Modeling and Simulation of Shape Memory Alloys using Microplane Model

In this chapter, a three-dimensional phenomenological constitutive model for the simulation of shape memory alloys is introduced. The proposed macromechanical model is based on microplane theory. Microplane approach is chosen to have limited material parameters in that all of those are measurable by simple tests. User material subroutine is developed to implement the proposed model in a commercial finite element package. NiTi hollow tube specimens are under various loading conditions in order to experimentally study the superelastic response of shape memory alloys. Comparing experimental data with numerical results in simple tension and pure torsion as well as proportional and nonproportional tension-torsion loadings demonstrates the capability of proposed model in constitutive modeling of shape memory alloys

Experimental Investigation of Impacting Flow between a Sub-Scale Twin-Rotor Configuration

In this paper, a series of experiments have been performed to understand the semi-quiescent and the impacting flow structure beneath the twin-rotor configuration body using a multipurpose test stand with a sub-scale model airframe in the ground effects. So, the main purpose was to perform a qualitative investigation on the recirculated impacting flow between the twin-rotors. Pressure and velocity measurements were performed by the pressure ports embedded longitudinally along the airframe. The results show that for a single rotor an impinging jet-like small region and rearward and upward flows were below the body. The presence of the second rotor in configurations causes an impacting flow formation in the longitudinal center region below the airframe and a semi-quiescent flow formed there. The positive effects of this flow includes increasing the sub-body pressure and lifting force, the pressure distribution balance, and desirable pressure gradient on sidewalls of the airframe. Tuft tests observations confirm that the location of the impacting flow formation is affected by the pressure and velocity measurements. The mentioned impacting flow aerodynamic effects must be taken into account in design of the flight controls trims and stability systems of twin-rotor configurations

A model-based approach to predict muscle synergies using optimization: application to feedback control

This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.This paper presents a new model-based method to define muscle synergies. Unlike the conventional factorization approach, which extracts synergies from electromyographic data, the proposed method employs a biomechanical model and formally defines the synergies as the solution of an optimal control problem. As a result, the number of required synergies is directly related to the dimensions of the operational space. The estimated synergies are posture-dependent, which correlate well with the results of standard factorization methods. Two examples are used to showcase this method: a two-dimensional forearm model, and a three-dimensional driver arm model. It has been shown here that the synergies need to be task-specific (i.e., they are defined for the specific operational spaces: the elbow angle and the steering wheel angle in the two systems). This functional definition of synergies results in a low-dimensional control space, in which every force in the operational space is accurately created by a unique combination of synergies. As such, there is no need for extra criteria (e.g., minimizing effort) in the process of motion control. This approach is motivated by the need for fast and bio-plausible feedback control of musculoskeletal systems, and can have important implications in engineering, motor control, and biomechanics.The authors wish to thank the Natural Sciences and Engineering Research Council of Canada (NSERC) for funding this study

Modeling of NiTiHf Using Finite Difference Method

NiTiHf is a high temperature and high strength shape memory alloy with transformation temperatures above 100oC. A constitutive model based on Gibbs free energy is developed to predict the behavior of this material. Two different irrecoverable strains including transformation induced plastic strain (TRIP) and viscoplastic strain (VP) are considered when using high temperature shape memory alloys (HTSMAs). The first one happens during transformation at high levels of stress and the second one is related to the creep which is rate-dependent. The developed model is implemented for NiTiHf under uniaxial loading. Finite difference method is utilized to solve the proposed equations. The material parameters in the equations are calibrated from experimental data. Simulation results are captured to investigate the superelastic behavior of NiTiHf. The extracted results are compared with experimental tests of isobaric heating and cooling at different levels of stress and also superelastic tests at different levels of temperature. More results are generated to investigate the capability of the proposed model in the prediction of the irrecoverable strain after full transformation in HTSMAs

(E)-N′-(3,3-Diphenyl­allyl­idene)-p-toluene­sulfonohydrazide

In the title compound, C22H20N2O2S, the mol­ecule adopts a twisted E configuration around the C=N bond. The two phenyl rings are twisted from each other, making a dihedral angle of 78.00 (12)°. The methyl-substituted benzene ring makes dihedral angles of 32.37 (14) and 69.70 (12)° with the two phenyl rings. In the crystal structure, mol­ecules are linked into extended chains along the b axis through inter­molecular N—H⋯O hydrogen bonds

Effects of adjuvant omega-3 fatty acid supplementation on dry eye syndrome following cataract surgery: A randomized clinical trial

AbstractPurposeTo investigate the effect of omega-3 polyunsaturated fatty acid supplement on qualitative and quantitative subjective (ocular surface disease index: OSDI) and objective (Schirmer's test, tear break up time [TBUT], and tear osmolarity) dry eye indices after cataract surgery.MethodsIn this randomized clinical study, 61 eyes of 48 patients complaining of new onset dry eye symptoms after phacoemulsification were enrolled. Subjects were randomly allocated into two groups using urn randomization. Controls received conventional treatment. The treatment group received omega-3 dietary supplement in addition to conventional therapy.ResultsThere was no significant difference between the control and treatment groups in pre-treatment indices of Schirmer (3.50 ± 3.13and 2.96 ± 3.39, respectively, P = 0.582), TBUT (6.67 ± 1.36 and 4.87 ± 2.22, respectively, P = 0.687), osmolarity (316.66 ± 8.50 and 315.4 ± 17.06, respectively, P = 0.906), and OSDI (32.99 ± 19.03 and 35.32 ± 18.99, respectively, P = 0.635).Mean pre-treatment OSDI in the control group was 32.99 ± 19.03, which improved significantly after treatment to 25.43 ± 14.49 (P = 0.003). The mean pre-treatment OSDI in the treatment group was 35.32 ± 18.99 (range: 7.5–77.77), which improved significantly after treatment to 16.31 ± 13.72 (range: 2.77–47.22) (P < 0.001). OSDI improvement was significantly higher in the treatment group than the control group (P = 0.026).TBUT improved in both the control and treatment groups after treatment (P < 0.001). However, TBUT was affected significantly more in the treatment group compared with the control group (P = 0.038).Mean tear film osmolarity in the control group was 316.67 ± 8.50 (range: 308–325), which improved insignificantly after treatment to 311.33 ± 6.35 (range: 304–315) (P = 0.157). Mean pre-treatment tear film osmolarity in the treatment group was 315.40 ± 17.06 (range: 279–340), which improved significantly after treatment to 296.90 ± 14.39 (range: 260–310) (P < 0.001). Also, post-treatment Schirmer results between the two groups were not statistically significant (P = 0.155).ConclusionOmega-3 dietary supplements have an additive effect on tear film indices of patients with dry eye syndrome after phacoemulsification

Predictive Simulation of Reaching Moving Targets Using Nonlinear Model Predictive Control

This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.This article investigates the application of optimal feedback control to trajectory planning in voluntary human arm movements. A nonlinear model predictive controller (NMPC) with a finite prediction horizon was used as the optimal feedback controller to predict the hand trajectory planning and execution of planar reaching tasks. The NMPC is completely predictive, and motion tracking or electromyography data are not required to obtain the limb trajectories. To present this concept, a two degree of freedom musculoskeletal planar arm model actuated by three pairs of antagonist muscles was used to simulate the human arm dynamics. This study is based on the assumption that the nervous system minimizes the muscular effort during goal-directed movements. The effects of prediction horizon length on the trajectory, velocity profile, and muscle activities of a reaching task are presented. The NMPC predictions of the hand trajectory to reach fixed and moving targets are in good agreement with the trajectories found by dynamic optimization and those from experiments. However, the hand velocity and muscle activations predicted by NMPC did not agree as well with experiments or with those found from dynamic optimization.The authors would like to thank the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Research Chairs program for financial support of this research

Seroprevalence and Molecular Evaluation of Toxoplasmosis in Patients Undergoing Chemotherapy for Malignancies in the Bushehr Province, Southwest Iran

Background: Toxoplasmosis is a life-threatening infection in organ transplant recipients, people receiving corticosteroid or radiation therapy, people with malignancies, and AIDS patients. Objectives: The current study aimed to determine the prevalence of toxoplasmosis in patients receiving chemotherapy for malignancies in the Bushehr province of southwest Iran. Methods: Blood samples were taken from 86 patients who were continuously referred to the chemotherapy center in Bushehr province and evaluated by ELISA to determine anti-Toxoplasma IgG and IgM antibodies. Moreover, a blood buffy coat of each sample was assessed by polymerase chain reaction (PCR), targeting a 529 bp gene of T. gondii. PCR products of the positive samples were sequenced to determine the genotype of the parasite. Results: Anti-Toxoplasma IgG antibodies were detected in the sera of 21 (24.4%) cases. All of the patients were negative for anti- Toxoplasma IgM antibodies. No statistically significant correlation was found between seropositivity to Toxoplasma and duration of chemotherapy or having contact with cats. PCR detected a 529 bp band of T. gondii in the buffy coats of two out of 86 (2.3%) cases. The sequence analysis demonstrated that both cases were 95% identical to type III (VEG strain) of T. gondii. Conclusions: Findings of this study demonstrated the presence of type III T. gondii in the buffy coats of patients undergoing chemotherapy. Given that toxoplasmosis is a life-threatening infection in immunocompromised patients, these patients should be screened for toxoplasmosis before and during chemotherapy to prevent acute toxoplasmosi

Seroprevalence and Molecular Evaluation of Toxoplasmosis in Patients Undergoing Chemotherapy for Malignancies in the Bushehr Province, Southwest Iran

Toxoplasmosis is a life-threatening infection in organ transplant recipients, people receiving corticosteroid or radiation therapy, people with malignancies, and AIDS patients. Objectives: The current study aimed to determine the prevalence of toxoplasmosis in patients receiving chemotherapy for malignancies in the Bushehr province of southwest Iran. Methods: Blood samples were taken from 86 patients who were continuously referred to the chemotherapy center in Bushehr province and evaluated by ELISA to determine anti-Toxoplasma IgG and IgM antibodies. Moreover, a blood buffy coat of each sample was assessed by polymerase chain reaction (PCR), targeting a 529 bp gene of T. gondii. PCR products of the positive samples were sequenced to determine the genotype of the parasite. Results: Anti-Toxoplasma IgG antibodies were detected in the sera of 21 (24.4%) cases. All of the patients were negative for anti- Toxoplasma IgM antibodies. No statistically significant correlation was found between seropositivity to Toxoplasma and duration of chemotherapy or having contact with cats. PCR detected a 529 bp band of T. gondii in the buffy coats of two out of 86 (2.3%) cases. The sequence analysis demonstrated that both cases were 95% identical to type III (VEG strain) of T. gondii. Conclusions: Findings of this study demonstrated the presence of type III T. gondii in the buffy coats of patients undergoing chemotherapy. Given that toxoplasmosis is a life-threatening infection in immunocompromised patients, these patients should be screened for toxoplasmosis before and during chemotherapy to prevent acute toxoplasmosis