Generation of tunable q-switched erbium-doped fiber laser based on graphite flakes saturable absorber

Pulsed fiber laser has tremendous application in laser processing and laser sensor. The key element to produce a passively Q-switched fiber laser is by using a saturable absorber (SA). Passively Q-switched fiber laser is the most desirable pulse in laser technology due to its ability to generate optical pulses in microsecond and nanosecond. The aim of this study is to construct a single ring erbium-doped fiber (EDF) laser based on graphite flakes SA to produce short pulse laser. Graphite flakes SA were prepared by mechanical exfoliation techniques and was transferred onto a fiber ferrule tip. The saturable absorption property of the graphite was measured using twin detector method which resulted in a modulation depth of 23.82% with a saturation intensity of 0.031 MW/cm2. Surface morphology, elemental analysis and absorbance characteristics of the graphite flakes were analyzed by the field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX) and ultraviolet visible spectroscopy (UV-VIS). The result showed that the carbon element on the SA has a very strong peak intensity. The two different EDF coefficient of 6.43 dB/m and 18.93 dB/m (EDF M-5 and EDF I-12) showed a repetition rate of 41.62 kHz and 60.00 kHz with a pulse width of 6.45 μs and 3.38 μs, respectively at a pump power of 268.8 mW. The wavelength tunability of passively Q-switched fiber laser for EDF M-5 and EDF I-12 were optimized at fixed pump power where the tuning range of EDF M-5 occurred between 1544 nm to 1560 nm and 1552 nm to 1570 nm for EDF I-12. The passively Q-switched fiber laser with different EDF coefficients were successfully constructed in a single ring configuration with more selection of wavelength that is up to L band by using higher EDF coefficient

After the philosopher's stone : aesthetic interrogations and navigations : an exegesis presented in partial fulfilment of the requirements for the degree of Masters of Fine Arts at Massey University, Wellington, New Zealand

“One becomes two, two becomes three, and out of the third comes the One as the fourth.” Maria Prophetessai The axiom of Maria is an alchemical percept illustrating a processual procedure across time that accords with the Jungian concept of individuation (from undifferentiated unconsciousness to unique individualised wholeness). The process concerns transformations of materialities and psychological state as movement in time. My research project is situated at a nexus between three simultaneous aims and procedures which relate to this precept; One: Art as magick, (magickal operations, in this case sigil constructions, aimed at altering psychological and material conditions under intentional application of imagination and will); Two: Art as spiritual practice and religious devotion, (a devotional orientation through art practiced on a relational line of enquiry and association via ‘theophanic’ and ‘active’ imagination’); Three: Art as a psychotherapeutic vehicle (oblique means for mending disturbed subjective conditions, generating processes and affects of integration and connectivity across an experiential and theorised fragmented subject terrain). The ‘fourth’ here is what is brought to the moment of reception and reading by a given audience. All concern alchemical transmutation as matter-mind relations; from an immersive, undifferentiated ‘one’ in relative unconsciousness, to compounding relational reflexivities of correspondence, doubling of associations, ‘two’, through to a ‘third that becomes a One as the fourth’, a ‘transcendent function’, as a held space weaving all of the varying threads and development together into a new unified configuration, co-ordinated but remaining unfixed as end and determination. Each point in this axiomatic evolution is polymorphous, yet relates to origins and concerns guiding it at the outset. Drawings, objects, materialities, substances, space, become the axes and in potentia through which this metamorphic generation takes place and manifests in form

Performance and wake analysis of rotors in axial flight using computational fluid dynamics

Flow field around rotors in axial flight is known to be complex especially in steep descent where the rotor is operating inside its own wake. It is often reported that, in this flight condition, the rotor is susceptible to severe wake interactions causing unsteady blade load, severe vibration, loss of performance, as well as poor control and handling. So far, there is little data from experimental and numerical analysis available for rotors in axial flight. In this paper, the steady Reynolds-Averaged Navier-Stokes Computational Fluid Dynamics solver Helicopter Multi-Block was used to predict the performance of rotors in axial flight. The main objective of this study was to improve the basic knowledge about the subject and to validate the flow solver used. The results obtained are presented in the form of surface pressure, rotor performance parameters, and vortex wake trajectories. The detailed velocity field of the tip vortex for a rotor in hover was also investigated, and a strong self-similarity of the swirl velocity profile was found. The predicted results obtained when compared with available experimental data showed a reasonably agreement for hover and descent rate, suggesting unsteady solution for rotors in vortex-ring state

Social housing and digital exclusion

This report by the National Housing Federation Futures Project analyses the concept of digital exclusion, its effects, the role of housing associations in tackling its consequences and possible interventions that may arise

Paradoxes of rational agency and formal systems that verify their own soundness

We consider extensions of Peano arithmetic which include an assertibility predicate. Any such system which is arithmetically sound effectively verifies its own soundness. This leads to the resolution of a range of paradoxes involving rational agents who are licensed to act under precisely defined conditions.Comment: 10 page