Product distribution and kinetic scheme for the fixed bed thermal decomposition of sewage sludge

In this paper, a new kinetic model for the thermal decomposition of dry sewage sludge was determined. In order to achieve this main objective, various experiments were carried out to collect enough information for the estimation of the different numerical parameters of the model. These experiments include both results from a fixed bed pyrolysis installation and a thermogravimetric analysis device. The experiments allowed for the detailed monitoring of the dynamical evolution of the mass of the sample under investigation, together with the cumulative amounts of tars and permanent gases produced during thermal decomposition of sewage sludge at low heating rates (5–20 °C/min). Solid mass loss during the pyrolysis shows two regions, between 150 °C and 600 °C, where most of the tar is depleted from the solid and non-condensible gases are formed, and a second one between 600 °C and 900 °C where mainly only non-condensible gases are produced. The solid fraction accounted for about 50% of the initial weight, tar around 30% and gases the remaining 20%.Regarding the formation of non-condensible gases from low temperature, a new kinetic scheme was proposed involving an initial decomposition step of the sludge yielding tar and gases as gas phase products and a solid intermediate compound which decomposes at higher temperatures, giving the char fraction and more non-condensible gases. The comparison between the numerical prediction and the experimental results was excellent.     

Corrosion of ceramics for vinasse gasification in supercritical water

Supercritical water gasification (SCWG) is a very efficient process to convert wet biomass into energetic gases. Unfortunately, SCWG reactor may strongly corrode due to the addition of temperature, pressure and the presence of corrosive species. In the present paper, the corrosion of various ceramic materials in subcritical and supercritical water (SCW) gasification process was studied in a batch reactor. We compare the corrosion in distillated water and the corrosion in sugar beet slurry that will be gasified under supercritical conditions. The experimental temperatures were 350 °C and 550 °C and the pressure was 25 MPa. Technical ceramics (SiC, alumina, Y stabilized zirconia, Si₃N₄, BN, aluminosilicate, cordierite-mullite) show poor capability to sustain corrosion whereas graphite and glassy carbon are the highest performance materials in our working conditions.     

A registration framework for the comparison of mammogram sequences

In this paper, we present a two-stage algorithm for mammogram registration, the geometrical alignment of mammogram sequences. The rationale behind this paper stems from the intrinsic difficulties in comparing mammogram sequences. Mammogram comparison is a valuable tool in national breast screening programs as well as in frequent monitoring and hormone replacement therapy (HRT). The method presented in this paper aims to improve mammogram comparison by estimating the underlying geometric transformation for any mammogram sequence. It takes into consideration the various temporal changes that may occur between successive scans of the same woman and is designed to overcome the inconsistencies of mammogram image formation.     

Automatic stress analysis from facial videos based on deep facial action units recognition

Pattern Analysis and Applications - Stress conditions are manifested in different human body’s physiological processes and the human face. Facial expressions are modelled consistently through...     

Mathematical modelling of slow pyrolysis of a particle of treated wood waste

Low-temperature pyrolysis is a possible method for the disposal of wood waste treated with chromated copper arsenic (CCA). A mathematical model (heat and mass transfer) including chemical reactions of the thermal degradation of a particle of wood is presented. A spherical particle is heated by a convective nitrogen flow. The progress of the pyrolysis process is characterized by three main steps: (1) drying of the wet sample; (2) heating of the sample until ignition of pyrolysis reactions; (3) pyrolysis and subsequent production of char and volatiles. The mathematical model is based on the volume averaging concept and it uses Shafizadeh and Chin [F. Shafizadeh, P.S. Chin, Thermal deterioration of wood, wood technology: chemical aspects, ACS Symposium Series 43 (1977) 57–81] pyrolysis model to describe the reaction pathway.It is solved by the line method, taking time as the preferred variable. Our model predicts intra-particle profiles for several variables (temperature, moisture content, concentration of wood). Simulations are presented with a spherical particle of 1 cm radius.     

Pattern recognition and pharmacokinetic methods on DCE-MRI data for tumor hypoxia mapping in sarcoma

The main purpose of this study is to analyze the intrinsic tumor physiologic characteristics in patients with sarcoma through model-free analysis of dynamic contrast enhanced MR imaging data (DCE-MRI). Clinical data were collected from three patients with two different types of histologically proven sarcomas who underwent conventional and advanced MRI examination prior to excision. An advanced matrix factorization algorithm has been applied to the data, resulting in the identification of the principal time-signal uptake curves of DCE-MRI data, which were used to characterize the physiology of the tumor area, described by three different perfusion patterns i.e. hypoxic, well-perfused and necrotic one. The performance of the algorithm was tested by applying different initialization approaches with subsequent comparison of their results. The algorithm was proven to be robust and led to the consistent segmentation of the tumor area in three regions of different perfusion, i.e. well-perfused, hypoxic and necrotic. Results from the model-free approach were compared with a widely used pharmacokinetic (PK) model revealing significant correlations.     

Two-tier framework for channel acquisition in public wireless LANs

Recently, hot spots served by public area wireless networks (PAWNs) have been proposed as cost-effective complementary infrastructures to third-generation cellular systems. PAWNs are base-station-oriented wireless LANs, offering tens of megabits per second to public or private hot spot users. Since PAWNs operate in the unlicensed spectrum, channel control methodologies are needed to overcome potential interference conditions. Also, to meet the requirements of future wireless applications, their deployment should take into account quality of service requirements and the fluctuations of network traffic. These issues are addressed here, and a centralized two-tier dynamic resource reservation framework suitable for PAWN deployments is proposed and analyzed.     

An enhanced intelligent DCA technique for unlicensed wLANs and PAWNs

Over the last years, a number of mechanisms have been proposed for scheduling different types of traffic over base stations-oriented wireless and mobile systems. The majority of these mechanisms focus on access control in the base station-to-mobile units segment of the wireless and mobile system. Recent proposals for the unlicensed spectrum in the 5 GHz band have redefined the problem, since base stations, operated by different operators in overlapping geographical areas, need access resolution mechanisms to allocate wireless resources. This issue is addressed here, and a novel mechanism for dynamic channel allocation in unlicensed wireless LANs (wLANs) or public area wireless networks (PAWNs) environments is presented. The proposed method exploits the learning automata technique for the efficient allocation of wireless resources in a distributed manner. Nearby base stations that compete to access and reserve time on separate frequencies are driven by the output of a learning automaton, which determines the available carrier that demonstrates minimal competition. The paper discusses contention resolution disciplines while the learning automaton algorithm as well as its knowledge base structure are also discussed and evaluated.     

Brokering Positioning Data From Heterogeneous Infrastructures

Over the last years, cellular operators, service and content providers, have been trying to identify the needs of a fully connected user, facilitating pervasiveness communications and ubiquitous computing concepts. One of the most promising directions is the so-called context-aware environment. Positioning is an essential component for the deployment of the evolving context-aware concepts. This article introduces a unified positioning component (POS), which establishes a generic, open, modular, and efficient quality of service (QoS) enabled framework, offering independence from the underlying heterogeneous network infrastructures and positioning techniques. The design objectives of POS are presented, as well as its functionality, the technical specifications and the prototype implementation of the POS component, elaborating on the features and services that it offers to the PoLoS platform and middleware location brokering applications.