Heat-integrated reactor concepts for catalytic reforming and automotive exhaust purification

Optimal solutions in environmental catalysis require a well-coordinated development of catalysts and of process design. This contribution is devoted to energy integrated design concepts for fuel reforming and for automotive exhaust purification. The examples presented demonstrate the importance of an innovative process design for optimal utilization of existing catalysts and show the potential of future developments.

New concepts for steam reforming through the efficient coupling of the endothermic reforming reaction with an exothermic combustion reaction are discussed in the first part. These concepts have been implemented for methanol steam reforming in a counter-current reactor with distributed side feed of burner gas and for methane steam reforming in a modular reactor with a co-current reaction section for the endothermic and the combustion reaction and attached counter-current heat exchangers. Both applications employ the so-called folded sheet reactor design, which ensures an excellent heat transfer between the reforming and combustion channels and efficient heat recovery.

A similar design solution is introduced for the apparently different case of automotive exhaust purification. The proposed concept aims at decoupling exhaust after-treatment from engine control. Its main component is a counter-current heat exchanger with integrated purification stages for HC-oxidation, NO_X storage and reduction and soot filtering. A small catalytic burner at the hot end of the heat exchanger provides both heat and oxidizing or reducing agents on demand. A new soot filter design allows for safe soot filter regeneration.     

Using particle swarm optimization to solve effectively the school timetabling problem

A new hybrid adaptive algorithm based on particle swarm optimization (PSO) is designed, developed and applied to the high school timetabling problem. The proposed PSO algorithm is used to create feasible and efficient timetables for high schools in Greece. Experiments with real-world data coming from different high schools have been conducted to show the efficiency of the proposed PSO algorithm. As well as that, the algorithm has been compared with four other effective techniques found in the literature to demonstrate its efficiency and superior performance. In order to have a fair comparison with these algorithms, we decided to use the exact same input instances used by these algorithms. The proposed PSO algorithm outperforms, in most cases, other existing attempts to solve the same problem as shown by experimental results.     

Analysis and performance evaluation of a pilot-aided interpolated channel estimator for OFDM systems

In this paper, we propose a novel pilot-aided channel estimator through interpolation for Orthogonal Frequency Division Multiplexing (OFDM) systems that replaces part of the virtual subcarriers with pilot subcarriers (pilots) reducing the interpolation error while keeping the code rate stable. A novel thorough analysis of the Mean Square Error (MSE) of the proposed estimator is given for the general case where data subcarriers are positioned before the first and after the last pilot. Simulations show the improvement of the proposed scheme in MSE and Bit Error Rate (BER) when applied to a practical OFDM wireless local area network type of system with realistic channel conditions.     

FPGA-based architecture and implementation techniques of a low-complexity hybrid RAKE receiver for a DS-UWB communication system

In this paper, the architecture of a low-complexity Direct Sequence Ultra-Wideband (DS-UWB) receiver subsystem which incorporates a Channel Estimator (CE) and a novel hybrid Partial/Selective (HPS) maximal ratio combining (MRC) RAKE receiver is presented. Three different design techniques followed by FPGA implementation are investigated and compared and system performance results are provided. The proposed architectures combine the benefits of both partial and selective RAKE receiver algorithms and the obtained results demonstrate the trade-off between energy capture, performance and receiver complexity. All design approaches focus on a highly parallel, modular and optimized for high performance system which is necessary for demanding and low-cost applications of UWB communications.     

Efficient and flexible anonymization of transaction data

Transaction data are increasingly used in applications, such as marketing research and biomedical studies. Publishing these data, however, may risk privacy breaches, as they often contain personal information about individuals. Approaches to anonymizing transaction data have been proposed recently, but they may produce excessively distorted and inadequately protected solutions. This is because these approaches do not consider privacy requirements that are common in real-world applications in a realistic and flexible manner, and attempt to safeguard the data only against either identity disclosure or sensitive information inference. In this paper, we propose a new approach that overcomes these limitations. We introduce a rule-based privacy model that allows data publishers to express fine-grained protection requirements for both identity and sensitive information disclosure. Based on this model, we also develop two anonymization algorithms. Our first algorithm works in a top-down fashion, employing an efficient strategy to recursively generalize data with low information loss. Our second algorithm uses sampling and a combination of top-down and bottom-up generalization heuristics, which greatly improves scalability while maintaining low information loss. Extensive experiments show that our algorithms significantly outperform the state-of-the-art in terms of retaining data utility, while achieving good protection and scalability.     

Characterization of anisotropic permeability from flow front angle measurements

Textile permeability is a generally anisotropic material property, which characterizes the ease of establishing a resin flow through the fibrous reinforcement in Liquid composite molding (LCM) processes. Unidirectional injection experiments are commonly performed to determine in‐plane permeability. Effective permeability values have to be measured along three different textile directions to calculate the full in‐plane permeability tensor. This article presents a strategy to reduce the number of the required unidirectional experiments to two or even one by considering the angle that the flow front forms with the measurement direction. The relationship between this flow front angle and the permeability tensor elements was derived theoretically and verified by both simulations and experiments with various textile reinforcements. In addition, two methods were investigated to measure the flow front angle and the effective permeability during the experiments: a standard approach based on visual observations and a new method that relies on three pressure sensors, applicable also in the case of nontransparent tooling. The results show that: (I) the two methods provide consistent measurements and are substantially equivalent; (II) the strategy devised to characterize permeability by measuring the flow front angle is effective and accurate; (III) the proposed procedure allows reducing considerably the time and the material samples required for permeability characterization by unidirectional experiments. POLYM. COMPOS., 37:2037–2052, 2016. © 2015 Society of Plastics Engineers     

Fibroblast Growth Factor 21 Response in a Preclinical Alcohol Model of Acute-on-Chronic Liver Injury

Background and Aims: Fibroblast growth factor (FGF) 21 has recently been shown to play a potential role in bile acid metabolism. We aimed to investigate the FGF21 response in an ethanol-induced acute-on-chronic liver injury (ACLI) model in Abcb4^−/− mice with deficiency of the hepatobiliary phospholipid transporter. Methods: Total RNA was extracted from wild-type (WT, C57BL/6J) and Abcb4⁻/⁻ (KO) mice, which were either fed a control diet (WT-Cont and KO-Cont groups; n = 28/group) or ethanol diet, followed by an acute ethanol binge (WT-EtOH and KO-EtOH groups; n = 28/group). A total of 58 human subjects were recruited into the study, including patients with alcohol-associated liver disease (AALD; n = 31) and healthy controls (n = 27). The hepatic and ileal expressions of genes involved in bile acid metabolism, plasma FGF levels, and bile acid and its precursors 7α- and 27-hydroxycholesterol (7α- and 27-OHC) concentrations were determined. Primary mouse hepatocytes were isolated for cell culture experiments. Results: Alcohol feeding significantly induced plasma FGF21 and decreased hepatic Cyp7a1 levels. Hepatic expression levels of Fibroblast growth factor receptor 1 (Fgfr1), Fgfr4, Farnesoid X-activated receptor (Fxr), and Small heterodimer partner (Shp) and plasma FGF15/FGF19 levels did not differ with alcohol challenge. Exogenous FGF21 treatment suppressed Cyp7a1 in a dose-dependent manner in vitro. AALD patients showed markedly higher FGF21 and lower 7α-OHC plasma levels while FGF19 did not differ. Conclusions: The simultaneous upregulation of FGF21 and downregulation of Cyp7a1 expressions upon chronic plus binge alcohol feeding together with the invariant plasma FGF15 and hepatic Shp and Fxr levels suggest the presence of a direct regulatory mechanism of FGF21 on bile acid homeostasis through inhibition of CYP7A1 by an FGF15-independent pathway in this ACLI model. Lay Summary: Alcohol challenge results in the upregulation of FGF21 and repression of Cyp7a1 expressions while circulating FGF15 and hepatic Shp and Fxr levels remain constant both in healthy and pre-injured livers, suggesting the presence of an alternative FGF15-independent regulatory mechanism of FGF21 on bile acid homeostasis through the inhibition of Cyp7a1.     

Tocopherol and tocotrienol compositions of raw table olive fruit

The tocopherol (Tp) and tocotrienol (Tt) compositions of raw Greek olive fruit pericarp were determined by high-performance liquid chromatography. The following four types of fruit collected from three main varieties of olive trees were analysed: ‘Conservolea’ (green), ‘Halkidiki’ (green), ‘Conservolea’ (black) and ‘Calamon’ (black). α-Tp was found to be the predominant Tp in all types. The variety and stage of maturity influenced the Tp and Tt composition. β-Tp and α-Tt were found only in trace quantities in green olives. The same was true for α-Tp in all types and γ-Tp in ‘Conservolea’ (green). The calculated α-Tp equivalents (Tp and Tt compositions expressed as α-Tp according to their relative biological activities) were 21·6, 29·7, 36·8 and 39·4 μg g^?1 pericarp or 138, 132, 189 and 196 μg g^?1 lipid for ‘Conservolea’ (green), ‘Halkidiki’ (green), ‘Conservolea’ (black) and ‘Calamon’ (black), respectively.     

Assessing Disclosure Risk and Data Utility Trade-off in Transaction Data Anonymization

Organizations and businesses, including financial institutions and healthcare providers, are increasingly collecting and disseminating information about individuals in the form of transactions. A transaction associates an individual with a set of items, each representing a potentially confidential activity, such as the purchase of a stock or the diagnosis of a disease. Thus, transaction data need to be shared in a way that preserves individuals'' privacy, while remaining useful in intended tasks. While algorithms for anonymizing transaction data have been developed, the issue of how to achieve a "desired" balance between disclosure risk and data utility has not been investigated. In this paper, we assess the balance offered by popular algorithms using the R-U confidentiality map. Our analysis and experiments shed light on how the joint impact on disclosure risk and data utility can be examined, which allows the production of high-quality anonymization solutions.     

Synthesis of A356 Al–high-Ca fly ash composites by pressure infiltration technique and their characterization

Eight types of A356 Al–fly ash composites were produced by pressure infiltration of high-Ca lignite fly ash. This type of ash was used for the first time in Al-composites synthesis, and particularly by liquid metal infiltration techniques. After examining mineralogy and chemistry, specific, narrow ash size fractions were used for the synthesis of composites, and properties linked to microstructure and wear strength of the materials. The effect of using ground ash particles on the microstructure and tribological performance of the composites was also investigated. It was concluded that using fine, high-Ca ash particles can improve the properties of composites, and that using ash particles in a ground form can better facilitate the production process of MMCs.