183 research outputs found
Thermal inertia effect of reactive sources on one-dimensional discrete combustion wave propagation
In the present work, the discrete flame model [1] is augmented by introducing
the thermal inertia of particles in the preheating zone. The effect of particle
thermal inertia on flame speed, propagation limits, and near-limits dynamics of
one-dimensional discrete combustion waves is studied using the new model. It is
found that, with the increase of particle thermal inertia, the propagation
velocity of the discrete flame decreases due to a smaller heating rate of the
particles. Besides, particle thermal inertia extends the propagation limits
compared to the prediction of the old model. Furthermore, it is mathematically
proven that the nonphysical branch of the solutions for the discrete flame
speeds, found using the old discrete model, is a set of solutions for the
propagation limits of steady-state discrete flames with particle thermal
inertia included. The flame speed predicted using the new model is also
compared with that determined analytically using a continuum model considering
the thermal inertia of the condensed phase [2]. We find that the discrete flame
speeds predicted by the both models become closer to each other with increasing
particle thermal inertia. Finally, the two models converge regardless of the
discrete nature of the heat sources when particle thermal inertia is large
enough so that can limit the flame propagation. The particle thermal inertia
controlled flames could be regarded as a new kind of combustion regime
Development of a methodology for estimating the heat loss of buildings based on neural networks
The study describes a methodology for estimating the heat loss of a building, including the calculation of the heat loss of a building. The features of the wooden housing stock were studied for developing a methodology for estimating the heat loss of a building based on neural networks. The stage of images collecting for training a neural network,the stage of training an optimal neural network for solving the problem of object detection are described. The technologies necessary to solve the problem are described
Numerical simulation of the upward propagation of a flame in a vertical tube filled with a very lean mixture.
Upwardpropagation of a premixed flame in averticaltubefilled with a very leanmixture is simulated numerically using a single irreversible Arrhenius reaction model with infinitely high activation energy. In the absence of heat losses and preferential diffusion effects, a curved flame with stationary shape and velocity close to those of an open bubble ascending in the same tube is found for values of the fuel mass fraction above a certain minimum that increases with the radius of the tube, while the numerical computations cease to converge to a stationary solution below this minimum mass fraction. The vortical flow of the gas behind the flame and in its transport region is described for tubes of different radii. It is argued that this flow may become unstable when the fuel mass fraction is decreased, and that this instability, together with the flame stretch due to the strong curvature of the flame tip in narrow tubes, may be responsible for the minimum fuel mass fraction. Radiation losses and a Lewis number of the fuel slightly above unity decrease the final combustion temperature at the flame tip and increase the minimum fuel mass fraction, while a Lewis number slightly below unity has the opposite effect
Veiling glare removal: synthetic dataset generation, metrics and neural network architecture
In photography, the presence of a bright light source often reduces the quality and readability of the resulting image. Light rays reflect and bounce off camera elements, sensor or diaphragm causing unwanted artifacts. These artifacts are generally known as "lens flare" and may have different influences on the photo: reduce contrast of the image (veiling glare), add circular or circular-like effects (ghosting flare), appear as bright rays spreading from light source (starburst pattern), or cause aberrations. All these effects are generally undesirable, as they reduce legibility and aesthetics of the image. In this paper we address the problem of removing or reducing the effect of veiling glare on the image. There are no available large-scale datasets for this problem and no established metrics, so we start by (i) proposing a simple and fast algorithm of generating synthetic veiling glare images necessary for training and (ii) studying metrics used in related image enhancement tasks (dehazing and underwater image enhancement). We select three such no-reference metrics (UCIQE, UIQM and CCF) and show that their improvement indicates better veil removal. Finally, we experiment on neural network architectures and propose a two-branched architecture and a training procedure utilizing structural similarity measure
ΠΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΡΠ΅ Π΄ΠΎΠΊΡΠΌΠ΅Π½ΡΡ ΠΈ Π±ΠΈΠ±Π»ΠΈΠΎΡΠ΅ΠΊΠΈ Π² ΠΌΠ΅ΡΡΠ°Ρ Π»ΠΈΡΠ΅Π½ΠΈΡ ΡΠ²ΠΎΠ±ΠΎΠ΄Ρ Π² Π ΠΎΡΡΠΈΠΈ: ΠΏΡΠΎΠ±Π»Π΅ΠΌΡ Π΄ΠΎΡΡΡΠΏΠ½ΠΎΡΡΠΈ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΠΈ
In modern Russian conditions the number of persons held in isolation from society, is about 1 million people. Persons serving a sentence of actual imprisonment upon conviction, shall have access to the values concentrated in the libraries. Users of library services in prisons can get the information for their self-education with the help of the Internet .Π Π½Π°ΡΡΠΎΡΡΠ΅Π΅ Π²ΡΠ΅ΠΌΡ ΠΊΠΎΠ»ΠΈΡΠ΅ΡΡΠ²ΠΎ Π»ΠΈΡ, ΡΠΎΠ΄Π΅ΡΠΆΠ°ΡΠΈΡ
ΡΡ Π² ΡΡΠ»ΠΎΠ²ΠΈΡΡ
ΠΈΠ·ΠΎΠ»ΡΡΠΈΠΈ ΠΎΡ ΠΎΠ±ΡΠ΅ΡΡΠ²Π°, Π΄ΠΎΡΡΠ°ΡΠΎΡΠ½ΠΎ Π²Π΅Π»ΠΈΠΊΠΎ. ΠΠΈΡΠ°, ΠΎΡΠ±ΡΠ²Π°ΡΡΠΈΠ΅ Π½Π°ΠΊΠ°Π·Π°Π½ΠΈΠ΅ Π² Π²ΠΈΠ΄Π΅ ΡΠ΅Π°Π»ΡΠ½ΠΎΠ³ΠΎ Π»ΠΈΡΠ΅Π½ΠΈΡ ΡΠ²ΠΎΠ±ΠΎΠ΄Ρ ΠΏΠΎ ΠΏΡΠΈΠ³ΠΎΠ²ΠΎΡΡ ΡΡΠ΄Π°, Π΄ΠΎΠ»ΠΆΠ½Ρ ΠΈΠΌΠ΅ΡΡ Π΄ΠΎΡΡΡΠΏ ΠΊ ΡΠ΅Π½Π½ΠΎΡΡΡΠΌ, ΡΠΎΡΡΠ΅Π΄ΠΎΡΠΎΡΠ΅Π½Π½ΡΠΌ Π² Π±ΠΈΠ±Π»ΠΈΠΎΡΠ΅ΠΊΠ°Ρ
, Π° ΡΠ°ΠΊΠΆΠ΅ Ρ ΠΏΠΎΠΌΠΎΡΡΡ ΠΠ½ΡΠ΅ΡΠ½Π΅ΡΠ° ΠΏΠΎΠ»ΡΡΠ°ΡΡ Π½Π΅ΠΎΠ±Ρ
ΠΎΠ΄ΠΈΠΌΡΡ Π΄Π»Ρ ΡΠ°ΠΌΠΎΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΡ
Experimental and theoretical study of single iron particle combustion under low-oxygen dilution conditions
In the present study, a novel in situ particle sizing approach is proposed and used to measure the characteristic timescales of micron-sized iron particle combustion under low-oxygen (10β17 vol%) dilution conditions. The particle size is determined by probing the light emission intensity of a burning particle during melting, which is proportional to the cross-section area of the particle projected to the camera. Detailed descriptions of the calibration, validation, and characterization of the experimental method are elaborated. With systematic measurements, we obtain one-to-one correlations between combustion timescales and single particle diameters at various diluted oxygen concentrations. Furthermore, we formally derive a theoretical model for heterogeneous combustion of growing (iron) particles in the diffusion-limited regime. The model suggests that the diffusion-limited burn time scales with the initial particle diameter squared (i.e., a new, generalized d2-law). Owing to accounting for the particle growth, the newly derived model suggests a significantly (1.66 times) shorter combustion duration compared to the conventional d2-law for shrinking particle combustion. It turns out that the new model agrees well with the experiment. This agreement also suggests that under low-oxygen dilution conditions, the combustion regime of iron particles during the intensive burning stage (i.e., from ignition to the peak particle temperature) is limited by external oxygen diffusion.</p
Structure and stability of premixed flames stabilized behind the trailing edge of a cylindrical rod at low Lewis numbers
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