Dual-wavelength cascaded Raman fibre laser

Dual-wavelength lasing at 1480 and 1500 nm has been demonstrated from a cascaded Raman fibre laser with a WDM coupler and two pairs of Bragg gratings. Intensity-adjustable, wavelength-tunable laser operation was achieved by tensile stress wavelength tuning of the gratings     

Investigation of organic n-type field-effect transistor performance on the polymeric gate dielectrics

We report a copper hexadecafluorophthalocyanine (F₁₆CuPc) based n-type organic field-effect transistor (OFET) with polymeric gate dielectrics with different physical/electrical properties. The gate dielectrics are four types of cross-linked poly(4-vinylphenol) and newly prepared poly(4-phenoxy methyl styrene) and those are characterized based on surface tension, leakage current and capacitance. The performance of F₁₆CuPc OFETs with those gate dielectrics was compared. We found that the composition of the gate dielectrics and the interfacial interaction of F₁₆CuPc with the gate dielectric play a decisive role in the performance of OFETs. The effect of physical/electrical properties, composition and processing condition of the gate dielectrics on the device performance was investigated.     

Fabrication of Al matrix composite reinforced with submicrometer-sized Al<Subscript>2</Subscript>O<Subscript>3</Subscript> particles formed by combustion reaction between HEMM Al and V<Subscript>2</Subscript>O<Subscript>5</Subscript> composite particles during sintering

To fabricate an Al-V matrix composite reinforced with submicron-sized Al₂O₃ and Al_xV_y (Al₃V, Al₁₀V) phases, high energy mechanical milling (HEMM) and sintering were employed. By increasing the milling time, the size of mechanically milled powder was significantly reduced. In this study, the average powder size of 59 μm for Al, and 178 μm for V₂O₅ decreased with the formation of a new product, Al-Al₂O₃-Al_xV_y, with a size range from 1.3 μm to 2.6 μm formed by the in-situ combustion reaction during sintering of HEM milled Al and V₂O₅ composite powders. The in-situ reaction between Al and V₂O₅ during the HEMM and sintering transformed the Al₂O₃ and Al_xV_y (Al₃V, Al₁₀V) phases. Most of the reduced V reacted with excess the Al to form Al_xV_y (Al₃V, Al₁₀V) with very little V dissolved into Al matrix. By increasing the milling time and weight percentage of V₂O₅, the hardness of the Al-Al₂O₃-Al_xV_y composite sintered at 1173 K increased. The composite fabricated with the HEMM Al-20wt.%V₂O₅ composite powder and sintering at 1173 K for 2 h had the highest hardness.     

Some block- and trellis-coded modulations for the Rayleigh fadingchannel

The error performance of a modulation code over a channel depends on several distance parameters and the path multiplicity of the code. For the AWGN channel, the error performance of a modulation code depends mainly on its minimum squared Euclidean distance and path multiplicity. For the Rayleigh fading channel, however, the error performance of a modulation code depends strongly on its minimum symbol distance, minimum product distance, and path multiplicity. It depends on the minimum squared Euclidean distance in a lesser degree. This paper is concerned with the construction of block and trellis MPSK modulation codes for the Rayleigh fading channel. In each construction, the distance parameters are chosen to achieve good error performance with reduced decoding complexity     

Binary blends of nylons with ethylene vinyl alcohol copolymers: Morphological,thermal, rheological,and mechanical behavior

Binary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH-62) and 71 (EVOH-71) mole percent vinyl alcohols, with nylons (nylon-6, nylon-6/12, and nylon-12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH-62/nylon-6 and EVOH-71/nylon-6 blends showed homogeneous phase morphologies in the nylon-6-rich region, and fine phase separations (c.a. 2 × 10^?7 m) in the EVOH-rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH-71/nylon-6/12 and EVOH-71 /nylon-12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanical property drop were also observed.     

Enhancing impedance imaging through multimodal tomography

Several noninvasive modalities including electrical impedance tomography (EIT), magnetic induction tomography (MIT), and induced-current EIT (ICEIT) have been developed for imaging the electrical conductivity distribution within a human body. Although these modalities differ in how the excitation and detection circuitry (electrodes or coils) are implemented, they share a number of common principles not only within the image reconstruction approaches but also with respect to the basic principle of generating a current density distribution inside a body and recording the resultant electric fields. In this paper, we are interested in comparing differences between these modalities and in theoretically understanding the compromises involved, despite the increased hardware cost and complexity that such a multimodal system brings along. To systematically assess the merits of combining data, we performed 3-D simulations for each modality and for the multimodal system by combining all available data. The normalized sensitivity matrices were computed for each modality based on the finite element method, and singular value decomposition was performed on the resultant matrices. We used both global and regional quality measures to evaluate and compare different modalities. This study has shown that the condition number of the sensitivity matrix obtained from the multimodal tomography with 16-electrode and 16-coil is much lower than the condition number produced in the conventional 16-channel EIT and MIT systems, and thus, produced promising results in terms of image stability. An improvement of about 20% in image resolution can be achieved considering feasible signal-to-noise ratio levels.     

Modeling of power supply noise in large chips using the circuit-based finite-difference time-domain method

In this paper, a multilayered on-chip power distribution network consisting of two million passive elements has been modeled using the finite-difference time-domain (FDTD) method. In this method, a branch capacitor has been used. The use of the branch capacitor is important for simulating multilayered power grids. In addition, a method for including the CMOS inverter characteristics into the FDTD simulation has been presented. As an example of the application of this method, an H-tree clock network was simulated to compute the power supply noise distribution across an entire chip. Various scenarios with varying decoupling capacitances, load capacitances, number of clock buffers, and rise times have been analyzed to demonstrate the importance of circuit nonlinearity on power supply noise. Also, a method has been presented for analyzing package and board planes. Based on the methods presented, the interaction between chip and package has been discussed for capturing the resonant behavior that is otherwise absent when each section of the system is analyzed separately.     

IPTV的关键广播构建模块

电信运营商和电视运营商在为消费者提供视频内容服务上不断展开竞争。然而，与电视运营商相比，大部分电信运营商的基础设施还不具备传输高质量视频所需的带宽。因此，在内容分配上，电信运营商没有使用正交振幅调制（QAM）和MPEG2视频编码等数字调制技术，而是采用了互联网协议（IP）网络，利用MPEG4-Part10（也称为H．264-AVC）等新的编码方案来为消费者提供视频内容。     

Accelerometers and force sensing resistors for optimal control of walking of a hemiplegic

We developed a method for use of accelerometers and force sensing resistors (FSRs) within an optimal controller of walking for hemiplegic individuals. The data from four dual-axis accelerometers and four FSRs were inputs, while six muscle activation profiles were outputs. The controller includes two stages: 1) estimating the target gait pattern using artificial neural networks; and 2) optimal control minimizing tracking errors (from the estimated gait pattern) and muscle efforts. The controller was tested using data collected from six healthy subjects walking at five speeds (0.6–1.4 m/s). The average root mean square errors (RMSEs) normalized by the peak-to-peak value of the target signals [normalized RMSE (NRMSE)] were below 6%, 7%, 8%, and 3% for estimation of joint angles, hip acceleration, ground reaction force, and movement of the center of pressure, respectively. Using the estimated data as inputs, the simulation generated the target healthy-like gait patterns and reproducible muscle activation profiles in 90% of 300 tested gait trials. Overall tracking NRMSE was between 2% and 9%. The optimal controller was developed for testing the feasibility of healthy-like gait patterns in hemiplegic individuals, and generating a knowledge base that is required for the synthesis of a sensory-driven control of walking assisted by functional electrical stimulation.