RF Energy Harvesting System and Circuits for Charging of Wireless Devices Using Spectrum Sensing

Recently, lots of works have been done on the optimal power management of wireless devices. This leads to the main idea of ambient energy harvesting. Among various energy harvesting approaches, one is to use radio waves existing in the ambient environment for battery charging, called RF energy harvesting. In this chapter, in order to improve the RF energy harvesting performance, we utilize spectrum sensing to allow the wireless devices to select the frequency band with maximum power that exceeds a predefined threshold to charge the device (this power threshold can be determined according to battery type and its required charging power) and the device can use this power for battery charging. Also, a novel voltage multiplier circuit is proposed. By means of simulations and experimental tests, it can be seen that after detection of our desired 1 mW RF signal, system output power is about 532μ W and 450μ W in simulation and practical situations respectively

Stochastic Finite Element Modelling of Char Forming Filler Addition and Alignment – Effects on Heat Conduction into Polymer Condensed Phase

Micro- and nano-filler particles have been considered as char-forming flame retardants for polymers. It has been shown that suitable particles may operate in the condensed phase to prevent or delay the escape of fuel into the gas phase. Good flame retardancy performance may be achieved in composites with comparatively low filler loadings. However, many candidate filler materials, such as rod-like and plate-like carbon allotrope fillers with high aspect ratio, will effectively enhance the composite’s thermal conductivity, and hence, may greatly increase heat input into the condensed phase. Moreover, anisotropy in terms of thermal conductivity must be considered when rod-like and plate-like particles are aligned, for example as a result of manufacturing processes. The presented study investigates these effects, i.e., thermal conductivity enhancement due to filler addition and alignment, using a modeling framework based on Monte Carlo simulation that was developed for predicting effective composite properties considering filler-matrix and particle-to-particle interfacial effects. A stochastic finite element analysis was performed to model rod-shaped carbon particles embedded in a polymer matrix. The chosen analysis is demonstrated to be an effective means for elucidating the effect of filler addition and alignment on the heat conduction into polymer materials containing fillers as char-forming flame retardants

Quantum gravitational optics in the field of a gravitomagnetic monopole

Vacuum polarization in QED in a background gravitational field induces interactions which {\it effectively} modify the classical picture of light rays as the null geodesics of spacetime. After a short introduction on the main aspects of the quantum gravitational optics, as a nontrivial example, we study this effect in the background of NUT space characterizing the spacetime of a spherical mass endowed with a gravitomagnetic monopole charge, the so called NUT factor.Comment: 9 pages, title changed and the text abridged for publication in the Journal of Physics: Conference serie

Sensitivity or resistance to steroid therapy in children with idiopathic nephrotic syndrome is not associated with polymorphism of angiotensin converting enzyme (ACE)

It's about years that the relation between renin angiotensin aldosterone system (RAS) and involving enzymes such as angiotensin converting enzyme (ACE) with nephrotic syndrome is under the focus of researchers and also there are a lot of meta-analyses. However there were few studies investigated the relation of ACE polymorphism and sensitivity or resistance to steroid therapy in children. So we intend to do that. In the current study the sample size was 40 children. Among them, 22 patients were sensitive and 18 patients were resistant to steroid therapy. The samples were collected from Ali-Asghar pediatric hospital in Tehran, Iran. We used polymerase chain reaction (PCR) for the genotyping. After that, we used Chi-squared test for statistical analysis. The statistical analysis showed no significant correlation between ACE polymorphism and sensitivity or resistance to steroid therapy (P = 0.77). Although the frequency of DD genotype was higher in the resistant group, but this difference was not statistically significant. Finally we found that although based on previous studies, D allele and DD genotype are more frequent in children with idiopathic nephrotic syndrome in comparison to healthy children, but the resistance or sensitivity to steroid therapy in children is not associated with ACE polymorphism. Further meta-analysis on the studies done on children is suggested. � 2016 Parisadat Ahmadi et al

An experimental study on condensation heat transfer characteristics of R-600a in tubes with coiled wire inserts

In this experimental research, condensation heat transfer enhancement of R-600a as a consequence of used spring inserts inside a horizontal condenser is studied. The condenser was a copper tube with the internal diameter, wall thickness, and length of 8.1, 0.71, and 1000 mm, respectively. Five coiled wires with various coil pitches of 10, 20 and 30 mm, and various wire diameters of 0.5, 1 and 1.5 mm were used inside the test pipe. Tests were conducted at vapor qualities within the range of 0.03-0.79 and mass velocities between 115-365 kg/m2s. Results indicated that coiled wires are advantageous instruments in heat transfer improvement of the condenser. In this regard, the coiled wire with the wire diameter of 1.5 mm and coil pitch of 10 mm showed the best performance among all inserts by the heat transfer coefficient increased up to 107% over the smooth tube. It was also observed that the use of springs affects the transition of flow pattern from annular to intermittent, and the annular regime was observable at a lower vapor quality in comparison to the smooth tube. Finally, a new correlation is developed to predict the condensation heat transfer coefficients of R-600a in coiled wire inserted tubes

Fermat's principle in quantum gravitational optics

Interactions incorporating the vacuum polarization effects in curved backgrounds modify the null cone structure in such a way that the photon trajectories would not be the space-time geodesics anymore. The gravitational birefringence introduced as a direct consequence of these effects, will allow shifts in the photon velocities leading to polarization dependent superluminal propagation. Taking these effects into account we study Fermat's principle in the context of the 1+3 (threading) formulation of the space-time decomposition. We find an expression for the modified spacetime refractive index and show it is proportional to the light cone correction to the first order. Consequences of this modification on polarization sum rules and spatial light paths are considered.Comment: 13 Pages, REVTex format, section on gravitomagnetic monopoles is removed along with its references, new references adde

Life cycle assessment of novel biomethane systems

Climate mitigation and supply of renewable energy are global challenges. The main cause of climate change is anthropogenic activities, including consumption of fossil energy sources and land use change. Biomethane, a biomass-derived renewable energy carrier, is interchangeable with fossil-based natural gas and can provide energy services (e.g. heat, electricity and vehicle fuel) and high-value products such as chemicals. However, the availability of feedstock suitable for anaerobic digestion, the limited grid infrastructure in certain regions and problems relating to storage and distribution are barriers to increased deployment of biomethane systems. This thesis aims to provide decision support for the development and implementation of future biomethane systems, by describing the energy performance and climate impact of some promising novel technologies related to biomethane production, conversion of biomethane to high-value products and biomethane distribution in a life cycle perspective. Anaerobic digestion of maize and pyrolysis of willow for production of biomethane were assessed and compared, while gas-to-liquid (GTL) technologies were studied as potential routes for conversion of biomethane to liquid transportation fuels or platform chemicals. Gas hydrates were assessed as a means of biomethane distribution. The results showed that transition from maize-based anaerobic digestion to willowbased pyrolysis for biomethane production improved energy performance (higher external energy ratio) and environmental performance (lower climate impact), mainly due to buildup of soil organic carbon and use of biochar as a soil amendment or as an energy source to replace fossil coal. Use of biomethane for production of dimethyl ether as a GTL fuel was competitive relative to the conventional compressed biomethane system regarding energy performance and climate impact. Formation and disassociation of gas hydrates was associated with high energy use, and thus technological development is required to overcome the high primary energy inputs and related high climate impact of gas hydrate distribution