Search results

This paper aims to evaluate the inhibitive effect and adsorption behavior of the 2-amino-5-thiol-1,3,4-thiadiazole vanillin (A) on copper in 3 per cent NaCl solution.

A thiazole Schiff bases were synthesized, named, 2-amino-5-thiol-1,3,4-thiadiazole vanillin (A), which was fabricated respectively on copper surface by the molecular self-assembled. Evaluation was carried out by electrochemical measurement and surface analysis techniques. Measurement of static friction coefficient scanning electron microscopy and Contact angle analysis were applied, and it is finally confirmed the existence of the adsorbed film. The inhibitive mechanism of A was evaluated by means of quantitative calculation and molecular dynamics simulation.

The electrochemical measurement indicated that the self-assembled molecular film can effectively inhibit the corrosion of copper sheet, when the concentration was 15 mmol⋅L⁻¹ and the assembly time was 6 h, the corrosion inhibition effect was the best, reaching as high as 97.5 per cent. Scanning electron microscopy results showed that the Schiff base compound forms a protective film on the surface of the copper, which effectively blocks the transfer of corrosion particles to the metal substrate, thereby inhibiting the occurrence of corrosion. Adsorption behavior of A followed the Langmuir’s adsorption isotherm and attributed to mixed-type adsorption. The results of Quantitative calculation and molecular dynamics simulation showed that A was adsorbed on Cu (111) surface in parallel.

In this study, the corrosion inhibition properties of Schiff base film were investigated by combining theory with experiment. Theoretical calculation is helpful to guide the synthesis of efficient and environmentally friendly corrosion inhibitors.

The damage caused by metal corrosion is great. The self-assembled Schiff base membrane synthesized in this paper is simple and compact, and the corrosion inhibition efficiency of copper in 3 per cent NaCl solution is 97.5 per cent.

Inhibition of metal corrosion can better save energy and reduce economic losses.

The synthesized Schiff base was prepared on the copper surface by the molecular self-assembled. The Schiff base membrane has a good corrosion inhibition effect on copper in 3 per cent NaCl solution, and the corrosion inhibition efficiency is up to 97.5 per cent.

The purpose of this paper is to study the microstructure and the high-temperature tribology behavior of a high-speed steel (HSS) roller material with boron as the main alloy element under different heat treatments, aiming to provide some theoretical references for its engineering application.

The samples of high boron HSS were quenched at 900°C, 1,000°C, 1,050°C and 1,150°C. The microstructure, composition and phase composition of this new HSS were analyzed by OM, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffractometer. The surface hardness and the tribology behavior under high temperature were measured by Rockwell hardness tester and the high-temperature friction and wear tester. The wear morphology was observed by SEM.

The high-temperature friction coefficient and the relative wear rate of the high boron HSS decrease first, then increase with the rise of the quenching temperature. When the quenching temperature is 1,050°C, both the friction coefficient (0.425) and the relative wear rate (79 per cent) are the smallest. Under the high-temperature friction environment, the high boron HSS mainly includes oxidation wear, adhesive wear and abrasive wear. The effect of abrasive wear is weakened gradually with the rise of the quenching temperature, and the high-temperature wear resistance is improved significantly. Compared with the traditional roll materials, the service life of the new high boron HSS is greatly improved. It is an ideal substitute product for the high chromium cast iron roll.

The boron element replaces other precious metals in high boron HSS, which has the advantage of low production cost, and it has a wide application in the field of roll materials. In this paper, the microstructure, the transformation of hard phases and the high-temperature tribology behavior of this new high boron HSS under different heat treatments were studied, aiming to provide some theoretical references for its engineering application.

The purpose of this paper is to present an up-to-date survey on the non-orthogonal multiple access (NOMA) technique with co-operative strategy, a fast-evolving fifth-generation (5 G) technology. NOMA is used for serving many mobile users, both in power and code domains. This paper considers the power-domain NOMA, which is now discussed as NOMA.

The first part of the paper discusses NOMA-based cooperative relay systems using different relay strategies over different channel models. In various research works, the analytical expressions of many performance metrics were derived, measured and simulated for better performance of the NOMA systems. In the second part, a brief introduction to diversity techniques is discussed. The multiple input and multiple output system merged with cooperative NOMA technology, and its future challenges were also presented in this part. In the third part, the paper surveys some new conceptions such as cognitive radio, index modulation multiple access, space-shift keying and reconfigurable intelligent surface that can be combined with NOMA systems for better performance.

The paper presents a brief survey of diverse research projects being carried out in the field of NOMA. The paper also surveyed two different relaying strategies that were implemented in cooperative NOMA over different channels and compared several performance parameters that were evaluated and derived in these implementations.

The paper provides a scope for recognizable future work and presents a brief idea of the new techniques that can be united with NOMA for better performance in wireless systems.

The purpose of this paper is to improve the degradation efficiency of Rhodamine B (RhB) by new photocatalytic materials.

Binary Z-scheme g-C₃N₄/Bi₂WO₆ photocatalytic material was synthesized by the one-step hydrothermal reaction. The construction of Z-scheme heterojunction led to the rapid separation of photogenerated electrons and holes, which would degrade RhB into small molecular substances to achieve the purpose of degradation.

It was found that Bi₂WO₆/25%g-C₃N₄ displayed the highest photocatalytic activity, which was about 1.44 and 1.34 times higher than that of pure Bi₂WO₆ and g-C₃N₄, respectively. According to the trapping experiments, the superoxide radical (·O²⁻) was the major active species of the RhB decomposition in Bi₂WO₆/g-C₃N₄ catalysts.

The successful synthesis of Z-scheme Bi₂WO₆/g-C₃N₄ provides new ideas and references for the design of catalysts with high photocatalytic activity, which should have wide applications in the future.

This study aims to provide an understanding of the multi-layered managerial and organizational challenges of mega sporting events such as the Olympic and Paralympic Games, identify key competencies that address the complexities and uncertainties when planning and organizing the Olympic and Paralympic Games and provide a framework to classify sporting events according to their complexity and uncertainty.

This study uses in-depth semi-structured interview with key organizing actor of the Olympic and Paralympic Games in Rio in 2016.

Planning and organizing complex and long-term mega sporting events such as the Olympic and Paralympic Games require a set of key competencies, including a range of soft skills (collaboration, negotiation, communication), goal-setting, persistence and resilience, paradox thinking and timing.

Presenting the findings in an unedited and raw interview format provides practitioners and scholars alike with unfiltered and rich data that allows to choose, apply and adapt key competencies and heuristics from Rio 2016 to their own mega sporting projects or research agendas; allows to differentiate between sporting events according to their complexity and uncertainty.

The purpose of this study is to investigate the effects of capital market liberalization on audit reporting and pricing. The authors use the announcement of the Shanghai-Hong Kong Stock Connect program in China as a shock to capital market liberalization.

The authors use the difference-in-differences method to study the difference in changes in the frequency of modified audit opinions and audit fees between the treatment group and the control group.

This study finds that capital market liberalization increases reputational and litigation risks for auditors and leads to more conservative audit reports. In addition, capital market liberalization stimulates the management of eligible firms to improve the information environment, helps to reduce information asymmetry and decreases audit fees. Specifically, the authors identify the channels of active foreign institutional investors as a new governance mechanism through which capital market liberalization impacts eligible firm and auditor decisions.

This study complements the literature by showing that capital market liberalization may bring a new and strong governance mechanism for eligible firms and auditors.

This study may provide new references for active foreign institutional shareholders as a new and strong governance mechanism in weak institutional regimes such as China, auditors’ optimization decisions when litigation risks increase and management’s improvements in the information environment under the monitoring of foreign institutional shareholders.

Overall, this study contributes to the literature by showing that capital market liberalization can bring a new governance mechanism for the management of eligible firms and auditors in a weak institutional environment. Foreign institutional shareholders may be superior to the domestic market forces and other corporate governance in the role of monitoring the management of eligible firms and auditors.

The purpose of this study is to examine the effects of nitrogen (N) deposition on clonal growth in a rhizome clonal plant, Leymus chinensis (Trin.) Tzvel.

The study established seven N concentration gradients (0, 2, 4, 8, 16, 32 and 64 g N m⁻²) to simulate the continuous increase in N deposition for the cultivation of L. chinensis seedlings and assess the response mechanism of the cloned L. chinensis plant at different N levels by analyzing the aboveground and belowground plant appearance traits, parent ramets and daughter ramets of resource allocation and biomass allocation.

The results of this study showed that the different N treatment levels could promote clonal growth and had certain regularity under the seven treatments. The addition of N could significantly increase the ramet number, rhizome length, rhizome spacer length, biomass of mother ramets, daughter ramets and belowground L. chinensis population when the N addition was greater than 4 g m⁻²; however, the clonal growth ability of L. chinensis decreased and the rhizome length, ramet number, stem and leaf biomass of daughter ramets and stem biomass of mother ramets significantly decreased when the N addition was greater than 32 g N m⁻².

With global warming, atmospheric N deposition is increasing and it is of great significance to explore the response mechanism of different N levels for the growth of clone plants. This study provides basic data and a theoretical basis for the survival prediction of cloned plants under the background of a global climate change strategy and has important theoretical and practical significance for the scientific management of grasslands in the future.

Fix-position preloading, centrifugal force and higher temperatures cause the bearing units in angular contact ball bearings to expand, changing the contact load and affecting bearing life. This study aims to examine the effect of thermal and centrifugal expansion on the fatigue life of fix-position preloaded angular contact ball bearings in high-speed operating conditions.

The contact loads on the inner and outer bearing rings were resolved according to the thermal and centrifugal expansion factors in the quasi-static position preloading model. The pressure and frictional stress distribution were used to calculate the subsurface stress in the contact area, while the Zaretsky model was used to determine the relative fatigue life of the inner and outer bearing rings.

Under fix-position bearing preloading, thermal and centrifugal expansion significantly affected the contact load and relative fatigue life. At the same axial preload, the inner ring contact load was higher than the outer ring contact load, with a maximum difference of 132.3%. The decrease in the inner ring relative life exceeded the outer ring contact load, with a maximum difference of 7.5%, compared to the absence of thermal and centrifugal expansion.

This study revealed the influence of thermal and centrifugal expansion on the fatigue life of angular contact ball bearings in high-speed service conditions.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2023-0065/

The purpose of this paper is to examine the cross-sectional predictive power and the information content of volatility smirks for future stock returns using single stock options.

The study uses Fama-Macbeth procedure and portfolio approach to investigate the predictability and informativeness in a setup when options settlement style is changed from American to European.

The study reports that the volatility smirk of European style options, unlike American style options, predict the underlying cross-sectional equity returns. Firms with steepest volatility smirk underperform firms with flatter volatility smirks, by an average of 3.28 and 4.01 per cent annually for American and European options, respectively. The results are robust to the control of idiosyncratic and systematic risk factors.

The results confirm that a trader with negative information prefers to trade out-of-the-money put options. The more pronounced results of European options designate the trader’s preference to less risky European style stock options. Results are robust and signify the delay of equity market in incorporating information impounded in the volatility smirk.

Very few studies examine smirk and returns relationship and to the best of the authors’ knowledge, no study exists that examine the unique case of change in options style and its role in affecting relationship between smirk and future returns.

The purpose of this paper is to investigate the relationship between option’s implied volatility smirk (IVS) and excess returns in the Germany’s leading stock index Deutscher-Aktien Index (DAX) 30.

The study defines the IVS as the difference in implied volatility derived from out-of-the-money put options and at-the-money call options. This study employs the ordinary least square regression with Newey-West correction to analyse the relationship between IVS and excess DAX 30 index returns in Germany.

The authors find that the German market adjusts information in an efficient way. Consequently, there is no information linkage between option volatility smirk and market index returns over the nine years sample period after considering the control variables, global financial crisis dummies, and the subsample test.

This study finds that the option market and the DAX 30 index are informationally efficient. Implications of the findings are that the investors cannot profit from the information contained in the IVS since the information is simultaneously incorporated into option prices and the stock index prices. The findings of this study are applicable to other markets with European options and for market participants who seek to exploit short-term market divergence from efficiency.

The relationship between IVS and stock price changes has not been investigated sufficiently in academic literature. This study looks at this relationship in the context of European options using high-frequency transactions data. Prior studies look at this relationship for only American options using daily data. Pricing efficiency of the European option market using high-frequency data have not been studied in the prior literature. The authors find different results for the German market based on this high-frequency data set.