5,780 research outputs found
Moisture uptake in monolithic and composite materials: edge correction for rectanguloid samples
No full textExperiments on moisture uptake of monolithic and composite materials are generally performed by immersing rectanguloid (square plate) samples in water. An edge correction factor is derived which, in a mathematically simple way, takes water uptake through all 6 faces (2 broad and 4 smaller faces) into account. Analysis shows this edge correction factor to be very accurate (deviations typically less than 2%). New expressions for moisture uptake in composites with unidirectionally aligned fibres are derived, by incorporating this edge correction factor as well as proper boundary conditions which depend on volume fraction of fibres. Experimental data on moisture uptake in these types of composite samples is successfully analysed using these expressions
Detection of gases and gas mixtures by correlation spectroscopy
No full textThe reliable detection and monitoring of gases and gas mixtures is known to play a crucial role in many real-world environmental and industrial applications. It is of considerable importance to utilise techniques that are not susceptible to poisoning, are specific to a target gas in a mixture, are unaffected by contaminants, and can be adapted for in-process monitoring. Ever-more stringent requirements in this field dictate a need for ongoing research in this area. As many common gases exhibit their fundamental optical absorption in the infra-red and visible regions, novel optical absorption methods for the detection of gases and gas mixtures have application in a variety of real-world situations. Of these, correlation spectroscopy is an established non-dispersive technique that is attractive in offering appreciable sensitivity and discrimination for gas detection, with the potential for real-time measurement of different gas species within a mixture using a single sensing instrument. We present new results for the detection of O2, CO, and CO2 gases using a method of real-time correlation spectroscopy involving the modulation of the absorption spectrum of a reference gas sample relative to that of the gas to be measured. We believe it is the first time O2 has been sensed in this manner and the use of low-cost sources and detectors suggests attractive commercial potential for this device. <br/
The effect of embedded fibre optic strain sensors on the post-mechanical performance of woven carbon fibre reinforced composite materials
No full textFibre optic LED-based correlation spectroscopy for O<sub>2</sub> detection
No full textThis paper describes the first detection of O2 by Complementary-Source-Modulation (CoSM) correlation spectroscopy over optical fibre with compact LED sources. Theoretical results for the selective detection of O2 by the CoSM method are also presented, based on spectral absorption data from the Hitran database
Investigation of the peak power enhancement available from a surface emitting GaAlAs near-infrared light emitting diode by cooling and pulsing
No full textLight emitting diode (LED) light sources are required for many illumination and optical sensing applications, due to their compact dimensions, low cost and low power consumption. The optimization of optical power output in a specific wavelength band is often of critical importance. We are interested in using LEDs for optical sensing systems, particularly for gas sensing. We have conducted a very comprehensive engineering study to show that, by packaging a commercial surface emitting LED in a cooled heat-sunk package and optimizing the drive current for this lower temperature, the power from the LED may be substantially improved, particularly when pulsed at low duty cycle. We have found that, even with moderate cooling using a Peltier heat pump, the intensity in our required spectral band was improved by a factor of 5 compared to that attainable under normal drive conditions. We have also verified that almost all spectral changes in the LED were due to temperature changes in the emitting chip, rather than from other effects related to injection current, such as internal optical gain
Detection of gases by correlation spectroscopy (In special issue: Proceedings of the 6th European Conference on Optical Chemical Sensors and Biosensors EUROPT(R)ODE VI)
No full textThis paper describes the detection of various common gases by means of Correlation Spectroscopy, employing a Complementary-Source-Modulation (CoSM) approach based on compact light-emitting diode (LED) sources. Theoretical results for the quantitative detection of O in air are presented, with the use of practical low cost LED sources
Illustrating potential efficiency gains from using cost-effectiveness evidence to reallocate Medicare expenditures
No full textThis article is available open access through the publisher’s website at the linke below. Copyright @ 2013, International Society for Pharmacoeconomics and
Outcomes Research (ISPOR).This article has been made available through the Brunel Open Access Publishing Fund.Objectives - The Centers for Medicare & Medicaid Services does not explicitly use cost-effectiveness information in national coverage determinations. The objective of this study was to illustrate potential efficiency gains from reallocating Medicare expenditures by using cost-effectiveness information, and the consequences for health gains among Medicare beneficiaries.
Methods - We included national coverage determinations from 1999 through 2007. Estimates of cost-effectiveness were identified through a literature review. For coverage decisions with an associated cost-effectiveness estimate, we estimated utilization and size of the “unserved” eligible population by using a Medicare claims database (2007) and diagnostic and reimbursement codes. Technology costs originated from the cost-effectiveness literature or were estimated by using reimbursement codes. We illustrated potential aggregate health gains from increasing utilization of dominant interventions (i.e., cost saving and health increasing) and from reallocating expenditures by decreasing investment in cost-ineffective interventions and increasing investment in relatively cost-effective interventions.
Results - Complete information was available for 36 interventions. Increasing investment in dominant interventions alone led to an increase of 270,000 quality-adjusted life-years (QALYs) and savings of $12.9 billion. Reallocation of a broader array of interventions yielded an additional 1.8 million QALYs, approximately 0.17 QALYs per affected Medicare beneficiary. Compared with the distribution of resources prior to reallocation, following reallocation a greater proportion was directed to oncology, diagnostic imaging/tests, and the most prevalent diseases. A smaller proportion of resources went to cardiology, treatments (including drugs, surgeries, and medical devices, as opposed to nontreatments such as preventive services), and the least prevalent diseases.
Conclusions - Using cost-effectiveness information has the potential to increase the aggregate health of Medicare beneficiaries while maintaining existing spending levels.The Commonwealth Fun
Vacuum Insulation Panels Applied in Building Constructions
No full textDue to sustainability and due to international treaties, it is desired and required to reduce greenhouse gas emissions drastically. One contributor to these emissions is the burning of fossil fuels for generating power and electricity to be used in and for buildings. Buildings and building-related processes are responsible for about 40% of the primary energy consumption in the European Union. More than half of this energy is applied for heating systems in dwellings and commercial buildings. The European Union therefore has laid down new energy performance requirements for buildings in the European Directive on the Energy Performance of Buildings. Moreover, a reduction of energy losses of buildings during their occupational phase is important for facilitating the implementation of sustainable energy sources in the built environment. Increasing the insulation value of the envelope of buildings may contribute to this reduction of primary energy use. Two strategies can be followed. The first strategy is to increase the thickness of the thermal insulation layer. Until recently, this strategy has primarily been adopted. If, however, German or Swiss Passivhaus standard is applied, the thickness of this insulation layer would increase to beyond 30 cm, resulting in very thick building enclosures. The second, more innovative, strategy for reducing energy losses through the building skin would be the application of more effective thermal insulators. One such more effective thermal insulator is a vacuum insulation panel, abbreviated as VIP. A VIP consists of an open-celled core material which is evacuated and then tightly sealed into a barrier envelope to maintain this vacuum. The vacuum inside the pores of the core material reduces the thermal conductivity of the product significantly, as a result of which the thickness of the insulation layer can be reduced to obtain a certain performance. This reduction of thickness is among the most promising features for large-scale application of VIPs in the building industry. However, integration of VIPs into buildings must be performed very meticulously for several reasons; first, due to its nature a VIP cannot be processed on site and needs careful planning in advance; second, it is very sensitive to mechanical damage thus requiring careful handling; third, thermal bridges along the panel’s edges reduce its performance; fourth, the composite system is highly subjected to aging. This dissertation therefore looks into many of these aspects, presents several calculation tools and shows how VIPs can be applied in façade panels, EPS insulation boards and as under-floor insulation. With the wide-spread proliferation of VIPs in buildings a more sustainable and healthy environment can then be achieved.Building TechnologyArchitectur
Frequency Domain Gaussian Estimation of Temporally Aggregated Cointegrated Systems
No full textThis paper discusses the joint estimation of the long run equilibrium coe cients and the parameters governing the short run dynamics of a fully parametric cointegrated system formulated in continuous time.The model allows the stationary disturbances to be generated by a stochastic di erential equation system and for the variables to be a mixture of stocks and flows.We derive a precise form for the exact discrete analogue of the continuous time model in triangular error correction form, which acts as the basis for frequency domain Gaussian estimation of the unknown parameters using discrete time data.We formally establish the order of consistency and the asymptotic sampling properties of such an estimator.The function of the data that estimates the cointegrating parameters is shown to converge at the rate of the sample size to a mixed normal distribution, while that estimating the short run parameters converges at the rate of the square root of the sample size to a limiting normal distribution.estimation;aggregation;cointegration;general equilibrium
Book Review: Reginald M.J. Oduor’s Introduction to Ethics
No full textTITLE OF BOOK: Introduction to Ethics
AUTHOR: Reginald M.J. Oduor
Nairobi: Sophia Publications Ltd., 2009, 116 pages
COVER: Paperback
ISBN: 9966-7457-0-X
This book is a product of more than a decade of Oduor’s experience in teaching ethics (moral philosophy) at the University of Nairobi. In the course of this introduction, the reader gets to see the techniques of philosophic reflection in action, as they are employed to scrutinise various pertinent moral questions
- …
