An evolutionary strategy based motion estimation algorithm for H.264 video codecs

In this paper, we propose a new motion estimation algorithm based on evolutionary strategy (ES) for the H.264 video codec applied to monoscopic video. The proposed technique applies in macroblock basis and performs a parallel local search for the motion vector associated with the minimum motion compensated residue. For this purpose (/spl mu/+/spl lambda/)-ES is used with heuristically and randomly generated population of initial motion vectors. Experimental results show that the proposed scheme can reduce the computational complexity up to 50% of the motion estimation algorithm used in the H.264 reference codec at the same picture quality. Therefore, the proposed algorithm provides a significant improvement in motion estimation in the H.264 video codec

Numerical modelling of sandstone uniaxial compression test using a mix-mode cohesive fracture model

A mix-mode cohesive fracture model considering tension, compression and shear material behaviour is presented, which has wide applications to geotechnical problems. The model considers both elastic and inelastic displacements. Inelastic displacement comprises fracture and plastic displacements. The norm of inelastic displacement is used to control the fracture behaviour. Meantime, a failure function describing the fracture strength is proposed. Using the internal programming FISH, the cohesive fracture model is programmed into a hybrid distinct element algorithm as encoded in Universal Distinct Element Code (UDEC). The model is verified through uniaxial tension and direct shear tests. The developed model is then applied to model the behaviour of a uniaxial compression test on Gosford sandstone. The modelling results indicate that the proposed cohesive fracture model is capable of simulating combined failure behaviour applicable to rock

Stress analysis of buried pipes

Pipeline plays a vital role in transporting water, gas and oil from one place to another. Over the years, several failures have been reported in pipeline mainly due to aging (i.e., corrosion). The failure occurs when the stresses in a pipe segment due to applied loads exceed the capacity of the pipe. Therefore, it is important to predict the realistic pipe stress at the design and assessment stages to ensure the safety across the entire lifetime. As significant portion of the pipeline is buried in the underground in most of the occasions, the soil-structure interaction analysis is important as part of the stress analysis. Depending on the location of the network, the pipe will be subjected to varying levels of traffic and pressure loads that need to be accurately determined in order to perform reliable pipe stress estimations. Several pipe stress prediction methods have been developed over the years and reported in the literature. However, these methods are either analytical or empirical based models. The former uses the structural mechanics of the pipe by discarding the complex soil-structure interaction effect while the later fully depends on the experimental results. To overcome these problems, the numerical methods can be used to incorporate the soil-structure interaction effect more efficiently in pipe stress analysis together with traffic and internal pressure loads. In this study, the finite element method is used to analyse the pipe-soil system subjected to external traffic and internal pressure loads. Further, the model developed is used to understand the effect of soil properties, pipeline characteristics, and loading on pipe stress through sensitivity analysis. Finally, the response surface method is used to develop a new pipe stress predictive equation using the results of finite element analyses

Efficient coding unit size selection based on texture analysis for HEVC intra prediction

Determining the best partitioning structure for a given Coding Tree Unit (CTU) is one of the most time consuming operations within the HEVC encoder. The brute force search through quadtree hierarchy has a significant impact on the encoding time of high definition (HD) videos. This paper presents a fast coding unit size decision-taking algorithm for intra prediction in HEVC. The proposed algorithm utilizes a low complex texture analysis technique based on the local range property of a pixel in a given neighborhood. Simulation results show that the proposed algorithm achieves an average of 72.24% encoding time efficiency improvement with similar rate distortion performance compared to HEVC reference software HM12.0 for HD videos

Effective coding unit size decision based on motion homogeneity classification for HEVC inter prediction

© 2014 IEEE. Determining the best partitioning structure for a given Coding Tree Unit (CTU) is one of the most time consuming operations within the HEVC encoder. The brute force search through quad tree hierarchy has a significant impact on the encoding time especially on high definition (HD) videos. This paper presents a fast coding unit size decision-taking algorithm for inter prediction in HEVC. The proposed algorithm uses a motion homogeneity based classification approach utilizing RD cost as a feature vector. Simulation results show that the proposed algorithm achieves an average of 73.25% encoding time efficiency improvement with similar rate distortion performance compared to HEVC HM12.0 reference software

Successive Cambia in the mangrove <i>Avicennia</i>: A study on the three-dimensional structure of the Cambia and the functioning of the internal phloem tissue

Mangrove forests grow in conditions which must be considered extreme for woody angiosperms: high and changing salinity, frequent inundation with associated hypoxia, low relative humidity of the air and high temperatures. As ‘marine formations’, mangrove ecosystems are characteristic for the intertidal area of estuaries, creeks, sheltered bays and coastlines in tropical and sub-tropical areas worldwide. The genus Avicennia has been shown to be eurytopic as regards the above mentioned environmental conditions. Locally, Avicennia can often be found at the seaward as well as at the landward side (Disjunct zonation pattern) of the mangrove forest, sites with highly contrasting environmental conditions, while globally it has the largest latitudinal range in both the Eastern and the Western biogeographic mangrove regions (i.e. Indo-West Pacific and East Africa vs. America and West Africa respectively). The question is how Avicennia copes with this large and varying range of environmental conditions? It already has been proven that the wood anatomy of Avicennia is especially adapted to harsh environmental conditions. Properties of the wood (transport tissues) were suggested to be adapted to reduce cavitation events, defined as air bubble formation in the xylem sap. Inside vessels, those air bubbles can enlarge and therewith block the water transport (i.e. vessel embolism) so that cavitation and subsequent embolism is highly influencing the functionality of the hydraulic system. Amongst mangrove trees, the genus Avicennia L. (Acanthaceae) stands out by its successive cambia (i.e. having not one cambial layer but subsequent active cambia possibly conferring many sites of active growth in the stem). Secondary growth by successive cambia can offer Avicennia ecological advantages since (1) the internal phloem tissue can store water that could be used in refilling air-filled vessels with water and (2) the special, patchy growth can offer the tree woody tissue that is well-adapted to the conditions of the moment. In this study we investigate the organization of the successive cambia in Avicennia in three dimensions in order to complete the already investigated three dimensional network of transport tissues (phloem and xylem). Small stems (max. diameter: 3 cm) and branches of Avicennia marina (Forssk.) Vierh. and A. officinalis L. were sampled from the Rekawa lagoon in Sri Lanka, where the two species encounter spatially and temporally varying conditions as regards salinity, inundation. Serial sections and microscopic observation of the samples allow the reconstruction and visualization of the three-dimensional organization of the successive cambia. The working hypothesis of the research is: ‘successive cambia are important for Avicennia to survive in extreme high environmental conditions and explains the genus eurytopic nature as compared to other mangrove genera’

Toward effective structural identification of medium-rise building structures

Structural Identification (St-Id) is the process of constructing and calibrating a physics-based model based on the measured static and/or dynamic response of the structure. Over the last two decades, although the St-Id methods have become increasingly popular amongst civil-structural engineering communities, most complete and successful applications are often found with flexible structures such as long-span bridges and towers. Very few comprehensive studies were reported on building structures, especially those with medium-rise characteristics which are often associated with complicated analytical modelling and different degrees of parameter uncertainties. To address this need, this paper presents an in-depth study on St-Id of a benchmark medium-rise building firstly demonstrating the importance of developing appropriate initial analytical models that can be used for the automated model calibration techniques. Then, a novel parametric study based sensitivity analysis approach is introduced to identify tuning parameters as well as their appropriate ranges to maximise the correlation of the calibrated model whilst preserving the physical relevance of the calibrated model. Modal data of the first few modes measured under ambient vibration conditions are used in this study