3,442 research outputs found
Terminal area guidance along curved paths: A stochastic control approach
Stochastic control theory is applied to the problem of designing a digital flight compensator for terminal guidance along a helical flight path as a prelude to landing. The development of aircraft, wind, and measurement models is discussed along with a control scheme consisting of feedback gains multiplying estimate of the aircraft and wind states obtained from a Kalman one step predictor. Preliminary results are presented which indicate that the compensator performs satisfactorily in the presence of both steady winds and gusts
Beyond "the Relationship between the Individual and Society": broadening and deepening relational thinking in group analysis
The question of âthe relationship between the individual and societyâ has troubled group analysis since its inception. This paper offers a reading of Foulkes that highlights the emergent, yet evanescent, psychosocial ontology in his writings, and argues for the development of a truly psychosocial group analysis, which moves beyond the individual/society dualism. It argues for a shift towards a language of relationality, and proposes new theoretical resources for such a move from relational sociology, relational psychoanalysis and the âmatrixial thinkingâ of Bracha Ettinger which would broaden and deepen group analytic understandings of relationality
The effect of quantization on the FCIQMC sign problem
The sign problem in Full Configuration Interaction Quantum Monte Carlo
(FCIQMC) without annihilation can be understood as an instability of the
psi-particle population to the ground state of the matrix obtained by making
all off-diagonal elements of the Hamiltonian negative. Such a matrix, and hence
the sign problem, is basis dependent. In this paper we discuss the properties
of a physically important basis choice: first versus second quantization. For a
given choice of single-particle orbitals, we identify the conditions under
which the fermion sign problem in the second quantized basis of antisymmetric
Slater determinants is identical to the sign problem in the first quantized
basis of unsymmetrized Hartree products. We also show that, when the two
differ, the fermion sign problem is always less severe in the second quantized
basis. This supports the idea that FCIQMC, even in the absence of annihilation,
improves the sign problem relative to first quantized methods. Finally, we
point out some theoretically interesting classes of Hamiltonians where first
and second quantized sign problems differ, and others where they do not.Comment: 4 pages w/ 2 page appendix, 2 figures, 1 tabl
Breeding for improved nitrogen use efficiency in oilseed rape
Oilseed rape has a high requirement for nitrogen (N) fertiliser relative to its seed yield. This paper uses published and unpublished work to explore the extent to which the N use efficiency (seed yield Ă· N supply) of oilseed rape could be improved without reducing seed yield. It was estimated that if the concentration of N in the stem and pod wall at crop maturity could be reduced from 1.0 to 0.6%, the root length density increased to 1 cm/cm3 to 100 cm soil depth and the post flowering N uptake increased by 20 kg N/ha then the fertiliser requirement could be reduced from 191 to 142 kg N/ha and the N use efficiency could be increased from 15.2 to 22.4 kg of seed dry matter per kg N. Genetic variation was found for all of the traits that were estimated to be important for N use efficiency. This indicates that there is significant scope for plant breeders to reduce N use efficiency in oilseed rape
Control augmentation for lateral control wheel steering
Flight control system design for lateral control wheel steering is discussed. Two alternate designs are presented. The first design is a roll-rate command, bank-angle hold system with a wings-level track-hold submode. The second is a curved-track-hold system. Design details and real-time flight simulator results are included
Using a model of group psychotherapy to support social research on sensitive topics
This article describes the exploratory use of professional therapeutic support by social researchers working on a sensitive topic. Talking to recently bereaved parents about the financial implications of their child's death was expected to be demanding work, and the research design included access to an independent psychotherapeutic service. Using this kind of professional support is rare within the general social research community, and it is useful to reflect on the process. There are likely to be implications for collection and interpretation of data, research output and the role and experience of the therapist. Here, the primary focus is the potential impact on researcher well-being
On the Growth of Al_2 O_3 Scales
Understanding the growth of Al2O3 scales requires knowledge of the details of the chemical reactions at the scaleâgas and scaleâmetal interfaces, which in turn requires specifying how the creation/annihilation of O and Al vacancies occurs at these interfaces. The availability of the necessary electrons and holes to allow for such creation/annihilation is a crucial aspect of the scaling reaction. The electronic band structure of polycrystalline Al2O3 thus plays a decisive role in scale formation and is considered in detail, including the implications of a density functional theory (DFT) calculation of the band structure of a ÎŁ7 View the MathML source bicrystal boundary, for which the atomic structure of the boundary was known from an independent DFT energy-minimization calculation and comparisons with an atomic-resolution transmission electron micrograph of the same boundary. DFT calculations of the formation energy of O and Al vacancies in bulk Al2O3 in various charge states as a function of the Fermi energy suggested that electronic conduction in Al2O3 scales most likely involves excitation of both electrons and holes, which are localized on singly charged O vacancies, View the MathML source and doubly charged Al vacancies, View the MathML source, respectively. We also consider the variation of the Fermi level across the scale and bending (âtiltingâ) of the conduction band minimum and valence band maximum due to the electric field developed during the scaling reaction. The band structure calculations suggest a new mechanism for the âreactive elementâ effectâa consequence of segregation of Y, Hf, etc., to grain boundaries in Al2O3 scales, which results in improved oxidation resistanceânamely, that the effect is due to the modification of the near-band edge grain-boundary defect states rather than any blocking of diffusion pathways, as previously postulated. Secondly, Al2O3 scale formation is dominated by grain boundary as opposed to lattice diffusion, and there is unambiguous evidence for both O and Al countercurrent transport in Al2O3 scale-forming alloys. We postulate that such transport is mediated by migration of grain boundary disconnections containing charged jogs, rather than by jumping of isolated point defects in random high-angle grain boundaries
Can explicit training in Cued Speech improve phoneme identification?
When identifying phonemes in new spoken words, lipreading is an important source of information for many deaf people. Because many groups of phonemes are virtually indistinguishable by sight, deaf people are able to identify about 30% of phonemes when lipreading non-words. Cued speech (CS) is a system of hand shapes and hand positions used alongside speech to disambiguate similarities in lip patterns. Deaf children exposed to CS from under 3 years of age go on to develop age-appropriate language and literacy skills. However, there are no studies evaluating the explicit training of CS with older deaf children. This study is the first part of a long-term project to develop and evaluate a computer-delivered programme to teach school-aged deaf children to recognize cued phonemes. Sixty-two adult hearing participants were allocated to a single training session in one of three training conditions: cued speech training (CST), lipreading training and auditory training in noise. They were all tested on their ability to identify 13 phonemes in non-words when denied access to sound. The CST group made highly significant improvements in identifying cued phonemes and these changes could not be explained by lipreading practice or familiarization with a closed set of phonemes. Improvements generalized to non-words that were not used in training. This suggests that explicit training in CS could help deaf children to identify cued phonemes in new words. Practical implications of introducing the teaching of CS to selected deaf children are discussed
A Quantum-Quantum Metropolis Algorithm
Recently, the idea of classical Metropolis sampling through Markov chains has
been generalized for quantum Hamiltonians. However, the underlying Markov chain
of this algorithm is still classical in nature. Due to Szegedy's method, the
Markov chains of classical Hamiltonians can achieve a quadratic quantum speedup
in the eigenvalue gap of the corresponding transition matrix. A natural
question to ask is whether Szegedy's quantum speedup is merely a consequence of
employing classical Hamiltonians, where the eigenstates simply coincide with
the computational basis, making cloning of the classical information possible.
We solve this problem by introducing a quantum version of the method of
Markov-chain quantization combined with the quantum simulated annealing (QSA)
procedure, and describe explicitly a novel quantum Metropolis algorithm, which
exhibits a quadratic quantum speedup in the eigenvalue gap of the corresponding
Metropolis Markov chain for any quantum Hamiltonian. This result provides a
complete generalization of the classical Metropolis method to the quantum
domain.Comment: 7 page
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