Current Issue : October-December Volume : 2023 Issue Number : 4 Articles : 5 Articles
Water demand is steadily increasing, and usable water supply is constantly decreasing. It is urgent to find a cheap and efficient way to recycle water. Currently, membrane technologies are getting promising results, but some factors drastically reduce their effectiveness. In membrane filtration, biofouling is one of the most limiting factors, reducing filtration efficiency. In this work, the micro- and nanofibres-composed membranes were modified with diethylenetriamine (DETA), and silver nanoparticles were attached to a modified surface to minimize biofouling risk during filtration. Different conditions were tested for reaction with DETA and attachment of nanoparticles. Antimicrobial tests were performed, and the leaching of nanoparticles over time was checked. The modified membranes (Nadir® MV020T and PA PVDF) containing silver nanoparticles ranging in size from 20 to 50 nm showed antibacterial properties against Escherichia coli in the form of 3–4mm inhibitory zones. The percentage of released AgNPs was 0.47% and 2.12% for Nadir® MV020T and PA PVDF membrane after 21 days, respectively. Polyvinylpyrrolidone was used to increase the stability of the nanoparticles, and the results were compared....
Group II–VI cadmium sulfide nanoparticles (CdS NPs), a potential alternative to antibiotics, were synthesized using cadmium acetate [Cd(Ac)2] as a precursor, sodium sulfate as a reducing agent, and starch as a capping agent through chemical precipitation techniques. The CdS NPs were characterized using different characterizing techniques; X-ray diffraction and selected area electron diffraction patterns verify that the nanoparticles had cubic zinc blende structure with average dimension size of 2.43nm. Scanning electron mictroscope and transmission electron microscope images illustrated that the particles were uniformly distributed in cluster form, and FTIR and EDX confirmed the synthesized nanoparticles were pure. The CdS NPs show relevant antimicrobial sensitivity against Grampositive and Gram-negative bacterial strains and the zone of inhibition increases with the increase in the concentration of nanoparticles. In comparison to Gram-positive and Gram-negative bacteria, the synthesized nanoparticles were reported to be more effective toward Staphylococcus aureus, Gram-positive bacteria....
The structural bionicism of the knee joint of an automobile crash dummy is an important factor affecting the accuracy of the dummy’s knee displacement and knee flexion angle measurements in automobile crash tests. This study focused mainly on the optimization of the bionic structure of the knee joint of an automobile crash dummy to ensure that the dummy has a kinematic response closer to that of the knee joint of a real human. Forty sets of high-speed photographic images of the sphyrion were acquired by performing a trajectory-measurement test at the lower tibial point. Subsequently, the high-flexion motion trajectory of the knee joint was obtained by solving vector equations and by multicurve fitting. This trajectory, combined with the bionic structure design method, optimized the structure of the existing dummy’s knee joint. Thereby, its motion can be altered from a fixed-axis rotation to a non-fixed-axis curve motion close to how the human tibial plateau rotates around the femoral condyle. This increases the degrees of freedom of the dummy’s knee joint from two to three. The knee joint structures before and after the optimization were simulated kinematically using a multibody dynamics method. The results showed that the peak of the motion trajectory deviation of the optimized sphyrion decreased from 3.7% to 1.9%, and the average deviation decreased from 2.0% to 0.2%. This indicates that the structural optimization scheme improved the motion bionics of the crash dummy’s knee joint....
In this study, a graphic simulator that is used to simulate problems related to kinematics and dynamics for an exoskeleton robot arm with 5 degrees of freedom (DoF) was presented. The graphic simulator utilized the advantages of design software SolidWorks, Catia, and the computing and simulation power of SimMechanics Toolbox in Matlab. The core of the proposed graphic simulator is algorithm to solve the kinematics and dynamic problems of a developing upper-limb rehabilitation robot. The study used the proposed optimization-based algorithm to solve the inverse kinematics (IK) problem for the redundant robot model. Endpoint trajectories were imported from measurement data. The joints variable solutions obtained before entering the dynamics problem were smoothed to ensure feasibility in the later calculation process. A process to solve the inverse dynamics problem using physical model by combining the power of two software SolidWorks and SimMechanics was also proposed. This process ensured that the Robot’s design could be changed and updated to the kinematics calculation fast and easily. To evaluate this procedure, we also compared these dynamics results with results when applying the Lagrange–Euler formulation. All these calculation and simulation processes have been integrated into the graphic simulator software to show efficiency and user-friendliness....
A flexible pneumatic wrist with spatial position maintenance function is developed in this paper to settle the matter of insufficient flexibility of the robot wrist and self-braking technology. The wrist is made up of four artificial muscles and a pneumatic spherical brake in parallel, with 2 degrees of freedom. The wrist can realize multidirectional bending and adjust the wrist damping and braking in real time as required to achieve position maintenance. The theoretical model of the wrist bending angle is built based on torque balance. The variation of wrist bending angle and motion trajectory with air pressure is acquired through experiments. Simultaneously, the validity of the bending angle theoretical model is verified experimentally. A normally open pneumatic spherical brake is developed, and the mathematical model of braking torque is built and experimentally validated. Using a 3D dynamic capture system to compare the dynamic characteristics of the wrist under different excitation signals and different damping conditions. The experimental results reveal that the wrist has good flexibility and can achieve the functions of human hand pitch and yaw. The bending angle is 20.72° at 0.34 MPa. The pneumatic spherical brake has the function of spatial multidirection braking, and the braking force is adjustable. The maximum braking torque can reach 1.4Nm at 0.35 MPa....
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