Ring width of a given year can be highly variable throughout the cross section of a stem. This is... more Ring width of a given year can be highly variable throughout the cross section of a stem. This is especially true for roots. Therefore, the entire circumference of tree rings is often needed for studies focusing on specific reactions of individual trees on certain environmental conditions. Also, ring reconstructions are of interest for biomass calculations estimated by the cross-sectional area. The aim of the study is thus to reconstruct tree rings of cross sections within a 3D root-surface model, which will be the basis for an upcoming 3D root-development model. A FARO ScanArm was used for the acquisition of the 3D root structure (Technologies Inc., 2010). Afterwards ring-width data was measured along 4 radii per cross section and the resulting ring boundaries were integrated into the 3D root model. A weighted interpolation algorithm was used to reconstruct entire ring-width profiles of the cross sections. The algorithm considered the ring-width variations of the adjacent radii as well as the outer shape of the cross section. Hence, the intention was to estimate ring width around the root circumference using ring widths measured along 4 radii and the surface dimensions of roots. Interpolated ring-width data was compared to the measured tree-ring data as a control for the developed interpolation algorithm. Comparisons between modelled and empirical values showed a mean absolute error of about 0.06 mm deviation, and with a few exceptions the growth patterns could be accurately simulated. This has permitted additional radii measurements to be replaced by model interpolations.
Adjunct Proceedings of the 2021 ACM International Joint Conference on Pervasive and Ubiquitous Computing and Proceedings of the 2021 ACM International Symposium on Wearable Computers
Verbal and non-verbal activities convey insightful information about people's affect, empathy, an... more Verbal and non-verbal activities convey insightful information about people's affect, empathy, and engagement during social interactions. In this paper, we investigate the usage of inertial sensors to recognize verbal (e.g., speaking), non-verbal (e.g., head nodding, shaking) and other activities (e.g., eating, no movement). We implement an end-to-end deep neural network to distinguish among these activities. We then explore the generalizability of the approach in three scenarios: (1) using new data to detect a known activity from a known user, (2) detecting a novel activity of a known user and (3) detecting the activity of an unknown user. Results show that using accelerometer and gyroscope sensors, the model achieves a balanced accuracy of 55% when tested on data from a new user, 41% on a new activity of an existing user, and 80% on new data of a known activity from an existing user. The results are between 7-47 percentage points higher than baseline classifiers. CCS CONCEPTS • Human-centered computing → Ubiquitous and mobile computing systems and tools.
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies
The widespread adoption of mobile and wearable devices enables new approaches for the unobtrusive... more The widespread adoption of mobile and wearable devices enables new approaches for the unobtrusive and continuous monitoring of humans' behavior, physiological state, interactions and more. Within this line of research, we focus on the physiological synchrony between a presenter and her audience and investigate whether it can be used to characterize the experience of presenters and audience members during presentations. To this end, we collect data from 17 presenters and six audience members during a two-days conference. For 40, unique presenter-audience pairs we gather electrodermal activity (EDA) signals and self-reports on different aspects of the experience: engagement, immersion and enjoyment/satisfaction. For 28 of these pairs, we also collect inter-beat interval (IBI) traces. We then apply seven approaches for measuring the synchrony of physiological signals and we contextualize these measures using metrics derived from the self-reports. We find that physiological synchron...
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies
Modern wearable devices enable the continuous and unobtrusive monitoring of human physiological p... more Modern wearable devices enable the continuous and unobtrusive monitoring of human physiological parameters, including heart rate and electrodermal activity. Through the definition of adequate models these parameters allow to infer the wellbeing, empathy, or engagement of humans in different contexts. In this paper, we show that off-the-shelf wearable devices can be used to unobtrusively monitor the emotional engagement of students during lectures. We propose the use of several novel features to capture students' momentary engagement and use existing methods to characterize the general arousal of students and their physiological synchrony with the teacher. To evaluate our method we collect a data set that -- after data cleaning -- contains data from 24 students, 9 teachers, and 41 lectures. Our results show that non-engaged students can be identified with high reliability. Using a Support Vector Machine, for instance, we achieve a recall of 81% -- which is a 25 percentage points ...
This volume contains the scientific contributions accepted for presentation at the 6th DACH+ Conf... more This volume contains the scientific contributions accepted for presentation at the 6th DACH+ Conference on Energy Informatics (EnInf 2017). The objective of the DACH+ conference series on Energy Informatics is to promote the research, development, and implementation of information and communication technologies in the energy domain and to foster the exchange between academia, industry, and service providers across Germany (D), Austria (A) and Switzerland (CH) and their neighboring countries (DACH+). The Energy Informatics conference series is a joint initiative of the Swiss Federal Office of Energy, the Austrian Ministry for Transport, Innovation and Technology, and the German Federal Ministry for Economic Affairs and Energy and is also supported by the German Informatics Society, the Austrian Computer Society, and the Swiss Informatics Society. The 6th edition of the conference took place in Lugano, Switzerland, on October 5-6, 2017 at the Università della Svizzera italiana (USI). More than 90 participants from six different European countries as well as the USA attended the event. This makes the 2017 edition one of the most successful in terms of number of attendees and diversity. The conference provided a forum for very vivid discussion between researchers and also offered the opportunity to exchange ideas and experiences with several representatives from industry. As in the previous years, the conference was accompanied by a Ph.D. workshop organized by Prof. Sebastian Lehnhoff and Dr. Astrid Niesse, which took place the day before the conference. We would like to thank the B Silvia Santini
There is a long-standing dispute on whether and when thread-based programming should be preferred... more There is a long-standing dispute on whether and when thread-based programming should be preferred over the event-based paradigm. This dispute has also extended into the wireless sensor networks domain. Many existing operating systems rely on events due to their efficiency, but make code management difficult. Others rely on threads for developer comfort, but at the cost of reduced runtime efficiency. In this paper we try to combine the best of both worlds by offering a full-fledged cooperative thread abstraction with blocking I/O to the C programmer that is compiled into efficient event-based code. We present the basic code transformations and investigate their efficiency using a representative application case study. We find that RAM usage of generated code competes with hand-written code, but further optimizations are required to reduce the code size and the number of CPU cycles. Categories and Subject Descriptors
Proceedings of the 11th ACM Conference on Embedded Networked Sensor Systems - SenSys '13, 2013
ABSTRACT Comparing experimental results obtained on different wireless sensor network deployments... more ABSTRACT Comparing experimental results obtained on different wireless sensor network deployments is typically very cumbersome and in most cases unfeasible. This is due to the lack of a methodology to describe the properties of network deployments and the experimental conditions under which experiments have been run. Our work focuses on the design and development of a site properties assessment framework, called SiteWork, that aims at providing the means to quickly, automatically and accurately quantify their properties. This poster abstract describes the preliminary design and evaluation of the basic site properties assessment mechanisms provided by SiteWork.
... continuously reflects the best bid, and the data dependency between the best bid and ... may ... more ... continuously reflects the best bid, and the data dependency between the best bid and ... may be provided with TAG [52], an aggregation service for in-network processing of data. ... replicate] set num_children [length children] set num_replies 0 set maxvolume [query volume value ...
2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM), 2012
In tree-structured data collection sensor networks, packets are routed towards a sink node by ite... more In tree-structured data collection sensor networks, packets are routed towards a sink node by iteratively choosing a node's immediate parent node as the next hop. It is however beyond the scope of these routing protocols to transfer messages along the reverse path, i.e., from the sink to individual nodes in the network. In this paper, we present CBFR, a novel routing scheme that builds upon collection protocols to enable efficient point-to-point communication. We propose the use of spaceefficient data structures known as Bloom filters to efficiently store routing tables on the networked devices. In particular, each node in the collection tree stores the addresses of its direct and indirect child nodes in its local Bloom filter. A packet is forwarded down-tree only if the node's local filter indicates the presence of the packet's destination address among the node's descendants. In order to cater for the presence of mobile nodes, we apply the concept of counting Bloom filters to allow for the removal of elements from the filter by means of gradual forgetting. The effectiveness of our approach in achieving both high delivery rates and low overhead is demonstrated by means of simulations and experiments.
Ring width of a given year can be highly variable throughout the cross section of a stem. This is... more Ring width of a given year can be highly variable throughout the cross section of a stem. This is especially true for roots. Therefore, the entire circumference of tree rings is often needed for studies focusing on specific reactions of individual trees on certain environmental conditions. Also, ring reconstructions are of interest for biomass calculations estimated by the cross-sectional area. The aim of the study is thus to reconstruct tree rings of cross sections within a 3D root-surface model, which will be the basis for an upcoming 3D root-development model. A FARO ScanArm was used for the acquisition of the 3D root structure (Technologies Inc., 2010). Afterwards ring-width data was measured along 4 radii per cross section and the resulting ring boundaries were integrated into the 3D root model. A weighted interpolation algorithm was used to reconstruct entire ring-width profiles of the cross sections. The algorithm considered the ring-width variations of the adjacent radii as well as the outer shape of the cross section. Hence, the intention was to estimate ring width around the root circumference using ring widths measured along 4 radii and the surface dimensions of roots. Interpolated ring-width data was compared to the measured tree-ring data as a control for the developed interpolation algorithm. Comparisons between modelled and empirical values showed a mean absolute error of about 0.06 mm deviation, and with a few exceptions the growth patterns could be accurately simulated. This has permitted additional radii measurements to be replaced by model interpolations.
Adjunct Proceedings of the 2021 ACM International Joint Conference on Pervasive and Ubiquitous Computing and Proceedings of the 2021 ACM International Symposium on Wearable Computers
Verbal and non-verbal activities convey insightful information about people's affect, empathy, an... more Verbal and non-verbal activities convey insightful information about people's affect, empathy, and engagement during social interactions. In this paper, we investigate the usage of inertial sensors to recognize verbal (e.g., speaking), non-verbal (e.g., head nodding, shaking) and other activities (e.g., eating, no movement). We implement an end-to-end deep neural network to distinguish among these activities. We then explore the generalizability of the approach in three scenarios: (1) using new data to detect a known activity from a known user, (2) detecting a novel activity of a known user and (3) detecting the activity of an unknown user. Results show that using accelerometer and gyroscope sensors, the model achieves a balanced accuracy of 55% when tested on data from a new user, 41% on a new activity of an existing user, and 80% on new data of a known activity from an existing user. The results are between 7-47 percentage points higher than baseline classifiers. CCS CONCEPTS • Human-centered computing → Ubiquitous and mobile computing systems and tools.
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies
The widespread adoption of mobile and wearable devices enables new approaches for the unobtrusive... more The widespread adoption of mobile and wearable devices enables new approaches for the unobtrusive and continuous monitoring of humans' behavior, physiological state, interactions and more. Within this line of research, we focus on the physiological synchrony between a presenter and her audience and investigate whether it can be used to characterize the experience of presenters and audience members during presentations. To this end, we collect data from 17 presenters and six audience members during a two-days conference. For 40, unique presenter-audience pairs we gather electrodermal activity (EDA) signals and self-reports on different aspects of the experience: engagement, immersion and enjoyment/satisfaction. For 28 of these pairs, we also collect inter-beat interval (IBI) traces. We then apply seven approaches for measuring the synchrony of physiological signals and we contextualize these measures using metrics derived from the self-reports. We find that physiological synchron...
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies
Modern wearable devices enable the continuous and unobtrusive monitoring of human physiological p... more Modern wearable devices enable the continuous and unobtrusive monitoring of human physiological parameters, including heart rate and electrodermal activity. Through the definition of adequate models these parameters allow to infer the wellbeing, empathy, or engagement of humans in different contexts. In this paper, we show that off-the-shelf wearable devices can be used to unobtrusively monitor the emotional engagement of students during lectures. We propose the use of several novel features to capture students' momentary engagement and use existing methods to characterize the general arousal of students and their physiological synchrony with the teacher. To evaluate our method we collect a data set that -- after data cleaning -- contains data from 24 students, 9 teachers, and 41 lectures. Our results show that non-engaged students can be identified with high reliability. Using a Support Vector Machine, for instance, we achieve a recall of 81% -- which is a 25 percentage points ...
This volume contains the scientific contributions accepted for presentation at the 6th DACH+ Conf... more This volume contains the scientific contributions accepted for presentation at the 6th DACH+ Conference on Energy Informatics (EnInf 2017). The objective of the DACH+ conference series on Energy Informatics is to promote the research, development, and implementation of information and communication technologies in the energy domain and to foster the exchange between academia, industry, and service providers across Germany (D), Austria (A) and Switzerland (CH) and their neighboring countries (DACH+). The Energy Informatics conference series is a joint initiative of the Swiss Federal Office of Energy, the Austrian Ministry for Transport, Innovation and Technology, and the German Federal Ministry for Economic Affairs and Energy and is also supported by the German Informatics Society, the Austrian Computer Society, and the Swiss Informatics Society. The 6th edition of the conference took place in Lugano, Switzerland, on October 5-6, 2017 at the Università della Svizzera italiana (USI). More than 90 participants from six different European countries as well as the USA attended the event. This makes the 2017 edition one of the most successful in terms of number of attendees and diversity. The conference provided a forum for very vivid discussion between researchers and also offered the opportunity to exchange ideas and experiences with several representatives from industry. As in the previous years, the conference was accompanied by a Ph.D. workshop organized by Prof. Sebastian Lehnhoff and Dr. Astrid Niesse, which took place the day before the conference. We would like to thank the B Silvia Santini
There is a long-standing dispute on whether and when thread-based programming should be preferred... more There is a long-standing dispute on whether and when thread-based programming should be preferred over the event-based paradigm. This dispute has also extended into the wireless sensor networks domain. Many existing operating systems rely on events due to their efficiency, but make code management difficult. Others rely on threads for developer comfort, but at the cost of reduced runtime efficiency. In this paper we try to combine the best of both worlds by offering a full-fledged cooperative thread abstraction with blocking I/O to the C programmer that is compiled into efficient event-based code. We present the basic code transformations and investigate their efficiency using a representative application case study. We find that RAM usage of generated code competes with hand-written code, but further optimizations are required to reduce the code size and the number of CPU cycles. Categories and Subject Descriptors
Proceedings of the 11th ACM Conference on Embedded Networked Sensor Systems - SenSys '13, 2013
ABSTRACT Comparing experimental results obtained on different wireless sensor network deployments... more ABSTRACT Comparing experimental results obtained on different wireless sensor network deployments is typically very cumbersome and in most cases unfeasible. This is due to the lack of a methodology to describe the properties of network deployments and the experimental conditions under which experiments have been run. Our work focuses on the design and development of a site properties assessment framework, called SiteWork, that aims at providing the means to quickly, automatically and accurately quantify their properties. This poster abstract describes the preliminary design and evaluation of the basic site properties assessment mechanisms provided by SiteWork.
... continuously reflects the best bid, and the data dependency between the best bid and ... may ... more ... continuously reflects the best bid, and the data dependency between the best bid and ... may be provided with TAG [52], an aggregation service for in-network processing of data. ... replicate] set num_children [length children] set num_replies 0 set maxvolume [query volume value ...
2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM), 2012
In tree-structured data collection sensor networks, packets are routed towards a sink node by ite... more In tree-structured data collection sensor networks, packets are routed towards a sink node by iteratively choosing a node's immediate parent node as the next hop. It is however beyond the scope of these routing protocols to transfer messages along the reverse path, i.e., from the sink to individual nodes in the network. In this paper, we present CBFR, a novel routing scheme that builds upon collection protocols to enable efficient point-to-point communication. We propose the use of spaceefficient data structures known as Bloom filters to efficiently store routing tables on the networked devices. In particular, each node in the collection tree stores the addresses of its direct and indirect child nodes in its local Bloom filter. A packet is forwarded down-tree only if the node's local filter indicates the presence of the packet's destination address among the node's descendants. In order to cater for the presence of mobile nodes, we apply the concept of counting Bloom filters to allow for the removal of elements from the filter by means of gradual forgetting. The effectiveness of our approach in achieving both high delivery rates and low overhead is demonstrated by means of simulations and experiments.
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Papers by Silvia Santini