1,676 research outputs found
Wind risk assessment in urban environments: the case of falling trees during windstorm events in Lisbon
Trees bring many benefits to the urban environment. However, they may also cause hazards to human
population, being the major causes of injuries and infrastructural damage during strong wind events. In the
city of Lisbon, strong winds rather frequently result in tree falls, depending on the season and meteorological
conditions. This paper presents a methodology to analyse tree damage due to strong wind events in urban
environments. Each occurrence has been recorded by the Lisbon Fire Brigade and Rescue Services (Regimento de
Sapadores Bombeiros de Lisboa - RSBL). Information provided by RSBL relating to the period of 1990-2005 was
considered along with hourly wind speed and direction, species, fitossanitary conditions and urban parameters.
To ensure that the fallen trees were caused by strong winds, only days with three or more occurrences of fallen
trees were selected. It was found that in summer, northerly winds are responsible for 11% of tree falls, with
winds from other directions (west, southwest and south) responsible for 5%. From autumn to spring, perturbed
weather conditions originating from the west, southwest and south are responsible for 84% of fallen trees.
The majority of tree falls occurred when wind speed surpassed 7 m/s in the six hours prior to their fall. Some
recommendations to the Civil Protection Agency and the Fire Department are presented to improve the mission
of collecting information. This research is a contribution to the assessment of wind risk in Lisbon
Analytical approach to directed sandpile models on the Apollonian network
We investigate a set of directed sandpile models on the Apollonian network,
which are inspired on the work by Dhar and Ramaswamy (PRL \textbf{63}, 1659
(1989)) for Euclidian lattices. They are characterized by a single parameter
, that restricts the number of neighbors receiving grains from a toppling
node. Due to the geometry of the network, two and three point correlation
functions are amenable to exact treatment, leading to analytical results for
the avalanche distributions in the limit of an infinite system, for .
The exact recurrence expressions for the correlation functions are numerically
iterated to obtain results for finite size systems, when larger values of
are considered. Finally, a detailed description of the local flux properties is
provided by a multifractal scaling analysis.Comment: 7 pages in two-column format, 10 illustrations, 5 figure
Numerical methods to predict vibration serviceability on high frequency stairs
With the increasingly deepen knowledge on structural dynamic behaviour,
nowadays, monumental staircases and their steps are usually designed with high stiffness and
low mass, obtaining high fundamental frequencies, out of the interval of step frequencies
excitable by the human walking. However, neglecting the structure's mass can also result in
with high levels of impulsive responses. Furthermore, often the connection between the
staircase and its steps experience an almost null rotational stiffness, which can cause local
vibrations in steps, where the structural behaviour of two elements is nearly independent from
each other. In this scenario, steps will most likely exhibit undesirable vibrations. Hence,
intending to improve future designs, this paper compares different numerical methods that can
be used to predict human induced vibrations in this type of structures, applying them to a real
staircase with a high local liveness. The results showed that the footfall force time histories
method could realistically predict the vibrations for almost all tested step frequencies, while the
effective impulse could accurately estimate the vibrations for descents at different step
frequencies. The walking models defined by Fourier coefficients only generated close
vibrations for descents at 3.3 Hz.info:eu-repo/semantics/publishedVersio
Human Mobility in Large Cities as a Proxy for Crime
We investigate at the subscale of the neighborhoods of a highly populated
city the incidence of property crimes in terms of both the resident and the
floating population. Our results show that a relevant allometric relation could
only be observed between property crimes and floating population. More
precisely, the evidence of a superlinear behavior indicates that a
disproportional number of property crimes occurs in regions where an increased
flow of people takes place in the city. For comparison, we also found that the
number of crimes of peace disturbance only correlates well, and in a
superlinear fashion too, with the resident population. Our study raises the
interesting possibility that the superlinearity observed in previous studies
[Bettencourt et al., Proc. Natl. Acad. Sci. USA 104, 7301 (2007) and Melo et
al., Sci. Rep. 4, 6239 (2014)] for homicides versus population at the city
scale could have its origin in the fact that the floating population, and not
the resident one, should be taken as the relevant variable determining the
intrinsic microdynamical behavior of the system.Comment: 17 pages, 8 Figure
Intelligent event broker: a complex event processing system in big data contexts
In Big Data contexts, many batch and streaming oriented technologies have emerged to deal with the high valuable sources of events, such as Internet of Things (IoT) platforms, the Web, several types of databases, among others. The huge amount of heterogeneous data being constantly generated by a world of interconnected things and the need for (semi)-automated decision-making processes through Complex Event Processing (CEP) and Machine Learning (ML) have raised the need for innovative architectures capable of processing events in a streamlined, scalable, analytical, and integrated way. This paper presents the Intelligent Event Broker, a CEP system built upon flexible and scalable Big Data techniques and technologies, highlighting its system architecture, software packages, and classes. A demonstration case in Bosch’s Industry 4.0 context is presented, detailing how the system can be used to manage and improve the quality of the manufacturing process, showing its usefulness for solving real-world event-oriented problems.This work has been supported by FCT –Fundação para a Ciência e Tecnologiawithin the Project Scope: UID/CEC/00319/2019 and the Doctoral scholarship PD/BDE/135101/2017. This paper uses icons made by Freepik, from www.flaticon.com
Specific electrical energy consumption and CO2 emissions assessment of agrifood industries in the central region of Portugal
This paper provides a characterization of the electrical energy consumption of agrifood
industries located in the central region of Portugal that use refrigeration systems to ensure the food
safety. The study is based on the result analysis of survey data and energy characteristics of the
participating companies belonging to the following agrifood sectors: meat, dairy, horticultural,
distribution and wine. Through the quantification of energy consumption of companies is possible to
determine the amount of greenhouse gases (GHGs) emissions indexed to its manufacturing process.
Comparing the energy and GHGs emissions indexes of companies of a sector and between sectors is
possible to create reference levels. With the results of this work is possible to rating the companies in
relation to reference levels of energy and GHGs emissions and thus promote the rational use of energy
by the application of practice measures for the improvement of the energy efficiency and the reduction
of GHGs emissions.info:eu-repo/semantics/publishedVersio
The characterization of the specific energy consumption of electricity in the Portuguese sausage industry
The sausage is an ancient food type that is nowadays considered as a delicatessen.
Sausages are categorized within the deli sector as meat sub products. It is a food
product preferred by consumers due to its nutritional value and organoleptic
characteristics (wide range of flavours and textures). There are many types of
sausages, with around 1200 different varieties (according to German
classification), classified into types according to different criteria such as types of
ingredients, consistency, and preparation (raw, cooked, pre-cooked, dry). In the
UK, 196,152 metric tons of sausages were consumed during 2011, valued in 20.4 billion two years before. The
heating and cooling processes during sausage production are indispensable
technologies to ensure both the specific organoleptic characteristics and properties
conservation through time. This paper characterizes the production process and
the energy consumption of sausages processing industry in Portugal (20 industries)
and discusses the average specific energy consumption (SEC) of electricity and its
standard deviation. The average value of this indicator for the sample was 660
kWhe/ton raw material. The energy consumption of this type of industry is mainly
that of electricity (82%). Several electricity savings, estimated at 23.9%, can be
achieved by implementing simple practice measures in the refrigeration systems.info:eu-repo/semantics/publishedVersio
Characterization of the specific electrical energy consumption of agrifood industries in the central region of Portugal
This paper provides a characterization of the electrical energy consumption of agrifood industries located in the central region of Portugal that use refrigeration systems to ensure the food safety. The study is based on the result analysis of survey data and energy characteristics of the participating companies. The agrifood industries included in the survey belong to the following sector: meat, dairy, horticultural, distribution and wine. The comparison of energy indicators for the specific electrical energy consumption of companies of a sector and between sectors is analysed and discussed, providing reference levels for the energy performance of agrifood industries. Since the agrifood sector accounts for high level of energy consumption, the energy performance level knowledge can promote the rational use of energy as well as helping on the decision making of practice measures for the improvement of the energy efficiency.info:eu-repo/semantics/publishedVersio
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