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1.
普通话声调及其组合的统计特性 总被引:1,自引:0,他引:1
本文对普通话书面语中声调及其组合的出现率作了统计,结果表明:声调及其组合的动态与静态的出现率有差异,反映了语言和人类其他行为一样,受最小用力原则制约。声调的动态和静态的分布趋势一致,四声出现率按去声、阳平、阴平、上声的顺序递减。声调组合出现率与多音节词音节的组合数量、组合位置、组合结构有关,受语词节奏的支配,节奏成为多音节词的构词要素之一。声调搭配结构反映了对声调组合出现率起决定作用的是说着简捷、省力和听着清晰、可懂的发音原则。双、三、四音节词的声调分布所形成的语音节奏,似乎反映了声带振动频率由高至低的渐变过程是多音节词中声调分布的一般趋势。统计结果为进一步研究普通话口语中连读变调的统计特性提供了依据。文中列有普通话声调和双、三、四音节词的全部声调组合的动态分布数据。 相似文献
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基于可压缩多介质流动问题,分析AC(acoustic),MFCAV(multi fluid channel on averaged volume)和HLLC等近似Riemann解算器的优缺点,通过加权组合的方式设计一种自适应近似Riemann解算器ADRS(adaptive Riemann solver),详细介绍加权组合的自适应选取原则.将ADRS写成AC解算器的修正形式应用于健壮性好的相容中心型拉氏方法.给出Taylor Green vortex稳态流问题的误差分析等数值算例. 相似文献
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本文基于电子线路的多级过电压保护装置的设计原则,提出了把低通滤波器件和限幅器件组合在一起的组合防雷系统,并采用电磁暂态计算程序EMTP分析了低虎波器元件参数对保护性能的影响和其幅频特性。同时,本文还提出了过电压冲击自动报警与计数系统设计的可行性方案。 相似文献
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天文/惯性组合导航模式研究 总被引:14,自引:3,他引:11
简要分析了惯性导航及天文导航系统的工作原理和特点,根据以自主惯性导航为主发展的组合导航系统的方向,提出天文/惯性组合导航系统不同的组合模式,重点探讨了直接校正陀螺漂移的天文/惯性导航新的组合模式并进行理论分析。 相似文献
5.
富勒烯/高聚物组合体系是物理化学,材料等交叉学科研究的一个热点,该组合体系中电荷会对组合体系的物理,光学及非线性光学特性产生很大的影响。文章对富勒烯/高聚物组合体系中电荷转移的发生条件,其对体系特性的影响及研究电荷转移过程的实验方法和结果作了全面扼要的介绍。 相似文献
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在n、γ混合脉冲辐射场的裂变中子测量中,为了抑制γ内本底,提高探测系统的信噪比,采用加Pb过滤片的方法,建立了两套组合闪烁探测系统,即:“Pb过滤片加塑料闪烁体加光电倍增管”系统(简称组合PMT系统)、“Pb过滤片加塑料闪烁体加光电管”系统(简称组合PD系统)。通过理论计算和多能点实验标定,获得了在厚度为3cm的Pb过滤片条件下,不同厚度的ST.40l、ST-1422或ST-1423闪烁体的组成的“组合PMT系统和组合PD系统”的中子灵敏度能量响应。 相似文献
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端-侧面组合抽运方案是提高DPL调Q脉冲峰值功率和压缩脉冲宽度的有效技术途径。借助给出的一组端-侧面组合抽运DPL声光调Q实验结果,依据调Q速率方程,理论分析了组合抽运光的空间分布对调Q脉冲特性的影响,数值计算结果与实验结果一致。实验和理论研究发现:组合抽运时的脉冲宽度明显小于侧面抽运时的脉冲宽度,峰值功率明显高于侧面抽运时的峰值功率。实验和分析结果表明:在总抽运功率和抽运结构确定的情况下,端面抽运光功率在总抽运功率中的占有率越大,脉冲宽度越窄,脉冲峰值功率越高。通过调整端面抽运光功率占有率,改变组合抽运光的空间分布,可以实现对DPL调Q脉冲特性的控制。 相似文献
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Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs. 相似文献
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A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users. 相似文献
13.
S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
14.
References: 《声学学报:英文版》2008,27(1):23-33
The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results. 相似文献
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With a novel light-weight and absolutely calibrated ultraviolet (UV) spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands (320 - 335 nm) using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model (Tracy). The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon. 相似文献
16.
For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters. 相似文献
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Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers. 相似文献
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We propose a novel methodology based on the projector-camera (ProCam) system to address the photometric compensation issue for the projection display on the patterned screen.The patterned screen is treated as the combination of a perfect white screen and a color modulator.The perfect white screen is used to automatically and accurately characterize the ProCam system offline using the polynomial model,and the parameters of the color modulator can be efficiently recovered by employing only two gray images based on the linear reflectance model.The experimental results show that the color artifacts of the display image can be greatly improved with this methodology,which demonstrates its feasibility and validity in the photometric compensation. 相似文献
19.
An approach to direction-of-arrival (DOA) estimation for multiple narrowband farfield signals is proposed. The technique uses a novel matrix spatial prefiltering approach. Specifically, a matrix filter is designed to spatially filter the incoming data snapshots. The un-wanted components arriving from the stopband angular sectors are attenuated and the desired components from the angular sector of interest pass with minimal distortion. The matrix filter spatially filters the element-space data and the output reserves the element-space data property, which makes it very useful by passing sensor data through a spatial prefilter prior to applying many other array processors to attenuate interferences and improve system performance. Several examples of DOA estimation problem are presented to illustrate the performance of the proposed spatial prefiltering approach. Results of simulation and real data show that the pre-filter can efficiently attenuate the spatial interferences and significantly improve the estimation and resolution capability of DOA estimators at low signal-to-noise ratios for the sources located inside the passband sector. In addition, the use of spatial prefilter makes it possible to estimate DOAs for multiple sources more than the number of the elements of an array. 相似文献
20.
A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion (SPDC) effect of nonlinear crystal.An absolute calibration system of detector quantum efficiency is performed.And its principle and experimental setup are introduced.A continuouswave (CW) ultraviolet (351 nm),diode-pumped,frequency-doubled,and solid-state laser is used to pump BBO crystal.The quantum efficiencies of the photomultiplier at 633,702,and 789 nm are measured respectively.The coincidence peaks are observed using coincidence circuit.Some measurement factors including the filter bandwidth of trigger channel,the detector position alignment and polarization of the pump light are analyzed.The uncertainties of this calibration method are also analyzed,and the relative uncertainties of total calibration are less than 5.8%.The accuracy of this method could be improved in the future. 相似文献