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1.
2009年3月10-11日,用沿海声层析仪在我国台州大陈岛近海进行了一次双方向声传播测流实验。采用5 kHz的10阶M序列信号,利用GPS时钟进行异地时间同步,完成了水下信号的发射和接收,实现了双向声传播时间的精确测量。2个声传播站位间距为11km,实验历时26h。与此同时,在2个声传播站位间还进行了6次温度、盐度和流速的断面走行观测。2个站接收到的信号的信噪比达到了180以上,由双向声传播时间差得到的测线间的平均流速显示了典型的半日潮的变化。声传播观测所得的平均流速与声学多普勒流速剖面仪(ADCP)断面走行观测结果基本一致,两者之差的平均值为0.04m/s。  相似文献   

2.
宽带声学多普勒流速剖面仪通过处理水下体积回波信号进行流速估计,回波模型的准确度决定了理论仿真的正确性。针对回波的散射特性,通过分析水层回波信号的时空关系,提出一种球面散射水层回波模型,并利用坐标旋转方法推导出该水层回波解析式。相比其他方法,该模型解析式充分体现了散射体模型形状对回波的作用,更加接近实际情况。对该模型下回波信号进行频谱和自相关特性分析,采用复相关算法估算流速。通过与实测数据进行对比,结果证明了该回波信号模型与解析式的正确性。  相似文献   

3.
相关测速声纳工作原理及海试验证   总被引:5,自引:2,他引:5       下载免费PDF全文
“波形不变性”原理是相关测速声纳的基本工作原理,利用射线声学方法对此原理进行了论述。分析了相关测速声纳的两种设计思路:时间相关和空间相关。提出了采用空间相关的思路设计相关测速声纳样机的具体方法,包括阵型设计、信号设计和软件工作流程,并分别在西太平洋和中国南海进行了两次试验。将海试数据结果与声多普勒流速剖面仪和差分GPS从速度大小和方向上进行了比较,证明了相关测速的可行性,验证了流混响和底混响的相关理论模型、声纳阵设计以及信号处理方法的正确性。  相似文献   

4.
李鹏飞  彭东立 《声学技术》2015,34(6):545-550
相对于活塞式声学多普勒流速剖面仪,相控阵声学多普勒流速剖面仪的换能器体积大大缩小,并且依托相控阵本身的物理特性,无需进行声速补偿。利用窄带相控阵声学多普勒流速剖面仪系统进行编码信号的发射与接收,从而提高相控阵声学多普勒流速剖面仪的设备性能。首先介绍了相控阵ADCP的波束形成方法,然后分别介绍了相控阵的相移波束形成和时延波束形成原理,对编码信号相移相控波束形成情况下,相控阵发射和接收信号波束开角进行了对比,并对作用距离、测量精度、系统复杂度等系统性能进行了分析。分析结果表明:窄带相控阵声学多普勒流速剖面仪可以进行编码信号的发射和接收,能够提高系统的空间分辨率和测量精度,从而提高相控阵声学多普勒流速剖面仪的性能。  相似文献   

5.
宽带声学多普勒流速剖面仪,由于其具有很高的空间分辨率和时间分辨率,所以在水文、运输、测控等方面都有很广泛的应用,而其最大作用距离对于其应用范围具有重要意义。根据主动声纳方程各项的意义,分析了深度单元厚度、温度和频率等条件因素对宽带声学多普勒流速剖面仪作用距离的影响,从而对宽带声学多普勒流速剖面仪的最大作用距离进行估计,得到理论计算值。将理论计算值与RDI公司的宽带声学多普勒流速剖面仪作用距离进行比较,作用距离范围吻合性很好。对BBADCP以及具有相同工作原理的声相关计程仪、多普勒计程仪和NBADCP进行对比分析,指出它们在作用距离上的区别。  相似文献   

6.
周亦军  彭东立 《声学技术》2012,31(2):179-183
宽带声学多普勒流速剖面仪(Broadband Acoustic Doppler Current Profile,BBADCP)通过接收海洋体积混响信号进行频偏估计,体积散射模型的准确性决定了理论仿真的正确性。针对BBADCP的信号模型特点,建立了散射体单元散射叠加效应的海洋体积回波时空特性及散射模型,推导了叠加噪声后散射回波的具体表达式。通过散射回波的离散化,把各参数(幅度、频率、调制)分离开来,单独考虑各参数对测速精度的影响。利用复协方差算法对水流流速进行估计,分析了信噪比、水流流速、紊流效应等因素对BBADCP流速估计的影响,验证了体积散射模型的正确性。  相似文献   

7.
基于声学多普勒流速剖面仪测得的不同水位河流截面的平均流速,研究了走航式宽带声学多普勒流量测量系统中,流量与速度水位关系的拟合表达式。采用窄深矩形截面和梯形截面流速分布模型,结合声学多普勒流速剖面仪求得不同水位下的平均流速值,在MATLAB平台下,对两种不同截面中流量与速度水位关系进行了拟合,并求得均方根误差检验拟合的精度。仿真结果表明:通过走航式宽带声学多普勒流量测量算法求得的河流截面流量,与由流速分布模型求得的流量真值间的误差,满足单次流量测验允许的误差要求,表明给出的流量与速度水位关系拟合公式能够较好地表现河流截面的流量变化趋势。对于天然明渠流量推算具有重要的参考价值。  相似文献   

8.
为了配合各地水情中心或预警预报系统的建设,研制了一款多普勒测流剖面仪,它具有真实反映流场,并且一次可以测量一个剖面上的若干层水流速度等优点。首先对这款多普勒测流剖面仪的系统功能进行了描述,结合Modbus协议特点,给出了本系统的读写数据的Modbus通信实例;在TI的OMAPL137硬件和嵌入式Linux操作系统的基础上,给出了实现Modbus RTU协议从站的设计方案;通过将从站采集到的水流速度传输至主站实时显示验证了该方案。实验证明该方案有效地实现了多普勒流速剖面仪在水利系统的现场数据传输。  相似文献   

9.
针对声学多普勒流速剖面仪(ADCP)现场校准困难的问题,介绍了一种基于频偏应答的ADCP流速现场校准方法。通过声信号应答器,设置回发信号相对于发射信号的频偏实现速度矢量的模拟,并以频率为溯源量,对ADCP发射的信号及应答器回发频偏信号进行频率校准,进而实现ADCP流速参数的现场校准。研制了一套基于频偏应答的ADCP流速现场校准装置,在实验室消声水池条件下,以四波束300kHz ADCP为校准对象,开展了1~2m/s的流速校准实验,进行不确定度分析。结果表明,该装置对流速校准的不确定度达到1%模拟流速+7mm/s,验证了该校准方法的可行性。  相似文献   

10.
宽带声学多普勒流量剖面仪的系统仿真   总被引:10,自引:2,他引:10       下载免费PDF全文
90年代初发展起来的宽带声学多普勒流量剖面仪克服了传统窄带ADCP存在距离分辨力与速度分辨力之间的矛盾,从而解决了低速浅水河流流量(流速)精确测量的问题,是一种有着广泛应用前景的先进水文遥测仪器。文章中着重分析了BBADCP(宽带声学多普勒流量剖面仪)如何通过时间选通采样从河流不同深度返回的后向散射回波,实现测距离的目的;如何测量回波的多普勒频移,实现测流速的目的。文中从二维信号矢量的角度分析了多普勒频移调制和解调的过程,推导出提取速度信息的信号处理方法。文中最后采取等效基带仿真方法,运用匹配滤波器理论设计了一个BBADCP系统模型,通过仿真手段验证了文中对BBADCP的分析结果。  相似文献   

11.
This paper describes methods of integrating the digital subscriber line (DSL) automated test, data from network elements, analyses, and DSL operations, including work-force administration. Fiber-to-the-node systems using very-high-rate DSL 2 will particularly need the integrated DSL test to increase customer satisfaction and streamline operations to reduce costs. The integrated DSL test extends beyond copper tests to encompass all elements of DSL service, all through the network and at higher layers. An integrated test system queries multiple test points, including network elements, allowing physical and higher layer problems to be identified. Diagnosis, fault isolation, and even suggested reconfigurations are all automated in software. A number of techniques, which are implementable in software, are described, which can show the root cause of many intricate troubles to relatively unskilled technicians. Automated maintenance routines can isolate faults in flowthrough testing, automatically issuing trouble tickets toward the correct work center: Internet service providers, central offices, outside plants, user PCs, etc. New triple-play services have high customer expectations for easy-to-use TV and voice services, with demanding bit rates and reliability requirements that can be ensured with an integrated test.  相似文献   

12.
The benefits of Raman signal enhancement and improved measurement precision are demonstrated using 180° backscattering Fourier transform Raman (FT-Raman) spectroscopy from drilled cylindrical-conical holes within pharmaceutical tablet cores. Multiple scattering of the incident laser light within the holes results in an increased Raman signal due to the larger Raman sampling volume. This is important for overcoming typical sub-sampling issues encountered when employing FT-Raman backscattering of heterogeneous pharmaceutical tablets. Hole depth and diameter were found to be important experimental parameters and were optimized to yield the greatest signal enhancement. The FT-Raman spectra collected using backscattering from cylindrical-conical holes is compared to typical 180° backscattering from flat surfaces using tablet cores of Excedrin? and Vivarin?. Raman chemical images are used to establish a representative sampling area. We observe a three- to five-fold increase in the Raman intensity and a two-fold improvement in the measurement precision when sampling from cylindrical-conical holes rather than classic backscattering from flat tablet cores. Self-absorption effects on analyte band ratios are negligible in the fingerprint region but are more significant at the higher near-infrared (NIR) absorbances found in the C-H/O-H/-N-H stretching region. The sampling technique will facilitate developing quantitative FT-Raman methods for application to pharmaceutical tablets using the fingerprint spectral region.  相似文献   

13.
Cross-project defect prediction (CPDP) aims to predict the defects on target project by using a prediction model built on source projects. The main problem in CPDP is the huge distribution gap between the source project and the target project, which prevents the prediction model from performing well. Most existing methods overlook the class discrimination of the learned features. Seeking an effective transferable model from the source project to the target project for CPDP is challenging. In this paper, we propose an unsupervised domain adaptation based on the discriminative subspace learning (DSL) approach for CPDP. DSL treats the data from two projects as being from two domains and maps the data into a common feature space. It employs cross-domain alignment with discriminative information from different projects to reduce the distribution difference of the data between different projects and incorporates the class discriminative information. Specifically, DSL first utilizes subspace learning based domain adaptation to reduce the distribution gap of data between different projects. Then, it makes full use of the class label information of the source project and transfers the discrimination ability of the source project to the target project in the common space. Comprehensive experiments on five projects verify that DSL can build an effective prediction model and improve the performance over the related competing methods by at least 7.10% and 11.08% in terms of G-measure and AUC.  相似文献   

14.
聚碳酸亚丙酯型聚氨酯/聚甲基丙烯酸甲酯互穿网络?…   总被引:3,自引:0,他引:3  
用同步法合成了聚碳酸亚丙酯聚氨酯/聚甲基丙烯酸甲酯互穿网络聚合物(PPCPU/PMMA IPN),调节IPN中两组分配比制备出多种高聚物合金。用DSC、TEM对IPN的研究结果表明,PPCPU/PMMA IPN的两组分是互不相容的。同时对各种组成比的IPN材料进行了力学性能测试,并用SEM对断面进行了观察解释。实验结果发现,IPN的密度大于相应体系体积加和值。  相似文献   

15.
评价松质骨状况的一种背散射频谱方法   总被引:1,自引:0,他引:1       下载免费PDF全文
采用超声背散射信号的质心偏移量来评价松质骨,并对牛胫骨和人体跟骨中背散射信号的质心偏移量与松质骨表观密度的关系,以及人体跟骨松质骨中背散射信号频谱质心位置与年龄的关系进行了分析讨论。分析结果表明,随松质骨表观密度的增大,背散射信号频谱的质心向低频方向移动;随年龄的增大,质心位置越接近于发射超声的中心频率。根据超声背散射信号质心偏移量的大小,可用于评价松质骨健康状况。  相似文献   

16.
Winter  V. Kniesel  G. Siy  H. Zand  M. 《Software, IET》2009,3(3):219-237
A generic syntax-based approach is presented by which a fixed set of aspect-oriented features belonging to an aspect language family LA can be applied to a domain-specific language (DSL). The approach centres on the construction of a grammar in which a predefined and fixed set of abstract join points and join point environments are linked with their concrete counterparts within the DSL. This connection enables the behaviour of static weaving to be expressed in a generic manner. The resulting framework is one in which aspect orientation is accessible to non-experts across a wide spectrum of abstractions.  相似文献   

17.
Underwater target detection and ranging in seawater are of interest in unmanned underwater vehicles. This study presents an underwater detection system that synchronously scans a collimated laser beam and a narrow field of view to circumferentially detect an underwater target. Hybrid methods of range-gated and variable step-size least mean squares (VSS-LMS) adaptive filter are proposed to suppress water backscattering. The range-gated receiver eliminates the backscattering of near-field water. The VSS-LMS filter extracts the target echo in the remaining backscattering and the constant fraction discriminator timing method is used to improve ranging accuracy. The optimal constant fraction is selected by analysing the jitter noise and slope of the target echo. The prototype of the underwater detection system is constructed and tested in coastal seawater, then the effectiveness of backscattering suppression and high-ranging accuracy is verified through experimental results and analysis discussed in this paper.  相似文献   

18.
随着目标声源级不断减小、环境噪声级不断增大,常规的基于单节点的被动定位方式已经不能满足声纳探测的需求,因此提出一种新的将网络化探测系统和模基处理技术相结合的被动定位方法,可以从空间不同角度对目标进行观察并充分利用环境声场的复杂性对目标进行定位。模基处理方法主要有匹配场处理、匹配模处理等,以匹配场处理为例进行分析,将常规波束形成(Conventional Beamforming, CBF)、自适应波束形成(Minimum Variance Distortionless Response, MVDR)两种匹配场处理器和阵间相干、非相干信号处理方法相结合进行仿真,对单阵和多阵、MVDR和CBF、相干处理和非相干处理、宽带和窄带之间的定位性能进行了对比。仿真结果显示,基于多节点的阵间模基相干处理方式在定位性能上明显优于单节点的模基处理结果。  相似文献   

19.
We present the results of a study of optical scattering and backscattering of particulates for three coastal sites that represent a wide range of optical properties that are found in U.S. near-shore waters. The 6000 scattering and backscattering spectra collected for this study can be well approximated by a power-law function of wavelength. The power-law exponent for particulate scattering changes dramatically from site to site (and within each site) compared with particulate backscattering where all the spectra, except possibly the very clearest waters, cluster around a single wavelength power-law exponent of -0.94. The particulate backscattering-to-scattering ratio (the backscattering ratio) displays a wide range in wavelength dependence. This result is not consistent with scattering models that describe the bulk composition of water as a uniform mix of homogeneous spherical particles with a Junge-like power-law distribution over all particle sizes. Simultaneous particulate organic matter (POM) and particulate inorganic matter (PIM) measurements are available for some of our optical measurements, and site-averaged POM and PIM mass-specific cross sections for scattering and backscattering can be derived. Cross sections for organic and inorganic material differ at each site, and the relative contribution of organic and inorganic material to scattering and backscattering depends differently at each site on the relative amount of material that is present.  相似文献   

20.
Scientometric analysis of geostatistics using multivariate methods   总被引:3,自引:1,他引:3  
Multivariate methods were successfully employed in a comprehensive scientometric analysis of geostatistics research, and the publications data for this research came from the Science Citation Index and spanned the period from 1967 to 2005. Hierarchical cluster analysis (CA) was used in publication patterns based on different types of variables. A backward discriminant analysis (DA) with appropriate statistical tests was then conducted to confirm CA results and evaluate the variations of various patterns. For authorship pattern, the 50 most productive authors were classified by CA into 4 groups representing different levels, and DA produced 92.0% correct assignment with high reliability. The discriminant parameters were mean impact factor (MIF), annual citations per publication (ACPP), and the number of publications by the first author, for country/region pattern, CA divided the top 50 most productive countries/regions into 4 groups with 95.9% correct assignments, and the discriminant parameters were MIF, ACCP, and independent publication (IP); for institute pattern, 3 groups were identified from the top 50 most productive institutes with nearly 88.0% correct assignment, and the discriminant parameters were MIF, ACCP, IP, and international collaborative publication; last, for journal pattern, the top 50 most productive journals were classified into 3 groups with nearly 98.0% correct assignment, and its discriminant parameters were total citations, impact factor and ACCP. Moreover, we also analyzed general patterns for publication document type, language, subject category, and publication growth.  相似文献   

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