Uncountable automatic classes and learning

In this paper we consider uncountable classes recognizable by ω-automata and investigate suitable learning paradigms for them. In particular, the counterparts of explanatory, vacillatory and behaviourally correct learning are introduced for this setting. Here the learner reads in parallel the data of a text for a language L from the class plus an ω-index α and outputs a sequence of ω-automata such that all but finitely many of these ω-automata accept the index α if and only if α is an index for L.It is shown that any class is behaviourally correct learnable if and only if it satisfies Angluin’s tell-tale condition. For explanatory learning, such a result needs that a suitable indexing of the class is chosen. On the one hand, every class satisfying Angluin’s tell-tale condition is vacillatorily learnable in every indexing; on the other hand, there is a fixed class such that the level of the class in the hierarchy of vacillatory learning depends on the indexing of the class chosen.We also consider a notion of blind learning. On the one hand, a class is blind explanatorily (vacillatorily) learnable if and only if it satisfies Angluin’s tell-tale condition and is countable; on the other hand, for behaviourally correct learning, there is no difference between the blind and non-blind version.This work establishes a bridge between the theory of ω-automata and inductive inference (learning theory).     

Optimal quadtrees for image segments

Quadtrees are compact hierarchical representations of images. In this paper, we define the efficiency of quadtrees in representing image segments and derive the relationship between the size of the enclosing rectangle of an image segment and its optimal quadtree. We show that if an image segment has an enclosing rectangle having sides of lengths x and y, such that 2N-1 × max (x, y) ? 2N, then the optimal quadtree may be the one representing an image of size 2N × 2N or 2N+1 × 2N+1. It is shown that in some situations the quadtree corresponding to the larger image has fewer nodes. Also, some necessary conditions are derived to identify segments for which the larger image size results in a quadtree which is no more expensive than the quadtree for the smaller image size.     

Elastohydrodynamic analysis of a cylindrical journal bearing with a flexible bearing shell

The effect of the elastic deformation of a bearing shell was considered in the determination of the performance characteristics of a hydrodynamic journal bearing. The finite element method with an iteration scheme was employed to solve the Reynolds equation governing flow in the clearance space and the three-dimensional linear elasticity equations representing the displacement vector field in the bearing shell. For design convenience a nondimensional deformation coefficient ψ relating μ, E_m, U₀ , C, R_j and tis defined. The performance characteristics were obtained in terms of load-carrying capacity, fluid flow, power loss and attitude angle for an aspect ratio $\text{L}\text{D = 1}$, eccentricity ? = 0.6 and for a wide range of deformation coefficients. The results are compared for bearing materials having Poisson's ratio v equal to 0.3 and 0.4.     

CAE FOR THE MANUFACTURING ENGINEER: THE ROLE OF PROCESS SIMULATION IN CONCURRENT ENGINEERING

As America refocuses its attention on the factory, design and manufacturing engineers must work together closely to design the appropriate products, and matching production process in a team effort. By building off the designer's CAE tools that predict product performance, the manufacturing engineer is today able to simulate the proposed production process. Process simulations for the following manufacturing processes are available or being developed:

▪Forging, ▪Machining, ▪Injection Molding, ▪Die Casting, ▪Investment Casting, ▪Metal Forming, ▪Heat Treating, ▪Assembly Tolerancing

By utilizing the same 3-D solid model and finite element modeling tools used by the designer, coupled to powerful analysis simulation tools to predict the transient nonlinear heat transfer and plastic material flow found in many manufacturing processes, the manufacturing engineer is able to explore alternative processing plans, evaluate trade-offs and even influence the design to produce superior products.

Process simulation brings a science to support the manufacturing engineers experience for reduced lead time, lower cost, increase product quality and better understanding of the process. The next step will be to directly link the process simulation to an expert system.

This paper describes the current state of technology in the area of manufacturing process computer simulation for a number of manufacturing operations and suggests how these tools can be used “up-front” and lead to concurrent engineering.     

From template to image: reconstructing fingerprints from minutiae points

Most fingerprint-based biometric systems store the minutiae template of a user in the database. It has been traditionally assumed that the minutiae template of a user does not reveal any information about the original fingerprint. In this paper, we challenge this notion and show that three levels of information about the parent fingerprint can be elicited from the minutiae template alone, viz., 1) the orientation field information, 2) the class or type information, and 3) the friction ridge structure. The orientation estimation algorithm determines the direction of local ridges using the evidence of minutiae triplets. The estimated orientation field, along with the given minutiae distribution, is then used to predict the class of the fingerprint. Finally, the ridge structure of the parent fingerprint is generated using streamlines that are based on the estimated orientation field. Line integral convolution is used to impart texture to the ensuing ridges, resulting in a ridge map resembling the parent fingerprint. The salient feature of this noniterative method to generate ridges is its ability to preserve the minutiae at specified locations in the reconstructed ridge map. Experiments using a commercial fingerprint matcher suggest that the reconstructed ridge structure bears close resemblance to the parent fingerprint     

A grey approach for forecasting in a supply chain during intermittentdisruptions

The supply chains today have become vulnerable to frequent disruptions, and with continuing emphasis on efficiency, lacks robustness to deal with them. A part of the solution lies in forecasting the disruption beforehand and the other part in knowing which policies will suit such disrupted conditions best. Accurate and immediate forecasts are a must in a supply chain and hence play a huge role in stabilizing. This study compares the performance of three established forecasting methods (moving average, weighted moving average and exponential smoothing) as well as grey prediction method, during disruptions and stable situations. The experiments are performed in the form of discrete event simulation, on a four stage beer game settings. The results show that moving average and weighted moving average methods become incompetent during disruptions, and are useful only during stable times, when the demand hovers around a predefined mean value. Exponential smoothing and grey method seems to give better results during disruptions and also during stable times in upstream tiers. Grey prediction method in particular is the best method when the disruption frequency is high and also when the disruption impact is gradual rather than sudden.