1,721,120 research outputs found
Translucent silica aerogel: Properties, preparation and applications
No full textSilica translucent aerogels are unique materials able to improve the thermal insulation performance of buildings without compromising daylight transmission. The aim of the book is to give a general overview on state of the art research on translucent aerogels and their applications in buildings and to provide a data set about thermal and physical properties, useful in buildings’ energy performance simulation and design. Silica aerogels are nanostructured solid materials made of approximately 96% air and 4% silica. They show a thermal conductivity in the 0.012-0.020 W/mK range and excellent optical properties, especially visible transmission. They come in granular and monolithic form. Granular aerogels are relatively easy to produce and less expensive than monolithic panes, but show worse optical and thermal performance. Monolithic aerogels enable vision through the material, but their fabrication process is not developed at an industrial scale
Caratterizzazione tassonomica ed ecofisiologica di funghi associati a piante e suolo di un area dell’Appennino Settentrionale monitorata per il cambiamento climatico
No full textProperties and energy performance of wood waste sustainable panels resulting from the fabrication of innovative monolithic aerogel glazing systems
No full textThe combined effect of pine wood waste panels resulting from the different industrial processes to produce window frames and double glazing systems with monolithic aerogel of different hydrophobicity in the gap on the heating, cooling, and artificial lighting energy demand of a typical 70 s residential building in different climatic conditions is evaluated. The scraps obtained from the production of the innovative transparent glazing systems are used to fabricate eco-sustainable panels using natural flour-based glue. A thermal conductivity value of the opaque panels equal to 0.077 W/mK is measured by means of a thermal flux meter methodology. As regards the glazing systems, thermal resistance values of 0.86 and 0.92 m2K/W are measured for hydrophilic HY 0 and hydrophobic HY 10 unit, respectively; as a consequence, a thermal transmittance reduction equal to 65-67 % is obtained with respect to the double glazing unit with air in the gap. However, visible transmittance equal to 0.66 is measured as increasing hydrophobicity with respect to 0.81 of the conventional air glazing unit (reduction of 16 and 19 % with HY 0 and HY 10, respectively), as measured by means of a large integrating sphere spectrophotometer. The experimental data measured on eco-sustainable opaque panels and innovative transparent solutions are implemented in dynamic simulation models. The results show an annual heating energy demand reductions (in the 17 (Bolzano) - 39 % (Palermo) range) and cooling (in the 2 (Bolzano) - 11 % (Rome) range) in different climatic areas. Hydrophobicity has a negligible influence on the results. On the other hand, the energy demand for artificial lighting is not affected by the investigated solutions (maximum increase of 10 % is obtained in Bolzano with hydrophobic glazing system). This work is preparatory for the future possibility of starting a production chain of wood fiber insulating panels in the area, which will be in case fabricated at industrial scale in order to reduce the environmental impacts in the construction process of a building in a circular economy perspective and to improve the energy efficiency of the building envelopes by means of innovative materials
Joint scheduling and routing with power control for centralized wireless sensor networks
No full textWe consider a TDMA-based multi-hop wireless sensor network, where nodes send data to a sink, which is aware of received powers at all receivers; the sink is responsible for creating the network topology and assigning time slots to links. Under this centralized approach, we propose two algorithms that jointly define the tree topology connecting nodes to the sink, and assign time slots, avoiding any packet loss. In contrast with previous works, the proposed algorithms accurately account for interference effects; when evaluating the signal-to-interference ratio to establish the tree and schedule transmissions, we consider the sum of all actual interfering signals, a fact of relevance for networks with increasing number of nodes. Optimal selection of transmit powers, minimizing energy consumption, is also applied. Our algorithms are compared to a benchmark solution and other proposals from the literature; it is shown that they bring to better radio resource utilization, higher throughput and lower energy consumption, while keeping the average delay limited
Thermal comfort in open plan offices in northern Italy: An adaptive approach
No full textThe analysis of the thermal comfort in nine open plan offices was carried out in the present work. An objective evaluation, by means of environmental parameters experimentally-acquired in the selected work-places, was performed. In addition, a subjective evaluation was achieved by the distribution of a dedicated multiple response questionnaire, already developed in previous studies. The questionnaire is comprehensive of information for the application of the traditional static model and also the adaptive model, proposed by UNI EN ISO7730:2006 and ASHRAE 55.Predicted Mean Vote (PMV) values derived from questionnaire data were compared with those of the Operative Temperature. A significant correlation was found. Furthermore, the Neutral Temperature, corresponding to thermal comfort, was calculated and correlated to the Operative Temperature and to the External Temperature by means of linear regression method. In addition, a comparison between data obtained by the 588 questionnaires and data from experimental campaigns, for each work place in both morning and afternoon, is here presented. As a conclusion, parameters useful for the application of adaptive models have been elaborated according to the statistical approach suggested by recent standards. © 2012 Elsevier Ltd
Thermal- hygrometry comfort in university classrooms: experimental results in north and central Italy Universities conducted with new methodologies based on the adaptive model
No full textUNI EN ISO 7730 (1997), about thermal – hygrometry comfort, is based on a static model
where occupants are considered as passive subjects in thermal exchange. In the last years adaptive models were
developed,where occupant acts with environment, reducing individual reaction to environmental stimuli. None of
the proposed adaptive models found a full confirmation, therefore a revised version of 7730 is treating adaptation
only in a generic way. In the present paper a multiple response questionnaire was elaborated, comprehensive
of information for the static and adaptive model. It was applied in autumn in a classroom of the University of
Perugia with 120 students and in winter in two classrooms (University of Pavia, with 130 students and University
of Perugia, Terni, with 20 students). The thermal hygrometry conditions were monitored; finally questionnaire
and experimental data were compared and a correlation for the static and the adaptive model is here proposed
Indagini spettrofotometriche per la valutazione dell'invecchiamento di vetrate artistiche
No full textA 2.4 GHz LoRa-Based Protocol for Communication and Energy Harvesting on Industry Machines
Full text linkThe fourth industrial revolution is paving the way for Industrial Internet of Things applications where large number of wireless nodes, equipped with sensors and actuators, monitor the production cycle of industrial goods. This paper proposes and analyses LoRaIN, a network architecture and MAC-layer protocol thought for on-demand monitoring of industrial machines. Our proprietary system is an energy-efficient, reliable and scalable solution, where the protocol is built on top of LoRa at 2.4 GHz. Indeed, the low-power characteristics of LoRa allow to reduce energy consumption, while Wireless Power Transfer is used to recharge batteries, avoiding periodic battery replacement. High reliability is obtained through the joint use of Frequency and Time Division Multiple Access. A dynamic LoRaIN scheduler manages the communication and recharging phases depending on the tasks assigned to the nodes, as well as the number of monitoring devices. Performance is measured in terms of network throughput, energy consumption and latency. Results demonstrate that the proposed solution is suitable for monitoring applications of industry machines
OCDMA: a MAC Protocol for Industrial Intra-machine TeraHertz Network
Full text linkThis paper considers an industrial machine, where wireless sensor nodes (denoted as tags or nodes) support control applications. This scenario poses very challenging communication requirements: hundreds of tags per cubic meter can provide an overall offered throughput of tens of Gbit/s; at the same time, control applications require a latency of less than 0.1 ms. To fulfill them, this work proposes an Orthogonal Chirp Division Multiple Access (OCDMA) scheme to be used in the TeraHertz (THz) frequency band. With THz communications, even at short distances, propagation delays can be of the same order of magnitude as the packet transmission time. This requires proper consideration of such delays in the protocol design and performance evaluation. This paper mathematically derives network throughput and latency of the proposed protocol, comparing it to benchmarks; two scenarios are considered, where tags are in fixed positions or move. Results show that OCDMA outperforms the two benchmark protocols, Aloha and Polling, for static and crowded networks, and the performance is compatible with the communication requirements of industrial control applications
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