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  1. Free, publicly-accessible full text available September 28, 2022
  2. Resin uptake plays a critical role in the stiffness-to-weight ratio of wind turbine blades in which sandwich composites are used extensively. This work examines the flexural properties of nominally half-inch thick sandwich composites made with polyvinyl chloride (PVC) foam cores (H60 and H80; PSC and GPC) at several resin uptakes. We found that the specific flexural strength and modulus for the H80 GPC sandwich composites increase from 82.04 to 90.70 kN  m/kg and 6.03 to 7.13 MN  m/kg, respectively, with 11.0% resin uptake reduction, which stands out among the four core sandwich composites. Considering reaching a high stiffness-to-weightmore »ratio while preventing resin starvation, 32% to 38% and 40% to 45% resin uptakes are adequate ranges for the H80 PSC and GPC sandwich composites, respectively. The H60 GPC sandwich composites have lower debonding toughness than H60 PSC due to stress concentration in the smooth side skin-core interphase region. The ailure mode of the sandwich composites depends on the core stiffness and surface texture. The H60 GPC sandwich composites exhibit core shearing and bottom skincore debonding failure, while the H80 GPC and PSC sandwich composites show top skin cracking and core crushing failure. The findings indicate that an appropriate range of resin uptake exists for each type of core sandwich composite, and that within the range, a low-resin uptake leads to lighter blades and thus lower cyclic gravitational loads, beneficial for long blades.« less
  3. 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 themore »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.« less
  4. 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,more »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.« less
  5. 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,more »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.« less
  6. Free, publicly-accessible full text available May 1, 2023
  7. Free, publicly-accessible full text available April 1, 2023
  8. Abstract We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC–2020 March 27 17:00 UTC). We conduct two independent searches: a generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds nomore »evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate.« less
    Free, publicly-accessible full text available April 1, 2023
  9. Free, publicly-accessible full text available March 1, 2023
  10. Intermediate-mass black holes (IMBHs) span the approximate mass range 100−10 5   M ⊙ , between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150  M ⊙ providing direct evidencemore »of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200  M ⊙ and effective aligned spin 0.8 at 0.056 Gpc −3 yr −1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc −3 yr −1 .« less
    Free, publicly-accessible full text available March 1, 2023