Considerable progress of ultrasound simulation on blood has enhanced the characterizing of red blood cell (RBC) aggregation.A novel simulation method aims at modeling the blood with different RBC aggregations and concentrations is proposed.The modeling process is as follows: (i) A three-dimensional scatterer model is first built by a mapping with a Hilbert space-filling curve from the one-dimensional scatterer distribution. (ii) To illustrate the relationship between the model parameters and the RBC aggregation level, a variety of blood samples are prepared and scanned to acquire their radiofrequency signals in-vitro. (iii) The model parameters are determined by matching the Nakagami-distribution characteristics of envelope signals simulated from the model with those measured from the blood samples.Nakagami metrics m estimated from 15 kinds of blood samples (hematocrits of 20%, 40%, 60% and plasma concentrations of 15%, 30%, 45%, 60%, 75%) are compared with metrics estimated by their corresponding models (each with different eligible parameters). Results show that for the three hematocrit levels, the mean and standard deviation of the root-mean-squared deviations of m are 0.27 ± 0.0026, 0.16 ± 0.0021, 0.12 ± 0.0018 respectively.The proposed simulation model provides a viable data source to evaluate the performance of the ultrasound-based methods for quantifying RBC aggregation.
Air gap defects inside a spacer reduce its insulation performance, resulting in stress concentration, partial discharge, and even flashover. If such gap defects are located at the interface between the insulation and conductor, a decrease in mechanical stress may occur. In this work, a finite element method-based simulation model is developed to analyze the influence of gap defects on the electrical and mechanical properties of a ±320 kV direct current gas insulated line (DC GIL) spacer. Present findings reveal that a radially distributed air gap produces a more significant effect on the electric field distribution, and an electric field strength 1.7 times greater than that of the maximum surface value is observed at the air gap. The axial distribution dominates the distortion of the surface stress by generating a stress concentration region in which the maximum stress of the air gap is twice the pressure in the surrounding area.
In this paper, harmonic concise atoms for the mean scatterer spacing (MSS) estimation was proposed to distinguish the normal and the ablated liver tissues. First, the second harmonic RF echo signals are separated with the Butterworth bandpass filter from the ultrasound RF echo signals, and a series of Gabor atoms are found to represent the local components with the concentrated energy. Then, the concise atoms are selected from the found Gabor atoms to optimal match the coherent components in the harmonic signals. Finally, the locations of the adjacent concise atoms are used to estimate the MSSs. In the microwave ablation experiments, the fundamental and second-harmonic RF echo signals were collected from the regions of interest in the normal untreated porcine tissues and thermally coagulated tissues ablated for 300 s, respectively. The MSSs, as well as the means and standard deviations of the MSSs were calculated from the collected signals for further comparation. The experiment results showed that the harmonic-based MSSs had large difference between the normal and the ablated liver tissues. The decrement in the harmonic-based mean MSS, and standard deviation in the ten tissues were 56.33 %, and 8.33 % greater than the fundamental-based results. It indicated that the harmonic-based MSS results with the concise atoms could improve the MSS estimation accuracy to distinguish the normal and the thermal coagulated liver tissues induced by the microwave ablation.
The effect of cooling rate on the composition, morphology, size, and volume fraction of the secondary phase in as‐cast Mg–Gd–Y–Zr alloy is investigated. In the study, a casting containing five steps with thickness of 10–50 mm is produced, in which cooling rate ranging from 2.6 to 11.0 K s −1 is created. The secondary phase is characterized using optical microscope (OM), scanning electron microscope (SEM), and electron probe micro‐analyzer (EPMA). The volume fraction of the secondary phase is determined using OM and quantitative metallographic analysis, and Vickers hardness test is conducted to verify the analysis results. The effect of the cooling rate on the volume fraction of the secondary phase is discussed in detail. The result shows that with the increase of the cooling rate, the size of the secondary phase decreases. The effect of the cooling rate on the volume fraction of the secondary phase is complicated somewhat. A comprehensive analysis on the experimental data shows that a critical cooling rate may exist, over which the volume fraction of the secondary phase decreases with the increase of the cooling rate, however under which the volume fraction increases with the increase of the cooling rate.
Abstract Mean scatterer spacing (MSS) is a quantitative signature for disease diagnosis and tissue characterization. However, it is difficult to objectively extract the coherent components from the ultrasound RF echo signals to improve the accuracy performance of the MSS estimation. In the present study, a novel MSS estimation method with the matched Gabor atoms selected based on Nakagami parameters is proposed. Firstly, the ultrasound signals are decomposed into a series of Gabor atoms, and the envelopes of the residual signals are fitted with the Nakagami distribution. Then, the second order difference (SOD) of the shape parameters in Nakagami distribution is calculated to select the optimal atoms to match the coherent components. Finally, the locations of the selected Gabor atoms are used to estimate the MSS. In order to evaluate the performance of the proposed method, the simulated RF echo signals are modelled based on four regular degrees of the scatterer distributions, and then the optimally matched atoms are selected to estimate MSSs. The results based on simulated signals demonstrate that the propose method can provide accurate MSS estimation, which are advantageous for improving quantitative diagnosis of diseases and tissue characterization
Abstract Non‐enzymatic glucose sensor is greatly expected to take over its enzymatic counterpart in the future. In this paper, we reported on a facile strategy to construct a non‐enzymatic glucose sensor by use of NiCo 2 O 4 hollow nanocages (NiCo 2 O 4 HNCs) as catalyst, which was derived from Co‐based zeolite imidazole frame (ZIF‐67). The NiCo 2 O 4 HNCs modified glassy carbon electrode (NiCo 2 O 4 HNCs/GCE), the key component of the glucose sensor, showed highly electrochemical catalytic activity towards the oxidation of glucose in alkaline media. As a result, the proposed non‐enzymatic glucose sensor afforded excellent analytical performances assessed with the aid of cyclic voltammetry and amperometry (i–t). A wide linear range spanning from 0.18 μΜ to 5.1 mM was achieved at the NiCo 2 O 4 HNCs/GCE with a high sensitivity of 1306 μA mM −1 cm −2 and a fast response time of 1 s. The calculated limit of detection (LOD) of the sensor was as low as 27 nM (S/N=3). Furthermore, it was demonstrated that the non‐enzymatic glucose sensor showed considerable anti‐interference ability and excellent stability. The practical application of the sensor was also evaluated by determination of glucose levels in real serum samples.
In this paper, an experimental evidence of enhanced laser-induced breakdown spectroscopy (LIBS) emission using nanoparticles and amphiphiles was reported. The measurement showed an enhanced emission from the K-I lines at the wavelengths of 766.5 and 769.9 nm when the cationic amphiphile of hexadecyl trimethyl ammonium bromide was adsorbed on Au NPs, but no LIBS signal was observed for the anionic amphiphile of sodium dodecyl sulfate or for Au NPs alone. This significant enhancement can be attributed to Coulombic force of attraction between the cationic amphiphile and negatively charged Au NPs and hence the enhanced electric field due to the existence of Au NPs. The detection limit for potassium was shown to be 13 ppb. The new technique provides an effective method for the improvement of the detection sensitivity of LIBS.
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