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  • 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.
721

The sensitivity analysis of the quantitative multiple attribute decision making methods / Kiekybinių daugiatikslių sprendimo priėmimo metodų jautrumo analizė

Simanavičienė, Rūta 27 February 2012 (has links)
The problems, associated with sensitivity of quantitative multiattribute decision-making methods to the initial data and the reliability of the decision obtained by using these methods, are considered in the presented dissertaition. The methods discussed are applied to solving decision-making problems, consisting in the selection of one alternative out of the available several options, when a decision-making person seeks to achieve a number of aims, rather than a single aim, and the alternatives are evaluated based on a set of attribute, which may be conflicting. The research object is sensitivity of the popular quantitative multiattribute decision-making methods: TOPSIS, SAW and COPRAS to the initial data errors. The initial data inaccuracy may be caused by the errors made by a person, entering the data. The estimates of the alternatives may have some errors, which are not taken into account, when the considered methods are used with these data. The analysis of the related works has shown that there are methods for evaluating sensitivity with respect to one attribute, based on varying the significance values, such as the method of the most critical criterion (Triantaphyllou 2000) and to many attributes - Tornado diagram. However, these methods do not show either the errors of solution results or the reliability level of the result obtained. The main aim of the dissertation is the evaluation of the stochastic nature of multiattribute decision-making methods, based on... [to full text] / Disertacijoje nagrinėjamas kiekybinių daugiatikslių sprendimo priėmimo metodų jautrumas ir juos taikant gautų sprendimų patikimumas. Daugiatiksliai sprendimo priėmimo metodai taikomi sprendimo priėmimo uždaviniuose, renkantis vieną alternatyvą iš keleto galimų, kai sprendimą priimantis asmuo siekia ne vieno, o kelių tikslų, o alternatyvos vertinamos pagal daugelį efektyvumo rodiklių, kurie gali būti tarpusavyje prieštaraujantys (pvz. kainos ir naudos rodikliai). Pagrindinis tyrimo objektas yra metodų TOPSIS, SAW ir COPRAS jautrumas pradinių duomenų netikslumams. Duomenų netikslumai galimi dėl pradinių duomenų reikšmes nustatančio asmens padarytų klaidų. Tokiu atveju, kai taikant minėtus metodus, alternatyvų vertinimui naudojami pradiniais duomenys turintys tam tikras paklaidas, alternatyvų vertinimai gali būti su paklaidomis, kurios, taikant šiuos metodus, nebėra vertinamos. Išanalizavus susijusius darbus, nustatyta, jog yra metodų, skirtų vertinti sprendimo jautrumą vieno rodiklio atžvilgiu, keičiant reikšmingumo reikšmes, tai - kritiškiausio kriterijaus metodas (Triantaphyllou 2000) ir daugelio rodiklių atžvilgiu - Tornado diagrama. Tačiau šie metodai nepateikia nei sprendimo rezultatų paklaidų, nei rezultato patikimumo laipsnio. Pagrindinis disertacijos tikslas – įvertinti daugiatikslių, kiekybiniais matavimais pagrįstų sprendimo priėmimo metodų stochastiką. Sukurtų metodų taikymo sritis – sprendimo paramos sistemų projektavimas, sprendimų patikimumo ir sprendimų priėmimo... [toliau žr. visą tekstą]
722

Analysis of Flash Flood Routing by Means of 1D - Hydraulic Modelling

Tesfay Abraha, Zerisenay 23 October 2013 (has links) (PDF)
This study was conducted at the mountainous catchment part of Batinah Region of the Sultanate of Oman called Al-Awabi watershed which is about 260km2 in area with about 40 Km long Wadi main channel. The study paper presents a proposed modeling approach and possible scenario analysis which uses 1D - hydraulic modeling for flood routing analysis; and the main tasks of this study work are (1) Model setup for Al-Awabi watershed area, (2) Sensitivity Analysis, and (3) Scenario Analysis on impacts of rainfall characteristics and transmission losses. The model was set for the lower 24 Km long of Al-Awabi main channel (Figure 13). Channel cross-sections were the main input to the 1D-Hydraulic Model used for the analysis of flash flood routing of the Al-Awabi watershed. As field measurements of the Wadi channel cross-sections are labor intensive and expensive activities, availability of measured channel cross-sections is barely found in this study area region of Batinah, Oman; thereby making it difficult to simulate the flood water level and discharge using MIKE 11 HD. Hence, a methodology for extracting the channel cross-sections from ASTER DEM (27mX27m) and Google Earth map were used in this study area. The performance of the model setup was assessed so as to simulate the flash flood routing analysis at different cross-sections of the modeled reach. And from this study, although there were major gap and problems in data as well as in the prevailing topography, slope and other Hydro Dynamic parameters, it was concluded that the 1D-Hydraulic Modelling utilized for flood routing analysis work can be applied for the Al-Awabi watershed. And from the simulated model results, it was observed that the model was sensitive to the type of Boundary Condition chosen and taken, channel cross sections and its roughness coefficient utilized throughout the model reach.
723

On the Dynamics and Statics of Power System Operation : Optimal Utilization of FACTS Devicesand Management of Wind Power Uncertainty

Nasri, Amin January 2014 (has links)
Nowadays, power systems are dealing with some new challenges raisedby the major changes that have been taken place since 80’s, e.g., deregu-lation in electricity markets, significant increase of electricity demands andmore recently large-scale integration of renewable energy resources such aswind power. Therefore, system operators must make some adjustments toaccommodate these changes into the future of power systems.One of the main challenges is maintaining the system stability since theextra stress caused by the above changes reduces the stability margin, andmay lead to rise of many undesirable phenomena. The other important chal-lenge is to cope with uncertainty and variability of renewable energy sourceswhich make power systems to become more stochastic in nature, and lesscontrollable.Flexible AC Transmission Systems (FACTS) have emerged as a solutionto help power systems with these new challenges. This thesis aims to ap-propriately utilize such devices in order to increase the transmission capacityand flexibility, improve the dynamic behavior of power systems and integratemore renewable energy into the system. To this end, the most appropriatelocations and settings of these controllable devices need to be determined.This thesis mainly looks at (i) rotor angle stability, i.e., small signal andtransient stability (ii) system operation under wind uncertainty. In the firstpart of this thesis, trajectory sensitivity analysis is used to determine themost suitable placement of FACTS devices for improving rotor angle sta-bility, while in the second part, optimal settings of such devices are foundto maximize the level of wind power integration. As a general conclusion,it was demonstrated that FACTS devices, installed in proper locations andtuned appropriately, are effective means to enhance the system stability andto handle wind uncertainty.The last objective of this thesis work is to propose an efficient solutionapproach based on Benders’ decomposition to solve a network-constrained acunit commitment problem in a wind-integrated power system. The numericalresults show validity, accuracy and efficiency of the proposed approach. / <p>The Doctoral Degrees issued upon completion of the programme are issued by Comillas Pontifical University, Delft University of Technology and KTH Royal Institute of Technology. The invested degrees are official in Spain, the Netherlands and Sweden, respectively.QC 20141028</p>
724

Įmonės pelno-išlaidų-veiklos apimties vertinimas / The cost-volume-profit evaluation of the company

Marčiulionytė, Asta 26 June 2014 (has links)
Pelningumo siekimas yra pagrindinis verslo įmonės tikslas, dažnai lemiantis vadovų pasirinkimą sprendžiant problemas susijusias su pardavimo kainomis, įvairiomis išlaidomis. Pelno-išlaidų-veiklos apimties vertinimas teikia apibendrinantį planavimo proceso vaizdą ir išlaidų kitimo supratimą, todėl gauta informacija yra nepakeičiama, siekiant užtikrinti racionalų įmonės valdymą. Šio darbo tikslas – išanalizavus pelno-išlaidų-veiklos apimties metodologiją, atlikti įmonės pelno-išlaidų-veiklos apimties vertinimą ir sudaryti modelį, leidžiantį efektyviai planuoti ir analizuoti įmonės kaštų, veiklos apimties ir pelno ryšį. Taigi, šio darbo objektas-įmonės pelningumas, jo priklausomybė nuo įmonės pajamų, kaštų ir veiklos apimties. Siekiant įgyvendinti darbo tikslą, keliami tokie uždaviniai: išanalizuoti pelno-išlaidų-veiklos apimties vertinimo metodologiją, suformuoti prielaidas pelno-išlaidų-veiklos apimties vertinimo modeliavimui, atlikti įmonės pelno-išlaidų-veiklos apimties vertinimą, bei sudaryti pelno-išlaidų-veiklos apimties vertinimo modelį. Darbą sudaro trys pagrindinės dalys: metodologinė, analitinė ir rezultatų. Pirmojoje darbo dalyje nagrinėjami pelno-išlaidų-veiklos apimties vertinimo metodologijos aspektai-pateikiamos analizės prielaidos, vertinimo reikšmė ir galimybės. Antrasis darbo skyrius apima prielaidų pelno-išlaidų-veiklos apimties vertinimo modeliavimui analizę: tiriami ir lyginami pelno-išlaidų-veiklos apimties vertinimo modeliavimo metodai, bei pateikiama... [toliau žr. visą tekstą] / The main purpose of business enterprise is striving for profitability and this purpose usually decides the head‘s of enterprise choice when he tackles the problems about prices of sales and different expenses. Cost-volume-profit evaluation gives resumptive view about planning process and understanding of costs range so given information is irreplaceable because of trying to ensure rational management. The purpose of this work is to do cost-volume-profit evaluation and make a model according the analysis of cost-volume-profit methodology. This model will let to plan and analyse enterprise‘s cost, activity‘s size and profit‘s relation in effective way. So the object of this work is the profitability of an enterprise, its dependence from enterprises revenue, cost and activity‘s volume. In purpose to realize work‘s aim there are these objectives: to analyse cost-volume-profit evaluation methodology, to structure presumptions for cost-volume-profit evaluation modeling, to do enterprises cost-volume-profit evaluation and to make cost-volume-profit evaluation model. Three main parts makes this work: methodological, analytical, results. In the first part of this work there is an analyses of cost-volume-profit evaluation methodology‘s aspects, there are analysis presumptions, evaluations mean and possibilities. The second part includes presumptions analysis to cost-volume-profit evaluation modeling: here are researched and compared cost-volume-profit evaluation modeling methods and is... [to full text]
725

A study of atom and radical kinetics

Hanning-Lee, Mark Adrian January 1990 (has links)
This thesis describes the measurement of rate constants for gas phase reactions as a function of temperature (285 ≤ T/K ≤ 850) and pressure (48 ≤ P/Torr ≤ 700). One or both reactants was monitored directly in real time, using time–resolved resonance fluorescence (for atoms) and u.v. absorption (for radicals). Reactants were produced by exciplex laser flash photolysis. The technique was used to measure rate constants to high precision for the following reactions under the stated conditions: • H+O2+He->HO2+He and H+O2−→OH+O, for 800 ≤ T/K ≤ 850 and 100 ≤ P/Torr ≤ 259. A time–resolved study was performed at conditions close to criticality in the H2–O2 system. The competition between the two reactions affected the behaviour of the system after photolysis, and the rate constants were inferred from this behaviour. • H+C2H4+He<-->C2H5+He (T = 800 K, 97 ≤ P/Torr ≤ 600). The reactions were well into the fall–off region at all conditions studied. At 800 K, the system was studied under equilibrating conditions. The study provided values of the forward and reverse rate constants at high temperatures and enabled a test of a new theory of reversible unimolecular reactions. The controversial standard enthalpy of formation of ethyl, DH0f,298 (C2H5), was determined to be 120.2±0.8 kJ mol−1. Master Equation calculations showed that reversible and irreversible treatments of an equilibrating system should yield the same value for both thermal rate constants. • H+C3H5+He->C3H6+He (T = 291 K, 98 ≤ P/Torr ≤ 600) and O+C3H5 −→ products (286 ≤ T/K ≤ 500, 48 ≤ P/Torr ≤ 348). Both reactions were pressure–independent, and the latter was also independent of temperature with a value of (2.0±0.2) ×10−10 cm3 molecule−1 s−1. • H+C2H2+He<-->C2H3+He (298 ≤ T/K ≤ 845, 50 ≤ P/Torr ≤ 600). At 845 K, both reactions were in the fall–off region; rate constants were used to determine the standard enthalpy of formation of vinyl, ¢H0f,298 (C2H3), as 293±7 kJ mol−1. The value of this quantity has until recently been very controversial. • H+CH4 <--> CH3+H2. The standard enthalpy of formation of methyl, DH0 f,298 (CH3), was determined by re–analysing existing kinetic data at T = 825 K and 875 K. A value of 144.7±1.1 kJ mol−1 was determined. Preliminary models were examined to describe the loss of reactants from the observation region by diffusion and pump–out. Such models, including diffusion and drift, should prove useful in describing the loss of reactive species in many slow–flow systems, enabling more accurate rate constants to be determined.
726

A Methodology For Determining The Cluster Of A New Project

Yigit, Aybeniz 01 June 2005 (has links) (PDF)
By definition, all projects are unique / however R&amp / D projects have specific characteristics that make them harder to manage. The project management methodology applied to R&amp / D projects may show differences due to the categorization of them. But if there exists a categorization of projects, one can analyze the properties of the project classes and then manage similar projects similarly. In this study, the R&amp / D projects of a main military electronics company of Turkey, are analyzed. Tun&ccedil / (2004) has developed a methodology for clustering the projects of this electronics company. Continuing from his studies, a methodology for determining the class of a new project of this electronics company is developed. For defining the projects in a project space, a Project Identification Card (PIC) is developed. The measurement scale of the PIC is constructed by using the absolutemeasurement Analytic Hierarchy Process. A clustering Tabu Search algorithm is generated for using in the sensitivity analyses of the clusters to projects. And a methodology for determining the cluster of a new project is developed.
727

Quadratic power system modeling and simulation with application to voltage recovery and optimal allocation of VAr support

Stefopoulos, Georgios Konstantinos 02 July 2009 (has links)
The main objectives of this research are (a) to develop advanced simulation methods for voltage-recovery phenomena using improved, realistic system models and accurate solution techniques and (b) to develop methods for the mitigation of problems related to slow voltage recovery. Therefore, this work concentrates on the areas of voltage-recovery analysis in electric power systems, dynamic load modeling with emphasis on induction-motor models, dynamic simulation with emphasis on the numerical integration methods, and optimal allocation and operation of static and dynamic VAr resources. In the first part of this work, a general framework for power-system analysis is presented the main characteristics of which are (a) the utilization of full three-phase models and (b) the use of a "quadratized" mathematical formulation, which models the system under study as a set of mathematical equations of order no more than two. The modeling approach is essentially the same for steady-state, quasi-steady-state, and dynamic analysis. Furthermore, a new approach for time-domain transient simulation of electric power systems and dynamical systems, in general, is introduced in this research. The new methodology has been named quadratic integration method. The method is based on a numerical integration scheme that assumes that the system states vary quadraticaly within an integration time step. Accurate modeling and simulation of voltage-recovery phenomena allows the development of mitigation methodologies via the optimal allocation and operation of static and dynamic VAr resources over the planning horizon. This problem is solved with successive dynamic programming techniques with the following two innovations: (a) the states at each stage (candidate solutions) are obtained with static and dynamic (trajectory) sensitivity analysis and (b) each candidate solution is evaluated by considering the optimal operation of installed static and dynamic VAr sources utilizing concepts from the theory of applied optimal control and trajectory optimization.
728

Identification of Damping Contribution from Power System Controllers

Banejad, Mahdi January 2004 (has links)
With the growth of power system interconnections, the economic drivers encourage the electric companies to load the transmission lines near their limits, therefore it is critical to know those limits well. One important limiting issue is the damping of inter-area oscillation (IAO) between groups of synchronous machines. In this Ph.D. thesis, the contribution of power system components such as load and static var compensators (SVC) that affect the IAO of the power system, are analysed. The original contributions of this thesis are as follows: 1-Identification of eigenvalues and mode shapes of the IAO: In the first contribution of this thesis, the eigenvalues of the IAO are identified using a correlation based method. Then, the mode shape at each identified resonant frequency is determined to show how the synchronous generators swing against each other at the specific resonant frequencies. 2-Load modelling and load contribution to damping: The first part of this contribution lies in identification of the load model using cross-correlation and autocorrelation functions . The second aspect is the quantification of the load contribution to damping and sensitivity of system eigenvalues with respect to the load. 3- SVC contribution to damping: In this contribution the criteria for SVC controller redesign based on complete testing is developed. Then the effect of the SVC reactive power on the measured power is investigated. All of the contributions of this thesis are validated by simulation on test systems. In addition, there are some specific application of the developed methods to real data to find a.) the mode shape of the Australian electricity network, b.) the contribution of the Brisbane feeder load to damping and c.) the effect of the SVC reactive power of the Blackwall substations on the active power supplying Brisbane.
729

Advances in power system small signal stability analysis considering load modeling and emerging generation resource

Yateendra Mishra Unknown Date (has links)
With the increasing complexity of the power system, electromechanical oscillations are becoming one of the major problem. Several blackouts have been reported in the past due to insufficient damping of the oscillatory modes. The starting point to avoid catastrophic behaviors would be to simulate actual power system and study the response of the system under various outages leading to blackouts. Recently, it has been identified that appropriate modeling of the load is necessary to match the actual system behavior with the computer simulated response. This research throws some insight into the detailed load modeling and its impact on the system small signal stability. In particular, Composite load model is proposed and its effect on the system small signal stability is investigated. Modeling all the loads in a large power system would be a cumbersome job and hence the method for identifying the most sensitive load location is also proposed in the thesis. The effect of load modeling on the eigenvalue movement is also investigated. The low damped electromechanical modes are always undesirable in the large inter-connected power systems as they might get excited under some event leading to growing oscillations. Proper damping of these modes is essential for effective and reliable system operation. Power system stabilizers have been proved to be an effective way of damping these electromechanical modes. The optimal number and location of PSS to effectively damp the modes via improved Differential algorithm is proposed. Moreover, the effect of TCSC, series compensated FACTs device, on enhancing the system damping is investigated. A fixed order model matching technique is presented to design a damping controller for the TCSC. With the increasing global pressure for reducing carbon emissions, there is a great amount of interest in the renewable sources of energy, particularly Wind Energy Conversion Systems. Of all the present methods of wind generation systems, Doubly Fed Induction Generation (DFIG) based wind farms are gaining popularity. The comparison of various methods of wind generation techniques is presented. In particular, the impact of DFIG based wind farms on the system small signal stability is investigated in this work. Co-ordinated tuning of the controllers is performed using Bacterial Foraging Technique, which is another member of Evolutionary algorithms. Damping controller for the DFIG system is proposed to enhance the damping of the electromechanical modes. Results have proved the effectiveness of the control methodology. The contributions made in this thesis could be utilized to promote the further development of the damping controllers for large power systems.
730

Advances in power system small signal stability analysis considering load modeling and emerging generation resource

Yateendra Mishra Unknown Date (has links)
With the increasing complexity of the power system, electromechanical oscillations are becoming one of the major problem. Several blackouts have been reported in the past due to insufficient damping of the oscillatory modes. The starting point to avoid catastrophic behaviors would be to simulate actual power system and study the response of the system under various outages leading to blackouts. Recently, it has been identified that appropriate modeling of the load is necessary to match the actual system behavior with the computer simulated response. This research throws some insight into the detailed load modeling and its impact on the system small signal stability. In particular, Composite load model is proposed and its effect on the system small signal stability is investigated. Modeling all the loads in a large power system would be a cumbersome job and hence the method for identifying the most sensitive load location is also proposed in the thesis. The effect of load modeling on the eigenvalue movement is also investigated. The low damped electromechanical modes are always undesirable in the large inter-connected power systems as they might get excited under some event leading to growing oscillations. Proper damping of these modes is essential for effective and reliable system operation. Power system stabilizers have been proved to be an effective way of damping these electromechanical modes. The optimal number and location of PSS to effectively damp the modes via improved Differential algorithm is proposed. Moreover, the effect of TCSC, series compensated FACTs device, on enhancing the system damping is investigated. A fixed order model matching technique is presented to design a damping controller for the TCSC. With the increasing global pressure for reducing carbon emissions, there is a great amount of interest in the renewable sources of energy, particularly Wind Energy Conversion Systems. Of all the present methods of wind generation systems, Doubly Fed Induction Generation (DFIG) based wind farms are gaining popularity. The comparison of various methods of wind generation techniques is presented. In particular, the impact of DFIG based wind farms on the system small signal stability is investigated in this work. Co-ordinated tuning of the controllers is performed using Bacterial Foraging Technique, which is another member of Evolutionary algorithms. Damping controller for the DFIG system is proposed to enhance the damping of the electromechanical modes. Results have proved the effectiveness of the control methodology. The contributions made in this thesis could be utilized to promote the further development of the damping controllers for large power systems.

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