3,365 research outputs found
Enhanced algorithm of image mapping method for computer-generated integral imaging system
No full text
Multi-centre assessment of the Spiegelberg compliance monitor: interim results
No full textY Yau, I Piper, C Contant, G Citerio, K Kiening, P Enblad, P Nilsson, S Ng, J Wasserberg, M Kiefer, W Poon, L Dunn, I Whittlehttp://lib.bioinfo.pl/pmid:1216829
Estimation of on-road PM₂.₅ distributions by combining satellite top-of-atmosphere with microscale geographic predictors for healthy route planning
No full text202505 bcchVersion of RecordOthersNational Key R&D Program of China (2019YFB2103102); Otto Poon Charitable Foundation Smart Cities Research Institute; The Hong Kong Polytechnic University (Work Program: CD03)PublishedC
Physics of the flow of concentrated suspensions
Get PDFA particulate suspension under shear is a classic example of a system driven out
of equilibrium. While it is possible to predict the equilibrium phase behaviour of
a quiescent suspension, linking microscopic details to bulk properties under flow
remains an open challenge. Our current understanding of sheared suspensions is
restricted to two disparate regimes, the colloidal regime, for particle sizes d < 1
μm and the granular regime, for d > 50 μm. The physics of the industrially-relevant
intermediate size regime, 1 μm ≲ d ≲ 50 μm, is unclear and has not
been explored previously.
In this thesis, we use conventional rheometry on a range of model spheres to
develop the foundations of a predictive understanding of suspension flow across
the entire size spectrum. In the first part of the thesis, we show that in repulsive
particulate systems the rheology is characterised by two viscosity "branches"
diverging at different volume fractions ϕRCP and ϕm, which represent states of
flow with lubricated (frictionless) and frictional interactions between particles.
In the intermediate size regime, there is a transition between these two branches
above a critical onset stress σ* which manifests as shear thickening. This σ* is
related to a barrier (invariably due to the charge or steric stabilisation) keeping
particle surfaces apart. Our data are quantitatively fit by the Wyart and Cates
theory for frictional thickening [1] if we assume that probability distribution of
forces in the system is similar to in dry granular media.
The onset stress for shear thickening is found to decrease with the inverse square of
the particle size σ* / d¯ ² for diverse systems. We show that it is the competition
between the scaling of σ*(d) and the size dependence of the entropic stress scale (~
d¯ ³) that controls the crossover from colloidal to granular rheology with increasing
size. Granular systems are "always shear thickened" under typical experimental
conditions, while colloidal systems are always in a frictionless state. In the second part of the thesis, we explore the validity of the frictional
framework for shear thickening. Although it quantitatively predicts our steady-state
rheology, the frictional framework contradicts traditional fluid-mechanical
thinking and has yet to be rigorously tested experimentally. In fact, there is a
large body of literature that attributes thickening to purely hydrodynamic effects.
Using dimensional analysis and simple physical arguments we examine possible
physical origins for thickening and show that previously-proposed mechanisms
can be subdivided into three types: two-particle hydrodynamic thickening,
many-particle hydrodynamic thickening ("hydroclusters") and frictional-contact
driven thickening. Many of these mechanisms can are inconsistent with the
experimental two-branch phenomenology and can be disregarded. We further
narrow down possible causes of thickening using the technique of flow reversal,
which disentangles the relative contributions of contact and hydrodynamic forces
to the viscosity. Consistent with recent simulations [2] and theory [1], we find
that in each case thickening is dominated by the formation of frictional contacts
and that hydrodynamic thickening, if present, is subdominant
Ge-implantation-enhanced defect-state absorption in C-band silicon waveguide photodiode monitors
No full textWe demonstrate Ge-implantation-enhanced defect-state absorption in the C-band in a 225-μm-long silicon waveguide photodiode, with a responsivity of ~54.8 mA/W/mm and a 1 nA dark current upon -3 V bias after a 10-minute 350°C annealing.</p
Resilience and longevity: expert survivorship of centenarians
Get PDFCentenarians are survivors, and many among them exemplify sustained competence into very old age. This paper highlights three important resilience domains among centenarians: personal resilience (e.g., personality), cognitive resilience (e.g., intellectual functioning), and social and economic resilience (e.g., social support and economic resources).This chapter is published as Martin, P., MacDonald, M., Margrett, J. A., & Poon, L. W. (2010). Resilience among the oldest-old. In P. S. Fry & C. L. M. Keyes (Eds.), Frontiers of Resilient Aging, 213-238. Cambridge University Press. Posted with permission.</p
Air quality during the 2008 Beijing Olympics : secondary pollutants and regional impact
No full textAuthor name used in this publication: Wang T.Author name used in this publication: Nie, W.Author name used in this publication: Gao, J.Author name used in this publication: Xue, L. K.Author name used in this publication: Gao, X. M.Author name used in this publication: Wang, X. F.Author name used in this publication: Qiu, J.Author name used in this publication: Poon, C. N.Author name used in this publication: Meinardi, S.Author name used in this publication: Blake, D.Author name used in this publication: Wang, S. L.Author name used in this publication: Ding, A. J.Author name used in this publication: Chai, F. H.Author name used in this publication: Zhang, Q. Z.Author name used in this publication: Wang, W. X.2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedC
Dialkoxyosmium(IV) Porphrins. Crystal and Molecular Structures of Diethoxy-, Diphenoxy-, and Bis(2-propanolato)(meso-tetraphenyl-porphrinato)osmium(IV)
No full textGe-implantation-enhanced defect-state absorption in C-band silicon waveguide photodiode monitors
No full textWe demonstrate Ge-implantation-enhanced defect-state absorption in the C-band in a 225-μm-long silicon waveguide photodiode, with a responsivity of ~54.8 mA/W/mm and a 1 nA dark current upon -3 V bias after a 10-minute 350̊C annealing.</p
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