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

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

Wiek wody w sieci wodociągowej jako czynnik ryzyka zdrowotnego związanego ze zbiorowym zaopatrzeniem w wodę

The correct operation of collective water supply system requires continuous monitoring of water quality at various stages (collection, treatment, pumping and distribution). An important parameter associated with water quality is water age – the time from the moment of pumping the water into water supply system to its collection by people. In the case of water contamination at the exit of the water treatment plant, water age is exual to contamination time spread in the water supply network. The length of contamination time spread determines how many people will be affected by the bad water quality which can affect health or life. The paper presents a methodology for determining the risks associated with the appearance of water contamination using hydraulic model, as well as application case for selected collective water supply system.Poprawna eksploatacja systemu zbiorowego zaopatrzenia w wodę wymaga ciągłego monitoringu jakości wody na różnych etapach (ujmowania, uzdatniania, pompowania, dystrybucji). Istotnym parametrem związanym z jakością wody jest wiek wody, czyli czas od momentu wpompowania wody do sieci wodociągowej do jej pobrania przez odbiorców. W przypadku skażenia wody na wyjściu ze stacji uzdatniania wody wiek wody jest tożsamy z czasem rozprzestrzeniania się zanieczyszczenia w sieci wodociągowej. Od długości czasu rozprzestrzeniania zależy, ile osób korzystających z wodociągu będzie narażonych za spożycie wody o jakości zagrażającej zdrowiu lub życiu. W pracy przedstawiono metodykę określania ryzyka związanego z pojawieniem się w sieci wodociągowej zanieczyszczonej wody wykorzystującą model hydrauliczny, a także przykład aplikacyjny dla wybranego systemu zbiorowego zaopatrzenia w wodę

Matching the parameter values of digital measurement to workpiece surface profile irregularities

W pracy przedstawiono dopasowanie parametrów pomiaru do rodzaju powierzchni i analizy częstotliwościowej nierówności powierzchni toczonych dla celów rozpoznawania ich głównych składowych. Podano zależności parametrów cyfrowych pomiaru nierówności warunkujące ich częstotliwościowe zakresy rozpatrywania. W podsumowaniu podano zakres analizy częstotliwościowej nierówności powierzchni z dolno- i górnopasmowymi rodzajami ograniczeń oraz wskazówki doboru parametrów pomiaru dla otrzymania właściwego zakresu analizy nierówności powierzchni.Conditions of measurement, the analogue-to-digital conversion and the frequency analysis of turned surface irregularities for the purpose of its main components identification are presented in the paper. A range of digital parameters have been defined along with their relation to each other, specifying the ranges in which they should be used in order to measure surface irregularity (Tab.1). The parameter values obtained by digital measurement vary within specific ranges, and hence determine the surface irregularities [1, 2, 3]. For this measurement, it is essential to select proper sampling interval hp and the number of measured data N for the value and character of the irregularities measured [4, 5] (Fig.2). The method of frequency analysis for periodical surface irregularities, with the application of power spectral density and the use of fast Fourier transformation (FFT), has been presented in papers [6, 7]. The required conditions for the method presented in this paper, and the possible matching of frequency to wide-band surface irregularities are presented. The maximum frequency of the given irregularity is determined by the value of the sampling interval. Due to this fact, the sampling interval values should be selected in a way to include the low-frequency range of dominant components of the surface irregularity [8] (Fig.3). To summarise, the resulting frequency range of surface irregularities, with high and low-frequency limitations, has been given. Furthermore, the indication of the suitable selection range to capture significant surface irregularities has been included

Proposal for water supply systems evaluation due to diversification of water intakes and water tanks

The aim of the study was to compare the various water supply systems – from rural to agglomerations, in terms of continuity of water supply to the inhabitants in a crisis situation. The work included the diversification of water intakes with their number and the maximum daily production capacity and the diversification of water in the water tanks, knowing their number and volume. RB1 and RB2 diversification indexes have been proposed. Assessment criteria were included with comment. The research component is a two-parameter assessment of diversification for selected water supply systems using the indicators proposed by the authors. The use of proprietary indicators to assess the diversification of water supply using preference functions gives the ability to perform calculations easily and accurately

Analysis and evaluation of hazards in emergency situations in water supply systems

The new regulation concerning the quality of drinking water offers a number of delegations on the waterworks inform users about the quality of tap water. The study analysis on the public risk health should be prepared. In the paper the analysis and assessment method of the population and property related to failure occurrence of collective water supply systems is presented. Four categories of factors having impact on the multiplicative risk: purity category or probability of danger occurrence, material damage, loss of population health and security were adopted. On this basis four-parametric risk matrix was developed. In the study also examples of application methods were presented. The method can provide a planning tool in crisis management at the local government level

Analysis of risk of failure in water main pipe network and of delivering poor quality water

The method of identifying areas of risk of failure in water pipe network has been presented including presentation and analysis of risk factors for failure in water main pipe network, the proposal of the method for identifying risk areas using a simulation model of the water distribution subsystems (WDS) operation, and an example of application. In the hydraulic model, the failures of main water pipes as well as the operation of the WDS in the case of contamination were simulated. The proposed method consists of preparing the so-called risk maps and the designation of areas in which the limit values for the identified risk, the first type and the second type according to the assumed risk categories (tolerated, controlled and unacceptable) were exceeded