Building tomorrow’s society / Bâtir la société de demain

Abstract: Lattice towers are extensively used in overhead transmission lines, owing primarily to their lightness and cost-effectiveness. The modeling of such structures is usually laborious due to various complex factors including connection eccentricities, rotational stiffness of connections, bolt slippage, among others. Therefore, full-scale tests are usually performed for the qualification of new overhead line supports, which is a time-consuming and expensive process. Numerical models used in practice rely on simplified hypotheses, using linear truss/beam elements assumed to be pin-connected at both ends. Such models are combined with standard design equations to only evaluate the members’ axial capacities. Finite element models involving solid/shell elements are generally more accurate, though, the computational cost of the resulting problems makes it very difficult to evaluate the response of a complete tower. This paper presents an advanced numerical approach using beam elements aimed at predicting the load-bearing resistance of steel lattice towers under static load cases. Such approach will serve not only to verify the design of new towers, but also to understand various phenomena leading to the collapse of towers in the case of premature failures. The proposed model is developed using the finite element package Code_Aster, wherein lattice towers are modeled using spatial beams. The highly nonlinear problem is solved in an incremental way using advanced features to deal with both geometric and material nonlinearities. An example of a lattice tower loaded until failure is presented and compared with analogous experimental test. The effect of different geometric imperfections on the failure is particularly highlighted

Simulation of Seasonal Snow Microwave TB Using Coupled Multi-Layered Snow Evolution and Microwave Emission Models

The accurate quantification of SWE has important societal benefits, including improving domestic and agricultural water planning, flood forecasting and electric power generation. However, passive-microwave SWE algorithms suffer from variations in TB due to snow metamorphism, difficult to distinguish from those due to SWE variations. Coupled snow evolution-emission models are able to predict snow metamorphism, allowing us to account for emissivity changes. They can also be used to identify weaknesses in the snow evolution model. Moreover, thoroughly evaluating coupled models is a contribution toward the assimilation of TB, which leads to a significant increase in the accuracy of SWE estimates

Growing with youth / Croître avec les jeunes

Abstract: Lattice towers are the most commonly used structures in the field of overhead power transmission lines. In the design process of transmission lines, there are several methods for the evaluation of their capacity. The most common design method involves the use of three-dimensional linear elastic truss analyses to evaluate the axial forces in the pin-ended members. The resulting design is normally validated by full-scale experimental tests. These tests are very expensive and time-consuming. Moreover, the rarity of the testing facilities represents an additional difficulty. Hence there is an interest of using substructured pseudo-dynamic testing methods in which the experimental substructure, tested in a laboratory environment, interacts with a numerical model to emulate the structural behaviour of a complete structure. This method has several advantages but requires several preliminary analyses and planning for defining the critical substructure, dynamic parameters, and the setup’s flexibility. This work aims to develop a completely numerical substructuring strategy using the finite element software Code_Aster to ensure relevance and simplify the preparation and planning of pseudo-dynamic tests on lattice towers. An example of a lattice tower, under quasi-static load case is presented and compared with reference numerical analyses’ results. The effect of dynamic parameters (time step, damping ratio and load rate) on the emulated structure’s behaviour is analyzed in detail. Finally, the effects due to the flexibility of a simplified test set-up on the accuracy of the test results is studied

Testing steel lattice towers with a hybrid (numerical/ experimental) method

Abstract : The analysis of transmission line steel lattice towers is usually performed with linear numerical methods. However, the actual behaviour of bolted lattice towers is complex and may be highly affected by different factors such as rotational stiffness of connections, bolt slipping, eccentricities in the connections, initial out-of-straightness, etc. For this reason, most power utilities perform full-scale tests for the qualification of novel steel lattice transmission tower designs. These tests are expensive and add delays in the planning of the construction of new transmission lines. Over the past years, advanced numerical methods were developed and they may effectively provide more insight into the force distribution found in lattice structures. However, the actual capacity and failure modes remain difficult to identify numerically and experimental tests are often required. On the other hand, over the last decades, the civil engineering field has seen the development of a completely new testing technique called hybrid testing that combines both experimental and numerical methods. This testing technique involves the experimental testing of a substructure and the interaction during the test with a numerical model of the remainder of the structure. This technique was mostly used for the dynamic analyses of buildings and bridges under the action of seismic loads. To adapt hybrid techniques to lattice towers, a methodology needs to be put in place to identify the substructure of interests to be tested experimentally. The work presented here aims at developing a hybrid testing technique for the evaluation of the failure modes and structural capacity of lattice towers. The long term objective of this research program is to provide a new testing technique that would be an advantageous alternative to advanced numerical methods and reduce the need for full-scale tests. This paper presents hybrid tests that were performed on reduced-scale lattice tower sections. Firstly, an existing 32 m lattice tower was adapted to be able to build a reduced 1:4 scale model. Secondly, a numerical model was developed to identify load cases and substructures that could allow to obtain similar capacities and failure modes to those obtained for the complete structure model. Then, experimental tests on complete 1:4 reduced scale towers were performed to serve as references. Finally, hybrid tests were performed on a 1:4 reduced scale substructure corresponding to a critical section of the tower. The hybrid tests yielded results that were in agreement with the complete tower experimental tests. The test results were also coherent with the numerical model’s results

Knowledge Graph Question Answering for Materials Science (KGQA4MAT): Developing Natural Language Interface for Metal-Organic Frameworks Knowledge Graph (MOF-KG)

We present a comprehensive benchmark dataset for Knowledge Graph Question Answering in Materials Science (KGQA4MAT), with a focus on metal-organic frameworks (MOFs). A knowledge graph for metal-organic frameworks (MOF-KG) has been constructed by integrating structured databases and knowledge extracted from the literature. To enhance MOF-KG accessibility for domain experts, we aim to develop a natural language interface for querying the knowledge graph. We have developed a benchmark comprised of 161 complex questions involving comparison, aggregation, and complicated graph structures. Each question is rephrased in three additional variations, resulting in 644 questions and 161 KG queries. To evaluate the benchmark, we have developed a systematic approach for utilizing ChatGPT to translate natural language questions into formal KG queries. We also apply the approach to the well-known QALD-9 dataset, demonstrating ChatGPT's potential in addressing KGQA issues for different platforms and query languages. The benchmark and the proposed approach aim to stimulate further research and development of user-friendly and efficient interfaces for querying domain-specific materials science knowledge graphs, thereby accelerating the discovery of novel materials.Comment: In 17th International Conference on Metadata and Semantics Research, October 202

Evidence for polyploidy in the globally important diazotroph Trichodesmium

Polyploidy is a well-described trait in some prokaryotic organisms; however, it is unusual in marine microbes from oligotrophic environments, which typically display a tendency towards genome streamlining. The biogeochemically significant diazotrophic cyanobacterium Trichodesmium is a potential exception. With a relatively large genome and a comparatively high proportion of non-protein-coding DNA, Trichodesmium appears to allocate relatively more resources to genetic material than closely related organisms and microbes within the same environment. Through simultaneous analysis of gene abundance and direct cell counts, we show for the first time that Trichodesmium spp. can also be highly polyploid, containing as many as 100 genome copies per cell in field-collected samples and >600 copies per cell in laboratory cultures. These findings have implications for the widespread use of the abundance of the nifH gene (encoding a subunit of the N2-fixing enzyme nitrogenase) as an approach for quantifying the abundance and distribution of marine diazotrophs. Moreover, polyploidy may combine with the unusual genomic characteristics of this genus both in reflecting evolutionary dynamics and influencing phenotypic plasticity and ecological resilience

Building Open Knowledge Graph for Metal-Organic Frameworks (MOF-KG): Challenges and Case Studies

Metal-Organic Frameworks (MOFs) are a class of modular, porous crystalline materials that have great potential to revolutionize applications such as gas storage, molecular separations, chemical sensing, catalysis, and drug delivery. The Cambridge Structural Database (CSD) reports 10,636 synthesized MOF crystals which in addition contains ca. 114,373 MOF-like structures. The sheer number of synthesized (plus potentially synthesizable) MOF structures requires researchers pursue computational techniques to screen and isolate MOF candidates. In this demo paper, we describe our effort on leveraging knowledge graph methods to facilitate MOF prediction, discovery, and synthesis. We present challenges and case studies about (1) construction of a MOF knowledge graph (MOF-KG) from structured and unstructured sources and (2) leveraging the MOF-KG for discovery of new or missing knowledge.Comment: Accepted by the International Workshop on Knowledge Graphs and Open Knowledge Network (OKN'22) Co-located with the 28th ACM SIGKDD Conferenc

Protocol for the development of guidance for stakeholder engagement in health and healthcare guideline development and implementation

Stakeholder engagement has become widely accepted as a necessary component of guideline development and implementation. While frameworks for developing guidelines express the need for those potentially affected by guideline recommendations to be involved in their development, there is a lack of consensus on how this should be done in practice. Further, there is a lack of guidance on how to equitably and meaningfully engage multiple stakeholders. We aim to develop guidance for the meaningful and equitable engagement of multiple stakeholders in guideline development and implementation. METHODS: This will be a multi-stage project. The first stage is to conduct a series of four systematic reviews. These will (1) describe existing guidance and methods for stakeholder engagement in guideline development and implementation, (2) characterize barriers and facilitators to stakeholder engagement in guideline development and implementation, (3) explore the impact of stakeholder engagement on guideline development and implementation, and (4) identify issues related to conflicts of interest when engaging multiple stakeholders in guideline development and implementation. DISCUSSION: We will collaborate with our multiple and diverse stakeholders to develop guidance for multi-stakeholder engagement in guideline development and implementation. We will use the results of the systematic reviews to develop a candidate list of draft guidance recommendations and will seek broad feedback on the draft guidance via an online survey of guideline developers and external stakeholders. An invited group of representatives from all stakeholder groups will discuss the results of the survey at a consensus meeting which will inform the development of the final guidance papers. Our overall goal is to improve the development of guidelines through meaningful and equitable multi-stakeholder engagement, and subsequently to improve health outcomes and reduce inequities in health

Rain-On-Snow Events, Ecology and Community Recording

No abstract availabl