A fair server adaptation algorithm for HTTP adaptive streaming using video complexity

Multimedia Tools and Applications - The increasing popularity of online video content and adaptive video streaming services, especially those based on HTTP Adaptive Streaming (HAS) highlights the...     

A sequential Bayesian approach to color constancy using non-uniform filters

This paper introduces a non-uniform filter formulation into the Brainard and Freeman Bayesian color constancy technique. The formulation comprises sensor measurements taken through a non-uniform filter, of spatially-varying spectral sensitivity, placed on the camera lens. The main goal of this paper is twofold. First, it presents a framework in which sensor measurements obtained through a non-uniform filter can be sequentially incorporated into the Bayesian probabilistic formulation. Second, it shows that such additional measurements obtained reduce the effect of the prior in Bayesian color constancy. For the purposes of testing the proposed framework, we use a filter formulation of two portions of different spectral sensitivities. We show through experiments on real data that improvement in the parameter estimation can be obtained inexpensively by sequentially incorporating additional information obtained from the sensor through the different portions of a filter by Bayesian chaining. We also show that our approach outperforms previous approaches in the literature.     

Continuous consensus via common knowledge

This paper introduces the continuous consensus problem, in which a core M[k] of information is continuously maintained at all correct sites of the system. All local copies of the core must be identical at all times k, and every interesting event should eventually enter the core. The continuous consensus problem is studied in synchronous systems with crash and omission failures, assuming an upper bound of t on the number of failures in any given run of the system. A simple protocol for continuous consensus, called ConCon, is presented. This protocol is knowledge-based: The actions processes take depend explicitly on their knowledge, as well as on their knowledge of what other processes know about failures and about events that occurred in the system. A close connection between continuous consensus and knowledge is established by showing that in every continuous consensus protocol, the information in the core at any given time must be common knowledge. Based on the characterization of common knowledge by Moses and Tuttle, it is shown that ConCon is an optimum protocol for continuous consensus, maintaining the most up-to-date core possible at all times: For every pattern of failures and external inputs and each point in time, the core provided by ConCon contains the cores of all correct protocols for continuous consensus. Indeed, the ConCon protocol can be viewed as a simplification of the Moses and Tuttle construction for computing the common knowledge at a given point. Finally, a uniform version of continuous consensus is considered, in which all processes (faulty and nonfaulty) are guaranteed to maintain the same core at any given time. An algorithm for uniform continuous consensus is presented, and is also shown to be an optimum solution. A preliminary version of this paper appeared in the Proceedings of the TARK X conference, Singapore 2005. Work on this paper was performed in part during a sabbatical at the School of Computer Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia, where it was partially supported by ARC Discovery Grant RM02036.     

Detection, Localization, and Sex Classification of Faces from Arbitrary Viewpoints and under Occlusion

This paper presents a novel framework for detecting, localizing, and classifying faces in terms of visual traits, e.g., sex or age, from arbitrary viewpoints and in the presence of occlusion. All three tasks are embedded in a general viewpoint-invariant model of object class appearance derived from local scale-invariant features, where features are probabilistically quantified in terms of their occurrence, appearance, geometry, and association with visual traits of interest. An appearance model is first learned for the object class, after which a Bayesian classifier is trained to identify the model features indicative of visual traits. The framework can be applied in realistic scenarios in the presence of viewpoint changes and partial occlusion, unlike other techniques assuming data that are single viewpoint, upright, prealigned, and cropped from background distraction. Experimentation establishes the first result for sex classification from arbitrary viewpoints, an equal error rate of 16.3 percent, based on the color FERET database. The method is also shown to work robustly on faces in cluttered imagery from the CMU profile database. A comparison with the geometry-free bag-of-words model shows that geometrical information provided by our framework improves classification. A comparison with support vector machines demonstrates that Bayesian classification results in superior performance.     

Reliability demonstration for safety-critical systems

This paper suggests a new model for reliability demonstration of safety-critical systems, based on the TRW Software Reliability Theory. The paper describes the model, the test equipment required, and test strategies based on the various constraints occurring during software development. The paper also compares a new testing method, single risk sequential testing (SRST), with the common probability ratio sequential testing method (PRST), and concludes that: (i) SRST provides higher chances of success than PRST; (ii) SRST takes less time to complete than PRST; and (iii) SRST satisfies the consumer-risk criterion, whereas PRST provides a much smaller consumer-risk than the requirement     

Stress Analysis of Monolithic Circular Arches Strengthened with Composite Materials

This paper presents an analytical approach for the elastic stress analysis of monolithic circular arches strengthened with externally bonded fiber-reinforced polymer (FRP) strips. Emphasis is placed on the interfacial stresses between the existing structure and the supplemental reinforcement layers. Two analytical models are presented: The first model formulates the governing equations in terms of the displacements in the arch and the FRP strip and the tangential distribution of the shear stresses in the adhesive layer as unknowns without involving any assumptions on the stress and displacement fields in the adhesive layer. The second model uses the functional form of the displacement field derived in the first model yielding a formulation in terms of displacement unknowns only. Two numerical examples that examine the capabilities of the analytical approach are discussed. The first example focuses on the stress analysis of a strengthened arch under a localized load. The second example studies the elastic response of a partially strengthened arch to a symmetric load and a horizontal support settlement. The numerical study quantifies the interfacial shear and peeling stresses between the old and the new components underlining the stress concentrations. Finally, conclusions are presented and directions for future research on the application of the theory to masonry arches are outlined.     

A fast triangle to triangle intersection test for collision detection

The triangle‐to‐triangle intersection test is a basic component of all collision detection data structures and algorithms. This paper presents a fast method for testing whether two triangles embedded in three dimensions intersect. Our technique solves the basic sets of linear equations associated with the problem and exploits the strong relations between these sets to speed up their solution. Moreover, unlike previous techniques, with very little additional cost, the exact intersection coordinates can be determined. Finally, our technique uses general principles that can be applied to similar problems such as rectangle‐to‐rectangle intersection tests, and generally to problems where several equation sets are strongly related. We show that our algorithm saves about 20% of the mathematical operations used by the best previous triangle‐to‐triangle intersection algorithm. Our experiments also show that it runs 18.9% faster than the fastest previous algorithm on average for typical scenarios of collision detection (on Pentium 4). Copyright © 2006 John Wiley & Sons, Ltd.     

Soil properties, foundation stability, groundwater conditions, characteristics of building stones and mortar used in construction and proposed measures for restoration at the site of ancient Ayla in a Qaba, Jordan

Ancient Ayla in Aqaba, Jordan was destroyed during a major earthquake incident that occurred in Aqaba in 1067 AD. The Gulf of Aqaba is a seismically active region. The latest strong earthquake incident occurred on November 22, 1995 when an earthquake of local magnitude 6.2 rocked the Gulf of Aqaba region. The main shock was followed by thousands of aftershocks. The Gulf of Aqaba-convering the geologic coordinates 28.0–29.6 N; 34.5–35..2 E is one of two natural bays surrounding the Sinai Peninsula which itself is located at the northernmost end of the Red Sea. The soil profile underlying Aqaba city consists of interlayering of various sedimentory Holocene Alluvium deposits. This study is aimed at investigating the soil and foundation condition at the site of the ancient Ayla. This includes groundwater conditions, bearing capacity of the strata supporting the walls of ancient Ayla, and structural stability of these walls. The study included an investigation of the characteristics of building stones used in the earlier construction as well as those proposed for use in the restoration of Ancient Ayla. Furthermore, the physical and chemical properties of existing mortars were evaluated. Gradation analyses were conducted to select a proper sand for use in the mortar mix. Mortar mix tests were conducted for the purpose of recommending a mortar mix for use in restoration works. Trends in the results of various mix tests were analyzed. Sample borings were made at the site to obtain soi profile and extract soil and water samples. Standard Penetration test was conducted at different depths. Laboratory tests were performed on these samples to determine pertinent physical properties of the soil and salinity of the water. Soils at the site were found to be predominantly granular with archaeological fill overlying beach sand which in turn overlies the coarser sand and gravel of the natural deposits. Except for the wadi area, groundwater was encountered at about 3 m below existing ground levels. Bearing capacity of the foundation was evaluated to be 3.5 kg/cm² for the dense granular materials (that represent the probable founding layer of the existing walls), and 2.0 kg/cm² for the weaker silty/clayed zone. Back analysis yields a safe wall height of at least 6.0 m. Therefore, no stability problems are present. Tilting and sinking were noted in some portions of the exterior walls as a result of dynamic lateral earth pressures exerted during the major earthquake incident of 1067 AD. Measures for wall foundation support during archaelogical excavations are suggested. Permanent excavations for exposing the walls should be limited to a free height of about 3 m at the location of western wall, and about 2.5 m at the location of the eastern wall. Stones used in the construction of ancient Ayla were found to consist of precut sandstone, siltstone, mudstone and granite. Weathering effects were clearly noted on the exposed stones in the walls. It is proposed to use a replacement stone consisting of sandstone group located at a source 35 km North of Aqaba. Measures suggested for the restoration of the walls addressed the lack of mortar in the inner walls and the replacement of disintegrated stone pieces in the external walls. Existing mortars were found to consist primarily of three types, namely a brown silty mixture, a gray mixture, but predominantly a mixture of fine gravel and a lime/gypsum binder. The major chemical constituents of the original mortar are 18 % SiO₂, 23 % CaO, and 34 % SO₃. X-ray diffraction peaks indicate the presence of gypsum, calcite and quartz. Comparative analysis data gave 7 % CaCO₃, 53 % Sand, and 40 % Solubles as average values of the constituents. Following the selection of two sand sources for use in the mortar mix, recommended mortar for restoration was a mix of lime, sand, ash, with ratios of 1:3:1.5.     

An optimizing compiler for an SPAP architecture using AI tools

A methodology that allows users to efficiently bridge the gap between high-level language and low-level microcode when implementing intensive mathematical operations and manipulations algorithms is discussed. The use of an optimized special-purpose array processor (SPAP) architecture for numerical computation and a host microprocessor for nonnumerical computation operations is described. The advantages of the optimizing compiler, the target architecture, and the compiler's implementation using AI tools are examined