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Effect of microwave post-curing upon the micromechanics of model Kevlar/epoxy composites
Get PDFMicrowave processing of materials has the potential to deliver several major advantages over conventional thermal processing. One of these is an decrease in the time necessary for manufacture since the microwave energy is absorbed throughout the body of the material rather than relying on thermal conduction and convection. Another potential advantage is that the power is directed to the sample, this together with the decrease in processing time leads to lower energy being consumed. One question which needs to be addressed in the case of polymer composites is whether microwave processed materials are of as good quality as the thermally processed ones. In this work the interfacial properties of model Kevlar fibre reinforced epoxy composites post-cured by both conventional and microwave heating have been examined. Raman spectroscopy was employed to measure the fibre strain distributions along embedded fibres and from this information the interfacial shear stress distribution was calculated. The results show that the interfacial shear strengths and critical lengths of the microwave post-cured composites are comparable to those for thermally post-cured ones. This is potentially of interest in the commercial manufacture of composites since the process could be considerably shortened by the use of microwave post-curing leading to lower cycle times and costs without any deterioration in the interfacial properties of the composites
Nanomagnetic domains of chromium deposited on vertically-aligned carbon nanotubes
Get PDFThe drive to create ever smaller magnetic memory devices has led to the development of new nanomagnetic domains on surfaces. This paper reports the development of nano-chromium magnetic domains obtained using electrodeposition on vertically aligned carbon nanofibers arrays. Attempts to achieve this using conventional aqueous solutions were unsuccessful even after thin nickel underlayers were applied. The use of a novel electrolyte, a deep eutectic solvent, made from choline chloride: chromium (III) chloride enabled highly conformal overcoatings of chromium on individual bare carbon nanotubes to be obtained. Very high aspect ratio metal microstructures could be obtained by this novel technology. Magnetic imaging of the coated nanoarrays showed there to be clear magnetic character to the coating when the thin coatings were applied but this disappeared when the deposits were thicker and more contiguous
Transition regime analytical solution to gas mass flow rate in a rectangular micro channel
Get PDFWe present an analytical model predicting the experimentally observed gas mass flow rate in rectangular microchannels over slip and transition regimes without the use of any fitting parameter. Previously, Sone reported a class of pure continuum regime flows that requires terms of Burnett order in constitutive equations of shear stress to be predicted appropriately. The corrective terms to the conventional Navier-Stokes equation were named the ghost effect. We demonstrate in this paper similarity between Sone ghost effect model and newly so-called ‘volume diffusion hydrodynamic model’. A generic analytical solution to gas mass flow rate in a rectangular micro channel is then obtained. It is shown that the volume diffusion hydrodynamics allows to accurately predict the gas mass flow rate up to Knudsen number of 5. This can be achieved without necessitating the use of any adjustable parameters in boundary conditions or parametric scaling laws for constitutive relations. The present model predicts the non-linear variation of pressure profile along the axial direction and also captures the change in curvature with increase in rarefaction
Rapid Control Prototyping Platform for the Design of Control Systems for Automotive Electromechanical Actuators
Get PDFThis article introduces and discusses the development of a low-cost Rapid Control Prototyping Platform (RCPP). The aim of RCPP is to automate design of control algorithm of electromechanical actuators and simultaneous implementation it into a target microprocessor. The RCPP is stand-alone system containing software tools and electronic hardware in order to provide all development steps from system identification, model-based control design and code generation up to hardware implementation. The system can be used for development of a torque, speed or position controller for low power electromechanical actuators especially in the area of automotive application. The hardware of the platform is based on a 16-bit microcontroller and includes essential power semiconductor switches, sensors and communication interfaces. The presented RCPP system supports Real-Time-Work interface of MATLAB/Simulink and Calibration Protocol for CAN-Bus communication
The use of diffractive imitator optics as calibration artefacts
Get PDFThe testing of highly aspheric optics often requires complex test arrangements: these test systems can be multi-element and will have both fabrication and alignment errors present in the test wavefront. It may not be feasible to calibrate such systems with conventional optical shop practice. The use of diffractive imitator optics, with carefully controlled fabrication uncertainties, can be used to characterise these systems.
We describe the use of reflective imitator CGH optics as calibration artefacts in the calibration of an optical test system used to test ELT primary mirror segments. The optical test system is designed to have two operational modes: one to measure a spherical reference optic; and one to measure the primary mirror segment. The use of diffractive imitators in this test system is designed to provide traceability between these two operational configurations, to quantify residual alignment aberrations, and to quantify fabrication errors in the test system. We outline the design of the optical test system, the design of three imitator CGH artefacts required to provide traceability between the two optical test modes, and our calibration approach.
We demonstrate the calibration performance achieved with this approach. Without the use of these imitator artefacts, the absolute accuracy of the optical test is estimated to be 149 nm RMS wavefront, of which 47 nm RMS is attributed to midspatial wavefront errors and 141 nm RMS is attributed to alignment and prescription errors. The repeatability of this calibration has been established as better than 3 nm wavefront standard deviation, with an absolute accuracy of 19 nm RMS wavefront
Police officer physical fitness to work: A case for health and fitness training
Get PDFThere is no reference point currently available to the Irish police force (An Garda Síochána) for measurement of baseline physical fitness or for tracking its current members, as no such data exists. Currently there is no defined health and fitness policy or strategy following a trainee Irish police force two year training period. Measurements of the various health-related components of physical fitness have been developed and, in some cases, standardised, with good to excellent accuracy and reliability (American College of Sports Medicine (ACSM, 2011), as physiological measures (as a proxy for actual physical fitness) with predictive accuracy of an individual’s health outcomes better than physical activity recall (Bovet et al., 2007). These measures were utilised within this research to ascertain if there were fitness changes within a group of Irish police force trainees during their period in college training. An improvement was predicted for the trainee group that was at odds with the actual findings. The focus of this particular study is to provide the information to establish if there is a need for mandatory health and fitness testing (while allowing for individual differences) for this unique Irish work force
A Surrogate Model Assisted Evolutionary Algorithm for Computationally Expensive Design Optimization Problems with Discrete Variables
Get PDFReal-world computationally expensive design optimization problems with discrete variables pose challenges to surrogate-based optimization methods in terms of both efficiency and search ability. In this paper, a new method is introduced, called surrogate model-aware differential evolution with neighbourhood exploration, which has two phases. The first phase adopts a surrogate-based optimization method based on efficient surrogate model-aware search framework, the goal of which is to reach at least the neighbourhood of the global optimum. In the second phase, a neighbourhood exploration method for discrete variables is developed and collaborates with the first phase to further improve the obtained solutions. Empirical studies on various benchmark problems and a real-world network-on-chip design optimization problem show the combined advantages in terms of efficiency and search ability: when only a very limited number of exact evaluations are allowed, the proposed method is not slower than one of the most efficient methods for the targeted problem; when more evaluations are allowed, the proposed method can obtain results with comparable quality compared to standard differential evolution, but it requires only 1% to 30% of exact function evaluations
The Evaluation of the Welsh Assembly Government Food and Fitness Grant Scheme: Final Report
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Exploring the ethical issues of the research interview in the cancer context
No full textThis paper sets out to reflect on ethical issues in the context of a study exploring cancer patients’, relatives’ and nurses’ experience of a day hospital chemotherapy service. Interviewing can be considered as a well-used approach within qualitative methodology, yet little attention has been paid to a many of the ethical deliberations that are inherent when adopting this approach, particularly in the context of cancer. It is the intention of the authors that this paper might raise awareness of these issues, contribute to the ongoing debate about conducting research interviews on sensitive topics and provide a ‘real-world’ application of these principles. It is considered that the article potentially raises more questions that answers and illustrates that there are not always quick-fix solutions for the ‘real-world’ problems qualitative researchers’ experience
Psychological type preferences of male British Assemblies of God Theological college students: tough-minded and tender-hearted?
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Psychological type theory proposes that people make decisions through using one or two dichotomous judging functions (thinking and feeling). People who prefer thinking make judgements based on impersonal logic and tend to be objective and tough-minded, while people who prefer feeling make judgements based on personal values and tend to be compassionate and tender-hearted. This study explores the notion that the judging functions are key predictors of individual differences in terms of religiosity. The psychological type preferences of a sample of 190 male Assemblies of God theological college students were assessed using form G (Anglicised) of the Myers-Briggs Type Indicator. The data revealed preferences for thinking over feeling, and the implications of this finding are explored