• Title/Summary/Keyword: Upper-bound Analysis

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Prediction Model Using Upper Bound Theorem of Shear Strength for RC Beams Strengthened by FRP (상한계 이론을 이용한 FRP로 보강된 RC보의 전단강도 예측 모델)

  • 홍성걸;문선혜
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.05a
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    • pp.908-911
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    • 2003
  • This study was performed to verify the effect of reinforcement of RC Beams strengthened($90^{\circ}$ strip type) by FRP(CFRP) and Predited the shear strength of them using the upper bound theorem. The prediction model was confirmed with the result of the FEM analysis. The analyzed result showed thar shear-damaged RC beams by strengthened by FRP was improved their shear capacity.

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Degrees of Freedom of Two-Cluster MIMO Multiway Relay Interference Channels Using Blind Interference Neutralization

  • Zhang, Bowei;Feng, Wenjiang;Dong, Tingting;Deng, Yina
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.10 no.1
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    • pp.168-186
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    • 2016
  • In this paper, we investigate the degrees of freedom (DoF) of a two-cluster multiple-input multiple-output (MIMO) multiway relay interference channel (mRIC), where there are two relays and two users per cluster. In this channel, users within the same cluster exchange messages among themselves with the help of two relays.We first obtain the DoF upper bound of the considered MIMO mRIC based on cut-set bound. Then, we propose a novel transmission strategy, blind interference neutralization (BIN), to approach the DoF upper bound. This new method utilizes the overheard information at two relays and focuses on the beamforming matrix designs at two relays so that the channel state information (CSI) at users is not required. Through theoretical analysis and numerical simulations, we show that the DoF upper bound can be obtained by using the BIN scheme. From simulation results, we show that the proposed BIN scheme can provide significant performance gain over the conventional time division multiple access (TDMA) scheme in terms of DoF. In addition, we show that the BIN scheme is a superior approach to the existing signal space alignment (SSA) schemes for the considered mRIC.

An Analysis of the Effect of Doppler Spread on Transparent Multi-hop Relays Systems Based on OFDM (OFDM 기반의 트랜스패런트 다중 홉 릴레이 시스템에서 도플러 확산의 영향 분석)

  • Woo, Kyung-Soo;Cho, Yong-Soo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.5
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    • pp.40-46
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    • 2007
  • In this paper, the effect of a Doppler Spread caused by a mobile station (MS) is analyzed for transparent mobile multi-hop relays (MMR) systems based on orthogonal frequency division multiplexing (OFDM). The exact expression of interchannel interference (ICI) power and the upper bounds of ICI power are derived for OFDM systems with cooperative MMR or non-coopeartive throughput enhancement (TE) MMR. Also, the exact signal-to-interference ratio (SIR) and its lower bound as well as ICI power and its upper bound, derived in this paper, are evaluated by computer simulation with the OFDM parameter set used for mobile WiMax (WiBro) systems.

An Upper-Bound Analysis for Closed-Die Forging of the Involute Spur Gears with Circular Arc Fillet (원호필렛-인벌류트 스퍼어 기어의 밀폐단조에 관한 상계해석)

  • Choi, J.C.;Hur, K.D.;Kim, C.H.;Choi, Y.
    • Transactions of Materials Processing
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    • v.3 no.1
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    • pp.97-109
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    • 1994
  • Closed-die forging of the spur gears with circular are fillet has been analyses by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, the tooth profile consists of the involute curve and the circular arc fillet. In the analysis, the deformation regions have been divided into eight zones. A constant frictional stress has been assumed on the contacting surfaces Utilizing the formulated velocity field, numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, addendum modification coefficient and friction factor, on the relative forging pressure of spur gears. As the result of numerical calculations, the relative forging pressure does not change so much against the variation of module. On the other hand, the relative forging pressure increases at the final filling stage as the addendum modification coefficient increases.

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Stability assessment of tunnel face in a layered soil using upper bound theorem of limit analysis

  • Khezri, Nima;Mohamad, Hisham;Fatahi, Behzad
    • Geomechanics and Engineering
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    • v.11 no.4
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    • pp.471-492
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    • 2016
  • Underground tunnelling is one of the sustainable construction methods which can facilitate the increasing passenger transportation in the urban areas and benefit the community in the long term. Tunnelling in various ground conditions requires careful consideration of the stability factor. This paper investigates three dimensional stability of a shallow circular tunnel in a layered soil. Upper bound theorem of limit analysis was utilised to solve the tunnel face stability problem. A three dimensional kinematic admissible failure mechanism was improved to model a layered soil and limiting assumptions of the previous studies were resolved. The study includes calculation of the minimum support pressure acting on the face of the excavation in closed-face excavations. The effects of the characteristics of the layers on the minimum support pressure were examined. It was found that the ratio of the thickness of cover layers particularly when a weak layer is overlying a stronger layer, has the most significant influence on the minimum tunnel support pressure. Comparisons have been made with the results of the numerical modelling using FLAC3D software. Results of the current study were in a remarkable agreement with those of numerical modelling.

A Study on Determination of Bearing Capacity of Eccentrically Loaded Strip Footing (편심하중을 받는 줄기초의 지지력 산정에 관한 연구)

  • Kwon, Oh Kyun;Chung, Choong-Ki;Kim, Tae Soo;Kim, Myoung Mo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.13 no.5
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    • pp.245-254
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    • 1993
  • In this study, the influence of eccentricity on bearing capacity of strip footing has been investigated by the model tests using the carbon rods, the upper bound method of limit analysis, and Meyerhof method of the limit equilibrium method. In applying the upper bound, the failure mechanism based on model tests was used. There was good agreement between the result of model tests and the upper bound method of limit analysis, but Meyerhof method yielded low bearing capacity and underestimated the effect of eccentricity on bearing capacity. Besides, the influences of footing width, embedment depth and base friction on the bearing capacity have been examined.

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A Study on the Extrusion Using Two-Step Processes for Manufacturing Helical Gear (2단계공정을 이용한 헬리컬기어 압출에 관한 연구)

  • Jung, Sung-Yuen;Park, Joon-Hong;Kim, Chang-Ho;Chang, Young-June;Kim, Chul
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.8 s.197
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    • pp.34-40
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    • 2007
  • In this study, focusing on reducing a load in forming helical gears, the extrusion using two-step processes for manufacturing helical gear is proposed. The process is composed of the extrusion step in which spur gear to be used as a preform in next step is formed, and the torsion step in which the preform of spur gear is formed to helical gear. Upper-bound theory for the two-step process is applied and compared with the results of experiment. The result of upper-bound solution has a good agreement with that of the experiment and the FE analysis. The newly proposed method can be used as an advanced forming technique to remarkably reduce a forming load, to prolong a tool life, and to replace the conventional forming process of helical gears. Results obtained from the extrusion using two-step processes enable the designer and manufacturer of helical gear to be more efficient in this field.

ANALYSIS OF THE UPPER BOUND ON THE COMPLEXITY OF LLL ALGORITHM

  • PARK, YUNJU;PARK, JAEHYUN
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.20 no.2
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    • pp.107-121
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    • 2016
  • We analyze the complexity of the LLL algorithm, invented by Lenstra, Lenstra, and $Lov{\acute{a}}sz$ as a a well-known lattice reduction (LR) algorithm which is previously known as having the complexity of $O(N^4{\log}B)$ multiplications (or, $O(N^5({\log}B)^2)$ bit operations) for a lattice basis matrix $H({\in}{\mathbb{R}}^{M{\times}N})$ where B is the maximum value among the squared norm of columns of H. This implies that the complexity of the lattice reduction algorithm depends only on the matrix size and the lattice basis norm. However, the matrix structures (i.e., the correlation among the columns) of a given lattice matrix, which is usually measured by its condition number or determinant, can affect the computational complexity of the LR algorithm. In this paper, to see how the matrix structures can affect the LLL algorithm's complexity, we derive a more tight upper bound on the complexity of LLL algorithm in terms of the condition number and determinant of a given lattice matrix. We also analyze the complexities of the LLL updating/downdating schemes using the proposed upper bound.

Analysis of the Curving Phenomenon of Curved Circular Shaped Product by the Upper Bound Analysis and the DEFORMTM-3D in Eccentric Extrusion (곡봉(曲奉)의 편심압출가공에 대하여 상계굽힘해석과 DEFORMTM-3D에 의한 굽힘해 석 비교)

  • 김진훈;김한봉;진인태
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1997.10a
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    • pp.45-48
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    • 1997
  • The kinematically admissible velocity field is developed for the eccentric extrusion of circular shaped products. The curving of product in extrusion is caused by the difference of the linearly distributed longitudinal velocity on the cross-section of the workpiece at the dies exit. The results of the eccentric extrusion by upper bound analysis show that the curvature of product increases with the increase in eccentricity of gravity center of the cross-section of workpiece at dies entrance from that of the corss-section at the dies exit end. By the DEFORMTM-3D analysis, the curving of circular shaped product in extrusion is changed by the eccentricity, die land length and the die length. The result of the analysis by DEFORMTM-3D software shows that the curvature of circular shaped product increases with the eccentricity. The two analysis and one experiment show the curving phenomenon in eccentric extrusion process.

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Discretization technique for stability analysis of complex slopes

  • Hou, Chaoqun;Zhang, Tingting;Sun, Zhibin;Dias, Daniel;Li, Jianfei
    • Geomechanics and Engineering
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    • v.17 no.3
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    • pp.227-236
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    • 2019
  • In practice, the natural slopes are frequently with soils of spatial properties and irregular features. The traditional limit analysis method meets an inherent difficulty to deal with the stability problem for such slopes due to the normal condition in the associated flow rule. To overcome the problem, a novel technique based on the upper bound limit analysis, which is called the discretization technique, is employed for the stability evaluation of complex slopes. In this paper, the discretization mechanism for complex slopes was presented, and the safety factors of several examples were calculated. The good agreement between the discretization-based and previous results shows the accuracy of the proposed mechanism, proving that it can be an alternative and reliable approach for complex slope stability analysis.