查询词典 acoustic velocity

Based on the acoustic absorption theory of microperforated panel and by the means of the theoretical analysis and emulation, the paper focuses on the acoustic characteristic including acoustic impedance, frequency and acoustic absorption coefficient of microperrforated panel working in the combustion chamber which has high temperature and great temperature gradient.

摘要根据微穿孔板吸声理论，采用理论分析和仿真的方法，着重讨论微穿孔板在温度梯度下的声阻抗、共振频率和吸声系数等声学特性，分析其受温度影响变化的机理。

The experimental results show the validness of the mechanism analyses.2. According to the generation mechanism of the leak acoustic signal, the characteristics of the leak acoustic signal are investigated. The auto correlation technology is adopted to descript the leak signal characteristics due to the ability to analyze the coherence of time series. A new procedure to identify the leak acoustic signal from the disturbed noises is proposed based on the conjunction of correlation and approximate entropy algorithm.3. The principle and application in leak location of the correlation and the adaptive filter techniques are introduced. The problems of the traditional leak location methods are analyzed.4. In order to establish the leak detection signal model, the leak acoustic propagation characteristics are investigated experimentally.

从泄漏声产生机理出发，分析了管道泄漏处湍流拟序结构与空泡间相互作用的机理，认为在该机理作用下，泄漏声信号产生过程具有&不可重复&的特征；由于相关函数具有分析时间序列拟序结构的能力，且近似熵从统计的角度区别时间过程的复杂性，因此，提出将信号相关分析和近似熵理论相结合的方法，提取泄漏声信号&不可重复&的特征，辨识管道泄漏故障发生；在实际检测现场，由于各种管内和管外固定声源噪声(如阀门噪声、工地施工噪声等)常导致泄漏误判和漏点定位错误，重点分析了管内固定噪声源的产生机理和特征，为复杂干扰环境下的泄漏辨识提供理论支持。

Igor Sposobin ? book " the harmony Guide", Paul Hindemith ? book "A Concise Course of traditional and acoustic",Rimsky Korsakov ? book "Practical Guide and acoustic",Percy ? The Stankevicius book and acoustic, Theodore Dubois ? a "theory and practice and acoustic Guide", Walter ?

伊·斯波索宾等人合著的《和声学教程》、保罗·兴德米特著《传统和声学简明教程》、里姆斯基·科萨科夫著《和声学实用教程》、柏西·该丘斯著《和声学》、泰奥多尔·杜布瓦著《理论与实践和声学教程》、瓦尔特·辟斯顿著《辟斯顿和声学》这六本和声教科书，是多年来沿用至今的六本较好的和声教材。

In this thesis, the basic arithmetic of PIV software - cross-correlation arithmetic is introduced in detail, During the data process, through processing the two sequential images by the cross-correlation arithmetic, the vector charts of particles velocity can be obtained, so is the chart of absolute velocity, with velocity decomposed into the radial velocity and axial velocity.

本文对试验所获得的连续图像通过互相关算法，获得颗粒速度矢量图，并将速度分解为径向速度和轴向速度，对每一小区域内的颗粒按速度方向不同进行速度平均，获得颗粒的平均速度分布曲线。

The experimental results show that:(1) for ideal spheres, the attenuation coefficient of velocity is constant, the air drag coefficient is slightly affected by the initial velocity and is a linear function of initial velocity, and (2) for real fragments formed by a warhead, the flight performances are different from ideal spheres, the air drag coefficient is affected by the flight velocity and is a linear function of flight velocity.

实验结果表明：(1)对于理想球形钨合金破片，在同一初始速度条件下，衰减系数为常数，空气阻力系数与初始速度有关，两者成线性关系；(2)对于经历爆轰驱动的球形钨合金破片，由于有轻微的质量损失和变形，速度衰减规律与理想球形钨合金破片有明显的区别，空气阻力系数与飞行速度有关，两者成线性关系。

The average desired velocity of the drivers has been assumed to be proportional to the instantaneous velocity by M ndez and Velasco when a alternative model was proposed. Based on this postulate, the desired velocity of a single driver delineates to be proportional to the local instantaneous velocity in this paper, which is a property of aggressive drivers who all want to drive with the maximum velocity. However, the deriver does not occupy this aggressive characteristic all the time.

基于M ndez 和Velasc关于司机平均期望速度与瞬时速度成比例的假设，认为个体司机的期望速度与其局域瞬时速度成比例，期望以更大的速度行驶，然而并非所有的司机都具有这样的进取特性，为了抑制司机这样的进取特性，引入适应性公式来近似表达单个司机期望速度随时间的变化率。

The main research work of this paper are focused on following areas:(1) Based on review of the theory and methods on measurements of particle fields, a new idea for obtaining particle size and velocity distribution within a spray through imaging the particle field with a laser light sheet was put forward;(2) A DPIV (Digital Particle Image Velocimetry) system, is fit for velocity measurements of low speed flows, was developed and expended to particle size distribution measurement;(3) An arithmetic for particle velocity field reconstruction was developed, and the velocity distribution of water mist was also obtained;(4) A software system for particle analysis, which based on image geometry emend, de-noise and image partition was developed, the parameters such as particle size distribution, mean diameter, number of particles, minimum and maximum diameter can be got with this system;(5) A water mist system was developed and its characteristics, such as droplet velocity, size distribution, number of droplets and spray cone angle under different conditions were obtained from experiments with PIVS;(6) The measurement results of water mist characteristics with PIVS were compared and analyzed with the simply simulated results, and in addition, in order to verify the accuracy of PIVS, some experiments were conducted with the standard particles, such as glass-ball with known mean diameter of 50μm and 115μm, metallic coated tracing particle with mean diameter of 12μm;(7) Some experimental studies on interaction of water mist with liquid pool fires were conducted.

本论文的主要工作包括以下几个方面：（1）在对粒子场测量的相关理论和具体方法进行综述分析的基础上，提出了通过采用激光片光对粒子场进行成像以获取其粒径和速度等参数分布的新思路；（2）研制了适宜于低速流动速度场测量的DPIV(Digital Particle Image Velocimetry)系统，并使其实现了对粒子场粒径分布的测量功能；（3）研制了基于粒子运动轨迹的速度场重建算法，获取了细水雾雾场的速度分布；（4）研制了基于几何校正、去噪、图象分割等图象处理方法的"粒度分析软件系统"，该系统既可分析给出粒子场的粒径分布直方图和平均粒径，还可给出粒子的数目以及最大、最小粒径等信息；（5）建立了一细水雾发生系统，并应用上述方法对不同压力条件下细水雾系统的雾场特性（如速度分布、雾滴粒径分布、雾滴的数目、喷雾张角以及雾化长度等）进行了实验测量研究；（6）对细水雾特性参数的PIVS测量结果与计算机简单模拟计算结果进行了定性比较分析，并利用平均粒径为50μm和115μm的玻璃球以及12μm的标准示踪粒子对PIVS系统的粒径和速度测量结果进行了实验验证，同时对其局限性进行了分析讨论；（7）对不同工况条件下细水雾与油池火相互作用的过程进行了模拟实验研究。

Therefore the dispersion curves obtained in the field are primarily consisted of the first mode. For a heterogeneous elastic solid consisting of three homogeneous layers whose interlayer has low velocity, the phase velocity V〓 of the first mode will also close up to the Rayleigh wave velocity of the bottom layer when frequency f→OHz, but V〓 of the first mode will close up to the shear wave velocity of the interlayer when f→∞, and there is a cut-off frequency at high frequency region for the first mode and V〓 close up to the compressional velocity of interlayer when interlayer is liquid.

当三层固体介质中存在软夹层时，若f→OHz，则其基阶模式的相速度V〓→V〓（V〓为最底层介质的瑞利波速度）；若f→∞，其基阶模式V〓→V〓（V〓为中间层介质的横波速度）；若三层介质中存在液体夹层，当f→OHz时，基阶模式V〓→V〓，而基阶模式在高频段存在一个截止频率，截止频率处的瑞利波速度V〓→V〓；由此可判定，野外实测的相速度频散曲线不仅有基阶导波模式，同时还应有高阶导波模式波的存在，接收信号中存在模式间的跳跃，因此频散曲线会产生"之"字形现象。

Results show that floes' VC and D at the surface water were closely related to current velocity; and the peaks of VC lag those of the current velocity. The lag variation during ebb and flood tides is 10-30min and 30-50 min, respectively. Current velocity at 50 cm/s is a turning point of D vs. vertical average current velocity, before the point, Dm increases with current velocity, and decreases after the point. Similarly, VC at 75μl/L becomes a critical point in the surface water, below the point, D increases with VC, and above the point, D stabilizes.Δp is D dependent, larger floes have much lower Δp than smaller floes. Both D and Δp of floes affect ω. In the surface water during spring tide and neap tide, a power exponent relationship exists between Δp and D, and ω and D.

研究表明：①长江口徐六泾表层絮凝体体积浓度主要受水流流速影响，再悬浮现象明显，体积浓度过程线滞后流速过程线，落潮期间滞后10-30min，涨潮则滞后30-50min；②小于一定流速时絮凝体平均粒径随流速增大而增大，大于一定流速时絮凝体平均粒径则随流速增大而减小，徐六泾夫、小潮表层絮凝体在50cm/s的垂线平均流速时出现平均粒径与垂线平均流速关系的转折；③徐六注大、小潮表层絮凝体平均粒径在体积浓度75μl/L时出现平均粒径与体积浓度关系的转折，体积浓度小于75μl/L时粒径随体积浓度增加而增大，超过75μl/L时粒径随体积浓度的增加变化不明显；④絮凝体有效密度由粒径大小控制，粒径大，有效密度小，反之亦然，粒径和有效密度共同决定絮凝体静水沉速，有效密度和沉速与平均粒径之间均存在良好的幂指数关系。

It was suggested that aging did not only influence diastolic filling period, but also influence STI. 3. With increasing age, whether at rest or during exercice, fractional shortening of minor semiaxis, mean velocity of circumferential fiber shortening, cardiac index and ejection fraction did not change, but immediately post pacing, PEP prolonged and PEP/ LVET increased in elderly group and did not change in young group. It was suggested that STI was sensitivity in detecting systolic function of LV. 4. There was a good correlation between aging and decreased compliance and diastolic function of left ventricle which was manifested by a reduction of early diastolic peak folw velocity, time-velocity integral of early diastole, 1/3 filling fraction (1/3FF)(r=-0.958,-0.875 and -0.937, P＜0.01～0.001) and a significant compansatory increase in peak flow velocity of atrial contraction, time-velocity integral of atrial contraction, the ratio between APFV and EPFV and the ratio of ATVI and Total TVI (r=0.958, 0.956, 0.966 and 0.986, P＜0.001) and the prolongation of Dec T and RFP with increasing age. It was particularly true for the subgroups above the age of 50 years.

静息状态下收缩时间间期与年龄无相关性，负荷后即刻，老年组射血前期延长(P＜0.05)，射血前期与射血期比值加大(P＜0.05)，青年组无变化，提示年龄因素亦影响STI，但由于静息状态下得到代偿，STI变化往往表现不明显。3、静息及负荷状态左室短轴缩短率、平均周径缩短率、心指数及射血分数均不随年龄增长而变化，而负荷后即刻老年组PEF延长，PEP/LVET加大，提示STI是检测左室收缩功能的敏感指标。4、随年龄增长，心房收缩期充盈峰值流速、流速积分、充盈分数及心房收缩期与舒张早期充盈峰值流速之比值显著增高(r＝0.958、0.956、0.986及0.966，P均＜0.001)，舒张早期充盈峰值流速及流速积分、1/3充盈分数(1/3FF)下降(r＝-0.958、-0.875及-0.937，P＜0.01～0.001)。

In the days of sailing vessels the crew were afraid they would be becalmed on the ocean.

在使用帆船的时代，船员们担心他们会因为无风而无法在海洋上航行。

As long as foreign donors pay the PA's salary bill, few expect a new intifada.

只要外国继续为巴权力机构的薪水买单，希望发动新暴动的人便寥寥无几。