Applied Mechanics and Materials Vols. 236-237

Abstract: A new control method based on least squares support vector machine (LSSVM) and model predictive control (MPC) is proposed for the control of fermenter temperature. Existing PID control doesn’t consider the model of controlled object, so it tends to bring steady-state error. The proposed method utilizes LSSVM to obtain fermenter temperature’s model and then uses it to implement MPC. The simulation results show that our method has better control performance than traditional PID control

Abstract: This paper describes a robust algorithm for detecting zebra crossings to provide information for intelligent vehicles’ autonomous navigation in urban environment. First, transform images framed by the camera to the top view by an Inverse Perspective Mapping (IPM); extract the region of interest (ROI) from IPM image by local threshold segmentation. Then, extract datum band from RIO by analysis of every region’s length, direction, as well as mutual relations between the bands; finally, extract all bands belonging to the zebra crossing. The zebra crossing’s distance and direction are easily calculated in the IPM image. Experiments from 6000 street scenes with and without crossings demonstrate the robustness of the proposed algorithm.

Abstract: This paper provided the manufacturing process planning method of the double main spindles for the turn-mill machine based on model volume. Firstly, the cross section information of the 3D grid data model was obtained by using the algorithms of extracting partitions plane information. Secondly, differentiated the cross section shape to recognize the milling and turning process according to extracting partitions plane information. Then, it computed the treated volume in order to obtain equal division plane by extracting partitions plane information. According to readjusting the equal division plane defined the process machining boundary. The boundary divided the complex process workpiece into main and sub spindle process for the double spindles. At last, the machining experiment verifies the adaptability and accuracy of the process planning method.

Abstract: Image segmentation is a classical problem in image processing and image analysis, image-based 3D reconstruction techniques has become a hot research topic segmentation effect directly affects the accuracy of the model after the three-dimensional reconstruction. The complex topography, constitute the main part of the contour of the topology change of the complexity and randomness, it is powerless to describe the shape of the change process parameters of the curve or surface. Thesis level set theory to split the topography image, and laid the foundation for image-based 3D terrain reconstruction.

Abstract: Digital CR of head and neck overcomes the disadvantage of regular X-ray radiography, which can not reveal bone and soft tissue position deficiency in one exposing, and reduces the X-ray radiation dose. Meanwhile, various factors cause the decline of image quality, and images must be enhanced in order to meet demands of doctor's clinical diagnosis. The general enhancement algorithms don’t consider body's structure differences and density characteristics. A new adaptive CR enhancement algorithm was proposed in this article, and head and neck CR images were processed with this method and compared with linear unsharp masking method. The experiment proves that the details of CR image enhanced were abundant and enhanced CR image had good visual effect, SNR was high, as well as detail variance /background variance (DV/BV) indicating that this algorithm is suitable for head and neck CR medical images

Abstract: By using fracture mechanics theory of rock, the rock fragmentation mechanism of tunnel boring machine (TBM) cutters is analyzed and the analysis of forces of cutter is carried out. A new method to predict disc cutter specific energy for TBM is developed in this study. By using the dynamic models of TBM cutters interaction with the rock, specific energy prediction model for TBM cutter head is developed. The data from the actual tunnel construction is analyzed by using an example of Qinling tunnel and the comparison is made with the field data. The results indicate that the model developed in this study could not only replace the experiment to disc cutter specific energy for TBM, but also provide a theoretical basis for the performance prediction and optimal design of cutter head for TBM.

Abstract: In order to solve the problems such as more restriction conditions, complicated interference and longer design periods in the design process of segment erector for Tunnel Boring Machine, it is necessary to study on the kinematics simulation of TBM segment erector. First of all, the kinematics characteristics of segment erector are analyzed; the 3-D model is designed in Pro/E environment; the model is imported into ADAMS and the dynamic simulation is finished finally. After the analysis of simulation of this mechanism, the curves of the speed for the driving parts are obtained and the maximum speeds of driving parts are identified with the method of space search technology. The kinematics characteristics of TBM segment erector are obtained. The simulation results provide an important reference for the mechanism design and type selection design for the power system and design cycle is shortened for TBM segment erector.

Abstract: This study was undertaken to analytically investigate factors which influence the performance of the HSK toolholder-spindle connection. The change of contact area and the contact stress distribution of HSK-A63 toolholder-spindle interface were analyzed with the finite element software ANSYS. The analysis results showed that the contact area and contact stress are significantly affected by clamping force and spindle speed, and that enough magnitude of interference can offset the gap between spindle and toolholder under high rotational speed and also affect the clamping force assigned to the flange face.

Abstract: This study examined the surface defects and surface roughness of optical glass polished by mechanochemical machining. BK7 optical glass material was polished using cerium oxide (CeO₂) solutions of different concentrations and temperatures. During machining, the optical glass specimen was placed between the ceramic working ring and the polishing pad. The effects of slurry concentration and temperature, polishing time, rotational speed and axial load on the surface roughness were examined. Significant improvement in surface roughness could be attained by polishing with CeO₂ slurry of 95^。°C. Both SEM and AFM images of BK7 polished under conditions: slurry concentration, 15%; slurry temperature, 95^。C; rotational speed, 40 rpm; axial loading, 6 kg; and polishing time, 8 min show that the optical glass specimen surface had high transmittancy and became smooth with all scratches removed. The best mechanical properties in terms of Young’s modulus of elasticity and hardness were obtained by polishing with CeO₂ slurry of 60^。C. Although better surface roughness can be attained with further increase in slurry temperature, the enhanced reaction under high slurry temperature undermined the mechanical properties of the glass specimen.

Abstract: Based on the classical theory of welding structure, the welding residual distortion for laser welded sandwich structure was simulated using finite element method(FEM). The results showed that welding front all and then to back may lead to a relatively high welding residual distortion. The maximum distortion in Z-direction is higher than 0.5mm. The distortion can be obviously decreased when the welding sequence is welded from front to back and then back to front alternatively. The maximum distortion in Z-direction is less than 0.1 mm.