Development of subminiature multi-sensor hot-wire probes

Limitations on the spatial resolution of multisensor hot wire probes have precluded accurate measurements of Reynolds stresses very near solid surfaces in wind tunnels and in many practical aerodynamic flows. The fabrication, calibration and qualification testing of very small single horizontal and X-array hot-wire probes which are intended to be used near solid boundaries in turbulent flows where length scales are particularly small, is described. Details of the sensor fabrication procedure are reported, along with information needed to successfully operate the probes. As compared with conventional probes, manufacture of the subminiature probes is more complex, requiring special equipment and careful handling. The subminiature probes tested were more fragile and shorter lived than conventional probes; they obeyed the same calibration laws but with slightly larger experimental uncertainty. In spite of these disadvantages, measurements of mean statistical quantities and spectra demonstrate the ability of the subminiature sensors to provide the measurements in the near wall region of turbulent boundary layers that are more accurate than conventional sized probes

The Two-Dimensional Analogue of General Relativity

General Relativity in three or more dimensions can be obtained by taking the limit $\omega\rightarrow\infty$ in the Brans-Dicke theory. In two dimensions General Relativity is an unacceptable theory. We show that the two-dimensional closest analogue of General Relativity is a theory that also arises in the limit $\omega\rightarrow\infty$ of the two-dimensional Brans-Dicke theory.Comment: 8 pages, LaTeX, preprint DF/IST-17.9

The Three-Dimensional BTZ Black Hole as a Cylindrical System in Four-Dimensional General Relativity

It is shown how to transform the three dimensional BTZ black hole into a four dimensional cylindrical black hole (i.e., black string) in general relativity. This process is identical to the transformation of a point particle in three dimensions into a straight cosmic string in four dimensions.Comment: Latex, 9 page

Conformal entropy from horizon states: Solodukhin's method for spherical, toroidal, and hyperbolic black holes in D-dimensional anti-de Sitter spacetimes

A calculation of the entropy of static, electrically charged, black holes with spherical, toroidal, and hyperbolic compact and oriented horizons, in D spacetime dimensions, is performed. These black holes live in an anti-de Sitter spacetime, i.e., a spacetime with negative cosmological constant. To find the entropy, the approach developed by Solodukhin is followed. The method consists in a redefinition of the variables in the metric, by considering the radial coordinate as a scalar field. Then one performs a 2+(D-2) dimensional reduction, where the (D-2) dimensions are in the angular coordinates, obtaining a 2-dimensional effective scalar field theory. This theory is a conformal theory in an infinitesimally small vicinity of the horizon. The corresponding conformal symmetry will then have conserved charges, associated with its infinitesimal conformal generators, which will generate a classical Poisson algebra of the Virasoro type. Shifting the charges and replacing Poisson brackets by commutators, one recovers the usual form of the Virasoro algebra, obtaining thus the level zero conserved charge eigenvalue L_0, and a nonzero central charge c. The entropy is then obtained via the Cardy formula.Comment: 21 page

Two-dimensional gravitation and Sine-Gordon-Solitons

Some aspects of two-dimensional gravity coupled to matter fields, especially to the Sine-Gordon-model are examined. General properties and boundary conditions of possible soliton-solutions are considered. Analytic soliton-solutions are discovered and the structure of the induced space-time geometry is discussed. These solutions have interesting features and may serve as a starting point for further investigations.Comment: 23 pages, latex, references added, to appear in Phys.Rev.

Access to information, concerns, myths and truths on food safety during COVID-19: an overview of Portuguese population

Purpose: The COVID-19 pandemic raised questions and concerns about the possibility of transmission of SARS-CoV-2 via foods. While cases of COVID were rapidly rising, information related to the virus and ways of prevention was also increasing, with much of this information being provided by the media and the general population. In this context, this study had two main objectives: 1) To understand the doubts and concerns of the Portuguese population related to food safety during the first wave of COVID-19 and how they clarified these issues and 2) to analyze the population's opinion on myths and truths related to the transmission of the infection. Methods & Materials: A survey including questions about a) concerns and information on food safety during the first wave of COVID-19 pandemic; b) myths and truths about COVID-1 and c) respondents’ profile. The survey was released online between June and October of 2020.Results: The main doubt of the respondents was related to the manipulation of food (40,7%) followed by the possibility of transmission of COVID-19 through food (12,6%) and which foods should be avoided due to the pandemic (12,6%). 33,3% of the participants stated that television was the main mean of information accessed to clarify these doubts, followed by a Guideline launched by the Directorate-General of Health (31,8%). However, 50,3% said that they had only found answers to some of their questions. 50% of the respondents with higher level of education and 30% of the respondents with lower level of education had doubts about the possibility of the transmission of COVID-19 through food. Also, most of the survey participants disagreed with the affirmations regarding popular ways of disinfecting food to prevent infection. Conclusion: COVID-19 pandemic raised several doubts, however when related to food safety, the main doubt was about the manipulation of food due to the concern of SARS-CoV-2 transmission. Most respondents do not believe myths about COVID-19 and food safety, but this was dependent on the level of education.info:eu-repo/semantics/publishedVersio

Computing Parity Space Residuals’ Computational Form With MIMO Predictive Models

Trabalho apresentado em 12th Mediterranean Conference on Control and Automation MED’04, 6-9 de Junho de 2004, Kusadasi, Turquia.N/

Stability of Discrete Systems Controlled in the Presence ofIntermittent Sensor Faults

info:eu-repo/semantics/publishedVersio