Dielectric Breakdown Strength of Polyethylene Nanocomposites

The term “nanometric dielectrics” or simply “nanodielectrics” was introduced in 1994 when Lewis [1] anticipated the potential property changes that would benefit electrical insulation due to nano-sized inclusion. Such materials, containing homogenous dispersion of small amount (normally less than 10wt%) of nanoparticles (with at least one dimension in nanometre range) in host matrix, are of specific dielectric interest. Although much effort has been put forth to investigate the potential dielectric benefit of such newly emerging materials, many uncertainties remain unanswered, and much remains to be explored [2]. Current experimental work is to investigate the preparation of nanodielectrics via solution blending approach. Polyethylene blend composed of 20wt% of high density polyethylene (HDPE) in low density polyethylene (LDPE) is proposed as the base polymer, with varying content of nanosilica (between 0wt% and 10wt%) as the fillers. Although expensive, solution blending method, when compared with melt compounding method, is expected to provide better dispersion of nanoparticles in polymers, thus providing qualitative data in understanding the behaviour of nanodielectrics [3]. Upon successful preparation of polyethylene nanocomposites, breakdown strength based on ASTM Standard D149-87 is to be conducted to determine the feasibility of such dielectric materials in engineering point of view. Figure 1 illustrates the schematic diagram of the breakdown test configuration. The samples are placed between two 6.3mm diameter steel ball bearings immersed in silicone fluid. AC voltage at a preset ramp rate will be applied until the samples fail and the values of breakdown voltages will be recorded and analysed using two-parameter Weibull distribution. Based upon top-down research approach, the underlying physics and chemistry associated with dielectric property changes will then be explored

Evaluation of present thermal barrier coatings for potential service in electric utility gas turbines

The resistance of present-day thermal barrier coatings to combustion gases found in electric utility turbines was assessed. The plasma sprayed coatings, both duplex and graded types, were primarily zirconia-based, although a calcium silicate was also evaluated. Both atmospheric burner rig tests and high pressure tests (135 psig) showed that several present-day thermal barrier coatings have a high potential for service in gas turbines burning the relatively clean GT No. 2 fuel. However, coating improvements are needed for use in turbines burning lower grade fuel such as residual oil. The duplex ZrO2.8Y2O3/NiCrA1Y coating was ranked highest and selected for near-term field testing, with Ca2SiO4/NiCrA1Y ranked second. Graded coatings show potential for corrosive turbine operating conditions and warrant further development. The coating degradation mechanisms for each coating system subjected to the various environmental conditions are also described

Sequence of phase formation in planar metal-Si reaction couples

A correlation is found between the sequence of phase formation in thin-film metal-Si interactions and the bulk equilibrium phase diagram. After formation of the first silicide phase, which generally follows the rule proposed by Walser and Bené, the next phase formed at the interface between the first phase and the remaining element (Si or metal) is the nearest congruently melting compound richer in the unreacted element. If the compounds between the first phase and the remaining element are all noncongruently melting compounds (such as peritectic or peritectoid phases), the next phase formed is that with the smallest temperature difference between the liquidus curve and the peritectic (or peritectoid) point

Passive mode locking of buried heterostructure lasers with nonuniform current injection

In this letter we report on a novel method to passively mode lock a semiconductor laser. We present experimental results of GaAlAs buried heterostructure semiconductor laser with a split contact coupled to an external cavity. The split contact structure is used to introduce a controllable amount of saturable absorption which is necessary to initiate passive mode locking. Unlike previous passive mode locking techniques, the method presented does not rely on absorption introduced by damaging the crystal and is consequently inherently more reliable. We have obtained pulses with a full width at half-maximum of 35 ps at repetition frequencies between 500 MHz and 1.5 GHz

Persistent junk solutions in time-domain modeling of extreme mass ratio binaries

In the context of metric perturbation theory for non-spinning black holes, extreme mass ratio binary (EMRB) systems are described by distributionally forced master wave equations. Numerical solution of a master wave equation as an initial boundary value problem requires initial data. However, because the correct initial data for generic-orbit systems is unknown, specification of trivial initial data is a common choice, despite being inconsistent and resulting in a solution which is initially discontinuous in time. As is well known, this choice leads to a "burst" of junk radiation which eventually propagates off the computational domain. We observe another unintended consequence of trivial initial data: development of a persistent spurious solution, here referred to as the Jost junk solution, which contaminates the physical solution for long times. This work studies the influence of both types of junk on metric perturbations, waveforms, and self-force measurements, and it demonstrates that smooth modified source terms mollify the Jost solution and reduce junk radiation. Our concluding section discusses the applicability of these observations to other numerical schemes and techniques used to solve distributionally forced master wave equations.Comment: Uses revtex4, 16 pages, 9 figures, 3 tables. Document reformatted and modified based on referee's report. Commentary added which addresses the possible presence of persistent junk solutions in other approaches for solving master wave equation

A Study of Factors Influencing Green IT Practices, Buying and Subscription Behaviours of Computer and Mobile Devices, and Streaming Services

The pressure of environmental sustainability and the introduction of strict transnational and local environment laws, regulations and targets have catalysed the emergency of Green IT. On individual level, Green IT can be achieved through environmentally responsible behaviour to purchase, use and disposal of products and services without damaging the environment. This research aims to investigate the Green IT behaviour of young consumers including their day-to-day Green IT practices, buying behaviour of mobile and computer devices and subscription behaviour of streaming services. The findings show that: 1) Understanding of Green IT practices (specific knowledge) has a positive influence on PBC, 2) Consumer’s PBC has a positive influence on Green IT behaviour and 3) The communication strategy has a positive influence on PBC. Research results also show that young consumers’ buying and subscribing decision are strongly influenced by factors such as appearance, specification, features, content and price than Green IT factors. Available at: https://aisel.aisnet.org/pajais/vol11/iss1/4

An integrated programme of exercise, self-management and active coping strategies for patients with knee osteoarthritis – a proof-of-concept study for a Hong Kong Chinese speaking population

Knee osteoarthritis (KOA) is a degenerative joint disorder that affects the whole of the joint unit resulting in pain and decreased function. Current evidence recommends core management strategies of exercise, education for self-management and weight reduction (as appropriate) for KOA at all levels of severity. ESCAPE pain is evidence based integrated exercise and self-management intervention for KOA. Previous work has demonstrated it is a clinical and cost-effective intervention in the United Kingdom population. In the absence of a similar intervention in Hong Kong (HK), this work aimed to establish the feasibility of this intervention for a HK Chinese population.The systematic literature review of combined programmes for Chinese populations showed a significant short-term effect in pain relief, and although self-efficacy improved long-term evidence was limited. Exercise dosage and intensity were variable.The ESCAPE programme was then adapted for cultural relevance by translating the patient information booklet that supports self-management into Chinese with pictures and text amended to fit local culture. The programme was also reduced to 10 sessions in 5 weeks to fit the local delivery context. Relevant outcome measures in Chinese were identified and local physiotherapists were trained to provide the programme. The preliminary culturally adapted ESCAPE-knee pain was tested in a proof-of-concept study (N=21). Feasibility of this programme in HK was established by recruitment rate 30.9%, retention rate 82.6% and positive change in self-reported outcomes after the intervention. Finally acceptability was determined by a focus group (n=8). The findings showed that participants learned active coping for self-management through interactive education. They set goals to facilitate continued exercise participation and expressed their willingness to stay active. Increased confidence to undertake exercise and improved function were reported. The field observation suggested adjustments to the literacy level of the patient information booklet to improve patient understanding, with further guidance on goal setting at the beginning of the programme.The findings suggest that the ESCAPE-knee pain programme is feasible and acceptable to the Chinese population in HK. This novel combined programme adds to the evidence that KOA is a chronic disease that should be targeted with lifestyle behavioural change interventions. The next steps will be to conduct a small-scale pilot study to estimate effect-size to inform a fully powered randomised controlled trial

Checklist of spiders in Sungai Dusun Wildlife Reserve, Selangor, Malaysia

Sungai Dusun Wildlife Reserve, Selangor was established since 1964. It comprises an area of 4,330 hectares. It is considered one of the important biodiversity hotspots and also the first reserved area to protect Sumatran Rhinos. A study of the biodiversity of spider was carried out during the Biodiversity Inventory Program at Sungai Dusun Wildlife Reserve, Selangor from 26th to 31st October 2009. Samples were collected at selected area. Throughout the program a total of 89 spiders were collected. Among them, spiders from the family Agelenidae, Araneidae, Lycosidae, Oxyopidae, Pisauridae, Salticidae, Sparassidae and Tetragnathidae were recorded. Members of Lycosidae and Araneidae were easily spotted in this area

Emotional Competence as a Positive Youth Development Construct: A Conceptual Review

The concept of emotional competence as a positive youth development construct is reviewed in this paper. Differences between emotional intelligence and emotional competence are discussed and an operational definition is adopted. Assessment methods of emotional competence with an emphasis on its quantitative nature are introduced. In the discussion of theories of emotional competence, the functionalist and developmental perspectives and the relationships with positive youth development are highlighted. Possible antecedents, especially the influence of early child-caregiver, and expected outcomes of emotional competence are examined. Practical ways to promote emotional competence among adolescents, particularly the role of parents and teachers, and the future direction of research are also discussed