The effect of disruptive events on spatial and social interactions: An assessment of structural changes in pre-and post-COVID-19 pandemic networks

Disruptive events significantly alter spatial and social interactions among people and places. To examine the structural changes in spatial and social interaction networks in pre- and post-periods of the COVID-19 pandemic, we employ the Louvain method to algorithmically detect regions (communities) within the county-to-county networks of the SafeGraph mobility and Facebook social connectedness. We then utilize a range of partition similarity metrics, including adjusted Rand, z-Rand, Normalized Mutual Information (NMI), and Jaccard indices, to quantitatively measure the similarity of regions between the pre- and post-periods partitions of each network. Our findings reveal that in the post-pandemic period, spatial interactions led to the formation of localized geographic communities or regions characterized by higher modular activity within each region. In contrast, online social interactions shifted towards longer distance connections, resulting in the emergence of larger regions marked by strong friendship ties that often encompassed multiple states. By understanding these changes, we contribute to a better comprehension of the pandemic's impact on our interconnected physical-virtual world, providing valuable insights for future research and informing strategies to adapt to the evolving dynamics of human interactions.Comment: Proceedings of GIScience 2023 Workshop on Disruptive Movement Analysis, September 12, 2023, Leeds, U

Exploring banking competition in Croatia by using the Panzar-Rosse model

The performance commercial banks in the Croatia have been widely studied, but there is little known about the examination of the nature of competition. For these reasons, it is important to investigate whether the banking sector in Croatia exerts monopoly or monopolistic behavior. This research empirically explores the nature of competition in the Croatian banking sector by covering 24 commercial banks between 2008 and 2018. In this vein, the panel data analysis was used along with H-Statistics. This study for Croatia and its findings confirms early findings of the existence of monopolistic competition in the most transition and developing countries. In fact, the findings obtained from this study reveals that the commercial banks in Croatia operate under monopolistic structure. Moreover, the results reveal that variable of RIETD, RLTA, RETA, and RDTA are statically significant. It indicates that banks operated in Croatia are focus more on traditional loans than other activities

FlowMapper.org: A web-based framework for designing origin-destination flow maps

FlowMapper.org is a web-based framework for automated production and design of origin-destination flow maps (https://flowmapper.org). FlowMapper has four major features that contribute to the advancement of existing flow mapping systems. First, users can upload and process their own data to design and share customized flow maps. The ability to save data, cartographic design and map elements in a project file allows users to easily share their data and cartographic design with others. Second, users can customize the flow line symbology by including options to change the flow line style, width, and coloring. FlowMapper includes algorithms for drawing curved line styles with varying thickness along a flow line, which reduces the visual cluttering and overlapping by tapering flow lines at origin and destination points. The ability to customize flow symbology supports different flow map reading tasks such as comparing flow magnitudes and directions and identifying flow and location clusters that are strongly connected with each other. Third, FlowMapper supports supplementary layers such as node symbol, choropleth, and base maps to contextualize flow patterns with location references and characteristics such as net-flow, gross flow, net-flow ratio, or a locational attribute such as population density. FlowMapper also supports user interactions to zoom, filter, and obtain details-on-demand functions to support visual information seeking about nodes, flows and regions. Finally, the web-based architecture of FlowMapper supports server side computational capabilities to process, normalize and summarize large flow data to reveal natural patterns of flows

All-chalcogenide glass omnidirectional photonic band gap variable infrared filters

Cataloged from PDF version of article.We report on the design, fabrication, and characterization of spatially variable infrared photonic band gap filter that consists of thermally evaporated, high refractive index contrast, amorphous chalcogenide glass multilayers. Due to graded thickness structure, the filter exhibits a position dependent stop band and a cavity mode ranging from 1.8 to 3.4 μm wavelengths. Reflection measurements on the variable filter agree well with theoretical calculations. These results pave the way to low-loss infrared mirrors, filters, spectral imaging, and miniaturized spectrometers at infrared region. © 2009 American Institute of Physics

Soot nucleation and growth in weakly-buoyant laminar jet diffusion flames

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76524/1/AIAA-1994-428-986.pd

Implementation of Advanced Fuels and Combustion for Internal Combustion Engines

Track II: Transportation and BiofuelsIncludes audio file (19 min.)Advanced engine designs for transportation has shown significant reduction in engine-out emissions while simultaneously achieving gains in fuel efficiency by using Low Temperature Combustion (LTC) modes and feedback control of the combustion processes. The work of this group has considered the difficulties encountered in using these combustion modes through implementation of advanced control methodologies, novel sensor techniques as well as expanding usage of fuels such as bio-fuels and hydrogen. The methods used to obtain the lower combustion temperatures include lean mixtures and high levels of exhaust gas recirculation. For example, LTC modes such as Homogeneous Charge Compression Ignition (HCCI) and Partially Premixed Compression Ignition (PCCI) engines show real gains in reduced engine out emissions with improved efficiency. However, implementation of these advanced combustion modes presents combustion timing and stability issues due to stronger dependence of these advanced combustion modes on the physical and chemical properties of the fuel, inlet temperature, and inlet composition than traditional diffusion burning (“diesel” type) modes. Progress in these advanced combustion modes requires a “smart” engine capable of sensing heat release patterns and adjusting combustion system parameters. Hence collaborative work between several researchers at Missouri S&T are considering the required combustion analysis, nonlinear control, sensor development and fuel property issues surrounding the implementation of several LTC modes. Analysis methods currently considered are based on surface accelerations for use on both conventional and premixed auto-ignited combustion types that can robustly indicate combustion characteristics. Surface mount accelerometers are being used to indicate combustion characteristics needed for closed loop engine control but which have minimal structural influence. Acceleration frequency bands are being identified where the structural characteristics has the most influence (i.e. structure resonant modes), thereby allowing indication of other surface acceleration frequency bands which are minimally affected by the structure and more indicative of the combustion behavior. Active control necessitates an advanced control strategy such as adaptive neural networks which we have shown can function satisfactorily even when the dynamics of the engine combustion process are unknown. A near optimal nonlinear adaptive controller using Approximate Dynamic Programming (ADP), based on a phenomenological LTC engine model is being developed. The conceived controller would reduce cyclic variability in start-of-combustion, limit pressure rise rates and control to maximize efficiency through control of heat release pattern phasing. With advanced control algorithms, low-cost sensor technologies need to be developed before robust control of auto-ignited combustion can be achieved on a production scale. Interferometer based sensors packaged in small fiber optics are being developed for the high temperature and pressure combustion chamber environment with response times on the order of microseconds. Finally, advancing the application of advanced LTC modes to enable the use of bio-fuels or hydrogen has become increasingly important for energy security. Consequently, the distinct characteristics of hydrogen combustion in engines are being investigated using advanced simulation techniques to examine more efficient and cleaner operating strategies (e.g., dual-fuel operation)

Carbon monoxide and soot emissions from liquid-fueled buoyant turbulent diffusion flames

Carbon monoxide concentrations, soot concentrations, and mixture fractions were measured in the fuel-lean (overfire) region of liquid-fueled buoyant turbulent diffusion flames burning in still air. Pool-fire configurations were studied with the liquids burning from horizontal round wicks, considering both sooting (toluene, benzene, n-heptane, and isopropanol) and nonsooting (methanol and ethanol) fuels. Flame heights and characteristic residence times also were measured, both for the turbulent flames and at the normal smoke point (for the sooting fuels). Carbon monoxide and soot generation factors (mass of CO or soot emitted per unit mass of fuel carbon burned) were uniform throughout the overfire region and were relatively independent of flame residence times (which were generally an order of magnitude longer than the normal smoke point residence times of the sooting fuels). Processes of carbon monoxide and soot emission for the nonalcohols are closely related, based on the good correlation between their emission factors: 0.37 kg CO/per kg soot with a standard deviation of 0.09. However, nonsooting methanol and ethanol/air flames still emitted low levels of CO so that there is a component of CO emissions that is not associated with soot.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29094/1/0000130.pd