Experiments on the generation of activated carbon from biomass

Activated carbon is generated from various waste biomass sources like rice straw, wheat straw, wheat straw pellets, olive stones, pistachios shells, walnut shells, beech wood and hardcoal. After drying the biomass is pyrolysed in the temperature range of 500-600 °C at low heating rates of 10 K/min. The activation of the chars is performed as steam activation at temperatures between 800 °C and 900 °C. Both the pyrolysis and activation experiments were run in lab-scale facilities. It is shown that nut shells provide high active surfaces of 1000-1300 m/g whereas the active surface of straw matters does hardly exceed 800 m/g which might be a result of the high ash content of the straws and the slightly higher carbon content of the nut shells. The active surface is detected by BET method. Besides the testing of a many types of biomass for the suitability as base material in the activated carbon production process, the experiments allow for the determination of production parameters like heating rate and pyrolysis temperature, activation time and temperature as well as steam flux which are necessary for the scale up of the process chain. © 2006 Elsevier B.V. All rights reserved.

Multi-harmonic optical comb generation

We present a novel optical comb generation technique based on the use of a multi-harmonic electrical signal for driving the MZM. The proposed scheme is highly power efficient and gives rise to square shaped combs of advanced flatness and side mode suppression ratio while maintaining a stable performance over a long time period. © 2012 OSA.

Spectrally controlled, picosecond pulse generation from an InGaN violet diode laser

Self-seeded, gain-switched operation of an InGaN multi-quantum-well diode laser is reported for the first time. Narrow-line, wavelength-tunable, picosecond pulses have been generated from a standard, uncoated diode laser in an external cavity.

Educating the iPod generation:undergraduate attitudes, experiences and knowledge of vodcast and podcast use

There is an increasing pressure on university staff to provide ever more information and resources to students. This study investigated student opinions on (audio) podcasts and (video) vodcasts and how well they met requirements and aided learning processes. Two experiments within the Aston University looked at student opinion on, and usage of, podcasts and vodcasts for a selection of their psychology lectures. Recordings were produced first using a hand-held camcorder, and then using the in-house media department. WebCT was used to distribute the podcasts and vodcasts, attitude questionnaires were then circulated at two time points. Overall students indicated that podcasts and vodcasts were a beneficial addition resource for learning, particularly when used in conjunction with lecturers’ slides and as a tool for revision/assessment. The online material translated into students having increased understanding of the material, which supplemented and enhanced their learning without being a substitute for traditional lectures. There is scope for the provision of portable media files to become standard practice within higher education; integrating distance and online learning with traditional approaches to improve teaching and learning.

On the Generation of Heronian Triangles

We describe several algorithms for the generation of integer Heronian triangles with diameter at most n. Two of them have running time O(n^(2+ε)). We enumerate all integer Heronian triangles for n ≤ 600000 and apply the complete list on some related problems.

Generation dynamics of the narrowband Yb-doped fiber laser

We present direct real-time experimental measurements and numerical modeling of temporal and statistical properties for the Ytterbiumdoped fiber laser with spectral bandwidth of ∼2 GHz. The obtained results demonstrate nearly exponential probability density function for intensity fluctuations. A significant decrease below the Gaussian probability has been experimentally observed for intensity fluctuations having value more than 2.5 of average intensity that may be treated as indication of some mode correlations. © 2013 Optical Society of America.

Generation of dissipative solitons in an actively mode-locked ultralong fibre laser

A single-pulse actively mode-locked fibre laser with a cavity length exceeding 1 km has been developed and investigated for the first time. This all-fibre erbium-doped laser has a normal intracavity dispersion and generates dissipative 8-ns solitons with a fundamental repetition rate of 163.8 kHz; the energy per pulse reaches 34 nJ. The implemented mode locking, based on the use of intracavity intensity modulator, provides self-triggering and high stability of pulsed lasing. A possibility of continuous tuning of the centre lasing wavelength in the range of 1558 - 1560 nm without any tunable spectral selective elements in the cavity is demonstrated. The tuning occurs when controlling the modulation signal frequency due to the forced change in the pulse repetition time (group delay) under the conditions of intracavity chromatic dispersion. © 2013 Kvantovaya Elektronika and Turpion Ltd.

Real-time heterodyne-based measurements of fiber laser spectral dynamics

We present a method to measure in real-time the instantaneous generation spectrum of fiber lasers over consecutive cavity round-trips. © 2015 OSA.

Self-adaptive probabilistic roadmap generation for intelligent virtual agents

Agents inhabiting large scale environments are faced with the problem of generating maps by which they can navigate. One solution to this problem is to use probabilistic roadmaps which rely on selecting and connecting a set of points that describe the interconnectivity of free space. However, the time required to generate these maps can be prohibitive, and agents do not typically know the environment in advance. In this paper we show that the optimal combination of different point selection methods used to create the map is dependent on the environment, no point selection method dominates. This motivates a novel self-adaptive approach for an agent to combine several point selection methods. The success rate of our approach is comparable to the state of the art and the generation cost is substantially reduced. Self-adaptation therefore enables a more efficient use of the agent's resources. Results are presented for both a set of archetypal scenarios and large scale virtual environments based in Second Life, representing real locations in London.

Raman gain and random distributed feedback generation in nitrogen doped silica core fiber

Recently, the concept of a random distributed feedback (DFB) lasing in optical fibers has been demonstrated [1], A number of different random DFB fiber lasers has been demonstrated so far including tunable, multiwalength, cascaded generation, generation in different spectral bands etc [2-7]. All systems are based on standard low-loss germanium doped silica core fibres having relatively low Rayleigh scattering coefficient. Thus, the typical length of random DFB fiber lasers is in the range from several kilometres to tens of kilometres to accumulate enough random feedback. Here we demonstrate for the first time to our knowledge the random DFB fiber laser based on a nitrogen doped silica core (N-doped) fiber. The fiber has several times higher Rayleigh scattering coefficient compared to standard telecommunication fibres. Thus, the generation is achieved in 500 meters long fiber only. © 2013 IEEE.

Generation of drifting optical pulses

The radiation in the form of Airy and Gaussian optical pulses is investigated. It is shown that the pulse envelope moves decelerating in the time-spatial coordinates on the surface of a parabolic cylinder for the Airy pulse and a hyperbolic cylinder for the Gaussian. © 2013 IEEE.

FREADMAN, AnneThe Livres-Souvenirs of Colette Genre and the Telling of Time Oxford: Legenda, August 2012200 pp., £40.00, ISBN: 978-1-906540-93-7

Full text: The title of the book gives us a major clue on the innovative approach developed by Anne Freadman in her analysis of a particular Colette corpus, the one devoted to auto-biographical writing: Les Vrilles de la vigne, Mes apprentissages, La Maison de Claudine, Sido ,L’E ́toile Vesper and Le Fanal bleu. Freadman follows the powerful lure of Rimbaldianvieilles vieilleries and its echoes with Colette’s fondness for collecting objects, people and memories. To this must be added a technical aspect, that of the study of the genre of Colette’s writing. Freadman argues that, by largely avoiding the autobiographical form, the writer achieves a new way of ‘telling time’, collecting anecdotes and detail taken from the quotidian and setting them within an all-encompassing preoccupation with time. This provides the second part of the title.The sonata form directs the sequence of the book, orchestrated into five parts,from ‘exposition’ to ‘first subject’ to‘bridge’ to ‘second subject’ to ‘recapitulation’. This has the advantage of enabling Freadman to move and progress between distinct themes—autobiography first,then alternative forms—with grace,whilst preserving within her own writing what she sees as the essence of Colette’s relationship to time in her ‘Livres-Souvenirs’, the telling of time. This‘telling of time’ is itself therefore cleverly subjected to the time constraints and freedoms of musical composition. Freadman’s ‘Exposition’ takes us through a discussion of the autobiographical genre, analysing the texts against anumber of theorists, from Lejeune to Benjamin and Ricoeur, before launching into ‘Colette and Autobiography’. It argues pertinently that Colette did not write a ‘sustained’ autobiography, even inthe most autobiographical of her writings, Mes apprentissages. Measured against Goodwin’s three sources for autobiography, confession, apologia and memoirs, Colette’s autobiographical writings appear to be at odds with all of them. Freadman then goes on in Part II of her argument, to persuasively uncover a project that rejects self-scrutiny and with no autobiographical strategy. In ‘Collecting Time’, despite claims of continuity, narrative logic and causality areabandoned in favour of a collection offragments, family stories that are built up generation after generation into familylegends. A close and fruitful analysis of Sidoleads us to a study of ‘The Art of Ending’, concentrating on L’E ́toile Vesperandle Fanal Bleu. The closing chapter gives a fascinating reading of La Naissance du jouras an exemplar of the way in which the two subjects developed in Freadman’s volume are cast together:Colette’s own working through the autobiographical genre, and her refusal to write memoirs, in favour of collecting memories, and the strategies she uses for her purpose. In ‘Recapitulation’, her concluding chapter, Freadman adroitlyen capsulates her analysis in a fetching title: ‘Fables of Time’. Indeed, the wholepremise of her book is to move away from autobiographical genre, having acknowledged the links and debt the corpus owes to it, and into a study of the multiple and fruitful ways in which Colette tells time.The rich and varied readings of thematerial, competently informed by theoretical input, together with acute sensitivity to the corpus, mark out this study as incontournable for Colette scholars.

Real-time high-resolution heterodyne-based measurements of spectral dynamics in fibre lasers

Conventional tools for measurement of laser spectra (e.g. optical spectrum analysers) capture data averaged over a considerable time period. However, the generation spectrum of many laser types may involve spectral dynamics whose relatively fast time scale is determined by their cavity round trip period, calling for instrumentation featuring both high temporal and spectral resolution. Such real-time spectral characterisation becomes particularly challenging if the laser pulses are long, or they have continuous or quasi-continuous wave radiation components. Here we combine optical heterodyning with a technique of spatiooral intensity measurements that allows the characterisation of such complex sources. Fast, round-trip-resolved spectral dynamics of cavity-based systems in real-time are obtained, with temporal resolution of one cavity round trip and frequency resolution defined by its inverse (85 ns and 24 MHz respectively are demonstrated). We also show how under certain conditions for quasi-continuous wave sources, the spectral resolution could be further increased by a factor of 100 by direct extraction of phase information from the heterodyned dynamics or by using double time scales within the spectrogram approach.

Generation of decelerating Airy pulses

The explicit expression for spatial-temporal Airy pulse is derived from the Maxwell's equations in paraxial approximation. The trajectory of the pulse in the time-space coordinates is analysed. The existence of a bifurcation point that separates regions with qualitatively different features of the pulse propagation is demonstrated. At this point the velocity of the pulse becomes infinite and the orientation of it changes to the opposite. © 2011 IEEE.

Comparison of cost- and energy-efficient signal modulations for next generation passive optical networks

Extensive numerical investigations are undertaken to analyze and compare, for the first time, the performance, techno-economy, and power consumption of three-level electrical Duobinary, optical Duobinary, and PAM-4 modulation formats as candidates for high-speed next-generation PONs supporting downstream 40 Gb/s per wavelength signal transmission over standard SMFs in C-band. Optimization of transceiver bandwidths are undertaken to show the feasibility of utilizing low-cost and band-limited components to support next-generation PON transmissions. The effect of electro-absorption modulator chirp is examined for electrical Duobinary and PAM-4. Electrical Duobinary and optical Duobinary are powerefficient schemes for smaller transmission distances of 10 km SMFs and optical Duobinary offers the best receiver sensitivity albeit with a relatively high transceiver cost. PAM-4 shows the best power budget and costefficiency for larger distances of around 20 km, although it consumes more power. Electrical Duobinary shows the best trade-off between performance, cost and power dissipation.