2002
Journal article
Unknown
All-sky astrophysical component separation with fast independent
Maino D., Farusi A., Baccigalupi C., Perrotta F., Banday A. J., Bedini L., Burigana C., De Zotti G., Gorski K. M., Salerno E.
We present a new, fast, algorithm for the separation of astrophysical components superposed in maps of the sky. The algorithm, based on the Independent Component Analysis (ICA) technique, is aimed at recovering both the spatial pattern and the frequency scalings of the emissions from statistically independent astrophysical processes, present along the line-of-sight, from multi-frequency observations, without any a priori assumption on properties of the components to be separated, except that all of them, except possibly one, must have non-Gaussian distributions. The analysis starts from very simple toy-models of the sky emission in order to assess the quality of the reconstruction when inputs are well known and controlled. In particular, we study the dependence of the results of separation conducted on and off the Galactic plane independently, showing that optimal separation is achieved for sky regions where components are smoothly distributed. Then we consider simulated observations of the microwave sky with angular resolution and instrumental noise, supposed to be white and stationary, at the mean nominal levels for the Planck satellite. The angular response function is assumed to be identical at each frequency since this is, up to now, one of the Fast Independent Component Analysis (FASTICA) limitations. We consider several Planck observation channels containing the most important known diffuse signals: the cosmic microwave background (CMB), Galactic synchrotron, dust and freefree emissions. A method for calibrating the reconstructed maps of each component at each frequency has been devised. The spatial patterns of all the components have been recovered on all scales probed by the instrument. In particular, the CMB angular power spectra is recovered at the per cent level up to l_max = 2000. Frequency scalings and normalization have been recovered with better than 1 per cent precision for all the components at frequencies and in sky regions where their signal-to-noise ratio >1.5; the error increases at 10 per cent level for signal-to-noise ratios =1. Runs have been performed on a Pentium III 600-MHz computer; although the computing time slightly depends on the number of channels and components to be recovered, FASTICA typically took about 10 min for all-sky simulations with 3.5-arcmin pixel size. Although the quoted results have been obtained under a number of simplifying assumptions, we conclude that FASTICA is an extremely promising technique for analysing the maps that will be obtained by the forthcoming high-resolution CMB experiments.Source: Monthly notices of the Royal Astronomical Society (Print) 334 (2002): 53–68.
Maino D., Farusi A., Baccigalupi C., Perrotta F., Banday A. J., Bedini L., Burigana C., De Zotti G., Gorski K. M., Salerno E.
We present a new, fast, algorithm for the separation of astrophysical components superposed in maps of the sky. The algorithm, based on the Independent Component Analysis (ICA) technique, is aimed at recovering both the spatial pattern and the frequency scalings of the emissions from statistically independent astrophysical processes, present along the line-of-sight, from multi-frequency observations, without any a priori assumption on properties of the components to be separated, except that all of them, except possibly one, must have non-Gaussian distributions. The analysis starts from very simple toy-models of the sky emission in order to assess the quality of the reconstruction when inputs are well known and controlled. In particular, we study the dependence of the results of separation conducted on and off the Galactic plane independently, showing that optimal separation is achieved for sky regions where components are smoothly distributed. Then we consider simulated observations of the microwave sky with angular resolution and instrumental noise, supposed to be white and stationary, at the mean nominal levels for the Planck satellite. The angular response function is assumed to be identical at each frequency since this is, up to now, one of the Fast Independent Component Analysis (FASTICA) limitations. We consider several Planck observation channels containing the most important known diffuse signals: the cosmic microwave background (CMB), Galactic synchrotron, dust and freefree emissions. A method for calibrating the reconstructed maps of each component at each frequency has been devised. The spatial patterns of all the components have been recovered on all scales probed by the instrument. In particular, the CMB angular power spectra is recovered at the per cent level up to l_max = 2000. Frequency scalings and normalization have been recovered with better than 1 per cent precision for all the components at frequencies and in sky regions where their signal-to-noise ratio >1.5; the error increases at 10 per cent level for signal-to-noise ratios =1. Runs have been performed on a Pentium III 600-MHz computer; although the computing time slightly depends on the number of channels and components to be recovered, FASTICA typically took about 10 min for all-sky simulations with 3.5-arcmin pixel size. Although the quoted results have been obtained under a number of simplifying assumptions, we conclude that FASTICA is an extremely promising technique for analysing the maps that will be obtained by the forthcoming high-resolution CMB experiments.Source: Monthly notices of the Royal Astronomical Society (Print) 334 (2002): 53–68.
See at: CNR ExploRA
2002
Journal article
Unknown
An adaptive approach to achieving hardware and software fault tolerance in a distributed computing environment
Bondavalli A., Chiaradonna S., Di Giandomenico F., Xu J.
This paper focuses on the problem of providing tolerance to both hardware and software faults in independent applications running on a distributed computing environment. Several hybrid-fault-tolerant architectures are identified and proposed. Given the highly varying and dynamic characteristics of the operating environment, solutions are developed mainly exploiting the adaptation property. They are based on the adaptive execution of redundant programs so as to minimise hardware resource consumption and to shorten response time, as much as possible, for a required level of fault tolerance. A method is introduced for evaluating the proposed architectures with respect to reliability, resource utilisation and response time. Examples of quantitative evaluations are also given.Source: Journal of systems architecture 47 (2002): 763–781.
Bondavalli A., Chiaradonna S., Di Giandomenico F., Xu J.
This paper focuses on the problem of providing tolerance to both hardware and software faults in independent applications running on a distributed computing environment. Several hybrid-fault-tolerant architectures are identified and proposed. Given the highly varying and dynamic characteristics of the operating environment, solutions are developed mainly exploiting the adaptation property. They are based on the adaptive execution of redundant programs so as to minimise hardware resource consumption and to shorten response time, as much as possible, for a required level of fault tolerance. A method is introduced for evaluating the proposed architectures with respect to reliability, resource utilisation and response time. Examples of quantitative evaluations are also given.Source: Journal of systems architecture 47 (2002): 763–781.
See at: CNR ExploRA
2002
Journal article
Unknown
An automatic method for the recognition and classification of the A-phases of the cyclic alternating pattern
Navona C., Barcaro U., Bonanni E., Di Martino F., Maestri M., Murri L.
Objective: The aim of the research has been to introduce an automatic method, simple from the mathematical and computational points of view, for the recognition and classification of the A-phases of the Cyclic Alternating Pattern. Method: The automatic method was based on the computation of five descriptors, which were derived from the EEG signal and were able to provide a meaningful data reduction. Each of them corresponded to a different frequency band. Results: The computation of these descriptors, followed by the introduction of two suitable thresholds and of simple criteria for logical discrimination, provided results with were in good agreement with those obtained with visual analysis. The method was versatile and could be applied to the study of other important microstructure phenomena by means of very small adaptations. Conclusions: The simplicity of the method lead to a better understanding and a more precise definition of the visual criteria for the recognition and classification of the microstructure phenomena.Source: Clinical neurophysiology 113 (2002): 1826–1831.
Navona C., Barcaro U., Bonanni E., Di Martino F., Maestri M., Murri L.
Objective: The aim of the research has been to introduce an automatic method, simple from the mathematical and computational points of view, for the recognition and classification of the A-phases of the Cyclic Alternating Pattern. Method: The automatic method was based on the computation of five descriptors, which were derived from the EEG signal and were able to provide a meaningful data reduction. Each of them corresponded to a different frequency band. Results: The computation of these descriptors, followed by the introduction of two suitable thresholds and of simple criteria for logical discrimination, provided results with were in good agreement with those obtained with visual analysis. The method was versatile and could be applied to the study of other important microstructure phenomena by means of very small adaptations. Conclusions: The simplicity of the method lead to a better understanding and a more precise definition of the visual criteria for the recognition and classification of the microstructure phenomena.Source: Clinical neurophysiology 113 (2002): 1826–1831.
See at: CNR ExploRA
2002
Journal article
Unknown
Bandwidth allocation in a multiservice satellite network based on long-term weather forecast scenarios
Bolla R., Celandroni N., Davoli F., Ferro E., Marchese M.
The paper compares two alternative hierarchical bandwidth allocation and admission control schemes suited for the multiservice Ka-band satellite environment, where the attenuation of the transmitted signals due to bad weather conditions has a heavy impact on the systems performance. The two schemes are compared by using data derived from a real case study. The aim is to demonstrate that a high level control mechanism for the assignment of the satellite bandwidth to earth stations, which takes into consideration the rain attenuation probabilities of a certain geographical area, improves the systems performance, with respect to an assignment mechanism insensitive to the geographical fade probabilities.Source: Computer communications 25 (2002): 1037–1046.
Bolla R., Celandroni N., Davoli F., Ferro E., Marchese M.
The paper compares two alternative hierarchical bandwidth allocation and admission control schemes suited for the multiservice Ka-band satellite environment, where the attenuation of the transmitted signals due to bad weather conditions has a heavy impact on the systems performance. The two schemes are compared by using data derived from a real case study. The aim is to demonstrate that a high level control mechanism for the assignment of the satellite bandwidth to earth stations, which takes into consideration the rain attenuation probabilities of a certain geographical area, improves the systems performance, with respect to an assignment mechanism insensitive to the geographical fade probabilities.Source: Computer communications 25 (2002): 1037–1046.
See at: CNR ExploRA
2002
Journal article
Unknown
Computational complexity analysis of a 3D neural network approach to volume matching
Di Bona S., Niemann H., Salvetti O., Wolf M.
Automatic registration of digital images is an important support in the medical field for physicians and surgeons. In fact, comparison of anatomical scan is a fundamental procedure for disease prediction, lesions quantification or for evaluating the results of a therapy. A new proposed approach implements three-dimensional neural networks to match, and hence to register, volumetric data sets of the brain in order to evaluate the differences between two volumes. The high computational complexity of this approach has been improved by implementing a more efficient method to train the networks.Source: Pattern recognition 12 (2002): 63–69.
Di Bona S., Niemann H., Salvetti O., Wolf M.
Automatic registration of digital images is an important support in the medical field for physicians and surgeons. In fact, comparison of anatomical scan is a fundamental procedure for disease prediction, lesions quantification or for evaluating the results of a therapy. A new proposed approach implements three-dimensional neural networks to match, and hence to register, volumetric data sets of the brain in order to evaluate the differences between two volumes. The high computational complexity of this approach has been improved by implementing a more efficient method to train the networks.Source: Pattern recognition 12 (2002): 63–69.
See at: CNR ExploRA
2002
Journal article
Unknown
Degradation identification and model parameter estimation in discontinuity-adaptive visual reconstruction
Tonazzini A., Bedini L.
This paper describes our recent experiences and progress towards an efficient solution of the highly ill-posed and computationally demanding problem of blind and unsupervised visual reconstruction. Our case study is image restoration, i.e. deblurring and denoising. The methodology employed makes reference to edge-preserving regularization. This is formulated both in a fully Bayesian framework, using a MRF image model with explicit, and possibly geometrically constrained, line processes, and in a deterministic framework, where the line process is addressed in an implicit manner, by using a particular MRF model which allows for self-interactions of the line and an adaptive variation of the model parameters. These MRF models have been proven to be efficient in modeling the local regularity properties of most real scenes, as well as the local regularity of object boundaries and intensity discontinuities.In both cases, our approach to this problem attempts to effectively exploit the correlation between intensities and lines, and is based on the assumption that the line process alone, when correctly recovered and located, can retain a good deal of information about both the hyperparameters that best model the whole image and the degradation features. We show that these approaches offer a way to improve both the quality of the reconstructed image, and also the estimates of the degradation and model parameters, and significantly reduce the computational burden of the estimation processes.Source: Advances in imaging and electron physics 120 (2002): 193–284. doi:10.1016/S1076-5670(02)80036-2
DOI: 10.1016/s1076-5670(02)80036-2
Metrics:
Tonazzini A., Bedini L.
This paper describes our recent experiences and progress towards an efficient solution of the highly ill-posed and computationally demanding problem of blind and unsupervised visual reconstruction. Our case study is image restoration, i.e. deblurring and denoising. The methodology employed makes reference to edge-preserving regularization. This is formulated both in a fully Bayesian framework, using a MRF image model with explicit, and possibly geometrically constrained, line processes, and in a deterministic framework, where the line process is addressed in an implicit manner, by using a particular MRF model which allows for self-interactions of the line and an adaptive variation of the model parameters. These MRF models have been proven to be efficient in modeling the local regularity properties of most real scenes, as well as the local regularity of object boundaries and intensity discontinuities.In both cases, our approach to this problem attempts to effectively exploit the correlation between intensities and lines, and is based on the assumption that the line process alone, when correctly recovered and located, can retain a good deal of information about both the hyperparameters that best model the whole image and the degradation features. We show that these approaches offer a way to improve both the quality of the reconstructed image, and also the estimates of the degradation and model parameters, and significantly reduce the computational burden of the estimation processes.Source: Advances in imaging and electron physics 120 (2002): 193–284. doi:10.1016/S1076-5670(02)80036-2
DOI: 10.1016/s1076-5670(02)80036-2
Metrics:
See at:
doi.org 
| biblioproxy.cnr.it | CNR ExploRA
2002
Journal article
Restricted
Diving behaviour differs between incubating and brooding Brunnich's guillemoth's, Uria lomvia
Benvenuti S., Dall'Antonia S., Falk K.
Bird-borne data loggers were used to investigate the foraging strategies of Brünnich's guillemots breeding in a colony in the North Water Polynya: the flight performance and diving activity of incubating birds were compared to those of chick-rearing individuals. No significant differences were recorded between the bird groups in the potential foraging range. Conversely, clear differences were revealed between incubating and chick-rearing birds in diving behaviour. Chick-rearing birds were generally foraging at a significantly greater depth, and spent significantly higher proportions of the time submerged, than brooding individuals. Despite these differences, the estimated average daily energy expenditure of chick-rearing Brünnich's guillemots was only about 6% higher than that during incubation.Source: Polar biology (Print) 25 (2002): 474–478. doi:10.1007/s00300-002-0372-0
DOI: 10.1007/s00300-002-0372-0
Metrics:
Benvenuti S., Dall'Antonia S., Falk K.
Bird-borne data loggers were used to investigate the foraging strategies of Brünnich's guillemots breeding in a colony in the North Water Polynya: the flight performance and diving activity of incubating birds were compared to those of chick-rearing individuals. No significant differences were recorded between the bird groups in the potential foraging range. Conversely, clear differences were revealed between incubating and chick-rearing birds in diving behaviour. Chick-rearing birds were generally foraging at a significantly greater depth, and spent significantly higher proportions of the time submerged, than brooding individuals. Despite these differences, the estimated average daily energy expenditure of chick-rearing Brünnich's guillemots was only about 6% higher than that during incubation.Source: Polar biology (Print) 25 (2002): 474–478. doi:10.1007/s00300-002-0372-0
DOI: 10.1007/s00300-002-0372-0
Metrics:
See at:
Polar Biology | www.scopus.com | CNR ExploRA
2002
Journal article
Open Access
Foraging behaviour of thick-billed murres breeding in different sectors of the North Water polynya: an intercolony comparison
Falk K., Benvenuti S ., Dall'Antonia L., Gilchrist G., Kampp K.
The North Water polynya is an area of open water that occurs year round between northwest Greenland and Canada. Oceanographic conditions differ between the western ('latent heat' polynya type) and extreme eastern ('sensible heat' polynya type) sectors of the polynya, and the effects of this variation on prey availability and foraging conditions for high trophic-level predators are unknown. Thick-billed murres Uria lomvia breed on both sides of the polynya, and we conducted inter-colony comparisons of their foraging ecology. We measured time allocation and foraging efforts of chick-rearing adults using electronic data-loggers which recorded dive profiles and flight activity. Murres on the western side of the North Water polynya foraged at relatively shallow depths and rarely (4.4% of dives) explored depths beyond 70 m. In contrast, murres on the eastern side searched for prey at >70 m in 23% of all dives, and spent a greater share of each trip actively diving. The Canadian birds made foraging trips of longer duration than the Greenland murres, but they also spent more time 'resting' at the sea surface. Rest time at sea was apparently the only time buffer available for increasing foraging effort. The Greenland birds had little room for increasing foraging effort, while the Canadian birds had spare capacity for additional work. Maximum potential foraging ranges were equal at the 2 colonies (75% within 50 km), and the murres had access to approximately equally-sized areas of open sea. We estimate that the density of foraging birds at sea within the 50 km of colonies would be 6.5 times higher on the Canadian side due to the large breeding colony at Coburg Island. Intra-specific competition for food should increase with increasing colony size because the predators may reduce food resources within their foraging range. Nevertheless, the Canadian birds worked less than Greenland murres, indicating a relatively good food availability in the western part of the polynya. However, the higher foraging effort by Greenland murres paid off in a higher chick growth rate, so it remains unclear why the Canadian birds did not also make use of their spare capacity to increase foraging effort. Since high-level zooplankton/fish stock interactions are seldom part of oceanographic studies in the Arctic, seabird foraging behaviour and breeding ecology serve as two of the few indicators of possible local variation within the polynya ecosystem.Source: Marine ecology. Progress series (Halstenbek) 231 (2002): 293–302. doi:10.3354/meps231293
DOI: 10.3354/meps231293
Metrics:
Falk K., Benvenuti S ., Dall'Antonia L., Gilchrist G., Kampp K.
The North Water polynya is an area of open water that occurs year round between northwest Greenland and Canada. Oceanographic conditions differ between the western ('latent heat' polynya type) and extreme eastern ('sensible heat' polynya type) sectors of the polynya, and the effects of this variation on prey availability and foraging conditions for high trophic-level predators are unknown. Thick-billed murres Uria lomvia breed on both sides of the polynya, and we conducted inter-colony comparisons of their foraging ecology. We measured time allocation and foraging efforts of chick-rearing adults using electronic data-loggers which recorded dive profiles and flight activity. Murres on the western side of the North Water polynya foraged at relatively shallow depths and rarely (4.4% of dives) explored depths beyond 70 m. In contrast, murres on the eastern side searched for prey at >70 m in 23% of all dives, and spent a greater share of each trip actively diving. The Canadian birds made foraging trips of longer duration than the Greenland murres, but they also spent more time 'resting' at the sea surface. Rest time at sea was apparently the only time buffer available for increasing foraging effort. The Greenland birds had little room for increasing foraging effort, while the Canadian birds had spare capacity for additional work. Maximum potential foraging ranges were equal at the 2 colonies (75% within 50 km), and the murres had access to approximately equally-sized areas of open sea. We estimate that the density of foraging birds at sea within the 50 km of colonies would be 6.5 times higher on the Canadian side due to the large breeding colony at Coburg Island. Intra-specific competition for food should increase with increasing colony size because the predators may reduce food resources within their foraging range. Nevertheless, the Canadian birds worked less than Greenland murres, indicating a relatively good food availability in the western part of the polynya. However, the higher foraging effort by Greenland murres paid off in a higher chick growth rate, so it remains unclear why the Canadian birds did not also make use of their spare capacity to increase foraging effort. Since high-level zooplankton/fish stock interactions are seldom part of oceanographic studies in the Arctic, seabird foraging behaviour and breeding ecology serve as two of the few indicators of possible local variation within the polynya ecosystem.Source: Marine ecology. Progress series (Halstenbek) 231 (2002): 293–302. doi:10.3354/meps231293
DOI: 10.3354/meps231293
Metrics:
See at:
Marine Ecology Progress Series 
| Marine Ecology Progress Series | CNR ExploRA
2002
Journal article
Open Access
Foraging strategies of the black-legged kittiwake Rissa tridactyla at a North Sea colony: evidence for a maximum foraging range
Daunt F., Benvenuti S., Harris M. P., Dall'Antonia L., Elston D. A., Wanless S.
Black-legged kittiwakes Rissa tridactyla on the Isle of May, southeast Scotland, feed predominantly on the lesser sandeel Ammodytes marinus, an abundant, pelagic fish that is currently the subject of the largest fishery in the North Sea. The population of black-legged kittiwakes on the Isle of May is declining, and the fishery has been implicated. In order to assess this concern, there is an urgent need to improve our understanding of the factors that affect black-legged kittiwake foraging behaviour. During 1999, we carried out a detailed study of the foraging strategies of black-legged kittiwakes using purpose-built activity loggers that allowed us to distinguish 4 key behaviours: travelling flight, foraging flight, presence on the sea surface and attendance at the nest. We used the data to model 2 key aspects of time allocation at sea: (1) the relationship between the travelling time and trip duration and (2) the ratio of time spent actively foraging to time of inactivity on the sea surface at the foraging grounds. We found that a broken-stick model with a flat asymptote was the best fit for the relationship between travelling time and trip duration. Using published flight speeds for this species, we calculate that breeding black-legged kittiwakes on the Isle of May had a maximum range of 73 ± 9 km from the colony. We speculate that this upper limit is dictated by the distribution of prey rather than any energetic constraint on flight costs: a large sand bank complex, known to have high concentrations of lesser sandeels, lies entirely within this range. There was no consistent pattern in the ratio of the active to inactive components of the foraging trip, suggesting that this species exhibits highly flexible foraging strategies at sea, probably reflecting the patchy and unpredictable distribution and availability of its prey. Our findings suggest that the birds are feeding on sandeels at the same time and in the same area as the operations of the sandeel fishery.Source: Marine ecology. Progress series (Halstenbek) 245 (2002): 239–247. doi:10.3354/meps245239
DOI: 10.3354/meps245239
Metrics:
Daunt F., Benvenuti S., Harris M. P., Dall'Antonia L., Elston D. A., Wanless S.
Black-legged kittiwakes Rissa tridactyla on the Isle of May, southeast Scotland, feed predominantly on the lesser sandeel Ammodytes marinus, an abundant, pelagic fish that is currently the subject of the largest fishery in the North Sea. The population of black-legged kittiwakes on the Isle of May is declining, and the fishery has been implicated. In order to assess this concern, there is an urgent need to improve our understanding of the factors that affect black-legged kittiwake foraging behaviour. During 1999, we carried out a detailed study of the foraging strategies of black-legged kittiwakes using purpose-built activity loggers that allowed us to distinguish 4 key behaviours: travelling flight, foraging flight, presence on the sea surface and attendance at the nest. We used the data to model 2 key aspects of time allocation at sea: (1) the relationship between the travelling time and trip duration and (2) the ratio of time spent actively foraging to time of inactivity on the sea surface at the foraging grounds. We found that a broken-stick model with a flat asymptote was the best fit for the relationship between travelling time and trip duration. Using published flight speeds for this species, we calculate that breeding black-legged kittiwakes on the Isle of May had a maximum range of 73 ± 9 km from the colony. We speculate that this upper limit is dictated by the distribution of prey rather than any energetic constraint on flight costs: a large sand bank complex, known to have high concentrations of lesser sandeels, lies entirely within this range. There was no consistent pattern in the ratio of the active to inactive components of the foraging trip, suggesting that this species exhibits highly flexible foraging strategies at sea, probably reflecting the patchy and unpredictable distribution and availability of its prey. Our findings suggest that the birds are feeding on sandeels at the same time and in the same area as the operations of the sandeel fishery.Source: Marine ecology. Progress series (Halstenbek) 245 (2002): 239–247. doi:10.3354/meps245239
DOI: 10.3354/meps245239
Metrics:
See at:
Marine Ecology Progress Series | Marine Ecology Progress Series | CNR ExploRA
2002
Journal article
Open Access
Greedy algorithms for tracking mobile users in special mobility graphs
Olariu S., Pinotti M. C., Wilson L.
An important issue in wireless networks is the design and analysis of strategies for tracking mobile users. Several strategies have been proposed that aim at balancing the cost of updating the user position and the cost of locating a mobile user. The recently proposed reporting center strategy partitions the cellular network into reporting and non-reporting cells, and associates with each reporting cell a set of non-reporting cells, called its vicinity. The users report their position only when they visit a reporting cell. When a call arrives, the user is searched for only in the vicinity of the last visited reporting center. For a given constant "Z", the reporting center problem asks for a set of reporting cells of minimum cardinality such that each selected cell has a vicinity of size at most "Z" so that the update cost is minimized and the locating cost is bounded by "Z". The problem was shown to be "NP"-hard for arbitrary graphs and "Z>=2". The main contribution of this work is to propose algorithms to optimally solve the reporting center problem for vicinity 2 on interval graphs and for arbitrary vicinity on proper interval graph.Source: Discrete applied mathematics 121 (2002): 215–227. doi:10.1016/S0166-218X(01)00238-4
DOI: 10.1016/s0166-218x(01)00238-4
Metrics:
Olariu S., Pinotti M. C., Wilson L.
An important issue in wireless networks is the design and analysis of strategies for tracking mobile users. Several strategies have been proposed that aim at balancing the cost of updating the user position and the cost of locating a mobile user. The recently proposed reporting center strategy partitions the cellular network into reporting and non-reporting cells, and associates with each reporting cell a set of non-reporting cells, called its vicinity. The users report their position only when they visit a reporting cell. When a call arrives, the user is searched for only in the vicinity of the last visited reporting center. For a given constant "Z", the reporting center problem asks for a set of reporting cells of minimum cardinality such that each selected cell has a vicinity of size at most "Z" so that the update cost is minimized and the locating cost is bounded by "Z". The problem was shown to be "NP"-hard for arbitrary graphs and "Z>=2". The main contribution of this work is to propose algorithms to optimally solve the reporting center problem for vicinity 2 on interval graphs and for arbitrary vicinity on proper interval graph.Source: Discrete applied mathematics 121 (2002): 215–227. doi:10.1016/S0166-218X(01)00238-4
DOI: 10.1016/s0166-218x(01)00238-4
Metrics:
See at:
Discrete Applied Mathematics | CNR ExploRA
2002
Journal article
Restricted
Grid programming: some indications where we are headed
Laforenza D.
Grid computing enables the development of large scientific applications on an unprecedented scale. Grid-aware applications, also called meta-applications or multi-disciplinary applications, make use of coupled computational resources that are not available at a single site. In this light, the Grids let scientists solve larger or new problems by pooling together resources that could not be coupled easily before. It is well known that the programmer's productivity in designing and implementing efficient distributed/parallel applications on high-performance computers is still usually a very time-consuming task. Grid computing makes the situation worse. Consequently, the development of Grid programming environments that would enable programmers to efficiently exploit this technology is an important and hot research issue.After an introduction on the main Grid programming issues, this paper will review the most important approaches/projects conducted in this field worldwide.Source: Parallel computing 28 (2002): 1733–1752. doi:10.1016/S0167-8191(02)00186-2
DOI: 10.1016/s0167-8191(02)00186-2
Metrics:
Laforenza D.
Grid computing enables the development of large scientific applications on an unprecedented scale. Grid-aware applications, also called meta-applications or multi-disciplinary applications, make use of coupled computational resources that are not available at a single site. In this light, the Grids let scientists solve larger or new problems by pooling together resources that could not be coupled easily before. It is well known that the programmer's productivity in designing and implementing efficient distributed/parallel applications on high-performance computers is still usually a very time-consuming task. Grid computing makes the situation worse. Consequently, the development of Grid programming environments that would enable programmers to efficiently exploit this technology is an important and hot research issue.After an introduction on the main Grid programming issues, this paper will review the most important approaches/projects conducted in this field worldwide.Source: Parallel computing 28 (2002): 1733–1752. doi:10.1016/S0167-8191(02)00186-2
DOI: 10.1016/s0167-8191(02)00186-2
Metrics:
See at:
Parallel Computing | CNR ExploRA
2002
Journal article
Restricted
Integrated support based on task models for the design, evaluation, and documentation of interactive safety-critical systems: a case study in the air traffic control domain
Paternò F., Santoro C.
This paper presents an approach to using task models in both the design and the evaluation phases of interactive safety-critical applications. We explain how it is possible to use information contained in task models for supporting the design and development of effective user interfaces. Moreover, we show how task models can also support a systematic inspection-based usability assessment by examining possible deviations that can occur while users interact with the system, an important issue especially when coping with the peculiar requirements of safety-critical applications. Such evaluation provides useful technical documentation in order to help users achieve an in-depth understanding of the system and its design rationale. Lastly, a description of the application of our approach to a real case study in the air traffic control domain will illustrate the main features of the proposed method. In particular, we discuss examples taken from an application for air traffic controllers in an aerodrome supported by graphical user interfaces for data-link communications with pilots.Source: International Journal of Systems Science 33 (2002): 513–527. doi:10.1080/00207720210133688
DOI: 10.1080/00207720210133688
Metrics:
Paternò F., Santoro C.
This paper presents an approach to using task models in both the design and the evaluation phases of interactive safety-critical applications. We explain how it is possible to use information contained in task models for supporting the design and development of effective user interfaces. Moreover, we show how task models can also support a systematic inspection-based usability assessment by examining possible deviations that can occur while users interact with the system, an important issue especially when coping with the peculiar requirements of safety-critical applications. Such evaluation provides useful technical documentation in order to help users achieve an in-depth understanding of the system and its design rationale. Lastly, a description of the application of our approach to a real case study in the air traffic control domain will illustrate the main features of the proposed method. In particular, we discuss examples taken from an application for air traffic controllers in an aerodrome supported by graphical user interfaces for data-link communications with pilots.Source: International Journal of Systems Science 33 (2002): 513–527. doi:10.1080/00207720210133688
DOI: 10.1080/00207720210133688
Metrics:
See at:
International Journal of Systems Science | CNR ExploRA
2002
Journal article
Open Access
Load balanced and optimal disk allocation strategy for partial match queries on multidimensional files
Das S. K., Pinotti M. C.
A multidimensional file is one whose data are characterized by several attributes, each specified in a given domain. A partial match query on a multidimensional file extracts all data whose attributes match the values of one or more attributes specified in the query. The disk allocation problem of a multidimensional file F on a database system with multiple disks accessible in parallel is the problem of distributing F among the disks such that the data qualifying for each partial match query are distributed as evenly as possible among the disks of the system. We propose an optimal solution to this problem for multidimensional files with pairwise prime domains based on a large and flexible class of maximum distance separable codes, namely, the redundant residue codes. We also introduce a new family of residue codes, called the redundant nonpairwise prime residue codes, to deal with files whose attribute domains are nonpairwise prime.Source: IEEE transactions on parallel and distributed systems (Print) 13 (2002): 1211–1219. doi:10.1109/TPDS.2002.1158260
DOI: 10.1109/tpds.2002.1158260
Metrics:
Das S. K., Pinotti M. C.
A multidimensional file is one whose data are characterized by several attributes, each specified in a given domain. A partial match query on a multidimensional file extracts all data whose attributes match the values of one or more attributes specified in the query. The disk allocation problem of a multidimensional file F on a database system with multiple disks accessible in parallel is the problem of distributing F among the disks such that the data qualifying for each partial match query are distributed as evenly as possible among the disks of the system. We propose an optimal solution to this problem for multidimensional files with pairwise prime domains based on a large and flexible class of maximum distance separable codes, namely, the redundant residue codes. We also introduce a new family of residue codes, called the redundant nonpairwise prime residue codes, to deal with files whose attribute domains are nonpairwise prime.Source: IEEE transactions on parallel and distributed systems (Print) 13 (2002): 1211–1219. doi:10.1109/TPDS.2002.1158260
DOI: 10.1109/tpds.2002.1158260
Metrics:
See at:
IEEE Transactions on Parallel and Distributed Systems | IEEE Transactions on Parallel and Distributed Systems | CNR ExploRA
2002
Journal article
Open Access
Longitudinal changes of body mass index, spirometry, and diffusion in general population
Bottai M., Pistelli F., Di Pede F. ., Carrozzi L., Baldacci S., Matterelli G., Scognamiglio A., Viegi G.
Aim of this study was to evaluate the effects of BMI changes, over an eight-year follow-up, on longitudinal changes of VC, FVC, FEV1, and DLCO indices in a general population sample of North Italy.To avoid including weight changes possibly related to physical growth, only the 1426 (46% males) adults (over 24 years) with complete follow-up were selected. Median linear regression models were applied to estimate the medians of changes (computed as follow-up minus baseline values) of VC, FVC, FEV1, and DLCO indices as functions of changes of BMI over follow-up period, separately by gender, after considering several potential confounders and effect modifiers. The extent of lung function loss tended to be higher among those who, at baseline, reported greater BMI values. Males experienced larger losses than females (20 and 16 ml FEV1 median reduction for a BMI unit increase in males and females, respectively). Conversely, longitudinal changes of BMI caused a slight and non-significant increase in DLCO values in both sexes. Over an eight-year follow-up, the detrimental effect of gaining weight might be reversible for many adults as most of those who reduced their BMI values also increased their lung function. Overweight patients with ventilatory impairment should be routinely encouraged to lose weight for improving their lung function.Source: European Respiratory Journal 20 (2002): 665–673. doi:10.1183/09031936.02.01282001
DOI: 10.1183/09031936.02.01282001
Metrics:
Bottai M., Pistelli F., Di Pede F. ., Carrozzi L., Baldacci S., Matterelli G., Scognamiglio A., Viegi G.
Aim of this study was to evaluate the effects of BMI changes, over an eight-year follow-up, on longitudinal changes of VC, FVC, FEV1, and DLCO indices in a general population sample of North Italy.To avoid including weight changes possibly related to physical growth, only the 1426 (46% males) adults (over 24 years) with complete follow-up were selected. Median linear regression models were applied to estimate the medians of changes (computed as follow-up minus baseline values) of VC, FVC, FEV1, and DLCO indices as functions of changes of BMI over follow-up period, separately by gender, after considering several potential confounders and effect modifiers. The extent of lung function loss tended to be higher among those who, at baseline, reported greater BMI values. Males experienced larger losses than females (20 and 16 ml FEV1 median reduction for a BMI unit increase in males and females, respectively). Conversely, longitudinal changes of BMI caused a slight and non-significant increase in DLCO values in both sexes. Over an eight-year follow-up, the detrimental effect of gaining weight might be reversible for many adults as most of those who reduced their BMI values also increased their lung function. Overweight patients with ventilatory impairment should be routinely encouraged to lose weight for improving their lung function.Source: European Respiratory Journal 20 (2002): 665–673. doi:10.1183/09031936.02.01282001
DOI: 10.1183/09031936.02.01282001
Metrics:
See at:
European Respiratory Journal | European Respiratory Journal | CNR ExploRA
2002
Journal article
Restricted
Mappings for conflict-free access of paths in bidimensional array, circular lists, and complete trees
Bertossi A. A., Pinotti M. C.
Since the divergence between the processor speed and the memory access rate is progressively increasing, an efficient partition of the main memory into multibanks is useful to improve the overall system performance. The effectiveness of the multibank partition can be degraded by memory conflicts, that occur when there are many references to the same memory bank while accessing the same memory pattern. Therefore, mapping schemes are needed to distribute data in such a way that data can be retrieved via regular patterns without conflicts. In this paper, the problem of conflict-free access of arbitrary paths in bidimensional arrays, circular lists and complete trees is considered for the first time and reduced to variants of graph-coloring problems. Balanced and fast mappings are proposed which require an optimal number of colors (i.e., memory banks). The solution for bidimensional arrays is based on a particular Latin Square. The functions that map an array node or a circular list node to a memory bank can be calculated in constant time. As for complete trees, the mapping of a tree node to a memory bank takes time that grows logarithmically with the number of nodes of the tree. The problem solved here has further application in minimizing the number of frequencies assigned to the stations of a wireless network so as to avoid interference.Source: Journal of parallel and distributed computing (Print) 62 (2002): 1314–1333. doi:10.1006/jpdc.2002.1860
DOI: 10.1006/jpdc.2002.1860
Metrics:
Bertossi A. A., Pinotti M. C.
Since the divergence between the processor speed and the memory access rate is progressively increasing, an efficient partition of the main memory into multibanks is useful to improve the overall system performance. The effectiveness of the multibank partition can be degraded by memory conflicts, that occur when there are many references to the same memory bank while accessing the same memory pattern. Therefore, mapping schemes are needed to distribute data in such a way that data can be retrieved via regular patterns without conflicts. In this paper, the problem of conflict-free access of arbitrary paths in bidimensional arrays, circular lists and complete trees is considered for the first time and reduced to variants of graph-coloring problems. Balanced and fast mappings are proposed which require an optimal number of colors (i.e., memory banks). The solution for bidimensional arrays is based on a particular Latin Square. The functions that map an array node or a circular list node to a memory bank can be calculated in constant time. As for complete trees, the mapping of a tree node to a memory bank takes time that grows logarithmically with the number of nodes of the tree. The problem solved here has further application in minimizing the number of frequencies assigned to the stations of a wireless network so as to avoid interference.Source: Journal of parallel and distributed computing (Print) 62 (2002): 1314–1333. doi:10.1006/jpdc.2002.1860
DOI: 10.1006/jpdc.2002.1860
Metrics:
See at:
Journal of Parallel and Distributed Computing | CNR ExploRA
2002
Journal article
Restricted
Model checking fault tolerant systems
Bernardeschi C., Fantechi A., Gnesi S.
This paper proposes a modelling approach suitable for formalizing fault tolerant systems, taking into account different fault scenarios. Verification of the properties of such systems is then performed using model checking. A general framework for the formal specification and verification of fault tolerant systems is defined starting from these principles, and experience with its application to two case studies is then presented.Source: Software testing, verification & reliability 12 (2002): 251–275. doi:10.1002/stvr.258
DOI: 10.1002/stvr.258
Metrics:
Bernardeschi C., Fantechi A., Gnesi S.
This paper proposes a modelling approach suitable for formalizing fault tolerant systems, taking into account different fault scenarios. Verification of the properties of such systems is then performed using model checking. A general framework for the formal specification and verification of fault tolerant systems is defined starting from these principles, and experience with its application to two case studies is then presented.Source: Software testing, verification & reliability 12 (2002): 251–275. doi:10.1002/stvr.258
DOI: 10.1002/stvr.258
Metrics:
See at:
Software Testing Verification and Reliability | CNR ExploRA
2002
Journal article
Restricted
Nonlinear least Lp-norm filters for nonlinear autoregressive (alfa)-stable processes
Kuruoglu E. E.
The ?-stable distribution family has received great interest recently, due to its ability to successfully model impulsive data. ?-stable distributions have found applications in areas such as radar signal processing, audio restoration, financial time series modeling, and image processing. Various works on linear parametric models with ?-stable innovations have been reported in the literature. However, some recent work has demonstrated that linear models are not in general adequate to capture all characteristics of heavy-tailed data. Moreover, it is known that the optimal minimum dispersion estimator for ?-stable data is not necessarily linear. Therefore, in this paper, we suggest a shift in the interest to nonlinear parametric models for problems involving ?-stable distributions. In particular, we study a simple yet analytic nonlinear random process model namely polynomial autoregressive ?-stable processes. Polynomial autoregression and Volterra filtering have been successful models for some biomedical and seismic signals reflecting their underlying nonlinear generation mechanisms. In this paper, we employ ?-stable processes instead of classical Gaussian distribution as an innovation sequence and arrive at a model capable of describing asymmetric as well as impulsive characteristics. We provide a number of novel adaptive and block type algorithms for the estimation of model parameters of this class of nonlinear processes efficiently. Simulation results on synthetic data demonstrate clearly the superiority of the novel algorithms to classical techniques. The paper concludes with a discussion of the application areas of the techniques developed in the paper, including impulsive noise suppression, nonlinear system identification, target tracking, and nonlinear channel equalization.Source: Digital signal processing (Print) 12 (2002): 119–142. doi:10.1006/dspr.2001.0416
DOI: 10.1006/dspr.2001.0416
Metrics:
Kuruoglu E. E.
The ?-stable distribution family has received great interest recently, due to its ability to successfully model impulsive data. ?-stable distributions have found applications in areas such as radar signal processing, audio restoration, financial time series modeling, and image processing. Various works on linear parametric models with ?-stable innovations have been reported in the literature. However, some recent work has demonstrated that linear models are not in general adequate to capture all characteristics of heavy-tailed data. Moreover, it is known that the optimal minimum dispersion estimator for ?-stable data is not necessarily linear. Therefore, in this paper, we suggest a shift in the interest to nonlinear parametric models for problems involving ?-stable distributions. In particular, we study a simple yet analytic nonlinear random process model namely polynomial autoregressive ?-stable processes. Polynomial autoregression and Volterra filtering have been successful models for some biomedical and seismic signals reflecting their underlying nonlinear generation mechanisms. In this paper, we employ ?-stable processes instead of classical Gaussian distribution as an innovation sequence and arrive at a model capable of describing asymmetric as well as impulsive characteristics. We provide a number of novel adaptive and block type algorithms for the estimation of model parameters of this class of nonlinear processes efficiently. Simulation results on synthetic data demonstrate clearly the superiority of the novel algorithms to classical techniques. The paper concludes with a discussion of the application areas of the techniques developed in the paper, including impulsive noise suppression, nonlinear system identification, target tracking, and nonlinear channel equalization.Source: Digital signal processing (Print) 12 (2002): 119–142. doi:10.1006/dspr.2001.0416
DOI: 10.1006/dspr.2001.0416
Metrics:
See at:
Digital Signal Processing | CNR ExploRA
2002
Journal article
Closed Access
Optimal tree access by elementary and composite templates in parallel memory systems
Auletta V., Das S. K., De Vivo A., Pinotti M. C., Scarano V.
In this paper, we study efficient strategies for mapping onto parallel memory systems complete trees that are accessed by fixed templates (like complete subtrees, paths, or any combinations their of). These mappings are evaluated with respect to the following criteria: (1) the largest number of data items that can be accessed in parallel without memory conflicts; (2) the number of memory conflicts that can occur when accessing templates of size equal to the number of available memory modules, thereby exploiting the full parallelism of the system; (3) the complexity of the memory addressing scheme, i.e., the cost of retrieving the module where a given data item is mapped. We show that there exist trade-offs between these three criteria and the performance of different mapping strategies depends on the emphasis given on each of these criteria. More specifically, we describe an algorithm for mapping complete binary trees of height H onto M memory modules and prove that it achieves the following performance results: (1) conflict-free access to complete subtrees of size K and paths of size N such that N + K - [log K] /spl les/ M; (2) at most 1 conflict in accessing complete subtrees and paths of size M; (3) O(K/M + c) conflicts when accessing a composite template of K nodes consisting of c disjoint subsets, each subset being a complete subtree, or a path or a set of consecutive nodes in a level of the tree.Source: IEEE transactions on parallel and distributed systems (Print) 13 (2002): 399–411. doi:10.1109/71.995820
DOI: 10.1109/71.995820
DOI: 10.1109/ipdps.2001.924972
Metrics:
Auletta V., Das S. K., De Vivo A., Pinotti M. C., Scarano V.
In this paper, we study efficient strategies for mapping onto parallel memory systems complete trees that are accessed by fixed templates (like complete subtrees, paths, or any combinations their of). These mappings are evaluated with respect to the following criteria: (1) the largest number of data items that can be accessed in parallel without memory conflicts; (2) the number of memory conflicts that can occur when accessing templates of size equal to the number of available memory modules, thereby exploiting the full parallelism of the system; (3) the complexity of the memory addressing scheme, i.e., the cost of retrieving the module where a given data item is mapped. We show that there exist trade-offs between these three criteria and the performance of different mapping strategies depends on the emphasis given on each of these criteria. More specifically, we describe an algorithm for mapping complete binary trees of height H onto M memory modules and prove that it achieves the following performance results: (1) conflict-free access to complete subtrees of size K and paths of size N such that N + K - [log K] /spl les/ M; (2) at most 1 conflict in accessing complete subtrees and paths of size M; (3) O(K/M + c) conflicts when accessing a composite template of K nodes consisting of c disjoint subsets, each subset being a complete subtree, or a path or a set of consecutive nodes in a level of the tree.Source: IEEE transactions on parallel and distributed systems (Print) 13 (2002): 399–411. doi:10.1109/71.995820
DOI: 10.1109/71.995820
DOI: 10.1109/ipdps.2001.924972
Metrics:
See at:
IEEE Transactions on Parallel and Distributed Systems | doi.org | CNR ExploRA
2002
Journal article
Restricted
Porosity detection in composite aeronautical structures
Ciliberto A., Cavaccini G., Salvetti O., Chimenti M., Azzarelli L., Bison P. G., Marinetti S., Freda A., Grinzato E.
The paper is devoted to the identification of porosity anomalous levels on composite structures by thermography. The thermal properties mapping of local diffusivity is used for this purpose. Experimental results obtained in different experimental conditions are reported. These results are compared with findings given by Ultrasounds. In particular, enhancement of the defect identification by means of 2D Wavelet transform is presented.Source: Infrared physics & technology 43 (2002): 139–143. doi:10.1016/S1350-4495(02)00132-9
DOI: 10.1016/s1350-4495(02)00132-9
Metrics:
Ciliberto A., Cavaccini G., Salvetti O., Chimenti M., Azzarelli L., Bison P. G., Marinetti S., Freda A., Grinzato E.
The paper is devoted to the identification of porosity anomalous levels on composite structures by thermography. The thermal properties mapping of local diffusivity is used for this purpose. Experimental results obtained in different experimental conditions are reported. These results are compared with findings given by Ultrasounds. In particular, enhancement of the defect identification by means of 2D Wavelet transform is presented.Source: Infrared physics & technology 43 (2002): 139–143. doi:10.1016/S1350-4495(02)00132-9
DOI: 10.1016/s1350-4495(02)00132-9
Metrics:
See at:
Infrared Physics & Technology | CNR ExploRA
2002
Journal article
Restricted
Preventing untestedness in data-flow based testing
Forgacs I., Bertolino A.
A large number of path-oriented testing criteria have been proposed in the last twenty years. Surprisingly, almost all of them suffer from a serious weakness, which is called the untestedness syndrome: even though a criterion is satisfied, some statements of the program under test may remain 'untested', i.e., the observed test output does not depend on them. A new data-flow based testing criterion is introduced which does not suffer from untestedness, called the All Program Function (APF) criterion. Intuitively, it requires that each possible computation to every output statement in a program be covered by some test; but for lots of programs APF would require an infinite number of tests. A second, applicable criterion is thus introduced, derived fromAPF and called the Basic Program Function (BPF) criterion. BPF leaves no statement untested and yields finite test suites. Some examples show the application of BPF and investigate the failure-detection capability of the proposed criterion.Source: Software testing, verification & reliability 12 (2002): 29–58. doi:10.1002/stvr.234
DOI: 10.1002/stvr.234
Metrics:
Forgacs I., Bertolino A.
A large number of path-oriented testing criteria have been proposed in the last twenty years. Surprisingly, almost all of them suffer from a serious weakness, which is called the untestedness syndrome: even though a criterion is satisfied, some statements of the program under test may remain 'untested', i.e., the observed test output does not depend on them. A new data-flow based testing criterion is introduced which does not suffer from untestedness, called the All Program Function (APF) criterion. Intuitively, it requires that each possible computation to every output statement in a program be covered by some test; but for lots of programs APF would require an infinite number of tests. A second, applicable criterion is thus introduced, derived fromAPF and called the Basic Program Function (BPF) criterion. BPF leaves no statement untested and yields finite test suites. Some examples show the application of BPF and investigate the failure-detection capability of the proposed criterion.Source: Software testing, verification & reliability 12 (2002): 29–58. doi:10.1002/stvr.234
DOI: 10.1002/stvr.234
Metrics:
See at:
Software Testing Verification and Reliability | CNR ExploRA