99,000 research outputs found

### Comparative performance of double-focus and quadrupole mass spectrometers

Light-weight flight type double focus and quadruple mass spectrometer models were compared. Data cover size, weight, and power sensitivity required to achieve same resolution sensitivity at given mass number. Comparison was made using mathematical relationships. Analysis was confined to equal ion source area sensitivity variations not more than 40% over mass range

### Comparative performance of double focused and quadrupole mass spectrometers

Comparative performance analysis of double focused and quadrupole mass spectrometer

### Universal scaling behavior at the upper critical dimension of non-equilibrium continuous phase transitions

In this work we analyze the universal scaling functions and the critical
exponents at the upper critical dimension of a continuous phase transition. The
consideration of the universal scaling behavior yields a decisive check of the
value of the upper critical dimension. We apply our method to a non-equilibrium
continuous phase transition. But focusing on the equation of state of the phase
transition it is easy to extend our analysis to all equilibrium and
non-equilibrium phase transitions observed numerically or experimentally.Comment: 4 pages, 3 figure

### Gravity-driven draining of a thin rivulet with constant width down a slowly varying substrate

The locally unidirectional gravity-driven draining of a thin rivulet with constant width but slowly varying contact angle down a slowly varying substrate is considered. Specifically, the flow of a rivulet in the azimuthal direction from the top to the bottom of a large horizontal cylinder is investigated. In particular, it is shown that, despite behaving the same locally, this flow has qualitatively different global behaviour from that of a rivulet with constant contact angle but slowly varying width. For example, whereas in the case of constant contact angle there is always a rivulet that runs all the way from the top to the bottom of the cylinder, in the case of constant width this is possible only for sufficiently narrow rivulets. Wider rivulets with constant width are possible only between the top of the cylinder and a critical azimuthal angle on the lower half of the cylinder. Assuming that the contact lines de-pin at this critical angle (where the contact angle is zero) the rivulet runs from the critical angle to the bottom of the cylinder with zero contact angle, monotonically decreasing width and monotonically increasing maximum thickness. The total mass of fluid on the cylinder is found to be a monotonically increasing function of the value of the constant width

Recommended from our members

### Co-Created Personas: Engaging and Empowering Users with Diverse Needs Within the Design Process

Personas are powerful tools for designing technology and envisioning its usage. They are widely used to imagine archetypal users around whom to orient design work. We have been exploring co-created personas as a technique to use in co-design with users who have diverse needs. Our vision was that this would broaden the demographic and liberate co-designers of their personal relationship with a health condition. This paper reports three studies where we investigated using co-created personas with people who had Parkinson’s disease, dementia or aphasia. Observational data of co-design sessions were collected and analysed. Findings revealed that the co-created personas encouraged users with diverse needs to engage with co-designing. Importantly, they also aforded additional benefts including empowering users within a more accessible design process. Refecting on the outcomes from the diferent user groups, we conclude with a discussion of the potential for co-created personas to be applied more broadly

### Lattice $\phi^4$ theory of finite-size effects above the upper critical dimension

We present a perturbative calculation of finite-size effects near $T_c$ of
the $\phi^4$ lattice model in a $d$-dimensional cubic geometry of size $L$ with
periodic boundary conditions for $d > 4$. The structural differences between
the $\phi^4$ lattice theory and the $\phi^4$ field theory found previously in
the spherical limit are shown to exist also for a finite number of components
of the order parameter. The two-variable finite-size scaling functions of the
field theory are nonuniversal whereas those of the lattice theory are
independent of the nonuniversal model parameters.One-loop results for
finite-size scaling functions are derived. Their structure disagrees with the
single-variable scaling form of the lowest-mode approximation for any finite
$\xi/L$ where $\xi$ is the bulk correlation length. At $T_c$, the large-$L$
behavior becomes lowest-mode like for the lattice model but not for the
field-theoretic model. Characteristic temperatures close to $T_c$ of the
lattice model, such as $T_{max}(L)$ of the maximum of the susceptibility
$\chi$, are found to scale asymptotically as $T_c - T_{max}(L) \sim L^{-d/2}$,
in agreement with previous Monte Carlo (MC) data for the five-dimensional Ising
model. We also predict $\chi_{max} \sim L^{d/2}$ asymptotically. On a
quantitative level, the asymptotic amplitudes of this large -$L$ behavior close
to $T_c$ have not been observed in previous MC simulations at $d = 5$ because
of nonnegligible finite-size terms $\sim L^{(4-d)/2}$ caused by the
inhomogeneous modes. These terms identify the possible origin of a significant
discrepancy between the lowest-mode approximation and previous MC data. MC data
of larger systems would be desirable for testing the magnitude of the
$L^{(4-d)/2}$ and $L^{4-d}$ terms predicted by our theory.Comment: Accepted in Int. J. Mod. Phys.

### The Stokes boundary layer for a thixotropic or antithixotropic fluid

We present a mathematical investigation of the oscillatory boundary layer (‘Stokes layer’) in a semi-infinite fluid bounded by an oscillating wall (the socalled ‘Stokes problem’), when the fluid has a thixotropic or antithixotropic rheology. We obtain asymptotic solutions in the limit of small-amplitude oscillations, and we use numerical integration to validate the asymptotic solutions and to explore the behaviour of the system for larger-amplitude oscillations. The solutions that we obtain differ significantly from the classical solution for a Newtonian fluid. In particular, for antithixotropic fluids the velocity reaches zero at a finite distance from the wall, in contrast to the exponential decay for a thixotropic or a Newtonian fluid. For small amplitudes of oscillation, three regimes of behaviour are possible: the structure parameter may take values defined instantaneously by the shear rate, or by a long-term average; or it may behave hysteretically. The regime boundaries depend on the precise specification of structure build-up and breakdown rates in the rheological model, illustrating the subtleties of complex fluid models in non-rheometric settings. For larger amplitudes of oscillation the dominant behaviour is hysteretic. We discuss in particular the relationship between the shear stress and the shear rate at the oscillating wall

### Quantum Random Walks do not need a Coin Toss

Classical randomized algorithms use a coin toss instruction to explore
different evolutionary branches of a problem. Quantum algorithms, on the other
hand, can explore multiple evolutionary branches by mere superposition of
states. Discrete quantum random walks, studied in the literature, have
nonetheless used both superposition and a quantum coin toss instruction. This
is not necessary, and a discrete quantum random walk without a quantum coin
toss instruction is defined and analyzed here. Our construction eliminates
quantum entanglement from the algorithm, and the results match those obtained
with a quantum coin toss instruction.Comment: 6 pages, 4 figures, RevTeX (v2) Expanded to include relation to
quantum walk with a coin. Connection with Dirac equation pointed out. Version
to be published in Phys. Rev.

### The frictions of slow tourism mobilities: conceptualising campervan travel

This paper discusses the materialities of campervan travel as a relatively ‘slow’ form of tourism mobilities. The research is based upon qualitative research with campervan owners and users in the UK. Previous research has emphasised notions of freedom associated with campervan travel and how it has developed its own subculture. However, we seek to move beyond this to examine the frictions of socially and physically embodied practices of campervan travel in order to address the call for more multi-sensory understandings of tourism mobilities. In our discussion of campervan travel, mobility is understood as intensities of circulations, uncertainties and relational affects where different aspects of friction are central. We conclude by discussing the campervan in relation to wider aspects of slow travel

### Porous squeeze-film flow

The squeeze-film flow of a thin layer of Newtonian fluid filling the gap between a flat impermeable surface moving under a prescribed constant load and a flat thin porous bed coating a stationary flat impermeable surface is considered. Unlike in the classical case of an impermeable bed, in which an infinite time is required for the two surfaces to touch, for a porous bed contact occurs in a finite contact time. Using a lubrication approximation an implicit expression for the fluid layer thickness and an explicit expression for the contact time are obtained and analysed. In addition, the fluid particle paths are calculated, and the penetration depths of fluid particles into the porous bed are determined. In particular, the behaviour in the asymptotic limit of small permeability, in which the contact time is large but finite, is investigated. Finally, the results are interpreted in the context of lubrication in the human knee joint, and some conclusions are drawn about the contact time of the cartilage-coated femoral condyles and tibial plateau and the penetration of nutrients into the cartilage

- …