Lu Luo, Kang Qi and Hualiang Huang
The purpose of this paper is to investigate the effects of chloride ion concentration and applied bias voltage on the electrochemical migration (ECM) behavior between Cu and Ag…
Abstract
Purpose
The purpose of this paper is to investigate the effects of chloride ion concentration and applied bias voltage on the electrochemical migration (ECM) behavior between Cu and Ag under an NaCl thin electrolyte layer (TEL).
Design/methodology/approach
A self-made experimental setup for the ECM behavior between Cu and Ag was designed. An HD video measurement microscopy was used to observe the typical dendrite/corrosion morphology and pH distribution. Short-circuit time (SCT), short-circuit current density and the influence of the galvanic effect between Cu and Ag on their ECM behavior were studied by electrochemical tests. The surface morphology and composition of dendrite were characterized by FESEM/EDS.
Findings
The SCT increased with increasing NaCl concentration but decreased with increasing applied bias voltage, and the SCT between Cu and Ag was less than that between Cu and Cu because their galvanic effect accelerated the dissolution and migration of Cu. When NaCl concentration was less than or equal to 6 mmol/L, cedar-like dendrite was formed, whereas no dendrite formed and only precipitation occurred at high chloride ion concentration (100 mmol/L). The composition of the dendrite between Cu and Ag was copper.
Research limitations/implications
The significance of this study is to clarify the ECM failure mechanism of printed circuit board (PCB) with an immersion silver surface finish (PCB-ImAg).
Practical implications
This study provides a basic theoretical basis for the selection of protective measures and metal coatings for PCB.
Social implications
The social implication of this study is to predict the service life of PCB.
Originality/value
The ECM behavior of dissimilar metals under a TEL was investigated, the influence of the galvanic effect between them on their ECM was discussed, and the SCT increased with increasing NaCl concentration.
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The purpose of this study is to provide a theoretical basis for the study of the galvanic corrosion mechanism of copper coupled silver-coating under a thin electrolyte layer in…
Abstract
Purpose
The purpose of this study is to provide a theoretical basis for the study of the galvanic corrosion mechanism of copper coupled silver-coating under a thin electrolyte layer in electronic systems.
Design/methodology/approach
Electrochemical measurements and surface characterizations.
Findings
The results indicate that the potential difference between copper and silver electrodes first quickly increases, and then reaches a relatively stable and large value with the extension of the immersion time. With the significant increase in the cathode/anode area ratio in electronic systems, the area ratio effect obviously accelerates the corrosion of copper due to the remarkable promotion of the cathode process. For a large cathode/anode area ratio, the galvanic current density always maintains a large value and exhibits an increasing trend with the extension of the immersion time, which is attributed that the area ratio effect reduces the protection of corrosion products. For the same area of cathode and anode, the galvanic current density always maintains a small value with the extension of the immersion time due to a low galvanic effect and protective corrosion products.
Practical implications
This work provides some information for the establishment of reliably protective measures for electronic systems in service.
Social implications
This work not only provides some information for the establishment of reliably protective measures for electronic systems in service, but also provides a theoretical basis for the selection of metal materials in microelectronic systems.
Originality/value
This work provides not only a theoretical basis for the study of the galvanic corrosion mechanism of Cu/Ag under a thin electrolyte layer, but also provides some information for the establishment of reliably protective measures for electronic systems in service.
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Sudan Liu, Hualiang Huang and Jinbei He
As a commonly engine coolant, ethylene glycol can produce corrosive acid byproducts at high temperatures when the car is running, specifically oxalic acid (OA), which can shorten…
Abstract
Purpose
As a commonly engine coolant, ethylene glycol can produce corrosive acid byproducts at high temperatures when the car is running, specifically oxalic acid (OA), which can shorten the service life of engine. At the same time, chloride ions can also be introduced during coolant preparation processes. Therefore, this paper aims to investigate the synergistic corrosion behavior of Cl− and OA on ADC12 aluminum alloy.
Design/methodology/approach
The electrochemical tests, scanning electron microscopy, energy dispersive spectrometer, X-ray diffraction and X-ray photoelectron spectroscopy) were used.
Findings
The results showed that the corrosion rate of the aluminum alloy increased with the increase of OA and Cl− concentrations. After adding Cl−, the surface film of the aluminum alloy was further damaged, Cl− has a synergistic effect with OA and their interaction further accelerated the corrosion of the aluminum alloy. Nevertheless, as the immersion time increased, the corrosion rate of the aluminum alloy gradually diminished due to the formation of aluminum oxalate.
Originality/value
The corrosion of ADC12 aluminum alloy was studied in OA, Cl− and their mixed solutions; the synergistic effect of OA and Cl− on the corrosion of ADC12 aluminum alloy was discussed, and aluminum oxalate formed inhibited its corrosion.
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Fang Li, Shuyi Feng, Hualiang Lu, Futian Qu and Marijke D'Haese
This paper investigates the relationship between plot size and fertilizer use efficiency (FE) in Chinese large-scale farming and searches for the underlying mechanisms that…
Abstract
Purpose
This paper investigates the relationship between plot size and fertilizer use efficiency (FE) in Chinese large-scale farming and searches for the underlying mechanisms that explain this relationship.
Design/methodology/approach
Based on a household- and plot-level data set of large-scale production units (LSPUs) from Jiangsu and Jiangxi Provinces, the technical and fertilizer use efficiency of large-scale rice production is estimated by applying a translog stochastic frontier production function. The authors impose a monotonicity condition on the translog frontier using a three-step procedure to get theoretically consistent efficiency estimates. A beta regression model is then used to explore the association between plot size and LSPUs' efficiency in fertilizer application.
Findings
The average FE for the sampled plots is around 30%, which shows a large potential for LSPUs to reduce fertilizer use. A U-shaped relationship is observed between plot size and FE. The authors relate this non-linear pattern to the substitution of labour with capital-intensive technology and the efficiency differences in terms of farming performance between family and hired workers.
Originality/value
First, according to the authors’ knowledge, this paper is a first attempt to study the size–efficiency relationship focussing on fertilization practices of large-scale farming. The second contribution lies in the large-scale ranges of the plot-level data set. Third, efforts are made to reveal the mechanisms determining the plot size–FE relationship. Fourth, the authors provide guiding evidence for policymaking, as they show that the size of individual plots deserves equal attention in land consolidation decisions. Methodologically, this paper improves existing estimates of single-factor technical efficiency issued from a restricted production frontier model.
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Guanghui Liu, Lijin Fang, Bing Han and Hualiang Zhang
This paper aims to propose a hybrid force/position control algorithm based on the stiffness estimation of the unknown environment. A frequency-division control scheme is developed…
Abstract
Purpose
This paper aims to propose a hybrid force/position control algorithm based on the stiffness estimation of the unknown environment. A frequency-division control scheme is developed to improve the applicability and reliability of the robot in welding, polishing and assembly.
Design/methodology/approach
The stiffness estimation algorithm with time-varying forgetting factors is used to improve the speed and accuracy of the unknown environmental estimation. The sensor force control and robot position control are adopted in different frequencies to improve system stability and communication compatibility. In the low frequency of sensor force control, the Kalman state observer is used to estimate the robot’s joints information, whereas the polynomial interpolation is used to ensure the smoothness of the high frequency of robot position control.
Findings
Accurate force control, as well as the system stability, is attained by using this control algorithm.
Practical implications
The entire algorithm is applied to a six-degrees-of-freedom industrial robot, and experiments are performed to confirm its applicability.
Originality/value
The frequency-division control strategy guarantees the control stability and improves the smoothness of the robot movement.
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Keywords
Yong Yin, Hualiang Luo, Jiming Sa and Qi Zhang
The segmentation of printed circuit board (PCB) images is an important process in PCB inspection. The circuit traces, pads and vias in a PCB are dense and curved, and the PCB…
Abstract
Purpose
The segmentation of printed circuit board (PCB) images is an important process in PCB inspection. The circuit traces, pads and vias in a PCB are dense and curved, and the PCB image obtained using different cameras or in different conditions may exhibit a large image gradient, which leads to inaccuracy and inefficiency in the PCB image segmentation. This paper aims to propose an improved local binary fitting level set method with prior graph cut, aiming to improve the accuracy and efficiency of the segmentation of PCB images obtained using different cameras or in different environments.
Design/methodology/approach
First, the paper constructs a 4-connected undirected graph using a given PCB image and classifies it based on the graph cut. Second, an adaptive initialization level set is implemented using the priori information obtained from the graph cut. Finally, the paper constructs a priori energy term using the prior information and introduces it into the energy function of the level set.
Findings
The approach results in an improved accuracy of segmentation in the context of a large gradient within the image. Experimental results demonstrate that the method can solve the deviation of artificially initialized level set from targets and improve the efficiency and accuracy of segmentation.
Research limitations/implications
This study only considers level set method as the research object. Iteration of the level set method takes a long time for a given huge PCB picture, which makes it impossible to apply to scenes with high real-time requirements.
Practical implications
PCB image segmentation is an important process in the PCB inspection. Since template matching and morphology techniques are well-established, image segmentation quality has a significant impact on the accuracy of detection.
Originality/value
This paper studies the segmentation of PCB images, improves the efficiency and accuracy of segmentation and facilitates the subsequent applications, such as in the nondestructive testing of PCB.
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Zhixu Zhu, Hualiang Zhang, Guanghui Liu and Dongyang Zhang
This paper aims to propose a hybrid force/position controller based on the adaptive variable impedance.
Abstract
Purpose
This paper aims to propose a hybrid force/position controller based on the adaptive variable impedance.
Design/methodology/approach
First, the working space is divided into a force control subspace and a position subspace, the force control subspace adopts the position impedance control strategy. At the same time, the contact force model between the robot and the surface is analyzed in this space. Second, based on the traditional position impedance, the model reference adaptive control is introduced to provide an accurate reference position for the impedance controller. Then, the BP neural network is used to adjust the impedance parameters online.
Findings
The experimental results show that compared with the traditional PI control method, the proposed method has a higher flexibility, the dynamic response accommodation time is reduced by 7.688 s and the steady-state error is reduced by 30.531%. The overshoot of the contact force between the end of robot and the workpiece is reduced by 34.325% comparing with the fixed impedance control method.
Practical implications
The proposed control method compares with a hybrid force/position based on PI control method and a position fixed impedance control method by simulation and experiment.
Originality/value
The adaptive variable impedance control method improves accuracy of force tracking and solves the problem of the large surfaces with robot grinding often over-polished at the protrusion and under-polished at the concave.