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用扫描电镜对鸭绿江茴鱼（Thymallus arcticus yaluensis）鳃的表面结构特征进行了详细的观察.结果表明：鳃耙、鳃弓、鳃丝及鳃小片细胞都有不同形状的隆嵴和刻纹等结构;鳃耙上有两种刺状骨质突起;鳃弓上有大小不同的空洞;鳃小片的上皮细胞表面凸凹不平;鳃丝上皮细胞隆起和刻纹较为发达,这些形态结构是与它的生理功能及生活习性密切相关的. 相似文献
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目前,在对三维激光点位误差模型进行推导的过程中,都是假设三维激光点位误差是服从正态分布的,而由于三维激光点位误差源与传统测量仪器中的误差源不同,同时外界环境对激光点位误差的影响也不相同,因此,不能直接断定点位误差服从正态分布,需要对其理论分析及数据统计分析验证。针对三维激光点位误差分布状况,本文对激光点位误差模型进行了推导,并通过大量数据统计分析验证了激光点位误差服从的分布状况。 相似文献
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《Journal of Cultural Heritage》2014,15(3):283-291
Metallographic features of ancient bronze artefacts often hide peculiar micro-chemical processes and corrosion behaviours, which are worth to be studied as they can provide conservators and archaeologists with valuable tools and information. It is widely documented that Chinese bronzes were cast and the way to adjust their properties was to change the alloy composition. In particular, addition of lead, which is insoluble in the bronze matrix, results in the formation of inclusions or globules, which undergo oxidation processes leading to their conversion into corrosion products. The mechanisms through which this occurs were still poorly investigated. The present work was conducted to further study the corrosion behaviour of high-leaded bronze, especially focusing on the behaviour of lead globules. To this aim, a collection of Chinese archaeological bronzes, showing intermediate steps of degradation, were selected and investigated. The use of combined microscopy-based, molecular and elemental, analytical techniques allowed the characterization as well as the precise location of corrosion products, thus enabling us to propose a degradation pathway basing on thermodynamic data provided by Pourbaix diagram. The achieved results will be useful for researchers involved in these kinds of studies to better interpret data obtained. 相似文献
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赵卫东 《阜阳师范学院学报(社会科学版)》2001,(3):102-103,,106,
本文通过分析阅读教学中的设问及其与图式的关系,探讨这些图式对阅读四大技能——略读、寻读、细读和批评性阅读的培养所起的作用,然后提出如何利用和完善这些图式来提高阅读理解能力。 相似文献
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Ferrospheres in fly ashes from a coal-fired power plant were extracted by a magnetic separation technique and their microstructure was studied by scanning electron microscopy （SEM）, energy dispersive X-ray analysis （EDX） and environmental scanning electron microscopy （ESEM）. Ferrospheres in fly ashes show significant iron enrichment compared to their respective fly ashes. Iron oxides in ferrospheres mainly occur as minerals magnetite （Fe3O4） and hematite （α-Fe2O3）, which are derived mainly from the decomposition and oxidation of iron-bearing minerals in coal during combustion. EDX data indicate that ferrospheres also contain Si, S, Al and Ca resulting from quartz, mullite, anhydrite and amorphous materials. A large percentage of ferrospheres are commonly 5-50 μm in size. The microstructure of ferrospheres includes smooth, polygonal, dendritic, granular and molten drop characteristics. SEM coupled with EDX provided fast and accurate results of the microstructure and chemical composition of ferrospheres, and helped us to assess environmental issues related to the disposal and utilization of fly ashes. 相似文献
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在扫描探针显微镜系统中,本文采用基于虚拟仪器的计算机控制步进电机,控制它的正转、反转及启动和停止,从而实现样品与探针的自动逼近。利用计算机通过I/O接口来直接产生各种方波信号,采用L abV IEW编程完成控制算法,以此来实现步进电机运动,提高了逼近系统的自动化性能和控制精度。 相似文献
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就大学英语当中应注重学生泛读的培养谈了一些观点。阅读也是今后有效交际的重要手段之一，本文就其作用及如何能够提高泛读的水平与阅读速度做了一些较为详尽的阐述。掌握泛读的技巧对于学生今后有效获取信息知识，与有效的进行交流有看至关重要的作用。 相似文献
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Ling ZHANG Tian TANG Zhen-liang ZHANG Bing LIANG Xiao-miao WANG Bai-ping FU 《Journal of Zhejiang University. Science. B》2013,14(11):1013-1024
Objective:This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths(μTBSs)of conventional and resin-modified glass ionomer cements(GICs/RMGICs).Methods:Forty-eight bovine incisors were prepared into rectangular blocks.Highly-polished labial enamel surfaces were either acid-etched,conditioned with liquids of cements,or not further treated(control).Subsequently,two matching pre-treated enamel surfaces were cemented together with one of four cements[two GICs:Fuji I(GC),Ketac Cem Easymix(3M ESPE);two RMGICs:Fuji Plus(GC),RelyX Luting(3M ESPE)]in preparation forμTBS tests.Pre-treated enamel surfaces and cement-enamel interfaces were analyzed by scanning electron microscopy(SEM).Results:Phosphoric acid etching significantly increased the enamelμTBS of GICs/RMGICs.Conditioning with the liquids of the cements produced significantly weaker or equivalent enamelμTBS compared to the control.Regardless of etching,RMGICs yielded stronger enamelμTBS than GICs.A visible hybrid layer was found at certain enamelcement interfaces of the etched enamels.Conclusions:Phosphoric acid etching significantly increased the enamelμTBSs of GICs/RMGICs.Phosphoric acid etching should be recommended to etch the enamel margins before the cementation of the prostheses such as inlays and onlays,using GICs/RMGICs to improve the bond strengths.RMGICs provided stronger enamel bond strength than GICs and conditioning did not increase enamel bond strength. 相似文献