8,245 research outputs found
Frequency doubling, absorption and grating deformation in glass fibres: effective defects or defective effects?
No full textThe present understanding of colour centres in germanosilicate glass fibres and the diverse effects attributed to colour centre activity are reviewed. Drawing on a wide range of up-to-date research results, an attempt is made to piece together as far as possible a unified picture of the defect processes behind second harmonic generation, nonlinear transmission and photorefractive grating formation in optical fibres
Optically induced creation, transformation and organisation of defects and color centers in optical fibres
No full textOver the past five years, a colour-centre model for the dynamics of the absorption induced in germanosilicate fibres upon exposure to blue/green light has been under development at Southampton. This model is introduced and its predictions used for the first time to test our proposed Kramers-Kronig mechanism for the concurrent refractive index changes induced in the visible and the infra-red. It is found that the predicted colour-centre population changes in the UV are to explain these refractive index changes. A possible alternative model, based on density changes in the glass triggered by colour-centre formation, is assessed experimentally and analytically. The implications of this result to photonically driven self-organisation in fibres is briefly assessed, and reference made to recent experimental results
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Picosecond laser micro-machining of glass for optics manufacture
Get PDFGlass-based aspheric optics are attractive for compact optical setups. In addition,
custom optics are useful for the correction of pointing errors of High Power Diode Lasers
(HPDL). The machining of fused silica (Corning HPFS® 7980), Schott N-BK7®, Schott
N-LaF21 and Ohara S-TiH53 using a Trumpf TruMicro 5X50 laser which provides a 6
picosecond pulse duration with a maximum pulse repetition rate of 400 kHz and
maximum average power of 50 W has been explored in this thesis. The machining of
these glass materials was carried out using laser wavelengths λ = 1030 nm, 515 nm and
343 nm at different pulse spatial overlap and fluence values. Two scan strategies were
used, namely the sequential raster scan strategy and the novel interlaced scan strategy. In
this thesis, we show the differences in the machining outcome. The sequential scan
strategy is similar to the standard raster scan technique and is limited to lower pulse
repetition rates of 20 kHz due to a thermal build-up effect manifesting itself in the
formation of fibres and fused debris on the surface. On the other hand, given the same
conditions of total pulse energy deposited on the surface, the interlaced scan strategy is
found to provide up to 3 times larger ablation depths. Furthermore, as the interlaced scan
strategy has been found to suppress the effects of thermal accumulation, higher repetition
rates up to 400 kHz could be used providing higher ablation rates up to 60 times more
than the sequential scan strategy on the laser used. A high-speed camera was used to
observe the mechanism of material removal for the two scan strategies providing insight
into the cause of the higher ablation efficiency of the interlaced scan strategy. We
demonstrate the capability of this process by machining cylindrical lenses. One batch of
the picosecond laser machined lenses was shipped to Fraunhofer ILT while another
similar batch of lenses was shipped to PowerPhotonic Ltd. for polishing using their CO2
laser polishing techniques. The polished lenses were tested for their performance, and
the accuracy of the process was measured. Finally, the future scope of this technology
along with its applications is discussed
Illustrated type catalogue of Amphidromus Albers, 1850 in the Natural History Museum, London, and descriptions of two new species
Get PDFCopyright Chirasak Sutcharit et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article.NHM Repositor
Discomfort Threshold Evaluation for Hand and Elbow Regions: A Basis for Hand-Held Device Design
No full textThis study aimed to analyse the discomfort threshold (that could be linked to sensitivity or sensation) of different regions in hand and elbow to support hand-held devices' design. Indeed, there are no studies regarding the hand and elbow discomfort threshold or sensitivity. To overcome these literature gaps, the discomfort threshold of hand and elbow were recorded at 24 spots by pushing a cylinder with a diameter of 10 mm until the participants reported not to be longer comfortable. Experiments were performed with 24 participants, 13 females and 11 males. The results showed the map of discomfort threshold (or sensitivity) for the hand and elbow. The olecranon, situated at the ulna's upper (proximal) end, one of the two bones in the forearm, could withstand more pressure than the elbow area surrounding it. The fingertips and the area close to the metacarpals were most sensitive (lower discomfort threshold).Accepted Author ManuscriptMaterials and Manufacturin
sj-pdf-2-jhs-10.1177_17531934211064185 - Supplemental material for The importance of embryology for parents of children with congenital hand differences
No full textSupplemental material, sj-pdf-2-jhs-10.1177_17531934211064185 for The importance of embryology for parents of children with congenital hand differences by Andrew D. Clelland, Órla Duncan and Wee L. Lam in Journal of Hand Surgery (European Volume)</p
sj-pdf-5-jhs-10.1177_17531934211064185 - Supplemental material for The importance of embryology for parents of children with congenital hand differences
No full textSupplemental material, sj-pdf-5-jhs-10.1177_17531934211064185 for The importance of embryology for parents of children with congenital hand differences by Andrew D. Clelland, Órla Duncan and Wee L. Lam in Journal of Hand Surgery (European Volume)</p
sj-pdf-3-jhs-10.1177_17531934211064185 - Supplemental material for The importance of embryology for parents of children with congenital hand differences
No full textSupplemental material, sj-pdf-3-jhs-10.1177_17531934211064185 for The importance of embryology for parents of children with congenital hand differences by Andrew D. Clelland, Órla Duncan and Wee L. Lam in Journal of Hand Surgery (European Volume)</p
sj-pdf-4-jhs-10.1177_17531934211064185 - Supplemental material for The importance of embryology for parents of children with congenital hand differences
No full textSupplemental material, sj-pdf-4-jhs-10.1177_17531934211064185 for The importance of embryology for parents of children with congenital hand differences by Andrew D. Clelland, Órla Duncan and Wee L. Lam in Journal of Hand Surgery (European Volume)</p
- …
