Topic Modeling and Text Analysis for Qualitative Policy Research

This paper contributes to a critical methodological discussion that has direct ramifications for policy studies: how computational methods can be concretely incorporated into existing processes of textual analysis and interpretation without compromising scientific integrity. We focus on the computational method of topic modeling and investigate how it interacts with two larger families of qualitative methods: content and classification methods characterized by interest in words as communication units and discourse and representation methods characterized by interest in the meaning of communicative acts. Based on analysis of recent academic publications that have used topic modeling for textual analysis, our findings show that different mixed‐method research designs are appropriate when combining topic modeling with the two groups of methods. Our main concluding argument is that topic modeling enables scholars to apply policy theories and concepts to much larger sets of data. That said, the use of computational methods requires genuine understanding of these techniques to obtain substantially meaningful results. We encourage policy scholars to reflect carefully on methodological issues, and offer a simple heuristic to help identify and address critical points when designing a study using topic modeling.     

汉代漆器的剖析

通过制备并分析一系列模拟漆膜样品。建立了有助于鉴定汉代漆器成分的剖析方法。经裂解气相色谱、差热分析、色谱一红外联用等现代分析技术对出土的汉代漆器残片样品的综合分析,证实在西汉漆器制造中已使用桐油或其它的添加剂,并依据剖析的结果,对某些汉代漆器的原材料差异作了初步探讨。     

The Geochemical Fingerprint of Tufo Lionato Blocks from the Area Sacra di Largo Argentina: Implications for the Chronology of Volcanic Building Stones in Ancient Rome

We use trace element discrimination diagrams to provide a geochemical fingerprint for Tufo Lionato, the volcanic rock most commonly used in the ancient Roman dimension stone technique. Based on the comparison of their geochemical signatures, we identify different rock facies of Tufo Lionato employed since the fourth to third centuries and through the second century bce in the construction of the temples of the Area Sacra di Largo Argentina. These rock facies correspond to two previously identified building stones: Aniene Tuff and Monteverde Tuff, named after their supposed source areas located in the Aniene River Valley and in the homonymous locality of the Tiber River Valley, respectively. However, the results of our study demonstrate previous misidentification of these volcanic rocks in the different construction phases of Temple C, providing a revision of the dating system currently accepted for the diffusion of Tufo Lionato architecture. We show that the Aniene facies has been exploited since the end of the fourth century bce and that it was employed along with Tufo Giallo della Via Tiberina in the podium and staircase of Temple C, whereas observations at Largo Argentina suggest that the ‘Monteverde Tuff’ was only sporadically used in the early phases of the dimension stone construction technique.     

饱水木质文物的风冷干燥脱水研究

许多出土饱水木质文物因其降解严重、含水率较高,容易在脱水过程中出现不可逆的收缩变形以及开裂现象,从而遭到严重破坏。因此,饱水木质文物脱水方法的研究是文物保护工作中的重要课题。为探究风冷冷冻法对饱水木质文物脱水的效果,以一批无法复原的出土饱水木质文物为研究对象,在对其材种、含水率、基本密度及化学成分进行了测定和分析后,使用一台风冷电冰箱在-18℃条件下对样品进行了风冷干燥脱水处理,记录脱水时间和脱水效果,并分析了该方法的传质传热特点,证明了风冷干燥法用于饱水木质文物的脱水干燥能够取得良好效果,并且具有对文物干预小、适用性广、操作简便、成本低廉等优点,为饱水木质文物的脱水处理提供了一种新的思路。     

Multiphase flow simulation through porous media with explicitly resolved fractures

Accurate simulation of multiphase flow in fractured porous media remains a challenge. An important problem is the representation of the discontinuous or near discontinuous behaviour of saturation in real geological formations. In the classical continuum approach, a refined mesh is required at the interface between fracture and porous media to capture the steep gradients in saturation and saturation‐dependent transport properties. This dramatically increases the computational load when large numbers of fractures are present in the numerical model. A discontinuous finite element method is reported here to model flow in fractured porous media. The governing multiphase porous media flow equations are solved in the adaptive mesh computational fluid dynamics code IC‐FERST on unstructured meshes. The method is based on a mixed control volume – discontinuous finite element formulation. This is combined with the P_N+1DG‐P_NDG element pair, which has discontinuous (order N+1) representation for velocity and discontinuous (order N) representation for pressure. A number of test cases are used to evaluate the method's ability to model fracture flow. The first is used to verify the performance of the element pair on structured and unstructured meshes of different resolution. Multiphase flow is then modelled in a range of idealised and simple fracture patterns. Solutions with sharp saturation fronts and computational economy in terms of mesh size are illustrated.     

Interconnected Epistyles of Marble Monuments Under Axial Loads

The restoration of destroyed connections of epistyles joined together by means of metallic connectors is among the most difficult problems encountered by scientists working for the conservation/restoration of monuments made of marble. The complexity of the geometry and the interaction of three completely different materials (metal-filling material-marble) constituting the connection render the study (either experimental or analytic) extremely complicated. In this direction a numerical analysis is presented here in order to deeply understand the response of a typical ancient connection subjected to axial loads as well as to quantify the influence of some geometric parameters on its response. The parameters studied include the length of the connector, the width of its flanges, the depth of the groove (mortise), the existence or not of relieving space and the filling material’s volume. The numerical model was calibrated and validated according to the results of an earlier experimental study realized on the worksite of the Parthenon Temple. It was concluded that the interventions required to relieve the stress field by changing the size of the connector are disproportional to the respective positive effect on the response of the connection. Moreover it was proved that the most beneficial parameter is the relieving space.     

Updating Numerical Models of Masonry Arch Bridges by Operational Modal Analysis

This article aims at presenting and discussing the strategies for updating the finite element numerical modeling of stone masonry arch bridges using operational modal analysis. The study comprehended three bridges: two old ones, the St. Lázaro and the Lagoncinha bridges, and a recently constructed bridge in Vila Fria, Portugal. Updating of the bridge models is performed by comparing the numerical and experimental modal parameters. Three-dimensional detailed numerical models are used to perform modal analysis of the bridges. Experimental modal identification of the bridges is based on the measurement of their acceleration responses during normal operation. The assigned material properties are also based on available results obtained from in situ and laboratory tests and on the results of visual inspection and historical research carried out for both old bridges.     

Petrochemical Identification and Insights on Chronological Employment of the Volcanic Aggregates Used in Ancient Roman Mortars

Through the assistance of trace element and petrographic analyses on 14 samples of mortar aggregates from Roman monuments, including the Porticus Aemilia, the Temple of Concordia, the Temple of the Dioscuri, Temple B and other structures of the Area Sacra di Largo Argentina, and the Villa di Livia, we establish the source area and we investigate the chronological employment of the volcanic materials used in ancient Rome's masonry. In contrast to previous inferences, the petrochemical data presented here show that systematic exploitation of the local ‘Pozzolane Rosse’ pyroclastic deposit has occurred since the early development of concrete masonry, at the beginning of the second century bc , through the early Imperial age. Subsequently, exploitation was extended to the overlying Pozzolane Nere and Pozzolanelle deposits. Only during the early phase of development of the concrete masonry in Rome, volcaniclastic sediments outcropping near the construction sites were mixed with the sieved remains of the tuff employed as the coarse aggregate, to produce the fine aggregate. The results of the study on the investigated monuments suggest the possibility of establishing the chronological identification of three different types of mortars, as a function of the composition of the volcanic material employed in the fine aggregate, which, when implemented by future studies, may contribute to the dating of monuments and archaeological structures.     

Seismic vulnerability assessment and fragility analysis of stone masonry monastic temples in Sikkim Himalayas

Buddhist monasteries in Sikkim Himalayas constitute important religious and architectural heritage. These random rubble (RR) stone masonry structures located in high seismically active regions of the Himalayas have suffered varied degrees of damages in the past earthquakes. The study presents seismic vulnerability assessment of four archetypal monastic temples using finite element (FE) analyses. Linear and nonlinear analyses of these structures were conducted in Abaqus FE environment. These analyses identified the damage prone areas of the structures and provided load-deformation behavior under lateral loads. Fragility analyses indicate a high probability of collapse for the specified design level earthquake of the region. The study shows that performance of the structure can be enhanced by improving the strength and stiffness of the stone masonry walls.