Criteria for \sigma-ampleness

In the noncommutative geometry of Artin, Van den Bergh, and others, the twisted homogeneous coordinate ring is one of the basic constructions. Such a ring is defined by a $\sigma$-ample divisor, where $\sigma$ is an automorphism of a projective scheme X. Many open questions regarding $\sigma$-ample divisors have remained. We derive a relatively simple necessary and sufficient condition for a divisor on X to be $\sigma$-ample. As a consequence, we show right and left $\sigma$-ampleness are equivalent and any associated noncommutative homogeneous coordinate ring must be noetherian and have finite, integral GK-dimension. We also characterize which automorphisms $\sigma$ yield a $\sigma$-ample divisor.Comment: 16 pages, LaTeX2e, to appear in J. of the AMS, minor errors corrected (esp. in 1.4 and 3.1), proofs simplifie

Fujita's Conjecture and Frobenius amplitude

We prove a version of Fujita's Conjecture in arbitrary characteristic, generalizing results of K.E. Smith. Our methods use the Frobenius morphism, but avoid tight closure theory. We also obtain versions of Fujita's Conjecture for coherent sheaves with certain ampleness properties.Comment: 8 pages. Erratum added to replace Lemma 2.

The flashing behavior of thunderstorms

Lightning flash distribution in thunderstorms - statistical analysi

An Economics Capstone Course from Creation to Presentation

This paper details a methodology used to construct a capstone course for the economics major. The capstone course should require students to utilize key concepts that they have learned. The lack of a meaningful topic, however, detracts from a showcase for student understanding. The author details the use of Michael Porter's (1998) location quotients and competitive cluster theory in a capstone course. Applying these concepts increases student understanding of state industries as well as exposing them to an alternative theory of competition not necessarily included in intermediate microeconomic theory.

Effect of engine, tank and propellant specific cost on single stage recoverable booster economics

Reusable first stages using hydrogen-oxygen, hydrogen-fluorine and kerosine-oxygen are compared with non-reusable stages using a solid in addition to the liquid combinations. The criterion used for comparison is the minimum specific cost of the "loaded and ready for launch" stage cost per unit of stage payload mass. A closed form relationship is used in which the empty stage mass without payload is taken to scale in part proportional to propellant mass, and in part to mass flow rate. The stage specific cost is proportional to specific cost of engine (or nozzle) tank and propellant. In the second part the hydrogen-oxygen combination is consiaered,in more detail. The sensitivity of the results to changes in various specific costs including that of refurbishing are described. Throughout, the stage velocity increments are compared in the 3000-6000 metres/second range with losses

Marketing images and consumers' experiences in selling environments

In a well-functioning market, consumers exert choices not just in purchases of products but also in selections of locations to enjoy shopping. Scholarly research has demonstrated that retail atmospheres impact on shoppers’ pleasurable shopping experiences. Demonstrating the marketing concept in action, shoppers consistently respond to this empowerment by for example, spending more time shopping and spending more money in retail facilities that are perceived to offer a pleasanter atmosphere and experience. This research pivots round an in-depth qualitative study that evaluated the impact of a plasma screens and specific informational content on shopping centre user behaviour. A phenomenological study of the effects of the medium, and the way in which these systems influence behaviour, permitted a far deeper investigation of our sample group vis-àvis increased browsing time and the propensity to spend. A series of eight focus discussions were conducted with local user groups of varying age and gender. Key themes drawn from the group discussions using axial coding indicated that the influence created by the images varied with subjects and settings. The general consensus was that such ‘screens’ created a certain ambience that influenced the way our subjects felt about the selling environment under study. Moreover, for our sample groups, there was clearly a link between the screened images and modern expectations of a selling environment. The plasma screens provided added enjoyment to shoppers’ experiences, providing them with more information enabling more informed shopping choices. The research concludes with implications for strategic marketing, theory and practice

Measuring the Common Component of Stock Market Fluctuations in the Asia-Pacific Region

This paper fits Generalized Auto-Regressive Conditional Heteroskedasticity (GARCH) models to the daily closing stock market indices of Australia, China, Hong Kong, Indonesia, Japan, Korea, Malaysia, Philippines, Singapore, and Taiwan to compute for time-varying weights associated with the volatilities of individual indices. These weights and the returns of the various indices were then used to determine the common component of stock market returns. Our results suggest that a common component of the Asia-Pacific stock market returns exists, which significantly explains the individual country’s stock market returns. We also find that stock markets of Korea and Hong Kong are the two most sensitive to changes in the common component stock returns, while China’s stock market is the least sensitive.Common Component, Volatility, GARCH model