Modeling and analysis of flow energy harvesters made of PZT ceramics considering different patches,cross-sections,and tip bodies

A nonlinear developed model for various PZT wind energy harvesters with arbitrary dimensions and location of electroceramics has been prepared. This model can describe unimorph and bimorph harvesters with different cantilever cross-sections attached to a tip body with different shapes. The system model has been validated with results reported in the literature. A set of parametric studies has been conducted to examine the influences of the cantilever shape in addition to the shape of the tip body. Furthermore, the impacts of load resistance and wind speed on the output power have been analyzed. The effects of number, position, and dimensions of piezoceramics on the harvester performance have also been investigated. It is found that by increasing the total area of electroceramics (including the length, width, or the number of PZT patches), the peak of the wind critical speed and the middle resistance range where the instability speed is very sensitive to the electrical load shifts toward the lower resistances. Moreover, several instrumental points to design efficient and affordable vibrating wind harvesters at low and high flows have been obtained.     

Corrosion behavior of polypyrrole/hydroxyapatite nanocomposite thin films electropolymerized on NiTi substrates in simulated body fluid

Hydroxyapatite (HAp) nanoparticles synthesized via microwave irradiation. Polypyrrole (PPy)/HAp nanocomposite was obtained using electropolymerization on nitinol (Ni) titanium (Ti) substrates. Fourier transform infrared was employed to characterize the nanocomposite formation. Electrochemical properties of the nanocomposite were investigated using polarization and electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF, 37 ± 0.1 °C). It was concluded that the NiTi specimen coated with PPy/HAp nanocomposite, has higher corrosion resistance than the NiTi coated with pure PPy in the SBF; however, NiTi was better than both coated NiTi. EIS results confirmed corrosion properties. Also, EIS was used to predict the morphology of the coatings. It predicted fine and compact morphology of the nanocomposite that was confirmed using scanning electron microscopy.     

Moving towards a collaborative decision support system for aeronautical data

The recent effort in global information standardization within the aviation industry has triggered an increased need for aviation data to be readily available, accurate and easy for stakeholders to use. Aviation management systems are generally based on old proprietary disparate systems, so there is a growing need for a system which could act as a collaborative decision support system, where the same right data can be provided at the right time to the right users. This system would not only eliminate the need to manually retrieve required information from multiple systems and reduce the possibility of human error, it would also allow the discovery of any hidden knowledge, a task otherwise not possible from separate systems. This paper presents our proposed approach to build an integrated system for data-intensive collaborative decision support. Each stage in the proposed framework is explained, including a section on the performance evaluation of the proposed system.     

Effect of Calculation Method on Values of Hansen Solubility Parameters of Polymers

Summary The simplest experimental method to determine the Hansen Solubility Parameters (HSP) for a polymer is to evaluate whether or not it dissolves in selected solvents. The solvents dissolve the polymer have HSP closer to it than those which don’t. Then a computer program can be used to find the HSP of the selected polymer. In this work, the effect of calculation method on the values of HSP has been analyzed completely. The results show that optimization method for calculation of HSP is an important factor in the precision of obtained values of these parameters.     

The Relationship Between the Productivity Index and the Diffusivity Coefficient and Its Application in Reservoir Characterization

Abstract

The authors offer a reliable means to determine the diffusivity coefficient and permeability distribution throughout a reservoir while minimizing the number of expensive well tests. To explain this inexpensive procedure, data of the Asmari Reservoir—located in Iran on the Coast of Persian Gulf—are used. Using well test, petrophysical, pressure-volume-temperature, and production data, a relationship between the productivity index and the diffusivity coefficient is established for the Asmari Reservoir without relying on the reservoir radius value, which is uncertain when obtained from drawdown well testing. This method determines the optimum locations for new wells in development of giant fields.     

Sudden Fracture from U-Notches in Fine-Grained Isostatic Graphite Under Mixed Mode I/II Loading

The U-notched maximum tangential stress (UMTS) criterion, proposed originally and utilized previously by the author and his co-researcher for predicting mixed mode I/II fracture in plexi-glass (PMMA) and also pure mode II fracture in PMMA and soda-lime glass, was employed to estimate the experimental results reported in literature dealing with brittle fracture of many U-notched fine-grained isostatic graphite plates under combined tensile/shear loading conditions. By using the fracture curves of the UMTS criterion, which can predict the onset of brittle fracture in terms of the notch stress intensity factors (NSIFs) in the entire domain from pure mode I to pure mode II, the mixed mode fracture toughness (i.e. the load-bearing capacity) of U-notched graphite plates was successfully estimated.     

Entropy generation in a hollow cylinder with temperature dependent thermal conductivity and internal heat generation with convective–radiative surface cooling

This article investigates entropy generation in an asymmetrically cooled hollow cylinder with temperature dependent thermal conductivity and internal heat generation. The inside surface of the cylinder is cooled by convection on its inside surface while the outside surface experiences simultaneous convective–radiative cooling. The thermal conductivity of the cylinder as well as the internal heat generation within the cylinder are linear functions of temperature, introducing two nonlinearities in the one-dimensional steady state heat conduction equation. A third nonlinearity arises due to radiative heat loss from the outside surface of the cylinder. The nonlinear system is solved analytically using the differential transformation method (DTM) to obtain the temperature distribution which is then used to compute local and total entropy generation rates in the cylinder. The accuracy of DTM is verified by comparing its predictions with the analytical solution for the case of constant thermal conductivity and constant internal heat generation. The local and total entropy generations depend on six dimensionless parameters: heat generation parameter Q, thermal conductivity parameter β, conduction–convection parameters Nc₁ and Nc₂, conduction–radiation parameter Nr, convection sink temperature δ and radiation sink temperature η.     

Convective‐radiative fins with simultaneous variation of thermal conductivity,heat transfer coefficient,and surface emissivity with temperature

This paper is a numerical study of thermal performance of a convective‐radiative fin with simultaneous variation of thermal conductivity, heat transfer coefficient, and surface emissivity with temperature. The convective heat transfer is assumed to be a power function of the local temperature between the fin and the ambient which allows simulation of different convection mechanisms such as natural convection (laminar and turbulent), boiling, etc. The thermal conductivity and the surface emissivity are treated as linear functions of the local temperature between the fin and the ambient which provide a satisfactory representation of the thermal property variations of most fin materials. The thermal performance is governed by seven parameters, namely, convection–conduction parameter Nc, radiation–conduction parameter Nr, thermal conductivity parameter A, emissivity parameter B, the exponent n associated with convective heat transfer coefficient, and the two temperature ratios, θ_a and θ_s, that characterize the temperatures of convection and radiation sinks. The effect of these parameters on the temperature distribution and fin heat transfer rate are illustrated and the results interpreted in physical terms. Compared with the constant properties model, the fin heat transfer rate can be underestimated or overestimated considerably depending on the values of the governing parameters. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20408     

Application of Taguchi Method for Characterization of Corrosion Behavior of TiO2 Coating Prepared by Sol‐Gel Dipping Technique

Titanium oxide (TiO₂) nanoparticle coatings were deposited on the 316L stainless steel substrates by sol‐gel method. The morphology, structure, and corrosion resistance of the coating were analyzed using SEM, AFM, X‐ray diffraction, and electrochemical techniques. The deposition parameters employed to realize the anticorrosion performance including calcinations temperature, polyethylene glycol (PEG) content, pH value, and number of dipping cycles were investigated. Taguchi statistical experiments were carried out to determine the influence of the deposition variables on anticorrosion properties and optimal conditions. The results indicated that a higher anticorrosion performance of TiO₂ films could be achieved using 1 g of PEG in a sol with pH in range of 7–9, six cycles of dipping, and calcination temperature at 400°C. The Tafel polarization measurements indicate that i_corr value decreases about 200 times and the R_corr value increases around 57 times compared with uncoated 316L stainless steel.