposed in this paper with the conventional frame energy method, it was confirmed that the error rate at the start point of speech is 7% and the error rate at the end point is improved by 11%.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.1
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• pp.38-42
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• 2002

Conditions are discussed for operating a dissymmetric human master-small (or micro) slave system in best (large position gain-small velocity gain) conditions allowing higher operator dexterity when real effects (joint compliance, link flexion delay and transmission distortion) are taken into account. It is shown that position PD feedback law advantage for ideal case no longer holds, and that more complicated feedback law depending on real effects has to be implemented with adapted transmission line. Drawback is slowdown of master slave interaction, suggesting to use more advanced predictive methods for the master and more intelligent control law for the slave.