11 |
Rädda Korset : En kvalitativ studie av Röda Korsets uttalanden under af Donner-skandalenSjölund, Danielle January 2015 (has links)
Kommunikationschefen på Röda Korset, Johan af Donner, förskingrade åtta miljoner kronor från både Röda Korset och Cancerfonden. Detta nådde till slut de svenska tidningarna som skrev om skandalen, främst under år 2009 och 2010. Den här uppsatsen undersöker hur Röda Korsets representanter kommunicerade om skandalen i svenska tidningar samt hur kommunikationen förändrades över tiden. Uttalandena i tidningarna analyseras med hjälp av teorier om image-reparation och kriskommunikation, för att få reda på vilka strategier som Röda Korset använde sig av. Uppsatsen undersöker även hur förtroendet – i form av medlemsantal och verksamhetsintäkter – påverkades av skandalen, genom en analys av Röda Korsets årsredovisningar och med teorier om förtroende och skandaler. Resultatet visar att den strategi som Röda Korset använde sig mest av var att framhäva organisationens goda sidor, vilket gjordes i 20 uttalanden. Kommunikationen förändrades lite över tiden, då förnekandet av handlingen skedde i början av perioden och skuldförflyttandet mot mitten och slutet. Strategin där organisationen erkänner sitt misstag och ber om förlåtelse skedde nästan uteslutande i slutet av undersökningsperioden. Andra strategier har varit representerade över hela perioden och inte visat på någon förändring över tiden. Medlemsantalet har sjunkit varje år från 2009 fram till 2014, och verksamhetsintäkterna sjönk från 2010 fram till 2013 då en liten ökning skedde. Intäkterna sjönk ytterligare året därpå. Enligt teorierna kan man konstatera att af Donner-skandalen var en moralisk förtroendekris samt en medieskandal. Det går inte att med säkerhet säga att Röda Korset fick ett minskat förtroende efter skandalen, men medlemstappet kan ha varit en konsekvens av att Röda Korset använde sig av ”fel” strategier vid kommunicerandet av skandalen.
|
12 |
Performance analyses for large-scale antennas equipped two-way AF relaying and heterogeneous networksDai, Yongyu 14 September 2016 (has links)
In this dissertation, performance analyses for large-scale antennas equipped two-way amplify-and-forward (AF) relaying and heterogeneous network (HetNet) are carried out. Energy-efficiency oriented design becomes more important for the next generation of wireless systems, which motivates us to study the strong candidates, such as massive multiple-input multiple-output (MIMO) combined with cooperative relaying and HetNet. Based on the achievable rate analyses for both massive MIMO two-way AF relaying, effective power allocation schemes are presented to further improve system performance. Focusing on the MIMO downlinks in the HetNet, mean square error (MSE) based precoding schemes are designed and employed by the macro base station (BS) and the small cell (SC) nodes. Considering a HetNet where both macro BS and SC nodes are equipped with large-scale antenna arrays, the capacity lower bounds are derived, followed by the proposed user scheduling algorithms.
The work on multi-pair two-way AF relaying with linear processing considers a system where multiple sources exchange information via a relay equipped with massive antennas. Given that channel estimation is non-ideal, and that the relay employs either maximum-ratio combining/maximum-ratio transmission (MRC/MRT) or zero-forcing reception/zero-forcing transmission (ZFR/ZFT) beamforming, we derive two corresponding closed-form lower bound expressions for the ergodic achievable rate of each pair sources. The closed-form expressions enable us to design an optimal power allocation (OPA) scheme that maximizes the sum spectral efficiency under certain practical constraints. As the antenna array size tends to infinity and the signal to noise ratios become very large, asymptotically optimal power allocation schemes in simple closed-form are derived. The capacity lower bounds are verified to be accurate predictors of the system performance by simulations, and the proposed OPA outperforms equal power allocation (EPA). It is also found that in the asymptotic regime, when MRC/MRT is used at the relay and the link end-to-end large-scale fading factors among all pairs are equal, the optimal power allocated to a user is inverse to the large-scale fading factor of the channel from the user to the relay, while OPA approaches EPA when ZFR/ZFT is adopted.
The work on the MSE-based precoding design for MIMO downlinks investigates a HetNet system consisting of a macro tier overlaid with a second tier of SCs. First, a new sum-MSE of all users based minimization problem is proposed aiming to design a set of macro cell (MC) and SC transmit precoding matrices or vectors. To solve it, two different algorithms are presented. One is via a relaxed-constraints based alternating optimization (RAO) realized by efficient alternating optimization and relaxing non-convex constraints to convex ones. The other is via an unconstrained alternating optimization with normalization (UAON) implemented by introducing the constraints into the iterations with the normalization operation. Second, a separate MSE minimization based two-level precoder is proposed by considering the signal and interference terms corresponding to the macro tier and the individual SCs separately. Furthermore, robust precoders are designed correspondingly with estimated imperfect channel. Simulation results show that the sum-MSE based RAO algorithm provides the best MSE performance among the proposed schemes under a number of system configurations. When the number of antennas at the macro-BS is sufficiently large relative to the number of MUEs, the MSE of the separate MSE-based precoding is found to approach those of RAO and UAON. Together, this thesis provides a suite of three new precoding techniques that is expected to meet the need in a broad range of HetNet environments with balance between performance and complexity.
The work on a large-scale HetNet studies the performance for MIMO downlink systems where both macro BS and SC nodes are equipped with large-scale antenna arrays. Suppose that the large-scale antenna arrays at both macro BS and SC nodes employ MRT or ZFT precoding, and transmit data streams to the served users simultaneously. A new pilot reuse pattern among small cells is proposed for channel estimation. Taking into account imperfect CSI, lower capacity bounds for MRT and ZFT are derived, respectively, in closed-form expressions involving only statistical CSI. Then asymptotic analyses for massive arrays are presented, from which we obtain the optimal antenna number ratio between BS and SCs under specific power scaling laws. Subsequently, two user scheduling algorithms, that is, greedy scheduling algorithm and asymptotical scheduling algorithm (ASA), are proposed based on the derived capacity lower bounds and asymptotic analyses, respectively. ASA is demonstrated to be a near optimal user scheduling scheme in the asymptotic regime and has low complexity. Finally, the derived closed-form achievable rate expressions are verified to be accurate predictors of the system performance by Monte-Carlo simulations. Numerical results demonstrate the effectiveness of the asymptotic analysis and the proposed user scheduling schemes. / Graduate / 0544 / 0984
|
13 |
Outsourcingavtal : Avtalsinnehåll utifrån praktiska och kommersiella övervägandenaf Sandeberg, Edward January 2013 (has links)
Denna uppsats syftar till att utreda, precisera och analysera innehållet i den förhållandevis okända kontraktstypen outsourcingavtal. Det faktum att outsourcing idag är en vanligt förekommande transaktion gör det både möjligt och angeläget att fånga de gemensamma dragen i outsourcingavtal. Undersökningar visar också att långt ifrån alla som begagnar sig av outsourcing är nöjda med det avtal som reglerar deras affär. Den rättsvetenskapliga ansatsen är därför att belysa denna avtalstyp på samma sätt som mer konventionella avtalstyper, som exempelvis köpavtal, entreprenadavtal och hyresavtal men också mer moderna avtalstyper som franchising och leasing, har behandlats inom doktrinen.
|
14 |
Distributed Beamforming with Finite-bit Feedback in Time-Varying Cooperative NetworksWang, Yan- Siang 30 August 2010 (has links)
In the thesis, we investigate transmit beamforming strategies in a wireless cooperative network consisting of one source, one destination and multi relays that adopt amplify-and-forward (AF). In our scheme, small amount of information feedback from the destination, each relays perturbs individually based beamforming coefficient. Perturbation-based beamforming have been proposed in [16], where the authors assume that the channel is time-invariant, and every relay node can not acquire channel state information (CSI) after receiving pilot sequence signals, the relays multiply the pilot sequence with two perturbed beamforming vectors, and forward
two weighted training sequence to destination. At the destination, the signal to noise ratio (SNR) of two received training sequence are evaluated and compared. Finally, the destination compare with SNRs. To indicate the result of compared SNRs,
destination feedback one-bit message to inform relays the comparison results, and then relays update beamforming vector based on one-bit message. After several iteration, the beamforming vector will approach the optimum one. However, in time-varying environment, the updating rata of beamforming vector in the method with one-bit feedback may be more slowly than rate of channel variation. The contribution of this thesis is to propose transmit beamforming scheme with two-bit or finite-bit feedback to accommodate to the time-varying environment. In our proposed scheme, the destination linearly combines two received sequence corresponding to two different beamforming vectors with various weighting factors. After evaluating and comparing the SNRs of combined signals, the destination notifies the optimum linear combining factors using a multi-bit feedback message. Based on the feedback message, relays can update the beamforming vector correspondingly. In chapter five, it shows through computer simulations that our proposed scheme can raise average SNR and reduce bit error rate effectively.
|
15 |
Membrane based separation of nitrogen, tetrafluoromethane and hexafluoropropylene / Bissett, H.Bissett, Hertzog January 2012 (has links)
Pure fluorocarbon gases can be sold for up to 30 USD/kg, if they were manufactured
locally. Due to the absence of local demand, South Africa at present has less than
0.3 % of the fluorochemical market and most fluoro–products used in the South African
industry are currently imported. The depolymerisation of waste polytetrafluoroethylene
(PTFE or Teflon) filters in a nitrogen plasma reactor results in the mixture of gases
which includes N2, CF4 and C3F6. An existing challenge entails the separation of these
gases, which is currently attained by an energy intensive cryogenic distillation process.
Both the small energy requirements as well as the small process streams required,
make a membrane separation an ideal alternative to the current distillation process.
Based on our research groups existing expertise in the field of zeolite membranes, it
was decided to investigate the separation capability of zeolite (MFI, NaA, NaY, and
hydroxysodalite) coated tubular ceramic membranes for the separation of the above
mentioned gases. The separation study was subdivided into adsorption studies as well
as single and binary component studies.
CxFy gas adsorption on MFI zeolites. Tetrafluoromethane (CF4) and
hexafluoropropylene (C3F6) were adsorbed on zeolite ZSM–5 and silicalite–1 to help
explain permeation results through zeolite membranes. According to the obtained data,
the separation of CF4 and C3F6 would be possible using adsorption differences. The
highest ideal selectivities (~ 15) were observed at higher temperatures (373 K). While
the CF4 adsorption data did not fit any isotherm, the heat of adsorption for C3F6
adsorbed on ZSM–5 and silicalite–1 was calculated as –17 and –33 kJ/mol respectively.
Single gas permeation. A composite ceramic membrane consisting of a ceramic
support structure, a MFI intermediate zeolite layer and a Teflon AF 2400 top layer was
developed for the separation of N2, CF4 and C3F6. The adsorption properties of the
Teflon AF 2400 sealing layer was investigated. A theoretical selectivity, in terms of the
molar amount of gas adsorbed, of 26 in favour of the C3F6 vs CF4 was calculated, while
the N2 adsorption remained below the detection limit of the instrument. While the ideal
N2/CF4 and N2/C3F6 selectivities for the MFI coated support were either near or below
Knudsen, it was 5 and 8 respectively for the Teflon coated support. Ideal selectivities
improved to 86 and 71 for N2/CF4 and N2/C3F6 when using the composite ceramic membrane, while CF4/C3F6 ideal selectivities ranged from 0.9 to 2, with C3F6 permeating
faster though the composite ceramic membrane.
Zeolite based membrane separation. Inorganic membranes (?–alumina support, NaA,
NaY, hydroxysodalite, MFI) and composite membranes (Teflon layered ceramic and
composite ceramic membrane) were synthesized and characterized using the
non–condensable gases N2, CF4 and C3F6. For the inorganic membranes either near or
below Knudsen selectivities were obtained during single gas studies, while higher
selectivities were obtained for the composite membranes. Subsequently, the MFI,
hydroxysodalite and both composite membranes were chosen for binary mixture
separation studies. The membranes exhibited binary mixture permeances in the order
Teflon layered ceramic > hydroxysodalite > MFI > composite ceramic, which was
comparable to the single gas permeation results. The highest separation for N2/CF4 (4)
and N2/C3F6 (2.4) was obtained with the composite ceramic membrane indicating that
the Teflon layer was effective in sealing non–zeolitic pore in the intermediate zeolite
layer.
The aim of this project was met successfully by investigating a method of fluorocarbon
gas separation by zeolite based membranes using various inorganic and composite
membranes with single and binary mixtures. / Thesis (Ph.D. (Chemistry))--North-West University, Potchefstroom Campus, 2012.
|
16 |
Membrane based separation of nitrogen, tetrafluoromethane and hexafluoropropylene / Bissett, H.Bissett, Hertzog January 2012 (has links)
Pure fluorocarbon gases can be sold for up to 30 USD/kg, if they were manufactured
locally. Due to the absence of local demand, South Africa at present has less than
0.3 % of the fluorochemical market and most fluoro–products used in the South African
industry are currently imported. The depolymerisation of waste polytetrafluoroethylene
(PTFE or Teflon) filters in a nitrogen plasma reactor results in the mixture of gases
which includes N2, CF4 and C3F6. An existing challenge entails the separation of these
gases, which is currently attained by an energy intensive cryogenic distillation process.
Both the small energy requirements as well as the small process streams required,
make a membrane separation an ideal alternative to the current distillation process.
Based on our research groups existing expertise in the field of zeolite membranes, it
was decided to investigate the separation capability of zeolite (MFI, NaA, NaY, and
hydroxysodalite) coated tubular ceramic membranes for the separation of the above
mentioned gases. The separation study was subdivided into adsorption studies as well
as single and binary component studies.
CxFy gas adsorption on MFI zeolites. Tetrafluoromethane (CF4) and
hexafluoropropylene (C3F6) were adsorbed on zeolite ZSM–5 and silicalite–1 to help
explain permeation results through zeolite membranes. According to the obtained data,
the separation of CF4 and C3F6 would be possible using adsorption differences. The
highest ideal selectivities (~ 15) were observed at higher temperatures (373 K). While
the CF4 adsorption data did not fit any isotherm, the heat of adsorption for C3F6
adsorbed on ZSM–5 and silicalite–1 was calculated as –17 and –33 kJ/mol respectively.
Single gas permeation. A composite ceramic membrane consisting of a ceramic
support structure, a MFI intermediate zeolite layer and a Teflon AF 2400 top layer was
developed for the separation of N2, CF4 and C3F6. The adsorption properties of the
Teflon AF 2400 sealing layer was investigated. A theoretical selectivity, in terms of the
molar amount of gas adsorbed, of 26 in favour of the C3F6 vs CF4 was calculated, while
the N2 adsorption remained below the detection limit of the instrument. While the ideal
N2/CF4 and N2/C3F6 selectivities for the MFI coated support were either near or below
Knudsen, it was 5 and 8 respectively for the Teflon coated support. Ideal selectivities
improved to 86 and 71 for N2/CF4 and N2/C3F6 when using the composite ceramic membrane, while CF4/C3F6 ideal selectivities ranged from 0.9 to 2, with C3F6 permeating
faster though the composite ceramic membrane.
Zeolite based membrane separation. Inorganic membranes (?–alumina support, NaA,
NaY, hydroxysodalite, MFI) and composite membranes (Teflon layered ceramic and
composite ceramic membrane) were synthesized and characterized using the
non–condensable gases N2, CF4 and C3F6. For the inorganic membranes either near or
below Knudsen selectivities were obtained during single gas studies, while higher
selectivities were obtained for the composite membranes. Subsequently, the MFI,
hydroxysodalite and both composite membranes were chosen for binary mixture
separation studies. The membranes exhibited binary mixture permeances in the order
Teflon layered ceramic > hydroxysodalite > MFI > composite ceramic, which was
comparable to the single gas permeation results. The highest separation for N2/CF4 (4)
and N2/C3F6 (2.4) was obtained with the composite ceramic membrane indicating that
the Teflon layer was effective in sealing non–zeolitic pore in the intermediate zeolite
layer.
The aim of this project was met successfully by investigating a method of fluorocarbon
gas separation by zeolite based membranes using various inorganic and composite
membranes with single and binary mixtures. / Thesis (Ph.D. (Chemistry))--North-West University, Potchefstroom Campus, 2012.
|
17 |
Dalin--Botin--Lagerbring historieforskning och historieskrivning i Sverige 1747-1787 /Eriksson, Nils, January 1973 (has links)
Thesis--Gothenburg. / Summary in French. Includes bibliographical references (leaves 234-245) and index.
|
18 |
Outage Probability Analysis of Full-Duplex Amplify-and-Forward MIMO Relay SystemsJanuary 2018 (has links)
abstract: Multiple-input multiple-output systems have gained focus in the last decade due to the benefits they provide in enhancing the quality of communications. On the other hand, full-duplex communication has attracted remarkable attention due to its ability to improve the spectral efficiency compared to the existing half-duplex systems. Using full-duplex communications on MIMO co-operative networks can provide us solutions that can completely outperform existing systems with simultaneous transmission and reception at high data rates.
This thesis considers a full-duplex MIMO relay which amplifies and forwards the received signals, between a source and a destination that do not a have line of sight. Full-duplex mode raises the problem of self-interference. Though all the links in the system undergo frequency flat fading, the end-to-end effective channel is frequency selective. This is due to the imperfect cancellation of the self-interference at the relay and this residual self-interference acts as intersymbol interference at the destination which is treated by equalization. This also leads to complications in form of recursive equations to determine the input-output relationship of the system. This also leads to complications in the form of recursive equations to determine the input-output relationship of the system.
To overcome this, a signal flow graph approach using Mason's gain formula is proposed, where the effective channel is analyzed with keen notice to every loop and path the signal traverses. This gives a clear understanding and awareness about the orders of the polynomials involved in the transfer function, from which desired conclusions can be drawn. But the complexity of Mason's gain formula increases with the number of antennas at relay which can be overcome by the proposed linear algebraic method. Input-output relationship derived using simple concepts of linear algebra can be generalized to any number of antennas and the computation complexity is comparatively very low.
For a full-duplex amplify-and-forward MIMO relay system, assuming equalization at the destination, new mechanisms have been implemented at the relay that can compensate the effect of residual self-interference namely equal-gain transmission and antenna selection. Though equal-gain transmission does not perform better than the maximal ratio transmission, a trade-off can be made between performance and implementation complexity. Using the proposed antenna selection strategy, one pair of transmit-receive antennas at the relay is selected based on four selection criteria discussed. Outage probability analysis is performed for all the strategies presented and detailed comparison has been established. Considering minimum mean-squared error decision feedback equalizer at the destination, a bound on the outage probability has been obtained for the antenna selection case and is used for comparisons. A cross-over point is observed while comparing the outage probabilities of equal-gain transmission and antenna selection techniques, as the signal-to-noise ratio increases and from that point antenna selection outperforms equal-gain transmission and this is explained by the fact of reduced residual self-interference in antenna selection method. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018
|
19 |
PREPARACIÓN DE ZEOLITAS DE PORO PEQUEÑO CON CONTROL DE SUS PROPIEDADES FÍSICO-QUÍMICAS PARA SU APLICACIÓN EN CATÁLISISMartín García, Nuria 15 January 2018 (has links)
La presente tesis doctoral se centra en la preparación de zeolitas de poro pequeño (3.5-4 Å), en concreto, aquellas cuya estructura presenta además cavidades grandes. Este tipo de materiales ha despertado un enorme interés en los últimos años debido al potencial que presentan como catalizadores en procesos de relevancia industrial y medioambiental, tales como el proceso de transformación de metanol a olefinas (MTO) o la reducción catalítica selectiva (RCS) de NOx.
Por ello, existe un interés creciente en la preparación de nuevas estructuras de poro pequeño y en la mejora de las propiedades físico-químicas o de los métodos de preparación de las zeolitas ya existentes. Esto se debe, a que en ocasiones, la aplicación industrial de estas zeolitas se ve limitada, tanto por las condiciones de síntesis, como por el coste del agente director de estructura orgánico (ADEO) empleado en la preparación. En este sentido, el desarrollo de nuevas estrategias de síntesis podría dar lugar a la obtención de algunas estructuras de poro pequeño con propiedades físico-químicas mejoradas (relación Si/Al, acidez, tamaño de cristal, entre otras), así como a una reducción en los costes de preparación eliminando el uso de ADEOs o sustituyéndolos por moléculas de menor coste. Todo ello favorecería la posible aplicación industrial de dichas zeolitas de poro pequeño.
La primera parte de la tesis se centra en la optimización del proceso de síntesis de dos estructuras zeolíticas de poro pequeño, CHA y AEI, con elevado contenido en sílice y buenos rendimientos de síntesis. Para ello, se desarrolla una nueva metodología de síntesis que combina el uso de agentes directores de estructura orgánicos con el uso de una zeolita cristalina como única fuente de Si y Al. Mediante dicho procedimiento se obtienen ambas zeolitas con unas propiedades físico-químicas (tamaño de cristal y acidez) óptimas para su empleo como catalizadores del proceso MTO.
En la segunda parte de la tesis se preparan diferentes zeolitas de poro pequeño (CHA, AEI, AFX y ERI) que contienen cobre o hierro como centros activos aislados. Para la introducción de especies metálicas en su interior, se emplean tanto métodos convencionales de intercambio iónico como métodos de síntesis directa, que eliminan la necesidad de tratamientos post-síntesis, además de permitir obtener una dispersión más homogénea en los cristales de la zeolita. La actividad catalítica y estabilidad hidrotermal de estas zeolitas, se evalúa para la RCS de NOx. / The present doctoral thesis focuses on the preparation of small-pore zeolites (3.5-4 Å), preferentially those also containing large cavities. This type of materials has attracted great technological interest during the last years due to their recent commercial application as catalysts in relevant industrial and environmental processes, such as the transformation of methanol into light olefins (MTO), or the selective catalytic reduction (RSC) of NOx.
Therefore, there is an increasing interest in the preparation of new small pore structures and/or the improvement of the physico-chemical properties or the synthesis protocols of the zeolites currently in use. In fact, the industrial application of a particular zeolite could be limited by the high costs associated to its preparation, and in particular, to the high costs associated to the organic structure directing agent (OSDA) employed. In this sense, the discovery and development of new synthetic strategies could not only favor the crystallization of novel small-pore zeolites with improved physico-chemical properties (i.e. Si/Al ratio, crystal size, among others), but also optimizing the production costs, avoiding the use of expensive OSDAs or, at least, substituting those by less-expensive organic molecules. These features could encourage the potential commercialization of such novel small pore zeolites as competitive catalysts for relevant industrial processes.
In the first part of this thesis, the synthesis protocols of two different high-silica small pore zeolites, CHA and AEI, have been intensively evaluated in order to develop a new procedure to direct the crystallization of these two zeolites with excellent solid yields. It has been found that the combination of a particular OSDA with a crystalline zeolite as the sole Si and Al sources, as FAU, allows the obtention of both zeolites with optimal physico-chemical properties (crystal size and acidity) for its application as efficient catalysts for the MTO process.
In the second part of this thesis, different small-pore zeolites (CHA, AEI, AFX y ERI) containing copper or iron as isolated active catalytic sites, have been prepared. To introduce these metallic species within the zeolite crystals, either conventional ion-exchange methods or direct 'one-pot' synthetic methods have been employed. Interestingly, the use of 'one-pot' synthesis methods not only eliminates the need for post-synthetic ion-exchange treatments, but also allows obtaining better metal dispersions along the zeolite crystals. The catalytic activity and hydrothermal stability of such zeolites has been evaluated for the SCR of NOx. / Aquesta tesi doctoral es centra en la preparació de zeolites de por menut (3.5-4 Å), i en particular, aquelles amb una estructura que presenta, a més, grans cavitats. Aquest tipus de materials han despertat un gran interès als últims anys, degut al potencial que presenten com a catalitzadors eficients en processos rellevants per la indústria i el medi ambient, com son el processos de transformació de metanol a olefines (MTO) o la reducció catalítica selectiva (RCS) de NOx.
Per aquest motiu, existeix un interès creixent tant en la preparació de noves estructures de por menut, com en la millora de les propietats fisico-químiques o dels mètodes de preparació de les zeolites ja existents. Aquest motiu es deu a que en ocasions, l'aplicació industrial d'aquestes zeolites, es pot veure limitada per els costs associats a la seua preparació, en particular de l'agent director d'estructura orgànic (ADEO) emprat. En aquest sentit, el desenvolupament de noves estratègies de síntesi podria donar lloc a l'obtenció d'algunes estructures de por menut amb propietats físico-químiques millorades (relació Si/Al, acidesa, tamany de cristall, entre altres), així com a una reducció dels costos de preparació, eliminant l'ús de ADEOs o substituint-los per molècules de menor cost. Tot això, podria afavorir la possible aplicació industrial d'aquestes noves zeolites de por menut.
La primera part de la tesi es centra en l'optimització del procés de síntesi de dos estructures zeolítiques de por menut, CHA i AEI, amb un elevat contingut de sílice i amb bons rendiments de síntesi. Per això, s'ha desenvolupat una nova metodologia de síntesi que combina l'ús d'agents directors d'estructura orgànics (ADEO) amb una zeolita cristal¿lina com a única font de Si i Al. Mitjançant aquest procediment, s'han pogut obtenir els dos materials amb unes propietats físico-químiques (tamany de cristall i acidesa) òptimes per al seu ús com a catalitzadors en el procés MTO.
En la segona part de la tesi s'han preparat diverses zeolites de por menut (CHA, AEI, AFX I ERI), amb àtoms de coure o ferro com a centres catalítics aïllats. Per a la introducció de les espècies metàl¿liques al seu interior, s'han utilitzat tant mètodes convencionals d'intercanvi iònic com mètodes de síntesi directa. En particular, els mètodes directes eliminen la necessitat de introduir diferents tractament post-síntesi, a més de permetre una dispersió més homogènia del metall als cristalls de la zeolita. L'activitat catalítica i l'estabilitat hidrotermal d'aquestes zeolites s'ha avaluat per a la RCS de NOx. / Martín García, N. (2017). PREPARACIÓN DE ZEOLITAS DE PORO PEQUEÑO CON CONTROL DE SUS PROPIEDADES FÍSICO-QUÍMICAS PARA SU APLICACIÓN EN CATÁLISIS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/94628 / TESIS
|
20 |
Sensorimotor Integration Following Training on a Tactile Discrimination Maze TaskPickersgill, Jake 11 1900 (has links)
Sensorimotor integration refers to the process of combining incoming sensory information with outgoing motor commands to control movement. Short-Latency Afferent Inhibition (SAI), Long-Latency Afferent Inhibition (LAI) and Afferent Facilitation (AF) are three neurophysiological measures collected using Transcranial Magnetic Stimulation (TMS) to assess sensorimotor integration in humans. No studies to date have investigated the influence of tactile discrimination training on these measures. This study aimed to determine whether SAI, LAI, and AF are modulated following training on a custom-designed sensorimotor task which required participants to use their sense of touch to successfully navigate 3D printed maze with interchangeable paths. The maze training was separated into “high difficulty” and “low difficult” conditions which reflected the tactile challenge embedded within the maze. On an additional visit, no maze training was performed to serve as a control condition. Despite evidence of performance improvements during training, there were no significant changes in SAI, LAI or AF following training in either condition. Further, there was no correlation between the % change in SAI/LAI and improvements in total dwell time on the maze. As the functional significance of these measures is still unclear, these findings suggest that changes in SAI, LAI or AF may not be a valid metric to measure meaningful or functional changes related to skills or performance improvements induced by training. / Thesis / Master of Science in Kinesiology / Sensorimotor integration refers to the combination of incoming sensory information with outgoing motor commands in the nervous system to control movement. Short- Latency Afferent Inhibition, Long-Latency Afferent Inhibition and Afferent Facilitation are three measures that probe sensorimotor integration in humans using Transcranial Magnetic Stimulation. Although these measures have been well studied in both healthy and clinical populations in a variety of contexts, the influence of sensorimotor training on these measures remains unclear. This thesis aimed to determine if SAI, LAI and AF change following training on a novel tactile discrimination maze task. Further, the relationship between changes in sensorimotor integration and improvements in maze performance was explored. SAI, LAI and AF were not shown to be influenced by training, and there was no association between the changes in these measures and improvements in maze performance.
|
Page generated in 0.0462 seconds