激光划切机中工件对准的图像定位方法

针对激光划切机中对LTCC工件定位对准的高精度性要求,对于如何根据工件边角信息进行定位,提出了一种基于对比度增强、Canny双阂值边缘提取和Hough变换的定位方法。将这种图像检测方法应用于激光划切机,工件定位精度小于2μm,满足系统的要求。     

利用变形反射镜和激光导星扩大校正视场

为了扩大自适应光学(AO)系统的校正视场,在主要湍流层的共轭面上设置两个变形反射镜(DM),即采用分层共轭自适应光学(MCAO)的方法.主湍流层的共轭面位置设置两个变形反射镜和激光导星可以将湍流层上不同高度位置产生的波前畸变进行分离,并使焦距非等晕性几乎完全消除.在自适应光学系统中,角度的非等晕性产生的波前误差主要取决于校正的模式数、大气介质折射率结构常数(C2n)的分布和系统的几何尺寸.结果表明:对于孔径为3.5 m的望远镜,利用两个变形反射镜能够达到3弧分的校正视场.     

Air-fuel mixing and combustion in a small-bore direct injection optically accessible diesel engine using a retarded single injection strategy

In this paper, the air-fuel mixing and combustion in a small-bore direct injection optical diesel engine were studied for a retarded single injection strategy. The effects of injection pressure and timing were analyzed based on in-cylinder heat release analysis, liquid fuel and vapor fuel imaging by Laser induced exciplex fluorescence technique, and combustion process visualization. NOx emissions were measured in the exhaust pipe. Results show that increasing injection pressure benefits soot reduction while increases NOx emissions. Retarding injection timing leads to simultaneous reduction of soot and NOx emissions with premixed homogeneous charge compression ignition (HCCI) like combustion modes. The vapor distribution in the cylinder is relatively homogeneous, which confirms the observation of premixed combustion in the current studies. The postulated path of these combustion modes were analyzed and discussed on the equivalence ratio-temperature map.     

Kinetics of the thermal dissociation of ZnO exposed to concentrated solar irradiation using a solar‐driven thermogravimeter in the 1800–2100 K range

The two‐step H₂O‐splitting thermochemical cycle based on the Zn/ZnO redox reactions is considered for solar H₂ production, comprising the endothermal dissociation of ZnO followed by the exothermal hydrolysis of Zn. A solar‐driven thermogravimeter, in which a packed‐bed of ZnO particles is directly exposed to concentrated solar radiation at a peak solar concentration ratio of 2400 suns while its weight loss is continuously monitored, was applied to measure the thermal dissociation rate in a set‐up closely approximating the heat and mass transfer characteristics of solar reactors. Isothermal thermogravimetric runs were performed in the range 1834–2109 K and fitted to a zero‐order Arrhenius rate law with apparent activation energy 361 ± 53 kJ mol^?1 K^?1 and frequency factor 14.03 × 10⁶ ± 2.73 × 10⁶ kg m^?2 s^?1. Application of L‘vov’s kinetic expression for solid decomposition along with a convective mass transport correlation yielded kinetic parameters in close agreement with those derived from experimental data. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

An investigation of particle behavior in gas–solid horizontal pipe flow by an extended LDA technique

An extended Laser Doppler Anemometry (LDA) technique has been developed to measure the distributions of particle velocities and particle number rates over a whole pipe cross-section in a dilute pneumatic conveying system. The first extension concentrates on the transform matrix for predicting the laser beams’ cross point in a pipe according to the shift coordinate of the 3D computer-controlled traverse system on which the probes of the LDA system were mounted. The second focuses on the proper LDA sample rate for the measurement of gas–solid pipe flow with polydisperse particles. A suitable LDA sample rate should ensure that enough data is recorded in the measurement interval to precisely calculate the particle mean velocity or other statistical values at every sample point. The present study explores the methodology as well as the fundamentals of measurements, using a laser facility, of the cross-sectional distributions of solid phase. In the horizontal gas–solid pipe flow (glass beads less than 110 μm), the experimental data show that the cross-sectional flow patterns of the solid phase can be classified by annulus-like flow describing the axial particle velocity contours and stratified flow characterising particle number rate distribution over a cross-section. Thus, the cross-sectional flow pattern of the solid phase in a horizontal pipe may be annular or stratified dependent on whether the axial particle velocity or particle number rate is the phenomenon studied.     

电梯井道空间尺寸的智能化检测

分析了轿底至缓冲器的顶面距离用激光测距仪进行测量的可行性。并把激光测距仪和PDA相结合,测得了大量的实验数据。实验证明,该方法实现了电梯距离测量的自动化、数字化和精确化。     

3Cr2W8V模具钢表面激光相变淬火的显微组织及耐磨性能研究

采用高功率CO2激光束对3Cr2W8V模具钢表面进行相变淬火,研究了相变强化层的显微组织与耐磨性能。结果表明：激光表面强化处理后的显微组织由品粒细小的码氏体和残余奥氏体组成,显微硬度比处理前提高了1．5倍,耐磨性能提高了1倍,同时变形小,可用于模具的表面处理。     

Preparation of Ultrafine Fe–Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis

We prepared ultrafine Fe–Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe–Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5–3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe–Pt nanoparticles and UV–visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe–Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed.     

一种用于激光标识的塑料添加剂的研发和应用

从产品标识的角度,介绍了在塑料产品表面进行激光标识技术的原理,探讨了应用激光打印产品标识的优点,得出塑料添加剂技术在产品永久性标识的发展前景,成功地将塑料添加剂添加于企业产品生产中.     

High-resolution lidar-based landslide hazard mapping and modeling,UCSF Parnassus Campus,San Francisco,USA

Airborne lidar (light detection and ranging) was used to create a high-resolution digital elevation model (DEM) and produce landslide hazard maps of the University of California, San Francisco Parnassus Campus. The lidar DEM consisted of nearly 2.8 million interpolated elevation values covering approximately100 ha and posted on an 0.6 m horizontal grid, from which a set of 16 maps was produced. The first subset of maps showed aspects of the topography useful for landslide mapping, an engineering geological map and a qualitative slope hazard map. The second subset consisted of physics-based probabilistic landslide hazard maps for wet static, wet seismic, and dry seismic conditions. This case history illustrates the utility of lidar-based products, supplemented by field-based geological observations and physics-based probabilistic slope stability modeling, for the evaluation of existing and potential slope stability hazards on a steep and heavily forested site.