Data interpolation for participatory sensing systems

In this paper, we study the problem of applying data interpolation techniques in Participatory Sensing (PS) systems using an air quality/pollution monitoring application as an example. While traditional environmental monitoring systems consist of very few static measuring stations, PS systems rely on the participation of many mobile stations. As a result, the structure of the data provided by each system is different and instead of a multivariate time series with a few gaps in the same space, now we have a multivariate time-space series with many gaps in time and space. First, two data interpolation techniques, Markov Random Fields and kriging, are analyzed. After showing the trade-offs and superiority of kriging, this technique is used to perform a one-variable data interpolation. Then, the problems of cokriging for multivariate interpolation are introduced and Principal Component Analysis and Independent Component Analysis are utilized along with kriging to overcome these problems. Finally, an alternative approach to interpolate data in time and space is proposed, which is really useful for PS systems. The results indicate that the accuracy of the estimates improves with the amount of data, i.e., one variable, multiple variables, and space and time data. Also, the results clearly show the advantage of a PS system compared with a traditional measuring system in terms of the precision and granularity of the information provided to the users.     

Internet of things: Survey on security

The Internet of things (IoT) is intended for ubiquitous connectivity among different entities or “things”. While it provides effective and efficient solutions to many real world challenges, the security aspect of it has always been questioned. The situation is further exacerbated by the number of connected devices growing exponentially. As a result, security and privacy has emerged as a significant challenge for the IoT. In this paper, we aim to provide a thorough survey on IoT security and privacy challenges from the perspective of technologies and architecture used. This work focuses on IoT intrinsic vulnerabilities and their implications to the fundamental information security challenges in confidentiality, integrity, and availability. The approach of this survey is to summarize and synthesize published work in IoT; relate it to the security conjuncture of the field; and project future research directions.     

A distributed low tree-depth decomposition algorithm for bounded expansion classes

We study the distributed low tree-depth decomposition problem for graphs restricted to a bounded expansion class. Low tree-depth decomposition have been introduced in 2006 and have found quite a few applications. For example it yields a linear-time model checking algorithm for graphs in a bounded expansion class. Recall that bounded expansion classes cover classes of graphs of bounded degree, of planar graphs, of graphs of bounded genus, of graphs of bounded treewidth, of graphs that exclude a fixed minor, and many other graphs. There is a sequential algorithm to compute low tree-depth decomposition (with bounded number of colors) in linear time. In this paper, we give the first efficient distributed algorithm for this problem. As it is usual for a symmetry breaking problem, we consider a synchronous model, and as we are interested in a deterministic algorithm, we use the usual assumption that each vertex has a distinct identity number. We consider the distributed message-passing \(\mathcal {CONGEST}_\mathrm{BC}\) model, in which messages have logarithmic length and only local broadcast are allowed. In this model, we present a logarithmic time distributed algorithm for computing a low tree-depth decomposition of graphs in a fixed bounded expansion class. In the sequential centralized case low tree-depth decomposition linear time algorithm are used as a core procedure in several non-trivial linear time algorithms. We believe that, similarly, low tree-depth decomposition could be at the heart of several non-trivial logarithmic time algorithms.     

Plastic deformation of nanocrystalline aluminum at high temperatures and strain rate

The deformation of nanocrystalline aluminum was studied using molecular dynamics simulation at homologous temperatures up to 0.97. The microstructures and stress–strain response were examined in a polycrystalline and bicrystal configuration. The activation energies for dislocation-based deformation as well as grain boundary sliding and migration were quantified by fitting simulation data to temperature using an Arrhenius relation. The activation energy for the flow stress response suggests that deformation is largely accommodated by sliding and migration of grain boundaries. This is in agreement with simulated microstructures, indicating a negligible degree of dislocation interaction within each grain, and microstructural observations from high strain rate processes are also consistent with this result. A steady-state grain size is maintained in the recrystallized structure following yielding due to boundary migration and grain rotation mechanisms, rather than by diffusion-based dislocation climb.     

SeDAR: Reading Floorplans Like a Human—Using Deep Learning to Enable Human-Inspired Localisation

International Journal of Computer Vision - The use of human-level semantic information to aid robotic tasks has recently become an important area for both Computer Vision and Robotics. This has...     

Impact of the spectral and spatial properties of natural light on indoor gas‐phase chemistry: Experimental and modeling study

The characteristics of indoor light (intensity, spectral, spatial distribution) originating from outdoors have been studied using experimental and modeling tools. They are influenced by many parameters such as building location, meteorological conditions, and the type of window. They have a direct impact on indoor air quality through a change in chemical processes by varying the photolysis rates of indoor pollutants. Transmittances of different windows have been measured and exhibit different wavelength cutoffs, thus influencing the potential of different species to be photolysed. The spectral distribution of light entering indoors through the windows was measured under different conditions and was found to be weakly dependent on the time of day for indirect cloudy, direct sunshine, partly cloudy conditions contrary to the light intensity, in agreement with calculations of the transmittance as a function of the zenithal angle and the calculated outdoor spectral distribution. The same conclusion can be drawn concerning the position within the room. The impact of these light characteristics on the indoor chemistry has been studied using the INCA‐Indoor model by considering the variation in the photolysis rates of key indoor species. Depending on the conditions, photolysis processes can lead to a significant production of radicals and secondary species.     

Microstructural Parameters Controlling High-Temperature Creep Life of the Nickel-Base Single-Crystal Superalloy MC2

The influence of both topologically close-packed (TCP) phase precipitation and pores on the creep life of a single-crystal superalloy has been studied at 1323?K (1050?°C)/160?MPa. Despite very reproducible primary and secondary creep stages, the creep life is scattered for this specific condition where a very steep tertiary creep stage is observed, corresponding to a highly localized failure process. Image processing was performed after failure to determine the stereological parameters characterizing pores and TCP-phase particles. It was determined that pores are major determinants of creep life under these temperature and stress conditions. It was also observed that the average surface area or the density of pores is not sufficient to explain creep life variability. A homogenization method including modified ??/???? microstructure area surrounding pores and TCP-phase particles was developed and correlated to creep life. It is shown that the greater the extent of the modified microstructure, the lower the creep life. Moreover, a better understanding of the TCP-phase role in controlling the creep life was obtained: TCP-phase particles modified the local stress field and disturbed the local ??/???? microstructure. They enhance the generation of vacancies and subsequent nucleation and growth of pores.     

Multiband reduced‐size patch antenna by employing a modified DMS‐spur‐line combo technique

In this article, a simple but effective combination of DMS and spur‐lines is achieved to obtain a multiband patch antenna. The advantage of this technique is the simplicity to elaborate and the good performance compared to other methods where nulls are present in the radiation pattern at the main lobe. The antenna presents five resonant frequencies, which are fully controllable by modifying the dimensions of the defected microstrip structures and spur‐lines, obtaining the characteristic directive radiation pattern and maximum gain above 6 dBi in all bands.     

Bilateral tubo-ovarian abscesses four years after total abdominal hysterectomy

Using rat paw dextran-induced and carrageenan-induced edemas, the anti-inflammatory activity of gallic acid (I), triacetylgallic acid (II) and monohydrate copper(II) triacetylgallate (III) was assayed. All compounds tested were applied i.p. in a single dose of 50 mumol/kg body weight, calculated for the RCOO-fragment. The average antiedematous activities in dextran/carrageenan edemas were decreasing in the following order: III (55.9/41.8%) > I (38.6/31.1%) > II (-3.4/13.3%). The relationship between the biological effects found and gallic acid as well as its structural derivatives is discussed.