Uncertainty in estimating the performance of solar thermal systems

The scope of this article is to present a methodology for the estimation of the uncertainty characterizing the energy performance of solar domestic hot water systems. The work concentrates on the uncertainty characterizing the expected annual energy output, as calculated through tests implemented according to the valid international standards. In order to cope with difficulties related to the algorithmic character of the measurement model, which cannot be explicitly formulated, Monte-Carlo simulation techniques are implemented. The component of uncertainty associated with measurement errors is estimated, on the basis of the metrological quality anticipated by the relevant testing standards. Errors due to imperfections of the energy model used through the test are also counted in, as well as uncertainties attributed to the variability of meteorological conditions. The proposed uncertainty analysis allows the realistic assessment of the actual energy provided to the user by a solar domestic hot water system. Implementation of the proposed methodology for a typical system leads to an expanded uncertainty in the order of 9% for the expected annual energy output.     

A Configurable Logic Based Architecture for Real-Time Continuous Speech Recognition Using Hidden Markov Models

An architecture is presented for real-time continuous speech recognition based on a modified hidden Markov model. The algorithm is adapted to the needs of continuous speech recognition by efficient encoding of the state space, and logarithmic encoding of the weights so that products can be computed as sums. The paper presents the algorithm and its application related modifications, the mapping of the algorithm to a special purpose architecture, and the detailed design of this architecture using configurable logic. Emphasis is given on how the attributes of the algorithm are exploited in a configurable logic based design. A concrete design example is presented with a coprocessor engine having one large FPGA, 64 Mbytes of synchronous DRAM (SDRAM), a small FPGA as a SDRAM controller, and 2 Mbytes SRAM. This engine operating at 66 MHz performs roughly nine times as fast as a high end personal computer running a fully optimized version of the same algorithm.     

Accurate and large-scale privacy-preserving data mining using the election paradigm

With the proliferation of the Web and ICT technologies there have been concerns about the handling and use of sensitive information by data mining systems. Recent research has focused on distributed environments where the participants in the system may also be mutually mistrustful. In this paper we discuss the design and security requirements for large-scale privacy-preserving data mining (PPDM) systems in a fully distributed setting, where each client possesses its own records of private data. To this end we argue in favor of using some well-known cryptographic primitives, borrowed from the literature on Internet elections. More specifically, our framework is based on the classical homomorphic election model, and particularly on an extension for supporting multi-candidate elections. We also review a recent scheme [Z. Yang, S. Zhong, R.N. Wright, Privacy-preserving classification of customer data without loss of accuracy, in: SDM’ 2005 SIAM International Conference on Data Mining, 2005] which was the first scheme that used the homomorphic encryption primitive for PPDM in the fully distributed setting. Finally, we show how our approach can be used as a building block to obtain Random Forests classification with enhanced prediction performance.     

Design, Implementation and Validation of an Open Source IP-PBX/VoIP Gateway Multi-Core SoC

The telephony world is consistently moving to the transmission of voice through packet networks, so as to unify data and voice and to enable the provisioning of new services in a less costly manner. Service providers are offloading the task of converting analog voice to VoIP to the end-points. In this paper we present an IP-PBX/VoIP Gateway system based on a single, multi-core SoC that performs all the required processing. The system targets the low density market of home gateways and SME IP-PBXs, where cost is the main factor. We prove it is feasible to implement a 4-channel IP-PBX/VoIP gateway on a SoC based purely on both software and hardware provided by the open-source community, reducing both upfront and final product costs thus allowing new players into the market. The highly configurable design allows the integration of multiple embedded cores in the same die increasing channel density while reducing clock cycles per channel. The idea of using one or more open-source embedded cores can be extended to many different applications requiring moderate DSP performance, resulting in a “DSP-free”, low-cost system, with minimal design effort.     

Finding the K highest-ranked answers in a distributed network

In this paper, we present an algorithm for finding the k highest-ranked (or Top-k) answers in a distributed network. A Top-K query returns the subset of most relevant answers, in place of all answers, for two reasons: (i) to minimize the cost metric that is associated with the retrieval of all answers; and (ii) to improve the recall and the precision of the answer-set, such that the user is not overwhelmed with irrelevant results. Our study focuses on multi-hop distributed networks in which the data is accessible by traversing a network of nodes. Such a setting captures very well the computation framework of emerging Sensor Networks, Peer-to-Peer Networks and Vehicular Networks. We present the Threshold Join Algorithm (TJA), an efficient algorithm that utilizes a non-uniform threshold on the queried attribute in order to minimize the transfer of data when a query is executed. Additionally, TJA resolves queries in the network rather than in a centralized fashion which further minimizes the consumption of bandwidth and delay. We performed an extensive experimental evaluation of our algorithm using a real testbed of 75 workstations along with a trace-driven experimental methodology. Our results indicate that TJA requires an order of magnitude less communication than the state-of-the-art, scales well with respect to the parameter k and the network topology.     

rfid in pervasive computing: State-of-the-art and outlook

rfid has already found its way into a variety of large scale applications and arguably it is already one of the most successful technologies in the history of computing. Beyond doubt, rfid is an effective automatic identification technology for a variety of objects including natural, manufactured and handmade artifacts; humans and other species; locations; and increasingly media content and mobile services. In this survey we consider developments towards establishing rfid as the cost-effective technical solution for the development of open, shared, universal pervasive computing infrastructures and look ahead to its future. In particular, we discuss the ingredients of current large scale applications; the role of network services to provide complete systems; privacy and security implications; and how rfid is helping prototype emerging pervasive computing applications. We conclude by identifying common trends in the new applications of rfid and ask questions related to sustainable universal deployment of this technology.     

Understanding and measuring the urban pervasive infrastructure

The increasing popularity of mobile computing devices has allowed for new research and application areas. Specifically, urban areas exhibit an elevated concentration of such devices enabling potential ad-hoc co-operation and sharing of resources among citizens. Here, we argue that people, architecture and technology together provide the infrastructure for these applications and an understanding of this infrastructure is important for effective design and development. We focus on describing the metrics for describing this infrastructure and elaborate on a set of observation, analysis and simulation methods for capturing, deriving and utilising those metrics.

Can we do without GUIs? Gesture and speech interaction with a patient information system

We have developed a gesture input system that provides a common interaction technique across mobile, wearable and ubiquitous computing devices of diverse form factors. In this paper, we combine our gestural input technique with speech output and test whether or not the absence of a visual display impairs usability in this kind of multimodal interaction. This is of particular relevance to mobile, wearable and ubiquitous systems where visual displays may be restricted or unavailable. We conducted the evaluation using a prototype for a system combining gesture input and speech output to provide information to patients in a hospital Accident and Emergency Department. A group of participants was instructed to access various services using gestural inputs. The services were delivered by automated speech output. Throughout their tasks, these participants could see a visual display on which a GUI presented the available services and their corresponding gestures. Another group of participants performed the same tasks but without this visual display. It was predicted that the participants without the visual display would make more incorrect gestures and take longer to perform correct gestures than the participants with the visual display. We found no significant difference in the number of incorrect gestures made. We also found that participants with the visual display took longer than participants without it. It was suggested that for a small set of semantically distinct services with memorable and distinct gestures, the absence of a GUI visual display does not impair the usability of a system with gesture input and speech output.