Abstract: A glass including silica and titania is disclosed. An average hydroxyl concentration of a plurality segments of the glass is in a range from about 20 ppm to about 450 ppm, an average titania concentration of the plurality of segments is in a range from about 6 wt. % to about 12 wt. %, and each segment of the plurality of segments has a length of about 12.7 mm, a width of about 12.7 mm, and a height of about 7.62 mm. The hydroxyl concentration of each segment is measured using a Fourier transform infrared spectroscopy in transmission, the refractive index is measured using an optical interferometer with a 633 nm operating wavelength and a resolution of 270 microns×270 microns pixel size, and the average titania concentration is determined based upon the measured refractive index.

Abstract: A glass comprising titania and silica is disclosed. A plot of average hydroxyl concentration of each segment of a plurality of segments vs. distance along the glass is provided by: y=Ax2+Bx+C, wherein A (in ppm/mm2) is in a range from about 0.0 to about ?0.1, B (in ppm/mm) is in a range from about ?10 to about 10, C (in ppm) is about 450 or less, y is the average hydroxyl concentration (in ppm), and x is distance (in mm) such that the hydroxyl concentration of each segment is measured using a Fourier transform infrared spectroscopy in transmission and the plot extends a distance of about 50 mm or more along the glass.

Abstract: Arrangements for communication and/or noise attenuation within an aircraft, and aircraft and methods for making aircraft including such arrangements are provided. In one example, an arrangement includes an array of first microphones cooperatively configured to be directed towards a first aircraft operator when disposed in a first cockpit seat to receive a first communication input from the first aircraft operator. An array of first speakers is cooperatively configured to be directed towards the first aircraft operator when disposed in the first cockpit seat to provide a first communication output to the first aircraft operator.

Abstract: Arrangements for communication and/or noise attenuation within an aircraft, and aircraft and methods for making aircraft including such arrangements are provided. In one example, an arrangement includes an array of first microphones cooperatively configured to be directed towards a first aircraft operator when disposed in a first cockpit seat to receive a first communication input from the first aircraft operator. An array of first speakers is cooperatively configured to be directed towards the first aircraft operator when disposed in the first cockpit seat to provide a first communication output to the first aircraft operator.

Abstract: Embodiments of thermal-acoustic sections for an aircraft for reducing noise along an acoustic path produced from an acoustic source are provided herein. The thermal-acoustic section comprises a first porous layer having a first characteristic acoustic impedance. A second porous layer is disposed adjacent to the first porous layer and has a second characteristic acoustic impedance that is greater than the first characteristic acoustic impedance. The thermal-acoustic section is configured to be positioned along the acoustic path such that at least a portion of the noise from the acoustic source is directed through the first porous layer to the second porous layer to promote absorption of the noise.

Abstract: Embodiments of thermal-acoustic sections for an aircraft for reducing noise along an acoustic path produced from an acoustic source are provided herein. The thermal-acoustic section comprises a first porous layer having a first characteristic acoustic impedance. A second porous layer is disposed adjacent to the first porous layer and has a second characteristic acoustic impedance that is greater than the first characteristic acoustic impedance. The thermal-acoustic section is configured to be positioned along the acoustic path such that at least a portion of the noise from the acoustic source is directed through the first porous layer to the second porous layer to promote absorption of the noise.

Abstract: The invention is directed to a low expansion glass with reduced striae, the glass have a point-to-point variation in titania content is 0.1 wt % or less through its thickness and a CTE of 0±3 ppb/° C. throughout the temperature range 5-35° C. The invention is further directed to a method for producing the low expansion glass by using a method in which the time for repetition of the oscillation patterns used in the process are 10 minutes or less. In addition, the low expansion glass of the invention can have striae further reduced by heat-treating the glass at temperatures above 1600° C. for a time in the range of 48-160 hours. The invention is also directed to optical elements suitable for extreme ultraviolet lithography, which elements are made of a titania-containing silica glass having a titania content in the range of 5-10 wt. %, a polished and shaped surface have a peak-to-valley roughness of less than 10 nm, an average variation in titania content of less than ±0.1 wt.

Abstract: The invention is directed to a low expansion glass with reduced striae, the glass have a point-to-point variation in titania content is 0.1 wt % or less through its thickness and a CTE of 0±3 ppb/° C. in the temperature range 5-35° C. The invention is further directed to a method for producing the low expansion glass by using a method in which the time for repetition of the oscillation patterns used in the process are 10 minutes or less. In addition, the low expansion glass of the invention can have striae further reduced by heat-treating the glass at temperatures above 1600° C. for a time in the range of 48-160 hours.

Abstract: The invention is directed to a method for reducing striae in ultra-low expansion glass by heat-treating the glass at temperatures above 1600° C. for a time in the range of 72-288 hours. In one embodiment of the invention the glass is heat treated without forcing the glass to flow or “move”. The invention was found to reduce the magnitude of striae in an ultra-low expansion glass by 500%, and particularly reduces most of the “higher frequency” striae.

Abstract: Disclosed are high purity synthetic silica glass material having a high OH concentration homogeneity in a plane perpendicular to the optical axis, and process of making the same. The glass has high refractive index homogeneity. The glass can have high internal transmission of at least 99.65%/cm at 193 nm. The process does not require a post-sintering homogenization step. The controlling factors for high compositional homogeneity, thus high refractive index homogeneity, include high initial local soot density uniformity in the soot preform and slow sintering, notably isothermal treatment during consolidation.

Abstract: Titania-containing silica glass bodies and extreme ultraviolet elements having low levels of striae are disclosed. Methods and apparatus for manufacturing and measuring striae in glass elements and extreme ultraviolet elements are also disclosed.