What is the effect of technological shocks? A natural experiment from manufacturing industry in the United States of America from 2000 to 2010

This research studies from a firm level experiment in which we explored an exogenous technological change in firm's productivity. We present evidence from the manufacturing industry in the United States of America from 2000 to 2010, when the artificial intelligence are widely introduced across manufacturing sector. The result suggests that positive technological shocks affect the productivity in a positive way. Analysis of the data shows that the sector effect and the geographical effect exist but both are limited. These results highlight the universal impact of technological shocks and the interplay among innovations, firms and employees

On hydrodynamic characteristics of gap resonance between two fixed bodies in close proximity

The resonant water motion inside a narrow gap between two identical fixed boxes that are in side-by-side configuration is investigated using a two-dimensional (2D) numerical wave tank based on OpenFOAM®, an open source CFD package. Gap resonance is excited by regular waves with various wave heights, ranging from linear waves to strong nonlinear waves. This paper mainly focuses on the harmonic analyses of the free-surface elevation in the narrow gap and wave loads (including the horizontal wave forces, the vertical wave forces and the moments) on the bodies. It is found that the influences of the incident wave height on the higher-order harmonic components of different physical quantities are quite different. The effects of the incident wave height on the reflection, transmission and energy loss coefficients are also discussed. Finally, aiming at the quantitative estimation of the response time and the damping time of gap resonance, two different methods are proposed and verified for the first time on gap resonance.</p

Optimisation of the Hydrodynamic Performance of a wave energy converter in an Integrated Cylindrical WEC-Type Breakwater System

Wave energy converters (WECs) are built to extract wave energy. However, this kind of device is still expensive for commercial utilization. To cut down the cost of WECs by sharing the construction cost with breakwaters, an integrated cylindrical WEC-type breakwater system that includes a cylindrical WEC array in front of a very long breakwater is proposed to extract wave energy and attenuate incident waves. This paper aims to optimize the performance of the integrated cylindrical WEC-type breakwater system. A computational fluid dynamics tool, openfoam®, and a potential flow theory-based solver, HAMS®, are utilized. openfoam® provides viscosity corrections to a modified version of HAMS® in order to accurately and efficiently predict the integrated system’s performance. Parametric studies are conducted to optimize the integrated system, and a novel setup with an extra arc structure is found to significantly improve the performance of the integrated system