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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Untersuchungen zur Nutzung der Solarenergie für die Wärme-Kälte-Kopplung unter tropischen Bedingungen

Phan, Qui Tra 22 April 2008 (has links) (PDF)
Die Untersuchungen zur Nutzung der Solarenergie werden für die klimatischen Bedingungen von Vietnam durchgeführt. Um das Problem der Elektroenergieversorgung in Vietnam zu verringern und um speziell den Lebensstandard in den ländlichen Gebieten zu erhöhen, werden Anstrengungen unternommen, um Anwendungen der Solarenergie zu entwickeln. Es wäre erstrebenswert, wenn ein komplettes Solartechniksystem zur Hausversorgung zur Verfügung stehen würde. Der Konzipierung und Auslegung der Solartechnik wird ein sog. Referenzhaus zugrunde gelegt, das hinsichtlich seiner Bauweise und Größe typisch für die ländlichen Gegenden in Mittel- und Südvietnam ist. Der Gesamtenergiebedarf orientiert sich an der Lebensweise und der Anzahl der Hausbewohner. Erforderlich ist die Bereitstellung von Warmwasser am Tage sowie von Kälte, die für Frischhaltung von Nahrungsmitteln auch nachts erzeugt werden kann. Dies wird als solares Warmwasser- und Kälteerzeugungssystem bezeichnet. Für die Überwindung von Höhenunterschieden bei der Wasserförderung wird ein solarer Stirlingmotor als Pumpenantrieb in Betracht gezogen. Zur Warmwasserbereitung sollen geeignete Solarkollektoren verwendet werden. Zur Kälteerzeugung scheint sich ein Adsorptionskälteaggregat vorteilhaft in das Gesamtsystem einzuordnen.
2

Analysis of dropbox assisted hydraulic traction / Analys av en dropboxstödd hydraulisk drivlina

LI, Zhen January 2017 (has links)
The research looks at the advantages and disadvantages of a hydraulic auxiliary drive (HAD) system which is installed on a 25 meter long timber transport vehicle. The purpose is to investigate the performance with regard to energy, economy and environment of the system due to the added components, the hydraulic accumulators. The auxiliary system that is used on the vehicle is simply a hydrostatic transmission system. Ideally, the fuel consumption and cost can be reduced by using accumulators. To verify this hypothesis, model-based simulations were performed in a software environment and the result was analyzed for a linear and repeatedly accelerating and decelerating driving cycle. Additionally, comparisons were made between the HAD system with and without the assistance of accumulators. From the simulation results, the system assisted by accumulators consumes approximately 14% less fuel than the other. And it produces 15% more tractive effort when the vehicle is accelerating. The paper also includes the determination of the size of accumulators, both theoretically and with simulations. By comparison, there is a small difference between the results from the theoretical calculation and the simulations, which might be caused by a neglecting the volumetric losses in the simulation process. Ideally, an accumulator with a size of 57 L was found to be the most efficient size for the studied driving cycle. Beyond that speed, the efficiency will decrease to some extent. Physical tests are not presented in this paper, but they will be done in the future. / Den presenterade forskningen studerade fördelar och nackdelar med ett hydraulisk hjälpsystem för fordonsdrift (HAD) för en 25 meter lång timmerlastbil. Syftet var att undersöka hur drivlinans prestanda med avseende på energy, ekonomi och miljöpåverkan, påverkas av de adderade komponenterna, de hydrauliska ackumulatorerna. Hjälpsystemet är helt enkelt ett hydrostatiskt transmissionssystem. Idealt, kan bränsleförbrukning och kostnad reduceras genom att använda ackumulatorer i systemet. För att verifiera denna hypotes, har modell-baserade simuleringar utförts och resultaten har analyserats för konstantfartskörning och en körcykel med upprepade accelerationer och inbromsningar. Dessutom, har ett HAD-system med och utan ackumulator jämförts. Simuleringsresultaten visar att ett system med ackumulatorer förbrukar ca 14% mindre bränsle än ett system utan ackumulatorer. Ett ackumulatorstött system ger också 15% högre framdrivningseffekt vid accelereration. I avhandlingen dimensionera också storleken på ackumulatorerna, både teoretiskt och med simuleringar. Det finns en liten skillnad mellan resultaten från den teoretiska beräkningen och simuleringarna, som kan bero på att volymetriska förlusterna inte har tagits med i simuleringarna. En ackumulator med en storlek på 57 L visar sig ha den mest effektiva storleken för den studerade körcykeln. Vid högre körhastigheter, kommer verkningsgraden att minska till viss del. Inga fysiska tester har gjorts, men de kommer att utföras i framtiden.
3

Untersuchungen zur Nutzung der Solarenergie für die Wärme-Kälte-Kopplung unter tropischen Bedingungen

Phan, Qui Tra 01 December 2006 (has links)
Die Untersuchungen zur Nutzung der Solarenergie werden für die klimatischen Bedingungen von Vietnam durchgeführt. Um das Problem der Elektroenergieversorgung in Vietnam zu verringern und um speziell den Lebensstandard in den ländlichen Gebieten zu erhöhen, werden Anstrengungen unternommen, um Anwendungen der Solarenergie zu entwickeln. Es wäre erstrebenswert, wenn ein komplettes Solartechniksystem zur Hausversorgung zur Verfügung stehen würde. Der Konzipierung und Auslegung der Solartechnik wird ein sog. Referenzhaus zugrunde gelegt, das hinsichtlich seiner Bauweise und Größe typisch für die ländlichen Gegenden in Mittel- und Südvietnam ist. Der Gesamtenergiebedarf orientiert sich an der Lebensweise und der Anzahl der Hausbewohner. Erforderlich ist die Bereitstellung von Warmwasser am Tage sowie von Kälte, die für Frischhaltung von Nahrungsmitteln auch nachts erzeugt werden kann. Dies wird als solares Warmwasser- und Kälteerzeugungssystem bezeichnet. Für die Überwindung von Höhenunterschieden bei der Wasserförderung wird ein solarer Stirlingmotor als Pumpenantrieb in Betracht gezogen. Zur Warmwasserbereitung sollen geeignete Solarkollektoren verwendet werden. Zur Kälteerzeugung scheint sich ein Adsorptionskälteaggregat vorteilhaft in das Gesamtsystem einzuordnen.
4

Regenerativ stötdämpning : i eldrivna fordon

Brink, Kasper, Orang, Elias January 2022 (has links)
Energy consumption in vehicles is challenging from an environmental standpoint as well asan economical one. This study is investigating the possibility of implementing regenerativedamping in vehicles. With traditional shock absorbers, the vertical linear motion is dampenedby converting the kinetic energy into heat. The purpose of regenerative damping is to convertthe kinetic energy into electricity instead. The electricity can then be used to charge batteriesor power various systems in the vehicle. Since the authors study mechanical engineering, thisproject mostly involves different concepts and the mechanical aspect of the system. Aliterature study, experiments, interviews and observations were performed to acquire atheoretical foundation. Five different concepts were then developed, one of them wasdetermined the best and further developed. The result of this thesis is that regenerativedamping is not yet mature enough to be used in vehicles. The technology is not justifiable asit does not save enough energy, compared to how much more it would cost to develop andbuild a regenerative shock absorber and the challenges associated with it.
5

The effect of calcium silicate-based cements on viability and differentiation of human stem cells from the dental apical papilla. : Future aspects in endodontic regeneration.

Abdalla, Lahood, Soltani, Bagir January 2023 (has links)
Introduction: Pulp necrosis in immature permanent teeth stops root development and may lead to higher risk of cervical fractures and a challenging treatment. Regenerative endodontic treatment (RET) aims to continue tooth development and implies the use of calcium silicate-based cements, such as Mineral trioxide aggregate (MTA) and Biodentine to seal the root canal. However, its effect on stem cells has been poorly explored.  Aims: Examine the effect of two different calcium silicate-based cements on the viability and the odonto-/osteogenic potential of Stem Cells from Apical Papilla (SCAP). Material and method:  Isolated SCAPs from three healthy donors (donor I, II and III) were used and exposed for different concentration extracts of ProRoot® MTA and BiodentineTM for 21 days. Cell viability was studied using the neutral red cytotoxicity test. Osteogenic differentiation was analyzed by the alkaline phosphatase test (ALP). Results:  No difference in SCAPs viability was detected by the type of cements used, Biodentine or ProRoot MTA. However, material concentration could be associated with cells cytotoxicity.  Osteogenic differentiation was not based on the type of cement used but the environment conditions (aerobic/anaerobic) and the genetical background. Conclusions: The type of cement used in RET, Biodentine or MTA, showed similar effect on SCAPs viability and differentiation potential in vitro. Further studies should be performed to analyze their effect -in -vivo.
6

Värmeåtervinning av luft i kycklingstallar : Återanvändning av energin i frånluften för luftförvärmning / Heat recovery of air in chicken stables : Reuse the energy in the exhaust air for air preheating

Alegrim, Georg, Anaje, Alexander January 2019 (has links)
I Sverige har konsumtionen av kyckling per invånare ökat de senaste åren och idag konsumeras 23,2kg per person och år. Eftersom tillväxten för svensk kyckling är hög ökar också medvetenheten hos företag att investera i klimatsmarta alternativ för att minska energibehovet som leder till en minskad uppvärmningskostnad. Det valda djurstallet värms upp med en flispanna där vattenburna värmeelement förser stallet med värme längs väggarna. Syftet med studien är att undersöka hur mycket värmeenergi som går att spara genom att använda den utsugna luften för att värma den luften som sugs in med hjälp av en värmeväxlare. Det har ansetts problematiskt att använda stallets frånluft för att tillgodose energi i form av värme eftersom den oftast är dammig och detta bidrar till att filter och kanaler täpps igen. Idag finns det ett antal luftvärmeväxlare som klarar denna typ av damm och partiklar.  Två olika värmeväxlare har jämförts, en rekuperativ (plattvärmeväxlare) och en regenerativ (roterande värmeväxlare). Stallet måste hålla ett lågt CO2 värde och kycklingarnas ströbädd måste hållas torr med hjälp av en låg luftfuktighet. Ventilationens volymflöde är ett beräknat teoretiskt värde. Resultatet av de två jämförda värmeväxlarna visar att den regenerativa (roterande) värmeväxlaren återför fukt vilket som bidrar till en fuktigare ströbädd jämfört med den rekuperativa (plattvärmeväxlare) som inte återför fukt. Studien genomfördes under kycklingarnas uppfödningstid, vilket varade från första januari i 34 dagar framåt. Dag 28–30 blir stallet självförsörjande på värme och värmeväxlaren kan då generera den värmen som krävs utan anläggningens tillhörande flispanna. Med hänsyn till skallklimatet är det att föredra en plattvärmeväxlare då den roterande värmeväxlaren återför vatten av tre gram per kg torr luft. Undersökningen visar det totala värmebehovet, som idag är cirka 48,2 MWh under en uppfödningsomgång, kan minskas med 24,8 MWh med hjälp av en värmeväxlare under denna omgång. / The consumption of chicken per inhabitant have increased in Sweden the last couple of years and today 23,2 kg is consumed per inhabitant and year. Because of this rise of Swedish chicken consumption, the awareness of investing in climate-smart alternatives have increased by the companies. The companies are decreasing the energy required during production, which ultimately leads to a reduced heating cost. The animal stall is heated by a boiler where water-based heating elements are providing the animal stall with heat along the walls.  It has been considered problematic to heat up the animal stall by reintroducing the air from inside the stall due to the fact that this air often is too dusty, which contributes to blockage of filters and ducts. There are a number of different heat exchangers that can handle this kind of dust and particles today.  Two different heat exchangers will be compared, a recuperative plate heat exchanger and a regenerative rotary heat exchanger. The animal stall must keep a low CO2 value and it is important to keep the chickens bedding dry by a low humidity inside the stall. The study shows that the total heat for one breeding round, which today is approximately 48,2MWh, which equals a saving by using an air heat exchanger of 24,8MWh. The result of the comparison of the two heat exchangers has shown that the regenerative (rotary) heat exchanger reintroduces moisture in the stall, which the recuperative (plate heat exchanger) does not. The follow up for this study was 34 days, from the chickens’ birth to the slaughter. During day 28-30 the animal stall becomes self-sufficient considering heat, which means that the heat exchanger could generate the heat required for the facility without the use of the stalls chip boiler. The study is implemented with a calculated volume flow due to a short outlet channel on the system, this can lead to a risk of a minor faulty value. Regard to the humidity in the stall, it is preferable to use a plate heat exchanger as the rotating heat exchanger precipitates water of 3 grams/kg of dry air.
7

Simulations of the hydrogen storage capacities of carbon materials

Zhechkov, Lyuben 29 October 2007 (has links) (PDF)
Many methods have been proposed for efficient storage of molecular hydrogen for fuel cell applications. However, despite intense research efforts, so far, the industrial parameters of 6.5% mass ratio and 62 kg/m3 volume density are still questionable though the results are obtained by either experimentally or via theoretical simulations on reversible model systems. Carbon-based materials, have always been regarded as the most attractive physisorption substrates for the storage of hydrogen. Theoretical and experimental studies on various model carbon systems, however, failed to reach the elusive goal. In this work, it is shown that insufficiently accurate carbon - hydrogen diatomic interaction potentials, together with the neglect and incomplete treatment of the quantum effects in previous theoretical investigations, led to misleading conclusions for the absorption capacities of different carbon materials. A proper account of the contribution of quantum effects to the free energy and the equilibrium constant for hydrogen adsorption suggest that the industry specifications can be approached in a graphite-based physisorption system. The theoretical prediction can be realised by optimising the topology, the cavity shape and the accessible surface of the carbon structures.
8

Socialt och ekologiskt byggande på Nya Jägersro : Ett platsspecifikt planeringskoncept för fastigheten Nya Jägersro i Malmö / Social and ecological development at Nya Jägersro : A site specific planning concept for the property Nya Jägersro in Malmö

Nilsson Öhrn, Nora, Jakob, Fagerström January 2021 (has links)
Denna uppsats har skapats för att agera underlag vid framtagandet av en strukturskiss över fastigheten Nya Jägersro i Malmö. Uppsatsen syftar till att skapa ett planeringskoncept som kombinerar social och ekologisk hållbarhet genom att ta hänsyn till platsens specifika egenskaper. Både kommunen och fastighetsägaren, de två mest inflytelserika aktörerna för fastigheten, lägger stort fokus på hållbar utveckling. Uppsatsens frågeställningar baseras i två problematiker. Den första är fastighetsägarens separation av hållbarhetsaspekter som genom resonemanget om att hållbarhet skapas genom interaktioner mellan hållbarhetsaspekter kan bli problematisk. Den andra är hur Nya Jägersro som plats påverkas av ideal om förtätning i syfte att bygga hållbart. För att adressera dessa problem är uppsatsens syfte att ta fram ett planeringskoncept som kombinerar social och ekologisk hållbarhet och som tar hänsyn till platsens specifika egenskaper. Det teoretiska ramverket består av tre teorier som behandlar hållbar platsspecifik planering och design för att utveckla hållbara städer. De metoder av datainsamling som har använts är platsläsning, litteraturstudier och semistrukturerade intervjuer. Planeringskonceptet som slutligen presenteras benämns som JägersGro, vilket sammanfaller i flera avseenden med SMT:s och Malmö Stads agendor, men avviker delvis i vissa aspekter. Den största avvikande faktorn i relation till SMT är att JägersGro utgår från att hållbarhet utgörs av kombinationen mellan olika hållbarhetssystem. Ytterligare en avvikande faktor från båda aktörerna är att JägersGro förespråkar idén om att människans påverkan på de naturliga systemen inte enbart bör reduceras. Istället anses hållbara stadsdelar behöva vara med i återskapande processer för att kunna fungera i ett balanserat kretslopp med naturen. / This thesis has been created to act as a basis for the preparation of a structural sketch of the property Nya Jägersro in Malmö. The thesis aims to create a planning concept that combines social and ecological sustainability by taking into account the specific characteristics of the site. Both the municipality and the property owner, the two most influential stakeholders, place great focus on sustainable development. The thesis examines two problems. The first is the property owner's separation of sustainability aspects, which through the reasoning that sustainability is created through interactions between different sustainability aspects can become problematic. The second is how Nya Jägersro as a place is affected by ideals of densification in order to build sustainably. To address these problems the purpose of the thesis is to develop a planning concept that combines social and ecological sustainability by taking into account the specific characteristics of the site. The theoretical framework consists of three theories that deal with sustainable site-specific planning and design for developing sustainable cities. The methods of data collection that have been used are site reading, literature studies and semi-structured interviews. The planning concept that is finally presented is referred to as JägersGro, which coincides in several respects with SMT's and Malmö Stad's agendas, but also deviates in some aspects. The biggest deviating factor in relation to SMT is that JägersGro assumes that sustainability consists of the combination of different sustainability systems. Another deviating factor from both actors is that JägersGro advocates the idea that the human impact on the natural systems should not only be reduced. Instead, sustainable districts are considered to be involved in regenerative processes in order to function in a balanced cycle with nature.
9

Metaanalyse klinischer Studien 1983-2016 zur langfristigen Gebrauchsfähigkeit von Sportpferden nach Behandlung von natürlich entstandenen Erkrankungen der oberflächlichen und der tiefen Beugesehne und des Fesselträgers entweder allein mit kontrollierter Bewegung oder kombiniert mit einem potenziell regenerativen Therapeutikum

Doll, Sarah Eva Marie 22 May 2019 (has links)
Die equine Regenerationsmedizin versucht nach einer Sehnenverletzung (oberflächliche, tiefe Beugesehne: OBS, TBS) oder Bandverletzung (Fesselträger FT) die konsekutive Narbenbildung mit intraläsional applizierten potenziell regenerativen Therapeutika (prT) zu vermeiden. PrT sind mesenchymale stromale multipotente Progenitorzellen (MSC) aus unterschiedlichen Gewebequellen, sowie blutzellbasierende - meist Platelet Rich Plasma (PRP) - oder azelluläre Blutprodukte. Ein Langzeiterfolg ist noch nicht evident nachgewiesen; die Arbeit möchte dazu beitragen, die bestehende Lücke zu schließen. Die Arbeitsfrage lautet: Wie kann mit einer einzigen quantitativen Effektvariable bei Sportpferden, die nach einer natürlich entstandenen Erkrankung der OBS,TBS oder FT konservativ, mit kontrollierter Bewegung allein (KtrB) oder regenerativ (PrTB) behandelt werden, die ‚langfristige Gebrauchsfähigkeit’ (GF) valide gemessen und bisherige Studienergebnisse verglichen werden? Material: Inkludiert sind 51 in vivo Studien (1983-2016) entsprechend der Arbeitsfrage. Exkludiert sind in vivo Studien mit künstlich induzierten Erkrankungen, mit konventioneller oder chirurgischer Behandlung sowie in vitro Studien Methoden: Da die Studienergebnisse nicht direkt vergleichbar sind, wird ein evidenzbasiertes einfaches Evaluationsmodell mit der neuen quantitativen Effektgröße 'Gebrauchsfähigkeitsrate' GFR entworfen. Die metaanalytische gepoolte Reanalyse kann damit unabhängig von den Ergebnissen der Primärstudien die GF der Sportpferde neu bewerten. Als maßgebliche Einflussfaktoren auf GF werden u.a. definiert: Gewebestruktur, prT, sportliche Disziplin, Läsionsgrad, Altersklasse der Pferde, Prüfzeitdauer nach Rehabilitation zur Kontrolle des ‚Erfolgsmerkmals’ (EM) auf ein Rezidiv. Die Daten werden aus den Studien extrahiert und zu sog. Behandlungsgruppen (BehG) zusammengefasst. Nach Gewebestruktur (OBS-TBS, FT-Ursprung/-Körper/-Schenkel) und Behandlungsform (KtrB, PrTB) geordnete BehG werden soweit vergleichbar zu größeren BehG mit präziserem GFR gepoolt. Der Effektunterschied zwischen prT wird gegebenenfalls statistisch gesichert. Als EM ist definiert: 'Nach Rehabilitation kehren die Sportpferde zur Arbeit auf (mindestens) dem ursprünglichen Leistungsniveau zurück'. Die Erfolgsrate bzgl. EM ist E. In der Prüfzeitdauer nach Rehabilitation wird die Rezidivrate (R) ermittelt. E und R ergeben die Effektgröße GFR = E(1-R). Diese wird mittels 3 ganzzahliger Variablen A, B, C normiert: GFR = (N-A-B-C)/(N-A). A, B, C sind disjunkte Fallgruppen der N Patienten einer BehG. Die standardisierte Studiendauer ergibt sich aus der projektierten Rehabilitationsdauer (proj. Reha) und der ‚standardisierten Prüfzeit’ (P). Im Konsens mit den untersuchten Studien ist sie bei OBS-TBS 3 Jahre (1 Jahr proj. Reha + 2 Jahre P), beim FT 2,25 Jahre (0,75 Jahre proj. Reha + 1,5 Jahre P). Ergebnisse und Schlussfolgerung: Bei der OBS erscheint die Chance (OR, odds ratio) auf die zweijährige GF mit Amnion-MSC (2GFR = 94,1 %, n* = 34) 7-fach größer (OR = 7,2 [1,7-31,4]) sowohl vs. Knochenmark-MSC (2GFR = 68,8 %, n* = 145) als auch 9-fach größer (OR = 9,7 [2,1-45]) vs. PRP (2GFR = 60,4 %, n* = 51) sowie 11-fach größer (OR = 11,4 [2,5-52,1]) vs. KtrB (2GFR = 57,5 %, n* = 60). Erstmals kann bei diesen prT die Effektdifferenz dGFR > 25 % mittels Poweranalyse per Signifikanznachweis (Power >90 %; p < 0,025) durch die erforderliche Fallzahl statistisch gesichert werden. Allerdings stützt sich das Ergebnis für Amnion-MSC noch auf nur eine Studie. Bei TBS und FT fehlen Vergleichsgruppen noch. Da replizierbare wissenschaftliche Ergebnisse mit hoher interner und externer Evidenz nur mit standardisierten Parametern erzielt werden können, erscheint das GFR-Modell für zukünftige Studien von wesentlichem Interesse. / The equine regenerative medicine is seeking to avoid the subsequent scarring after a tendon (superficial and deep digital flexor tendon: SDFT, DDFT) or ligament (suspensory ligament: SL) injury by intralesionally applicated potential regenerative therapeutics (prT). PrT are mesenchymal stromal multipotential progenitor cells (MSC) from different sources of tissue, as well as products of blood, based on blood cells (PRP in most cases, platelet rich plasma) or acellular. Evidence of long-term treatment-success has not yet provided. This study wants to go towards closing the gap on this front. The leading question is: How can the 'long-term fit for use' (FfU) of sport horses, which are treated either conservatively with controlled exercise allone (CtrT) or regeneratively (PrTT) after suffering from naturally occuring tendinopathies of SDFT, DDFT or FT, be quantified in a valid way with a single effect variable? And how can the results of previous research studies be compared? Material: Includet are 51 in vivo studies (1983-2016) relating to the leading question. Excluded are in vivo studies with artificially induced lesions, with conventional or surgical treatment as well as in vitro studies. Methods: Findings of the studies are not directly comparable. As a consequence an evidence-based simple evaluation-model with the new quantitative effect size called ‘rate of fit for use’ (FFU) is developed. Based on this model the meta-analytical pooled re-analysis can re-assess FfU of the sport horses independently from findings of primary studies. The following influencing factors affecting FfU are defined: Structure of tissue, prT, sportive kind-of-use, degree of lesion, age class of horses, duration of monitoring after rehabilitation to controll the outcome (OC) for recurrence. The data are extracted from the studies and configured to so-called treatment groups (TGs). According to structure of tissue (SDFT, DDFT, SL-body, SL-origin, SL-branches) and kind of treatment (CtrT, PrTT) comparable TGs are pooled to bigger TGs with more precise FFU. If possible difference of effect between prTs is statistically assured. OC is defined as: 'After rehabilitation the sport horses return to work at (not less than) the initial level of performance'. Rate of OC is E. During duration of monitoring after rehabilitation the rate of recurrence (R) is checked. E and R are combined to FFU = E(1-R). In addition FFU is standardized in accord with the formula FFU = (N-A-B-C)/(N-A). A, B, C are integer variables representing disjunctive case groups of N, which is the total number of treated patients of a TG. The standardized duration of study results from the 'planned duration of rehabilitation' (planReha) and ‘standardized duration of monitoring’ (DoM). In consence with research studies it adds up to 3 years at SDFT-DDFT (1 year planReha +2 years DoM) and 2.25 years at SL (0.75 year planReha +1.5 years DoM). Results and conclusion: The chance (OR, odds ratio) with AM-MSC for biennial FfU (2FFU = 94.1 %, N-A = 34) appears to be more than at least 7-fold (OR = 7.2 [1.7-31.4]) as high as with BM-MSC (2FFU = 68.8 %, N-A = 145) as well as 9-fold (OR = 9.7 [2.1-45]) high as with PRP (2FFU = 60.4 %, N-A = 51) as well as 11-fold (OR = 11.4 [2.5-52.1]) high as with CtrT (2FFU = 57.5 %, N-A = 60). For the first time, power-analysis can statistically assure the difference of effect 25 % < dFFU (power > 90 %; p < 0.025) between these TGs through significant evidence based on the needed number of cases. However 2FFU with AM-MSC still relies on only 1 study. At DDFT and at LS comparison groups still are lacking. Because replicable scientific results with high internal and external evidence only can be approached based on standardized parameters, FFU-model seems to be essential for future studies.
10

Simulations of the hydrogen storage capacities of carbon materials

Zhechkov, Lyuben 23 October 2007 (has links)
Many methods have been proposed for efficient storage of molecular hydrogen for fuel cell applications. However, despite intense research efforts, so far, the industrial parameters of 6.5% mass ratio and 62 kg/m3 volume density are still questionable though the results are obtained by either experimentally or via theoretical simulations on reversible model systems. Carbon-based materials, have always been regarded as the most attractive physisorption substrates for the storage of hydrogen. Theoretical and experimental studies on various model carbon systems, however, failed to reach the elusive goal. In this work, it is shown that insufficiently accurate carbon - hydrogen diatomic interaction potentials, together with the neglect and incomplete treatment of the quantum effects in previous theoretical investigations, led to misleading conclusions for the absorption capacities of different carbon materials. A proper account of the contribution of quantum effects to the free energy and the equilibrium constant for hydrogen adsorption suggest that the industry specifications can be approached in a graphite-based physisorption system. The theoretical prediction can be realised by optimising the topology, the cavity shape and the accessible surface of the carbon structures.

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