大规模风电高压脱网分析及协调预防控制策略

由于受扰系统在故障切除后恢复过程中出现高电压引起风电机组大规模脱网的事故近年来频发,因此基于近年来已发生的大规模风电机群脱网事故,从风电机组故障穿越期间动态无功控制策略和风电场附加无功补偿装置控制特性两个方面分析了受扰后电网发生高电压现象的主要原因,并通过现场测试验证了机组动态无功控制策略对机端电压的影响。在此基础上,提出了避免风电机组高电压脱网的协调预防控制策略,即风电机组在满足高电压穿越要求的前提下根据电压变化参与系统无功调节,风电场附加无功补偿装置根据并网点电压以及场内机组脱网情况实现快速调节和退出。最后,通过仿真验证了协调预防控制策略的有效性。     

MTBE装置催化剂使用周期缩短的原因及对策

针对MTBE装置催化剂使用周期缩短,结合装置原料以及工艺操作,对催化剂失活的原因进行分析,并对延长催化剂使用周期可采取的措施进行探讨。     

Two-stage image denoising by principal component analysis with local pixel grouping

This paper presents an efficient image denoising scheme by using principal component analysis (PCA) with local pixel grouping (LPG). For a better preservation of image local structures, a pixel and its nearest neighbors are modeled as a vector variable, whose training samples are selected from the local window by using block matching based LPG. Such an LPG procedure guarantees that only the sample blocks with similar contents are used in the local statistics calculation for PCA transform estimation, so that the image local features can be well preserved after coefficient shrinkage in the PCA domain to remove the noise. The LPG-PCA denoising procedure is iterated one more time to further improve the denoising performance, and the noise level is adaptively adjusted in the second stage. Experimental results on benchmark test images demonstrate that the LPG-PCA method achieves very competitive denoising performance, especially in image fine structure preservation, compared with state-of-the-art denoising algorithms.     

Learning motion and content-dependent features with convolutions for action recognition

A variety of recognizing architectures based on deep convolutional neural networks have been devised for labeling videos containing human motion with action labels. However, so far, most works cannot properly deal with the temporal dynamics encoded in multiple contiguous frames, which distinguishes action recognition from other recognition tasks. This paper develops a temporal extension of convolutional neural networks to exploit motion-dependent features for recognizing human action in video. Our approach differs from other recent attempts in that it uses multiplicative interactions between convolutional outputs to describe motion information across contiguous frames. Interestingly, the representation of image content arises when we are at work on extracting motion pattern, which makes our model effectively incorporate both of them to analysis video. Additional theoretical analysis proves that motion and content-dependent features arise simultaneously from the developed architecture, whereas previous works mostly deal with the two separately. Our architecture is trained and evaluated on the standard video actions benchmarks of KTH and UCF101, where it matches the state of the art and has distinct advantages over previous attempts to use deep convolutional architectures for action recognition.     

基于词性标注序列特征提取的微博情感分类

传统的n-gram文本特征提取方法会产生高维度的特征向量,高维数据不但增大了分类的难度,同时也会增加分类的时间。针对这一问题,提出了一种基于词性（POS）标注序列的特征提取方法,根据词性序列能够代表一类文本的这一个特点,利用词性序列组作为文本的特征以达到降低特征维度的效果。在实验中,词性序列特征提取方法比n-gram特征提取方法至少提高了9%的分类精度,降低4816个维度。实验结果表明,该方法能够适用于微博情感分类。     

典型大时变时滞系统的鲁棒fuzzy-PID控制及应用

针对典型大时变时滞系统, 设计新的鲁棒fuzzy_PID控制器, 实现系统参数大范围失配情况下的闭环鲁棒稳定, 并且使闭环系统达到设定值无静差跟踪及满意的动态性能. 现场应用效果良好.     

合成气一步法制二甲醚过程热力学模拟的研究

使用美国商用过程模拟软件PRO/Ⅱ,根据最小化青布斯自由能方法,研究合成气一步法制二甲醚过程的热力学模拟.考察温度、压力、合成气组成等因素对热力学平衡条件下一氧化碳转化率、二甲醚选择性和产率的影响,为二甲醚合成过程反应器的模拟计算和开发,提供理论依据.结果表明:低温高压有利于二甲醚的合成;为提高一氧化碳的转化率,最佳的氢炭比为1.4～2.0;在一定范围内二氧化碳含量对热力学平衡组成的影响不大,而水蒸气不利于合成反应.模拟与固定床微反装置的实验结果比较,不分伯仲.     

Globally Stable Adaptive Tracking Control for Uncertain Strict‐Feedback Systems Based on Neural Network Approximation

This paper addresses the problem of globally stable adaptive neural tracking control for a class of strict‐feedback nonlinear systems. Compared with the existing works, the salient properties of the proposed scheme are given as follows. First, a novel switching controller is developed, which consists of a traditional adaptive neural controller and an extra robust controller to pull back the transient outside of the approximation domain. Second, only two adaptive parameters need to be tuned online, and the computational burden is considerably alleviated in practice. Third, to design the desired switching controller via the backstepping technique, a novel switching function, which has continuous derivatives up to the nth order, is constructed. It is shown that the system output converges to a small neighborhood of the reference signal and the closed‐loop system is globally stable. Finally, an example is provided to verify the effectiveness of the proposed control method.     

基于图像视觉特征的火灾自动识别

传统的火灾检测方法是感烟、感温、感光探测器以及红外对射探测，对于装有监控设备的大空间建筑物，该文提出了一种基于图像视觉特征的火灾检测方法。通过对摄像头摄取的图像进行处理，提取其色彩特征和小波特征，然后利用神经网络通过有监督的学习建立图像特征向量与三维火灾向量的联系，达到利用图像进行火灾识别的目的.     

On speeding up an asymptotic-analysis-based homogenisation scheme for designing gradient porous structured materials using a zoning strategy

Structural and Multidisciplinary Optimization - Surrogate modeling is commonly used to replace expensive simulations of engineering problems. Kriging is a popular surrogate for deterministic...