Nonintrusive measurements of temperature and size of single falling raindrops

A nonintrusive laser technique, based on the detection of a rainbow, is presented that permits one to determine simultaneously the temperature and size of droplets. Therefore the Airy theory for a rainbow and a calibration rainbow pattern at isothermal conditions are applied. Rainbow patterns coming from droplets in the millimeter range have been recorded on a linear CCD array. It has been found that the sphericity of the droplets plays an important role for this rainbow-based technique.     

Fabrication of extreme-ultraviolet point-diffraction interferometer aperture arrays

Interferometric testing at the design wavelength is required for accurately characterizing the wave front of an imaging system operating in the extreme ultraviolet. The fabrication of point-diffraction interferometer apertures for extreme ultraviolet wave-front aberration analysis is described. The apertures are formed in a 200-nm-thick low-pressure chemical-vapor-deposited Si(3)N(4) film and vary in size from approximately 0.10 to 0.50 μm to generate a reference wave front of varying numerical aperture. A graded absorber overcoat is used to control the intensity of the aberrated wave front.Optimal fringe contrast can be obtained when the aperture that provides the maximum uniformity and contrast in the interference plane is selected.     

Room-temperature tests of an optical transducer for resonant gravitational wave detectors

A two-oscillator transducer incorporating a laser-illuminated Fabry-Perot cavity with a finesse of 77,500 and a power dissipation of 1.2 μW was tested at room temperature. The energy of the last resonator with a mass of 1.25 g was measured to be k(B)T within 8%, and no back action from the sensor could be detected. The lowest value of the noise measured away from resonance was 1.0 × 10(-15)m/√Hz, and the electronic noise was 3.2 × 10(-17) m/√Hz. That transducer is designed for a 2400-kg gravitational wave antenna operating at cryogenic temperatures. At 4.2 K and for mechanical quality factors of 3 × 10(6), the measured thermal and electronic noise levels would translate into a sensitivity in h equal to 7.0 × 10 (-19) and 1.5 × 10(-19), respectively.     

Effects of hypergravity on the cell shape and on the organization of cytoskeleton and extracelluar matrix molecules of in vitro human dermal fibroblasts

In vitro human dermal fibroblasts were submitted to normal gravity (1 g) or to chronic hypergravity ranging from 2 to 20 g for 8 days. Changes only appeared above 15 g. The majority of 20 g-subjected cells showed fine filipods in the shape of a star whereas most control cells had rounded shapes and spread by forming lamellipodia. Indirect immunofluorescence staining of vinculin, alpha-actinin and actin stress fibers showed changes of the arrangement anchoring points of stress fibers under hypergravity. Tubulin staining showed that the centrosomal material generally located above the nucleus in control cells had migrated to the nucleus side in 20 g-exposed cells. After 8 d of culture under 20 g hypergravity the thickness of fibronectin network seemed to be increased and bundles of fibrils appeared linking ordered arrays of fibers. The fibrils of collagen I formed better delimited and thicker bundles of fibers. We may assume that 20 g hypergravity can induce changes in fibroblast cell shape, migration way, and anchorage leading to a reorganization of extracellular matrix without concomitant change of cell proliferation.     

增材316L不锈钢的激光冲击强化研究

增材制造与激光冲击强化技术相结合,以提高增材制造打印产品的力学性能。本文以316L不锈钢粉末为实验原料,通过同轴送粉式增材制造工艺获得实验试件;利用SIA LSP 23系列激光冲击强化系统在不同激光能量下对增材316L不锈钢试件进行处理,研究了增材316L不锈钢实验试件激光冲击强化处理前后的残余应力、显微硬度和抗拉强度。经激光冲击强化处理,增材316L不锈钢近表面引入了残余压应力、并伴随着显微硬度和抗拉强度的显著提高;所引入的残余压应力、显微硬度和抗拉强度随激光能量的增加而增加,表明较高的激光能量能够获得较好的激光冲击强化效果;激光冲击强化作用后的增材316L不锈钢的截面显微硬度分布规律与残余应力分布规律类似,但显微硬化层深度要比残余压应力层深度要深0.15～0.25mm。激光冲击强化可作为一项后处理技术用来提高增材制造打印产品的力学性能。     

近红外空间碎片激光测距光束准直性标校方法

将1064nm波长激光应用于漫反射空间碎片激光测距,具有大气透过率高、回波光子数多、白天天空背景噪声低的优势。由于近红外激光束后向散射图像的信噪比与对比度较低,导致图像中光束边界模糊,光尖坐标提取困难,无法精确控制发射准直性和望远镜收发光轴平行性,不利于回波获取。为此,提出了一种基于图像处理的光束准直性标校方法,实现光束闭环控制,修正激光束出射准直性,提高望远镜收发光轴平行性。实验结果表明,所提方法能够显著改善1064nm波长激光束出射准直性,实现了望远镜收发光轴平行性的闭环控制。     

Recovery of the refractive-index profile from the wigner distribution of an optical waveguide

We propose a new method for the recovery of the refractive-index profile of a single-mode or multimode optical guided structure. We solve the inverse problem using the Wigner distribution and reduce it to the solution of a linear system of equations.     

Coherence-multiplexed acousto-optic correlator for signal processing: theory and applications

A method of multichannel processing to compute correlation products simultaneously is introduced. The signals that process are encoded on a single light beam through the use of an electro-optic modulators that induce optical delays greater than the coherence length of light. The coherence-modulated light beam thus obtained is then spatially and temporally modulated through an acousto-optic Bragg cell. The potential number of channels is estimated to be approximately 5-10. The method can be combined with other existing systems, such as time-, space-, or frequency-multiplexed correlators, to increase the channel number. The method also applies to high-resolution spectral analysis.     

Electromagnetic-field calculations for irregularly shaped, axisymmetric layered particles with focused illumination

Theoretical procedures are presented for the determination of the internal and the near-surface electromagnetic fields for an arbitrary monochromatic field (e.g., a focused laser beam) incident upon an irregulary shaped, axisymmetric layered particle. The layered spherical particle solution is also given as a special case of the general solution. Systematic calculations are presented that demonstrate the effects of particle shape and incident focused-beam orientation on the electromagnetic-field distributions.     

Determination of sulfur dioxide in wine using a quartz crystal microbalance

A new method for the analysis of both total and bound SO(2) in wine is proposed, based on a quartz crystal microbalance (QCM), and it is compared with the widely used Ripper method. The proposed method is faster than the Ripper's, and the instrumentation is either home-made or widely available. When both methods are applied to the same sample, the results obtained using the QCM method are bracketed in an interval less than one-tenth the size of that obtained using the Ripper method. Although the SO(2) concentrations found using the QCM method correlate well with the ones obtained with the Ripper method, the results are systematically higher, which can be explained as due to the absence of interferences known to affect the Ripper method.