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  1. Additively manufactured thermoplastic polymers, such as polylactic acid (PLA), hold significant promise for sustainable engineering structures, including wind turbine blades. Upscaling these structures beyond the limitations of 3D printer build volumes is a challenge; fusion joining presents a potential solution. This paper introduces a displacement-controlled resistance welding process for PLA, as an alternative to the typical force controlled methods. We investigated the bonding quality of resistance-welded and adhesive-bonded PLA beams through three-point bending and measured the surface deformations using digital image correlation. Different metal meshes (30 %/0.11 mm Ni–Cu, 34 %/0.07 mm Ni–Cu, and 36 %/0.25 mm Co–Ni) served as heating elements. The process parameters were varied for the 34 %/0.07 mm Ni–Cu mesh to identify an optimum set of parameters. Results showed that this optimized displacement-controlled welding achieved 94 % of the original strength of monolithic samples. This indicates that the new welding process not only ensures high quality bonding and fine surface finishing but also promotes sustainability, recyclability, and economic efficiency in various polymer and composite structural applications. 
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    Free, publicly-accessible full text available July 1, 2025
  2. Strong, tough, and lightweight composites are increasingly needed for diverse applications, from wind turbines to cars and aircraft. These composites typically contain sheets of strong and high-modulus fibers in a matrix that are joined with other materials to resist fracture. Coupling these dissimilar materials together is challenging to enhance delamination properties at their interface. We herein investigate using a trace amount of carbon nanotube sheets to improve the coupling between composite skins and core in a composite sandwich. Ultra-thin (~100 nm) forest-drawn multi-walled carbon nanotube (MWNT) sheets are interleaved within the skin/core interphase, with MWNTs aligned in the longitudinal direction. The mechanical behavior is characterized by end notched flexural testing (ENF). With two MWNT sheets placed in the skin/core interphase, the following performance enhancements are achieved: 36.8 % increase in flexural strength; 127.3 % and 125.7 % increases in mode I & II fracture toughness values, respectively; and 152.8 % increase in interfacial shear strength (IFSS). These are achieved with negligible weight gain of the composite sandwich (0.084 wt% increase over the baseline sandwich without MWNT sheets). The finite element simulation results show that MWNT sheets enhance the skin/core coupling by reducing stress concentration, enabling the transition from catastrophic brittle failure to a stable ductile failure mode. The MWNT sheets interleaved sandwich composites are thus demonstrated to be stronger and tougher while providing electrical conductivity (4.3 × 104 S/m) at the skin/core interface for potential de-icing, electromagnetic interference shielding, and structural health monitoring. 
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    Free, publicly-accessible full text available July 1, 2025
  3. We describe an inertial rotation sensor with a 30-cm cylindrical proof-mass suspended from a pair of 14 μm thick BeCu flexures. The angle between the proof-mass and support structure is measured with a pair of homodyne interferometers, which achieve a noise level of ∼5prad/Hz. The sensor is entirely made of vacuum compatible materials, and the center of mass can be adjusted remotely.

     
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  4. The COVID-19 pandemic has underscored the importance of research and development in maintaining public health. Facing unprecedented challenges, the scientific community developed antiviral drugs, virucides, and vaccines to combat the infection within the past two years. However, an ever-increasing list of highly infectious SARS-CoV-2 variants (gamma, delta, omicron, and now ba.2 stealth) has exacerbated the problem: again raising the issues of infection prevention strategies and the efficacy of personal protective equipment (PPE). Against this backdrop, we report an antimicrobial fabric for PPE applications. We have fabricated a nanofibrous silk-PEO material using electrospinning followed by zinc oxide thin film deposition by employing the atomic layer deposition technique. The composite fabric has shown 85% more antibacterial activity than the control fabric and was found to possess substantial superoxide dismutase–mimetic activity. The composite was further subjected to antiviral testing using two different respiratory tract viruses: coronavirus (OC43: enveloped) and rhinovirus (RV14: non-enveloped). We report a 95% reduction in infectious virus for both OC43 and RV14 from an initial load of ∼1 × 10 5 (sample size: 6 mm dia. disk), after 1 h of white light illumination. Furthermore, with 2 h of illumination, ∼99% reduction in viral infectivity was observed for RV14. High activity in a relatively small area of fabric (3.5 × 10 3 viral units per mm 2 ) makes this antiviral fabric ideal for application in masks/PPE, with an enhanced ability to prevent antimicrobial infection overall. 
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  5. In 2019/2020, Australia experienced its largest wildfire season on record. Smoke covered hundreds of square kilometers across the southeastern coast and reached the site of the 2020 COALA (Characterizing Organics and Aerosol Loading over Australia) field campaign in New South Wales. Using a subset of nighttime observations made by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), we calculate emission ratios (ERs) and factors (EFs) for 21 volatile organic compounds (VOCs). We restrict our analysis to VOCs with sufficiently high lifetimes to be minimally impacted by oxidation over the ~8 h between when the smoke was emitted and when it arrived at the field site. We use oxidized VOC to VOC ratios to assess the total amount of radical oxidation: maleic anhydride/furan to assess OH oxidation, and (cis-2-butenediol + furanone)/furan to assess NO3 oxidation. We compare ERs calculated from the freshest portion of the plume to ERs calculated using the entire nighttime period. Finding good agreement between the two, we are able to extend our analysis to VOCs measured in more chemically aged portions of the plume. Our analysis provides ERs and EFs for 9 compounds not previously reported for temperate forests in Australia: acrolein, pentanones/methylbutanal, methyl propanoate, methyl methacrylate, propene, maleic anhydride, benzaldehyde, methyl guaiacol, and methylbenzoic acid. We compare our results with two studies in similar Australian biomes, and two studies focused on US temperate forests. We find mixed agreement for EFs presented from previous studies of Australian wildfires, and generally good agreement with studies focused on fires in the Western US. This suggests that comprehensive field measurements of biomass burning VOC emissions in other regions may be applicable to Australian temperate forests. 
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  6. The objective of this paper is to outline the details of a recently-funded National Science Foundation (NSF) Advanced Technological Education (ATE) project that aims to educate and enable the current and future manufacturing workforce to operate in an Industry 4.0 environment. Additionally, the startup procedures involved, the major ongoing activities during year-one, and preliminary impressions and lessons learned will be elaborated as well. Industry 4.0 refers to the ongoing reformation of advanced manufacturing (Operation Technologies - OT) enabled by advances in automation/data (Information Technologies - IT). Cyber-enabled smart manufacturing is a multidisciplinary approach that integrates the manufacturing process, its monitoring/control, data science, cyber-physical systems, and cloud computing to drive manufacturing operations. This is further propelled by the dissolution of boundaries separating IT and OT, presenting optimization opportunities not just at a machine-level, but at the plant/enterprise-levels. This so-called fourth industrial revolution is rapidly percolating the discrete and continuous manufacturing industry. It is therefore critical for the current and future US workforce to be cognizant and capable of such interdisciplinary domain knowledge and skills. To meet this workforce need, this project will develop curricula, personnel and communities in cyber-enabled smart manufacturing. The key project components will include: (i) Curriculum Road-Mapping and Implementation – one that integrates IT and OT to broaden the educational experience and employability via road-mapping workshops, and then to develop/implement curricula, (ii) Interdisciplinary Learning Experiences – through collaborative special-projects courses, industry internships and research experiences, (iii) Pathways to Industry 4.0 Careers – to streamline career pathways to enter Industry 4.0 careers, and to pursue further education, and (iv) Faculty Development – continuous improvement via professional development workshops and faculty development leaves. It is expected that this project will help define and chart-out the capabilities demanded from the next-generation workforce to fulfill the call of Industry 4.0, and the curricular ingredients necessary to train and empower them. This will help create an empowered workforce well-suited for Industry 4.0 careers in cyber-enabled smart manufacturing. The collaborative research team’s experience so far in starting up and establishing the project has further shed light on some of the essentials and practicalities needed for achieving the grand vision of enabling the manufacturing workforce for the future. Altogether, the experience and lessons learned during the year-one implementation has provided a better perception of what is needed for imparting a broader impact through this project. 
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  7. The objective of this paper is to outline the details of a recently-funded National Science Foundation (NSF) Advanced Technological Education (ATE) project that aims to educate and enable the current and future manufacturing workforce to operate in an Industry 4.0 environment. Additionally, the startup procedures involved, the major ongoing activities during year-one, and preliminary impressions and lessons learned will be elaborated as well. Industry 4.0 refers to the ongoing reformation of advanced manufacturing (Operation Technologies - OT) enabled by advances in automation/data (Information Technologies - IT). Cyber-enabled smart manufacturing is a multidisciplinary approach that integrates the manufacturing process, its monitoring/control, data science, cyber-physical systems, and cloud computing to drive manufacturing operations. This is further propelled by the dissolution of boundaries separating IT and OT, presenting optimization opportunities not just at a machine-level, but at the plant/enterprise-levels. This so-called fourth industrial revolution is rapidly percolating the discrete and continuous manufacturing industry. It is therefore critical for the current and future US workforce to be cognizant and capable of such interdisciplinary domain knowledge and skills. To meet this workforce need, this project will develop curricula, personnel and communities in cyber-enabled smart manufacturing. The key project components will include: (i) Curriculum Road-Mapping and Implementation – one that integrates IT and OT to broaden the educational experience and employability via road-mapping workshops, and then to develop/implement curricula, (ii) Interdisciplinary Learning Experiences – through collaborative special-projects courses, industry internships and research experiences, (iii) Pathways to Industry 4.0 Careers – to streamline career pathways to enter Industry 4.0 careers, and to pursue further education, and (iv) Faculty Development – continuous improvement via professional development workshops and faculty development leaves. It is expected that this project will help define and chart-out the capabilities demanded from the next-generation workforce to fulfill the call of Industry 4.0, and the curricular ingredients necessary to train and empower them. This will help create an empowered workforce well-suited for Industry 4.0 careers in cyber-enabled smart manufacturing. The collaborative research team’s experience so far in starting up and establishing the project has further shed light on some of the essentials and practicalities needed for achieving the grand vision of enabling the manufacturing workforce for the future. Altogether, the experience and lessons learned during the year-one implementation has provided a better perception of what is needed for imparting a broader impact through this project. 
    more » « less