Rapid-convergent sliding mode proportional-integral technology with fuzzy gain scheduling for hydrogen energy applications

This paper presents a rapid-convergent sliding mode proportional-integral (PI) technology with fuzzy gain scheduling for hydrogen energy applications. The rapid-convergent sliding mode control can provide insensitivity to system uncertainties and finite system-state convergence time to origin, however undesirable chattering behavior exists. The proposed technology utilizes the expansion of the plant model for designing the formation of a rapid-convergent sliding mode PI control and then the chatter is remarkably lessened. Moreover, a fuzzy gain scheduling assists in tuning the PI control parameters against uncertain disturbances. Simulations show that the presented hydrogen energy system leads to low distorted output-voltage under nonlinear load and fast transience under step-load change. Lab experiments obtained with a developed hydrogen energy system using a digital signal processing algorithm have been offered to demonstrate the performance improvement, especially in the presence of seriously nonlinear circumstance. In contrast with the proposed hydrogen energy system, the classic sliding mode-controlled hydrogen energy system has also been evaluated via both simulation and experiment.     

Gain scheduling adaptive control applied to a particular mixer-settler equipment

The mixer-settler based on phase inversion (MSBPI) is a system used for treatment of wastewaters in order to reduce the content of oils and greases from wastewaters produced in oil industry. Its operation principle combines mixing, extraction and separation by decantation in a unique process. In particular, for control purpose, the level of the interface between organic solvent and water, in the separation section, is a critical variable to guarantee performance and security during operation of the MSBPI. In this work, an image-based detector to monitor the organic solvent–water interface level is proposed and a feedback control loop for the process is presented. Initially, a conventional controller (PID) was implemented and, subsequently, a strategy of gain scheduling adaptive control was developed in order to improve the process response in closed-loop. The experimental results showed that the adaptive control presented an efficient performance, even when disturbances of significant magnitude were applied to the process.     

一种用于影像组学的多级特征选择方法

针对医学影像中高维特征的问题,提出一种用于影像组学的多级特征选择方法(MSOM-GA)。用组内相关系数过滤对边界敏感的特征。用混合F-Score和信息增益的方法,去除不相关特征。用遗传算法去除冗余特征,选择最优特征子集。该算法在河南省人民医院脑胶质瘤影像数据上进行验证,实验显示,特征选择算法能显著提升特征的质量,算法的auc、acc、敏感度、特异性分别为0.9756、92.29%、93.70%、89.26%,与对照组相比具体数值有较为显著的提升。结果表明,该特征选择方法能有效地去除肿瘤边界不稳定特征、冗余特征和不相关特征,提高模型的训练精度。     

Excited state characteristics of the Li2B4O7 and KLiB4O7 glasses activated by Cr3+ ions

The excited state characteristics by means of the excited state absorption (ESA), optical gain and bleaching spectra have been measured for prototype glasses with Li₂B₄O₇ (LBO) and KLiB₄O₇ (KLBO) compositions activated by Cr³⁺ ions. The work addressed to search for novel attractive media for broadband lasers and amplifiers, is a completion of detailed spectroscopic evaluation described in earlier papers. One of the examined materials (KLBO), in accordance with optimistic comments given in previous work, reveals a very broad gain spectrum in the near IR, which itself is interesting in view of very few reports on glasses showing optical gain for Cr³⁺ ions in the low-field local environment. The ESA/gain/bleaching spectra, registered with equipment of improved sensitivity, have been reproduced by calculations, and detailed single configuration coordinate diagram, based on experimental data, has been created for interpretation.     

Asymptotic stability, ℓ2 gain,boundness analysis,and control synthesis for switched systems: a switching frequency approach

In this paper, several concepts of switching frequency are introduced to analyze the properties and performance of switched systems in infinite as well as finite‐time intervals. The observation is very motivating that different system properties and performances depend on different switching frequencies. Sufficient conditions ensuring asymptotic stability, ?₂ gain performance, and state boundness are derived on the basis of the notions of switching frequency, respectively. Then, on the basis of the analysis results, the control synthesis problems are addressed. LMI‐based design algorithms are proposed to meet different control synthesis requirements. Numerical design examples are provided to demonstrate our results. Copyright © 2011 John Wiley & Sons, Ltd.     

Adaptive-gain fast super-twisting sliding mode fault tolerant control for a reusable launch vehicle in reentry phase

In this paper, a novel adaptive-gain fast super-twisting (AGFST) sliding mode attitude control synthesis is carried out for a reusable launch vehicle subject to actuator faults and unknown disturbances. According to the fast nonsingular terminal sliding mode surface (FNTSMS) and adaptive-gain fast super-twisting algorithm, an adaptive fault tolerant control law for the attitude stabilization is derived to protect against the actuator faults and unknown uncertainties. Firstly, a second-order nonlinear control-oriented model for the RLV is established by feedback linearization method. And on the basis a fast nonsingular terminal sliding mode (FNTSM) manifold is designed, which provides fast finite-time global convergence and avoids singularity problem as well as chattering phenomenon. Based on the merits of the standard super-twisting (ST) algorithm and fast reaching law with adaption, a novel adaptive-gain fast super-twisting (AGFST) algorithm is proposed for the finite-time fault tolerant attitude control problem of the RLV without any knowledge of the bounds of uncertainties and actuator faults. The important feature of the AGFST algorithm includes non-overestimating the values of the control gains and faster convergence speed than the standard ST algorithm. A formal proof of the finite-time stability of the closed-loop system is derived using the Lyapunov function technique. An estimation of the convergence time and accurate expression of convergence region are also provided. Finally, simulations are presented to illustrate the effectiveness and superiority of the proposed control scheme.     

Development and analysis of a tool for speed up of EnergyPlus through parallelization

This paper describes how the EPparallel tool splits a single annual simulation into 12 simulations of one month each and runs them in parallel. The paper also describes the methodology to prepare input files, enable file sharing between nodes, collate results generated by the nodes, and ensure quality check on the simulations. The EPparallel tool uses Message Passing Interface library and runs on Linux. The tool has been tested on 16 commercial reference buildings over 16 US weather files. The results of these 256 runs which include the run times, computing time overheads, speed gains and accuracy of results are presented in this paper. The speed gain ranged from 2.9×to 7.8×and deviation (percentage of output values obtained in parallel simulation which were off by more than 1% as compared to output values obtained in annual simulation) ranged from 0% to 4%.     

Evaluating the precision of eight spatial sampling schemes in estimating regional means of simulated yield for two crops

We compared the precision of simple random sampling (SimRS) and seven types of stratified random sampling (StrRS) schemes in estimating regional mean of water-limited yields for two crops (winter wheat and silage maize) that were simulated by fourteen crop models. We found that the precision gains of StrRS varied considerably across stratification methods and crop models. Precision gains for compact geographical stratification were positive, stable and consistent across crop models. Stratification with soil water holding capacity had very high precision gains for twelve models, but resulted in negative gains for two models. Increasing the sample size monotonously decreased the sampling errors for all the sampling schemes. We conclude that compact geographical stratification can modestly but consistently improve the precision in estimating regional mean yields. Using the most influential environmental variable for stratification can notably improve the sampling precision, especially when the sensitivity behavior of a crop model is known.     

Experimental and numerical studies on the receiving gain enhancement modulated by a sub-wavelength plasma layer

A novel technique based on sub-wavelength plasma structure effects on enhancement of RF communication signals on a receiving antenna is carried out in this paper in laboratory experiments and analyzed by corresponding numerical simulations. Considerable intensification on receiving signal gain up to～10 dB in comparison with that without the plasma modulation is observed experimentally in～1 GHz RF band, with an effective enhancement bandwidth of～340 MHz and the fractional bandwidth of～34％. Then, the optimal modulation parameters of plasma are further studied by a numerical simulation. It is shown that the number density, the layer thickness, and the collision frequency of the plasma, as well as the relative distance between the plasma layer and antenna synergistically affect the modulation. Compared to the metallic antenna with the same overall dimension, the modulated antenna covered by the subwavelength plasma structure features higher receiving efficiency and lower radar cross section in the studied RF band. The mechanism of the reception enhancement is further revealed by analyzing characteristics of electromagnetic scattering and electric field distribution in the subwavelength plasma layer. The results then exhibit scientific significance and application potential of sub-wavelength plasma modulation on compact receiving antennas with higher performance and better feature of radar stealth.     

Symmetry between the transfer properties of micro-ring resonators with gain and with loss

Gain and loss affect the performance of dispersive micro-ring resonator systems significantly. Through analysing the transfer functions of two-port ring-resonator (TPRR) circuits and coupled micro-ring resonators, the symmetry between the transfer properties of micro-ring resonators with loss and with gain is discovered. For two TPRRs whose attenuation and gain coefficients are equal to each other, or for two coupled micro-ring resonators whose counterparts have equal gain and loss respectively, their intensity transmissions are reciprocal, while the phase shifts and dispersions are the same. This symmetry demonstrates the action mechanism of loss and gain on the transmissions and dispersions of these micro-ring resonators. It is useful for analysing and designing micro-ring resonators in group velocity control and dispersion compensation applications.