摘要：
Dispersions around the Dirac points in sonic crystals give rise to various extraordinary transport proper-ties of sound waves. In particular, with tilted Dirac cones, the acoustic Dirac crystals will exhibit obvious anisotropic properties. When the Dirac cone is titled to a certain degree, a unique type-III Dirac point emerges with the extreme anisotropic-wave-transport property, which features the crossing of flat bands and linear dispersions. Recently, some quantum and artificial structures have been proposed to realize dif-ferent types of Dirac points, where the type-III Dirac point in sonic crystals has rarely been studied so far. Here, we utilize the orbital modes in an acoustic honeycomb lattice to obtain strictly flat bands through eliminating & pi; bonding. The type-III Dirac points emerge with modulated intercell and intracell couplings, which are simulated with specific structural parameters. At type-III Dirac points, the acoustic wave propa-gation is extremely anisotropic and manifests as plaquette states that exist in the two-dimensional flat-band systems. Inspired by the unique properties at the type-III Dirac points, hybrid acoustic Dirac lattices of regions characterized by different wave-propagation directions are used to conduct the montage operation of plaquette states. The orbital type-III Dirac cones and the montage operation of plaquette states provide opportunities for manipulating energy flow in exotic ways and expanding the potential applications of Dirac materials.
摘要：
Castor seed oil, as an important biomass fuel, has attracted extensive attention worldwide due to inclusive applications. Castor seed screw mechanical extraction is in fact seed shear damage and oil output. Seed shearing mechanism has been investigated with a developed tribometer. Influences of pressing load, shearing speed, roller roughness were analyzed. Castor seed structural damage was in-situ observed with optical microscope, and in-depth analyzed with Scanning Electron Microscopy and Energy Dispersive Spectroscopy. The results reveal that shear interaction can be divided into three stages: coat damage, transition shearing and endosperm oil output. Seed shear mechanism includes coat peeling, endosperm plowing, tissue transferring and oil lubrication. High pressing load leads to more damage of coat and endosperm, causing more oil to flow out. With shearing speed increasing, coat is easily peeled, obvious endosperm shear plowing and oil lubrication happened in contact area. Coat damage by high roughness leads more oil output. Castor oil enters the contact area and work as lubricant, leading to the decrease of friction resistance.
摘要：
The insulated-gate bipolar transistor (IGBT) represents a crucial component within the domain of power semiconductor devices, which finds ubiquitous employment across a range of critical domains, including new energy vehicles, smart grid systems, rail transit, aerospace, etc. The main characteristics of its operating environment are high voltage, large current, and high power density, which can easily cause issues, such as thermal stress, thermal fatigue, and mechanical stress. Therefore, the reliability of IGBT module packaging has become a critical research topic. This study focuses on the damage of power device solder layers and applies heat transfer theory. Three typical solders for welding IGBTs (92.5Pb5Sn2.5Ag, Sn3.0Ag0.5Cu (SAC305), and nano-silver solder paste) are analyzed using JMatPro software to simulate their characteristics. First, a finite element analysis method is used to simulate the entire IGBT module with ANSYS Workbench platform. The study compares the impact of three types of solders on the overall heat transfer of the IGBT module under normal operation and welding layer damage conditions. The characteristics are analyzed based on changes in the junction temperature, heat flow path, and the law of thermal stress and deformation. The findings indicated that under steady-state working conditions, adjacent chips in a multi-chip IGBT module had significant thermal coupling, with a maximum temperature difference between chip junctions reaching up to 13 °C, and a phenomenon of heat concentration emerged. The three types of solders could change the thermal conductivity and heat transfer direction of the IGBT module to varying degrees, resulting in a temperature change of 3-6 °C. Under conditions of solder layer damage, the junction temperature increased linearly with the severity of the damage. In the 92.5Pb5Sn2.5Ag and Sn3.0Ag0.5Cu (SAC305) solders, the presence of intermetallic compounds (IMCs) led to more stress concentration points in the solder layer, with the maximum stress reaching 7.14661 × 10(7) MPa and concentrated at the edge of the solder layer. The nano-silver solder layer had the best thermal conductivity, and the maximum thermal deformation under the same conditions was only 1.9092 × 10(-5) m.
关键词：
Ship collision;Raked bow;Ship side shell;Experiments;Numerical simulations;Damage characteristics
摘要：
Experimental and numerical simulation studies are conducted on a scaled ship side-shell quasi-statically punched at the mid-span by a raked bow indenter to investigate its damage characteristics from deformation to a large opening. A scaled stiffened panel and a raked bow indenter are designed in model tests. Numerical simulation is performed to simulate the indentation responses. The experimental and numerical results are compared well in terms of resistance-penetration curves, final damage shapes and especially the three failure models, i.e., initial fracture, model “I” crack and model “III” crack. In addition, the whole damage process, the energy dissipation characteristics of the specimen and failure related parameters in three specific failed elements corresponding to the three failure models are analyzed through numerical simulation. The results demonstrate that the energy dissipated by the stiffener and frictional effect is substantial during the crack propagation process. In addition, shell elements involved with three failure models prior to fracture are mainly subjected to tension and bending effects, as shell elements cannot satisfactorily simulate the transverse shear effect. Finally, the influences of collision parameters, the failure sequence of integration points, modeling of weld seams, mesh resolution and failure criteria on the numerical simulation results are discussed.
通讯机构：
[Li, Bin] S;School of Mechanical Engineering, Wuhan Polytechnic University, Wuhan Hubei, China
关键词：
Person re-identification;measurement model;LDA;semi-supervised learning
摘要：
Person re-identification identify a specific person in surveillance network by similarity measurement between images of different camera views. However, existing metric learning based methods suffer from over-fitting problem. To solve this problem, a resampled linear discriminant analysis (LDA) method was proposed based on the statistical and topological characteristics of pedestrian images. This method utilized the k-nearest neighbours to form potential positive sample pairs. The potential positive pairs are used to improve the metric model and generalize the metric model to the test data. By minimizing the inter-class divergence of potential positive sample pairs, a semi-supervised re-sampling LDA person re-identification algorithm was established. It was then tested on the VIPeR, CUHK01 and Market 1501datasets. The results show that the proposed method achieves the best performance compared to some available methods. Especially, the proposed method outplays the best comparison method by 0.6% and 5.76% at rank-1 identification rate on the VIPeR and CUHK01 datasets respectively. At the same time, the improved LDA algorithm has improved the rank-1 identification accuracy of traditional LDA method by 9.36% and 32.11% on these two datasets respectively. Besides, the proposed method is limited to Market-1501 dataset when the test data is of large size.
通讯机构：
[Yang, L ] W;Wuhan Polytech Univ, Coll Mech Engn, Wuhan 430048, Hubei, Peoples R China.
关键词：
crack initiation;damage behavior;finite element modeling;rice grain
摘要：
Understanding the rice grain breakage mechanism is important to increase head rice yield. In this work, a developed mechanical experimental setup is produced, combing a texture analyzer with in situ observation. Grain damage behavior was researched with experimental and finite element modeling. Experimental results showed rice breaking force is closely related to pressing speed and rice length. Three models simulation (ellipsoidal model E model, three section model T model, real shape model R model) results show that the E model is not suitable for quasi-static compression simulation, the peak force is 35.897% error with testing. T and R modeling results error is within 10%, the broken form is closely related to the dorsal groove and ridge. Initial cracks exit in the area close to the probe and expand inward. Surface cracks happen when element stress exceeds the tensile strength. These findings provide a theoretical basis for broken rice rate reduction during processing.
通讯机构：
[Li, YN ] ;Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430023, Peoples R China.
关键词：
Bio-based polymer;active and smart packaging;antibacterial;blending ratio
摘要：
Food Science and Technology International, Ahead of Print. <br/>A series of biodegradable colorimetric films were prepared by using chitosan and polyvinyl alcohol as matrix, in which, the weight ratio of chitosan: Polyvinyl alcohol was 100: 0, 80: 20, 50: 50, 20: 80, or 0: 100, with addition of 10% (w/w, relative to chitosan) anthocyanins extracted from purple tomatoes (purple tomatoes anthocyanin) as pigment. The aim of this study was to observe the effect of weight ratio (chitosan: Polyvinyl alcohol) on the mechanical properties, contact angle, swelling rate, pH sensitivity, antioxidant properties of chitosan-polyvinyl alcohol/purple tomatoes anthocyanins films, and the antibacterial activity of films produced for pork packaging. In addition, the films as a smart colorimetric indicator for monitoring the freshness of pork was investigated. The results showed that as the ratio of chitosan to polyvinyl alcohol decreases, the elongation at break, hydrophilicity, and swelling rate of the films increased especially from 16.5% to 174.2% for elongation at break and 93.0° to 53.8° for water contact angle, however, the tensile strength decreased from 67.3 to 24.7 MPa. With decreasing of chitosan: Polyvinyl alcohol, the antibacterial activity on pork was decreased, and the antioxidant properties of films increased first then decreased. Fourier transform infrared spectroscopy indicated there were interactions among chitosan, polyvinyl alcohol, and purple tomatoes anthocyanins. The color response of films was depended on pH, as well as the immersion time. The longer immersion resulted in a more pronounced color change. The color changed from purplish red (pH 2–4) to green (pH 5–10) to yellow (pH 10–12). In monitoring the freshness of pork, the film showed a nice visual color change, indicating a potential application in smart packaging. These bio-based materials may be useful alternatives to synthetic plastics for food applications such as active and smart packaging, thereby improving the environmental friendliness and sustainability of the food supply.
通讯机构：
[Shilin Yan; Pin Wen] A;Authors to whom correspondence should be addressed.<&wdkj&>Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics, School of Science, Wuhan University of Technology, Wuhan 430070, China
关键词：
triply periodic minimal surface;selective laser melting;mechanical properties;energy absorption;mathematical model
摘要：
Compared with the traditional lattice structure, the triply periodic minimal surface (TPMS) structure can avoid stress concentration effectively. Here, it is promising in the fields of lightweight and energy absorption. However, the number of structural parameters and mechanical properties of the TPMS structure is plentiful, and the relationship between them is unclassified. In this paper, for the first time, a unified mathematical model was proposed to establish the relationship between TPMS structural design parameters and mechanical properties. Fifteen primitive models were designed by changing the structural parameters (level-set value C and thickness T) and manufacturing by selective laser melting. The geometric defects and surface quality of the structures were explored by optical microscope and scanning electron microscopy (SEM). The mechanical properties were investigated by quasi-static compression test and finite element simulation. The influence of building direction on structural mechanical behavior (failure mode, stress-strain curve) was studied. The real mechanical properties (Young’s modulus and plateau stress) of the structure could be predicted according to different C and T combinations. Finally, the energy absorption characteristics were explored. The results showed that when the C value is 0.6 in the range of 0–0.6, the energy absorption performance of the structure is at the maximum level.
通讯机构：
[Liu, XP ] W;Wuhan Polytech Univ, Sch Anim Sci & Nutr Engn, Wuhan 430023, Peoples R China.
关键词：
brown rice kernels;bonding parameters;discrete element;bonded particle model;orthogonal test
摘要：
Aiming to resolve the practical problem of brown rice kernels being easily broken due to overprocessing during processing (milling and polishing), brown rice kernels of Japonica rice, after hulling, were used as the research object in this study. Firstly, through a texture meter test, the discrete element bonding parameters (K-n is normal stiffness per unit area, K-tau is tangential stiffness per unit area, C-n is critical normal stiffness, C-tau is critical shear stiffness) were obtained. Secondly, a brown rice kernels' bonding particle model was established by EDEM, and then a second orthogonal rotational combination test was carried out to calibrate the discrete bonding parameters, K-n = 4.43 x 10(12) N/m(3), K-tau = 6.13 x 10(11) N/m(3), C-n = 2.55 x 10(7) Pa, and C-tau = 7.92 x 10(7) Pa. The error of parameter calibration was within 5%, and the results were able to reflect the actual situation more realistically. Finally, analysis of the crushing process of brown rice kernels showed that their ability to withstand shear damage was not as great as their pressure-bearing capacity. The design of the relevant mechanism and the setting of parameters should be based on the critical shear stiffness of brown rice kernels, and the actual shear force F-tau* set during the processing should be smaller than the theoretical critical shear force F-tau (F-tau* < F-tau = 9.11 N). This study can provide a theoretical basis for optimizing the key structure and operating parameters of rice milling machines and polishing machines to effectively solve the practical problem of increased crushing of brown rice kernels due to overprocessing.
通讯机构：
[Bin Li] S;School of Mechanical Engineering, Wuhan Polytechnic University, Wuhan, Hubei 430023, China
摘要：
Deep eutectic solvent (DES) was synthesized from urea (U), acrylamide (AM) and choline chloride (ChCl), sodium alginate (SA) was selected as filler, and SA/P(U-AM-ChCl) composite hydrogel was prepared by thermal initiation frontal polymerization (FP). The hydrogels were characterised by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The effects of SA on the swelling properties, mechanical properties and self-healing properties of the composite hydrogels were investigated. The results show that the swelling properties of the composite hydrogel with the addition of SA are greatly enhanced due to the large number of hydroxyl groups contained in the SA chain. The tensile strength of the hydrogel gradually increased with increasing SA content, with the maximum tensile strength increasing by a factor of 2.89. The self-healing efficiency of the composite hydrogel gradually increased with the increase of SA, and the healing rate of FP5 reached 94.4% after 48 h of healing. This study provides a simple and rapid method for the preparation of composite hydrogels with good mechanical properties and self-healing properties.
摘要：
In this paper, betaine (Bet) was used as a hydrogen bond acceptor (HBA), and acrylic acid (AA) and acrylamide (AM) were used as hydrogen bond donors (HBD) and mixed to form a deep eutectic solvent (DES). Different concentrations of beta-cyclodextrin (beta-CD) were dispersed in the DES, and a novel beta-CD/P(AA-co-AM) hydrogel was prepared by frontal polymerization (FP). The characteristic structure and morphology of the hydrogels were analyzed using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), and the properties of the hydrogels were investigated. The results show that the mechanical properties of the hydrogel were improved by beta-CD acting as a second cross-linking agent in the polymerization process, thus increasing the cross-link density of the hydrogel. Because the carboxyl groups contained in the acrylic acid dissociate under alkaline conditions, the composite hydrogel shows excellent pH responsiveness under alkaline conditions. Tetracycline hydrochloride was used as a drug model to test the drug loading and drug release performance of the hydrogels. With the increase of beta-CD content, the loading capacity of the hydrogels for tetracycline hydrochloride gradually increased. The data of drug release indicated that the hydrogel has good drug delivery performance and has promising applications in drug delivery systems and other areas.
通讯机构：
[Wu, Y ] W;Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430023, Peoples R China.
关键词：
second phase particles;AZ31 Mg alloy;phase field models;microstructure refinement
摘要：
In this study, the phase field method has been used to study the effect of second phase particles with different shapes and different orientations on the grain growth of AZ31 magnesium alloy, after annealing at 350 °C for 100 min. The results show that the shape of the second phase particles would have an effect on the grain growth; the refinement effect of elliptical particles and rod-shaped particles was similar, and better than the spherical particles; the spatial arrangement direction of the second phase particles had no significant effect on the grain growth. On the other hand, when the microstructure of AZ31 magnesium alloy contained second phase particles with different shapes, the effect of mixing different shapes of second phase particles on the grain refinement was enhanced gradually with the decrease im the volume fraction of spherical particles.
摘要：
Recently, graph neural networks have achieved good performance in graph representation learning. However, most graph neural networks only utilize node low-frequency signals and destroy node similarity when aggregating graph structure and node features, which limits their ability to represent graph-structured data. Therefore, we propose a node similarity preserving graph convolutional network based on full-frequency information (FSP-GCN). It extracts relevant information to the greatest extent from graph structure and node features while preserving node similarity for aggregation. Precisely, to better capture full-frequency information, we propose an improved aggregation component called MFGCN that adopts a multi-head attention mechanism to integrate signals in different frequency domains adaptively. Then we design a node similarity aggregation method to aggregate a k-nearest neighbor(kNN) graph constructed from the original graph with the feature graph learned from the MFGCN aggregation component to preserve node similarity. Finally, we employ contrastive learning to preserve node similarity further. We also compare the performance of the FSP-GCN model with that of ten real-world networks, using well-known assortative and disassortative datasets. The results demonstrate that FSP-GCN offers significant performance improvement compared to representative baselines. In addition, extensive comparative experiments are conducted on the robustness of the model and alleviating the over-smoothing problem. The results show that the FSP-GCN model can effectively alleviate the over-smoothing problem and resist the adversarial attack of the graph structure.
关键词：
Porous material;Oxidation resistance;High temperature oxidation;Oxidation mechanism
摘要：
MoAlB possesses the characteristics of both metals and ceramic materials, which has attracted extensive attention due to its excellent high-temperature oxidation resistance. For this reason, porous MoAlB is considered appli-cable to the practice of filtration under harsh environment. In this study, the high-temperature oxidation behavior of porous MoAlB ceramics is systematically studied at the temperatures ranging from 800 to 1100 degrees C. According to the results, the porous MoAlB exhibits good oxidation resistance at a maximum temperature of 1000 degrees C. The oxidation kinetics of porous MoAlB can be divided into three stages, and the estimated activation energies of the three stages are 253.83 kJ & sdot;mol-1, 367.48 kJ & sdot;mol-1 and 317.84 kJ & sdot;mol-1, respectively. In the stable stage at 1000 degrees C, the quadratic mass gain per unit area shows linearity over time, and the oxidation rate of porous MoAlB reaches 37.31 mg2 & sdot;cm-4 & sdot;h-1. As revealed by the analysis of the composition and microstructure of oxide layers, the main components of the oxide layer include MoO3, MoO2, Al2O3, B2O3. With the extension of oxidation time, the content of Al2O3 in the oxide films increases. The average pore size, permeability and open pore porosity of porous MoAlB show a trend of first decreasing and then tending to be stable. In addition, a discussion is conducted on the high-temperature oxidation mechanism of porous MoAlB.
摘要：
Ce-MnOx composite oxide catalysts with different proportions were prepared using the coprecipitation method, and the CO-removal ability of the catalysts with the tested temperature range of 60-140 degrees C was investigated systematically. The effect of Ce and Mn ratios on the catalytic oxidation performance of CO was investigated using X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), H-2 temperature programmed reduction (H-2-TPR), CO-temperature programmed desorption (CO-TPD), and in situ infrared spectra. The experimental results reveal that under the same test conditions, the CO conversion rate of pure Mn3O4 reaches 95.4% at 170 degrees C. Additionally, at 140 degrees C, the Ce-MnOx series composite oxide catalyst converts CO at a rate of over 96%, outperforming single-phase Mn3O4 in terms of catalytic performance. With the decrement in Ce content, the performance of Ce-MnOx series composite oxide catalysts first increase and then decrease. The Ce MnOx catalyst behaves best when Ce:Mn = 1:1, with a CO conversion rate of 99.96% at 140 degrees C and 91.98% at 100 degrees C.
关键词：
Brown rice kernel;crack detection;image processing;model migration;ResNet-18
摘要：
The occurrence of cracks in brown rice kernels has a substantial impact on grain quality. The timely and accurate detection of rice grains with cracks is crucial for enhancing the overall quality and flavor of processed rice. In this study, we developed an optical observation platform and optimized the original ResNet-18 neural network structure to improve the detection and classification of grain cracks. We established image datasets for japonica and indica rice varieties, and employed image augmentation and model migration techniques during training. In addition, we compared the performance of the optimized model with DenseNet-121 and GoogLeNet. The results demonstrate a notable enhancement in crack detection accuracy for japonica, reaching 96%, which is a 3.67% improvement over the original model. Furthermore, we achieved a substantial reduction in average training time, reduced by 58.66%. For indica rice, after model optimization and migration, the accuracy reached 96.67%. It's important to note that the optimized model has limitations and is not suitable for mixed datasets with limited training data. This technology offers the capability to accurately identify and detect cracks in brown rice kernels under visible light conditions, presenting a promising solution for enhancing grain quality during processing.
关键词：
high-molybdenum-vanadium high-speed steel;JMatPro;austenitic carbon content;martensite transformation temperature;heat treatment process
摘要：
High-molybdenum-vanadium high-speed steel is a new type of high-hardenability tool steel with excellent wear resistance, castability, and high-temperature red hardness. This paper proposes a composition design of high-molybdenum-vanadium high-speed steel for rolls, and its specific chemical composition is as follows (wt.%): C2%, Mo7.0%, V7.0%, Si0.3%, Mn0.3%, Ni0.4%, Cr3.0%, and the rest of the iron. This design is characterized by the increase in molybdenum and vanadium in high-speed steel to replace traditional high-speed steel rolls with the tungsten element in order to reduce the heavy elements' tungsten-specific gravity segregation caused by centrifugal casting so that the roll performance is uniform and the stability of use is improved. JMatPro (version 7.0) simulation software is used for the composition design of high-molybdenum-vanadium high-speed steel. The phase composition diagram is analyzed under different temperatures. The content of different phases of the organization in different temperatures is also studied. The martensitic transformation temperature and different tempering temperatures with the different types of compounds and grain sizes are calculated. The process parameters of heat treatment of high-molybdenum-vanadium high-speed steel are optimized. The selection of carbon content and the temperature of M50 are calculated and optimized, and the results show that the range of pouring temperatures, quenching temperatures, annealing temperatures, and tempering temperatures are 1360 similar to 1410 degree celsius, 1190 similar to 1200 degree celsius, 818 similar to 838 degree celsius, and 550 similar to 600 degree celsius, respectively. Scanning electron microscope (SEM) analysis of the samples obtained by using the above heat treatment parameters is consistent with the simulation results, which indicates that the simulation has important reference significance for guiding the actual production.
通讯机构：
[Li, B ] W;Wuhan Polytech Univ, Sch Mech Engn, Wuhan 430023, Hubei, Peoples R China.
关键词：
local thermal non-equilibrium;multi-physics field simulation;porous media;rice drying
摘要：
In this article, the flow and temperature fields of the deep‐bed drying process of rice grain were simulated based on the flow field theory of porous media and the local thermal nonequilibrium method. The moisture change rate of rice seeds under deep bed drying was described using thin layer equation. Based on this, a coupled multi‐physical field model of the deep‐bed drying process of rice under an angular air duct was established by COMSOL. The reasonableness of the simulation results was verified by building an experimental platform. Abstract The deep‐bed drying process of rice grains was investigated through numerical simulation, employing the porous medium flow field theory and the local thermal nonequilibrium method. Moisture field of rice grains described using thin‐layer equations. On this basis, the deep‐bed drying of rice grains modeled with COMSOL, and verified its plausibility. The results showed that the drying rate of rice grains was significantly accelerated when the hot air temperature was increased from 40°C to 70°C, but the inhomogeneity of rice grains temperature increased by 29.79%, 22.31%, and 17.41% for every 10°C increase. Drying grains faster with vertically arranged an angular air duct, with a 4.88% increase in drying speed in 300 min. The temperature difference between the top and the bottom of an angular air duct with a small width is smaller, about 11°C, and the heating efficiency is better at the top, by 31.28%. Practical Applications Grain dryers are often used in high‐volume grain drying operations and it has been a great challenge to save the energy consumption of the drying process. It is necessary to use numerical simulation to design a reasonable structure of the heating section to improve the energy utilization efficiency of the heating section of the grain dryer. The numerical model proposed in this article can effectively simulate the spatial distribution of moisture content of rice under different structures of grain drying units, which can be used not only for the prediction of drying time but also for analyzing the optimal heating structure from it. A technical basis is provided for the design of grain dryers.
