Effect of the tank geometry on the storage and destocking of hydrogen on metal hydride (LaNi5H2)

The present numerical study aimed at studying the solid-statehydrogen storage and destocking in the LanthanumNickel (LaNi₅H₂) in a concentric triple-tube heat exchanger. Moreover, the influence of the thermal-reactor geometry for the storage and destocking hydrogen have been examined by changing the diameters of the heat exchanger. The performance of LanthanumNickel was compared with those of the hydride (MmNi₄.₆Fe₀.₄) and activated carbon. The flowing parameters: kinetics of hydrogen absorption/desorption, chemical reactions, enthalpy of fusion, equilibrium pressure, hydrogen concentration and the storage capacity were considered for calculating the terms of mass and energy equations. The hydride thermal and mass behaviour was integrated in the CFD Fluent with software (C++). A good agreement between the presented model and the literature experimental results was obtained. Additionally, the mentioned above parameters have shown a significant impact on the geometry of the reactor.     

On the Robust Nonlinear Motion Position and Force Control of Flexible Joints Robot Manipulators

The design of a robust nonlinear position and force controller for a flexible joints robot manipulator interacting with a rigid environment is presented. The controller is designed using the concept of feedback linearization, sliding mode techniques, and LQE estimation methodologies. It is shown that the nonlinear robot manipulator model is feedback linearizable. A robust performance of the proposed control approach is achieved by accounting for the system parameters uncertainties in the derivation of the nonlinear control law. An upper bound of the error introduced by parametric uncertainties in the system is computed. Then, the feedback linearizing control law is modified by adding a switching action to compensate the errors and to guarantee the achievement of the desired tracking performance. The relationship between the minimum achievable boundary layer thickness and the parametric uncertainties is derived. The proposed controller is tested using an experimental flexible joints robot manipulator, and the results demonstrate its potential benefits in reducing the number of sensors required and the complexity of the design. This is achieved by eliminating the need for nonlinear observers. A robust performance is obtained with minimum control effort by taking into account the effect of system parameter uncertainties and measurement noise.     

Ergonomics risk assessment among maintenance operators in a Tunisian railway company: A case study

Railway truck maintenance plays a crucial role for rail transport. It aims at ensuring the availability of the equipment and the safety of the operations. However, maintenance activities often involve uncommon work and nonroutine tasks and it is obvious that maintenance operators are more threatened than other employees to be exposed to various hazards in their workplace. In Tunisia, the prevalence of occupational accidents and injuries among maintenance workers is not well documented. The target of this cross‐sectional study is to assess ergonomics risks associated with maintenance activities in a railway company. Data collection was carried out through a self‐administrated questionnaire and via direct observations. The Body Parts Symptom Survey (BPSS) was used to identify the discomfort level of the workers. More than 100 maintenance operators working in nine different workshops were involved in this study. From BPSS results, this paper proposed a new method to calculate the discomfort index related to each body part in order to calculate the global discomfort index (GDI) for each workshop. Results showed that the most hazardous workshop was rail‐car maintenance workshop (GDI = 43.06). Four main tasks were assessed with normalized score. Final scores were found to be extremely high. To remedy the raised problems, new adjustable workstations were proposed, which showed a considerable improvement on workers’ postures.     

Induction of Oxidative Stress and Mitochondrial Dysfunction by Juglone Affects the Development of Bovine Oocytes

Juglone, a major naphthalenedione component of walnut trees, has long been used in traditional medicine as an antimicrobial and antitumor agent. Nonetheless, its impact on oocyte and preimplantation embryo development has not been entirely clarified. Using the bovine model, we sought to elucidate the impact of juglone treatment during the in vitro maturation (IVM) of oocytes on their maturation and development of embryos. Results showed a severe reduction in oocyte nuclear maturation and cumulus expansion and a significant increase in mitochondrial dysfunction and reactive oxygen species (ROS) levels in cumulus–oocyte complexes (COCs) treated with juglone (12.5, 25.0, and 50.0 µM). In addition, RT–qPCR showed downregulation of the expansion-related (HAS2, TNFAIP6, PTX3, and PTGS2) and mitochondrial (ATPase6 and ATP5F1E) genes in juglone-treated COCs. Moreover, the development rates of day 4 total cleavage and 8–16 cell stage embryos, as well as day 8 blastocysts, were significantly reduced following exposure to juglone. Using immunofluorescence, the apoptotic marker caspase-9 was overexpressed in oocytes exposed to juglone (25.0 µM) compared to the untreated control. In conclusion, our study reports that exposing bovine oocytes to 12.5–50.0 µM of juglone can reduce their development through the direct induction of ROS accumulation, apoptosis, and mitochondrial dysfunction.     

On the performance of OFDM and single carrier communication over wideband HF channel: theory and practice

Telecommunication Systems - Using wideband High Frequency (WBHF) communication has not been a luxury now due to the urgent need for the transfer of large files over long distances without the need...     

PPG-based human identification using Mel-frequency cepstral coefficients and neural networks

Multimedia Tools and Applications - One of the known problems in security systems is to identify persons based on certain signatures. Biometrics have been adopted in security systems to identify...     

An overview of selective laser sintering and melting research using bibliometric indicators

The aim of this paper is to present an overview of published research in selective laser sintering/melting (SLS/M), by using bibliometric indicators. Bibliometrics is the quantitative statistical analysis of written publications, such as articles or books. It is useful for displaying and classifying information according to selected variables, such as authors, journals, citations, countries, and institutions. This type of review provides a clear picture of research in a targeted area, such as the most cited research, author with most publications, journal with most published papers, and universities and countries producing the largest amount of research in the target area. The Web of Science database was used to collect data on the topic of interest. The results reveal that the Rapid Prototyping journal is the most productive journal in this field, where the Huazhong University Science Technology is the most effective institution. Also China is the most productive country, whereas USA is the most influential country.