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101.
Dimitris Kiritsis 《Computer aided design》2011,43(5):479-501
With the advent of the information and related emerging technologies, such as RFID, small size sensors and sensor networks or, more generally, product embedded information devices (PEID), a new generation of products called smart or intelligent products is available in the market.Although various definitions of intelligent products have been proposed, we introduce a new definition of the notion of Intelligent Product inspired by what happens in nature with us as human beings and the way we develop intelligence and knowledge. We see an intelligent product as a product system which contains sensing, memory, data processing, reasoning and communication capabilities at four intelligence levels. This future generations of Intelligent Products will need new Product Data Technologies allowing the seamless interoperability of systems and exchange of not only Static but of Dynamic Product Data as well. Actual standards for PDT cover only lowest intelligence of today’s products. In this context, we try to shape the actual state and a possible future of the Product Data Technologies from a Closed-Loop Product Lifecycle Management (C-L PLM) perspective.Our approach is founded in recent findings of the FP6 IP 507100 project PROMISE and follow-up research work. Standards of the STEP family, covering the product lifecycle to a certain extend (PLCS) as well as MIMOSA and ISO 15926 are discussed together with more recent technologies for the management of ID and sensor data such as EPCglobal, OGC-SWE and relevant PROMISE propositions for standards.Finally, the first efforts towards ontology based semantic standards for product lifecycle management and associated knowledge management and sharing are presented and discussed. 相似文献
102.
Dimitris Kalles Athanasios Papagelis 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2010,14(9):973-993
When genetic algorithms are used to evolve decision trees, key tree quality parameters can be recursively computed and re-used
across generations of partially similar decision trees. Simply storing instance indices at leaves is sufficient for fitness
to be piecewise computed in a lossless fashion. We show the derivation of the (substantial) expected speedup on two bounding
case problems and trace the attractive property of lossless fitness inheritance to the divide-and-conquer nature of decision
trees. The theoretical results are supported by experimental evidence. 相似文献
103.
Ioannis Basdekis Iosif Klironomos Ioannis Metaxas Constantine Stephanidis 《Universal Access in the Information Society》2010,9(2):185-190
This communication reports on the results of a web accessibility audit of public Web sites in Greece. The audit was conducted
in 2008 by the Human Computer Interaction Laboratory of the Institute of Computer Science of FORTH, in its capacity as the
Greek National Contact Centre of the European Design for All e-Accessibility Network. In an earlier e-Accessibility study
in 2004, that evaluated approximately 250 public and commercial Web sites in Greece, 73% of the sample failed to meet the
most basic requirements for web accessibility (). Four years later, in the context of a re-audit, a similar sample was examined for compliance with the same web accessibility
standard (WCAG 1.0), as set by the Web Accessibility Initiative of the World Wide Web Consortium. The accessibility checks
were conducted during the period from March to September 2008. A comparison of the results indicates that although new web
development technologies may have been employed, instead of improving the overall status of e-accessibility, this has resulted
in a serious deterioration in overall accessibility levels. Such findings—85% of sites failed to comply with Level A—suggest
that Greek Web sites are likely to present even more significant access barriers to people with disability than in the past.
As Web Accessibility is poorly understood and, until today, new platforms have failed to deliver products that conform to
WCAG, the need emerges for a concrete legislative framework to set accessibility specifications for all public Web sites in
Greece. 相似文献
104.
Dimitris Vassis Petros Belsis Christos Skourlas Grammati Pantziou 《Personal and Ubiquitous Computing》2010,14(6):563-573
Advances on sensor technology, wireless environments and data mining introduce new possibilities in the healthcare sector,
realizing the anytime-anywhere access to medical information. Towards this direction, integration of packet-switched networks
and sensor devices can be effective in deploying assistive environments, such as home monitoring for elderly or patients.
In this paper we describe a policy-based architecture that utilizes wireless sensor devices, advanced network topologies and
software agents to enable remote monitoring of patients and elderly people; through the aforementioned technologies we achieve
continuous monitoring of a patient’s condition and we can proceed when necessary with proper actions. We also present a software
framework and network architecture that realizes the provision of remote medical services, in compliance with the imposed
security and privacy requirements. A proof of concept prototype is also deployed, along with an evaluation of the overall
architecture’s performance. 相似文献
105.
Any application or service utilizing the Internet is exposed to both general Internet attacks and other specific ones. Most of the times the latter are exploiting a vulnerability or misconfiguration in the provided service and/or in the utilized protocol itself. Consequently, the employment of critical services, like Voice over IP (VoIP) services, over the Internet is vulnerable to such attacks and, on top of that, they offer a field for new attacks or variations of existing ones. Among the various threats–attacks that a service provider should consider are the flooding attacks, at the signaling level, which are very similar to those against TCP servers but have emerged at the application level of the Internet architecture. This paper examines flooding attacks against VoIP architectures that employ the Session Initiation Protocol (SIP) as their signaling protocol. The focus is on the design and implementation of the appropriate detection method. Specifically, a bloom filter based monitor is presented and a new metric, named session distance, is introduced in order to provide an effective protection scheme against flooding attacks. The proposed scheme is evaluated through experimental test bed architecture under different scenarios. The results of the evaluation demonstrate that the required time to detect such an attack is negligible and also that the number of false alarms is close to zero. 相似文献
106.
SQL injection attacks involve the construction of application input data that will result in the execution of malicious SQL statements. Many web applications are prone to SQL injection attacks. This paper proposes a novel methodology of preventing this kind of attacks by placing a secure database driver between the application and its underlying relational database management system. To detect an attack, the driver uses stripped-down SQL queries and stack traces to create SQL statement signatures that are then used to distinguish between injected and legitimate queries. The driver depends neither on the application nor on the RDBMS and can be easily retrofitted to any system. We have developed a tool, SDriver, that implements our technique and used it on several web applications with positive results. 相似文献
107.
Michalis Savelonas Dimitris Maroulis Manolis Sangriotis 《Computer methods and programs in biomedicine》2009,96(1):25-32
In this paper, a novel computer-based approach is proposed for malignancy risk assessment of thyroid nodules in ultrasound images. The proposed approach is based on boundary features and is motivated by the correlation which has been addressed in medical literature between nodule boundary irregularity and malignancy risk. In addition, local echogenicity variance is utilized so as to incorporate information associated with local echogenicity distribution within nodule boundary neighborhood. Such information is valuable for the discrimination of high-risk nodules with blurred boundaries from medium-risk nodules with regular boundaries. Analysis of variance is performed, indicating that each boundary feature under study provides statistically significant information for the discrimination of thyroid nodules in ultrasound images, in terms of malignancy risk. k-nearest neighbor and support vector machine classifiers are employed for the classification tasks, utilizing feature vectors derived from all combinations of features under study. The classification results are evaluated with the use of the receiver operating characteristic. It is derived that the proposed approach is capable of discriminating between medium-risk and high-risk nodules, obtaining an area under curve, which reaches 0.95. 相似文献
108.
Dimitris Karlis 《Computational statistics & data analysis》2009,53(4):894-899
An EM type algorithm for estimating the parameters of the exponential Poisson distribution has recently been proposed. This algorithm uses a Newton Raphson approach at the M-step. An alternative approach, where the Newton Raphson step is replaced by another EM algorithm is described. This approach has simple closed form expressions, making use of a nested EM scheme where the M-step itself is solved with an EM algorithm. An advantage of this algorithm is that it provides estimates in the admissible range when the initial values are in the admissible range, and avoids overflow problems that may occur during Newton-Raphson iterations and, in certain cases, it can be faster. Some simulation evidence on the speed of the new approach compared to the one that uses Newton-Raphson is provided. 相似文献
109.
The geometric element transformation method (GETMe) is a geometry-based smoothing method for mixed and non-mixed meshes. It
is based on a simple geometric transformation applicable to elements bounded by polygons with an arbitrary number of nodes.
The transformation, if applied iteratively, leads to a regularization of the polygons. Global mesh smoothing is accomplished
by averaging the new node positions obtained by local element transformations. Thereby, the choice of transformation parameters
as well as averaging weights can be based on the element quality which leads to high quality results. In this paper, a concept
of an enhanced transformation approach is presented and a proof for the regularizing effect of the transformation based on
eigenpolygons is given. Numerical examples confirm that the GETMe approach leads to superior mesh quality if compared to other
geometry-based methods. In terms of quality it can even compete with optimization-based techniques, despite being conceptually
significantly simpler. 相似文献
110.
Vafeiadis Thanasis Bora-Senta Efthimia Kugiumtzis Dimitris 《Simulation Modelling Practice and Theory》2011,19(5):1384-1398
We propose a method to detect the onset of linear trend in a time series and estimate the change point T from the profile of a linear trend test statistic, computed on consecutive overlapping time windows along the time series. We compare our method to two standard methods for trend change detection and evaluate them with Monte Carlo simulations for different time series lengths, autocorrelation strengths, trend slopes and distribution of residuals. The proposed method turns out to estimate T better for small and correlated time series. The methods were also applied to global temperature records suggesting different turning points. 相似文献