Search for: All records

Abstract The recurrence of epidemic waves has been a hallmark of infectious disease outbreaks. Repeated surges in infections pose significant challenges to public health systems, yet the mechanisms that drive these waves remain insufficiently understood. Most prior models attribute epidemic waves to exogenous factors, such as transmission seasonality, viral mutations, or implementation of public health interventions. We show that epidemic waves can emerge autonomously from the feedback loop between infection dynamics and human behavior. Our results are based on a behavioral framework in which individuals continuously adjust their level of risk mitigation subject to their perceived risk of infection, which depends on information availability and disease severity. We show that delayed behavioral responses alone can lead to the emergence of multiple epidemic waves. The magnitude and frequency of these waves depend on the interplay between behavioral factors (delay, severity, and sensitivity of responses) and disease factors (transmission and recovery rates). Notably, if the response is either too prompt or excessively delayed, multiple waves cannot emerge. Our results further align with previous observations that adaptive human behavior can produce nonmonotonic final epidemic sizes, shaped by the trade-offs between various biological and behavioral factors—namely, risk sensitivity, response stringency, and disease generation time. Interestingly, we found that the minimal final epidemic size occurs on regimes that exhibit a few damped oscillations. Altogether, our results emphasize the importance of integrating social and operational factors into infectious disease models, in order to capture the joint evolution of adaptive behavioral responses and epidemic dynamics. 

Understanding the mechanical properties of three-dimensional (3D)-printed ceramics while keeping the parts intact is crucial for advancing their application in high-performance and biocompatible fields, such as biomedical and aerospace engineering. This study uses non-destructive nanoindentation techniques to investigate the mechanical performance of 3D-printed zirconia across pre-conditioned and sintered states. Vat photopolymerization-based additive manufacturing (AM) was employed to fabricate zirconia samples. The structural and mechanical properties of the printed zirconia samples were explored, focusing on hardness and elastic modulus variations influenced by printing orientation and post-processing conditions. Nanoindentation data, analyzed using the Oliver and Pharr method, provided insights into the elastic and plastic responses of the material, showing the highest hardness and elastic modulus in the 0° print orientation. The microstructural analysis, conducted via scanning electron microscopy (SEM), illustrated notable changes in grain size and porosity, emphasizing the influencing of the printing orientation and thermal treatment on material properties. This research uniquely investigates zirconia’s mechanical evolution at the nanoscale across different processing stages—pre-conditioned and sintered—using nanoindentation. Unlike prior studies, which have focused on bulk mechanical properties post-sintering, this work elucidates how nano-mechanical behavior develops throughout additive manufacturing, bridging critical knowledge gaps in material performance optimization. 

Abstract This study explores the potential of single crystal barium titanate (BTO) platelets to fabricate nontoxic ceramics with enhanced material properties through texturization of grain structure. The proposed methodology relies on direct ink write additive manufacturing to enable grain‐oriented growth of BTO ceramics by utilizing a combination of spherical and platelet‐shaped particles. The use of platelet‐shaped particles in the ceramic ink guides particle alignment parallel to the build plate due to shear forces at the nozzle during the printing process. While platelet contents ranging from 0 to 40 wt.% showed a decrease in density as the content increased, experimental data revealed an incremental trend between platelet content, dielectric properties, and the degree of alignment of the particles on the F200 crystal plane, achieving a maximum texturized orientation of 65%. Such orientation resulted in 29.55% improved dielectric properties compared with randomly oriented BTO ceramic. The findings of this research validate the effectiveness of additive manufacturing technologies to tailor the microstructural characteristics of ceramics for specific functional applications. 

The accurate soil frost depth measurement is critical for understanding freeze–thaw cycles and their impact on infrastructure stability, agricultural productivity, and ecosystem dynamics. This study introduces a novel pressure-based sensor integrated with wireless sensor networks (WSNs) to monitor frost depth in real time, offering a significant advancement over traditional manual frost tube methods. By leveraging the expansion of water upon freezing, the sensor detects pressure changes and transmits high-resolution data through a low-power, long-range (LoRa) wireless network. Field experiments demonstrated a strong correlation between the pressure sensor and manual frost tube measurements, with Pearson and Spearman correlation coefficients of 0.80 and 0.78, respectively, validating the sensor’s accuracy. The high temporal resolution of the system, which captures data at 5-min intervals, enabled a detailed analysis of freeze–thaw cycles, revealing rapid changes in frost depth during the early thaw periods. Designed for resilience in harsh winter conditions, the sensor offers a scalable, low-maintenance solution for long-term remote frost monitoring. These results underscore the system’s potential to enhance environmental monitoring, optimize agricultural practices, and mitigate infrastructure risks in response to changing climate conditions. 

Recently, the manufacturing of porous polydimethylsiloxane (PDMS) with engineered porosity has gained considerable interest due to its tunable material properties and diverse applications. An innovative approach to control the porosity of PDMS is to use transient liquid phase water to improve its mechanical properties, which has been explored in this work. Adjusting the ratios of deionized water to the PDMS precursor during blending and subsequent curing processes allows for controlled porosity, yielding water emulsion foam with tailored properties. The PDMS-to-water weight ratios were engineered ranging from 100:0 to 10:90, with the 65:35 specimen exhibiting the best mechanical properties with a Young’s Modulus of 1.17 MPa, energy absorption of 0.33 MPa, and compressive strength of 3.50 MPa. This led to a porous sample exhibiting a 31.46% increase in the modulus of elasticity over a bulk PDMS sample. Dowsil SE 1700 was then added, improving the storage capabilities of the precursor. The optimal storage temperature was probed, with −60 °C resulting in great pore stability throughout a three-week duration. The possibility of using these water emulsion foams for paste extrusion additive manufacturing (AM) was also analyzed by implementing a rheological modifier, fumed silica. Fumed silica’s impact on viscosity was examined, revealing that 9 wt% of silica demonstrates optimal rheological behaviors for AM, bearing a viscosity of 10,290 Pa·s while demonstrating shear-thinning and thixotropic behavior. This study suggests that water can be used as pore-formers for PDMS in conjunction with AM to produce engineered materials and structures for aerospace, medical, and defense industries as sensors, microfluidic devices, and lightweight structures.