Observation of the Energy Gap above T c in (Bi,Pb)2Sr2Ca2Cu3O10+δ using Break-Junction Tunneling

Tunneling measurements of (Bi,Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O ₁₀₊ have been carried out with break junction to study the gap feature above T _c = 106 K. The decreasing gap magnitude with increasing the temperature does not disappear at T _c for the most significant data. The gap-closing temperature is found to be T* 160 K.     

Study of the cause of the temperature rise at the muscle-bone interface during ultrasound hyperthermia

Undesirable temperature rise at the muscle-bone interface has been one of the major problems during ultrasound hyperthermia treatment. In this study, we examined by both computer calculation and phantom experiment the cause of this problem. Ultrasound penetrates a bone in two different waveforms, longitudinal and transversal. The transmission coefficient of these two waves vary greatly with the incident angle. From both theoretical and experimental results, the incident angle dependency of the interface heat was confirmed. When the incident angle is less than the critical angle of the longitudinal wave, the main cause of the temperature elevation is the absorption of the longitudinal wave in the bone. When the incident angle is larger than the critical angle of the longitudinal wave, the transversal wave becomes the major cause of the heat generation. At the incident angles larger than the critical angle of the transversal wave, no temperature rise is produced by the absorption of the ultrasound at the bone; the incident longitudinal wave, strengthened by the reflected wave, is absorbed in the muscle just in front of the bone. The heat generated in the muscle is transported to the interface so that the temperature of the interface and bone increases slightly.     

Phase Transformation and Temperature Dependence of Relative Permittivity for A-site Substituted Sr(Y0.5Ta0.5)O3Perovskites

A-site cation substitution with Ba²⁺ or Ca²⁺ ions was made for the ordered complex perovskite Sr(Y_0.5Ta_0.5)O₃ to correlate the structure evolution and the change in the temperature coefficient of relative permittivity (TC_r) with the cation substitution. The crystal symmetry of the solid solutions at room temperature changed as monoclinic rhombohedral cubic with the corresponding A-site cation species of Ca²⁺ Sr²⁺ Ba²⁺. On heating, the rhombohedral phase of Sr(Y_0.5Ta_0.5)O₃ was firstly transformed to the cubic phase with a lower symmetry (F43m or F432) at 1000°C and further to the ideal cubic phase (Fm3m) at 1300°C. The similar phase transformation behavior at elevated temperatures was observed for each of the Ba²⁺-substituted perovskites, both the phase transformation temperatures being lowered with increasing Ba²⁺ content. TC_r of the ordered perovskites monotonously increased over the temperature range where the phase transformation regions from monoclinic to rhombohedral or from rhombohedral to cubic (F43m or F432) occurred. On the other hand, a subtle symmetry change in the cubic phase from F43m (F432) to Fm3m caused a remarkable change in the TC_r from positive to negative at the transformation temperature. These results suggested that the positive TC_r is essentially correlated to the relaxation of the tilting of the BO₆ octahedra in the perovskite structure on heating.     

An Efficient Sound and Data Steganography Based Secure Authentication System

The prodigious advancements in contemporary technologies have also brought in the situation of unprecedented cyber-attacks. Further, the pin-based security system is an inadequate mechanism for handling such a scenario. The reason is that hackers use multiple strategies for evading security systems and thereby gaining access to private data. This research proposes to deploy diverse approaches for authenticating and securing a connection amongst two devices/gadgets via sound, thereby disregarding the pins’ manual verification. Further, the results demonstrate that the proposed approaches outperform conventional pin-based authentication or QR authentication approaches. Firstly, a random signal is encrypted, and then it is transformed into a wave file, after which it gets transmitted in a short burst via the device’s speakers. Subsequently, the other device/gadget captures these audio bursts through its microphone and decrypts the audio signal for getting the essential data for pairing. Besides, this model requires two devices/gadgets with speakers and a microphone, and no extra hardware such as a camera, for reading the QR code is required. The first module is tested with real-time data and generates high scores for the widely accepted accuracy metrics, including precision, Recall, F1 score, entropy, and mutual information (MI). Additionally, this work also proposes a module helps in a secured transmission of sensitive data by encrypting it over images and other files. This steganographic module includes two-stage encryption with two different encryption algorithms to transmit data by embedding inside a file. Several encryption algorithms and their combinations are taken for this system to compare the resultant file size. Both these systems engender high accuracies and provide secure connectivity, leading to a sustainable communication ecosystem.     

Solution to the topology optimization problem using a time-evolution equation

This article describes a numerical solution to the topology optimization problem using a time-evolution equation. The design variables of the topology optimization problem are defined as a mathematical scalar function in a given design domain. The scalar function is projected to the normalized density function. The adjoint variable method is used to determine the gradient defined as the ratio of the variation of the objective function or constraint function to the variation of the design variable. The variation of design variables is obtained using the solution of the time-evolution equation in which the source term and Neumann boundary condition are given as a negative gradient. The distribution of design variables yielding an optimal solution is obtained by time integration of the solution of the time-evolution equation. By solving the topology optimization problem using the proposed method, it is shown that the objective function decreases when the constraints are satisfied. Furthermore, we apply the proposed method to the thermal resistance minimization problem under the total volume constraint and the mean compliance minimization problem under the total volume constraint.     

Effects of Al-Ni powder addition on dissimilar friction stir welding between AA7075-T6 and 304 L

Friction stir welding between AA7075-T6 aluminum alloy and 304 L stainless steel sheet metal was performed with the addition of Al−Ni powder between the joining interfaces to increase the joining performance. The welding tool was rotated at 200 min⁻¹ to 800 min⁻¹ with the constant traverse speed of 25 mm/min. The resulting joint interfaces were analyzed using a field emission-scanning electron microscope and energy-dispersive x-ray spectroscopy analysis. The tensile strength was greater for the Al−Ni powder added specimens at the lower tool rotational speeds. The tensile strength of 360 MPa was obtained for the ‘with-powder’ specimen as compared to 220 MPa for the ‘without-powder’ specimen at the 200 min⁻¹ tool speed. Electron microscope images of the stir zone showed a significant mixing of the Al−Ni powder with the base materials, increased contact at the interface, which resulted in increased joining strength at the lower tool rotational speeds. However, based on the images, intermetallic compound that may contribute to the joining strength in the vicinity of the interfacial region was not detected.     

Effect of particle morphology on mechanical properties of liquid marbles

In order to better understand the influence of the shape of solid particles on the stability of liquid marbles, we investigated liquid marbles stabilized by hydrophobized calcium carbonate particles with spherical and rod-shaped morphologies. Static properties, such as the effective surface tension, and the dynamic behavior i.e. the compression-decompression features for several cycles of the liquid marbles were investigated. Liquid marbles stabilized with spherical CaCO₃ particles show an elastic response to mechanical deformation almost up to collapse. In contrast, liquid marbles prepared with rod-like particles exhibit a more plastic response to compression. It is concluded that the main differences in behavior of the prepared liquid marbles arise from how the solid particles can arrange/orient at the air/water interface.     

Calculation of Direct Tunneling Current through Ultra-Thin Gate Oxides Using Complex Band Models For SiO2

We report the calculation of gate leakage currents through the ultra-thin gate oxides (2.6–3.4 nm) in MOSFETs. We simulate J-V characteristics for the direct tunneling of valence electrons and inversion layer holes, which are measured using a charge separation technique. A two-band model is employed to express the complex band structure of the gate oxide, and its validity is discussed by calculating the complex band structure of -cristobalite based on the second nearest neighbor sp ³ s* tight-binding scheme.