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Selective laser melting (SLM) process is an additive manufacturing method that uses computer-aided design to fabricate complex components layer-by-layer. Surface roughness is one of the primary drawbacks of SLM process; hence, the purpose of this paper is to present a parametric study and optimisation of fundamental parameters, including scan power, speed, inclined angle and layer thickness on surface roughness during selective laser melting of Hastelloy X.

Parametric significance on surface finish was analysed using analysis of variance and response surface methodology. General agreement between predicted and measured values was achieved. Surface characteristics of both up-skin and down-skin with various angles were covered within the investigated range.

Both experimental and statistical analysis showed that surface roughness of up-skin was primarily influenced by scan power, inclined angle and layer thickness while down-skin was more affected by the former two factors. Melt pool shape and staircase size were found to determine the up-skin surface, whereas attached particles were responsible for down-skin surface roughness.

As per our understanding, this manuscript provides valuable insight into the surface quality problem of SLM, which is a very critical issue for up-grading the process for manufacturing real components. This manuscript helps promote improved knowledge and understanding of the attributes and capabilities of this rapidly evolving 3D printing technology. Moreover, it establishes usable processing window and helps obtain optimal conditions, thus offering useful information to professionals working in this field. By combining experiments with statistical analysis, both practice and theory relevant to SLM process are further developed.

Limited research has attempted to reveal the different modes of the melt pool formation in additive manufacturing. This paper aims to study the mechanisms of surface roughness formation, especially on the aspect of melt pool formation which determine the surface profile and consequently significantly influence the surface roughness.

In this study, the conditions under which different modes of melt pool formation (conduction mode and keyhole mode) occur for the case of as-fabricated Hastelloy X using direct metal laser solidification (DMLS) are derived and validated experimentally. Top surfaces of uni-directionally built samples under various processing conditions are cut, grinded, polished and etched to reveal their individual melt pool morphologies. Similarly, up-skin (slope angle < 90°) and down-skin (slope angle > 90°) melt pool morphologies are also investigated to compare the differences. Surface tension gradients and resultant Marangoni flow, which dominate the melt flow in the melt pool, is also calculated to help better evaluate the melt pool shape forming.

Two types of melt pool formation modes are dominating in DMLS: conduction mode and keyhole mode. Melt pool formed by conduction mode generally has an aspect ratio of 1:2 (depth vs width) and is in elliptical shape. Appropriate selection of scanning laser power and speed are required to maintain a low characteristic length and width ratio to prevent ballings. Melt pool formed by keyhole mode has an aspect ratio of 1:1 or less. High-energy contour promotes formation of key-hole-shaped melt pool which fills the gaps between layers and smoothens the up-skin surface roughness. Low-energy contour scan is necessary for down-skin surface to form small melt pool profiles and achieve low Ra.

This paper provides valuable insight into the origins of surface quality problem of DMLS, which is a very critical issue for upgrading the process for manufacturing real components. This paper helps promote the understanding of the attributes and capabilities of this rapidly evolving three-dimensional printing technology and allow appropriate control of processing parameters for successful fabrication of components with sound surface quality.

Electronic wallets (e-wallet) systems have revolutionized transactional activities, prompting individuals to adopt digital payment methods. This study investigates the determinants of the continuance intention of the e-wallet system Touch 'n Go in Malaysia. We propose a framework integrating the diffusion of innovation theory (DOI) and mental accounting theory, thereby assessing the impacts of product-related factors (convenience, compatibility, perceived risk and perceived compatibility) and the moderating role of personal-related factors [personal innovativeness (PI) and personal anxiety].

Data were collected involving 381 Malaysian Touch 'n Go users. The partial least squares structural equation modeling (PLS-SEM) was applied as a data analysis technique.

As demonstrated by the results, convenience serves as a facilitator, while perceived risk acts as an inhibitor, influencing the continuance intention of the application. Compatibility and perceived complexity are found to be insignificant antecedents. However, neither PI nor personal anxiety was found as moderators.

This research brings contributions to the electronic commerce literature by extending the understanding of the predictors and moderators of the continuance intention of Touch 'n Go users in Malaysia. We discuss how these findings implicate the two theories and offer insights for service providers and policymakers to promote the post-adoption intentions of Touch 'n Go.

This survey focuses on two families of nonlinear vector time series models, the family of vector threshold regression (VTR) models and that of vector smooth transition regression (VSTR) models. These two model classes contain incomplete models in the sense that strongly exogeneous variables are allowed in the equations. The emphasis is on stationary models, but the considerations also include nonstationary VTR and VSTR models with cointegrated variables. Model specification, estimation and evaluation is considered, and the use of the models illustrated by macroeconomic examples from the literature.

This study aims to propose a vertical coupling dynamic analysis method of vehicle–track–substructure based on forced vibration and use this method to analyze the influence on the dynamic response of track and vehicle caused by local fastener failure.

The track and substructure are decomposed into the rail subsystem and substructure subsystem, in which the rail subsystem is composed of two layers of nodes corresponding to the upper rail and the lower fastener. The rail is treated as a continuous beam with elastic discrete point supports, and spring-damping elements are used to simulate the constraints between rail and fastener. Forced displacement and forced velocity are used to deal with the effect of the substructure on the rail system, while the external load is used to deal with the reverse effect. The fastener failure is simulated with the methods that cancel the forced vibration transmission, namely take no account of the substructure–rail interaction at that position.

The dynamic characteristics of the infrastructure with local diseases can be accurately calculated by using the proposed method. Local fastener failure will slightly affect the vibration of substructure and carbody, but it will significantly intensify the vibration response between wheel and rail. The maximum vertical displacement and the maximum vertical vibration acceleration of rail is 2.94 times and 2.97 times the normal value, respectively, under the train speed of 350 km·h⁻¹. At the same time, the maximum wheel–rail force and wheel load reduction rate increase by 22.0 and 50.2%, respectively, from the normal value.

This method can better reveal the local vibration conditions of the rail and easily simulate the influence of various defects on the dynamic response of the coupling system.

In this chapter, we explore the dark side of the metaverse and the need for user protection. While the metaverse offers multiple opportunities it also poses significant risks for users, such as privacy concerns, addiction, harassment, and cyberbullying. First, we discuss the various threats that users may encounter such as online harassment, assaults, cyberbullying, hate speech, identity theft, and virtual property theft. As per the Center for Countering Digital Hate, an incident of violation occurs every seven minutes within VRChat, a popular virtual reality game. The level of misconduct in the metaverse can surpass the extent of internet harassment. Virtual reality gaming has been associated with various health issues like sleep deprivation, and insomnia as well as mental health concerns such as depression, anger, and anxiety. We examine how these issues may impact user’s physical and mental health. The sensors and devices used in the metaverse collect a vast amount of user biometric data and spatial data. Interactions between users and metaverse could be leaked. We examine different methods that improve user protection, including everyone from enhanced security protocols via the application of privacy-enhanced technology to several avatars, two-factor authentication, and user educational and awareness programs. Moreover, we explore how the newest technologies, like blockchain and artificial intelligence, play a role in making user safety more important. We finished the course with the study of the case of Second Life, the virtual reality gaming platform, and pointing out some of the problems that exist within it.

The higher education industry has undergone major transformation because of the COVID-19, including a move away from globalization. Deglobalization is the process of reducing global interconnectedness and increasing self-reliance, often through the imposition of trade barriers and the localization of economic activity (Eftimie, 2017). Many nations have had to resort to placing travel restrictions and virtually closed their borders during the pandemic time, making it even more challenging for overseas students to pursue higher education abroad. Additionally, the pandemic has increased opportunities towards online education, making it simpler for students to receive quality education from their home countries making it possible for students who may not have been able to otherwise attend in-person classes (Ashour et al., 2021). This trend has also been influenced by political and economic forces like nationalism, protectionism, and international economic difficulties. Higher education institutions are consequently putting more emphasis on partnerships and collaborations at the local and regional levels (James, 2017; Pan, 2021).

Based on the data from “Thousand village surveys” project of Shanghai University of Finance and Economics, we employ the ordered logistic method to do the empirical analysis on consumption, life and satisfaction (subjective well-being) of Chinese rural elderly. First, the result shows that the consumption (exclude medical expenses) has positive effect on the satisfaction of Chinese rural elderly, while the rural elderly are not preferred to compare with others. Good participation in social life and medical care condition could enhance the satisfaction of rural elderly. Second, the authors divided the sample into two groups as high-consumption group and low-consumption group. The result shows that the low-consumption group more tend to rely on their family members than high-consumption group. The authors suggest that in order to improve the rural elderly life satisfaction, the government needs to improve medical care system.

Misunderstanding and harmful stereotyping have become commonplace amongst people in the United States and the Middle East/North Africa (MENA) region since 2001, if not earlier. If universities are the locus of transformative education, work remains towards remedying these issues.One non-profit organisation, “Natafaham (pseudonym, Arabic for « we understand each other”), works to undo this negativity student by student. It brings participants from the MENA and Europe/North America into dialogue via Zoom each week. The inter-cultural dialogue availed to participants is empowering to actors, including the dialogue facilitator. This narrative is an autoethnographic exploration of my experience as an intercultural dialogue facilitator. Yet reviewing contemporaneous notes and reflections revealed structural aspects of this programme that empower voices from the MENA region, while facilitating learning amongst participants on both sides of the Atlantic. Such aspects include the format and the location of the programme, its focus on individuals rather than institutions or groups, its mixed top-down and bottom-up approach, and the opportunities it avails for ascension to positions of authority. This narrative analyses these aspects through several lenses and academic traditions, including those of global citizenship, critical internationalisation, (reciprocal) global service learning, and socio-cultural frameworks of second language acquisition. The chapter urges that these aspects are recognised as key catalysts of (more) equal relationships between youth in the MENA region and the United States, which merit widespread replication. It concludes by envisioning a still more equal relationship predicated upon more equitable language usage.