Dither signal effects on the resolution of nonlinear quantizers

The consequences of dithering on nonlinear quantizers are analyzed. A model of the nonlinear quantizer is considered, and a model of the same quantizer with dither is proposed. By means of this approach, relationships are given for the total quantization error in the case of discrete binary, uniform, and Gaussian dither signals     

Estimating thermal stress in BIPV modules

The thermal stress on building‐integrated photovoltaic modules (BIPV) in Espoo, Finland, was studied with field‐testing of amorphous silicon modules. Based on these results, the thermal stress at two other European locations (Paris and Lisbon) was estimated. The estimation procedure entailed thermal modelling of heat transfer in the façade with meteorological data as input. The results indicate that the thermal stress on BIPV modules in Lisbon is, in this case, approximately 50% higher that in Espoo and between 80 and 200% higher than in Paris, depending on the activation energy of the degradation process. The difference in stress between a BIPV module and a free‐standing module in Espoo was 50–200%. Copyright © 2006 John Wiley & Sons, Ltd.     

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Adsorption of mercaptopropionic acid onto Au(1 1 1): Part II. Effect on copper electrodeposition

Copper deposition in the presence of an organic additive (3-mercaptopropionic acid, MPA) was studied by cyclic voltammetry and in situ scanning tunneling microscopy (STM) and the results are compared to those for additive-free solutions. It is shown that underpotential deposition (upd) of copper onto a fully MPA-covered electrode produces a defect-rich substrate, but the defects are blocked by the dense organic film for bulk deposition, resulting in a low number of nuclei. A grain-refining effect of MPA, however, was found, when Cu deposition was initiated shortly after addition of MPA to the solution, i.e., for a low-coverage MPA adlayer.     

Usability study of ME2.0

Mobile context-aware applications execute in the background of hosts mobile devices. The applications source process and aggregate hosts’ contextual and personal information. This information is disclosed to ubiquitously pervasive services that adapt their offerings to individual preferences. Unfortunately, many developers continue to ignore the user perspective in context-aware application designs as they complicate their overall task and generate exponential requirements. The additional incorporation of privacy mechanisms in context-aware applications to safeguard context and personal information disclosures also complicates users’ tasks resulting to misconfigured or completely abandoned applications. Misconfigured applications give end-users a false assurance of privacy exposing them to comprising services. We present a usability study on Mobile Electronic Personality Version 2 a privacy enhanced context-aware mobile application for personalising ubiquitous services and adapting pervasive smart-spaces. We draw conclusions on key issues related to user needs, based on user interviews, surveys, prototypes and field evaluations. Users’ needs are evaluated against five themes, learn-ability, efficiency, memorability, errors, satisfaction and privacy contention. In addition, design layout preferences, privacy manageability and consensus design comprehension are also evaluated. Clarity of priorities in context-aware mobile applications shaped by usability studies effectively increases the acceptance of levels of potential users.     

A portable device for intensive care brain function monitoring with event-related potentials

Monitoring level of consciousness or depth of sedation is essential in modern intensive care units and emergency rooms. Current methods are based on spontaneous EEG providing only indirect information on the reactivity of the brain. Measurement of auditory event-related potentials (ERPs) has been shown to have additional potential for evaluation of the level of consciousness. Unfortunately, compact and easy-to-use devices are not commercially available. In this study a portable battery-powered device for clinical auditory ERP measurements was designed, constructed and validated. The device consists of a five-channel data logger and a 16-bit stereo audio stimulator. The signals are digitized with a 22-bit sigma-delta analogue-to-digital converter and stored to a PC Card hard disk. Prior to the in vivo application, the device was validated with extensive technical tests. Importantly, the RMS noise amplitude of the EEG channels was found to be less than 1 mivroV and the delivered auditory stimulus intensity corresponded accurately the settings (mean difference 0.2+/-0.5 dB). In addition to technical tests the device was successfully validated in vivo. To summarize, a novel portable instrument for measurement of auditory event-related potentials in intensive care environment is introduced.     

On the optimality of field-line routing in massively dense wireless multi-hop networks

We consider the load balancing problem in large wireless multi-hop networks by applying the continuum approximation. The task is to find routes, geometric curves, such that the maximal traffic load in the network is minimized. In finite fixed networks, multi-path routes generally yield a lower congestion and thus allow higher throughput. In contrast, we show that in dense wireless multi-hop networks, the optimal load balancing can be achieved by a destination based single-path routing referred to as field-line routing. This is because any routing can be transformed to the corresponding field-line routing with the same or better performance, by using as paths, the field lines of the so-called destination flow associated with the original routing. The concepts are illustrated with two examples. In the case of a unit disk with unit traffic, the maximal load of 0.389 of a multi-path routing system is reduced to 0.343 by using the field-line routing. Similar improvements are also demonstrated for the unit square.     

Non-myopic vehicle and route selection in dynamic DARP with travel time and workload objectives

In dial-a-ride problems, a fleet of n vehicles is routed to transport people between pick-up and delivery locations. We consider an elementary version of the problem where trip requests arrive in time and require an immediate vehicle assignment (which triggers an appropriate route update of the selected vehicle). In this context, a relatively general objective can be stated as a weighted sum of the system's effort and the customers' inconvenience. However, optimizing almost any objective in this immensely complex stochastic system is prohibitively difficult. Thus the earlier work has largely resorted to heuristic cost functions that arise, e.g., from the corresponding static systems. By using the framework of Markov decision processes and the classical M/M/1 queue as a highly abstract model for a single vehicle, we explain why certain intuitive cost functions indeed give satisfactory results in the dynamic system, and also give an explicit interpretation of different components appearing in a general cost function. The resulting family of heuristic control policies is demonstrated to offer a desired type of performance thus justifying the assumed analogy between a multi-queue and dial-a-ride systems.