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Noise Sensitivity of Teager-Kaiser Energy Operators and Their Ratios  [PDF]
Pradeep Kr. Banerjee,Nirmal B. Chakrabarti
Computer Science , 2015,
Abstract: The Teager-Kaiser energy operator (TKO) belongs to a class of autocorrelators and their linear combination that can track the instantaneous energy of a nonstationary sinusoidal signal source. TKO-based monocomponent AM-FM demodulation algorithms work under the basic assumption that the operator outputs are always positive. In the absence of noise, this is assured for pure sinusoidal inputs and the instantaneous property is also guaranteed. Noise invalidates both of these, particularly under small signal conditions. Post-detection filtering and thresholding are of use to reestablish these at the cost of some time to acquire. Key questions are: (a) how many samples must one use and (b) how much noise power at the detector input can one tolerate. Results of study of the role of delay and the limits imposed by additive Gaussian noise are presented along with the computation of the cumulants and probability density functions of the individual quadratic forms and their ratios.
基于Teager-Kaiser能量算子Rife-Vincent窗频谱校正的电压闪变测量  [PDF]
高云鹏,李峰,陈婧,姚文轩,黄纯,滕召胜
电工技术学报 , 2014,
Abstract: 分析了Teager-Kaiser能量算子的构成和Rife-Vincent窗的旁瓣特性,通过Teager-Kaiser算子快速提取电压闪变包络,将包络参数进行Rife-Vincent窗改进FFT谱分析与校正,简化IEC推荐的闪变测量过程,提出并建立了基于Teager-Kaiser能量算子Rife-Vincent窗频谱校正的电压闪变测量算法。仿真试验结果表明,本文提出的算法能有效克服单一频率调幅波频率变化、多频率成分调幅波、电网基波频率波动、谐波与间谐波以及白噪声对检测结果的影响,与传统电压闪变检测方法相比,设计实现简单、计算量小,测量结果精确、稳定,可用于电压闪变参数的在线监测。
A Highly Efficient Generalized Teager-Kaiser-Based Technique for LOS Estimation in WCDMA Mobile Positioning  [cached]
Ridha Hamila,Abdelmonaem Lakhzouri,Elena Simona Lohan,Markku Renfors
EURASIP Journal on Advances in Signal Processing , 2005, DOI: 10.1155/asp.2005.698
Abstract: Line-of-sight signal delay estimation is a crucial element for any mobile positioning system. Estimating correctly the delay of the first arriving path is a challenging topic in severe propagation environments, such as closely spaced multipaths in multiuser scenario. Previous studies showed that there are many linear and nonlinear techniques able to solve closely spaced multipaths when the system is not bandlimited. However, using root raised cosine (RRC) pulse shaping introduces additional errors in the delay estimation process compared to the case with rectangular pulse shaping due to the inherent bandwidth limitation. In this paper, we introduce a novel technique for asynchronous WCDMA multipath delay estimation based on deconvolution with a suitable pulse shape, followed by Teager-Kaiser operator. The deconvolution stage is employed to reduce the effect of the bandlimiting pulse shape.
基于Teager-Kaiser算子的改进波束域MUSIC时延估计算法  [PDF]
周非,王路凯,范馨月
重庆邮电大学学报(自然科学版) , 2011,
Abstract: 为了降低波束域多重信号分类(multiplesignalclassification,MUSIC)算法估计接收信号到达时间(timeofarrival,TOA)的计算复杂度,提高算法的抗噪性能,提出一种基于TK算子(Teager-Kaiseroperator)的改进算法。利用TK算子对数据瞬时变化敏感的特性,将接收信号与参考信号的相关函数经过TK算子处理,估计出波束域转换矩阵和波束域输出数据,再用MUSIC时延估计算法估计TOA。仿真结果说明,该方法比波束域MUSIC时延估计算法计算量小,并更好地抑制了多径信号噪声影响,高分辨率的估计性能得到了明显改善。
An improved beam-space MUSIC time delay estimation algorithm based on TK operator
基于Teager-Kaiser算子的改进波束域MUSIC时延估计算法

周非,王路凯,范馨月
重庆邮电大学学报(自然科学版) , 2011,
Abstract: 为了降低波束域多重信号分类(multiple signal classification,MUSIC)算法估计接收信号到达时间(time of arrival,TOA)的计算复杂度,提高算法的抗噪性能,提出一种基于TK算子(Teager-Kaiser operator)的改进算法。利用TK算子对数据瞬时变化敏感的特性,将接收信号与参考信号的相关函数经过TK算子处理,估计出波束域转换矩阵和波束域输出数据,再用MUSIC时延估计算法估计TOA。仿真结果说明,该方法比波束域MUSIC时延估计算法计算量小,并更好地抑制了多径信号噪声影响,高分辨率的估计性能得到了明显改善。
Imaging of double slit interference by scanning gate microscopy  [PDF]
K. Kolasiński,B. Szafran,M. P. Nowak
Physics , 2014, DOI: 10.1103/PhysRevB.90.165303
Abstract: We consider scanning gate microscopy imaging of the double slit interference for a pair of quantum point contacts (QPCs) defined within the two-dimensional electron gas. The interference is clearly present in the scattered electron wave functions for each of the incident subbands. Nevertheless, we find that the interference is generally missing in the experimentally accessible conductance maps for many incident subbands. We explain this finding on the basis of the Landauer approach. A setup geometry allowing for observation of the double slit interference by the scanning gate microscopy is proposed.
Detection of Retinitis Pigmentosa by Differential Interference Contrast Microscopy  [PDF]
Juyeong Oh, Seok Hwan Kim, Yu Jeong Kim, Hyunho Lee, Joon Hyong Cho, Young Ho Cho, Chul-Ki Kim, Taik Jin Lee, Seok Lee, Ki Ho Park, Hyeong Gon Yu, Hyuk-jae Lee, Seong Chan Jun, Jae Hun Kim
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0097170
Abstract: Differential interference contrast microscopy is designed to image unstained and transparent specimens by enhancing the contrast resulting from the Nomarski prism-effected optical path difference. Retinitis pigmentosa, one of the most common inherited retinal diseases, is characterized by progressive loss of photoreceptors. In this study, Differential interference contrast microscopy was evaluated as a new and simple application for observation of the retinal photoreceptor layer and retinitis pigmentosa diagnostics and monitoring. Retinal tissues of Royal College of Surgeons rats and retinal-degeneration mice, both well-established animal models for the disease, were prepared as flatmounts and histological sections representing different elapsed times since the occurrence of the disease. Under the microscopy, the retinal flatmounts showed that the mosaic pattern of the photoreceptor layer was irregular and partly collapsed at the early stage of retinitis pigmentosa, and, by the advanced stage, amorphous. The histological sections, similarly, showed thinning of the photoreceptor layer at the early stage and loss of the outer nuclear layer by the advanced stage. To count and compare the number of photoreceptors in the normal and early-retinitis pigmentosa-stage tissues, an automated cell-counting program designed with MATLAB, a numerical computing language, using a morphological reconstruction method, was applied to the differential interference contrast microscopic images. The number of cells significantly decreased, on average, from 282 to 143 cells for the Royal College of Surgeons rats and from 255 to 170 for the retinal-degeneration mouse. We successfully demonstrated the potential of the differential interference contrast microscopy technique’s application to the diagnosis and monitoring of RP.
Capturing the Surface Texture and Shape of Pollen: A Comparison of Microscopy Techniques  [PDF]
Mayandi Sivaguru, Luke Mander, Glenn Fried, Surangi W. Punyasena
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039129
Abstract: Research on the comparative morphology of pollen grains depends crucially on the application of appropriate microscopy techniques. Information on the performance of microscopy techniques can be used to inform that choice. We compared the ability of several microscopy techniques to provide information on the shape and surface texture of three pollen types with differing morphologies. These techniques are: widefield, apotome, confocal and two-photon microscopy (reflected light techniques), and brightfield and differential interference contrast microscopy (DIC) (transmitted light techniques). We also provide a first view of pollen using super-resolution microscopy. The three pollen types used to contrast the performance of each technique are: Croton hirtus (Euphorbiaceae), Mabea occidentalis (Euphorbiaceae) and Agropyron repens (Poaceae). No single microscopy technique provided an adequate picture of both the shape and surface texture of any of the three pollen types investigated here. The wavelength of incident light, photon-collection ability of the optical technique, signal-to-noise ratio, and the thickness and light absorption characteristics of the exine profoundly affect the recovery of morphological information by a given optical microscopy technique. Reflected light techniques, particularly confocal and two-photon microscopy, best capture pollen shape but provide limited information on very fine surface texture. In contrast, transmitted light techniques, particularly differential interference contrast microscopy, can resolve very fine surface texture but provide limited information on shape. Texture comprising sculptural elements that are spaced near the diffraction limit of light (~250 nm; NDL) presents an acute challenge to optical microscopy. Super-resolution structured illumination microscopy provides data on the NDL texture of A. repens that is more comparable to textural data from scanning electron microscopy than any other optical microscopy technique investigated here. Maximizing the recovery of morphological information from pollen grains should lead to more robust classifications, and an increase in the taxonomic precision with which ancient vegetation can be reconstructed.
Cell shape identification using digital holographic microscopy  [PDF]
Johan Zakrisson,Staffan Schedin,Magnus Andersson
Physics , 2015, DOI: 10.1364/AO.54.007442
Abstract: We present a cost-effective, simple and fast digital holographic microscopy method based upon Rayleigh-Sommerfeld back propagation for identification of the geometrical shape of a cell. The method was tested using synthetic hologram images generated by ray-tracing software and from experimental images of semi-transparent spherical beads and living red blood cells. Our results show that by only using the real part of the back-reconstructed amplitude the proposed method can provide information of the geometrical shape of the object and at the same time accurately determine the axial position of the object under study. The proposed method can be used in flow chamber assays for pathophysiological studies where fast morphological changes of cells are studied in high numbers and at different heights.
Electron paths and double-slit interference in the scanning gate microscopy  [PDF]
K. Kolasiński,B. Szafran
Physics , 2015, DOI: 10.1088/1367-2630/17/6/063003
Abstract: We analyze electron paths in a solid-state double-slit interferometer based on the two-dimensional electron gas and their mapping by the scanning gate microscopy (SGM). A device with a quantum point source contact of a split exit and a drain contact used for electron detection is considered. We study the SGM maps of source-drain conductance ($G$) as functions of the probe position and find that for a narrow drain the classical electron paths are clearly resolved but without any trace of the double-slit interference. The latter is present in the SGM maps of backscattering ($R$) probability only. The double-slit interference is found in the $G$ maps for a wider drain contact but at the expense of the loss of information on the electron trajectories. Stability of $G$ and $R$ maps versus the geometry parameters of the scattering device is also discussed. We discuss the interplay of the Young interference and interference effects between various electron paths introduced by the tip and the electron detector.
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