Polarization compensator for optical communications

An optical data communication system is provided whereby two orthogonal polarization states of a light beam carrier correspond to digital states. In such a system, automatic polarization compensation is provided by applying a dither modulating voltage to a cell exhibiting the electro-optic effect. The cell controls the relative phase of electric field components of an input light beam enabling the dither frequency component of the difference of the instantaneous powers in the two polarization states to be coherently detected. A signal derived from the coherent detection process is fed back to the cell via an integrator to form polarization bias compensating servo loop ot Type 1

Dynamic polarization compensating system for optical communications receiver

Electro-optic cell is located in optical path of input light beam. Cell includes crystal for controlling phase between two polarization states. Cell axes are rotated 45 deg to receiver axes defined by vertical and horizontal polarization states. Voltage across cell compensates for bias by introducing different phase retardation along crystal axes

An analysis of RNG based turbulence models for homogeneous shear flow

In a recent paper, the authors compared the performance of a variety of turbulence models including the k-epsilon model and the second-order closure model based on Renormalization Group (RNG) Methods. The performance of these RNG models in homogeneous turbulent shear flow was found to be quite poor, apparently due to the value of the constant C(sub epsilon1) in the modeled dissipation rate equation which was substantially lower than its traditional value. However, recently a correction has been made in the RNG based calculation of C(sub epsilon1). It is shown that with the new value of C(sub epsilon1), the performance of the RNG k-epsilon model is substantially improved. On the other hand, while the predictions of the revised RNG second-order closure model are better, some lingering problems still remain which can be easily remedied by the addition of higher order terms

ASL-English Interpreters and Anxiety

Reflective of the American population, there are a number of interpreters who have Generalized Anxiety Disorder. Using a mixed methods approach, credentialed interpreters share their experience with anxiety as a professional interpreter. Participants relate both the positive and negative effects of anxiety on their interpreting work. Several anxiety coping strategies are explored, as well as, detailing the importance of finding a confidant. Issues such as potential professional stigma and the consequences of declining assignments for anxiety reasons are discussed

Prelaunch testing of the GEOS-3 laser reflector array

The prelaunch testing performed on the Geos-3 laser reflector array before launch was used to determine the lidar cross section of the array and the distance of the center of gravity of the satellite from the center of gravity of reflected laser pulses as a function of incidence angle. Experimental data are compared to computed results

The shock response of biomaterials

© Cranfield University, 2018The shock response of microorganisms is of particular interest to many different areas of research including, but not limited to: asteroid and meteoritic impacts and origins of life; food sterilisation; and deep-sea organisms. The primary interest behind the investigation presented in this thesis is the origins of life and how, if life began elsewhere in the universe, it could survive transfer from one planetary body to the next. This ties in with the theory of panspermia and suggests that life on Earth, or its building blocks, may have originated elsewhere in the universe and was transferred here via an asteroid or meteor. Aside from the many other caveats that travel through space would present to an organism, such as extreme temperatures and ionising radiation, to survive a meteoritic impact onto a planetary body would be to survive extreme shock pressures as well. The purpose of this investigation, therefore, was to examine a number of organisms under quasi-one-dimensional shock loading conditions in order to assess the organisms’ response to shock pressure. The microorganisms chosen were Escherichia coli NCTC 10538 and Saccharomyces cerevisiae ATCC 18824, two model organisms, a prokaryote and a eukaryote, respectively, whose biochemistry is well characterised. The shock loading experiments were carried out in a 50 mm bore single stage gas gun using the plateimpact technique. The bio-samples were contained within a capsule system that allowed them to be safely contained and retrieved after the shock so that their growth rates could be assessed. E. coli was subjected to shock pressures ranging from 0.55 to 10 GPa under various different shock conditions, yielding growth rates of 6% to 0.09%, respectively. S. cerevisiae was shock loaded to from 0.49 to 2.33 GPa with resulting growth rates ranging from 1.8% to zero growth. Additionally, to probe further into how life forms of varying complexity might respond to these shock pressures, the multicellular organism, Artemia salina, was shock loaded under the same conditions, but only up to a maximum pressure of 1.5 GPa. It was noted that Artemia cysts showed hatching rates of up to 18% at this pressure, but this was not always without residual damage to the shell and the embryo within. Since pressure gauges could not be attached to the target capsule due to the complexity of the set-up, validated numerical models had to be employed to interrogate the pressures occurring within the sample. This also gave an indication as to the type of loading occurring within the sample. It was also desired to measure temperatures occurring during shock loading and to explore methods to better control this so that samples could be shocked to a particular pressure, while still controlling temperature. This was achieved using a novel type of flyer plate called Surfi-Sculpt® while validated numerical models were again used to estimate peak temperatures inside the capsule containing the biological sample. From the findings of a variety of shock experiments carried out throughout this project, a number of mechanisms were proposed to explain some of the results seen, providing insight into how microorganisms in particular might survive high shock pressures

Guitars with Ambisonic Spatial Performance (GASP) An immersive guitar system

The GASP project investigates the design and realisation of an Immersive Guitar System. It brings together a range of sound processing and spatialising technologies and applies them to a specific musical instrument – the Electric Guitar. GASP is an ongoing innovative audio project, fusing the musical with the technical, combining the processing of each string’s output (which we called timbralisation) with spatial sound. It is also an artistic musical project, where space becomes a performance parameter, providing new experimental immersive sound production techniques for the guitarist and music producer. Several ways of reimagining the electric guitar as an immersive sounding instrument have been considered, the primary method using Ambisonics. However, additionally, some complementary performance and production techniques have emerged from the use of divided pickups, supporting both immersive live performance and studio post-production. GASP Live offers performers and audiences new real-time sonic-spatial perspectives, where the guitarist or a Live GASP producer can have real-time control of timbral, spatial, and other performance features, such as: timbral crossfading, switching of split-timbres across strings, spatial movement where Spatial Patterns may be selected and modulated, control of Spatial Tempo, and real-time performance re-tuning. For GASP recording and post-production, individual string note patterns may be visualised in Reaper DAW,2 from which, analyses and judgements can be made to inform post-production decisions for timbralisation and spatialisation. An appreciation of auditory grouping and perceptual streaming (Bregman, 1994) has informed GASP production ideas. For performance monitoring or recorded playback, the immersive audio would typically be heard over a circular array of loudspeakers, or over headphones with head-tracked binaural reproduction. This paper discusses the design of the system and its elements, investigates other applications of divided pickups, namely GASP’s Guitarpeggiator, and reflects on productions made so far

On the effects of powder morphology on the post-comminution ballistic strength of ceramics

In this paper in order to try and elucidate the effects of particle morphology on ballistic response of comminuted systems, a series of experiments were carried out via the use of powder compacts with differing initial particle morphologies. This approach provided a route to readily manufacture comminuted armour analogues with significantly different microstructural compositions. In this study pre-formed `fragmented-ceramic' analogues were cold-pressed using plasma-spray alumina powders with two differing initial morphologies (angular and spherical). These compacts were then impacted using 7.62-mm FFV AP (Förenade Fabriksverken Armour Piercing) rounds with the subsequent depth-of-penetration of the impacting projectile into backing Al 6082 blocks used to provide a measure of pressed ceramic ballistic response. When material areal density was accounted for via differing ballistic efficiency calculations a strong indication of particle morphology influence on post-impact ceramic properties was apparent. These results were reinforced by a separate small series of plate-impact experiments, whose results indicated that powder morphology had a strong influence on the nature of compact collapse

Bacterial survival following shock compression in the GigaPascal range

The possibility that life can exist within previously unconsidered habitats is causing us to expand our understanding of potential planetary biospheres. Significant populations of living organisms have been identified at depths extending up to several km below the Earth's surface; whereas laboratory experiments have shown that microbial species can survive following exposure to GigaPascal (GPa) pressures. Understanding the degree to which simple organisms such as microbes survive such extreme pressurization under static compression conditions is being actively investigated. The survival of bacteria under dynamic shock compression is also of interest. Such studies are being partly driven to test the hypothesis of potential transport of biological organisms between planetary systems. Shock compression is also of interest for the potential modification and sterilization of foodstuffs and agricultural products. Here we report the survival of Shewanella oneidensis bacteria exposed to dynamic (shock) compression. The samples examined included: (a) a "wild type" (WT) strain and (b) a "pressure adapted" (PA) population obtained by culturing survivors from static compression experiments to 750 MPa. Following exposure to peak shock pressures of 1.5 and 2.5 GPa the proportion of survivors was established as the number of colony forming units (CFU) present after recovery to ambient conditions. The data were compared with previous results in which the same bacterial samples were exposed to static pressurization to the same pressures, for 15 minutes each. The results indicate that shock compression leads to survival of a significantly greater proportion of both WT and PA organisms. The significantly shorter duration of the pressure pulse during the shock experiments (2-3 μs) likely contributes to the increased survival of the microbial species. One reason for this can involve the crossover from deformable to rigid solid-like mechanical relaxational behavior that occurs for bacterial cell walls on the order of seconds in the time dependent strain rate

On the shock behaviour and response of Ovis Aries vertebrae

When investigating a biological system during shock loading, it is best practice to isolate different components to fully comprehend each individual part [1,2] before building up the system as a whole. Due to the high acoustic impedance of bone in comparison to other biological tissues [3] the majority of the shock will be transmitted into this medium, and as such can cause large amounts of damage to other parts of the body potentially away from the impact area