Designing optimal controllers for nonlinear frames by considering the effect of response feedback

AbstractThe effect of response feedback on designing optimal controllers for nonlinear frames has been studied. Different combinations of response feedback have been used in the performance index. The Newmark based nonlinear instantaneous optimal control algorithm has been used as the control algorithm in controlling the response of an eight-story bilinear hysteretic frame subjected to white noise excitation and real earthquakes, and controlled by either eight actuators or a single actuator. While the objective has been to minimize the maximum control force for reducing the maximum drift to below the yielding level, the distributed genetic algorithm (DGA) has been used to determine the proper set of weighting matrices in the performance index. Results show that the performance of the active control system depends on the combination of response feedback, where the velocity feedback has been more effective than acceleration and displacement. Also, although using the full feedback of response in the performance index leads to the design of optimal controllers that require the smallest control force, it is costlier, because it requires more online measurements. Finally, it has been concluded that amongst all possibilities, using only velocity feedback can provide the best results regarding the maximum required control force and online measurement, simultaneously

Implementing active force control to reduce vibration of a short length drive shaft

Vibration is a physical phenomenon involving repeated oscillatory movements or fluctuations at certain frequency and typically undesirable in many applications since it may cause undue failure or damage to the system. In this paper, the vibration of a three degree-of-freedom (DOF) model representing a short length drive shaft has been effectively and robustly suppressed through the implementation of a novel Active Force Control (AFC) used in conjunction with a classic proportional-integral-derivative (PID) controller. The shaft vibration caused by its support and constraint during its operation was simulated using MATLAB and Simulink considering a number of operating and loading conditions. The results proved that when a pure PID controller was implemented, the vibration is indeed reduced but at the expense of longer execution time and producing noticeable frequency oscillation with slight offset. On the other hand, when the AFC loop was engaged by adding it directly in series with the PID controller (PID+AFC) to produce a 2 DOF controller without any need to further tune the PID controller gains, the vibration is significantly reduced with the amplitude hovering a zero datum without any offset and yielding an extremely low frequency trending

Effect of Head Misalignment in Horizontal & Vertical Dimensions on the Magnification Rate of Digital Panoramic Radiography in Different Parts of the Jaws

ABSTRACT ARTICLE INF

Phytoplankton of Aras dam reservoir (Iran): an attempt to assess water quality

The Aras reservoir, located in the north-west of Iran, plays an important role in fisheries, drinking and agricultural water supplies and recreational activities in the region. This study was performed to characterize the seasonal fluctuations of phytoplankton communities and their relationship with environmental factors in the Aras reservoir from August 2013 to May 2014. Sampling was carried out seasonally from 5 sampling locations. In each location three samples were taken for phytoplankton identification and enumeration, chemical analysis and chlorophyll a determination. In total, 72 species belonging to 5 divisions were determined. Cyanobacteria contained the highest density (74%) during the study period with Pseudanabaena limnetica as the most abundant species. This group retained its dominance the whole year round which indicated the poor quality and high nutrient load of the Aras reservoir, mainly due to human activities. On average, Trophic State Index (TSI) showed that water in the reservoir was eu-hypereutrophic. The results indicated that phytoplankton density negatively correlated with Secchi disc depth (R^2 = -0.479), total alkalinity (R^2 = -0.564), total hardness (R^2 = -0.727) and HCO_3 concentration (R^2 = -0.589). On the other hand, there was a positive correlation between the phytoplankton density and TP (R^2 = 0.734). A comparison between the present and a previous study indicated that the cyanobacterial bloom pattern in the Aras reservoir has shifted from warm season toward an all year round cycle which in addition to basin pollution due to anthropogenic activities, can be related to global warming and climate change

Serum biochemical status and morphological changes in mice ovary associated with copper oxide nanoparticles after thiamine therapy

Introduction: Nanoparticles (NPs) can induce inflammatory responses and oxidative stress and are also cytotoxic to the genital organs of animals after exposure. The aim of this study was to assess the effects of copper oxide (CuO) and CuO NPs alone and in combination with thiamine on the ovaries of mice and on antioxidant enzymes.Methods: Sixty adult mice were randomly divided into five groups. Group A served as the control. Group B received CuO NPs and group C received CuO at 0.2 mL/kg intraperitoneally (IP). Mice in groups D and E respectively received CuO and CuO NPs along with thiamine (30 mg/L) therapy. The responses of the ovaries to the treatments were appraised by histopathology studies. The values for catalase (CAT), superoxide dismutase (SOD), and lipid peroxidation were determined after 20 days of treatment.Results: The degree of degeneration and apoptosis of the different zones within the ovaries were recorded in groups B and C. The decrease in CAT value and increase in SOD activity were significant for groups B and C at 20 days compared to the control group. The thiobarbituric acid reactive substances (TBARS) level in groups B, C and E were significantly higher at 20th day when compared with control group. The groups treated with thiamine showed histopathological and enzymatic results that were similar to those of the control group.Conclusion: These findings suggest the combination of CuO NPs and CuO with thiamine improves serum enzyme activity and has positive effects on the ovary

Oil characteristics and fatty acid profile of seeds from three varieties of date palm (Phoenix dactylifera) cultivars in Bushehr-Iran

Studies were conducted on properties of seed oils extracted from three date palm (Phoenix dactylifera) varieties Shahabi, Shekar and Kabkab, grown in Bushehr-Iran. The primary objective of this study was to extract seed-oil from the three native date varieties and then analyzed their fatty acids (FAs). Also the chemical parameters of PV, AV, p-anisidin, and Totox values of oils, as indicators of the quality and safety, and oxidative status of edible oils, as well as refractive index as an objective method for evaluation of rancidity were also evaluated. Date seeds are approximately 10% of the fruits weight. Seeds contained about 8.5% fat that can serve as a useful source of fatty acids to replace other vegetable oils. The following mean of values from the three varieties were obtained from samples: peroxide value (1.05), acid value (1.4), p-anisidine value (2.54), Totox (4.64) and refractive index (1.46). Also, flame ionization based detection gas chromatography (GC-FID) revealed that oleic acid was the primary fatty acid in all varieties. It was followed by lauric, myristic, palmitic, linoleic and stearic acids and trace amounts of the other fatty acids like undecylic, capric, nonanoic (pelargonic) and caprylic acids. Depending on the regional industry, these data suggest that the potential applications of date seed oil for humans and animals are feeding, cosmetic formulations such as in body creams, shaving soap and shampoos, and pharmaceutical products.Keywords: Seed oil (Phoenix dactylifera), fatty acid, gas chromatograph

Assessment of pH-responsive nanoparticles performance on laboratory column flotation cell applying a real ore feed

Nanoparticles (NPs) can promote the column flotation process in mining industry. Nanoparticles’ effects on column flotation process (copper recovery, grade and flotation rate constant) are assessed in Sarcheshmeh Copper Complex, Iran, through response surface methodology (RSM) optimization technique. The γ-Al2O3, α-Fe2O3, SiO2, and TiO2 nanoparticles are selected for these experiments. A flotation rate constant is chosen as a response to assess the effect of nanoparticles on flotation in its kinetic sense. The process pH and nanoparticle dosage are selected as the influential parameters. Results obtained from RSM indicated that the maximum percentage of Cu recovery and grade is obtained at pH of 12 and nanoparticle dosage of 6 kg/t, through α-Fe2O3 and γ-Al2O3 nanoparticles, respectively. Applying nanoparticles in particular γ-Al2O3 and α-Fe2O3 increases the Cu recovery by 8–10% together with the grade by 3–6% in a significant manner. It is revealed that nanoparticles could effectively be applied in enhancing the flotation performance