Simple tools for achieving self-compacting ability of concrete according to the nature of the limestone filler

WOS:000327561200100International audienceThis paper reports the assessment of self-compacting ability at the scale of concrete whatever the nature of the limestone filler (LF). In practice, differences in chemical and physical properties of LF are rarely taken into account during the design process, yet they are most often considered as the causes of segregation during and after placing, and of poor external aspects. The actual cause of the design defect can be resolved by developing tools capable of uniting the properties and the interactions among all components in order to achieve self-compacting flow. Basically, a two-phase approach was exploited by using existing test methods. At the scale of paste (cement + LF + High Range Water Reducer Admixture (HRWRA or superplasticizer) + water), the arrangement of particles in suspension was determined through the wet packing measurement. Starting from the maximum packing density as the reference state related to the water volume needed just to fill the voids between the solid particles, the rheological properties of pastes designed with different cements (OPC, slag cement) and different LF were measured and analyzed according to the excess water to solid surface area ratio. The water absorbed and adsorbed by the aggregates was also determined for the gravel/sand mass ratio, which was optimized from the packing measurement. Irrespective of the nature of the cement/filler combination, and provided that the HRWRA content was sufficient to lower the yield stress of the paste (the yield stress was then no longer affected by excess water variation), the association of the two phases (paste + wet aggregates) enabled a unique viscosity criterion to be evidenced at the paste scale for the design of easy flowing, stable self-compacting concretes. The viscosity criterion was validated by using another skeleton of aggregates and different natures of cement, LF and HRWRA

Value in use of lime in BOF steelmaking process

In the BOF steelmaking process, lime quality and quantity directly affect slag quality, affecting metallurgical results, liquid metal yield, productivity, and therefore the total cost and environmental impact of the steel production. In this paper, a value in use model based on mass balance and heat balance was developed and used to evaluate the impact of lime quality on the BOF process. The model is capable of calculating the consumption of scrap, lime, oxygen, the volume and composition of the slag and the volume and composition of off-gas and facilities to calculate the cost-benefit contributions and potential cost saving for a configured choice of various types of lime and operating parameters. The model has been successfully validated using the data of the Steel Plant. Then three types of lime with different qualities were used to elaborate on the impact of lime characteristics in optimizing the steelmaking process, metallurgical benefits, overall cost impact, potential savings, and environmental benefits. The calculation results show that good-quality lime could increase the scrap ratio, reduce the lime consumption, and reduce iron loss, accordingly, improve the steel quality, increase steel yield, reduce the smelting costs, stabilize smelting operations, and reduce CO2 emissions

The nature of limestone filler and self-consolidating feasibility Relationships between physical, chemical and mineralogical properties of fillers and the flow at different states, from powder to cement-based suspension

International audienceThis paper is a part of a large study aimed at identifying the physical and chemical properties of limestone fillers (LF) that govern their behaviour towards self-consolidating flow. Five LF were studied, complying with the standards and selected for their significant differences in properties on the basis of the supplier's database. Despite their specific manufacturing, a thorough characterization showed that the selected LFs had very different properties in terms of surface charges, morphology, wettability and size distribution. Then, relationships were sought between these properties and the flow of LF in powder form and suspended in water, or water + polycarboxylate type High Range Water Reducer Admixture (HRWRA), or water + HRWRA + cement (OPC or slag blended cement). The flow measurements concerned flowability, floodability and shear under consolidation in the dry state, and static yield stress and apparent viscosity in the suspension state. The main results show that the LFs act in the same way on the flow as long as cement is not incorporated into the suspension. From the dry state to the water + HRWRA suspensions, the flow is dependent on the fineness of the LF. The significant relationships between the surface charges, wettability and fineness of LFs show that impurities like clays are key factors in the flow of LF suspensions. When cement was incorporated into the suspension, the flow was dependent on the interactions existing among all the constituents. Then, with a view to self-consolidating applications, it becomes possible to identify how best to incorporate LF in a cement-based matrix through the measurement of the arrangement of cement and filler particles in suspension

Multimodal and Multimedia Image Analysis and Collaborative Networking for Digestive Endoscopy

International audienceObjective: The ultimate goal of the Syseo project is to create a chain of collaborative processes to allow the hepato-gastroenterology endoscopy specialist to manage images easily. Methods: Syseo contributes to several domains of computer science. First, the proposed storage system relies on DICOM, one of the most important medical standards. Results: Syseo consists in four main components: (1) a data management system relying on the well-known standard DICOM format; (2) a polyp ontology and description logics to manage gastroenterological images; (3) measuring tools to estimate the size of neoplasias from images and (4) pearly User Interfaces to enhance collaboration. Discussion: Preliminary results of Syseo are quite promising since the proposed solutions enable to efficiently store, annotate, retrieve medical data, while providing relatively accurate measuring tools for physicians and medical staff

Fitting a high total impulse electric propulsion system in a student CubeSat to compensate the atmosphericdrag in low-earth orbit

International audienceIn this era where the interest in nanosatellites is growing rapidly, the next big step for them is to integrate a propulsion subsystem in order to accomplish more complex missions. With electric propulsion in particular, nanosatellites will be able to perform new maneuvers and new missions, such as missions in LEO by compensating the drag with a thruster. However, designing such a mission and the satellite for it is not easily feasible for a student project. Here we present a preliminary design for a 6U CubeSat capable of maintaining an altitude of about 300 km for more than several months. This project is a fully student project, and it is supported by the CNES and École polytechnique in Paris. It is planned to be ready for launch in the early 2020s. The phase B planning of this project allowed us to design a nanosat capable of withstanding the high demand for power and capable of performing all maneuvers necessary to reach the target altitude and maintain it. All the technical choices allowing these performances are explained: high-capacity batteries capable of providing energy for one whole thrust sequence (50Wh), large, deployable but not steerable solar panels to recharge them and a balanced ADCS strategy allowing both a high energy intake and regular thrust phases to keep a stable altitude. It is shown that a three-axis reaction wheels stabilization is necessary for such a mission, even while rotating the satellite only around a fixed thrust axis. Finally, the trajectography algorithm, for now based on periapsis raising based on GPS data, under constraints of battery charge and eccentricity, is described, as well as the structure of the on-board computer and the technical choices around them. This preliminary design shows how a satellite can handle atmospheric drag at around 300 km for several months with the constraints of a student-designed CubeSat

Botulinum toxin for the treatment of hypercontractile esophagus: Results of a double‐blind randomized sham‐controlled study

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