Net Exports, Consumption Volatility and International Real Business Cycle Models

Conventional two-country RBC models interpret countercyclical net exports as reflecting, in large part, the dynamics of capital. I show that, quantitatively, theoretical economies rely on counterfactual terms of trade effects: trade fluctuations, on the contrary, are driven primarily by consumption smoothing, thus generating procyclical net trade in goods. I then consider a class of preferences that embeds home production in a reduced form: consumption volatility increases so that countercyclical net exports reflect primarily a strong relation between import of goods and income, as in the data. The major discrepancy between theory and data concerns the variability of international prices.Net exports; Home production; Consumption volatility.

THE SUGAR MARKET IN COLOMBIA AND ITS INTERACTIONS WITH THE USA MARKET

En este artículo se propone un modelo de equilibrio parcial para entender el comportamiento del mercado del azúcar en Colombia y sus interacciones comerciales con la economía norteamericana. Se evalúan los posibles efectos de un TLC con Estados Unidos sobre el mercado, al igual que la incidencia de otros factores internos y externos. Se prueba que el impacto de un TLC entre Colombia y Estados Unidos depende del balancede dos fuerzas contrapuestas: el incremento en la proporción de la cuota que corresponde a las exportaciones colombianas, y la baja progresiva que se ha venido presentando en la cuota total de la economía norteamericana.In this paper it is proposed a partial equilibrium model for the sugar market of Colombia to understand its trade relations with the North-American economy. The possible effects of a Free Trade Agreement and of other internal and external factors are examined modelling the functioning of the North-American sugar market. It is proved that the impact of a FTA between Colombia and the USA depend of two forces: the impact of the increase in the proportion of the quota affecting the Colombian exports, and the effectof progressive decreases in the value of the total North-American quota.Sugar market, international trade, freetrade agreement, import quotas / Mercado del azúcar, comercio internacional,tratado de libre comercio,cuotas de importación.

Dynamic strain aging during the creep and tensile testing of a molybdenum-titanium- carbon alloy

Dynamic strain aging during creep and tensile tests of molybdenum-titanium-carbon alloy

Yielding and fracture in tungsten and tungsten-rhenium alloys

Mechanical properties of tungsten and tungsten rhenium alloy

Suspended Load Path Tracking Control Using a Tilt-rotor UAV Based on Zonotopic State Estimation

This work addresses the problem of path tracking control of a suspended load using a tilt-rotor UAV. The main challenge in controlling this kind of system arises from the dynamic behavior imposed by the load, which is usually coupled to the UAV by means of a rope, adding unactuated degrees of freedom to the whole system. Furthermore, to perform the load transportation it is often needed the knowledge of the load position to accomplish the task. Since available sensors are commonly embedded in the mobile platform, information on the load position may not be directly available. To solve this problem in this work, initially, the kinematics of the multi-body mechanical system are formulated from the load's perspective, from which a detailed dynamic model is derived using the Euler-Lagrange approach, yielding a highly coupled, nonlinear state-space representation of the system, affine in the inputs, with the load's position and orientation directly represented by state variables. A zonotopic state estimator is proposed to solve the problem of estimating the load position and orientation, which is formulated based on sensors located at the aircraft, with different sampling times, and unknown-but-bounded measurement noise. To solve the path tracking problem, a discrete-time mixed $\mathcal{H}_2/\mathcal{H}_\infty$ controller with pole-placement constraints is designed with guaranteed time-response properties and robust to unmodeled dynamics, parametric uncertainties, and external disturbances. Results from numerical experiments, performed in a platform based on the Gazebo simulator and on a Computer Aided Design (CAD) model of the system, are presented to corroborate the performance of the zonotopic state estimator along with the designed controller

Development of a prototype plastic space erectable satellite Quarterly report, Dec. 1965 - Feb. 1966

Plastic space erectable satellit

Work and taxes: allocation of time in OECD countries

Policymakers devote a great deal of attention to short-run fluctuations in the labor market. Central banks monitor indicators of labor market tightness in the conduct of monetary policy due to the potential implications for inflation. And fiscal authorities are concerned with the budget consequences of fluctuations in the labor market because they affect both revenues and expenditure programs. More generally, these fluctuations may be associated with significant losses in welfare. ; This article stems from a striking empirical observation about long-run variations in labor market outcomes: Long-run changes in total hours of work in OECD countries exceed the variation of hours worked over the business cycle in a representative country (say, the United States) by almost an order of magnitude. If understanding changes in hours of work of the magnitude of business cycle fluctuations is an important policy concern, then understanding the sources of these trend differences is also crucial. Surprisingly, the academic and policy debates have focused on the business cycle movements in the labor market, almost ignoring low frequency changes. ; Lee Ohanian, Andrea Raffo, and Richard Rogerson describe the steep decline in average hours worked and the large variation across countries in the magnitude of this decline. Next, they find that changes in labor taxes account for a large share of the trend differences. Finally, they find that countries with high tax rates devote less time to market work, but more time to home activities, such as cooking and cleaning. Moreover, this reallocation of time from market work to home work is much stronger for females than for males.Taxation ; Labor market ; Hours of labor

Reverse engineering of CAD models via clustering and approximate implicitization

In applications like computer aided design, geometric models are often represented numerically as polynomial splines or NURBS, even when they originate from primitive geometry. For purposes such as redesign and isogeometric analysis, it is of interest to extract information about the underlying geometry through reverse engineering. In this work we develop a novel method to determine these primitive shapes by combining clustering analysis with approximate implicitization. The proposed method is automatic and can recover algebraic hypersurfaces of any degree in any dimension. In exact arithmetic, the algorithm returns exact results. All the required parameters, such as the implicit degree of the patches and the number of clusters of the model, are inferred using numerical approaches in order to obtain an algorithm that requires as little manual input as possible. The effectiveness, efficiency and robustness of the method are shown both in a theoretical analysis and in numerical examples implemented in Python

Long-Term Changes in Labor Supply and Taxes: Evidence from OECD Countries, 1956-2004

We document large differences in trend changes in hours worked across OECD countries over the period 1956-2004. We then assess the extent to which these changes are consistent with the intratemporal first order condition from the neoclassical growth model. We find large and trending deviations from this condition, and that the model can account for virtually none of the changes in hours worked. We then extend the model to incorporate observed changes in taxes. Our findings suggest that taxes can account for much of the variation in hours worked both over time and across countries.

Influence of boron additions on physical and mechanical properties of arc-melted tungsten and tungsten - 1 percent tantalum alloy

Influence of boron additions on physical and mechanical properties of arc-melted tungsten and of tungsten-tantalum allo