爱乐之路（48） 音乐作品中常见体裁和形式——交响曲

交响曲(Symphany)原文的意思是“共同发声”。在17世纪以前,这个名词用法不一。既指多声部的器乐曲,或由几件乐器演奏的片段,也用它称呼由速度快慢不同的、三段组成的意大利歌剧序曲。1741年,德国作曲家亨德尔创作清唱剧《弥赛亚》,其中有一段乐队间奏曲“田园”,作曲家也称之为“交响曲”。由于这些乐曲本身存在“快-慢-快”段落的鲜明对比,到18世纪逐渐形成了早期分乐章的“交响曲”。     

基于慢度估计的次声台阵信号自动检测算法及应用

针对次声监测研究领域广泛使用的短时间与长时间信号功率比检测方法性能不能满足要求,渐进多通道互相关检测算法虚警率较高的缺点,利用信号的时、频、波数域特性和次声台阵各子台信号的互相关性特性,提出了一种基于次声台阵信号慢度估计的自动检测算法。次声信号慢度估计结果的合理性、一致性是该检测算法的依据。考虑到该检测算法计算量较大,在具体应用中加入其他计算量较小的传统算法,进行逐次检测,最后应用的慢度估计方法既是一种检测方法,也是对其他检测算法结果的最终审核,一方面可以降低单项检测方法对检测参数的敏感性,另一方面也可提高检测的正确率(虚警率和漏警率同时降低)。该复合检测算法应用于某实验次声台站信号的检测(信噪比大于1.1),结果虚警率为4.0%,漏警率为5.0%,表明了该方法的优良性能。从检测应用处理结果还可以推测,结合一个区域现有密集的地震台站数据和2~3个次声台阵的数据,可以方便地识别、监控爆破方式日益复杂的人工爆破事件和真正的地震(余震)事件,为地震灾害减灾防灾、采矿监控等多领域服务,具有重大推广价值。     

制备工艺对（LaCe）1.0（NiCoMnAl）5.2高功率贮氢合金微观结构及电化学性能的影响

对铸态(LaCe)1.0(NiCoMnAl)5.2高功率合金采用热处理、快淬、快淬+热处理的工艺进行处理。合金通过XRD、SEM、EDS等分析发现无论是铸态还是快淬态合金通过热处理后其相组成和成分组成都变得更加均匀。电化学测试结果表明,不同制备工艺对合金的活化性能无明显影响。铸态合金表现出良好的高倍率性能,其1、3、5和10C HRD分别达到95%、76%、72%和35%。热处理后的铸态合金的循环性能提高,但合金的高倍率性能降低。快淬使合金的各项性能均降低,快淬态合金通过热处理后循环性能显著提高,50次容量保持率达到96.7%,其高倍率性能和铸态合金相当。     

如何正确的掌握钢琴的慢练技巧

正确的掌握钢琴的慢练技巧,对于每个学琴者来说都是至关重要的.一开始学琴是这样,学成之后亦是这样.不论乐曲的技术难度大或小,速度快或慢,都应该坚持"先慢练,后加速"的原则,即使一首乐曲很熟练了,也应该常坚持这种方法来对曲子的技巧部分加以巩固,不断的加强乐曲的完整性.……     

H.264帧内预测与帧间块模式选择快速算法

针对H.264帧间预测时的多子块模式选择和帧内预测的多模式选择问题,提出了一种实用的基于统计门限的模式快速选择算法,通过门限设定有效限定了编码模式的选择范围.多组视频序列的实验结果表明,基于统计门限的帧内预测模式选择算法在Ⅰ帧的PSNR值有微小变化的情况下,大大降低了编码时间,Ⅰ帧的编码时间降低17%～23%,PSNR下降不到0.4%.基于统计门限的帧间块模式选择算法使得平均PSNR值下降了0.047dB(PSNR最大下降不到1%),但是相对全模式预测时,编码器速度提高了20%～30%.     

GPS接收机伪码捕获自适应判决门限估计算法(英文)

GPS接收机输入信号的功率随时间而变化,如果采用固定门限判决是否完成捕获会出现检测概率降低或虚警概率提高的问题.鉴于此,提出了采用自适应捕获门限判决策略完成信号捕获.采用最大似然估计原理,根据判决统计量的样本值得到了噪声方差的最大似然估计,进而求得恒虚警率下的自适应捕获门限.同时,信号的平均捕获时间是GPS接收机性能的重要指标之一,研究了载波频率与伪码相位均为不确定值时的平均捕获时间的计算方法,推导了平均捕获时间与信噪比及门限值之间的约束关系.分析结果表明,自适应门限捕获方法能减小平均捕获时间,实现信号的快速捕获.     

初始化(Initialize)

将MIDI设备的所有参数恢复到原厂设置。它一般在应用模式（UTILITY或GLOBAL）中,通常在标准MIDI乐曲开头自动发送的系统专有信息,就是将对应的音源初始化,抹去前面播放的乐曲对音源所做的各种修改,使客观存在还原到缺省值,然后再进行相应的设置,（如改变声部模式,弯音范围,编辑音色等）以保证正确发音,这种操作比在音源上手工调节要快速和准确得多。初始化(Initialize)     

智能包装检测系统中光源波长研究

目的通过优化智能包装检测系统中的光源条件,提高多层包装中缺陷内衬纸智能检测的识别率和包装的良品率。方法在智能包装检测系统中,通过改变光源的波长来检测不同颜色的缺陷内衬纸,并对缺陷内衬纸面积检测的像素数量进行分析,来确定合适的光源波长。结果色相性导致红光、绿光及蓝光等可见单色光不能使相同颜色的内衬纸在智能包装检测系统中成像,但在白光、红外光和紫外光照射下可以检测出所有的缺陷内衬纸。进一步分析得知,智能包装检测系统在红外光照射下缺陷内衬纸的成像效果最好;在白光、红外光和紫外光照射下的识别率分别为90.5%, 99.5%, 96.5%,红外光照射下的识别率最高。结论在实际包装车间生产中,为使智能包装检测系统的准确率最高,可根据色相性选择光源或者直接选择红外光光源。     

智能语音产品的唤醒率体验研究

目的针对智能语音产品的唤醒率体验,探讨不同环境音量、不同交互距离条件下用户满意和可接受的唤醒率范围。方法通过9(唤醒率)×3(交互距离)×2(环境音量)混合实验设计,探索不同环境音量和交互距离下的唤醒率水平对体验的影响。结果低声压级40dB环境音量下,1米、3米、5米距离时用户满意的唤醒率下限分别是93.6%、92.9%、90.4%,可接受的唤醒率下限分别是74.6%、72.0%、69.0%;中声压级60dB环境音量下,1米、3米、5米距离时用户满意的唤醒率下限分别是91.3%、89.2%、85.8%,可接受的唤醒率下限分别是69.5%、67.1%、55.4%。结论语音唤醒体验的诸多影响因素中,用户对唤醒率体验的感知重要性最高,不同环境音量和交互距离的情况下,用户满意及可接受的唤醒率存在差异。     

慢起慢落时磁浮车辆与钢轨道框架耦合共振分析

磁浮车辆在钢轨道框架慢起慢落的过程中会发生车轨耦合共振的情况，针对上海磁浮车在调试过程中遇到此类问题，进行了现场测试。测试数据说明：发生共振的频率是33Hz左右，这与钢轨道框架的垂向自振频率相同。理论分析表明，系统过程的稳定与二次悬挂的频率与阻尼、控制器的频带和阻尼、轨道的频率和阻尼及系统的基本参数（额定平衡位置、车轨质量比、线圈电阻及电感）都有关。因此在系统其他参数不变的情况下，通过改变钢轨道框架立柱的侧向刚度，也即改变钢轨道框架的自振频率，可以使系统在慢起慢落过程中稳定。     

船舶螺旋桨空化噪声解调包络形状仿真研究

船舶螺旋桨空化噪声解调包络是一系列形状基本一致、间隔基本相等、高度有一定随机性、成组结构的波包。而波包形状会直接影响到解调谱的结构形状。通过分析比较实测信号、解调包络形状,将波包形状分为两大类：圆滑型和尖锐型,并分别设置了对应的两种仿真模型：半正弦模型和高斯模型。仿真信号和实测信号的检验结果表明,半正弦模型能够更好地模拟圆滑型包络的特点,高斯模型能够更好地模拟尖锐型包络的特点。     

A real‐time feature extraction method for PVC detection in bedside monitor

Abstract

This paper describes a fast and very efficient feature extraction method for discrimination of QRS and Premature Ventricular Contraction (PVC) beats in a microprocessor‐based bedside monitoring system. It converts each QRS and PVC beat into a positive‐pulse waveform by signal preprocessing. Two characteristic factors, the positive‐pulse and the pulse duration, are calculated when the onset and end points of each pulse have been detected by threshold detection. The prominent feature is extracted from a product of these two factors. This algorithm has been examined using 40 different patients’ electrocardiograph (ECG). The accuracy of QRS detection was 99.3 percent in the tests performed. The identification sensitivity of PVC was 81.2 percent with 18‐ different arrhythmia patients.     

滚动轴承故障的EMD诊断方法研究

提出了一种基于经验模式分解（Empirical Mode Decomposition，EMD）的滚动轴承故障诊断方法。这种方法中，局部损伤滚动轴承产生的高频调幅信号成分被EMD分解作为本征模函数分离出来，然后用Hilbert变换得到其包络信号，计算包络谱，就能够提取滚动轴承故障特征频率。该方法被用于分析实验台上采集的具有内圈损伤及外圈损伤的滚动轴承振动信号。分析结果表明，与传统的包络解调方法相比，新方法能够更有效地提取轴承故障特征，诊断轴承故障，因而具有重要的实用价值。     

State-resolved spectroscopy of high vibrational levels of water up to the dissociative continuum

We summarize here our experimental studies of the high rovibrational energy levels of water. The use of double-resonance vibrational overtone excitation followed by energy-selective photofragmentation and laser-induced fluorescence detection of OH fragments allowed us to measure previously inaccessible rovibrational energies above the seventh OH-stretch overtone. Extension of the experimental approach to triple-resonance excitation provides access to rovibrational levels via transitions with significant transition dipole moments (mainly OH-stretch overtones) up to the dissociation threshold of the O-H bond. A collisionally assisted excitation scheme enables us to probe vibrations that are not readily accessible via pure laser excitation. Observation of the continuous absorption onset yields a precise value for the O-H bond dissociation threshold, 41?145.94 ± 0.15?cm(-1). Finally, we detect long-lived resonances as sharp peaks in spectra above the dissociation threshold.     

Decentralized random decrement technique for efficient data aggregation and system identification in wireless smart sensor networks

Smart sensors have been recognized as a promising technology with the potential to overcome many of the inherent difficulties and limitations associated with traditional wired structural health monitoring (SHM) systems. The unique features offered by smart sensors, including wireless communication, on-board computation, and cost effectiveness, enable deployment of the dense array of sensors that are needed for monitoring of large-scale civil infrastructure. Despite the many advances in smart sensor technologies, power consumption is still considered as one of the most important challenges that should be addressed for the smart sensors to be more widely adopted in SHM applications. Data communication, the most significant source of the power consumption, can be reduced by appropriately selecting data processing schemes and the related network topology. This paper presents a new decentralized data aggregation approach for system identification based on the Random Decrement Technique (RDT). Following a brief overview of the RDT, which is an output-only system identification approach, a decentralized hierarchical approach is described and shown to be suitable for implementation in the intrinsically distributed computing environment found in wireless smart sensor networks (WSSNs). RDT-based decentralized data aggregation is then implemented on the Imote2 smart sensor platform based on the Illinois Structural Health Monitoring Project (ISHMP) Services Toolsuite. Finally, the efficacy of the RDT method is demonstrated experimentally in terms of the required data communication and the accuracy of identified dynamic properties.     

Performance comparison between multiple-quantum-well modulator-based and vertical-cavity-surface-emitting laser-based smart pixels

We compared multiple-quantum-well modulator-based smart pixels and vertical-cavity-surface-emitting laser (VCSEL) based smart pixels in terms of optical switching power, switching speed, and electric-power consumption. Optoelectronic circuits integrating GaAs field-effect transistors are designed for smart pixels of both types under the condition that each pixel has an optical threshold and gain. It is shown that both types perform maximum throughput of ~3 Tbps/cm(2). In regard to design flexibility, the modulator type is advantageous because switching time can be reduced by supplying large electric power, whereas switching time and electric-power consumption are limited to larger than certain values in the VCSEL type. In contrast, in regard to optical implementation, the VCSEL type is advantageous because it does not need an external bias-light source, whereas the modulator type needs bias-light arrays that must be precisely located because the small modulator diameter, <10 μm, is essential to high-speed operation. A bias-light source that increases the total power consumption of the system may offset the advantages of the modulator type.     

NURBS curve interpolation algorithm based on tool radius compensation method

This paper focuses on developing an algorithm that can generate toolpaths in NURBS form for smooth, high speed and accurate machining. The initial toolpaths are obtained by tool radius compensation method which is based on the workpiece boundary offsetting. According to different lengths and the continuous short block (CSB) criterion, these offset linear segments can be regarded as CSBs or long straight segments. Junctions are located where the curvature value is greater than the preset curvature threshold value or where it changes abruptly, or at the two end points of any long straight segment. During machining, the NURBS fitting module first looks ahead several CSBs and converts them into parametric curves in real time. During the conversion, continuities of the position, slope or even curvature at the transition of the parametric curves and unfitted line segments can be guaranteed. Then the acceleration/deceleration feedrate-planning scheme is proposed to determine the transition feedrate at the junction between the fitted curves and unfitted long straight segments, and the corner feedrate within the fitted curve. Simulations and experiments show that the proposed algorithm can significantly improve machining accuracy and reduce cutting time to satisfy today’s high-speed and high-accurate machining requirements.     

Varied threshold with laser flight time in scannerless range-gated ladar

We present a method based on maximum-likelihood estimation to calculate the threshold of the number of converted photoelectrons according to Poisson and Gaussian statistics. The calculations for detection and false-alarm probabilities are given including a proposal of error probability. An efficient approach of setting threshold according to laser flight time is discussed as the laser power decreases in propagation. Comparison of the fixed threshold and the varied threshold in Poisson and Gaussian statistics is provided. The varied threshold approach tends to keep the error probability at the lowest level. This varied threshold approach is found to have a similar effect on ranging accuracy as a threshold-fixed approach.     

Controlled-intensity detection peaks in a binary joint transform correlator

In multiobject pattern recognition the height of the correlation peaks should be controlled when the power spectrum of ajoint transform correlator is binarized. In this paper a method to predetermine the value of detection peaks is demonstrated. The technique is based on a frequency-variant threshold in order to remove the intraclass terms and on a suitable factor to normalize the binary joint power spectrum. Digital simulations and experimental hybrid implementation of this method were carried out.