A discontinuous Galerkin method for the wave equation

We present a new discontinuous Galerkin method for solving the second-order wave equation using the standard continuous finite element method in space and a discontinuous method in time directly applied to second-order ode systems. We prove several optimal a priori error estimates in space–time norms for this new method and show that it can be more efficient than existing methods. We also write the leading term of the local discretization error in terms of Lobatto polynomials in space and Jacobi polynomials in time which leads to superconvergence points on each space–time cell. We discuss how to apply our results to construct efficient and asymptotically exact a posteriori estimates for space–time discretization errors. Numerical results are in agreement with theory.     

Temperature field,H2 and H2O mass transfer in SOFC single cell: Electrode and electrolyte thickness effects

The temperature increment in electrodes and electrolyte of a fuel cell is mainly attributed to the chemical reaction and the irreversibilities. The aim of this work is to study the increasing temperature of a SOFC single cell under the influence of the electrode and electrolyte thicknesses for its type of heat source. The hydrogen and water field are also discussed according to anode thickness.     

Covalent modification of boron-doped diamond electrodes with an imidazolium-based ionic liquid

An ionic liquid (IL, 1-(methylcarboxylic acid)-3-octylimidazolium-bis (trifluoromethylsulfonyl)imide) was covalently coupled onto a boron-doped diamond (BDD) surface through an esterification reaction. The resulting surface was characterized by X-ray photoelectron spectroscopy, water contact angle and electrochemical measurements. Selective electron transfer towards positively and negatively charged redox species was recorded. While the presence of Fe(CN)₆⁴⁻ could be detected on the IL-modified BDD interface, no surface-immobilized Ru(NH₃)₆³⁺ was recorded. The IL-modified BDD electrode showed in addition changes in surface wettability when immersed into aqueous solution containing different anions.     

Effect of wood powder on polymer foam nucleation

It is usually reported that wood particles in wood/polymer composite foams can act as nucleating sites. Since high wood contents are used, it is difficult to determine exactly the effect of wood particles. In this study, LDPE was chemically foamed in a twin‐screw extruder, and small amounts of wood (0–5 phr) were added to determine their effect. Particle size was investigated by using three mesh sizes: 45–61, 104–125, and 180–210 μm. As expected, wood particles acted as nucleating agents that substantially reduced cell size and increased cell density. J. VINYL. ADDIT. TECHNOL., 12:19–24, 2006. © 2006 Society of Plastics Engineers     

A SIP servlets-based framework for service provisioning in stand-alone MANETs

Mobile Ad hoc Networks (MANETs) are transient networks formed dynamically by a collection of arbitrarily located wireless mobile nodes without relying on any existing network infrastructure or centralized administration. They are either stand alone or connected to a fixed infrastructure such as 3G. They are useful in situations such as natural disasters, and their use is gaining more and more momentum. This paper proposes a framework for service provisioning in stand-alone MANETs. It focuses on the invocation and execution phases of the service life cycle. The framework is based on SIP servlets and comprises a novel business model and an overlay network. The business model enables service invocation and execution. The overlay network is used for service execution and is based on a distributed SIP servlets engine. Validation aspects are also discussed.     

Higher degree immersed finite element spaces constructed according to the actual interface

We discuss the construction of higher degree immersed finite element (IFE) spaces that can be used to solve two dimensional second order elliptic interface problems having general interfaces without requiring the mesh to be aligned with the material interfaces. The optimal approximation capability of the proposed piecewise $p$th degree IFE spaces are demonstrated by numerical experiments with interpolations. Numerical solutions to interface problems generated from a partially penalized method based on the proposed higher order IFE spaces also suggest optimal convergence in both the $L^2$ and $H^1$ norms under mesh refinement.     

A novel chaotic image cryptosystem based on DNA sequence operations and single neuron model

Multimedia Tools and Applications - In this paper, a novel image cryptosystem based on DNA sequence operations, Single Neuron Model (SNM) and chaotic map is designed. The initial conditions and...     

Comparison of different oxidation techniques on single-crystal and nanocrystalline diamond surfaces

Various oxidation techniques (plasma-beam, sulfo-chromic acid, UV-ozone, heating in air) were applied to single-crystalline (111) and (100) diamond surfaces as well as nanocrystalline diamond (NCD) films and analyzed by X-ray photoelectron spectroscopy (XPS) with respect to oxygen content and type of carbon–oxygen groups formed upon oxidation. Due to their increased surface, NCD films show a significantly higher oxygen uptake as compared to their single-crystal counterparts. No marked differences were observed between the different oxidation techniques. For all oxidation techniques used, several carbon–oxygen groups are simultaneously present on the surface. The relative fraction of singly-oxidized carbon atoms (attributed to isolated ether or epoxy-like groups) generally decreases slightly with increasing oxygen content, but always remains the dominating species.