208 research outputs found
Geographic profiling in Nazi Berlin: fact and fiction
No full textGeographic profiling uses the locations of connected crime sites to make inferences about the probable location of the offender’s ‘anchor point’ (usually a home, but sometimes a workplace). We show how the basic ideas of the method were used in a Gestapo investigation that formed the basis of a classic German novel about domestic resistance to the Nazis during the Second World War. We use modern techniques to re-analyse this case, and show that these successfully locate the Berlin home address of Otto and Elise Hampel, who had distributed hundreds of anti-Nazi postcards, after analysing just 34 of the 214 incidents that took place before their arrest. Our study provides the first empirical evidence to support the suggestion that analysis of minor terrorism-related acts such as graffiti and theft could be used to help locate terrorist bases before more serious incidents occur
Granual Jamming Gripper: The Design of a Universal Gripper And Accompanying Capacitive Sensor Array
No full textThis document describes the design and modification of a Universal Jamming Gripper. On the existing idea is expanded in such a way that it can be used in a low power environment. For the gripper a capacitive sensor is proposed to measure the deformation of the flexible part. This measurement can be used to aid in centring an object in the gripper to optimise the jamming. Another application would be to autonomously grab objects when other sensor data is absent or not feasible for quick processing. All parts described are as universal and modular as possible. This permits them to be used in other designs and projects without modification. The capacitive sensors can be used in other shape measurements, as long as the environment permits placement and shielding of the electrodes. A full test plan of the gripper and the sensor array are included in the appendix. As a prototype is not yet finished, no results are included.Electronic InstrumentationElectrical EngineeringElectrical Engineering, Mathematics and Computer Scienc
Delfi-C3 ontvanger voor scholieren
No full textElectrical Engineering, Mathematics and Computer Scienc
Structured design of an external NMOS based linear voltage regulator for automotive applications
No full textThe electronization of automobiles is considered to be a revolution in automotive technology development progress. System level integrated circuits are needed to simplify the automotive electronics design and increase the reliability of automobiles. In this thesis, a prototype of a linear voltage regulator is designed for system level integration. Instead of a conventional Internal PMOS or NMOS linear regulator topology, an external NMOS transistor produced by NXP is chosen as the pass device on considerations of certain commercial application. The parasitic inductance and capacitors of PCB traces and packaging are both modeled and calculated. The requirement differences of internal and external NMOS linear regulators are compared. This external NMOS transistor complicates the high-frequency design of this voltage regulator. The development of frequency compensation strategies as well as their implementation is the core of this work. Based on transistor models made by the author and the Root-Locus analysis method, the effectiveness of conceptual active compensation is examined in this thesis, and a passive frequency compensation scheme is proposed. This proposed scheme is not only able to accommodate the wide variation of load capacitor (470nF to 47μF) and the wide variation of load current (0 to 250mA) but also able to be compatible with the external NMOS. The effectiveness of passive frequency compensation is examined by both Root Locus analysis and transistor level simulation. The over-current protection of the NMOS linear regulator is also designed, which is realized by applying another current regulation loop to the voltage regulator. This voltage regulator is able to maintain a constant output current around 400mA in over-current protection scenario. The regulator quiescent current is 10μA, the output voltage accuracy is ±2%. At the end of this thesis, the performance aspects are discussed and analyzed, and the influence of parasitic PCB trace and packaging is examined.Electrical Engineering, Mathematics and Computer ScienceMicroelectronic
UAV Camera System for Object Searching and Tracking
No full textAn embedded electronic camera system for unmanned aerial vehicles (UAV) was developed in the scope of the final bachelor project at the TU Delft in 2012. The aim of the project was to develop a prototype for a new UAV competition. The electronic system of the prototype had to able to track an object, make a picture of it and send it to a ground station, where the picture and flight data is visualized. To whole project is divided into three subgroups each designing a specific part of the system. This thesis provides the design choices and performance results regarding the image processing and object detection of the whole system. It was considered that a literature study would usefully supplement the choice of hard- and software. The literature study was extended by creating an overview of existing hardware for embedded video processing. To perform embedded image processing the hardware components were selected first. It was decided that the system consists out of a camera, a processing board and a power converter. As camera a webcam was chosen, because it is robust, fast, small and it has the ability to buffer data, so no buffering on the processing board was needed. The Beagleboard, an ARM based prototyping board, was picked as a processing board, because it is the fastest of the compared boards. Furthermore it doesn’t use much power, is compatible with the hardware used by the other project groups and enough drivers for peripheral devices are available. A buck converter was selected to down convert the voltage of a battery to the lower input voltage needed by the Beagleboard, as it had the highest efficiency of the considered converters. The Beagleboard had to be capable of multiple sensor communication, real time image processing and running location and velocity estimation algorithms. It was decided to run Linux on the Beagleboard, because it allows high level programming. For prototyping reasons, C++ was used to implement the algorithms, because it is easy to implement, fast and can be handled well by the Beagleboard. The Open Computer Vision library was selected to make the implementation of the readout of the webcam fast and the implementation of the algorithms facile. Algorithms were implemented for colour detection, real location estimation of the object and velocity estimation. Different object detection approaches were considered and colour detection by thresholding each pixel of the captured video frame, was selected as the most convenient algorithm, because it is the fastest and least complex algorithm of the compared methods. The design brief laid explicit constraints on a high frame rate such that colour thresholding was selected, as being the fastest algorithm. The pixel coordinate of the object in the frame was found by a centre of mass calculation of the selected pixels. A moving average filter was implemented to remove noise from the object detection algorithm. Trigonometric based algorithms were deduced to estimate the real location from the pixel coordinates. The velocity of the object was found by the displacement of the object between two frames over the time between those frames. The designed prototype was tested in two different approaches; a test setup with a static camera and one with a moving camera, mounted on a quadrocopter. In both configurations it was shown the built system is capable of reliable object detection, location and velocity estimation. From the results of these experiments, it could be concluded that the system can achieve an accuracy of up to 99 % in the static and 90 % in the moving camera setup for the estimation of both the location and the velocity. Furthermore, around 14 frames per second on a resolution of 320 x 240 could be processed using the Beagleboard and running all algorithms described above. The prototype built within this bachelor project and documented in this thesis, is able to fulfil the tasks defined in the assignment. It therefore meets the specifications regarding the image processing and object detection defined in the design brief of the clients. Some suggestions for future improvements of the system are testing it on the fixed wing UAV and further enhancing and optimizing the various algorithms. Although the system is not ready for the UAV competition yet, the first milestone on the way to a UAV with camera system has been reached within this thesis. The work performed in the scope of this thesis clearly contributed to the electronic system of the final fixed wing UAV demonstrating the task of the new UAV competition.Electrical EngineeringElectrical Engineering, Mathematics and Computer Scienc
"Even if the test result is negative, they should be able to tell us what is wrong with us": a qualitative study of patient expectations of rapid diagnostic tests for malaria.
No full textBACKGROUND: The debate on rapid diagnostic tests (RDTs) for malaria has begun to shift from whether RDTs should be used, to how and under what circumstances their use can be optimized. This has increased the need for a better understanding of the complexities surrounding the role of RDTs in appropriate treatment of fever. Studies have focused on clinician practices, but few have sought to understand patient perspectives, beyond notions of acceptability. METHODS: This qualitative study aimed to explore patient and caregiver perceptions and experiences of RDTs following a trial to assess the introduction of the tests into routine clinical care at four health facilities in one district in Ghana. Six focus group discussions and one in-depth interview were carried out with those who had received an RDT with a negative test result. RESULTS: Patients had high expectations of RDTs. They welcomed the tests as aiding clinical diagnoses and as tools that could communicate their problem better than they could, verbally. However, respondents also believed the tests could identify any cause of illness, beyond malaria. Experiences of patients suggested that RDTs were adopted into an existing system where patients are both physically and intellectually removed from diagnostic processes and where clinicians retain authority that supersedes tests and their results. In this situation, patients did not feel able to articulate a demand for test-driven diagnosis. CONCLUSIONS: Improvements in communication between the health worker and patient, particularly to explain the capabilities of the test and management of RDT negative cases, may both manage patient expectations and promote patient demand for test-driven diagnoses
A Robotic Arm for Zebro
No full textThis thesis describes the choices, the implementation and the testing of the robotic arm for the Zebro. The Zebro is a rover designed for the European Rover Challenge (ERC). The design of the arm should be modular and be able to perform the tasks of the ERC. An arm was designed with five degrees of freedom. The motors chosen to drive the joints are of the brushless DC type. The control system to control the joints is implemented using a fuzzy P controller and the driver electronics are built on a PCB. The internal communication in the arm is done using the I2C protocol. Two master devices were defined in the base and in the end effector, the individual joints and temperature sensors are connected as slaves. The method of reduction of degrees of freedom is chosen as a way to solve the inverse kinematics problem. The constraints in order to implement trajectory planning is based on the stability of the Zebro during operation. A test plan is written and most tests are performed. It is found that the PCB did not function properly due to design errors. The motor control does function as expected.ElektronicaElektronicaElectrical Engineering, Mathematics and Computer Scienc
AR.Drone autonomous control and position determination
No full textIn this thesis first a study is conducted on which position determination method should be used in a UAV and especially in the Parrot AR.Drone. Then an autonomous control for the AR.Drone is designed. The best position determination method in this case appeared to be a combination of a GPS sensor and a barometer. The autonomous control is designed with a three layer model. The four control parameters of the Parrot AR.Drone are controlled by this control model.Electrical EngineeringElectrical Engineering, Mathematics and Computer Scienc
Zebro Drive System
No full textDit document beschrijft de ontwerpkeuzes die gemaakt zijn bij het ontwerpen van het systeem dat zorgt voor de voortbeweging van de Zebro. De 'Zebro Explorer' is een robot die gemaakt wordt om mee te doen aan de European Rover Challenge. Voor deze wedstrijd dient een Mars rover equivalent gebouwd te worden die verschillende taken kan uitvoeren, zoals het nemen van grondmonsters, het vervoeren daarvan en het instellen en in werking stellen van een reactor. De beschreven ontwerpkeuzes betreffen de motor met bijbehorende motorbesturing, zowel de hardware als de software.ElectronicaElectronicaElectrical Engineering, Mathematics and Computer Scienc
UAV IR & Zigbee based Object Tracking
No full textIn deze thesis laten we zien hoe we een sensor-node hebben ontwikkeld om te gebruiken in een Self Deploying Sensor Swarm (SDSS). Het doel van de opdracht is een systeem te maken dat het concept van follow-the-data demonstreert ter inspiratie voor verder onderzoek. De opdracht is opgesplitst in drie delen. Een deel intelligentie, een deel aansturing van de Unmanned Aerial Vehicles (UAV’s) en de in deze thesis behandelde positiebepaling van de crawlers. Deze crawlers zijn de objecten die vrij door het veld bewegen en moeten in de demonstratie de data representeren. Voor het bepalen van de positie van de crawlers maken we gebruik van poolcoördinaten. Op die manier bepalen we de relatieve positie ten opzichte van de UAV. Voor het bewijzen van het concept is meer niet nodig en is dit ook stukken flexibeler. De hoek ten opzichte van de UAV bepalen we middels meerdere Infrarood (IR)-sensoren. Door deze in verschillende richtingen te plaatsen kunnen we aan de hand van de ontvangen signalen bepalen in welke richting een crawler zich bevindt. Voor het bepalen van de afstand maken we gebruik van een ZigBee-module. Deze kan de Received Signal Strength Indication (RSSI) van een verzonden bericht bepalen. Door een meting en kalibratie van de RSSI kunnen we in een omgeving geschikt voor de demonstratie bepalen wat de afstand tot de crawler is. Dit geheel is te integreren tot een complete sensor-node welke onder elke UAV te plaatsen is. In deze demo maken we voor de UAV’s gebruik van quadcoptersElectronics Research LaboratoryMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
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