M. J. Towler

Simulations and Games: Use and Barriers in Higher Education.

This article explores the use of simulations and games in tertiary education. It examines the extent to which academics use different simulation-based teaching approaches and how they perceive the barriers to adopting such techniques. Following a review of the extant literature, a typology of simulations is constructed. A staff survey within a UK higher education (HE) institution is conducted to investigate the use of the different approaches identified within the typology. The findings show significant levels of use of both computer and non-computer-based simulations and games. The main barrier to teaching with simulations, as perceived by the respondents, is the availability of resources. However, further analysis indicates that use of simulations is not associated with perceptions of resource issues, but rather is influenced by views on the suitability of, and risk attached to, such learning methods. The study concludes by recommending improved promotion of simulation-based teaching through enhanced information provision on the various techniques available and their application across subject areas.

The “JOERS/Alvey” ferroelectric multiplexing scheme

Abstract Ferroelectric liquid crystal displays offer an attractive matrix addressed alternative for complex displays. However, their potential can only be realised by using novel addressing schemes suitable for the fast responding, DC sensitive, ferroelectric electro-optic effect. Over a period of several years, a high performance, novel, ferroelectric drive scheme1 has been developed in a UK, JOERS/Alvey funded, collaborative programme. The JOERS/Alvey drive scheme is based on monopulse strobe waveforms2,3,4 and utilises the response time - voltage minimum5,6 found in certain materials. Using this novel drive scheme, complex ferroelectric displays with a high contrast ratio, wide operating range and fast addressing times have been made7,8,9,10 The JOERS/Alvey drive scheme is described, compared with other published drive schemes, and the operating principles discussed.

Fast, high-contrast ferroelectric liquid crystal displays and the role of dielectric biaxiality

Abstract The operation of ferroelectric liquid crystal displays depends strongly on the material properties and the electrical addressing method. Fast, high-contrast displays with high levels of multiplexing and wide operating ranges are possible using materials showing a minimum in their response time-voltage characteristic operated with JOERS/Alvety and related drive schemes. These utilize materials with significant dielectric biaxialities and relatively low values of the ferroelectric polarization so that a minimum is observed in the switching characteristic. The route for material improvement is explored.

OPTICAL STUDIES OF THIN LAYERS OF SMECTIC-C MATERIALS

The optical behaviour of surface-stabilized ferroelectric liquid crystal samples cannot be described using a uniform director profile. The simplest model based on the chevron layer structure and the surface alignment is a triangular director profile. Analytical expressions for the resulting transmitted light were calculated using the Jones matrix formalism and fitted to experimental data results of a smectic-C host made using an optical multichannel analyser (OMA). This simple model gives an excellent fit, with results that are consistent with X-ray measurements of the chevron structure.

Simulations and games: Overcoming the barriers to their use in higher education

Based on a categorization of simulation and gaming barriers developed in a previous study, this work seeks to explore in greater depth the composition and nature of these obstacles. It examines the interrelationships between the barriers and the impact of other contextual factors in the pedagogic environment. A series of in-depth interviews were conducted with 11 staff involved in teaching with simulations and games within a UK higher education institution. The findings underline the significant linkages apparent between three broad barriers to teaching with simulations, games and role-play: suitability, resource and risk. Further analysis of the interview transcripts facilitated the identification of a range of mechanisms which may be employed to overcome the aforementioned barriers: freeing up academics’ time, providing training and development, enabling informal learning, providing resource support, facilitating access to networks and providing access to secondary information sources. These mechanisms are discussed and evaluated in relation to the broader educational context.

The role of surface tilt in the operation of pi-cell liquid crystal devices

The role of surface tilt in the operation of pi-cells (OCB) is discussed. We show the effect of tilt on the relative stability of the H and V states, the switching characteristics and the domain growth speed. We further study the effects of temperature and cell thickness on the domain growth.

The importance of dielectric biaxiality for ferroelectric liquid crystal devices

Abstract The dielectric biaxiality of SCE13, a commercially available ferroelectric liquid crystal (FLC) mixture, has been measured. The results have been used to compare theoretically predicted AC field stabilization effects and the voltages for response time minima with experiment.

The effect of the biaxial permittivity tensor and tilted layer geometries on the switching of ferroelectric liquid crystals

Abstract Using a simple uniform switching model, we investigate the behaviour of the voltage dependent switching time of surface stabilized ferroelectric liquid crystals as a function of the biaxial permittivity tensor and the layer tilt angle. We show that the dielectric biaxiality can markedly effect the response time (τ) of the device and is the origin of the minimum in τ as a function of voltage (V) in tilted layer systems. The dielectric biaxiality should, therefore, be optimized for multiplexing schemes which use the τ—V minimum.

Dielectric Biaxiality in SC Host Systems

Abstract AC field stabilisation of ferroelectric SC* liquid crystals with the chevron layer geometry requires that there is a significant dielectric biaxiality.1,2 To investigate this, the electric permittivities of an SC host mixture based on the phenyl pyrimidines and exhibiting an N-SA-SC phase sequence are reported. A large relaxation of e∥ occurred, which caused a sign reversal of the dielectric anisotropy with a crossover frequency of 25 kHz at 25°C. The host electro-optic behaviour was then characterised using extinction angle measurements as a function of applied voltage at frequencies corresponding to Δ≈ > 0, Δe ≈ 0 and δe < 0, and the results explained using a tilted layer model with a biaxial dielectric tensor. The magnitude of the SC dielectric biaxiality, the layer tilt angle in the planar homogeneous geometry and the cone angle are determined. Measurements for several other hosts commonly used in commercial FLC mixtures are reported and it is shown that in each case the dielectric biaxiality...

On the response speed of pi-cells

We discuss the role of the Miesowicz viscosities on director reorientation in pi-cells, showing that the symmetry of this system allows for a simplification of the dynamical equations. We consider practical aspects of material optimisation for increased pi-cell switching speed. We make an observation regarding the switching speeds of positive and negative dielectric anisotropy surface mode devices.