Incipient Slip Conditions in the Rolling Contact of Tyred Wheels

2010 ◽  
Vol 224 (10) ◽  
pp. 2049-2054 ◽  
Author(s):  
S Reina ◽  
D A Hills ◽  
D Dini
Keyword(s):  
Contact Problem ◽  
Closed Form ◽  
Rolling Contact ◽  
Simplified Model ◽  
Practical Case ◽  
Closed Form Solutions ◽  
Steel Wheel ◽  
State Of Stress ◽  
Wide Range ◽  
Tractive Rolling

The contact problem of a driving tyred wheel, pressed and rolling over an elastically similar half-plane, is considered. Although applicable to a wide range of shrink-fitted assemblies, the simplified model is solved to study the practical case of an elastically similar steel tyre mounted on a locomotive steel wheel subjected to tractive rolling. The behaviour of the system at the tyre—substrate interface is studied using closed-form solutions to calculate the state of stress within the tyre. Conditions leading to incipient slip and/or plasticity are identified and mapped for different loads and geometries.

WORST-OF OPTIONS AND CORRELATION SKEW UNDER A STOCHASTIC CORRELATION FRAMEWORK

2012 ◽  
Vol 15 (07) ◽  
pp. 1250051 ◽  
Author(s):  
JACINTO MARABEL ROMO
Keyword(s):  
Closed Form ◽  
Stochastic Volatility ◽  
Term Structure ◽  
Stochastic Volatility Model ◽  
Closed Form Solutions ◽  
Stochastic Correlation ◽  
Term Structures ◽  
Volatility Model ◽  
Wide Range ◽  
Correlation Term

This article considers a multi-asset model based on Wishart processes that accounts for stochastic volatility and for stochastic correlations between the underlying assets, as well as between their volatilities. The model accounts for the existence of correlation term structure and correlation skew. The article shows that the Wishart specification can generate different patterns corresponding to the correlation skew for a wide range of correlation term structures. Another advantage of the model is that it is analytically tractable and, hence, it is possible to obtain semi-closed-form solutions for the prices of plain vanilla options, as well as for the price of exotic derivatives. In this sense, this article develops semi-closed-form formulas for the price of European worst-of options with barriers and/or forward-start features. To motivate the introduction of the Wishart volatility model, the article compares the prices obtained under this model and under a multi-asset stochastic volatility model with constant instantaneous correlations. The results reveal the existence of a stochastic correlation premium and show that the consideration of stochastic correlation is a key element for the valuation of these structures.

scholarly journals Generalized Truncated Methods for an Efficient Solution of Retrial Systems

2008 ◽  
Vol 2008 ◽  
pp. 1-15 ◽  
Author(s):  
Ma Jose Domenech-Benlloch ◽  
Jose Manuel Gimenez-Guzman ◽  
Vicent Pla ◽  
Jorge Martinez-Bauset ◽  
Vicente Casares-Giner
Keyword(s):  
Closed Form ◽  
State Space ◽  
Efficient Solution ◽  
Analytic Solution ◽  
Computational Cost ◽  
Retrial Queues ◽  
Performance Parameters ◽  
Approximate Methods ◽  
Closed Form Solutions ◽  
Wide Range

We are concerned with the analytic solution of multiserver retrial queues including the impatience phenomenon. As there are not closed-form solutions to these systems, approximate methods are required. We propose two different generalized truncated methods to effectively solve this type of systems. The methods proposed are based on the homogenization of the state space beyond a given number of users in the retrial orbit. We compare the proposed methods with the most well-known methods appeared in the literature in a wide range of scenarios. We conclude that the proposed methods generally outperform previous proposals in terms of accuracy for the most common performance parameters used in retrial systems with a moderated growth in the computational cost.

scholarly journals A Semidefinite Relaxation Method for Elliptical Location

Electronics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 128
Author(s):  
Xin Wang ◽  
Ying Ding ◽  
Le Yang
Keyword(s):  
Maximum Likelihood ◽  
Closed Form ◽  
Maximum Likelihood Estimator ◽  
Communication Systems ◽  
Computational Cost ◽  
Semidefinite Relaxation ◽  
Noise Levels ◽  
Likelihood Estimator ◽  
Closed Form Solutions ◽  
Wide Range

Wireless location is a supporting technology in many application scenarios of wireless communication systems. Recently, an increasing number of studies have been conducted on range-based elliptical location in a variety of backgrounds. Specifically, the design and implementation of position estimators are of great significance. The difficulties arising from implementing a maximum likelihood estimator for elliptical location come from the nonconvexity of the negative log-likelihood functions. The need for computational efficiency further enhances the difficulties. Traditional algorithms suffer from the problems of high computational cost and low initialization justifiability. On the other hand, existing closed-form solutions are sensitive to the measurement noise levels. We recognize that the root of these drawbacks lies in an oversimplified linear approximation of the nonconvex model, and accordingly design a maximum likelihood estimator through semidefinite relaxation for elliptical location. We relax the elliptical location problems to semidefinite programs, which can be solved efficiently with interior-point methods. Additionally, we theoretically analyze the complexity of the proposed algorithm. Finally, we design and carry out a series of simulation experiments, showing that the proposed algorithm outperforms several widely used closed-form solutions at a wide range of noise levels. Extensive results under extreme noise conditions verify the deployability of the algorithm.

Closed Form Solutions of Joint Water-Filling for Coordinated Transmission

2010 ◽  
Vol E93-B (12) ◽  
pp. 3461-3468 ◽  
Author(s):  
Bing LUO ◽  
Qimei CUI ◽  
Hui WANG ◽  
Xiaofeng TAO ◽  
Ping ZHANG
Keyword(s):  
Closed Form ◽  
Closed Form Solutions ◽  
Water Filling
Sign in / Sign up

Export Citation Format

Share Document