On the error of calculation of heat gains through walls by methods using constant decrement factor and time lag values

A transient heat transfer model was developed to numerically predict the thermal behaviour of the external walls of a room under realistic outdoor conditions. The excitation is not simply sinusoidal even though it is considered to have daily periodicity. The numerical model is based on the finite difference method and handles one-dimensional heat conduction through multilayered walls. The boundary condition at the outer surface of the wall is described with the sol-air temperature concept. The temperatures of indoor air and of other internal surfaces in the room are assumed to be equal and constant. The numerical results were used to calculate values of the decrement factor and time lag of several walls. The calculation followed two methods found in literature, in which these parameters are assumed constant, distinguished by the temperature evolution used: the sol-air or the wall's outer surface. Additionally, the inner surface temperature is used in both methods. The walls investigated range from low to high mass construction, face towards various directions and have light or dark coloured sunlit outer surfaces. The heat fluxes at the inner surface of the walls predicted by numerical modelling and estimated by the simplified methods are compared in detail to conclude on the validity of these simplified methods. As a by-product it is also possible to conclude on the dependence of the decrement factor and of the time lag on the outer surface colour and on the orientation of different types of walls. The results show that both simplified methods have poor accuracy in a significant number of cases. Also, it was found that the wall's azimuth significantly affects the time lag

Compost quality from biowaste treatment in West Africa

9ª Jornadas Técnicas Internacionais de Resíduos, realizadas no IP de Viana do Castelo, de 14-16 setembro de 2015.Composting is generally considered as a cost effective waste management option for stabilising waste and produce a soil improver/organic fertilizer. Passive aerated open windrows is a typical low cost option feasible in in São Tomé and Principe (pop. 197 900), a small island state in West Africa. Here the European Union, in partnership with Instituto Camões, UCCLA and the local authority, invested in the waste management system upgrade. A composting plant integrated with biowaste collection has been working since 2013. In order to assess the composting process efficiency, a novelty in São Tomé on this scale, temperature was regularly measured and registered. The matured compost was analysed in Portuguese Laboratories, targeting parameters such as: humidity, pH, electrical conductivity, organic matter, macronutrients and heavy metals. The results are encouraging suggesting that composting is a good option for treating biowaste collected separately at households, central markets, supermarkets, rest homes, restaurants, municipal gardens…etc. Compost output has high C/N ratio and concentration of organic matter, thus evidencing agronomic value. However, some heavy metals (Cr, Ni) content are a matter of concern, and require further assessment in order to prevent their presence. Besides the financial benefits, composting allows saving natural resources by transforming biowaste into a product, reducing harmful impact of chemical fertilizers to soil. This article paves the way to further research and should encourage more experiences in this field, transforming waste into ready available compost.info:eu-repo/semantics/publishedVersio

Response of CFRP laminates under high strain rate compression until failure

This work describes an experimental characterization: the non-linear rate-dependent mechanical behavior of a composite material under compression. Fiber reinforced polymer matrix composites exhibit non-linear mechanical behavior, except in fiber direction, which is rate-dependent. In this work the Texipreg (R) HS160 REM material system was used, comprising high strength carbon fiber and epoxy resin. Unidirectional laminates were tested under uniaxial compression tests on a universal testing machine. The stress/strain curves of several specimens were obtained at three different strain rates of 0.07, 0.001 and 0.0001/s. In all cases tests were continued until failure was reached to measure the strain rate effect on strength. A 3-parameter constitutive viscoplastic model /6,7/ was used to describe the mechanical behavior. This model was developed based on data for strain rate between 0.0001 and 0.07/s. In transverse direction the viscoplastic model was able to predict the high strain rate experiments conducted on a Split Hopkinson Pressure Bar

OCD-FI, On-Chip Debugging and Fault Injection for validating microprocessor based dependable systems

This paper proposes a set of modifications to theon-chip debugging infrastructures present in manyactual microprocessor cores, with the objective ofsupporting the validation and verification steps offault-tolerant mechanisms through fault injectioncampaigns. A synthesisable microprocessor core forprogrammable components was used as a targetsystem an. a debugging infrastructure compliantwith the NEXUS 5001 proposed standard for onchipdebugging was implemented on this target. Toimprove the process of real-time memory faultinjection, an upgraded infrastructure designated asOn-Chip Debugging and Fault Injection (OCD-FI)was developed. The complete system was analysedin terms of area overhead and fault injectioncapabilities and performance. All elements weredesigned as synthesizable VHDL modules andevaluated in simulation

An Enhanced Debugger for Real-Time Fault Injection on Microprocessor Systems

As electronic devices get smaller and more complex, dependability assurance is becoming fundamental for many mission critical computer based systems. This paper presents a case study on the possibility of using the on-chip debug infrastructures present in most current microprocessors to execute real time fault injection campaigns. The proposed methodology is based on a debugger, customized for fault injection and designed for maximum flexibility, and consists on injecting bit-flip type faults on memory elements without modifying or halting the target application. The proposed solution is easily portable and applicable to different architectures, providing a flexible and efficient mechanism for verifying and validating fault tolerant components.info:eu-repo/semantics/publishedVersio

Directional field-dependence of magnetoimpedance effect on integrated YIG/Pt-stripline system

We investigated the magnetization dynamics through the magnetoimpedance effect in an integrated YIG/Pt-stripline system in the frequency range of 0.5 up to 2.0 GHz. Specifically, we explore the dependence of the dynamic magnetic behavior on the field orientation by analyzing beyond the traditional longitudinal magnetoimpedance effect of the transverse and perpendicular setups. We disclose here the strong dependence of the effective damping parameter on the field orientation, as well as verification of the very-low damping parameter values for the longitudinal and transverse configurations. We find considerable sensitivity results, bringing to light the facilities to integrate ferrimagnetic insulators in current and future technological applications.This research was funded by CNPq grand numbers 304943/2020-7 and 407385/2018-5, Capes grand number 88887.573100/2020-00 and FCT grant number CTTI-31/18-CF(2)

High performance of metallic thin films for resistance temperature devices with antimicrobial properties

Titanium-copper alloy films with stoichiometry given by Ti1−xCux were produced by magnetron co-sputtering technique and analyzed in order to explore the suitability of the films to be applied as resistive temperature sensors with antimicrobial properties. For that, the copper (Cu) amount in the films was varied by applying different DC currents to the source during the deposition in order to change the Cu concentration. As a result, the samples showed excellent thermoresistivity linearity and stability for temperatures in the range between room temperature to 110 °C. The sample concentration of Ti0.70Cu0.30 has better characteristics to act as RTD, especially the αTCR of 1990 ×10−6°C−1. The antimicrobial properties of the Ti1−xCux films were analyzed by exposing the films to the bacterias S. aureus and E. coli, and comparing them with bare Ti and Cu films that underwent the same protocol. The Ti1−xCux thin films showed bactericidal effects, by log10 reduction for both bacteria, irrespective of the Cu concentrations. As a test of concept, the selected sample was subjected to 160 h reacting to variations in ambient temperature, presenting results similar to a commercial temperature sensor. Therefore, these Ti1−xCux thin films become excellent antimicrobial candidates to act as temperature sensors in advanced coating systems.This work was supported by FCT-UIDB/04650/2020. A.L.R.S. thanks CAPES (88887.572905 /2020-00) and CNPq. M.A.C. thanks CAPES (8887.573100/2020-00) and CNPq. A.F. thanks the FCT (CTTI-31/18-C.F. (2) junior researcher contract)