A design method for substrate integrated waveguide electromagnetic bandgap (SIW-EBG) filters

An efficient design method for substrate integrated waveguide electromagnetic bandgap (SIW-EBG) filters is proposed which provides direct dimensional synthesis approach for desired filter objectives without using network representations. The method is applied to the design of an X band SIW-EBG filter and its response is compared with HFSS (high frequency structure simulator) simulations for validation purposes. Fairly good agreement between the results shows the applicability of the proposed method for SIW-EBG filter design.     

Phase/State Transitions of Confectionery Sweeteners: Thermodynamic and Kinetic Aspects

Abstract: It has been said that the key to making high‐quality candy is understanding and controlling the transitions of sugar. Whether found as crystal, glass, or fluid solution, sugars impart the texture necessary to distinguish one confection from another and to provide a unique experience to the consumer. In principle, the phase/state transitions of sugars are best understood through careful application of the phase diagram. However, many, if not all, confections are not at equilibrium, meaning that the phase diagram is simply a starting point for understanding and controlling the state of sugars. An understanding of the thermodynamic driving forces that push a confection towards equilibrium and the kinetic constraints that control the rate of approaching that equilibrium are key elements to creating products with the desired texture, quality, and shelf life. In this review, we summarize the thermodynamic and kinetic aspects of controlling phase/state transitions in sweeteners, with particular emphasis on applications to confectionery products.     

Hygrothermal Fracture Analysis of Orthotropic Materials Using J k -Integral

A new computational method based on the J _k -integral is put forward for the purpose of conducting fracture analysis of orthotropic materials subjected to hygrothermal stresses. By utilizing the constitutive relations of plane orthotropic hygrothermoelasticity, an alternative expression for the J _k -integral is derived to replace the general limit definition. A numerical procedure is developed and integrated into a finite element analysis software to implement the proposed form of the J _k -integral. Temperature and specific moisture concentration fields, which are required in fracture calculations, are also computed through finite element analysis. Numerical results are generated by considering an embedded crack in a polymer matrix fibrous composite laminate, that is subjected to steady-state hygrothermal loading. Comparisons of the mixed-mode stress intensity factors computed by the J _k -integral based method to those evaluated via the displacement correlation technique demonstrate that, the proposed form of the J _k -integral is domain independent and leads to numerical results of high accuracy. Presented parametric analyses illustrate the influences of the fiber volume fraction and the crack location on the modes I and II stress intensity factors, the energy release rate, and the T-stress.     

Thermal fracture analysis of orthotropic functionally graded materials using an equivalent domain integral approach

A new computational method based on the equivalent domain integral (EDI) is developed for mode I fracture analysis of orthotropic functionally graded materials (FGMs) subjected to thermal stresses. By using the constitutive relations of plane orthotropic thermoelasticity, generalized definition of the J-integral is converted to an equivalent domain integral to calculate the thermal stress intensity factor. In the formulation of the EDI approach, all the required thermomechanical properties are assumed to have continuous spatial variations through the functionally graded medium. Developed methodology is integrated into a fracture mechanics research finite element code FRAC2D using graded finite elements that possess cubic interpolation. Steady-state and transient temperature distribution profiles in orthotropic FGMs are computed using the finite elements based heat transfer analysis software HEAT2D. EDI method is validated and domain independence is demonstrated by comparing the numerical results obtained using EDI to those calculated by an enriched finite element method and to those available in the literature. Single and periodic edge crack problems in orthotropic FGMs are examined in order to study the influences of principal thermal expansion coefficient and thermal conductivity components, relative crack length and crack periodicity on the thermal stress intensity factors. Numerical results show that among the three principal thermal expansion coefficient components, the in-plane component perpendicular to the crack axis has the most significant influence on the mode I stress intensity factor. Gradation profile of the thermal expansion coefficient parallel to the crack axis is shown to have no effect on the outcome of the fracture analysis.     

A highly selective and sensitive benzothiazole‐based ‘turn‐on’ fluorescent sensor for Hg2+ ion

A simple benzothiazole‐based fluorescent probe (TDA) for the determination of Hg²⁺ ion in aqueous solutions was synthesised in one step and characterised by ¹H NMR, ¹³C NMR, APT, COSY, FTIR, and elemental analysis. TDA shows a significant fluorescence change upon the interaction of Hg²⁺ ion in DMF–water (v/v = 1/1), while only minor changes in fluorescence intensity are observed with 18 other metal ions. Fluorescence enhancement by a factor of 15 is achieved upon selective interaction with Hg²⁺ ion. The Hg²⁺ ion detection process is found to be pH dependent; therefore, TDA could be feasible within a pH range of 4.0–7.0.     

Synthesis and microstructural characterization of nano-size calcium phosphates with different stoichiometry

Calcium phosphates with Ca/P molar ratios of 0.5, 0.75, 1.33, 1.5, 1.55, 1.67, 2.0, and 2.5 were synthesized by a wet chemistry precipitation method and sintered at 500 °C, 700 °C, 900 °C, 1100 °C and 1300 °C for 2 h. Presence of phases and microstructures of calcium phosphates were determined by X-ray diffraction and scanning electron microscopy. In all different Ca/P ratios, the precipitated phase was always hydroxyapatite with very small size and/or partial disorderness regardless of the Ca/P ratios in the starting precipitating medium. For samples with 0.5 and 0.75 Ca/P ratios in starting solution, tricalcium phosphate and calcium pyrophosphate phases were observed. In contrast, for samples with 1.0 and 1.33 Ca/P ratios, the only stable phase was tricalcium phosphate. For the samples with Ca/P ratio of 1.5, the tricalcium phosphate phase was dominant. However, small amounts of hydroxyapatite started to appear. For samples with Ca/P ratio of 1.67, the hydroxyapatite phase was dominant. Lastly, for samples with the Ca/P ratios of 2.0 and 2.5, the CaO phase started to appear in addition to the hydroxyapatite phase which was the dominant phase. Moreover, the average grain size, porosity (%) and the average pore size decreased with increasing the Ca/P ratios.     

Classification of EEG signals using neural network and logistic regression

Epileptic seizures are manifestations of epilepsy. Careful analyses of the electroencephalograph (EEG) records can provide valuable insight and improved understanding of the mechanisms causing epileptic disorders. The detection of epileptiform discharges in the EEG is an important component in the diagnosis of epilepsy. As EEG signals are non-stationary, the conventional method of frequency analysis is not highly successful in diagnostic classification. This paper deals with a novel method of analysis of EEG signals using wavelet transform and classification using artificial neural network (ANN) and logistic regression (LR). Wavelet transform is particularly effective for representing various aspects of non-stationary signals such as trends, discontinuities and repeated patterns where other signal processing approaches fail or are not as effective. Through wavelet decomposition of the EEG records, transient features are accurately captured and localized in both time and frequency context. In epileptic seizure classification we used lifting-based discrete wavelet transform (LBDWT) as a preprocessing method to increase the computational speed. The proposed algorithm reduces the computational load of those algorithms that were based on classical wavelet transform (CWT). In this study, we introduce two fundamentally different approaches for designing classification models (classifiers) the traditional statistical method based on logistic regression and the emerging computationally powerful techniques based on ANN. Logistic regression as well as multilayer perceptron neural network (MLPNN) based classifiers were developed and compared in relation to their accuracy in classification of EEG signals. In these methods we used LBDWT coefficients of EEG signals as an input to classification system with two discrete outputs: epileptic seizure or non-epileptic seizure. By identifying features in the signal we want to provide an automatic system that will support a physician in the diagnosing process. By applying LBDWT in connection with MLPNN, we obtained novel and reliable classifier architecture. The comparisons between the developed classifiers were primarily based on analysis of the receiver operating characteristic (ROC) curves as well as a number of scalar performance measures pertaining to the classification. The MLPNN based classifier outperformed the LR based counterpart. Within the same group, the MLPNN based classifier was more accurate than the LR based classifier.     

Image enhancement via space-adaptive lifting scheme exploiting subband dependency

This paper proposes an image enhancement method based on space-adaptive, 2-D lifting scheme. In the space-adaptive update-first lifting scheme, the prediction stage is adapted to the signal structure point-by-point which results in a better signal representation and enhancement result. In this paper, a novel edge-sensitive adaptive prediction method is introduced in the 2-D lifting framework. The method adaptively chooses the best predictor among a set of predictors minimizing the prediction error. The proposed prediction method is sensitive to both even and odd indexed edge pixels in the 2-D lifting context. The bivariate shrinkage which assumes the dependence of the subband wavelet coefficients is used for subband image enhancement. As an objective quality measure, the peak signal-to-noise ratio test is applied to the results of the proposed image enhancement algorithm. Results of the proposed algorithm are compared with those of the VisuShrink, BayesShrink, and NorShrink. Experimental and objective quality test results prove the superior performance of the proposed image enhancement method.     

Physical and mechanical properties of Gokceada: Imbros (NE Aegean Sea) Island andesites

The physical and mechanical properties of the andesite forming much of the island of Gökçeada (Imbros), Turkey, were investigated using 54 mm samples cores from 12 blocks obtained from a quarry. The results were evaluated using regression analysis and good empirical relationships were obtained.