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The purpose of this paper is to illustrate the new technical demands and reliability challenges to printed circuit board (PCB) designs, materials and processes when the transmission frequency increases from Sub-6 GHz in previous generations to millimeter (mm) wave in fifth-generation (5G) communication technology.

The approach involves theoretical analysis and actual case study by various characterization techniques, such as a stereo microscope, metallographic microscope, scanning electron microscope, energy dispersive spectroscopy, focused ion beam, high-frequency structure simulator, stripline resonator and mechanical test.

To meet PCB signal integrity demands in mm-wave frequency bands, the improving proposals on copper profile, resin system, reinforcement fabric, filler, electromagnetic interference-reducing design, transmission line as well as via layout, surface treatment, drilling, desmear, laminating and electroplating were discussed. And the failure causes and effects of typical reliability issues, including complex permittivity fluctuation at different frequencies or environments, weakening of peel strength, conductive anodic filament, crack on microvias, the effect of solder joint void on signal transmission performance and soldering anomalies at ball grid array location on high-speed PCBs, were demonstrated.

The PCB reliability problem is the leading factor to cause failures of PCB assemblies concluded from statistical results on the failure cases sent to our laboratory. The PCB reliability level is very essential to guarantee the reliability of the entire equipment. In this paper, the summarized technical demands and reliability issues that are rarely reported in existing articles were discussed systematically with new perspectives, which will be very critical to identify potential reliability risks for PCB in 5G mm-wave applications and implement targeted improvements.

This study aims to investigate the impact of mandatory audit partner rotation (MAPR) on Chinese listed firms’ insider trading, as well as the moderating effects of firm characteristics on this impact. The economic mechanism behind this impact is also explored.

This study conducts a regression analysis on firms associated with mandatory and voluntary audit partner rotation based on 2009–2019 firm data and examines whether corporate insiders of these two types of firms increase their share sales within 12 months before their financial statements are submitted to a new rotated auditor.

Client firms’ corporate insiders increase their share sales within 12 months before their financial statements are submitted to a new mandatory rotated auditor. In addition, such an association is less pronounced for client firms that changed from Big 4 auditors to those with higher financial constraints. This is more pronounced for client firms with higher information asymmetry. The economic mechanism of the finding is that is the MAPR implementation reduces earnings management activities from client firms. Moreover, client firms’ buy-and-hold stock returns decline in the first year after MAPR.

This study should assist investors, corporate shareholders and Chinese policymakers. Investors can be well protected through the adoption of MAPR because upcoming auditors enhance the audit quality of clients by restraining managers’ manipulation of reported earnings and declining firms’ insider trading afterwards. Investors, Chinese policymakers and corporate shareholders should pay more attention to firms’ financial report quality, auditor selection, financial situation, corporate governance and the information environment. Explicitly, firms with less transparent financial report quality, non-big 4 auditors and fewer financial constraints are more likely to be involved in insider trading.

To the best of the authors’ knowledge, none of the extant studies have examined the impact of MAPR on insider sales. This study extends the research on the effect of the audit process on firm market performance by investigating the impact of audit partner rotation policy on insider trading behaviors.

The purpose of the study is to investigate the international opportunity development process of born global firms embedded in two different institutional contexts: China, an emerging economy and Italy, a developed country. Drawing on the entrepreneurial opportunity literature and institutional theory, this study explores and draws insights into how home country institutions of born globals can influence the international opportunity development process of the firms.

This paper adopts a qualitative case study approach with in-depth, semi-structured interviews of six born global companies from China and Italy. In doing so, this study uses a flexible pattern matching design, which is consistent with the qualitative research design of the paper.

The findings of the study indicate that home institutions play an influential, yet differential role in the international opportunity development processes of Chinese and Italian born global firms. While the Italian firms shape their opportunities mainly through product innovation, their Chinese counterparts develop opportunities primarily through networks embedded in their home institutional context.

The key contributions of the paper relate to an integrated analysis of the international opportunity development process of born globals in China and Italy based on institutional theory, which has received limited attention in the international entrepreneurship literature. In addition, the study advances the similarities and differences in the international opportunity development process in two different countries, thus providing valuable insights for policymakers and practitioners to enter international markets successfully.

This paper aims to examine the relationship among corporate environmental disclosure (CED), earnings management (EM) practices and accounting conservatism in Chinese listed firms and determine how internal corporate governance (CG) mechanisms moderate these relationships.

This study uses two different EM practices, accrual-based EM (AEM) and real EM (REM), to analyze the relationship between CED and EM practices, as well as accounting conservatism. The final sample consisted of 1,619 observations, documented between 2015 and 2019. The panel data method was applied to estimate the relationship among CED, AEM and REM, as well as the moderating effect of CG on this relationship.

This study finds a negative relationship between CED and EM (both AEM and REM) and a positive relationship between CED and accounting conservatism. Further, CG, measured as the independent director ratio, institutional ownership and state-owned entities, was found to moderate these relationships.

Chinese policymakers should reinforce CED because it reduces corporate EM practices and improves accounting conservatism. Further, CED, as a mandatory requirement, may be expanded to all industries, that is, beyond the highly polluting industries listed on China’s stock exchanges.

This study is among the first to examine the relationship between CED and EM practices from both the AEM and REM perspectives and the one between CED and accounting conservatism. It also extends extant analyses by investigating the moderating effect of CG on these relationships in China.

The purpose of this paper is to investigate the influence of key parameters on the bond strength and failure modes of laminated structures made of different aluminum alloys (i.e. Al 2024 and Al 7075) via the ultrasonic consolidation (UC) process.

The UC is used to fabricate laminated structures with various parameters. The push-pin tests were performed on the specimens of different materials and parameters, and the force and displacement were recorded during the tests. The peak punch force was used to represent the bond quality of the laminated structure, and the curves of force versus displacement were used to study the failure modes of the structures.

It is found that the lower normal force, the larger vibration amplitude and the lower travel speed can result in stronger bonding. Three different failure modes are observed in the tests, due to the different relations between the toughness of interface and raw materials. The process parameters have influence on the interface toughness of a laminated structure, which further leads to different failure modes.

The overall mechanical properties of a laminated structure highly depend on the bond quality between laminated layers. The push-pin test can easily and effectively evaluate the bond quality of the laminated structure. This paper not only focuses on the bond strength evaluation, but also analyzes the different failure modes of laminated structures made of different aluminum alloys, which can give an opportunity to optimize the parameters for different materials.

The purpose of this review is to comprehensively consider the material properties and processing of additive titanium alloy and provide a new perspective for the robotic grinding and polishing of additive titanium alloy blades to ensure the surface integrity and machining accuracy of the blades.

At present, robot grinding and polishing are mainstream processing methods in blade automatic processing. This review systematically summarizes the processing characteristics and processing methods of additive manufacturing (AM) titanium alloy blades. On the one hand, the unique manufacturing process and thermal effect of AM have created the unique processing characteristics of additive titanium alloy blades. On the other hand, the robot grinding and polishing process needs to incorporate the material removal model into the traditional processing flow according to the processing characteristics of the additive titanium alloy.

Robot belt grinding can solve the processing problem of additive titanium alloy blades. The complex surface of the blade generates a robot grinding trajectory through trajectory planning. The trajectory planning of the robot profoundly affects the machining accuracy and surface quality of the blade. Subsequent research is needed to solve the problems of high machining accuracy of blade profiles, complex surface material removal models and uneven distribution of blade machining allowance. In the process parameters of the robot, the grinding parameters, trajectory planning and error compensation affect the surface quality of the blade through the material removal method, grinding force and grinding temperature. The machining accuracy of the blade surface is affected by robot vibration and stiffness.

This review systematically summarizes the processing characteristics and processing methods of aviation titanium alloy blades manufactured by AM. Combined with the material properties of additive titanium alloy, it provides a new idea for robot grinding and polishing of aviation titanium alloy blades manufactured by AM.

The paper aims to show the existence of the systemic yoyo structure in human thoughts so that the human way of thinking is proven to have the same structure as that of the material world.

Parallel comparison is used to reveal the underlying structure existing in human thoughts.

After highlighting all the relevant ideas and concepts, which are behind each and every crisis in the foundations of mathematics, it becomes clear that some difficulties in the authors' understanding of nature are originated from confusing actual infinities with potential infinities, and vice versa. By pointing out the similarities and differences between these two kinds of infinities, then some hidden contradictions existing in the system of modern mathematics are handily picked out. Then, theoretically, using the authors' yoyo model, it is predicted that the fourth crisis in the foundations of mathematics has appeared. And, a plan of resolution of this new crisis is provided.

This paper shows the first time in history that human thought, the material world, and each economic entity, share a common structure – the systemic yoyo structure. And it proves the arrival of the fourth crisis in mathematics by using systems modeling and listing several; contradictions hidden deeply in the foundations of mathematics.

Mao Zedong was the representative figure in the Sinicisation of Marxism. At the beginning of the May 4th Movement, he advocated promoting the transformation of society by proceeding from the actualities of China and inheriting critically the legacy of Chinese and Western cultures. After he became a Marxist, he firmly resisted the tendency towards divination of the directives of the Communist International, and the Soviet experience of revolution, and tried hard to integrate the universal principles of Marxism with Chinese culture and Chinese revolutionary practice, thus opening up the way to the revolution in 1949. However, after the founding of the New China he patterned the economic construction on the Soviet model, and stressed criticism of the culture of the bourgeois, but dropped his guard against the pernicious influences of feudal society; so the historical sediment of the feudal culture became thicker and thicker under cover of Marxism, and finally there occurred the historical tragedy of the “Great Leap Forward” and the “Great Cultural Revolution”. The Third Plenary Session of the Eleventh Central Committee of the Chinese Communist Party repudiated the theoretical basis of the “Great Cultural Revolution” and brought in a new phase of political restructuring and cultural openness. The author holds that the evolution of Mao Zedong′s concept of Chinese and Western cultures should be studied and summarised, so that lessons may be drawn from it for the building of a socialist spiritual civilisation.

The uniformity of electrodeposition is the key to successful application of pattern plating because the quality of electrodeposited copper layer has a huge impact on the performance of printed circuit boards (PCBs). The multi-physics coupling technology was used to accurately analyze and forecast the characteristics of electrochemical system. Further, an optimized plating bath was used to achieve a uniform electrodeposition.

A multi-physics coupling numerical simulation based on the finite element method was used to optimize electrodeposition conditions in pattern plating process. The influences of geometric and electrochemical factors on uniformity of current distribution and electrodeposited layer thickness were discussed by multi-physics coupling.

The model results showed that the distance between cathode and anode and the insulating shield had a great impact on uniformity of electrodeposition. By numerical simulation, it had been proved that using an auxiliary cathode was an effective and simple way to improve uniformity of electrodeposition due to redistributing of the current. This helped to achieve more uniform surface of the copper patterns by preventing the edge effect and the roughness of the copper layer was reduced to 1 per cent in the secondary current distribution model.

The research is still in progress with the development of high-performance computers.

A multi-physics coupling platform is an excellent tool for quickly and cheaply studying the process behaviors under a variety of operating conditions.

The numerical simulation method has laid the foundation for the design and improvement of the plating bath.

By multi-physics coupling technology, we built a bridge between theoretical and experimental study for control of uniformity of pattern plating in PCB manufacturing. This method can help optimize the design of plating bath and uniformity of pattern plating in PCB manufacturing.

The transportation of fresh food requires cold chain logistics to maintain a low-temperature environment, which can reduce food waste and ensure product safety. Therefore, temperature control is a major challenge that cold chain logistics face.

This research proposes a prediction model of refrigerated truck temperature and air conditioner status (air speed and air temperature) based on hybrid mayfly algorithm (MA) and extreme learning machine (ELM). To prove the effectiveness of the proposed method, the mayfly algorithm–extreme learning machine (MA-ELM) is compared with the traditional ELM and the ELM optimized by classical biological-inspired algorithms, including the genetic algorithm (GA) and particle swarm optimization (PSO). The assessment is conducted through two experiments, including temperature prediction and air conditioner status prediction, based on a case study.

The prediction method is evaluated by five evaluation indicators, including the mean relative error (MRE), mean absolute error (MAE), mean squared error (MSE), root mean square error (RMSE) and coefficient of determination (R²). It can be concluded that the biological algorithm, especially the MA, can improve the prediction accuracy. This result clearly proves the effectiveness of the proposed hybrid prediction model in revealing the nonlinear patterns of the cold chain logistics temperature.

The case study illustrates the effectiveness of the proposed temperature prediction method, which helps to keep the product fresh. Even though the performance of MA is better than GA and PSO, the MA has the disadvantage of premature convergence. In the future, the modified MA can be designed to improve the performance of MA-ELM.

In prior studies, many scholars have conducted related research on the subject of temperature monitoring. However, this monitoring method can only identify temperature deviations that have occurred that harmed fresh food. As a countermeasure, research on the temperature prediction of cold chain logistics that can actively identify temperature changes has become the focus. Once a temperature deviation is predicted, temperature control measures can be taken in time to resolve the risk.