Urban Computing and Mobile Devices

In this issue's Works in Progress department, we have 12 urban computing and mobile device entries that span a wide range of computing and social areas. The first entry examines how an urban environment could operate as a large-scale, real-time control system. One project focuses on annotating public spaces and sharing the tags with others. Two projects tie together social networking in cyberspace with local urban communities. Two projects examine computing and social interactions in physical spaces. Two entries explore how to combine synthetic and physical views of urban environments. Four entries investigate how we explore urban spaces, interact with technology in those spaces, and create shared community histories.     

The relation of steady evaporating drops fed by an influx and freely evaporating drops

We discuss a thin film evolution equation for a wetting evaporating liquid on a smooth solid substrate. The model is valid for slowly evaporating small sessile droplets when thermal effects are insignificant, while wettability and capillarity play a major role. The model is first employed to study steady evaporating drops that are fed locally through the substrate. An asymptotic analysis focuses on the precursor film and the transition region towards the bulk drop and a numerical continuation of steady drops determines their fully non-linear profiles. Following this, we study the time evolution of freely evaporating drops without influx for several initial drop shapes. As a result we find that drops initially spread if their initial contact angle is larger than the apparent contact angle of large steady evaporating drops with influx. Otherwise they recede right from the beginning.     

Network Control in ATM-Based LEO Satellite Networks

Low Earth Orbiting (LEO) satellite networks with on-board asynchronous transfer mode (ATM) switches hold the promise of offering an economically viable extension of terrestrial ATM systems by providing connectivity to areas where existing terrestrial networks are either infeasible or impractical. Network management in ATM LEO satellite networks is typically performed by the Network Control Center (NCC). The main contribution of this paper is to propose a network management system configuration with a stand-by solution and to describe an experimental Satellite Management Information Base (SMIB) that we have developed for implementation in ATM LEO satellite networks.     

Assessment of mitigation options for the energy system in Bulgaria

The Bulgarian greenhouse gas (GHG) emission profile reveals the energy sector as the most significant emission source and also as an area where great potential for GHG emissions reduction exists. Mitigation options in energy supply were selected considering the potential of fossil fuel substitution and new energy technology implementation in the context of the existing structure of energy system and projects for mid- and long-term development. Basically three modules of ENPEP were used: BALANCE — to calculate the energy flows and energy cost from primary fuel resources and fuel import to energy end-use, IMPACT — to calculate GHG emissions, and ELECTRIC — to project the electric system long-term development. Different mitigation measures combined in four scenarios were developed. The integrated mitigation scenario incorporated a mix of mitigation measures in the energy demand and supply. Implementation of CO₂ mitigation measures both in energy demand and energy supply would reduce the 2020 emission level by 34.3 Tg (29.1%), and by 544.2 Tg (21.7%) for the entire study period 2000 – 2020, compared to the baseline scenario.     

Interface Behavior of a Bimaterial Plate under Dynamic Loading

The paper deals with interface behavior of bimaterial ceramic-metal composites under dynamic time-harmonic load. The first plate is precracked with a normal crack touching the interface between the plates. It is assumed that the respective restriction for the ratio of energy release rates of the plates allowing the occurrence of an interface single delamination before the initiation of the normal crack in the second plate is satisfied. The growth of interface delamination is not considered. The used approximate shear-lag dynamic approach gives a possibility to obtain solutions in a closed form for axial and shear stresses of the structure. At an elastic-brittle interface behavior theoretical predictions for single debond length of two bimaterial structures are calculated. The parametric analysis reveals the sensitivity of the interface single debond length and shear stress to the type of bimaterial structure and to the characteristics of the dynamic load—in particular its frequency and amplitude. All results are illustrated in figures and tables and are discussed.     

Context-based object-class recognition and retrieval by generalized correlograms

We present a novel approach for retrieval of object categories based on a novel type of image representation: the Generalized Correlogram (GC). In our image representation, the object is described as a constellation of GCs where each one encodes information about some local part and the spatial relations from this part to others (i.e., the part's context). We show how such a representation can be used with fast procedures that learn the object category with weak supervision and efficiently match the model of the object against large collections of images. In the learning stage, we show that by integrating our representation with Boosting the system is able to obtain a compact model that is represented by very few features, where each feature conveys key properties about the object's parts and their spatial arrangement. In the matching step, we propose direct procedures that exploit our representation for efficiently considering spatial coherence between the matching of local parts. Combined with an appropriate data organization such as Inverted Files, we show that thousands of images can be evaluated efficiently. The framework has been applied to different standard databases and we show that our results are favorably compared against state-of-the-art methods in both computational cost and accuracy.     

MEMBERSHIP FUNCTIONS SHAPE AND ITS INFLUENCE ON THE DYNAMICAL BEHAVIOUR OF FUZZY LOGIC CONTROLLER

In the present paper, the influence of membership functions shape on the fuzzy logic controller output surface is investigated and discussed. Bell-shaped membership functions with two parameters are used. An example with linear object under control is shown. The results are presented graphically and can serve to determine two parameters with respect to the desired action of fuzzy controller.     

On the Decoding Process in Ternary Error-Correcting Output Codes

A common way to model multiclass classification problems is to design a set of binary classifiers and to combine them. Error-Correcting Output Codes (ECOC) represent a successful framework to deal with these type of problems. Recent works in the ECOC framework showed significant performance improvements by means of new problem-dependent designs based on the ternary ECOC framework. The ternary framework contains a larger set of binary problems because of the use of a “do not care” symbol that allows us to ignore some classes by a given classifier. However, there are no proper studies that analyze the effect of the new symbol at the decoding step. In this paper, we present a taxonomy that embeds all binary and ternary ECOC decoding strategies into four groups. We show that the zero symbol introduces two kinds of biases that require redefinition of the decoding design. A new type of decoding measure is proposed, and two novel decoding strategies are defined. We evaluate the state-of-the-art coding and decoding strategies over a set of UCI Machine Learning Repository data sets and into a real traffic sign categorization problem. The experimental results show that, following the new decoding strategies, the performance of the ECOC design is significantly improved.     

Validation of an EEG-derived spectral frequency index (SFx) for continuous monitoring of sleep depth in humans

Sleep in humans is classically assessed by recording a multichannel electroencephalogram (EEG) in connection with an electrooculogram (EOG) and an electromyogram (EMG). In general, human sleep is manually staged into 6 categories (from awake through REM sleep to stage 4 reflecting deep sleep) on the basis of a visual inspection of EEG periods (epochs) of 20 - 30 s duration. This cumbersome methodology is still used in practice and for reference purposes. - The conversion of EEG-signals by means of Fast Fourier Transformation provides objective and reproducible information reflecting specific communicative features of the central nervous system. A special part of this information based on a specific algorithm is defined by the so-called spectral frequency index (SFx). This SFx-algorithm contains relationships among some particular EEG frequencies and provides objective percentage values about the state of consciousness of a person. In order to validate this new SFx-method, sleep as a physiological state of continuous alterations of consciousness and vigilance was chosen. A total of 36 nights of sleep from 18 healthy volunteers were staged manually by a scientist unaware of the protocol. The volunteers received either placebo or lormetazepam prior to commencement of the nocturnal recordings. The manually staged data were compared with the data obtained by the SFx-analysis. Both data sets SFx values and manually staged data were made comparable by averaging their values to a basic period length of 2 min duration giving 7960 pairs of data. The SFx data for sleep were found within a range from 35% to 100%. The SFx-medians of the manually staged data from "awake" to stage 4 were found in a decending order ("awake": 83% (lower and upper quartile 78% / 87%);"REM": 68% (63%/74%),"stage 1" :63% (57%/70%),"stage 2" :51% (47%/57%), "stage 3" :44% (42%/46%) and "stage 4" :42% (40%/44%). The rank correlation coefficient between the data pairs was calculated to be 0.79 indicating a substantial matching between the manually staged score and the SFx. We therefore conclude that the SFx is a suitable and objective indicator of sleep depth in humans.