Driving matrix liquid crystal displays

Liquid crystal displays had a humble beginning with wrist watches in the seventies. Continued research and development in this multi-disciplinary field have resulted in displays with increased size and complexity. After three decades of growth in performance, LCDs now offer a formidable challenge to the cathode ray tubes (CRT). A major contribution to the growth of LCD technology has come from the developments in addressing techniques used for driving matrix LCDs. There are several approaches like passive matrix addressing, active matrix addressing and plasma addressing to drive a matrix display. Passive matrix LCD has a simple construction and uses the intrinsic non-linear characteristic of the LCD for driving. Departure from conventional line by line addressing of a passive matrix has resulted in improved performance of the display. Orthogonal functions have played a crucial role in the development of passive matrix addressing. Simple orthogonal functions that are useful for driving a matrix LCD are introduced. The basics of driving several rows simultaneously (multi-line addressing) are discussed by drawing analogies from multiplexing in communication. The impact of multi-line addressing techniques on the performance of the passive matrix LCDs in comparison with the conventional technique will be discussed.     

On the governing equations for the compressing process and its coupling with other processes

As a continuation of a recent linear analysis by Mao et al.(Acta Mech Sin,2010,26:355),in this paper we propose a general theoretical formulation for the compressing process in complex Newtonian fluid flows,which covers gas dynamics,aeroacoustics,nonlinear thermoviscous acoustics,viscous shock layer,etc.,as its special branches.The principle on which our formulation is based is the maximally natural and dynamic Helmholtz decomposition of the Navier-Stokes equation,along with the kinematic Helmholtz decompos...     

Elastic and inelastic scattering of slow positrons from a LiF(100) surface

The intensity profile for the elastic specular reflection of 5–100 eV positrons from a LiF(100) surface (ang1e of incidence 45°) has been measured using a simple time-of-flight spectrometer. The profile exhibits strong maxima below 25 eV and a smaller peak at 57 eV. Positron energy loss spectra have also been measured for a range of incident energies by retarding field analysis of the scattered beam. The mean energy loss appears to increase with increasing incident beam energy. Both the elastic and inelastic results are compared with similar data for slow-electron scattering obtained with the same apparatus.     

Crossed beam measurement of binding energies of positronium compounds: A proposal

We describe an experiment to establish the chemical stability and measure the binding energies of compounds containing positronium atoms. The method consists of crossing a monoenergetic beam of low energy (1–25 eV) positrons with a supersonic adiabatic expansion molecular beam, and, after a dissociative attachment reaction takes place, detecting the resulting ¡gnature ion while measuring its kinetic energy. Except for the use of a positron beam instead of an electron beam, this is similar to electron impact MS/IKES (mass spectrometry/ion kinetic energy spectrometry). The start signal for the IKES measurement is provided by the remoderation of the positron beam. Among the benefits of the proposed research are the study of: (1) a new class of resonances, those involving temporarily bound positrons to molecules in excited electronic states; and (2) the surprising sub-threshold fragmentation observed by Surko and Hulett in positron-molecule scattering.     

Demonstration of positron re-emission microscopy using an immersion objective

Hulett et al. have suggested forming a magnified image of the positrons re-emitted from a surface having a negative positron affinity as a new kind of microscope, the positron re-emission microscope (PRM). We have built an immersion objective (cathode lens) for the PRM and obtained the first images using a Ni film back-illuminated with 5 keV positrons from a brightness enhanced slow positron beam. The magnification at the detector plane is 330x and the resolution is better than 1m. With the addition of a projector lens the magnification and resolution should be sufficient to observe defect structures and large molecules on the surface.     

Proficiency testing in analytical chemistry,microbiology and laboratory medicine: discussions on current practice and future directions

Accreditation and Quality Assurance - A summary of the working group discussions on proficiency testing (PT) and external quality assessment (EQA) held at the Eurachem Workshop, Portorož,...