Capacitated Arc Research Articles

An Adaptive Iterated Local Search for the Mixed Capacitated General Routing Problem

We study the mixed capacitated general routing problem (MCGRP) in which a fleet of capacitated vehicles has to serve a set of requests by traversing a mixed weighted graph. The requests may be located on nodes, edges, and arcs. The problem has theoretical interest because it is a generalization of the capacitated vehicle routing problem (CVRP), the capacitated arc routing problem (CARP), and the general routing problem. It is also of great practical interest since it is often a more accurate model for real-world cases than its widely studied specializations, particularly for so-called street routing applications. Examples are urban waste collection, snow removal, and newspaper delivery. We propose a new iterated local search metaheuristic for the problem that also includes vital mechanisms from adaptive large neighborhood search combined with further intensification through local search. The method utilizes selected, tailored, and novel local search and large neighborhood search operators, as well as a new local search strategy. Computational experiments show that the proposed metaheuristic is highly effective on five published benchmarks for the MCGRP. The metaheuristic yields excellent results also on seven standard CARP data sets, and good results on four well-known CVRP benchmarks, including improvement of the best known upper bound for one instance.

Electro-mechanical efficiency of plasma synthetic jet actuator driven by capacitive discharge

A simplified model is established to estimate the jet exit density variation of a plasma synthetic jet actuator (PSJA) driven by a capacitive arc discharge. This model, in conjunction with phase-locked planar particle imaging velocimetry (PIV) measurements, enables the calculation of jet mechanical energy for different operating conditions. Discharge energy is directly calculated based on waveforms of applied voltage and discharge current. The ratio of jet mechanical energy to discharge energy provides the absolute electro-mechanical efficiency. Results indicate that PSJA is characterized by a rather low electro-mechanical efficiency in the order of 0.1%, while the maximum observed value under tested conditions is 0.22%. Electro-mechanical efficiency improves significantly with nondimensional energy deposition, and appears largely independent of jet exit diameter.

Memetic algorithm with route decomposing for periodic capacitated arc routing problem

In this paper, the Periodic Capacitated Arc Routing Problem (PCARP) is investigated. PCARP is an extension of the well-known CARP from a single period to a multi-period horizon. In PCARP, two objectives are to be minimized. One is the number of required vehicles (nv), and the other is the total cost (tc). Due to the multi-period nature, given the same graph or road network, PCARP can have a much larger solution space than the single-period CARP counterpart. Furthermore, PCARP consists of an additional allocation sub-problem (of the days to serve the arcs), which is interdependent with the routing sub-problem. Although some attempts have been made for solving PCARP, more investigations are yet to be done to further improve their performance especially on large-scale problem instances. It has been shown that optimizing nv and tc separately (hierarchically) is a good way of dealing with the two objectives. In this paper, we further improve this strategy and propose a new Route Decomposition (RD) operator thereby. Then, the RD operator is integrated into a Memetic Algorithm (MA) framework for PCARP, in which novel crossover and local search operators are designed accordingly. In addition, to improve the search efficiency, a hybridized initialization is employed to generate an initial population consisting of both heuristic and random individuals. The MA with RD (MARD) was evaluated and compared with the state-of-the-art approaches on two benchmark sets of PCARP instances and a large data set which is based on a real-world road network. The experimental results suggest that MARD outperforms the compared state-of-the-art algorithms, and improves most of the best-known solutions. The advantage of MARD becomes more obvious when the problem size increases. Thus, MARD is particularly effective in solving large-scale PCARP instances. Moreover, the efficacy of the proposed RD operator in MARD has been empirically verified.

Electrochemical impedance spectroscopy fingerprints the ion selectivity of microgel functionalized ion-exchange membranes

Surface modification methods are applied to alter interfacial phenomena and improve ion transport through membranes. In this work we present a novel method for tailoring the surface of cation-exchange membranes based on the deposition of thin microgel monolayers. The charge of such layers exerts a strong influence on the monovalent-ion-selectivity, and this is reflected in the electrochemical impedance responses. Membranes coated with uncharged microgels show similar behavior to that of unmodified ones, with impedance spectra dominated by low-frequency diffusional arcs. However, membranes modified with positively charged microgels exhibit an increased resistance due to the hindered transport of cations through the modification. An additional high-frequency capacitive arc is obtained with the monovalent-ion-selective membranes, which is attributed to concentration polarization effects at the membrane/modification interface. The characteristic frequency of this arc decreases with the valency of the ion, thus proving that multivalent ions pass through the modification layer at rates much slower than monovalent ones. Accordingly, electrochemical impedance spectroscopy has been used to feature monovalent-ion-selective properties of layered membranes.

Immune clonal algorithm based on directed evolution for multi-objective capacitated arc routing problem

The capacitated arc routing problem is playing an increasingly important role in our society, engendering increasing attention from the research community. Among the various models, multi-objective capacitated arc routing problem comes much closer to real-world problems. Therefore, this paper proposes an immune clonal algorithm based on directed evolution to solve this problem. Firstly, the proposed algorithm adopts the framework of the immune clonal algorithm and expands the scale of the initial antibody population in the initialization process to increase the diversity of the antibodies. Secondly, the proposed algorithm is combined with a decomposition strategy in the operations of the immune gene. Antibodies are classified to perform the immune genetic operations, which helps the antibody populations to share the neighborhood information in a timely manner. Thirdly, the proposed algorithm applies a novel kind of comparison operator to build the total population, which helps it to evolve in the direction of a better population and improves the quality of the antibodies. Experimental results suggest that the proposed algorithm can generate better non-dominant solutions than several compared state-of-the-art algorithms, especially for large-scale sets.

Magnesium Alloy Corrosion Under Thin Electrolyte Layer Using Electrochemical Impedance Spectroscopy and Polarization Curve

Here, we reported some simulated atmospheric corrosion studies of magnesium alloy (including AZ91D and AM60) based on electrochemical impedance spectroscopy and polarization technology, and the effect of rare earth element Ce or La on corrosion behavior of magnesium alloy. In the case of AZ91D magnesium alloy, the electrochemical results reveal that the corrosion rate of AZ91D under thin electrolyte layers (TELs) is slower than that in bulk solution and decreases with the TEL thickness thinning. Bothe the anodic and cathodic reactions are restrained under TELs, especially in thickness thinning to around 200 μm and lower. For AM60 magnesium alloy and pure magnesium, the corrosion processes are also inhibited by decreasing thickness of TEL. All those corrosion rates and behavior of magnesium and its alloy are different from that of aluminum, copper and zinc alloy, which are due to the special cathodic reaction for magnesium alloy. Rare earth elements Ce or La have a strong effect on the dissolution of AM60 magnesium alloy under TEL. Typical impedance diagrams consist of two capacitive arcs at high and intermediate frequencies in all cases. At low frequencies, an arc or tail in the Nyquist plots appears sometimes disappears due to the complex corrosion reaction. Comparing to AM60, AM60 with rare earth element addition presents the 3rd capacitive loop sometimes instead of an inductive tail under the TEL thicknesses of 200 and 300 μm, which is associated with reaction taking place on the cathodic intermetallic compounds formed with rare earth elements. The EIS and polarization measurements indicate the rare earth element alloying can reduce corrosion rate of AM60 and AZ91D both under TEL and in bulk electrolyte.

The Effect of Hydrogen on the Corrosion and Anodic Behavior of 13Cr Stainless Steel in Chloride Solution

The effects of charged-hydrogen in 13Cr stainless steel on corrosion and anodic behavior in 200 ppm (wt%) NaCl solution is investigated with immersion tests, potentiodyanmic polarization, potentiostatic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the charged-hydrogen decreases the open circuit potential, increases the anodic current density, decreases the capacitive arcs both in the high frequency region and frequency region of the EIS Nyquist diagram. Charged hydrogen increases the ratio of Fe/Cr of the specimen surface after immersion in NaCl solution.

A Scalable Approach to Capacitated Arc Routing Problems Based on Hierarchical Decomposition.

The capacitated arc routing problem (CARP) is a challenging optimization problem with lots of applications in the real world. Numerous approaches have been proposed to tackle this problem. Most of these methods, albeit showing good performance on CARP instances of small and median sizes, do not scale well to large-scale CARPs, e.g., taking at least a few hours to achieve a satisfactory solution on a CARP instance with thousands of tasks. In this paper, an efficient and scalable approach is proposed for CARPs. The key idea of the proposed approach is to hierarchically decompose the tasks involved in a CARP instance into subgroups and solve the induced subproblems recursively. The output of the subproblems at the lower layer in the hierarchy is treated as virtual tasks and new subproblems are formulated based on these virtual tasks using clustering techniques. By this means, the number of tasks (or virtual tasks) decreases rapidly from the bottom to the top layers of the hierarchy, and the sizes of all subproblems at each layer can be kept tractable even for very large-scale CARPs. Empirical studies are conducted on CARP instances with up to 3584 tasks, which are an order of magnitude larger than the number of tasks involved in all CARP instances investigated in the literature. The results show that the proposed approach significantly outperforms existing methods in terms of scalability. Since the proposed hierarchical decomposition scheme is designed to obtain a good permutation of tasks in a CARP instance, it may also be generalized to other hard optimization problems that can be formulated as permutation-based optimization problems.

Enhancing the Electrochemical Behavior of Pure Copper by Cyclic Potentiodynamic Passivation: A Comparison between Coarse- and Nano-Grained Pure Copper

Electrochemical behavior of coarse- and nano-grained pure copper were modified and improved to a large extent by the application of cyclic potentiodynamic passivation. The efficacy of this method was evaluated on the basis of grain size which is of great importance in corrosion studies. In this study, the eight passes of accumulative roll bonding process at room temperature were successfully performed to produce nano-grained pure copper. Transmission electron microscopy image indicated that the average grain size reached below 100 nm after eight passes. On the basis of cyclic voltammetry and also the electrochemical tests performed after that, it was revealed that cyclic potentiodynamic passivation had a significant improving effect on the passive behavior of both coarse- and nano-grained samples. In addition, a superior behavior of nano-grained sample in comparison to coarse-grained one was distinguished by its smaller cyclic voltammogram loops, nobler free potentials, larger capacitive arcs in the Nyquist plots, and less charge carrier densities within the passive film.

Location arc routing problem with inventory constraints

Dust suppression of hauling roads in open pit mines is done by periodically spraying water from a water truck. The objective of this paper is to present and compare two methods for locating water depots along the road network so that penalty costs for the lack of humidity in roads and routing costs are minimized. Because the demands are located on the arcs of the network and the arcs require service more than once in a time horizon, this problem belongs to the periodic capacitated arc routing domain. We compare two methods for finding the initial depot location. We then use an exchange algorithm to modify the initial location and an adaptive large neighborhood search algorithm to modify the initial routing of vehicles. This method is the first one used for depot location in periodic arc routing problems.

Splitting procedures for the Mixed Capacitated Arc Routing Problem under Time restrictions with Intermediate Facilities

This paper develops optimal and quick near-optimal splitting procedures for the Mixed Capacitated Arc Routing Problem under Time restrictions with Intermediate Facilities. Splitting procedures are a key component of giant tour-based solution methods for Arc Routing Problems. The optimal and near-optimal splitting procedures are tested within a multi-start constructive heuristic, and a fixed execution-time limit is imposed. Results on benchmark instances show that the constructive-heuristic linked with the new optimal splitting algorithm performs better than the near-optimal versions.

Application of electrochemical impedance spectroscopy: A phase behavior study of babassu biodiesel-based microemulsions

Microemulsions are thermodynamically stable systems of two immiscible liquids, one aqueous and the other of organic nature, with a surfactant and/or co-surfactant adsorbed in the interface between the two phases. Biodiesel-based microemulsions, consisting of alkyl esters of fatty acids, open a new means of analysis for the application of electroanalytical techniques, and is advantageous as it eliminates the required pre-treatment of a sample. In this work, the phase behaviours of biodiesel-based microemulsions were investigated through the electrochemical impedance spectroscopy (EIS) technique. We observed thatan increase in the amount of biodiesel in the microemulsion formulation increases the resistance to charge transfer at the interface. Also, the electrical conductivity measurements revealed that a decrease or increase in electrical properties depends on the amount of biodiesel. EIS studies of the biodiesel-based microemulsion samples showed the presence of two capacitive arcs: one high-frequency and the other low-frequency. Thus, the formulation of microemulsions plays an important role in estimating the electrical properties through the electrochemical impedance spectroscopy technique.

Origin of low frequency inductive impedance loops of O2 reduction reaction of solid oxide fuel cells

Inductive impedance loop at low frequencies on electrochemical impedance spectroscopy curves is a common phenomenon in electrochemical reactions such as fuel cells. Here, we study the occurrence of low frequency inductive impedance loops and their evolution for the oxygen reduction reaction on Gd0.2Ce0.8O1.9 infiltrated La0.8Sr0.2MnO3 (GDC-LSM), GDC infiltrated Pt (GDC-Pt) and mixed ionic and electronic conducting (MIEC) La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathodes under solid oxide fuel cells (SOFCs) operation conditions. The incorporation of GDC nanoparticles (NPs) substantially enhances the electrochemical activity of LSM and Pt electrodes with the concomitant occurrence of an inductive impedance loop at low frequencies. However, the low frequency impedance loop disappears for the GDC-LSM with GDC NPs larger than 41nm or after polarization at 200mAcm−2 for more than 60min. In the case of LSCF electrode the low frequency inductive loop transfers to capacitive arc after polarization for 30min. The occurrence of low frequency inductive loops is closely related to the electrode electrocatalytic activity and microstructure and is primarily determined by the ability of the electrode materials to supply atomic oxygen for the reaction at the interface. A mechanism of competitive atomic oxygen supply and dissociative oxygen adsorption and diffusion is proposed for the occurrence of the inductive loops at low frequencies for the O2 reduction reaction of SOFCs.

The Effect of Hydrogen on the Corrosion and Anodic Behavior of 13Cr Stainless Steel in Chloride Solution

Hydrogen evolution is one of the common cathodic reactions involved in corrosion of metals and alloys in aqueous solutions. The reduction of hydrogen ions is a source of atomic hydrogen on the surfaces of metals. Corrosion reactions, the application of cathodic protection and electroplating, etc., can introduce hydrogen into metals via diffusion. The presence of hydrogen in metals can have a significant influence on the mechanical properties and electrochemical behavior of metals depending on the environments. Stainless steels generally corrode at very low rates in high temperature aqueous environments because of their tendency to form a protective oxide film. Hydrogen is incorporated into the structural alloys during production, fabrication, processing, from in service conditions, and from the electrochemical reaction during corrosion. The transport of hydrogen through passive films is involved in many corrosion processes such as pitting, stress corrosion cracking and corrosion fatigue. The nature of passive films on metals and alloys is a decisive factor that controls their corrosion behavior. Mmuch work has been devoted to the study of the electronic properties and chemical composites of passive films on metals and alloys. Based on the fact that the potential-dependent transpassive dissolution varies with the electronic properties of the passive film, Sato proposed a breakdown mechanism of the passive film on metals, the electrochemical stability of a passive film strongly depends on the electron energy band structure in the film. Bianchiet al. concluded that the high susceptibility of stainless steel to pitting nucleation was connected to n-type conductivity of the oxide film. Cr-bearing stainless steels have been widely used in power generation systems and other industrial systems. The effects of hydrogen on the surface film and electrochemical behavior of 13Cr stainless steel in a chloride solution were investigated in the present work. Hydrogen was introduced into the samples by cathodic charging under galvanostatic condition at 25 oC in sulfuric acid solution with thiourea. The specimens were charged at a current density 2 mA/cm2 for 2 h. Electrochemical measurements were carried out on both uncharged and hydrogen charged specimens for evaluating their corrosion resistance. Potentiodynamic anodic polarization curves were carried out in 200 ppm wt.% NaCl solution at 25 oC, as shown in Figure. 1. Pre-charged hydrogen specimen showed a significantly lower open-circuit potential of about -0.67 V(SCE), and the non-charged specimen showed OCP of about -0.11V (SCE). Anodic current density in the anodic polarization curves of the hydrogen-charged specimen was significantly higher than that of the non-charged specimen. These results indicate that the corrosion resistance of 13Cr steel was significantly reduced by charged-hydrogen. Figure 2 show the electrochemical impedance spectra (EIS) for hydrogen-charged and non-charged specimens after different immersion periods in 200ppm wt.% NaCl solution at 25 oC. EIS diagrams of hydrogen-charged and non-charged specimens exhibited two parts: a capacitive loop in the high-frequency region and a capacitive loop in the low-frequency region. The second capacitive arc radius for the hydrogen-charged specimen was significantly less than that of the non-charged specimen. The scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) was used for the element and surface morphology analysis of the specimens after immersion tests in 200ppm wt.% NaCl solution at 25 oC for 68 h. Little corrosion product could be found on the non-charged specimen surface while more corrosion product appeared on the hydrogen-charged specimen surface, as shown in Fig. 3. Cr content in the film formed on hydrogen-charged specimen was lower than that on non-charged specimen, indicating the effect of hydrogen on the chemical composition of surface film. Figure 1

Effect of extrusion on corrosion behavior and corrosion mechanism of Mg-Y alloy

AbstractThe influences of the hot extrusion process on the microstructure, corrosion behavior and corrosion mechanism for Mg-Y magnesium alloy were studied by means of the microstructure observation, weight loss test, electrochemical test and corrosion morphology test. The results showed that with increasing of the extrusion ratio, the shear flow line on the vertical section of the extruded alloy increased, the shear bands parallel lines became more clearly visible, and a large number of fine equiaxed grains distributed in parallel with the flow lines. The open circuit potential had a certain degree of improvement after extrusion, the open circuit potential increased with increment of extrusion ratio, and the corrosion potential of the vertical section was higher than that of the same alloy in the same compression ratio. The shift rate of the corrosion potential relatively became larger with increasing of the extrusion ratio, and the cathode corrosion current corresponding to the branch migration shifted to the positive direction. The high frequency capacitive arc increased with increment of the extrusion ratio, and the radius of capacitive arc of the vertical section was slightly larger than that of the transverse section. The corrosion morphologies of Mg-0.25Y alloy were uniform corrosion, and the corrosion morphologies of Mg-(2.5, 5, 8 and 15) were the pitting corrosion and the small range, deep depth localized corrosion.

Estimation of the Distribution Algorithm With a Stochastic Local Search for Uncertain Capacitated Arc Routing Problems

The uncertain capacitated arc routing problem is a challenging problem in which the demands of tasks, the costs of edges, and the presence of tasks and edges are uncertain. The objective of this problem is to find a robust optimal solution for a finite set of possible scenarios. In this paper, we propose a novel robust optimization approach, called an estimation of distribution algorithm (EDA) with stochastic local search (SLS), to tackle this problem. The proposed method integrates an EDA with a novel two phase SLS procedure to minimize the maximal total cost over a set of different scenarios. The SLS procedure avoids excessive fitness evaluations of unpromising moves in local search. Our experimental results on two sets of benchmark problems (a total of 55 problem instances) showed that the proposed approach outperformed existing state-of-the-art algorithms.

Algoritmo memético con operadores de inteligencia artificial para el CARP con inicio y fin no determinado y bi-objetivo

El Problema de ruteo de vehículos sobre arcos con punto de inicio/fin variable (Open Capacitated Arc Routing Problem - OCARP), en su versión clásica, busca determinar la mejor estrategia para servir un conjunto de clientes localizados en los arcos de una red usando vehículos. A diferencia del Capacitated Arc Routing Problem (CARP), el OCARP no tiene las restricciones que aseguran que cada vehículo debe iniciar y terminar su ruta en un vértice dado (también conocido como depósito). El objetivo de este trabajo es proponer una heurística para encontrar la frontera eficiente dados dos objetivos: minimizar el número de vehículos y minimizar el costo total. Adicionalmente se propone complementar la heurística, la cual es basada en algoritmos genéticos, con operadores de inteligencia artificial.

Non-contact wafer thickness measurement of capacitance sensor circuit based on CAV424

Non-contact wafer thickness measurement with the CAV424 capacitance sensor special integrated circuit and arc pole plate capacitor sensor has good stability and linearity under low capacity of the bottom of sensor and lowe C condition. This method has a high technical advantages and practical value. Two capacitance sensors Cb, Ca measurement spacing 4mm install at the same axis which constitutes the size condition for measuring thickness. The static capacity of Ca and Cb is a constant value. The capacity of Cb and Ca will change when the silicon wafer is involved. This change is checked by the CAV424 capacitive sensor which has better linearity and higher thickness resolution.

Corrosion and cell behaviour of phosphate mineral coating on magnesium alloy

Event Abstract Back to Event Corrosion and cell behaviour of phosphate mineral coating on magnesium alloy Bin Jiang1, Lilan Zeng1, Ying Zhao1 and Kelvin Wk Yeung2 1 Shenzhen Institute of Advanced Technology, Chinese Academy of Science, Center for Human Tissues and Organs Degeneration, China 2 The University of Hong Kong, Department of Orthopaedics & Traumatology, Hong Kong, SAR China Introduction: Magnesium-based metals have attracted much attention in recent years due to their potential applications on cardiovascular stents and bone implants. However, their inadequate corrosion resistance in a physiological environment becomes the major obstacle limiting wider applications. A number of surface treatments have been adopted to enhance corrosion resistance. However, most surface coatings only provide a barrier against corrosive species but not tailor the biocompatibility. In this study, biocompatible phosphate mineral coatings are synthesized using hydrothermal treatment on WE43 magnesium alloy surfaces and their corrosion resistance and cytocompatibility are examined systematically. Materials and Methods: As cast WE43 Mg alloys were treated in K2HPO4 solution at 200°C for 1 to 3h, respectively. X-ray diffraction (XRD) with Cu Ka radiation and scanning electron microscopy (SEM) were conducted to characterize the phase composition and microstructure. The electrochemical impedance spectroscopy (EIS) of the samples in phosphate buffered saline at 37°C was measured on an electrochemical workstation (CHI660E). The cytoskeleton and cell nuclei were observed by fluorescence microscopy. Results and Discussion: Fig. 1a shows that the sample surfaces are partially covered with petal-like-shaped products after 1 h of hydrothermal treatment. With the increase of the treated time, an intact and dense coating with petal-like-shaped structure is formed on the surface of samples (Fig. 1b-c). The XRD patterns (Fig.1d) show the coatings are mainly composed of Mg(OH)2 and KMgPO4·6H2O. After 5 h of culture, most of the MC3T3-E1 cells on the untreated WE43 alloys fail to spread well (Fig.1e). In contrast, the 3 h-treated sample shows obvious filopodia and flattened membranes (Fig.1f), suggesting that the phosphate mineral coating with better cytocompatibility. The Nyqusit plot (Fig.2a) exhibits that the diameter of the capacitive arcs is increased with the extension of the hydrothermal treated time. And the Bode diagram (Fig.2b) shows similar enhancing trend. The 3 h-treated sample exhibits the largest diameter and the biggest impedance in the Nyquist plot and Bode diagram as compared to the other samples, suggesting the best corrosion resistance due to the protective screen of compact phosphate mineral coatings. Proper reduction of the degradation rate creates a relatively stable interface for cell growth, thus leading to improved cytocompatibility of WE43 magnesium alloys. Conclusions: Phosphate mineral coatings with petal-like-shaped structure are formed on the WE43 Mg alloys by hydrothermal treatment. The coatings are mainly composed of Mg(OH)2 and KMgPO4·6H2O, which effectively improve the corrosion resistance of WE43 magnesium alloys. At the same time, proper reduction of the degradation rate creates a relatively stable interface for cell growth, leading to improved cytocompatibility. Science and Technology Department of Guangdong Province (2014A010105033); Shenzhen overseas high level talents of innovation and Entrepreneurship (110811003586331，KQCX20140521115045444); Guangdong Natural Science Foundation Doctoral project (2014A030310129)

Construction and Analysis of Extended Double-Layer Capacitated Arc Routing Problem Optimization Model Based on Express Logistics

Construction and Analysis of Extended Double-Layer Capacitated Arc Routing Problem Optimization Model Based on Express Logistics