共查询到20条相似文献,搜索用时 15 毫秒
1.
From modern control theory, an active control method to synchronize two modified Chua circuits with each other,which exhibit chaos, is presented. Some sufficient conditions of linear stability of the chaotic synchronization are obtained from rigorous mathematic justification. On the basis of the state-observer, the controller is analytically deduced using the active control. It is shown that this technique can be applied to achieve synchronization of the two systems with each other, whether they are identical or not. Finally, numerical simulations show the effectiveness of the proposed control scheme. 相似文献
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《Waves in Random and Complex Media》2013,23(4):682-707
We develop a new theory of the optical theorem for scalar fields in nonhomogeneous media which can be bounded or unbounded. It applies to arbitrary lossless backgrounds and quite general probing fields. The derived formulation holds for arbitrary passive scatterers, which can be dissipative, as well as for the more general class of active scatterers which are composed of a (passive) scatterer component and an active, radiating (antenna) component. The generalization of the optical theorem to active scatterers is relevant to many applications such as surveillance of active targets including certain cloaks and invisible scatterers and wireless communications. The derived theoretical framework includes the familiar real power optical theorem describing power extinction due to both dissipation and scattering as well as a novel reactive optical theorem related to the reactive power changes. The developed approach naturally leads to three optical theorem indicators or statistics which can be used to detect changes or targets in unknown complex media. The paper includes numerical simulation results that illustrate the application of the derived optical theorem results to change detection in complex and random media. 相似文献
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L. B. Sjogren H. -x. L. Liu T. Liu F. Wang C. W. Domier N. C. Luhmann Jr. 《International Journal of Infrared and Millimeter Waves》1993,14(6):1175-1189
Control techniques for millimeter-wave active arrays are considered. In addition to voltage control, optical and quasi-optical approaches are discussed as analog control techniques. Digital control techniques discussed include on/off switching arrays and designs with superimposed device and/or grid structures for multi-bit capability. A quasi-optical Q switch, capable of high peak power pulse generation, is discussed as an example application of these techniques. 相似文献
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Carsten Schmidt-Langhorst Hans-Georg Weber 《Journal of Optical and Fiber Communications Reports》2005,2(1):86-114
The optical sampling technique is a novel method to perform
time-resolved measurements of optical data signals at high bit
rates with a bandwidth that cannot be reached by conventional
photodetectors and oscilloscopes. The chapter reviews the
techniques that are used in optical sampling systems to perform
the ultrafast sampling of the signal under investigation. In
addition to the various nonlinear materials and effects used for
the optical sampling gates and pulse sources, the realized optical
sampling systems also differ in the way, in which the system is
synchronized to the data signal. Systems have been reported using
synchronous, random and software synchronized configurations.
Applications of optical sampling systems include high bit rate
waveform and eye diagram measurements, measurements of
constellation diagrams of phase modulated data signals,
time-resolved measurements of the state-of-polarization as well as
investigations of fiber transmission impairments. 相似文献
6.
Repetition-rate multiplication has been shown by use of a fiber ring oscillator with a semiconductor optical amplifier as the gain medium and by use of fast saturation and recovery of the amplifier from an external optical pulse train. Repetition-frequency multiplication up to 6 times and up to 34.68-GHz frequency have been achieved. 相似文献
7.
Te -kao Wu Charles W. Chandler 《International Journal of Infrared and Millimeter Waves》1993,14(6):1191-1199
Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are 1) the fiber replacement of conventional RF phased array distribution and control components, 2) spatial beam forming, and 3) optical beam splitting techniques. Two novel optical beam forming approaches, i.e., the spatial beam forming with a smart pixel spatial light modulator (SLM) and the optical beam splitting approaches are conceived with integrated quasi-optical components. Also presented are the transmit and receive array architectures with the new SLM. 相似文献
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利用激光二极管或发光二极管混合双稳态回路(BILD/BILED)的组合,得到了光学多稳态,光学异或逻辑门和光学R-S触发器.这种光电子学的逻辑回路与大规模集成技术完全相容,因此有希望应用于光学信息处理,光通信和光计算. 相似文献
11.
By exploiting the polarization multistability of polaritons, we show that polarized signals can be conducted in the plane of a semiconductor microcavity along controlled channels or "neurons." Furthermore, because of the interaction of polaritons with opposite spins it is possible to realize binary logic gates operating on the polarization degree of freedom. Multiple gates can be integrated together to form an optical circuit contained in a single semiconductor microcavity. 相似文献
12.
W. Cuypers N. Van Gestel A. Voet J.-P. Kruth J. Mingneau P. Bleys 《Optics and Lasers in Engineering》2009,47(3-4):292-300
Dimensional inspection tasks are often carried out on conventional coordinate measuring machines (CMMs). These CMMs can differ in layout and size depending on the application area. They can have measurement volumes up to 100 m3. However, when measuring large objects it is not always possible to bring a large object to these conventional CMMs. That is why for these applications mobile measuring systems are an ideal solution. These systems often measure the dimensions through optical techniques, like interferometry and optical triangulation. After a short survey of common optical measurement techniques for mobile and large-scale measurements, this paper focuses on two industrial cases where different techniques were used to solve a measurement problem. The first case covers the measurement of a large iron casting with an optical LED-based triangulation system. It was possible to predict problems that would occur with the machining of the part, like unfinished surfaces after milling due to material shortage, and adapt the alignment of the part to prevent these problems. The second case covers the measurement of a double-decker train by means of photogrammetry, as an alternative for the currently used total station. Despite some specific drawbacks of photogrammetry systems it was possible to obtain the same accuracy and to reduce the overall inspection time significantly in comparison with the current situation. 相似文献
13.
Three flow measurement techniques make use of fast digital correlators. The most widely spread is photon correlation velocimetry using crossed laser beams, and detecting Doppler shifted light scattered by small particles in the flow. Depending on the processing of the photon correlation output, this technique yields mean velocity, turbulence level, and even the detailed probability distribution of one velocity component. An improved data processing scheme is demonstrated on laminar vortex flow in a curved channel. In the second method, rate correlation based upon threshold crossings of a high pass filtered laser Doppler signal can be used to obtain velocity correlation functions. The most powerful set-up developed in our laboratory uses a phase locked loop type tracker and a multibit correlator to analyze time-dependent Taylor vortex flow. With two optical systems and trackers, cross-correlation functions reveal phase relations between different vortices. The last method makes use of refractive index fluctuations (eg in two phase flows) instead of scattering particles. Interferometry with bidirectional counting, and digital correlation and probability analysis, constitutes a new quantitative technique related to classical Schlieren methods. Measurements on a mixing flow of heated and cold air contribute new ideas to the theory of turbulent random phase screens. 相似文献
14.
This paper briefly reviews the basics of optical Fourier techniques (OFT) and applications for medical image processing as well as phase contrast imaging of live biological specimens. Enhancement of microcalcifications in a mammogram for early diagnosis of breast cancer is the main focus. Various spatial filtering techniques such as conventional 4f filtering using a spatial mask, photoinduced polarization rotation in photosensitive materials, Fourier holography, and nonlinear transmission characteristics of optical materials are discussed for processing mammograms. We also reviewed how the intensity dependent refractive index can be exploited as a phase filter for phase contrast imaging with a coherent source. This novel approach represents a significant advance in phase contrast microscopy. 相似文献
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光学合成孔径成像技术及发展现状 总被引:1,自引:0,他引:1
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Akio Sugita Katsuhide Onose Yasuji Ohmori Mitsuho Yasu 《Fiber and Integrated Optics》1993,12(4):347-354
To enable alignmentfree optical fiber coupling to single-mode silica-based waveguides, fiber-guiding grooves are fabricated in the same substrate as waveguide circuits.These grooves are used successfully to couple optical fiber to Waveguides. An average, fiber-to-waveguide coupling loss of 0.6 dB per interface is obtained with eight arrayedguiding grooves, and it is expected that this will further be reduced to 0.2 dB per interface. The coupling loss varies by ±0.3 dB during thermal cycling between -10°C and +60°C. 相似文献
18.
W. Mertin 《Optical and Quantum Electronics》1996,28(7):801-817
Since the invention of the electrooptic sampling technique about ten years ago, this contactless test technique based on ultra-short optical pulses has become more and more attractive to microwave engineers developing monolithic microwave integrated circuits (MMICs). The electrooptic sampling technique was originally used for circuit internal measurements of very high-speed waveforms only at discrete test points. During the last five years, a new test technique, the two-dimensional electrooptic field mapping technique, has been developed and widely used. This test technique which measures the magnitude and phase of the microwave signal gives information not only of one discrete test point but also of a greater area within the circuit and therefore insight into the microwave field distribution. This two-dimensional electrooptic field mapping technique could be a powerful tool for studying fundamental properties of wave propagation in monolithic integrated microwave devices and circuits. The aim of this paper is to present the state-of-art of this new test technique and to show an example of its application. 相似文献
19.
V. I. Denisov I. P. Denisova V. G. Zhotikov 《Journal of Experimental and Theoretical Physics》2005,101(2):202-211
The complex permittivity tensor of a magnetically active isotropic medium is expanded, to third-order accuracy, in terms of a small parameter equal to the ratio of the mean distance between the atoms of the medium to the wavelength of an electromagnetic wave. A dispersion equation is constructed. On the basis of this equation, the refractive indices of the medium for normal waves are obtained when a longitudinal magnetic field is applied to the medium. It is shown that calculations to third-order accuracy yield different values for the velocities of all four normal waves that propagate in the medium in forward and backward directions. Calculations are carried out for the experiment conducted with the use of a ring laser for measuring the expansion coefficients of the complex permittivity tensor that are responsible for the small difference between the velocities of the normal waves propagating in forward and backward directions. It is shown that, in the case of an isotropic optically nonactive medium, the third-order expansion coefficients can be measured by means of a ring laser with an absolute accuracy on the order of 10?14. 相似文献
20.
Gerard R. Lemaitre 《Optical Review》2013,20(2):103-117
Optical designs for astronomy involve implementation of active optics and adaptive optics from X-ray to the infrared. Developments and results of active optics methods for telescopes, spectrographs and coronagraph planet finders are presented. The high accuracy and remarkable smoothness of surfaces generated by active optics methods also allow elaborating new optical design types with high aspheric and/or non-axisymmetric surfaces. Depending on the goal and performance requested for a deformable optical surface analytical investigations are carried out with one of the various facets of elasticity theory: small deformation thin plate theory, large deformation thin plate theory, shallow spherical shell theory, weakly conical shell theory. The resulting thickness distribution and associated bending force boundaries can be refined further with finite element analysis. 相似文献