Modeling and control of multibody system with flexible appendages

The objective of this work is to describe the design and the implementation of an experiment to study the dynamics and the active control of a slewing multi-link flexible structure. The experimental apparatus was designed to be representative of a flexible space structure such as a satellite with multiple flexible appendages. In this study we describe the design procedures, the analog and digital instrumentation, the analytical modeling together with model validation studies carried out through experimental modal testing and parametric system identification studies in the frequency domain. Preliminary results of a simple positional control where the sensor and the actuator are positioned physically at the same point is also described.

Prediction of transients and control reactions in a transonic wind tunnel

This work describes a lumped parameter mathematical model for the prediction of transients in an aerodynamic circuit of a transonic wind tunnel. Control actions to properly handle those perturbations are also assessed. The tunnel circuit technology is up to date and incorporates a novel feature: high-enthalpy air injection to extend the tunnel’s Reynolds number capability. The model solves the equations of continuity, energy and momentum and defines density, internal energy and mass flow as the basic parameters in the aerodynamic study as well as Mach number, stagnation pressure and stagnation temperature, all referred to test section conditions, as the main control variables. The tunnel circuit response to control actions and the stability of the flow are numerically investigated. Initially, for validation purposes, the code was applied to the AWT ("Altitude Wind Tunnel" of NASA-Lewis). In the sequel, the Brazilian transonic wind tunnel was investigated, with all the main control systems modeled, including injection.

Nonlinear dynamics and control of multibody systems

The dynamics of flexible systems, such as robot manipulators , mechanical chains or multibody systems in general, is becoming increasingly important in engineering. This article deals with some nonlinearities that arise in the study of dynamics and control of multibody systems in connection to large rotations. Specifically, a numerical scheme that adresses the conservation of fundamental constants is presented in order to analyse the control-structure interaction problems.

Proposal of methodology for the modeling and control of manipulators

Industrial applications demand that robots operate in agreement with the position and orientation of their end effector. It is necessary to solve the kinematics inverse problem. This allows the displacement of the joints of the manipulator to be determined, to accomplish a given objective. Complete studies of dynamical control of joint robotics are also necessary. Initially, this article focuses on the implementation of numerical algorithms for the solution of the kinematics inverse problem and the modeling and simulation of dynamic systems. This is done using real time implementation. The modeling and simulation of dynamic systems are performed emphasizing off-line programming. In sequence, a complete study of the control strategies is carried out through the study of several elements of a robotic joint, such as: DC motor, inertia, and gearbox. Finally a trajectory generator, used as input for a generic group of joints, is developed and a proposal of the controller's implementation of joints, using EPLD development system, is presented.

Rapid diagnosis of resistance to imidazolinone herbicides in barnyardgrass (Echinochloa crus-galli) and control of resistant biotypes with alternative herbicides

The resistance of barnyardgrass (Echinochloa crus-galli) to imidazolinone herbicides is a worldwide problem in paddy fields. A rapid diagnosis is required for the selection of adequate prevention and control practices. The objectives of this study were to develop expedite bioassays to identify the resistance to imidazolinone herbicides in barnyardgrass and to evaluate the efficacy of alternative herbicides for the post-emergence control of resistant biotypes. Three experiments were conducted to develop methods for diagnosis of resistance to imazethapyr and imazapyr + imazapic in barnyardgrass at the seed, seedling and tiller stages, and to carry out a pot experiment to determine the efficacy of six herbicides applied at post-emergence in 13 biotypes of barnyardgrass resistant to imidazolinones. The seed soaking bioassay was not able to differentiate the resistant and susceptible biotypes. The resistance of barnyardgrass to imidazolinones was effectively discriminated in the seedlings and tiller bioassays seven days after incubation at the concentrations of 0.001 and 0.0001 mM, respectively, for both imazethapyr and imazapyr + imazapic. The biotypes identified as resistant to imidazolinones showed different patterns of susceptibility to penoxsulam, bispyribac-sodium and pyrazosulfuron-ethyl, and were all controlled with profoxydim and cyhalofop-butyl. The seedling and tiller bioassays are effective in the diagnosis of barnyardgrass resistance to imidazolinone herbicides, providing an on-season opportunity to identify the need to use alternative herbicides to be applied at post-emergence for the control of the resistant biotypes.

Heparan sulfate and control of cell division: adhesion and proliferation of mutant CHO-745 cells lacking xylosyl transferase

We have examined the role of cell surface glycosaminoglycans in cell division: adhesion and proliferation of Chinese hamster ovary (CHO) cells. We used both wild-type (CHO-K1) cells and a mutant (CHO-745) which is deficient in the synthesis of proteoglycans due to lack of activity of xylosyl transferase. Using different amounts of wild-type and mutant cells, little adhesion was observed in the presence of laminin and type I collagen. However, when fibronectin or vitronectin was used as substrate, there was an enhancement in the adhesion of wild-type and mutant cells. Only CHO-K1 cells showed a time-dependent adhesion on type IV collagen. These results suggest that the two cell lines present different adhesive profiles. Several lines of experimental evidence suggest that heparan sulfate proteoglycans play a role in cell adhesion as positive modulators of cell proliferation and as key participants in the process of cell division. Proliferation and cell cycle assays clearly demonstrate that a decrease in the amount of glycosaminoglycans does not inhibit the proliferation of mutant CHO-745 cells when compared to the wild type CHO-K1, in agreement with the findings that both CHO-K1 and CHO-745 cells take 8 h to enter the S phase.

The selective and non-selective cyclooxygenase inhibitors valdecoxib and piroxicam induce the same postoperative analgesia and control of trismus and swelling after lower third molar removal

We compared the clinical efficacy of orally administered valdecoxib and piroxicam for the prevention of pain, trismus and swelling after removal of horizontally and totally intrabony impacted lower third molars. Twenty-five patients were scheduled to undergo removal of symmetrically positioned lower third molars in two separate appointments. Valdecoxib (40 mg) or piroxicam (20 mg) was administered in a double-blind, randomized and crossed manner for 4 days after the surgical procedures. Objective and subjective parameters were recorded for comparison of postoperative courses. Both agents were effective for postoperative pain relief (N = 19). There was a similar mouth opening at suture removal compared with the preoperative values (86.14 ± 4.36 and 93.12 ± 3.70% of the initial measure for valdecoxib and piroxicam, respectively; ANOVA). There was no significant difference regarding the total amount of rescue medication taken by the patients treated with valdecoxib or piroxicam (173.08 ± 91.21 and 461.54 ± 199.85 mg, respectively; Wilcoxon test). There were no significant differences concerning the swelling observed on the second postoperative day compared to baseline measures (6.15 ± 1.84 and 8.46 ± 2.04 mm for valdecoxib and piroxicam, respectively; ANOVA) or on the seventh postoperative day (1.69 ± 1.61 and 2.23 ± 2.09 mm for valdecoxib and piroxicam, respectively; ANOVA). The cyclooxygenase-2 selective inhibitor valdecoxib is as effective as the non-selective cyclooxygenase inhibitor piroxicam for pain, trismus and swelling control after removal of horizontally and totally intrabony impacted lower third molars.

Production optimization and characterization of immunomodulatory peptides obtained from fermented goat placenta

The goat placental immunomodulatory peptides were produced by fermentation with Aspergillus Niger. The objective of the present study was to investigate the effects of fermentation parameters (carbon source content, pH, and time) on spleen lymphocyte proliferation for the highest immune activity of the fermentation broth using response surface methodology (RSM). According to the data analysis by the Design-Expert® software, the stimulation index value (23.51%), which is the maximum immune activity, was obtained under the following conditions: content of carbon source 1.97 g·L-1, initial pH 5.0, and 74.43 h of fermentation time. Under the optimized fermentation conditions, at a certain concentration range, the fermentation broth produced a significant effect on the proliferation of mouse spleen lymphocytes. Ultrafiltration technique was performed to separate the fermentation broth with different MW (molecular weight). It was found that peptides in the range of <10 KDa were the main bioactivity fractions for the immunomodulatory and antioxidant activities.

Production, solubility and antioxidant activity of curcumin nanosuspension

Curcumin is a powerful bioactive agent and natural antioxidant, but it is practically water-insoluble and has low bioavailability; a possible solution to this obstacle would be formulations of curcumin nanoparticles. Surfactants such as tween 80 can be used to stabilize low-solubility molecules preventing particle aggregation. The objectives of this study were the preparation of a suspension with curcumin nanoparticles in tween 80, the testing of pure curcumin solubility and of a simple mixture of curcumin with tween 80 and nanosuspension in water and ethanol as solvents, and finally the assessment of the antioxidant activity. We prepared the nanosuspension by injecting a curcumin solution in dichloromethane at low flow in water with tween 80 under heating and ultrasound. The analysis of particles size was conducted through dynamic light scattering; the non-degradation of curcumin was verified through thin-layer chromatography. The analyses of antioxidant activity were carried out according to the DPPH method. The method applied to reduce the particles size was efficient. Both the curcumin suspension and nanosuspension in tween 80 increased its solubility. Curcumin and the formulations presented antioxidant activity.

Survey, survival and control of Alternaria alternata in wheat seeds

The fungus Alternaria alternata was quantified in 75 wheat seed samples collected from three different regions of southern Brazil for Cropping and Use Value (CUV) I, II and III. Fungal presence was evaluated in two hundred disinfested seeds per sample before sowing in a potato-dextrose-agar medium + antibiotic (PDA+A). Fungus survival was evaluated every 45 days for 180 days for three seed batches from six wheat cultivars stored in propylene bags in a storehouse, with air temperature varying between 18 to 22 °C and relative air humidity around 60%. The efficacy of carboxin+thiram, difenoconazol, thiram, triadimenol, triticonazol and triticonazol + iprodione fungicides to control A. alternata was determined. A. alternata was detected in all the samples with an incidences of 39.6 %, 38.8% and 35.9% for the CUV I, CUV II and CUV III regions, respectively. The highest mean incidence of the fungus was found in the CUV I region, the coolest and most humid, and was significantly different from the other two regions. The average reduction in A. alternata viability in the wheat cultivar seeds was 49.5% during the 180 days of storage (inter-harvest period), demonstrating that infected seeds are the primary inoculum source for the fungus. The triticonazol + iprodione fungicide mixture efficiently controls A. alternata.