Determination of interfacial heat flux of stainless steel solidification on copper substrate during the first 0.2 s

Interfacial heat transfer is a key issue in many solidification processes. In the paper, a novel experimental apparatus has been designed and on this basis, the instantaneous interfacial heat transfer between molten steel or solidified shell and copper substrate during the first 0.2 s has been studied. The investigated parameters include melt superheat, substrate temperature and surface roughness. The results show that the peak value of the interfacial heat flux in the first stage of liquid/solid contact increases with melt superheat and changes slightly with substrate temperature and surface roughness. The interfacial heat flux in the stage of solid/solid contact has a similar trend of slow decrease in most conditions.     

Industry foundation classes based integration of architectural design and structural analysis

The numerous construction projects in China provide the best environment for the development of information technology applied in building design. Various commercial CAD/CAE software applications are purchased by design firms for multi-disciplinary design tasks. However, researches on integration and interoperability are seldom considered. This study pursues a breakthrough point of integration in the architectural and structural domains and expects further development in other aspects. A central building information modeling (BIM) framework based on the industry foundation classes (IFC) is proposed to handle the data exchange between IFC-compatible architectural models and structural models. A central XML(extensible markup language)-based unified finite element model (FEM) is proposed for model conversion among various commercial structural CAE software applications. In addition to bidirectional data interfaces among IFC-based BIM, XML-based FEM and various commercial FEMs, some other components such as visualization, calculation and model editing/check are also equipped into the prototype system.     

Model test for dynamic construction mechanical effect of large-span loess tunnel

It has been a focus of debate for a large time on construction methods for large-span loess tunnel. Reasonable construction method has much effect on stability of tunnel and construction schedule. Deformation and failure of surrounding rock are quite complex. Associating with the large-span loess tunnel of Zhengzhou—Xi’an high-speed passenger rail line in China, large scale model test with geometric proportion 1:20 is applied to study on dynamic mechanical behavior of various construction methods. They include full-face excavation with support and no support, and benching method with support. It is found that pre-deformation and stress accumulation take place ahead of working face. The effects of three construction methods are further studied, particularly in terms of tunnel displacement and stress changes. It is revealed that benching method transfers load to an unexcavated area, limits horizontal deformation, reduces stress concentration effectively, lengthens the distance between location of peak for stress concentration and working face, and consequently increases stability. The model test results not only supply theoretical foundation for determination of reasonable construction method, but also can act as reference for similar tunnel and underground engineering construction.     

Evaluation and optimization of intersection process between voxelized mesh models and homocentric spheres

In the field of 3D model matching and retrieval, an effective method for feature extraction is spherical harmonic or its mutations, and is acted on the spherical images. But the obtainment of spherical images from 3D models is very time-consuming, which greatly restrains the responding speed of such systems. In this paper, we propose a quantitative evaluation of the whole process and give a detailed two-sided analysis based on the comparative size between pixels and voxels. The experiments show that the resultant optimized parameters are fit for the practical application and exhibit a satisfactory performance.     

Human and bicycle detection system using range sensor

This paper presents a full-scale solution to the detection of the traffic data using laser device. Range images, gathered by a particular laser camera, are used in the multi-threshold segmentation. The multi-threshold segmentation is based on the height of the moving objects. In order to get the precise height of the moving objects, mapping of the original terrain is performed on the first step. On each layer, the clustering algorithm called iteration-self organizing data analysis techniques algorithm (ISODATA) is conducted afterwards. Kalman filtering technique is applied to recognize and track the moving objects. Extensive experiments show that these algorithms are effective in object recognition and tracking, as well as robust in the applications.     

Fusion of remote sensing images based on nonsubsampled contourlet transform and region segmentation

The purpose of remote sensing images fusion is to produce a fused image that contains more clear, accurate and comprehensive information than any single image. A novel fusion method is proposed in this paper based on nonsubsampled contourlet transform (NSCT) and region segmentation. Firstly, the multispectral image is transformed to intensity-hue-saturation (IHS) system. Secondly, the panchromatic image and the component intensity of the multispectral image are decomposed by NSCT. Then the NSCT coefficients of high and low frequency subbands are fused by different rules, respectively. For the high frequency subbands, the fusion rules are also unalike in the smooth and edge regions. The two regions are segregated in the panchromatic image, and the segmentation is based on particle swarm optimization. Finally, the fusion image can be obtained by performing inverse NSCT and inverse IHS transform. The experimental results are evaluated by both subjective and objective criteria. It is shown that the proposed method can obtain superior results to others.     

An efficient threshold key-insulated signature scheme

To tackle the key-exposure problem in signature settings, this paper introduces a new cryptographic primitive named threshold key-insulated signature (TKIS) and proposes a concrete TKIS scheme. For a TKIS system, at least k out of n helpers are needed to update a user’s temporary private key. On the one hand, even if up to k−1 helpers are compromised in addition to the exposure of any of temporary private keys, security of the non-exposed periods is still assured. On the other hand, even if all the n helpers are compromised, we can still ensure the security of all periods as long as none of temporary private keys is exposed. Compared with traditional key-insulated signature (KIS) schemes, the proposed TKIS scheme not only greatly enhances the security of the system, but also provides flexibility and efficiency.     

Looper-tension <Emphasis Type="Italic">H</Emphasis><Subscript>∞</Subscript> control for hot strip finishing mills

The development of an innovative H _∞ controller for looper and tension control in hot strip finishing mills is traced based on approximately linearized model. This solution has been considered thanks to its well-known robustness and simplicity characteristics concerning disturbances’ attenuation. The controller is designed based on an optimal problem with linear matrix inequality (LMI) constraints, and the problem is solved by the mincx function of Matlab LMI Toolbox. Simulation results show the effectiveness of the proposed controller compared with conventional ones.     

Numerical simulation of macrosegregation during steel ingot solidification using continuum model

A continuum model is adopted to study the macrosegregation phenomena during solidification of large steel ingots. Evolution of temperature, melt velocity, and compositional concentration field during a 22 t steel ingot solidification are illustrated by using the finite volume method. Numerical results of temperature distribution are validated by experiments. The influence of local permeability relates to the friction that the melt experienced in mushy region is investigated. It is shown that the continuum model is able to predict the temperature field, and the variation of permeability obviously affects the melt flowing behavior and the final compositional distribution.     

Implementation of dynamic matrix control on field programmable gate array

High performance computer is often required by model predictive control (MPC) systems due to the heavy online computation burden. To extend MPC to more application cases with low-cost computation facilities, the implementation of MPC controller on field programmable gate array (FPGA) system is studied. For the dynamic matrix control (DMC) algorithm, the main design idea and the implemental strategy of DMC controller are introduced based on a FPGA’s embedded system. The performance tests show that both the computation efficiency and the accuracy of the proposed controller can be satisfied due to the parallel computing capability of FPGA.