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The purpose of this paper is to identify if the implementation of ultrasonic vibration in laser engineered net shaping (LENS) process can help to reduce internal weaknesses such as porosity, coarse primary TiB whisker and heterogeneous distribution of TiB reinforcement in the LENS-fabricated TiB reinforced Ti matrix composites (TiB-TMC) parts.

An experimental investigation is performed to achieve the results for comparative studies under different fabrication conditions through quantitative data analysis. An approach of microstructural characterization and mechanical testing is conducted to obtain the output attributes. In addition, the theoretical analysis of the physics of ultrasonic vibration in the melting materials is presented to explain the influences of ultrasonic vibration on the microstructural evolution occurred in the part fabrication.

Because of the nonlinear effects of acoustic streaming and cavitation induced by ultrasonic vibration, porosity is significantly reduced and a relatively small variation of pore sizes is achieved. Ultrasonic vibration also causes the formation of smaller TiB whiskers that distribute along grain boundaries with a homogeneous dispersion. Additionally, a quasi-continuous network (QCN) microstructure is considerably finer than that produced by LENS process without ultrasonic vibration. The refinements of both reinforcing TiB whiskers and QCN microstructural grains further improve the microhardness of TiB-TMC parts.

The novel ultrasonic vibration-assisted (UV-A) LENS process of TiB-TMC is conducted in this work for the first time to improve the process performance and part quality.

The purpose of this paper is to clarify the influence of low earth orbit space environment on the wear mechanism of TC4 alloy material and crank rocker mechanism.

In this study, friction experiments were carried out on TC4 alloy friction discs and crank rocker mechanisms, both before and after exposure to atomic oxygen and proton irradiation. Nanoindentation, grazing incidence X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy were employed to systematically characterize alterations in mechanical properties, surface phase, and chemical composition.

The results show that the wear mechanism of TC4 alloy friction disc is mainly adhesive wear in vacuum environment, while the wear mechanism of crank rocker mechanism includes not only adhesive wear but also abrasive wear. Atomic oxygen exposure leads to the formation of more oxides on the surface of TC4 alloy, which form abrasive particles during the friction process. Proton irradiation will lead to a decrease in fatigue performance and an increase in hardness on the surface of TC4 alloy, thus causing fatigue wear on the surface of TC4 alloy, and more furrows appear on the crank rocker mechanism after proton irradiation. In the three environments, the characteristics of abrasive wear of the crank rocker mechanism are more obvious than those of the TC4 alloy friction disc.

These results highlight the importance of understanding the subtle effects of atomic oxygen and proton irradiation on the wear behavior of TC4 alloy and provide some insights for optimizing its performance in space applications.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2024-0051/

This paper aims to investigate the effects of the pia matter on cerebral cortical folding.

A three-layer buckling simulation model composited by the white matter, gray matter and the pia matter is adopted to analyze the effect of the pia matter on cortical folding. The volume growth of brain tissues is simulated using thermal expansion. The effects of the pia matter growth rate, thickness and stiffness on cortical folding is investigated.

The simulation results show that all of these three aforementioned factors of pia matter have obvious effects on cerebral cortical folding. Especially, the thickening of the pia matter may lead to cortical folding malformation such as polymicrogyria, which is in good agreement with the recent reported anatomical findings.

The three-layer model in this paper composited by the white matter, gray matter and the pia matter is different from the usually used two-layer model only composited by the white matter and gray matter. This three-layer model has successfully validated the effect of the pia matter on cerebral cortical folding. The simulation results can explain the anatomical findings very well.

The study delves into the influence of wear cycles on these parameters. The purpose of this paper is to identify characteristic patterns of σ_RS and ε_PEEQ that discern varying wear situations, thereby contributing to the enrichment of wear theory. Furthermore, the findings serve as a foundational basis for nondestructive and in situ wear detection methodologies, such as nonlinear ultrasonic detection, known for its sensitivity to σ_RS and ε_PEEQ.

This paper elucidates the wear mechanism through the lens of residual stress (σ_RS) and plastic deformation within distinct fretting regimes, using a two-dimensional cylindrical/flat contact model. It specifically explores the impact of the displacement amplitude and cycles on the distribution of residual stress and equivalent plastic strain (ε_PEEQ) in both gross slip regime and partial slip regimes.

Therefore, when surface observation of wear is challenging, detecting the σ_RS trend at the center/edge, region width and ε_PEEQ distribution, as well as the maximum σ_RS distribution along the depth, proves effective in distinguishing wear situations (partial or gross slip regimes). However, discerning wear situations based on ε_PEEQ along the depth direction remains challenging. Moreover, in the gross slip regime, using σ_RS distribution or ε_PEEQ along the width direction rather than the depth direction can effectively provide feedback on cycles and wear range.

This work introduces a novel perspective for investigating wear theory through the distribution of residual stress (σ_RS) and equivalent plastic strain (ε_PEEQ). It presents a feasible detection theory for wear situations using nondestructive and in situ methods, such as nonlinear ultrasonic detection, which is sensitive to σ_RS and ε_PEEQ.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0005/

The main purpose of this study is to examine whether economic policy uncertainty affects the stock liquidity. Furthermore, this study explores the influencing factors, transmission mechanism and solution path between economic policy uncertainty and the stock liquidity.

A data set comprising 97,729 firm-quarter observations of Chinese firms with A-shares listed on the Shenzhen and Shanghai stock exchanges was selected, China's economic policy uncertainty was measured by using the China Economic Policy Uncertainty Index and the impact of economic policy uncertainty on the stock liquidity over the period 2004–2017 was empirically tested. The empirical analysis was based on ordinary least square regression model, and mediation and moderation effect models were used in the further analysis.

The empirical results show that the higher the economic policy uncertainty, the lower the stock liquidity, which is more significant in firms with an opaque information environment, less investor attention and weak risk resistance ability. The authors argue that the transmission mechanism can be explained by the quality of information disclosure and investor sentiment. Moreover, the negative impact of economic policy uncertainty on the stock liquidity can be mitigated by increasing voluntary disclosures.

This study enriches the literature on factors affecting the stock liquidity from the perspective of macroeconomic policy and provides a reference for policymakers to formulate relevant measures to improve the stock liquidity in emerging markets.

The governing equations for dynamic transient analysis of a fluid‐saturated two‐phase porous medium model based on the mixture theory are presented. A penalty finite element formulation is derived with the general Galerkin procedure of the finite element method (FEM), and the obtained dynamic system equation can be solved with implicit or explicit time integration method, which is discussed in this paper. Using this method, a porous medium column under impulsive loading is analyzed and the results reveal the phenomena of one‐dimensional wave propagation, which are consistent with analytical solutions. Furthermore, two numerical examples of two‐dimensional problems demonstrate the existence of two body waves, i.e. longitudinal (P‐type) and transverse (S‐type) waves in porous media, and the Rayleigh wave in the vicinity of the surface of porous media.

Executives are searching for ways to deliver consistent improvements in productivity and profitability while addressing economic realities. One initiative that has been discovered by many organizations is the integration a quality process into their or ganization that is based on the Malcolm Baldrige National Quality Award (MBNQA). Many studies have been done showing that award winning companies tend to out perform peers and competitors, yet many managers are reluctant to under take the large initiative required to work toward the award. This reluctance may stem from the belief that the reported benefits are not those that are important for managers to justify the effort. The purpose of this research is to begin an exploratory study that examines the expectations of company managers, executives, and other professionals regarding the types of firm performance and returns that would be needed to justify undertaking the MBNQA process. The results showed that while financial performance of the firm is the strongest justification managers consider, and that while their expectations for improved financial performance are some what high, the financial returns are certainly not out of the realm of normal expectations for returns from other projects.

The purpose of this paper is to systematically study the dynamic contact stress, frictional heat and temperature field of femoral head-on-acetabular cup contact pairs in a gait cycle.

In this paper, four common femoral head-on-acetabular cup contact pairs are used as the research objects, mathematical calculations and finite element simulations are adopted. The contact model of hip joint head and acetabular cup was established by finite element simulation to analyze the stress and temperature distribution of the contact interface.

The results show that the contact stress of the head-on-cup interface is inversely proportional to the contact area; high contact stress directly leads to greater frictional heat. However, hip joints with metal-on-polyethylene or ceramic-on-polyethylene paired interfaces have lower frictional heat and show a significant temperature rise in one gait cycle, which may be related to the material properties of the acetabular cup.

Previous studies about calculating the interface frictional heat always ignore the dynamic change process in the contact load and the contact area. This study considered the dynamic changes of the contact stress and area of the femoral head-on-acetabular cup interface, and four common contact pairs were systematically analyzed.

This study examines the use of dark humor in brand-to-brand communications on social media and its impact on consumers' brand perceptions. In particular, this study looks at roasting messages in which a brand humorously insults its peers.

The authors used a sampling method to recruit 286 participants from the United States. They employed an ANOVA and Tukey's post hoc analysis to test the hypotheses, as well as Hayes' PROCESS to test the mediation and moderation effects, including Johnson–Neyman procedure.

The authors found that not all customers find roasting messages funny. Rather, consumers' personality and age will influence their perceived humor of the messages and their brand evaluations. Customers who are young and extroverted are likely to believe roasting messages to be funny. They thus perceive the brand to be cooler and more sincere when using such a communication approach, compared to when the brand neutrally interacts with others. Meanwhile, brands may find less success with old and introverted customers.

This research sheds light on how the consumers' perception of humor in a roasting type of brand-to-brand communication has an impact on consumers' psychological perceptions of brand coolness and brand sincerity. To guide practitioners, it explored how the interaction between a consumer's personality and age moderates the aforementioned relationship.