Exploring the Formation Mechanism of Deformation Twins in CrMnFeCoNi High Entropy Alloy

The deformation twins initiated in CrMnFeCoNi high entropy alloy at cryogenic temperature are experimentally studied. Under the external loading, a three-dimensional shear stress concentration originating from dislocation tangling at both the grain boundaries and twin boundaries could be formed, which promotes emission of partial dislocations from the planar defects and is thus considered to be the key factor for twin formation. A sympathetic nucleation mechanism is proposed to describe the nucleation behaviors of twins.     

Interfacial Oxides Evolution of High-Speed Steel Joints by Hot-Compression Bonding

The interfacial oxidation behavior of Cr4Mo4V high-speed steel (HSS) joints undergoing hot-compression bonding was investigated by using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In the heating and holding processes, dispersed rod-like and granular $\delta - {\text{Al}}_{{2}} {\text{O}}_{{3}}$ oxides were formed at the interface and in the matrix near the interface due to the selective oxidation and internal oxidation of Al, while irregular Si–Al–O compounds and spheroidal SiO₂ particles were formed at the interface. After the post-holding treatment, SiO₂ oxides and Si–Al–O compounds were dissolved into the matrix, and $\delta - {\text{Al}}_{{2}} {\text{O}}_{{3}}$ oxides were transformed into nanoscale $\alpha - {\text{Al}}_{{2}} {\text{O}}_{{3}}$ particles, which did not deteriorate the mechanical properties of the joints. The formation and migration of newly-formed grain boundaries by plastic deformation and post-holding treatment were the main mechanism for interface healing. The tensile test results showed that the strength of the healed joints was comparable to that of the base material, and the in-situ tensile observations proved that the fracture was initiated at the grain boundary of the matrix rather than at the interface. The clarification of interfacial oxides and microstructure is essential for the application of hot-compression bonding of HSSs.     

海河平原区地下水累计可恢复超采量评价

地下水累计可恢复超采量评价对于地下水超采态势评判和超采综合治理实施都具有重要意义。本文以海河平原区为研究对象，提出超采量评价方法，旨在客观准确评价地下水累计可恢复超采量。针对浅层地下水超采量，提出生态临界水位作为传统“水位动态法”评价浅层地下水超采量的临界水位，据此得到研究区1959-2019年累计浅层超采量为869亿m³；针对深层地下水超采量，提出“不可恢复超采量”评价指标，采用地面沉降体积法评价深层地下水超采量，根据地面沉降体积计算深层承压含水层系统压密释水量体积，据此估算1970-2019年深层累计超采量为756亿m³；通过建立的一维非线性压密释水数值模型，模拟了深层承压含水层系统压密释水过程，计算得到非弹性压密释水量，评估研究区累计不可恢复超采量为558亿m³。因此本文认为，自1960年代以来，海河平原区地下水浅层和深层累计超采量1625亿m³，其中可恢复的超采量仅为1067亿m³。该研究结果可为未来地下水回补水量和南水北调规划调水量的确定提供参考。     

Graph learning in low dimensional space for graph convolutional networks

Multimedia Tools and Applications - Graph Convolutional Networks (GCNs) recently have been adopted in several feature representation studies for different classification tasks. While many of these...     

Finite-time adaptive fuzzy control for a class of output constrained nonlinear systems with dead-zone

The article investigates the finite-time adaptive fuzzy control for a class of nonlinear systems with output constraint and input dead-zone. First, by skillfully combining the barrier Lyapunov function, backstepping design method, and finite-time control theory, a novel adaptive state-feedback tracking controller is constructed, and the output constraint of the nonlinear system is not violated. Second, the fuzzy logic system is used to approximate unknown function in the nonlinear system. Third, the finite-time command filter is introduced to avoid the problem of “complexity explosion” caused by repeated differentiations of the virtual control signal in conventional backstepping control schemes. Meanwhile, a new saturation function is added in the compensating signal for filter error to improve control accuracy. Finally, based on Lyapunov stability analysis, all the signals of the closed-loop are proved to be semi-globally uniformly ultimately bounded, and the tracking error converges to a small neighborhood region of the origin in a finite time. A simulation example is presented to demonstrate the effectiveness for the proposed control scheme.     

Deployment simulation of membrane structures based on elastic-plastic behavior parameterization of the crease

Journal of Mechanical Science and Technology - Aiming at the problem that the membrane structure is prone to creases in the process of folding and compaction, a proxy model is used to replace the...     

Identifying Community Fire Hazards from Citizen Communication by Applying Transfer Learning and Machine Learning Techniques

Fire Technology - A cross-region transfer learning method is proposed to identify community (e.g. car parks, public spaces and shopping centers) fire hazards based on text input provided by...     

Electric Vehicle Charging Simulation Framework Considering Traffic, User, and Power Grid

The traffic and user have significant impacts on the electric vehicle (EV) charging load but are not considered in the existing research. We propose a novel integrated simulation framework considering the traffic, the user, and power grid as well as the EV traveling, parking and charging based on cellular automaton (CA). The traffic is modeled by the traffic module of the proposed framework based on CA, while the power grid and user are modeled in the EV charging module. The traffic flow, user’s charging preference, user’s charging satisfaction, and the total supply capability (TSC) in the surveyed region are considered in the proposed framework. Two cases are carried out to show the interactions between the user and power grid. It is shown that the proposed framework can accurately simulate the interactions among traffic situation, user’s behavior and TSC， which are significantly lacking in the existing research. The proposed framework is scalable in considering additional interrelated elements.     

城市地下浅层疏松病害雷达图谱快速探测

城市道路病害因其突发性、无明显预兆性,对交通安全、城市畅通造成了重大安全隐患,而雷达探测技术因其高效、无损的特点,成为具有高优先级的道路病害检测技术手段.首先对雷达探测原理做出了简单说明,给出了图谱的病害解释;通过将该技术手段应用于某开挖道路探测,在路口C南侧发现疑似病害区域,结合对应道路沉降监测数据,对道路安全状况作出评价,实践结果验证了雷达检测在城市道路病害探查中的科学性和有效性,为道路病害应急处置和安全预警提供了有效依据.