Optimal Rectification Research Articles

Track geometry defect rectification based on track deterioration modelling and derailment risk assessment

Analysing track geometry defects is critical for safe and effective railway transportation. Rectifying the appropriate number, types and combinations of geo-defects can effectively reduce the probability of derailments. In this paper, we propose an analytical framework to assist geo-defect rectification decision making. Our major contributions lie in formulating and integrating the following three data-driven models: (1) A track deterioration model to capture the degradation process of different types of geo-defects; (2) A survival model to assess the dynamic derailment risk as a function of track defect and traffic conditions; (3) An optimization model to plan track rectification activities with two different objectives: a cost-based formulation (CF) and a risk-based formulation (RF). We apply these approaches to solve the optimal rectification planning problem for a real-world railway application. We show that the proposed formulations are efficient as well as effective, as compared with existing strategies currently in practice.

Optimal rectification in the ultrastrong coupling regime.

We study the effect of ultrastrong coupling on the transport of heat. In particular, we present a condition for optimal rectification, i.e., flow of heat in one direction and complete isolation in the opposite direction. We show that the strong-coupling formalism is necessary for correctly describing heat flow in a wide range of parameters, including moderate to low couplings. We present a situation in which the strong-coupling formalism predicts optimal rectification whereas the phenomenological approach predicts no heat flow in any direction, for the same parameter values.

Effect of Al/Cu ratios on the optical, electrical, and electrochemical properties of Cu–Al–Ca–O thin films

This study systematically investigated the effect of various Al/Cu ratios on the optical, electrical, and electrochemical properties of sputter-deposited CuAlx−0.2Ca0.2O (x=1, 1.25, 1.5, 1.75, 2) thin films. The as-sputtered Cu–Al–Ca–O films were all amorphous regardless of Al/Cu ratio. Both the transmittance and resistivity of the Cu–Al–Ca–O films increased with increasing Al/Cu ratios. Heterojunction diodes fabricated using Al-doped ZnO, ZnO, and Cu–Al–Ca–O thin films of various Al/Cu ratios exhibited high breakdown-voltage values when Cu–Al–Ca–O thin films with high Al/Cu ratios. Optimal rectification ratio and electrical properties were determined in diodes that had CuAl1.3Ca0.2O as their p-layer deposited film. Cu–Al–Ca–O films with high Al/Cu ratios exhibited low average corrosion current density (icorr) values and high breakdown-voltages (Ebr) values, indicating that the corrosion resistance of Cu–Al–Ca–O film increases with increasing Al/Cu ratios.

Unsteady Analysis of the Flow Rectification Performance of Conical Microdiffuser Valves for Valveless Micropump Applications

AbstractA numerical analysis of the unsteady flows in conical microdiffusers appropriate for valveless micropump applications is performed. The rectification efficiency of the diffuser valve is calculated directly as a function of geometric and operational parameters, including diffuser angle, diffuser slenderness, sizes of actuation chamber and inlet/outlet port, actuation frequency, and amplitude of actuation pressure. The computational results show that the diffuser with diverging angle of 10° and slenderness of 7.5 has the best rectification performance. For large actuation pressure amplitude, the optimal rectification efficiency and its corresponding Roshko number are relatively high. At the optimal Roshko number, the flow impedance is found to be dominated by fluid inertia. Sizes of the pump chamber and inlet/outlet port are shown to have a prominent effect on valve performance. Small actuation chamber or small inlet/outlet port can significantly deteriorate the valving performance of the diffuser.

Fast bowtie effect elimination for MODIS L1B data

The bowtie effect refers to geometry distortions for the moderate resolution imaging spectrum-radiometer (MODIS) level 1B (L1B) data. Till now, to eliminate the bowtie effect, numerous methods are proposed. However, most of them have limitations in computation efficiency. Through a comparative study of existing methods, this article puts forward a fast method to eliminate the bowtie effect using the ephemeris data. In this method, the rough positions of overlapping data are first detected. Because of the influence caused by the instrument characters and the earth's curvature, the positions of overlapping data need to be rectified to obtain more precise results. The optimal rectification method used in this article is selected by comparing three methods. By using the optimal method, the rectified MODIS data can be obtained. The experiments demonstrate that the bowtie effect can be eliminated in less than 1 s. In contrast, other traditional methods spend at least 3 s, thus the proposed method is faster and more effective.

Optimal rectification column, reboiler vessel, connection pipe selection and optimal control of batch distillation considering hydraulic limitations

In this article the optimal selection of the reboiler vessels, rectification columns and connection pipes with regard to reboiler swelling, and tray and pipe flooding is investigated. Since the reboilers are constrained by liquid swelling, while pipes and columns are constrained by flooding it is important to pair the equipment so that the vapor rate limitations are as close as possible, thus ensuring maximal equipment capacity usage. Calculations at 1 and 0.25 bar pressure are performed for the standardized 1.6, 2.5, 4 and 6.3 m 3 reboiler vessels [Rührbehälter Basler Norm, N 253, 1977] and sieve tray rectification columns with nominal diameters ranging from 0.2 up to 0.6 m. The dynamic operation of the batch distillation process having the vapor load and reflux ratio as input profiles is evaluated by formulating and solving an optimal control problem constrained by the hydraulic limitations. The open-loop optimization problem is solved using a dedicated Matlab tool – OptCon – which implements the multiple shooting strategy and the large-scale non-linear programming problem is handled by the HQP engine.

Anomalous interstitial dynamics, Stokes’ drift, and current inversion in AC-driven vortex lattices in superconductors with arrays of asymmetric double-well traps

Using numerical simulations, we study the response, to an AC square-wave Lorentz force, of an assembly of magnetic vortices interacting with a square lattice of double-well asymmetric pinning centers. The collective AC-driven vortex dynamics becomes rectified for drive amplitudes within an optimal rectification window. Here we focus on the dynamics right above the first matching field, where there are slightly more vortices than pinning traps. Remarkably, for low drive amplitudes the excess vortices, i.e., not sitting in the pinning centers, behave either like highly mobile interstitials confined between two adjacent columns of vortices, or like stable discommensurations of single lattice columns. In both cases these excess vortices exhibit a variety of dynamical responses (e.g., current inversion, Stokes’ drift) depending on the amplitude of the applied force.

On-line optimization of free radical bulk polymerization reactors in the presence of equipment failure

An on-line optimizing control scheme has been developed for bulk polymerization of free radical systems. The effects of random errors, as well as one kind of a major disturbance (heating system failure), have been studied. A model-based, inferential state estimation scheme was incorporated to estimate, on-line, the parameters of the model (and thereby, the monomer conversion and molecular weight of the polymer) using experimental data on temperature and viscosity. A sequential quadratic programming technique was used for this purpose. A major disturbance, such as heating system failure, leads to a deteriorated final product unless an on-line optimal temperature trajectory (history) is recomputed and implemented on the reactor. Genetic algorithm was used for this purpose. It has been found that, if the “sensing” of the major temperature deviation from the optimal value and rectification of the heating system is achieved well in advance of the onset of the Trommsdroff effect, use of a reoptimized temperature history is sufficient to produce the desired product without significantly altering reaction time. However, if such a disturbance occurs late, a single-shot intermediate addition of an optimal amount of initiator needs to be used in addition to changing the temperature history to produce polymers having the desired properties in the minimum reaction time. Other types of failures can similarly be handled using the methodology developed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2101–2120, 1999