The application of transmission-line modelling to the simulation ofan induction motor drive

The simulation of a complete induction motor drive is presented. The entire network is modelled using the transmission-line modelling (TLM) technique. The network is split into three sections which are solved independently and are joined together by link transmission-line models. Advantages of this approach are the explicit nature of the algorithm which remains unaltered irrespective of the network topology, unconditional stability, and straightforward modelling of switching elements. Results are presented for a complete drive which illustrate the capabilities and flexibility of the simulation technique     

Application of an allosteric ternary complex model to the technique of pharmacological resultant analysis

A simple ternary complex model of drug-receptor interaction has been used to extend the procedure of pharmacological resultant analysis, enabling the quantitation of interactions between allosteric modulators and orthosteric antagonists. Equations derived in the theoretical treatment were used to analyse functional data for the interaction between the allosteric modulator gallamine and the orthosteric antagonist scopolamine, with oxotremorine as the agonist, at rat tracheal muscarinic acetylcholine receptors. Quantitative estimates of the affinity of gallamine for the allosteric site (pKz = 4.7) and the extent of negative, heterotropic co-operativity between gallamine and scopolamine (alpha' = 13.1) were obtained. Furthermore, an alternative direct, model-fitting approach, that does not rely on the determination of concentration ratios, was also developed, and yielded similar results. It is suggested that the approach presented in this paper is useful for quantifying interactions between orthosteric antagonists and allosteric modulators, particularly when the extent of co-operativity is low or the modulators possess multiple pharmacological properties, or both.     

Time-domain simulation of nonlinear transformers displaying hysteresis

This paper introduces a novel technique for modeling, in the time domain, a power transformer with nonlinear and hysteretic behavior. The model is particularly suitable for harmonic or protection studies where the transformer is driven into the nonlinear regime. The technique uses a single-phase two-winding transformer model based on the Jiles-Atherton model of ferromagnetic hysteresis. It includes eddy-current loss by adding an extra single-turn winding so that the transients are modeled as fully as possible.     

Relative concentrations of carbon related defects in silicon

Irradiation induced defects in silicon are technologically important as they impact the electronic properties. Calculations based on density functional theory employing hybrid functionals have been previously used to investigate the structures and relative energies of defect clusters formed between vacancies, self-interstitials, carbon and oxygen atoms in silicon. In this study we employ a model to calculate the relative concentrations of carbon related defects in silicon. It is calculated that the carbon content has a significant impact upon the concentration of carbon-related defects. The C_iC_s defect is the most populous for all the conditions considered followed by the C_iO_iSi_I and the C_iO_i defects. C_iO_iSi_I and the C_iO_i become increasingly important for silicon with high carbon concentrations.     

A Complete Model for Simulating Magnitude and Phase of Emissions from a DUT Placed Inside a GTEM Cell

Since the publication of IEC 61000-4-20, the gigahertz transverse electromagnetic (GTEM) cell has gained popularity in radiated emission and immunity electromagnetic compatibility tests. Various numerical methods such as finite-difference time-domain, finite element method, and method of moments have been used to model the GTEM cell in the pursuit of getting to know the characteristic of the GTEM cell with varying degrees of verification. In this paper, the time-domain transmission line model will be used to model the GTEM cell. The advantages of this method include high accuracy and the ability to model different materials. Thus, the GTEM is realistically modeled including radio absorbing material (RAM) and lumped terminations. In addition, the model of a realistic device under test (DUT) was also included in the GTEM model. The DUT consists of a standard sized box with an aperture, placed in different orientations inside the GTEM for power and phase measurements. The particular features of this paper are: 1) the inclusion of a realistic numerical model of RAM, 2) the inclusion of a realistic DUT model, 3) systematic verification of the model against measurements, and 4) the method of phase measurement in a GTEM cell. Good agreement between the experimental results and simulations is obtained.     

Blue lasing at room temperature in an optically pumped lattice-matched AlInN=GaN VCSEL structure

Laser action with low threshold average pump power density (~50 W - cm^-2 ) at room temperature is reported for a crack-free planar vertical cavity surface emitting laser (VCSEL) structure based on a bottom lattice-matched AllnN/GaN distributed Bragg reflector (DBR) and a top dielectric DBR. The cavity region, formed by n- and p-type GaN layers surrounding only three InGaN/GaN quantum wells, corresponds to a typical active region suitable for an electrically driven VCSEL. In addition to low threshold, a spontaneous emission coupling factor beta ~ 2 x 10^-10 is derived for this ready-to-be-processed laser structure.     

A discrete approach to the modeling of power electronic switchingnetworks

An approach to time-domain analysis and modeling of power electronic circuits is described. All circuit components (including active and passive elements) are modeled in a discrete manner by transmission-line sections using the transmission-line modeling (TLM) method. This method requires a fixed system matrix which depends only upon the circuit configuration and time step and not on the switching states of the circuit. Since this method adopts a discrete approach, it provides an exact solution to the discrete model and is stable even for stiff networks. Errors are due to the modeling process only and not to the approximate solution of an approximate calculus model. A simulation on a switched-mode power supply is used to illustrate the modeling method, and the simulated results are compared with measurements     

A nonpilot phase selector based on superimposed components forprotection of double circuit lines

This paper gives details of a new phase-selection scheme for simultaneous phase-ground faults on both circuits of double circuit EHV transmission lines. Fast phase selection (within half a cycle) can be achieved by using the information contained within the fault transients. The theory is presented along with results obtained through simulations using EMTP. The scheme enables single pole tripping to be employed for simultaneous faults. The proposed scheme does not require communication between the two ends of the line. Limitations due to the low bandwidth of CVTs have not caused problems and the method has shown immunity to system noise