Penetration Depth Research Articles

Study on the influencing factors of combined processing of active and passive surface-wave data on dispersion imaging

Active and passive surface-wave methods have garnered significant attention in the near-surface geophysical community for their non-destructive, non-invasive, low-cost, and accurate advantages in delineating subsurface shear (S)-wave velocity structures. They are increasingly being utilized to address numerous engineering and environmental problems. Surface waves obtained from actively excited sources such as a hammer and a harmonic shaker, however, lack low-frequency components, resulting in limited investigation depth. Conversely, passive surface waves such as microseisms (< 0.4 Hz, associated with natural ocean wave activity) and microtremor (>1 Hz, generated by cultural and wind sources) retrieved from ambient seismic noise typically lack high-frequency components, which is not conductive to characterizing fine near-surface structures. To overcome these frequency limitations, we employ a “mixed-source data” strategy, imposing active shot gathers into ambient noise data, to widen the frequency range of dispersion images and depth of investigative capabilities. We simulate both active and passive surface-wave data based on a two-layer model, noting that their dispersion images suffer from a mode kissing phenomenon at lower frequencies. By analyzing influencing factors such as the amplitude intensity, the signal-to-noise ratio and the excitation locations of active shot gathers, as well as the length of passive surface-wave data, we better understand their impacts on dispersion images from mixed-source surface-wave data. Simulation tests demonstrate that processing mixed-source data can effectively distinguish the mode kissing phenomenon. Moreover, the effectiveness of this strategy in enhancing the quality of dispersion image is verified, especially when surface-wave dispersion images perform poorly in either the low- or high-frequency bands. Additionally, a real-world example further demonstrates that processing mixed-source data offers significant advantages in improving the quality of dispersion images. This way provides a convenient and efficient measurement strategy for delineating shear-wave velocity profiles in finer shallow layers and deeper penetration depths.

Alkaline Phosphatase Activated Near-Infrared Frequency Upconversion Photosensitizers for Tumor Photodynamic Therapy.

Photodynamic therapy (PDT) is a promising anticancer method due to its noninvasive features, high efficiency, and superior accuracy. The activated near-infrared upconversion photosensitizer has a high tissue penetration depth and could be explicitly released with minimal side effects. Therefore, we designed and synthesized a series of Br-substituted compounds (NFh-Br) based on the near-infrared upconversion hemicyanine dye. The heavy atomic effect improves the generation of 1O2 and upconversion luminous efficiency. Especially, NFh-Br11 exhibited an excellent 1O2 generation rate under 808 nm excitation and effectively killed tumor cells in vitro, and the alkaline phosphatase (ALP)-activatable photosensitizer (NFh-ALP) was obtained by modifying the NFh-Br11. NFh-ALP could be activated by ALP and release NFh-Br11, which induces apoptosis of tumor cells and has outstanding anticancer effects in vitro and in vivo. This work could provide a strategy for designing activatable upconversion photosensitizers.

Could light be a broad-spectrum antimicrobial?

A review on antimicrobial resistance mechanisms discussing the main light-based antimicrobial approaches including ultraviolet light (UV), antimicrobial photodynamic therapy (aPDT), and antimicrobial blue light (aBL). To describe antimicrobial resistance mechanisms and to present potential light-based alternatives to conventional antimicrobials. The paper was divided into different topics, starting with an approach to antimicrobial resistance mechanisms. Subsequently, emphasis was placed on innovative light-based antimicrobials approaches, including aBL, UV, and aPDT. The review suggests that blue light (400-470 nm) acts on endogenous porphyrins with peak absorption at 405 nm, thus not requiring the administration of photosensitizers, to trigger antimicrobial effects. In this regarding, the direct effect of aBL could be attributed to both the generation of reactive oxygen species (ROS), which induces microbicidal effects, and the inactivation of bacterial defense mechanisms. In turn, blue light combined with curcumin has been used in the treatment of dental infections. Otherwise, green light (495-570 nm) associated with the photosensitizer Rose Bengal has shown promising results both in wound closure due to the induction of additional collagen cross-link formation and in reducing the viability of Pseudomonas aeruginosa. Red light (620-750 nm) is the wavelength most commonly used in aPDT, presenting superior tissue penetration capability compared to blue and green light. Both red and infrared light act directly as photobiomodulation agents, promoting tissue repair with greater penetration depth for the infrared spectrum. Conversely, red light combined with methylene blue is the most commonly used technique in the treatment of localized infections. Meanwhile, infrared light associated with indocyanine green acts as a photothermal and photosensitizing agent, promoting thermal damage and production of ROS. Ultraviolet lights UVA, UVB, and UVC (200-400 nm) have antimicrobial potential related to inducing changes in DNA and generating both ROS and singlet oxygen. Furthermore, light can enhance the efficacy of traditional antimicrobial agents by deactivating microbial resistance, both through increasing the permeability of the cell membrane and by inhibiting the efflux pump and β-lactamases of the bacteria. The antimicrobial potential of light is extensive; however, there is a limitation regarding the depth of penetration of certain wavelengths into infected areas. Furthermore, there is a need for additional studies to determine the safety and efficacy of various approaches using light at its different wavelengths.

Tumor microenvironment-modulated nanoparticles with cascade energy transfer as internal light sources for photodynamic therapy of deep-seated tumors

Photodynamic therapy (PDT) is an appealing modality for cancer treatments. However, the limited tissue penetration depth of external-excitation light makes PDT impossible in treating deep-seated tumors. Meanwhile, tumor hypoxia and intracellular reductive microenvironment restrain the generation of reactive oxygen species (ROS). To overcome these limitations, a tumor-targeted self-illuminating supramolecular nanoparticle T-NPCe6-L-N is proposed by integrating photosensitizer Ce6 with luminol and nitric oxide (NO) for chemiluminescence resonance energy transfer (CRET)-activated PDT. The high H2O2 level in tumor can trigger chemiluminescence of luminol to realize CRET-activated PDT without exposure of external light. Meanwhile, the released NO significantly relieves tumor hypoxia via vascular normalization and reduces intracellular reductive GSH level, further enhancing ROS abundance. Importantly, due to the different ROS levels between cancer cells and normal cells, T-NPCe6-L-N can selectively trigger PDT in cancer cells while sparing normal cells, which ensured low side effect. The combination of CRET-based photosensitizer-activation and tumor microenvironment modulation overcomes the innate challenges of conventional PDT, demonstrating efficient inhibition of orthotopic and metastatic tumors on mice. It also provoked potent immunogenic cell death to ensure long-term suppression effects. The proof-of-concept research proved as a new strategy to solve the dilemma of PDT in treatment of deep-seated tumors.

Investigation of effective parameters on Fe/Ta thin films by plasma focus device: number of shots and distance from tip anode

This experimental investigation is the first to generate a surface iron-tantalum (Fe/Ta) alloy as a sublayer-layer using a plasma focus device. Examining how ion beams from a plasma focus device alloy iron and tantalum with varying melting points is one of the key objectives of this study. Fe/Ta thin film nanostructure and surface morphology were also examined. The distance from the tip anode and the varied number of shots are the experimental variables. Although tantalum's melting point (3020 ∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ{\\rm C}$$\\end{document}) is generally known to be near to that of iron (2862 ∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ{\\rm C}$$\\end{document}), it is possible that iron vaporizes and partial alloying of iron with tantalum occurs before tantalum reaches its melting point. Fe/Ta thin film identification techniques include scanning electron microscopy, mapping of cross-section, energy dispersive X-ray spectroscopy, and X-ray diffraction pattern. Additionally, the composition of multilayer structures is examined using EDS. In conclusion, the results of the X-ray diffraction pattern showed that the number of shots had a significant impact on the residual strain degree of the thin films that were deposited. Furthermore, structures made of FeTa and Fe2Ta were produced. Additionally, photos from scanning electron microscopy and cross-section mapping verify that the sample with five shots at an 8 cm distance from the tip anode formed a uniform Fe/Ta alloy structure. The sample with five shots at a distance of 4 cm from the tip anode formed micro-island structures, as seen by scanning electron microscopy, with decreasing distance. Furthermore, depth elemental distribution revealed that the optimal depth of penetration in a homogenous material to develop alloying is best determined by number of PF shots.

Penetration Depth of 5.25% Sodium Hypochlorite Solution Using Different Irrigation Needles and Activation Systems: An In Vitro Radiographic Assessment

Penetration Depth of 5.25% Sodium Hypochlorite Solution Using Different Irrigation Needles and Activation Systems: An In Vitro Radiographic Assessment

Enhancing Quality Management of PHC Piles through Improved Driving Formulas: A Comprehensive Review and Analysis

In construction projects, conducting dynamic load tests on all piles proves impractical. Selective testing estimates bearing capacity, while the remaining piles rely on penetration depth for management. This approach, however, faces reliability issues due to varying conditions among piles. Technological advancements, such as non-contact hammers and sensors, have enhanced the accuracy of penetration depth measurements during final driving. Nonetheless, relying solely on penetration depth for construction and quality management remains problematic. This study, therefore, focuses on enhancing the use of driving formulas to improve pile quality management, particularly for the widely used pre-stressed high-strength concrete (PHC) piles. To improve pile quality management, existing driving formulas underwent review and refinement. Utilizing 258 dynamic load test data from various sites, the Hiley, Gates, and Danish formulas underwent validation through statistical analysis and graphical comparison. Enhancements to the Gates formula, achieved through curve fitting with actual data and the application of segment-based coefficients, demonstrated increased accuracy in bearing capacity estimation. These improvements offer a more reliable approach to pile quality management in construction projects.

The influence of adjustable ring-mode laser on the formation of intermetallic compounds and mechanical properties of ultra-thin Al-Cu lap welded joints

Aluminum-copper dissimilar welding is a highly demanded connection process; however, welding defects and the excessive growth of intermetallic compounds (IMCs) cause pose challenges for its application. This study uses an adjustable ring-mode (ARM) laser technology to achieve lap welding of ultra-thin Al-Cu plates. Lap-welding experiments were conducted using three laser modes—fixed core power, fixed ring power, and varying welding speed—to investigate the evolution of material mixing, intermetallic compound distribution, and joint strength under different modes. Our results indicate that the high energy density of the core laser is beneficial for increasing the penetration depths of joints, whereas the large action area of the ring laser is beneficial for improving the stabilities of melt pools. The joint action of the adjustable ring-mode (ARM) laser increased the melting width and depth of the joint, and the mixing of Al and Cu was controlled in the Al-Cu mixed zone at the upper part of the weld, to limit element mixing in the Cu-rich zone of the weld interface and suppress the distribution of intermetallic compounds. In addition, the ring laser induced the aluminum in the upper part of the molten pool to invade from both sides of the interface to the bottom, forming a certain Al invasion depth. This limited the accumulation of intermetallic compounds at the interface, optimized the path of shear fracture propagation, and improved the shear strength of the joint. This study provides a research basis for further exploring the material flow mechanism and optimizing the intermetallic compound distribution during the Al-Cu adjustable ring-mode (ARM) laser dissimilar welding process.

Advance of Near-Infrared Emissive Carbon Dots in Diagnosis and Therapy: Synthesis, Luminescence, and Application.

Carbon dots (CDs) with good optical properties, biocompatibility, easy functionalization, and small size have attracted more and more attention and laid a good foundation for their applications in the biomedicine field. CDs emitted in near-infrared regions (NIR-CDs) can achieve high penetration depth imaging and produce high cytotoxic substance for disease treatment. Therefore, NIR-CDs are promising materials to realize high-quality imaging-guided diagnostic and therapeutic integration. This review first introduces the current mainstream synthesis methods of NIR-CDs by "top-down" and "bottom-up". Second, the luminescence modes of NIR-CDs are introduced, and the luminescence mechanisms based on carbon core state, surface state, molecular state, and crosslinking enhanced emission are summarized. Third, the applications and principles of NIR-CDs in imaging, drug delivery, and non-invasive therapeutics are introduced from a view of diagnosis and therapy. Finally, their prospects and challenges in biomedical and biotechnological applications are outlined.

Investigation of keratolytic impact of synthetic bolalipids on skin penetration of a model hydrophilic permeant

Synthetic single-chain bolalipids (SSCBs) are novel excipients in drug delivery, with potential as stabilizers or solubilizers. However, their impact on skin barrier function has not been comprehensively studied. Therefore, two SSCBs (PC-C24-PC and PC-C32-PC) were studied in aqueous systems for their impact on penetration of a model permeant into porcine skin. Concentrations of 0.05 – 5 % w/w were tested; PC-C24-PC formulations were low-viscosity liquids while PC-C32-PC formed viscous dispersions to gels at room temperature. Formulations were compared for their ability to enhance sodium fluorescein penetration (SF, 0.1 % w/w) into skin via tape stripping. Using NIR-densitometry, the effect of SSCB formulations on corneocyte cohesion was evaluated. Data were compared with phospholipid mixture Lipoid S-75, sodium dodecyl sulfate (SDS), and polyethylene glycol 12-hydroxystearate (PEG-HS), and distilled water as negative control. Contrary to the hypothesis, both SSCBs failed to increase SF penetration into the stratum corneum, but rather showed a significant decrease in penetration depth compared to water. Both SSCBs exhibited a keratolytic effect at 5 % w/w, leading to substantial removal of proteins from the skin surface. Consequently, SSCBs may not enhance penetration of hydrophilic drugs into skin, but could be used as keratolytic agents.

Functional ultrasound (fUS) imaging of displacement-guided focused ultrasound (FUS) neuromodulation in mice

Focused ultrasound (FUS) stimulation is a promising neuromodulation technique with the merits of non-invasiveness, high spatial resolution, and deep penetration depth. However, simultaneous imaging of FUS-induced brain tissue displacement and the subsequent effect of FUS stimulation on brain hemodynamics has proven challenging thus far. In addition, earlier studies lack in situ confirmation of targeting except for the magnetic resonance imaging-guided FUS system-based studies. The purpose of this study is 1) to introduce a fully ultrasonic approach to in situ target, modulate neuronal activity, and monitor the resultant neuromodulation effect by respectively leveraging displacement imaging, FUS, and functional ultrasound (fUS) imaging, and 2) to investigate FUS-evoked cerebral blood volume (CBV) response and the relationship between CBV and displacement. We performed displacement imaging on craniotomized mice to confirm the in situ targeting for neuromodulation site. We recorded hemodynamic responses evoked by FUS and fUS revealed an ipsilateral CBV increase that peaks at 4 s post-FUS. We saw a stronger hemodynamic activation in the subcortical region than cortical, showing good agreement with the brain elasticity map that can also be obtained using a similar methodology. We observed dose-dependent CBV response with peak CBV, activated area, and correlation coefficient increasing with ultrasonic dose. Furthermore, by mapping displacement and hemodynamic activation, we found that displacement colocalizes and linearly correlates with CBV increase. The findings presented herein demonstrated that FUS evokes ipsilateral hemodynamic activation in cortical and subcortical depths and the evoked hemodynamic responses colocalized and correlate with FUS-induced displacement. We anticipate that our findings will help consolidate accurate targeting as well as an understanding of how FUS displaces brain tissue and affects cerebral hemodynamics.

Quantification of Mixing Depth Using the Gradient Richardson Number in Submerged Aquatic Vegetation Meadows

AbstractUpper layer thickness (mixing depth) is an essential parameter for estimating the dissolved inorganic carbon and carbon flux at the water surface based on their association with the vertical flux of dissolved inorganic carbon. Previous studies quantified the mixing depth without SAV meadow or penetration depth in the SAV meadow without stratification and wind stress. However, mixing depth related to interaction with submerged aquatic vegetations (SAVs), stratification, and wind stress has yet to be quantified in the previous studies. Our study is the first to quantify the theoretical mixing depth with SAVs according to wind stress, SAV height, and drag coefficient. Theoretical mixing depth was quantified from modeled vertical temperature profile, vertical profile of horizontal velocity, and gradient Richardson number (Rig,veg). We found that mixing depth at a Rig,veg of 100 demonstrated good agreement with numerical results on average, with the mixing depth estimated in this study (hU,this study) showing high applicability to observations at Komuke Lagoon. Moreover, hU,this study increased with the increasing wind stress and decreasing drag coefficient and SAV height. Further, we found that SAV meadows with stratification and wind stress could be divided into four hydrodynamic regimes: non‐vegetated layers, upper vegetated layers, thermoclines, and benthic boundary layers. Our findings help us estimate mixing depth or vertical flux without complicated numerical simulation and understand flow interaction with SAV, wind stress, and stratification.

Prediction of free chloride concentration in fly ash concrete by machine learning methods

Free chloride concentration distribution is important for assessing the corrosion risk of steel bars in reinforced concrete structures under chloride environment. In this study, a group of 3150 free chloride concentration data sets were obtained. Afterwards, three machine learning methods, namely support vector regression (SVR), multilayer perceptron (MLP) and one-dimensional convolutional neural network (1D-CNN) were adopted to construct models to predict chloride concentration distribution. The results show that 1D-CNN and MLP models are better at predicting the chloride concentration in fly ash concrete, whereas the prediction capability of SVR is relatively poor. Moreover, free chloride concentration prediction based on unmeasured parameters was conducted. The results show that the 1D-CNN and MLP models both have high prediction abilities – that is, predicted results are consistent with experimental measurements, performing generally better than the time-varying model constructed based on Fick's second law. When the free chloride concentrations were higher than 0.1%, the SVR model had a better prediction effect, but had unsatisfactory results and differed significantly from the actual chloride concentration when at a lower concentration. Overall, the 1D-CNN model performs the best in predicting free chloride concentration of concrete at different penetration depths, exposure time and with different fly ash content.

A light-fueled self-rolling unicycle with a liquid crystal elastomer rod engine

Active materials hold substantial potential for self-sustaining motion, however, the dependency on movable light or extensive area illumination in current structures often restricts the design and practical deployment of such active machines. In this study, we report a novel zero-energy-mode, self-rolling unicycle equipped with a liquid crystal elastomer rod engine, which fueled by a fixed, small-area light source. By employing an elaborate dynamic model for liquid crystal elastomer, we derive the lateral curvature of the liquid crystal elastomer rod and the driving moment necessary for the unicycle's self-rolling. The study results demonstrate that the self-rolling of the unicycle is driven by a moment induced by the shift in the center of gravity of the curved liquid crystal elastomer rod. Our numerical simulations indicate the presence of a supercritical Hopf bifurcation point delineating the transition between the self-rolling mode and the static mode within the unicycle system. Additionally, the rolling velocity of the unicycle relies on a handful of key system parameters, notably including light intensity, light penetration depth, length of the liquid crystal elastomer rod, rolling friction coefficient, total mass of the unicycle, and wheel radius of the unicycle. The experimental validation of a self-rolling unicycle with zero-energy-mode has been conducted. The self-rolling unicycle constructed in this paper has excellent characteristics of simple structure, zero-energy-mode, horizontal constant light source, and small area light source, providing valuable insights for the utilization of photoresponsive liquid crystal elastomer rods in soft robotics, medical devices, energy harvesting systems, and actuators.

Comparative study on in-situ resilient modulus of subgrade estimated using in-situ modulus detector

This study presents a comprehensive evaluation of the resilient modulus of unsaturated subgrade soils using a novel in-situ modulus detector (IMD) along with various laboratory and field-testing methods. The current study employs several testing devices, including bender elements, standard dynamic cone penetrometer, and crosshole-type dynamic cone penetrometer (CDP), to assess the reliability of the IMD in estimating the resilient modulus profiles of small-scale homogeneous subgrade models in unsaturated conditions. The index properties, compaction and strength characteristics of the compacted soils, are evaluated. The resilient modulus values obtained from the IMD are compared with those obtained from repeated load triaxial tests under various stress states. Experimental results show a decrease in the penetration depth per blow with increased dry unit weight. In addition, elastic modulus and shear wave velocity increase with soil density. The resilient modulus estimated from the IMD increase with both depth and soil density. A robust correlation has been established between the resilient modulus values estimated from the IMD and those estimated from the CDP or bender element tests. Furthermore, the resilient moduli estimated from the universal model and the IMD demonstrate linear relationships with a coefficient of determination greater than 0.8. Thus, the IMD may be useful for the in-situ evaluation of resilient modulus in unsaturated subgrade soils, considering influencing factors such as soil density and confining pressure.

Protocol for dissection of Drosophila abdomens for fluorescent imaging

Fluorescent imaging in Drosophila species is indispensable for investigating dynamic biological processes and visualizing gene expression patterns with cellular precision. This technique leverages the transparency of Drosophila larvae and pupae, combined with advanced microscopy, to enable real-time observation of developmental events such as morphogenesis and organogenesis. Genetically encoded fluorescent proteins and dyes allow specific labeling of cells and proteins, facilitating detailed studies of spatial and temporal dynamics within intact tissues. Techniques like confocal and two-photon microscopy provide high resolution and depth penetration, essential for 3D reconstruction and quantitative analysis of complex biological structures. Fluorescent imaging in Drosophila supports disease modeling, drug screening, and therapeutic exploration, bridging insights from basic biology to potential clinical applications. It is therefore necessary to develop imaging techniques and protocols that accurately capture and profile gene expression patterns in a wide range of Drosophila tissues. In this study, we present a detailed protocol for preparing and imaging transgenic Drosophila abdomen, which will enable researchers investigate gene expression patterns underlying fundamental biological processes in the abdomen.

Macroscopic and microscopic element distribution in transition zones of GTAW Alloy 52M weld joint and its PWSCC growth behaviour

The microstructure and element distribution in the transition zone (TZ) of Alloy 52M buttering (52Mb) layer near the fusion boundary to the SA508III low alloy steel in a dissimilar metal weld joint with post-weld heat treatment (PWHT) is characterized. Two macroscopic TZs in the heat-affected zone have lower Cr and Ni contents than the bulk Alloy 52Mb. The first TZ near the fusion boundary has the lowest Cr and Ni compositions, accompanying the highest Fe content. Cr depletion and Ni enrichment along with slight Fe enrichment at the dendrite boundaries in the TZs, are more significant than those in the bulk Alloy 52Mb. The number and the maximum depth of local oxidation penetrations at the alloy-inner oxide interface based on the oxidation tests, the number and the maximum length of locally interdendritic cracks, as well as the average crack growth rate (CGR) in terms of the stress corrosion cracking (SCC) band based on the SCC tests in the first TZ are higher than those in the second TZ. The average SCC CGR is enhanced by macroscopic element dilution, while local oxidation penetration, as well as locally interdendritic SCC, are thought to be enhanced by both the macroscopic dilution of Cr in the TZs and the microscopic Cr depletion at dendrite boundaries.

Detection of subsurface archaeological features using the GPR method with a 250 MHz antenna in Borsippa site, Babylon, Iraq

The GPR method was used to determine the depth and extent of the subsurface archaeological features at the archaeological site of Borsippa. The extensions of the archaeological walls were identified through the creation of three-dimensional maps. The LMX200 device conducted the survey using a 250 MHZ antenna. sixty parallel profiles were collected and processed by GPR Slice software. Several reflections of possible archaeological walls buried at different depths and extensions of 2, 4, 6, 11, and 20 m were identified. The 250 MHz antenna gave clear reflections of the archaeological walls, with a penetration depth of up to 4 meters. The time slice map identified a buried archaeological structure at 1–1.1 m deep, consisting of many rooms with thick walls up to 2-3 m.

Plume active control in high-power fiber laser welding based on high-speed shielding gas microbeam

Plume is an inherent physical phenomenon in fiber laser keyhole welding, negatively affecting welding quality. This paper proposes a new type of high-speed shielding gas microbeam (HSGM) based on the limitation of conventional shielding gas regulating plumes. The gas flow characteristics of the HSGM on the molten pool surface were explored using numerical simulation. Then, the coaxial double-layer shielding nozzle was trial-manufactured to clarify the regulation law for the HSGM on the plume. The gas velocity and pressure produced by the HSGM on the molten pool surface were positively correlated with the shielding gas flow rate, and the gas flow pattern was an acute triangle shape. The suitable HSGM can significantly restrain plume formation, improve the weld surface forming quality, increase the weld penetration depth (about 15.4%), and reduce the mass loss of the weld (about 58.7%). The significant blowing pressure effect of HSGM on plumes and splashes was the key to regulating the welding process. Compared with conventional shielding gas, the use of HSGM was significantly reduced.

Ballistic impact response of reinforced concrete panels subjected to diverse multiple projectile impact scenarios: A numerical study

Concrete has wide applications in civil and military infrastructures. Thorough ballistic damage evaluation of these structures is crucial to safeguard these structures against potential threats. Past studies on reinforced concrete (RC) panels primarily focused on single-impact scenarios. However, real-world situations often involve multiple impacts that need to be examined. Hence, this paper critically examines multiple impact scenarios on RC panels to provide a realistic understanding of their ballistic resilience. A three-dimensional finite element model was developed and validated with the experimental data from the literature to simulate the impact of a 2 kg hemispherical-nosed projectile on an RC panel. Extended analyses further investigated the RC panel subjected to multiple impact scenarios. Four distinct scenarios were studied: (1) single impacts at four separate locations, (2) simultaneous impacts at these four locations, (3) sequential impacts of four projectiles, and (4) single projectile impact with energy equivalent to the combined impact of the four projectiles. The study assessed local damage failures, including penetration depth, crater formation, energy absorption, deceleration and reaction forces on projectiles. Results revealed reduced ballistic performance of RC panels under multiple impacts compared to single impacts. Specifically, simultaneous impacts (case 2) and the equivalent single impact (case 4) caused more damage in terms of spalling and scabbing than single impacts (case 1) and sequential impacts (case 3). Additionally, cases 2 and 4 exhibited similar performance in terms of projectile penetration. This study is useful in understanding RC panels’ ballistic performance under multiple impacts.