ParisTech

About: ParisTech is a education organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Residual stress. The organization has 1888 authors who have published 1965 publications receiving 55532 citations. The organization is also known as: Paris Institute of Technology & ParisTech Développement.

Blind Source Separation and Sparse Bump Modelling of Time Frequency Representation of Eeg Signals: New Tools for Early Detection of Alzheimer’s Disease

Abstract: The early detection of Alzheimer's disease (AD) is an important challenge. In this paper, we propose a novel method for early detection of AD using only electroencephalographic (EEG) recordings for patients with mild cognitive impairment (MCI) without any clinical symptoms of the disease who later developed AD. In our method, first a blind source separation algorithm is applied to extract the most significant spatiotemporal uncorrelated components; afterward these components are wavelet transformed; subsequently the wavelets or more generally time frequency representation (TFR) is approximated with sparse bump modeling approach. Finally, reliable and discriminant features are selected and reduced with orthogonal forward regression and the random probe methods. The proposed features were finally fed to a simple neural network classifier. The presented method leads to a substantially improved performance (93% correctly classified - improved sensitivity and specificity) over classification results previously published on the same set of data. We hope that the new computational and machine learning tools provide some new insights in a wide range of clinical settings, both diagnostic and predictive

Thermochemical effects on the smectite alteration of GMZ bentonite for deep geological repository

Abstract: Gaomiaozi (GMZ) bentonite has been recognized as the first choice for using as buffer/backfill material in deep geological repository for the disposal of high-level nuclear waste in China. High salinity and high pH of the pore solutions may cause changes in the mineralogical composition, and the swelling capacity of the bentonite results in affecting the long-term performance of the engineering barrier system. In the present work, a series of hydrothermal reactivity experiments were performed using batch reactors at 20, 35 and 80 °C for evaluating the chemical and mineralogical responses of GMZ bentonites. The results show that the dissolution of smectite releases Si and Al under the conditions of 1 M KOH at 35 and 80 °C and the released Si and Al may work as a cementing agent in GMZ bentonite. XRD pattern results show that alteration of the GMZ bentonite is expected to be insignificant for reaction with NaCl, KCl and NaOH solutions under low temperatures. However, it is obviously reacted with KOH solutions especially at 80 °C, during which cementitious material was produced leading to kaolinitization. When contacted with KOH solutions, the basal spacing (d001) of the main primary diffraction peaks (001) value of GMZ bentonite increases with increasing temperature. Salinity also can influence the smectite stability and accordingly loss of swelling capacity. This conclusion could be explained by the diffusing double-layer effects induced by salt solutions and ion exchange.

Microstructural Parameters Controlling High-Temperature Creep Life of the Nickel-Base Single-Crystal Superalloy MC2

Abstract: The influence of both topologically close-packed (TCP) phase precipitation and pores on the creep life of a single-crystal superalloy has been studied at 1323 K (1050 °C)/160 MPa. Despite very reproducible primary and secondary creep stages, the creep life is scattered for this specific condition where a very steep tertiary creep stage is observed, corresponding to a highly localized failure process. Image processing was performed after failure to determine the stereological parameters characterizing pores and TCP-phase particles. It was determined that pores are major determinants of creep life under these temperature and stress conditions. It was also observed that the average surface area or the density of pores is not sufficient to explain creep life variability. A homogenization method including modified γ/γ′ microstructure area surrounding pores and TCP-phase particles was developed and correlated to creep life. It is shown that the greater the extent of the modified microstructure, the lower the creep life. Moreover, a better understanding of the TCP-phase role in controlling the creep life was obtained: TCP-phase particles modified the local stress field and disturbed the local γ/γ′ microstructure. They enhance the generation of vacancies and subsequent nucleation and growth of pores.

Indexing of Satellite Images With Different Resolutions by Wavelet Features

Abstract: Space agencies are rapidly building up massive image databases. A particularity of these databases is that they are made of images with different, but known, resolutions. In this paper, we introduce a new scheme allowing us to compare and index images with different resolutions. This scheme relies on a simplified acquisition model of satellite images and uses continuous wavelet decompositions. We establish a correspondence between scales which permits us to compare wavelet decompositions of images having different resolutions. We validate the approach through several matching and classification experiments, and we show that taking the acquisition process into account yields better results than just using scaling properties of wavelet features.

Total Hip Prostheses in Standing, Sitting and Squatting Positions: An Overview of Our 8 Years Practice Using the EOS Imaging Technology

Abstract: More total hip arthroplasty (THA) is performed worldwide and especially in younger and more active patients compared to earlier decades. One of the focuses of THA research in the future will be on optimizing the radiological follow-up of these patients using 2D and 3D measurements of implants position while reducing the radiation dose delivered. Low-dose EOS® imaging is an innovative slot-scanning radiograph system providing valuable information in patient functional positions (standing, sitting and even squatting positions). EOS has been proven accurate and reliable without significant inconvenience caused by the metallic artifacts of implants. The ability to obtain precise data on implant orientation according to the patient posture opens new perspectives for a comprehensive analysis of the pelvic frontal and sagittal balance and its potential impact on implants function and failures. We report our 8 years experience on our first 300 THA patients using this technology routinely for pre and post op evaluation. Our results will be compared and confronted with the actual literature about this innovative technology. We shall especially emphasize our experience about patients with abnormal posture and the evolution of the subject over time, because the phenomenon of an aging spine is frequently associated with the process of aging hips.