Search

This paper proposes a new consensus criterion for nonlinear complex systems with edge betweenness centrality measure. By construction of a suitable Lyapunov-Krasovskii functional, the consensus criterion for such systems is established in terms of linear matrix inequalities (LMIs) which can be easily solved by various effective optimization algorithms. One numerical example is given to illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

This paper considers the problem of delay-dependent state estimation for neural networks with time-varying delays and stochastic parameter uncertainties. It is assumed that the parameter uncertainties are affected by the environment which is changed with randomly real situation, and its stochastic information such as mean and variance is utilized in the proposed method. By constructing a newly augmented Lyapunov-Krasovskii functional, a designing method of estimator for neural networks is introduced with the framework of linear matrix inequalities (LMIs) and a neural networks model with stochastic parameter uncertainties which have not been introduced yet. Two numerical examples are given to show the improvements over the existing ones and the effectiveness of the proposed idea. [ABSTRACT FROM AUTHOR]

This paper deals with the problems of ℋ∞ performance and stability analysis for linear systems with interval time-varying delays. It is assumed that the parameter uncertainties are of stochastic properties to represent random change of various environments. By constructing a newly augmented Lyapunov-Krasovskii functional, less conservative criteria of the concerned systems are introduced with the framework of linear matrix inequalities (LMIs). Four numerical examples are given to show the improvements over the existing ones and the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of stability analysis for neural networks with time-varying delays. By utilizing the Wirtinger based integral inequality and constructing a suitable augmented Lyapunov-Krasovskii functional, two less conservative delay dependent criteria to guarantee the asymptotic stability of the concerned networks are derived in terms of linear matrix inequalities (LMIs). Three numerical examples are included to explain the superiority of the proposed methods by comparing maximum delay bounds with the recent results published in other literature. [ABSTRACT FROM AUTHOR]

The problem of passivity analysis for neural networks with time-varying delays and parameter uncertainties is considered. By the consideration of newly constructed Lyapunov-Krasovskii functionals, improved sufficient conditions to guarantee the passivity of the concerned networks are proposed with the framework of linear matrix inequalities (LMIs), which can be solved easily by various efficient convex optimization algorithms. The enhancement of the feasible region of the proposed criteria is shown via two numerical examples by the comparison of maximum allowable delay bounds. [ABSTRACT FROM AUTHOR]

The problem of stability analysis and H∞ output tracking control for linear systems with time-varying delays is studied. First, by construction of a newly augmented Lyapunov-Krasovskii functional, a delay-dependent stability criterion for nominal systems with time-varying delays is established in terms of linear matrix inequalities (LMIs). Second, based on the H∞ sense, the proposed method is extended to solve the problem of designing an H∞ output tracking controller to track the output of a given reference model. Finally, three examples are included to show the validity and effectiveness of the presented delay-dependent stability and the H∞ output tracking controller design. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the problem of ℋ∞ synchronization for chaotic neural networks with time-varying delays. A new model of the networks with disturbances in both master and slave systems is presented. By constructing a suitable Lyapunov—Krasovskii functional and using a reciprocally convex approach, a novel ℋ∞ synchronization criterion for the networks concerned is established in terms of linear matrix inequalities (LMIs) which can be easily solved by various effective optimization algorithms. Two numerical examples are given to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this study, a fibre-optic dosemeter (FOD) using an organic scintillator with a diameter of 0.5 mm for photon-beam therapy dosimetry was fabricated. The fabricated dosemeter has many advantages, including water equivalence, high spatial resolution, remote sensing and real-time measurement. The scintillating light generated from an organic-dosemeter probe embedded in a solid-water stack phantom is guided to a photomultiplier tube and an electrometer via 20 m of plastic optical fibre. Using this FOD, the skin dose and the percentage depth dose in the build-up region according to the depths of a solid-water stack phantom are measured with 6- and 15-MV photon-beam energies with field sizes of 10×10 and 20×20 cm2, respectively. The results are compared with those measured using conventional dosimetry films. It is expected that the proposed FOD can be effectively used in radiotherapy dosimetry for accurate measurement of the skin dose and the depth dose distribution in the build-up region due to its high spatial resolution. [ABSTRACT FROM PUBLISHER]

This paper designs a delay-dependent leader-following protocol for multiagent systems with both communication delay and randomly occurring self-delay. Based on the randomly occurring mode of self-delay, a new model of switched multi-agent systems which have not been introduced yet is constructed. By constructing a newly piecewise Lyapunov-Krasovskii functional, a leaderfollowing stability criterion of the switched multi-agent systems is derived by the framework of linear matrix inequalities (LMIs) and the average dwell time with the randomly occurring mode. Based on the result of the derived stability criterion, a designing leader-following protocol for the system will be proposed. One numerical example is included to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate a delay-dependent robust synchronization analysis for coupled stochastic discrete-time neural networks with interval time-varying delays in networks coupling, a time delay in leakage term, and parameter uncertainties. Based on the Lyapunov method, a new delay-dependent criterion for the synchronization of the networks is derived in terms of linear matrix inequalities (LMIs) by constructing a suitable Lyapunov-Krasovskii's functional and utilizing Finsler's lemma without free-weighting matrices. Two numerical examples are given to illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

We consider multi-agent systems with time-varying delays and switching interconnection topologies. By constructing a suitable Lyapunov-Krasovskii functional and using the reciprocally convex approach, new delay-dependent consensus criteria for the systems are established in terms of linear matrix inequalities (LMIs), which can be easily solved by using various effective optimization algorithms. Two numerical examples are given to illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

This study is concerned with the stability problem for uncertain discrete-time systems with interval time-varying delays. By construction of an augmented Lyapunov-Krasovskii's functional and utilisation of new zero equalities, improved delay-dependent criteria for the stability of the systems are derived for guaranteeing the asymptotic stability of the concerned systems. The effectiveness and the reduced conservatism of the derived results are demonstrated by three illustrative examples. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the delay-dependent stability analysis for discrete-time neural networks with interval time-varying delays. Based on Lyapunov method, improved delaydependent criteria for the stability of the networks are derived in terms of linear matrix inequalities LMIs by constructing a suitable Lyapunov-Krasovskii functional and utilizing reciprocally convex approach. Also, a new activation condition which has not been considered in the literature is proposed and utilized for derivation of stability criteria. Two numerical examples are given to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A new formula for the gain of an open-ended rectangular waveguide is presented. The gain is simulated using commercial electromagnetic software and curve-fitted to derive a new formula. The proposed formula includes the effect of waveguide wall thickness. The accuracy of the proposed formula is compared with existing formulas and measured data. [ABSTRACT FROM AUTHOR]

Threshold switching is a phenomenon where the resistivity of an insulating material changes and the insulator exhibits metallic behavior. This could be explained by phase transformation in oxide materials; however, this behavior is also seen in amorphous insulators. In this study, through an ex-situ experiment using transmission electron microscopy (TEM), we proved that threshold switching of amorphous NbO2 accompanies local crystallization. The change in I-V characteristics after electroforming was examined by evaluating the concentration profile. Atom probe tomography (APT) combined with in-situ TEM probing technique was performed to understand the threshold switching in amorphous NbO2. The local crystallization in amorphous NbO2 was validated by the observed difference in time-of-flight (ToF) between amorphous and crystalline NbO2. We concluded that the slower ToF of amorphous NbO2 (a-NbO2) compared with crystalline NbO2 (c-NbO2) is due to the resistivity difference and trap-assisted recombination., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This paper proposes a new consensus criterion for nonlinear complex systems with edge betweenness centrality measure. By construction of a suitable Lyapunov-Krasovskii functional, the consensus criterion for such systems is established in terms of linear matrix inequalities (LMIs) which can be easily solved by various effective optimization algorithms. One numerical example is given to illustrate the effectiveness of the proposed methods.

This paper is about a glass-type wireless bio-signal transmitter that can monitor the user's health state in daily life. The device implemented in this study consists of the transmission part and the receiving part. The transmission part includes a photoplethysmography(PPG) sensor for detecting pulse wave signals, accelerometer for detecting kinetic signals, and a wireless controller for transmitting acquired bio-information. The receiving part is designed to check and process transmitted data through interoperation with a PC. In the experiments, we collected data during a sitting posture and repeated sit-to-stand motion in laboratory environment, and analyzed the data. As to accuracy, the correlation between the peak-to-peak intervals in the signals of the Biopac equipment and the developed device measured in a sitting posture was 97.5%, and that measured in sit-to-stand motion was 87%. In addition, when bio-signals were transmitted through wireless communication, the transmission was successful 100% without any error. When pulse wave signals and kinetic signals were obtained and compared, the results proved the accuracy and daily applicability of the developed device, and the glass-type wireless bio-signal transmission system is expected to be applicable to unobtrusive health monitoring for the user.

Heart sound occurs when the heart contracts and expands. It provides information on myocardial contractility and blood vessels, which is not obtainable from ECG. For this reason, stethoscopy of heart sound in anesthesiology is a very crucial means for acquiring cardiac information and preventing intraoperative medical accidents, and it requires a system for precise objective measurement and analysis of heart sound and murmur. Thus, this study purposed to develop portable digital esophageal stethoscope (PDES) that can objectify and quantify heart sound and murmur. In this study, we designed PDES for precise measurement and analysis of heart sound and murmur data. Heart sound information obtained by inserting the sensor of the PDES into the patient's esophagus can be transmitted to a terminal or a PC and displayed on the screen The amplitude and waveform of heart sound are displayed using self-developed software Heart Sound 1.0. The results of experiment with the developed PDES showed that data on the amplitude and waveform of heart sound and murmur were produced stably in real-time. In addition, when heart sound was heard using a headphone, the sound was clear without external murmur. The PDES developed in this study, which complements the disadvantages of traditional esophageal stethoscope while preserving its advantages, could not only examine heart sound and murmur using an esophageal catheter but also display the amplitude and waveform of heart sound and murmur and measure the patient's body temperature. Accordingly, the developed PDES is expected to be useful in the continuous stethoscopy of heart sound during operation and to contribute to research on heart sound by providing heart sound data.

Photoplethysmography (PPG) offers the clinically meaningful parameters, such as, heart rate, and respiratory rate. In this study, we presented three respiratory signal detection algorithms using photoplethysmography raw data generated from commercial PPG sensor: (1)Min-Max (2)Peak-to-Peak (3)Pulse Shape. As reference signal, nasal sensor signal was acquired simultaneously and compared and analyzed. We used two types of moving average filtering technique to process three PPG parameters. In laboratory experiment, 6 subjects' PPG signals were measured when they respire ten and fifteen, and arbitrary times per minute. From the results, following conclusions were drawn. Min-Max and Peak-to-Peak algorithms perform better than Pulse shape algorithm. They can be used to detect respiratory rate. But, Pulse Shape algorithm was accurate for subject 4 only. More experimental data is necessary to improve the accuracy and reliability.

The objective of this paper is to present a new technique which can provide both active respiration source pressure and lung impedance in a single noninvasive test. The method is based upon a Thévenin equivalent circuit model of respiratory mechanics. Using this model, the equivalent source pressure and source impedance can be computed from the measured changes of respiratory pressures and flows in two consecutive cycles before and after addition of purely resistive loads to the mouth. In maximal breathing the source parameters were reproducible in six normal human subjects. The total respiratory resistance during maximal breathing had an average value of 3.46 cmH2O l-1 s-1, and the total dynamic compliance had an average value of 0.078 l cmH2O-1. The airway resistances measured using a plethysmographic method were within the range of 45-65% of the estimated total respiratory resistances. These two resistances were related with a correlation coefficient of 0.98. An average value of the magnitudes of the fundamental components of the source pressure was 6.73 cmH2O during maximal breathing and 2.09 cmH2O during spontaneous breathing.

Preoperative factors that may lead to poor results in bipolar prostheses were examined in 34 patients with aseptic failures of their prostheses. Nineteen cases were revised for acetabular pain, seven for failure of the bearing insert, seven for a loose stem, and one for dislocation. The single significant factor that predicted a poor outcome was the angle of the sourcil of the acetabular roof. The group with acetabular pain had an average sourcil angle of 15.6 degrees compared with 5 degrees in those that failed for other reasons.

An automated cooling system for vagal cold blockade was developed. A simple electronic circuit is described that enabled regulation of the steady-state nerve or circulant temperature to within +/- 0.1 degree C by alternating the cold circulant between low and high flows (10 and 350 ml/min, respectively). The 90% rise time ranged from 15 to 40 s depending on the desired steady state and the surrounding temperatures. The present apparatus can be conveniently and safely used, especially for differential vagal cold blockade.

The esophageal balloon technique for measuring pleural surface pressure (Ppl) has recently been shown to be valid in recumbent positions. Questions remain regarding its validity at lung volumes higher and lower than normally observed in upright and horizontal postures, respectively. We therefore evaluated it further in 10 normal subjects, seated and supine, by measuring the ratio of esophageal to mouth pressure changes (delta Pes/delta Pm) during Mueller, Valsalva, and occlusion test maneuvers at FRC, 20, 40, 60, and 80% VC with the balloon placed 5, 10, and 15 cm above the cardia. In general, delta Pes/delta Pm was highest at the 5-cm level, during Mueller maneuvers and occlusion tests, regardless of posture or lung volume (mean range 1.00-1.08). At 10 and 15 cm, there was a progressive increase in delta Pes/delta Pm with volume (from 0.85 to 1.14). During Valsalva maneuvers, delta Pes/delta Pm also tended to increase with volume while supine (range 0.91-1.04), but was not volume-dependent while seated. Qualitatively, observed delta Pes/delta Pm fit predicted corresponding values (based on lung and upper airway compliances). Quantitatively there were discrepancies probably due to lack of measurement of esophageal elastance and to inhomogeneities in delta Ppl. At every lung volume in both postures, there was at least one esophageal site where delta Pes/delta Pm was within 10% of unity.

The effect of decreased lung volume on ventilatory responses to arteriovenous fistula-induced increased cardiac output was studied in four chronic awake dogs. Lung volume decreases were imposed by application of continuous negative-pressure breathing of -10 cmH2O to the trachea. The animals were surgically prepared with chronic tracheostomy, indwelling carotid artery catheter, and bilateral arteriovenous femoral shunts. Control arteriovenous blood flow was 0.5 l/min, and test flow level was 2.0 l/min. Arterial blood CO2 tension (PaCO2) was continuously monitored using an indwelling Teflon membrane mass spectrometer catheter, and inhaled CO2 was given to maintain isocapnia throughout. Increased fistula flow alone led to a mean 52% increase in cardiac output (CO), whereas mean systemic arterial blood pressure (Psa) fell 4% (P less than 0.01). Negative-pressure breathing alone raised Psa by 3% (P less than 0.005) without a significant change in CO. Expired minute ventilation (VE) increased by 27% (P less than 0.005) from control in both of these conditions separately. Combined increased flow and negative pressure led to a 50% increase in CO and 56% increase in VE (P less than 0.0025) without any significant change in Psa. Effects of decreased lung volume and increased CO appeared to be additive with respect to ventilation and to occur under conditions of constant PaCO2 and Psa. Because both decreased lung volume and increased CO occur during normal exercise, these results suggest that mechanisms other than chemical regulation may play an important role in the control of breathing and contribute new insights into the isocapnic exercise hyperpnea phenomenon.

Lung volume changes during CO2 inhalation and exercise were compared in seven human subjects. Expiratory reserve volume (ERV) normalized by vital capacity (VC) was used as an index of end-expiratory lung volume (EELV). Work loads tried were 30, 60, and 90 W and inspired CO2 concentrations were 3.5 and 5.0%. Exercise at 30 W led to a significant decrease in EELV, by 7% VC (P less than 0.005), with no further change at higher levels of exercise (P greater than 0.1). Both 3.5 and 5.0% CO2 inhalation resulted in an increase in EELV that was not statistically significant (3% VC, P greater than 0.1). A possible linkage of this different EELV behavior to breathing pattern was tested. The tidal volume-inspiratory duration curve shifted to a higher volume region during exercise compared with CO2 inhalation. Consequently, the volume-time threshold characteristic was better described by an end-inspiratory lung volume-inspiratory duration plot, resulting in a common relationship under these two different stimuli. These results suggest that the depth and rate of breathing in humans can be affected by not only phasic but also tonic components. A decrease in functional residual capacity or EELV was peculiar to exercise and should be associated with increased mechanical efficiency compared with CO2 inhalation. Theoretical predictions based on work of breathing optimization via a decreased EELV seemed to be capable of explaining isocapnic exercise hyperpnea in conjunction with proportional control of arterial CO2 tension.

To study the phenomenon of lung hyperinflation (LHI), i.e., an increase in lung volume without a concomitant rise in airway pressure, we measured lung volume changes in isolated dog lungs during high-frequency oscillation (HFO) with air, He, and SF6 and with mean tracheal pressure controlled at 2.5, 5.0, and 7.5 cmH2O. The tidal volume and frequency used were 1.5 ml/kg body wt and 20 Hz, respectively. LHI was observed during HFO in all cases except for a few trials with He. The degree of LHI was inversely related to mean tracheal pressure and varied directly with gas density. Maximum expiratory flow rate (Vmax) was measured during forced expiration induced by a vacuum source (-150 cmH2O) at the trachea. Vmax was consistently higher than the peak oscillatory flow rate (Vosc) during HFO, demonstrating that overall expiratory flow limitation did not cause LHI in isolated dog lungs. Asymmetry of inspiratory and expiratory impedances seems to be one cause of LHI, although other factors are involved.