Online user activities discovery based on time dependent data

Network evolution is a hot research topic especially when social networking has become an important Web application. The access histories of Web users which contain the users traces' on a social network have not been considered useful data. However, they may reveal more about the network's connectedness if the history's time-sensitive characteristic is analyzed and studied. In this paper, we model the user's daily activities in a time series model to reflect the dynamic nature of a social network due to various user behavior patterns over a period of time. We begin to study the activity pattern for a single user. We then expand that study over the whole network. Through the model, we can quantitatively analyze the user's contribution to the social network and predict the user's response when there is a new action by another user. © 2009 IEEE

Dynamic privacy management: A plug-in service for the middleware in pervasive computing

Context-aware applications can better meet users' needs when sensing agents installed in the environment automatically provide input relevant to the application. However, this nonintrusive context usage may cause privacy concerns since sensitive user data could be leaked to unauthorized parties. Therefore, data privacy protection becomes one of the major issues for context-aware applications. In this paper, in order to provide services based on various levels of privacy concerns, we extend the Platform for Privacy Preferences of W3C and define a specification for representing user privacy preferences for context-aware applications. We also propose a privacy infrastructure, which could be installed as a plug-in service for middleware supporting context-aware applications. This infrastructure enables the middleware to automatically generate a privacy policy and the user preference file according to the current context. The middleware simply matches these two files to decide whether to proceed with the application. We demonstrate the efficacy of this approach through a prototype implementation. Copyright 2005 ACM

Requirements elicitation for the design of context-aware applications in a ubiquitous environment

With the invention of new interaction devices and the requirements for ubiquitous access to application systems, user's interactions have moved beyond the desktop and evolved into a trend of ongoing development. The context in which the application is being used becomes an integral part of the activity carried out with the system. The inclusion of context-awareness provides convenience and efficiency to users for their ubiquitous access. Traditional human-computer interface (HCI) theories are now inadequate for developing these context-aware applications, as we believe that the notion of context should be extended to different categories: computing contexts, user contexts, and physical contexts for ubiquitous computing. This demands a new paradigm for system requirements elicitation and design in order to make good use of such extended context information. In this paper, we introduce a methodology for the elicitation of context-aware requirements and the matching of context-awareness features to the target context by capability matching. Based on this model, we analyze the design issues of some common ubiquitous access situations and show how to fit them systematically into a context-aware application by considering the requirements of a ubiquitous tourist application. Copyright 2005 ACM

Structural and optical properties of Si-doped GaN

Structural and optical properties of Si-doped GaN thin films grown by metal-organic chemical vapor deposition have been studied by means of high resolution x-ray diffraction (XRD), atomic force microscopy, photoluminescence, photothermal deflection spectroscopy, and optical transmission measurements. The incorporation of silicon in the GaN films leads to pronounced tensile stress. The energy position of the neutral donor bound excitonic emission correlates with the measured stress. The stress induced near band gap luminescence shift is estimated to 19^+_-2 meV/GPa. An increasing concentration of dopant impurities in the films leads to asymmetries of the XRD and photoluminescence spectra, which are probably related to a Stress induced inhomogeneous distribution of dopants. Atomic force microscopy observations of surface modulation with increasing silicon doping support this latter statement. Transmission and photothermal deflection spectroscopy measurements are used to determine the band gap energy and Urbach energy of highly doped samples

On a Quest for Good Process Models: The Cross-Connectivity Metric

Business process modeling is an important corporate activity, but the understanding of what constitutes good process models is rather limited. In this paper, we turn to the cognitive dimensions framework and identify the understanding of the structural relationship between any pair of model elements as a hard mental operation. Based on the weakest-link metaphor, we introduce the cross-connectivity metric that measures the strength of the links between process model elements. The definition of this new metric builds on the hypothesis that process models are easier understood and contain less errors if they have a high cross-connectivity. We undertake a thorough empirical evaluation to test this hypothesis and present our findings. The good performance of this novel metric underlines the importance of cognitive research for advancing the field of process model measurement