An application of eigenspace methods to symmetric flutter suppression

An eigenspace assignment approach to the design of parameter insensitive control laws for linear multivariable systems is presented. The control design scheme utilizes flexibility in eigenvector assignments to reduce control system sensitivity to changes in system parameters. The methods involve use of the singular value decomposition to provide an exact description of allowable eigenvectors in terms of a minimum number of design parameters. In a design example, the methods are applied to the problem of symmetric flutter suppression in an aeroelastic vehicle. In this example the flutter mode is sensitive to changes in dynamic pressure and eigenspace methods are used to enhance the performance of a stabilizing minimum energy/linear quadratic regulator controller and associated observer. Results indicate that the methods provide feedback control laws that make stability of the nominal closed loop systems insensitive to changes in dynamic pressure

The return of an English pluperfect subjunctive?

The introduction of the superfluous morpheme [әv] into past unfulfilled if-clauses in modern English raises serious questions of analysis. How is one to parse a clause like: “If I had’ve known that...”? It is proposed that the intrusive morpheme can be viewed as a marker of subjunctivity, whereby “real” and “unreal” pluperfects can be explicitly distinguished

Carbon capture in the cement industry: technologies, progress, and retrofitting

Several different carbon-capture technologies have been proposed for use in the cement industry. This paper reviews their attributes, the progress that has been made toward their commercialization, and the major challenges facing their retrofitting to existing cement plants. A technology readiness level (TRL) scale for carbon capture in the cement industry is developed. For application at cement plants, partial oxy-fuel combustion, amine scrubbing, and calcium looping are the most developed (TRL 6 being the pilot system demonstrated in relevant environment), followed by direct capture (TRL 4–5 being the component and system validation at lab-scale in a relevant environment) and full oxy-fuel combustion (TRL 4 being the component and system validation at lab-scale in a lab environment). Our review suggests that advancing to TRL 7 (demonstration in plant environment) seems to be a challenge for the industry, representing a major step up from TRL 6. The important attributes that a cement plant must have to be “carbon-capture ready” for each capture technology selection is evaluated. Common requirements are space around the preheater and precalciner section, access to CO2 transport infrastructure, and a retrofittable preheater tower. Evidence from the electricity generation sector suggests that carbon capture readiness is not always cost-effective. The similar durations of cement-plant renovation and capture-plant construction suggests that synchronizing these two actions may save considerable time and money

Phase diagram of Janus Particles

We deeply investigate a simple model representative of the recently synthesized Janus particles, i.e. colloidal spherical particles whose surface is divided into two areas of different chemical composition. When the two surfaces are solvophilic and solvophobic, these particles constitute the simplest example of surfactants. The phase diagram includes a colloidal-poor (gas) colloidal-rich (liquid) de-mixing region, which is progressively suppressed by the insurgence of micelles, providing the first model where micellization and phase-separation are simultaneously observed. The coexistence curve is found to be negatively sloped in the temperature-pressure plane, suggesting that Janus particles can provide a colloidal system with anomalous thermodynamic behavior.Comment: 5 pages, 5 figures, Phys. Rev. Lett. in pres

Spangolite: an s=1/2 maple leaf lattice antiferromagnet?

Spangolite, Cu6Al(SO4)(OH)12Cl.3H2O, is a hydrated layered copper sulphate mineral. The Cu2+ ions of each layer form a systematically depleted triangular lattice which approximates a maple leaf lattice. We present details of the crystal structure, which suggest that in spangolite this lattice actually comprises two species of edge linked trimers with different exchange parameters. However, magnetic susceptibility measurements show that despite the structural trimers, the magnetic properties are dominated by dimerization. The high temperature magnetic moment is strongly reduced below that expected for the six s=1/2 in the unit cell.Comment: Accepted for JPCM Frustrated Magnetism special issue, added reference [5] in replacemen

A fifteenth century baker’s price-list: MS. Douce Charters a 1, no. 62

The origin of MS. Douce Charters a 1, no. 62 is to be found in the so called "Assisa Panis", a 13th-century legal instrument that established for the first time a relationship between the cost of wheat and the price of bread to be observed throughout the land, and abolished only in 1824. The "Assisa Panis" was an informal instrument, since the text was always different from one copy to another. It detailed the different kind of breads known in the realm, the official measure of capacity for grains, and it gives now an insight into the material culture of Medieval England. The MS. Douce was written around the half of the 15th Century on a sheet of smooth parchment, and must have hung from a wall or perhaps the back of a door. The text was divided into five columns, with a drawing atop of each to represent its content and an explanation of every type of bread that was to be sold, its weight and its price. The drawings seemed to focus on the leavening of the bread, instead of the shape of the single loaf. The essay considers as well one case in which documents such as MS. Douce impinge upon literary texts

Scaling Property with Professor Ellickson

Presented at the 2008 Brigham-Kanner Property Rights Conference