Design of differential amplifier with negative impedance compensation

Design of differential amplifier with high gain accuracy and high linearity is presented in the paper. The amplifier design is based on the negative impedance compensation technique reported by the authors in [1]. A negative impedance with high precision, low sensitivity, wide input signal range and simple structure is used for the compensation of differential amplifier. Analysis and simulation results show that gain accuracy and linearity can be improved significantly with the negative impedance compensation

Stability analysis of the amplifier with negative impedance compensation

A novel amplifier design technique based on negative impedance compensation has been proposed in our recent paper. In this paper, we investigate the stability of this amplifier system. The parameter space approach has been used to determine system parameters in the negative impedance circuit such that the stability of the amplifier system can be guaranteed in a certain region represented by those parameters. The simulation results have demonstrated that stable circuit behavior for the amplifier can be achieved

Numerical analysis of thermal stresses induced during VFM encapsulant curing

Encapsulant curing using a Variable Frequency Microwave (VFM) system is analysed numerically. Thermosetting polymer encapsulant materials require an input of heat energy to initiate the cure process. In this article, the heating is considered to be performed by a novel microwave system, able to perform the curing process more rapidly than conventional techniques. Thermal stresses are induced when packages containing materials with differing coefficients of thermal expansion are heated, and cure stresses are induced as thermosetting polymer materials shrink during the cure process. These stresses are developed during processing and remain as residual stresses within the component after the manufacturing process is complete. As residual stresses will directly affect the reliability of the device, it is necessary to assess their magnitude and the effect on package reliability. A coupled multiphysics model has been developed to numercially analyse the microwave curing process. In order to obtain a usefully accurate model of this process, a holistic approach has been taken, in which the process is not considered to be a sequence of discrete steps, but as a complex coupled system. An overview of the implemented numerical model is presented, with particular focus paid to analysis of induced thermal stresses. Results showing distribution of stresses within an idealised microelectronics package are presented and discussed.

The kinetics of water loss from zinc phosphate and zinc polycarboxylate dental cements

The water desorption behaviour of three different zinc oxide dental cements (two polycarboxylates, one phosphate) has been studied in detail. Disc-shaped specimens of each material were prepared and allowed to lose water by being subjected to a low humidity desiccating atmosphere over concentrated sulfuric acid. In all three cements, water loss was found to follow Fick's second law for at least 6 h (until M(t)/M(infinity) values were around 0.5), with diffusion coefficients ranging from 6.03 x 10(-8 )cm(2 )s(-1) (for the zinc phosphate) to 2.056 x 10(-7 )cm(2 )s(-1) (for one of the zinc polycarboxylates, Poly F Plus). Equilibration times for desorption were of the order of 8 weeks, and equilibrium water losses ranged from 7.1% for zinc phosphate to 16.9% and 17.4% for the two zinc polycarboxylates.

Interprofessional attitudes amongst undergraduate students in the health professions: a longitudinal questionnaire survey

Background: Interprofessional education (IPE) introduced at the beginning of pre-registration training for healthcare professionals attempts to prevent the formation of negative interprofessional attitudes which may hamper future interprofessional collaboration. However, the potential for IPE depends, to some extent, on the readiness of healthcare students to learn together. Objectives: To measure changes in readiness for interprofessional learning, professional identification, and amount of contact between students of different professional groups; and to examine the influence of professional group, student characteristics and an IPE course on these scores over time. Design: Annual longitudinal panel questionnaire survey at four time-points of pre-registration students (n = 1683) drawn from eight healthcare groups from three higher education institutions (HEIs) in the UK. Results: The strength of professional identity in all professional groups was high on entry to university but it declined significantly over time for some disciplines. Similarly students’ readiness for interprofessional learning was high at entry but declined significantly over time for all groups, with the exception of nursing students. A small but significant positive relationship between professional identity and readiness for interprofessional learning was maintained over time. There was very minimal contact between students from different disciplines during their professional education programme. Students who reported gaining the least from an IPE course suffered the most dramatic drop in their readiness for interprofessional learning in the following and subsequent years; however, these students also had the lowest expectations of an IPE course on entry to their programme of study. Conclusion: The findings provide support for introducing IPE at the start of the healthcare students’ professional education to capitalise on students’ readiness for interprofessional learning and professional identities, which appear to be well formed from the start. However, this study suggests that students who enter with negative attitudes towards interprofessional learning may gain the least from IPE courses and that an unrewarding experience of such courses may further reinforce their negative attitudes.