Comment on Market Discipline and Monetary Policy by Carl Walsh

This paper aims at correcting flaws in the way expectations are set in a paper by Walsh (2000) in order to assess with precision the impact of complex market rigidities and market expectations in the optimal choices of inflation in a monetary game between society and central bankers. After setting the expectations right, one of the results achieved indicates that the optimal inflation under any type of central banker is higher than that obtained in the original paper, suggesting that the time inconsistency phenomenon plays a more important role in explaining an inflationary bias than originally interpreted by Walsh (2000). However, if society organizes itself towards shorter tenure wage contracts, inflation will be lower. The results obtained for the output gap of the economy also differ from those achieved by Walsh in the sense that a central banker who is highly committed to previously announced inflation targets will have more opportunities to generate output growth above equilibrium rates and still commit. Finally, the stability of the premises regarding the contractual structure of the economy proposed by Walsh is tested under a game theoretic approach. The outcome of the test is that stability can be guaranteed only under strong assumptions and high symmetry in the sectoral distribution of firms. By using a social welfare function in which price surprises in any direction lead to welfare loss, the results indicate that society is better off by choosing longer tenure wage contracts, moving away from shorter tenure ones, at the cost of higher inflation.

The Role of Consumer's Risk Aversion on Price Rigidity

This paper aims to contribute to the research agenda on the sources of price rigidity. Based on broadly accepted assumptions on the behavior of economic agents, we show that firms’ competition can lead to the adoption of sticky prices as a sub-game perfect equilibrium strategy to optimally deal with consumers’ risk aversion, even if firms have no adjustment costs. To this end, we build a model economy based on consumption centers with several complete markets and relax some traditional assumptions used in standard monetary policy models by assuming that households have imperfect information about the inefficient time-varying cost shocks faced by the .rms. Furthermore, we assume that the timing of events is such that, at every period, consumers have access to the actual prices prevailing in the market only after choosing a particular consumption center. Since such choices under uncertainty may decrease the expected utilities of risk-averse consumers, competitive firms adopt some degree of price stickiness in order to minimize the price uncertainty and "attract more customers".

Inspection, calibration and other ways of improving the efficiency of air assistance sprayer in the purpose of applying small and medium application rates in fruit production

Poste

Optimization of 3D Cooling Channels in Injection Molding using DRBEM and Model Reduction

Issu de : ESAFORM 2009 - 12th ESAFORM Conference on material forming, Enschede, THE NETHERLANDS, 27-29 April 2009International audienceToday, around 30% of manufactured plastic goods rely on injection moulding. The cooling time can represent more than 70% of the injection cycle. In this process, heat transfer during the cooling step has a great influence both on the quality of the final parts that are produced, and on the moulding cycle time. In the numerical solution of three-dimensional boundary value problems, the matrix size can be so large that it is beyond a computer capacity to solve it. To overcome this difficulty, we develop an iterative dual reciprocity boundary element method (DRBEM) to solve Poisson’s equation without the need of assembling a matrix. This yields a reduction of the computational space dimension from 3D to 2D, avoiding full 3D remeshing. Only the surface of the cooling channels needs to be remeshed at each evaluation required by the optimisation algorithm. For more efficiency, DRBEM computing results are extracted stored and exploited in order to construct a model with very few degrees of freedom. This approach is based on a model reduction technique known as proper orthogonal (POD) or Karhunen-Loève decompositions. We introduce in this paper a practical methodology to optimise both the position and the shape of the cooling channels in 3D injection moulding processes. First, we propose an implementation of the model reduction in the 3D transient BEM solver. This reduction permits to reduce considerably the computing time required by each direct computation. Secondly, we present an optimisation methodology applied to different injection cooling problems. For example, we can minimize the maximal temperature on the cavity surface subject to a temperature uniformityconstraint. Thirdly, we compare our results obtained by our approach with experimental results to show that our optimisation methodology is viable

Coil-On-Plug Ignition for Oxygen/Methane Liquid Rocket Engines in Thermal-Vacuum Environments

A coil-on-plug ignition system has been developed and tested for Liquid Oxygen (LOX)/liquid methane (LCH4) rocket engines operating in thermal vacuum conditions. The igniters were developed and tested as part of the Integrated Cryogenic Propulsion Test Article (ICPTA), previously tested as part of the Project Morpheus test vehicle. The ICPTA uses an integrated, pressure-fed, cryogenic LOX/LCH4 propulsion system including a reaction control system (RCS) and a main engine. The ICPTA was tested at NASA Glenn Research Center's Plum Brook Station in the Spacecraft Propulsion Research Facility (B-2) under vacuum and thermal vacuum conditions. A coil-on-plug ignition system has been developed to successfully demonstrate ignition reliability at these conditions while preventing corona discharge issues. The ICPTA uses spark plug ignition for both the main engine igniter and the RCS. The coil-on-plug configuration eliminates the conventional high-voltage spark plug cable by combining the coil and the spark plug into a single component. Prior to ICPTA testing at Plum Brook, component-level reaction control engine (RCE) and main engine igniter testing was conducted at NASA Johnson Space Center (JSC), which demonstrated successful hot-fire ignition using the coil-on-plug from sea-level ambient conditions down to 10(exp -2) torr. Integrated vehicle hot-fire testing at JSC demonstrated electrical and command/data system performance. Lastly, hot-fire testing at Plum Brook demonstrated successful ignitions at simulated altitude conditions at 30 torr and cold thermal-vacuum conditions at 6 torr. The test campaign successfully proved that coil-on-plug technology will enable integrated LOX/LCH4 propulsion systems in future spacecraft