A conceptual design tool: Sketch and fuzzy logic based system

A real time sketch and fuzzy logic based prototype system for conceptual design has been developed. This system comprises four phases. In the first one, the system accepts the input of on-line free-hand sketches, and segments them into meaningful parts by using fuzzy knowledge to detect corners and inflection points on the sketched curves. The fuzzy knowledge is applied to capture user’s drawing intention in terms of sketching position, direction, speed and acceleration. During the second phase, each segmented sub-part (curve) can be classified and identified as one of the following 2D primitives: straight lines, circles, circular arcs, ellipses, elliptical arcs or B-spline curves. Then, 2D topology information (connectivity, unitary constraints and pairwise constraints) is extracted dynamically from the identified 2D primitives. From the extracted information, a more accurate 2D geometry can be built up by a 2D geometric constraint solver. The 2D topology and geometry information is then employed to further interpretation of a 3D geometry. The system can not only accept sketched input, but also users’ interactive input of 2D and 3D primitives. This makes it friendly and easier to use, in comparison with ‘sketched input only’, or ‘interactive input only’ systems. Finally, examples are given to illustrate the system

Effective 3D Geometric Matching for Data Restoration and Its Forensic Application

3D geometric matching is the technique to detect the similar patterns among multiple objects. It is an important and fundamental problem and can facilitate many tasks in computer graphics and vision, including shape comparison and retrieval, data fusion, scene understanding and object recognition, and data restoration. For example, 3D scans of an object from different angles are matched and stitched together to form the complete geometry. In medical image analysis, the motion of deforming organs is modeled and predicted by matching a series of CT images. This problem is challenging and remains unsolved, especially when the similar patterns are 1) small and lack geometric saliency; 2) incomplete due to the occlusion of the scanning and damage of the data. We study the reliable matching algorithm that can tackle the above difficulties and its application in data restoration. Data restoration is the problem to restore the fragmented or damaged model to its original complete state. It is a new area and has direct applications in many scientific fields such as Forensics and Archeology. In this dissertation, we study novel effective geometric matching algorithms, including curve matching, surface matching, pairwise matching, multi-piece matching and template matching. We demonstrate its applications in an integrated digital pipeline of skull reassembly, skull completion, and facial reconstruction, which is developed to facilitate the state-of-the-art forensic skull/facial reconstruction processing pipeline in law enforcement

Sistema Anti-Melgas I: identificação e localização de fontes sonoras

This dissertation addresses the development of an acoustic localisation system with the aim of detecting mosquitoes indoors. It starts with a brief study of the sound produced by insects, with special focus on the case of female mosquitoes, aimed at understanding the spectral characteristics; A review was carried out on our auditory system and its ability to spatially locate sound sources. The main 2D cues are ITD (interaural time difference) and ILD (interaural level difference). The example of human hearing shows how spatial diversity of sensors is indispensable for sound localisation; A 2D scenario was assumed, thus reducing the problem to azimuth estimation, which requires two microphones. Assuming that the distance from the source to the receiver is much greater than the distance between microphones (far-field approximation) the sought azimuth angle can be obtained by an approximate formula. The intrinsic error caused by the far-field approximation itself was assessed, as well as the impact of possible estimation errors in the calculation parameters: speed of sound, microphone spacing and time delay; The development work, carried out on a MATLAB environment, was based on an existing simulator. The central element of the system is the digital processing of the signals received at the two microphones. The cross-correlation method is used to work out the time delay between them. Interpolation was applied to increase the resolution of the cross-correlation peak estimate; A script featuring a graphical interface was developed to combine the predictor with the simulator. It makes it easy for the user to specify the trajectory to be reproduced in the simulator. The audio file to be injected is also chosen by the user. The simulator returns a stereo file with the microphone signals. The script generates a pointer moving in real time to indicate the estimated position of the source; Several other simulations and experimental tests were carried out, based on an anechoic room without additional sources of noise. The azimuth estimation error measured in simulation confirmed the predicted behaviour taking into account the sources of error intrinsic to the far-field approximation. The error is smaller when the source is between 45° and 135°. Outside this range, it increases, peaking at the extremes (0° and 180°). It approaches zero when the source is at 90°, forming a symmetric U-shaped pattern around this value. When noise is introduced, the estimations made lose quality, as expected; for SNR less than -10 dB, the error exceeds 10°; The experimental tests involved two microphones, a loudspeaker and an audio interface for communication with the computer. An absorbing chamber has been created to reduce sound reflections and external noise. Recordings of long duration were made for each azimuth angle. With all the files processed, the pattern of the azimuth estimation error was also U-shaped, although not perfectly symmetric.Esta dissertação aborda o desenvolvimento de um sistema de localização acústica com o objectivo de detectar mosquitos dentro de casa. Começou com um breve estudo do som produzido pelos insectos, especialmente os mosquitos fêmea, com o objectivo de compreender as características espectrais; Foi realizada uma revisão do nosso sistema auditivo e da sua capacidade de localizar espacialmente fontes sonoras. As principais pistas 2D são ITD (interaural time difference) e ILD (interaural level difference). O exemplo da audição humana mostra como a diversidade espacial dos sensores é indispensável para a localização do som; Assumiu-se um cenário 2D, reduzindo assim o problema da estimativa de azimute, que requer dois microfones. Assumindo que a distância da fonte ao receptor é muito maior do que a distância entre microfones (aproximação “far-field”), o ângulo de azimute procurado pode ser obtido através de uma fórmula aproximada. Foi avaliado o erro intrínseco causado pela própria aproximação “far-field”, bem como o impacto de possíveis erros na estimativa dos parâmetros de cálculo: velocidade do som, espaçamento entre microfones e atraso temporal; O trabalho de desenvolvimento, realizado no ambiente MATLAB, foi baseado num simulador existente. O elemento central do sistema é o processamento digital dos sinais recebidos nos dois microfones. O método de correlação cruzada é utilizado para calcular o tempo de espera entre eles. A interpolação foi aplicada para aumentar a resolução da estimativa do pico de correlação cruzada; Foi desenvolvido um script com uma interface gráfica para combinar o preditor com o simulador. Facilita ao utilizador a especificação da trajectória a reproduzir no simulador. O ficheiro de áudio a ser injectado é também escolhido pelo utilizador. O simulador devolve um ficheiro estéreo com os sinais do microfone. O script gera um ponteiro que se move em tempo real para indicar a posição estimada da fonte; Foram realizadas simulações e testes experimentais, numa sala anecóica sem fontes adicionais de ruído. O erro da estimativa de azimute medido na simulação confirmou o comportamento previsto, tendo em conta as fontes de erro intrínsecas à aproximação “far-field”. O erro é menor quando a fonte se situa entre 45° e 135°. Fora deste intervalo, aumenta, atingindo um pico nos extremos (0° e 180°). Aproxima-se de zero quando a fonte está a 90°, formando um padrão simétrico em forma de U em torno deste valor. Quando o ruído é introduzido, as estimativas feitas perdem qualidade, como esperado; para SNR inferior a -10 dB, o erro ultrapassa os 10°; Os testes experimentais consistiram em dois microfones, um altifalante e uma interface de áudio para comunicar com o computador. Foi criada uma câmara de absorção para reduzir os reflexos acústicos e o ruído externo. Foram feitas gravações para cada ângulo de azimute, com longa duração. Com todos os ficheiros processados, o padrão do erro de estimativa do azimute também teve a forma de U, embora não tenha tido uma simetria perfeita.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Seismological data acquisition and signal processing using wavelets

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This work deals with two main fields: a) The design, built, installation, test, evaluation, deployment and maintenance of Seismological Network of Crete (SNC) of the Laboratory of Geophysics and Seismology (LGS) at Technological Educational Institute (TEI) at Chania. b) The use of Wavelet Transform (WT) in several applications during the operation of the aforementioned network. SNC began its operation in 2003. It is designed and built in order to provide denser network coverage, real time data transmission to CRC, real time telemetry, use of wired ADSL lines and dedicated private satellite links, real time data processing and estimation of source parameters as well as rapid dissemination of results. All the above are implemented using commercial hardware and software which is modified and where is necessary, author designs and deploy additional software modules. Up to now (July 2008) SNC has recorded 5500 identified events (around 970 more than those reported by national bulletin the same period) and its seismic catalogue is complete for magnitudes over 3.2, instead national catalogue which was complete for magnitudes over 3.7 before the operation of SNC. During its operation, several applications at SNC used WT as a signal processing tool. These applications benefited from the adaptation of WT to non-stationary signals such as the seismic signals. These applications are: HVSR method. WT used to reveal undetectable non-stationarities in order to eliminate errors in site’s fundamental frequency estimation. Denoising. Several wavelet denoising schemes compared with the widely used in seismology band-pass filtering in order to prove the superiority of wavelet denoising and to choose the most appropriate scheme for different signal to noise ratios of seismograms. EEWS. WT used for producing magnitude prediction equations and epicentral estimations from the first 5 secs of P wave arrival. As an alternative analysis tool for detection of significant indicators in temporal patterns of seismicity. Multiresolution wavelet analysis of seismicity used to estimate (in a several years time period) the time where the maximum emitted earthquake energy was observed

RFID Gazebo-Based Simulator With RSSI and Phase Signals for UHF Tags Localization and Tracking

Radio Frequency Identification (RFID) technology is becoming very popular in the new era of Industry 4.0, especially for warehouse management, retails, and logistics. RFID systems can be used for objects identification, localization, and tracking, facilitating everyday operators' efforts. However, the deployment of RFID tags and reader antennas in real-world application scenarios is crucial and takes time. Indeed, deciding where to place tags and/or readers' requires examining many conditions. If some weaknesses appear in the design, the arrangement must be reconsidered. The proposed work presents a novel open-source RFID simulator that allows modeling environments and testing the deployment of RFID tags and antennas apriori. In such a way, validating the performance of the localization or tracking algorithms in simulation, possible weaknesses that could arise may be fixed before facilities are applied on the field. Any number of tags and antennas can be placed in any position in the created scenario, and the simulator provides the phase and the RSSI signals for each tag. Every reader antenna is parametrized so that different antennas of different vendors can be reproduced. The simulator is implemented as a plugin of Gazebo, a widely used robotic framework integrated with the Robot Operating System (ROS), to reach a broad audience. In order to validate the simulator, a warehouse scenario is modeled, and a tag localization algorithm that uses the phase unwrapping technique and hyperbolae intersection method employing a reader antenna mounted on a mobile robot is used to estimate the position of the tags deployed in the scenario. The outcomes of the experiments showed realistic results

The exponentially convergent trapezoidal rule

It is well known that the trapezoidal rule converges geometrically when applied to analytic functions on periodic intervals or the real line. The mathematics and history of this phenomenon are reviewed and it is shown that far from being a curiosity, it is linked with computational methods all across scientific computing, including algorithms related to inverse Laplace transforms, special functions, complex analysis, rational approximation, integral equations, and the computation of functions and eigenvalues of matrices and operators

Optimisation of performance in running jumps

Running jumps such as the high jump and the long jump involve complex movements of the human body. The factors affecting performance include approach conditions, strength of the athlete and the muscle activation timings at each joint. In order to investigate the mechanics of jumping performances and the effect of these factors, an eight-segment, subject specific, torque-driven computer simulation model of running jumps was developed, evaluated and used to optimise performances of jumps for height and distance. Wobbling masses within the shank, thigh and trunk segments, and the ground-foot interface were modelled as non-linear spring-damper systems. The values for the stiffness and damping constants were determined through optimisation. The inertia data were obtained from anthropometric measurements on the subject using the inertia model of Yeadon (1990b). Joint torques predicted by the simulation model were expressed as a function of angular velocity and angle using data collected from an isovelocity dynamometer. The simulation model was evaluated by comparing the actual performances with simulations using kinematic and kinetic data collected. Movement of the wobbling masses was found to be in the region of 40 mm in the shank and thigh and 90 mm in the trunk. This movement resulted in a lower, more realistic initial peak in the ground reaction force. Co-contraction was found to occur at the joints during impact in order to increase the initial level of eccentric activation and also the rise time to maximum eccentric activation. Differences of 2% and 1% in the height and distance achieved were obtained between actual performances and simulations. An optimisation procedure was used to maximise the height reached and distance travelled by the mass centre, in simulations of jumps for height and distance respectively, by varying the torque generator activation time histories at each joint. An increase of 12% in the height reached by the mass centre in the jump for height and 14% in the distance reached by the mass centre in the jump for distance were achieved