Teaching Multibody Dynamics from Modeling to Animation

This paper presents a student project which takes place just after the lecture in classical mechanics for undergraduate students in engineering. The pedagogical objectives of this learning layer cover various aspects, namely: give the student the opportunity to exploit and analyze the equations of motion for a real application, make them able to formulate consistent hypotheses for such applications and promote an actual multi-disciplinarity activity (mechanics, numerical methods, computer science and CAD). The project is performed by groups of 6–8 students and is organized in the frame of a global active pedagogical process which characterizes our undergraduate engineering.     

Microfluidic encapsulation of cells in alginate particles via an improved internal gelation approach

An improved internal gelation approach is developed to encapsulate single mammalian cells in monodisperse alginate microbeads as small as 26 μm in diameter and at rates of up to 1 kHz with high cell viability. The cell damage resulting from contact with calcium carbonate nanoparticles as gelation reagents is eliminated by employing a co-flow microfluidic device, and the cell exposure to low pH is minimized by a chemically balanced off-chip gelation step. These modifications significantly improve the viability of cells encapsulated in gelled alginate particles. Two different mammalian cell types are encapsulated with viability of over 84 %. The cells are functional and continue to grow inside the microparticles.     

Enhanced water flux through ultrafiltration polysulfone membrane via addition‐removal of silica nano‐particles: Synthesis and characterization

In the present paper, hierarchically structured ultrafiltration polysulfone (PSf) membrane was prepared to explore the effect of addition and subsequent removal of SiO₂ nano‐particles on the membrane morphology, hydrophilicity, and separation properties. The PSf based membranes namely PSf, PSf/SiO₂ and PSf/WSiO₂ (i.e. SiO₂ nano‐particles was acid‐washed and removed from PSf/SiO₂), were synthesized and characterized by different characterization methods. Pure water flux through the membranes was determined using a filtration unit operating at a continuous dead‐end flow mode. The modification enhanced the morphology, hydrophobicity, porosity and transport properties of the modified membranes, although the molecular weight cut‐off (MWCO) of the membranes was not changed considerably. In comparison, PSf/WSiO₂ membrane exhibited excellent pure water flux (about 4.5 times the flux of PSf, and 17 times the flux of PSf/SiO₂), although antifouling property of PSf/SiO₂ in separation of bovine serum albumin (BSA) was better than that of PSf and PSf/WSiO₂ membranes. The results suggested that the addition/removal of sacrificial solid fillers within/from a membrane matrix may provide a promising strategy to enhance PSf membrane transport property. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43556.     

Brain drain and brain gain in Russia: Analyzing international migration of researchers by discipline using Scopus bibliometric data 1996–2020

Scientometrics - We study international mobility in academia, with a focus on the migration of published researchers to and from Russia. Using an exhaustive set of over 2.4 million Scopus...     

Biomineralization‐Inspired Green Synthesis of Zinc Phosphate‐Based Nanosheets in Gelatin Hydrogel

Diffusion of inorganic salts in gels is a simple, inexpensive, and versatile technique for the synthesis of inorganic/organic hybrid nanocomposite particles with various morphologies. This paper introduces a novel method for producing zinc phosphate (ZP) nanosheets using single diffusion of zinc ions in gelatin at ambient temperature. FTIR spectra showed the entrapment of gelatin in ZP sheets due to electrostatic interactions between charged groups of gelatin and diffused ions. This study demonstrated that hydrogels can be used for crystallization of ZP. Such a nanocomposite particle may open a new window for producing antimicrobial and materials for use in tissue engineering.     

PVA/starch/propolis/anthocyanins rosemary extract composite films as active and intelligent food packaging materials

Active and intelligent food packaging films has taken more importance over conventional packaging. The aim of this study was to develop active and intelligent food packaging films based on bio-degradable polymers like polyvinyl alcohol and starch, incorporated with natural additives, that is, propolis extract (PE) and Anthocyanin. Boric acid was used as a cross-linker. The results proved the compatibility of films mixture. The mechanical strength was also measured and highest value was achieved 6.1 MPa for films containing 20% PE. Moreover, the maximum zone of inhabitation, that is, 21 and 15 mm, was also achieved at same composition against Escherichia coli and methicillin-resistant Staphylococcus aureus, respectively. Furthermore, all films had shown great color response against different pH ranging from 2 to 14. Finally, food spoilage test was performed using pasteurized milk. Films responded visibly by changing color and protected milk from spoilage. Hence, formulated bio-degradable active and intelligent films can be used as food packaging material.     

Antibacterial activity of natural polymer gels and potential applications without synthetic antibiotics

Antibiotics' use has increased, resulting in disadvantages like patients' drug resistance. Consequently, urgent action is required to develop a new generation of antibacterial agents. Most antibacterial platforms still require a modification with further antibacterial agents (e.g., antibiotics) for adequate antibacterial efficiency. Thus, a nonantibiotic methodology is immediately needed. Furthermore, bactericidal agents used for this purpose are usually based on metal nanoparticles, carbon materials, and polymers. Still, chemicals, antibiotics, and biocides lead to environmental damage. Therefore, the help of biocompatible yet durable materials and polymers is highly appreciated. In addition, if a polymer is not biodegradable, it will remain in the environment for more than one hundred years due to its low degradation rate. Moreover, non-biodegradable polymers are harmful to in vivo applications. Hence, the use of biodegradable and non-toxic materials has received many considerations. Over the last few years, the design and synthesis of new polymer gels have gained increasing attention. A polymer gel, also known as a hydrogel, is a three-dimensional and cross-linked network filled with water or other liquid solvents. Besides, the hydrogels supercritical drying method results in aerogels, and the freeze-drying method generates cryogels, where their porous and sponge-like structures are preserved. Additionally, antibacterial polymer gels are a new generation of polymers considered attractive due to their unique properties. The most recent studies and the latest innovations in polymer gels and hybrid polymers with intrinsic antibacterial properties were discussed in the present review. The reviewed studies from 2015 to April 2022 showed a tremendous revival in research about biopolymer hydrogel, aerogel, and cryogel as antibacterial agents.     

Piecewise Overactuation of Parallel Mechanisms Following Singular Trajectories: Modeling,Simulation and Control

The present approach aims at using the principle of redundant actuation for parallel robotic structures in order to follow complex trajectories in a so-called mechanically advantageous way, meaning that for any trajectory configuration the actuators can bear important loads (internal and/or external). Multibody system formalisms using relative coordinates and a robust technique to solve the closed-loop kinematic constraints, which are used for the purpose of modeling, are briefly reviewed. The notion of robot manipulability (and its relation to the velocity and force ellipsoids) is then recalled. As an initial step of the approach developed, suitable locations for the actuators of the non-overactuated system are proposed, the criteria being based on the theoretical concepts mentioned above. Then, according to some possible customer requirements, the number of actuators and their location are optimally specified on the basis of a piecewise trajectory planning. Both static and dynamic aspects are treated, depending on the application. Once the number and the locations of the actuators have been determined, a solution for the overdetermined inverse dynamics is proposed. Finally, the approach is validated via two examples of multibody parallel structures that are modeled, simulated and controlled in a suitable environment.     

Precision positioning using a novel six axes compliant nano-manipulator

In this paper, a novel micro-scale nano-manipulator capable of positioning in six degrees of freedom (DOF) is introduced. Undesired deflections, while operating in a specific DOF, are restricted by the aid of distinctive design of flexure hinges and actuators’ arrangements. The compliant mechanism is actuated by thermo-electro-mechanical actuators, as they could be integrated and exert large forces in a nanometer resolution. The actuators are bidirectional capable of applying force in both transverse and longitudinal directions. Performance of the two degrees of freedom actuator is thoroughly explored via numerical and analytical analyses, showing a good agreement. The workspace and performance of the precision positioner is studied using finite element methods. Finally, identification of forward and inverse kinematic of the nano-manipulator is performed utilizing neural network concept. A well-trained and appropriate neural network can efficiently replace the time-consuming and complex analytical and experimental methods.