Simulation of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (V): Discrete Element Approach

ABSTRACT

The analysis of the shaking table test of a 3-wall stone masonry structure performed with a discrete element model is presented. The numerical model, created with the code 3DEC, employed a rigid block representation and a Mohr-Coulomb joint model. Joint stiffness calibration to match the experimental natural frequencies is discussed, as well as the boundary conditions to simulate the shake table. Comparisons are made with the measured displacements at key locations, and the modes of deformation and fracture of the walls. The DEM model was able to reproduce important features of the shaking table tests. The experimental deformation and near collapse patterns were clearly identifiable in the numerical simulations, which produced displacements within the observed orders of magnitude, for the various levels of excitation.     

Detecting modes in low-dimensional archaeological data

An approach to testing for modes in low-dimensional data, Silverman’s test, novel in an archaeological setting, is described and illustrated. ‘Patterns’ in archaeological data can be suggested by the presence of modes. Reassurance is needed that modes suggested by graphical analysis are genuine before attempting substantive archaeological interpretation. The test either provides such reassurance, or else guards against over-interpretation, particularly with small samples. Data on loomweight dimensions, lead isotope ratios, and ceramic compositions are used to illustrate use of the test, dealing with issues concerning outliers and small samples as they arise. The focus is on univariate mode detection.     

古代青铜器修复钎焊用钎剂与钎料的改性研究

锡铅钎料和氯化锌钎剂的烙铁钎焊是传统的工艺方法。由于氯化锌钎剂中含有大量的氯离子,对青铜物的长期保存带来不利的影响。本工作通过对钎剂筛选和复配及钎料的选择,研制了针对青铜物修复钎焊用新型无氯钎剂和含银钎料匹配,并在8种古青铜模拟试样上进行一系列性能测试,结果表明新型无氯钎剂和含银钎料匹配有良好的工艺性、抗腐蚀性、可获得高强度的钎缝。新型无氯钎剂和含银钎料匹配在青铜物修复中应用结果表明,新型无氯钎剂和含银钎料有较好的钎焊工艺,钎焊接头饱满光亮,对于不同时期及不同合金的青铜物具有很好的钎焊性,钎焊后青铜物存放半年,钎焊接头依然保持光亮,焊缝周围没有出现锈蚀物和氧化现象。用新型无氯钎剂替代传统氯化锌钎剂,并且和含银钎料匹配进行古青铜的钎焊是可行的,改良后的钎剂进行青铜物修复过程符合物保护原则,避免了钎剂在钎焊过程中产生的气体对操作人员身体健康的影响。     

银纳米薄膜试片在博物馆藏展材料评估筛选中的应用

Oddy测试法是一种最为常用的评估材料是否适合博物馆文物储藏与展示的测试方法,其缺点在于采用活性低的块状金属试片,需要28天的测试周期,同时试片表面平整度以及人为主观因素会影响目测结果的准确性.本工作制备了银纳米薄膜试片替代Oddy测试法中块状金属试片,以半径10mm玻璃圆片为基质,银薄膜厚度约为200～220nm.实验结果表明,采用银纳米薄膜试片后,腐蚀现象在14d后可充分显现并分化,延长至28d时腐蚀现象基本无大变化,有效的缩短了测试周期.同时尝试结合数码图像采集技术,有利于进一步的腐蚀现象数据化分析研究工作,从而得到更加客观准确的测试结果.     

薄膜试片测试法试片图像采集分析系统

薄膜试片测试法是一种能够全面有效地对博物馆藏展材料进行评估筛选的测试方法,对其腐蚀现象进行图象采集及进行数据化分析能够得到更为客观准确的测试结果.本工作对应该测试法设计了专门图像采集的硬件装置,采用密闭光源和彩色工业摄像机,可以得到清晰的试片图像.软件系统将采集图像、打开原始图像、图像分割处理、材料分级评价等功能模块化,并根据具体功能设计实现了基本应用的可视化界面.实验表明,该系统能够快速、准确地对藏展材料对试片的腐蚀现象进行数据化分析,使藏展材料的评估分级由人工目测走向计算机视觉计算,具有快速、客观、误差小等特点.     

Finite element modeling of slug tests in an aquifer with stratigraphical and structural heterogeneities

Slug interference tests using an array of multilevel active and monitoring wells permit enhanced aquifer characterization. Analyses of these field test data rely on numerical inverse models. In order to provide synthetic data sets and to have a better understanding of the flow mechanisms, we used a three-dimensional finite element analysis (FEHM) to explore the effects of idealized, stratigraphical (strata) and structural (faults) heterogeneities with low permeability values on the transient head field that is associated with slug tests in an aquifer. Firstly, we tested our model on homogeneous aquifers and the effectiveness of our modeling strategies have been validated via the excellent agreement of our modeling results with those of the semi-analytical model of Liu & Butler (1995) . In our heterogeneity investigations, we embedded vertical and horizontal zones of lower permeability into a homogenous, isotropic, and confined aquifer to represent low-permeability faults and strata respectively. A slugged interval is located at the center of the aquifer. Effects of strata thickness and permeability contrast as well as other effects associated with the offset of low-permeability strata were explored. In particular, modeling results are represented by contour maps of peak travel time and maximum head perturbation of generated hydraulic pulses. Furthermore, various phenomena, such as real-time matrix diffusion, intermittent matrix–fracture interactions, and faster pulse arrival through a longer flow trajectory, are concretely presented in the snapshots of head perturbations in the aquifer. Our finite element modeling provides useful information for understanding the behaviors of diffusive pressure propagation in an aquifer with stratigraphical and/or structural heterogeneities, and for designing hydraulic tomography to enhance aquifer characterization.     

The colourless glass of Iulia Felix

The present paper focuses on 85 colourless glass samples selected among the recycling cullet found in the Roman ship Iulia Felix, wrecked off the town of Grado (province of Udine, North Italy) in the first half of the 3rd century AD, with the aim of examining their chemical composition, investigating similarities within and between the three established group types (cups, plates, bottles), and comparing the chemical compositions of the Iulia Felix glass samples with groups reported in the literature for colourless glasses. Chemical analyses, performed by X-ray fluorescence and electron microprobe, indicate that the samples were all soda-lime–silica in composition, with natron as flux, according to typical Roman production technologies. Chemical data are treated by multivariate statistical tools, such as cluster analysis and the NPC test. Statistical analyses allow us to conclude that the Iulia Felix colourless glasses were produced by at least two different production technologies related to group type, confirming the trend recently identified in the literature. In addition, the trace element patterns (particularly those of Sr, Zr and Ba) suggest that beach sand with differing amounts of alkali feldspars was predominantly used as raw material, like those specifically mentioned by Pliny for glass production.     

侯马东周祭祀遗址出土玉器材质的矿物学测试及产源分析

山西侯马西高及晋田热力公司东周祭祀遗址4件出土玉器残片样品经过比重测试、红外光谱物相分析、X射线粉晶衍射分析、显微结构观察及稳定同位素等矿物学测试和产源分析,发现其中的西高(J580、J332)和热力公司(JK728)3件样品是来自新疆和田地区的闪玉石,热力公司(JK659)样品是蛇纹石化大理岩。     

Radiocarbon Dating of the Turin Shroud: New Evidence from Raw Data

In 1988, three laboratories performed a radiocarbon analysis of the Turin Shroud. The results, which were centralized by the British Museum and published in Nature in 1989, provided ‘conclusive evidence’ of the medieval origin of the artefact. However, the raw data were never released by the institutions. In 2017, in response to a legal request, all raw data kept by the British Museum were made accessible. A statistical analysis of the Nature article and the raw data strongly suggests that homogeneity is lacking in the data and that the procedure should be reconsidered.     

Clyve Jones and Parliamentary History

The ‘constitutional revolution’ which occurred in Ireland after 1691 meant that parliamentary management became one of the prime functions of the viceroyalty. Interest focused on the Commons, where supply legislation was drafted. But the upper House, though smaller, less busy, and on the whole more easily managed, could not be ignored, since it could still cause major problems for government. The situation for the incoming ministers in 1714 was problematic, since the Lords had been a tory stronghold, and the ‘Church party’, buttressed by the bishops, remained powerful. The situation was a mirror image of Westminster in 1710, when Robert Harley's tory ministry had to cope with a whig-dominated house of lords. This essay analyses the means by which Lord Lieutenant Sunderland (1714–15), and his successors, Lords Justices Grafton and Galway, brought the Irish upper House under control, constructing a court party with some of the elements which Clyve Jones has identified as having been crucial to Harley's strategy in 1710–14: moderate or non-party men, pensioners and placemen depending on government largess, new episcopal appointments and a block creation of peerages. In Ireland it was the new peers who played the most important part. The whigs were able to make some inroads into the episcopal bench, previously a stronghold of toryism, until the issue of relief for dissenters rekindled anxiety over the maintenance of the ecclesiastical establishment, prefiguring future problems.