Positivity Of Equivariant Gromov–Witten Invariants

We show that the equivariant Gromov–Witten invariants of a projective homogeneous space G/P exhibit Graham-positivity: when expressed as polynomials in the positive roots, they have nonnegative coefficients

Equivariant Quantum Schubert Polynomials

We establish an equivariant quantum Giambelli formula for partial flag varieties. The answer is given in terms of a specialization of universal double Schubert polynomials. Along the way, we give new proofs of the presentation of the equivariant quantum cohomology ring, as well as Graham-positivity of the structure constants in equivariant quantum Schubert calculus. (C) 2013 Elsevier Inc. All rights reserved

K-classes of Brill-Noether loci and a determinantal formula

We prove a determinantal formula for the K-theory class of certain degeneracy loci, and apply it to compute the Euler characteristic of the structure sheaf of the Brill-Noether locus of linear series with special vanishing at marked points. When the Brill-Noether number $\rho$ is zero, we recover the Castelnuovo formula for the number of special linear series on a general curve; when $\rho=1$, we recover the formulas of Eisenbud-Harris, Pirola, and Chan-L\'opez-Pflueger-Teixidor for the arithmetic genus of a Brill-Noether curve of special divisors. Our degeneracy locus formula also specializes to new determinantal expressions for the double Grothendieck polynomials corresponding to 321-avoiding permutations, and gives double versions of the flagged skew Grothendieck polynomials recently introduced by Matsumura. Our result extends the formula of Billey-Jockusch-Stanley expressing Schubert polynomials for 321-avoiding permutations as generating functions for skew tableaux.Comment: 31 pages; v2: stronger Theorem C, and improved expositio

Hydrocarbon emissions from a modern commercial airliner

We report selected carbon species emission indices (EIs) for a Rolls Royce RB211-535-E4 turbofan engine that were acquired during the NASA EXperiment to Characterize Aircraft Volatile Aerosol and Trace-species Emissions (EXCAVATE). Conducted during winter 2002, the mission focused upon characterizing the exhaust constituents of the NASA Boeing 757 aircraft during ground-based operation. Carbon species concentrations were determined by chromatographic analyses of whole air samples collected 10 m behind the engine exit plane as engine power was varied from ground idle to about 60% of maximum rated thrust. Ambient air samples were also collected and analyzed to facilitate correction of calculated EIs for background concentrations. Results are consistent with previous observations and indicate that, on a relative basis, turbine engines emit considerable amounts of light hydrocarbon species at idle, but significantly lesser amounts at higher engine powers. © 2005 Elsevier Ltd. All rights reserved

Gaussian pulse dynamics in gain media with Kerr nonlinearity

Using the Kantorovitch method in combination with a Gaussian ansatz, we derive the equations of motion for spatial, temporal and spatiotemporal optical propagation in a dispersive Kerr medium with a general transverse and spectral gain profile. By rewriting the variational equations as differential equations for the temporal and spatial Gaussian q parameters, optical ABCD matrices for the Kerr effect, a general transverse gain profile and nonparabolic spectral gain filtering are obtained. Further effects can easily be taken into account by adding the corresponding ABCD matrices. Applications include the temporal pulse dynamics in gain fibers and the beam propagation or spatiotemporal pulse evolution in bulk gain media. As an example, the steady-state spatiotemporal Gaussian pulse dynamics in a Kerr-lens mode-locked laser resonator is studied

Novel orbits of Mercury, Venus and Mars enabled using low-thrust propulsion

Exploration of the inner planets of the Solar System is vital to significantly enhance the understanding of the formulation of the Earth and other planets. This paper therefore considers the development of novel orbits of Mars, Mercury and Venus to enhance the opportunities for remote sensing of these planets. Continuous acceleration is used to extend the critical inclination of highly elliptical orbits at each planet and is shown to require modest thrust magnitudes. This paper also presents the extension of existing sun-synchronous orbits around Mars. However, unlike Earth and Mars, natural sun-synchronous orbits do not exist at Mercury or Venus. This research therefore also uses continuous acceleration to enable circular and elliptical sun-synchronous orbits, by ensuring that the orbit's nodal precession rate matches the planets mean orbital rate around the Sun, such that the lighting along the ground-track remains approximately constant over the mission duration. This property is useful both in terms of spacecraft design, due to the constant thermal conditions, and for comparison of images. Considerably high thrust levels are however required to enable these orbits, which are prohibitively high for orbits with inclinations around 901. These orbits therefore require some development in electric propulsion systems before becoming feasible

Novel orbits of Mercury and Venus enabled using low-thrust propulsion

Exploration of the inner planets of the Solar System is vital to significantly enhance the understanding of the formulation of Earth and other planets. This paper therefore considers the development of novel orbits of both Mercury and Venus to enhance the opportunities for remote sensing. Continuous low-thrust propulsion is used to extend the critical inclination of highly elliptical orbits at each planet, which are shown to require very small acceleration magnitudes. Unlike other bodies in the Solar System, natural sun-synchronous orbits do not exist at Mercury or Venus. This research therefore also uses continuous acceleration to enable both circular and elliptical sun-synchronous orbits, which could significantly simplify the spacecraft thermal environment. Considerably high thrust levels are however required to enable these orbits, which could not be provided by current propulsion systems

Practices for strategic capacity management in Malaysian manufacturing firms

While the notion of manufacturing capabilities is a long-standing notion in research on operations management, its actual implementation and management has been hardly researched. Five case studies in Malaysia offered the opportunity to examine the practice of manufacturing managers with regard to strategic capability management. The data collection and analysis was structured by using the notion of Strategic Capacity Management. Whereas traditionally literature has demonstrated the beneficial impact of an appropriate manufacturing strategy on the business strategy and performance, the study highlights the difficulty of managers to set the strategy, let alone implementing it. This is partly caused by the immense pressure of customers in these dominantly Make-To-Order environments for SMEs. Current concepts for manufacturing capabilities have insufficiently accounted this phenomenon and an outline of a research agenda is presented