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For weakly inertial particles subjected to volumetric forces and Stokes drag force in fluid flows, we can solve the simplified particle motion equation using the perturbation method. This method allows us to obtain a recursive formula for the nth-order correction of the asymptotic solution of particle velocity. We verified the error of the asymptotic solution under two typical flow fields: a time-varying uniform flow field with a volumetric force field and a two-dimensional non-uniform cellular flow field. In the former, the relative error of the asymptotic solution of particle velocity and position increases with the Stokes number, and we provided a quantitative analysis of the results. In the latter, we verify and analyze the asymptotic solution from two perspectives: the behavior of a single particle and the collective behaviors of many particles. For asymptotic solutions with maximum velocity and position errors of less than 5%, we select the solution with the lowest order correction and designate it as the optimal asymptotic solution. The order of the optimal asymptotic solution increases with increasing Stokes numbers and motion durations. However, in most cases, for weakly inertial particles [St ∼ O(10−3)], and the time t* ∼ O(10), the first-order asymptotic solution can achieve accuracy, where both St and t* are defined using the flow field characteristic time, Tf = 4π s. The results validate the rationale behind utilizing first-order asymptotic solutions in the fast Eulerian method for turbulent dispersion of weakly inertial particles. [ABSTRACT FROM AUTHOR]

Operating mode identification is an important prerequisite for precise deceptive jamming technology against synthetic aperture radar (SAR). In order to solve the problems of traditional spaceborne SAR operating mode identification, such as low identification accuracy, poor timeliness, and limitation to main lobe reconnaissance, an efficient identification method based on sidelobe reconnaissance and machine learning is proposed in this paper. It can identify four classical SAR operating modes, including stripmap, scan, spotlight and ground moving target indication (GMTI). Firstly, the signal models of different operating modes are presented from the perspective of sidelobe reconnaissance. By setting the parameters differently, such as the SAR trajectory height, antenna length, transmit/receive gain and loss, signal–noise ratio, and so on, the feature samples based on multiple parameters can be obtained, respectively. Then, based on the generated database of feature samples, the initialized neural network can be pre-trained. As a result, in practice, with the intercepted sidelobe signal and the pre-trained network, we can precisely infer the SAR operating mode before the arrival of the main lobe beam footprint. Finally, the effect of SNR and the jammer's position on the identification accuracy is experimentally detailed in the simulation. The simulation results show that the identification accuracy can reach above 91%. [ABSTRACT FROM AUTHOR]

The ambiguity suppression is a technical challenge for the present generation of spaceborne synthetic aperture radar (SAR) systems since this kind of suppression does not take the high spatial resolution and wide coverage into account simultaneously. The transmitting scheme based on the waveform diversity technique is a promising candidate for the conventional (one transmit, one receive channel) SAR systems and has been widely discussed, because it has almost no extra system costs and the ambiguity suppression performance is not closely related to pulse repetition frequency (PRF). However, the accurate method to evaluate the ratio of the intensities of the ambiguities to that of the signal is still a gap. To this end, starting from the precise signal model formulated in this paper, the ambiguity evaluation for spaceborne SAR with waveform diversity has been analyzed in detail. Particularly, the modified azimuth ambiguity-to-signal ratio (AASR) and range ambiguity-to-signal ratio (RASR) formulas are given for the single polarization SARs and quadrature-polarimetric (quad-pol) SARs, which contributes a lot, for the system designer, to precisely evaluating the ambiguity performance. Finally, detailed simulation experiments exploiting the system parameters of the LuTan (LT-1) system are carried out to corroborate the theoretical developments. [ABSTRACT FROM AUTHOR]

A super-resolution reconstruction model for the subgrid scale (SGS) turbulent flow field in large-eddy simulation (LES) is proposed, and it is called the meta-learning deep convolutional neural network (MLDCNN). Direct numerical simulation (DNS) data of isotropic turbulence are used as the dataset of the model. The MLDCNN is an unsupervised learning model, which only includes high-resolution DNS data without manually inputting preprocessed low-resolution data. In this model, the training process adopts the meta-learning method. First, in the a priori test, the SGS turbulent flow motions in the filtered DNS (FDNS) flow field are reconstructed, and the energy spectrum and probability density function of the velocity gradient of the DNS flow field are reconstructed with high accuracy. Then, in the a posteriori test, the super-resolution reconstruction of the LES flow field is carried out. The difficulty of LES flow field reconstruction is that it contains filtering loss and subgrid model errors relative to the DNS flow field. The super-resolution reconstruction of the LES flow field achieves good results through this unsupervised learning model. The proposed model makes a good prediction of small-scale motions in the LES flow field. This work improves the prediction accuracy of LES, which is crucial for the phenomena dominated by small-scale motions, such as relative motions of particles suspended in turbulent flows. [ABSTRACT FROM AUTHOR]

With the explosive growth of data, how to efficiently cluster large-scale unlabeled data has become an important issue that needs to be solved urgently. Especially in the face of large-scale real-world data, which contains a large number of complex distributions of noises and outliers, the research on robust large-scale real-world data clustering algorithms has become one of the hottest topics. In response to this issue, a robust large-scale clustering algorithm based on correntropy (RLSCC) is proposed in this paper, specifically, k-means is firstly applied to generated pseudo-labels which reduce input data scale of subsequent spectral clustering, then anchor graphs instead of full sample graphs are introduced into spectral clustering to obtain final clustering results based on pseudo-labels which further improve the efficiency. Therefore, RLSCC inherits the advantages of the effectiveness of k-means and spectral clustering while greatly reducing the computational complexity. Furthermore, correntropy is developed to suppress the influence of noises and outlier the real-world data on the robustness of clustering. Finally, extensive experiments were carried out on real-world datasets and noise datasets and the results show that compared with other state-of-the-art algorithms, RLSCC can improve efficiency and robustness greatly while maintaining comparable or even higher clustering effectiveness. [ABSTRACT FROM AUTHOR]

Recently, Siamese‐based trackers have drawn amounts of attention in visual tracking field because of their excellent performance. However, visual object tracking on Unmanned Aerial Vehicles platform encounters difficulties under circumstances such as small objects and similar objects interference. Most existing tracking methods for aerial tracking adopt deeper networks or inefficient policies to promote performance, but most trackers can hardly meet real‐time requirements on mobile platforms with limited computing resources. Thus, in this work, an efficient and lightweight siamese tracker (MobileTrack) is proposed for high‐time Unmanned Aerial Vehicles tracking, realising the balance between performance and speed. Firstly, a lightweight convolutional network (D‐MobileNet) is designed to enhance the characterisation ability of small objects. Secondly, an efficient object‐aware module is proposed for local cross‐channel information exchange, enhancing the feature information of the tracking object. Besides, an anchor‐free region proposal network is introduced to predict the object pixel by pixel. Finally, deep and shallow feature information is fully utilised by cascading multiple anchor‐free region proposal networks for accurate locating and robust tracking. Extensive experiments on the three Unmanned Aerial Vehicles benchmarks show that the proposed tracker achieves outstanding performance while keeping a beyond‐real‐time speed. [ABSTRACT FROM AUTHOR]

With the development of automatic measurement and data storage, vast quantities of data can be recorded and analyzed for heat transfer processes, which provides an opportunity to discover the transient heat transfer governing laws from the data. In this study, a machine learning-based sequential threshold ridge regression (STRidge) approach is applied to extract partial differential equations (PDEs) and tested on the heat conduction equation and conductive–convective heat transfer equation subjected to different boundary conditions, data volumes, and noise levels. Moreover, we studied the learning of governing equation of nonlinear transient heat transfer and used the improved STRidge with genetic algorithm to learn PDE with incomplete candidate library. The results showcase highly accurate identification of governing equations for heat transfer. And our results reveal the vast potential of the data-driven method in complex geothermal problems. [ABSTRACT FROM AUTHOR]

An alternate transmitting mode (ATM) is an important synthetic aperture radar (SAR) imaging mode as it can provide rich waveform design degrees of freedom to improve the system performance, especially to mitigate range ambiguities. However, the azimuth ambiguity issue caused by the differences between the autocorrelation functions of transmitted waveforms is ignored in existing studies. In this article, a deep understanding of the ambiguities in the ATM allows a correct evaluation of the ambiguity-to-signal ratio and the design of quasi-orthogonal nonlinear frequency modulation (NLFM) waveforms optimized for ambiguity suppression. Moreover, a novel azimuth compensation method is developed to remove the azimuth ambiguities caused by waveform diversity. Finally, detailed simulation experiments are carried out to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

This article deals with the synthesis and analysis of quasi-orthogonal nonlinear frequency modulation (NLFM) waveforms to mitigate the impairments of ambiguous returns in quadrature-polarimetric (quad-pol) synthetic aperture radars (SARs). To this end, focusing on signals with a continuous piecewise linear instantaneous frequency, the design of a waveform pair exhibiting both a low cross correlation energy (CCE) and low peak to sidelobe ratios (PSLRs), is considered. To handle the resulting nondeterministic polynomial (NP) hard problem, a coordinate descent (CD) method is employed, where, at each step, the marginal minimization is tackled via a MATLAB optimization toolbox. Hence, transmission/reception schemes jointly capitalizing quasi-orthogonal NLFM waveforms and azimuth phase coding (APC) techniques are proposed to suppress ambiguity interference. Moreover, a systematic framework for the evaluation of the resulting azimuth ambiguity-to-signal ratio (AASR) and range ambiguity-to-signal ratio (RASR) is provided. Finally, detailed simulation experiments based on the LuTan (LT-1) parameters are carried out to verify the practicability and effectiveness of the newly proposed transceiver schemes. [ABSTRACT FROM AUTHOR]

In this paper, the free vibration behaviors of composite laminated annular and circular plates under complex elastic boundary constraints are investigated. Firstly, Reddy's high-order shear deformation theory (HSDT) and Jacobi polynomial method are effectively combined to establish the unified vibration analysis model of composite laminated annular and circular plates. Secondly, the simulation of complex elastic boundary and coupling boundary is realized by using artificial virtual spring technology. Then, the energy equation of the composite laminated plate is established by using Rayleigh–Ritz energy technology. Finally, the free vibration solution equation of the laminated plate is obtained through the Hamilton differential principle. The fast and uniform convergence of this method and the accuracy of the calculated results are verified by numerical examples and the model experimental method. On this basis, the parameterization study is conducted, and the effects of material parameters, geometric parameters, spring stiffness values, and lamination scheme on the vibration characteristics of the annular or circular plate are fully discussed, which can provide a theoretical basis for future research. [ABSTRACT FROM AUTHOR]

The echo separation issue associated with different transmit antennas is the most technical challenge in realizing the multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) system. In this article, a novel MIMO-SAR imaging scheme based on an advanced radar waveform, namely, segmented-phase-code (SPC) waveform, is proposed. Compared with the state-of-the-art short-term shift-orthogonal (STSO) waveform beamforming schemes, this scheme relieves the short-term shift-orthogonality condition of transmitted waveforms without losing the imaging performance, which extends the optional waveform space. In this scheme, the separation of the echoes from close arrival angles is ensured by a simple time-shift weighting processing. Furthermore, a range bandpass filter bank and the digital beamforming (DBF) technique are employed to ensure that the echoes from far arrival angles are separable. Finally, detailed simulation experiments are performed to verify the feasibility of the proposed scheme, and in-depth discussions of different waveforms and MIMO-SAR imaging schemes are presented. [ABSTRACT FROM AUTHOR]

Resolvent operator has been increasingly used to investigate turbulent flows and develop control strategies. Recently, Towne et al. (J Fluid Mech 883:A17, 2020) proposed a resolvent-based estimation (RBE) method for predicting turbulent statistics in a channel flow. In this paper, we utilize the RBE method to predict the root-mean-square (RMS) and space–time energy spectra of streamwise velocity fluctuation, where the input is the space–time energy spectra at a reference horizontal plane located in the logarithmic layer and the output is the space–time energy spectra in the buffer layer. The explicit formulas for the RBE method are given in detail for numerical implementation. The results show the capability of the RBE method in the prediction of the convection velocity and bandwidth of the space–time energy spectra. Furthermore, we make a systematic evaluation of the performance of the RBE method by varying the input configurations, including the wall-normal location of the reference plane, the inclusion or exclusion of the pressure as an input variable, the implementation approach of the pressure boundary condition, and the choice of the window function. It is found that the results of both RMS velocity and space–time energy spectra obtained from the RBE method are sensitive to the location of the reference plane. However, the pressure boundary conditions and inclusion of pressure as an input do not cause significant change in the RMS velocity and space–time energy spectra. Although it does not influence the prediction of the RMS velocity, a window function is found crucial in the RBE method for the prediction of the space–time energy spectra. [ABSTRACT FROM AUTHOR]

LuTan-1 (LT-1), i.e., TwinSAR-L, mission is an innovative spaceborne bistatic synthetic aperture radar (SAR) mission that is based on two satellites operating at L-band with flexible formation flying, which is planned to launch in 2020. The primary objective of LT-1 is to generate a highly accurate global digital elevation model (DEM). Beyond that, LT-1 will serve for the demonstration of some state-of-the-art technologies in radar field and some applications, such as biomass inversion, disaster forecasting, and climate and environmental monitoring, and phase synchronization is a technical challenge in realizing the highly accurate topography and deformation measurements. The pulsed alternate synchronization scheme, which is proposed to solve the synchronization problem of TerraSAR-X add-on for Digital Elevation Measurements (TanDEM)-X, is an efficient and accurate method. However, it interrupts the normal work of the TanDEM-X, accordingly flowing a series of problems. For LT-1, a novel synchronization scheme, in which the phase synchronization signal is exchanged by virtue of a time slot between radar signals, is applied. Thus, the working efficiency and synchronization accuracy can further be improved. Furthermore, the performance prediction and phase synchronization experiment for this synchronization scheme is presented, which verifies the feasibility of the proposed scheme. Finally, in order to guarantee the transmission quality of the synchronization signal, the illumination combinations and gain variation of the synchronization antenna in an orbital period are detailed. [ABSTRACT FROM AUTHOR]

With the development of high-resolution radar satellite for global comprehensive environmental monitoring, day-and-night and all-weather surveillance has become an active and growing research field. However, in all cases, these applications require radar to have a high-efficiency radar module (e.g., T/R module), and high system transmitting power. These requirements may put an important limitation on the performance of a radar satellite with a high-power configuration. In this paper, we report a novel waveform optimization framework. Through this framework, an advanced nonlinear frequency modulation (NLFM) waveform with lower sidelobes and a smaller main lobe, which can significantly relieve the restriction of very limited satellite power, is constructed. In addition, we apply it in a real synthetic aperture radar (SAR) system with a bandwidth of 100 MHz at 9.6-GHz carrier frequency and the whole process of the NLFM waveform for radar imaging is discussed in detail, including the system architecture and configuration, a system error compensation method, and a modified chirp scaling algorithm (CSA). The imaging results demonstrate the excellent performance of the advanced NLFM waveform. Moreover, we observe that the SAR system with the advanced waveform has a higher signal-to-noise ratio (SNR) of 1.29 dB compared with the conventional linear frequency modulation (LFM) waveform. The improvement of 1.29-dB SNR means that the real radar system can reduce transmitting power with a ratio of 25%. This effect is likely to be a potential feature of NLFM waveform, which can reduce the transmitting power requirement, especially for radar satellite. [ABSTRACT FROM AUTHOR]

In this paper we discuss an extended kalman filter with novel magnetic vector measurement model for attitude estimation of unmanned aerial vehicles (UAVs). As MARG (Magnetic, Angular Rate and Gravity) sensors are used, this extended kalman filter selects attitude error and angular rate drift as the filter states, and performs the information fusion using the magnetic and gravity vector respectively measured by the three-axis accelerometer and the three-axis magnetometer. We propose a new method of magnetic vector fusion different from the past ones. Firstly, the measured earth magnetic vector is transformed from body frame to local frame using estimate direction cosine matrix. And then the innovation is carefully constructed using the cross product between measured vector and referenced earth magnetic vector, which is different from the past vector subtract way. Finally, the measurement model of magnetic vector and equations of kalman filter is presented. Proposed algorithm is implemented on the Cortex-M4 microprocessor platform and experiments is taken relied on three-axis turntable. The results show that the proposed method has a lower computational cost than the past methods, and is able to track the attitude of motions precisely. [ABSTRACT FROM AUTHOR]

The lattice Boltzmann method (LBM) is coupled with the multiple-relaxation-time (MRT) collision model and the three-dimensional 19-discrete-velocity (D3Q19) model to resolve intermittent behaviors on small scales in isotropic turbulent flows. The high-order scaling exponents of the velocity structure functions, the probability distribution functions of Lagrangian accelerations, and the local energy dissipation rates are investigated. The self-similarity of the space-time velocity structure functions is explored using the extended self-similarity (ESS) method, which was originally developed for velocity spatial structure functions. The scaling exponents of spatial structure functions at up to ten orders are consistent with the experimental measurements and theoretical results, implying that the LBM can accurately resolve the intermittent behaviors. This validation provides a solid basis for using the LBM to study more complex processes that are sensitive to small scales in turbulent flows, such as the relative dispersion of pollutants and mesoscale structures of preferential concentration of heavy particles suspended in turbulent flows. [ABSTRACT FROM AUTHOR]

The response of turbulent enstrophy to a sudden implementation of spanwise wall oscillation (SWO) is studied in a turbulent channel flow via direct numerical simulation. In the beginning of the application of SWO, a significant correlation is formed between ω and ω . A transient growth of turbulent enstrophy occurs, which directly enhances turbulent dissipation and drifts the turbulent flow towards a new lower-drag condition. Afterwards, the terms related to the stretching of vorticity ( ω , ω , and ω ), the inclination of ω by $$\frac{\partial w}{\partial y}$$ , the turn of ω̄ by $$\frac{\partial v\prime}{\partial z}$$ , and the horizontal shear of ω̄ by $$\frac{\partial w\prime}{\partial x}$$ are suppressed due to the presence of SWO, leading to attenuation of the turbulent enstrophy. [ABSTRACT FROM AUTHOR]

Particle-laden turbulent flows are ubiquitous in natural and engineering flows. The preferential concentration and pair-statistics of heavy particles at small and intermediate Stokes numbers are mainly related to the small-scale motions, which are missing in conventional large-eddy simulation (LES). Therefore, studies on the effects of subgrid scale (SGS) motions on particle-pair statistics are significant. This paper will study the effects of SGS motions on the collision-related statistics of a bidisperse system that involves two groups of particles at different Stokes numbers using a direct numerical simulation (DNS), filtered DNS (FDNS) and LES. Compared with a monodisperse system at a single Stokes number, the relative error of the collision rates in the bidisperse system is much smaller than that in the monodisperse one. For given filter widths and Stokes numbers, the relative errors between the FDNS and LES are much smaller than their relative errors to DNS, implying that the error caused by the filtering operation in LES plays a leading role in the overall error of the particle collision rate at Stokes numbers less than 3. A particle SGS model is, thus, necessary to consider the effect of SGS motions on bidisperse heavy particles. [ABSTRACT FROM AUTHOR]

This research work is aimed at proposing models for the hydrodynamic force and torque experienced by a spherical particle moving near a solid wall in a viscous fluid at finite particle Reynolds numbers. Conventional lubrication theory was developed based on the theory of Stokes flow around the particle at vanishing particle Reynolds number. In order to account for the effects of finite particle Reynolds number on the models for hydrodynamic force and torque near a wall, we use four types of simple motions at different particle Reynolds numbers. Using the lattice Boltzmann method and considering the moving boundary conditions, we fully resolve the flow field near the particle and obtain the models for hydrodynamic force and torque as functions of particle Reynolds number and the dimensionless gap between the particle and the wall. The resolution is up to 50 grids per particle diameter. After comparing numerical results of the coefficients with conventional results based on Stokes flow, we propose new models for hydrodynamic force and torque at different particle Reynolds numbers. It is shown that the particle Reynolds number has a significant impact on the models for hydrodynamic force and torque. Furthermore, the models are validated against general motions of a particle and available modeling results from literature. The proposed models could be used as sub-grid scale models where the flows between particle and wall can not be fully resolved, or be used in Lagrangian simulations of particle-laden flows when particles are close to a wall instead of the currently used models for an isolated particle. [ABSTRACT FROM AUTHOR]

Titanium (Ti) has been widely used as orthopedic and dental implants, it is very important to improve the osteogenic activity and antibacterial ability of titanium implants. The objective of this work was to investigate the osteogenic and antibacterial ability of the zinc (Zn) ion implanted Ti at different implantation voltage. X-ray photoelectron spectroscopy results indicate that Zn was successfully implanted into titanium. Zn-implanted titanium surfaces exhibit enhanced cell proliferation ability, alkaline phosphatase (ALP) activity, and partial resistance to both Escherichia coli ( E . coli ) and Staphylococcus aureus ( S . aureus ). The excellent osteogenic and antibacterial ability are highly related to the implantation voltage. The cell proliferation and antibacterial ability can be enhanced by increasing the implantation voltage from 15 kV to 30 kV, indicating that Zn implantation at 30 kV is more beneficial to both osteogenic and antibacterial ability. [ABSTRACT FROM AUTHOR]

Space-time correlation is a staple method for investigating the dynamic coupling of spatial and temporal scales of motion in turbulent flows. In this article, we review the space-time correlation models in both the Eulerian and Lagrangian frames of reference, which include the random sweeping and local straining models for isotropic and homogeneous turbulence, Taylor's frozen-flow model and the elliptic approximation model for turbulent shear flows, and the linear-wave propagation model and swept-wave model for compressible turbulence. We then focus on how space-time correlations are used to develop time-accurate turbulence models for the large-eddy simulation of turbulence-generated noise and particle-laden turbulence. We briefly discuss their applications to two-point closures for Kolmogorov's universal scaling of energy spectra and to the reconstruction of space-time energy spectra from a subset of spatial and temporal signals in experimental measurements. Finally, we summarize the current understanding of space-time correlations and conclude with future issues for the field. [ABSTRACT FROM AUTHOR]

The rotational motion and orientational distribution of ellipsoidal particles in turbulent flows are of significance in environmental and engineering applications. Whereas the translational motion of an ellipsoidal particle is controlled by the turbulent motions at large scales, its rotational motion is determined by the fluid velocity gradient tensor at small scales, which raises a challenge when predicting the rotational dispersion of ellipsoidal particles using large eddy simulation (LES) method due to the lack of subgrid scale (SGS) fluid motions. We report the effects of the SGS fluid motions on the orientational and rotational statistics, such as the alignment between the long axis of ellipsoidal particles and the vorticity, the mean rotational energy at various aspect ratios against those obtained with direct numerical simulation (DNS) and filtered DNS. The performances of a stochastic differential equation (SDE) model for the SGS velocity gradient seen by the particles and the approximate deconvolution method (ADM) for LES are investigated. It is found that the missing SGS fluid motions in LES flow fields have significant effects on the rotational statistics of ellipsoidal particles. Alignment between the particles and the vorticity is weakened; and the rotational energy of the particles is reduced in LES. The SGS-SDE model leads to a large error in predicting the alignment between the particles and the vorticity and over-predicts the rotational energy of rod-like particles. The ADM significantly improves the rotational energy prediction of particles in LES. [ABSTRACT FROM AUTHOR]

Titanium implants possessing simultaneous osseointegration and antibacterial ability are desirable. In this work, three types of Zn/Ag micro-galvanic couples are fabricated on titanium by plasma immersion ion implantation to investigate the osseointegration and antibacterial effects as well as the involved mechanisms. The in vitro findings disclose enhanced proliferation, osteogenic differentiation, and gene expressions of the rat bone mesenchymal stem cells (rBMSCs), as well as good antibacterial ability on all three micro-galvanic couples. Excellent antimicrobial ability is also observed in vivo and the micro-CT and histological results reveal notable osseointegration in vivo despite the presence of bacteria. The Zn/Ag micro-galvanic couple formed on Zn/Ag dual-ion co-implanted titanium shows the best osseointegration as well as good antibacterial properties in vivo obtained from a rabbit tibia model. The difference among the three Zn/Ag micro-galvanic couples can be ascribed to the contact between the Ag NPs and Zn film, which affects the corrosion process. Our results indicate that the biological behavior can be controlled by the corrosion process of the Zn/Ag micro-galvanic couples. [ABSTRACT FROM AUTHOR]

Abstract: Zinc (Zn) and silver (Ag) are co-implanted into titanium by plasma immersion ion implantation. A Zn containing film with Ag nanoparticles (Ag NPs) possessing a wide size distribution is formed on the surface and the corrosion resistance is improved due to the micro-galvanic couples formed by the implanted Zn and Ag. Not only are the initial adhesion, spreading, proliferation and osteogenic differentiation of rBMSCs observed from the Zn/Ag implanted Ti in vitro, but also bacteria killing is achieved both in vitro and in vivo. Electrochemical polarization and ion release measurements suggest that the excellent osteogenic activity and antibacterial ability of the Zn/Ag co-implanted titanium are related to the synergistic effect resulting from the long-range interactions of the released Zn ions and short-range interactions of the embedded Ag NPs. The Zn/Ag co-implanted titanium offers both excellent osteogenic activity and antibacterial ability and has large potential in orthopedic and dental implants. [Copyright &y& Elsevier]

Fractured reservoirs are highly heterogeneous in both matrix and fracture properties, which results in significant variations in well production. Assessing and quantifying the influence of fractures on fluid flow is essential for developing unconventional reservoirs. The complicated effects of fractures in unconventional fractured reservoirs on fluid flow highly depend on fracture geometry, fracture distribution, and fracture properties, which can be reflected in pressure transient testing. The biggest challenge lies in delineating the pre-existing natural fracture distribution pattern, density, azimuth, and connectivity. Using the advanced finite element method, this paper builds a finely characterized near-wellbore model to numerically simulate the pressure transient testing process in naturally fractured reservoirs and further evaluates fracture-related effects to obtain a more accurate solution. First, the numerical program is benchmarked by the analytical solutions and numerical results of Eclipse. Next, different fracture models with single fractures or fracture networks are set up to investigate the effects of fracture parameters numerically (e.g., fracture location, fracture dip angle, fracture spacing, the ratio of fracture permeability to matrix permeability, fracture network orientation, horizontal fracture distribution, etc.) on pressure transient behaviors in naturally fractured reservoirs. Velocity and pressure profiles are presented to visualize and analyze their effects, and new features in the flow regimes of the derivative plots of the bottom-hole pressure are identified and discussed. Finally, based on geological and geophysical data, including image logs, core descriptions, wireline logs, and seismic and well test data, a practical fractured model of the Dalwogan 2 well in the Surat basin is built, analyzed, and compared with homogenous and measured data. The results show significance in characterizing the complex fracture networks in near-wellbore models of unconventional fractured reservoirs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zn was implanted into titanium using plasma immersion ion implantation technology. [•] The Zn-implanted titanium surfaces exhibited excellent osteogenic activity. [•] The Zn-implanted titanium surfaces possessed partly antibacterial effect. [Copyright &y& Elsevier]

This paper is devoted to addressinga multiscale coupling frameworkfor modeling of large-size biomass particle gasification in fluidizedbeds, where the large diffusions due to the temperature and concentrationgradients in large-size particles strongly affect gasification process.Directly incorporating a single particle model (SPM) into a conventionalfluidized-bed model tremendously increases the computational cost.In this paper, we propose a loose coupling framework between the SPMand the discrete element method (DEM)–Eulerian continuum model.The SPM is based on detailed reaction mechanisms and has been validatedagainst experimental results. The rationality of the coupling is basedon the observations from the SPM that the temperature is the dominatingfactor and the surrounding gas velocity is a secondary one to thegasification. For this purpose, we use sand particles as thermal carrierto keep the surrounding temperature statistically stable. We thensimulated the gasification of beech wood particles mixed with sandparticles in a bubbling fluidized bed. The entrainment and mixingof wood particles with sand particles can be observed and the particledistribution and the composition of gas phase can be obtained. Theproposed method provides a potential way to account for the gasificationprocess of large-size biomass particles in fluidized beds. [ABSTRACT FROM AUTHOR]

Particle clustering in turbulent flows is ubiquitousin particle-fluidtwo-phase flows in the riser of fast fluidized beds. Controlling thelevel of clustering is very crucial for improving the reactive efficiencyin such flows. The present paper is devoted to numerically studyingparticle clustering in turbulent flows, where both point particlesand finite-size particles are taken into account, respectively. Apseudospectral method with the particle tracking method is used tosimulate the point particle clustering in the forced isotropic turbulentflows, while the lattice Boltzmann method is used to simulate thefinite-size particles in decaying isotropic turbulent flows. It isobserved that the mean drift velocity, caused by forces such as gravity,could reduce the level of particle clustering for point particles.However, the particle clustering is very weak for the particles ofsizes larger than the characteristic viscous scales of turbulent flows,which is consistent with the previous experimental results. The observationssuggest that the mean drift velocity and particle sizes can be usedto control the level of particle clustering in chemical reactors. [ABSTRACT FROM AUTHOR]

Abstract: We present results of simulations based on a physics-based depositional model of sandstone. The initial rock sediment is modeled as a pack of spherical grains. The absolute permeability is estimated directly from the digitized images of computer-generated rock using lattice-Boltzmann flow simulations. The local connectivity of the pore space is analyzed using the local porosity theory. In the simulated scenarios, the porosity and permeability are reduced by compaction and cementation. The computed porosity–permeability relationships match well the laboratory measurements, and are similar to the power-law of Kozeny–Carman equation. It turns out that the exponent depends on the grain size distribution and cementation pattern. Therefore, it is not universal. The approach and results are also applicable for predicting permeability modification caused by mineral precipitation and chemical reactions in transport problems. [Copyright &y& Elsevier]

Synthetic aperture radar (SAR) systems have the capacity for day-and-night and all-weather surveillance, which has become increasingly indispensable for military surveillance and global comprehensive environmental monitoring. With the development of the high-resolution SAR imaging technique, studies on SAR jamming have also received much interest. Traditional jamming methods are based on linear-frequency-modulated (LFM) signals, and this method can achieve high main-lobe jamming gain. However, its sidelobe jamming energy is very low. To solve this issue, a novel nonlinear frequency modulation (NLFM) waveform design method for SAR jamming is proposed in this paper. Compared with LFM waveforms, the designed waveforms have the same main-lobe jamming gain and very high sidelobes, which can significantly improve jamming performance. Moreover, detailed simulation experiments were carried out to verify the effectiveness of the newly proposed jamming scheme. [ABSTRACT FROM AUTHOR]

Abstract: We develop and compare two formulations of the random-walk method, grain-based and voxel-based, to simulate the nuclear-magnetic-resonance (NMR) response of fluids contained in various models of porous media. The grain-based approach uses a spherical grain pack as input, where the solid surface is analytically defined without an approximation. In the voxel-based approach, the input is a computer-tomography or computer-generated image of reconstructed porous media. Implementation of the two approaches is largely the same, except for the representation of porous media. For comparison, both approaches are applied to various analytical and digitized models of porous media: isolated spherical pore, simple cubic packing of spheres, and random packings of monodisperse and polydisperse spheres. We find that spin magnetization decays much faster in the digitized models than in their analytical counterparts. The difference in decay rate relates to the overestimation of surface area due to the discretization of the sample; it cannot be eliminated even if the voxel size decreases. However, once considering the effect of surface-area increase in the simulation of surface relaxation, good quantitative agreement is found between the two approaches. Different grain or pore shapes entail different rates of increase of surface area, whereupon we emphasize that the value of the “surface-area-corrected” coefficient may not be universal. Using an example of X-ray-CT image of Fontainebleau rock sample, we show that voxel size has a significant effect on the calculated surface area and, therefore, on the numerically simulated magnetization response. [Copyright &y& Elsevier]

Teleservice is a new service pattern that offers various application services and technology resources to clients via the Internet. It promotes cooperation among enterprises through resource-sharing and advantage-reciprocating. This paper proposes a web-based teleservice system that integrates a series of management tools in terms of client, business, project, resource and collaboration. An organizational view of project management, which contains four parts—client, system administrator, project manager and project engineer— is also given; and the responsibility of each part and the connections between them are analyzed. Based on an analysis of the running process of teleservice, methods of configuring project and workflow are put forward, and the workflow templates and node templates are designed to fit different client demands corresponding to their services. Finally, the paper briefly describes system realization and uses injection part development as an example to explain the project management of teleservice. [ABSTRACT FROM AUTHOR]

The paper analyzes characteristics of multidisciplinary collaborative design (MCD) of product and proposes a new MCD-oriented product information model (MCDPM) that integrates physical structure, design semantic and collaboration management data. Better understanding and coordination among the different disciplines can be achieved through the multi-level relations at the semantic level, structure level, and management level. An extended object-oriented method is introduced to represent the MCDPM. As a component and its attributes are all defined recursively in class form, the model can be continually extended and has good modularity, flexibility, and evolution ability. The class inheritance methods in network environment, the concept of discipline view model (DVM) and the method generating the DVM are given. The coordination and consistency maintenance among multiple DVMs is discussed. [ABSTRACT FROM AUTHOR]

Abstract: A multi-scale model for the gas–liquid–solid three-phase fluidized beds is developed on the basis of the principles of the EMMS model. For this purpose, the flowing structure in the gas–liquid–solid system is divided into five phases and considered under different spatial scales: a solid–liquid phase describing the micro-scale interaction between solid particles and liquid, a gas phase, a bubble wake phase and two inter-phases that, respectively, describe the meso-scale interaction of the dispersed bubbles and bubble wakes with the surrounding liquid–solid pseudo-homogeneous suspension. In order to obtain the steady state of such a system with eight unknowns, in addition to seven mass and momentum conservation conditions and an inequality constraint for the mean bubble diameter, the stability condition N st →min is used. The model is solved and checked with the experimental data available in several references which cover a broad range of operating conditions from the conventional expanded fluidized bed to the circulating fluidized bed, indicating that the model is capable of describing the global hydrodynamics of the complex flow in the three-phase system with acceptable accuracy. [Copyright &y& Elsevier]

Abstract: Pulsed fluidization is of considerable interest in process engineering for improving fluidization quality. Quantitative understanding of the pulsed two-phase flow behaviors is very important for proper design and optimum operation of such contactors. The main objective of this study is to understand the mathematical models for liquid pulsed particulate fluidization and its dynamic processes. The state of the arts of the Two-Fluid Model (TFM) and its constitutive relationships are discussed and then, the Local Equilibrium Model (LEM), a simplified version of TFM, is developed and solved for liquid pulsed fluidization. LEM is proposed to describe the liquid pulsed fluidization with acceptable engineering accuracy as compared with the experimental data, and its shortcomings are also discussed at length by analyzing the relaxation processes of the two-phase flow due to a jump change of fluidizing velocity and the structure of concentration discontinuity which forms in the bed collapse process. The main shortcoming of LEM is that some detailed information in the flow fields is lost. However, errors only exist in a time interval of tens of milliseconds (several times of particle relaxation time) and a spatial span of several millimeters (several times of particle diameter). [Copyright &y& Elsevier]

The echo separation issue for multiple-input–multiple-output (MIMO) synthetic aperture radar (SAR) is usually regarded as a more technical challenge. Spotlighted as a promising solution to echo separation, the well-known short-term shift-orthogonal (STSO) beamforming scheme has become increasingly popular. However, for airborne MIMO SAR systems, the digital beamforming (DBF) involved in the STSO scheme usually encounters more issues, e.g., the direction-of-arrival (DOA) mismatch induced by topography variation. Up until now, relatively less research on robust DBF processing has been conducted for airborne MIMO SAR systems. In this respect, an adaptive DBF technique, based on interference plus noise covariance matrix (IPNCM) reconstruction and desired signal steering vector estimation, has been proposed in this article. IPNCM reconstruction and steering vector estimation can not only cope with the DOA mismatch problem but also remove the desired signal component in the training data cells to increase the beamformer convergence rates. Consequently, the proposed approach really improves the array output signal-to-interference-plus-noise ratio (SINR). Moreover, numerous discussions and simulations are carried out to prove the effectiveness of the proposed DBF technique under various disturbance environments. Compared with the current DBF techniques, the proposed method provides a bright application prospect for the STSO scheme. [ABSTRACT FROM AUTHOR]

In recent years, machine learning theory has set off a wave of research in the field of radar signal processing. In this study, a novel algorithm for sea‐surface target detection based on a stacked autoencoder (SAE) is proposed, which has already been applied in the authors' coastal defense radar system. In the proposed algorithm, the sea surface echo data are cut into a large number of two‐dimensional (2‐D) images through a sliding window, mapping the cell under test (CUT) and the 2‐D images one by one and performing classification or detection from the perspective of 2‐D signal processing. Experimental results of simulated data and real radar data show that the proposed algorithm based on the SAE has better target detection performance compared with the traditional cell averaging constant false alarm rate (CA‐CFAR) algorithm. Besides, the proposed algorithm shows certain interference suppression ability in real data processing. As far as it is known, there is no public report on the detection of 2‐D sea surface targets based on the SAE algorithm in coastal defense radar. [ABSTRACT FROM AUTHOR]

A novel method is proposed to combine the wall-modeled large-eddy simulation (LES) with the diffuse-interface direct-forcing immersed boundary (IB) method. The new developments in this method include: (i) the momentum equation is integrated along the wall-normal direction to link the tangential component of the effective body force for the IB method to the wall shear stress predicted by the wall model; (ii) a set of Lagrangian points near the wall are introduced to compute the normal component of the effective body force for the IB method by reconstructing the normal component of the velocity. This novel method will be a classical direct-forcing IB method if the grid is fine enough to resolve the flow near the wall. The method is used to simulate the flows around the DARPA SUBOFF model. The results obtained are well comparable to the measured experimental data and wall-resolved LES results. [ABSTRACT FROM AUTHOR]

A scale-similarity model of a two-point two-time Lagrangian velocity correlation (LVC) was originally developed for the relative dispersion of tracer particles in isotropic turbulent flows (HE, G. W., JIN, G. D., and ZHAO, X. Scale-similarity model for Lagrangian velocity correlations in isotropic and stationary turbulence. Physical Review E, 80, 066313 (2009)). The model can be expressed as a two-point Eulerian space correlation and the dispersion velocity V. The dispersion velocity denotes the rate at which one moving particle departs from another fixed particle. This paper numerically validates the robustness of the scale-similarity model at high Taylor micro-scale Reynolds numbers up to 373, which are much higher than the original values (Rλ = 66, 102). The effect of the Reynolds number on the dispersion velocity in the scale-similarity model is carefully investigated. The results show that the scale-similarity model is more accurate at higher Reynolds numbers because the two-point Lagrangian velocity correlations with different initial spatial separations collapse into a universal form compared with a combination of the initial separation and the temporal separation via the dispersion velocity. Moreover, the dispersion velocity V normalized by the Kolmogorov velocity Vη ≡ η/τη in which η and τη are the Kolmogorov space and time scales, respectively, scales with the Reynolds number Rλ as V/Vη∝Rλ1.39 obtained from the numerical data. [ABSTRACT FROM AUTHOR]

A kinematic simulation with an approximate deconvolution (KSAD) hybrid model is proposed to predict the Lagrangian relative dispersion of fluid particles in a large eddy simulation (LES) of isotropic turbulent flows. In the model, a physical connection between the resolved and subgrid scales is established through the energy flux rate at the filter width scale. Due to the lack of subgrid-scale (SGS) turbulent structures and SGS model errors, the LES cannot accurately predict the two- and multi-point Lagrangian statistics of the fluid particles. To improve the predictive capability of the LES, we use an approximate deconvolution model to improve the resolved scales near the filter width and a kinematic simulation to recover the missing velocity fluctuations beneath the subgrid scales. To validate the proposed hybrid model, we compare the Lagrangian statistics of two- and four-particle dispersion with the corresponding results from the direct numerical simulation and the conventional LES. It is found that a significant improvement in the prediction of the Lagrangian statistics of fluid particles is achieved through the KSAD hybrid model. Furthermore, a parametric study regarding the wavenumbers and orientation wavevectors is conducted to reduce the computational cost. Good results can be obtained using a small number of wavenumber modes and orientation wavevectors. Thus, we can improve the prediction of the Lagrangian dispersion of fluid particles in the LES by applying the KSAD hybrid model at an acceptable computational cost. [ABSTRACT FROM AUTHOR]

The single-, two- and multi-particle dispersions in isotropic turbulent flows are investigated using the direct numerical simulation (DNS), filtered DNS (FDNS) and large-eddy simulation (LES) with a spectral eddy viscosity subgrid scale (SGS) model. The contributions of filtering operation and SGS model to the dispersions are separately studied by comparing the statistics obtained from the three methods. The missing SGS motions in LES can be observed to significantly hinder two-particle and four-particle dispersions if the initial separations are less than or comparable to the filter width. A theoretical analysis of the non-monotonic behavior at short time of the one-time, two-point Lagrangian velocity correlation functions with large initial separations based on the Taylor expansion and the Kolmogorov similarity theory is derived, and the Reynolds number effect on the performance of the spectral eddy viscosity SGS model is also investigated. The results show that the SGS model used performs better with increasing Reynolds numbers. It is concluded that the particle SGS model is needed to be developed to correctly capture the Lagrangian two- and multi-point dispersion statistics of fluid particles. [ABSTRACT FROM AUTHOR]

The origins of early Paleozoic orogen in South China have two different models: subduction model and intra‐continental model. Here we report two new identification of ~440 Ma arc‐related ultramafic intrusions in Tingzifan (TZF) and Fomuting (FMT) along Jiangshan‐Shaoxing fault (JSF) in South China, respectively. The Silurian ultramafic intrusions are composed of olivine pyroxenite, the SiO2, MgO and TiO2 contents of olivine pyroxenites are 39.67–41.25 wt%, 28.98–31.38 wt% and 0.23–0.51 wt%, respectively. The geochemical compositions of the olivines, clinopyroxenes and hornblendes suggest an arc‐related environment for these intrusions. As for the whole‐rock trace elements, the ultramafic intrusions contain low total rare earth element (REE) contents (27.59–34.26 μg/g) and high field strength elements (HFSEs), such as Nb, Zr, Hf, Ti, and are systematically enriched in large ion lithophile elements and light rare earth elements (LREEs). Trace element compositions share most features of Alaskan‐type ultramafic‐mafic intrusions. Isotopically, the TZF and FMT ultramafic intrusions are characterized by negative Zircons εHf(t) values (0.38–7.54). Combined with their whole‐rock and mineral chemistry as well as zircon Hf isotope, we suggest that the Alaskan‐type TZF and FMT pyroxenite were formed at the root of the continental arc by underplating and fractional crystallization of mafic magma which derived from subduction metasomatized mantle source. Thus, we proposed that the early Paleozoic ultramafic–mafic along Jiangshan‐Shaoxing fault were most likely related to early Paleozoic subduction of the Paleo‐South China Ocean between Cathaysia and Yangtze blocks, arguing that the origins of early Paleozoic orogen in the South China Block is a typical subduction‐accretionary collisional‐type orogenic belt rather than an intraplate belt. [ABSTRACT FROM AUTHOR]

We proposed a new analytical solution for a population balance equation for fractal-like agglomerates. The new analytical solution applies to agglomerates with any mass fractal dimensions. Two well-known numerical methods, including the Taylor-series expansion method of moments and the quadrature method of moments, were selected as references. The reliability of the analytical solution with three mass fractal dimensions of 1.0, 2.0, and 3.0 in the continuum-slip regime was verified. The accuracy of the new analytical solution is affected by both the Knudsen number and the mass fractal dimension. The new analytical solution can be further improved in accuracy by introducing a correction factor to the originally derived mathematical formula. The new analytical solution was finally confirmed to possess potential for replacing the numerical solution in the continuum-slip regime. [ABSTRACT FROM AUTHOR]

Polyetheretherketone (PEEK) is desirable in orthopedic and dental applications because its mechanical properties are similar to those of natural bones but the bioinertness and inferior osteoconduction of PEEK have hampered many clinical applications. In this work, PEEK is sulfonated by concentrated sulfuric acid to fabricate a three-dimensional (3D) network. A hydrothermal treatment is subsequently conducted to remove the residues and the temperature is adjusted to obtain different sulfur concentrations. In vitro cell proliferation and real-time PCR analyses disclose enhanced proliferation and osteogenic differentiation of rat bone mesenchymal stem cells (rBMSCs) on the samples with small sulfur concentrations. The in vitro antibacterial evaluation reveals that all the sulfonated samples possess excellent resistance against Staphylococcus aureus and Escherichia coli . The in vivo rat femur implantation model is adopted and X-ray, micro-CT, and histological analyses indicate that not only the premeditated injected bacteria cells are sterilized, but also new bone forms around the samples with small sulfur concentrations. The in vitro and in vivo results reveal that the samples subjected to the hydrothermal treatment to remove excess sulfur have better osseointegration and antibacterial ability and PEEK modified by sulfonation and hydrothermal treatment is promising in orthopedic and dental applications. [ABSTRACT FROM AUTHOR]

A new analytical solution is first proposed to solve the population balance equation due to Brownian coagulation in the continuum-slip regime. An assumption for a novel variable g ( g = m 0 m 2 / m 1 2 , where m 0 , m 1 and m 2 are the first three moments, respectively) is successfully applied in executing a separate variable method for ordinary differential equations of the Taylor expansion method of moments. The sectional method is selected as a reference to verify the new solution. The accuracy between the new solution and Lee et al. analytical solution ( Lee et al., 1997 , Journal of Colloid and Interface Science, 188, 486 – 492) is mainly compared. The geometric standard deviation of number distribution for the new analytical solution is revealed to be limited to 1.6583. Within the valid range of the geometric standard deviation, the new analytical solution is confirmed to solve the population balance equation undergoing Brownian coagulation with the very nearly same accuracy as Lee et al. analytical solution. For the total particle number concentration, the new solution usually yields higher accuracy. The new solution and Lee et al. analytical solution approximately become one solution as the Knudsen number is smaller than 0.1000. The new solution has the potential to become a competitive analytical solution for solving population balance equation regarding its accuracy and very straightforward derivation. [ABSTRACT FROM AUTHOR]

Surface modification of titanium based materials with balanced biological property, i.e. inhibit the adhesion of pathogenic bacteria but promote the positive functions of mammalian cells, is highly desired. Accordingly, titanium was successively treated with magnesium and silver plasma immersion ion implantation & deposition (Mg–Ag PIII&D). Scanning electron microscopy (SEM) observations revealed that nanoparticles were precipitated and bound to the titanium surface after Mg–Ag PIII&D. X-ray photoelectron spectroscopy (XPS) results indicated that these particles are metallic silver. Responses of both bacterial and mammalian cells were studied with Escherichia coli ( E. coli ) and osteoblast-like cell line MG63. The results indicated that the Mg–Ag PIII&D treated titanium inhibits the adhesion and proliferation of E. coli , but promotes the initial adhesion and alkaline phosphatase (ALP) expression of MG63 cells. It can be concluded that the antibacterial and osteogenic activities of titanium can be balanced by simultaneously taking advantage of the biological nature of magnesium and silver. [ABSTRACT FROM AUTHOR]

Multiple-input–multiple-output synthetic aperture radar (MIMO-SAR) has extensive application prospects, mainly including the acquisition of multidimensional scattering information, high-resolution and wide-width (HRWS) imaging, and moving target indication (MTI). Its echo separation is the most technical challenge, and so far, the confirmation for orthogonal waveform encoding MIMO-SAR by airborne experiments has not been reported in any literature. Here, an echo separation experiment based on the segmented phase code (SPC) waveforms and an airborne digital beamforming SAR (DBF-SAR) system is demonstrated for the first time. In the experiment, the SPC waveforms are cyclically transmitted within the adjacent pulse repetition intervals (PRIs) to simulate multiple transmitters, and the scattered echoes are received by the 16-channel antennas in elevation at the same time. In the postprocessing, the echo signals of continuous PRIs are added to obtain the mixed echoes, and a detailed echo separation method is adopted. In the method, the mixed echo signals from close arrival angles and far arrival angles are separated by the time shift and weighting, and by the bandpass filtering and DBF technique, respectively. Through the presented method, the mixed echoes of dual-transmit and 16-receive (2T16R) SAR imaging mode are separated and imaged successfully. The experimental results not only validate the echo separation scheme but also indicate that it is very promising in future MIMO-SAR missions. [ABSTRACT FROM AUTHOR]

Velocity estimation of ocean surface currents is of great significance in the fields of the fishery, shipping, sewage discharge, and military affairs. Over the last decade, along-track interferometric synthetic aperture radar (along-track InSAR) has been demonstrated to be one of the important instruments for large-area and high-resolution ocean surface current velocity estimation. The calculation method of the traditional ocean surface current velocity, as influenced by the large-scale wave orbital velocity and the Bragg wave phase velocity, cannot easily separate the current velocity, characterized by large error and low efficiency. In this paper, a novel velocity estimation method of ocean surface currents is proposed based on Conditional Generative Adversarial Networks (CGANs). The main processing steps are as follows: firstly, the known ocean surface current field diagrams and their corresponding interferometric phase diagrams are constructed as the training dataset; secondly, the estimation model of the ocean surface current field is constructed based on the pix2pix algorithm and trained by the training dataset; finally, the interferometric phase diagrams in the test dataset are input into the trained model. In the simulation experiment, processing results of the proposed method are compared with those of traditional ocean surface current velocity estimation methods, which demonstrate the efficiency and effectiveness of the novel method. [ABSTRACT FROM AUTHOR]

In this paper, we study the issues of modeling, numerical methods, and simulation with comparison to experimental data for the particle-fluid two-phase flow problem involving a solid-liquid mixed medium. The physical situation being considered is a pulsed liquid fluidized bed. The mathematical model is based on the assumption of one-dimensional flows, incompressible in both particle and fluid phases, equal particle diameters, and the wall friction force on both phases being ignored. The model consists of a set of coupled differential equations describing the conservation of mass and momentum in both phases with coupling and interaction between the two phases. We demonstrate conditions under which the system is either mathematically well posed or ill posed. We consider the general model with additional physical viscosities and/or additional virtual mass forces, both of which stabilize the system. Two numerical methods, one of them is first-order accurate and the other fifth-order accurate, are used to solve the models. A change of variable technique effectively handles the changing domain and boundary conditions. The numerical methods are demonstrated to be stable and convergent through careful numerical experiments. Simulation results for realistic pulsed liquid fluidized bed are provided and compared with experimental data. [Copyright &y& Elsevier]