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.     

Force analysis of bearings on a modified mechanism using proposed recurrent hybrid neural networks

Due to different load conditions on four-bar mechanisms, it is necessary to analyze force distribution on the bearing systems of mechanisms. A proposed neural network was developed and designed to analyze force distribution on the bearings of a four bar mechanism. The proposed neural network has three layers: input layer, output layer and hidden layer. The hidden layer consists of a recurrent structure to keep dynamic memory for later use. The mechanism is an extended version of a four-bar mechanism. Two elements, spring and viscous, are employed to overcome big force problem on the bearings of the mechanism. The results of the proposed neural network give superior performance for analyzing the forces on the bearings of the four-bar mechanism undergoing big forces and high repetitive motion tracking. This continuation of simulation analysis of bearings should be a benefit to bearing designers and researchers of such mechanisms.     

Effect of an organic compound (Methyl Red) interfacial layer on the calculation of characteristic parameters of an Al/Methyl Red/p-Si sandwich Schottky barrier diode

An Al/Methyl Red/p-Si sandwich Schottky barrier diode (SBD) has been fabricated by adding a solution of the organic compound Methyl Red in chloroform onto a p-Si substrate, and then evaporating the solvent. Current-voltage (I-V) measurements of the Al/Methyl Red/p-Si sandwich SBD have been carried out at room temperature and in the dark. The Al/Methyl Red/p-Si sandwich SBD demonstrated rectifying behavior. Barrier height (BH) and ideality factor values of 0.855 eV and 1.19, respectively, for this device have been determined from the forward-bias I-V characteristics. The Al/Methyl Red/p-Si sandwich SBD showed non-ideal I-V behavior with the value of ideality factor greater than unity. The energy distribution of the interface state density determined from I-V characteristics increases exponentially with bias from 3.68 × 10¹² cm^− 2 eV^− 1 at (0.81 − E_v) eV to 9.99 × 10¹³ cm^− 2 eV^− 1 at (0.69 − E_v) eV.     

Aptamer-based optical biosensor for rapid and sensitive detection of 17β-estradiol in water samples

Required routine monitoring of endocrine disrupting compounds (EDCs) in water samples, as posed by EPA Unregulated Contaminant Regulation (UCMR3), demands for cost-effective, reliable and sensitive EDC detection methods. This study reports a reusable evanescent wave aptamer-based biosensor for rapid, sensitive and highly selective detection of 17β-estradiol, an EDC that is frequently detected in environmental water samples. In this system, the capture molecular, β-estradiol 6-(O-carboxy-methyl)oxime-BSA, was covalently immobilized onto the optical fiber sensor surface. With an indirect competitive detection mode, samples containing different concentrations of 17β-estradiol were premixed with a given concentration of fluorescence-labeled DNA aptamer, which highly specifically binds to 17β-estradiol. Then, the sample mixture is pumped to the sensor surface, and a higher concentration of 17β-estradiol leads to less fluorescence-labeled DNA aptamer bound to the sensor surface and thus to lower fluorescence signal. The dose-response curve of 17β-estradiol was established and a detection limit was determined as 2.1 nM (0.6 ng mL(-1)). The high specificity and selectivity of the sensor were demonstrated by evaluating its response to a number of potentially interfering EDCs. Potential interference of real environmental sample matrix was assessed by spiked samples in several tertiary wastewater effluents. The sensor can be regenerated with a 0.5% SDS solution (pH 1.9) over tens of times without significant deterioration of the sensor performance. This portable sensor system can be potentially applied for on-site real-time inexpensive and easy-to-use monitoring of 17β-estradiol in environmental samples such as effluents or water bodies.     

Topographic and biomechanical evaluation of cornea in patients with ichthyosis vulgaris

PurposeTo compare the topographic and biomechanical properties of corneas in eyes of patients with ichthyosis vulgaris (IV) and eyes of healthy individuals.MethodsThirty healthy individuals (control group) and 30 patients with IV (study group) were enrolled in this prospective study. Topographic measurements, including keratometry values, irregularity, and surface asymmetry index in the right eye of each participant were obtained using Scheimpflug camera with a Placido disc topographer (Sirius). Corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc) and Goldman-related intraocular pressure (IOPg) were measured using the Reichert Ocular Response Analyzer (ORA). Central corneal thickness (CCT) was also measured with ultrasonic pachymetry and the Sirius corneal topography system.ResultsTopographic parameters were not significantly different between both groups (p > 0.05). Although mean CH was not significantly different between the groups, the CRF was significantly lower in patients with IV (p = 0.249 and p = 0.005, respectively). The CCT was significantly lower in patients with IV compared to healthy controls (p < 0.001). The IOPg and IOPcc were significantly lower in the patients with ichthyosis than in healthy controls (p = 0.001 and p = 0.004, respectively).ConclusionsThe study demonstrated that while the eyes of patients with IV had corneal topographic findings and corneal hysteresis similar to those of healthy controls, some of corneal biomechanical properties such CRF and CCT and IOP values such as IOPg and IOPcc were significantly lower in patients with IV. These results should be taken into account when planning a corneal refractive surgery and glaucoma screening for patients with IV.     

Analog circuit sizing via swarm intelligence

Together with the increase in electronic circuit complexity, the design and optimization processes have to be automated with high accuracy. Predicting and improving the design quality in terms of performance, robustness and cost is the central concern of electronic design automation. Generally, optimization is a very difficult and time consuming task including many conflicting criteria and a wide range of design parameters. Particle swarm optimization (PSO) was introduced as an efficient method for exploring the search space and handling constrained optimization problems. In this work, PSO has been utilized for accommodating required functionalities and performance specifications considering optimal sizing of analog integrated circuits with high optimization ability in short computational time. PSO based design results are verified with SPICE simulations and compared to previous studies.     

Experimental investigation on transverse low-speed impact behavior of adhesively bonded similar and dissimilar clamped plates

This experimental study investigates the low-speed impact behavior of adhesively bonded similar (Al–Al, St–St) and dissimilar (Al–St, St–Al) plates. The after-impact geometries of the front and back faces of the bonded plates, which were visualized by measuring the displacements, were in good agreement with the simulated surface geometries obtained by using explicit finite element method. The plate stiffness was affective on the deflections of the bonded plates; thus, the bonded Al–Al plates exhibited maximum deflections, contact durations, and minimal contact force levels, whereas the bonded St–St plates had minimum deflections, contact durations, and maximum contact force levels. As the impact energy is increased, the impact forces, durations, and deflections increased naturally; however, the impact force-time histories were not affected evidently. The bonded Al–Al plates can dissipate the impact energy more effectively than the bonded St–St plates. The experimental and simulated contact force-time histories were generally in good agreement. Based on the cross-section photographs of the damaged impact regions the bonded Al–Al plates with low stiffness can deform plastically and dissipate most of the impact energy, and the adhesive layer remains compatible with the deformation of the plates. The interfacial fractures appear along the back plate–adhesive interface for the low impact energy but along both front and back plate–adhesive interfaces and cracks propagated to the back interface to lower interface through the adhesive thickness near the boundaries of the impactor trace. The bonded St–St plates behave more rigid, transmit the impact energy directly to the adhesive layer and the high impact force distributions result severe fractures not only interfacially but also through the adhesive thickness. The color transformations, which are indications of fracture formation and propagation speed in some way, were observed around the adhesive fractures. Although the bonded St–Al and Al–St plates had a fracture mechanism similar to those of the bonded Al–Al plates but the color transformation near the fractures and the crack opening displacement levels were more evident. The existence of a stiffer plate affects considerably the damage formation in the adhesive layer and in the plates, whereas the less stiff plates can dissipate the impact energy by deforming plastically and the adhesive layer experiences less local damages.     

Drift estimation using pairwise slope with minimum variance in wireless sensor networks

Time synchronization is mandatory for applications and services in wireless sensor networks which demand common notion of time. If synchronization to stable time sources such as Coordinated Universal Time (UTC) is required, employing the method of flooding in order to provide time synchronization becomes crucial. In flooding based time synchronization protocols, current time information of a reference node is periodically flooded into the network. Sensor nodes collect the time information of the reference node and perform least-squares regression in order to estimate the reference time. However, least-squares regression exhibits a poor performance since sensor nodes far away from the reference node collect the time information with large deviations. Due to this fact, the slopes of their least-squares line exhibit large errors and instabilities. As a consequence, the reference time estimates of these nodes also exhibit large errors.This paper proposes a new slope estimation strategy for linear regression to be used by flooding based time synchronization protocols. The proposed method, namely Pairwise Slope With Minimum Variance (PSMV), calculates the slope of the estimated regression line by considering the pairwise slope between the earliest and the most recently collected data points. The PSMV slope is less affected by the large errors on the received data, i.e. it is more stable, and it is more computationally efficient when compared to the slope of the least-squares line. We incorporated PSMV into two flooding based time synchronization protocols, namely Flooding Time Synchronization Protocol (FTSP) and PulseSync. Experimental results collected from a testbed setup including 20 sensor nodes show that PSMV strategy improves the performance of FTSP by a factor of 4 and preserves the performance of PulseSync in terms of synchronization error with 40% less CPU overhead for linear regression. Our simulations show that these results also hold for networks with larger diameters and densities.     

rGO/CuO/PEDOT nanocomposite formation,its characterisation and electrochemical performances for supercapacitors

ABSTRACT

Supercapacitor properties of rGO, CuO, PEDOT and rGO/CuO at [rGO]_o/[CuO]_o?=?1:1; 1:1.5; 1:2 and rGO/CuO/PEDOT nanocomposite at [rGO]_o/[CuO]_o/[EDOT]_o?=?1:1:1; 1:1:3; 1:1:5 were investigated using chemical reduction of GO and in-situ polymerisation process. SEM-EDX, HRTEM, BET surface area analysis confirm the nanocomposite formations. Nanocomposite materials are also analysed through FTIR-ATR, Raman, TGA-DTA, GCD, CV and EIS. The highest specific capacitance of C _sp?=?156.7 F/g at 2?mV/s is determined as rGO/CuO/PEDOT at [rGO]_o/[CuO]_o/[EDOT]_o?=?1:1:5. In addition, two-electrode supercapacitor device for rGO/CuO/PEDOT at [rGO]_o/[CuO]_o/[EDOT]_o?=?1:1:5 are found to provide a maximum specific energy (E?=?14.15 Wh/kg at 20?mA) and specific power (P?=?24730 W/kg at 50?mA), electrical serial resistance (ESR?=?13.33 Ω) with good capacity retention after 3000 cycles. An equivalent circuit model of LR1(CR2)(QR3) is proposed to interpret the EIS data. The supercapacitor performance of the rGO/CuO/PEDOT nanocomposite electrode indicates the synergistic effect of hybrid supercapacitors.     

Parallel four‐dimensional Haralick texture analysis for disk‐resident image datasets

Texture analysis is one possible method of detecting features in biomedical images. During texture analysis, texture‐related information is found by examining local variations in image brightness. Four‐dimensional (4D) Haralick texture analysis is a method that extracts local variations along space and time dimensions and represents them as a collection of 14 statistical parameters. However, application of the 4D Haralick method on large time‐dependent image datasets is hindered by data retrieval, computation, and memory requirements. This paper describes a parallel implementation using a distributed component‐based framework of 4D Haralick texture analysis on PC clusters. The experimental performance results show that good performance can be achieved for this application via combined use of task‐ and data‐parallelism. In addition, we show that our 4D texture analysis implementation can be used to classify imaged tissues. Copyright © 2006 John Wiley & Sons, Ltd.