242 resultados para conditions of contact


Relevância:

90.00% 90.00%

Publicador:

Resumo:

This paper seeks to contribute to the emerging stream of literature on the problematics of accountability ( [McKernan, in this issue], [Messner, 2009] and [Roberts, 2009]) and the possibilities of accounterability (Kamuf, 2007) by questioning whether and how accounterability can appear as a response to the problematics of accountability's operationalisation. To answer this question, this research considers the problematics of accountability found in the limits inherent to the giving of an account (Messner, 2009), in the ambiguous relationship between accountability and transparency (Roberts, 2009), and in the as yet unresolved contradictions of accountability (McKernan, in this issue). Accounterability is seen as a practice of resisting accountability demands while giving an account. Alternative practices arising out of such resistance are inductively identified through an ethnographic study of the day-to-day practices of the Salvation Army used as an extreme case. This case shows how an ideal form of accountability raises more questions than it answers in practice, thereby leading individuals to develop their own counter-abilities. Because accountability to a Higher-Stakeholder appears to be an unreachable ideal, identifying to whom one should give an account of oneself becomes problematic. A working response to the problematics of accountability, accounterability emerges as the mechanism whereby the limits and contradictions of account giving are transformed into the conditions of its realisation: unreachable accountability is transformed into tangible day-to-day practices that may differ slightly from expected ideal conduct. It transpires from this study that the main strength of accountability lies in its ability to absorb and to override its limits and contradictions, transforming them into conditions of its possibility. As such, accounterability emerges as the ultimate manifestation of this strength.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Honing and Ladinig (2008) make the assertion that while the internal validity of web-based studies may be reduced, this is offset by an increase in external validity possible when experimenters can sample a wider range of participants and experimental settings. In this paper, the issue of internal validity is more closely examined, and it is agued that there is no necessary reason why internal validity of a web-based study should be worse than that of a lab-based one. Errors of measurement or inconsistencies of manipulation will typically balance across conditions of the experiment, and thus need not necessarily threaten the validity of a study’s findings.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Purpose. To devise and validate artist-rendered grading scales for contact lens complications Methods. Each of eight tissue complications of contact lens wear (listed under 'Results') was painted by a skilled ophthalmic artist (Terry R. Tarrant) in five grades of severity: 0 (normal), 1 (trace), 2 (mild), 3 (moderate) and 4 (severe). A representative slit lamp photograph of a tissue response of each of the eight complications was shown to 404 contact lens practitioners who had never before used clinical grading scales. The practitioners were asked to grade each tissue response to the nearest 0.1 grade unit by interpolation. Results. The standard deviation (± s.d.) of the 404 responses for each tissue complication is tabulated below:_ing_ 0.5 Endothelial pplymegethisjij-4 0.7 Epithelial microcysts 0.5 Endothelial blebs_ 0.4 Stromal edema_onjunctiva! hyperemia 0.4 Stromal neovascularization 0.4 Papillary conjunctivitis 0.5 The frequency distributions and best-fit normal curves were also plotted. The precision of grading (s.d. x 2) ranged from 0.8 to 1.4, with a mean precision of 1.0. Conclusions. Grading scales afford contact lens practitioners with a method of quantifying the severity of adverse tissue responses to contact lens wear. It is noteworthy that the statistically verified precision of grading (1.0 scale unit) concurs precisely with the essential design feature of the grading scales that each grading step of 1.0 corresponds to clinically significant difference in severity. Thus, as a general rule, a difference or change in grade of > 1.0 can be taken to be both clinically and statistically significant when using these grading scales. Trained observers are likely to achieve even greater grading precision. Supported by Hydron Limited.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

A wireless sensor network system must have the ability to tolerate harsh environmental conditions and reduce communication failures. In a typical outdoor situation, the presence of wind can introduce movement in the foliage. This motion of vegetation structures causes large and rapid signal fading in the communication link and must be accounted for when deploying a wireless sensor network system in such conditions. This thesis examines the fading characteristics experienced by wireless sensor nodes due to the effect of varying wind speed in a foliage obstructed transmission path. It presents extensive measurement campaigns at two locations with the approach of a typical wireless sensor networks configuration. The significance of this research lies in the varied approaches of its different experiments, involving a variety of vegetation types, scenarios and the use of different polarisations (vertical and horizontal). Non–line of sight (NLoS) scenario conditions investigate the wind effect based on different vegetation densities including that of the Acacia tree, Dogbane tree and tall grass. Whereas the line of sight (LoS) scenario investigates the effect of wind when the grass is swaying and affecting the ground-reflected component of the signal. Vegetation type and scenarios are envisaged to simulate real life working conditions of wireless sensor network systems in outdoor foliated environments. The results from the measurements are presented in statistical models involving first and second order statistics. We found that in most of the cases, the fading amplitude could be approximated by both Lognormal and Nakagami distribution, whose m parameter was found to depend on received power fluctuations. Lognormal distribution is known as the result of slow fading characteristics due to shadowing. This study concludes that fading caused by variations in received power due to wind in wireless sensor networks systems are found to be insignificant. There is no notable difference in Nakagami m values for low, calm, and windy wind speed categories. It is also shown in the second order analysis, the duration of the deep fades are very short, 0.1 second for 10 dB attenuation below RMS level for vertical polarization and 0.01 second for 10 dB attenuation below RMS level for horizontal polarization. Another key finding is that the received signal strength for horizontal polarisation demonstrates more than 3 dB better performances than the vertical polarisation for LoS and near LoS (thin vegetation) conditions and up to 10 dB better for denser vegetation conditions.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Work integrated learning (WIL) or professional practice units are recognised as providing learning experiences that help students make successful transitions to professional practice. These units require students to engage in learning in the workplace; to reflect on this learning; and to integrate it with learning at university. However, an analysis of a recent cohort of property economics students at a large urban university provides evidence that there is great variation in work based learning experiences undertaken and that this impacts on students’capacity to respond to assessment tasks which involve critiquing these experiences in the form of reflective reports. This paper highlights the need to recognise the diversity of work based experiences; the impact this has on learning outcomes; and to find more effective and equitable ways of measuring these outcomes. The paper briefly discusses assessing learning outcomes in WIL and then describes the model of WIL in the Faculty of Built Environment and Engineering at the Queensland University of Technology (QUT). The paper elaborates on the diversity of students’ experiences and backgrounds including variations in the length of work experience, placement opportunities and conditions of employment.For example, the analysis shows that students with limited work experience often have difficulty critiquing this work experience and producing high level reflective reports. On the other hand students with extensive, discipline relevant work experience can be frustrated by assessment requirements that do not take their experience into account. Added to this the Global Financial Crisis (GFC) has restricted both part time and full time placement opportunities for some students. These factors affect students’ capacity to a) secure a relevant work experience, b) reflect critically on the work experiences and c) appreciate the impact the overall experience can have on their learning outcomes and future professional opportunities. Our investigation highlights some of the challenges faced in implementing effective and equitable approaches across diverse student cohorts. We suggest that increased flexibility in assessment requirements and increased feedback from industry may help address these challenges.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

At the core of our uniquely human cognitive abilities is the capacity to see things from different perspectives, or to place them in a new context. We propose that this was made possible by two cognitive transitions. First, the large brain of Homo erectus facilitated the onset of recursive recall: the ability to string thoughts together into a stream of potentially abstract or imaginative thought. This hypothesis is sup-ported by a set of computational models where an artificial society of agents evolved to generate more diverse and valuable cultural outputs under conditions of recursive recall. We propose that the capacity to see things in context arose much later, following the appearance of anatomically modern humans. This second transition was brought on by the onset of contextual focus: the capacity to shift between a minimally contextual analytic mode of thought, and a highly contextual associative mode of thought, conducive to combining concepts in new ways and ‘breaking out of a rut’. When contextual focus is implemented in an art-generating computer program, the resulting artworks are seen as more creative and appealing. We summarize how both transitions can be modeled using a theory of concepts which high-lights the manner in which different contexts can lead to modern humans attributing very different meanings to the interpretation of one concept.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

This article examines the formal processing of domestic violence as accomplished by institutionalized policing in Singapore. The description of the process through which domestic calls for assistance were shaped and translated into relevant categories for appropriating a particular police response was facilitated through the use of the participant observation method. The ethnographic fieldwork reported here, including observations of call screening in action, is an attempt to explicate the phenomenological grounds employed by organizational members to constitute calls as instances of categories for practical policing purposes. Theoretically, the data point to the need for a reconceptualization of the problem of policing domestic violence by emphasizing the point that the eventual institutional response be understood as a product of the relationship that exists between police subculture and structural conditions of policing unique to contemporary Singapore society.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

A breaker restrike is an abnormal arcing phenomenon, leading to a possible breaker failure. Eventually, this failure leads to interruption of the transmission and distribution of the electricity supply system until the breaker is replaced. Before 2008, there was little evidence in the literature of monitoring techniques based on restrike measurement and interpretation produced during switching of capacitor banks and shunt reactor banks in power systems. In 2008 a non-intrusive radiometric restrike measurement method and a restrike hardware detection algorithm were developed by M.S. Ramli and B. Kasztenny. However, the limitations of the radiometric measurement method are a band limited frequency response as well as limitations in amplitude determination. Current restrike detection methods and algorithms require the use of wide bandwidth current transformers and high voltage dividers. A restrike switch model using Alternative Transient Program (ATP) and Wavelet Transforms which support diagnostics are proposed. Restrike phenomena become a new diagnostic process using measurements, ATP and Wavelet Transforms for online interrupter monitoring. This research project investigates the restrike switch model Parameter „A. dielectric voltage gradient related to a normal and slowed case of the contact opening velocity and the escalation voltages, which can be used as a diagnostic tool for a vacuum circuit-breaker (CB) at service voltages between 11 kV and 63 kV. During current interruption of an inductive load at current quenching or chopping, a transient voltage is developed across the contact gap. The dielectric strength of the gap should rise to a point to withstand this transient voltage. If it does not, the gap will flash over, resulting in a restrike. A straight line is fitted through the voltage points at flashover of the contact gap. This is the point at which the gap voltage has reached a value that exceeds the dielectric strength of the gap. This research shows that a change in opening contact velocity of the vacuum CB produces a corresponding change in the slope of the gap escalation voltage envelope. To investigate the diagnostic process, an ATP restrike switch model was modified with contact opening velocity computation for restrike waveform signature analyses along with experimental investigations. This also enhanced a mathematical CB model with the empirical dielectric model for SF6 (sulphur hexa-fluoride) CBs at service voltages above 63 kV and a generalised dielectric curve model for 12 kV CBs. A CB restrike can be predicted if there is a similar type of restrike waveform signatures for measured and simulated waveforms. The restrike switch model applications are used for: computer simulations as virtual experiments, including predicting breaker restrikes; estimating the interrupter remaining life of SF6 puffer CBs; checking system stresses; assessing point-on-wave (POW) operations; and for a restrike detection algorithm development using Wavelet Transforms. A simulated high frequency nozzle current magnitude was applied to an Equation (derived from the literature) which can calculate the life extension of the interrupter of a SF6 high voltage CB. The restrike waveform signatures for a medium and high voltage CB identify its possible failure mechanism such as delayed opening, degraded dielectric strength and improper contact travel. The simulated and measured restrike waveform signatures are analysed using Matlab software for automatic detection. Experimental investigation of a 12 kV vacuum CB diagnostic was carried out for the parameter determination and a passive antenna calibration was also successfully developed with applications for field implementation. The degradation features were also evaluated with a predictive interpretation technique from the experiments, and the subsequent simulation indicates that the drop in voltage related to the slow opening velocity mechanism measurement to give a degree of contact degradation. A predictive interpretation technique is a computer modeling for assessing switching device performance, which allows one to vary a single parameter at a time; this is often difficult to do experimentally because of the variable contact opening velocity. The significance of this thesis outcome is that it is a non-intrusive method developed using measurements, ATP and Wavelet Transforms to predict and interpret a breaker restrike risk. The measurements on high voltage circuit-breakers can identify degradation that can interrupt the distribution and transmission of an electricity supply system. It is hoped that the techniques for the monitoring of restrike phenomena developed by this research will form part of a diagnostic process that will be valuable for detecting breaker stresses relating to the interrupter lifetime. Suggestions for future research, including a field implementation proposal to validate the restrike switch model for ATP system studies and the hot dielectric strength curve model for SF6 CBs, are given in Appendix A.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

This paper analyses the attempted installation of the 1990 Australian Education Council commissioned report 'Teacher Education in Australia' (the Ebbeck Report), a document which proposed a radical reformulation and relative standardization of the content and structure of initial teacher education in Australia. The paper draws on Michel Foucault's concept of 'governmentality' to examine the discursive and technological dimensions of this programme of political rule. The paper makes apparent the 'microphysics of power' that were generated within, particularly, the Queensland educational community in the attempt to operationalise this report. Analysing educational policy from the perspective of 'government', the paper contends, directs attention to the conditions of operation of policy practices and reveals the dependence of educational policy on particular technical conditions of existence, routines and rituals of bureaucracy, forms of expertise and intellectual technologies, and the enlistment of agencies and authorities both within and outside the boundaries of the state.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Much of our understanding of human thinking is based on probabilistic models. This innovative book by Jerome R. Busemeyer and Peter D. Bruza argues that, actually, the underlying mathematical structures from quantum theory provide a much better account of human thinking than traditional models. They introduce the foundations for modelling probabilistic-dynamic systems using two aspects of quantum theory. The first, "contextuality", is a way to understand interference effects found with inferences and decisions under conditions of uncertainty. The second, "entanglement", allows cognitive phenomena to be modelled in non-reductionist ways. Employing these principles drawn from quantum theory allows us to view human cognition and decision in a totally new light...

Relevância:

90.00% 90.00%

Publicador:

Resumo:

The Texas Department of Transportation (TxDOT) is concerned about the widening gap between pavement preservation needs and available funding. Thus, the TxDOT Austin District Pavement Engineer (DPE) has investigated methods to strategically allocate available pavement funding to potential projects that improve the overall performance of the District and Texas highway systems. The primary objective of the study presented in this paper is to develop a network-level project screening and ranking method that supports the Austin District 4-year pavement management plan development. The study developed candidate project selection and ranking algorithms that evaluated pavement conditions of each project candidate using data contained in the Pavement Management Information system (PMIS) database and incorporated insights from Austin District pavement experts; and implemented the developed method and supporting algorithm. This process previously required weeks to complete, but now requires about 10 minutes including data preparation and running the analysis algorithm, which enables the Austin DPE to devote more time and resources to conducting field visits, performing project-level evaluation and testing candidate projects. The case study results showed that the proposed method assisted the DPE in evaluating and prioritizing projects and allocating funds to the right projects at the right time.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

The renovation of biomass waste in the form of Mahogany seed waste into bio-fuel as well as activated carbon by fixed bed pyrolysis reactor has been taken into consideration in this study. The mahogany seed in particle form is pyrolyzed in an enormously heated fixed bed reactor with nitrogen as the carrier gas. The reactor is heated from 4000C to 6000C using a external heater in which rice husk and charcoal are used as the heater biomass fuel. Reactor bed temperature, running time and feed particle size have been varied to get the optimum operating conditions of the system. The parameters are found to influence the product yields to a large extent. A maximum liquid and char yield are 49 wt. % and 35 wt. % respectively obtained at a reactor bed temperature 5000C when the running time is 90 minutes. Acquired pyrolyzed oil at these optimal process conditions were analyzed for some of their properties as an alternative fuel. The oil possesses comparable flame temperature, favorable flash point and reasonable viscosity along with somewhat higher density. The kinematic viscosity of the derived fuel is 3.8 cSt and density is 1525 kg/m3. The higher calorific value is found 32.4 MJ/kg which is significantly higher than other biomass derived fuel. Moderate adsorption capacity of the prepared activated carbon in case of methyl blue & tea water was also revealed.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Formative assessment is increasingly being implemented through policy initiatives in Chinese educational contexts. As an approach to assessment, formative assessment derives many of its key principles from Western contexts, notably through the work of scholars in the UK, the USA and Australia. The question for this paper is the ways that formative assessment has been interpreted in the teaching of College English in Chinese Higher Education. The paper reports on a research study that utilised a sociocultural perspective on learning and assessment to analyse how two Chinese universities – an urban-based Key University and a regional-based Non-Key University – interpreted and enacted a China Ministry of Education policy on formative assessment in College English teaching. Of particular interest for the research were the ways in which the sociocultural conditions of the Chinese context mediated understanding of Western principles and led to their adaptation. The findings from the two universities identified some consistency in localised interpretations of formative assessment which included emphases on process and student participation. The differences related to the specific sociocultural conditions contextualising each university including geographical location, socioeconomic status, and teacher and student roles, expectations and beliefs about English. The findings illustrate the sociocultural tensions in interpreting, adapting and enacting formative assessment in Chinese College English classes and the consequent challenges to and questions about retaining the spirit of formative assessment as it was originally conceptualised.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Purpose: The aim of this cross-over study was to investigate the changes in corneal thickness, anterior and posterior corneal topography, corneal refractive power and ocular wavefront aberrations, following the short term use of rigid contact lenses. Method: Fourteen participants wore 4 different types of contact lenses (RGP lenses of 9.5 mm and 10.5 mm diameter, and for comparison a PMMA lens of 9.5 mm diameter and a soft silicone hydrogel lens) on 4 different days for a period of 8 h on each day. Measures were collected before and after contact lens wear and additionally on a baseline day. Results: Anterior corneal curvature generally showed a flattening with both of the RGP lenses and a steepening with the PMMA lens. A significant negative correlation was found between the change in corneal swelling and central and peripheral posterior corneal curvature (all p ≤ 0.001). RGP contact lenses caused a significant decrease in corneal refractive power (hyperopic shift) of approximately 0.5 D. The PMMA contact lenses caused the greatest corneal swelling in both the central (27.92 ± 15.49 μm, p < 0.001) and peripheral (17.78 ± 12.11 μm, p = 0.001) corneal regions, a significant flattening of the posterior cornea and an increase in ocular aberrations (all p ≤ 0.05). Conclusion: The corneal swelling associated with RGP lenses was relatively minor, but there was slight central corneal flattening and a clinically significant hyperopic change in corneal refractive power after the first day of lens wear. The PMMA contact lenses resulted in significant corneal swelling and reduced optical performance of the cornea.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Purpose To determine the prevalence of papillary changes of the upper palpebral conjunctiva and folliculosis of the lower palpebral conjunctiva in Chinese children with no history of contact lens wear. Method Ninety-nine subjects (aged 6–15 years old) who were interested in a myopia control study were screened for papillary changes and folliculosis of the palpebral conjunctiva. Photodocumentation was performed under white and blue light (after the application of fluorescein) with a yellow filter and the photographs were graded by a group of practitioners according to a pre-set grading scale. Analysis was performed with the subjects divided into groups according to gender and age. Results More than 48% of the subjects had clinically significant (≥Grade 3) papillary changes in the upper palpebral conjunctiva. The prevalence of significant folliculosis in the lower lid was about 33%. The prevalence of significant papillary changes and folliculosis were similar between genders. No differences were observed between younger (age ≤ 10 years old) and older (age > 10 years old) in papillary changes but younger subjects showed a higher prevalence of folliculosis. Conclusions The prevalences of clinically significant papillary changes and folliculosis of unknown aetiology are high in Chinese children.