oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 3 )

2018 ( 20 )

2017 ( 14 )

2016 ( 16 )

Custom range...

Search Results: 1 - 10 of 7918 matches for " Ivan Voznyuk;Herve Tortel;Amelie Litman "
All listed articles are free for downloading (OA Articles)
Page 1 /7918
Display every page Item
Scattered Field Computation with an Extended Feti-Dpem2 Method
Ivan Voznyuk;Herve Tortel;Amelie Litman
PIER , 2013,
Abstract: Due to the increasing number of applications in engineering design and optimization, more and more atention has been paid to full-wave simulations based on computational electromagnetics. In particular, the finite-element method (FEM) is well suited for problems involving inhomogeneous and arbitrary shaped objects. Unfortunately, solving large-scale electromagnetic problems with FEM may be time consuming. A numerical scheme, called the dual-primal finite element tearing and interconnecting method (FETI-DPEM2), distinguishes itself through the partioning on the computation domain into non-overlapping subdomains where incomplete solutions of the electrical field are evaluated independently. Next, all the subdomains are ``glued'' together using a modified Robintype transmission condition along each common internal interface, apart from the corner points where a simple Neumann-type boundary condition is imposed. We propose an extension of the FETI-DPEM2 method where we impose a Robin type boundary conditions at each interface point, even at the corner points. We have implemented this Extended FETI-DPEM2 method in a bidimensional configuration while computing the field scattered by a set of heterogeneous, eventually anistropic, scatterers. The results presented here will assert the efficiency of the proposed method with respect to the classical FETI-DPEM2 method, whatever the mesh partition is arbitrary defined.
On the Calibration of a Multistatic Scattering Matrix Measured by a Fixed Circular Array of Antennas
Amelie Litman;Jean-Michel Geffrin;Herve Tortel
PIER , 2010, DOI: 10.2528/PIER10090302
Abstract: The calibration of the multistatic scattering matrix plays an important part in the construction of a quantitative microwave imaging system. For scattering measurement applications, the calibration must be performed on the amplitude and on the phase of the fields of interest. When the antennas are not completely identical, as for example with a multiplexed antennas array, a specific calibration procedure must be constructed. In the present work, we explain how a complex calibration matrix can be defined which takes advantage of the geometrical organization of the antennas. Indeed, for arrays of antennas positioned on a circle, the inherent symmetries of the configuration can be fully exploited by means of an adequate reorganization of the multistatic scattering matrix. In addition, the reorganization permits to detect antenna pairs which are not properly functioning and to estimate the signal-to-noise ratio. Experimental results obtained within a cylindrical cavity enclosed by a metallic casing are provided to assess the performance of the proposed calibration procedure.This calibration protocol, which is described here in detail, has already been applied to provide quantitative images of dielectric targets [1, 2].
Development and Preliminary Validation of the Shared Professional Leadership Inventory for Teams (SPLIT)  [PDF]
Amelie Grille, Simone Kauffeld
Psychology (PSYCH) , 2015, DOI: 10.4236/psych.2015.61008
Abstract: Shared leadership is viewed as an effective management form to encounter increased complexity in modern work life. However, the lack of reliable and valid instruments to assess shared leadership behaviors has limited empirical research. Based on literature in leadership and team work research a questionnaire was developed to assess four different aspects of shared leadership behavior—task-, relation-, change- and micropolitic-oriented leadership. The final version consisted of 20 items. Confirmatory factor analyses confirmed the theoretically hypothesized model in two independent German samples. Significant correlations with related scales support convergent and criterion validity. This study therefore provides researchers with a valid and reliable instrument to assess different aspects of shared leadership behavior and its advantages for research and human resource development are discussed.
Cue Phrase Classification Using Machine Learning
Diane J. Litman
Computer Science , 1996,
Abstract: Cue phrases may be used in a discourse sense to explicitly signal discourse structure, but also in a sentential sense to convey semantic rather than structural information. Correctly classifying cue phrases as discourse or sentential is critical in natural language processing systems that exploit discourse structure, e.g., for performing tasks such as anaphora resolution and plan recognition. This paper explores the use of machine learning for classifying cue phrases as discourse or sentential. Two machine learning programs (Cgrendel and C4.5) are used to induce classification models from sets of pre-classified cue phrases and their features in text and speech. Machine learning is shown to be an effective technique for not only automating the generation of classification models, but also for improving upon previous results. When compared to manually derived classification models already in the literature, the learned models often perform with higher accuracy and contain new linguistic insights into the data. In addition, the ability to automatically construct classification models makes it easier to comparatively analyze the utility of alternative feature representations of the data. Finally, the ease of retraining makes the learning approach more scalable and flexible than manual methods.
Cue Phrase Classification Using Machine Learning
D. J. Litman
Computer Science , 1996,
Abstract: Cue phrases may be used in a discourse sense to explicitly signal discourse structure, but also in a sentential sense to convey semantic rather than structural information. Correctly classifying cue phrases as discourse or sentential is critical in natural language processing systems that exploit discourse structure, e.g., for performing tasks such as anaphora resolution and plan recognition. This paper explores the use of machine learning for classifying cue phrases as discourse or sentential. Two machine learning programs (Cgrendel and C4.5) are used to induce classification models from sets of pre-classified cue phrases and their features in text and speech. Machine learning is shown to be an effective technique for not only automating the generation of classification models, but also for improving upon previous results. When compared to manually derived classification models already in the literature, the learned models often perform with higher accuracy and contain new linguistic insights into the data. In addition, the ability to automatically construct classification models makes it easier to comparatively analyze the utility of alternative feature representations of the data. Finally, the ease of retraining makes the learning approach more scalable and flexible than manual methods.
Classifying Cue Phrases in Text and Speech Using Machine Learning
Diane J. Litman
Computer Science , 1994,
Abstract: Cue phrases may be used in a discourse sense to explicitly signal discourse structure, but also in a sentential sense to convey semantic rather than structural information. This paper explores the use of machine learning for classifying cue phrases as discourse or sentential. Two machine learning programs (Cgrendel and C4.5) are used to induce classification rules from sets of pre-classified cue phrases and their features. Machine learning is shown to be an effective technique for not only automating the generation of classification rules, but also for improving upon previous results.
Cocoa Exports of Cameroon: Structure and Mechanism of Operation  [PDF]
Ze Engamba Herve, Guiyu Zhao
Theoretical Economics Letters (TEL) , 2018, DOI: 10.4236/tel.2018.814200
Abstract: The aim of this paper is to study the cocoa market in Cameroon over the period 2000 to 2016. The study consisted in presenting in a general way the organization, structure and operating mechanisms of the Cameroon cocoa market, particularly the value chains from family farmers to final consumers through exports; it also allowed us to highlight some issues and prospects for reviving the cocoa sector in Cameroon. It shows that Cameroon, like most cocoa-producing countries, also faces many difficulties not only externally, but also because of the international environment (the volatility of the prices of export products), internally through implemented policy measures, their consistency and phasing, as well as their deadlines. Starting from the liberalization of the sector in the early 1990s to the devaluation of the CFA franc in January 1994, a relative stagnation of the country’s agricultural performance has been noted so far. The problem is therefore not only institutional and structural but also cyclical. With regard to domestic marketing, the government’s option of a return to stabilization will reaffirm the place and the role of the State in the management of the sector. As far as external marketing is concerned, to remedy this, the government option consists of setting up a state-controlled advanced sale system through the centralization of sales and the monitoring of their quantitative execution. However, for a development of Cameroon’s artisanal, semi-industrial and industrial cocoa processing industry, we need strong support and protection of the local industry in order to attract foreign investors and encourage local initiatives, with accompanying measures that make cocoa processing more profitable in Cameroon as in other producing countries.
Impacts of Competitive Choice Methods on Cocoa Yields in Cameroon  [PDF]
Ze Engamba Herve, Guiyu Zhao
Open Journal of Social Sciences (JSS) , 2018, DOI: 10.4236/jss.2018.611005
Abstract: In Cameroon, cocoa is the first export product after oil. It represents about 25% of the total value of the country’s exports. It is grown in 7 of Cameroon’s 10 regions and covers an area of about 400,000 hectares. It involves about 600,000 producers and nearly 8 million people live directly or indirectly from the cocoa economy. Increasing cocoa production and meeting quality standards are among the goals set by the government to improve this economic growth, in order to raise the low purchasing power of the rural population through a strong and sustainable economy. The basis of this paper was therefore to evaluate the impact of two cultural approaches taken individually or mixed on the agricultural yield in Cameroon in the cocoa sector in the period 2000-2016. The estimation of time-series data from a two-sided system by the ordinary least squares method allowed us to obtain significantly positive results from the impact of different farming approaches on agricultural yield in Cameroon. The different approaches mentioned here reveal a real problem of choice in terms of agricultural policy in Cameroon. Public authorities should opt for a mixed approach for profitable and sustainable cocoa farming.
Star formation in the cluster CLG0218.3-0510 at z=1.62 and its large-scale environment: the infrared perspective
Joana S. Santos,Bruno Altieri,Masayuki Tanaka,Ivan Valtchanov,Amelie Saintonge,Mark Dickinson,Sebastien Foucaud,Tadayuki Kodama,Tim D. Rawle,Ken-ichi Tadaki
Physics , 2013, DOI: 10.1093/mnras/stt2376
Abstract: The galaxy cluster CLG0218.3-0510 at z=1.62 is one of the most distant galaxy clusters known, with a rich muti-wavelength data set that confirms a mature galaxy population already in place. Using very deep, wide area (20x20 Mpc) imaging by Spitzer/MIPS at 24um, in conjunction with Herschel 5-band imaging from 100-500um, we investigate the dust-obscured, star-formation properties in the cluster and its associated large scale environment. Our galaxy sample of 693 galaxies at z=1.62 detected at 24um (10 spectroscopic and 683 photo-z) includes both cluster galaxies (i.e. within r <1 Mpc projected clustercentric radius) and field galaxies, defined as the region beyond a radius of 3 Mpc. The star-formation rates (SFRs) derived from the measured infrared luminosity range from 18 to 2500 Ms/yr, with a median of 55 Ms/yr, over the entire radial range (10 Mpc). The cluster brightest FIR galaxy, taken as the centre of the galaxy system, is vigorously forming stars at a rate of 256$\pm$70 Ms/yr, and the total cluster SFR enclosed in a circle of 1 Mpc is 1161$\pm$96 Ms/yr. We estimate a dust extinction of about 3 magnitudes by comparing the SFRs derived from [OII] luminosity with the ones computed from the 24um fluxes. We find that the in-falling region (1-3 Mpc) is special: there is a significant decrement (3.5x) of passive relative to star-forming galaxies in this region, and the total SFR of the galaxies located in this region is lower (130 Ms/yr/Mpc2) than anywhere in the cluster or field, regardless of their stellar mass. In a complementary approach we compute the local galaxy density, Sigma5, and find no trend between SFR and Sigma5. However, we measure an excess of star-forming galaxies in the cluster relative to the field by a factor 1.7, that lends support to a reversal of the SF-density relation in CLG0218.
Radiated Ultrashort High-Power Electromagnetic Pulses Induce ATP Release in B16F10 Murine Melanoma Cells  [PDF]
Sabrina Macaire, Alexandre Catrain, Stéphane Tortel, Jean-Christophe Joly, Sébastien Girard, Pierre Bonnet, Alain Vian
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2015, DOI: 10.4236/jemaa.2015.73008
Abstract: Ultrawideband electromagnetic pulses with high amplitude and short duration are reported to affect several aspects of cell physiology. They are usually delivered to the living material through electrodes in small dedicated chambers. Here we showed, using a totally different experimental setup, that radiated EM pulses illuminating the living material through a specialized antenna (without any direct contact) are able to trigger a rapid release of ATP in cultured murine cells that was concomitant with a drop of intracellular AEC. Despite this rapid and strong response, we found that cell viability and clonogenicity were only slightly affected by the EMF exposure.
Page 1 /7918
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.