5,036 research outputs found
L'instabilité de la détermination du taux de change dans un modèle monétariste
No full textDie Instabilität der Bestimmung des Wechselkurses in einem monetaristischen Modell,
von Jacques Luzi, Jamel Trabelsi.
In diesem Artikel werden die kurzfristigen Verhaltensweisen des nominalen Wechselkurses und des inländischen Preisniveaus in einem Gleichgewichtsmodell mit rationalen Vorwegnahmen untersucht und miteinander verglichen. Die übermäßigen Schwankungen des nominalen Wechselkurses ergeben sich aus dem Einfluß der Wechselkursvorwegnahmen auf das inländische Preisniveau und der Preisvorwegnahmen auf den nominalen Wechselkurs. Eine Simulation bescheinigt die Plausibilität dieses Ergebnisses für die Entwicklungen des Dollar / Yen- Wechselkurses und des Niveaus der amerikanischen Preise.The Instability of Establishing the Exchange Rate in an Open Economy,
by Jacques Luzi, Jamel Trabelsi.
This paper examines the short-term behaviour of the nominal exchange rate and the domestic price level and compares them with one another using an equilibrium model with rational expectations. The huge volume of nominal exchange rate movements is due to the influence of the exchange rate expectations on the domesticprice level and that of price expectations on the nominal exchange rate. The plausibility of these findings for changes in the dollar / yen exchange rate and the level of prices in America is confirmed in a simulation.L'instabilité de la détermination du taux de change dans un modèle monétariste,
par Jacques Luzi, Jamel Trabelsi.
Cet article étudie et compare les comportements à court terme du taux de change nominal et du niveau des prix domestiques dans un modèle d'équilibre à anticipations rationnelles. L'ampleur excessive des mouvements du taux de change nominal résulte de l'influence des anticipations de change sur le niveau des prix domestiques et des anticipations de prix sur le taux de change nominal. Une simulation atteste la plausibilité de ce résultat pour les évolutions du taux de change dollar / yen et du niveau des prix américains.Inestabilidad de la determinación de los tipos de cambio en un modelo monetarista,
por Jacques Luzi y Jamel Trabelsi.
En el presente artículo se estudia y se compara el comportamiento a corto plazo del tipo de cambio nominal y del nivel de los precios domésticos, en un modelo de equilibrio fundado en antitipaciones racionales. La variación excesiva del tipo de cambio nominal se debe a la influencia de las anticipaciones de cambio sobre el nivel de los precios domésticos y a la influencia de las anticipaciones de precios sobre el tipo de cambio nominal. Una simulación demuestra la plausibilidad de estos resultados para la evolución del tipo de cambio dólar/yen y del nivel de precios en los Estados Unidos.Luzi Jacques, Trabelsi Jamel. L'instabilité de la détermination du taux de change dans un modèle monétariste. In: Économie & prévision, n°104, 1992-3. Politique budgetaire, taux d'intérêt, taux de change. pp. 73-85
On minimal non-<i>PC</i>-groups
No full textA group G is said to be a PC-group, if G/CG (Xg)
is a polycyclic-by-finite group for all xEG. A minimal non-PC-group is a group which is not a PC-group but all of whose proper subgroups are PC-groups. Our main result is that a minimal non-PC-group having a non-trivial finite factor group is a finite cyclic extension of a divisible abelian group of finite rank
GIS-based subsurfacedatabeses and 3-d geological modeling as a tool for the set up of hydrogeological framework: Nabeul Hammamet coastal aquifer case study (Nortgeast Tunisia)
No full textThe subsurface data are a basic requirement for the set up of hydrogeological framework. Geographic information systems (GIS) tools have proved their usefulness in hydrogeology over the years which allow for management, synthesis, and analysis of a great variety of subsurface data. However, standard multi-layered systems are quite limited for modeling, visualizing, and editing subsurface data and geologic objects and their attributes. This paper presents a methodology to support the implementation of hydrogeological framework of the multi-layered aquifer system in Nabeul-Hammamet (NH) coastal region (NE, Tunisia). The methodology consists of (1) the development of a complete and generally accepted hydrogeological classification system for NH aquifer system (2) the development of relational databases and subsequent GIS-based on geological, geophysical and hydrogeological data, and (3) the development of meaningful three-dimensional geological and aquifer models, using GIS subsurface software, RockWorks 2002. The generated 3-D geological models define the lithostratigraphy and the geometry of each depositional formation of the region and delineate major aquifers and aquitards. Where results of the lithologic model revealed that there is a wide range of hydraulic conductivities in the modeled area, which vary spatially and control the groundwater flow regime. As well, 17 texturally distinct stratigraphic units were identified and visualized in the stratigraphic model, while the developed aquifer model indicates that the NH aquifer system is composed of multi-reservoir aquifers subdivided in aquifers units and separated by sandy clay aquitards. Finally, this study provides information on the storing, management and modeling of subsurface spatial database. GIS has become a useful tool for hydrogeological conceptualization and groundwater management purposes and will provide necessary input databases within different groundwater numerical models
Les tests de racine unitaire et les modèles Arch : application au taux de chômage
No full textUnit Root Tests and ARCH Models: Unemployment Rate Applications
by Jamel Trabelsi
We propose to test for the effects of hysteresis, or the persistence of the unemployment rate in the leading industrialised countries. We use a procedure based on Phillips curves that incorporates imperfections in labour market information to justify the possible emergence of such phenomena. We have developed an econometric approach based on Dickey and Fuller Tests with GARCH disturbances on the basis of the conclusions put forward by Kim and Schmidt, which state that the null hypothesis for the unit root is rejected when there are ARCH effects under certain conditions, such as an integrated and degenerated process. We show that the unemployment rate is persistent in the leading European countries. This effect may be explained by the persistence of volatility shocks.Les tests de racine unitaire et les modèles Arch : application au taux de chômage
par Jamel Trabelsi
d'informations sur le marché du travail sont prises en compte. Sur la base des conclusions avancées par Kim et Schmidt, selon lesquelles l'hypothèse nulle de racine unitaire est rejetée en présence d'effets Arch sous certaines conditions (processus intégré et dégénéré), nous élaborons une approche économétrique fondée sur les tests de Dickey et Fuller avec des perturbations Garch. Nous montrons que, pour les principaux pays européens, le taux de chômage est persistant. L'existence d'un tel effet pourrait être expliquée par la persistance des chocs de volatilité.Trabelsi Jamel. Les tests de racine unitaire et les modèles Arch : application au taux de chômage. In: Économie & prévision, n°131, 1997-5. pp. 177-190
The Set Cover Conjecture and Subgraph Isomorphism with a Tree Pattern
No full textIn the Set Cover problem, the input is a ground set of n elements and a collection of m sets, and the goal is to find the smallest sub-collection of sets whose union is the entire ground set. The fastest algorithm known runs in time O(mn2^n) [Fomin et al., WG 2004], and the Set Cover Conjecture (SeCoCo) [Cygan et al., TALG 2016] asserts that for every fixed epsilon>0, no algorithm can solve Set Cover in time 2^{(1-epsilon)n} poly(m), even if set sizes are bounded by Delta=Delta(epsilon). We show strong connections between this problem and kTree, a special case of Subgraph Isomorphism where the input is an n-node graph G and a k-node tree T, and the goal is to determine whether G has a subgraph isomorphic to T.
First, we propose a weaker conjecture Log-SeCoCo, that allows input sets of size Delta=O(1/epsilon * log n), and show that an algorithm breaking Log-SeCoCo would imply a faster algorithm than the currently known 2^n poly(n)-time algorithm [Koutis and Williams, TALG 2016] for Directed nTree, which is kTree with k=n and arbitrary directions to the edges of G and T. This would also improve the running time for Directed Hamiltonicity, for which no algorithm significantly faster than 2^n poly(n) is known despite extensive research.
Second, we prove that if p-Partial Cover, a parameterized version of Set Cover that requires covering at least p elements, cannot be solved significantly faster than 2^n poly(m) (an assumption even weaker than Log-SeCoCo) then kTree cannot be computed significantly faster than 2^k poly(n), the running time of the Koutis and Williams' algorithm
An MLP-ANN-based approach for assessing nitrate contamination
No full textThis paper investigates the feasibility of predicting nitrate contamination from agricultural sources using multi-layer perceptron artificial neural networks (MLP-ANNs). The approach consists in training an MLP-ANN to predict nitrate concentrations based on a set of indirect measurements, such as pH, electrical conductivity, temperature and groundwater level. These are simpler and more economical than direct measurements, and they can be continuously collected on-site, rather than by performing laboratory tests. The approach has been validated in the nitrate vulnerable zone of the Arborea plain (central western Sardinia, Italy) by comparing the results obtained with different MLP-ANN models in order to find the most efficient model. The results show that the MLP-ANN-based model is a time- and cost-efficient method for predicting nitrate concentration
Conditional Lower Bounds for All-Pairs Max-Flow
No full textWe provide evidence that computing the maximum flow value between every pair
of nodes in a directed graph on nodes, edges,and capacities in the
range , which we call the All-Pairs Max-Flow problem, cannot be solved
in time that is significantly faster (i.e., by a polynomial factor) than
even for sparse graphs. Since a single maximum -flow can be solved
in time [Lee and Sidford, FOCS 2014], we conclude that
the all-pairs version might require time equivalent to
computations of maximum -flow,which strongly separates the directed case
from the undirected one. Moreover, if maximum -flow can be solved in time
,then the runtime of computations is needed.
The latter settles a conjecture of Lacki, Nussbaum, Sankowski, and Wulf-Nilsen
[FOCS 2012] negatively.
Specifically, we show that in sparse graphs , if one can compute
the maximum -flow from every in an input set of sources
to every in an input set of sinks in time ,for some , , and a constant ,then
MAX-CNF-SAT with variables and clauses can be solved in time
for a constant ,a problem for
which not even algorithms are known. Such runtime for
MAX-CNF-SAT would in particular refute the Strong Exponential Time Hypothesis
(SETH). Hence, we improve the lower bound of Abboud, Vassilevska-Williams, and
Yu [STOC 2015], who showed that for every fixed and
, if the above problem can be solved in time
, then some incomparable conjecture is false. Furthermore,
a larger lower bound than ours implies strictly super-linear time for maximum
-flow problem, which would be an amazing breakthrough
Rhythmic Exercises Before Basketball Training: A Study on Motor Skills, Static Balance, and Reaction Speed in School-Aged Children
No full textThe aim of this study was to investigate the effects of combining rhythmic exercises with basketball training on the improvement of basic motor and physical skills in children. Thirty-four female subjects, all from the same secondary school and aged 12 6 0.7 years, participated in a 6-week training program (3 times per week). They were randomly divided into 3 groups: one group practiced rhythmic exercises in combination with basketball training (R-BT, n 5 12), another group practiced basketball only (BT, n 5 11), and a control group (CON, n 5 11). The subjects underwent assessments that included regular and irregular rhythmic exercises, flexibility, coordination, and static balance. After the intervention, all groups showed improvements in their motor skills (MS) when they followed a regular rhythm. The R-BT group showed significantly higher performance in hopping and jumping from preintervention to postintervention [p 5 0.003, effect size (ES) 5 0.67 and p 5 0.005, ES 5 0.64, respectively] and differed significantly from the other 2 groups (p, 0.01). In addition, the R-BT group showed a greater improvement in the implementation of irregular rhythms (p, 0.001) and differed significantly from the other groups in all parameters (p, 0.01). The Stork Stand Balance Test improved in the R-BT group and outperformed the other 2 groups, whereas the Alternate-Hand Wall-Toss Test improved in both the R-BT and the BT groups compared with the control group, indicating better coordination. In summary, basketball training preceded by a regular rhythm can lead to greater improvement in MS, resulting in improved coordination and leg stability. These results could be considered crucial for young school-age children who play basketball
La communication du sens dans le contexte d'une tradution du français vers l'anglais d'un roman contemporain marocain,Une Via à Trois, par Bahaa Travelsi
No full textIncludes abstract.Includes bibliographical references.This thesis examines the communication of meaning in the context of the translation from French into English of a contemporary Moroccan novel, Une Vie à Trois, by Bahaa Trabelsi. To explore the notion of a faithful translation, the approach of the Ecole Superieure d'lnterpretes et de Traducteurs (ESIT) is examined. This approach, developed by Danica Seleskovitch and Marianne Lederer, emphasises the communication of meaning and the crucial role that interpretation plays in the act of translation. The project is composed of two parts - the practical application of the ESIT approach in the production of a translation of Une Vie à Trois and a theoretical study of the approach
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