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This paper presents a hybrid simulation (HS) with a proposed substructuring technique that captures the effect of first‐story column local buckling and axial shortening on the frame behavior. The HS is applied to examine the seismic response of a two‐dimensional seven‐story, two‐bay steel dual system. The experimental substructure consists of a full‐scale interior column and beam cruciform subassemblage, including a moderately ductile first‐story built‐up box column and two I‐shaped beams. Under combined axial and lateral loads, local buckling can occur near the column base, resulting in column shortening. The specimen is loaded through a four‐degree‐of‐freedom (DOF) mixed‐mode control (three displacement‐ and one force‐control) actuation system that simplifies the actual complex boundary conditions of the frame structure. To account for column shortening in the HS, a new approach consisting of a set of fictitious equivalent forces applied to columns in the numerical model to achieve compatible displacements with the experiment is implemented. Shortening of the two exterior columns in the model is simulated through finite element analysis using the computer program ABAQUS in an attempt to capture the redistribution of axial loads with column shortening. The test results confirm that the proposed modeling and control methods successfully integrate the experimental substructure and ABAQUS simulation into the HS, resulting in a more realistic frame response that captures the effect of column shortening in the analysis. The moderately ductile built‐up box column is verified to perform well in near‐fault earthquake loadings. [ABSTRACT FROM AUTHOR]

Steel ingot with a large height-to-diameter ratio is utilized to produce multiple products by one stock in practice. Water cooling is a usual way to enhance production efficiency. However, the combination of the two factors will generate internal defects, such as shrinkage porosity and hot crack. The characteristic of internal shrinkage crack in a 10 t water-cooled steel ingot with a large height-to-diameter ratio was examined by an ultrasonic test. A slice was sectioned from the ingot middle part where billets containing star-like crack were further extracted. The billets were examined by X-ray high energy industrial CT, and the compactness was reconstructed in three dimensions. Microstructure near the crack was observed using scanning electron microscopy, and the solidification process and grain size were studied by high temperature confocal microscopy. Moreover, thermomechanical simulation and post-processing were carried out to analyze the formation of shrinkage porosity and hot crack. A new criterion considering mushy zone mechanical behavior in brittle temperature as well as grain size distribution was proposed to evaluate hot cracking potential in the ingot. The results show that a deep shrinkage porosity band easily forms in the center line of such an ingot with a large height-to-diameter ratio, and water-cooling further generates excessive tensile stress tearing the liquid films around the porosities. Then, hot cracks begin to propagate along grain boundaries. The grain size in the upper and center of the ingot is large, which leads to an inverted cone shape defects zone in the ingot center. [ABSTRACT FROM AUTHOR]

Macrosegregation is the major defect in large steel ingots caused by solute partitioning and melt convection during casting. In this study, a three-phase (liquid, columnar dendrites, and equiaxed grains) model is proposed to simulate macrosegregation in a 36-t steel ingot. A supplementary set of conservation equations are employed in the model such that two types of equiaxed grains, either settling or adhering to the solid shell, are well simulated. The predicted concentration agrees quantitatively with the experimental value. A negative segregation cone was located at the bottom owing to the grain settlement and solute-enriched melt leaving from the mushy zone. The interdendritic liquid flow was carefully analyzed, and the formation of A-type segregations in the mid-height of the ingot is discussed. Negative segregation was observed near the riser neck due to the specific relationship between flow direction and temperature gradient. Additionally, the as-cast macrostructure of the ingot is presented, including the grain size distribution and columnar-equiaxed transition. [ABSTRACT FROM AUTHOR]

Macrosegregation as a consequence of solidification of a binary Pb-48 wt% Sn alloy in two-dimensional rectangle cavity was investigated by two-phase model instead of the common used continuum model. The macroscopic transport of mass, momentum, species and energy was coupled with the microscopic descriptions of grain nucleation and growth. The mathematic equations of the two-phase model were discretized on staggered grids and solved by the finite volume method. The final tin concentrations along different heights over the bottom face were compared with the experiment measurements. Simulations with different microstructure parameters (second dendrite arm spacing ( SDAS)) were conducted to ascertain the influence of microstructure on the final macrosegregation. The results show that with the decrease in SDAS value, the drag force as the resistance to relative motion between solid and liquid phase increases, and the macrosegregation during solidification is alleviated. [ABSTRACT FROM AUTHOR]

Although previous studies showed that transthoracic echocardiography (TTE) can be used to guide transcatheter closure of atrial septal defect (ASD), whether TTE can be used to guide transcatheter closure of secundum ASD with a deficient superior-anterior rim is unknown and this critical issue was addressed in the present study. A total of 280 patients with secundum ASD who underwent transcatheter ASD closure were recruited and divided into groups A and B depending on ASD superior-anterior rim>4 mm (n = 118) or ⩽4 mm (n = 162). TTE was used to guide Amplatzer-type septal occluder (ASO) positioning and assess residual shunt. Procedure success was defined as no, trivial and small residual shunt immediately after the procedure as assessed by color Doppler flow imaging. Group A and group B did not differ in complication rate (8.55% vs.7.55%), procedure success rate (98.3% vs. 95.0%) or complete closure rate immediately after the procedure (89.7% vs. 89.3%) or at 6-month follow-up (98.3% vs. 96.8%). The mean procedure and fluoroscopy time in group B were much longer than those in group A. In conclusion, the absence of a sufficient superior-anterior rim in patients undergoing percutaneous closure of secundum-type ASDs using fluoroscopic and TTE guidance is associated with slightly greater device malposition and migration as well as increased procedural and fluoroscopic times, but the overall complication rate did not differ with TTE guidance when compared to historical controls that used TEE guidance. [ABSTRACT FROM AUTHOR]

A two-phase model for the prediction of macrosegregation formed during solidification is presented. This model incorporates the descriptions of heat transfer, melt convection, solute transport, and solid movement on the system scale with microscopic relations for grain nucleation and growth. Then the model is used to simulate the solidification of a benchmark industrial 3.3-t steel ingot. Simulations are performed to investigate the effects of grain motion and pipe shrinkage formation on the final macrosegregation pattern. The model predictions are compared with experimental data and numerical results from literatures. It is demonstrated that the model is able to express the overall macrosegregation patterns in the ingot. Furthermore, the results show that it is essential to consider the motion of equiaxed grains and the formation of pipe shrinkage in modelling. Several issues for future model improvements are identified. [ABSTRACT FROM AUTHOR]

ABSTRACT: The incompressible lattice Bhatnager-Gross-Krook (BGK) model of computational fluid dynamics, from which the unsteady incompressible Navier-Stokes equations can be exactly derived with the limit of small Mach number, was established in continuous casting mold. An asymmetric flow pattern in the two-dimensional central plane of continuous slab casting mold was simulated, and the flow pattern is not stationary but changes over frequently if the Reynolds number is larger than 3000 or so. The results are found to be in excellent agreement with previous experimental results. [Copyright &y& Elsevier]

Prefabrication has drawn wide attention in China during the last decade. However, the market share of prefabricated buildings in China remains comparatively low. The Importance-Performance Analysis approach is employed in this study to investigate the crucial risk factors associated with prefabricated buildings in China. A preliminary list of risks associated with prefabricated buildings in China was developed based on a critical literature review, which was consequently refined by the interview with related experts. A questionnaire survey was then conducted with selected industry professionals to solicit their expert opinions of critical risks associated with prefabricated buildings in China. Findings show that attention should be paid to the following risks: improper decomposition system, low level of factory management, incompetent quality assurance system, deviation in specification of prefabricated components, defects of component system, missing catalogue of building parts and components, poor adaptability of prefabricated building during the operational stage, and lack of actual cases to prove the environmental benefits of prefabricated buildings. This study also revealed the discrepancy between perceived critical risks and those risks with comparatively lower management performance. These findings offer useful inputs for the future development of prefabricated buildings in China and beyond. [ABSTRACT FROM AUTHOR]

A class of measurement phase operators of dual-mode is defined and their properties in a class of entangle coherent states are investigated. Numerical results indicate that the entangle coherent states display some non-classical squeezed effects. [ABSTRACT FROM AUTHOR]