The advanced engine has been the core technology of the aviation industry for several decades. The air-breathing hypersonic propulsion is the top problem for future aerospace flight. The engine's performance depends on its energy conversion method and combustion mode, and its relevant theory is of fundamental and revealing significance. In this paper, the supersonic combustion is discussed first since it is the theoretical basis for the research and development of scramjet engines. Then, by reviewing related research progresses, three criteria of the air-breathing hypersonic ramjet propulsion are established. The first one can be used to determine the local subsonic or supersonic flow states of combustion products in supersonic reacting gas flows, revealing the mechanism of the upstream-traveling shock wave. The second one defines the critical Mach number for hypersonic ramjet operation for all the combustion modes, and is a necessary condition that needs to be considered in the engine design under the equivalent ratio combustion. The last one gives a critical wedge angle corresponding to the CJ oblique detonation, and its physical basis is the critical initiation state of detonation. Finally, the experimental research progress on the stationary oblique detonation ramjet (Sodramjet) engine is summarized, and its feasibility as a hypersonic engine for future aerospace flight is demonstrated.

Since the birth of modern aerodynamics, various theories on lift and drag have been developed and validated extensively in aeronautical applications. However, the far-field force theory had long remained at low-speed incompressible flow. Based on the analytical solutions of the linearized Navier-Stokes equations in the steady far field, the authors and their collaborators extended the classic Kutta-Joukowski lift theorem to both two- and three-dimensional viscous and compressible flows, and thus filled the long-standing gap in theoretical aerodynamics. Why can the simple formulas based on linearized approximation still be accurately valid for highly nonlinear complex flows? This issue of great interest involves the methodological characteristics and physical mechanism behind the unified force theory and is the first task of this article. Moreover, there has been an abnormal phenomenon regarding the physical origin of lift that, despite the already mature and fully verified rigorous lift theory, various different hypotheses still keep surfacing frequently in various nonscientific publications and media. This indicates that the issue is really complicated and has not been thoroughly clarified in textbooks, monographs, and classrooms around the world. Now, the universality and high conciseness of the unified theory enable one to reach a clear answer to this issue by rigorous logical arguments in the most direct way. This is the second task of this article.

This review article systematically summarizes the neural energy theory and methods proposed by our team in the field of brain science, and the internal relationship between mechanics and neural energy theory. This paper introduces how to construct an equivalent W-Z neuron model with the H-H model using the idea of analytic dynamics. Based on this, a large-scale neural model with neural energy as the core and a theoretical framework of global neural coding are proposed in the field of neuroscience. The unique functions and advantages of this novel neuron model are confirmed in the aspects of information processing, including visual perception, brain intelligence exploration, prediction of new working mechanisms of neurons and explanation of experimental phenomena challenging to explain in neuroscience. Because plasticity is the core of cognitive neuroscience and intelligent behavior, through the classical mechanical analysis of protein molecular machines, it is further clarified that the plasticity and neurodevelopment of neurons are not only biochemical reaction processes but also the role and contribution of mechanics are indispensable and important factors. It shows that the research thought of mechanics science in neuroscience and life science and its profound influence on internal logic. These studies will promote the integration of experimental neuroscience and theoretical neuroscience in the future, abandon the shortcomings in the research methods of reductionism and holism in the field of neuroscience, and integrate their respective advantages effectively. It is extremely important to promote the penetration of theories and methods of mechanical science.

The biomechanics of injury and prevention is an important branch of modern biomechanics and a multi-disciplinary subject that is applied to the analysis of the mechanism of biological tissue or organ damage and its prevention. The goal of it is to prevent the human body from damage or minimize injury for tissue or organ when subjected to loads. It covers the study of the response of tissue subjected load, the mechanism and the tolerance of injury, and the methods and effective devices to reduce injury. Higher loads have high lethality due to its short-term action and explosiveness. Therefore, the ability to anti-injury under overload has been a severe constraint for the development of aircraft, the improvement of automobile performance and the enhancement of athletes' competitive ability. In particular, the emergence of the modern faster and more flexible fighter, the life-saving of supersonic ejection and the protective of maneuver flight of high load and load has presented new challenges for the subject of injury and prevention biomechanics but also provided enormous opportunities for the development of it. In recent years, the impact injury involved in aerospace, traffic accidents, sports and falls of the elder has presented the features of high incidence and low protection efficiency. However, it is difficult to obtain the actual data due to the damage caused by experiments to humans. Meanwhile, since the biological tissue has the characteristics of nonlinearity, viscoelasticity, regeneration and reconstruction, it involves how to describe the constitutive relations of biological tissue or organs, and the correlation between the anatomical features and its mechanical properties accurately. It also involves how to establish the mechanism and tolerance of tissue injury at multi-scales, the methods and the principle to design protective devices. The present paper focuses on the summarization of the major research contents and its methods to the biomechanics of injury and prevention. The types, mechanisms (including the response of the biomechanics and mechanobiology), tolerance, and the protective method of injury under complex loading for the human body are summarized, and the primary advancement and the possible tendency of development in these fields are introduced. The study on the biomechanics of injury and prevention is of great significance to protect and improve human safety under complex load. It could guide the establishment of standards and evaluation methods of musculoskeletal injuries involved in aerospace, transportation, and sports. This research is vital to guide the optimization design of protective devices and has great potential to the development and application of bionic engineering materials and protective devices.

The development ofshale gas involves two critical processes including fracturing andtransportation. To realize reticular fractures in the shale layerof multi-phase under more than 2000 m subjected to complexgeo-stress and to collect the free and adsorbed gases encapsulatedin the layer, we face many key mechanical challenges to beaddressed. There are several cut-on-edge research topicsassociated with shale gas development: the huge span in structuralsize and fracture eveents from nanoscale to even severalkilometers, free and adsorbed gas transporting at temperal scalesfrom microseconds to the life-long mining of a shale-gas well, thefluid-solid interaction at different time and length scales, andthe in-situ monitoring on internal damage states duringfracturing. In view of the achievements in shale-gas explorationand the mechanical research frontiers for subsequent development,we give a comprehensive review on the basic characteristics anddevelopment techniques of shale-gas reservoirs. We cover in thisreview six aspects of the latest research progress, the mechanicalproperties of shales and their characterization, shale gasreservoir experimental techniques, shale gas micro-flow mechanismand fluid-solid coupling characteristics, numerical simulation ofhydraulic fracturing process, micro-seismic monitoring technologyof hydraulic fracturing process and high-efficiency andenvironmentally friendly waterless fracturing technology.Combining with the engineering practice of shale-gas reservoirdevelopment, the key issues of mechanics are presented, to providea theoretical basis for the practitioners engaged in thedevelopment and research of shale-gas field. We suspect that theprogress summarized here may help guide general research inmechanics, especially in geotechnical mechanics.

Interface Defeat, which can effectively defeat the long-rod projectile (LRP), is a specific phenomenon of ceramic armor. Studies on this area have been conducted for the last three decades both at home and abroad proving that delaying dwell time or increasing interface defeat/penetration transition velocity can defeat projectile and enhance the ballistic performance of ceramic armor. Related researches on the experimental techniques, theoretical models and numerical simulations of interface defeat are introduced, including the study of interface defeat at the micro and macro scale, a method for the design of the ceramic composite armor, etc. According to the insufficient work of interface defeat, some suggestions are proposed in this paper.

Generally, peridynamics is a theory focusing on the evolution of a physical system, which is based on the assumption that each material point interacts with the other material points within a certain domain through non-contact or nonlocal interactions. It provides a unified mathematical framework for analyzing problems involving the evolving discontinuities and nonlocality. After a brief introduction of the peridynamic solid models and the urgent requirements on multi-physics models and corresponding commercial software, which have the capability of dealing with the evolving discontinuities, we made a systematic review on peridynamic nonlocal diffusion and peridynamic multi-physics coupled modeling. It can be found that the existing multi-physics coupled modeling studies mostly concentrated on the problems in the electronic components, electronic packaging and geotechnical engineering fields, including the un-coupled, partial coupled and fully coupled models about thermo-mechanics, hygro-thermo-mechanics, thermo-oxidative, thermo-mechanics-oxidative, mechanics-electronics, thermo-electronics, thermo-mechanics-electronics, fluid-solid interaction model for porous medium. Finally, several potential problems in the theoretical model, numerical algorithm and engineering application of peridynamic diffusion modeling and multi-physics coupled modeling are suggested.