共查询到20条相似文献，搜索用时 31 毫秒
1.
基于有限元理论,文章运用HyperWorks和MSC.Patran软件建立了某微型车车架的有限元模型,并通过有限元分析的方法对车架的结构进行仿真分析。对静态弯曲与静态扭转两种典型工况下车架的受力情况进行了计算和应力分析,分析结果表明:该车架受到的最大应力值远小于材料屈服极限,满足设计的要求,为改进结构和轻量化设计提供了重要依据。 相似文献
2.
目前,高职高专的教育改革正在不断深化,相关教材也应随之改革修订,要突出高职高专教育特色,突出职业性、应用性,加强理论联系实际。教材内容重点放在理论、原理的应用思路、应用方法、操作技能以及案例分析等方面。明确市场定位,注重市场需求,加强作者队伍建设,策划出一系列符合市场需求的计算机公共课教材。 相似文献
3.
混沌时间序列最大Lyapunov指数的计算 总被引：11，自引：0，他引：11
考虑到已有的计算最大Lyapunov指数的方法具有结果不准确或计算烦难的不足，我们提出了计算最大Lyapunov指数的新方法。此方法先在虚假领域概念基础上确定最佳嵌入参数，然后根据最大Lyapunov指数的定义计算其值，这样，使得此方法在理论上可靠，实施容易，克服了已有方法的不足。最后的应用实例对此进行了验证。 相似文献
4.
有机物料对高产稻区土壤肥力影响的研究 总被引：1，自引：1，他引：1
对高产稻区土壤在氮、磷、钾化肥高水平施用条件下,投入有机物料后对土壤肥力及其产量的影响作了探讨.研究结果表明:增添有机物料后不仅使土壤有机质、速效磷、速效钾含量增加,而且对土壤的团聚水平、团聚度和结构稳定性、通气孔隙、水容量等的土壤物理性状有显著提高;土壤内在的自动调控性能增强,其抗逆性也增加.而单施化肥区土壤有机质略有下降,速效磷增加.速效钾却亏缺.尽管单化区土壤团聚水平、团聚度比试前土壤有所增加,但孔隙水平仍与试前土壤基本类似.所以土壤内在的自动调控性能和土壤的抗逆性均不及稻厩,麦厩区.因此在灾年(多雨)是稻厩、麦厩区产量较单化区分别高10.60％和14.23％,而在正常年景其产量却无明显差异,这可能与高水平化肥施用有关. 相似文献
5.
加工过程中高分子材料形态控制的研究进展 总被引：2，自引：0，他引：2
高分子材料的性能不仅依赖于大分子的化学结构和链结构，而且在
很大程度上依
赖于结晶、取向形态及多相体系的相形态。开展高分子材料在加工过程中的热、应力场作用
下形态形成、演化、调控及“定构”研究对发展高分子成型加工基础理论、开发高性能化、
复
合化、多功能化、低成本化及清洁化高分子材料有重要意义。本文简述了加工过程中高分子
材料形态控制的研究进展，包括国内外研究现状、存在的问题和我国的差距及未来研究的重
要科学问题。 相似文献
6.
While mobile health applications (mHealth apps) have attracted considerable practical and research attention in recent years, very few information systems (IS) studies have ever investigated patients’ use of mHealth apps. We draw insights from attachment theory, which states that when individuals experience fatigue or stress, they tend to develop affectionate bonds with objects that attend to their needs. Our study provides an evolutionary view on how patients’ attaining satisfaction of their basic needs through using mHealth apps leads to their emotional bonding with the mHealth apps and consequently contributes to their overall well-being. We surveyed 113 patients who used an mHealth app for hospitalization and discharge advice and education. We found that (a) patients’ emotional bonding with the apps mediated the impacts of autonomy and relatedness needs satisfaction on their well-being in terms of enhanced IT-enabled self-esteem and reduced post-surgery physical symptoms; and (b) autonomy need satisfaction positively and negatively moderated the impacts of competence and relatedness needs satisfaction, respectively, on patients’ emotional bonding with mHealth apps. Our findings not only contribute to the technology use literature and extend the interpretation of attachment theory in the IS field, but also yield practical insights for managers and developers who work in the mHealth industry. 相似文献
7.
深部矿井高应力影响下软岩巷道支护的稳定性问题,是世界巷道支护中普遍存在的难题,各国业内专家都从理论和实践,技术与工艺,材料与装备上进行大量研究,提出了主动性支护的理念和原则。然而,对这一理念和原则的推广应用,却又因不同国度和自然条件而呈现不同的状况。本文结合唐山矿的实际情况,研究制定了深部高应力影响下软岩巷道支护技术方案,并取得了良好的支护效果。 相似文献
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9.
Yong Cui Huifeng Yao Ling Hong Tao Zhang Yabing Tang Baojun Lin Kaihu Xian Bowei Gao Cunbin An Pengqing Bi Wei Ma Jianhui Hou 《国家科学评论(英文版)》2020,7(7):1239
The development of organic photoactive materials, especially the newly emerging non-fullerene electron acceptors (NFAs), has enabled rapid progress in organic photovoltaic (OPV) cells in recent years. Although the power conversion efficiencies (PCEs) of the top-performance OPV cells have surpassed 16%, the devices are usually fabricated via a spin-coating method and are not suitable for large-area production. Here, we demonstrate that the fine-modification of the flexible side chains of NFAs can yield 17% PCE for OPV cells. More crucially, as the optimal NFA has a suitable solubility and thus a desirable morphology, the high efficiencies of spin-coated devices can be maintained when using scalable blade-coating processing technology. Our results suggest that optimization of the chemical structures of the OPV materials can improve device performance. This has great significance in larger-area production technologies that provide important scientific insights for the commercialization of OPV cells. 相似文献
10.
Yingying Hu Shiyao Bian John Grotberg Marcel Filoche Joshua White Shuichi Takayama James B. Grotberg 《Biomicrofluidics》2015,9(4)
Fluid dynamics of mucus plug rupture is important to understand mucus clearance in lung airways and potential effects of mucus plug rupture on epithelial cells at lung airway walls. We established a microfluidic model to study mucus plug rupture in a collapsed airway of the 12th generation. Mucus plugs were simulated using Carbopol 940 (C940) gels at concentrations of 0.15%, 0.2%, 0.25%, and 0.3%, which have non-Newtonian properties close to healthy and diseased lung mucus. The airway was modeled with a polydimethylsiloxane microfluidic channel. Plug motion was driven by pressurized air. Global strain rates and shear stress were defined to quantitatively describe plug deformation and rupture. Results show that a plug needs to overcome yield stress before deformation and rupture. The plug takes relatively long time to yield at the high Bingham number. Plug length shortening is the more significant deformation than shearing at gel concentration higher than 0.15%. Although strain rates increase dramatically at rupture, the transient shear stress drops due to the shear-thinning effect of the C940 gels. Dimensionless time-averaged shear stress, Txy, linearly increases from 3.7 to 5.6 times the Bingham number as the Bingham number varies from 0.018 to 0.1. The dimensionless time-averaged shear rate simply equals to Txy/2. In dimension, shear stress magnitude is about one order lower than the pressure drop, and one order higher than yield stress. Mucus with high yield stress leads to high shear stress, and therefore would be more likely to cause epithelial cell damage. Crackling sounds produced with plug rupture might be more detectable for gels with higher concentration. 相似文献
11.
The effect of an imperfectly bonded laminar composite is examined in terms of the intensification of the torsional stresses operative near the imperfection which is assumed to be a circular shaped area. The laminar composite is modelled by four layers of different materials with the two outer layers being infinite in height and debonding occurs at the interface of the two inner layers. The analysis based on the application of Hankel transforms and the solution of a pair of dual integral equations can be easily extended to a multilayered system. Depending on the size of the layer thickness relative to the radius of the debonded area, delamination may take place either in a stable or unstable fashion. The analytical results also indicate that the influence of lamination tends to lower the stress intensity around an interface imperfection as compared to the stress state in a homogeneous solid containing the same imperfection. Numerical results are obtained for two special laminate geometries and discussed with reference to the pertinent parameters used in the current theory of fracture mechanics. 相似文献
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13.
为了体现功能梯度材料的耐高温性,本文采用顺序耦合法,通过对Cu和WC组成的双材料和功能梯度材料在热-机耦合作用下进行了ANSYS有限元模拟,结果表明,功能梯度材料较双材料具有大大缓和热应力的作用,同时也证明了Cu/WC功能梯度材料较双材料更适合用作大电流滑动触头用耐磨材料。 相似文献
14.
The chaos characteristics of melt index have been first explored, and the Hilbert–Huang transform method and time delay embedding method are applied to multiscale dynamic analysis on the time series of the melt index (MI) in the propylene polymerization industry. The research results show that the embedding delay is 2, the embedding dimension is 5, the correlation dimension D2 is 1.57, and the maximum Lyapunov exponent is 0.143 for the melt index series, which provide clear evidence of chaotic multiscale features in the propylene polymerization process. Three intrinsic mode functions (IMFs) are decomposed from the melt index time series; the presence of non-integer fractal correlation dimension and positive finite maximum Lyapunov exponent are found in some IMF components. The PP melt index series are divided into two chaotic signals, a determined signal and a random signal respectively, and its complexity is therefore reduced. Furthermore, the coupling of subscale structures of the propylene polymerization is explored with the dimension of interaction dynamics and a robust algorithm for detecting interdependence. It is found that IMF(2) is the main driver in the coupling system of IMF(1)and IMF(2). All these provide a guideline for studying propylene polymerization process with chaotic multiscale theory and may offer more candidate tools to model and control propylene polymerization system in the future. 相似文献
15.
The atomic force microscope system (AFM) has become a popular and useful instrument to measure the intermolecular forces with atomic resolution that can be applied in electronics, biological analysis, materials, semiconductors, etc. This paper studies the bifurcation phenomenon and complex nonlinear dynamic behavior of the probe tip between the sample and microcantilever of an atomic force microscope using the differential transformation method. The dynamic behavior of the probe tip is characterized with reference to bifurcation diagrams, phase portraits, power spectra, Poincaré maps, and maximum Lyapunov exponent plots produced using the time-series data obtained from differential transformation method. The results indicate that the probe tip behavior is significantly dependent on the magnitude of the vibrational amplitude. Specifically, the probe tip motion changes from T-periodic to 3T-periodic, then from 6T-periodic to multi-periodic, and finally to chaotic motion with windows of periodic motion as the vibrational amplitude is increased from 0 to 5.0. Furthermore, it is demonstrated that the differential transformation method is in good agreement for the considered system. 相似文献
16.
M. Farshad 《Journal of The Franklin Institute》1978,305(3):125-135
A two-dimensional theory for the incremental deformations of an initially stressed continuum with couple stresses is established in this paper. As applications of theory, the problems of internal instability and wave propagation are studied. It is found that the otherwise non-dispersive waves become dispersive, and additional local modes of buckling and vibratory motion are observed. To complete the theory, a stress function formulation of equations is also presented. 相似文献
17.
中国粮食生产易损性的灰色关联分析 总被引：4，自引：0，他引：4
用灰色系统理论的方法对影响我国粮食生产易损性的因素进行了灰色关联分析,认为最主要的３个因素是：灌溉面积、国家粮食定购价格和粮田复种指数;而农户的生产性固定资产投资、化肥投入的影响相对较小。并指出了提高我国粮食生产抗灾能力的主要途径。 相似文献
18.
John Grist Brainerd 《Journal of The Franklin Institute》1942,233(2):135-142
Numerous relatively simple physical systems give rise under appropriate circumstances to oscillations which obey the equation y″ + ?(1 + k cos t)y = 0 (Mathieu's equation). These oscillations may be either stable, periodic, or unstable, depending upon parameters of the physical system as expressed by the parameters ? and k in the basic equation. It has been customary to distinguish between the stable and unstable states by diagrams of the type of Fig. 1, from which it is possible to tell whether a given set of values of the parameters ?, k will yield a stable or unstable solution. In this paper are given curves which not only present this information, but in addition give for an important part of the stable state the values of the characteristic exponent μ. The solution of the equation y″ + ?(1 + k cos t)y = 0 depends to a large extent on this exponent, and the availability of values of μ should greatly facilitate the practical application of the equation. 相似文献
19.
基于复杂网络的高技术虚拟产业集群网络演化模型与仿真研究 总被引：1，自引：0，他引：1
从复杂网络视角,分析了高技术虚拟产业集群网络及网络演化的内涵,建立了揭示网络演化机理的HTVIC网络演化框架模型。在此基础上,分析了包含增长、择优连接、自增长、反择优衰退的HTVIC网络演化规则,同时以BA无标度网络演化模型为基础,构建了HTVIC双向择优网络演化模型,并运用平均场理论对该网络演化模型度分布与幂指数进行了详细求解。最后运用Matlab对HTVIC网络演化过程进行了模拟仿真,得出HTVIC双向择优网络演化模型是一种无标度网络演化模型、具有无标度特征的结论。 相似文献
20.
考虑应力集中效应的散体材料桩复合地基固结解析分析 总被引：10，自引：0，他引：10
提出了考虑应力集中效应的散体材料桩复合地基固结数学模型，给出了相应的解析解，并探讨了此类复合地基固结的一般规律，沿用已有理论进行了计算得到的平均固结度较本文理论的计算结果偏小。 相似文献