Some improvements on free surface simulation by the particle finite element method

The Lagrangian method has become increasingly popular in numerical simulation of free surface problems. In this paper, after a brief review of a recent Lagrangian method, namely the particle finite element method, some issues are discussed and some improvements are made. The least‐square finite element method is adopted to simplify the solving of the Navier–Stokes equations. An adaptive time method is derived to obtain suitable time steps. A mass correction procedure is imported to improve the mass conservation in long time calculations and time discretization scheme is adopted to decrease the pressure oscillations during the calculations. Finally, the method is used to simulate a series of examples and the results are compared with the commercial FLOW3D code. Copyright © 2008 John Wiley & Sons, Ltd.     

Stability regions for Mathieu equation with imperfect periodicity

We consider a mean square stability for Mathieu equation with a random phase modulation in parametric excitation. An efficient numerical scheme is proposed for obtaining the stability charts for this equation. The influence of the random phase modulation on the shape of parametric resonance regions is studied. It is found that this influence can lead to stabilization under some conditions. A comparison with a case of Gaussian parametric excitation is presented.     

Predictive visual tracking based on least absolute deviation estimation

To cope with the occlusion and intersection between targets and the environment, location prediction is employed in the visual tracking system. Target trace is fitted by sliding subsection polynomials based on least absolute deviation （LAD） estimation, and the future location of target is predicted with the fitted trace. Experiment results show that the proposed location prediction algorithm based on LAD estimation has significant robustness advantages over least square （LS） estimation, and it is more effective than LS-based methods in visual tracking.     

线性模型中部分根方估计的优良性

在均方误差矩阵(MSE-M)准则和在Pitman Closeness(PC)准则下,比较了部分根方估计相对于最小二乘估计的优良性.     

Exponential stability of numerical solutions to a stochastic age-structured population system with diffusion

The main aim of this paper is to investigate the exponential stability of the Euler method for a stochastic age-structured population system with diffusion. The definition of exponential mean square stability of numerical method is introduced. It is proved that the Euler scheme is exponentially stable in mean square sense. An example is given for illustration.     

Neutron scattering perspectives for protein dynamics

After a double decade of intensive neutron scattering studies of the biological physics of protein dynamics on a few well-characterised model systems, the time has come to extend the method to address the vast biological diversity of proteins and their dynamics-function relationships. The time-scale and length-scale dependent mean square displacement and effective force constant, measured by neutron elastic intensity temperature scans, are proposed as relevant experimental parameters, and examples are given of their correlation with biological function. The parameters are directly calculable from molecular dynamics simulations, and their proposed deposit in an accessible data bank will greatly strengthen the links between experimental and theoretical approaches to protein dynamics.     

Electrochemical Determination of Boron in Natural Waters

Abstract

A sensitive voltammetric method for the determination of trace boron, based on the formation of the complex of boric acid with 4‐hydroxy‐5‐[salicylideneamino]‐2‐7‐naphthalenedisulfonic acid (azomethine H) is described. The reduction of the boric acid‐azomethine H complex at a hanging mercury drop electrode was exploited by square wave voltammetry (SWV) and cyclic voltammetry to determine boron in natural water samples, which were collected in the regions surrounding the boron mines of Central Anatolia. A reduction peak that belongs to the boric acid‐azomethine H complex at this electrode was observed at ?1.05 V vs. Ag/AgCl/KCl_(sat.). The effects of various parameters, such as ligand concentration, boric acid concentration, and formation time of the boric acid‐azomethine H complex, were investigated. Electrochemical experiments were conducted in 1.0 M HOAc/0.5 M NH₄OAc buffer at pH of 4.4±0.2. Linear working range was established by regression analysis between 5.0×10^?8 M and 1.0×10^?4 M. The probable metal cation interferences in water samples were eliminated by adding EDTA (ethylenediaminetetraacetic acid) to the samples. Data obtained using the square wave voltammetric (SWV) technique was compared statistically with inductively coupled plasma mass spectroscopy (ICP‐MS) data. Evaluation of the method based on statistical data was performed and the values of the limit of detection (LOD) and limit of quantitation (LOQ) were found to be 4.17×10^?6 M and 1.39×10^?5 M, respectively.     

Disposable Screen-Printed Electrodes (Spe) Mercury-Free for Lead Detection

ABSTRACT

Strategies to modify screen-printed electrodes (SPE) for lead determination are reported. Dithizone was mixed with graphite ink to obtain a modified screen-printed strip to detect ppb levels of lead(II) (detection limit 12 μg/l) using square wave anodic stripping voltammetry (SWASV). In addition, screen-printed electrodes were also modified by casting a few μl of a Nafion® solution onto the working electrode surface. In this case, ppb levels of lead were detected (detection limit 15 μg/1), using potentiometric stripping analysis (PSA). The addition of an ionophore to Nafion® polymer was also investigated, but this did not yield a significant improvement.     

Genetic Algorithm Applied to Selection of Wavelength in Partial Least Squares for Simultaneous Spectrophotometric Determination of Nitrophenol Isomers

Abstract

Ternary mixtures of nitrophenol isomers have been simultaneously determined in synthetic and real matrix by application of genetic algorithm and partial least squares model. All factors affecting the sensitivity were optimized and the linear dynamic range for determination of nitrophenol isomers found. The simultaneous determination of nitrophenol mixtures by using spectrophotometric methods is a difficult problem, due to spectral interferences. The partial least squares modeling was used for the multivariate calibration of the spectrophotometric data. A genetic algorithm is a suitable method for selecting wavelength for PLS calibration of mixtures with almost identical spectra without loss prediction capacity. The experimental calibration matrix was designed by measuring the absorbance over the range 300–520 nm for 21 samples of 1–20 µg mL^?1, 1–20 µg mL^?1, and 1–10 µg mL^?1 of m‐nitrophenol, o‐nitrophenol, and p‐nitrophenol, respectively. The root mean square error of prediction for m‐nitrophenol, o‐nitrophenol, and p‐nitrophenol with genetic algorithms and without genetic algorithms were 0.3732, 0.5997, 0.3181 and 0.7309, 0.9961, 1.0055, respectively. The proposed method was successfully applied for the determination of m‐nitrophenol, o‐nitrophenol, and p‐nitrophenol in synthetic and water samples.     

Electrochemical Analysis of Mercury Using a Kryptofix Carbon‐Paste Electrode

Abstract

Successful applications of different analytical procedures to determine quantitatively mercury in aqueous media can be found in recent literature. Fundamentally it has made use of Cold Vapour Atomic Absorption Spectrometry (CV‐AAS), X‐Ray Fluorescence or UV Spectrophotometry, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP‐AES), or Inductively Coupled Plasma Mass Spectrometry (ICP‐MS), which are the techniques commonly used for trace measurement of heavy metal in the laboratory. In this paper a new and alternative methodology to determine quantitatively mercury in aqueous media is reported. A kryptofix carbon‐paste electrode has been used to determine voltammetrically mercury. The detection limit for mercury was evaluated to be 0.12 µg/l.