Dissertations / Theses on the topic 'Steady-state analysi'
To see the other types of publications on this topic, follow the link: Steady-state analysi.
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 'Steady-state analysi.'
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
MEMON, ZAIN ANWER. "Novel Modeling and Simulation Concepts for Power Distribution Networks." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2922916.
Full text
2
Nguyen, Henry Q. "Steady state analysis of resonant converters." Honors in the Major Thesis, University of Central Florida, 1993. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/118.
Full textAbstract:
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering
Electrical Engineering
3
Pan, Wen Hsiung. "Steady State Analysis of Tropospheric Chemistry." PDXScholar, 1991. https://pdxscholar.library.pdx.edu/open_access_etds/1262.
Full textAbstract:
Hydroxyl radical HO plays a central role in controlling chemical processes in the troposphere. Current mechanisms are believed to accurately describe its formation, destruction and interaction with other atmospheric trace gases in clean air. Hydroperoxyl radical H0₂ is Iinked to HO in several chain processes and serves among other roles as a reservoir for HO. The relative concentration (H0₂/HO) in clean air is believed to be the order of 10². We here examine the conditions under which steady-state kinetics apply to HO₁ chemistry and derive simple relationships which can be used to predict HO and H0₂ concentration from measurable concentrations of the more stable trace gases. The equations assume a simple form for conditions where the ambient nitrogen oxide concentration is less than 1 ppb. These equations allow closed-form evaluation of the sensitivity of [HO] and [H0₂] to changes in the concentrations of the controlling species and allow assignment of uncertainty limits to the predictions of current tropospheric chemical models. Although most current efforts to test fast tropospheric photochemistry center upon measurements of ambient [HO], our equations indicate that tropospheric [H0₂] determinations may provide a more direct and accurate initial test of our knowledge of HO₁ chemistry in the unpolluted lower atmosphere. Overall the goal of this study is to benefit the experimenter by providing the information of insight and simple but reliable equations and to understand the conditions under which these measurements should be made and how best to interpret their results.
4
Fung, Tat-ching. "Steady state solutions of nonlinear dynamic systems /." [Hong Kong] : University of Hong Kong, 1989. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12760055.
Full text
5
馮達淸 and Tat-ching Fung. "Steady state solutions of nonlinear dynamic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31231809.
Full text
6
Tucher, Christopher A. "Steady-state oscillations of linear and nonlinear systems /." Online version of thesis, 1992. http://hdl.handle.net/1850/10990.
Full text
7
Yassin, Menna. "Steady State Hydroplaning Risk Analysis and Evaluation of Unsteady State Effects." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7990.
Full textAbstract:
Hydroplaning is a major concern on high speed roadways during heavy rainfall events. Hydroplaning tools are widely used by designers to reduce their roadway’s hydroplaning potential, therefore reducing the possibilities of severe crashes. This dissertation presents two methodologies for improving the prediction of hydroplaning potential.
The first phase focused on improving an existing widely used software called PAVDRN. Using multiple datasets from the Florida Department of Transportation, the author filtered the data using specific criteria to leave only truly dynamic hydroplaning crashes. The author then evaluated PAVDRN’s prediction capabilities and assessed its reliability in predicting a hydroplaning crash. Using past accident statistics, the author accounted for extraneous factors that are difficult to capture, such as driver behavior, and obtained probability factors for a more realistic estimate of hydroplaning risk on roadways. The second phase focused on improving the modeling technique used in hydroplaning prediction tools. Currently when assessing a roadway’s hydroplaning potential, the roadside drainage is not considered in the analysis. The author modeled a combined pavement-drainage system using a 1D/2D method to better capture the effects of roadside drainage, especially in the events of flooding. The methodology used in modeling successfully captures the backwater effects that are caused under critical flooding conditions. Lastly the author created a new tool (MY-PAVDTCH) to provide design engineers with updated waterfilm thickness values under roadside drainage flooded conditions.
8
McNulty, Craig R. "The complex reality of VO2 kinetics to steady state: Reassessment of the models used to quantify and interpret VO2 kinetics, steady state, and time to steady state." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/108025/2/Craig_McNulty_Thesis.pdf.
Full textAbstract:
This thesis developed new methods of modelling oxygen uptake in exercising humans during cycling exercise sessions to steady-state. The results will contribute to the redefinition of conventional methods of data acquisition, processing, and modelling across exercise physiology, sports science, and respiratory disease research and application. The thesis identified misconceptions within current methods of data handling, and proposed innovative methods for improved data modelling.
9
Lee, Chong Kyong 1973. "Continuation methods for steady state analysis of oscillators." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99777.
Full textAbstract:
Oscillator circuits are an integral component of wireless communications systems and are increasingly in demand. As such systems gain widespread use, price becomes a very important factor in the design process, and the design cycle must be optimized. This puts an increasing emphasis on the proficiency of oscillator design automation tools. At the same time, as the performance requirements of such systems are becoming more stringent, the required simulation complexity is also increasing. More specifically, high frequency selectivity and low phase noise require very high quality factor oscillators, which in turn negatively affect the convergence performance of current simulation techniques. This thesis proposes a new continuation method for improving the convergence of oscillator simulations and compares this method to some of the methods reported in the literature. The proposed approach does not require a very good initial guess in order to converge to a final solution.
10
Cresswell, Charles. "Steady state load models for power system analysis." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3846.
Full textAbstract:
The last full review of load models used for power system studies occurred in the 1980s. Since then, new types of loads have been introduced and system load mix has changed considerably. The examples of newly introduced loads include drive-controlled motors, low energy consumption light sources and other modern power electronic loads. Their numbers have been steadily increasing in recent years, a trend which is expected to escalate. Accordingly, the majority of load models used in traditional power system studies are becoming outdated, as they are unable to accurately represent power demand characteristics of existing and future loads. Therefore, in order to accurately predict both active and non-active power demand characteristics of aggregated modern power system loads in different load sectors (e.g. residential, commercial or industrial), existing load models should be updated and new models developed. This thesis aims to fill this gap by developing individual, generic and aggregated steady state models of the most common loads in use today, as well as of those expected to show significant growth in the future. The component-based approach is adopted for load modelling, where individual load models are obtained in detailed simulations of physical devices. Whenever possible, the developed individual load models are validated by measurements. These detailed individual load models are then simplified and expressed as equivalent circuit and analytical models, which allowed the establishment of generic load models that can be easily aggregated. It should be noted that since all non-active power characteristics are correctly represented, the developed aggregated load models allow for a full harmonic analysis, which is not the case with the standard steady state load models. Therefore, the proposed load models form an extensive library of comprehensive load models that are suitable for use in multiple areas of power system research. Based on the results of research related to typical domestic/residential sector load mix, the newly developed load models are aggregated and then applied to a typical UK/Scotland distribution network. Considerable differences are seen between network characteristics of newly proposed and previously developed models. The voltage distortion of a typical distribution system bus is investigated, and it is shown that distortion of the system voltage is likely to increase significantly in the future. The results of the presented research also suggest that neglecting the harmonic characteristics from the set of general load attributes may introduce errors in standard load flow studies.
11
Skånøy, Thomas. "Steady-state and dynamic converter modeling in system analysis." Thesis, Norwegian University of Science and Technology, Department of Electrical Power Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9545.
Full textAbstract:
This master thesis was executed at the Department of Electrical Power Engineering at the Norwegian University of Science and Technology (NTNU). The thesis was initiated to establish and evaluate an alternative model representation of the facility at Ormen Lange. Traditionally, a PQ-model has been used to represent Ormen Lange. This thesis, however, has implemented three two-terminal dc line models (converter models) to represent the facility. The first part of the thesis starts with an overall introduction to the basic principles of configuration, operation and control of HVDC systems. The objective of this part is to provide an overview of the HVDC technology which is treated in detail later in the thesis. The software tool Power System Simulator for Engineering (PSS/E) was used for both power flow and dynamic simulations performed in this thesis. The second part of the thesis describes the power flow establishment, and constitutes the basis for both power flow and dynamic simulations. The main focus in this part is the modeling of the two-terminal dc line model which is implemented at Nyhamna. Data for the two-terminal dc line model is presented on three consecutive data records. Since these data enables not only power flow analysis but also establishes the initial steady-state for the dynamic analysis, a detailed description is presented in this section. The latter data is based on technical information provided by ABB and default values in PSS/E. The third part of the thesis presents the power flow simulations. The objective of this part is to gain knowledge about the performance of the two-terminal dc line model implemented at Ormen Lange. This knowledge facilitates the understanding of the following dynamic simulations. Two cases were studied to simulate the action of the converter control system when exposed to a depression in rectifier bus voltage. In the first case the rectifier transformer tap settings were adjustable. In the second case the rectifier tap settings were locked to its initial value. The purpose of locking the tap setting was to represent a transient situation where the tap changer action is too slow and hence not considered. The result showed that with adjustable rectifier tap settings, the depression in rectifier bus voltage is handled by reducing the rectifier transformer tap position and firing delay angle. This increased the voltage on the valve side of the rectifier transformer and enabled the rectifier to maintain dc current control. Consequently, the scheduled dc values were unaffected by the depression in rectifier bus voltage. However, with the rectifier tap setting locked, the transformer did not boost the voltage on the valve side of the rectifier transformer. This caused the control logic to reduce the rectifier firing delay angle to its minimum, and the inverter assumed control of the dc current. With the inverter in control of the current, the scheduled dc current was reduced by a fraction equal to the current margin along with the remainder dc values. Hence, the presence of an adequate rectifier transformer setting is essential for the two-terminal dc line model to maintain scheduled dc values during voltage depression. All simulations showed that a voltage depression at the rectifier bus leads to a reduction in rectifier reactive power consumption. This is due to the action from the control logic which reduced the rectifier firing delay angle to counteract the voltage depression. The greatest reduction in rectifier reactive consumption was experienced when the rectifier firing delay angle was reduced to its minimum value. Hence, in situations with depressed bus voltage, the latter operation of the converter control logic causes the two-terminal dc line model to exhibit less stress to the ac system than the PQ-model. The fourth part of this thesis contains a detailed description of the dynamic modeling of the two-terminal dc line model (CDC4T). Many of the chosen parameters are based on an example in [15], and do not necessary represent realistic values. The final part of this thesis presents the dynamic simulations. The objective of this part is to analyze the control actions of the CDC4T model under normal regulation and during temporary overriding the normal regulation. This was performed by introducing ac system faults which depressed the rectifier bus voltage to a varying degree. Further, this part analyzed the consequence of using the dynamic model CDC4T to represent Ormen Lange instead of a PQ-model. The purpose was to determine whether the response from the ac system differs when using the CDC4T model instead of a PQ-model. It is important to emphasize that this part does not evaluate stability issues associated with the implementation of CDC4T. The results from the dynamic simulations showed that CDC4T exhibited an instantaneous response to changes in rectifier ac voltage. This is because CDC4T is a pseudo steady-state dynamic model which omits the L/R dynamic of the dc system and high frequency firing angle controller dynamics. Further, the results revealed an important characteristic of the CDC4T model. After fault clearance, the rectifier bus exhibited small voltage fluctuations. The rectifiers compensated these fluctuations by adjusting their firing delay angles correspondingly. Consequently, the latter resulted in fluctuations in reactive power consumption. This means that the ac system perceives the CDC4T model as a varying reactive load following fault clearance. Comparing the ac system response when using the CDC4T model and when using the PQ-model, the results showed that the main difference was CDC4Ts generation of reactive power fluctuations. These fluctuations were experienced in the transmission line going into Nyhamna and Viklandet, and were substantial compared to the initial loading of the transmission lines. Two arguments were used to substantiate why the response from the CDC4T model only differs from the PQ-model in terms of reactive power fluctuations: I. The calculated value of the short circuit ratio at Nyhamna indicated a strong interconnected ac/dc system. II. The dynamic behavior of the pseudo-steady state model, CDC4T, is limited. Both the L/R dynamic of the dc line, smoothing reactors and high frequency controller dynamics are omitted. In further studies where converter modeling at Ormen Lange is considered, a more complex dynamic dc model should be utilized to represent the converters. This model should include L/R dynamic of the dc system and high-speed controller dynamics, and will thus influence the ac system to a greater extent than CDC4T. Further, the model establishment should focus on achieving a sufficiently realistic load representation of Ormen Lange. In this manner, the converters influence on system stability can be evaluated.
12
Hill, Nathan R. "Analysis of non-steady state physiological and pathological processes." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:c96c88a6-5dd4-43ce-989b-ac524d2654ea.
Full textAbstract:
The analysis of non steady state physiological and pathological processes concerns the abstraction, extraction, formalisation and analysis of information from physiological systems that is obscured, hidden or unable to be assessed using traditional methods. Time Series Analysis (TSA) techniques were developed and built into a software program, Easy TSA, with the aim of examining the oscillations of hormonal concentrations in respect to their temporal aspects – periodicity, phase, pulsatility. The Easy TSA program was validated using constructed data sets and used in a clinical study to examine the relationship between insulin and obesity in people without diabetes. In this study fifty-six non-diabetic subjects (28M, 28F) were examined using data from a number of protocols. Fourier Transform and Autocorrelation techniques determined that there was a critical effect of the level of BMI on the frequency, amplitude and regularity of insulin oscillations. Second, information systems formed the background to the development of an algorithm to examine glycaemic variability and a new methodology termed the Glycaemic Risk in Diabetes Equation (GRADE) was developed. The aim was to report an integrated glycaemic risk score from glucose profiles that would complement summary measures of glycaemia, such as the HbA1c. GRADE was applied retrospectively to blood glucose data sets to determine if it was clinically relevant. Subjects with type 1 and type 2 diabetes had higher GRADE scores than the non-diabetic population and the contribution of hypo- and hyperglycaemic episodes to risk was demonstrated. A prospective study was then designed with the aim to apply GRADE in a clinical context and to measure the statistical reproducibility of using GRADE. Fifty-three (Male 26, Female 27) subjects measured their blood glucose 4 times daily for twenty-one days. The results were that lower HbA1c’s correlated with an increased risk of hypoglycaemia and higher HbA1c’s correlated with an increased risk of hyperglycaemia. Some subjects had HbA1c of 7.0 but had median GRADE values ranging from 2.2 to 10.5. The GRADE score summarized diverse glycaemic profiles into a single assessment of risk. Well-controlled glucose profiles yielded GRADE scores <= 5 and higher GRADE scores represented increased clinical risk from hypo or hyperglycaemia. Third, an information system was developed to analyse data-rich multi-variable retinal images using the concept of assessment of change rather than specific lesion recognition. A fully Automated Retinal Image Differencing (ARID) computer system was developed to highlight change between retinal images over time. ARID was validated using a study and then a retrospective study sought to determine if the use of the ARID software was an aid to the retinal screener. One hundred and sixty images (80 image pairs) were obtained from Gloucestershire Diabetic Eye Screening Programme. Images pairs were graded manually and categorised according to how each type of lesion had progressed, regressed, or not changed between image A and image B. After a 30 day washout period image pairs were graded using ARID and the results compared. The comparison of manual grading to grading using ARID (Table 4.3) demonstrated an increased sensitivity and specificity. The mean sensitivity of ARID (87.9%) was increased significantly in comparison to manually grading sensitivity (84.1%) (p<0.05). The specificity of the automated analysis (87.5%) increased significantly from the specificity (56.3%) achieved by manually grading (p<0.05). The conclusion was that automatic display of an ARID differenced image where sequential photographs are available would allow rapid assessment and appropriate triage. Forth, non-linear dynamic systems analysis methods were utilised to build a system to assess the extent of chaos characteristics within the insulin-glucose feedback domain. Biological systems exist that are deterministic yet are neither predictable nor repeatable. Instead they exhibit chaos, where a small change in the initial conditions produces a wholly different outcome. The glucose regulatory system is a dynamic system that maintains glucose homeostasis through the feedback mechanism of glucose, insulin, and contributory hormones and was ideally suited to chaos analysis. To investigate this system a new algorithm was created to assess the Normalised Area of Attraction (NAA). The NAA was calculated by defining an oval using the 95% CI of glucose & Insulin (the limit cycle) on a phasic plot. Thirty non-diabetic subjects and four subjects with type 2 diabetes were analysed. The NAA indicated a smaller range for glucose and insulin excursions with the non-diabetics subjects (p<0.05). The conclusion was that the evaluation of glucose metabolism in terms of homeostatic integrity and not in term of cut-off values may enable a more realistic approach to the effective treatment and prevention of diabetes and its complications.
13
Ferroni, Paolo Ph D. Massachusetts Institute of Technology. "Steady state thermal hydraulic analysis of hydride fueled BWRs." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41263.
Full textAbstract:
Includes bibliographical references (p. 205-208).Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.
(cont.) Since the results obtained in the main body of the analysis account only for thermal-hydraulic constraints, an estimate of the power reduction due to the application of neutronic constraints is also performed. This investigation, focused only on the "New Core" cases, is coupled with an increase of the thickness of the gap separating adjacent bundles from 2 to 5 mm. Under these more conservative conditions, the power gain percentages are lower, ranging between 24% and 43% (depending on the discharge burnup considered acceptable) for the upper pressure drop limit, and between 17% and 32% for the lower pressure drop limit.
(cont.) The benefits of the latter approach are evident since the space occupied by the bypass channel for cruciform control rod insertion becomes available for new fuel and a higher power can be achieved. The core power is constrained by applying thermal-hydraulic limits that, if exceeded, may induce failure mechanisms. These limits concern Minimum Critical Power Ratio (MCPR), core pressure drop, fuel average and centerline temperature, cladding outer temperature and flow-induced vibrations. To limit thermal-hydraulic instability phenomena, core power and coolant flow are constrained by fixing their ratio to a constant value. In particular, each BWR/5 core has been analyzed twice, each time with a different pressure drop limit: a lower limit corresponding to the pressure drop of the reference core and an upper limit 50% larger. It has been demonstrated that, in absence of neutronic constraints and with the maximum allowed pressure drop fixed at the upper limit, the implementation of the hydride fuel yields power gain percentages, with respect to oxide cores chosen as reference, of the order of 23% when its implementation is performed following the "Backfit" approach and even higher (50-70%) when greater design freedom is allowed in the core design, i.e. in the "New Core" approach. Should the maximum allowed pressure drop be fixed at the lower limit, the power gain percentage of the "Backfit" approach would decrease to 17%, while that of the "New Core" approach would remain unchanged, i.e. 50-70%.
This thesis contributes to the Hydride Fuel Project, a collaborative effort between UC Berkeley and MIT aimed at investigating the potential benefits of hydride fuel use in Light Water Reactors (LWRs). Considerable work has already been accomplished on hydride fueled Pressurized Water Reactor (PWR) cores. This thesis extends the techniques used in the PWR analysis to examine the potential power benefits resulting from the implementation of the hydride fuel in Boiling Water Reactors (BWRs). This work is the first step towards the achievement of a complete understanding of the economic implications that may derive from the use of this new fuel in BWR applications. It is a whole core steady-state analysis aimed at comparing the power performance of hydride fueled BWR cores with those of typical oxide-fueled cores, when only thermal-hydraulic constraints are applied. The integration of these results with those deriving from a transient analysis and separate neutronic and fuel performance studies will provide the data required to build a complete economic model, able to identify geometries offering the lowest cost of electricity and thus to provide a fair basis for comparing the performance of hydride and oxide fuels. Core design is accomplished for two types of reactors: one smaller, a BWR/5, which is representative of existing reactors, and one larger, the ESBWR, which represents the future generation of BWRs. For both, the core design is accomplished in two ways: a "Backfit" approach, in which the ex-bundle core structure is identical to that of the two reference oxide cores, and a "New Core" approach, in which the control rods are inserted into the bundles in the form of control fingers and the gap between adjacent bundles is fixed optimistically at 2 mm.
by Paolo Ferroni.
S.M.
14
Parathiras, Achilleas N. "Steady state of deformation analysis for a clayey sand." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/46057.
Full textAbstract:
The steady state of deformation was analyzed for a clayey sand. The use of lubricated end platens was evaluated and proved to reduce the scatter in steady state data. The effect of different data corrections in a steady state analysis was also evaluated. For this investigation the parabolic area assumption better approximated the deformed specimen shape than the right cylinder assumption. It was concluded that the use of different area corrections greatly influences the slope and position of the steady state line.
Master of Science
15
Haddleton, Steven W. "Steady-state performance of discrete linear time-invariant systems /." Online version of thesis, 1994. http://hdl.handle.net/1850/11795.
Full text
16
Karamullaoglu, Gulsun. "Dynamic And Steady-state Analysis Of Oxidative Dehydrogenation Of Ethane." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606269/index.pdf.
Full textAbstract:
In this research, oxidative dehydrogenation of ethane to ethylene was studied over Cr-O and Cr-V-O mixed oxide catalysts through steady-state and dynamic experiments. The catalysts were prepared by the complexation method. By XRD, presence of Cr2O3 phase in Cr-Oand the small Cr2O3 and V2O4 phases of Cr-V-O were revealed. In H2-TPR, both catalysts showed reduction behaviour. From XPS the likely presence of Cr+6 on fresh Cr-O was found. On Cr-V-O, the possible reduction of V+5 and Cr+6 forms of the fresh sample to V+4, V+3 and Cr+3 states by TPR was discovered through XPS. With an O2/C2H6 feed ratio of 0.17, Cr-O exhibited the highest total conversion value of about 0.20 at 447°
C with an ethylene selectivity of 0.82. Maximum ethylene selectivity with Cr-O was obtained as 0.91 at 250°
C. An ethylene selectivity of 0.93 was reached with the Cr-V-O at 400°
C. In the experiments performed by using CO2 as the mild oxidant, a yield value of 0.15 was achieved at 449°
C on Cr-O catalyst. In dynamic experiments performed over Cr-O, with C2H6 pulses injected into O2-He flow, the possible occurrence of two reaction sites for the formation of CO2 and H2O was detected. By Gaussian fits to H2O curves, the presence of at least three production ways was thought to be probable. Different from Cr-O, no CO2 formation was observed on Cr-V-O during pulsing C2H6 to O2-He flow. In the runs performed by O2 pulses into C2H6-He flow over Cr-V-O, formation of CO rather than C2H4 was favored.
17
Fuerte, Esquivel Claudio Rubén. "Steady state modelling and analysis of flexible AC transmission systems." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/4616/.
Full textAbstract:
As electric utilities move into more competitive generation supply regimes, with limited scope to expand transmission facilities, the optimisation of existing transmission corridors for power transfer becomes of paramount importance. In this scenario, Flexible AC Transmission System (FACTS) technology, which aims at increasing system operation flexibility, appear as an attractive alternative. Many of the ideas upon which the foundations of FACTS rest were conceived some time ago. Nevertheless, FACTS as a single coherent integrated philosophy is a newly developed concept in electrical power systems which has received the backing of the major manufacturers of electrical equipment and utilities around the world. It is looking at ways of capitalising on the new developments taking place in the area of high-voltage and highcurrent power electronics in order to increase the control of the power flows in the high voltage side of the network during both steady state and transient conditions, so as to make the network electronically controllable. In order to examine the applicability and functional specifications of FACTS devices, it is necessary to develop accurate and flexible digital models of these controllers and to upgrade most of the software tools used by planners and operators of electric power systems. The aim of this work is to develop general steady-state models FACTS devices, suitable for the analysis of positive sequence power flows in, large-scale real life electric power systems.Generalised nodal admittance models are developed for the Advance Series Compensator (ASC), Phase Shifter (PS), Static Var Compensator (SVC), Load Tap Changer (LTC) and Unified Power Flow Controller (UPFC). In the case of the ASC, two models are presented, the Variable Series Compensator (VSC) and the Thyristor Controlled Series CapacitorFiring Angle (TCSC-F A). An alternative UPFC model based on the concept of Synchronous Voltage Source (SVS) is also developed. The Interphase Power Controller (IPC) is modelled by combining PSs and VSCs nodal admittance models. The combined solution of the power flow equations pertaining to the FACTS devices models and the power network is described in this thesis. The set of non-linear equations is solved through a Newton-Rapshon technique. In this unified iterative environment, the FACTS device state variables are adjusted automatically together with the nodal network state variables so as to satisfy a specified nodal voltage magnitudes and specified power flows. Guidelines and methods for implementing FACTS devices and their adjustments within the Newton-Rapshon algorithm are described. It is shown that large increments in the adjustments of FACTS devices and nodal network state variables during the backward substitution may dent the algorithm's quadratic convergence. Suitable strategies are given which avoid large changes in these variables and retain the Newton-RapshRapshon method's quadratic convergence. The influence of initial conditions of FACTS devices state variables on the iterative process is investigated. Suitable initialisation guidelines are recommended. Where appropriate, analytical equations are given to assure good initial conditions.
18
Refoufi, L. "Steady state analysis of the chopper controlled static Kramer drive." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239814.
Full text
19
Sukhavasi, Vijay Krishna. "Steady State Testing and Analysis of a Phasor Measurement Unit." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/46328.
Full textAbstract:
Phasor Measurement Units (PMUs) have been instrumental in building a reliable and robust Power System. Recent blackouts have increased the importance of PMUs and PMUs from various manufacturers are being installed in the in large quantities in the North American Grid. The interoperability and accuracy of these PMUs is important to obtain full benefit of the wide area monitoring systems. With the large number of installed PMUs it has become necessary to validate their performance and understand the limitations of each model. A test system was built by NIST in cooperation with NASPI to test for compliance to the existing IEEE C37.118 standard. This thesis presents the development of a Steady State Test System at Virginia Tech based on the NIST Steady State Testing system. The various issues that were faced during the process of development are discussed and the methodology implemented for solving these problems is described. This thesis also presents the additional benefits derived from the results obtained when different PMUs were tested using the Virginia Tech PMU Steady State Test System.Master of Science
20
Han, Peipei. "Decoding Steady-State VisualEvoked Potentials(SSVEPs)- Implementation and Performance Analysis." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-432289.
Full textAbstract:
Steady-state visual evoked potential (SSVEP)-based brain-computer interfaces(BCIs) have been widely investigated. Algorithms from the canonical correlation analysis(CCA) family perform extremely well in detecting stimulus targets by analyzing the relationship of frequency features between electroencephalogram (EEG) signals and stimulus targets. In addition to CCA algorithms, convolutional neural networks(CCNs) also improve the performance of SSVEP-based BCIs by generalizing well on the frequency features of the EEG signals. To find a new method for speeding up an online SSVEP decoding system, we have evaluated three CCA methods which are standard CCA, individual-template CCA(IT-CCA), and Extended CCA, together with the complex spectrum CNN(C-CNN). The results have proved that algorithms requiring individual subject training highly outperform standard CCA.
21
Jordi, Bastien. "Steady-state solvers for stability analysis of vortex dominated flows." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/31875.
Full textAbstract:
To compute stability analysis numerically with high accuracy, it is crucial to carefully choose the base flow around which the governing equations will be linearised. The steady-state solution is mathematically appropriate because it is a genuine solution of the fluid motion equations. In this thesis we introduce an encapsulated formulation of the selective frequency damping (SFD) method. The SFD method is an alternative to Newton's method to obtain unstable equilibria of dynamical systems. In its encapsulated formulation, the SFD method makes use of splitting methods, which means that it can be wrapped around an existing time-stepping code as a 'black box'. This largely simplifies the implementation of a steady-state solver into an already existing unsteady code. However this method has two main limitations: it does not converge for arbitrary control parameters; and when it does, it may take a very long time to reach a steady-state solution. Hence we also present an adaptive algorithm to address these two issues. We show that by evaluating the dominant eigenvalue of a 'partially converged' steady flow, we can select SFD parameters that ensure an optimum convergence of the method. We apply this adaptive method to several classical two-dimensional test cases of computational fluid dynamics and we show that a steady-state solution can be obtained with a very limited (or without any) a priori knowledge of the flow stability properties. Eventually, we study the three-dimensional behaviour of the interaction between two identical co-rotating trailing vortices. We use the SFD method to obtain steady base flows and compute Tri-Global stability analysis. We show that there is a fundamental qualitative difference between the least stable eigenmode observed at Re = 250 and the most unstable eigenmode obtained at Re = 600.
22
Repalle, Jalaja. "ROBUST SHAPE DESIGN TECHNIQUES FOR STEADY-STATE METAL FORMING PROCESSES." Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1158776359.
Full text
23
Camacho, José Roberto. "Steady-state analysis of directly connected synchronous machines and HVdc converters." Thesis, University of Canterbury. Electrical and Electronic Engineering, 1993. http://hdl.handle.net/10092/6015.
Full textAbstract:
In this thesis the results from a conventional ac-dc load flow program for modelling the steady state behaviour of a unit connect salient-pole generator-converter are compared with those obtained from degree by degree dynamic simulation. The Transient Converter Simulation (TCS) program is used to give benchmark results. The unacceptable level of error from the load flow program indicates that the conventional ac-dc formulation is not directly applicable to the unit connected generator-converter.
A salient-pole generator converter model has been developed to reduce the errors, which allows for a voltage behind a varying sub-transient reactance to be used as the commutating voltage. The characteristics obtained from this model are better than for the conventional model but are still significantly different from the TCS results. A dynamic simulation of the operation of the unit connected generator converter is necessary, before steady state results can be obtained.
Unit and Group-Connections are also compared under varying steady state loading conditions and by reducing the number of generators in service in both schemes at nominal frequency.
An accurate algorithm of general applicability, called the Equivalent Inverter, is proposed which used unit-connection characteristics derived from a time domain simulation.
Finally the steady state model for an alternative unit connected generator converter scheme is presented. This is based on the use of dc ripple re-injection, which permits using a single bridge (instead of two) to obtain a twelve-pulse converter operation. The proposed scheme considerably reduces the number of transformers and converter bridges, without increasing the harmonic levels with respect to the double bridge configuration.
24
Huning, Alexander. "A steady state thermal hydraulic analysis method for prismatic gas reactors." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52196.
Full textAbstract:
A new methodology for the accurate and efficient determination of steady state thermal hydraulic parameters for prismatic high temperature gas reactors is developed. Two conceptual reactor designs under investigation by the nuclear industry include the General Atomics GT-MHR and the Department of Energy MHTGR-350. Both reactors use the same hexagonal prismatic block, TRISO fuel compact, and circular coolant channel array design.
Steady state temperature, pressure, and mass flow distributions are determined for the base reference designs and also for a range of values of the important parameters. Core temperature distributions are obtained with reduced computational cost over more highly detailed computational fluid dynamics codes by using efficient, correlations and first-principles-based approaches for the relevant thermal fluid and thermal transport phenomena. Full core 3-D heat conduction calculations are performed at the individual fuel pin and lattice assembly block levels. The fuel compact is treated as a homogeneous medium with heat generation. A simplified 1-D fluid model is developed to predict convective heat removal rates from solid core nodes. Downstream fluid properties are determined by performing a channel energy balance down the axial node length. Channel exit pressures are then compared and inlet mass flows are adjusted until a uniform outlet pressure is reached. Bypass gaps between assembly blocks as well as coolant channels are modeled. Finite volume discretization of energy, and momentum conservation equations are then formed and explicitly integrated in time. Iterations are performed until all local core temperatures stabilize and global convective heat removal matches heat generation.
Several important observations were made based on the steady state analyses for the MHTGR and GT-MHR. Slight temperature variation in the radial direction was observed for uniform radial powers. Bottom-peaked axial power distributions had slightly higher peak temperatures but lower core average temperatures compared to top and center-peaked power distributions. The same trend appeared for large bypass gap sizes cases compared to smaller gap widths. For all cases, peak temperatures were below expected normal operational limits for TRISO fuels. Bypass gap flow for a 3 mm gap width was predicted to be between 10 and 11% for both reactor designs. Single assembly hydrodynamic and temperature results compared favorably with those available in the literature for similar prismatic HTGR thermal hydraulic, computational fluid dynamics analyses.
The method developed here enables detailed local and core wide thermal analysis with minimal computational effort, enabling advanced coupled analyses of high temperature reactors with thermal feedback. The steady state numerical scheme also offers a potential for select transient scenario modeling and a wide variety of design optimization studies.
25
Gorbushin, Nikolai. "Analysis of admissible steady-state fracture processes in discrete lattice structures." Thesis, Aberystwyth University, 2017. http://hdl.handle.net/2160/352f6a78-6e2f-4936-9389-a439e02fdfc0.
Full textAbstract:
The purpose of this work is to study physically possible crack propagation at constant velocity inside a discrete solid by means of theoretical analysis supported by numerical simulations. Analytical solutions are delivered for fracture problems in one dimensional chains, a double chain and square lattices. Evaluation of obtained solutions required implementation of numerical algorithms for computation of integral transforms. Consideration of one-dimensional cases, namely a simple chain of oscillators and a chain of masses with non-local interactions, allowed to examine the validity of derived formulae by a complementary computer simulation of a corresponding dynamic system. Starting from simple models, the analysis of physically admissible and forbidden fracture regimes has been performed. The analytical predictions of possible steady states found a good agreement with a purely numerical scheme. The work discusses the advantages of different approaches to study steady-state failure processes: either with energetic or load characteristics. These attributes of fracture mechanics are shown to be effient for quantifying global predictions, e.g. a choice a particular loading condition for achieving a certain value of a crack speed. However, it was demonstrated that derivation of these characteristics is not enough and consideration of the displacement or stress fields should be performed. The results on chains with non-local interactions between the oscillators illustrated the features of failure at micro-level. Namely, different combinations of microscopic parameters, that result in the same bulk quantities, reflect different patterns of crack propagation in discrete solids. A problem of a separation a double chain compounded by two chains with different properties shows the peculiarities of parameters mismatch. Particularly, it was established that, contrary to quasi-static problems, a steady-state separation is necessarily caused by forces, applied to each chain, of different values. Furthermore, distinct material parameters of chains give a chance for the observation of the supersonic fracture of the structure. Increasing the problem dimension from chains to lattices, several new features emerged. For instance, the behaviour of displacements along a crack path changes. Moreover, the admissibility analysis is expanded to the consideration of possible fracture behind a crack tip. The outcomes predict crack propagation regimes with high energy release rates be accompanied by snapping of the springs on the faces of the original moving crack. The evaluation of displacement eld in the direction orthogonal to a crack path is also presented. The contrast in material properties in anisotropic lattices and mismatch of material properties in dissimilar lattices unveiled different scenarios of admissible regimes. Furthermore, the question of the choice of a particular fracture criterion is addressed. Two history-dependent criteria are compared to the classical one of threshold elongation for linear bonds. The results show that steadystate regimes can be reached in the low subsonic crack speed range which can not be according to the classical criterion. Repercussions in terms of load and crack opening versus velocity are explained in details. Once known the steady-state regimes of fracture propagation, a procedure for applying history-dependent criteria emerges as not restricted to the two examined ones and opens the way to dierent and more complex problems.
26
OTT, Gustavo. "Performance analysis of a framework for auditory steady-state response detection." Universidade Catolica de Pelotas, 2017. http://tede.ucpel.edu.br:8080/jspui/handle/tede/617.
Full textAbstract:
Submitted by Cristiane Chim (cristiane.chim@ucpel.edu.br) on 2017-07-17T13:47:32Z
No. of bitstreams: 1
Gustavo_Ott.pdf: 10434305 bytes, checksum: bba092ff1742babb456df8013f50778c (MD5)Made available in DSpace on 2017-07-17T13:47:32Z (GMT). No. of bitstreams: 1 Gustavo_Ott.pdf: 10434305 bytes, checksum: bba092ff1742babb456df8013f50778c (MD5) Previous issue date: 2017-02-17
The Auditory Steady-State Response (ASSR) is a periodic electrical response from the brain which is generated by a healthy or impaired ear without conduction hearing loss subject. This response is evoked by presenting a subject to a periodically varying continuous acoustic signal, typically a sinusoidally modulated tone. The response consists of a waveform whose constituent discrete frequency components have the same periodicity as that of the acoustic signal and remain constant in amplitude and phase over an infinitely long time period. ASSR has been used to objectively assess hearing thresholds for hearing impairment diagnosis, in contrast to traditional subjective methods such as auditory brain-stem responses and audiometry. The objective of this study is to implement experimental setups that detect simulated ASSRs in single and multiple response recordings in order to asses detector performance in different approaches of signal recording parameters and signal processing techniques. The experimental setups were implemented using the MATLAB environment, in which three test scenarios were also developed: (i) a single channel ASSR detector in which the statistical detection tests F test, phase coherence (PC), magnitude-squared coherence (MSC) and Hotteling’s T 2 circular (T2) were used for comparative performance evaluation; (ii) a single channel ASSR detector in which the traditional sweep-by-sweep (SBS) averaging approach performance was compared to the proposed epoch-by-epoch (EBE) averaging aproach; and (iii) a multiple channel ASSR detector in which three Independent Component Analysis (ICA) algorithms – JADE, SOBI, and WASOBI – were applied for comparative performance evaluation from the reference method, in which ICA was not applied. The performance evaluation method was the Receiver Operating Characteristic (ROC) analysis, in which the Area Under the Curve (AUC) metric was used to estimate the detector’s accuracy levels for ASSR detection. From the results of the first test scenario it was concluded that the T2 and MSC tests presented the best overall performance, specially at lower SNR conditions. Results from scenario 2 indicated that the SBS approach resulted in higher accuracy levels after the transitory period of the AUC curve related to test time duration, while the EBE resulted in the steepest AUC curves for the first seconds of test time duration. From the results of scenario 3 it was not observed significant ASSR’s detection time reduction when ICA algorithms were applied in situations closely related to hearing threshold estimation.
A Resposta Auditiva de Estado Estável (RAEE) é uma resposta elétrica periódica gerada pelo cérebro em pacientes com ouvidos saudáveis. Esta resposta é evocada ao ser apresentado ao paciente um estímulo acústico contínuo que varia periodicamente, tipicamente um tom modulado por um sinal sinusoidal. A resposta é constituída por componentes em frequência que têm a mesma periodicidade do estímulo e permanecem constantes em termos de amplitude e fase por um período de tempo infinitamente longo. As RAEEs têm sido utilizadas para avaliar de forma objetiva os limiares de audição para diagnóstico de perda auditiva, em contraste aos métodos tradicionais subjetivos, como a audiometria. O objetivo deste trabalho é a implementação de estruturas experimentais que detectem RAEEs simuladas em abordagens de captação de canal único e de múltiplos canais a fim de avaliar o desempenho do detector em diferentes abordagens de processamento de sinal. As estruturas experimentais foram implementadas utilizando o ambiente MATLAB, no qual três cenários de teste foram desenvolvidos: (i) um detector de RAEE para canal simples com o qual os desempenhos dos testes estatísticos F, coerência de fase (PC), coerência da magnitude ao quadrado (MSC) e T 2 circular de Hotteling (T2) foram comparados; (ii) um detector de RAEE para canal simples com o qual o desempenho a abordagem de promediação tradicional sweep-a-sweep (SBS) foi comparado com o método proposto época-a-época (EBE); e (iii) um detector de RAEE para múltiplos canais com o qual o desempenho de três algoritmos de análise de componentes independentes (ICA) – JADE, SOBI e WASOBI – foram comparados com a detecção sem o uso de ICA. O método de avaliação do desempenho foi a análise Receiver Operating Characteristic (ROC), no qual a métrica de área sob a curva (AUC) for utilizada para estimar os níveis de acurácia da detecção das RAEEs. A partir dos resultados do cenário 1 concluiu-se que os testes T2 e MSC apresentaram os melhores desempenhos, especialmente para condições de baixa razão sinal-ruído. Resultados do cenário 2 indicaram que a abordagem SBS apresentou maiores níveis de acurácia após o período transitório da curva AUC, enquanto a abordagem EBE resultou em incrementos de acurácia mais abruptos para os primeiros segundos de duração do teste. A partir dos resultados do cenários 3 não foi observada uma redução significativa no tempo de detecção das RAEEs quando o ICA foi aplicado em situações próximas da estimação de limiar auditivo.
27
Kathi, Lokesh. "Steady-State Analysis of PWM Z-Bridge Source DC-DC Converter." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1453223069.
Full text
28
PIRES, Robson Celso. "Complex-Valued Steady-State Models as Applied to Power Flow Analysis and Power System State Estimation." reponame:Repositório Institucional da UNIFEI, 2018. http://repositorio.unifei.edu.br/xmlui/handle/123456789/1359.
Full textAbstract:
Submitted by repositorio repositorio (repositorio@unifei.edu.br) on 2018-06-15T13:12:49Z
No. of bitstreams: 1
tese_2018_pires_robson.pdf: 2114807 bytes, checksum: d730bc3798b4777ca67282b62e72c7e0 (MD5)Made available in DSpace on 2018-06-15T13:12:49Z (GMT). No. of bitstreams: 1 tese_2018_pires_robson.pdf: 2114807 bytes, checksum: d730bc3798b4777ca67282b62e72c7e0 (MD5) Previous issue date: 2018-06
Nonlinear systems of equations in complex domain are frequently encountered in applied mathematics, e.g., power systems, signal processing, control theory, neural networks and biomedicine, to name a few. The solution of these problems often requires a first- or second-order approximation of these nonlinear functions to generate a new step or descent direction to meet the solution iteratively. However, such methods cannot be applied to real functions of complex variables because they are necessarily non-analytic in their argument, i.e., the Taylor series expansion in their argument alone does not exist. To overcome this problem, the nonlinear function is usually redefined as a function of the real and imaginary parts of its complex argument so that standard methods can be applied. Although not widely known, it is possible to build an expansion of these nonlinear functions in its original complex variables by noting that functions of complex variables can be analytic in their argument and its complex conjugate as a whole. This property lies in the fact that if a function is analytic in the space spanned by ℜ{} and ℑ{}in ℝ, it is also analytic in the space spanned by and * in ℂ. The main contribution of this work is the application of this methodology to a complex Taylor series expansions aiming algorithms commonly used for solving complex-valued nonlinear systems of equations emerged from power systems problems. In our proposal, a complex-valued power ow analysis (CV PFA) model solved by Newton-Raphson method is revisited and enhanced. Nonetheless, especially emphasis is addressed to Gauss-Newton method when derived in complex domain for solving power system state estimation (CV PSSE) problems, whichever they are applied in transmission or distribution systems. The factorization method of the complex Jacobian matrices emerged from CV PFA and CV PSSE approaches is the Three Angle Complex Rotation (TACR) algorithm that comes from the Givens Rotations algorithm in real domain. In this research one demonstrates that Wirtinger derivatives can lead to greater insights in the structure of both problems, i.e., CV PFA & CV PSSE. Moreover, it can often be exploited to mitigate computational overhead, storage cost and enhance the network's component modeling as FACTS devices, e.g., STATCOM, VSC-HVDC, besides easily handle PMU measurements and embedding new technologies towards smart grids. Finally, in order to add numerical robustness, a fourth-order Levenberg-Marquardt algorithm is employed to the CV PFA & CV PSSE approaches because of its nice bi-quadratic convergence property, instead of the well-known quadratic convergence property of the classical Newton-Raphson and Gauss-Newton algorithms. Recall that these latter algorithms are prone to collapse when the power system network is ill-conditioned, i.e., it is heavily loaded or presents branches with high R/X ratio. These results are partially presented in this thesis because they are still under study and development. But most of them will appear in forthcoming papers submitted to IEEE-PES Transactions on Power Systems and coming up Top Conferences.
29
Bandali, Bardia. "Steady State Analysis of Nonlinear Circuits using the Harmonic Balance on GPU." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26251.
Full textAbstract:
This thesis describes a new approach to accelerate the simulation of the steady-state response of nonlinear circuits using the Harmonic Balance (HB) technique. The approach presented in this work focuses on direct factorization of the sparse Jacobian matrix of the HB nonlinear equations using a Graphics Processing Unit (GPU) platform. This approach exploits the heterogeneous structure of the Jacobian matrix. The computational core of the proposed approach is based on developing a block-wise version of the KLU factorization algorithm, where scalar arithmetic operations are replaced by block-aware matrix operations. For a large number of harmonics, or excitation tones, or both the Block-KLU (BKLU) approach effectively raises the ratio of floating-point operations to other operations and, therefore, becomes an ideal vehicle for implementation on a GPU-based platform. Motivated by this fact, a GPU-based Hybrid Block KLU framework is developed to implement the BKLU. The proposed approach in this thesis is named Hybrid-BKLU. The Hybrid-BKLU is implemented in two parts, on the host CPU and on the graphic card’s GPU, using the OpenCL heterogeneous parallel programming language. To show the efficiency of the Hybrid-BKLU approach, its performance is compared with BKLU approach performing HB analysis on several test circuits. The Hybrid-BKLU approach yields speedup by up to 89 times over conventional BKLU on CPU.
30
Mavros, Georgios. "Tyre models for vehicle handling analysis under steady-state and transient manoeuvres." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/7904.
Full textAbstract:
The work presented in this thesis is devoted to the study of mechanism of tyre force generation and its influence on handling dynamics of ground vehicles. The main part of the work involves the development of tyre models for use under steady-state and transient operating conditions. The general capability of these models is assessedin a full vehicle simulation environment. The interaction between tyre and vehicle dynamics is critically evaluated and the observed vehicle behaviour is related to the inherent characteristics of different tyre models. In the field of steady-state tyre modelling, two versions of a numerical tyre model are developed. The modelling procedure is carried out in accordance with the viscoelastic properties of rubber, which influence the mechanical properties of the tyre structure and play a significant role in the determination of friction in the tyre contact patch. Whilst the initial simple version of the tyre model assumes a parabolic pressure distribution along the contact, a later more elaborate model employs a numerical method for the calculation of the actual normal pressure distribution. The changes in the pressure distribution as a result of variations in the rolling velocity and normal load influence mainly the levels of self-aligning moment, whilst the force characteristics remain practically unaffected. The adoption of a velocity dependent friction law explains the force generating behaviour of tyres at high sliding velocities. The analysis is extended to the area of transient tyre behaviour with the development of a tyre model appropriate for the study of transient friction force generation within the contact patch. The model incorporates viscoelasticity and inertial contributions, and incorporates a numerical stick-slip law. These characteristics are combined together for the successful simulation of transient friction force generation. The methodologies developed for the modelling of transient friction and steady-state tyre force generation are combined and further extended in order to create a generic transient tyre model. This final model incorporates a discretised flexible viscoelastic belt with inertia and a separate fully-dynamic discretised tread, also with inertia and damping, for the simulation of actual prevailing conditions in the contact patch. The generic tyre model appears to be capable of performing under a variety of operating conditions, including periodic excitations and transient inputs which extend to the non-linear range of tyre behaviour. For the evaluation of the influence of the aforementioned tyre models on the handling responses of a vehicle, a comprehensive vehicle model is developed, appropriate for use in handling simulations. The two versions of the steady-state models and the generic transient model are interfaced with the vehicle model, and the response of the vehicle to a step-steer manoeuvre is compared with that obtained using the Magic Formula tyre model. The comparison between the responses is facilitated by the definition of a new measure, defined as the non-dimensional yaw impulse. It is found that the transience involved in tyre behaviour may largely affect the response of a vehicle to a prescribed input.
31
Al-Zahawi, B. A. T. "Steady-state analysis of the static Kramer drive with alternative recovery systems." Thesis, University of Newcastle Upon Tyne, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380751.
Full text
32
Khan, Shahbaz. "Reappraisal of steady state and time-variant analysis of tile drainage systems." Thesis, University of Birmingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690128.
Full text
33
Nazário, Rafael Igor. "Kinematical analysis during swmming at and above the maximal lactate steady state." Master's thesis, Faculdade de Desporto da Universidade do Porto, 2011. http://hdl.handle.net/10216/57114.
Full text
34
Jiang, Wenwei. "Spectral-based Substructure Transfer Path Analysis of Steady-state and Transient Vibrations." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1273168454.
Full text
35
Nazário, Rafael Igor. "Kinematical analysis during swmming at and above the maximal lactate steady state." Dissertação, Faculdade de Desporto da Universidade do Porto, 2011. http://hdl.handle.net/10216/57114.
Full text
36
Aktaran-Kalayci, Tuba. "Steady-State Analyses: Variance Estimation in Simulations and Dynamic Pricing in Service Systems." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/13993.
Full textAbstract:
In this dissertation, we consider analytic and numeric approaches to the solution of probabilistic steady-state problems with specific applications in simulation and queueing theory.
Our first objective on steady-state simulations is to develop new estimators for the variance parameter of a selected output process that have better performance than certain existing variance estimators in the literature. To complete our analysis of these new variance estimators, called linear combinations of overlapping variance estimators, we do the following: establish theoretical asymptotic properties of the new estimators; test the theoretical results on a battery of examples to see how the new estimators perform in practice; and use the estimators for confidence interval estimation for both the mean and the variance parameter. Our theoretical and empirical results indicate the new estimators' potential for improvements in accuracy and computational efficiency.
Our second objective on steady-state simulations is to derive the expected values of various competing estimators for the variance parameter. In this research, we do the following: formulate the machinery to calculate the exact expected value of a given estimator for the variance parameter; calculate the exact expected values of various variance estimators in the literature; compute these expected values for certain stochastic processes with complicated covariance functions; and derive expressions for the mean squared error of the estimators studied herein. We find that certain standardized time series estimators outperform their competitors as the sample size becomes large.
Our research on queueing theory focuses on pricing of the service provided to individual customers in a queueing system. We find sensitivity results that enable efficient computational procedures for dynamic pricing decisions for maximizing the long-run average reward in a queueing facility with the following properties: there are a fixed number of servers, each with the same constant service rate; the system has a fixed finite capacity; the price charged to a customer entering the system depends on the number of customers in the system; and the customer arrival rate depends on the current price of the service. We show that the sensitivity results considered significantly reduce the computational requirements for finding the optimal pricing policies.
37
Lakkireddy, Jahnavi. "Steady State Voltage Stability Enhancement Using Shunt and Series FACTS Devices." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1881.
Full textAbstract:
It is specifically important to focus on voltage stability analysis of the power system to avoid worst case scenarios such as voltage collapse. The purpose of this thesis is to identify methods for enhancing the steady-state voltage stability using FACTS devices and determining their impact on real and reactive power losses, improvement of bus voltage magnitude, and transmission line loadability. To achieve this, FACTS devices such as Static VAR Compensator (SVC), Static Synchronous Compensator (STATCOM), and Thyristor Controlled Series Capacitor (TCSC) are used in the test system as three separate test cases. The results obtained assist in drawing conclusions on the effectiveness of each FACTS devices at generator, load and swing buses, on lines between two load buses, and between a load bus and a generator bus, in terms of metrics such as voltage magnitude profile, PV curves, and active and reactive power losses.
38
Al-Hoor, Wisam. "UNIFIED STEADY-STATE COMPUTER AIDED MODEL FOR SOFT-SWITCHING DC–DC CONVERTERS." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3959.
Full textAbstract:
For many decades, engineers and students have heavily depended on simulation packages such as Pspice to run transit and steady-state simulation for their circuits. The majority of these circuits, such as soft switching cells, contain complicated modes of operations that require the Pspice simulation to run for a long time and, finally, it may not reach a convergent solution for these kinds of circuits. Also, there is a need for an educational tool that provides students with a better understanding of circuit modes of operation through state-plan figures and steady-state switching waveforms. The unified steady-state computer aided model proposes a simulation block that covers common unified soft-switching cells operations and can be used in topologies simulation. The simulation block has a simple interface that enables the user to choose the switching cell type and connects the developed simulation model in the desired topology configuration. In addition to the measured information that can be obtained from the circuitry around the unified simulation model, the simulation block includes some additional nodes (other than the inputs and outputs) that make internal switching cell information, such as switching voltages and currents, easy to access and debug. The model is based on mathematical equations, resulting in faster simulation times, smaller file size and greatly minimized simulation convergence problems. The Unified Model is based on the generalized analysis: Chapter 1 discusses the generalized equation concept along with a detailed generalization example of one switching cell, which is the zero current switching quasi-resonant converter ZCS-QRC. Chapter 2 presents a detailed discussion of the unified model concept, the unified model flow chart and the unified model implementation in Pspice. Chapter 3 presents the unified model applications; generating the switching cell inductor current and the switching cell capacitor voltage steady-state waveforms, the State-Plane Diagram , the feedback design using the unified model, and the chapter concludes with how the model can be used with different topologies. Finally, chapter 4 presents the summary and the future workM.S.E.E.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering
39
Nabavi, Seyed Ghavamoddin. "Statistical Analysis of Steady State Response in RF Circuits via Decoupled Generalized Polynomial Chaos." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35293.
Full textAbstract:
One of the major factors in RF circuit design is the ability to predict the performance of these circuits in the presence of uncertainty in the key design parameters. This is referred to as uncertainty quantification in the mathematical literature. Uncertainty about the key design parameters arises mainly from the difficulty of controlling the physical or geometrical features of the underlying design, especially at the nanometer level. With the constant trend to scale down the process feature size, uncertainty quantification becomes crucial in shortening the design time.
This thesis presents a new approach to statistically characterize the
variability of the Harmonic Balance analysis and its application to Intermodulation distortion analysis in the presence of uncertainty in the design parameters. The new approach is based on the concept of Polynomial Chaos (PC) and Stochastic Galerkin (SG) methods. However, unlike the traditional PC, the proposed approach adopts a new mathematical formulation that decouples the Polynomial Chaos problem into several problems whose sizes are equal to the size of the original Harmonic Balance problem. The proposed algorithm produces significant CPU savings with equivalent accuracy to traditional Monte Carlo and standard PC approaches.
40
Ballukja, Erjon. "Power Quality Analysis in DC/DC Converters under Steady State and Transient Conditions." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Find full textAbstract:
The modern electric power systems are going through significant changes because of continuous increasing demand of electric power. Further, a growing number of renewable energy systems that directly deliver DC power jointly considered with the advance in DC technology allows a more efficient and affordable use of energy. Furthermore, a rising use of DC systems and microgrids in a wide number of applications has motivated the study of Power Quality (PQ). The concept of power quality in DC systems and microgrids brings many challenges and the aim of this thesis is to understand the delivered power quality in DC microgrid systems. In this thesis, the effects of low frequency range (0-2 kHz) conducted emissions on power quality from a microgrid based DC/DC converter under steady state and transient loading conditions represent the main purpose of this work. Indeed, for a DC distribution network there is a lack of standards and guidelines concerning power quality issues and acceptable levels of conducted disturbances in the aforementioned frequency range. Consequently, the objective of this thesis is to quantify adequate power quality indices for DC systems or networks with connected loads such as Low Frequency Sinusoidal Disturbance (% LFSD) and Amplitude Probability Distribution (APD) indices.
41
Spicer, Timothy C. "Sensitivity analysis of transient and steady state characteristics of surface ship progressive flooding." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA370876.
Full textAbstract:
Thesis (M.S. in Mechanical Engineering) Naval Postgraduate School, September 1999."September 1999". Thesis advisor(s): Fotis A. Papoulias. Includes bibliographical references (p. 59). Also available online.
42
Hioe, Yunior. "Mold thermal design and quasi steady state cycle time analysis in injection molding." Connect to resource, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141840509.
Full text
43
Zatschler, Harf. "Steady-state and response time analysis of modulated queues and networks with batches." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409310.
Full text
44
Zhang, Shuqi, and 张书奇. "Periodic steady-state analysis of nonlinear oscillators based on multivariate polynomial roots finding." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208018.
Full textAbstract:
Periodic steady-state analysis plays an important role in both theoretical topics and numerical simulations. It has been applied to numerous fields such as electronics, economics, biology, chemistry and so on. Particularly in electronics it is the basis of microwave and radio frequency (RF) circuit simulation. Although the topic has been studied for decades, periodic steady-state analysis still remains a difficulty in certain aspects including the analysis of the exact analytical formulas of limit cycles, as well as fast and accurate approximation of periodic steady states with unknown frequencies. In this thesis, two innovative methods are proposed in order to overcome two difficulties in the field of periodic steady-state analysis accordingly: on the one hand, a limit cycle identification method is developed to provide a robust method for computation of the exact analytical formulas of limit cycles. The method can be further extended to a wide range of nonlinear systems by the technique called state immersion. On the other hand, a method for highly accurate periodic steady-state approximation based on harmonic balancing is proposed. It combines the robustness of Macaulay matrix approach for small size polynomial root(s) finding, and the efficiency of a guided global optimization for higher order approximations. Thus, it is capable of computing approximations of periodic steady states with a high accuracy. Together, the two methods establish a reliable framework where highly accurate periodic steady-state analysis for a wide range of nonlinear systems can be performed.published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy
45
CHACON, AMERICO BUSTAMANTE. "A COMPUTER IMPLEMENTATION FOR FINITE ELEMENT ANALYSIS OF UNCONFINED STEADY STATE FLOW PROBLEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1515@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO presente trabalho apresenta a implementação computacional pelo método dos elementos finitos de procedimentos para análise de problemas de escavação e de fluxo permanente bidimensional, não confinado, para solos saturados. Tais procedimentos, particularmente indicados para investigação do comportamento mecânico/hidráulico de barragens de terra, vem completar o trabalho iniciado por Parra (1996) para análise do comportamento de barragens sob carregamentos estático e sísmico. Foram implementadas duas técnicas para simulação de escavações, obtendo-se, em ambas, resultados numéricos praticamente idênticos. O procedimento para análise de fluxo permanente foi baseado na proposição de Bathe e Khoshgoftarr (1979), a qual considera a situação de fluxo não-confinado como problema não linear, porém conservando a configuração original da malha de elementos finitos. Os resultados numéricos obtidos neste trabalho foram detalhadamente comparados com os valores publicados na literatura, numéricos ou analíticos, como forma de assegurar a confiabilidade das implementações computacionais. A previsão do comportamento da barragem de terra Macusani, a ser construída no Peru, foi estudada neste trabalho, nos aspectos referentes às fases de escavação, construção, primeiro enchimento do reservatório e determinação da superficie de infiltração de fluxo permanente. Os resultados assim obtidos podem ser eventualmente úteis no detalhamento do projeto final da obra.
This work presents a computer implementation for finite element analysis of excavation problems and unconfined steady state flow through saturated soils. These computer routines are particularly useful for the study of earth dams and they were written with the aim to pursue the development of a numerical model (Parra, 1996) devised to investigate the behavior of earth dams under static and seismic loading. Two techniques were implemented for excavation simulations, with both yielding the some numerical results. For the unconfined fluid flow problem the technique proposed by Bathe and Khoshgoftaar (1979) was adopted, which recasts the problem in a non-linear form but keeps the same basic finite element mesh. The results computed in this research were compared with other analytical and numerical values published in the literature, in order to ensure, as much as possible, the feasibility and efficiency of the computer implementations. The behavior prediction of the Macusani earth dam, to be built in Peru, was also studied in this research, focusing on several aspects related to its planned construction: the excavation, the construction itself and the first reservoir filling. This results may eventually be useful for the final engineering design of the Macusani dam.
El presente trabajo presenta la implementación computacional de procedimentos para análisis de problemas de excavación y de flujo permanente bidimensional, para suelos saturados utilizando el método de elementos finitos. Tales procedimentos, particularmente indicados para la investigación del comportamiento mecánico/hidráulico de represas, completa el trabajo iniciado por Parra(1996) para análisis del comportamiento de represas bajo sobrecarga estática y sísmica. Se implementaron dos técnicas para simulación de excavaciones, obteniendo, en ambas, resultados numéricos prácticamente idénticos. El procedimento para análisis de flujo permanente tubo como base la propuesta de Bathe y Khoshgoftarr (1979), que considera la situación de flujo no confinado como problema no lineal, pero conservando la configuración original de la malla de elementos finitos. Los resultados numéricos obtenidos em este trabajo fueron detalladamente comparados con los valores publicados en la literatura, numéricos o analíticos, para asegurar la confiabilidad de las implementaciones computacionales. La previsión del comportamiento de la represa de Macusani, que será construida en Perú, fue estudiada en este trabajo, especifícamente los aspectos vinculados a las fases de excavación, construcción y determinación de la superficie de infiltración de flujo permanente. Los resultados obtenidos pueden ser eventualmente útiles en el proyecto final de la obra.
46
Chien, Ying-Che. "Some exact and approximate methods for large scale systems steady-state availability analysis." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187066.
Full textAbstract:
System availability is the probability of the system being operable at instant t. Markov chains are a model used for system availability analysis. The exact analytical solution in terms of component failure rates and repair rates for steady-state system availability is complex to find solving the large numbers of simultaneous linear equations that result from the model. Although exact analytical solutions have been developed for series and parallel systems and for some other small size systems, they have not been developed for large scale general systems with n distinct components. Some methods for approximate analytical solutions have been suggested, but limitations on network types, over simplified states merge conditions and lack of predictions of approximation errors make these methods difficult to use. Markov state transition graphs can be classified as symmetric or asymmetric. A symmetric Markov graph has two-way transitions between each pair of communicating nodes. An asymmetric Markov graph has some pair(s) of communicating nodes with only one-way transitions. In this research, failure rates and repair rates are assumed to be component dependent only. Exact analytical solutions are developed for systems with symmetric Markov graphs. Pure series systems, pure parallel systems and general k out of n systems are examples of systems with symmetric Markov graphs. Instead of solving a large number of linear equations from the Markov model to find the steady-state system availability, it is shown that only algebraic operations on component failure rates and repair rates are necessary. In fact, for the above class of systems, the exact analytical solutions are relatively easy to obtain. Approximate analytical solutions for systems with asymmetric Markov graphs are also developed based on the exact solutions for the corresponding symmetric Markov graphs. The approximate solutions are shown to be close to the exact solutions for large scale and complex systems. Also, they are shown to be lower bounds for the exact solutions. Design principles to improve systems availability are derived from the analytical solutions for systems availability. Important components can be found easily with the iteration procedure and computer programs provided in this research.
47
Li, Fang. "An Analysis of the Linked-pulse in Steady-state Free Precession in MRI." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4769.
Full textAbstract:
The steady-state free precession (SSFP) is one type of the fast scanning technique in MRI. So far most of its analysis are concentrated on the gradient echo SSFP (GR SSFP), very few paper~discuss the spin echo (SSFP (SE SSFP), and they are usually based on the simplified the hard pulse assumption. The advantage of the SE SSFP is that it can refocus the dephasing caused by the magnetic field inhomogeniety, which is the disadvantage of the GR SSFP. Also the hard pulse model can provide very limited information. The purpose of this paper is to establish the soft pulse model for both GR SSFP and SE SSFP. By using the spinor method to describe the interaction between the RF pulse, magnetic field, and the spin's magnetization, we create the steady state equations of the GR SSFP and SE SSFP, and give their analytical solutions. Because the SE SSFP's mathematical model is very complicated, we introduce a new concept, the linked-pulse, to simplify the problem, and provide the valuable results. Based on both traditional hard pulse model and our soft pulse model, we did a series of simulations, and compared both results. First of all, the soft pulse model can provide the slice profile and gradient effects, which is impossible for the hard pulse model. Second, in both models, the signal intensities are all depended on the Tl/T2 ratio, which is the characterization of the SSFP image. Third, we also observed how the pulse shape and the flip angles affect the slice profile and the signal intensity. In conclusion, the soft pulse model can give more information than hard pulse model can, such as slice profile and gradient effects, etc., provide more aspects for analyzing the SSFP image.
48
Bradfield, M. F. A. (Michael Ford Alexander). "Continuous production of succinic acid by Actinobacillus succinogenes : steady state metabolic flux variation." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/40826.
Full textAbstract:
Continuous fermentations were performed in a novel external-recycle, biofilm reactor using D-glucose and CO2 as carbon substrates. Corn steep liquor (CSL) and yeast extract (YE) served as nitrogen sources.
In anaerobic fermentations using medium containing CSL and YE, succinic acid (SA) yields were found to be an increasing function of glucose consumption. The ratio of SA to the major by-product, acetic acid (YAASA), increased from 2.4 g g-1 at a glucose consumption of 15 g L-1, to 5.7 g g-1 at a glucose consumption of 46 g L-1. For medium containing no CSL, YAASA remained near 1.97 g g-1, exceeding this for cases where biofilm grown on CSL-containing medium was present.
The ratio of formic acid to acetic acid (YAAFA), for CSL-containing medium, decreased from an equimolar value (0.77 g g-1) at a glucose consumption of 10 g L-1 to zero at 46 g L-1 glucose consumed. In contrast, YAAFA for YE-only medium remained at 0.77 g g-1. Therefore, pyruvate was metabolised solely by pyruvate-formate lyase when no CSL was present.
The highest SA yield obtained on glucose, SA titre and SA productivity were 0.91 g g-1, 48.5 g L-1 and 9.4 g L-1 h-1, respectively, all for medium containing CSL. Medium that included CSL significantly outperformed medium that excluded CSL, achieving 64%, 21% and 203% greater SA titres, yields on glucose and productivities respectively.
Metabolic flux analyses based on the established C3 and C4 metabolic pathways of Actinobacillus succinogenes revealed that the increase in YAASA, for CSL-containing fermentations, could not be attributed to the decrease in formate and biomass formation, and that an additional source of reducing power was present. The fraction of reducing power (NADH) unaccounted for increased with glucose consumption, suggesting that the maintenance or non-growth metabolism encountered at higher SA titres differs from the growth metabolism. It is postulated that the additional reducing power originates from an active pentose phosphate pathway in non-growing cells or from an undetected component(s) in the fermentation medium. No major metabolic flux variations were found in fermentations that excluded CSL.Dissertation (MEng)--University of Pretoria, 2013.
gm2014
Chemical Engineering
unrestricted
49
Eickhoff, Mirko. "Sequential Analysis of Quantiles and Probability Distributions by Replicated Simulations." Thesis, University of Canterbury. Computer Science and Software Engineering, 2007. http://hdl.handle.net/10092/1238.
Full textAbstract:
Discrete event simulation is well known to be a powerful approach to investigate behaviour of complex dynamic stochastic systems, especially when the system is analytically not tractable. The estimation of mean values has traditionally been the main goal of simulation output analysis, even though it provides limited information about the analysed system's performance. Because of its complexity, quantile analysis is not as frequently applied, despite its ability to provide much deeper insights into the system of interest. A set of quantiles can be used to approximate a cumulative distribution function, providing fuller information about a given performance characteristic of the simulated system. This thesis employs the distributed computing power of multiple computers by proposing new methods for sequential and automated analysis of quantile-based performance measures of such dynamic systems. These new methods estimate steady state quantiles based on replicating simulations on clusters of workstations as simulation engines. A general contribution to the problem of the length of the initial transient is made by considering steady state in terms of the underlying probability distribution. Our research focuses on sequential and automated methods to guarantee a satisfactory level of confidence of the final results. The correctness of the proposed methods has been exhaustively studied by means of sequential coverage analysis. Quantile estimates are used to investigate underlying probability distributions. We demonstrate that synchronous replications greatly assist this kind of analysis.
50
Chang, Byeong-Yun. "Estimation Techniques for Nonlinear Functions of the Steady-State Mean in Computer Simulation." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4917.
Full textAbstract:
A simulation study consists of several steps such as data collection, coding
and model verification, model validation, experimental design, output data analysis,
and implementation. Our research concentrates on output data analysis. In this field,
many researchers have studied how to construct confidence intervals for the mean u
of a stationary stochastic process. However, the estimation of the value of a nonlinear
function f(u) has not received a lot of attention in the simulation literature. Towards
this goal, a batch-means-based methodology was proposed by Munoz and Glynn (1997).
Their approach did not consider consistent estimators for the variance of the point
estimator for f(u). This thesis, however, will consider consistent variance estimation
techniques to construct confidence intervals for f(u). Specifically, we propose methods
based on the combination of the delta method and nonoverlapping batch means
(NBM), standardized time series (STS), or a combination of both. Our approaches
are tested on moving average, autoregressive, and M/M/1 queueing processes. The
results show that the resulting confidence intervals (CIs) perform often better than
the CIs based on the method of Munoz and Glynn in terms of coverage, the mean of
their CI half-width, and the variance of their CI half-width.