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Book Review of Re-membering Culture: Erasure and Renewal in Hmong American Education
No full textRe-membering Culture: Erasure and Renewal in Hmong American Education is a valuable contribution to the growing field of critical Hmong studies and education studies in general. This ethnographic study critically examines power dynamics between U.S. schools and Hmong Americans by centering narratives that highlight Hmong knowledge systems. The book provides insights from over 50 Hmong American leaders, parents, students, and district staff (Hmong and non-Hmong) that exemplifies re-membering, the recovery of culture and history to reclaim rights, space, and voice in the present. Although education is often seen as the great equalizer, especially for immigrants and refugees, the realities of persistent racial equity gaps among Hmong Americans challenge this liberal narrative on schooling. The author offers a nuanced analysis of how schools contribute to the erasure of Hmong culture and identity. The book provides examples of how the Hmong community has refused hegemonic logic and re- claimed their culture and identity to dismantle the assumption that Western schools are designed for all students to succeed
Enhancing High Cycle Fatigue Perfomance Of Electron Beam Melted Ti6Al4V: A Study On Shot Peening And Hot Isostatic Pressing
No full textThe qualification of electron beam powder bed fusion (PBF-EB) for safety-critical applications is hindered by variability in high cycle fatigue performance, largely due to surface roughness and internal defects. While Hot Isostatic Pressing (HIP) effectively reduces internal porosity, it does not address surface-initiated fatigue failures. This study investigated the combined effects of HIP and shot peening on enhancing the fatigue performance of PBF-EB Ti6Al4V. Over 50 specimens, including both vertical and horizontal build orientations, underwent high cycle fatigue testing per ASTM E466. X-Ray computed tomography confirmed decrease in defect distribution following HIP, while shot peening resulted in a more uniform surface. Combined HIP and shot peening led to a 100 MPa increase in fatigue compared to machined samples by introducing compressive residual stresses and delaying crack initiation. This study highlights the necessity of integrating combined post-processing strategies in extending the fatigue life of PBF-EB Ti6Al4
Influence On Shot Peening And Blast Polishing For Rotating Bending Fatigue Strength Of Vacuum Carburized Steel With Circumferential Notch
No full textIn order to improve fuel efficiency in automobiles, weight reduction is necessary as well as improving engine efficiency. For transmission gears, thickness reduction is necessary for weight reduction. When the thickness is reduced, the cross-sectional area becomes smaller, and the load stress increases. Therefore, higher fatigue strength is required. Most gears carry out carburizing. Shot peening is often used to improve the fatigue strength of carburized heat-treated parts. After shot peening, compressive residual stress is introduced, but at the same time, surface roughness is increased. Therefore, the processing conditions of shot peening are very important. Blast polishing is a processing method in which resin media containing abrasive grains is sprayed at the workpiece. Compared to other polishing methods, the processing time is short. In addition, it is easy to apply to complex shapes.
In this study, shot peening and blast grinding were carry out on circumferential notch specimens to improve the fatigue strength of vacuum carburized materials commonly used in automotive transmission gears.
As a result, the fatigue limit of test pieces applied with double shot peening improved by 81% compared to unprocessed specimens, blast polished specimens which are carry out double shot peening achieved a 100% improvement in fatigue limit compared to unprocessed specimens. This is due to compressive residual stress and low surface roughness
Comparison Of Anti-Fouling Performance Of Textured Glass Surface Fabricated By Ductile-Mode Peening And Precision Grinding
No full textRecently, there has been a growing demand for precision processing glass. In addition to dimensional accuracy, surface texturing to impart functional properties has attracted increasing attention. For example, anti-fouling performance against powder adhesion is required for cover glasses of solar cells. Powder adhesion is governed by van der Waals forces, which depend on the surface texture of the substrate, suggesting that surface structures influence adhesion behavior. Our previous study demonstrated that angled fine particle peening (FPP) could fabricate a nanoscale fine texture on glass surfaces through ductile-mode peening—glass processing without brittle fracture. In this study, the effect of surface texturing by angled-FPP on anti-fouling performance was evaluated and compared to other surface texturing methods: the electrolytic in-process dressing (ELID) grinding that can fabricate a precise structure according to the copying principle. Results from powder adhesion tests and microscopic observations revealed that both processed surfaces exhibited better anti-fouling properties, with less powder residue compared to unprocessed surfaces
Biochar-amended engineered cementitious composites
No full textThis study investigates the incorporation of biochar as a sustainable cement replacement in high-strength ECC, focusing on mechanical properties, durability, microstructural characteristics, and environmental impacts. Biochar was added at 5%, 10%, 20%, and 30% replacement levels by cement weight, and its effects were assessed through compressive and tensile strength tests, TGA, SEM, and LCA. Results showed that biochar-enhanced ECC achieved 28-day compressive strengths of 95.4–99.6 MPa, with a peak tensile strength of 8.58 MPa at 20% biochar content, though higher dosages reduced strain capacity. TGA confirmed increased pozzolanic activity with reduced portlandite content, while SEM images revealed a denser ITZ at 5–10% biochar, enhancing fiber-matrix bonding. Although higher biochar levels increased water sorptivity and gas permeability, drying shrinkage was reduced by up to 24%. LCA results indicated an 80% reduction in carbon emissions, with biochar sequestering 2.0 kg CO₂-eq per kg. These findings highlight biochar-amended ECC as a promising solution for sustainable construction, balancing mechanical performance and environmental benefits
Enhancing the post-crack tensile strain capacity of Metakaolin- Portland Limestone Cement blend by using Carbon Nanotubes
No full textIncorporating metakaolin (MK) into cementitious materials is known to enhance strength and stiffness, however, this yields a relatively brittle material with a significant loss of the ultimate strain capacity. To compensate for the loss in ductility, well-dispersed carbon nanotubes (CNTs) are incorporated in MK-Portland Limestone Cement (PLC) mortar to reinforce the Interfacial Transition Zone (ITZ) which is crucial for controlling the crack formation and propagation. Nanoscale imaging and mechanical property mapping at the ITZ between the nanomodified MK-PLC matrix and aggregates revealed that the local nanostructure and morphology of the ITZ were modified, resulting in an increase in the modulus of elasticity by 35.1%. Results of the three-point bending test on the notched beam specimens indicated a 1.5× higher tensile load-carrying capacity and an enhanced strain energy absorption capacity of the CNT-reinforced MK-PLC mortar compared to the MK-PLC mortar at both the pre-crack/elastic and post-crack stages of deformation
The role of Graphene-based nanomaterials in enhancing Resiliency and Ductility in Engineered Concrete
No full textGraphene-based nanomaterials have gained significant attention for enhancing cement matrices due to their exceptional surface area and remarkable mechanical, physical, and chemical properties. These characteristics make them ideal candidates for improving the overall performance of engineered cementitious materials. This study focuses on accelerating the carbonation kinetics within nanostructured interfaces of cement systems by incorporating 2D graphene-based nanomaterials. Exfoliated graphene nanoplatelets (GNPs), with a surface area 3-5 times greater than that of cement grains, were used. Experimental results revealed that concrete reinforced with exfoliated, few-layer GNPs demonstrated 1.5 times higher carbonation uptake and mineralization capacity. Additionally, quantitative nanomechanical property mapping highlighted a 50-80% increase in nanoscale modulus of elasticity and elastic strain energy absorption in carbonated nanostructured interfaces compared to concrete without the reinforcement. These improvements in carbonation kinetics and mechanical properties suggest enhanced durability and strength, as well as increased resiliency in the carbonated concrete. The study illustrates how the incorporation of carbon-based nanomaterials can significantly improve both the performance and long-term serviceability of engineered concrete
Effect of chemical additives on performance of low-clinker 3D printing mortar
No full textThe study investigates the effect of three chemical accelerators, nano-C-S-H solution agent (NCSH), organic composite accelerator (OC), and an aluminum sulfate-based accelerator (FA), on the performance of low-clinker 3D printing mortar. The mixture with 80% clinker replacement, consisting of 20% cement, 40% limestone filler, and 40% slag was set. Using 2% OC significantly enhanced the compressive strength, increasing 3- and 28-day compressive strength by 47% and 18%, respectively, compared to ref. mixture. Adding 2% OC can accelerate setting time by 35%, compared to the ref mixture. The OC-type accelerator was recommended for low-clinker 3D printing mixture
Additive Manufacturing of Ultra-High-Performance Concrete: From Mechanical Characterization to Large-Scale Application
No full textIn this work, extensive experimental investigations were conducted on 3D printable Ultra-High-Performance Concrete (UHPC) at multiple scales. Initially, nanomodification techniques were employed to transform the self-leveling nature of UHPC into a more viscous mix using nanomaterials such as nano clay, which showed no detrimental effects on the mechanical performance of cast samples tested under uniaxial compression, split tension, and notched three-point bending. The developed mix then underwent a comprehensive experimental program to evaluate its rheological performance and was subsequently tested using various 3D printing systems featuring different automation setups, extrusion mechanisms, pumps, and nozzle configurations. To assess mechanical performance without compromising the integrity of printed features, novel surface preparation techniques were introduced, unlike conventional approaches that typically involve cutting or coring printed elements. Additionally, innovative interlayer enhancement methods were implemented to mitigate the anisotropic behavior characteristic of layered structures. Large-scale experiments were also conducted on two-way 3D printed laminated slabs with varying layer orientations. The results revealed that printability is not solely a material property but also a process-dependent characteristic. The novel capping method provided optimal conditions for mechanical testing while preserving the integrity of printed features. Furthermore, the proposed interlayer enhancement techniques significantly improved interlayer bonding and effectively prevented failure at the interfaces. Overall, the laminated 3D printed slabs exhibited excellent mechanical performance, outperforming their traditionally cast counterparts
Assessing the Synergistic Role of Nanosilica in the Performance of Concrete with Natural Pozzolans
No full textWith the diminishing availability of traditional supplementary cementitious materials, alternative options such as natural pozzolans (NPs) are emerging as promising alternatives. While NPs can significantly enhance the durability of concrete, their use often results in reduced early-age strength. Existing technical literature shows that when used in concrete, nanosilica (nS) provides nucleation sites for deposition of the hydrates, thus accelerating the hydration process and enhancing early-age strength development. Consequently, combining nS with NPs offers a promising, yet largely unexplored, pathway toward more sustainable and practical solutions for concrete construction. This study evaluates the combined effects of using NPs and nS in portland cement concrete for pavement applications. Two types of nS and three NPs (one calcined clay and two of volcanic ashes) were used. Concrete mixtures were prepared both with and without nS, incorporating NPs as a 25% weight replacement for cement. All concrete mixtures were evaluated for fresh properties, early and long-term compressive strength, and durability characteristics, including rate of water absorption, formation factor, and parameters of the air void system in hardened concrete. Additionally, pastes with the same compositions as those in corresponding concrete mixtures were subjected thermogravimetric (TG) analysis to quantify the calcium hydroxide content, providing insight into the extent of the pozzolanic reaction. The presentation will showcase both the benefits and challenges associated with the combined use of nS and NPs in concrete, offering insights related to performance and practical applications