Diagnosis of ball bearing with various degree rolling element defects based on local mean decomposition

This paper aims to explore fault characteristics extraction method to deal with the light and severe rolling element faults based on local mean decomposition (LMD) and Fourier transform (FT). The characteristics of LMD are studied by processing multi-component frequency modulation and amplitude modulation (FM-AM) signal, which are usually used to describe the bearing fault signals. Based on the simulation analysis, the envelope spectrum method called LMD-FT is used to deal with the vibration signals of rolling balling bearing with various element faults. Moreover, the fault features extracted by LMD are compared with those obtained from conventional Hilbert transform (HT). The results demonstrate that LMD method is an effective way to identify the characteristics of rolling element defect generated at the initial stage

Coaching or gaming? Implications of strategy choice for home based stroke rehabilitation

Background: The enduring aging of the world population and prospective increase of age-related chronic diseases urge the implementation of new models for healthcare delivery. One strategy relies on ICT (Information and Communications Technology) home-based solutions allowing clients to pursue their treatments without institutionalization. Stroke survivors are a particular population that could strongly benefit from such solutions, but is not yet clear what the best approach is for bringing forth an adequate and sustainable usage of home-based rehabilitation systems. Here we explore two possible approaches: coaching and gaming. Methods: We performed trials with 20 healthy participants and 5 chronic stroke survivors to study and compare execution of an elbow flexion and extension task when performed within a coaching mode that provides encouragement or within a gaming mode. For each mode we analyzed compliance, arm movement kinematics and task scores. In addition, we assessed the usability and acceptance of the proposed modes through a customized self-report questionnaire. Results: In the healthy participants sample, 13/20 preferred the gaming mode and rated it as being significantly more fun (p < .05), but the feedback delivered by the coaching mode was subjectively perceived as being more useful (p < .01). In addition, the activity level (number of repetitions and total movement of the end effector) was significantly higher (p <.001) during coaching. However, the quality of movements was superior in gaming with a trend towards shorter movement duration (p=.074), significantly shorter travel distance (p <.001), higher movement efficiency (p <.001) and higher performance scores (p <.001). Stroke survivors also showed a trend towards higher activity levels in coaching, but with more movement quality during gaming. Finally, both training modes showed overall high acceptance. Conclusions: Gaming led to higher enjoyment and increased quality in movement execution in healthy participants. However, we observed that game mechanics strongly determined user behavior and limited activity levels. In contrast, coaching generated higher activity levels. Hence, the purpose of treatment and profile of end-users has to be considered when deciding on the most adequate approach for home based stroke rehabilitation

Investigation of flow field characteristics and performance of carbon-hydrogen/oxygen-rich air rotating detonation engine

Numerical simulations were conducted to investigate the flow field characteristics and performance of a carbon-hydrogen/oxygen-rich air rotating detonation engine (RDE). Three distinct flow field structures were observed in the gas-solid two-phase RDE. The results show that reducing the hydrogen equivalence ratio and particle diameter both contribute to the transition from gas-phase single-front detonation to gas-solid two-phase double-front detonation and further to gas-solid two-phase single-front detonation. The effects of solid fuel particle diameter and hydrogen equivalence ratio on the flow field characteristics and performance are revealed. The results show that reducing the particle diameter enhances the speed of the two-phase detonation wave, improves the pressure gain in the combustion chamber, and increases the specific impulse. Decreasing the hydrogen equivalence ratio reduces the detonation wave speed, enhances the stability of the detonation flow field, increases the pressure gain in the detonation wave and combustion chamber and boosts thrust. Furthermore, the selection of operational conditions to ensure stable operation and optimal performance of the RDE is discussed. In order to take into account the requirements of stability, pressure gain performance and propulsion performance, two-phase single-front detonation should be realized in gas-solid two-phase RDE, and smaller hydrogen equivalent ratio and appropriate particle diameter should be selected. According to the conclusion of this study, the particle diameter should be 0.5-1 {\mu}m. Under such conditions, the detonation flow field demonstrates good stability, allowing the RDE to achieve higher pressure gain and specific impulse while maintaining stable operation

Tuning the Magnetism in Ultrathin CrxTey Films by Lattice Dimensionality

Two-dimensional (2D) magnetic transition metal compounds with atomic thickness exhibit intriguing physics in fundamental research and great potential for device applications. Understanding the correlations between their macrosopic magnetic properties and the dimensionality of microscopic magnetic exchange interactions are valuable for the designing and applications of 2D magnetic crystals. Here, using spin-polarized scanning tunneling microscopy, magnetization and magneto-transport measurements, we identify the zigzag-antiferromagnetism in monolayer CrTe2, incipient ferromagnetism in bilayer CrTe2, and robust ferromagnetism in bilayer Cr3Te4 films. Our density functional theory calculations unravel that the magnetic ordering in ultrathin CrTe2 is sensitive to the lattice parameters, while robust ferromagnetism with large perpendicular magnetic anisotropy in Cr3Te4 is stabilized through its anisotropic 3D magnetic exchange interactions

Application of blended learning approach in clinical skills to stimulate active learning attitudes and improve clinical practice among medical students

Background The recent application of blended educational methods has impacted medical education and has drawn attention to a new teaching method. This teaching style presents unique opportunities and challenges. We investigated the effects of blended learning and traditional teaching methods on clinical skill development. Methods We sorted 200 medical students from Tongji Medical College at Huazhong University of Science and Technology into a control or experimental group. The control group was taught with a traditional lecture-based learning method and the experimental group was taught using a blended learning method. The two groups were compared after training to assess their theoretical and practical differences. A student satisfaction survey was given to participants in both groups. Results The results of the experimental group’s theoretical and practical assessments were found to be significantly higher (p < 0.05) than that of the control group. The student satisfaction survey showed that blended learning was significantly more effective for acquiring relevant knowledge, enhancing student-centered learning and improving clinical practice. Conclusions Blended learning may address deficiencies in clinical skills, make up for limited time and space, and ensure learning efficiency and quality

Identification of key sectors of water resource utilization in China from the perspective of water footprint.

We identified the key sectors of water resource use in China from the perspective of the water footprint to improve the use of water resources. The empirical results showed that there were six key sectors (including Crop Cultivation; Forestry; Livestock and Livestock Products; Fishery, Technical Services for Agriculture, Forestry, Livestock and Fishing; Other Food Products, and Scrap and Waste) for water consumption in China in 2015.We analyzed the use of green water, blue water, and grey water. These six sectors accounted for 66.15% of the total impact and 90.76% of the direct impact. Seven key sectors (the six sectors above plus Steel Processing)for the consumption of blue water in China can explain 59.70% of the total impact and 86.94% of the direct effect in 2015. Eight key sectors (Crop cultivation, Other food products, Scrap and Waste, Railway Freight Transport, Highway Freight and Passengers Transport, Water Freight and Passengers Transport, Pipeline Transport, and Health Services) responsible for the consumption of grey water in China in 2015 can explain 81.28% of the total impact and 95.73% of the direct impact. Therefore, the Chinese government should focus on the departments that manage water resources in these sectors when designing water-saving policies and improving water-use efficiency, such as promoting water-saving irrigation technology (including sprinkler irrigation and drip irrigation) in the agricultural sector

A study on the cavitating flow around an elliptical disk-shaped cavitator for non-body-of-revolution underwater vehicles

Supercavitation has been recently presented as an effective method for the drag reduction of underwater vehicles. However, maintaining the supercavitating state requires a lot of energy, making vehicles difficult to control. Therefore, it is necessary to design an underwater vehicle with low drag in the fully wetted state while being able to move at ultra-high speed in the supercavitating state. In this study, a detachable fairing design for underwater vehicles is proposed, which has the advantage of increasing the total voyage and avoiding the problem of difficult steering in the supercavitating state. On the other hand, the study of non-body-of-revolution (non-BOR) has become a prevalent area of interest in the shape design of underwater vehicles. The cavity generated by an elliptical disk-shaped cavitator is studied numerically. It is found that the cavity profile on the cross-section near the cavitator is approximately elliptical. The cavity length of an elliptical disk-shaped cavitator is almost the same as that of a disk-shaped cavitator when they have the same inflow area. Based on these two characteristics, the parameters of the internal elliptical disk-shaped cavitator are optimized, which provides a promising strategy for the issue of cavitators increasing drag in a fully wetted state

Research on the Frequency-Dependent Halfwave Voltage of a Multifunction Integrated Optical Chip in an Interferometric Fiber Optic Gyroscope

The multifunction integrated optical chip (MIOC) is one of the most critical parts of the interferometric fiber optic gyroscope (IFOG), and research on the halfwave voltage of the MIOC is meaningful for a high-precision IFOG. In this paper, the correlation between the frequency and halfwave voltage, which affects the interference light intensity of IFOG, is presented theoretically. A widespread measurement method for frequency dependence of the halfwave voltage, based on lock-in amplification and sinusoidal modulation, is proposed. Further, the measurement result and the oscillation of interference light intensity in the Sagnac interferometer are presented, which are in great agreement with the theory. This paper proposes the frequency dependence of the halfwave voltage and provides a new error research direction for the improvement of the MIOC in a high-precision IFOG