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The work shows the objective necessity of mastering the range of millimeter waves for building systems for detecting and tracking air and other targets. The features of propagation of millimeter waves in the Earth's atmosphere are analyzed. The mechanism of their absorption in molecular oxygen, water vapor and hydrometeors is described. The results of calculating the attenuation of millimeter waves as a function of wavelength and viewing angle are presented. The fundamentals of radio-thermal radiation of physical bodies and the features of its reception, the principle of which is based on the fact that any body with a thermodynamic temperature above absolute zero, capable of emitting electromagnetic energy in a wide spectral range, in particular, in the range of millimeter waves, are presented. The resulting radio-thermal radiation of a real body is formed by two components: its own radiation and reflected electromagnetic oscillations falling on the body from the surrounding space. The results of experimental studies of the measure of scattering and reflection of millimeter waves by aircraft skin in active and passive modes are presented. It was found that the distribution of the radio-thermal signal over the surface of the aircraft is uniform, in contrast to the distribution of the reflected signal in the active mode. Experimental studies have shown that in the range of millimeter waves it is possible to obtain an energy portrait of an aircraft under conditions when it is a distributed target, when it is scanned line by line by a narrow antenna pattern in both active and passive modes. Based on the results obtained, it can be concluded that the radiometric method of target detection can be used as the basis for the construction of correlation-extreme navigation systems for cruise missiles, passive missile homing heads, earth surface survey locators installed on artificial earth satellites, aircraft, unmanned aerial vehicles. devices, airfield survey locators, etc.

Article provides a brief overview of the complications arising during the construction of oil and gas wells in conditions of abnormally high and abnormally low formation pressures. Technological properties of the solutions used to eliminate emergency situations when drilling wells in the intervals of catastrophic absorption and influx of formation fluid have been investigated. A technology for isolating water influx in intervals of excess formation pressure has been developed. The technology is based on the use of a special device that provides control of the hydrodynamic pressure in the annular space of the well. An experiment was carried out to determine the injection time of a viscoelastic system depending on its rheology, rock properties and technological parameters of the isolation process. A mathematical model based on the use of a special device is presented. The model allows determining the penetration depth of a viscoelastic system to block water-bearing horizons to prevent interformation crossflows and water breakthrough into production wells.

Here we demonstrate a distributed fibre optic sensor for the detection of liquid hydrocarbons. Two commercially available low-density ethylene-octene polyolefin elastomers with different properties are used to coat fibre optic cables, where the swelling of the coating upon absorption of hydrocarbons imparts strain on the fibre. By frequency domain analysis of the backscatter, the location of oil on the fibre is determined with high precision. The elastomer with the highest flexural modulus, hardness and tensile strength (Engage 8150) imposes more than three times more strain on the fibre compared to the softer elastomer (Engage 8180), despite the Engage 8180 expanding more than three times more in volume compared to the Engage 8150. A response occurs within a few seconds following oil interaction, and a maximum response of 700 microstrain ( $\mu \varepsilon $ ) is achieved with a response time of 1.5 minutes (t63) when a dry fibre is exposed to oil, whereas a maximum response of $400~\mu \varepsilon $ is achieved when the fibre is exposed to oil when submerged in water. The results demonstrate that optical fibres coated in this way are able to detect and locate small quantities of oil with high degree of spatial resolution. The technique could be scaled to fibre covering long distances, and makes the sensor interesting for pipeline leak detection both on -and offshore, as well as for oil production monitoring purposes downhole.

In our previous works, we presented a theoretical approach to describe the behavior of a single-mode step-index optical fiber or polymer optical fiber such as poly (methyl methacrylate) or PMMA fiber coated by moisture-sensitive polymers (MSPs) and moisture-insensitive polymers periodically. The periodic structure is surrounded by a high young's modulus material such as stainless steel mesh. Absorption of the moisture by the MSPs causes to deform the optical fiber, such that the optical fiber gratings are induced. Induced fiber gratings are the basis of the proposed relative moisture sensor. Due to the low Young's modulus of polymers, the polymer fiber sensors are more sensitive relative to the glass optical fiber sensors. The difference between the coefficient of thermal expansion of different polymers is the origin of errors in the sensor's outputs. In this paper, a theoretical approximate method is employed to optimize the moisture density in the presence of temperature variation and as a result, the error due to temperature change is investigated, and finally, a structure for temperature-compensated distributed optical fiber moisture sensor is proposed. By the development of this numerical approach, it is shown that the proposed sensor can be employed for moisture and temperature measurement simultaneously. The optimal design of a long length distributed optical fiber moisture sensor makes it a good candidate for application in the agriculture fields and gardens’ smart irrigation.

The advances in additive manufacturing (AM) over the past decades have enabled the manufacturing of increasingly complex parts which were previously difficult or infeasible to be fabricated using traditional formative or subtractive manufacturing processes. Various configurations of periodic lattice structures are now designed and fabricated via AM in virtue of the advantages they provide such as weight reduction, high energy absorption, and superior stiffness-to-weight ratio. Such functional and mechanical properties can be tuned to meet the application requirements by varying the unit cell type, unit cell size, and volume fraction. Exploring the achievable volume fraction ranges of different lattice structure configurations and precise control of the volume fraction of AM fabricated lattice structures will significantly enlarge the scope of the application, which are the main objectives of the present study. A simple strategy is developed for periodic mesoscale lattice structures fabricated via laser-powder bed fusion (L-PBF) process to quantify the manufacturable volume fraction ranges and the relationship between designed and fabricated volume fractions. Firstly, the relationship between the lattice design parameters (unit cell type, unit cell size, and strut diameter) and designed volume fraction was formulated. Next, the theoretically achievable volume fraction ranges of lattice structures were calculated. The lattice coupons of specific designed volume fractions within the previously obtained ranges were built and the fabricated volume fractions were measured. A multiple linear regression model was set up to determine correlation factors between designed and fabricated volume fractions based on the available data and the model accuracy was validated. In the current work, AlSi12 was utilized as a model material system to demonstrate the applicability of the proposed framework. It is worth mentioning that this framework is applicable to other material systems. Based on the case study results on AlSi12, insights were developed to aid the design and manufacturing processes of periodic mesoscale lattice structures in general for fabrication by L-PBF.

The shielding of radio wave by steel-containing structures is desirable for electronics protection but undesirable for telecommunication signal reception. This work investigates the shielding behavior of steel structures consisting of members in various configurations, with the practical aim of determining how the configuration can be exploited to control the shielding. Differently oriented continuous steel reinforcement (stranded/unstranded wires in the unidirectional, crossply and planar coil configurations) are evaluated for electromagnetic interference (EMI) shielding at 600-2000 MHz, using unpolarized radiation. The absorption loss SE (A) dominates the reflection loss SE (R). The crossply configuration gives the highest SE (A), SE (A)/thickness and SE (A)/SE (T) (SE (T) = total loss); the planar coil configuration gives the lowest values. The SE (A), SE (A)/thickness and SE (A)/SE (T) are moderately higher for the crossply configuration than the unidirectional configuration, because steel's electrical isotropy allows the 0 degrees electric field to interact with the 90 degrees wire. The SE (A)/SE (T) is comparable for the stranded and unstranded wires.

In order to improve the ductilityof cement-based materials, rubber is often added to cement-based materials. But the rubber-cement interface will introduce more initial defects, and make the three dimensional images obtained by the X-ray micro-computed tomography (X-ray μCT) technology more complex, and finally,which leads to the full threshold method no longer applicable to analysis of the internal three-dimensional cracks.This paper presents an improved image processing method, which can accurately identify mesoscopic cracks and achieve the separation of pores and cracks. In order to verify this method, X-ray computed tomography (XCT) in-situ observation technology is used to obtain the crack formation of rubber mortar with different replacement ratios. Pores and cracks are well identified and separated by this method. Quantitative analysis shows that the new method has higher accuracy and better identification of mesoscopic cracks than traditional methods. Due to the incorporation of rubber, there are more initial cracks in the rubber mortar, but the rubber will improve the overall absorption of the input energy of the sample, resulting in a decrease in the number of large cracks and the total crack volume when the specimen is failure.Compared with the sample without rubber content, the total crack volume of the sample with 5% and 10% mass fraction of rubber decreases by 30% and 45%, respectively.

On the quest towards efficiently eliminating noises, the development of a subwavelength sound absorber with the capability of free ventilation remains challenging. Here, we theoretically propose and experimentally demonstrate an asymmetric metamaterial absorber constructed by tuned Mie resonators (MRs) with unbalanced intrinsic losses. The lossy MR layer is highly dissipative to consume the sound energy while the lossless one acts as an acoustically soft boundary. Thus, the absorber presents quasi-perfect absorption (95% in experiment) for sound waves incident from the port nearer the dissipative MR and large-amount reflection (71% in experiment) from the opposite port. Moreover, the fluid dynamics investigation confirms the superior character of free air circulation owing to the ultrasparsity (volume filling ratio as low as 5%) of the absorber and its robustness to the velocity of airflows. Due to the multiple-order resonant modes of MR, we further demonstrate the flexibility of a methodology to extend asymmetric absorptions into multibands. Coupled mode analysis is employed to reveal the physical mechanism and further indicates that sparsity can be tuned by attentively controlling the reference leakage factor and intrinsic loss.

The manufacture of fabrics and textiles is one of the industries that has witnessed a great development in recent times in the whole world significantly, which has led to the production of many types of fabrics and textiles with special characteristics such as Waterproof. This type of waterproof fabrics has become one of the most important fabrics widely used in the field of ready-made garments, especially for the production of winter jackets, which are known commercially as (pump jackets), which are used by various categories and ages, women, men and children. This is due to its distinctive appearance properties in addition to its ability to prevent water penetration with the ability to ventilate the body by allowing the absorption of sweat and the exit of water vapor. This type of fabric is usually coated with a waterproofing material such as rubber, polyvinyl chloride (PVC), polyurethane (PU), acetyl silicone, fluoropolymers and waxes, so it requires a high technical level in dealing with it, during its production stages or during its decoration with various decorative methods. Machine embroidery is one of the most appropriate decorative methods used to add a distinctive decorative character to these fabrics, making them richer, but some technical defects of that process may appear, which directly affects the appearance of the cloth and distorts its surface due to its special nature, hence the idea of Research to study the effect of machine embroidery variables on the appearance of waterproof fabrics as an attempt to set standardized standards for embroidery. The research problem can be summarized in the following questions: 1- What are the natural and mechanical properties of waterproof fabrics? 2- What is the effect of the difference in the density of the machine embroidery stitches on the appearance of the waterproof fabrics? 3- What is the effect of the difference in the type of yarn used in machine embroidery on the appearance of waterproof fabrics? 4- What is the effect of the strengthening methods used in machine embroidery on the appearance of waterproof fabrics? 5- Access to the best technologies for dealing with waterproof fabrics. Research objectives: 1- Determine the natural and mechanical properties of waterproof fabrics. 2- Determine the effect of the difference in the density level of the machine embroidery stitches on the appearance of waterproof fabrics. 3- Determine the effect of the difference in the type of machine embroidery yarn on the appearance of waterproof fabrics. 4- Determine the effect of strengthening ways on the appearance of waterproof fabrics. 5- Determining the best techniques for automatic embroidery on waterproof fabrics, which achieve the highest appearance. Research Significance: The results of this study are useful in overcoming the technical defects that occur during machine embroidery on waterproof fabrics. And identifying the aspects and limitations in it, which may result from the wrong choice (for the level of stitch density - the type of embroidery yarn - strengthening ways). This keeps preserving the aesthetics of the fabric and the appearance of the embroidery on it. Methodology: The current research follows the experimental approach to suitability to achieve the research objectives. Results ; By studying the effect of the machine embroidery variables (stitch type - stitch density - embroidery yarn type - strengthening methods) on the appearance of embroidery on waterproof fabrics, it was found that: -- The best effect of the stitches and densities of machine embroidery on the appearance of the embroidery on waterproof fabrics is the Counter stitch with medium density (1.50), followed by the Run stitch with high density (0.80), and finally the Satin stitch with low density (0.85). - The best types of machine embroidery yarns for the appearance of embroidery on waterproof fabrics is silk thread, followed by polyester thread, then metallic thread. - The best strengthening methods when embroidering on waterproof fabrics are strength with paper with non-stick wadding, followed by strength with non-stick wadding, and finally strength with paper.

The oscillating buoy wave energy converter (OBWEC) captures wave energy through the undulating movement of the buoy in the waves. In the process of capturing wave energy, the hydrodynamic performance of the buoy plays an important role. This paper designed the “Haida No. 1” OBWEC, in which the buoy adopts a form of swinging motion. In order to further improve the hydrodynamic performance of the buoy, a 2D numerical wave tank (NWT) model is established using ADINA software based on the working principle of the device. According to the motion equation of the buoy in the waves, the influence of the buoy shape, arm length, tilt angle, buoy draft, buoy width, wave height and Power Take-off (PTO) damping on the hydrodynamic performance of the buoy is studied. Finally, a series of physical experiments are performed on the device in a laboratory pool. The experimental results verify the consistency of the numerical results. The research results indicate that the energy conversion efficiency of the device can be improved by optimizing the hydrodynamic performance of the buoy. However, the absorption efficiency of a single buoy for wave energy is limited, so it is very difficult to achieve full absorption of wave energy.

The aim of this work is to help inform the decision for choosing a convenient material for the PGAA (Prompt Gamma Analysis Activation) collimator plug to be installed at the tangential channel of the Moroccan Triga Mark II Research Reactor. Two families of materials are usually used for collimator construction: a mixture of high-density polyethylene (HDPE) with boron, which is commonly used to moderate and absorb neutrons, and heavy materials, either for gamma absorption or for fast neutron absorption. An investigation of two different collimator designs was performed using N-Particle Monte Carlo MCNP6.2 code with the ENDF/B-VII.1 and MCLIP84 libraries. For each design, carbon steel and lead materials were used separately as collimator heavy materials. The performed study focused on both the impact on neutron beam quality and the neutron–gamma background at the exit of the collimator beam tube. An analysis and assessment of the principal findings is presented in this paper, as well as recommendations.

In this paper, a new path integration algorithm is proposed specifically for the stochastic vibro-impact system. By introducing the concept of absorption surface and the impact completion condition, this new path integration algorithm can be directly used to study the stochastic response of vibro-impact systems without any non-smooth approximation. The algorithm is suitable for arbitrary recovery coefficients and can retain the non-smooth characteristics of the vibro-impact system. Linear and nonlinear vibro-impact systems excited by the Gaussian white noise are used as examples to show the unique results obtained by our method. Finally, the Monte Carlo method is used to verify the efficiency and accuracy of this new algorithm.

The research was to determine the more efficient design of the swirler from the point of view of hydrodynamics and heat and its optimal parameters. Various swirl designs were manufactured and tested. After preliminary studies conducted on a laboratory installation with a glass working apparatus, several swirlers were selected taking into account their hydraulic resistance, the structure of the swirling gas-liquid flow, and the amount of liquid entrainment by gas. The results of an experimental study of the hydrodynamics of a hollow vortex apparatus with one and two tangential and axial swirlers. Hydraulic losses in the channel and in the swirls during the direct downward movement of gas and gas-liquid flow are determined. In addition, studies of the hydraulic resistance of a vortex-type device allow us to determine the energy consumption of this device for conducting complex processes of dust collection and absorption or contact heat exchange. The hydraulic resistance in the presence of a liquid film is higher than in the case of a single-phase gas flow. The pressure drop in the studied vortex apparatus does not exceed the resistance of high-performance cyclones and vortex-type devices of other designs. The effect of the twist coefficient of gas swirlers, gas velocity, and liquid flow on the pressure drop in the vortex apparatus is established

Ballistic-resistant organoplastics made from layers of aramid fabric, adhesively bonded by a binder film, exhibit an increased tendency to absorb moisture, water and technical fluids in comparison with organoplastics monolithic structures. The absorption of liquids is anisotropic and manifests itself most intensively through the butt ends of the samples. The use of protective paintwork ensures stability of the characteristics of ballistic-resistant materials when exposed to environmental factors (environment, water, fuel, oil, natural climatic conditions).

Silica sand smaller than 70 microns can be used as a partial substitute for cement. This study partially demonstrated the properties of cement made of ceramic scrap and micro-silica instead of sand and cement. The effect of this recycled material was investigated by compressive strength tests and durability tests such as water absorption rate, absorption test and sulfate attack test.

This study investigates the possibility of exploiting the porous structure of wood for absorbing sound. With this aim, the following system is proposed: 1 ) the cross section of wood should be exposed to sound waves so that these can activate the vibration of air inside the wood pores; 2) the cross section should be cut to have small thickness to realize a thorough open cell absorber; 3 ) a void cavity should be left on the back to activate the absorption effect. This setup has been conceived to absorb sound by Helmoltz resonance. To preliminary assess the effectiveness of the system, cross sections of poplar wood were cut 1 mm thick and paired with rear void cavities 15, 30 and 50 mm thick. The normal sound absorption coefficient α was determined through the impedance tube method. Multiple absorption peaks and several α values higher than 0.6-0.7 (α max =0.99) were measured in the medium-low frequency range. Building on these results, further studies are envisaged to model the acoustic behavior of the system and to set the technical aspects relevant to its feasibility in practice.

This study focuses on the absorption characteristics and evolution of key properties of silicone rubber (SiR) in the presence of silicone grease; a typical material used in power cable accessories. Diffusion mechanism of silicone grease within the SiR is investigated and the results indicate that it follows Langmuir diffusion model in the absence of significant swelling. Silicone grease absorption behavior is also explored under tensile strain and at various temperatures. The tensile strain accelerates and increases the absorption of silicone grease. In addition, the influence of the absorbed silicone grease on the key electrical and mechanical properties of SiR is surveyed. The investigation shows that the properties deteriorate. In addition, the mechanism of the mechanical property deterioration of SiR is discussed.

The need to reduce waste is driving the development of new materials and technologies that support the transition of societies towards a more environmentally sustainable world. Wood-polymer composites (WPCs) can be produced by using waste products deriving from wood and plastic manufacturing industries. Enhanced mechanical and physical properties of WPCs also allow for these materials to substitute their conventional counterparts, especially the ones intended to be used in dry and hot environments. This paper examined how the addition of various reinforcements influenced the properties of polymer matrix-based WPC. More closely, this paper focused on assessing the mechanical properties of Polymethylmethacrylate (PMMA) and date palm leaves-based composite samples with different reinforcement types of recycled Polyethylene Terephthalate (PETE) fibers and nano-Aluminum Oxide (nano-Al2O3) particles. A two-way ANOVA and multivariate linear regression models are developed to predict and examine the effects and the interaction between the effect of batches and series on density, absorption, strength, modulus and absorbed energy before and after aging. The results suggest that combining the PMMA with recycled date palm leaves and including a mixture of commercially available PETE fiber reinforcements along with nano-Al2O3 particles produces samples that show enhanced mechanical and water resistance properties compared to composites without such reinforcements. The analysis used to detect the WPC combination and reinforcements embedded in the composite structure indicated that the reinforcements limited the absorption of water. The mechanical tests conducted on the reinforced WPC samples showed an improvement of mechanical characteristics. Adding both recycled PETE fibers and nano-Al2O3 particles to the samples increases the flexural characteristics and shows the largest capacity to absorb energy at impact followed by single reinforcement samples. For samples that underwent aging in chloride solution (offshore simulation), the enhanced capabilities were reduced by 8 and 15%.

Herein, a type of syntactic foam, consisting of silicone-modified resin and hollow polymer microspheres, is developed and tested for the application of a composite cross-arm. The physical properties, electrical properties, and hydrolysis-resistance are tested and analyzed. Suitable microspheres can reduce the density of the syntactic foam to 46.63% of the resin. The dielectric strength of the syntactic foam decreases from 37.9 to 26.1 kV/mm with increasing microsphere content, which is still much higher than the operational requirement of 3 kV/mm. The water-absorption rate (

A common concern with electronics packaging is the reduction of moisture ingress into the devices. One option to consider is the use of water absorption desiccant. Its criteria for selection should be its water capacity property, while its regeneration temperature has to be taken into account. Electronic devices are exposed to all kinds of harsh cyclic environments, and assuring a low level of humidity inside the devices implies the replacement of the desiccant once its saturation content is reached. This may not be applicable, or the frequency of replacement may represent a high cost. Using the dissipated heat from the electronic devices during the “ON” time may be a low-cost process for the regeneration of the desiccant, therefore increasing its lifetime. This article presents the experimental investigation of the performance of different desiccants on water absorption and regeneration. Analysis and test results show that the desiccant system continuously maintains a lower humidity inside the electronic enclosures over the tested time of cyclic exposure if they can be regenerated using device self-heating.

The article is devoted to the study of the influence of the brake control elements of passenger vehicles on the stability of their braking properties. The analysis of the influence of uneven braking forces on the wheels of one axle of vehicles on the deviation of the distribution of braking forces between the axles from its calculated value is carried out. When assessing the error in regulating the distribution of braking forces between the axles of vehicles, three components were taken into account: the theoretical error due to the imperfection of the selected control method (the difference between the actual calculated control characteristic from the ideal), the error created due to the instability of the ratio of the braking forces on the front and rear wheels, an additional error caused by the unevenness of the braking forces on the wheels of individual axles, since the fulfillment of the most stringent requirements of international and national standards for the efficiency of braking of vehicles and is inextricably linked with the need to increase the energy consumption of brake mechanisms. The energy consumption of braking mechanisms is understood as the ability of the latter to dissipate the greatest amount of energy of the braking machine without reducing the braking efficiency indicators to the minimum permissible level. Excessive heating of the braking mechanisms leads to a decrease in the friction coefficient μ of the friction surfaces and increased wear of the friction linings, and the brakes are the most unstable element of the braking control, which ensures the absorption and dissipation of the vehicle's energy during braking. The instability of the braking torques on the front and rear wheels, caused by a change in the coefficients of friction of friction pairs, leads not only to a change in the distribution of braking forces between the axles and individual wheels, but also to a decrease in the braking efficiency of vehicles under operating conditions. A method is proposed that makes it possible to assess the quality of regulation of the distribution of braking forces between the axles of a car, taking into account the instability of the braking forces on the wheels.

Intravascular photoacoustic tomography (IVPAT) is a newly developed imaging modality for the diagnosis and intervention of coronary artery diseases. It is an ill-posed nonlinear least squares (NLS)...

Fibreglass, foam, mineral fibres and their composites are the conventional materials used in applications that require absorption of sound. However, due to the health risks associated with the trad...

The capability of the glass pyramid shape with multi-shelf solar system to extract water from humid air is explored. Two pyramids were used with different types of beds on the shelves. The beds are saturated with 30% concentrated Calcium Chloride solution. The pyramid sides were opened at night to allow the bed saturated with moist air and closed during the day to extract the moisture from the bed by solar radiation. The bed in the first pyramid was made of saw wood while it is made of only clothes in the second pyramid with the same dimensions. The system was experimentally investigated at different climatic conditions to study the effect of pyramid shape on the absorption and regeneration processes. Preliminary results have shown that the cloths bed absorbs more solution (9 kg) as compared to the saw wood bed (8 kg), Adopting this approach produce 2.8 Liter/day.m2. The use of the pyramid shape with four glass surfaces and multi-shelves enhances the produced water by about 90-95 % compared with solar desiccant/collector system with horizontal and corrugated beds. Results shows also that the clothes bed has higher productivity than that of saw wood bed by about 5% This is due mainly to the greater carrying solution at the onset of the experimental work. The obtained results may help in designing more efficient system.

Heavyweight concrete can be used when particular properties, such as combined high strength and good radiation shielding, are required. Such concrete, using Ilmenite aggregates, can have a density in the range 4.2 t/m3, significantly higher than the density of concretes made with normal aggregate. The present paper deals with sand-llmenite heavy weight concrete, llmenite has been used as coarse aggregate because of high specific gravity compared with gravel. In the present work, 21 mixes were selected to achieve a slump above 5± 2 cm and strength up to 40 MPa at 56 days. The investigation used three levels of fine aggregates to total aggregates ratio (0.25, 0.4, 0.48), three cement content (350, 400, 450 kg/m3) and four levels of llmenite aggregate to total coarse aggregate (gravel + Ilmenite) ratio (0.25, 0.5, 0.75, 1) were used. The investigation provided information on compressive strength, shielding properties and indicated clear benefits from the use of lImenite as a coarse aggregate. For all type of coarse aggregate (gravel, Ilmenite), increasing the amount of fine aggregate leads to reduction in each of compressive strength and absorption co-efficient. Replacing the gravel with llmenite yields about 35% increase in absorption co-efficient.

This paper studies the influence of factors such as printing speed, layer height, infill density, and type of material, over the mechanical properties of 3D printed pieces. A statistical analysis was conducted in order to determine the effect of each factor over the impact resistance of the 3D printed specimens. Samples of polycarbonate (PC) and nylon + carbon fiber (PA + CF) were tested using conventional Charpy equipment. Initially, the design of experiments was used to evaluate the significance of the studied factors, then, a sequential design was carried out to determine the process parameters that result in the maximum absorption of energy on the material. Finally, the results showed that during the selection phase, the type of material was the factor with the most significant effect, with a 99.5% of importance which is affected by the layer height and infill density. It was found that the absorbed energy was higher for the material PA + CF, according to the statistical results obtained.

As the problem of electromagnetic wave pollution is becoming more and more serious in our daily life, it is urgent to develop a kind of electromagnetic interference (EMI) shielding materials with high-strength and high absorptivity to meet the demand of industrial application. In this study, a facile method is developed to prepare EMI shielding composites with both powerful absorbing and robust mechanical properties by impregnating the suspensions of graphite nanoplatelets (GNP) and polyacrylate expandable foam particles (PEFP) into the porous glass fiber mat reinforced thermoplastics (GMT), and then hot forming and pressing, the thickness of GMT/PEFP/GNP composites is 2 mm. GNP not only acted as an efficient conductive pathway in the GMT/PEFP/GNP composites matrix, but also formed a conductive cell structure with the foamed PEFP, which increased the electromagnetic waves absorption. The total shielding efficiency (SET) of the GMT/PEFP/GNP-4.0 wt% composite is up to 33.8 dB at 11 GHz, and the power coefficient of reflectivity is 0.71, which is lower 17% than that of GMT/GNP composites without the cell structure constructed by PEFP in the matrix. Furthermore, the melting of polypropylene (PP) in the mats act as the interface adhesive for glass fiber (GF) and GNP, so the tensile strength is enhanced up to 22.8 MPa for the GMT/PEFP/GNP-4.0 wt% composites with lightweight, due to the formation of cell structure constructed by the PEFP. Therefore, this paper provides a simple method to prepare lightweight and high-strength GMT/PEFP/GNP composites for EMI shielding, which is of great significance for industrial application.

An analytical and experimental investigation of air-cooled condensers for small-scale ammonia-water absorption heat pumps is presented. Conventional round-tube corrugated fin design and a novel multi-pass tube array design are considered for a condenser operating at severe ambient conditions within a compact footprint. Segmental heat and mass transfer models are developed to gain a deeper understanding of the characteristics of each design. Predicted heat duties are within 5% of the measured values. The limitations of correlations to predict air-side pressure drop in corrugated fins are identified. The performance of the novel multi-pass tube array condenser was comparable to that of conventional condensers, but is determined to be air-side limited throughout length of the heat exchanger. An improved multi-pass condenser design with fins for increased air-side area is proposed using the insights gained from the modeling and experiments. This design meets the heat duty requirements at severe ambient conditions, while decreasing the size of the heat exchanger by 33%.

Conventional channel-based room equalisation can reduce overall colouration caused by the room response, however it cannot separately correct the colouration caused by the late and early parts of the response, or consider the reverberance in the source signal. A room compensation method is developed here for a source signal in which the dry source sound and the associated target reverberant response are encoded separately, which is possible in an object-based audio framework. The target response is modified using the reproduction room response. Subject to some conditions the combined response approximates the target, with accurate early and late equalisations, reverberant balance, and decay timing. Stochastic assumptions are used to simplify the processing, enabling efficient real-time processing of the encoded audio.

Some important properties of the metal foams that make them attractive materials for various purposes are their excellent stiffness to weight ratio (light-weight structure), ability to take up strain by crushing at controlled pressure (energy and impact absorption), order of magnitude higher damping capacity as compared to the solids (mechanical damping), higher natural flexural vibration frequencies (vibration control), reasonable sound absorbing capacity accompanied by durability and fire resistance (acoustic absorption), and, high area of contact accompanied by high thermal conductivity (heat exchanger). Often foam is joined or connected to cover sheets of the same metal and the whole part together is called a foam sandwich. Among all the metal foams aluminium metal foam has found the widest and diverse application. This article covers important recent literature on laser processing viz. laser forming, laser welding, laser cutting and laser additive manufacturing of metal foams. Prior to this, a link is established between foam/foam sandwich and laser processing techniques stating the limitations of other relatively more conventional processing techniques. Future research direction regarding different laser processing techniques using metal foams has also been outlined.

Journal of synchrotron radiation 28(1), 158 - 168 (2021). doi:10.1107/S1600577520014344, Many scientific questions require X-ray experiments conducted at varying temperatures, sometimes combined with the application of electric fields. Here, a customized sample chamber developed for beamlines P23 and P24 of PETRA III at DESY to suit these demands is presented. The chamber body consists mainly of standard vacuum parts housing the heater/cooler assembly supplying a temperature range of 100 K to 1250 K and an xyz manipulator holding an electric contact needle for electric measurements at both high voltage and low current. The chamber is closed by an exchangeable hemispherical dome offering all degrees of freedom for single-crystal experiments within one hemisphere of solid angle. The currently available dome materials (PC, PS, PEEK polymers) differ in their absorption and scattering characteristics, with PEEK providing the best overall performance. The article further describes heating and cooling capabilities, electric characteristics, and plans for future upgrades of the chamber. Examples of applications are discussed., Published by Wiley-Blackwell, [S.l.]

A lot of airstrikes are being reported and other operations are done by the defense sector using modern aircraft that are not detected by radar in which this technology is named as stealth technology. Radar Absorbing Materials (RAM) is a type of stealth application process in aircraft that are composites that absorbs electromagnetic radiation from the source radar. In this work, the radar absorption material properties were analyzed by using High-Frequency Selective Surface (HFSS) software in ANSYS electronics desktop, and two different materials at different thickness 1 mm, 1.5 mm, 2mm, 2.5 mm&3mm are analyzed for the comparison of the input properties such as Permittivity, Permeability, Reflection loss, tan loss and bulk conductivity for impedance matching and reflection loss to analyze their absorbing properties. From which the efficient material is found out from the analysis for stealth application.

The main objective of our research is to design a Collision Energy Absorption System that overcomes the drawback of all preliminary systems and to design a mechanism which absorbs the impact energy during the one to one collision which will reduce the damages caused to the car by impact energy i.e. collision and to save the lives of the humans who sit inside in a car. During the collision the hydraulic oil which is placed inside the cylinder will be pressurized. Since there is no space for movement of piston, the pressure continues to rise. This rise in pressure will be reduced by breaking of the balls which is placed inside the cylinder with oil. As the balls goes on breaking the piston has the space for movement and so that the pressure decreases. This is way the impact energy produced during collision is being dissipated inside the cylinder. The main goal of our project is inventing a absorption system which will protect the vehicle and the people inside. To design a mechanism this absorbs the impact energy during the one to one collision. To reduce the damages caused to the car by impact energy during the one to one collision. To save the lives of the people who sit inside in a car.

In recent decades, problems with electromagnetic interference (EMI) radiation problems have arisen, that can seriously reduce the performance of precision devices nearby and threaten human health. In consequence, it is important to seek high efficiency materials to suppress EMI pollution. Generally, high magnetic permeability or electrical conductivity is essential for efficient EMI shielding. Conventionally, various forms of metal construction (sheet/films, coatings, etc.) are used for EMI shielding. However, metallic shielding has drawbacks that include high density, lack of corrosion resistance and expensive processing, which restrict its use in the modern electronic world. By contrast, conductive polymer composites (CPCs), formed from insulative polymers and conductive fillers, have attracted more and more interest from both industry and academia. CPCs have properties that offer great potential for application in efficient EMI shielding. These include low density, high flexibility, good chemical stability and easy processing and forming. From a theoretical viewpoint, it is generally accepted that the shielding of EM waves is due to the three basic mechanisms of reflection, absorption and multiple internal reflections. However, it must be recognized that the SE of CPCs has a close relation to the reflection mechanism, which can cause secondary EMI pollution. Therefore, materials with charge carriers or magnetic/electric dipoles as well as cellular structure should be the focus for the development of EMI shielding materials with strong absorption properties. On that basis, the main aim of this paper is to review the current position in research of the design of inorganic based foams (metal, carbon or MXene) and polymer composite foams as EMI shielding materials. On the one hand, these composite foams have the merit of being lightweight, and on the other hand, the special porous structure can effectively harvest microwaves by prolonging the travel path. As a result, absorption dominates EMI shielding, which satisfies current requirements of EMI shielding applications. This review also points out the future challenges and gives guidelines for finding solutions for the next generation of shielding applications using composite foams.

Electrocaloric (EC) cooling technology has rejuvenated rapidly in recent years and gained the great attention in both academia and industrial. Currently, there are only handful studies of EC cooling devices reported over the years, and most of them are focusing on small-scale cooling applications. For practical application, however, it is essential for an EC device to achieve a kilowatt level of cooling power. In this work, we develop a rotary EC device, in which the working bodies are rotating in-plane, and the heat transfer fluid flow through the working bodies in out-of-plane direction. The design allows the continuous fluid–solid conjugated heat transfer and exhibits kilowatt level of cooling power. Numerical study has been performed to explore the internal correlation between the key parameters of the working condition and performance of the device. For a given EC working body, the electric-induced heat generation/absorption is found to significantly affect the cooling power. Meanwhile, parametric studies on the temperature span and cyclic period of the system are conducted. By fine-tuning the operation parameters, the system achieves an optimized overall performance, i.e., a cooling power of 1729.90 W, when operated over a temperature span of 10 K and cyclic period of 10 s. This work provides a general topological design of a rotary device that employs fluid–solid conjugated heat transfer, and guides the optimization of operation parameters to achieve giant cooling power.

Recycled aggregates RA is the one of the most popular methods used to improve road sustainability, whether from concrete or asphalt pavement materials. The life cycle perspective for all construction material are important to find the way it plays in contributing to the sustainability of the paving system. When evaluate the life cycle the responsible people can check the possibility social, environmental and economic impacts that appeared in life cycle, as well as to evaluate potential trade-offs. This study represents the possibility of using recycled aggregates in the paving to provides the required durability and strength. There are several factors that affect the behavior of the aggregates including strength of aggregates, gradation, specific weight, shape, permeability … etc.). The most important parameter in mix design of pavement is the water absorption of the aggregates. The RA saturated in water more than 24 h and to observe the absorption of aggregates water absorption most be determined. The experimentation shows that pavement contains (recycled asphalt pavement RAP or recycled concrete aggregate RCA)can enhance the performance and durability of the pavement due to the high permeability of the old material that covered the virgin aggregate (mortar in RCA and bituminous in RAP), the interfacial transition zone ITZ enhanced by the new bituminous and made stronger bond between the recycled aggregate (RCA or RAP) and the asphalt. Water absorption measurement of aggregates was analyzed. The results are closely aligned with the time depend on the entire absorption period and when saturation is complete the change become constant. The saturation time of RA that obtained was more than 24 h.

The deformation behavior and crashworthiness of functionally-graded foam-filled tubes (FGFTs) under drop-weight impact loading were investigated. Closed cell aluminum, A356 alloy and zinc foams fabricated by the liquid state processing were used as axial grading fillers for the manufacture of single-layer and multilayer structures with different configurations. The results indicate that the deformation of multilayer foam filled tubes initiates from the low-strength components, and then propagates in the high-strength components through the gradual increment of stress. The use of more A356 alloy and aluminum foam layers provides greater specific energy absorption (SEA) for the graded structures, whereas the high-strength zinc foam has no positive effect on the crash performance. The progressive collapse of graded structures consisting of the aluminum and A356 alloy foams occurs in a symmetric mode under quasi-static and drop-weight impact conditions. However, the zinc foam causes a combination of symmetric and extension modes as well as greater localized deformation under dynamic loading and greater local rupture in quasi-static loading condition. The Al−A356 foam-filled tubes with a combination of the highest SEA (10 J/g) and the lowest initial peak stress (σmax of 10.2 MPa) are considered as the best lightweight crashworthy structures.

Mass-exchange random packing made of polymer materials have a longer service life than mass-exchange packing of a similar design made of ceramics, thereby reducing the frequency of repairs and increasing the safety of mass-exchange apparatus for the production of sulfuric acid. The article presents a comparative analysis of technical and economic indicators of irregular packing made of Raschig rings with diameters of 50 mm and 75 mm, which allows us to reasonably choose the most rational packing material for the drying apparatus of the drying and absorption unit of sulfuric acid production.

Passive acoustic liners, used in aeronautic engine nacelles to reduce radiated fan noise, have a quarter-wavelength behavior. The simplest systems are SDOF-type (single degree of freedom), consisting of a perforated sheet backed with a honeycomb, whose absorption ability is limited to frequencies near the Helmholtz frequency. Thus, to widen the absorption frequency range, manufacturers use a 2DOF (double degree of freedom) system, with an internal layer over another honeycomb (stack of two resonators). However, one constraint is the limited thickness of the overall system, which reduces the space allotted to each honeycomb. A possible approach, based on a previous concept called LEONAR (long elastic open-neck acoustic resonator), could be to link each perforated layer to hollow tubes inserted in each honeycomb layer, in order to shift resonance frequencies to lower frequencies by extending the air column lengths. The presence of an empty chamber on both sides of the internal perforated layer also allows the tube length to be increased through tubes crossing both cavities, preserving the liner thickness. The main aim of this article is to mathematically describe the principle of a 2DOF LEONAR and to show the relevance of the mathematical model through FEM simulations and experiments performed in an impedance tube. Moreover, its behavior is analyzed through a parametric study, in order to explore its potential for an aeronautic application. A remarkable feature of 2DOF LEONAR-type materials with insertion of bottom tubes in the higher cavity is the possibility of maintaining the low frequency band provided by the original LEONAR concept, while adding a second absorption peak at a higher frequency, by the second layer and the accompanying tubes. There is a fundamental difference from classical SDOF/2DOF resonators, for which the thicknesses are obviously different.

In recent years, the construction of enclosed material yard projects has becoming an urgent requirement to improve ecological environment and living environment quality. Thin membrane structures have been widely used in industrial building, especially for storage building roofs. Due to the thermal-optical properties of translucent thin fabric material, such as the absorption and transmittance of solar radiation, the indoor thermal environment is seriously disturbed. Moreover, membrane building structures are usually irregular. Compared with conventional buildings material, the translucent thin fabric material particularly responsive to changes in external environment conditions. As a result, the solar radiation heat gain calculation of membrane buildings is complicated. It is worth exploring measures to tackle this problem. Therefore, in order to solve the problem that the relevant thermal-optical parameter is difficult to obtain. The 13 thin membrane samples were tested and the thermal optical characteristic parameters were analyzed in this paper. A practical enclosed membrane structure building was selected as the research object. In addition, a solar radiation heat transfer model was established. The indoor solar heat gain under the action of solar radiation heat was calculated and the effect of different light transmittance and absorptance on the indoor radiation heat gain was studied. It can provide reference for heat gain calculation and ventilation design of membrane structure storage buildings.

Solar-driven evaporation is an emerging process to acquire freshwater from saline water or wastewater, in which photothermal materials play a crucial role. Significant effort has been devoted to promoting energy conversion efficiency by material and device design. In the current review, we discuss the major factors affecting evaporator efficiency and long-term performance, including selection of photothermal materials, promotion of evaporation efficiency, and solutions to the problem of scaling. Both the material components and structure will affect the absorption and reflection of the incident light, and the evaporation efficiency can be enhanced by reducing heat loss, enlarging surface area, and recycling latent heat. Scaling can be addressed by tailoring surface properties and structure.

In the present work, solar energy utilizations by different solar systems such as solar water treatment, solar water heating, stem generation for the purpose of electricity generation; solar pumps, etc. have been introduced. Out of these, a focused approach for the solar water heating, solar water distillation by utilizing different solar collectors have been extensively reviewed to identify the generalized usability in that field. The collection of different solar collectors have different capabilities towards the absorption of direct and diffused solar radiations based on its materials, geometry, design, etc. and for that a rigorous observations have been made in the present effort. As the Earth has a solar energy rich surfaces so related technology search in other fields such as mechanical devices such as in mechanical devices, pneumatic suspension cars, thermal devices, pneumatic pumps, etc. is a worthwhile approach with the help of the current study. In the present study, solar thermal collectors such as vacuum tube collectors, flat plate collectors, concentrated reflectors, trough collectors, etc. have been recognized in this study. The parabolic concentrator covers the larger area of solar energy and evacuated tubes efficiently hold the available solar energy. And, polygeneration systems presents better options for the multi-disciplinary utilizations of renewable energy resources. Depending on the targeted approach, a dignified discussion and a concise conclusion have been framed with its futuristic recommendations.

The paper discusses a simple and low-cost method to design four microphone impedance tube of measuring the acoustic properties of building materials. The acoustic properties of the material are defined by the reflection coefficient, absorption coefficient, and transmission coefficient. The experimental setup follows the ASTM-E2611 standard of four microphone impedance tube with two load boundary conditions to measure these coefficients. The setup consists of four microphones around a brass tube with the speaker at one end and termination at the other. Raw data from the four microphones is obtained through a Virtual Instrument (VI) program developed in LabView. The novelty in the design is the tapered connection between the two pipes connected via the sample holder. The mathematical equation involved in estimating acoustical properties is solved in MATLAB 2019a. The reflection and absorption coefficient data of ephony fibbrette of 15 mm thickness are compared with the data provided by an accredited laboratory. The experimental results of the in-house designed impedance tube are in good agreement with the lab results. This material is used in the auditorium, theatres for hearing comfort. Further, two new samples of ephony fibbrette along with wood fibre cement and damper has been analysed. It has been found that adding a layer of wood fibre results in an increase in the absorption coefficient whereas the addition of the damper results in an increase in the reflection coefficient.

In recent days “honeycomb sandwich panels” are widely used against high intensity blast load due to the high energy absorption capability of the honeycomb structure. In this research paper determined the structural behavior of the honeycomb sandwich panel is subjected to the blast loading. Different honeycomb cores like square and octagonal structures are used to determine the minimum deflections for the top and back plates and also maximum energy absorption for the sandwich panel. The honeycomb sandwich panel is consists of the two solid plates (top plate and bottom plate) and one honeycomb core shell type structure. The blast is applied at a constant standoff distance from top plate of the sandwich panel. The sandwich panel is subjected to the blast load using the different masses of explosive charges such as 1 kg, 2 kg and 3 kg of the Trinitrotoluene (TNT) for the explosion in the air, at a constant standoff point distance from the top plate of sandwich panel. The finite element model is performed by ABAQUS software to determine the dynamic response for the sandwich panel. The quarter part of the honeycomb sandwich structure was modeled and imposed symmetry boundary conditions for the honeycomb sandwich panel to minimize the memory storage of the system and reduced the computation time of the analysis. The top and back face deflections of the square honeycomb sandwich panel have been validated with experimental results available in the literature in square honeycomb sandwich panel. There is a possibility of under estimation of the front face and back face deflections for the sandwich panel, if the honey comb structures are not considered an octagonal sandwich panels for different blast loads.

Rasorbers with a single passband (narrow or wide) or multiple narrow passbands have been reported for stealth applications over the past few years. In this work, a method of designing the multi-band rasorber with wide passband(s) is proposed for the stealth of wideband antennas. Firstly, the method of designing multi-band FSS is proposed based on the theory of N-band resonator, in which all the passbands exhibit second-order response. Secondly, a parallel resonator combining spiral inductor and interdigital capacitor is proposed to satisfy wide passband requirements at lower frequency of the operating band. Finally, to verify the proposed method, a dual-band rasorber consisting of FSS and resistive layer is fabricated and measured. The measured results illustrate two passbands within 4.9-6 GHz (20.0%) and 8.6-9 GHz (6.3%), respectively. Three absorption bands with 48.4%, 25.7%, and 22.0% fractional bandwidths are also achieved.

In case of a crash due to collision of vehicles, effective impact energy absorption by the vehicle safety structure is significant as it reduces the damage to the vehicle and its occupants. Components made of composite materials have a more complex mode of deformation, unlike metals, which in general deform with buckling or bending modes. The deformation mode of the component made of a composite is of great importance as the energy absorption level depends on it. Deformation mode can be modified by introducing special geometric features known as triggers in the design of the crash box. A trigger can also be useful in achieving required deformation mode and thereby helpful in attaining target energy and force values. The present study focuses on the effect of geometric shapes along with three novel trigger types on the level of energy absorbed for the GFRP composite material passenger car crash box in a low-velocity impact, named as “RCAR Test” in the automobile industry. All possible combinations of four different types of geometric cross sections, namely, square, cylindrical, hexagonal, and decagonal, and three novel patterns of notch trigger, imparted to a GFRP crash box were considered for study in the present work. The force distribution, energy absorbed, and SEA (specific energy absorption) were estimated. The relative merit of crash boxes with different combinations of cross-sections and trigger types for these parameters was assessed. The best performing combinations made from various notch triggers and different cross sections of crash boxes have been identified.

A solar powered air conditioning system using a liquid desiccant is proposed to overcome the latent heat part of the cooling load in the air conditioning system. A solar air heater containing a porous material is used as a heat absorber. In addition, a rotating wheel containing a honeycomb clothes saturated with Calcium Chloride solution, is utilized for the regeneration and absorption processes. Different system parameters are investigated. The effect of airflow rate and solar radiation intensity on the system regeneration and absorption abilities are studied. The obtained results show that the system is highly effective in the regeneration process. Also, the system is feasible and energy-efficient in comparison with the traditional electric dehumidification. Furthermore, the system can be used to extract a reasonable amount of water from air. An empirical equation to calculate the removed moisture as a function of air flow rate at solar noon is obtained.

Advanced mechanical and structural applications require accurate assessment and better knowledge of the damage state during elaboration and service. The development of life prediction methodologies for Glass Fiber Reinforced Polymers (GFRPs) has increased with the use of composites in different industries. It is important to develop through thickness degradation analyses due to ageing in order to predict its effect on the lifetime of composite structures. This study aims to model the moisture absorption, the concentration of the absorbed fluid and the reduction of mechanical properties in the through the thickness direction of a GFRPs structure. The water absorption behavior of woven glass fiber reinforced cyanate ester composites used in the plenum of the air conditioning pack of aircraft environmental control system has been modeled. The combined models describe the diffusion procedure primarily at material level and continuously at structure level. The amount of the absorbed moisture can be crucial for the mechanical behavior of the structure. Therefore, there is a need for a better understanding of the evolution of mechanical properties during ageing. The procedure utilizes the results of the diffusion model to calculate the moduli degradation during the water uptake process. Predictive models have been proposed by considering different sections throughout the thickness and provide a solid background for modeling the long term behavior of a structure exposed at different temperature and different time period. This work performed the numerical studies on the effect of moisture, temperature and presents some useful instructions for the evaluation of such composite structures.

Steel pipe dampers offer advantages such as a simple structure, low cost, high energy absorption and dissipation, consistent functionality under cyclic loading, and ductility. Dual-pipe dampers show improved performance over single pipe dampers in terms of strength. The current study focused on the structural performance of the dual-pipe system. The seismic performance of steel-framed structures having 4, 8, or 16 stories with either a simple moment frame or a braced frame equipped with pipe dampers were subjected to seismic loading and investigated using the finite element method. The performance of the models was examined by considering the base shear and lateral displacement of the roof as well as the von Mises distribution. The stress distribution caused by the plastic damage concentration increased in the pipe dampers in the 4- and 8-story models and the base shear decreased 50% in the 4-story models equipped with a pipe damper. The results showed that, in the 16-story models, the strength in the damping system should be designed in accordance with the other elements. In addition, the strength of the damping system can be increased by increasing the number of pipes and their thickness.

The periodic calibration and testing of acoustic sensors, often involve extensive measurements in acoustic tanks. These are usually small facilities whose boundaries are covered with phono-absorption material to suppress reflections. The characteristics of such tanks are defined by the design of absorption planes and the choice of phono-absorption material. Since these characteristics are fixed, an acoustic tank may suppress reflections only for a certain frequency range and setup of the acoustic sensors within the tank, thereby limiting the applications supported by the tank. In this paper, we describe a novel design of an acoustic tank whose absorption characteristics are made adjustable. Inspired by Origami paper folding, this is achieved by changing the shape of the absorption plates with a single degree of freedom. Performing channel estimation between a projector and hydrophone for a required frequency range, the adjustment of the plates involves an iterative genetic-based optimization that finds the best Pareto front to maximize reflection mitigation. We report results from a prototype we contracted that shows a fast convergence of the tank to the best reflection suppression for frequency ranges of 20–30kHz and 35–40kHz. The outcome is an acoustic tank that adapts to various tested frequency ranges and setup of sensors, and can thus improve productivity of acoustic sensor calibration and testing in an efficient manner.