• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송∙미디어공학회 2021년도 하계학술대회
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• pp.78-80
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• 2021

In this paper, we proposed an improved method on the picture order of coding (POC) of MPEG-5 Essential video Coding (EVC) encoder to support a short intra period for Video-based Point Cloud Compression (V-PCC). As a codec-agnostically designed standard, V-PCC claimed to be able to work with a lot of codecs. Current EVC test model software shows that the baseline profile could not provide appropriate POC calculation. The proposed method offers a solution to this POC-related problem and provides up to 44.6% coding grains for EVC based V-PCC.

• 지구물리와물리탐사
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• 제12권1호
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• pp.77-84
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• 2009

GPR 탐사는 천부 지하 대상체 탐지에 유용한 방법이다. 그러나 다수의 GPR 적용사례에서 보여지듯이 천부 대상체에 의한 신호들은 지표에 의한 강한 반사파에 묻혀서 나타난다. 따라서 대상체에 의한 반사파를 이러한 강한 신호로부터 분리해낼 수 있는 신호처리 기법의 적용이 요구된다. 이 연구에서 사용된 파형압축기법은 신호의 폭을 압축시키는 것으로 심하게 오염되어 흐트러진 파형들로부터 신호를 분리해내는 방법이다. 이 논문에서는 위너필터링 (Wiener filtering) 기법을 사용하여 GPR 자료의 파형압축을 수행하는 자료처리방법을 소개하였다. 이 필터는 매설된 관로 위에서 얻어진 수치모형자료 및 현장 GPR 자료에 적용되었다. 이 분별방법은 강한 지표반사로부터 대상체의 반사신호를 구분해 내는 것과 파형압축을 위한 기준신호로서의 지표반사를 분리해 내기 위한 두 곳 모두에 사용 되었다. 파형압축 필터에 있어서 기준신호의 선정은 매우 중요한 문제이다. 그 이유는 특별히 기준신호의 신호대 잡음비가 낮을 경우 신호의 복이 압축될수록 잡음수준이 증가하게 되기 때문이다. GPR 수치모형자료와 현장 자료에 적용시킨 결과 GPR 영상의 눈에 띄는 개선을 보여주었다 즉, 지표반사파와 대상체에 의한 반사파의 구별이 뚜렷해지고 이를 통해 훨씬 좋은 결과를 나타내었다. 그러나, 현장자료에서는 잡음의 고주파성분을 포함하는 넓은 대역폭을 갖는 기준신호 때문에 약간의 잡음수준의 증가로 나타났다. 지표반사파를 기준신호로 사용하면 GPR자료의 파형의 복을 압축시킬 수 있이 지하 대상체에 의한 반사 영상의 질을 향상시킬 수 있다.

• Design & Manufacturing
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• 제15권2호
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• pp.23-29
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• 2021

The specific strength of magnesium alloy is four times that of iron and 1.5 times that of aluminum. For this reason, its use is increasing in the transportation industry which is promoting weight reduction. At room temperature, magnesium alloy has low formability due to Hexagonal closed packed (HCP) structure with relatively little slip plane. However, as the molding temperature increases, the formability of the magnesium alloy is greatly improved due to the activation of other additional slip systems, and the flow stress and elongation vary greatly depending on the temperature. In addition, magnesium alloys exhibit asymmetrical behavior, which is different from tensile and compression behavior. In this study, a jig was developed that can measure the plane deformation behavior on the surface of a material in tensile and compression tests of magnesium alloys in warm temperature. A jig was designed to prevent buckling occurring in the compression test by applying a certain pressure to apply it to the tensile and compression tests. And the tensile and compressive behavior of magnesium at each temperature was investigated with the developed jig and DIC equipment. In each experiment, the strain rate condition was set to a quasi-static strain rate of 0.01/s. The transformation temperature is room temperature, 100℃. 150℃, 200℃, 250℃. As a result of the experiment, the flow stress tended to decrease as the temperature increased. The maximum stress decreased by 60% at 250 degrees compared to room temperature. Particularly, work softening occurred above 150 degrees, which is the recrystallization temperature of the magnesium alloy. The elongation also tended to increase as the deformation temperature increased and increased by 60% at 250 degrees compared to room temperature. In the compression experiment, it was confirmed that the maximum stress decreased as the temperature increased.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.478-481
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• 2002

In this paper, the zerotrees of DWT is proposed to be used in a speech based digital watermarking for digital images. Since in this research work the raw speech and its content are used as a watermark signal, in the watermarking scheme, the PCM coded speech signal is embedded into a sequence of images. The performance of the scheme is evaluated by the PSNR obtained from the watermarked images and the strength of attacks the embedded speech signal can survive. Moreover, since in this research work the contents contained in the speech is used to identify the specific information hidden in the embedded signal. The speech signal after being extracted from the watermarked images is played back to the listeners to determine whether its content is intelligible or not. The experimental results show impressive performance of the scheme implementing our proposed technique, judged by the higher robustness obtained form the embedded signal against various types of attack, including brightness/contrast enhancement, Twirling, highpass filtering and JPEG compression standard.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.1117-1121
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• 2010

Several isotropic compression-expansion tests and a series of drained conventional traxial tests with various confining pressures for relative density of Beakma river sand 25%, 50%, 80% and 100% selecting Lade's Single Work-Hardening constitutive model. This examination materials use regression analysis as a basis, depending on the relative density of soil parameters change statement attributes. Yield fuction represent the soil parameters h and $\alpha$ is not affected by the changes in the relative density. $\eta_1$ could be replaced by fomula. And Numerical analysis results predicted very good and could confirm that.

• 소성∙가공
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• 제10권3호
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• pp.206-213
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• 2001

Dynamic deformation of metallic materials mostly accompanies substantial amounts of deformation heat. Since the flow stress of deformation is sensitive to temperature, implication of heat due to plastic work is essential to the evaluation of constitutive relations. In this study, a series of compression tests were conducted for SAF 2507 super duplex stainless steel at various temperatures and strain rates. The accumulation of plastic work was calculated through numerical integration and converted into the elevation of temperature. Subsequent logarithmic interpolation deduced isothermal flow surfaces, which were primary input data of finite element analysis. Simple closed die forging process was analyzed and optimized with commercial FEM code applying both raw and calibrated material database. The effect of accounting deformation heat was more noticeable in high-speed forming process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.517-522
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• 2000

When a body including a crack inside is subjected to the compressive forces, the crack is closed and sliding occurs on the crack surfaces. In this work, a subsurface crack subjected to a static or moving compressive load is analyzed with the finite element method considering friction on the crack surface. The friction on the crack surface is assumed to follow the Coulomb friction law. A numerical method based on the finite element method and iterative method is applied in this work. And the result is compared with the frictional contact of crack by ANSYS using contact 12 element. The numerical results of two methods are compared with the wellknown analytical solutions, and the accuracy of iterative method is checked..

• 한국농공학회지
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• 제38권2호
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• pp.133-144
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• 1996

To get accurate results, the realistic stress-strain relationships of soils are dependent on a number of factors such as soil types, density, stress levels and stress path. Such attempts are continuously being made by the developement of analytical models for soils incorporating all such factors. Isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress path for Baekma river sand were performed to investigate parameters characteristics of Lade's single work hardening model dependant on the stress path. Using the computer program based on the regression analysis, the values of parameters for the model were determined. In conclusion, the parameters of Lade's model are little influenced by the stress paths. Though yield criterion parameters ( h, ${\alpha}$a) are much influenced by stress level and stress path, the parameters don't have influence on stress-strain behavior.

• 한국표면공학회지
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• 제36권4호
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• pp.347-355
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• 2003

Roughening of metal surfaces frequently enhances the adhesion strength of metals to polymers by mechanical interlocking. When a failure occurs at a roughened metal/polymer interface, the failure prone to be cohesive. In a previous work, an adhesion study on a roughened metal (oxidized copper-based leadframe)/polymer (Epoxy Molding Compound, EMC) interface was carried out, and the correlation between adhesion strength and failure path was investigated. In the present work, an attempt to interpret the failure path was made under the assumption that microvoids are formed in the EMC as well as near the roots of the CuO needles during compression-molding process. A simple adhesion model developed from the theory of fiber reinforcement of composite materials was introduced to explain the adhesion behavior of the oxidized copper-based leadframe/EMC interface and failure path. It is believed that this adhesion model can be used to explain the adhesion behavior of other similarly roughened metal/polymer interfaces.

• Computers and Concrete
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• 제10권1호
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• pp.35-47
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• 2012

The ideal gradating curve is used in this study to estimate densified aggregate blended ratio and total surface area of aggregate, there by under assigned paste amount of concrete, and coating paste thickness can then be deduced. Four groups of concrete mixtures were prepared and the corresponding concrete properties, such as workability, compression strength, ultrasonic velocity, surface resistivity and chloride ion penetration, were measured and finally the results are interpreted in terms of "coating thickness". The result shows as the coating thickness of the concrete is higher than critical one, the coating thickness on aggregate does affect the workability, and whatever workability is required the superplasticizer can be adjusted to achieve the demand workability. Under a fixed paste quality at the same age, coating paste thickness is inversely proportional to the concrete properties, especially as the coating thickness gets thinner.