• 전자공학회논문지
• /
• 제51권2호
• /
• pp.38-45
• /
• 2014

본 논문에서는 메모리 컴파일러를 정확하고 빠르게 특성화할 수 있도록 기준 메모리를 기반으로 특성화하는 방법을 제안하였다. 제안한 특성화 방법은 메모리 컴파일러의 정확도를 유지하면서 특성화 시간을 최소화하기 위해 메모리 컴파일러의 타이밍 경향을 분석하고 분석 결과를 토대로 기준 메모리를 선정하고, 메모리간의 경향성을 대변할 수 있도록 모델링하였다. 본 논문에서 제안한 방법론을 검증하기 위하여 130nm에서 개발된 메모리 컴파일러를 제안한 방법을 이용하여 110nm 메모리 컴파일러를 특성화하였다. 이를 통해 생성한 메모리들의 특성과 SPICE를 사용하여 특성화한 결과를 비교하여 메모리 타이밍의 평균 오차율은 ${\pm}0.1%$ 이내였으며 실제 110nm 공정을 사용하여 제작된 메모리 BIST(Built-In Self Test) 테스트 칩으로 기능 검사한 결과, 수율(Yield)이 98.8% 임을 확인하였다. 또한, 180nm 공정을 사용하여 비교한 결과, 수율이 98.3%로 그 유용성을 확인할 수 있었다.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.205-210
• /
• 2001

In this work, virtual material characterization of 3D orthogonal woven composites is performed to predict the elastic properties by a full scale FEA. To model the complex geometry of 3D orthogonal woven composites, an accurate unit structure is first prepared. The unit structure includes warp yarns, filler yarns, stuffer yams and resin regions and reveals the geometrical characteristics. For this virtual experiments by using finite element analysis, parallel multifrontal solver is utilized and the computed elastic properties are compared to available experimental results and the other analytical results. It is founded that a good agreement between material properties obtained from virtual characterization and experimental results. Using the method of this virtual material characterization, the effects of inconsistent filler yarn distribution on the in-plane shear modulus and filler yarn waviness on the transverse Young's modulus are investigated. Especially, the stiffness knockdown of 3D woven composite structures is simulated by virtual characterization. Considering these results, the virtual material characterization of composite materials can be used for designing the 3D complex composite structures and may supplement the actual experiments.

• 한국세라믹학회지
• /
• 제55권4호
• /
• pp.376-380
• /
• 2018

Microstructural characterization of Ni-yttria-stabilized zirconia (YSZ) anodes using secondary electron images has been limited by a lack of contrast between Ni and YSZ phases. This paper reports a sample preparation method for obtaining secondary electron images that allow the detection of Ni, YSZ, and pore phases together. Ni-YSZ anode samples were obtained by reducing NiO-YSZ samples prepared by using the mixed oxide method. Colloidal silica polishing and electrolytic etching were performed on the Ni-YSZ samples. The morphological change of the sample surface after each polishing process is examined.

• 한국정밀공학회지
• /
• 제13권12호
• /
• pp.120-128
• /
• 1996

An attempt is made to characterize and synthesize engineered surfaces. The proposed method is not only an analytical tool to characterize but also to generate/synthesize three-dimensional surfaces. The developed method expresses important engineered surface characteristics such as the autocorrelation or power spectrum density functions in terms of the two-dimensional autoregressive coefficients.

• Nuclear Engineering and Technology
• /
• 제38권4호
• /
• pp.375-382
• /
• 2006

Characterization tests (load vs. displacement curve) are conducted for the springs of Zirconium alloy spacer grids for an advanced LWR fuel assembly. Twofold testing is employed: strap-based and assembly-based tests. The assembly-based test satisfies the in situ boundary conditions of the spring within the grid assembly. The aim of the characterization test via the aforementioned two methods is to establish an appropriate assembly-based test method that fulfills the actual boundary conditions. A characterization test under the spacer grid assembly boundary condition is also conducted to investigate the actual behavior of the spring in the core. The stiffness of the characteristic curve is smaller than that of the strap-wised boundary condition. This phenomenon may cause the strap slit condition. A spacer grid consists of horizontal and vertical straps. The strap slit positions are differentiated from each other. They affords examination of the variation of the external load distribution in the grid spring. Localized legions of high stress and their values are analyzed, as they may be affected by the spring shape. Through a comparison of the results of the test and FE analysis, it is concluded that the present assembly-based analysis model and procedure are reasonably well conducted and can be used for spring characterization in the core. Guidelines for improving the mechanical integrity of the spring are also discussed.

• 한국컴퓨터정보학회논문지
• /
• 제11권2호
• /
• pp.43-52
• /
• 2006

최근 유비쿼터스 컴퓨팅의 관심이 증대되면서, 방대하고 다양한 형태의 데이터에 대한 효율성과 효과성을 고려한 지식 탐사연구의 필요성이 요구된다. 공간 특성화 방법은 공간과 비공간 속성들을 고려하여 특성화 지식을 발견하는 방법으로, 기존의 특성화 방법을 확장하여 공간 영역에 대한 다양한 형태의 지식을 발견할 수 있다. 기존 공간 특성화기법에 대한 연구들은 다음과 같은 문제점을 가진다. 첫째, 기존의 연구는 탐사된 지식의 결과가 다각적인 공간 분석을 수행하지 못하는 문제점을 가진다 둘째, 공간 탐색 시 사용자에 의해 미리 정해진 위치 영역만을 고려하여 탐색함으로 유용한 지식탐사를 보장하지 못하는 문제점을 가진다. 따라서 본 연구에서는 밀도 기반의 클러스터링이 적용된 새로운 공간 특성화기법을 제안한다.

• 한국분말재료학회지
• /
• 제27권6호
• /
• pp.509-519
• /
• 2020

A well-established characterization method is required in powder bed fusion (PBF) metal additive manufacturing, where metal powder is used. The characterization methods from the traditional powder metallurgy process are still being used. However, it is necessary to develop advanced methods of property evaluation with the advances in additive manufacturing technology. In this article, the characterization methods of powders for metal PBF are reviewed, and the recent research trends are introduced. Standardization status and specifications for metal powder for the PBF process which published by the ISO, ASTM, and MPIF are also covered. The establishment of powder characterization methods are expected to contribute to the metal powder industry and the advancement of additive manufacturing technology through the creation of related databases.

• 열처리공학회지
• /
• 제33권4호
• /
• pp.185-192
• /
• 2020

In this study, materials characterization of pure copper and copper based carbon nano-tube composite prepared by powder metallurgy method were investigated. Prior to evaluate materials characterization, spark plasma sintering processing variables such as sintering temperature, pressure, thickness and diameter of compacts was optimized to ensure the microstructure and materials property of pure Cu and Cu-CNT composite. In addition, corrosion behavior of Cu-based CNT composite produced by powder sintering method was investigated. It was confirmed from this study that the corroded surfaces of the composite shows less dissolution compared with pure copper in 3.5 wt% NaCl solution. The measured corrosion current density (I_corr) indicates improved corrosion property of Cu based composite containing small additions of CNTs in chloride containing media. Micro-galvanic activity between Cu and CNT was not observed in given sintering condition.

• 한국표면공학회지
• /
• 제39권5호
• /
• pp.229-234
• /
• 2006

Diamonds have been widely employed as polishing media for precise machining and noble substrates for microelectronics. The recent development of the split sphere press has led to the enhancement of low quality natural diamonds. Synthesized and treated diamonds are sometimes traded deceptively as high quality natural diamonds because it is hard to distinguish among these diamonds with conventional gemological characterization method. Therefore, we need to develop a new identification method that is non-destructive, fast, and inexpensive. We proposed using new methods of UV fluorescence and X-ray Lang topography for checking the local HPHT stress field to distinguish these diamonds from natural ones. We observe unique differences in the local stress field images in treated diamonds using UV fluorescence and Lang topography characterization. Our result implies that our proposed methods may be appropriate for identification of the treated diamonds.

• Structural Engineering and Mechanics
• /
• 제70권2호
• /
• pp.209-219
• /
• 2019

By normalizing the internal hysteresis variable and eliminating the redundant parameter, the normalized Bouc-Wen model is considered to be an improved and more reasonable form of the Bouc-Wen model. In order to facilitate application and further research of the normalized Bouc-Wen model, some key aspects of the model need to be uncovered. In this paper, hysteresis characterization of the normalized Bouc-Wen model is first studied with respect to the model parameters, which reveals the influence of each model parameter to the shape of the hysteresis loops. The parameter identification scheme is then proposed based on an improved genetic algorithm (IGA), and verified by experimental test data. It is proved that the proposed method can be an efficacious tool for identification of the model parameters by matching the reconstructed hysteresis loops with the target hysteresis loops. Meanwhile, the IGA is shown to outperform the standard GA. Finally, a simplified identification method is proposed based on parameter sensitivity, which indicates that the efficiency of the identification process can be greatly enhanced while maintaining comparable accuracy if the low-sensitivity parameters are reasonably restricted to narrower ranges.