Support vector machine-based expert system for reliable heartbeat recognition

This paper presents a new solution to the expert system for reliable heartbeat recognition. The recognition system uses the support vector machine (SVM) working in the classification mode. Two different preprocessing methods for generation of features are applied. One method involves the higher order statistics (HOS) while the second the Hermite characterization of QRS complex of the registered electrocardiogram (ECG) waveform. Combining the SVM network with these preprocessing methods yields two neural classifiers, which have been combined into one final expert system. The combination of classifiers utilizes the least mean square method to optimize the weights of the weighted voting integrating scheme. The results of the performed numerical experiments for the recognition of 13 heart rhythm types on the basis of ECG waveforms confirmed the reliability and advantage of the proposed approach.     

MQW wavelength-tunable DBR lasers with monolithically integrated external cavity electroabsorption modulators with low-driving voltages fabricated by selective-area MOCVD

The design and operation of multiple-quantum-well (MQW) wavelength-tunable distributed Bragg reflector (DBR) InGaAs QW lasers with nonabsorbing gratings and monolithically integrated external cavity electroabsorption modulators fabricated by selective-area MOCVD are presented. Uncoated devices exhibit CW threshold currents as low as 10.5 mA with slope efficiencies of 0.21 W/A from the laser facet. Wavelength tuning of 7 nm is obtained by injection current heating of the DBR section. These devices also exhibit extinction ratios of 18 dB from the modulator facet at a low modulator bias of 1 V, when measured with a broad-area detector. When coupled to a singlemode fiber, these devices exhibited high extinction ratios of 40 dB at a modulator bias of 1.25 V.     

Wavelength-tunable asymmetric cladding ridge-waveguide distributedBragg reflector lasers with very narrow linewidth

Narrow-linewidth ridge-waveguide distributed Bragg reflector (DBR) lasers with asymmetric cladding are demonstrated. This design requires only a single epitaxial growth of an asymmetric cladding laser structure while the grating and the ridge waveguide are fabricated after the growth. These lasers have a threshold current as low as 9 mA, a slope efficiency of 0.3 W/A, and a T₀ of 100 K. Wavelength tuning of 8 nm is achieved by current injection heating of the DBR section. A spectral-linewidth minimum of 36 kHz is achieved at an output power of 20 mW and is limited by linewidth rebroadening due to current injection in both the gain section and DBR section     

Mn site substitution of La0.67Ca0.33MnO3 with closed shell ions: Effect on magnetic transition temperature

Mn site is substituted with closed shell ions (Al, Ga, Ti, Zr and a certain combination of Zr and Al) and also with Fe and Ru ions carrying the magnetic moment (S=5/2 and 2 respectively) at a fixed concentration of 5 at %. Substitution did not change either the crystal symmetry or the oxygen stoichiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures (T _p(ρ) and T _C, respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising due to difference in the ionic radii between the substituent (r _M) and the Mn³⁺ ion (r _Mn ³⁺) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and that of the neighboring Mn ion.     

Low-threshold narrow-linewidth InGaAs-GaAs ridge-waveguide DBR lasers with first-order surface gratings

The design and operation of InGaAs-GaAs ridge-waveguide distributed Bragg reflector (DBR) single quantum-well lasers with first-order surface gratings fabricated using only a single growth step are presented. Uncoated devices exhibit CW threshold currents as low as 6 mA with slope efficiencies of 0.46 W/A. By varying the period of the first-order DBR grating, a wavelength range of 540 /spl Aring/ (/spl sim/15.2 THz) is obtained with the threshold currents and slope efficiencies remaining below 10 mA and above 0.40 W/A, respectively, over the entire wavelength range. High characteristic temperature, T/sub 0/, values of 450 K, as measured between T=10/spl deg/C and 40/spl deg/C, are obtained for devices with Bragg wavelengths positively detuned from the peak gain wavelength. The spectral linewidth minimum of these devices is below 25 kHz, which is the resolution limit of the self-heterodyning system used to measure the spectral linewidth.     

Effect of p-contact metallization on the performance ofgain-coupled DFBs with oxide-defined surface gratings

The effect of p-contact metallization on the performance of a single-growth-step ridge waveguide InGaAs-GaAs distributed feedback (DFB) laser with a silicon dioxide defined titanium surface grating is analyzed. The metallic surface grating introduces a periodic variation of the loss in the cavity to promote single-frequency emission. Device characteristics for DFBs with 50, 150, and 300 Å of titanium are compared. Under continuous-wave (CW) conditions, the devices with a titanium adhesion layer of only 50 Å operate on single-longitudinal and single-lateral modes, with threshold currents of roughly 14 mA, slope efficiencies of 0.16 W/A and sidemode suppression ratios (SMSRs) of greater than 40 dB     

Rational admittance function realisation using two operational amplifiers

The technique of the realisation of nth-order transfer functions with only two operational amplifiers is presented.     

Very narrow linewidth asymmetric cladding InGaAs-GaAs ridge waveguide distributed Bragg reflector lasers

Asymmetric cladding InGaAs-GaAs ridge waveguide distributed Bragg reflector (RW-DBR) lasers are demonstrated with a spectral linewidth as low as 39 kHz for an output power of 24 mW. The fabrication requires only a single standard epitaxial growth of a laser structure while the use of a thin top cladding layer allows for a shallow reactive ion etch of the distributed Bragg reflector. These RW-DBR lasers have a threshold current of 12.4 mA, a slope of 0.3 W/A, and over 40 dB side-mode suppression at a wavelength of 1010 nm.     

The politics of conservative elites and the 'liberal media' argument

Recent evidence suggests that conservative elites' claims of a liberal media are having an impact upon public perceptions of news coverage. With this in mind, we examined two related questions in the context of the 1988, 1992, and 1996 presidential elections. First, what factors may be prompting conservative elites to make allegations of liberal media bias? Second, what factors may influence when news media report these criticisms during presidential campaigns? Findings suggest that these criticisms of news media are at least partly strategic and reflect a dynamic relationship between political elites and journalists during a presidential campaign.