Axisymmetric problem of a nonhomogeneous elastic layer

Summary The paper deals with a theoretical treatment of elastic behavior for a medium with nonhomogeneous materials property, which is defined by the relation , i.e., shear modulus of elasticity G varies with the dimensionless axial coordinate by the power product form, arbitrarily. Fundamental differential equation for such nonhomogeneous medium has been already proposed in [5]. It is given by a second-order partial differential equation. However, it was found that the fundamental equation is not sufficient in general to solve several kinds of boundary-value problems. On the other hand, it is shown in the present paper making use of the fundamental equations system for a nonhomogeneous medium, which has been proposed in our previous paper [7], it is possible to solve axisymmetric problems for a thick plate (layer) subjected to an arbitrarily distributed load or a concentrated load on its surfaces. Numerical calculations are carried out for several cases, taking into account the variation of the nonhomogeneous parameter m. The numerical results for displacements stress and components are shown in graphical form. Accepted for publication 25 March 1997     

Acquisition time minimisation techniques for high-speed analoguesignal processing

Acquisition time minimisation techniques using a two-stage amplifier for high-speed analogue signal processing in mixed-mode circuits are presented. The proposed techniques reduce overshoots and undershoots of the amplifier by adjusting its transconductance and achieve high-speed performance with little modification to the conventional amplifier architecture. The measured signal-to-noise-and-distortion ratio of the prototype 12 bit CMOS ADC based on the proposed techniques is improved by >5 dB at a 50 MHz sampling clock     

12 nm tunable WDM source using an integrated laser array

A 12 nm tunable source with up to 15 mW fibre coupled power has been fabricated by integrating four DFB lasers and a booster amplifier to provide a single output. High-yield and low-cost techniques are used, such as quarter-wave-shifted phase-masks for wavelength definition and an integration technique with only two regrowths     

Wideband wavelength tunable modelocked fibre laser over 1557-1607nm

An electronically wavelength tunable modelocked fibre laser operating over a 50 nm range using an all-fibre acousto-optic tunable filter is presented. The tuning range is 1557-1607 nm, for a 70 m long erbium-doped fibre (EDF) with a 270 ppm concentration     

Design and analysis of TX/RX dual microstrip antenna using FDTD at Ku-band

A TX/RX dual microstrip 8/spl times/4 array antenna for satellite communication is designed, fabricated and measured and its element characteristics are analysed using finite difference time domain (FDTD) method. TX/RX frequency ranges are 14.0-14.5 GHz, 11.7-12.75 GHz, respectively, and vertical and horizontal polarisations are used for TX and RX. This antenna uses microstrip direct feeding for RX and aperture coupled stripline feeding for TX and accommodates stacked elements for a high directivity and wide impedance bandwidth. FDTD gives more accurate results because of the consideration of finite structure and two imperfect ground planes. This element has a return loss below -8 and -14 dB over the TX and RX frequency ranges and a gain of 7.5 and 8.3 dBi at the centre frequency of TX and RX. Return loss below -10 and -14 dB and a gain of 21.4 and 20.0 dBi were achieved for the TX and RX array, respectively.     

Pilot Symbol Assisted Hybrid Detection for OFDM‐Based Spatial Multiplexing Systems

In this paper, we provide a new detection scheme for a pilot symbol assisted interference nulling and cancellation operation to reduce unexpected effects owing to parallel transmission in orthogonal frequency division multiplexing (OFDM)‐based spatial multiplexing systems. We have shown that the investigated OFDM vertical Bell laboratories layered space time (VBLAST) detection based on hybrid processing performs better than ordinary OFDM‐VBLAST detections based on serial processing and parallel processing, respectively.     

Hafnium or zirconium high-k fab cross-contamination issues

Hf and Zr contamination during immersion in process solutions is most likely to occur in neutral and caustic solutions. Both Hf and Zr contamination are introduced onto the wafer surface if they are present in an ammonium hydroxide peroxide mixture solution (which is caustic), but such contamination is removed using existing acid cleans. Large amounts of wafer-to-wafer cross contamination occurs in plasma etch tools. Particles can cause cross contamination in a thermal reactor during high-temperature anneals of high-k dielectric layers. Residual surface cross contamination does not diffuse into the wafers during thermal processing. If contamination remains on a wafer, gate oxide integrity degradation is only observed at high concentrations. Near surface minority carrier lifetime is also affected, but bulk lifetime is not.     

Design and performance evaluation of a new medium access controlprotocol for local wireless data communications

This paper proposes a new medium access control protocol for wireless data communications in local area, called the reservation-based multiple access with variable frame length (RMAV). We design RMAV under the consideration that the population of wireless terminals and the system load frequently change and are almost unpredictable in wireless data communications. RMAV is based on the slot reservation scheme and adopts a frame structure with variable length. The frame length increases as the number of active terminals and/or the system load increases. We evaluate the performance of RMAV by analysis and computer simulation. Due to its adaptability to traffic patterns, RMAV offers short delay in light load conditions and high throughput in heavy load conditions     

Flux observer with online tuning of stator and rotor resistancesfor induction motors

This paper proposes an adaptive flux observer for induction motors, where stator and rotor resistances are estimated in online environments. The variation of motor parameters during operation degrades the performance of the controller and the flux observer. Among the parameters of induction motors, rotor resistance is a crucial one for flux estimation, and stator resistance also becomes critical in the low-speed region. Under the persistent excitation condition, the proposed method estimates the actual values of stator and rotor resistances simultaneously, which guarantees the exact estimation of the rotor flux. The persistent excitation condition is not satisfied when the electric torque of an induction motor is absent due to the lack of rotor currents. Even in this case, the proposed method achieves the correct estimation of the rotor flux. Simulations and actual experiments show that the rotor flux is estimated in all operating conditions and that both resistances converge to their actual values when the electrical motor torque exists     

New developments in the dye-doped polymer dispersed liquid crystals gratings: A review

In this study, the dye-doped polymer dispersed liquid crystals (PDLC) gratings techniques performed by the various research groups or being developed are briefly reviewed. Especially, the electrically switched diffraction and holographic gratings, have attained much attention by various research groups working in the PDLC-related display studies. The fabrication methodologies used for such grating texture, include like the conventional dye-doped PDLC grating, Azo-dye doped PDLC gratings, and lasing techniques etc., adopted for dye-doped PDLC gratings. The useful features and characteristics of their fabrication process of such gratings are discussed. Finally, some of the future perspectives on this particular research field are presented.