Abstract: An online concierge system determines a quantity of a resource available in a timeslot to fulfill orders during the timeslot. The orders include immediate orders placed during the timeslot and scheduled orders that are scheduled for fulfillment during the timeslot. The online concierge system applies the quantity of the resource to a machine learning model to produce a predicted relationship between a value of a fulfillment metric and an allocation of the quantity of the resource reserved for immediate orders. The online concierge system determines, based on the predicted relationship, an expected optimal allocation of the quantity of the resource that maximizes the fulfillment metric. The online concierge system reserves the expected optimal allocation of the quantity of the resource for immediate orders.

Abstract: Disclosed is a device for measuring speed of a tennis ball, which includes: a housing, a power supply, a main control device, a sensor device, a transmission device, a clamping device and a limiting device. The clamping device is clamped at the serve opening of a tennis ball machine, which can detect the serve speed of a tennis ball accurately with simple operation. The transmission device is engaged with the second sensor device, and the housing is slidably connected with the second sensor device. The emitting ends of the second sensor device and the first sensor device are positioned in the same vertical plane. The limiting device is connected with the second sensor device to limit excessive operation of the transmission device.

Abstract: Disclosed is an unloading apparatus, which includes: an insert plate forming a loading space, a bottom plate configured for lifting up and down relative to the insert plate, a lifting device, an unloading plate and a frame plate. The lifting device is connected to the bottom plate, when the lifting device is in an extended state, the lifting device drives the bottom plate to rise as a whole to achieve the lifting function; an angle is formed between the bottom plate and the frame plate.

Abstract: Disclosed is a device for measuring speed of a tennis ball, which includes: a housing, a power supply, a main control device, a sensor device, a transmission device, a clamping device and a limiting device. The clamping device is clamped at the serve opening of a tennis ball machine, which can detect the serve speed of a tennis ball accurately with simple operation. The transmission device is engaged with the second sensor device, and the housing is slidably connected with the second sensor device. The emitting ends of the second sensor device and the first sensor device are positioned in the same vertical plane. The limiting device is connected with the second sensor device to limit excessive operation of the transmission device.