301 research outputs found
Traditional Houses with Stone Walls in Temperate Climates: The Impact of Various Insulation Strategies
The present chapter focuses on the yearly behaviour of a traditional farmhouse in a
temperate Italian climate and analyses the impact of alternative energy saving strategies on
summer comfort and winter consumptions.
The aim of the current study was to:
- identify combinations of thermal insulation interventions which: optimise winter
energy saving and summer internal comfort without modifying the close relationship
between architecture and specific climate typical of traditional buildings; respect the
building material consistency and the façades aesthetic appearance.
- compare the performance of this traditional architecture (after the retrofit intervention)
with that of a modern building, of the type encouraged by new energy saving
legislation (lightweight and super-insulated).
To that aim a series of monitoring activities in summer and in winter were carried out to
investigate the internal environmental conditions and to calibrate a simulation model with
the software Energyplus. This model was used to assess the impact of various energy-saving
strategies on winter energy consumptions and summer comfort with the method of
Percentage outside the comfort range (EN 15251:2007-08)
A Macroscopic Mathematical Model For Cell Migration Assays Using A Real-Time Cell Analysis
Experiments of cell migration and chemotaxis assays have been classically
performed in the so-called Boyden Chambers. A recent technology, xCELLigence
Real Time Cell Analysis, is now allowing to monitor the cell migration in real
time. This technology measures impedance changes caused by the gradual increase
of electrode surface occupation by cells during the course of time and provide
a Cell Index which is proportional to cellular morphology, spreading, ruffling
and adhesion quality as well as cell number. In this paper we propose a
macroscopic mathematical model, based on \emph{advection-reaction-diffusion}
partial differential equations, describing the cell migration assay using the
real-time technology. We carried out numerical simulations to compare simulated
model dynamics with data of observed biological experiments on three different
cell lines and in two experimental settings: absence of chemotactic signals
(basal migration) and presence of a chemoattractant. Overall we conclude that
our minimal mathematical model is able to describe the phenomenon in the real
time scale and numerical results show a good agreement with the experimental
evidences
Power Minimizing MEC Offloading with QoS Constraints over RIS-Empowered Communications
This work lies at the intersection of two cutting edge technologies
envisioned to proliferate in future 6G wireless systems: Multi-access Edge
Computing (MEC) and Reconfigurable Intelligent Surfaces (RISs). While the
former will bring a powerful information technology environment at the wireless
edge, the latter will enhance communication performance, thanks to the
possibility of adapting wireless propagation as per end users' convenience,
according to specific service requirements. We propose a joint optimization of
radio, computing, and wireless environment reconfiguration through an RIS, with
the goal of enabling low power computation offloading services with reliability
guarantees. Going beyond previous works on this topic, multi-carrier frequency
selective RIS elements' responses and wireless channels are considered. This
opens new challenges in RIS optimization, accounting for frequency dependent
RIS response profiles, which strongly affect RIS-aided wireless links and, as a
consequence, MEC service performance. We formulate an optimization problem
accounting for short and long-term constraints involving device transmit power
allocation across multiple subcarriers and local computing resources, as well
as RIS reconfiguration parameters according to a recently developed Lorentzian
model. Besides a theoretical optimization framework, numerical results show the
effectiveness of the proposed method in enabling low power reliable computation
offloading over RIS-aided frequency selective channels.Comment: IEEE GLOBECOM 202
Control Aspects for Using RIS in Latency-Constrained Mobile Edge Computing
This paper investigates the role and the impact of control operations for
dynamic mobile edge computing (MEC) empowered by Reconfigurable Intelligent
Surfaces (RISs), in which multiple devices offload their computation tasks to
an access point (AP) equipped with an edge server (ES), with the help of the
RIS. While usually ignored, the control aspects related to channel estimation
(CE), resource allocation (RA), and control signaling play a fundamental role
in the user-perceived delay and energy consumption. In general, the higher the
resources involved in the control operations, the higher their reliability;
however, this introduces an overhead, which reduces the number of resources
available for computation offloading, possibly increasing the overall latency
experienced. Conversely, a lower control overhead translates to more resources
available for computation offloading but impacts the CE accuracy and RA
flexibility. This paper establishes a basic framework for integrating the
impact of control operations in the performance evaluation of the RIS-aided MEC
paradigm, clarifying their trade-offs through theoretical analysis and
numerical simulations.Comment: Paper submitted to Asilomar Conference on Signals, Systems, and
Computers 2023. Copyright may be transferred without further notic
Dual-Layer Single-Varactor Driven Reflectarray Cell for Broad-Band Beam-Steering and Frequency Tunable Applications
A dual-layer active reflectarray configuration is proposed for broad-band beam-steering and/or frequency-tunable applications. A unit cell composed by two stacked fixed-size rectangular patches, properly loaded with a single varactor diode, is designed to realize the dynamic phase tuning mechanism. The proposed approach offers wider bandwidths, with respect to the existing varactor-based reflectarray cells, and quite good frequency reconfigurability features, as demanded by several radar or satellite communication applications. An X-band reflectarray cell is fabricated and tested, to prove the effectiveness of the proposed approach, achieving a 318° phase agility within a measured frequency range of about 14.6% with respect to the central design frequency (i.e., 11 GHz). Wideband beam-steering reflectarray designs are demonstrated, showing 1-dB gain bandwidths equal to 9-10%
Dual-Band Dual-Linear Polarization Reflectarray for mmWaves/5G Applications
A dual-band dual-linear polarization reflectarray configuration is developed for future 5G cellular applications. A single layer unit cell including two pairs of miniaturized fractal patches is designed to operate at two distinct frequencies within the Ka-band (27/32 GHz), in a dual-polarization mode. An in-depth analysis of the unit cell behavior is carried out, to demonstrate the total independence between the designed frequency bands and polarizations. The proposed configuration offers a very simply and thin structure, small unit cell sizes, and low losses, while leading to an independent optimization of the phase at each frequency and polarization. A dual-band/dual-polarized reflectarray prototype is designed and tested, thus demonstrating the unit cell flexibility to offer arbitrary beam directions/shapes at each frequency, for both polarizations
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