model ECG—6511心电图机故障一例

故障现象:心电图出现不规律的基线不稳、杂波现象。分析与检修:出现此类故障原因有两大类:一是仪器使用不当时出现。如电极与皮肤接触太松,病人身体的移动等;二是仪器本身引起故障。首先排除第一种情况,然后确定故障部位。将本仪     

基于Markov model的容错计算机联锁系统可靠性分析

容错设计是提高计算机系统可靠性的有效手段。本文研究了容错控制系统可靠性概念的内涵和定义,并结合工程实践讨论了我国的一种典型容错计算机联锁系统,且建立了考虑故障恢复和故障处理能力的多阶马尔可夫模型,进行了定量分析。     

An informationally complete Wigner function for the Tavis–Cummings model

Journal of Computational Electronics - Here we consider an informationally complete Wigner function approach to look at multiple atoms (qubits) coupled to a field mode. We consider the...     

A current-based model of an IPFC for Newton–Raphson power flow

In this paper a new approach to modeling an interline power flow controller (IPFC) for power flow calculations by applying the Newton–Raphson method is presented as a continuation of the ideas already applied to static synchronous series compensator (SSSC). The presented approach differs from the methods proposed by other authors in terms of the interpretation of the device's branches. They are considered on the basis of their currents, and so it can, therefore, be denoted as a current-based model of an IPFC. First, the basic features of the IPFC are presented; as this is the basis for the current-based model that is incorporated into the Newton–Raphson load-flow model. Next, the basic equations are derived from the generic IPFC model. Further handling of the constraints is then discussed. The derived model was tested on the IEEE 57, IEEE 118 and IEEE 300 bus systems. The effectiveness of the proposed model's iteration procedure is compared with other models. The comparison is based on data available in the references. We have shown that the proposed model exhibits a faster convergence than other models, and in addition, the number of iterations needed to achieve the prescribed accuracy is almost constant, regardless of the location, a consideration of the constraints or the selection of the controlled variable.     

A two-dimensional mathematical model of a Zn-MnO2 alkaline cell(1)

A two-dimensional mathematical model based on the macrohomogeneous theory of porous electrodes was developed for a cylindrical Zn-MnO2 alkaline cell. The model was applied to understand the effect of the length of the anode current collector on the cell performance. Results are presented for the continuous discharge at a high rate of 1A and a moderate rate of 0.2A for a AA-sized cell. With a typical length of an anode current collector at about 70%of the cell height, the analysis showed that an increase in the length of the anode current collector would benefit the lower rate of discharge more than the higher rate of discharge.     

A two-dimensional mathematical model of a Zn-MnO2 alkaline cell(3)

Overpotential:η The change of the chemical potential for solid phases is equal to zero as Zn and ZnO are considered as single-component materials.By combining the Ohm’s law in the matrix phase and the chemical potential in the solution phase, the overpotential for the anode can be written as     

A two-dimensional of a Zn-MnO2 mathematical model alkaline cell （4）

Cathode- Cathode Current Collector Interface The boundary conditions for the cathode- cathode current collector interface includes：     

A two-dimensional mathematical model of a Zn-MnO2 alkaline cell(2)

Surface Overpotential:The driving force of the electrochemical reaction rate is the surface overpote ntial,ηs=η-Uw,ref,where Uw,ref is the potential of an imaginary reference ele ct-rode positioned adjacent to the working electrode just beyond the double lay er.Hence,     

A two-dimensional mathematical model of a Zn-MnO2 alkaline cell(4)

Cathode-Cathode Current Collector Interface The boundary conditions for the cathode-cathode current collector interface includes:     

Multi-objective mean–variance–skewness model for generation portfolio allocation in electricity markets

This paper proposes an approach for generation portfolio allocation based on mean–variance–skewness (MVS) model which is an extension of the classical mean–variance (MV) portfolio theory, to deal with assets whose return distribution is non-normal. The MVS model allocates portfolios optimally by considering the maximization of both the expected return and skewness of portfolio return while simultaneously minimizing the risk. Since, it is competing and conflicting non-smooth multi-objective optimization problem, this paper employed a multi-objective particle swarm optimization (MOPSO) based meta-heuristic technique to provide Pareto-optimal solution in a single simulation run. Using a case study of the PJM electricity market, the performance of the MVS portfolio theory based method and the classical MV method is compared. It has been found that the MVS portfolio theory based method can provide significantly better portfolios in the situation where non-normally distributed assets exist for trading.     

An extended Hückel theory based atomistic model for graphene nanoelectronics

An atomistic model based on the spin-restricted extended Hückel theory (EHT) is presented for simulating electronic structure and I–V characteristics of graphene devices. The model is applied to zigzag and armchair graphene nano-ribbons (GNR) with and without hydrogen passivation, as well as for bilayer graphene. Further calculations are presented for electric fields in the nano-ribbon width direction and in the bilayer direction to show electronic structure modification. Finally, the EHT Hamiltonian and NEGF (Nonequilibrium Green’s function) formalism are used for a paramagnetic zigzag GNR to show 2e ²/h quantum conductance.     

Poisson–Nernst–Planck model for an ionic transistor based on a semiconductor membrane

In this paper we developed a Poisson–Nernst–Planck model of an ionic current flowing through a nanopore in a layered solid-state membrane made of a single highly-doped \(n\) -Si layer sandwiched between two thick oxide layers which we call the ionic transistor. We studied this layered membrane for a range of source-drain voltages while keeping the gate (the semiconductor membrane) voltage fixed at a certain value, which was later varied too. We find that for this ionic transistor to be effective in controling the ion fluxes through the nanopore, the gate voltage must be kept relatively large. Another solution could be to increase the surface negative charge on the membrane or to replace the outer oxide layers with the semiconductor material, such as the \(p\) -Si material. The developed model can be applied to study ionic filtering and separation properties of membranes of different composition and nanopore geometries.     

An analytical model to calculate the current–voltage characteristics of AlGaN/GaN HEMTs

Journal of Computational Electronics - In this paper, a simple analytical model is presented to determine the sheet carrier density and the current–voltage characteristics of different...     

A simple implementation of power mismatch STATCOM model into current injection Newton–Raphson power-flow method

This paper presents a simple implementation of Static Shunt Compensator (STATCOM) into Newton–Raphson current injection load flow method. The controlled STATCOM bus in the network is represented by voltage-controlled bus with zero active power generation at the required voltage magnitudes. The power mismatch equation of the connected STATCOM bus is included in Newton–Raphson current injection load flow algorithm, while the other PQ buses are represented by current mismatch equations. Moreover, the parameters of STATCOM can be calculated during iterative process and the final value will be updated after the convergence is achieved. This representation of generator buses reduces the number of required equations with respect to the classical and improved versions of the current injection methods. In addition of that the developed model reduces the complexities of the computer program codes and enhances the reusability by avoiding modifications in the Jacobian matrix. The performance of the developed STATCOM model has been tested using standard IEEE systems.     

An experimental study of a VVER reactor’s steam generator model operating in the condensing mode

Results obtained from an experimental study of a VVER reactor’s steam generator model operating in the condensing mode are presented. The obtained empirical dependence for calculating the power of heat exchangers operating in the steam condensation mode is presented.     

Fuzzy bilinear state feedback control design based on TS fuzzy bilinear model for DC–DC converters

This paper proposes a fuzzy bilinear state feedback controller based on Tagaki–Sugeno (TS) fuzzy bilinear model for DC–DC converters. The DC–DC converters can be approximated to bilinear model via Taylor series expansion. For achieving the output voltage regulation, we formulate the extended system of bilinear DC–DC converter model, one of whose state variables is the error between the output voltage and the reference output voltage. The extended system can be described to TS fuzzy bilinear model. We design a fuzzy bilinear state feedback controller to track the reference output voltage. The closed loop system is globally asymptotically stable via the proposed controller. Lyapunov theory is employed to guarantee the stability of the closed loop system. Numerical examples are given to demonstrate the validity of our proposed control approach with comparative results.     

ATC with ZIP load model – A comprehensive evaluation with third generation FACTS in restructured electricity markets

In this paper, an optimal power flow based approach has been applied for multi-transactions in deregulated environment for ATC determination with third generation FACTS devices. The main contribution of the paper is (i) OPF based approach for evaluation of ATC with multi-transactions, (ii) ATC enhancement with third generation FACTS devices viz. Static Compensator (STATCOM), Static Synchronous Series Compensator (SSSC), and Unified Power Flow Controller (UPFC) for intact and line contingency cases (iii) Impact of ZIP load on ATC determination and comparison of ATC obtained with ZIP load model and constant P,Q load model, (iv) Comparison of ATC obtained with DC/AC-PTDFs based method along with FACTS devices for comparison. The results have been determined for intact and line contingency cases taking simultaneous as well as single transaction cases for IEEE 24 bus RTS.     

A current-based model of the static synchronous series compensator (SSSC) for Newton–Raphson power flow

In this paper, a new approach to modeling a static synchronous series compensator (SSSC) for power-flow calculations by applying the Newton–Raphson method is presented. This new approach differs from known methods in terms of the interpretation of the device's branch. It is considered on the basis of its current and is therefore denoted as a current-based model of an SSSC. This approach might in principle be applicable also for other FACTS devices (i.e., UPFC, IPFC, GUPFC). In the paper, the current-based model of an SSSC is presented as the models of this device have difficulties with convergence in power-flow calculations and there are very few references covering these topics. First, the basic features of an SSSC are presented, as it is the basis for the current-based model that is incorporated into the Newton–Raphson load-flow model. The results of the tests at the IEEE 57-bus system are discussed in detail and compared with the existing injection SSSC load-flow model [X.P. Zhang, Advanced modeling of the multicontrol functional static synchronous series compensator (SSSC) in Newton power flow, IEEE Trans. Power Syst. 18 (November (4)) 2003].     

Discrete space vector modulation and optimized switching sequence model predictive control for three-level voltage source inverters

This paper proposes a discrete space vector modulation and optimized switching sequence model predictive controller for three-level neutral-point-clamped inverters in grid-connected applications. The proposed strategy is based on cascaded model predictive control (MPC) for controlling the grid current while maintaining the capacitor voltage balanced without weighting factor. To enhance the closed-loop performance, the external MPC evaluates 19 basic and 138 virtual vectors (VV) of the proposed space vector method. The optimal control voltage is then selected using an extended deadbeat method to reduce the execution time of the proposed control algorithm. By using the discrete space vector modulation principle, the VV are synthesized based on switching sequence (SS) and are divided into negative and positive SSs considering their impact on the neutral point (NP) potential. The inner MPC evaluates both types of SSs and selects the one that keeps the capacitor voltage balanced. Various controllers are evaluated and compared against the proposed control strategy. The results show that the proposed strategy improves performance without weighting factor, while maintaining a total harmonic distortion of current to be less than 2%. Compared to the modulated MPC which provides the same fxed switching frequency, the proposed controller reduces the computational burden by over 50% while also providing better NP voltage balance accuracy