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F. Arpino M. Dell��Isola G. Ficco L. Iacomini V. Fernicola 《International Journal of Thermophysics》2011,32(11-12):2727-2734
Accurate heat flux measurements are needed to gain a better knowledge of the thermal performance of buildings and to evaluate the heat exchange among various parts of a building envelope. Heat flux meters (HFMs) are commonly used both in laboratory applications and in situ for measuring one-dimensional heat fluxes and, thus, estimating the thermal transmittance of material samples and existing buildings components. Building applications often requires heat flux measurements below 100 W · m?2. However, a standard reference system generating such a low heat flux is available only in a few national metrology institutes (NMIs). In this work, a numerical study aimed at designing an HFM calibration apparatus operating in the heat flux range from 5 W·m?2 to 100 W · m?2 is presented. Predictions about the metrological performance of such a calibration system were estimated by numerical modeling exploiting a commercial FEM code (COMSOL®). On the basis of the modeling results, an engineered design of such an apparatus was developed and discussed in detail. The system was designed for two different purposes: (i) for measuring the thermal conductivity of insulators and (ii) for calibrating an HFM with an absolute method (i.e., by measuring the applied power from the heater and its active cross section) or by a relative method (i.e., by measuring the temperature drop across a reference material of known thickness and thermal conductivity). The numerical investigations show that in order to minimize the uncertainty of the generated heat flux, a fine temperature control on the thermal guard is needed. The predicted standard uncertainty is within 2% at 10W·m?2 and within 0.5% at 100 W · m?2. 相似文献
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Design methods have been studied by researchers for decades. Academia considers their impact on industry to be insufficient.
The objective of this research is to understand the use and impact of design methods in the context of a specific company,
Volvo Car Corporation (VCC), by describing the behaviour of engineers in relation to methods, to assist in the future development
of design methods and tools. We mainly concentrate on concept selection methods because of their relevance in this company.
The data presented is the result of qualitative research carried out during 4 years at VCC, where the authors were located
as researchers. The research shows that many methods are employed besides those with an academic name, that some in-company
methods used contain improvements to methods researched by academia, that some modifications to academic methods lead to unreliable
results, and that there is a lack of objectivity in method modification. For these reasons, the authors suggest further research
on understanding the principles of successful and unreliable modification of concept selection methods. 相似文献
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Tino Schulz Bert J��ttler 《Applicable Algebra in Engineering, Communication and Computing》2011,22(4):265-288
Given a rational family of planar rational curves in a certain region of interest, we are interested in computing an implicit
representation of the envelope. The points of the envelope correspond to the zero set of a function (which represents the
envelope condition) in the parameter space combining the curve parameter and the motion parameter. We analyze the connection
of this function to the implicit equation of the envelope. This connection enables us to use approximate implicitization for
computing the (exact or approximate) implicit representation of the envelope. Based on these results, we formulate an algorithm
for computing a piecewise algebraic approximation of low degree and illustrate its performance by several examples. 相似文献
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Sergey A. Krasnikov Sergey I. Bozhko Kevin Radican Olaf Lübben Barry E. Murphy Sundar-Raja Vadapoo Han-Chun Wu Mohamed Abid Valery N. Semenov lgor V. Shvets 《Nano Research》2011,4(2):194-203
The growth and ordering of C60 molecules on the WO2/W(110) surface have been studied by low-temperature scanning tunnelling microscopy and spectroscopy (STM and STS), low-energy
electron diffraction (LEED), and density functional theory (DFT) calculations. The results indicate the growth of a well-ordered
C60 layer on the WO2/W(110) surface in which the molecules form a close-packed hexagonal structure with a unit cell parameter equal to 0.95 nm.
The nucleation of the C60 layer starts at the substrate’s inner step edges. Low-temperature STM of C60 molecules performed at 78 K demonstrates well-resolved molecular orbitals within individual molecules. In the C60 monolayer on the WO2/W(110) surface, the molecules are aligned in one direction due to intermolecular interaction, as shown by the ordered molecular
orbitals of individual C60. STS data obtained from the C60 monolayer on the WO2/W(110) surface are in good agreement with DFT calculations. 相似文献