Página 21 dos resultados de 2122 itens digitais encontrados em 0.034 segundos

‣ Effect of sample disturbance in opalinus clay shales

Pei, Jianyong, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 213 p.; 9849752 bytes; 9877336 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25181%
The sample disturbance problem for different geomaterials is reviewed in this thesis. A general discussion on the disturbance sources and complexities of the disturbance problem is followed by detailed reviews on disturbance mechanisms and effects in soil and rock. This investigation leads to the conclusions that the combination of theoretical and physical modeling is an effective way to study the disturbance problem. Following the discussion of sample disturbance in soil and rock, the main aspects of shale behavior and shale sample disturbance are introduced in order to evaluate the applicability of theoretical and physical modeling in shale. It is shown that the coupled chemical - thermal - poromechanical effects of shale behavior may be a major barrier to a successful application of these modeling methods and to a better handling of sample disturbance.; by Jianyong Pei.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2004.; Includes bibliographical references (p. 209-213).

‣ From nanohardness to strength properties of cohesive-frictional materials : application to shale materials

Ganneau, Francois P., 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 221 p.; 9290986 bytes; 9318273 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25181%
Advanced experimental and theoretical micromechanics such as nanoindentation makes it possible today to break down highly heterogeneous materials to the scale where physical chemistry meets (continuum) mechanics, to extract intrinsic material properties that do not change from one material to another, and to upscale the intrinsic material behavior from the sub-microscale to the macroscale. While well established for elastic properties, the extraction of strength properties of cohesive-frictional materials from nanoindentation tests has not been investigated in the same depth. The focus of this thesis is to investigate in depth the link between nanohardness of cohesive-frictional materials and strength properties. To address our objectives, we develop a rational methodology based on limit analysis theorems and implement this methodology in a finite element, based computational environment. By applying this technique to indentation analysis, we show that it is possible to extract the cohesion and the friction angle from two conical indentation tests having different apex angles. The methodology is validated on a model cohesive-frictional material, bulk metallic glass, and a first application to a highly heterogeneous natural composite material...

‣ Long term behavior of cable strayed bridges

Scotti, Andrea, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 56 leaves; 1849964 bytes; 1849770 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25181%
In the design of a structure, one of the most difficult parameter to assess is how the initial condition of a structure will change with time. During its life span, a structure can be subjected to different loads, changes in geometric configuration and even changes in its mechanical properties. Among all factors that can affect the geometrical reconfiguration of a structure (i.e. settlements and overloads) creep is one of the most important given its inevitability and because of its persistent effects (normally estimated as ten thousand days). Due to the effect of creep, a structure tends to amplify its deformation under a given load condition over time, and the final deformation can even reach values five or six time grater than the initial ones. During the design, the fact that deformations grow with time can be a difficult condition especially for highly indeterminate structures like cable stayed bridges where the stresses are related to the geometric configuration of the structure itself. In concrete cable stayed bridges, in fact, the increase in the deformation of the deck and the pylons over time leads to a decrease in the initial tension in the stays with an obvious difficulty in the design phase of the structure. The first chapter of this thesis illustrates and explains one approximate method used to estimate the effect of creep on a concrete structure. The method proposed in this thesis is the "Age-Adjusted Effective Modulus Method". It was chosen among others because it is one of the most commonly used...

‣ Spirasol : improvements to semi-continuous solar disinfection water treatment systems; Improvements to semi-continuous solar disinfection water treatment systems

Loux, Brian Michael, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 77 leaves; 5410666 bytes; 5418818 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25181%
An experimental study was carried out to determine the feasibility of an original point of use solar water disinfection system created by the author and named "Spirasol." The study primarily focused on the comparison of microbial removal levels in the Spirasol system and the more traditional solar disinfection method called SODIS that uses a Polyethylene Terephthalate (PET) bottle. To address microbial removal capacity, the two systems were assembled and tested in Nairobi, Kenya and later in Cambridge, Massachusetts. The issue of economic feasibility and component availability were also addressed and factored in heavily during the design phase of the project. The results suggest that the Spirasol system is equally as effective as the traditional SODIS system with respect to microbial inactivation. Analysis of the costs required for continuous and semi-continuous solar disinfection system implied that such systems were not a good match for sites of extreme urban poverty such as the Kibera slum in Nairobi, Kenya. However, the overall low cost among semi-continuous point of use treatment systems and the wide availability of the required pieces made them a sustainable technology for other areas in the developing world where available capital is marginally higher.; by Brian Michael Loux.; Thesis (M. Eng.)--Massachusetts Institute of Technology...

‣ Database design development : i-LINK, an integrated messaging framework; i-LINK, an integrated messaging framework

Chahine, Pamela Michel, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 74 leaves; 2463606 bytes; 2463413 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25181%
For many people, online communication has meant a plethora of communication media - emails, instant messages, blogs, etc. Often this has led to clustered desktop displays and ineffective integration between communication media. Software development teams are adversely affected by the lack of integration between applications. When project managers, software developers and clients come together to work on one or more projects, certain communication and managerial considerations and requirements become apparent. A server-based Integrated Messaging Framework (IMF) provides all communication media messages with a common messaging format. i-LINK, an intelligent client application uses IMF to send, receive, log, and store messages from different communication channels. There are contrasting database models from which to choose when designing the IMF data model (i.e.: flat file, relational, object oriented, objected relational). However, the IMF was designed using a relational data model due to the stability it offered, the protection provided through referential integrity and constraints, as well as other unique benefits. When considering the services that IMF is designed to provide, certain existing messaging standards are conceptually useful to analyze before designing the IMF data model. The RFC 2778 provides a universal Instant Messaging (IM) data model which can be mapped to provide such services as presence and instant messaging. Microsoft Outlook...

‣ Modelling the performance of revenue management systems in different competitive environments

Dar, Maital
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 129 p.; 8563549 bytes; 8569866 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25181%
In the wake of contemporary widespread fare simplification in many major airline markets, this thesis is concerned with the possibilities and the potential for airline revenue management in less-differentiated fare environments. Traditional revenue management has relied upon the assumption that independent demands exist for different fare class products, and can be forecast as such. However, in less-differentiated fare environments this assumption has been shown to lead to "spiral-down" in revenues. Hence, in this thesis, seat inventory control methods are simulated in less-differentiated fare environments and their relative performances are compared. The methods tested are: EMSRb-based Fare Class Yield Management (FCYM); Heuristic Bid Price (HBP); Displacement Adjusted Virtual Nesting (DAVN); and Probabilistic Bid Price (ProBP). Each of the methods is tested in conjunction with two different demand forecasting philosophies: the traditional pickup (or moving average) forecaster which is based on the assumption of independent demands; and a hybrid forecasting method based on the notion that there is one demand for flexible products and another demand for the cheapest product. The methods are simulated in two different competitive airline network environments: a symmetric network with simplified fares; and a more complex non-symmetric network with mixed fare structures. Simulation shows that the performance of all four revenue management methods suffers in less-differentiated fare environments if they continue to use traditional forecasting. Methods that forecast demand at the path level see inflated forecasts for more expensive products...

‣ Improving the transfer experience at intermodal transit stations through innovative dispatch strategies

Desautels, Andrew T. (Andrew Thomas)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 169 p.
Português
Relevância na Pesquisa
128.25181%
This research introduces the concept of a bus hold light system that is based on headways of arriving trains in an effort to improve rail-to-bus transfer connectivity through a simple-to-implement, low-cost dispatching strategy. An analytical model and a simulation model are developed to analyze the impacts of the proposed headway-based hold light system on total passenger wait time and other relevant measures of transfer performance. The application of the two models to the cases of Alewife and Wellington Stations in the Massachusetts Bay Transportation Authority (MBTA) system and to 79 Street Station in the Chicago Transit Authority (CTA) system shows that the headway-based hold light system can produce substantial passenger wait time savings if implemented in an appropriate setting. Throughout these analyses, the sensitivity of the headway-based hold light system to various factors is analyzed, and the results obtained with the headway-based hold light system are compared with those obtained from the application of other bus dispatching strategies, most notably the strategy of holding each departing bus for passengers transferring from the next train arrival.; (cont.) Based on the case study results and sensitivity analyses, a set of guidelines for the implementation of headway-based hold light systems is proposed. In .the comparison of the headway-based hold light system and the hold-all-buses strategy...

‣ Bus passenger Origin-Destination Matrix estimation using Automated Data Collection systems; Bus passenger OD Matrix estimation using ADC systems

Cui, Alex
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 134 p.
Português
Relevância na Pesquisa
128.25181%
Automatic Data Collection (ADC systems can enhance the ability of transit agencies to obtain useful planning information that was previously too expensive to obtain. This thesis documents the development of an algorithm to estimate a Bus Passenger Trip Origin-Destination Matrix (OD Matrix) based on ADC system archived data including Automated Fare Collection (AFC data, Automatic Passenger Count (APC data, and Automatic Vehicle Location (AVL) data. This algorithm consists of three steps: data preparation, estimation of a Single Route OD Matrices for all routes, and estimation of a Network Level OD Matrix using transfer flow information. The single route OD matrix estimation requires the development of a "seed" matrix derived primarily from AFC data and the "marginal" control totals, i.e. the boarding and alighting counts, derived primarily from APC data. Both Iterative Proportional Fitting (IPF) and Maximum Likelihood Estimation (LE) techniques are used to estimate the single route OD matrices based on seed matrices and marginal values, and the results from these two techniques are compared. For the network level OD matrix estimation, we estimate the transfer flows by considering the consecutive transactions from AFC data.; (cont.) The resulting network level OD matrix is provided at a route segment level (3-5 combined stops) of detail. This OD estimation algorithm is illustrated by its application to a selected corridor of the Chicago Transit Authority (CTA) bus network This OD estimation algorithm can be practically applied to a full-size bus network It is recommended that the MLE method be used to estimate the single route OD matrices and the proportional distribution method be used to estimate the transfer flow OD matrix.; by Alex Cui.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ A remedial approach to stabilize a deep excavation in Singapore

Ferrari, Alessia Alexandra
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 103 leaves
Português
Relevância na Pesquisa
128.25181%
Ground improvement methods are commonly adopted in deep excavation to minimize wall deflection, wall bending moment and strut force. In this thesis a different approach to the application of ground improvement techniques is analyzed in the form of a parametric study developed with the use of a commercial finite element code. A new remedial ground improvement solution applied to an existing deep excavation located in Singapore and part of the Circle Line Project (CCL) for the construction of a new subway line is considered and computationally modeled. The soil profile in the site mainly consists of deep marine soft clay dated for the most part in the Holocene period, principally characterized by a normally to very low overconsolidation ratio, in some location even underconsolidated. The parametric analysis aims to evaluate short-term effects of the application of cementing agents to the lower portion of the marine clay externally to the excavation side. The effectiveness of the proposed ground improvement is examined using a finite element model corresponding to a key cross-section of CCL1 project.; (cont.) Parametric analyses are used to assess how the dimensions of the treatment zone and strength of soilcrete columns affect the computed wall deflections...

‣ Control of human induced floor vibrations

Homen, Sean Manuel
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 88 leaves
Português
Relevância na Pesquisa
128.25181%
With the growing demand for open, column-free floor spaces and the advances in material strength, floor vibration serviceability criterion has been of growing importance within the past 20-30 years. All floor systems are flexible and when introduced to a dynamic loading respond in a vibratory manner. The issues with floor serviceability arise when the floor vibrates in an uncomfortable way when exposed to everyday loading, for example human footfall in an office building. Vibrating floors have been divided into 4 categories based on the perceptibility by humans: (a) vibration, though present, is not perceived by the occupants; (b) vibration is perceived but it does not annoy the occupant; (c) vibration annoys and disturbs; (d) vibration is so severe that it makes people sick. This thesis is focused on the control of human induced floor vibrations. In order to provide the reader with practical insight on the subject, a case study of an existing steel framed office building that experienced excessive and annoying floor vibrations will be discussed and analyzed.; (cont.) As a result of this case study, it has been determined that the Alan and Rainer scale, along with the Modified Reiher Meister scale and the Wiss and Paremelee scale, accurately describe the human response criteria. Also determined was that the American Institute of Steel Construction Floor Vibrations Due to Human Activity (Design Guide 11) has extremely conservative acceleration criteria that basically aim to make the vibration not noticeable at all.; by Sean Manuel Homen.; Thesis (M. Eng.)--Massachusetts Institute of Technology...

‣ Model-based design of an ultra high performance concrete support structure for a wind turbine

Wang, Zheng, M. Eng. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 48 leaves
Português
Relevância na Pesquisa
128.25181%
A support tower is the main structure which would support rotor, power transmission and control systems, and elevates the rotating blades above the earth boundary layer. A successful design should ensure safe, efficient and economic design for the whole wind turbine system. It should provide easy construction and easy access for maintenance of the rotor components and sub-components. UHPC materials have been used in various structural applications, such as highway bridge girders. There is no much research about its application in support structures of wind turbines. After meeting the requirements for loads, minimizing cost is the next most important design driver. Here at MIT, Chuang and Professor Ulm developed a new constitutive model for fiber reinforced cementitious composite materials, which is particularly suitable for high performance cementitious composites including UHPC. On the basis of UHPC material model and the load requirements for wind turbines, the objective of this work is to carry out a tentative design of the UHPC support tower for a prototype wind turbine.; (cont.) Two tube-type cross sections are examined. The 3-d analysis reveals a sufficient flexural performance of the UHPC support tower when subjected to the extreme wind loads. Since this work only focuses on the extreme wind load case...

‣ Routing in heterogeneous wireless ad hoc networks

Cheekiralla, Sivaram M. S. L., 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 146 p.
Português
Relevância na Pesquisa
128.25305%
Wireless ad hoc networks are used in several applications ranging from infrastructure monitoring to providing Internet connectivity to remote locations. A common assumption about these networks is that the devices that form the network are homogeneous in their capabilities. However in reality, the networks can be heterogeneous in the capabilities of the devices. The main contribution of this thesis is the identification of issues for efficient communication in heterogeneous networks and the proposed solutions to these issues. The first part of the thesis deals with the issues of unambiguous classification of devices and device identification in ad hoc networks. A taxonomical approach is developed, which allows devices with wide range of capabilities to be classified on the basis of their functionality. Once classified, devices are characterized on the basis of different attributes. An IPv6 identification scheme and two routing services based on this scheme that allow object-object communication are developed. The identification scheme is extended to a multi-addressing scheme for wireless ad hoc networks. These two issues and the developed solutions are applicable to a broad range of heterogeneous networks. The second part of the thesis deals with heterogeneous networks consisting of omnidirectional and directional antennas. A new MAC protocol for directional antennas...

‣ Capital project development in biotechnology industry

Kristinsdottir, Asbjorg
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 62 p.
Português
Relevância na Pesquisa
128.25305%
The biotechnology industry has experienced fast growth during the first 30 years of its existence but is now reaching a stage of maturity. Companies are being challenged by weak pipelines and patent expirations, as well as increasing regulation. Mergers and acquisitions are frequent, and companies are forced to reduce planned capital expenditures, as well as restructure with personnel cuts and facility reductions. This thesis focuses on the affect those changes are having on the development of capital projects. It researches the environment as it used to be and what is now bringing the changes. Through literature search and case study, the thesis aims to capture the reasons for why the main driver of new facilities construction has shifted from time to cost and the affect that is having on the management and delivery of such projects.; by Asbjorg Kristinsdottir.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2008.; Includes bibliographical references (p. 61-62).

‣ Modeling driving decisions with latent plans

Choudhury, Charisma Farheen, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 238 p.
Português
Relevância na Pesquisa
128.25305%
Driving is a complex task that includes a series of interdependent decisions. In many situations, these decisions are based on a specific plan. The plan is however unobserved or latent and only the manifestations of the plan through actions are observed. Examples include selection of a target lane before execution of the lane change, choice of a merging tactic before execution of the merge. Change in circumstances (e.g. reaction of the neighboring drivers, delay in execution) can lead to updates to the initially chosen plan. These latent plans are ignored in the state-of-the-art driving behavior models. Use of these myopic models in the traffic simulators often lead to unrealistic traffic flow characteristics and incorrect representation of congestion. A modeling methodology has been formulated to address the effects of unobserved plans in the decisions of the drivers and hence overcome the deficiency of the existing driving behavior models and simulation tools. The actions of the driver are conditional on the current plan. The current plan can depend on previous plans and be influenced by anticipated future conditions. A Hidden Markov Model is used to address the effect of previous plans in the choice of the current plan and to capture the state-dependence among decisions. Effects of anticipated future circumstances in the current plan are captured through predicted conditions based on current information. The heterogeneity in decision making and planning capabilities of drivers are explicitly addressed. The methodology has been applied in developing driving behavior models for four traffic scenarios: freeway lane changing...

‣ Effects of buoyancy source composition on multiphase plume behavior in stratification

Chow, Aaron C. (Aaron Chunghin), 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 179 p.; 3564769 bytes; 3564522 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25305%
Experiments are performed where a dense multiphase plume is released vertically in a salinity stratified ambient. The constituent phase composition of the initial buoyancy flux can be dense brine, particles, or a mixture of the two in a prescribed ratio. The resulting trapping heights and peeling depths are recorded by visual acquisition and from dye fluorescence measurements. Also, the radial concentration distribution of the dispersed phase after the first peeling event is obtained by collecting the settled particles from the bottom of the tank. Analytical models assuming plug flow and well-mixed particle distributions within the intrusion layer are used to predict the spread of the particle distribution based on initial buoyancy flux, momentum flux, stratification parameter and particle fall velocity. The effects of initial momentum and volume flux on peel and trap depths were studied by comparing the predictions from these models. Finally the observed results are compared to a single-phase plume numerical prediction (CORMIX) and a multiphase numerical plume model. Observed peeling depths were not sensitive to buoyancy composition, while observed trap depths decreased slightly with high particle fractions, possibly from the 'lift-off' phenomenon where particle fallout decreases the bulk buoyancy of the intrusion layer. The observed radial distribution was Gaussian...

‣ Rural groundwater supply for the Volcanoes National Park region, Rwanda

Zoghbi, Christiane A. (Christiane Antoine)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 92 leaves
Português
Relevância na Pesquisa
128.25305%
Water scarcity is a major issue faced by both developed and developing countries. According to the Millennium Development Goals set by the United Nations, the number of people that do not have access to an improved water supply should be halved by the year 2015. Rwanda is a Sub-Saharan developing country where water scarcity is an issue. This thesis presents results from a preliminary evaluation of possible groundwater supply to the village of Bisate, located in the Northern Province of Rwanda. Suffering from the "walk for water", the Bisate community has to give up vital activities such as school and agriculture in order to fetch water. During the dry season, the people are obliged to go into the Volcanoes National Park to get water from springs and swamps, disrupting the fragile ecosystem by the human activity. All these factors make it important to provide water at the point of use. Since the region receives a considerable amount of rain and the groundwater recharge rate is high (0.3 m/year), groundwater supply could be a feasible alternative for the Bisate community. For this thesis, three major tasks were achieved.; (cont.) First, a description of the park's hydrogeology was developed based on previous studies and field observations. Second...

‣ Assessment of impact of dynamic route guidance through variable message signs

Rathi, Vaibhav
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 139 p.
Português
Relevância na Pesquisa
128.25305%
Integration of Intelligent Transportation Systems (ITS) technologies with traffic surveillance has the potential of reducing the delays and costs incurred due to non-recurrent congestion through the dissemination of dynamic route guidance to drivers. Variable Message Signs (VMS), installed on freeways, are used for incident management and provide information about the incidents and diversion routes. VMS can prove to be a significant tool used by the Traffic Management Center (TMC) to improve the efficiency of the network by providing dynamic route guidance. Dynamic Traffic Assignment (DTA) tools can be used to generate predictive guidance, and the TMC can disseminate it through VMS to the drivers. However, on-line evaluation of such systems is very costly and there is a need to simulate the real traffic conditions to evaluate the DTA tools before their implementation in the field. The current state of the art is to provide measured travel time information to drivers. The objective of this study will be to evaluate the network performance with the dissemination of predictive route guidance in case of severe incidents through the Variable Message Signs.; (cont.) Evaluation is done by developing a tool using the 'closed loop' integration between MITSIMLab...

‣ Matching of lowest fare seat availability in airline revenue management systems

Lua, Wenyi Fabian
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 150 p.
Português
Relevância na Pesquisa
128.25305%
By enabling passengers to compare easily and book directly from airline inventories, Internetbased ticket distribution has forced airlines to compete for the lowest price level and more importantly, to ensure seat availability at that price. To retain market share, many airlines track and match the lowest fare of their competitors -- both the price level and the associated seat availability through the use of revenue management seat inventory controls. This thesis uses simulation to examine the impacts of an airline matching its competitor's lowest fare seat availability. In a single symmetric market, simulations demonstrate that the airline using a more sophisticated revenue management system generally obtains lower revenues the more it matches the seat availability of its competitor's lowest fares -- losing as much as 9.2%. At the same time, the matched airline benefits consistently in terms of improved revenues. These findings extend to a much larger mixed-fare simulation network with four airlines: when a legacy airline matches the lowest fare seat availability of a "low-cost carrier" (LCC), the legacy airline loses at least 3.4% and as much as 8.5% in revenue. At the same time, the LCC and the other two peripheral competitors gain as much as 5.3% in revenue. The legacy airline's revenue management system recovers from the damage done to a degree that depends on the sophistication of the revenue management methods it uses. In the absence of seat availability matching...

‣ Private risk

Mattar, Mahdi H. (Mahdi Haidar), 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 79 leaves; 2728667 bytes; 2728476 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25305%
In the first essay of this thesis, we extend the traditional decision analysis theory of buying price and selling price of a lottery. We allow the decision maker to rebalance his financial portfolio in the course of determination of a lottery's buying (selling) price. We build on the classical portfolio allocation problem in complete markets, generalizing to include both traded and non-traded unique risks. Our principal focus is on private risks-risks that are not tradable in financial markets. The first essay: Generalizes the treatment of the buying price and the selling price of a private risk lottery by allowing portfolio rebalancing in the course of determining these prices and Outlines the implications of this generalization for distributive bargaining. The second essay is a study of methods for pricing unique risks in real options problems. This essay is a critical evaluation of how methods currently in vogue for pricing private risks affect real option value. We build a framework for valuing investments under uncertainty in the presence of private risks and demonstrate by example that different methods for pricing private risk can lead to decisively different real option values. To this end we use the classical oil and gas exploration and development example pioneered by Paddock...

‣ Lateral systems for tall buildings

Chok, Kermin, 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 198 p.; 5395488 bytes; 5395297 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
128.25305%
The advances in three-dimensional structural analysis and computing resources have allowed the efficient and safe design of increasingly taller structures. These structures are the consequence of increasing urban densification and economic viability. The modern skyscraper has and will thus continue to feature prominently in the landscape of urban cities. The trend towards progressively taller structures has demanded a shift from the traditional strength based design approach of buildings to a focus on constraining the overall motion of the structure. Structural engineers have responded to this challenge of lateral control with a myriad of systems that achieve motion control while adhering to the overall architectural vision. An investigation was carried out to understand the behavior of the different lateral systems employed in today's skyscrapers. The investigation examined the structural behavior of the traditional moment frame, the braced frame, the braced frame with outriggers and finally the tubular structure. The advantages and disadvantages of all schemes were explored from both an architectural and structural efficiency standpoint. Prior to the computer modeling of each lateral system, each scheme was understood from an analytical standpoint to both verify computer results and to illustrate the importance of hand calculations. The study repeatedly illustrated that motion was the governing condition and this led to the proposal of an approach for the design of braced frames.; by Kermin Chok.; Thesis (M. Eng.)--Massachusetts Institute of Technology...