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Thermo-mechanical responses of fiber-reinforced epoxy composites exposed to high temperature environments. Part I: Experimental data acquisition
No full textThis first part of a series of papers on the thermo-mechanical responses of fiber-reinforced composites at elevated temperatures reports the experimental results required as input data in order to validate the kinetic, heat transfer, and thermo-mechanical models being developed and to be discussed in subsequent papers. Here the experimental techniques used for the determination of physical, thermal, and mechanical properties and their significance for particular models are discussed. The fire retardant system used to improve the fire performance of glass fiber-reinforced epoxy composites is a combination of a cellulosic charring agent and an interactive intumescent, melamine phosphate. Thermogravimetry is used to obtain kinetic parameters and to evaluate the temperature-dependent physical properties such as density, thermal conductivity, and specific heat capacity, determined using other techniques. During flammability evaluation under a cone calorimeter at 50 kW/m2 heat flux, thermocouples are used to measure temperatures through the thicknesses of samples. To investigate their thermo-mechanical behavior, the composites are exposed to different heating environments and their residual flexural modulus after cooling to ambient temperatures determined. At a low heating rate of 10°C/min and convective conditions, there was a minimal effect of fire retardant additives on mechanical property retention, indicating that fire retardants have no effect on the glass transition temperature of the resin. On the other hand, the fire-retarded coupons exposed to a radiant heat from cone calorimeter, where the heating rate is about 200°C/min, showed 60% retention of flexural modulus after a 40-s exposure, compared to 20% retention observed for the control sample after cooling specimens to ambient temperatures
Development of an advanced personal protective equipment garment for protection against slashes and pathogenic bacteria. Part 1: Development and evaluation of slash resistant garments
No full textKnife is the most commonly used single weapon in the UK, being 32% of the weapons employed in violent incidents. Studies reveal that the majority (63.3%) of the knife inflicted wounds were slash type and could be disfiguring or life threatening if the blood vessels are ruptured. The stab resistant armours currently available do not protect the arms, neck and face as they are very rigid to be worn comfortably and are expensive and heavy for everyday use by the civilian population. The main objectives of this research programme are; a) to develop and characterise a novel cut resistant and slash proof material that is lightweight, comfortable and efficient; and b) to integrate barrier properties in such garments which would incorporate suitable antimicrobial and other suitable chemicals to provide protection against a range of micro organisms.During this research programme, various composite yarns were thoroughly investigated, at different proportions, to determine the most appropriate yarn for the slash proof material. The slash proof fabric structures were developed by using knitting technology as it offers significant advantages in terms of cost, design flexibility and versatility. The fabrics were characterised by using the most stringent test method stipulated for a slash proof application, namely, Home Office Scientific Development Branch (HOSDB) Slash Resistance Standard for UK Police (2006), Publication No. 48/05.The paper discusses the results obtained during the development of the novel slash proof material for the police, armed forces, children and the public, that is lightweight, comfortable and efficient, and can be utilised for long periods
Report of the results of an IMS learning design expert workshop.
No full textAn IMS Learning Design Expert Workshop was held at the University of Vienna on November 20 & 21, 2008. This report contains a description of the purpose of the workshop, its methodologies and results. Participating experts first brainstormed visions and problems of IMS Learning Design (IMS LD), and then developed potential solutions to some of the identified problems. Three groups formed to work on two of the identified problems in more depth: the usability and utility problem, and the life cycle of a unit of learning problem. The proposed solutions regarding the usability and utility problem were to investigate how teachers' and learners' representations of a learning design can be brought together, and to set up a research program to identify how teachers cognitively proceed when designing courses and to map this knowledge to IMS LD. In regard to the life cycle of a unit of learning problem, the group suggested a system that continually exchanges information between runtime and editing systems so that units of learning can be updated accordingly
Elastic constants of 3-, 4- and 6-connected chiral and anti-chiral honeycombs subject to uniaxial in-plane loading
No full textFinite Element models are developed for the in-plane linear elastic constants of a family of honeycombs comprising arrays of cylinders connected by ligaments. Honeycombs having cylinders with 3, 4 and 6 ligaments attached to them are considered, with two possible configurations explored for each of the 3- (trichiral and anti-trichiral) and 4- (tetrachiral and anti-tetrachiral) connected systems. Honeycombs for each configuration have been manufactured using rapid prototyping and subsequently characterised for mechanical properties through in-plane uniaxial loading to verify the models. An interesting consequence of the family of 'chiral' honeycombs presented here is the ability to produce negative Poisson's ratio (auxetic) response. The deformation mechanisms responsible for auxetic functionality in such honeycombs are discussed
Thermo-mechanical properties of polystyrene-based shape memory nanocomposites
No full textShape memory nanocomposites were fabricated using chemically cross-linked polystyrene (PS) copolymer as a matrix and different nanofillers (including alumina, silica and clay) as the reinforcing agents. Their thermo-mechanical properties and shape memory effects were characterized. Experimental results revealed that the nanofillers provide significant reinforcement of the PS, and the nanocomposites exhibit better thermal and mechanical properties, including shape memory properties, than unreinforced PS. Both experimental and theoretical analyses have shown that the rod-shaped clay nanofillers offer better reinforcement than spherical nanoparticles, because of their high aspect ratio and ability to reinforce in multiple directions
Validating the distinction between computer addiction and engagement: Online game playing and personality
No full textThis article considers validatory evidence for the previously made distinction between (pathological) computing-related addictions and (non-pathological) high engagement in computing activities, and an associated distinction between core and peripheral criteria for diagnosing computing-related addictions. Using data provided by 388 players of a Massively Multiplayer Online Role Playing Game (MMORPG) via an online questionnaire, psychometric measures of engagement and addiction to the MMORPG taking into account the distinction between core and peripheral addiction criteria are shown to be differentially related to personality factors (extraversion, emotional stability, agreeableness, negative valence and attractiveness). Addiction scale scores are shown to increase as negativity on all five personality characteristics increases, with these characteristics predicting 20% of the variance in addiction scores, but the same pattern is shown to occur for only one characteristic (negative valence) for the engagement scale, with personality characteristics predicting only around 2% of the variance in engagement scores. It is concluded that there is reasonable support for the distinctions between addiction and engagement and between core and peripheral criteria. Implications are discussed
Aluminium Nitride thin Film Acoustic Wave Device for Microfluidic and Biosensing Applications
No full textFiber-reinforced epoxy composites exposed to high temperature environments. Part II: modeling mechanical property degradation
No full textThis article is part of a series on the thermo-mechanical responses of fiber-reinforced composites at elevated temperatures and it follows the first part containing experimental results. A flame-retardant system consisting of a cellulosic charring agent and an interactive intumescent additive (melamine phosphate) has been used in order to improve the post-fire mechanical performance of glass fiber-reinforced epoxy composites. The effect of one-sided radiant heat on the residual flexural stiffness of laminate coupons exposed to incident heat fluxes of 25 and 35 kW m(-2) was investigated. The flame-retarded coupons retained a higher percentage of their original room temperature flexural modulus after heat exposure while the control specimens showed inferior material property retention over the same exposure periods. A heat transfer (thermal) model based on Henderson's equation is used to predict the through thickness temperature profiles and subsequently the mass loss due to the resin matrix decomposition at elevated temperatures. The theoretical results from the heat transfer model are validated against experimentally obtained data and then coupled with a mechanics model that describes material property-temperature dependence in order to predict the residual flexural stiffness, after heat damage. The accuracy of the thermo-mechanical model was validated against the experimental data and a good agreement was observed
Human factors and their influence on the Irish online hospitality consumer process
No full textThe purpose of this chapter was to examine how consumers use the Internet to purchase Irish hospitality products specifically trips, holidays or breaks and to monitor how these purchases are influenced by human factors. The aim was to examine the process sequentially in order to attempt to model or structure this behaviour. Irish consumers attitudes were to be contrasted with international consumer research starting with their acceptance or rejection of the Internet medium and online factors such as price, trust and loyalty. The purchase decisions were then to be examined to determine the effects of human factors on the purchase method and subsequently the Irish hospitality stakeholders.Quantitative research was gathered from two main groups, offline consumers and their acceptance and adoption of the Internet medium and online consumers who were observed for their online human factors of their online search and decisions.The research found that Irish hospitality consumers’ online behaviour is consistent with international developed nations’ norms. Using the Technology Acceptance Model (TAM) and Flow Theory consumers were found to be very competent and comfortable with the Internet medium. Price, trust and loyalty were determining factors in the method in which the consumer decided to purchase the Irish hospitality product. The navigational pathway chosen using these human factors in turn determined whether the consumer booked directly with the Irish hospitality industry stakeholder or booked using an international intermediary resulting in revenue being lost to the Irish hospitality industry
Simulation of energy dissipation for adiabatic switching of CMOS based reversible logic circuits
No full textComparison of power dissipation characteristics for a range of reversible logic elements when operated with conventional and adiabatic logic switching are investigated by SPICE simulation techniques. Results show reduced power dissipation when using adiabatic logic switching but that this deviates from theoretical expectations due to the finite threshold voltage of the pMOS and nMOS devices