Modeling and visualizing semantic and spatio-temporal evolution of topics in interpersonal communication on Twitter

Interpersonal communication on online social networks has a significant impact on the society by not only diffusing information, but also forming social ties, norms, and behaviors. Knowing how the conversational discourse semantically and geographically vary over time can help uncover the changing dynamics of interpersonal ties and the digital traces of social events. This article introduces a framework for modeling and visualizing the semantic and spatio-temporal evolution of topics in a spatially embedded and time-stamped interpersonal communication network. The framework consists of (1) a topic modeling workflow for modeling topics and extracting the evolution of conversational discourse; (2) a geo-social network modeling and smoothing approach to projecting connection characteristics and semantics of communication onto geographic space and time; (3) a web-based geovisual analytics environment for exploring semantic and spatio-temporal evolution of topics in a spatially embedded and time-stamped interpersonal communication network. To demonstrate, geo-located and reciprocal user mention and reply tweets over the course of the 2016 primary and presidential elections in the United States from 1 August 2015 to 15 November 2016 were analyzed. The large portion of the topics extracted from mention tweets were related to daily life routines, human activities, and interests such as school, work, sports, dating, wearing, birthday celebration, music, food, and live-tweeting. Specific focus on the analysis of political conversations revealed that the content of conversational discourse was split between civil rights and election-related discussions of the political campaigns and candidates. These political topics exhibited major shifts in terms of content and the popularity in reaction to primaries, debates, and events throughout the study period. While civil rights discussions were more dominant and in higher intensity across the nation and throughout the whole time period, election-specific conversations resulted in temporally varying local hotspots that correlated with locations of primaries and events.     

Historical earthquake activity of the northern part of the Dead Sea Fault Zone, southern Turkey

The northern part of the Dead Sea Fault Zone is one of the major active neotectonic structures of Turkey. The main trace of the fault zone (called Hacıpaşa fault) is mapped in detail in Turkey on the basis of morphological and geological evidence such as offset creeks, fault surfaces, shutter ridges and linear escarpments. Three trenches were opened on the investigated part of the fault zone. Trench studies provided evidence for 3 historical earthquakes and comparing trench data with historical earthquake records showed that these earthquakes occurred in 859 AD, 1408 and 1872. Field evidence, palaeoseismological studies and historical earthquake records indicate that the Hacıpaşa fault takes the significant amount of slip in the northern part of the Dead Sea Fault Zone in Turkey. On the basis of palaeoseismological evidence, it is suggested that the recurrence interval for surface faulting event is 506 ± 42 years on the Hacıpaşa fault.     

A local identification technique for geotechnical and geophysical systems

Geotechnical structures and natural soil deposits are massive multi‐phase particulate systems characterized by the development of localized response mechanisms under extreme loading conditions. Identification and analysis of such systems based on inverse boundary value problem formulations and sparse measurements are generally indeterminate. This paper presents an alternative local inverse problem technique. Point‐wise identification analyses of the constitutive behaviour of water‐saturated geotechnical and geophysical systems are performed using acceleration and pore pressure records provided by a cluster of closely spaced sensors. The developed novel technique does not require the availability of boundary condition measurements, or solution of an associated boundary value problem. The constitutive behaviour at a specific location of a soil‐system is analysed independently of adjacent response mechanisms or material properties. Numerical simulations and centrifuge tests of a soil‐retaining wall system are used to demonstrate the capabilities of the developed technique. Copyright © 2003 John Wiley & Sons, Ltd.     

Mapping family connectedness across space and time

Understanding the structure and evolution of family networks embedded in space and time is crucial for various fields such as disaster evacuation planning and provision of care to the elderly. Computation and visualization can potentially play a key role in analyzing and understanding such networks. Graph visualization methods are effective in discovering network patterns; however, they have inadequate capability in discovering spatial and temporal patterns of connections in a network especially when the network exists and changes across space and time. We introduce a measure of family connectedness that summarizes the dynamic relationships in a family network by taking into account the distance (how far individuals live apart), time (the duration of individuals’ coexistence within a neighborhood), and the relationship (kinship or kin proximity) between each pair of individuals. By mapping the family connectedness over a series of time intervals, the method facilitates the discovery of hot spots (hubs) where family connectedness is strong and the changing patterns of such spots across space and time. We demonstrate our approach using a data set of nine families from the US North. Our results highlight that family connectedness reflects changing demographic processes such as migration and population growth.     

Local system identification analyses of the dynamic response of soil systems

The seismic behavior of massive geotechnical systems exhibits complex response patterns and mechanisms under severe loading conditions. Some of these mechanisms are localized in space, but nevertheless impact significantly the entire system response and ultimately its stability. A thorough monitoring and identification of the whole response of a distributed soil system commonly constitutes a significant challenge, and would generally be prohibitively expensive. This study presents a point-wise identification technique of soil-systems using the acceleration records provided by local instrument arrays. The newly developed identification algorithm consists of: (1) evaluation of strain tensor time histories using the motions recorded by a cluster of instruments (arranged in an appropriate multi-dimensional configuration), (2) estimation of the stress tensors corresponding to the evaluated strains utilizing a pre-selected class of constitutive models of soil response, (3) computation of accelerations associated with estimated stresses using the equations of motion, and (4) calibration and evaluation of an optimal model of soil response by minimizing discrepancies between recorded and computed accelerations. Computer simulations and analysis of centrifuge tests of a soil–quay wall system showed that the proposed technique provides an effective tool to identify local soil characteristics and properties.     

A survey of geotechnical system identification techniques

Identification and inverse problem techniques play an important role in the characterization and modeling of geotechnical systems. These techniques have been used in estimation of system parameters, model development and calibration, as well as simulation of earthquake ground motions. The recent availability of high quality seismic records of sites equipped with downhole accelerometer arrays led to a burgeoning of identification and inverse problem studies involving geotechnical systems. This paper presents a survey of system identification techniques and analyses of full- and small-scale soil systems, with an emphasis on geotechnical earthquake engineering problems.     

Investigation of soil dynamic characteristics at seismic stations using H/V spectral ratio method in Marmara Region,Turkey

Natural Hazards - The North Anatolian Fault Zone (NAFZ) between the Arabian, Eurasian and African plates is one of the world’s most dangerous tectonic units. After the 1939 Erzincan...     

Benthic foraminiferal biostratigraphy of the tertiary sediments from the Elazig and Malatya Basins,Eastern Turkey

Tertiary sequences in the Elazig and Malatya Basins, eastern part of Taurus Orogenic Belt, are investigated with the aim of defining the benthic foraminiferal biozones. Tertiary geological units from bottom to top are as follows: Basement rocks, Zorban Formation, Yildiztepe Formation, Suludere Formation, Gedik Formation (Malatya Basin); Elazig Magmatics, Keban Metamorphics, Harami Formation, Kuscular Formation, Seske Formation, Kirkgecit Formation (Elazig Basin). Middle-Upper Eocene Yildiztepe, Suludere and Gedik Formations; Upper Paleocene-Lower Eocene Seske Formation and Middle-Upper Eocene Kirkgecit Formation are all characterized by interbedded clastics and carbonate rocks. Six stratigraphic sections are studied in detail for foraminiferal biostratigraphy. Eight benthic foraminiferal biozones are reported. These are; Coskinolina rajkae biozone in the Late Paleocene (Thanetian), Assilina yvettae, Idalina sinjarica biozones in the Late Paleocene; Asterocyclina alticostata gallica biozone in the Early Eocene (Late Cuisian), Nummulites millecaput biozone in the Middle Eocene (Middle Lutetian), Nummulites aturicus biozone in the Middle Eocene (Late Lutetian), Nummulites perforatus biozone in the Middle Eocene (Bartonian), Nummulites fabianii biozone in the Late Eocene (Priabonian). Some key taxa are illustrated.     

Groundwater-level recovery following closure of open-pit mines

Hydrogeology Journal - Open-pit mining has increased substantially over the past two decades. Many currently operating open-pit mines are facing the end of mine-life over the next few decades and,...