查询词典 band spectrum

In order to make use of time-frequency characteristic of signal,a new method of variational estimation on signal frequency by using AR model power spectrum estimation,designing band-pass filter to gain approximatively source signals and underdetermined mixed matrix,and constructing completed observation signals by expanded subspace primer vector is proposed.

充分利用信号的时频特性，提出了AR模型功率谱估计法滑动估计信号频率，设计带通滤波器近似获取源信号和欠定混合矩阵，以及扩展子空间向量基构造完备观测信号的方法，将问题转化为完备情况下的盲分离，最后运用FastICA方法实现了信号盲分离。

The following results are made from this research: Assessing data quality and band combination of different bands in line with geo-target features in desertification areas, and determining basic bands for desertification monitoring. And understanding and studying the spectral features and variation rules of geo-targets in the experimental area, raising that it is the basis of geo-targets information collection with imaging spectrometer data to understand spectral features and variation rules of geo-targets, realizing that in a great extent spectral-integrated-form-based classification method can remove the phenomenon of "different spectrum with same objects" resulted from reflection ratio curve translation because of the angle change among sensor, targets and observation direction, and the average and variance images can be introduced to solve the problem of two kinds of geo-target with similar spectral forms and much different values of whole reflectionratio. It is suggested that "red edge" range bands of vegetation, which has close relationship with vegetation cover and biomass, is the main characteristic bands and important basis for careful vegetation classification and quantitative retrieval, and pixel-based derivative spectral analysis is very useful for removing the effects of soil background values and quantitatively retrieving vegetation biomass and cover. The remote sense quantitative retrieval model is developed for main appraisable factors of desertification monitoring assessment with imaging spectrometer data and then the applicability of model is analyzed.

研究结果如下：首先针对荒漠化地区的地物特征，对高光谱数据不同波段的数据质量、波段组合进行了评价，提出了适用于荒漠化监测的基本波段选择集；初步了解和掌握了研究地区的地物光谱特性及变异规律，进一步明确了掌握地物光谱特征和变异规律是用成像光谱仪数据提取地物信息的基础；发现了基于光谱整体形状的分类方法在很大程度上能够消除由于传感器、地物目标观测方向之间的角度变化引起的反射率曲线整体平移的&同物异谱&现象，对于谱形相似而整体反射率的值相差较大的两类地物，通过引入均值和方差图像参与分类得到解决；研究还表明在植被&红边&范围内的波段是进行荒漠化监测的主要特征波段，这些波段与植被生物量和盖度都有密切的关系，是开展精细植被分类研究和植被定量反演的重要基础；像元的导数光谱分析可以消除土壤背景的影响，是进行植被生物量和盖度定量反演的有力工具；建立了荒漠化监测主要评价因子的定量反演模型，并分析了模型的适用性。

This dissertation comprehensibly researches the performance of hybrid DS/FH spread spectrum communication systems, operating in a combined additive white gaussian noise , multiple access interference, and channel fading, particularly operating in hostile interference (partial band interference and multitone jamming). At the same time, the dissertation investigates performance of forward error correction coding and diversity technology against channel noise.

本文以此为背景，较为详细地研究了在信道中出现各种噪声干扰（高斯白噪声、多址干扰和信道衰落），特别是敌方的人为干扰（部分带宽噪声干扰和部分带宽多频干扰）时，混合DS/FH扩频通信系统的性能，以及前向纠错信道编码和分集技术对混合扩频通信系统信道出现噪声干扰时系统性能的改进情况。

Because It has stronger ability of resisting narrow band,multipath and jamming interference than that of the conservational communication systems,and also has advantages of concealed information and multiple access secure communication,thus the spread spectrum communication technology draws the people's attention more and more.

由于扩频通信系统与常规的通信系统相比，具有很强的抗窄带干扰，抗多径干扰，抗人为干扰的能力，并具有信息隐蔽、多址保密通信等优点，因而越来越受人们的重视。

By time-varying filtering, we realize the signal selectivity and interference suppression, especially for the signals with time-varying power spectrum. It is shown herein that conventional eigenstructure based methods are lower dimensional special case of the time-frequency subspace fitting method. The closed-form array response estimation algorithms for blind source separation in wireless communication is also developed in the dissertation by exploiting the data structure of second-order statistics of the array output in the presence of multipath. The proposed method achieves array response estimation with little constraint on signal property and propagation environment such as scatters or angular spread. Moreover, the array utilized here can be of arbitrary geometry and even uncalibrated. Since the closed-form solution is obtained, no misconvergency may occur and large amount of computation can be saved. The equivalent feed model and corresponding optimization designation are proposed to realize the downlink multi-user selective transmission. By coherent and non-coherent superposition of the electromagnetical field, multiple beams can be formed using a single array, so that each co-channel user signal is transmitted in each beam and will not interfered with each other. The proposed system scheme implements the digital beamforming and the channel allocation in the base band, therefore is suitable for the utilization of the radio software technology. The feasibility and effectiveness of the proposed model are proved by the RF experiment.

在窄带条件下，GSC－SSF方法还可以提高阵列的虚拟孔径，从而提高估计的性能；可以证明，Cyclic DOA 和SC-SSF方法可看作该方法的特例或近似； 3、提出了二维GSC－SSF方法和宽带谱相关DOA矩阵方法，利用信号的循环平稳特性解决了宽带条件下二维 DOA 估计问题，并具有阵元数少、计算量较小的特点； 4、提出了时频子空间拟合和宽带时频DOA估计算法，将联合时频分析的理论和方法引入到阵列信号的空间谱估计研究中，利用时变滤波实现信号选择性测向和干扰抑制，特别适合于谱时变信号；可以证明传统特征结构法可看作是时频子空间拟合方法的特例； 5、提出了多用户环境下阵列响应的估计方法——CARE方法，该方法对信号结构和传播参数（主要是散射源分布与角度散布）的约束较少，适用于各种几何结构的阵列甚至未校准的阵列，能够直接得到阵列响应的闭式解，因此计算量小、稳健性好，不存在收敛问题； 6、提出了针对多用户下行选择性发送的阵列等效激励模型、优化设计方法及其系统实现方案，通过空间场的相干叠加与非相干叠加使得单一阵列能够形成多个波束，并保证各波束内的用户信号各不相同且相互干扰最小；其系统方案具有在基带实现数字波束成形、信道分配并便于软件无线电实现的特点，其有效性已得到外场实测数据的证实。

However, the interceptive white noise process must be used for design if the seismic power spectrum concentrates at high frequency band.

但是，如果地震功率谱集中在高频，必须按高频部分截断白噪声设计。

As one of major monitoring techniques for forecasting the disasters in mine, Microseismic signal contains some special characteristics, such as rich composition of the spectrum and wide frequency band.

在煤矿开采过程中，煤层底板突水、淹井事故时有发生，严重影响煤矿的正常生产，但目前其预测的可靠程度与生产实际还有较大的差距。

As the thermal radiation of coating surface on Low E glass is strongly influenced by its spectrum, the nongray band model in diffusing enclosure was used to numerically simulate the surface radiative characteristics of Low E glass in combination with the glass properties of absorptivity and transmissivity.

由于建筑节能的需要，低辐射率玻璃被大量地应用于建筑物等公共场合。为保证安全使用，这些玻璃必须经过物理钢化处理，即将玻璃制品加热到其转变温度Tg 以上 50～60°C ，然后在冷却介质中急速均匀冷却，使玻璃表面生成均匀分布的压应力层。

The photoluminescent spectrum of the complex in solid state exhibited a strong emission band at 450 nm.

最后分析了其在防伪包装方面的应用前景。

The very raw sound fits perfectly within the rather limited musical spectrum of the band just as the screamy vocals of new kid on the block Kenny Winter.

非常原始的声音完全符合在相当有限的音乐谱波段正如screamy歌唱新孩子的块肯尼冬季。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。