Data compression becomes increasingly an important issue for reducing data storage spaces as well as transmis-sion time in network environments. In 3D geometric models, the normal vectors of faces or meshes take a major portion of the data so that the compression of the vectors, which involves the trade off between the distortion of the images and compression ratios, plays a key role in reducing the size of the models. So, raising the compression ratio when the normal vector is compressed and minimizing the visual distortion of shape model's shading after compression are important. According to the recent papers, normal vector compression is useful to heighten com-pression ratio and to improve memory efficiency. But, the study about distortion of shading when the normal vector is compressed is rare relatively. In this paper, new normal vector compression method which is clustering normal vectors and assigning Representative Normal Vector (RNV) to each cluster and using the angular deviation from actual normal vector is proposed. And, using this new method, Visually Undistinguishable Lossy Compression (VULC) algorithm which distortion of shape model's shading by angular deviation of normal vector cannot be identified visually has been developed. And, being applied to the complicated shape models, this algorithm gave a good effectiveness.

Putting a high value on individual preferences is a modern trend that more and more companies are considering for their product design and development and the apartment design is not an exception. Most apartments today are built using similar design with no room for customization. People in general want their tastes to be reflected in the design of their apartment. However, delivering what customers like to the construction company may not be an easy task in practice. For this reason, an intuitive and effective medium between the company and customers for effective communication is needed to ameliorate such a difficulty and in response to this necessity, we developed a test platform for the virtual model house which provides a user with the customization of the apartment using haptic interactions. In our virtual environment, a user can explore an apartment and change the interior based on their taste and feel through intuitive haptic interactions.

Shipbuilding industries have been struggling to reduce production time and cost of their products in many aspects. Manufacturing systems have been changed, new production lines and robots have been installed, and new planning and scheduling systems have been adopted in order to achieve shorter time-to-market and higher productivity. Simulation based manufacturing, digital manufacturing, or virtual manufacturing simulation, whatever the name means, is an approach to achieve such a goal. In order to improve productivity in a shipbuilding process at a shipyard, a digital shipyard development has been driven. This paper proposed how to implement the digital shipyard, what to do with it, and what to obtain from it. This digital shipyard will help simulate and optimize the entire shipbuilding life cycle with its virtual environment through shipbuilding process from the initial development stage to the launch.

Digital Virtual Manufacturing is a technology facilitating effective product developments and agile productions via digital models representing the physical and logical schema and the behavior of real manufacturing systems. A digital virtual factory as a well-designed and integrated environment is essential for successful applications of this technology. In this research, we construct a sophisticated digital virtual factory for the section steel shop in a Korean shipbuilding company by 3-D CAD and virtual manufacturing simulation. The NIST-AMRF CIM hierarchical model and workflow analysis using IDEF methodology are also applied. This digital virtual factory can be applied for diverse engineering activities in design, manufacturing and control of the real factory, and improvements in quality of engineering and savings in time from design to production in shipbuilding are possible.

This paper proposes a modeling and simulation process of a panel production line (PPL) in a shipyard. The panel production line is an assembly process to produce a main panel of a flat block and a curved block. In this paper, its activity analysis is carried out using expression of IDEF0, and its process is qualitatively and quantitatively analyzed and modeled by Petri Nets. A commercial discrete event simulation tool, $QUEST^{TM}$, is used for virtual PPL and simulation. The modeling results by Petri Net are mapped to elements of the simulation tool. Finally, an integrated simulation environment of PPL is implemented in order to efficiently utilize the virtual PPL model. With the help of IDEF0 and Petri Nets, we could systematically analyze and describe the PPL process that are characterized as being concurrent, asynchronous, distributed, parallel, nondeterministic, and/or stochastic. Also, the dynamic and concurrent activities of a PPL system were able to be simulated. A timing concept can be included into the Petri nets model to evaluate performance and dependability issues of the system.

A submarine good military weapon because of its confidentiality and intimidating power. Therefore, training warfighters how to maneuver submarine is very important. Because submarine is very expensive and has regional and temporal limitations, M&S(Modeling and Simulation) can be a good alternative. However, as the existing M&S systems of submarine generally use expensive commercial software and dedicated hardware, which cause the warfighters to take troubles to visit the secured places, and then to train themselves during limited time slots. Also, many M&S systems have only one-channel display system which reduces the sense of immersiveness. Another problem is that many heterogeneous simulators can hardly be used as an integrated system. To solve these problems, X3D, a platform-independent and open standard graphic file format, is used with the general-purpose PCs. To increase immersiveness, multi-channel display system and a motion chair are used. Finally, HLA/RTI is used to integrate individual components of the simulator. All of these are verified through experiments.

The artificial discs have recently used to preserve the motion of the treated segment in lumbar spine surgery. However, there have been lack of biomechanical information of the artificial discs to explain current clinical controversies such as long-term results of implant wear and excessive facet contact forces. In this study, we investigated the biomechanical effects of three artificial implants on the lumbar spinal segments by finite element analysis. The finite element model of intact lumbar spine(L1-S) was developed and the three implants were inserted in L4-L5 segment of the spine model. 5 Nm of flexion and extension moments were applied on the superior plate of L1 with 400 N of compressive load. Excessive motions and high facet contact forces at the surgical level were generated in the all three implanted models. In the flexion, the peak von-Mises stresses in the semi-constrained type implant was higher than those in the un-constrained type implant which would cause wear on the polyethylene core. The results of the study would provide a biomechanical guideline for selecting optimal surgical approach or evaluating the current design of the implants, or developing a new implant.

In spite of rapidly increasing interests in digital manufacturing, there still lacks of a systematic approach in manufacturing line flow analysis via modeling and simulation; currently, the parameters for designing manufacturing line are defined by being solely based on engineers experiences. The paper proposes an application of the genetic algorithm to a discrete event line simulation finding optimal set of parameters for manufacturing line balancing problem. The proposed method has been applied to two example problems-one is a simple manufacturing model and the other for shipyard industry-in order to demonstrate its validity and usefulness.