An experimental investigation on friction characteristics of air flow in microtube with structured surface roughness

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Experiments were conducted in this research to investigate roughness effect to flow characteristics and heat transfer coefficient of air and CO2 flow in circular micro-tubes. The internal surface of tested tube included smooth, structure helical fin surfaces and random roughness surfaces. Smooth tube is a commercial S. S. 304 tube with internal diameter of 962 μm and average roughness Ra=0.8 μm, while rough circular tubes were lab made Nickel tube with diameters ranging from 926 μm to 977 μm and roughness elements from 5.3 μm to 44.6 μm in height. The experimental results indicated that f and Nu in smooth tube was predicted very well by conventional correlations both for air and CO2. In rough tubes the friction factor was significant higher than the prediction of conventional correlations both in laminar and turbulent flow. Heat transfer enhancement in laminar flow is slightly, nevertheless, in turbulent flow the heat transfer enhancement was significant and the enhancement increases with the increasing of Re. The random rough tubes revealed a higher heat transfer enhancement than the structured helical fin tubes

Experimental observation of chiral phonons in monolayer WSe2

Chirality characterizes an object that is not identical to its mirror image. In condensed matter physics, Fermions have been demonstrated to obtain chirality through structural and time-reversal symmetry breaking. These systems display unconventional electronic transport phenomena such as the quantum Hall effect and Weyl semimetals. However, for bosonic collective excitations in atomic lattices, chirality was only theoretically predicted and has never been observed. We experimentally show that phonons can exhibit intrinsic chirality in monolayer tungsten diselenide, whose lattice breaks the inversion symmetry and enables inequivalent electronic K and -K valley states. The time-reversal symmetry is also broken when we selectively excite the valley polarized holes by circularly polarized light. Brillouin-zone-boundary phonons are then optically created by the indirect infrared absorption through the hole-phonon interactions. The unidirectional intervalley transfer of holes ensures that only the phonon modes in one valley are excited. We found that such photons are chiral through the transient infrared circular dichroism, which proves the valley phonons responsible to the indirect absorption has non-zero pseudo-angular momentum. From the spectrum we further deduce the energy transferred to the phonons that agrees with both the first principle calculation and the double-resonance Raman spectroscopy. The chiral phonons have significant implications for electron-phonon coupling in solids, lattice-driven topological states, and energy efficient information processing

Dual use of LED traffic signal system

The dual use, signaling and communication, of LED traffic signal system is described and analyzed. The primary function of a traffic light system is to give traffic and pedestrian signals. A prototype of LED traffic signal head is developed to perform a secondary function: communication. A wireless communication link is set up using the LED traffic signal head as the transmitter. The LEDs are modulated to transmit information-carrying light. The receiver uses a silicon photodiode to detect the transmitted radiation. Using visible light as the transmission medium, a 1 Mbit/s wireless data link is obtained.published_or_final_versio

Block CUR: Decomposing Matrices using Groups of Columns

A common problem in large-scale data analysis is to approximate a matrix using a combination of specifically sampled rows and columns, known as CUR decomposition. Unfortunately, in many real-world environments, the ability to sample specific individual rows or columns of the matrix is limited by either system constraints or cost. In this paper, we consider matrix approximation by sampling predefined \emph{blocks} of columns (or rows) from the matrix. We present an algorithm for sampling useful column blocks and provide novel guarantees for the quality of the approximation. This algorithm has application in problems as diverse as biometric data analysis to distributed computing. We demonstrate the effectiveness of the proposed algorithms for computing the Block CUR decomposition of large matrices in a distributed setting with multiple nodes in a compute cluster, where such blocks correspond to columns (or rows) of the matrix stored on the same node, which can be retrieved with much less overhead than retrieving individual columns stored across different nodes. In the biometric setting, the rows correspond to different users and columns correspond to users' biometric reaction to external stimuli, {\em e.g.,}~watching video content, at a particular time instant. There is significant cost in acquiring each user's reaction to lengthy content so we sample a few important scenes to approximate the biometric response. An individual time sample in this use case cannot be queried in isolation due to the lack of context that caused that biometric reaction. Instead, collections of time segments ({\em i.e.,} blocks) must be presented to the user. The practical application of these algorithms is shown via experimental results using real-world user biometric data from a content testing environment.Comment: shorter version to appear in ECML-PKDD 201

Dyadic joint visual attention interaction in face-to-face collaborative problem-solving at K-12 Maths Education: A Multimodal Approach

Collaborative problem-solving (CPS) is an essential skill in the workplace in the 21st century, but the assessment and support of the CPS process with scientifically objective evidence are challenging. This research aims to understand in-class CPS interaction by investigating the change of a dyad's cognitive engagement during a mathematics lesson. Here, we propose a multimodal evaluation of joint visual attention (JVA) based on eye gazes and eye blinks data as non-verbal indicators of dyadic cognitive engagement. Our results indicate that this multimodal approach can bring more insights into students' CPS process than unimodal evaluations of JVA in temporal analysis. This study contributes to the field by demonstrating the value of nonverbal multimodal JVA temporal analysis in CPS assessment and the utility of eye physiological data in improving the interpretation of dyadic cognitive engagement. Moreover, a method is proposed for capturing gaze convergence by considering eye fixations and the overlapping time between two eye gazes. We conclude the paper with our preliminary findings from a pilot study investigating the proposed approach in a real-world teaching context

Split-Drain Magnetic Field-Effect Transistor Channel Charge Trapping and Stress Induced Sensitivity Deterioration

Session EB: Materials for ApplicationsThis paper proposed an analytical model on the deterioration of magnetic sensitivity of sectorial split-drain magnetic field-effect transistors (SD-MAGFETs). The deterioration is governed by the trap fill rate at the channel boundary traps, which is geometric dependent. Experimental results are presented which show good consistency with the analytical derivation. The deterioration is the most severe at a sector angle of 54.6°, which shows a design tradeoff with sensing hysteresis. Design guidelines for sectorial SD-MAGFET to obtain high sensitivity hysteresis and slow sensitivity deterioration are also presented which provide important information for efficient design. © 2013 IEEE.published_or_final_versio

Luminescent Cyclometalated Gold(III) Alkyl Complexes: Photophysical and Photochemical Properties

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Air-sea transfer of gas phase controlled compounds

Gases in the atmosphere/ocean have solubility that spans several orders of magnitude. Resistance in the molecular sublayer on the waterside limits the air-sea exchange of sparingly soluble gases such as SF6 and CO2. In contrast, both aerodynamic and molecular diffusive resistances on the airside limit the exchange of highly soluble gases (as well as heat). Here we present direct measurements of air-sea methanol and acetone transfer from two open cruises: the Atlantic Meridional Transect in 2012 and the High Wind Gas Exchange Study in 2013. The transfer of the highly soluble methanol is essentially completely airside controlled, while the less soluble acetone is subject to both airside and waterside resistances. Both compounds were measured concurrently using a proton-transfer-reaction mass spectrometer, with their fluxes quantified by the eddy covariance method. Up to a wind speed of 15 m s-1, observed air-sea transfer velocities of these two gases are largely consistent with the expected near linear wind speed dependence. Measured acetone transfer velocity is ~30% lower than that of methanol, which is primarily due to the lower solubility of acetone. From this difference we estimate the "zero bubble" waterside transfer velocity, which agrees fairly well with interfacial gas transfer velocities predicted by the COARE model. At wind speeds above 15 m s-1, the transfer velocities of both compounds are lower than expected in the mean. Air-sea transfer of sensible heat (also airside controlled) also appears to be reduced at wind speeds over 20 m s-1. During these conditions, large waves and abundant whitecaps generate large amounts of sea spray, which is predicted to alter heat transfer and could also affect the air-sea exchange of soluble trace gases. We make an order of magnitude estimate for the impacts of sea spray on air-sea methanol transfer

Resummation of heavy jet mass and comparison to LEP data

The heavy jet mass distribution in e+e- collisions is computed to next-to-next-to-next-to leading logarithmic (NNNLL) and next-to-next-to leading fixed order accuracy (NNLO). The singular terms predicted from the resummed distribution are confirmed by the fixed order distributions allowing a precise extraction of the unknown soft function coefficients. A number of quantitative and qualitative comparisons of heavy jet mass and the related thrust distribution are made. From fitting to ALEPH data, a value of alpha_s is extracted, alpha_s(m_Z)=0.1220 +/- 0.0031, which is larger than, but not in conflict with, the corresponding value for thrust. A weighted average of the two produces alpha_s(m_Z) = 0.1193 +/- 0.0027, consistent with the world average. A study of the non-perturbative corrections shows that the flat direction observed for thrust between alpha_s and a simple non-perturbative shape parameter is not lifted in combining with heavy jet mass. The Monte Carlo treatment of hadronization gives qualitatively different results for thrust and heavy jet mass, and we conclude that it cannot be trusted to add power corrections to the event shape distributions at this accuracy. Whether a more sophisticated effective field theory approach to power corrections can reconcile the thrust and heavy jet mass distributions remains an open question.Comment: 33 pages, 14 figures. v2 added effect of lower numerical cutoff with improved extraction of the soft function constants; power correction discussion clarified. v3 small typos correcte

An Efficient Representation of Euclidean Gravity I

We explore how the topology of spacetime fabric is encoded into the local structure of Riemannian metrics using the gauge theory formulation of Euclidean gravity. In part I, we provide a rigorous mathematical foundation to prove that a general Einstein manifold arises as the sum of SU(2)_L Yang-Mills instantons and SU(2)_R anti-instantons where SU(2)_L and SU(2)_R are normal subgroups of the four-dimensional Lorentz group Spin(4) = SU(2)_L x SU(2)_R. Our proof relies only on the general properties in four dimensions: The Lorentz group Spin(4) is isomorphic to SU(2)_L x SU(2)_R and the six-dimensional vector space of two-forms splits canonically into the sum of three-dimensional vector spaces of self-dual and anti-self-dual two-forms. Consolidating these two, it turns out that the splitting of Spin(4) is deeply correlated with the decomposition of two-forms on four-manifold which occupies a central position in the theory of four-manifolds.Comment: 31 pages, 1 figur