67 research outputs found
The distant music of a flute
No full textAamer Hussein has contributed to The Young Wife and Other Stories as a content introducer. Born in Karachi, Hussein moved to London in 1970. He reviews for The Independent and the TLS. He is the author of Turquoise, This Other Salt, and editor of Kahani: Short Stories by Pakistani Women. He has held visiting posts at the University of Southampton and the University of London, and is a Fellow of the Royal Society of Literature
NIR spectroscopy for personal screening
Get PDFThis work presents investigations into the use of the near-infrared (NIR) signals to
interrogate, detect and image specific chemical compounds of interest in a security
screening application, including when such compounds are hidden behind single layers
of clothing fabric.
In an initial set of experiments, the mechanisms governing the interaction of NIR
signals with clothing fabrics and similar materials has been studied, in order to account
for the influence of fabric layers when detecting hidden chemicals. Throughout the rest
of the work, NIR spectroscopy has been used as a means to perform qualitative and
quantitative analysis, in order to detect the presence of chemicals, and quantify the
concentration in aqueous solution of liquids.
It has been shown that, while the compounds can be identified on the basis of the
characteristic features that appear in the relevant NIR spectra, the origin and nature of
these spectra necessitate that such identification be performed with a chemometricsbased
approach. Accordingly, multivariate calibration models based on neural networks
and partial least squares regression (PLSR) have been developed to perform the
requisite analyses. Results of calibration and testing with a range of data are reported.
In order to facilitate operation in practical security screening, the development and
testing of a software-based lock-in amplifier is reported, as a mean to enhance the
signal-to-noise ratio (SNR) of the spectral data. It is shown that the amplifier can
process up to 40 wavelength channels in parallel, to extract the spectral data buried in
noise in each channel. Hence, with the SNR of the input signal set as low as -60 dB (by
introducing software-generated additive white noise in the spectra), adequate noise
suppression has been obtained, allowing the resulting spectral data to be used for
requisite chemical detection.
Finally, an integrated spectroscopic imaging application is developed to perform twodimensional
cross-sectional scans of chemical samples, carry out lock-in amplification
of the recorded intensity spectra, and plot the results of neural network-based chemical
detection in the form of intensity images colour-coded to depict the presence of the
pertinent chemicals at the scanned coordinates
This other salt
No full textBetrayal, bereavement, exile, belonging - these are the themes that resonate throughout This Other Salt. A writer torn between two loves looks for his lost words in the gap between memory, mourning and desire; a poet revenges herself on her faithless lover by turning their romance into a legend of biblical proportions; and a teenage boy's life uncannily begins to resemble the role he plays in a school operetta ...Combining satire, legend, poetry, history and memoir, the linked stories of This Other Salt reveal an author of uncommon talent at the height of his craft
Silicon slow-light-based photonic mixer for microwave-frequencyconversion applications
Get PDFThis paper was published in OPTICS LETTERS and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.37.001721. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law[EN] We describe and demonstrate experimentally a method for photonic mixing of microwave signals by using a silicon electro-optical Mach¿Zehnder modulator enhanced via slow-light propagation. Slow light with a group index of ~11, achieved in a one-dimensional periodic structure, is exploited to improve the upconversion performance of an input frequency signal from 1 to 10.25 GHz. A minimum transmission point is used to successfully demonstrate the upconversion with very low conversion losses of ~7¿¿dB and excellent quality of the received I/Q modulated QPSK signal with an optimum EVM of ~8%.Financial support from FP7-224312 HELIOS project and Generalitat Valenciana under PROMETEO-2010-087 R&D Excellency Program (NANOMET) are acknowledged. F. Y.Gardes, D. J. Thomson, and G. T. Reed are supported by funding received from the UK EPSRC funding body under the grant “UK Silicon Photonics.” The author A. M. Gutiérrez thanks D. Marpaung for his useful
help.Gutiérrez Campo, AM.; Brimont, ACJ.; Herrera Llorente, J.; Aamer, M.; Martí Sendra, J.; Thomson, DJ.; Gardes, FY.... (2012). Silicon slow-light-based photonic mixer for microwave-frequencyconversion applications. Optics Letters. 37(10):1721-1723. https://doi.org/10.1364/OL.37.001721S17211723371
NIR spectroscopy for personal screening
Get PDFThis work presents investigations into the use of the near-infrared (NIR) signals to interrogate, detect and image specific chemical compounds of interest in a security screening application, including when such compounds are hidden behind single layers of clothing fabric. In an initial set of experiments, the mechanisms governing the interaction of NIR signals with clothing fabrics and similar materials has been studied, in order to account for the influence of fabric layers when detecting hidden chemicals. Throughout the rest of the work, NIR spectroscopy has been used as a means to perform qualitative and quantitative analysis, in order to detect the presence of chemicals, and quantify the concentration in aqueous solution of liquids. It has been shown that, while the compounds can be identified on the basis of the characteristic features that appear in the relevant NIR spectra, the origin and nature of these spectra necessitate that such identification be performed with a chemometricsbased approach. Accordingly, multivariate calibration models based on neural networks and partial least squares regression (PLSR) have been developed to perform the requisite analyses. Results of calibration and testing with a range of data are reported. In order to facilitate operation in practical security screening, the development and testing of a software-based lock-in amplifier is reported, as a mean to enhance the signal-to-noise ratio (SNR) of the spectral data. It is shown that the amplifier can process up to 40 wavelength channels in parallel, to extract the spectral data buried in noise in each channel. Hence, with the SNR of the input signal set as low as -60 dB (by introducing software-generated additive white noise in the spectra), adequate noise suppression has been obtained, allowing the resulting spectral data to be used for requisite chemical detection. Finally, an integrated spectroscopic imaging application is developed to perform twodimensional cross-sectional scans of chemical samples, carry out lock-in amplification of the recorded intensity spectra, and plot the results of neural network-based chemical detection in the form of intensity images colour-coded to depict the presence of the pertinent chemicals at the scanned coordinates.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Analytical model for calculating the nonlinear distortion in silicon-based electro-optic Mach-Zehnder modulators
Get PDFIn this study, an analytical model for calculating the nonlinear harmonic/intermodulation distortion for RF signals in silicon-based electro-optic modulators is investigated by considering the nonlinearity on the effective index change curve with the operation point and the device structure simultaneously. Distortion expressions are obtained and theoretical results are presented showing that optimal modulator parameters can be found to linearize it. Moreover, the harmonic distortion of a 1 mm silicon-based asymmetric MZI is RF characterized and used to corroborate the theoretical results. Based on the present model, the nonlinear distortion in terms of bias voltage or operating wavelength is calculated and validated by comparing with the experimental data, showing a good agreement between measurements and theory. Analog photonic link quality parameter like carrier-to-distortion is one of the parameters that can be found with that model. Finally, the modulation depth is measured to assure that no over-modulation is produced
Slow-Light-Enhanced Silicon Optical Modulators Under Low-Drive-Voltage Operation
Get PDF[EN] The integration of nanophotonics components with advanced complementary metal-oxide-semiconductor (CMOS) electronics requires drive voltages as low as 1 V for enabling next-generation CMOS electrophotonics transceivers. Slow-light propagation has been recently demonstrated as an effective mechanism to enhance the modulation efficiency in free-carrier-based electrooptical silicon modulators. Here, we exploit the use of slow light to reduce the driving voltage of carrier-depletion-based Mach-Zehnder modulators. The slow-light phase shifter consists of a p-n junction positioned in the middle of a corrugated waveguide. A modulation efficiency as high as V pi L pi similar to 0: 6 V . cm is achieved, thus allowing data transmission rates up to 10 Gb/s with a 1.5-V-pp drive voltage and an insertion loss of similar to 12 dB. The influence of the drive voltage on the modulation speed as well as the variation of the insertion losses with a group index is also analyzed and discussed.© 2009-2012 IEEE.Manuscript received April 24, 2012; revised June 29, 2012; accepted July 2, 2012. Date of current version July 25, 2012. This work was supported by the European Commission under Project HELIOS (photonics electronics functional integration on CMOS), FP7224312, and by the TEC2008-06333 SINADEC and PROMETEO-2010-087 R&D Excellency Program (NANOMET). The work of F. Y. Gardes, D. J. Thomson, and G. T. Reed was supported by the UK Environmental and Physical Sciences Research Council funding body under the grant "UK Silicon Photonics." [Corresponding author: P. Sanchis (e-mail: [email protected]).Brimont, ACJ.; Gutiérrez Campo, AM.; Aamer, M.; Thomson, DJ.; Gardes, FY.; Fedeli, J.; Reed, GT.... (2012). Slow-Light-Enhanced Silicon Optical Modulators Under Low-Drive-Voltage Operation. IEEE Photonics Journal. 4(5):1306-1315. https://doi.org/10.1109/JPHOT.2012.2207884S130613154
Finding Systematical Transport Solution for Crushed Limestone on Example of AS Kunda Nordic Tsement
No full textPeamiseks probleemiks antud töös oli peagi avatava karjääri ja tehase vaheline süsteemne purustatud lubjakivi transpordilahenduse puudumine. Lisaks puudus hetkel tulevases karjääris infrastruktuur ning pole tehtud ühtegi kalkulatsiooni leidmaks süsteemset transpordilahendust. Käesolevas lõputöös leiti süsteemne transpordilahendus purustatud lubjakivi transportimiseks AS Kunda Nordic Tsemendi Toolse-Lääne karjäärist tehasesse. Töö käigus andis autor ülevaate ettevõtte hetkeolukorrast ja transpordi kasutusest, make-or-buy otsusest, võimalikest transpordilahendustest ja nende komponentidest, ning leidis süsteemseima transpordilahenduse. Vajalike andmete teada saamiseks tegi autor erinevate võtmeisikutega mittestruktureeritud intervjuud ning viis läbi vaatlusi. Intervjuude käigus kogus autor andmeid taristute ehituse, ehituse komponentide ja transpordi hindade kohta. Vaatluste käigus tutvus autor erinevate transpordivahendite töömehhanismiga ning mõõtis tootlikkuse arvutamise jaoks laadimise vahemaid ja kiiruseid. Arvutused koostas autor kopplaaduri, kallurautode, raudtee- ja konveiertranspordi kohta. Autor arvutas välja kopplaaduri tootlikkuse võttes aluseks 12 tunnilise töövahetuse, kopa suuruseks 5,2 kuupmeetrit ning laadimisdistantsiks 50 meetrit. Sellisel juhul on kopplaadur võimeline aastas laadima 1,04 miljonit tonni. Samuti arvutas autor välja sisseostetava teenuse ja oma kopplaaduri omamise hinnavahe kui kopp laeb aastas üks miljon tonni. Sisseostetava teenuse hinnaks kujunes 0,20 eurot/t, laaduri omamise hinnaks kujunes 0,13 eurot/t. Aastase toormevajaduse laadimise korral oma kopaga võidaks ettevõte 70000 eurot. Kallurauto tootlikkuse arvutustes selgus, et vaja läheb 7 veoühikut 12 tunnilise töövahetuse korral. Kallurauto omahinnaks kujunes 0,94 eurot/t ning sisseotsetava teenuse puhul 0,98 eurot/t. Aastase toormevajaduse transportimise korral oma kopplaaduriga ja ettevõtte masinapargiga võidaks aastas 40000 eurot. Konveiertranspordi ehituse maksumuseks kujunes 5 773167 eurot. Arvestades erinevaid hooldus-ja elektrikulusid ning võttes konveieri amortisatsiooni ajaks 30 aastat on ühe tonni transpordi hind karjäärist tehasesse 1,12 eurot/t. Raudtee ehituse hinnaks kujunes 990203 eurot. Raudteetranspordi hinnapakkumise alusel on ühe tonni hind karjäärist tehasesse 1,30 eurot/t. Siinkohal tuleb arvestada raudtee amortisatsiooni ajaks 30 aastat ning raudtee hoolduskulusid. Raudteetranspordi lõpphinnaks koos laadimisega kujunes 1,46 eurot/t. Võrdluse ja analüüsi käigus selgus, et kõige odavam variant on omada kallurautosid ning laadida neid masinaid ettevõtte oma kopplaaduriga. Küll aga autori arvates ei ole selline variant parim. Parimaks variandiks peab autor osta kallurautode teenust sisse ja neid laadida ettevõtte kopplaaduriga. Sellisel juhul oleksid ettevõtet puudutavad riskid maandatud ning ettevõte saab keskenduda oma põhitööle ehk tootmisele ja tootearendusele. Antud järelduste aluseks võttis autor 2015 aasta järsu turumuutuse kui toorme vajadus oli kõigest 500000 tuhat tonni aastas ning 2016 langes see arv veelgi. Sellises olukorras oleks oma autopark üledimensioneeritud ning jooksvad kulud tõuseksid märkimisväärselt seisva autopargi näol. Küll aga sisseostetava teenuse puhul on võimalik kiiresti reageerida turumuutusele, kuna transpordihind on pandud sõltuma toorme kogusest. Sellisel juhul makstakse ainult selle eest, mitu tonni on reaalselt karjäärist tehasesse transporditud.AS Kunda Nordic Tsement is a manufacturing company which main production is cement. For producing cement there are several raw materials needed. One of the raw materials is crushed limestone. At the moment blast limestone is mined from Aru-Lõuna quarry. Due to limestone reserve run out, there is a need for a new quarry. According to geological survey best location for mining limestone is Toolse-Lääne. In Toolse-Lääne quarry the limestone will be mined, loosened and crushed. After all these processes crushed limestone needs to be transported to the factory where it is used for producing cement. At the moment there haven’t been done any calculations for systemical transport solution. The aim of this paper is to find systemical transport solution to transport crushed limestone from quarry to factory. The author investigated different transporting ways and found that possible solutions are: railway transport, tipper truck transport and conveyor transport. To use railway transport there is a need to built two km of railway. To use conveyor mode there is a need to built full conveyor system which is ten km long. For tipper truck transport solution there is no need to built road because it will be built anyway to serve clients and workers. To find the most systemical solution, the author made calculation for each transport mode. Author made three price inquries to identify transport costs. Railway building costs 990203 euros and transport due to offer costs 1,30 euro/t. Final railtransport price is 1,46 euro/t. Conveyor solution building costs 5773167 euros. Final conveyor transport price is 1,12 euro/t. If company buys tipper truck service then price is 1,11 euro/t and if company owns their own tipper trucks then price is 1,07 eurot/t. The result showed that most optimized way is to own seven tipper trucks and one wheel loader. Allthough it is the cheapest way to transport, author doesn’t agree with this kind of result and provides other solution. Author suggestion is that the most reasonable solution is to buy tipper truck service and use companys own wheel loader. The differents between these two solution per year will be 40000 euros total, it is 3,6%. In that way company spreads it’s risks and can focus on producing and merchandising
Joint Optimization of Interference and Cost in Cognitive Radio Heterogeneous Network Using Fuzzy Logic Powered Ants
Get PDFThe advent of emerging wireless technologies has increased the demand of spectrum resources. On the other hand, present spectrum assignment is fixed and underutilized. Cognitive radio (CR) provides good solution to spectrum scarcity problem to accommodate new wireless applications. The network selection is an important mechanism in cognitive radio heterogeneous network (CRHN) to provide optimal Quality of Service (QoS) to both Primary Users (PUs) and Secondary Users (SUs). The aim of this work is to provide optimal QoS to SUs by appropriate network selection and channel assignment. The proposed FLACSA selects the best network while maximizing the data rate and minimizing the interference and cost simultaneously. Simulation results show the attractive performance of our proposed algorithm.</jats:p
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