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21.
Michael N. Gardos 《Tribology Letters》1995,1(1):67-85
440C steel thrust ball bearing races lubricated with 1 m thick sputtered films of MoS2 were tested in the unidirectional and oscillatory modes against bare steel balls in moderate (10–4–10–5 Pa 10–6–10–7 Torr) vacuum and in 1 atmosphere of 99.999% pure ( 1 ppm water) N2 in the same unbaked environmental chamber. Over 90% of the residual gases in the chamber vacuum consisted of H2O vapor. The bearings operated in N2 showed substantially longer lives compared to the specimens tested in vacuum. Scanning electron microscope (SEM) tribometry was also performed on an MoS2 film powder-burnished onto a 440C flat. This flat was repeatedly oscillated against bare, hemispherical-tipped 440C pins on fresh wear tracks in the same type of N2 and column vacuum of ~10–3 Pa 10–5 Torr itself containing over 90% residual H2O. The SEM-generated results on the burnished film confirmed the same, atmosphere-dependent difference in wear life observed with the sputtered layers. Varying the moisture content of the burnished flat and its immediate environment by cryosorption predictably manipulated the coefficient of friction and wear life of MoS2. The various possible causes of this perplexing phenomenon are reviewed, and a plausible hypothesis is offered attributing the unexpected wear life reduction to the physico-chemical consequences of residual H2O hydrogen-bonding to the oxidized and/or hydrated edge and basal plane sites of MoS2 in moderate vacuum. The site-specific sorption of water is severely hindered in 1 atm N2 by the gas molecules disrupting the H-bonding mechanism. 相似文献
22.
This paper proposes an asymptotic rejection algorithm for rejecting exotic disturbances in nonlinear systems. The disturbances, which are produced by nonlinear exosystems, are nonharmonic and periodic. A new internal model is proposed to deal with the disturbances. Further, an adaptive output feedback controller is designed to ensure that the system's state variables can asymptotically converge to zero, and the disturbances can be completely rejected. The proposed algorithm can be used in many applications, e.g. active vibration control, and the avoidance of nonharmonic distortion in nonlinear circuits. An example is performed to demonstrate that the proposed algorithm can completely reject the nonharmonic periodic disturbances produced by nonlinear exosystems. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
23.
M. Abdulkareem A. Ganiyu O. Nathaniel I. Mallum W. Dunu 《Materialwissenschaft und Werkstofftechnik》2021,52(10):1064-1072
Various damage detection methods have been proposed by several researchers in the past few decades. Amongst them, the efficiency of mode shapes in detecting damage has been demonstrated by many researchers when further processed. In most cases, the processing involves expansion or reduction of the mode shape data. However, vital information that are damage-prints are often lost during processing of the mode shape data. In addition, most of these processes involve long and complex computation, thus, leading to inaccurate damage identification. In this study, a simple and fast damage identification technique is proposed to identify damage in beam structures. Interval analysis is applied to the mode shapes of a beam structure in the damaged and undamaged states. The interval situations of each of the beam's segment via mode shape are derived to obtain the upper and lower bounds and the derived bounds are compared. To establish a relationship for identify the damaged point, a possibility of damage existence is defined for each segment of the beam structure. The mode shape increment is defined as the increase in the mode shape value. Furthermore, a damage measure index that provide enhance damage information is obtained as the product of the possibility of damage existence and mode shape increment. A numerical model of a simply supported steel beam is applied to demonstrate this method by imposing damage through thickness reduction of elements in segments. In addition, a parametric analysis is carried out to evaluate noise effect by considering varying damage severities and different noise levels. The results showed that this method is simple and provides considerable accurate results. 相似文献
24.
A new expression of the equations describing the locked states of two oscillators coupled through a resistor is presented in this article. This theory has led to the elaboration of a CAD tool which provides, in a short simulation time, the frequency locking region of two coupled differential oscillators. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012. 相似文献
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High Broad‐Band Photoresponsivity of Mechanically Formed InSe–Graphene van der Waals Heterostructures 下载免费PDF全文
27.
If due to the market analysis a company makes the decision for the production of a new product by application of soldering and special the soldering with temporarily liquid solder, this one is then made specifically after that the company specific construction and production preparation. Either the decision for soldering is technically and/or economically well‐founded or she is even unavoidable by so‐called mixed material connections in the assemblies. This hybrid design finds application increasing today. In the contribution on hand the analysis and assessment of the soldering theory and practice is carried out under the point of view of the possible production of “ideal soldered connections” and “optimal soldered connections”. 相似文献
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Mark Burry 《Architectural Design》2016,86(2):30-35
As Senior Architect to the Basilica of the Sagrada Família in Barcelona, Mark Burry has been ‘thinking parametrically’ for almost his entire career. Here he describes how his longstanding role overseeing the completion of Antoni Gaudí's masterpiece has afforded unique insights into the work of a great geometer and parametric thinker. Burry places the contribution of Gaudí alongside that of Frei Otto – the other eminent 20th-century Proto-Parametricist. 相似文献
30.
Elena Manferdini 《Architectural Design》2015,85(6):32-39
What happens when you subvert the standardised repetition of the Modernist grid? In Building the Picture, a series of drawings that architect Elena Manferdini produced for an exhibition at the Art Institute of Chicago that ran during the spring and summer of 2015, visual effects and colour were applied to counteract Mies's highly uniform and modular mass-producible systems. 相似文献