• Title/Summary/Keyword: Closed cell

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Tensile Behaviour of Foamed Metal Matrix Composite Using Stochastic FE Model (통계적 유한요소모델을 이용한 발포된 금속기지 복합재료의 인장특성)

  • 전성식
    • Composites Research
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    • v.17 no.2
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    • pp.34-39
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    • 2004
  • In this paper, a modified and representative unit cell model was employed to study the tensile behaviour of closed-cell metallic foams with varying spatial density distribution as well as material imperfections. The density variation was assumed to follow a statistical probability distribution of the Gaussian type. A multiple cell finite element model, utilising the modified unit cell, was developed. The model exhibits deformation patterns similar to those observed in tensile testing. The nominal stress-strain curve obtained from quasistatic tensile of the foam was compared with experimental findings and was found to be in good agreement in the scheme of maximum strength only if the appropriate density distribution and volume fraction of internal imperfections are taken into account. Moreover, maximum tensile strength of the aluminium foam was found to be more sensitive to the volume fraction of imperfection than standard deviation of the density.

Investigation of Open-Loop Transmit Power Control Parameters for Homogeneous and Heterogeneous Small-Cell Uplinks

  • Haider, Amir;Sinha, Rashmi Sharan;Hwang, Seung-Hoon
    • ETRI Journal
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    • v.40 no.1
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    • pp.51-60
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    • 2018
  • In Long Term Evolution (LTE) cellular networks, the transmit power control (TPC) mechanism consists of two parts: the open loop (OL) and closed loop. Most cellular networks consider OL/TPC because of its simple implementation and low operation cost. The analysis of OL/TPC parameters is essential for efficient resource management from the cellular operator's viewpoint. In this work, the impact of the OL/TPC parameters is investigated for homogeneous small cells and heterogeneous small-cell/macrocell network environments. A mathematical model is derived to compute the transmit power at the user equipment, the received power at the eNodeB, the interference in the network, and the received signal-to-interference ratio. Using the analytical platform, the effects of the OL/TPC parameters on the system performance in LTE networks are investigated. Numerical results show that, in order to achieve the best performance, it is appropriate to choose ${\alpha}_{small}=1$ and $P_{o-small}=-100dBm$ in a homogenous small-cell network. Further, the selections of ${\alpha}_{small}=1$ and $P_{o-small}=-100dBm$ in the small cells and ${\alpha}_{macro}=0.8$ and $P_{o-macro}=-100dBm$ in the macrocells seem to be suitable for heterogeneous network deployment.

Modeling of the Elasto-plastic Deformation Behavior of Two-Dimensional Anisotropic Foam under Compressive Loads using Voronoi Cells (보로노이 셀을 이용한 2 원 비등방성 폼 구조 모델링 및 탄소성 압축변형 해석)

  • Han, Won-Hee;Choi, Byoung-Ho;Kim, Il-Hyun;Lee, Jeong-Moo
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.7
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    • pp.785-792
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    • 2012
  • Foam structure is usually hard to model due to the complexity of the geometry of cells. So, many simplified models to represent complicated foam structures have been proposed, but most of them are not actually describe the random feature of the cell structure well. So, in this study, two dimensional isotropic and anisotropic closed cell structures of the foam were modeled using the concept of Voronoi cells. The elasto-plastic deformation behavior under compressive loads was investigated by finitie element analysis, and the results were compared with ideal honeycomb structure. In addition, the effect of anisotropy of Voronoi cell structures of the foam on Young's modulus and yield stress under compressive loads was studied.

Research on three-point bending fatigue life and damage mechanism of aluminum foam sandwich panel

  • Wei Xiao;Huihui Wang;Xuding Song
    • Steel and Composite Structures
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    • v.51 no.1
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    • pp.53-61
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    • 2024
  • Aluminum foams sandwich panel (AFSP) has been used in engineering field, where cyclic loading is used in most of the applications. In this paper, the fatigue life of AFSP prepared by the bonding method was investigated through a three-point bending test. The mathematical statistics method was used to analyze the influence of different plate thicknesses and core densities on the bending fatigue life. The macroscopic fatigue failure modes and damage mechanisms were observed by scanning electron microscopy (SEM). The results indicate that panel thickness and core layer density have a significant influence on the bending fatigue life of AFSP and their dispersion. The damage mechanism of fatigue failure to cells in aluminum foam is that the initial fatigue crack begins the cell wall, the thinnest position of the cell wall or the intersection of the cell wall and the cell ridge, where stress concentrations are more likely to occur. The fatigue failure of aluminum foam core usually starts from the semi-closed unit of the lower layer, and the fatigue crack propagates layer by layer along the direction of the maximum shear stress. The results can provide a reference for the practical engineering design and application of AFSP.

An Approximation Method for the Performance Evaluation of AGV Systems (자동 유도 운반차량 시스템의 성능평가를 위한 근사적 방법)

  • Lee, Hyo-Seong;Cho, Myeon-Sig
    • Journal of Korean Institute of Industrial Engineers
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    • v.16 no.2
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    • pp.23-36
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    • 1990
  • A unit-load automated guided vehicle system is considered in which a single vehicle is operated on a unidirectional path in a closed loop. The vehicle serves a manufacturing cell moving pallets from one station to another based on the "First-Encountered-First-Serve" dispatching rule. An approximation method is developed to compute the mean waiting time of an arbitrary pallet at each station. Extensive numerical experiments, performed for various problems, yield fairly good results in most of the cases compared with those obtained by simulation method.

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Sintering Distortion of Barrier Ribs Formed via Capillary Molding Route

  • Chang, Tae-Jung;Kim, Yong-Seog
    • 한국정보디스플레이학회:학술대회논문집
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    • 2003.07a
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    • pp.362-364
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    • 2003
  • In this study, sintering behavior of closed-cell type barrier ribs formed via capillary molding route was examined. Sintering of the molded barrier ribs revealed asymmetric shrinkage, leading to distortion of the cells. The effects of the parameters such as solid loading in the paste, presintering temperature, and morphology of the barrier ribs on the sintering shrinkage of the barrier ribs were investigated.

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난연 및 전기전도성 폐PET/PE 복합 발포체의 제조 및 특성

  • 송종혁;강영구
    • Proceedings of the Korean Institute of Industrial Safety Conference
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    • 2001.11a
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    • pp.242-247
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    • 2001
  • Foam Plastics, cellular plastics, expanded plastics, plastic foam 등 여러 가지 이름으로 불리우고 있는 발포플라스틱은 plastic matrix 내에 무수한 cell이 open 형태 혹은 closed 형태로 존재하는 플라스틱 재료이며/sup 1)/ 원료플라스틱 보다 경량성, 열전도성, 충격흡수성 등 제반물성이 우수하여 포장재료, 보온재, 완충재 및 각종 구조재료로써 널리 사용되고 있으며 소재 plastic의 특성에 따라 PE, PP, PVC, PS, ABS 등 다양하게 개발되어 있다.(중략)

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Effect of the Holding Temperature and Vacuum Pressure for the Open Cell Mg Alloy Foams

  • Yue, Xue-Zheng;Hur, Bo-Young
    • Korean Journal of Materials Research
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    • v.22 no.6
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    • pp.309-315
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    • 2012
  • Metal foam has many excellent properties, such as light weight, incombustibility, good thermal insulation, sound absorption, energy absorption, and environmental friendliness. It has two types of macrostructure, a closed-cell foam with sealed pores and an open-cell foam with open pores. The open-cell foam has a complex macrostructure consisting of an interconnected network. It can be exploited as a degradable biomaterial and a heat exchanger material. In this paper, open cell Mg alloy foams have been produced by infiltrating molten Mg alloy into porous pre-forms, where granules facilitate porous material. The granules have suitable strength and excellent thermal stability. They are also inexpensive and easily move out from open-cell foamed Mg-Al alloy materials. When the melt casting process used an inert gas, the molten magnesium igniting is resolved easily. The effects of the preheating temperature of the filler particle mould, negative pressure, and granule size on the fluidity of the open cell Mg alloy foam were investigated. With the increased infiltration pressure, preheat temperature and granule sizes during casting process, the molten AZ31 alloy was high fluidity. The optimum casting temperature, preheating temperature of the filler particle mould, and negative pressure were $750^{\circ}C$, $400-500^{\circ}C$, and 5000-6000 Pa, respectively, At these conditions the AZ31 alloy had good fluidity and castability with the longest infiltration length, fewer defects, and a uniform pore structure.

Solanum Nigrum Polysaccharide (SNL) Extract Effects in Transplanted Tumor-bearing Mice - Erythrocyte Membrane Fluidity and Blocking of Functions

  • Yuan, Hong-Liang;Liu, Xiao-Lei;Liu, Ying-Jie
    • Asian Pacific Journal of Cancer Prevention
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    • v.15 no.23
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    • pp.10469-10473
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    • 2015
  • Background: Solanum nigrum L. has been used in traditional Chinese medicine because of its diuretic and antipyretic effects. The present research concerned effects of crude polysaccharides isolated from Solanum nigrum L. on erythrocyte membranes of tumor-bearing $S_{180}$ and $H_{22}$ in mice. Materials and Methods: Fluorescence-labeled red blood cell membranes were used with DPH fluorescence spectrophotometry to examine erythrocyte membrane fluidity, and colorimetry to determine degree of erythrocyte surface membrane blocking. Extent of reaction by tumor-bearing mice with the enzyme erythrocyte membrane bubble shadow detection of red cell membrane variation in the degree of closure before and after administration. Results: Solanum nigrum polysaccharide could significantly improve the $S_{180}$ and $H_{22}$ tumor-bearing mice erythrocyte membrane fluidity, compared with the control group, the difference was significant (p<0.01), SNL can significantly improve the red blood cell membrane and then $S_{180}$ tumor-bearing mice sealing ability, compared with the negative control group, the difference was significant(p<0.05, p<0.01). $H_{22}$ tumor-bearing mice can increase red cell membrane and then sealing ability, the difference was significant (p<0.05). Solanum nigrum polysaccharide degree of fluidity and blocking two transplanted tumors in mice restored the ability to raise the red cell membrane has a significant effect. Conclusions: Solanum nigrum L.-type mice transplanted tumor can affect the red blood cell membrane fluidity and re-closed, through the red cell membrane of red blood cells to enhance the immune function of the possibility of erythrocyte immunity against tumor formation garland provide experimental basis.

Comparison of Performance of stepwise serial processing and stepwise parallel processing for Cell Search in WCDMA System (WCDMA 시스템에서 셀 탐색의 단계별 직렬 처리 및 병렬 처리의 성능 비교)

  • 오호근;송문규
    • Proceedings of the IEEK Conference
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    • 2000.11a
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    • pp.73-76
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    • 2000
  • We investigate the stepwise parallel processing of the serial search which can success the co]1 search at low Ec/Io. The single path Rayleigh fading channel which is worst-case channel model is considered. The typical 3-step cell search is used. The probabilities of detection, miss and false alarm for each step are used in closed forms based on the statistics of CDMA noncoherent demodulator output. The optimal power allocation to each channel and The optimal number of post-detection integrations for each step is obtained. Also, the cumulative probability distribution of the average eel] search time for serial search methods are compared.

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