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Atomistic Simulations of Short-range Ordering with Light Interstitials in Inconel Superalloys
No full textThis study employed hybrid Monte Carlo Molecular Dynamics simulations to investigate the short-range ordering behavior of Ni-based superalloys doped with boron or carbon. The simulations revealed that both boron and carbon dissociated from their host Ti atoms to achieve energetically favored ordering with Cr, Mo, and Nb. Boron clusters formed as B2, surrounded by Mo, Nb, and Cr, while carbon preferentially clustered with Cr to form a Cr23C6 local motif and with Nb to form Nb2C. Distinct preferences for interstitial sites were observed, with boron favoring tetrahedral sites and carbon occupying octahedral sites. In the presence of a vacancy, B2 shifted from the tetrahedral site to the vacancy, where it remained coordinated with Mo, Nb, and Cr. Similarly, carbon utilized vacancies to form Nb2C clusters. Excess energy calculations showed that B and C exhibited strong thermodynamic stability within their short-range ordered configurations. However, under Ti-rich conditions, C was more likely to segregate into TiC, despite preexisting ordering with Cr. This shift in stability suggests that increased Ti availability would alter carbide formation pathways, drawing C away from Cr-rich networks and promoting the development of TiC. Such redistribution may disrupt the continuity of Cr-based carbide networks, which play a critical role in stabilizing grain boundaries and impeding crack propagation. These effects further underscore the impact of interstitial-induced ordering on phase stability and microstructural evolution. This work provides an atomistic perspective on how boron- and carbon-induced ordering influences microstructure and mechanical properties. These findings highlight the critical role of interstitial-induced short-range ordering and demonstrate that this mechanism can be leveraged as a design principle to fine-tune alloy microstructures for specific engineering applications.
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Preliminary investigation of planar Sun-Ceres trajectories in variable restricted dynamical models
No full textExcerpt: The dwarf planet Ceres is the largest body in the Asteroid Belt and represents a key destination for planetary science missions seeking to understand the evolution of small bodies. Due to its location on the boundary between the inner and outer planets of the Solar System, Ceres could become a lucrative base camp location for asteroid mining and surveying operations, or a way-station for outer planet missions. This paper, for the first time in literature, presents 93 unique planar periodic and quasi-periodic orbits discovered in the Sun-Ceres system that may be employed for Ceres-focused missions. The Circular Restricted Three-Body Problem (CR3BP) and Circular Restricted N-Body Problem (CRNBP) are used as the primary dynamical models for orbit generation
Creating Effective Response Communications
No full textThis chapter synopsizes several emergency response communication approaches and strategies from government and private sector emergency management practitioners. Many of the suggestions come from lessons learned in the aftermath of major disasters. The first step is understanding the scope of emergency response communications, which includes four strategic communication elements: stakeholders, organizational leadership, planning, and situational awareness. The second step is an awareness of the systemic structures of response communications, which are characterized by communications planning, information coming in, information going out, messengers, staffing, training and exercise, and monitoring, updating, and adapting. Finally, the chapter describes the important aspects of social media in planning emergency response communications and developments with social media
Atomistic mechanisms of oxidation and chlorine corrosion in Ni-based superalloys: The role of boron and light interstitial segregation
No full textHybrid Monte Carlo and molecular dynamics simulations were used to investigate the interaction of light interstitials in multi-element Ni-based alloys. We show that light interstitials such as boron and oxygen fundamentally alter interfacial chemistry by reshaping alloy-element distribution and segregation. Oxygen adsorption drove boron migration from the grain boundary to the free surface, where it co-enriched with Cr, Fe, and Mo and formed BO3 trigonal motifs embedded within mixed-metal oxide networks. Oxygen also promoted M-O-M chain formation, including Nb2O5 clusters at the free surface. In the absence of oxygen, boron segregated to the grain boundary, altering local metal chemistry and underscoring a dynamic, environment-sensitive behavior. Following chlorine exposure, the oxidized surfaces retained strong O-mediated connectivity while forming new Cl-M associations, particularly with Nb and Cr, and exhibited further surface enrichment in Cr, Fe, and Mo. High-temperature MD simulations revealed a dynamic tug-of-war: chlorine exerted upward pull and disrupted weakly anchored sites, while Nb- and BO3-rich oxide motifs resisted deformation. A new stabilization mechanism was identified in which subsurface boron atoms anchored overlying Cr centers, suppressing their mobility and mitigating chlorine-driven displacement. These results demonstrate boron\u27s dual role as a modifier of alloy-element segregation and a stabilizer of oxide networks, and identify Nb as a key element in reinforcing cohesion under halogen attack. More broadly, this study highlights the need to track light interstitial cross-talk and solute migration under reactive conditions, offering atomistic criteria for designing corrosion-resistant surface chemistries in Ni-based superalloys exposed to halogenated or oxidative environments
Model validation levels: an automatable framework for model validation
No full textThis paper presents a detailed mathematical framework for computing a Model Validation Level (MVL), a metric for quantifying the amount of trust that can be placed in the results of a model. The framework is founded in three key pillars of validation: fidelity, referent authority, and scope. Each of these three pillars can be quantified to enable an objective and automatable comparison between model results and referent data. Combined, these pillars result in an MVL between zero and nine for the model that quickly communicates the model’s validity for a given intended use case. Additionally, the framework provides opportunities for identifying areas of model improvement to increase trust. The paper presents analysis on several metrics, demonstrating results for a variety of possible validation scenarios. Ultimately, the MVL framework provides an objective methodology for automating validation, enabling models to be quickly evaluated for trust in the ongoing digital transformation
Interface and Mechanical Properties of 1D and 1D-2D Carbon Nanomaterials in Copper Matrix
No full textLow-dimensional carbon nanomaterials have unique electron density distributions which warrant their classification as 1D and 2D, and they are useful for a wide variety of nanocomposite applications. This group includes 1D carbyne, which has high stiffness, and a 1D-2D hybrid composed of carbyne and a highly elastic cyclo[18]carbon ring (2D). We use density functional theory and molecular dynamics methods to study the interface properties of carbyne and the hybrid on Cu (111) surface and determine the mechanical properties of nanocomposites comprised of the nanomaterials as a fiber in Cu matrix at varying temperatures. We predict that on Cu (111) surface, the hybrid case has a higher adsorption energy than carbyne. During tensile loading, we find the elastic moduli of Cu-carbyne and Cu-hybrid nanocomposites are dependent on the Cu–C interface and nanomaterial dimension (1D or 1D-2D). We observe that high adsorption energy at the Cu–C interface contributes to higher elastic moduli for a Cu-hybrid nanocomposite than a Cu-carbyne nanocomposite at 300K. Above 300K, strain from thermal expansion coefficient mismatch between the 1D and 2D components of the hybrid cause Cu-hybrid elastic modulus to decrease. The thermal strain and volumetric strain of the Cu FCC lattice are affected by the dimension of the nanomaterial, and causes Cu-carbyne elastic moduli to be higher than Cu-hybrid for temperatures ≥ 600K. We also find high nanomaterial density causes Cu lattice distortion, leading to low elastic moduli at all temperatures. We conclude that carbyne and the hybrid are promising nanomaterials for Cu nanocomposites
Navigating Together: The CoNaV Testbed and Framework for Benchmarking Cooperative Localization
No full textThis paper presents CoNaV, a comprehensive framework for creating a multi-vehicle cooperative localization (CL) testbed designed to support the benchmarking, development, and deployment of cooperative navigation algorithms. Given the essential role of CL in improving localization accuracy for both defense and civilian applications, CoNaV provides a robust environment for rigorously validating algorithms under real-world conditions. By establishing a benchmark for CL algorithms, CoNaV lays a foundation for advancing research into more sophisticated and distributed CL solutions. This framework highlights the potential of cooperative navigation to enhance multi-vehicle operations and offers a scalable, practical approach for future developments in CL technology
Workforce Development for Global Manufacturing and Technology Transfer: An Integrated Systems Approach
No full textExcerpt: Many countries are now emerging as new hubs for international manufacturing due to the increasing costs in traditional outsourcing locations. The success of this transition will rely heavily on the establishment and maintenance of a reliable manufacturing infrastructure through an integrated systems approach
High-resolution 3D-printed Plastic Scintillators with Tertiary Dye
No full textAdditive manufacturing offers efficient production of plastic scintillators with nontrivial geometries using vat polymerization, allowing fabrication of geometries which would be difficult or even impossible to produce using conventional subtractive manufacturing. This work presents a novel photocurable scintillator formula that includes coumarin 450 as a tertiary dye to enable high-resolution 3D printing via the manipulation of the 405 nm cure light. Bulk photocured and 3D printed (with and without tertiary dye) samples were compared through observational assessment and spectral response. All samples showed pulse shape discrimination between neutron and gamma events. Inclusion of the tertiary dye has minimal impact on emission spectrum and light output, but significant impact on print resolution as shown by comparison of printed high-complexity geometries and feature resolution test objects. With the use of a cure-limiting dye, unsupported features — such as freestanding pillars — were resolvable down to 0.7 mm. Even finer resolution at or below 0.1 mm was achieved in fully supported, integrated structures printed with off-the-shelf 405 nm desktop 3D printer. Scintillators demonstrated a light output up to 50% of EJ-200 with a PSD figure of merit up to 1.35 at 0.9–1.1 MeVee