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Ballistic impact testing of acrylic and alumina thin-films
No full textHigh velocity projectiles cause damage to critical structures in space. Many of them travel at speeds of a few km/s to several hundered km/s. Such projectiles can punch through aircraft. In addition, bullets from modern weapons might reach 2.5 km/s. Spherical projectiles are tested against Poly-Methyl-Metha-Acrylate (PMMA) glasses and single-crystal corundum alumina (?-Al2O3). PMMA is created from two configurations: random and oriented. The penetration velocity (V50) of PMMA is found to be 400 m/s and that of alumina to be 4.5 km/s, 9 times higher than that of PMMA. PMMA thin films, where the chains are oriented along impact direction, heats up to 2628 K, which is less than 5450 K in random films at 5 km/s. Peak temperatures of up to 1615 K are reached in ?-Al2O3. The specific penetration energy (Ep) of PMMA is 0.322 MJ/kg at 400 m/s. In comparison, alumina shows higher specific penetration energies (Ep) of 16.5 MJ/kg and reduces the projectile velocity from 4.5 km/s to a residual velocity (Vr) of 576 m/s. This study indicates that PMMA sandwiched between two layers of alumina can be produced, with a thickness that can be calculated using specific penetration energies (Ep) from the projectile radius, to stop most projectiles effectively
DY?: A Modular Symbolic Verification Framework for Executable Cryptographic Protocol Code
No full textWe present DY star, a new formal verification framework for the symbolic security analysis of cryptographic protocol code written in the F-star programming language. Unlike automated symbolic provers, our framework accounts for advanced protocol features like unbounded loops and mutable recursive data structures, as well as low-level implementation details like protocol state machines and message formats, which are often at the root of real-world attacks. Our work extends a long line of research on using dependent type systems for this task, but takes a fundamentally new approach by explicitly modeling the global trace-based semantics within the framework, hence bridging the gap between trace-based and type-based protocol analyses. This approach enables us to uniformly, precisely, and soundly model, for the first time using dependent types, long-lived mutable protocol state, equational theories, fine-grained dynamic corruption, and trace-based security properties like forward secrecy and post-compromise security. DY star is built as a library of F-star modules that includes a model of low-level protocol execution, a Dolev-Yao symbolic attacker, and generic security abstractions and lemmas, all verified using F-star. The library exposes a high-level API that facilitates succinct security proofs for protocol code. We demonstrate the effectiveness of this approach through a detailed symbolic security analysis of the Signal protocol that is based on an interoperable implementation of the protocol from prior work, and is the first mechanized proof of Signal to account for forward and post-compromise security over an unbounded number of protocol rounds
Flowpath modification to reduce electrodialysis module size and energy consumption
No full textThermodynamic equipartition of ideal electrodialysis (ED) through the time-varying batch operation that maintains a constant current or instantaneous entropy generation rate has been proposed in the literature to reduce its specific energy consumption at fixed module size. In this study, the optimal current density distribution to minimize the specific energy consumption of ED in the presence of diffusive salt and water fluxes is evaluated. The local current density must increase as the salinity difference between the diluate and concentrate streams widens to reduce the impact of diffusive losses, but maintaining such a current density variation requires adjusting the applied potential continuously. As a practical alternative, we propose and numerically evaluate a novel recirculation flow architecture to improve the energetic performance of steady-state ED while using a conventional constant voltage power source. Like other methods that implement equipartition, maximum savings are obtained at a large baseline system size. Unlike multi-staging, no further savings are observed by adding additional recirculation cell pairs beyond two passes. A modified channel aspect ratio to maintain feed flow velocity in the channels is proposed to keep overall pressure drop and pumping energy similar to the baseline design. Energy (at fixed size) and area (at fixed energy consumption) can be reduced compared to conventional single-stage ED by up to 5% and 25% respectively for seawater brine concentration, and 35% and 55% respectively for seawater desalination
Gender preferences and stereotypes in local communities: evidences from various Indian contexts
No full textMachine Learning for New Physics Searches in B0 → K∗0μ+μ− Decays
No full textWe report on a novel application of computer vision techniques to extract beyond the Standard Model (BSM) parameters directly from high energy physics (HEP) flavor data. We develop a method of transforming angular and kinematic distributions into “quasi-images" that can be used to train a convolutional neural network to perform regression tasks, similar to fitting. This contrasts with the usual classification functions performed using ML/AI in HEP. As a proof-of-concept, we train a 34-layer Residual Neural Network (ResNet) to regress on these images and determine the Wilson Coefficient C9 in MC (Monte Carlo) simulations of B0 → K∗ μ+ μ− decays. The technique described here can be generalized and may find applicability across various HEP experiments and elsewhere
Image of ideals under linear K-derivations and the LNED conjecture
No full textLet K be a field of characteristic zero and K[X]=K[x1,x2,…,xn] be the polynomial algebra in n variables over K. We show that, for a linear K-derivation d of K[X] and the maximal ideal m=(x1,x2,…,xn) of K[X], if d(m) is a Mathieu-Zhao subspace of K[X], then the image of every m-primary ideal under d forms a Mathieu-Zhao subspace of K[X]. Additionally, we observe that the image of all monomial ideals under the K-derivation d=f∂x1 of K[X], for f∈K[X] forms an ideal of K[X]. Finally, we prove that the image of certain monomial ideals under a linear locally nilpotent K-derivation of K[x1,x2,x3] defined by d=x2∂x1+x3∂x2 forms a Mathieu-Zhao subspace
Cyclic and Post-Cyclic Response of Compacted Coal Ash
No full textIn the present study, effect of shear strain amplitude and frequency on cyclic and post-cyclic response of coal ash was investigated under simple shear conditions. A series of multistage tests on coal ash specimens including strain-controlled cyclic loading and post-cyclic undrained monotonic direct simple shear tests were conducted. Another series of undrained monotonic direct simple tests on coal ash specimens without cyclic loading history was also carried out to evaluate the effect of prior cyclic loading on post-cyclic response of coal ash. The results depicted that the shear modulus was found to be decreasing with loading cycles for coal ash specimens on increasing the cyclic shear strain amplitude except 0.01%. The damping ratio was observed to be increasing with loading cycles for shear strain amplitudes ranging from 0.5 to 1.5%. The effect of frequency indicated negligible shear modulus degradation behaviour on increasing the frequency from 0.1 to 1.5 Hz. However, greater shear modulus degradation was observed for specimens subjected to 2 Hz frequency. The post-cyclic stress–strain response indicated that coal ash specimens exhibited higher failure shear stress as compared to the specimens with no cyclic history. With an increase in the cyclic frequency, post-cyclic stress–strain response exhibited higher failure shear stress as compared to the specimen with no cyclic history
Community conserved areas in Northeast India and their role in addressing human-wildlife conflict
No full textShifting dynamics of peoples, livelihoods and territories, influenced by global warming, require new ways of thinking and new kinds of politics beyond the sovereignties of idealized traditional European nation-states. The Routledge International Handbook of Himalayan Environments, Development and Wellbeing features over 70 scholars from the social sciences, humanities and natural sciences who explore the interrelationships between environmental change, development and wellbeing across the entire Himalayan region – from the Indian Himalayas in the east to Bhutan, Nepal, Tibet (TAR), India and Gilgit-Baltistan in the west.
Within over 50 chapters, the handbook presents engaging field-based research on the region’s socio-cultural diversity, climate adaptation and socio-economic transformation. It examines creative ways Himalayan communities adapt, seek wellbeing and respond to environmental and development challenges. Lessons about learning from Indigenous and local peoples, about governance of forests and water, and grassroots conservation practices from the Himalayan region can help inform global networks of researchers and practitioners.
The handbook will interest scholars, students, stakeholders and the public about the evolving relationships between Himalayan peoples, territories and global warming, offering insights into people’s creative ways for understanding, adapting, and seeking wellbeing in environmental relations and development possibilities
Elevation controls bacterial branched GDGT-based temperature proxies: A regional to global perspective
No full textBranched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial lipids used as proxies for past temperature and pH reconstruction in terrestrial environments. Nevertheless, global calibrations often show discrepancies between observed and proxy-based predictions across soils spanning both latitudinal and elevational gradients. As orographic barriers in mountain regions create distinct elevation-dependent environmental conditions, soils across elevational transects may result in distinct growth conditions of brGDGT producers than expected from their latitude. To assess the impact of elevation on brGDGT proxies, we investigated a Western Himalayas (300–5500 m) transect spanning natural gradients in soil properties, precipitation, temperature and seasonality. BrGDGT-estimated pH agrees with the observed soil pH, while brGDGT-estimated temperatures show deviations of −10 to +10 °C from observed mean annual temperatures across our transect as well as other Himalayan transects. We find that these deviations are dependent on cumulative heat, quantified as growing degree days above 0 °C (GDD0). An analysis of globally distributed soils and peats (n = 1795) shows that GDD0 is positively correlated with the degree of methylation of brGDGTs, suggesting that microbial lipid production is seasonally biased and favors colder-season signals in warm climates (high GDD0) and warm-season signals in cool climates (low GDD0) across elevational and latitudinal gradients. We further suggest that scatter in brGDGT temperature estimates increases in regions where elevation-driven orographic effects create localized variability in bacterial growth conditions. Such non-uniform growth conditions induced by regional (orographic) factors can locally modulate broader climate trends, which results in biases and scatter within global calibrations and paleotemperature reconstructions