Summary Replacement algorithms have been widely used as key technologies for cache management in areas such as file systems or database management. A replacement algorithm determines which page to be evicted when the cache is full and a new page is referenced. Because replacement policies considering only recency or frequency such as LRU (Least Recently Used) and LFU (Least Frequently Used) do not perform well, replacement polices that take both recency and frequency into account have been intensively studied. As a classical replacement policy, LRFU (Least Recently/Frequently Used) policy subsumes the LRU and LFU policy. However, because LFU is not able to adapt to the change of page accessing pattern and it is hard to select a suitable λ for each certain trace, LRFU cannot always guarantee a good performance. In this paper, we propose a Window‐LRFU policy, to subsume the LRU and Window‐LFU policies. Experimental results show that the Window‐LRFU policy outperforms LRFU and has at least competitive performance than other classical algorithms. Copyright © 2015 John Wiley & Sons, Ltd.

In ad hoc wireless networks, a Connected Dominating Set (CDS) has been extensively used as a Virtual Backbone (VB) for routing. The majority of approximation algorithms for constructing a small CDS in wireless ad hoc networks follow a general two-phased approach. The first phase is to construct a Dominating Set (DS) and the second phase is to connect the nodes in it. Generally, in the first phase, a Maximum Independent Set (MIS) is used as the DS. The relation between the size of a Maximum Independent Set and a Minimum Connected Dominating Set (MCDS) plays the key role in the performance analyses of these two-phased algorithms. In homogeneous wireless ad hoc networks modeled as Unit Disk Graphs (UDG) and Unit Ball Graphs (UBG), the relation between them has been well studied. However, in heterogeneous wireless networks which generally modeled as Disk Graphs with Bidirectional links (DGB) and Ball Graphs with Bidirectional links (BGB), upper bounds for the size of MISs have seldom been studied. In this paper, we give tighter upper bounds for the size of MISs in heterogeneous wireless ad hoc networks. When the maximum and minimum transmission range are relatively close, our result is much better. In DGB, when the transmission range ratio is (1,1.152], (1.152,1.307], (1.307,1.407], (1.407,1.462], (1.462,1.515], (1.515,1.618], (1.618,1.932], we prove that the size of any Maximal Independent Set (MIS) is upper bounded by 6opt + 1, 7opt + 1, 8opt + 1, 9opt + 1, 10opt + 1, 11opt + 1, 16.7778opt + 1.2222, where opt denotes the size of an optimal solution of the CDS problem.

Pyramidal Lucas-Kanade (LK) optical flow is a real-time registration technique widely employed by a variety of cutting edge consumer applications. Traditionally, the LK algorithm is applied selectively to image feature points that have strong spatial variation, which include outliers in textured areas. To detect and discard the falsely selected features, previous methods generally assess the goodness of each feature after the flow computation is completed. Such a screening process incurs additional cost. This paper provides a handy (but not obvious) tool for the users of the LK algorithm to remove false features without degrading the algorithm's efficiency. We propose a confidence predictor, which evaluates the ill-posedness of an LK system directly from the underlying data, at a cost lower than solving the system. We then incorporate our confidence predictor into the course-to-fine LK registration to dynamically detect false features and terminate their flow computation at an early stage. This improves the registration accuracy by preventing the error propagation and maintains (or increases) the computation speed by saving the runtime on false features. Experimental results on state-of-the-art benchmarks validate that our method is more accurate and efficient than related works.

Based on globally supported radial basis functions, this paper presents a hierarchical approach to 3D scattered data interpolation. Given a scattered data set distributed along a surface, we first obtain a sparse approximation of the scattered data set by filtering the scattered data with two different steps, and identify the characteristic points by the measurements of bounding cube and the distance between the points and the interpolating surface. Then using multi-level hierarchy of point sets, the accuracy of interpolating surface can be gradually improved. On the basis of effective selection of the off-surface normal points, the number of constraint conditions is reduced, and trivial solutions of the interpolating equations can be avoided. Above all, we can identify the characteristic points in the model with less data points, and obtain interpolating surface with higher fitting accuracy by solving equations with lower order. The numerical experiments show that the method is more efficient and easy to implement.

The generalized 3x+1 function T(z) can generate fractal images. So a complex mapping F(z) is constructed based on T(z), and visualized it using escape time algorithm. Because the images of T(z) and F(z) are intricate and rich with certain artistic value, several methods are proposed to generate pseudo-3D artistic fractal images. The methods are all based on escape time algorithm and color map, which use the distance divided approach to draw non escape areas and the orbit trap to draw the escape areas. The experiments show that these methods have better effect, are fast and easy to implement.

Intensity degradations are a familiar problem for fluorescein angiogram sequences. In this paper, we attempt to restore a noisy fluorescein angiogram, and to keep the high intensity pixels from degrading. To this end, we incorporate a new constraint, called intensity constraint, to Miller's regularization formulation with a smoothness constraint. Considering the specified requirement for fluorescein angiograms, we also modify the Q-th order converging algorithm for implementation purpose. In our scheme, including its formulation and implementation, image restoration can not only handle the traditional problems, such as blur and noise, but also achieve an important feature, intensity preservation. The experiments show that our approach has satisfactory results in the two aspects.

For the NURBS curve that hold the arbitrary degrees and generally structured knots, under the assumption of unchanging the knot vector and the degree of NURBS curve, we present the constraint conditions for elevating the parametric continuity order of NURBS curve at the interior knots by modifying their control points and weights. Meanwhile, we obtain the freedom degree of the control points and the weights when the parametric continuity order of NURBS curve elevates by one. Furthermore, we obtain the conditions for elevating the parametric continuity order of NURBS surface along its isoparametric line by modifying their control points and weights. Meanwhile, the freedom degree of the control points and the weights when the parametric continuity order of NURBS surface elevates by one is presented at the end.

According to the results on the G/sup 1/ continuity conditions for two arbitrary degree B-spline surfaces with generally structured knots, this paper analyzes the property of the connecting functions of G/sup 1/ continuity first, then obtains the necessary and sufficient condition of G/sup 2/ continuity for two arbitrary degree B-spline surfaces with generally structured knots, meanwhile present a kind of sufficient conditions of G/sup 2/ continuity. In particular, this paper obtain the uniform smooth conditions for the above G/sup 2/ sufficient conditions. At the end, this paper give a constructing algorithm and examples for adjacent B-spline surfaces to be of G/sup 2/ continuity.