Engineering

Considerations for optimisation of the MFMOS(Multi-input Floating-gateMosfet) multiplier for gain, minimal total harmonic distortion, low supplyvoltage operation and offset trimming are considered in this paper. Analysis shows that good matching between pairs of devices are essential forlow harmonic distortion. Results from simulation studies show that offsettrimming can be facilitated by connecting the dc bias inputs in pairs andbiasing them separately. A ±1.5 volt supply MFMOS multiplier has been designed and fabricated. Measured THD and nonlinearity at fullscale input are 0.8% and 0.5%, respectively. Bandwidth is more than 20 MHz and input dynamic range over a 0-1 MHz bandwidth is92.6 db. The lowest measured operable supply voltage is w±0.9 volt.

A novel four-quadrant analog multiplier using multiinput floating-gate MOS (MFMOS) transistors has been designed and fabricated using a 2-pm double-poly double-metal P-well CMOS process. It is essentially based on the quarter-square technique which relies on the square-law characteristic of the MOS transistor in the saturation region. The multiplier is realized with only four MFMOS transistors and a current source. The input range is 100% of the supply voltage and accepts either differential, single-ended, or floating input signals. Measured nonlinearity and total harmonic distortion are 0.2% and O S % , respectively, under full scale input conditions. Input noise is 170 pV (rms), giving a 95 dB input dynamic range. The power dissipation is 1.1 mW and bandwidth is 12 MHz. Second-order effects on the multiplier performance have also been analyzed.

A pseudologarithmic rectifier using multi-input floating-gate MOS (MFMOS) transistors is presented in this paper. The rectifiers consist of unbalanced bias matched MFMOS transistor differential pairs. The transfer characteristics of each subrectifier are determined by an appropriate choice of transistor aspect ratio and capacitive input coupling ratio such that in the summation of the output currents from each rectifier stage, the overall transfer characteristics closely approximates that of a true logarithmic behavior. It is operable at low supply voltage (60.9 V) and has low temperature dependence. Measured dynamic range of 27 dB and 16.5 dB, with a corresponding logarithmic error of 60.7 dB and 60.35 dB, has been obtained for three-stage and two-stage pseudologarithmic rectifiers, respectively, at room temperature. The measured logarithmic error for the three-stage pseudologarithmic rectifier at 125 C is 61.05 dB which is an increase of 60.35 dB over a 100 C range.

A wide regulatory reform is taking place in world-wide level in the continuing airworthiness domain.  The major influences for promoting changes in how continuing airworthiness is managed are civil and military aircraft accidents contributed by fatigue, corrosion, wear, deterioration in ageing aircraft and the need for regulatory harmonisation of the International Civil Aviation Organisation (ICAO) signatory states and the military.  Another emerging factor is the conversion of older passenger aircraft to freighters which brings forth the concern where aircraft are being used in the capacity of which they were not designed.  The challenges of the regulatory reform are acceptance, certification of maintenance organizations and personnel, education and training, information sharing and administration. This paper presents both the drivers and challenges in these areas and proposes a related change management framework.

The problem of ratcheting, defined as the progressive
plastic strain accumulation in cyclic loading, is
considered to be one of the unsolved difficulties of
plasticity and furthermore fatigue modeling. Towards
this direction many models within the frame of
constitutive plasticity, based on the well known
Armstrong and Frederick (AF) kinematic hardening
rule have been introduced. In this paper further
implementation of the multiplicative AF kinematic
hardening model proposed in ASIP Conference 2007
and by Dafalias et el, is performed more extensively in
the area of ratcheting simulation. Uniaxial
experimental results, extracted from published results,
were used for the validation, as well as for the
assessment in terms of its capability to predict
ratcheting response in steel alloys. In addition, the
results of the commonly used Chaboche model with
Threshold term have been compared with the relevant
results of the multiplicative AF model, indicating an
improved response. This model has been formulated
for use in multiaxial loading cases, yet ratcheting
simulation in specific published bi-axial results is an
ongoing project and is expected to be presented in
future works.

This study aims to translate needed future skills to the university classroom for the aerospace and aviation industry personnel, given the fast-paced change taking place in both the industry and the education sectors. A synopsis of the current challenges faced in the educational field is outlined, followed by a mapping of the future of both education and air platforms, in an attempt to set the basis of the needed skills framework. The Assessment and Teaching of 21 st Century Skills Project is used as a baseline for the definition of the future " critical " skill set, which is considered well aligned with the future needs of the aerospace industry. It is suggested that this critical skill set can be translated to the higher education environment through an effective redesign of the existing teaching and learning philosophy and the practices.