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This paper presents an analytical investigation of the impact response and failure mechanisms of reinforced concrete (RC) beams—including both bending- and shear-type beams reinforced with carbon fiber-reinforced polymer (CFRP) grids and polymer cement mortar (PCM)—under single and repeated impact loads. A simplified smoothed particle hydrodynamics (SPH) method was used for the simulation, incorporating a virtual particle concept to model the debonding of the strengthening layers. Compared to the experimental results, the simulation method accurately predicted the response of the bending-failure-type beams with an average error margin of 7%. However, concerning shear failure beams, the simulation accuracy is significantly influenced by the adhesion model between the concrete and steel bars. The findings indicate that different impact velocities alter the crack propagation under repeated impact conditions, with two distinct failure modes observed: CFRP rupture in the high-flexibility grids and debonding in the low-flexibility grids. Nonetheless, if no debonding occurred, the strengthening layer reduced the displacement and crack development in bending-failure beams by 20% while having no effect on shear-failure beams. A parametric study conducted to assess the key parameters affecting strengthening effectiveness, emphasizing the importance of optimizing the PCM layer to enhance reinforcement while minimizing debonding risks, revealed that an excessively high PCM strength and thickness did not yield significant improvements and increased the risk of debonding. Additionally, lower-flexibility CFRP grids increased the occurrence of debonding, particularly in thicker grid layers, whereas thinner grids provided a more effective strengthening solution, highlighting the influence of grid flexibility on failure mechanisms. [ABSTRACT FROM AUTHOR] more...

This article focuses on the key issue of energy dissipation in passive rockfall protection structures when exposed to impact by a rock block. As an application case, a structure consisting of a wall made of interconnected concrete blocks is considered. A Non-Smooth Contact Dynamics (NSCD) model of this structure was previously developed and calibrated with respect to the spatio-temporal impact response obtained from real-scale impact experiments. The NSCD model accounts for energy dissipation due to friction between the system bodies and to plastic strain at contacts. The energy dissipation computation method is detailed and its exactness is demonstrated considering two impact cases. The evolution with time of energy dissipation by each dissipative mechanism provides insights into the global structure response with time in terms of displacement and contact force amplitude. The influence of the model parameters on the contribution of these two dissipative mechanisms is evaluated. A ratio between energy dissipation by friction to energy dissipation by plastic strain is proposed as a criterion for structural response evaluation. The variability in energy dissipation varying the impact conditions is addressed. In the end, this study reveals the benefits derived from a precise quantification of energy dissipation in passive rockfall protection structures. Beyond the considered application case, such an approach focusing on energy dissipation opens up promising prospects for improving the design of all passive rockfall mitigation structures. Highlights: A rigorous scheme is proposed for computing energy dissipation by both friction and plastic strain in the Non-smooth contact dynamics (NSCD) framework. The structure dissipative capacities computed from simulation results are addressed in terms of the ratio Rf/p between the energy that is dissipated by friction to that dissipated by plastic strain. The structure dissipative capacities assessed from simulation results, including the ratio Rf/p, reveal sensitive to the way how the model parameters were calibrated and, to a larger extent, to the impact conditions. The ratio Rf/p appears relevant for describing the whole structure response over a wide range of realistic impact conditions. [ABSTRACT FROM AUTHOR] more...

Previous studies on the dynamic problems of magneto-electro-elastic (MEE) beams mainly focused on the buckling and free vibration, no literature paid attention to the low-velocity impact response problem. More importantly, no one conducted the investigation on the nonlinear low-velocity impact of MEE beams with considering the effect of initial geometric imperfection. To fill this gap, this article aims to study the low-velocity impact problem of MEE beams with initial geometric imperfection. Firstly, the nonlinear Hertz contact law is used to describe the displacement and contact force of the MEE beam, and the initial conditions for the beam and impactor are given. Subsequently, considering the multiple coupling effect, the dynamic model is established through Hamilton's principle. Taking the simply-supported boundary condition into account, the Galerkin principle is utilized to reduce the dimensionality, resulting in a nonlinear equation regarding contact time, lateral central displacement and contact force. Meanwhile, two comparative analyses are conducted to confirm the rationality of the present work. Finally, the Runge–Kutta method is employed to solve the low-velocity impact response, in which the effects of electric potential, magnetic potential, initial geometric imperfection, temperature rise, prestress, damping coefficient, the radius and velocity of the impactor as well as the geometric dimension of the beam are discussed. [ABSTRACT FROM AUTHOR] more...

In this study, we address the challenge of hidden damages in FRP composites, such as delamination, matrix cracking, and fibre breakage resulting from transverse low-velocity impact (LVI)—damages often elusive on the surface. Our methodology operates at the meso-scale, depicting laminates as stacked homogenized plies incorporating interfaces. To capture the mechanical behaviour and damages, we extend an existing nonlinear mean-field debonding model (NMFDM), accommodating asymmetric matrix plasticity (AAMP), fibre–matrix interface debonding failure, and in-plane progressive failure. In a key enhancement, we introduce a strain rate term to the AAMP model, addressing strain rate effects associated with LVI loading. Additionally, we incorporate a novel strain-driven 3D failure criteria, offering a more precise assessment of progressive failure subjected to LVI loading. The interfaces between plies are modelled using surface-based cohesive behaviour to capture interaction phenomena. To validate the developed NMFDM, we conduct impact simulations at various energies on a UD composite laminate consisting of AS4/8552 carbon fibre and epoxy matrix. These simulations showcase the predictive capability and accuracy of the NMFDM in capturing the intricate behaviour and damage progression of UD composites subjected to LVI. [ABSTRACT FROM AUTHOR] more...

To investigate the enhancement mechanism of polyurea elastomeric coating on the anti-impact of unidirectional graded auxetic honeycomb sandwich panels. With the help of LS-DYNA finite element analysis software, the dynamic response of the sandwich panel to a cylindrical impact is simulated numerically. The influence of polyurea coating by the method of outline volume analysis position on its anti-impact is first analyzed. On this basis, the effects of impact velocity, impact angle of the cylinder, coating thickness, and coating area of polyurea elastomer on the sandwich panel are further discussed by the method of outline volume analysis. Finally, the polyurea thickness on both sides of the coated polyurea sandwich panel (type C) on both sides is optimized. The results show that the coating of polyurea elastomer can effectively enhance the impact protection performance of sandwich panels. By comparison with sandwich panel of uncoated structure (Type O), type C achieves the best anti-impact, and the maximum post deflection (Defl) is reduced by 61.6%. The increase in impact velocity and the decrease in impact angle will increase the maximum deflection of the sandwich panel if other variables remain constant. When the cylinder impact speed is certain, preference is given to sandwich panels that are thicker, larger, and have polyurea sprayed on both sides. The optimization by the response surface method shows that the sandwich panel with the best anti-impact may be obtained when the polyurea thickness ratio of the impact side to the back side is 1.3:0.7. [ABSTRACT FROM AUTHOR] more...

In previous earthquakes, a significant number of adjacent buildings in a series have been damaged due to collisions. Pounding between adjacent structures in a series causes them to inflict multiple blows on one another, which is a complex type of collision. Previous studies have produced inconsistent or conflicting research conclusions due to various parameters of buildings and excitation. It is challenging to determine a universal law of collision reactions between adjacent buildings in a row. To address the complexity of these parameters, the dimensional analysis method is used. This work establishes a mathematical model for the dimensionless collision response of adjacent structures in a row. The layout of the structures is considered through three different configurations, and the effects of unilateral and bilateral collisions are compared. The analysis also considers the impacts of the frequency ratio, mass ratio and gap size of the oscillators. According to the impact of pounding, the displacement and velocity responses of the outer structures with low mass and stiffness can be divided into multiple spectral regions based on the frequency ratio of the structure and excitation. The effects of the mass ratio and frequency ratio on the responses of the outer flexible structures are correlated with the spectral regions. The results indicate that placing a structure with a small mass and stiffness outside is dangerous, since it causes a much larger pounding force and displacement of the outer structure. Compared with the unilateral impact response, the bilateral impact response induces a smaller displacement of the middle structure with a slight mass and stiffness. [ABSTRACT FROM AUTHOR] more...

The responses of sandwich cylindrical shells containing fluid to free vibrations and low-velocity impact were studied. The high-order shear deformation theory and Bernoulli's equation for the structure-fluid interface were used. To solve the equations obtained and validate the results, the Galerkin method and Abaqus finite element software were employed. The main innovation of this research is the calculation of the effective mass of the top layer and the entire sandwich cylindrical shell containing fluid using displacement field relations, their equivalent density, and indentation force due to impact. In addition, to calculate the impact force and the structure-fluid interaction, a two-degree-of-freedom model of mass, spring, and damper with the effect of the crushing resistance of the core was used. The results show that the fluid is an important and effective factor in calculating the natural frequency and low-velocity impact on the structure. The presence of fluid reduces the fundamental natural frequency of the sandwich cylindrical shell by 69%. Parameters such as core and layer thickness, length, and radius of the sandwich cylindrical shell, presence of the fluid, various boundary conditions, wave number, fiber orientation angles, velocity, and mass of the impactor are essential and influential factors in studying vibrations, impact, and optimal design of structures. [ABSTRACT FROM AUTHOR] more...

The paper presents the results of research into the influence of the titanium foil thickness on the impact response of metal-ceramic ZrO2/Ti/ZrO2/Ti composites consisting of nonrigidly joined plane-parallel layers. The difference is shown between the deformation behavior of the metal foils in composites with foil thicknesses of 100, 200, and 500 μm. It is found that an increase in the thickness of reinforcing metal layers leads to a higher structure dispersion in the deformation localization zone. The deformation and fracture features of each layer of the composites are studied in detail. A comparative analysis is made of the structural characteristics of materials before and after impact loading. [ABSTRACT FROM AUTHOR] more...

Carbon fiber reinforced-polylactic acid (CF-PLA) composites nowadays are widely researched alternative structural materials for their potential application in prosthetic and orthotic implants. The present work firstly consolidates the findings on the application of 3D printing in biomedical and allied fields. Fatigue life and impact strength of 3D printed CF-PLA test specimens were determined. The test specimens were fabricated through the fused deposition modeling (FDM) approach at two printing temperatures. The pronounced effect of printing temperature is characterized by the significant change in fatigue life and impact strength of the FDM specimen. The fatigue life at the printing temperature of 240°C was 2.7 times greater than that at 225°C, whereas the impact strength was greater by 5.93%. The microscopy findings revealed increased diffusion and a reduced number of ridges and pores at higher printing temperature testifying that printing temperature prominently controls the durability and impact response of FDM printed parts. [ABSTRACT FROM AUTHOR] more...

Reinforced concrete (RC) structural members could be subjected to impulsive impact loads due to various effects such as the collision of masses driven by rockfall, flood, landslide, avalanche, the crash of vehicles to structural elements in highway and seaway, airplane landing contact, the acting of explosion-induced air shock waves on structural elements as impulsive loads. The conventional design of RC slabs and similar structural members is carried out regarding vertical static and lateral dynamic loads such as earthquake and wind effects. However, the design phase mostly ignores impulsive loads such as impact and blast. Thus, these effects pose risks that the structures experience heavy damage or total collapse. Strengthening RC slabs with textile strips has become a preferred strengthening technique to prevent the collapse of structures and limit damage to structural elements. This study strengthened RC slabs with basalt textile reinforced mortar (TRM) strips in different widths, and layout patterns were tested for low-velocity impact load. In addition, the effects of BFRP fan-type anchors near the impact point on the behavior have also been investigated. The effect of various applied strengthening patterns on impact load transferred to specimens, dynamic responses such as acceleration, displacement, maximum strain, and dynamic failure modes occurred were investigated and interpreted in detail. The experimental results have also been compared with the improved finite element model (FEM) generated. It is demonstrated that the present FEM can be used to evaluate the impact response of the RC slabs with TRM strips. [ABSTRACT FROM AUTHOR] more...

The use of additive manufacturing for the fabrication of sacrificial cladding is becoming increasingly popular as it facilitates the production of complex yet space-saving protective structures. Despite this, the effect of several structural parameters on their capacity to mitigate high-velocity impacts remains elusive. Toward this end, the shock-mitigating capacity of various short fiber-reinforced polymer samples was evaluated regarding impact velocity and mass (raging from 1 to 8.3 m/s and 5.5 to 7.5 Kg, respectively). Among the assessed parameters were peak force (measured to vary by up to 46.6%), max. and mean deceleration values (with max. differences documented at 29.5% and 48.2%, respectively) and cushion factor. As expected, the progressive crushing modes differed significantly across the spectrum of the tested samples. Structural failure involved the growth of inter- and intra-laminar cracks, fiber-matrix de-bonding and de-lamination, which was dependent on equivalent pore volume fraction and compressive strength. Increasing infill density led in most cases to higher peak forces during impact, as did the deposition of more solid peripheral layers, with the latter producing a superior deceleration plateau. Evaluated collectively, the results indicate that an infill density of 37% with 4 solid external (protective) layers exhibited the superior impact response among the tested samples. [ABSTRACT FROM AUTHOR] more...

Sandstone impact is a common occurrence that can have critical implications, especially in the transportation sector. In order to enhance the ability of structures such as aircraft and other vehicles to withstand impacts from sandstone debris, simulation tools can be employed during the structural design stage. To determine the rate-dependent constitutive parameters of sandstone that can be used for creating a material model to simulate sandstone impacts, a detailed investigation on the dynamic mechanical properties of sandstone was performed by conducting quasi-static, dynamic, and impact tests. The results demonstrate that the determined parameters of Holmquist–Johnson–Cook (HJC) model can accurately describe the mechanical behaviour of sandstone in static and dynamic compression tests. The model also predicts well the impact response of sandstone against aluminum target plates. Parametric studies were conducted to explore the sensitivity of the constitutive parameters as well as to provide guidance for determining the values for constitutive parameters that are difficult to determine experimentally. The simulation model presented in this study provides a valuable tool for designing vehicles or aircraft that can better tolerate impact damage from sandstone debris. Highlights: Constitutive parameters of the Holmquist–Johnson–Cook (HJC) model for sandstone are experimentally and numerically determined. The developed model predicts reasonably well the quasi-static, dynamic, and impact failure behavior of sandstone. The relationship of target deformation, energy absorption, and impact velocity of the sandstone are systematically investigated. Sensitivity of Plock for the HJC model is numerically studied. [ABSTRACT FROM AUTHOR] more...

This paper proposes an experimental method to evaluate the structural performance of full-scale piles subjected to pile driving condition. A pendulum mechanism was used to deliver impact forces on a pile which was placed horizontally on supports and restrained at the tip with large blocks to mimic the critical real-world condition of reaching a strong/hard layer. Accordingly, driving forces were transferred to the pile by an impactor that was designed to deliver impact energies comparable to those of typical pile driving hammers. To swing the impactor and to guarantee a stable motion, four cables connected to two out of three 50 ft. tall steel pylons were attached to the impactor through lifting eyebolts, while another cable pulled back the impactor toward the third pylon to a desired drop height from where the impactor was released. The restraining blocks placed at the tip also minimized excessive displacement. Friction between the restraining blocks and the piles as well as friction between the soil and the pile surface limited displacement at the pile tip. The experimental method evaluated in this study effectively simulated pile driving for assessing structural performance and pile driveability, especially when evaluating new materials with an unknown impact response. This method of pile testing provided laboratory conditions for a pile impact test that is usually carried out in the field. [ABSTRACT FROM AUTHOR] more...

The composite cushion of sand and non-vented flexible airbags offers a promising application in protecting galleries against rockfall. This research focuses on a numerical study that aims to more effectively characterize the global mechanical behavior of the cushion rock shed system with sand layer, as well as the sand-airbag composite cushion system. The impact response properties during a collision between cushion and rockfall, including, the penetration depth, and the vertical displacement of the plate, the impact forces on the gallery surface, and the impact forces on the bottom of the RC slab were studied. It was found the impact force affected the surface of the cushion and the bottom of the RC plate with the type of cushion materials. The impact forces of the novel composite cushion and vertical deformation of the plate are lower than the sand cushion, while the penetration depth of the granular cushion is greater than that of the composite cushion. It was also found that increasing the thickness of the sand layer can only reduce the impact forces on the bottom of the slab and increase the impact forces on the upper surface of the cushion. On the other hand, a new calculation method based on dynamic analysis is proposed to determine the impact force on the bottom of the RC slab. The proposed method was verified by comparison with the numerical and laboratory results. [ABSTRACT FROM AUTHOR] more...

The paper reports the results of investigation of the impact response of ZrB2/Ti and ZrB2/Al ceramic-metal composites with non-rigidly fixed layers. It is shown that, as the energy dissipates from layer to layer, the dispersion of the structure of metal foils and ceramic plates increases. The fracture toughness of the ZrB2/Ti composites exceeds that of the ZrB2/Al composites, while the fracture toughness of the latter is close to that of the monolithic ceramics. [ABSTRACT FROM AUTHOR] more...

A cutter ring is a consumable tool used by a tunnel boring machine (TBM) to break rock, affecting the cost and time limit of tunnel engineering. In this paper, based on the working principle of the cutter ring, the failure form of cutter rings, and the mechanical properties of rock, a variable cross-section (VCS) cutter ring is optimized based on the existing constant cross-section (CCS) cutter ring. The finite element method was used to model the Beishan granite, and the mechanical properties of the granite were simulated. The average discrepancy rate of the four key parameters was 1.19% compared with the experimental results. The linear rock cutting experiment of the disc cutter in Beijing University of Technology was simulated, the simulation results of normal force are similar to the reality. The digital models of the 20-in CCS cutter ring and 30 types of VCS cutter rings are established, and modal, impact response, and cutting rock simulations are conducted. The results demonstrate that the natural frequencies of the two types of cutter rings are very close to 6.72 rad/s, confirming the feasibility of interchange. The impact resistance of most of the 30 VCS rings is higher than that of CCS rings, and the rock-breaking effect of all VCS rings outperforms that of the CCS rings. The VCS ring with the highest crushing adaptability of the rock model in this simulation experiment was obtained by statistical analysis of 3D data. This experimental method of rock adaptability can obtain the optimal design parameters of VCS cutter rings for a particular rock model. VCS cutter rings have the potential to support establishing a tool selection system with rock adaptability based on extensive experimental data in the future. Highlights: According to the working principle, failure mode of TBM disk cutter and rock characteristics, a variable cross-section (VCS) disk cutter is designed. The simulation model of linear rock cutting is established according to the real experiment, and the validity of the simulation model is verified. The impact resistance and damaged rock performance of 30 kinds of VCS cutter rings were ranked using a statistical analysis method with 3D data. [ABSTRACT FROM AUTHOR] more...

The tuning of the structural batteries for various applications of transportation is an ambitious target. The pollutant emission and mostly the process for battery recycling and recovery are peculiar aspects to consider for new designs. The goal is to reduce the weight. In this frame, taking into account that the traditional battery packs do not contribute to the structural performance, it is worth to underline the solution of the structural batteries allows to increase the mechanical properties as they are integrated into the primary structure. The paper establishes the response of a composite structural battery model subjected to low-velocity impact tests. The process used to manufacture the structural battery model is described, and the experimental activities are performed by a customized drop tower and finally replicated numerically by explicit code to enhance the comprehension of the structural dynamics. Differences with respect to a carbon fiber laminate are highlighted both for the force released at the impact and dart displacement, for the same levels of energy. [ABSTRACT FROM AUTHOR] more...

B. Palmieri et al. in "Investigation on Stress Relaxation of Discontinuous Recycled/Repurposed Carbon Fiber Composites" investigate the thermo-mechanical and viscoelastic behavior of composites made at different recycled carbon fiber (rCF) content. These are similar in structure to carbon fiber composites, where the matrix features dielectric characteristics, making the structure capable of storing electric energy. This special issue focus is dedicated to the fourth edition of the "International Symposium on Dynamic Response and Failure of Composite Materials, Draf2022" held in Ischia, Naples, from June 21-24, 2022. [Extracted from the article] more...

In the present work, the response of composite hybrid laminates made of carbon and glass fibers in different stacking configurations was tested under low-velocity impact loads. Experimental drop impact tests were conducted on three different stacking sequences and three rising impact energy levels. The results from the tests were assumed for the development and validation of a numerical impact model reproducing for each stacking sequence and all the impact energy levels, the laminates impact response. The validated model investigated the occurred damage mechanisms, their distribution in the panel thickness and their extension on the plane of the laminate. Depending on the stacking sequence and the impact energy level, the energy absorption capacity was related to the dominant damage mechanism. The percentage contribution of interlaminar and intralaminar damages was presented and conclusions were drawn about the influence of stacking sequences on energy absorption and damage characteristics. [ABSTRACT FROM AUTHOR] more...

The nonlocal strain gradient and velocity gradient theories were applied to study sandwich nanoplates’ dynamic response to low-velocity impact. The impact force comes from the van der Waals contact forces between the impactor and nanoplate. Combining nonlocal velocity gradient and strain gradient theories add three scale parameters to the constitutive equations and produce more accurate results. The displacement equations were calculated using layer-wise first-order zig-zag theory. The governing equations were solved using the Ritz and fourth-order Runge–Kutta techniques. The dynamic responses of the contact force, reflected velocity, plate deflection, and impactor displacement were investigated using the numerical findings. The nonlocal parameters, nanoplate fiber orientation, and impactor material are all important components. A case comparison study verified the technique and outcomes, demonstrating great accuracy. Some nonlocal characteristics, such as the kinetic material length scale parameter, enhance the nanoplate softness, and cause the impactor to waste more energy on it, increasing the nanoplate deflection and decreasing the contact force. Increasing the kinetic length scale parameter by up to 300% results in a decrease in interaction force to 4% and an increase in deflection to 15%. Different impactor materials significantly alter impact dynamics. Impactors with higher Lennard-Jones force parameters interact with the nanoplate earlier. The silicon impactor with a Lennard-Jones attraction parameter three times greater than that of platinum, reaches the plate 0.0015 nanoseconds earlier. A high impactor density increases the nanoplate deflection and contact force. However, this occurrence lowers the impactor reflected velocity and displacement slope. [ABSTRACT FROM AUTHOR] more...

Fibre metal laminates (FMLs) can be widely used in structural (automobile, aerospace industries, etc.) applications where performance enhancement (FMLs provide good impact and fatigue resistance, etc.) and cost effectiveness play a vital role. Hybridization (glass/carbon) of FMLs may result in performance enhancement and improved longevity when subjected to various loading conditions. Therefore, in the present study Charpy test was carried out using 300 J Charpy hammer according to ASTM E-23 in flat-wise orientation to understand the influence of 1wt% of alumina (Al2O3), zirconium oxide (ZrO2), titanium oxide (TiO2) nanoparticles reinforcement on impact response of hybrid FMLs. Mean particle size of Al2O3(5.1 nm), ZrO2(25.3 nm), TiO2(63.2 nm) was estimated with the help of X-ray diffraction analysis using Scherer equation. It is observed from the results that hybridization of GLARE (glass laminate aluminium-reinforced epoxy) enhanced the impact strength by 2.4%, but degradation of 0.9%, 1.4%, 1.8% is noticed in Al2O3-, ZrO2-, TiO2-reinforced hybrid FMLs, respectively. Maximum impact strength was identified in Al2O3-reinforced hybrid FMLs when compared to other nano-hybrid FMLs. Nanoparticles dispersion in the matrix, interface region and fractured surface morphology were analysed using scanning electron microscope. However, it is summarized that the impact response of nano-hybrid FMLs strongly depends on the type of fibre and nanoparticles size introduced in the polymer matrix. [ABSTRACT FROM AUTHOR] more...

The low-velocity impact response of aluminum honeycomb sandwich panels with composite face sheets is investigated using an LS-DYNA-based finite-element simulation. The finite-element model incorporates the damage, delamination, and failure capabilities, and a verification analysis of the results found. Suitable prediction models for the specific energy absorption and peak load at different values of geometrical parameters of the panels are developed using the response surface methodology. The effects of face sheet thickness, cell size, cell height, and cell thickness on the specific energy absorption and peak load are investigated. A multi-objective optimization of the panels is carried out for the maximum specific energy absorption and the minimum peak load. [ABSTRACT FROM AUTHOR] more...

The present study investigates tensile strength and impact resistance of alumina (Al2O3) filled carbon-S2-glass (CG) and carbon-Kevlar-49 (CK) reinforced epoxy hybrid composites, for three, five and seven layers. Nanoparticles of 40-nm size are dispersed in the epoxy matrix at a concentration of 2 wt.% of the matrix. Composites are manufactured employing the vacuum-assisted resin transfer molding method. Mechanical properties are determined by tensile and Charpy-V-notch impact tests. It is shown that number of layers affects tensile and impact characteristics. Ultimate tensile stress of CK laminates increases by approximately 35%; however, it decreases for CG laminates by 20%, per addition of a single layer of a particular fiber, whereas a similar trend in elongation at break and tensile modulus is observed for both types of composites. Stress–strain curves follow a particular pattern, characterized by unstable delamination and gradual fragmentation of a single laminae. With the addition of nanoparticles, both modulus of elasticity and ultimate tensile stress are greatly decreased by approximately one and two orders of magnitude. Values of ultimate tensile stress and strain increase with number of layers for CK laminates, while it is the other way around for CG laminates. Charpy impact tests reveal that impact energy and impact strength of the CG laminates are larger than those of the CK laminates; and impact strength increases with number of layers. Micro-scale damage analysis is conducted via scanning electron microscope (SEM) technique. Accordingly, fiber breakage, fiber pull-out and matrix cracks occur in the composites. [ABSTRACT FROM AUTHOR] more...

Peening technology is a cold working processing in which peening mediums impinge on a part to improve fatigue life or form a desired shape. The peening medium can be spherical shot, hammer or needle, etc. The shape of the peening medium varies due to processing technology and loading deformation. This paper aims to investigate the effect of peening medium shape on peening results. The peening medium head is assumed to be ellipsoidal and its shape is controlled by aspect ratio. An analytical model of ellipsoid impact response is established based on the expanding cavity model. From the solution of the analytical model, the evolution of shot velocity, indentation size, plastic layer depth, shot deformation and contact pressure are obtained. Finite element simulations are carried out to study the impact results of different ellipsoids , which are verified by peening experiments. The analytical, numerical and experimentally measured indentation sizes are in good agreement. The effects of sharp peening medium and blunt peening medium are compared on indentation geometry, plastic zone size and residual stress field. It is concluded that shallow dimple and thick strengthening layer can be obtained by using blunt peening mediums with high kinetic energy. [ABSTRACT FROM AUTHOR] more...

Synthetic surrogate head models are used in biomechanical studies to investigate skull, brain, and cervical spine injury. To ensure appropriate biofidelity of these head models, the stiffness is often tuned so that the surrogate's response approximates the cadaveric response corridor. Impact parameters such as energy, and loading direction and region, can influence injury prediction measures, such as impact force and head acceleration. An improved understanding of how impact parameters affect the head's structural response is required for designing better surrogate head models. This study comprises a synthesis and review of all existing ex vivo head stiffness data, and the primary factors that influence the force–deformation response are discussed. Eighteen studies from 1972 to 2019 were identified. Head stiffness statistically varied with age (pediatric vs. adult), loading region, and rate. The contact area of the impactor likely affects stiffness, whereas the impactor mass likely does not. The head's response to frontal impacts was widely reported, but few studies have evaluated the response to other impact locations and directions. The findings from this review indicate that further work is required to assess the effect of head constraints, loading region, and impactor geometry, across a range of relevant scenarios. [ABSTRACT FROM AUTHOR] more...

In the present article, the finite element (FE) simulation of the low-velocity impact of a sandwich plate with a nearly incompressible compliant hyperelastic core and SMA face sheets is accomplished for the first time, using a 3D pseudoelasticity phase transformation model and a semi-3D layerwise sandwich plate theory. The changes in the thickness and the time/load-dependence of the stiffness of the contact region are taken into account and various (neo-Hookean, Mooney-Rivlin, and Yeoh) hyperelasticity models and clamped and simply supported boundary conditions are examined. The resulting nonlinear coupled governing finite element equations of the damped impact response of the hyperelastic and pseudoelastic plate are solved by an iterative updating algorithm that is capable of tracing the impact and complete/incomplete direct and converse 3D phase transformation events. The modeling procedure, formulation, and solution algorithm feature apparent superiorities, even on the well-known commercial finite element analysis codes, due to employing higher scientific and mathematical accuracies. It is found that while the Mooney-Rivlin model induces larger compliance in comparison with the neo-Hookean and Yeoh hyperelasticity models, the SMA face sheets significantly reduce the resulting lateral deflections but increase the global stiffness of the contact region and the contact force, and that simply supported plates feature larger recovery strains and hysteresis loops that lead to higher damping and smoother time histories. [ABSTRACT FROM AUTHOR] more...

This study deals with an innovative type of protection structure for gravity-driven natural hazards such as landslides (slope failures, rockfalls, etc.) consisting of a vertical wall made up of interconnected concrete blocks. This type of articulated structure presents many advantages including reduced footprint, versatility and easy maintenance. The response of such a structure under impact is investigated considering projectiles with kinetic energies of 520 and 1020 kJ, based on real-scale impact experiments and numerical simulations. The finite difference model is described in detail as well as the experiments. The model was developed focusing on the global structural impact response while keeping the computation time reasonable. The model parameter calibration is based on data in the literature and complemented with specific measurements. The experimental data allows us to describe the impact response of the structure and identify the main mechanisms controlling this response (sliding, tilting, and fracturing). The simulation results revealed that the model is efficient in mimicking this response, in terms of deformation amplitude and evolution with time. Finally, the numerical model made it possible to highlight complex mechanisms that were not possible to experimentally determine such as the different energy dissipation modes within the wall. Highlights: Full-scale impact experiments demonstrating the impact strength of articulated walls made of concrete blocks and metallic elements up to 1000 kJ. Finite difference model of the structure validated against experimental data. Highlights of the prevailing mechanisms involved in the impact response of the structures based on both numerical and experimental investigations. Based on simulation results, friction between concrete blocks and damage to concrete contribute up to 70% of the projectile kinetic energy. [ABSTRACT FROM AUTHOR] more...

In this present work, the ballistic impact resistance of Uni-directional E-Glass/Epoxy laminates is numerically simulated for various projectile nose shapes. For this purpose, a finite element explicit software package, ABAQUS/CAE, is used to simulate the 3D model of the Specimen and Bullet. The dynamic analysis is done for four different layup configurations, (i) [0/90/0/90-rep-], (ii) [45/-45/45/-45-rep-], (iii) [0/90/0/90-sym-], and (iv) [45/-45/45/-45-sym-]. These target plates are tested against projectile nose shapes such as flat, hemispherical, ogival, conical, and spherical. The residual velocities, the kinetic energy of the projectile have been plotted for different ply orientations and nose shapes, and they are compared to get a clear picture of the effect of nose shapes of projectiles. [ABSTRACT FROM AUTHOR] more...

Introduction and hypothesis: It is unknown whether gabapentin modulates the therapeutic effect of anticholinergics (AC) in patients with overactive bladder. We hypothesized that pre-existing gabapentin use would improve response rates in these patients. Methods: Female patients treated with AC between 2010–2018 were identified. Data were collected on gabapentin use, indication, dose and duration of use as well as demographic and clinical characteristics. Patients were stratified by those that only took AC and those that took both AC and gabapentin ("combination therapy"). Response was determined through chart review. Descriptive statistics were expressed as medians and interquartile ranges (IQR). Pairwise analysis was performed using Wilcoxon rank-sum. Multivariable logistic regression was used to identify independent variables predicting response. A subgroup analysis was performed in patients with chronic pain disorders. Results: Seven hundred fifty-six subjects met all criteria; 16.5% (n = 125) were on combination therapy. Those taking gabapentin were more likely to have chronic (49.6% vs. 22.5%, p < 0.001) or neuropathic pain (25.6% vs. 9.4%, p < 0.001) and to use narcotics (41.6% vs. 15.5%, p < 0.001). Patients taking combination therapy were not more likely to improve compared to patients taking AC alone (41.6% vs. 47.7%, p = 0.211), which persisted after adjusting for confounders (aOR = 1.02, 95% CI: 0.63–1.65). In the 182 patients with chronic pain, those receiving combination therapy were more likely to respond than those taking AC alone (35.2% vs. 21.9%, p = 0.0015), although this did not persist after adjusting for confounders (aOR = 1.15, 95% CI: 0.70–1.90). Conclusions: Pre-existing gabapentin use does not seem to influence response to AC in patients with overactive bladder. [ABSTRACT FROM AUTHOR] more...

Traffic accidents and derailed train-related incidents have occurred more often than ever in recent years, resulting in some economic damage and casualties. Reinforced concrete (RC) constructions often involve derailed train and vehicle accidents. Rarely are such side collisions studied in previous studies. To do this, high-fidelity simulation-based finite-element (FE) models are created in this paper to accurately simulate the collision of circular RC members with a derailed train. The reinforced concrete member structure is common in high-speed railway stations. The impact energy of the impact body is significant, causing structural member failure. It analyses the dynamic behavior of reinforced concrete members under unequal span impact loads. Numerical implementations of impact issues are discussed from the perspective of geometric, contact, and material properties. The reliability and precision of the ABAQUS code to solve impact issues are verified by comparing failure modes, impact, and deflection time history experimental outputs. By analysing the impact response characteristics, used the control variables to study the failure process and mode (including the characteristics of impact and reaction forces, deflection time history curve, impact force–deflection curve, and bearing reaction force–deflection curve). The reinforcement ratio, impact velocity, concrete strength, and slenderness ratio significantly affect shear crack pattern and development. Changes in impact velocity and slenderness ratio also affect member failure modes. [ABSTRACT FROM AUTHOR] more...

The blade of a gas turbine is one of the most sensitive parts so that it can be called the heart of the gas turbine. Blades work in strict operational and environmental conditions and thus require careful analysis, inspection, and visits to prevent the sudden extinction of the gas turbine. This paper analyzes gas turbine compressor blades in three conditions (a notch-free blade, a blade with one notch in the root, and a blade with two notches in the root) by modal test and finite element methods. According to the analysis of the results obtained from the two methods for the blade sample in the expressed conditions, it is observed that the natural frequencies and critical speeds were decreased by about 6.5 and 9.5% in the sample with one notch and two notches in the root compared to the notch-free blade, respectively. The presence of a notch on the blade root has a significant effect on the impact response and frequency of the blade. The presence of two notches on the root of the blade has a twice as great impact on reducing the damping and stiffness of the blade, because of which the natural frequencies of the blade are also reduced. [ABSTRACT FROM AUTHOR] more...

A new type of thin-walled circular tubes (CTs), which is inspired by the bamboo with highly-efficient energy absorption (EA) capability, was proposed and designed for the potential application of the energy absorber of rail vehicles in this study. And then, the axial crushing behavior and crashworthiness of the bamboo-inspired bionic tube (BT) were experimentally and numerically investigated, compared with the single CT and foam-filled tube (FT). The typical crushing responses (e.g., deformation mode, load-displacement response, energy absorption, and strain distribution) and quantitative crashworthiness indicators (EA, SEA, FP, Fm, and CFE) of these three types of CTs were presented and discussed. Effects of impact velocity and foam relative density on the crashworthiness of tested tubes were also explored. The experimental and simulation results show that the BT specimen exhibits the best capability of load-carrying, energy absorption, and crashworthiness among three types of tubes. Compared with the CT specimen, the EA value of BT specimens increased by 93.1%, while the corresponding Fm value raised from 74.2 kN to 143.4 kN. [ABSTRACT FROM AUTHOR] more...

With the fast growth of high-speed rail in recent years, derailment has become the first hidden danger of high-speed rail transportation. The high-speed train passes near the station building. So the train may derail and hit the station building. Building a high-speed railway station usually uses a reinforced concrete structure. As a result of high impact energy on the impact body, the reinforced concrete (RC) member may fail; the impact point is near the member's foot; the structural member's constraint can be considered fixed support. This paper investigates the dynamic behavior of four types of circular reinforced concrete members under unequal lateral impact loads. The RC member's failure mechanism and dynamic response addressed the significance of unequal lateral impact load. The usual circular reinforced concrete members are used as the model to perform the drop-weight impact test. The specimens' crack pattern, failure mechanism, impact, deflection, and strain time–history curves are obtained. Findings show that between the impact point and the adjacent support, shear fractures occur that fail in shear mode. Shear cracks are based on impact velocity, longitudinal reinforcement ratio, and stirrup ratio. One type is more destructive to members and nodes. A shear fracture occurs when a longitudinal reinforcement fractures towards the closer support. The effects of impact velocity, longitudinal reinforcement ratio, and stirrup ratio on the dynamic impact response are studied. The experimental results may help improve structural member impact resistance. The critical section (right side) computed the static shear resistance using shear force, whereas the maximum external load resistance determines static bending moment resistance. Understanding how circular members fail to be subjected to unequal lateral impact loads provides insight into circular RC members' impact design and damage evaluation. [ABSTRACT FROM AUTHOR] more...

Background: Plastic dissipation at inter-granular contacts during elasto-plastic wave propagation plays a significant role in wave attenuation. However, it is unknown if plastic dissipation during impact is enhanced if the granular medium is initially in an unconfined 'fluid-like' state or that of a more rigid 'solid-like' state caused by applying a confining pressure. Objective: The goal of this work is to investigate both experimentally and numerically the impact response of a two-dimensional hexagonal granular array consisting of metallic spheres enclosed in a polymeric membrane subjected to different levels of confining pressure. We seek to quantify the granular trajectories, the effect of the membrane, and the ratio of the dissipated plastic energy to the net input energy between the unconfined and confined states. Methods: We perform experiments using a modified split Hopkinson pressure bar on a specimen of monodisperse brass spheres confined by a polymeric membrane and record the impact event using high-speed photography so that particle tracking can be used to track granular motion. After impact, the sphere surfaces are examined to measure plastic contact areas, allowing the dissipated plastic energy to be estimated. To support the experiments, capture the lateral confining effect of the membrane and applied pressure, and investigate larger arrays, discrete element simulations are conducted. Results: When the granular array is confined, we observed shorter and consistent granular trajectories between trials, a greater dissipated energy to net input energy ratio, and a stiffer membrane response. Conclusion: Experimental and numerical results indicate that the external confining pressure increases plastic dissipation. [ABSTRACT FROM AUTHOR] more...

The impact behavior of sandwich structures was studied using experimental and numerical methods. Polypropylene with 0.5 wt% of graphene (PP/0.5% G) or pure polypropylene (PP) was sandwiched between aluminum face sheets for experimental tests. Impact tests revealed that the nanoreinforced structures had a higher contact force and a shorter contact duration than pure core structures. Both the damage area and the dent depth were lower for nano-reinforced structures. More energy absorbed the pure structures. The higher absorbed energy can be explained by the higher amount of damage that occurred in the structure. To further investigate the impact response of the sandwich structures, a three-dimensional quarter model was developed and implemented in the ABAQUS software. The strain-rate-dependent behavior of the core and face sheets was investigated using the Johnson–Cook material model to simulate the impact behavior of aluminum, PP, and G/PP layers. Simulation results were compared with experimental data, and a good agreement between them was found to exist. The validated finite-element model was used for studying the effects of geometrical and material parameters, including the thickness of aluminum and PP layers, different weight ratios of nanoparticles, and different mechanical properties of the aluminum layers, on the impact response of sandwich structures. By introducing graphene up to 0.5 wt% into the PP material, all of the impact outputs reached their extremum amounts, which were considerably affected by the yield strength and elastic modulus of aluminum layers. [ABSTRACT FROM AUTHOR] more...

Most reports simulating in-flight particle temperatures in polymer cold spray ignore intra-particle thermal gradients that develop in-flight, and, to date, no research group has simulated the effects of thermal gradients on polymer particle impact dynamics. This report investigates the effects of intra-particle thermal gradients on the impact response of thermoplastics, using properties of polyether-ether-ketone (PEEK) in a simulated like-on-like cold spray deposition process. Particle velocities and internal temperatures are calculated from compressible flow models of the spray process under several heat transfer assumptions. The commonly used lumped thermal capacitance assumption differs in average particle impact temperature by over 70 °C from simulations involving a more physically representative thermal gradient model assuming finite-rate heat conduction. Additionally, the intra-particle temperature differences of over 100 °C in some particles imply significant variation in material properties within a particle. The predicted average temperatures and temperature gradients are used as initial conditions for a finite element-based impact model that shows distinct mechanical responses of isothermal and thermally graded particles. These results suggest that thermal gradients in polymer particles should be considered for further refinements of model-based predictions for the cold spray of polymers and optimized by process design. [ABSTRACT FROM AUTHOR] more...

High-velocity impact response of fiber metal laminates (FMLs) is investigated using finite element method. The strain-based three-dimensional Hashin failure criterion was used, and the effect of strain rate on composite modulus and failure strain was accounted for. A user-defined material subroutine in Abaqus/Explicit was used to define the composite material model. The surface-based cohesive behavior was applied to describe the delamination. The numerical results show a reasonable agreement with published experimental results. This numerical model was utilized to investigate the impact response of AZ31B magnesium-based carbon fiber metal laminate. According to the results, the perforation process can be subdivided into three phases and the damage area of different damage modes of composite layers was also studied. Besides, the impact behavior of magnesium-based FML with hybrid composite (glass–carbon/epoxy) was studied and compared with glass/epoxy and carbon/epoxy. The results show that the damage area and impact resistance of the hybrid composite are between that of glass/epoxy and that of carbon/epoxy. [ABSTRACT FROM AUTHOR] more...

This paper describes an experimental investigation performed to evaluate the low-velocity impact behavior of prepreg-based carbon fiber reinforced polymers (CFRPs) and fiber metal laminates (FMLs) with and without open holes subjected to different impact energies. The laminates were made of carbon fiber/epoxy prepregs and aluminum layers and manufactured by using autoclave. The impact responses of these laminates were experimentally obtained using a drop-weight tower at impact energies of 15, 20 and 30 J. After testing, the impact damage area of tested specimens was quantified from C-scan ultrasonic technique. In addition, an X-ray tomography analysis was performed to assess the through-thickness distribution of damage in FMLs with and without open holes. The results showed that the woven FMLs exhibit the highest impact peak force compared to that of CFRP plates due to the presence of aluminum layers, which induce a higher deformation capability to the laminates. The presence of open holes in laminates tends to augment their damage extension and decreases their impact peak force due to the local stress concentration effect. Nevertheless, it was observed by C-scan ultrasonic images that the aluminum layers reduce the extent of delamination of laminates during the impact event. Postimpact evaluation using X-ray computed tomography showed that impact causes a severe damage to the laminates around their impact point and confirmed that matrix cracking and delamination are the principal damage mechanisms induced on the through-thickness direction of the FML plates. In specific, the results confirm that the aluminum layers provide good impact properties and damage resistance when they are added to the CFRPs. [ABSTRACT FROM AUTHOR] more...

In this paper, the low velocity impact analysis of carbon nanotube (CNT)/carbon fiber (CF)-reinforced hybrid nanocomposite plates is presented using variational differential quadrature (VDQ) method due to its numerical essence and the framework of implementation. The hybrid nanocomposite plate deformation is formulated based on classical plate theory and the contact force between the plate and projectile is estimated using Hertzian contact law. Also, a new micromechanics approach is presented to calculate the effective mechanical properties of the CNT/CF polymer hybrid nanocomposites. Five important factors including, random orientation and random distribution of CNTs, CNT/polymer interphase region, waviness and transversely isotropic behavior of CNT are incorporated in the micromechanical analysis. The accuracy of the present approach is verified with the available open literature results showing a clear agreement. The effects of various factors such as volume fraction and non-straight shape of CNT, CNT/polymer interphase region, CF volume fraction, random and regular arrangement of CFs, plate geometrical parameters and impactor velocity on the low velocity impact behavior of the CNT/CF-reinforced hybrid nanocomposite plates are studied. [ABSTRACT FROM AUTHOR] more...

Background: Although obsessive compulsive disorder (OCD) is effectively treated by cognitive behavior therapy (CBT), less is known about mechanisms underlying treatment response. Anxiety sensitivity (AS) may impact symptom change (velocity) and the rate of change in velocity (acceleration) during CBT for OCD. Latent Difference Score (LDS) analysis was used to show path-analytic dynamic modelling of OCD symptom velocity and acceleration during CBT, as a function of baseline AS. Method: Eighty-four participants with a principal diagnosis of OCD completed 12 weeks of CBT group therapy, and measures assessing AS at pre-treatment, and obsession and compulsion severity at pre-treatment, sessions 4, 8, and end of treatment. Results: LDS velocity models demonstrated that higher levels of baseline AS were associated with subsequent elevations in obsessions throughout treatment, and obsession scores were temporally associated with subsequent changes in compulsion scores. An LDS acceleration model demonstrated that higher levels of baseline AS scores were associated with rapid increases in the severity of obsessions, whereas lower AS scores were associated with rapid decreases in the severity of obsessions. Discussion: These results have implications for theoretical and treatment modelling of obsessions and compulsions, as well as AS, in OCD. Conclusion: Higher levels of baseline AS negatively impact response to CBT for OCD. [ABSTRACT FROM AUTHOR] more...

In this study, effect of mechanical milling on the mechanical, dry sliding wear and impact response of spark plasma sintered Ni-17Cr6.5Co1.2Mo6Al4W7.6Ta superalloy has been investigated. Two nickel-based superalloy were sintered, firstly in their as-received elemental particle sizes, while the matrix, nickel of the second alloy, was milled to 10 h prior blending with other elements and subsequent sintering. The impact response was explored using computational modelling approach via finite element analysis, Abaqus CAE/2019. Results show that the superalloy with the milled nickel powder exhibited better mechanical properties such hardness, elastic modulus, elastic and plastic strain from impact response than the superalloys with unmilled nickel. Sliding wear tests under dry sliding conditions at three different loads of 20, 25 and 30 N revealed that the superalloy with the milled nickel have lower wear rate when compared to the other with unmilled nickel. It was observed that the wear rate reduced unexpectedly at the applied load of 30 N which may be attributed to the continuous formation of tribo-oxide layer from retained wear debris on worn surface. [ABSTRACT FROM AUTHOR] more...

Treatment of acute lymphoblastic leukemia (ALL) requires the combination of multiple drugs to integrate a complete remission. The different prognostic factors (age, leukocytes, risk, cytogenetic alterations) allow identifying those patients with a high risk of relapse, but there are few described factors that impact the induction response. The objective was to identify the utility of different risk factors (overexpression of the ABCB1 drug resistance gene, favorable response to steroids (FRS) and early response at day + 8 of treatment) on the percentage of complete remissions and overall survival. This is a prospective, observational study in adult patients with B-ALL without specific cytogenetic alterations, who started induction treatment based on a pretreatment with prednisone and subsequently vincristine (1.6 mg/m2 subcutaneous) plus daunorubicin (45 mg/m2 subcutaneously) on days + 1, + 8, + 15. The ABCB1 resistance gene was evaluated at diagnosis, the FRS at the end of the pretreatment and the early response during day + 8. A total of 53 adult patients diagnosed with ALL Philadelphia negative chromosome (Ph-), with immunophenotype B, with a normal karyotype, were studied. Cases with genetic abnormalities with a poor prognosis were excluded in order to reduce bias. The mean age was 48 years (range 17-68 years). 62.3% of patients were at high risk of relapse. When analyzing the risk factors, 30.2% showed high levels of the ABCB1 resistance gene, without showing an impact on the induction response (OR: 1.218, p = 0.743), but its overexpression was associated with a poor response to steroids as in the absence of early response. Individually, both the FRS (OR: 5.7, p = 0.004) and the absence of early response to day + 8 (OR: 6.42, p = 0.002) showed significance. By combining the different factors, having more than 2 was directly related to a failure (OR: 9.514, p = 0.000). The identification of factors such as FRS such as the persistence of blasts at the end of the first week of treatment is useful to identify patients at risk of failure in induction. [ABSTRACT FROM AUTHOR] more...

Soil-Structure Interaction (SSI) is an outstanding factor that influences the linear and nonlinear performance of any structure, and it can be taken into account as one of the most important and effective considerations on the seismic behavior of buildings. On the other hand, historic masonry buildings are specific and important structures, which are significantly affected by SSI. Preservation of these buildings is one of the main demands of every culture and every society; and evaluating the behavior of these buildings under natural events such as earthquake, considering aforementioned SSI phenomenon, is an essential step, in this regard. In this paper, the impact of SSI on the out-of-plane behavior of an ancient building in Iran, named Arge-Tabriz, has been investigated utilizing Finite Element Method (FEM). Modal and nonlinear Time-History (TH) analyses results revealed that SSI has a significant decreasing effect on the acceleration response due to removing the effective mode vectors from the resonance area of the acceleration response spectra. On the contrary, SSI has a remarkable increasing impact on the displacement response of Arg's walls according to the displacement response spectra. [ABSTRACT FROM AUTHOR] more...

This paper gives an important contribution by investigating the effectiveness of core/facing interface performance of aluminum honeycomb sandwich panels under low-velocity impact energy. Low-velocity drop tests were conducted on five different panels under 50, 75, and 100 J impact energies (loads). The following procedure is followed to evaluate the impact response of panels: the force–time histories are acquired; the numerical integration method is applied, and force–displacement histories are obtained; and then the damage mechanism and theoretical energy balance modeling are used to analyze the effectiveness of core/facing interface performance on the impact behavior of the panels. Scanning electron microscopy is used to examine the microstructural and the morphology of the core/face sheet interface of the aluminum honeycomb sandwich panels. The effects of voids, interface, and cohesive cracks on the impact behavior of the panels are analyzed. Energy balance modeling proved that energy absorbed in the bending and shear deflections increased as the resistance at the core/facing interface is increased. In addition, changing the initial impact energy from 50 to 100 J produced more than 120% increase in the effectiveness of the panels in terms of energy absorbed in shear and bending deformations. [ABSTRACT FROM AUTHOR] more...

At present, the publishing industry in China has entered the stage of knowledge-based service in digital transformation. This article introduces the four stages of the digital transformation in the Chinese publishing industry with a focus on knowledge-centered service, including the origin and meaning of the concept, the service transformation of traditional Chinese publishing industry, and the knowledge management of Internet companies and new media companies. In China, knowledge-based service of the publishing industry usually refers to a brand-new service model that integrates content creation, production, dissemination, and even application. In response to the impact of the Internet and seize the development opportunities brought by big data and artificial intelligence, the Chinese publishing industry, from traditional publishing houses to Internet-based We-Media, is actively exploring various ways and models of knowledge-based service transformation. This article illustrates the current knowledge-based services of the publishing industry in China with the case study of some pilot projects and paying for knowledge online. [ABSTRACT FROM AUTHOR] more...

Diacritics in Arabic are optional orthographic symbols used to alter the pronunciation of a letter or distinguish between words of similar spellings, which may add or subtract complexity by imposing additional loads on the individual's information-processing system. In this study, we explored how reading Arabic text with and without diacritical signs (known as ḥarakāt) can influence readers' brain activation. An electroencephalogram (EEG) recording of 18 subjects was used in this study to assess the differences in brain activation while reading in two reading conditions (with and without ḥarakāt). The results showed that ḥarakāt had a significant impact on the cognitive responses of subjects as exemplified by differences in cortical activity between the conditions. Our results imply promising results in the application of reading skills where diacritical marks may play a key role in increasing the level of attention an individual pays to text, thus improving information-processing accuracy. [ABSTRACT FROM AUTHOR] more...

TP53 aberrations reportedly predict favorable responses to decitabine (DAC) in acute myeloid leukemia (AML). We evaluated clinical features and outcomes associated with chromosome 17p loss or TP53 gene mutations in older, unfit DAC-treated AML patients in a phase II trial. Of 178 patients, 25 had loss of 17p in metaphase cytogenetics; 24 of these had a complex (CK+) and 21 a monosomal karyotype (MK+). In analyses in all patients and restricted to CK+ and MK+ patients, 17p loss tended to associate with higher rates of complete remission (CR), partial remission (PR), or antileukemic effect (ALE). Despite favorable response rates, there was no significant OS difference between patients with or without loss of 17p in the entire cohort or in the CK+ and MK+ cohort. TP53 mutations were identified in eight of 45 patients with material available. Five of the eight TP53-mutated patients had 17p loss. TP53-mutated patients had similar rates of CR/PR/ALE but shorter OS than those with TP53 wild type (P = 0.036). Moreover, patients with a subclone based on mutation data had shorter OS than those without (P = 0.05); only one patient with TP53-mutated AML had a subclone. In conclusion, 17p loss conferred a favorable impact on response rates, even among CK+ and MK+ patients that however could not be maintained. The effect of TP53 mutations appeared to be different; however, patient numbers were low. Future research needs to further dissect the impact of the various TP53 aberrations in HMA-based combination therapies. The limited duration of favorable responses to HMA treatment in adverse-risk genetics AML should prompt physicians to advance allografting for eligible patients in a timely fashion. [ABSTRACT FROM AUTHOR] more...

Detailed finite element (FE) models are often employed to predict the impact responses of reinforced concrete (RC) columns. However, they always require substantial investments of time and effort in modeling and analysis so that they are not widely used in practice, particularly in preliminary designs. Moreover, although some simplified models have been established for beams and slabs under impact loading, few attempts have been made on modeling RC columns. For these reasons, this paper proposes a simplified modeling method to accurately capture the impact-induced response and damage of circular RC columns. In the proposed method, a two-degree-of-freedom (DOF) system was used to describe the interaction between the impactor and the impacted column. The formulas, and procedure to estimate the force–deformation relationship with strain-rate effects were presented according to the section-based analysis. The influence of the unloading stiffness on the residual deformation was addressed, and the method to determine the unloading stiffness of circular columns was proposed. Furthermore, a fiber-based beam-column element modeling method was developed to estimate the force–deformation relationship of the columns with strain-rate effects. The proposed simplified method was demonstrated by the drop-hammer impact tests to be capable of predicting the impact response of RC columns well. Its accuracy in the residual deformation is superior to that of the detailed FE simulation. Parametric studies were performed to investigate the damage characteristics of axially-loaded circular RC columns under various impact scenarios. [ABSTRACT FROM AUTHOR] more...

The impact of the response speed of a microelectromechanical system (MEMS) bolometer on the quality of terahertz (THz) imaging with rapid scan has been investigated and compared with a pyroelectric detector (PED). The imaging system was an active imaging composed of the MEMS bolometer, THz quantum cascade laser, and two-dimensional translation stage. The scanning process of the imaging system consisted of continuous scans in the X direction and step scans in the Z direction. The MEMS bolometer had a beam resonator with a resonant peak of 422 kHz, and it was operated in the frequency modulation detection mode. The frequency shifts in the resonant peak due to the irradiation of the THz waves were tracked using the phase-locked loop system built in the lock-in amplifier. In the measurement of the response characteristics using a 100-μm pinhole, the peak intensity was almost constant against the stage speed in the case of the MEMS bolometer. For the PED, there was a decrease in the peak intensity and delay in the peak positions with increasing stage speed due to the insufficient response speed. When the images were acquired using the MEMS bolometer with a stage speed of 25 mm/s, fine structures of a metal bookmark were clearly observed and no degradation in the resolution was observed with changing stage speed. In the case of the PED, the resolution gradually degraded with increasing stage speed. [ABSTRACT FROM AUTHOR] more...

The present study aimed to investigate how Persian-Turkish bilingual children tend to respond to forced-choice questions pertaining to objects. A total of 42 bilingual 5- and 6-year-old children were asked two-option forced-choice questions about a set of four familiar and four unfamiliar objects. The analysis of participants' responses showed that older preschoolers are less susceptible to two-option forced-choice questions. That is, 5- and 6-year-old bilingual preschoolers are less likely to show a recency tendency unless they are asked about unfamiliar objects. Overall, the results evidenced that children's familiarity with objects influenced their responses, whereas children's language did not have any impact on their responses. The implications of the findings are discussed. [ABSTRACT FROM AUTHOR] more...