• 대한임베디드공학회논문지
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• 제16권5호
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• pp.233-240
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• 2021

We propose a novel, highly accurate approximate multiplier using different types of inexact 4-2 compressors. The importance of low hardware costs leads us to develop approximate multiplication for error-resilient applications. Several rules are developed when selecting a topology for designing the proposed multiplier. Our highly accurate multiplier design considers the different error characteristics of adopted compressors, which achieves a good error distribution, including a low relative error of 0.02% in the 8-bit multiplication. Our analysis shows that the proposed multiplier significantly reduces power consumption and area by 45% and 26%, compared with the exact multiplier. Notably, a trade-off relationship between error characteristics and hardware costs can be achieved when considering those of existing highly accurate approximate multipliers. In the image blending, edge detection and image sharpening applications, the proposed 8-bit approximate multiplier shows better performance in terms of image quality metrics compared with other highly accurate approximate multipliers.

• Smart Structures and Systems
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• 제23권3호
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• pp.215-225
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• 2019

In the present paper, the nonlocal strain gradient refined model is used to study the thermal stability of sandwich nanoplates integrated with piezoelectric layers for the first time. The influence of Kerr elastic foundation is also studied. The present model incorporates two small-scale coefficients to examine the size-dependent thermal stability response. Elastic properties of nanoplate made of functionally graded materials (FGMs) are supposed to vary through the thickness direction and are estimated employing a modified power-law rule in which the porosity with even type of distribution is approximated. The governing differential equations of embedded sandwich piezoelectric porous nanoplates under hygrothermal loading are derived through Hamilton's principle where the Galerkin method is applied to solve the stability problem of the nanoplates with simply-supported edges. It is indicated that the thermal stability characteristics of the porous nanoplates are obviously influenced by the porosity volume fraction and material variation, nonlocal parameter, strain gradient parameter, geometry of the nanoplate, external voltage, temperature and humidity variations, and elastic foundation parameters.

• Coupled systems mechanics
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• 제8권5호
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• pp.459-471
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• 2019

This paper presents post-buckling analysis of a functionally graded beam under hygro-thermal effect. The material properties of the beam change though height axis with a power-law function. In the nonlinear kinematics of the post-buckling problem, the total Lagrangian approach is used. In the solution of the problem, the finite element method is used within plane solid continua. In the nonlinear solution, the Newton-Raphson method is used with incremental displacements. Comparison studies are performed. In the numerical results, the effects of the material distribution, the geometry parameters, the temperature and the moisture changes on the post-buckling responses of the functionally graded beam are presented and discussed.

• ETRI Journal
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• 제43권1호
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• pp.152-162
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• 2021

In the last few years, detection has become a powerful methodology for network protection and security. This paper presents a new detection scheme for data recorded over a computer network. This approach is applicable to the broad scientific field of information security, including intrusion detection and prevention. The proposed method employs bidimensional (time-frequency) data representations of the forms of the short-time Fourier transform, as well as the Wigner distribution. Moreover, the method applies matrix factorization using singular value decomposition and principal component analysis of the two-dimensional data representation matrices to detect intrusions. The current scheme was evaluated using numerous tests on network activities, which were recorded and presented in the KDD-NSL and UNSW-NB15 datasets. The efficiency and robustness of the technique have been experimentally proved.

• International Journal of Computer Science & Network Security
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• 제21권2호
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• pp.40-43
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• 2021

In the article of instability on the peak power level, duration and repetition period of a multifrequency space-time signal, we calculated the maximum values of the errors of the parameters of the laws of spatial-phase-frequency control. Requirements for the accuracy of the location of the phase centers of the emitters in a cylindrical phased array antenna with pyramidal horns; it is advisable to calculate the radiation field using single-stage and multi-stage distribution laws. The phase centers of individual radiation sources of a cylindrical phased array antenna have been studied; they have almost no effect on the duration and period of recurrence.

• Journal of Information Processing Systems
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• 제18권6호
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• pp.755-762
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• 2022

The existing electrical engineering design method and the dynamic objective function in the application process of automatic control system fail to meet the unbounded condition, which affects the control tracking accuracy. In order to improve the tracking control accuracy, this paper studies the electrical engineering design method based on neural network and the application of automatic control system. This paper analyzes the structure and working mechanism of electrical engineering automation control system by an automation control model with main control objectives. Following the analysis, an optimal solution of controllability design and fault-tolerant control is figured out. The automatic control power coefficient is distributed based on an ideal control effect of system. According to the distribution results, an automatic control algorithm is based on neural network for accurate control. The experimental results show that the electrical automation control method based on neural network can significantly reduce the control following error to 3.62%, improve the accuracy of the electrical automation tracking control, thus meeting the actual production needs of electrical engineering automation control system.

• Coupled systems mechanics
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• 제13권2호
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• pp.171-186
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• 2024

In the present paper, thermal buckling characteristics of functionally graded rectangular plates made of porous material that are integrated with surface-bonded piezoelectric actuators subjected to the combined action of thermal load and constant applied actuator voltage are investigated by utilizing a Navier solution method. The uniform temperature rise loading is considered. Thermomechanical material properties of FGM plates are assumed to be temperature independent and supposed to vary through thickness direction of the constituents according to power-law distribution (P-FGM) which is modified to approximate the porous material properties with even and uneven distributions of porosities phases. The governing differential equations of stability for the piezoelectric FGM plate are derived based on higher order shear deformation plate theory. Influences of several important parameters on the critical thermal buckling temperature are investigated and discussed in detail.

• 대한전자공학회논문지TC
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• 제48권9호
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• pp.27-34
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• 2011

무선 통신 시스템의 효율을 높이기 위해 제안된 무선인지 (Cognitive Radio) 시스템은 2차 사용자가 주사용자 (primary user)의 스펙트럼을 서로 공유하는 시스템이다. 2차 사용자가 주사용자에게 간섭을 일으키지 않으면서 효율적으로 데이터를 전송하기 위해서 NC-OFDM (Non-contiguous Orthogonal Frequency Division Multiplexing)을 사용한다. 하지만 NC-OFDM은 기존 OFDM과 마찬가지로 높은 PAPR (Peak-to-Average Power Ratio)을 발생시켜 시스템 성능을 저하시킨다. 본 논문에서는 첫 번째로 NC-OFDM에서 부반송파의 분포에 따른 PAPR에 대해 분석하였다. 두 번째로 기존 OFDM의 PAPR 감소기법인 PTS (Partial Transmit Sequence)와 SLM (Selective Mapping)을 NC-OFDM에 적용하여 PAPR 감소성능을 확인하였다. 마지막으로 pruned-FFT가 적용된 PAPR 감소기법을 NC-OFDM에 적용할 경우 계산복잡도를 기존 OFDM과 비교하였다. 시뮬레이션을 통해 pruned-FFT가 적용된 NC-OFDM이 기존 OFDM보다 PAPR 감소성능 및 계산복잡도 측면에서 보다 효율적임을 검증하였다.

• 한국통신학회논문지
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• 제24권10A호
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• pp.1462-1470
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• 1999

본 논문에서는 레일레이 페이딩 채널 하에서 ALOHA방식을 이용한 패킷 무선망의 성능을 분석한다. 접속을 획득하고 접속률을 높이는 방안으로 켑춰효과를 이용하고 셀룰러 환경을 고려하기 위해서 트래픽 모델을 절단된 종형 분포로 가정한다. 논문에서 제안된 패킷 구조는 접속시 서로 충돌하는 확률을 줄여 채널처리용량을 향상시킬 수 있도록, 여러 사용자가 접속을 획득하기 위해 서로 경쟁하는 경쟁영역과 사용자의 데이터 정보가 들어있는 데이터 영역으로 나뉜다. 경쟁영역에서는 공통확산부호를 갖는 DS방식을 이용하여 신호를 전송하고 데이터 영역에서는 하이브리드 DS/FH방식을 이용하여 신호를 전송한다. BPSK 변조를 사용하였으며 수신기는 선형상관수신기와 hard-limiting상관수신기를 사용하였다. 하이브리드 DS/FH 방식은 간섭전력의 변화에 큰 영향을 받지 않으므로 비트 당 칩 개수 N과 도약 주파수의 수q의 값을 적절히 선택하면 간섭전력의 변화가 심한 환경에도 일정한 시스팀 성능을 얻을 수 있고 hard-limiting상관수신기를 이용함으로써 레일레이 페이딩과 같은 현상이 심한 환경에서 좋은 패킷 무선망의 성능을 얻을 수 있다.

• 한국응용과학기술학회지
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• 제33권1호
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• pp.118-128
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• 2016

대기오염에 관한 관심은 국내 외에서 점진적으로 상승하고 있으며, 자동차와 연료 연구자들은 청정(친환경 대체연료) 연료와 연료품질 향상 등을 이용하여 새로운 엔진 설계, 혁신적인 후 처리 시스템 등의 많은 접근을 통하여 차량 유해 배기가스를 감소시키려고 노력하고 있다. 이러한 연구들은 가솔린 자동차의 배출가스 및 가솔린 차량의 PM 입자 배출 등의 두 가지 이슈로 진행되고 있다. 자동차의 배출가스 및 PM(입자상 물질) 입자는 환경오염과 인체에 악영향을 주는 많은 문제를 일으키고 있다. 추가로, 함산소 첨가제로서 연료에 포함된 MTBE (Methyl Tertiary Butyl Ether)에 대한 환경 문제점을 연구하고 있다. 연구자들은 MTBE가 건강에 미치는 영향에 대한 많은 데이터를 가지고 있다. 이러한 데이터는 높은 MTBE 용량에서 잠재적인 발암 물질 임을 결론짓고 있다. 함산소 연료첨가제 유형 (MTBE, 바이오 ETBE, 바이오 에탄올, 바이오 부탄올)에 기초하여, 본 논문은 가솔린 연료 물성 및 증발가스 배출 특성에 대해 산소함량의 영향을 검토하였다. 또한, 연료물성에 대한 휘발유 차량의 가속 및 출력 성능을 평가하였다.