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排序方式: 共有238条查询结果,搜索用时 46 毫秒
1.
Sveva Longo Enricomaria Mormina Francesca Granata Domenico Mallamace Marcello Longo Silvia Capuani 《文物保护研究》2018,63(7):383-390
A modern approach to the diagnosis of artistic heritage makes use of non-destructive techniques which avoid damage to artworks or signs of interaction with the analytical technique used. For this reason, today, the employment of X-rays to study artistic heritage is quite widespread. Computed tomography (CT) Imaging was first used as specialized medical diagnostic tool in the early 1970s. Today, CT scanners have become more common, and non-destructive three-dimensional imaging has found an increasing number of uses in different areas such as materials research, geology, archaeology, and museum conservation. In this work, a new generation of clinical CT (based on the Dual Energy and multi-slice acquisition principle) is used to investigate an Egyptian wooden mummy board with a total acquisition time of 93.23 seconds and a voxel size of 0.078?×?0.078?×?1.5?mm. The use of two distinct techniques of image post-processing, the two-dimensional multi-planar reconstruction (MPR) and the three-dimensional volume rendering technique (VRT) allowed us to: evaluate the state of conservation of the mummy board, determine how the wooden object was implemented, recognize a nineteenth-century intervention of consolidation, and advance the hypothesis that the wooden planks were reused. In particular, we highlight the use of the cardiovascular and pulmonary filter with VRT reconstruction, which allows a virtual elimination of different parts of the mummy board to investigate those areas otherwise accessible only by removing parts of the board and thus damaging the work. 相似文献
2.
Kristina L. Kendall David H. Fukuda Parker N. Hyde Abbie E. Smith-Ryan Jordon R. Moon Jeffrey R. Stout 《Journal of sports sciences》2017,35(7):624-633
The purpose of this study was to investigate the accuracy of fat-free mass (FFM) estimates from two-compartment (2C) models including air displacement plethysmography (ADP), ultrasound (US), near-infrared interactance (NIR), and the Jackson and Pollock skinfold equation (SKF) against a criterion four-compartment (4C) model in elite male rowers. METHODS: Twenty-three elite-level male rowers (mean± SD; age 24.6 ± 2.2 years; stature: 191.4 ± 7.2 cm; mass: 87.2 ± 11.2 kg) participated in this investigation. All body composition assessments were performed on the same day in random order, except for hydrostatic weighing (HW), which was measured last. FFM was evaluated using a 4C model, which included total body water from bioimpedance spectroscopy, body volume from HW, and total body bone mineral via dual-energy X-ray absorptiometry. The major findings of the study were that the 2C models evaluated overestimated FFM and should be considered with caution for the assessment of FFM in elite male rowers. Future studies should use multiple-compartment models, with measurement of TBW and bone mineral content, for the estimation of FFM. 相似文献
3.
Dorota M. Jankowska Aleksandra Gajda Maciej Karwowski 《International Journal of Science Education》2019,41(8):1096-1117
This article explores how creative visual imagination and creative thinking can help children to construct mental models of space. A mixed-method study, integrating quantitative and qualitative approaches and involving 98 five-year-old children (54 girls and 44 boys) demonstrated that creative visual imagination, rather than creative thinking, is linked with the knowledge and understanding of space. These results support the notion that creative visual imagination contributes to improvements in children's understanding of basic astronomical concepts. Interestingly, creative thinking was not associated with understanding and knowledge of cosmic phenomena in models taking into account creative imagination. The qualitative analysis showed differences in children's representations of space. We discuss the consequences of these findings for science education, particularly the teaching of elementary astronomy. 相似文献
4.
王仁宇 《南阳师范学院学报》2002,1(5):6-9
张衡是中国古代博学的天学家,托勒密是西方古代学的集大成,他们的天学理论受中西古代哲学思想的影响很深,比较他们哲学思想的异同对于中西化的比较与交流都是十分有意义的事。具体来讲,张衡的天学思想的哲学基础是中国古代的天人合一理论、气一元论和阴阳五行论以及群体本位主义;而托勒密的天学思想的哲学基础是毕达哥拉斯的天体运动正圆说、柏拉图的世界二分法和源于古希腊的人类中心论和个体本位主义。张衡与托勒密天学思想的差异深深地植根于中西早期化的差异之中。 相似文献
5.
Conversion efficiency of soft X-ray from 0.35 μm pulse laser-irradiated aluminium planar target at laser intensities 1013–1015 W/cm2 on the Xingguang-II facility (laser energy 5–90 J, focal spot ⊃ Ф 200 μm full width of half maximun (FWHM) 400–800 ps) was measured. A simple model was given to explain soft X-ray conversion
efficiency. In this model, because of the heat conduction from the laser-heated spot, the conversion was very small at lower
irradiance limit, while at higher limit it was bounded by the energy lost in blow off plasma. Consequently, at the laser intensity
around 2×1014 W/cm2, the X-ray conversion efficiency reaches a maximum.
Project suppoted by Shanghai Leading Academic Discipline Foundation (Grant No. T0104), and Science Foundation of Shanghai
Municipal Commission of Education (Grant No. 214680) 相似文献
6.
介绍了一种柴油机电控喷油器喷射开启控制系统。为实现柴油机电控喷油器的开启、持续喷油、关闭功能,应用STC12系列单片机构成电控喷油器的控制系统。开启时为使喷油器开启迅速,应用单周期控制技术的IR1150S芯片,产生高压为112 V的高压电源为喷油器供电。试验结果表明,开发的柴油机电控喷油器控制系统符合X光相衬成像技术研究柴油机喷雾雾化机理的要求,喷油开启迅速、喷油持续稳定、关闭干脆。本系统根据设定可实现电控喷油器的单次及多次连续开启,进一步可以推广应用于柴油机喷油器相关环节教学实验中。 相似文献
7.
David Hradil Tom Grygar Janka Hradilov Petr Bezdi
ka Veronika Grnwaldov Igor Foga Costanza Miliani 《Journal of Cultural Heritage》2007,8(4):377-386
The work is focused on identification of lead tin yellow types I and II, Naples yellow, and also on discrimination of a less common, distinct yellow pigment, the ternary Pb-Sb-Sn oxide.The knowledge about all those Pb-based yellows was in fact forgotten after introduction of modern synthetic yellows in 19th century. As late as in the last decade of the 20th century, the existence of Pb-Sb-Sn yellow and its production have been rediscovered, and only then it has been identified in colour layer of artworks.Pb-Sb-Sn yellow has recently been identified in colour layer of 17th century Italian paintings by Sandalinas and Ruiz-Moreno [C. Sandalinas, S. Ruiz-Moreno, Lead tin-antimony yellow, historical manufacture, molecular characterization and identification in seventeenth-century Italian paintings, Stud. Conserv. 49 (2003) 41–52], and here we report the finding of this pigment in Mid-European painting of the 18th and 19th centuries. Lead tin yellows, lead antimony yellow (Naples yellow), and lead antimony tin yellow were synthesized in laboratory following historical recipes, their colour was analyzed, and their structure was confirmed to provide a basis for their routine identification in microsamples of artworks by X-ray microdiffraction. Unequivocal identification of Pb-based yellows could help in authentication of traditional European paintings, because their use was temporally and also geographically specific. Combination of elemental microanalysis (X-ray fluorescence electron microanalysis) and X-ray powder microdiffraction were found very efficient in the microanalysis of colour layers of artworks with Pb-based yellows and their unequivocal identification. 相似文献
8.
9.
自20世纪20年代至今,中国学者对中外天文交流史的研究经历了四次明显变化。本文综合中外天文交流史的已有研究,及前人对该领域研究方法的论述,对三次重大变化加以归纳,并在统计分析近几年几种重要期刊相关研究的基础上,简述对近年出现新趋势的看法。 相似文献
10.
《Journal of Cultural Heritage》2014,15(3):266-274
Most of the historical paints are mainly constituted by inorganic pigments, either pure or mixed, spread on the surfaces using different binding agents. The knowledge of the exact amount of different constituents of the paint, as well as of the mixing and pictorial techniques, is crucial for a careful program of conservation of polychrome works. Moreover, since the availability of these pigments has been changing through the centuries, their identification and chemical characterisation is useful to acquire or deepen information about the artist and his/her work. This information can also be useful for authentication purposes through relative dating because the identification of one pigment respect to another one can be used as a terminus post quem or ante quem the artwork was realized. In this work, X-ray fluorescence data from historical pigments, both pure and mixed, will be presented, in order to obtain quantitative information on the samples and to extract calibration curves to the aim of evaluating the pigment concentration in unknown mixtures. 相似文献