This paper presents a precise solution to predict the behavior of steel fiber reinforced concrete (SFRC) under the four point bending test (FPBT). All the force components at the beam section (before and after cracking) are formulated by applying these assumptions: a realistic stress-strain model is used for concrete behavior in compression, a linear response is considered for the uncracked tension region in a concrete constitutive model, and an exponential relationship is proposed as a stress-crack opening in the crack region which requires two parameters. Then the moment capacity of the critical cracked section is calculated by using these forces and satisfying equilibrium law at the section. Parametric studies are done on the behavior of SFRC to assess the sensitivity of the solution. Finally, this solution is validated with some existing experimental data. The result shows the proposed solution is able to estimate the behavior of SFRC under FPBT.

This paper deals with the hydration of a blend of Portland cement and activated coal gangue in order to determine the relationship between the degree of hydration and compressive strength development. The hydration process was investigated by various means: isothermal calorimetry, thermal analysis, non-evaporable water measurement, and X-ray diffraction analysis. The results show that the activated coal gangue is a pozzolanic material that contributes to the hydration of the cement blend. The pozzolanic reaction occurs over a period of between 7 and 90 d, consuming portlandite and forming both crystal hydrates and ill-crystallized calcium silicate hydrates. These hydrates are similar to those found in pure Portland cement. The results show that if activated coal gangue is substituted for cement at up to 30% (w/w), it does not significantly affect the final compressive strength of the blend. A long-term compressive strength improvement can in fact be achieved by using activated coal gangue as a supplementary cementing material. The relationship between compressive strength and degree of hydration for both pure Portland cement and blended cement can be described with the same equation. However, the parameters are different since blended cement produces fewer calcium silicate hydrates than pure Portland cement at the same degree of hydration.

Tidal current turbines (TCTs) are newly developed electricity generating devices. Aiming at the stabilization of the power output of TCTs, this paper introduces the hydraulic transmission technologies into TCTs. The hydrodynamics of the turbine was analyzed at first and its power output characteristics were predicted. A hydraulic power transmission system and a hydraulic pitch-controlled system were designed. Then related simulations were conducted. Finally, a TCT prototype was manufactured and tested in the workshop. The test results have confirmed the correctness of the current design and availability of installation of the hydraulic system in TCTs.

In this study, we report an analysis of cylinder head vibration signals at a steady engine speed using short-time Fourier transform (STFT). Three popular time-frequency analysis techniques, i.e., STFT, analytic wavelet transform (AWT) and S transform (ST), have been examined. AWT and ST are often applied in engine signal analyses. In particular, an AWT expression in terms of the quality factor Q and an analytical relationship between ST and AWT have been derived. The time-frequency resolution of a Gaussian function windowed STFT was studied via numerical simulation. Based on the simulation, the empirical limits for the lowest distinguishable frequency as well as the time and frequency resolutions were determined. These can provide insights for window width selection, spectrogram interpretation and artifact identification. Gaussian function windowed STFTs were applied to some cylinder head vibration signals. The spectrograms of the same signals from ST and AWT were also determined for comparison. The results indicate that the uniform resolution feature of STFT is not necessarily a disadvantage for time-frequency analysis of vibration signals when the engine is in stationary state because it can more accurately localize the frequency components excited by transient excitations without much loss of time resolution.

An analytical model for straight hemming was developed based on minimum energy method to study the effect of flanging die corner radius on hemming qualities. In order to calculate plastic strain and strain energy more exactly, the neutral layer of specimen corner after hemming is assumed to be a half ellipse with its major semi-axis unknown. Isotropic hardening rule is adopted to describe bending and reverse bending processes neglecting Bauschinger effect. The model takes into account the material property parameters in order to satisfy a wide application range of different materials. Specimen profile, creepage/growing (roll-in/roll-out) and maximum equivalent strain are predicted, which are greatly influenced by the flanging die corner radius. Experimental facilities were designed and hemming experiments were undertaken. The predicted results of the present analytical model were compared to experimental data as well as finite element (FE) simulation results. It was confirmed that they are in good agreement, and the model can be used to evaluate whether the material used as an outer panel for hemming is appropriate and to optimize process parameters when the material used for hemming is changed.

Inspired by the successful applications of biological non-smoothness, we introduced bionic non-smooth surfaces as appendices into vehicle body design, aiming to further reduce aerodynamic drag. The size range of the non-smooth units with pits and grooves was determined according to our analysis with the mechanisms underlying non-smooth unit mediated aerodynamic drag reduction. The bionic non-smooth units reported here were designed to adapt the structure of a given vehicle body from the point of boundary layer control that reduces the burst and the loss of turbulent kinetic energy. The engine cover lid and vehicle body cap were individually treated with the non-smooth units, and the treated vehicles were subjected to aerodynamic drag coefficient simulation tests using the computational fluid dynamics (CFD) analysis method. The simulation results showed that, in comparison with smooth surfaces, properly designed non-smooth surfaces can have greater effects on drag reduction. The mechanism underlying drag reduction mediated by non-smooth surfaces was revealed by further analyses, in which the effects of non-smooth and smooth surfaces were directly compared.

The Arlequin framework proposed by Ben Dhia in 1998 is a flexible and robust method for conducting global/local analysis of structures and materials. A penalty version of the Arlequin framework for the study of structural problems involving large deformation is considered here. The implementation of the penalty-based Arlequin framework into ABAQUS is then explored and the corresponding Arlequin user element subroutine is developed. Geometric nonlinear simulations of a cantilever beam and a shallow arch are conducted and the choice of the coupling operator with an appropriate penalty parameter is studied. The numerical results justify the feasibility of the proposed method, ensuring its further application to more complicated problems involving geometric or material nonlinearities.

ZnNiO thin films with different contents of Ni (0–10 at.%) were fabricated on quartz and Si (100) substrates by pulsed laser deposition (PLD). We measured the samples by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectrometer (UV-VIS), and Hall testing. When the Ni contents were below 3 at.%, partial Zn²⁺ ions were replaced by the Ni²⁺ ions without forming any other phases, which enhanced the conductivity of the film. When the Ni contents were above 3 at.%, Ni ions were at the interstitial sites, and Ni-related clusters and defects were able to emerge in the films, resulting in a worsening of electrical and optical properties. A ferromagnetic hysteresis with a coercive force of approximately 30 Oe was observed in the ZnNiO film with a Ni content of 3 at.% at room temperature.

The simulation of a high-temperature gas-cooled reactor pebble-bed module (HTR-PM) plant is discussed. This lumped parameter model has the form of a set differential algebraic equations (DAEs) that include stiff equations to model point neutron kinetics. The nested approach is the most common method to solve DAE, but this approach is very expensive and time-consuming due to inner iterations. This paper deals with an alternative approach in which a simultaneous solution method is used. The DAEs are discretized over a time horizon using collocation on finite elements, and Radau collocation points are applied. The resulting nonlinear algebraic equations can be solved by existing solvers. The discrete algorithm is discussed in detail; both accuracy and stability issues are considered. Finally, the simulation results are presented to validate the efficiency and accuracy of the simultaneous approach that takes much less time than the nested one.