Thermal conductivity is a crucial factor for selecting appropriate phase change material (PCM) for use in the field of thermal storage. In the current work, sodium acetate trihydrate (SAT) was ...combined with xanthan gum and copper foam to prepare a composite PCM using a vacuum impregnation method, with the main purpose of increasing its thermal conductivity. The latent heat of SAT/xanthan gum (SAT/X) containing 98 wt% SAT and 2 wt% xanthan gum was measured to be 255.5 J/g, close to the theoretical value according to the content of SAT in the composite SAT/X. The saturated mass fraction of SAT/X in SAT/xanthan gum/copper foam (SAT/X/CF) was calculated to be equal to 77.2%, therefore the SAT/X/CF can have an estimated latent heat of 197.2 J/g. The thermal conductivity of final composite PCM was 2.10 W/(m·K), 1.76 times higher than that of SAT/X, suggesting that copper foam performs well in the area of thermal conductivity enhancement. A heating/cooling cycle was carried out 200 times to examine the cycling stability of SAT/X and SAT/X/CF. The experimental analysis illustrated that the latent heat of SAT/X decreased by only 5.9%, as compared with that of the prepared one. Improved thermal conductivity, high heat storage capacity together with great thermal cycling stability make SAT/X/CF a very promising material in solar thermal energy storage.
•Xanthan gum was proved to be an efficient thickening agent for SAT.•The thermal conductivity of PCM composite was significantly improved by copper foam.•SAT/xanthan gum/copper foam composite PCM exhibited excellent thermal reliability.
The shaped charge jet formation of a Zr-based amorphous alloy and the applicability of different numerical algorithms to describe the jet formed were experimentally and numerically investigated. ...X-ray experiments were performed to study jet characteristics. The numerical results for the Zr-based amorphous alloy jet formed via the Euler and smooth particle hydrodynamics (SPH) algorithms were compared and analyzed using the Autodyn hydrocode. Particle motion was examined based on material properties. The Zr-based amorphous alloy formed a noncohesive jet driven by an 8701 explosive. Both the Euler and SPH algorithms achieved high accuracy for the determination of jet velocity. When the improved Johnson-Holmquist constitutive model (JH-2) was used, numerical results confirmed the model's suitability for the Zr-based amorphous alloy. The Euler algorithm effectively reflected jet shape within a short computing time, whereas the SPH algorithm was highly suitable for showing the shape of the jet tail within a long computing time. In the 3D Euler model, the flared jet mouth indicated radial particle dispersion; however, in the 2D model, particle dispersion in the head was directly observed by using the JH-2 material model. The brittle fracture of the material reduced the proportion of particles near the liner apex forming a jet. Furthermore, a new method in which stagnation pressure was used to predict jet formation and its coherence was proposed since the collapse angle was difficult to obtain.
The flow stress of face-centered cubic (FCC) metals exhibits a rapid increase near a strain rate of 104 s−1 under fixed-strain conditions. However, many existing constitutive models either fail to ...capture the mechanical characteristics of this plastic deformation or use piecewise strain-rate hardening models to describe this phenomenon. Unfortunately, these piecewise models may suffer from issues such as discontinuity of physical quantities and difficulties in determining segment markers, and struggle to reflect the underlying physical mechanisms that give rise to this mutation phenomenon. In light of this, this paper proposes that the abrupt change in flow stress sensitivity to strain rate in FCC metals can be attributed to microstructural evolution characteristics. To address this, a continuous semiempirical physical constitutive model for FCC metals is established based on the microstructural size evolution proposed by Molinari and Ravichandran and the dislocation motion slip mechanism. This model effectively describes the mutation behavior of strain-rate sensitivity under fixed strain, particularly evident in an annealed OFHC. The predicted results of the model across a wide range of strain rates (10−4–106 s−1) and temperatures (77–1096 K) demonstrate relative errors generally within ±10% of the experimental values. Furthermore, the model is compared with five other models, including the mechanical threshold stress (MTS), Nemat-Nasser–Li (NNL), Preston–Tonks–Wallace (PTW), Johnson–Cook (JC), and Molinari–Ravichandran (MR) models. A comprehensive illustration of errors reveals that the proposed model outperforms the other five models in describing the plastic deformation behavior of OFHC. The error results offer valuable insights for selecting appropriate models for engineering applications and provide significant contributions to the field.
•This paper verifies the applicability of BSMPM, GIMP, and CPDI in mesoscale simulating the SCJs.•BSMPM based on cubic and quartic splines is most suitable for mesoscale simulating, whose SCJs are in ...great continuity with little cavity and small surface roughness.•For SCJs material, the strain evolution is hierarchical and the particle trajectories can be classified as a laminar layer, transition layer, and turbulent layer from outer to the axis, consistent with the grain size evolution.
Shaped charge (SC) generates a fluid-like high-speed jet (SCJ) undergoing extremely large ductile stretching without fracture. It is a formidable challenge to accurately track and monitor the mesoscale deformation characteristics of materials using fluid simulation algorithms. To address this issue, the Material Point Method (MPM) is introduced as an efficient particle-based method that discretizes the continuum into Lagrangian particles moving through a fixed Eulerian grid. By possessing all material properties, these particles facilitate tracking throughout the deformation process and enable the implementation of history-dependent constitutive models. Regrettably, the utilization of MPM in the study of SCJ formation is restricted. The objective of this study is to assess the capability of 2D-axisymmetric MPMs in modeling SCJ formation and free flight at the mesoscale, thereby providing valuable guidelines for their application in SCJs. The MPMs employed in this study are based on the B-spline (BSMPM) and domain interpolations (generalized and convected particle domain interpolations in MPM). The numerical results indicate that BSMPM with cubic and quartic splines is the most suitable method for calculating SCJs due to its exceptional continuity and alignment with the experimental data. The mesoscale evolution of particles reveals that the material undergoes impact crushing and tensile tearing, transforming into a low-speed slug and a high-speed jet. The equivalent plastic strain (EPS) in SCJs exhibits a radial expansion from the exterior to the axis in a layered manner. Particles in the outer layer with a thickness of approximately 1/2 exhibit a 'laminar' distribution, while particles near the axis exhibit 'turbulent' distribution and undergo severe deformation. The hierarchical progression of EPS and particle motion traces provides insight into the underlying causes of mesoscale experimental phenomena, such as the axial elongation of voids in the SCJ slug and the radial distribution of the material in three concentric circles.
How to effectively reduce the damage of frequent accidental explosions and explosion attacks to existing walls is an important concern of the blast resistance field. In the present study, the ...influence of the foamed concrete (density 820 kg/m3, water-cement ratio 0.4) coating thickness on the blast resistance of a 120 mm RC (reinforced concrete) wall was studied through blast experiments, numerical simulations, and shock wave theory. Results show that the influences of foamed concrete on the blast resistance of RC walls are jointly decided by the stress drop caused by impedance effect and exponential attenuation and the stress rise caused by high-speed impact compression. The coating thickness mainly affects the foam concrete’s fragmentation degree and stress attenuation. A lower critical coating thickness exists in foamed concrete-coated RC walls. The blast resistance of the RC wall will decrease when the coating thickness is less than that value. The lower critical coating thickness is related to the intensity of blast load and the energy absorption capacity of foamed concrete, and it can be predicted by monitoring the explosive stress and energy incident to the RC wall.
Intervertebral disc degeneration (IDD) has been identified as one of the predominant factors leading to persistent low back pain and disability in middle-aged and elderly people. Dysregulation of ...Prostaglandin E2 (PGE2) can cause IDD, while low-dose celecoxib can maintain PGE2 at the physiological level and activate the skeletal interoception. Here, as nano fibers have been extensively used in the treatment of IDD, novel polycaprolactone (PCL) nano fibers loaded with low-dose celecoxib were fabricated for IDD treatment. In vitro studies demonstrated that the nano fibers had the ability of releasing low-dose celecoxib slowly and sustainably and maintain PGE2. Meanwhile, in a puncture-induced rabbit IDD model, the nano fibers reversed IDD. Furthermore, low-dose celecoxib released from the nano fibers was firstly proved to promote CHSY3 expression. In a lumbar spine instability-induced mouse IDD model, low-dose celecoxib inhibited IDD in CHSY3
mice rather than CHSY3
mice. This model indicated that CHSY3 was indispensable for low-dose celecoxib to alleviate IDD. In conclusion, this study developed a novel low-dose celecoxib-loaded PCL nano fibers to reverse IDD by maintaining PGE2 at the physiological level and promoting CHSY3 expression.
Sensory nerves are long being recognized as collecting units of various outer stimuli; recent advances indicate that the sensory nerve also plays pivotal roles in maintaining organ homeostasis. Here, ...this study shows that sensory nerve orchestrates intervertebral disc (IVD) homeostasis by regulating its extracellular matrix (ECM) metabolism. Specifically, genetical sensory denervation of IVD results in loss of IVD water preserve molecule chondroitin sulfate (CS), the reduction of CS bio‐synthesis gene chondroitin sulfate synthase 1 (CHSY1) expression, and dysregulated ECM homeostasis of IVD. Particularly, knockdown of sensory neuros calcitonin gene‐related peptide (CGRP) expression induces similar ECM metabolic disorder compared to sensory nerve denervation model, and this effect is abolished in CHSY1 knockout mice. Furthermore, in vitro evidence shows that CGRP regulates nucleus pulposus cell CHSY1 expression and CS synthesis via CGRP receptor component receptor activity‐modifying protein 1 (RAMP1) and cyclic AMP response element‐binding protein (CREB) signaling. Therapeutically, local injection of forskolin significantly attenuates IVD degeneration progression in mouse annulus fibrosus puncture model. Overall, these results indicate that sensory nerve maintains IVD ECM homeostasis via CGRP/CHSY1 axis and promotes IVD repair, and this expands the understanding concerning how IVD links to sensory nerve system, thus shedding light on future development of novel therapeutical strategy to IVD degeneration.
The first evidence which demonstrates how sensory nerves communicate with intervertebral disc (IVD) nucleus pulposus cell to maintain its homeostasis. Particularly, IVD water‐preserving molecule chondroitin sulfate (CS) and CS bio‐synthetic gene chondroitin sulfate synthase 1 (CHSY1) are found to be under control by sensory nerve secretion of calcitonin gene‐related peptide (CGRP) via receptor activity‐modifying protein 1 (RAMP1)/cyclic AMP response element‐binding protein (CREB) signaling; dysregulation of this pathway accelerates IVD degeneration. In addition, therapeutic role of intradiscal forskolin injection is established.
In this paper, the effect of external magnetic field loaded at the initial period of inertial stretching stage on a jet produced by Ø56-mm shaped charge is evaluated through the depth-of-penetration ...(DOP) test method. Experimental results are compared with the results obtained under the field loaded at the later inertial stretching stage. A standoff of 650 mm is used in the experiments, in which the shaped charge jet can undergo formation, elongation, breakup, rotation, and drift. The initial energy is provided by a capacitor bank, which is loaded on the solenoid to generate a magnetic field used for coupling with the jet. The external magnetic field loaded at the initial period of inertial stretching stage can enhance the stability of the jet and increase its DOP. The penetration capability of the jet in the above-mentioned condition is increased by 77.4%.
This study proposes to utilize modified Nano-SiO₂/fluorinated polyacrylate emulsion that was synthesized with a semi-continuous starved seed emulsion polymerization to improve the hydrophobicity, ...thermal stability, and UV-Vis absorption of polyacrylate emulsion film. To verify the proposed method, a series inspection had been conducted to investigate the features of the emulsion film. The morphological analysis indicated that Nano-SiO₂ was surrounded by a silane molecule after modification, which can efficiently prevent silica nanoparticles from aggregating. Fourier transform infrared spectra confirmed that modified SiO₂ and dodecafluoroheptyl methacrylate (DFMA) were successfully introduced to the copolymer latex. The particle size of latex increased with the introduction of modified Nano-SiO₂ and DFMA. UV-Vis absorption spectra revealed that modified silicon nanoparticles can improve the ultraviolet shielding effect obviously. X-ray photoelectron spectroscopy illustrated that the film⁻air interface was richer in fluorine than film section and the glass side. The contact angle of modified Nano-SiO₂/fluorinated polyacrylate emulsion containing 3 wt % DFMA was 112°, slightly lower than double that of polyacrylate emulsion, indicating composite emulsion films possess better hydrophobicity. These results suggest that introducing modified Nano-SiO₂ and fluorine into polyacrylate emulsion can significantly enhance the thermal stability of emulsion films.
Phase change materials (PCMs) play significant roles in solar thermal energy storage. In this work, a novel PCM, light-to-thermal conversion phase change hydrogel (LTPCH) consisting of NaAc·3H2O, ...acrylamide-acrylic acid sodium co-polymer and CuS was prepared using a melt impregnation process. The morphologies, thermal physical properties, light-to-thermal conversion performance and cycling lifetimes of prepared LTPCHs were investigated. A fluid leakage test showed that LTPCH containing 87 wt% NaAc·3H2O can keep a solid-gel structure without liquid leakage in the phase change process. Scanning electron microscope micrographs confirmed that LTPCH was structured by near-spherical particles which were mainly composed of NaAc·3H2O confined in the three-dimensional polymer networks. Differential scanning calorimeter tests revealed that the melting temperature of LTPCH was 57.1 °C, close to that of NaAc·3H2O, and its latent heat was as high as 202.4 J/g. The light-to-thermal conversion experiments indicated that CuS was an effective photon capturer and it can provide LTPCH with an excellent light-to-thermal conversion efficiency of 87.1%. After 300 melting/freezing cycles, LTPCHs maintained good thermal physical properties and high light-to-thermal conversion efficiency, and therefore showed great potential for use in solar thermal energy storage.
•NaAc·3H2O can combine with 80A-51 to produce a form-stable phase change hydrogel.•CuS can greatly promote the light absorption of phase change hydrogel.•The resultant LTPCH possessed excellent light-to-thermal conversion efficiency.
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