Diagnosis of lossy resonator filters with source–Load coupling using Y‐parameters

This article presents a novel approach to extract the coupling matrix (CM) of a lossy cross‐coupled resonator bandpass filter with source–load coupling using admittance parameters (also known as Y‐parameters). The Y‐parameters are calculated by characteristic polynomials corresponding to the measured S‐parameters. The unloaded quality factor of resonators and the CM can be extracted from the Y‐parameters. The method allows one to diagnose a filter with source–load coupling without necessity of dealing with the degenerate poles problem of the Y‐parameters and the measurement noise. The proposed diagnosis method can be used in a filter tuning and speeds up its physical realization. The method is verified by a fabricated fourth‐order bandpass filter and a simulated substrate integrated waveguide dual‐mode filter with source–load couplings. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:713–717, 2014.     

气相反应产物中固相沉积始现的反应温度点计算

许多气相反应不希望出现固相产品,如燃烧过程不希望有积碳。本文研究气相反应产物在什么条件下出现固体。根据Gibbs自由能最小等热力学原理,提出1种将化学反应平衡和固体饱和蒸汽压数据相结合,求气相反应产物中固相沉积始现的反应温度点的计算方法。举出氯硅烷氢化等7个体系的算例。结果表明:本法与传统的Gibbs自由能最小法结果相同;在同样的进料条件下,每个体系均存在1个固相沉积的温度范围。本文确定的这种温度范围对探讨气体反应的固相沉积现象具有很好的指导意义,所选算例得出:SiHCl_3氢化等4个体系有2个沉积温度点(TD_1,TD_2),即这些平衡体系有2个沉积的温度转折点,如果不希望有沉积,就必须使进料温度小于TD_1或者大于TD_2;而CH_4部分氧化等3个体系只有1个沉积温度点TD,此类平衡体系如果不希望有沉积,进料温度就应大于TD。     

Simulation study of single‐cell‐gap transflective liquid crystal display with nonuniform potential

A single‐cell‐gap transflective liquid crystal display with a nonuniform electric potential is demonstrated. The top substrate has a top planar common electrode, a transparent dielectric layer with a general dielectric constant is coated on the bottom substrate, and two planar pixel electrodes with the same size are coated on the dielectric layer and the bottom substrate, respectively. With the different gaps between the two planar pixel electrodes and top planar pixel electrode, the nonuniform electric potential from the transmissive region (T region) to the reflective region (R region) is generated, while a bumpy reflector is coated under the bottom substrate. In this device, with the dielectric layer, the pixel and common electrodes generate a strong electric potential in the T region and a relatively weak electric potential in the R region. Consequently, the T and R regions accumulate the same optical phase retardation. The simulation results show that the display exhibits reasonably low operating voltage, high optical efficiency, and well‐matched voltage‐dependent transmittance and reflectance curves. Besides, the fabrication process and the driving mode of the transflective liquid crystal display are relatively simple, and it is suitable for mobile applications.     

Robust fusion time‐varying Kalman estimators for multisensor networked systems with mixed uncertainties

This paper addresses the problem of designing robust fusion time‐varying Kalman estimators for a class of multisensor networked systems with mixed uncertainties including multiplicative noises, missing measurements, packet dropouts, and uncertain‐variance linearly correlated measurement and process white noises. By the augmented approach, the original system is converted into a stochastic parameter system with uncertain noise variances. Furthermore, applying the fictitious noise approach, the original system is converted into one with constant parameters and uncertain noise variances. According to the minimax robust estimation principle, based on the worst‐case system with the conservative upper bounds of the noise variances, the five robust fusion time‐varying Kalman estimators (predictor, filter, and smoother) are presented by using a unified design approach that the robust filter and smoother are designed based on the robust Kalman predictor, which include three robust weighted state fusion estimators with matrix weights, diagonal matrix weights, and scalar weights, a modified robust covariance intersection fusion estimator, and robust centralized fusion estimator. Their robustness is proved by using a combination method, which consists of Lyapunov equation approach, augmented noise approach, and decomposition approach of nonnegative definite matrix, such that their actual estimation error variances are guaranteed to have the corresponding minimal upper bounds for all admissible uncertainties. The accuracy relations among the robust local and fused time‐varying Kalman estimators are proved. A simulation example is shown with application to the continuous stirred tank reactor system to show the effectiveness and correctness of the proposed results.     

A new view of anti‐windup design for uncertain linear systems in the frequency domain

This paper presents a new perspective on the stability problem for uncertain LTI feedback systems with actuator input amplitude saturation. The solution is obtained using the quantitative feedback theory and a 3 DoF non‐interfering control structure. Describing function (DF) analysis is used as a criterion for closed loop stability and limit cycle avoidance, but the circle or Popov criteria could also be employed. The novelty is the combination of a controller parameterization from the literature and describing function‐based limit cycle avoidance with margins for uncertain plants. Two examples are given. The first is a benchmark problem and a comparison is made with other proposed solutions. The second is an example that was implemented and tested on an X‐Y linear stage used for nano‐positioning applications. Design and implementation considerations are given. An example is given on how the method can be extended to amplitude and rate saturation with the help of the generalized describing function, and a novel anti‐windup compensation structure inspired by previous contributions. Copyright © 2015 John Wiley & Sons, Ltd.     

Necessary and sufficient conditions for bounded distributed mean square tracking of multi‐agent systems with noises

This paper is concerned with the distributed control problem of second‐order agents under directed network topology. The control input of each agent only depends on its own state and the states of its neighbors corrupted by white noises. By using the algebraic graph theory and stochastic analysis method, necessary and sufficient conditions are presented for mean square bounded tracking. Finally, several simulation examples are given to illustrate the results. Copyright © 2015 John Wiley & Sons, Ltd.     

Pressure Rise due to SF6 Arcing and Energy Balance in a Closed Container

From an environmental viewpoint, when carrying out internal arc tests on SF₆‐insulated power equipment, it is necessary to prevent SF₆ from being released into the atmosphere or to replace SF₆ with air in accordance with IEC standards. However, the pressure rise and the thermal effect of the hot gas exhausted during arcing when testing in air are still considerably different from those for testing in SF₆. Thus, it is necessary to propose a specific procedure to replace SF₆ with air and to select appropriate parameters for the tests. Therefore, it is desirable to clarify the equivalent conditions causing these phenomena both experimentally and analytically. In this paper, we describe the effect of the charged gas pressure in a closed container on the pressure rise due to air and SF₆ arcing and the ratio of the arc energy to the energy contributing to the internal pressure rise () from an experimental viewpoint. Additionally, to research the energy balance resulting from SF₆ arcing in the container, the energy balance is discussed on the basis of chemical reactions, radiation, and the melting and vaporization of the electrodes. It is found that the maximum pressure rise increases for both gases upon increasing the gas pressure from 0.1 MPa to 0.4 MPa. Subsequently, good agreement with the energy balance was obtained under reasonable assumptions by taking account of the energy components related to the chemical reactions, radiation, and the melting and vaporization of the electrodes. The ratio of the radiation energy loss to the total consumption energy increased upon increasing the charged gas pressure.     

Dynamic modeling of a dual active bridge DC to DC converter with average current control and load‐current feed‐forward

Bidirectional power flow is needed in many power conversion systems like energy storage systems, regeneration systems, power converters for improvement of the power quality and some DC‐DC applications where bidirectional high power conversion and galvanic isolation are required. The dual active bridge (DAB) is an isolated, high voltage ratio DC‐DC converter suitable for high power density and high power applications, being a key interface between renewable energy sources and energy storage devices. This paper is focused on the modeling and control design of a DC‐DC system with battery storage based on a DAB converter with average current mode control of the output current and output voltage control. The dynamic response of the output voltage to load steps is improved by means of an additional load‐current feed‐forward control loop. An analytical study of the load‐current feed‐forward is presented and validated by means of both simulations and experimental results. Copyright © 2014 John Wiley & Sons, Ltd.     

Design and analysis of power‐CMOS‐gate‐based switched‐capacitor DC–DC converter with step‐down and step‐up modes

A unified multi‐stage power‐CMOS‐transmission‐gate‐based quasi‐switched‐capacitor (QSC) DC–DC converter is proposed to integrate both step‐down and step‐up modes all in one circuit configuration for low‐power applications. In this paper, by using power‐CMOS‐transmission‐gate as a bi‐directional switch, the various topologies for step‐down and step‐up modes can be integrated in the same circuit configuration, and the configuration does not require any inductive elements, so the IC fabrication is promising for realization. In addition, both large‐signal state‐space equation and small‐signal transfer function are derived by state‐space averaging technique, and expressed all in one unified formulation for both modes. Based on the unified model, it is all presented for control design and theoretical analysis, including steady‐state output and power, power efficiency, maximum voltage conversion ratio, maximum power efficiency, maximum output power, output voltage ripple percentage, capacitance selection, closed‐loop control and stability, etc. Finally, a multi‐stage QSC DC–DC converter with step‐down and step‐up modes is made in circuit layout by PSPICE tool, and some topics are discussed, including (1) voltage conversion, output ripple percentage, and power efficiency, (2) output robustness against source noises and (3) regulation capability of converter with loading variation. The simulated results are illustrated to show the efficacy of the unified configuration proposed. Copyright © 2003 John Wiley & Sons, Ltd.     

WGZ75/39-6 型煤粉炉冷态试验分析

介绍了湘潭钢铁公司热电厂６＃锅炉进行冷态试验的情况,同时说明了煤粉锅炉冷态试验的内容、方法．详细分析了试验中所出现的问题和结果,探讨了影响炉内空气动力场的有关因素,就如何组织良好的炉内空气动力场结构,保证燃料喷入炉膛后迅速着火和燃烬,防止炉内结渣,使该锅炉在最佳运行工况下运行,提高锅炉的效率,提供了改进措施．