Abstract: Disclosed is a method of adaptively adjusting lift and drag on an airfoil-shaped sail. The method includes: (1) mounting at least one airfoil-shaped sail body having an airfoil-shaped cross section; (2) defining a Y-shaped air jet channel in the airfoil-shaped sail body; (3) arranging a flow regulating gate in the Y-shaped air jet channel; (4) adjusting the flow regulating gate to automatically adjust the gate opening extent and the cross section opening or closing extent in response to an oncoming flow with a varying direction and speed, to regulate the airflow within the air jet channel and accordingly change the angle of attack, so that the lift and drag on the sail body can be automatically adjusted as the wind speed changes. Further disclosed are an airfoil-shaped sail implementing the above method as well as a vertical-axis wind turbine employing the airfoil-shaped sail.

Abstract: Disclosed are a precision casting wax based on graphite oxide modified rosin and its production method. The precision casting wax is composed of 20%˜30% of modified rosin, 50%˜65% of paraffin, 5%˜10% of an adhesion agent, 5%˜40% of PE wax, and 0%˜3% of montan wax (in mass percentage), and the total content adds up to 100%. The modified rosin is composed of first-grade rosin, graphite oxide, zinc oxide and pentaerythritol. The graphite oxide, zinc oxide, and pentaerythritol have a mass equal to 5%˜8%, 0.3%˜0.5%, and 5%˜8% of the mass of the first-grade rosin respectively. The modified rosin has a softening point of 98° C.˜103° C. and an acidity value of 15 KOH/g˜25 KOH/g. The present invention has the features of small needle penetration, small linear shrinkage rate, large bending strength, and small ash content, and thus can satisfy the requirements of high size precision and high surface quality of the precision casting.