The present invention provides a structure that improves sound absorption coefficient. The present invention provides a structure comprising: a foam resin layer formed of a foam material having a foaming ratio of 1.1 to 8 times; and a sound absorbing layer formed of a foam material having a foaming ratio of 10 to 30 times, the sound absorbing layer laminated on the foam resin layer.

The present invention provides a structure that improves sound absorption coefficient. The present invention provides a structure comprising: a foam resin layer formed of a foam material having a foaming ratio of 1.1 to 8 times; and a sound absorbing layer formed of a foam material having a foaming ratio of 10 to 30 times, the sound absorbing layer laminated on the foam resin layer.

Described herein are noise attenuating ducts and vehicles using these ducts for environmental control systems. A duct comprises an exoskeleton structure and a sound-absorbing structure, disposed within and conforming to the exoskeleton structure. The exoskeleton structure provides external mechanical support to the sound-absorbing structure thereby helping to maintain the tubular shape of the sound-absorbing structure. This external support does not interfere with the airflow inside the sound-absorbing structure. Furthermore, the external positioning of the exoskeleton structure allows the integration of various support mounting features for the installation of the duct in a vehicle. In some examples, the exoskeleton structure comprises a plurality of enclosed openings to reduce the weight of the exoskeleton structure and provide additional flexibility. Furthermore, additive manufacturing of the exoskeleton structure allows achieving a monolithic structure with various features and characteristics described above.

A pumping system is provided, including a rough-vacuum pump; a Roots vacuum pump including a pumping stage having a stator inside which two Roots rotors are configured to rotate synchronously in opposite directions to drive a gas to be pumped between an inlet orifice and an outlet orifice; and a pipeline connecting the outlet orifice to an intake of the rough-vacuum pump, a shortest distance between an edge of the outlet orifice and each of the Roots rotors in the pumping stage being less than 3 cm, and the outlet orifice being situated at the end of an upstream tube of the pipeline that passes into the pumping stage.

A method for producing a fibrous web includes: (a) a fibrous ply containing polylactide fibers and, as necessary, other fibers are laid on a substrate in a random fiber arrangement, (b) initially a loose, pre-compressed nonwoven is created by applying a first pressure to the fibrous ply, the tear resistance of which nonwoven permits free bridging of a span between 0.1 m and 1 m before the nonwoven tears, (c) the pre-compressed nonwoven is then passed through the calender gap, wherein a pattern consisting of point or linear pressure zones is formed in the gap, with the fibers in the pressure zones being exposed to a second pressure, which is higher than the first pressure, and to a temperature such that the fibers fuse.

The present double walled grease duct includes a tubular outer shell surrounding a tubular inner liner, wherein a spacer is positioned perpendicular to the walls of the outer shell and the inner liner. The spacer can include a plurality of vertical metal strips extend from a top edge of the spacer to the bottom edge of the spacer, wherein the top edge of the spacer contacts the walls of the outer shell and wherein the bottom edge of the spacer contacts the walls of the inner liner. The metal strips resist the different rates of thermal expansion between the outer shell and inner liner ultimately preventing the collapse of the inner liner under pressure from thermal expansion.

The present double walled grease duct includes a tubular outer shell surrounding a tubular inner liner, wherein a spacer is positioned perpendicular to the walls of the outer shell and the inner liner. The spacer can include a plurality of vertical metal strips extend from a top edge of the spacer to the bottom edge of the spacer, wherein the top edge of the spacer contacts the walls of the outer shell and wherein the bottom edge of the spacer contacts the walls of the inner liner. The metal strips resist the different rates of thermal expansion between the outer shell and inner liner ultimately preventing the collapse of the inner liner under pressure from thermal expansion.

Systems and methods according to one or more embodiments are provided for providing a durable and thermally insulated duct network. A duct network may be provided by coupling two or more foam ducts to each other. In one example, a system includes a plurality of foam ducts and a plurality of foam bellows configured to couple the foam ducts to each other. The foam bellows include one or more bellow folds to allow an expansion and contraction of the foam ducts. A plurality of structural fastening systems couple the duct network to a structure of a vessel. The structural fastening systems allow for an axial movement of the duct network as the foam ducts expand and contract. Additional systems and methods are also provided.

The present double walled grease duct includes a tubular outer shell surrounding a tubular inner liner, wherein a spacer is positioned perpendicular to the walls of the outer shell and the inner liner. The spacer can include a plurality of vertical metal strips extend from a top edge of the spacer to the bottom edge of the spacer, wherein the top edge of the spacer contacts the walls of the outer shell and wherein the bottom edge of the spacer contacts the walls of the inner liner. The metal strips resist the different rates of thermal expansion between the outer shell and inner liner ultimately preventing the collapse of the inner liner under pressure from thermal expansion.

The present double walled grease duct includes a tubular outer shell surrounding a tubular inner liner, wherein a spacer is positioned perpendicular to the walls of the outer shell and the inner liner. The spacer can include a plurality of vertical metal strips extend from a top edge of the spacer to the bottom edge of the spacer, wherein the top edge of the spacer contacts the walls of the outer shell and wherein the bottom edge of the spacer contacts the walls of the inner liner. The metal strips resist the different rates of thermal expansion between the outer shell and inner liner ultimately preventing the collapse of the inner liner under pressure from thermal expansion.