1,801 research outputs found
The 32nd CDC: Robust stabilizer synthesis for interval plants using Nevanlina-pick theory
The synthesis of robustly stabilizing compensators for interval plants, i.e., plants whose parameters vary within prescribed ranges is discussed. Well-known H(sup infinity) methods are used to establish robust stabilizability conditions for a family of plants and also to synthesize controllers that would stabilize the whole family. Though conservative, these methods give a very simple way to come up with a family of robust stabilizers for an interval plant
Force Distributions in Frictional Granular Media
We report a joint experimental and theoretical investigation of the
probability distribution functions (pdf's) of the normal and tangential
(frictional) forces in amorphous frictional media. We consider both the joint
pdf of normal and tangential forces together, and the marginal pdf's of normal
forces separately and tangential forces separately. A maximum entropy formalism
is utilized for all these cases after identifying the appropriate constraints.
Excellent agreements with both experimental and simulational data are reported.
The proposed joint pdf (which appears new to the literature) predicts giant
slip events at low pressures, again in agreement with observations.Comment: 13 pages, 15 figure
Negative forms and path space forms
We present an account of negative differential forms within a natural
algebraic framework of differential graded algebras, and explain their
relationship with forms on path spaces.Comment: 12 pp.; the Introduction has been rewritten and mention of cohomology
dropped in Proposition 3.2; material slightly reorganize
Theoretical Study of Physisorption of Nucleobases on Boron Nitride Nanotubes: A New Class of Hybrid Nano-Bio Materials
We investigate the adsorption of the nucleic acid bases, adenine (A), guanine
(G), cytosine (C), thymine (T) and uracil (U) on the outer wall of a high
curvature semiconducting single-walled boron nitride nanotube (BNNT) by first
principles density functional theory calculations. The calculated binding
energy shows the order: G>A\approxC\approxT\approxU implying that the
interaction strength of the (high-curvature) BNNT with the nucleobases, G being
an exception, is nearly the same. A higher binding energy for the G-BNNT
conjugate appears to result from a stronger hybridization of the molecular
orbitals of G and BNNT, since the charge transfer involved in the physisorption
process is insignificant. A smaller energy gap predicted for the G-BNNT
conjugate relative to that of the pristine BNNT may be useful in application of
this class of biofunctional materials to the design of the next generation
sensing devices.Comment: 17 pages 6 figure
Achieving minimum-error discrimination of an arbitrary set of laser-light pulses
Laser light is widely used for communication and sensing applications, so the
optimal discrimination of coherent states--the quantum states of light emitted
by a laser--has immense practical importance. However, quantum mechanics
imposes a fundamental limit on how well different coher- ent states can be
distinguished, even with perfect detectors, and limits such discrimination to
have a finite minimum probability of error. While conventional optical
receivers lead to error rates well above this fundamental limit, Dolinar found
an explicit receiver design involving optical feedback and photon counting that
can achieve the minimum probability of error for discriminating any two given
coherent states. The generalization of this construction to larger sets of
coherent states has proven to be challenging, evidencing that there may be a
limitation inherent to a linear-optics-based adaptive measurement strategy. In
this Letter, we show how to achieve optimal discrimination of any set of
coherent states using a resource-efficient quantum computer. Our construction
leverages a recent result on discriminating multi-copy quantum hypotheses
(arXiv:1201.6625) and properties of coherent states. Furthermore, our
construction is reusable, composable, and applicable to designing
quantum-limited processing of coherent-state signals to optimize any metric of
choice. As illustrative examples, we analyze the performance of discriminating
a ternary alphabet, and show how the quantum circuit of a receiver designed to
discriminate a binary alphabet can be reused in discriminating multimode
hypotheses. Finally, we show our result can be used to achieve the quantum
limit on the rate of classical information transmission on a lossy optical
channel, which is known to exceed the Shannon rate of all conventional optical
receivers.Comment: 9 pages, 2 figures; v2 Minor correction
Successful inoculation of Artemia and production of cysts in the coastal saltpans of Bangladesh II
Bangladesh has no naturally occurring Artemia, and all the growing shrimp hatcheries of the country depend entirely on import of cysts from foreign countries. Following successful inoculation of Artemia and production of cysts for the first time in this country in a coastal saltpan (at Chanua, Banskhali) by the senior author (in 1989-90), a similar second attempt was made under this programme in a saltpan (1000 m super(2)) of Demoshia, Chakaria, Cox's Bazar, Bangladesh between January and April 1992. A total of 1639.9 g (dry weight) of cysts (i.e. 5.46 kg DW/ha/month) have been produced using the Red Jungle Brand, whereas the previous attempt obtained 517 g of cysts (i.e. 2.07 kg DW/ha/month) using the Great Salt Lake Brand
Linear optics and photodetection achieve near-optimal unambiguous coherent state discrimination
Coherent states of the quantum electromagnetic field, the quantum description
of ideal laser light, are prime candidates as information carriers for optical
communications. A large body of literature exists on their quantum-limited
estimation and discrimination. However, very little is known about the
practical realizations of receivers for unambiguous state discrimination (USD)
of coherent states. Here we fill this gap and outline a theory of USD with
receivers that are allowed to employ: passive multimode linear optics,
phase-space displacements, auxiliary vacuum modes, and on-off photon detection.
Our results indicate that, in some regimes, these currently-available optical
components are typically sufficient to achieve near-optimal unambiguous
discrimination of multiple, multimode coherent states.Comment: 18 pages, 10 figures, and 2 tables. Appendices included. Additional
references added. Comments welcome
Gravitational wave bursts from cosmic (super)strings: Quantitative analysis and constraints
We discuss data analysis techniques that can be used in the search for
gravitational wave bursts from cosmic strings. When data from multiple
interferometers are available, we describe consistency checks that can be used
to greatly reduce the false alarm rates. We construct an expression for the
rate of bursts for arbitrary cosmic string loop distributions and apply it to
simple known solutions. The cosmology is solved exactly and includes the
effects of a late-time acceleration. We find substantially lower burst rates
than previous estimates suggest and explain the disagreement. Initial LIGO is
unlikely to detect field theoretic cosmic strings with the usual loop sizes,
though it may detect cosmic superstrings as well as cosmic strings and
superstrings with non-standard loop sizes (which may be more realistic). In the
absence of a detection, we show how to set upper limits based on the loudest
event. Using Initial LIGO sensitivity curves, we show that these upper limits
may result in interesting constraints on the parameter space of theories that
lead to the production of cosmic strings.Comment: Replaced with version accepted for publication in PR
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