Wire antenna versus modified transmission line approach to the transient analysis of grounding grid

The paper deals with transient analysis of grounding grids using two different approaches, wire antenna theory and modified transmission line model. The Pocklington integro-differential equations, in frequency domain, arising from the wire antenna theory are numerically handled via the Galerkin–Bubnov variant of indirect Boundary Element Method (GB-IBEM), while the transient response was obtained using inverse Fourier transform. The modified transmission line equations are treated using the finite difference time domain (FDTD) method. Some illustrative numerical results are presented and discussed in the paper.     

Frequency domain boundary element versus time domain finite element model for the transient analysis of horizontal grounding electrode

The paper deals with two different approaches to the assessment of the transient impedance of a horizontal grounding electrode: frequency domain boundary element analysis, based on the straight thin wire antenna model (AM) and generalized telegrapher’s equations combined with inverse Fast Fourier Transform (FFT); and time domain finite element analysis based on the transmission line model (TLM) and standard telegrapher’s equations. Extensive numerical experiments have been undertaken and some of illustrative numerical results are presented in this paper.     

Root-mean-square measure of nonlinear effects to the transient response of thin wires

A root-mean-square (rms) measure of effect of nonlinear loading on the transient response of thin wires is proposed. The transient behavior of nonlinearly loaded wires is analyzed directly in the time domain. The problem is formulated via the space-time Hallen integral equation. The equation is solved by the space-time Galerkin Bubnov boundary element procedure. Numerical results for the transient response of a thin wire computed by a time domain code based on this method are compared with results obtained from a frequency domain code. Some illustrative numerical results for the spatial distribution of the rms values of time varying currents are also presented.     

A dynamic adaptive sampling technique in frequency-domain transient analysis

The transient response of a structure may be obtained directly by solving a problem in the time domain. However, there are certain advantages in obtaining the time-domain waveform from frequency-domain data. Taking samples to characterize the frequency spectrum of a resonant structure with no prior knowledge of its behavior, poses difficulty. There is no foolproof way to determine the sampling resolution that will yield an accurate result while keeping the number of samples to a minimum. We propose a frequency sampling technique using a dynamic adaptive algorithm. The algorithm zeroes in on the resonant peaks without user intervention and computes the samples to the required resolution. The resolution is relaxed where appropriate, to achieve economy of samples. A modified discrete Fourier transform formula is used to process the nonuniformly spaced frequency data into the time-domain waveform. Computation time is vastly reduced. This technique enables the frequency-domain approach to be used for modeling transients in very high-Q structures accurately.     

Nonlinear-coupled electric-thermal modeling of underground cable systems

An original nonlinear-coupled electric-thermal model of underground cables with the solid sheaths is proposed. The model deals with the numerical evaluation of losses, heating, and ampacity. The computation of the current dependent losses is undertaken by means of the filament method, where conductors and sheaths are represented by a number of smaller subconductors or filaments. Furthermore, heat-transfer phenomena through an "infinite" domain beneath the soil surface are modeled combining the finite and the mapped infinite elements, respectively. The corresponding finite-element meshes are generated by the advancing front method. The numerical results presented throughout this work suggest that the International Electrotechnical Commission relation concerning the external thermal resistance for touching cables, placed in flat formation, having appreciable sheath losses, should be re-examined.     

Time domain modeling of a thin wire in a two-media configuration featuring a simplified reflection/transmission coefficient approach

The paper deals with a transient analysis of a straight thin wire in a presence of a two-media configuration using a simplified reflection coefficient approach. A direct time domain formulation is based on thin wire antenna theory and on the corresponding space–time integral equation for the wire above a dissipative half-space, or buried in a real ground. The effect of a half-space is taken into account via the simplified reflection/transmission coefficient arising from the modified image theory. The resulting space–time integral equation for the wire above and below ground, respectively, is handled via the time domain Galerkin–Bubnov variant of the indirect boundary element method (GB-IBEM) and some illustrative numerical results are presented.The transient response computed via the simplified reflection/transmission coefficient approach is compared, where possible, to the results obtained via the Fresnel coefficients approach.     

Molecular identification and population dynamic of Anisakis pegreffii (Nematoda: Anisakidae Dujardin, 1845) isolated from the European anchovy (Engraulis encrasicolus L.) in the Adriatic Sea

Anchovy Engraulis encrasicolus (L.) is a coastal pelagic and euryhaline species that represents the only European species of the family Engraulidae, with a widespread distribution. In Croatia, it is marketed fresh, frozen, salted or marinated and mainly exported to Italy and Spain, however Anisakis sp. larval infection is frequently the reason for border rejection. Since it is known that the prevalence and intensity of Anisakis infection varies with fish species, fishing area and season, the aim of our study was to identify Anisakis sp. parasitizing European anchovy and infer its population dynamic through a 2.5-year period. Larvae were found coiled and encysted on the external wall of intestine (94%) and reproductive organs (6%), rarely in fillets. Prevalence was 76.1% (95% confidence limits 74.51-77.56%), mean abundance 6.59 (bootstrap 95% confidence limits 5.81-7.26) and mean intensity 8.67 (bootstrap 95% confidence limits 7.82-9.35). The partial CO2 mitochondrial DNA sequence of the isolated anisakids confirmed clustering of the anchovy parasite within A. pegreffii sister group. Parasite population structure showed plasticity inferred by fishing ground, sampling year and fish gender and size. Compared to anisakid prevalence/abundance in other fish, the European anchovy in the Adriatic Sea represents a moderately high-infected paratenic host, although in the Mediterranean and Atlantic waters, anchovies have shown strikingly lesser values of prevalence. Since this host represents one of the most attractive Mediterranean fisheries products traditionally consumed without thermal preparation that in any case would not disrupt larval antigenicity and prevent human allergies, and given the high prevalence of the anisakid within the host, it is necessary to include anchovy into more firm risk assessment frames in order to develop measures that will support the safe alimentary production and consumption of seafood.     

Thermodynamics of antigen-antibody binding using specific anti-lysozyme antibodies

Titration calorimetry measurements on the binding of hen lysozyme to the specific monoclonal IgG antibodies D1.3, D11.15, D44.1, F9.13.7, F10.6.6, their papain-cleaved antigen binding fragments (Fab) and their protein-engineered fragments consisting of non-covalently linked heavy variable chain and light variable chain domains (Fv) were performed between 6-50 degrees C in 0.15 M NaCl, 0.01 M sodium phosphate pH 7.1. The binding thermodynamic free energy change (delta G degrees b), enthalpy change (delta Hb), and entropy change (delta Sb) were the same for the whole IgG and its Fv and Fab fragments. With the exception of F9.13.7 at 13 degrees C, all the binding reactions were enthalpically driven with enthalpy changes ranging from -129 +/- 7 kJ mol-1 (D1.3 at 49.8 degrees C) to -26.2 +/- 0.6 kJ mol-1 (D44.1 at 8.0 degrees C). The heat capacity changes for the binding reaction (delta Cp) ranged from -2.72 +/- 0.16 kJ mol-1 K-1 (F9.13.7) to -0.95 +/- 0.06 kJ mol-1 K-1 (F10.6.6). The apolar surface areas buried at the binding sites estimated from the heat capacity changes indicate that the binding reactions are primarily hydrophobic, contrary to the mainly observed enthalpy-driven nature of the reactions. Conformational stabilization and the presence of water at the antigen-antibody interface may account for this discrepancy.     

Amino Acid analysis of peptides and proteins on the femtomole scale by gas chromatography/mass spectrometry

Amino acid analysis (AAA) is a useful aid in protein chemistry, but its routine application is limited by a modest limit of detection. Typically, 10 pmol of material is required, but even at this level the reproducibility can be poor. We have employed isotope dilution gas chromatography electron capture negative ionization mass spectrometry (GC/ECNI/MS) to provide accurate and reliable data on less than 100 fmol of material. Precision and accuracy are good, and all 20 non-hydrolyzed amino acids can be determined in this manner. The protein is hydrolyzed (HCl), and then a cocktail, composed of all 20 amino acids as stable isotope-labeled forms (i.e., (13)C and (2)H), is added. The mixture of protein-derived and stable isotope-labeled amino acids is then converted to volatile electron-capturing derivatives with a multistep approach employing heptafluorobutyric anhydride (HFBA), pentafluorobenzyl bromide (PFBBr), and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). These derivatives are then injected directly into the GC/MS system. Groups of selected ions, characteristic of each derivatized amino acid, are thereafter monitored at appropriate time intervals. The ratios of the ion current for the selected ions for the native amino acid and its labeled form are determined and converted to absolute amounts of the native amino acids in the protein hydrolyzate by reference to standard samples prepared at the time of the analysis.     

Analytical versus boundary element modelling of horizontal ground electrode

Different approaches to the analysis of horizontal ground electrode, based on the wire antenna theory have been used in this work. The spatial distribution of the induced current along the electrode is obtained by solving the homogeneous Pocklington integro-differential equation. The spatial distribution of the scattered voltage along the electrode is computed using the generalized telegrapher's equation. The assessment of current and voltage induced along the electrode is carried out using both analytical and numerical approaches. The numerical solution of integral expressions arising from the antenna theory model is numerically handled via the Galerkin–Bubnov scheme of the Indirect Boundary Element Method (GB-IBEM). Some illustrative results for the current and voltage induced along the horizontal electrode are given in the paper.