18,962 research outputs found

    Brave New World: Can We Engineer a Better Start for Freshers?

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    Abstract - The crucial importance of first experiences in shaping future success has been widely acknowledged. Creating the best foundations in large cohorts of students from diverse backgrounds presents special problems of its own. But a secure foundation can enhance student achievement and improve retention – and the students may even have fun too. Research has suggested that building learning communities can enhance student engagement and achievement. This paper examines how introducing non-technical activities can establish sound foundations for a university career by a) addressing objectives in the wider curriculum and b) promoting non-technical skills and experience of group working. A set of changes introduced to five degree cohorts in our academic school were designed to complement enhancements to our technical curriculum introduced during many years of debate and consideration. The changes have impacted upon generic and technical educational experiences. The paper presents an evaluation of the programme of changes through two iterations from the perspective of both faculty and student

    Acoustical Society Of America Helmholtz-Rayleigh Interdisciplinary Silver Medal In Physical Acoustics, Biomedical Acoustics, And Engineering Acoustics: Armen Sarvazyan

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    The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics

    The effect of combined glutamate receptor blockade in the NTS on the hypoxic ventilatory response in awake rats differs from the effect of individual glutamate receptor blockade.

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    Ventilatory acclimatization to hypoxia (VAH) increases the hypoxic ventilatory response (HVR) and causes persistent hyperventilation when normoxia is restored, which is consistent with the occurrence of synaptic plasticity in acclimatized animals. Recently, we demonstrated that antagonism of individual glutamate receptor types (GluRs) within the nucleus tractus solitarii (NTS) modifies this plasticity and VAH (J. Physiol. 592(8):1839-1856); however, the effects of combined GluR antagonism remain unknown in awake rats. To evaluate this, we exposed rats to room air or chronic sustained hypobaric hypoxia (CSH, PiO2 = 70 Torr) for 7-9 days. On the experimental day, we microinjected artificial cerebrospinal fluid (ACSF: sham) and then a "cocktail" of the GluR antagonists MK-801 and DNQX into the NTS. The location of injection sites in the NTS was confirmed by glutamate injections on a day before the experiment and with histology following the experiment. Ventilation was measured in awake, unrestrained rats breathing normoxia or acute hypoxia (10% O2) in 15-min intervals using barometric pressure plethysmography. In control (CON) rats, acute hypoxia increased ventilation; NTS microinjections of GluR antagonists, but not ACSF, significantly decreased ventilation and breathing frequency in acute hypoxia but not normoxia (P < 0.05). CSH increased ventilation in hypoxia and acute normoxia. In CSH-conditioned rats, GluR antagonists in the NTS significantly decreased ventilation in normoxia and breathing frequency in hypoxia. A persistent HVR after combined GluR blockade in the NTS contrasts with the effect of individual GluR blockade and also with results in anesthetized rats. Our findings support the hypotheses that GluRs in the NTS contribute to, but cannot completely explain, VAH in awake rats

    Dynamic airfoil stall investigations

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    Experimental and computational investigations of the dynamic stall phenomenon continue to attract the attention of various research groups in the major aeronautical research laboratories. There are two reasons for this continued research interest. First, the occurrence of dynamic stall on the retreating blade of helicopters imposes a severe performance limitation and thus suggests to search for ways to delay the onset of dynamic stall. Second, the lift enhancement prior to dynamic stall presents an opportunity to achieve enhanced maneuverability of fighter aircraft. A description of the major parameters affecting dynamic stall and lift and an evaluation of research efforts prior to 1988 has been given by Carr. In this paper the authors' recent progress in the development of experimental and computational methods to analyze the dynamic stall phenomena occurring on NACA 0112 airfoils is reviewed. First, the major experimental and computational approaches and results are summarized. This is followed by an assessment of our results and an outlook toward the future

    Quantum phase transitions in the Fermi-Bose Hubbard model

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    We propose a multi-band Fermi-Bose Hubbard model with on-site fermion-boson conversion and general filling factor in three dimensions. Such a Hamiltonian models an atomic Fermi gas trapped in a lattice potential and subject to a Feshbach resonance. We solve this model in the two state approximation for paired fermions at zero temperature. The problem then maps onto a coupled Heisenberg spin model. In the limit of large positive and negative detuning, the quantum phase transitions in the Bose Hubbard and Paired-Fermi Hubbard models are correctly reproduced. Near resonance, the Mott states are given by a superposition of the paired-fermion and boson fields and the Mott-superfluid borders go through an avoided crossing in the phase diagram.Comment: 4 pages, 3 figure

    Tunable tunneling: An application of stationary states of Bose-Einstein condensates in traps of finite depth

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    The fundamental question of how Bose-Einstein condensates tunnel into a barrier is addressed. The cubic nonlinear Schrodinger equation with a finite square well potential, which models a Bose-Einstein condensate in a quasi-one-dimensional trap of finite depth, is solved for the complete set of localized and partially localized stationary states, which the former evolve into when the nonlinearity is increased. An immediate application of these different solution types is tunable tunneling. Magnetically tunable Feshbach resonances can change the scattering length of certain Bose-condensed atoms, such as 85^{85}Rb, by several orders of magnitude, including the sign, and thereby also change the mean field nonlinearity term of the equation and the tunneling of the wavefunction. We find both linear-type localized solutions and uniquely nonlinear partially localized solutions where the tails of the wavefunction become nonzero at infinity when the nonlinearity increases. The tunneling of the wavefunction into the non-classical regime and thus its localization therefore becomes an external experimentally controllable parameter.Comment: 11 pages, 5 figure

    Bose-Einstein condensates with attractive interactions on a ring

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    Considering an effectively attractive quasi-one-dimensional Bose-Einstein condensate of atoms confined in a toroidal trap, we find that the system undergoes a phase transition from a uniform to a localized state, as the magnitude of the coupling constant increases. Both the mean-field approximation, as well as a diagonalization scheme are used to attack the problem.Comment: 4 pages, 4 ps figures, RevTex, typographic errors correcte

    Macroscopic quantum tunnelling of Bose-Einstein condensates in a finite potential well

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    Bose-Einstein condensates are studied in a potential of finite depth which supports both bound and quasi-bound states. This potential, which is harmonic for small radii and decays as a Gaussian for large radii, models experimentally relevant optical traps. The nonlinearity, which is proportional to both the number of atoms and the interaction strength, can transform bound states into quasi-bound ones. The latter have a finite lifetime due to tunnelling through the barriers at the borders of the well. We predict the lifetime and stability properties for repulsive and attractive condensates in one, two, and three dimensions, for both the ground state and excited soliton and vortex states. We show, via a combination of the variational and WKB approximations, that macroscopic quantum tunnelling in such systems can be observed on time scales of 10 milliseconds to 10 seconds.Comment: J. Phys. B: At. Mol. Opt. Phys. in pres

    Relativistic linear stability equations for the nonlinear Dirac equation in Bose-Einstein condensates

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    We present relativistic linear stability equations (RLSE) for quasi-relativistic cold atoms in a honeycomb optical lattice. These equations are derived from first principles and provide a method for computing stabilities of arbitrary localized solutions of the nonlinear Dirac equation (NLDE), a relativistic generalization of the nonlinear Schr\"odinger equation. We present a variety of such localized solutions: skyrmions, solitons, vortices, and half-quantum vortices, and study their stabilities via the RLSE. When applied to a uniform background, our calculations reveal an experimentally observable effect in the form of Cherenkov radiation. Remarkably, the Berry phase from the bipartite structure of the honeycomb lattice induces a boson-fermion transmutation in the quasi-particle operator statistics.Comment: 6 pages, 3 figure

    Exploring efficacy in personal constraint negotiation: an ethnography of mountaineering tourists

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    Limited work has explored the relationship between efficacy and personal constraint negotiation for adventure tourists, yet efficacy is pivotal to successful activity participation as it influences people’s perceived ability to cope with constraints, and their decision to use negotiation strategies. This paper explores these themes with participants of a commercially organised mountaineering expedition. Phenomenology-based ethnography was adopted to appreciate the social and cultural mountaineering setting from an emic perspective. Ethnography is already being used to understand adventure participation, yet there is considerable scope to employ it further through researchers immersing themselves into the experience. The findings capture the interaction between the ethnographer and the group members, and provide an embodied account using their lived experiences. Findings reveal that personal mountaineering skills, personal fitness, altitude sickness and fatigue were the four key types of personal constraint. Self-efficacy, negotiation-efficacy and other factors, such as hardiness and motivation, influenced the effectiveness of negotiation strategies. Training, rest days, personal health, and positive self-talk were negotiation strategies. A conceptual model illustrates these results and demonstrates the interplay between efficacy and the personal constraint negotiation journey for led mountaineers
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