Chemical evolution of ultra-faint dwarf galaxies in the self-consistently calculated IGIMF theory

The galaxy-wide stellar initial mass function (gwIMF) of a galaxy in dependence of its metallicity and star formation rate (SFR) can be calculated by the integrated galactic IMF (IGIMF) theory. Lacchin et al. (2019) apply the IGIMF theory for the first time to study the chemical evolution of the ultra-faint dwarf (UFD) satellite galaxies and failed to reproduce the data. Here, we find that the IGIMF theory is naturally consistent with the data. We apply the time-evolving gwIMF calculated at each timestep. The number of type Ia supernova explosions per unit stellar mass formed is renormalised according to the gwIMF. The chemical evolution of Bo\"otes I, one of the best observed UFD, is calculated. Our calculation suggests a mildly bottom-light and top-light gwIMF for Bo\"otes I, and that this UFD has the same gas-consumption timescale as other dwarfs but was quenched about 0.1 Gyr after formation, being consistent with independent estimations and similar to Dragonfly 44. The recovered best fitting input parameters in this work are not covered in the work of Lacchin et al. (2019), creating the discrepancy between our conclusions. In addition, a detailed discussion of uncertainties is presented addressing how the results of chemical evolution models depend on applied assumptions. This study demonstrates the power of the IGIMF theory in understanding the star-formation in extreme environments and shows that UDFs are a promising pathway to constrain the variation of the low-mass stellar IMF.Comment: 17 pages, 16 figures, accepted for publication in A&

Reinsurance Contracting with Adverse Selection and Moral Hazard: Theory and Evidence

This dissertation includes two essays on adverse selection and moral hazard problems in reinsurance markets. The first essay builds a competitive principal-agent model that considers adverse selection and moral hazard jointly, and characterizes graphically various forms of separating Nash equilibria. In the second essay, we use panel data on U.S. property liability reinsurance for the period 1995-2000 to test for the existence of adverse selection and moral hazard. We find that (1) adverse selection is present in private passenger auto liability reinsurance market and homeowners reinsurance market, but not in product liability reinsurance market; (2) residual moral hazard does not exist in all the three largest lines of reinsurance, but is present in overall reinsurance markets; and (3) moral hazard is present in the product liability reinsurance market, but not in the other two lines of reinsurance

A survey of sustainable development of intelligent transportation system based on urban travel demand

This paper provides a comprehensive exploration of urban travel demand forecasting and its implications for intelligent transportation systems, emphasizing the crucial role of intelligent transportation systems in promoting sustainable urban development. With the increasing challenges posed by traffic congestion, environmental pollution, and diverse travel needs, accurate prediction of urban travel demand becomes essential for optimizing transportation systems, fostering sustainable travel methods, and creating opportunities for business development. However, achieving this goal involves overcoming challenges such as data collection and processing, privacy protection, and information security. To address these challenges, the paper proposes a set of strategic measures, including advancing intelligent transportation technology, integrating intelligent transportation systems with urban planning, enforcing policy guidance and market supervision, promoting sustainable travel methods, and adopting intelligent transportation technology and green energy solutions. Additionally, the study highlights the role of intelligent transportation systems in mitigating traffic congestion and environmental impact through intelligent road condition monitoring, prediction, and traffic optimization. Looking ahead, the paper foresees an increasingly pivotal role for intelligent transportation systems in the future, leveraging advancements in deep learning and information technology to more accurately collect and analyze urban travel-related data for better predictive modeling. By combining data analysis, public transportation promotion, shared travel modes, intelligent transportation technology, and green energy adoption, cities can build more efficient, environmentally friendly transportation systems, enhancing residents’ travel experiences while reducing congestion and pollution to promote sustainable urban development. Furthermore, the study anticipates that intelligent transportation systems will be intricately integrated with urban public services and management, facilitating efficient and coordinated urban functions. Ultimately, the paper envisions intelligent transportation systems playing a vital role in supporting urban traffic management and enhancing the overall well-being of urban construction and residents’ lives. In conclusion, this research not only enhances our understanding of urban travel demand forecasting and the evolving landscape of intelligent transportation systems but also provides valuable insights for future research and practical applications in related fields. The study encourages greater attention and investment from scholars and practitioners in the research and practice of intelligent transportation systems to collectively advance the progress of urban transportation and sustainable development

Sensitivity Analysis for Iceberg Geometry Shape in Ship-Iceberg Collision in View of Different Material Models

The increasing marine activities in Arctic area have brought growing interest in ship-iceberg collision study. The purpose of this paper is to study the iceberg geometry shape effect on the collision process. In order to estimate the sensitivity parameter, five different geometry iceberg models and two iceberg material models are adopted in the analysis. The FEM numerical simulation is used to predict the scenario and the related responses. The simulation results including energy dissipation and impact force are investigated and compared. It is shown that the collision process and energy dissipation are more sensitive to iceberg local shape than other factors when the elastic-plastic iceberg material model is applied. The blunt iceberg models act rigidly while the sharp ones crush easily during the simulation process. With respect to the crushable foam iceberg material model, the iceberg geometry has relatively small influence on the collision process. The spherical iceberg model shows the most rigidity for both iceberg material models and should be paid the most attention for ice-resist design for ships