PCPro a Novel Technology for Rapid Prototyping and Rapid Manufacturing

PCPro stands for Precise Cast Prototyping, which is a combination of casting technologies and milling. This method was developed at Fraunhofer IWS in Dresden, Germany. It is patented in Germany [1] and is applied in the USA under US 10/794,936. The main goal for this development was to shorten the process chain for making plastic prototypes accompanied by higher quality. The casting technology was integrated in a machining center in order to enable a high degree of automation and to avoid an external casting system. This means that Rapid Manufacturing can be easily implemented using such an automated combination of casting and machining. This article describes the PCPro method by means of the fabrication of sample parts. The advantages and the limitations in comparison to common Rapid Prototyping and Rapid Manufacturing process chains will be discussed. In addition, the manufacturing of a prototype machine is presented.Mechanical Engineerin

On the Indeterminacy of New-Keynesian Economics

We study identification in a class of three-equation monetary models. We argue that these models are typically not identified. For any given exactly identified model, we provide an algorithm that generates a class of equivalent models that have the same reduced form. We use our algorithm to provide four examples of the consequences of lack of identification. In our first two examples we show that it is not possible to tell whether the policy rule or the Phillips curve is forward or backward looking. In example 3 we establish an equivalence between a class of models proposed by Benhabib and Farmer and the standard new-Keynesian model. This result is disturbing since equilibria in the Benhabib-Farmer model are typically indeterminate for a class of policy rules that generate determinate outcomes in the new-Keynesian model. In example 4, we show that there is an equivalence between determinate and indeterminate models even if one knows the structural equations of the modelIndeterminacy, identification

On the indeterminacy of determinacy and indeterminacy

A number of authors have attempted to test whether the U.S. economy is in a determinate or an indeterminate equilibrium. We argue that to answer this question, one must impose a priori restrictions on lag length that cannot be tested. We provide examples of two economic models. Model 1 displays an indeterminate equilibrium, driven by sunspots. Model 2 displays a determinate equilibrium driven by fundamentals. Given assumptions about the shock distribution of model 2, it is possible to find a distribution of sunspot shocks that drive model 1 such that the two models are observationally equivalent. JEL Classification: C39, C62, D51Identification, indeterminacy

On the indeterminacy of new-Keynesian economics

We study identiÞcation in a class of three-equation monetary models. We argue that these models are typically not identiÞed. For any given exactly identiÞed model, we provide an algorithm that generates a class of equivalent models that have the same reduced form. We use our algorithm to provide four examples of the consequences of lack of identiÞcation. In our Þrst two examples we show that it is not possible to tell whether the policy rule or the Phillips curve is forward or backward looking. In example 3 we establish an equivalence between a class of models proposed by Benhabib and Farmer [1] and the standard new-Keynesian model. This result is disturbing since equilibria in the Benhabib-Farmer model are typically indeterminate for a class of policy rules that generate determinate outcomes in the new-Keynesian model. In example 4, we show that there is an equivalence between determinate and indeterminate models even if one knows the structural equations of the model. JEL Classification: C39, C62, D51, E52, E58IdentiÞcation, indeterminacy, new-Keynesian model, transparency

A method to generate structural impulse-responses for measuring the effects of shocks in structural macro models

We develop a technique for analyzing the response dynamics of economic variables to structural shocks in linear rational expectations models. Our work differs fromstandard SVARs since we allow expectations of future variables to enter structural equations. We show how to estimate the variance-covariance matrix of fundamental and non-fundamental shocks and we construct point estimates and confidence bounds for impulse response functions. Our technique can handle both determinate and indeterminate equilibria. We provide an application to U.S. monetary policy under pre and post Volcker monetary policy rules. JEL Classification: C39, C62, D51, E52, E58Identification, indeterminacy, rational expectations models

Identifying the monetary transmission mechanism using structural breaks

We propose a method for estimating a subset of the parameters of a structural rational expectations model by exploiting changes in policy. We define a class of models, midway between a vector autoregression and a structural model, that we call the recoverable structure. As an application of our method we estimate the parameters of a model of the US monetary transmission mechanism. We estimate a vector autoregression and find that its parameters are unstable. However, using our proposed identification method we are able to attribute instability in the parameters of the VAR solely to changes in the parameters of the policy rule. We recover parameter estimates of the recoverable structure and we demonstrate that these parameters are invariant to changes in policy. Since the recoverable structure includes future expectations as explanatory variables our parameter estimates are not subject to the Lucas [24] critique of econometric policy evaluation. JEL Classification: C51, E43, E52, E58Fed, Identification, monetary transmission, recoverable structure, structural breaks

Galileo early cruise, including Venus, first Earth, and Gaspra encounters

This article documents Deep Space Network (DSN) support for the Galileo cruise to Jupiter. The unique trajectory affords multiple encounters during this cruise phase. Each encounter had or will have unique requirements for data acquisition and DSN support configurations. An overview of the cruise and encounters through the asteroid Gaspra encounter is provided

The Arts, School Practice, and Cultural Transformation

Attempts at articulating and instituting socially responsive programs in art education are heartening and long overdue. The work of the Caucus on Social Theory and Art Education and the Bulletin as a reflection of the issues dealt with by the caucus, are laudatory and provocative. I seek to further these efforts in this essay by: 1) elaborating the social context within which schools function, and detailing how the political, economic, and ideological interests our educational system serves affect school policy, organizational structures within education, and school practice generally; and 2) suggest how the arts may be an effective force in countering the socially useful practices which schools embody. By situating the study of the arts within the literature on schools as agents of social reproduction we may see more clearly both the problems and possibilities for education in the arts that is socially responsive, politically sensitive, and ethically just