1 

PMU Based Line Impedance Estimation
This thesis is focused on the the line impedance calculation and the most important part is to find a suitable error compensation to increase the accuracy of calculation results. First of all, adequate PMU based calculation methods are necessary. Among methods found in the literature, the best ones are tested in laboratory and field conditions, including impedance calculation, sensitivity analysis and error compensation.

[DOCX]
[Abstract]

2 

Monolithic Integration of Rectifiers and Drivers for low power SSL applications on a Rigid to Flex Substrate
Solid State Lighting (SSL) is one of the prominent light sources for future lighting applications with benefits such as high energy savings, long lifetimes and high efficiency. The main drawback in solid state lighting system is that the total initial cost of the system is high for large scale production. Packaging and electronics components in the system account to about 60% of the total cost. Silicon based wafer level packaging offers great advantages for large scale cheap production. Furthermore it also helps to create to create miniaturized and multifunctional system with integrated electronics with LEDs. In this thesis, a novel schottky diode in BiCMOS having high current conduction and high breakdown is designed and fabricated. A monolithically integrated rectifiers composed with four schottky diodes is presented. The rectifiers designed using schottky diodes are fabricated in a simple and low cost DIMES BiCMOS7 process. A detailed modeling and simulation of schottky diodes in a standard BiCMOS process is done to derive design parameters to achieve high current and high breakdown voltage. It has been found that with guard rings and a n well doping concentration determined by a phosphor dose of 6e12, schottky diodes with a breakdown voltage of 27V and forward current of 1A at 0.68V are fabricated in this process. A complete design, fabrication, characterization and spice modeling of the schottky diodes are presented. NMOS and NPN bipolar transistor fabricated in the BiCMOS process are characterized and modeled. A basic linear and switch mode driver using the devices fabricated in the BiCMOS process is analyzed. A design proposal for integrating the rectifiers and drivers on a Rigid to flex substrate is presented. The developed concept offers great advantage for wafer level integration of SSL system to reduce cost and create smart multifunctional miniaturized products.

[PDF]
[Abstract]

3 

Ask the Right Expert: Question Routing based on User Expertise in Web Questions Answering Systems
Question Routing systems aim at routing questions to users that are more suited to answer them. Different techniques are used to match candidate users to questions, by considering properties of both. Existing techniques however do not consider the expertise of the candidate.
This work proposes an approach to Question Routing in which the user expertise is considered for question routing purposes. The proposed approach is a three stage process which allows for different configurations of existing matching techniques and user expertise. An experiment is set up in order to compare different Question Routing configurations. In total thirteen different configurations are evaluated, all based on three different contentbased baseline methods. Stack Overflow is used as the source for questions, answers and users for the evaluation of the performance of different Question Routing configurations. A dataset containing 6 months worth of questions is used for the evaluation. The results show that incorporating expertise into Question Routing algorithms can provide significant performance increase.

[PDF]
[Abstract]

4 

Improvement and Adaption of Bearing Monitoring System
With the ongoing developments in the offshore wind turbine industry, weight reduction is an important aspect. With these weight reduction, manufacturers are trying to increase the effciency and size of their turbines. An example of such a technique is a single bearing drive train. These designs use a special bearing which is extra stiff due to the support of axial raceways. Manufacturers are still proving the robustness of this promising design. At the moment, some manufacturers already constructed a prototype. An example of this prototype is the XD115 of XEMC Darwind. This turbine is permanently monitored with the use of a health monitoring system. This system mainly consists of accelerometers which are located throughout the whole turbine. This monitoring system can be extended by performing spectral analysis on the measured generator current. The purpose of this thesis is to investigate if it is possible to measure mechanical vibrations in the current output of a generator with full converter.
The bearing is one of the most complex elements in this single bearing drive train. There fore, the focus is put on monitoring the bearing. In order to investigate in this topic, two types of tests are performed, lab tests and full scale tests. During the lab tests, a small setup is made and some bearings are tested. The full scale tests are performed on the XD115 prototype. During the tests in the lab most of the characteristic bearing frequen cies could be measured. An increase in the amplitude of these frequencies was measured after damaging the bearing. In these lab tests, an increase in friction was also measurable. The characteristic bearing frequencies could be identied much easier in the frequency spectrum of the current than in the frequency spectrum of the accelerometer. The re sults of the tests in the full scale turbine were less promising. Neither in the frequency spectrum of the accelerometer and current, a characteristic bearing frequency could be identied. However, when the rotational speed synchronisation algorithm is used, some mechanical vibrations could be identied. The shaft speed and each time a blade passes the tower were identied in the frequency spectrum of the current. This means that a mechanical vibration was measured in the generator current.

[PDF]
[Abstract]

5 

TweetBased Election Prediction
Twitter is a microblogging service that has more than 500 million messages on a daily basis. Scholars has been utilizing Twitter to monitor people reactions in political activities, such as debates and campaigns. By doing so, some of them claim that a forecast or prediction to an election can be made. Using the data from 2014 Indonesia Presidential Election, we calculate predictions with many different parameters. Our analysis of the prediction results shows the importance of a proper data collection method, removing spam, incorporating sentiment detection to the tweets, and performing data normalization using demographic information. Although looks very promising, our results show that result prediction is not applicable to any election. Dividing the data into 33 provinces, the data suggests that applying the methodology to provinces with a small dataset leads into inaccurate predictions.

[PDF]
[Abstract]

6 

Visionbased velocity control on a Philips Experimental Robot Arm
The challenge in this thesis is to find out if an offtheshelf embedded system can replace an offtheshelf laptop or desktop computer when its task is to perform visionbased velocity control using inverse kinematics on a robotic arm.
The results of this thesis are that an algorithm was developed which had to be tested in simulation and should run (semi)autonomously on an embedded system but there are no good test results on the algorithm.
Developing and testing an algorithm using an existing simulation proves to be very problematic as the used simulation software is very complex and has gone out of support by its developers.
Although the embedded system was chosen because it is equiped with a digital signal processor, I sadly found out that its proprietary driver is mutually exclusive with robotmessaging middleware, when it comes to operating systems ́ kernel support: the choice was between the driver by using an old kernel or the middleware by using a new kernel. The latter was chosen.
A realtime software kernelpatch necessary to communicate with the robotic arm unfortunately was still in development in the final stage of this work.
Porting an inverse kinematics algorithm from Matlab to C++ and adapting the trajectory generating algorithm for middleware went well, but could not be tested thoroughly because of simulation and realtime issues. This also holds for testing the velocity control algorithm.
The conclusion of this report is that there is future work necessary in order to see if the developed algorithm for visionbased velocity control actually works.

[PDF]
[Abstract]

7 

DICOMmunicator: An Online Medical Image Transfer Service
Medical doctors and researchers have to send medical image files to each other. This may be for a consult, because a patient is treated by a different doctor or because the files are to be used for research. The files contain personal health information, and privacy rules have to be satisfied before the files may be sent. To securely send the files the data should be encrypted and anonymized.
The problem led to the development of DICOMmunicator, a single page web application. It allows clinicians to use the selfdescriptive application to send DICOM files to another doctor. DICOMmunicator removes patient information from the files that are uploaded, encrypts the files and stores them in a database. The recipient of the files is sent an email containing the key used for decryption allowing only that person to download the files.

[PDF]
[Abstract]

8 

Estimating the extreme value index for imprecise data
In extreme value theory the focus is on the tails of the distribution. The main focus is to estimate the tail distribution for a rounded data set. To estimate this tail distribution the extreme value index should be estimated, but due to the rounded data this extreme value index oscillates heavily. Therefore a correct estimate can not be obtained. By adding a small uniform stochast the rounded data can be smoothend out and in this way the oscillation can be cancelled.

[PDF]
[Abstract]

9 

Optimal boundary point control for linear elliptic equations
This master thesis is concerned with optimal boundary point and function control problems for linear elliptic equations subject to control constraints. The elliptic partial differential equation with Robin boundary condition is considered. The control is chosen as a linear combination of the Dirac delta functions in the point control problem. The weak formulation and optimality conditions are obtained for the function control problem. The main goal is to examine the existence of the weak solution and to derive optimality conditions of boundary point control. Introducing sufficient discretization methods such as a finite volume and a finite element methods, we obtain finite dimensional problem.
We apply efficient numerical methods including primaldual active set strategy, projected gradient and conjugate gradient methods. The test examples are presented clarifying the performance of numerical methods mentioned earlier. The conjugate gradient method is compared to the unconstrained matlab function QUADPROG and primaldual active set strategy is compared to the constrained QUADPROG. The projected conjugate gradient method is applied to improve the projected gradient method. Due to its importance, the sparse point and function control problems are studied. We apply primaldual active set strategy where the sparse parameter f is chosen differently. All of the results are presented in both point and function control problems.

[PDF]
[Abstract]

10 

Optimal distributed point control of linear elliptic equations
In this master thesis, we consider the optimal function and point control problems governed by linear elliptic partial differential equations together with bilateral control constraints. The aim of this work is to choose a control function by linear combination of the Dirac delta and solve the optimal distributed point control problem. In this work, optimality systems of point and function control problems are derived by Lagrangian principle and reduced functional respectively. The optimality system is discretized by the finite element method (FEM) and finite volume method (FVM). We apply a semismooth Newton (SSN) method which is equivalent to a Primal dual active set strategy (PDASS) to solve the discretized optimality system. As a second solution method, we propose Projected gradient (PG) method for the same problem. For each method, we compare the result of FEM and FVM and give a preference. In order to have the best solution method, we compare the results of PDASS and PG methods to the results of matlab command QUADPROG. We have to solve two partial differential equations in every iteration, namely the state and the adjoint equations. Therefore, we develop a Multigrid Preconditioned Conjugate Gradient (MGPCG) method for solving the discretized optimality system as fast as possible. Finally, we consider the linear elliptic optimal control problems with L1 norms in the cost functional which results sparse control problem. Due to L1 norm, objective functional becomes nondfferentiable and the optimal controls are identically zero on large parts of the control domain. Using an appropriate smoothing of the nondifferentiable terms for the cost functional, we solve the optimal sparse control problems theoretically and numerically.

[PDF]
[Abstract]

11 

An Algorithmic Readout Approach for Thermal Conductivity Based CO2 Sensors
This thesis presents a new approach to reading out thermalconductivitybased gas sensors. This method is intended for the readout of a CMOS compatible resistive thermalconductivity transducer for indoor CO2 sensing applications, without requiring precision offchip components. Instead of accurately regulating the power dissipated in the transducer and measuring its temperature, the temperature and power dissipation are both measured using an algorithmic approach. A highresolution ADC digitizes the voltage drop across the transducer and the current through it, measured using an onchip reference resistor. Moreover, by digitizing several baseemitter voltages of an onchip bipolar transistor, a precision bandgap voltage reference is constructed in the digital domain, and accurate information about the ambient temperature is obtained, which is used to temperature compensate the voltage reference and the reference resistor. Thus, all necessary ingredients are obtained to calculate the power dissipation and temperature of the transducer, from which the thermal conductivity of the surrounding air, and hence CO2 concentration, can be obtained.
A prototype integrated circuit implementing this readout approach has been realized in 0.16um CMOS. It has been tested in a climate chamber in combination with a platinum resistor mimicking the transducer. The digitallyconstructed voltage reference has a temperature coefficient of 9ppm/°C, while ambient temperature is sensed with accuracy of ±0.2°C, with a resolution of 0.15°C. The resistance readings have an inaccuracy ranging between 1mOhms to 4mOhms on a nominal resistance of about 100Ohms (10ppm  40ppm) with a resolution of around 2mOhms in the temperature range from 10°C to 40°C; for the power measurements, the circuit achieved an accuracy between 0.03% and 0.06%, with an 800nW of resolution (in the same temperature range) which is one order of magnitude better than results presented in previous work.
Although no CO2 measurements have been performed, an estimated thermal resistance accuracy of around 2862ppm with a resolution of 155.64[K/W] should be possible, which would enable detection of the CO2 levels in the air with an accuracy of around 0.72% and a resolution of 7705ppm.

[PDF]
[Abstract]

12 

Investigation of Different Solvers for Radiotherapy Treatment Planning Problems
Radiotherapy treatment planning involves solving inequality constrained minimization problems. The currently used interior point solver performs well, but is considered relatively slow. In this thesis we investigate two different solvers based on the logarithmic barrier method and Sequential Quadratic Programming (SQP) respectively. We argue that the behaviour of the logarithmic barrier solver is uncertain, thereby making it generally unreliable in this context. In addition we substantiate that the performance of the SQP solver is solid, but lacks efficiency in computing the minimizers of its related quadratic subproblems.
We conclude that without serious improvements, none of the solvers investigated are faster than the currently used interior point optimizer.

[PDF]
[Abstract]

13 

Determining Performance Boundaries and Automatic Loop Optimization of HighLevel System Specifications
Designers are confronted with high timetomarket pressure and an increasing demand for computational power. As a result, they are required to identify as early as possible the quality of a specification for an intended technology. The designer needs to know if this specification can be improved, and at what cost. Specification tradeoffs are often based on the experience and intuition of a designer, which in itself is not enough to make design decisions given the complexity of modern designs. Therefore, we need to identify the performance boundaries for the execution of a specification on an intended technology.
The degree of parallelism, required resources, scheduling constraints, and possible optimizations, etc. are essential in determining design tradeoffs (e.g., power consumption, execution time, etc). However, existing tools lack the capability of determining relevant performance parameters and the option to automatically optimize highlevel specifications to make meaningful design tradeoffs.
To address these problems, we present in this thesis a new profiler tool, cprof. The Clang compiler frontend is used in this tool to parse highlevel specifications, and to produce instrumented source code for the purpose of profiling. This tool automatically determines, from highlevel specifications, the degree of parallelism of a given source code, specified in C and C++ programming languages. Furthermore, cprof estimates the number of clock cycles necessary to complete a program, it automatically applies loop optimization techniques, it determines the lower and upper bound on throughput capacity, and finally, it generates hardware execution traces. The tool assumes that the specification is executed on a parallel Model of Computation (MoC), referred to as a Polyhedral Process Network (PPN).
The proposed tool adds new functionality to existing technologies: the estimated performance by cprof of PolyBench/C benchmarks, as compared to realistic implementations in FieldProgrammable Gate Arrays (FPGA) platforms, showed to be almost identical. Cprof is capable of estimating the lower and upper bound on throughput capacity, making it possible for the designer to make performance tradeoffs based on real design points. As a result, only the highlevel specification is used by cprof to assist in Design Space Exploration (DSE) and to improve
design quality.

[PDF]
[Abstract]

14 

Investigation of Different Solvers for Radiotherapy Treatment Planning Problems
Radiotherapy treatment planning involves solving inequality constrained minimization problems. The currently used interior point solver performs well, but is considered relatively slow. In this thesis we investigate two different solvers based on the logarithmic barrier method and Sequential Quadratic Programming (SQP) respectively. We argue that the behaviour of the logarithmic barrier solver is uncertain, thereby making it generally unreliable in this context. In addition we substantiate that the performance of the SQP solver is solid, but lacks efficiency in computing the minimizers of its related quadratic subproblems. We conclude that without serious improvements, none of the solvers investigated are faster than the currently used interior point optimizer.

[PDF]
[Abstract]

15 

Design of a Boost DCDC Converter for Energy Harvesting Applications in 40nm CMOS Process
DCDC converters are critical building blocks in energy harvesting systems which are applied to provide the energy for the implantable biomedical devices. They are required to meet very strict specifications and consume as less power as possible. Therefore, their power conversion efficiency and stability of the functionality in the varying environment become the major considerations in this thesis project, the target of which is to design a DCDC converter for energy harvesting applications.
The conventional PWM control is not usually suitable for the DCDC converters applied in energy harvesting applications because of its bad stability and low power conversion efficiency over wide input voltage and load current ranges. It is demonstrated that the adaptive ontime/offtime (AOOT) control proposed in this thesis is an excellent alternative to deal with the issue and the zero current switching (ZCS) adjustment technique can be applied to improve further the performance of the DCDC converter by the fine tuning of the offtime.
In this thesis, a systematic design flow of a boost DCDC converter has been presented from the design of the power plant, to the selection of the most suitable control technique, then to the transistorlevel implementation and finally to the layout design. Moreover, the circuitry of a boost DCDC converter and the layout of its most parts have been implemented in TSMC 40nm CMOS process. The postlayout simulation results prove that the proposed boost DCDC converter can generate a stable 1V output voltage with very small ripples (<~10mV) and achieve more than 90% (maximum about 95%) power conversion efficiency over a wide input voltage range (0.35V~0.65V) and a wide load current range (1mA~10mA).

file embargo until: 20151201
[Abstract]

16 

Solving Stochastic PDEs with Approximate Gaussian Markov Random Fields using Different Programming Environments
This thesis is a study on the implementation of the Gaussian Markov Random Field (GMRF) for random sample generation and also the Multilevel Monte Carlo (MLMC) method to reduce the computational costs involved with doing uncertainty quantification studies. The GMRF method is implemented in different programming environments in order to evaluate the potential performance enhancements given varying levels of language abstraction. It is seen that the GMRF method can be used to generate Gaussian Fields with a Mat{\'e}rn type covariance function and reduces the computational requirements for large scale problems. Speedups of as much as 1000 can be observed when compared to the standard Cholesky Decomposition sample generation method, even for a relatively small problem size. The MLMC method was shown to be at least 6 times faster than the standard Monte Carlo method and the speedup increases with grid size. It is also seen that in any Monte Carlo type methods, a Krylov subspace type solver is almost always recommended together with a suitable preconditioner for robust sampling.
This thesis also studies the ease of implementation of these methods in varying levels of programming abstraction. The methods are implemented in different languages ranging from the most common language used by mathematicians (MATLAB), to the more performance oriented language (C++PETSc/MPI), and ends with one of the newest programming concept (ExaStencils). The GMRF method featured in this thesis also is one of the earliest application to be implemented in ExaStencils.

[PDF]
[Abstract]

17 

A Stochastic Approach for Selective Search Algorithms
This thesis introduces a new algorithm that generates candidate proposals for an object detection pipeline. We introduce Stochastic Selective Search (SSS), a segmentation based selective search method, which differs from previous work in two ways. First and most importantly, SSS is much faster than current stateoftheart algorithms while maintaining comparable accuracy. This is a result of our efficient stochastic segment merging process. Other work requires the computation of features to determine the order in which segments are merged. We show that currently used features from other work does not improve the results of SSS significantly and are therefore omitted. This makes our algorithm nearly twice as fast as the fastest prior selective search algorithms. Secondly, due to the stochastic merging process of SSS, it is not critically affected when two wrong segments are merged during the merging process, which leads to object proposals of higher quality. We show that SSS outperforms existing deterministic selective search methods while generating the same amount of proposals in less time. Additionally, we demonstrate the performance of our SSS algorithm in a stateoftheart object detection pipeline based on convolutional networks.

[PDF]
[PDF]
[Abstract]

18 

Design of a DutyCycled FractionalN ADPLL Based on Instantaneous Startup LC DCO and Highprecision DTCs
This thesis deals with the design of a dutycycled, fractionalN and lownoise Phase Locked Loop (PLL) used for UltraWideband applications in 40 nm process. This is the firstever DutyCycled PLL (DCPLL) that is designed with an LC oscillator and brings down the noise record for DCPLLs by more than 1 order of magnitude. Due to the special architecture used in this design, the DCPLL presented in this thesis can support fractionalN operation without difficulty and achieve a much better fractionalN resolution than its ring oscillator counterpart while requiring little additional hardware and power cost. Furthermore, the latest AllDigital PLL (ADPLL) architecture and techniques are mapped and tailored for this firstever LC oscillator based DutyCycled AllDigital PLL (DCADPLL). The performance of this DCADPLL is verified by VerilogAMS simulations.

file embargo until: 20151222
[Abstract]

19 

Radar Doppler Polarimetry of Wind Turbines using the Sband PARSAX radar
Due to the necessity of more sources of renewable wind generated energy, the number of wind turbines in the Netherlands has grown in the past. Unfortunately, big sizes and movements of the blades negatively impact groundbased Doppler radars in the form of Doppler clutter. Such clutter leads to a downgrade of the surveillance radar performance in airplanes and precipitation detection, their parameters estimation. Our goal is to characterize and possibly eliminate the Doppler clutter from the wind turbine, where polarization is used as an important tool to reach this goal. As Doppler frequency and polarization are key characteristics for this study, a theoretical model based on these characteristics is built to predict the behavior of the rotated rotor blades of the wind turbine which shows promising results for amplitude and phase analysis. To evaluate this model, real measurements have been done with the PARSAX radar, which gives possibility to represent the wind turbine data in Dopplerrange domain or Dopplertime domain in terms of amplitudes and phases of all four elements of the polarization scattering matrix. Using orthogonal LFMwaveforms for simultaneous polarimetric measurements, despite of huge benefits, has one serious drawback a different residual phases in different polarimetric channels. Testing and analysis of a few algorithms, the use of zero Doppler frequency range profile of phases with different algorithms of phase unwrapping, for their estimation and compensation did not result, unfortunately, in reliable compensation of residual phases. As a result, the analysis of wind turbines clutter has been focused on analysis of amplitude polarization characteristics only. For an experimental study a wind turbine was selected, which is located in Zoeterwoude near a highway. Such location allows to observe scattering from wind turbine and automotive targets simultaneously at the same range distance, with the possibility of data comparison. The goal of data analysis is to find polarimetric features, which for both types of targets behave differently, there is a possibility to eliminate the clutter from the wind turbine only. For comparative analysis, the absolute terms of the averaged covariance matrix are used in terms of 2D histograms to find differences between the wind turbine and automotive targets. This is done for consecutive time frames, where the results show different and similar behavior depending on the time frame. Another approach is to obtain and compare the so called target Euler parameters, which are related to a physical of the specific target to extend our study, a few polarimetric decomposition techniques (Pauli and H/®) are used to study feasibility of targets classification. Using comparative analysis with the covariance matrix, shows great potential with correlation coefficient algorithms in combination with polarization. The results are promising, but vary as the correlation coefficient highly depends on the vehicle and the orientation angle of the blades. The results of direct estimation of Euler parameters and the H/® decomposition both show differences between vehicles and blades and therefore potential in distinguishing both targets. Though, the results are affected by the residual phase and therefore additional research is recommended on this problem for better reliability.

[PDF]
[Abstract]

20 

Modelling and Transient Analysis of a 10 MW Superconducting Wind Turbine Generator
The number of installed wind turbines is growing every year as the need for energy increases in an exponential manner. As the wind turbines are trying to fulfill these requirements, the demand for output power from each individual turbine is increasing as well. Although this is great, implementation of new technologies such as direct drive superconducting generators are required as they have a great potential for becoming a great contender for satisfying the increasing demand of individual turbine power output.
The efficiency and the mass reduce by using this technology but other issues have to be checked regarding its transient performance. Due to the low subtransient, transient and synchronous reactance, compared to a conventional machine, the transient properties such as shortcircuit current, field current and electromagnetic torque is much higher. This may cause problems as high values may damage the windings and turbine properties and even cause the superconducting field windings to lose its superconducting property. The thesis report will try to model a superconducting generator for a 10 MW wind turbine and analyse its transient properties. Also several important parameter calculations will be made taking into account the saturation due to iron in the generator. This simulation will be made for three different topologies of generator while taking into account their own individual generator geometry.

[PDF]
[Abstract]
