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51.
Based on the Mach-Zehnder interferometer, we introduce a novel construction of the optical correlator for color pattern recognition. This system could remove the zero order term, which decreases the discrimination ability of the system, in only one step. Since each color can be separated into 3 channels, we propose the multi-level quantized reference functions (MQRF) for each color channel, and utilize them in spatial domain. Consequently, a total of 3 MQRFs and 3 color channels of the test image could be implemented at the input plane of liquid crystal spatial light modulator (LCSLM) of Mach-Zehnder joint transform correlator. Each LCSLM is modulated along the real-valued axis. 相似文献
52.
The fabrication of freestanding GaN microstructures using AlN sacrificial layers (SLs) is reported. GaN layers were grown by plasma assisted molecular beam epitaxy (PAMBE) on polycrystalline AlN sacrificial layers that have been deposited at 600 °C. Isotropic wet chemical etching of the AlN film released GaN microbridges and – cantilevers. The stress gradient and the compressive stress in the GaN‐film was extracted by analysis of the relation between beam geometry and displacement. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
53.
M. Marinelli F. Mercuri U. Zammit R. Pizzoferrato 《Applied Physics A: Materials Science & Processing》1991,52(2):115-118
Thermal diffusivity of various compounds used as coupling fluids in photopyroelectric experiments have been measured at room temperature and at 80 K. Measurements on high vacuum silicone grease have also been performed as a function of temperature and an increase in the thermal diffusivity values with decreasing temperature has been found. Two phase transitions in the LiTaO3 pyroelectric transducer have been observed at 200 and 225 K. 相似文献
54.
S. B. Peralta Z. H. Chen A. Mandelis 《Applied Physics A: Materials Science & Processing》1991,52(5):289-294
A novel photothermal technique is developed, which enables the simultaneous measurement of the thermal diffusivity , thermal conductivity , and the specific heat C of a sample. The technique is based on frequency-modulated time-delay photopyroelectric spectrometry (FM-TDPS), which consists of chirped laser excitation of the sample and detection of the thermal impulse response by a thin-film pyroelectric detector. No calibration is required for the measurements; absolute values for , , and C may be obtained without having to employ a reference sample. Results on superconducting YBa2Cu3O7–x
are reported for the temperature range 50–300 K; the values obtained compare favorably with reported measurements of , , and C for YBa2Cu3O7–x
, which previously required separate experiments for their determination. 相似文献
55.
R. Ryf G. Montemezzani P. Günter Y. Furukawa K. Kitamura 《Applied physics. B, Lasers and optics》2001,72(6):737-742
We demonstrate a Vander Lugt type correlator based on photorefractive stoichiometric LiTaO3 as the volume holographic material. Accurate correlator output was obtained for binary phase-modulated input images. The
correlator is tested with binary amplitude- and phase-modulated input images. Phase-modulated images show a high-quality correlation,
whereas amplitude-modulated images suffer in part from a photorefractive self-focusing effect. Using 100 previously stored
holograms as filters, a rate of 10000 correlations/s are demonstrated. A paraxial theoretical analysis of the correlator,
giving analytic expressions for the shift invariance, is also described in detail.
Received: 22 November 2000 / Revised version: 9 February 2001 / Published online: 20 April 2001 相似文献
56.
T. Kawahara J. Morimoto K. Tahira T. Miyakawa 《Applied Physics A: Materials Science & Processing》2000,70(4):407-409
Photoacoustic (PA) amplitude and phase spectra are studied on porous silicon (PS) samples. For the sample with a thinner PS
layer and a rough interface observed by field-emission scanning electron microscope (FE-SEM), PA amplitude decays rapidly
at short wavelengths but stays at a higher level above 650 nm compared with a sample with a thicker PS layer and a smooth
interface. In this latter long-wavelength region, phase delay for the former sample is smaller. A model calculation for the
two-layer model taking account of scattering of light in the porous media and interface reflection of light gives at least
a qualitative explanation of these differences.
Received: 30 June 1999 / Accepted: 11 October 1999 / Published online: 23 February 2000 相似文献
57.
赵凯 《数学的实践与认识》1999,29(3)
本文我们讨论了一类Calder(?)n-Zygmund型算子在Heisenberg群G上由极大函数定义的Hardy空间/H~P(G)(O
相似文献
58.
Received: 17 December 1998 相似文献
59.
Stability properties of the homonuclear diatomic one-electron system are investigated by finite-elements methods. Assuming the Born-Oppenheimer approximation and parallel magnetic fields, the computed critical charges for stability and metastability reveal a surprisingly simple dependence on the magnetic field strength B. 相似文献
60.
Received: 14 April 1998/Accepted: 22 April 1998 相似文献