Impact of Auger recombination parameterisations on predicting silicon wafer solar cell performance

For high-efficiency silicon wafer solar cells, Auger recombination is becoming one of the most important efficiency limiting factors. For this purpose it is desirable to be able to use different Auger recombination parameterisations in advanced computer simulations. In this paper we present a method to implement arbitrary Auger parameterisations in the software package Sentaurus TCAD, enabling two- and three-dimensional simulation of solar cells using different Auger parameterisations. As examples, we implemented and investigated three different Auger parameterisations (proposed by Altermatt et al., by Kerr and Cuevas, and by Richter et al.) from the literature. For verification, we simulate Auger lifetimes for different doping densities and injection levels in crystalline silicon. The simulated Auger lifetimes are found to agree well with analytical solutions (differences less than 0.001 %). We then employ the three different Auger parameterisations for fitting measured effective lifetime curves of both \(n\) -type and \(p\) -type float-zone silicon lifetime samples and show which models are applicable under which conditions. We further compare the difference between the three Auger parameterisations by simulating characteristics of a screen-printed aluminium local back surface field silicon wafer solar cell. The simulation results agree well with the characterisation results. We find that the choice of Auger parameterisation can lead to significant differences in the predicted solar cell behaviour under one-Sun illumination. We demonstrate that different Auger parameterisations may result in significant differences in the blue response, by simulating a heavily doped emitter of an aluminium local back surface field silicon wafer solar cell.     

A way to measure power-quality indices in devices for monitoring processes that take place in overhead power-transmission lines

A generalized structure of an algorithm for measuring the power-quality indices is examined. The specific features of the algorithm’s blocks and possible ways to interpret it for different purposes and soft- and hardware abilities are shown. Ways to test the algorithm at every stage of development (from verification of the mathematical model to software debugging) are described. We analyze the algorithm’s operation in the LabView environment for measuring power-quality indices. A multifunctional device for measuring power quality in accordance with GOST (State Standard) 30804.4.30-2013 is presented. Bench tests of the multi-functional device under different operating conditions and when carrying out different functions in the frame of one soft- and hardware platform are carried out.     

Electronic transport across a layered structure of Fe/\upbeta -poly vinylidene fluoride/Fe using DFT calculations

Quantum electronic transport across a \(\upbeta \) -poly(vinylidene fluoride) ( \(\upbeta \) -PVDF) ferroelectric barrier structured between two ferromagnetic Fe layers is explored using DFT calculations. The multifunctional junction is organized in capacitor like structure, as FM (ferromagnetic metal)/FE (ferroelectric)/FM to understand the mechanism of electron transfer by controlling the spin polarization of the electrodes and also the ferroelectric polarization of the barrier. These studies are carried on a single bcc layer of Fe atoms in both the electrodes and two monomers of PVDF is utilized as a barrier. We investigated the dependence of total density of states (DOS), projected DOS, transmission coefficient and I–V characteristics on applied bias voltage using SIESTA & TRANSIESTA package.     

Two-dimensional accelerated MP-RAGE imaging with flexible linear reordering

Object

Implementation of an accelerated Magnetization Prepared RApid Gradient Echo (MP-RAGE) sequence for T1 weighted neuroimaging; exploiting modern MRI technologies to minimize scan time while preserving the image quality.

Materials and methods

A custom MP-RAGE sequence was implemented on a state-of-the-art 3T MR scanner equipped with a 32-channel receiver array head coil. The sequence utilized a shifted CAIPIRINHA k _y –k _z under-sampling pattern combined with elliptical scanning and a two-dimensional view ordering scheme to achieve high parallel imaging acceleration factors at maintained image contrast.

Results

It could be shown that MP-RAGE accelerated in two k-space directions outperforms single direction acceleration, which is the common practice with standard view ordering. Applying the CAIPIRINHA technique in conjunction with elliptical scanning further increased this benefit.

Conclusion

By combining MP-RAGE with CAIPIRINHA sampling and elliptical scanning, the scan time can be reduced from 4–5 min to 2–3 min with insignificant reduction in image quality.     

Quantum drift-diffusion model for IMPATT devices

Quantum correction is necessary on the classical drift-diffusion (CLDD) model to predict the accurate behavior of high frequency performance of ATT devices at frequencies greater than 200 GHz when the active layer of the device shrinks in the range of 150–350 nm. In the present work, a quantum drift-diffusion model for impact avalanche transit time (IMPATT) devices has been developed by incorporating appropriate quantum mechanical corrections based on density-gradient theory which macroscopically takes into account important quantum mechanical effects such as quantum confinement, quantum tunneling, etc. into the CLDD model. Quantum potentials (synonymous as Bohm potentials) have been incorporated in the current density equations as necessary quantum mechanical corrections for the analysis of millimeter-wave (mm-wave) and Terahertz (THz) IMPATT devices. It is observed that the large-signal (L-S) performance of the device is degraded due to the incorporation of quantum corrections into the model when the frequency of operation increases above 200 GHz; while the effect of quantum corrections are negligible for the devices operating at lower mm-wave frequencies.     

Substrate constructed by an array of split ring resonators for a THz planar antenna

Metamaterials are artificial materials offering unique properties which render them useful for various applications. In the present paper, we examine whether it is possible to design a split ring resonators’ (SRRs) based metamaterial substrate for enhancing the performance of planar antennas operating at THz frequencies. Initially, the radiating characteristics of a simple rectangular patch antenna over two well-known SRR substrates are studied. The yielded results are then compared to those of two novel designs of metamaterial antenna substrate with SRRs of decreasing size which are proposed to improve the antenna’s performance.     

Analysis of the response to a lightning strike of a towers cascade equipped with its grounding systems

This paper presents an analysis of the response to a direct and indirect lightning strike of a transmission line towers cascade using a direct time domain approach based on the corresponding transmission lines equations and finite difference time domain (FDTD) method. The proposed work deals with a real case of towers being connected by ground wires and equipped with grounding systems with different topologies (vertical or horizontal conductor buried in the ground). In particular, this work realistically represents the tower geometry and accounts for the propagation phenomena along the tower and between the towers. The analysis carried out in time domain deals with rather complex electrical devices (towers, ground wires and grounding systems), but at the same time requires very low computational cost and also provides relatively simple implementation. Some illustrative computational examples related to some engineering applications are given in the paper.     

A compact modelling of double-walled gate wrap around carbon nanotube array field effect transistors

The effects of multi-walled CNTs and array of channels are combined to form Double-walled Gate Wrap Around Carbon Nano Tube array Field Effect Transistor (DWGWA CNTFET). Numerical model is proposed for the device to study its performance. Screening and imaging effects of adjacent and inter walls in array of channels are included for calculating the drive capacitance, subsequently the drive current. This model suits for a wide range of chiralities and diameters. The change in drive capacitance of double-walled and single-walled device with respect to various drain and gate voltage for different values of number of channels, diameters are studied. The number of channels, CNTs diameters, chiralities of the tubes, source/drain length are varied and the corresponding responses of drive current, cut off frequency, signal delay time for both double and single walled devices are compared. In all cases, DWGWA CNTFET excels in its performance over Single-walled Gate Wrap Around Carbon Nano Tube array Field Effect Transistor (SWGWA CNTFET).The model of the proposed device can be utilized for designing the Nano devices with high power and high speed capability.     

Role of inelastic electron–phonon scattering in electron transport through ultra-scaled amorphous phase change material nanostructures

The electron transport through ultra-scaled amorphous phase change material (PCM) GeTe is investigated by using ab initio molecular dynamics, density functional theory, and non-equilibrium Green’s function, and the inelastic electron–phonon scattering is accounted for by using the Born approximation. It is shown that, in ultra-scaled PCM device with 6 nm channel length, \(<\) 4 % of the energy carried by the incident electrons from the source is transferred to the atomic lattice before reaching the drain, indicating that the electron transport is largely elastic. Our simulation results show that the inelastic electron–phonon scattering, which plays an important role to excite trapped electrons in bulk PCM devices, exerts very limited influence on the current density value and the shape of current–voltage curve of ultra-scaled PCM devices. The analysis reveals that the Poole–Frenkel law and the Ohm’s law, which are the governing physical mechanisms of the bulk PCM devices, cease to be valid in the ultra-scaled PCM devices.     

Hierarchies of transport equations for nanopores

We review transport equations and their usage for the modeling and simulation of nanopores. First, the significance of nanopores and the experimental progress in this area are summarized. Then the starting point of all classical and semiclassical considerations is the Boltzmann transport equation as the most general transport equation. The derivation of the drift-diffusion equations from the Boltzmann equation is reviewed as well as the derivation of the Navier–Stokes equations. Nanopores can also be viewed as a special case of a confined structure and hence as giving rise to a multiscale problem, and therefore we review the derivation of a transport equation from the Boltzmann equation for such confined structures. Finally, the state of the art in the simulation of nanopores is summarized.     

Enhancing the calculation accuracy of performance characteristics of power-generating units by correcting general measurands based on matching energy balances

General principles of a procedure for matching energy balances of thermal power plants (TPPs), whose use enhances the accuracy of information-measuring systems (IMSs) during calculations of performance characteristics (PCs), are stated. To do this, there is the possibility for changing values of measured and calculated variables within intervals determined by measurement errors and regulations. An example of matching energy balances of the thermal power plants with a T-180 turbine is made. The proposed procedure allows one to reduce the divergence of balance equations by 3–4 times. It is shown also that the equipment operation mode affects the profit deficiency. Dependences for the divergence of energy balances on the deviation of input parameters and calculated data for the fuel economy before and after matching energy balances are represented.     

Accelerated redistancing for level set-based process simulations with the fast iterative method

The finite iterative method is compared to an industry-hardened fast marching method for accelerating the redistancing step essential for Level Set-based process simulations in the area of technology computer-aided design. We discuss our implementation of the finite iterative method and depict extensions to improve the method for process simulations, in particular regarding stability. Contrary to previously published work, we investigate real-world structures with varying resolutions, originating from the area of process simulation. The serial execution performance as well as error norms are used to compare our approach with an industry-hardened fast marching method implementation. Parallel scalability is discussed based on a shared-memory OpenMP implementation. We show that our approach of the finite iterative method is an excellent candidate for accelerating Level Set-based process simulations, as it offers considerable performance gains both in serial and parallel execution mode, albeit being inferior with respect to accuracy.     

Improving sequencing by tunneling with multiplexing and cross-correlations

Sequencing by tunneling is a next-generation approach to read single-base information using electronic tunneling transverse to the single-stranded DNA (ssDNA) backbone while the latter is translocated through a narrow channel. The original idea considered a single pair of electrodes to read out the current and distinguish the bases [1, 2]. Here, we propose an improvement to the original sequencing by tunneling method, in which \(N\) pairs of electrodes are built in series along a synthetic nanochannel. While the ssDNA is forced through the channel using a longitudinal field it passes by each pair of electrodes for long enough time to gather a minimum of \(m\) tunneling current measurements, where \(m\) is determined by the level of sequencing error desired. Each current time series for each nucleobase is then cross-correlated together, from which the DNA bases can be distinguished. We show using random sampling of data from classical molecular dynamics, that indeed the sequencing error is significantly reduced as the number of pairs of electrodes, \(N\) , increases. Compared to the sequencing ability of a single pair of electrodes, cross-correlating \(N\) pairs of electrodes exponentially improves this sequencing ability due to the approximate log-normal nature of the tunneling current probability distributions. We have also used the Fenton–Wilkinson approximation to analytically describe the mean and variance of the cross-correlations that are used to distinguish the DNA bases. The method we suggest is particularly useful when the measurement bandwidth is limited, allowing a smaller electrode gap residence time while still promising to consistently identify the DNA bases correctly.     

A new modeling and placement of shunt FACTS devices in the secondary voltage regulation environment

Recently, the Secondary Voltage Regulation (SVR) is installed in some power systems in order to ensure the coordination voltage control devices. In other hand, the shunt FACTS devices such as the Static Var Compensator (SVC) and the STATic COMpensator (STATCOM) are extensively used for the local voltage control without any coordination with other voltage control devices, without any reciprocal coordination. In this paper, new models of SVC and STATCOM are proposed to be adopted in power flow models that include the SVR. The proposed models are implemented and tested on a model of the Italian power system. Furthermore, a new method based on sensitivity analysis is proposed to find the most sensitive placements for the installation of SVC and STATCOM. The results obtained show the highly computational performance of the propose models and also the effectiveness of the sensitivity analysis to find the best placements of SVC and STATCOM taking into account the SVR.     

Optimization of I-shape Microstrip patch antenna using PSO and curve fitting

This paper presents an optimization of Microstrip patch antenna, based on Particle Swarm Optimization (PSO) with curve fitting. An I shape antenna is used to demonstrate the optimization technique. An initial antenna is designed by cutting slots in rectangular patch to form shape I. By varying different parameters of the antenna, the data for developing PSO program in MATLAB is obtained. For Simulation, software IE3D and Graphmatica is used for Curve Fitting. Thus the optimized antenna is obtained, and finally the performance of the initial antenna is compared with the PSO optimized antenna. The result yields that obtained antenna have resonance near at 2.4 GHz and it also shows remarkable improvement over Fractional Bandwidth. For the Microstrip line feed I shape antenna, the Fractional Bandwidth is increased by 25 % as compared to the initial antenna.     

Testing the steam generator model with helical coiled lead-heated tubes

Results obtained from testing the model of a lead-heated steam generator containing helical coiled tubes with longitudinal flow of coolants and consisting of two identical three-tube modules are presented. The program for investigating the steam generator model during operation of one module and during joint operation of two modules was aimed at studying heat transfer and, to a larger extent, the thermalhydraulic stability of steam-generating tubes during parallel (joint) operation of two modules at the parameters of partial-load and startup modes of operation. With the parameters of rated operating mode, the steam temperature at the module outlet corresponded to its design values even with a longitudinal flow pattern of coolants. No pulsation modes involving circulation reversal in the secondary coolant circuit were revealed in the entire variation range of operating parameters during operation in both partial-load and startup modes under the conditions of the considered lead circuit of the SPRUT experimental setup. The data obtained in the course of tests on this steam generator model will be conservative in regard of heat transfer in the post-burnout region and in terms of thermodynamically nonequilibrium conditions of steam-water flow for the steam generator used as part of the BREST-OD-300 reactor plant that is being developed at the Dollezhal Research and Development Institute of Power Engineering (NIKIET). These data should be used for verifying computation codes.     

Impact of Stone-Wales and lattice vacancy defects on the electro-thermal transport of the free standing structure of metallic ZGNR

We report the effect of topological as well as lattice vacancy defects on the electro-thermal transport properties of the metallic zigzag graphene nano ribbons at their ballistic limit. We employ the density function theory–Non equilibrium green’s function combination to calculate the transmission details. We then present an elaborated study considering the variation in the electrical current and the heat current transport with the change in temperature as well as the voltage gradient across the nano ribbons. The comparative analysis shows, that in the case of topological defects, such as the Stone-Wales defect, the electrical current transport is minimum. Besides, for the voltage gradient of 0.5 Volt and the temperature gradient of 300 K, the heat current transport reduces by \({\sim }62\,\%\) and \({\sim }50\,\%\) for the cases of Stones-Wales defect and lattice vacancy defect respectively, compared to that of the perfect one.     

An accurate computation method based on artificial neural networks with different learning algorithms for resonant frequency of annular ring microstrip antennas

An annular ring compact microstrip antenna (ARCMA) constructed by loading a circular slot in the center of the circular patch antenna is a popular microstrip antenna due to its favorable properties. In this study, a method based artificial neural networks (ANNs) has been firstly applied for the computing the resonant frequency of ARCMAs. Multilayered perceptron model based on feed forward back propagation ANN has been utilized, and the constructed model have been separately trained with 8 different learning algorithms to achieve the best results regarding the resonant frequency of ARCMAs at dominant mode. To this end, the resonant frequencies of 80 ARCMAs with varied dimensions and electrical parameters in accordance with UHF band covering GSM, LTE, WLAN and WiMAX applications were simulated with a robust numerical electromagnetic computational tool, \(\hbox {IE3D}^\mathrm{TM}\) , which is based on method of moment. Then, ANN model was constructed with the simulation data, by using 70 ARCMAs for training and the remaining 10 for test. As the performances of the 8 learning algorithms are compared with each other, the best result is obtained with Levenberg–Marquardt algorithm. The proposed ANN model were confirmed by comparing with the suggestions reported elsewhere via measurement data published earlier in the literature, and they have further validated on an ARCMA fabricated in this study. The results achieved in this study show that ANN model learning with LM algorithm can be successfully used to compute the resonant frequency of ARCMAs without involving any sophisticated methods.