Abstract-Point clouds are one of the most promising technologies for 3D content representation. In this paper, we describe a study on quality assessment of point clouds, degraded by octreebased compression on different levels. The test contents were displayed using Screened Poisson surface reconstruction, without including any textural information, and they were rated by subjects in a passive way, using a 2D image sequence. Subjective evaluations were performed in five independent laboratories in different countries, with the inter-laboratory correlation analysis showing no statistical differences, despite the different equipment employed. Benchmarking results reveal that the state-of-the-art point cloud objective metrics are not able to accurately predict the expected visual quality of such test contents. Moreover, the subjective scores collected from this experiment were found to be poorly correlated with subjective scores obtained from another test involving visualization of raw point clouds. These results suggest the need for further investigations on adequate point cloud representations and objective quality assessment tools.

Any damage to the column and in particular the reducing of the cross section, requires steps to repair the columns, taking temporary measures in the form of taking part of the load and / or reducing the useful load on the damaged column. In order for these measures to be applied more adequately and at the same time preventing adverse effects, it is necessary to define the actual impact of certain cross-sectional damage on the bearing capacity. In this paper the conceptual, mathematical and system dynamics models of the effect of the force on damaged reinforced-concrete column were developed, according to the real values of the failure force. The prediction model is adaptable and it can also be used for the other length slender, the other angle of damage or the depth of damage. The methods of modelling and conceptualization of such situations contribute significantly to protection of architectural heritage. In addition, the economic component of the system should also be taken into consideration. The developed adaptive model allows setting the optimal parameters of the model according to the needs.

The purpose of the article is to develop a methodology for determining the need for the amount of investment resources needed to build the investment potential (IP) of the construction sector. The methodology is found in economic and mathematical modelling. We developed a model for the analysis of the investment potential of the construction sector (IPCS) by selecting the three-factor Cobb-Douglas production function for the IPCS study and by constructing a functional dependence from the collected statistical information, which allowed us to analyse the effect of changing the value of one of the selected factors on the resulting factor. The paper shows that market participants can use the proposed methodology to determine the factors that influence the improvement of IPCS, the degree of their influence and the determination of the values necessary to achieve a given level of investment potential.

By 2018, in Croatia, the agglomerations for collecting the sewage and water treatment systems are going to be constructed. All devices will be based on the mechanical-biological method of purification. However, the work of water treatment system produces a problem of sludge management. The paper presents the challenges of wastewater sludge handling and makes a decision on further sludge management. The hierarchical model of the decision making problem by defining the goal, criteria and alternative solutions is developed. On each level of the hierarchical model the elements of the model are compared with each other in pairs, and the preferences are expressed by using the Saaty’s scale. Moreover, the APH model compares the alternative pairs (thermal processing, deposition on agricultural land, disposal to waste repositories and composting) among each others. The intensities and weight preferences of one alternative over another are selected within the required criteria (economic, environmental, organisational and sociological).

Point clouds have been gaining importance as a solution to the problem of efficient representation of 3D geometric and visual information. They are commonly represented by large amounts of data, and compression schemes are important for their manipulation transmission and storing. However, the selection of appropriate compression schemes requires effective quality evaluation. In this work a subjective quality evaluation of point clouds using a surface representation is analyzed. Using a set of point cloud data objects encoded with the popular octree pruning method with different qualities, a subjective evaluation was designed. The point cloud geometry was presented to observers in the form of a movie showing the 3D Poisson reconstructed surface without textural information with the point of view changing in time. Subjective evaluations were performed in three different laboratories. Scores obtained from each test were correlated and no statistical differences were observed. Scores were also correlated with previous subjective tests and a good correlation was obtained when compared with mesh rendering in 2D monitors. Moreover, the results were correlated with state of the art point cloud objective metrics revealing poor correlation. Likewise, the correlation with a subjective test using a different representation of the point cloud data also showed poor correlation. These results suggest the need for more reliable objective quality metrics and further studies on adequate point cloud data representations.