Antenna model of the horizontal grounding electrode for transient impedance calculation: Analytical versus boundary element method

The paper deals with a simple and efficient procedure for the calculation of the transient impedance of the horizontal grounding electrode. This work represents an extension of a previous paper, published by the authors, on the antenna modeling of the grounding electrode with corresponding Pocklington integro-differential equation. The governing equation is solved in the frequency domain, both numerically and analytically, thus obtaining the solution for the current induced along the electrode. The numerical solution is undertaken via Galerkin–Bubnov scheme of the Indirect Boundary Element Method. Scattered voltage along the electrode is then calculated using Generalized Telegrapher?s equation. Time domain scattered voltage is evaluated via the Inverse Fast Fourier Transform. Subsequently, transient impedance is determined as a ratio of time domain voltage and current at the feeding point. Results obtained via different methods seem to agree satisfactorily.     

Detection of human papillomaviruses in tissue specimens

During the past decade, molecular methods based on the detection of viral DNA have become a key tool for the detection of human papillomaviruses (HPVs) in tissue. The methods can be divided into two groups: those in which tissue destruction is unavoidable for the detection of HPV DNA, and those in which the detection of viral DNA is performed in a way that allows tissue morphology preservation. Polymerase chain reaction is currently the most sensitive method for HPV detection and an excellent research tool. However, because of frequent contamination problems and lack of standardization, it is not readily applicable to diagnostic laboratories. The recent improvements in in situ hybridization have made it possible for this method to become the most appropriate method for routine detection of HPVs in tissue. At present, however, the use of at least two independent HPV DNA detection methods is indispensable for accurate determination of HPVs.     

Simplified dipole concept for the assessment of transient electromagnetic field in the vicinity of grounding grid

The objective of this work is to provide a simplified model to analyse the electromagnetic emission of the grounding grid thus enabling engineers to perform parametric studies rapidly without greater loss of accuracy. The proposed approach is based on the use of the transmission line theory and the concept of dipole radiation in the presence of a lossy half‐space including the Sommerfeld integral approach. The model proposes to determine the electromagnetic fields (soil and air) and current distribution in a grounding system. The proposed model is described and illustrated with applications. The limitations and advantages are also discussed and compared against antenna theory counter parts. Copyright © 2014 John Wiley & Sons, Ltd.     

Magnetic current loop as a source model for finite thin‐wire antennas

The paper deals with the concept of magnetic current loop as a source model for finite thin‐wire antennas. The formulation is based on the Pocklington integro‐differential equation with reduced kernel, which is handled by means of various numerical techniques, mostly using the Galerkin–Bubnov variant of Indirect Boundary Element Method. Extensive numerical experiments were carried out on various dipole and monopole antennas using different sources (delta gap, magnetic frill, and magnetic current loop), and results for input admittance are compared with measured data. The magnetic current loop source ensures accurate solution for input admittance. Copyright © 2014 John Wiley & Sons, Ltd.     

Human equivalent antenna model for transient electromagnetic radiation exposure

Thin-wire antenna model of the human body exposed to the transient excitation is presented in the paper. The analysis is based on the solution of the corresponding integral equation and it is carried out directly in the time domain (TD) . The integral equation is handled via the TD Galerkin-Bubnov scheme of the boundary element method. Numerical results are presented for the time-harmonic and transient exposures.     

Robust identification

Convenient identification techniques based on maximum likelihood estimators (MLE) are very sensitive to deviations from assumed distributions of observations. Huber's approach to robust estimation is highly fruitful for solving identification problems under incomplete information. In the paper some robust estimators for nonlinear regression problems are proposed and their features are discussed.     

Evaluating Enzymatic Productivity—The Missing Link to Enzyme Utility

Kinetic productivity analysis is critical to the characterization of enzyme catalytic performance and capacity. However, productivity analysis has been largely overlooked in the published literature. Less than 0.01% of studies which report on enzyme characterization present productivity analysis, despite the fact that this is the only measurement method that provides a reliable indicator of potential commercial utility. Here, we argue that reporting productivity data involving native, modified, and immobilized enzymes under different reaction conditions will be of immense value in optimizing enzymatic processes, with a view to accelerating biotechnological applications. With the use of examples from wide-ranging studies, we demonstrate that productivity is a measure of critical importance to the translational and commercial use of enzymes and processes that employ them. We conclude the review by suggesting steps to maximize the productivity of enzyme catalyzed reactions.     

The assessment of human exposure to low frequency and high frequency electromagnetic fields using the boundary element analysis

Analysis of the human body exposed to low frequency and high frequency electromagnetic fields is presented in this work. The formulation of the problem is based on a simplified thick wire model of the human body. The current distribution induced in the body is determined by solving the Pocklington integral equation for a straight thick wire via the Galerkin–Bubnov boundary element method. Once the axial current along the equivalent antenna of the body is obtained, one may calculate the induced current density, electric field, specific absorption rate, and the total absorbed power in the human body. Several realistic exposure examples are given.     

Checking robust nonsingularity is NP-hard

We consider the following problem: givenk+1 square matrices with rational entries,A ₀,A ₁,...,A _k , decide ifA ₀+r ₁ A ₁+···+r _k A _k is nonsingular for all possible choices of real numbersr ₁, ...,r _k in the interval [0, 1]. We show that this question, which is closely related to the robust stability problem, is NP-hard. The proof relies on the new concept ofradius of nonsingularity of a square matrix and on the relationship between computing this radius and a graph-theoretic problem.     

Node and edge relaxations of the Max-cut problem

We study an upper bound on the max-cut problem defined via a relaxation of the discrete problem to a continuous nonlinear convex problem, which can be solved efficiently. We demonstrate how far the approach can be pushed using advanced techniques from numerical linear algebra and nonsmooth optimization. Various classes of graphs with up to 50 000 nodes and up to four million edges are considered. Since the theoretical bound can be computed only with a certain precision in practice, we use duality between node- and edge-oriented relaxations to estimate the difference between the theoretical and the computed bounds.