Structure–function relationship during the early and long-term hydration of one-part alkali-activated slag

Understanding the mechanisms controlling the early (fresh) and long-term (hardened) hydration of one-part alkali-activated slags (AAS) is key to extend their use as low CO2 substitutes for ordinary Portland cement (OPC). Their “just add water” use makes them easier and less hazardous to manipulate than the more studied two-part ones. This is due to the absence of liquid alkaline activators, which are environmentally and energy demanding. In this work, numerous experimental techniques have been linked to obtain a comprehensive physico-chemical characterization of a one-part AAS activated with Na2CO3 and Ca(OH)2 powders at several water to solid ratios (w/s). Calorimetry and pH/conductivity measurements describe the functioning of the activators immediately after contact with water. Early reactivity is characterized through in situ X-ray powder diffraction (XRPD) and small amplitude oscillatory shear (SAOS) rheology, which reveal a rapid precipitation of nanometric hydration products (nano-C-A-S-H), which results in a continuous increase in the paste cohesivity until setting. Moreover, SAOS shows that rejuvenating the paste by means of shearing (performed externally to the rheometer in this study) is enough to restore the initial cohesion (i.e., workability) for long time spans until setting occurs. The long-term hydration is characterized by ex situ XRPD on aged AAS pastes, in parallel with mechanical testing on AAS mortar. A correlation can be observed between the amount of nano-C-A-S-H and the increase in compressive strength. Overall, this formulation shows satisfactory fresh and solid properties, demonstrating suitability for low- and normal-strength applications

Formalism for physical attacks

International audienceSecurity is a key component for information technologies and communication. Among the security threats, a very important one is certainly due to vulnerabilities of the integrated circuits that implement cryptographic algorithms to ensure confidentiality, authentication or data integrity (such as smartcards). Among them, the attacks that require a physical access to the circuit, also called “hardware attacks”, enable to retrieve the cryptographic material (such as ``keys'') in a really efficient and powerful way. There are two main kinds of such attacks. The first one, called “side channel attacks”, consists in observing some physical characteristics (such as power consumption or electromagnetic radiation) which are modified during the circuit's computation. The second technique, called “fault attacks”, consists in disrupting the circuit's behavior. Our work is, to our knowledge, the first attempt to describe these two kinds of attacks, which seem very different at first sight, with a common formalism, i.e. with a small set of concepts and algorithms.In the first part of the talk, the side channel and fault attacks will be shortly presented. Next, the concepts and the algorithms which are common to these attacks will be detailed. Then, we’ll show that our proposed formalism easily fits with several representative examples (such as DPA, DFA, DBA, FSA, etc.). At last, the perspectives of our work will be highlighted. For example, we plan to define ``new'' attacks as new combinations of the concepts and the algorithms of our formalism. Then, we plan to provide efficient and modular implementation of these attacks. The long-term aim of this work is to merge the advantages of attack-specific protections to enable a more generic set of countermeasures

Template-based Fault Injection Analysis of Block Ciphers

We present the first template-based fault injection analysis of FPGA-based block cipher implementations. While template attacks have been a popular form of side-channel analysis in the cryptographic literature, the use of templates in the context of fault attacks has not yet been explored to the best of our knowledge. Our approach involves two phases. The first phase is a profiling phase where we build templates of the fault behavior of a cryptographic device for different secret key segments under different fault injection intensities. This is followed by a matching phase where we match the observed fault behavior of an identical but black-box device with the pre-built templates to retrieve the secret key. We present a generic treatment of our template-based fault attack approach for SPN block ciphers, and illustrate the same with case studies on a Xilinx Spartan-6 FPGA-based implementation of AES-128

Do Zebra Finch Parents Fail to Recognise Their Own Offspring?

Individual recognition systems require the sender to be individually distinctive and the receiver to be able to perceive differences between individuals and react accordingly. Many studies have demonstrated that acoustic signals of almost any species contain individualized information. However, fewer studies have tested experimentally if those signals are used for individual recognition by potential receivers. While laboratory studies using zebra finches have shown that fledglings recognize their parents by their “distance call”, mutual recognition using the same call type has not been demonstrated yet. In a laboratory study with zebra finches, we first quantified between-individual acoustic variation in distance calls of fledglings. In a second step, we tested recognition of fledgling calls by parents using playback experiments. With a discriminant function analysis, we show that individuals are highly distinctive and most measured parameters show very high potential to encode for individuality. The response pattern of zebra finch parents shows that they do react to calls of fledglings, however they do not distinguish between own and unfamiliar offspring, despite individual distinctiveness. This finding is interesting in light of the observation of a high percentage of misdirected feedings in our communal breeding aviaries. Our results demonstrate the importance of adopting a receiver's perspective and suggest that variation in fledgling contact calls might not be used in individual recognition of offspring

Influence of different external lubricants and their deposition mode on green nuclear fuel pellets during cold compaction

In the framework of manufacturing future nuclear fuels, some solutions set out to optimize the nuclear powder compaction process. Lubrication is used in the fabrication process to reduce friction between the actinide oxide grains and press tools. A higher plutonium content and an isotopic composition with more $^{238}$Pu for the purpose of plutonium multi-recycling would increase the level of radioactivity and the temperature in future UO$_2$ + PuO$_2$ powder mixtures. This temperature could be detrimental to maintaining the lubricant-s properties within the mixture.A solution to this problem could be to replace the internal lubricant by a lubricant deposit on the die wall (external lubrication) during compaction process. This lubrication technique, when combined with internal lubrication, is known to enhance the mechanical strength and density of the pellets produced by powder compaction.This paper investigates the influence of this kind of lubricant deposition on the die wall for UO$_2$ powder pelletization without any admixed internal lubricant. Different lubricants and various ways of depositing lubricant on the die wall were investigated through different parameters during powder compaction and pellets characterization. We have thus compared depositing zinc stearate solid by lubricant powder pelletization with spraying. Results show that the tensile strength of green pellets is enhanced and surface defects are reduced when the lubricant is sprayed. Furthermore, the application of viscous oil on the die wall does not make it possible to manufacture UO$_2$ pellets, which is probably due to the tribological inefficiency of this form of lubricant under our conditions, while an industrial grease makes it possible to obtain green pellets with good properties and fewer surface defects. The lubrication mechanism changes from one lubricant to another and acts on the wall friction, the friction index, the ejection force, and the characteristics of the final green pellets. The ejection force seems to be more sensitive with respect to assessing the performance of a lubricant when only external lubrication is used in nuclear powder compaction

Synthesis of zirconia sol stabilized by trivalent cations (yttrium and neodymium or americium): a precursor for Am-bearing cubic stabilized zirconia.

International audienc

Comparison of two powder conditioning methods to improve UO2 powder flowability for press die filling

International audienc

Development of a sustainable binder made of recycled high-performance concrete (HPC)

The high consumption of ordinary Portland cement (OPC) in high-performance concrete (HPC), combined with the growing accumulation of construction and demolition wastes (CDW), raises severe environmental and economic concerns. This study addresses both issues by proposing a novel sustainable binder made of milled recycled HPC (mRHPC). A series of HPC mix designs (R-HPC) was developed replacing OPC by mRHPC (0-100%), and characterized in fresh and hard-ened states. The residual reactivity of mRHPC was detected using X-ray diffraction, calorimetry, and rheological oscillatory measurements (SAOS). Replacement up to 30% resulted in comparable 28-day compressive and flexural strengths to that of the OPC reference specimen while slightly improving fresh properties. Furthermore, the performance of steel fiber reinforced R-HPC over-lays was investigated in repair application, and 30% replacement ratio enhanced the tensile bond strength by a factor of 2.4. The measured improved flow properties and reduced drying shrinkage can explain this remarkable result

Development of a sustainable binder made of recycled high-performance concrete (HPC)

The high consumption of ordinary Portland cement (OPC) in high-performance concrete (HPC), combined with the growing accumulation of construction and demolition wastes (CDW), raises severe environmental and economic concerns. This study addresses both issues by proposing a novel sustainable binder made of milled recycled HPC (mRHPC). A series of HPC mix designs (R-HPC) was developed replacing OPC by mRHPC (0–100%), and characterized in fresh and hardened states. The residual reactivity of mRHPC was detected using X-ray diffraction, calorimetry, and rheological oscillatory measurements (SAOS). Replacement up to 30% resulted in comparable 28-day compressive and flexural strengths to that of the OPC reference specimen while slightly improving fresh properties. Furthermore, the performance of steel fiber reinforced R-HPC overlays was investigated in repair application, and 30% replacement ratio enhanced the tensile bond strength by a factor of 2.4. The measured improved flow properties and reduced drying shrinkage can explain this remarkable result

Immobilisation of actinides in phosphate matrices

RADIOCHIn the field of the immobilisation of high-activity-level and long-life radwaste (HAVL) for a deep underground repository, several phosphate matrices were already proposed as good candidates to delay the release of actinides in the near-field of such disposal. Among them, thorium phosphate–diphosphate (TPD), monazites/brabantites, britholites, and TPD/monazite compositeswere extensively studied. The synthesis of samples doped with actinides (Th, U...) through wet and dry chemistry methods then their complete characterisation are reported. Their chemical durability is also examined. These materials appear as promising matrices to immobilise tetravalent and/or trivalent actinide