Electric energy generation from small-scale solar and wind power in Brazil: The influence of location,area and shape

Power production from renewable sources is identified as one of the tools to attain sustainable development in economic and social terms in Brazil. Awareness of how to prioritize renewable energy sources and technologies becomes increasingly important. Solar and wind energy have been highlighted in this context as being clean, safe and also relatively mature technologies. In addition, they are also renowned for having great energy potential and allowing different mounting options for energy harvesting systems. This article seeks to contribute to the knowledge of the effects that the key attributes, location, area and shape, of a site can have on the potential of renewable generation. In order to incorporate these attributes into an integrated analysis, a comparison method is developed and subsequently applied in a case study for two Brazilian cities. Results indicate that the amount of energy obtained by a given power generation system can undergo large variations depending on the characteristics of attributes such as site location, area and shape. This variation may ultra-pass 200%, in some cases, which demonstrates the importance of a better understanding of the role of these attributes in determining energy production.     

The dynamic characteristics of taper seals

Abstract

The dynamic characteristics of taper seal has been investigated. The approach is similar to Black's analysis; the stiffness and damping coefficients are derived. The results showed that the taper seals presented more stable characteristics comparing with plain seals. The practical application of this theory is increasingly used in industry.     

Numerical and experimental studies on aluminum sandwich plates of variable thickness

Abstract

The elastic flexural behavior of static deformation and free vibration of sandwich plates of variable thickness is investigated numerically and experimentally. In the analysis, the face plates are treated as Marguerre shells, and the core is assumed to be an antiplane core and to provide resistance to transverse shear and normal stresses only. Displacement continuity conditions are used at the interfaces between face plates and the core to derive the displacement field. Energy formulations are obtained and solved by the isoparametric finite element method. The numerical results are obtained to compare with the results in the existing literature and to show the effects of taper constant and face plate thickness on deflections and natural frequencies. Finally, experimental works based on the method of holographic interferometry are conducted to confirm the theoretical findings. Experimental and numerical data agree quite well in this work.     

Normalized load‐deflection curves of lateral piles in homogeneous elasto‐plastic soils

Abstract

In this paper, the procedure of normalizing load‐deflection curves of lateral piles in a homogeneous elasto‐plastic soil is presented. An analytical method using subgrade reactions reveals that the normalized relation of load‐deflection exists for force, moment or combined load. The normalized curves for force and moment load fit very well with the predictions using the equations. For the combined load, the normalized curves are distributed between the force and moment load curves, so it is easy to use interpolation from a family of curves. These normalized curves provide a very convenient way for calculating the pile load or deflection in the design stage.     

Optimum design of a wideband planar N-way fork power divider with arbitrary power division and input-to-output impedance matching

An effective design procedure based on method of least squares is proposed for multi-section and multi-output fork power divider/combiner with arbitrary power division ratios among its outputs in a specified frequency bandwidth together with impedance matching among its arbitrary source/load impedances. Transmission and scattering matrices are obtained for its equivalent circuit. An error function is constructed based on design specifications on its output power division ratios, isolations among output ports, return losses at its input and output ports and source/load impedances in a desired frequency bandwidth. The design procedure is fully developed, which determines the widths and lengths of microstrip line sections and resistor values. A design example is described for unequal power division ratio and unequal input/output impedances. A 3-section and 3-output fork power divider is designed for equal power division and load/source impedances for 2–12 GHz band. It is fabricated and measured. Variations of its transmission coefficients are less than 0.5 dB, isolations at its outputs are better than −15 dB and reflection coefficients at its ports are better than −10 dB. Excellent agreement is observed among the results of the proposed design procedure, full wave computer software and measurement data.     

General equivalence between two kinds of noise-correlation filters

A recent comment (Chang, 2014) theoretically demonstrated that for the linear system with the correlated process and measurement noises, the GASF framework proposed in the paper Wang et al. (2012) was equivalent to the conventional de-coupling filtering framework. In this note, we would further show that such equivalence between the two frameworks can be justified in a more general way, even for the nonlinear system.     

Parameter estimation of discrete systems via Hahn polynomials

This paper presents a procedure for using Hahn polynomials for the analysis and parameter estimation of linear discrete-time single-input/single-output systems described by difference equations. An advantage is gained through transforming a linear difference equation into a set of algebraic equations of the system parameters and the Hahn coefficients of the system variables. The key to the equation conversion is the derivation of a relation between the Hahn coefficients of a function and its time-shifted ones. Examples are provided to show the utilization of the procedure.     

A note on a plane creeping corner flow

Abstract

A simple method of similarity transformation is formulated to analyze a two‐dimensional creeping corner flow. By this peculiar transformation, governing equations for the plane velocity are reduced to a pair of ordinary differential equations. With a particular selection of appropriate boundary conditions, the field variables of velocity, pressure, vorticity, and stream function are obtained analytically. A special case with constant velocity at one boundary is explored. The salient characteristics of this example are used to compare with previous investigations. The present study shows that both approaches provide exactly the same solutions. A very interesting feature is that the velocity components in the coordinate system are independent of the radial direction.