Dissertations / Theses on the topic 'RTFRTW'

Scheduling is a complex activity that is needed in a large number of fields, which can involve heterogeneous factors and that may have different goals. In this thesis, scheduling problems that involve the air traffic field at different phases are faced. At each phase, the different characteristics of the problems are considered, devoting special attention to uncertainty. Given the heterogeneous characteristics and goals of the problems, different models and methods are proposed to solve each of them. The first analyzed phase is the strategic phase. It takes place around six months before the operation of flights, when they need to be assigned scheduled departure and arrival times at the airports where they operate. Future capacity realizations are very difficult to forecast at this phase, as capacity is influenced by weather conditions. A two-stage stochastic programming model with two alternative formulations is proposed to capture this uncertainty. Since the number of scenarios may be extreme, Sample Average Approximation is used to solve the model. The utilization of the proposed model allows to identify advantageous tradeoffs between schedule/request discrepancies, i.e., the distance between the allocated schedule and airline requests, and operational delays. This tradeoff can result in substantial reductions of the cost of delays for airlines. In the computational experiments, delays were reduced up to 45% on an instance representing a network of European airports. The second considered phase is the tactical phase, which takes place on the day of operation of flights. At this time, complete flight plans need to be defined, specifying the route and operation times of flights. This is done considering two different sources of uncertainty. First, uncertainty on capacity availability is taken into account, similarly to the strategic phase. However, the number of capacity realization scenarios is now small, as they can be defined using available weather forecasts. The problem of minimizing delay costs considering this source of uncertainty is the Stochastic Air Traffic Flow Management problem. A two-stage stochastic programming model with two alternative formulations is proposed to solve this problem. An ad-hoc heuristic that takes advantage of the good structure of the model is used to solve problem instances within short computation times. The analysis of the Value of the Stochastic Solution shows that the proposed stochastic model can significantly reduce delay costs when bad weather affects the whole network. Second, the implicit uncertainty on the departure time of flights is taken into account. This kind of uncertainty involves operations that may cause a delay on the scheduled departure time of a flight. The flexibility of the scheduled time of departure, as well as the other flight operations, is determined defining time windows within which flights are granted capacity resources to operate. The narrower a time window, the more critical a flight operation. The problem of minimizing delay cost and maximizing time windows is faced by the Air Traffic Flow Management Problem with Time Windows. The problem is formulated with two alternative deterministic models, one of which is able to provide time windows in 40" on average for instances involving over 6,000 flights. Less conservative criteria to reserve capacity within time windows can also be used. Despite not granting the possibility for a flight to execute its operations at every instant of a time window, the implementation of these alternative criteria is shown to be viable. In fact, less than 0.14% of flights were subject to capacity shortages in the analyzed cases. Finally, the operational phase takes place when operations are being executed. The goal at this phase is to manage the final departure times announced by flights - with uncertain information becoming deterministic - allowing them to depart at the announced time even if this time exceeds the assigned departure time window. This problem is named Real Time Flight Rescheduling with Time Windows. Resources are provided to flights that need them by reallocating previously reserved capacity with an algorithm that follows the Ration-By-Schedule mechanism. Both the practical usage of time windows and the impact of collaboration among airlines are studied. While airline collaboration limits time window flexibility up to some time before the scheduled departure of a flight, it can allow to reduce additional flight delays by over 14%. This thesis is a first work that involves determining flight schedules from the moment of their definition to the time of execution of flights. Providing cost reductions by considering the different factors that influence each decision phase can lead to a global improvement of the management of flight operations, whose delays are very expensive in practice for airlines.

O estudo reolÃgico do Cimento AsfÃltico de PetrÃleo (CAP) Ã de fundamental importÃncia para a determinaÃÃo de sua performance na fabricaÃÃo de estradas. Usualmente os parÃmetros reolÃgicos deste material sÃo obtidos por meio de ensaios dinÃmicos atravÃs de um reÃmetro de cisalhamento. O presente trabalho tem por objetivo estudar as propriedades microreolÃgicas do CAP atravÃs da tÃcnica de espectroscopia de forÃa utilizando um microscÃpio de forÃa atÃmica. A Microscopia de ForÃa AtÃmica mostra ser uma ferramenta Ãtil na investigaÃÃo de propriedades mecÃnicas de sistemas microscÃpicos. O principio bÃsico de atuaÃÃo do AFM Ã medir as forÃas micromecÃnicas entre a sonda do equipamento e a amostra analisada podendo-se obter nÃo apenas o mapa topogrÃfico da superfÃcie em anÃlise, mas tambÃm informaÃÃes a respeito das propriedades reolÃgicas do material tais como elasticidade, viscosidade, adesÃo do material, entre outras, assim como observar regiÃes onde essas propriedades diferem numa mesma amostra. Amostras de CAP puro 50/70, CAP envelhecido e aditivado com 2% de LCC e 1% de PPA foram analisadas. A partir dos dados das curvas de forÃa, com base em uma ferramenta computacional desenvolvida para esse tipo de anÃlise, foram obtidos o mÃdulo de Young, a viscosidade, a adesÃo, work difference e slope. Para cada tipo de amostra foram confeccionados 3 lamÃnulas, as quais seriam usadas para fazer as medidas no AFM, e cada lamÃnula, analisadas em 3 regiÃes diferentes de 50 Âm X 50 Âm. As identaÃÃes foram realizadas em 4 frequÃncias diferentes: 0,5 hz, 1 hz, 5 hz e 28 hz. AlÃm dessas medidas, foram obtidos imagens de fase, imagens topogrÃficas e imagens de friction para cada tipo de amostra.

CAVALCANTE, Priscilla Noronha. Propriedades mecânicas de cimento asfáltico RTFOT e adicionados de PPA e LCC por microscopia de força atômica. 2012. 120 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2012.
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O estudo reológico do Cimento Asfáltico de Petróleo (CAP) é de fundamental importância para a determinação de sua performance na fabricação de estradas. Usualmente os parâmetros reológicos deste material são obtidos por meio de ensaios dinâmicos através de um reômetro de cisalhamento. O presente trabalho tem por objetivo estudar as propriedades microreológicas do CAP através da técnica de espectroscopia de força utilizando um microscópio de força atômica. A Microscopia de Força Atômica mostra ser uma ferramenta útil na investigação de propriedades mecânicas de sistemas microscópicos. O principio básico de atuação do AFM é medir as forças micromecânicas entre a sonda do equipamento e a amostra analisada podendo-se obter não apenas o mapa topográfico da superfície em análise, mas também informações a respeito das propriedades reológicas do material tais como elasticidade, viscosidade, adesão do material, entre outras, assim como observar regiões onde essas propriedades diferem numa mesma amostra. Amostras de CAP puro 50/70, CAP envelhecido e aditivado com 2% de LCC e 1% de PPA foram analisadas. A partir dos dados das curvas de força, com base em uma ferramenta computacional desenvolvida para esse tipo de análise, foram obtidos o módulo de Young, a viscosidade, a adesão, work difference e slope. Para cada tipo de amostra foram confeccionados 3 lamínulas, as quais seriam usadas para fazer as medidas no AFM, e cada lamínula, analisadas em 3 regiões diferentes de 50 µm X 50 µm. As identações foram realizadas em 4 frequências diferentes: 0,5 hz, 1 hz, 5 hz e 28 hz. Além dessas medidas, foram obtidos imagens de fase, imagens topográficas e imagens de friction para cada tipo de amostra.

This project was aimed to study the degradation of polystyrene-butadiene-styrene block copolymer (SBS). SBS is used to modify bitumen, the binder in asphalt. From earlier studies it is known that SBS degrades in bitumen, but the degradation products have not been identified. To be able to determine the long term effects of SBS in the environment, degradation products need to be identified. Polystyrene forms rigid blocks with polybutadiene as a rubbery matrix between the ridgid blocks. When blended in bitumen, the polystyrene blocks are crosslinked to form a three dimensional network. SBS is an elastomer and has the ability to regain its shape after being a subject of mechanical force. According to the pre references the polymers had to be degraded in similar ways as they would in bitumen. Since bitumen is a very complex matrix with high boiling point and viscosity, there would be difficulties separating polymers from the bitumen. We made an assumption that it would be plausible for the degradation products formed in bitumen to form even with no bitumen present. Four different SBS polymers were used. One of the polymers was branched. Another had a high content of 1-2 polybutadiene. The third was a diblock copolymer (SB) with low styrene content compared to the others. The last was a linear SBS. The polymers were degraded in pieces of apparatus used for study ageing characteristics of bitumen as well as they were aged by refluxing in hexane. The degradation products were extracted by Solid Phase Extraction (SPE) and identified by GC-MS. Due to instrumental limits there were not many degradation products identified. The main products detected included saturated hydrocarbons in the range of 16-31 carbon atoms as well as squalene.

I det här projektet studerades nedbrytning av styren-butadien-styren block kopolymerer (SBS). SBS används för att modifiera bitumen vars användningsområde är som bindemedel i asfalt. Tidigare studier har visat att SBS bryts ned i bitumen, men nedbrytningsprodukterna har inte identfierats. För att kunna avgöra vad SBS har för långsiktiga effekter på miljön måste nedbrytnignsprodukterna identifieras. I SBS bildar polystyren styva block medan polybutadien fungerar som flexibla bryggor mellan polystyrenblocken. När SBS blandas med bitumen korslänkas polystyrenblocken så att ett tredimensionellt nätverk bildas. Eftersom SBS är en elastomer har den förmågan att återfå sin ursprungliga form efter att ha blivit utsatt för mekanisk stress. Enligt de givna förutsättningarna för studien skulle polymererna brytas ned på samma sätt som om de skulle ha varit lösta i bitumen. Eftersom bitumen är en komplex matris med hög kokpunkt och viskositet skulle det varit svårt att separera polymererna och deras nedbrytningsprodukter från bitumenet. Vi gjorde ett antagande om att det förmodligen bildas samma nedbrytningsprodukter som om bitumen varit närvarande även om nedbrytningen sker utan bitumen närvarande. Fyra olika SBS polymerer användes. En av polymererna var grenad. En annan hade en stor andel 1,2-polybutadien. Den tredje var en diblock kopolymer (SB) med lågt styren innehåll jämfört med de andra. Den sista polymeren var linjär. Polymererna åldrades i apparatur framtagen för att studera åldring av bitumen. Polymererna åldrades även genom att återloppskokas i hexan. Nedbrytningsprodukterna extraherades via fastfasextraktion (SPE) och identifierades med GC-MS. Genom instrumentella begränsningar kunde bara ett fåtal nedbrytningsprodukter identifieras. Bland de produkter som identifierades fanns alkaner och alkener med mellan 16 och 31 kolatomer, men även skvalen identifierades som nedbrytningsprodukt. Lågmolekylära ämnen kan ha ventilerats bort för att vi inte hade tillgång till apparatur för adsorbtion av flyktiga ämnen för injektion i GC-MS.

Le problematiche ambientali e socio – economiche legate alla costruzione di nuove infrastrutture viarie, impongono la progettazione e costruzione di strade che combinino ad elevati standard prestazionali, la riduzione dell’impatto ambientale in fase realizzativa e manutentiva. Quanto detto avvalora il crescente utilizzo di materiali bituminosi modificati con polimeri ed additivati con cere. I primi conferiscono alla miscela maggiore elastoplasticità, incrementandone la durabilità e la resistenza a fatica. Nei secondi la presenza del materiale paraffinico contribuisce a ridurre la viscosità del bitume, il che consente il notevole abbassamento della temperatura di produzione e stesa della miscela. Numerosi studi inoltre hanno dimostrato che le caratteristiche meccaniche della pavimentazione sono fortemente influenzate dal grado di ossidazione delle componenti organiche del bitume, ovvero dal fenomeno dell’invecchiamento o aging. Risulta pertanto fondamentale affiancare allo studio reologico del bitume, prove di simulazione dell’ invecchiamento nel breve e lungo termine. Nel corso della seguente ricerca si provvederà pertanto ad analizzare leganti modificati ed additivati secondo la teoria della viscoelasticità, simulando le reali condizioni di carico ed invecchiamento alle quali il bitume è sottoposto. Tutte le prove di caratterizzazione reologica avanzata prevederanno l’utilizzo del DSR (Dynamic Shear Rheometer) in varie configurazioni di prova e si simulerà l’invecchiamento a breve termine mediante RTFOT (Rolling thin film oven test). Si proporrà inoltre una nuova procedura di aging invecchiando il bitume alla temperatura di equiviscosità o Twork , ovvero a quel valore della temperatura tale per cui, in fase di messa in opera, si avrà una distribuzione molecolare omogenea del modificante all’interno del bitume. Verranno quindi effettuate ulteriori prove reologiche sui leganti invecchiati a tale temperatura. Si darà infine supporto ai risultati della ricerca effettuando prove chimiche con la tecnica analitica FTIR (Fourier Transform Infrared Spectroscopy), analizzando i cambiamenti molecolari avvenuti nel bitume a seguito dell’aggiunta del modificante e dell’invecchiamento.

Asphalt binder ageing and experiences with various ageing methods from abroad are described in this thesis. The practical part deals with the RTFOT aging and with the influence of the duration of this test. The comparison of test results is conducted before and after the aging by values of needle penetration, elastic recovery, softening point and resilience tests are evaluated and compared.

A study of bitumen aging effects on the rheological properties and fatigue behavior is carried out on five polymer modified bitumen provided by an oil company. Dynamic Shear Rheometer (DSR), is used to perform advanced experimental investigation. It allows practicing frequency sweep tests, fatigue tests and time sweep tests. Polymer modified bitumen with different percentage of SBS with or without the presence of crumb rubber are tested before and after short and long aging processes. Master curves were generated based on frequency sweep tests data, they are studied, and a comparison was conducted between each bitumen before and after aging. In this thesis, the DSR is presented, as well as the testing procedure and the tested materials. A fatigue life analysis of the results, based on the use of two different criteria, the first criterion is classically used: it consists in defining the failure as a 50% loss of the initial stiffness. The other criteria based on dissipated energy data. This thesis provides results which show the effects of several factors on fatigue and healing response such as bitumen type, ageing, the presence of rubber and polymer modification.

The comparison of rheological properties (complex shear modulus and phase angle and dynamic viscosity) of four paving bitumens and two polymer modified bitumens is performed in this diploma thesis. Furthermore, the empirical tests (needle penetration and softening point) were determined on these binders. Effect of asphalt binders aging was modeled using RTFOT test and modified RTFOT test (3 x RTFOT).

The theoretical part of this thesis describes the rheology of bituminous binders, aging of asphalt binders and laboratory methods simulating short and long term aging. The following describes an empirical tests (needle penetration, softening point ring ball method) and functional tests (complex shear modulus and phase angle, dynamic viscosity), which are performed in the dynamic shear rheometer. At the end of this section, laboratory aging of bituminous binders using method RTFOT and method RTFOT + PAV is described in more detail. In the practical part of this thesis, the results of all tests performed on the binders aged using RTFOT + PAV are introduced and compared with results of properties of non-aged binders and binders aged by 3xRTFOT.

The thesis describes the relaxation properties of bituminous binders determined in dynamic shear rheometer (DSR). Paving bitumen, polymer modified bitumen (PMB) and crumb rubber modified bitumen (CRmB) were chosen for comparison. In order to describe the effects of ageing on asphalt binders relaxation properties, the laboratory simulation of ageing using RTFOT and 3xRTFOT method was performed. For each binder were simultaneously conducted tests of needle penetration, softening point and elastic recovery. Selected bitumens were used for the production of asphalt mixtures. The low-temperature properties tests (TSRST) were performed for these mixtures, when the results were compared to the relaxation properties of binders determined in the DSR.

Dissertation thesis is focused on rheological properties of asphalt binders and on changes of their performance during the lifetime in road structures. Aging processes of asphalt binders and methods of laboratory aging are described in the theoretical part of the thesis. Furthermore, basic rheological models and related test methods for the evaluation of asphalt binders are described. In the practical part, properties of asphalt binders are investigated after aging process and their performance is evaluated by empirical and functional test methods. The various methods of aging are compared with each other and a relationship between real conditions and laboratory aging is researched. In the next section, vacuum flashed cracked residue (VFCR) is added to the selected asphalt binders and their influence on rheological properties during description of aging of asphalt binders is investigated. The results were used in publication of two certified methodology under the title „The methodology for the evaluation of paving bitumen in terms of susceptibility to thermal oxidative aging“ and „The methodology describes laboratory aging of asphalt mixtures“. The results of the thesis are listed in the conclusion.

The diploma thesis is focused on the appropriate dosage of rejuvenating agents in asphalt mixtures with high content of RAP. The empirical and functional laboratory tests are described in the theoretical part. The practical part deals with the estimation of the optimal amount of rejuvenating agents by means of laboratory tests so that the rheological properties of the degraded asphalt binder can be restored by suitable dosing into the RAP. As part of the TAČR ZÉTA project, an experimental section of asphalt mixture containing 50 % of the RAP and an appropriate amount of the rejuvenating agents was created. The aim of the thesis is to find an optimal dosage of the rejuvenating agents in the samples of the RAP and laboratory aged asphalt binder of gradation 50/70, to determine the effectiveness of selected rejuvenating agents and to monitor changes in the parameters of the experimental section during the period of time.

The subject of the thesis is to describe the effect of fluxing additives on the behaviour of asphalt binders. Emphasis will be placed on changes in rheological properties of asphalt binders at intermediate temperatures, stability during aging and influence of fluxing agents on their low-temperature properties. Theoretical part will deal with the principle of asphalt binders aging and it will summarize knowledge about fluxing additives. Further, empirical and functional tests will be described in order to evaluate asphalt binders. In the practical part, all laboratory tests will be evaluated and the effects of two different fluxing additives will be compared.

碩士
大同大學
事業經營學系(所)
103
In recent years, due to the rapid development of the Internet , the convenience of e-commerce transactions, setting off a network of consumption opportunities. Not only is the distance between the consumer and the seller is shortened, but also means the Internet marketing channels to expand. The significant rolls that consumers make a decision to buy a product comes from their self distinction and habit as well as influence from seller reputation. A business owner has to understand these factors and find a way that makes consumers choose their product from thousands of others. This research sample from students in Tatung University and base on internet business. It discusses reputation evaluation from internet of the seller and self construal which influence to consumer. As well as classify consumer self distinction Included friend, product categories as disturb factors. According to internet purchase evaluate table from 280 students for this research. Graded from 0-10 related to seller as 0 is the worst and 10 means best. Formula 1：2(selling reputation: up/down side) x 2(self construal: interdependence/independence) x 2(friend purchased: Yes/No.) and Formula 2：2( selling reputation: up/down side) x 2( self construal: interdependence/independence) x 3 (product categories：search, experience, and credence goods). The results showed that consumers in different shopping situations, the seller reputation and self construal to the consumer purchase intention. However, accompanied by a friend, and product categories will affect the consumer's purchase intention. And the seller reputation and self construal interaction under the influence of product categories actually interfere with the consumer's willingness；Similarly, the seller reputation and self construal interaction under the influence of friend actually interfere with the consumer's willingness.