Memory effects in vibrated granular systems

Granular materials present memory effects when submitted to tapping processes. These effects have been observed experimentally and are discussed here in the context of a general kind of model systems for compaction formulated at a mesoscopic level. The theoretical predictions qualitatively agree with the experimental results. As an example, a particular simple model is used for detailed calculations.Comment: 12 pages, 5 figures; to appear in Journal of Physics: Condensed Matter (Special Issue: Proceedings of ESF SPHINX Workshop on ``Glassy behaviour of kinetically constrained models.''

Scaling and aging in the homogeneous cooling state of a granular fluid of hard particles

The presence of the aging phenomenon in the homogeneous cooling state (HCS) of a granular fluid composed of inelastic hard spheres or disks is investigated. As a consequence of the scaling property of the $N$-particle distribution function, it is obtained that the decay of the normalized two-time correlation functions slows down as the time elapsed since the beginning of the measurement increases. This result is confirmed by molecular dynamics simulations for the particular case of the total energy of the system. The agreement is also quantitative in the low density limit, for which an explicit analytical form of the time correlation function has been derived. The reported results also provide support for the existence of the HCS as a solution of the N-particle Liouville equation.Comment: 17 pages, 3 figures; v3 revised version (minor changes, corrected typos, v2=v1 due to a submission error)accepted for publication in J. Phys. A: Math. Theo

Reducing the Learning Domain by Using Image Processing to Diagnose COVID-19 from X-Ray Image

Over the last months, dozens of artificial intelligence (AI) solutions for COVID-19 diagnosis based on chest X-ray image analysis have been proposed. All of them with very impressive sensitivity and specificity results. However, its generalization and translation to the clinical practice are rather challenging due to the discrepancies between domain distributions when training and test data come from different sources. Consequently, applying a trained model on a new data set may have a problem with domain adaptation leading to performance degradation. This research aims to study the impact of image pre-processing on pre-trained deep learning models to reduce the learning domain. The dataset used in this research consists of 5,000 X-ray images obtained from different sources under two categories: negative and positive COVID-19 detection. We implemented transfer learning in 3 popular convolutional neural networks (CNNs), including VGG16, VGG19, and DenseNet169. We repeated the study following the same structure for original and pre-processed images. The pre-processing method is based on the Contrast Limited Adaptive Histogram Equalization (CLAHE) filter application and image registration. After evaluating the models, the CNNs that have been trained with pre-processed images obtained an accuracy score up to 1.2% better than the unprocessed ones. Furthermore, we can observe that in the 3 CNN models, the repeated misclassified images represent 40.9% (207/506) of the original image dataset with the erroneous result. In pre-processed ones, this percentage is 48.9% (249/509). In conclusion, image processing techniques can help to reduce the learning domain for deep learning applications

Optimized LTE Data Transmission Procedures for IoT: Device Side Energy Consumption Analysis

The efficient deployment of Internet of Things (IoT) over cellular networks, such as Long Term Evolution (LTE) or the next generation 5G, entails several challenges. For massive IoT, reducing the energy consumption on the device side becomes essential. One of the main characteristics of massive IoT is small data transmissions. To improve the support of them, the 3GPP has included two novel optimizations in LTE: one of them based on the Control Plane (CP), and the other on the User Plane (UP). In this paper, we analyze the average energy consumption per data packet using these two optimizations compared to conventional LTE Service Request procedure. We propose an analytical model to calculate the energy consumption for each procedure based on a Markov chain. In the considered scenario, for large and small Inter-Arrival Times (IATs), the results of the three procedures are similar. While for medium IATs CP reduces the energy consumption per packet up to 87% due to its connection release optimization

On the fringe: tracking and evaluating changes in land use in the areas surrounding three national parks in Spain and Portugal

Naturbanization analyses territorial changes in the surroundings of national parks brought about by the arrival of new settlers and economic activities, both of which are attracted by the value of the environment and landscape. This paper presents a comparison of the naturbanization processes in three national parks in Spain and Portugal (Doñana and Sierra Nevada National Parks, and Peneda-Gêres National Park, respectively) and in their areas of influence. Data is taken from Corine-Land Cover (1990-2006), which is the only available source of information about land use and land cover changes in the whole of the European Union. These changes have been interpreted and analysed using the Cross Tabulation Matrix developed by Pontius (2004). Land use changes connected to naturbanization processes are measured using Gains and Loss measurements. The intensification of changes in land use is one of the most significant developments associated with these processes, which have implications for the sustainable development and conservation of these areas

Recherche et identification des premiers sous-produits d'oxydation de l'isoproturon par le système ozone/peroxyde d'hydrogène

Une solution aqueuse tamponnée par des phosphates (pH initial - 8) dopée en isoproturon (N- (isopropyl-4-phényl)-N-N'-diméthylurée) (~ 20 mg 1-1), a été oxydée par le système perozone, combinant l'ozone et le peroxyde d'hydrogène dans un rapport molaire de 0,5 à 0,6 moles de H2O2 par mole d'ozone. Les disparitions du composé parent, du carbone organique total (COT), du carbone total (CT) et de la consommation d'ozone, ont été suivies au cours de l'oxydation. Les premiers sous-produits d'oxydation, ceux susceptibles de conserver une formulation moléculaire proche de celle du composé initial, et par conséquent de posséder encore une activité toxique, ont été isolés et caractérisés par chromatographie gazeuse couplée à la spectrométrie de masse.Il a été trouvé que l'isoproturon requiert un taux d'oxydation molaire de 10 moles d'ozone par mole d'isoproturon introduit, pour obtenir une élimination complète de cet herbicide. En revanche, le COT n'est pratiquement pas minéralisé, même avec de très forts taux d'ozone, ce qui indique la présence dans le milieu de sous-produits rémanents.La plupart des premiers sous-produits d'oxydation détectés conservent le cycle aromatique dans leur structure, et au moins un atome d'azote, et sont présents à des concentrations significatives. Ces composés semblent aussi réactifs que l'isoproturon vis-à-vis de la perozonation puisqu'ils disparaissent lorsqu'on prolonge l'oxydation. De plus, l'identification de ces sous-produits laisse supposer que l'attaque des radicaux hydroxyles générés par le procédé perozone, entraîne la rupture d'une liaison C-N ou d'une liaison C-H, conduisant à la formation de composés oxygénés.The goal of our study was to identify the initial oxidation by-products (IOBP) of isoproturon (N-(isopropyl 4 phenyl)-N-N'-dimethylurea) formed during a combined ozone/hydrogen peroxide (peroxone system) treatment. Solution of isoproturon (20 mg · l-¹ or 10[sup]4 M) were prepared in ultrapure water buffered with phosphate ions (45.9 mg · l-¹ KH2PO4 + 457.2 mg · l-¹ Na2HPO4) at an initial pH dose to 8 and an ionic strength of about 10-2 mol · l-¹, and in the absence of radical scavengers (bicarbonate ions) and organic matter. Each experiment was conducted in a glass semi-continuous reactor (bubble column, capacity: 2.81, ID=40 mm, H=2 m) with recirculation of the aqueous phase (60-651 · h-¹) counter current to the gaseous phase. Ozonized air produced in the laboratory (TRAILIGAZ Labo 76 apparatus) was applied at the bottom of the column through a porous glass frit (porosity: 15 to 40 µm) at a flow rate of about 2.81 · h-¹ (ozone concentration in gas: 76 to 124 mg l-¹). The hydrogen peroxide solution (dilution from a 30 % solution FLUKA) was introduced at the level of the ozonized air entrance. The applied hydrogen peroxide/ozone molar ratio was equal to about 0.5 (or 0.4 g/g). In the first phase of our work, primary experiments were conducted to determine the efficiency of peroxone oxidation (combined O3/H2O2) in removing isoproturon and carbon. For these experiments, the analysis of isoproturon was performed by HPLC on a SUPELCOSIL C8 column (15 cm x 4.6 mm) with UV detection at 236 nm (WATERS Model 500 pump with SPECTROMONITOR 3100 detector), using a methanol/water carrier phase (50/50 v/v, 1 ml · min-¹). Each five minute during the oxidation, total organic carbon (TOC) and total carbon (TC=TOC + mineral carbon) were controlled with DOHRMANN DC80 carbon analyser. The pH and ozone concentrations were also monitored (ozone introduced and in the off-gas by potassium iodure method, and dissolved ozone by indigotrisulfonate method). Calculation of consumed ozone was obtained by the following equation: consumed O3=introduced O3 - O3 in off-gas - dissolved O3. The results are expressed as curves showing removals of isoproturon, TOC, TC versus the oxidation dosage (as moles of introduced ozone per mole of initial isoproturon). Their interpretation has shown that the complete disappearance of isoproturon is achieved in 12 minutes and requires about 10 moles of ozone per mole of pesticide. However, TOC was removed to only 50% for a three times higher ozone dose (27 moles per mole reached in 30 minutes). The presence of this remaining TOC (65 mg · l-¹) for such high ozone dose indicates that some by-products remain in the solution. These by-products visualised on the HPLC chromatograms for the isoproturon dosage (4 well-separated and significant peaks) seem to be as reactive as pesticide itself because of their disappearance during oxidation.In a second phase of our work, a similar experiment was conducted over a period of 7 minutes for having up to 90% removal of isoproturon. A 1.5 litre of oxidized isoproturon solution was collected for liquid-liquid extraction with methylene dichloride ((50 ml (2 min), 25 ml (2 min), 25 ml (2 min)) after adding acid (HCI to pH 2) and salt (NaCl). After desiccation on anhydrous sodium thiosulphate (Na2SO4) and concentration under nitrogen flow, the methylene dichloride extract (extract A) was analysed by gas chromatography/mass spectrometry (VARIAN 3300 coupled with a FINNIGAN ITS 40, on-column injector: 280°C, carrier gas: helium) on DB5 capillary column (50°C to 250°C at 3°C · min), for structural identification of the oxidation by-products. Two other extracts were obtained by the same way and analysed as blanks: the initial isoproturon solution not oxidized (extract B), and the buffer solution without isoproturon oxidized under the same conditions as the pesticide solution (extract C). These two blanks have allowed to distinguish the peaks really appeared after oxidation of those either present before oxidation or produced by the oxidation/extraction of the buffer. The GC/MS chromatogram of extract A has revealed 15 peaks really issued from the oxidation of isoproturon. The molecular weights given by the mass spectra have been correlated by chemical ionisation. The identified oxidation by-products (7 on the 15) are phenylated and/or nitrated compounds which are: 4-isopropylaniline, 4-amino-benzaldehyde, paraquinon, 4-isopropylnitrobenzene, 4-isopropylbenzene-N-for-mamide, N-(4-phenol)-N-N'-dimethylurea or « oxoisoproturon » and N-(isopropyl-4-phenyl)-N-N'- (methyl-formyl) urea. Mechanisms are suggested for the formation of these products from isoproturon. It seems that the hydroxyl radicals (OH) generated by the peroxone system attack either a C-N bond (as in the case of atrazine) or a C-H bond. The subsequent attacks (OH· or O3, O2) lead to the formation of oxygenated molecules (alcohol, carboxyl groups)

Temperature dependence of the magnetization processes in Co/Al oxide/Permalloy trilayers

The magnetization process of Co/Al oxide/Py trilayers and its evolution with the temperature have been analyzed. The particular behavior of the Co layers, including the shift of the hysteresis loops and a coercivity increase with the decrease of temperature, is related with the apparition of a CoO layer at the Co/Al-oxide interface

Linear response of vibrated granular systems to sudden changes in the vibration intensity

The short-term memory effects recently observed in vibration-induced compaction of granular materials are studied. It is shown that they can be explained by means of quite plausible hypothesis about the mesoscopic description of the evolution of the system. The existence of a critical time separating regimes of ``anomalous'' and ``normal'' responses is predicted. A simple model fitting into the general framework is analyzed in the detail. The relationship between this work and previous studies is discussed.Comment: 10 pages, 6 figures; fixed errata, updtated reference

Semi-automatic assessment of unrestrained Java code: a Library, a DSL, and a workbench to assess exams and exercises

© ACM 2015. This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in http://dx.doi.org/10.1145/2729094.2742615Automated marking of multiple-choice exams is of great interest in university courses with a large number of students. For this reason, it has been systematically implanted in almost all universities. Automatic assessment of source code is however less extended. There are several reasons for that. One reason is that almost all existing systems are based on output comparison with a gold standard. If the output is the expected, the code is correct. Otherwise, it is reported as wrong, even if there is only one typo in the code. Moreover, why it is wrong remains a mystery. In general, assessment tools treat the code as a black box, and they only assess the externally observable behavior. In this work we introduce a new code assessment method that also verifies properties of the code, thus allowing to mark the code even if it is only partially correct. We also report about the use of this system in a real university context, showing that the system automatically assesses around 50% of the work.This work has been partially supported by the EU (FEDER) and the Spanish Ministerio de Economíay Competitividad (Secretaría de Estado de Investigación, Desarrollo e Innovación) under grant TIN2013-44742-C4-1-R and by the Generalitat Valenciana under grant PROMETEOII2015/013. David Insa was partially supported by the Spanish Ministerio de Educación under FPU grant AP2010-4415.Insa Cabrera, D.; Silva, J. (2015). Semi-automatic assessment of unrestrained Java code: a Library, a DSL, and a workbench to assess exams and exercises. ACM. https://doi.org/10.1145/2729094.2742615SK. A Rahman and M. Jan Nordin. A review on the static analysis approach in the automated programming assessment systems. In National Conference on Programming 07, 2007.K. Ala-Mutka. A survey of automated assessment approaches for programming assignments. In Computer Science Education, volume 15, pages 83--102, 2005.C. Beierle, M. Kula, and M. Widera. Automatic analysis of programming assignments. In Proc. der 1. E-Learning Fachtagung Informatik (DeLFI '03), volume P-37, pages 144--153, 2003.J. Biggs and C. Tang. Teaching for Quality Learning at University : What the Student Does (3rd Edition). In Open University Press, 2007.P. Denny, A. Luxton-Reilly, E. Tempero, and J. Hendrickx. CodeWrite: Supporting student-driven practice of java. In Proceedings of the 42nd ACM technical symposium on Computer science education, pages 09--12, 2011.R. Hendriks. Automatic exam correction. 2012.P. Ihantola, T. Ahoniemi, V. Karavirta, and O. Seppala. Review of recent systems for automatic assessment of programming assignments. In Proceedings of the 10th Koli Calling International Conference on Computing Education Research, pages 86--93, 2010.H. Kitaya and U. Inoue. An online automated scoring system for Java programming assignments. In International Journal of Information and Education Technology, volume 6, pages 275--279, 2014.M.-J. Laakso, T. Salakoski, A. Korhonen, and L. Malmi. Automatic assessment of exercises for algorithms and data structures - a case study with TRAKLA2. In Proceedings of Kolin Kolistelut/Koli Calling - Fourth Finnish/Baltic Sea Conference on Computer Science Education, pages 28--36, 2004.Y. Liang, Q. Liu, J. Xu, and D. Wang. The recent development of automated programming assessment. In Computational Intelligence and Software Engineering, pages 1--5, 2009.K. A. Naudé, J. H. Greyling, and D. Vogts. Marking student programs using graph similarity. In Computers & Education, volume 54, pages 545--561, 2010.A. Pears, S. Seidman, C. Eney, P. Kinnunen, and L. Malmi. Constructing a core literature for computing education research. In SIGCSE Bulletin, volume 37, pages 152--161, 2005.F. Prados, I. Boada, J. Soler, and J. Poch. Automatic generation and correction of technical exercices. In International Conference on Engineering and Computer Education (ICECE 2005), 2005.M. Supic, K. Brkic, T. Hrkac, Z. Mihajlovic, and Z. Kalafatic. Automatic recognition of handwritten corrections for multiple-choice exam answer sheets. In Information and Communication Technology, Electronics and Microelectronics (MIPRO), pages 1136--1141, 2014.S. Tung, T. Lin, and Y. Lin. An exercise management system for teaching programming. In Journal of Software, 2013.T. Wang, X. Su, Y. Wang, and P. Ma. Semantic similarity-based grading of student programs. In Information and Software Technology, volume 49, pages 99--107, 2007