89,268 research outputs found
An experimental and theoretical investigation of a wick-type solar still for water desalination
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Solar distillation using a wick-type solar still was investigated theoretically and experimentally. A tilled flat plate wick-type solar still was designed and constructed.
Charcoal cloth was used as an absorber/evaporator material and for saline water transport. A theoretical model for the performance of the wick-type solar still has been developed and analysed. It investigates the effect of various factors on the still productivity. A Fortran computer program has been developed and a finite difference technique was used to solve the main equations and to determine related parameters.
Indoor experimental testing was carried out to investigate the effect of input water flow rate and salinity on the still productivity together with the variation of the solar still efficiency with absorber temperature. The tests were conducted using the irradiance from a lamp array. Outdoor testing was carried out with and without a V-trough solar concentrator on clear days in summer and winter. Representative daily efficiencies of the still with and without the solar concentrator were about 60% and 50% respectively on clear days in summer. The solar absorptances of samples of charcoal cloth and blackened hessian cloth were determined before and after environmental exposure. The solar reflectances of samples of 3M Scotchcal Films and aluminised plastic (as potential reflecting materials for the concentrator mirrors) were investigated before and after environmental exposure and also exposure to elevated temperatures and humidities. It has been concluded that: charcoal cloth is a good material for use as an absorber/evaporator and also as a water transport medium. Increase of the input water mass flow rate leads to a reduction in the efficiency of the wick-type solar still. The still efficiency decreased linearly with Increase of salinity of the input saline water. The productivity of the still Increases linearly with absorber temperature. The best absorber-cover separation Is found to be in the range 20-25 mm. Wind speed has no significant effect (up to about 10 m/s) on the performance of a well sealed still. The transmittance of the glass cover has a strong influence on the still efficiency. Use of the solar concentrator with the inclined wick-type solar still leads to a greater fractional increase In still productivity on clear days in winter than on clear days in summer
Modeling and Design Optimization of Ultra-Thin Vapor Chambers for High Heat Flux Applications
No full textPassive phase-change thermal spreaders, such as vapor chambers have been widely employed to spread the heat from small-scale high-flux heat sources to larger areas. In this paper, a numerical model for ultrathin vapor chambers has been developed, which is suitable for reliable prediction of the operation at high heat fluxes and small scales. The effects of boiling in the wick structure on the thermal performance are modeled, and the model predictions are compared with experiments on custom-fabricated vapor chamber devices. The working fluid for the vapor chamber is water and a condenser side temperature range of 293 K–333 K is considered. The model predictions agree reasonably well with experimental measurements and reveal the input parameters to which thermal resistance and vapor chamber capillary limit are most sensitive. The vapor space in the ultrathin devices offers significant thermal and flow resistances when the vapor core thickness is in the range of 0.2 mm–0.4 mm. The performance of a 1-mm-thick vapor chamber is optimized by studying the variation of thermal resistance and total flow pressure drop as functions of the wick and vapor core thicknesses. The wick thickness is varied from 0.05 to 0.25 mm. Based on the minimization of a performance cost function comprising the device thermal resistance and flow pressure drop, it is concluded that the thinnest wick structures (0.05 mm) are optimal for applications with heat fluxes below 50 W/cm2, while a moderate wick thickness of 0.1 mm performs best at higher heat flux inputs (\u3e50 W/cm2)
Christliche Trauungs-Rede gehalten aus Anlasz der ehelichen Verbindung Herrn ... Johannes Burckhardt mit Jungfrau Dorothea Iselin in der Kirche bey St. Jakob den 18. Nov. 1813
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Wick polynomials in non-commutative probability: A group-theoretical approach
No full textWick polynomials and Wick products are studied in the context of non-commutative probability theory. It is shown that free, boolean and conditionally free Wick polynomials can be defined and related through the action of the group of characters over a particular Hopf algebra. These results generalize our previous developments of a Hopf algebraic approach to cumulants and Wick products in classical probability theory
Process gg?h0??? in the Lee-Wick standard model
No full textThe process gg?h0??? is studied in the Lee-Wick extension of the standard model (LWSM) proposed by Grinstein, O’Connell, and Wise. In this model, negative norm partners for each SM field are introduced with the aim to cancel quadratic divergences in the Higgs mass. All sectors of the model relevant to gg?h0??? are diagonalized and results are commented on from the perspective of both the Lee-Wick and higher-derivative formalisms. Deviations from the SM rate for gg?h0 are found to be of the order of 15%–5% for Lee-Wick masses in the range 500–1000 GeV. Effects on the rate for h0??? are smaller, of the order of 5%–1% for Lee-Wick masses in the same range. These comparatively small changes may well provide a means of distinguishing the LWSM from other models such as universal extra dimensions where same-spin partners to standard model fields also appear. Corrections to determinations of Cabibbo-Kobayashi-Maskawa (CKM) elements |Vt(b,s,d)| are also considered and are shown to be positive, allowing the possibility of measuring a CKM element larger than unity, a characteristic signature of the ghostlike nature of the Lee-Wick fields
Wick polynomials in non-commutative probability
No full textWick polynomials and Wick products are studied in the context of non-commutative probability theory. It is shown that free, boolean and conditionally free Wick polynomials can be defined and related through the action of the group of characters over a particular Hopf algebra. These results generalize our previous developments of a Hopf algebraic approach to cumulants and Wick products in classical probability theory
Phenomenology of the N=3 Lee-Wick Standard Model
No full textabstract: With the discovery of the Higgs Boson in 2012, particle physics has decidedly moved beyond the Standard Model into a new epoch. Though the Standard Model particle content is now completely accounted for, there remain many theoretical issues about the structure of the theory in need of resolution. Among these is the hierarchy problem: since the renormalized Higgs mass receives quadratic corrections from a higher cutoff scale, what keeps the Higgs boson light? Many possible solutions to this problem have been advanced, such as supersymmetry, Randall-Sundrum models, or sub-millimeter corrections to gravity. One such solution has been advanced by the Lee-Wick Standard Model. In this theory, higher-derivative operators are added to the Lagrangian for each Standard Model field, which result in propagators that possess two physical poles and fall off more rapidly in the ultraviolet regime. It can be shown by an auxiliary field transformation that the higher-derivative theory is identical to positing a second, manifestly renormalizable theory in which new fields with opposite-sign kinetic and mass terms are found. These so-called Lee-Wick fields have opposite-sign propagators, and famously cancel off the quadratic divergences that plague the renormalized Higgs mass. The states in the Hilbert space corresponding to Lee-Wick particles have negative norm, and implications for causality and unitarity are examined.
This dissertation explores a variant of the theory called the N = 3 Lee-Wick
Standard Model. The Lagrangian of this theory features a yet-higher derivative operator, which produces a propagator with three physical poles and possesses even better high-energy behavior than the minimal Lee-Wick theory. An analogous auxiliary field transformation takes this higher-derivative theory into a renormalizable theory with states of alternating positive, negative, and positive norm. The phenomenology of this theory is examined in detail, with particular emphasis on the collider signatures of Lee-Wick particles, electroweak precision constraints on the masses that the new particles can take on, and scenarios in early-universe cosmology in which Lee-Wick particles can play a significant role.Dissertation/ThesisDoctoral Dissertation Physics 201
Canonical Wick Rotations in 3-Dimensional Gravity
No full textWe develop a ``canonical Wick rotation-rescaling theory in 3-dimensional gravity''. This includes: (a) A simultaneous classification that shows how generic maximal globally hyperbolic spacetimes of constant curvature, which admit a complete Cauchy surface (in particular a compact one), as well as complex projective structures on arbitrary surfaces, are all encoded by pairs (H,L), H being a ``straight convex sets'' in the hyperbolic plane, and L a ``measured geodesic laminations'' suitably defined on H. (b) Canonical geometric correlations: spacetimes of different curvature, that share a same encoding pair (H,L), are related to each other by ``canonical rescaling''; they can be transformed by ``canonical Wick rotations'' in hyperbolic 3-manifolds, that carry asymptotically the corresponding projective structures. Both Wick rotations and rescalings act along the "canonical cosmological time" and have ``universal rescaling functions''. These correlations are functorial with respect to isomorphisms of the respective geometric categories. We analyze the behaviour along a ray of measured laminations, (broken) T-symmetry by spacetimes of negative curvature, the relationship with ``earthquake theory'', beyond the case of compact Cauchy surface. WR-rescaling does apply on the ``ends'' of geometrically finite hyperbolic 3-manifolds, that hence realize concrete interactions of their globally hyperbolic ``ending spacetimes'' of constant curvature. It also provides further "classical amplitudes" of these interactions, beyond the volume of the hyperbolic convex cores
Narcissus: Woman, water and the West
No full textThis essay explores the symbiotic relationship between European modernity, its vision of woman and water. The union of these three metaconcepts is consecrated by the Ovidian story of Narcissus and his other, Echo. The West finally found itself completely through Hegel, the Ur-narcissist, who explains the immutable link between that European monopoly, history (by which he means the potential for becoming modern), and the sea. The narcissism of modernity is the great theme of Marx and Engels in the Communist Manifesto, which shows how the bourgeoisie seeks to remake the entire world in its own image. Psychoanalysis, through the writings of Ferenczi, joined in cementing the connection, likening woman to the primal sea to which the male ever yearns to return. And Foucault suggests a potential conclusion from this metaconceptual constellation: that Man, a Western creation, may well disappear like a face drawn on a sandy beach. © 2013 Feminist Review.Bachelard G., 1983, WATER DREAMS; BASKINS CL, 1993, OXFORD ART J, V16, P25; Baudrillard F., 1975, MIRROR PRODUCTION; Butler J., 2006, GENDER TROUBLE; Chakrabarty D, 2000, PROVINCIALIZING EURO; Deleuze Gilles, 1987, 1000 PLATEAUS CAPITA; Eagleton Terry, 1990, IDEOLOGY AESTHETIC; Ferenczi S., 1968, THALASSA THEORY GENI; Foucault M., 1989, MADNESS CIVILIZATION; Foucault Michel, 1970, ORDER THINGS; Freud S., 1957, STANDARD EDITION COM, V14; Hegel Georg, 1975, LECT PHILOS WORLD HI; Irigaray L., 1993, MARINE LOVER F NIETZ; Irigaray L., 1985, THIS SEX WHICH IS NO; Kristeva J, 1987, TALES LOVE; Lacan Jacques, 1977, ECRITS SELECTION; Lerner Daniel, 1958, PASSING TRADITIONAL; Marx K, 1992, COMMUNIST MANIFESTO; Marx Karl, 1990, CAPITAL CRITIQUE POL, V1; Massad Joseph, 2007, DESIRING ARABS; Michelet J., 1875, SEA; Mitchell T., 1988, COLONISING EGYPT; Ovid, 1958, METAMORPHOSES; Smith Adam, 1994, WEALTH NATIONS; SPIVAK GC, 1993, NEW LITERARY HIST, V24, P17, DOI 10.2307-4692670
A conducting surface in Lee–Wick electrodynamics
No full textLee–Wick electrodynamics in the vicinity of a conducting plate is investigated. The propagator for the gauge field is calculated and the interaction between the plate and a point-like electric charge is computed. The boundary condition imposed on the vector field is taken to be the one that makes, on the plate, the normal component of the dual field strength to the plate vanish. It is shown that the image method is not valid in Lee–Wick electrodynamics
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