Performance of some metaheuristic algorithms for localization in wireless sensor networks

In this paper we propose two novel and computationally efficient metaheuristic algorithms based on tabu search (TS) and particle swarm optimization (PSO) principles for locating the sensor nodes in a distributed wireless sensor network (WSN) environment. The WSN localization problem is formulated as a non‐linear optimization problem with mean squared range error resulting from noisy distance measurement as the objective function. Unlike gradient descent methods, both TS and PSO methods ensure minimization of the objective function without the solution being trapped into local optima. We further implement a refinement phase with error propagation control for improvement of the results. The performance of the proposed algorithms are compared with each other and also against simulated annealing based WSN localization. The effects of range measurement error, anchor node density and uncertainty in the anchor node position on localization performance are also studied through various simulations. The simulation results establish better accuracy, computational efficiency and convergence characteristics for TS and PSO methods. Further, the efficacy of the proposed methods is verified with data collected from an experimental sensor network reported in the literature. Copyright © 2008 John Wiley & Sons, Ltd.     

采用硬件加速发挥MicroBlaze处理能力 使MicroBlaze内核性能超越标准控制器或DSP

有许多算法可以转化为纯硬件来加速处理器,诸如平均标准偏差算法、给定时间内创建最小值或最大值、滤波器以及FFT等。不过,诸如位反转等一些不常见的算法可采用合适的硬件加速器也能移植到硬件上。本文以赛灵思的MicroBlaze为例,探讨了在FPGA上采用此种硬件加速方法,使系统性能可超过标准处理器、控制器甚至DSP。     

The Possibilities of Particle Analysis Demonstrated by the Measurement of the Colloidal Stability of Filtered Beer

Long‐term stability is one of the most important quality criteria of beer. Three groups of measuring methods are available for its determination: real time tests, predictive tests and indicative tests. One of the most common methods is the predictive forcing test, which is a time‐consuming method for accelerating beer ageing, e.g., at 0°C and 60°C. Two ways exist to perform this test: (1) follow‐up of haze development and determination of the lag phase or (2) the measurement of haze values after several days. The first option was evaluated by performing a long‐term Forcing test over a period of 4 months by analyzing a bottom‐fermented beer. It was shown that the haze curve followed a typical course with a lag phase, an increase phase and a stationary phase. Significant differences between the measurement after the cooling and the warm period were shown. In search of quicker methods and more accurate predictive indicators, the charge titration method was developed as an alternative to determine the particle charge of filtered beers, whereupon the relationship was elucidated between the increase in hazing and decrease of potential along with the advanced aging of beer. The results showed that with increased particle size due to agglomeration, the total charge decreased. In this array of trials, two differently stabilized beers were examined. Although both beers showed different haze values in the beginning (0.32 EBC and 1.30 EBC), the less stabilized beer had only 10 warm days and in contrast the beer with the good stabilization had over 20 warm days. With the help of the total charge, predictions were possible regarding the long‐term stability of the beer.     

Struggle for quality in determination of perfluorinated contaminants in environmental and human samples

The first worldwide interlaboratory study on the analyses of 13 perfluorinated compounds (PFCs) in three environmental and two human samples indicates a varying degree of accuracy in relation to the matrix or analyte determined. The ability of 38 participating laboratories from 13 countries to determine the analytes in the various matrices was evaluated by calculation of z-scores according to the Cofino model. The PFCs which were reported most frequently by the laboratories, and assessed with the most satisfactory agreement, were perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). In general, the level of agreement between the participating laboratories decreased in the following order: PFC standard solution (76% satisfactory z-scores of <[2]1 for PFOS) < human blood (67%) < human plasma (63%) < fish liver extract (55%) < water (31%) < fish tissue (17%). This shows that relative good agreement between laboratories was obtained for the study of standard and human matrices. For the fish extract, most laboratories underestimated the actual PFOS concentration due to matrix effects. The results for the fish tissue and water are also poor, indicating that the extraction and cleanup steps require further improvement. It was concluded that the PFC determinations in various matrices are not yet fully mastered.     

A fluorine scan at the catalytic center of thrombin: C--F, C--OH, and C--OMe bioisosterism and fluorine effects on pKa and log D values

A series of 16 tricyclic thrombin inhibitors was prepared by using the 1,3-dipolar cycloaddition of azomethine ylides derived from 3- or 4-hydroxyproline and 4-bromobenzaldehyde, with N-(4-fluorobenzyl)maleimide as the key step. The terminal pyrrolidine ring of the inhibitors was systematically substituted to explore the potential bioisosteric behavior of C-F, C-OH, and C-OMe residues pointing into the environment of the catalytic center of a serine protease. X-ray crystal structure analyses revealed a distinct puckering preference of this ring. Substitution by F, HO, and MeO has a strong effect on the basicity of the adjacent pyrrolidine nitrogen center which originates from two sigma-inductive pathways between this center and the electronegative O and F atoms. gem-Difluorination decreases the pKa value of this tertiary amine center to <2, making the conjugated ammonium ion a moderately strong acid. Unexpectedly, F substitution next to the nitrogen center reduced the lipophilicity of the ligands, as revealed by measurements of the logarithmic partition coefficient log D. The biological assays showed that all compounds are thrombin inhibitors with activities between Ki=0.08 and 2.17 microM. Bioisosteric behavior of F, HO, and MeO substituents was observed. Their electronegative F and O atoms undergo energetically similar polar interactions with positively polarized centers, such as the N atom of His 57 which is hydrogen bonded to the catalytic Ser 195. However, for energetically similar polar interactions of C-F, C-OH, and C-OMe to occur, sufficient space is necessary for the accommodation of the Me group of the C-OMe residue, and a H-bond acceptor must be present to prevent unfavorable desolvation of the C-OH residue.     

Dynamic analyses of regenerative fuel cell power for potential use in renewable residential applications

A model of a solar-hydrogen powered residence, in both stand-alone and grid parallel configurations, was developed using Matlab/Simulink^®$\mathrm{Matlab}/{\mathrm{Simulink}}^{\circledR }$. The model assesses the viability of employing a regenerative fuel cell (RFC) as an energy storage device to be used with photovoltaic (PV) electrical generation. Other modes of energy storage such as batteries and hybrid storage were also evaluated. Analyses of various operating conditions, system configurations, and control strategies were performed. Design requirements investigated included RFC sizing, battery sizing, charge/discharge rates, and state of charge limitations. Dynamic load demand was found to be challenging to meet, requiring RFC and or battery sizes significantly larger than those required to meet average power demand. Employing a RFC with batteries in a hybrid configuration increased PV utilization and both battery efficiency and power density. Grid parallel configurations were found to alleviate many of the difficulties associated with energy storage costs and meeting peak demand.     

Aerial Design in Inductive Loop Telemetry

Two problems are considered which concern circular loop receiving aerials used in inductive loop telemetry. The first is that certain transmitter orientations give rise to signal nulls. The second is the optimum aerial size. By inverting the roles of the transmitting and receiving aerials, a simple way of describing the orientations which give rise to signal nulls is found. The factors which limit the range of an aerial are discussed and a simple method for deciding whether or not it is advantageous to enlarge or reduce the aerial radius is given.