Comparative Advantage and Government Price Intervention Policies in Forestry

The export log ban would have the same effect as imposing an export tax. Similar to the quota system, a complete log ban on exports raises no revenue and only by accident would it accomplish the right output limitation. These are few among the many observations that this paper professes. It also notes a strong comparative advantage in producing logs and processing them for exports.forestry sector, price intervention, comparative advantage

A characterisation of generically rigid frameworks on surfaces of revolution

A foundational theorem of Laman provides a counting characterisation of the finite simple graphs whose generic bar-joint frameworks in two dimensions are infinitesimally rigid. Recently a Laman-type characterisation was obtained for frameworks in three dimensions whose vertices are constrained to concentric spheres or to concentric cylinders. Noting that the plane and the sphere have 3 independent locally tangential infinitesimal motions while the cylinder has 2, we obtain here a Laman-Henneberg theorem for frameworks on algebraic surfaces with a 1-dimensional space of tangential motions. Such surfaces include the torus, helicoids and surfaces of revolution. The relevant class of graphs are the (2,1)-tight graphs, in contrast to (2,3)-tightness for the plane/sphere and (2,2)-tightness for the cylinder. The proof uses a new characterisation of simple (2,1)-tight graphs and an inductive construction requiring generic rigidity preservation for 5 graph moves, including the two Henneberg moves, an edge joining move and various vertex surgery moves.Comment: 23 pages, 5 figures. Minor revisions - most importantly, the new version has a different titl

Preliminary investigation of high power microwave plasmas for electrothermal thruster use

Results are reported from preliminary tests to evaluate the high power microwave electrothermal thruster (MET) concept, which employs a free-floating plasma discharge maintained by applied CW microwave power to heat a propellant gas flow. Stable plasmas have been created and maintained in helium (He), nitrogen (N2), and hydrogen (H2) as propellants in both the TM(sub 011) and TM(sub 012) modes at discharge pressures from 10 Pa to 69 kPa. Reproducible starting conditions of pressure and power have been documented for all the plasmas. Vortical inflow of the propellant gas was observed to cause the formation of on-axis 'spike' plasmas. The formation and unformation conditions of these plasmas were studied. Operation in the spike plasma condition enables maximum power absorption with minimum wall heating and offers maximum efficiency in heating the propellant gas. In the spike condition, plasmas of the three propellant gases were investigated in an open channel configuration to a maximum applied power level of 11.2 kW (in N2). Microwave power coupling efficiencies of over 90 percent were routinely obtained at absorbed power levels up to 2 kW. Magnetic nozzle effects were investigated with a superconducting solenoid Al magnet applying a high magnetic field to the plasmas in and exiting from the discharge tube

Development of a high power microwave thruster, with a magnetic nozzle, for space applications

This paper describes the current development of a high-power microwave electrothermal thruster (MET) concept at the NASA Lewis Research Center. Such a thruster would be employed in space for applications such as orbit raining, orbit maneuvering, station change, and possibly trans-lunar or trans-planetary propulsion of spacecraft. The MET concept employs low frequency continuous wave (CW) microwave power to create and continuously pump energy into a flowing propellant gas at relative high pressure via a plasma discharge. The propellant is heated to very high bulk temperatures while passing through the plasma discharge region and then is expanded through a throat-nozzle assembly to produce thrust, as in a conventional rocket engine. Apparatus, which is described, is being assembled at NASA Lewis to test the MET concept to CW power levels of 30 kW at a frequency of 915 MHz. The microwave energy is applied in a resonant cavity applicator and is absorbed by a plasma discharge in the flowing propellant. The ignited plasma acts as a lossy load, and with optimal tuning, energy absorption efficiencies over 95 percent (based on the applied microwave power) are expected. Nitrogen, helium, and hydrogen will be tested as propellants in the MET, at discharge chamber pressures to 10 atm

Cotton Futures Dynamics: Structural Change, Index Traders and the Returns to Storage

The commodity bull cycle of 2006-2008 and subsequent dramatic price decline have been a source of hardship for traditional commodity market participants such as producers and merchant/shippers. The usefulness of futures markets has been called into question, especially given that some market movements did not appear to be justified by economic fundamentals. An emerging research literature examines the possible influence of futures traders, and particularly the non-traditional Index Traders, on the well-functioning of futures markets and underlying commodity markets. Cotton is a relatively under-studied commodity that is of particular importance for producers in the South and Southwest. To this end, this paper asks the following questions: (1) What role have (primarily long-only) Index Traders played, if we simultaneously account for important ongoing changes in cotton economic fundamentals? (2) Have seasonal and long-run patterns of convenience yield and price volatility changed during or since the commodity bull cycle? (3) How well do the data support a theory of storage model using the concept of convenience yield, and has the relationship changed with the commodity bull cycle? The results presented in this paper suggest that traditional, well-established economic relationships for cotton futures markets clearly have been disrupted during the period 2006- 2009. However, we find no direct evidence to support the claim that Index Traders are responsible for changes in prices or volatility.Cotton, futures markets, theory of storage, convenience yield, Index Traders, Agribusiness, Agricultural Finance, Crop Production/Industries, Demand and Price Analysis, Farm Management, Financial Economics, Marketing, Research Methods/ Statistical Methods, Risk and Uncertainty,

An analysis of the role of the textbook in the construction of accounting knowledge

This report examines the role of the textbook and training manual in the teaching of introductory financial accounting. Although it has long been recognised that the textbook plays an important role in the education process, the issue has not been systematically examined in a comprehensive manner with respect to the teaching of introductory financial accounting. Based on research carried out in 2005, the current report addresses this issue. It does so using a research framework proposed by Thompson (1990) which recommends a comprehensive approach to the understanding of texts involving three separate aspects: the production of the textbook/training manual; the content of the textbook/training manual; the usage of the textbook/training manual

Coalgebraic Semantics for Timed Processes

We give a coalgebraic formulation of timed processes and their operational semantics. We model time by a monoid called a “time domain”, and we model processes by “timed transition systems”, which amount to partial monoid actions of the time domain or, equivalently, coalgebras for an “evolution comonad ” generated by the time domain. All our examples of time domains satisfy a partial closure property, yielding a distributive law of a monad for total monoid actions over the evolution comonad, and hence a distributive law of the evolution comonad over a dual comonad for total monoid actions. We show that the induced coalgebras are exactly timed transition systems with delay operators. We then integrate our coalgebraic formulation of time qua timed transition systems into Turi and Plotkin’s formulation of structural operational semantics in terms of distributive laws. We combine timing with action via the more general study of the combination of two arbitrary sorts of behaviour whose operational semantics may interact. We give a modular account of the operational semantics for a combination induced by that of each of its components. Our study necessitates the investigation of products of comonads. In particular, we characterise when a monad lifts to the category of coalgebras for a product comonad, providing constructions with which one can readily calculate. Key words: time domains, timed transition systems, evolution comonads, delay operators, structural operational semantics, modularity, distributive laws

Constructing meaning in the service of power : an analysis of the typical modes of ideology in accounting textbooks

This paper provides an analysis of the typical modes of ideology in introductory financial accounting textbooks and training materials. Drawing on Thompson's (1990) schema concerning the typical linguistic modes through which ideology operates, this research suggests that the operation of ideology is apparent within educational accounting texts, with particular strategies being more evident than others: in particular, the strategies of universalization, narrativization, rationalization and naturalization. Given the predominantly technical nature of introductory financial accounting textbooks and training manuals, the modes of ideology identified in the texts were often quite subtle; more specifically, the ideological characteristics displayed in each of the six texts analysed were often expressions of implicit or taken-for-granted assumptions