共查询到20条相似文献,搜索用时 0 毫秒
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Gunter Radig 《Ultrasonics》1967,5(4):235-238
This article describes in detail the elucidation of an equivalent RF-circuit diagram for an electronic ultrasonic image converter tube, and discusses practical aspects of the construction of the tube itself. 相似文献
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本文叙述了近年来医学超声体成像技术的信号采集,三维重建与显示等方面的新进展,探讨了应用的前景。 相似文献
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Most electronic ultrasonic image converter tubes suffer severe limitations which preclude their use in technology. This article describes ways in which these limitations can be overcome, and an efficient image convertor tube produced. 相似文献
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Yu Chen Hengchang Guo Wei Gong Luye Qin Hossein Aleyasin Rajiv R Ratan Sunghee Cho Jianxin Chen Shusen Xie 《中国光学快报(英文版)》2013,(1):59-66
In the past two decades, two-photon microscopy (TPM) transforms biomedicalresearch, allowing nondestructive high-resolution fluorescent molecular imaging and label-free imaging in vivo and in real time. Here we review the recent advances of TPM technologyincluding novel laser sources, new image acquisition paradiams, and microendoscopicimaging systems. Then, we survey the capabilities of TPM imagingof biological relevant molecules such as nicotinamideadenine dinucleotide (NADH), flavin adenine dinucleotide (FAD),and reactive oxygen species (ROS). Biomedical applications of TPM in neuroscience and cancer detection are demonstrated. 相似文献
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In addition to its well-known capabilities in imaging and spectroscopy, scanning near-field optical microscopy (SNOM) has recently shown its great potentials for fabricating various structures at the nanoscale. A variety of SNOM-based fabrication techniques have been developed for different applications. In this paper, the SNOM-based techniques involving three major functions: material modification, addition, and removal, are examined with emphasis on their abilities and reliability to make structures with resolutions at the nanometer level. The principles and procedures underlying each technique are presented, and the differences and uniqueness among them are subsequently discussed. Finally, concluding remarks are provided to summarize the major techniques studied and to recommend the scopes for technology improvement and future research. 相似文献
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Ott E. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1994,22(1):43-46
A brief review of chaotic dynamics is presented. Topics discussed include basic concepts, recent developments, and applications 相似文献
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Price GJ 《Ultrasonics sonochemistry》2003,10(4-5):277-283
High intensity ultrasound has been applied to two classes of step-growth polymerisation. The ring-opening polymerisation of cyclic lactones to polyesters was accelerated under 20 kHz ultrasound but, in the case of delta-valerolactone, sonication also promoted a depolymerisation reaction so that the molecular weight fell during later stages of the reaction. Sonication was also applied to the preparation of polyurethanes from a number of diisocyanates and diols. In all cases, the sonochemical reactions proceeded faster in the early stages and led to higher molecular weight polymers. The effect of changing the ultrasound intensity is discussed and some speculation as to the mechanisms of the reaction enhancements is given. 相似文献
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D. J. Bradley 《Optics & Laser Technology》1979,11(1):23-28
Recent developments in the techniques of generation and measurement of picosecond and sub-picosecond pulses from mode-locked lasers are reviewed. Particular attention is paid to frequency tunable, bandwidth-limited pulses from dye lasers, especially the cw dye laser. In measurement the main emphasis is put on the rapid advances of the last few years in ultra-fast streak-cameras, ans the recent developments in streak-camera synchronization to a cw mode-locked laser is described. Future prospects for shorter wavelenght pulses in the uv and vuv are briefly considered. 相似文献
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Brandon Carter 《International Journal of Theoretical Physics》1997,36(11):2451-2458
This article provides a concise overview of recent theoretical results concerning the theory of vortons, which are defined
to be (centrifugally supported) equilibrium configurations of (current-carrying) cosmic string loops. Following a presentation
of the results of work on the dynamical evolution of small circular string loops, whose minimum energy states are the simplest
examples of vortons, recent order-of-magnitude estimates of the cosmological density of vortons produced in various kinds
of theoretical scenarios are briefly summarized. 相似文献
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Recent developments in arc spraying 总被引:1,自引:0,他引:1
Steffens H.-D. Babiak Z. Wewel M. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1990,18(6):974-979
New trends in arc-spraying processes and materials are reviewed. The wide field of applications for arc-sprayed coatings is demonstrated and discussed. Coating systems against corrosion, against wear, and for special applications (e.g. coatings for casting molds or biocompatible layers on artificial implants) are described. New process variants, e.g. spraying with a controlled-wire feed system, use of a pulse power source, or vacuum-arc spraying with one or two wires, are expected to appear with further commercial applications of these techniques 相似文献
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Yukihiro Ishii 《Optics and Lasers in Engineering》1991,14(4-5):293-309
Laser-diode (LD) interferometry based on heterodyne techniques is described. The developments covered include: sinusoidal phase- modulating, distance-measuring feedback and phase-shifting interferometry. The wavelength is controlled by the laser injection current and is continuously or stepwise changed to introduce a time-varying phase difference between the two beams of an interferometer with unbalanced optical path lengths. A feedback interferometer is described with electronics to stabilize the phase shift and to lock the interferometer on a preset phase condition by controlling the injection current of the LD. An automated phase-measuring interferometric system is developed in which the laser current is changed to synchronize intensity data acquisition with the clocks of a charge-coupled device. A typical experimental result shows measurements of the profile of a diamond- turned Al surface. 相似文献
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Apoorva Patel 《Pramana》1993,41(1):139-165
I review the current status of several lattice QCD results. I concentrate on new analytical developments and on numerical results relevant to phenomenology. 相似文献
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We give a review of Boson expansion methods applied in the quantum theory as e.g. expansions of spin, bifermion and Fermion operators in cases of the finite and infinite number of degrees of freedom. The basic purpose of the paper is to formulate the most general criterions allowing to get so called finite spin approximation of any given Bose field theory, and the class of Fermion theories associated with it. Quite the converse, we need also to be able to reconstruct the primary Bose field theory while any finite spin or Fermi systems are given. 相似文献
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《Physics Reports》1998,306(3):109-211
In this review we present a pedagogical introduction to recent, more mathematical developments in the Skyrme model. Our aim is to render these advances accessible to mainstream nuclear and particle physicists. We start with the static sector and elaborate on geometrical aspects of the definition of the model. Then we review the instanton method which yields an analytical approximation to the minimum energy configuration in any sector of fixed baryon number, as well as an approximation to the surfaces which join together all the low energy critical points. We present some explicit results for B=2. We then describe the work done on the multibaryon minima using rational maps, on the topology of the configuration space and the possible implications of Morse theory. Next we turn to recent work on the dynamics of Skyrmions. We focus exclusively on the low energy interaction, specifically the gradient flow method put forward by Manton. We illustrate the method with some expository toy models. We end this review with a presentation of our own work on the semi-classical quantization of nucleon states and low energy nucleon–nucleon scattering. 相似文献
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We are investigating the use of capacitive micromachined ultrasonic transducers (cMUT's) for use in medical imaging. We propose an ultrasound probe architecture designed to provide volumetric ultrasound imaging from within an endoscope channel. A complete automated experimental system has been implemented for testing the imaging performance of cMUT arrays. This PC-based system includes custom-designed circuit boards, a software interface, and resolution test phantoms. We have already fabricated 1D and 2D cMUT arrays, and tested the pulse-echo imaging characteristics of 1D arrays. Beamforming and image formation algorithms that aim to reduce the complexity of data acquisition hardware are tested via numerical simulations and using real data acquired from our system. 相似文献
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The transfer functions for focussed and defocussed, coherent and confocal optical imaging systems have been applied to the equivalent ultrasonic imaging systems. The transfer functions with varying degrees of defocus were calculated to show the defocus effects for ultrasonic imaging systems. Assuming that the acoustic waves are reflected perfectly on the surface of the step edge, the theoretical line-scans for small amplitude signals across a step edge, with various degrees of defocus, were generated. The first derivative of the line-scan for a step edge is shown theoretically to yield the same impulse response as that calculated using the inverse Fourier transform applied to the original transfer function. These results show how the real and imaginary parts of the transfer functions contribute to ultrasonic image formation. A method for the experimental determination of the impulse response, and the transfer functions for the characterization of an ultrasonic imaging system, such as an acoustic microscope, is provided. 相似文献