53 research outputs found
Multiple irradiation sensing of the optical effective attenuation coefficient for spectral correction in handheld OA imaging
No full textAbstractSpectral optoacoustic (OA) imaging enables spatially-resolved measurement of blood oxygenation levels, based on the distinct optical absorption spectra of oxygenated and de-oxygenated blood. Wavelength-dependent optical attenuation in the bulk tissue, however, distorts the acquired OA spectrum and thus makes quantitative oxygenation measurements challenging. We demonstrate a correction for this spectral distortion without requiring a priori knowledge of the tissue optical properties, using the concept of multiple irradiation sensing: recording the OA signal amplitude of an absorbing structure (e.g. blood vessel), which serves as an intrinsic fluence detector, as function of irradiation position. This permits the reconstruction of the bulk effective optical attenuation coefficient μeff,λ. If performed at various irradiation wavelengths, a correction for the wavelength-dependent fluence attenuation is achieved, revealing accurate spectral information on the absorbing structures. Phantom studies were performed to show the potential of this technique for handheld clinical combined OA and ultrasound imaging
Spectral correction of OA signals based on multiple irradiation sensing: experimental validation
No full textIn this study we show that the spectral distortion of OA signals, caused by wavelength-dependent optical attenuation inside the bulk tissue, can be corrected based on OA imaging, when using multiple-irradiation sensing. The tissue is modeled as a strongly scattering background, in which a discrete number of blood vessels, characterized by a higher absorption than the background, are sparsely distributed. OA signals generated by these vessels, which serve as intrinsic “fluence detectors”, are recorded as a function of irradiation position. In order to account for realistic situations, we have developed a semi-empirical light diffusion model that is fitted to the recorded signals, so as to determine the background’s optical effective attenuation coefficient for arbitrarily shaped tissues. The experimental validation of this model was performed on tissue-mimicking phantoms. The results demonstrate a successful correction of the measured OA spectrum of the embedded vessel-like inclusions, in the presence of lateral geometrical boundaries and when vessel-like absorbing structures influence the light propagation
Avoiding Carbon Lock-In: Policy Options for Advancing Structural Change
No full textA major obstacle for the transformation to a low-carbon economy is the risk of a carbon lock-in: fossil fuel-based ('dirty') technologies dominate the market although their carbon-free ('clean') alternatives are dynamically more efficient. We study the interaction of learning-by-doing spillovers and the substitution elasticity between the clean and the dirty sector in an intertemporal general equilibrium model. We find that the substitution possibilities between the two sectors have an ambivalent effect: although a high substitution elasticity requires less aggressive mitigation policies than a low one, it creates a greater lock-in in the absence of regulation. The optimal policy response consists of a permanent carbon tax as well as a learning subsidy for clean technologies. A single policy instrument can also avoid high welfare losses, but a more stringent mitigation target can only be achieved at painful costs. We demonstrate that the policy implication of [Acemoglu et al. 2012] is limited in scope. Our numerical results also highlight that infrastructure provision is crucial to facilitate the low-carbon transformation.structural change, low-carbon economy, carbon lock-in, mitigation policies, learning-by-doing
PDV particle velocity measurements for the Expanded and Large Scale Gap Test
No full textAuthor Institution: U.S. Army Research LaboratoryAuthor Institution: Naval Surface Warfare CenterSlides presented at the 7th Annual Photonic Doppler Velocimetry (PDV) Workshop held at Sandia National Laboratory, Albuquerque, New Mexico, October 22-23, 2012
How Cannibalistic is the Internet Channel?
No full textDuring the past decade, irrational exuberance has turned into a possibly equally irrational pessimism about what the Internet can accomplish. The fear of getting ruined through cannibalization losses has recently deterred many firms from deploying the Internet as a distribution channel. But do Internet channels really cannibalize firms' entrenched channels, or is this widely held assumption exaggerated? To answer this question, we apply recent structural-break time-series econometrics to quantify the impact of an Internet channel addition on the long-run performance evolution of a firm's established channels. Using a database of 85 Internet channel additions over the last ten years in the British and Dutch newspaper industries, we find that the often-cited cannibalization fears have been largely overstated. The Internet therefore need not be disruptive to established companies and channels. This does, however, not imply that firms enjoy free play in setting up Internet channels. In cases where the newly established Internet channel too closely mimics the entrenched channels, substantial cannibalization is more likely to take place.cannibalization;internet channel;structural-break time-series analysis
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The Secret Six and Their Theory of Autonomous Individualism
No full textThis paper focuses on the Secret Six who consisted of Theodore Parker, Thomas Wentworth Higginson, Franklin Benjamin Sanborn, Samuel Gridley Howe, George Luther Stearns, and Gerrit Smith, and the concepts that these men believed in regarding the type of society they wanted established in the United States. The dominant theme in the minds of this Secret Six was the romantic belief in the free individual. The belief in the free individual living in a free, progressive society held out the promise that America could become a perfect community of autonomous individuals and an example for all the world. But the Secret Six realized that for America to be this perfect community of autonomous individuals, America had to be freed of any determinism in its institutions. These six crusaders had such faith in their theories of individualism, that they abandoned moral persuasion and accepted violence as the principal means of establishing their society. These men believed that only the type of an individual who was willing to use violence if necessary and to die for the dictates of his conscience, could reform America into a community that exemplified to the world a belief in the free individual
Interpreting the Image of the Human Body in Pre-modern India
No full textThis paper sets out two main arguments. In part one, a description of the adherents of the various intellectual disciplines and religious faiths in premodern India is given, each having developed distinct and different imagined bodies; for example, the body described in Tantric circles had little or nothing in common with the body described in medical circles. In part two, an account is given of the encounter between Ayurvedic anatomy and early colonial European anatomy which led initially to attempts at synthesis; these gave way to an abandonment of the syncretist vision of the body and the acceptance of an epistemological suspension of judgment, in which radically different body conceptualizations are simultaneously held in unacknowledged cognitive dissonance
An overview of the heat-affected zone sensitization and stress corrosion cracking behaviour of 12% chromium type 1.4003 ferritic stainless steel
No full textProfessor Madeleine du Toit of the University of Pretoria has won the Harvey Shacklock Gold Medal. Prof du Toit works in the Department of Materials Science and Metallurgical Engineering.
The decision to declare her a winner was made at a recent meeting of the council of the Southern African Institute of Welding (SAIW).
This award is made to the author of an outstanding paper presented to a SAIW conference or technical meeting. The award was first presented as long ago as 1949 and is donated by Afrox in recognition of Harvey Shacklock – the former managing director of Afrox and the first President of SAIW in 1948.
Du Toit presented this paper to the SAIW meeting held in Johannesburg. Her paper was titled: ‘Failure of type 1.4003 welds due to intergranular stress corrosion cracking and pitting corrosion in the HAZ’.
“I know the award is well earned in this our 60th anniversary year– many congratulations,” said Jim Guild, Executive Director of SAIW.
Du Toit said that she feels very honoured to be the recipient of the Harvey Shacklock Gold Medal in the 60th anniversary year of the Southern African Institute of Welding (SAIW).
“Over the last 60 years, the Southern African Institute of Welding has grown into South Africa's leading provider of internationally accredited training and certification programmes in the field of welding. It is a privilege to be recognised by the Institute on occasion of such a milestone,” she said.
Du Toit will receive her award at the annual dinner to be held at the Balalaika Hotel on the 25th July 2008.This document presents an overview of the findings of several investigations into the
susceptibility of 12% chromium type 1.4003 ferritic stainless steel to heat-affected zone
sensitization and intergranular stress corrosion cracking. A description of the sensitization
behaviour of these steels is complicated by the partial transformation of d-ferrite to austenite
on cooling. During slow cooling or annealing below the A1 temperature, this austenite
decomposes to form desensitized ferrite and M23C6-type carbide precipitates. The rapid
cooling rates associated with welding, however, prevent the transformation of austenite to
ferrite at lower temperatures, and any austenite formed on cooling transforms to martensite
below the Ms-temperature. Four distinct modes of heat-affected zone sensitization have
been identified to date. Sensitization of the martensite phase may occur on welding material
inadvertently annealed above the A1 temperature (Mode 1), or when multiple welds are
positioned in such a way that the heat-affected zone of the 2nd pass overlaps the heataffected
zone of the 1st pass (Mode 2). Rapid cooling after very low heat input welding may
sensitize the ferrite phase (Mode 3), whereas very slow cooling after welding at excessively
high heat input levels may lead to sensitization of the austenite phase (Mode 4). Results
examining the influence of Modes 1 and 2 heat-affected zone sensitization on the incidence
of intergranular stress corrosion cracking are presented.http://www.saiw.co.za
3D FE analysis of four legged jack-up vessels during preloading in cohesive soil
No full textSince the exploitation of wind as a renewable energy resource, jack-up vessels equipped with more than three independent legs are increasingly employed to transport and install the components of offshore wind turbines. By lowering the movable legs the vessel is able to elevate the hull from sea water level. In elevated position the vessel provides a stable platform to perform installation activities. The legs are equipped with spudcans which serve as foundation of the vessel. The elevating process consists of a preload phase to ensure sufficient capacity to withstand operational and possible storm conditions. The preloading of four-legged jack-ups is performed by alternately applying vertical loads on diagonally opposite leg pairs, up to achieving a stable condition in which nearly constant load levels can be held by each leg. The aim of this research is to develop a 3D model to asses the preload duration of the jack-up vessel Aeolus in cohesive soil. The viscous behaviour of cohesive soil, like clay, influence the acting leg load during preload of the jack-up vessel. The shear strength of clay is a function of strain rate meaning that resistance increases due to viscous effects with increasing penetration rate. During spudcan penetration the shearing resistance is high but will reduce significantly when penetration is stopped as the viscoplastic resistance diminishes. Together with the onset of isotach soil behaviour this causes the loads to redistribute between the legs occurs. In this study it is assumed that sufficient preloading is achieved when the leg load reduction is limited to 400 ton / 15 min. To satisfy this criterionmultiple load cycles of each leg pair are performed. Site specific geotechnical data and information on the structural stiffness of the Aeolus have been available for this research and allowed for an accurate analysis of the processes during the preload procedure. The Soft Soil Creep (SSC) model is used as constitutive model and accounts for viscous effects by formulating irreversible strains by means of viscoplasticity. The soil at the project site is classified and the constitutive model is calibrated based upon the available soil test results. The structural behaviour of the vessel is captured via a simplified beam configuration representing the deck structure and legs, the stiffness of the beams is verified using the results from a so-called predrive analysis. The extension of the legs is established bymeans of negatively pre-stressed node-to-node anchors. Simulations of a single spudcan penetrating at various depths and penetration rates are performed to identify the extent of viscous strain rate effects fromthe results. With the developed 3D model Small Deformation Finite Element analyses of the preload procedure are performed. The leg loads and penetrations are monitored and compared to jacking data fromthe actual project site. The processes in the soil and structure are analysed and the influence on the preload procedure and preload duration is identified. For both type of simulations six different case-calculations are performed addressing variation in the initial spudcan depth, the OCR, the penetration rate, the permeability and the type of preload procedure. The simulations indicated that the penetration of a spudcan influences the penetration of an adjacent spudcan, this reciprocal influence of the spudcans emphasizes the importance of onemodel comprising all spudcans in the same 3D soil domain. The developed model slightly overestimates the spudcan penetration and underestimates the total preload duration. Simulations of the overshooting preload procedure and an alternative preload procedure are performed with the FE model. For the soil conditions used in this research, both the overshooting and the alternative procedure are effective in reducing the number of preload cycles to satisfy the preload criterion. Compared to the normal preload procedure, it is expected the overshooting procedure improves the preload duration. For the alternative procedure however, the duration of a preload cycle increases significantly and consequently the procedure does not improve the preload duration. Using a lower spudcan penetration rate during the normal preload procedure is also effective in reducing the number of preload cycles but significantly increases the elapsed time to complete the preload procedure. The above conclusions have been made on the basis of the model results, which is calibrated for the soil conditions at the specific project site.Civil Engineering | Structural Engineering | Structural MechanicsGeo-Engineerin
The impact of food allergy on household level
No full textAdverse reactions to food can be caused by food hypersensitivity. Prominent examples include food allergy or food intolerance. Patients suffering from food hypersensitivity have inappropriate autoimmune system reactions to potentially harmless food components. Symptoms can vary from uncomfortable skin rashes to cardiovascular problems such as anaphylactic shock. To date, no general cure is available. As a consequence, the management of food allergy consists of allergen avoidance, which may cause negative consequences in terms of patient anxiety and their experience of quality of life. Furthermore, implementation of dietary restrictions can have a negative effect on the quality of life and economic functioning of not only the food allergic patient but also their family members. An important issue in the assessment of the impact of food hypersensitivity and food allergy is the assessment of the economic costs that accrue to afflicted consumers. This information will contribute to the prioritising of healthcare resources, as well as developing effective policies to insure consumer protection. It is also important to evaluate whether wellbeing and welfare are affected. If this is indeed the case, a question arises as how to best manage dietary avoidance strategies. The aim of the research reported in this thesis is to provide information salient to the assessment of the impact of food hypersensitivity and allergy on households with respect to costs (time and money), welfare, well-being, and information search strategies. A systematic review of the existing literature revealed that researchers had not yet developed and validated an instrument to measure the individual and household costs of food hypersensitivity and/ or allergy. This thesis describes the development of the “household costs of food allergy” questionnaire and the exploratory analyses applied to validate the instrument. Thereafter, the “household costs of food allergy” questionnaire was used on a large sample of clinician-diagnosed food hypersensitive patients to confirm these cost effects. This study was part of an epidemiological study to investigate the prevalence of food allergy and food intolerance in four European countries, data were collected in The Netherlands, Poland, Spain and the United Kingdom. The respondents in this study were either diagnosed with food allergy or food intolerance. For the purposes of this discussion, the term food hypersensitivity will be used to indicate both diseases. Contrary to expectation, households with food hypersensitive respondents had significantly lower direct and indirect costs across all countries compared to households without food hypersensitive members. In addition, no differences in welfare between food hypersensitive respondents and respondents asymptomatic to foods were found. However, adult food hypersensitive respondents and their spouses reported significantly less happiness than respondents, or their spouses, who were asymptomatic. Thus, the results presented in this thesis do not support the commonly held belief of clinical researcher and patient organisations that all food allergies incur high costs to the individual. Given that an individual’s experience of quality of life is negatively impacted by food hypersensitivity, it is feasible that this might be improved by the implementation of more effective management strategies. As the primary viable management strategy involves avoidance of problematic foods, facilitating consumer choice in the retail environment may optimise risk management. The labelling preferences of food allergic consumers were investigated in two European countries, The Netherlands and Greece. At the time the research was conducted, food legislation had been developed to facilitate management of food allergens in order to protect food allergic consumers, rather than food intolerant consumers. For this reason, the research was confined to the study of the information needs of food allergic patients, and how this related to the current legislative situation. The research utilised ethnographic interviews with food allergic consumers during the course of shopping in a supermarket. The results suggest that current labelling practice is perceived to be inadequate for food allergic consumers if safe food choices are to be made. This is due to inappropriate use of fonts, colours with low contrasts and inconsistencies in the different languages, application of precautionary labelling, and lack of European and international harmonisation in labelling legislation. Based on these results, new information scenarios, such as uniform labelling, information booklet and ICT solutions, were developed and tested through an online survey. The results were used to develop prototype information delivery tools. An experiment was conducted to understand if the information delivery was in fact optimal, and to confirm if the additional attributes of the prototype tools were sufficient to facilitate allergen avoidance. The results suggested that the label should show the percentages of the allergens in the food product, as well as provide specific details about allergy management in the food chain, and use standardised symbols and standardised location of allergy information on the package. Additional visual and auditory warnings were also treated as being important for the ICT driven information delivery approaches, the results indicated that ICT methods are not appropriate replacements for effective food labelling on packaging, but may be used to supplement information provided by labels. To conclude, this thesis provides insight in the financial impact of food hypersensitivity, as well as the welfare and well-being. The “household costs of food allergy” questionnaire can be used by regulators and policy makers to prioritise healthcare resources, as well as to test the effectiveness of policy interventions. Limitations in current risk management strategies based on consumer information were also identified. The results of the consumer preferences studies can be used by policy makers and food industry to optimise the information delivery to food allergic consumers and therewith improve their quality of life. The combination of economic research and consumer research is relevant to investigate the dynamic impact of food allergy on individuals and their families. <br/
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