Monotonically convergent iterative learning control for linear discrete-time systems

In iterative learning control schemes for linear discrete time systems, conditions to guarantee the monotonic convergence of the tracking error norms are derived. By using the Markov parameters, it is shown in the time-domain that there exists a non-increasing function such that when the properly chosen constant learning gain is multiplied by this function, the convergence of the tracking error norms is monotonic, without resort to high-gain feedback.     

The light fading mechanism of dyes derived from rhubarb extract

The effect of relative humidity and mordanting on the fading kinetics and colour change of dyes derived from rhubarb extract on wool and silk has been investigated. Wool samples showed negligible change in colour even after 100 h of exposure, whereas silk samples became significantly darker. Relative humidity in the range of 10–45% and mordanting did not appear to affect the rate of fading on both the fibres. However, the rate and extent of change in colour (ΔE) on exposure was different for different mordants. The high resistance of the dye to light fading indicates that the dye is present in a highly aggregated form in silk and wool.     

Modeling ultrashort field dynamics in surface emitting lasers by using finite-difference time-domain method

An approach based on the finite-difference time-domain (FDTD) method is developed for simulating the dynamics of vertical-cavity surface-emitting lasers (VCSELs). The material response is incorporated in our FDTD algorithm by the effective semiconductor Bloch equations, and its effects are accounted for through a resonant polarization term in the Maxwell's equations. Moreover, nonlinear gain saturation is incorporated through a gain suppression factor in the equation governing the dynamics of the resonant polarization. This approach is verified by modeling a /spl lambda/-cavity VCSEL, with a multiple quantum-well (MQW) gain region; the corresponding continuous-wave operation is obtained at the expected wavelength. The dynamics of ultrashort pulses generated by a monolithic passively mode-locked one-dimensional VCSEL with a MQW gain region and a single QW saturable absorber are studied and it is demonstrated that a stable mode-locked pulse train can be generated. It is also demonstrated that with our FDTD approach subcycle temporal precision can be achieved. The need for this fine temporal resolution is established by investigating pulse propagation through the semiconductor saturable absorber. Fine features of the spatial profile of the mode-locked pulses are also examined within this approach. This knowledge of the fine spatial features is then used for lowering the current threshold through gain structure optimization. Various approaches for the reduction of the total simulation time are also discussed.     

Nitridation of sol--gel derived DMDEOS--TEOS copolymer gels to silicon carboxynitride (SiCNO)

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

New microstrip slot radiator for medical applications

A microstrip slot radiator for local heating of biological tissue operating at 2.45 GHz was designed and tested. The radiator is well matched within a relatively wide range of frequencies (v.s.w.r. < 1.5 for 2.45 ± 0.3 GHz) and provides energy deposition within an area of about 1.5 cm × 1 cm.     

Multifunction SAG process for high-yield, low-cost GaAs microwaveintegrated circuits

A new fully planar, multifunction refractory self-aligned gate (MSAG) technology suitable for the fabrication of GaAs small-signal and power microwave monolithic integrated circuits (MMICs) is demonstrated in a manufacturing environment. Data on the distribution of DC and RF performance and yield for pilot production of discrete FETs and MMICs are presented. The heart of the MSAG process is a planar, self-aligned gate FET. It uses a refractory TiWN Schottky gate and exhibits high performance for small-signal microwave, power microwave, and digital circuit applications. Lots with good wafer yields have demonstrated average chip yields on PCM good wafers of 45%, 49%, and 36% for 2-10-GHz distributed amplifiers, 1-W C-band power amplifiers, and 4-W power amplifiers, respectively     

Development of glass-like carbon from phenol formaldehyde resins employing monohydric and dihydric phenols

A study on the development of glass-like carbon from phenol formaldehyde resins employing monohydric (simple) and dihydric phenols (resorcinol and catechol) has been made. It is revealed that to obtain a good glass-like carbon, the optimum molar ratio of formaldehyde to resorcinol in the resorcinol formaldehyde resin is 1.5, as was found earlier in the case of a simple phenol formaldehyde resin, whereas for catechol formaldehyde resin, the optimum molar ratio of formaldehyde to catechol is found to be 2.0. Further, it is observed that the three types of resins lead to glass-like carbons of essentially the similar characteristics, except that the catechol formaldehyde based carbons possess the highest strength of 326 M Pa. A mechanism has been proposed on the basis of three types of phenolic rings designated as attached, bridging and cross-linking, in the structure of the three cured phenol formaldehyde resins to explain the respective optimum molar ratio of formaldehyde to type of phenol.