98,477 research outputs found

    Human comfort in relation to sinusoidal vibration

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    An investigation was made to assess the overall subjective comfort levels to sinusoidal excitations over the range 1 to 19 Hz using a two axis electrohydraulic vibration simulator. Exposure durations of 16 minutes, 25 minutes, 1 hour, and 2.5 hours have been considered. Subjects were not exposed over such durations, but were instructed to estimate the overall comfort levels preferred had they been constantly subjected to vibration over such durations

    Teaching Spoken English at Junior High School: A Comparison of TPR and PPP

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    This article reports on an experimental methods-comparison study, which was undertaken with beginner level junior high school students (aged 12 and 13) in Japan. The study aimed to investigate which type of teaching, Total Physical Response (TPR) or Present Practice Produce (PPP), was more effective in developing productive and receptive knowledge of a set of collocations. Results showed that both types of teaching had a significant impact upon the development of understanding and using the target language. However, there were no significant differences between the effectiveness of TPR and PPP, apart from a short-term benefit for PPP in terms of receptive knowledge. This shows that both types of teaching can have a positive impact upon learners of this age and level and that there is a need for further research to investigate the effectiveness of these communicative methodologies in this context

    Gallium Arsenide preparation and QE Lifetime Studies using the ALICE Photocathode Preparation Facility

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    In recent years, Gallium Arsenide (GaAs) type photocathodes have become widely used as electron sources in modern Energy Recovery Linac based light sources such as the Accelerators and Lasers in Combined Experiments (ALICE) at Daresbury Laboratory and as polarised electron source for the proposed International Linear Collider (ILC). Once activated to a Low Electron Affinity (LEA) state and illuminated by a laser, these materials can be used as a high-brightness source of both polarised and un-polarised electrons. This paper presents an effective multi-stage preparation procedure including heat cleaning, atomic hydrogen cleaning and the activation process for a GaAs photocathode. The stability of quantum efficiency (QE) and lifetime of activated to LEA state GaAs photocathode have been studied in the ALICE load-lock photocathode preparation facility which has a base pressure in the order of 10^-11 mbar. These studies are supported by further experimental evidence from surface science techniques such as X-ray Photoelectron Spectroscopy (XPS) to demonstrate the processes at the atomic level.Comment: Presented at First International Particle Accelerator Conference, IPAC'10, Kyoto, Japan, from 23 to 28 May 201

    Hemicelluloses in Hardwoods Growing on Southern Pine Sites

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    Aspects of the chemistry of the two more common hemicelluloses found in hardwoods growing on southern pine sites are outlined. The 4-O-methylglucuronoxylans have been investigated chemically by several groups of workers and have been shown to consist of an essentially linear backbone of 1,4-β-linked D-xylopyranose residues. To this backbone are attached in a random fashion, α-linked 4-O-methyl-D-glucuronopyranosyl residues through position 2 of about one in ten of the D-xylopyranosyl groups. O-Acetyl residues may also be present. The glucomannans have received less attention. They consist of essentially linear polymers formed of 1,4-β-linked-D-glucopyranose and 1,4-β-linked-D-mannopyranose residues joined in random sequence and may also contain O-acetyl residues. The ratio of the sugars varies between 1:2 and 1:1
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