Xiantao Cai

A method for topological entity correspondence in a replicated collaborative CAD system

In order to utilize the potential advantages of replicated collaborative CAD system to support natural, free, fast and less-constrained multi-user human-to-human interaction, a local-locking mechanism, which can provide fast modeling response, is adopted as concurrency control mechanism for a replicated on-line collaborative CAD system. A human-human interactive modeling is achieved by immediate local execution of modeling operations and exchange of modeling operations across all collaborative sites real-time. In particular, an approach to achieve topological entity correspondence across collaborative sites during modeling procedure, which is critical to guarantee the correctness and consistency of collaborative modeling result, is proposed. A prototype system based on the ACIS geometric modeling kernel is implemented to verify availability of the proposed solution.

A hybrid optimization approach for sustainable process planning and scheduling

Process planning and scheduling are important stages in manufacturing, and good strategies can significantly improve the energy performance of manufacturing to achieve sustainability. In this paper, an innovative optimization approach has been developed to facilitate sustainable process planning and scheduling. In the approach, honeybee mating and annealing processes are simulated to optimize multi-objectives including energy consumption, makespan, and the balanced machine utilization. Experiments on practical cases show that the optimization results from this approach are promising in comparison with those from a genetic algorithm, a honeybee mating optimization algorithm, ant colony optimization, and a simulated annealing algorithm, respectively.

Efficient Random Saliency Map Detection

Most image retargeting algorithms rely heavily on valid saliency map detection to proceed. However, the inefficiency of high quality saliency map detection severely restricts the application of these image retargeting methods. In this paper, we propose a random algorithm for efficient context-aware saliency map detection. Our method is a multiple level saliency map detection algorithm that integrates multiple level coarse saliency maps into the resulting saliency map and selectively updates unreliable regions of the saliency map to refine detection results. Because of the randomized search, our method requires very little additional memory beyond that for the input image and result map, and does not need to build auxiliary data structures to accelerate the saliency map detection. We have implemented our algorithm on a GPU and demonstrated the performance for a variety of images and video sequences, compared with state-of-the-art image processing.

Encryption based partial sharing of CAD models

Model security for collaborative product development ina networked environment (or called networked manufacturing, grid manufacturing, and cloud manufacturing) is an important and also challenging research issue. An encryption based partial sharing approach for CAD models has been developed and presented in this paper. First, a random invertible decimal matrix to support the encryption approach is proposed, with which parts of a CAD model can be selected flexibly by the model owner for encrypting by different keys; Second, in order to guarantee the security, a dual-key mode and a key based authorization mechanism are proposed. Based on the model, different levels of security are achieved based on different key spaces, and the key based authorization mechanism is used for the model owner to control the partial access of the CAD model flexibly.

Using procedure recovery approach to exchange feature-based data among heterogeneous CAD systems

Data exchange is one of key issues in collaborative design. The purpose of feature-based data exchange is that the target model is editable after being exchanged. This is the reason why nowadays feature-based data exchanges become the research focus beyond the traditional geometry-based data exchange. This paper presents a two-stage mechanism to recover a complete modeling process of a parametric CAD mode in source systems. Therefore, what we exchange is the procedure of modeling steps. In target systems, we use the exchanged procedure to simulate a real human to reconstruct the parametric CAD mode in any heterogeneous CAD systems. The proposed method has been tested with case studies among typical CAD systems, such as SolidWorks, UG, Pro/E and Catia.

Collaborative Naming for Replicated Collaborative Solid Modeling System

In this paper, a framework of full replicated collaborative solid modeling and a method for multi-user interaction to support natural, free, fast and less-constrained multi-user human-to-human interaction is proposed. Particularly, the challenges and problems of topological entity correspondence by name across collaborative modeling sites in replicated CSM system is analyzed. And a method to achieve name correspondence during collaborative modeling sessions in replicated CSM system is proposed. The proposed method is tested in a prototype system of replicated CSM, which employs ACIS as the geometric modeling kernel and adopts winsocket API for communication purpose, developed by our research group.Copyright

CAD data exchange based on the recovery of feature modelling procedure

Feature-based data exchange (FBDE) among CAD systems is one of the most important problems in collaborative product development. In this article, we present a procedure recovery-based solution for FBDE. The main difference between our solution and previous approaches is that a peer-to-peer architecture is adopted and the feature modelling procedure is recovered to retrieve the information that exists in the procedure. Our approach is composed of three key steps. First, in a source CAD system, first-order feature information is retrieved from a feature model. Then, the retrieved first-order feature information is used to recover the feature modelling procedure in the source CAD system and second-order feature information is retrieved during the procedure recovery. Finally, in a target CAD system, the feature model is reconstructed by using the retrieved information. The prototype implementation demonstrates that our approach works well for FBDE among various commercial CAD systems and improves the previous approaches in both the architecture and the retrieval of the procedure.

A multi-user selective undo/redo approach for collaborative CAD systems

The engineering design process is a creative process, and the designers must repeatedly apply Undo/Redo operations to modify CAD models to explore new solutions. Undo/Redo has become one of most important functions in interactive graphics and CAD systems. Undo/Redo in a collaborative CAD system is also very helpful for collaborative awareness among a group of cooperative designers to eliminate misunderstanding and to recover from design error. However, Undo/Redo in a collaborative CAD system is much more complicated. This is because a single erroneous operation is propagated to other remote sites, and operations are interleaved at different sites. This paper presents a multi-user selective Undo/Redo approach in full distributed collaborative CAD systems. We use site ID and State Vectors to locate the Undo/Redo target at each site. By analyzing the composition of the complex CAD model, a tree-like structure called Feature Combination Hierarchy is presented to describe the decomposition of a CAD model. Based on this structure, the dependency relationship among features is clarified. B-Rep re-evaluation is simplified with the assistance of the Feature Combination Hierarchy. It can be proven that the proposed Undo/Redo approach satisfies the intention preservation and consistency maintenance correctness criteria for collaborative systems.

A Direct Feature Retrieval and Reuse Method for Heterogeneous Collaborative CAD Systems

Nowadays a lot of enterprises develop the products collaboratively using heterogeneous CAD systems. Feature based data exchange and interoperation among heterogeneous CAD systems are very important in pervasive computing environments. The key techniques in feature based data exchange are feature retrieval (extraction) and feature reuse (reconstruction). This paper presents a direct approach for feature retrieval and feature reconstruction. At first, most of feature information is directly retrieved by first retrieval mechanism in source systems. Then, the secondary retrieval mechanism acquires related information which can not be retrieved in first retrieval. At last the feature model is reconstructed one by one accurately in target systems by the model reconstruction mechanism.

A honey-bee mating optimization approach of collaborative process planning and scheduling for sustainable manufacturing

The environmental impact of manufacturing processes is closely associated with energy consumption. Decreasing energy consumption of manufacturing processes can significantly improve the environmental performance of manufacturing to obtain sustainability. However, in most manufacturing process planning and scheduling methods, little attention has been paid to the energy consumption. In this paper, an energy consumption model and a honey-bee mating optimization (HBMO) approach have been developed to take the energy consumption into account as an objective to facilitate sustainable manufacturing process planning and scheduling. In the approach, a honey-bee mating process is simulated to achieve the optimization process where makespan and energy consumption are used as the performance criteria. A case study of process planning and scheduling is given. The experimental results are promising and compare well with the final results of the genetic algorithm based optimization approach.