Extraction of epicuticular wax and nonacosan-10-OL fromEphedra herb utilizing supercritical carbon dioxide

Experimental results concerning the processing feasibility of using supercritical CO₂ were reported for the extraction of epicuticular wax fromEphedra herb. Subsequently the isolability of nonacosan-10-ol from the total extract of epicuticular wax was evaluated by TLC and gas chromatography. Also, Soxhlet extractions ofEphedra herb by n-hexane and chloroform were performed and these results were compared with those obtained by supercritical CO₂ extraction. As a result, we could demonstrate that supercritical CO₂ can be an economical alternative to the organic solvents in processing the medicinal plant.     

Long-term corrosion resistance of metallic reinforcements in concrete—a study of corrosion mechanisms based on archaeological artefacts

This paper presents an analytical study on ferrous reinforcements embedded in binders found in ancient buildings aged from the Gallo-Roman period to the beginning of the 20th c. AD. The study of this kind of archaeological analogues is necessary to improve knowledge on the long-term corrosion behaviour of low carbon steels that could be used in concrete to build the substructure of nuclear wastes storage or reversible disposal facilities. The corrosion system can be described as a multi-layer pattern made of metal, a dense corrosion product layer, a transformed medium and a binder. The morphological, and physico-chemical properties like composition, structure and porosities of each part were studied with different analytical methods like optical and electronical microscopies, Energy Dispersive Spectrometry coupled with Scanning Electron Microscopy, Electron Probe MicroAnalysis, Mercury porosimetry, micro-Raman spectroscopy and micro-Diffraction under Synchrotron Radiation. Moreover, average corrosion rates were evaluated. These rates are relatively low compared to the same parameters measured on low alloyed contemporary steels and are comparable with corrosion rates noted for passivated systems.     

Q235D激光熔覆实验研究

在Q235D钢表面激光熔覆Fe基合金粉末,通过对熔覆层外观形貌、表面硬度、金相组织和显微硬度的对比分析得出了双层熔覆时的最优工艺参数,当两层工艺参数相同且均为:激光功率600W、扫描速度2mm/s、搭接率24.2%、送粉电压10V时,所得熔覆层的表面较为平整均匀,通过金相组织分析发现,基体与熔覆层的冶金结合性较好,无裂纹,并且基本无气孔出现,熔覆层的显微硬度显著高于基体且从熔覆层→过渡区→基体呈梯度降低。在两熔覆层交界处,显微硬度从界面处往第一熔覆层方向先减小后增加直到最高值,从界面处往第二熔覆层方向显微硬度呈阶梯状上升逐渐增加到熔覆层硬度的最高值,尽管两熔覆层交界处显微硬度有所降低,但是仍然大大高于基体的显微硬度,对熔覆层性能基本无影响,在工业生产中有着较好的发展前景。     

Fused deposition modeling with polypropylene

This paper addresses the potential of polypropylene (PP) as a candidate for fused deposition modeling (FDM)-based 3D printing technique. The entire filament production chain is evaluated, starting with the PP pellets, filament production by extrusion and test samples printing. This strategy enables a true comparison between parts printed with parts manufactured by compression molding, using the same grade of raw material. Printed samples were mechanically characterized and the influence of filament orientation, layer thickness, infill degree and material was assessed. Regarding the latter, two grades of PP were evaluated: a glass-fiber reinforced and a neat, non-reinforced, one. The results showed the potential of the FDM to compete with conventional techniques, especially for the production of small series of parts/components; also, it was showed that this technique allows the production of parts with adequate mechanical performance and, therefore, does not need to be restricted to the production of mockups and prototypes.     

基于空间分层索引模型的数控加工碰撞检测法

文章提出了一种基于微机的用于实现数控加工碰撞检测的新方法。该方法的基本思路是：建立机床最大加工范围的分层空间索引模型；在各层内，将刀具截面收缩为刀轴上一点，同时相应放大碰撞检测另一方的截面，使两物体之间的三维碰撞问题转化成判断二维平面内一点与一封闭轮廓曲线相对位置的问题。文中举例说明了该方法在ＮＣ验证系统中的应用。     

Riccati equation in projecting solenoidal fields

Unexpected relationship between the Riccati equation of the Layer Stripping Method and the projecting solenoidal vector fields is found out. A transform which diagonalizes a family of projectors on increasing subspaces of solenoidal fields is constructed. Due to the Ricatti equation the transform turns out to be isometrical.