Abstract: In the present disclosure, the multi-level AC/DC conversion circuit and the multi-level DC/DC conversion circuit calculate the duty ratio of synchronous rectification switch according to the input voltage, the output voltage, the interval time of turning on the main switch, the switching cycle and the duty ratio of main switch, thereby eliminating the need for additional zero-current detecting function or zero-crossing detection circuit in conventional AC/DC conversion circuits. Accordingly, for the multi-level AC/DC conversion circuit and the multi-level DC/DC conversion circuit of the present disclosure, the cost is reduced, and the reliability is enhanced.

Abstract: A multi-level conversion circuit and a control method for flying capacitor voltage thereof are provided. In the multi-level conversion circuit, each flying capacitor is connected between a common connection node of the lower switches connected therewith and a common connection node of the upper switches connected therewith. When the conversion circuit works in a DCM, the control method includes steps of: (a) determining the main switch and synchronous rectification switch of the lower and upper switches; (b) acquiring an adjustment value corresponding to each flying capacitor; and (c) adjusting a duty ratio of the main switch according to the adjustment value corresponding to the flying capacitor connected therewith, wherein the adjustment trend of the duty ratio under D<(N?2)/(N?1) is opposite to that under (N?2)/(N?1)<D?1, and D is the duty ratio before the adjustment.

Abstract: A multi-level conversion circuit and a control method for flying capacitor voltage thereof are provided. In the multi-level conversion circuit, each flying capacitor is connected between a common connection node of the lower switches connected therewith and a common connection node of the upper switches connected therewith. The control method includes steps of: (a) determining the main switch and synchronous rectification switch of the lower and upper switches; (b) acquiring an adjustment value corresponding to each flying capacitor; (c) adjusting a duty ratio of the main switch according to the adjustment value corresponding to the flying capacitor connected therewith; and (d) when the multi-level conversion circuit working in a CCM, increasing a phase-shift angle between the main switches by an angle to make a peak value or a valley value of an inductor current remain unchanged before and after adjusting the duty ratio.

Abstract: Provided are a tour guiding method and apparatus, an electronic device and a storage medium. The method includes receiving a video stream collected by a user in a current location area of a target scenic spot and sent by an application device; determining, based on the collected video stream and prestored three-dimensional point cloud data of the target scenic spot, an augmented-reality-based content resource package corresponding to the current location area, where the augmented-reality-based content resource package includes at least six-degrees-of-freedom attitude data of the application device; and sending the augmented-reality-based content resource package corresponding to the current location area to the application device to enable the application device to provide the augmented-reality-based content resource package corresponding to the front location area for the user.

Abstract: Provided are a tour guiding method and apparatus, an electronic device and a storage medium. The method includes receiving a video stream collected by a user in a current location area of a target scenic spot and sent by an application device; determining, based on the collected video stream and prestored three-dimensional point cloud data of the target scenic spot, an augmented-reality-based content resource package corresponding to the current location area, where the augmented-reality-based content resource package includes at least six-degrees-of-freedom attitude data of the application device; and sending the augmented-reality-based content resource package corresponding to the current location area to the application device to enable the application device to provide the augmented-reality-based content resource package corresponding to the front location area for the user.

Abstract: The invention relates to elastomeric compositions containing filler particles that are predominantly two-dimensional in shape. The elastomeric compositions exhibit significantly improved thermal, chemical, and mechanical properties as compared with elastomers containing conventional fillers such as natural clay, carbon black, and carbon fiber. In addition, the elastomeric compositions of the invention exhibit improved resistance to solvent-induced swelling and to unwanted permeation of gases such as hydrogen sulfide. The invention also provides a method of forming such elastomeric compositions and methods of using such elastomeric compositions to prepare elastomeric articles with improved resistance to thermal, chemical, and mechanical stresses.

Abstract: The present disclosure discloses a method and apparatus for constructing a three-dimensional map. A specific embodiment of the method includes: acquiring multiple frames of a monocular image containing a target object collected by a monocular camera, and constructing a three-dimensional map containing the target object and other objects in the monocular image based on the monocular image; determining an absolute scale of the target object, and determining a ratio of a relative scale corresponding to the target object to the absolute scale; and adjusting a scale of each object in the three-dimensional map to obtain a three-dimensional map meeting a preset condition based on the ratio. The method and apparatus provided by the present disclosure achieves the construction of a world coordinate system with absolute scales in a three-dimensional map constructed based on a monocular image.

Abstract: A packer unit to be used in an annular blowout preventer. The packer unit includes an elastomer body including a compound of a nitrile rubber base polymer having a polymer chain, and a quantity of fluorine atoms attached to the polymer chain. The compound includes between 50 and 60% of the nitrile elastomer, between 25 to 35% carbon black, and the rest includes other materials. The quantity of fluorine atoms comprises short-chain fluorocarbon chain molecules The quantity of fluorine atoms displaces at least an equal quantity of hydrogen atoms from the polymer chain when the elastomer body is fluorinated.

Abstract: A method and apparatus for generating image information. A specific embodiment of the method includes: acquiring a rotation angle and a scaling of a target image relative to a reference image, and acquiring an intrinsic parameter of a video camera collecting the reference image; generating a projective transformation matrix based on the rotation angle, the scaling and the intrinsic parameter; generating a coordinate offset of the each neighborhood pixel of the feature point in the reference image; generating, based on a coordinate of the feature point in the reference image, the coordinate offset of the each neighborhood pixel of the feature point in the reference image and the projective transformation matrix, coordinates of the each neighborhood pixel of the feature point in the reference image; and generating a feature point descriptor of the feature point.

Abstract: The present disclosure discloses a method and apparatus for constructing a three-dimensional map. A specific embodiment of the method includes: acquiring multiple frames of a monocular image containing a target object collected by a monocular camera, and constructing a three-dimensional map containing the target object and other objects in the monocular image based on the monocular image; determining an absolute scale of the target object, and determining a ratio of a relative scale corresponding to the target object to the absolute scale; and adjusting a scale of each object in the three-dimensional map to obtain a three-dimensional map meeting a preset condition based on the ratio. The method and apparatus provided by the present disclosure achieves the construction of a world coordinate system with absolute scales in a three-dimensional map constructed based on a monocular image.

Abstract: A method and apparatus for generating image information. A specific embodiment of the method includes: acquiring a rotation angle and a scaling of a target image relative to a reference image, and acquiring an intrinsic parameter of a video camera collecting the reference image; generating a projective transformation matrix based on the rotation angle, the scaling and the intrinsic parameter; generating a coordinate offset of the each neighborhood pixel of the feature point in the reference image; generating, based on a coordinate of the feature point in the reference image, the coordinate offset of the each neighborhood pixel of the feature point in the reference image and the projective transformation matrix, coordinates of the each neighborhood pixel of the feature point in the reference image; and generating a feature point descriptor of the feature point.

Abstract: The invention relates to elastomeric compositions containing filler particles that are predominantly two-dimensional in shape. The elastomeric compositions exhibit significantly improved thermal, chemical, and mechanical properties as compared with elastomers containing conventional fillers such as natural clay, carbon black, and carbon fiber. In addition, the elastomeric compositions of the invention exhibit improved resistance to solvent-induced swelling and to unwanted permeation of gases such as hydrogen sulfide. The invention also provides a method of forming such elastomeric compositions and methods of using such elastomeric compositions to prepare elastomeric articles with improved resistance to thermal, chemical, and mechanical stresses.

Abstract: A packer unit to be used in an annular blowout preventer. The packer unit includes an elastomer body including a compound of a nitrile rubber base polymer having a polymer chain, and a quantity of fluorine atoms attached to the polymer chain. The compound includes between 50 and 60% of the nitrile elastomer, between 25 to 35% carbon black, and the rest includes other materials. The quantity of fluorine atoms comprises short-chain fluorocarbon chain molecules The quantity of fluorine atoms displaces at least an equal quantity of hydrogen atoms from the polymer chain when the elastomer body is fluorinated.