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71.
Jenq-Shiou?LeuEmail author Hui-Ching?Hsieh Yen-Chiu?Chen 《Multimedia Tools and Applications》2011,53(1):285-301
In the era of IP-based service, people expect a simple, cheap, and competent Voice over IP (VoIP) service as an alternative
of the traditional voice over PSTN. The introduction of the SIP protocol realizes the expectation. Following the cost saving
spirit of VoIP, we focus on studying inexpensive high availability solutions for the SIP-based VoIP Service. In this paper,
Peer-to-Peer (P2P) based and DN-LB based schemes are mainly compared in the paper. A P2P-based scheme enables an inexpensive
high availability solution to the VoIP service by the shared computation resources form P2P nodes. Such a P2P-based solution
may be appropriate for an individual VoIP user. However, a caller may take a large volume of messages to find out a callee
via the proxy nodes in the P2P network. This inherent property of a P2P network may induce the message overhead and long call
setup delay. Based on above, another inexpensive scheme, which is a probing-based name resolution solution, is proposed to
achieve high availability and load balancing for the VoIP service. We tag the probing mechanism onto the open source project
Domain Name Relay Daemon (DNRD) to become a domain name resolution based load balancer (DN-LB). With DN-LB, all request messages
from clients can be fairly distributed to all failure-proof proxy servers in the server farm without using any additional
costly intermediate network device and changing the standard SIP architecture. Such a DN-LB based solution may be a good choice
for a VoIP service provider. 相似文献
72.
Shin-Chih Tu Guey-Yun Chang Jang-Ping Sheu Wei Li Kun-Ying Hsieh 《Journal of Parallel and Distributed Computing》2010
With the advancement of MEMS technologies, sensor networks have opened up broad application prospects. An important issue in wireless sensor networks is object detection and tracking, which typically involves two basic components, collaborative data processing and object location reporting. The former aims to have sensors collaborating in determining a concise digest of object location information, while the latter aims to transport a concise digest to sink in a timely manner. This issue has been intensively studied in individual objects, such as intruders. However, the characteristic of continuous objects has posed new challenges to this issue. Continuous objects can diffuse, increase in size, or split into multiple continuous objects, such as a noxious gas. In this paper, a scalable, topology-control-based approach for continuous object detection and tracking is proposed. Extensive simulations are conducted, which show a significant improvement over existing solutions. 相似文献
73.
The Lucas–Kanade tracker (LKT) is a commonly used method to track target objects over 2D images. The key principle behind
the object tracking of an LKT is to warp the object appearance so as to minimize the difference between the warped object’s
appearance and a pre-stored template. Accordingly, the 2D pose of the tracked object in terms of translation, rotation, and
scaling can be recovered from the warping. To extend the LKT for 3D pose estimation, a model-based 3D LKT assumes a 3D geometric
model for the target object in the 3D space and tries to infer the 3D object motion by minimizing the difference between the
projected 2D image of the 3D object and the pre-stored 2D image template. In this paper, we propose an extended model-based
3D LKT for estimating 3D head poses by tracking human heads on video sequences. In contrast to the original model-based 3D
LKT, which uses a template with each pixel represented by a single intensity value, the proposed model-based 3D LKT exploits
an adaptive template with each template pixel modeled by a continuously updated Gaussian distribution during head tracking.
This probabilistic template modeling improves the tracker’s ability to handle temporal fluctuation of pixels caused by continuous
environmental changes such as varying illumination and dynamic backgrounds. Due to the new probabilistic template modeling,
we reformulate the head pose estimation as a maximum likelihood estimation problem, rather than the original difference minimization
procedure. Based on the new formulation, an algorithm to estimate the best head pose is derived. The experimental results
show that the proposed extended model-based 3D LKT achieves higher accuracy and reliability than the conventional one does.
Particularly, the proposed LKT is very effective in handling varying illumination, which cannot be well handled in the original
LKT. 相似文献
74.
Chun-Chieh Wang Kuo-Hsien Hsia Kuo-Lan Su Yi-Chun Hsieh Chyun-Luen Lin 《Artificial Life and Robotics》2010,15(3):284-290
As one of the major steps toward a fully intelligent autonomous robotic weapon, we have made progress in three major areas,
(1) design of the surveillance system by an AVR microcontroller, (2) implementation of the design mechanism, and (3) performance
of the human- machine interface surveillance system via the LabVIEW graphical programming environment, so that the supervisor
can control the vehicle with a keyboard or a specially adapted mouse. In order to accomplish all these achievements, there
have been major additions and overhauls in both system software codes and system circuit board developments. All these developments,
including a new algorithm and hardware implementation, are described in this article. The experimental results have shown
the practicality of the AVR microcontroller, the LabVIEW graphical programming environment, and ZigBee wireless technology
applied to a robotic weapon. 相似文献
75.
Comparing e-Learning tools’ success: The case of instructor–student interactive vs. self-paced tools
e-Learning tools have profoundly transformed modern pedagogical approaches. Vendors provide different types of systems, such as self-paced (SP) and instructor–student interactive (ISI) e-Learning tools. Although both types of tools represent promising solutions to facilitate the learning process, it is important to theoretically identify a framework to evaluate the success of these tools and assess whether one type of tool is more effective than another. Toward this end, we (1) propose a model to evaluate e-Learning tools’ success by extending and contextualizing Seddon’s information systems (IS) success model for the e-Learning environment and (2) formulate four hypotheses to predict the differences in the success factors between SP and ISI tools. We test the model and hypotheses using data from 783 students across seven higher education institutions in Hong Kong. The results support the proposed e-Learning tool success model and three of the four hypotheses. ISI tools outperform SP tools in terms of system quality, perceived usefulness, satisfaction, and learning outcome. 相似文献
76.
This paper presents a knowledge exchange framework that can leverage the interoperability among semantically heterogeneous learning objects. With the release of various e-Learning standards, learning contents and digital courses are easy to achieve cross-platform sharing, exchanging, and even reorganizing. However, knowledge sharing in semantic level is still a challenge due to that the learning materials can be presented in any form, such as audios, videos, web pages, and even flash files. The proposed knowledge exchange framework allows users to share their learning materials (also called “learning objects”) in semantic level automatically. This framework contains two methodologies: the first is a semantic mapping between knowledge bases (i.e. ontologies) which have essentially similar concepts, and the second is an ontology-based classification algorithm for sharable learning objects. The proposed algorithm adopts the IMS DRI standard and classifies the sharable learning objects from heterogeneous repositories into a local knowledge base by their inner meaning instead of keyword matching. Significance of this research lies in the semantic inferring rules for ontology mapping and learning objects classification as well as the full automatic processing and self-optimizing capability. Focused on digital learning materials and contrasted to other traditional technologies, the proposed approach has experimentally demonstrated significantly improvement in performance. 相似文献
77.
Feature selection aims at finding the most relevant features of a problem domain. It is very helpful in improving computational speed and prediction accuracy. However, identification of useful features from hundreds or even thousands of related features is a nontrivial task. In this paper, we introduce a hybrid feature selection method which combines two feature selection methods – the filters and the wrappers. Candidate features are first selected from the original feature set via computationally-efficient filters. The candidate feature set is further refined by more accurate wrappers. This hybrid mechanism takes advantage of both the filters and the wrappers. The mechanism is examined by two bioinformatics problems, namely, protein disordered region prediction and gene selection in microarray cancer data. Experimental results show that equal or better prediction accuracy can be achieved with a smaller feature set. These feature subsets can be obtained in a reasonable time period. 相似文献
78.
Qin Liu Nancy R. Cook Anna Bergstrm Chung-Cheng Hsieh 《Computational statistics & data analysis》2009,53(12):4157-4167
To estimate a summarized dose–response relation across different exposure levels from epidemiologic data, meta-analysis often needs to take into account heterogeneity across studies beyond the variation associated with fixed effects. We extended a generalized-least-squares method and a multivariate maximum likelihood method to estimate the summarized nonlinear dose–response relation taking into account random effects. These methods are readily suited to fitting and testing models with covariates and curvilinear dose–response relations. 相似文献
79.
In this paper, a novel clustering method in the kernel space is proposed. It effectively integrates several existing algorithms to become an iterative clustering scheme, which can handle clusters with arbitrary shapes. In our proposed approach, a reasonable initial core for each of the cluster is estimated. This allows us to adopt a cluster growing technique, and the growing cores offer partial hints on the cluster association. Consequently, the methods used for classification, such as support vector machines (SVMs), can be useful in our approach. To obtain initial clusters effectively, the notion of the incomplete Cholesky decomposition is adopted so that the fuzzy c‐means (FCM) can be used to partition the data in a kernel defined‐like space. Then a one‐class and a multiclass soft margin SVMs are adopted to detect the data within the main distributions (the cores) of the clusters and to repartition the data into new clusters iteratively. The structure of the data set is explored by pruning the data in the low‐density region of the clusters. Then data are gradually added back to the main distributions to assure exact cluster boundaries. Unlike the ordinary SVM algorithm, whose performance relies heavily on the kernel parameters given by the user, the parameters are estimated from the data set naturally in our approach. The experimental evaluations on two synthetic data sets and four University of California Irvine real data benchmarks indicate that the proposed algorithms outperform several popular clustering algorithms, such as FCM, support vector clustering (SVC), hierarchical clustering (HC), self‐organizing maps (SOM), and non‐Euclidean norm fuzzy c‐means (NEFCM). © 2009 Wiley Periodicals, Inc.4 相似文献
80.
The star graph is viewed as an attractive alternative to the hypercube. In this paper, we investigate the Hamiltonicity of
an n-dimensional star graph. We show that for any n-dimensional star graph (n≥4) with at most 3n−10 faulty edges in which each node is incident with at least two fault-free edges, there exists a fault-free Hamiltonian
cycle. Our result improves on the previously best known result for the case where the number of tolerable faulty edges is
bounded by 2n−7. We also demonstrate that our result is optimal with respect to the worst case scenario, where every other node of a cycle
of length 6 is incident with exactly n−3 faulty noncycle edges. 相似文献