A type system for components

In modern distributed systems, dynamic reconfiguration, i.e., changing at runtime the communication pattern of a program, is chal- lenging. Generally, it is difficult to guarantee that such modifications will not disrupt ongoing computations. In a previous paper, a solution to this problem was proposed by extending the object-oriented language ABS with a component model allowing the programmer to: i) perform up- dates on objects by means of communication ports and their rebinding; and ii) precisely specify when such updates can safely occur in an object by means of critical sections. However, improper rebind operations could still occur and lead to runtime errors. The present paper introduces a type system for this component model that extends the ABS type system with the notion of ports and a precise analysis that statically enforces that no object will attempt illegal rebinding

WHOOPING CRANE AND SANDHILL CRANE MONITORING AT FIVE WIND ENERGY FACILITIES

Biologists have expressed concern that individuals of the Aransas-Wood Buffalo Population of the federally endangered whooping crane (Grus americana), numbering about 300, may be injured or killed by wind turbines during migration. To help address this concern and curtail (stop) turbine operations when whooping cranes approached turbines, we monitored the area around 5 wind energy facilities in North and South Dakota during spring and fall migration for whooping cranes and sandhill cranes (G. canadensis). Observers monitored cranes for 3 years at each facility from 2009 to 2013 (1,305 total days of monitoring), recording 14 unique observations for a total of 45 whooping cranes for which curtailment occurred during portions of 9 days. Observers also searched for dead cranes at the base of every turbine each day of monitoring. This resulted in approximately 92,022 cumulative individual inspections, during which no dead or injured cranes were detected. Based on our results and monitoring efforts at other wind energy facilities in the migration corridor, no whooping crane fatalities have been documented. Although migrating cranes use areas near turbines, they do not appear to be overly susceptible to collisions with wind turbines

Patchy Reconnection in a Y-Type Current Sheet

We study the evolution of the magnetic field in a Y-type current sheet subject to a brief, localized magnetic reconnection event. The reconnection produces up- and down-flowing reconnected flux tubes which rapidly decelerate when they hit the Y-lines and underlying magnetic arcade loops at the ends of the current sheet. This localized reconnection outflow followed by a rapid deceleration reproduces the observed behavior of post-CME downflowing coronal voids. These simulations support the hypothesis that these observed coronal downflows are the retraction of magnetic fields reconnected in localized patches in the high corona.Comment: 4 pages, 3 figure

Ground-state van der Waals forces in planar multilayer magnetodielectrics

Within the frame of lowest-order perturbation theory, the van der Waals potential of a ground-state atom placed within an arbitrary dispersing and absorbing magnetodielectric multilayer system is given. Examples of an atom situated in front of a magnetodielectric plate or between two such plates are studied in detail. Special emphasis is placed on the competing attractive and repulsive force components associated with the electric and magnetic matter properties, respectively, and conditions for the formation of repulsive potential walls are given. Both numerical and analytical results are presented.Comment: 16 pages, 8 figures, minor correction

Characterization of quantum angular-momentum fluctuations via principal components

We elaborate an approach to quantum fluctuations of angular momentum based on the diagonalization of the covariance matrix in two versions: real symmetric and complex Hermitian. At difference with previous approaches this is SU(2) invariant and avoids any difficulty caused by nontrivial commutators. Meaningful uncertainty relations are derived which are nontrivial even for vanishing mean angular momentum. We apply this approach to some relevant states.Comment: 10 pages, Two column. New section II and some clarifying comment

High dynamic range beam profile measurements

In future high intensity, high energy accelerators, beam loss has to be minimized to maximize performance and reduce activation of accelerator components. It is imperative to have a clear understanding of the mechanisms that can lead to halo formation and to have the possibility to test available theoretical models with an adequate experimental setup. Measurements based on optical transition radiation (OTR) provide an interesting opportunity for high resolution measurements of the transverse beam profile. In order to be applicable for measurements within the beam halo region, it is of utmost importance that a high dynamic range is covered by the image acquisition system. The existing camera system as it is installed in the CLIC Test Facility (CTF3) is compared to a step-by-step measurement with a photo multiplier tube (PMT) and measurements with a cooled charge injection device (CID) camera. The latter acquisition technique provides an innovative and highly flexible approach to high dynamic range measurements and is presented in some detail

Dispersive forces on bodies and atoms: a unified approach

A unified approach to the calculation of dispersive forces on ground-state bodies and atoms is given. It is based on the ground-state Lorentz force density acting on the charge and current densities attributed to the polarization and magnetization in linearly, locally, and causally responding media. The theory is applied to dielectric macro- and micro-objects, including single atoms. Existing formulas valid for weakly polarizable matter are generalized to allow also for strongly polarizable matter. In particular when micro-objects can be regarded as single atoms, well-known formulas for the Casimir-Polder force on atoms and the van der Waals interaction between atoms are recovered. It is shown that the force acting on medium atoms--in contrast to isolated atoms--is in general screened by the other medium atoms.Comment: 10 pages, 2 embedded figure

Thermally-driven morphing with high temperature composites

The thermal expansion mismatch between heat-resisting metals and high-temperature composite materials is explored as a method of achieving thermally-driven morphing in elevated-temperature environments, with an eye towards applications in variable-geometry hot structures in gas turbine engines. Three concepts are presented and demonstrated. The first thermal morphing system is a bimorph laminate which exploits the CTE mismatch between a titanium metal matrix composite and its parent titanium matrix material. The second concept is similar to the first, but uses a diffusion-bonded austenitic stainless steel alloy as the high expansion layer. The third concept utilizes a carbon fiber, silicon carbide matrix ceramic matrix composite joined to a stainless steel skin in a trailing-edge flap arrangement. Furnace-based experiments of cantilever-mounted specimens are performed to evaluate the displacement response of the metal-matrix and ceramic-matrix concepts at temperatures up to 606°C and 1035°C, respectively.</p

Fresnel Representation of the Wigner Function: An Operational Approach

We present an operational definition of the Wigner function. Our method relies on the Fresnel transform of measured Rabi oscillations and applies to motional states of trapped atoms as well as to field states in cavities. We illustrate this technique using data from recent experiments in ion traps [D. M. Meekhof et al., Phys. Rev. Lett. 76, 1796 (1996)] and in cavity QED [B. Varcoe et al., Nature 403, 743 (2000)]. The values of the Wigner functions of the underlying states at the origin of phase space are W(0)=+1.75 for the vibrational ground state and W(0)=-1.4 for the one-photon number state. We generalize this method to wave packets in arbitrary potentials.Comment: 4 pages include 4 figures, submitted to PR