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1
Jaržemskis, Andrius. "Logistikos veiksnių įtakos transporto srautų pasiskirstymui tyrimas". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2004. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2004~D_20041216_102159-77986.
Testo completoAbstract (sommario):
Pasaulio ekonomikos augimas, spartėjantis globalizacijos procesas, technologijų pažanga didina atstumus tarp žaliavų gavimo, gamybos ir pagamintų prekių naudojimo taškų. Gausėjant prekybinių ryšių bei plečiantis jų geografijai, didėja reikalavimai transporto ir logistikos paslaugas teikiančiam sektoriui. Regionų ekonominis augimas priklauso nuo to, kaip transporto sistema geba patenkinti žaliavų tiekėjų, gamintojų, prekybininkų ir vartotojų logistikos poreikius laiko, greičio, saugumo, sąnaudų prasmėmis. Transporto srautai ilgainiui prisitaiko prie kintamų regiono logistikos poreikių, tačiau dėl transporto sistemos inertiškumo tam sugaištama laiko. Lietuvoje reikšminga dalis bendrojo nacionalinio produkto sukuriama transporto ir logistikos sektoriuje, kadangi šalis yra stambių tranzitinių krovinių srautų kryžkelėje. Lietuvai tapus Europos Sąjungos nare, atsiveria tarptautinės prekybos augimo galimybes, Lietuva tampa Europos Sąjungos buferine zona prekybai su Rytų bloko šalimis, taigi teisinga Lietuvos transporto sistemos plėtros strategija gali suteikti Lietuvai didžiulį ekonominį potencialą, bendrojo vidaus produkto ir darbo vietų skaičiaus augimo perspektyvas. Transporto srautams užtikrinti būtina transporto infrastruktūra, kurios plėtrai yra labai svarbu nustatyti potencialius krovinių srautus. Transporto infrastruktūra labai imli kapitalui, todėl jos plėtros kryptys turi tiksliai atitikti logistikos poreikius, priešingu atveju milžiniškos investicijos nepateisinamos... [to full text]Relevance of the dissertation is determined by the object of research – the influence of logistical factors on transport flows distribution. The growth of world economics, business globalization, progress in technology skills extends the distances between geographical points of raw materials resources, manufacturers and consumers. Due to the membership in the European Union (EU) Lithuania has got new opportunities for international trade growth, and all the Eastern Baltic countries have become the buffer region for the EU trading with the countries of the Eastern Europe and Asia. A proper transport policy and infrastructure development would increase significantly the GNP in warehousing, transport and distribution sectors. Forecasting of potential transport flows according to logistical requirements of freight suppliers is most important for transport network optimization. Scientific problem. Contemporary transport engineering theory approaches the peculiarities of transport flows formation too narrowly, only as an analysis of internal factors determining freight flows. There is no analysis of external factors. Many researchers assume that transport flows are determined only by the existing transport network and its characteristics. Other researchers consider transport flows as a result of logistic elements only. The estimating of internal and external logistical factors provides a possibility to forecast the transport flows. Aim of the research is to create a model of... [to full text]
2
Jaržemskis, Andrius. "The research of the influence of logistical factors on transport flows distribution". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2004. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2004~D_20041216_141558-30742.
Testo completoAbstract (sommario):
Relevance of the dissertation is determined by the object of research – the influence of logistical factors on transport flows distribution. The growth of world economics, business globalization, progress in technology skills extends the distances between geographical points of raw materials resources, manufacturers and consumers. Due to the membership in the European Union (EU) Lithuania has got new opportunities for international trade growth, and all the Eastern Baltic countries have become the buffer region for the EU trading with the countries of the Eastern Europe and Asia. A proper transport policy and infrastructure development would increase significantly the GNP in warehousing, transport and distribution sectors. Forecasting of potential transport flows according to logistical requirements of freight suppliers is most important for transport network optimization.
Scientific problem. Contemporary transport engineering theory approaches the peculiarities of transport flows formation too narrowly, only as an analysis of internal factors determining freight flows. There is no analysis of external factors. Many researchers assume that transport flows are determined only by the existing transport network and its characteristics. Other researchers consider transport flows as a result of logistic elements only. The estimating of internal and external logistical factors provides a possibility to forecast the transport flows.
Aim of the research is to create a model of... [to full text]Pasaulio ekonomikos augimas, spartėjantis globalizacijos procesas, technologijų pažanga didina atstumus tarp žaliavų gavimo, gamybos ir pagamintų prekių vartojimo taškų. Lietuva tapusi Europos Sąjungos nare, tampa Europos Sąjungos buferine zona prekybiniams mainams su Rytų Europos ir Azijos šalimis. Lietuvos transporto sistemą būtina pritaikyti esamiems ir potencialiems tarptautiniams krovinių srautams aptarnauti. Transporto srautų formavimosi išorinių veiksnių nustatymas ir įvertinimas Lietuvos transporto strategijoje gali suteikti šaliai didžiulį ekonominį potencialą.
3
Volpe, Adua <1996>. "Protein engineering for drug transport". Master's Degree Thesis, Università Ca' Foscari Venezia, 2021. http://hdl.handle.net/10579/20470.
Testo completoAbstract (sommario):
Negli ultimi anni, le nanoparticelle sono emerse come nuovi vettori promettenti per la somministrazione di terapie e farmaci. Le molecole naturali, come le proteine, sono un ottimo sostituto dei polimeri sintetici comunemente impiegati nella sintesi di nanoparticelle grazie alla loro sicurezza, biodisponibilità, biocompatibilità, biodegradabilità e bassissima tossicità. Inoltre la loro sintesi è ecologica e non prevede l'utilizzo di sostanze chimiche tossiche. I sistemi di somministrazione più utilizzati sono quelli basati su proteine naturali, come l'albumina sierica umana. L'albumina sierica umana è la proteina più abbondante nel corpo umano con una lunga emivita. La sua struttura caratteristica consente il legame multiplo di sostanze terapeutiche sulla sua superficie, rendendo l'HSA la proteina più utilizzata e prominente per i sistemi di somministrazione di farmaci a base di proteine. È noto che l'HSA tende ad accumularsi all'interno del sito del tumore o nei tessuti infiammati a causa del trasporto mediato dal recettore.
Lo scopo di questa tesi era cercare di ingegnerizzare l'albumina sierica umana per i sistemi di somministrazione di farmaci. Alcuni studi hanno rivelato che gli oligomeri di HSA, in un certo intervallo di dimensioni, sembrano molto promettenti come carrier per le terapie. Infatti, grazie alla loro dimensione specifica, l'assorbimento da parte del fegato e la distruzione da parte del sistema immunitario sono notevolmente ridotti o evitati. Questa tesi illustra la proteina impiegata (albumina sierica umana) e i metodi utilizzati nella generazione di oligomeri proteici, come la clonazione, la tecnica di assemblaggio di Gibson, l'elettroforesi su gel.
4
Kahkeshan, Siavoche. "Marine log supply : a transport engineering analysis". Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27117.
Testo completoAbstract (sommario):
This thesis investigates the marine transport-inventory system of Coastal British Columbia.
The intrinsic characteristics of marine log transportation in this region are the vulnerability of marine transportation to adverse weather conditions and the presence of time-related economic costs.
The system is confined to the Powell River operation. Three origins, one storage area and three pulp log types are considered. The formulated problem is classified as a sequential decision-making process. A deterministic model using the network flow theory and a simulation model using GPSS are developed. Due to considerable uncertainty in the system operation, the computer simulation model is selected.
The model includes all of the important system variables and their interactions and assesses alternative operational doctrines by calculating variation in a key aspect of system performance, total logistic cost.
It is found that: 1) the use of barges as the transportation mode leads to the least logistic cost, 2) the second best transportation alternative is the direct shipment of logs from origins to the mill and 3) if higher value saw log is considered, the log-taxi alternative may become attractive.
However, to improve the capability of the developed model, more information on the salt contamination and teredo damage and accurate estimation of cost consequences of a mill shutdown are required. Future works should focus on these areas.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
5
Tylleman, Benoît. "Molecular engineering of anthradithiophenes for charge transport". Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209650.
Testo completoAbstract (sommario):
L’électronique organique est un nouveau domaine de recherche qui combine les propriétés électriques de l’électronique avec les propriétés mécanique des matériaux organiques. De nouvelles applications telles que des écrans flexibles, de l’éclairage de surface ou des cellules photovoltaïques flexibles, qui ne sont pas possible avec l’électronique basée sur le silicium, sont envisagées. Les semi-conducteurs organiques sont les matériaux clés de ces dispositifs électroniques. Pour le design moléculaire, deux paramètres doivent être optimisés :l’énergie de réorganisation qui doit être minimisée et l’intégrale de transfert qui doit être maximisée. Avec un noyau aromatique rigide et étendu, les acènes linéaires tels que le pentacène et les anthradithiophènes (ADT) possèdent des énergies de réorganisation parmi les plus petites. Quant à l’intégrale de transfert, son intensité va dépendre de l’arrangement moléculaire qui ne peut malheureusement pas encore être prédit. Divers substituents peuvent être introduit sur le noyau aromatique afin de moduler l’arrangement moléculaire et ainsi maximiser l’intégrale de transfert.Durant cette thèse, nous nous sommes intéressés à l’amélioration du transport de charge des anthradithiophènes par design moléculaire. Deux approches ont été envisagées :l’approche moléculaire et l’approche macromoléculaire. L’approche moléculaire se base sur les travaux de Takimiya sur les naphtodithiophènes. Dans ces travaux, il est montré que la mobilité de charge est supérieure lorsque l’isomère anti est utilisé plutôt que l’isomère syn. Les anthradithiophènes sont généralement utilisés en tant que mélange d’isomères syn et anti ;ceci est une conséquence de la voie de synthèse utilisée. Il est raisonnable de penser qu’utiliser des ADT isomériquement purs donnera des mobilités de charge plus élevées, à l’instar des naphtodithiophènes. Le premier objectif de cette thèse est donc de développer une méthodologie permettant d’obtenir des ADT isomériquement purs. L’approche macromoléculaire est basée sur les travaux théoriques d’Antoine Van Vooren sur le couplage électronique via pont éthylène (non conjugué). Selon ces calculs, le couplage électronique entre deux noyaux aromatiques est plus important lorsqu’ils sont reliés par un pont éthylène que lorsqu’ils sont indépendants. Le second objectif de cette thèse est de développer une méthodologie qui permet d’attacher deux ADTs via a pont éthylène.
Une stratégie de synthèse menant à l’anti-ADT a été développée. La quantité d’anti-ADT disponible via cette méthodologie est assez faible. Par conséquent, une autre méthodologie a été développée. En fonctionnalisant un des intermédiaires de réaction, il est possible de séparer les deux isomères et ainsi d’obtenir de plus grandes quantités d’anti-ADT et de syn-ADT. Les spectres d’absorption UV-vis du mélange et des différents isomères ont été comparés. Des études sur des dispositifs électroniques utilisant des ADT isomériquement purs sont en cours.
Une stratégie de synthèse menant à l’ADT ponté a été développée. Dans cette stratégie, le pont éthylène est synthétisé en premier et les entités anthradithiophènes générées dans un deuxième temps. L’ADT ponté a été obtenu à l’état de traces, détectées uniquement par spectrométrie de masse. Des efforts synthétique supplémentaire sont nécessaire afin d’obtenir l’ADT ponté dans des quantités suffisantes pour fabriquer des dispositifs électroniques. La fabrication de dispositifs électroniques est une étape cruciale dans la détermination de l’impact du pont sur la mobilité de charge.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
6
Oliveira, Daliana Damaceno Gil de 1972. "Implantação integrada de infraestruturas de transportes : Caso do rodoanel e ferroanel no trecho norte, em São Paulo". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258372.
Testo completoAbstract (sommario):
Orientador: Carlos Alberto Bandeira GuimarãesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-26T04:42:12Z (GMT). No. of bitstreams: 1 Oliveira_DalianaDamacenoGilde_M.pdf: 964791 bytes, checksum: 7035668583ec53d4289bd006d1fa2a90 (MD5) Previous issue date: 2014
Resumo: Os estudos de implantação do Trecho Norte dos empreendimentos Rodoanel e Ferroanel, com traçados próximos, pode potencializar e viabilizar uma série de ações conjuntas, como o compartilhamento das plataformas de terraplenagem em alguns segmentos, otimizando as interferências, drenagem, tratamentos de solos moles, contenções, obras de proteção ambiental, remanejamento de interferências, adequações funcionais dos sistemas viários lindeiros e áreas de apoio, além de procurar minimizar as necessidades de desapropriações e reassentamentos complementares aos previstos para o Rodoanel, reduzindo de forma significativa os custos em relação a hipótese dos empreendimentos a serem implantados independentemente. Este trabalho, utilizando como suporte metodológico o estudo de caso, estuda a integração dos modais rodoviários e ferroviários e a apresenta as alternativas das implantações nas formas isoladas e faz um comparativo da possibilidade de compatibilização das implantações das linhas férreas com a rodovia. E apresenta como resultado, uma opção para os problemas de infraestrutura de transporte no Brasil, a possibilidade de se pensar em uma integração na construção dos vários modais básicos
Abstract: The implantation studies of road and rail ring roads in São Paulo can enhance and facilitate a series of joint actions , such as sharing of earthwork in some segments platforms , optimizing interference , drainage, soft soil treatment , containment , protection works environmental , relocation interference , functional adaptations of the bordering road systems and support areas , and seek to minimize the needs of expropriation and resettlement complementary to that provided to the Beltway , significantly reducing costs in relation to the hypothesis of projects to be implemented independently . This work , using as methodological support the case study examines the integration of road and rail modes and presents alternative deployments in isolated forms and makes a comparison of the possibility of compatibility between implementations of the railways with the highway . And as a result has an option for the problems of transportation infrastructure in Brazil , the possibility of thinking about integration in the construction of several basic modes
Mestrado
Transportes
Mestra em Engenharia Civil
7
Stavrinidou, Eleni. "Understanding and engineering ion transport in conducting polymers". Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2013. http://tel.archives-ouvertes.fr/tel-00968227.
Testo completoAbstract (sommario):
Many organic electronic and bioelectronics devices rely on mixed (electronic and ionic) transport within a single organic layer. Although electronic transport in these materials is relatively well understood, a fundamental understanding of ion transport is missing. I developed a simple analytical model that describes ion transport in a planar junction between an electrolyte and a conducting polymer film. The model leads to predictions of the temporal evolution of drift length of ions and current. These predictions are validated by numerical simulations and by using realistic parameters, I show that the analytical model can be used to obtain the ion mobility in the film. Furthermore, I developed an experimental method which allows the application of the analytical model and leads to a straightforward estimation of the ion drift mobilities in conducting polymers. PEDOT:PSS was found to support efficient transport of common ions, consistent with extensive swelling of the film in water. Crosslinking the film decreased its swelling and the ion mobility. Understanding the high correlation of hydration and ionic conductivity enables us to engineer materials with high and defined ion mobilities. As an example tuning of ion mobility by adjusting the relative ratio of the hydroscopic phase to PEDOT:TOS is presented. Finally I performed electrochemical impedance spectroscopy during a moving front experiment, in order to give a physical interpretation of the impedance spectra at a conducting polymer/electrolyte junction.
8
Akyol, Fatih. "Nanoscale Electron Transport Engineering for GaN Optoelectronic Devices". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462897011.
Testo completo
9
ZERO, ENRICO. "Systems engineering approaches to safety in transport systems". Doctoral thesis, Università degli studi di Genova, 2022. http://hdl.handle.net/11567/1064736.
Testo completoAbstract (sommario):
During driving, driver behavior monitoring may provide useful information to prevent road traffic accidents caused by driver distraction. It has been shown that 90% of road traffic accidents are due to human error and in 75% of these cases human error is the only cause. Car manufacturers have been interested in driver monitoring research for several years, aiming to enhance the general knowledge of driver behavior and to evaluate the functional state as it may drastically influence driving safety by distraction, fatigue, mental workload and attention. Fatigue and sleepiness at the wheel are well known risk factors for traffic accidents.
The Human Factor (HF) plays a fundamental role in modern transport systems. Drivers and transport operators control a vehicle towards its destination in according to their own sense, physical condition, experience and ability, and safety strongly relies on the HF which has to take the right decisions. On the other hand, we are experiencing a gradual shift towards increasingly autonomous vehicles where HF still constitutes an important component, but may in fact become the "weakest link of the chain", requiring strong and effective training feedback.
The studies that investigate the possibility to use biometrical or biophysical signals as data sources to evaluate the interaction between human brain activity and an electronic machine relate to the Human Machine Interface (HMI) framework. The HMI can acquire human signals to analyse the specific embedded structures and recognize the behavior of the subject during his/her interaction with the machine or with virtual interfaces as PCs or other communication systems. Based on my previous experience related to planning and monitoring of hazardous material transport, this work aims to create control models focused on driver behavior and changes of his/her physiological parameters. Three case studies have been considered using the interaction between an EEG system and external device, such as driving simulators or electronical components. A case study relates to the detection of the driver's behavior during a test driver. Another case study relates to the detection of driver's arm movements according to the data from the EEG during a driver test. The third case is the setting up of a Brain Computer Interface (BCI) model able to detect head movements in human participants by EEG signal and to control an electronic component according to the electrical brain activity due to head turning movements. Some videos showing the experimental results are available at https://www.youtube.com/channel/UCj55jjBwMTptBd2wcQMT2tg.
10
Kim, Wonjung Ph D. Massachusetts Institute of Technology. "Optimal transport strategies". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79309.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 103-112).
It is generally presupposed that the shapes and mechanisms encountered in nature have evolved in such a way as to maximize the robustness of a species. However, most such optimization problems arising in biology are sufficiently complex that it is neither clear what is being optimized, nor what are the relevant constraints. We here consider a number of natural fluid transport systems that may be framed in terms of constrained optimization problems. We first examine natural drinking strategies. We classify the drinking strategies of a broad range of creatures according to the principal forces involved, and present physical pictures for each style. Simple scaling arguments are developed and tested against existing data. While suction is the most common drinking strategy, various alternative styles have evolved among creatures whose morphological, physiological and environmental constraints preclude it. Many small creatures rely on relatively subtle capillary effects for fluid uptake. Particular attention is given to nectar drinking strategies. Nectar drinkers must feed quickly and efficiently due to the threat of predation. While the sweetest nectar offers the greatest energetic rewards, the sharp increase of viscosity with sugar concentration makes it the most difficult to transport. An optimal sugar concentration is thus expected for which the energy intake rate is maximized. An extensive data set indicates that the sugar concentration that optimizes energy transport depends exclusively on the drinking technique employed. We identify three nectar drinking techniques: active suction, capillary suction, and viscous dipping and rationalize the reported optimal concentrations for each through consideration of the appropriate constrained optimization problem. Blood flow in vertebrates and phloem flow in plants are known to be optimized for efficient transport of oxygen and sugar, respectively. Efficient transport of material is similarly advantageous in engineered transport systems such as traffic and wireless networks. We thus develop a general framework for determining the concentration that maximizes the material flow in a number of transport systems.
by Wonjung Kim.
Ph.D.
11
Lewis, Dale B. (Dale Brian). "Freight mode choice : air transport versus ocean transport in the 1990s". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11828.
Testo completo
12
Downs, Christopher Stephen Charles. "A route to strain-engineering electron transport in graphene". Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/18897.
Testo completoAbstract (sommario):
Graphene, a single atomic layer of graphite, has many exciting electronic and mechanical properties. On a fundamental level, the quasi-relativistic behaviour of the charge carriers in graphene arises from the honeycomb-like atomic structure. Deforming the lattice changes the lengths of the carbon-carbon bonds, breaking the hopping symmetry between carbon sites. Mathematically, elastic strain in a graphene membrane can be described by additional terms in the low-energy effective Hamiltonian, analogous to the vector potential of an external magnetic field. Hence, certain non-uniform strain geometries produce so-called `pseudo-magnetic fields', leading to a predicted zero-field quantum Hall effect. These fictitious magnetic fields are distinct from an external magnetic field in that they are only observed by charge carriers within the membrane, and have opposing polarity for electrons in the K and K' valleys, preserving time-reversal symmetry of the lattice as a whole. Deforming graphene in the non-uniform manner required to produce a homogeneous pseudo-magnetic field has proven to be a huge technological challenge, however, restricting experimental evidence to scanning tunnelling spectroscopy measurements on, for example, highly deformed nanobubbles formed by the thermal expansion of an epitaxially grown sheet on a platinum substrate. These results stimulated a large amount of interest in strain-engineering electron transport in graphene, partly due to the extreme magnitude of the observed pseudo-magnetic field, a direct consequence of the strain components strongly varying over the space of a few nanometres, but the formation of nanobubbles is a highly stochastic process which cannot be reliably reproduced. Subsequent research found a way to fabricate nanobubbles with a high degree of consistency, but the measurements were still limited to local-probe techniques due to the nanoscale size of the devices. As such, a method to reliably induce a homogeneous pseudo-magnetic field within a micron-sized membrane would be an attractive proposition, and is the basis for the work presented within this thesis. The non-uniform strain required precludes a simple bending or elongation of the substrate, hence a more local method is required. A novel nanostructure consisting of suspended gold beams surrounding a graphene membrane will deform upon cooling to cryogenic temperatures, and crucially, the actuation mechanism can be designed to produce any configuration of strain, including uniaxial strain, triaxial strain and a fan-shaped deformation, the latter two of which are predicted to create homogeneous pseudo-magnetic fields within a membrane. Strain patterns which are predicted to produce experimentally significant pseudo-magnetic fields (~1 T) may be generated with complex actuation beams that are physically achievable. Furthermore, the actuation mechanisms may be utilised as electrical contacts to the membrane, allowing its conductivity to be measured in the context of a two- or multi-terminal measurement, in conjunction with an external magnetic field. The design of the devices was developed using finite-element analysis, and the behaviour verified by low-temperature imaging of prototypes. While, after careful annealing, some conventional two-terminal suspended devices exhibited quantum Hall features at very low fields, the fabricated strain-inducing devices did not display pseudo-Landau quantisation, nor Landau quantisation, due to the difficulties of using current annealing to clean devices post-fabrication. The presented work, however, could pave the way towards observing signatures of pseudo-magnetic fields in a range of experimental measurements, as well as creating alternative strain geometries.
13
Garabedian, Stephen P. "Large-scale dispersive transport in aquifers : field experiments and reactive transport theory". Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14645.
Testo completo
14
Tyagi, Rajesh Kumar. "Transport studies in pervaporation". Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6575.
Testo completoAbstract (sommario):
In the theoretical part of this work, mathematical equations were derived for describing steady state pervaporation transport considering the chemical potential gradient as the driving force for the flow of penetrant. The membrane is split perpendicular to the penetrant flow direction into small segments in which an imaginary liquid (or vapor) phase is in thermodynamic equilibrium with each membrane segment. The mathematical equations obtained for pure penetrant permeation are the same as derived by the pore flow model. Based on the analysis of binary mixture system, the possibility of concentration polarization phenomena occurring inside the membrane was pointed out. In the analysis of binary mixture system, coupling was considered in the liquid-filled region of the membrane but no coupling was considered in the vapor-filled region of the membrane. The theoretical prediction of concentration polarization occurring inside the membrane was substantiated by experimental data. In the experimental part of the work separation of acetic acid/water mixture by pervaporation in the entire composition range was investigated using symmetric and dense aromatic polyamide membrane. Aromatic polyamide is a highly hydrophilic material. The effect of downstream pressure on the pure component permeation was studied at 25$\sp{\circ}$C. First, the penetrant concentration profiles of pure water inside the membrane were established at different downstream pressures by performing steady state pervaporation experiments. Secondly, the profiles of the binary penetrant mixture (acetic acid/water) inside the membrane were established. The process variables studied were; feed temperature (25$\sp{\circ}$C, 35$\sp{\circ}$C and 40$\sp{\circ}$C), downstream pressure (467 Pa, 1200 Ps and 2666 Pa) and feed composition covering the complete range of the binary mixture composition. These experiments were performed by using a stack of identical membranes during steady state pervaporation, stopping the pervaporation experiment, dividing the stack into substacks, desorbing and analyzing the penetrants sorbed from each substack. Sorption experiments were performed from liquid phase and vapor phase for the binary mixture of acetic acid-water. The sorption experiments from the liquid phase were performed at 25$\sp{\circ}$C, 35$\sp{\circ}$C and 40$\sp{\circ}$C for the entire binary mixture composition range. Vapor sorption isotherms were also established at these temperatures. The value obtained for the amount of penetrant in the membrane during steady state pervaporation in some cases was higher than the corresponding equilibrium sorption value. This seems impossible from the thermodynamic point of view. It was concluded that there are two different equilibria. The first one is the static equilibrium achieved during sorption experiments and the second one is the dynamic equilibrium achieved during pervaporation experiments. The structure of the polymeric membrane is different under these two circumstances. Based on the experimental data a novel design for the pervaporation membrane has been proposed. State of permeant (penetrant) study for acetic acid-water-polyamide system was performed using differential scanning calorimetry technique. Acetic acid present in the membrane did not show any response in the thermogram corresponding to the phase change. It was concluded that acetic acid present in the membrane was in non-freezable bound state. Some spectroscopic studies were also undertaken using FTIR-ATR (Attenuated Total Reflection) technique to study the penetrant interaction with the polymeric membrane. Penetrant concentration profiles predicted from the newly developed transport model were compared with the experimental penetrant profiles.
15
Wendell, Dawn M. (Dawn Marie) 1983. "Transport in granular systems". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69499.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 93-98).
There are many situations in which a continuum view of granular systems does not fully capture the relevant mechanics. In order for engineers to be able to design systems for transporting granular materials, there needs to be an understanding of the mechanics of granular systems and how their non-continuous behavior affects their dynamics. This thesis takes an example of a granular system from nature and uses this system to analyze the way granular materials interact with flexible boundaries. This thesis focuses on digging in granular materials. Pinto bean plant roots were used as a model biological system, and experiments using photoelastic grains were performed to quantify the effect of the inhomogeneous forces in the substrate on the root growth. It was determined that the pinto bean roots grew between grains when the force between those grains was less than 0.5 N. This value was time-dependent and showed a previously-unquantified strengthening of the roots over time. Also, while the roots were growing in the granular substrate, they altered the forces between grains by an average of 110 mN. An analytical model of digging energy was developed to investigate the differences between diggers that are much larger than the grain size and diggers that are much smaller than the grain size. Based on this model, a design tool was created so that designers could quickly identify promising technologies for digging based on the size scale of the grains and the desired size of the digger. Finally, two elements of the plant roots, mechanical flexibility and an actuated tip, were used to create robotic diggers to quantify the associated savings in digging energy. Increasing the mechanical flexibility of the digger was shown to result in energy savings of more than 50% when decreasing the bending modulus by one order of magnitude. However, large variations in the data were observed as a result of the inhomogeneity of the granular system. These variations were quantified and were consistent with previous literature regarding forces in granular systems. Also, a numerical model was created that demonstrates that the increase in digging efficiency can be attributed to the flexibility of the digger. Experiments with diggers whose tip orientation cycled from side to side show that it is more energy-efficient to dig with this active tip only if the energy used to create the changing tip orientation is less than 2.5 x 10-⁵ J per mm dug.
by Dawn Marie Wendell.
Ph.D.
16
Swartz, Melody A. "Interstitial-lymphatic transport phenomena". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50376.
Testo completo
17
Bledsoe, Keith C. "Inverse Methods for Radiation Transport". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259206496.
Testo completo
18
Hollewand, Michael Paul. "Transport in porous catalysts". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281985.
Testo completo
19
Whitehead, Lorne Arthur. "Transport and distribution of light energy for illuminating engineering applications". Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29318.
Testo completoAbstract (sommario):
This thesis concerns the transport of light along a class of cylindrical hollow optical structures, with an aim to develop practical light transport and distribution systems for illuminating engineering applications.
Based on intuition, it is postulated that it may be possible to guide light energy in a hollow cylindrical optical structure, by means of total internal reflection on the external surfaces. Such a development would allow light to be guided with the efficiency of optical fibres, but with reduced material costs.
In order to assess this possibility, a new technique is presented for analytic ray tracing in general cylindrical structures. The technique makes it possible to trace ray paths in the cross sectional plane of the structure, with the motion in the dimension out of the cross sectional plane precisely taken into account with a simple correction. This technique greatly simplifies the ray tracing calculations which are necessary to study the light transport properties of the proposed structures. It is then shown with the aid of this technique that a certain class of prismatic structures do indeed have the capability of guiding light, and members of this class are termed prism light guides.
In any real prism light guide, light is not conducted perfectly, but is lost as a result of a number of deviations from the ideal model. Of these, the one intrinsic loss mechanism, which distinguishes a prism light guide from optical fibres, is diffraction at the corners of the prismatic surfaces. Fortunately, diffraction effects are significantly smaller than losses from practical imperfections in prism light guides. A detailed study of the other types of loss mechanisms is then presented. These arise from imperfections of the optical material comprising the prism light guide (absorption and scatter), and imperfections in the shape of the prism light guide. The importance of these effects is discussed first in an approximate assessment, and they are then modelled precisely by means of computer ray tracing Monte Carlo techniques. These predictions are compared with experimental measurements of actual prism light guides, with substantial agreement.
Consideration is then given to the use of a prism light guide in illuminating engineering applications. In these situations light is distributed along the length of a prism light guide, and is uniformly emitted from the surface. The performance of such a system is modelled with Monte Carlo computer ray tracing, and experimentally tested, with substantial agreement.
This study concludes with a measurement of diffraction losses. These losses were enhanced by the use of longer wavelength radiation (3mm wavelength microwaves). The results confirm that diffraction losses are small relative to other loss mechanisms.
In general, the results reported in this thesis demonstrate the existence of a useful class of light guidance structures which are particularly well suited to the requirements for distribution and transport of optical radiation for illuminating engineering applications.Science, Faculty of
Physics and Astronomy, Department of
Graduate
20
Park, Heechul. "Biologically engineering nanostructures to maximize energy, electron, and ion transport". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89841.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 159-168).
Human intellectual desire inspires recent research to expand to interdisciplinary areas across biology, chemistry, and physics. Interdisciplinary research in unexplored areas is challenging, but holds great promise to elucidate what people did not see before. Scientific discoveries bring us not only intellectual pleasures, but also opportunities to contribute to the advancement of mankind. Photosynthesis is a representative interdisciplinary research field. Conducting research in photosynthesis requires a collaborative work of biology, photochemistry, and quantum physics. Nature has optimized photosystems in bacteria, algae, and plants over three billion years in an evolutionary fashion to utilize solar energy for their survival. The way nature has mastered such systems can provide insights into designing efficient solar energy conversion applications. This thesis explores artificial photosystems as proofs of nature's design concept using a biological scaffold of M13 bacteriophage. The main ideas in the thesis focus on maximizing transport phenomena in the systems, resulting in performance improvements. Genetic engineering of M13 bacteriophage enables nano-scale multi-component assemblies to create tunable, artificial photosystems for solar energy utilization. Artificial photosystems include light-harvesting antenna complexes and oxygen-evolving photocatalytic systems. In particular, a solid collaboration with Seth Lloyd's theory group inspires me to design a quantum light-harvesting antenna complex. The genetically engineered light-harvesting antenna complex creates a chromophore network interplaying between quantum and semi-classical mechanisms, thus maximizing exciton transport.
by Heechul Park.
Ph. D.
21
Pearson, Natalie Clare. "Mathematical modelling of flow and transport phenomena in tissue engineering". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:43688cc7-b523-4676-8c41-72db7fc07814.
Testo completoAbstract (sommario):
Tissue engineering has great potential as a method for replacing or repairing lost or damaged tissue. However, progress in the field to date has been limited, with only a few clinical successes despite active research covering a wide range of cell types and experimental approaches. Mathematical modelling can complement experiments and help improve understanding of the inherently complex tissue engineering systems, providing an alternative perspective in a more cost- and time-efficient manner. This thesis focusses on one particular experimental setup, a hollow fibre membrane bioreactor (HFMB). We develop a suite of mathematical models which consider the fluid flow, solute transport, and cell yield and distribution within a HFMB, each relevant to a different setup which could be implemented experimentally. In each case, the governing equations are obtained by taking the appropriate limit of a generalised multiphase model, based on porous flow mixture theory. These equations are then reduced as far as possible, through exploitation of the small aspect ratio of the bioreactor and by considering suitable parameter limits in the subsequent asymptotic analysis. The reduced systems are then either solved numerically or, if possible, analytically. In this way we not only aim to illustrate typical behaviours of each system in turn, but also highlight the dependence of results on key experimentally controllable parameter values in an analytically tractable and transparent manner. Due to the flexibility of the modelling approach, the models we present can readily be adapted to specific experimental conditions given appropriate data and, once validated, be used to inform and direct future experiments.
22
Ahmed, Sheaza. "Metabolic Engineering of Plants by Manipulating Polyamine Transport and Biosynthesis". Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1507393675673047.
Testo completo
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Jagintavičius, Darius. "Transporto sektoriaus analizė darnaus vystymosi požiūriu". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120620_131137-66778.
Testo completoAbstract (sommario):
Darbo tikslas – atlikti Lietuvos autotransporto sektoriaus rodiklių analizę darnaus aplinkos būklės, ekonominio ir socialinio vystymosi aspektais 2000–2011 m.
Vykdant išsikeltus darbo uždavinius buvo renkami, grupuojami, ir analizuojami statistiniai duomenys susiję su transporto sektoriaus darniu vystymusi ir apimantys šio sektoriaus aplinkosauginius, ekonominius bei socialinius aspektus.
Analizuojamas laikotarpis apima 2000 – 2010 metus. Per šį laikotarpį Lietuvos transporto sektorius labai vystėsi.. Kelių transporto priemonių skaičius 2000 – 2006 padidėjo 40 %. Vėliau šis augimas nebuvo toks ryškus. Kuro sunaudojimas transporto sektoriuje per analizuojamą laikotarpį išaugo 50 proc. Kuro suvartojimas transporto sektoriuje sumažėjo dabartinės ekonominės krizės metu. Vis didesnę dalį krovinių ir keleivių apyvartos užima kelių transportas. Keleivių vežimas viešojo naudojimo autobusais iki 2008 metų padidėjo 22 %.
Transporto sektoriaus sukuriama BVP dalis 2000 – 2008 metų periodu augo 25 %. Darbuotojų skaičius transporto sektoriuje per 2000 – 2010 metų laikotarpį sumažėjo 16 %, tai rodo, kad net ir maža dalis dirbančiųjų transporto sektoriuje sukuria gan didelę dalį bendrojo Lietuvoje sukuriamo BVP. Bendras kelių tinklas išaugo 10 %. Lietuvoje gyventojų mirtingumas dėl transporto įvykių sumažėjo 54 %. Krovinių vežimas visomis transporto rūšimis iki 2008 metų augo, vėliau pastebimas sumažėjimas dėl finansų krizės. Ir tik nuo 2009 metų pastebimas pervežamų krovinių skaičiaus... [toliau žr. visą tekstą]The purpose - to carry out motor Lithuania sector analysis of indicators of sustainable environmental, economic and social aspects of development in 2000-2011. The performance targets set for itself were collected, grouped and analyzed statistical data related to the transport sector and the sustainable development of the sector covering the environmental, economic and social aspects. The analysis covers the period 2000 - 2010 years. During this period the Lithuanian transport sector is very developed .. Road vehicles 2000 - 2006 increased by 40%. Later, the increase was less pronounced. Fuel consumption in the transport sector during the analysis period increased by 50 percent. Fuel consumption in the transport sector dropped in the current economic crisis. An increasing share of freight and passenger turnover of road transport occupies. Passengers carried by public buses by the year 2008 increased by 22%. Transport sector in the GDP of 2000 - 2008 season increased by 25%. Number of employees in the transport sector during 2000 - 2010 the period decreased by 16%, suggesting that even a small proportion of workers in the transport sector creates a relatively large part of total GDP generated in Lithuania. The total road network grew by 10%. Lithuania mortality rate of traffic accidents decreased by 54%. Freight transport by all modes of transport by the year 2008 to grow at appreciable reduction of the financial crisis. It is only since the year 2009 appreciable increase... [to full text]
24
Simo, John A. (John Alfred). "Turbulent transport of inertial aerosols". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/38716.
Testo completo
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Kosto, Kimberly Bryan 1977. "Hindered transport in composite hydrogels". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28358.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2004.Includes bibliographical references (leaves 143-152).
The ultimate goal of this research was to develop a greater understanding of the structural components needed to describe transport within the glomerular basement membrane (GBM). Specifically, dimensionless diffusive and convective hindrance factors were investigated by measuring macromolecular permeability through synthetic, two-fiber, agarose-dextran hydrogels at very small or very high Pe, respectively. By comparing diffusion and convection in the synthetic hydrogel with corresponding measurements in isolated rat GBM, further insight regarding the structure responsible for transport through the GBM was gained. In order to compare diffusive hindrances in the synthetic gels with those in isolated GBM, partitioning in agarose-dextran hydrogels was also examined. Additionally, hindered transport theories were tested. In studying diffusion, partitioning, and convection, macromolecules with Stokes-Einstein radii (r) ranging from 2.7 to 5.9 nm were used. Gels with agarose volume fractions of 0.040 and 0.080 were studied with dextran volume fractions (assuming dextran acts as a fiber) ranging from 0 to 0.0076 and 0 to 0.011, respectively. For the diffusion studies, two globular proteins (ovalbumin and bovine serum albumin) and three narrow fractions of Ficoll, a spherical polysaccharide, were used. For the partitioning and convection studies, four narrow fractions of Ficoll were used. Diffusivities of fluorescein-labeled macromolecules were measured in dilute aqueous solution (D[infinity]), agarose gels (D[alpha]), and agarose-dextran composite gels (D) using fluorescence recovery after photobleaching.
(cont.) For both agarose concentrations, the Darcy permeability (K) decreased by an order of magnitude as the dextran concentration in the gel was increased from zero to its maximum value. For a given gel composition, the relative diffusivity (D/D[infinity]) decreased as r increased, a hallmark of hindered diffusion. For a given test molecule, D/D[infinity] was lowest in the most concentrated gels, as expected. As the dextran concentration was increased to its maximum value, 2-3 fold decreases in relative diffusivity resulted for both agarose gel concentrations. The reductions in macromolecular diffusivities caused by incorporating various amounts of dextran into agarose gels could be predicted fairly accurately from the measured decreases in K, using an effective medium model. This suggests that one might be able to predict diffusivity variations in complex, multicomponent hydrogels (e.g. those in body tissue) in the same manner, provided that values of K can be obtained. Equilibrium partition coefficients ([Phi],the concentration in the gel divided by that in free solution) of fluorescein-labeled Ficolls in pure agarose and agarose-dextran composite gels were measured as a function of gel composition and Ficoll size. As expected, [Phi] generally decreased as the Ficoll size increased (for a given gel composition) or as the amount of dextran incorporated into the gel increased (for a given agarose concentration and Ficoll size). The decrease in [Phi] that accompanied dextran addition was predicted well by an excluded volume theory in which agarose and dextran were both treated as rigid, straight, randomly positioned and oriented fibers ...
by Kimberly Bryan Kosto.
Ph.D.
26
Kinsey, Michael Jon. "Vertical transport evacuation modelling". Thesis, University of Greenwich, 2011. http://gala.gre.ac.uk/7786/.
Testo completoAbstract (sommario):
Within any high-rise structure or underground/subway station, occupants often heavily rely on vertical transport devices (e.g. escalators, lifts, etc) to travel vertically between levels. Typically such devices provide a faster and more comfortable means to travel than the equivalent stairs. Such devices also provide an additional means for occupant egress. However, the provision for utilising such devices in actual buildings for evacuations is rare. Despite a select number of structures throughout the world allowing the use of vertical transport devices within evacuation scenarios, little is understood with regards to evacuation vertical transport strategies and to what extent such strategies may be influenced by associated human factors. This thesis is intended to address this lack of understanding. The thesis provides an in depth review of evacuation usage of vertical transport devices in actual evacuations, their provision in building codes, empirical studies analysing human factors, representation within simulated environments, and analysis of previously explored operational strategies. The review provides a broad set of research questions that the thesis is intended to address. Human factors data associated with vertical transport device usage have been collected via an online survey and video analysis. The data analysis has instructed the development of the vertical transport device models and associated agent models within the buildingEXODUS evacuation software. The models include the representation of device selection, the influence of local conditions in close proximity to a device, and the influence of wait time upon device selection. The developed models have been used to demonstrate the influence of different vertical transport strategies and to what extent such strategies are influenced by human factors. Finally, the thesis concludes by summarising the increased understanding achieved through the work presented.
27
Chrastina, Daniel. "Transport in silicon-germanium heterostructures". Thesis, University of Warwick, 2001. http://wrap.warwick.ac.uk/2574/.
Testo completoAbstract (sommario):
The work presented here describes the electrical characterization of n- and p-type strained silicon- germanium systems. Theories of quantum transport in low magnetic fields at low temperature are discussed in terms of weak-localization: the traditional theory is shown not to account for the dephasing in a 2-dimensional hole gas behaving in a metallic manner and emergent alternative theories, while promising, require refinement. The mobility as a function of sheet density is measured in a p-type pseudomorphic Si0.5Ge0.5 across the temperature range 350 mK–282 K; it is shown that calculations of the mobility based on semi-classical scattering mechanisms fail below 10 K where quantum transport effects become relevant. A room temperature Hall scattering factor has been extracted. A new functional form has been presented to fit the resistivity as a function of temperature, below 20 K: traditional theories of screening and weak localization appear not to be applicable. It is also demonstrated that simple protection circuitry is essential if commercial-scale devices are to be meaningfully investigated. Mobility spectrum analysis is performed on an n-type strained-silicon device. Established analysis methods are discussed and a new method is presented based on the Bryan’s Algorithm approach to maximum entropy. The breakdown of the QHE is also investigated: the critical current density compares well to that predicted by an existing theory. Finally, devices in which both electron and hole gases can be induced are investigated. However, it is shown that the two carrier species never co-exist. Design rules are presented which may allow more successful structures to be created. Results are presented which demonstrate the success and the utility of implanted contacts which selectively reach different regions of the structure.
28
Chiloyan, Vazrik. "Variational approach to solving the phonon Boltzmann transport equation for analyzing nanoscale thermal transport experiments". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115727.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 133-140).
Over time, technology has shrunk to smaller length scales, and as a result the heat transport in these systems has entered the nanoscale regime. With increasing computational speed and power consumption, there is a need to efficiently dissipate the heat generated for proper thermal management of computer chips. The ability to understand the physics of thermal transport in this regime is critical in order to model, engineer, and improve the performance of materials and devices. In the nanoscale regime, thermal transport is no longer diffusive, and the Fourier heat conduction equation, which we commonly utilize at the macroscale, fails to accurately predict heat flow at the nanoscale. We model the heat flow due to phonons (crystal lattice vibrations), the dominant heat carriers in semiconductors and dielectrics, by solving the Boltzmann transport equation (BTE) to develop an understanding of nondiffusive thermal transport and its dependence on the system geometry and material properties, such as the phonon mean free path. A variety of experimental heat transfer configurations have been established in order to achieve short time scales and small length scales in order to access the nondiffusive heat conduction regime. In this thesis, we develop a variational approach to solving the BTE, appropriate for different experimental configurations, such as transient thermal grating (TTG) and time-domain thermoreflectance (TDTR). We provide an efficient and general methodology to solving the BTE and gaining insight into the reduction of the effective thermal conductivity in the nondiffusive regime, known as classical size effects. We also extend the reconstruction procedure, which aims to utilize both modeling efforts as well as experimental measurements to back out the material properties such as phonon mean free path distributions, to provide further insight into the material properties relevant to transport. Furthermore, with the developed methodology, we aim to provide an analysis of experimental geometries with the inclusion of a thermal interface, to provide insight into the role the interface transmissivity plays in thermal transport in the nondiffusive regime. Lastly, we explore a variety of phonon source distributions that are achieved by heating a system, and show the important link between the system geometry and the distribution of phonons initiated by the heating. We show the exciting possibility that under certain nonthermal phonon distributions, it is possible to achieve enhanced thermal transport at the nanoscale, contrary to the current understanding of size effects only leading to reduced thermal conductivities at the nanoscale for thermal phonon distributions.
by Vazrik Chiloyan.
Ph. D.
29
Dondo, Chiedza. "Spatial information system for public transport". Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/10328.
Testo completoAbstract (sommario):
Bibliography: leaves 72-79.One way of reducing traffic congestion is through the promotion of public transport over private cars. Many countries, South Africa included, have set up policies to prioritise this issue. In accordance with these policies, public transport service planners are working to improve public transport services. This requires the collection of data on public transport usage, public transport timetables and the location of the routes, stops and termini. This data needs to be managed and integrated for use in decision-making on public transport services planning. As some of the data is spatial in nature, a spatial information system is proposed as the best tool for capturing, storing and analysing the data.
30
Pongsaksawad, Wanida. "Numerical modeling of interface dynamics and transport phenomena in transport-limited electrolysis processes". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36209.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 111-117).
Electrochemical reactions in materials and processes induce morphological instability on the cathode, which can lead to porous deposits or system failure. The growth of the protrusion is a complex phenomenon which involves chemical, electrical, and momentum driving forces in the system. Thus, it is important to understand the effect of electrochemistry in phase boundary evolution in order to optimize the performance of such processes. This thesis contributes to predicting and controlling such interface instability phenomena by developing a computational model that captures them. Successful application of the model to emerging metal extraction processes demonstrates its usefulness. A phase field model of electrochemical interface is developed for transport-limited electrolysis with rapid charge redistribution. This new Cahn-Hillard phase field formulation includes a model electrostatic free energy term, which captures the behavior of the diffuse interface under the applied electric field, in addition to transport by free energy gradient and convection. The model agrees with published stability criterion for a solid cathode. When the electrodes and electrolyte are low-viscosity fluids, flow stabilizes the interface.
(cont.) A new stability criterion for metal reduction in a liquid-liquid system is derived and agrees well with the model results. Next, the phase field model is extended for a ternary system to model titanium reduction in a supported electrolyte system. The model can simulate phase boundaries migration depending on the composition of the electrolyte and also electronically mediated reactions. Finally, Solid Oxide Membrane Electrolytic Smelting with Rotating Cathode (SOMERC), an emerging technology to electrolytically reduce titanium oxide from molten salt, is investigated. In the SOMERC process, rotational flow is introduced to create shear force that is expected to stabilize the interface. Computational fluid dynamics models of rotational flow are carried out to estimate the relationship between cathode rotational speed, shear strain rate, and boundary layer thicknesses. The phase field model presented in this thesis can be applied to any electrochemical reduction processes that are in the mass-transport controlled regime. Stability criteria and detailed morphology in two and three dimensions can be explored.
by Wanida Pongsaksawad.
Ph.D.
31
Dhunput, Ashvin. "Oil transport in piston ring assemblies". Thesis, City University London, 2009. http://openaccess.city.ac.uk/11916/.
Testo completoAbstract (sommario):
The interface between the piston, piston-rings and the cylinder liner represents one of the most hostile environments the crankcase lubricant experiences in reciprocating engines. The role of piston rings is also becoming more complex in line with the increasing requirements for lower oil consumption and friction. A test rig has been developed to simulate under idealised conditions the lubrication action between the piston-ring and the cylinder-liner in reciprocating engines. This approach attempts to separate the tribological conditions from some of the fundamental and unsteady conditions occurring in production engine piston assemblies such as lubricant starvation, ring and piston dynamics, thermal and elastic deformations and blow by, thus allowing the lubricant film characteristics to be examined in isolation. The current work proposes a methodology in assessing the rheological behaviour of various base oils and their additive chemistry with a view to establishing the likely field performance in formulated lubricating oil. The experiment comprised of testing different types of engine oils where the lubricant film thickness, oil film pressure and friction were simultaneously measured throughout the stroke as a function of speed, load and temperature. Furthermore, laser induced fluorescence (LIF) was used to identify the onset of cavitation occurring in the diverging part of the lubricant film between the piston ring specimen and the liner wall. Recognition that lubricant films under certain condition may cavitate opens up a new area for research, focusing on possible links between cavitation, oil consumption, friction and wear. Oil flow visualisation in the test rig using a high speed video camera allowed observation of cavitation in the diverging part of the ring through an optical liner. The high recording framing rates of the camera have permitted the initiation, development and disintegration of the cavities throughout the stroke to be revealed. An attempt was made to extend the oil film visualisation to a motored diesel engine, with parts of the liner cut and fitted with quartz windows, to confirm the presence of cavitation in the piston-rings interface. Moreover the identification of sub-atmospheric pressure in the rings provided additional support to the visualisation of cavitation found in the engine, albeit of much inferior resolution to that of the idealised piston-ring assembly.
32
Öberg, Maria. "Governance structure for transport corridors". Licentiate thesis, Luleå tekniska universitet, Arkitektur och vatten, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18742.
Testo completoAbstract (sommario):
Transport plays essential roles in almost all economic activities and our daily lives. Transport flows are often agglomerated in soͲcalled transport corridors linking urban and/or commercially important areas.Clearly, it is desirable for transport to be efficient and sustainable, thus there are several onͲgoing initiatives to develop major, often transnational, transport corridors.Diverse stakeholders are affected by and/or involved in the development of these corridors, including travellers, transport buyers,transport service providers and transport authorities (local, regional, national and transnational). Governance of the corridors can be regarded as the interactive involvement of these stakeholders in their development and subsequent management.This is a licentiate by publications based on a covering essay that summarises and synthetises four articles. The topic focuses on the development of a framework for designing governance structures formajor transport corridors, by examining the variables that should be considered, the structural and procedural organisational possibilities, and both stakeholders’ participation and interactions. A qualitative research approach has been applied, as deeper understanding of the underlying issues is needed. Several studies have been performed, in conjunction with the Bothnian green logistic corridorproject, to illustrate key concerns. These studies have included literature reviews, studies of documents describing governance of major European transport initiatives, and interviews with key individualsinvolved in the development of European transport corridors. An international study has been established and supervised to gather experiences from other research projects, including an open workshop for discussion between representatives of various stakeholder groups. In addition, a casestudy of the Bothnian corridor has been performed, including focus group discussions with principal stakeholders.Main findings from the literature studies concern both the design of governance structures and their socioͲpolitical integration. The findings show that there is no universal solution for governance structuresas they have to be adapted to the social, economic and political context, and should have a sufficient flexibility to meet changing requirements. They also show that collaboration between public, private and other stakeholders to address issues earlier handled by a single authority is becoming increasinglycommon, also within the field of transport, particularly when public investment budgets are restricted. Another main finding is that broad stakeholder inclusion is advantageous and engaged leadership crucial for a successful outcome. Both structural and procedural aspects of a governance structure influence theoutcome and need to be considered when designing one. The international study and the workshop confirmed most of these literature findings and additionally highlighted the need for clear goals, objectives and rules for collaboration. Stakeholders´ diverse needs of connecting to a governancestructure were discussed in the workshop. The document studies and the interviews enhanced knowledge of European transport corridor establishment and management practices.Godkänd; 2014; 20140516 (obemar); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Maria Öberg Ämne: Arkitektur/Architecture Uppsats: Governance Structure for Transport Corridors Examinator: Professor Kristina L Nilsson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: PhD, Senior Advisor/Research Fellow Björn Hasselgren, Div. Samhällsplanering och miljö, KTH, Stockholm Tid: Fredag den 19 september 2014 kl 10.00 Plats: F1031, Luleå tekniska universitet
33
Jin, Shi 1963. "Numerical transport in diffusive regimes". Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/565536.
Testo completo
34
Fingerle, Garrett Philip. "Engineering an extensible model for a public transport journey planning system". Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342762.
Testo completo
35
Wang, Chunhai. "Transport through macromolecular solutions and gels". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/36422.
Testo completo
36
Mehrabi, M. Reza. "Modeling transport processes in directional solidification". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11999.
Testo completo
37
Johnston, Scott Travis 1971. "Convective transport of macromolecules in gels". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85359.
Testo completo
38
MacLean, Heather J. (Heather Jean) 1974. "Silver transport in CVD silicon carbide". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17745.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2004.Includes bibliographical references.
Ion implantation and diffusion couple experiments were used to study silver transport through and release from CVD silicon carbide. Results of these experiments show that silver does not migrate via classical diffusion in silicon carbide. Silver release is, however, likely dominated by vapor transport through cracks in SiC coatings. The results of silver ion implantation in silicon carbide and subsequent annealing at 1500ʻC place an upper limit on the silver diffusion coefficient in SiC of 5x10-21 m2/s, a value which is roughly 6 orders of magnitude less than the previous values reported in the literature. Silver diffusion should have been easily observable, but was not detected in SiC plates after heat treatments at 1500ʻC for times ranging between 200 h and 500 h. A detailed investigation of the silver morphology within the SiC both before and after heating showed that silver was immobilized at SiC grain boundaries and did not diffuse along them as expected. Novel spherical diffusion couples were fabricated containing silver inside shells of either graphite or SiC which were coated with CVD SiC. Mass measurements clearly revealed silver release from the diffusion couples after heating, but no silver was detected during concentration profile measurements in the SiC. Leak testing results, however, gave evidence of the presence of cracks in many of the SiC coatings, which may have provided pathways for silver escape. A simple vapor flow model was applied to estimate crack sizes that would account for silver release from SiC coatings in the current diffusion couples and coated fuel particle tests from the literature.
(cont.) These calculated crack sizes are small enough that they would not have been detected during normal investigation or post-irradiation examination. A diffusive mechanism has been assumed to control silver transport in silicon carbide based on silver release observations reported previously in the literature, but no direct evidence of silver diffusion has been offered. Additionally, variations in silver release from particle to particle indicate that silver transport does not occur equally in all silicon carbide samples and is not consistent with diffusion. The findings presented in this dissertation are important to coated particle fuel design and fabrication because they indicate that SiC can successfully retain silver but that some SiC coatings permit silver release. Future work must be directed at identifying the pathways for silver release and their root causes in order to prevent silver release from coated fuel particles.
by Heather J. MacLean.
Ph.D.
39
Lu, Zhengmao. "Evaporation from nanopores : probing interfacial transport". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118723.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 82-87).
Evaporation, a commonly found phenomenon in nature, is widely used in thermal management, water purification, and steam generation as it takes advantage of the enthalpy of vaporization. Despite being extensively studied for decades, the fundamental understanding of evaporation, which is necessary for making full use of evaporation, remains limited up to date. It is in general difficult to experimentally characterize the interfacial heat and mass transfer during evaporation. In this thesis, we designed and microfabricated an ultrathin nanoporous membrane as an experimental platform to overcome some critical challenges including: (1) realizing accurate and yet non-invasive interface temperature measurement; (2) decoupling the interfacial transport resistance from the thermofluidic resistance in the liquid phase and the diffusion resistance in the vapor phase; and (3) mitigating the blockage risk of the liquid-vapor interface due to nonevaporative contaminants. Our nano device consisted of an ultrathin free-standing membrane (~200 nm thick) containing an array of nanopores (pore diameter ~100 nm). A gold layer deposited on the membrane served as an electric heater to induce evaporation as well as a resistive temperature detector to closely monitor the interface temperature. This configuration minimizes the thermofluidic resistance in the liquid and mitigates the contamination risk. We characterized evaporation from this nano device in air as well as pure vapor. We demonstrated interfacial heat fluxes of ~~500 W/cm² for evaporation in air, where we elucidated that the Maxwell- Stefan equation governed the overall transport instead of Fick's law, especially in the high flux regime. In vapor, we achieved kinetically limited evaporation with an interfacial heat transfer coefficient up to 54 kW/cm² K. We utilized the kinetic theory with the Boltzmann transport equation to model the evaporative transport. With both experiments and modeling, we demonstrated that the kinetic limit of evaporation is determined by the pressure ratio between the vapor in the far field and that generated by the interface. The improved fundamental understanding of evaporation that we gained indicates the significant promise of utilizing an ultrathin nanoporous design to achieve high heat fluxes for evaporation in thermal management, desalination, steam generation, and beyond.
by Zhengmao Lu.
Ph. D.
40
Lee, Justin Wu. "Experimental transport of intensity diffraction tomography". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67621.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 89-98).
In this thesis, I perform intensity-based tomographic phase imaging in two ways. First, I utilize the paraxial transport of intensity equation (TIE) to construct phase maps of a phase object at multiple projection angles and reconstruct the object 3- dimensionally using basic tomographic principles. Then, I use an Intensity Diffraction Tomography (IDT) approach to improve the quality of reconstruction by accounting for diffraction effects under 1st order Rytov Approximation. I improve both approaches by applying compressive sensing techniques to estimate missing points in the undersampled data. Finally, I compare I-DT with single-shot, Gabor-type digital holography (also integrating use of compressive sensing principles) and discuss improvements and extensions of the presented implementation of IDT.
by Justin Wu Lee.
S.M.
41
Wu, Yanling. "Molecular Interactions in Facilitated Membrane Transport". University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1144176753.
Testo completo
42
Berglund, Tony. "Secure DNS transport methods". Thesis, Umeå universitet, Institutionen för datavetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-175880.
Testo completoAbstract (sommario):
The Domain Name System (DNS) is a large cornerstone in internet traffic. It translates domain names to IP addresses. Standard DNS(Do53) does not encrypt any of its traffic which leads to some security issues. Mainly that others are able to extract information and tamper with the DNS requests and responses. Two promising secure DNS protocols are DNS over HTTPS (DoH) and DNS over TLS (DoT). They use encryption and authentication in the transfer of data to prevent the issues caused by standard DNS. In this paper a study is presented that compares the two mentioned secure DNS protocols along with Do53 in terms of latency in resolving request. The findings show that DoT latency is in general higher then DoH under the testing circumstances. Do53 latency is lower then both of the secure protocols except in some edge cases where DoH received the lowest latency from a single request. Included with the finding is also several recommendations on how the testing can be expanded to cover a larger scope of DNS transport methods than the test performed in this study.
43
Karlsson, Albin, e Anton Lomaeus. "Transport Aircraft Conceptual Design". Thesis, KTH, Skolan för teknikvetenskap (SCI), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210778.
Testo completoAbstract (sommario):
A conceptual design for a transport aircraft has been created, tailored for human-itarian missions along the equator with its home base in the European Union while optimizing for fuel eciency and speed. An initial estimate of the empty weight was made using historical data and Breguet equations, based on a required payload of 60 tonnes and range of 5 500 nautical miles. A constraint diagram consisting of require-ments for stall speed, takeo distance, climb rate and landing distance was used to determine wing loading and thrust to weight ratio, resulting in a main wing area of 387m 2 and thrust to weight ratio of 0:224, for which two Rolls Royce Trent 1000-H engines were selected. A high aspect ratio wing was designed with blended winglets to optimize against lift induced drag. Wing placement and tail volume were decided by iterative calculations, resulting in a centre of lift located aft of the centre of gravity during all stages of the mission. The resulting aircraft model has a high wing with a span of 62 m, length of 49m with a takeo gross weight of 221 tonnes, of which 83 tonnes are fuel.
44
Nicolaides, Christos. "Anomalous transport in complex networks". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66871.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 43-45).
The emergence of scaling in transport through interconnected systems is a consequence of the topological structure of the network and the physical mechanisms underlying the transport dynamics. We study transport by advection and diffusion in scale-free and Erdős-Rényi networks. Using stochastic particle simulations, we find anomalous (nonlinear) scaling of the mean square displacement with time. We show the connection with existing descriptions of anomalous transport in disordered systems, and explain the mean transport behavior from the coupled nature of particle jump lengths and transition times. Moreover, we study epidemic spreading through the air transportation network with a particle-tracking model that accounts for the spatial distribution of airports, detailed air traffic and realistic (correlated) waitingtime distributions of individual agents. We use empirical data from US air travel to constrain the model parameters and validate the model's predictions of traffic patterns. We formulate a theory that identifies the most influential spreaders from the point of view of early-time spreading behavior. We find that network topology, geography, aggregate traffic and individual mobility patterns are all essential for accurate predictions of spreading.
by Christos Nicolaides.
S.M.
45
Jin, Shi. "Numerical transport in diffusive regimes". Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185688.
Testo completoAbstract (sommario):
In highly scattering regimes, the transport equation with anisotropic boundary conditions has a limit in which the leading behavior of its solution is determined by the solution of a diffusion equation with associated boundary conditions. In order for a numerical scheme to be effective in these regimes, it must have both a correct interior diffusion limit and a correct boundary condition limit. The behavior of several numerical methods are studied in these limits and formulas for the resulting diffusion equations and its boundary conditions are derived. Theoretic and numerical results show that with correct diffusion limits, the numerical methods will give promising results with coarse grids throughout the domain, even if the boundary layers are not resolved. We also prove that with correct diffusion limits, the numerical solutions will converge to the transport solution uniformly in ε, although the collision operators have a ε⁻¹ contribution to the truncation error that generally gives rise to a nonuniform consistency with the transport equation for small ε. In last part of this dissertation we study numerical methods for the hyperbolic systems with long time parabolic behavior. In this regime the lower order terms of the hyperbolic systems break the conservation law and the systems become parabolic. Most of the numerical methods for conservation laws fail to capture this long time behavior, as shown in our analysis. We will solve the general Riemann problem of the shallow water equations and use it to modified higher order Godunov schemes in order to capture the long time behavior of the nonlinear river equations.
46
Du, Preez Jacobus Frederick. "The integration of informal minibus-taxi transport services into formal public transport planning and operations - A data driven approach". Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29885.
Testo completoAbstract (sommario):
The MiniBus Taxi (MBT) mode is poorly understood by planning and operational authorities, yet plays a big role in the economies of developing countries transporting the workforce to and from their places of employment and offering employment to thousands in the operations of these services, as well as the numerous rank-side services and amenities offered to patrons. In recent years, research focussed on mapping paratransit services, including MBTs, in cities of the developing world has contributed significantly to the understanding of the mode in terms of its spatial extent in its respective service areas. In South Africa, experience has shown that the wholesale replacement of MBTs with scheduled services is an unattainable goal. Instead, planning authorities and researchers have, more recently, shown interest in investigating feasible methods of integrating the scheduled and unscheduled services as hybrid planned-trunk and paratransit-feeder networks. The objective of this research is to present the case for simple methods of planning and carrying out onboard surveys of paratransit services to classify and to better understand the operations of individual routes, identified route classes, the network as a whole, as well as revealed passenger demand for the services and, ultimately, how this information can be wielded in the planning and implementation of hybrid routes or networks. The data central to this study consist of onboard captured MBT data, which was collected with a public transport data capturing application using GPS enabled smartphones in the City of Cape Town from April to August 2017 as part of a City of Cape Town’s Transport and Urban Development Authority (TDA) data collection project. The purpose of the project was to clarify the actual extent of MBT services within the City and to improve the representation of the MBT mode in the City of Cape Town’s travel demand model. An Android smartphone application, purpose-built for collecting operational information onboard public transport vehicles, was used to collect spatial and temporal data on the operations of a sample of active MBT routes in Cape Town. The application, which saw some functionality updates specifically for the project, was used to collect the following information per MBT trip:
· Location of stops;
· Time of arrival and departure at stops;
· Number of passengers boarding and alighting at each stop;
· The relative boarding and alighting stop of each specific passenger;
· The amount paid in fare money per passenger at each stop;
· The actual path travelled by the vehicle as a GPS route trace; and
· The origin and destination route description of each route captured.
It is estimated that there are more than 800 active and operational routes in the Cape Town. The objective of the data collection project was to survey each one of these routes for a prespecified number of trips. As the project was still underway when this research was carried out, the information listed above collected for a sample of trips for 278 routes (556 if the reverse direction is considered as a unique route designation) formed the basis of this study. During the course of this study, the analyses of these data have shown that while the operational characteristics of individual routes are relatively consistent and stable, it is possible to distinguish between different service typologies within the larger route network. From the raw data structure listed above, the operational characteristics that were calculated for each trip and aggregated at the route level included:
· Trip and route distances;
· Average operating speeds;
· Travel times;
· Number of stops per trip;
· Load factors between stops along the route; and
· Fare rates and trip revenues.
In addition to the identification of the operational characteristics of the MBT network, service classes and routes, the outcomes of the study include providing a framework of methods for the collection, extraction, cleansing, analysis and visualisation of the data. It also includes the identification of metrics which are key in describing the difference in service types. The descriptive operational characteristics that were calculated for each trip record, inbound and outbound per route, were evaluated to establish whether they can be used to determine if different service typologies can be observed in the data. It was found that simple k-means clustering procedures may be used to classify the routes into separate, distinguishable service classes. For the purpose of this study, it was decided, nominally, that the classification should be executed for three classes. Three was subjectively considered a good value to be inclusive of traditional Trunk and Feeder or Distribution, route types as well as the possibility of the existence of a yet to be defined third type. The clustering procedures were carried out for different combinations of the operational variables for which the most consistent results were obtained for the combination distance – stop density1 – passenger turnover. Analysis of the within-class operational characteristics indicates that these three service classes clearly differ in terms of their stop frequencies, distances, speeds and their spatial network coverage.
The study furthermore provides evidence that the understanding of the MBT network and sub-networks of service classes within this network, including its interaction with other public transport modes and infrastructure, provides planning and operating authorities with key information for effectively planning and implementing hybrid networks. Finally, the study demonstrates many additional insights can be garnered from these data by implementing improved statistical sampling and survey methods at the route level and by analysing aspects of the data that were not considered central to the research. These aspects include route adherence studies, origin – destination studies and methods of expanding the onboard data samples accurately by marrying it with data collected during static rank departure and arrival counts. Ultimately, the study shows that an unprecedented knowledge of the operations of MBT routes and networks may be obtained through detailed yet simple analysis of onboard data and that this knowledge may be very useful in the planning and operations of integrated public transport networks.
47
Iasenza, Robert. "Mixing and transport processes in wastewater basins". Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21303.
Testo completoAbstract (sommario):
The hydraulic behavior and mixing processes in wastewater basins are studied experimentally in a laboratory scale model. The laboratory basin is modeled after a full scale aerated lagoon system operating in Saint-Julie, Quebec. Three experimental techniques are used to reach the objectives: (i) video flow visualization, (ii) tracer studies and (iii) two-dimensional flow measurements using hot-film anemometry. Experiments are conducted on non-aerated basins, as well as on artificially aerated basins.The flow visualization and flow measurements show that the hydraulic behavior of non-aerated wastewater basins is very complex, due to the formation of flow patterns such as stagnant zones and recirculation. The location and size of these flow patterns are determined using the measured velocity flow field and the flow visualization images. Mixing in these basins is highly non-uniform since flow is clearly segregated into high-velocity and low-velocity areas. The exchange between these areas is very low, affecting the distribution of solids and contaminants.
When artificial aeration is introduced, mixing becomes more uniform. Flow measurements and visualization indicate that the size of stagnant zones and the extent of recirculation decreases. The tracer studies show that, in general, aeration tends to decrease the actual residence time of the waste material. Calculation of the dispersion number, d, and the dead volume, Vd, are not sufficient to characterize the effect of aeration on mixing.
The understanding of mixing and transport mechanisms in wastewater basins is important, because such basins are often used in applications which require settling or mixing of solids and contaminants.
48
Murphy, George John. "The West Midlands road transport industry". Thesis, Aston University, 1988. http://publications.aston.ac.uk/14283/.
Testo completoAbstract (sommario):
The object of this project was to identify those elements of management practice which characterised firms in the West Midlands Road Transport Industry. The object being to establish the contents of what might be termed a management policy portfolio for growth. The First Phase was the review of those factors which were generally accepted as having an influence on the success rate of transport firms in order to ascertain if they explained observed patterns. Secondly, if this were not the case, to instigate a field work study to isolate those policies which were associated with growth organizations. Investigation of the vehicle movements for the entire West Midlands Fleet over a complete licence cycle suggested that conventional explanations could not fully account for the observed patterns. To carry out the second phase of the study a sample of growth firms were visited in order to measure their attitudes on a range of factors hypothesised to affect growth. Field data were analysed to establish management activities over a wide range of areas and the results further investigated through a Principal Components and Cluster Analysis programme. The outcome of the study indicates that some past attitudes on the skills and attitudes of transport managers may have to be re-examined. As a result, the project produced a new classification of road transport firms based not on the conventional categories of long and short haul, or the types of traffics carried, but on the marketing policies and management skills employed within the organization.
49
Albrektsson, Jörgen. "Optimisation of Off-Road Transport Missions". Licentiate thesis, Linköpings universitet, Fordonssystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-152787.
Testo completoAbstract (sommario):
Mines, construction sites, road construction and quarries are examples of applications where construction equipment are used. In a production chain consisting of several construction machines working together, the work needs to be optimised and coordinated to achieve an environmental friendly, energy efficient and productive production. Recent rapid development within positioning services, telematics and human machine interfaces (HMI) opens up for control of individual machines and optimisation of transport missions where several construction machines co-operate. The production chain on a work site can be split up in different sub-tasks of which some can be transport missions. Taking off in a transport mission where one wheel loader ("loader" hereinafter) and two articulated haulers ("haulers" hereinafter) co-operate to transport material at a set production rate [ton/h], a method for fuel optimal control is developed. On the mission level, optimal cycle times for individual sub-tasks such as wheel loader loading, hauler transport and hauler return, are established through the usage of Pareto fronts. The haulers Pareto fronts are built through the development of a Dynamic Programming (DP) algorithm that trades fuel consumption versus cycle time for a road stretch by means of a time penalty constant. Through varying the time penalty constant n number of times, discrete fuel consumption - cycle time values can be achieved, forming the Pareto front. At a later stage, the same DP algorithm is used to generate fuel optimal vehicle speed and gear trajectories that are used as control signals for the haulers. Input to the DP algorithm is the distance to be travelled, road inclination, rolling resistance coefficient and a max speed limit to avoid unrealistic optimisation results. Thus, a method to describe the road and detect the road related data is needed to enable the optimisation. A map module is built utilising an extended Kalman Filter, Rauch-Tung-Striebel smoother and sensor fusion to merge data and estimate parameters not observable by sensors. The map module uses a model of the vehicle, sensor signals from a GPS or GNSS sensor and machine sensors to establish a map of the road. The wheel loader Pareto front is based on data developed in previous research combined with Volvo in-house data. The developed optimisation algorithms are implemented on a PC and in an interactive computer tablet based system. A human machine interface is created for the tablet, guiding the operators to follow the optimal control signals, which is speed for the haulers and cycle time for the loader. To evaluate the performance of the system it is tested in real working conditions. The contributions develop algorithms, set up a demo mission control system and carry out experiments. Altogether rendering in a platform that can be used as a base for a future design of an off-road transport mission control system.
50
Hsing, Jeff M. (Jeff Mindy) 1972. "Quantification of myocardial macromolecular transport". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9068.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (leaves 66-68).
The needs and impacts of drug administration have evolved from a systemic to a local focus. Local drug delivery would allow a higher local drug concentration at lower systemic toxicity than what can be achieved if delivered systemically. One of the tissues of interest for local delivery is the heart, or myocardium. Increasingly, clinicians are looking to direct myocardial delivery for therapy of complex cardiovascular diseases. Yet, there is little quantitative data on the rates of macromolecular transport inside the myocardium. A porcine model was used in this work as it is most closely similar to humans in size, structure and morphology. Using a technique previously developed in this laboratory to quantify the distribution of macromolecules, the delivery of compounds directly into the myocardium was evaluated. To make quantification generic and not specific for a particular drug or compound, fluorescent-labeled 20kDa and 150kDa dextrans were used to simulate small and large diffusing macromolecules. Diffusion in the myocardium in two directions, transmural and cross-sectional, were investigated to look at diffusion of compounds along and against the myocardium fiber orientation. Fluorescent microscopy was used to quantify concentration profiles, and then the data was fit to a simple diffusion model to calculate diffusivities. This validated the technique developed. The diffusivities of 20kDa dextran in the transmural and cross-sectional direction were calculated to be 9.49 ± 2.71 um2/s and 20.12 ± 4.10 um2/s respectively. The diffusivities for 150kDa were calculated to be 2.39 ± 1.86um 2/s and 3.23 ± 1.76um2/s respectively. The diffusivities of the two macromolecules were statistically different (p < 0.02 for transmural direction and p < 0.01 for cross-section direction). While the diffusion for the larger macromolecule was isotropic, it was not the case for the smaller one. The calculated diffusivity values in the myocardium correlated with previously published data for dextran in the arterial media, suggesting that the transport properties of the myocardium and arterial media may be similar. Applications of quantitative macromolecular transport may include developing novel therapies for cardiovascular diseases in the future.
by Jeff M. Hsing.
S.M.