scholarly journals The phaseon line: a new criterion for the stability of fullerenes

2001 ◽  
Vol 1 (1) ◽  
pp. 151-162 ◽  
Author(s):  
M. Yoshida ◽  
M. Fujita ◽  
H. Gotō ◽  
E. Ōsawa
Keyword(s):  
The Stability ◽  
New Criterion

scholarly journals Prediction of the Shear Failure of Opened Rock Fractures and Implications for Rock Slope Stability Evaluation

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Yingchun Li
Keyword(s):  
Shear Strength ◽  
Rock Slope ◽  
Shear Failure ◽  
Rock Slope Stability ◽  
Rock Fractures ◽  
Asperity Contact ◽  
Direct Shear Tests ◽  
Proposed Model ◽  
The Stability ◽  
New Criterion

Rock slope commonly fails due to the shear failure of rock fractures. Shear strength of rock fractures are reduced substantially once the fracture surfaces are mismatched or opened. We propose a new criterion to predict the shear strength of rock fractures in different opening states. The degree of interlocking representing the true asperity contact area is incorporated into the modified model of Saeb and Amadei. The effect of fracture opening on asperity dilation and degradation is separately considered. The transitional stress that is a critical parameter involved in the model is analytically determined based on energy consideration. The new model is validated with experimental results from direct shear tests on synthetic fractures with regular-shaped asperities. Good agreement between the analytical solution and the experimental data confirms the capacity of the proposed model. Therefore, the model has great potential for assessing the stability of rock slopes where fractures are often opened due to stress relief and engineering disturbances.

A Comparison of Two Different IMPSAT Models in Compositional Simulation

SPE Journal ◽  
2007 ◽  
Vol 12 (01) ◽  
pp. 145-151 ◽  
Author(s):  
Jarle Haukas ◽  
Ivar Aavatsmark ◽  
Magne Espedal ◽  
Edel Reiso
Keyword(s):  
Explicit Solution ◽  
Oil And Gas ◽  
Compositional Simulation ◽  
Flow Equations ◽  
Gas Phases ◽  
Compositional Model ◽  
The Difference ◽  
The Stability ◽  
New Criterion ◽  
Nonlinear Iteration

Summary A new IMPSAT model, with explicit solution of variables that are isochoric (i.e., complementary to volumes), is compared to the conventional IMPSAT model, which determines phase mole fractions explicitly. The compared properties are performance of the nonlinear iteration and numerical stability. The use of complementary variables in the new IMPSAT model makes the nonlinear system better conditioned. Consequently, fewer nonlinear iteration steps are required. The resulting speedup more than compensates for the added costs of introducing and using the isochoric variables. The stability criterion associated with the new IMPSAT model is in many cases significantly less conservative than the conventional criterion. However, for cases in which there is little or no saturation change between the hydrocarbon phases (e.g., for retrograde gas condensate cases or single hydrocarbon phase cases), the difference between the criteria is insignificant. The timestep sizes for which instabilities occur are practically the same for the two models, and no oscillations have been observed unless both the new and the conventional criterion are violated. Consequently, the stability properties are similar, and the new criterion seems to apply to both models. Our conclusions are supported by numerical results. Introduction An isothermal compositional model of Nc components involves the solution of Nc flow equations per gridblock (e.g., the mass balance equations): (Eq. 1) where ?ni is the change in the amount of component i during timestep ?t, while fi and qi are the component interblock flow and source rates. In addition, phase equilibrium between the oil and gas phases (e.g., equalities of fugacities), (Eq. 2) must be taken into account. Because of the large number of equations and the complex thermodynamics, it is too demanding to determine all variables implicitly (i.e., simultaneously in all gridblocks). Instead, we use a partially explicit approach, where some variables are determined implicitly, while others are determined explicitly, gridblock by gridblock. The explicit solution relies on explicit treatment of variables (i.e., evaluating parts of the interblock flow with variables from the previous time level).

scholarly journals New criterion for the stability of a human body in floodwaters

2014 ◽  
Vol 52 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Junqiang Xia ◽  
Roger A. Falconer ◽  
Yejiang Wang ◽  
Xuanwei Xiao
Keyword(s):  
Human Body ◽  
The Stability ◽  
New Criterion

A New Method to Detect Regenerative Chatter Using Spectral Analysis, Part 1: Basic Study on Criteria for Detection of Chatter

1997 ◽  
Vol 119 (4A) ◽  
pp. 461-466 ◽  
Author(s):  
E. Kondo ◽  
H. Ota ◽  
T. Kawai
Keyword(s):  
Spectral Analysis ◽  
Numerical Simulations ◽  
Vibration Amplitude ◽  
Orthogonal Cutting ◽  
Stability Limit ◽  
Regenerative Chatter ◽  
Basic Study ◽  
Workpiece Surface ◽  
The Stability ◽  
New Criterion

The purpose of this study is to introduce a new criterion for detecting regenerative chatter by application of spectral analysis. From the regenerative chatter theory, it can be seen that the vibration amplitude perpendicular to a workpiece surface comes equal to the amplitude of surface undulation at the stability limit. So the regenerative chatter theory is applied to the criterion introduced in this study to detect regenerative chatter. Validity of this criterion was examined by using numerical simulations assumed to be orthogonal, and then experiments for verification of criterion validity were carried out using the regenerative chatter of a turning workpiece in orthogonal cutting. We concluded that this criterion is reliable enough to detect regenerative chatter.

scholarly journals New criterion for the stability of a human body in floodwaters

2015 ◽  
Vol 53 (4) ◽  
pp. 540-541 ◽  
Author(s):  
Hubert Chanson ◽  
Richard Brown
Keyword(s):  
Human Body ◽  
The Stability ◽  
New Criterion

More rapid analysis of rock slopes

1984 ◽  
Vol 21 (4) ◽  
pp. 678-683
Author(s):  
D. M. Cruden
Keyword(s):  
Factor Of Safety ◽  
Rock Slope ◽  
Rapid Analysis ◽  
Rock Slopes ◽  
Equal Area ◽  
Slope Analysis ◽  
The Stability ◽  
New Criterion ◽  
Spherical Projection ◽  
Rock Wedge

When the normals to two discontinuities forming a tetrahedral wedge in a rock slope lie in the opposite halves of a spherical projection divided by a diameter through the line of intersection of the discontinuities, sliding will take place down the line of intersection of the discontinuities if this is statically possible. This new criterion simplifies the analysis of the stability of rock wedges whose motion is driven only by gravity and resisted only by friction. A factor of safety can be simply calculated for all these wedges from plots of the normals to discontinuities on an overlay of a polar, equal-area spherical projection to which the great circles of a similar equatorial projection have been added. Key words: rock, slope analysis, rock wedge, graphical methods.

scholarly journals A new criterion of asymptotic stability for Hopfield neural networks with time-varying delay

2022 ◽  
Vol 25 (6) ◽  
pp. 753-761
Author(s):  
Weiru Guo ◽  
Fang Liu
Keyword(s):  
Neural Networks ◽  
Asymptotic Stability ◽  
Integral Inequality ◽  
Hopfield Neural Networks ◽  
Time Varying ◽  
Time Varying Delay ◽  
Communication Time ◽  
The Stability ◽  
New Criterion ◽  
Varying Delay

The objective of this paper is to analyze the stability of Hopfield neural networks with time-varying delay. For the system to operate in a steady state, it is important to guarantee the stability of Hopfield neural networks with time-varying delay. The Lyapunov-Krasovsky functional method is the main method for investigating the stability of time-delayed systems. On the basis of this method, the stability of Hopfield neural networks with time-varying delay is ana-lysed. It is known that due to such factors as communication time, limited switching speed of various active devices, time delays often arise in various technical systems, which significantly degrade the performance of the system, which can in turn lead to a complete loss of stability. In this regard, a Lyapunov-Krasovsky type delay-product functional was con-structed in the paper, which allows more information about the time delay and reduces the conservatism of the method. Then a generalized integral inequality based on the free matrix was used. A new criterion for asymptotic stability of Hop-field neural networks with time-varying delay, which has less conservatism, was formulated. The effectiveness of the proposed method is illustrated. Thus an asymptotic stability criterion for Hopfield neural networks with time-varying delay was formulated and justified. The expanded Lyapunov-Krasovsky functional is constructed on the basis of delay and quadratic multiplicative functional, and the derivative of the functional is defined by a matrix integral inequality with free weights. The effectiveness of the method is illustrated by a model example.

scholarly journals First-Principles Study of The Structural Phase Transition Process of Solid Nitrogen Under Pressure

2021 ◽  
Author(s):  
Zhi-Xin Bai ◽  
Cheng-Lu Jiang ◽  
Sheng-Hai Zhu ◽  
Mi Zhong ◽  
Ming-Jian Zhang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
First Principles ◽  
Structural Phase ◽  
Transition Process ◽  
Whole Process ◽  
Solid Nitrogen ◽  
Phase Transition Process ◽  
The Stability ◽  
New Criterion

Abstract Due to the diversity of solid nitrogen structure, its phase transition has been a hot topic for many scientists. Herein, we first studied the structural softening of rhombohedral solid nitrogen under pressure using first-principles calculations. Then, a new criterion, Egret criterion, was proposed to predicting the whole process from beginning to end of structural phase transition of solid nitrogen. Based on the discussion of acoustic phonons, we concluded that the phase transition of rhombohedral solid nitrogen starts from k-point F along the [-1, -1, 0] direction in a-axis, and the structural phase transition velocity is slow. Also, we use the Egret criterion proposed by us to predict the emergence of ξ-N2 and the stability of ξ-N2 at 17 GPa and 22 GPa, respectively, and this result is in good agreement with the phase diagram of nitrogen.

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