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1.
In recent years, artificial neural networks (ANNs) have been applied to many geotechnical engineering problems with some degree of success. In the majority of these applications, data division is carried out on an arbitrary basis. However, the way the data are divided can have a significant effect on model performance. In this paper, the issue of data division and its impact on ANN model performance is investigated for a case study of predicting the settlement of shallow foundations on granular soils. Four data division methods are investigated: (1) random data division; (2) data division to ensure statistical consistency of the subsets needed for ANN model development; (3) data division using self-organizing maps (SOMs); and (4) a new data division method using fuzzy clustering. The results indicate that the statistical properties of the data in the training, testing, and validation sets need to be taken into account to ensure that optimal model performance is achieved. It is also apparent from the results that the SOM and fuzzy clustering methods are suitable approaches for data division.  相似文献
2.
应用ProcessingMap研究D2钢高温变形的动态应变时效   总被引:2,自引:0,他引:2  
应用以动态材料模型为基础的ProcessingMap研究了D2钢在变形温度900~1160℃、变形速率0.01~10.00s-1区间的动态应变时效规律。结果表明,D2钢在变形温度为1120~1150℃、变形速率为0.01s-1条件下发生动态应变时效,并表现出强烈的硬化效应。同时,应变速率敏感系数小于零可以作为发生动态应变时效的一个标志。  相似文献
3.
粉末冶金TiAl合金热变形行为及加工图的研究   总被引:2,自引:1,他引:1  
采用热模拟压缩试验研究了粉末冶金TiAl合金在温度1000~1150℃、应变速率0.001~1s~(-1)范围内的高温变形特性,发现合金的流动应力-应变曲线具有应力峰和流变软化特性.为了研究TiAl合金在有限应变下的变形行为,基于动态材料模型(DMM)建立起了TiAl合金加工图.试验结果表明,在高应变速率(>0.1s~(-1))变形时,材料落人流动失稳区域,出现表面开裂.这对材料的变形是有害的,要避免在流动失稳区进行热加工处理.而在温度为1000~1050℃,应变速率为0.001~O.01s~(-1)时,功率耗散率η值在35%~50%之间.这个区域对应的变形机制为动态再结晶,适合进行热加工.在高温(≥1100℃),低应变速率(0.001s~(-1))变形时,功率耗散率η达到最大值60%,此时材料发生超塑性变形.  相似文献
4.
6069铝合金的热变形行为和加工图   总被引:2,自引:0,他引:2  
采用Gleeble-1500热模拟实验机在温度为300~450℃,应变速率为0.01~10 s?1条件下对6069铝合金进行热压缩实验,研究该合金的热变形行为及热加工特征,建立热变形本构方程和加工图。结果表明,6069铝合金热变形过程中的流变行为可用双曲正弦模型来描述,在实验条件下的平均变形激活能为289.36 kJ/mol。真应变为0.7的加工图表明合金在高温变形时存在2个安全加工区域,即变形温度为300~350℃、应变速率为1~10 s?1的区域和变形温度为380~450℃、应变速率为0.01~0.3 s?1的区域。适合加工的条件是变形温度为350℃,应变速率0.01 s?1。  相似文献
5.
StudyonHotDeformationCracksofSteelD2UsingProcesingMapGaoShan,LiuXianghua,WangGuodongABSTRACTThehotdeformationbehaviorsofsteel...  相似文献
6.
In 4 experiments, the authors investigated the reversal of spatial congruency effects when participants concurrently practiced incompatible mapping rules (J. G. Marble & R. W. Proctor, 2000). The authors observed an effect of an explicit spatially incompatible mapping rule on the way numerical information was associated with spatial responses. The authors also observed an effect of an incompatible numerical mapping rule (if smaller than 5, press right; if larger than 5, press left) on the Simon effect. This effect was observed only when both tasks used the same effectors. The results point to a shared spatial representation for explicit spatial information (locations) and implicit spatial information (numbers). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献
7.
The authors argue that the ways in which people--scientists and laymen--use probabilistic reasoning is predicated on a set of often questionable assumptions that are implicit and frequently go untested. They relate to the correspondence between the terms of a theory and the observations used to validate the theory and to the implicit understandings of intention and prior knowledge that arise between the conveyer and the receiver of information. The authors show several ways in which the use of probabilistic reasoning rests on a priori commitments to a partitioning of an outcome space and demonstrate that there are many more assumptions underlying the use of probabilistic reasoning than are usually acknowledged. They unfold these assumptions to show how several different interpretations of the same results in behavioral decision theory and cognitive psychology are equally well supported by "the facts." They then propose a more comprehensive approach to mapping cognitive processes than those currently used, one that is based on the analysis of all of the relevant alternative interpretations presented in the article. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献
8.
采用MMS-200热模拟试验机,在变形速率为0.1~10 s-1、变形温度为900~1 150℃以及最大变形量为70%的变形条件下对SAE4137钢进行等温热压缩试验。依据试验结果,基于动态材料模型以及Murthy失稳判定准则下,绘制出SAE4137钢在不同真应变下的热加工图,得到SAE4137钢在成形时的加工稳定区、失稳区以及推荐加工区间。通过微观组织分析进行验证,并结合南钢中间方坯(215 mm×235 mm)经过4道次精轧轧制φ150 mm大棒材实际情况,预判SAE4137钢棒材生产过程中表面可能产生的缺陷及位置。  相似文献
9.
通过等温恒应变速率压缩试验,研究了2种FGH98合金粉末热等静压锭坯在1 050~1 150℃/0.005~1.000 s-1的变形行为。基于动态材料模型,建立了2种粉末锭坯的热加工图。结果表明,2种粉末锭坯的流变曲线特征相似,同种变形条件下,氩气雾化(AA)粉末锭坯的峰值应力小于等离子旋转电极(PREP)粉末锭坯。AA粉末锭坯的最佳变形窗口为1 088~1 108℃/0.005~0.016 s-1,功率耗散效率η大于42%;PREP粉末锭坯的最佳变形窗口为1 098~1 120℃/0.010~0.016 s-1,η大于40%。  相似文献
10.
在MTS810试验机上进行了MX246A合金的热压缩试验,获得了不同变形条件下该合金的真应力-真应变曲线,建立了MX246A合金的热加工图。结果表明,Ni3Al基MX246A合金的流变应力随着变形程度的增加先达到峰值应力,之后逐渐降低,趋于稳态流变。在较高的应变速率变形时容易达到稳态流变,在较低的应变速率时,随着应变量从临界应变逐渐增大,流变应力单调递减,并且随着温度的升高,单调递减的速率逐渐增大。真应变量为0.7的MX246A合金的加工图上存在一个安全加工区,对应的温度在1 220℃附近,应变速率在0.001s-1附近。随着真应变量的增大,功率耗散峰值区域逐渐向高温区移动,功率耗散的微观机制随之由动态回复向γ′相的回溶转变。  相似文献
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