Ultrafast Sodium/Potassium‐Ion Intercalation into Hierarchically Porous Thin Carbon Shells

The large‐scale application of sodium/potassium‐ion batteries is severely limited by the low and slow charge storage dynamics of electrode materials. The crystalline carbons exhibit poor insertion capability of large Na⁺/K⁺ ions, which limits the storage capability of Na/K batteries. Herein, porous S and N co‐doped thin carbon (S/N@C) with shell‐like (shell size ≈20–30 nm, shell wall ≈8–10 nm) morphology for enhanced Na⁺/K⁺ storage is presented. Thanks to the hollow structure and thin shell‐wall, S/N@C exhibits an excellent Na⁺/K⁺ storage capability with fast mass transport at higher current densities, leading to limited compromise over charge storage at high charge/discharge rates. The S/N@C delivers a high reversible capacity of 448 mAh g^‐1 for Na battery, at the current density of 100 mA g^‐1 and maintains a discharge capacity up to 337 mAh g^‐1 at 1000 mA g^‐1. Owing to shortened diffusion pathways, S/N@C delivers an unprecedented discharge capacity of 204 and 169 mAh g^‐1 at extremely high current densities of 16 000 and 32 000 mA g^‐1, respectively, with excellent reversible capacity for 4500 cycles. Moreover, S/N@C exhibits high K⁺ storage capability (320 mAh g^‐1 at current density of 50 mA g^‐1) and excellent cyclic life.     

X-Ray Micro-Calorimeter Based on Si Thermistors for X-Ray Astronomy: Design and First Measurements

X-ray Astronomy provides a unique window on a wide variety of astrophysical phenomena. The currently operating X-ray space observatories perform X-ray spectral imaging with the use of CCDs. When available, cryogenic X-ray microcalorimeter arrays will far outperform CCDs in terms of spectral resolution, energy bandwidth and count rate. Experience has been gained with Infra-Red bolometer arrays at CEA-LETI (Grenoble) in collaboration with the CEA-SAp (Saclay); taking advantage of this background, we are now developing an X-ray spectro-imaging camera for the next generation space astronomy missions, using silicon technology (implanted and high temperature diffused thermistors). Each pixel of this array detector is made of a tantalum absorber bound, by indium bump hybridization, to a silicon thermistor. The absorber array is bound to the thermistor array in a single automatic step. The thermo-mechanical link, provided by hybridization, is being improved in terms of thermal capacitance. Finally, our main effort is in developing arrays of silicon thermistors with negligible excess 1/f noise. The thermistor has been simulated with the 2D simulator ATHENA (SILVACO International). We studied the effects of the implants and their thermal treatment on both vertical and lateral dopant distributions at the edges of the thermistor. Prototypes have been created following the procedure optimized by the ATHENA simulation. We present the status of the development and results of measurements performed on these four main building blocks required to create a detector array up to 32×32 pixels in size.      

Fabrication of Oxygen‐Vacancy Abundant NiMn‐Layered Double Hydroxides for Ultrahigh Capacity Supercapacitors

The rational design of advanced structures consisting of multiple components with excellent electrochemical capacitive properties is one of the crucial hindrances to be overcome for high‐performance supercapacitors (SCs). Herein, a superfast and facile synthesis of flower‐like NiMn‐layered double hydroxides (NiMn‐LDH) with high SC performance using an electrodeposition process on nickel foam is proposed. Oxygen vacancies are then modulated via mild H₂O₂ treatment for the first time, significantly promoting the electrochemical energy storage performance. The oxygen‐vacancy abundant NiMn‐LDH (Ov‐LDH) reaches a maximum specific capacity of 1183 C g^?1 at the current density of 1 A g^?1 and retains a high capacity retention of 835 C g^?1 even at a current density of up to 10 A g^?1. Furthermore, the assembled asymmetric SC device achieves a high specific energy density of 46.7 Wh kg^?1 at a power density of 1.7 kW kg^?1. Oxygen vacancies are proven to play a vital role in the improvement of electrochemistry performance of LDH based on experimental and theoretical studies. This vacancy engineering strategy provides a new insight into SC active materials and should be beneficial for the design of the next generation of energy storage devices.     

A declarative language to support dynamic evolution of web service business protocols

We investigate the problem of web service instances migration in the context of business protocol evolution, i.e., how to convert active instances of web services from an old version of a business protocol into a new one? We propose a framework based on a declarative approach to support service providers in defining fine-grained migration strategies of active instances. While the existing approaches for instances migration force the migrated instances to reflect the original ones as accurately as possible, in our approach we give to service providers the ability to declaratively define the constraints that drive the instances migration process. A migration strategy is expressed as a set of instances migration rules which are specified using an instance mapping language made of a set of generic migration patterns. The proposed approach has been implemented in a software tool that provides useful functionalities for protocol managers.     

Effects of restraint on expansion due to delayed ettringite formation

Delayed ettringite formation (DEF) is a chemical reaction that causes expansion in civil engineering structures. The safety level of such damaged structures has to be reassessed. To do this, the mechanical conditions acting on DEF expansions have to be analysed and, in particular, the variation of strength with expansion and the effect of restraint on the DEF expansion. This paper highlights several points: DEF expansion is isotropic in stress-free conditions, compressive stresses decrease DEF expansion in the direction subjected to restraint and lead to cracks parallel to the restraint, and expansion measured in the stress-free direction of restrained specimens is not modified. Thus restraint causes a decrease of the volumetric expansion and DEF expansion under restraint is anisotropic. Moreover, the paper examines the correlation between DEF expansion and concrete damage, providing data that can be used for the quantification of the effect of stresses on DEF induced expansion.     

A framework to prepare the application of virtual worlds in distance education in developing countries

Universal Access in the Information Society - This paper presents a framework to help preparing the implementation of virtual worlds, emphasizing on the requirements that distance education...     

A Universal Strategy for Hollow Metal Oxide Nanoparticles Encapsulated into B/N Co‐Doped Graphitic Nanotubes as High‐Performance Lithium‐Ion Battery Anodes

Yolk–shell nanostructures have received great attention for boosting the performance of lithium‐ion batteries because of their obvious advantages in solving the problems associated with large volume change, low conductivity, and short diffusion path for Li⁺ ion transport. A universal strategy for making hollow transition metal oxide (TMO) nanoparticles (NPs) encapsulated into B, N co‐doped graphitic nanotubes (TMO@BNG (TMO = CoO, Ni₂O₃, Mn₃O₄) through combining pyrolysis with an oxidation method is reported herein. The as‐made TMO@BNG exhibits the TMO‐dependent lithium‐ion storage ability, in which CoO@BNG nanotubes exhibit highest lithium‐ion storage capacity of 1554 mA h g^?1 at the current density of 96 mA g^?1, good rate ability (410 mA h g^?1 at 1.75 A g^?1), and high stability (almost 96% storage capacity retention after 480 cycles). The present work highlights the importance of introducing hollow TMO NPs with thin wall into BNG with large surface area for boosting LIBs in the terms of storage capacity, rate capability, and cycling stability.     

Superconducting Ti/TiN Thin Films for mm-Wave Absorption

Polarization-sensitive detectors at 120–500 GHz are required for the observation of the cosmic microwave background radiation. In this paper, superconducting thin films based on Ti/TiN bilayers are developed to be integrated as electromagnetic wave absorbers in suspended cooled silicon bolometers. The critical temperature (T_c) is tuned in the range of 600–800 mK through the superconductivity proximity effect between Ti and TiN to optimize the absorption of the incident power while minimizing the heat capacity of the system at low temperature. Ti/TiN bilayer samples are fabricated on silicon with two different thicknesses (100/5 and 300/5 nm). Electrical characterizations at low temperature have been performed and revealed the effect of thermal annealing (20–250 °C) on residual stress, T_c, critical magnetic field (H_c) and resistance above T_c. A physical characterization by X-ray photoelectron spectroscopy provides evidences of oxidized states which may explain these effects.