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Lightweight, scalable, mechanically flexible conductive polymer composite was always desirable for electromagnetic interference (EMI) shielding applications. In this work, we showcased a novel approach to the superior EMI shielding composite materials by orchestrating the multilayered structure and synergistic system. The asymmetric structure with the carbonyl irons (CI)-rich Ti3C2Tx/poly(vinylidene fluoride) (PVDF) magneto-electric layer jointly behind the Ti3C2Tx nanosheets filled PVDF layer was designed and fabricated in aid of a facile but efficient magnetic field-induced method and was then hot-pressed into multilayer structured film. Ti3C2Tx nanosheets were excluded by CI agglomeration layer in asymmetric film to form the complete 3D electrical conductive skeletons. Based on this strategy, EMI shielding properties of the asymmetric multilayer structured composite was superior to the homogeneous blend and sandwiched or alternating layered composites. In addition, an increase in CI content in the composite referred to the thickening of CI-rich layers, making it gain the most powerful EMI SE values, i.e. 42.8 dB for DCMP20-10 film (20 wt% CI, 10 wt% Ti3C2Tx) at 0.4 mm thickness. More importantly, the composite transformed from a reflection type to an absorption dominating EMI shielding material due to the multireflections and magneto-electric synergism in the CI-rich Ti3C2Tx/PVDF layers. Meanwhile, the EMI SE of the composites can be adjusted by not only increase of the overall thickness, but also the layer number of m-DCMP sheets. The thickness specific EMI SE was calculated as 165.25 dB mm−1 for 4-sheet composite film, a record high value amongst the high efficiency polymer-based EMI shielding materials. This method offered an alternative protocol for preferential integration of excellent EMI shielding performance with high mechanical performance in CPC materials.

The microwave auditory effect has been widely recognized as one of the most interesting and significant biological phenomena from microwave exposure. The hearing of pulsed microwaves is a unique exception to the airborne or bone-conducted sound energy, normally encountered in human auditory perception. This chapter describes the research studies leading to scientific documentation that absorption of a single microwave pulse impinging on the head may be perceived as an acoustic zip, click, or knocking sound, depending on the incident microwave power. A train of microwave pulses to the head may be sensed as an audible buzz, chirp, or tone by humans. It discusses the neurophysiological, psychophysical, and behavioral observations from laboratory studies involving humans and animals as subjects. The objective is to present what is scientifically known about the microwave auditory effect.

In this brief, for the first time, we propose commonmode (CM) and differential-mode (DM) reflectionless balanced bandpass filters (BPFs) using half-wavelength ring resonator. By loading absorptive stubs at input/output ports and the ends of the coupled-lines (CLs), the BPFs can realize input-/two-port wideband CM and DM reflectionless performance from dc, as well as wide filtering band and all-stop CM suppression. As for the inputreflectionless type, two extra transmission zeros (TZs) can be obtained by loading λ/2 stubs between the CLs. Besides, the impedances of the CLs can determine the CM suppression level, and the absorption performance can be independently adjusted. The operational foundations and explicit equations are discussed and derived. Good agreements between the simulated and measured results verify the design theory.

Now a day's automobile industries are developing materials in such a way that, the materials should be light in weight and environmentally friendly with excellent mechanical properties. Flax fiber is a naturally available fiber material own excellent mechanical properties. Two reinforced composites were manufactured. One was a complete flax fiber-reinforced composite, the second one was flax fiber metal laminates (combination of flax fiber and aluminum mesh). The manufacturing process of composite materials is also more important, and it is cost-dependent. The hand lay-up method is one of the manufacturing techniques and the cost is very less as compared to other techniques. Manufactured flax fiber and flax fiber metal laminate reinforced composite materials were tested under experimental tests. The experimental test results of flax fiber and hybrid composite materials were compared with each other. The sound transmission loss of flax fiber-reinforced composite material has 15% higher than flax fiber metal laminate reinforced material at the frequency ranges of (400 Hz). The vibration-damping factor of flax fiber metal laminate has 26% higher than flax fiber-reinforced composite. Electromagnetic radiation absorption of flax fiber metal laminate material has 20 db & 15 db higher than flax fiber-reinforced composite material at frequency ranges of (8.16 GHz &12 GHz). The flexural strength and tensile strength of flax fiber material were higher than flax fiber metal laminate material. Finally, the results of the experimental tests were compared with the simulation results of both flax fiber-reinforced composites and flax fiber metal laminate materials. Except for, vibration-damping factor the remaining properties of flax fiber composite material gave better results than the flax fiber metal laminate.

This paper proposed a metamaterial design method that uses soft matter for constructing a unique soft acoustic boundary to effectively improve broadband sound absorption performance. Specifically, attaching a flexible polyvinyl chloride (PVC) gel layer with an elastic modulus as low as a few kilopascals and a thickness of a few millimeters to the inner wall of a cavity-type sound-absorbing metamaterial structure significantly improved the absorption performance of the composite structure in low-frequency broadband ranges. The sound absorption enhancement mechanism differed from those proposed in previous research. On the one hand, the soft PVC gel layer acted as a soft acoustic boundary, substantially reducing the sound speed and reflection and producing considerable elastic strain energy at the interface between two different media to improve the sound absorption performance. On the other hand, this PVC gel layer displayed extremely low stiffness and high damping, producing an abundance of plasmon-like resonance modes in low-frequency broadband ranges, achieving a resonance absorption effect. Since this sound absorption enhancement method did not require an increase in the external dimensions or a change in the structural parameters of the original absorber and achieved robust enhancement in a wide frequency band, it displayed potential application value in various engineering fields.

Laser-assisted 3D printing process of fabricating carbon fibre reinforced plastic parts by sandwiching fibres between plastic layers was developed to improve the bond strength of the fibres to the plastic layers. Here, bundled carbon fibres are placed on the 3D-printed lower plastic layer, and the upper plastic layer is deposited on the fibres. Next, the two layers sandwiching the fibres are laser-heated using a blue diode laser beam. The plastic colour changed the heating temperature at the interface between the fibres and the plastic layer due to the transmittance and absorption phenomena; the translucent layer having high transmittance was most appropriate. The strength and rigidity of the 3D-printed carbon fibre reinforced plastic parts were improved by laser heating. Carbon fibre reinforced plastic parts having closed cross-sections are manufactured and strengthened by optimising the sandwiched fibre orientation. Besides, a tailored part locally reinforced by the carbon fibres is easily 3D-printed, and the deformation behaviours are observed.

An optimal hydrogen storage reactor should have a higher chemical reaction rate by which the heat can be exchanged as fast as possible. The configuration of heat exchanger structure design plays a crucial role in improving heat and mass transfer effect in metal hydride beds. Consequently, a variety of different metal hydride bed configurations have been investigated in experimental and simulation works for the improvement of absorption/desorption rate. In this work, the development of metal hydride bed design in recent decades has been reviewed to help the readers summarize and optimize the reactor configuration. The summarization and review of metal hydrides design can be broadly classified into five distinct categories, which are: 1) design of cooling tubes, 2) design of fins, 3) increasing and arrangement of cooling tubes, 4) other geometric design, and 5) utilization of phase change material. This work is concentrated on assessing the heat and mass transfer effectiveness of various reactor structure configurations. The superiority and weakness of different configurations are summarized to give a comparison of the heat exchange effects. Moreover, the structural parameter analysis for each configuration is also reviewed from the heat and mass transfer aspect. Finally, some recommendations are provided for future metal hydride bed structural designs.

A low radar cross section (RCS) slot array antenna based on absorptive frequency-selective structure (AFSS) is presented in this letter. The AFSS unit cell is constructed by two lossy layers and four double-sided parallel strip lines (DSPSLs). The radiation performance of the antenna can be preserved due to the transmission window of the lossy layers. Wide absorption bands of the AFSS are achieved due to periodic impedance of the DSPSL and the combination of the lossy layers. The operating principle of the design is demonstrated, and a prototype is fabricated and measured to validate the design. The proposed design features both wide RCS reduction band of the antenna and wide transmission band of the AFSS.

In this paper, we talk about the use of Auxetics in Sports Helmets, orientation, and the type of auxetic used. It also covers how the newly designed auxetic structures can sustain more impact energy when compared to the existing auxetic structures. This comparison gives us more clarity about the uses of auxetics in various other applications. Auxetics in simple terms are structures that have a negative Poisson's ratio. This is just a structural property and does not depend upon the material. Hence, it can be used in so many different applications such as defense applications, sports applications, impact absorption, drug dispensers when pores are open, test bay containment, etc. On moving forward, modifying a structure showed that there are improvements concerning Poisson's ratio as well as impact resistance. The challenge was then to make the foam such that it can absorb maximum impact energy. Based on this hypothesis, the proposed design was tested against an existing structure to postulate the difference in the impact energy. The Poisson’s ratio obtained was a staggering improvement from −0.73 to −1.27 which shows 75% decrease in Poisson’s ratio while boasting an increase in the overall energy of 330% from 50 J to 165 J.

This study includes the possibility of using animal products (wool) as a reinforcing material in epoxy resin as an alternative to wood and plastic based ingredients. specimens of composite materials were prepared by using hand lay-up method These specimens were represented by composite materials that consist of epoxy resin as a material matrix reinforced with wool with different volume ratios (0%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%). Mechanical tests (impact hardness (and some physical tests (Density،absorption) were carried out. All the tests were done at the temperature of the lab. The results of the specimens tests prepared showed an improvement in the mechanical properties (impact، hardness) when adding reinforcement fiber ، physical tests showed a slight increase in the values of density and absorption.

One of the main problems of modern building ceramics based on low-melting raw materials is the increased CaO content in the charge. This deviation from the normative values of the technological parameters of production leads to defects - underburning / overburning, quirks, looseness, low strength. Firing mode, molding parameters, addition of additives, preparation of raw materials are the factors for solving this problem. The Alekseevsk low-melting clay and the Yarmysh (Uzbekistan) loess-like loam were investigated, the destruction of the sample structure upon absorption of moisture from the CaO air was graphically modeled, the diagrams of the dependence of the fi ring temperature on the compressive strength were plott ed, the infl uence of molding and the fi neness of grinding of raw materials on the compressive strength and the nature of the formation of ceramic defects was derived.

Various sources of noise in cities and ways to combat them are considered. The effi ciency of two types of acoustic screens is analyzed: single-layer and two-and three-layer. The positive and negative characteristics of various designs of existing acoustic screens are listed. A fundamentally new design of the acoustic screen is described: the panels have a ridge profi le, they are located along the vertical axis of the frame with a step at which the panels above the located ridge cover the top of the lower ridge, the outer surfaces of the panels and their end parts are made of a material that has sound-refl ecting properties, and the inner surfaces of the panels are made of sound-absorbing material. Such an acoustic screen is devoid of the disadvantages inherent in acoustic screens of other structures and is more effi cient. The considered invention allows due to the use of the ridge shape of acoustic panels: prevent the refl ection of sound energy in the direction of noise sources (a small part will be directed upwards); provide almost complete absorption of sound energy as it passes through the channels formed by the ridge panels; provide the same effective protection against noise sources located on both sides of the screen; prevent the formation of snow and ice crust on sound-absorbing surfaces, which ensures the constant eff ectiveness of the screen in diff erent seasons of the year; reduce metal consumption, which will reduce the weight of the structure without reducing its effi ciency and reduce the cost of acoustic screens.

This study discusses the acoustic property variations by introducing new absorption materials. An experimental set up established to simulate virtually as well as experimentally with various biodegradable, biocompatible and naturally absorbable materials for a truck cabin of carrier capacity 3.5Tonnes. The materials were embedded on the sidewall and base of the cabin covering the entire cabin not leaving any air pockets. Experimental and simulation study was carried out for six materials and in the later part a combination of these materials also carried out to see through the possible optimal cases providing due Weightage to cost and weight. A sound quality index study being made to see with each case of material how the sound pressure level affects the rider and the subordinates seating in a cabin. A detailed simulation study carried out to understand the material behavioral characteristics along with convergence study using ANSYS Workbench. The exhaustive work emphasis on percentage error study with simulation and experimental work and proposes an optimal material from sound pressure level and rider comfort aspects.

Current artificial magnetic conductor (AMC) designs use metallic patterns on rigid substrates and focus on shapes and sizes of AMC structures, rather than on material performance, which has hindered operation bandwidth and design flexibility. Here, we introduce printed graphene AMC-based broadband and flexible microwave radar absorbers, which not only redirect but also absorb the incident wave so to broaden the operation bandwidth. Contrasting to other reported works, the phase characteristics of the AMCs are realized through the control of the surface resistance provided by printed graphene laminates. We produced a variety of AMC structures, composed of printed graphene circular ring arrays with exactly the same shape and size, but different sheet resistances. By carefully designing the sheet resistance of printed graphene laminates, the optimized anti-phase reflection cancellation between AMCs can be achieved. With printed graphene AMCs and flexible dielectric substrate, the absorber presented in this work has a broadband effective absorption (above 90% absorptivity) from 7.58 GHz to 18 GHz, is polarization insensitive under normal incident and can work at relatively wide incident angles. Furthermore, this absorber is capable of bending easily with notable performance, which makes it ideal for applications with irregular and uneven shapes.

The nearly perfectly matched layer (NPML) is a non-split perfectly matched layer that directly transforms the wave field. Compared to other non-split perfectly matched layers, NPML is computationally efficient and has advantages such as not changing the form of the equation and being easy to implement. However, in TTI medium simulations it is found that the NPML is very unstable and cannot absorb near-grazing incident waves. This explains why the CPML is currently used more frequently. In this study, the complex frequency shifted transform is used to enhance the absorption of near-grazing incident waves with NPML and to avoid the generation of low-frequency singular values. At the same time, the double damping profile is used to improve the stability of the boundary we called MCFS-NPML. Subsequently, this method is also applied to seismic wave equations in poroelastic media. In order to further improve the absorption capacity of the boundary and weaken the deviation caused by the discrete difference, a new attenuation function is proposed.

While scholars are aware of the suction force of particles (FDn) in gas-solid flow, until recently, most researchers have considered the drag force (FD) to be FDn, and there are few application functions for the calculation of FDn; this will affect the design of air-suction seeders, check valves, or other machines based on particle absorption. Therefore, it is necessary to re-build an applicable function of FDn and verify the equivalence between FDn and FD. In the present study, the empirical formula of FDn, which includes the suction hole diameter (D), particle diameter (dp), distance from the particle center to the suction hole (Lp), pressure difference (ΔP), gas density (ρg), and gas viscosity (μg), is established via dimensional analysis, and the application scope is 0.571 ≤ D/dp ≤ 1, 0.5 ≤ L/dp ≤ 0.634, and 3000 Pa ≤ ΔP ≤ 5000 Pa. Some conjectures are provided based on the comparison of the results of CFD simulations and experiments. For instance, FDn may be a combination of multiple forces, one of which is the dominant force FD. This research introduces a new method and device for measuring FDn for use by other researchers, and contributes to the existing research on particle absorption.

Background The introduction of a photothermal layer on absorbent surface is a potential solution to produce heat for promoting the absorbent performance against viscous heavy oil, but the developed photothermal absorbent is still highly desirable but challenging, considering their complicated, tedious synthesis processes and susceptible surface to mechanical damage. Methods A simple sugar-templating strategy was promoted to fabricate a porous PVDF/candle soot sponge using sugar as a sacrificial template. The encapsulated-candle soot can not only roughen the PVDF struts for superhydrophobicity but also endows the sponge with nearly full sunlight absorption (96.5%). Significant findings Under sunlight exposure, the generated heat in situ reduced the viscosity of the surrounding heavy oil. Consequently, the sponge attains a remarkable oil absorbent rate of 82.5 g/g, reaching up to the state-of-the-art levels. Benefitting from high elasticity and mechanical robustness, the sponge maintains more than 96% of its sorption capacity after 10 cycles. Moreover, the UV resistance and chemical durability in a highly salty environment enable it to respond efficiently to heavy oil spills under complex marine conditions. Owing to its simple fabrication method and outstanding integrated properties, this composite sponge is of great potential for remediating heavy oil spill.

As a typical lightweight material, carbon materials have great application prospects in fabricating microwave absorbers. In this work, the Fe3C@Fe/C composites with porous microstructure are obtained by a simple and environmentally friendly method with wasted cornstalks as raw materials. The reflection loss of absorbing composites reaches the minimum value which is less than −50 dB when the thickness is 1.13 mm, while widest effective absorbing bandwidth reaches 5.1 GHz when thickness is 1.50 mm. The stalk-made nanocomposites’ excellent absorbing ability is mainly credit to excellent impedance matching and attenuation characteristics of composites, which is further credit to a synergistic influence of the dielectric loss from the multiple interfaces in porous microstructure and magnetic loss from iron nanoparticles. A low-cost method to obtain microwave absorption materials and realize high-value utilization of agricultural waste to reduce pollution caused by burning cornstalks is put forward.

Carbon fiber reinforced plastics (CFRP) with the matrix of thermoplastic resin called as carbon fiber reinforced thermoplastics (CFRTPs) has been widely used in the industrial fields. Recently, a thermoplastic epoxy resin (TP-EP resin) has been developed as the matrix of CFRTP and carbon fiber reinforced TP-EP strands (CF/TP strands) molded by pultrusion method began to be used as tension rods for infrastructure under water absorption. On the other hand, an accelerated testing methodology (ATM) for predicting statistically long-term creep and fatigue strengths of CFRP was established by the authors. This study examines the prediction of statistical life time for these developed CF/TP strands at creep and fatigue tension loadings under the wet condition of water absorption with comparison to similar prediction under a dry condition by using our developed ATM. First, the static, creep, and fatigue tensile strengths of CF/TP strands were measured statistically at various constant temperatures under wet and dry conditions. The statistical long-term creep and fatigue tensile strengths for CF/TP strands under wet and dry conditions are predicted by substituting the measured data into the formulations of these strengths on our developed ATM. Finally, the influences of water absorption on the statistical long-term creep and fatigue strengths of CF/TP strands are cleared. In particular, the degradation of relaxation modulus of matrix TP-EP resin with increasing of elapsed time is accelerated with the water absorption, and the degradation of creep strength of CF/TP strand with increasing of elapsed time is also accelerated with the water absorption in the similar manner of matrix resin. On the other hand, the fatigue strength of CF/TP strand decreases scarcely with water absorption although this fatigue strength depends remarkably on the number of cycles to failure.

With the further exploration of the Moon, lunar landers need to land in complex and unexplored areas. However, current lunar landers are confined to basic landing conditions (low landing velocity and plain terrains). This research proposes a novel lunar lander with magnetorheological fluid (MRF) dampers that can adapt its damping forces to various complex landing conditions. The design process and coupled electromagnetic hydrodynamic model analysis of the lunar lander were systematically elucidated. According to the derived theory model of the damping force, a fuzzy control law is proposed. The controllable damping forces under different control currents are simulated according to the proposed fuzzy control law. Additionally, landing dynamic simulations of landers with different dampers are carried in MSC. Adams to compare with their landing performances. MRF dampers under fuzzy control can decrease the largest acceleration of the lander cabin by 63.6%. Finally, prototype drop simulations and experiments are performed, which results match each other well. By increasing the control current from 1 A to 2 A, the damping forces of the MRF damper increase approximately 20% in both the simulations and experiments. Simulations and experiments prove that MRF dampers can be used for energy impact absorption as variable dampers.

PurposeThe purpose of this paper is to provide an optimization schedule of structural parameters for the sound absorption performance of a cellular ceramic foam in the sound frequency range of 200–4,000 Hz.Design/methodology/approachThe cellular ceramic foam with porosity of about 60–75% and the pore size of about 1–7 mm was successfully prepared by using natural zeolite powder as the main raw material. For this ceramic foam, the sound absorption performance was measured, and the absorption structure was optimized by some important structural parameters. With orthogonal experiment, optimization of structural parameters was found for absorption performance. By means of the range analysis method, the main factor is known to influence the performance of ceramic foam.FindingsThe present ceramic foam may have good absorption performance although at relatively low frequencies of 400–4,000 Hz while structural parameters of sample are appropriately combined. With orthogonal experiment, optimization of structural parameters for the absorption performance was found to be as follows: sample thickness, 25 mm; porosity, 73.5%; pore size, 4–5 mm and air gap depth, 20 mm. To influence the performance, sample thickness is the main factor, air gap depth is the second and both of pore size and porosity would have a relatively slight effect.Originality/valueThis paper presents a method to optimize the structural parameters of a cellular ceramic foam for sound absorption performance by means of orthogonal experiment.

The experimental and analytical study of semi-rigid steel connections with dual pipe dampers (DPD) are discussed in this research. The main goal of the paper is to investigate experimental and analytical models of semi-rigid connections with DPDs in steel buildings. The FEM methodology is used for analytical models of two beam-to-column connections equipped with DPDs to generate semi-rigid connections. In the next step, experimental tests are performed in laboratory and the achieved results are compared with the FEM ones. The use of DPDs has not yet been implemented in structures under construction, this solution can be used to deplete the energies caused by damaging excitations to the structures. The authors believe that these methods can be very practical for seismic retrofit and improvement of steel structures and the cost is less than other retrofitting alternatives. Two samples were selected to the investigation. The difference in the samples considered in this study is the thickness and diameter of the dampers. Therefore, the following general results were obtained: 1) Reducing the diameter of the pipes can increase the amount of force applied to the dampers to achieve a constant displacement; 2) by increasing the thickness of the damper, the amount of force applied to the device to achieve a constant displacement is greater. So, it can be said that the diameter and thickness of this type of dampers are very sensitive parameters for seismic energy dissipation in structures. DPDs have special advantages over many existing metal dampers such as low weigh and high energy absorption.

This paper presents the use of crude oil ash in asphalt flexible pavement and concrete rigid pavement. Conventional micro-size fly ash produced from burning crude oil in Jizan electrical power plant in Saudi Arabia was used in this study. The size of conventional crude oil ash waste reduced from micro-scale to nano-scale using ball-milling techniques. The first series of testing investigate the development of flexible pavement using asphalt bituminous AC60/70 incorporated conventional and nano-crude oil fly ash waste. The percentage of conventional and nano-ash used in asphalt mixes was varied from 0 to 15% of asphalt binder. The use of nano-fly ash increases the rutting factor by 0%, 33%, 61% and 38% at 0%, 5%, 10% and 15% nano-fly ash content, respectively. The nano-fly ash improves the rutting factors and bearing load capacity of flexible pavement mixes more than the control mix and mixes containing conventional micro-fly ash. The second series of testing investigates the use of nano-fly ash in rigid pavement asphalt concrete. Conventional and nano-fly ash replaced cement content in concrete material at 0%, 5%, 10%, and 15%. Concrete material incorporated nano-fly ash shows higher compressive strength and lower absorption compared to concrete control sample and concrete containing conventional micro-fly ash. The strength of concrete incorporated nano-fly ash increases by 14.8%, while absorption of concrete improves by 20.1% at 10% nano-fly ash content. The optimum nano-fly ash content was 10% to achieve the highest performance of both pavement materials. The use of nano-crude oil fly ash improves the performance of both pavement materials and helps in reducing the cost of repair in road and highway construction. Moreover, the use of nano-fly ash in paving materials can help in the recycling of this toxic waste to produce sustainable and environmentally friendly road construction materials.

Since the first publishing of district heat driven heat pumps at AGFW fair in 2014 in Frankfurt am Main, Germany, introducing a concept how to use additionally the district heat return line as low temperature heat source, the topic gains more and more international scientific and public interest. Hydraulic concepts with and without an additional heat exchanger in the district heat supply line are tested at least in China and Germany. In theory, a reduction of temperature in the district heating return line (DH-rl) can be expected in the range of 25 to 30 K in comparison to standardized DH house connection stations (HCS). However, when the same heat pump is used in cooling mode during summer time, DH-rl temperature reduction in heating mode is limited to a range of 15 to 20 K, due to absorption chiller hydraulics and system design. In the first part of this contribution experimental results are presented which show how the expected reduction of 25 to 30 K has been achieved in practice by an adapted heat pump design. In the second part a new hydraulic design and control concept for the district heat supply flow rate will be presented which enables even higher DH glides also for retrofitted heating systems. Operating a house heating system at 65/45 °C with a conventional HCS may lead to a temperature in DH-rl in the range of 48 – 55 °C. With the first concept of an absorption HCS from 2014 a DH return temperature of 30 – 35 °C is possible, whereas, with the new hydraulic concept the return temperature may decrease down to 20 – 30 °C for layout conditions. In comparison to conventional HCS the enhanced absorption HCS allows to save 15 – 40 % of volume flow rate for the same heating capacity, mainly depending on temperature level of district heat and house heating system. By means, the heat losses in DH networks can be reduced and the transport capacity (i.e. the number of potential households to be served) can by increased. Concept and calculated results for the enhanced absorption HCS are presented.

Different structural lightweight concrete mixtures of specific density and strength classes were produced by using various lightweight aggregates (LWAs) such as pumice, perlite, and rice husk ash. Their properties were evaluated in fresh and hardened states with regards to compressive strength and durability parameters such as water absorption (open porosity and capillary absorption), chloride’s penetration resistance, and carbonation depth. According to the results, most LWA concrete mixtures performed satisfactorily in terms of the designed strength and density and they could be used as structural LWA concrete mixtures. As far as the durability of LWA concrete was concerned, open porosity and resistance to the carbonation of LWA concrete were burdened with the porous nature of LWAs, while sorptivity in some mixtures and especially chlorides’ penetration resistance in all mixtures were reported to be significantly improved. The overall strength and durability performance of the designed LWA concrete mixtures could mitigate the concerns stemming from its vulnerability to extreme exposure conditions.

Viscoelastic material acoustic coating plays an important role in noise and vibration control of underwater equipment. The dynamic mechanical properties of the viscoelastic material have a direct effect on the sound absorption performance of the acoustic coating. The influence of Poisson’s ratio on sound absorption performance is studied. A finite element model was established to calculate the sound absorption performance of three typical acoustic coatings: homogeneous acoustic coatings, Alberich acoustic coatings, and trumpet cavity acoustic coatings, and the influence of Poisson’s ratio on the sound absorption performance of the three kinds of acoustic coatings was analyzed. The results show that when Poisson’s ratio varies from 0.49 to 0.4999, the larger Poisson’s ratio is, the larger the frequency of the first absorption peak is, the smaller the absorption coefficient below the frequency of the first absorption peak is, and the smaller the average absorption coefficient in the whole analysis frequency range is. The dynamic Poisson’s ratio with the change of frequency is obtained by interpolating the test results and static Poisson’s ratio finite element calculation results. The calculation results show that the dynamic Poisson’s ratio can get more accurate calculation results. This work can provide a reference for researchers to set Poisson’s ratio in theoretical analysis and finite element analysis of acoustic coating.

An innovative solar heat collector system was developed from low-cost materials by applying innovative design technology and using adaptive technologies. The system design entails placing long black polymer pipes connected in series circulation, mounted and positioned in grooves of inverted box rib galvanised steel plating. The grooves reflect and focus the incident rays on the centre piping, concentrating incident sun rays on the black piping and increasing the absorption of thermal energy in the piping filled with circulating water. The circulation of the water is facilitated by a direct-current solar-driven pump powered by a small photovoltaic panel. The thermal energy as collected is stored in a standard household geyser tank. A 3 × 4 m heat absorber of this type collects approximately 10 kWh of energy per day. The estimated cost of the system, considering the capital outlay over an expected ten-year life cycle for the product was estimated at R0.25 per kWh. This pricing competes extremely favourably with the general cost of grid electricity in South Africa for medium-sized households, which is of the order of R2 per kWh up to 1000 kWh per month, including taxes. With an estimated electricity cost escalation of above 5% every year, the ten-year saving for a household using this prototype can be approximately R200 000. The technology and designs developed through the study can create many new business opportunities in South Africa in both urban and rural environments, through manufacturing, installing, repairing, and maintaining the systems.

CO2 removal in raw natural gas is required to meet the sale gas specifications. The chemical solvent absorption method is one of the most commonly used technologies. The absorption-based processes, however, require an enormous amount of energy to regenerate the solvent, and are designed to discharge the captured CO2 into the atmosphere directly. The energy efficiency and greenhouse gas emissions should be considered in the gas treatment process. In this study, a new process, combining CO2 removal and compression, is proposed for raw natural gas treatment complexes. Compared with the conventional absorption-based processes, in the new process CO2 is not stripped from rich solvent in one distillation column but through multi-stage flash separators operating under different pressures and temperatures. The CO2 removed from each stage is then compressed separately to the proper pressure for carbon transportation and storage. A mathematical model is then developed to determine the optimum process configuration and operating conditions. A surrogate-based optimization framework is presented in order to strike a good balance between computational efficiency and model accuracy. The complex units are replaced by Kriging surrogate models. Aspen HYSYS is used to generated sampling points for the construction of surrogates. A method of dimension reduction is introduced to compact the surrogate models by selecting essential variables. Finally, a hybrid optimization model comprising of the surrogate models for “complex” units and explicit models for the rest of the process is formulated. The cases show the total annual cost of the CO2 removal and compression can be reduced by 20.6%–28.8% for different sweet gas purity specifications.

This article proposes a hybrid numerical-analytical approach to effectively predict the sound absorption coefficient of complex periodic metamaterials with a reasonably low computation time. A variation of an existing metamaterial, consisting of a periodic succession of necks and cavities, is also proposed. The design variation was intended to decrease the frequencies of the absorption coefficient resonant peaks and consists in adding eccentricity in the neck position. The hybrid approach combines a thermoviscous-acoustic (TVA) approach with the transfer matrix (TM) method. The TVA approach estimates the thermoviscous losses of acoustic waves in a periodic unit cell (PUC) of the metamaterial. The TM method is used to simulate the acoustic behaviour of the complete metamaterial from the TM of the PUC calculated numerically. The approach is compared to impedance tube measurements on prototypes of the metamaterial. The comparison shows that the proposed approach is in good agreement with the measured sound absorption coefficient. In addition, numerical simulations and experiments demonstrate that the proposed variation of the existing metamaterial results in a shift of the absorption peaks down in frequency without deteriorating their sound absorption performance.

One of the major challenges faced by passive on-body wireless Internet of Things (IoT) sensors is the absorption of radiated power by tissues in the human body. We present a battery-less, wearable knitted Ultra High Frequency (UHF, 902-928 MHz) Radio Frequency Identification (RFID) compression sensor (Bellypatch) antenna and show its applicability as an on-body respiratory monitor. The antenna radiation efficiency is satisfactory in both free-space and on-body operations. We extract RF (Radio Frequency) sheet resistance values of three knitted silver-coated nylon fabric candidates at 913 MHz. The best type of fabric is selected based on the extracted RF sheet resistance. Simulated and measured performance of the antenna confirm suitability for on-body applications. The proposed Bellypatch antenna is used to measure the breathing activity of a programmable infant patient emulator mannequin (SimBaby) and a human subject. The antenna is highly sensitive to respiratory compression and relaxation. Fluctuations in the backscatter power level/Received Signal Strength Indicator (RSSI) in both cases range from 6 dB to 15 dB. The improved on-body read range of the proposed sensor antenna is 5.8 m, about 10 times higher than its predecessor wearable knitted strain sensing Bellyband antenna (0.6 m). The maximum simulated Specific Absorption Rate (SAR) on a human torso model is 0.25 W/kg, lower than the maximum allowable limit of 1.6 W/kg.

Carbon-containing shielding materials, especially with absorbing properties, received a lot of attention from the scientific community as having flexibility, lightness and corrosion resistance. Reducing the thickness of such materials (usually a few millimeters) is also an urgent task. In this paper, we offered results of studying the reflective and absorbing properties of shielding materials from natural graphene-containing shungite. Flexible shungite plates with a thickness of 10–20 μm showed good reflection and absorption similar shielding performance to a thicker 2–3 mm synthetic polymer/carbon based composites. Such characteristics are associated with the fact that shungites are unique natural composites with a conductive carbon matrix and micro-sized dielectric mineral inclusions. Shungite could be considered as a raw to manufacture shielding materials, and as a model for more complete understanding of interaction of radiation with graphene-containing conducting solids in order to improve the shielding performances.

A method of heating an oil bed by means of the energy of electromagnetic and acoustic fields introduced into an oil-saturated bed is investigated. Different variants are considered: electromagnetic heating alone, acoustic heating alone, joint heating of the bed by both radiators located on the well within the power of the oil bed. As a result of the dissipation of the energy of the waves, volumetric heat sources appear in the medium the magnitude of which can be calculated by the Umov–Pointing theorem. The densities of the heat sources originating in the bed on propagation of acoustic waves at different frequencies (6, 16, and 22 kHz, with the frequency of electromagnetic waves 13.56 MHz) are compared. This article uses an exact expression for calculating the volume density of heat sources from acoustic waves, and simplified formulas are given for the far-lying and close-lying radiation zones. The character of distribution of the density of heat sources in the bed at different distances from the radiators is investigated.

Micro-perforated panels (MPPs) are one of the most promising alternatives to conventional porous sound-absorbing materials. Traditionally, the theory of the sound absorption properties of MPPs is based on the assumption that MPPs are a homogeneous material with identical pores at regular intervals. However, in recent years, some MPPs have not met these conditions, and although a variety of designs have been created, their properties and prediction methods were studied in only fewer works. In this paper, considering the wide variety of MPP designs, we made a trial production of heterogeneous MPPs, which are MPPs with holes of different diameters, and studied the prediction method applicable to these MPPs. We measured the normal incidence sound absorption characteristics of those MPPs, backed by a rigid backing and air-cavity in-between, in an impedance tube. The prediction method proposed in this work is to treat the heterogeneous MPPs as combinations of several homogeneous components, and to combine them after applying the existing theory on homogeneous MPPs to each component. As a result, except in a few cases, the measured and predicted values of the absorption properties agreed relatively well. We also found that the arrangement of the holes in the material and the depth of the back cavity affected the agreement between the measured and predicted results.

A single layer of four parallel-arranged inhomogeneous microperforated panels (iMPP) absorber is proposed to achieve low-frequency sound absorption and wider frequency bandwidth. The hole diameter of the four parallel-arranged iMPP is set to be equal to or less than 1 mm. The theoretical formula for calculating the absorption coefficient under normal incident sound is established based on an electrical equivalent circuit model (ECM). The parametric study has been performed on the MATLAB software, and the expected results are obtained. The results indicate that the proposed model can produce a wider absorption bandwidth of 195–455 Hz in the low-frequency region with an average absorption coefficient of more than 90% (α = 0.91). To achieve the desired effect, the absorption coefficient and the bandwidth can be tuned by adjusting the aperture size, perforation ratio, thickness of iMPP with depth and width of the back cavity. Also, it is found that iMPP can produce wider bandgaps with good absorption peaks in the low-frequency region by designing sub-MPP of smaller hole diameter, large perforation ratio, and with large cavity depths and the sub-MPP of large hole diameter, small perforation ratio, and with short cavity depths. The finite element method has been employed on COMSOL Multiphysics 5.5a to simulate the acoustic absorption performance of the model and compared with the ECM-based predicted and square impedance tube-based experimental results. Compared with other homogeneous MPPs of different arrangements, this absorber provides exceptional absorption performance in a low-frequency range due to its lightweight structure, and convenient manufacturing availability, this enhanced form of iMPP absorber has great potential in acoustics and noise control applications.

Textile materials can be used as a soft solution to protect the human body of the soldier and as a hard solution to provide more efficient armour for various types of vehicles. Their advantages are numerous in terms of performance versus weight, forming ability and availability of different types of high-performance yarns. Special attention has been given to the 3D warp interlock fabrics structure in the above applications. For the soft protection application, a body armour adapted to the female breast was designed based on different layers of 3D warp interlock fabric made of para-aramid yarns. A compromise was found between the formability criterion, which facilitates the adaptation of the body armour to the body, and the kinetic energy absorption in ballistic impact, which tends to minimize the blunt trauma criterion. For hard protection, a new vehicle up-armour was found to protect the interior from the high-velocity impact of projectiles. A compromise was also found to optimize the kinetic energy absorption in this high-velocity impact and the capacity of dynamic deformation of the protection solution to avoid structural damage and keep the integrity of the armour solution safe.

The research collection aims at finding the various possible opportunities for the effective integration of shallow geothermal energy (SGE) to decrease the energy demand in the built environment and to reduce emission associated with it. The direct utilization of SGE using a ground source heat pump (GSHP) has been reviewed in comprehensive review part I and part II. From the extensive review, it is found that the hybrid GSHP is needed to avoid ground thermal imbalance and peak demand. Hybrid GSHP can adopt various supplemental heat sources and sinks according to the local climatic conditions and the balance of energy demands. The primary focus on the integration of subsystems such as biomass, solar energy (PV, PVT, and collector), phase change material, micro gas turbine, and absorption heat pump with GSHP is presented for heating application. This comprehensive review part III highlights the recent research findings and a potential gap in hybrid GSHP for further research and developments

Accurate measurements of the three-dimensional structure characteristics of urban buildings and their greenhouse effect are important for evaluating the impact of urbanization on the radiation energy budget and research on the urban heat island (UHI) effect. The decrease in evapotranspiration or the increase in sensible heat caused by urbanization is considered to be the main cause of the UHI effect, but little is known about the influence of the main factor “net radiant flux” of the urban surface heat balance. In this study, experimental observation and quantitative model simulation were used to find that with the increase of building surface area after urbanization, the direct solar radiation flux and net radiation flux on building surface areas changed significantly. In order to accurately quantify the relationship between the positive and negative effects, this study puts forward the equivalent calculation principle of “aggregation element”, which is composed of a building’s sunny face and its shadow face, and the algorithm of the contribution of the area to thermal effect. This research clarifies the greenhouse effect of a building with walls of glass windows. Research shows that when the difference between absorption rates of a concrete wall and grass is −0.21, the cooling effect is shown. In the case of concrete walls with glass windows, the difference between absorption rates of a building wall and grass is −0.11, which is also a cooling effect. The greenhouse effect value of a building with glass windows reduces the cooling effect value to 56% of the effect of a building with concrete walls. The simulation of changes in net radiant flux and flux density shows that the greenhouse effect of a 5-story building with windows yields 15.5% less cooling effect than one with concrete walls, and a 30-story building with windows reduces the cooling effect by 23.0%. The simulation results confirmed that the difference in the equivalent absorption rate of the aggregation element is the “director” of cooling and heating effects, and the area of the aggregation element is the “amplifier” of cooling and heating effects. At the same time, the simulation results prove the greenhouse effect of glass windows, which significantly reduces the cold effect of concrete wall buildings. The model reveals the real contribution of optimized urban design to mitigating UHI and building a comfortable environment where there is no atmospheric circulation.

This work investigates the effect of hybridization and stacking sequence on the ballistic impact response of S2-glass/aramid/epoxy laminates. Different laminates were manufactured by vacuum infusion, one with only aramid fabrics (12 layers, K12), two with only S2-glass fabrics (12 or 18 layers, Gl12 and Gl18) and five interply hybrids (Gl3K9, [GlK]6, K6Gl6, Gl6K6, Gl9K3). Ballistic tests were performed according to EN1522- FB3, with the .357 Magnum FMJ projectile. The ballistic curves were determined to obtain the ballistic limit velocity (VBL), and in-plane damage area and through-the-thickness damage were analyzed. For the impact at 430 m/s, all laminates were perforated, and the Gl18 exhibited greater specific absorbed energy (26.6 J.m2/kg), with lower thickness and in-plane damage than the K12 (22.6 J.m2/kg) with a similar areal density (≈0.77 g/cm2). No significant differences in ballistic limits (pairing effect) were observed for the [GlK]6, Gl6K6 and K6Gl6 hybrids, and the Gl3K9 hybrid exhibited a positive hybrid effect. The areal density of laminates has shown a great influence on the final ballistic response. The results have shown that hybridization of aramid composites with S2-glass may enhance the impact absorption capability of hard composite armors, however, the ballistic limit velocity, which is a crucial parameter to assess ballistic shield performance, reduced.

Purpose Almost one in four lumpectomies fails to fully remove cancerous tissue from the breast, requiring reoperation. This high failure rate suggests that existing lumpectomy guidance methods are inadequate for allowing surgeons to consistently identify the proper volume of tissue for excision. Current guidance techniques either provide little information about the tumor position or require surgeons to frequently switch between making incisions and manually probing for a marker placed at the lesion site. This article explores the feasibility of thermo-acoustic ultrasound (TAUS) to enable hands-free localization of metallic biopsy markers throughout surgery, which would allow for continuous visualization of the lesion site in the breast without the interruption of surgery. In a TAUS-based localization system, microwave excitations would be transmitted into the breast, and the amplification in microwave absorption around the metallic markers would generate acoustic signals from the marker sites through the thermo-acoustic effect. Detection and ranging of these signals by multiple acoustic receivers on the breast could then enable marker localization through acoustic multilateration. Methods Physics simulations were used to characterize the TAUS signals generated from different markers by microwave excitations. First, electromagnetic simulations determined the spatial pattern of the amplification in microwave absorption around the markers. Then, acoustic simulations characterized the acoustic fields generated from these markers at various acoustic frequencies. TAUS-based one-dimensional (1D) ranging of two metallic markers - including a biopsy marker that is FDA-approved for clinical use - immersed in saline was also performed using a bench-top setup. To perform TAUS acquisitions, a microwave applicator was driven by 2.66 GHz microwave signals that were amplitude-modulated by chirps at the desired acoustic excitation frequencies, and the resulting TAUS signal from the markers was detected by an ultrasonic transducer. Results The simulation results show that the geometry of the marker strongly impacts the quantity and spatial pattern of both the microwave absorption around the marker and the resulting TAUS signal generated from the marker. The simulated TAUS signal maps and acoustic frequency responses also make clear that the marker geometry plays an important role in determining the overall system response. Using the bench-top setup, TAUS detection and 1D localization of the markers was successfully demonstrated for multiple different combinations of microwave applicator and metallic marker. These initial results indicate that TAUS-based localization of biopsy markers is feasible. Conclusions Through microwave excitations and acoustic detection, TAUS can be used to localize metallic biopsy markers. With further development, TAUS opens new avenues to enable a more intuitive lumpectomy guidance system that could help to achieve better lumpectomy outcomes.

Potential radar absorbing material (RAM) for suppressing electromagnetic (EM) wave over a range of oblique angles of incidence are needed in many applications. In this article, an attempt is being made to build cost-effective and efficient RAM using the EM characterization of microwave heat-treated (MHT) electronic waste followed by an EM mixing model-assisted analytical approach. The robust and facile top-down fabrication technique is employed for the development of heterogeneous composites, which are further subjected to microwave heat treatment at distinct power wattages. The magneto-dielectric spectrographic analysis of samples is carried out in the range of 8.2 to 12.4 GHz. The Debye parameters are optimized and succeeded to obey EM property of the synthesized samples. Jaya's algorithm is adopted for the optimal design of single and dual-layer RAMs at normal and oblique angle incidence based on the constitutive EM parameters under certain restrictive conditions. The embraced MHT method prompts an improvement in microstructure coherency that further increases absorption bandwidth (BW). As a result, a 2.1 mm thick single layer RAM achieves a minimum reflection coefficient (RC) of −17.1 dB at 10.3 GHz with a 100% BW below −10 dB threshold. The groundbreaking findings are obtained by performing a three-fold study of dual-layer RAMs, culminating a minimum RC of −47.8 dB at 11.8 GHz with a layer thickness of 1.8 mm. This article shows that the microwave heat-treated composites have enormous potential in the development of lightweight and broadband RAMs for stealth applications.

International audience; In the context of building acoustics and the acoustic diagnosis of an existing room, this paper introduces and investigates a new approach to estimate mean absorption coefficients solely from a room impulse response (RIR). This inverse problem is tackled via virtually-supervised learning, namely, the RIR-to-absorption mapping is implicitly learned by regression on a simulated dataset using artificial neural networks. We focus on simple models based on well-understood architectures. The critical choices of geometric, acoustic and simulation pa- rameters used to train the models are extensively discussed and studied, while keeping in mind conditions that are representative of the field of building acoustics. Estimation errors from the learned neural models are compared to those obtained with classical formulas thatrequire knowledge of the room's geometry and reverberation times. Extensive comparisons made on a variety of simulated test sets highlight different conditions under which the learned models can overcome the well-known limitations of the diffuse sound field hypothesis under-lying these formulas. Results obtained on real RIRs measured in an acoustically configurable room show that at 1 kHz and above, the proposed approach performs comparably to classical models when reverberation times can be reliably estimated, and continues to work even when they cannot.

It is of great significance for absorber designers to correctly understand impedance matching and its related calculation methods, because excellent impedance matching effect is an important prerequisite for absorber to consume electromagnetic wave (EMW). However, there are some problems in literatures, such as the lack of deep understanding of impedance matching and application conditions of Eq. (3) for the calculation of reflection loss (RL). Based on the transmission line theory of electronic circuit, this paper expounds the definition, symbol, property of various impedances and their influence on impedance matching effect. On the basis of simplifying the actual situation in the process of EMW absorption to the correct transmission line model, the original transmission line model of RL calculation formula and its limitation are pointed out. The doubts about the validity of the quarter wavelength theory in literatures are explained from three aspects: the reduction of EMW length, the multiple reflection and the impedance transformation of absorber.

Retrofitting concrete with fiber-reinforced polymer (FRP) wrap has been considered as an effective method to compensate for the loss of the compressive strength of the concrete at an elevated temperature. This paper presents a study on the axial compressive behavior of heat-damaged steel fiber-reinforced concrete strengthened with carbon FRP (CFRP) wraps. To this effect, steel fibers were added to two concrete mixtures with volume fractions of 0.5% and 1%. The effect of full and partial wrapping with CFRP composites on the compressive behavior of the heated concrete was examined. A stress–strain model was also proposed to predict the behavior of CFRP-confined post heated steel fiber-reinforced concrete. It was found that heated concrete wrapped with CFRP layers exhibits a higher compressive strength, peak axial strain, maximum volumetric strain, toughness and relative energy absorption than that of unwrapped concrete. The results also showed that the exposure of concrete to the heat leads to a slight decrease in the ascending and descending slopes of the axial stress–strain relationship. The comparison between the model predictions and experimental results revealed that the proposed model accurately predicts the axial stress-axial strain and axial stress-lateral strain of the heated concrete. These results are promising and demonstrate the benefits of full and partial FRP wrapping in the development of high-performance structural members subjected to an elevated temperature.

User interaction can significantly degrade handset antenna performances through frequency detuning and absorption. In this article, the relationships between the hand effects and the radiation patterns of the antennas are investigated using characteristic mode theory. First, we calculate the characteristic far fields of a typical monopole-loaded handset antenna with metal frames. Afterward, the radiation patterns of the handset antenna are simulated and obtained in two different scenarios, i.e., in free space and with hand. Then we map the antenna patterns in two scenarios to the characteristic mode patterns by calculating the weighting coefficients, which stand for the power contributions of the modes. By inspecting the variations of the weighting coefficients in free space and with hands, it is found that the modes with less radiation at the boresight and the backward directions are more robust to the hands. Accordingly, a handset antenna with little radiating power toward the boresight is designed. Compared to the reference antenna with the same feeding location, the efficiencies of the proposed antenna have been improved by 4.1 and 6.3 dB, respectively, for the left-hand and right-hand scenarios. Experiments have been carried out for the hand effects, with the measured results agreeing reasonably with the simulated ones.

This paper presents accurate models evaluating the hydrodynamic and separation behavior of an innovative packing structure called Tetra Spline (TS) packing. The newly designed internal is a wire-based lattice packing fabricated via additive manufacturing for gas-liquid contact systems, such as distillation and absorption columns. Using dimensional analysis, four correlations are developed for the prediction of dry and wet pressure drops, flooding velocity, and HETP of the TS internals in a two-phase system, regardless of its physicochemical properties. The performances are modeled based on extensive experimental data described in a previous work. These data are obtained by performing hydrodynamic and mass transfer characterizations on fifteen different TS configurations. Then, some of the proposed correlations are compared to other models available in literature. The final step will highlight that after optimization of the geometrical parameters the TS packing can reach high performances.

An absorptive device for broadband low-frequency sound with ventilation is essential but challenging in acoustic engineering, which is subjected to the narrow-band limitation and difficulty of balancing high-efficiency absorption and excellent ventilation. Here, we have theoretically and experimentally demonstrated an ultra-sparse (with filling ratio of 53.7%) broadband metamaterial absorber which can efficiently absorb (absorptance >90%) sound energy ranging from 307 to 341 Hz, while enabling air to flow freely. The broadband absorber is constructed by parallel coupling four ventilated metamaterials absorbers (VMAs) showing different operating frequencies. Each VMA is composed of three folded Fabry–Perot resonators as paste components, which are patched subsequently to the walls of a waveguide and correspondingly act as dark, middle, and bright modes following the coupled mode theory. In the VMA, the dark mode is highly over-damped to absorb sound energy, while the bright mode is highly under-damped to be an effective acoustic soft boundary, and the middle mode in-between should be slightly over-damped to strengthen the absorptions. Further investigation demonstrates that broadband high-efficiency absorption is robust against oblique incident angles. The proposed VMA provides a clear scheme for efficiently absorbing low-frequency sound while allowing free air flow simultaneously, which may prompt versatile applications in noise control.

Reinforced soil wall has proved to have excellent impact resistance in engineering, but less attention has paid to their failure process and dynamic response subjected to impact loading. The authors performed model tests and numerical simulations of reinforced soil walls with and without cushion under differential impact loading. The deformation, failure process and impact stress of three retaining walls were mainly analyzed, and the influence mechanism of geosynthetic and cushion on the impact performance of retaining wall were discussed qualitatively. The results showed that the impact deformation of reinforced soil wall with cushion was mainly concentrated on the cushion. The failure process of retaining wall could be divided into two stages: the soil around the impact point of retaining wall was compacted (stage I), a sliding surface formed in retaining wall gradually and retaining wall would failure (stage II). Geosynthetics benefited the sliding surface move back and cushion improved the impact resistance of retaining wall. Furthermore, stress absorption of geosynthetic and cushion was confirmed. The absorption rate of geosynthetic was related to the impact energy positively. The absorption rate of cushion was related to the impact energy positively and related to the thickness of cushion negatively. Engineers can consider the impact energy and the absorption rate of geosynthetic and cushion to design reinforced soil wall with cushion under impact loading.

In the face of increasingly severe electromagnetic (EM) wave pollution, the research of EM wave absorbing materials is an effective solution. To reduce the density of traditional absorbing materials, in this work, FeCo/CoFe2O4/carbon nanofiber composites were successfully prepared by electrospinning for the EM wave attenuation application. Benefiting from the loss ability of interface polarization, dipole polarization, and magnetic loss, the composites obtained a bandwidth of 5.0 GHz at a 1.95 mm thickness and an absorption peak of -52.3 dB. More importantly, the radar cross section (RCS) reduction of composite coatings calculated by ANSYS Electronics Desktop 2018 (HFSS) can reach 34.5 dBm2, and the RCS value is almost less than -10 dBm2 when the incident angle is greater than 20°, demonstrating great scattering ability of the material coating to EM waves. This work, combined with the exploration of the mechanism and the simulation analysis of the absorbing coating, will be of significance for the development of absorbing materials.

Several recent theoretical dosimetric studies above 6 GHz apply generic layered skin models. For this frequency range, new experimental phantoms for over-the-air performance of wireless devices were proposed that simulate the impedance matching effects of the stratum corneum layer (SCL) with a low-loss coating layer. The aim of this study was to verify the skin models by comparing their reflection coefficients S11 with measurements of 37 human volunteers (21 males, 16 females, 5-80 years) at 21 body locations (10 at palm, 11 at arm/face) with different SCL thicknesses, using waveguides covering frequencies from 40 to 110 GHz. Such measurements were also carried out with the phantom material. The statistical analysis showed strong evidence that S11 depends on the SCL thickness and no evidence that S11 depends on sex. The measured S11 values for thin and thick skin can be represented by SCL layers of 15 and 140 μm, respectively. These values correspond well to the assumptions of previous studies. (The cohort did not include volunteers doing heavy manual work.) The phantom material mimics the matching effect of the SCL with deviations from the waveguide measurements of less than 0.85 dB (22%), which confirms the suitability of layered phantoms to represent the electromagnetic reflection/absorption of human skin. © 2021 Bioelectromagnetics Society.

Carbon fiber paper reinforced thermoplastics (CPT) have broad application prospects because of its simple production process and good mechanical properties. Currently, polyamide 6 (PA6) is a promising matrix for CPT and is widely used for mass-production. However, the performance of CPT materials in marine and harsh environments must be evaluated because of its environmental sensitivity. In this study, the seawater absorption of CPT was analyzed using Fick’s diffusion law. The flexural properties of CPT in harsh and marine environments were studied by three-point bending. Based on the results, it was concluded that seawater and high temperatures have negative effects on the flexural properties of CPT. Microscopy results showed the mechanisms of failure under the action of seawater and high temperatures. Droplet test was employed to analyze the interfacial shear properties between the fiber and resin. The results showed that after seawater immersion, the interfacial shear strength had a discernable decrease.