Effects of eccentricity defect on the nonlinear dynamic behavior of the mechanism clutch-helical two stage gear

This paper investigates the nonlinear dynamic behavior of an automotive clutch coupled with a helical two stage gear system. The nonlinear dynamic model is simulated by twenty seven degrees of freedom and including three types of nonlinearity: dry friction path, double stage stiffness and spline clearance. The utility of the proposed nonlinear model is illustrated by the industrial need to clearly identify the dynamic behavior of mechanical elements (shafts, bearings, gears, flywheel, pressure plate, hub of the clutch…) and reduce vibration. The governing nonlinear time varying motion equation formulated is resolved by the analytic Runge Kutta method.Then the modeling of the eccentricity defect located on the gear and the flywheel of the clutch is done. The effect of this defect on the nonlinear dynamic behavior of the system is investigated.     

Alumina supported tungsten hydrides, new efficient catalysts for alkane metathesis

Silica and alumina supported tantalum and tungsten hydrides were tested in alkane metathesis, for comparison of their catalytic properties. In propane metathesis [W]–H/Al₂O₃ proves to be twice more efficient than the usual [Ta]–H/SiO₂ catalyst which is still better than [Ta]–H/Al₂O₃ and [W]–H/SiO₂. Tungsten based catalysts lead to a narrower distribution in the products selectivity and to a higher amount of linear products than [Ta]–H/SiO₂. [W]–H/Al₂O₃ is also a better catalyst than [Ta]–H/SiO₂ for butane metathesis but is less efficient with ethane. Whereas the results in the case of propane or butane can involve the higher initial activity and a lower deactivation of the tungsten catalyst, in the case of ethane, mechanistic or kinetic aspects can be envisaged in particular concerning the difficulty to dehydrogenate ethane into ethylene.     

IoT scheduling for higher throughput and lower transmission power

Wireless Networks - The massive increase in the Internet of Things (IoT) has brought a diverse long-range, low-power, and low bit-rate wireless network technologies. The LoRa a low-power wide area...     

Combined effects of blasting and geological structure on rock mass stability—a case study from the Marrakech–Agadir highway,Morocco

Bulletin of Engineering Geology and the Environment - The Marrakech–Agadir highway crosses mountainous areas of the Western High Atlas of Morocco with a high risk of slope instability. The...     

Prevalence of JC virus viraemia in HIV-infected patients with or without neurological disorders: a prospective study

Superoxide dismutase (SOD) and catalase (CAT) activities were measured in blood from 420 individuals: control population 126, males and females, age between 50 to 93 years of age without any relevant pathology. Pathological population: 294 patients, males and females, age between 50 to 93 years of age, with some disease in the cardiovascular system and in the osteoarticular system, myoma, prostatic pathologies, Chronic Obstructive Pulmonary Disease (EPOC), and Acute Cerebral Vascular Accident (ACVA). The method of Minami and Yoshikawa (SOD) and the method of Aebi (CAT) were judged the techniques of choice for a population study. Statistical methods: ANOVA and Student's "t". 1) The results were that levels of activity for SOD and CAT were increased for women in control population, and 2) the level of activity for CAT decreases with aging. In the pathological population, we detected: 3) increased activity for SOD in cardiovascular diseases, myomas, EPOC and ACVA. 4) for CAT the level of activity decreases in cardiovascular and prostatic diseases, EPOC and ACVA. 5) while in osteoarticular diseases levels of activity for SOD and CAT were standard, but SOD level decreases with aging, for CAT in cardiovascular diseases and EPOC, too. Both enzymes work to balance the antioxidant system.     

Electromagnetic wave propagation in anisotropic metamaterial waveguides

In this paper, we present the formalism of the transverse operator method (TOM). A rigorous study of propagation in anisotropic and multi‐layer medium using the tensor character of the permeability and permittivity is presented. With the application of the Galerkin method, the propagating modes in metallic rectangular waveguides filled with anisotropic metamaterial are exploited. The results are compared with those previously published and show a good agreement. The complex modes have been obtained. The advantages of the techniques used in this paper lie in the proper analytical formulation of the problem studied, on the one hand, and the speed of convergence, on the other hand. TOM offers a fast convergence of the propagation constant. This shows the effectiveness of our numerical model. As such, the formulation of the transverse operator could be a useful tool for microwave engineers. This type of materials known as metamaterial is widely used and needed by industries and information technology, especially in microwave and radiofrequency devices such as patch antennas, antennas waveguides, resonators, circulators, isolators, phase shifters, and filters. Copyright © 2014 John Wiley & Sons, Ltd.     

H/D Exchange on Silica-Grafted Tantalum(V) Imido Amido [(≡SiO)<Subscript>2</Subscript>Ta<Superscript>(V)</Superscript>(NH)(NH<Subscript>2</Subscript>)] Synthesized from Either Ammonia or Dinitrogen: IR and DFT Evidence for Heterolytic Splitting of D<Subscript>2</Subscript>

The silica-grafted Ta^(V) imido amido complex [(≡SiO)₂Ta(NH)(NH₂)], 2, obtained from the reaction of either ammonia or dinitrogen plus hydrogen with the silica-grafted hydrides [(≡SiO)₂Ta^(III)H], 1a, and [(≡SiO)₂Ta^(V)H₃], 1b, undergoes H/D exchange with D₂. In situ IR spectroscopy shows that the fully labelled compound [(≡SiO)₂Ta(ND)(ND₂)], 2-d, can be obtained by moderate heating (60 °C, 3 h) under D₂ atmosphere (550 torr, 300 eq. with respect to Ta), and that the exchange is reversible. The observed stretching and bending frequencies of 2-d are in agreement with the expected isotopic shift upon H/D replacement with respect to literature values reported for 2 and have been corroborated by the independent synthesis of 2-d by reaction of deuterated 1a and 1b with N₂ and D₂. Density functional theory (DFT) calculations, performed using a periodic or a cluster model, explored the structures and energetics of all minima involved in the reaction with H₂ and showed that among the explored pathways the energetically preferred mechanisms for H₂ reaction with [{(μ-O)[(HO)₂SiO]₂}Ta^(V)(NH)(NH₂)], 2q, is the heterolytic cleavage of either the imido Ta=N or the amido Ta-N bonds, to yield respectively [{(μ-O)[(HO)₂SiO]₂}TaH(NH₂)₂], 3q (ΔE = −9.5 kcal mol⁻¹ and ΔG_298K = +2.6 kcal mol⁻¹ with respect to 2q) and [{(μ-O)[(HO)₂SiO]₂}Ta(NH)(NH₃)], 4q (ΔE = −6.0 kcal mol⁻¹ and ΔG_298K = +7.9 kcal mol⁻¹ with respect to 2q). All activation barriers are moderate (between 17.7 and 30.2 kcal mol⁻¹) in agreement with the observed mild heating conditions necessary for the reaction to occur.     

Coding graphene metasurface modeling using MoM‐GEC method for dynamic diffusion and scattering control at Terahertz range

In this article, we present an electromagnetic study of electrically programmable graphene‐based metasurface with individual scattering control. Our investigation is based on the method of moments combined with the generalized equivalent circuit (MoM‐GEC) approach. We show that, tuning the unit cell's conductivity leads to change its input impedance and scattering matrix. So, each unit cell of the metasurface exhibits' a dynamic phase response that can be switched between 0° and ?180° by controlling high transmission and total reflection states. Based on this feature, a 1‐bit coding metasurface consisting of discrete codes of “0” and “1” is used to synthesis 3D beams. Hence, tailorable anomalous reflection and diffusion are studied under normal incidence at a fixed frequency of 3.9 THz. This survey opens new opportunities in the domain of Terahertz beam engineering and security scanner applications.