Acoustic emission frequency discrimination

In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered

A Surprise Occurrence in Acoustic Bottom Backscatter Measurements Conducted in the Eastern Bering Sea

Acoustic backscatter measurements at different frequencies were made in the eastern Bering Sea in August 2006 from the NOAA Ship Fairweather. The measurements consisted of approximately 2,250 nm of trackline acoustic backscatter data from a 100 kHz RESON model 8111; 2,250 nm of trackline acoustic backscatter data from a 40 kHz Reson model 8160; 750 nm of trackline acoustic backscatter data from a 455 kHz Klein model 5410; and 750 nm of trackline acoustic backscatter data from a 180 kHz pre-production Klein model 7180. The two Klein systems were each towed SW-NE once along the same specified 750 nm of tracklines. The two RESON systems were each operated twice SW-NE and once NE-SW along the same tracklines as the Klein systems. The acoustic backscatter was typically what might be expected from a flat, featureless expanse of fine grained sediments. However, there was a chance encounter with an embedded community of gastropods that was documented both with bottom grab samples and video footage of the seabed. The presence of the embedded community of gastropods drastically changed the level and angle dependence of the backscatter. This paper presents a comparative analysis of the backscatter properties of the gastropod community that were observed at 40 kHz, 100 kHz, 180 kHz and 455 kHz

Towards a public ECEC system

Expanding Fields of Architectural Discourse and Practice presents a selection of essays, architectural experiments and works that explore the diversity within the fields of contemporary architectural practice and discourse. Specific in this selection is the question of how and why architecture can and should manifest in a critical and reflective capacity, as well as to examine how the discipline currently resonates with contemporary art practice. It does so by reflecting on the first 10 years of the architectural journal, P.E.A.R. (2009 to 2019). The volume argues that the initial aims of the journal – to explore and celebrate the myriad forms through which architecture can exist – are now more relevant than ever to contemporary architectural discourse and practice. Included in the volume are architectural practitioners, design researchers, artists, architectural theorists, historians, journalists, curators and a paleobiologist, all of whom contributed to the first seven issues of the journal. Here, they provide a unique presentation of architectural discourse and practice that seeks to test new ground while forming distinct relationships to recent, and more longstanding, historical legacies

The Interplay between attention, experience and skills in online language teaching

The demand for online teaching is growing as is the recognition that online teachers require highly sophisticated skills to manage classrooms and create an environment conducive to learning. However, there is little rigorous empirical research investigating teachers’ thoughts and actions during online tutorials. Taking a sociocultural perspective, this study explores the interplay between the attention focus of language teachers during synchronous online tutorials and their reflections on their own teaching practices. Eyetracking data show that patterns of attention focus on different areas of the screen (representing technical facilities, social interaction and content) are related to practitioners’ experience in online teaching including familiarity with a particular platform. In particular, those with less online teaching experience display greater attention to technical areas than their more experienced colleagues. These findings are confirmed in the teachers’ reflective interviews, stimulated by watching gazeplot videos of their online tutorials. Their reflections also yield deeper insight into reasons for particular actions. Thematic analysis was used to relate the reflections on teaching strategies to the levels of online teaching skills (Hampel & Stickler 2005, New skills for new classrooms: Training tutors to teach languages online. Computer Assisted Language Learning 18(4). 311–326). Our research has extended Bax’s normalisation (2003, CALL – past, present and future. System 31(1). 13–28. doi: 10.1016/s0346-251x(02)00071-4) of the use of technology in face-to-face classroom learning into online learning environments. Mirroring the ontogenetic development of increasing digitalisation, teachers in online environments appropriate the skills necessary to free cognitive resources for attending to social and pedagogic aspects of their teaching

Adaptive interference techniques for mobile antennas

The results of a study performed to investigate effective, low cost adaptive signal processing techniques for suppressing mutual satellite interference that can arise in a mobile satellite (MSAT) communication system are discussed. The study focused on the use of adaptive sidelobe cancelling as a method to overcome undesired interference caused by a multiplicity of satellite transmissions within the field of view of the ground station. Results are presented which show that the conventional sidelobe canceller produces undesired reduction of the useful signal. This effect is due to the presence of the useful component in the reference antenna element. An alternative structure, the generalized sidelobe canceller (GSC), has been proposed to overcome this difficulty. A preliminary investigation of possible implementations of the GSC was conducted. It was found that at most 8 bits would be required to implement the GSC processor under conditions in which the desired signal-to-interference ratio is 25 dB

Adapting horse-drawn mowers to tractor power

Caption title.Digitized 2006 AES MoU