473 research outputs found
An Assisted High-Sensitivity Acquisition Technique for GPS Indoor Positioning
No full textThe extremely low signal-to-noise ratio experienced indoors impairs the acquisition stage of common GPS receivers, since reliable correlation peaks are hardly detected. The optimal strategy to increase the acquisition sensitivity is the extension of the coherent integration time, but the presence of data bits limits the maximum achievable performance. Noncoherent processing is typically used to improve the detection performance, but it requires a large amount of accumulations when applied to indoor signals, resulting in relevant "squaring loss". Additionally, the two strategies require high computational efforts, possibly not affordable by mass-market terminals (e.g. mobile phones). The "assisted GPS" paradigm, included for instance in 3GPP specifications for GSM/EDGE and UMTS networks, allows for both reducing the overall acquisition complexity and for increasing the acuqisition sensitivity, eventually enabling indoor GPS positioning of low-cost/low-power receivers. In this paper we describe an assisted High-Sensitivity acquisition engine for GPS signals suitable for the indoor location of mobile terminals. A low-complexity data wipe-off technique enables coherent integration times up to 2s. We finally show the results of some tests carried out with indoor signals and the results obtained with both high- and lowaccuracy local oscillator
A test-bed implementation of an acquisition system for indoor positioning
No full textIndoor GNSS signals are typically received with poor signal-to-noise ratio, which impairs the acquisition stage of common global positioning system (GPS) receivers. Extending the coherent integration time increases the acquisition sensitivity, but the data-bit-rate limits the maximum achievable performance. Non-coherent processing also improves the detection performance, but indoor signals require a large amount of accumulations resulting in significant squaring loss. Moreover, both strategies have high computational complexity which fixes demanding requirements for stand alone mass-market terminals operating in real time. A sensitivity-complexity trade-off is therefore mandatory. Assisted-GPS, which is included in 3GPP specifications, reduces the overall acquisition complexity and enhances sensitivity. In this paper we describe a low-complexity-assisted data-wipe-off technique that enables the high-sensitivity acquisition of GPS signals. The method is based on the acquisition of the strongest signal in order to obtain information that eases the acquisition of the weaker ones. The analysis also addresses sources of sensitivity loss, such as Doppler effects and local oscillator inaccuracies. A test campaign with real signals and integration times up to 2 s validates the method, demonstrating the effectiveness of the proposed technique in indoor environment
Multi-step process to prepare bulk BSCCO (2223) superconductor with improved transport properties
No full textVers une gestion des connaissances tacites pour la veille anticipative stratégique dans les PME-PMI : retours d'expérience.
No full textA Business Intelligence Model for SMEs Based on Tacit Knowledge
No full textThis paper proposes a specific model of business intelligence in relation with SMEs practices, culture and competitive environment. This model is based on the mobilization of corporate tacit knowledge and informal information, aiming at interpreting anticipatory environmental information and assist strategic decision making. An empirical survey assessing the existing business intelligence practices in 20 French SMEs has identified seven necessary acceptance conditions of a business intelligence project as well as a managerial tool allowing tacit knowledge traceability.business intelligence; tacit knowledge; SMEs; sense-making
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Precision linear shaped charge analyses for severance of metals
No full textThe Precision Linear Shaped Charge (PLSC) design concept involves the independent fabrication and assembly of the liner (wedge of PLSC), the tamper/confinement, and explosive. The liner is the most important part of a linear shaped charge (LSC) and should be fabricated by a more quality controlled, precise process than the tamper material. Also, this concept allows the liner material to be different from the tamper material. The explosive can be loaded between the liner and tamper as the last step in the assembly process rather than the first step as in conventional LSC designs. PLSC designs have been shown to produce increased jet penetrations in given targets, more reproducible jet penetration, and more efficient explosive cross-section geometries using a minimum amount of explosive. The Linear Explosive Shaped Charge Analysis (LESCA) code developed at Sandia National Laboratories has been used to assist in the design of PLSCs. LESCA predictions for PLSC jet tip velocities, jet-target impact angles, and jet penetration in aluminum and steel targets are compared to measured data. The advantages of PLSC over conventional LSC are presented. As an example problem, the LESCA code was used to analytically develop a conceptual design for a PLSC component to sever a three-inch thick 1018 steel plate at a water depth of 500 feet (15 atmospheres)
Adult phenotype of KCNQ2 encephalopathy
No full textBackground: Pathogenic KCNQ2 variants are a frequent cause of developmental and epileptic encephalopathy. Methods: We recruited 13 adults (between 18 years and 45 years of age) with KCNQ2 encephalopathy and reviewed their clinical, EEG, neuroimaging and treatment history. Results: While most patients had daily seizures at seizure onset, seizure frequency declined or remitted during childhood and adulthood. The most common seizure type was tonic seizures (early) infancy, and tonic-clonic and focal impaired awareness seizures later in life. Ten individuals (77%) were seizure-free at last follow-up. In 38% of the individuals, earlier periods of seizure freedom lasting a minimum of 2 years followed by seizure recurrence had occurred. Of the 10 seizure-free patients, 4 were receiving a single antiseizure medication (ASM, carbamazepine, lamotrigine or levetiracetam), and 2 had stopped taking ASM. Intellectual disability (ID) ranged from mild to profound, with the majority (54%) of individuals in the severe category. At last contact, six individuals (46%) remained unable to walk independently, six (46%) had limb spasticity and four (31%) tetraparesis/tetraplegia. Six (46%) remained non-verbal, 10 (77%) had autistic features/autism, 4 (31%) exhibited aggressive behaviour and 4 (31%) destructive behaviour with self-injury. Four patients had visual problems, thought to be related to prematurity in one. Sleep problems were seen in six (46%) individuals. Conclusion: Seizure frequency declines over the years and most patients are seizure-free in adulthood. Longer seizure-free periods followed by seizure recurrence are common during childhood and adolescence. Most adult patients have severe ID. Motor, language and behavioural problems are an issue of continuous concern
Epilepsy-causing mutations in Kv7.2 C-terminus affect binding and functional modulation by calmodulin
No full textMutations in the KCNQ2 gene, encoding for voltage-gated Kv7.2K(+) channel subunits, are responsible for early-onset epileptic diseases with widely-diverging phenotypic presentation, ranging from Benign Familial Neonatal Seizures (BFNS) to epileptic encephalopathy. In the present study, Kv7.2 BFNS-causing mutations (W344R, L351F, L351V, Y362C, and R553Q) have been investigated for their ability to interfere with calmodulin (CaM) binding and CaM-induced channel regulation. To this aim, semi-quantitative (Far-Western blotting) and quantitative (Surface Plasmon Resonance and dansylated CaM fluorescence) biochemical assays have been performed to investigate the interaction of CaM with wild-type or mutant Kv7.2 C-terminal fragments encompassing the CaM-binding domain; in parallel, mutation-induced changes in CaM-dependent Kv7.2 or Kv7.2/Kv7.3 current regulation were investigated by patch-clamp recordings in Chinese Hamster Ovary (CHO) cells co-expressing Kv7.2 or Kv7.2/Kv7.3 channels and CaM or CaM1234 (a CaM isoform unable to bind Ca(2+)). The results obtained suggest that each BFNS-causing mutation prompts specific biochemical and/or functional consequences; these range from slight alterations in CaM affinity which did not translate into functional changes (L351V), to a significant reduction in the affinity and functional modulation by CaM (L351F, Y362C or R553Q), to a complete functional loss without significant alteration in CaM affinity (W344R). CaM overexpression increased Kv7.2 and Kv7.2/Kv7.3 current levels, and partially (R553Q) or fully (L351F) restored normal channel function, providing a rationale pathogenetic mechanism for mutation-induced channel dysfunction in BFNS, and highlighting the potentiation of CaM-dependent Kv7.2 modulation as a potential therapeutic approach for Kv7.2-related epilepsies
Predictive testing in the context of pregnancy: experience in Huntington's disease and autosomal dominant cerebellar ataxia
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