• Title, Summary, Keyword: constrained warping

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Stress Analysis of Rectangular Bar under Torsion (비틀림을 받는 사각주의 응력해석)

  • Kim, Dong-Hyun;Ji, Joong-Jo;Yoon, Kab-Young
    • Journal of the Korean Society for Precision Engineering
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    • v.3 no.4
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    • pp.53-63
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    • 1986
  • In this study, the stress distribution of rectangular bar under torsion, when warping of both ends is free or constrained, is investigated. Method of separation of variable and Fourier Series are used for the theoretical analysis, and 3dimensional photoelastic stress-freezing method for experimental analysis. The main results are as follows; 1) In the case of warping-constrained rectangular bar, the normal stresses are negligible because they are less then 0.5% of the shear stresses. The maximum normal stress is placed on the point of y=0.61 b when b/a=1 and it gradually moves to the corner y=b when the value of b/a is increased. 2) According to increase of the value of b/a, on the crossection, the maximum shear stress is placed on the middle point of the long side (x=${\pm}a$, y=0) when warping of both ends is free but the middle of the short side (x=0, y=${\pm} b$) when warping is constrained. The stress distribution is straight line when warping is constrained, namely, the stress distribution is proportional to the distance from the axis of centroid, but parabolic when warping is free. 3) The values of the combined stress of warping-constrained bar, if the influence of the loaded point is neglected, are generally smaller than those of warping-free.

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Finite Element Structural Analysis of Open-Section Composite Beams Considering Transverse Shear (전단변형을 고려한 개방형 단면 복합재료 보의 유한요소 구조해석)

  • 정성남
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.161-164
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    • 2000
  • In this paper, a finite element structural analysis for thin-walled open-section composite beams with elastic couplings has been performed. The analysis includes the effects of transverse shear across beam sections, torsion warping and constrained warping. Reissner's semi-complementary energy functional is used to obtain the beam st illness coefficients The bending and torsion related warpings and the shear correct ion factors are obtained as part of the analysis. The resulting theory describes the beam kinematics in terms of the axial, flap and lag bending, flap and lag shear, torsion and torsion-warping deformations. The static response has been validated against finite element predict ions, closed form solutions, and experimental data for rectangular sol id and I-beams with elastic couplings. The free vibration results are also compared with available literature.

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A continuum mechanics based 3-D beam finite element with warping displacements and its modeling capabilities

  • Yoon, Kyungho;Lee, Youngyu;Lee, Phill-Seung
    • Structural Engineering and Mechanics
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    • v.43 no.4
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    • pp.411-437
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    • 2012
  • In this paper, we propose a continuum mechanics based 3-D beam finite element with cross-sectional discretization allowing for warping displacements. The beam element is directly derived from the assemblage of 3-D solid elements, and this approach results in inherently advanced modeling capabilities of the beam element. In the beam formulation, warping is fully coupled with bending, shearing, and stretching. Consequently, the proposed beam elements can consider free and constrained warping conditions, eccentricities, curved geometries, varying sections, as well as arbitrary cross-sections (including thin/thick-walled, open/closed, and single/multi-cell cross-sections). We then study the modeling and predictive capabilities of the beam elements in twisting beam problems according to geometries, boundary conditions, and cross-sectional meshes. The results are compared with reference solutions obtained by analytical methods and solid and shell finite element models. Excellent modeling capabilities and solution accuracy of the proposed beam element are observed.

A Study on Assessment of Composite Couplings for Helicopter Rotor Blades with Multi-cell Sections

  • Jung, Sung-Nam;Park, Il-Ju;Shi, Eui-Sup;Chopra, Inderjit
    • International Journal of Aeronautical and Space Sciences
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    • v.4 no.1
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    • pp.9-18
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    • 2003
  • In this work, a closed-form analysis is performed for the structural response of coupled composite blades with multi-cell sections. The analytical model includes the effects of shell wall thickness, transverse shear, torsion warping and constrained warping. The mixed beam approach based on Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. The theory is validated against experimental test data and other analytical results for coupled composite beams and blades with single-cell box-sections and two-cell airfoils. Correlation of the present method with experimental results and detailed finite element results is found to be very good.

Perceptual Quality Improvement of KLT based Entropy-Constrained Quantizer using a SAW Filter (SAW 필터를 이용한 KLT 기반 Entropy-Constrained Quantizer 성능 향상)

  • Lim, Dong-Seok;Kim, Moo Young
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • pp.1-2
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    • 2013
  • KLT-AECQ 는 지각적인 성능 향상을 위하여 formant weighting 필터를 사용한다.Code Excited Linear Prediction(CELP) 코더는 사람의 음성신호를 압축하는 대표적인 방식이다. CELP 의 Rate-Distortion 성능을 향상 시키기 위해서 Karhunen-Loeve-Transform (KLT) 기반의 Classified Vector Quantization (KLT-CVQ) 방식이 제안되었으며, 이는 KLT 기반의 Adaptive Entropy-Constrained Quantization (KLT-AECQ) 방식으로 확장되었다. 기존의 KLT-AECQ 에서는 지각적인 성능 향상을 위하여 formant weighting 필터를 사용한다. 본 논문에서는 이 필터 대신에 Spectral Amplitude Warping (SAW) 필터를 적용함으로써, KLT-AECQ 코더의 지각적인 성능을 향상하였다.

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Cross-sectional Constants of Thin-walled Composite Blades with Elliptical Profiles (타원형 단면형상을 갖는 복합재료 박판 블레이드의 단면상수 계산)

  • 박일주;이주영;정성남;신의섭
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.95-98
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    • 2003
  • In this work, a closed-form analysis is performed to obtain the stiffness coefficients of thin-walled composites beams with elliptical profiles. The analytical model includes the effects of elastic couplings, shell wall thickness, torsion warping and constrained warping. Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. The theory is validated against MSC/NASTRAN results for coupled composites beams with single-cell elliptical sections. Very good correlation has been noticed for the test cases considered.

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A Method of Designing Low-power Feedback Active Noise Control Filter for Headphones/Earphones (헤드폰/이어폰을 위한 저전력 피드백 능동 소음 제어 필터 설계 방법)

  • Seo, Ji-ho;Youn, Dae-Hee;Park, Young-Cheol
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.10 no.1
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    • pp.57-65
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    • 2017
  • This paper presented a method of designing low-power feedback active noise control filter optimized for headphones/earphones. Using constrained optimization, we obtained a high order FIR noise control filter to ensure reasonable noise attenuation performance at high sampling frequency environment. Then using infinite impulse response (IIR) approximation method called Balanced Model Truncation (BMT), we obtained a low order IIR noise control filter suitable for low-power digital signal processing system like headphones/earphones. For further performance improvement, we utilized frequency warping method so that we could obtain more accurately approximated IIR filter and we ensured system stability by reconstructing the low order IIR filter in form of cascaded second order IIR filters. ANC simulation with white noise and stability test verified that the proposed algorithm had superior attenuation performance and better robustness compared to the conventional algorithm.

A Pattern-based Query Strategy in Wireless Sensor Network

  • Ding, Yanhong;Qiu, Tie;Jiang, He;Sun, Weifeng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.6
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    • pp.1546-1564
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    • 2012
  • Pattern-based query processing has not attracted much attention in wireless sensor network though its counterpart has been studied extensively in data stream. The methods used for data stream usually consume large memory and much energy. This conflicts with the fact that wireless sensor networks are heavily constrained by their hardware resources. In this paper, we use piece wise representation to represent sensor nodes' collected data to save sensor nodes' memory and to reduce the energy consumption for query. After getting data stream's and patterns' approximated line segments, we record each line's slope. We do similar matching on slope sequences. We compute the dynamic time warping distance between slope sequences. If the distance is less than user defined threshold, we say that the subsequence is similar to the pattern. We do experiments on STM32W108 processor to evaluate our strategy's performance compared with naive method. The results show that our strategy's matching precision is less than that of naive method, but our method's energy consumption is much better than that of naive approach. The strategy proposed in this paper can be used in wireless sensor network to process pattern-based queries.

Virtual View Generation by a New Hole Filling Algorithm

  • Ko, Min Soo;Yoo, Jisang
    • Journal of Electrical Engineering and Technology
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    • v.9 no.3
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    • pp.1023-1033
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    • 2014
  • In this paper, performance improved hole-filling algorithm which includes the boundary noise removing pre-process that can be used for an arbitrary virtual view synthesis has been proposed. Boundary noise occurs due to the boundary mismatch between depth and texture images during the 3D warping process and it usually causes unusual defects in a generated virtual view. Common-hole is impossible to recover by using only a given original view as a reference and most of the conventional algorithms generate unnatural views that include constrained parts of the texture. To remove the boundary noise, we first find occlusion regions and expand these regions to the common-hole region in the synthesized view. Then, we fill the common-hole using the spiral weighted average algorithm and the gradient searching algorithm. The spiral weighted average algorithm keeps the boundary of each object well by using depth information and the gradient searching algorithm preserves the details. We tried to combine strong points of both the spiral weighted average algorithm and the gradient searching algorithm. We also tried to reduce the flickering defect that exists around the filled common-hole region by using a probability mask. The experimental results show that the proposed algorithm performs much better than the conventional algorithms.