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Energy carriers including elasticity play central roles in development of societies. In this paper, we estimate residential electricity demand among the selected counties of Tehran province, i.e., Tehran, Varamin, Firouzkooh, Damavand, using dynamic panel data model over the period 2000- 2014. The most effective variables which explain demand for residential electricity are per capita income, natural gas real price, weather coldness and hotness index and electricity real price. The estimation results of the short run model reveal that demand for electricity decreases by 0.42 percent for one percent increase in electricity real price. The price of substitute energy carrier such as natural gas is of low effect on electricity demand. There is a positive and significant relationship between electricity demand and household's income. The last period electricity demand is the key effective factor in explaining the current electricity demand with a coefficient of 0.65. The estimation results of the long run model show that one percent change in electricity price changes the demand for electricity by -1.2 percent. In addition, demand for electricity increases by 0.1 percent with one percent increase in income.
 

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In this article, the effect of optimal selection of vibration and cutting parameters on cutting forces in the machining process with ultrasonic vibration assistance has been investigated and the results have been compared in two modes of conventional machining and of ultrasonic vibration assisted machining. In the investigation of the effect of ultrasonic vibration assistance on the machining process, analyzes have been carried out in different cutting speeds, and the effect of changing the cutting speed in relation to the tool's oscillation speed has been investigated. Finite element modeling and simulation has been done with DEFORM finite element software. The results show that the application of ultrasonic vibration in the machining process leads to the reduction of tangential and axial cutting and the reduction of heat resulting from the cutting process. By examining the results, it was found that in the machining process with ultrasonic vibration assistance, when the cutting speed is at least 30% lower than the vibration speed of the tool tip, the process has a favorable efficiency, and the favorable effects of applying ultrasonic vibration on the process include reducing shear forces, reducing the heat generated From cutting, reducing the friction coefficient between the tool and the workpiece, helping to improve the chip flow, etc.