Abstract: An acoustic core includes an array of resonant cells. The array may include a plurality of coupled resonant cells respectively defining an antecedent resonant space and a subsequent resonant space, with at least one cell wall having one or more wall-apertures defining a pathway between the antecedent resonant space and the subsequent resonant space. The array may include a plurality of high-frequency resonant cells respectively defining a high-frequency resonant space and being matched with respective ones of the plurality of coupled resonant cells. A cross-sectional dimension of the one or more wall-apertures defining the pathway between the antecedent resonant space and the subsequent resonant space may be less than a cross-sectional dimension of the antecedent resonant space and/or a cross-sectional dimension of the subsequent resonant space.

Abstract: Systems and methods for controlling an unducted turbofan engine to limit noise. The unducted turbofan engine may include an unducted fan drivingly coupled with a low-pressure turbine and a plurality of unducted outlet guide vanes. The unducted fan may include a plurality of fan blades and a pitch angle of the fan blades may be variable. A pitch angle of the unducted outlet guide vanes may be variable. A controller is configured to control the engine to limit noise based on a noise sensitive condition.

Abstract: An acoustic core may include an array of resonant cells configured as a plurality of resonant cell groups. The resonant cell groups may include a plurality of resonant cells configured as a partitioned resonant cell that include a converging resonant cell and a diverging resonant cell. The converging resonant cell and the diverging resonant cell may be defined by a plurality of cell walls integrally formed with one another and a partition integrally formed with the plurality of cell walls. The partition may at least partially delimit the converging resonant cell from the diverging resonant cell. The converging resonant cell may define an upper resonant space delimited by the partition and a top face of the array of resonant cells. The diverging resonant cell may define a lower resonant space delimited by the partition and a bottom face of the array of resonant cells.

Abstract: An aircraft defines a longitudinal direction and includes a fuselage extending between a forward end and an aft end along the longitudinal direction of the aircraft. An aft engine is mounted to the aft end of the fuselage. The aft engine further includes a nacelle including a forward section. An airflow duct extends at least partially through the nacelle of the aft engine and defines an outlet on the forward section of the nacelle for providing an airflow to the forward section of the nacelle.

Abstract: An acoustic core includes an array of resonant cells. The array may include a plurality of coupled resonant cells respectively defining an antecedent resonant space and a subsequent resonant space, with at least one cell wall having one or more wall-apertures defining a pathway between the antecedent resonant space and the subsequent resonant space. The array may include a plurality of high-frequency resonant cells respectively defining a high-frequency resonant space and being matched with respective ones of the plurality of coupled resonant cells. A cross-sectional dimension of the one or more wall-apertures defining the pathway between the antecedent resonant space and the subsequent resonant space may be less than a cross-sectional dimension of the antecedent resonant space and/or a cross-sectional dimension of the subsequent resonant space.

Abstract: In some embodiments, an airfoil comprises a proximal end; a distal end opposite said proximal end; a distal portion extending adjacent said distal end; an edge extending between said proximal end and said distal end; and a surface extending between said proximal end and said distal end, said edge and said surface defining a sweep and a cahedral through said distal portion, wherein the distal portion extends over an acoustically active portion of the airfoil.

Abstract: An aircraft defines a longitudinal direction, a vertical direction, and a transverse direction. The aircraft includes a fuselage; and a wing extending from the fuselage generally along the transverse direction and defining an outer end along the transverse direction. The wing includes a wing tip assembly at the outer end of the wing, the wing tip assembly defining an axis substantially parallel to the longitudinal direction of the aircraft and a circumferential direction extending about the axis, the wing tip assembly including at least three stationary guide vanes spaced along the circumferential direction from one another.

Abstract: An aircraft assembly includes an engine, and intake, and a propeller assembly. The engine is mounted to at least one of a wing or fuselage of an aircraft. The intake is configured to provide air to the engine. The intake includes a body having an engine inlet through which air enters the intake. The propeller assembly includes propeller blades coupled to and driven by the engine. The propeller assembly is spaced an axial distance from the inlet opening of the intake wherein air passing by the propeller blades enters the intake. The propeller assembly has a propeller configuration that is at least one of sized or shaped to optimize performance of the propeller assembly based on an interaction between the propeller assembly and the intake.

Abstract: An aircraft defines a longitudinal direction, a vertical direction, and a transverse direction. The aircraft includes a fuselage; and a wing extending from the fuselage generally along the transverse direction and defining an outer end along the transverse direction. The wing includes a wing tip assembly at the outer end of the wing, the wing tip assembly defining an axis substantially parallel to the longitudinal direction of the aircraft and a circumferential direction extending about the axis, the wing tip assembly including at least three stationary guide vanes spaced along the circumferential direction from one another.

Abstract: An aircraft assembly includes an engine, and intake, and a propeller assembly. The engine is mounted to at least one of a wing or fuselage of an aircraft. The intake is configured to provide air to the engine. The intake includes a body having an engine inlet through which air enters the intake. The propeller assembly includes propeller blades coupled to and driven by the engine. The propeller assembly is spaced an axial distance from the inlet opening of the intake wherein air passing by the propeller blades enters the intake. The propeller assembly has a propeller configuration that is at least one of sized or shaped to optimize performance of the propeller assembly based on an interaction between the propeller assembly and the intake.

Abstract: An aircraft defines a longitudinal direction and includes a fuselage extending between a forward end and an aft end along the longitudinal direction of the aircraft. An aft engine is mounted to the aft end of the fuselage. The aft engine further includes a nacelle including a forward section. An airflow duct extends at least partially through the nacelle of the aft engine and defines an outlet on the forward section of the nacelle for providing an airflow to the forward section of the nacelle.

Abstract: Electronic documents may be large and have numerous pages, sections and areas of information that are useful to some individuals and not others. It is common for large documents to include some information that is intended for only certain recipients and other information that is intended for other recipients. One example may provide receiving a document that has a number of pages, identifying an extraction attribute, querying the document for the extraction attribute, applying a coordinate to information associated with the extraction attribute, extracting information based on the extraction attribute and a predefined area associated with the at least one coordinate, and creating a new document including the information extracted.

Abstract: An apparatus configured to reduce acoustic interactions between a propeller and a surface of an aircraft positioned downstream of the propeller includes a surface modification element of the surface of the aircraft. The surface modification element defines a modified contour of the surface. The modified contour is configured to decorrelate a phase distribution of a plurality of sound sources within a source field positioned on at least a portion of the surface.

Abstract: Noise attenuation structures, such as acoustic liners for gas turbine engines, are provided. For example, an acoustic liner comprises a face sheet, a backing sheet spaced apart from the face sheet, and a plurality of cavities defined between the face and backing sheets. The cavities are defined by cavity walls. A plurality of backing sheet walls extends from the backing sheet toward the face sheet. The backing sheet walls extend adjacent the cavity walls, and the backing sheet is movable with respect to the face sheet such that the cavities have a variable depth. Other embodiments of noise attenuation structures also are provided.

Abstract: An integer division circuit includes a first bit-shifting circuit configured to shift the bits of a dividend to produce a normalized dividend. The circuit also includes a second bit-shifting circuit configured to shift the bits of a divisor to produce a normalized divisor. A divider tree circuit is configured to divide the normalized dividend by the normalized divisor to produce a normalized quotient. The circuit further includes a third bit-shifting circuit configured to shift the bits of the normalized quotient to produce a quotient.

Abstract: An airfoil assembly including a composite body having a mounting edge and a trailing edge which is secured to a leading edge element defining a 3-D leading edge geometry with both chord and camber variation.

Abstract: An aircraft defines a longitudinal direction, a vertical direction, and a transverse direction. The aircraft includes a fuselage; and a wing extending from the fuselage generally along the transverse direction and defining an outer end along the transverse direction. The wing includes a wing tip assembly at the outer end of the wing, the wing tip assembly defining an axis substantially parallel to the longitudinal direction of the aircraft and a circumferential direction extending about the axis, the wing tip assembly including at least three stationary guide vanes spaced along the circumferential direction from one another.

Abstract: In some embodiments, an airfoil comprises a proximal end; a distal end opposite said proximal end; a distal portion extending adjacent said distal end; an edge extending between said proximal end and said distal end; and a surface extending between said proximal end and said distal end, said edge and said surface defining a sweep and a cahedral through said distal portion, wherein the distal portion extends over an acoustically active portion of the airfoil.

Abstract: In some embodiments, an airfoil comprises a proximal end; a distal end opposite said proximal end; a distal portion extending adjacent said distal end; an edge extending between said proximal end and said distal end; and a surface extending between said proximal end and said distal end, said edge and said surface defining a sweep and a cahedral through said distal portion, wherein the distal portion extends over an acoustically active portion of the airfoil.

Abstract: Noise attenuation structures, such as acoustic liners for gas turbine engines, are provided. For example, an acoustic liner comprises a face sheet, a backing sheet spaced apart from the face sheet, and a plurality of cavities defined between the face and backing sheets. The cavities are defined by cavity walls. A plurality of backing sheet walls extends from the backing sheet toward the face sheet. The backing sheet walls extend adjacent the cavity walls, and the backing sheet is movable with respect to the face sheet such that the cavities have a variable depth. Other embodiments of noise attenuation structures also are provided.