MC2: A framework and service for MPEG-7 content-modelling communities

This article is available open access through the publisher’s website through the link below. Copyright @ The Author 2012.Harnessing the power of Web communities, the effort on creating metadata can be greatly reduced. Collaborative communities can create, update and maintain content models for multimedia resources more effectively than single users working alone. This paper presents MC2, a framework for MPEG-7 content-modelling communities. MC2 is based on the challenges to collaborative multimedia content modelling reported in the research literature and the results of an experiment undertaken to investigate user behaviour in collaborative content modelling. An MC2 service has also been implemented as a proof of concept for this framework, which is evaluated with a population of users and against the challenges.EPSR

Determination of embedded length and general condition of utility poles using non-destructive testing methods

University of Technology, Sydney. Faculty of Engineering and Information Technology.Timber utility poles play a key role for electricity distribution systems in Australia and in many other countries. There are over 5 million timber utility poles currently used in Australian energy networks which are more than 80% of total utility poles in the network. Lack of knowledge about the current condition of existing poles such as embedded length, the degree of deterioration and damage below the ground level or on top of the pole, leads to uncertainty for replacement or maintenance works. Hence, it is essential to develop a cost effective and reliable non-destructive method to ensure safety and to reduce maintenance costs. Different Non-destructive Testing (NDT) methods such as Sonic Echo, Bending Waves and Ultraseismic methods have been used in field applications over the past decades as simple and cost-effective tools for identifying the condition and underground depth of embedded structures, such as timber poles or piles in service. Despite the wide spread use of these methods by consultants around the world, reports describing field applications have shown that the results lack both consistency and reliability. Difficulties faced in field applications are often associated with complicated and imperfect/deteriorated materials, environmental effects, interaction of soil and structure and unknown boundary conditions, which lead to a great deal of uncertainties. In order to address this problem and develop reliable methods for embedment length determination and identification of damage below ground level, an R&D program commenced in 2008 at the University of Technology Sydney in collaboration with the Electricity Network Association of Australia. The aim of this study is to investigate and future develop the current non-destructive test methods with acceptable accuracy and repeatability, whilst being cost efficient for condition assessment of timber poles and piles as a part of the main program. To tackle the problems and evaluate effects of various factors associated with timber materials, on these NDT methods, thorough numerical investigations using Finite Element (FE) was necessary. In this study on isotropic model was used for timber material as the main object of the numerical study was to get a better understanding of wave travel in materials without any other uncertainties. The numerical evaluation will start with a free timber pole without embedment to understand the behaviour of the timber poles under surface NDT Methods. The results will be used for benchmarking in further investigations involving structure and soil interaction and boundary conditions. The model is verified with static analysis. Then, the FE beam model is enhanced with more advanced features requiring more steps to simulate other boundary conditions. According to the results, stress wave velocity will decrease with increase in embedded length. Therefore, two different velocities, one for stress wave travelling above the soil level and one travelling inside the soil with around 20% decrease in velocity was calculated. The error of length estimation averaged between 5% and 9% depending on the boundary conditions and the reference sensor for calculations. In order to address this problem and develop a reliable method for embedment length and identification of damage below ground level, also the bending wave method is fully investigated and verified for the potentials and limitations. The success of determining these parameters (embedded length and location of damage) mainly depends on the accuracy of measuring the bending wave velocity. However, bending wave is highly dispersive in nature and, hence, it is important to find its frequency dependent velocity. Short Kernel Method (SKM) has been used as a signal processing tool to calculate the frequency dependent velocity and also the embedded length. As there are no guidelines to select those kernel frequencies, different kernel frequencies were selected based on the results of FFT and then applying the SKM method. As a result of the bending wave velocity investigation, the appropriate kernel frequency is identified to be between 600 to 800 Hz. The results are verified using Bernoulli-Euler Beam theory and Timoshenko beam theory. Based on the length estimation, the kernel frequency of between 650 Hz to 800 Hz will result in less than 8% error in embedded length estimation. Furthermore, the Ultraseimic method is also applied on the results of timber modelling. Based on the results of velocities below and above the soil, the stress wave velocity is decreased by 22% overall below the soil in comparison with stress wave velocity above the soil. Based on the Ultraseimic method, the length of the timber pole is estimated by cross correlating the first arrival and reflection waves. Ultraseiemic test applying impact at the middle was also investigated for a 12m timber pole. It was found that, impact at middle of the specimen generated two compressional waves (travelling down and reflecting at the butt) and tensile waves (travelling up and reflecting at the top). This wave interference makes the analysis complicated. In addition, impact from the middle with 45 degree angle generates the combination of horizontal and vertical forces which result in contribution of bending waves to longitudinal waves. As a result, the signal will include multiple wave modes which are required to be separated before calculation of velocity and length determination. It should be mentioned that, Timber pole is modelled as an isotropic material here and if the anisotropy of the material is included the analysis will be more complicated. This study also presents the results of Sonic Echo, Impulse Response, Bending Wave and Ultraseimic methods, investigated for determining the stress wave velocity and embedded length of poles with different testing conditions in the structural laboratories at UTS and in the field at Mason Park (NSW) and Horsham (Victoria). According to the laboratory results, the coefficient of variation of velocity estimation of timber pole is relatively higher than steel beam and timber beam due to uncertainties in timber material such as anisotropy of timber material, stress direction in regards to grain angle of timber, location of a sensor relative to other sensors in regards to the annual growth ring orientation and existence of knots or any imperfections in timber. Choosing the reflection peak for length determination is one of the main parts of these methods and this could be affected by geotechnical conditions. Based on the results, the stress wave velocity will decrease inside the soil and a reduction factor is required to be applied to stress wave velocity above the soil to obtain the stress wave velocity below the soil. This reduction factor varies depending on the different testing/boundary conditions as well as the soil depth. In SE method, the scatter of the average error for the pole specimen, associated with different tests, ranged between 1% and 20% for all cases except layer 6 with 26% using sensor 1 for calculations. By using sensor 2 for estimation of the length, the average error becomes less than 9% for all cases except for layer 7 with 32%. However, more uncertainties are involved in terms of length calculation using sensors 3 and 4 located 1.5m and 2m from the impact location in comparison with using sensors 1 and 2 for calculations. The phase velocity is calculated for each kernel frequency under different pull out testing conditions. Also based on the results of bending wave method, the kernel frequency between of 400-800 Hz was identified for use in SKM method for phase velocity calculations. Using the SKM to estimate the length of the pole with Bending Wave method for a 5m timber pole under different pull out conditions shows the percentage of error for all boundary conditions to be between -10.5% and 0%. If the kernel frequency above 600Hz is selected, the average error for length estimation becomes less than 5% for most boundary conditions. Also Ultraseismic method was considered for stress wave velocity estimation of timber poles impacted at the top. According to the results, using sensors close to impact location (up to 2-3m) will result in good estimation of the velocity calculations. However, these will not necessarily lead to accurate estimations. According to the results, the average error in length determination for timber poles under different pull out conditions which is more relevant to timber poles in-service is less than 18%. According to the results for Ultraseismic method using impact at the top in Horsham, the stress wave velocities were calculated with relatively good accuracy. By considering relatively good and damaged poles in Horsham, it was found that the severe termite damage can be identified by the irregular patterns of FFT from impacted timber pole. This can be used to classify which timber poles are required to be replaced in the field

MC2: MPEG-7 content modelling communities

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityThe use of multimedia content on the web has grown significantly in recent years. Websites such as Facebook, YouTube and Flickr cater for enormous amounts of multimedia content uploaded by users. This vast amount of multimedia content requires comprehensive content modelling otherwise retrieving relevant content will be challenging. Modelling multimedia content can be an extremely time consuming task that may seem impossible particularly when undertaken by individual users. However, the advent of Web 2.0 and associated communities, such as YouTube and Flickr, has shown that users appear to be more willing to collaborate in order to take on enormous tasks such as multimedia content modelling. Harnessing the power of communities to achieve comprehensive content modelling is the primary focus of this research. The aim of this thesis is to explore collaborative multimedia content modelling and in particular the effectiveness of existing multimedia content modelling tools, taking into account the key development challenges of existing collaborative content modelling research and the associated modelling tools. Four research objectives are pursued in order to achieve this; first, design a user experiment to study users’ tagging behaviour with existing multimedia tagging tools and identify any relationships between such user behaviour; second, design and develop a framework for MPEG-7 content modelling communities based on the results of the experiment; third, implement an online service as a proof of concept of the framework; fourth, validate the framework through the online service during a repeat of the initial user experiment. This research contributes first, a conceptual model of user behaviour visualised as a fuzzy cognitive map and, second, an MPEG-7 framework for multimedia content modelling communities (MC2) and its proof of concept as an online service. The fuzzy cognitive model embodies relationships between user tagging behaviour and context and provides an understanding of user priorities in the description of content features and the relationships that exist between them. The MC2 framework, developed based on the fuzzy cognitive model, is deep-rooted in user content modelling behaviour and content preferences. A proof of concept of the MC2 framework is implemented as an online service in which all metadata is modelled using MPEG-7. The online service is validated, first, empirically with the same group of users and through the same experiment that led to the development of the fuzzy cognitive model and, second, functionally against the folksonomy and MPEG-7 content modelling tools used in the initial experiment. The validation demonstrates that MC2 has the advantages without the shortcomings of existing multimedia tagging tools by harnessing the ease of use of folksonomy tools while producing comprehensive structured metadata.Supported by UK Engineering and Physical Sciences Research Council (EPSRC