3,375 research outputs found
Expenditures, conspicuous consumption and living standard of a nineteenth-century Habsburg family
This paper analyses the expenditures and food consumption of a nineteenth-century Habsburg family, the Bossi Fedrigotti. Drawing upon the household budgets and the documents of their private archives, this study investigates the type, composition, and variation in expenditures during two benchmark decades, 1835-1844 and 1855-1864. The relatively small share of expenses for food as compared to leisure, cultural activities, charity and conspicuous consumption reflects the household\u2019s quest for social status and reputation befitting the noble title obtained in the previous century. The Fedrigotti also represented a pillar in the economic system of Rovereto where they lived, which they actively supported through a variety of economic and non-economic actions, helping the city to prosper and advance
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Numerical characterization of silicon DC electro-osmotic pumps: the role of the micro channel geometry
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A numerical analysis of silicon DC open channel EOPs is presented to show which parameters should be taken into account in the design of these devices. Particular attention is paid to the influence of the channel cross-section geometry on pump behavior, especially in relation to the electrical properties of the fluid. Rectangular and trapezoidal, micro and nano channels chemically etched on silicon wafers are considered and a broad range of operative conditions are analyzed. In order to make all the results available, two user-friendly correlations that predict the characteristic curves of the pumps are given as functions of the relevant parameters. The EOP model used to obtain the results is explained extensively, as well as the method used to solve it. A brief discussion on the domain in which it applies is also presented
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The Influence of Geometry on the Thermal Performance of Microchannels in Laminar Flow with Viscous Dissipation
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Micro heat exchangers (MHXs) may achieve very high heat transfer coefficients thanks to their
small dimensions and high Area-to-Volume ratio even in laminar flow. The main drawback of these devices
is the high frictional losses – especially for liquid flows – that make viscous dissipation no longer negligible.
In order to enhance heat transfer, modification of the channels’ cross-section is a viable strategy. In the
present work the fully developed steady laminar flow of a Newtonian liquid through a microchannel subject
to H1 boundary conditions in the presence of viscous dissipation is investigated. Entropy generation numbers
and FG1a performance evaluation criterion are employed to assess the influence of smoothing the corners of
an initially rectangular cross-section, with an aspect ratio ranging from 1 to 0.03 under four different types of
geometrical constraints. The governing equations and the results are expressed in non-dimensional form, the
intensity of viscous dissipation being exemplified by the Brinkman number, which is demonstrated to
increase its maximum allowable value when corners are smoothed. The results are reported as a function of
the non-dimensional radius of curvature Rc and aspect ratio and show that smoothing the corners almost
invariably brings about a benefit for a fixed heated perimeter
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Poiseuille and Nusselt numbers for laminar flow in microchannels with rounded corners
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.This work investigates the frictional and heat transfer behaviour of laminar, fully-developed flow in microchannels with trapezoidal and rectangular cross-section and rounded corners under H1 boundary
conditions. The equations of momentum and energy are solved numerically, and the results validated with analytical data, when available. The runs have been carried out for different aspect ratios and nondimensional radii of curvature Rc, with either all sides or three sides heated, one short side adiabatic for rectangular geometries and three sides heated, the longest one adiabatic for trapezoidal geometries. The Poiseuille and Nusselt numbers are reported and show, for the rectangular cross-section heated on all sides, a maximum increase for the highest value of the aspect ratio (β=1) with increments in the Poiseuille and Nusselt numbers of about 11% and 16% respectively for values of Rc * of 0.5, increasing as the geometry approaches the circular duct (12.5% and 21%). The increase is less pronounced as β decreases and also when only three sides are heated (maximum increase of Nu around 10%); in the case of the trapezoidal geometry
the effects of rounding the corners are almost negligible (a maximum increase in Nu of around 2%)
System engineering study of electrodynamic tether as a spaceborne generator and radiator of electromagnetic waves in the ULF/ELF frequency band
The transmission and generation by orbiting tethered satellite systems of information carrying electromagnetic waves in the ULF/ELF frequency band to the Earth at suitably high signal intensities was examined and the system maintaining these intensities in their orbits for long periods of time without excessive onboard power requirements was investigated. The injection quantity power into electromagnetic waves as a function of system parameters such as tether length and orbital height was estimated. The basic equations needed to evaluate alternataing current tethered systems for external energy requirements are presented. The energy equations to tethered systems with various lengths, tether resistances, and radiation resistances, operating at different current values are applied. Radiation resistance as a function of tether length and orbital height is discussed. It is found that ULF/ELF continuously radiating systems could be maintained in orbit with moderate power requirements. The effect of tether length on the power going into electromagnetic waves and whether a single or dual tether system is preferable for the self-driven mode is discussed. It is concluded that the single tether system is preferable over the dual system
Optimised Electro-Osmotic Flow in Rectangular Microchannels with Smoothed Corners
Electro-osmotic flows are a means of circulating polar fluids through microchannels without resorting to mechanical pumping. The lack of moving parts, of noise and the ease of integration in silicon chips make them an interesting option for microchip cooling and miniaturized total analysis systems. This paper describes an optimization in terms of first- and second-law analysis of the cross-section of a microchannel subject to electro-osmotic flow. Starting from rectangular cross-sections of different aspect ratios, its corners are progressively smoothed and the resulting Poiseuille and Nusselt numbers computed. Performance evaluation criteria are then used to assess the change in, among others, heat transfer rate, temperature difference between wall and bulk fluid, and equivalent pumping power. The entropy number is also computed and the results commented. It is found that the latter criterion highlights a configuration of minimum entropy generation, whereas the trends of the heat transfer and temperature difference are opposite to that of the equivalent pumping power
Modelling of Natural Convective Heating of a Standard Wet Brick for Oven Energy Consumption Tests
The environmental impact of buildings is directly influenced by low-efficiency appliances like electric ovens. Their energy class is estimated through a test prescribed by the EN 60350 European standard, where a wet clay brick is heated under set conditions and the energy consumption is measured; throughout the test, particular attention is devoted to the control of air temperature. In this work, a transient model of the oven suitable for control design was realized including the heat and mass transfer within the brick. A lumped-parameter approach was used to ensure good predictive properties and low computational cost. The dynamics of the cavity air and the Pt500, which is used in normal operation to maintain the desired set point, was also included in the model. Model parameters were determined through an optimization procedure based on the experimental data collected during energy consumption tests with the oven in natural convective heating mode. The model was then validated. Good results were obtained in the prediction of both temperature and heating time
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The effect on the Nusselt number of the non-linear axial temperature distribution of gas flows through commercial microtubes
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.The characteristics of nitrogen convective heat transfer through commercial stainless steel microtubes with inner diameter of 172 μm and 750 μm are investigated both experimentally and numerically. In this work is highlighted that the axial local gas bulk temperature distribution can present a strong nonlinearity along the flow direction especially for microtubes having a small inner diameter and a thick solid wall. It is also demonstrated that the trend of the experimental Nusselt numbers as a function of the Reynolds number can be considered in good agreement with the conventional correlations if the average bulk temperature is calculated by taking into account the axial non-linearity of the gas bulk temperature. This fact explains the low values of the Nusselt numbers obtained in the previous experimental works appeared in literature where the convective heat transfer for gas flows through microtubes has been investigated assuming the gas bulk temperature distribution between the inlet and the outlet of the microtube as linear without verifying this hypothesis.European Community's Seventh Framework Programme (ITN - FP7/2007-2013) under grant agreement no 215504
Vespa orientalis (Hymenoptera; Vespidae), the first record in Marche region
Vespa orientalis (Hymenoptera Vespidae), prima segnalazione nella Regione Marche. Viene segnalata per la prima volta nel versante orientale della Penisola italiana, ad Ancona (Regione Marche) la presenza di Vespa orientalis Linnaeus, 1771 (Hymenoptera Vespidae). Dopo un primo avvistamento da parte di un apicoltore, sono stati effettuati dei campionamenti direttamente in apiario e l’identità degli insetti catturati è stata successivamente confermata in laboratorioThe presence of Vespa orientalis Linnaeus, 1771 (Hymenoptera Vespidae) was reported for the first time on the eastern side of the Italian peninsula, in Ancona (Marche Region). After an initial sighting by a beekeeper, sampling was carried out directly in the apiary and the identity of the insects captured was subsequently confirmed in the laborator
Diagnostic performance of imaging investigations in detecting and differentiating cardiac amyloidosis: a systematic review and meta-analysis
AIMS: The study aims to systematically assess the diagnostic performance of cardiac magnetic resonance (CMR) and nuclear scintigraphy (index tests) for the diagnosis and differentiation of subtypes of cardiac amyloidosis. // METHODS AND RESULTS: MEDLINE and Embase electronic databases were searched for studies evaluating the diagnostic performance of CMR or nuclear scintigraphy in detecting cardiac amyloidosis and subsequently in differentiating transthyretin amyloidosis (ATTR) from immunoglobulin light-chain (AL) amyloidosis. In this meta-analysis, histopathological examination of tissue from endomyocardial biopsy (EMB) or extra-cardiac organs were reference standards. Pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio were calculated, and a random effects meta-analysis was used to estimate diagnostic odds ratios. Methodological quality was assessed using a validated instrument. Of the 2947 studies identified, 27 met the criteria for inclusion. Sensitivity and specificity of CMR in diagnosing cardiac amyloidosis was 85.7% and 92.0% against EMB reference and 78.9% and 93.9% with any organ histology reference. Corresponding sensitivity and specificity of nuclear scintigraphy was 88.4% and 87.2% against EMB reference and 82.0% and 98.8% with histology from any organ. CMR was unable to reliably differentiate ATTR from AL amyloidosis (sensitivity 28.1-99.0% and specificity 11.0-60.0%). Sensitivity and specificity of nuclear scintigraphy in the differentiation of ATTR from AL amyloidosis ranged from 90.9% to 91.5% and from 88.6% to 97.1%. Pooled negative likelihood ratio and positive likelihood ratio for scintigraphy in this setting were 0.1 and 8, with EMB reference standard. Study quality assessed by QUADAS-2 was generally poor with evidence of bias. // CONCLUSIONS: Cardiac magnetic resonance is a useful test for diagnosing cardiac amyloidosis but is not reliable in further classifying the disease. Nuclear scintigraphy offers strong diagnostic performance in both the detection of cardiac amyloidosis and differentiating ATTR from AL amyloidosis. Our findings support the use of both imaging modalities in a non-invasive diagnostic algorithm that also tests for the presence of monoclonal protein
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