Distributed memory systems for simulating artificial neural networks

In executing tasks involving intelligent information processing, the human brain performs better than the digital computer. The human brain derives its power from a large number [O(10¹¹)] of neurons which are interconnected by a dense interconnection network [O(10⁵) connections per neuron]. Artificial neural network (ANN) paradigms adopt the structure of the brain to try to emulate the intelligent information processing methods of the brain. ANN techniques are being employed to solve problems in areas such as pattern recognition, and robotic processing. Simulation of ANNs involves implementation of large number of neurons and a massive interconnection network. In this paper, we discuss various simulation models of ANNs and their implementation on distributed memory systems. Our investigations reveal that communication-efficient networks of distributed memory systems perform better than other topologies in implementing ANNs.     

Performance of in-call buffer/window allocation schemes for short intermittent file transfers over broadband packet networks

While static open loop rate controls may be adequate for handling continuous bit rate (CBR) traffic, relatively smooth data traffic, and relatively low speed bursty data traffic over broadband integrated networks, high speed bursty data sources need more dynamic controls. Burst level resource allocation is one such dynamic control. Potential benefits and other issues for burst level resource parameter negotiations for bursty data traffic over high speed wide area packet networks have been discussed earlier.^1–6 A detailed analysis of an adaptive buffer/window negotiation scheme for long file transfers using these concepts is presented in Reference 1. In this paper we discuss two burst level buffer/window negotiation schemes for short intermittent file transfers, focusing on the specific needs of such traffic streams. We develop closed network of queues models to reflect the behaviour of the proposed schemes. These models, while being simple, capture essential details of the control schemes. Under fairly general assumptions, the resulting network of queues is of product form and can be analysed using the mean value analysis. We use such an analysis to compare the proposed schemes and to determine appropriate sizes of trunk buffers to achieve the desired balance between bandwidth utilization and file transfer delay. The effects of other parameters on the performance of these schemes as well as on the buffer sizing rules are also discussed. Burst level (in-call) parameter negotiation may be carried out by the end system with the network elements or by an interface system (access controller) with the broadband network elements. We discuss implications of this location as well as the needed protocol features. Finally, the service discrimination capabilities desired at the trunk controllers in switching nodes are briefly discussed.     

Dynamics of fluid circulation in coupled free and heterogeneous porous domains

Fluid flow in coupled free and porous domain, particularly when the porous medium is heterogeneous, is encountered in many hydro-environmental conditions, e.g., leakage from underground pipe, combined groundwater lake-subsurface interactions. One of the most difficult problems in the study of coupled flow behaviour has been the development of a universally applicable modelling scheme for combining the flow regimes. This is because the free/porous interfacial properties (e.g., shear-stress; velocity slip) that govern the coupled flow behaviour are difficult to determine experimentally under hydro-environmental conditions. On the other hand, the implications of various forms of heterogeneity in the porous media properties can be very different on the fluid-flow behaviour. Difficulties may also arise in direct coupling of the model equations that govern the fluid flow in the individual regions (e.g., Navier-Stokes for free-flow region and the Darcy's equation for the porous flow region). Consequently, models of coupled free and porous flow for hydro-environmental conditions are not very well developed at the moment. While there are some indications that fluids in coupled free and porous domains may circulate (i.e., development of flow cells), there is a lack of appropriate 3D analysis on how heterogeneities in porous media may affect such flow patterns. In this paper, we aim to analyse how porous media heterogeneity affects the dynamics of flow circulation in the porous side of a coupled free and porous domain. For this purpose, we analyse flow patterns in several model domains made up of two porous layers with differing permeabilities. The governing model equations are discretised and solved using the standard finite volume method on a staggered cell-centred mesh. The temporal discretisation is done using the explicit method. An in-house graphical user interface (GUI) has been created specifically to aid in the visualisation of otherwise complex flow patterns. The GUI contains many post-processing options and provides a comprehensive tool for the analysis of hydrodynamics and contaminant motion (not discussed in this paper) in coupled free and porous flow domains. This GUI is described in this paper briefly. The effects of altering the aspect ratio (i.e., multi-scale) of the domain on the coupled flow pattern have also been discussed.     

Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters

The alkali hydrolysis of poly(ethylene terephthalate), anionic copolymer of poly(ethylene terephthalate), and block copolymer of poly(ethylene terephthalate)–poly(ethylene glycol) is investigated under a variety of conditions of alkali concentration in aqueous bath, additives, time, and temperature. Measurements of loss in weight, linear density, breaking load, tenacity, elongation to break apart from intrinsic viscosity, fiber density, COOH-end group content, diameter of filaments, and scanning electron micrographs have been analyzed to identify the differences in the action of alkali on these polymer materials.     

An investigation of phase transformation behavior in sputter-deposited PtMn thin films

Sputter-deposited, equiatomic PtMn thin films have application in giant magnetoresistive spin valves, tunneling magnetoresistive spin valves, and magnetic random access memory. However, the as-deposited films are found to be a disordered A1 phase in a paramagnetic state rather than an antiferromagnetic phase with L1₀ structure, which is needed for device operation. Therefore, a postannealing step is required to induce the phase transformation from the asdeposited A1 face-centered-cubic phase to the antiferromagnetic L1₀ phase. The A1 to L1₀ metastable transformation was studied by x-ray diffraction and differential-scanning calorimetry. An exothermic transformation enthalpy of −12.1 kJ/mol of atoms was determined. The transformation kinetics were simulated using the Johnson-Mehl-Avrami analysis.     

Vibration and damping characteristics of CNTR viscoelastic skewed shell structures under the influence of hygrothermal conditions

Engineering with Computers - The vibration and damping characteristics of carbon nanotubes reinforced (CNTR) skewed shell structure under a hygrothermal environment have been investigated using the...     

Quickly locating efficient, equitable deals in automated negotiations under two-sided information uncertainty

This paper develops an automated negotiation procedure inclusive of mechanism design and agent design for bilateral multi-issue negotiations under two-sided information uncertainty. The proposed negotiation mechanism comprises a protocol called MUP (Monotonic Utility-granting Protocol) and a matching strategy called WYDIWYG (What You Display Influences What You Get). The proposed preference elicitation procedure makes the agents faithful surrogates of the user they represent while the proposed Frontier Tracking Proposal Construction Algorithm (FTPCA) makes them learn the opponent's flexibility in negotiation and respond appropriately. The mechanism design and the agent design together help in locating efficient and equitable deals quickly. The efficiency, stability, simplicity, distribution symmetry and incentive compatibility of the proposed procedure are demonstrated through negotiation simulation experiments.     

Discovering excitatory relationships using dynamic Bayesian networks

Mining temporal network models from discrete event streams is an important problem with applications in computational neuroscience, physical plant diagnostics, and human–computer interaction modeling. In this paper, we introduce the notion of excitatory networks which are essentially temporal models where all connections are stimulative, rather than inhibitive. The emphasis on excitatory connections facilitates learning of network models by creating bridges to frequent episode mining. Specifically, we show that frequent episodes help identify nodes with high mutual information relationships and that such relationships can be summarized into a dynamic Bayesian network (DBN). This leads to an algorithm that is significantly faster than state-of-the-art methods for inferring DBNs, while simultaneously providing theoretical guarantees on network optimality. We demonstrate the advantages of our approach through an application in neuroscience, where we show how strong excitatory networks can be efficiently inferred from both mathematical models of spiking neurons and several real neuroscience datasets.     

The Term Vector Database: fast access to indexing terms for Web pages

We have built a database that provides term vector information for large numbers of pages (hundreds of millions). The basic operation of the database is to take URLs and return term vectors. Compared to computing vectors by downloading pages via HTTP, the Term Vector Database is several orders of magnitude faster, enabling a large class of applications that would be impractical without such a database. This paper describes the Term Vector Database in detail. It also reports on two applications built on top of the database. The first application is an optimization of connectivity-based topic distillation. The second application is a Web page classifier used to annotate results returned by a Web search engine.