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排序方式: 共有85条查询结果,搜索用时 15 毫秒
1.
浑仪、简仪(以下简称两仪)在高PH、大气污染和日晒雨淋环境中的腐蚀是一种动态加速腐蚀过程。采用合成的双唑胺铜缓蚀剂和有机硅改性的甲基丙烯酸树脂,并分别复配成协同缓蚀剂群和含有增效稳定剂的封护剂。采用这两种材料和脱水后再防护的工艺,使带锈防护后的浑仪、简仪的腐蚀低于无污染大气中的速率。用电化学方法评价了防护技术的可行性,根据腐蚀与人工老化试验结果讨论了防护材料性能与腐蚀环境和带锈防护的关系,采用XPS分析方法探索了双唑胺比BTA更适用于两仪防护的原因。  相似文献   
2.
In this paper, we argue that place mapping is useful for approaching children's conception of place and that this is of relevance when designing physical activity interventions. We contend that socio-material factors influence children's perception and use of places, and are crucial to understand in relation to their use of local neighbourhoods for physical activity. A place mapping of children's understandings and everyday use of their local neighbourhood in suburban Copenhagen was conducted with a fifth grade elementary school class. The mapping and subsequent analysis resulted in three categories of relevance to children's conceptions of place; located social experiences, experiences of the unknown, and children's contested spaces. We argue that such knowledge can provide useful information in the development and evaluation of activities that promote physical activity in urban spaces.  相似文献   
3.
为了研究刚出土的青铜器在新的环境中的发展变化情况,在宝鸡眉县27件国宝级西周窖藏青铜器出土一年半后,对这批器物出土前后的锈蚀类型及特征进行了分析和描述,并对每一器物的锈蚀产物进行了系统检测分析。结果显示,这批青铜器腐蚀类型主要为封闭环境中的大气腐蚀,主要产物为碳酸盐和氧化物。但同时在其中一个器物上发现了氯化物类有害锈成分,分析认为,出土前后环境的变化是有害锈得以产生和发展的根本原因。  相似文献   
4.
Major corrosion has been found at depth in carbonate hydrocarbon reservoirs from different geologic provinces. Fluid inclusion microthermometry and stable isotopic compositions of carbonate cements, predating major corrosion, constrain the interpretation of the evolution of parental fluids during progressive burial and prior to the major corrosion event. Post‐major corrosion mineral paragenesis includes pyrite (‐marcasite), anhydrite, kaolinite (dickite) and fluorite. Although the post‐corrosion mineral paragenesis represents minor volumes of rock, it may provide valuable insights into the post‐corrosion brine chemistry. Using reactive transport numerical models, the roles of cooling and/or mixing of brines on corrosion have been evaluated as controls for dolomitization, deep burial corrosion and precipitation of the post‐corrosion mineral paragenesis. Modelling results show that cooling of deep‐seated fluids moving upward along a fracture may cause minor calcite dissolution and porosity generation. Significant dolomitization along a fracture zone and nearby host‐rock only occurs when deep‐seated fluids have high salinities (4 mol Cl kg?1 of solution) and Darcian flow rates are relatively high (1 m3 m?2 year?1). Only minor volumes of quartz and fluorite precipitate in the newly formed porosity. Moreover, modelling results cannot reproduce the authigenic precipitation of kaolinite (dickite at high temperatures) by cooling. As an alternative to cooling as a cause of corrosion, mixing between two brines of different compositions and salinities is represented by two main cases. One case consists of the flow up along a fracture of deep‐seated fluids with higher salinities than the fluid in the wall rock. Dolomite does not precipitate at a fracture zone. Nevertheless, minor volumes of dolomite are formed away from the fracture. The post‐corrosion mineral paragenesis can be partly reproduced, and the results are comparable to those obtained from cooling calculations. Minor volumes of quartz and fluorite are formed, and kaolinite‐dickite does not precipitate. The major outputs of this scenario are calcite dissolution and slight net increase in porosity. A second case corresponds to the mixing of low salinity deep‐seated fluids, flowing up along fractures, with high salinity brines within the wall rock. Calculations predict major dissolution of calcite and precipitation of dolomite. The post‐corrosion mineral paragenesis can be reproduced. High volumes of quartz, fluorite and kaolinite‐dickite precipitate and may even completely occlude newly formed porosity.  相似文献   
5.
Active learning is increasingly promoted within institutions of higher education to assist students develop higher order thinking and link knowledge to meaning. In this paper, the authors evaluate the use of weekly online quizzes based on prescribed preparatory material as a tool to incentivize preparatory reading in order to enable and encourage active learning. The study is based on mixed data sources, including three years of student-evaluation data, to understand student perceptions of the role and value of online quizzes. The study shows a high level of student engagement with the quizzes and positive assessment of their role in encouraging the completion of prescribed reading. Online quizzes were found to be an effective mechanism for incentivizing student completion of preparatory work, enhancing active learning (such as through in-class discussions), and were relatively time efficient from the perspective of the educator.  相似文献   
6.
The most recent national Census demonstrated that Australian Muslims continue to occupy a socioeconomically disadvantaged position. On key indicators of unemployment rate, income, type of occupation and home ownership, Muslims consistently under-perform the national average. This pattern is evident in the last three Census data (2001, 2006 and 2011). Limited access to resources and a sense of marginalisation challenge full engagement with society and the natural growth of emotional affiliation with Australia. Muslim active citizenship is hampered by socioeconomic barriers. At the same time, an increasingly proactive class of educated Muslim elite has emerged to claim a voice for Muslims in Australia and promote citizenship rights and responsibilities.

最近的全国普查显示,澳大利亚的穆斯林仍处于社会经济的弱势地位。在诸如失业率、收入、就业类型、家居拥有等关键指标看,穆斯林一直位于国家平均水平之下。这一模式在最近三次普查(2001、2006、2011)中非常明显。获得资源渠道的有限以及边缘化感觉阻碍着他们充分参与社会,以及在情感上融入澳大利亚。穆斯林的公民意识受困于社会经济障碍。与此同时,也出现了一班受到良好教育的穆斯林精英,这个积极进取的阶层开始为澳大利亚的穆斯林代言,促进他们的公民权利和义务。  相似文献   

7.
Current research on USS Arizona is focused on a minimum-impact technique for calculating corrosion rate of the battleship's steel hull by analysing physical and chemical properties of marine encrustation covering the exposed hull. An equation is derived that allows concretion thickness, density, and total iron content to be used to calculate corrosion rate of steel hull plate.
© 2006 The Authors  相似文献   
8.
To thermally upgrade exterior masonry walls, interior insulation is often the only possible retrofitting technique, especially when dealing with historic buildings. Unfortunately, it is also the riskiest post-insulation technique, as frost damage, interstitial condensation, and other damage patterns might be induced. To diminish those risks, nowadays so-called capillary active interior insulation systems are often promoted. These systems aim a minimal reduction of the inward drying potential, while interstitial condensation is buffered.

Currently, several capillary active systems are on sale. These different types have, however, widely varying properties. In this article, a closer look at the hygrothermal properties and the working principle of a number of “capillary active” interior insulation systems is made. The spread in capillary absorption coefficients and the vapor diffusion resistances of the different systems is discussed and their influence is illustrated. Based on all this, a more nuanced view on capillary active insulation systems is pursued.

Abbreviations: AC: aerated concrete; CaSi: calcium silicate; GM: glue mortar; GB: gypsum board; HAMFEM: Heat Air and Moisture Finite Element Method; MW: mineral wool; PE: polyethylene; PIR: polyisocyanurate; PUR: polyurethane; VIP: vacuum insulation panel; WFB: wood fiber board; XPS: extruded polystyrene; sddry: dry vapor diffusion resistance factor; µdry: dry vapor diffusion resistance  相似文献   

9.
青铜文物缓蚀剂效率及封护剂抗腐蚀能力的比较研究   总被引:1,自引:0,他引:1  
为评价青铜文物缓蚀剂效率及封护剂抗腐蚀能力进行了两项电化学实验。一是利用直流腐蚀的极化电阻法对缓蚀效率评价,二是应用恒电位交流阻抗法对涂层的抗腐蚀效率评价。实验表明,复合缓蚀剂的缓蚀效率优于单一缓蚀剂如AMT、BTA,在模拟中性土壤介质的水溶液中各自缓蚀效率分别为88.7%、94.6%,两者组成复合缓蚀剂后其缓蚀效率高达98.8%,这是发挥其缓蚀剂各组分的协同效应的结果。应用恒电位交流阻抗实验,可以更好地理解附着有封护层时复杂的腐蚀过程。结果表明,石蜡涂层样品的Nyquist谱图出现扩散过程引起的阻抗特征;聚乙烯醇缩丁醛涂层、Paraloid B72涂层、空白样(缓蚀层BTA)三种样品Nyquist谱图均是由于涂层微孔引起的阻抗特征,在同一浓度下其抗腐蚀性能排序呈依次递减趋势。  相似文献   
10.
关于校园暴力的成因分析及应对措施   总被引:1,自引:0,他引:1  
严琦华 《攀登》2005,24(4):117-118
校园暴力是一种无政府的破坏校园安定和学生学习环境的行径。对此如不进行积极的预防和有效的遏制,就会破坏学校的学习秩序,严重危害学生的学习、生活和身心健康,给社会的安定团结带来不利影响。为此,全枉会都应十分关注校园暴力问题。本文正是针对校园暴力问题,从社会学、教育学、伦理学、心理学等方面对其产生的成因作出分析并提出了相应的对策。  相似文献   
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