A system for human interaction with virtual objects comprises: a touch sensitive surface, configured to detect a position of a contact made on the touch sensitive surface; a reference layer rigidly attached to the touch sensitive surface and comprising one or more patterns; a display device, configured to display a virtual object that is registered in a reference coordinate fixed with respect to the touch sensitive surface; one or more image sensors rigidly attached to the display device, configured to capture an image of at least a portion of the one or more patterns; and at least one processor, configured to determine a position and an orientation of the display device with respect to the touch sensitive surface based on the captured image, and identify an interaction with the virtual object based on the detected position of the contact made on the touch sensitive surface.

A system for human interaction with virtual objects comprises: a touch sensitive surface, configured to detect a position of a contact made on the touch sensitive surface; a reference layer rigidly attached to the touch sensitive surface and comprising one or more patterns; a display device, configured to display a virtual object that is registered in a reference coordinate fixed with respect to the touch sensitive surface; one or more image sensors rigidly attached to the display device, configured to capture an image of at least a portion of the one or more patterns; and at least one processor, configured to determine a position and an orientation of the display device with respect to the touch sensitive surface based on the captured image, and identify an interaction with the virtual object based on the detected position of the contact made on the touch sensitive surface.

Firearm discharge location systems and methods are described. According to one aspect, a firearm discharge location system includes a plurality of microphones spaced from one another, timing circuitry configured to generate a plurality of asynchronous timing references, wherein data capture operations with respect to the microphones of a first pair are synchronized with one another using a first of the timing references and data capture operations with respect to the microphones of a second pair are synchronized with one another using a second of the timing references, and processing circuitry configured to use outputs of the first and second pairs of the microphones to identify a location of a firearm discharge.

Firearm discharge location systems and methods are described. According to one aspect, a firearm discharge location system includes a plurality of microphones spaced from one another, timing circuitry configured to generate a plurality of asynchronous timing references, wherein data capture operations with respect to the microphones of a first pair are synchronized with one another using a first of the timing references and data capture operations with respect to the microphones of a second pair are synchronized with one another using a second of the timing references, and processing circuitry configured to use outputs of the first and second pairs of the microphones to identify a location of a firearm discharge.

Systems and methods for controlling display of content using objects are disclosed. Objects may be placed on a surface and one or more computing devices may be configured to identify the objects, determine the shape of the objects, and/or determine the locations of the objects with respect to the surface. Content displayed on the surface may be updated based at least in part on interaction of the object with the surface, such as changing locations of the objects, object proximities, object flipping, and/or object stacking, for example.

Provided are an apparatus, a method, and a system for determining speeding of a vessel. According to an embodiment of the present disclosure, the method may include: receiving, by sound signal receiving apparatuses installed at at least two points, a sound signal of a first vessel operating at a preset section; extracting operation vibration information of the first vessel from each sound signal received by the sound signal receiving apparatuses installed at the at least two points; measuring an operation speed of the first vessel from each of the received sound signals; and constructing a database including operation speed range information matching the operation vibration information of the first vessel.

Provided are an apparatus, a method, and a system for determining speeding of a vessel. According to an embodiment of the present disclosure, the method may include: receiving, by sound signal receiving apparatuses installed at at least two points, a sound signal of a first vessel operating at a preset section; extracting operation vibration information of the first vessel from each sound signal received by the sound signal receiving apparatuses installed at the at least two points; measuring an operation speed of the first vessel from each of the received sound signals; and constructing a database including operation speed range information matching the operation vibration information of the first vessel.

A method for determining a change in a distance, a location prompting method and an apparatus and a system thereof are provided. The method includes: sending, by a receiving terminal, a paring request to a server for the server to forward the paring request to a transmitting terminal, and to allocate a frequency band for the receiving terminal and the transmitting terminal after the transmitting terminal accepts the paring request; acquiring, by the receiving terminal, an acoustic wave signal of a frequency sent by the transmitting terminal, wherein the frequency is determined by the transmitting terminal based on the allocated frequency band; determining, by the receiving terminal, a change in the acquired acoustic wave signal; and determining, by the receiving terminal, a change in a distance between the transmitting terminal and the receiving terminal according to the change in the acquired acoustic wave signal.

A method for determining a change in a distance, a location prompting method and an apparatus and a system thereof are provided. The method includes: sending, by a receiving terminal, a paring request to a server for the server to forward the paring request to a transmitting terminal, and to allocate a frequency band for the receiving terminal and the transmitting terminal after the transmitting terminal accepts the paring request; acquiring, by the receiving terminal, an acoustic wave signal of a frequency sent by the transmitting terminal, wherein the frequency is determined by the transmitting terminal based on the allocated frequency band; determining, by the receiving terminal, a change in the acquired acoustic wave signal; and determining, by the receiving terminal, a change in a distance between the transmitting terminal and the receiving terminal according to the change in the acquired acoustic wave signal.

Sensor receiver nulls and null steering. One example embodiment is method in which a direction from a sensor position to a noise source is determined. A coordinate rotation is applied to a first set of signal values, wherein each signal value of the first set of signal values is based on an output of a corresponding component of a three-component particle motion sensor at the sensor position. The applying generates a rotated set of signal values. The coordinate rotation comprises a coordinate rotation transforming a first set of coordinate axes to a second set of coordinate axes, wherein the first set of coordinate axes has each coordinate axis aligned with a corresponding component of the three-component particle motion sensor at the sensor position, and the second set of coordinate axes comprises a first axis pointed in a direction opposite the direction from the sensor position to the noise source.