• 소성∙가공
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• 제3권2호
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• pp.215-228
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• 1994

The purpose of this paper is to pursue a general method to determine both the flow stress of a material and the friction factor by ring compression test. The materials are assumed to obey the expanded n-power hardening rule including the strain-rate effect. Ring compression is simulated by the rigid-plastic finite element method to obtain the database used in determining the flow stress and friction factor. The Simulation is conducted for various strain hardening exponent, strain-rate sensitivity, friction factor, and compressing speed, as variables. It is assumed that the friction factor is constant during the compression process. To evaluate the compatibility of the database, experiments are carried out at room and evaluated temperature using specimens of aluminum 6061-T6 under dry and grease lubrication condition. It is shown that the proposed test method is useful and easy to use in determining the flow stress and the friction factor.

• 대한전자공학회논문지SD
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• 제48권4호
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• pp.51-56
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• 2011

본 논문에서는 CAN 버스로드를 줄여 CAN 네트워크 비용을 줄이고 오류 확률을 낮추기 위해서 메시지를 압축하는 방법을 제안한다. 제안하는 비트 재배열 방법은 기존의 메시지 변화량만 전송하는 압축방식과 달리 각 변화량의 하위 비트들로부터 시작하여 전송데이터를 재구성하도록 하여 결과적으로 데이터가 압축되는 방법이다. 차량 CAN 로깅 파일을 이용하여 제안한 방법으로 압축한 결과 전송 데이터량이 기존 압축알고리즘에 비해 26% 더 감소함을 보였다.

• International Journal of Precision Engineering and Manufacturing
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• 제8권1호
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• pp.38-45
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• 2007

We propose a preprocessing method for removing floating particles from underwater images based on an analysis of the image features. We compared baseline JPEG and wavelet codec methods to determine the method best suited for underwater images. The proposed preprocessing method enhanced the compression ratio and resolution, and provided an efficient means of compressing the images. The wavelet codec method yielded better compression ratios and image resolutions. The results suggest that the wavelet codec method linked with the proposed preprocess method provides an efficient codec processor and transmission system for underwater images that are used for searches and transmitted via ultrasonic communications.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제2권1호
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• pp.38-42
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• 2002

A fast iterative solving method of fuzzy relational equation is proposed. It is derived by eliminating a redundant comparison process in the conventional iterative solving method (Pedrycz, 1983). The proposed method is applied to image reconstruction, and confirmed that the computation time is decreased to 1 / 40 with the compression rate of 0.0625. Furthermore, in order to make any initial solution converge on a reconstructed image with a good quality, a new cost function is proposed. Under the condition that the compression rate is 0.0625, it is confirmed that the root mean square error of the proposed method decreases to 27.34% and 86.27% compared with those of the conventional iterative method and a non iterative image reconstruction method, respectively.

• 대한전자공학회논문지SD
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• 제49권3호
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• pp.30-36
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• 2012

BTC 압축은 간단하고 효율적인 압축 알고리즘으로 알려져 있다. 본 논문에서는, 컬러 이미지 압축을 위한 RMC-BTC 알고리즘(RMC : reduction method chrominace data)을 제안한다. RMC-BTC coding은 chrominace data를 축소시키기 위해서, 각 BTC 블록에서, chrominace data를 평균으로 표현하는 방법과, luminance 데이터 의 bit-map을 chrominace 데이터의 bit-map으로 활용하여 chrominace 데이터를 표현하는 방법을 사용하였다. 시뮬레에션 결과는 기존의 BTC 알고리즘의 PSNR과 압축비율의 비교를 통해서, 제안한 알고리즘의 효율성을 확인하였다.

• 방송공학회논문지
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• 제19권2호
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• pp.174-183
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• 2014

본 논문에서는 다양한 재생환경에서 적응적으로 홀로그램 비디오를 서비스하기 위한 스케일러블 코딩 방법을 제안한다. 이 방법은 광원정보와 디지털 홀로그램 모두를 스케일러블 부호화 및 복호화에서 사용하는 방법으로, 복원된 영상의 해상도, 즉 영상의 크기를 스케일링하는 해상도-스케일러블 코딩 방법이다. 이 방법은 광원정보와 디지털 홀로그램 각각의 차영상을 압축하는 방식을 사용하고 있으며, 디지털 홀로그램의 차영상은 손실압축, 광원정보의 차영상은 무손실압축 방법으로 압축한다. 제안하는 방법을 실험한 결과 기존의 방법에 비해 압축률 대비 화질이 매우 우수하고, 특히 압축률이 증가할수록 기존방법보다 월등한 성능을 보였다.

• Journal of Mechanical Science and Technology
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• 제16권11호
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• pp.1379-1394
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• 2002

In case of a single input single output (SISO) system with a nonlinear term, a signal compression method is useful to identify a system because the equivalent impulse response of linear part from the system can be extracted by the method. However even though the signal compression method is useful to estimate uncertain parameters of the system, the method cannot be directly applied to a unique system with hysteresis characteristics because it cannot estimate all of the two different dynamic properties according to its motion direction. This paper proposes a signal compression method with a pre-processor to identify a unique system with two different dynamics according to its motion direction. The pre-processor plays a role of separating expansion and retraction properties from the system with hysteresis characteristics. For evaluating performance of the proposed approach, a simulation to estimate the assumed unknown parameters for an arbitrary known model is carried out. A motion platform with several single-rod cylinders is a representative unique system with two different dynamics, because each single-rod cylinder has expansion and retraction dynamic properties according to its motion direction. The nominal constant parameters of the motion platform are experimentally identified by using the proposed method. As its application, the identified parameters are applied to a design of a sliding mode controller for the simulator.

• 전기학회논문지
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• 제62권7호
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• pp.1003-1008
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• 2013

This paper proposes a compression scheme based on the modified reversible integer transform (MRIT) and forward adaptive prediction for lossless image compression. JPEG XR is the newest image coding standard with high compression ratio and that composed of the Photo Core Transform (PCT) and backward adaptive prediction. To improve the efficiency and quality of compression, we substitutes the PCT and backward adaptive prediction for the modified reversible integer transform (MRIT) and forward adaptive prediction, respectively. Experimental results indicate that the proposed method are superior to the previous method of JPEG XR in terms of lossless compression efficiency and computational complexity.

• 대한기계학회논문집
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• 제18권9호
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• pp.2386-2395
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• 1994

An experimental study on heat transfer and flow in compression molding of clss-B and A SMC(Sheet Molding Compounds) in a flat plate and a cross-sectional T-shape was carried out. The temperature was measured with thermocouples at two locations in the 4 layered SMC charge and pressure was measured at the center of the top mold during compression molding. Three different mold speeds, 15, 45, 50 mm/min and two different mold temperature, $130^{\circ}C{\;}and{\;}150^{\circ}C$ were used for compression molding experiments. Experiments with different colored SMC layers were used to study flow patterns at various compression stages. In oder to predict the pressure and load in SMC compression molding, slab method was used. The predicted values of pressure and load from the slab analysis were compared well with the measured data.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 1997년도 추계학술대회 발표논문집:21세기를 향한 정보통신 기술의 전망
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• pp.91-101
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• 1997

The demand for handling images in digital form has increased dramatically in recent years. Digital image compression is required to store and transmit mass information in different from general information. JPEG(Joint Photographic Experts Group) committee founded by CCITT and ISO is define the still-image standard compression/restoration algorithm. JPEG is proposed the standard of grayscale and color still-image compression/restoration. In the image quality, JPEG is applicable to the various applications in which compression is able to from 1/10 to 1/50 without the visible obstacle. In this paper, we proposed that the proposed method enhance the compression ratio which is reducing the higher frequency in order to increasing the spatial redundancy in the image. The proposed method is using the low pass filter in order to reducing the higher frequency. The low-pass filters are using the median filter and convolution filter in the spatial domain, FFT filter in the frequency domain. We acquired the additive compression ratio reducing the higher frequency using the low-pass filter.