Experimental study on the effects of big particles physical characteristics on the hydraulic transport inside a horizontal pipe

This paper presents an experimental study of the physical characteristic effects of large particles on hydraulic transport in a horizontal pipe. The particles are spherical and are large with respect to the diameter of the pipe (8%, 10%, 16%and 25%). Experiments were done to test the important parameters in solid transport (pressure, velocity, etc.). As a result, the relationship between the pressure gradient forces and the mixture velocity was sub-stantially different from the pure liquid flow. However, in a single-phase flow a monotonous behavior of the pres-sure drop curve is observed, and the curve of the solid particle flow attains its minimum at the critical velocity. The regimes are characterized with differential pressure measurements and visualizations.     

Taxonomy of quality metrics for assessing assurance of security correctness

Assurance is commonly considered as “something said or done to inspire confidence” (Webster dictionary). However, the level of confidence inspired from a statement or an action depends on the quality of its source. Similarly, the assurance that the deployed security mechanisms exhibit an appropriate posture depends on the quality of the verification process adopted. This paper presents a novel taxonomy of quality metrics pertinent for gaining assurance in a security verification process. Inspired by the systems security engineering capability maturity model and the common criteria, we introduce five ordinal quality levels for a verification process aimed at probing the correctness of runtime security mechanisms. In addition, we analyse the mapping between the quality levels and different capability levels of the following verification metrics families: coverage, rigour, depth and independence of verification. The quality taxonomy is part of a framework for the Security Assurance of operational systems. These metrics can also be used for gaining assurance in other areas such as legal and safety compliance. Furthermore, the resulting metrics taxonomy could, by identifying appropriate quality security requirements, assist manufacturers of information technology (IT) in developing their products or systems. Additionally, the taxonomy could also empower consumers in IT security product selection to efficaciously and effectively match their organisational needs, while IT security evaluators can use it as a reference point when forming judgments about the quality of a security product. We demonstrate the applicability of the proposed taxonomy through access control examples.     

Experimental and fuzzy modelling analysis on dynamic cutting force in micro milling

Prediction of cutting forces is very important for the design of cutting tools and for process planning. This paper presents a fuzzy modelling method of cutting forces based on subtractive clustering. The subtractive clustering combined with the least-square algorithm identifies the fuzzy prediction model directly from the information obtained from the sensors. In the micro-milling experimental case study, four sets of cutting force data are used to generate the learning systems. The systems are tested against each other to choose the best model. The obtained results prove that the proposed solution has the capability to model the cutting force in spite of uncertainties in the micromilling process.     

Design of a Fixed‐Order RST Controller for Interval Systems: Application to the Control of Piezoelectric Actuators

This paper presents a technique for designing a robust polynomial RST controller for parametric uncertain systems. The uncertain parameters are assumed to be bounded by intervals. The computation of the controller is addressed by introducing the interval arithmetic. The controller synthesis is formulated as a set inversion problem that can be solved using the SIVIA algorithm. The proposed method is afterwards applied to design a robust controller for a piezoelectric microactuator. The experimental results show the efficiency of the proposed method. Finally, a fine stability analysis is performed to analytically prove the robustness of the designed controller.     

Synthesis and characterization of composite Hg-polyaniline powder material

A simple synthesis method is proposed to obtain a composite powder material constituted by polyaniline powder containing mercury droplets closely linked into PANI matrix. ¹⁹⁹Hg solid state NMR spectroscopy indicates that incorporated mercury is in a metallic form and proves a redox reaction between polyaniline (leucoemeraldine form) and an aqueous solution of Hg(I). This composite powder material has been studied by voltammetry with a cavity microelectrode (CME). This electrode appears suitable for characterizing such a material. CME containing Hg-polyaniline (Hg-PANI) powder has been used as an electrochemical microsensor for lead trace analysis by anodic stripping voltammetry of water without electrolyte addition.     

Average end-to-end delay computation in IEEE 802.11 ad hoc networks

In this study, we present a new analytic model for evaluating average end-to-end delay in IEEE 802.11 multihop wireless networks. Our model gives closed expressions for the end-to-end delay in function of arrivals and service time patterns. Each node is modelled as a G/G/1/K queue from which we can derive expressions for service time via queueing theory. By combining this delay evaluation with different admission controls, we design a protocol called DEAN (Delay Estimation in Ad hoc Networks). DEAN is able to provide delay guarantees for quality of service applications in function of the application level requirements. Through extensive simulations, we compare the performance evaluation of DEAN with other approaches.     

A model-free design of reduced-order controllers and application to a DC servomotor

This paper presents a new model-free technique to design fixed-structure controllers for linear unknown systems. In the current control design approaches, measured data are used to first identify a model of the plant, then a controller is designed based on the identified model. Due to errors associated with the identification process, degradation in the controller performance is expected. Hence, we use the measured data to directly design the controller without the need for model identification. Our objective here is to design measurement-based controllers for stable and unstable systems, even when the closed-loop architecture is unknown. This proposed method can be very useful for many industrial applications. The proposed control methodology is a reference model design approach which aims at finding suitable parameter values of a fixed-order controller so that the closed-loop frequency response matches a desired frequency response. This reference model design problem is formulated as a nonlinear programming problem using the concept of bounded error, which can then be solved to find suitable values of the controller parameters. In addition to the well-known advantages of data-based control methods, the main features of our proposed approach are: (1) the error is guaranteed to be bounded, (2) it enables us to avoid issues related to the use of minimization methods, (3) it can be applied to stable and unstable plants and does not require any knowledge about the closed-loop architecture, and (4) the controller structure can be selected a priori, which means that low-order controllers can be designed. The proposed technique is experimentally validated through a real position control problem of a DC servomotor, where the results demonstrate the efficacy of the proposed method.     

A time-averaged model for gas-solids flow in a one-dimensional vertical channel

In this study, we are interested in deriving time-smoothed governing and constitutive equations for gas-solids flow in moderately dense systems where particle-particle collision is the main energy dissipation mechanism. Results obtained from dynamic simulations of a gas-solids flow in a 1D channel are used to show that it is possible to obtain expressions for the time-averaged constitutive relations based on Taylor series expansion. We demonstrate, by comparing with time-averaged transient results, that the 1st term (or laminar) in the series expressions of most non-linear constitutive relations can yield inaccurate quantitative and qualitative results. This means that steady-state models derived by simply removing the partial time derivative from the governing equations are not suitable for gas-solids flows. This study shows that it was necessary to include many terms of the Taylor series expression of non-linear constitutive relations (such as the granular energy dissipation term) due to large-scale oscillations that were computed for all flow variables at all locations in the 1D domain. In some cases, the Taylor series expansion diverged and the Euler transformation was used to improve the convergence of these series. In this moderately dense flow system, turbulence in the gas-phase was found to be just a reaction to turbulence in the solids phase that resulted from the large-scale motion of solids clusters. This resulted in a negative turbulent gas viscosity computed due to the fact that gas (in the horizontal direction) flows only to occupy regions vacated by clusters of solids. The steady-state results obtained using the time-smoothed gas-solids flow model compared well with the time-averaged results obtained using the transient model for all flow variables.     

Automatic Hand Detection in Color Images based on skin region verification

Multimedia Tools and Applications - Among the modern means of communications that appeared recently, there is the natural computer interaction using hands. Several methods have been proposed for...     

First principles study of structural,electronic and magnetic properties of SnGen(0,±1) (n =1-17) clusters

The structures,relative stability and magnetic properties of pure Gen+1,neutral cationic and anionic SnGen (n =1-17) clusters have been investigated by using the first principles density functional theory implemented in SIESTA packages.We find that with the increasing of cluster size,the Gen+1 and SnGen(0,±1) clusters tend to adopt compact structures.It has been also found that the Sn atom occupied a peripheral position for SnGen clusters when n ＜ 12 and occupied a core position for n ＞ 12.The structural and electronic properties such as optimized geometries,fragmentation energy,binding energy per atom,HOMO-LUMO gaps and second-order differences in energy of the pure Gen+1 and SnGen clusters in their ground state are calculated and analyzed.All isomers of neutral SnGen clusters are generally nonmagnetic except for n =1 and 4,where the total spin magnetic moments is 2μb.The total (DOS) and partial density of states of these clusters have been calculated to understand the origin of peculiar magnetic properties.The cluster size dependence of vertical ionization potentials,vertical electronic affinities,chemical hardness,adiabatic electron affinities and adiabatic ionization potentials have been calculated and discussed.