Abstract: A blockchain-based transaction system for a green certificate includes an audit node, a proxy node, and an off-chain node. The proxy node is used by a power producer and a purchaser; the audit node verifies qualification information of the power producer, and send a green certificate to the power producer; the off-chain node predicts a transaction price of a next transaction; when receiving sale information of the power producer and purchase information of the purchaser, the proxy node sends the sale information, a digital signature of the power producer, the purchase information, and a digital signature of the purchaser to the off-chain node; the off-chain node matches the sale information and the purchase information, and sends successfully matched transaction information to the proxy node; the proxy node sends the successfully matched transaction information to a transaction smart contract; and the transaction smart contract performs transaction processing.

Abstract: A racket-free tennis training device includes a maneuverable platform on which an elevation mechanism is mounted. A ball receiving and shooting mechanism is mounted on the elevation mechanism. The ball receiving and shooting mechanism includes a ball receiving mechanism, a ball management mechanism, and a ball shooting mechanism. The ball receiving mechanism includes a ball receptacle. The ball management mechanism includes a ball collection barrel and an advancing mechanism. The above arrangement allows for correctly receiving a tennis ball from an opponent site and then serving a ball to the opponent site to simulate an actual tennis game.

Abstract: A racket-free tennis training device includes a maneuverable platform on which an elevation mechanism is mounted. A ball receiving and shooting mechanism is mounted on the elevation mechanism. The ball receiving and shooting mechanism includes a ball receiving mechanism, a ball management mechanism, and a ball shooting mechanism. The ball receiving mechanism includes a ball receptacle. The ball management mechanism includes a ball collection barrel and an advancing mechanism. The above arrangement allows for correctly receiving a tennis ball from an opponent site and then serving a ball to the opponent site to simulate an actual tennis game.

Abstract: A method for spin-on wafer cleaning. The method comprises controlling spin speed and vertical water jet pressure. The vertical jet pressure and the spin speed are substantially maintained in inverse proportion. Wafer spin speed is between 50 to 1200 rpm. Vertical wafer jet pressure is between 0.05 to 100 KPa.

Abstract: A method for spin-on wafer cleaning. The method comprises controlling spin speed and vertical water jet pressure. The vertical jet pressure and the spin speed are substantially maintained in inverse proportion. Wafer spin speed is between 50 to 1200 rpm. Vertical wafer jet pressure is between 0.05 to 100 KPa.