An Equalization Time Reduction Method Using a Pseudo‐Random Number Sequence for a Cell Voltage Equalization Circuit with an LC Series Circuit

When the cells of energy storage devices such as electric double‐layer capacitors are connected in series, it results in voltage imbalance in each cell because of the nonuniform properties of the individual cells. In a previous research, the authors proposed a novel cell voltage equalization circuit using an LC series circuit, and they examined the effectiveness of this circuit. However, the characteristics of the cell voltage equalization operation depend on each cell voltage difference. Therefore, the proposed circuit has a disadvantage that the equalization time tends to be longer than other cell voltage equalization circuits with a boosting circuit. This paper proposes an equalization time reduction method that uses a pseudo‐random number sequence generated by the linear congruential generators. The proposed method can reduce the average equalization time without adding any other active or passive elements. The effectiveness of the proposed method is verified through the experimental results. According to the experimental results, the proposed equalization time reduction method reduces the equalization time to 86.5% of the conventional method.     

Development of a novel device for applying uniform doses of electron beam irradiation on carcasses

The Maxim's Electron Scatter Chamber (Maxim Chamber) was developed to obtain uniform dose distribution when applying electron beam (e-beam) irradiation to materials of irregular surface. This was achieved by placing a stainless steel mesh surrounding a cylindrical area where the target sample was placed. Upon contact with the mesh, electrons scatter and are directed onto the target from multiple angles, eliminating the e-beam linearity and resulting in a uniform dose distribution over the target surface. The effect of irradiation in the Maxim Chamber on dose distribution and pathogen reduction was tested on rabbit carcasses to simulate other larger carcasses. The dose uniformity ratio (DUR) on the rabbit carcasses was 1.8, indicating an acceptable dose distribution. On inoculated carcasses, this treatment reduced Escherichia coli O157:H7 by > 5 log cycles. These results indicate that carcass irradiation using e-beam is feasible using the Maxim's electron scattering chamber. Appropriate adjustments will be further needed for commercial application on beef and other animal carcasses.     

A combined method using modified routh stability array and MSE criterion for the reduction of discrete‐time systems

Abstract

A new mixed method using modified stability array and mean‐square error (MSE) criterion is proposed for deriving reduced‐order 2‐transfer functions for discrete‐time systems. More precisely, the modified Routh stability array is used to obtain the reduced‐order denominator, thus ensuring stability preservation, while the numerator is obtained by minimizing the mean‐square error between the unit step responses of the original system and reduced model. The main feature of the method is that it does not actually evaluate the system and model responses in the step of minimizing mean‐square error.     

Dimension reduction in principal component analysis for trees

The statistical analysis of tree structured data is a new topic in statistics with wide application areas. Some Principal Component Analysis (PCA) ideas have been previously developed for binary tree spaces. These ideas are extended to the more general space of rooted and ordered trees. Concepts such as tree-line and forward principal component tree-line are redefined for this more general space, and the optimal algorithm that finds them is generalized.An analog of the classical dimension reduction technique in PCA for tree spaces is developed. To do this, backward principal components, the components that carry the least amount of information on tree data set, are defined. An optimal algorithm to find them is presented. Furthermore, the relationship of these to the forward principal components is investigated, and a path-independence property between the forward and backward techniques is proven.These methods are applied to a brain artery data set of 98 subjects. Using these techniques, the effects of aging to the brain artery structure of males and females is investigated. A second data set of the organization structure of a large US company is also analyzed and the structural differences across different types of departments within the company are explored.     

DFT study of the oxygen reduction reaction on iron,cobalt and manganese macrocycle active sites

The best performing non-precious metal based catalysts for polymer electrolyte membrane fuel cells are manufactured by incorporation of nitrogen into a carbon structure in the presence of iron and cobalt. Herein, density functional theory (DFT) calculations have been performed to investigate the oxygen reduction reaction on catalyst active sites modelled as transition metal macrocycles with iron, cobalt or manganese central atoms. The effects of the transition metal and macrocycle structure have been investigated. The structure of the most promising active sites has been proposed, and the detailed potential energy profiles of the oxygen reduction reaction have been obtained over the active sites, including all intermediate steps with corresponding activation barriers. The efficiency of the active sites depends primarily on the transition metal nature, and the central iron atom accounts for the higher catalytic activity than cobalt and manganese. The central manganese atom can favour the two-electron oxygen reduction pathway and thus yielding hydrogen peroxide.     

Reduced order finite element model for elastohydrodynamic lubrication: Circular contacts

This paper presents an extension of the reduced order finite element model to the case of circular elastohydrodynamic lubricated (EHL) contacts under isothermal Newtonian considerations. The line contact model was developed and validated in a previous work (Advances in Engineering Software, 2013; 56:51−62). The model is based on a finite element discretization of the EHL equations: Reynolds, linear elasticity and load balance with a reduced order model for the linear elasticity part. All equations are solved simultaneously in a fully-coupled framework using a damped-Newton procedure allowing fast convergence rates for the global solution. This model combines fast convergence rates, reduced memory requirements and negligible model reduction errors compared to the full model which makes it an attractive tool for EHL contact performance prediction.     

Applying artificial optimization methods for transformer model reduction of lumped parameter models

Detailed R-C-L-M models of power transformers, which are based on lumped parameters, are used extensively not only for transient analysis of power transformers to determine electrical stresses in windings, but also for studying transients in power systems. Models with few elements are generally more practicable for power system studies but at the expense of accuracy. The use of artificial methods to reduce an R-C-L-M model is the main contribution of this paper. Advantages of the suggested method include: (1) a reduced loss of accuracy compared with the original model and (2) the flexibility to choose the number of model elements to achieve the desired model depending on size and accuracy. The ability of three different artificial methods, genetic algorithm, particle swarm optimization, and bacterial foraging algorithm, to model reduction is evaluated using measurements on an actual 400 kV test object and the results are compared with those obtained by common analytical formulae.     

Enhanced catalytic activity of nanoshell carbon co-doped with boron and nitrogen in the oxygen reduction reaction

The use of carbon cathode catalysts in polymer electrolyte fuel cells instead of the current platinum catalysts is attracting increasing attention. We claim that two factors are important for enhancing the activity of carbon cathode catalysts in the oxygen reduction reaction (ORR): the formation of a nanoshell structure and co-doping with boron and nitrogen. Herein, we investigate the preparation and characterization of active ORR carbon catalysts that combine the above factors. Boron and nitrogen (BN)-doped nanoshell-containing carbon (BN-NSCC) was prepared by carbonizing a mixture of poly(furfuryl alcohol), cobalt phthalocyanine, melamine, and a trifluoroborane–methanol complex at 1000 °C. Transmission electron microscopy and X-ray photoelectron spectroscopy revealed the formation of nanoshell structures with distorted graphitic layers and the introduction of boron and nitrogen atoms, respectively. The ORR activity was evaluated in oxygen-saturated 0.5 mol dm^?3 H₂SO₄ using Koutecky–Levich analysis. The BN-NSCC showed an eight to ten times higher ORR activity than undoped NSCC, with an increased number of electrons participating in the reaction. Tafel analysis revealed a change in the rate-determining step caused by BN-doping. Thus, the combination of a nanoshell structure and co-doping with boron and nitrogen was found to improve the ORR activity of carbon catalysts.     

H∞ model reduction for negative imaginary systems

This paper is concerned with the H_∞ model reduction for negative imaginary (NI) systems. For a given linear time-invariant system that is stable and NI, our goal is to find a stable reduced-order NI system satisfying a pre-specified H_∞ approximation error bound. Sufficient conditions in terms of matrix inequalities are derived for the existence and construction of an H_∞ reduced-order NI system. Iterative algorithms are provided to solve the matrix inequalities and to minimise the H_∞ approximation error. Finally, a numerical example is used to demonstrate the effectiveness of the proposed model reduction method.     

Development of shape-engineered α-MnO2 materials as bi-functional catalysts for oxygen evolution reaction and oxygen reduction reaction in alkaline medium

In this work, three kinds of α-MnO₂ nano shapes, namely, nano-wires, nano-tubes and nano-particles have been prepared with a fine control over α-crystallographic form by employing hydrothermal procedure. The materials have been thoroughly characterized by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) spectrometry, field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The MnO₂ nano shapes are used as a model system for examining the shape-influenced bi-functional electrocatalytic activity towards oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in alkaline medium. The bi-functional role has been investigated by cyclic voltammetry and linear sweep voltammetry with rotating ring disc electrode (RRDE) techniques. It is found that α-MnO₂ nano-wires possess enhanced electrocatalytic activity compared to other two shapes namely nano-tubes and nano-particles despite the nano-tubes having a much higher specific surface area. The insight of bi-functional electrocatalytic activity is analysed in terms of catalyst surface with the help of first principles density functional theory (DFT) calculations based on the fact of surface energies and adsorption of water on the surface for a facile reaction.