299 research outputs found
Evaluation of ilmenite, manganese ore, LD slag and iron sand oxygen carriers for chemical looping gasification with microalgae
No full textMicroalgae could be a sustainable feedstock for production of liquid biofuels. However, as such fuels contain significant fractions of reactive ash species, it is necessary to deploy synthesis routes which can handle such “dirty” fuels. Chemical-looping gasification (CLG) has the potential to convert such feedstocks and generate a concentrated syngas stream, a common precursor for liquid fuel production. Suitable functional oxygen carriers are key for CLG, and herein we report our new work in fluidized-bed tests with four oxygen carriers, namely ilmenite, MnGBhne, LD slag and iron sand. These materials are economically viable natural ores or industrial by-products. The oxygen carrier is reduced to different oxidation degrees (0.2, 0.5, 1) at typical temperatures (850, 900, 950 °C) to define equal material states prior to the gasification. We found that the LD slag and iron sand had the highest gasification rate and fluidized well without agglomeration, thus they are selected as suitable oxygen carriers for the process. Several factors including catalysis, water splitting and water-gas shift are comprehensively discussed with regard to the outstanding performance of LD slag and iron sand. Calcium catalysis is deemed as a key reason for the fast gasification and a mechanism of this is proposed
Use of a high-entropy oxide as an oxygen carrier for chemical looping
No full text8 figures, 3 tables.-- Supplementary information available.One mixed oxide with 5 cations in equimolar proportions in the sublattice, to fulfil high-entropy oxide (HEO) criteria, has been developed and investigated as oxygen carrier for chemical looping combustion processes. As far as we know, nobody has explored this class of material for chemical looping combustion. Material is prepared by direct mixing of five metal oxides (CuO, Mn2O3, Fe2O3, TiO2, MgO), followed by calcination at 1000, 1100 and 1200 °C for 6 h in air. XRD characterization provides strong evidence that the synthesized oxygen carriers possess the hallmark properties of HEO, and SEM-EDX analysis shows an overall homogeneous metal distribution. Materials have one main cubic phase with the empirical formula MnCuMgFeTiO7, dominating under all conditions. One of the key objectives of this study is achieved, reduce chemical stress during redox cycles. Oxygen transfer capability is investigated by thermogravimetric analysis and batch fluidized bed reactor experiments for different fuels and atmospheres. Mass-based oxygen transport capacities for lattice oxygen and oxygen uncoupling are around 5.5 wt% and 1.1 wt%, respectively. This work opens up a new dimension for the future preparation of oxygen carriers for chemical looping processes, since the vast compositional space of HEO provides opportunities to tune both chemical and physical characteristics.This work was partiatially funded by the Swedish Research Council (2020–03487) and the Gobierno de Aragón – Dpto. de Ciencia, Universidad y Sociedad del Conocimiento - Project LMP166_21. I. Adánez-Rubio acknowledges for “Juan de la Cierva” Program (Grant IJC2019-038987-I funded by MCIN/AEI/10.13039/501100011033) and for the “José Castillejo” international mobility program for young researchers (CAS21/00200)Peer reviewe
On The Use of Nauta's Transconductor in Low-Frequency CMOS gm-C Bandpass Filters
No full textThis paper discusses the use of a transconductor, first proposed by Nauta for high frequency applications, in low frequency CMOS g(m) - C bandpass filters. The behavior of the transconductor is examined in detail, showing that the robust implementation of higher-order low-voltage filters is possible for center frequencies in the lower megahertz region. The experimental results are presented of the realization of two prototypes, a 0.6-mum CMOS 18th-order real bandpass filter and a 0.35-mum CMOS 7th-order complex (14th-order bandpass) filter, both with a center frequency of 3 MHz and a passband of 1 MHz. These filters comply with the specifications for the channel-select stage of the Bluetooth short-range radio receiver
A CMOS gm-C IF filter for Bluetooth
No full textAn 18th (4th+14th) order gm -C IF filter for the Bluetooth short-range radio, implemented in a 0.6 μm CMOS process, is presented. The filter bandwidth is 1 MHz, the center frequency fc is 3 MHz, the in-band group delay variation is 0.75 μs, and the stop-band attenuation at fc±1 MHz is at least 47 dB. The noise floor is 250 μVr.m.s. and the spurious free dynamic range is at least 58 dB for out-of-band signals, thus exceeding the Bluetooth requirements. Current consumption is 2.4 mA from a 2.5 V power suppl
Mosquitoes and tigers of the cultural mafia : A literary sociological study of literature criticism and master suppression techniques in a newspaper debate
No full textThe aim of this Master’s thesis is to examine how the literature criticism are in the Swedish media in the reception of the novel Mosquitoes and tigers from 2007 written by the Swedish author Maja Lundgren. A second aim is to examine how master suppression techniques have been used by the literature critics in the newspaper debate. This qualitative study is based upon a total of 52 articles and reviews from five big Swedish newspapers. The theoretical approach, literature criticism, mainly originates from the Swedish professor in Literature Science Tomas Forser and the literature scholar Gunnar Hansson. The theory of master suppression techniques founded by Berit Ås, Norwegian professor in Social Psychology, are used as an analytic tool. The method of analysis is textual, qualitative text analysis. The conclusion of this study shows that the literature criticism usually is divided in one ethical and one aesthetic part. The aesthetic criticism includes the book not being entertaining or well written or too long, and also that the form is a problem for the readers who do not know if the genre is fact or fiction. The criticism about the form issue is also ethical while the author can be vague about the truth. The ethical criticism also consists from the author using name of authentic people. Another conclusion of this study shows that mainly three of the master suppression techniques are visible in the debate: “making invisible”, “ridicule” and “heap blame/put to shame”. By merging various articles, it was possible to interpret the master suppression technique “double bind”. There was no sign of “withhold information”. This study also shows that the writer Maja Lundgren uses master suppression techniques herself.Program: Bibliotekari
Right on track? Performance of satellite telemetry in terrestrial wildlife research
No full textSatellite telemetry is an increasingly utilized technology in wildlife research, and current devices can track individual animal movements at unprecedented spatial and temporal resolutions. However, as we enter the golden age of satellite telemetry, we need an in-depth understanding of the main technological, species-specific and environmental factors that determine the success and failure of satellite tracking devices across species and habitats. Here, we assess the relative influence of such factors on the ability of satellite telemetry units to provide the expected amount and quality of data by analyzing data from over 3,000 devices deployed on 62 terrestrial species in 167 projects worldwide. We evaluate the success rate in obtaining GPS fixes as well as in transferring these fixes to the user and we evaluate failure rates. Average fix success and data transfer rates were high and were generally better predicted by species and unit characteristics, while environmental characteristics influenced the variability of performance. However, 48% of the unit deployments ended prematurely, half of them due to technical failure. Nonetheless, this study shows that the performance of satellite telemetry applications has shown improvements over time, and based on our findings, we provide further recommendations for both users and manufacturers
Integroituja CMOS-piirejä lasertutkan lähetin-vastaanottimiin
No full textAbstractThe main aim of this work was to design CMOS receiver channels for the integrated receiver chip of a pulsed time-of-flight (TOF) laser rangefinder. The chip includes both the receiver channel and the time-to-digital converter (TDC) in a single die, thus increasing the level of integration of the system, with the corresponding advantages of a cheaper price and lower power consumption, for example. Receiver channels with both linear and leading edge timing discriminator schemes were investigated. In general the receiver channel consists of a preamplifier, a postamplifier and a timing comparator. Since a large systematic timing error may occur due to high variation in the amplitude of the received echo, a leading edge timing discriminator scheme with time domain walk error compensation is proposed here, making use of the TDC already available in the chip to measure the slew rate of the pulse and using that information to evaluate the timing error. This compensation scheme benefits from the fact that compensation can be continued even though the signal is clipped in the amplitude domain, because the slew rate continues to increase even then. The receiver channel with leading edge detection and time domain walk error compensation achieved a compensated timing walk error of ±4.5 mm within a dynamic range of more than 1:10000. The standard deviation in single shot precision was less than 25 mm with an SNR of more than 20. The usability of the receiver channel in pulsed TOF laser rangefinders was verified by making actual time-of-flight measurements on a calibrated measurement track. The linearity of the receiver chip was better than ±5 mm in a measurement range from 3 m to 21 m, with the dynamic range of the receiver channel reaching more than 1:2000. An integrated CMOS laser diode pulser was also demonstrated to prove its functionality for generating ampere-scale peak current pulses through a low ohmic load and a laser diode. The CMOS pulser achieved a peak current pulse with the amplitude of ~1 A, an optical pulse width of ~2.5 ns and a rise time of ~1 ns with a 5 V power supply. TiivistelmäTyön ensisijaisena tavoitteena oli suunnitella CMOS-vastaanottimia valopulssin kulkuajan mittaukseen perustuvan lasertutkan integroituun vastaanotinpiiriin. Vastaanotinpiiri sisältää sekä vastaanotinkanavan että aika-digitaalimuuntimen yhdellä integroidulla sirulla. Tällöin systeemin integrointiastetta saadaan kasvatettua, mikä merkitsee esimerkiksi halvempaa hintaa ja pienempää tehon kulutusta. Työssä on tutkittu vastaanotinkanavia, jotka käyttävät joko lineaariseen ilmaisuun tai etureunailmaisuun perustuvaa ajoitusilmaisutekniikkaa. Yleisesti vastaanotinkanava sisältää esivahvistimen, jälkivahvistimen ja ajoituskomparaattorin. Vastaanotetun signaalin tason voimakas vaihtelu saattaa aiheuttaa suuren systemaattisen virheen etureunailmaisuun perustuvassa ajoitusilmaisussa. Tässä työssä on esitetty etureunailmaisua käyttävä ajoitusilmaisin, jossa syntyvää ajoitusvirhettä voidaan korjata mittaamalla pulssin nousunopeutta aika-digitaalimuuntimella, joka on integroitu samalle sirulle. Aikatasossa tapahtuvan virheenkorjauksen etuna on mahdollisuus jatkaa virheenkorjausta amplituditasossa tapahtuvan signaalin leikkautumisen jälkeenkin, koska signaalin nousunopeus kasvaa leikkaantumisesta huolimatta. Etureunailmaisua käyttävällä vastaanotinkanavalla, jossa ajoitusvirhettä korjattiin pulssin nousunopeutta mittaamalla, saavutettiin ±4,5 mm ajoitusvirhe 1:10000 dynaamisella alueella. Kertamittaustarkkuuden keskihajonta oli vähemmän kuin 25 mm, kun signaalikohinasuhde oli enemmän kuin 20. Vastaanotinkanavan käytettävyys osana lasertutkaa todettiin tekemällä tutkamittauksia kalibroidulla mittaradalla. Mittauksissa saavutettu lineaarisuus oli ±5 mm mittausalueen vaihdellessa 3 metristä 21 metriin ja signaalin dynamiikan ollessa enemmän kuin 1:2000. Lisäksi työssä esitellään integroitu CMOS-pulssitin, joka pystyy tuottamaan ampeeri-luokan virtapulsseja laserdiodiin. CMOS-pulssittimella voitiin tuottaa 5 V käyttöjännitteellä ~1 A virtapulsseja optisen pulssin leveyden ja nousuajan ollessa ~2,5 ns ja ~1 ns. Academic dissertation to be presented with the assent of the Faculty of Technology of the University of Oulu for public defence in OP-sali (Auditorium L10), Linnanmaa, on 3 November 2011, at 12 noonAbstract
The main aim of this work was to design CMOS receiver channels for the integrated receiver chip of a pulsed time-of-flight (TOF) laser rangefinder. The chip includes both the receiver channel and the time-to-digital converter (TDC) in a single die, thus increasing the level of integration of the system, with the corresponding advantages of a cheaper price and lower power consumption, for example.
Receiver channels with both linear and leading edge timing discriminator schemes were investigated. In general the receiver channel consists of a preamplifier, a postamplifier and a timing comparator. Since a large systematic timing error may occur due to high variation in the amplitude of the received echo, a leading edge timing discriminator scheme with time domain walk error compensation is proposed here, making use of the TDC already available in the chip to measure the slew rate of the pulse and using that information to evaluate the timing error. This compensation scheme benefits from the fact that compensation can be continued even though the signal is clipped in the amplitude domain, because the slew rate continues to increase even then.
The receiver channel with leading edge detection and time domain walk error compensation achieved a compensated timing walk error of ±4.5 mm within a dynamic range of more than 1:10000. The standard deviation in single shot precision was less than 25 mm with an SNR of more than 20. The usability of the receiver channel in pulsed TOF laser rangefinders was verified by making actual time-of-flight measurements on a calibrated measurement track. The linearity of the receiver chip was better than ±5 mm in a measurement range from 3 m to 21 m, with the dynamic range of the receiver channel reaching more than 1:2000.
An integrated CMOS laser diode pulser was also demonstrated to prove its functionality for generating ampere-scale peak current pulses through a low ohmic load and a laser diode. The CMOS pulser achieved a peak current pulse with the amplitude of ~1 A, an optical pulse width of ~2.5 ns and a rise time of ~1 ns with a 5 V power supply.Tiivistelmä
Työn ensisijaisena tavoitteena oli suunnitella CMOS-vastaanottimia valopulssin kulkuajan mittaukseen perustuvan lasertutkan integroituun vastaanotinpiiriin. Vastaanotinpiiri sisältää sekä vastaanotinkanavan että aika-digitaalimuuntimen yhdellä integroidulla sirulla. Tällöin systeemin integrointiastetta saadaan kasvatettua, mikä merkitsee esimerkiksi halvempaa hintaa ja pienempää tehon kulutusta.
Työssä on tutkittu vastaanotinkanavia, jotka käyttävät joko lineaariseen ilmaisuun tai etureunailmaisuun perustuvaa ajoitusilmaisutekniikkaa. Yleisesti vastaanotinkanava sisältää esivahvistimen, jälkivahvistimen ja ajoituskomparaattorin. Vastaanotetun signaalin tason voimakas vaihtelu saattaa aiheuttaa suuren systemaattisen virheen etureunailmaisuun perustuvassa ajoitusilmaisussa. Tässä työssä on esitetty etureunailmaisua käyttävä ajoitusilmaisin, jossa syntyvää ajoitusvirhettä voidaan korjata mittaamalla pulssin nousunopeutta aika-digitaalimuuntimella, joka on integroitu samalle sirulle. Aikatasossa tapahtuvan virheenkorjauksen etuna on mahdollisuus jatkaa virheenkorjausta amplituditasossa tapahtuvan signaalin leikkautumisen jälkeenkin, koska signaalin nousunopeus kasvaa leikkaantumisesta huolimatta.
Etureunailmaisua käyttävällä vastaanotinkanavalla, jossa ajoitusvirhettä korjattiin pulssin nousunopeutta mittaamalla, saavutettiin ±4,5 mm ajoitusvirhe 1:10000 dynaamisella alueella. Kertamittaustarkkuuden keskihajonta oli vähemmän kuin 25 mm, kun signaalikohinasuhde oli enemmän kuin 20. Vastaanotinkanavan käytettävyys osana lasertutkaa todettiin tekemällä tutkamittauksia kalibroidulla mittaradalla. Mittauksissa saavutettu lineaarisuus oli ±5 mm mittausalueen vaihdellessa 3 metristä 21 metriin ja signaalin dynamiikan ollessa enemmän kuin 1:2000.
Lisäksi työssä esitellään integroitu CMOS-pulssitin, joka pystyy tuottamaan ampeeri-luokan virtapulsseja laserdiodiin. CMOS-pulssittimella voitiin tuottaa 5 V käyttöjännitteellä ~1 A virtapulsseja optisen pulssin leveyden ja nousuajan ollessa ~2,5 ns ja ~1 ns
Oxy-polishing of gas from chemical looping combustion: Fuel-nitrogen transformation and model-aided gas purity optimization
No full text17 figures, 7 tables.Chemical looping combustion (CLC) is a carbon capture technology for heat, power and hydrogen production. This work focuses on fuel-nitrogen transformation in fuel reactor and its further conversion in oxy-polishing step of CLC system. A 100 kW CLC pilot equipped with an oxy-polishing chamber (called POC) was used to perform experiment study and a zero-dimensional reactor model combining elementary reaction kinetics was developed and used for oxy-polishing simulation and reaction path analyses. An ilmenite and a manganese ore called Sinaus were used as oxygen carriers, and a coal and a coal-biomass mixture are the fuels in the CLC tests. It was found that in the fuel reactor, part of the fuel-nitrogen was converted to NO and the rest remained as NH3 which was then oxidized to NO in the POC. The concentrations of HCN and NO2 were negligible in the fuel reactor and POC. According to the simulation, when the oxygen excess is too low it is difficult to reach 1150–1200 °C which are temperatures needed for oxidizing the unconverted fuel gases. In a reference case, a high conversion was reached when the overall oxygen ratio was above 1.03 and temperature above 925 °C. With a fuel reactor temperature of 950 °C, the oxygen demand needed could be up to around 8 %. Based on the model, optimal geometrical designs of the POC were proposed. With a gas residence time of 3 s in the POC, it was possible to decrease the content of impurities (O2, H2, CO, NO, CH4) to 3.3 %.This work was supported by the Swedish Research Council, project Nitrogen Chemistry in Chemical-Looping Combustion and Oxygen-Carrier Aided Combustion (2016-05487) and the Swedish Energy Agency, as part of the projects OxyCar-FBC, conducted within the framework of ERA-NET Bioenergy, (P43936-1) and the project Kemcyklisk förbränning av biomassa och avfall (51585-1).Peer reviewe
Sleep, physical activity & schoolperformance : is there a connection?
No full textSyfte: Syftet med denna studie var att visa om faktorer som sömn- och motionsvanor samvarierar med gymnasieelevers studieresultat. Hypotesen vi arbetat utifrån var att en god balans mellan sömn och motion har en bättre inverkan på studieresultaten än vad ett obalanserat förhållande har. De tre frågeställningarna vi arbetade efter var Finns det något samband mellan de antal timmar per natt under en skolvecka som en gymnasieelev sover och dennes studieresultat? Ser sambandet sömn-studieresultat samt träning-studieresultat annorlunda ut mellan de praktiska och studieförberedande programmen? Finns det något samband mellan den mängd lätt motion som gymnasieelever företar sig och deras studieresultat? Metod Vi har valt att genomföra en enkätundersökning. Enkäten innehöll frågor rörande elevers sömn-, motions- och studievanor samt en fråga kring deras betyg i vissa av kärnämnena. Antalet enkäter uppgick till 149 stycken. Enkätundersökningen genomfördes på en gymnasieskola i en mellanstor stad i Svealand. Resultat: Studien påvisar ett svagt samband mellan sömn, motion och studieprestation. Störst samband finns på de teoretiska programmen. Slutsats: Våra resultat stöder till viss del tidigare forskning inom området på så vis att sömn har en inverkan på studieresultatet, detsamma gäller för motion. Våra samband är dock inte lika starka som hos vissa tidigare studier.Aim: The aim of this study has been to show if factors like sleep and physical activity interacts with schoolperformance. The hypothes we have presupposed was that a good relation in balance between sleep and physical activity have a better influence on schoolperformance compared with an unbalanced relation. Our three main questions were: Is there a connection between the number of hours of sleep a highschoolstudent gets during a schoolweek and the students schoolperformance? Is the relation sleep-schoolperformance and physical activity-schoolperformance the same between theoretical and practical programs? Is there any connection between the amount of moderate physical activity for a highschoolstudent and his or hers schoolperformance? Method We have choosen to do a questionnairestudy. The questionnaire contained questions regarding the pupils sleep-, physical activity- and study habits and their grades in certain main subjects. The number of questionnaires was 149. The questionnairestudy was done at a highschool i a medium large city in Svealand, Sweden. Results: The study shows a weak connection between sleep, physical activity and schoolperformance. The strongest connection was found among the students at the theoretical programs. Conclusions: Our findings do to some extent support previous research in this area, in the way sleep and physical activity influence on schoolperformance. Our findings did not show as strong connections as previous studies have
A 100MHz CMOS gm-C bandpass filter
No full texthas a center frequency of 100MHz and a passband of 10MHz. The filter architecture is insensitive to parasitic capacitances, which allows for the implementation of bandpass filters over a very large frequency range. Intrinsic parasitic Q-enhancement techniques have been used, thus, obviating the need for any additional Q-tuning circuitry. The presented filter has small implementation losses with characteristics suitable for a first IF filter of a wideband system like a WLAN (e.g. DS-CDMA 802.11)
- …
