Computer Science & I.T

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Linear Scaling Solution of the Time-Dependent Self-Consistent-Field Equations

Author(s):Matt Challacombe
Journal: Computation
Publisher:
Abstract
| Pages: 1-11
 A new approach to solving the Time-Dependent Self-Consistent-Field equations is developed based on the double quotient formulation of Tsiper 2001 (J. Phys. B). Dual channel, quasi-independent non-linear optimization of these quotients is found to yield convergence rates approaching those of the best case (single channel) Tamm-Dancoff approximation. This formulation is variational with respect to matrix truncation, admitting linear scaling solution of the matrix-eigenvalue problem, which is demonstrated for bulk excitons in the polyphenylene vinylene oligomer and the (4,3) carbon nanotube segment.

Ab Initio Research on a New Type of Half-Metallic Double Perovskites, A2CrMO6 (A = IVA Group Elements; M = Mo, Re and W)

Author(s):Yun-Ping Liu -- Huei-Ru Fuh -- Yin-Kuo Wang
Journal: Computation
Publisher:
Abstract
| Pages: 12-22
 The research based on density functional theory was carried out using generalized gradient approximation (GGA) for full-structural optimization and the addition of the correlation effect (GGA + U (Coulomb parameter)) in a double perovskite structure, A2BB’O6. According to the similar valance electrons between IIA(s2) and IVA(p2), IVA group elements instead of alkaline-earth elements settled on the A-site ion position with fixed BB' combinations as CrM (M = Mo, Re and W). The ferrimagnetic half-metallic (HM-FiM) properties can be attributed to the p-dhybridization between the Crd-Mp and the double exchange. All the compounds can be half-metallic (HM) materials, except Si2CrMoO6, Ge2CrMo and Ge2CrReO6, because the strong-correlation correction should be considered. For M = W, only A = Sn and Pb are possible candidates as HM materials. Nevertheless, an examination of the structural stability is needed, because Si, Ge, Sn and Pb are quite different from Sr. All compounds are stable, except for the Si-based double perovskite structure.

A 3-D Model of a Perennial Ryegrass Primary Cell Wall and Its Enzymatic Degradation

Author(s):Indrakumar Vetharaniam -- William J. Kelly -- Graeme T. Attwood -- Philip J. Harris
Journal: Computation
Publisher:
Abstract
| Pages: 23-46
We have developed a novel 3-D, agent-based model of cell-wall digestion to improve our understanding of ruminal cell-wall digestion. It offers a capability to study cell walls and their enzymatic modification, by providing a representation of cellulose microfibrils and non-cellulosic polysaccharides and by simulating their spatial and catalytic interactions with enzymes. One can vary cell-wall composition and the types and numbers of enzyme molecules, allowing the model to be applied to a range of systems where cell walls are degraded and to the modification of cell walls by endogenous enzymes. As a proof of principle, we have modelled the wall of a mesophyll cell from the leaf of perennial ryegrass and then simulated its enzymatic degradation. This is a primary, non-lignified cell wall and the model includes cellulose, hemicelluloses (glucuronoarabinoxylans, 1,3;1,4-β-glucans, and xyloglucans) and pectin. These polymers are represented at the level of constituent monosaccharides, and assembled to form a 3-D, meso-scale representation of the molecular structure of the cell wall. The composition of the cell wall can be parameterised to represent different walls in different cell types and taxa. The model can contain arbitrary combinations of different enzymes. It simulates their random diffusion through the polymer networks taking collisions into account, allowing steric hindrance from cell-wall polymers to be modelled. Steric considerations are included when target bonds are encountered, and breakdown products resulting from enzymatic activity are predicted.

Can the Thermodynamic Hodgkin-Huxley Model of Voltage-Dependent Conductance Extrapolate for Temperature?

Author(s):Michael D. Forrest
Journal: Computation
Publisher:
Abstract
| Pages: 47-60
Hodgkin and Huxley (H-H) fitted their model of voltage-dependent conductances to experimental data using empirical functions of voltage. The thermodynamic H-H model of voltage dependent conductances is more physically plausible, as it constrains and parameterises its empirical fit by assuming that ion channel transition rates depend exponentially on a free energy barrier that in turn, linearly or non-linearly, depends on voltage. The original H-H model contains no explicit temperature terms and requires Q10 factors to describe data at different temperatures. The thermodynamic H-H model does have explicit terms for temperature. Do these endow the model with extrapolation for temperature? We utilised voltage clamp data for a voltage-gated K+ current, recorded at three different temperatures. The thermodynamic H-H model’s free parameters were fitted (Marquardt-Levenberg algorithm) to a data set recorded at one (or more) temperature(s). Then we assessed whether it could describe another data set, recorded at a different temperature, with these same free parameter values and its temperature terms set to the new temperature. We found that it could not.

Radio Spectrum Monitoring simulation and Design

Author(s):Nabil Ali sharaf, Abdirasoul Jabar Alzubaidi
Journal: International Journal of Computational Engineering Research(IJCER)
Publisher:IJCER
Abstract
| Pages: 15-18
With rapid development of communication industry, the kinds of communication service vary. According to the increasing use of radio waves, the intelligent and effective radio monitoring system needs to be developed, which is replaced for previous radio monitoring system. Next-Generation Intelligent Radio Monitoring System based on ITU-R, Rule of wireless facilities, and Radio Waves Act is used, and which can accurately and effectively function as effective radio monitoring system through spectrum analysis of channel power, frequency deviation, offset, and an occupied frequency bandwidth, about the analog and digital signal in On-Air of V/UHF bandwidth. In this paper, we proposes method of radio measurement and radio management through the radio quality measurement, unwanted electromagnetic signals(spurious, harmonic) measurement, high-speed spectrum measurement, frequency usage efficiency investigation, illegal radio exploration

The Role of Processes Re-Engineering and Workflow in the Transformation Of E-Government

Author(s):Faisal Mohammed Nafie, Samani A. Talab
Journal: International Journal of Computational Engineering Research(IJCER)
Publisher:IJCER
Abstract
| Pages: 19-25
This paper aims to support the concept of workflow and the transition to e-government through a new technology by applied Arabdox for workflow system and design models electronic transfer operations from station to another (from one user to another) according to a high-security controls for users. Our case study is vacation request which various kinds in the National Pensions Fund (NPF) and use monitors and reports showing the path of the flow process and follow-up workflow .This process focuses in controlling the requests of vacations of the organization, from the initial request up to its approval or rejection.

THEMIS: A Mutually Verifiable Billing Transactions For Cloud Computing Environment

Author(s):B.Harshini , M. Venkata Krishna Reddy
Journal: International Journal of Computational Engineering Research(IJCER)
Publisher:IJCER
Abstract
| Pages: 11-14
With the widespread adoption of cloud computing, the ability to record and account for the usage of cloud resources in a credible and verifiable way has become critical for cloud service providers and users alike. The success of such a billing system depends on several factors: the billing transactions must have integrity and non-repudiation capabilities; the billing transactions must be non obstructive and have a minimal computation cost; and the service level agreement (SLA) monitoring should be provided in a trusted manner. Existing billing systems are limited in terms of security capabilities or computational overhead. In this paper, we propose a secure and non-obstructive billing system called THEMIS as a remedy for these limitations. The system uses a novel concept of a cloud notary authority for the supervision of billing. The cloud notary authority generates mutually verifiable binding information that can be used to resolve future disputes between a user and a cloud service provider in a computationally efficient way. Furthermore, to provide a forgery-resistive SLA monitoring mechanism, we devised a SLA monitoring module enhanced with a trusted platform module (TPM), called S-Mon. The performance evaluation confirms that the overall latency of THEMIS billing transactions (avg. 4.89 ms) is much shorter than the latency of public key infrastructure (PKI)-based billing transactions (avg. 82.51 ms), though THEMIS guarantees identical security features as a PKI. This work has been undertaken on a real cloud computing service called iCube Cloud

Development of A Powerful Signal Processing Approach Using Multi Resolution Analysis & Speech Denoising

Author(s):N.V. Narendra Babu ,Prof.Dr.G.Manoj Someswar
Journal: International Journal of Computational Engineering Research(IJCER)
Publisher:IJCER
Abstract
| Pages: 01-10
Speech denoising has been a long lasting problem in audio processing community. There exist lots of algorithms for denoising if the noise is stationary. For example, Wiener filter is suitable for additive Gaussian noise. However, if the noise is non-stationary, the classical denoising algorithms usually have poor performance because the statistical information of the non-stationary noise is difficult to estimate.

An Analytical Model of the Rip Current Flow

Author(s):Dr. Evans F. Osaisai
Journal: International Journal of Computational Engineering Research(IJCER)
Publisher:IJCER
Abstract
| Pages: 1-12
In this paper we develop an analytical theory for the interaction between waves and currents induced by breaking waves on time-scales longer than the individual waves. We employed the waveaveraging procedure that is commonly used in the literature. The near-shore zone is often characterized by the presence of breaking waves. Hence we develop equations to be used outside the surf zone, based on small-amplitude wave theory, and another set of equations to be used inside the surf zone, based on an empirical representation of breaking waves. Suitable matching conditions are applied at the boundary between the offshore shoaling zone and the near-shore surf zone. Essentially we derive a model for the interaction between waves and currents. Both sets of equation are obtained by averaging the basic equations over the wave phase. Thus the analytical solution constructed is a free vortex defined in both shoaling and surf zones. The surf zone solution is perturbed by a longshore component of the current. Thus the presence of the rip current cell combined with the longshore modulation in the wave forcing can drive longshore currents along the beach. The outcome, for our set of typical beach profile, is a description of rip currents.
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