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Three dose-response experiments were conducted separately to study the effect of several adjuvants on nicosulfuron efficacy for controlling Amaranthus retroflexus L., Chenopodium album L. and Echinochloa crus-galli L. The experiments were arranged in a completely randomized block design with a factorial arrangement of the treatments and four replications. The treatments consisted of six doses of nicosulfuron at 0 (control), 5, 10, 20, 40, and 80 g a.i.ha^-1 of the recommended dose with and without the adjuvants of cotton oil, rocket oil, soybean oil, maize oil, Adigor®, Volck^®, HydroMax^™ at 0.5% (v/v), Cytogate, Trend^® 90, and D-octil^® at 0.2 % (V/V). The efficacy of nicosulfuron in control of A. retroflexus, C. album, and E. crus-galli increased significantly when the adjuvants were used. HydroMax^™ and Trend^® 90 were the best adjuvants, considering enhanced nicosulfuron efficacy for controlling C. album, E. crus-galli, and A. retroflexus. In the presence of HydroMax^™ nicosulfuron efficacy was raised by a factor of 4.02, 3.45, and 1.65-fold for controlling A. retroflexus, E. crus-galli, and C. album, respectively. In general, the efficacy of nicosulfuron to control A. retroflexus and E. crus-galli was higher than C. album.






 

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The purpose of this study is to investigate the economic effects of world food and oil price shocks on macroeconomic variables (industrial output growth, inflation, stock price indices, lending rate, and real exchange rate) in Iran. For this purpose, the Structural Vector Auto Regressive (SVAR) method is used to examine the autonomous and simultaneous effects of food and oil prices within 3 models. This study uses monthly data from 21th March 2001 to 20th March 2011. The results show that oil price shock has small effect on industrial output growth. The biggest effect of the oil and food price shocks is observed on the exchange rate. About 5 percent of the variation in oil and food prices is explained by inflation shock. Furthermore, results from the simultaneous study of shocks to the oil price and global food price indicate that oil shocks significantly affect global food prices.  

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Nonlinear factors such as air compressibility, leakage and friction make the control of pneumatic systems complex. Model-based robust control strategies are appropriate candidates for pneumatic systems, however in such controllers the measurement of state variables of the system are needed. In a pneumatic system the state variables are position and velocity of the actuator, and pressure in both sides of the cylinder. Pressure measurement is usually obtained by means of costly and low response sensors. A better way to deal with the measurement problem is to use observers to reconstruct the missing velocity and pressure signals. However the problem in a pneumatic system is that the system is not observable and pressure signals could not be observed by means of position signals only. To deal with this problem, in this paper, the pneumatic actuator is modeled as two separate chambers and the resulting subsystems are observable independently. High gain observers are designed for mentioned subsystems and for each chamber the pressure of the other chamber is considered as a disturbance. The input signal for each observer is the actuator position signal only. Finally a sliding-mode control strategy is designed for position tracking and experimental results verify that both controller and observer objectives are satisfied.

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The electrohydraulic valves are commonly used in the engineering applications. These valves, as the medium elements, prepare the hydraulic systems for the electrical control applications. For the precise performance of these valves, disturbances in the valve elements dynamics will disturb the control process of the system. The electrohydraulic servo valves are greatly affected by the external acceleration, for instance in the aerospace applications. In a two stage flapper- nozzle electrohydraulic valve, the external acceleration changes the pressure of the fluid leaving the nozzles and it affects the flapper and spool of the valve like a virtual force. Thus, when the applied current is zero, the acceleration diverts the spool of the valve from the equilibrium point, and unwanted performance in the valve occurs. In this study the pilot pressures of the spool is modeled in unsteady state condition. The effects of the acceleration on the flapper and the spool of the two stage electrohydraulic valve are investigated. At the end, the obtained model is verified by use of the experimental data.

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Stability and transparency are both very important conditions in bilateral teleoperation systems. For the design of such systems, different methods have been suggested. Among the approaches presented, passivity framework is widely utilized in which human and environment is considered passive. The operator does not make the closed-loop system unstable. In addition, it is passive against an external input. Thus the adoption of this assumption is correct for the human. Nevertheless it is a conservative presumption for the environment and according to some modern applications of teleoperation systems such as cardiac surgery, it is absolutely not acceptable. In this paper a novel control structure for nonlinear bilateral teleoperation systems interacting with active environments is addressed. In this approach, first a criterion for measuring activity of the environment is presented. Then by developing a PD controller, an algorithm that guarantees master-slave position coordination and static force reflection is introduced. The overall stability of closed loop system is proved using passivity concept and Lyapunov-Krasovskii technique. Simulations are performed to verify the performance of the proposed bilateral teleoperation systems in contact with passive and non-passive environments. Experimental results were carried out to validate the theoretical consequences.