聚醋酸乙烯酯乳液的表征、性能及其在彩绘类文物保护中的应用

聚醋酸乙烯酯(PVAc)乳液是常见的彩绘类文物保护材料。采用激光粒度仪、热重/差热分析、红外光谱、X-射线衍射、扫描电镜、透射电镜等表征了PVAc乳液的粒径以及胶膜的热稳定性、结构和形貌;采用粘度计、表面张力仪、pH计、电导率仪等研究了乳液浓度与其粘度、表面张力、pH、电导率的关系;通过冻融、室温-高温放置、离心分离研究了乳液的稳定性;同时用PVAc乳液对模拟起甲和酥碱的壁画进行了修复。结果表明,PVAc乳液粒径呈双峰分布,小粒子的平均粒径为380 nm,大粒子的平均粒径为5.85μm;乳液胶膜为非结晶物质,胶膜热重的最终质量残留为1.54%,335℃出现放热峰。PVAc乳液的电导率随浓度的增大而增大,pH随浓度的增大而下降;相同温度下表面张力随浓度的增大而基本呈现低浓度下降,高浓度上升的趋势。相同浓度下,表面张力随温度升高而无显著变化,表明PVAc乳液的表面张力受温度变化影响不大。相同温度下,乳液粘度随浓度的增大而增大;相同浓度下,乳液的粘度随温度的升高而降低。冻融、离心分离和不同温度下静置发现,该乳液出现分层。用该乳液对模拟起甲和酥碱壁画修复后,再分别老化20个循环和12个循环,发现颜料层再次空鼓、起甲。综合分析,说明实验中所使用的该种PVAc稳定性和抗老化能力较弱,在修复彩绘类文物中应慎重选择PVAc的种类,综合考虑PVAc的使用浓度、环境因素对其性能的影响,以达到最佳使用效果。     

中国钱币的内涵

中国钱币的内涵是什么？它所包涵的内容涉及的范围该作如何界定,对于钱币学来说是一个基本概念,似乎不难解释,但事实上,我们的钱币爱好者、收藏者未必都清楚,即使是专业人员、专门的研究人员说法也未必一致,而作为一门学科——中国的钱币学,必须对它有一个完整的诠释。     

云神:"夸父"神话叙事本源

一、《山海经》:"夸父"神话叙事源头 说到"夸父",我们立即想到"夸父逐日"神话."夸父逐日"神话见于《山海经·海外北经》、《山海经·大荒北经》与《列子·汤问》、《博物志·史补》.     

Estimating the number of components in an OSL decay curve using the Bayesian Information Criterion

The optically stimulated luminescence (OSL) decay curve is assumed to consist of a number of first-order exponential components. Improper estimation of the number of components leads to under-or over-fitting of the curve under consideration. Hence, correct estimation of the number of components is important to accurately analyze an OSL decay curve. In this study, we investigated the possibility of using the Bayesian Information Criterion to estimate the optimal number of components in an OSL decay curve. We tested the reliability of this method using several hundred measured decay curves and three simulation scenarios. Our results demonstrate that the quality of the identification can be influenced by several factors: the measurement time and the number of channels; the variability of the decay constants; and the signal-to-noise ratios of a decaying component. The results also suggest that the Bayesian Information Criterion has great potential to estimate the number of components in an OSL decay curve with a moderate to high signal-to-noise ratio.     

商业文化与民族饮食文化——以土家烧饼为例

一、土家烧饼风靡全国2005年,一种名叫“土家烧饼”的风味小吃风靡全国,似乎一夜之间遍及各地的大街小巷。“土家烧饼”来自湖北土家族的聚集地恩施,土家人结合自己的饮食习惯,做成别具风味的表面撒有馅料的圆形烤饼。自2005年5月第一家土家烧饼店在武汉出现至今,土家烧饼已由我国的西部逐渐向东扩张。这些“土家烧饼”店无一例外地有着相似的店铺装饰,翠竹、红线、簸箕等“土家族”店面装饰元素;叫着相似的店名:“土家族烧饼”、“土老冒烧饼”、“土家烧饼大王”、“掉渣烧饼”、“土掉渣烧饼”、“掉馅的烧饼”、“土家西施烧饼”等。短…     

20世纪初英国的社会改革及其影响

20世纪初,在英国自由党的支持和推动下,英国政府进行了一系列旨在减少贫困、缓解矛盾的社会改革,推出了养老金条例和国民保险法案,调节了社会各阶层之间的关系,打下了社会保障的基础,从而对20世纪英国社会的发展产生了深远的影响.     

云梦秦律新解(六则)

本文对云梦睡虎地秦墓出土的秦律文献中六处简文提出不同于睡虎地秦简整理小组注译的解读意见,重新探讨秦人的立法意图,寻求揭示秦法制相关内容的历史真实。     

Calibration and Test of a Discrete Choice Model with Endogenous Choice Sets

Conventional discrete choice models assume implicitly that the choice set is independent of the decisionmaker's preferences conditional on the explanatory variables of the models. This assumption is implausible in many choice situations where the decisionmaker selects his or her choice set. This paper estimates and tests a discrete choice model with endogenous choice sets based on Horowitz' theoretical work. To calibrate the model, a new probability simulator is introduced and a sequential estimation procedure is developed. The model and calibration methods are tested in an empirical application as well as Monte Carlo simulations. The empirical results are used to test the theory of endogenous choice sets and to examine the differences between the new model and a conventional choice model in parameter estimates and predicted choice probabilities. The empirical results strongly suggest that ignoring the endogeneity of choice sets in choice modeling can have serious consequences in applications.     

我国各级中心城市界定的方法与实践

提出了中心城市的内涵与判定方法, 运用复合指标法测定了全国中等以上城市和各省域及９ 大经济区的实力指数,判定了地区级、省级、大区级和全国性中心城市。     

汉冶萍公司的钢铁销售与我国近代钢铁市场（1908-1927）

汉冶萍公司改制组建以来,其产品销售机构和规章制度逐步完善,并多方开展了营销活动;在钢铁煤焦矿石各种产品销售中,钢铁销售收入占据重要地位,构成公司运转常年经费开支的主要来源;但当年国内市场十分狭小,钢铁销售既被外国列强挤压,又受国内政府挟制（主要在钢轨销售方面）;而在国外主要对日销售中,更遭其百般盘剥打击,致使我国惟一一个钢铁煤焦联合企业被迫沦为单纯为其供给铁矿石的开采机构。