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This study aims to obtain the speed and angle during safe and comfortable standing of elderly people. With the advancement of society, it is becoming increasingly difficult for the elderly to sit-to-stand (STS) independently and comfortably in a safe and comfortable manner. Safety is essentially a prerequisite for the elderly to achieve a comfortable STS. The speed, angle and power of the STS process can all affect safe STS. From the standpoint of health-care delivery and administration, comfortable STS can be realized easily by addressing the safety issues during STS.

This paper summarizes the research progress on speed and angle during safe and comfortable standing of older people. The authors analyzed the speed and angle of the STS using the Vicon optical gait acquisition system and plantar pressure sensor to find the appropriate angle and speed thresholds.

The center of gravity movement is a prerequisite for the elderly to achieve a comfortable STS. The authors found that the standing speed during the STS process should not be higher than 103.8 mm/s so that the elderly can stand comfortably and safely (safe and dangerous speeds are 72.8 mm/s and 125.2 mm/s). The limitations of waist angle, waist angle speed and the acceleration are also obtained.

This paper analyzes and summarizes the research status of speed and angle during safe and comfortable standing of elderly people, which is essentially a prerequisite for the elderly to achieve a comfortable STS. These results can lay the foundation for the development of assistive devices and related technologies that meet the needs of older adults.

The stability characteristics of an oil film directly influence the safety and service life of mill oil-film bearings. However, very limited work has been done to address the stability characteristics of mill oil-film bearings. To this end, this paper aims to investigate the stability characteristics of mill oil-film bearings through theoretical and experimental analysis.

For the first time, a special designed experiment platform was developed to investigate the stability characteristics of mill oil-film bearings. In addition, a theoretical model of lubricating film of the tested bearings was established to analyze the oil-film stability. The theoretical results were compared with the experimental results.

The comparison results demonstrate that the critical influential factors on the bearing stability were the eccentricity ratio and the ratio of bearing length to diameter. The mill bearing was likely to be unstable under a small load and at a high rotational speed.

The paper includes implications for suitable operation conditions in practical use of mill oil-film bearings.

This paper fulfills an identified need to investigate oil-film stability of mill bearings for practical applications.

Carbon emission is one of the most important problems of today. In this framework, it is important for countries to take the necessary actions to solve this problem. Energy use is one of the most important causes of carbon emissions. Choosing fossil fuels in this process increases the carbon emission problem. Therefore, it is understood that countries should be more sensitive about energy types. In this context, renewable energy (RE) sources are recommended by experts. However, due to some problems of these energy types, it does not seem possible to meet all energy needs from these sources. It is thought that nuclear energy will produce a permanent solution to the carbon emission problem. In this context, it is recommended that the use of nuclear energy be put on the agenda by countries.

Water-lubricated bearings can significantly reduce the pollution to environment because the traditional oil lubricant is replaced by water in the bearings. The ultrahigh molecular weight polyethylene (UHMWPE) has proven to be effective and reliable for the manufacturing of water-lubricated bearings. However, limited work has been done to address the improvement of the tribological performance of the UHMWPE-based water-lubricated bearings using surface texture processing. This paper aims to investigate the effects of bar-grooved surface on the tribological performance improvement of UHMWPE-based water-lubricated bearings.

For the first time, the bar grooves were processed on the surfaces of UHMWPE-based water-lubricated bearings. The CBZ-1 friction and wear tester have been used to test the wear and friction performance of the bearing samples. The LI laser interference surface contour graph and the digital microscope have been used to measure the surface morphology of the specimens. The tribological characteristics of the tested bearings were analyzed.

With bar grooves added on the surfaces of the specimens, the friction coefficient of the specimens were lower than that of the specimens without surface texture processing; the wear quantity of the two kinds of specimens were almost the same; by using the LI laser interference surface contour graph and the digital microscope to measure the surface morphology of the specimens, the furrows of the specimens with bar grooves were narrower and shallower than that of the specimens without bar grooves.

The paper implicates that the surface texture processing using bar grooves can reduce the friction coefficient and prolong the service life of the water-lubricated bearings in practical applications.

This paper fulfills an identified need to provide important theoretical and experimental support to the design of water-lubricated bearings in practical applications.

This paper aims to research the tribological and dynamic characteristics of aeroengine hybrid ceramic bearings through wear experiments and simulation analysis.

First, the authors carried out wear experiments on Si₃N₄–GCr15 and GCr15–GCr15 friction pairs through the ball-disc wear test rig to explore the tribological properties of their materials. Second, using ANSYS/LS-DYNA simulation software, the dynamic simulation analysis of hybrid bearings was carried out under certain working conditions, and the dynamic contact stress of all-steel bearings of the same size was simulated and compared. Finally, the change of the maximum contact stress of the main bearing under the change of load and rotation speed was studied.

The results show that the Si₃N₄–GCr15 pair has better tribological performance. At the same time, under the conditions of high speed and heavy load, the simulation analysis shows that the contact stress between the ceramic ball and the raceway of the ring is smaller than the steel ball. That is, hybrid bearings have better transient mechanical properties than all-steel bearings. With the speed increasing to 12,000 r/min, the maximum stress point will shift in the inner and outer rings.

In this study, the tribological and transient mechanical properties of Si₃N₄ material were comprehensively analyzed through wear experiments and dynamic simulation analysis, which provided a reference for the design of hybrid bearings for next-generation aeroengines.

The purpose of this paper is to research on CuO-water nanofluid Non-Darcy flow because of magnetic field. Porous cavity has circular heat source and filled with nanofluid. Lattice Boltzmann Method (LBM) has been used to simulate this problem.

In this research, LBM has been applied as mesoscopic approach to simulate water-based nanofluid free convection. Koo–Kleinstreuer–Li model is used to consider Brownian motion impact on nanofluid properties. Impacts of Rayleigh number, Darcy number, nanofluid volume fraction and Hartmann number on heat transfer treatment are illustrated.

It is found that temperature gradient decreases with rise of while it enhances with augment of Ha. Darcy number can enhance the convective flow.

The originality of this work is to analyze the to investigate magnetic field impact on water based CuO-H₂O nanofluid natural convection inside a porous cavity with elliptic heat source.

Selective laser melting (SLM) enables the fabrication of lightweight and complex metallic structures. Support structures are required in the SLM process to successfully produce parts. Supports are typically lattice structures, which cost much time and material to manufacture. Besides, the manufacturability of these supports is undesirable, which may impact the quality of parts or even fail the process. The purpose of this paper is to investigate the efficiency and mechanical properties of advanced internal branch support structures for SLM.

The theoretic weight of a branch support and a lattice support of the same plane were calculated and compared. A group of standard candidates of branch support structures were manufactured by SLM. The weight and scanning time of specimens with different design parameters were compared. Then, these samples were tested using an MTS Insight 30 compression testing machine to study the influence of different support parameters on mechanical strength of the support structures.

The results show that branch type supports can save material, energy and time used needed for their construction. The yield strength of the branch increases with the branch diameter and inclined branch angle in general. Furthermore, branch supports have a higher strength than traditional lattice supports.

To the best of the authors’ knowledge, this is the first work investigating production efficiency and mechanical properties of branch support structures for SLM. The findings in this work are valuable for development of advanced optimal designs of efficient support structures for SLM process.

The purpose of this paper is to present the entropy analysis of ferrofluid inside a porous space with magnetic force. Homogenous model with second law analysis is also taken into account.

Innovative model has been proposed and designed using control volume finite element method.

Experimental results demonstrate that Bejan number augments with augment of Rayleigh. As Hartmann number rises, exergy loss enhances. Exergy loss increases by increasing Hartmann number, whereas magnetic entropy generation reduces with the decrease of Ha. The proposed model can be used for combustion process and optimizing the performance of energy conversion system like gas turbine.

To the best of authors’ knowledge, this model is reported for the first time.

Preprint has become an important vehicle for academic communications and discussions. However, in preprint, there is a lack of a sufficient quality control mechanism such as peer review, which is a proven quality assurance practice that is used in traditional academic publishing services. To address the problem leveraging on the power of this practice, the authors introduce into preprint a self-organizing peer review method by applying the concept of token economy and the blockchain technology.

Specifically, this paper proposes an idea that applies the token economy concept to the design of the incentive and penalty mechanisms for peer reviewers in preprint to assure the qualities of its publications. Steemit has been studied to demonstrate the characteristics of the mechanisms.

A token economy-enhanced framework for self-organizing peer review in preprint is also proposed. The resulting preprint system is an academic community-oriented, self-organizing and blockchain-based content publishing system that is designed to run on both permissioned and permissionless blockchains.

First, since peer review is on a voluntary basis and not profits oriented, the “monetary” incentive and penalty mechanisms borrowed from Steemit may conflict with academic ethics. Second, the authors proposed to deploy the authors’ token economy on blockchain, but the current mainstream decentralized blockchain services are too few to warrant a foreseeable successful future for the authors’ application. In fact, as the flagship of blockchain 2.0, the Ethereum blockchain suffers from the problem of scalability, which leads to its applications' lower performances, longer response times and eventually more negative user experiences as time goes by. Finally, the authors’ proposed version of preprint has not been implemented, and hence, its practical effectiveness and acceptance by academia are yet to be evaluated.

In this paper, the authors proposed a token economy-based framework for self-organizing peer review in preprint leveraging on blockchain technology. This framework encourages positive interactions between authors and reviewers, which helps to establish a healthy academic ecology that produces more contents with better qualities. Application of a solution based on the authors’ framework should impact the current academic communities by offering a new academic peer reviewing tool that has a built-in mechanism for self-behavior correction and quality assurance.

Through adaption, the framework can be applied to other domains as well. In such domains, a large amount of feedbacks from partakers are needed and there exists a tremendous amount of work to filter noises in feedbacks so as to ensure that as many the quality ones as possible are delivered for a variety of purposes. The authors’ framework essentially impacts almost all domains where there exists a need to collect and filter large amount of feedbacks, and using the authors’ framework-based solution is cost-saving, which can be seen as a major potential contribution of the research.

The incentive and penalty mechanisms encourage positive interactions between authors and reviewers, and it helps to establish a healthy academic ecology that produces high-volume contents with good qualities.