• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 29
  • 7
  • 6
  • 4
  • 4
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 70
  • 70
  • 19
  • 18
  • 16
  • 13
  • 11
  • 10
  • 8
  • 8
  • 8
  • 8
  • 8
  • 7
  • 7
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

An examination of urban area S.T.O.L. airports

Morris, David William January 1970 (has links)
This thesis is an examination of the problems that may arise from the location of S.T.O.L. airports within urbanized areas. The role of air transportation as a passenger travel mode is considered and the problems facing the existing air transportation system are explored. The potential role of S.T.O.L. aircraft within the air transportation system is examined in detail. Additionally, the benefits that may accrue from the use of S.T.O.L. aircraft in a regional air transport system are discussed extensively. The criteria to be used when looking for potential S.T.O.L. airport sites are examined in detail. These criteria are applied to three potential S.T.O.L. airport sites within the Vancouver urban area. In some cases the locational criteria were found to be difficult to operationalize. Data on community reaction to noise exposure is inadequate and noise standards are difficult to apply on a wide basis. The concept of land use compatibility around airports is useful but only to the extent that it does not obscure the fact that aircraft operations can cause community disruptions beyond the boundaries of the so-called compatible land uses. With specific reference to Vancouver, the available data indicates, that on the average, very little terminal access or egress time will be saved if a S.T.O.L. airport were built at a suitable location between the existing airport and the downtown area. Finally, the paper concludes by suggesting that despite the fact that S.T.O.L. aircraft cannot bring substantial time savings to regional air passengers, a S.T.O.L. air service may mean that many of the regions under utilized conventional airports could be converted to S.T.O.L. airports and yeild substantial savings in the money used to maintain and operate the publically owned airports in the province. / Applied Science, Faculty of / Community and Regional Planning (SCARP), School of / Graduate
12

Differences in Ground Reaction Forces between Take-Offs that are Out, On, or Under in the Pole Vault

Francis, Shawn Michael January 2012 (has links)
Aim. The take-off is regarded as the most important phase of the pole vault yet there is an insufficient amount of research on the ground reaction forces of the pole vault takeoff. At this time there is not any scientific research comparing force and time between takeoffs that are out, on and under. The purpose of this study is to compare the differences in ground reaction forces between pole vault take-offs that are out, on or under. Methods. Over five days, 15 male and female college pole vaulters completed 226 vaults on a (AMTI Accupower) force plate. The jumps were put into categories of out, on and under and analyzed by Accupower, and Dartfish software. Separate mixed modal ANOVAs (SAS 9.3) were applied (P≤.05) for comparison between jump types. Conclusions. There is no significant difference between ground reaction forces of the three jump types.
13

Producera mängdgrafer genom BIM : Produce quantity take-off graphs using BIM

El-Zouki, Robert January 2017 (has links)
Avvikelser i ett byggprojekt leder till bland annat förseningar. De kan även leda till för tidigt avslutadeaktiviteter. Oavsett blir detta ett problem då kontraktstiden för underentreprenörer är bestämda.Vad detta betyder är att blir en underentreprenör färdig för tidigt kommer det finnas en tidbuffert itidplan mellan färdig- och nästa aktivitet. Detta anses som en kostnad eftersom det inte utförs någotarbete. Blir en underentreprenör sen med färdigställande av en aktivitet blir detta ocksåproblematiskt då detta skjuter fram aktiviteter på den kritiska linjen. Förutsatt att de aktiviteternaligger på den kritiska linjen. Det ska förtydligas att fler former av avvikelser finns. Bland annatfelleverans, försenad transport, oförutsedda hinder under produktion m.m. En metod att åskådliggöra avvikelser tidigt efter initiering är att kontinuerligt under produktion följaupp aktiviteter med hjälp av mängdgrafer. Mängdgrafer är diagram som visar byggd mängd pertidsenhet och kumulativ byggd mängd. De ger en visuell bild över hur produktionen ligger till inuläget och med hjälp av dessa kan beslut fattas om ändringar i produktionen för att projektet skatidsmässigt åter hamna i fas. Mängdgrafer kommer i tre former. Planerade-, aktuella- &prognostiserade mängdgrafer. Syftet med detta examensarbete är att undersöka hur BIM-verktyg under projektering kan stödja ettprojekt under produktion genom att förutse avvikelser. Ifall avvikelser upptäcks tidigt kan resurserjusteras eller arbetstider ändras för att projektet färdigställs enligt tidplan. Studien visar att mängdgraferna kan utvecklas relativt enkelt men det krävs väl genomtänktplanering och struktur på arbetet. Det rekommenderas att samordna en bra arbetsmetod för helaarbetet från början till slut genom att ha en samordnare som styr över modellen men också andratjänstemän som känner till programmet tillräckligt bra för att stötta och avlasta samordnaren vidbehov. Studien visar också att det är viktigt att modellutvecklare levererar modellen med bra ochstrukturerad namnbeteckning för objekten. Detta för att enklare kunna koppla KPI-tal till korrektmängdgraf. CoClass-klassifikationssystem (projektnamn BSAB 2.0) borde ligga till grund förnamngivning av objekt. / Deviations in a construction project lead to delays. They can also lead to prematurely completed activities. In any case, this will be a problem since the contract period for subcontractors is determined. What this means is that if a subcontractor completes its task prematurely, there will be a time buffer in the timetable between completed and next activity. This is considered a cost because no work is being done. If a subcontractor completes an activity late, this is also problematic as it displaces activities on the critical line. If the activities are on the critical line. It should be clarified that more types of deviations exist. Including delivery, delayed transport, unforeseen obstructions during production, etc. One method of avoiding deviations is to continuously monitor production activities using quantity take-off graphs. These graphs are charts showing built-up amount per unit of time and cumulative built-up amount. They give a visual picture of the state of production, and from there, decisions can be made about changes in production so that the project will follow the time schedule again. Quantity take-off charts come in three forms. Planned, actual & forecast quantity take-off graphs. The purpose of this degree project is to investigate how BIM tools during design phase can support a project under production phase by predicting deviations. If deviations are early discovered, resources can be adjusted or working hours changed to complete the project according to time schedule. The study shows that the quantity graphs can be developed relatively easily, but well thought out planning and structure are required. It is recommended to coordinate a good working method for the entire work from start to finish by having a coordinator who controls the model but also other officials who know the program well enough to support and relieve the coordinator if necessary. The study also shows that it is important that model developers deliver the model with a good and structured designation of object. This is easier to connect KPI-numbers to the correct quantity takeoff graph. CoClass classification system (project name BSAB 2.0) should be used as the basis for naming of objects.
14

Effect of a nonlinear power take off on a wave energy converter

Bailey, Helen Louise January 2011 (has links)
This thesis is titled The influence of a nonlinear Power Take Off on a Wave Energy Converter. It looks at the effect that having a nonlinear Power Take Off (PTO) has on an inertial referenced, slack moored, point absorber, Wave Energy Converter (WEC). The generic device studied utilizes relative heave motion between an axi-symmetric cylinder and an internal mass, for the PTO to operate between. The PTO is the part of the WEC that transforms the relative motion into electricity. In this work, three different types of nonlinear PTO and a linear PTO are presented, tested, analysed and compared. The three nonlinear PTO types are: • A PTO that extracts energy in only one direction, either in relative compression or expansion. • A linear PTO and an additional endstop or peripheral PTO, that can only extract energy when the relative position of the internal mass has reached a pre-determined position. • A PTO that has damping forces that are quadratically proportional to the relative velocity. A numerical simulation has been built based upon a Runge-Kutta time series progression. The model uses the summation of the excitation force from the waves, the radiation force from the movement of the cylinder, the buoyancy force and the PTO forces. These combine to cause acceleration of the mass of the external cylinder, with an equal and opposite PTO force acting on the internal mass. The excitation force and added mass values are obtained from the boundary element method software, WAMIT. Prony’s method is used to obtain an approximate radiation force, based upon the radiation time force history. This numerical model operates on both a 1:40 scale and a full sized model. The numerical model finds the optimal PTO parameters, for different PTO setups, in irregular sea states. This optimum is based on the power extracted as well as indications of the reliability and lifetime of the system. The numerical simulation presents results showing how the nonlinearity of the PTO influences the motions of the WEC, resulting in dissimilarities between the Response Amplitude Operator (RAO) results, obtained from regular seas, and the Linear Transfer Function (LTF), found from irregular sea testing. The experimental model has been tested in the Curved Wave Tank facility at the University of Edinburgh, with a 1:40 scaled model. It used a central rod both as a support structure and to limit the movement of the cylinder and internal mass to heave. Between the cylinder and internal mass a spring and pneumatic damper operate in parallel, in various setups. It was tested in regular and irregular sea states and the position of the internal mass and cylinder was monitored. The experimental model was tested to ascertain the time series motions, RAO, LTF, the relative phase between the bodies and the power extracted for different wave climates. The numerical and experimental work were compared to allow confidence in both models. They showed relatively good agreement for the RAOs, LTFs and predictions of the relative phase but there was discrepancies in the predicted power for both regular and irregular seas. This difference is due to the difficulties in obtaining the relative velocities in the experimental model, resulting in a significant error in power prediction, since the power is proportional to the square of the relative velocities. The conclusions show that having a mono-directional PTO as opposed to a bi-directional PTO results in an approximately equal or greater power extraction in a variety of different sea states. An additional endstop or peripheral damper can increase the total power that a WEC extracts, in some situations, and may be advantageous depending upon the other potential benefits it brings to the WEC.
15

Etapas do desenvolvimento econômico no Brasil - um exercício rostowiano / Stages of economic development in Brazil: exercise rostowiano

Sarmento, Alexandre Dellamura 08 April 2009 (has links)
O principal objetivo desta dissertação é a aplicação do modelo de etapas do desenvolvimento econômico de Walt Whitman Rostow ao Brasil, identificando o arranco brasileiro como fim dos surtos industrias e início da industrialização regular entre 1929 e 1954. Além disso a teoria de Rostow serviu de contraponto às duas principais teorias de desenvolvimento econômico brasileiras existentes até meados da década de 1950, os liberais e os desenvolvimentistas. As discussões e os pontos divergentes entre essas teorias contribuíram para o entendimento do processo de industrialização brasileiro, sua produtividade, concentração e contribuição ao desenvolvimento econômico. A identificação das etapas se realizou de modo a comprovar, principalmente, as teses de Rostow em relação ao arranco brasileiro e os mecanismos para sua propagação, que deveriam desembocar nas fases subseqüentes da teoria e, em conseqüência, ao desenvolvimento econômico mais igualitário e ao Estado de Bem-Estar. / The main objective of this dissertation is the application of the model of stages of the economical growth of Walt Whitman Rostow to Brazil, identifying the Brazilian takeoff as end of the industrials outbreaks and beginning of the regular industrialization between 1929 and 1954. Besides the Rostow theory served from counterpoint to the two main theories of economical growth existent Brazilians to middles of the decade of 1950, the liberal school and the development school. The discussions and the divergent points among those theories contributed to the understanding of the Brazilian industrialization process, his productivity, concentration and contribution to the economical growth. The identification of the stages took place from way to prove, mainly, the theories of Rostow in relation to the Brazilian take-off and the mechanisms for his propagation, that they should end in the subsequent phases of the theory and, in consequence, to the more equalitarian economical growth and the Welfare State.
16

Kinematic and Kinetic Tumbling Take-off Comparisons of a Spring-floor and an Air FloorTM: A Pilot Study

Sands, William A., Kimmel, Wendy L., McNeal, Jeni R., Smith, Sarah L., Penitente, Gabriella, Murray, Steven Ross, Sato, Kimitake, Mizuguchi, Satoshi, Stone, Michael H. 01 January 2013 (has links)
Tumbling take-offs on floor exercise apparatuses of varying stiffness properties may contribute to apparatus behaviors that lead to increased injury exposure. The purpose of this pilot study was to compare the kinematics, kinetics, and timing performance characteristics of a springfloor and a spring-floor with an added Air FloorTM. Five male international gymnasts performed a forward handspring to forward somersault and a round off, flic flac, backward somersault on a standard spring-floor and a spring-floor with an Air FloorTM. Performances were measured via high-speed video kinematics (lower extremity joint angles and positions), electromyography of eight lower extremity muscles, mean peak forces on the feet, and timing. Comparisons of spring-floor types, lower extremity joint angles, lower extremity muscle activations, foot forces, and selected durations were determined. The spring floor with Air FloorTM resulted in longer take-off contact durations than spring-floor alone. Dynamic knee angles may indicate an unexpected and potentially injurious motion of the triceps surae musculotendinous structures. This pilot and hypothesis generating study has suggested future research examining dynamic knee position and angle changes, the role of spring-floor vibration and stiffness in take-offs, and take-off muscle activation alignment with the stiffness of the spring-floor. Pragmatically, there appears to be a convergence of evidence indicating that a slower frequency response of the spring floor may assist tumbling performance and reduce stress and strain in the lower extremity.
17

Prediction of Circulation Control Performance Characteristics for Super STOL and STOL Applications

Naqvi, Messam Abbas 22 August 2006 (has links)
The rapid air travel growth during the last three decades, has resulted in runway congestion at major airports. The current airports infrastructure will not be able to support the rapid growth trends expected in the next decade. Changes or upgrades in infrastructure alone would not be able to satisfy the growth requirements, and new airplane concepts such as the NASA proposed Super Short Takeo and Landing and Extremely Short Takeo and Landing (ESTOL) are being vigorously pursued. Aircraft noise pollution during Takeoff and Landing is another serious concern and efforts are aimed to reduce the airframe noise produced by Conventional High Lift Devices during Takeoff and Landing. Circulation control technology has the prospect of being a good alternative to resolve both the aforesaid issues. Circulation control airfoils are not only capable of producing very high values of lift (Cl values in excess of 8.0) at zero degree angle of attack, but also eliminate the noise generated by the conventional high lift devices and their associated weight penalty as well as their complex operation and storage. This will ensure not only satisfying the small takeoff and landing distances, but minimal acoustic signature in accordance with FAA requirements. The Circulation Control relies on the tendency of an emanating wall jet to independently control the circulation and lift on an airfoil. Unlike, conventional airfoil where rear stagnation point is located at the sharp trailing edge, circulation control airfoils possess a round trailing edge, therefore the rear stagnation point is free to move. The location of rear stagnation point is controlled by the blown jet momentum. This provides a secondary control in the form of jet momentum with which the lift generated can be controlled rather the only available control of incidence (angle of attack) in case of conventional airfoils. The use of Circulation control despite its promising potential has been limited only to research applications due to the lack of a simple prediction capability. This research effort was focused on the creation of a rapid prediction capability of Circulation Control Aerodynamic Characteristics which could help designers with rapid performance estimates for design space exploration. A morphological matrix was created with the available set of options which could be chosen to create this prediction capability starting with purely analytical physics based modeling to high fidelity CFD codes. Based on the available constraints, and desired accuracy metamodels has been created around the two dimensional circulation control performance results computed using Navier Stokes Equations (Computational Fluid Dynamics). DSS2, a two dimensional RANS code written by Professor Lakshmi Sankar was utilized for circulation control airfoil characteristics. The CFD code was first applied to the NCCR 1510-7607N airfoil to validate the model with available experimental results. It was then applied to compute the results of a fractional factorial design of experiments array. Metamodels were formulated using the neural networks to the results obtained from the Design of Experiments. Additional validation runs were performed to validate the model predictions. Metamodels are not only capable of rapid performance prediction, but also help generate the relation trends of response matrices with control variables and capture the complex interactions between control variables. Quantitative as well as qualitative assessments of results were performed by computation of aerodynamic forces and moments and flow field visualizations. Wing characteristics in three dimensions were obtained by integration over the whole wing using Prandtl's Wing Theory. The baseline Super STOL configuration was then analyzed with the application of circulation control technology. The desired values of lift and drag to achieve the target values of Takeoff and Landing performance were compared with the optimal configurations obtained by the model. The same optimal configurations were then subjected to Super STOL cruise conditions to perform a tradeoff analysis between Takeoff and Cruise Performance. Supercritical airfoils modified for circulation control were also thoroughly analyzed for Takeoff and Cruise performance and may constitute a viable option for Super STOL and STOL Designs. The prediction capability produced by this research effort can be integrated with the current conceptual aircraft modeling and simulation framework. The prediction tool is applicable within the selected ranges of each variable, but methodology and formulation scheme adopted can be applied to any other design space exploration.
18

Conceptual Quantity Modeling Of Single Span Highway Bridges By Regression, Neural Networks And Case Based Reasoning Methods

Asikgil, Mert 01 June 2012 (has links) (PDF)
Conceptual estimation techniques play an important role in determining the approximate costs of construction projects especially during feasibility stages. Moreover, pre-design estimates are also crucial for the contractors. With the help of the conceptual predictions companies can determine approximate project costs and can gain several advantages before tendering phase. The main objective of this thesis is to focus on modeling of quantities instead of costs and to develop quantity take-off models for pre-design cost estimation of bridge projects. Majority of the existing studies focus on modeling of costs for conceptual cost estimation. This study includes modeling of the quantity take off items in a specific single span highway bridge using three different techniques namely, linear regression, neural network and case based reasoning. During this study 40 single span highway bridge projects whose owner is Republic of Turkey General Directorate of Railways, Ports and Airports Constructions were investigated and models for each work item were developed. Then by integrating the quantity take off estimations with unit costs, total project costs were calculated. As a result by evaluating the prediction performance of the models, comparison of the methods was achieved. Results are discussed along with the advantages of the proposed method for conceptual cost estimation of bridge projects.
19

Self-Reacting Point Absorber Wave Energy Converters

Beatty, Scott J. 31 August 2015 (has links)
A comprehensive set of experimental and numerical comparisons of the performance of two self-reacting point absorber wave energy converter (WEC) designs is undertaken in typical operating conditions. The designs are either currently, or have recently been, under development for commercialization. The experiments consist of a series of 1:25 scale model tests to quantify hydrodynamic parameters, motion dynamics, and power conversion. Each WEC is given a uniquely optimized power take off damping level. For hydrodynamic parameter identification, an optimization based method to simultaneously extract Morison drag and Coulomb friction coefficients from decay tests of under-damped, floating bodies is developed. The physical model features a re-configurable reacting body shape, a feedback controlled power take-off, a heave motion constraint system, and a mooring apparatus. A theoretical upper bound on power conversion for single body WECs, called Budal's upper bound, is extended to two body WECs. The numerical analyses are done in three phases. In the first phase, the WECs are constrained to heave motion and subjected to monochromatic waves. Quantitative comparisons are made of the WEC designs in terms of heave motion dynamics and power conversion with reference to theoretical upper bounds. Design implications of a reactive power take-off control scheme and relative motion constraints on the wave energy converters are investigated using an experimentally validated, frequency domain, numerical dynamics model. In the second phase, the WECs are constrained to heave motion and subjected to panchromatic waves. A time domain numerical model, validated by the experimental results, is used to compare the WECs in terms of power matrices, capture width matrices, and mean annual energy production. Results indicate that the second WEC design can convert 30% more energy, on average, than the first design given the conditions at a representative location near the West coast of Vancouver Island, British Columbia, Canada. In the last phase, the WECs are held with three legged, horizontal, moorings and subjected to monochromatic waves. Numerical simulations using panelized body geometries for calculations of Froude-Krylov, Morison drag, and hydrostatic loads are developed in ProteusDS. The simulation results---mechanical power, mooring forces, and dynamic motions---are compared to model test results. The moored WEC designs exhibit power conversion consistent with heave motion constrained results in some wave conditions. However, large pitch and roll motions severely degrade the power conversion of each WEC at wave frequencies equal to twice the pitch natural frequency. Using simulations, vertical stabilizing strakes, attached to the reacting bodies of the WECs are shown to increase the average power conversion up to 190% compared to the average power conversion of the WECs without strakes. / Graduate / scottb@uvic.ca
20

Kvalitetssäkring vid en monteringslina : ett projekt på Swepart i Liatorp / Securing quality at an assembly line : a project at Swepart in Liatorp

Kallenberg, Hampus, Lohman, André January 2015 (has links)
För att Swepart Transmission AB ska fortsätta att hålla en hög standard på produkter som levereras till kunder, ska monteringslinan för Power Take-Off säkras. Budgeten som är avsatt till att kvalitetssäkra monteringslinan är 500 000 kr. Pick-to-Light och Pick-to-Voice är system som kan användas för att kvalitetssäkra monteringen av Power Take-Off. Systemen jämfördes med systemet med monteringskort som används i nuläget. Det mest lämpliga att införa har visat sig vara Pick-to-Light. I samband med införandet av detta system måste utredningar göras för vilka komponenter som behöver sensorer och vilka som kan säkras på andra sätt. Detta arbete innefattar också att utreda placeringen av komponenter som är optimalt för monteringen.

Page generated in 0.0248 seconds