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High-throughput numerical modeling of the tunable synaptic behavior in 2D MoS2 memristive devices
Memristive devices based on two-dimensional (2D) materials have emerged as potential synaptic candidates for next-generation neuromorphic computing hardware. Here, we introduce a numerical modeling framework that facilitates efficient exploration of the large parameter space for 2D memristive synaptic devices. High-throughput charge-transport simulations are performed to investigate the voltage pulse characteristics for lateral 2D memristors and synaptic device metrics are studied for different weight-update schemes. We show that the same switching mechanism can lead to fundamentally different pulse characteristics influencing not only the device metrics but also the weight-update direction. A thorough analysis of the parameter space allows simultaneous optimization of the linearity, symmetry, and drift in the synaptic behavior that are related through tradeoffs. The presented modeling framework can serve as a tool for designing 2D memristive devices in practical neuromorphic circuits by providing guidelines for materials properties, device functionality, and system performance for target applications.
SWEMniCS: a software toolbox for modeling coastal ocean circulation, storm surges, inland, and compound flooding
Flooding from storm surges, rainfall-runoff, and their interaction into compounding events are major natural hazards in coastal regions. To assess risks of damages to life and properties alike, numerical models are needed to guide emergency responses and future assessments. Numerical models, such as ADCIRC have over many decades shown their usefulness in such assessments. However, these models have a high threshold in terms of new user engagement as development and compilation is not trivial for users trained in compiled programming languages. Here, we develop a new open-source finite element solver for the numerical simulation of flooding. The numerical solution of the underlying PDEs is developed using the finite element framework FEniCSx. The goal is a framework where new methods can be rapidly tested before time-consuming development into codes like ADCIRC. We validate the framework on several test cases, including large-scale computations in the Gulf of Mexico for Hurricane Ike (2008).
Suppressing nonperturbative gauge errors in the thermodynamic limit using local pseudogenerators
With recent progress in quantum simulations of lattice-gauge theories, it is becoming a pressing question how to reliably protect the gauge symmetry that defines such models. Recently, an experimentally feasible gauge-protection scheme has been proposed that is based on the concept of a local pseudogenerator, which is required to act identically to the full gauge-symmetry generator in the target gauge sector, but not necessarily outside of it. The scheme has been analytically and numerically shown to reliably stabilize lattice gauge theories in the presence of perturbative errors on finite-size analog quantum-simulation devices. In this work, through uniform matrix product state calculations, we demonstrate the efficacy of this scheme for nonperturbative errors in analog quantum simulators up to all accessible evolution times in the thermodynamic limit, where it is a priori neither established nor expected that this scheme will succeed. Our results indicate the presence of an emergent gauge symmetry in an adjusted gauge theory even in the thermodynamic limit, which is beyond our analytic predictions. Additionally, we show through quantum circuit model calculations that gauge protection with local pseudogenerators also successfully suppresses gauge violations on finite quantum computers that discretize time through Trotterization. Our results firm up the robustness and feasibility of the local pseudogenerator as a viable tool for enforcing gauge invariance in modern quantum simulators and noisy intermediate-scale quantum devices.
Spatial evolution of traditional waterside settlements south of the Yangtze River and the distribution of settlement heritage: evidence from the Nanxi River Basin
The study of ancient settlements in the traditional waterside towns of Jiangnan is an important part of scientific research on architectural heritage. This study examines ancient settlements in the Nanxi River Basin during various historical periods, such as the Neolithic Age, Eastern Han Dynasty, Tang-Five Dynasty, Song-Yuan Dynasty, Ming Dynasty, and Qing Dynasty. It investigates their temporal and spatial evolution and the factors that influence their distribution, with a particular focus on the role of intangible cultural heritage. This study focuses on the relationship between the spatial evolution of traditional waterside settlements in the Nanxi River Basin and the distribution of intangible heritage and analyzes the driving factors of their development. How settlements changed over time and space was examined with geographic information systems (GIS) software and by using kernel density, elliptical variance, and spatial autocorrelation methods on 204 ancient settlement points. This study also employs buffer and data overlay methods to analyze the factors that affect settlement distribution by elevation, slope, water system distance, and distance to intangible cultural heritage points. The study reveals the following. (1) During the Ming and Qing Dynasties, clans, culture, and the economy drove the expansion of early settlements, which relied on water systems and flat terrain, to form a multicenter distribution. (2) The settlement distribution in the Nanxi River Basin has undergone a transformation from single-point distribution to multipoint aggregation and divergence during the evolution from the Neolithic Age to the Qing Dynasty. The overall center of gravity of the settlements shifts from south to north and east, and the overall distribution of the settlements is in a state of aggregation. (3) The spatial and temporal evolution of settlements is jointly influenced by the natural environment and cultural factors. The natural environment determines the spatial distribution of early settlements, while cultural factors promote the evolution and development of the settlement space. This study further clarifies the key role of intangible cultural heritage in the formation and development of settlements and provides a reference framework for future heritage protection policies.
Socially vulnerable communities face disproportionate exposure and susceptibility to U.S. wildfire and prescribed burn smoke
While air pollution from most U.S. sources has decreased, emissions from wildland fires have risen. Here, we use an integrated assessment model to estimate that wildfire and prescribed burn smoke caused $200 billion in health damages in 2017, associated with 20,000 premature deaths. Nearly half of this damage came from wildfires, predominantly in the West, with the remainder from prescribed burns, mostly in the Southeast. Our analysis reveals positive correlations between smoke exposure and various social vulnerability measures; however, when also considering smoke susceptibility, these disparities are systematically influenced by age. Senior citizens, who are disproportionately White, represented 16% of the population but incurred 75% of the damages. Nonetheless, within most age groups, Native American and Black communities experienced the greatest damages per capita. Our work highlights the extraordinary and disproportionate effects of the growing threat of fire smoke and calls for targeted, equitable policy solutions for a healthier future.
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