X-ray photoelectron spectroscopic study of the ability to monofunctionalize polymer surfaces by low energy atomic bombardment

Low energy atomic bombardment is designed to limit the potentially reactive species to the atoms which are present in a radiofrequency (r.f.) plasma discharge. This might give the ability to monofunctionalize surfaces for specific applications such as biocompatibility. Bombardment of polystyrene and poly(trans)isoprene with nitrogen atoms does not result in the incorporation of any heteroatoms at the polymer surface. Other attempts were made on poly(acrylic acid) and poly(methyl methacrylate) without any results, even though the samples had been activated by argon ion bombardment; the thermalized atoms seem to have insufficient energy to functionalize these polymers. In contrast, ion bombardment performed with low energy nitrogen ions (500–1500eV) is able to incorporate a majority of amine functions. © 1998 Society of Chemical Industry.     

Degradation process of an industrial thermoplastic elastomer polyurethane-coated fabric in artificial weathering conditions

The aging of an industrial thermoplastic elastomer polyurethane (TPU)-coated fabric, based on a polyether diol and an aromatic diisocyanate, is studied in artificial weathering tests. It is noticed that the degradation of this TPU-coated fabric leads to a weight loss, to the formation of a reticulated layer in sample surface, and to a change of surface relief. The degradation layer and the surface relief have been observed by optical microscopy. The weight loss has been followed with aging time. The main degradation products causing weight loss are volatile. Therefore, they have been analyzed by gas chromatography–mass spectroscopy. The weight loss degradation takes place in the exposed part of the reticulated layer by volatile products emission, which implies the urethane and the polyether bonds. Water is involved in degradation process: without external water supply, weight loss is limited; with a permanent contact of vapor or liquid water, the weight loss rate is constant and depends on aging conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2525–2534, 1999     

Microwave,biquadratic, active-RC filter development

We present a number of computer-simulated results for a recently developed family of active-RC, microwave, biquadratic filters. These circuits are gyrator-based and contain negative second-generation current conveyors (CCII−s) realized as cascades of MMIC GaAs FETs. First, the circuit family is extended to include asymmetric band-reject filters. As with the previous circuits of the group, we use optimization to obtain an accurate frequency response when the CCII−s are implemented as cascaded pairs of GaAs FETs. Second, we illustrate how cascades of three or four devices become necessary for the CCII−s of bandpass biquads as their center frequencies are increased. Next, we show how third- and fourth-order filters may be obtained by cascading optimized lower-order sections. In our examples, the slight interaction between the stages is eliminated by adjusting a single element. Finally, we discuss the topological origins of the biquad family and consider alternative circuit structures which may possess particular practical advantages. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 102–115, 1998.     

All-Electrical Detection of the Spin-Charge Conversion in Nanodevices Based on SrTiO3 2-D Electron Gases

The Magnetoelectric Spin-Orbit (MESO) technology aims to bring logic into memory by combining a ferromagnet with a magnetoelectric (ME) element for information writing, and a spin-orbit (SO) element for information read-out through spin-charge conversion. Among candidate SO materials to achieve a large MESO output signal, oxide Rashba two-dimensional electron gases (2DEGs) have shown very large spin-charge conversion efficiencies, albeit mostly in spin-pumping experiments. Here, all-electrical spin-injection and spin-charge conversion experiments in nanoscale devices harnessing the inverse Edelstein effect of SrTiO₃ 2DEGs are reported. Nanodevices aredesigned, patterned, and fabricated in which a spin current injected from a cobalt layer into the 2DEG is converted into a charge current. The spin-charge conversion signal is optimized by applying back-gate voltages and studied its temperature evolution. It further disentangles the inverse Edelstein contribution from spurious effects such as the planar Hall effect, the anomalous Hall effect, or the anisotropic magnetoresistance. The combination of non-volatility and high energy efficiency of these devices can potentially lead to new technology paradigms for beyond-CMOS computing architectures.     

Personal Information Self-Management:A Survey of Technologies Supporting Administrative Services

This paper presents a survey of technologies for personal data self-management interfacing with administrative and territorial public service providers.It classifies a selection of scientific technologies into four categories of solutions:Personal Data Store (PDS),Identity Manager (IdM),Anonymous Certificate System and Access Control Delegation Ar-chitecture.Each category,along with its technological approach,is analyzed thanks to 18 identified functional criteria that encompass architectural and communication aspects,as well as user data lifecycle considerations.The originality of the survey is multifold.First,as far as we know,there is no such thorough survey covering such a panel of a dozen of existing solutions.Second,it is the first survey addressing Personally Identifiable Information (PII) management for both administrative and private service providers.Third,this paper achieves a functional comparison of solutions of very different technical natures.The outcome of this paper is the clear identification of functional gaps of each solution.As a result,this paper establishes the research directions to follow in order to fill these functional gaps.     

Physicochemical and consolidation properties of compacted lateritic soil treated with cement

The consolidation of a fine-grained lateritic soil, treated with compound Portland cement (CEMII/BM 32.5 N) up to 9% by weight of the dry soil and prepared at three different molding water contents (ω_DRY, OMC, and ω_WET), was investigated by means of a one-dimensional consolidation test. The physicochemical and microstructural properties of the compacted lateritic soil-cement mixture were investigated using Raman spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), and pH measurement. The results show that cement admixtures resulted in the formation of tobermorite, afwillite, ettringite, portlandite, and calcite. However, tobermorite and afwilite, which are calcium silicate hydrates (CSH) whose mechanisms of formation are the pozzolanic and alkali silica reactions, appear from 6% added cement. The fixing point of the pH (12.4) is also obtained from 6% added cement. It is the threshold value at which the material begins to develop an adequate mechanical performance. In general, as the content of cement in the soil is increased, the yield stress increases from 1 to 3 times in comparison to untreated soil. For effective vertical stresses smaller than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is 2–7 times faster than that for specimens not treated with cement, while for effective vertical stresses higher than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is about 0.5–1.5 times faster than that for specimens not treated with cement. Permeability and secondary compression are reduced 1–9 times and 2–11 times that of the untreated samples, respectively. These changes are attributed to the creation of chemical bonds and aggregation that accompany the addition of cement. The results also show that it would be desirable for soil samples to be prepared at the dry side of optimum (ω_DRY) when the optimum moisture content (OMC) is not reached at the site. These results indicate that significant and desirable changes in soil behavior can be achieved when the soil is admixed with CEM II/BM 32.5 N cement, thus providing the possibility of using the tested lateritic soil in road construction.     

Estimating the poroelastic properties of cracked materials

We present a comparative study of the ability of some micromechanics estimates to predict the overall properties of heterogeneous materials. We focus mainly on cracked materials, for which this task is difficult and many estimates fail. We study particularly the interaction direct derivative estimate, proposed by Zheng and Du, which is an approximation of the generalized self-consistent scheme, but has the very convenient property to be always explicit. A modified version of this estimate, called full-range IDD by Zheng and Du, yields good results when comparing all poromechanical coefficients predicted by the estimate to finite element simulations of a 2D cracked material in plane strain, up to crack density factors of 1 for aligned cracks and 0.60 for randomly oriented cracks. The accuracy of finite element computations of the overall moduli is also commented by plotting the convergence of the average of the properties as well as the confidence intervals on these averages.     

Collapses and Watersheds in Pseudomanifolds of Arbitrary Dimension

This work is settled in the framework of abstract simplicial complexes. We propose a definition of a watershed and of a collapse (i.e., a homotopic retraction) for maps defined on pseudomanifolds of arbitrary dimension. Then, we establish two important results linking watersheds and homotopy. The first one generalizes a property known for distance transforms in a continuous setting to any map on pseudomanifolds: a watershed of any map is a subset of an ultimate collapse of the support of this map. The second result establishes, through an equivalence theorem, a deep link between watershed and collapse of maps: any watershed of any map can be straightforwardly obtained from an ultimate collapse of this map, and conversely any ultimate collapse of the initial map straightforwardly induces a watershed.