7,146 research outputs found
On the Nature of Capital Adjustment Costs
This paper studies the nature of capital adjustment at the plant-level. We use an indirect inference procedure to estimate the structural parameters of a rich specification of capital adjustment costs. In effect, the parameters are optimally chosen to reproduce the nonlinear relationship between investment and profitability that we uncover in the plant-level data. Our findings indicate that a model which mixes both convex and nonconvex adjustment costs with irreversibility fits the data best.
Locating the pseudogap closing point in cuprate superconductors: absence of entrant or reentrant behavior
Current descriptions of the pseudogap in underdoped cuprates envision a
doping-dependent transition line which descends monotonically towards
zero just beyond optimal doping. There is much debate as to the location of the
terminal point where vanishes, whether or not there is a phase
transition at and exactly how behaves below within the
superconducting dome. One perspective sees cutting the dome and
continuing to descend monotonically to zero at holes/Cu
referred to here as `entrant behavior'. Another perspective derived from
photoemission studies is that intersects the dome near holes/Cu then turns back below , falling to zero again
around referred to here as `reentrant behavior'. By
examining thermodynamic data for BiSrCaCuO we show
that neither entrant nor reentrant behavior is experimentally supported.
Rather, sharply delimits the pseudogap regime and for
the pseudogap is always present, independent of temperature. Similar
results are found for YCaBaCuO. For both
materials is not a temperature but a crossover scale, , reflecting instead the underlying pseudogap energy which
vanishes as .Comment: 20 Pages, 9 Figures, in press Phys. Rev.
Body-Soul Question: Can We Be Both Confessional and Reformational?
This feature article is based on a paper given during the 1991 Spring Ministers\u27 Conference at Dordt College under the theme To Belong Body and Soul...
Dynamics of Labor Demand: Evidence from Plant-level Observations and Aggregate Implications
This paper studies the dynamics of labor demand at the plant and aggregate levels. The correlation of hours and employment growth is negative at the plant level and positive in aggregate time series. Further, hours and employment growth are about equally volatile at the plant level while hours growth is much less volatile than employment growth in the aggregate data. Given these differences, we specify and estimate the parameters of a plant-level dynamic optimization problem using simulated method of moments to match plant-level observations. Our findings indicate that non-convex adjustment costs are critical for explaining plant-level moments on hours and employment. Aggregation generates time series implications which are broadly consistent with observation. Further, we find that a model with quadratic adjustment costs alone can also broadly match the aggregate facts.
Multidisciplinary analysis of actively controlled large flexible spacecraft
The control of Flexible Structures (COFS) program has supported the development of an analysis capability at the Langley Research Center called the Integrated Multidisciplinary Analysis Tool (IMAT) which provides an efficient data storage and transfer capability among commercial computer codes to aid in the dynamic analysis of actively controlled structures. IMAT is a system of computer programs which transfers Computer-Aided-Design (CAD) configurations, structural finite element models, material property and stress information, structural and rigid-body dynamic model information, and linear system matrices for control law formulation among various commercial applications programs through a common database. Although general in its formulation, IMAT was developed specifically to aid in the evaluation of the structures. A description of the IMAT system and results of an application of the system are given
Flight test techniques for the X-29A aircraft
The X-29A advanced technology demonstrator is a single-seat, single-engine aircraft with a forward-swept wing. The aircraft incorporates many advanced technologies being considered for this country's next generation of aircraft. This unusual aircraft configuration, which had never been flown before, required a precise approach to flight envelope expansion. This paper describes the real-time analysis methods and flight test techniques used during the envelope expansion of the x-29A aircraft, including new and innovative approaches
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