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Fluid–structure interaction (FSI) problems with large fluid deformations can be a great challenge for numerical simulations using conventional methods. In this paper, we propose a novel hybrid approach of an improved Smoothed Particle hydrodynamics and smoothed finite Element Method (SPEM) for modeling FSI problems. In SPEM, the edge-based smoothed finite element method (S-FEM) is developed in Lagrangian frame and is used for the first time to model both elastic structures and incompressible flows. For fluid regions with large deformations, the associated finite elements are adaptively converted into particles and the corresponding regions are subsequently modeled using the decoupled finite particle method (DFPM), which is an improved smoothed particle hydrodynamics (SPH) method suitable for modeling incompressible flows with free surfaces. A ghost particle-based interface algorithm to couple existing S-FEM elements and DFPM particles is developed in SPEM to implement the modeling of FSI problems. As the smoothed FEM and decoupled FPM are enhanced FEM and SPH respectively and DFPM is only used for local fluid regions with large deformations, it is expected that SPEM is more accurate and more efficient than the existing coupling approaches of conventional FEM and SPH. Five numerical examples are tested using the proposed SPEM and the comparative studies with results from other sources reveal that SPEM is an effective approach for modeling FSI problems with large fluid deformations.

In particulate flows, particle-particle collisions play a very important role in determining the flow behavior of the fluid-particle two-phase systems. Thus, it is very important in the numerical simulations of particulate flows to treat the particle-particle interactions with a felicitous method. In this paper, a recently developed direct numerical simulation (DNS) technique, the Finite Element Fictitious Boundary Method (FEM-FBM), for thermal convective particulate flows is used for the simulations of dense particulate suspensions of elliptic shaped particles. The momentum and temperature flow fields are coupled with the aid of Boussinesq approximation. The thermal and momentum interactions between solid and fluid phases are handled by using the Fictitious boundary method (FBM). The continuity, momentum, and energy equations are solved on a fixed Eulerian mesh which is independent of flow features by using a multi-grid finite element scheme. A modified collision model is proposed that can handle not only the interactions between the circular particles but also effectively treat the collisions between the elliptic shaped particles. Firstly, we validate the newly developed collision model for isothermal circular particles together with a comparative study of “drafting, kissing and tumbling” (DKT) motion of both elliptic and circular shaped isothermal particles. Then we investigated the DKT motions of the hot and cold elliptic particles with energy exchange and studied the lateral behavior of the particles in numerous settings. Further, we studied the DKT motion of catalyst particles and investigate the particles behavior at different Grashof numbers. Numerical tests are performed to show that the present method is robust and provides an efficient approach for the simulations of particulate flows with a large number of elliptic particles.

Particulate flows with thermal convection are very challenging to simulate numerically due to the existence of constantly moving boundaries and complex heat-fluid coupling effects. Meshfree and particle methods have special advantages in modeling complex fluid flows with moving boundaries. However, previous works based on meshfree modeling mainly focused on either particulate flows only with momentum exchange or natural thermal convection. In this paper, a finite particle method integrated with particle shifting technique (FPM-PST) is developed for modeling particulate flows with thermal convection. FPM is an improved smoothed particle hydrodynamics (SPH) method with better accuracy while extremely irregular particle distribution may lead to ill-conditioned corrective matrix and terminate the simulation. PST can achieve regular particle distribution through shifting highly disordered particles while current PST is based on conventional SPH of poor accuracy. A number of numerical examples demonstrated that FPM-PST is a novel approach for modeling thermal particulate flows with good performance in accuracy and stability. It has better accuracy than the conventional SPH and can obtain comparable results with those from other sources. The unphysical voids can also be avoided by FPM-PST. From the FPM-PST simulations, it is observed that at relatively low Reynolds numbers thermal convection between hotter or colder particles and the fluid causes significant increase or decrease in the drag force acting on particles, while the thermal convection has little influence on the particle motion at relatively high Reynolds numbers.

Explosive welding involves processes like the detonation of explosive, impact of metal structures and strong fluid---structure interaction, while the whole process of explosive welding has not been well modeled before. In this paper, a novel smoothed particle hydrodynamics (SPH) model is developed to simulate explosive welding. In the SPH model, a kernel gradient correction algorithm is used to achieve better computational accuracy. A density adapting technique which can effectively treat large density ratio is also proposed. The developed SPH model is firstly validated by simulating a benchmark problem of one-dimensional TNT detonation and an impact welding problem. The SPH model is then successfully applied to simulate the whole process of explosive welding. It is demonstrated that the presented SPH method can capture typical physics in explosive welding including explosion wave, welding surface morphology, jet flow and acceleration of the flyer plate. The welding angle obtained from the SPH simulation agrees well with that from a kinematic analysis.

The coarse-grained rhenium’s deformation behavior under the high-pressure torsion at room temperature, including its structure evolution, is examined. It showed that this refractory HCP-metal behaves like a ductile metal: i.e., it can withstand severe deformation, while the ultra-fine grain structure is forming in the samples.

This paper conducts the simulation of natural convection in a differentially heated square cavity at high Rayleigh numbers by using the smoothed particle hydrodynamics (SPH) method. Due to the decrease of the accuracy and stability, it is challenging for the SPH method to simulate natural convection at high Rayleigh numbers, and there are few reported SPH literatures of natural convection at R a > 10 6 for air (Pr = 0.71). In this study, four integrated SPH models are presented to simulate the natural convection and their accuracy and stability are assessed. These four SPH models are associated with Kernel Gradient Correction (KGC) to improve approximation accuracy and Particle Shifting Technology (PST) to regularize particle distribution while they are different in treating density diffusion and calculating the pressure term. The numerical results show that SPH model_4 (KGC, PST, δ -SPH and asymmetric pressure approximation) is the most suitable for simulating the closed natural convection problems, especially at high Rayleigh numbers. Good agreements with reference solutions are obtained by SPH model_4 for the natural convection at 10 4 ≤ R a ≤ 10 8 . Furthermore, the simulation of natural convection at R a = 10 9 is conducted by SPH model_4. The evolutions of thermal convection are described in detail. It is found that dynamics characteristic reveals that the dominant force is the pressure gradient, rather than the buoyancy force before the quasi-steady state. In addition, the chaotic motion at R a = 10 9 has significant influence to the heat transfer characteristic in the vertical boundary layers.

Novel low temperature sintered Li4Mg3[Ti0.8(Mg1/3Ta2/3)0.2]2O9 (LMT0.8(MT)0.2) ceramics with 1–5 wt% LiF additives were successfully prepared by the solid-state reaction method. The effects of LiF additives on the phase composition, sintering characteristic, microstructure and microwave dielectric properties of LMT0.8(MT)0.2 ceramics were investigated in detail for the first time. The sintering temperature of LMT0.8(MT)0.2 ceramics could be effectively lowered to 950 °C by the addition of LiF. A single rock salt crystalline phase structure belonging to a space group of Fm-3m (No.225) was obtained through X-ray diffraction patterns. Dense uniform morphology was observed at 950 °C for LMT0.8(MT)0.2 ceramics with 3–5 wt% LiF in terms of scanning electron microscopy photographs. Particularly, the LMT0.8(MT)0.2-4 wt% LiF ceramics sintered at 950 °C for 4 h possessed optimum microwave dielectric properties of er = 16.10, Q·f = 114,313 GHz (at 8.18 GHz) and τf = −7.72 ppm/°C. In addition, the excellent chemical compatibility with silver metal electrodes indicated that the LMT0.8(MT)0.2-4 wt% LiF ceramics might be a promising candidate for the low-loss low temperature co-fired ceramics (LTCC) applications in microwave devices.

Liquid sloshing in partially filled containers is widely observed in various engineering systems where the forces exerted by the liquid on tank walls may result in the instability of tank or even a structural failure. To enhance the hydrodynamic damping ratio and consequently decrease the sloshing forces, baffles have been designed as effective internal components inside containers in most of the practical engineering problems. In this work, we numerically investigate the sloshing mitigation using elastic baffles through our recently developed methodology based on the coupling strategy of smoothed finite element method (SFEM) and an improved version of smoothed particle hydrodynamics (SPH) offering better accuracy. First, we simulate a benchmark problem of sloshing flow interacting with an elastic baffle installed in a container, and the numerical results agree well with the experimental data. Further, various cases are conducted to study the sloshing mitigation by using deformable baffles with different configurations and elasticities. Our current observations and findings based on the simulation results demonstrate that the impact pressure on the tank wall is significantly influenced by the geometric orientations and complex configurations of elastic baffles. The timing of sloshing flow impacting on the container wall can be passively controlled by adequately choosing the baffle elasticity. The damping performances of different elastic baffles are quantified by the numerically obtained Pressure- E b a f f l e lines. The relevant analysis in this paper can greatly help explore the effective solutions to mitigate the liquid sloshing in engineering systems.

In this paper, a recently developed direct numerical simulation technique, the Finite Element Fictitious Boundary Method (FEM-FBM) [K. Walayat et al., “An efficient multi-grid finite element fictitious boundary method for particulate flows with thermal convection,” Int. J. Heat Mass Transfer 126, 452–465 (2018)], is used to simulate sedimentation of an elliptic particle with thermal convection. The momentum and temperature flow fields are coupled with the aid of Boussinesq approximation. The thermal and momentum interactions between solid and fluid phases are handled by using the fictitious boundary method (FBM). The continuity, momentum, and energy equations are solved on a fixed Eulerian mesh which is independent of flow features by using a multi-grid finite element scheme. Two validation tests are conducted to show the accuracy of the present method, and then the effects of thermal properties of fluid on the sedimentation of an elliptic particle are studied. It is demonstrated that the dynamics of hot elliptic particle sedimentation depend on the thermal diffusivity and thermal expansion of the fluid. A comparative study of the forces and torque acting on the hot, cold, and isothermal particle is reported. Moreover, different sedimentation modes of hot and cold elliptic particles are identified in an infinitely long channel. The mechanism of transitions of particle settling modes from tumbling to inclined and then to the horizontal mode is discovered. Also, we discovered a new sedimentation mode of the hot elliptic particle in cold fluid, i.e., the vertical mode. Furthermore, buoyancy effects for the catalyst particle are studied at different initial orientations.

Organic light-emitting diodes with 8-hydroxy-quinolinato lithium doped 4′7-diphyenyl-1, 10-phenanthroline as electron transport layer (ETL), and etrafluro-tetracyano-quinodimethane doped 4,4′,4″-tris(3-methylphenylphenylamono) triphenylamine as hole transport layer (HTL) are demonstrated. The conductivity of carrier transport layers with different doping concentration is examined by hole-only and electron-only devices. Compared with the referenced device (without doping), the current efficiency and power efficiency of the p–i–n device are enhanced by approximately 51% and 89%, respectively. This improvement is attributed to the improved conductivity of the transport layers and the efficient charge balance in the emission zone.

An experimental study of non-linear vibrations in a loudspeaker cone was made. The sub-harmonic, super sub-harmonic and beat between them are observed. Our experimental results show that non-linear vibrations in a thin shell are related to bending resonance.

Impurity segregation to grain boundaries in ultra low carbon steel was investigated by Auger electron spectroscopy and SEM during isothermal annealing at 900°C and continuous cooling. The results of isothermal annealing at 900°C show that a concentration peak appears at different times for phosphorus, sulphur, and boron, which is contrary to the equilibrium segregation theory of McLean. The phenomena could be satisfactorily explained by the non-equilibrium segregation theory based on the impurity–vacancy complex mechanism. Under continuous cooling, the segregation concentration at the grain boundary largely depends on the cooling rate. At a low cooling rate the concentration of phosphorus and boron at the grain boundary is higher than that of sulphur, while at the higher cooling rate the concentration of sulphur is higher.

Submicron, single-crystal gallium arsenide (SC-GaAs) actuators have been designed, fabricated, and operated. The fabrication process, called SCREAM-II (single crystal reactive etching and metallization II), uses chemically assisted ion beam etching (CAIBE) and reactive ion etching (RIE) to produce suspended and movable SC-GaAs structures with up to a 25:1 aspect ratio of vertical depth (10 mu m) to lateral width (400 nm). Integrated actuators with predominantly vertical sidewall (PVS) aluminum electrodes are used to move the structures. Silicon nitride is used as an etch mask, structural stiffener, and electrical insulator. An x-y stage with integrated actuators produces controllable x-y displacements of +or-1.8 mu m when a voltage of 54.5 V is applied to either or both of the x and y actuators. The x-y stage resonates for an applied sinewave of 20 V (peak to peak) with f=10.5 kHz and a DC offset of 10 V. The structural vibration amplitude is 0.6 mu m. >

Organic light emitting diodes (OLED) with blue or white emission have been made from a new blue emitting material 9,10-bis(3'5'-diaryl)phenyl anthracene (JBEM). The two devices have the same structure except for a red dye doped in JBEM layer of the white device. The white device shows higher quantum efficiency and more than twice stability than that of the blue device. Mmaximum luminance of 14850cd/m 2 , quantum efficiency of 1.75% and a half lifetime of 2860h at initial luminance of 100cd/m 2 were achieved. This indicates that the doping is very important for improving the EL properties, particularly the stability. With comparison of a blue device from distyrylarylene derivatives, the blue device using JBEM shows 5 times better stability, indicating JBEM is a promising blue emitter.