• Title/Summary/Keyword: Size reduction

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Size Effect of Concrete Structures with Dissimilar Initial Cracks (비유사 균열이 있는 콘크리트 구조의 크기효과)

  • 김진근;어석홍;장정수;조성찬
    • Magazine of the Korea Concrete Institute
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    • v.2 no.1
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    • pp.91-100
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    • 1990
  • In most of the structural members with initial cracks(or initial notches), the strength tends to decmase as the member size increases. This phenomenon is known as size effect. Among the structural materials of glass, metal or concrete, etc., concrete represents the size effect even without initial crack. According to the previous size effect law, the concrete mem¬ber of very large size can resist little stress. Actually, however, even the large size member can resist some stress if there is no initial crack made artificially, consequently showing a rather milder strength reduction compared to the severe strength reduction by tbe previously derived size effect law. In this study, the theoretical size effect law previously derived by Z.P. Bazant was discussed based on nonlinear fracture mechanics of concrete structures With dissimilar initial cracks, and the prediction models are proposed by regression analysis with the existing test data of more large size speciments for splitting tensile strength, shear strength and uniaxial compressive strength tests.

Experiment Design Parameter for the Effect of Surface Texturing on Metal Surface (금속표면의 Surface texturing 효과에 대한 실험적 설계변수)

  • Chae Y.H.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.1145-1150
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    • 2005
  • The aim of this paper is to investigate the effect of surface texturing on metal surface and to understand the potential of friction reduction through micro-scale dimple to fabricate by photolithography on pin-on-disk test using flat-on-flat contact geometry. It was verify that the friction property with respect to the same pitch has been influence on the size of dimple under lubricated sliding contact. Also, we can recognize from Stribeck curve that the friction property has a connection with the size of dimple. It can explain a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. The friction property has been an effect on the size of surface texture on reduction friction, not only because the density of dimple, but also because the ratio of diameter/pitch. This ratio of approximately 0.5 is recommend under the tested friction condition. It suggested that the ratio of d/p is an important parameter for surface texture design.

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An Ensemble Classifier using Two Dimensional LDA

  • Park, Cheong-Hee
    • Journal of Korea Multimedia Society
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    • v.13 no.6
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    • pp.817-824
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    • 2010
  • Linear Discriminant Analysis (LDA) has been successfully applied for dimension reduction in face recognition. However, LDA requires the transformation of a face image to a one-dimensional vector and this process can cause the correlation information among neighboring pixels to be disregarded. On the other hand, 2D-LDA uses 2D images directly without a transformation process and it has been shown to be superior to the traditional LDA. Nevertheless, there are some problems in 2D-LDA. First, it is difficult to determine the optimal number of feature vectors in a reduced dimensional space. Second, the size of rectangular windows used in 2D-LDA makes strong impacts on classification accuracies but there is no reliable way to determine an optimal window size. In this paper, we propose a new algorithm to overcome those problems in 2D-LDA. We adopt an ensemble approach which combines several classifiers obtained by utilizing various window sizes. And a practical method to determine the number of feature vectors is also presented. Experimental results demonstrate that the proposed method can overcome the difficulties with choosing an optimal window size and the number of feature vectors.

Efficient Signal Reordering Unit Implementation for FFT (FFT를 위한 효율적인 Signal Reordering Unit 구현)

  • Yang, Seung-Won;Lee, Jang-Yeol
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.6
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    • pp.1241-1245
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    • 2009
  • As FFT(Fast Fourier Transform) processor is used in OFDM(Orthogonal Frequency Division Multiplesing) system. According to increase requirement about mobility and broadband, Research about low power and low area FFT processor is needed. So research concern in reduction of memory size and complex multiplier is in progress. Increasing points of FFT increase memory area of FFT processor. Specially, SRU(Signal Reordering Unit) has the most memory in FFT processor. In this paper, we propose a reduced method of memory size of SRU in FFT processor. SRU of 64, 1024 point FFT processor performed implementation by VerilogHDL coding and it verified by simulation. We select the APEX20KE family EP20k1000EPC672-3 device of Altera Corps. SRU implementation is performed by synthesis of Quartus Tool. The bits of data size decide by 24bits that is 12bits from real, imaginary number respectively. It is shown that, the proposed SRU of 64point and 1024point achieve more than 28%, 24% area reduction respectively.

Synthesis of Nanostructured Fe-Co Alloy Powders from Metal Salts

  • Lee, Young-Jung;Lee, Jea-Sung;Seo, Young-Ik;Kim, Young-Do
    • Journal of Powder Materials
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    • v.13 no.5 s.58
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    • pp.336-339
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    • 2006
  • Magnetic properties of nanostructured materials are affected in complicated manner by their microstructure such as pain size (or particle size), internal strain and crystal structure. Thus, studies on the synthesis of nanostructured materials with controlled microstructure are necessary fur a significant improvement in magnetic properties. In the present work, nanostructured Fe-Co alloy powders with a grain size of 50 nm were successfully fabricated from the powder mixtures of (99.9% purity) $FeCl_2$ and $CoCl_2$ by chemical solution mixing and hydrogen reduction.

Synthesis and Characteristics of W-l5wt%Cu Nanocomposite Powder by Oxide Reduction (산화물환원에 의한 W-15wt%Cu 나노복합분말의 합성과 특성)

  • 윤의식
    • Journal of Powder Materials
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    • v.4 no.4
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    • pp.304-309
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    • 1997
  • The synthesis of W-l5wt%Cu nanocomposite powder by hydrogen reduction of ball milled W-Cu oxide mixture was investigated in terms of powder characteristics such as particle size, mixing homogeneity and micropore structure. It is found that the micropores in the ball milled oxide (2-50 nm in size) act as an effective removal path of water vapor, followed by the formation of dry atmosphere at reaction zone. Such thermodynamic condition enhances the nucleation of W phase but suppresses the growth process, being in favor of the formation of W nanoparticles (about 21 nm in size). In addition, the superior mixing homogeneity of starting oxide mixture turned out to Play a significant role for forming extraordinary chemical homogeneity of W-l5wt%Cu nanocomposite powder.

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GPS/PCS Dual Polarization Compact Microstrip patch Antenna (GPS/PCS 이중편파 소형 마이크로스트립 패치 안테나)

  • Kim, Ho-Yong;Cho, Jung-Yong;Won, Chung-Ho;Lee, Hong-Min
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.473-477
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    • 2003
  • In this paper, a integrated structure of a two-element microstrip patch antenna with two feeds for GPS/PCS dual-band operation is proposed. The radiating element for PCS operation is a novel broad band low-profile cylindrical monopole top-loaded with a shorted meander patch, which gives linearly polarized conical radiation pattern and size reduction of patch due to meander line. The radiating element for GPS operation is a novel square-ring microstrip patch with truncated corners and slits. which provide circularly polarized broadside radiation patterns and size reduction due to slots. using dielectric substrate in GPS antenna of proposed antenna provide to improve isolation between two feeds and reduce size of patch. The proposed antenna achieves the bandwidth and polarization requirements of GPS and PCS systems.

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A Design of Miniaturized Ring-Hybrid Coupler with Broadband Harmonic Attenuation Property (광대역 고조파 감쇠특성을 갖는 소형화된 링-하이브리드의 설계)

  • Lee Hong-Seop;Choi Kyoung;Hwang Hee-Yong
    • 한국정보통신설비학회:학술대회논문집
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    • 2006.08a
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    • pp.197-201
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    • 2006
  • Folded lines are applied to design a compact microstrip ring hybrid. Using the proposed structure we achieve both significant size reduction and good harmonic suppression with the same results of conventional ring hybrid at 2.41GHz. Including the third harmonic frequency, up to 11GHz band harmonics are suppressed to -20dB. The size of the proposed ring-hybrid is reduced to one forth of the conventional ring hybrid. The measured frequency responses agree well with simulated ones.

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The Effective ROM Design for Area and Power Dissipation Reduction (면적 및 전력소모 감소를 위한 효율적인 ROM 설계)

  • Jung, Ki-Sang;Kim, Yong-En;Cho, Seong-Ik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.11
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    • pp.2017-2022
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    • 2007
  • In a memory, most power is dissipated in line of high capacitance such as decoder lines, word lines, and bit * lines. The decoder size as well as the parastic capacitances of the bit-line are going to reduce, if ROM core size reduces. This paper proposes to reduce a mathod of power dissipation for reducing ROM core size. Design result of ROM used in FFT[2], proposed method lead to up to 40.6%, 42.12%, 37.82% reduction in area, power consumption and number of Tr. respectively compared with previous method.

Effect of Reaction Conditions on the Preparation of Nano-sized Ni Powders inside a Nonionic Polymer

  • Kim, Tea-Wan;Kim, Dong-Hyun;Park, Hong-Chae;Yoon, Seog-Young
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.462-463
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    • 2006
  • Monodispersed and nano-sized Ni powders were synthesized from aqueous nickel sulfate hexahydrate $(NiSO_4{\cdot}6H_2O)$ inside nonionic polymer network by using wet chemical reduction process. The sucrose was used as a nonionic polymer network source. The effect of reaction conditions such as the amount of sucrose and a various reaction temperature, nickel sulfate hexahydrate molarity. The influence of a nonionic polymer network on the particle size of the prepared Ni powders was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis (PSA). The results showed that the obtained Ni powders were strong by dependent of the reaction conditions. In particular, the Ni powders prepared inside a nonionic polymer network had smooth spherical shape and narrow particle size distribution.

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