Observer‐based decentralized adaptive control for large‐scale pure‐feedback systems with unknown time‐delayed nonlinear interactions

This paper presents an approximation design for a decentralized adaptive output‐feedback control of large‐scale pure‐feedback nonlinear systems with unknown time‐varying delayed interconnections. The interaction terms are bounded by unknown nonlinear bounding functions including unmeasurable state variables of subsystems. These bounding functions together with the algebraic loop problem of virtual and actual control inputs in the pure‐feedback form make the output‐feedback controller design difficult and challenging. To overcome the design difficulties, the observer‐based dynamic surface memoryless local controller for each subsystem is designed using appropriate Lyapunov‐Krasovskii functionals, the function approximation technique based on neural networks, and the additional first‐order low‐pass filter for the actual control input. It is shown that all signals in the total controlled closed‐loop system are semiglobally uniformly bounded and control errors converge to an adjustable neighborhood of the origin. Finally, simulation examples are provided to illustrate the effectiveness of the proposed decentralized control scheme. Copyright © 2013 John Wiley & Sons, Ltd.     

Genetic algorithm‐based neural‐network modeling approach applied to AlGaN/GaN devices

An accurate equivalent circuit large‐signal model (ECLSM) for AlGaN‐GaN high electron mobility transistor (HEMT) is presented. The model is derived from a distributed small‐signal model that efficiently describes the physics of the device. A genetic neural‐network‐based model for the gate and drain currents and charges is presented along with its parameters extraction procedure. This model is embedded in the ECLSM, which is then implemented in CAD software and validated by pulsed and continuous large‐signal measurements of on‐wafer 8 × 125‐μm GaN on SiC substrate HEMT. Pulsed IV simulations show that the model can efficiently describe the bias dependency of trapping and self‐heating effects. Single‐ and two‐tone simulation results show that the model can accurately predict the output power and its harmonics and the associated intermodulation distortion (IMD) under different input‐power and bias conditions. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

灌区不同空间尺度显热通量测定方法的对比分析

摘要：本文利用安装在山东省位山灌区典型农田内的大孔径激光闪烁仪 （LAS） 和涡度相关系统 （EC） ,测定了不同空度尺度上的显热通量,对比分析了两个系统测定结果在不同作物条件下的相关关系,讨论了造成二者偏差的可能原因。结果显示,在研究区域的农田下垫面条件下LAS和EC系统测定的显热通量之间存在较好的一致性;LAS的测量结果略大于EC测量值,这可能是由下垫面不均匀性、二者源区不一致以及EC测量值偏小造成的。研究证明,LAS是测定区域平均显热通量较为可靠的方法。     

大采高综放开采煤岩损伤统计力学模型

根据特厚煤层大采高综放开采煤壁前方支承压力的分布特征,从煤岩内部缺陷的随机性分布特征出发,基于反映煤岩内部缺陷的微元强度服从韦布分布的概念,建立了支承压力作用下煤岩的损伤统计力学模型,确定了特厚煤层大采高综放面在煤壁片帮不影响生产的情况下的合理采高,并分析了特厚煤层大采高综放面合理采高与煤壁片帮程度、煤层内摩擦角、煤层...     

RTK配合数字测深技术在大比例水下地形测量中的应用

为了解水库的泥沙淤积现状,采用RTK技术和数字测深技术,并使二者相配合实现同步测量,使其在大比例尺地形测量中得到成功应用,测绘质量和工作效率明显提高,测量成本显著降低.本文以黄河刘家峡水库坝前1:200水下地形测量的生产实践为例,叙述了大比例尺水下地形测量实施过程和测量所取得的成果及体会,为今后的水库水下地形测量积累了...     

基于Matlab的大规模电网低频振荡仿真

大电网互联产生的低频振荡现象严重危害电力系统的稳定运行。论文主要介绍如何在MATLAB中建立大电网的仿真模型,并根据低频振荡的产生机理,模拟了低频振荡现象。仿真结果表明,该模型符合电网实际运行状况,为后续研究如何抑制低频振荡提供了平台基础。     

Large wood aids spawning Chinook salmon (Oncorhynchus tshawytscha) in marginal habitat on a regulated river in California

To determine whether large wood (LW, ≥1‐m length, ≥10‐cm diameter) plays a role in Chinook salmon (Oncorhynchus tshawytscha) redd (i.e. egg nest) placements in a regulated, Mediterranean‐climate, medium‐sized river (where channel width is less than the upper quartile of length of potential instream wood pieces), characteristics of 527 large wood pieces, locations of 650 redds, and mesohabitat delineations (riffle, run, glide, pool) were collected during a spawning season along a 7.7 km reach directly below Camanche Dam on the Mokelumne River, CA. LW was regularly distributed across the study reach an average 70 LW pieces km^‐1. Some LW clustering was evident at islands and meander bends. Spawners built 85% of redds within one average channel width (31 m) of LW. Spawners utilized LW within a 10 m radius 36% of the time in the upper 3 km rehabilitated reach, and 44% of the time in the lower 4.7 km marginal habitat reach. A greater percentage of LW was utilized in riffles in the upper 3 km reach where 90% of redds were built, while a larger percentage of spawners used LW in riffles in the lower 4.7 km reach. LW‐redd interactions occurred at greater rates than by random chance alone in the lower 4.7 km reach, which implies that LW aids spawning in marginal habitats. River managers and salmonid spawning habitat rehabilitation (SHR) projects should take LW additions into consideration as an important component of river rehabilitation. Copyright © 2010 John Wiley & Sons, Ltd.     

三方柱绕流的大涡模拟及频谱分析

高雷诺数条件下,无论来流是均匀还是非均匀,多方柱绕流情况下方柱受力及尾流的相互干扰都是相当复杂的.为了研究方柱受力及下游尾流的相互干扰,基于大涡模拟紊流模型对后品字等边布置的三方柱绕流进行了数值模拟,数值模拟结果表明,上游两个方柱的阻力系数要明显小于下游方柱,而上游两方柱升力系数远大于下游方柱,且下游方柱的升力系数基本...     

大型机械设备三维仿真训练系统的关键技术

大型机械设备具有体积庞大、价格昂贵、操作复杂、生产环境恶劣等特点,这些都给学习和操作此类设备带来了很多不便。针对这种实际情况,开发出以计算机仿真技术为核心大型机械设备三维仿真训练系统,可应用于对大型机械设备操作人员的培训。介绍了开发大型机械设备三维仿真训练系统应解决的关键问题,并以采用Java3D技术开发的锻压机三维仿真训练系统为例进行了验证。在应用中表明,大型机械设备三维仿真训练系统具有安全性、实用性、经济性等特点。