Oil whip-induced wear in journal bearings

This paper investigates the effect of oil whirl and oil whip in fluid film radial bearings due to possible metallic contact. The degree of metallic contact and thereby wear and tear between rotating shafts and bearing bushes is assessed by measuring electric currents through the oil film. The current as well as the voltage varied in accordance with the contact ratio between the shaft and bush in the fluid film radial bearing. The gauge signal thus indicates the degree of metallic contact based on the thickness of the oil film in the load zone. Some experimental results are provided to illustrate that at low normalised loads involving oil whirl and oil whip, no electric current is detected, while high levels of electric current are registered at high load levels when no oil whirl or oil whip occurred. It is therefore concluded that at low loads, oil whirl and oil whip have little influence on wear and tear in a journal bearing.     

A new model to mitigating random disruption risks of facility and transportation in supply chain network design

In this article, we study the design problem of a reliable stochastic supply chain network in the presence of random disruptions in the location of distribution centers (DCs) and the transportation modes. It is assumed that a disrupted DC does not necessarily fail the whole of its capacity, and may lose a fraction of that, and rest of demand can be served by other DCs. We introduce a new strategy called soft-hardening strategy where the fraction of the lost capacity depends on the amount of investment for opening and operating. Additionally, the conditional value-at-risk (CVaR) approach is applied to control the risk of model. Finally, to solve the model, first we present an exact solution method by reformulating the problem as a second-order cone programming model, and second a hybrid algorithm combining tabu search and simulated annealing algorithms is developed.     

Extended Kalman Filter frequency tracker for nonstationary harmonic signals

In this paper, we propose a frequency tracking algorithm based on an Extended Kalman Filter (EKF). We introduce a generalized state space model to estimate and track frequency of a harmonic signal embedded in broad-band noise. Such nonstationary noisy harmonic signals are characterized by time-varying frequencies and amplitudes. Developing a modified state-space model, we improve performance of EKF frequency tracker for these signals. The proposed method is also used in an adaptive algorithm to estimate noise variance which is assumed to be unknown. Simulation results reveal superiority of the proposed method compared with typical EKF, short time Fourier transform, and interpolated discrete Fourier transform.     

Semi-active vibration control of an eleven degrees of freedom suspension system using neuro inverse model of magnetorheological dampers

A semi-active controller-based neural network for a suspension system with magnetorheological (MR) dampers is presented and evaluated. An inverse neural network model (NIMR) is constructed to replicate the inverse dynamics of the MR damper. The typical control strategies are linear quadratic regulator (LQR) and linear quadratic gaussian (LQG) controllers with a clipped optimal control algorithm, while inherent time-delay and non-linear properties of MR damper lie in these strategies. LQR part of LQG controller is also designed to produce the optimal control force. The LQG controller and the NIMR models are linked to control the system. The effectiveness of the NIMR is illustrated and verified using simulated responses of a full-car model. The results demonstrate that by using the NIMR model, the MR damper force can be commanded to follow closely the desirable optimal control force. The results also show that the control system is effective and achieves better performance and less control effort than the optimal in improving the service life of the suspension system and the ride comfort of a car.     

Periodic inspection optimization model for a multi-component repairable system with failure interaction

This paper proposes a model to find optimal periodic inspection interval for a multi-component repairable system with failure interaction. Failure of one component of the system is hard, i.e., as soon as it occurs, the system stops operating. Failures of the other components are soft, namely, they do not cause the system stop. Soft failures increase the system operating costs and are detected only if inspection is performed. Thus, the components with soft failure are periodically inspected simultaneously and are repaired if found failed. When the component with hard failure fails, it is also repaired. However, it increases the failure rate of the other components. The objective is to find the optimal inspection interval such that, on a finite time horizon, the expected total cost is minimized. The proposed modeling approach is illustrated through a simplified numerical example for a general infusion pump.     

Shape identification problems on detecting of defects in a solid body using inverse heat conduction approach

In this paper, a new shape identification method in the inverse heat conduction problem (IHCP) is applied to detect the location and size of defects in a solid body. Different defects are modeled in a solid body as an elliptical geometry whose parameters are estimated with a proposed inverse algorithm. The inverse algorithm consists of direct, inverse analysis, and gradient-based optimization method. The direct analysis is used a finite-element method in an unstructured grid system to solve the direct heat conduction problem. The inverse analysis is based on recording temperatures data on surface of solid body that calculates the objective function. The employed gradient-based optimization method is constructed using the adjoint, sensitivity, and conjugate gradient method (Powell-Beal’s version) that are used to calculate the gradient of objective function, step size, and minimizing the objective function, respectively. The effects of different noisy temperature data, different cavities on some domains, and different type of defects such as poor cure, porosity, and crack are investigated in this work. The results show that this proposed inverse algorithm is more efficient in detection of defects.     

Ballistic limit evaluation for impact of cylindrical projectiles on honeycomb panels

In this paper the perforation of honeycomb panels under impact of cylindrical projectiles is studied and the ballistic limit velocity is determined by the energy method. The results show that the increase of panel thickness, compression and shear yield strengths and cell wall thickness increase the ballistic limit velocity, while an increase in the size of the cell and projectile mass decrease it. These results are in good agreement with available experimental data.     

State of Florida hurricane loss projection model: Atmospheric science component

The State of Florida has developed an open, public model for the purpose of probabilistic assessment of risk to insured residential property associated with wind damage from hurricanes. The model comprises atmospheric science, engineering, and financial/actuarial components and is planned for submission to the Florida Commission on Hurricane Loss Projection Methodology. The atmospheric component includes modeling the track and intensity life cycle of each simulated hurricane within the Florida threat area. When a model storm approaches within a damage threshold distance of a Florida zip code location, the wind field is computed by a slab model of the hurricane boundary layer coupled with a surface layer model based on the results of recent GPS sonde research. A time series of open terrain surface winds is then computed for each zip code in the threatened area. Depending on wind direction, an effective roughness length is assigned to each zip code based on the upstream fetch roughness as determined from remotely sensed land cover/land use products. Based on historical hurricane statistics, thousands of storms are simulated allowing determination of the wind risk for all residential zip code locations in Florida. The wind risk information is then provided to the engineering and loss models to assess damage and average annual loss, respectively.     

Optimal zoning in the unconstrained Hotelling game

This paper studies a zoning mechanism that gives the optimal locations of two firms in a linear city under mill prices. A regulator biased towards consumers allows a central area of the city to be shared by firms and consumers and thus firms are not allowed to locate outside the city limits. A regulator more concerned about firms extends this central zone outside the city limits and the city has a residential use only if the firms so decide. Finally, a regulator highly biased towards firms allows them to locate only beyond a set distance from the city, so there is a strip of land outside the city but close to its boundaries, for alternative uses.     

Detail design,building and commissioning of tall building structural models for experimental shaking table tests

In the areas of seismic engineering, shaking table tests are powerful methods for assessing the seismic capacity of buildings. Since the size and capacity of existing shaking tables are limited, using scale structural models seems to be necessary. In recent years, many experimental studies have been performed using shaking table tests to determine seismic response of structural models subjected to various earthquake records. However, none of the past research works discussed practical procedure for creating the physical model. Therefore, in this study, a comprehensive procedure for design, building and commissioning of scale tall building structural models has been developed and presented for practical applications in shaking table test programmes. To validate the structural model, shaking table tests and numerical time history dynamic analyses were performed under the influence of different scaled earthquake acceleration records. Comparing the numerical predictions and experimental values of maximum lateral displacements, it became apparent that the numerical predictions and laboratory measurements are in a good agreement. As a result, the scale structural model can replicate the behaviour of real tall buildings with acceptable accuracy. It is concluded that the physical model is a valid and qualified model that can be employed for experimental shaking table tests. Copyright © 2015 John Wiley & Sons, Ltd.