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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.
221

Statistical Modelling of Price Difference Durations Between Limit Order Books: Applications in Smart Order Routing / Statistisk modellering av varaktigheten av prisskillnader mellan orderböcker: Tillämpningar inom smart order routing

Backe, Hannes, Rydberg, David January 2023 (has links)
The modern electronic financial market is composed of a large amount of actors. With the surge in algorithmic trading some of these actors collectively behave in increasingly complex ways. Historically, academic research related to financial markets has been focused on areas such as asset pricing, portfolio management and financial econometrics. However, the fragmentation of the financial market has given rise to a different set of problems, namely the order allocation problem, as well as smart order routers as a tool to comply with these. In this thesis we consider price discrepancies between order books, trading the same instruments, as a proxy for order routing opportunities. A survival analysis framework for these price differences is developed. Specifically, we consider the two widely used Kaplan-Meier and Cox Proportional Hazards models, as well as the somewhat less known Random Survival Forest model, in order to investigate whether such a framework is effective for predicting the survival times of price differences. The results show that the survival models outperform random models and fixed routing decisions significantly. Thus suggesting that such models could beneficially be incorporated into existing SOR environments. Furthermore, the implementation of order book parameters as covariates in the CPH and RSF models add additional performance. / Den moderna elektroniska marknaden består av ett stort antal aktörer som, till följd av ökningen av algoritmisk handel, beter sig alltmer komplext. Historiskt sett har akademisk forskning inom finans i huvudsak fokuserat på områden som prissättning av tillgångar, portföljförvaltning och finansiell ekonometri. Fragmentering av finansiella marknader har däremot gett upphov till nya sorters problem, däribland orderplaceringsproblemet. Följdaktligen har smart order routers utvecklats som ett verktyg för att tillmötesgå detta problem. I detta examensarbete studerar vi prisskillnader mellan orderböcker som tillhandhåller handel av samma instrument. Dessa prisskillnader representerar möjligheter för order routing. Vi utvecklar ett ramverk inom överlevnadsanalys för dessa prisskillnader. Specifikt används de välkända Kaplan-Meier- och Cox Proportional Hazards-modellerna samt den något mindre kända Random Survival Forest, för att utvärdera om ett sådant ramverk kan användas för att förutspå prisskillnadernas livstider. Våra resultat visar att dessa modeller överträffar slumpmässiga modeller samt deterministiska routingstrategier med stor marginal och antyder därmed att ett sådant ramverk kan integreras i SOR-system. Resultaten visar dessutom att användning av orderboksparametrar som variabler i CPH- och RSF-modellerna ökar prestandan.
222

Energy-efficient multistable valve driven by magnetic shape memory alloys

Schiepp, Thomas, Schnetzler, René, Riccardi, Leonardo, Laufenberg, Markus 03 May 2016 (has links) (PDF)
Magnetic shape memory alloys are active materials which deform under the application of a magnetic field or an external stress. Due to their internal friction, recognizable from the strain-stress hysteresis, this new material technology allows the design of multistable actuators. This paper describes and characterizes an innovative airflow control valve whose aperture is proportional to the deformation of the active material and thus controllable by the input voltage. The multistability of the material is partially exploited within an airflow control loop to reduce the energy losses of the valve when a specific airflow value must be hold.
223

n Ontleding van direkte Kleurlingverteenwoordiging op die munisipale vlak in Suid-Afrika tot 1971 / An analysis of the direct representation of the coloured population group at the municipal level in South Africa until 1971

Cloete, Gideon Stephanus 12 1900 (has links)
Thesis (MA)--Stellenbosch University, 1976. / ENGLISH ABSTRACT: In this study the representation of the Coloured population group in the local evaluation process in South Africa until 1971, is analysecd to determine the effectiveness of this system of representation. In theory representatives selected in an open democratic election are supposed to act in the interest of the voters they represent, in a manner responsive to them. In this way the voters or citizens have access to and control over the decision-making centres of government, and are represented in the legislative structures of government. Representation can be analysed in two ways. / INLEIDING: Gedurende die periode 1960 - 1972 was die Kaapprovinsie die enigste provinsie binne die Republiek van Suid-Afrika waar Kleurlinge (en Indiërs) saam met Blankes deelgeneem het aan die plaaslike bestuursprosesse, sonder dat daar formeel ‘n rasse- of kleuronderskeid gemaak is tussen munisipale kiesers. Hierdie gesamentlike deelname het egter nie sonder "wrywing" plaasgevind nie, en dit was dan ook een van die redes vir die verwydering van die Kleurlingkiesers op 14 Januarie 1972 vanaf die gemeenskaplike munisipale kieserslys en die ontneming daardeur van hul direkte stemreg op die plaaslike bestuursvlak ten gunste van verteenwoordiging in sekere adviserende bestuurs- of raadplegende komitees vir Kleurlinge wat in ‘n ondergeskikte posisie teenoor die munisipale- of afdelingsraad in die betrokke plasslike owerheidsgebied verkeer.
224

Design and Optimization of Controllers for an Electro-Hydraulic System

André, Simon January 2014 (has links)
Electro-Hydraulic (EH) systems are commonly used in the industry for applications that require high power-weight ratios and large driving forces. The EH system studied in this master thesis have recently been upgraded with new hardware components and as a part of this upgrade a new controller was requested. The system consists of a controller that computes a control signal for an electric motor. The motor drives a gear pump that generates a flow of hydraulic fluid. The flow is then directed to a cylinder. The movements of a piston in the cylinder is affected by the flow and the piston position can be measured. The measured piston position is then fed back to the controller and the control loop is complete. The system was previously controlled using a Proportional-Integral-Derivative (PID) controller and the purpose of this thesis is to compare the old controller with alternative control strategies suitable for this application. The evaluation of the controllers is based on both software and hardware simulations and results in a recommendation for final implementation of the best suited controller. The control strategies chosen for investigation are: a retuned PID controller, a PID controller with feed forward from reference, a PID based cascade controller, a Linear Quadratic (LQ) controller, and a Model Predictive Controller (MPC). To synthesize the controllers an approximate model of the system is formed and implemented in the software environment Matlab Simulink. The model is tuned to fit recorded data and provides a decent estimation of the actual system. The proposed control strategies are then simulated and evaluated in Simulink with the model posing as the real system. These simulations resulted in the elimination of the cascade controller as a possible candidate since it proved unstable for large steps in the reference signal. The remaining four controllers were all selected for simulation on the real hardware system. Unfortunately the MPC was never successfully implemented on the hardware due to some unknown compatibility error and hence eliminated as a possible candidate. The three remaining control strategies, PID, PID with feed forward from reference and the LQ controller, were all successfully implemented and simulated on hardware. The results from the hardware simulations compared to simulations made with the old controller, as well as the results from the software simulations, were then evaluated. Depending on the purpose one of two control strategies is recommended for this application. The LQ controller achieved the best overall performance and is presented as the control strategy best suited for this application.
225

Model-Based Design of a Fork Control System in Very Narrow Aisle Forklifts

Bodin, Erik, Davidsson, Henric January 2017 (has links)
This thesis explains the model-based design of a fork control system in a turret head operated Very Narrow Aisle forklift in order to evaluate and push the limits of the current hardware architecture. The turret head movement consists of two separate motions, traversing and rotation, which both are hydraulically actuated. The plant is thoroughly modeled in the Mathworks softwares Simulink/Simscape to assist in the design of the control system. The control system is designed in Simulink/Stateflow and code-generated to be evaluated in the actual forklift. Optimal control theory is used to generate a minimum-jerk trajectory for auto-rotation, that is simultaneous traversing and rotation with the load kept in centre. The new control system is able to control the system within the positioning requirements of +/- 10 mm and +/- 9 mrad for traversing and rotation, respectively. It also shows good overall performance in terms of robustness since it has been tested and validated with different loads and on different versions of the forklift. However, the study also shows that the non-linearities of the system, especially in the hydraulic proportional valves, causes problems in a closed-loop control system. The work serves as a proof of concept for model-based development at the company since the development time of the new control system was significantly lower than for the original control system.
226

Povišenje energetske efikasnosti programabilnog pneumatskog manipulatora u kontaktnim zadacima / Increasing energy efficiency of programmable pneumatic manipulator in contact tasks

Šulc Jovan 23 September 2016 (has links)
<p>Dat je pregled mogućnosti za povišenje energetske efikasnosti<br />pneumatskog programabilnog manipulatora primenjenog u kontaktnim<br />zadacima. Projektovano je i realizovano ispitno postrojenje. Posebno<br />je ukazano na mogućnosti projektovanja različitih upravljačkih<br />sistema. Razvijeni su primeri PWM i proporcionalnog upravljanja.<br />Ispitana su predložena rešenja iz različitih aspekata energetske<br />efikasnosti i kvaliteta praćenja trajektorije pri korišćenju<br />različitih vrsta materijala i alata. Izvučeni su potrebni zaključci.</p> / <p>This paper contains an overview of possibilities for increasing the energy<br />efficiency of programmable pneumatic manipulator in contact tasks.<br />Experimental station is designed and realized as a testbed. Especially, point<br />is on possibilities of designing of new control systems. Examples of PWM<br />and proportional control are developed. Proposed solutions are examined<br />from aspects of energy efficiency and quality of trajectory tracking, by using<br />various types of materials and tools. Necessary conclusions are drawn.</p>
227

Volební systém do poslanecké sněmovny v ČR: geneze, vývoj a jeho další směřování / The electroral system for the Chamber of Deputies of Czech Republic: genesis, evolution and its future direction

Peškar, Michal January 2012 (has links)
This final thesis deals with electoral system to the Chamber of Deputies of the Parliament of the Czech Republic. Its genesis, evolution and future are presented in 3 chapters and in the Conclusion. Work is designed as a case-study and it employs two methods - from general to particular, and from earlier to later. These methods are used in whole work as well as in particular chapters and subchapters. The first chapter introduces readers to the issue of electoral system in general. There are described two main voting systems - proportional and majority vote. Stress is put to the proportional system which has used for elections to the Chamber of Deputies. Also the question "which electoral system is the best" is mentioned. Following chapter surveys history of the electoral system and evolution from its establishment to the present. Main part of this chapter deals with a reform introduced in the year 2000 which was declared by the Constitutional Court as unconstitutional. New law, instead of blank spaces after the decision of the Constitutional Court, was adopted in the year 2002 and since that it has been valid till the present. The third chapter presents proposals of electoral reform from the year 2008 prepared by a group of experts on the basis of political assignment of contemporary Government....
228

Simulation-based estimation in regression models with categorical response variable and mismeasured covariates

Haddadian, Rojiar 27 July 2016 (has links)
A common problem in regression analysis is that some covariates are measured with errors. In this dissertation we present simulation-based approach to estimation in two popular regression models with a categorical response variable and classical measurement errors in covariates. The first model is the regression model with a binary response variable. The second one is the proportional odds regression with an ordinal response variable. In both regression models we consider method of moments estimators for therein unknown parameters that are defined via minimizing respective objective functions. The later functions involve multiple integrals and make obtaining of such estimators unfeasible. To overcome this computational difficulty, we propose Simulation-Based Estimators (SBE). This method does not require parametric assumptions for the distributions of the unobserved covariates and error components. We prove consistency and asymptotic normality of the proposed SBE's under some regularity conditions. We also examine the performance of the SBE's in finite-sample situations through simulation studies and two real data sets: the data set from the AIDS Clinical Trial Group (ACTG175) study for our logistic and probit regression models and one from the Adult Literacy and Life Skills (ALL) Survey for our regression model with the ordinal response variable and mismeasured covariates. / October 2016
229

Estimation of fatigue life by using a cyclic plasticity model and multiaxial notch correction

Johansson, Nils January 2019 (has links)
Mechanical components often possess notches. These notches give rise to stress concentrations, which in turn increases the likelihood that the material will undergo yielding. The finite element method (FEM) can be used to calculate transient stress and strain to be used in fatigue analyses. However, since yielding occurs, an elastic-plastic finite element analysis (FEA) must be performed. If the loading sequence to be analysed with respect to fatigue is long, the elastic-plastic FEA is often not a viable option because of its high computational requirements. In this thesis, a method that estimates the elastic-plastic stress and strain response as a result of input elastic stress and strain using plasticity modelling with the incremental Neuber rule has been derived and implemented. A numerical methodology to increase the accuracy when using the Neuber rule with cyclic loading has been proposed and validated for proportional loading. The results show fair albeit not ideal accuracy when compared to elastic-plastic finite element analysis. Different types of loading have been tested, including proportional and non-proportional as well as complex loadings with several load reversions. Based on the computed elastic-plastic stresses and strains, fatigue life is predicted by the critical plane method. Such a method has been reviewed, implemented and tested in this thesis. A comparison has been made between using a new damage parameter by Ince and an established damage parameter by Fatemi and Socie (FS). The implemented algorithm and damage parameters were evaluated by comparing the results of the program using either damage parameter to fatigue experiments of several different load cases, including non-proportional loading. The results are fairly accurate for both damage parameters, but the one by Ince tend to be slightly more accurate, if no fitted constant to use in the FS damage parameter can be obtained.
230

Análise de sobrevivência de bancos privados no Brasil / Survival analysis of private banks in Brazil

Alves, Karina Lumena de Freitas 16 September 2009 (has links)
Diante da importância do sistema financeiro para a economia de um país, faz-se necessária sua constante fiscalização. Nesse sentido, a identificação de problemas existentes no cenário bancário apresenta-se fundamental, visto que as crises bancárias ocorridas mundialmente ao longo da história mostraram que a falta de credibilidade bancária e a instabilidade do sistema financeiro geram enormes custos financeiros e sociais. Os modelos de previsão de insolvência bancária são capazes de identificar a condição financeira de um banco devido ao valor correspondente da sua probabilidade de insolvência. Dessa forma, o presente trabalho teve como objetivo identificar os principais indicadores característicos da insolvência de bancos privados no Brasil. Para isso, foi utilizada a técnica de análise de sobrevivência em uma amostra de 70 bancos privados no Brasil, sendo 33 bancos insolventes e 37 bancos solventes. Foi possível identificar os principais indicadores financeiros que apresentaram-se significativos para explicar a insolvência de bancos privados no Brasil e analisar a relação existente entre estes indicador e esta probabilidade. O resultado deste trabalho permitiu a realização de importantes constatações para explicar o fenômeno da insolvência de bancos privados no Brasil, bem como, permitiu constatar alguns aspectos característicos de bancos em momentos anteriores à sua insolvência. / The financial system is very important to the economy of a country, than its supervision is necessary. Accordingly, the identification of problems in the banking scenario is fundamental, since the banking crisis occurring worldwide throughout history have shown that and instability of the financial system generates huge financial and social costs. The banking failure prediction models are able to identify the financial condition of a bank based on the value of its probability of insolvency. Thus, this study aimed to identify the main financial ratios that can explain the insolvency of private banks in Brazil. For this, it was used the survival analysis to analize a sample of 70 private banks in Brazil, with 33 solvent banks and 37 insolvent banks. It was possible to identify the key financial indicators that were significantly to explain the bankruptcy of private banks in Brazil and it was possible to examine the relationship between these financial ratios and the probability of bank failure. The result of this work has enabled the achievement of important findings to explain the phenomenon of the bankruptcy of private banks in Brazil, and has seen some characteristic of banks in times prior to its insolvency.

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