How far has the molecular alignment of liquid crystals been elucidated?

Liquid crystal displays (LCDs) - born in late 1960s - have become a 45 billion-dollar industry in 2004. Today's LCD panels cover a wide range of sizes from 0.2 to 82 in diagonal. The electro-optical characteristics of any field effect LCD are determined by the orientation of its liquid crystal (LC) molecules at the display boundaries. Until recently most LCD alignment processes were based on rubbing polymer coated LCD substrates with a cloth. Despite its key importance, the complex mechanism governing the alignment of LC molecules on display substrates is still not well understood. Do the microgrooves generated by rubbing induce LC-alignment or does the stretching of polymer chains as a result of brushing cause it? To overcome the drawbacks of conventional aligning techniques, new alignment processes have recently been proposed and developed. Examples are micro embossing, ion bombardment, fringe field effects and photo-alignment. In this paper, some mechanisms of LC alignment are discussed and various alignment techniques and methods to investigate the interaction of LC molecules with substrates are reviewed.     

Hemocompatible cellulose dialysis membranes modified with phospholipid polymers

Hemocompatibility is one of the most important properties for hemodialysis membranes. For improvement of the hemocompatibility on a cellulose dialysis membrane, modifications with new blood-compatible phospholipid polymers were carried out. These methods included a direct grafting of the phospholipid monomer on the membrane surface, coating the membrane surface with a water-soluble graft copolymer composed of a cellulose backbone and phospholipid polymer as a branch, and covalent bonding with a reactive phospholipid polymer on the membrane surface. These modified membranes could reduce protein adsorption as well as complement activation and platelet adhesion on the surface without any adverse effects on the membrane performance.     

A numerical integration method for long-term power system dynamic simulation

Large power system frequency/voltage fluctuations due to severe faults in trunk transmission lines or major generating units may trip-off other facilities and result in large-scale power system blackout. To prevent such blackout, development of an accurate and fast long-term power system dynamic simulation tool is required. With respect to the development stage, selection of a numerical integration method available for step-size adjustment, and the development of a scheme for the adjustment are principal subjects. The trapezoidal and the second-order Gear methods were selected as possible candidates for the step-size adjustment from the viewpoint of numerical stability. The trapezoidal method is selected from the viewpoint of accuracy and applicability to power system dynamic simulations. A new scheme for the automatic step-size adjustment is proposed for the trapezoidal method to achieve fast simulation of the long-term power system dynamics. The validity of the proposed scheme is verified through simulation studies on a single-machine-to-infinite bus system.     

Principal decomposition by-products generated at variousabnormalities in gas-insulated transformers

Gas analysis provides a promising means for a diagnosis of gas-insulated equipment. Although many studies have been concentrated on SF₆ gas decomposition, they were mostly related to the faults in GIS systems and not directly applicable to gas-insulated transformers, which have much more complicated material structure. An experimental survey on decomposition by-products at various abnormal conditions was carried out by use of simulation models to develop a diagnostic method for gas-insulated transformers based on gas and ion chromatograph analyses. Major components characteristic in each abnormality, such as SO₂ on metal overheat, SO₂F ₂ on partial discharges, etc. were identified by the experiments     

An instantaneous response CMOS optical receiver IC with widedynamic range and extremely high sensitivity using feed-forwardauto-bias adjustment

An instantaneous response CMOS optical-receiver IC is described with wide input dynamic range and high sensitivity. In a TCM (time compression multiplexing)-TDMA (time division multiple access) fiber-optic subscriber system, a receiver should be able to handle burst-data packets with different amplitude. This requires quick response and a wide dynamic range. Instantaneous response is achieved with a new feed-forward auto-bias adjustment technique. In addition, multistaged offset compensation provides a wide dynamic range without any external elements and adjustments. Using these design techniques, an optical receiver IC was fabricated in a standard 0.8-μm CMOS technology. The receiver has a wide dynamic range of more than 25 dB for burst-mode optical input at 29 Mb/s. It has high transimpedance gain of 150 dBΩ and high sensitivity of -42 dBm with stable operation for FET threshold voltage and power supply voltage fluctuation     

Patterning characteristics under small vibrations of the mask and wafer in SR lithography

Patterning characteristics under mechanical vibrations between mask and wafer are investigated in terms of pattern profile deformation, linewidth change, and exposure dose margin by performing exposure experiments and using a Fresnel diffraction simulation. A small vibration works as a smoothing filter and provides a smooth profile in patterning. Stronger vibrations, generally, make the linewidth bigger, thereby reducing the dose margin. However, given vibrations of a particular amplitude, there is a certain range of doses in which the vibrations donot significantly affect the linewidth. Below the range, the linewidth becomes smaller; and above, it becomes larger. And it is possible to obtain the desired dimensions of delineated pattern even when the amplitude of the vibrations was a quarter of the minimum feature size.     

Passively aligned hybrid WDM module integrated with spot-sizeconverter integrated laser diode and waveguide photodiode on PLCplatform for fibre-to-the-home

A low cost and high performance hybrid WDM module assembled by passive alignment has been developed for FTTH systems. High coupling efficiency of a spot-size converter integrated laser diode to a PLC waveguide, which facilitates mass production of the module, is achieved. A minimum optical received power of -37 dBm for a 50 Mbit/s burst signal is also achieved     

A single protein catalyzes both N-deacetylation and N-sulfation during the biosynthesis of heparan sulfate

Heparan sulfate is a highly sulfated carbohydrate polymer that binds to and modulates the activities of numerous proteins. The formation of these protein-binding domains in heparan sulfate is dependent on a series of biosynthetic reactions that modify the polysaccharide backbone; the initiating and rate-limiting steps of this process are the N-deacetylation and N-sulfation of N-acetylglucosamine residues in the polymer. We now report that in the rat liver, biosynthesis of heparan sulfate utilizes a single protein that possesses both N-deacetylase and N-sulfotransferase activities. This was accomplished by demonstrating that both activities resided in a purified soluble fusion protein containing the Golgi-lumenal portion of the enzyme. We propose that this protein be renamed the rat liver Golgi heparan sulfate N-deacetylase/N-sulfotransferase.     

AE behaviors evaluation with bp neural network

This paper reports our experiment on training a three layer forwards neural network with backpropagation algorithm (BP) to memorise acoustic emission (AE) behaviors of magnesium alloy during fatigue test process and perform the mapping from AE behaviors to fatigue crack propagation. This study reveals the potential possibility of using artificial neural networks for automated AE testing. Simulation results are very encouraging and conclusively in favor of this attempt.