Focused Ultrasonic Beam Behavior at a Stress-Free Boundary and Applicability for Measuring Nonlinearity Parameter in a Reflection Mode

Measurements of the acoustic nonlinearity parameter β are frequently made for early detection of damage in various materials. The practical implementation of the measurement technique has been limited to the through-transmission setup for determining the nonlinearity parameter of the second harmonic wave. For the purpose of practical applications, a pulse-echo measurement technique is more desirable which enables the single-side access of test components. The issue with using the second harmonic wave reflected from the stress-free interface is that such a boundary destructively alters the nonlinear generation process and consequently makes it difficult to obtain the reliable results of β. In this work, we employ a focused beam theory to modify the phase reversal at the stress-free boundary, and consequently enhance the second harmonic generation during its back-propagation toward the initial source position. We first confirm this concept through experiment by using a spherically focused beam at the water-air interface, and measuring the reflected second harmonic and comparing with a planar wave reflected from the same stress-free or a rigid boundary. In order to test the feasibility of this idea for measuring the nonlinearity parameter of solids in a reflection mode, an array transducer beam is modeled for focusing at and reflection from a stress-free boundary. A nonlinearity parameter expression is then defined together with diffraction and attenuation corrections

Focused Ultrasonic Beam Behavior at a Stress-Free Boundary and Applicability for Measuring Nonlinearity Parameter in a Reflection Mode

Measurements of the acoustic nonlinearity parameter β are frequently made for early detection of damage in various materials. The practical implementation of the measurement technique has been limited to the through-transmission setup for determining the nonlinearity parameter of the second harmonic wave. For the purpose of practical applications, a pulse-echo measurement technique is more desirable which enables the single-side access of test components. The issue with using the second harmonic wave reflected from the stress-free interface is that such a boundary destructively alters the nonlinear generation process and consequently makes it difficult to obtain the reliable results of β. In this work, we employ a focused beam theory to modify the phase reversal at the stress-free boundary, and consequently enhance the second harmonic generation during its back-propagation toward the initial source position. We first confirm this concept through experiment by using a spherically focused beam at the water-air interface, and measuring the reflected second harmonic and comparing with a planar wave reflected from the same stress-free or a rigid boundary. In order to test the feasibility of this idea for measuring the nonlinearity parameter of solids in a reflection mode, an array transducer beam is modeled for focusing at and reflection from a stress-free boundary. A nonlinearity parameter expression is then defined together with diffraction and attenuation corrections.</p

A Novel Scheme for Generating Context-Aware Images Using Generative Artificial Intelligence

Humans possess the remarkable capacity to comprehend narratives presented in text and subsequently conjure associated mental images through their imagination. This cognitive ability enhances their grasp of the content and augments their overall enjoyment. Consequently, the development of an automated system aimed at producing visually faithful images based on textual descriptions, often referred to as the text-to-image task, stands as a profoundly meaningful endeavor. For this reason, a variety of text-to-image generating artificial intelligences (AIs) have been devised until now. Nevertheless, the generative AIs introduced thus far encounter an issue wherein they struggle to uphold the coherence of input sentences, particularly when multiple sentences are provided. Within this paper, we present a remedy to this challenge through the application of prompt editing. Furthermore, our experimental results substantiate that our proposed solution more effectively preserves contextual coherence among the generated images in comparison to other preexisting generative artificial intelligence models. The experimental results demonstrate that the proposed scheme improves performance by at least 30 percent in terms of the similarity of the generated image and by 130 percent in terms of $ROUGE_{recall}$

Solution Combustion Synthesis of Ni-Based Nanocatalyst Using Ethylenediaminetetraacetic Acid and Nickel-Carbon Nanotube Growth Behavior

We studied the influence of the ethylenediaminetetraacetic acid (EDTA) content used as combustion fuel when fabricating nickel oxide (NiO) nanocatalysts via solution combustion synthesis, as well as the growth behavior of carbon nanotubes (CNTs) using this catalyst. Nickel nitrate hexahydrate (Ni(NO3)2∙6H2O) was used as the metal precursor (an oxidizer), and the catalysts were synthesized by adjusting the molar ratio of fuel (EDTA) to oxidizer in the range of 1:0.25 to 2.0. The results of the crystal structure analysis showed that as the EDTA content increased beyond the chemical stoichiometric balance with Ni(NO3)2∙6H2O (F/O = 0.25), the proportion of Ni metal within the catalyst particles decreased, and only single-phase NiO was observed. Among the synthesized catalysts, the smallest crystallite size was observed with a 1:1 ratio of Ni ions to EDTA. However, an increase in the amount of EDTA resulted in excessive fuel supply, leading to an increase in crystallite size. Microstructure analysis revealed porous NiO agglomerates due to the use of EDTA, and differences in particle growth based on the fuel ratio were observed. We analyzed the growth behavior of CNTs grown using NiO nanocatalysts through catalytic chemical vapor deposition (CCVD). As the F/O ratio increased, it was observed that the catalyst particles grew excessively beyond hundreds of nanometers, preventing further CNT growth and leading to a rapid termination of CNT growth. Raman spectroscopy was used to analyze the structural characteristics of CNTs, and it was found that the ID/IG ratio indicated the highest CNT crystallinity near an F/O ratio of 1:1

Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat Treatment

The phase formation and stabilization behaviors of calcia partially stabilized zirconia (Ca-PSZ) were investigated with regard to the CaO content and post-heat treatment. Sintered specimens were prepared by adding 2, 3, 4, and 5 mol% to CaO to ZrO2, and post-heat treatment were conducted. In the X-ray diffraction pattern, the monoclinic peak decreased, the tetragonal peak increased upon CaO doping, and no CaZrO3 peak was observed. Transmission electron microscopy images of the Ca-PSZ showed that the d-spacing of 4CSZ (200)m extended from 0.260 nm to 0.266 nm subsequent to post-heat treatment. The coefficient of thermal expansion gradually increased in accordance with the dopant concentration, in addition, it increased even after the post-heat treatment. These results are related to the increase in tetragonal phase, which has a relatively higher coefficient of thermal expansion than that of the monoclinc phase. According to the Vickers hardness measurement, the hardness of all specimens increased gradually as the concentration of CaO increased, and the hardness of the 5CSZ was improved from 676 to 774 Hv by the post-heat treatment

Diallyl disulphide-loaded spherical gold nanoparticles and acorn-like silver nanoparticles synthesised using onion extract: catalytic activity and cytotoxicity

AbstractOnion (Allium cepa) extract was used for the green synthesis of gold and silver nanoparticles. Each colloidal solution exhibited surface plasmon resonance, with a peak at 532 nm for gold nanoparticles and 391 nm for silver nanoparticles. Microscopic results confirmed the presence of spherical shapes. The X-ray diffraction pattern demonstrated a face-centered cubic structure. Both nanoparticles had negative zeta potentials and retained colloidal stability in cell culture medium. Catalytic applications were evaluated for 4-nitrophenol reduction and methyl orange degradation reactions by monitoring with UV-visible spectrophotometry. Furthermore, the nanoparticles demonstrated no significant cytotoxicity against human pancreas ductal adenocarcinoma cells (PANC-1) and human colorectal adenocarcinoma cells (HT-29). PEGylation and diallyl disulphide loading of the gold and silver nanoparticles meaningfully reduced the cell viability of both cell lines. Furthermore, diallyl disulphide loading resulted in more cytotoxicity against PANC-1 cells than against HT-29 cells. Additionally, the gold nanoparticles were more cytotoxic than the silver nanoparticles upon diallyl disulphide loading. Interestingly, after PEGylation and diallyl disulphide loading, the silver nanoparticles exhibited acorn-like shapes, while the gold nanoparticles retained spherical shapes. This result suggested that nanoparticles green-synthesised by onion extract have possibilities as nanocatalysts and drug delivery nanocarriers for catalytic and nanomedicine applications