An efficient wavelet collocation method for nonlinear two-space dimensional Fisher–Kolmogorov–Petrovsky–Piscounov equation and two-space dimensional extended Fisher–Kolmogorov equation

Engineering with Computers - In this paper, we consider two-space dimensional nonlinear Fisher–Kolmogorov–Petrovsky–Piscounov (Fisher–KPP) equation and two-space dimensional...     

Empirical Characterization of Session–Based Workload and Reliability for Web Servers

The growing availability of Internet access has led to significant increase in the use of World Wide Web. If we are to design dependable Web–based systems that deal effectively with the increasing number of clients and highly variable workload, it is important to be able to describe the Web workload and errors accurately. In this paper we focus on the detailed empirical analysis of the session–based workload and reliability based on the data extracted from actual Web logs of eleven Web servers. First, we introduce and rigourously analyze several intra–session and inter–session metrics that collectively describe Web workload in terms of user sessions. Then, we analyze Web error characteristics and estimate the request–based and session–based reliability of Web servers. Finally, we identify the invariants of the Web workload and reliability that apply through all data sets considered. The results presented in this paper show that session–based workload and reliability are better indicators of the users perception of the Web quality than the request–based metrics.     

Extended multi bottom–up tree transducers

Extended multi bottom–up tree transducers are defined and investigated. They are an extension of multi bottom–up tree transducers by arbitrary, not just shallow, left-hand sides of rules; this includes rules that do not consume input. It is shown that such transducers, even linear ones, can compute all transformations that are computed by linear extended top–down tree transducers, which are a theoretical model for syntax-based machine translation. Moreover, the classical composition results for bottom–up tree transducers are generalized to extended multi bottom–up tree transducers. Finally, characterizations in terms of extended top–down tree transducers and tree bimorphisms are presented.     

Age differences rendezvousing: reminders for side-stepping

This paper reports a diary study of the use of mobile telephones for rendezvousing by young adults (aged 18–30) and mature adults (aged 31–45) in the UK. A number of age differences were found. Specifically, 31–45s more frequently: (1) attributed problems rendezvousing to the overrunning of previous activities, and to the spontaneous performance of additional tasks (‘side-stepping’); (2) reported that ‘problem’ rendezvous resulted in unnecessary sacrifices; and (3) changed plans for the rendezvous. These differences arose, because additional family commitments encouraged 31–45s to pack their daily programme of activities more tightly than 18–30s. Mobile phones might better target 31–45s, if they, for example, enhanced To Do Lists with context-sensitive reminders, in the first instance, reminders triggered by location (GSM network cellID) and logging off from PCs.

---

     

A framework for exploring numerical solutions of advection–reaction–diffusion equations using a GPU-based approach

In this paper we describe a general purpose, graphics processing unit (GP-GPU)-based approach for solving partial differential equations (PDEs) within advection–reaction–diffusion models. The GP-GPU-based approach provides a platform for solving PDEs in parallel and can thus significantly reduce solution times over traditional CPU implementations. This allows for a more efficient exploration of various advection–reaction–diffusion models, as well as, the parameters that govern them. Although the GPU does impose limitations on the size and accuracy of computations, the PDEs describing the advection–reaction–diffusion models of interest to us fit comfortably within these constraints. Furthermore, the GPU technology continues to rapidly increase in speed, memory, and precision, thus applying these techniques to larger systems should be possible in the future. We chose to solve the PDEs using two numerical approaches: for the diffusion, a first-order explicit forward Euler solution and a semi-implicit second order Crank–Nicholson solution; and, for the advection and reaction, a first-order explicit solution. The goal of this work is to provide motivation and guidance to the application scientist interested in exploring the use of the GP-GPU computational framework in the course of their research. In this paper, we present a rigorous comparison of our GPU-based advection–reaction–diffusion code model with a CPU-based analog, finding that the GPU model out-performs the CPU implementation in one-to-one comparisons.     

GHZ States,Almost-Complex Structure and Yang–Baxter Equation

Recent research suggests that there are natural connections between quantum information theory and the Yang–Baxter equation. In this paper, in terms of the almost-complex structure and with the help of its algebra, we define the Bell matrix to yield all the Greenberger–Horne–Zeilinger (GHZ) states from the product basis, prove it to form a unitary braid representation and presents a new type of solution of the quantum Yang–Baxter equation. We also study Yang–Baxterization, Hamiltonian, projectors, diagonalization, noncommutative geometry, quantum algebra and FRT dual algebra associated with this generalized Bell matrix.      

Numerically Pricing Nonlinear Time-Fractional Black–Scholes Equation with Time-Dependent Parameters Under Transaction Costs

Computational Economics - One of the assumptions of the classical Black–Scholes (B–S) is that the market is frictionless. Also, the classical B–S model cannot show the memory...     

A Hopfield neural network approach for power optimization of real-time operating systems

The RTOS (Real-Time Operating System) is a critical component in the SoC (System-on-a-Chip), which is the main body for consuming total system energy. Power optimization based on hardware–software partitioning of a RTOS (RTOS–Power partitioning) can significantly minimize the energy consumption of a SoC. This paper presents a new model for RTOS–Power partitioning, which helps in understanding the essence of the RTOS–Power partitioning techniques. A discrete Hopfield neural network approach for implementing the RTOS–Power partitioning is proposed, where a novel energy function, operating equation and coefficients of the neural network are redefined. Simulations are carried out with comparison to other optimization techniques. Experimental results demonstrate that the proposed method can achieve higher energy savings up to 60% at relatively low costs of less than 4k PLBs while increasing the performance compared to the purely software realized SoC–RTOS.     

Effect algebras with the subsequential interpolation property

We prove Brooks–Jewett, Vitali–Hahn–Saks and NikodymBoundedness theorems for modular measures on lattice-ordered effect algebras with the subsequential interpolation property. Supported by G.N.A.M.P.A.     

Liquid–liquid microflows in micro-sieve dispersion devices with dual pore size

Here we present the liquid–liquid microflows and dispersion rules in micro-sieve devices with two different sized pores. The flow pattern, flux distribution and droplet size were investigated to discuss the effect of pore size deviation. Three flow patterns including dripping flow from a single active pore, dripping–dripping flow and dripping–jetting flow from two active pores were identified. A modified active pore model based on a pressure drop balance has been established. The model can predict the transition from a single active pore flow regime to a two active pore flow regime very well. In the latter regime, interactions between the small and large pores can result in dripping–dripping flow at low trans-pore flux and dripping–jetting flow at high trans-pore flux. Controlling the flow pattern in dripping–dripping flow is favorable to decreasing droplet polydispersity.     

Thinking About Evolution in Terms of Cellular Computing

The past five decades of molecular genetics have produced many discoveries about genome structure and function that can only be understood from an informatic perspective: – distinct sequence codes to mark the individual steps in packaging, expression, replication, transmission, repair and restructuring of DNA molecules; – modularity of data files for RNA and protein products; – combinatoric organization of signals to format the genome for differential functioning during cellular and organismal cycles; – direct participation of DNA in the execution of biological algorithms (formation of highly structured nucleoprotein complexes); – hierarchical organization of genomic subsystems to form higher level system architectures. This review will discuss aspects of genome organization and genome change that require a more formal computational analysis. We will see how modern results indicate that genome evolution has many similarities to computer system engineering. The ability of cells to control the function of natural genetic engineering systems is central to the genome’s potential as a Read–Write information storage system.     

Hot embossing of microstructures: characterization of friction during demolding

Today, hot embossing and injection molding belong to the established plastic molding processes in microengineering. Based on experimental findings, a variety of microstructures have been replicated so far using the above processes. However, with increasing requirements regarding the embossing surface and the simultaneous decrease of the structure size down into the nanorange, increasing know––how is needed to adapt hot embossing to industrial standards. To reach this objective, a German–Canadian cooperation project has been launched to study hot embossing theoretically by a process simulation and experimentally. The present publication shall report about an important aspect––the determination of friction during the demolding of microstructures.     

Choosing the parameter of a modified additive-averaged splitting algorithm

The problem-solving time and the solution accuracy are expressed as functions of a parameter. An optimization problem of choosing the parameter using a “time cost–solution accuracy” criterion is considered. A Pareto-optimal set of solutions is obtained. The best value of the parameter is chosen by the ideal-point method. Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 98–105, July–August 2009.     

Algebraic Fractional-Step Schemes for Time-Dependent Incompressible Navier–Stokes Equations

The numerical investigation of a recent family of algebraic fractional-step methods (the so called Yosida methods) for the solution of the incompressible time-dependent Navier–Stokes equations is presented. A comparison with the Karniadakis–Israeli–Orszag method Karniadakis et al. (1991, J. Comput. Phys. 97, 414–443) is carried out. The high accuracy in time of these schemes well combines with the high accuracy in space of spectral methods.     

The Neural Network Approach to Input–Output Analysis for Economic Systems

Economic practitioners in China are giving up the classical Leontief’s Input–Output analysis methods. This paper offers an alternative method of input–output analysis. The proposed method is based on the layered neural network model. It shows that neural networks method can be useful for input–output analysis for a dynamic economic system.       

On Parabolic Boundary Layers for Convection–Diffusion Equations in a Channel: Analysis and Numerical Applications

In this article we discuss singularly perturbed convection–diffusion equations in a channel in cases producing parabolic boundary layers. It has been shown that one can improve the numerical resolution of singularly perturbed problems involving boundary layers, by incorporating the structure of the boundary layers into the finite element spaces, when this structure is available; see e.g. [Cheng, W. and Temam, R. (2002). Comput. Fluid. V.31, 453–466; Jung, C. (2005). Numer. Meth. Partial Differ. Eq. V.21, 623–648]. This approach is developed in this article for a convection–diffusion equation. Using an analytical approach, we first derive an approximate (simplified) form of the parabolic boundary layers (elements) for our problem; we then develop new numerical schemes using these boundary layer elements. The results are performed for the perturbation parameter ε in the range 10⁻¹–10⁻¹⁵ whereas the discretization mesh is in the range of order 1/10–1/100 in the x-direction and of order 1/10–1/30 in the y-direction. Indications on various extensions of this work are briefly described at the end of the Introduction.Dedicated to David Gottlieb on his 60th birthday.     

Numerical analysis on electroosmotic flows in a microchannel with rectangle-waved surface roughness using the Poisson–Nernst–Planck model

The present study has numerically investigated two-dimensional electroosmotic flows in a microchannel with dielectric walls of rectangle-waved surface roughness to understand the roughness effect. For the study, numerical simulations are performed by employing the Nernst–Planck equation for the ionic species and the Poisson equation for the electric potential, together with the traditional Navier–Stokes equation. Results show that the steady electroosmotic flow and ionic-species transport in a microscale channel are well predicted by the Poisson–Nernst–Planck model and depend significantly on the shape of surface roughness such as the amplitude and periodic length of wall wave. It is found that the fluid flows along the surface of waved wall without involving any flow separation because of the very strong normal component of EDL (electric double layer) electric field. The flow rate decreases exponentially with the amplitude of wall wave, whereas it increases linearly with the periodic length. It is mainly due to the fact that the external electric-potential distribution plays a crucial role in driving the electroosmotic flow through a microscale channel with surface roughness. Finally, the present results using the Poisson–Nernst–Planck model are compared with those using the traditional Poisson–Boltzmann model which may be valid in these scales.     

On the application of the minimum polynomial extrapolation method to incompressible flows with heat transfer

In this paper, the Minimum Polynomial Extrapolation method (MPE) is used to accelerate the convergence of the Characteristic–Based–Split (CBS) scheme for the numerical solution of steady state incompressible flows with heat transfer. The CBS scheme is a fractional step method for the solution of the Navier–Stokes equations while the MPE method is a vector extrapolation method which transforms the original sequence into another sequence converging to the same limit faster then the original one without the explicit knowledge of the sequence generator. The developed algorithm is tested on a two-dimensional benchmark problem (buoyancy–driven convection problem) where the Navier–Stokes equations are coupled with the temperature equation. The obtained results show the feature of the extrapolation procedure to the CBS scheme and the reduction of the computational time of the simulation.     

Electroosmotic flow at a liquid–air interface

This paper presents the first experimental evidence on electroosmotic flow at a liquid–air interface. A PDMS microchannel with an opening to air was created to allow for the formation of a liquid–air interface. Polystyrene particles were used to visualize the liquid motion and the experiments found that the particle velocity at the liquid–air interface was significantly slower than the particle velocity in the bulk. This result agrees with a mathematical model that considers the effects of electrical surface charges at the liquid–air interface in electroosmotic flow.     

Relational structures model of concurrency

The paper deals with the foundations of concurrency theory. We show how structurally complex concurrent behaviours can be modelled by relational structures (X, ¨, \sqsubset){(X, \diamondsuit, \sqsubset)} , where X is a set (of event occurrences), and ¨{\diamondsuit} (interpreted as commutativity) and \sqsubset{\sqsubset} (interpreted as weak causality) are binary relations on X. The paper is a continuation of the approach initiated in Gaifman and Pratt (Proceedings of LICS’87, pp 72–85, 1987), Lamport (J ACM 33:313–326, 1986), Abraham et al. (Semantics for concurrency, workshops in computing. Springer, Heidelberg, pp 311–323, 1990) and Janicki and Koutny (Lect Notes Comput Sci 506:59–74, 1991), substantially developed in Janicki and Koutny (Theoretical Computer Science 112:5–52, 1993) and Janicki and Koutny (Acta Informatica 34:367–388, 1997), and recently generalized in Guo and Janicki (Lect Notes Comput Sci 2422:178–191, 2002) and Janicki (Lect Notes Comput Sci 3407:84–98, 2005). For the first time the full model for the most general case is given.