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Automatic segmentation of spinal cord lesions in MS: A robust tool for axial T2-weighted MRI scans
No full textReactive extrusion recycling of polymethyl methacrylate to methyl methacrylate and methacrylic acid
Get PDFABSTRACT: The global production of polymethyl methacrylate (PMMA) reached 4 million tonnes annually, yet only 10% of PMMA, primarily post-industrial scraps, is recycled. Recycling end-of-life PMMA, which often contains additives or composite components, poses challenges in achieving crude methyl methacrylate (MMA) monomer with comparable purity to post-industrial scraps. Hydrolyzing end-of-life PMMA presents a viable alternative to produce methacrylic acid (MAA) and simplifies the purification process of crude MMA. However, current PMMA hydrolysis is limited to lab-scale and batch operations in fluidized/fixed beds and stirred tank reactors. In this study, we demonstrate a pilot-scale, two-stage reactive hydrolysis extrusion system for the continuous conversion of injection- and extrusion-grade PMMA scraps into MMA and/or MAA at 330 ◦C to 370 ◦C. Residence time distribution (RTD) tests characterized the hydrodynamics of the screw configuration for PMMA extrusion, revealing that lower screw speed and feeding rate increase reaction time. A Plackett-Burman design identified temperature and catalyst type as significant factors for MMA hydrolysis. Under optimized conditions, hydrolysis extrusion without any catalysts achieved the highest MMA yield of 89% and 96% PMMA conversion. Hydrolysis extrusion with 10% H-type zeolite Y with an SiO2/Al2O3 ratio of 80 at 370 ◦C resulted in a 5.3% MAA yield, a 67% MMA yield, and near-complete PMMA conversion. Liquid acid catalysts directly hydrolyzed PMMA to poly(MMA-co-MAA) copolymer and/or PMAA, followed by dehydration of two adjacent acid groups to form six-member glutaric anhydride. KOH solution hydrolyzed PMMA to poly(MMA-co-MAA) and/or PMAA potassium salt
Access Inequality in LEO Satellite Networks: A Case Study of High-Latitude Coverage in Northern Québec
Get PDFABSTRACT: Low Earth orbit (LEO) satellite networks play a crucial role in bridging the digital divide, particularly in remote and high-latitude regions. However, access inequality remains a significant challenge, limiting broadband connectivity for communities in northern areas compared to mid-latitude urban regions. This study reviews recent advancements in non-terrestrial networks (NTNs). We conduct a detailed analysis of coverage disparities in LEO satellite networks considering LEO networks, namely Starlink, Telesat-like, Kuiper-like, and OneWeb, with a specific focus on Québec, Canada versus urban centers in New York City, USA. Our findings highlight a significant disparity in the number of visible satellites resulting in increased transmission delays and reduced network reliability in high-latitude regions. Additionally, we observe that higher elevation angles, more accessible in mid-latitude regions especially for Starlink and Kuiper, contribute to superior signal quality and transmission rates. To mitigate this gap, we propose an inter-constellation/orbit roaming mechanism that enables ground users to be served by different LEO constellations—leveraging OneWeb’s and Telesat’s strong polar coverage along with the high satellite density of Starlink and Kuiper at mid-latitudes. Jointly, terrestrial network (TN) expansion can enhance signal quality and transmission efficiency, particularly in underserved areas where NTNs act as edge computing and backhaul infrastructures. Additionally, the associated challenges—such as roaming handovers, and radio resource and network slicing management are discussed in detail, where designing a unified management and control entity to ensure seamless interoperability is not a trivial task. Furthermore, we envision wireless power transfer through either relay-based (ground-to-satellite-to-ground) or direct (satellite-to-ground) power beaming as a sustainable approach to energize TN components in remote regions. These strategies collectively support the scalability and resilience of NTNs in bridging the global access inequality
Numerical Study of the Influence of Weber and Reynolds Numbers on Global Wave Shapes Before Impact
No full textPredictive equations for rotation and sliding of shallow footings under seismic loads using Bayesian regression and ANN
Get PDFABSTRACT: Accurate estimation of footing movement is essential for evaluating its contribution to story drift, which is a critical metric for seismic design. For this reason, this study develops predictive equations to estimate the rotation and sliding of shallow foundations under the combination of seismic and gravity loads. Archetype low-rise concentrically braced frame buildings with shallow footings are designed for Vancouver, Canada, and are modeled using OpenSees. Uncertainty in demand and capacity of the buildings is considered using incremental Latin hypercube sampling (iLHS). A range of footing sizes, from small foundations designed per the US code to larger capacity-protected (CP) footings following the Canadian code, are analyzed to ensure comprehensive coverage of footing size for deriving reliable equations. Two soil sites are considered to account for varying soil conditions. Bayesian regression is used to develop reliable equations for footing rotation and sliding. An artificial neural network (ANN) model further improves prediction accuracy by incorporating complex variable combinations beyond Bayesian regression. Both new approaches are compared to the guidance in the commentary of CSA A23.3, as there is little guidance in the US and other international standards. This study concludes that both current guidance and the proposed new equations accurately estimate footing rotation for CP footings when sliding is minimal. However, the existing guidance tends to underestimate the rotation of smaller footings and does not adequately estimate the footing movement when significant sliding occurs. Therefore, the equations developed here are recommended for a more accurate estimate of footing movement under seismic load
Magnetic nanoparticles for single-neuron manipulation to design a customized neural circuit
No full textechoGAN: Extending the field of view in Transthoracic Echocardiography through conditional GAN-based outpaintin
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