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In this paper, we proposed and studied a Leslie-Gower prey-predator system which considered various ecological factors, such as the Allee effect and harvesting effect in prey populations and the hunting cooperation in predator populations. The positivity and boundedness of the system's solutions were determined. The conditions for the uniformly persistence of the system and the extinction of populations have been established. We studied the existence and type of singularities, including primary singularities and higher-order singularities. Using topological equivalent and the blow-up method, we proved that the origin was the attractor, and a defined basin of attraction was given. As the parameters change, the system may experience two saddle-node bifurcations and a Hopf bifurcation. The direction and stability of Hopf bifurcation solutions were established. Numerical simulations were given to validate the primary theoretical findings. In this paper, we found that there existed critical thresholds for Allee threshold, prey harvesting, and hunting cooperation, beyond which both predator and prey populations faced the risk of extinction.

In this paper, we investigate a novel T-S fuzzy parameter varying system with Markov jump, in which parameters depend not only on a Markov chain but also on linear parameter varying elements that take values in convex polytopic sets. Stable conditions and the gain-scheduling controller design method for this system are obtained. Applying Lyapunov function depending on the operation mode and full block S-procedure lemma, we obtain stochastic stabilization conditions. We find that this novel system has two distinct advantages. On the one hand, it inherits the advantages of traditional T-S fuzzy systems in handling nonlinear objects under the frame of T-S fuzzy systems; on the other, it obtains the advantages of dealing with time-varying characteristics from the point of linear parameter varying (LPV) systems. Finally, the theory results are illustrated via numerical simulation.

The paper deals with the effect of the morphology characteristics, grain size, and the volume fraction of AlN- and NbC-precipitated particles on the prior austenite grain growth behavior in the Al- and Nb-microalloying 20MnCr gear steel during pseudo-carburizing heat treatments. The results indicate that the Nb addition in 20MnCr gear steel have a better effect on preventing austenite grain growth. The coarsening time after pseudo-carburizing in the Nb-microalloyed 20MnCr steel are improved by about 4 h compared with the Al-microalloyed steel. The precipitated particles coarsen and the number decreases with the pseudo-carburization temperature increasing, resulting in a reduction in the pinning pressure of the precipitated particles on the austenite grain boundaries. When the pseudo-carburization temperature reaches 1150 °C, the precipitated particles no longer have the ability to pin the austenite grain boundaries. In addition, the kinetics model for austenite grain growth under the process of the pinning and coarsening of the precipitated particles was established.

Eutectic high-entropy alloys (EHEAs) feature attractive strength–ductility balance at both ambient and cryogenic temperatures. Nevertheless, microstructural origins underpinning these balanced mechanical properties remain elusive. Here the deformation mechanisms of a recently-reported Al19Co20Fe20Ni41 EHEA were comparatively investigated at 298 and 77 K, which revealed a high frequency and density of dislocation multi-slip scenario in the soft eutectic lamellae and the corresponding compatible co-deformation in the adjacent hard lamellae that collectively endowed strong hetero-deformation-induced (HDI) hardening and excellent forest-dislocation hardening. Therefore, better ductility and tensile strength, in comparison to the other widely-studied EHEA system, could be sustained even at liquid-nitrogen temperatures.

A two-step temperature-controlled magnetron sputtering procedure was adopted to obtain a bilayer hierarchical Fe25.2Co25.2Ni27.4Cr22.2 high entropy alloy (HEA) thin film consisting of the external nano-lamellar layer and internal equiaxed zone, which displayed combined advantages of high hardness, good modulus and excellent corrosion resistance. The roles of heterogeneous nanostructure on the mechanical and corrosion behavior were revealed by nano-indentation and Scanning Kelvin probe (SKP) methods. Compared to the substrate 304 ASS, the hierarchical HEA film not only shows much higher nano-hardness and modulus values, but also possesses a higher electron transfer resistance (12158 vs 4567 Ω.cm2) and lower overall corrosion rate (6.28*10−4 vs 6.84*10−3 mm·year−1). Moreover, the outer nano-lamellar layer shows higher nano-hardness (∼8.1 GPa) but lower surface potential values (∼-261 mV) than those of the inter equiaxed zone (∼5.9 GPa and ∼−150 mV). The former arises from the significant grain refinement strengthening effect, while the latter is attributed to an obvious increase in the high energy and chemically active areas such as grain boundaries and triple junctions. This work demonstrates the capability of hierarchy to adjust the comprehensive performance of multi-functional films, which possess superior mechanical property and comparable corrosion performance than those of the as-cast bulk HEA alloys.

In this work, the effects of the micro-alloying of Mn, Ni, and Si on the microstructure and mechanical properties of high-carbon pearlite steels were investigated. The results indicated that the addition of solely Ni to high-carbon pearlitic steel can enhance the strength through the refinement of interlamellar spacing, but work-hardening in the ferrite of the pearlite colony may be delayed, leading to a reduction in area. The multiple additions of Ni and the increase in Mn and Si contents in high-carbon pearlitic steel were beneficial to obtaining a balance between ultimate tensile strength and reduction in area. Three-dimensional atom probe tomography results showed Si partitioning into ferrite and Mn and Ni elements partitioning into cementite. The addition of Si inhibited the formation of a continuous network of grain-boundary cementite, leading to high strength and high ductility through optimization of the microstructure.

In this paper, the fatigue resistance of superelastic NiTi shape memory alloy (SMA) wires was improved by combining mechanical training and nanocrystallization. Fatigue tests were performed after mechanical training with a peak stress of 600 MPa for 60 cycles of nanocrystalline (NC) NiTi wires, and the associated microscopic mechanism was investigated by using transmission electron microscopy (TEM) and transmission Kikuchi diffraction (TKD). The results showed that stress-controlled training effectively improved the functional stability (the accumulated residual strain decreased by 83.8% in the first 5000 cycles) of NC NiTi SMA wires, as well as increased the average structural fatigue life by 187.4% (from 4538 cycles to 13,040 cycles). TEM observations and TKD results revealed that training-induced dislocations resulted in lattice rotation and preferential grain orientation. The finite element method (FEM) simulation results indicated that the training-induced preferential grain orientation tended to decrease the local stress concentration and strain energy density. Combined with fractography analysis, the uniform deformation caused by mechanical training changed the crack growth mode from multi-regional propagation to single-regional propagation, improving the structural fatigue life.

In the paper, Ti-18Nb-5X (X = Mo and Sn) and Ti-33Nb-2X (X = Al, Sn, Fe and Mo) alloys were investigated to evaluate the effects of Al, Mo, Sn and Fe doping and different heat treatments on the properties and microstructures of the Ti-Nb-based alloys. The results show that Al decreased the volume of βM in the water-quenched Ti-33Nb-2Al alloy and promoted the formation of β phase in the furnace-cooled Ti-33Nb-2Al alloy. Fe-doping was proven to stabilize the β phase. Sn-doping plays a complicated role to promote the formation of α′′ phase in the water-quenched Ti-33Nb-2Sn alloys but increases the β phase in the furnace-cooled Ti-33Nb-2Sn alloys and Ti-18Nb-5Mo-5Sn. The alloys containing α′′ and βM phases show larger superelastic strains and lower Young’s moduli. In the water-quenched Ti-based alloys, the Young’s modulus decreases, and the superelastic strain is enhanced with the increasing volume of α′′.

Accompanied by the formation of pearlite, Widmanstätten ferrite (WF), grain boundary ferrite and cementite are often found to nucleate at the prior austenite grain boundary during isothermal heat treatment. A hypereutectoid pearlitic steel transformed isothermally at temperatures ranging from 607 to 707 °C was investigated to clarify the evolution of different phases. At 607 °C, WF grains, which had a Kurdjumov–Sachs orientation relationship with the remaining austenite, were found to be aligned with the grain boundary. At 707 °C, lath WF grains, which were arranged parallel to each other, were at a certain angle to the grain boundary. The formation of pearlite showed two-stage kinetics in the dilatometer curve, and the grain boundary’s abnormal structure was suppressed.

The reaction-diffusion equations have been widely used in physics, chemistry, and other areas. Forest fire can also be described by such equations. We here propose a fighting forest fire model. By using the normal form approach theory and center manifold theory, we analyze the stability of the trivial solution and Hopf bifurcation of this model. Finally, we give the numerical simulations to illustrate the effectiveness of our results.