Cavity length dependence of high-speed 1.55-/spl mu/m multiple-quantum-well laser diode characteristics

Spontaneous emission spectra below threshold were measured from the side wall of InGaAs QW laser diodes to extract laser design parameters such as cavity length dependence of gain, linewidth enhancement factor, and serial resistance. The threshold current varies according to the change of cavity length, and thus, the lasing peak shifts and the serial resistance changes. It is interesting that the linewidth enhancement factor, however, is not deteriorated by shortening cavity length. The short cavity length would rather improve the linewidth enhancement factor mainly by shifting the lasing peak to smaller wavelength side, where the linewidth enhancement factor is inherently low.     

A 68% PAE, GaAs power MESFET operating at 2.3 V drain bias for lowdistortion power applications

A high-efficient GaAs power metal semiconductor field effect transistor operating at a drain voltage of 2.3 V has been developed for low distortion power applications. The device has been fabricated on an epitaxial layer with a high-low doped structure grown by molecular beam epitaxy. The MESFET with a gate length of 0.8 μm and a total gate width of 21.16 mm showed a maximum drain current of 5.9 A at V_gs =0.5 V, a knee voltage of 1.0 V and a gate-to-drain breakdown voltage of 28 V. The MESFET tested at a 2.3 V drain bias and a 900 MHz operation frequency displayed the best power-added efficiency of 68% with an output power of 31.3 dBm. The associate power gain at 20 dBm input power and the linear gain were 11.3 dB and 16.0 dB, respectively. The power characteristics of the device operating under a bias of 2 V exhibit power-added efficiency of 67% and output power of 30.1 dBm at an input power of 20 dBm. Two tone test measured at 900.00 MHz and 900.03 MHz shows that 3rd-order intermodulation and power-added efficiency at an output power of 27 dBm were -30.6 dBc and 36%, respectively, which are good for CDMA digital applications. A third-order intercept point and a linearity figure-of-merit were measured to be 49.5 dBm and 53.8, respectively     

A Supervised Feature-Projection-Based Real-Time EMG Pattern Recognition for Multifunction Myoelectric Hand Control

Electromyographic (EMG) pattern recognition is essential for the control of a multifunction myoelectric hand. The main goal of this study was to develop an efficient feature- projection method for EMG pattern recognition. To this end, a linear supervised feature projection is proposed that utilizes a linear discriminant analysis (LDA). First, a wavelet packet transform (WPT) is performed to extract a feature vector from four-channel EMG signals. To dimensionally reduce and cluster the WPT features, an LDA, then, incorporates class information into the learning procedure, and identifies a linear matrix to maximize the class separability for the projected features. Finally, a multilayer perceptron classifies the LDA-reduced features into nine hand motions. To evaluate the performance of the LDA for WPT features, the LDA is compared with three other feature-projection methods. From a visualization and quantitative comparison, it is shown that the LDA produces a better performance for the class separability, plus the LDA-projected features improve the classification accuracy with a short processing time. A real-time pattern-recognition system is then implemented for a multifunction myoelectric hand. Experiments show that the proposed method achieves a 97.4% recognition accuracy, and all processes, including the generation of control commands for the myoelectric hand, are completed within 97 ms. Consequently, these results confirm that the proposed method is applicable to real-time EMG pattern recognition for multifunction myoelectric hand control.     

Synthesis, characterization and adsorption study of the uranyl ions by hydrogels based on polyethylene glycol and methacrylic acid copolymers

The water swelling polymeric hydrogels were obtained by γ-initiated radiation copolymerization of polyethylene glycol (PEG) with methacrylic acid (MAA) and three-ethylene glycol dimethacrylate (TEGDMA) as cross-linking agent. The main regularities of PEG-MAA network formation, deformation properties, structure and thermal characteristics depending on copolymer composition, molecular weight of PEG have been studied. The sorption of uranyl ions by PEG-MAA hydrogels in comparison with homopolymer PMAA was investigated. The effect of uranyl ions concentration on sorption efficiency of hydrogels was shown. The ability to regeneration in desorption process was demonstrated for PEG-MAA hydrogels in comparison with PMAA gel.     

Growth and X-ray Diffraction Study of YCa4O(BO3)3:Ce,Er,Yb Crystals

YCa₄O(BO₃)₃crystals (sp. gr. Cm), nominally pure and activated with Yb, Er, and/or Ce, were grown by the Czochralski technique. The crystal structure of YCa₄O(BO₃)₃was refined by single-crystal x-ray diffraction, and the site compositions were determined: (Y_0.792Ca_0.208(6))(Ca_0.938Y_0.062(4))₂Ca₂O_0.96(2)[ ]_0.04(BO₃)₃([ ] = vacancy). The data set for YCa₄O(BO₃)₃was found to contain additional reflections which were inconsistent with space group Cmbut could be indexed in a cell with doubled a. No superlattice reflections were detected in the case of the activated crystals. Structural data for LnCa₄O(BO₃)₃were used to derive relations for the lattice parameters and average cation–anion distances as functions of r _Lnand weighted-average cation radii on the mixed-occupancy sites, which made it possible to assess the distributions of Y, Yb, Er, Ce, and Ca over the mixed-occupancy sites. Absolute structure determination showed that the pure and Yb³⁺-activated YCa₄O(BO₃)₃crystals differed in polarity.     

Association between Microbiota and Nasal Mucosal Diseases in terms of Immunity

The pathogenesis of nasal inflammatory diseases is related to various factors such as anatomical structure, heredity, and environment. The nasal microbiota play a key role in coordinating immune system functions. Dysfunction of the microbiota has a significant impact on the occurrence and development of nasal inflammation. This review will introduce the positive and negative roles of microbiota involved in immunity surrounding nasal mucosal diseases such as chronic sinusitis and allergic rhinitis. In addition, we will also introduce recent developments in DNA sequencing, metabolomics, and proteomics combined with computation-based bioinformatics.     

Inducing and Probing Localized Excitons in Atomically Thin Semiconductors via Tip-Enhanced Cavity-Spectroscopy

In atomically thin semiconductors, localized exciton (X_L) coupled to light provides a new class of optical sources for potential applications in quantum communication. However, in most studies, X_L photoluminescence (PL) from crystal defects has mainly been observed in cryogenic conditions because of their sub-wavelength emission region and low quantum yield at room temperature. Hybrid-modality of cavity-spectroscopy to induce and probe the X_L emissions at the nanoscale in atomically thin semiconductors is presented. By placing a WSe₂ monolayer on the two extremely sharp Au tips in a bowtie antenna with a radius of curvature of <1 nm, tensile strain of ≈0.3% is effectively induced in a <30 nm region to create robust X_L states. The Au tip then approaches the strained crystal region to enhance the X_L emissions and probe them with tip-enhanced photoluminescence (TEPL) spectroscopy at room temperature. Through this triple-sharp-tips cavity-spectroscopy with <15 nm spatial resolution, TEPL enhancement as high as ≈4.0 × 10⁴ by the Purcell effect is achieved, and peak energy shifts of X_L up to ≈40 meV are observed. This approach combining nano-cavity and -spectroscopy provides a systematic way to induce and probe the radiative emission of localized excitons in 2D semiconductors offering new strategies for dynamic quantum nano-optical devices.     

Scalable image decomposition

Neural Computing and Applications - Image decomposition, which separates a given input image into structure and texture images, has been used for various applications in the fields of computer...