My Final Scene

Morgan Gerke ’16 has always been an actor at heart, but her busy schedule didn’t allow her to participate in Linfield Theatre. Until now. From acting exercises, through exams and a final performance, she shares her January Term experience

Robust monetary policy in a new Keynesian model with imperfect interest rate pass-through

We use robust control to study how a central bank in an economy with imperfect interest rate pass-through conducts monetary policy if it fears that its model could be misspecified. The effects of the central bank's concern for robustness can be summarised as follows. First, depending on the shock, robust optimal monetary policy under commitment responds either more cautiously or more aggressively. Second, such robustness comes at a cost: the central bank dampens volatility in the inflation rate preemptively, but accepts higher volatility in the output gap and the loan rate. Third, if the central bank faces uncertainty only in the IS equation or the loan rate equation, the robust policy shifts its concern for stabilisation away from inflation. --optimal monetary policy,commitment,model uncertainty

The Role of Money Demand in a Business Cycle Model with Staggered Wage Contracts

The question of the main determinants of persistent responses due to nominal shocks captures, at least since Chari et al. (2000), a major part of the recent macroeconomic debate. However, the question whether sticky wages and/or sticky prices are sufficient for persistent reactions of key economic variables remains open. In the present model we allow for nominal rigidities due to Taylor- like wage setting as well as price adjustment costs. However, as our analysis illustrates, smoothing marginal costs seems crucial to derive a contract multiplier, wage staggering alone is not sufficient. Without considering a more specific analysis of factor market frictions, we enforce a point made by Erceg (1997) by analyzing the structure of money demand. In particular, we analyze a `standard' consumption based money demand function by varying the interest rate elasticity of money demand as well as the steady state rate of money holdings. Our results show that the persistency of the output/price dynamics can be affected crucially by the form of the implicit money demand function. In particular, it is shown that staggered wage contracts have to be accompanied by a sufficiently low interest rate elasticity, otherwise the model fails to reproduce reasonable responses of real variables.Monetary Policy Shocks, Sticky Prices, Staggered Wages, Money Demand

Analysis of damage and fracture mechanisms in ductile metals under non-proportional loading paths

The paper discusses biaxial experiments and corresponding numerical simulations to analyze the effect of non-proportional loading paths on damage and fracture behavior of ductile metals. Newly developed specimens are taken from thin metal sheets and are tested under different biaxial loading conditions covering a wide range of stress states. In this context, an anisotropic continuum damage model is presented based on yield and damage conditions as well as on evolution laws for plastic and damage strain rates. Different branches of the damage criteria are taken into account corresponding to various damage and failure processes on the micro-level depending on stress triaxiality and Lode parameter. Experiments with biaxially loaded specimens have been performed. Results for proportional and corresponding non-proportional loading histories are discussed. During the experiments strain fields in critical regions of the specimens are analyzed by digital image correlation (DIC) technique while the fracture surfaces are examined by scanning electron microscopy (SEM). Numerical simulations of the experiments have been performed and numerical results are compared with experimental data. In addition, based on the numerical analyses stress distributions in critical parts of specimens are detected. The results demonstrate the efficiency of the new specimen’s geometries covering a wide range of stress states in the shear/tension and shear/compression regime as well as the effect of loading history on damage and fracture behavior in ductile metal sheets

Modeling of ductile damage using numerical analyses on the micro-scale

The presentation deals with a continuum damage model which has been generalized to take into account the effect of stress state on damage criteria as well as on evolution equations of damage strains. It is based on the introduction of damaged and corresponding undamaged configurations. Plastic behavior is modeled by a yield criterion and a flow rule formulated in the effective stress space (undamaged configurations). In a similar way, damage behavior is governed by a damage criterion and a damage rule considering the damaged configurations. Different branches of the damage criterion are considered corresponding to various damage mechanisms depending on stress intensity, stress triaxiality and the Lode parameter. Experiments with carefully designed specimens are performed and the test results are used to identify basic material parameters. However, it is not possible to determine all parameters based on these tension and shear tests. To be able to get more insight in the complex damage behavior under different loading conditions, additional series of micro-mechanical numerical analyses of void containing unit cells have been performed. These finite element calculations on the micro-level cover a wide range of stress triaxialities and Lode parameters in the tension, shear and compression domain. The numerical results are used to show general trends, to develop equations for the stress-statedependent damage criteria, to propose evolution equations of damage strains, and to identify parameters of the continuum model

Social and Cultural Dimensions of Market Expansion

We have identified three dimensions of market expansion: the growth of market oriented production and trade, internal and external market integration and the creation of virtual markets. These three processes can occur side by side and are connected with social and cultural change.markets culture market expansion

Linfield Graduate Joins NASA Research Team

Humanitarian, explorer and Wall Street businessman Scott Hamilton ’77 has ventured to the tops of the world’s tallest mountains. His most recent endeavor looks even farther to the skies. Hamilton was invited to join a NASA research team searching for a countermeasure for visual impairment intracranial pressure syndrome (VIIP)

Nominal rigidities and the dynamic effects of a monetary shock

Two dynamic sticky price models with monopolistic competition in the goods market are presented. In the first model, each intermediate goods producer faces quadratic costs of adjusting its nominal price as introduced by Rotemberg (1982); the second model incorporates staggered price setting as proposed by Taylor (1980) and recently discussed by Chari/Kehoe/McGrattan (2000). Using the approximation method and the toolkit of Uhlig (1999) these models are used to derive theoretical impulse response functions. One aim is to check whether these two different forms of nominal price rigidities imply quantitatively and qualitatively different impulse response functions. Interestingly, both models do not seem to imply as much persistence as empirical impulse response functions typically indicate. However, qualitative differences do exist.