230,098 research outputs found
Some Closed-Form Results for Adhesive Rough Contacts Near Complete Contact on Loading and Unloading in the Johnson, Kendall, and Roberts Regime
No full textRecently, generalizing the solution of the adhesiveless random rough contact proposed by Xu, Jackson, and Marghitu (XJM model), the first author has obtained a model for adhesive contact near full contact, under the Johnson, Kendall, and Roberts (JKR) assumptions, which leads to quite strong effect of the fractal dimension. We extend here the results with closed-form equations, including both loading and unloading which were not previously discussed, showing that the conclusions are confirmed. A large effect of hysteresis is found, as was expected. The solution is therefore competitive with Persson's JKR solution, at least in the range of nearly full contact, with an enormous advantage in terms of simplicity. Two examples of real surfaces are discussed
Characterization of acoustic emission signals from particulate filled thermoset and thermoplastic polymeric coatings in four point bend tests
No full textFour point bend tests were conducted on two previously characterized particulate filled thermoplastic andthermoset polymeric coatings, the acoustic emission (AE) method being utilized to monitor the damageprogress during the tests. Different damage mechanisms operating in the polymeric coatings can berecognized by the different amplitude range of the AE signals emitted. AE can be used to assess the relativestrength of particle/matrix bonds in particulate filled polymeric coatings.Highlights* Damage mechanisms in the particulate filled polymeric coatings can be distinguished from the AE signals.* AE can be used to assess the relative strength of particle/matrix bonds in particulate filled polymeric coatings.* No sudden load drop is associated with the formation of cracks in the coating during the elastic deformation of the steel substrate
Degradation of groundwater resources under African cities: Technical and Socio-economic challenges.
No full text1 Issues of groundwater pollution in Africa Y. Xu Department of Earth Sciences, University of the Western Cape, Bellville, South Africa BH Usher Institute ..
Sublytic complement C5b-9 complexes induce thrombospondin-1 production in rat glomerular mesangial cells via PI3-k/Akt: association with activation of latent transforming growth factor-beta1
No full textMesangial cell proliferation is a common cellular response to a variety of different types of glomerular injury. Complement C5b‐9 is a prime candidate to mediate mesangial cell proliferation, especially sublytic C5b‐9, which can induce the production of multiple inflammatory factors and cytokines. Transforming growth factor (TGF)‐β1 plays a major role in the accumulation of extracellular matrix (ECM), while thrombospondin (TSP)‐1 has been identified as an activator of latent TGF‐β1 in an in vitro system. Using rat glomerular mesangial cells (GMCs) as a model system, we assessed the effect of sublytic C5b‐9 on the expression of TSP‐1 and TGF‐β1 and explored the relevant pathway of signal transduction. First, we ensured the concentrations of anti‐Thy1 antibody and complement, which were regarded as a sublytic C5b‐9 dose, and examined whether the sublytic C5b‐9 induced expression of TSP‐1 in rat GMCs which, in turn, activated latent TGF‐β1 by real‐time polymerase chain reaction (PCR) and enzyme‐linked immunosorbent assay (ELISA), respectively. Then, we investigated the role of the PI3‐k/Akt pathway in sublytic C5b‐9‐induced TSP‐1 production in rat GMCs by Western blot analysis. The addition of sublytic C5b‐9 (5% anti‐Thy1 antibody and 4% normal serum) to rat GMCs induced activation of latent TGF‐β1 via TSP‐1. The addition of sublytic C5b‐9 apparently increased the protein of Akt phosphorylation, whereas PI3‐k inhibitor LY294002 could clearly reduce the increase of TSP‐1 induced by sublytic C5b‐9. These results indicate that TSP‐1 is an activator of latent TGF‐β1 in sublytic C5b‐9‐induced rat GMCs; furthermore, the PI3‐k/Akt signal transduction pathway may play a key role in sublytic C5b‐9‐induced TSP‐1 production
Effect of linear feedback control on the optimal transient growth in particle-laden channel flow
No full textThe optimal transient growth process in a particle-laden channel flow is studied under the influence of the linear feedback control. The equilibrium Eulerian approach with the assumption that the particles are small and spherical is adopted. The effect of initial distribution of particles on the optimal transient growth of perturbations is discussed. The LQG control of the particle-laden flow system is considered and compared with the no control cases
A novel calibration method for PD measurement in power cables and joints using capacitive couplers
No full textPartial discharge (PD) measurements are universally accepted as a technique giving some indication of the state of the insulation in high voltage apparatus. Cable end users are keen to adopt an on-line PD monitoring during commissioning of systems. However, because of noisy environments and the problems of interference the conventional methods are difficult to implement. As a consequence, ultra-high frequency (UHF) / very high frequency (VHF) techniques of on-site detection of partial discharges have been developed. A technique based on the capacitive coupling has received much attention. It has been demonstrated that it is possible to using the technique to monitor the partial discharge in cables, particularly in joints/terminations. However, in order to obtain quantitative information about PD, calibration is required for this technique. Existing calibration methods are difficulty to implement on-site. In this paper a novel method is proposed and compared with the conventional method on a short piece of cable. It has been shown that individual capacitive coupler can also be accurately calibrated on-site and online using the new method, therefore it provides quantitative information about the amount of apparent discharge. In practice this is important for electricity utilities as the quantitative information about PD can be used to determine the quality of cable system and to decide whether the system needs to be repaired or replaced
Authors' reply to Xu
No full textComment on : Xu Y. One female perspective on diversity in peer review. BMJ. 2023 Jul 19;382:1656. doi: 10.1136/bmj.p1656
Xu Shen's graphic analysis revisited
No full textInternational audienceLike other writing systems, the Chinese writing is based on a limited number of basic elements. Compared to the 26 letters of the alphabet, or the 70 hiragana and katakana signs for (modern) Japanese, the precise number of basic units is unknown in the Chinese case. It is almost never touched upon, or varies a lot, not only between specialists and corpora, but even within the same corpus. In trying to elucidate the reason for such a different treatment in the case of the Chinese script, one cannot but focus on the first author who developed a proper analysis of the script. When Xu Shen wrote the Shuo wen jie zi , the first dictionary of Chinese characters compiled at the end of the first century, he provided a systematic analysis of more than 9 000 characters. Considering that their structure was best brought out by the older style of graphs known as the small seal script, he based his analysis on this older style, which kept graphemes more clearly apart. If compound characters can include more than 10 basic graphemes, Xu Shen basically only retained 2 main constituents to which he attributed a phonetic or a semantic function. Most characters (about 86% in Shuowen) consist in the combination of a semantic and a phonetic constituent (). In these cases, Xu Shen's distinction between semantic and phonetic constituents considerably simplified the graphic analysis. Once a constituent is attributed a phonetic function, there is no need to try to understand its meaning in a character (or provide ad hoc interpretations for it). But what about semantic compound characters without identifiable phonetic constituent, included in the other 14% characters in Shuo wen jie zi? The study of semantic compound characters is more complex and, at times, more subjective, but it allows a better understanding of Xu Shen's motivation. I shall present the different strategies and formulae (X, X, X , X Y, etc.,) employed by Xu Shen in these cases, with concrete examples, and discuss the interpretation of the relative location of the constituents (such as for example in :). The latter as well as the different kinds of motivated explanations, Xu Shen often adds, show that the graphic analysis is designed to ascertain the gloss of the character. We will see that even though Xu Shen provided some graphic analyses with 3, 4 or even 5 constituents, in most cases, he basically retained 2 main semantic constituents. Systematic and sound as it may appear, Xu Shen's analysis in terms of constituents, clearly motivated by the semantic interpretation of the characters, has eluded the fundamental question concerning the basic units of the Chinese writing system
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