Direction-sensitive graphene flow sensor

Graphene flow sensors hold great prospects for applications, but also encounter many difficulties, such as unwanted electrochemical phenomena, low measurable signal and limited dependence on the flow direction. This study proposes a novel approach allowing for the detection of a flow direction-dependent electric signal in aqueous solutions of salts, acids and bases. The key element in the proposed solution is the use of a reference electrode which allows external gating of the graphene structure. Using external gating enables to enhance substantially the amplitude of the flow-generated signal. Simultaneous measurement of the reference electrode current allows us to recover a flow-direction-sensitive component of the flow-induced voltage in graphene. The obtained results are discussed in terms of the Coulomb interaction and other phenomena which can be present at the interface of graphene with the aqueous solution.Comment: 7 pages, 6 figure

Nonlinear multidimensional scaling and visualization of earthquake clusters over space, time and feature space

International audienceWe present a novel technique based on a multi-resolutional clustering and nonlinear multi-dimensional scaling of earthquake patterns to investigate observed and synthetic seismic catalogs. The observed data represent seismic activities around the Japanese islands during 1997-2003. The synthetic data were generated by numerical simulations for various cases of a heterogeneous fault governed by 3-D elastic dislocation and power-law creep. At the highest resolution, we analyze the local cluster structures in the data space of seismic events for the two types of catalogs by using an agglomerative clustering algorithm. We demonstrate that small magnitude events produce local spatio-temporal patches delineating neighboring large events. Seismic events, quantized in space and time, generate the multi-dimensional feature space characterized by the earthquake parameters. Using a non-hierarchical clustering algorithm and nonlinear multi-dimensional scaling, we explore the multitudinous earthquakes by real-time 3-D visualization and inspection of the multivariate clusters. At the spatial resolutions characteristic of the earthquake parameters, all of the ongoing seismicity both before and after the largest events accumulates to a global structure consisting of a few separate clusters in the feature space. We show that by combining the results of clustering in both low and high resolution spaces, we can recognize precursory events more precisely and unravel vital information that cannot be discerned at a single resolution

On roughness measurement by angular speckle correlation

In this work, the influence of both characteristics of the lens and misalignment of the incident beams on roughness measurement is presented. To investigate how the focal length and diameter affect the degree of correlation between the speckle patterns, a set of experiments with different lenses is performed. On the other hand, the roughness when the beams separated by an amount are non-coincident at the same point on the sample is measured. To conclude the study, the uncertainty of the method is calculated

Multi-Particle Collision Dynamics -- a Particle-Based Mesoscale Simulation Approach to the Hydrodynamics of Complex Fluids

In this review, we describe and analyze a mesoscale simulation method for fluid flow, which was introduced by Malevanets and Kapral in 1999, and is now called multi-particle collision dynamics (MPC) or stochastic rotation dynamics (SRD). The method consists of alternating streaming and collision steps in an ensemble of point particles. The multi-particle collisions are performed by grouping particles in collision cells, and mass, momentum, and energy are locally conserved. This simulation technique captures both full hydrodynamic interactions and thermal fluctuations. The first part of the review begins with a description of several widely used MPC algorithms and then discusses important features of the original SRD algorithm and frequently used variations. Two complementary approaches for deriving the hydrodynamic equations and evaluating the transport coefficients are reviewed. It is then shown how MPC algorithms can be generalized to model non-ideal fluids, and binary mixtures with a consolute point. The importance of angular-momentum conservation for systems like phase-separated liquids with different viscosities is discussed. The second part of the review describes a number of recent applications of MPC algorithms to study colloid and polymer dynamics, the behavior of vesicles and cells in hydrodynamic flows, and the dynamics of viscoelastic fluids

Profile irregularities of turned surfaces as a result of machine tool interactions

The paper describes the influence of the machining operation on a surface, which disturbs the projection of the tool profile in the form of its relative movements with respect to the object. The elements of the machine tool undergo constant wear during the machining process, it is therefore important to recognize the effects of their influence on the surface's irregularities. Amplitude-frequency analysis of lateral profiles has been used to evaluate and changes of turned lateral profiles. The results of simulation of radial and axial effects of the machine tool on surface and their spectral components were analyzed. Surfaces obtained in similar machining conditions on lathes operated in various time periods were analyzed spectrally. From the analysis of surface irregularity changes caused by disturbances in movements of the tool against the object, testifying the wear of main machine elements during its operation, the modulated, amplitude-frequency character of changes in surface irregularities of workpiece can be noticed

Profile Irregularities of Turned Surfaces as a Result of Machine Tool Interactions

The paper describes the influence of the machining operation on a surface, which disturbs the projection of the tool profile in the form of its relative movements with respect to the object. The elements of the machine tool undergo constant wear during the machining process, it is therefore important to recognize the effects of their influence on the surface's irregularities. Amplitude-frequency analysis of lateral profiles has been used to evaluate and changes of turned lateral profiles. The results of simulation of radial and axial effects of the machine tool on surface and their spectral components were analyzed. Surfaces obtained in similar machining conditions on lathes operated in various time periods were analyzed spectrally. From the analysis of surface irregularity changes caused by disturbances in movements of the tool against the object, testifying the wear of main machine elements during its operation, the modulated, amplitude-frequency character of changes in surface irregularities of workpiece can be noticed

Surface irregularities as a complex signal of tool representation together with uneven displacement in respect to the workpiece

In a dynamic machining process, distortion in surface irregularity is a very complex phenomenon. Surface irregularities form a periodic representation of the tool profile with various kinds of disturbance in a broad range of changes in the height and length of the profile. To discern these irregularity disturbances, interactions of the tool in the form of changes perpendicular and parallel relative to the workpiece were analyzed and simulated. The individual kinds of displacement of the tool relative to the workpiece introduce distortions in the changes of height and length. These changes are weakly represented in standard height and length irregularity parameters and their discernment has been found through amplitude-frequency functions

SURFACE IRREGULARITIES AS A COMPLEX SIGNAL OF TOOL REPRESENTATION TOGETHER WITH UNEVEN DISPLACEMENT IN RESPECT TO THE WORKPIECE

In a dynamic machining process, distortion in surface irregularity is a very complex phenomenon. Surface irregularities form a periodic representation of the tool profile with various kinds of disturbance in a broad range of changes in the height and length of the profile. To discern these irregularity disturbances, interactions of the tool in the form of changes perpendicular and parallel relative to the workpiece were analyzed and simulated. The individual kinds of displacement of the tool relative to the workpiece introduce distortions in the changes of height and length. These changes are weakly represented in standard height and length irregularity parameters and their discernment has been found through amplitude-frequency functions