• The KSFM Journal of Fluid Machinery
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• v.13 no.4
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• pp.11-17
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• 2010

The developed control valves, installed on the hot water distribution manifolds for the floor heating system, consist of the balancing valves and the shut-off valves. The balancing valve was designed to improve the flow control performance and to reduce the noise emitted from the valve by modification of the general V port. The port of the shut-off valve was designed with two ceramic plates, working by rotating upper plate, to improve the duration and to reduce the noise. For the evaluation of the new valves, the flow rate was measured and noise level test was carried out. The test results showed that the error of the flow rate accuracy test for the flow balance of each manifold circuit was less than ${\pm}3%$ and the noise level was less than 35 dB(A).

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.2
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• pp.80-88
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• 1988

As a method to improve harmonics in the voltage source PWM inverter, 5 level stair case wave method is used. The complementary transistor inverter (CTI) bridge circuit has this characteristics. This circuit required synchronous type 3 level PWM signal. In this paper, the 3 phase PWM digital signals within about 10 modulation error of the natural sampling was caculated, and a ROM table out of it for the digital signal of the control system was made. According to this table, the digital control method was proposed, and DTI circuit operated by this method was reviewed. It was confirmed to make V/F control possible by the select modulation ratio to the frequency.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2470-2472
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• 2001

This paper describes the application of a fuzzy-tuning PID controller to a 3-DOF attitude control of a small model helicopter in hover for the compensation of coupling effects between each axis and system uncertainties due to the variation of engine RPM. A Low-level PID controller is designed by Ziegler-Nichols method and its gains are tuned by a high-level fuzzy system based on error states and its time derivatives. The experimental results show that the attitude control performance of fuzzy-tuning PID controller is improved comparing with that of a Ziegler-Nichols PID controller and fuzzy controller.

• Electrical & Electronic Materials
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• v.8 no.5
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• pp.633-639
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• 1995

Dropouts in magnetic media are a primary quality deficiency which is detrimental to magnetic signal quality and thus the major impediment to error-free recording, especially in high density digital recorders. The specific form of defects and causes found to be responsible for signal dropouts occurring in magnetic tape were studied. Dropout occurred when the RF signal falls to low level due to the various types of surface defects. However, the fall in the level of the RF signal in gravure roll coated tapes was most often caused by foreign particles adhering to the magnetic tape. It was also shown from the present study that scattered particles trapped under the tape surface or put on the top can lift it as it crosses the head, creating a spherical tent shaped defect and causing a temporary signal drop. Dropout producing substances were identified through optical and microchemical analyses. The results were correlated with measured electrical signal losses combined with analytical microscopy to clarify source identification of defects.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.389-395
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• 2000

It is usually the contractual responsibility of HRSG(Heat Recovery Steam Generator) supplier to limit combustion turbine exhaust noise at cogeneration sites. Thus, it is necessary to predict the noise level from HRSG at the stage of preliminary design. HRSG is usually composed of inlet duct, main casing, outlet duct, stack. To satisfy the noise limit level, additional equipments are sometimes required - duct shroud, silencer. We develop algorithms for predicting the noise emission from all these equipments of HRSG units. For the convenience of user, we develop the GUI window version program, named NP-HRSG program. To evaluate the accuracy of this program, predicted noise levels from a real HRSG model are compared with measured data. Through this comparison, we observe that the maximum error is just about 3dB.

• Earthquakes and Structures
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• v.12 no.4
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• pp.389-395
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• 2017

In this paper a simple approach is presented for spectral matching of ground motions utilizing the wavelet transform and a recently developed metaheuristic optimization technique. For this purpose, wavelet transform is used to decompose the original ground motions to several levels, where each level covers a special range of frequency, and then each level is multiplied by a variable. Subsequently, the vibrating particles system (VPS) algorithm is employed to calculate the variables such that the error between the response and target spectra is minimized. The application of the proposed method is illustrated through modifying 12 sets of ground motions. The results achieved by this method demonstrate its capability in solving the problem. The outcomes of the VPS algorithm are compared to those of the standard colliding bodies optimization (CBO) to illustrate the importance of the enhancement of the algorithm.

• ETRI Journal
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• v.43 no.4
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• pp.728-745
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• 2021

Carbon nanotube field-effect transistors (CNTFETs) have been widely studied as a promising technology to be included in post-complementary metal-oxide-semiconductor integrated circuits. Despite significant advantages in terms of delay and power dissipation, the fabrication process for CNTFETs is plagued by fault occurrences. Therefore, developing a fast and accurate method for estimating the reliability of CNTFET-based digital circuits was the main goal of this study. In the proposed method, effects related to faults that occur in a gate's transistors are first represented as a probability transfer matrix. Next, the target circuit's graph is traversed in topological order and the reliabilities of the circuit's gates are computed. The accuracy of this method (less than 3% reliability estimation error) was verified through various simulations on the ISCAS 85 benchmark circuits. The proposed method outperforms previous methods in terms of both accuracy and computational complexity.

• Proceedings of the Korean Society of Computer Information Conference
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• 2024.01a
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• pp.387-390
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• 2024

본 논문에서는 효율적인 2차 오차 함수를 이용하여 입자 기반에서 EMC(Extended Marching Cubes) 알고리즘을 구현할 수 있는 새로운 알고리즘을 제안한다. Smoothing 커널(Kernels)을 통해 계산한 입자 평균 위치에서 레벨셋(Level-set)을 계산해 스칼라장을 구축한다. 그리고 난 뒤 SPH(Smoothed particle hydrodynamics)기반의 커널을 통해 밀도, 입자 평균 위치를 계산한다. 스칼라장을 이용해 등가 곡면(Isosurface)을 찾고 음함수로 표현된 표면을 구성한다. SPH 커널을 공간에서 미분하면 공간상의 어느 위치에서나 기울기를 계산할 수 있고, 이를 통해 얻어진 법선벡터를 이용하여 일반적인 EMC나 DC(Dual contouring)에서 사용하는 2차 오차 함수를 효율적으로 설계한다. 결과적으로 제안하는 방법은 메쉬와 같이 연결정보다 없는 입자 기반 데이터에서도 EMC 알고리즘을 구현하여 볼륨(Volume) 손실을 줄이고, 복잡한 음함수 표면을 표현할 수 있게 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.77-85
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• 2009

This paper proposes an efficient system level simulation method for MIMO-OFDM based system in the multi-cell environment. The proposed method analyzes effects of the cell structure, radio channel characteristics and user mobility. The user mobility effect on the system level performance is considered in both channel gain and distance. The receiver SINR calculation procedure is presented in the system which adopts MIMO-OFDM scheme under various system environments. This method can be flexibly extensible to various system environments and provides computationally efficient system level simulation technique which utilizes link level performance analysis. Extensive computer simulations results are presented to obtain the system performance in the various mobile cellular channels using the proposed method. Also this results are analyzed based on the packet error rate for different distances between the base station located in the center of the cell and the mobile user.

• Journal of Navigation and Port Research
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• v.29 no.4
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• pp.327-333
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• 2005

Sea level (MSL, MHWL, or MLWL) change has been main concern to scientists and engineers and it can be primarily due to both change of climate and vertical movement of land. This paper reports the intensive analysis of the sea level changes and broad discussion of the future at the southwestern coast of Korean peninsula. Regression analysis was conducted to investigate general tendency and periodicity of the sea levels at the six different study sites such as Gunsan-I(inner port), Gunsan-O(outer port), Mokpo, Yeosu, Heuksan and Jeju and the results were compared with global values. Besides the changes of sea levels due to global warming, the influence of the man-made structure such as seadike and seawall was attempted to quantify using the minimization of the Root Mean Square(RMS) error. The results show that it is a general tendency that the values of mean sea level rise at the southwestern coast of Korean Peninsula, especially at Gunsan-I and Jeju, are somewhat larger compared to global average values. There is also some evidence that tidal amplifications are found just after construction of man-made structure at Gunsan-I and Mokpo. However, both sites show different mechanism in relation to tidal choking, tidal flat and river discharge. The impact due to construction of man-made structure is considerably larger at Mokpo site, while the impacts due to man-made structure and the effect of sea level rise are relatively identical at Gunsan-I site. This study is expected to provide some intuition to future design.