Applications of model structure determination to flight test data

Several statistical and information criteria need to be considered when selecting an adequate model. Incorrect stability and control derivates result from inadequate aerodynamic model structure. Stepwise regression is used to determine the structure for an adequate model. Flight data which covers a nonlinear aerodynamic model range may be analyzed as a single data set or partitioned into several distinct sets. Stepwise regression for model structure detemination and parameter estimation was successfully applied to three aircraft types (single engine general aviation, unaugmented modern jet fighter, jet transport)

Validity of the Taylor Hypothesis for Linear Kinetic Waves in the Weakly Collisional Solar Wind

The interpretation of single-point spacecraft measurements of solar wind turbulence is complicated by the fact that the measurements are made in a frame of reference in relative motion with respect to the turbulent plasma. The Taylor hypothesis---that temporal fluctuations measured by a stationary probe in a rapidly flowing fluid are dominated by the advection of spatial structures in the fluid rest frame---is often assumed to simplify the analysis. But measurements of turbulence in upcoming missions, such as Solar Probe Plus, threaten to violate the Taylor hypothesis, either due to slow flow of the plasma with respect to the spacecraft or to the dispersive nature of the plasma fluctuations at small scales. Assuming that the frequency of the turbulent fluctuations is characterized by the frequency of the linear waves supported by the plasma, we evaluate the validity of the Taylor hypothesis for the linear kinetic wave modes in the weakly collisional solar wind. The analysis predicts that a dissipation range of solar wind turbulence supported by whistler waves is likely to violate the Taylor hypothesis, while one supported by kinetic Alfven waves is not.Comment: 10 pages, 3 figures, Accepted for publication in The Astrophysical Journa

Determination of airplane model structure from flight data using splines and stepwise regression

A procedure for the determination of airplane model structure from flight data is presented. The model is based on a polynomial spline representation of the aerodynamic coefficients, and the procedure is implemented by use of a stepwise regression. First, a form of the aerodynamic force and moment coefficients amenable to the utilization of splines is developed. Next, expressions for the splines in one and two variables are introduced. Then the steps in the determination of an aerodynamic model structure and the estimation of parameters are discussed briefly. The focus is on the application to flight data of the techniques developed

Entrepreneurshoip and the Economic Theory of the Firm Any Gains from Trade?

Although they have developed very much in isolation from each other, we argue the theory of entrepreneurship and the economic theory of the firm are closely related, and each has much to learn from the other. In particular, the notion of entrepreneurship as judgment associated with Frank Knight and some Austrian school economists aligns naturally with the theory of the firm. In this perspective, the entrepreneur needs a firm, that is, a set of alienable assets he controls, to carry out his function. We further show how this notion of judgment adds to the key themes in the modern theory of the firm (i.e., the existence, boundaries, and internal organization). In our approach, resource uses are not data, but are created as entrepreneurs envision new ways of using assets to produce goods. The entrepreneur’s decision problem is aggravated by the fact that capital assets are heterogeneous. Asset ownership facilitates experimenting entrepreneurship: Acquiring a bundle of property rights is a low cost means of carrying out commercial experimentation. In this approach, the existence of the firm may be understood in terms of limits to the market for judgment relating to novel uses of heterogeneous assets; and the boundaries of the firm, as well as aspects of internal organization, may be understood as being responsive to entrepreneurial processes of experimentation.Entrepreneurship, heterogeneous assets, judgment, ownership, firm boundaries, internal organization

The Theory of the Firm and Its Critics A Stocktaking and Assessment

Ever since its emergence in the 1970s the modern economic or Coasian theory of the firm has been discussed and challenged by sociologists, heterodox economists, management scholars, and other critics. This chapter reviews and assesses these critiques, focusing on behavioral issues (bounded rationality and motivation), process (including path dependence and the selection argument), entrepreneurship, and the challenge from knowledge-based theories of the firm.

Structural and mechanical effects of interstitial sinks Interim technical report, 8 Mar. 1968 - 8 Mar. 1969

Structural and mechanical effects of interstitial sinks in niobium and alloys of niobium and tantalu

Structural and mechanical effects of interstitial sinks

Structural changes in niobium base alloys induced by exposure to titanium interstitial sink at elevated temperatur