Beihang University

About: Beihang University is a education organization based out in Beijing, China. It is known for research contribution in the topics: Computer science & Control theory. The organization has 67002 authors who have published 73507 publications receiving 975691 citations. The organization is also known as: Beijing University of Aeronautics and Astronautics.

A highly stretchable, super-hydrophobic strain sensor based on polydopamine and graphene reinforced nanofiber composite for human motion monitoring

Abstract: Much attention has been given to flexible electronic devices in recent years. Conductive polymer composites (CPCs) have been utilized to fabricate strain sensors owing to their lightweight and high flexibility. It is a great challenge to develop flexible and wearable strain sensors with light weight, good skin affinity and gas permeability, high sensitivity and excellent corrosion resistance. In this work, electrospun thermoplastic polyurethane (TPU) nanofibers were first decorated by graphene through ultra-sonication, followed by polydopamine (PDA) modification and then hydrophobic treatment with 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT). The obtained electrical conductive polymer nanofiber composites (CPNCs) have a hierarchical polymer core/graphene shell structure and exhibit super-hydrophobicity even under harsh environments. The introduction of PDA not only improves the interfacial interaction between individual graphene sheets but also the interaction between graphene and the TPU nanofibers. Their mechanical properties including Young's modulus, tensile strength and elongation at break are significantly improved, compared to those of TPU nano-fibrous membranes. When CPNC is used as a strain sensor, it displays high stretchability, controllable sensitivity, excellent cyclical stability and durability. Hence, the nanofiber composite based strain sensor can be attached on the skin for precise monitoring of different human motions, such as tiny and large body movements and thus has promising applications in wearable devices.

Generic gamma correction for accuracy enhancement in fringe-projection profilometry

Abstract: Fringe-projection profilometry is one of the most commonly used noncontact methods for acquiring the three-dimensional (3D) shape information of objects. In practice, the luminance nonlinearity caused by the gamma effect of a digital projector and a digital camera yields undesired fringe intensity changes, which substantially reduce the measurement accuracy. In this Letter, we present a robust and simple scheme to eliminate the intensity nonlinearity induced by the gamma effect by combining a universal phase-shifting algorithm with a gamma correction method. First, by using three-step and large-step phase-shifting techniques, the gamma value involved in the measurement system can be detected. Then, a gamma pre-encoding process is applied to the system for actual 3D shape measurements. With the proposed technique, high accuracy of measurement can be achieved with the conventional small-step phase-shifting algorithm. The validity of the technique is verified by experiments.

Unidirectional Wetting Properties on Multi-Bioinspired Magnetocontrollable Slippery Microcilia.

Abstract: Here, a smart fluid-controlled surface is designed, via the rational integration of the unique properties of three natural examples, i.e., the unidirectional wetting behaviors of butterfly's wing, liquid-infused “slippery” surface of the pitcher plant, and the motile microcilia of micro-organisms. Anisotropic wettability, lubricated surfaces, and magnetoresponsive microstructures are assembled into one unified system. The as-prepared surface covered by tilted microcilia achieves significant unidirectional droplet adhesion and sliding. Regulating by external magnet field, the directionality of ferromagnetic microcilia can be synergistically switched, which facilitates a continuous and omnidirectional-controllable water delivery. This work opens an avenue for applications of anisotropic wetting surfaces, such as complex-flow distribution and liquid delivery, and extend the design approach of multi-bioinspiration integration.

Recent development in studies of alternative jet fuel combustion: Progress, challenges, and opportunities

Abstract: With the growing air transport demand and concerns about its environmental impacts, alternative jet fuels derived from non-conventional sources have become an important strategy for achieving a sustainable and green aviation. In the past 10 years, governments around the world along with aviation industry have invested significant efforts into exploring all sorts of alternative jet fuels that can be used to power aircraft engines. Among all the alternative jet fuels explored, the aviation sector has agreed that hydrocarbon-based ‘drop-in’ replacement fuels, which are fully interchangeable and compatible with current conventional jet fuels, would be the best choice in the near future, as they can be used without any modifications to today׳s aircraft or fuel infrastructure. This paper reviews the current state of development of ‘drop-in’ alternative jet fuels including various Fisher–Tropsch synthetic jet fuels and bio-jet fuels. Recent advances in research activities on alternative jet fuels, including fuel property evaluations, combustor component tests, engine tests, and flight tests, are highlighted. Furthermore, basic research needs for understanding the combustion characteristics of alternative jet fuels are underlined and discussed by reviewing recent fundamental combustion studies on ignition, extinction, flame propagation, emissions, and species evolution of various conventional and alternative jet fuels. Recognizing that the use of ‘simpler’ surrogate fuels to emulate the behavior of ‘complex’ alternative jet fuels is of fundamental and practical importance for the development of physics-based models to enable quantitative emissions and performance predictions using combustion modeling, recent studies on surrogate formulation for alternative jet fuels are also reviewed and discussed. This review concludes with a brief discussion of future research directions.