Bending artificial muscle from nylon filaments

Highly oriented nylon and polyethylene fibers shrink in length and expand in diameter when heated. Using this property, in this work, for the first time we are introducing a type of bending artificial muscle from nylon filaments such as fishing line. Reversible radius of curvature of 0.23 mm-1 was achieved with maximum reversible bending amplitude of 115 mm for the nylon bending actuator. Peak force of up to 2040 mN was measured with a catch-state force of up to 40% of the active force. A 3 dB roll-off frequency of around 0.7 Hz was observed in the frequency response of the bending actuator in water.Natural Sciences and Engineering Research Council of Canada (Alexander Graham Bell Graduate Fellowship

Biochemical, liver and renal toxicities of Melissa officinals hydroalcoholic extract on balb/C mice

Introduction: Melissa officinalis is usually used as antispasmodic, antiaxiety and antibacterial agent. However, its toxicity has not been evaluated, yet. In this study biochemical, liver and renal toxicities of Melissa officinals hydroalcoholic extract were evaluated in balb/C mice. Methods: In an experimental study, 21 balb/C male mice were randomly designated to three equal groups. Group I was treated with normal saline and groups II and III were respectively treated with 0.450 and 1.350 g/kg, hydroalcoholic extract of Melissa officinals daily for two weeks, intraperitoneally. Then on 15th day of the experiment, blood samples were obtained from the heart. The blood was centrifuged and then the sera were evaluated for alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, urea and creatinine, using autoanalyzer and commercial kits. The liver and kidney tissues were also hystopathologically evaluated. The data were analyzed by one-way ANOVA, Tukey&rsquo;s post hoc test, and Kruskal-Wallis at a significance level of p&lt;0.05. Results: Melissa officinals dose dependently caused a significant reduction in alkaline phosphatase and alanine aminotransferase levels compared to the control group. Furthermore, Melissa officinals extract had no effect on the amount of urea and creatinine compared to the control group. The liver and kidney histopathological changes in the groups that received different doses of the extract showed mild, moderate, and severe tissue injuries. Conclusion: The biochemical analysis in this study indicates that the extract of Melissa officinals causes liver tissue damage in mice; therefore, its consumption in high doses should be avoided.</p

Histopatological and biochemical effects of subcute toxicity of lemon balm hydroalcoholic extract on liver and kidney tissues in the surri mice

Background and aims: Lemon balm (Melissa officinalis) in many countries is used as a nerve calming, spasmolytic, and antibacterial agent. Anyway, more investigations are needed to determine toxic effects of this plant. In this study, we investigated the effects of lemon balm hydroalcoholic extract on some biochemical enzymes and tissue changes (in kidney and liver) in mice. Methods: In this experimental study, 21 male mice were randomly divided into three groups of seven mice each. Group I was treated with normal saline as control and experimental groups II and III were treated with hydroalcoholic extract of lemon balm daily for two weeks intraperitoneally in doses of 0.450 and 1.350 g/kg, respectively. At the end of the experimental period (15 days), blood samples were obtained from the heart and centrifuged, and then the sera were evaluated to determine the concentrations of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatinine, and urea using autoanalyzer and commercial kits. In addition, the liver and kidney tissues were removed and examined after fixation in formalin buffer 10% and hematoxyline-eosin staining. The data were analyzed at a significance level of p<0.05 by one-way ANOVA, Tukey's post hoc test, and Kruskal-Wallis. Results: Lemon balm caused a significant reduction in alanine aminotransferase and alkaline phosphatase levels compared to the control group. Also, it showed a dose-dependent effect. Furthermore, lemon balm extract had no effect on the amount of urea and creatinine compared to the control group. Histopathological changes of the liver and kidney in the groups that received different doses of the extract showed mild, moderate, and severe tissue injuries. Conclusion: The biochemical analysis in this study indicates that the extract of lemon balm causes liver tissue damage in mice therefore, plant’s consumption in high doses should be avoided

A torsional artificial muscle from twisted nitinol microwire

Nitinol microwires of 25 μm in diameter can have tensile actuation of up to 4.5% in less than 100 ms. A work density of up to 480 MPa can be achieved from these microwires. In the present work, we are showing that by twisting the microwires in form of closed-loop two-ply yarn we can create a torsional actuator. We achieved a revisable torsional stroke of 46°/mm with peak rotational speed of up to 10,000 rpm. We measured a gravimetric torque of up to 28.5 N•m/kg which is higher than the 3-6 N•m/kg for direct-drive commercial electric motors. These remarkable performance results are comparable to those of guest-infiltrated carbon nanotube twisted yarns.Natural Sciences and Engineering Research Council of Canada (Alexander Graham Bell Graduate Fellowship

Scram Incidence Statistic Survey in a Research Nuclear Reactor Considering System Hardware And Human Errors

ABSTRACT One of the major events in nuclear reactors is scram or immediate emergency shutdown. Qualitative and quantitative study of this event, as well as the main causative factors in evaluating reactor safety is an important point. In this study, safety of Tehran research reactor is assessed probabilistically and the human error possibility is evaluated using SPAR-H method. In this regard, scram fault tree associated with hardware failures and human errors are drawn by using SAPHIRE software. The calculated total scram possibility is found to be 1.0E-2

Simple and strong: twisted silver painted nylon artificial muscle actuated by Joule heating

Highly oriented nylon and polyethylene fibres shrink in length when heated and expand in diameter. By twisting and then coiling monofilaments of these materials to form helical springs, the anisotropic thermal expansion has recently been shown to enable tensile actuation of up to 49% upon heating. Joule heating, by passing a current through a conductive coating on the surface of the filament, is a convenient method of controlling actuation. In previously reported work this has been done using highly flexible carbon nanotube sheets or commercially available silver coated fibres. In this work silver paint is used as the Joule heating element at the surface of the muscle. Up to 29% linear actuation is observed with energy and power densities reaching 840 kJ m[superscript -3] (528 J kg[superscript -1]) and 1.1 kW kg[superscript -1] (operating at 0.1 Hz, 4% strain, 1.4 kg load). This simple coating method is readily accessible and can be applied to any polymer filament. Effective use of this technique relies on uniform coating to avoid temperature gradients

Niobium nanowire yarns and their application as artificial muscle

Since the discovery of carbon nanotubes, various devices have been made in different fields of science and engineering. The mechanical and electrical properties that carbon nanotubes offer make them a great candidate for use in the structure of artificial muscles. In this thesis, for the first time, we have demonstrated that metallic nanowires can be engineered to become strong and comparable to the CNT yarns in mechanical and electrical properties. The niobium yarns offer conductivity of up to 3×10⁶ S m-¹, tensile strength of up to 1.1 GPa and Young’s modulus of 19 GPa. The niobium nanowire fibres are fabricated by extracting the niobium nanowires from copper-niobium nano-composite matrix, which was made by using a severe plastic deformation process. As a practical application, torsional artificial muscles were made out of the niobium yarns by twisting and impregnating them with paraffin wax. Upon applying voltage to the twisted yarn the wax melts and expands due to the heat generated by the current. Thermal expansion of wax untwists the yarn, which translated to torsional actuation. Torsional speeds of 7,200 RPM (in a destructive test) and 1,800 RPM (continuous) were achieved. In addition to torsional actuation, niobium yarns also can provide up to 0.24% of isobaric tensile actuation along the yarn’s axis at 20 MPa load. Due to the high conductivity of the niobium yarns, the actuator can be made to actuate by even one single 1.5 V battery (for a 1 cm of niobium yarn). The electrochemical capacitance of niobium yarns was measured to be 1.3×10⁷ F m-³ at a scan rate of 25 mV s-¹ in 0.2 M TBAPF₆ salt dissolved in acetonitrile. This value is comparable to the electrochemical capacitance of the carbon multi-walled nanotube yarns.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat

High performance materials for artificial muscles and energy storage devices

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.Includes bibliographical references.Artificial muscles (i.e., stimuli-responsive materials) are muscle-like materials and devices that mimic muscle's functionality (e.g., contraction, rotation, and bending) in different aspects. Some of the common performance metrics used for evaluating artificial muscles are cycle life, gravimetric/volumetric energy and/or power density, efficiency, cost, and controllability of muscle. Having a good combination of these performance metrics is very desirable and an active field of research. Many of the state-of-the-art designs are made from some exotic materials such as carbon nanotubes and metal nanowires which are not yet commercially available; here, new designs are proposed which their performance favorably compares to those of the rival materials and yet made of readily available materials. In addition to artificial muscles, designs for fast charging micro-supercapacitors are also proposed. Fast charging energy storage devices such as supercapacitors have applications in different industries ranging from automobile to telecommunication. Cellphones, for example, use fast charging micro-supercapacitors in their GSM/GPRS modulus to generate high current pulses for signal transmission purposes. The current technologies, such as tantalum/niobium oxide micro-supercapacitors are evolving around enhancing the energy and power density by increasing the specific capacitance and operating voltage. Yet, increasing the specific capacitance is still a major challenge. In this thesis, aside from discrete component geometry, flexible (e.g., yam-based) supercapacitors have various applications from flexible circuits to wearable devices. Design and fabrication of high performance supercapacitors by utilizing metal nanowires (e.g., niobium nanowires) in both forms (i.e., flexible and solid/rigid devices) are investigated as well.by Seyed M. Mirvakili.Ph. D

Generalization of Pawlak’s Approximations in Hypermodules by Set-Valued Homomorphisms

The initiation and majority on rough sets for algebraic hyperstructures such as hypermodules over a hyperring have been concentrated on a congruence relation. The congruence relation, however, seems to restrict the application of the generalized rough set model for algebraic sets. In this paper, in order to solve this problem, we consider the concept of set-valued homomorphism for hypermodules and we give some examples of set-valued homomorphism. In this respect, we show that every homomorphism of the hypermodules is a set-valued homomorphism. The notions of generalized lower and upper approximation operators, constructed by means of a set-valued mapping, which is a generalization of the notion of lower and upper approximations of a hypermodule, are provided. We also propose the notion of generalized lower and upper approximations with respect to a subhypermodule of a hypermodule discuss some significant properties of them

Neutronics investigation of CANada Deuterium Uranium 6 reactor fueled (transuranic–Th) O2 using a computational method

Background: 241Am, 243Am, and 237Np isotopes are among the most radiotoxic components of spent nuclear fuel. Recently, researchers have planned different incineration scenarios for the highly radiotoxic elements of nuclear waste in critical reactors. Computational methods are widely used to predict burnup rates of such nuclear wastes that are used under fuel matrixes in critical reactors. Methods: In this work, the Monte Carlo N-particle transport code was used to calculate the neutronic behavior of a transuranic (TRU)-bearing CANada Deuterium Uranium 6 reactor. Results: The computational data showed that the 1.0% TRU-containing thorium-based fuel matrix presents higher proliferation resistance and TRU depletion rate than the other investigated fuel Matrixes. The fuel matrix includes higher negative temperature reactivity coefficients as well. Conclusion: The investigated thorium-based fuel matrix can be successfully used to decrease the production of highly radiotoxic isotopes