Wen Zhan, Shengpeng Zhan, HaiTao Duan, Xinxiang Li, Jian Li, Bingxue Cheng and Chengqing Yuan
This paper aims to study the thermal oxidation performance of antioxidant additives in ester base oils deeply.
Abstract
Purpose
This paper aims to study the thermal oxidation performance of antioxidant additives in ester base oils deeply.
Design/methodology/approach
ReaxFF molecular dynamics was used to simulate the thermal oxidation process of butyl octyl diphenylamine and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate as two antioxidant additives act on the Trimethylolpropane trioleate (TMPTO) base oil. Meanwhile, combining with the infrared spectroscopy characterization results of the thermal oxidation test, this paper provides theoretical support for the development of high-performance synthetic lubricants and their antioxidant additives.
Findings
The results show that butyl octyldiphenylamine easily removes the hydrogen atom on the secondary amine, which promotes the formation of more long carbon chain diene radicals or polyene hydroperoxides from TMPTO. Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate could easily decompose into octadecyl hydroperoxide and 2,6-di-tert-butyl 4-propionylphenol, which could convert into 2-tert-butyl-4-peroxyethyl-6-hydroperoxy-tert-butylphenol in the middle of the thermal oxidation reaction, prompting TMPTO to form more short-chain alkenyl and olefin hydroperoxide or other oxide.
Originality/value
The main change characteristics of base oil molecules are the first thermal decomposition to form oleic acid groups and ethane cyclopropane methyl oleate. Under the action of butyl octyldiphenylamine and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate, the deep oxidation and decomposition reaction are slowed down.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0037/
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Xinxiang Li, Wen Zhan, Xuzheng Qian, Yunhe Zu, Fan Xie, Feng Tian, Xiaohui Liu and Yunhu Ding
This paper aims to focus the synchronous chemical conversion technology–based titanium/zirconium composite on 6061, 7075 aluminum alloys and galvanized steel.
Abstract
Purpose
This paper aims to focus the synchronous chemical conversion technology–based titanium/zirconium composite on 6061, 7075 aluminum alloys and galvanized steel.
Design/methodology/approach
The effects of pH, temperature, reaction time and other process parameters on the corrosion resistance of the three metal surface coatings were investigated by copper sulfate drop and electrochemical corrosion performance tests under a certain content of H2TiF6 and H2ZrF6. The surface morphology and element distribution of the conversion coating were analyzed by scanning electron microscope and X-ray photoelectron spectroscopy.
Findings
The results show that the optimal synchronization chemical conversion conditions of 6061/7075 aluminum alloys/galvanized steel are controlled as follows: H2TiF6 2.2 mL/L, H2ZrF6 1 mL/L, pH 3.9, conversion temperature 35°C and conversion time 120 s.
Originality/value
Multi-metals chemical conversion coating can be obtained simultaneously with uniform corrosion resistance and surface morphology. The presence of microdomain features in multiple metals facilitates simultaneous chemical conversion into coatings.
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Xiaobo Wang, Wen Zhan and Boyi Gui
The purpose of this paper is to develop a chrome-free and phosphorus-free chemical conversion coating with good corrosion resistance, a novel chemical conversion coating was…
Abstract
Purpose
The purpose of this paper is to develop a chrome-free and phosphorus-free chemical conversion coating with good corrosion resistance, a novel chemical conversion coating was prepared by adding cerium nitrate hexahydrate and salicylic acid in the treatment solution containing titanium/zirconium ions on 6061 aluminum alloy.
Design/methodology/approach
Compared with the AA6061 aluminum alloy matrix, the self-corrosion potential of the conversion coating is significantly positively shifted, the self-corrosion current density is greatly reduced and its corrosion resistance is significantly improved. Morphology and composition of the conversion coatings were observed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The microdomain structure of conversion coatings at different formation stages was analyzed by electron probe microanalyzer.
Findings
An optimized preparation technique of titanium–zirconium chemical conversion coating for AA6061 aluminum alloy is obtained: H2TiF6 4 mL/L, H2ZrF6 0.4 mL/L, salicylic acid 0.35 g/L, Ce(NO3)3·6H2O 0.14 g/L, reaction temperature 30°C, reaction time 120 s and pH 4.0.
Originality/value
The coating forms on the Al(Fe)Si intermetallic compound, and Ce3+ is preferentially adsorbed on the intermetallic compound. The hydrolysis of Ce3+ causes the local pH of the solution to decrease, which promotes matrix dissolution and charge migration. As the microanode/microcathode reaction occurs, the local pH of the solution increases, and Al2O3/ZrO2/TiO2 begins to deposit on the surface of the metal substrate.
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Wen Zhan, Dan Jia, YongLiang Jin, HaiTao Duan, Jian Li and Jun Liu
The purpose of this paper is to synthesize amines/phenolic antioxidants by a new method and to characterize the influence of antioxidants on thermo-oxidative degradation in…
Abstract
Purpose
The purpose of this paper is to synthesize amines/phenolic antioxidants by a new method and to characterize the influence of antioxidants on thermo-oxidative degradation in trimethylolpropane trioleate (TMPTO) base oil.
Design/methodology/approach
The molecule structures of antioxidants and lubricants were confirmed using Fourier transform infrared spectroscopy (FTIR). The oxidative stability of antioxidants and lubricants was evaluated by pressurized differential scanning calorimetry (PDSC).
Findings
These findings suggested that butyl-octyl-diphenylamine has obvious advantage on kinematic viscosity inhibition, and amine-phenol combination antioxidant has a slightly better suppression of total acid in TMPTO under thermal oxidation at 200°C for 96 h. The FTIR characterizations showed that all antioxidants could protect the basic structure of TMPTO in the early stage of thermal degradation.
Originality/value
Under the action of butyl-octyl-diphenylamine, the dehydrogenation of TMPTO is easily met with the alkenyl hydrogen = C–H bond in the unsaturated C = C. Meanwhile, as octadecyl 3-(3, 5-di-tert-butyl-4-hydroxyphenyl)propionate protects TMPTO, the unsaturated C = C bond in the base oil molecule easily breaks down during transition.
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Xiaobo Wang, Zhipeng Li, Wen Zhan, Jesong Tu, Xiaohua Zuo, Xiangyi Deng and Boyi Gui
This study aims to expand the reliability and special functions of lightweight materials for high-end equipment and green manufacturing, so that it is the first such research to…
Abstract
Purpose
This study aims to expand the reliability and special functions of lightweight materials for high-end equipment and green manufacturing, so that it is the first such research to carry out nano-composite technology of nickel-coated carbon nanotubes (Ni-CNTs)-based titanium-zirconium chemical conversion on aluminum alloy substrate.
Design/methodology/approach
Corrosion behavior of various coatings was investigated using dropping corrosion test, linear polarization and electrochemical impedance spectroscopy. The results showed that the corrosion resistance of the nano-composite conversion coatings was significantly improved to compare with the conventional titanium-zirconium conversion coating. The morphology and microdomain characteristics of the nano-composite conversion coatings were characterized by SEM/eds/EPMA, which indicated that the CNT or Ni-CNTs addition promoting the integrity coverage of coatings in a short time.
Findings
Surface morphology of titanium-zirconium (Ti-Zr)/Ni-CNT specimens exhibited smooth, compact and little pores. The nano-composite conversion coatings are mainly composed of Al, O, C and Ti elements and contain a small amount of F and Zr elements, which illuminated that CNT or Ni-CNT addition could co-deposit with aluminum and titanium metal oxides.
Originality/value
The study of corrosion resistance of nano-composite conversion coatings and the micro-zone film-formation characteristics would be provided theoretical support for the development of basic research on surface treatment of aluminum alloys.
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Haoning Pu, Zhan Wen, Xiulan Sun, Lemei Han, Yanhe Na, Hantao Liu and Wenzao Li
The purpose of this paper is to provide a shorter time cost, high-accuracy fault diagnosis method for water pumps. Water pumps are widely used in industrial equipment and their…
Abstract
Purpose
The purpose of this paper is to provide a shorter time cost, high-accuracy fault diagnosis method for water pumps. Water pumps are widely used in industrial equipment and their fault diagnosis is gaining increasing attention. Considering the time-consuming empirical mode decomposition (EMD) method and the more efficient classification provided by the convolutional neural network (CNN) method, a novel classification method based on incomplete empirical mode decomposition (IEMD) and dual-input dual-channel convolutional neural network (DDCNN) composite data is proposed and applied to the fault diagnosis of water pumps.
Design/methodology/approach
This paper proposes a data preprocessing method using IEMD combined with mel-frequency cepstrum coefficient (MFCC) and a neural network model of DDCNN. First, the sound signal is decomposed by IEMD to get numerous intrinsic mode functions (IMFs) and a residual (RES). Several IMFs and one RES are then extracted by MFCC features. Ultimately, the obtained features are split into two channels (IMFs one channel; RES one channel) and input into DDCNN.
Findings
The Sound Dataset for Malfunctioning Industrial Machine Investigation and Inspection (MIMII dataset) is used to verify the practicability of the method. Experimental results show that decomposition into an IMF is optimal when taking into account the real-time and accuracy of the diagnosis. Compared with EMD, 51.52% of data preprocessing time, 67.25% of network training time and 63.7% of test time are saved and also improve accuracy.
Research limitations/implications
This method can achieve higher accuracy in fault diagnosis with a shorter time cost. Therefore, the fault diagnosis of equipment based on the sound signal in the factory has certain feasibility and research importance.
Originality/value
This method provides a feasible method for mechanical fault diagnosis based on sound signals in industrial applications.
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Wen‐zhan Dai, Zi‐heng Wu and Ai‐ping Yang
The purpose of this paper is to solve the problem existing in the forecast of impact disturbance grey system.
Abstract
Purpose
The purpose of this paper is to solve the problem existing in the forecast of impact disturbance grey system.
Design/methodology/approach
Under the axiomatic system of buffer operator in grey system theory, a novel kind of buffer operators with variable weight λ based on the principle of average tempo of time sequence and using new information is proposed. The optimization solution for variable weight λ is obtained by using genetic algorithm. It is proved that the new buffer operators are effective.
Findings
The results show that the new buffer operators accord with the buffer operator's three axioms and the monotonicity non‐variable axiom. It is proved theoretically and in practice that the new buffer operators are more useful than other buffer operators in grey modeling for sequence with impact disturbance.
Practical implications
The novel buffer operators can reduce the randomness of grey sequence distorted by impact factors, and the forecast accuracy of a model which is built through the process with a novel buffer operator is significantly increased.
Originality/value
The paper succeeds in constructing two novel buffer operators with variable weight and the properties of novel operators are studied. The method to solve optimization value of weight is proposed. The method widens the scope of grey model application.
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Marco Bisogno and Pierre Donatella
Research dealing with earnings management in the public-sector context is expanding. This paper aims to review the existing literature to understand how research is developing and…
Abstract
Purpose
Research dealing with earnings management in the public-sector context is expanding. This paper aims to review the existing literature to understand how research is developing and points out gaps deserving further investigation.
Design/methodology/approach
This study uses the structured literature methodology to investigate the state-of-the-art and future directions of the literature on earnings management in the public sector. In total, 78 articles were explored.
Findings
The critical analysis of the literature shows that different but related streams of literature are emerging, focused on both a macro- and a micro-level perspective (mainly local governments and state-owned enterprises).
Originality/value
This study is the first that offers a comprehensive review of the literature on the emerging topic of earnings management in the public-sector context. The structured literature review enables the identification of future directions for the literature in this field.
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The purpose of this paper is to explore the dynamics and stability of switched supply system considering the influence of the retailer competition and deteriorating items.
Abstract
Purpose
The purpose of this paper is to explore the dynamics and stability of switched supply system considering the influence of the retailer competition and deteriorating items.
Design/methodology/approach
A discrete dynamic switched model is developed to analyze the evolution process of the switched supply chain. The existence and the local stability of the switched supply chain are analyzed using an analytical method and a parameter plot basin.
Findings
The author finds the switched supply chain will exhibit stable, periodic, and divergent behaviors with different parameters due to the system’s switching mechanism and the switched supply chain presents complex dynamics when the stable and unstable subsystem coexist.
Originality/value
The originality and value of the research rests on this paper considering the influence of the retailers’ competition and deteriorating items on the supply chain dynamics under stock-dependent demand. The obtained results provide the decision maker with some guidelines on how to make stable designs for the switched supply chain design according to the parameter values.
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Jia Liao, Yun Zhan and Kangbo Liu
This study investigates the impact of customer stability on the cost of debt and the moderating effect of environmental uncertainty on the above relationship.
Abstract
Purpose
This study investigates the impact of customer stability on the cost of debt and the moderating effect of environmental uncertainty on the above relationship.
Design/methodology/approach
An empirical analysis based on the ordinary least squares (OLS) regression model is conducted using China’s A-share listed companies on the Shanghai and Shenzhen Stock Exchanges from 2007 to 2021.
Findings
The results indicate that customer stability significantly inhibits the cost of debt, and the higher the environmental uncertainty, the more significant the inhibitory effect of customer stability on the cost of debt. The results of heterogeneity analyses indicate that the more intense the industry competition, the higher the customer concentration or the older the average customer age, the more significant the inhibiting effect of customer stability on the cost of debt.
Research limitations/implications
This study highlights the importance of customer relationship management and supply chain risk management, which have both theoretical and managerial implications. Despite its contributions, this study has limitations, such as China’s institutional context limits, which the generalisability of our results, and the sample size for this study is small because of limitations in measuring customer stability.
Originality/value
Existing literature has not yet reached a consistent conclusion on how customer relationships affect the cost of debt, and such studies are mainly centered around perspectives such as customer concentration and the contagion effect of supply chains. This study constructs an indicator of customer stability using detailed information on the top five customers of China’s A-share listed companies and dynamically examines the impact of customer stability on the cost of debt, which expands the research on the influencing factors of the cost of debt, the economic consequences of customer stability and the theory of customer relationship management.