Theoretical model and numerical solution of gas desorption and flow mechanism in coal matrix based on free gas density gradient

2021 ◽  
Vol 90 ◽  
pp. 103932
Author(s):  
Wei Liu ◽  
Hao Xu ◽  
Yueping Qin ◽  
Xiangyu Chu ◽  
Jia Liu ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Numerical Solution ◽  
Density Gradient ◽  
Flow Mechanism ◽  
Gas Density ◽  
Free Gas ◽  
Coal Matrix ◽  
Gas Desorption

Modeling of Gas Transport Driven by Density Gradients of Free Gas within a Coal Matrix: Perspective of Isothermal Adsorption

2020 ◽  
Vol 34 (11) ◽  
pp. 13728-13739
Author(s):  
Wei Liu ◽  
Yueping Qin ◽  
Wei Zhao ◽  
Deyao Wu ◽  
Jia Liu ◽  
...  
Keyword(s):  
Gas Transport ◽  
Density Gradients ◽  
Isothermal Adsorption ◽  
Free Gas ◽  
Coal Matrix

Non-linear gas desorption and transport behavior in coal matrix: Experiments and numerical modeling

Fuel ◽  
2018 ◽  
Vol 214 ◽  
pp. 1-13 ◽  
Author(s):  
Peng Liu ◽  
Yueping Qin ◽  
Shimin Liu ◽  
Yongjiang Hao
Keyword(s):  
Numerical Modeling ◽  
Coal Matrix ◽  
Transport Behavior ◽  
Gas Desorption ◽  
Non Linear

Helical Shift Mechanics of Rubber V-Belt Variators

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Francesco Sorge ◽  
Marco Cammalleri
Keyword(s):  
Theoretical Model ◽  
Numerical Solution ◽  
Closed Form ◽  
Operating Conditions ◽  
The Other ◽  
Experimental Comparison ◽  
Axial Thrust ◽  
Shooting Technique ◽  
Strongly Nonlinear ◽  
Tension Level

A very common configuration of V-belt variators for motorcycles considers the correction of the belt tensioning depending on the resistant torque by means of suitable helical-shaped tracks allowing the driven half-pulleys to close/open. The theoretical model for belt-pulley coupling is rather complex for this configuration, where one half-pulley may run in advance and the other one behind with respect to the belt, and requires the repeated numerical solution of a strongly nonlinear differential system by a sort of shooting technique, until all the operating conditions are fulfilled (angular contact extent, torque, and axial force). After solving the full equations, the present study develops closed-form approximations, which are characterized by an excellent correspondence with the numerical plots, and suggests a simple and practical formulary for the axial thrust as a function of the torque and of the tension level. Then, the results of a theoretical–experimental comparison are also reported, and they indicate a fine agreement between the model and the real operation.

The gas density gradient for three dark interstellar clouds

1984 ◽  
Vol 287 ◽  
pp. 723 ◽  
Author(s):  
S. A. Fulkerson ◽  
F. O. Clark
Keyword(s):  
Density Gradient ◽  
Gas Density ◽  
Interstellar Clouds

Experimental Evidence of the Isoperichoric Focusing of Nanosize Polyaniline Particles in Density Gradient Formed by Colloidal Silica

1996 ◽  
Vol 61 (6) ◽  
pp. 819-824 ◽  
Author(s):  
Josef Janča ◽  
Milena Špírková
Keyword(s):  
Theoretical Model ◽  
Experimental Evidence ◽  
Density Gradient ◽  
Colloidal Silica ◽  
A Priori ◽  
Transport Phenomena ◽  
Silica Particles ◽  
Size Ratio ◽  
Nanosize Particles

The isoperichoric focusing transport phenomena were recently described by a rigorous theoretical model. Contrary to the generally accepted supposition that a density gradient forming liquid in isopycnic focusing should behave as continuum regarding the focused species, the model predicts the focusing with no a priori imposed size ratio of the focused to the density gradient forming species. This prediction was evidenced by focusing of the polyaniline nanosize particles in a density gradient formed by colloidal silica particles suspended in water. The size ratio of the polyaniline to silica particles was low.

DISTRIBUTION OF ATTACKS ON SPRUCE STUMPS BY THE SPRUCE BEETLE, DENDROCTONUS RUFIPENNIS (KIRBY) (COLEOPTERA: SCOLYTIDAE), AND EFFECTS ON THE LENGTH OF EGG GALLERIES

1988 ◽  
Vol 120 (1) ◽  
pp. 85-94 ◽  
Author(s):  
L. Safranyik ◽  
D.A. Linton
Keyword(s):  
British Columbia ◽  
Theoretical Model ◽  
Density Gradient ◽  
Exponential Function ◽  
Mineral Soil ◽  
Vertical Gradient ◽  
Average Process ◽  
Dendroctonus Rufipennis ◽  
Discrete Step ◽  
Spruce Beetle

AbstractThe distribution of spruce beetle attacks and length of associated egg galleries were investigated on 21 spruce stumps over a 4-year period in central British Columbia. Attack density formed a distinct vertical gradient which peaked near the duff line at about one-third stump height above the mineral soil. The proportion of attacks on the stumps that were located below the duff was linearly related to the ratio of stump height below duff and total stump height above mineral soil. Attack density was significantly higher below the duff than above. A three-parameter exponential function gave satisfactory fit to the attack density gradient on normalized stump height. A discrete-step theoretical model was also developed based on assumptions regarding beetle behavior during landing and imitation of the egg gallery and the physical characteristics of the host. This model gave an excellent fit to the attack density gradient as an average process over all stumps. Average egg gallery length was a curvilinear function of attack density with maximum average egg gallery length occurring at about 0.33 attacks per 100 cm2.

scholarly journals Multi-Field-Coupled Model and Solution of Active Electronically Scanned Array Antenna Based on Model Reconstruction

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Dan Han ◽  
Jin Huang ◽  
Jinzhu Zhou ◽  
Mei Wang ◽  
Sen Xu ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Numerical Solution ◽  
Coupled Model ◽  
Reconstruction Algorithm ◽  
Surface Fitting ◽  
Local Model ◽  
Model Reconstruction ◽  
Feed System ◽  
Fitting Algorithm ◽  
Surface Fitting Algorithm

Active electronically scanned array antenna (AESA antenna) is capable of controlling the radiation pattern by controlling the feeding phase of the radiating elements. It has good performance and plays an important role in radar systems. With the development of AESA antenna towards high-frequency bands and high-density arrays, the structural-electromagnetic-thermal (SET) coupling becomes increasingly significant. It seriously restricts the realization of high performances of AESA antennas. However, the previously reported theoretical multi-field-coupled model for the coupling problem ignores the effect of the deformations of the feed system and array elements on the electrical performance. It only considers the positional deviations of the array elements in the coupling field. As a result, the accuracy of the numerical solution by the theoretical model is reduced. To overcome the above problems, this paper first establishes the field-circuit coupling model by introducing the deformation errors of the feed system into the existing theoretical model. Secondly, this paper proposes a new numerical solution for the multi-field-coupled problem of AESA antennas based on model reconstruction. And the model reconstruction includes the following: the NURBS (nonuniform rational B-spline) surface fitting algorithm that completes the mapping from finite element models to geometric models by the surface equations established by the node information and the local model reconstruction algorithm that determines the local geometric models by the positions and the directions. The NURBS surface fitting algorithm guarantees the accuracy of both the positions and shapes of array elements. The local model reconstruction algorithm ensures the accuracy of the amplitudes and phases of feed connectors. Finally, the numerical solution was applied to the 32-element AESA antenna and the simulations are close to the measurements.

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