Wireless passive flexible accelerometer fabricated using micro-electro-mechanical system technology for bending structure surfaces

We propose an inductor-capacitor(LC)wireless passive flexible accelerometer,which eliminates the difficulty in measuring the acceleration on the surface of a bending structure.The accelerometer is composed of a flexible polyimide(PI)substrate and a planar spiral inductance coil(thickness 300 nm),made using micro-electro-mechanical system(MEMS)technology.It can be bent or folded at will,and can be attached firmly to the surface of objects with a bending structure.The principle of radio frequency wireless transmission is used to measure the acceleration signal by changing the distance between the accelerometer and the antenna.Compared with other accelerometers with a lead wire,the accelerometer can prevent the lead from falling off in the course of vibration,thereby prolonging its service life.Through establishment of an experimental platform,when the distance between the antenna and accelerometer was 5 mm,the characterization of the surface of bending structures demonstrated the sensing capabilities of the accelerometer at accelerations of 20-100 m/s2.The results indicate that the acceleration and peak-to-peak output voltage were nearly linear,with accelerometer sensitivity reaching 0.27 mV/(m·s-2).Moreover,the maximum error of the accelerometer was less than 0.037%.

A comprehensive study on the heat transfer characteristics of windward bend lattice frame structure

The windward bend lattice frame structure(WB structure)is characterized by a high heat transfer coefficient and low friction factor.The WB structure can be applied for ther-mal protection system,protecting outer walls of afterburner and nozzles from being damaged by the heating load of hot gas,for air cooling system of the power battery module,dissipating the heat generated during its charging and discharging.In this paper,the heat transfer charac-teristics of the windward bend lattice frame structure have been comprehensively studied.A systematic 3D numerical simulation has been conducted to investigate the effects of the struc-tural parameters of the WB structure,including the pitches in both flow direction and transverse direction,the diameter and the inclination angle of windward bend ligament,on its flow resis-tance and heat transfer enhancement,which has been evaluated by comparing its Nusselt num-ber under an equal pumping power.Furthermore,the contribution of an important parameter,i.e.,the ratio of the interstitial heat transfer rate to the end-wall heat transfer rate(RQ),to the overall heat transfer rate has been fully discussed.As a result,the case of 6 units in the longi-tudinal direction and 2.5 units in the transverse direction,i.e.(nx Z 6,nz Z 2.5)exhibits the best performance in the light of the value of the Nusselt number. Moreover, the structure with aratio of RQ ranges in 4.5e5.0 achieves a better heat transfer performance. Finally, two colorcontour graphs showing an optimal range of Nusselt number coordinated by unit numbers(nx, nz) for pumping powers of 2500 and 3000 have been presented. The graphs correctly reflectthe variation of Nusselt numbers of structures with different nx and nz, and the conclusionsremain consistent with the discussion in sections 4.2 and 4.3, instructing the reasonable selec-tion of structural parameters of a thermal protection system embedded with WB structure.

新型仿颈部多层横向弯曲隔振结构

基于椎间盘和周围肌肉的共同作用,颈部结构在外部振动下可以保持头部稳定.受此启发,本文基于椎间盘构型和肌肉作动机制提出了一种新型仿生多层隔振结构.该结构具有足够的承载能力,并且实现了对0.1~1 Hz范围的超低频激励的振动隔离.首先,在荷载作用下,建立了弯曲变形下的势能、恢复力与单层结构构型的关系;其次,基于非线性隔振结构高承载能力和低动态刚度的需求,提出了满足轴向承载的高阶零刚度设计准则,将该多层隔振结构弯曲振动的有效隔振频带起始点向低频范围扩展至0.08 Hz.结果显示,创新构建的仿生多层隔振结构在超低频段内表现出了显著的动态稳定效果.研究不仅为人类晕车晕船现象提供了生物学解释,还建立了柔性细长结构横向动态稳定的新结构和新方法,因此,其在机械臂、卫星传感器等领域具有显著的应用潜力.

DNA Hydrogels Formed of Bended DNA Scaffolds and Properties Study

In recent years, DNA supramolecular hydrogels have attracted much attention due to their injectability, biocompatibility, responsiveness and self-healing properties. In this work, we designed a linear DNA brick containing one duplex with two cytosine（C）-rich sequence on both ends. This brick can first assemble to form duplex under p H 8 condition. After adjusting the p H to 5, the C-rich sequence tends to form intermolecular i-motif structure, which joins the linear DNA molecules together to form interlocked cyclic structures and yield the DNA hydrogel. By adjusting the length and bending curvature of the duplex part of the molecule, one can change the basic unit of the hydrogel structure to tune the properties of the DNA hydrogel.