1,720,980 research outputs found
Reviving the Low-Frequency Response of a Rupestrian Church by Means of FDTD Simulation
No full textRupestrian churches are spaces obtained from excavation of soft rocks that are frequently found in many Mediterranean countries. In the present paper the church dedicated to Saints Andrew and Procopius, located close to the city of Monopoli in Apulia (Italy) is studied. On-site acoustical measures were made, obtaining a detailed description of the acoustics in the current state pointing out, thanks to a combination of analysis techniques, the presence of significant modal behavior in the low frequencies, causing reverberation time to be about 2 s, four times longer than in the other bands, as well as being strongly dependent on source and receiver position (with variations of about 1 s when source is moved outside the chancel). However, as the church is characterized by significant degradation of surfaces and large amounts of debris cover the floor, the original acoustic conditions can be expected to somewhat differ. Acoustical modelling can be very helpful in grasping the original conditions, but given the small dimensions of the space, conventional geometrical acoustic prediction methods cannot be applied to simulate the low-frequency behavior. Thus, the present paper proposes an application of finite-difference-time-domain (FDTD) computation to simulate the low-frequency behavior and analyze a possible reconstruction of the original state. Results showed that a very good agreement was obtained between predictions and measurements, both in terms of resonance frequencies and reverberation times that differed by less than 5%. Modal response strongly affected the acoustical conditions also in the hypothetical reconstruction of the original state, although the sound field proved to be more uniform than in the current state
Experimental and numerical analysis of heat transfer in the cavities of hollow blocks
No full textGiven the importance of the assessment of the insulation performance of the building envelope in the context of energy certification of buildings, a detailed analysis of the reliability of the methods of evaluation of heat transfer in the air cavities of hollow blocks has been carried out.
An experimental study was conducted in the laboratory. Heat transfer measurements on specimens with parallelepiped cavities were done, through a guarded hot plate device according to UNI EN 12664. A numerical analysis of the heat transfer in the specimens through the software ANSYS FLUENT was carried out.
The analysis of the numerical and experimental results when compared with the predictions obtained from simplified models of technical standards, have called attention to the order of magnitude of the calculation accuracy obtainable with such procedures. For some geometric configurations and boundary conditions, the application of the standards can lead to large errors of evaluation of the thermal resistance of the cavity
Sustainable Sound Absorbers to Improve Acoustical Comfort in Atria: A Methodological Approach
No full textResource-efficient buildings are one of the most important challenges of the construction industry, which could be achieved by limiting the extraction of natural resources and by replacing them with industrial residues. The present work proposes innovative panels made from textile wastes as an efficient solution for making the semi-open atrium in the Polytechnic University of Bari, acoustically suitable for use as an area of study. Several measurements were carried out in the atrium under empty and occupied conditions in order to characterize the sound field of the space (i.e., the reverberation time and the sound pressure level) and the actual sound sources (i.e., the sound power level of the students occupying the space). The on-site measurement results were useful to calibrate a geometrical acoustic model implemented in CATT-Acoustic software and used to predict the effect of the proposed treatments. About 700 m(2) of absorbent panels were distributed, leading to a predicted reduction in the reverberation time from 2.4 s to 1.4 s at 500 Hz, and consequently to an estimated 3 dB reduction in sound pressure level, resulting in a reduction in the background noise level due to speech. Furthermore, as a consequence of the "Lombard effect", a decrease in the background noise level will likely reduce the sound power level of the speakers by 2 dB, with an expected overall reduction of 5 dB
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Using neural networks to predict hourly energy consumptions in office and industrial buildings as a function of weather data
No full textOffice and industrial premises are among the most energy consuming type of buildings. Compared to residential buildings, they are characterized by more regular occupation patterns and stricter control of building systems. Under these conditions, it is expected that energy consumptions may be more easily predictable and may be significantly influenced by outdoor conditions more than by individual preferences. This may result in availability of straightforward predictions of energy use (at daily or hourly basis) which may contribute to trade energy at lower costs, make a better use of renewable energies, while balancing energy saving and occupants’ comfort. An essential contribution to the ability to
easily and accurately predict energy consumptions, is given by the ever-increasing number of smart and IoT-based devices that collect data inside and outside buildings and consequently make them available for processing. Taking advantage of such data, it is worth investigating if advanced artificial intelligence methods (like neural networks and machine learning) are capable of yielding predictions of energy consumptions and, ideally, indoor conditions. For the
purpose of the present paper, the dataset (including both input and output parameters) was obtained through simulation (using the popular EnergyPlus tool), including one office and one industrial reference building, and using three different climatic datasets. Finally, artificial neural networks were trained assuming daily and hourly energy consumptions (subdivided by category) as the target variable, showing that in most of the cases very accurate predictions
could be obtained
A nearly Zero Energy Building in Mediterranean climate: A case study in Mesagne (Apulia)
Full text linkThis paper presents the case study of an nZEB building located in the municipality of Mesagne (Apulia, BR). It is a building of 309 m2 of usable floor space with two floors above ground. The building is a proof that a correct integrated design of the HVAC system and the building envelope can easily lead to an nZEB building with high performance in terms of energy consumption and comfort. The external envelope of the building is a structure in tufa blocks plus a mixture of hemp and hydraulic lime plus blocks of hemp and lime. Hemp lime is a mix of renewably sourced hemp shiv, a specially formulated lime binder and water. The air conditioning system is based on a controlled mechanical ventilation with air pre-treatment through an underground tube exchanger. A numerical simulation of the overall building-plant system performance was made with DesignBuilder in order to evaluate the energy consumption for air conditioning and the thermohygrometric comfort in the building. Several simulations were carried out to compare the incidence of different building-plant system on total energy consumptions: one without earth-to-air heat exchanger, one without heat-recovery and recirculation, one without solar shading
Circular building design: a case study in Pakistan
No full textA major transformation from the current, linear practice to a closed-loop system, linked with a circular economy, is required to transform the negative effects of buildings on the environment. Pakistan has one of the fastest growing populations, and conventional building construction is increasing in urban areas due to urban sprawl. This research aims to demonstrate the possible shift to a circular construction industry in Pakistan by comparing the linear design components with the circular design components of exterior walls of a case study taking advantage of life cycle assessment. The results of life cycle assessment applied to the external walls of a house in Karachi show that finding the solution with the lowest impacts is not obvious and that use of apparently "green" solutions may turn out to have higher impacts. Study suggests that building components can be gradually replaced with more circular ones to create a circular built environment
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