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针对薄宽带钢冷轧过程中易发多发的局部型中浪瓢曲缺陷,引入非均匀载荷宽度、弹性约束系数及平均张应力建立了屈曲变形的解析计算模型。应用能量最低原理对屈曲变形区域进行搜索求解,得到了局部型中浪屈曲临界条件(包括临界应力、屈曲波长和屈曲波宽),获得了其与非均匀载荷宽度、弹性约束系数、平均张应力的关系,并发现平均张应力是产生局部型中浪的重要影响因素。应用样条有限元方法对局部型中浪进行数值仿真分析,验证了屈曲解析计算方法的正确性。在实验轧机上进行了轧制研究,通过轧制获得了局部型中浪屈曲模态,对实验结果分析得到了相对应的屈曲临界条件,与解析法和样条有限元法结果基本吻合,证明了样条有限元计算方法与解析计算方法的正确性及其工程应用价值。 相似文献
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INFLUENCE OF DAMPING MODELS ON DYNAMIC ANALYSES OF A BASE-ISOLATED COMPOSITE STRUCTURE UNDER EARTHQUAKES AND ENVIRONMENTAL VIBRATIONS 下载免费PDF全文
Structural design simultaneously governed by earthquakes and environmental vibrations has received a lot of attention in recent years.Base-isolated composite structures are typically used in the above-mentioned structural design.The corresponding analysis involves validating structural safety under earthquakes and human comfort under environmental vibrations through a time-history analysis.Thus,a reasonable damping model is essential.In this work,the representatives of viscous damping model and rate-independent damping model,namely the Rayleigh damping model and uniform damping model,were adopted to investigate the influence of damping models on the time-history analysis of such structural designs.The energy dissipation characteristics of the above-mentioned damping models were illustrated via a dynamic test of recycled aggregate concrete specimens.A case study was performed on a base-isolated steelconcrete composite structure.The dynamic responses under the excitation of earthquakes and environmental vibrations were compared using different damping models.The uniform damping model was found to be more flexible than the Rayleigh damping model in dealing with excitations with different frequency components.The uniform damping model is both theoretically advantageous and easy to use,demonstrating its potential in dynamic analysis of structures designed simultaneously governed by earthquakes and environmental vibrations. 相似文献
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Effective vibration recognition can improve the performance of vibration control and structural damage detection and is in high demand for signal processing and advanced classification.Signal-processing methods can extract the potent time-frequency-domain characteristics of signals;however,the performance of conventional characteristics-based classification needs to be improved.Widely used deep learning algorithms(e.g.,convolutional neural networks(CNNs))can conduct classification by extracting high-dimensional data features,with outstanding performance.Hence,combining the advantages of signal processing and deep-learning algorithms can significantly enhance vibration recognition performance.A novel vibration recognition method based on signal processing and deep neural networks is proposed herein.First,environmental vibration signals are collected;then,signal processing is conducted to obtain the coefficient matrices of the time-frequency-domain characteristics using three typical algorithms:the wavelet transform,Hilbert-Huang transform,and Mel frequency cepstral coefficient extraction method.Subsequently,CNNs,long short-term memory(LSTM)networks,and combined deep CNN-LSTM networks are trained for vibration recognition,according to the time-frequencydomain characteristics.Finally,the performance of the trained deep neural networks is evaluated and validated.The results confirm the effectiveness of the proposed vibration recognition method combining signal preprocessing and deep learning. 相似文献
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中国电影资料馆珍藏着大量早期影片,其中许多具有珍贵的保存价值.1936年由蔡楚生编导、任光谱曲的<迷途的羔羊>是我国第一部以流浪儿童为题材的影片,也是我国儿童影片中的第一部有声片.此片在思想和艺术上都取得了突破,尤其是以童谣形式演唱的主题歌<月光光歌>感人至深,充分发挥了音乐的魅力,增强了整部影片的感染力.影片公映后,深受广大观众的欢迎和电影工作者的赞扬.七十多年过去了,当我们准备再次让它同观众见面时,却发现能够最真实、最原始记录影音效果的原底、声底片却出现了许多问题,给复制工作带来了空前的难度,这是我们从事资料影片复制工作三十多年来从未遇到过的难题.主要有以下几方面问题: 相似文献
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1989年是照片诞生后的第150周年.自从第一次将光影与化学结合起来用于从大自然中获得永恒的图片后,自然风光摄影就倍受争议.不管怎样,无论艺术还是科学,技艺还是职业,摄影都是产生于客观性与选择性之间,创造性与现实性之上的一种档案媒介.在最新的一次统计后,国家档案馆现今保存有1500万以上的照片档案.不管是百年前拍摄的还是上个星期刚刚拍摄的,照片所要传递出的要素通常是些非常独特的信息.无论照片、底片和幻灯片,是黑白的还是彩色的,无论旧与新,不管是退色了的还是色彩艳丽的,单独的还是成集合的,最为关键的是它们都见证了加拿大历史与社会的发展与兴衰. 相似文献
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We have synthesized a variety of alkali-metal and ammonium fluorosulfatometallates (titanates, zirconates, and hafnates). The alkali fluorosulfatozirconates and fluorosulfatohafnates have been shown to exhibit efficient roentgenoluminescence (RL) in the UV through visible spectral region, with a maximum at 390–440 nm. Their RL spectra depend significantly on their composition (cation, anion, and water content), coordination of KF and K2SO4, and relative amounts of fluorine and SO4 groups. We have examined the effect of heat treatment on the RL of these compounds. The rubidium and cesium fluorosulfatozirconates Rb3Zr2F9SO4 · 2H2O, Cs2ZrF2(SO4)2 · 2H2O, Cs8Zr4F2(SO4)11 · 16H2O, and Cs2ZrF4SO4 offer the most efficient RL. 相似文献
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A. M. Grishin 《Journal of Engineering Physics and Thermophysics》2001,74(4):895-903
Basic definitions and concepts of the physicomathematical theory of natural catastrophes are given. Possibilities of mathematical modeling of natural and technogenic catastrophes are discussed in the context of the theory of heat and mass transfer and the mechanics of reacting media. The importance of taking into account conjugate heat and mass exchange in modeling catastrophes is emphasized. A formula for evaluating the probability of a collisional catastrophe is given. 相似文献
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Wiwanitkit V 《Hemodialysis international. International Symposium on Home Hemodialysis》2012,16(1):116; author reply 116-116; author reply 117
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Velev JP Jaswal SS Tsymbal EY 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1948):3069-3097
The existence of multiple ferroic orders in the same material and the coupling between them have been known for decades. However, these phenomena have mostly remained the theoretical domain owing to the fact that in single-phase materials such couplings are rare and weak. This situation has changed dramatically recently for at least two reasons: first, advances in materials fabrication have made it possible to manufacture these materials in structures of lower dimensionality, such as thin films or wires, or in compound structures such as laminates and epitaxial-layered heterostructures. In these designed materials, new degrees of freedom are accessible in which the coupling between ferroic orders can be greatly enhanced. Second, the miniaturization trend in conventional electronics is approaching the limits beyond which the reduction of the electronic element is becoming more and more difficult. One way to continue the current trends in computer power and storage increase, without further size reduction, is to use multi-functional materials that would enable new device capabilities. Here, we review the field of multi-ferroic (MF) and magnetoelectric (ME) materials, putting the emphasis on electronic effects at ME interfaces and MF tunnel junctions. 相似文献
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Garny A Nickerson DP Cooper J Weber dos Santos R Miller AK McKeever S Nielsen PM Hunter PJ 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2008,366(1878):3017-3043
We have, in the last few years, witnessed the development and availability of an ever increasing number of computer models that describe complex biological structures and processes. The multi-scale and multi-physics nature of these models makes their development particularly challenging, not only from a biological or biophysical viewpoint but also from a mathematical and computational perspective. In addition, the issue of sharing and reusing such models has proved to be particularly problematic, with the published models often lacking information that is required to accurately reproduce the published results. The International Union of Physiological Sciences Physiome Project was launched in 1997 with the aim of tackling the aforementioned issues by providing a framework for the modelling of the human body. As part of this initiative, the specifications of the CellML mark-up language were released in 2001. Now, more than 7 years later, the time has come to assess the situation, in particular with regard to the tools and techniques that are now available to the modelling community. Thus, after introducing CellML, we review and discuss existing editors, validators, online repository, code generators and simulation environments, as well as the CellML Application Program Interface. We also address possible future directions including the need for additional mark-up languages. 相似文献
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Yongkang Chen Mike Bacich Cory Nardin Albert Sitorus Mark M. Weislogel 《Microgravity science and technology》2005,17(4):14-24
The behavior of wall-bound drops and bubbles is fundamental to many natural and industrial processes. Key characteristics
of such capillary systems include interface shape and stability for a variety of gravity levels and orientations. Significant
solutions are in hand for axisymmetric pendent drops for a variety of uniform boundary conditions along the contact line with
gravity acting normal to a planar wall. The special case of a wall-bound drop or bubble that is also pinned at an edge (i.e.
a ‘wall-edge-bound’ drop) is considered here where numerical solutions are obtained for interface shape and stability as functions
of drop volume, contact angle, fluid properties, and uniform gravity vector. For a semi-infinite zero-thickness planar wall
(plate), a critical contact angle is identified below which wall-edge-bound drops are always stable. The critical contact
angle is computed as a function of the gravity vector. The numerical procedure, which makes no account for contact angle hysteresis,
predicts that such wall-edge-bound drops are unconditionally unstable for any gravity field with a component that is tangent
to the wall while inwardly normal to the edge. Select experiments are conducted that support the conclusions drawn from the
numerical results. 相似文献