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排序方式: 共有141条查询结果,搜索用时 93 毫秒
31.
针对我国金属矿产资源的开采利用量大、浪费严重和我国金属矿产资源评价模型研究匮乏等问题,本文首次提出金属矿产资源能级的概念——金属矿产资源为国民经济和社会发展提供商品或服务的能量大小.建立了基于金属矿产资源质量M、数量Q、重要程度I和技术条件T等4个指标的定量评价模型,对各指标进行细化、归一化并划分等级.以金属铁、铝、金、铜、钼、钨、锡为例的分析表明,其能级分别为1.748、1.015、1.65、1.353、2.419、2.953、2.025,能级模型可对我国所有的金属矿产资源进行能级测算和划分,从而针对不同能级的金属矿产资源采取不同的开采、管理措施,实现我国金属矿产资源的有效管理. 相似文献
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通过传统的陶瓷工艺在较低的温度(〈1000℃)下制备了以ZnO陶瓷为基体的ZnO陶瓷/Ag复合材料.主要考察和讨论了其电学性能及相关问题. 相似文献
34.
中国金属工艺历史悠久,影响深远,拥有非常精湛的工艺技术。在其漫长的发展历程中,产生过大量具有鲜明特色的装饰形式和作品,具有极高的历史和艺术价值。我国现代金属装饰艺术不仅要继承和学习古代金属装饰艺术中精湛的工艺技术,同时还应继承其设计理念和设计文化,发展和提高现代工业技术在金属装饰艺术中的应用水平,始终与现代科学技术和社会生活保持紧密结合。 相似文献
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《文物保护研究》2013,58(2):117-128
AbstractA system for continuous monitoring of atmospheric corrosivity has been developed. An electronic unit measures and records changes in the electrical resistance of a thin metal track applied on an insulating substrate. If the metal corrodes, the effective cross sectional area of the track decreases and the electrical resistance increases. Sensors made of silver, copper, iron/steel, zinc, lead, tin, aluminium, bronze, and brass at thicknesses from 50 nm to 250 µm were tailored for environments with different corrosivities. The developed technology proved capable of providing high sensitivity, allowing for real-time corrosion monitoring even in low-corrosive indoor cultural heritage facilities. Laboratory tests showed good reproducibility with the standard deviation of parallel measurements at less than ±20% for metals which corrode uniformly in the tested environments. Several examples selected from a broad testing programme in partner museums, libraries, and other institutions show successful applications of the logger system for characterization of air quality control in indoor locations, during transport and in temporary exhibitions; assessment of new buildings and storage facilities; and fundamental studies of optimal conservation and storage procedures. A first outline of a classification system for lead, which is particularly sensitive to the presence of carboxylic acids, is given. The technique has a large potential as an independent method for monitoring air quality in facilities displaying and storing valuable objects of cultural heritage. 相似文献
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在焊接实验实训中,采用CO2气体保护焊与焊条电弧焊两种焊接方法在同等的条件下现场施焊,进行工艺及成本分析。 相似文献
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QIN Feng CHEN Jiang-ping ZHANG Wen-feng CHEN Zhi-jiu 《浙江大学学报(A卷英文版)》2007,8(2):197-204
INTRODUCTION Metal hydrides are special alloys which absorb and desorb hydrogen reversibly. At room temperature, metal hydrides could absorb as much hydrogen as liquid hydrogen of the same volume under much lower pressure and much higher temperature (Güther and Otto, 1999). Massive reaction heat is generated accompanying this reaction, which could be used for waste heat recovery, solar energy utilization and re-frigeration with no side effect to environment (Izhvanov et al., 1996). Con… 相似文献
38.
Marine Cotte Emilie Checroun Wout De Nolf Yoko Taniguchi Laurence De Viguerie Manfred Burghammer 《文物保护研究》2017,62(1):2-23
The origin(s) and role(s) of metal soaps in paints are a worldwide concern today. These hybrid compounds, containing both fatty acid chains and metals associated with a carboxylate function, are increasingly identified in paints. As reviewed in the first part of this work, the presence of metal soaps in paints is differently interpreted in scientific publications: metal soaps are sometimes considered to play a positive role as anchor points, during paint drying processes; they can also be considered as responsible for many degradation processes (protrusions, efflorescences, darkening, etc.). Their origins are also interpreted in various ways. In some paintings (in particular from the twentieth century), they have sometimes introduced on purpose, as additives, to modify the physical properties of the painting materials. In older paintings, metal soaps are usually thought to result from an uncontrolled reaction of oil with lead-based pigments, in particular lead white, red lead, and lead tin yellow. In the second part of this work, the review of historical recipes of lead-based paint shows an important number of recipes based on controlled mixing of oil with lead driers. In the third part, the experimental reproduction of such traditional recipes using walnut oil and litharge (PbO) shows that lead soaps can be formed, both in about one hour at ~100°C, or in about one month at room temperature. It shows as well that after a few years, litharge is no longer detected in the paint medium, while different lead carbonates are. Finally, the micro-infrared spectroscopy and micro-X-ray diffraction re-analysis of protrusions from a nine-year model painting shows together with lead soaps, the presence of Pb5(CO3)3(OH)2O (‘synthetic plumbonacrite’), an unusual phase recently observed in a protrusion from a painting by Vincent Van Gogh. This work highlights (i) the multiple origins and roles of metal soaps in paints and (ii) the importance of combining the analysis of fragments from historical paintings with the analysis and reproduction of historical recipes. In particular, we show that the components detected today in historical paintings may severely differ from those originally used or prepared by the painter, complicating the assessment of the painter's intentions. More than the presence of metal soaps, the key questions to be tackled should be about their origins and (re)mobilization. 相似文献
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通过湖南花垣和苏仙两矿区野外踏查,数据检测Pb、Zn、Cu、Cd在两矿区相应植物土壤及植物中的含量及相关分析。结果表明:两矿区均受到Pb、Zn、Cd的污染。Pb元素在苏仙矿区是重污染,Zn对花垣矿区为中度污染,Cd对两矿区污染均为重污染,综合污染指数表明两矿区均为重污染。通过富集系数、转移系数、滞留率分析,发现14种优势植物表现出不同的吸收和富集特征,其中箬竹(Indocalamus tessella?tus)、油茶(Camellia oleifera)为富集型植物,菖蒲(Acorus calamus)、灯心草(Juncus effusus)、节节草(Equisetum ramosissimum)、毛萼莓(Rubus chroosepalus)、茅草(Imperata cylindrica)为根部囤积型植物,飞龙掌血(Todda?lia asiatica)为规避型植物。 相似文献
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采用人工智能技术——专家系统的构造思想方法,来构建焊接生产定额计算机辅助制订的原型研究系统。并运用VB程序语言和数据库技术,设计与开发了系统计算机辅助制订软件,实现了焊接生产中焊条电弧焊方法、埋弧焊方法的焊接工时定额与材料消耗定额的计算。经系统软件运行表明:软件运行稳定、运行结果与实际较好吻合,具有扩充性好和实用性强的特点。 相似文献