An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.

The Self-Organizing Map

We explore the effect of dimensionality on the nearest neighbor problem. We show that under a broad set of conditions (much broader than independent and identically distributed dimensions), as dimensionality increases, the distance to the nearest data point approaches the distance to the farthest data point. To provide a practical perspective, we present empirical results on both real and synthetic data sets that demonstrate that this effect can occur for as few as 10-15 dimensions. These results should not be interpreted to mean that high-dimensional indexing is never meaningful; we illustrate this point by identifying some high-dimensional workloads for which this effect does not occur. However, our results do emphasize that the methodology used almost universally in the database literature to evaluate high-dimensional indexing techniques is flawed, and should be modified. In particular, most such techniques proposed in the literature are not evaluated versus simple linear scan, and are evaluated over workloads for which nearest neighbor is not meaningful. Often, even the reported experiments, when analyzed carefully, show that linear scan would outperform the techniques being proposed on the workloads studied in high (10-15) dimensionality!.

When is nearest neighbor meaningful

Computational geometry

We give a deterministic algorithm for triangulating a simple polygon in linear time. The basic strategy is to build a coarse approximation of a triangulation in a bottom-up phase and then use the information computed along the way to refine the triangulation in a top-down phase. The main tools used are the polygon-cutting theorem, which provides us with a balancing scheme, and the planar separator theorem, whose role is essential in the discovery of new diagonals. Only elementary data structures are required by the algorithm. In particular, no dynamic search trees, of our algorithm.

Triangulating a simple polygon in linear time

Teaching And Researching Reading

We present an unsupervised approach for abnormal event detection in videos. We propose, given a dictionary of features learned from local spatiotemporal cuboids using the sparse coding objective, the abnormality of an event depends jointly on two factors: the frequency of each feature in reconstructing all events (or, rarity of a feature) and the strength by which it is used in reconstructing the current event (or, the absolute coefficient). The Incremental Coding Length (ICL) of a feature is a measure of its entropy gain. Given a dictionary, the ICL computation does not involve any parameter, is computationally efficient and has been used for saliency detection in images with impressive results. In this paper, the rarity of a dictionary feature is learned online as its average energy, a function of its ICL. The proposed approach is applicable to real world streaming videos. Experiments on three benchmark datasets and evaluations in comparison with a number of mainstream algorithms show that the approach is comparable to the state-of-the-art.

https://www.aaai.org/ocs/index.php/AAAI/AAAI15/paper/viewFile/9923/9808

Online detection of abnormal events using incremental coding length

In problem solving a goal/subgoal is either solved by generating needed information from current information, or further decomposed into additional subgoals. In traditional problem solving, goals, knowledge, and problem states are all modeled as expressions composed of symbolic predicates, and information generation is modeled as rule application based on matching of symbols. In problem solving with diagrams on the other hand, an additional means of generating information is available, viz., by visual perception on diagrams. A subgoal is solved opportunistically by whichever way of generating information is successful. Diagrams are especially effective because certain types of information that is entailed by given information is explicitly available – as emergent objects and emergent relations – for pickup by visual perception. We add to the traditional problem solving architecture a component for representing the diagram as a configuration of diagrammatic objects of three basic types, point, curve and region; a set of perceptual routines that recognize emergent objects and evaluate a set of generic spatial relations between objects; and a set of action routines that create or modify the diagram. We discuss how domain-specific capabilities can be added on top of the generic capabilities of the diagram system. The working of the architecture is illustrated by means of an application scenario.

An Architecture for Problem Solving with Diagrams

A method of tuning a hearing device includes sending a test signal to a model of a hearing device that may be remote from the actual hearing device being tuned. The test signal is encoded by the model and sent to the hearing device being tuned. The user of that hearing device sends a response signal based at least in part on the encoded test signal. This response is received and compared to the original test signal. Thereafter, an operational parameter is sent to the hearing device based on the comparison.

Systems and methods for remotely tuning hearing devices

Outlier detection has been an active area of research for a few decades. We propose a new definition of outlier that is useful for high-dimensional data. According to this definition, given a dictionary of atoms learned using the sparse coding objective, the outlierness of a data point depends jointly on two factors: the frequency of each atom in reconstructing all data points (or its negative log activity ratio, NLAR) and the strength by which it is used in reconstructing the current point. A R arity based O utlier D etection algorithm in a S parse coding framework (RODS) that consists of two components, NLAR learning and outlier scoring, is developed. This algorithm is unsupervised; both the offline and online variants are presented. It is governed by very few manually-tunable parameters and operates in linear time. We demonstrate the superior performance of the RODS in comparison with various state-of-the-art outlier detection algorithms on several benchmark datasets. We also demonstrate its effectiveness using three real-world case studies: saliency detection in images, abnormal event detection in videos, and change detection in data streams. Our evaluations shows that RODS outperforms competing algorithms reported in the outlier detection, saliency detection, video event detection, and change detection literature.

/pdf/rods-rarity-based-outlier-detection-in-a-sparse-coding-2ympsw2v92.pdf

RODS: Rarity based Outlier Detection in a Sparse Coding Framework

In recent years, there has been an exponential increase in photo and video manipulation by easy-to-use editing tools (e.g., Photoshop). Especially, ‘face digital manipulations’ (e.g., face swapping) is a critical issue for automated face recognition systems (AFRSs) as it detrimentally effects the AFRS’ performance. Also, the advent of powerful deep learning methods has led to realistic face sample generation and manipulation. Despite recent advances in face manipulation detection techniques, manipulations-aware AFRSs and face synthetic sample/manipulation generation, detecting sophisticated face manipulations is still a challenge to human examiners and existing technologies. Devising more effective universal face manipulation detectors and manipulations-aware AFRSs will immensely improve the trust in biometric applications and digital communications. This paper presents an overview of the recent technologies on face manipulation generation, detection, recognition, and databases. Also, potential future research directions and challenges are discussed.

Bonny Banerjee

Papers

Online detection of abnormal events using incremental coding length

An Architecture for Problem Solving with Diagrams

Systems and methods for remotely tuning hearing devices

RODS: Rarity based Outlier Detection in a Sparse Coding Framework

Face Authenticity: An Overview of Face Manipulation Generation, Detection and Recognition