Transient electromagnetic scattering from dielectric objects using the electric field Integral equation with Laguerre polynomials as temporal basis functions

In this paper, we propose a time-domain electric field integral equation (TD-EFIE) formulation for analyzing the transient electromagnetic response from three-dimensional (3-D) dielectric bodies. The solution method in this paper is based on the Galerkin's method that involves separate spatial and temporal testing procedures. Triangular patch basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D dielectric structures. The time-domain unknown coefficients of the equivalent electric and magnetic currents are approximated using a set of orthonormal basis function that is derived from the Laguerre functions. These basis functions are also used as the temporal testing functions. Use of the Laguerre polynomials as expansion functions for the transient portion of response enables one not only to handle the time derivative terms in the integral equation in an analytic fashion but also completely separates the space and the time variables. Thus, the time variable along with the Courant condition can be eliminated in a Galerkin formulation using this procedure. We also propose an alternative formulation using a different expansion of the magnetic current. The total computational cost for this new method is similar to that of an implicit marching-on in time (MOT)-EFIE scheme, even though at each step this procedure requires more computations. Numerical results involving equivalent currents and far fields computed by the two proposed methods are presented and compared.     

Finite element analysis of the three-dimensional transient temperature field in steam turbine casings

One of the important considerations going into the process of optimization of start-up schedules for steam turbines is the estimation of thermal stresses during the transients. This in turn requires prediction of the transient temperature fields. In the case of the turbine casing, the procedures are complex in view of the irregular geometrical shape. Finite element analysis offers better scope in this regard and has been employed in the present work to compute the 3-D transient temperature distribution in the casing metal. The results obtained by a code developed for a specific type of turbine casing have been compared with the values measured by experiment and have been found to validate the code. Time-temperature histories for two typical locations inside the casing metals are presented. Isotherm surfaces across the metal at a given instant are shown.     

An adaptive multipath routing scheme for connectionless traffic in an ATM network

This paper addresses the problem of routing connectionless traffic through an ATM network. A solution is proposed based on a per-packet adaptive multipath routing scheme which is added to the routing algorithm implemented at the Inter-Working Units. A scheme is presented that distributes packets among multiple Virtual Paths (VPs) according to the utilization of the links on these VPs. The utilization of the VPs is determined by a periodic feedback mechanism. Simulation studies show the effectiveness of the proposed adaptive multipath routing scheme.The work by J. Sole-Pareta was supported in part by a CIRIT (Generalitat de Catalunya) grant (expedient number EE92/2-338), and in part by the National Science Foundation under Grant No. INT-94033646. The work by I. Akyildiz was supported in part by the National Science Foundation under Grant No. INT-94033646.     

Deconvolution and total least squares in finding the impulseresponse of an electromagnetic system from measured data

Total least squares (TLS) is a method of solving over-determined sets of linear equations AX≈b when there are errors both in the observation vector b(m×1) and in the data matrix A(m×n). This method is particularly useful when the data matrix A is singular or highly ill conditioned. We present the method of finding the TLS by applying the singular value decomposition to the discrete deconvolution problem. Numerical results are presented for finding the impulse response of a transmission line from experimental data. The advantage of this approach is that this method can be automated based on the signal to noise ratio of the measured data     

KINETICS STUDIES OF THE DEVOLATILIZATION OF INDIAN COALS IN ISOTHERMAL AND NONISOTHERMAL CONDITIONS IN THERMOBALANCE AND IN A BATCH REACTOR

Kinetics studies of devolati1ization of Indian coals in inert gas atmosphere have been carried out under isothermal and nonisothermal conditions. Heating rates had negligible effects on the kinetic parameters under nonisothermal conditions. The devolati1ization reaction was found to be of the first order. The overall activation energy was found to be around 30 Kcal/mole. Isothermal data obtained from the batch reactor were also found to fit in the rate expression for a homogeneous first order, reversible reaction within temperature range of 380-445°C. The reaction was found to be kinetically controlled within the coal particles.     

Volume/surface formulation for analyzing scattering from coatedperiodic strips

A surface/surface formulation was used by Perte et al. (see IEEE Trans. Antennas. Propagat.) to analyze the scattering from periodic planar coated strips. This paper is an extension of that work where a combined volume/surface formulation has been used to solve the same problem. This formulation can be applied to problems which involve an inhomogeneous dielectric medium or/and a thick dielectric which requires the inclusion of the edge currents which were neglected as a simplification. Results obtained using the volume/surface formulation have been compared with the results published in the paper written by Petre et al. which were obtained using a surface/surface formulation     

The variation in optical gap of amorphous In33Se33Sb33 thin films with temperatures of heat treatment

Amorphous thin films of the ternary compound In₃₃Se₃₃Sb₃₃ have been produced by a vacuum evaporation technique. The optical gap Eg^opt of In₃₃Se₃₃Sb₃₃ thin films is measured as a function of temperature of heat treatment. It was found that the optical gap has a higher value than that of the binary compound In₅₀Se₅₀ at the initial stages of heat treatment, but after a particular temperature (423 K) of heat treatment, the value of optical gap decreases appreciably in the case of In₃₃Se₃₃Sb₃₃ thin films, while it increased in the case of In₅₀Se₅₀ thin films.     

The modal performance measure for parameter optimization of powersystem stabilizers

This paper develops an optimization approach using the modal performance measure for the selection of power system stabilizer (PSS) parameters in multimachine power systems. The goal of the optimization problem is to damp out the sustained low frequency oscillations in the outputs of a linearized power system. Thus, the modal performance measure optimization problem is to select a set of PSS parameters so that the area under the envelop of the oscillatory output response will be minimum. This paper also considers bounded and unbounded PSS parameters and compares the effects of bounds on the end results. Furthermore, this work also shows that the performance measure is not a convex function in the PSS parameters. That is, there exist many local minima and possibly a global minimum. Single-machine infinite-bus and two-machine three-bus power systems are used to show the effectiveness of the proposed work     

Photo-cross-linking of rabbit skeletal troponin I deletion mutants with troponin C and its thiol mutants: the inhibitory region enhances binding of troponin I fragments to troponin C

Contraction of vertebrate striated muscle is regulated by the strong Ca(2+)-dependent interaction between troponin I (TnI) and troponin C (TnC). To critically evaluate this interaction, we generated four recombinant deletion fragments of rabbit fast skeletal TnI: the NH2-terminal fragment (TnI1-94), the NH2 terminus and the inhibitory region (TnI1-120), the inhibitory region and the COOH terminus (TnI96-181), and the COOH-terminal fragment (TnI122-181) containing amino acid residues 1-94, 1-120, 96-181, and 122-181, respectively. Native TnC and seven thiol mutants, containing single cysteine residues in the two globular domains and in the central helix of TnC, e.g., Cys-12, Cys-21, Cys-57, Cys-89, Cys-122, Cys-133, and Cys-158, were labeled with 4-maleimidobenzophenone, and their interaction with the recombinant TnI fragments and the synthetic inhibitory peptide (TnI98-114, residues 98-114) was studied by photo-cross-linking. Extensive cross-linking occurred between various domains of TnC and TnI. The cross-linking patterns (a) showed that both NH2- and COOH-terminal fragments of TnI are accessible to both of the globular domains of TnC, (b) indicated that linkage of the NH2- and COOH-terminal sequences to the inhibitory region of TnI (TnIir) caused marked enhancement of cross-linking with native TnC and all seven thiol mutants, and (c) identified the region in TnC where TnIir binds as that containing residues 98, 133, 158, and 57. Thus, the results suggest that TnI and TnC may adopt flexible and dynamic conformations in which multiple interactions involving various domains of the two polypeptides occur and TnIir acting as a linker facilitates these interactions. The interaction of TnI and its fragments with actin, TnC, and TnT, considered together with the biological activity indicates that residues 96-120 represent a key structural and functional region of TnI. Whereas the NH2-terminal region of TnI stabilizes binding to TnC and TnT, the COOH-terminal region stabilizes TnC and actin binding.     

Molecular characterization and in situ localization of a mouse retinal taurine transporter

Various ocular tissues have a higher concentration of taurine than plasma. This taurine concentration gradient across the cell membrane is maintained by a high-affinity taurine transporter. To understand the physiological role of the taurine transporter in the retina, we cloned a taurine transporter encoding cDNA from a mouse retinal library, determined its biochemical and pharmacological properties, and identified the specific cellular sites expressing the taurine transporter mRNA. The deduced protein sequence of the mouse retinal taurine transporter (mTAUT) revealed >93% sequence identity to the canine kidney, rat brain, mouse brain, and human placental taurine transporters. Our data suggest that the mTAUT and the mouse brain taurine transporter may be variants of one another. The mTAUT synthetic RNA induced Na+- and Cl(-)-dependent [3H]taurine transport activity in Xenopus laevis oocytes that saturated with an average Km of 13.2 microM for taurine. Unlike the previous studies, we determined the rate of taurine uptake as the external concentration of Cl- was varied, a single saturation process with an average apparent equilibrium constant (K(Cl-)) of 17.7 mM. In contrast, the rate of taurine uptake showed a sigmoidal dependence when the external concentration of Na+ was varied (apparent equilibrium constant, K(Na+) approximately 54.8 mM). Analyses of the Na+- and Cl(-)-concentration dependence data suggest that at least two Na+ and one Cl- are required to transport one taurine molecule via the taurine transporter. Varying the pH of the transport buffer also affected the rate of taurine uptake; the rate showed a minimum between pH 6.0 and 6.5 and a maximum between pH 7.5 and 8.0. The taurine transport was inhibited by various inhibitors tested with the following order of potency: hypotaurine > beta-alanine > L-diaminopropionic acid > guanidinoethane sulfonate > beta-guanidinopropionic acid > chloroquine > gamma-aminobutyric acid > 3-amino-1-propanesulfonic acid (homotaurine). Furthermore, the mTAUT activity was not inhibited by the inactive phorbol ester 4alpha-phorbol 12,13-didecanoate but was inhibited significantly by the active phorbol ester phorbol 12-myristate 13-acetate, which was both concentration and time dependent. The cellular sites expressing the taurine transporter mRNA in the mouse eye, as determined by in situ hybridization technique, showed low levels of expression in many of the ocular tissues, specifically the retina and the retinal pigment epithelium. Unexpectedly, the highest expression levels of taurine transporter mRNA were found instead in the ciliary body of the mouse eye.