内燃机排气噪声的分析研究

内燃机排气噪声是内燃机的主要噪声源。本文对产生排气噪声的机理进行了理论探讨。认为内燃机排气噪声属于空气动力性噪声,主要是在排气阀附近区域中排气流紊动扩散引起的。在低频域,内燃机排气噪声具有简单源特性;在中、高频域排气噪声具有四极子源特性。     

圆片冲击法硅片强度测试中简支半径问题研究

分析了圆片冲击法硅片强度测试中简支半径对动载荷挠度及强度测试值的影响，实验求得直径50．8mm硅片抗弯强度测试值的校正系数为0．8．     

可识强码的分解

研究强码,得到以下三个结果:(1)任意一个群都可以成为X~*的句法么半群,其中X是某个极大强码;(2)可识强码X可分解为两个可识强码复合的充要条件为接受X~*的最小自动机上存在真同余;(3)句法么半群为单群的极大强码称为单极大强码,任一可识强码可分解为有限个单可识强码的复合.     

公用技术组合逻辑电路设计方法的初步探讨

通过最简逻辑函数,可以很简单的实现组合逻辑电路。但是利用最简逻辑函数实现的逻辑电路却不一定是最简的逻辑电路。本针对此问题提出公用技术组合逻辑电路设计方法这一新的逻辑电路设计方法来进行探讨。通过实例的分析证明了使用公用技术组合逻辑电路设计方法实现的逻辑电路比使用最简逻辑函数实现的逻辑电路更简单,从而提高了逻辑电路的性价比。     

黑箱系统的一种简便自适应预测控制策略

采用一种输入输出增量式一元线性回归模型作为黑箱系统的预测模型,应用投影算法估计模型参数.该模型将对象输出增量分解为2个分量:一个为非零控制增量作用下的强制分量,另一个为控制增量为零时的自由分量,是一种非齐次时变线性模型.此外,应用广义预测控制理论,提出了一种基于该模型的自适应多步预测控制策略,导出了基于该模型的多步最优预测算式和最优控制律.该控制策略不仅具有广义预测控制的强自适应能力和强鲁棒性,且模型参数少,算法简单,适用于黑箱系统的控制.仿真结果表明该控制策略是有效的.     

Involvement of secondary motor areas in externally-triggered single-finger movements of dominant and non-dominant hands

Abstract Whether the secondary motor areas are involved in simple voluntary movements remains controversial. Differences in the neural substrates of movements with the dominant and the non-dominant hands have not been well documented. In the present study, functional magnetic resonance imaging (fMRI) was used to investigate the hemodynamic response in the primary motor cortex (M1), supple-mentary motor area (SMA) and premotor cortex (PMC) in six healthy right-handed subjects while performing a visually-guided finger-tapping task with their dominant or non-dominant hands. Significant activation was observed in M1, SMA and PMC during this externally triggered simple voluntary movement task. While dominant hand movements only activated contralateral motor areas, non-domi-nant hand movements also activated ipsilateral SMA and PMC. The results provide strong evidence for the involvement of the secondary motor areas in simple voluntarymovements, and also suggest that movements of the dominant hand primarily engage the contralateral secondary motor areas, whereas movements of the non-dominant hand engage bilateral secondary motor areas.     

p—adic域上单代数群的存在性定理

设k为p-adic域,给出了所有定义在k上,具有不同类型k-指标的单线性代数群的统一构造方法,从而给出了定义在k上单代数群的存在性的统一证明,并且给出了所有定义在k上单线性代数群的k-有理点群的统一构造。     

关于热力学函数关系简图记忆规律的再探讨

本文用六个简图归纳了热力学中31个重要的函数关系式,并指明了记忆规律。     

Digital modulation classification using multi-layer perceptron and time-frequency features

Considering that real communication signals corrupted by noise are generally nonstationary, and time-frequency distributions are especially suitable for the analysis of nonstationary signals, time-frequency distributions are introduced for the modulation classification of communication signals. The extracted time-frequency features have good classification information, and they are insensitive to signal to noise ratio (SNR) variation. According to good classification by the correct rate of a neural network classifier, a multilayer perceptron (MLP) classifier with better generalization, as well as, addition of time-frequency features set for classifying six different modulation types has been proposed. Computer simulations show that the MLP classifier outperforms the decision-theoretic classifier at low SNRs, and the classification experiments for real MPSK signals verify engineering significance of the MLP classifier.