To see the other types of publications on this topic, follow the link: Mobility engineering.
Dissertations / Theses on the topic 'Mobility engineering'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Mobility engineering.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Bathawab, Fatma Mirfat. "Engineering surface mobility to direct stem cell fate." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8110/.
Full textAbstract:
Since the first contact and fusion of an egg and sperm and throughout development, a cell lives a life of constant communication with its environment. Cells interact with the external environment via a layer of proteins and respond to not only biochemical cues but also physical properties including stiffness and topography of adjacent surfaces. However, even though polymeric biomaterials have been described as one of the cornerstones of tissue engineering, the effect of an intrinsic polymer property known as mobility on cell behaviour is poorly characterised. Mobility is a physical property of polymers inversely proportional to the glass transition temperature (Tg); the temperature at which polymers undergo a transition between a rubbery viscous state to a glassy brittle solid. Therefore, films of four poly(alkyl acrylates) with similar surface chemistry but different glass transition temperatures achieved by varying branch chain lengths (1, 2, 4 or 6 methyl groups) were used in this work to investigate the role of polymer mobility on cell behaviour. I verified using atomic force microscopy the similarity in topography and stiffness between the four substrate surfaces and ascertained that fibronectin molecules adsorb in a globular conformation on the polymer with the shortest side chain (1 methyl group) compared with a more extended conformation on the rest of the polymers. My study of the fibronectin coatings using fluorescence recovery after photobleaching (FRAP) on the different polymer surfaces suggested that the mobility of the polymer substrate is translated to the interfacial protein layer. This interesting finding highlighted a possible pathway for cells cultured on fibronectin coated polymer surfaces to detect the underlying polymer mobility via the fibronectin coating. The interaction of cells with surfaces occurs via membrane proteins which interact with specific structural sites within extracellular matrix proteins; these include the cell binding site (RGD: Arginine Glycine Aspartic acid amino acid motif) and the Synergy site (PHSRN: Proline Histidine Serine Asparagine amino acid motif). My ELISA analyses indicated a higher exposure of these important cell-binding sites on the more extended fibronectin compared with the globular one however, this did not correlate to the mobility of polymers or the mobility of the fibronectin layer. This was also the case for myogenic cell differentiation, which was indiscriminately higher on polymers with extended fibronectin, however, cytoskeletal contractility was found to play an essential role in the myogenic differentiation of cells on these polymers in a mobility dependent manner. We then sought to understand the role of 21 mobility in modulating osteogenic differentiation of human MSCs in the presence and absence of stimulation with BMP-2. The Fibronectin network-forming polymer with the lowest mobility (side chain of 2 methyl groups) induced the highest expression of osteogenic markers in the absence of BMP-2 stimulation. My mechanistic studies using specific inhibitors also revealed that the Erk1/2 pathway was required for this increase in osteogenic markers, while contractility, unlike in myogenesis produced only minimal effects on osteogenic differentiation. In this set of polymers, mobility increases with side chain length, while all the polymers with more than one methyl group in their side chain induced the independent formation fibronectin networks upon adsorption. The polymer with two methyl groups in its side chain is characterised with the lowest mobility among the three fibrillogenesis - inducing polymers, and the highest expression of osteogenic markers in the absence of BMP-2. In the presence of BMP-2, smad phosphorylation was also higher on this polymer suggesting a combined synergistic effect towards osteogenic differentiation provided by the simultaneous activation of the Erk1/2 pathway and high phosphorylation of smad1/5/8. My observations suggest that fibronectin fibrils coating a polymer with low mobility may be most suited for osteogenic differentiation of hMSCs by simultaneously exposing cell-binding sites to a higher degree. Thus, inducing Erk1/2 signalling and presenting BMP-2 in a manner that stimulates the highest phosphorylation of smad1/5/8 hence achieving a stronger synergistic effect on the overall expression of osteogenic markers. The findings from this work strongly support previous studies suggesting that polymer mobility is a subtle change in the substrate with significant downstream biological significance and is crucial to understand to improve the application of polymeric biomaterials.
2
Yu, Haoyong 1966. "Mobility design and control of personal mobility aids for the elderly." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8143.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.<br>Includes bibliographical references (p. 127-130).<br>Delaying the transition of the elderly to higher level of care using assistive robotic devices could have great social and economic significance. The transition, necessitated by the degradation of physical and cognitive capability of the elderly, results in drastic increase of cost and rapid decrease of quality of life. A Personal Aid for Mobility and Health Monitoring system (PAMM) has been developed at MIT Field and Space Robotics Laboratory for the elderly living independently or in senior assisted living facilities so as to delay their transition to nursing homes. This thesis research addresses the mobility design and control issues of such devices. Eldercare environments are semi-structured, usually congested, and filled with static and/or dynamic obstacles. Developing effective mobility designs to achieve good maneuverability is a great challenge. An omni-directional mobility concept using conventional wheels has been developed independently in this research. Mobility systems based on this concept are simple, lightweight, energy efficient, and capable of operating on a range of floor surfaces. Assistive mobility devices work in shared workspace and interact directly with their users with limited physical and cognitive capabilities. The users may not be well trained, nor fully understand system. The challenge is to design an ergonomic and intuitive human machine interaction and a control system that can properly allocate control authority between the human and the machine. For this purpose, the admittance-based control methodology is used for the human machine interaction control. An adaptive shared control framework allocates control based on metrics of the demonstrated human performance has been developed.<br>(cont.) Substantial amount of field experiments have been conducted with the actual users to validate control system design. The mobility design and control system implemented and tested on PAMM, will also be applicable to other cooperative mobile robots working in semi-structured indoor environments such as a factory or warehouse.<br>by Haoyong Yu.<br>Ph.D.
3
Zhao, Xu S. M. Massachusetts Institute of Technology. "Electric field engineering in GaN high electron mobility transistors." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/43062.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2008.<br>Includes bibliographical references (leaves 66-70).<br>In the last few years, AlGaN/GaN high electron mobility transistors (HEMTs) have become the top choice for power amplification at frequencies up to 20 GHz. Great interest currently exists in industry and academia to increase the frequency to mm-wave frequencies. The goal of this thesis has been to identify new solutions to some of the main challenges to increase this frequency performance even further. Electron velocity is a critical parameter affecting the transistor performance. In standard GaN transistors, the extremely high electric fields present in the channel of the device reduce the average electron velocity well below the peak electron velocity, resulting in low cutoff frequencies. In this thesis, we introduced a partial recess in the drain access region of the transistor to engineer the electric field along the channel of the device without introducing parasitic capacitances. By reducing the peak electric field, the average electron velocity is increased by 50%. This new technology has the potential to improve not only the cutoff frequencies, but also the breakdown voltage of GaN transistors. To successfully engineer the electric field in GaN devices, an accurate, reliable and low damage etching technology is needed. However none of the traditional GaN dry etching technologies meets these requirements. This lack of suitable technology has motivated us to develop a new atomic layer etching technique of AlGaN/GaN structures. This technology has been shown to be a self limited process with very high reliability and low damage, which will be very useful both in electric field engineering and gate recess. Finally, another factor hindering GaN HEMTs from competing with InGaAs devices at high frequencies are their high parasitic capacitances and resistances. In this thesis, ohmic drain contacts are replaced with Schottky drain contacts to reduce the drain access resistance.<br>(cont) ADS simulations predict a very significant increase in the cutoff frequencies by virtue of the lowered parasitic resistances. In conclusion, the theoretical and experimental work developed during this project has demonstrated the great potential of three new technologies to overcome the main challenges of mm-wave GaN HEMTs. The application of these technologies to actual devices is under way and it will represent an important element of the ultra-high GaN transistors of the future.<br>by Xu Zhao.<br>S.M.
4
Hsieh, I.-Yun Lisa. "Insights into future electric mobility." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127890.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, May, 2020<br>Cataloged from the official PDF of thesis.<br>Includes bibliographical references (pages 218-239).<br>Growing global awareness of the environmental impacts of combustion is accelerating electric vehicles (EVs) adoption. However, future sustainable mobility cannot be achieved without substantial changes in vehicle technology, consumer behavior, infrastructure systems, and policy. Great impacts and uncertainties are anticipated during the transition towards electric mobility. This thesis examines key areas of interest such as battery techno-economic characteristics, EV recharging ecosystem, dynamics behind the market evolution, the prospects and challenges for the transition to electrification, and the impacts of evolving EV policies. For example, given that the battery prices have been dropping rapidly in the past several years, a recurring question is how much lower battery prices can be expected to go.<br>Greater production volumes and improvements in manufacturing efficiency will drive down costs, but the prices will eventually stabilize as they get closer to the cost of the materials they are made of. A 2-stage learning curve model is developed to investigate how the essential materials, especially expensive elements (lithium, nickel and cobalt) used in current battery technologies, will constrain the declining trajectory of production costs and set practical lower bounds on battery prices. Another big uncertainty surrounding EVs is whether they could really create a cleaner planet. EVs avoid tailpipe emissions of CO2 and air pollutants from fossil fuel combustion but may lead to greater emissions from the upstream stage of electricity generation, especially in the world's largest EV market, China, where coal-fired power generation has been the backbone of the electricity supply.<br>The current lifecycle emissions comparison for vehicles with different powertrains is presented and how China's sustainable mobility policy will affect future climate change, air quality, and public health is also explored. This thesis provides information that will help stakeholders anticipate and navigate some of the changes that lie ahead owing to a policy-driven shift from liquid fuels to electrification. The evaluation focuses mostly on private passenger vehicle sector, which in part reflects a recognition that this is the segment that is likely to be responding most proactively to the developments in advanced powertrains, alternative fuels, and environmental policies.<br>by I-Yun Lisa Hsieh.<br>Ph. D.<br>Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering
5
Undeland, Elisabeth. "Residual Gas Mobility in Ormen Lange." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18398.
Full textAbstract:
The topic of this report is "Mobility of Residual Gas in Ormen Lange" and it has been prepared as a part of the course TPG4915 Petroleum Engineering - Reservoir Engineering, Master Thesis at the Norwegian University of Science and Technology (NTNU). The work has been performed on Ormen Lange, a natural gas field on the Norwegian continental shelf, operated by A/S Norske Shell.Substantial volumes of residual gas are present in the Ormen Lange field as a result of the hydrodynamic aquifer flow9. Total residual gas volume in 2007 is 80±30 Bcm gas depending on the residual gas saturation, Sgr. Depending on scenario 15±6 Bcm of the residual gas is recovered in 2040, and the recovery factor of residual gas is 15±5%. In general, with increasing residual gas saturation, residual gas volume increases and the recovery factor of the residual gas zones decreases.The main challenge and purpose of this project has been to understand the physics of residual gas during depletion, and to assess the potential recovery from the residual gas in different parts of the reservoir. A literature study aiming to identify the main driving parameters with respect to residual gas mobility has been conducted and used as a basis for subsequent simulation work.The need to understand the charge history of the field became important in 2008 when an appraisal well in the northern part of the field encountered only residual gas saturations in the crest of the structure and in the middle of the Direct Hydrocarbon Indicator (DHI). Core analyses, well logs and geological interpretation obtained during drilling and gas production in Ormen Lange so far allows the assessment of residual gas, and gives indications of where it resides in the reservoir. Residual gas saturations (Sgr) in the range of 0.21 to 0.41 have been observed in water-flood core measurements. Recovery of residual gas depends on the final reservoir pressure. The recovery from the residual gas zone in the south, where the reservoir is well depleted, is good compared to the north where the pressure depletion is limited. Applying the base case residual gas saturation value of 0.3 and assuming no mobility threshold above residual gas saturation (critical gas saturation is equal to residual gas saturation), the total recovery in 2040 of residual gas is 19%, see Figure 1. Future development plans will increase total residual gas recovery, as the pressure will be further depleted.In the South where an acting aquifer is present, recovery from residual gas highly depends on the strength of the aquifer. Earlier breakthrough of water with a potential stronger aquifer results in earlier shut-in of the wells, hence higher abandonment pressure and lower recovery of residual gas in the south. The critical gas saturation is one of the parameters that has been extensively investigated in this project. The critical gas saturation is the saturation at which a continuous gas flow can be first observed, coinciding with a non-zero gas relative-permeability. Most literature indicates that residual gas requires approximately 5% increase of gas saturation units in order to reach critical gas saturation. The implementation of the latter mobility threshold for residual gas in Ormen Lange reduces the total residual gas recovery by 2%. The flow rate of the remobilized gas depends on how fast the gas relative permeability increases during secondary drainage. Hence changing the slope of the gas relative permeability curve, Ng, and the endpoint value, krg, also affects the ultimate recovery of residual gas.
6
Song, Xiang Ph D. Massachusetts Institute of Technology. "Personalization of future urban mobility." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/120637.
Full textAbstract:
Thesis: Ph. D. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 91-97).<br>In the past few years, we have been experiencing rapid growth of new mobility solutions fueled by a myriad of innovations in technologies such as automated vehicles and in business models such as shared-ride services. The emerging mobility solutions are often required to be profitable, sustainable, and efficient while serving heterogeneous needs of mobility consumers. Given high-resolution consumer mobility behavior collected from smartphones and other GPS-enabled devices, the operational management strategies for future urban mobility can be personalized and serve for various system objectives. This thesis focuses on the personalization of future urban mobility through the personalized menu optimization model. The model built upon individual consumer's choice behavior generates a personalized menu for app-based mobility solutions. It integrates behavioral modeling of consumer mobility choice with optimization objectives. Individual choice behavior is modeled through logit mixture and the parameters are estimated with a hierarchical Bayes (HB) procedure. In this thesis, we first present an enhancement to HB procedure with alternative priors for covariance matrix estimation in order to improve the estimation performance. We also evaluate the benefits of personalization through a Boston case study based on real travel survey data. In addition, we present a sequential personalized menu optimization algorithm that addresses trade-off between exploration (learn uncertain demand of menus) and exploitation (offer the best menu based on current knowledge). We illustrate the benefits of exploration under different conditions including different types of heterogeneity.<br>by Xiang Song.<br>Ph. D. in Transportation
7
Hiveluah, O. T. "Mobility sketch planning tool for Windhoek." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5039.
Full textAbstract:
Includes bibliographical references (leaves 111-113).<br>The research attempted to model the trip generation and the subsequent modal splits resulting thereof. The sketch planning tool to be developed attempted to predict within reasonable accuracy limits, the travel trends and hence the transport modes used for the undertaking of these trips. To gain an in depth understanding of the task, the "status quo" mobility conditions for Windhoek had to be well understood. Only once when the existing trends are fully understood, can one begin to derive a model that is able to model, the expressed mobility trends.
8
Tripathi, Vishrant. "Age of information and mobility." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122705.
Full textAbstract:
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 99-105).<br>Age of information is a recently proposed metric that measures the freshness of information at a destination receiving data from an information source. It has become popular in the networking and queuing community, especially for studying delivery of real time status updates. In this thesis, we explore applications of AoI to mobile and adhoc networks. More specifically, we look at two problems - 1) Age optimal information collection and dissemination from locations arranged on a graph, using a mobile agent that travels between them, and 2) Age-based transmission schemes for a group of mobile agents which need to continuously exchange information while moving around in a cell partitioned network. We also derive expressions for age metrics for discrete time queuing systems under various service disciplines, and service and arrival time distributions.<br>by Vishrant Tripathi.<br>S.M.<br>S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
9
McCloskey, Kara E. "Theoretical and experimental characterization of magnetophoretic mobility /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488204276534697.
Full text
10
Buchhold, Valentin [Verfasser], and D. [Akademischer Betreuer] Wagner. "Advancing Urban Mobility with Algorithm Engineering / Valentin Buchhold ; Betreuer: D. Wagner." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1239180551/34.
Full text
11
Yan, Yanjun. "Appearance based face recognition system with mobility." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2009. http://wwwlib.umi.com/cr/syr/main.
Full text
12
Cai, Wei 1977. "Atomistic and mesoscale modeling of dislocation mobility." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8682.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2001.<br>Vita.<br>Includes bibliographical references (p. 297-320).<br>Dislocation is a line defect in crystalline materials, and a microscopic carrier of plastic deformation. Because dislocation has both a localized core and a long-range stress field, linking atomistic and meso scales is often the most challenging step in studying its dynamics. This Thesis presents theories and simulations of dislocations in Si and BCC transition metals, with emphasis on the atomistic-mesoscale coupling. Contributions are made in both methods development and mechanistic understanding of dislocation mobility. For atomistic studies of defects embedded in a mesoscale surrounding, we have given rigorous treatments of two types of boundary effects. A method is derived for quantifying artificial image energies in dislocation simulations with a periodic cell, in which a longstanding conditional convergence problem in lattice summation is resolved. We have also developed a systematic approach based on the linear response theory, which minimizes boundary wave reflections in molecular dynamics simulations without artificial damping. When predictive models are confronted with experiments at the level of mesoscale kinetics, the challenge is to properly incorporate atomistic details into a coarse-grained simulation.<br>(cont.) We have investigated dislocation core and kink mechanisms and obtained deeper understandings on the shuffle-glide controversy in Si and edge versus screw dislocations in BCC Mo, with some of these breakthroughs related to a better control of artificial boundary effects. The atomistic-mesoscale coupling is then manifested in our formulation of a kinetic Monte Carlo description of dislocation glide in Si at the mesoscale, based on kink mechanisms. As a result, the nature of "weak obstacles" to kink propagation, a long-standing postulate for interpreting low stress dislocation mobility data, is clarified. This model is then generalized to incorporate cross slip for modeling screw dislocation motion in a BCC lattice. Lastly, a physically-motivated procedure is derived for removing the stress singularity in mesoscale dislocation dynamics simulations.<br>by Wei Cai.<br>Ph.D.
13
Vu, Tran Mai Anh. "Nutrient Mobility From Biosolids Land Application Sites." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/74.
Full textAbstract:
Three types of biosolids (lime-stabilized, aerobically digested, and anaerobically digested biosolids) were applied on 0.13-ha test plots on disturbed rangelands in Western Utah at rates of up to twenty times (20X) the estimated N-based agronomic rate. Soil samples at depths up to 1.5 m were collected and analyzed for nitrogen, phosphorus, regulated metals, pH, and electrical conductivity for up to two years after biosolids application. NH4-N at the soil surface (0.2 m) was primarily lost through ammonia volatilization and nitrification. This observation was consistent with reported increases in nitrate (NO3-N) concentrations found within the soil surface on the biosolids-amended sites. A nitrogen mass balance on the surface soil control volume indicated that the nitrogen residual field measurements were significantly higher than the nitrogen level estimated by accounting for nitrogen inputs (biosolids) and outputs (vegetative yield, nitrogen volatilization and nitrate leaching). Biosolids land application led to increases in vegetative growth and dry matter yield when compared to vegetation grown on control plots. Based on the Root Zone Water Quality Model (RZWQM), the model predicted NH4 and NO3 storage values at biosolids-amended sites were significantly different from the field data, which suggests that the model default and limited measured values were inappropriate for a non-irrigated rangeland landscape. The majority of total P and plant available P accumulation was found to occur primarily within the soil surface (0.2 m). Phosphorus soil residual measurements were higher than phosphorus accumulation based on a phosphorus mass balance at soil surface. The phosphorus leachability to ground water at the biosolids-amended treatment sites was low based on the molar ratio of ([P]/([Al]+[Fe])) and the potential formation of calcium phosphate (Ca3(PO4)2). Aerobically digested biosolids appeared to be the optimal biosolids type with regard to minimizing the adverse environmental effects of phosphorus based on the Phosphorus Site Index (PSI). Regulated metal concentrations (As, Cd, Cu, Pb, Mo, Ni, Se, and Zn) were well below the cumulative pollutant loading limits for biosolids-amended soils. Finally, nutrients as well as regulated heavy metals associated with biosolids land application to disturbed rangelands do not pose any significant threat to the environment.
14
Hache, Gaetanne. "Development of a wearable mobility monitoring system." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28511.
Full textAbstract:
Monitoring mobility at home and in the community, and understanding the environment and context in which mobility occurred, is essential for rehabilitation medicine.
This thesis introduces a Wearable Mobility Monitoring System (WMMS) for objective measurement of community mobility. This prototype WMMS was created using a smartphone-based approach that allowed for an all-in-one WMMS. The wearable system is worn freely on a person's belt, like a normal phone.
The WMMS was designed to monitor a user's mobility state and to take a photograph when a change-of-state was detected. These photographs are used to identify the context of mobility events (i.e., using an elevator, walking up/down stairs, type of walking surface).
Mobility evaluation using the proposed WMMS was performed on five able-bodied subjects. System performance for detecting changes-of-state and the ability to identify context from the photographs was analyzed. The WMMS demonstrated good potential for community mobility monitoring.
15
Yuen, Nicholas Y. "Communication on limited-mobility underwater sensor networks." Scholarly Commons, 2013. https://scholarlycommons.pacific.edu/uop_etds/232.
Full textAbstract:
More than 70% of Earth's surface is covered by water. Earth's underwater world holds many exciting forms of life and undiscovered possibilities. It is sometimes referred to as "The Unexplored Frontier." We still do not fully understand the entirety of what happens in this mysterious world. The field of underwater sensor networks is a means of monitoring these environments. However, underwater sensor networks are still fraught with challenges; one of the main challenges being communication. In this thesis we look to improve communication in underwater sensor networks. We expand a simulation environment that models node to node communication in an underwater sensor network that utilizes AquaNodes. We address issues with the first iteration of the environment, expand it to include packet-loss for acoustic communication, and make the addition of three dimensional topologies. We found that acoustic packet-loss had a larger impact on the energy consumption of the communication algorithms with more acoustic communication and three dimensional topologies do not affect the communication algorithms. In addition to expanding the simulation environment we also explore using UAVs as a means of extracting data out of underwater sensor network. We conduct field experiments to characterize radio communication, develop an energy model to understand the energy limitations of an UAV, and develop overall policies for using an UAV with an underwater sensor network that utilizes AquaNodes. We learned that node to node radio communication range on the surface of the water had shorter ranges than on land. We also learned that node to UAV communication range was dependant on the altitude of the UAV. Overall, we found that using an UAV as a data mule was a viable method of extracting data out of certain underwater sensor network configurations.
16
Berzin, Oleg Daryoush Afshin Samimi. "Mobility management architecture and modeling for label switched networks (mobility label based network) a thesis /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3217.
Full text
17
Hussain, Ishfaq. "Scalable Device Mobility – Mobile DCXP." Thesis, Mittuniversitetet, Avdelningen för informations- och kommunikationssystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-23324.
Full textAbstract:
The continuously increasing Internet coverage and its availability has give rise to an issue that was once considered not important to take into consideration. Today a number of applications use the Internet to de-liver time critical messages. The usage of wireless Access Points involves a considerable percentage to connect mobile devices to the Internet pro-vider. However, these relatively cheaper Internet Access Points have their own disadvantages as compared to the GSM and ADSL. The access points cover a very limited area and thus in order to cover a wider area multiple access points must needs to be installed. In other words, as the user moves he/she is supposed to switch between access points. Never-theless, the basic problem in such cases is involves packet loss during handover. In today’s technological advancements these issues, though very small, are no more insignificant but are required to be handled prop-erly. So protocols such as MobileIP, LISP, HOST have been proposed and are currently being used for such a purpose. Furthermore, in this thesis a mechanism to reduce such packet losses has been studied and proposed in relation to the SensibleThings Internet-of-things platform. A workaround solution known as Mobile DCXP has been proposed and implemented and comparisons with the existing system have been carried out. In addition, a generic solution has been discussed in detail and compared with the Mobile DCXP. However, the implementation of the generic solution has been deferred to the future. The concept of Mobile DCXP has been illustrated with proof-of-concept apps and an implementation of a simple Android Application known as IChat has been conduct. The IChat is a simple chat app that is used in the experi-ment to determine out the packet lost during handover and to carry out a comparison. Finally, based on the data collected from IChat, an evaluation of Mobile DCXP has been presented and a performance comparison with Mobile Proxy DCXP has been illustrated with charts. Furthermore, in the conclusion Mobile DCXP could minimize packet loss as compared to the existing system.
18
Johansson, Mårten. "Mobility as a Service: Exploring Young People’s Mobility Demands and Travel Behavior." Thesis, KTH, Samhällsplanering och miljö, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215509.
Full textAbstract:
Increasing vehicular travel and environmental issues are trends increasing the pressure on urban transport systems. The new concept Mobility as a Service (MaaS) is one approach to tackle these challenges. The aim of MaaS is to reduce the need of the private car and increase the use of shared resources by providing one single application that integrates all transport modes, payment, and services. Several ongoing societal trends such as urbanization, technologic development, and sharing economy are examples of reasons for the emergence of MaaS. Young people are often leading the development and are early adopters of new technologies. The mobility demands of young people today and in the future will therefore play an important role in the implementations of MaaS. This qualitative study uses focus groups to explore mobility demands today and in the envisioned future of young people (aged 15-23) living in Stockholm. Our understanding of travel behaviour and mobility demands among young people is limited, and this study also aims to get deeper understanding of the underlying values and attitudes towards mobility that influence those demands and behaviours. This study aims to answer how young people’s mobility demands look like and if they correspond to the visions of MaaS as stated by developers and experts of the concept. Findings indicate that mobility demands and behaviour are strongly influenced by parents, and underlying values such as ‘Freedom’ and ‘Comfortable life’ affect mobility more than factors such as availability and travel time. There is little need for increased accessibility to transport today and in the envisioned future. Findings also indicate a relatively widespread environmental awareness, but an unwillingness to convert awareness to change of behaviour. The demands of young people correspond to some extent with the visions of MaaS, and the probability of young people to adopt MaaS and to choose environmentally friendly journey is high if demands for convenience and comfort are fulfilled.
19
Johansson, Arbab Arvin. "Mobility Simulation - An exploration and evaluation." Thesis, Umeå universitet, Institutionen för datavetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-156288.
Full textAbstract:
Mobility simulation is an important tool for a wide variety of cases. When provisioning computational resources for telecom networks, mobility simulation can be used as a tool for modeling user behavior. This thesis paper explores and evaluates naïve mobility simulation that builds upon models available within the RECAP project, as well as highfidelity state-of-the-art mobility simulation using SUMO. Significant qualitative trade-offs were found between these methods of simulating mobility, in terms of effort that would have to allocated towards each method, flexibility, demands on data, and realism. Using mobility traces is presented as a third option that sidesteps the issues involved in setting up a mobility simulation scenario, but introduces its own inflexibilities.
20
Bergh, Andre E. "Prediction assisted fast handovers for seamless IP mobility." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/5248.
Full textAbstract:
Word processed copy.<br>Includes bibliographical references (leaves 94-98).<br>This research investigates the techniques used to improve the standard Mobile IP handover process and provide proactivity in network mobility management. Numerous fast handover proposals in the literature have recently adopted a cross-layer approach to enhance movement detection functionality and make terminal mobility more seamless. Such fast handover protocols are dependent on an anticipated link-layer trigger or pre-trigger to perform pre-handover service establishment operations. This research identifies the practical difficulties involved in implementing this type of trigger and proposes an alternative solution that integrates the concept of mobility prediction into a reactive fast handover scheme.
21
Zupac, Dragan. "Radiation-induced mobility degradation in DMOS transistors." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186456.
Full textAbstract:
Effects of radiation-induced interface-trapped charge and oxide-trapped charge on the inversion-layer carrier mobility in double-diffused metal-oxide-semiconductor (DMOS) power transistors are investigated. Interface-trapped charge is more effective in scattering inversion-layer carriers than oxide-trapped charge. However, the effects of oxide-trapped charge must be taken into account in order to properly describe the mobility behavior. An effective approach to detecting effects of oxide-trapped charge and separating these effects from effects of interface-trapped charge is demonstrated. Detection is based on analyzing mobility data sets which have different functional relationships between the two trapped charge components. These relationships may be linear or nonlinear. Separation of effects of oxide-trapped charge and interface-trapped charge is possible only if these two trapped charge components are not linearly dependent. A significant contribution of oxide-trapped charge to mobility degradation is demonstrated and quantified. Effects of oxide-trapped charge may be dominant in non-hardened DMOS transistors irradiated at relatively high dose rates. In addition, DMOS devices have been irradiated at room temperature and mobility measurements performed at room temperature and at 77 K to analyze mobility degradation due to the same density of radiation-induced defects at these two different temperatures. Radiation-induced mobility degradation is more pronounced at 77 K than at room temperature, due to increased relative importance of Coulomb scattering from trapped charge when phonon scattering is significantly reduced. Effects of oxide-trapped charge on mobility are more pronounced at cryogenic temperatures than at room temperature.
22
Zachariadis, Stefanos Zacharias. "Adapting mobile systems using logical mobility primitives." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/5645/.
Full textAbstract:
Mobile computing devices, such as personal digital assistants and mobile phones, are becoming increasingly popular, smaller, more capable and even fashionable personal items. Combined with the recent advent of wireless networking techniques, users are equipped with mobile devices of significant computational abilities, which are able to wirelessly access information by dynamically connecting to many different networks. Despite the ubiquity of mobile devices, mobile systems are built using monolithic architectures, use a small set of predefined interaction paradigms and do not exploit or adapt to the dynamicity of their local or remote context. Applications deployed on mobile devices face considerable challenges posed by their changing surroundings. One of the main peculiarities of mobile devices is heterogeneity, which may occur in software, hardware and network protocols. Mobile systems may carry a large number of different applications, use different operating systems and middleware and, often, have more than one network interface. A further challenge is their considerable variation in the computational resources available, such as battery power, CPU speed, network bandwidth and volatile and persistent memory. Moreover, mobile computing systems are highly dynamic systems, in terms of their surroundings, implying that the requirements for applications deployed on a mobile device are a moving target. Changes in the requirements (such as integration with a new service) may require changes to the application. Consequently, these changes may mean that the application behaviour needs to adapt. This thesis argues that the potential of the ubiquity of mobile devices cannot be realised using static and monolithic architectures, as mobile systems need to be able to adapt to accommodate changes to their environment. It investigates the use of three technologies to offer adaptation to mobile devices: Logical mobility techniques, component systems and middleware technologies. More specifically, this thesis presents the SATIN (System Adaptation Targeting Integrated Networks) component metamodel, a lightweight local component metamodel that offers the flexible use of logical mobility primitives. The metamodel is instantiated to build the SATIN middleware system, a component-based mobile computing middleware that uses the mobility primitives exported by the metamodel to reconfigure itself and applications running on top of it. The suitability of SATIN for the creation of adaptable mobile systems is demonstrated, by using it to implement and evaluate a number of applications showing different aspects of adaptation. Moreover, existing projects are reengineered to run as SATIN components, showing the flexibility of the approach and the advantages gained over the originals.
23
Yang, Yingxiang S. M. Massachusetts Institute of Technology. "Understanding human mobility patterns from digital traces." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82863.
Full textAbstract:
Thesis (S.M. in Transportation)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 93-102).<br>Our current digital age is characterized by the shift from traditional industry to an economy based on the information computerization. The sweeping changes brought about by digital computing have provided new data sources for transportation modeling. In this thesis, two mainstream trends in utilizing digital traces in transportation modeling are explored. The first approach is to incorporate mobile phone records and digital map point of interests into commuting flow prediction models such as the gravity model and the radiation model. An extension to the radiation model is proposed to adjust to the different degrees of homogeneity of opportunities when the scale of the study region changes. The density of the point of interests is a suitable proxy for commuting flow attraction rates at all the scales. Moreover, the parameter a in the extension to the radiation model is predictable given the size of the study region. When traditional data sources are not available, mobile phone records is shown to be an ideal alternative. Home and work locations can be inferred at individual level and then aggregated to show its equivalence to the census data. This method is applied to Rwanda, Dominican Republic and Portugal. The second approach is using low-frequency bus GPS records to evaluate transit service. The analysis under such data scarcity requires careful data handling. This thesis demonstrates that how the data pre-processing procedure, namely map-matching and kernel density estimation, step by step turns the raw GPS data into information for service evaluation. Bus service quality is analyzed by measuring statistics of headway and in-vehicle travel time. The headway analysis helps to identify bottlenecks caused by the road network layout and passenger volumes while the comparison of peak vs. off-peak hour travel speed helps to identify bottlenecks caused by traffic conditions. To sum up, the thesis explores new digital data sources and methods in transportation modeling. The purpose is to provide analysis procedures that are of lower costs, higher accuracy and are readily applicable to different countries in the world.<br>by Yingxiang Yang.<br>S.M.in Transportation
24
Hua, Sean (Sean X. ). "Mobility of the future : typologizing global cities for the simulation of future urban mobility patterns and energy scenarios." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/119524.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 67-69).<br>The MITEI-sponsored Mobility of the Future project sets out to create a viable framework for analyses and predictions of urban transportation behavior in response to inevitable changes such as improved vehicle technologies, emergence of novel transit services, and policy changes motivated by population growth and emission control. In order to feasibly simulate these scenarios on a global scale, we need to first determine a few prototypical cities that best represent the entire world, each exhibiting qualities that encompass the group to which it belongs. Our methodology for accomplishing this is centered around machine learning. After collecting and pruning relevant, up-to-date data, we perform dimension reduction and clustering to ultimately generate appropriate prototype cities. These cities will be used as test beds for future mobility scenario exploration and analyses.<br>by Sean Hua.<br>M. Eng.
25
Shivakumar, Ashutosh. "Smart EV Charging for Improved Sustainable Mobility." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1496320380627769.
Full text
26
Padmanabha, Akshay. "Smart mobility : behavioral data collection and simulation." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113118.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (page 45).<br>On-demand ridesharing services, such as Uber and Lyft, and autonomous vehicles are significantly changing the landscape of transportation and mobility. In light of these disruptions, we aim to determine consumer preferences with regards to transportation and use this data to simulate and analyze the urban effects of smart mobility solutions. We collect behavioral data using Future Mobility Sensing (FMS), a smartphone and prompted-recall-based integrated activity-travel survey, and create simulations using the data with SimMobility, a simulation platform that integrates various mobility-sensitive behavioral models with state-of-the-art scalable simulators to predict the impact of mobility demands on transportation networks, intelligent transportation services, and vehicular emissions. Enhancing these projects with on-demand preferences, individual patterns, and incentives as inputs, we aim to simulate and analyze a wide range of viable smart mobility solutions.<br>by Akshay Padmanabha.<br>M. Eng.
27
Snoeren, Mark Alexander Connell 1975. "A session-based architecture for Internet mobility." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8027.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2003.<br>Includes bibliographical references (p. 179-189).<br>The proliferation of mobile computing devices and wireless networking products over the past decade has led to an increasingly nomadic computing lifestyle. A computer is no longer an immobile, gargantuan machine that remains in one place for the lifetime of its operation. Today's personal computing devices are portable, and Internet access is becoming ubiquitous. A well-traveled laptop user might use half a dozen different networks throughout the course of a day: a cable modem from home, wide-area wireless on the commute, wired Ethernet at the office, a Bluetooth network in the car, and a wireless, local-area network at the airport or the neighborhood coffee shop. Mobile hosts are prone to frequent, unexpected disconnections that vary greatly in duration. Despite the prevalence of these multi-homed mobile devices, today's operating systems on both mobile hosts and fixed Internet servers lack fine-grained support for network applications on intermittently connected hosts. We argue that network communication is well-modeled by a session abstraction, and present Migrate, an architecture based on system support for a flexible session primitive. Migrate works with application-selected naming services to enable seamless, mobile "suspend/resume" operation of legacy applications and provide enhanced functionality for mobile-aware, session-based network applications, enabling adaptive operation of mobile clients and allowing Internet servers to support large numbers of intermittently connected sessions. We describe our UNIX-based implementation of Migrate and show that sessions are a flexible, robust, and efficient way to manage mobile end points, even for legacy applications.<br>(cont.) In addition, we demonstrate two popular Internet servers that have been extended to leverage our novel notion of session continuations to enable support for large numbers of suspended clients with only minimal resource impact. Experimental results show that Migrate introduces only minor throughput degradation (less than 2% for moderate block sizes) when used over popular access link technologies, gracefully detects and suspends disconnected sessions, rapidly resumes from suspension, and integrates well with existing applications.<br>by Mark Alexander Connell Snoeren.<br>Ph.D.
28
Mwangi, Xavier K. "Scalable mobility support in future internet architectures." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/117328.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged student-submitted from PDF version of thesis.<br>Includes bibliographical references (pages 50-51).<br>In this thesis, we present MobileNDN, a scalable design for producer mobility support in the Named Data Network (NDN) architecture. While the initial design of NDN provided support for consumer mobility automatically via its stateful forwarding plane, a solution for producer mobility was left unspecified. The mobility support scheme we propose decouples the tasks of 1) detecting whether data may exist on a mobile producer, and of 2) forwarding interest packets towards the mobile producer. First, we use NDNS to detect zones that may be served by mobile producers. Second, based on insights from MobilityFirst, we introduce a scalable global mapping service to locate mobile producers. The combination of these two components yields a mobility solution that allows NDN's forwarding to operate and scale in the face of mobile consumers and producers.<br>Funded under NSF Grant 1413973<br>by Xavier K. Mwangi.<br>M. Eng.
29
Chang, Jinpeng 1974. "Atomistics of defect nucleation and mobility : dislocations and twinning." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/16601.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2003.<br>Includes bibliographical references (p. 199-211).<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Multiscale materials modeling has emerged in recent years as a significant concept and the only viable approach to understand the mechanical response of materials by linking modeling research at different length scales and time scales, including quantum mechanics, atomistics modeling, mesoscale modeling and continuum modeling together. The role that atomistic modeling plays is important and indispensable in that it can generate understanding of the physics and pass this mechanistic understanding as well as important parameters to higher level simulations. This thesis presents theories and simulations of defect nucleation and mobility in BCC transition metal molybdenum using atomistic methods, with the two primary defects of interest being dislocations and deformation twinning, and emphasis on the atomistic mechanisms and measures. The contributions presented in the thesis may be regarded as advances in both methods development and mechanistic understanding of dislocation mobility and twinning nucleation. For atomistic studies of dislocations in a simulation cell of finite size, new methods have been derived to (1) calculate the atomic displacement field under PBC and generate atomic dislocation configuration from this displacement field; (2) quantify artificial image effect for a dislocation moving within the periodic cell and optimize geometry of simulation cell to minimize such effects. These methodological breakthroughs serve as the basis for atomistic studies of dislocations and are used repeatedly in this thesis. To understand the complex plasticity behavior of BCC metal molybdenum, we need to first understand the most fundamental problem of core structure<br>(cont.) and lattice resistance of straight dislocations before considering more complicated structures including kinks, jogs, junctions, etc. In this thesis, we examine the two major types of dislocations that are of primary interest in BCC molybdenum: screw dislocations, which is the major plasticity carrier at low temperatures, and edge dislocations, which become important at elevated temperatures. For screw dislocations, the issue of whether core is polarized or not is explored by a static calculation of core structure for the first time by a tight-binding potential. The screw core structure is determined to be non-polarized; however, the magnitude of Peierls stress, which is a measure of the lattice resistance to dislocation motion and is calculated accurately using a local-driving-force method in this thesis, remains rather high despite of the non-polarized core, suggesting that core polarization is a secondary and less important effect compared to core planarity. For edge dislocations in molybdenum, the core structure and Peierls stress is calculated using a Finnis-Sinclair potential and it is shown that edge dislocation in Mo has a planar core structure and a core width of approximately 11[angstroms], is indeed very mobile and has a Peierls stress of only 25 MPa, after correction for image effects due to boundary conditions. This new result is consistent with experimental observations of high mobility of edge dislocations and clearly rejects the proposal of kink mechanisms operating on edge dislocations that arose in the literature as a result of previous inaccurate Peierls stress calculations yielding an unrealistically high value of 700 MPa ...<br>by Jinpeng Chang.<br>Ph.D.
30
Dextras, Philip. "Method for single-cell mass and electrophoretic mobility measurement." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61235.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 137-146).<br>Analysis of single cells using flow cytometry techniques has created a wealth of knowledge about cellular phenomena that could not be obtained by population average measurements. As these techniques are integrated with others to increase the number of parameters that can be measured on single cells and these measurements are made more quantitative, their ability to discriminate between sub-populations of cells increases. Microfabricated sensors offer unique advantages in this area because their internal geometries can be engineered at a size scale comparable to the cell's, making them naturally well-suited for single-cell measurements. The suspended microchannel resonator (SMR) is a versatile flow cytometry platform which is capable measuring the mass of single cells with femtogram resolution. The net frequency shift of a resonant cantilever as the cell transits the fluid-filled microchannel running through it is proportional to the buoyant mass of the cell. The resonance frequency of the SMR is also highly sensitive to a cell's position along the cantilever's length. This thesis presents a new method which makes use of this property to accurately quantify the electrophoretic mobility (EPM) of cells transiting the SMR while subjected to oscillatory electric fields. Recorded resonance frequency time courses can be analyzed to extract both the buoyant mass and EPM of individual cells. This instrument has been used to simultaneously measure the EPM and buoyant masses of discrete polystyrene microspheres and Escherichia coli bacteria. As it has been applied to microspheres of known density, the integrated measurement makes it possible to compute the absolute mass and surface charge of individual microspheres. It has been shown that integrated single-microsphere mass and surface charge measurement enables differentiation of complex aqueous suspensions which is not possible by either measurement alone.<br>by Philip Dextras.<br>Ph.D.
31
Adjei, Eric. "Travel behaviour dynamics: a mobility biography study towards change." Doctoral thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31369.
Full textAbstract:
Travel demand management (TDM) strategies continue to receive attention in recent years as a means of managing congestion in cities and promoting more sustainable transport systems. Most TDM measures focus on effecting travel behaviour change amongst commuters. Clearly such measures are likely to have the greatest impact when targeted at commuters most receptive to changing their travel behaviour at the right time. The study of commuters in order to understand their travel behaviour patterns, when they are most open to change and what causes them to change, is therefore imperative in drawing up effective TDM strategies. Also important is identifying the period within which commuters are deliberating and seeking information in order to change their mode of transport. Many studies have been conducted, in various contexts, to understand the dynamics of travel behaviour change. Some studies have argued travel behaviour to be rational, thus, an individual engage in active deliberation whenever there is a mode use choice decision problem. These studies suggest variability in travel patterns. Other studies have argued travel behaviour to be habitual in nature and characterised by non-deliberative repetition travel decisions. They argued that deliberate reappraisal of travel choices generally occur when triggered by 'key life course events’ or 'life shocks’. Such habitual behaviour suggests fairly stable travel patterns in a city’s transport network. The process through which the individual goes through in making a mode use change decision when triggered by 'key life course events’ however remain largely unexplored. This study, through the use of a qualitative mobility biography survey, firstly investigated the proposition that commuters in Cape Town engage for long periods of time in non-deliberative habitual mode choice behaviour while exhibiting considerable levels of intra-personal variability. These nondeliberative habitual mode use choice behaviours were posited to change when infrequent key life course events or incidents induce deliberation. Average duration between mode use changes among commuters was found to be about six years, confirming the habitual nature of mode use choice - especially among private vehicle users. Variations were, however, found in other attributes of travel choices such as departure time and route choice. Changes in mode use were observed to be in all directions, with the net change over the long-term being from public to private transport - an indication of 'asymmetric churn’. Key life course events found to cause mode use changes included changes in employment, changes in residential location and car ownership. The study then investigated the process a commuter goes through in making mode use changes when experiencing one of these three major life course events. The time when commuters start to deliberate on mode use change and seek information was investigated. Commuters were found to start deliberating on mode use changes and seek information about thirty and twenty-five days before the life course event occurs respectively and stopped about a day after. Information sought after during deliberation included; operational cost, comfort, travel time, convenience of mode use and safety. Commuters, however thought more about what they would gain by changing mode rather than what they would lose. The study concludes by recommending travel demand management strategies to be targeted at commuters that are about to experience a life course event and not after, as it may be too late. Information aimed at changing mode use choices from private to public transport should lay emphasis on what commuters would gain by changing to public transport rather than what they would lose. Information such as travel cost, travel time, convenience, safety, environmental and health impacts may be included in the design of information packs.
32
Goyal, Anupam. "Mobility management in global wireless communication networks." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284056.
Full textAbstract:
Several issues have become important due to recent developments in communication devices and services, especially with increase in wireless and wireline devices and networking options. These are, congestion in area codes, number portability, need to support intelligent networking, wireless-wireline integration, and demand for new user services. For meeting the requirements needed to overcome the associated problems, new numbering schemes are being proposed. Such schemes would not only relieve the extra burden on conventional geographical area codes due to the addition of vast numbers of wireless units, but also provide additional implementation benefits. Such schemes would also make it possible to associate multiple devices with a person, and multiple persons with a device, while giving people the option to have a single point where they can define who can reach them, at what device, and at what times. The proposed scheme, termed Globally Unique Portable Numbering (GUPN), uses data compression to achieve a format which has the same number of digits as the North American Numbering Plan and offers easy integration into current telephone numbering. An addressing scheme is also proposed for fixed components of communication systems and for reporting current locations of mobile devices. We call this the Globally Unique Fixed Location Numbering (GUFLN) addressing for fixed components. A performance analysis of the proposed scheme is conducted in comparison with existing schemes by considering the following criteria---number congestion with increase in number of persons and devices, amount of data transmitted and stored, and call routing and location update costs. Further studies are conducted using a queuing theory framework for evaluating a variety of possible database architectures with different levels of data replication for implementation of this person-based numbering scheme. Delays in query and update operations are used as the performance metrics for four such representative database architectures. The practical issues arising from implementation considerations are also discussed with possible solutions. This scheme is expected to offer contributions towards Number Portability (NP), Wireless Intelligent Networks (WIN), and wireless-wireline integration.
33
Leitz, Christopher W. (Christopher William) 1976. "High mobility strained Si/SiGe heterostructure MOSFETs : channel engineering and virtual substrate optimization." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8440.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002.<br>Includes bibliographical references (leaves 163-174).<br>High quality relaxed silicon-germanium graded buffers are an important platform for monolithic integration of high speed heterostructure field-effect transistors and III-V-based optoelectronics onto silicon substrates. In this thesis, dislocation dynamics in compositionally graded SiGe layers are explored and mobility enhancements in strained Si/SiGe metal-oxide-semiconductor field-effect transistors (MOSFETs) are evaluated. These results demonstrate the dramatic increases in microelectronics performance and functionality that can be obtained through use of the relaxed SiGe integration platform. By extending and modifying a model for dislocation glide kinetics in graded buffers to SiGe/Si, a complete picture of strain relaxation in SiGe graded buffers emerges. To investigate dislocation glide kinetics in these structures, a series of identical samples graded to 30% Ge have been grown at temperatures between 650ʻC and 900ʻC on (001)-, (001) offcut 6ʻ towards an in-plane <110>-, and (001) offcut 6ʻ towards an in-plane <100>-oriented Si substrates. The evolution of field threading dislocation density (TDD) with growth temperature in the on-axis samples indicates that dislocation nucleation and glide kinetics together control dislocation density in graded buffers. The TDD of samples grown on offcut substrates exhibits a more complicated temperature dependence, due to their reduced tendency towards dislocation pile-up formation at low temperature and dislocation reduction reactions at high temperature. Finally, by evaluating field threading dislocation density and dislocation pile-up density in a wide variety of SiGe graded buffers, a correlation between dislocation pile-up formation and increases in field threading dislocation density emerges.<br>(cont.) Record mobility strained Si p-MOSFETs have been fabricated on relaxed 40% Ge virtual substrates. Hole mobility enhancements saturate at virtual substrate compositions of 40% Ge and above, with mobility enhancements over twice that of co-processed bulk Si devices. In contrast, hole mobility in strained Si p-MOSFETs displays no strong dependence on strained layer thickness. These results indicate that strain is the primary variable in determining hole mobility in strained Si p-MOSFETs and that symmetric electron and hole mobility enhancements in strained Si MOSFETs can be obtained for virtual substrate compositions beyond 35% Ge. The effect of alloy scattering on carrier mobility in tensile strained SiGe surface channel MOSFETs is measured directly for the first time. Electron mobility is degraded much more severely than hole mobility in these heterostructures, in agreement with theoretical predictions. Dual channel heterostructures, which consist of the combination of buried compressively strained SiilyGey buried channels and tensile strained Si surface channels, grown on relaxed SilxGex virtual substrates, are explored in detail for the first time. Hole mobilities exceeding 700 cm2/V-s have been achieved by combining tensile strained Si surface channels and compressively strained 80% Ge buried channels grown on relaxed 50% Ge virtual substrates. This layer sequence exhibits nearly symmetric electron and hole mobilities, both enhanced relative to bulk Si ...<br>by Christopher W. Leitz.<br>Ph.D.
34
Danaf, Mazen(Mazen Salah). "Online discrete choice models : applications in smart mobility." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123227.
Full textAbstract:
Thesis: Ph. D. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 100-108).<br>Discrete choice models have been widely applied in different fields to better understand behavior and forecast market shares. Because of their ability to capture taste heterogeneity, logit mixture models have gained increasing interest among researchers and practitioners. However, since the estimation of these models is computationally expensive, their applications have been limited to offline contexts. On the other hand, online applications (such as recommender systems) require users' preferences to be updated frequently and dynamically. The objective of this dissertation is to develop a methodology for estimating discrete choice models online, while accounting for inter- and intra-consumer heterogeneity. An offline-online framework is proposed to update individual-specific parameters after each choice using Bayesian estimation.<br>The online estimator is computationally efficient, as it uses the data of the individual making the choice only in updating his/her individual preferences. Periodically, data from multiple individuals are pooled, and population parameters are updated offline. Online estimation allows for new and innovative applications of discrete choice models such as personalized recommendations, dynamic personalized pricing, and real-time individual forecasting. This methodology subsumes the utility-based advantages of discrete choice models and the personalization capabilities of common recommendation techniques by making use of all the available data including user-specific, item specific, and contextual variables. In order to enhance online learning, two extensions are proposed to the logit mixture model with inter- and intra-consumer heterogeneity.<br>In the first extension, socio-demographic variables and contextual variables are used to model systematic inter- and intra-consumer taste heterogeneity respectively. In the second extension, a latent class model is used to allow for more flexibility in modeling the inter- and intra-consumer mixing distributions. Finally, the online estimation methodology is applied to Tripod, an app-based travel advisor that aims to incentivize and shift travelers' behavior towards more sustainable alternatives. Stated preferences data are collected in the Greater Boston Area and used to estimate the population parameters, which are then used by the app in online estimation. Using the collected data, a large number of synthetic users is simulated, and the recommendation system is tested over several days, and under different scenarios. The results show that the average hit-rate generally increases over time as we learn individual preferences and population parameters.<br>"funding from the Advanced Research Projects Agency-Energy (ARPA-E), Ford, the Civil and Environmental Engineering Department at MIT, and the MIT-Singapore Alliance for Research and Technology (SMART)"--Page 5<br>by Mazen Danaf.<br>Ph. D. in Transportation<br>Ph.D.inTransportation Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
35
Byström, Kim. "Mobility Analysis of Zoo Visitors." Thesis, Linköpings universitet, Reglerteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158522.
Full textAbstract:
In a collaboration between Kolmården Zoo and Linköping University, supported by the Norrköping municipality’s fund for research and innovation, mobility measurements have been performed inside the zoo. These measurements have been done by six WiFi sniffers collecting anonymised MAC addresses from the visitors smartphones. The aim of this thesis is to analyse these data to understand visitor flows in the park and other statistics using a model based mobility analysis. The work implies that one can make a rather good prediction of the geographical visitor distribution using this equipment and statistical models.<br>I ett samarbete mellan Kolmården djurpark och Linköpings universitet, sponsrat av Norrköpingskommuns fond för forskning och utveckling, har rörelsemätningar gjorts inuti parken. Mätningarna har utgjorts av sex WiFi-sniffers som samlar in anonymiserade MAC-adresser från besökares smartphones. Målet med detta arbete är att analysera denna data för att förstå besökarflöden i parken och annan statistik genom att använda en modellbaserad rörelseanalys. Arbetet visar att man med denna utrsutning och statistiska metoder kan skapa en god prediktion av hur den geografiska besökardistributionen ser ut över tid.
36
Hasfura, Andrés Michael Levering. "Pedestrian detection and tracking for mobility on demand." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106011.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 69-72).<br>This paper presents a pedestrian detection and tracking system to be used aboard mobility on demand systems. Mobility on demand is a transportation paradigm in which a fleet of vehicles is shared among a community, with rides provided upon request. The proposed system is capable of robustly gathering pedestrian paths in space using 2D LiDAR and monocular cameras mounted onboard a moving vehicle. These gathered pedestrian paths can later be used to infer network traffic to learn to anticipate the location of ride requests throughout a day. This allows mobility on demand systems to more efficiently utilize resources, saving money and time while providing a more favorable experience for customers. The onboard LiDAR is used to cluster and track objects through space using the Dynamic Means algorithm. Pedestrian detection is performed on images from the mounted cameras by extracting a combination of histogram of oriented gradients and LUV color channel features which are then classified by a set of learned decision trees. Temporal information is leveraged to achieve higher detection quality by accruing classification votes. Both a standard fusion technique and a novel extrinsic calibration error-resistant fusion method are tested to fuse camera and LiDAR information for pedestrian path collection. The novel error-resistant fusion system is shown to outperform standard fusion techniques under both normal conditions and when synthetic extrinsic calibration noise is added. System robustness and quality is demonstrated by experiments carried out in real world environments, including the target environment, a university campus.<br>by Andrés Michael Levering Hasfura.<br>M. Eng.
37
Joh, Jungwoo. "Degradation mechanisms of GaN high electron mobility transistors." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38670.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.<br>Includes bibliographical references (p. 83-85).<br>In spite of their extraordinary performance, GaN high electron mobility transistors (HEMT) have still limited reliability. In RF power applications, GaN HEMTs operate at high voltage where good reliability is essential. However, physical understanding of the fundamental reliability mechanisms of GaN HEMTs is still lacking today. In this thesis, we carry out systematic reliability experiments on industrial GaN HEMTs provided by our collaborators, TriQuint Semiconductor and BAE systems. In our study, GaN HEMTs have been electrically stressed at various bias conditions while they are being characterized by a benign characterization suite. We have confirmed that electrical stress on devices results in an increase in drain resistance RD and a decrease in maximum drain current IDmax. During the stress, traps are found to be generated. We have seen that this degradation is driven mostly by electric field, and current is less relevant to electrical degradation.<br>(cont.) From a set of our experiments, we have hypothesized that the main mechanism behind device degradation is defect formation through the inverse piezoelectric effect and subsequent electron trapping. Unlike current conventional wisdom, hot electrons are less likely to be the direct cause of electrical degradation in the devices that we have studied. Our studies suggest a number of possibilities to improve the electrical reliability of GaN HEMTs.<br>by Jungwoo Joh.<br>S.M.
38
Brooks, Jamar (Jamar G. ). "Mobile interface for mobility incentives schemes : FMS-Advisor." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112901.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (page 57).<br>Reducing energy consumption is a common research topic in the United States because of its importance in environmental, health, and industrial fields. In this project, we aim to reduce global energy consumption for the Greater Boston Area by encouraging users to make more energy-efficient travel plans. We believe that if users can be provided with energy-efficient routes, alongside differing mode options and departure time, and provided the proper incentive in the form of rewards, they will be willing to modify their plans in order to obtain them. Therefore, we have created an interface on Android where users can plans trips, view past trips, and earn rewards.<br>by Jamar Brooks.<br>M. Eng.
39
Ekelem, Andrew. "Control Methods for Improving Mobility for Persons with Lower Limb Paralysis." Thesis, Vanderbilt University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13877286.
Full textAbstract:
<p> Paralysis or paresis induced by upper motor neuron damage often leaves the lower limbs dysfunctional for basic activities such as walking and climbing stairs. Nearly five and one half million people in the United States, or approximately one in fifty, have some degree of paralysis [4]. The sustained duration and high level of impairment attributed to paralysis motivates research and development for technologies that alleviate the associated deficiencies.</p><p> The Indego exoskeleton (Parker-Hannifin, OH) and Chimera muscle stimulator are mechatronic devices developed for the reanimation of paretic limbs. Indego employs electric motors to actuate an orthosis for the restoration of controlled legged mobility, while the Chimera interfaces with the nervous system through transcutaneous electrical stimulation to administer functional electrical stimulation (FES). Described herein are rehabilitative intervention methods that: 1) enable paraplegics to ascend and descend stairs with a lower limb exoskeleton; 2) enhance exoskeleton assisted walking with supplemental FES to overcome moderate to severe spasticity; and 3) suppress clonus using FES during seated mobility. Chapter 2 describes the hardware developed for and/or employed in this research.</p><p> Chapter 3 describes the development and assessment of a controller for the Indego that enables paraplegics to ascend and descend stairs. The stair controller expands on a previous implementation of predefined trajectory tracking with an emulated passive state that enables gravity to extend the leg until it meets the next stair tread, then a trajectory is calculated in real-time to perform the intended task of stair ascent independent of step height. The ascent and descent controllers were evaluated by three paraplegic users who traversed numerous size stairs safely within two hours of tuning and training. The resulting controller enabled stair climbing with light exertion despite complete paraplegia.</p><p> Subjects with moderate to severe spasticity are typically ineligible for exoskeleton assisted gait due to pathological muscle activation that opposes exoskeleton mediated motion. A novel supplemental stimulation controller was implemented with the Indego exoskeleton and integrated Chimera stimulator in an effort to expand the inclusion criteria of exoskeletons to individuals with severe spasticity whereby FES enhances the synergy between muscles and motors. Chapter 4 explores the effects of spasticity and FES on robot mediated gait for paraplegics and describes the hybrid system’s controller that enabled two paraplegic individuals with moderate to severe spasticity to achieve substantially improved gait kinematics.</p><p> Mobility impairment of paraplegia can also entail clonus, a self-exciting reflex that can manifest as involuntary shaking of the ankle, a common pathology experienced during wheelchair propulsion. Chapter 5 expands the frontiers of clonus research with the first reported evaluation methods wheelchair clonus 2 and the efficacy of a novel FES intervention to treat pathological clonus during wheelchair propulsion over rough terrain. The clonus intervention was shown to robustly suppress clonus. The treatment may provide a noninvasive and economical alternative to invasive and commonplace pharmacological interventions. </p><p> The remainder of the introduction serves to provide background information pertaining to the nervous system, neurological impairment and the state of the technologies used to restore deficiencies that arise from comorbidities of paralysis.</p><p>
40
Nguyen, Man Hoang, and Jon Ole Nødtvedt. "Mobility and context-awareness in workflow systems." Thesis, Norwegian University of Science and Technology, Department of Computer and Information Science, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-264.
Full textAbstract:
<p>This project aims to describe how workflow systems can integrate and make use of context information from context rich environments, to enhance the execution of workflow processes. Context information can for example be used to control transitions between activities, activity enactment and process/activity coordination. A dynamic contextual environment also requires that a workflow system is capable of responding to contextual events. A set of requirements for a context-aware workflow system, based on existing workflow standards, theory behind context-aware computing and activity theory, will be presented and elaborated. Prototypes, which illustrate how these requirements can be implemented in a standard based workflow system, are also provided. Based on the solutions presented in the prototypes, a new interface for a workflow enactment service is presented. This new interface serves as the link between the contextual environment and the workflow system. We also present a solution for handling context related exception states. The definition of basic terms in workflow systems are expanded to better support context-aware behaviour. Ideas and solutions for more complex requirements not met in our prototypes are also discussed, such as situated activity coordination.</p>
41
Justo, Filho João F. "Atomistics of dislocation mobility in silicon : core structure and mechanisms." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46072.
Full text
42
Godding, Sara J. (Sara Jean) 1977. "Field tests on a personal mobility aid for the elderly." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/17478.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.<br>Includes bibliographical references (p. 87-88).<br>The number of elderly Americans is currently rising and will continue to do so. These elderly individuals face several problems in the later years of their lives including the move into an eldercare facility. Personal mobility and monitoring aids are being developed to assist the elderly with this transition. One of these devices is the Personal Aid for Mobility and Monitoring (PAMM). PAMM is in the beginning stages of its development in the MIT Mechanical Engineering Field and Space Robotics Laboratory with an initial prototype recently constructed. This prototype was tested with many residents at an eldercare facility. Several conclusions about the control, ergonomics and overall user acceptance of the device were made. The PAMM prototype was changed accordingly and recommendations for future work are provided.<br>by Sara J. Godding.<br>S.B.
43
Deshmukh, Suhrid Avinash. "Impact of ride-sharing on mobility trends and vehicle stock." Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/122891.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 137-141).<br>North American transportation industry is on the verge of a revolutionary change. With the advent of car-sharing services and ride-sharing companies, the transportation industry is experiencing a fundamental way in which people choose to travel. This particular thesis looks at the impact of these disruptive changes in transportation on the way people choose to travel, the car based vehicle miles travelled (VMT) and the national vehicle stock. In particular, this work tries to look at how people choose to make a travel decision when embarking on a particular trip and how that translates to an effect on the national level vehicle stock. When presented with a particular mode of travel, the most relevant aspects associated with that particular mode of travel were explored and evaluated. Each mode was evaluated based on cost, time and comfort associated with the mode.<br>Multi-attribute utility theory was used to study and evaluate how people make decisions about mode choice when choosing a particular mode for a trip. This work tries to look at the impact of ride-sharing on modal changes and shits that result in a less or more use of personal car travel. Apart from the travel behavior associated with modes, this work also estimates impact of ride-sharing on the total vehicle usage in urban areas. Once the modal share of different modes was estimated, an overall passenger trip demand was generated at the national level. This trip demand was broken down into car-based trips and non-car based trips from the modal share result. Combined with occupancy assumptions, this passenger trip demand was converted into a car based VMT estimate. Finally, combining the car based vehicle miles travelled with the average vehicle utilization, the national vehicle stock was calculated.<br>In order to measure the impact of these futuristic technologies on modal share, VMT and the national vehicle stock, scenario analysis was the method chosen. In order to have a reference case, a base case scenario was designed assuming the world remains as it is today and nothing changes. A series of progressive scenarios related to ride-sharing were then tested to gauge the impact of ride-sharing. It was found that ride sharing has the most significant impact in the urban areas for short trips. The national level vehicle stock in the year 2050 declined by approximately 1.0% in the improved ride-sharing scenario. Higher-electrification of vehicles along with improvements in ride-sharing did not decrease the stock further by much, as compared to just the improved ride-sharing scenario. In an aggressive scenario, with improved ride-sharing, improved transit and anti-car policies, the national level stock value in year 2050 declined by approximately 6% compared to the base case scenario.<br>Finally, in the scenario with improved ride-sharing and higher autonomy, the national level VMT increased by 1.3%, but the vehicle stock declined by 9.9%. The results from this work can be further used to inform certain decisions regarding changing travel behaviors or explore questions related to higher level policy analysis.<br>by Suhrid Deshmukh.<br>Ph. D.<br>Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
44
Abrey, Gareth Roy. "Multiple interface management and flow mobility in next generation networks." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5229.
Full textAbstract:
Includes bibliographical references (leaves 79-80).<br>Next Generation networks will consist of a number of different access networks interconnected to provide ubiquitous access to the global resources available on the Internet. The coverage of these access networks will also overlap, allowing users a choice of access net-works. Increasingly, mobile devices have more than one type of radio access interface built-in. In current mobile devices, a single primary radio interface performs all communications with the service provider. The availability of multiple different radio interfaces proves most beneficial if all these interfaces can connect with the service provider and carry data in collaboration or individually. This means that a control system is needed to route the correct traffic over each different interface, depending on the requirements of that traffic. Having multiple interfaces available provides the opportunity to aggregate two or more interfaces for faster transfer speeds and can provide redundancy. If one interface is expe-riencing high packet loss or no coverage an alternate interface will be available. Multiple interface schemes aim to enable traditional networks to support devices with more than one interface. This is usually achieved by introducing a new agent into the network architecture that acts as the packet redirection point. Incoming packet flows are routed to the different interfaces of the mobile device by this agent according to the traffic types of each packet flow. In this thesis an evaluation platform is developed to investigate whether the possible functionality of a multiple interfaced device provides useful traffic routing options. The evaluation platform consists of three key components evident in schemes from the literature, namely a Corresponding Node, Mobile Node and Router. The Router is emulated with a script-based routing software and configured as the packet redirection point in the evaluation platform. Four test scenarios emulate traffic travelling over two interfaces of a practical mobile node. A mid-flow handover from one interface to the other is investigated to determine that this process can be seamless under certain conditions. Dual Interface Aggregation shows good performance when the limits of each interface are not exceeded. Distinct improvement in combined packet loss of two lossy links carrying duplicate packet streams shows that two interfaces can provide a reliable link in critical situations where both interfaces have poor performance when used separately. Finally, a Bandwidth-on-Demand scenario shows that having two interfaces can allow automatic bandwidth allocation when data-rate is increased beyond the limits of one interface.
45
Enlund, Åström Isabelle. "Mobility-based Key Sharing Using Visible Light Communication." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-333031.
Full textAbstract:
Visible Light Communication (VLC) has become an increasingly interesting topicamong researchers. The LEDs used in VLC have important characteristics which differfrom radio waves, and which enables a vast spectrum to be used with many security aspects. Light cannot pass through walls and can be directed. Directing different light sources to different locations, keys can be distributed to these locations. Using this, a mobility pattern can be defined by a user. This thesis considers the Shamir's Secret Sharing algorithm and how it can be used to create a mobility pattern where each distributed key need to be picked up in a specific order, following the pattern. A design solution has been created that considers some of the scenarios where and how this mobility pattern can be used.
46
Lontine, Derek Michael. "Stress Modulated Grain Boundary Mobility." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7348.
Full textAbstract:
This thesis consists of a thermodynamically based kinetic model that more accurately predicts grain boundary mobility (GBM) over a large range of thermodynamic states including changes in temperature, pressure and shear stress. The form of the model was validated against calculated GBM values for Al bicrystals via molecular dynamics (MD) simulations. A total of 98,786 simulations were performed (164 different GBs, each with a minimum of 250 different thermodynamic states, and 2 different driving forces). Methodology for the computation of the GBM via MD simulations is provided. The model parameters are directly linked to extensive thermodynamic quantities and suggest potential mechanisms for GBM under combined thermal and triaxial loads. This thesis also discusses the influence of GB character on the thermodynamic mobility parameters. The resulting insights about GB character and thermodynamic state on GBM suggest an opportunity to achieve designed microstructures by controlling thermodynamic state during microstructure evolution.
47
Sumrak, Joseph Charles. "Organic semiconductor co-crystals: reactivity, mobility, and spectroscopy." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1183.
Full textAbstract:
Organic semiconductors are of interest because low processing temperatures and cost which make such materials candidates for flexible electronics. The charge transport properties of the material are largely dependent on solid-state arrangement of the molecules. This thesis focuses on co-crystallization as a means to achieve [2+2] photodimerization with organic semiconductors, the impact the co-crystal former has on mobility, the use of a co-crystal former to obtain different conformations of a flexible system, and the ability to detect the change in conformation by infrared spectroscopy.
[2+2] photodimerization is studied as a way to alter the orientation of the π-systems in the solid state. To align a semiconductor building block into an orientation suitable for [2+2] photodimerization a co-crystallization method was used. The result of the photoreaction is the formation of a dimer in which the π-systems of the semiconductor building block are in a different orientation then before. Changes in the physical properties of the material through photodimerization are explored as a method for patterning thin films.
The impact the second component has on the overall mobility in our system is examined. The second component is not expected to act as a semiconductor and the impact on mobility the by its inclusion in the solid is unknown. The impact of a second component on mobility is studied by observing the mobility of multiple co-crystals along with the mobility of the single component. It was found that the mobility could be increased by a factor of approximately 200 with addition of a second component. The mobility change seen in the two-component crystals is equated to the changes observed in the crystal packing.
The conformation a molecule adopts in a solid can vary. It was discovered that the addition of a second component can be used to select the major conformation a bithiophene adopts in a solid. The change in conformation changes the orientation of the π-systems between molecules within the solid. The ability for a second component to alter the conformation of a bithiophene is explored. Infrared spectroscopy is used as a facial method to detect the change in the bithiophene conformation.
48
Cheung, Natalie Wen Yua. "Energy Mobility Network : system design, interfaces, and future interactions." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66412.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 128-129).<br>The Energy Mobility Network is a mobile, networked energy production, consumption and sharing system that is designed to motivate users to be more aware of their energy consumption. In particular, the system provides a just-in-time message to the user before using the device, which allows the user to evaluate his/her needs and the cost of the device. Furthermore, the idea of minimizing electrical costs are extended into the social realm; the system creates a social network among users which allow social energy etiquettes to come into play. With these etiquettes, the system aims to use social means as a way to minimize the use of electricity. In the thesis, I discuss the goals and ideas developed that led to the creation of the network and the technical infrastructure behind the system. I will be going in depth with the prototyping, the pros and cons, as well as the multiple versions of the system that have been prototyped. Finally, I will discuss the future possibilities the Energy Mobility Network will bring when introduced to the general public.<br>by Natalie Wen Yua Cheung.<br>M.Eng.
49
Castelino, Judith Andrea. "Estimating mobility values from electroluminescence measurements on organic polymers." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35470.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.<br>Includes bibliographical references (leaves 73-74).<br>by Judith Andrea Castelino.<br>M.Eng.
50
Li, Yujin. "Mobility and Traffic Correlations in Device-to-Device (D2D) Communication Networks." Thesis, North Carolina State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3690209.
Full text