132,824 research outputs found
Aerospace vehicle
A dual structure aerospace vehicle is described which has an aeroshell structure and an internally disposed separable and reusable integral tank/thrust structure. The tank/thrust structure is inuslated for cryogenic fuels and the cavity within aeroshell is insulated from the tank/thrust structure. An internal support ring within the cavity serves as an attachment for lugs on the tank/thrust structure via double hinges. The aft end of tank/thrust structure is provided with rocket engines and exit nozzles with a trunnion supporting the tank/thrust structure within the aeroshell
Entanglement entropy and differential entropy for massive flavors
In this paper we compute the holographic entanglement entropy for massive
flavors in the D3-D7 system, for arbitrary mass and various entangling region
geometries. We show that the universal terms in the entanglement entropy
exactly match those computed in the dual theory using conformal perturbation
theory. We derive holographically the universal terms in the entanglement
entropy for a CFT perturbed by a relevant operator, up to second order in the
coupling; our results are valid for any entangling region geometry. We present
a new method for computing the entanglement entropy of any top-down brane probe
system using Kaluza-Klein holography and illustrate our results with massive
flavors at finite density. Finally we discuss the differential entropy for
brane probe systems, emphasising that the differential entropy captures only
the effective lower-dimensional Einstein metric rather than the ten-dimensional
geometry.Comment: 54 pages, 8 figures; v2 references and comments adde
Entanglement entropy in top-down models
We explore holographic entanglement entropy in ten-dimensional supergravity
solutions. It has been proposed that entanglement entropy can be computed in
such top-down models using minimal surfaces which asymptotically wrap the
compact part of the geometry. We show explicitly in a wide range of examples
that the holographic entanglement entropy thus computed agrees with the
entanglement entropy computed using the Ryu-Takayanagi formula from the
lower-dimensional Einstein metric obtained from reduction over the compact
space. Our examples include not only consistent truncations but also cases in
which no consistent truncation exists and Kaluza-Klein holography is used to
identify the lower-dimensional Einstein metric. We then give a general proof,
based on the Lewkowycz-Maldacena approach, of the top-down entanglement entropy
formula.Comment: 40 page
Fundamental constraints on particle tracking with optical tweezers
A general quantum limit to the sensitivity of particle position measurements
is derived following the simple principle of the Heisenberg microscope. The
value of this limit is calculated for particles in the Rayleigh and Mie
scattering regimes, and with parameters which are relevant to optical tweezers
experiments. The minimum power required to observe the zero-point motion of a
levitating bead is also calculated, with the optimal particle diameter always
smaller than the wavelength. We show that recent optical tweezers experiments
are within two orders of magnitude of quantum limited sensitivity, suggesting
that quantum optical resources may soon play an important role in high
sensitivity tracking applications
Digital computing cardiotachometer
A tachometer is described which instantaneously measures heart rate. During the two intervals between three succeeding heart beats, the electronic system: (1) measures the interval by counting cycles from a fixed frequency source occurring between the two beats; and (2) computes heat rate during the interval between the next two beats by counting the number of times that the interval count must be counted to zero in order to equal a total count of sixty times (to convert to beats per minute) the frequency of the fixed frequency source
Cardiotachometer displays heart rate on a beat-to-beat basis
Electronics for this system may be chosen so that complete calculation and display may be accomplished in a few milliseconds, far less than even the fastest heartbeat interval. Accuracy may be increased, if desired, by using higher-frequency timing oscillator, although this will require large capacity registers at increased cost
Daze fasteners
A daze fastener system for connecting two or more structural elements wherein the structural elements and fastener parts have substantially different coefficient of thermal expansion physical property characteristics is employed in this invention. By providing frusto-conical abutting surfaces between the structural elements and fastener parts any differences in thermal expansion/contraction between the parts is translated to sliding motion and avoids deleterious thermal stresses in the connection. An essential feature for isotropic homogeneous material connections is that at least two sets of mating surfaces are required wherein each set of mating surfaces have line element extensions that pass through a common point
Modeling and control of a plastic film manufacturing web process
This paper is concerned with the modelling of aplastic film manufacturing process and the development and implementation of a model-based Cross-Directional (CD) controller. The model is derived from first-principles and some empirical relationships. The final validated nonlinear model could provide a useful off-line platform for developing control and monitoring algorithms.A new controller is designed which has a similar structureto that of Internal Model Control (IMC) with the addition ofan observer whose gain is designed to minimise process andmodel mis-match. The observer gain is obtained by solving amulti-objective optimisation problem through the application of a genetic algorithm. The controller is applied to the nonlinear model and simulation results are presented demonstrating improvements that can be achieved by the proposed controller over two existing CD controllers
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