75 m/s simulation and experiment of two-stage reluctance coilgun

Magnetic launchers are divided into three main techniques, with one of them being the reluctance coilgun. The projectile in this method is rather simple and the obtained velocity is relatively low, which is its main disadvantage. Also, theoretical simulations for high velocity usually predict much higher velocities than that of the experiments. The aim of this work is to demonstrate an accurate simulation of a two-stage coilgun and show experimental validation of high launching velocity. A two-stage coilgun was designed and optimized by numerical simulations. Accordingly, it was implemented and tested experimentally. As an outcome, the highest reported velocity of 75 m/s was obtained both in the simulation and experiment. This outcome contributes to the understanding that adding stages can increase the launching velocity by carefull implementation of the initial position of the projectile, together with proper timing of the second stage. It is concluded that with this approach a multi-stage coilgun can reach even higher velocity.

     

Obtaining small photovoltaic array operational curves for arbitrary cell temperatures and solar irradiation densities from standard conditions data

The paper presents a simple approach to deriving I–V curves of photovoltaic panels and small arrays for arbitrary environmental conditions on the basis of three points of a single operating curve data and short current temperature coefficient only. The proposed method does not employ fitting of any type and is solely based on a numerical solution of a system of transcendental equations. The equations are expressed in a dimensionless form, simplifying both the solution and photovoltaic panel parameters' representation. The solution is used to find the values of normalized equivalent circuit elements for the available data and then perform an appropriate adjustment to obtain the operating curves for arbitrary conditions. The proposed method was applied to monocrystalline and polycrystalline commercial solar panels and was compared with both manufacturer‐provided and experimentally measured operating curves to analyze the approach applicability and accuracy. Copyright © 2012 John Wiley & Sons, Ltd.     

Classification of spatio-temporal patterns in charging and discharging of Li-ion batteries

We classify the dynamic patterns that emerge in charging or discharging of Li-ion batteries, under galvanostatic conditions, using simulations of the two-phase one-dimensional (1D) porous electrode model. This work examines the effect of the exchange current function, R₀(X), which expresses the nature of kinetics. This extends our previous study with R₀ = 1 where the same pattern emerges in charging or discharging, whether as a homogeneous or a step-wise process made of multiple symmetry breaking events. With commonly-used asymmetric R₀(X), the emerging patterns may be one of the two above or as fronts that follow single SB event and the lithiation/delithiation behaviors are different. These effects are clear when parameters are uniform; nonuniformity leads to noise that mask the behavior. The full four-variable model exhibits SB, even in absence of noise, since the liquid potential gradient (${\varphi }_l$) works like a perturbation. This similarity allows us to derive approximations to the full model behavior.     

Particulate multi‐phase polymeric nanocomposites

The present research focuses on a model system of a blend of two immiscible polymers containing an inorganic nanofiller, exploring the effect of various melt processing procedures on structuring and on the resulting properties. Binary polypropylene/alumina and ternary polypropylene/nylon/alumina composites were produced by batch compounding under various processing conditions and compositions. Several types of polypropylene and alumina grades were examined. The alumina nanoparticles vary primarily in their mean particle size (13, 50, 500 nm). The morphology of the nanocomposites produced and their thermal, and rheological properties were studied. It was found that under certain processing conditions the nanoparticles significantly affect the morphology of the polypropylene/nylon polymer blend causing compatibilization. Also, the alumina nanoparticles affect the melt viscosity of the polypropylene/nylon blends, whereas their effect on either polypropylene or nylon melts was found insignificant. POLYM. COMPOS., 27:425–430, 2006. © 2006 Society of Plastics Engineers