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21.
R. Ravi Y. V. R. K. Prasad V. V. S. Sarma R. S. Raidu 《Materials and Manufacturing Processes》2006,21(8):756-760
Processing maps are developed using the Dynamic Materials Model (DMM) and instability criterion, which help in choosing optimum process parameters for hot-working of materials. Certain high-level expertise is required to interpret and extract the information on instability regimes to be avoided during processing. In recent years, Artificial Neural Network (ANN) models have been developed to predict flow stress by using the input vector; namely, temperature, strain rate and strain. In this study, using the available Cu-Zn alloy data, ANN model has been developed to classify the hot-working process parameters, such as temperature, strain rate and flow stress for instability regime, directly from the corrected flow stress data without applying the DMM. This model uses 10 compositions of Cu-Zn system, ranging from 3% Zn to 51% Zn. The developed ANN model has been able to learn the nonlinear classifier, which separates unstable region from the stable region in the Cu-Zn alloy system with zinc content less than 40%. 相似文献
22.
In this paper, a particular class of nano-diamond films deposited by energetic species is described. Deposition is carried out using the direct-current glow-discharge (DC GD) deposition technique from a methane/hydrogen mixture. In this method, film growth occurs from energetic species being accelerated and incorporated into the film surface. The growth of the nano-diamond film occurs on top of a preferentially oriented graphitic precursor with its basal planes perpendicular to the substrate surface. The nano-diamond films consist of an agglomerate of diamond particles with particle sizes in the 3-5 nm range with amorphous grain boundaries. The hydrogen concentration in the graphitic precursor is only a few percent; however, it increases to ∼15-20 at.% in the nano-diamond film.From a microscopic perspective nano-diamond film and growth from energetic species is explained as a sub-surface process in terms of a four-step cyclic process. The DC GD-deposited nano-diamond films were comprehensively explored by a number of complementary techniques. The hydrogen content and its role in nano-diamond film formation were assessed. The experimental methods used in our studies comprise near-edge X-ray adsorption fine structure (NEXAFS) to prove the short-range coordination of the carbon films and indirectly their phase composition. The surface and grain boundary phase composition were investigated by a combination of electron energy loss spectroscopy (EELS) measured as a function of incident electron energy and hydrogen etching experiments. By transmission electron microscopy (TEM), the micro-structural evolution and their visualization were achieved. The density evolution of the films was determined by X-ray reflectivity (XRR). The hydrogen content and its distribution in the films were studied by secondary ion microscopy spectroscopy (SIMS) and elastic recoil detection (ERD). The hydrogen bonding was investigated by high-resolution electron energy loss spectroscopy (HREELS).Most likely, hydrogen is bonded within the amorphous grain boundaries and saturates the nano-diamond particles. The surface of the films is amorphous in nature. 相似文献
23.
Edgar M. Barriga Jae G. Jeong Makarand Hastak Matt Syal 《Canadian Metallurgical Quarterly》2005,21(2):91-98
A manufactured home is a factory-built house constructed in a controlled factory environment according to federal standards known as the Department of Housing and Urban Development (HUD) code. The manufactured home shares approximately 20% of the total housing units in the United States and plays an important role in providing affordable housing. However, in terms of material engineering, advanced techniques are scarcely used in the manufactured housing (MH) industry. The current material flow and control systems are characterized as independent demand systems that are based on the personal experience of the material managers. Although independent inventory control systems are widely used in many manufacturing industries, these systems lead to a large amount of inventory and have many drawbacks for the MH industry. On the other hand, dependent inventory systems can reduce unfavorable inventory levels using new techniques and present substantial benefits for the MH industry. This paper applies lean inventory control systems and supply chain management techniques to the current systems of the MH industry and proposes a new framework of material control systems as one of the system management tools. 相似文献
24.
基于分形参数的中药材显微图象纹理分析 总被引:2,自引:0,他引:2
提出了一种基于分形维数分析中药材显微图象的方法。将中药材显微图象视为灰度纹理图象,依据分形布朗运动性质和功率谱法对4种中药材显微图象进行分维数计算。结果表明:中药材显微图象具有分形的特征,分维数能有效地描述纹理的结构与灰度,不同的显微图象对应不同的分维数,分维数可作为分析图象及进一步识别图象的一个定量参数。 相似文献
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27.
单壁碳纳米管及应用现状 总被引:5,自引:0,他引:5
邹莉 《昆明冶金高等专科学校学报》2004,20(1):21-23
讨论了单壁碳纳米管独特的结构、性质和制备方法。由于单壁碳纳米管独特的结构,而导致其独特的电性质、吸附性和力学性能,对单壁碳纳米管目前在电子领域、储氢和复合材料方面的应用研究作了综合阐述。 相似文献
28.
Melissa J. Spannuth Nathan W. Mueggenburg Heinrich M. Jaeger Sidney R. Nagel 《Granular Matter》2004,6(4):215-219
We explore the effect of stacking fault defects on the transmission of forces in three-dimensional face-centered-cubic granular crystals. An external force is applied to a small area at the top surface of a crystalline packing of granular beads containing one or two stacking faults at various depths. The response forces at the bottom surface are measured and found to correspond to predictions based on vector force balance within the geometry of the defects. We identify the elementary stacking fault as a boundary between two pure face-centered-cubic crystals with different stacking orders. Other stacking faults produce response force patterns that can be viewed as resulting from repetitions of this basic defect. As the number of stacking faults increases, the intensity pattern evolves toward that of an hexagonal-close-packed crystal. This leads to the conclusion that the force pattern of that crystal structure can be viewed as the extreme limit of a face-centered-cubic crystal with a stacking fault at every layer.This work was supported by NSF-CTS 0090490 and by the NSF MRSEC Program under DMR-0213745. MJS acknowledges support by the University of Chicago MRSEC Summer 2002 REU program. 相似文献
29.
Kevin K. Tseng 《Canadian Metallurgical Quarterly》2004,130(5):547-550
Many materials exhibit elasto–visco–plastic behavior when subjected to loadings with certain strain rate. Examples include natural materials such as metals, clays, and soils and manmade materials such as some biomimic materials. Some voids may exist or be introduced in these materials. The effects of the voids on the material response are important in predicting the strength, reliability, and service life of structural systems containing these materials. This paper presents the results of applying a statistical micromechanical approach to describe the macroscopic behavior of elasto–visco–plastic materials containing many randomly dispersed spherical voids. Most existing micromechanics based models are only applicable to monotonic proportional loadings. The limitation is removed by integrating the material model into the framework of continuum plasticity. With the discrete integration algorithm and local return mapping algorithm, the proposed computation method is applicable to any loading and unloading histories and is ready for implementing into finite element analysis. 相似文献
30.
固体氧化物燃料电池是一种全固态的能量转换装置,该电池通常采用陶瓷作组装材料,于600-1000℃的高温下操作。本文详细介绍了固体氧化物燃料电池各元件的材料,包括稳定化ZrO2电解质、Ni/稳定化ZrO2阳极、掺杂的LaMnO3阴极以及掺杂的LaCrO3双极分离器等。 相似文献