Search

The author has recently introduced the class of CNED sets in Euclidean space, generalizing the classical notion of NED sets, and shown that they are quasiconformally removable. A set E is CNED if the conformal modulus of a curve family is not affected when one restricts to the subfamily intersecting E at countably many points. We prove that several classes of sets that were known to be removable are also CNED , including sets of σ -finite Hausdorff (n - 1) -measure and boundaries of domains with n-integrable quasihyperbolic distance. Thus, this work puts in common framework many known results on the problem of quasiconformal removability and suggests that the CNED condition should also be necessary for removability. We give a new necessary and sufficient criterion for closed sets to be (C)NED. Applying this criterion, we show that countable unions of closed (C)NED sets are (C)NED. Therefore we enlarge significantly the known classes of quasiconformally removable sets. [ABSTRACT FROM AUTHOR]

Ferroelectric polymer-based separators, known for their flexibility, ease of synthesis, and modifiability through dopants, are currently under extensive study due its potential applications in electronic devices. PVDF nanocomposites, which combine the strengths of their constituents, currently lead in emerging technologies. This research employs Zinc oxide nanoparticles (ZnO NPs) as fillers in the PVDF matrix and investigates their structural, optical, thermal and electrical properties. ZnO NPs synthesized via the combustion method, are being incorporated with varying concentrations (2, 4, 6, 8, and 10 wt%), into PVDF nanocomposite (PNC) thin films through a solution casting process. The PNC thin films are characterized using XRD, FTIR, UV–Vis spectroscopy and thermogravimetric analysis (TGA). Dielectric properties are being explored across a frequency range from 20 to 2 MHz at room temperature, revealing enhanced dielectric constants at lower frequencies, decreasing with frequency due to Maxwell–Wagner interfacial polarization. With increasing frequency, AC conductivity and electric modulus exhibit enhancement. Complex impedance analysis via the Cole–Cole plot indicates a non-Debye type of dielectric relaxation with heightened conductivity. TGA demonstrates improved thermal stability in PNC thin films. These findings suggest the potential application of the prepared PNC thin films as separators in energy storage devices. [ABSTRACT FROM AUTHOR]

Filler content in dental composites is credited for affecting its physical and mechanical properties. This study evaluated the correlation between the filler percentage and strength, modulus, shrinkage stress, depth of cure, translucency and radiopacity of commercially available high- and low-viscosity dental composites. Filler weight percentage (wt%) was determined through the burned ash technique (800 °C for 15 min). Three-point bend flexural strength and modulus were measured according to ISO 4049 with 2 mm × 2 mm × 25 mm bars. Shrinkage stress was evaluated using a universal testing machine in which composite was polymerized through two transparent acrylic rods 2 mm apart. Shrinkage was measured from the maximum force following 500 s. The translucency parameter (TP) was measured as the difference in color (ΔE00) of 1 mm thick specimens against white and black tiles. The depth of cure was measured according to ISO 4049 in a cylindrical metal mold (4 mm diameter) with a 10 s cure. Radiopacity was measured by taking a digital X-ray (70 kVp for 0.32 s at 400 mm distance) of 1 mm thick specimens and comparing the radiopacity to an aluminum step wedge using image analysis software. The correlation between the filler wt% and properties was measured by Pearson's correlation coefficient using SPSS. There was a positive linear correlation between the filler wt% and modulus (r = 0.78, p < 0.01), flexural strength (r = 0.46, p < 0.01) and radiopacity (r = 0.36, p < 0.01) and negative correlation with translucency (r = −0.29, p < 0.01). Filler wt% best predicts the modulus and strength and, to a lesser extent, the radiopacity and translucency. All but two of the high- and low-viscosity composites from the same manufacturer had statistically equivalent strengths as each other; however, the high-viscosity materials almost always had a statistically higher modulus. For two of the flowable composites measured from the same manufacturer (3M and Dentsply), there was a lower shrinkage stress in the bulk-fill version of the material but not for the other two manufacturers (Ivoclar and Tokuyama). All flowable bulk-fill composites achieved a deeper depth of cure than the flowable composite from the same manufacturer other than Omnichroma Flow Bulk. [ABSTRACT FROM AUTHOR]

Anisotropy in naturally occurring or synthetic microcellular structures is an important feature for the development of materials with high specific stiffness and strength, in addition to creating materials with unique physical properties. Polymeric foams constitute a broad class of materials that are widely used for their advantages of low density, high specific mechanical properties and high insulative properties. Traditional synthetic routes are slow, energy demanding processes that employ the use of high temperature ovens, freezers, or high‐pressure equipment. Herein we present a convenient and energy efficient method to produce anisotropic high performance polymeric foams via rapid radically induced cationic frontal polymerization coupled with chemical blowing agents. The degree of pore orientation and degree of anisotropy are a result of the propagating front working in concert with the foam volume expansion. This paper presents results into FP foam formation to illustrate how changes in boundary conditions and front initiation position affect both the microcellular structure and their resulting physical and mechanical properties. Additionally, results are presented to show how changes in resin formulation, such as the addition of nanoparticles affect both properties as well as the microcellular structure and anisotropy. [ABSTRACT FROM AUTHOR]

The periodontal ligament plays a significant role in orthodontic and masticatory processes. To explicitly investigate the effects of dynamic force amplitude and frequency on the dynamic tensile properties of the periodontal ligament, in vitro tensile experiments were conducted using a dynamic mechanical analysis at various dynamic force amplitudes across a wide frequency range. Storage modulus, loss modulus, and loss factor values were measured. A Maxwell constitutive model based on modulus was established to describe the dynamic mechanical properties of the periodontal ligament. The results showed that the storage modulus ranged from 29.53 MPa to 158.24 MPa, the loss modulus ranged from 3.26 MPa to 76.16 MPa, and the loss factor values all increased with higher frequencies and higher dynamic force amplitudes. Based on the parameters obtained from the fitting results, it is evident that the short‐term response has a more pronounced impact on the elastic response of the periodontal ligament than the long‐term response. Increasing the dynamic force amplitude and its frequency amplified the viscous effects of the periodontal ligament and enhanced energy dissipation. The proposed constitutive model further demonstrated that the periodontal ligament acts as a viscoelastic biomaterial. These findings have implications for future research on the periodontal ligament. [ABSTRACT FROM AUTHOR]

We look at a momentum map associated with the Heisenberg group. We show that the cocycle associated with its momentum mapping is the value of a modulus of an associated coadjoint orbit. [ABSTRACT FROM AUTHOR]

This work investigates the AC conductivity, impedance spectroscopy, and modulus formulation of varied compositions of glass samples within the modified borovanadate glassy system, synthesized using the melt-quenching technique. Up to 10 mol% of BaO, the AC conductivity shows a rising trend as BaO content rises; however, for x = 15&20 mol%, there is a drop. The Almond West model fits the experimental data of ac conductivity and parameters such as crossover frequency, frequency exponent (s), and direct current conductivity are retrieved. All samples feature a CBH conduction mechanism at varying frequencies, except for VBa1, which has a small polaron quantum mechanical mechanism. There is good agreement in the activation energy derived from conductivity (0.565–0.742 eV), electric modulus (0.526–0.616 eV), and impedance research (0.530–0.743 eV). Dielectric studies reveal non-Debye-type behavior. According to impedance formalism, electric conduction occurs through Ba2+ ions and electron/polarons. This characteristic renders the glasses well-suited for energy storage devices. [ABSTRACT FROM AUTHOR]

Silicophosphate, prepared from Tunisian siliceous sand, has been investigated as a potential oxide ion conductor. XRD and Rietveld refinement analyses confirm the formation of pure single-phase Si5P6O25 that crystallizes in the trigonal system with R-3 space group. The electrical conductivities and dielectric properties of this material have been studied using complex impedance spectroscopy from 10 to 106 Hz at a temperature range from 600 to 680 °C. The results show that the ionic conductivity σdc increases from 5.43 × 10− 5 S.cm− 1 at 600 °C to 0.23 × 10− 3 S.cm− 1 at 680 °C with an activation energy of 1.33 eV. The frequency dependence of AC conductivity could be explained by Jonscher's power law. The dielectric constant's decrease with frequency indicates a region of dispersion resulting from a polarization process' relaxation. The simulation of the oxygen conduction using the Bond Valence Site Energy (BVSE) model shows the presence of four interstitial sites used with equilibrium sites to form a zigzag isosurface of oxygen migration. The calculated activation energy is about 1.43 eV. [ABSTRACT FROM AUTHOR]

The complex lead-free perovskite ceramics, (1-x) BiFeO3-X(B/K) Ti/MnO3, where X = 0.05, 0.10 were fabricated by using a solid-state chemical reactions technology. The X-ray diffraction analysis exhibits the formation of the sample in rhombohedral crystal symmetry (#R3c). The average crystallite size for BKTM with 5% content and BKTM with 10% content was determined utilizing the Scherrer formula, resulting in sizes of 21.83 nm and 27.81 nm, respectively. Fourier-transformed infrared spectroscopy spectrum analysis also supports the formation of compounds based on the characteristics peak corresponding to Bi-O and Ti-O bonds. Scanning electron microscope (SEM) shows the distribution of grain and surface morphology. The surface morphology indicates dense grain development with no fractures. The mean grain size for BKTM with 5% content is approximately 2.73 μm, whereas for BKTM with 10% content, it is about 0.49 μm. This discovery could help with grain and grain border resistive and capacitive properties. The impedance study reveals the electrical behavior of the sample. The semicircular arc of the complex impedance and electrical modulus spectrum plots reveal the substance’s semiconducting properties. [ABSTRACT FROM AUTHOR]

As advances in heat resistant ultrahigh molecular weight polyethylene (UHMWPE) fiber via ultraviolet (UV) crosslinking, it is worth paying attention to its thermal aging behavior and heat resistance mechanism. UHMWPE fibers in different forms, the fully drawn yarn (FDY) and the UV crosslinked FDY (UVFDY), are subjected to isothermal aging at 135°C. The effects of thermal aging on their surface morphology and mechanical properties are studied and compared initially. The results demonstrate that UVFDY is a kind of a heat‐resistant fiber. Subsequently, to reveal the heat resistance mechanism of UVFDY, its crystalline and orientation structure evolution during thermal aging are further studied. It is indicated that the formation of dense‐packing crystals and disorientation behavior lead to fiber shrink, so that a number of grooves appear on the fiber surface. Since the crosslinked stucture of UVFDY hinders its molecules movement, the crystallization and disorientation behavior of UVFDY are weaker than those of FDY, resulting in UVFDY possesses slighter thermal shrinkage (Ts), fewer grooves and better mechanical properties than those of FDY. Therefore, the heat resistance of the fiber improves effectively after UV crosslinking. This work provides insights into the structure–property relationship of UVFDY during thermal aging, and offers basis data for its application in specific conditions. [ABSTRACT FROM AUTHOR]

In this work, perovskite oxide SrCeO3 was synthesized using the solution combustion method (SCM). Synthesized samples have been characterized using X‐ray diffraction (XRD), Raman, ultra violet (UV)–visible spectroscopy, and scanning electron microscopy (SEM) techniques. The XRD and Rietveld refinement has confirmed the orthorhombic structure with space group Pnma. The average grain size of this ceramic sample is 1.2 µm. The dielectric constant, dissipation factor, modulus, impedance, and alternating current (AC) and direct current (DC) conductivities were analyzed in the temperature range RT to 600°C and frequency range 20 Hz–2 MHz. Further, it was observed that the role of grain boundaries in dielectric and electrical properties is significant, at low temperatures. The origin of the dielectric relaxation and conduction process is the same. The activation energy for DC conduction (Edc) was found to be.79 eV. Electrical conduction/relaxation is assigned to the diffusion of doubly ionized oxygen (Vo··). The value of DC conductivity (1.2 × 10−3 Ω−1 cm−1 at 600°C) and activation energy of.79 eV is very close to the values reported for doped CeO2‐based oxide ion conductors for SOFCs. This study has demonstrated that SrCeO3 can be an alternative candidate for the oxide ion conductor electrolyte application and the potential to be used as a thermally stable capacitor application for microwave dielectric applications. [ABSTRACT FROM AUTHOR]

BaBiLaNbVO9 is a lead-free compound and has been synthesized by solid-state technique. The formation of the compound was confirmed by X-ray diffraction and is found to be crystallized in the monoclinic (space group P 21) crystal system (a = 13.7464± 0.0015 Å, b = 4.0156± 0.0012 Å, c = 12.4946 ± 0.0018 Å, β = 93.48 ± 0.01o). The crystallite size was found to be 52.91 nm. SEM and EDX studies analyzed the morphology, composition, and elemental distribution in the specimen. The average grain size is about 1.0651 μm. Several properties, such as frequency and temperature response resistivity, conductivity, and dielectric behaviours of the compound, have been analyzed. The overlapping large polaron tunnelling (OLPT) and correlated barrier hopping (CBH) models are appropriate for electrical conduction in the compound. The energy band gap (Eg) of the material was 2.40 eV, suitable for optoelectronic devices. Ferroelectric behaviour may be deduced from symmetric and well-shaped P-E hysteresis loops. The impedance study satisfies the negative temperature coefficient of resistance (NTCR) behaviour, which is suitable for thermistor devices and its correlated application. [ABSTRACT FROM AUTHOR]

This paper discusses the structural, microstructure and electrical properties of perovskite oxide lanthanum nickel LaNiO3, synthesized by the sol–gel reaction technique that was investigated. The prepared material was doped with bismuth and niobium and studied their properties. The Rietveld refinement of the X-ray diffraction pattern suggests that the compound has a monoclinic phase at room temperature with a P21/n space group. Scanning electron microscopy surface morphology analysis of the sample showed closed packing of grains with good density and very little porosity. The frequency-dependent modulus of the material is investigated in the temperature range from 200 K to 360 K and in range frequency between 1 kHz and 1 MHz. The Cole–Cole model is used to analyze the dielectric relaxation phenomenon. The complex impedance data are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element, where the ideal capacitance part is replaced by a constant phase element. The frequency-dependent conductivity spectra follow the Jonscher power law. Nevertheless, the Arrhenius-type conduction mechanism was found to be active in the sample with activation energy of 0.168 eV. The electrical property of the sample was found to be independent of temperatures, making it a potential candidate for thermally stable capacitor application. [ABSTRACT FROM AUTHOR]

This study introduces the development of a novel bio-nano composite via the dispersion of cellulose nanofibers (CNF) in epoxy. The surface of cellulose nanofibers was functionalized using a two-step chemical treatment to enhance dispersion. The interfacial characteristics of CNF were improved using alcohol/acetone treatments. The modified CNF (M-CNF) demonstrated enhanced compatibility and improved dispersion in the epoxy matrix as evidenced by scanning electron microscopy. Based on the analysis of X-ray diffraction patterns, M-CNF did not disturb the crystalline phases at the interface. The results of mechanical testing showed that M-CNF worked as a reinforcing agent in the bio-nano composite. The flexural modulus increased from 1.4 to 3.7 GPa when M-CNF was introduced. A similar trend was observed for tensile strength and impact resistance. The optimum performance characteristics were observed at M-CNF of 0.6%. At higher dosages, some agglomeration was observed, which weakened the interfacial properties. This study promotes sustainability and resource conservation while offering CNF as a sustainable reinforcing agent to develop bio-nano composites. [ABSTRACT FROM AUTHOR]

This study introduces an advanced finite element model for the light weight deflectometer (LWD), which integrates contact mechanics with fully coupled models. By simulating LWD tests on granular soils at various saturation levels, the model accurately reflects the dependence of the LWD modulus on dry density, water content, and effective stress. This model addresses and overcomes the limitations of previous finite element models for this specific problem. Simultaneously, this research presents the first experimentally validated fully coupled contact impact model. Furthermore, the research provides a comparative assessment of elastoplastic and nonlinear elastic models and contrasts an enriched node-to-segment method (developed in this study) with the more precise mortar technique for contact mechanics. These comparisons reveal unique advantages and challenges for each method. Moreover, the study underscores the importance of careful application of the LWD modulus, emphasising the need for sophisticated tools to interpret soil behaviour accurately.

Ca and Cs doped barium titanate lead-free ceramic with the formula Ba 0.75 Ca 0.2 Cs 0.05 TiO 3 has been prepared by the solid-state reaction method. X-ray diffraction (XRD) confirms the crystallization of the sample in a tetragonal structure with a P 4 mm space group. The phase purity and grain morphology were evaluated using X-ray diffraction and scanning electron microscopy (SEM). The material exhibits a primary phase of Ba0.75Ca0.2Cs0.05TiO3 with a minor secondary phase of BaO 2 , and the average grain size is determined to be 1.66 μm. Using non-destructive complex impedance spectroscopy (CIS), we extensively studied the electrical behavior, including complex impedance (Z*), complex modulus (M*), electrical conductivity, and relaxation mechanisms, of Ba 0.75 Ca 0.2 Cs 0.05 TiO 3 over a wide temperature (85 K–290 K) and frequency range. The ac conductivity analysis reveals that the dominant conduction mechanism is the non-overlapping small polaron tunneling (NSPT) model. The impedance analysis indicates a single semi-circle in the real and imaginary parts, suggesting a single relaxation mechanism. Additionally, the activation energy was calculated to be approximately 0.0489 eV. These findings contribute to the understanding of the structural and electrical properties of Ba 0.75 Ca 0.2 Cs 0.05 TiO 3 , highlighting its potential applications in electronic devices such as capacitors, thermistors, and ferroelectric random access memories (FRAMs). [ABSTRACT FROM AUTHOR]

For their good randomness and long iteration periods, chaotic maps have been widely used in cryptography. Recently, we have revealed the correlation between Lyapunov exponent and sequence randomness of multidimensional chaotic maps based on modular operation. Since the modular operation can realize the boundedness of chaotic state points, it is important to further reveal the deterministic correlation between Lyapunov exponent and modulus. First, we constructed an n -dimensional nondegenerate hyperchaotic map model with the desired Lyapunov exponents. Then, we gave the existence and uniqueness proof of quadrature rectangle decomposition theorem and revealed the correlation between Lyapunov exponent and modulus. The novelty lies in that (1) in order to realize the irreversibility of the iterative processes of chaotic maps, we constructed a chaotic map based on modular exponentiation, and its inverse function is the discrete logarithm problem; and (2) we reveal for the first time the correlation between Lyapunov exponent and modulus, and give the lower bound of the modulus of the nondegenerate chaotic map. In addition, to verify the effectiveness of the scheme, we constructed four-dimensional and five-dimensional chaotic maps, respectively, and analyzed their dynamical behaviors, and the results revealed that there exist linear or nonlinear correlation between Lyapunov exponent and modulus. [ABSTRACT FROM AUTHOR]

The incorporation of sugar palm fiber (SPF) into polymer composites presents an environmentally conscious and promising alternative to synthetic reinforcement materials. These composites exhibit impressive mechanical stiffness, strength, elongation, and thermal stability. Extensive research has centered on characterizing the thermal, mechanical, and physical behaviors of SPF-reinforced polymer composites under varying conditions. Despite their exceptional qualities, these composites have mainly been utilized in traditional applications such as brooms, brushes, and ropes. This study conducts a comprehensive exploration of their properties, employing dynamic mechanical analysis (DMA) to assess the thermal stability of SPF-reinforced polymer composites in both thermoplastic and thermoset matrices. The investigation focuses on critical parameters including storage modulus (E′), loss modulus (E′′), complex modulus (E), and damping factor (tan δ), with particular attention to temperature-sensitive interfacial bonds between fibers and diverse polymer matrices. Factors such as matrix type, filler type, processing and post-processing conditions, frequency, temperature, fiber length, loading, volume fraction, orientation, and treatment significantly influence the DMA properties of natural fibers. This review synthesizes the latest literature of the past decade, offering an in-depth overview of SPF polymer composites, including hybrid composites, and exploring their diverse applications. Furthermore, the study evaluates the effects of integrating synthetic fibers and employing chemical treatments on the DMA properties, impact resistance, and post-impact performance of SPF-reinforced polymer composites. By advancing knowledge in this domain, this comprehensive review provides valuable insights into designing and optimizing these composites for a wide range of engineering applications. [ABSTRACT FROM AUTHOR]

In conventional foams, anisotropy within the microcellular structure can only be achieved through confinement in one or more directions during the foaming process. Herein, we present a novel, versatile, and energy efficient method to create unique high‐performance foams where the anisotropy of the microcellular and the microcellular structure itself is not dictated by external confinement during the foaming process. To generate such foams, an initial crosslinked gel is first created where the crosslink density of the gel can be tuned by UV intensity and cure time. Next, the gel can be foamed while simultaneously creating a second network via radically induced cationic frontal polymerization (RICFP). In this case, the anisotropy in the foam is dictated by propagation front during the RICFP and the microcellular morphology and cell surface area are dictated by the crosslink density of the gel. These two unique qualities lead to rigid foams that can be generated from a gel without the need for confinement where the microcellular size and shape can be tuned by the crosslink density of the gel precursor. A one‐pot liquid system composed of miscible epoxies, acrylates, and chemical blowing agents (CBAs), allows for control over the foam physical, mechanical, and thermal properties with glass transition temperatures ranging from 74.7 to 125.8°C. Additionally, by patterning the crosslink density of the initial gel through controlled exposure of UV, complex microcellular structures can be formed that are not possible in conventional foaming processes. This positions gel frontal polymerization and foaming as an advanced technique to produce high performing anisotropic foams with a wide array of tunable physical, mechanical, and thermal properties. [ABSTRACT FROM AUTHOR]

Smart wearable sensors are increasingly integrated into everyday life, interfacing with the human body to enable real-time monitoring of biological signals. This study focuses on creating high-sensitivity capacitive-type sensors by impregnating polyester-based 3D spacer fabric with a Carbon Nanotube (CNT) dispersion. The unique properties of conductive particles lead to nonlinear variations in the dielectric constant when pressure is applied, consequently affecting the gauge factor. The results reveal that while the fabric without CNT particles had a gauge factor of 1.967, the inclusion of 0.04 wt% CNT increased it significantly to 5.210. As sensor sensitivity requirements vary according to the application, identifying the necessary CNT wt% is crucial. Artificial intelligence, particularly the Multilayer Perception (MLP) model, enables nonlinear regression analysis for this purpose. The MLP model created and validated in this research showed a high correlation coefficient of 0.99564 between the model predictions and actual target values, indicating its effectiveness and reliability. [ABSTRACT FROM AUTHOR]

Hydraulic asphalt concrete is known for its excellent seepage control performance and strong deformation resistance. This engineering material has widespread applications in the seepage control structures of hydraulic buildings. Recent projects have investigated the use of acidic aggregates to improve economic efficiency. However, they have also highlighted the weaker adhesion between acidic aggregates and asphalt, which necessitates stringent construction process control. This study investigates the impact of resting conditions on the tensile properties of acidic aggregate hydraulic asphalt concrete. The results of the tensile testing indicate that the storage time significantly affects the performance of asphalt concrete. The tensile strength of the specimens without anti-stripping agents decreased from 1.711 MPa to 0.914 MPa after resting periods of 0, 10, 20, and 30 days. The specimens treated with anti-stripping agents also showed a decrease in tensile strength over time, similar to the trend observed in the previous specimens. Digital specimen simulations indicated a decrease in cohesion between the asphalt and the aggregate from 5.375 MPa to 2.664 MPa after 30 days, representing a reduction of 50.44%. To counteract the effect of the storage time on the bonding between acidic aggregates and asphalt, this study recommends reducing the grading index and maximum size of aggregates, decreasing the coarse aggregate content, and selecting smooth aggregate shapes. [ABSTRACT FROM AUTHOR]

In this paper, we establish six necessary and sufficient conditions for a homeomorphism of R n onto itself to be strongly quasisymmetric. These conditions are quantitative in terms of conformal moduli of disjoint continua as well as the geometric modulus, which was recently introduced by Tukia and Väisälä. Note that all of them are equivalent to bilipschitz continuity with parameters depending also on two fixed points. As an application, we obtain several quantitative characterizations for a homeomorphism of the Riemann sphere R ¯ n onto itself to be strongly quasimöbius. [ABSTRACT FROM AUTHOR]

This study focuses on the preparation of lithium diphosphate compound LiCeP2O7 via conventional solid-state reaction. Analysis using the Rietveld refinement of the X-ray diffraction pattern reveals that the sample adopts a monoclinic structure at room temperature. Surface morphology is further examined through SEM. Additionally, complex impedance and electrical modulus spectroscopy analyses indicate the presence of non-Debye-type relaxation behavior. The direct current (dc) conductivity exhibits Arrhenius behavior, with activation energies of 0.94 eV in region I and 1.21 eV in region II, indicating thermally activated lithium-ion conduction. The thermal behavior of the exponent parameter "s" suggests a transition in the conduction mechanism from large polaron tunneling to small polaron tunneling that occurs at 533 K. Electric modulus studies confirm that the ionic conduction relaxation process is thermally activated and exhibits a spread of relaxation time. Understanding the ionic conduction mechanism will facilitate the design of efficient ionic conductors for battery applications. [ABSTRACT FROM AUTHOR]

AbstractPoly (N-isopropyl acrylamide) (PNIPAm) and polyacrylamide (PAAm) are widely used in antifouling research because of their non-harmful nature and their high water-absorbing capacity. In addition, hydrogels such as these two, should be investigated for their mechanical properties because their mechanical properties influence the antifouling paint containing them remaining on the surface of the vessels. In this research PAAm, PNIPAm, and kappa carrageenan (κC) doped with graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) composite gels were examined for their mechanical properties for use in antifouling paints as a potential material. For increasing the mechanical properties of composites, GO and MWCNTs are often used as doping materials. In the research described here, a compressive test was used to determine the elasticity, and the modulus was calculated. The toughness was calculated from the slope of the stress-strain curve. The PAAm, PNIPAm, and κC doped with GO and MWCNT exhibited excellent swelling and deswelling behavior and good mechanical properties as composites. The results showed that the composites’ mechanical characteristics increased with an ideal loading concentration of GO and MWCNTs. This study was inspired by our belief of a shortage of research on antifouling materials that are sensitive to the environment. We wanted to create materials that were both effective against fouling and environmentally safe by integrating the beneficial characteristics of hydrogels with potential materials inside antifouling paint. This study, we suggest, is an important step toward the development of antifouling materials with high mechanical performance that are also environmentally friendly. [ABSTRACT FROM AUTHOR]

The rheological characteristics of manganese zinc (Mn-Zn) ferrite magnetic nanofluid synthesized using co-precipitation technique were examined in the absence and presence of magnetic fields. The research formulates required conditions needed for the formation of a gelly-like structure. The impact of magnetic field and temperature on the rheological properties of Mn-Zn ferrite ferrofluid is investigated. When a magnetic field was applied, higher magnetoviscoelasticity and magnetoviscosity were formed. Other rheological parameters such as damping factor which is crucial for regulating and restricting vibrations in a system was also analyzed. A stiff, gel-like structure is produced when a magnetic field is applied, and the gel-like quality grows as the magnetic field increases; when the magnetic field is removed, the gel-like and rigidity of the structure is lost. At low temperatures, the liquid phase is dominated by solid-like particles, whereas at high temperatures, the liquid-like structure is dominant. This study reveals the conditions required for the creation of high viscous effect and the viscoelastic behavior induced by the field offers important insights for optimizing the Mn-Zn ferrite ferrofluid for a range of applications. Other criterial for gel-like structure formation such as low torque and deflection angle of the ferrofluid were also established. [ABSTRACT FROM AUTHOR]

The relatively low melting point of a traditional Si bonding layer limits the upper servicing temperature of environmental barrier coatings (EBC). To explore suitable high temperature bonding layers and expedite the development of EBC, first-principles calculation was used to evaluate the mechanical properties and thermal conductivity of HfSi2, HfSi, Hf5Si4, Hf3Si2, and Hf2Si with much higher melting points than that of Si. Among them, HfSi2 has the lowest modulus capable of good modulus matching with SiC substrate. In addition, these Hf-Si compounds have much lower high temperature thermal conductivity with Hf2Si being the lowest of 0.63 W m−1 K−1, which is only half of Si, capable of improved heat insulation. [ABSTRACT FROM AUTHOR]

Physical layer secret key generation is a novel research direction that has attracted many researchers in recent years due to its low computational capacity and ability to obtain information-theoretic security. In this paper, we propose two methods based on the modulus and the real and imaginary parts of the channel impulse response (CIR) matrix to generate a secret key between two legitimate devices in massive Multiple-Input Multiple-Output (MIMO) wireless communication systems. For these methods, the legitimate devices first estimate the channel by using a probing signal to find their CIRs. Next, the CIR matrices are transformed into single-row vectors. The first method uses a simple quantization algorithm to convert the modulus of the complex components of the vector into the final key bit sequence. The second method uses the same quantization algorithm to transform the highest points of the real and imaginary parts into two sequences. The XOR operation between these two sequences generates the final key sequence. The key samples with different lengths generated from the system can be assessed by the most crucial performance metric of randomness according to the National Institute of Standards and Technology (NIST) version 800-22REV1A. The numerical results show that the first method has a higher pass rate and more randomness than the second method. Moreover, our proposed methods are superior to existing methods.

Organic‐inorganic metal halide single crystals have attracted a lot of attention due to their flexible structural design and excellent optoelectronic applications. This study details the synthesis of copper‐based [(CH3)4N]2CuBr4 hybrid metal halide single crystals via a slow evaporation method. The crystal structure, crystal habit, chemical groups, intermolecular interactions, electrical properties of the sample were studied via single crystal x‐ray diffraction, scanning electron microscopy, Raman and Fourier transform infrared spectrometer, Hirshfeld surface analysis, impedance spectroscopy, and modulus spectroscopy, respectively. An orthorhombic crystal system with the non‐centrosymmetric space group Pna21 was identified at room temperature. The deformation in the tetrahedra was calculated by the bond angle and bond length deformation index. The Cole‐Cole plot displayed the existence of depressed semicircles, which indicated the predominant distribution of grains, further confirmed by the SEM image. The deformed semi‐circular arcs on the electric modulus curve undeniably prove that the bulk effect dominates the material's electrical properties. Significantly, the compound presents a phase transition at ~240 K and excellent thermal stability up to a temperature of 400 K. Therefore, our research sheds light on the temperature dependence of electrical responses in these hybrid crystals and gives inspiration for the development of single crystal‐based efficient energy devices. [ABSTRACT FROM AUTHOR]

The MCrAlY bonding layer alloy was prepared by vacuum melting, and the alloy composition was NiCoCrAlY and NiCoCrAlYHfTa. The high-temperature cyclic oxidation experiment was carried out in air at 1050∘C until it failed. The results show that Hf and Ta have a significant influence on the oxidation resistance of the alloy. The doped specimens have longer oxidation lifetimes compared to the undoped samples. The study also found that the Hf would diffuse out and combine with O to form HfO2 in the thermally grown oxide (TGO) layer, which would improve the adhesion and reduce the wrinkles of the oxide layer. Ta in the doped specimens hinders the diffusion of Al and reduces the oxidation rate, while improving the thermal mismatch. Therefore, the specimens doped with both Hf and Ta have the highest oxidation lifetimes, though the oxidation lifetime was 10 times longer than that of the undoped specimens. It is indicated that the doping of Hf and Ta is an important method to improve the oxidation lifetime of thermal barrier coatings (TBCs). [ABSTRACT FROM AUTHOR]

Aluminum (Al), poly(etheretherketone) (PEEK) thermoplastics, and their individual composites have widely been used in many industries, including aerospace and biomedical fields. However, the joining process of those composites has not been explored much to date. In this context, the friction welding process (FWP) could be used as an alternative since it has the ability to join high-strength components with minimal distortion. Therefore, the present study aimed to develop PEEK/Al nanocomposites with varying Al concentrations of 10, 20, 30, and 40 vol% using powder metallurgical technique and further joined the similar composition composites by FWP. Then, the effect of reinforced particle concentrations on the physical, morphological, structural, thermal, and micromechanical behaviors of the joined nanocomposites has been characterized by microscopy, X-ray diffraction, differential scanning calorimetry, and nanoindentation tests. The concentrations of the reinforcement were found to have a significant effect on the crystallinity, melting temperature, glass transition temperature, and thereby micromechanical properties. The results were analyzed and correlated precisely for all the welded nanocomposites systematically. The interdiffusion mechanism was found to be involved in improving the mechanical properties of the present nanocomposites. The highest elastic modulus (13.91 GPa) or nanohardness (0.31 GPa) was obtained for the rotatory part of the PEEK/Al40 nanocomposites at 80 mN load. But, the applied load of 40 mN was the best loading condition due to the uniform change in modulus and nanohardness of all the nanocomposites. Therefore, the present alternative joining method of the PEEK/Al nanocomposites might be used for aerospace components. Highlights • Development of PEEK/aluminum with 10, 20, 30 and 40 vol% Al nanocomposites. • Friction welding of similar composite material, PEEK/Al-PEEK/Al nanocomposites. • Microstructural, thermal, and nanomechanical analyses. • Effect of metal particle reinforcement on the friction welded nanocomposites. • FW PEEK/Al40 nanocomposite is found to be the best. [ABSTRACT FROM AUTHOR]

The polymer with nanoparticles tethered at each end is a unique model for unraveling the effect of chain ends on the polymer dynamics. We investigated the rheological behavior of this kind of polymer by using nonequilibrium molecular dynamics simulation. The effect of polymer lengths and nanoparticle radii on the complex moduli and viscosity was examined. The dependence of complex moduli on the frequency becomes less pronounced as the polymer is short or the nanoparticle is large. The shear thinning behavior was revealed for these systems, and the scaling exponent of complex viscosity with respect to the frequency was found to change from −1/2 to −3/4 as the polymer shortens or the nanoparticle enlarges. The rheological behavior was further explained by analyzing the mean square distance of nanoparticles. The simulation results were compared with the existing experimental finding, showing an agreement. The work provides information for understanding the chain end effect on polymer rheology. [ABSTRACT FROM AUTHOR]

To promote resourceful utilization of argon oxygen decarburization (AOD) slag, this research developed a new three-ash stabilized recycled aggregate with AOD slag, cement, fly ash (FA), and recycled aggregate (RA) as raw materials. The AOD slag was adopted as an equal mass replacement for fly ash. The application of this aggregate in a road base layer was investigated in terms of its mechanical properties and mechanistic analysis. First, based on a cement: FA ratio of 1:4, 20 sets of mixed proportion schemes were designed for four kinds of cement dosage and AOD slag replacement rates (R/%). Through compaction tests and the 7-day unconfined compressive strength test, it was found that a 3% cement dosage met the engineering requirements. Then, the unconfined compressive strength test, indirect tensile strength test, compressive rebound modulus test, and expansion rate test were carried out at different age thresholds. The results showed that the mixture's strength, modulus, and expansion rate increased initially and then stabilized with age, while the strength and modulus initially increased and then decreased with increasing R. Secondly, based on X-ray diffraction (XRD) and scanning electron microscopy (SEM) used to analyze the mechanism, it was found that the strength, modulus, and expansion rate of the new material can be promoted by blending AOD slag, due to its ability to fully stimulate the hydration reaction and pozzolanic reaction of the binder. Finally, based on the strength and modulus results, R = 3% was identified as the optimal ratio, which provides a reference point for the effective application of AOD slag and RA in road base materials. [ABSTRACT FROM AUTHOR]

Carbonate gravelly soils are widely distributed in sub-tropical marine areas. During construction and engineering operations, carbonate gravel undergoes considerable particle crushing, which has remarkable effects on their engineering properties. A series of large-diameter oedometer tests, large-diameter drained and undrained triaxial shear tests were conducted on carbonate gravel specimens taken from the South China Sea. The carbonate gravel specimens exhibit significant particle crushing at common engineering pressure levels, and the particle crushing highly depends on the initial density, loading history and stress path. Three fragmentation modes, fracture, attrition, and abrasion, are notable in carbonate gravel specimens, which induces significant variations of PSD curves and greatly effects the mechanical properties. Particle crushing in carbonate gravel specimens increases the compressibility resulting in the compression index increases with the increase of surcharge pressure; decreases the pressure-hardening resulting in the initial Young's and secant moduli slightly increase with the increase of initial confining pressure; and decreases the dilatancy resulting in the peak and critical state friction angles significantly deceases with the increase of initial confining pressure. Particle crushing also shows great effect on the CSL of the carbonate gravel specimens in both p ′ - q space and e - p ′ space. [ABSTRACT FROM AUTHOR]

It is known that if L is a Dedekind complete Riesz space and (Ω, Σ) is a measurable space, then the partially ordered linear space of all L-valued, finitely additive and order bounded vector measures m on Σ is also a Dedekind complete Riesz space (for the natural operations). In particular, the modulus |m|o of m exists in this space of measures and |m|o is given by a well known formula. Some 20 years ago L. Drewnowski and W. Wnuk asked the question (for L not Dedekind complete) if there is an m for which |m|o exists but, |m|o is not given by the usual formula? We show that such a measure m does indeed exist. [ABSTRACT FROM AUTHOR]

Copyright of South Architecture / Nanfang Jianzhu is the property of South Architecture Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Throughout all the countries in the world, including Vietnam, nations with well-established mining industries have undertaken extensive research on the stability of rock masses when constructing underground tunnels in varied geological conditions. The present study aims to provide a comprehensive overview of the risk assessment related to rock masses during the construction of pit lines in mining operations. Consequently, the standing time of unsupported tunnels is assessed based on different values of the strength index and deformation characteristics of the rock mass. The objective was to perform both experimental and theoretical investigations to analyse how the stand-up time of rock masses surrounding a tunnel affects the unsupported span. The analyses were based on considering the rock parameters, including strain modulus; geological strength index; and allowable displacement values, and consideration of hereditary creep properties. By examining tunnels excavated in rock strata, it was concluded that varying geological strength index values resulted in distinct creep behaviour in the surrounding rock masses. Thus, it was reasonable to compute the unsupported span and stand-up time of tunnels. The research revealed that permissible displacements are significantly influenced by the types of rock materials surrounding the tunnel structure. Recognising the significance of time, the authors introduce a more practical interpretation and evaluation of the stability of rock masses, thus enhancing the precision of commonly available models. [ABSTRACT FROM AUTHOR]

A series of laboratory and large-scale field model footing tests were conducted to assess the modulus and stress distribution behavior of a clayey soil foundation, both with/without geogrid reinforcement, deviating from the conventional approach of evaluating the strength performance, such as bearing capacity. The modulus was evaluated at three settlement ratios of s/B = 1, 3, and 5%, while the stress distribution angle α was estimated at three applied surface pressures of 234 kPa, 468 kPa, and 936 kPa. The results indicated a stiffer load-settlement response when geogrid reinforcement was included. The modulus of reinforced clayey soil remained nearly constant for test sections with the same reinforced ratio, with the modulus improvement increasing as the reinforced ratio (Rr) increased. The modulus improvement also increased with the settlement ratio (s/B). These results demonstrated that the stress distribution improvement decreased as the surface pressure increased. Generally, both the modulus and stress distribution improvement exhibited an increase with an increase in the tensile modulus of the geogrid. While laboratory model tests consistently provided a higher improvement in the modulus than large-scale field model tests in this study due to a higher reinforced ratio, the stress distribution improvement was similar for both. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi are ubiquitous and impactful symbionts of most land plants and can regulate essential ecological processes. AM fungi can increase the cellulose content of root cell walls and hence the root tensile strength of grass. How AM fungi can alter other essential biomechanical properties is not clear. This study aims to study the contribution of AM fungi in altering biomechanical properties by comparing mycorrhizal and non‐mycorrhizal roots. We inoculated three fungal species to vetiver grass (Chrysopogon zizanioides) for comparison. Eight root biomechanical properties (i.e., yield strain, yield stress, break strain, tensile strength, Young's modulus, plastic modulus, plastic strain, and toughness) were determined for each root using a newly developed Fortran language‐based program. Inoculating AM fungi decreased both Young's modulus and plastic modulus by 23% and 17%, respectively, versus control, although it was species‐dependent. Yield stress was not significantly affected, but tensile strength was increased by 7%–17% upon fungal symbiosis. Together with the increases in break strain by 15%–20%, mycorrhizal roots possessed a notably higher toughness than non‐mycorrhizal roots by up to 36%. Greater root cohesion of mycorrhizal roots confirmed the enhanced (1.5‐fold) factor of safety in the soil‐root system. Our findings imply that AM fungi are of significant interest in plant biomechanics and geotechnical engineering. Applying AM fungi on soil slopes has considerable potential to improve vegetation and stability of green slopes. [ABSTRACT FROM AUTHOR]

Highly efficient perovskite solar cells typically rely on spiro‐OMeTAD as a hole transporter, achieving a 25.7 % efficiency record. However, these cells are susceptible to harsh 85 °C conditions. Here, we present a peri‐xanthenoxanthene‐based semiconducting homopolymer (p‐TNI2) with matched energy levels and a high molecular weight, synthesized nearly quantitatively through facile oxidative polymerization. Compared to established materials, p‐TNI2 excels in hole mobility, morphology, modulus, and waterproofing. Implementing p‐TNI2 as the hole transport layer results in n‐i‐p perovskite solar cells with an initial average efficiency of 24.6 %, rivaling 24.4 % for the spiro‐OMeTAD control cells under identical conditions. Furthermore, the p‐TNI2‐based cells exhibit enhanced thermostability at 85 °C and operational robustness. [ABSTRACT FROM AUTHOR]

Polymer Nanocomposites (PNC) comprising polyvinylidene fluoride (PVDF)/Multi-walled Carbon Nanotubes (MWCNT) were studied. The structural composition and thermal stability were confirmed from XRD and DSC/TGA data, respectively. The extent of distribution of MWCNT in the PNC increases and the clustering of MWCNT also increases with an increase in the volume fraction of MWCNT ( f MWCNT ) , as confirmed by FESEM. The PNC shows an insulator-to-metal transition (IMT), with both non-universal percolation threshold (f c) of f MWCNT = 0. 0 0 6 and scaling exponents [ s = 0. 3 6 ± 0. 0 3 , s ′ = 1. 2 6 ± 0. 1 ] , respectively, attributed to adhesiveness/cold pressing and the higher aspect ratio/conductivity of MWCNT. Modulus spectroscopy confirms a non-Debye type universal relaxation behavior (β = 0. 5 4) only for the percolative sample due to Maxwell–Wagner–Sillars/interfacial polarization, while only dipolar relaxation was probed or the samples below f c . The f c with static effective dielectric constant ∼ 2 1 1 and low tan δ may be suitable for charge storage applications. [ABSTRACT FROM AUTHOR]

BaBi4Zr2Sn2O15, a modified ceramic sample belonging to the oxide family of layered ferroelectrics, is synthesized using the mixed oxide process after firing for calcination at 810 °C for 6 hrs. XRD study of the compound exhibits the growth of an orthorhombic single-phase structure at atmospheric temperature. The electrical properties of the sample are investigated in a broad temperature range (30–500 °C) and frequency range (100 Hz - 106 Hz). The dielectric properties recommend the transition from ferro to paraelectric state at 410 °C which is much more than room temperature. The impact of frequency and temperature on complex immittance parameters (impedance and modulus) are analyzed by an impedance analyzer in broad frequencies and temperature ranges. The electrical properties show; (i) the existence of semiconductor-like negative temperature coefficients of resistance behavior, (ii) evidence of electrical relaxation phenomena as a function of temperature, and (iii) the existence of single electrical relaxation ascribed to the existence of grain contribution to the electric properties. [ABSTRACT FROM AUTHOR]

Third-degree burn injuries pose a significant health threat. Safer, easier-to-use, and more effective techniques are urgently needed for their treatment. We hypothesized that covalently bonded conjugates of fatty acids and tripeptides can form wound-compatible hydrogels that can accelerate healing. We first designed conjugated structures as fatty acid–aminoacid1–amonoacid2–aspartate amphiphiles (Cn acid–AA1–AA2–D), which were potentially capable of self-assembling into hydrogels according to the structure and properties of each moiety. We then generated 14 novel conjugates based on this design by using two Fmoc/tBu solid-phase peptide synthesis techniques; we verified their structures and purities through liquid chromatography with tandem mass spectrometry and nuclear magnetic resonance spectroscopy. Of them, 13 conjugates formed hydrogels at low concentrations (≥0.25% w/v), but C8 acid-ILD-NH2 showed the best hydrogelation and was investigated further. Scanning electron microscopy revealed that C8 acid-ILD-NH2 formed fibrous network structures and rapidly formed hydrogels that were stable in phosphate-buffered saline (pH 2–8, 37 °C), a typical pathophysiological condition. Injection and rheological studies revealed that the hydrogels manifested important wound treatment properties, including injectability, shear thinning, rapid re-gelation, and wound-compatible mechanics (e.g., moduli G″ and G′, ~0.5–15 kPa). The C8 acid-ILD-NH2(2) hydrogel markedly accelerated the healing of third-degree burn wounds on C57BL/6J mice. Taken together, our findings demonstrated the potential of the Cn fatty acid–AA1–AA2–D molecular template to form hydrogels capable of promoting the wound healing of third-degree burns. [ABSTRACT FROM AUTHOR]

Interfaces of glassy materials such as thin films, blends, and composites create strong unidirectional gradients to the local heterogeneous dynamics that can be used to elucidate the length scales and mechanisms associated with the dynamic heterogeneity of glasses. We focus on bilayer films of two different polymers with very different glass transition temperatures (Tg) where previous work has demonstrated a long-range (~200 nm) profile in local Tg(z) is established between immiscible glassy and rubbery polymer domains when the polymer-polymer interface is formed to equilibrium. Here, we demonstrate that an equally long-ranged gradient in local modulus ...(z) is established when the polymer-polymer interface (≈5 nm) is formed between domains of glassy polystyrene (PS) and rubbery poly(butadiene) (PB), consistent with previous reports of a broad Tg(z) profile in this system. A continuum physics model for the shear wave propagation caused by a quartz crystal microbalance across a PB/PS bilayer film is used to measure the viscoelastic properties of the bilayer during the evolution of the PB/PS interface showing the development of a broad gradient in local modulus ...(z) spanning ≈180 nm between the glassy and rubbery domains of PS and PB. We suggest these broad profiles in Tg(z) and ...(z) arise from a coupling of the spectrum of vibrational modes across the polymer-polymer interface as a result of acoustic impedance matching of sound waves with λ ~ 5 nm during interface broadening that can then trigger density fluctuations in the neighboring domain. [ABSTRACT FROM AUTHOR]