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The large compositional space of high entropy alloys (HEA) often presents significant challenges in comprehensively deducing the critical influence of atomic composition on their mechanical responses. We propose an efficient nonparametric kernel-based probabilistic computational mapping to obtain the optimal composition of HEAs under ballistic conditions by exploiting the emerging capabilities of machine learning (ML) coupled with molecular-level simulations. Compared to conventional ML models, the present Gaussian approach is a Bayesian paradigm that can have several advantages, including small training datasets concerning computationally intensive simulations and the ability to provide uncertainty measurements of molecular dynamics simulations therein. The data-driven analysis reveals that a lower concentration of Ni with a higher concentration of Al leads to higher dissipation of kinetic energy and lower residual velocity, but with higher penetration depth of the projectile. To deal with such conflicting computationally intensive functional objectives, the ML-based simulation framework is further extended in conjunction with multi-objective genetic algorithm for identifying the critical elemental compositions to enhance kinetic energy dissipation with minimal penetration depth and residual velocity of the projectile simultaneously. The computational framework proposed here is generic in nature, and it can be extended to other HEAs with a range of non-aligned multi-physical property demands. [ABSTRACT FROM AUTHOR]

We present here the fabrication at the wafer level and the electrical performance of two types of graphene diodes: ballistic trapezoidal-shaped graphene diodes and lateral tunneling graphene diodes. In the case of the ballistic trapezoidal-shaped graphene diode, we observe a large DC current of 200 µA at a DC bias voltage of ±2 V and a large voltage responsivity of 2000 v/w, while in the case of the lateral tunneling graphene diodes, we obtain a DC current of 1.5 mA at a DC bias voltage of ±2 V, with a voltage responsivity of 3000 v/w. An extended analysis of the defects produced during the fabrication process and their influences on the graphene diode performance is also presented. [ABSTRACT FROM AUTHOR]

The analysis was performed on six commonly used 5.56 x 45 mm projectile types (M193, M855, M855A1, L31A1, M995, and AP45). The projectile's impact velocity (chosen as 900 m/s) was the same in the examination process. This made it possible to assess how the projectile's design has affected its performance against a hard steel target. These evaluations included numerical simulations (Ansys Autodyn) of projectile impacts. Using the available experimental data, the materials in the computational model were first validated. A short description and CAD model of projectiles is also given. Relevant conclusions were reported. [ABSTRACT FROM AUTHOR]

Development of lightweight armors is vital in order to provide ballistic protection in a more effective way. The weight of steel armor can be decreased significantly by setting a front ceramic layer on it. In this paper, the influence of utilizing SiC and Al2O3 ceramic front layer on the ballistic behavior of 4140 bainitic steel was investigated experimentally. All steel plates were initially subjected to the austempering treatment by applying the austenitization at 860 °C for 1 h and then holding in a salt bath at 343 °C for 50 min to get fully bainitic microstructure. And then, the laminated composites, consisting of SiC or Al2O3 front layer (50 × 50 mm in size) and bainitic steel backing layer, were prepared by joining these layers with an acrylic adhesive. After the mechanical and microstructural characterization of the bainitic steel, the ballistic shots were made using 7.62 × 51 mm AP projectile with an average speed of 788.4 m/s on both monolithic steel and layered armor samples for comparison. The samples, which stopped the bullet at normal impact condition without complete perforation or disintegration of the bainitic steel layer, were termed as successful. The bainitic steel achieved the ballistic protection at a thickness ≥ 14 mm but the use of SiC layer provided the weight saving of at least 42.9% and the Al2O3 front layer enabled the weight reduction of 28.6% in the armor with respect to the monolithic 4140 bainitic steel. [ABSTRACT FROM AUTHOR]

The primary aim of fingermark research is to advance the quantity and quality of fingermarks detected using novel techniques or improvements on existing methods. Subsequently, there is a need to evaluate these methods to determine the quality of the developed mark, which is mostly done by the use of a numerical scale with descriptors to assist in the evaluation. However, this evaluation is often complicated due to a wide range of variables that impact the way quality assessment is performed. This is particularly true when considering it is currently unknown what assessment parameters are required to encompass the overall definition of quality. Likewise, the definition of fingermark quality is not universally agreed upon, which leads to significant subjective interpretation when a researcher chooses a scale. The purpose of this study was to investigate the factors contributing to fingermark quality in order to generate a deeper understanding of current approaches and definitions. A survey was created through a dataset that consisted of over 500 fingermarks detected in controlled laboratory conditions with a range of techniques. The images selected for the survey were based upon representing a full range of quality, each with a varying range of attributes. The survey looked at different parameters and descriptions used in current assessment protocols, asked participants to grade marks based on chosen parameters, and investigated current chosen methods by researchers in fingermark definition. The survey relied upon the participation of both examiners and researchers in fingermark detection. The results indicate that quality assessment methods implemented by researchers are not utilising all parameters that fingermark researchers and examiners deem important. This is especially true for contrast and background development, considered as two of the top parameters by examiners and researchers, which are not regularly used in most quality scale assessment methods. The survey ultimately demonstrated that the current subjective quality assessment methods were not always suitable and highlighted more appropriate parameters and descriptors that should be considered when assessing the quality of a fingermark. • Survey of researchers and examiners about fingermark quality evaluation. • Ridge detail, flow, visibility, contrast, technique development most important parameters. • Current scales often don't utilise parameters assessors consider important. • Continuous grading is too variable in comparison to traditional categorical scales. • Assessors' experience should be stated to help study cross-comparison. [ABSTRACT FROM AUTHOR]

The wounding potential of a projectile depends on its kinetic energy. The aim of the study was to investigate the deceleration of non-deforming full metal jacket handgun bullets (FMJ) in gelatine blocks of increasing length. The temporary cavity (TC) was visualized using a SA-X2 Photron camera. 126 test shots in 9 mm nominal calibre were fired under strict temperature control conditions (4°C) at small gelatine blocks ranging from 2 to 12 cm in length. The deposited energy was calculated based on the loss of bullet velocity through high-speed video analysis. The length of the TC was measured, when the TC reached its maximum height. The volume of the TC was approximated by a cylinder. Regression analysis showed a linear correlation between the length of the bullet path and the energy transfer. The constant deceleration of the FMJ bullets in gelatine up to 12 cm bullet path was confirmed across various brands and velocity ranges (270–450 m/s). Higher impact velocities correlated with increased loss of energy in the target medium. The shape of the bullet tip influenced the characteristic of deceleration. The volume of the tubular temporary cavity, derived from high-speed video records, was found to be proportional to the energy transferred. The proposed approach might be a valuable tool in advancing wound ballistics research. • Deceleration of FMJ bullets proportional to bullet path in compact target models. • Higher impact velocities resulted in greater loss of energy in the target medium. • The shape of the bullet tip influenced the characteristic of deceleration. • Proportionality of the temporary cavity to the transferred energy. [ABSTRACT FROM AUTHOR]

This research continues the research of Deng et al. (2022) [1], using Discrete Element Method (DEM) coupled with Finite Element Analysis to solve shotgun exterior ballistics. The simulation examples in this research are using an Italian-made 24 gm #9½ birdshot with 433 pellets fired from 30" long, 12-gauge cylinder and full choke barrels. The simulations of shotgun exterior ballistics of this research included pellet swarm velocity and the pellet dispersion at different distances until 50 yards away from the muzzle. The ballistics simulation of the pellet swarm is completed from interior to exterior consecutively after the shotshell is fired inside the chamber so all ballistics performances can be calculated at one time. Three forces were applied to the pellets for exterior ballistics simulation: the contact force between pellets, the aerodynamic separation force between pellets, and the drag force. Because of the complexity of the aerodynamic forces exerted on pellets, this research used an equivalent aerodynamic force to simulate this complex phenomenon. Two birdshot models with different pellet formations were created; the first one was simulated to calibrate the separation scale factor defined in aerodynamic separation force, and the second one was used for validation and sensitivity of the model. The simulation results show that for #9½ birdshots fired by cylinder barrel, the average Effective Shot Dispersion (ESD) of pellet dispersion of both birdshots inside the 30" diameter of the target circle at 40 yards from the muzzle is 398.53, which is remarkably close to 396.98 of the experiment result. The simulation of the average pellets' target hit rate is 77.14% (inside the 30" diameter of the target circle), which is also remarkably close to the experiment hit rate of 77.57%. The same birdshot fired from a full choke barrel shows that ESD and hit rate rose to 406.34 and 83.14%, respectively. These results demonstrate the effectiveness of using the discrete element method in conjunction with the proposed equivalent aerodynamic force to predict the shotgun's interior and exterior ballistics. [Display omitted] • The equivalent aerodynamic forces were formulated from experiments of two pellets flying near to each other. • An Italian made 12-gauge 24 gm. #9½ birdshot with 433 pellets fired from 30-in long cylinder and full choke barrels were simulated. • Two birdshot models with different pellet formations were created to validate the sensitivity of the model. • Average simulated pellet dispersion at 40 yards fired by cylinder has only 0.43% error compared to the experiment. • Birdshot fired by full-choke barrel has 6.0% higher target hit rate compared to cylinder barrel did. [ABSTRACT FROM AUTHOR]

• Created the first ballistic dataset for enhanced cross-laminated timber (ECLT). • Compared partial and full penetration results utilizing eight known ballistic resistant materials. • Developed benefit-cost assessment of panel configurations. Cross-laminated timber (CLT), an engineered wood product, has grown in popularity in the United States over the last decade due to its ease of assembly, aesthetic appeal, and potential to serve as a sustainable and renewable alternative building material. The improved robustness of CLT over light-frame timber structures has increased its potential in force-protected infrastructure that must resist blast waves and ballistic projectile penetration, but softwood CLT is typically not sufficient to fulfill standard criteria for ballistic threats. To address these threats, enhanced CLT (ECLT) composite panels were manufactured with layers of various reinforcing materials (e.g., steel, FRP) placed between wood laminations. These panels were tested against various ballistic threats during two sets of laboratory tests in order to provide a basis for future research. The first set of testing subjected laboratory-produced Southern Yellow Pine (SYP) ECLT to 84 shots of 0.50-inch (1.27 cm) steel sphere projectiles to evaluate the performance of various reinforcing materials, layups, and fastening methods. A subsequent set of tests subjected commercially produced ECLT of steel-reinforced Spruce-Pine-Fir (South) (SPF-S) to 36 shots of NATO ammunition projectiles traveling at realistic, standard striking velocities. Except for a panel using four layers of a thin and finely woven steel hardware cloth, steel reinforcement was effective in stopping projectiles from all three types of NATO ammunition fired. Ultimately considering the results of these two sets of tests, an initial cost-benefit structure was developed and discussed to compare ECLT configurations holistically, a multi-material wood analytical model framework was established and compared to experimental results, and the first ballistic experimental database for ECLT was created. [ABSTRACT FROM AUTHOR]

The last five decades have seen strong developments in irrigation modeling. In solid-set sprinkler irrigation, models have generally been applied to a few sprinklers in a regular arrangement, making them representative of a sector or a field. In this research, the Ador-Solid-Set model for whole-field solid-set sprinkler irrigation is presented, validated and applied to simulate an irrigation event in two fields: CA (10.2 ha) and ZA (24.5 ha), equipped with 12 and 26 sectors, respectively. The model couples pipeline hydraulics (EPANET), sprinkler ballistics and irrigation scheduling at execution time. Field experiments were used to validate the ballistic model in a solid-set combining full- and partial-circle sprinklers. Observed and simulated irrigation depths and coefficients of uniformity showed determination coefficients of 0.73*** and 0.89***, respectively. Optimization was used to estimate pipeline roughness based on pairs of pressure measurements (at the inlet and specific sprinklers): 26 pairs in CA and 58 pairs in ZA. Roughness parameters were estimated for the main pipeline, each sector and the sprinkler risers: 14 parameters in CA and 28 in ZA. More than a million hydraulic simulations were required to estimate roughness in each field. Maps were produced for applied water in CA and ZA following a sequential irrigation of their sectors lasting for 24 hours. The model produced whole-field coefficients of uniformity of 80.2 in CA and 80.9 in ZA. Finally, Ador-Solid-Set quantified the volume of drift outside the field (2.4 and 1.5% of the applied water in CA and ZA, respectively). This additional drift can be added to the wind drift and evaporation losses obtained from empirical equations, in a process that requires further analysis. Research efforts are also needed to enhance the current model capabilities and address the challenges related to water quantity and quality in sprinkler solid-sets. • A solid-set irrigation model has been presented, calibrated and validated. • The model has been applied to two solid-sets of 10.2 and 24.5 ha. • New thresholds may be required for whole-field Irrigation uniformity. • The model quantified drift outside the computational domain. [ABSTRACT FROM AUTHOR]

Polyurea (PU) elastomers have become increasingly popular in recent years due to their exceptional blast mitigation, ballistic protection, and wear resistance properties. However, their applications as protective materials are often limited as a result of their high flammability. In this study, aromatic dianhydrides (ArDAs) were employed to capture the thermal decomposing products of PU during combustion and facilitate the generation of highly heat-resistant aromatic polyimides (i.e., end group capturing effect), thus enhancing the material's char-forming ability and improving its flame retardancy. The ArDAs were found to significantly reduce the peak heat release rate (PHRR), total heat release (THR), total smoke release (TSR), and total CO release (TCO) of PU, and meanwhile increased the amount of char residue. At 20 wt% content of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), PHRR, THR, TSR and TCO of PU were reduced by 70.6%, 32.5%, 44.7% and 58.8%, respectively, the char residue was increased by 405%, and the mechanical properties of PU were well maintained (88.5% tensile strength and 91.0% elongation at break of pure PU). These findings demonstrate that ArDAs could serve as a new kind of halogen/phosphorus-free flame retardant for PU elastomers. [Display omitted] • Novel halogen/phosphorus-free flame retardants were designed for PU elastomers. • The flame retardant mechanism is end group capturing by aromatic dianhydrides (ArDAs). • PHRR, THR, TSR and TCO were simultaneously reduced, and char residue was improved. • Both excellent flame retardant property and high mechanical property were achieved. [ABSTRACT FROM AUTHOR]

The ongoing pursuit of space and hypersonic flight continues to expose critical gaps in the understanding of material behavior under hypervelocity impact (HVI) and hypersonic flow conditions. Such limitations pose serious risks for aerospace vehicles, spacecraft, hardened structures, defensive systems, etc. Consequently, the development of materials and systems that can endure HVIs and hypersonic flight is a major obstacle in the quest for sustainable space exploration, reusable air-breathing hypersonic vehicles, and enduring protective structures. HVIs (≥ 3.0 km/s) can induce severe material deformation, erosion, fracturing, fragmentation, melting, vaporization, and sublimation. At the same time, hypersonic (≥ Mach 5) vehicles may be subjected to intense thermal and mechanical loads. Addressing these grand challenges requires a multifaceted and interdisciplinary approach, combining well-designed experiments with physics-based analytical and numerical modeling. Studying material behavior under HVIs and hypersonic conditions has been facilitated by two-stage light gas gun (2SLGG) aeroballistic ranges for almost seven decades. This current study surveys over 90 2SLGG aeroballistic ranges operational since 1990 to assess global launch and experimental capabilities. The 2SLGG's origins and research applications are explored, highlighting its significance in various fields, including shock physics, planetary science/defense, military defense, nuclear physics, hypersonic vehicle survivability and performance, and spacecraft micro-meteoroid/orbital debris protection. A summary of relevant HVI phenomena is presented to underscore the importance of 2SLGGs and to elucidate similarities and differences among various 2SLGG aeroballistic ranges and their supporting methods/tools. The 2SLGG's working principles are explained, and configurations and operations are compared. Modifications resulting in "three-stage light gas guns" are briefly mentioned for completeness. The full range of current 2SLGG performance capabilities is assessed with impact kinetic energies ranging from ∼ 10 joules to nearly 100 megajoules, and the facility survey results are used to explain the variations in aeroballistic range tankage, experiment types, research applications, and diagnostic systems. Finally, an overview of 2SLGG performance prediction methods is provided, featuring notable empirical, analytical, and numerical approaches. • Survey of over 90 2SLGG aeroballistic ranges active since 1990 worldwide. • 2SLGG's impact in multiple fields like military and space highlighted. • Detailed 2SLGG working principles and three-stage gun modifications explained. • 2SLGG performance spectrum from 10 J to 100 MJ detailed. • Variability in 2SLGG ranges and their scientific uses described. [ABSTRACT FROM AUTHOR]

The first goal of this work is to find a regression law for PVC (Polyvinyl Chloride) coupled to hydrogen peroxide on a 10-N-scale hybrid thruster, which appears to be suitable for small satellites when, for example, manoeuvres are required for orbital control purposes. Different techniques were initially analysed in order to reconstruct the ballistics inside the combustion chamber, starting from the experimental data. Subsequently, even if the different techniques lead to similar results, the one that takes into consideration the greatest number of the experimental measurements was chosen for the post-processing, and three different regression curves were obtained according to various criteria. The resulting regression laws coming from the selected method appear to be in agreement with the experimental results and constitute a powerful means for designing engines with this fuel. Finally, a performance analysis has been performed and in-space thrust and specific impulse have been estimated. PVC shows excellent performance and can be a good candidate for this type of applications, on a par with other more popular polymeric materials. [ABSTRACT FROM AUTHOR]

Boron carbide, with a nominal stoichiometry of B 4 C, is a highly desired ceramic candidate for armor applications due to its high hardness derived from the complex crystal structure. However, stress-induced local amorphization can lead to failure and is a known challenge for this material which must be addressed for applications in ballistic environments. Understanding boron carbide's atomic structural behavior and bonding environment is critical in determining effective strategies to mitigate these issues. In this work, the thermo-structural behavior of B 4 C has been studied in detail using a conical nozzle levitator system coupled with in-situ synchrotron X-ray diffraction. Lattice expansion and the resulting thermal expansion coefficients (CTEs) were determined from 25-2100 °C. Rietveld refinements showed anisotropic atomic displacement for each of the 4 unique sites as a function of temperature. An exceptionally large z-axis displacement for the boron chain center is linked to bond weakness and may be linked to fa α 11 ster expansion of the α 33 relative to CTEs. Thermally induced lattice changes can inform the use of boron carbide at elevated temperatures as well as help develop strategies for mitigating structural failure for armor applications. [Display omitted] [ABSTRACT FROM AUTHOR]