Enhancement of Heat Transfer Using Delta-Winglet Type Vortex Generators with a Common-Flow-up Arrangement

Simulations of a coolant air flowing in a heat exchanger with delta-winglet type vortex generators in common-flow-up configuration have been performed to unveil the salient heat transfer characteristics. The heat exchanger is approximated as a periodic rectangular channel with heated walls and a pair of built-in tubes near the inlet and outlet. The heat transfer characteristics of the heat exchangers with vortex generators near the inlet, outlet, and both inlet and outlet have been compared. The Navier-Stokes equations together with the energy equation are solved employing unstructured finite volume method. The simulations reveal a significant enhancement in heat transfer because of the strong swirling motion originating from the streamwise longitudinal vortices behind the pair of delta winglets. The spiraling flow entrains air into the core and causes intermixing of the fluid layers to disrupt the growth of the thermal boundary layer. A parametric study on the angles of attack identifies the conditions under which enhancement in heat transfer can lead to significant miniaturization of the heat exchangers. The analysis also reveals interesting flow structures behind the winglets and correlates them to the mechanism of heat transfer.     

Steady mixed convection across a confined square cylinder

The effects of cross-buoyancy and of Prandtl number on the flow and heat transfer characteristics of an isothermal square cylinder confined in a channel has been investigated here. The numerical results have been presented for the range of conditions as: 1 ≤ Re ≤ 30, 0.7 ≤ Pr ≤ 100 (the maximum value of Peclet number being 3000) and 0 ≤ Ri ≤ 1for a fixed blockage ratio of 0.125. The overall drag and lift coefficients, local and average Nusselt numbers and the representative streamline and isotherm plots are presented to elucidate the role of Reynolds number, Prandtl number and Richardson number. The drag coefficient is found to be less sensitive to the Richardson number than the lift coefficient.     

A new algorithm for BTC image bit plane coding

A new look-up table technique for the coding of the block truncated image bit plane is presented which yields better images in the subjective as well as in the mean square sense compared to the one proposed by Mitchell and Delp (1980)     

New bit rate reduction techniques for block truncation coding

Two simple and fast block truncation coding algorithms which require reduced bit rates are presented in this paper. The proposed algorithms are compared with the modified block truncation coding technique (MBTC) with regard to the mean square error (MSE), bit rates and subjective quality of the reconstructed images. It is found that the results obtained with the proposed algorithms at reduced bit rates are comparable to those obtained with the MBTC. Further, it is shown that one of the proposed algorithms yields results which are comparable to those achieved with more complex hybrid algorithms     

QoS-based Task Group Deployment on Grid by Learning the Performance Data

Overhead of executing fine-grain tasks on computational grids led to task group or batch deployment in which a batch is resized according to the characteristics of the tasks, designated resource, and the interconnecting network. An economic grid demands an application to be processed within the given budget and deadline, referred to as the quality of service (QoS) requirements. In this paper, we increase the task success rate in an economic grid by optimally mapping the tasks to the resources prior to the batch deployment. The task-resource mapping (Advance QoS Planning) is decided based on QoS requirement and by mining the historical performance data of the application tasks using a genetic algorithm. The mapping is then used to assist in creating the task groups. Practical experiments are conducted to validate the proposed method and suggestions are given to implement our method in a cloud environment as well as to process real-time tasks.     

Design theory: a foundation of a new paradigm for design science and engineering

In recent years, the works on design theory (and particularly the works of the design theory SIG of the design society) have contributed to reconstruct the science of design, comparable in its structure, foundations and impact to decision theory, optimization or game theory in their time. These works have reconstructed historical roots and the evolution of design theory, conceptualized the field at a high level of generality and uncovered theoretical foundations, in particular the logic of generativity, the “design-oriented” structures of knowledge, and the logic of design spaces. These results give the academic field of engineering design an ecology of scientific objects and models, which allows for expanding the scope of engineering education and design courses. They have contributed to a paradigm shift in the organization of R&D departments, supporting the development of new methods and processes in innovation departments, and to establishing new models for development projects. Emerging from the field of engineering design, design theory development has now a growing impact in many disciplines and academic communities. The research community may play a significant role in addressing contemporary challenges if it brings the insights and applicability of design theory to open new ways of thinking in the developing and developed world.     

Performance evaluation of neural network and linear predictors for near-lossless compression of EEG signals.

This paper presents a comparison of the performances of neural network and linear predictors for near-lossless compression of EEG signals. Three neural network predictors, namely, single-layer perceptron (SLP), multilayer perceptron (MLP), and Elman network (EN), and two linear predictors, namely, autoregressive model (AR) and finite-impulse response filter (FIR) are used. For all the predictors, uniform quantization is applied on the residue signals obtained as the difference between the original and the predicted values. The maximum allowable reconstruction error delta is varied to determine the theoretical bound delta 0 for near-lossless compression and the corresponding bit rate rp. It is shown that among all the predictors, the SLP yields the best results in achieving the lowest values for delta 0 and rp. The corresponding values of the fidelity parameters, namely, percent of root-mean-square difference, peak SNR and cross correlation are also determined. A compression efficiency of 82.8% is achieved using the SLP with a near-lossless bound delta 0 = 3, with the diagnostic quality of the reconstructed EEG signal preserved. Thus, the proposed near-lossless scheme facilitates transmission of real time as well as offline EEG signals over network to remote interpretation center economically with less bandwidth utilization compared to other known lossless and near-lossless schemes.     

Optimal reduction of MCG in fetal MEG recordings

Recording fetal magnetoencephalographic (fMEG) signals in-utero is a demanding task due to biological interference, especially maternal and fetal magnetocardiographic (MCG) signals. A method based on orthogonal projection of MCG signal space vectors (OP) was evaluated and compared with independent component analysis (ICA). The evaluation was based on MCG amplitude reduction and signal-to-noise ratio of fetal brain signals using exemplary datasets recorded during ongoing studies related to auditory evoked fields. The results indicate that the OP method is the preferable approach for attenuation of MCG and for preserving the fetal brain signals in fMEG recordings.     

Two-Dimensional Analysis of Dam-Break Flow in Vertical Plane

This work presents numerical computations for the analysis of Dam-Break Flow using two-dimensional flow equations in a vertical plane. The numerical model uses the general approach of the simplified marker and cell method combined with the volume of fluid approach for the surface tracking. The time evolution of flow depth at the dam site and the evolution of the pressure distribution are investigated for both wet and dry bed conditions. The effect of the initially nonhydrostatic state on the long term surface profile and wave velocity are studied. These long term effects are found to be marginal in the case of wet-bed conditions, but are significant in dry-bed conditions. The dry-bed tip velocity immediately after the dam break, computed numerically, compares well with analytical results published previously. The time taken to obtain a constant flow depth at the dam site increases with decreasing initial depth ratio. The numerical result for this time elapse for dry-bed conditions is close to the experimentally obtained value.     

Bidirectional multiple‐valued neural network for pattern recognition and associative recall

A new neural network algorithm based on the counter‐propagation network (CPN) architecture, named MVL‐CPN, is proposed in this paper for bidirectional mapping and recognition of multiple‐valued patterns. The MVL‐CPN is capable of performing a mathematical mapping of a set of multiple‐valued vector pairs by self‐organization. The use of MVL‐CPN reduces considerably the number of nodes required for the input layers as well as the number of synaptic weights compared to the binary CPN. The training of the network is stable because all synaptic weights are monotonically nonincreasing. The bidirectional mapping and associative recall features of the MVL‐CPN are tested by using various sets of quaternary patterns. It is observed that the MVL‐CPN can converge within three or four iterations. The high‐speed convergence characteristics of the network can lead to the possibility of using this architecture for real‐time applications. An important advantage of the proposed type of neural network is that it can be implemented in VLSI with reduced number of neurons and synaptic weights when compared to a larger binary network needed for the same application. © 2000 John Wiley & Sons, Inc. Int J Imaging Syst Technol 11, 125–129, 2000