Daido University

About: Daido University is a education organization based out in Nagoya, Japan. It is known for research contribution in the topics: Ultimate tensile strength & Proton exchange membrane fuel cell. The organization has 209 authors who have published 423 publications receiving 3223 citations.

Invited: Transfer and pouring processes of casting by smoothed particle hydrodynamic method

Abstract: The casting process includes the transportation process and the pouring process. The transportation process is to carry the molten metal from the place where it is saved to the mold or the injection molding machine, and the pouring process is to pour and fill molten metal in the mold. In the transportation process, it is undesirable to expose the surface of the molten metal to air to suppress the defect (for instance, generation of the oxidizing layer). Therefore, it is necessary to move to pour it into the mold as soon as possible after the molten metal is bailed out by the ladle. However, it is also necessary to prevent overflow of the molten metal and intervention of air or gas. So the liquid vibration by the acceleration and deceleration of the transfer machine should be suppressed. Then, the development of the technique to control the liquid surface oscillation is needed. Computational fluid dynamics is expected to be effective as the means of the verification. The phenomenon handled here should treat the wall in the container to be a moving boundary, and the liquid surface as a free boundary. In the pouring process, the flow of the molten metal in the mold is the target of interest. Because the quality of a final article of cast is dependent on how the molten metal flows in complex shape of the mold. Also as for this process, the use of numeric fluid analysis on the process including the fission and the fusion on a free surface is expected to be effective. The particle-based fluid analysis methods are considered as the numerical computation technique which is applicable and useful in the treatment of these moving boundary and free boundary. However, quantitative comparative studies with the data of actual transportation and pouring process are few. We have applied the smoothed particle hydrodynamics method to the process of transportation and pouring and validated the results with experimental data. We report on the technique and the result because we saw the experimental data and our numerical results are a good agreement.

SkyCube-Tree Based Group-by Query Processing in OLAP Skyline Cubes

Abstract: SkyCube-tree has been developed to realize efficient range query processing for Skyline Cube (SC). Apart from range queries, this paper demonstrates that SkyCube-tree can be made use of efficient group-by query processing, though it is originally designed to realize efficient range query processing. Since a group-by query for SC includes the entire dataset as its processing range, the query processing time is potentially large. From the experimental evaluation, the followings are clarified: The size of SkyCube-trees is sufficiently allowable, since it is at most 2.5 times as large as that of materialized view. The time of SkyCube-tree based sequential processing is nearly equal to that of materialized view based one, regardless of its dedication to range query processing. The time of SkyCube-tree based parallel processing is comparatively small and stable. Even though cell-granularity is over 80 \(\%\), its processing time is around 10 \(\%\) of that of materialized view based one.

SkyCube-tree based query processing in OLAP skyline cubes

Abstract: Skyline Cube (SC) has been proposed as an extension of Data Cube by using the skyline operator. Although both range queries and group-by queries are useful for decision making support, they impose much burdens upon a query processing system. To cope with the difficulty, this paper presents efficient query processing methods for both type of queries. It is relied on SkyCube-tree, R-tree like hierarchical index structure, which organizes precomputed extended skyline information for processing queries efficiently. According to the performance evaluation, the query processing time for range queries and group-by queries is under 20% and 10% respectively compared with that of each corresponding materialized view based method, within allowable storage size of SkyCube-tree.

Polarity identification of ZnO(0001) surface by reflection high-energy electron diffraction

Abstract: We measured rocking curves of reflection high-energy electron diffraction (RHEED) from ZnO(0001) polar surfaces. It was found that the rocking curves for each Zn- and O-terminated surface differ considerably. The relaxed structure of each polar surface was obtained from first-principles calculations using density functional theory. The results reveal compression relaxation of the top bilayer. Experimental rocking curves of each polar surface have been successfully reproduced by dynamical calculation of RHEED based on their relaxed surface structures. It was demonstrated that the RHEED method can identify the polarity of ZnO(0001) surfaces.

A Comparative Study on Communication Protocols in Disaster Areas with Virtual Disaster Simulation Systems

Abstract: In this paper, we describe a comparative study on communication protocols based on ad-hoc network technologies in disaster situations. In disaster situations, mobility and density of persons are different from those in usual situations. Thus, in order to evaluate communication protocols, we propose a virtual disaster simulation system. In this simulation system, virtual disaster areas are constructed based on hazard maps which are provided for predicting damage of disaster. Virtual disaster areas enables us to conduct experiments for communication systems effectively since we cannot conduct experiments in real disaster situations. By using this simulation system, we compare three protocols from the viewpoints of data gathering performance and power consumption. Experimental results show that our proposed ad-hoc unicursal protocol shows good performance with respect to both viewpoints in disaster situations.