Relating geometry descriptions to its derivatives on the web

Sharing building information over the Web is becoming more popular, leading to advances in describing building models in a Semantic Web context. However, those descriptions lack unified approaches for linking geometry descriptions to building elements, derived properties and derived other geometry descriptions. To bridge this gap, we analyse the basic characteristics of geometric dependencies and propose the Ontology for Managing Geometry (OMG) based on this analysis. In this paper, we present our results and show how the OMG provides means to link geometric and non-geometric data in meaningful ways. Thus, exchanging building data, including geometry, on the Web becomes more efficient

Including widespread geometry formats in semantic graphs using RDF literals

The exchange of building data involves both geometric and non-geometric data. A promising Linked Data approach is to embed data from existing geometry formats inside Resource Description Framework (RDF) literals. Based on a study of relevant specifications and related work, this toolset-independent approach was found suitable for the exchange of geometric construction data. To implement the approach in practice, the File Ontology for Geometry formats (FOG) and accompanying modelling method is developed. In a proof-of-concept web application that uses FOG, is demonstrated how geometry descriptions of different existing formats are automatically recognised and parsed

Verificação da conformidade dos dados de projectos de construção com Linked Data

O sector da construção tem assistido nos últimos anos a uma tendência crescente para a digitalização, resultando num aumento substancial de dados. No entanto, es‑ tes dados tendem a ser segregados em sistemas e formatos de ficheiros específicos, o que dificulta a criação de uma representação abrangente do ativo construído. Uma solução potencial para colmatar a lacuna entre estes diversos modelos de dados é a aplicação dos princípios de Linked Data. A utilização de Linked Data leva à criação de uma representação estruturada e explícita do conhecimento, permitindo a ve‑ rificação da conformidade dos dados provenientes de várias fontes. Apesar do seu potencial, a escalabilidade da aplicação de Linked Data no domínio da construção tem sido impedida pela ausência de diretrizes de modelação claras. Estas diretrizes foram oficialmente introduzidas em 2022 com a norma EN 17632-1:2022: Building Information Modelling (BIM) – Semantic Modelling and Linking (SML). Esta norma de‑ fine um modelo de informação de alto nível e um conjunto de padrões genéricos de modelação da informação. Dado que o esquema de dados Industry Foundation Classes (IFC) é um esquema largamente utilizado ao longo do ciclo de vida de um ativo construído e normalizado a nível internacional (ISO 16739-1:2018), este estu‑ do examinará e demonstrará o processo de alinhamento do IFC com as orientações descritas na norma EN 17632. Além disso, estabelecerá uma ligação entre o IFC e o modelo de informação de alto nível, conforme especificado pela norma EN 17632. Por último, o estudo analisa o potencial de verificação da conformidade quando se trata de conjuntos de dados IFC convertidos.Esta investigação foi realizada com o apoio da União Europeia através da Bolsa Eras‑ mus Mundus, no âmbito do Mestrado Conjunto BIM A+ Erasmus Mundu

Supported metallocene catalysis as an efficient tool for the preparation of polyethylene/carbon nanotubes nanocomposites : effect of the catalytic system on the coating morphology

peer reviewedHomogeneous or periodical surface coating of multiwalled carbon nanotubes (MWNTs) can be achieved by in situ polymerization of ethylene as catalyzed directly from the nanotube surface- treated by a highly active metallocene-based complex, e.g., Cp*2ZrCl2/methylaluminoxane. This polyethylene (PE) coating allows for the break-up of the native nanotube bundles. Immobilization of methylaluminoxane onto the surface of the carbon nanotubes was evidenced by scanning electron microscopy (SEM) and confirmed by X-ray photoelectron microscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The thermal behaviour and degradation were studied by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) was used to image polymer-coated MWNTs, showing either a relatively smooth or a textured polymer coating present on the surface of individual, debundled nanotubes, i.e., PE/MWNT nanohybrid sausage-like or shish-kebab-like structures, respectively. It was clearly demonstrated that by modifying the design of the catalytic complexes, it was possible to tune by a reproducible way the morphology of the PE coating around the MWNTs

Scan-to-BIM output validation : towards a standardized geometric quality assessment of building information models based on point clouds

The use of Building Information Modeling (BIM) for existing buildings based on point clouds is increasing. Standardized geometric quality assessment of the BIMs is needed to make them more reliable and thus reusable for future users. First, available literature on the subject is studied. Next, an initial proposal for a standardized geometric quality assessment is presented. Finally, this method is tested and evaluated with a case study. The number of specifications on BIM relating to existing buildings is limited. The Levels of Accuracy (LOA) specification of the USIBD provides definitions and suggestions regarding geometric model accuracy, but lacks a standardized assessment method. A deviation analysis is found to be dependent on (1) the used mathematical model, (2) the density of the point clouds and (3) the order of comparison. Results of the analysis can be graphical and numerical. An analysis on macro (building) and micro (BIM object) scale is necessary. On macro scale, the complete model is compared to the original point cloud and vice versa to get an overview of the general model quality. The graphical results show occluded zones and non-modeled objects respectively. Colored point clouds are produced and integrated in the BIM. On micro scale, the relevant surface parts are extracted per BIM object and compared to the complete point cloud. Occluded zones are extracted based on a maximum deviation. What remains is classified according to the LOA specification. The numerical results are integrated in the BIM with the use of object parameters

Supported coordination polymerization: a unique way to performant polyolefin carbon nanotube nanocomposites

peer reviewedHomogeneous surface coating of long carbon nanotubes is achieved by in situ polymerization of ethylene as catalyzed directly from the nanotube surface-treated by a highly active metallocene-based complex and allows for the break-up of the native nanotube bundles leading, upon further melt blending with HDPE, to high-performance polyolefinic nanocomposites

Official communication of the SSC: Recommendations for future research in catheter-related arterial thrombosis in children.

Catheter-related arterial thrombosis (CAT) are increasingly recognized in infants and children. Insufficient data are available on the incidence, risk factors, treatment and outcome of these thrombotic events. This work provides consensus recommendations for future research on catheter-related arterial thrombosis in the paediatric population. In particular, future studies should distinguish between CAT due to indwelling arterial catheters or cardiac catheterization in two different subpopulations (neonates and older children). Further studies should investigate sensitivity and specificity of clinical signs and symptoms for early screening of CAT and the most appropriate imaging modality, focusing on ultrasound due to better feasibility in the very young pediatric population. Adequately powered, well-designed clinical trials should investigate efficacy and safety of different treatment and prevention strategies as well as the risk for and the optimal management of short- and long-term complications

Phase error estimation for synthetic aperture imagery.

The estimation of phase errors in synthetic aperture imagery is important for high quality images. Many methods of autofocus, or the estimation of phase errors from the measured data, are developed using certain assumptions about the imaged scene. This thesis develops improved methods of phase estimation which make full use of the information in the recorded signal. This results in both a more accurate estimate of the image phase error and improved imagery compared to using standard techniques. The standard phase estimation kernel used in echo-correlation techniques is shear-average. This technique averages the phase-difference between each ping over all range-bins, weighted by the signal strength. It is shown in this thesis that this is not the optimal method of weighting each phase estimate. In images where the signal to clutter ratio (SCR) is not proportional to the signal amplitude, shear-average does not meet the predicted error bound. This condition may be met by many image types, including those with shadows, distributed targets and varying surface structure. By measuring the average coherence between echos at each range-bin, it is possible to accurately estimate the variance of each phase estimate, and weight accordingly. A weighted phase-difference estimation (WPDE) using this coherence weighting meets the performance bound for all images tested. Thus an improved performance over shear-average is shown for many image types. The WPDE phase estimation method can be used within the framework of many echo-correlation techniques, such as phase-gradient autofocus (PGA), phase curvature estimation, redundant phase-centre or displaced phase-centre algorithms. In addition, a direct centre-shifting method is developed which reduces bias compared to the centre-shifting method used in PGA. For stripmap images, a weighted phase curvature estimator shows better performance than amplitude weighted shear-average for images with high SCR. A different method of phase estimation, known as sharpness maximisation, perturbs an estimate of the phase error to maximise the sharpness of the reconstructed image. Several improvements are made to the technique of sharpness maximisation. These include the reduction of over-sharpening using regularisation and an improvement in accuracy of the phase estimate using range-weighting based on the coherence measure. A cascaded parametric optimisation method is developed which converges significantly faster than standard optimisation methods for stripmap images. A number of novel insights into the method of sharpness maximisation are presented. A derivation of the phase that gives maximum intensity squared sharpness is extended from a noncoherent imaging system to a coherent spotlight system. A bound on the performance of sharpness-maximisation is presented. A method is developed which allows the direct calculation of the result of a sharpness maximisation for a single ping of a spotlight synthetic aperture image. The phase correction that maximises sharpness can be directly calculated from the signal in a manner similar to a high-order echo-correlation. This calculation can be made for all pings in a recursive manner. No optimisation is required, resulting in a significantly faster phase estimation. The techniques of sharpness maximisation and echo-correlation can be shown to be closely related. This is confirmed by direct comparisons of the results. However, the classical intensity-squared sharpness measure gives poorer results than WPDE and different sharpness measures tested for a distributed target. The standard methods of shear average and maximisation of the intensity-squared sharpness measure, both perform well below the theoretical performance bound. Two of the techniques developed, WPDE and direct entropy minimisation perform at the bound, showing improved performance over standard techniques. The contributions of this thesis add considerably to the body of knowledge on the technique of sharpness maximisation. This allows an improvement in the accuracy of some phase estimation methods, as well as an increase in the understanding of how these techniques work on coherent imagery in general