A reliability-based methodology for considering corrosion effects on fatigue deterioration in steel bridges - Part II: Case study of Neka Bridge -

The methodology presented in Part I is examined on Neka Bridge, a railway, truss bridge in northern Iran. The study includes: considerations of climate and air pollution, extraction of the stress-time histories from the FE model, prediction of future traffic volumes in a probabilistic manner and assessment of the effects of MR&R actions on the deterioration profile. PDF of D is determined using Monte Carlo simulations, and the reliability profile is calculated from the performance function. The study shows that for a target reliability of 2.0, the fatigue life of the bridge is reduced by either 29% or 31% if dose-response function or qualitative-based y-t function is used, respectively.     

Control of depth of anaesthesia using fractional‐order adaptive high‐gain controller

This study presents a fractional‐order adaptive high‐gain controller for control of depth of anaesthesia. To determine the depth of anaesthesia, the bispectral index (BIS) is utilised. To attain the desired BIS, the propofol infusion rate (as the control signal) should be appropriately adjusted. The effect of the propofol on the human body is modelled with the pharmacokinetic–pharmacodynamic (PK/PD) model. Physical properties of the patient such as gender, age, height and a like determine the parameters of the PK/PD model. This necessitates us to employ an appropriate adaptive controller. To attain this goal, a fractional‐order adaptive high‐gain controller is constructed to solve the tracking problem for minimum phase systems with relative degree two (such as the PK/PD model). This leads to a time‐varying gain adjusting according to a fractional‐order adaptation mechanism. Simulation results performed on various patients (considering the external disturbance and the measurement noise) show the effectiveness of the proposed method.Inspec keywords: medical control systems, gain control, adaptive control, closed loop systems, time‐varying systemsOther keywords: fractional‐order adaptive high‐gain controller, control signal, pharmacokinetic–pharmacodynamic model, fractional‐order adaptation mechanism, anaesthesia depth control, bispectral index, PK‐PD model, propofol infusion rate, tracking problem, minimum phase systems, time‐varying gain, BIS     

A Novel Method for Bandwidth and Phase Margin Enhancement of Folded-Cascode Amplifier

This article describes a method to enhance bandwidth and phase margin of conventional folded-cascode op amps. It achieves a larger bandwidth and/or phase margin in folded-cascode CMOS op amps than those of a conventional one in a given CMOS process. For the same bandwidth the new method allows a larger phase margin, and for a given phase margin a larger bandwidth can be obtained. Also, for equal bandwidth, power consumption of the new folded-cascode is lower than the traditional one with similar load.     

Adsorption and reaction induced morphological changes of the copper surface of a methanol synthesis catalyst

The morphology (surface structure) of the copper component of an industrial Cu/ZnO/Al₂O₃ methanol synthesis catalyst has been studied by carbon monoxide temperature programmed desorption (CO TPD). The initial state morphology produced by hydrogen reduction at 513 K showed evidence of the existence of Cu(111), Cu(110) and Cu(211) surfaces. Surface oxidation of the copper by CO₂ decomposition at 213 K followed by CO reduction at 473 K did not reproduce the initial state morphology, most of the Cu(110) surface being lost; at the same time there was a six-fold increase in the surface population of the (211) face. This new surface produced by CO₂ decomposition at 213 K and CO reduction at 473 K was considerably less active in its ability to decompose CO₂ at 213 K. Treatment of it with hydrogen at 513 K for 16 h caused the surface to reconstruct almost completely to its original state, with the Cu(110) face reappearing and the Cu(211) face being reduced in population to roughly its original value. The ability of the copper to decompose CO₂ was proportionately restored. It is evident that in the synthesis of methanol using CO/CO₂/H₂ mixtures over Cu/ZnO/Al₂O₃ catalysts, the morphology of the surface of the copper will be in a continuous state of restructuring, which, depending on the conditions, has the potential to result in chaotic behaviour. This revised version was published online in July 2006 with corrections to the Cover Date.     

A new high-speed, high-resolution open-loop CMOS sample and hold

A new open loop, high resolution CMOS sample and hold (S/H) circuit is introduced in this article. This circuit is constructed based on a new method which leads to a great reduction in dependency of the storing charge of the holding capacitors to the charge injection of transistors. It is a combination of dummy switches and auxiliary capacitors in order to decrease the voltage spikes that are produced during the sampling mode. Due to the high linearity feature of our proposed design in comparison with previous works, it is reached to a great improvement in signal to noise and distortion ratio up to about 15 dB and it’s ENOB is equivalent with about 16 bits. Another advantages of our proposed design are it’s lower power dissipation and it’s high input voltage range. Also the optimum functionality of our proposed circuit does not damaged by the threshold voltage’s variations in different corners. As our proposed S/H circuit has been designed in open loop structure, it is suitable for high speed applications.     

Conditionally Stable Multidimensional Schemes for Advective Equations

It is shown that the isotropic wave-like multidimensional spatial stencils combined with linear multistep and Runge-Kutta time marching schemes provide more favorable stability restrictions for advective initial-value problems. Under certain conditions the maximum allowable time step can be doubled compared to using conventional spatial stencils. Consequently, this paper shows that the multidimensional optimizations of spatial schemes, involving more grid points, are not inherently less efficient in terms of the processing time. Three numerical tests solving the two and three dimensional advection equations are carried out to experiment the stability restrictions found in the previous sections.     

Considering the business system’s complexity with a network approach

Business management involves collecting information, goods, and funds as they move from supplier to manufacturer to wholesaler to retailer to consumer. Such business comprises interconnected parts that can be fundamentally complex and dynamic. A disturbance in one subnet of the system may thus have an opposed impact on another subnets, thus disturbing the business. Disruptions can have expensive and extensive results. This research aims to improve an increased Bayesian network method to consider business disruptions. The goal is to develop strategies that can diminish the opposed impacts of the disruptions and improve overall system reliability. Two influence agents are specified: the Bayesian and junction lack influence agents. An industrial model is used to demonstrate the proposed application, making the business more reliable. Moreover, two network learning methodologies are reviewed to update the probabilities in a model. The neural network seems to be a more favorable updating tool.     

Local behavior of column-tree connections with considering bolt-hole clearance and bolt pretension effects

In this paper, effects of bolt-hole clearance and bolt pretension level on seismic performance of column-tree moment resisting frames with reduced beam section have been investigated. In a typical constructional environment, manufacturing tolerances and field situations cause inappropriate positioning of bolts in their corresponding holes in bolted connections, so bolt-hole diameter increases by incorrect methods like acetylene gas cutting method. On the other hand, nonlinear local behavior of the connection elements and effects of dynamic friction during the process of applying the bolt pretension cause wrong evaluation of bolt pretension level. In order to investigate these problems, models of column-tree connections with various bolt-hole clearances and bolt pretension levels subjected to cyclic loading were developed and analyzed with 3D FEM and their hysteresis curves were obtained and evaluated. Results show that bolt-hole clearance can reduce the flexural capacity of column-tree connections especially along with reduction in the bolt pretension level while interstory drift angle increases during inelastic cycles.