Investigation on milling force of thin-walled workpiece considering dynamic characteristics of workpiece

Journal of Mechanical Science and Technology - The idea of integral calculus is used in traditional milling force prediction methods. In the traditional method, the milling cutter is divided into...     

A quarter century of wine pigment discovery

The red grape berry pigments, anthocyanins, were characterized in the early 20th century, but investigations of wine pigments were stymied during that era. The question of their identity was a major challenge for wine chemists. A number of techniques showed that the pigments were polymeric in nature. Some structures were postulated by mid-century based on reactions between anthocyanins and condensed tannin, and later postulated wine pigments were observed in model reactions. Some related compounds were then observed in wine. By the end of the 20th century, the ionization of non-volatiles for mass spectrometry opened the door to these compounds. In addition, a new class of compounds was observed, the pyranoanthocyanins, a product of fermentation and aging metabolites with anthocyanins. These compounds possess the pigment stability to SO₂ and pH change that is characteristic of aged red wine. Aging experiments show a dynamic situation with shifts in the population of pigment classes over time. The very large number of diverse pigments explains why it has been so difficult to answer the century-old question of the structure of wine pigments. Our current understanding is founded on the use of mass spectral analysis using electrospray and related ionization techniques over the last 25 years. Future progress will rely on more sophisticated analysis of this very complex mixture of substances. © 2019 Society of Chemical Industry     

Comparative studies on thermal and toughness properties of polybenzoxazine composites with two functionalized graphene oxides

Abstract

Graphene oxide (GO) was functionalized by polyether amine (PEA) via two methods which were one-pot modification in acetone (GON) and two steps with the intermediate product of GOCO-Cl generated (GONS). There were more PEA successfully grafted onto GO for GONS than GON. The onset polymerization temperatures of the benzoxazine (Bz) composites decreased by the inclusion of 1?wt% of GO, GON or GONS. Thermal stability of the polybenzoxazine (PBz) composites was significantly improved indicated from the increase of weight loss temperature. T₁₀, T₂₀ and T₅₀ values of the composites with GONS were higher than that of the others. Toughness of PBzs may be enhanced by the incorporation of nanofillers, and GONS had stronger interfacial interaction with PBz matrix than GON.     

Growth Defects in Langasite Crystals Observed with White Beam Synchrotron Radiation Topography

Langasite single crystal was grown by the Czochralski method and its perfection was assessed by white beam synchrotron radiation topography. It is found that the growth core and the growth striations are the primary growth defects and they show strong X-ray kinematical contrast in the topographs. Another typical defect in LGS crystal is dislocation. The formation mechanisms of these growth defects in LGS crystals were discussed.     

人工颅骨用复合材料中微量甲基丙烯酸甲酯的气相色谱法测定

采用氢气焰离子化检测器(FID),以正丁醇为外标物,PEG-20M为固定相,甲醇作为溶剂,气相色谱法测定复合材料人工颅骨中微量MMA的含量。其相对标准偏差<0.022,平均回收率(n=4)为98.0％～99.1％。此方法操作简便,用于实际样品分析可得到满意的结果。     

Zk线性码的对称形式的MacWilliams恒等式

该文定义了Zk线性码的码字的对称重量计数公式，利用离散的Hadamard变换，建立了线性码与其对偶码之间的对称形式的MacWilliams恒等式．     

CO2激光治疗皮肤基底细胞癌14例临床观察

目的 :探求一种简单 ,安全 ,效果好的基底细胞癌的治疗方法。方法 :对 1 4例基底细胞癌患者在局麻下用CO2 激光行基底细胞癌切除术或切除 +气化术。结果 :患者术中、术后出血少 ,伤口恢复快 ,愈合良好 ,疤痕表浅 ,随访未见复发。结论 :CO2 激光用于治疗基底细胞癌效果良好 ,无明显副作用 ,操作简单值得推广。