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在岩土力学与工程领域,大变形测试方法与技术亟待开发。前期研究发现,利用炭黑/硅橡胶导电复合材料研发的力敏元件具有较好的大变形敏感特性。根据研究需要,通过试验方法研究了这种大变形力敏元件的热、力敏感耦合特性。对制作的力敏元件进行了两种加载试验,一是固定拉伸应变下温度循环试验;二是变应变下温度循环试验。试验结果表明,恒定应变下,试样电阻随温度循环而循环,且呈现出电阻松弛现象;应变与温度同时变化时,电阻的变化主要受应变影响,温度影响相对较弱。 相似文献
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以热塑性弹性体苯乙烯/乙烯/丁烯-苯乙烯(SEBS)和炭黑纳米颗粒为原料,采用熔融共混-模压成型法制备了SEBS/纳米炭黑复合电阻式应变传感膜.实验中,研究了该薄膜的力学性能及其电阻应变的传感性能.力学测试表明,该复合应变传感膜具有优异的弹性力学特性,断裂伸长率达410.8%,断裂强度达2.5 MPa,经1000次循环拉伸后,其形变率仅为3.0%.应变传感测试显示,随着复合膜拉伸倍率增大其电阻变化呈线性提高,并且动态拉伸电阻变化速率高于静态条件下的电阻变化速率.该复合应变传感膜应用于人体胳膊弯曲试验显示,可较为精准的记录胳膊弯曲量和弯曲次数,进而得知人体的运动活动量,在健身和康复等领域有重要的潜在应用价值. 相似文献
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利用溶剂法工艺制备了炭黑/硅橡胶导电复合材料,对其进行了拉伸及压缩敏感试验,研究其可重复性。拉伸试验结果表明,各配方试样电阻-拉伸应变曲线均具有较好的可重复性(最大应变达到24%左右);C4与C6试样的可重复性略差于C8~C18试样,这主要是由于炭黑含量小于6%时,复合材料内部导电网络不太稳定造成的。压缩试验结果表明,复合材料的压阻敏感性也具有一定的可重复性(最大压力达到15 MPa左右)。总体看来,炭黑/硅橡胶复合材料的拉伸及压缩敏感性在较大拉伸应变及压应力范围内都具有较好的可重复性及线性度,满足开发传感器的基本性能要求。 相似文献
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工程上,土工加筋带变形测试一直是个难题,主要是因为其应变较大且加筋带外层是相对较软的聚合物结构.利用纳米导电炭黑颗粒充填聚合物获得敏感材料,再通过印刷技术将其印刷在塑料薄片上,制作成传感元件.通过拉伸试验测试了四种不同底板传感元件的传感性能,试验结果表明,四种元件均具有拉伸敏感性,电阻值随拉伸应变的增大而增大,且满足模量匹配与较大应变要求.对比分析发现,PVC底板传感元件的综合性能最佳,适合作为土工筋带变形测试元件使用.另外,这种方法制作的传感元件可批量化生产,无需逐个标定,极大地提高了它的实用性. 相似文献
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European Community policy and the market 总被引:1,自引:0,他引:1
C. Lloyd 《Journal of Computer Assisted Learning》1993,9(2):86-91
Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven. 相似文献
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融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。 相似文献
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David Poole 《Computational Intelligence》1989,5(2):97-110
Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given. 相似文献
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Watts S. Humphrey 《Annals of Software Engineering》2002,14(1-4):39-72
This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)SM and Team Software Process (TSP){SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical. 相似文献
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基于复小波噪声方差显著修正的SAR图像去噪 总被引:4,自引:1,他引:3
提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。 相似文献
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R. NOSS 《Journal of Computer Assisted Learning》1987,3(1):2-12
Abstract This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development. 相似文献
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C. Xiang 《控制理论与应用(英文版)》2014,12(3):217-217
正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where 相似文献
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《浙江大学学报:C卷英文版》2014,(7)
正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere. 相似文献
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Alan V. Di Vittorio 《Remote sensing of environment》2009,113(9):1948-2750
The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm2, BIAS = 0.143 µg/cm2, RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm2, BIAS = − 0.992 µg/cm2, RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm2, BIAS = − 2.12 µg/cm2, RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data. 相似文献
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Philip Marks 《Cryptologia》2018,42(1):1-80
This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G). 相似文献