Risk Assessment and Preservative Measures for Volatile Organic Compounds in Museum Showcases

ABSTRACT

The first step in preservative measures for artworks in airtight showcases is the exclusion of outgassing from construction materials or, at least, limitation of the emissions to a minimum acceptable level if the volatile organic compounds (VOCs) generated may be qualified as harmless. Once it is ascertained that the objects in the showcases are responsible for VOC emissions, a step forward becomes necessary, implying showcase ventilation with air flowing through active sorbent materials. Solid phase micro-extraction (SPME) followed by GC separation and MS identification has been applied for checking the outgassing characteristics of different types of materials used for the construction of airtight showcases, and the method was found particularly attractive in terms of speed and sensitivity, suitable for measurements in presence of low-emitting materials. Sampling could also be done in the case interiors, thus making possible detection and recognition of emissions from art objects within a case. A comprehensive preventive conservation scheme has been further devised by means of active air circulation within the showcase and functional sorbent materials along the flow, for complete suppression of gaseous compounds. Control of the compounds in the air flow and of their filtration efficacy was achieved by direct sampling, also using SPME fibers. Continuous monitoring of the air quality in the showcases has been developed with insertion of a photoionization detector capable of detecting the VOCs in the air by inducing molecular ionization, and measuring the generated photocurrent. The system is not selective, but gives the total concentration, reaching ppb sensitivity with high-quality data. In addition it includes temperature and humidity sensors, making the whole a useful instrument for environment control.     

香港地区室内氡及环境γ辐射水平

采用活性炭吸附法测定了香港地区各类建筑物160个测量点的室内氡浓度。在上述筛选监测基础上,又在香港主要商业区选取居民住宅和工作场所数目相近的测量点,放置CR-39核径迹探测器和两种LiF热释光剂量计约3个月,测得71个测量点的室内平均氛浓度和v辐射空气吸收剂量率,各组测量结果均呈正态分布.     

序列检测器的一种简化实现算法

分析了序列检测器的内部原理,给出它的一种新硬件实现.利用它无需对状态图进行状态化简,极大地简化了时序线路的设计.最后结合具体实例说明了该设计思想的详细步骤和具体实现方法.     

红外热释电材料的研究进展

文章列出主要常规红外热释电材料及其主要参数 ,在对它们进行比较的同时 ,着重阐述国内外近年来红外热释电材料在红外热释电探测器方面应用研究的主要进展     

Application of 2-D Position Sensitive Detector in Spatial Straightness Measurement of Guide Rails

A laser collimating system based on 2-D position sensitive detector (PSD) is presented in this paper. The working principle of PSD is depicted in detail. A calibration device was developed to check the nonlinearity errors of PSD and a multilayer feedforward neural network based on error back-propagation algorithm was used to compensate errors. With the aid of computer-based data acquisition system, an automatic dynamic measuring process was realized. A series of experiments, including comparison tests with laser interferometer, were done to evaluate the performance of the measuring system. The experimental results show that the spatial straightness errors of guide rails can be measured with high accuracy. The maximum differences between the device and laser interferometer are 0. 027 mm in Y direction, and 0. 053 mm in X direction in the measuring distance of 6 m.     

基于STC89C52的酒精体积分数检测仪设计

为了方便的检测驾驶员体内酒精体积分数,研究了基于单片机酒精体积分数检测仪的设计方法。结果表明,该检测仪硬件电路设计简单,软件采用结构化程序设计方法,完成了系统的整体设计。该检测仪成本低廉,性能稳定,抗干扰能力强。     

Dependence patterns associated with the fundamental diagram： a copula function approach

Randomness plays a major role in the interpretation of many interesting traffic flow phenomena, such as hysteresis, capacity drop and spontaneous breakdown. The analysis of the uncertainty and reliability of traffic systems is directly associated with their random characteristics. Therefore, it is beneficial to understand the distributional properties of traffic variables. This paper focuses on the dependence relation between traffic flow density and traffic speed, which constitute the fundamental diagram （FD）. The traditional model of the FD is obtained essentially through curve fitting. We use the copula function as the basic toolkit and provide a novel approach for identifying the distributional patterns associated with the FD. In particular, we construct a rule-of-thumb nonparametric copula function, which in general avoids the mis-specification risk of parametric approaches and is more efficient in practice. By applying our construction to loop detector data on a freeway, we identify the dependence patterns existing in traffic data. We find that similar modes exist among traffic states of low, moderate or high traffic densities. Our findings also suggest that highway traffic speed and traffic flow density as a bivariate distribution is skewed and highly heterogeneous.     

基于AT89C2051的家用无线防盗报警器

提出并实现了一种基于单片机AT89C2051的家用无线防盗报警器设计方案。从系统结构、入侵探测器、微型报警发射机、无线接收报警控制器及单元电路等方面进行了详细论述。结果表明,该报警器所采用的元件简单,使用方便、成本较低,可靠性和稳定性高,并且在功能上具有良好的可扩展性,便于市场应用与推广。     

综合楼的火灾自动报警与消防联动控制

火灾自动报警与消防联动控制系统是各类综合高层建筑现代消防工程的核心。本文结合工程实例,阐述如何合理地对综合建筑的火灾自动报警与消防联动控制系统进行设计。     

黄土高原乡村聚落用地时空演变与影响因素

研究黄土高原乡村聚落用地规模演变及其影响因素,对优化乡村聚落空间格局,落实国家乡村振兴战略具有理论和现实意义。本文采用位序-规模法则、核密度分析和地理探测器方法,研究1990—2015年黄土高原乡村聚落用地的空间分布和规模等级特征,揭示乡村聚落用地规模格局形成影响因素与驱动机制。结果表明：①1990年以来,黄土高原乡村聚落斑块数量和用地规模总体呈现增加趋势,其中2000—2005年乡村聚落斑块数量增加最明显,2005—2010年用地规模扩大最显著。②黄土高原乡村聚落用地规模处于非均衡发展阶段,乡村聚落空间分布具有明显的历史继承性,在地理空间上表现为主体延伸和局部填充两种形式。乡村聚落密度在区域上呈现“一极两翼”的空间结构特征,关中平原地区是乡村聚落核心集聚区,银川平原—六盘山区—陇东高原、河套平原—汾河谷地—豫西盆地内乡村聚落集聚与分散趋势并存。③黄土高原乡村聚落用地规模格局的形成受到多重要素的综合作用。地形起伏度、年平均气温和年平均降水量等是主要的自然作用力,人均粮食产量、总人口数和乡村人口比重等是关键人文驱动力。其中,任意两个因子的交互作用对乡村聚落用地规模空间格局的影响均强于单个因子的影响。④各因素之间的交互作用对黄土高原地区乡村聚落用地规模格局的影响差异显著。自然地理因素与社会经济因素的交互作用对黄土高原沟壑区、土石山区和高原风沙区的乡村聚落用地规模格局影响最为广泛,社会经济因素之间的交互作用对黄土丘陵沟壑区和河谷平原区乡村聚落用地规模格局具有明显的协同增强效应,粮食生产与区位条件对灌溉农业区的乡村聚落用地规模格局具有显著的协同增强效应。