The recursive Green’s function method for graphene

We describe how to apply the recursive Green’s function method to the computation of electronic transport properties of graphene sheets and nanoribbons in the linear response regime. This method allows for an amenable inclusion of several disorder mechanisms at the microscopic level, as well as inhomogeneous gating, finite temperature, and, to some extend, dephasing. We present algorithms for computing the conductance, density of states, and current densities for armchair and zigzag atomic edge alignments. Several numerical results are presented to illustrate the usefulness of the method.     

The non-equilibrium Green’s function method: an introduction

We present an elementary introduction of the non-equilibrium Green’s function method, applied to stationary quantum transport in semiconductor nanostructures. This article provides an overview of the strengths and weaknesses of the method.     

Consistency of boundary conditions in nonequilibrium Green’s function simulations

The consistency of the boundary conditions imposed on the nonequilibrium Green’s function (NEGF) method is investigated by comparing the electron energy distribution at the drain end with the thermal equilibrium distribution. We show that the boundary condition is not consistently satisfied in the cases of ballistic transport and quasi-ballistic transport including scattering only in the channel region. It is pointed out that inclusion of scattering in the high-doped regions is inevitable to be consistent and crucial to obtain reliable transport characteristics.     

Atomistic non-equilibrium Green’s function simulations of Graphene nano-ribbons in the quantum hall regime

The quantum Hall effect in Graphene nano-ribbons (GNR) is investigated with the non-equilibrium Green’s function (NEGF) based quantum transport model in the ballistic regime. The nearest neighbor tight-binding model based on p _z orbital constructs the device Hamiltonian. GNRs of different edge geometries (Zigzag and Armchair) are considered. The magnetic field is included in both the channels and contact through Peierls substitution. Efficient algorithms for calculating the surface Green function are used to reduce computation time to enable simulating realistically large dimensions comparable to those used in experiments. Hall resistance calculations exactly reproduce the quantum Hall plateaus observed in the experiments. Use of large dimensions in the simulation is crucial in order to capture the quantum Hall effect within experimentally magnetic fields relevant 10–20 T. R. Golizadeh-Mojarad and A.N.M. Zainuddin contributed equally to this work.     

Determining a set of suspicious electricity customers using statistical ACL Tukey’s control charts method

Estimation a set of suspicious electricity customers is the first stage for detecting fraud of electricity. This paper deals with this stage. Based on historical data about monthly measurements of electricity, customers’ time series are formed and then analysis of these series is performed using Tukey’s control charts as one of the statistical method. The asymmetric control limit (ACL) Tukey’s control charts are chosen due to a rather expressed asymmetry and dominantly presented right distribution of time series data. As usual, the choice of upper (UCL) and lower (LCL) control limits is not based on allowed number of observations outside of the control limits. The choice of these limits is based on the balance of total energy, registered energy and energy losses. The essence of this approach is the simultaneous observation all customers’ time series of the controlled set with the same control limits and the same percentage of total and normalized energy losses in the observed distribution network. The criterion for finding the number of suspicious customers and their addresses is allowed error between the number of registered customers with one or more data (observations) outside the control limits for given losses and the number of suspicious customers’ indicators based on certain balance of energy and the estimated total percentage of losses in distribution network.     

A magnetic detecting and evaluation method of substation’s grounding grids with break and corrosion

The grounding grid buried in the earth will become a hidden danger to the safety of substations due to some faults of breaks or thinner conductors in corrosion. A novel method to get accurate status of grounding grid was proposed based on measuring magnetic induction intensity. The basic structure of grounding grid without working drawing was concluded, and the positions and the status of faults were diagnosed by this method. The completed detecting system, including hardware device of data measurement, diagnosis, and analysis software, was introduced concisely. The results of simulations and applications show that this method is simple and effective in the practical engineering.     

A method of using neural fuzzy models to determine the technical state of a diesel locomotive’s electrical equipment

Equipment for carrying out onboard diagnostics is an important component in systems for controlling the state and reliability of rolling stock, in particular, that of diesel locomotives. It makes it possible to monitor a locomotive’s service quality, to detect and predict changes in its technical state without interrupting the carriage process, and to efficiently use the high-cost stationary and local diagnostic means, as well as to correct service time and volume by taking into account the real technical state. Therefore, it is important to develop methods for determining the technical state of locomotive units by using an MCS-T(N,E) (micro-processor control system) locomotive’s diagnostic subsystem of a locomotive and software for processing the measurement data. The main aim of such a method is to monitor the technical state of a locomotive’s equipment and predict changes in it. At the present time, simplified diagnostic models are used to solve such problems. However, to increase the efficiency and reliability of the process of checking complicated objects such as a locomotive, it is necessary to use more complex diagnostic models based on artificial neural networks. A way to use a neural-network method and neural fuzzy diagnostic models for diagnosing the excitation system of traction generators of modern diesel locomotives is presented in this paper. Information collected by the MCS-TP subsystem is used as diagnostic information. It is transferred online to a remote diagnostic server. The method for diagnosing the excitation system of a traction generator is checked by processing the measurement information.     

Comparative effectiveness of using gas-turbine and gas-piston units for additional redundancy of an NPP’s own needs

Assessments of comparative effectiveness of the use of gas-turbine and gas-piston electricity-generating units (GPUs) for the general station reserves for the needs of a nuclear power plant with VVER-1000 reactors are presented.     

Dynamic MR imaging of a minipig’s knee using a high-density multi-channel receive array and a movement device

Object

To construct an optimised, high-density receive array and a movement device to achieve dynamic imaging of the knee in orthopedic large animal models (e.g., minipigs) at 1.5 T.

Materials and methods

A 13-channel RF receive array was constructed, and the crucial choice of the array element size (based on considerations like region of interest, geometry of the minipig’s knee, achievable signal-to-noise ratio, applicability of parallel imaging, etc.) was determined using the Q factors of loops with different sizes. A special movement device was constructed to guide and produce a reproducible motion of the minipig’s knee during acquisition.

Results

The constructed array was electrically characterised and the reproducibility of the cyclic motion was validated. Snapshots of dynamic in vivo images taken at a temporal resolution (308 ms) are presented. Some of the fine internal structures within the minipig’s knee, like cruciate ligaments, are traced in the snapshots.

Conclusion

This study is a step towards making dynamic imaging which can give additional information about joint injuries when static MRI is not able to give sufficient information, a routine clinical application. There, the combination of a high-density receive array and a movement device will be highly helpful in the diagnosis and therapy monitoring of knee injuries in the future.     

A new approach to modelling quantum distributions and quantum trajectories for density matrix and Green function simulation of nano-devices

In this paper we present a new formalism for quantum transport distribution functions based on density matrices and non-equilibrium Green’s functions that have practical computational advantages and better interpretive power than Wigner function and other phase-space distributions that rely on the centre-relative construction thus leading to non-compact support on phase-space. The new approach uses a mixed position-momentum basis and has manifest compact support in phase space, proving detailed accounting for nodal regions in both position and momentum. The relevant equations of motion and possible computational schemes are discussed within exactly soluble models that illustrate the formalism and its interpretation. The near-classical limit is easily obtained and lends itself to path-variable iterative methods including Monte Carlo schemes. The new distribution functions are complex valued and lead to coupled drift-diffusion style equations of motion. The methodology is compared with Wigner functions, density gradient and Bohm trajectory methods.     

Response to Jacobson and Delucchi’s rebuttal of my critique

This paper provides further arguments why Jacobson and Delucchi’s (JD) critiques of my paper are misplaced. It also provides additional references to work that reached different conclusions than Jacobson et al. Work by JD and others is useful in identifying the plethora of assumptions required to conclude that intermittent renewables can now be economically substituted for all current uses of fossil fuels throughout the entire economy.     

FERC’s Flawed Assessment of the Benefits and Costs of Regional Transmission Organizations

FERC’s Economic Assessment does not meet the minimal requirements of a cost–benefit analysis of RTOs. It fails to address critical incentive questions associated with the RTO structure, and begs the question of whether RTOs will in fact make electricity markets more competitive and efficient.     

Comment on “Efficient full-path optical calculation of scalar and vector diffraction using the Bluestein method”

The calculation of light diffraction is of great importance for many essential optical applications,including optical lithography,optical tweezers,and super-resolution imaging,and is a research topic that has been extensively studied over the past few decades.Because both scalar and vector diffraction can be formulated as Fourier transforms,the standard method is to use the fast Fourier transform(FFT)algorithm.However,the use of the FFT requires a fixed sampling relation between the discretization of the input field and that of the output field.For the vectorial case,this requirement often causes a significant waste of computational resources,which hinders real-time applications.     

Reply to Comments on “Efficient full-path optical calculation of scalar and vector diffraction using the Bluestein method”

Dear Editor,In ref.we present an efficient full-path optical calculation by using the Bluestein method.A real optical apparatus for laser processing,imaging,or optical tweezing normally involves diverse optical lenses with different physical and numerical apertures(NA).In such applications,the optical path is usually tortuous and long.To assist in the design,evaluation,and alignment of optical instruments,it is advantageous to retrieve the optical field in an arbitrary position along the entire optical path,which is termed the full-path calculation in our paper,with sufficient accuracy and efficiency.In particular,high flexibility is required to accommodate the mismatch between optical apertures of different components in the optical path.We present a fullpath optical calculation method by adopting the Bluestein method to address this realistic demand.     

Monitoring and correcting spatio-temporal variations of the MR scanner’s static magnetic field

The homogeneity and stability of the static magnetic field are of paramount importance to the accuracy of MR procedures that are sensitive to phase errors and magnetic field inhomogeneity. It is shown that intense gradient utilization in clinical horizontal-bore superconducting MR scanners of three different vendors results in main magnetic fields that vary on a long time scale both spatially and temporally by amounts of order 0.8–2.5 ppm. The observed spatial changes have linear and quadratic variations that are strongest along the z direction. It is shown that the effect of such variations is of sufficient magnitude to completely obfuscate thermal phase shifts measured by proton-resonance frequency-shift MR thermometry and certainly affect accuracy. In addition, field variations cause signal loss and line-broadening in MR spectroscopy, as exemplified by a fourfold line-broadening of metabolites over the course of a 45 min human brain study. The field variations are consistent with resistive heating of the magnet structures. It is concluded that correction strategies are required to compensate for these spatial and temporal field drifts for phase-sensitive MR protocols. It is demonstrated that serial field mapping and phased difference imaging correction protocols can substantially compensate for the drift effects observed in the MR thermometry and spectroscopy experiments.