15941775
Exploring Regression for Mining User Moving Patterns in a Mobile Computing System
In this paper, by exploiting the log of call detail records, we present a solution procedure of mining user moving patterns in a mobile computing system. Specifically, we propose algorithm LS to accurately determine similar moving sequences from the log of call detail records so as to obtain moving behaviors of users. By exploring the feature of spatial-temporal locality, we develop algorithm TC to group call detail records into clusters. In light of the concept of regression, we devise algorithm MF to derive moving functions of moving behaviors. Performance of the proposed solution procedure is analyzed and sensitivity analysis on several design parameters is conducted. It is shown by our simulation results that user moving patterns obtained by our solution procedure are of very high quality and in fact very close to real user moving behaviors.
14327978
On Exploring the Power-Law Relationship in the Itemset Support Distribution
We identify and explore in this paper an important phenomenon which points out that the power-law relationship appears in the distribution of itemset supports. Characterizing such a relationship will benefit many applications such as providing the direction of tuning the performance of the frequent-itemset mining. Nevertheless, due to the explosive number of itemsets, it will be prohibitively expensive to retrieve characteristics of the power-law relationship in the distribution of itemset supports. As such, we also propose in this paper a valid and cost-effective algorithm, called algorithm PPL, to extract characteristics of the distribution without the need of discovering all itemsets in advance. Experimental results demonstrate that algorithm PPL is able to efficiently extract the characteristics of the power-law relationship with high accuracy.
6334357
An energy-conserved on-demand data broadcasting system
We propose in this paper an energy-conserved on-demand data broadcasting system by employing the data indexing technique. We also propose algorithm AIDOA to adjust the degree of buckets according to system workload. Experimental results show that algorithm AIDOA is able to greatly reduce power consumption at the cost of slight increment in average access time and adjust the index and data organization dynamically to adapt to change of system workload.
12270343
SIFA: a scalable file system with intelligent file allocation
In this paper we propose and evaluate a new NAS based system which is a consolidated file system in a network environment. The consolidated file system utilizes storage boxes cooperating as peers to provide all file system services, and presents itself to its NFS clients as a unified storage server. We have prototyped several key operations in this system. To provide more performance insights, we build a comprehensive system simulator and conduct extensive performance studies for the system via the simulator This simulator has been run against a workload of a real Web server and the system behavior of this workload is studied. In light of the experimental results, a consolidated file system is being implemented in full scale.
669798
On the effect of group mobility to data replication in ad hoc networks
The growth in wireless communication technologies attracts a considerable amount of attention in mobile ad hoc networks. Since mobile hosts in an ad hoc network usually move freely, the topology of the network changes dynamically and disconnection occurs frequently. These characteristics make it likely for a mobile ad hoc network to be separated into several disconnected partitions, and the data accessibility is hence reduced. Several schemes are proposed to alleviate the reduction of data accessibility by replicating data items. However, little research effort was elaborated upon exploiting the group mobility where the group mobility refers to the phenomenon that several mobile nodes tend to move together. In this paper, we address the problem of replica allocation in a mobile ad hoc network by exploring group mobility. We first analyze the group mobility model and derive several theoretical results. In light of these results, we propose a replica allocation scheme to improve the data accessibility. Several experiments are conducted to evaluate the performance of the proposed scheme. The experimental results show that the proposed scheme is able to not only obtain higher data accessibility, but also produce lower network traffic than prior schemes.
21658897
A QoS-aware transcoding proxy using on-demand data broadcasting
The high diversity in the capabilities of various mobile devices such as display capabilities and computation power makes the design of mobile information systems more challenging. A transcoding proxy is placed between a client and an information server to coordinate the mismatch between what the server provides and what the client prefers. However, most research works in transcoding proxies in mobile computing environments are under the traditional client-server architecture and do not employ the data broadcast technique which is has been deemed a promising technique to design a power conservation, high scalable and high band-width utilization. In addition, the issue of QoS provision is also not addressed. In view of this, we design in this paper a QoS-aware transcoding proxy by utilizing the on-demand broadcasting technique. We first propose a QoS-aware transcoding proxy architecture, abbreviated as QTP, and model it as a queueing network. By analyzing the queueing network, several theoretical results are derived. We then propose a version decision policy and a service admission control scheme to provide QoS in QTP. The derived results are used to guide the execution of the proposed version decision policy and service admission control scheme to achieve the given QoS requirement. To measure the performance of QTP, several experiments are conducted. Experimental results show that the proposed scheme is more scalable than traditional client-server systems. In addition, the proposed scheme is able to effectively control the system load to attain the desired QoS
12035723
Testing and characterization of the one-bit first-order delta-sigma modulator for on-chip analog signal analysis
Delta-sigma modulation has become popular in modern analog-to-digital modulator design due to its relatively high immunity from process variations. We propose efficient characterization techniques to obtain the key performance parameters of the 1-bit first-order delta-sigma modulator which is intended to be used as an on-chip analog signal digitizer for BIST applications. Numerical simulations have been performed to validate the techniques and the results indicate that accurate estimation of the parameters can be obtained at the presence of noise.
4790911
Spanning k-arc-strong subdigraphs with few arcs in k-arc-strong tournaments
Given a k-arc-strong tournament T , we estimate the minimum number of arcs possible in a k-arc-strong spanning subdigraph of T . We give a construction which shows that for each k ≥ 2 there are tournaments T on n vertices such that every k-arc-strong spanning subdigraph of T contains at least nk+ k(k−1) 2 arcs. In fact, the tournaments in our construction have the property that every spanning subdigraph with minimum inand out-degree at least k has nk + k(k−1) 2 arcs. This is best possible since it can be shown that every k-arc-strong tournament contains a spanning subdigraph with minimum inand out-degree at least k and no more than nk + k(k−1) 2 arcs. As our main result we prove that every k-arcstrong tournament contains a spanning k-arc-strong subdigraph with no more than nk + 280k2 arcs. We conjecture that for every k-arc-strong tournament T , the minimum number of arcs in a k-arc-strong spanning subdigraph of T is equal to the minimum number of arcs in a spanning subdigraph of T with the property that every vertex has inand out-degree at least k. We also discuss the implications of our results on related problems and conjectures.
14059927
Test scheduling of BISTed memory cores for SoC
The test scheduling of memory cores can significantly affect the test time and power of system chips. We propose a test scheduling algorithm for BISTed memory cores to minimize the overall testing time under the test power constraint. The proposed algorithm combines several approaches for a near-optimal result, based on the properties of BISTed memory cores. By proper partitioning, an analytic exhaustive search finds optimal results for large memory cores, while a heuristic ordering with simulated annealing further handles a large amount of smaller memory cores. On the average, the results are within 1% difference of the optimal solution for the cases of 200 memory cores.
3062410
Conceptualizing the three dimensions of inter-organizational communities of practice
The paper describes and analyzes the way in which a particular case company stimulated the development of communities of practice as a vehicle for encouraging product and process innovation. Some unique features of these communities were explored. In particular the involvement of retired engineers and the inclusion of external parties were both found to contribute to the effectiveness of these communities. More specifically, the effectiveness of these communities were discussed in relation to three dimensions – structural, strategic and technological. Analysis of these three dimensions was useful in examining the role played by these communities within the case company. The paper concludes by considering the lessons for managers that can be drawn from this analysis. Newell,Huang,Galliers Conceptualizing the three dimensions of Inter-Organizational
4333882
Linear-Time Representation Algorithms for Proper Circular-Arc Graphs and Proper Interval Graphs
Our main result is a linear-time (that is, time $O(m+n)$) algorithm to recognize and represent proper circular-arc graphs. The best previous algorithm, due to A. Tucker, has time complexity $O(n^2)$. We take advantage of the fact that (among connected graphs) proper circular-arc graphs are precisely the graphs orientable as local tournaments, and we use a new characterization of local tournaments. The algorithm depends on repeated representation of portions of the input graph as proper interval graphs. Thus we also find it useful to give a new linear-time algorithm to represent proper interval graphs. This latter algorithm also depends on an orientation characterization of proper interval graphs. It is conceptually simple and does not use complex data structures. As a byproduct of the correctness proof of the algorithm, we also obtain a new proof of a characterization of proper interval graphs by forbidden subgraphs.