Detection and classification of sleep apnea using genetic algorithms and SVM‐based classification of thoracic respiratory effort and oximetric signal features

Sleep apnea is a relatively prevalent breathing disorder characterized by temporary interruptions in airflow during sleep. There are 2 major types of sleep apnea. Obstructive sleep apnea occurs when air cannot flow through the upper airway despite efforts to breathe. Central sleep apnea occurs when the brain fails to signal to the muscles to maintain breathing. The standard diagnostic test is polysomnography, which is expensive and time consuming. The aim of this study was to design an automatic diagnostic and classifying algorithm for sleep apneas employing thoracic respiratory effort and oximetric signals. This algorithm was trained and tested applying a database of 54 subjects who had undergone polysomnography. A feature extraction stage was conducted to compute features. An optimal genetic algorithm was applied to select optimal features of these 2 kinds of signals. The classification technique was based on the support vector machine classifier to classify the selected features in 3 classes as healthy, obstructive, and central sleep apnea events. The results show that our automated classification algorithm can diagnose sleep apnea and its types with an average accuracy level of 90.2% (87.5‐95.8) in the test set and 90.9% in the validation set with high acceptable accuracy.     

Robust Handwritten Character Recognition with Features Inspired by Visual Ventral Stream

This paper focuses on the applicability of the features inspired by the visual ventral stream for handwritten character recognition. A set of scale and translation invariant C2 features are first extracted from all images in the dataset. Three standard classifiers kNN, ANN and SVM are then trained over a training set and then compared over a separate test set. In order to achieve higher recognition rate, a two stage classifier was designed with different preprocessing in the second stage. Experiments performed to validate the method on the well-known MNIST database, standard Farsi digits and characters, exhibit high recognition rates and compete with some of the best existing approaches. Moreover an analysis is conducted to evaluate the robustness of this approach to orientation, scale and translation distortions.     

Numerical Simulation of Steady Mixed Convection Around Two Heated Circular Cylinders in a Square Enclosure

In this paper, a numerical study has been carried out to investigate the steady-state mixed convection around two heated horizontal cylinders in a square two-dimensional enclosure. The cylinders are located at the middle of the enclosure height and the walls of the cavity are adiabatic. Streamlines and isotherms are produced and the effects of cylinder diameter, Reynolds number, and Richardson number on the heat transfer characteristics are numerically analyzed. The average Nusselt number over the surface of cylinders and average nondimensional temperature in the enclosure are also presented. The results show that both heat transfer rates from the heated cylinders and the dimensionless fluid temperature in the enclosure increase with increasing Richardson number and cylinder diameter. However, the trend of average Nusselt number and nondimensional temperature variation is completely opposite when Reynolds number increases. In addition, by increasing the cylinders diameter and Richardson number, the left cylinder is less affected by the inlet flow than right one.     

Stress analysis in a cracked strip

The stress fields in a strip containing climb and glide edge dislocations are obtained utilizing a complex Fourier transform. The dislocation solutions are then employed to perform integral equations for the analysis of a strip weakened by multiple cracks with any configuration and arrangement. The integral equations are solved numerically for the dislocation density on the cracked surfaces. The stress-intensity factors for two straight cracks compared favorably with the results rendered in literature. Three new examples are solved to demonstrate the applicability of the procedure.     

A possibilistic programming approach for the location problem of multiple cross-docks and vehicle routing scheduling under uncertainty

This article considers the design of cross-docking systems under uncertainty in a model that consists of two phases: (1) a strategic-based decision-making process for selecting the location of cross-docks to operate, and (2) an operational-based decision-making process for vehicle routing scheduling with multiple cross-docks. This logistic system contains three echelons, namely suppliers, cross-docks and retailers, in an uncertain environment. In the first phase, a new multi-period cross-dock location model is introduced to determine the minimum number of cross-docks among a set of location sites so that each retailer demand should be met. Then, in the second phase, a new vehicle routing scheduling model with multiple cross-docks is formulated in which each vehicle is able to pickup from or deliver to more than one supplier or retailer, and the pickup and delivery routes start and end at the corresponding cross-dock. This article is the first attempt to introduce an integrated model for cross-docking systems design under a fuzzy environment. To solve the presented two-phase mixed-integer programming (MIP) model, a new fuzzy mathematical programming-based possibilistic approach is used. Furthermore, experimental tests are carried out to demonstrate the effectiveness of the presented model. The computational results reveal the applicability and suitability of the developed fuzzy possibilistic two-phase model in a variety of problems in the domain of cross-docking systems.     

General method of simulating radiation fields using measured boundary values

A general methodology integrating the Fresnell, Snell, and Beer-Lambert laws for modeling the radiant distribution in a medium is presented. The model considers refraction/reflection through/from the body of the UV lamp and sleeve, as well as the reflections from other sources, such as the reactor body. The measured boundary conditions are applied to realistically simulate the fluence/irradiance rate around the radiant source, in particular, in the zone closest to the radiant source. Different low-pressure UV lamps were tested under different operating conditions using photodiodes and a radiometer. The experimentally measured irradiance rate was in a very good agreement with the simulation results of the presented model.     

Occult hepatitis B infection in a hemodialysis population in Guilan province, northern Iran

Hemodialysis (HD) patients are vulnerable to transfusion-transmitted infections such as hepatitis B virus (HBV). HBV infection with undetectable hepatitis B surface antigens (HBsAg) is described as occult HBV and can lead to serious complications. The aim of this study was to evaluate the prevalence of occult HBV and concomitant factors in HD patients. Using a cross-sectional design, clinical and epidemiological data were obtained from May to September 2009 in 11 different HD units in Guilan province in northern Iran. After serological testing for HBV surface antigens in 514 HD patients using a third-generation enzyme-linked immunosorbent assay kit (Diapro, Milano, Italy), HBsAg-negative patients were tested for HBV DNA using a Qiagen PCR kit (Artus Qiagen GmbH, Hilden, Germany). After omission of seven HBsAg-positive patients, 507 patients were included in the study, 280 (55.2%) of whom were male and 227 (44.8%) were female. Patients ranged in age from 16 to 66 years (mean 53.2 years). No HBV DNA was detected in HBsAg-negative patients. Some 59 patients (11.6%) were anti-hepatitis C virus positive and 32 (6.3%) were hepatitis C virus positive according to polymerase chain reaction. The study results indicate that occult HBV infection is not a significant health problem in HD patients in Guilan province.     

Prediction of time required for onset of convection in a porous medium saturated with oil and a layer of gas underlying the oil

The onset of convection for a viscous oil confined in a cylindrical porous medium and contacted with a gas to diffuse into it from below is investigated experimentally and theoretically. Two experiments are carried out, both at a specific reservoir temperature and pressure, starting with the medium saturated with the oil and bringing the gas into contact with it from the base. In the first experiment, the setup is arranged horizontally in order to determine the diffusion coefficient of gas in the absence of convection. In the second experiment, the setup is vertical to investigate the onset of convection. The pressure is maintained constant during both experiments and the volume of gas dissolving in oil is measured vs. time. The dissolved gas data obtained from the vertical experiment show a sharp slope change at the onset of convection. The observed onset time is in excellent agreement with the value obtained by means of an instability theory developed in this study.