Three Essays on the Macroeconomic Consequences of Prices

To understand the workings of the macroeconomy, it is not enough to simply focus on the movements of the aggregate variables of the economy. It is necessary to also understand the behavior of its various components and their interactions. In this thesis, I study three important components of macroeconomic behavior; prices, wages, and the financial system and their connection to the behavior of the aggregate economy. In the first chapter (joint work with Andrew Usher), we use retail scanner data to show two previously unknown empirical facts about prices. First, the probability of price adjustment increases with product revenue. Second, the absolute size of price adjustment decreases with revenue. These facts are consistent with a menu cost model where the fixed cost of adjustment does not scale with product revenue. Taken together, these facts suggest that prices of products with higher revenues respond more to monetary policy than prices of products with lower revenues. Over the business cycle, both the mean and variance of the (log) revenue distribution across goods decrease with the unemployment rate. These empirical facts imply that monetary policy should have stronger effects on the economy in recessions than in expansions. We verify this property using a quantitative menu cost model, and we provide additional evidence of the state-dependence of monetary policy using aggregate data. In the second chapter (joint work with Miles S. Kimball), we study the optimal wage structure of a firm with imperfect monitoring of worker effort. We find that when firms can commit to (implicit) long-term contracts, imperfect monitoring leads to optimal wage profiles that reflect worker seniority. We provide a precise definition of seniority as a measure of worker value to the firm rather than the length of service by a worker. The paper illustrates how worker seniority will evolve over the worker's tenure with the firm and how wage, effort, and separation evolve with seniority. We also show that monitoring and amenities reflect seniority as well. To solve the optimal contract problem, we present a solution technique, the ``retrograde approach," of solving complex optimization problems with endogenous discounting and forward-looking state variables in a simple and intuitive way. In chapter three, I find that system wide runs can be triggered by small shocks to fundamental asset values. Informational frictions amplify small shocks causing large contractions in the amount of credit provided to financial institutions. Asset fire sales exacerbate these effects and force a complete collapse of lending to these institutions; a system wide run. The paper identifies the incentive of healthy institutions to differentiate themselves from distressed ones as the key channel driving the contraction in credit. This contrasts with traditional bank runs that stem from the coordination failures of lenders. The findings lead to direct policy implications; including a government clearing house for loans and quantitative easing.PHDEconomicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144157/1/dikang_1.pd

Flux Noise in MgB2 Thin Films

We have performed flux noise and AC-susceptibility measurements on two 400 nm thick MgB$_2$ films. Both measurement techniques give information about the vortex dynamics in the sample, and hence the superconducting transition, and can be linked to each other through the fluctuation-dissipation-theorem. The transition widths for the two films are 0.3 and 0.8 K, respectively, and the transitions show a multi step-like behavior in the AC-susceptibility measurements. The same phenomenon is observed in the flux noise measurements through a change in the frequency dependence of the spectral density at each step in the transition. The results are discussed and interpreted in terms of vortices carrying an arbitrary fraction of a flux quantum as well as in terms of different macroscopic regions in the films having slightly different compositions, and hence, different critical temperatures.Comment: 8 pages, 4 figures, conference contribution to "Fluctuations and Noise", Santa Fe, New mexico 1-4 june 200

Growth of superconducting MgB2 thin films via postannealing techniques

We report the effect of annealing on the superconductivity of MgB2 thin films as functions of the postannealing temperature in the range from 700 C to 950 C and of the postannealing time in the range from 30 min to 120 min. On annealing at 900 C for 30 min, we obtained the best-quality MgB2 films with a transition temperature of 39 K and a critical current density of ~ 10^7 A/cm^2. Using the scanning electron microscopy, we also investigated the film growth mechanism. The samples annealed at higher temperatures showed the larger grain sizes, well-aligned crystal structures with preferential orientations along the c-axis, and smooth surface morphologies. However, a longer annealing time prevented the alignment of grains and reduced the superconductivity, indicating a strong interfacial reaction between the substrate and the MgB2 film.Comment: 7 pages, 4 figures include

Feature extraction for classification from images: a look at the retina.

A method is proposed for the representation of localised features using disjoint sub-images taken from several datasets of retinal images for use within an incremental learning system. A tile-based localised adaptive threshold selection method was taken for vessel segmentation based on separate colour components. Arteriole-venous differentiation was done using the composite of these components and high quality fundal images. Vessel segmentation performance was evaluated on the DRIVE and STARE datasets achieving average specificity of 0.9379 and sensitivity of 0.5924

Durability Assessment Considering Residual Stress

The relative movement between the cylinder block and the piston may cause a seizure, and this seizure problem can be solved by pressing the bushing into the cylinder block. However, if the rates of shrink fit are insufficient, the copper bushing will be detached from the cylinder block, and if the rates of shrink fit are excessive, a residual stress higher than yield stress will be generated and adversely affect the durability of bushing and the cylinder block. Therefore, in this study, a clear and quantitative rate of shrink fit is presented to solve the above-mentioned problems, and the durability assessment process of mechanical parts where residual stress occurs is performed. Through this study, analytical technique that can predict the residual stress clearly according to the rates of shrink fit was obtained and durability assessment was completed based on the quantitative residual stress according to the rates of shrink fit