Simple methods for segmentation and measurement of diabetic retinopathy lesions in retinal fundus images

Diabetic retinopathy (DR) is one of the most important complications of diabetes mellitus, which causes serious damages in the retina, consequently visual loss and sometimes blindness if necessary medical treatment is not applied on time. One of the difficulties in this illness is that the patient with diabetes mellitus requires a continuous screening for early detection. So far, numerous methods have been proposed by researchers to automate the detection process of DR in retinal fundus images. In this paper, we developed an alternative simple approach to detect DR. This method was built on the inverse segmentation method, which we suggested before to detect Age Related Macular Degeneration (ARMDs). Background image approach along with inverse segmentation is employed to measure and follow up the degenerations in retinal fundus images. Direct segmentation techniques generate unsatisfactory results in some cases. This is because of the fact that the texture of unhealthy areas such as DR is not homogenous. The inverse method is proposed to exploit the homogeneity of healthy areas rather than dealing with varying structure of unhealthy areas for segmenting bright lesions (hard exudates and cotton wool spots). On the other hand, the background image, dividing the retinal image into high and low intensity areas, is exploited in segmentation of hard exudates and cotton wool spots, and microaneurysms (MAs) and hemorrhages (HEMs), separately. Therefore, a complete segmentation system is developed for segmenting DR, including hard exudates, cotton wool spots, MAs, and HEMs. This application is able to measure total changes across the whole retinal image. Hence, retinal images that belong to the same patients are examined in order to monitor the trend of the illness. To make a comparison with other methods, a Na?ve Bayes method is applied for segmentation of DR. The performance of the system, tested on different data sets including various qualities of retinal fundus images, is over 95% in detection of the optic disc (OD), and 90% in segmentation of the DR.     

MPLS over ATM and IP over ATM methods for multimedia applications

This paper presents fundamental aspects of MPLS over ATM method, IP over ATM method and multimedia application traffics with different quality of service (QoS) requirements. Using a simulation tool, the MPLS over ATM method providing ABR, CBR and VBR QoS support, and the IP over ATM method providing a primitive UBR QoS support for transferring data, voice and video traffics are modeled. Having simulated the models under varying offered loads, obtained simulation results are presented. Comparing the average end-to-end delay and delay variation graphs, not only does the MPLS over ATM method provide improved results for all of the multimedia traffics but also overcomes the worst disadvantage of the IP over ATM method producing similar and erratic results for the data, voice and video application traffics.     

An improved delay‐dependent bounded real lemma (BRL) and H∞ controller synthesis for linear neutral systems

In this paper, a novel delay‐dependent bounded real criterion and an improved sufficient condition are derived for the design of an H_∞ state‐feedback controller for linear neutral time‐delay systems. On the basis of an augmented Lyapunov‐Krasovskii functional, a new bounded real lemma is introduced in terms of a convex linear matrix inequality (LMI) condition that can be solved using interior point algorithms. The bounded real lemma is extended to obtain a sufficient condition for the existence of a delay‐dependent H_∞ memoryless state‐feedback controller. Neither any model transformation nor bounding of any of the cross terms are utilized while deriving the bounded real lemma. Moreover, the use of any free slack matrix variable approach is avoided to a certain extent in order not to increase the complexity of the synthesis problem. A cone complementary nonlinear minimization algorithm is employed to achieve a feasible solution set for the synthesis conditions. Finally, seven numerical examples are given to illustrate the effectiveness of the proposed method. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Analysis of the particle stability in a new designed ultrasonic levitation device

The use of acoustic levitation in the fields of analytical chemistry and in the containerless processing of materials requires a good stability of the levitated particle. However, spontaneous oscillations and rotation of the levitated particle have been reported in literature, which can reduce the applicability of the acoustic levitation technique. Aiming to reduce the particle oscillations, this paper presents the analysis of the particle stability in a new acoustic levitator device. The new acoustic levitator consists of a piezoelectric transducer with a concave radiating surface and a concave reflector. The analysis is conducted by determining numerically the axial and lateral forces that act on the levitated object and by measuring the oscillations of a sphere particle by a laser Doppler vibrometer. It is shown that the new levitator design allows to increase the lateral forces and reduce significantly the lateral oscillations of the levitated object.     

Linear prediction residual features for automatic speaker verification anti-spoofing

Automatic speaker verification (ASV) systems are highly vulnerable against spoofing attacks. Anti-spoofing, determining whether a speech signal is natural/genuine or spoofed, is very important for improving the reliability of the ASV systems. Spoofing attacks using the speech signals generated using speech synthesis and voice conversion have recently received great interest due to the 2015 edition of Automatic Speaker Verification Spoofing and Countermeasures Challenge (ASVspoof 2015). In this paper, we propose to use linear prediction (LP) residual based features for anti-spoofing. Three different features extracted from LP residual signal were compared using the ASVspoof 2015 database. Experimental results indicate that LP residual phase cepstral coefficients (LPRPC) and LP residual Hilbert envelope cepstral coefficients (LPRHEC) obtained from the analytic signal of the LP residual yield promising results for anti-spoofing. The proposed features are found to outperform standard Mel-frequency cepstral coefficients (MFCC) and Cosine Phase (CosPhase) features. LPRPC and LPRHEC features give the smallest equal error rates (EER) for eight spoofing methods out of ten spoofing attacks in comparison to MFCC and CosPhase features.     

New hybrid active power filter for harmonic current suppression and reactive power compensation

In the case of undistorted and balanced grid voltages, low ratio shunt active power filters (APFs) can give unity power factors and achieve current harmonic cancellation. However, this is not possible when source voltages are distorted and unbalanced. In this study, the cost-effective hybrid active power filter (HAPF) topology for satisfying the requirements of harmonic current suppression and non-active power compensation for industry is presented. An effective strategy is developed to observe the effect of the placement of power capacitors and LC filters with the shunt APF. A new method for alleviating the negative effects of a nonideal grid voltage is proposed that uses a self-tuning filter algorithm with instantaneous reactive power theory. The real-time control of the studied system was achieved with a field-programmable gate array (FPGA) architecture, which was developed using the OPAL-RT system. The performance result of the proposed HAPF system is tested and presented under nonideal supply voltage conditions.     

Anisotropic behaviors in polycrystalline Cd-doped GaSe thin films

GaSe thin films were deposited by thermal evaporation technique with Cd doping. X-ray diffraction analysis showed that Cd-doped films have polycrystalline structure with the preferred orientation along (008) direction. Temperature dependent electrical conductivity measurements were carried out in the temperature range of 100–400 K along perpendicular and parallel directions to the growth direction for the films exhibiting p-type conduction determined by hot probe technique. The room temperature conductivity values of the films were found to be as 1.5 × 10⁻⁸ and 4.9 × 10⁻¹² (Ω cm)⁻¹ due to the measurements along both perpendicular and parallel directions, respectively. The difference in the conductivity values is the indication of electrical anisotropy in the samples. Carrier conduction in the films was provided by the thermionic emission in the high temperature region (310–400 K) with almost the same activation energies in both directions. Space charge limited current analysis at different temperatures reveals the existence of two discrete sets of trap levels for both perpendicular and parallel directions. Calculated trap levels and trap concentrations are 99 meV, 3.5 × 10¹² cm⁻³ and 418 meV, 2.2 × 10⁵ cm⁻³ for perpendicular direction, 58 meV, 2.1 × 10¹⁸ cm⁻³ and 486 meV, 1.4 × 10¹² cm⁻³ for parallel direction. The differences in the values of the trap levels and concentrations for both directions confirm the existence of electrical anisotropy in Cd-doped GaSe thin films, because of the structural anisotropy between and inside the crystallites.     

The effect of silicon carbide additives on the stab resistance of shear thickening fluid treated fabrics

Applications of shear thickening fluids (STFs) with ballistic fabrics improve the protection performance of body protective systems. This article presents an innovative view of STF-impregnated ballistic fabrics by integrating silicon carbide (SiC) particles into targets. In this study, SiC particles were added into silica-based STFs, and Twaron fabrics were impregnated with this novel suspension. The effect of the SiC particles in the STFs was investigated with rheological testing. The results show that SiC particles are able to increase the viscosity profile of the suspension. In the stab testing, two types of impactors, such as spikes and knives, were dropped on the composite targets. According to the results, SiC particles enhance the protection performance of the STF-treated ballistic fabrics while keeping the flexibility.     

The temperature profile and bias dependent series resistance of Au/Bi4Ti3O12/SiO2/n-Si (MFIS) structures

The Bi₄Ti₃O₁₂ (BTO) thin film were fabricated on an n-type Si substrate and annealed by rapid thermal annealing methods. The temperature dependence of capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of the Au/Bi₄Ti₃O₁₂/SiO₂/n-Si metal-ferroelectric-insulator-semiconductor (MFIS) structures was investigated by taking the effects of series resistance (R_s) and interface states (N_ss) in the temperature range of 80-400 K. Both the density of interface states N_ss and series resistance R_s were found to be strongly temperature dependent. It is observed that the C-V and G/ω-V plots exhibit anomalous peaks at forward bias because of the influences of N_ss and R_s. It has been experimentally determined that these peak positions shift from accumulation to inversion region, and the maximum values of the capacitance (C) and conductance (G) generally increase with temperature. Also, the distribution profile of R_s-V shows a peak in the accumulation region. The effect of R_s on the C and G is more pronounced in the studied temperature range. The experimental C-V-T and G/ω-V-T characteristics of MFIS structures show the expected behavior due to N_ss in equilibrium with the semiconductor. The temperature dependent C-V and G/ω-V characteristics confirm that the R_s and N_ss play an important role and strongly affect the electrical parameters of MFIS structure.     

A framework for stress computation in single-walled carbon nanotubes under uniaxial tension

A procedure is proposed for computing the stresses in an armchair single-walled carbon nanotube (SWCNT) under uniaxial tension. Computation is based on molecular dynamics simulations and the virial stress theorem. The proposed approach is compared with other methods used in the literature for calculating the stresses in CNTs. The loading is applied under two different boundary conditions and different strain rates and the results are compared. It is shown that the method commonly used in the literature for calculating the stresses in CNTs under estimates the ultimate strength by around 35%. It is shown that the value of the displacement increment used to apply the tensile strain is crucial. A convergence study is done to eliminate the computational error due to large displacement increments.