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See detailBimodal and hysteretic expression in mammalian cells from a synthetic gene circuit
May, T.; Eccleston, L. J.; Markusic, D. et al

in Public Library of Science ONE (2008), 3(6),

In order to establish cells and organisms with predictable properties, synthetic biology makes use of controllable, synthetic genetic devices. These devices are used to replace or to interfere with ... [more ▼]

In order to establish cells and organisms with predictable properties, synthetic biology makes use of controllable, synthetic genetic devices. These devices are used to replace or to interfere with natural pathways. Alternatively, they may be interlinked with endogenous pathways to create artificial networks of higher complexity. While these approaches have been already successful in prokaryotes and lower eukaryotes, the implementation of such synthetic cassettes in mammalian systems and even animals is still a major obstacle. This is mainly due to the lack of methods that reliably and efficiently transduce synthetic modules without compromising their regulation properties. To pave the way for implementation of synthetic regulation modules in mammalian systems we utilized lentiviral transduction of synthetic modules. A synthetic positive feedback loop, based on the Tetracycline regulation system was implemented in a lentiviral vector system and stably integrated in mammalian cells. This gene regulation circuit yields a bimodal expression response. Based on experimental data a mathematical model based on stochasticity was developed which matched and described the experimental findings. Modelling predicted a hysteretic expression responsewhich was verified experimentally. Thereby supporting the idea that the system is driven by stochasticity. The results presented here highlight that the combination of three independent tools/methodologies facilitate the reliable installation of synthetic gene circuits with predictable expression characteristics in mammalian cells and organisms. [less ▲]

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See detailBiomechanical properties of five different currently used implants for open-wedge high tibial osteotomy
Diffo Kaze, Arnaud UL; Maas, Stefan UL; Waldmann, Danièle UL et al

in Journal of Experimental Orthopaedics (2015), 2(14),

Background: As several new tibial osteotomy plates recently appeared on the market, the aim of the present study was to compare mechanical static and fatigue strength of three newly designed plates with ... [more ▼]

Background: As several new tibial osteotomy plates recently appeared on the market, the aim of the present study was to compare mechanical static and fatigue strength of three newly designed plates with gold standard plates for the treatment of medial knee joint osteoarthritis. Methods: Sixteen fourth-generation tibial bone composites underwent a medial open-wedge high tibial osteotomyn(HTO) according to standard techniques, using five TomoFix standard plates, five PEEKPower plates and six iBalance implants. Static compression load to failure and load-controlled cyclic fatigue failure tests were performed. Forces, horizontal and vertical displacements were measured; rotational permanent plastic deformations, maximal displacement ranges in the hysteresis loops of the cyclic loading responses and dynamic stiffness were determined. Results: Static compression load to failure tests revealed that all plates showed sufficient stability up to 2400 N without any signs of opposite cortex fracture, which occurred above this load in all constructs at different load levels. During the fatigue failure tests, screw breakage in the iBalance group and opposite cortex fractures in all constructs occurred only under physiological loading conditions (<2400 N). The highest fatigue strength in terms of maximal load and number of cycles performed prior to failure was observed for the ContourLock group followed by the iBalance implants, the TomoFix standard (std) and small stature (sm) plates. The PEEKPower group showed the lowest fatigue strength. Conclusions: All plates showed sufficient stability under static loading. Compared to the TomoFix and the PEEKPower plates, the ContourLock plate and iBalance implant showed a higher mechanical fatigue strength during cyclic fatigue testing. These data suggest that both mechanical static and fatigue strength increase with a wider proximal T-shaped plate design together with diverging proximal screws as used in the ContourLock plate or a closed-wedge construction as in the iBalance design. Mechanical strength of the bone-implant constructs decreases with a narrow T-shaped proximal end design and converging proximal screws (TomoFix) or a short vertical plate design (PEEKPower Plate). Whenever high mechanical strength is required, a ContourLock or iBalance plate should be selected. [less ▲]

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See detailBiomechanik neuer Implantate für die HTO
Pape, Dietrich; Diffo Kaze, Arnaud UL; Hoffmann, Alexander et al

in Orthopade (Der) (2017), 46(7), 583-595

Biomechanical characteristics of 5 tibial osteotomy plates for the treatment of medial knee joint osteoarthritis were examined. Fourth-generation tibial bone composites underwent a medial open-wedge high ... [more ▼]

Biomechanical characteristics of 5 tibial osteotomy plates for the treatment of medial knee joint osteoarthritis were examined. Fourth-generation tibial bone composites underwent a medial open-wedge high tibial osteotomy, using TomoFix™ standard, PEEKPower®, ContourLock®, TomoFix™ small stature plates, and iBalance® implants. Static compression load to failure and load-controlled cyclic fatigue failure tests were performed. All plates had sufficient stability up to 2400 N in the static compression load to failure tests. Screw breakage in the iBalance® group and opposite cortex fractures in all constructs occurred at lower loading conditions. The highest fatigue strength in terms of maximal load and number of cycles performed prior to failure was observed for the ContourLock® group followed by the iBalance® implants, the TomoFix™ standard and small stature plates. PEEKPower® had the lowest fatigue strength. All plates showed sufficient stability under static loading. Compared to the TomoFix™ and the PEEKPower® plates, the ContourLock® plate and iBalance® implant showed a higher mechanical fatigue strength during cyclic fatigue testing, suggesting that both mechanical static and fatigue strength increase with a wider proximal T‑shaped plate design together with diverging proximal screws. Mechanical strength of the bone–implant constructs decreases with a narrow T‑shaped proximal end design and converging proximal screws (TomoFix™) or a short vertical plate design (PEEKPower®). Published results indicate high fusion rates and good clinical results with the TomoFix™ plate, which is contrary to our findings. A certain amount of interfragmentary motion rather than high mechanical strength and stiffness seem to be important for bone healing which is outside the scope of this paper. [less ▲]

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See detailBiopharm - the Influence of Macro-substrates & Conditioning on Pharmaceutical Removal Rates by Moving Bed Biofilm Reactors
Köhler, Christian UL

Doctoral thesis (2015)

Organic micropollutants with endocrine disruptive properties are present in the aquatic environment. A major part of their emission is caused by municipal wastewater treatment plants (WWTPs). For this ... [more ▼]

Organic micropollutants with endocrine disruptive properties are present in the aquatic environment. A major part of their emission is caused by municipal wastewater treatment plants (WWTPs). For this reason, a vast amount of research has been undertaken to remove xenobiotics from municipal wastewater by developing post-treatment technologies with some success. However, these technologies cause considerable environmental costs due their high demand for electrical energy implicating an increase in CO2 emissions. Consequently, existing biological treatments need first to be better understood and subsequently optimized regarding xenobiotic removal before post-treatments are employed. The study focused on the fate of xenobiotics during biological wastewater treatment. In particular, metabolic strategies of bacteria degrading pharmaceuticals were investigated within moving bed biofilm reactor (MBBR) processes. Two main objectives were tracked. On the one hand, it was to unfold the impact of macro-substrates in terms of type and molecular complexity on the activity of microorganisms and consequently pharmaceutical degradation performance. On the other hand, the study was set out to explore the adaptation of metabolic means regarding exoenzymes and consortia structure during continuous (long-term) exposure to pharmaceuticals. Accordingly, the ability to increase microbial competences during pharmaceutical short-term pulses was the general target of investigation. Both conditions continuous substance flow and short-term peak loads of xenobiotics are believed to occur in urban WWTPs. A pilot MBBR was set up next to a domestic WWTP. The pilot treated municipal sewage and served as inoculation reservoir for biofilm carriers used for in-depth laboratory experiments. The latter comprised six lab-scale MBBRs featuring flow through operation under controlled conditions regarding temperature, dissolved oxygen, pH, influent flow and influent load. The reactors were conditioned over four weeks with a synthetic sewage providing substrates and micro-nutrients in a similar manner as expected under real conditions. Biofilm was monitored by respirometry and a series of enzyme assays using fluorogenic substrates to capture esterase, phosphatase, alpha- and beta-glucosidase and aminopeptidase activity. All enzymes are essential during organic carbon metabolism. An array of macro-substrates with different molecular complexity was triggering individual enzyme activity profiles. After conditioning, 12 pharmaceuticals being subject to a range of anticipated metabolic pathways and degradation rates were spiked into the MBBRs. Their degradation kinetics were measured by liquid chromatography coupled with tandem mass spectrometry (LC MS/MS). Pseudo first-order kinetics revealed substrate related fingerprints and showed that readily biodegradable substrate leads generally to good pharmaceutical degradation performance compared to synthetic sewage with a mixture of several high molecular organic substrates. The latter was designed to induce the greatest metabolic effort of tested substrates before microbial uptake occurs. However, single substrates triggering exoenzyme activity in a more targeted manner such as maltose and cellobiose showed positive impact on the pseudo first-order rate coefficients of particular pharmaceuticals such as atenolol and diclofenac. Accordingly, alpha-glucosidase activity was found to be directly proportional to atenolol degradation kinetics. Phylogenetic characterisation of DNA and RNA involving state-of-the-art 16S ribosomal rRNA gene amplification and sequencing techniques was used to explore community structures. Prokaryote diversity in lab-scale MBBRs was in agreement to previous studies which investigated microbial consortia in full-scale systems. Multivariate analysis revealed that bacteria are adapting their active gene pool when the beta-blocker atenolol is continuously present with a concentration in ug/L range. Differential analysis unfolded that the prokaryotic genera Delftia and Lysobacter were thereby exclusively benefiting from the exposure to atenolol. Yet, compared to the influence of macro-substrates, biomass conditioning (training) with atenolol and diclofenac had no notable impact on the degradation performance of pharmaceutical short-term pulses. The outstanding comprehensive character of the study which encompassed sophisticated experimental design and powerful analytical tools from different scientific domains uncovered some interesting insights in xenobiotic degradation processes. The results finally show how biomass is reacting towards the presence of primary carbon sources and organic micro-pollutants. The outcomes highlight the importance of WWTP influent characterization being indicative of metabolic activity and therefore degradation capacity of xenobiotics. The study further suggests that xenobiotic metabolism and co-metabolism co-exist during biological treatment processes. Co-metabolism is the decisive actor when adaption time is relatively short as it was the case during the lab-scale experiments compared to real conditions. Further, the study indicates some potential of process enhancement of WWTPs ranging from straightforward implementations such as external carbon sources to more elaborated processes of bioaugmentation. [less ▲]

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See detailBlock Backstepping, NDI and Related Cascade Designs for Efficient Development of Nonlinear Flight Control Laws
Thunberg, Johan UL; Robinson, J.W.C.

in Proceedings of the AIAA Guidance, Navigation and Control Conference and Exhibit 2008 (2008)

A common feature of many aircraft configurations is that the actuation mainly effects the moments, and thereby the angular accelerations, whereas the desired normal acceleration is achieved by adjusting ... [more ▼]

A common feature of many aircraft configurations is that the actuation mainly effects the moments, and thereby the angular accelerations, whereas the desired normal acceleration is achieved by adjusting the location of the velocity vector in body coordinates. Thus, the main desired effects of the actuators appear after one integration, and if the actuators have dynamics the effect of the primary control variable occurs after more than one integration. This inherent cascade structure of many aircraft control problems is exploited in e.g. nonlinear dynamic inversion via time scale separation (NDI-TSS) to yield a powerful nonlinear design method. In the present work we present a family of multivariable (three axis) nonlinear cascade design techniques for flight control law design which includes block backstepping and NDI-TSS as special cases and we show that this family can offer a large design flexibility and excellent performance as well as short design cycles. We show stability for the family of techniques and illustrate the theory using simulations based on the ADMIRE model which is a realistic nonlinear model of an agile fighter with delta-canard configuration. [less ▲]

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See detailBlood flow simulation using smoothed particle hydrodynamics: application to thrombus generation
AL-SAAD, Mohammed; Kulasegaram, Sivakumar; Bordas, Stéphane UL

Scientific Conference (2016, March 31)

Blood flow rheology is considered to be a complex phenomenon. In order to understand the characteristics of blood flow, it is important to identify key parameters those influence the flow behaviour of ... [more ▼]

Blood flow rheology is considered to be a complex phenomenon. In order to understand the characteristics of blood flow, it is important to identify key parameters those influence the flow behaviour of blood. Further, the characterisation of blood flow will also enable us to understand flow parameters associated with physiological conditions such as atherosclerosis. Thrombosis plays a crucial role in atherosclerosis, or to stop bleeding when a blood vessel is injured. This article focuses on using meshless particle-based Lagrangian numerical technique named smoothed particles hydrodynamic (SPH) method to study the flow behaviour of blood and to explore flow condition that induces formation of thrombus in a blood vessel. Due its simplicity and effectiveness, the SPH method is employed here to simulate the process of thrombogenesis under the influence of various blood flow parameters. In the present SPH simulation, blood is modelled by particles that have characteristics of plasma and of platelets. To simulate coagulation of platelets which forms thrombus, the adhesion and aggregation process of platelets are modelled by an effective inter-particle force model. With these models, platelet motion in the flowing blood and platelet adhesion and aggregation are effectively coupled with viscous blood flow. In this study, the adhesion and aggregation of blood particles are performed on a bifurcated artery under a various low Reynolds number scenarios. The results are compared with experimental results and a good agreement is found between the simulated and experimental results. [less ▲]

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See detailBMS revisited
Aucher, Guillaume UL

in Proceedings of the 12th Conference on Theoretical Aspects of Rationality and Knowledge (2009)

The insight of the BMS logical framework (proposed by Baltag, Moss and Solecki) is to represent how an event is perceived by several agents very similarly to the way one represents how a static situation ... [more ▼]

The insight of the BMS logical framework (proposed by Baltag, Moss and Solecki) is to represent how an event is perceived by several agents very similarly to the way one represents how a static situation is perceived by them: by means of a Kripke model. There are however some differences between the definitions of an epistemic model (representing the static situation) and an event model. In this paper we restore the symmetry. The resulting logical framework allows, unlike any other one, to express statements about ongoing events and to model the fact that our perception of events (and not only of the static situation) can also be updated due to other events. We axiomatize it and prove its decidability. Finally, we show that it embeds the BMS one if we add common belief operators. [less ▲]

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See detailBoard Game Prototyping to Co-Design a Better Location-Based Digital Game
Jones, Catherine UL; Liapis; Lykourentzou, Ioanna et al

in Abstract book of the 2017 CHI Conference Extended Abstracts on Human Factors in Computing Systems - CHI EA '17 (2017)

In this case study we describe the iterative process of paper prototyping, using a board game, to co-design a location-based mobile application. The end goal of the application is to motivate reflection ... [more ▼]

In this case study we describe the iterative process of paper prototyping, using a board game, to co-design a location-based mobile application. The end goal of the application is to motivate reflection on historical topics about migration. The board game serves to capture the core concerns of this application by simulating movement through the city. Three play tests highlighted the users' interest and issues with the historical content, the way this content is represented, and the players' responses to the interactions and motivating mechanisms of the application. Results show that the board game helped capture important design preferences and problems, ensuring the improvement of our scenario. This feedback can help reduce development effort and implement a future technology prototype closer to the needs of our end users. [less ▲]

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See detailA Boolean Approach for Disentangling the Roles of Submodules to the Global Properties of a Biomodel
Czeizler, Elena; Mizera, Andrzej UL; Petre, Ion

in Fundamenta Informaticae (2012), 116(1-4), 51-63

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See detailA boolean control network approach to pursuit evasion problems in polygonal environments
Thunberg, Johan UL; Ogren, P.; Hu, X.

in Proceedings of the 2011 IEEE International Conference on Robotics and Automation (ICRA) (2011)

In this paper, the multi pursuer version of the pursuit evasion problem in polygonal environments is addressed. This problem is NP-hard, and therefore we seek good enough, but not optimal solutions. By ... [more ▼]

In this paper, the multi pursuer version of the pursuit evasion problem in polygonal environments is addressed. This problem is NP-hard, and therefore we seek good enough, but not optimal solutions. By modeling the problem as a Boolean Control Network, we can efficiently keep track of which regions are cleared, and which are not, while the input nodes of the network are used to represent the motion of the pursuers. The environment is partitioned into a set of convex regions, where each region correspond to a set of nodes in the network. The method is implemented in ANSI C, and efficiently solves complex environments containing multiple loops and requiring so-called recontamination. The provided examples demonstrate the effectiveness of the method in terms of computational time. [less ▲]

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See detailA boundary-enhanced supervoxel method for extraction of road edges in MLS point clouds
Sha, Zhengchuan; Chen, Yiping; Li, Wen et al

in A boundary-enhanced supervoxel method for extraction of road edges in MLS point clouds (2020)

Road extraction plays a significant role in production of high definition maps (HD maps). This paper presents a novel boundary-enhanced supervoxel segmentation method for extracting road edge contours ... [more ▼]

Road extraction plays a significant role in production of high definition maps (HD maps). This paper presents a novel boundary-enhanced supervoxel segmentation method for extracting road edge contours from MLS point clouds. The proposed method first leverages normal feature judgment to obtain 3D point clouds global geometric information, then clusters points according to an existing method with global geometric information to enhance the boundaries. Finally, it utilizes the neighbor spatial distance metric to extract the contours and drop out existing outliers. The proposed method is tested on two datasets acquired by a RIEGL VMX-450 MLS system that contain the major point cloud scenes with different types of road boundaries. The experimental results demonstrate that the proposed method provides a promising solution for extracting contours efficiently and completely. Results show that the precision values are 1.5 times higher and approximately equal than the other two existing methods when the recall value is 0 for both tested two road datasets. [less ▲]

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See detailBubble-Enriched Smoothed Finite Element Methods for Nearly-Incompressible Solids
Lee, Changkye; Natarajan, Sundararajan; Hale, Jack UL et al

in Computer Modeling in Engineering and Sciences (2021), 127(2), 411-436

This work presents a locking-free smoothed finite element method (S-FEM) for the simulation of soft matter modelled by the equations of quasi-incompressible hyperelasticity. The proposed method overcomes ... [more ▼]

This work presents a locking-free smoothed finite element method (S-FEM) for the simulation of soft matter modelled by the equations of quasi-incompressible hyperelasticity. The proposed method overcomes well-known issues of standard finite element methods (FEM) in the incompressible limit: the over-estimation of stiffness and sensitivity to severely distorted meshes. The concepts of cell-based, edge-based and node-based S-FEMs are extended in this paper to three-dimensions. Additionally, a cubic bubble function is utilized to improve accuracy and stability. For the bubble function, an additional displacement degree of freedom is added at the centroid of the element. Several numerical studies are performed demonstrating the stability and validity of the proposed approach. The obtained results are compared with standard FEM and with analytical solutions to show the effectiveness of the method. [less ▲]

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See detailCalculating the Malliavin derivative of some stochastic mechanics problems
Hauseux, Paul UL; Hale, Jack UL; Bordas, Stéphane UL

in PLoS ONE (2017), 12(12), 0189994

The Malliavin calculus is an extension of the classical calculus of variations from deterministic functions to stochastic processes. In this paper we aim to show in a practical and didactic way how to ... [more ▼]

The Malliavin calculus is an extension of the classical calculus of variations from deterministic functions to stochastic processes. In this paper we aim to show in a practical and didactic way how to calculate the Malliavin derivative, the derivative of the expectation of a quantity of interest of a model with respect to its underlying stochastic parameters, for four problems found in mechanics. The non-intrusive approach uses the Malliavin Weight Sampling (MWS) method in conjunction with a standard Monte Carlo method. The models are expressed as ODEs or PDEs and discretised using the finite difference or finite element methods. Specifically, we consider stochastic extensions of; a 1D Kelvin-Voigt viscoelastic model discretised with finite differences, a 1D linear elastic bar, a hyperelastic bar undergoing buckling, and incompressible Navier-Stokes flow around a cylinder, all discretised with finite elements. A further contribution of this paper is an extension of the MWS method to the more difficult case of non-Gaussian random variables and the calculation of second-order derivatives. We provide open-source code for the numerical examples in this paper. [less ▲]

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See detailCalibration of a microscopic simulation model for emission calculation
Li, Jie; Van Zuylen, Henk J.; Chen, Yusen et al

in Transportation Research. Part C : Emerging Technologies (2013), 31

Emissions by road traffic can be reduced by optimising traffic control. The impact of this optimisation on emission can be analysed ex ante by simulation. The simulation programs used for this analysis ... [more ▼]

Emissions by road traffic can be reduced by optimising traffic control. The impact of this optimisation on emission can be analysed ex ante by simulation. The simulation programs used for this analysis should be valid with respect to the traffic characteristics that determine the emissions. Thus calibration of the parameters is a prerequisite. In most cases, volumes, travel times and queues are used to calibrate simulation models, rather than detailed driving characteristics such as speed and acceleration patterns. However, these driving behaviour parameters determine the vehicular emissions to a great extent. A study was carried out in which the driving behaviour parameters in a microscopic simulation model (VISSIM) were calibrated using real trajectories collected by image processing at an intersection in Rotterdam. The sensitivity of the simulation results for driving behaviour parameters was investigated. The most influential parameters were identified and adjusted to ensure that the simulation results were consistent with the observed traffic and could provide valid estimations of the total production of emissions. [less ▲]

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See detailCardiff/Luxembourg Computational Mechanics Research Group
Bordas, Stéphane UL; Kerfriden, Pierre; Hale, Jack UL et al

Poster (2014, November)

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See detailA cascading Kalman filtering framework for real-time urban network flow estimation
Rinaldi, Marco UL; Viti, Francesco UL

in 2020 IEEE 23rd International Conference on Intelligent Transportation Systems (ITSC) (2020, December)

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See detailA Case Study On Computational Hermeneutics: E. J. Lowe's Modal Ontological Argument
Fuenmayor, David; Benzmüller, Christoph UL

in IfCoLog Journal of Logics and Their Applications (2018), 5(7), 1567-1603

Computers may help us to better understand (not just verify) arguments. In this article we defend this claim by showcasing the application of a new, computer-assisted interpretive method to an exemplary ... [more ▼]

Computers may help us to better understand (not just verify) arguments. In this article we defend this claim by showcasing the application of a new, computer-assisted interpretive method to an exemplary natural-language argument with strong ties to metaphysics and religion: E. J. Lowe’s modern variant of St. Anselm’s ontological argument for the existence of God. Our new method, which we call computational hermeneutics, has been particularly conceived for use in interactive-automated proof assistants. It aims at shedding light on the meanings of words and sentences by framing their inferential role in a given argument. By employing automated theorem reasoning technology within interactive proof assistants, we are able to drastically reduce (by several orders of magnitude) the time needed to test the logical validity of an argument’s formalization. As a result, a new approach to logical analysis, inspired by Donald Davidson’s account of radical interpretation, has been enabled. In computational hermeneutics, the utilization of automated reasoning tools effectively boosts our capacity to expose the assumptions we indirectly commit ourselves to every time we engage in rational argumentation and it fosters the explicitation and revision of our concepts and commitments. [less ▲]

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See detailCategorisation of building data in the digital documentation of heritage buildings
Khalil, Ahmed; Stravoravdis, Spyridon; Backes, Dietmar UL

in Applied Geomatics (2020)

The documentation of heritage buildings is the preliminary action to deal with any problem related to the built heritage. The procedure of documentation requires a very diverse range of data (quantitative ... [more ▼]

The documentation of heritage buildings is the preliminary action to deal with any problem related to the built heritage. The procedure of documentation requires a very diverse range of data (quantitative and qualitative) to be obtained and investigated in order to produce an accurate digital representation of the building. This type of work of data capture and interpretation is often conducted in isolation by different stakeholders and for a range of purposes, leading to a lack of communication between different data types, repeated effort and incomplete documentation. Heritage Building Information Modelling (H-BIM) is set to play a key role in the digital documentation of heritage buildings, as it can combine quantitative and qualitative data and facilitate the integration of different stakeholders and specialised data into the digital management of the different phases of dealing with heritage buildings. This paper aims to review the multitude of data types that could be included in the documentation and investigation process of the built heritage, in order to assess the breadth and depth by which heritage buildings can be documented. Four main categories that span the whole documentation data areas are being suggested which vary from outer geometry surveys, to subsurface materials and structural integrity investigations, to data concerning the building performance, as well as the historic records concerning the building’s morphology over time, which can help to create a more in-depth knowledge about the heritage building’s status and performance and can create a solid base for any required restoration and retrofitting processes (Khalil and Stravoravdis 2019a). [less ▲]

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See detailA cell - based smoothed finite element method for free vibration and buckling analysis of shells
Thai-Hoang, Chien; Nguyen-Thanh, Nhon; Nguyen-Xuan, Hung et al

in KSCE Journal of Civil Engineering (2011), 15(2), 347-361

This paper further extends a cell-based smoothed finite element method for free vibration and buckling analysis of shells. A four-node quadrilateral Mindlin-Reissner shell element with a gradient ... [more ▼]

This paper further extends a cell-based smoothed finite element method for free vibration and buckling analysis of shells. A four-node quadrilateral Mindlin-Reissner shell element with a gradient smoothing operator is adopted. The membrane-bending and geometrical stiffness matrices are computed along the boundaries of the smoothing cells while the shear stiffness matrix is calculated by an independent interpolation in the natural coordinates as in the MITC4 (the Mixed Interpolation of Tensorial Components) element. Various numerical results are compared with existing exact and numerical solutions and they are in good agreement. The advantage of the present formulation is that it retains higher accurate than the MITC4 element even for heavily distorted meshes without increasing the computational cost. © 2011 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg. [less ▲]

Detailed reference viewed: 88 (1 UL)