Abstract: According to one embodiment of the present invention, a rotating blade, having a collision face that collides with fluid and is rotated by the flow of said fluid, has at least one flow path that has been caved in from said colliding face; said flow path is located forward with respect to said rotation direction so that it is located in the rear with respect to the inlet wherein said flow is introduced and said rotation direction, and it has an outlet from which said fluid exits. Here, the cross-sectional area of said inlet may be greater than the cross-sectional area of said outlet. In addition, the cross-sectional area of said inlet may gradually decrease toward said outlet.

Abstract: Disclosed therein is a smart caster having a function of preventing free rolling, which prevents a rotation irrelevant to a user's intention in a stopped state. The smart caster includes: a wheel part having a wheel rotatably joined to a wheel shaft and a bearing interposed between the wheel and the wheel shaft; and a braking part rotatably joined to the wheel shaft, the braking part getting in contact with a wheel inner wall in a stopped state to provide braking force to the wheel and releasing a contact state between the braking part and the wheel inner wall in a rolling state of the wheel to remove the braking force of the wheel.

Abstract: According to one embodiment of the present invention, a rotating blade, having a collision face that collides with fluid and is rotated by the flow of said fluid, has at least one flow path that has been caved in from said colliding face; said flow path is located forward with respect to said rotation direction so that it is located in the rear with respect to the inlet wherein said flow is introduced and said rotation direction, and it has an outlet from which said fluid exits. Here, the cross-sectional area of said inlet may be greater than the cross-sectional area of said outlet. In addition, the cross-sectional area of said inlet may gradually decrease toward said outlet.