| 1. |
- El-Seedi, Hesham R., et al.
(författare)
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Anti-schistosomiasis triterpene glycoside from the Egyptian medicinal plant Asparagus stipularis
- 2011
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Ingår i: REV BRAS FARMACOGN. - : SOC BRASILEIRA FARMACOGNOSIA. - 0102-695X. ; 22:2, s. 314-318
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Tidskriftsartikel (refereegranskat)abstract
- Bioassay-guided isolation using an in vitro assay testing for anti-schistosomiasis yielded a novel triterpene saponin, asparagalin A, from the n-butanol extract of the roots of Asparagus stipularis Forssk., Asparagaceae. The structure was elucidated by spectroscopic analysis and chemical transformations. Administration of asparagalin A resulted in a retardation of worm growth and locomotion at the first day and showed a significant activity of egg-laying suppression at 200 mu g/mL concentration.
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| 2. |
- Jabir Hussain, Ahmed Fardan, 1996, et al.
(författare)
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Numerical modelling of particle impact and residual stresses in cold sprayed coatings: A review
- 2021
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 409
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Forskningsöversikt (refereegranskat)abstract
- Cold spray technology provides protective coatings, additive manufacturing and repair to a wide array of industrial sectors. Alternative tags for cold spray include, kinetic metallisation, kinetic fusion, hypersonic spray, gas dynamic cold spray, cold spray printing, and cold spray additive manufacturing. These processes employ the same physics principles of accelerating micrometre-sized particles to supersonic velocities that impact and adhere onto a suitably prepared substrate. Numerical modelling has been used extensively to study particle impact modelling. The prediction of critical velocity, deformation mechanism and, more recently, residual stresses have been areas of interest that have been evaluated by numerical methods such as Lagrangian, Eulerian, Smoothed Particle Hydrodynamics, Coupled Eulerian-Lagrangian, and Molecular Dynamics. The crucial findings of these models are summarised, and their comparative outcomes assessed with a critical analysis of their merits and weaknesses. The process parameters applied in the simulations such as particle diameter, impact velocity, pre-heat temperature and material chemistry is compiled. The experimental techniques used for residual stress measurements; such as X-ray diffraction, neutron diffraction, material removal, curvature measurement and deformation techniques, are concisely reviewed from the context of being applied to cold spray deposits.
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| 3. |
- Qureshi, Abdul Sattar, et al.
(författare)
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Fruit waste to energy through open fermentation
- 2017
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Ingår i: PROCEEDINGS OF THE 9TH INTERNATIONAL CONFERENCE ON APPLIED ENERGY. - Amsterdam : Elsevier. ; 142, s. 904-909
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Konferensbidrag (refereegranskat)abstract
- This study aims to examine the nonsterilized fermentation conditions for coproduction of pectinases and lipase enzymes using several fruit wastes as an energy source. Thermophilic fungal strain, Penicillium expansum CM,1 39671 was used as a fermenting strain. The effect of process conditions including; nitrogen sources, pH, temperature, time and moisture contents, on the production of both enzymes were studied. The highest activities of pectinase and lipase (2817, 1870 U/g dry substrate) enzymes were found with orange peel feedstock, whereas the lowest activities of 1662 U/g and 1266 U/g were found with banana peel and papaya peel feedstocks respectively. Overall, pectinase showed higher enzymatic activities than lipase enzymes, both having similar increasing and decreasing trends, at all studied conditions. The optimum process conditions of peptone as a nitrogen source, pH 7, 40 degrees C, 5 days and 70% moisture contents, were found to show highest enzymatic activities for both enzymes. The orange peel feedstock showed no significant difference in both enzymes' activities at sterilized and nonnotarized process conditions. Pectinase and lipase enzymes showed (13791 U/g) and (8114 U/g) for sterilized and (14091 U/g) and (8324 U/g) for nonnotarized process conditions respectively. In addition, the fungal strains also produce bacteriocin-like compounds that could inhibit microbial growth. These findings will help to design and develop robust, cost-effective and less energy intensive enzyme production processes and consequently an efficient fruit waste to energy system through open fermentation. (C) 2017 The Authors. Published by Elsevier Ltd.
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| 4. |
- Saxena, Shreya, et al.
(författare)
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Influence of Plasticity and Friction on the Contact Mechanics of Auxetic Materials
- 2021
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Ingår i: Journal of Tribology. - : ASME International. - 0742-4787 .- 1528-8897. ; 143:8
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Tidskriftsartikel (refereegranskat)abstract
- Contact interactions play an important role in the tribological behavior of engineering materials. This paper develops a finite element model to investigate the contact mechanics and stress distribution of auxetic materials, i.e., materials with negative Poisson's ratio. The model results are compared with numerical and mathematical models for isotropic auxetic polymers. The indentation of auxetic materials is analyzed for the effects of friction, plasticity and allowing separation after contact with a spherical indenter using a commercial software, abaqus. The results are discussed in terms of stress profiles, force-indentation depth curves, plasticity, friction, internal energy, compressibility, sink-in, and the pile-up of material. It is concluded that for purely elastic contact, the indentation resistance increases for auxetic materials and the inclusion of friction shifts subsurface stresses closer to the surface. However, the introduction of plasticity negates the improvement of increased indentation resistance. The pile-up of material around the indent reduces for auxetic materials which makes them more suitable for rolling/sliding contacts. The internal strain energy decreases for purely elastic contact and increases for an elastic/plastic contact.
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| 5. |
- Ahmed, Muhammad Rehan
(författare)
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Compliance Control of Robot Manipulator for Safe Physical Human Robot Interaction
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inspiration from biological systems suggests that robots should demonstrate same level of capabilities that are embedded in biological systems in performing safe and successful interaction with the humans. The major challenge in physical human robot interaction tasks in anthropic environment is the safe sharing of robot work space such that robot will not cause harm or injury to the human under any operating condition.Embedding human like adaptable compliance characteristics into robot manipulators can provide safe physical human robot interaction in constrained motion tasks. In robotics, this property can be achieved by using active, passive and semi active compliant actuation devices. Traditional methods of active and passive compliance lead to complex control systems and complex mechanical design.In this thesis we present compliant robot manipulator system with semi active compliant device having magneto rheological fluid based actuation mechanism. Human like adaptable compliance is achieved by controlling the properties of the magneto rheological fluid inside joint actuator. This method offers high operational accuracy, intrinsic safety and high absorption to impacts. Safety is assured by mechanism design rather than by conventional approach based on advance control. Control schemes for implementing adaptable compliance are implemented in parallel with the robot motion control that brings much simple interaction control strategy compared to other methods.Here we address two main issues: human robot collision safety and robot motion performance.We present existing human robot collision safety standards and evaluate the proposed actuation mechanism on the basis of static and dynamic collision tests. Static collision safety analysis is based on Yamada’s safety criterion and the adaptable compliance control scheme keeps the robot in the safe region of operation. For the dynamic collision safety analysis, Yamada’s impact force criterion and head injury criterion are employed. Experimental results validate the effectiveness of our solution. In addition, the results with head injury criterion showed the need to investigate human bio-mechanics in more details in order to acquire adequate knowledge for estimating the injury severity index for robots interacting with humans.We analyzed the robot motion performance in several physical human robot interaction tasks. Three interaction scenarios are studied to simulate human robot physical contact in direct and inadvertent contact situations. Respective control disciplines for the joint actuators are designed and implemented with much simplified adaptable compliance control scheme.The series of experimental tests in direct and inadvertent contact situations validate our solution of implementing human like adaptable compliance during robot motion and prove the safe interaction with humans in anthropic domains.
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| 6. |
- Ahmed, Muhammad Rehan, 1978-, et al.
(författare)
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Semi-active compliant robot enabling collision safety for human robot interaction
- 2010
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Ingår i: 2010 International Conference on Mechatronics and Automation (ICMA). - : IEEE. - 9781424451401 ; , s. 1932-1937
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Konferensbidrag (refereegranskat)abstract
- Human robot interaction (HRI) tasks requires robots to have safe sharing of work space and to demonstrate adaptable compliant behavior enabling eminent collision safety as well as maintaining high position accuracy. Robot compliance control normally can be achieved by using active compliance control of actuators based on various sensor data. Alternatively, passive devices allow controllable compliance motion but usually are mechanically complex. We proposed a unique method using semi-active compliant actuation mechanism having magneto-rheological (MR) fluid based actuator that introduces reconfigurable compliance characteristics into the robot joints. This enables high intrinsic safety coming from fluid mechanics as well as, it offers simpler interaction control strategy compared to other concurrent approaches. In this studies, we have described three essential modes of motions required for physical human system interaction. Furthermore, we have demonstrated robot collision safety in terms of static collision and experimentally validates the performance of robot manipulator enabling safe human robot interaction.
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| 7. |
- Ahmed, Muhammad Rehan, 1978-, et al.
(författare)
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Static and dynamic collisionsafety for human robot interaction using magneto-rheological fluid based compliant robot manipulator
- 2010
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Ingår i: IEEE international conference on robotics and biomimetics (ROBIO), 2010. - : IEEE conference proceedings. - 9781424493197 ; , s. 370-375
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Konferensbidrag (refereegranskat)abstract
- The success of human robot interaction (HRI) tasks is characterized by evaluating robot performance in terms of collision safety and position accuracy. Hence, both position accuracy and collision safety are equally indispensable. HRI refers to cognitive as well as physical interaction. Cognitive human robot interaction based on perception and awareness where as physical human robot interaction demands direct contact with the humans exhibiting adaptable compliant behavior. Therefore, development of ideal safe robot manipulator having adaptable compliant actuation is inevitable. Adaptable compliance can be achieved by using active compliant actuation requiring various sensor data or by using passive compliant devices with high mechanical complexity. We present magneto rheological fluid based compliant actuation mechanism introducing adaptable compliance directly into robotic joint with much simpler interaction control and higher intrinsic safety originating from fluid mechanics. In this study, we have discussed adaptable compliance in terms of essential modes of motion for safe physical HRI and evaluated the safety performance of our robot for static collision testing and dynamic collision testing based on impact force and head injury criterion. Finally, the experimental results validate the significance of our proposed method for both human robot collision safety and high position accuracy.
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| 8. |
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| 9. |
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| 10. |
- Ahmed, Rehan M., 1978-, et al.
(författare)
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Compliant motion control for safe human robot interaction
- 2009
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Ingår i: Robot motion and control 2009. - Berlin : Springer. - 9781848829848 ; , s. 265-274
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Konferensbidrag (refereegranskat)abstract
- Robots have recently been foreseen to work side by side and share workspace with humans in assisting them in tasks that include physical human-robot (HR) interaction. The physical contact with human tasks under uncertainty has to be performed in a stable and safe manner [6]. However, current industrial robot manipulators are still very far from HR coexisting environments, because of their unreliable safety, rigidity and heavy structure. Besides this, the industrial norms separate the two spaces occupied by a human and a robot by means of physical fence or wall [9]. Therefore, the success of such physical HR interaction is possible if the robot is enabled to handle this interaction in a smart way to prevent injuries and damages.
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