The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Andrew T Campbell - One of the best experts on this subject based on the ideXlab platform.
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Coda congestion detection and avoidance in sensor networks
International Conference on Embedded Networked Sensor Systems, 2003Co-Authors: Chiehyih Wan, Shane B Eisenman, Andrew T CampbellAbstract:Event-driven sensor networks operate under an idle or light load and then suddenly become active in response to a detected or monitored event. The transport of event impulses is likely to lead to varying degrees of congestion in the network depending on the sensing application. It is during these periods of event impulses that the likelihood of congestion is greatest and the information in transit of most importance to users. To address this challenge we propose an energy efficient congestion control scheme for sensor networks called Coda (COngestion Detection and Avoidance) that comprises three mechanisms: (i) receiver-based congestion detection; (ii) open-loop hop-by-hop backpressure; and (iii) closed-loop multi-source regulation. We present the detailed design, implementation, and evaluation of Coda using simulation and experimentation. We define two important performance metrics (i.e., energy tax and fidelity penalty) to evaluate the impact of Coda on the performance of sensing applications. We discuss the performance benefits and practical engineering challenges of implementing Coda in an experimental sensor network testbed based on Berkeley motes using CSMA. Simulation results indicate that Coda significantly improves the performance of data dissemination applications such as directed diffusion by mitigating hotspots, and reducing the energy tax with low fidelity penalty on sensing applications. We also demonstrate that Coda is capable of responding to a number of congestion scenarios that we believe will be prevalent as the deployment of these networks accelerates.
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Coda congestion detection and avoidance in sensor networks
International Conference on Embedded Networked Sensor Systems, 2003Co-Authors: Shane B Eisenman, Andrew T CampbellAbstract:Event-driven sensor networks operate under an idle or light load and then suddenly become active in response to a detected or monitored event. The transport of event impulses is likely to lead to varying degrees of congestion in the network depending on the sensing application. It is during these periods of event impulses that the likelihood of congestion is greatest and the information in transit of most importance to users. To address this challenge we propose an energy efficient congestion control scheme for sensor networks called Coda (COngestion Detection and Avoidance) that comprises three mechanisms: (i) receiver-based congestion detection; (ii) open-loop hop-by-hop backpressure; and (iii) closed-loop multi-source regulation. We present the detailed design, implementation, and evaluation of Coda using simulation and experimentation. We define two important performance metrics (i.e., energy tax and fidelity penalty) to evaluate the impact of Coda on the performance of sensing applications. We discuss the performance benefits and practical engineering challenges of implementing Coda in an experimental sensor network testbed based on Berkeley motes using CSMA. Simulation results indicate that Coda significantly improves the performance of data dissemination applications such as directed diffusion by mitigating hotspots, and reducing the energy tax with low fidelity penalty on sensing applications. We also demonstrate that Coda is capable of responding to a number of congestion scenarios that we believe will be prevalent as the deployment of these networks accelerates.
Luke Rendell - One of the best experts on this subject based on the ideXlab platform.
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individual unit and vocal clan level identity cues in sperm whale Codas
Royal Society Open Science, 2016Co-Authors: Hal Whitehead, Shane Gero, Luke RendellAbstract:The ‘social complexity hypothesis’ suggests that complex social structure is a driver of diversity in animal communication systems. Sperm whales have a hierarchically structured society in which the largest affiliative structures, the vocal clans, are marked on ocean-basin scales by culturally transmitted dialects of acoustic signals known as ‘Codas’. We examined variation in Coda repertoires among both individual whales and social units—the basic element of sperm whale society—using data from nine Caribbean social units across six years. Codas were assigned to individuals using photo-identification and acoustic size measurement, and we calculated similarity between repertoires using both continuous and categorical methods. We identified 21 Coda types. Two of those (‘1+1+3’ and ‘5R1’) made up 65% of the Codas recorded, were shared across all units and have dominated repertoires in this population for at least 30 years. Individuals appear to differ in the way they produce ‘5R1’ but not ‘1+1+3’ Coda. Units use distinct 4-click Coda types which contribute to making unit repertoires distinctive. Our results support the social complexity hypothesis in a marine species as different patterns of variation between Coda types suggest divergent functions, perhaps representing selection for identity signals at several levels of social structure.
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individually distinctive acoustic features in sperm whale Codas
Animal Behaviour, 2011Co-Authors: Ricardo Antunes, Hal Whitehead, Tyler M Schulz, Shane Gero, Jonathan Gordon, Luke RendellAbstract:Social animals may develop behavioural strategies that are based on individualized relationships among members. In these cases, there might be selection pressures for the development of identity signals and mechanisms that allow discrimination and recognition of particular individuals. Female sperm whales, Physeter macrocephalus, live in long-term, stable social units. Differential interactions among unit members suggest the need for an individual discrimination system. Sperm whales produce stereotyped series of click sounds called Codas, which are thought to be used for communication. Although Codas were initially proposed as individual signatures, later studies did not support this hypothesis. Using linear discriminant functions and Mantel tests, we tested variation within Coda types as a means for individual identification, using recordings where Codas were assigned to individual whales. While most Coda types showed no indication of individual-specific information, individual differences that were robust to variation among recording days were found in the 5 Regular Coda type. Differences in individual-specific information between Coda types suggest that different Coda types may have distinct functions.
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overlapping and matching of Codas in vocal interactions between sperm whales insights into communication function
Animal Behaviour, 2008Co-Authors: Tyler M Schulz, Hal Whitehead, Shane Gero, Luke RendellAbstract:Many animals engage in dyadic vocal exchanges. Studying the patterns of vocal output and spatial arrangement of individuals in these interactions can often reveal information concerning their function. Sperm whales, Physeter macrocephalus, frequently exchange short sequences of clicks, termed Codas, in social contexts. We analysed the Coda vocalizations of sperm whale social units encountered in two different oceans to test hypotheses about how Coda exchanges are organized. We also used a dynamic recording array to estimate the spatial scale of these vocal interactions. Coda production was influenced by the timing and types of Codas produced by other unit members, resulting in the production of duet-like sequences of Coda exchanges between pairs of whales. Codas were more likely to be made within 2 s of another Coda than expected by chance, and whales were more likely to match previously produced Codas than expected by chance, although matching appeared to be largely a result of the matching of one particular Coda type within each social unit. Patterns of overlapping and matching exchanges did not seem to be correlated with relatedness or social affiliation. These exchanges occurred over a range of spatial scales, and are thus likely to be functional both between whales that are near and between those that are comparatively far from one another. The context of these exchanges, reciprocity in Coda overlapping, and the sequencing of exchanges into duet-like chains all suggest that Coda overlapping and matching function to reinforce social bonds between whales.
Hal Whitehead - One of the best experts on this subject based on the ideXlab platform.
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individual unit and vocal clan level identity cues in sperm whale Codas
Royal Society Open Science, 2016Co-Authors: Hal Whitehead, Shane Gero, Luke RendellAbstract:The ‘social complexity hypothesis’ suggests that complex social structure is a driver of diversity in animal communication systems. Sperm whales have a hierarchically structured society in which the largest affiliative structures, the vocal clans, are marked on ocean-basin scales by culturally transmitted dialects of acoustic signals known as ‘Codas’. We examined variation in Coda repertoires among both individual whales and social units—the basic element of sperm whale society—using data from nine Caribbean social units across six years. Codas were assigned to individuals using photo-identification and acoustic size measurement, and we calculated similarity between repertoires using both continuous and categorical methods. We identified 21 Coda types. Two of those (‘1+1+3’ and ‘5R1’) made up 65% of the Codas recorded, were shared across all units and have dominated repertoires in this population for at least 30 years. Individuals appear to differ in the way they produce ‘5R1’ but not ‘1+1+3’ Coda. Units use distinct 4-click Coda types which contribute to making unit repertoires distinctive. Our results support the social complexity hypothesis in a marine species as different patterns of variation between Coda types suggest divergent functions, perhaps representing selection for identity signals at several levels of social structure.
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individually distinctive acoustic features in sperm whale Codas
Animal Behaviour, 2011Co-Authors: Ricardo Antunes, Hal Whitehead, Tyler M Schulz, Shane Gero, Jonathan Gordon, Luke RendellAbstract:Social animals may develop behavioural strategies that are based on individualized relationships among members. In these cases, there might be selection pressures for the development of identity signals and mechanisms that allow discrimination and recognition of particular individuals. Female sperm whales, Physeter macrocephalus, live in long-term, stable social units. Differential interactions among unit members suggest the need for an individual discrimination system. Sperm whales produce stereotyped series of click sounds called Codas, which are thought to be used for communication. Although Codas were initially proposed as individual signatures, later studies did not support this hypothesis. Using linear discriminant functions and Mantel tests, we tested variation within Coda types as a means for individual identification, using recordings where Codas were assigned to individual whales. While most Coda types showed no indication of individual-specific information, individual differences that were robust to variation among recording days were found in the 5 Regular Coda type. Differences in individual-specific information between Coda types suggest that different Coda types may have distinct functions.
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overlapping and matching of Codas in vocal interactions between sperm whales insights into communication function
Animal Behaviour, 2008Co-Authors: Tyler M Schulz, Hal Whitehead, Shane Gero, Luke RendellAbstract:Many animals engage in dyadic vocal exchanges. Studying the patterns of vocal output and spatial arrangement of individuals in these interactions can often reveal information concerning their function. Sperm whales, Physeter macrocephalus, frequently exchange short sequences of clicks, termed Codas, in social contexts. We analysed the Coda vocalizations of sperm whale social units encountered in two different oceans to test hypotheses about how Coda exchanges are organized. We also used a dynamic recording array to estimate the spatial scale of these vocal interactions. Coda production was influenced by the timing and types of Codas produced by other unit members, resulting in the production of duet-like sequences of Coda exchanges between pairs of whales. Codas were more likely to be made within 2 s of another Coda than expected by chance, and whales were more likely to match previously produced Codas than expected by chance, although matching appeared to be largely a result of the matching of one particular Coda type within each social unit. Patterns of overlapping and matching exchanges did not seem to be correlated with relatedness or social affiliation. These exchanges occurred over a range of spatial scales, and are thus likely to be functional both between whales that are near and between those that are comparatively far from one another. The context of these exchanges, reciprocity in Coda overlapping, and the sequencing of exchanges into duet-like chains all suggest that Coda overlapping and matching function to reinforce social bonds between whales.
Shane Gero - One of the best experts on this subject based on the ideXlab platform.
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individual unit and vocal clan level identity cues in sperm whale Codas
Royal Society Open Science, 2016Co-Authors: Hal Whitehead, Shane Gero, Luke RendellAbstract:The ‘social complexity hypothesis’ suggests that complex social structure is a driver of diversity in animal communication systems. Sperm whales have a hierarchically structured society in which the largest affiliative structures, the vocal clans, are marked on ocean-basin scales by culturally transmitted dialects of acoustic signals known as ‘Codas’. We examined variation in Coda repertoires among both individual whales and social units—the basic element of sperm whale society—using data from nine Caribbean social units across six years. Codas were assigned to individuals using photo-identification and acoustic size measurement, and we calculated similarity between repertoires using both continuous and categorical methods. We identified 21 Coda types. Two of those (‘1+1+3’ and ‘5R1’) made up 65% of the Codas recorded, were shared across all units and have dominated repertoires in this population for at least 30 years. Individuals appear to differ in the way they produce ‘5R1’ but not ‘1+1+3’ Coda. Units use distinct 4-click Coda types which contribute to making unit repertoires distinctive. Our results support the social complexity hypothesis in a marine species as different patterns of variation between Coda types suggest divergent functions, perhaps representing selection for identity signals at several levels of social structure.
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individually distinctive acoustic features in sperm whale Codas
Animal Behaviour, 2011Co-Authors: Ricardo Antunes, Hal Whitehead, Tyler M Schulz, Shane Gero, Jonathan Gordon, Luke RendellAbstract:Social animals may develop behavioural strategies that are based on individualized relationships among members. In these cases, there might be selection pressures for the development of identity signals and mechanisms that allow discrimination and recognition of particular individuals. Female sperm whales, Physeter macrocephalus, live in long-term, stable social units. Differential interactions among unit members suggest the need for an individual discrimination system. Sperm whales produce stereotyped series of click sounds called Codas, which are thought to be used for communication. Although Codas were initially proposed as individual signatures, later studies did not support this hypothesis. Using linear discriminant functions and Mantel tests, we tested variation within Coda types as a means for individual identification, using recordings where Codas were assigned to individual whales. While most Coda types showed no indication of individual-specific information, individual differences that were robust to variation among recording days were found in the 5 Regular Coda type. Differences in individual-specific information between Coda types suggest that different Coda types may have distinct functions.
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overlapping and matching of Codas in vocal interactions between sperm whales insights into communication function
Animal Behaviour, 2008Co-Authors: Tyler M Schulz, Hal Whitehead, Shane Gero, Luke RendellAbstract:Many animals engage in dyadic vocal exchanges. Studying the patterns of vocal output and spatial arrangement of individuals in these interactions can often reveal information concerning their function. Sperm whales, Physeter macrocephalus, frequently exchange short sequences of clicks, termed Codas, in social contexts. We analysed the Coda vocalizations of sperm whale social units encountered in two different oceans to test hypotheses about how Coda exchanges are organized. We also used a dynamic recording array to estimate the spatial scale of these vocal interactions. Coda production was influenced by the timing and types of Codas produced by other unit members, resulting in the production of duet-like sequences of Coda exchanges between pairs of whales. Codas were more likely to be made within 2 s of another Coda than expected by chance, and whales were more likely to match previously produced Codas than expected by chance, although matching appeared to be largely a result of the matching of one particular Coda type within each social unit. Patterns of overlapping and matching exchanges did not seem to be correlated with relatedness or social affiliation. These exchanges occurred over a range of spatial scales, and are thus likely to be functional both between whales that are near and between those that are comparatively far from one another. The context of these exchanges, reciprocity in Coda overlapping, and the sequencing of exchanges into duet-like chains all suggest that Coda overlapping and matching function to reinforce social bonds between whales.
Gustavo Yepes - One of the best experts on this subject based on the ideXlab platform.
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cosmic dawn ii Coda ii a new radiation hydrodynamics simulation of the self consistent coupling of galaxy formation and reionization
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Pierre Ocvirk, Dominique Aubert, Jenny G Sorce, Paul R Shapiro, Nicolas Deparis, Taha Dawoodbhoy, Joseph Lewis, Romain Teyssier, Gustavo YepesAbstract:Cosmic Dawn II (Coda II) is a new, fully-coupled radiation-hydrodynamics simulation of cosmic reionization and galaxy formation and their mutual impact, to redshift z < 6. With $4096^3$ particles and cells in a 94 Mpc box, it is large enough to model global reionization and its feedback on galaxy formation while resolving all haloes above $10^8$ M$_\odot$. Using a constrained realization of {\Lambda}CDM constructed from galaxy survey data to reproduce the large-scale structure and familiar objects of the present-day Local Universe, Coda II serves to model both global and local reionization, including its impact on the Local Group. Using the same hybrid CPU-GPU code RAMSES-CUDATON as Coda I in Ocvirk et al. (2016), Coda II modified and re-calibrated the subgrid star-formation algorithm, making reionization end earlier, at z $\gtrsim 6$, thereby better matching the observations of intergalactic Lyman-alpha opacity from quasar spectra and electron-scattering optical depth from cosmic microwave background fluctuations. The post-reionization UV background intensity is somewhat high, however, making the H I fraction after overlap lower than observed, a possible sign of missing bound-free opacity from unresolved substructure. Coda II predicts a UV continuum luminosity function in good agreement with observations of high-z galaxies, especially at z = 6. The cosmic star formation rate density from M1600 < -17 galaxies is only 63% (18%) of the total in all haloes at z = 6 (z = 10). As in Coda I, reionization feedback suppresses star formation in haloes below $\sim 2 \times 10^9 {\rm{M}}_\odot$ , though suppression here is less extreme, a possible consequence of modifying the star-formation algorithm. Suppression is environment-dependent, occurring earlier (later) in overdense (underdense) regions, in response to their local reionization times.