Molecular dynamics study on nanotube-resonators with mass migration applicable to both frequency-tuner and data-storage-media

We investigated the cantilevered carbon-nanotube-resonator including electromigratively movable nanoparticle via classical molecular dynamics simulations and continuum model. The change of the effective mass value, which was closely correlated with the position change of the encapsulated nanoparticle, could be regressed by a power function, the resonance frequency of the carbon-nanotube-resonator could be tuned by controlling the nanoparticle’s position, and the possible frequency-shift-ranges then reached 18–85%. The suggested device could be served as a data-storage-media for electromechanical nonvolatile-memory as well as a frequency-tuner.     

Optimisation of location and dimension of SMC precharge in compression moulding process

The main goal of the present study is to optimise the precharge conditions such as the precharge location and dimensions that give significant effects on the mechanical performance of composite structures manufactured by the compression moulding process. As preliminary step of optimisation, we developed a manufacturing simulation program to predict the fibre volume fraction and fibre orientation. And coupled with this simulation program and a structural analysis program, a genetic algorithm (GA) is implemented to optimise the precharge conditions. The penalty function method and the repair algorithm are modified for handling constraints. The repair algorithm is applied to a symmetric structure and an arbitrary shape structure to find optimal precharge conditions.     

Kink effect upon the electromagnetic generation of ultrasound in isotropic ferromagnets

The influence of the shape anisotropy on the field dependences of double electromagnetic-acoustic conversion in samples of an Invar alloy 29NK in the high-temperature range below the Curie point is experementally studied. It is shown that at a constant temperature the value of the polarizing field in which a jumplike generation of ultrasound occurs is determined by the demagnetizing factor of the sample, and the observed anomaly of the electromagnetic-acoustic conversion is caused by the kink effect.     

A risk management approach to safety assessment of trenchless technologies for culvert rehabilitation

Proper functioning of culverts is not only critical to protecting the transportation system from flooding but also critical to maintaining the expected service life of the overall transportation system. During the service life of culverts, they deteriorate due to many reasons such as corrosion caused by road salt, blockage by debris and sediment, poor construction techniques, etc. Trenchless technologies have been used by several State Departments of Transportation (DOTs) to rehabilitate deteriorated drainage structures without disrupting the traffic and within a relatively short span of time. These technologies provide many benefits in terms of cost, time, quality, and expected service life. However, the safety aspects of these techniques have not been discussed and documented in detail probably due to the complexity and the lack of safety standards and specifications directly associated with the techniques. This paper discusses the application of a risk assessment framework to assess potential safety issues of currently available trenchless technologies for culvert rehabilitation. The findings of the study will provide additional information to improve the decision making process in selecting and planning culvert rehabilitation projects.     

An analysis of signal-to-noise ratio and design parameters of aterahertz optical asymmetric demultiplexer

Analysis of the signal-to-noise ratio (SNR) as a function of the component parameters in a terahertz optical asymmetric demultiplexer (TOAD) can help optimize its performance as a demultiplexer or as a router in an optical time division multiplexed network. The analysis presented here accounts for crosstalk due to deviation from a perfect 3 dB splitting ratio in the TOAD's 2×2 coupler, and the degradation of SNR due to fluctuations in the control pulse energy. The spontaneous emission noise output of the semiconductor optical amplifier (SOA) contained in the TOAD is simulated under different degrees of saturation. The analysis indicates that leakage due to the asymmetric placement of the SOA contributes significantly to the crosstalk. To achieve a SNR of 21.5 dB or higher in a 100 Gb/s system, one must use a 2×2 coupler that deviates less than 1% from a perfect 3 dB splitting ratio. Also, control pulse energy fluctuations must be less than 10% for a 20-GHz bandwidth electronic receiver. Novel crosstalk-free designs are proposed and analyzed which meet the stringent requirements of current TOAD devices. A significant enhancement in SNR is predicted when the SOA is operated near the optimal saturation point     

Delay-Dependent Robust Stability of Stochastic Uncertain Systems with Time Delay and Markovian Jump Parameters

This paper is concerned with the delay-dependent stability for a class of stochastic uncertain systems with time delay and Markovian jump parameters. The uncertainties considered in this paper are norm-bounded and governed by the Markov process. Un like the topics in the existing literature, the stability criterion is expressed in terms of linear matrix inequalities, which can be efficiently solved by using a convex-optimization algorithm. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.     

An InGaP-GaAs HBT MMIC smart power amplifier for W-CDMA mobile handsets

We demonstrate a new linearized monolithic microwave integrated circuit smart power amplifier of extraordinary high power-added efficiency (PAE), especially at the most probable transmission power of wide-band code-division multiple-access handsets. A PAE of 21% at 16 dBm of output power, which is the maximum bound of the most probable transmission power in IS-95 systems, was obtained, as well as 40% at 28 dBm, the required maximum output power, with a single-chip MMIC power amplifier. The power amplifier has been devised with two InGaP-GaAs heterojunction bipolar transistor amplifying chains parallel connected, each chain being optimized for a different P/sub 1dB/ (1-dB compression point) value: one for 16 dBm for the low-power mode, targeting the most probable transmission power, and the other for 28 dBm for the high-power mode. The high-power mode operation shows 40% of PAE and -30 dBc of adjacent channel leakage power ratio (ACLR) at the maximum output power of 28 dBm. The low-power mode operation exhibits -34 dBc of ACLR at 16 dBm with 14 mA of a quiescent current. This amplifier improves power usage efficiency and, consequently, the battery lifetime of the handset by a factor of three.     

16‐QAM‐Based Highly Spectral‐Efficient E‐band Communication System with Bit Rate up to 10 Gbps

This paper presents a novel 16‐quadrature‐amplitude‐modulation (QAM) E‐band communication system. The system can deliver 10 Gbps through eight channels with a bandwidth of 5 GHz (71‐76 GHz/81‐86 GHz). Each channel occupies 390 MHz and delivers 1.25 Gbps using a 16‐QAM. Thus, this system can achieve a bandwidth efficiency of 3.2 bit/s/Hz. To implement the system, a driver amplifier and an RF up‐/down‐conversion mixer are implemented using a 0.1 µm gallium arsenide pseudomorphic high‐electron‐mobility transistor (GaAs pHEMT) process. A single‐IF architecture is chosen for the RF receiver. In the digital modem, 24 square root raised cosine filters and four (255, 239) Reed‐Solomon forward error correction codecs are used in parallel. The modem can compensate for a carrier‐frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of 10^?5 at a signal‐to‐noise ratio of about 21.5 dB.     

A Structurable Gel‐Polymer Electrolyte for Sodium Ion Batteries

In this work, a structurable gel‐polymer electrolyte (SGPE) with a controllable pore structure that is not destroyed after immersion in an electrolyte is produced via a simple nonsolvent induced phase separation (NIPS) method. This study investigates how the regulation of the nonsolvent content affects the evolving nanomorphology of the composite separators and overcomes the drawbacks of conventional separators, such as glass fiber (GF), which has been widely used in sodium ion batteries (SIBs), through the regulation of pore size and gel‐polymer position. The interfacial resistance is reduced through selective positioning of a poly(vinylidene fluoride‐co‐hexa fluoropropylene) (PVdF‐HFP) gel‐polymer with the aid of NIPS, which in turn enhances the compatibility between the electrolyte and electrode. In addition, the highly porous morphology of the GF/SGPE obtained via NIPS allows for the absorption of more liquid electrolyte. Thus, a greatly improved cell performance of the SIBs is observed when a tailored SGPE is incorporated into the GF separator through charge/discharge testing compared with the performance observed with pristine GF and conventional GF coated with PVdF‐HFP gel‐polymer.     

Highly stable optical add/drop multiplexer using polarization beam splitters and fiber Bragg gratings

We demonstrate a novel wavelength-division add/drop multiplexer employing fiber Bragg gratings and polarization beam splitters. The multiplexer is easy to fabricate without any special technique such as UV trimming, and yet shows very stable performance with less than 0.3-dB crosstalk power penalty in a 0.8-nm-spaced, 2.5-Gb/s-per-channel wavelength-division multiplexing (WDM) transmission system.