90 research outputs found
Shortest Path Computation with No Information Leakage
Shortest path computation is one of the most common queries in location-based
services (LBSs). Although particularly useful, such queries raise serious
privacy concerns. Exposing to a (potentially untrusted) LBS the client's
position and her destination may reveal personal information, such as social
habits, health condition, shopping preferences, lifestyle choices, etc. The
only existing method for privacy-preserving shortest path computation follows
the obfuscation paradigm; it prevents the LBS from inferring the source and
destination of the query with a probability higher than a threshold. This
implies, however, that the LBS still deduces some information (albeit not
exact) about the client's location and her destination. In this paper we aim at
strong privacy, where the adversary learns nothing about the shortest path
query. We achieve this via established private information retrieval
techniques, which we treat as black-box building blocks. Experiments on real,
large-scale road networks assess the practicality of our schemes.Comment: VLDB201
New structures to solve aggregated queries for trips over public transportation networks
Representing the trajectories of mobile objects is a hot topic from the
widespread use of smartphones and other GPS devices. However, few works have
focused on representing trips over public transportation networks (buses,
subway, and trains) where a user's trips can be seen as a sequence of stages
performed within a vehicle shared with many other users. In this context,
representing vehicle journeys reduces the redundancy because all the passengers
inside a vehicle share the same arrival time for each stop. In addition, each
vehicle journey follows exactly the sequence of stops corresponding to its
line, which makes it unnecessary to represent that sequence for each journey.
To solve data management for transportation systems, we designed a conceptual
model that gave us a better insight into this data domain and allowed us the
definition of relevant terms and the detection of redundancy sources among
those data. Then, we designed two compact representations focused on users'
trips (TTCTR) and on vehicle trips (AcumM), respectively. Each approach owns
some strengths and is able to answer some queries efficiently.
We include experimental results over synthetic trips generated from accurate
schedules obtained from a real network description (from the bus transportation
system of Madrid) to show the space/time trade-off of both approaches. We
considered a wide range of different queries about the use of the
transportation network such as counting-based or aggregate queries regarding
the load of any line of the network at different times.Comment: This research has received funding from the European Union's Horizon
2020 research and innovation programme under the Marie Sk{\l}odowska-Curie
Actions H2020-MSCA-RISE-2015 BIRDS GA No. 69094
Compact Trip Representation over Networks
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-46049-9_23[Abstract] We present a new Compact Trip Representation ( CTRCTR ) that allows us to manage usersâ trips (moving objects) over networks. These could be public transportation networks (buses, subway, trains, and so on) where nodes are stations or stops, or road networks where nodes are intersections. CTRCTR represents the sequences of nodes and time instants in usersâ trips. The spatial component is handled with a data structure based on the well-known Compressed Suffix Array ( CSACSA ), which provides both a compact representation and interesting indexing capabilities. We also represent the temporal component of the trips, that is, the time instants when users visit nodes in their trips. We create a sequence with these time instants, which are then self-indexed with a balanced Wavelet Matrix ( WMWM ). This gives us the ability to solve range-interval queries efficiently. We show how CTRCTR can solve relevant spatial and spatio-temporal queries over large sets of trajectories. Finally, we also provide experimental results to show the space requirements and query efficiency of CTRCTR .Ministerio de EconomĂa y Competitividad; TIN2013-46238-C4-3-RMinisterio de EconomĂa y Competitividad; TIN2013-47090-C3-3-PMinisterio de EconomĂa y Competitividad; IDI-20141259Ministerio de EconomĂa y Competitividad; ITC-20151305Ministerio de EconomĂa y Competitividad; ITC-20151247Xunta de Galicia; GRC2013/053Chile.Fondo Nacional de Desarrollo CientĂfico y TecnolĂłgico; 1140428Chile. Instituto de Sistemas Complejos de IngenierĂa ; FBO 1
Privacy-Preserving Release of Spatio-temporal Density
International audienceIn todayâs digital society, increasing amounts of contextually rich spatio-temporal information are collected and used, e.g., for knowledge-based decision making, research purposes, optimizing operational phases of city management, planning infrastructure networks, or developing timetables for public transportation with an increasingly autonomous vehicle fleet. At the same time, however, publishing or sharing spatio-temporal data, even in aggregated form, is not always viable owing to the danger of violating individualsâ privacy, along with the related legal and ethical repercussions. In this chapter, we review some fundamental approaches for anonymizing and releasing spatio-temporal density, i.e., the number of individuals visiting a given set of locations as a function of time. These approaches follow different privacy models providing different privacy guarantees as well as accuracy of the released anonymized data. We demonstrate some sanitization (anonymization) techniques with provable privacy guarantees by releasing the spatio-temporal density of Paris, in France. We conclude that, in order to achieve meaningful accuracy, the sanitization process has to be carefully customized to the application and public characteristics of the spatio-temporal data
Pleasure, arousal, dominance, and judgments about music in everyday life
The aim of the present research was to consider what particular features are significant predictors of whether music is present in a given situation, as well as what factors influence a personâs judgments about the music. Applying Mehrabian and Russellâs (1974) Pleasure-Arousal-Dominance model to everyday experiences of music, 569 people reported on their activity for the previous day via the Day Reconstruction Method (Kahneman, Krueger, Schkade, Schwarz, & Stone, 2004). Data concerning each event included the activity and location, and characterization of the experience using the PleasureâArousalâDominance measure. Moreover, for those events where music was present, participants also indicated how they heard the music and made four judgments about the music. Results indicated that the location, activity, and the personâs perception of dominance were significant predictors of the presence of music during everyday activities and that personâs judgments about the music. Contrary to prior research that has considered predominantly situational pleasure and arousal variables, the present results demonstrate that dominance is arguably the important variable in contextualized music listening
Listening to music reduces eye movements
Listening to music can change the way that people visually experience the environment, probably as a result of an inwardly directed shift of attention. We investigated whether this attentional shift can be demonstrated by reduced eye movement activity, and if so, whether that reduction depends on absorption. Participants listened to their preferred music, to unknown neutral music, or to no music while viewing a visual stimulus (a picture or a film clip). Preference and absorption were significantly higher for the preferred music than for the unknown music. Participants exhibited longer fixations, fewer saccades, and more blinks when they listened to music than when they sat in silence. However, no differences emerged between the preferred music condition and the neutral music condition. Thus, music significantly reduces eye movement activity, but an attentional shift from the outer to the inner world (i.e., to the emotions and memories evoked by the music) emerged as only one potential explanation. Other explanations, such as a shift of attention from visual to auditory input, are discussed
Spider-Inspired Electrohydraulic Actuators for Fast, Soft-Actuated Joints
The impressive locomotion and manipulation capabilities of spiders have led to a host of bioinspired robotic designs aiming to reproduce their functionalities; however, current actuation mechanisms are deficient in either speed, force output, displacement, or efficiency. Hereâusing inspiration from the hydraulic mechanism used in spider legsâsoftâactuated joints are developed that use electrostatic forces to locally pressurize a hydraulic fluid, and cause flexion of a segmented structure. The result is a lightweight, lowâprofile articulating mechanism capable of fast operation, high forces, and large displacement; these devices are termed spiderâinspired electrohydraulic softâactuated (SES) joints. SES joints with rotation angles up to 70°, blocked torques up to 70 mNâ
m, and specific torques up to 21 Nâ
m kg(â1) are demonstrated. SES joints demonstrate high speed operation, with measured rollâoff frequencies up to 24Â Hz and specific power as high as 230 W kg(â1)âsimilar to human muscle. The versatility of these devices is illustrated by combining SES joints to create a bidirectional joint, an artificial limb with independently addressable joints, and a compliant gripper. The lightweight, lowâprofile design, and high performance of these devices, makes them wellâsuited toward the development of articulating robotic systems that can rapidly maneuver
Thermal conductance measurements of bolted copper joints for SuperCDMS
Joint thermal conductance testing has been undertaken for bolted copper to copper connections from 60 mK to 26 K. This testing was performed to validate an initial design basis for the SuperCDMS experiment, where a dilution refrigerator will be coupled to a cryostat via multiple bolted connections. Copper used during testing was either gold plated or passivated with citric acid to prevent surface oxidation. Results obtained are well fit by a power law regression of joint thermal conductance to temperature and match well with data collected during a literature review
- âŠ