Dans les crypto-monnaies telles Bitcoin, l’anonymité des utilisateurs peut être compromise de plusieurs façons. Dans ce mémoire, nous effectuons une revue de littérature et une classification des différents protocoles existants pour anonymiser les usagers et analysons leur efficacité. S’appuyant sur certains critères désirables dans de tels protocoles, nous proposons un modèle de mixeur synchrone décentralisé. Nous avons ciblé deux approches qui s’inscrivent dans ce modèle, le plan de transaction et le réseau de transactions, le second étant une contribution originale de ce mémoire. Nous expliquons son fonctionnement puis analysons son efficacité dans le contexte actuel d’utilisation de Bitcoin / In cryptocurrencies such as Bitcoin, the anonymity of the users may be compromised in many ways. In this thesis, we review the literature concerning existing protocols used to increase anonymity by a method called mixing and produce a classification for such protocols. We propose a decentralized synchronous N-to-N mixing model that takes into account many considerations of mixers. We address two frameworks within this model, the transaction blueprint and the network of transactions, the second approach being a new contribution. We explain how it functions and analyse its efficiency in the current Bitcoin ecosystem.

L'agglomération humide est une étape cruciale dans la technologie de mise en forme des poudres de par son fort impact sur la qualité finale des produits élaborés. Malgré son intérêt lors de l'élaboration de nombreux produits (aliment, pharmaceutique, génie civil,…), ainsi que les différents modes technologiques (malaxeurs horizontaux, verticaux, à faible ou fort de taux de cisaillement, lit fluidisé, …), elle reste insuffisamment maîtrisée de par la difficulté à proposer des diagrammes de fonctionnement opérationnels qui couplent les contributions croisées des procédés et des produits. Ce travail de thèse s'inscrit dans cette problématique et porte sur l'étude des mécanismes d'agglomération en lien avec les caractéristiques de la formulation et les paramètres opératoires. L'identification et la représentation du mode d'assemblage des particules au cours de l'opération de mouillage/malaxage est l'un des enjeux central de ce travail. A partir d'expériences menées avec deux types de poudres alimentaires (semoule de blé dur et poudre de lait), l'agglomération est induite soit par contacts humides en malaxeur à faible taux de cisaillement soit par des collisions entre les particules collantes en lit fluidisé. Les mécanismes d'agglomération humide de la semoule de blé dur développés dans un malaxeur à faible cisaillement sont décrits selon un processus de morphogénèse qui corrèle la taille des agglomérats à leur texture via une dimension fractale. L'influence des propriétés physicochimiques des liants liquides sur les mécanismes d'agglomération est étudiée au regard des paramètres du modèle fractal. L'étude fine des distributions des propriétés hydrotexturales et dimensionnelles des structures agglomérées a permis d'identifier leur « règle » d'agencement : association par même classe hydro-texturale et dimensionnelle. Les régimes d'agglomération en fonction du mode d'apport d'eau (débit faible, débit fort) sont étudiés en se basant sur la notion de flux d'atomisation adimensionné. En ce qui concerne l'agglomération de la poudre de lait en lit fluidisé, les mécanismes d'agglomération sont étudiés en suivant l'évolution des tailles et des teneurs en eau des échantillons prélevés durant l'opération de mouillage/séchage et par la suite l'étude de l'impact de certaines conditions opératoires et de formulation sur les propriétés des agglomérats finaux et les régimes d'agglomération. Un lien entre les procédés est discuté et ouvre sur une requalification des régimes d'écoulement granulaire ainsi que de la réactivité de surface des particules. / Wet agglomeration is a crucial step in the shaping technology of powders because of its strong impact on the final quality of the elaborated products. Despite its interest in the elaboration of many products (food, pharmaceutical, engineering,...) as well as different technological process (horizontal mixers, vertical, low or high shear rate, fluidized bed, ...), it remains insufficiently mastered due to the difficulty in establishing operating diagrams taking into account, in the same time, products and process contributions. This thesis focuses on the study of the agglomeration mechanisms related to the characteristics of the formulation and process parameters. The identification and representation of the way particles come together during the wetting / mixing operation is one of the central challenges of this work. From experiments with two different food powders (durum wheat semolina and milk powder), agglomeration is induced either by wet contacts in mixer at low shear rate or by collisions between sticky particles in a fluidized bed. Mechanisms of semolina wet agglomeration developed in a low shear mixer are described as a process of morphogenesis that correlates the agglomerates size to their texture via a fractal dimension. The influence of the liquid binder physicochemical properties on the agglomeration mechanisms is studied according to the values taken by the fractal parameters of the model. The detailed study of the distribution of size and textural properties of agglomerated structures make it possible to identify the rule that lead to their layout: the association is mainly possible between structures belonging to the same class concerning their hydro-textural and dimensional characteristics. Agglomeration regimes depending on the mode of water supply (low flow, high flow) are studied based on the notion of dimensionless spray flux. Concerning milk powder agglomeration in a fluidized bed, agglomeration mechanisms are studied by following the evolution of the size and water content of the samples taken during the operation of wetting / drying and thereafter studying the impact of some operational conditions and formulation on the properties of the final agglomerates and agglomeration regimes. A link between the processes (low shear mixer and fluidized bed) is discussed and opens onto a redefinition of granular flow regimes and the surface reactivity of particles.

The current consumption of the IQ modulator is a significant part of the totalcurrent consumption of a mobile transmitter platform and reducing it is of greatinterest. Also, as the WCDMA/LTE standards specifies full duplex transmissionsand Tx and Rx are most often using the same antenna, it is crucial to have asolution with low noise generation. Two new proposals have been studied with theaim to reduce the current consumption and noise contribution of the IQ modulator. A current mode envelope tracking IQM is the first of the studied designs. Thisimplementation lowers the bias currents in the circuit in relation to the amplitudeof the baseband input signals, meaning that a low input amplitude results in alowering of the current consumption. It proves to be very efficient for basebandsignals with a high peak-to-average ratio. Simulations and calculations have shownthat an average current reduction of 56 % can be achieved for an arbitrary LTEbaseband signal. The second is an entirely new passive mixer design where the baseband voltagesare sequentially copied to the RF node, removing the need for V-to-I conversion inthe mixer which reduces current consumption and noise. Results from simulationshas proven that this design is fully capable of improving both current consumptionas well as the noise levels. With an output power of 4.0 dBm, the power consumptionwas 43.3 mW, including clock generating circuits. This, combined with thefact that the design is small and simple, means that there is definitely a possibilityto replace the present IQM design with a passive mixer.

Inductors are extensively used in the design of radio-frequency circuits. In the last decade, the integration of passive components, especially inductors on silicon chips, has led to the widespread development and implementation of Radio Frequency Integrated Circuits (RFICs) in CMOS technologies. However, on-chip passive inductors occupy a large silicon chip area and hardly scale down with technology scaling. Therefore, on-chip passive inductors become formidable obstacles to the realization of highly dense RFICs to be integrated with other highly dense digital circuits on a single chip using a common fabrication process. In recent years, researchers have focused on replacing passive inductors with transistor-only active circuits, namely active inductors. Active inductors can be realized with only a few transistors, which scale down with technology scaling. Therefore, they occupy a fraction of the chip area of their passive counterparts, and can be implemented densely in CMOS processes. Unlike passive inductors, bias dependent operations of active inductors allow for the tuning of their inductance and quality factor Q, and in turn, tuning the performance parameters of RFICs. This thesis focuses on the design and development of passive inductorless CMOS RFICs for ultra-wideband (UWB) receiver front-ends using active inductors. A new Q-enhanced and a new bandwidth-extended tunable active inductors are designed. Using the Q-enhanced active inductor, two tunable UWB low-noise amplifiers (LNAs) (two-stage and three-stage UWB LNAs), a UWB mixer and a wideband local-oscillator (LO) driver are designed. Active inductors are utilized to develop a novel wideband active shunt-peaking technique that decreases high-frequency losses to yield a flat gain over a wide bandwidth. A tunable multiband-UWB front-end integrating a two-stage UWB LNA, and a pair of UWB mixers driven by a pair of wideband LO drivers, is fabricated in a 90nm digital CMOS process. The passive inductorless two-stage UWB LNA, three-stage UWB LNA and UWB front-end occupy chip areas of only 0.0114mm2, 0.0227mm2, and 0.1485mm2, respectively. The active CMOS UWB front-end exhibits a measured flat gain of 22.5dB over 2.5-8.8 GHz bandwidth, and its tunability allows for varying the gain and bandwidth. / Integrated Circuits and Systems

This thesis describes the specification, design and implementation of a software-defined radio system on a two-channel 14-bit digitizer/generator. The multi-stage interpolations and decimations which are required to operate two analog-to-digital converters at 800 megasamples per second (MSps) and two digital-to-analog converters at 1600 MSps from a 25 MSps software-side interface, were designed and implemented. Quadrature processing was used throughout the system, and a combination of fine-tunable low-rate mixers and coarse high-rate mixers were implemented to allow frequency translation across the entire first Nyquist band of the converters. Various reconstruction filter designs for the transmitter side were investigated and a cheap implementation was done through the use of programmable base-band filters and polynomial approximation.

With the explosive growth in wireless applications, the last decade witnessed an ever-increasing test challenge for radio frequency (RF) circuits. While the design community has pushed the envelope far into the future, by expanding CMOS process to be used with high-frequency wireless devices, test methodology has not advanced at the same pace. Consequently, testing such devices has become a major bottleneck in high-volume production, further driven by the growing need for tighter quality control. RF devices undergo testing during the prototype phase and during high-volume manufacturing (HVM). The benchtop test equipment used throughout prototyping is very precise yet specialized for a subset of functionalities. HVM calls for a different kind of test paradigm that emphasizes throughput and sufficiency, during which the projected performance parameters are measured one by one for each device by automated test equipment (ATE) and compared against defined limits called specifications. The set of tests required for each product differs greatly in terms of the equipment required and the time taken to test individual devices. Together with signal integrity, precision, and repeatability concerns, the initial cost of RF ATE is prohibitively high. As more functionality and protocols are integrated into a single RF device, the required number of specifications to be tested also increases, adding to the overall cost of testing, both in terms of the initial and recurring operating costs. In addition to the cost problem, RF testing proposes another challenge when these components are integrated into package-level system solutions. In systems-on-packages (SOP), the test problems resulting from signal integrity, input/output bandwidth (IO), and limited controllability and observability have initiated a paradigm shift in high-speed analog testing, favoring alternative approaches such as built-in tests (BIT) where the test functionality is brought into the package. This scheme can make use of a low-cost external tester connected through a low-bandwidth link in order to perform demanding response evaluations, as well as make use of the analog-to-digital converters and the digital signal processors available in the package to facilitate testing. Although research on analog built-in test has demonstrated hardware solutions for single specifications, the paradigm shift calls for a rather general approach in which a single methodology can be applied across different devices, and multiple specifications can be verified through a single test hardware unit, minimizing the area overhead. Specification-based alternate test methodology provides a suitable and flexible platform for handling the challenges addressed above. In this thesis, a framework that integrates ATE and system constraints into test stimulus generation and test response extraction is presented for the efficient production testing of high-performance RF devices using specification-based alternate tests. The main components of the presented framework are as follows: Constraint-driven RF alternate test stimulus generation: An automated test stimulus generation algorithm for RF devices that are evaluated by a specification-based alternate test solution is developed. The high-level models of the test signal path define constraints in the search space of the optimized test stimulus. These models are generated in enough detail such that they inherently define limitations of the low-cost ATE and the I/O restrictions of the device under test (DUT), yet they are simple enough that the non-linear optimization problem can be solved empirically in a reasonable amount of time. Feature extractors for BIT: A methodology for the built-in testing of RF devices integrated into SOPs is developed using additional hardware components. These hardware components correlate the high-bandwidth test response to low bandwidth signatures while extracting the test-critical features of the DUT. Supervised learning is used to map these extracted features, which otherwise are too complicated to decipher by plain mathematical analysis, into the specifications under test. Defect-based alternate testing of RF circuits: A methodology for the efficient testing of RF devices with low-cost defect-based alternate tests is developed. The signature of the DUT is probabilistically compared with a class of defect-free device signatures to explore possible corners under acceptable levels of process parameter variations. Such a defect filter applies discrimination rules generated by a supervised classifier and eliminates the need for a library of possible catastrophic defects.

No description available.

Organophosphate (OP) pesticides, as a group, are the most widely used insecticides in Australia. Approximately 5 000 tonnes of active ingredient are used annually (Radcliffe, 2002). The OP pesticide group consists of around 30 identifiably distinct chemicals that are synthesised and added to approximately 700 products (Radcliffe, 2002). OP pesticides are used on fruit, vegetable, grain, pasture seed, ornamental, cotton, and viticultural crops, on livestock and domestic animals, as well as for building pest control. OP pesticides all act by inhibiting the nervous system enzyme acetylcholinesterase (AChE) and as such are termed anticholinesterase insecticides. The phosphorylation of AChE and the resultant accumulation of acetylcholine are responsible for the typical symptoms of acute poisoning with OP compounds. In addition to acute health effects, OP compound exposure can result in chronic, long-term neurological effects. The traditional method of health surveillance for OP pesticide exposure is blood cholinesterase analysis, which is actually biological effect monitoring. However, there are several drawbacks associated with the use of the blood cholinesterase test, including its invasive nature, the need for baseline levels and a substantial exposure to OP pesticide before a drop in cholinesterase activity can be detected. OP pesticides are metabolised fairly rapidly by the liver to form alkyl phosphates (DAPs). Approximately 70% of OP pesticides in use in Australia will metabolise into one or more of six common DAPs. During the last 30 years, scientists have developed a urine test that detects these six degradation products. However, unlike the blood cholinesterase test, there is currently no Biological Exposure Index (BEI) for the urine DAP metabolite test. Workers in the agricultural industry - particularly those involved with mixing, loading and application tasks - are at risk of exposure to OP pesticides. It is therefore important that these workers are able to assess their risk of health effects from exposure to OP pesticides. However, currently in Queensland, workplace health and safety legislation exempts the agricultural industry from hazardous substance legislation that incorporates the requirement to perform risk assessments and health surveillance (blood cholinesterase testing) for OP pesticide exposure. The specific aim of this research was to characterise OP pesticide exposure and to assess the feasibility of using urine DAP metabolite testing as a risk assessment tool for agricultural and related industry workers exposed to OP pesticides. An additional aim among farmers was to conduct an in-depth evaluation of their knowledge, attitudes and behaviours related to handling OP pesticides and how they assess the risks associated with their use of OPs. A cross-sectional study design was used to assess exposure to OP pesticides and related issues among four groups: fruit and vegetable farmers, pilots and mixer/loaders, formulator plant staff and a control group. The study involved 51 farmers in the interviewer-administered questionnaire and 32 in urine sample provision. Eighteen pilots and mixer/loaders provided urine samples and 9 exposed formulation plant staff provided urine and blood samples. Community controls from Toowoomba Rotary clubs provided 44 urine samples and 11 non-exposed formulation plant staff provided blood and urine samples; all groups also provided responses to a self-administered questionnaire. Participant farmers were drawn from the main cropping areas in south-east Queensland - Laidley/Lowood, Gatton, and Stanthorpe. The farmer group was characterised by small owner-operators who often had primary responsibility for OP pesticide mixing and application. Farmers had good knowledge of pesticide-related safety practices; however, despite this knowledge, use of personal protective equipment (PPE) was low. More than half of the farmers did not often wear a mask/respirator (56%), gloves (54%) or overalls (65%). Material Safety Data Sheets were never or rarely read and 88.2% of farmers never or rarely read OP pesticide labels before application. There were also problems with chemical suppliers providing farmers with MSDSs. The majority of farmers (90.2%) reported that they had never had any health surveillance performed and three-quarters had never read about or been shown how to perform a formal risk assessment. The main inhibitors to the use of PPE in the farmers' group included the uncomfortable and cumbersome nature of PPE, especially in hot weather conditions, and the fear of PPE use triggering neighbours' complaints to Government authorities. Factors associated with better PPE use included having positive attitudes and beliefs toward PPE use, higher knowledge scores and low risk perception. Farmers' use of OP pesticides was infrequent, of short duration and involved application via a boom on a tractor, a lower risk application method. Consequently, urine DAP metabolite levels in this group were generally low, with 36 out of 96 samples (37.5%) containing detectable levels. Detectable results ranged from 9.00-116.00 mol/mol creatinine. Formulators exposed to OP pesticides were found to have the highest urine DAP metabolite levels (detectable levels 13.20-550.00 mol/mol creatinine), followed by pilots and mixer/loaders (detectable levels 8.40-304.00 mol/mol creatinine) and then farmers. Despite this, pilots and mixer/loaders (particularly mixer/loaders) had the greatest number of samples containing detectable levels (94.4% of samples). The DAP metabolite most frequently detected across all groups was DMTP, which was the only metabolite found in control samples. Levels found in this study are similar to those reported in international research (Takamiya, 1994, Stephens et al., 1996, Simcox et al., 1999, Mills, 2001, Cocker et al., 2002). The observed DAP levels were not associated with a drop in cholinesterase activity among the formulation plant workers, as expected from the literature. Such exposure also is unlikely to be associated with acute health effects. In contrast, there is insufficient scientific knowledge to know whether levels recorded in this study and elsewhere may be associated with long-term, chronic health effects. Notably, DMTP levels also were observed among the presumably 'unexposed' comparison groups. Environmental background level exposures to OPs producing the DAP metabolite DMTP are therefore of potential significance and may be related, at least in part, to consumption of contaminated fruit and vegetables. There is also emerging evidence to suggest that exposure to DAP metabolites themselves through diet and other sources may contribute to the concentration of DAPs, including DMTP in urine, potentially complicating assessment of occupational exposures. Nevertheless, the urine DAP metabolite test was a useful, sensitive indicator of occupational OP pesticide exposure among agricultural workers and may be of use to the industry as part of the risk assessment process. Future research should aim to establish a BEI for the urine DAP test.

Os requisitos de linearidade e ruído em aplicações multi-banda e multi-protocolo fazem que o projeto de misturadores RF seja uma tarefa muito desafiadora. Nesta dissertação dois misturadores com base na topologia célula de Gilbert são propostas. Linearidade e ruído foram as principais figuras de mérito consideradas para o misturadores propostos. Para aumento linearidade, foi utilizada uma técnica de cancelamento de harmônicas pós-distorção (PDHC). E, para redução de ruído, foi utilizado um circuito de redução dinâmica de corrente combinada com um filtro LC sintonizado na frequência do LO e cancelamento de ruído térmico. A análise por séries Volterra do estágio transcondutância do misturador proposto é reportada para mostrar a eficácia da técnica de cancelamento de harmônicos com pósdistorção. O circuito de linearização adicionado não aumenta o tamanho do misturador, nem degrada ganho de conversão, figura de ruído, ou consumo de potência. Simulações elétricas foram realizadas em nível de pós-layout para a primeira topologia e nível esquemático para a segunda topologia, usando processo CMOS de 0.13 mm da IBM. As melhorias em IIP2 e IIP3 são apresentadas em comparação com o misturador do tipo célula de Gilbert convencional. Para a primeira topologia, foi obtido um ganho de conversão de 10.2 dB com uma NF de 12 dB para o misturador projetado funcionando a 2 GHz, com uma frequência intermediária de 500 kHz. E um IIP2 e IIP3 de 55 dBm e 10.9 dBm, respectivamente, consumindo apenas 5.3 mW de uma fonte de 1.2 V. Para a segunda topologia, foram obtidos um ganho de conversão de [13.8 ~11] dB, um coeficiente de reflexão na entrada (S11) de [-18 ~-9.5] dB e um NF de [8.5 ~11] dB no intervalo de 1 a 6 GHz. Para as especificações de linearidade, um valor médio de IIP3 de 0 dBm foi alcançado para toda a faixa de frequência, consumindo 19.3 mW a partir de uma fonte de 1.2 V. Especificações adequadas para operação multi-banda e multi-protocolo. / The linearity and noise requirements in multi-band multi-standard applications make the design of RF CMOS mixers a very challenging task. In this dissertation two downconversion mixers based on the Gilbert-cell topology are proposed. Linearity and noise were the principal figures of merit for the proposed mixers. For linearity improvement, post distortion harmonic cancellation (PDHC) was employed. And, for noise reduction, dynamic current injection combined with an LC filter tuned at the LO frequency and thermal-noise cancellation were used. A Volterra series analysis of the transconductance stage is reported to show the effectiveness of the post-distortion harmonic cancellation technique. The added linearization circuitry does not increase the size of the mixer, nor does it degrade conversion gain, noise figure, or power consumption. Electrical simulations were performed on extracted layout level from the first topology and schematic level from the second topology. Using an IBM 0.13 mm CMOS process improvements on IIP3 and IIP2 in comparison to the conventional Gilbert-cell mixer are demonstrated. For the first topology, we achieved a conversion gain of 10.2 dB with a NF of 12 dB for the designed mixer working at 2 GHz, with a low-IF of 500 kHz and an IIP2 and IIP3 of 55 dBm and 10.9 dBm, respectively, while consuming only 5.3 mW from a 1.2 V supply. For the second topology, we achieved a conversion gain range of [13.8 ~11] dB, an input reflection coefficient (S11) of [-18 ~-9.5] dB and a NF of [8.5 ~11] dB in the frequency range of 1 to 6 GHz. For the linearity specs, an IIP3 of 0 dBm was achieved for the whole frequency range, while consuming 19.3 mW from a 1.2 V supply, making the second topology well suited for multi-band and multi-standard operation.

High-speed and high-resolution digital-to-analog converters (DACs) are vital components in all telecommunication systems. Radio-frequency digital-to-analog converter (RFDAC) provides high-speed and high-resolution conversion from digital domain to an analog signal. RFDACs can be employed in direct-conversion radio transmitter architectures. The idea of RFDAC is to utilize an oscillatory pulse-amplitude modulation instead of the conventional zero-order hold pulse amplitude modulation, which results in DAC output spectrum to have high energy high-frequency lobe, other than the Nyquist main lobe. The frequency of the oscillatory pulse can be chosen, with respect to the sample frequency, such that the aliasing images of the signal at integer multiples of the sample frequency are landed in the high-energy high-frequency lobes of the DAC frequency response. Therefore the high-frequency images of the signal can be used as the output of the DAC, i.e., no need to the mixing stage for frequency up-conversion after the DAC in the radio transmitter. The mixing stage however is not eliminated but it is rather moved into the DAC elements and therefore the local oscillator (LO) signal with high frequency should be delivered to each individual DAC element. In direct-conversion architecture of IQ modulators which utilize the RFDAC technique, however, there is a problem of finite image rejection. The origin of this problem is the different polarity of the spectral response of the oscillatory pulse-amplitude modulation in I and Q branches. The conditions where this problem can be alleviated in IQ modulator employing RFDACs is also discussed in this work. ΣΔ modulators are used preceding the DAC in the transmitter chain to reduce the digital signal’s number of bits, still maintain the same resolution. By utilizing the ΣΔ modulator now the total number of DAC elements has decreased and therefore the delivery of the high-frequency LO signal to each DAC element is practical. One of the costs of employing ΣΔ modulator, however, is a higher quantization noise power at the output of the DAC. The quantization noise is ideally spectrally shaped to out-of-band frequencies by the ΣΔ modulator. The shaped noise which usually has comparatively high power must be filtered out to fulfill the radio transmission spectral mask requirement. Semi-digital FIR filter can be used in the context of digital-to-analog conversion, cascaded with ΣΔ modulator to filter the out-of-band noise by the modulator. In the same time it converts the signal from digital domain to an analog quantity. In general case, we can have a multi-bit, semi-digital FIR filter where each tap of the filter is realized with a sub-DAC of M bits. The delay elements are also realized with M-bit shift registers. If the output of the modulator is given by a single bit, the semi-digital FIR filter taps are simply controlled by a single switch assuming a current-steering architecture DAC. One of the major advantages is that the static linearity of the DAC is optimum. Since there are only two output levels available in the DAC, the static transfer function, regardless of the mismatch errors, is always given by a straight line. In this work, the design of SDFIR filter is done through an optimization procedure where the ΣΔ noise transfer function is also taken into account. Different constraints are defined for different applications in formulation of the SDFIR optimization problem. For a given radio transmitter application the objective function can be defined as, e.g., the hardware cost for SDFIR implementation while the constraint can be set to fulfill the radio transmitter spectral emission mask.