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Split Hopkinson Pressure Bar (SHPB) has become a frequently used technique for measuring uni-axial compressive stress-strain relationship of various engineering materials under high strain rates. The pulse shape generated in the incident bar is sensitive to the length of the striker bar. In this paper, a finite element simulation of a Split Hopkinson Pressure Bar is performed to estimate the effect of varying length of striker bar on the stress-strain relationship of a material. A series of striker bars with different lengths, from 200mm to 350mm, are employed to obtain the stress-strain response of AL6061-T6 in both simulation and experiment. A comparison is made between the experimental and the computed stress-strain curves. Finally the influence of variation of striker bar length on the sample's stress-strain response is presented.

Flexible radio-frequency (RF) capacitors and inductors on the plastic substrates have been fabricated and characterized under mechanical bending conditions. A novel method to predict the RF performance for them on different bending states is demonstrated. Artificial neural network (ANN) shows good modeling accuracy for the flexible RF passive components with bending strains from dc to resonant frequency ($\sim 13/2$ GHz for the capacitor/inductor). More importantly, the automatically generated ANN model, with no need of repeatedly tuning the model parameters, has demonstrated the ability to predict the RF responses for the flexible capacitors and inductors under arbitrary bending conditions with only a few sets of experimental data. Once established, this model can automatically learn the structure of the input date and predict the actual results on specific bending state which can provide an original method to measure the performance for flexible electronics on even extreme bent radius. The ANN model indicates good potential for accurate design, characterization and optimization of the high-performance flexible electronics.

Soil has obvious plastic characteristic. In civil engineering, some methods, such as reinforcing with natural fibres or synthetic fibres, are often adopted to strengthen soil's bearing capacity or the ability of deformation resistance. Experiences and studies indicate: length, mixture ratio, toughness and fineness of synthetic fibre have rather great influence on the strength of reinforcement soil. In order to further realize the extent of the influence and achieve relatively explicit quantization relation, taking polypropylene fibre as an example, this paper studied the impact rule of the filling quantity of polypropylene fibre (mixture ratio) on mechanical property of reinforcement soil by doing intensity experiments to plain soil and several classes of reinforcement soils with different fibre contents. As the same time, the empirical equation about soil strength varying with fibre content was established by the method of regression analysis. In the end, by simulating reinforcing status with real fibre reinforcement soil and constituting mechanical model according to various fibre contents, the variation situation of stress and strain of soil under loading was numerically simulated based on the plastic assumption about constitutive relation of soil. The study results can be generalized to engineering practice of various polypropylene fibre reinforcement soils.