Acoustic resolution photoacoustic Doppler flowmetry using a transducer array: optimising processing for velocity contrast

This work demonstrates the first measurements of blood flow velocity using photoacoustic flowmetry (PAF) employing a transducer array. The measurements were made in a flow phantom consisting of a tube (580 μm inner diameter) containing blood flowing steadily at physiological speeds ranging from 3 mm/s to 25 mm/s. Velocity measurements were based on the generation of two successive photoacoustic (PA) signals using two laser pulses with a wavelength of 1064 nm; the PA signals were detected using a 64-element transducer array with a -6 dB detection bandwidth of 11-17 MHz. We developed a processing pipeline to optimise a cross-correlation based velocity measurement method comprising the following processing steps: image reconstruction, filtering, displacement detection, and masking. We found no difference in flow detection accuracy when choosing different image reconstruction algorithms (time reversal, Fourier transformation, and delay-and-sum). High-pass filtering and wallfiltering were however found to be essential pre-processing steps in order to recover the correct displacement information. We masked the calculated velocity map based on the amplitude of the cross-correlation function in order to define the region of interest corresponding to highest signal amplitude. These developments enabled blood flow measurements using a transducer array, bringing PAF one step closer to clinical applicability

Análise de incertezas físicas em simulação computacional de edificações residenciais

Resumo O objetivo deste trabalho é analisar incertezas físicas em simulação computacional de uma edificação residencial e sua implicação no desempenho térmico. O experimento foi elaborado com o método de Monte Carlo, que envolve as propriedades térmicas e físicas dos materiais da edificação. Foi analisada a sensibilidade das variáveis com coeficientes de regressão e correlação. Considerou-se o critério de graus-hora de desconforto por calor e por frio para o clima de Florianópolis, SC, conforme limites de conforto térmico adaptativo. Os resultados mostraram que as incertezas obtidas nos graus-hora são relativamente grandes, sendo de 32% no desconforto por frio e de 53% no desconforto por calor. Grande parte da incerteza é decorrente da temperatura média mensal do solo. Outras variáveis, como a absortância solar da cobertura e o calor específico da argamassa das paredes, resultam em impacto relevante no desconforto por calor, bem como a massa específica da argamassa e o calor específico da cerâmica das paredes no desconforto por frio. Essas variáveis precisam de maior precisão, seja por meio de bases de dados mais confiáveis, ou mesmo por medições em campo e/ou em laboratório

Building performance optimization of net zero-energy buildings

Building performance optimization (BPO) paired with building performance simulation (BPS) is a promising solution for evaluating many different design options and obtaining the optimal or near-optimal solution for a given objective or combination of objectives while complying with constraints. This chapter discusses major obstacles to BPO in the building design and construction industry including lack of appropriate tools, lack of resources, and the requirement that the problem be very well defined. The chapter explains the state-of-the-art and future research and development needs for Net Zero-Energy Buildings (ZEB) optimization tools in practice and its use for design and operation of buildings for energy, comfort, and cost optimization. The content is intended to aid the reader in better understanding areas of active research in building optimization as well as tools and methods commonly used by researchers and designers

Energy and comfort performance benefits of early detection of building sensor and actuator faults

This paper presents a building performance simulation-based investigation to better understand the energy and comfort performance benefits of early detection of common sensor and actuator faults. Five types of air-handling unit faults and four types of zone-level faults were implemented to the energy management system application of the building performance simulation tool EnergyPlus. During 50-year simulation periods, the faults were randomly permitted to affect 75 different components of an archetype medium-sized office building model. The sensitivity of the simulation results with respect to three variables was studied: fault recurrence period, fault repair period, and discomfort threshold for simulated complaints. The results indicate that the energy use intensity and the predicted percentage of dissatisfied exhibit a power–law relationship with time, in which most of the performance reductions occur in the first 10 years. If the work-orders are issued only upon occupant complaints, the faults were estimated to cause a 16–62% increase in the energy use intensity for heating, ventilation, and air-conditioning and a 11–38% increase in the predicted percentage of dissatisfied at the end of the 50-year simulation periods. The results indicate that if the faults can be detected within a month after their first appearance, almost all their detrimental effects on a building’s energy and comfort performance can be mitigated. Practical application: The methodology and results presented in this article are of practical use for those who study on-going commissioning, fault detection and diagnostics, and energy management systems in buildings. The simulation-based parametric analysis approach can be used to estimate the range of energy and comfort savings expected through early detection of common sensor and actuator faults in commercial buildings. Insights gathered from such an analysis can be used in planning the frequency of retro-commissioning and investments for automated fault detection and diagnostics systems