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In this work, a new MEMS accelerometer with large detectable range of more than 50 g is designed. Three types of flexure designs were studied: the conventional straight flexure, newly proposed interlapped-L flexure and rectangular flexure. Their dimensions were optimized to achieve the desired requirements of the accelerometer. Capacitive sensing method and electrostatic actuation are selected to be the sensing and actuation methods. Governing equations derived from this model are used to compare with that of a second order spring-mass-damper system. These mathematical models are then used to formulate the various types of sensitivities. Finite Element Analysis software ANSYS is used in the design stage to simulate its dynamic behavior. The accelerometers with interlapped-L flexure and rectangular flexure present very large detectable range of 60 g and 80 g, sensitivity of 23.1 and 17.3 fF/g, with the noise floor of 17.9 and 18.2 μg/(Hz)^1/2 in atmosphere.

Railway sleepers in a track system are usually subjected to a wide range of loading conditions. A critical type of loading condition that causes cracking in the railway concrete sleepers is the dynamic transient wheel force. The transient wheel forces are often due to wheel or rail abnormalities. This paper presents a dynamic finite element model of a railway concrete sleeper in a track system, aimed at raising the consideration of dynamic effects in sleeper design. The railway concrete sleeper is modeled using the beam-on-elastic-foundation theory. Since in the actual tracks the ballast underneath does not provide any tensile resistance, the finite beam elements employed in this investigation take into account the bending and shear deformations, together with the tensionless nature of the elastic support. This paper places emphasis on the effect of the transient periods on the flexural responses of railway sleepers in track systems. Using the robust finite element software STRAND7, the finite element model of the railway concrete sleeper was previously established and validated against experimental data by the authors. The numerical analyses present the ratio between the dynamic and the static bending moment resultants, the dynamic magnification factor, of the railway concrete sleeper under different sinusoidal pulse durations.

The linear and nonlinear flexure analysis of laminated plates with twenty theories with the five variable higher order shear deformation theory (HSDT) is investigated using multiquadratic radial basis function based meshfree method. The mathematical formulation of the actual physical problem of the plate subjected to transverse loading is presented utilizing von Karman nonlinear kinematics. These non-linear governing differential equations of equilibrium are linearized using quadratic extrapolation technique. The different results for deflection and stresses are obtained for thin to a thick plate and compared with some published results. It is observed that some of the theories taken here are well suited for analysis of thin as well as a thick plate while some theories are suited only for thin plates.

To fulfill high-bandwidth and high-accuracy positioning requirements of hard disk drives (HDD), a novel slider-driven 3-dimensional electrostatic microactuator using dual-stage servo system was proposed in this paper. The microactuator is assembled between the suspension and the slider as the secondary actuator, and it is featured with the high aspect ratio 3-D silicon structure, high positioning bandwidth, low driving voltage and good reliability. The electrostatic microactuator has the parallel comb drives and mounting planes in the perpendicular planes, which greatly contributes to the large electrostatic force. The design and selection of the microflexures are crucial to the natural frequency and reliability of the microactuator. The flexure should have high stiffness effects and stiffness ratio. Four different flexure structures have been studied: straight-plate flexure, folded-plate flexure, curvy-plate flexure, and interlapped-L flexure. By analytical and numerical analysis, the interlapped-L flexure presents with higher stiffness effects and better actuation reliability, secondly is the straight-plate flexure. With ANSYS simulation, a servo bandwidth of over 2 kHz and a stroke of ±0.5 μm of the actuator can be obtained by utilizing interlapped-L flexure under a low driving voltage of 30V. It well satisfies the designed objective of the 3-D microactuators.

Cantilever-based piezoelectric has been the most preferred technique for energy harvesting and sensing application due to its simple design. The energy conversion efficiency has been continuously improved by exploring alternative cantilever geometries by increasing the stress distribution on the beam surface. In this paper, we have introduced half elliptical and full elliptical profile modification in the cantilever structure to improve and uniformly distribute the stress at the beam surface. Stress distribution characteristics of the modified cantilever beams were investigated and compared using finite element analysis. Based on the theoretical and finite element analysis, cantilever beams were fabricated using 3D print technology. Fabricated cantilever beams were then used to investigate the piezoelectric performances of polyvinylidene fluoride (PVDF) in composite of barium titanate (BaTiO₃) nanoparticles in the form of electrospun composite nanofibers. FTIR analysis shows successful conversion of alpha phase to beta phase of PVDF and PVDF/BaTiO₃ nanocomposites. During 6Hz cyclic actuating experiment, maximum voltage output of 0.15V and 1.5nA current output were observed. The concept was proposed to replace MEMS-based sensor in hand tremor quantification to assist Parkinson disease management.

The internal force calculation of the raft foundation of high- and low-rise buildings is complicated, and it is affected by many different factors. Consequently, it does not have a uniform calculation method. The internal force change rules for the thick raft foundation must be obtained to consider the effects of the soil, foundation, and complex high-rise building interactions through a large-scale model test. When the raft flexure is less than 0.2‰, the internal force is calculated by a simple local bending moment method. The control index of raft flexure is 0.5‰, which is useful to the designer.