17,703 research outputs found
Two-state shear diagrams for complex fluids in shear flow
The possible "phase diagrams'' for shear-induced phase transitions between two phases are collected. We consider shear-thickening and shear-thinning fluids, under conditions of both common strain rate and common stress in the two phases, and present the four fundamental shear stress vs. strain rate curves and discuss their concentration dependence. We outline how to construct more complicated phase diagrams, discuss in which class various experimental systems fall, and sketch how to reconstruct the phase diagrams from rheological measurements
Local density of states in the vortex lattice in a type II superconductor
Local density of states (LDOS) in the triangular vortex lattice is
investigated based on the quasi-classical Eilenberger theory. We consider the
case of an isotropic s-wave superconductor with the material parameter
appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the
LDOS shows cylindrical structure around a vortex core. On the other hand, at a
high field where the core regions substantially overlap each other, the LDOS is
sixfold star-shaped structure due to the vortex lattice effect. The orientation
of the star coincides with the experimental data of the scanning tunneling
microscopy. That is, the ray of the star extends toward the nearest-neighbor
(next nearest-neighbor) vortex direction at higher (lower) energy.Comment: 10 pages, RevTex, 32 figure
Subwavelength localization and toroidal dipole moment of spoof surface plasmon polaritons
We experimentally and theoretically demonstrate subwavelength scale localization of spoof surface plasmon polaritons at a point defect in a two-dimensional groove metal array. An analytical expression for dispersion relation of spoof surface plasmon polaritons substantiates the existence of a band gap where a defect mode can be introduced. A waveguide coupling method allows us to excite localized spoof surface plasmon polariton modes and measure their resonance frequencies. Numerical calculations confirm that localized modes can have a very small modal volume and a high Q factor both of which are essential in enhancing light-matter interactions. Interestingly, we find that the localized spoof surface plasmon polariton has a significant toroidal dipole moment, which is responsible for the high Q factor, as well as an electric quadrupole moment. In addition, the dispersion properties of spoof surface plasmon polaritons are analyzed using a modal expansion method and numerical calculations
The Importance of College Student Academic Goals: A Symbolic Interactionist Approach
A cross-sectional study of a sample of first and second year students attending a moderately-sized, Great Plains university is used to demonstrate the correlation between academic self-conceptions and academic goals. Multiple regression analysis shows that academic self-conceptions, academic role-taking, job goals, being a parent, and having a Job are excellent predictors of academic goals. The authors recommend that the symbolic interactionist perspective used in the study should be used to study how academic goals link academic self-conceptions with academic behaviors and outcomes
An intelligent, free-flying robot
The ground based demonstration of the extensive extravehicular activity (EVA) Retriever, a voice-supervised, intelligent, free flying robot, is designed to evaluate the capability to retrieve objects (astronauts, equipment, and tools) which have accidentally separated from the Space Station. The major objective of the EVA Retriever Project is to design, develop, and evaluate an integrated robotic hardware and on-board software system which autonomously: (1) performs system activation and check-out; (2) searches for and acquires the target; (3) plans and executes a rendezvous while continuously tracking the target; (4) avoids stationary and moving obstacles; (5) reaches for and grapples the target; (6) returns to transfer the object; and (7) returns to base
Consensual Qualitative Research: An Update
The authors reviewed the application of consensual qualitative research (CQR) in 27 studies published since the method’s introduction to the field in 1997 by C. E. Hill, B. J. Thompson, and E. N. Williams (1997). After first describing the core components and the philosophical underpinnings of CQR, the authors examined how it has been applied in terms of the consensus process, biases, research teams, data collection, data analysis, and writing up the results and discussion sections of articles. On the basis of problems that have arisen in each of these areas, the authors made recommendations for modifications of the method. The authors concluded that CQR is a viable qualitative method and suggest several ideas for research on the method itself
Experiments and numerical results on nonlinear vibrations of an impacting hertzian contact. Part 2: random excitation
Non linear dynamic behaviour of a normally excited preloaded Hertzian contact
(including possible contact losses) is investigated using an experimental test
rig. It consists on a double sphere plane contact loaded by the weight of a
rigid moving mass. Contact vibrations are generated by a external Gaussian
white noise and exhibit vibroimpact responses when the input level is
sufficiently high. Spectral contents and statistics of the stationary
transmitted normal force are analysed. A single-degree-of-freedom non linear
oscillator including loss of contact and Hertzian non linearities is built for
modelling the experimental system. Theoretical responses are obtained by using
the stationary Fokker-Planck equation and also Monte Carlo simulations. When
contact loss occurrence is very occasional, numerical results shown a very good
agreement with experimental ones. When vibroimpacts occur, results remain in
reasonable agreement with experimental ones, that justify the modelling and the
numerical methods described in this paper. The contact loss non linearity
appears to be rather strong compared to the Hertzian non linearity. It actually
induces a large broadening of the spectral contents of the response. This
result is of great importance in noise generation for a lot of systems such as
mechanisms using contacts to transform motions and forces (gears,
ball-bearings, cam systems, to name a few). It is also of great importance for
tribologists preoccupied to prevent surface dammage
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Complete Genome Sequence of the Citrobacter freundii Type Strain.
Citrobacter freundii is a species of facultative anaerobic Gram-negative bacteria of the family Enterobacteriaceae The complete genome is composed of a single chromosomal circle of 4,957,773 bp with a G+C content of 52%
Importance of maintained atrio-ventricular synchrony in patients with pacemarkers
The effect of atrial contraction on cardiac function is reviewed in patients with dual chamber and rate-responsive ventricular pacemakers. The question posed was is there any haemodynamic, clinical or prognostic advantage of AV synchrony in dual chamber pacemakers in comparison to rate-responsive ventricular pacemakers? Optimal A V delay in dual chamber pacing favours cardiac performance at rest, while during exercise the increase in heart rate rather than A V synchrony influences cardiac performance and working capacity. However, there is little information on the benefit of maintained A V synchrony in patients' daily activities. Patients with pacemakers which maintain AV synchrony seem to have less morbidity and mortality than patients with ventricular stimulation alone, and there are comparable rates of complication in carriers of single and dual chamber pacemakers, the former showing problems with the pacemaker syndrome and the latter with atrial sensing and pacemaker-induced tachycardias. The disadvantage of dual chamber pacemakers are higher costs and time-consuming control
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