Smart computing approach for design and scale-up of conical spouted beds with open-sided draft tubes

Open-sided draft tubes provide an optimal gas distribution through a cross flow pattern between the spout and the annulus in conical spouted beds.The design,optimization,control,and scale-up of the spouted beds require precise information on operating and peak pressure drops.In this study,a multi-layer perceptron(MLP)neural network was employed for accurate prediction of these hydrodynamic characteristics.A relatively huge number of experiments were accomplished and the most influential dimensionless groups were extracted using the Buckingham-pi theorem.Then,the dimensionless groups were used for developing the MLP model for simultaneous estimation of operating and peak pressure drops.The iterative constructive technique confirmed that 4-14-2 is the best structure for the MLP model in terms of absolute average relative deviation(AARD%),mean square error(MSE),and regression coefficient(R²).The developed MLP approach has an excellent capacity to predict the transformed operating(MSE=0.00039,AARD%=1.30,and R²=0.76099)and peak(MSE=0.22933,AARD%=11.88,and R2=0.89867)pressure drops.     

Effective enhanced model for a large deformable soft pneumatic actuator

Soft pneumatic actuators have been widely used for implementing sophisticated and dexterous movements,due to numerous fascinating features compared with their rigid counterparts.Relatively speaking,modeling and analysis of an entire soft pneumatic actuator considering contact interaction between two adjacent air chambers is extremely rare,which is exactly what we are particularly interested in.Therefore,in order to establish an accurate mechanical model and analyze the overall configuration and stress distribution for the soft pneumatic actuator with large deflection,we consider the contact interaction of soft materials rather than hard materials,to produce an effective enhanced model for soft contact of a large deformable pneumatic actuator.In this article,a multiple-point contact approach is developed to circumvent the mutual penetration problem between adjacent air chambers of the soft actuator that occurs with the single-point contact approach employed in linear elastic rigid materials.In contrast to the previous simplified rod-based model that did not focus on contact interaction which was adopted to clarify the entire deformation of the actuator,the present model not only elaborates nonlinear large deformation and overall configuration variations,but also accurately delineates stress distribution law inside the chamber structure and the stress concentration phenomenon.By means of a corresponding static experiment,a comparison of the simulation results with experimental data validates the effectiveness and accuracy of this model employing a multiple-point contact approach.Excellent simulation of the actual bending deformation of the soft actuator is obtained,while mutual penetration is successfully circumvented,whereas the model with single-point contact cannot achieve those goals.Finally,as compared with the rod-based model,the results obtained using the proposed model are more consistent with experimental data,and simulation precision is improved.     

Application of micro-morphology in the physical characterization of urban road dust

Urban road dust was collected from Vellore City,Tamil Nadu,India,and analyzed.Scanning electron microscopy(SEM)was used to examine road dust from nine sampling locations in the study region.SEM image analysis was used to identify various shape factors of collected dust particles.The equivalent spherical diameter of most particles was between 10μm and 30μm.Fine particles had greater concentrations at locations with higher traffic flow.Particles were categorized into four classes based on their shape factors,viz.,spherical,mineral,elongated,or irregular.Spherical particles had the smallest mean equivalent diameter(1.95μm)and mineral particles had the largest diameter(33.3μm).Spherical particles made up the smallest portion of road dust(0-12%)in the study region and mineral particles made up the largest(45-65%).Elongated and irregular particles,each made up 23-30%of road dust.Electron dispersive X-ray spectroscopy analysis was used to identify the elemental composition of dust particles.Spherical particles were mostly from combustion sources and mineral particles were largely of crustal origin.No individual source was found for irregular and elongated particles.Biological debris was the major source of irregular particles.     

Efficient algorithm for 3D bimodulus structures

The bimodulus material is a classical model to describe the elastic behavior of materials with tension-compression asymmetry.Due to the inherently nonlinear properties of bimodular materials,traditional iteration methods suffer from low convergence efficiency and poor adaptability for large-scale structures in engineering.In this paper,a novel 3D algorithm is established by complementing the three shear moduli of the constitutive equation in principal stress coordinates.In contrast to the existing 3D shear modulus constructed based on experience,in this paper the shear modulus is derived theoretically through a limit process.Then,a theoretically self-consistent complemented algorithm is established and implemented in ABAQUS via UMAT;its good stability and convergence efficiency are verified by using benchmark examples.Numerical analysis shows that the calculation error for bimodulus structures using the traditional linear elastic theory is large,which is not in line with reality.     

Tailoring particle shape for enhancing the homogeneity of powder mixtures:Experimental study and DEM modelling

The effect of particle shape modification on the segregation reduction of enzyme granules in laundry detergent powder mixtures was investigated,both experimentally and computationally using Deseret Element Method(DEM).The shape of modified enzyme particles was in such a way that the large and dense enzyme particles were layered by other fine particles in the detergent powder,by means of a process known in the literature as“seeded granulation”.It is found that the homogeneity of modified enzyme particles could be improved significantly comparing to the original spherical enzyme particles in powder mixtures.Overall,the results of this research demonstrated that the segregation-induced properties of the dense/spherical enzyme particles could be lowered by altering their shape,which could enable the enzyme particles to behave almost similar to other ingredients during the pile formation process.     

Theoretical analysis on elastic buckling of nanobeams based on stress-driven nonlocal integral model

Several studies indicate that Eringen's nonlocal model may lead to some inconsistencies for both Euler-Bernoulli and Timoshenko beams, such as cantilever beams subjected to an end point force and fixed-fixed beams subjected a uniform distributed load. In this paper, the elastic buckling behavior of nanobeams, including both EulerBernoulli and Timoshenko beams, is investigated on the basis of a stress-driven nonlocal integral model. The constitutive equations are the Fredholm-type integral equations of the first kind, which can be transformed to the Volterra integral equations of the first kind. With the application of the Laplace transformation, the general solutions of the deflections and bending moments for the Euler-Bernoulli and Timoshenko beams as well as the rotation and shear force for the Timoshenko beams are obtained explicitly with several unknown constants. Considering the boundary conditions and extra constitutive constraints, the characteristic equations are obtained explicitly for the Euler-Bernoulli and Timoshenko beams under different boundary conditions, from which one can determine the critical buckling loads of nanobeams. The effects of the nonlocal parameters and buckling order on the buckling loads of nanobeams are studied numerically, and a consistent toughening effect is obtained.     

Towards multi-fidelity simulation of flows around an underwater vehicle with appendages and propeller

Flow around a real-life underwater vehicle often happens at a high Reynolds number with flow structures at different scales from the boundary layer around a blade to that around the hull. This poses a great challenge for large-eddy simulation of an underwater vehicle aiming at resolving all relevant flow scales. In this work, we propose to model the hull with appendages using the immersed boundary method, and model the propeller using the actuator disk model without resolving the geometry of the blade. The proposed method is then applied to simulate the flow around Defense Advanced Research Projects Agency(DARPA) suboff. An overall acceptable agreement is obtained for the pressure and friction coefficients. Complex flow features are observed in the near wake of suboff. In the far wake, the core region is featured by a jet because of the actuator disk, surrounded by an annular region with velocity deficit due to the body of suboff.     

厚度与加载速率对铁素体钢断裂韧性影响的SP压杆法实验研究

采用SP压杆实验方法,在常温下研究小圆薄片断裂韧性的厚度效应及加载速率对断裂特性的影响.实验结果表明,随着厚度的增加,断裂变形能增加,断裂部分的外表面因双向应力状态表现出微突起,微突起四周存在微小裂纹;随着加载速度的增加,断裂变形能增加,剪切断裂表面表现出从密集韧窝到韧窝连接成片特征.考虑试件变形过程中不同部分的能量耗散,从SP试件的整体断裂变形能得到试件的断裂韧性的宏观表达,断裂韧性随着厚度的增加而增加,随着加载速度的增加而减少.采用临界塑性断裂应变作为裂纹起裂判据,单位面积的能量耗散率作为裂纹扩展和失效判据的断裂模型,用有限元方法对SP压杆实验进行模拟,得到与实验结果比较相符的模拟结果.     

基于UKF的GPS/SINS伪距(伪距率)组合导航系统设计

采用位置、速度组合的GPS/SINS组合导航系统由于GPS各量测量之间的相关性,影响了组合导航的整体精度.为了提高组合导航的精度和可靠性,采用了直接利用GPS接收机原始测量信息伪距、伪距率的组合方式.UKF(Unscented Kalman Filter)是针对非线性模型的滤波方法,它避免了对非线性方程线性化的过程,具有较高的精度和较好的鲁棒性.将UKF滤波方法应用于伪距、伪距率的组合导航系统中,并将UKF与卡尔曼滤波和自适应滤波方法进行了仿真比较研究.实验结果表明,UKF位置、航向估计的精度都要优于卡尔曼滤波和自适应滤波,使整个导航系统具有更高的精度和可靠性.     

Reaction performance of fluidized bed catalytic reactor of Group C+particles

Group C particles are often regarded as non-fluidizable but have proven to effectively fluidize with nanoparticle addition,which results in small bubbles and a high gas holdup in the dense phase during the experiments.Group C⁺particles provide an increased surface area for gas-solid contact and improve the reaction performance,especially for gas-phase catalytic reactions.On the basis of a previous study of the ozone decomposition reaction using Group C⁺particles,a two-phase model was used to evaluate the reactor contact efficiency,and was used to compare the partial oxidation performance of the n-butane to maleic anhydride reaction in fluidized-bed catalytic reactors of Group C⁺and Group A particles.The reactor with Group C⁺particles achieved a higher n-butane conversion and MAN yield compared with that using Group A particles,based on the identical catalyst quantity or on the same gas residence time.Therefore,the reactor with Group C⁺particles can achieve the same reaction conversion and yield with fewer catalysts or a smaller reactor size,or both.Therefore,the fluidized bed catalytic reactor of Group C⁺particles is expected to be of major significance in industrial processes,especially for gas-phase catalytic reactions.