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61.
62.
Vijaya Agarwala K. G. Satyanarayana R. C. Agarwala 《Materials Science and Engineering: A》1999,270(2):3897
With a view to developing a new metal–metal cast composite material as a possible substitute for ferrous materials in wear resistant applications, Al alloy (LM11) is reinforced with mild steel (ms) wires and it is heat treated to get ‘reaction interface’ (RI). Microhardness, tensile properties and wear characteristics of the matrix, as-cast and heat treated composites have been determined. While microhardness of the composite showed variation from 150 to 45 VHN across the interface in the as-cast composite, annealed (500–525°C) composite showed a microhardness of 350–420 VHN at the interface indicating the effectiveness of the heat treatment. It is seen that the % improvement in wear resistance increased with increase in number of wires when embedded in the aluminium alloy matrix. Further imrpovement of about 30% was observed when heat treated at 500°C for 15 h. These results have been discussed in terms of wetting between ms wires and the matrix, particularly the increase of hardness and tensile strength to the formation of ‘reaction interface’ due to annealing. The width of the interface increased with annealing time and temperature and the kinetics of reaction followed logarithmic and parabolic growth rate. The activation energy for the formation of intermetallics constituting the reaction interface is found to be 20.7 KJ mol−1. From the measured hardness and ultimate tensile strength of the constituents and composites an empirical relation was deduced. 相似文献
63.
介绍了三端稳压器LM317T芯片的工作过程及其输出电压的计算公式。基于电路板芯片供电电源的考虑,设计了一种采用LM317T的三端稳压器的电源电路,用于给控制板芯片供电。设计电路时,详细分析了其电路设计方法,给出了此电路主要参数的计算及实验波形。最后将此供电电源电路制成印刷电路板,测取各重要测试点的电压信号,用Protel对电源供电电路进行仿真,仿真的结果与实际测试计算值相符,证明设计的电源供电电路是可靠的,具有一定的实用价值。 相似文献
64.
针对目前数控机床故障复杂、诊断困难的问题,提出基于人工神经网络的故障诊断方法。在研究传统BP神经网络故障诊断模型基础上,引入改进的BP算法-LM算法,建立机床主轴系统LM-BP神经网络故障诊断模型,对机床主轴系统故障进行分析与诊断,再通过Matlab仿真与传统BP神经网络相对比,仿真结果表明:传统BP神经网络存在较难实现快速、准确的故障定位问题,而BP神经网络LM算法作为故障诊断的核心算法收敛速度快、识别准确。该方案设计合理可行,有较好的应用前景,并给出应用了实例。 相似文献
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66.
提出了一种莱文伯格—马夸特(LM)算法和支持向量机(SVM)有机结合的LM/SVM新算法,并将其应用于基于集总模型的二次反应清洁汽油研究法辛烷值的预测。借鉴复杂反应动力学研究中的集总方法,将汽油研究法辛烷值看成汽油饱和烃集总、烯烃集总、芳烃集总的函数,并采用支持向量机表达该函数。针对支持向量机参数及核函数参数难以选择的问题,通过莱文伯格-马夸特算法搜索支持向量机中的参数,并采取把训练集分割成工作样本和检验样本的策略,从而解决了过拟合的问题。利用经典测试函数对LM/SVM算法的性能测试结果表明:LM/SVM算法不但精度优于文献报道的遗传算法与支持向量机相结合的GA/SVM方法,而且其效率也远高于GA/SVM方法。LM/SVM方法对二次反应清洁汽油研究法辛烷值预测的相对误差绝对值的平均值为0.71%。 相似文献
67.
68.
设计了一种二线制电流型电阻变送器,能把1 000~2 000Ω的电阻量转化为4~20mA的电流量。该变送器由1片运算放大器芯片构成信号调理电路与二线制V/I转换电路,运用零温度系数的恒流源作为被测电阻的激励信号,具有电路简单、线性度高、性能稳定和成本低等特点,且不存在智能仪器可能出现的程序跑飞、死机等异常情况。测试结果表明,精度为0.1级,工作电源电压范围为15~30V。 相似文献
69.
Nadeem Ullah Ghazala Yasmeen Butt Mehwish Jaffer Quratul Ain 《Microscopy research and technique》2022,85(2):748-754
The study was carried out in four districts, that is, Gujranwala, Gujarat, Narowal and Sialkot of Punjab, Pakistan. The sampling was carried out randomly in different seasons from the water bodies especially from wastewater. Twenty-one species belonging to Euglenophycota were identified using light microscopy and scanning electron microscopy from which 04 species belong to genus Phacus, 02 species belonging to Trachelomonas and Euglena based on light microscopy. It was observed that Euglena was the most diverse genus and it is supposed to be the indicator species of the polluted water. It was observed that E. oblonga was found in maximum pH range, that is, 7.0–11.0. Similarly, E. brevicaudatus was found in maximum EC, that is, 169 ± 1.5 ms/cm these outcomes indicated that for internal examination along with LM, SEM was necessary for correct identification of algal sample up to specie level. 相似文献
70.
Daniel B. Carr Anthony R. Olsen Suzanne M. Pierson Jean-Yves P. Courbois 《Data mining and knowledge discovery》2000,4(1):43-67
The paper introduces linked micromap (LM) plots for presenting environmental summaries. The LM template includes parallel
sequences of micromap, label, and statistical summary graphics panels with attention paid to perceptual grouping, sorting
and linking of the summary components. The applications show LM plots for Omernik Level II Ecoregions. The summarized United
States continental data includes USGS digital elevation, 30-year normal precipitation and temperature, and 8 million AVHRR
pixels classified into 159 types of land cover. One LM plot uses a line-height glyph to represent all 159 land cover percentages
per ecoregion. LM plots represent new visualization methodology that is useful in the data and knowledge based pattern representation
and knowledge discovery process. The LM plots focus on providing an orienting overview. The overview provides a starting place
for subsequent drilling down to what could otherwise be viewed as an overwhelming mass of data. The overview also provides
a starting place to learn about the intellectual structure that lies behind the notion of ecoregions and begins to connect
this abstract structure to quantitative methods. 相似文献