Assessment of the Stability of Heterohedral Fullerenes: A Theoretical Analysis of C60-xNx and C60-xBx Where x = 1 and 2

1995 ◽  
Vol 99 (18) ◽  
pp. 6801-6807 ◽  
Author(s):  
Shu-Hsien Wang ◽  
F. Chen ◽  
Y.-C. Fann ◽  
M. Kashani ◽  
M. Malaty ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
The Stability

Mathematical Model Establishment and Analysis on the Pipe Deformation under External Pressure with the Ovality

2013 ◽  
Vol 760-762 ◽  
pp. 2263-2266
Author(s):  
Kang Yong ◽  
Wei Chen
Keyword(s):  
Mathematical Model ◽  
Theoretical Analysis ◽  
Yield Strength ◽  
Residual Stresses ◽  
Numerical Simulations ◽  
Significant Influence ◽  
External Pressure ◽  
Pipe Diameter ◽  
Axial Loads ◽  
The Stability

Beside the residual stresses and axial loads, other factors of pipe like ovality, moment could also bring a significant influence on pipe deformation under external pressure. The Standard of API-5C3 has discussed the influences of deformation caused by yield strength of pipe, pipe diameter and pipe thickness, but the factor of ovality degree is not included. Experiments and numerical simulations show that with the increasing of pipe ovality degree, the anti-deformation capability under external pressure will become lower, and ovality affecting the stability of pipe shape under external pressure is significant. So it could be a path to find out the mechanics relationship between ovality and pipe deformation under external pressure by the methods of numerical simulations and theoretical analysis.

The Stability of Weft Insertion of CRT – 83 Carpet Rapier Loom

2013 ◽  
Vol 457-458 ◽  
pp. 684-687
Author(s):  
Yong Dong Cai ◽  
Shun Bin Ma
Keyword(s):  
Theoretical Analysis ◽  
Initial Deformation ◽  
Weft Yarn ◽  
High Grade ◽  
Release Times ◽  
Factors Influencing ◽  
Main Factors ◽  
The Stability ◽  
Theory Research

CRT- 83 carpet rapier loom is a kind of high-grade rigid rapier loom，the weft yarn will give looms to demand higher stability of the weft insertion. Theoretical analysis based on the theory research of the stability of clamping weft and weft handover shows that the rapier deformation，slipping force and the depth of clamping are main factors influencing the stability of weft insertion.In order to obtain reasonable process of weft insertion，concerned with the following factors：the grip length and outrigger length of rapier，release times of clip yarn device，initial deformation angle of spring piece.

Synergistic Approach to Enterprise Management

2015 ◽  
Vol 4 (3) ◽  
pp. 4-13
Author(s):  
Заковоротный ◽  
Vilor Zakovorotnyy ◽  
Угнич ◽  
Ekaterina Ugnich ◽  
Флек ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Dynamic Model ◽  
Dynamic Systems ◽  
Self Organization ◽  
Enterprise Management ◽  
Economic Systems ◽  
Complex Dynamic ◽  
Complex Dynamic Systems ◽  
Synergistic Approach ◽  
The Stability

The research reveals the peculiarities of synergistic model of enterprise management in market conditions. The possibilities of synergistic approach application towards the study of economic systems are shown in the article. On the basis of theoretical analysis of complex dynamic systems basic rules are identified which must be taken into consideration while examining the enterprise as a system in which the processes of self-organization exist. A generalized dynamic model of an enterprise in market environment is presented. It is carried out the analysis of the established condition of the enterprise as a system and the stability of its stationary state.

Aircraft Behaviour in a Vertical Gradient of Wind Velocity

1963 ◽  
Vol 14 (3) ◽  
pp. 265-278 ◽  
Author(s):  
J. K. Zbrożek
Keyword(s):  
Theoretical Analysis ◽  
Wind Velocity ◽  
Wind Shear ◽  
Wind Profile ◽  
Numerical Study ◽  
Vertical Gradient ◽  
Jet Stream ◽  
Strong Wind ◽  
Aircraft Motion ◽  
The Stability

SummaryThe stability of the phugoid motion of an aircraft in the presence of wind shear is investigated. The effect of the wind shear on the phugoid frequency increases with increasing aircraft speed and can be stabilising or destabilising, depending on the aircraft orientation relative to the wind shear. The destabilising effect of wind shear is alleviated by the stabilising effect of the density gradient of the atmosphere. At the most critical combination of speed and altitude a strong wind shear may lead to divergence, with a time to double amplitude of the order of 10-15 seconds.A numerical study of the aircraft motion with controls fixed when descending through a wind profile similar to that in a jet stream indicates that the increase in the aircraft indicated speed can be of the same magnitude as, or larger than, the maximum wind velocity increment in the jet stream core. However, as the time to reach the excess speed is of the order of one minute, the actual behaviour of the aircraft strongly depends on the pilot's action and thus is not fully predictable by theoretical analysis.

Theoretical Analysis and Numerical Simulation of Oil Lubricated Foil Bearing With Elastic Supported Bump Foil Structure

2016 ◽  
Author(s):  
Guanghui Zhang ◽  
Qiang Chen ◽  
Jiajia Yan ◽  
Xianghe Wang ◽  
Zhansheng Liu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Theoretical Analysis ◽  
Reynolds Equations ◽  
Rotating Speed ◽  
Flexibility Matrix ◽  
Cavitation Effect ◽  
Foil Bearing ◽  
Deformation Equation ◽  
Bearing Load ◽  
The Stability

The oil lubricated multi-leaf foil bearing is developed to meet the demand of high rotating speed for hydraulic turbo-pump, where the lubricated oil is easy to obtain. For the stability of this kind oil lubricated foil bearing needs to be guaranteed, the bearing with elastic supported bump foil structure is proposed to improve the performance of foil bearing. Theoretical analysis and numerical simulation is carried out in this paper. The film thickness expression of multi-leaf foil bearing is established for the cases with and without top foil deformation. The total flexibility matrix considering elastic supported bump foil structure is developed based on Castigliano’s theorem. By employing the Reynolds boundary condition, the oil cavitation effect is presented. The established flexibility matrix is substituting into classical incompressible Reynolds equation, then the deformation equation of the foil and Reynolds equations are solved coupling by successive over relaxation method. The static characteristics such as pressure distribution, bearing load and static equilibrium position are obtained. By employing the perturbation method to Reynolds equations and foil deformation equation, the dynamic characteristics of multi-leaf foil bearing with elastic supported bump foil structure are acquired. The stability of the bearing is analyzed and compared with other type bearings by Routh-Hurwitz method. The effects of bearing load and sommerfeld parameter on the stiffness and damping coefficients are studied. The results indicate that the performance of foil bearing with elastic supported bump foil structure is improved and this kind bearing is suitable for high rotating speed application.

Theoretical analysis of the stability of slopes

Géotechnique ◽  
1978 ◽  
Vol 28 (4) ◽  
pp. 395-411 ◽  
Author(s):  
R. Baker ◽  
M. Garber
Keyword(s):  
Theoretical Analysis ◽  
Stability Of Slopes ◽  
The Stability

An adaptive control allocator for autonomous vehicles with parameter uncertainty

2018 ◽  
Vol 232 (7) ◽  
pp. 807-818
Author(s):  
Dong-liang Chen ◽  
Guo-ping Liu
Keyword(s):  
Adaptive Control ◽  
Theoretical Analysis ◽  
Parameter Uncertainty ◽  
Autonomous Vehicles ◽  
Reference Model ◽  
Digital Simulation ◽  
Control Allocation ◽  
Allocation Scheme ◽  
Negative Effects ◽  
The Stability

In this article, an adaptive control allocation scheme for a class of nonlinear vehicles is proposed. The parameter uncertainty of the effectors is considered in the design of the control allocation algorithm. A reference model is integrated in the framework to overcome the negative effects brought by the parameter uncertainty. The optimum of the solution is discussed for a class of objectives. Stability proof is given. Compared to most existing methods, the conditions to guarantee the stability of the system are relaxed, which is addressed in the theoretical analysis and the experiment. Finally, a digital simulation and an experiment based on a spacecraft simulator are implemented. The results of the simulation and the experiment validate the effectiveness and advantages of the proposed adaptive control allocator.

scholarly journals Stability Mechanism and Repair Method of U-Shaped Steel Reverse Arch Support in Soft Floor Roadway

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Chao Wang ◽  
Xiaoyi Chen ◽  
Jiandong Zhang ◽  
Yongping Wu
Keyword(s):  
Theoretical Analysis ◽  
Friction Factor ◽  
Critical Value ◽  
Breaking Point ◽  
Instability Criterion ◽  
Engineering Practice ◽  
Rotating Beam ◽  
Arch Support ◽  
Arch Structure ◽  
The Stability

This paper is aimed at the inverted arch support instability of track roadway with mining level +1100 m in Liuyuanzi Coal Mine. By means of field investigation, theoretical analysis, numerical calculation, and engineering practice, the instability reasons of inverted arch structure are expounded, the mechanical mechanism of instability of inverted arch structure is revealed, and the “sliding-rotating beam” for the instability of inverted arch structure is put forward. Based on Fenner’s formula and mechanics principle, the equilibrium equation of “sliding-rotating beam” is given. The results show the following: Firstly, the insufficient stiffness at the joint of the inverted arch structure and the U-shaped steel support on the floor is the key reason for the floor instability. Secondly, when the action stress of the “sliding-rotating beam” is less than the critical value, three kinds of instability modes of the inverted arch structure may occur, that is, sliding upward, rotating upward, or sliding-rotating upward. Each instability criterion and critical value are also different. Considering the axisymmetric condition, the critical value calculation formula of the three modes can be simplified into one formula. Thirdly, the equivalent friction factor restricts the stability of the “sliding-rotating beam,” and there is a “breaking point.” The relationship between the equivalent friction factor and the action stress of the “sliding-rotating beam” is “class hyperbola.” When the equivalent friction factor is greater than the “breaking point value,” the “sliding-rotating beam” may remain stable. Moreover, with the increase of equivalent friction factor, the action stress required for the stability of the “sliding-rotating beam” is smaller, and it tends to be more stable. The breaking point value of equivalent friction factor is 18.6. Finally, 36U-shaped steel round frame with bolt-mesh-shotcrete-combined support is applied to improve the equivalent friction factor and the foot stiffness of U-shaped support in roadway. After two months of on-site implementation, the floor heave was reduced by 69.1%. In conclusion, the theoretical analysis is correct and the control method is effective.

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