The goal of estimating a soundscape index, aimed at evaluating the contribution of the environmen... more The goal of estimating a soundscape index, aimed at evaluating the contribution of the environmental sound components, is to provide an accurate “acoustic quality” assessment of a complex habitat. Such an index can prove to be a powerful ecological tool associated with both rapid on-site and remote surveys. The soundscape ranking index (SRI), introduced by us recently, can empirically account for the contribution of different sound sources by assigning a positive weight to natural sounds (biophony) and a negative weight to anthropogenic ones. The optimization of such weights was performed by training four machine learning algorithms (decision tree, DT; random forest, RF; adaptive boosting, AdaBoost; support vector machine, SVM) over a relatively small fraction of a labeled sound recording dataset. The sound recordings were taken at 16 sites distributed over an area of approximately 22 hectares at Parco Nord (Northern Park) of the city Milan (Italy). From the audio recordings, we ext...
We have performed a detailed analysis of the soundscape inside an urban park (located in the city... more We have performed a detailed analysis of the soundscape inside an urban park (located in the city of Milan) based on simultaneous sound recordings at 16 locations within the park. The sound sensors were deployed over a regular grid covering an area of about 22 hectares, surrounded by a variety of anthropophonic sources. The recordings span 3.5 h each over a period of four consecutive days. We aimed at determining a soundscape ranking index (SRI) evaluated at each site in the grid by introducing 4 unknown parameters. To this end, a careful aural survey from a single day was performed in order to identify the presence of 19 predefined sound categories within a minute, every 3 minutes of recording. It is found that all SRI values fluctuate considerably within the 70 time intervals considered. The corresponding histograms were used to define a dissimilarity function for each pair of sites. Dissimilarity was found to increase significantly with the inter-site distance in space. Optimal v...
We study pentane depletion using a hybrid plasma system based on a surface dielectric barrier dis... more We study pentane depletion using a hybrid plasma system based on a surface dielectric barrier discharge (SDBD), with and without a catalyst, and as a function of plasma power and alkane concentration. We evaluate pentane decomposition efficiency based on plasma power and quantify the role of the catalyst in the resulting depletion of intermediate products. Analyses of the temporal evolution of pentane and the intermediate decomposition products allow us to estimate the corresponding decomposition rates according to the plasma parameters. We find that depletion efficiency increases as a function of pentane concentration. Furthermore, it is shown that the catalytic processes are responsible for a significant increase in the depletion rates of the intermediate reaction products, thus contributing to the total abatement process of pentane.
The-growing influence of urbanisation on green areas can greatly benefit from passive acoustic mo... more The-growing influence of urbanisation on green areas can greatly benefit from passive acoustic monitoring (PAM) across spatiotemporal continua to provide biodiversity estimation and useful information for conservation planning and development decisions. The capability of eco-acoustic indices to capture different sound features has been harnessed to identify areas within the Parco Nord of Milan, Italy, characterised by different degrees of anthropic disturbance and biophonic activity. For this purpose, we used a network of very low-cost sensors distributed over an area of approximately 20 hectares to highlight areas with different acoustic properties. The audio files analysed in this study were recorded at 16 sites on four sessions during the period 25–29 May (2015), from 06:30 a.m. to 10:00 a.m. Seven eco-acoustic indices, namely Acoustic Complexity Index (ACI), Acoustic Diversity Index (ADI), Acoustic Evenness Index (AEI), Bio-Acoustic Index (BI), Acoustic Entropy Index (H), Normal...
We discuss USA stock market data from 1789 until 2020, focusing our attention on the S&P 500 ... more We discuss USA stock market data from 1789 until 2020, focusing our attention on the S&P 500 index (1957–2020). We find that the data can be split into two periods, (1789–1948) and (1948–2020), displaying roughly 2% and 7% growth rates, respectively. The index variations from each trend appear similar, suggesting some degree of stationarity in market fluctuations. We then correlate market behavior to macroeconomic data, such as world (and USA) population growth and gross domestic product (GDP), on different time horizons. The analysis signals that the S&P 500 might be overvalued, possibly undergoing a series of bubbles, since the 1990s. To understand this behavior, we introduce a model for bubbles, showing that they can be caused by a lack of correlations between stock prices and a virtual market index, the latter calculated self-consistently from the stock prices. We argue that variations, $ \Delta\gamma $, in the "bubble parameter" (or decoupling factor $ \gamma $), are anticorrelated to variations of the Federal Funds Rate (FFR), which may trigger a bubble phenomenon ($ \gamma\to1 $) when persistent rate cuts become too pronounced. The FFR are confronted with the consumer price index (CPI) in the period (1955–2020) as an attempt to complete the picture. Our analyses suggest that the strong departure of the S&P 500 from historical fundamental trends within (1990–2020) may reflect the development of financial anomalies, in part related to monetary policies, which should be carefully addressed in the near future.
A steady regime dominated by intermittent blob and hole structures is identified in the plasma st... more A steady regime dominated by intermittent blob and hole structures is identified in the plasma state of a simple magnetized torus by achieving a quasi-stationary equilibrium using an open magnetic field line configuration. The open helical field line configuration is characterized by a connection length, L_c=2a(B_φ/B_z )≳1750 cm, and pitch ratio, r_B=B_z/B_φ ≲0.01. This is realized by superposing a vertical magnetic fied, B_z, to the toroidal field, B_φ, and the regime is achieved for B_z≤0.4 mT. The combined effect of plasma rotation, arising from a substantial radial electric field, together with an open field line, results in vertically elongated plasma profiles and an asymmetric sheared poloidal flow. The analysis shows the existence of density fluctuations exhibiting universal statistical properties, dominated by non-Gaussian blob events in the edge region and holes in the core plasma, separated by a region ascribed as blob birth zone corresponding to a velocity shear layer. Tw...
We discuss network models as a general and suitable framework for describing the spreading of an ... more We discuss network models as a general and suitable framework for describing the spreading of an infectious disease within a population. We discuss two types of finite random structures as building blocks of the network, one based on percolation concepts and the second one on random tree structures. We study, as is done for the SIR model, the time evolution of the number of susceptible (S), infected (I) and recovered (R) individuals, in the presence of a spreading infectious disease, by incorporating a healing mechanism for infecteds. In addition, we discuss in detail the implementation of lockdowns and how to simulate them. For percolation clusters, we present numerical results based on site percolation on a square lattice, while for random trees we derive new analytical results, which are illustrated in detail with a few examples. It is argued that such hierarchical networks can complement the well-known SIR model in most circumstances. We illustrate these ideas by revisiting USA ...
DYNAMAP, a European Life project, aims at developing a dynamical acoustic map of large urban area... more DYNAMAP, a European Life project, aims at developing a dynamical acoustic map of large urban areas such as the city of Milan based on a limited number of noise monitoring stations. Generally, traffic noise, recorded as time series by field monitoring stations, is affected by the presence of Anomalous Noise Events (ANEs), which are extraneous to the regular vehicle noise. A dedicated algorithm integrated in the DYNAMAP sensors helps the identification and removal of ANEs from the time series in real time. Traffic noise data from the distributed monitoring stations, each one representative of a group of roads sharing similar characteristics (e.g. traffic flow), are used to build-up a dynamic noise map. An evaluation of the reliability of this procedure is performed by comparing the map prediction and infield measurements. Preliminary results of this activity are presented. a) email: roberto.benocci@unimib.it e) email: eduardo.roman@mib.infn.it i) email: falias @salleurl.edu b) email: ...
We review a Dynamap European Life project whose main scope was the design, commissioning, and act... more We review a Dynamap European Life project whose main scope was the design, commissioning, and actual implementation of “real-time” acoustic maps in a district of the city of Milan (District 9, or Z9, composed of about 2000 road stretches), by employing a small number of noise monitoring stations within the urban zone. Dynamap is based on the idea of finding suitable sets of roads displaying similar daily traffic noise behavior, so that one can group them together into single dynamical noise maps. The Dynamap sensor network has been built upon twenty-four monitoring stations, which have been permanently installed in appropriate locations within the pilot zone Z9, by associating four sensors to each one of the six group of roads considered. In order to decide which road stretches belong to a group, a non-acoustic parameter is used, which is obtained from a traffic flow model of the city, developed and tested over the years by the “Enviroment, Mobility and Territory Agency” of Milan (E...
Noise energetic indicators, like Lden, show good correlations with long term annoyance, but shoul... more Noise energetic indicators, like Lden, show good correlations with long term annoyance, but should be supplemented by other parameters describing the sound fluctuations, which are very common in urban areas and negatively impact noise annoyance. Thus, in this paper, the hourly values of continuous equivalent level LAeqh and the intermittency ratio (IR) were both considered to describe the urban road traffic noise, monitored in 90 sites in the city of Milan and covering different types of road, from motorways to local roads. The noise data have been processed by clustering methods to detect similarities and to figure out a criterion to classify the urban sites taking into account both equivalent noise levels and road traffic noise events. Two clusters were obtained and, considering the cluster membership of each site, the decimal logarithm of the day-time (06:00–22:00) traffic flow was used to associate each new road with the clusters. In particular, roads with average day-time hourl...
DYNAMAP, a European Life project, aims at giving a real image of the noise generated by vehicular... more DYNAMAP, a European Life project, aims at giving a real image of the noise generated by vehicular traffic in urban areas developing a dynamic acoustic map based on a limited number of low-cost permanent noise monitoring stations. The system has been implemented in two pilot areas located in the agglomeration of Milan (Italy) and along the Motorway A90 (Rome-Italy). The paper reports the final assessment of the system installed in the pilot area of Milan. Traffic noise data collected by the monitoring stations, each one representative of a number of roads (groups) sharing similar characteristics (e.g., daily traffic flow), are used to build-up a “real-time” noise map. In particular, we focused on the results of the testing campaign (21 sites distributed over the pilot area and 24 h duration of each recording). It allowed evaluating the accuracy and reliability of the system by comparing the predicted noise level of DYNAMAP with field measurements in randomly selected sites. To this e...
2013 First International Symposium on Future Information and Communication Technologies for Ubiquitous HealthCare (Ubi-HealthTech), 2013
The advance in technologies of wireless sensor network (WSN) prompts the development of healthcar... more The advance in technologies of wireless sensor network (WSN) prompts the development of healthcare and, as a result, many wireless healthcare applications are springing up. In many scenarios, it is very common that nodes have the capability of mobility. For example, the nodes in body area networks move together with the movement of users. The MAC protocol in such applications should take the group mobility into account. We introduce a simple MAC protocol which combines TDMA and FDMA to deal with the mobile clusters in wireless sensor networks. Our solution is that the nodes are classified into two different sub-networks according to their mobility. The two sub-networks utilize different frequencies to communicate and then, through the cooperation between the two networks, the uploading of packets sensed is achieved. It is an efficient way to avoid collision and interference brought by a mobile cluster.
2012 IEEE International Conference on Intelligence and Security Informatics, 2012
Abstract We propose a novel approach to detect anomalous network traffic by analyzing communicati... more Abstract We propose a novel approach to detect anomalous network traffic by analyzing communication patterns in time series. The method is based on graph theory concepts such as degree distribution and maximum degree, and we introduce the new concept of dK-2 distance [1]. In our approach, we use traffic dispersion graphs (TDGs) to extract communication structure [2]. By analyzing differences of TDG graphs in time series we are able to detect anomalous events such as botnet command and control communications, ...
Wireless sensor networks (WSNs) are typically constituted by a large number of connected wireless... more Wireless sensor networks (WSNs) are typically constituted by a large number of connected wireless sensors (nodes), generally distributed at random on a given surface area. In such large-scale networks, the desired global system performance is achieved by gathering local information and decisions collected from each individual node. There exist two fundamental global issues on WSNs that we consider here, i.e. full network connectivity and network lifetime. Full connectivity can be obtained either by increasing transmission range, at the expense of consuming higher transmission power, or by increasing the number of sensors, i.e. by increasing network costs. Both of them are closely related to global network lifetime, in the sense that the higher the power consumption or the more sensors deployed the shorter the network lifetime [31]. So the main question is, how can one design large-scale random networks in order to have both global connectivity and maximum network lifetime? Although these questions have been addressed often in the past, a definite, simple predicting algorithm for achieving these goals does not exist so far. In this paper, we aim to discuss such a scheme and confront it with extensive simulations of random networks generated numerically. Specifically, we study the minimum number of nodes required to achieve full network connectivity, and present an analytical formula for estimating it. The results are in very good agreement with the numerical simulations as a function of transmission range. In addition, we study in detail several other statistical properties of large-scale WSNs, such as average path distance, clustering coefficient, degree distribution, etc., also as a function of the transmission range, both qualitatively and quantitatively. We discuss results on how to further improve network energy consumption from the original networks considered by switching off (deleting) some nodes at random but keeping whole network connectivity. The present results are expected to be useful for the design of more efficient large-scale WSNs.
Plasma-assisted supersonic jet deposition (PA-SJD) is a precise technique for the fabrication of ... more Plasma-assisted supersonic jet deposition (PA-SJD) is a precise technique for the fabrication of thin films with a desired nanostructured morphology. In this work, we used quadrupole mass spectrometry of the neutral species in the jet and the extensive characterization of TiO2 films to improve our understanding of the relationship between jet chemistry and film properties. To do this, an organo–metallic precursor (titanium tetra–isopropoxide or TTIP) was first dissociated using a reactive argon–oxygen plasma in a vacuum chamber and then delivered into a second, lower pressure chamber through a nozzle. The pressure difference between the two chambers generated a supersonic jet carrying nanoparticles of TiO2 in the second chamber, and these were deposited onto the surface of a substrate located few centimeters away from the nozzle. The nucleation/aggregation of the jet nanoparticles could be accurately tuned by a suitable choice of control parameters in order to produce the required s...
The goal of estimating a soundscape index, aimed at evaluating the contribution of the environmen... more The goal of estimating a soundscape index, aimed at evaluating the contribution of the environmental sound components, is to provide an accurate “acoustic quality” assessment of a complex habitat. Such an index can prove to be a powerful ecological tool associated with both rapid on-site and remote surveys. The soundscape ranking index (SRI), introduced by us recently, can empirically account for the contribution of different sound sources by assigning a positive weight to natural sounds (biophony) and a negative weight to anthropogenic ones. The optimization of such weights was performed by training four machine learning algorithms (decision tree, DT; random forest, RF; adaptive boosting, AdaBoost; support vector machine, SVM) over a relatively small fraction of a labeled sound recording dataset. The sound recordings were taken at 16 sites distributed over an area of approximately 22 hectares at Parco Nord (Northern Park) of the city Milan (Italy). From the audio recordings, we ext...
We have performed a detailed analysis of the soundscape inside an urban park (located in the city... more We have performed a detailed analysis of the soundscape inside an urban park (located in the city of Milan) based on simultaneous sound recordings at 16 locations within the park. The sound sensors were deployed over a regular grid covering an area of about 22 hectares, surrounded by a variety of anthropophonic sources. The recordings span 3.5 h each over a period of four consecutive days. We aimed at determining a soundscape ranking index (SRI) evaluated at each site in the grid by introducing 4 unknown parameters. To this end, a careful aural survey from a single day was performed in order to identify the presence of 19 predefined sound categories within a minute, every 3 minutes of recording. It is found that all SRI values fluctuate considerably within the 70 time intervals considered. The corresponding histograms were used to define a dissimilarity function for each pair of sites. Dissimilarity was found to increase significantly with the inter-site distance in space. Optimal v...
We study pentane depletion using a hybrid plasma system based on a surface dielectric barrier dis... more We study pentane depletion using a hybrid plasma system based on a surface dielectric barrier discharge (SDBD), with and without a catalyst, and as a function of plasma power and alkane concentration. We evaluate pentane decomposition efficiency based on plasma power and quantify the role of the catalyst in the resulting depletion of intermediate products. Analyses of the temporal evolution of pentane and the intermediate decomposition products allow us to estimate the corresponding decomposition rates according to the plasma parameters. We find that depletion efficiency increases as a function of pentane concentration. Furthermore, it is shown that the catalytic processes are responsible for a significant increase in the depletion rates of the intermediate reaction products, thus contributing to the total abatement process of pentane.
The-growing influence of urbanisation on green areas can greatly benefit from passive acoustic mo... more The-growing influence of urbanisation on green areas can greatly benefit from passive acoustic monitoring (PAM) across spatiotemporal continua to provide biodiversity estimation and useful information for conservation planning and development decisions. The capability of eco-acoustic indices to capture different sound features has been harnessed to identify areas within the Parco Nord of Milan, Italy, characterised by different degrees of anthropic disturbance and biophonic activity. For this purpose, we used a network of very low-cost sensors distributed over an area of approximately 20 hectares to highlight areas with different acoustic properties. The audio files analysed in this study were recorded at 16 sites on four sessions during the period 25–29 May (2015), from 06:30 a.m. to 10:00 a.m. Seven eco-acoustic indices, namely Acoustic Complexity Index (ACI), Acoustic Diversity Index (ADI), Acoustic Evenness Index (AEI), Bio-Acoustic Index (BI), Acoustic Entropy Index (H), Normal...
We discuss USA stock market data from 1789 until 2020, focusing our attention on the S&P 500 ... more We discuss USA stock market data from 1789 until 2020, focusing our attention on the S&P 500 index (1957–2020). We find that the data can be split into two periods, (1789–1948) and (1948–2020), displaying roughly 2% and 7% growth rates, respectively. The index variations from each trend appear similar, suggesting some degree of stationarity in market fluctuations. We then correlate market behavior to macroeconomic data, such as world (and USA) population growth and gross domestic product (GDP), on different time horizons. The analysis signals that the S&P 500 might be overvalued, possibly undergoing a series of bubbles, since the 1990s. To understand this behavior, we introduce a model for bubbles, showing that they can be caused by a lack of correlations between stock prices and a virtual market index, the latter calculated self-consistently from the stock prices. We argue that variations, $ \Delta\gamma $, in the "bubble parameter" (or decoupling factor $ \gamma $), are anticorrelated to variations of the Federal Funds Rate (FFR), which may trigger a bubble phenomenon ($ \gamma\to1 $) when persistent rate cuts become too pronounced. The FFR are confronted with the consumer price index (CPI) in the period (1955–2020) as an attempt to complete the picture. Our analyses suggest that the strong departure of the S&P 500 from historical fundamental trends within (1990–2020) may reflect the development of financial anomalies, in part related to monetary policies, which should be carefully addressed in the near future.
A steady regime dominated by intermittent blob and hole structures is identified in the plasma st... more A steady regime dominated by intermittent blob and hole structures is identified in the plasma state of a simple magnetized torus by achieving a quasi-stationary equilibrium using an open magnetic field line configuration. The open helical field line configuration is characterized by a connection length, L_c=2a(B_φ/B_z )≳1750 cm, and pitch ratio, r_B=B_z/B_φ ≲0.01. This is realized by superposing a vertical magnetic fied, B_z, to the toroidal field, B_φ, and the regime is achieved for B_z≤0.4 mT. The combined effect of plasma rotation, arising from a substantial radial electric field, together with an open field line, results in vertically elongated plasma profiles and an asymmetric sheared poloidal flow. The analysis shows the existence of density fluctuations exhibiting universal statistical properties, dominated by non-Gaussian blob events in the edge region and holes in the core plasma, separated by a region ascribed as blob birth zone corresponding to a velocity shear layer. Tw...
We discuss network models as a general and suitable framework for describing the spreading of an ... more We discuss network models as a general and suitable framework for describing the spreading of an infectious disease within a population. We discuss two types of finite random structures as building blocks of the network, one based on percolation concepts and the second one on random tree structures. We study, as is done for the SIR model, the time evolution of the number of susceptible (S), infected (I) and recovered (R) individuals, in the presence of a spreading infectious disease, by incorporating a healing mechanism for infecteds. In addition, we discuss in detail the implementation of lockdowns and how to simulate them. For percolation clusters, we present numerical results based on site percolation on a square lattice, while for random trees we derive new analytical results, which are illustrated in detail with a few examples. It is argued that such hierarchical networks can complement the well-known SIR model in most circumstances. We illustrate these ideas by revisiting USA ...
DYNAMAP, a European Life project, aims at developing a dynamical acoustic map of large urban area... more DYNAMAP, a European Life project, aims at developing a dynamical acoustic map of large urban areas such as the city of Milan based on a limited number of noise monitoring stations. Generally, traffic noise, recorded as time series by field monitoring stations, is affected by the presence of Anomalous Noise Events (ANEs), which are extraneous to the regular vehicle noise. A dedicated algorithm integrated in the DYNAMAP sensors helps the identification and removal of ANEs from the time series in real time. Traffic noise data from the distributed monitoring stations, each one representative of a group of roads sharing similar characteristics (e.g. traffic flow), are used to build-up a dynamic noise map. An evaluation of the reliability of this procedure is performed by comparing the map prediction and infield measurements. Preliminary results of this activity are presented. a) email: roberto.benocci@unimib.it e) email: eduardo.roman@mib.infn.it i) email: falias @salleurl.edu b) email: ...
We review a Dynamap European Life project whose main scope was the design, commissioning, and act... more We review a Dynamap European Life project whose main scope was the design, commissioning, and actual implementation of “real-time” acoustic maps in a district of the city of Milan (District 9, or Z9, composed of about 2000 road stretches), by employing a small number of noise monitoring stations within the urban zone. Dynamap is based on the idea of finding suitable sets of roads displaying similar daily traffic noise behavior, so that one can group them together into single dynamical noise maps. The Dynamap sensor network has been built upon twenty-four monitoring stations, which have been permanently installed in appropriate locations within the pilot zone Z9, by associating four sensors to each one of the six group of roads considered. In order to decide which road stretches belong to a group, a non-acoustic parameter is used, which is obtained from a traffic flow model of the city, developed and tested over the years by the “Enviroment, Mobility and Territory Agency” of Milan (E...
Noise energetic indicators, like Lden, show good correlations with long term annoyance, but shoul... more Noise energetic indicators, like Lden, show good correlations with long term annoyance, but should be supplemented by other parameters describing the sound fluctuations, which are very common in urban areas and negatively impact noise annoyance. Thus, in this paper, the hourly values of continuous equivalent level LAeqh and the intermittency ratio (IR) were both considered to describe the urban road traffic noise, monitored in 90 sites in the city of Milan and covering different types of road, from motorways to local roads. The noise data have been processed by clustering methods to detect similarities and to figure out a criterion to classify the urban sites taking into account both equivalent noise levels and road traffic noise events. Two clusters were obtained and, considering the cluster membership of each site, the decimal logarithm of the day-time (06:00–22:00) traffic flow was used to associate each new road with the clusters. In particular, roads with average day-time hourl...
DYNAMAP, a European Life project, aims at giving a real image of the noise generated by vehicular... more DYNAMAP, a European Life project, aims at giving a real image of the noise generated by vehicular traffic in urban areas developing a dynamic acoustic map based on a limited number of low-cost permanent noise monitoring stations. The system has been implemented in two pilot areas located in the agglomeration of Milan (Italy) and along the Motorway A90 (Rome-Italy). The paper reports the final assessment of the system installed in the pilot area of Milan. Traffic noise data collected by the monitoring stations, each one representative of a number of roads (groups) sharing similar characteristics (e.g., daily traffic flow), are used to build-up a “real-time” noise map. In particular, we focused on the results of the testing campaign (21 sites distributed over the pilot area and 24 h duration of each recording). It allowed evaluating the accuracy and reliability of the system by comparing the predicted noise level of DYNAMAP with field measurements in randomly selected sites. To this e...
2013 First International Symposium on Future Information and Communication Technologies for Ubiquitous HealthCare (Ubi-HealthTech), 2013
The advance in technologies of wireless sensor network (WSN) prompts the development of healthcar... more The advance in technologies of wireless sensor network (WSN) prompts the development of healthcare and, as a result, many wireless healthcare applications are springing up. In many scenarios, it is very common that nodes have the capability of mobility. For example, the nodes in body area networks move together with the movement of users. The MAC protocol in such applications should take the group mobility into account. We introduce a simple MAC protocol which combines TDMA and FDMA to deal with the mobile clusters in wireless sensor networks. Our solution is that the nodes are classified into two different sub-networks according to their mobility. The two sub-networks utilize different frequencies to communicate and then, through the cooperation between the two networks, the uploading of packets sensed is achieved. It is an efficient way to avoid collision and interference brought by a mobile cluster.
2012 IEEE International Conference on Intelligence and Security Informatics, 2012
Abstract We propose a novel approach to detect anomalous network traffic by analyzing communicati... more Abstract We propose a novel approach to detect anomalous network traffic by analyzing communication patterns in time series. The method is based on graph theory concepts such as degree distribution and maximum degree, and we introduce the new concept of dK-2 distance [1]. In our approach, we use traffic dispersion graphs (TDGs) to extract communication structure [2]. By analyzing differences of TDG graphs in time series we are able to detect anomalous events such as botnet command and control communications, ...
Wireless sensor networks (WSNs) are typically constituted by a large number of connected wireless... more Wireless sensor networks (WSNs) are typically constituted by a large number of connected wireless sensors (nodes), generally distributed at random on a given surface area. In such large-scale networks, the desired global system performance is achieved by gathering local information and decisions collected from each individual node. There exist two fundamental global issues on WSNs that we consider here, i.e. full network connectivity and network lifetime. Full connectivity can be obtained either by increasing transmission range, at the expense of consuming higher transmission power, or by increasing the number of sensors, i.e. by increasing network costs. Both of them are closely related to global network lifetime, in the sense that the higher the power consumption or the more sensors deployed the shorter the network lifetime [31]. So the main question is, how can one design large-scale random networks in order to have both global connectivity and maximum network lifetime? Although these questions have been addressed often in the past, a definite, simple predicting algorithm for achieving these goals does not exist so far. In this paper, we aim to discuss such a scheme and confront it with extensive simulations of random networks generated numerically. Specifically, we study the minimum number of nodes required to achieve full network connectivity, and present an analytical formula for estimating it. The results are in very good agreement with the numerical simulations as a function of transmission range. In addition, we study in detail several other statistical properties of large-scale WSNs, such as average path distance, clustering coefficient, degree distribution, etc., also as a function of the transmission range, both qualitatively and quantitatively. We discuss results on how to further improve network energy consumption from the original networks considered by switching off (deleting) some nodes at random but keeping whole network connectivity. The present results are expected to be useful for the design of more efficient large-scale WSNs.
Plasma-assisted supersonic jet deposition (PA-SJD) is a precise technique for the fabrication of ... more Plasma-assisted supersonic jet deposition (PA-SJD) is a precise technique for the fabrication of thin films with a desired nanostructured morphology. In this work, we used quadrupole mass spectrometry of the neutral species in the jet and the extensive characterization of TiO2 films to improve our understanding of the relationship between jet chemistry and film properties. To do this, an organo–metallic precursor (titanium tetra–isopropoxide or TTIP) was first dissociated using a reactive argon–oxygen plasma in a vacuum chamber and then delivered into a second, lower pressure chamber through a nozzle. The pressure difference between the two chambers generated a supersonic jet carrying nanoparticles of TiO2 in the second chamber, and these were deposited onto the surface of a substrate located few centimeters away from the nozzle. The nucleation/aggregation of the jet nanoparticles could be accurately tuned by a suitable choice of control parameters in order to produce the required s...
Uploads
Papers