城市建筑与园林景观

介绍了现代城市中,园林景观与建筑物的功能、风格及空间布局之间的相互影响,主要从园林植物的装饰作用、对空气的净化作用、局部小气候的改善等方面阐述了园林对建筑物的影响。     

风冷空调机组系统噪声综合治理

针对风冷中央空调机组系统噪声大、声源多、机组发热量大以及空间布置复杂等特点，采用结构简单、制作容易和降噪效果好的综合治理方案，不影响风冷效果和空调设备的监视、操作和维护。     

Real-time pixel based early apple bruise detection using short wave infrared hyperspectral imaging in combination with calibration and glare correction techniques

High speed data processing for online food quality inspection using hyperspectral imaging (HSI) is challenging as over hundred spectral images have to be analyzed simultaneously. In this study, a real-time pixel based early apple bruise detection system based on HSI in the shortwave infrared (SWIR) range has been developed. This systems consists of a novel, homogeneous SWIR illumination unit and a line scan camera. The system performance was tested on Jonagold apples bruised less than two hours before scanning. Partial least squares-discriminant analysis was used to discriminate bruised pixel spectra from sound pixel spectra. As the glossiness of many fruit and vegetables limits the accuracy in the detection of defects, several reflectance calibrations and pre-processing techniques were compared for glare correction and maximizing the signal to noise ratio. With the best combination of first derivative and mean centering, followed by image post-processing, this system was able to detect fresh bruises in thirty apples with 98% accuracy at the pixel level with a processing time per apple below 200 ms.     

一种基于位置信号线性拟合差分滤波器串联的二阶差分角加速度观测器

角加速度闭环能增加伺服控制系统的刚度,提高系统鲁棒性,但位置信号的二阶差分运算会放大高频噪声幅值,限制了加速度闭环在实际控制中的应用。首先,对三种基于多项式曲线拟合的角加速度观测器性能进行了分析,结果表明二次多项式角加速度观测器具有最优的综合性能;其次,为了抑制噪声,提出了一种基于位置信号线性拟合的串联二阶差分角加速度观测器,从截止频率、白噪声放大倍数和延时时间三个方面对其性能进行了分析,并与二次多项式角加速度观测器进行了对比,仿真和实验均验证了该方法具有更好的噪声抑制能力。     

基于KMM与超像素的SAR海面暗斑分割算法

提出了一种基于K乘性模型(K multiplicative model , KMM)与超像素分割算法的无监督的SAR海面暗斑检测算法。KMM算法采用矩估计法进行参数估计,应用于海表面含暗斑的感兴趣区域（region of interest, ROI）检测。通过对感兴趣区域生成的超像素进行聚类来完成最终暗斑的边缘分割。在边缘回撤率、遗漏误差、交叉误差上有较大改善,机载SAR的平均误差率为10%,而TerraSAR的平均误差率低于2%。在计算效率上也有较大提高,平均0.53 s内可处理104个像素点。实验基于高分辨率L波段机载SAR数据以及TerraSAR X数据进行,实验结果表明该方法具有较强的鲁棒性以及较高的计算效率。     

Nonparametric Autoregression with Multiplicative Volatility and Additive mean

For over a decade, nonparametric modelling has been successfully applied to studying nonlinear structures in financial time series. It is well known that the usual nonparametric models often have less than satisfactory performance when dealing with more than one lag. When the mean has an additive structure, however, better estimation methods are available which fully exploit such a structure. Although in the past such nonparametric applications had been focused more on the estimation of the conditional mean, it is equally if not more important to measure the future risk of the series along with the mean. For the volatility function, i.e. the conditional variance given the past, a multiplicative structure is more appropriate than an additive structure, as the volatility is a positive scale function and a multiplicative model provides a better interpretation of each lagged value's influence on such a function. In this paper we consider the joint estimation of both the additive mean and the multiplicative volatility. The technique used is marginally integrated local polynomial estimation. The procedure is applied to the deutschmark/US dollar daily exchange returns.     

Control and performance of a zero‐current‐switched,three‐phase PWM inverter equipped with resonant circuits on the ac side

This paper presents a zero‐current‐switched voltage‐fed inverter equipped with resonant circuits on the ac side. The current flowing through a switching device, that is, IGBT, is the sum of the load current and the resonant current. When the amplitude of the resonant current is larger than that of the load current, the current in the switching device becomes zero at an instant in each resonant cycle. This allows the switching device to be turned on or off at the zero current. The zero‐current switching makes a significant contribution to reduction of switching losses and electromagnetic noises. In this paper, the principle of zero‐current‐switching operation, along with a novel control scheme, is described from a theoretical and practical point of view. Experimental results obtained from a laboratory system of 5 kVA verify the practicability. Moreover, the switching and conduction losses of the proposed soft‐switched inverter are compared with those of a conventional hard‐switched inverter. © 2000 Scripta Technica, Electr Eng Jpn, 131(4): 85–95, 2000     

A statistical learning based image denoising approach

The image denoising is a very basic but important issue in the field of image procession. Most of the existing methods addressing this issue only show desirable performance when the image complies with their underlying assumptions. Especially, when there is more than one kind of noises, most of the existing methods may fail to dispose the corresponding image. To address this problem, we propose a two-step image denoising method motivated by the statistical learning theory. Under the proposed framework, the type and variance of noise are estimated with support vector machine (SVM) first, and then this information is employed in the proposed denoising algorithm to further improve its denoising performance. Finally, comparative study is constructed to demonstrate the advantages and effectiveness of the proposed method.     

风电机组噪声分析及检测

风电机组的噪声辐射对环境有很大影响,国外很早就开始了相关的研究和检测,但是国内对此一直缺乏足够的重视。介绍了风电机组的噪声危害,分析了风电机组噪声的产生原因,列举了国外风电发达国家的风电机组噪声辐射标准,描述了国际通用的风电机组噪声检测方法。     

利用欠阻尼二阶线性随机共振抑噪的模型设计及实现

以经典力学模型——质量-阻尼-弹簧欠阻尼二阶线性系统为研究对象,当系统的阻尼系数和固有频率同时受乘性高斯噪声干扰时,利用此系统产生的随机共振来消除此类噪声.理论分析表明,欠阻尼二阶线性系统中存在随机共振现象,系统的平均输出幅度增益呈现非单调变化,不仅在一定条件下大于无噪声时的增益,而且调节适当的系统参数和噪声强度能够提高幅度增益.因此,采用可视化仿真软件SIMULINK建立仿真模型,并进行实例模拟.仿真进一步表明,通过调节适当的系统参数或噪声强度,使系统处于共振区域,就会把夹杂在噪声中的被测信号突现出来,从而实现了弱信号的检测,证实该方法消除乘性噪声的可行性和有效性.