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The penetration characteristic of a following kinetic energy projectile to the concrete with a pre-drilled cavity is investigated through the theory and numerical simulations. With the precondition of the equivalent volume of the pre-drilled cavity, the results are compared in terms of the kinetic parameters of the penetration process, the depth of penetration of the following kinetic energy projectile. A theoretical model is then employed to assess the depth of penetration of the following kinetic energy projectile at the condition of variation of the diameter and the depth but the volume of the pre-drilled cavity being invariant. In addition, the numerical simulation is carried out to present the penetration process of the following kinetic energy projectile to the concrete with a pre-drilled cavity. The results show that the existence of the pre-drilled cavity is conducive to increase the depth of penetration of the following kinetic energy projectile on the concrete. In case of the same volume of the pre-drilled cavity, the depth of penetration of the following kinetic energy projectile on concreter increases initially and decreases afterwards with increase of the diameter of the pre-drilled cavity. The theoretical results correlate with the simulation results reasonably well.

Solar energy has been widely used in water heating systems. Latent thermal storage technology using phase change material (PCM) has also attracted great attention in energy storage field. In this study, two kinds of composite PCM- sodium acetate trihydrate/expanded graphite (SAT/EG) and sodium acetate trihydrate/graphene oxide/expanded graphite (SAT/GO/EG) were prepared using a physical hybrid method. The melting temperature and latent heat of SAT/EG were 57.9 °C and 218.1 J/g, respectively. GO showed a negligible influence on the thermal thermophysical characteristics of composite PCM. Exposed in solar radiation, two PCMs can experience phase change almost at same rate. The leakage tests were conducted on these PCMs with the purpose of confirming the density of PCMs. The highest densities at which the PCMs can keep good shape stabilities were 0.8 g/cm3 for SAT/EG and 1.0 g/cm3 for SAT/GO/EG, which indicates that traces of GO (less than 0.1 wt%) can improve the shape stability of compressed PCMs. A solar water heating system equipped with a new type of collector was constructed by employing SAT/GO/EG (1.0 g/cm3, 1628 g) as the solar-absorbing substance and thermal storage medium simultaneously. Under real solar radiation, the SAT/GO/EG can finish phase change and reach the temperature above 70 °C from 9:00 AM to 2:00 PM on a typical day in Zhuhai, China. The solar-to-thermal conversion efficiency of the system was calculated to be 54.5%. These results illustrate that SAT/GO/EG possesses excellent solar-absorbing performance and shows great promise in designing novel solar water heating system.

Scoliosis is a type of spinal deformity, which is harmful to a person's health. In severe cases, it can trigger paralysis or death. The measurement of Cobb angle plays an essential role in assessing the severity of scoliosis.The aim of this paper is to propose an automatic system for landmark detection and Cobb angle estimation, which can effectively help clinicians diagnose and treat scoliosis.A novel hybrid framework was proposed to measure Cobb angle precisely for clinical diagnosis, which was referred as W-Transformer due to its w-shaped architecture. First, a convolutional neural network of cascade residual blocks as our backbone was designed. Then a transformer was fused to learn the dependency information between spine and landmarks. In addition, a reinforcement branch was designed to improve the overlap of landmarks, and an improved prediction module was proposed to fine-tune the final coordinates of landmarks in Cobb angles estimation. Besides, the public Accurate Automated Spinal Curvature Estimation (AASCE) MICCAI 2019 challenge was served as data set. It supplies 609 manually labeled spine anterior-posterior (AP) X-ray images, each of which contains a total of 68 landmark labels and three Cobb Angles tags.From the perspective of the AASCE MICCAI 2019 challenge, we achieved a lower symmetric mean absolute percentage error (SMAPE) of 8.26% for all Cobb angles and the lowest averaged detection error of 50.89 in terms of landmark detection, compared with many state-of-the-art methods. We also provided the SMAPEs for the Cobb angles of the proximal-thoracic (PT), the main-thoracic (MT), and the thoracic-lumbar (TL) area, which are 5.27%, 14.59%, and 20.97% respectively, however, these data were not covered in most previous studies. Statistical analysis demonstrates that our model has obtained a high level of Pearson correlation coefficient of 0.9398 (This study offers a brand-new automatic approach that is potentially of great benefit of the complex task of landmark detection and Cobb angle evaluation, which can provide helpful navigation information about the early diagnosis of scoliosis.

Fragmentation is the main energy dissipation form of foam concrete under explosion loading. To characterize the energy dissipation of foam concrete fragmentation quantitatively, explosion loading experiments of foam concrete plates under different stand-offs and plate thicknesses were carried out. The statistical characteristics of fragments and the energy dissipation law of foam concrete plate fragmentation were studied using image processing, fracture mechanics theory and fractal theory. An engineering calculation model of fragmentation fractal dimension and energy dissipation density of foam concrete plates were established. Results show that: the fragmentation of foam concrete plates under different explosion conditions is a fractal in the statistical sense. With the increase in stand-off and plate thickness, the fragment size of foam concrete plates increases, and the fragmentation fractal dimension decreases linearly. The linear relationship between the energy dissipation density and the fragmentation fractal dimension of foam concrete are expressed as D f = 0.0165 ω + 1.053.

The coating of polyurea elastomers on walls is a hotspot in the protection field. This work combines a numerical simulation with experimental validation to examine the blast resistance after coating a polyurea elastomer on a 370 mm wall under a contact explosion. Firstly, the failure limit, failure mode, and failure mechanism of the 370 mm unreinforced wall under different strength loads are studied. In the case of the contact explosion, the increase in size of the 370 mm wall blasting pit gradually stops after the dose is increased to more than 1 kg. Thereafter, the energy of the explosive load wis released by splashing wall fragments as well as by the deflection and movement of the wall. Spraying double-sided polyurea reinforcement on the wall can effectively improve the resistance to damages caused by exposure to explosive loads and can inhibit the damage to the surrounding personnel and equipment caused by flying structural debris. When the polyurea thickness on the front surface is 6 mm, the optimal thickness of the back surface should be 2 mm.

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.

Given the fact that solvothermal synthesis is the most common synthetic method to obtain metal–organic frameworks (MOFs) on a gram scale, it still remains a great challenge to produce MOFs in a scalable and sustainable synthetic process. In this work, we develop a facile and rapid synthesis of copper-based MOF-505 by the exploitation of layered (Zn,Cu) hydroxy double salt as the intermediate for efficient MOF-505 crystallization at room temperature, in which [(Zn,Cu)(OH)NO3] is synthesized by reacting ZnO with Cu(NO3)2. Under an optimized reaction time of 25 min, MOF-505-25 exhibits a Brunauer–Emmett–Teller (BET) surface area of 1076 m2 g−1 and the pore size is narrowly distributed at 5.9 and 8.0 A. With respect to CO2 adsorption and separation performance, MOF-505-25 shows a moderate CO2 uptake of 3.51 mmol g−1 at 298 K and 100 kPa and high CO2/CH4 and CO2/N2 adsorption selectivities of 7 and 29. Particularly, the formation of MOF-505 can be completed within a short reaction time (less than 30 min) whilst maintaining high quality. This facile and rapid room temperature synthetic procedure would pave the way for promoting the development of MOF materials large-scale production with minimizing the energy input.

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.

The square cross-section aviation weapon platforms have lower radar cross-section and favorable aerodynamic characteristics that make it desirable. It is necessary to study the jet formation and penetration of square cross-section shaped charge (SSC). A theoretical analysis on collapse velocity of the liner of an SSC is performed. Numerical simulations are carried out by LS-DYNA to compare the distinctions of jet formation and penetration between an SSC and a circular cross-section shaped charge (CSC), where the diameter of CSC is equal to the length of the side of SSC. The result shows that the collapse velocity of SSC is periodic. The velocity of the jet top of SSC is slightly higher than that of CSC. The jet of SSC is almost the same length as the jet of CSC at different moments. The penetration of SSC is deeper than that of CSC at stand-off =80,120,160mm.

This work presents a Zn/graphite dual-ion battery using natural graphite as the cathode and metallic zinc as the anode, with ionic liquid-based electrolyte. Upon charge, the Zn2+ cations deposit on the zinc anode, and the trifluoromethanesulfonate (TfO−) anions simultaneously intercalate into the graphite cathode; upon discharge, both the ions are released back into the electrolyte. The 0.2 M Zn(TfO)2/EMImTfO ionic liquid-based electrolyte exhibits a high electrochemical window of 2.8 V (vs. Zn2+/Zn) as well as a high conductivity of 7.3 ms cm−1. The deposition/stripping of zinc on a copper working electrode is systematically studied, which reveals that Zn2+ cations are mobile in the ionic liquid electrolyte, and zinc can be deposited and stripped in this electrolyte. The insertion/extraction of TfO− into/from graphite is also investigated, demonstrating a reversible process. At a current of 0.2 mA cm−2 and within the voltage of 0.8–2.8 V, the Zn/graphite dual-ion cells exhibit a high sloping discharge plateau within 1.8–2.4 V (corresponding to a medium voltage of about 2.0 V), a discharge capacity of 33.7 mAh g−1, and an energy density of 65.1 Wh kg−1; cells deliver a cyclability of 93.5% Coulombic efficiency for 100 cycles. The SEM image reveals that the zinc deposits are compact and dense, and uniformly distribute on anodes with an average grain size of about 200 nm, without the formation of dendrites. The use of high-safety electrolyte and low-cost electrode materials may enable this cell configuration to be a promising candidate for future energy storage systems.

Latent thermal energy storage using phase change material (PCM) is an effective way to store and transport thermal energy. In this work, a shape-stabilized light-to-thermal conversion composite PCM containing 72.5 wt% CH3COONa·3H2O (SAT), 0.4 wt% Na2HPO4, 17.1 wt% expanded graphite (EG) and 10 wt% CuS was prepared using a physical blending and impregnation method. Experimental results showed that Na2HPO4 was an effective nucleating agent, greatly promoting SAT crystallization. EG as supporting material played an important role in preventing melting PCM from leakage. The addition of CuS can increase the light-to-thermal conversion efficiency from 66.9% to 94.1%. The resultant composite PCM had high phase change enthalpy of 194.8 J/g, low supercooling temperature and good thermal cycling performance. After 150 thermal cycles, the melting enthalpy and light-to-thermal conversion efficiency were decreased by only 5.9% and 2.6%, respectively. This material could be suggested as a potential candidate for storage of thermal energy in solar energy utilization.

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&ndash, 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&deg, 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.

This study aims to improve the heat dispersion of electronic equipment by utilization of thermal conductive adhesive composed of epoxy matrix and filler. AlN particles with different size, graphite, graphene oxide (GO) were used alone or in a synergistic manner to prepare thermal conductive adhesives. The structure of prepared GO was characterized by XRD, FT-IR, Raman spectra and AFM. The analysis indicates that most of prepared GO is in single layer structure. The thermal conductivity and viscosity of adhesive were measured by thermal constants analyzer and rotational viscometer respectively. The results show adhesives filled with larger AIN particles possess higher thermal conductivity than that filled with smaller particles at the given filling content. GO is better than graphite as the filler to improve the thermal conductivity of the epoxy resin. When 8 wt% GO or 70 wt% 5 μm-AlN particles was added, the thermal conductivities of adhesives were about 6.42 times and 11.8 times that of pure epoxy respectively. To further improve the thermal conductivity, 50 wt% 5 μm-AlN particles and 6 wt% GO hybrid filler were proposed, and the final thermal conductivity reached up to 2.77 W/m k, that was 14.6 times of that of neat epoxy. In addition, Agari equation as a systematic theoretical modelling was cited to analyze the effect of each filler on improvement of thermal conductivity of adhesive.

Phase change material (PCM) applied to solar energy storage should not only be concerned with light-to-thermal conversion performance but also consider heat loss. Therefore, a novel composite PCM with dual properties of light-to-thermal conversion and insulation was prepared in this work. Here, graphene oxide/silica hybrid aerogel with porous structure was synthesized using the sol-gel method, which has the advantages of low thermal conductivity and high specific surface area. The n-octadecanol (an organic PCM) was adsorbed into the hybrid aerogel to obtain composite PCM, which was then characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscope (FTIR), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and thermogravimetric analysis (TG). The results showed that the composite PCM supported by hybrid aerogel had a higher heat storage capacity, with a maximum value of 145.6 J/g when the hybrid aerogel contained with 0.5 wt% GO. Moreover, the thermal conductivity of the composite PCM mentioned above is 0.0808 W/(m·K) which reduces by 72% compared with those of pure n-octadecanol (0.3015 W/(m·K)). Furthermore, the temperature of the as-prepared composite PCM could reach its melting point under irradiation conditions, indicating its good light-to-thermal conversion performance.

Energy crisis and environmental problems motive a variety of research strategies to increase energy efficiency, decrease stress on energy infrastructure, and consequently reduce CO2 emissions. Improving efficiency of building heating applications by advanced techniques such as solar collectors and heat pumps, is considered as one research strategy. Utilization of phase change material (PCM) with the virtue of high energy storage density is another research strategy. However, a comprehensive review for intergrating these two research strategies, namely building heating applications with PCM, is still lacking. This study presents a comprehensive review of research works for these applications including PCM roofs, ceilings, and walls, PCM windows, PCM floors, solar chimneys with PCM, solar heating applications with PCM, heat pump applications with PCM, and electrical heaters with PCM. Research development for these passive and active applications including key findings, is sufficiently presented. Summaries and discussions are conducted to identify research gaps for each application. To better utilize the PCM, PCM types, encapsulation forms of PCM, and types of PCM units in these applications are analyzed and discussion. Research methods used in these review literatures are summarized and discussed to further determine research possibilities and limitations. Important conclusions and future recommendations for the research of these applications are given to guide scholars to perform further advances in research.