15,913 research outputs found
Clapeyron equation and phase equilibrium properties in higher dimensional charged topological dilaton AdS black holes with a nonlinear source
Using Maxwell's equal area law, we discuss the phase transition of higher
dimensional charged topological dilaton AdS black holes with a nonlinear
source. The coexisting region of the two phases is found and we depict the
coexistence region in diagrams. The two-phase equilibrium curves in
diagrams are plotted, and we take the first order approximation of volume
in the calculation. To better compare with a general thermodynamic system, the
Clapeyron equation is derived for higher dimensional charged topological black
hole with a nonlinear source. The latent heat of isothermal phase transition is
investigated. We also study the effect of the parameters of the black hole on
the region of two-phases coexistence. The results show that the black hole may
go through a small-large phase transition similar to those of usual non-gravity
thermodynamic systems.Comment: 21 pages,25 figures. published version in EPJC. arXiv admin note:
substantial text overlap with arXiv:1411.7202; text overlap with
arXiv:1506.01786, arXiv:hep-th/0605042 by other author
Analysis of controlled auto-ignition /HCCI combustion in a direct injection gasoline engine with single and split fuel injections
A multi-cycle three-dimensional CFD engine simulation programme has been developed and applied to analyze the Controlled autoignition (CAI) combustion, also known as homogeneous charge compression ignition (HCCI), in a direct injection gasoline engine. CAI operation was achieved through the negative valve overlap method by means of a set of low lift camshafts. In the first part of the paper, the effect of single injection timing on combustion phasing and underlying physical and chemical processes involved was examined through a series of analytical studies using the multi-cycle 3D engine simulation programme. The analyses showed that early injection into the trapped burned gases of a lean-burn mixture during the negative valve overlap period had a large effect on combustion phasing, due to localized heat release and the production of chemically reactive species. As the injection was retarded to the intake stroke, the charge cooling effect tended to slow down the autoignition process. However, further retard of fuel injection to the compression stroke caused the earlier start of main combustion as fuel stratification was produced in the cylinder. In order to optimize the engine performance and engine-out emissions, double injection was investigated by injecting part of the fuel first in the negative valve overlap period and the rest of fuel during the intake or compression strokes. By varying the fueling of each injection, the best engine performance was obtained with the 50/50 fuel injection split ratio, while the lowest total NOx and soot emissions were seen with the optimal split injection ratio of 10/90
Segmentation of ultrasound images of thyroid nodule for assisting fine needle aspiration cytology
The incidence of thyroid nodule is very high and generally increases with the
age. Thyroid nodule may presage the emergence of thyroid cancer. The thyroid
nodule can be completely cured if detected early. Fine needle aspiration
cytology is a recognized early diagnosis method of thyroid nodule. There are
still some limitations in the fine needle aspiration cytology, and the
ultrasound diagnosis of thyroid nodule has become the first choice for
auxiliary examination of thyroid nodular disease. If we could combine medical
imaging technology and fine needle aspiration cytology, the diagnostic rate of
thyroid nodule would be improved significantly. The properties of ultrasound
will degrade the image quality, which makes it difficult to recognize the edges
for physicians. Image segmentation technique based on graph theory has become a
research hotspot at present. Normalized cut (Ncut) is a representative one,
which is suitable for segmentation of feature parts of medical image. However,
how to solve the normalized cut has become a problem, which needs large memory
capacity and heavy calculation of weight matrix. It always generates over
segmentation or less segmentation which leads to inaccurate in the
segmentation. The speckle noise in B ultrasound image of thyroid tumor makes
the quality of the image deteriorate. In the light of this characteristic, we
combine the anisotropic diffusion model with the normalized cut in this paper.
After the enhancement of anisotropic diffusion model, it removes the noise in
the B ultrasound image while preserves the important edges and local details.
This reduces the amount of computation in constructing the weight matrix of the
improved normalized cut and improves the accuracy of the final segmentation
results. The feasibility of the method is proved by the experimental results.Comment: 15pages,13figure
Thermodynamics of phase transition in higher dimensional Reissner-Nordstr\"{o}m-de Sitter black hole
It is well known that there are black hole and the cosmological horizons for
the Reissner-Nordstr\"{o}m-de Sitter spacetime. Although the thermodynamic
quantities on the horizons are not irrelevant, they satisfy the laws of black
hole thermodynamics respectively. In this paper by considering the relations
between the two horizons we give the effective thermodynamic quantities in
-dimensional Reissner-Nordstr\"{o}m-de Sitter spacetime. The
thermodynamic properties of these effective quantities are analyzed, moreover,
the critical temperature, critical pressure and critical volume are obtained.
We carry out an analytical check of Ehrenfest equations and prove that both
Ehrenfest equations are satisfied. So the spacetime undergoes a second order
phase transition at the critical point. This result is consistent with the
nature of liquid--gas phase transition at the critical point, hence deepening
the understanding of the analogy of charged dS spacetime and liquid--gas
systems.Comment: 18 pages, 7 figures, 1 tabl
Phase transition of the higher dimensional charged Gauss-Bonnet black hole in de Sitter spacetime
We study the phase transition of charged Gauss-Bonnet-de Sitter (GB-dS) black
hole. For black holes in de Sitter spacetime, there is not only black hole
horizon, but also the cosmological horizon. The thermodynamic quantities on the
both horizons satisfy the first law of the black hole thermodynamics,
respectively; moreover, there are additional connections between them. Using
the effective temperature approach, we obtained the effective thermodynamic
quantities of charged GB-dS black hole. According to Ehrenfest classification,
we calculate some response functions and plot their figures, from which one can
see that the spacetime undergoes a second-order phase transition at the
critical point. It is shown that the critical values of effective temperature
and pressure decrease with the increase of the value of GB parameter .Comment: 9 pages, 16 figure
EMI shielding effectiveness of silver nanoparticle-decorated multi-walled carbon nanotube sheets
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