Techn. Universiẗat, Diss., 2005--Chemnitz.

Universiẗat Diss., 2005--Bonn.

Techn. Universiẗat, Diss., 2005--Chemnitz.

abstract: The work presented in this manuscript has the overarching theme of radiation. The two forms of radiation of interest are neutrons, i.e. nuclear, and electric fields. The ability to detect such forms of radiation have significant security implications that could also be extended to very practical industrial applications. The goal is therefore to detect, and even image, such radiation sources. The method to do so revolved around the concept of building large-area sensor arrays. By covering a large area, we can increase the probability of detection and gather more data to build a more complete and clearer view of the environment. Large-area circuitry can be achieved cost-effectively by leveraging the thin-film transistor process of the display industry. With production of displays increasing with the explosion of mobile devices and continued growth in sales of flat panel monitors and television, the cost to build a unit continues to decrease. Using a thin-film process also allows for flexible electronics, which could be taken advantage of in-house at the Flexible Electronics and Display Center. Flexible electronics implies new form factors and applications that would not otherwise be possible with their single crystal counterparts. To be able to effectively use thin-film technology, novel ways of overcoming the drawbacks of the thin-film process, namely the lower performance scale. The two deliverable devices that underwent development are a preamplifier used in an active pixel sensor for neutron detection and a passive electric field imaging array. This thesis will cover the theory and process behind realizing these devices. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

abstract: Electric field imaging allows for a low cost, compact, non-invasive, non-ionizing alternative to other methods of imaging. It has many promising industrial applications including security, safely imaging power lines at construction sites, finding sources of electromagnetic interference, geo-prospecting, and medical imaging. The work presented in this dissertation concerns low frequency electric field imaging: the physics, hardware, and various methods of achieving it. Electric fields have historically been notoriously difficult to work with due to how intrinsically noisy the data is in electric field sensors. As a first contribution, an in-depth study demonstrates just how prevalent electric field noise is. In field tests, various cables were placed underneath power lines. Despite being shielded, the 60 Hz power line signal readily penetrated several types of cables. The challenges of high noise levels were largely addressed by connecting the output of an electric field sensor to a lock-in amplifier. Using the more accurate means of collecting electric field data, D-dot sensors were arrayed in a compact grid to resolve electric field images as a second contribution. This imager has successfully captured electric field images of live concealed wires and electromagnetic interference. An active method was developed as a third contribution. In this method, distortions created by objects when placed in a known electric field are read. This expands the domain of what can be imaged because the object does not need to be a time-varying electric field source. Images of dielectrics (e.g. bodies of water) and DC wires were captured using this new method. The final contribution uses a collection of one-dimensional electric field images, i.e. projections, to reconstruct a two-dimensional image. This was achieved using algorithms based in computed tomography such as filtered backprojection. An algebraic approach was also used to enforce sparsity regularization with the L1 norm, further improving the quality of some images. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

Orientador: Celio Pasquini / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-15T04:25:20Z (GMT). No. of bitstreams: 1 Giachero_EduardoAlberto_M.pdf: 1521995 bytes, checksum: a202ae1d4c48dbb8607d5b36532d118a (MD5) Previous issue date: 2009 / Resumo: Este trabalho propõe o projeto e construção de um espectrofotômetro infravermelho próximo (NIR), compacto e de baixo custo, e a avaliação do seu desempenho na determinação de propriedades físico-químicas de combustíveis líquidos derivados do petróleo, visando a utilização do equipamento no controle dos processos de fabricação destes combustíveis. Na fase inicial do trabalho, foram investigados os tipos mais representativos de espectrofotômetros NIR utilizados atualmente pela indústria, analisando vantagens e desvantagens para auxiliar na definição dos componentes básicos do protótipo. Numa segunda etapa do projeto, foi executada a montagem de um protótipo baseado num detector de arranjo de sensores de PbS operando na faixa espectral de 2.100 a 2.500 nm, com a finalidade de determinar os parâmetros básicos do desempenho do equipamento (linearidade, repetibilidade, ruído e estabilidade do sinal). Numa terceira etapa foram introduzidas melhoras significativas no controle de temperatura do detector e optou-se pela mudança da faixa espectral de trabalho para 1600 a 2000 nm. Na última etapa foram construídos modelos PLS multivariados empregando-se espectros de 90 amostras de óleo diesel, visando a determinação de 5 parâmetros de qualidade deste combustível (índice de cetano e temperaturas de destilação de 10, 50, 85 e 90 % do volume do diesel). Os resultados obtidos foram comparados com os obtidos por um instrumento FT-NIR comercial, verificando-se desempenho equivalente. Os erros de estimação obtidos no protótipo (RMSECV) foram de 0,41 para o índice de cetano e de 3,1, 2,6, 3,4 e 4,0 °C para as temperaturas de destilação de 10, 50, 85 e 90 % do volume do diesel, respectivamente. Estes valores são inferiores ao erro de reprodutibilidade dos métodos analíticos de referência especificados pelas normas D86 e D4737 da ASTM. / Abstract: This work proposes the design and construction of a compact and low cost near infrared (NIR) spectrophotometer, and the evaluation of its performance in determination of physico-chemical properties of liquids fuels derived from petroleum with the aim of using the instrument in the process control of production of these fuels. In the initial step of this work, the more representatives NIR spectrophotometers used by the industry were investigated, analyzing their advantages and disadvantages to help in the definition of the basics components of the prototype. In a second step, a prototype was assembled using a PbS array detector, working in a spectral range from 2100 to 2500 nm to determine the basic parameters of system performance (linearity, repeatibility, signal noise, stability). In a third step, a critical improvement was made to better control the detector temperature. The spectral range was changed to 1600 ¿ 2000 nm, too. In the last step, PLS multivariate models were developed using the spectra set obtained for 90 samples of diesel with the objective of determine 5 quality parameters of this fuel (cetane index, distillation temperatures of 10, 50, 85 and 90% volume of diesel). The results were compared with those obtained by an FT-NIR commercial instrument, achieving equivalent performance. The estimated error obtained for the prototype (RMESV) were 0.41 to the cetane index and 3.1, 2.6, 3.4 and 4.0 for the distillation temperatures of 10, 50, 85 and 90% volume of diesel, respectively. These values are under the reproductibility error of the reference analytical methods especified by the D86 and D4737 ASTM standards. / Mestrado / Quimica Analitica / Mestre em Química

This thesis explains the design, fabrication and characterization steps of a high dynamic range CMOS-MEMS capacitive accelerometer array and on-chip environmental sensors for bias drift compensation. Inertial navigation under harsh environments requires a high dynamic range accelerometer that can survive and provide continuous readout accuracy through shock events, while having a large dynamic range to capture fine-scale motions. The dynamic range target is set as 156 dB in accordance with navigation standard macro-electromechanical accelerometers, which corresponds to around 1 mG acceleration resolution in 50 kG input range. The small accelerometer cell design ensures shock survivability (e.g. up to 50 kG) by keeping the stress at the anchors below the fracture strength of thin-film oxide. Arraying multiple accelerometer cells in parallel lowers the fundamental thermomechanical noise limit set by the small mass of the individual accelerometer cells. Resonance frequency staggering between accelerometer cells suppresses ring-down oscillations. Parasitic capacitance of the high-impedance transduction signal is important to mitigate; undercut of the underlying silicon substrate and an aluminum etch of the top metal layer, incorporated in the CMOS-MEMS process flow, reduces the parasitic capacitance and improves sensitivity. PTAT temperature sensors, piezoresistive stress sensors and resonator-oscillators integrated across the accelerometer chip provide high-resolution environmental measurements for the compensation of long-term bias and scale factor drift. Simultaneous measurements from the accelerometer and environmental sensors demonstrate the correlation between environmental variations and long-term drift. Finite-element analysis shows that the scale factor stability of the accelerometer can be improved up to 1 ppm given the sensor array’s measurement resolution. The CMOS-MEMS accelerometer system-on-chip is fabricated in a TowerJazz 0.18 μm CMOS process. The post-CMOS MEMS processing steps are tuned to reduce the top metal milling and sidewall polymer deposition. A reactive ion etch recipe is developed for the removal of the top metal in order to reduce the parasitic capacitance and eliminate the risk of metal creep at spring beam anchors, thereby improve the bias stability. The PTAT temperature sensors have 3.1 mV/K measured sensitivity and 7.1 mK resolution with high repeatability. The compensation of the accelerometer readout for temperature variations down to 7.1 mK translates to 2.6 ppm scale factor stability for the accelerometer. The characterization of the stress sensors through the application of normal stress on the device package leads to an uncertainty in the amount of stress transferred to the stress sensors on the chip surface. The maximum measured stress sensitivity is 36.5 pV/Pa, which leads to 24.7 kPa stress resolution and translates to 1.7 ppm scale factor stability for the accelerometer without taking the stress attenuation into account. The measured sensitivity sets a lower bound on the sensitivity of the stress sensors implying that the stress resolution and the corresponding accelerometer scale factor stability is higher in practice. The measured frequency stability of the resonator-oscillator is 0.4 ppm, thereby the resonance frequency based variations of the accelerometer readout can be compensated to reach up to 0.8 ppm scale factor stability. However, the initial drift in the resonance frequency of the oscillators due to dielectric charging requires a long wait-time before these sensors can be used for accelerometer drift compensation. The accelerometer array is demonstrated to have 23.7 mG/√Hz noise floor and 70 mG bias stability. The maximum input acceleration applied on the device is limited to 4 kG by the split Hopkinson bar test setup. Improvement of the setup to transfer acceleration amplitudes up to 50 kG should validate the designed input range of the accelerometer array and lead to 117 dB dynamic range for the current design. The measurement bandwidth is fundamentally set by the 126 kHz resonance frequency of the accelerometer cells and can be further limited by filtering the readout signal to attenuate the transient oscillations faster. The nonlinearity of the accelerometer response is better than 1.2% in ±10 kG input range; however, it gets up to 19.0% in ±50 kG maximum input range. The long term bias drift of the accelerometer is shown to be correlated with the temperature and stress variations. Compensation of the accelerometer readout based on the stress and temperature sensor measurements leads to an observable improvement in the long term drift. However, the bias stability of the accelerometer is limited by excessive flicker noise in the system, which is believed to result from noise folding from higher frequencies. Suppression of the flicker noise in the system should allow for a more detailed study of the effect of environmental variations on the accelerometer readout and evaluation of more elaborate fitting algorithms for model based prediction and compensation of the bias drift to reach the target bias stability and dynamic range.

The work deals with n-channel system enabling many sample analysis at sort time from sensor array using electrochemical methods. The 8x12 sensor arrays are formed from 3 electrodes system created on PCB which can be used for heavy metal analysis and toxic substances determination. The control unit switches each 3 electrode sensor to 8 channel precise potentiostat which was designed for electrochemical analysis with current sensitivity below 10 pA. The potentiostat can synchronize with control unit. Developed system is able to measure up to eight single inputs and may be simply converted to measure other nonchemical values. Measured data will be sent to user-friendly application in computer and analyzed or saved consequently.

No description available.

Since early 1960s, ultrasound has become one of the most widely used medical imaging device as a diagnostic tool or an image guider for surgical intervention because of its high portability, non-ionization, non-invasiveness and low cost. Although continuous improvements in commercial equipments have been underway for many years, almost all systems are developed with pulse-echo geometry. In this research, a newly invented ultrasound sensor array was incorporated into the developments of a projection imaging system. Three C-scan prototypes, which included prototypes #1, #2 and an ultrasound mammography system, were constructed. Systematic and Evaluative studies included ultrasound CT, 3-D ultrasound, and multi-modality investigations were also performed. Furthermore, a new analytical method to model ultrasound forward scattering distribution (FSD) was developed by employing a specific annular apparatus. After applying this method, the scattering-corrected C-scan images revealed more detail structures as compared to unprocessed images. This new analytical modelling approach is believed to be effective for most imaging systems operating in projection geometry. In summary, while awaiting additional clinical validation, the C-scan ultrasound prototypes with the state-of-the-art PE-CMOS sensor arrays can provide veritable value and holds real and imminent promise in medical diagnostic imaging. Potential future uses of C-scan ultrasound include but not limit to computerized tomography, biopsy guidance, therapeutic device placing, foreign object detection, pediatric imaging, breast imaging, prostate imaging, human extremities imaging and live animal imaging. With continuous research and development, we believe that C-scan ultrasound has the potential to make a significant impact in the field of medical ultrasound imaging. / Ph. D.