Concept Of Cube Research Articles

Cubes convexes

In various approaches, data cubes are pre-computed in order to answer efficiently OLAP queries. The notion of data cube has been declined in various ways: iceberg cubes, range cubes or differential cubes. In this paper, we introduce the concept of convex cube which captures all the tuples of a datacube satisfying a constraint combination. It can be represented in a very compact way in order to optimize both computation time and required storage space. The convex cube is not an additional structure appended to the list of cube variants but we propose it as a unifying structure that we use to characterize, in a simple, sound and homogeneous way, the other quoted types of cubes. Finally, we introduce the concept of emerging cube which captures the significant trend inversions. characterizations.

An elasto-plastic finite element model for polyethylene wear in total hip arthroplasty

A new finite element model (FEM) based on an elasto-plastic behavior of ultra high molecular weight polyethylene (UHMWPE) was used to study the wear behavior of UHMWPE acetabular cup, which has a 32 mm diameter femoral head. The model imposed a plastic yield stress of 8 MPa on the UHMWPE so that any stresses beyond this would automatically be redistributed to its neighbor. The FEM model adopted a unique mesh design based on an open cube concept which eliminated the problems of singularities. Wear prediction combined the influences of contact stress, sliding distance and a surface wear coefficient. The new model predicted significantly higher volumetric wear rate (57 mm 3/yr) well within the average reported clinical values. The model was also used to study the effect of friction and clearance between the acetabular cup and the femoral head. Increase in friction increased the volumetric wear rate but did not appear to affect the linear wear rate, which remained at 0.12±0.02 mm/yr. The predicted wear was sensitive to clearance. It was found that when the clearance was close to 0 and >0.5 mm, severe wear occurred. The best clearance range was between 0.1 and 0.15 mm where the average linear wear rate was 0.1 mm/yr and the volumetric wear was 55 mm 3/yr. The present work indicates the importance of avoiding too tight or too loose a diametrical clearance.

An efficient processing of range-MIN/MAX queries over data cube

On-Line Analytical Processing (OLAP) has become a crucial element of decision support systems. Since historical, summarized and consolidated data is used in OLAP, the concept of data cube is often used to provide multidimensional views for such information. Among range-aggregates that are typical operations over the data cube, we in this paper focus on efficient processing of range-MAX and range-MIN operations, which are commonly used but are still expensive even with other existing methods. We propose the concept of a maximal cover, which is an effective representation of data distribution information with respect to range-MAX and range-MIN processing. We show that the maximum and the minimum value of a given query range can be effectively computed by an appropriate maximal cover. Thus, the problem of processing range-MIN/MAX is transformed into the problem of finding an appropriate maximal cover. To speed up the search process, we propose the maximal cover network that is a search structure based on the containment relation between two maximal covers. Being different from the hierarchical tree proposed earlier, the search process in our maximal cover network completes when the first matching node is found. This property mainly contributes to the outperformance of our maximal cover network where the number of accessed nodes is significantly reduced. We compare the performance of the proposed maximal cover network with that of the hierarchical tree and show that maximal cover network works better.