伽马刀准直体三维立体定向孔的加工方法

伽马刀准直体上三维立体定向孔的聚焦精度是影响治疗效果的关键因素,也是加工的难点。介绍了伽马刀准直体三维立体定向孔的加工方法,设计了工装,并研究了关键精度控制的问题。     

Effects of Sr2+ substitution on the crystal structure,Raman spectra,bond valence and microwave dielectric properties of Ba3-xSrx(VO4)2 solid solutions

The effects of Sr²⁺ substitution for Ba²⁺ on microwave dielectric properties and crystal structure of Ba_3-xSr_x(VO₄)₂ (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr²⁺ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (∑_r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τ_f value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with ∑_r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τ_f = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B₂O₃ as sintering additive for the representative Sr₃V₂O₈ (SVO) ceramic and only 1 wt.% B₂O₃ addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication.     

Turning a Digital Camera into an Absolute 2D Tele‐Colorimeter

We present a simple and effective technique for absolute colorimetric camera characterization, invariant to changes in exposure/aperture and scene irradiance, suitable in a wide range of applications including image‐based reflectance measurements, spectral pre‐filtering and spectral upsampling for rendering, to improve colour accuracy in high dynamic range imaging. Our method requires a limited number of acquisitions, an off‐the‐shelf target and a commonly available projector, used as a controllable light source, other than the reflected radiance to be known. The characterized camera can be effectively used as a 2D tele‐colorimeter, providing the user with an accurate estimate of the distribution of luminance and chromaticity in a scene, without requiring explicit knowledge of the incident lighting power spectra. We validate the approach by comparing our estimated absolute tristimulus values (XYZ data in ) with the measurements of a professional 2D tele‐colorimeter, for a set of scenes with complex geometry, spatially varying reflectance and light sources with very different spectral power distribution.     

Automatic Image Checkpoint Selection for Guider‐Follower Pedestrian Navigation

In recent years guider‐follower approaches show a promising solution to the challenging problem of last‐mile or indoor pedestrian navigation without micro‐maps or indoor floor plans for path planning. However, the success of such guider‐follower approaches is highly dependent on a set of manually and carefully chosen image or video checkpoints. This selection process is tedious and error‐prone. To address this issue, we first conduct a pilot study to understand how users as guiders select critical checkpoints from a video recorded while walking along a route, leading to a set of criteria for automatic checkpoint selection. By using these criteria, including visibility, stairs and clearness, we then implement this automation process. The key behind our technique is a lightweight, effective algorithm using left‐hand‐side and right‐hand‐side objects for path occlusion detection, which benefits both automatic checkpoint selection and occlusion‐aware path annotation on selected image checkpoints. Our experimental results show that our automatic checkpoint selection method works well in different navigation scenarios. The quality of automatically selected checkpoints is comparable to that of manually selected ones and higher than that of checkpoints by alternative automatic methods.     

Evaluation of direct light processing for the fabrication of bioactive ceramic scaffolds: Effect of pore/strut size on manufacturability and mechanical performance

Bioactive ceramic scaffolds for bone regeneration consisting of a three-dimensional mesh of interpenetrating struts with square section were fabricated via Digital Light Processing (DLP). The ability of the technique to manufacture 3D porous structures from β-tricalcium phosphate (β-TCP) powders with different dimensions of struts and pores was evaluated, identifying the possibilities and limitations of the manufacturing process. Small pore sizes were found to seriously complicate the elimination of excess slurry from the scaffold’s innermost pores. The effect of the strut/pore size on the mechanical performance of the scaffolds under compressive stresses was also evaluated, but no significant influence was found. Under compressive stresses, the structures resulted weaker when tested perpendicularly to the printing plane due to interlayer shear failure. Interlayer superficial grooves are proposed as potential failure-controlling defects, which could also explain the lack of a Weibull size effect on the mechanical strength of the fabricated DLP scaffolds.     

扫描地图的计算机自动识别

扫描地图的计算机自动识别是当今地图制图学科的前沿课题，也是其重要的研究方向。为此，本文首先将模式识别技术引入到地图制图领域中，提出了四种地图符号的计算机描述方法，然后又讨论了扫描地图的信息获取与处理，并具体地分析了扫描地图的计算机识别方法及其识别系统．最后还给出了相应的符号识别实验。     

非金属矿深加工技术及其应用

介绍了目前国内外常采用的非金属矿深加工技术：提纯、超细粉碎、改型和改性、制备新型纳米材料．以及深加工技术在重质碳酸钙、滑石粉和膨润土应用中的具体加工工艺。     

混合型加工工业园区——城市化模式的新选择

东莞是我国在改革开放以后自下而上的城市化中比较典型的城市。由于占市域人口主要部分的外来务工人员无法融入城市化的进程,造成外来人口工业化、本地人口城市化两种形式的不统一,形成新的“二元城市”结构。混合型加工工业园区的规划建设,是解决外来人口城市化的一种有效途径。     

无机刚性粒子增韧PVC／CPE合金体系的加工流变性能（二）

研究了无机刚性粒子（超细CaCO3，轻质CaCO3）对PVC／CPE体系加工流变性能的影响，分别探讨了CPE用量、超细CaCO3粒子用量和粒径大小对PVC／CPE共混体的影响。实验表明：超细CaCO3增韧PVC／CPE体系，能有效地改善体系的塑化行为，缩短塑化时间；在保证最佳的综合力学性能的同时，超细CaCO3的加入对加工流变性能影响不大；并且，随其粒径的减小，体系的塑化时间明显减小。     

基于PLC的后膛弹处废自动生产线

基于PLC的后膛弹处废自动生产线,由控制系统和机械设备组成.其工序流程分上弹、卸引信防潮塞、卸底火、拔弹、吹倒药和切割倒药等步骤.PLC控制机械设备的具体动作.上位计算机为监控核心,负责设备动作命令的发送和接收当前PLC状态反馈.传感器采集动作到位信息,文本显示器用于调试时的控制.软件采用自动和手动2种模式对生产线进行操作.