Micro/meso ultra precision grinding of fibre optic connectors

The present paper reports on the development of a micro/meso grinding technology using inclined resin bond diamond cup wheels for machining spherical end faces of fibre optic connectors. The ground spherical end faces obtained using the wheel of grit size of 4 μm have an average roughness (R_a) value of 7 nm in the fibre area and a profile error of below 0.4 μm. The corresponding average return and insertion losses are 55 and 0.1 dB, respectively. The results are competitive to those obtained from the polishing process that is currently used in industries. Furthermore, this study has revealed the relationships between the ground surface quality characterized by roughness and profile accuracy and the optic performance evaluated by insertion and return losses.     

Pulsed laser noise analysis and pump-probe signal detection with a data acquisition card

A photodiode and data acquisition card whose sampling clock is synchronized to the repetition rate of a laser are used to measure the energy of each laser pulse. Simple analysis of the data yields the noise spectrum from very low frequencies up to half the repetition rate and quantifies the pulse energy distribution. When two photodiodes for balanced detection are used in combination with an optical modulator, the technique is capable of detecting very weak pump-probe signals (ΔI/I(0) ~ 10(-5) at 1 kHz), with a sensitivity that is competitive with a lock-in amplifier. Detection with the data acquisition card is versatile and offers many advantages including full quantification of noise during each stage of signal processing, arbitrary digital filtering in silico after data collection is complete, direct readout of percent signal modulation, and easy adaptation for fast scanning of delay between pump and probe.     

Oxidative stability of fish oil‐in‐water emulsions under high‐pressure treatment

Over the last decade, high‐pressure treatment has been of considerable interest as an alternative to thermal treatment for food preservation and processing. The impact of high‐pressure treatment on lipid oxidation in fish oil‐in‐water emulsions stabilised by 0.5 wt% whey protein isolate or sodium caseinate was investigated by determining thiobarbituric acid (TBA), propanal values and hydroperoxide values (PVs). The TBA value and the PV of all emulsions increased with increasing pressure at low temperature, indicating that lipid oxidation was promoted by high‐pressure treatment. The impact of high‐pressure treatment on the oxidative stability of lipids was increased when the temperature was increased as the TBA and propanal values were markedly enhanced by high pressure at high temperature. However, high‐pressure treatment did not affect the antioxidant properties of whey protein isolate and sodium caseinate in the fish oil‐in‐water emulsions, which may suggest that high‐pressure treatment does not alter the lipid oxidation pathway in emulsion systems. The promotion of lipid oxidation by high pressure is due mainly to increasing the pressure on a gas reaction shifts the position of equilibrium towards the side with fewer gas molecules.     

Friction and Wear Transitions in Carbons (Temperature and Stress Analysis)

In this paper, the friction and wear behavior of a carbon composite is studied. Friction tests were performed under constant friction mode. The power inputs were increased gradually to study their effects on friction transition at ambient air environment. Friction surfaces were examined using various macro and nanoscopic techniques to understand the evolution of friction transition. Structural changes of friction film have been observed from graphitic allotropic form to amorphous type structure. This sudden change leads to an increase of the coefficient of friction. It seems that the inter-laminar shearing, disruption of the film and sample cracking might cause the friction transition. Analysis from stress field simulation shows that cracks were more likely to occur at the trailing edge of the sample at the end of transition. This study shows that any type of failure (mechanical or thermal fatigue) of the friction film or bulk material is sufficient to generate friction and wear instabilities.     

Transport studies of NH4NO3 doped methyl cellulose electrolyte

This work reports on the transport properties of NH₄NO₃ doped methyl cellulose (MC) polymer electrolyte. The polymer electrolyte films were prepared by the technique of solvent casting. The highest room temperature conductivity of MC doped with 25 wt.% NH₄NO₃ is 2.10 ± 0.37 × 10^?6 S cm^?1. Conductivity–temperature relationship obeys the Vogel–Tamman–Fulcher (VTF) rule from which the glass transition temperature, T_g was evaluated. The mobility, μ and number density of charge carrier, n were calculated using the Rice and Roth model.     

Building adaption model in assessing adaption potential of public housing in Singapore

Building adaptation is instrumental in curbing building degradation and urban dilapidation. Owing to budget constraint, the policy decision makers who manage substantial public buildings always face the problems of which existing buildings should be selected for adaptation. A tool is required to aid them to prioritise existing buildings based on their adaptation potential. Thus, the aim of this study is to develop a model which acts as a tool for the policy decision makers to perform the challenging work of prioritising the existing public housing for adaption. This research presents a conceptual framework for assessing adaptation potential of existing public housing in Singapore and discusses its validation process. The results show that the proposed approach is effective in estimating the adaptation potential of existing residential buildings. In practice, the decision makers can use this model to rank existing buildings’ adaptation potential and select those buildings with high potential for adaptation, with the intention to optimise the allocation of a tight building adaptation budget.     

Controlling a Wheelchair Indoors Using Thought

Amyotrophic lateral sclerosis, or ALS, is a degenerative disease of the motor neurons that eventually leads to complete paralysis. We are developing a wheelchair system that can help ALS patients, and others who can't use physical interfaces such as joysticks or gaze tracking, regain some autonomy. The system must be usable in hospitals and homes with minimal infrastructure modification. It must be safe and relatively low cost and must provide optimal interaction between the user and the wheelchair within the constraints of the brain-computer interface. To this end, we have built the first working prototype of a brain-controlled wheelchair that can navigate inside a typical office or hospital environment. This article describes the BCW, our control strategy, and the system's performance in a typical building environment. This brain-controlled wheelchair prototype uses a P300 EEG signal and a motion guidance strategy to navigate in a building safely and efficiently without complex sensors or sensor processing     

Epoxy/polyhedral oligomeric silsesquioxane (POSS) hybrid networks cured with an anhydride: Cure kinetics and thermal properties

A new class of organic-inorganic hybrid networks was prepared via copolymerization of octakis(dimethylsiloxybutyl epoxide)octasilsesquioxane (OB), N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM) and hexahydrophthalic anhydride (HHPA). Kinetic studies show that even with 1H-imidazole as the catalyst, the rate for the curing of OB/HHPA is still significantly higher than that for TGDDM/HHPA in the temperature range studied. Two-stage reactions were thus carried out to allow OB to react with HHPA first (Stage I). The glass transition temperature (T_g) of the networks was found to be strongly dependent on Stage I reaction since too short a reaction time caused poor bonding of OB to the networks while too long a reaction time led to the formation of OB oligomers that de-homogenized the networks. With 5 mol.% OB, the hybrid prepared via the optimized two-stage reaction displayed a large jump of ∼20 °C in T_g, which was accompanied by slight improvements in thermal degradation temperature and storage modulus, as compared to TGDDM/HHPA.     

Thermal conductivity of nanocrystalline carbon films studied by pulsed photothermal reflectance

The effect of nanocrystals with preferred orientation on the thermal conductivity of carbon films is studied. During graphitization, the presence of biaxial compressive stress results in the formation of preferred orientation in the microstructure of graphitic nanocrystals if the corresponding activation energy is supplied. This formation of preferred orientation leads to the orientation of graphitic basal planes perpendicular to the substrate. Due to the high thermal conductivity of graphite in the basal planes, there is a significant increase in thermal conductivity of textured nanocrystalline films compared to amorphous film.