Autothermal reforming of methane over nickel catalysts supported on nanocrystalline MgAl2O4 with high surface area

In this paper autothermal reforming of methane (ATR) was carried out over MgAl₂O₄ supported Ni catalysts with various Ni loadings. MgAl₂O₄ spinel with high specific surface area, as nanocrystalline carrier for nickel catalysts was synthesized by co-precipitation method with the addition of pluronic P123 triblock copolymer as surfactant. The prepared samples were characterized by XRD, BET, TEM, SEM, TPR and TPH techniques. The results demonstrated that methane conversion is significantly increased with increasing the Ni content and methane conversion of 15% Ni/MgAl₂O₄ was higher than that of other catalysts in all operation temperatures. Furthermore the influences of H₂O/CH₄, and O₂/CH₄ molar ratio in feed and GHSV on activity of 5% Ni/MgAl₂O₄ catalyst were investigated.     

Autothermal reforming of methane over Ni catalysts supported on nanocrystalline MgO with high surface area and plated-like shape

Autothermal reforming of methane (ATRM), combination of partial oxidation and steam reforming was performed over MgO supported Ni catalysts. The preparation of MgO via surfactant-assisted precipitation method led to obtain a nanocrystalline carrier for nickel catalysts. The results demonstrated that methane conversion is significantly increased with increasing the Ni content (5, 7, 10 and 15%Ni) and methane conversion of 15%Ni/MgO was higher than that of other catalysts with lower Ni loading in all operation temperatures.In addition, increasing the system operation temperatures led to decrease in H₂/CO due to the fact that water-gas shift reaction was thermodynamically unfavorable at elevated temperatures. This catalyst also exhibited stable catalytic performance during 50 h time on stream. Furthermore, the influences of varying GHSV and feed ratio on activity of 15%Ni/MgO catalyst were investigated.     

Optimal power allocation for cognitive radio networks with relay‐assisted directional transmission

In this paper, the problem of power allocation in a cooperative cognitive radio (CR) network is investigated. An optimal power allocation is proposed to maximize efficiency of the secondary network in which secondary users transmit simultaneously over a spectral band assigned to the primary users. The CR network employs directional relays to improve efficiency of the communication links and minimize interference introduced to the primary users. Unlike the conventional cooperative relay‐assisted network, the directional relays are grouped in clusters. This clustering technique along with directional transmission can significantly reduce interference to the primary links and improve the system performance. Two algorithms are also developed on the basis of the penalty method to determine unknown transmission powers. Some corroborant numerical examples are provided to illustrate quick convergence behavior of the proposed algorithms and great superiority of employing clustered directional relays in cooperative CR networks. Copyright © 2013 John Wiley & Sons, Ltd.     

Koordination von Übernahmemanövern beim hochautomatisierten Fahren unter Berücksichtigung der Fahrerverfügbarkeit

Forschung im Ingenieurwesen - Eine der zentralen Problemstellungen beim bedingt- und hochautomatisierten Fahren liegt in der Gestaltung einer sicheren und komfortablen Aufgabenübertragung...     

Damage identification in connections of moment frames using time domain responses and an optimization method

Damage is defined as changes to the material and/or geometric properties of a structural system, comprising changes to the boundary conditions and system connectivity, adversely affecting the system’s performance. Inspecting the elements of structures, particularly critical components, is vital to evaluate the structural lifespan and safety. In this study, an optimization-based method for joint damage identification of moment frames using the time-domain responses is introduced. The beam-to-column connection in a metallic moment frame structure is modeled by a zero-length rotational spring at both ends of the beam element. For each connection, an end-fixity factor is specified, which changes between 0 and 1. Then, the problem of joint damage identification is converted to a standard optimization problem. An objective function is defined using the nodal point accelerations extracted from the damaged structure and an analytical model of the structure in which the nodal accelerations are obtained using the Newmark procedure. The optimization problem is solved by an improved differential evolution algorithm (IDEA) for identifying the location and severity of the damage. To assess the capability of the proposed method, two numerical examples via different damage scenarios are considered. Then, a comparison between the proposed method and the existing damage identification method is provided. The outcomes reveal the high efficiency of the proposed method for finding the severity and location of joint damage considering noise effects.     

Flow-injection spectrophotometric determination of vanadium with malachite green oxalate by bromate in acidic and micellar medium

A flow injection method is proposed for determining vanadium(V). The method is based on its catalytic effect on the oxidation of malachite green oxalate by bromate. The reaction was monitored spectrophotometrically by measuring malachite green oxalate absorbance at λmax = 625 nm. The reagents and manifold variables, which have influences on the sensitivity, were investigated and the optimum conditions were established. The optimized conditions made it possible to determine vanadium in the ranges of 10-140 ng/mL with a detection limit of 5.2 ng/mL and a sample rate of 20 ± 5 samples/h.     

A balanced scorecard for item-level RFID in the retail sector: a Delphi study

Item-level Radio Frequency Identification (RFID) adoption is on the agenda for many retailers. However, before adopting this technology, managers need to be able to identify its direct and indirect benefits. These benefits are expected to be significant and have begun to be studied empirically and analytically in narrow, isolated segments (e.g., supply chain management). In this paper, we focus on applications of RFID in the retail sector, specifically in store operations. We have adapted the balanced scorecard (BSC) model as a decision-making framework to build a holistic model of RFID-enabled changes throughout retail store operations including marketing, merchandising, and supply chain management. After reviewing the existing literature, we conducted a Delphi study in which 10 consultants and senior managers from leading U.S. retailers were interviewed. The results indicate that benefits in the areas of merchandising and marketing may not be realized as directly as those in the supply chain, but their effects should not be underestimated. The proposed BSC model can also indicate potential opportunities for item-level RFID use in retailing and serve as a guideline for further studies.     

Viscoelastic modeling of the contact interaction between a tactile sensor and an atrial tissue

Modeling and parameter identification of soft tissue are essential in establishing an accurate contact model for tool-tissue interaction, which can be used in the development of high-fidelity surgical instruments. This paper discusses the interaction between a tissue and a tactile sensor in minimally invasive surgery, the focus being a novel technique for robotic-assisted mitral valve repair, in which tactile sensors are used to distinguish between different kinds of tissue by their relative softness. A discrete viscoelastic model is selected to represent the tissue behavior. To populate the model of the tissue with actual data, a set of tissue-testing experiments is designed and implemented on the atrial tissue of a swine heart by analyzing its dynamic response. By means of a genetic algorithm, data of the complex compliance are extracted and used to find the coefficients of the model. Further, a viscoelastic contact model is developed to model the interaction between the tissue and the tactile sensor with annular shape. Finally, the relation among the indentation displacement, the ratio of the radii, and the applied force is established parametrically.     

Efficient resource-aware control on SIP servers in 802.11n wireless edge networks

World Wide Web - Voice transmission over wireless edge networks is a conventional, cost-effective technology to transmit voice calls over 802.11 edge networks. In this type of service, Session...     

Hand gesture recognition using topological features

Multimedia Tools and Applications - Hand Gestures Recognition (HGR) is one of the main areas of research for Human Computer Interaction applications. Most existing approaches are based on local or...