Comparative study of different methods for the assessment of print mottle

Print mottle is a print defect that occurs more or less on prints and has a negative influence on the evenness in print. Several methods to assess print mottle have been proposed. In this article, we analyzed three methods for print mottle evaluation: Histogram Mottle Macro, Gray level co‐occurrence matrix (GLCM) and M‐score. The aim was to compare them and to determine their relation to perceived non‐uniformity obtained by visual assessment. In the experimental part, we printed four different substrates with different optical properties with digital printing machine based on electrophotographic process. The surface of papers was characterized by measuring optical paper properties. The results obtained in this study suggest that GLCM method should be used for print mottle assessment. This method has the strongest correlation with the visual experience of print mottle. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 493–499, 2016     

Ignition of hydrogen–air mixtures using pulsed nanosecond dielectric barrier plasma discharges in plane-to-plane geometry

Ignition of preheated (400–500 K) H₂–air mixtures at low pressures (80–100 torr) excited by pulsed nanosecond dielectric barrier discharges is investigated through experiments and simulations. Time resolved absolute OH concentration and temperature data are obtained using Laser Induced Fluorescence (LIF) technique. Ignition is achieved in the decaying plasma after a burst of discharge pulses (repetition rate 10–40 kHz), with the time delay inferred from sudden rise in OH^* emission. One-dimensional simulations are performed to obtain information about the plasma generated radicals and heat release across the discharge gap. A plasma fluid formulation is used with ions and neutral species at gas temperature, and electrons in non-equilibrium. An accurate reduced chemistry mechanism is developed through sensitivity analysis to expedite the plasma simulations. The model predictions show excellent agreement with experimental measurements, validating the numerical framework and chemistry data. The input pulse energy and ignition characteristics are found to be highly sensitive to uncertainties in dielectric properties. Ignition delay exhibits a threshold-like dependence on input plasma energy, and increases steeply as the number of pulses in the burst is reduced. The nanosecond plasma assisted ignition is achieved through a two-step process. Firstly, the burst of discharge pulses produce a large pool of radicals and provide an average temperature rise of ∼1–2 K/pulse. In the next step, if the temperature exceeds a threshold value of ∼700 K, significant heat release from partial fuel oxidation is triggered. The process becomes self-sustaining and the temperature continues to rise even after the plasma source is switched off, accelerating the conventional H₂–O₂ chain branching pathways and leading to ignition. We provide conclusive evidence of large volume ignition with nanosecond plasma as opposed to thermal ignition at a hot-spot. Ignition is first observed at the center of the discharge gap, but the kernel expands rapidly to the entire volume, except near walls where heat losses keep the temperature low. It is demonstrated that the ignition occurs independently at different locations due to local plasma chemistry effects and heat transport does not play a significant role.     

Geometry,mechanical properties and mounting of perforated plates for ballistic application

In this paper, the ballistic resistance of perforated plates made of different types of steel, mounting and geometry was investigated. Different types of steel in various heat treatment conditions were tested. Target mounting was also varied: rigid, oblique and hanging. Furthermore, four different perforated plate geometries were tested: two plate thicknesses and two hole diameters. Their behaviour was tested using impact from firing 12.7 mm M-8 API ammunition at eleven perforated plate samples. These samples were placed by means of a steel frame over a 13 mm RHA plate, at two distances. Damaged area on targets was correlated to ballistic resistance of the whole armour to find the optimal perforated plate. It was found that perforated plates, in optimized case offer a frequent fracture of the penetrating core in up to five parts. This debris is unable to penetrate the basic plate, offering mass effectiveness of the whole armour model of 1.76 and the mass effectiveness of the perforated plate of 5.91.     

High fidelity information processing in folic acid chemotaxis of Dictyostelium amoebae

Living cells depend upon the detection of chemical signals for their existence. Eukaryotic cells can sense a concentration difference as low as a few per cent across their bodies. This process was previously suggested to be limited by the receptor–ligand binding fluctuations. Here, we first determine the chemotaxis response of Dictyostelium cells to static folic acid gradients and show that they can significantly exceed this sensitivity, responding to gradients as shallow as 0.2% across the cell body. Second, using a previously developed information theory framework, we compare the total information gained about the gradient (based on the cell response) to its upper limit: the information gained at the receptor–ligand binding step. We find that the model originally applied to cAMP sensing fails as demonstrated by the violation of the data processing inequality, i.e. the total information exceeds the information at the receptor–ligand binding step. We propose an extended model with multiple known receptor types and with cells allowed to perform several independent measurements of receptor occupancy. This does not violate the data processing inequality and implies the receptor–ligand binding noise dominates both for low- and high-chemoattractant concentrations. We also speculate that the interplay between exploration and exploitation is used as a strategy for accurate sensing of otherwise unmeasurable levels of a chemoattractant.     

RETENTION: A reactive trust-based mechanism to detect and punish malicious nodes in ad hoc grid environments

In ad hoc grid environments, resources are not always available since nodes can spontaneously connect and disconnect at any time. Thus, these environments demand the correct execution of tasks to guarantee good performance. However, there are malicious users that affect the normal operation of these grids. These users modify tasks results and even cheat security mechanisms. Therefore, to assure high performance in these grid computing scenarios, it is essential to use punishment procedures based on trust models. These solutions have been used in wireless ad hoc networks, but not in the context of ad hoc grid computing. Thus, in this paper, we first present an analysis of mathematical trust models in ad hoc grid scenarios, using different ways to treat detection information passed on by other nodes. Then, we provide a comparison and a performance evaluation of these models using a grid simulator platform. Besides that, we choose the most accurate trust model among the evaluated ones to propose RETENTION: a reactive trust-based mechanism to detect and punish malicious nodes in ad hoc grid environments. Simulation results demonstrate the effectiveness of the proposed approach in detecting and punishing up to 100% of malicious nodes without generating false-positives. The results can be a valuable tool for network designers in planning trust models in ad hoc grid network deployments.