Input Efficiency for Influencing Swarm

Many cooperative control problems ranging from formation following, to rendezvous to flocking can be expressed as consensus problems. The ability of an operator to influence the development of consensus within a swarm therefore provides a basic test of the quality of human-swarm interaction (HSI). Two plausible approaches are : Direct- dictate a desired value to swarm members or Indirect- control or influence one or more swarm members relying on existing control laws to propagate that influence. Both approaches have been followed by HSI researchers. The Indirect case uses standard consensus methods where the operator exerts influence over a few robots and then the swarm reaches a consensus based on its intrinsic rules. The Direct method corresponds to flooding in which the operator directly sends the intention to a subset of the swarm and the command then propagates through the remainder of the swarm as a privileged message. In this paper we compare these two methods regarding their convergence time and properties in noisy and noiseless conditions with static and dynamic graphs. We have found that average consensus method (indirect control) converges much slower than flooding (direct) method but it has more noise tolerance in comparison with simple flooding algorithms. Also, we have found that the convergence time of the consensus method behaves erratically when the graph’s connectivity (Fiedler value) is high

Sodium benzoate and potassium sorbate preservatives in food stuffs in Iran

A high-performance liquid chromatography method was applied for the determination of the levels of benzoate and sorbate in 400 food samples, including pickled cucumbers, canned tomato pastes, sour cherry jams, soft drinks, fruit juices and dairy products (UF-Feta cheeses, Lighvan cheeses, lactic cheeses, yogurts and doogh). The results showed that 270 (67.5%) of all samples contained benzoate ranging from 11.9 to 288.5 mg kg⁻¹ in lactic cheese and fruit juice, respectively. The levels of sorbate in 98 (24.5%) of the samples were 20.1 to 284.3 mg kg⁻¹ in doogh and fruit juice, respectively. Moreover, benzoate was detected in all dairy products ranging from 11.9 mg kg⁻¹ in lactic cheese to 91.2 mg kg⁻¹ in UF-Feta cheese. A low concentration of benzoate could originate naturally, due to specific biochemical mechanisms during cheese, yogurt and doogh maturation. In conclusion, a minimum level for benzoate in dairy products should be defined in the legislation. © 2015 Taylor & Francis

Power Loss Analysis in a SiC/IGBT Propulsion Inverter Including Blanking Time, MOSFET’s Reverse Conduction and the Effect of Thermal Feedback Using a PMSM Model

This paper presents a comparison of power losses for two silicon carbide (SiC) and one silicon insulated gate bipolar transistor (Si IGBT) power modules in a three-phase inverter, when considering the effect of blanking time and the MOSFET\u27s reverse conduction. The total power losses versus different switching frequencies are also compared for the three inverters. The focus of this paper is to determine the influence of junction temperature and thermal feedback on the power loss calculation. The analysis shows that, without accounting for the thermal feedback, the loss levels are substantially underestimated, 11-15% on the conduction losses of the SiC inverters and up to 18% on the switching losses of the IGBT inverter. The data is derived at a chosen high torque, low speed operating point of a permanent magnet synchronous machine (PMSM). The operating point is considered as a worse operating condition from the power loss perspective

Fast and Efficient Lenslet Image Compression

Light field imaging is characterized by capturing brightness, color, and directional information of light rays in a scene. This leads to image representations with huge amount of data that require efficient coding schemes. In this paper, lenslet images are rendered into sub-aperture images. These images are organized as a pseudo-sequence input for the HEVC video codec. To better exploit redundancy among the neighboring sub-aperture images and consequently decrease the distances between a sub-aperture image and its references used for prediction, sub-aperture images are divided into four smaller groups that are scanned in a serpentine order. The most central sub-aperture image, which has the highest similarity to all the other images, is used as the initial reference image for each of the four regions. Furthermore, a structure is defined that selects spatially adjacent sub-aperture images as prediction references with the highest similarity to the current image. In this way, encoding efficiency increases, and furthermore it leads to a higher similarity among the co-located Coding Three Units (CTUs). The similarities among the co-located CTUs are exploited to predict Coding Unit depths.Moreover, independent encoding of each group division enables parallel processing, that along with the proposed coding unit depth prediction decrease the encoding execution time by almost 80% on average. Simulation results show that Rate-Distortion performance of the proposed method has higher compression gain than the other state-of-the-art lenslet compression methods with lower computational complexity

Influence de la taille et de la gradation des particules sur la résistance au cisaillement et le comportement dilatant des matériaux granulaires

Résumé : Cette étude examine l'impact de la taille et de la gradation de particules sur les corrélations théoriques et empiriques existantes les plus connues entre la résistance au cisaillement et le comportement dilatatant des matériaux granulaires en condition de déformation plane et en compression triaxiale drainée. À cette fin, 276 tests de cisaillements symétriques directs et 35 tests de compressions triaxiales drainées ont été menés sur des échantillons composés de billes de basalte (particules rondes), et de sables constitués de particules angulaires (sable de Péribonka et sable d'Eastmain) sur une échelle de 63 µm à 2000 µm afin d'évaluer leur résistance au cisaillement et leur comportement de dilatance sur une vaste échelle de pressions normales et de densités relatives initiales. Premièrement, la fiabilité et l'applicabilité des limites de mesure à l’aide de tests physiques de cisaillements symétriques directs dans l'interprétation de la résistance au cisaillement frictionnel en déformation plane des matériaux granulaires ont été discutées et confirmées par l'usage du code informatique DEM, SiGran. L'accent a été particulièrement mis sur la validation du modèle DEM au moyen de comparaison des résultats des simulations DEM avec leurs équivalents physiques à une échelle macro. Les résultats virtuels DSA sont abordés du point de vue de la coaxialité entre les principales tensions et les principales directions des paliers de pression ainsi que de la déviation de la direction d'extension nulle à partir de la direction horizontale. Les résultats numériques fournissent également des données quantitatives sur les différentes formes d'énergie consommées durant le cisaillement confirmées par d'autres résultats physiques et numériques publiés. Sur la base des postulats précédents, un examen minutieux des résultats des essais de cisaillements directs et de données issues de la littérature a été accompli afin d'évaluer la fiabilité des formules empiriques bien connues de Bolton et Collins et al. avec leurs constantes couramment employées en condition de déformation plane. L'étude montre qu'une application des relations empiriques de force-dilatation de cisaillement avec les constantes proposées par Bolton (1986) et Collins et al. (1992) aux sables ayant une distribution de taille de particules différente peut conduire à surestimer leurs valeurs en terme de force de cisaillement. Dans cette étude, les coefficients des équations de Bolton et Collins et al. ont donc été ajustée afin de prendre en compte les caractéristiques des particules, en particulier le diamètre médian, D50. De manière analogue, les effets microstructuraux imposés par la géométrie interne des particules (par exemple la taille, la forme et la gradation des particules) sur la relation tension-dilatation très connue, celle de Rowe (1962), et son ajustement empirique en condition triaxiale drainée ont été examinés dans cette étude. Une comparaison des prédictions des formules proposées avec les données de force de cisaillement issues de la littérature fournit de nombreuses preuves en faveur des contraintes mises en place au sein des relations existantes de force-dilatation de cisaillement en condition de déformation plane et triaxiale. Ces comparaisons prouvent également que la prise en compte de la taille des grains conduit à des résultats plus tangibles que lorsque la taille de la particule n'est pas considérée. Les formules de force-dilatation ajustées peuvent se révéler avantageuses pour évaluer indépendamment la cohérence des forces de cisaillement déterminées expérimentalement et pour introduire des lois d’écoulement plus précises dans les analyses géotechniques analytiques et numériques.Abstract : The present study examines more closely the potential impact of particle size and gradation on the most famous existing theoretical and empirical correlations between the shear strength and the dilation behavior of granular materials in plane strain and drained triaxial compression conditions. For this purpose, 276 symmetrical direct shear and 35 drained triaxial compression tests have been carried out on samples made up of basalt beads (rounded particles), and sands consisting of angular particles (Péribonka sand and Eastmain sand) in the range of 63 µm to 2000 µm to evaluate their shear resistance and dilation behavior over a wide range of normal pressures and initial relative densities. First, the reliability and applicability of boundary measurements in physical symmetrical direct shear tests to interpret the plane strain frictional shearing resistance of granular material have been discussed and confirmed using DEM computer code SiGran. Particular emphasis is placed on the validation of the DEM model by comparing the results of DEM simulations with their physical counterparts at the macro-scale. The virtual DSA results are discussed in terms of the coaxiality between the principal stresses and the principal strains increments directions as well as the deviation of the zero extension direction from the horizontal direction. The numerical results also provide quantitative data on different forms of energy consumed during shearing confirming other published physical and numerical results found in the literature. Following the assumptions above, a close scrutiny of symmetrical direct shear test results and strength and dilation data from the literature have been done to evaluate the reliability of well-known empirical Bolton’s and Collins et al.’s formulations with their commonly used constants in plane strain condition. The study shows that an application of empirical shear strength-dilation relationships with the constants proposed by Bolton (1986) and Collins et al. (1992) to sands with different particle-size distribution may strongly over-predict their shear strength values. In this study, the coefficients of Bolton’s and Collins et al.’s equations have been, therefore, adjusted to account for particle characteristics, in particular for D50. Similarly, the microstructural effects imposed by internal particle geometry (e.g. particle-size, particle shape, and particle gradation) on most popular stress-dilatancy relationship of Rowe (1962), and its empirical adjustment in drained triaxial condition have been investigated in this study. A comparison of the predictions by the proposed formulas with shear strength data from the literature provides evidences in support of the implemented constraints into existing shear strength-dilation relations in plane strain and drained triaxial conditions. These comparisons also proves that accounting for the grain size yields more authentic results than when particle size is not considered. The adjusted strength-dilation formulas may be beneficial for independently assessing the consistency of the experimentally-determined shear strengths, and introducing more refined flow rules into analytical and numerical geotechnical analyses

HUMAN-DATA INTERACTION IN LARGE AND HIGH-DIMENSIONAL DATA

Human-Data Interaction (HDI) is an emerging field which studies how humans make sense of large and complex data. Visual analytics tools are a central component of this sensemaking process. However, the growth of big data has affected their performance, resulting in latency in interactivity or long query-response times, both of which degrade one's ability to do knowledge discovery. To address these challenges, a new paradigm of data exploration has appeared in which a rapid but inaccurate result is followed by a succession of gradually more accurate answers. As the primary objective of this thesis, we investigated how this incremental latency affects the quantity and quality of knowledge discovery in an HDI system. We have developed a big data visualization tool and studied 40 participants in a think-aloud experiment, using this tool to explore a large and high-dimensional data. Our findings indicate that although incremental latency reduces the rate of discovery generation, it does not affect one's chance of making a discovery per each generated visualization, and it does not affect the correctness of those discoveries. However, in the presence of latency, utilizing contextual layers such as a map result in fewer mistakes while exploring higher-dimensional visualizations lead to more incorrect discoveries. As the secondary objective, we investigated what strategies improved a subject's performance. Our observations suggest that successful participants explore the data methodically, by first examining simple and familiar concepts and then gradually adding complexity to the visualizations, until they build a correct mental model of the inner workings of the tool. With this model, they generate several discovery patterns, each acting as a blueprint for forming new insights. Ultimately, some participants combined their discovery patterns to create multifaceted data-driven stories. Based on these observations, we propose design guidelines for developing HDI platforms for large and high-dimensional data

Motion estimation with chessboard pattern prediction strategy

Due to high correlations among the adjacent blocks, several algorithms utilize movement information of spatially and temporally correlated neighboring blocks to adapt their search patterns to that information. In this paper, this information is used to define a dynamic search pattern. Each frame is divided into two sets, black and white blocks, like a chessboard pattern and a different search pattern, is defined for each set. The advantage of this definition is that the number of spatially neighboring blocks is increased for each current block and it leads to a better prediction for each block. Simulation results show that the proposed algorithm is closer to the Full-Search algorithm in terms of quality metrics such as PSNR than the other state-of-the-art algorithms while at the same time the average number of search points is less.info:eu-repo/semantics/publishedVersio

A minireview on the in vitro and in vivo experiments with anti-Escherichia coli O157 : H7 phages as potential biocontrol and phage therapy agents

Phage therapy is an old method of combating bacterial pathogens that has recently been taken into consideration due to the alarming spread of antibiotic resistance. Escherichia coli 0157:H7 is a foodborne pathogen that causes hemorrhagic colitis and life-threatening Hemolytic Uremic Syndrome (HUS). There are several studies on isolation of specific phages against E. coli 0157:H7 and more than 60 specific phase have been published so far. Although in vitro experiments have been successful in elimination or reduction of E. coli 0157:H7numbers, in vivo experiments have not been as promising. This may be due to escape of bacteria to locations where phages have difficulties to enter or due to the adverse conditions in the gastrointestinal tract that affect phage viability and proliferation. To get around the latter obstacle, an alternative phage delivery method such as polymer microen-capsulation should be tried. While the present time results are not very encouraging the work should be continued as more efficient phage treatment regimens might be found in future. (C)2016 Elsevier B.V. All rights reserved.Peer reviewe