Do Flexible Durable Goods Prices Undermine Sticky Price Models?

Multi-sector sticky price models have surprising implications when durable goods have flexible prices. While in actual data the production of virtually all durables exhibits strong negative responses to monetary contractions, in dynamic general equilibrium models a monetary contraction causes the output of flexibly priced durables to expand. Indeed, in the polar case in which only nondurables have sticky prices, the negative comovement of durable and nondurable production exactly offsets and the behavior of aggregate output mimics that of a model with fully flexible prices. While this neutrality' result is special, the comovement problem' -- the perverse response of flexibly priced durables to monetary policy shocks -- is highly robust. When some durables prices are flexible and others sticky, the comovement problem still applies strongly to the subset of durables with flexible prices. We argue that new housing construction might be best characterized as a flexible price industry for which the comovement problem is relevant. The underlying reason for the comovement problem is the combination of a naturally high intertemporal elasticity of substitution for the purchases of durables and temporarily low marginal costs associated with economic contractions.

Sticky Price Models and Durable Goods

This paper shows that there are striking implications that stem from including durable goods in otherwise conventional sticky price models. The behavior of these models depends heavily on whether durable goods are present and whether these goods have sticky prices. If long-lived durables have sticky prices, then even small durables sectors can cause the model to behave as though most prices were sticky. Conversely, if durable goods prices are flexible then the model exhibits unwelcome behavior. Flexibly priced durables contract during periods of economic expansion. The tendency towards negative comovement is very robust and can be so strong as to dominate the aggregate behavior of the model. In an instructive limiting case, money has no effects on aggregate output even though most prices in the model are sticky.Sticky prices, Durables, Comovement, Neutrality

Modern Laboratory-Based Education for Power Electronics and Electric Machines

The study of modern energy conversion draws upon a broad range of knowledge and often requires a fair amount of experience. This suggests that laboratory instruction should be an integral component of a power electronics and electric machines curriculum. However, before a single watt can be processed in a realistic way, the student must understand not only the operation of conversion systems but also more advanced concepts such as control theory, speed and position sensing, switching signal generation, gate drive isolation, circuit layout, and other critical issues. Our approach is to use a blue-box module where these details are pre-built for convenience, but not hidden from the students inside a black box. Recent improvements to our blue-box modules are described in this paper and include a dual-MOSFET control box with independently isolated FET devices, a triple silicon controlled rectifier control box, a discretely built, high quality pulse-width modulation inverter, a small discrete brushless dc drive system, and a high-performance computer-controlled brushless dc dynamometer motor drive system. Complete details, sufficient to allow the reader to duplicate these designs, are publicly available

A new global river network database for macroscale hydrologic modeling

Coarse-resolution (upscaled) river networks are critical inputs for runoff routing in macroscale hydrologic models. Recently, Wu et al. (2011) developed a hierarchical dominant river tracing (DRT) algorithm for automated extraction and spatial upscaling of river networks using fine-scale hydrography inputs. We applied the DRT algorithms using combined HydroSHEDS and HYDRO1k global fine-scale hydrography inputs and produced a new series of upscaled global river network data at multiple (1/16° to 2°) spatial resolutions. The new upscaled results are internally consistent and congruent with the baseline fine-scale inputs and should facilitate improved regional to global scale hydrologic simulations

Apparatus for Converting Direct Current to Alternating Current using Multiple Converters

An inverter for converting an input direct current (DC) waveform from a DC source to an output alternating current (AC) waveform for delivery to an AC grid includes an input converter, an output converter, and an active filter, each of which is electrically coupled to a bus. The bus may be a DC bus or an AC bus. The input converter is configured to convert the input DC waveform to a DC or AC bus waveform. The output converter is configured to convert the bus waveform to the output AC waveform at a grid frequency. The active filter is configured to reduce a double-frequency ripple power of the bus waveform by supplying power to and absorbing power from the power bus

Blue-Box Approach to Power Electronics and Machines Educational Laboratories

Our approach to laboratory education in power electronics and electric machines is presented. The approach centers upon blue-box laboratory components, that aid the student in rapid experiment assembly without disguising important aspects of the hardware. Several example experiments are presented. Schematics and construction techniques for the hardware are publicly available

Apparatus for Converting Direct Current to Alternating Current using Multiple Converters

An inverter for converting an input direct current (DC) waveform from a DC source to an output alternating current (AC) waveform for delivery to an AC grid includes an input converter, an output converter, and an active filter, each of which is electrically coupled to a bus. The bus may be a DC bus or an AC bus. The input converter is configured to convert the input DC waveform to a DC or AC bus waveform. The output converter is configured to convert the bus waveform to the output AC waveform at a grid frequency. The active filter is configured to reduce a double-frequency ripple power of the bus waveform by supplying power to and absorbing power from the power bus

Boreal forest CO2 exchange and evapotranspiration predicted by nine ecosystem process models: Intermodel comparisons and relationships to field measurements

Nine ecosystem process models were used to predict CO2 and water vapor exchanges by a 150-year-old black spruce forest in central Canada during 1994–1996 to evaluate and improve the models. Three models had hourly time steps, five had daily time steps, and one had monthly time steps. Model input included site ecosystem characteristics and meteorology. Model predictions were compared to eddy covariance (EC) measurements of whole-ecosystem CO2exchange and evapotranspiration, to chamber measurements of nighttime moss-surface CO2release, and to ground-based estimates of annual gross primary production, net primary production, net ecosystem production (NEP), plant respiration, and decomposition. Model-model differences were apparent for all variables. Model-measurement agreement was good in some cases but poor in others. Modeled annual NEP ranged from −11 g C m−2 (weak CO2source) to 85 g C m−2 (moderate CO2 sink). The models generally predicted greater annual CO2sink activity than measured by EC, a discrepancy consistent with the fact that model parameterizations represented the more productive fraction of the EC tower “footprint.” At hourly to monthly timescales, predictions bracketed EC measurements so median predictions were similar to measurements, but there were quantitatively important model-measurement discrepancies found for all models at subannual timescales. For these models and input data, hourly time steps (and greater complexity) compared to daily time steps tended to improve model-measurement agreement for daily scale CO2 exchange and evapotranspiration (as judged by root-mean-squared error). Model time step and complexity played only small roles in monthly to annual predictions

Apparatus and Method for Controlling DC-AC Power Conversion

An apparatus and method for controlling the delivery of power from a DC source to an AC grid includes an inverter configured to deliver power from the unipolar input source to the AC grid and an inverter controller. The inverter includes an input converter, an active filter, and an output converter. The inverter controller includes an input converter controller, an active filter controller and an output converter controller. The input converter controller is configured to control a current delivered by the input converter to a galvanically isolated unipolar bus of the inverter. The output converter is configured to control the output converter to deliver power to the AC grid. Additionally, the active filter controller is configured to control the active filter to supply substantially all the power that is deliver by the output controller to the AC grid at a grid frequency