钢筋混凝土膜单元的简化设计和剪切强度计算

提出了在面内剪应力与正应力联合作用下膜单元破坏模式识别、设计和强度计算的简化方法。该SMCS(合成应力简化模型)的非迭代方法以修正受压理论(MCFT)的简化结果为基础。除了钢筋的作用大于"平衡"钢筋用量而被忽略,以及最大剪应力不超过断裂强度以外,这种简化使得方程与塑性理论方程相类似,断裂强度从普通和高强混凝土(100兆帕)膜试验数据中得到。以平面内剪应力和正应力为条件,对84个钢筋混凝土膜试验结果进行对比,试验剪切力强度与计算结果的比值平均为1·03,变异系数为11.3%。对于原始的修正受压理论,对应的值分别为0.99和11.1%。所提出方法的结果与ACI规范、简化的修正受压理论以及塑性理论也进行了比较,得到了满意的结果。49个试件中有45个破坏模式可以用所提出的合成应力简化模型准确计算,通过设计和承载力计算案例,对简化模型进行了验证。     

Corrosion Behavior of a Superconductor with Different SnO2 Nanoparticles in Simulated Seawater Solution

The corrosion behavior of (SnO₂)_x(Bi_1.6 Pb_0.4)Sr₂Ca₂Cu₃O₁₀-_δ, (SnO₂)_x(Bi,Pb)-2223, in 0.5?M NaCl solutions at 30°C was studied using potentiodynamic polarization curves measurements, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques as well as scanning electron microscopy (SEM) and energy dispersive X-ray emission spectroscopy (EDX). The polarization data indicated that SnO₂ nanoparticles behave as a cathodic type inhibitor for the corrosion of (Bi–Pb)-2223 phase superconductors in simulating seawater solutions. The corrosion current density of (SnO₂)_x(Bi,Pb)-2223 in a NaCl solution decreases with the time elapsed from sample preparation. The CV of (SnO₂)_x(Bi–Pb)-2223 phase superconductors showed features similar to those of ideal capacitive behavior. The results indicated that a pure (Bi,Pb)-2223 phase superconductor is the most suitable choice for electrochemical capacitor applications in simulating seawater solutions. However, EIS measurements at different potentials revealed that the corrosion process is controlled not only by charge transfer but also by the diffusion process. These measurements also confirm that the corrosion rate of a cathodically polarized phase superconductor is less than that of an anodically polarized phase superconductor. SEM images and EDX analysis showed that the reduction of SnO₂ nanoparticles to Sn decreases the corrosion rates of the superconducting materials.     

Synergistic Effect between Fragaria ananassa and Cucurbita pepo L Leaf Extracts on Mild Steel Corrosion in Hydrochloric Acid Solutions

Protection of Metals and Physical Chemistry of Surfaces - The thermodynamic, inhibitive and synergistic properties of Fragaria ananassa (strawberry) and Cucurbita pepo L (zucchini) leaf extracts on...     

Towards the Development of Realistic DoS Dataset for Intelligent Transportation Systems

Wireless Personal Communications - Vehicular ad-hoc networks (VANETs) present security vulnerabilities, which make them prone to diverse cyberattacks. Denial of Service (DoS) is one of the most...     

Coxiella burnetti infectious endocarditis. Apropos of a case

Chronic forms of Q fever (endocarditis) are rare, but are responsible for severe and desperately recurrent infections, resulting in multiple valve replacements with a reserved prognosis. The authors report the case of a 35-year-old patient with a known history of rheumatic fever, who developed blood culture negative infectious endocarditis on a mitral bioprosthesis. The diagnosis of Q fever was based on serological arguments. Despite long-term antibiotic therapy, serology remained strongly positive and was associated with repeated mitral valve disinsertion. The patient died immediately after the fourth operation in a context of haemodynamic failure. This clinical case emphasizes the importance of performing Q fever serology in any case of culture negative endocarditis and the therapeutic difficulties encountered in chronic recurrent endocarditis.     

Repair of the anophthalmic cavity of rats with synthetic hydroxyapatite

We placed spheres of synthetic hydroxyapatite (calcium chloride combined with sodium phosphate) in the eviscerated or enucleated orbital cavity of rats in order to evaluate the biocompatibility of this material with the orbital cavity. The study was conducted on 50 albino rats, 25 of which were submitted to enucleation and 25 to evisceration of one eye. The animals were sacrificed 7, 15, 21, 30 and 60 days after surgery and the orbital content was submitted to histopathological examination. A reaction of the young granulation tissue type was observed first. The hydroxyapatite was gradually surrounded by a granulomatous macrophage inflammatory response and covered with dense connective tissue that formed a sort of "mesh" septating and supporting progressively smaller blocks of the substance. The same type of reaction was observed in the enucleated and eviscerated cavities. We conclude that synthetic hydroxyapatite is an inert nonallergenic material which is appropriate for volume replacement in the anophthalmic cavity.     

An improved configuration for the reduction of EMG in electrode cuff recordings: a theoretical approach

A theoretical investigation of different electroneurogram recording techniques using electrode cuffs is presented. A new screened tripole arrangement is proposed with a higher inherent signal to interference ratio than the true tripole, which also allows the nulling of the residual electromyogram signal. The reduction in interference is small because the electrode impedance is large compared to the source resistance.     

Variance noise and temperature fluctuations in semiconductors

Experimental evidence is given which shows that very small temperature fluctuations are able to explain the variance noise, as well as the slopes of the power spectral density between 1.2 and 2, often observed from the low-frequency fluctuations in semiconductors.