An Optimized Monetary Policy Rule for ToTEM

The authors propose a monetary policy rule for the Terms-of-Trade Economic Model (ToTEM), the Bank of Canada's new projection and policy-analysis model for the Canadian economy. They consider simple instrument rules such as Taylor-type and inflation-forecast-based rules. The proposed rule minimizes a loss function that reflects the assumed preferences of the monetary authority over inflation and output, as well as over the variability of its instrument. The authors also investigate how robust the proposed rule is with respect to a particular realization of shocks that differs from the historical distribution used to find the optimized rule.Economic models; Monetary policy framework; Transmission of monetary policy

Electric potential variations associated with yearly lake level variations

Electric potential variations have been recorded from November 1995 to February 1996 and continuously since October 1996 at 14 measurement points on a one km wide ridge separating two lakes in the French Alps. The levels of the lakes vary by several tens of meters on a yearly cycle, inducing stress variations and fluid percolation. At one point, unambiguous variations as large as 120 mV are observed over a year, linearly correlated with the levels of the lakes with a magnitude of 2 mV per meter of water level change. This particular measurement point lies at the edge of a SP anomaly, which supports the presence of a localized zone of ground water flow forced by the lake level, suggesting an electrokinetic mechanism. The observed correlation implies a ζ‐potential of the order of ‐8 mV for a 60 Ωm electrolyte, in agreement with laboratory measurements

Fluid flow near reservoir lakes inferred from the spatial and temporal analysis of the electric potential

Electric self-potential (SP) variations have been monitored continuously from 1995 to 1998 at 14 points on a ridge separating the Roselend and La Gittaz reservoir lakes in the French Alps. The lakes have level variations of at least 50 m over yearly cycles. Seasonal variations of SP associated with lake-level variations are observed on five points of the array. For three points located on the banks of the lakes, a positive correlation to the lake-level variations is observed with a maximal amplitude of about 180 mV, corresponding to an average response of 2.4 mV per meter of water. For two points located on the bottom of each lake, the correlation is negative, with a maximal magnitude of about −50 mV, corresponding to an average response of −1.1 mV per meter of water. Two independent temporary electrical arrays located on the banks of each lake confirm these measurements and allow a better spatial characterization of the sources associated with the observed SP variations. In particular, near the Roselend lake, the electrical response to lake-level variations is increasing for decreasing altitude. The measured SP variations are proposed to result from the electrokinetic coupling associated with a vertical groundwater flow connecting a constant pore pressure source to the bottom of the lakes. Numerical modeling indicates that the spatial variation of the response and the nonlinear response observed at one point can be explained by leakage currents in the conductive lake water. The values of the streaming potential coefficient (SPC), measured in the laboratory with crushed rock samples from the site, range from 14 to 50 mV/0.1 MPa for an electrolyte resistivity of 40 Ω m and are compatible, to first order, with the magnitude of the observed seasonal SP variations. A detailed quantitative electrokinetic modeling is currently limited mainly by the poor knowledge on the contribution of electrical leakage currents and the local variability of the SPC. This experiment indicates that spatial and temporal variations of the electric potential are promising tools to characterize and monitor shallow groundwater flow and provide practical data for the investigation of groundwater flow associated with volcanic or tectonic activity

Interactive Curvature Tensor Visualization on Digital Surfaces

International audienceInteractive visualization is a very convenient tool to explore complex scientific data or to try different parameter settings for a given processing algorithm. In this article, we present a tool to efficiently analyze the curvature tensor on the boundary of potentially large and dynamic digital objects (mean and Gaussian curvatures, principal curvatures , principal directions and normal vector field). More precisely, we combine a fully parallel pipeline on GPU to extract an adaptive triangu-lated isosurface of the digital object, with a curvature tensor estimation at each surface point based on integral invariants. Integral invariants being parametrized by a given ball radius, our proposal allows to explore interactively different radii and thus select the appropriate scale at which the computation is performed and visualized

Electrical structure of the Himalaya of Central Nepal: high conductivity around the mid-crustal ramp along the MHT

Twelve broadband magnetotelluric (MT) soundings were performed across the Himalaya of Central Nepal in 1996 in order to determine the electrical structure of the crust and its relation to geological structures and active tectonics. The MT impedance tensors were obtained for frequencies between 0.001 and 500 Hz. The 2‐D section, derived from joint inversion of TE‐ and TM mode after RRI and Groom/Bailey decomposition, shows high conductivity in the foreland basin (∼30 Ω.m) that contrasts with the resistive Indian basement (>300 Ω.m) and Lesser Himalaya (>1000 Ω.m). In addition, our MT sounding reveals a major conductive feature beneath the front of the Higher Himalaya, also characterized by intense microseismic activity, and the position of a mid‐crustal ramp along the major active thrust fault (MHT). This high conductivity zone probably reflects metamorphic fluids, released during underthrusting of the Indian basement and pervading well connected microcracks induced by interseismic stress build‐up, or distributed brittle deformation around the ramp

Seasonal modulation of seismicity in the Himalaya of Nepal

International audience[1] For the period 1995 –2000, the Nepal seismic network recorded 37 ± 8% fewer earthquakes in the summer than in the winter; for local magnitudes ML > 2 to ML > 4 the percentage increases from 31% to 63% respectively. We show the probability of observing this by chance is less than 1%. We find that most surface loading phenomena are either too small, or have the wrong polarity to enhance winter seismicity. We consider enhanced Coulomb failure caused by a pore-pressure increase at seismogenic depths as a possible mechanism. For this to enhance winter seismicity, however, we find that fluid diffusion following surface hydraulic loading would need to be associated with a six-month phase lag, which we consider to be possible, though unlikely. We favor instead the suppression of summer seismicity caused by stress-loading accompanying monsoon rains in the Ganges and northern India, a mechanism that is discussed in a companion article

Transfert : les déterminants de la performance des exploitations agricoles familiales

Le transfert des exploitations familiales est une étape cruciale du cycle de vie de la majorité des exploitations agricoles québécoises. Avec un taux élevé d’échec important de 40 à 50 % dans les cinq années suivant le transfert d’une PME, il est important de connaître les causes de ces échecs ainsi que les déterminants de la performance des exploitations survivantes après le cap des premières années. Cet article présente les déterminants financiers et technico-économiques de cette performance en s’appuyant sur trois périodes : le montage financier, l’année du transfert et l’évolution de la situation. Les résultats démontrent que ce sont les ratios technico-économiques de l’exploitation à l’année du transfert et durant la période post-transfert qui ont la plus grande influence sur la performance financière cinq années après.The transfer of family farms is a crucial step in the life cycle of the majority of farms in Quebec. Within five years following the transfer of SMEs about 40-50% fail. It is important to know the causes of their failures and the determinants of performance of farms after surviving the first course of years. This article presents the financial and technico-economic determinants of this performance based on three periods: the financing, the year of transfer and the evolution of the situation. The results show that the technico-economic ratios the year of transfer and during the post-transfer period have the greatest influence on financial performance five years after the transfer. (JEL: Q12

Streaming potential measurements 1. Properties of the electrical double layer from crushed rock samples

The ξ potential has been inferred from streaming potential measurements with crushed rock samples as a function of pH and electrolyte concentration for various salts. The value obtained for crushed Fontainebleau sandstone at pH = 5.7 and a KCl solution with a resistivity of 400 Ω m is −40 ± 5 mV, where the error is dominated by sample to sample variations. The sensitivity of the ξ potential to the electrolyte resistivity for KCl is given experimentally by ρ_f^(0.23±0.014) where ρ_f is the electrolyte resistivity. The point of zero charge (pzc) is observed for pH = 2.5 ± 0.1, and the ξ potential is positive for pH pzc. For pH > 5 the variations of the ξ potential with pH can be approximated by ξ(pH)/ξ(5.7) = 1 + (0.068 ± 0.004)(pH - 5.7) for ρ_f = 100 Ω m. The ξ potential has been observed to be sensitive to the valence of the ions and is approximately reduced by the charge of the cation, unless specific adsorption takes place like in the case of Al^3+. The experimental results are well accounted for by a three-layer numerical model of the electrical double layer, and the parameters of this model can be evaluated from the experimental data. The sensitivity of the ξ potential to the rock minerals has also been studied. The ξ potential obtained for granitic rocks is comparable to that obtained for Fontainebleau sandstone but can be reduced by a factor of 2–4 for sandstones containing significant fractions of carbonates or clay. To take into account the effect of the chemical composition of the electrolyte, a chemical efficiency is defined as the ratio of the ξ potential to the ξ potential measured for KCl. This chemical efficiency is measured to be ∼80% for typical groundwater but can be as low as 40% for a water with a high dissolved carbonate content. The set of empirical laws derived from our measurements can be used to assess the magnitude of the streaming potentials expected in natural geophysical systems

Stack or trash? Quality assessment of virtual slides

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Streaming potential measurements 2. Relationship between electrical and hydraulic flow patterns from rock samples during deformation

Streaming potential and resistivity measurements have been performed on Fontainebleau sandstone and Villejust quartzite samples in a triaxial device during compaction, uniaxial compression, and rupture. Measurements on individual samples do not show any clear intrinsic dependence of the streaming potential coefficient with permeability. An apparent dependence of the streaming potential coefficient with permeability is, however, observed during deformation. The effect of surface conductivity is taken into account and is small compared with the observed changes in the streaming potential coefficient. The observed dependence is therefore interpreted in terms of a difference in the evolution of the electrical and hydraulic connectivity patterns during deformation. This effect causes the streaming potential coefficient, and consequently the inferred ξ potential, to be reduced by a geometrical factor R_G representing the electrical efficiency of the hydraulic network. Estimates of the R_G factor varying between 0.2 and 0.8 for electrolyte resistivity larger than 100 Ωm are obtained by comparing the values of the ξ potential inferred from intact rock samples with the values obtained from crushed rock samples, where the geometrical effects are assumed to be negligible. The reduction of the streaming potential coefficient observed during compaction or uniaxial compression suggests that the tortuosity of the hydraulic network increases faster than the tortuosity of the electrical network. Before rupture, an increase in the streaming potential coefficient associated with the onset of dilatancy was observed for three samples of Fontainebleau sandstone and one sample of Villejust quartzite. The changes in streaming potential coefficient prior to failure range from 30% to 50%. During one experiment, an increase in the concentration of sulfate ions was also observed before failure. These experiments suggest that observable streaming potential and geochemical variations could occur before earthquakes