13407089
Event detection and period extraction using multi-scale symmetry and entropy
We present a system for detecting discrete periodic events over a short interval and in the presence of interference. In the first stage symmetries are identified using scale-space representation. This process detects signal events with a low signal-to-noise ratio but has the potential to introduce a number of false responses. This process is followed by an entropy-based algorithm that can robustly extract periodicities from a set of observed discrete events in the presence of a large number of false alarms. The event detection and period extraction processes have a low computational cost and can extract signal periodicity after a short observation time. This scheme was evaluated against four previously reported methods. Results demonstrate that the period extraction algorithm presented here is more reliable than three of the previously reported algorithms. The reliability of the algorithm presented here was similar to that of the fourth method but the computational cost was much less.
2089716
Augmented tracking with incomplete observation and probabilistic reasoning
Abstract An on-line algorithm for multi-object tracking is presented for monitoring a real-world scene from a single fixed camera. Potential objects are detected with adaptive backgrounds modelled by intensity-plus-chromaticity mixtures of Gaussians to cope with illumination variation. The region-based representations of each object are tracked and predicted using a Kalman filter. A scene model is created to help interpret the occluded or exiting objects. The uncertainty in the domain knowledge is encoded in a Bayesian network for reasoning about object status. Unlike traditional blind tracking during occlusion, the object states are estimated using partial observations whenever available. The observability of each object depends on the predicted measurement of the object, the foreground region measurement, and the scene model. This makes the algorithm more robust in terms of both qualitative and quantitative criteria.
19879470
The multiscale medial properties of interfering image structures
The multiscale medial axis (MMA) is a robust shape representation in analysing objects in greylevel images. It is computed as ridges in the medialness scale-space of an image. In this paper the multiscale medial properties of overlapping objects are investigated, the result of which is novel to the community in that the existing studies only concentrated on isolated objects. To improve the distinguishability of these objects, a sliding window algorithm is proposed to detect locally optimal scale ridges in scale space. When used in the medialness scale-space of an image, this efficient method can extract a complete set of MMAs for interfering objects, in contrast with the globally optimal scale ridge definition which has been widely used. This is demonstrated in the applications in medical images.
1185541
A serializability violation detector for shared-memory server programs
We aim to improve reliability of multithreaded programs by proposing a dynamic detector that detects potentially erroneous program executions and their causes. We design and evaluate a Serializability Violation Detector (SVD) that has two unique goals: (I) triggering automatic recovery from erroneous executions using backward error recovery (BER), or simply alerting users that a software error may have occurred; and (II) helping debug programs by revealing causes of error symptoms.Two properties of SVD help in achieving these goals. First, to detect only erroneous executions, SVD checks serializability of atomic regions, which are code regions that need to be executed atomically. Second, to improve usability, SVD does not require a priori annotations of atomic regions; instead, SVD approximates them using a heuristic. Experimental results on three widely-used multithreaded server programs show that SVD finds real bugs and reports modest false positives. The goal of this paper is to develop a detector suitable for (I) BER-based avoidance of erroneous program executions; and (II) alerting users as software errors occur. We argue that such a detector should have the following two properties.
39351233
Note on Infinite Families of Trivalent Semisymmetric Graphs
A simple undirected graph is said to be semisymmetric if it is regular and edge-transitive but not vertex-transitive. This paper uses the groups PSL (2, p) and PGL (2, p), where p is a prime, to construct two new infinite families of trivalent semisymmetric graphs.
1971121
A "flight data recorder" for enabling full-system multiprocessor deterministic replay
Debuggers have been proven indispensable in improving software reliability. Unfortunately, on most real-life software, debuggers fail to deliver their most essential feature --- a faithful replay of the execution. The reason is non-determinism caused by multithreading and non-repeatable inputs. A common solution to faithful replay has been to record the non-deterministic execution. Existing recorders, however, either work only for datarace-free programs or have prohibitive overhead.As a step towards powerful debugging, we develop a practical low-overhead hardware recorder for cachecoherent multiprocessors, called Flight Data Recorder (FDR). Like an aircraft flight data recorder, FDR continuously records the execution, even on deployed systems, logging the execution for post-mortem analysis.FDR is practical because it piggybacks on the cache coherence hardware and logs nearly the minimal threadordering information necessary to faithfully replay the multiprocessor execution. Our studies, based on simulating a four-processor server with commercial workloads, show that when allocated less than 7% of system's physical memory, our FDR design can capture the last one second of the execution at modest (less than 2%) slowdown.
16235334
Illumination-Invariant Motion Detection Using Colour Mixture Models
This paper tackles the problem of robust change detection in image sequences from static cameras. Motion cues are detected using frame differencing with an adaptive background estimation modelled by a mixture of Gaussians. Illumination invariance and elimination or detection of shadows is achieved by using a colour chromaticity representation of the image data. The combination of the colourand intensity-based models results in some promising applications.
206570343
Vertex-Primitive Graphs of Order a Product of Two Distinct Primes
Abstract Let k and p be odd primes with k p . All vertex-primitive graphs of order kp are classified, and those which are symmetric, or are edge-transitive but not symmetric. or are not Cayley graphs are identified. In addition, a classification is given of all vertex-primitive, edge-transitive lantisymmetric) directed graphs or order kp . The classification of the vertex-primitive symmetric graphs of order kp is used by the authors and others to complete the classification of symmetric graphs or order kp . The classification of the vertex-primitive non-Cayley graphs of order kp is used by B.D. McKay and the first author in an investigation of vertex-transitive non-Cayley graphs.