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101.
Study of the competing chemical reactions in the initiation and spread of smouldering combustion in peat 总被引:3,自引:0,他引:3
Rory M. Hadden Guillermo Rein Claire M. Belcher 《Proceedings of the Combustion Institute》2013,34(2):2547-2553
Smouldering combustion of natural fuel layers such as peatlands leads to the largest fires on Earth and posses a possible positive feedback mechanism to climate change. In this paper, we use an experimental methodology to study the smouldering combustion of samples of peat under a wide range burning conditions. Vertical samples (30 mm deep and 125 mm in diameter) are ignited by radiation on the top free surface and the smouldering front propagates downward against a forced flow of oxidizer. By varying the oxygen concentration ([O2]) and the ignition conditions we investigate the competing pyrolysis and oxidation reactions. A reaction framework with two regimes is consistently observed. The measurements show that a char species is formed by the competing pyrolysis and oxidation reactions in the first regime resulting in net char production and in the second regime char oxidation results in conversion of the char to ash. Lower mass loss rates and the larger residual mass at lower [O2] suggest that a wider smouldering front is required to sustain combustion as the [O2] is decreased. These results improve our understanding of smouldering phenomena and the role of the competing chemical reactions. 相似文献
102.
Oswald Fogelklou Warwick Tucker Gunilla Kreiss 《NoDEA : Nonlinear Differential Equations and Applications》2012,19(1):97-131
We establish the existence and local uniqueness of traveling wave solutions to the one-dimensional Euler equations with artificial
viscosity. The equations are expressed as a fixed-point problem, which is solved by a computer-assisted method based on Yamamoto’s
application of the Banach fixed-point theorem. 相似文献
103.
Traditional iris recognition systems transfer iris images to polar (or log-polar) coordinates and have performed very well on data that tends to have a centered gaze. The patterns of an iris are part of a 3-D structure that is captured as a two-dimensional (2-D) image and cooperative iris recognition systems are capable of correctly matching these 2-D representations of iris features. However, when the gaze of an eye changes with respect to the camera lens, many times the size, shape, and detail of iris patterns will change as well and cannot be matched to enrolled images using traditional methods. Additionally, the transformation of off-angle eyes to polar coordinates becomes much more challenging and noncooperative iris algorithms will require a different approach. The direct application of the scale-invariant feature transform (SIFT) method would not work well for iris recognition because it does not take advantage of the characteristics of iris patterns. We propose the region-based SIFT approach to iris recognition. This new method does not require polar transformation, affine transformation or highly accurate segmentation to perform iris recognition and is scale invariant. This method was tested on the iris challenge evaluation (ICE), WVU and IUPUI noncooperative databases and results show that the method is capable of cooperative and noncooperative iris recognition. 相似文献
104.
Karen E. Verrall Peter Warwick Andrew J. Fairhurst 《Colloids and surfaces. A, Physicochemical and engineering aspects》1999,150(1-3):261-273
The applicability of the Schulze–Hardy rule to haematite and haematite/humate mixtures has been investigated by measuring the rate of fast and slow coagulation after the addition of increasing concentrations of mono, di and trivalent ions. Haematite colloids follow the rule for mono, di and trivalent ions. Haematite colloids coated with humate generally follow the rule for mono and di valent ions with the exception of copper ions. Trivalent ions do not follow the Schulze–Hardy rule because of their relatively strong complexation with humate. The size of the counter ion has an effect on the de-stabilising ability of ions of the same charge. 相似文献
105.
Soft X-ray microscopy and spectroscopy at the molecular environmental science beamline at the Advanced Light Source 总被引:1,自引:0,他引:1
H. Bluhm K. Andersson T. Araki K. Benzerara G.E. Brown J.J. Dynes S. Ghosal M.K. Gilles H.-Ch. Hansen J.C. Hemminger A.P. Hitchcock G. Ketteler A.L.D. Kilcoyne E. Kneedler J.R. Lawrence G.G. Leppard J. Majzlam B.S. Mun S.C.B. Myneni A. Nilsson H. Ogasawara D.F. Ogletree K. Pecher M. Salmeron D.K. Shuh B. Tonner T. Tyliszczak T. Warwick T.H. Yoon 《Journal of Electron Spectroscopy and Related Phenomena》2006,150(2-3):86-104
We present examples of the application of synchrotron-based spectroscopies and microscopies to environmentally relevant samples. The experiments were performed at the molecular environmental science beamline (11.0.2) at the Advanced Light Source, Lawrence Berkeley National Laboratory. Examples range from the study of water monolayers on Pt(1 1 1) single crystal surfaces using X-ray emission spectroscopy and the examination of alkali halide solution/water vapor interfaces using ambient pressure photoemission spectroscopy, to the investigation of actinides, river water biofilms, Al-containing colloids and mineral–bacteria suspensions using scanning transmission X-ray spectromicroscopy. The results of our experiments show that spectroscopy and microscopy in the soft X-ray energy range are excellent tools for the investigation of environmentally relevant samples under realistic conditions, i.e., with water or water vapor present at ambient temperature. 相似文献
106.
Molecular emission cavity analysis (MECA) is shown to be useful for selective detection of sulphur or phosphorus compounds at the nanogram level in g.l.c. effluents. Introduction of a small oxygen flow into the cavity allows many other elements (e.g. Si, As, Sb, N, C) to be detected. The detection of microgram amounts of silylated amino acids is possible by measuring their SiO emission in the cavity at 580 nm. 相似文献
107.
Warwick L. Morison 《Photochemistry and photobiology》1996,64(2):267-268
Both methoxsalen plus UVA (PUVA) therapy and UVB phototherapy are commonly used in the management of human immunodeficiency virus-associated dermatoses but UVB phototherapy appears to be the preferred treatment. There are several considerations, in particular therapeutic efficacy and therapeutic profile, which suggest that PUVA therapy might be more effective, This needs to be established in clinical trials. 相似文献
108.
Several methods are described for the determination of thiol groups in organic samples weighing only 50 μg. Iodimetric methods were not widely applicable but the mercurimetric method of fritz and palmer in which thio-Michler's ketone serves as indicator was readily scaled down and gave excellent results (error ± 0.5% absolute) for all compounds tested. Diphenylcarbazone was also tried as the indicator; the procedure was satisfactory for most materials, but some anomalous results were obtained. 相似文献
109.
110.
This paper presents a problem in pattern recognition and formulates it in terms of a dynamic-programming model. Although dynamic programming is usually thought of as an O.R. tool applied to management problems, this paper shows that it has natural applications in pattern matching and recognition, developing aspects of fifth generation computing technology. 相似文献