Excellent Mechanical Features Research Articles

A Sector Ring Shape UWB Antenna by Tightly Coupling

In this paper, a sector ring shape UWB microstrip antenna based on the tight coupling is proposed. The continuous current and electric field distribution are formed by the coupling effect between microstrip patches. This design expanded the bandwidth of this antenna and realized a high-gain performance. To achieve the miniaturization design, the ring microstrip patches are staggered and the ground is removed to effectively reduce the size of the antenna. The ring shaped antenna has a 31 mm outside diameter and a 21 mm inside diameter, with a 2 mm thick substrate. Besides the excellent mechanical features, such as being compact and easy to fabricate, the proposed antenna also shows good characteristics in radiation patterns and time-domain behaviors. The results show that the antenna achieves the effect of S11 less than -10 dB in the working frequency band of 2 GHz to 8 GHz, and the simulated results are in good agreement with the measured ones. The antenna realizes low profile and broadband in a novel approach, and this antenna can be used in V2X vehicle systems and IoT networks.

Experimental programme on austenitic stainless steel RHS members subjected to monotonic and cyclic bending

Stainless steel is a corrosion resistant iron alloy with great potential in structural engineering due to its excellent mechanical features, durability and aesthetic properties. Since most of the existing research has concerned the behaviour of the material, the response of individual structural members, or the performance of simple structural systems under monotonic loading, one of the challenges that remains is the evaluation of the cyclic performance of members to promote its use in seismic design and exploit the excellent ductility and strain hardening properties of this material. For this reason, an experimental programme on austenitic stainless steel Rectangular Hollow Section (RHS) specimens was carried out at the Department of Civil Engineering of the Università degli Studi di Salerno in collaboration with the Universitat Politècnica de Catalunya. A total of eight RHS specimens were tested around the minor axis under both monotonic (three specimens) and cyclic (five specimens) loading, in an experimental set-up that followed a cantilever scheme. The main purpose of this study was to acquire information on the cyclic performance of austenitic steel structural members, focusing on the comparison between monotonic and cyclic behaviours. The outcomes of the tests included the load–displacement and the moment–rotation curves, the energy dissipation capacity, and the evaluation of the key rotation capacities of the members. The reported data are essential to enhance the still scarce research on the seismic behaviour of stainless steel structures.

Enhancing the fire-resistant performance of concrete-filled steel tube columns with steel fiber-reinforced concrete

Due to their excellent mechanical features, concrete-filled steel tube (CFST) columns are usually employed in high-rise constructions; it is also significant to consider fire safety while designing buildings. The fire-resistance performance of fibre-reinforced CFST columns is superior to that of unreinforced CFST columns under identical conditions. The post-peak behavior of CFST columns can be enhanced by incorporating fibres to reduce the brittleness of concrete. The research on this topic is limited and considerable research gaps are available in the literature. This research examines the structural performance of steel fibre-reinforced concrete (SFRC) filled steel tubes exposed to ambient and elevated temperatures. For this purpose, fourteen CFST columns were investigated and separated into two groups. The first group of CFST columns was filled with three diverse grades of conventional concrete with and without fibres, which was subjected to ambient temperature. The second group is identical to the first group except all columns are exposed to a temperature of 1050 ℃. The parameters examined were the mechanical properties of concrete, load-carrying capacity, load-deflection response, axial load, and axial strain and ductility ratio. Furthermore, using different codes, a comparison was made for the column's empirically determined load-carrying capacity with the theoretical value. Besides, the morphological characteristics of concrete were examined using energy dispersive spectroscopy (EDS), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The findings show that the SFRC-filled column has superior structural qualities when subjected to elevated temperatures. At high temperatures, calcium hydroxide decomposes, and the steel tube yields, causing the column to fail by premature local bucking.

Investigation of the electrochemical behavior of titanium dioxide coating on magnesium alloy

Biocompatibility and electrochemical corrosion resistance are one of the most important issues in bone implants. In the last decades, metal implants have received much attention because of their properties. Magnesium and its alloys have been widely used in orthopedics because of their biocompatibility and bone growth proprieties. Magnesium has low corrosion resistance; especially in biological environments of the body, or when exposed to blood plasma, this makes magnesium useful as an absorbable implant. To increase the corrosion resistance of magnesium alloys, and adjust the corrosion rate of the implant to the rate of bone growth, it is necessary to coat these implants. Ceramic coatings are one of the possibilities, because of their biocompatibility and high corrosion resistance. TiO2 possesses desirable properties, such as an excellent mechanical features, high corrosion resistance, and biocompatibility, which make it widely used as implant coatings material. Sol-gel is one of the effective methods for making various ceramic materials. In this study, the electrochemical properties of magnesium alloy Mg-5Gd-2.5Nd-0.5Zn-0.5Zr with and without coating with phosphate-buffered saline (PBS) are investigated through Tafel extrapolation and impedance test Titanium dioxide coating was applied to the alloys by the sol-gel method. The effect of four variables of fluoride ion content, etching time, immersion time, and the number of immersions were studied. The results of SEM images showed the optimal sample surface of a uniform coating with a thickness of 6 μm. The optimal sample corrosion current density reported 2.58 × 10−5 A/m2, which is the lowest current density in samples. The results of the impedance test also confirmed these data and the optimal sample indicated the highest value of Rp = 5003 Ω.cm2.

Recent Advances and Progress of Conducting Polymer-Based Hydrogels in Strain Sensor Applications

Conducting polymer-based hydrogels (CPHs) are novel materials that take advantage of both conducting polymers and three-dimensional hydrogels, which endow them with great electrical properties and excellent mechanical features. Therefore, CPHs are considered as one of the most promising platforms for employing wearable and stretchable strain sensors in practical applications. Herein, we provide a critical review of distinct features and preparation technologies and the advancements in CPH-based strain sensors for human motion and health monitoring applications. The fundamentals, working mechanisms, and requirements for the design of CPH-based strain sensors with high performance are also summarized and discussed. Moreover, the recent progress and development strategies for the implementation of CPH-based strain sensors are pointed out and described. It has been surmised that electronic skin (e-skin) sensors are the upward tendency in the development of CPHs for wearable strain sensors and human health monitoring. This review will be important scientific evidence to formulate new approaches for the development of CPH-based strain sensors in the present and in the future.

Progress in Graphene and Magic-angle Graphene Superlattice in the Aspect of Superconductivity

Graphene, a relevant new material first defined in 1986, is gathering more and more interest in the circle of science and engineering especially material and electrical fields. It exhibit excellent mechanical features, extraordinary electrical and thermal properties due to its single atomic layer thickness and honeycomb bonding structure. Graphene is used as an advanced alternative to many traditional materials in a wide range of applications. There are two main synthesis methods, the top-down and the bottom-up, with many branches. The current research state cannot fulfill the urgent demands from the application. Therefore, sub-subjects of graphene are created by splitting or restructuring such as graphene quantum dot and graphene nanotube. In 2018, Yuan Cao et al. have reported a newest research about twisted multilayer graphene. This derivative of graphene showed tunable superconductivity, which also inherited the mechanical structure and thermodynamic properties of graphene. The twisted graphene holds great promise and is likely to be a milestone in superconductivity. Therefore, in this work, the progress in graphene and magic-angle graphene superlattice in the aspect of superconductivity were introduced.

Tribological Study of Simply and Duplex-Coated CrN-X42Cr13 Tribosystems under Dry Sliding Wear and Progressive Loading Scratching

CrN coatings are widely used in the industry due to their excellent mechanical features and outstanding wear and corrosion resistance. Using scratch and ball-on-disk wear tests, the current study deals with the tribological characterisation of CrN coatings deposited onto an X42Cr13 plastic mould tool steel. Two surface conditions of the secondary-hardened substrate are compared—the plasma nitrided (duplex treated) and the un-nitrided (simply coated) states. The appropriate combination of secondary hardening providing the maximum toughness and the high-temperature nitriding of this high Cr steel is a great challenge due to the nitrogen-diffusion-inhibiting effect of Cr. The beneficial effect of the applied duplex treatment is proven by the 34% improvement of the adhesion strength and the 43% lower wear rate of the investigated duplex coatings. Detailed morphological analyses give insight into the characteristic damage mechanisms controlling the coating failure processes during scratching and wearing. For the simply CrN-coated sample, a new type of scratch damage mechanism, named “SAS-wings”, is identified, providing useful information in predicting the final failure of the coating. The tribological results obtained on tribosystems with the investigated high Cr steel/CrN constituents represent a novelty in the given field.

Effect of the variation of the electrodeposition time of hydroxyapatite/chitosan coatings on AISI 316L SS

Type AISI 316 L Stainless Steel (316 L SS) plays a crucial role in bone replacement surgery due to its excellent mechanical features, availability at low cost, and ease of fabrication, but its performance is low when in contact with the aggressive conditions of the human body fluids. Chitosan (CTS) is a biopolymer that blended with hydroxyapatite (HAp) could form coatings to improve surface properties of a metallic orthopedic prosthesis, i.e., corrosion-resistance to the base metal and biocompatibility of the ceramic on the metal surface. This work aims to obtain and evaluate HAp/CTS composite coatings deposited on the surface of AISI 316 L SS substrate by electrophoretic deposition (EDP) technique. The influence of the time of deposition on the coating’s characteristics and properties was characterized and discussed. The coatings were structural, elemental, and chemically characterized using X-Ray diffraction and Raman spectroscopy. HV values in a range of 64.7 to 111.5 were observed, showing the lowest HAp/CTS-30.0 coating values for all the loads applied. The lowest HV value was nearby to the reported value for human bone’s hardness, around 47HV; considering that the coating will be in constant contact motion with the bone surface, the contact with a softer surface could decrease the wear on the human bone. The hardness decreases with the coating thickness’s increment because the coating presented a higher plastic deformation than the 316 L SS surfaces. A decrease in the roughness average (Ra) was well noticed as the deposition time increased; meanwhile, the thickness increased as the deposition time increased.

Assessment of Mass Attenuation Coefficient, Effective Atomic Number and Electron Density of Some Aluminum Alloys

Aluminum alloys have numerous application fields in today's technology due to their excellent mechanical features, high electrical and thermal conductivity, magnificent corrosion resistance, good weldability, good formability and similar properties. In the present study, we investigated the mass attenuation coefficient (µm), effective atomic number (Zeff) and effective electron density (Ne) of four different type commercially available aluminum alloys. For his purpose, µm, Zeff, and Ne values of 5083, 5754, 6061 and 6082 coded aluminum alloys were determined by employing NaI(Tl) gamma ray spectrometry at 661.66,1173.23 and 1332.48 keV gamma ray energies obtained from 137Cs and 60Co radioactive sources. Also these parameters theoretically determined using PhyX-PSD computer program at the photon energies of 1 keV–1 GeV and compared with the experimental results. The variation of µm, Zeff, and Ne with incident photon energy presented graphically. From the obtained results it might be concluded that the µm, Zeff, and Ne values for studied alloy samples depend on the incident photon energy and elemental composition of alloys. In addition, it was observed from the theoretical and experimental results that aluminum alloys under study have almost the same gamma ray attenuation capacity.

Crystallization of discrete ZrO2 polymorph in the amorphous bioglass matrix comprising essential elements

The exceptional biocompatibility of bioglass in amorphous form is well-known; nevertheless, their crystallization to yield auxillary products during elevated heat treatments were considered as a major obstacle to retain specialized features. The excellent mechanical features of crystalline ZrO2 is deliberated as a primary choice in orthopaedic applications. The study aims to hold the well crystallized ZrO2 grains in amorphous bioglass matrix at elevated temperatures devoid of the crystallization of auxiliary products. The choice of elemental composition in bioglass to retain amorphous state in crystallized ZrO2 were explored. Preliminary investigation on the elements choice to design bioglass has been optimized followed by the specific formulation to integrate in ZrO2 component. Subsequently five different bioglass formulations with increment in the element concentrations has been designed and integrated in ZrO2 matrix. The characterization results ensured the impregnation of cubic ZrO2 (c-ZrO2) component in amorphous SiO2 matrix devoid of structural degradation until 1400 °C. The indentation tests accomplished better mechanical features of the resultant compositions that displayed good concurrence with the commercialized ZrO2 products.

Sound absorption of face-centered cubic sandwich structure with micro-perforations

This paper presents a novel ultra-lightweight micro-perforated sandwich structure with face-centered cubic (FCC) core as a sound absorber, which encompasses excellent mechanical features as well as acoustic properties. The structure, which consists of air cavities and small perforations on both the top panel and the corrugated plates, is considered as a combination of multi-layered micro-perforated panel absorbers (MPPAs). A theoretical model that makes use of an equivalent electrical circuit (EEC) approach is established. Validation of the model with experimental results and numerical simulations shows good agreement. The dependence of the acoustic absorption on features of the perforations and of the FCC structure is discussed. Based on the observations, an optimized structure is proposed by using simulated annealing method to yield good acoustic absorption property in the low frequency range.

Application of inorganic nanomaterials in bone tissue engineering and regenerative medicine

Recently, tissue engineering and regenerative medicine, especially bone tissue engineering and regenerative medicine have developed rapidly. Bone tissue engineering is a complicated and dynamic bone remodeling process that starts with recruitment and migration of osteoblasts and then regulates their proliferation, differentiation, and mineralization. Scaffold is typically biodegradable material that plays a crucial role as one of the three elements of bone tissue engineering and regenerative medicine. Bone scaffold provides the mechanical support during reformation and repair of damaged or diseased bone. For more than a decade, a large amount of research work has been carried out on the designing of scaffolds, processing techniques, performance assessment, and medical application. Significant progress has been made toward scaffold materials for structural support for desired osteogenesis and angiogenesis abilities. To date, depending on the advanced technologies, the bioresorbable scaffolds possess controlled porosity and high mechanical properties are possible used as bone scaffold. Natural bone has delicate architectural structure that spans nanoscale to macroscopic dimensions, which determine the unique mechanical properties of bone. The hierarchical structure of natural bone can be defined as a nanocomposite consisting of inorganic nanocrystalline hydroxyapatite (HA), organic components (mostly are collagens) and water. The outside proteins assemble together to form an extracellular matrix (ECM) with nanostructured which influences the adhesion, proliferation, differentiation, and mineralization of several cell types, such as bone lining cell, mesenchymal stem cells, osteoblasts, osteocytes, and osteoclasts. To better mimic the nanostructure in natural ECM, many research groups over the past decade developed nano-based scaffolds (nanotubes, nanofibers, nanoparticles, and hydrogel) to resemble the ECM for promising candidates in replacing defective tissues. The high biomimetic properties and excellent mechanical features of nano-based scaffolds plays a vital role in stimulating cell adhesion and proliferation, as well as directing bone tissue formation through mimetic the nanometer dimension of natural bone tissue. Besides, mechanical properties are key factors for bone regeneration and bone local function. Nowadays, a large number of research groups have tried to manipulate the mechanical properties of scaffolds through designing the different nanosturctures, including nanofiber, nanoparticle, polymer matrices to mimic the nanocomposite structure of natural bone. These materials have highly stiffness, strength, and toughness properties that are promising in bone tissue engineering. Nanobiomaterials, especially inorganic nanobiomaterials, have excellent mechanical properties and biocompatibility, and are ideal for the preparation of scaffold materials for bone tissue engineering and regenerative medicine, showing a broad application prospect. In this article, we systematically review the application of inorganic nanomaterials, including hydroxyapatite, silicon-based nanomaterials, carbon-containing nanomaterials and several metal nanomaterials in bone tissue engineering and regenerative medicine. Although nanotechnology represents a major frontier with potential to significantly advance the field of bone tissue engineering, the application in the clinical regenerative engineering has limited. Currently, there are several limitations in regenerative strategies, including low efficient cellular proliferation, differentiation and mineralization, insufficient mechanical strength of scaffolds, and limited production of growth factors necessary for efficient osteogenesis. Therefore, there are still some issues on the nano-based scaffold should be cleared: (1) The interaction of nano-based scaffold and bioactive molecules, growth factors, and genetic material, (2) the biocomptibility, cytotoxicity, and biodegradation of nano-based scaffold, and (3) nano-based scaffold mechanical stability, cellular survival, and molecular mechanism of inducing bone formation. As the development of nanotechnology, ultimate translation to the clinical application may allow for improved therapeutic outcomes in patients with large bone deficits and osteodegenerative diseases.

Recent Advances in Science and Technology of Single and Multi Wall Carbon Nanotubes and their Composites

Subsequent to their first perception more than two decades ago, Carbon Nanotubes (CNTs) have formed the epicenter for numerous important studies. Various researchers and scientists have stated striking bodily and perfunctory features for this unique form of carbon. These exhibit one of a kind microelectronic features and thermal conductivity greater than diamond and also mechanical features where the mechanical and electrical features, quality and flexibility surpasses any present material, study of CNTs offers many options for the improvement on a very basic level of new material frameworks. Specifically, the excellent mechanical features of CNTs, consolidated with their small width, propose degree aimed at advancement of Nanotube strengthened compound resources. The scope for nanocomposites strengthened with carbon tubes having remarkable improved mechanical features offer a lot of scope of rapid development in the field of science. This research study gives compact assessment of late developments in CNTs and related compounds. Also presented in this paper are details regarding configuration and handling of CNTs.

Mechanical Behavior of PCL Nanofibers

The biomedical applications of Poly (e-caprolactone) (PCL) have an extensive usage area such as tissue engineering, regenerative medicine, cartilage defects and biomedical implants. Because of the PCL’s high biocompatibility and excellent mechanical features some implants have been designed for getting remarkable results. Clinically approved fibers ranging from 500 nm to 750 nm were produced by electrospinning method. The mechanical properties of the fiber scaffolds were performed via tensile testing and results were measured by special programme. Five different fiber scaffolds which they produced in various compositions have been used for this research.

Flexible and high performing polymer electrolytes obtained by UV-induced polymer–cellulose grafting

A novel UV-induced procedure, in the presence of glycidyl acrylate and proper radical/cationic photoinitiators, is here proposed to promote the in situ grafting of a methacrylic polymer network to the surface of natural cellulose fibers. As a result, composite polymer membranes reinforced by cellulose handsheets are obtained and demonstrate excellent mechanical features. The reactivity of the monomers is studied by FT-IR in real time measurements and the successful grafting is confirmed by surface spectroscopies. The polymer membranes prepared show high elastic modulus and tensile resistance and maintain high flexibility even after activation by swelling into a standard liquid electrolyte solution. The swelling procedure allowed us to obtain high ionic conductivity and remarkable electrochemical behavior when tested in laboratory scale lithium polymer cells. The system shows attractive features such as intrinsic safety, eco-compatibility, and low production cost and industrialization potentials, and is highly suitable for the rapidly expanding field of Li-based flexible batteries.

Electrochemical characterization of hydroxyapatite coatings on HNO 3 passivated 316L SS for implant applications

Type 316L SS play a key role in the bone replacement surgery due to its excellent mechanical features, availability at low cost and ease of fabrication. However it fails miserably in vivo conditions due to corrosion-related problems. Hence an alternative method on the development of hydroxyapatite (HAP) coatings has been elucidated to impart corrosion resistance of the base metal and ensure biocompatibility of the ceramic on the metal surface. This also could not match the implant at the host site due to the continuous interaction of hostile environment with the implant and results in the dissolution of both ceramic and metal. An artificially induced passive layer on the metal surface prior to coating may improve the nature of implant on the resistance to corrosion. In the present study, the effect of HNO 3 treatments on 316L SS and the coatings on passivated 316L SS is being explored. Electrochemical studies involving cyclic anodic polarization experiments and impedance analysis in Ringer's solution were done to determine the corrosion resistance of the coatings. The leach out characteristics of the coatings was determined at the impressed potential. The results have indicated the efficiency of HAP coatings on HNO 3-treated surface.

AMINO ACID COMPOSITION-DEPENDENT ELASTICITY OF SPIDER SILK

Spider silk exhibits excellent mechanical features in both toughness and extensibility. In recent years considerable investigations have focused on it. The understanding of spider silk protein is important for the development bionic silk. In this paper, we study by Monte Carlo simulation the force-of-extension property of spider silk proteins as a function of the residue composition for major and minor ampullate glands of typical Araneid orb weaver as well as that for one artificial spider silk. The results are also compared with those from a designed protein whose amino acid composition is uniform. The results clearly show that the major and minor ampullate gland proteins are much tougher than the designed protein, whereas the artificial protein, as a model of a nature spider silk, does have good mechanical properties. Our simulation reveals that mechanical property of a spider silk protein is dependent on its amino acid composition and that an excellent result of natural evolution is manifest in the composition of the spider silk protein.

Elastic theory of single spider silk protein molecule

Spider silk exhibits two excellent mechanical features, toughness and extensibility. In recent years, considerable investigations have been focused on it. The understanding of spider silk protein is significant for the bionic silk. In this article, we study the force extension property of spider silk proteins as the function of the amino acid compositions for major and minor ampullate glands of typical Araneid orb weaver, as well as one artificial spider silk by Monte Carlo simulation. The results are also compared with a designed protein whose amino acid composition is uniform. It shows clearly that the major and minor ampullate gland proteins are much tougher than the designed protein, and the artificial protein as a model of a nature spider silk do have good mechanical properties. Our simulation reveals that the mechanical property of a spider silk protein is dependent on amino acid composition and the composition of spider silk protein is an excellent result of natural evolution.

Analysis and Design of Elementary Blinders for Large Horn Reflector Antennas

An analysis of E-plane (transverse) radiation from horn reflector antennas for horizontal (transverse) polarization is presented. This analysis was based on Geometrical Theory of Diffraction with modifications to account for (i) finite edges, (ii) grazing incident wave, and (iii) aperture illumination. Once proven valid for our purposes, the analysis was extended to permit blinders to be added to the antenna. Experimental and theoretical studies of single edge blinders have shown them to move the azimuth location of undesirable high sidelobes but not substantially reduce the sidelobe level. A half blinder, however, was shown to reduce the undesired 90-degree sidelobe to — 62 dB, an 8-dB reduction. Simultaneously, sidelobe levels are below — 62 dB for azimuths between 35 degrees and 180 degrees at both 3.74 and 6.325 GHz. Theoretical predictions indicate it is broadband at 4, 6, and 11 GHz. The half blinder also has excellent mechanical features.