Analog Vector-Matrix Multiplier Based on Programmable Current Mirrors for Neural Network Integrated Circuits

We propose a CMOS Analog Vector-Matrix Multiplier for Deep Neural Networks, implemented in a standard single-poly 180 nm CMOS technology. The learning weights are stored in analog floating-gate memory cells embedded in current mirrors implementing the multiplication operations. We experimentally verify the analog storage capability of designed single-poly floating-gate cells, the accuracy of the multiplying function of proposed tunable current mirrors, and the effective number of bits of the analog operation. We perform system-level simulations to show that an analog deep neural network based on the proposed vector-matrix multiplier can achieve an inference accuracy comparable to digital solutions with an energy efficiency of 26.4 TOPs/J, a layer latency close to 100 mu s and an intrinsically high degree of parallelism. Our proposed design has also a cost advantage, considering that it can be implemented in a standard single-poly CMOS process flow

Synthesis, Characterization, and Device Applications of Two-Dimensional Materials

Two-dimensional (2D) materials have attracted tremendous research interest, as they offer novel physics, facile visualization by electron and scanning probe microscopy, and the potential to become next-generation electronic materials, all due to reduced dimensionality. Large-area 2D single crystals are needed for both fundamental scientific experiments and electronic device applications. New methods need to be developed to exploit state-of-the-art microscopy in the scientific investigation of 2D materials. Mechanisms behind the behavior of 2D-material based devices need to be resolved and new device concepts and applications need to be explored. This dissertation addresses these three aspects of 2D materials research.Using chemical vapor deposition growth of graphene on copper as a platform, the first part of my research in this thesis demonstrates a facile method involving a simple in-situ treatment of the copper catalytic substrate right before the growth that results in mm-sized graphene single crystals, elucidating the key factors of achieving large-area 2D single crystals.The second part of this work developed experimental methods to resolve important issues in 2D materials research by employing modern transmission electron microscopy. Here, a method has been developed to determine the edge orientation and termination without imaging the edge down to the atomic scale of monolayer hexagonal boron nitride (h-BN), enabling a direct comparison to theoretical predictions. Another important issue in 2D materials research is the determination of the layer count and its lateral spatial uniformity. In this work, a method is developed to map the layer count of a 2D material at nanometer-scale lateral resolution over extended areas, utilizing a combination of mass-thickness mapping offered by STEM and element-specific quantization afforded by electron energy loss spectrum (EELS) mapping.The last part of this thesis work unravels the multiple mechanisms behind the behavior of field effect transistors (FETs) based on PdSe2. The change in device behavior in early reports from ambipolar to n channel was puzzling. As commonly encountered in device research, many factors, including channel material properties, defects, contaminants, and contact effects, are almost always entangled. Here, I use multiple control devices to unravel various mechanisms and provide consistent explanations for device behvior variations

Needle lift profile influence on the vapor phase penetration for a prototype diesel direct acting piezoelectric injector

In this study, Schlieren visualization tests have been performed for a prototype diesel common rail direct-acting piezoelectric injector, to understand the influence of fuel injection rate shaping on the vapor spray development under evaporative and non-reacting conditions. This state of the art injector presents a particular feature that permits full needle lift control through a parameter referred to as piezo stack charge level, enabling various fuel injection rate typologies. A fast camera and a two pass Schlieren visualization setup have been utilized to record high speed images of the injection event and later analyze, through the vapor phase, the transient evolution of the spray. The tests have been performed employing a novel continuous flow test vessel that provides an accurate control of ambient temperature and pressure up to 1000 K and 15 MPa respectively. The effect of ambient temperature, injection pressure, needle lift and needle lift profile were studied. Data obtained is correlated to previous liquid length and injection rate measurements of the same injector. Results show, as expected for all cases, that instant vapor penetration rate is closely related to instant injection rate. This is confirmed by the injection pressure test results, along with those obtained for the three different piezo stack charge levels, both affecting the vapor penetration in a similar way. Nevertheless, results obtained for the three different charge levels show that the influence of the charge level and the injection pressure differ in the very beginning of the injection event, where the spray development is largely determined by needle lift and not injection pressure. Ambient temperature alone seems not to have and important effect on vapor penetration. Finally, the effects of the needle lift profile in the instant injection rate and vapor penetration are presented, confirming the strong relation between these three parameters, and confirming also that the needle lift plays a determinant role in the spray development, especially at the early stages of the injection process. Both boot and ramp shaped injections proved the ability to strongly influence the vapor penetration rate. In comparison to the square shaped injection, the effect of the ramp shaped injection delays the vapor penetration right from the start of injection while the effect of the boot shaped injection takes considerably longer to become noticeable. From the results, the needle lift control feature has proven to be a very versatile tool for engine designers to control the injection process as desired, opening a new path with a plenty of room for improvement.he authors would like to thank general motors company for their financial support and its cooperation during the project and José Enrique del Rey* and Michele Bardi* for their collaboration in the experimental measurements and setup. (*) From CMT-Motores Térmicos. Universitat Politecnica de Valencia.Payri, R.; Gimeno, J.; Viera, JP.; Plazas Torres, AH. (2013). Needle lift profile influence on the vapor phase penetration for a prototype diesel direct acting piezoelectric injector. Fuel. 113:257-265. doi:10.1016/j.fuel.2013.05.057S25726511

A Clustering System for Dynamic Data Streams Based on Metaheuristic Optimisation

open access articleThis article presents the Optimised Stream clustering algorithm (OpStream), a novel approach to cluster dynamic data streams. The proposed system displays desirable features, such as a low number of parameters and good scalability capabilities to both high-dimensional data and numbers of clusters in the dataset, and it is based on a hybrid structure using deterministic clustering methods and stochastic optimisation approaches to optimally centre the clusters. Similar to other state-of-the-art methods available in the literature, it uses “microclusters” and other established techniques, such as density based clustering. Unlike other methods, it makes use of metaheuristic optimisation to maximise performances during the initialisation phase, which precedes the classic online phase. Experimental results show that OpStream outperforms the state-of-the-art methods in several cases, and it is always competitive against other comparison algorithms regardless of the chosen optimisation method. Three variants of OpStream, each coming with a different optimisation algorithm, are presented in this study. A thorough sensitive analysis is performed by using the best variant to point out OpStream’s robustness to noise and resiliency to parameter changes

Distributed Acoustic Sensing for Seismic Imaging and Reservoir Monitoring Applied to CO2 Geosequestration

The thesis is focused on the evaluation of distributed acoustic sensing (DAS) technique applied to seismic imaging and monitoring of CO2 geosequestration. It utilises the data acquired at the CO2CRC Otway site (Victoria) and the National Geosequestration Laboratory (Western Australia) to explore capabilities of the sensing technique, optimise data acquisition and processing, and compare it to other seismic sensors. Surface and downhole acquisition geometries and a range of fibre optic cables and deployment techniques were considered

ANALYSIS OF MIXING PROCESSES IN LIQUID AND VAPORIZED DIESEL SPRAYS THROUGH LIF AND RAYLEIGH SCATTERING MEASUREMENTS

Desde su introducción, los motores de combustión interna alternativos han sido desarrollados con el fin de reducir el consumo y mejorar el rendimiento y facilidad de conducción. Con el tiempo, la contaminación se ha convertido en un factor crítico para los gobiernos y como consecuencia se han introducido regulaciones para reducir las emisiones contaminantes de los motores. Con el constante progreso tecnológico requerido por las normas contra la contaminación, la inyección directa se ha vuelto indispensable en cuanto a los motores Diesel. La introducción de combustible en la cámara de combustión permite un alto nivel de control sobre la liberación de energía del proceso de combustión. Con las novedosas estrategias de combustión empleadas, el proceso de inyección se ha convertido en el tema principal y el chorro es el factor principal. El trabajo realizado a lo largo de este estudio para analizar el proceso de mezcla aire-combustible se basa en el desarrollo de técnicas láser de diagnóstico. Inicialmente, la inyección de Diesel se ha estudiado en una atmósfera isoterma para evitar la evaporación del combustible (dodecano) a través del uso de una iluminación estructurada para medir la distribución de la mezcla mediante el control de la dispersión de Mie. La aplicación de la dispersión de Rayleigh en la parte evaporada del chorro inyectado en una cámara a alta temperatura ha permitido la obtención de la distribución de combustible en una situación equivalente a la existente en un motor real. El análisis y comparación de los distintos parámetros del chorro inyectado en condiciones de baja o alta temperatura da la posibilidad de entender mejor lo que es el proceso de mezcla en los motores Diesel. Por otra parte, según el estado del fluido inyectado, líquido o gaseoso, las condiciones experimentales tendrán diferentes efectos y la mezcla aire-combustible también tendrá un comportamiento distinto.Manin ., JL. (2011). ANALYSIS OF MIXING PROCESSES IN LIQUID AND VAPORIZED DIESEL SPRAYS THROUGH LIF AND RAYLEIGH SCATTERING MEASUREMENTS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/10189Palanci

A New electronic image array: The Active pixel charge injection device

This is a Ph.D. thesis dissertation in which a new type of image sensor is investigated as possible successor to the charge coupled device (CCD) for scientific applications. As a result of the work described in this dissertation, the active pixel charge injection device (AP-CID) has been developed. This device retains most of the positive features of both the charge injection device (CJD) imager (random readout, non destructive readout, antiblooming, increased UV sensitivity, radiation tolerance, low power consumption, low manufacturing price) and the CCD imager (low noise, high dynamic range). The device lacks most of the drawbacks of the aforementioned devices. A functional array architecture was created. Based on this architecture several devices were fabricated. One of the arrays was fully measured, characterized and suggestions for improvement were formulated. Most of the characterizationalysis work described in this dissertation was centered on the following issues: temporal noise, linearity and FPN. The measured noise performance of the new device is excellent and comparable to the noise performance of the scientific CCD. The newly developed sensor is necessary for scientific imaging applications in space based operation. However due to its qualities, this device could be used in a much wider range of applications including commercial digital cameras, spectroscopy, biological, nuclear and other scientific applications

A stability and spatial-resolution enhanced laser absorption spectroscopy tomographic sensor for complex combustion flame diagnosis

A novel stable laser absorption spectroscopy (LAS) tomographic sensor with enhanced stability and spatial resolution is developed and applied to complex combustion flame diagnosis. The sensor reduces the need for laser collimation and alignment even in extremely harsh environments and improves the stability of the received laser signal. Furthermore, a new miniaturized laser emission module was designed to achieve multi-degree of freedom adjustment. The full optical paths can be sampled by 8 receivers, with such arrangement, the equipment cost can be greatly reduced, at the same time, the spatial resolution is improved. In fact, 100 emitted laser paths are realized in a limited space of 200mm×200 mm with the highest spatial resolution of 1.67mm×1.67 mm. The stability and penetrating spatial resolution of the LAS tomographic sensor were validated by both simulation and field experiments on the afterburner flames. Tests under two representative experiment states, i.e., the main combustion and the afterburner operation states, were conducted. Results show that the error under the main combustion state was about 4.32% and, 5.38% at the afterburner operation state. It has been proven that this proposed sensor can provide better tomographic measurements for combustion diagnosis, as an effective tool for improving performances of afterburners

Indirect microfabrication of biomimetic materials for locomotor tissues regeneration

Tissue Engineering is a new field of the scientific research with a final aim to develop techniques for regeneration, repair, maintenance and growth of tissues or organs to overcome the limitations intrinsic to current therapeutic strategies. A fundamental element of this approach is the scaffold. The scaffold is a 2D and 3D structure, made with natural or synthetic material, that emulates the extracellular matrix, that is it offers mechanical, topological, biochemical and chemical stimuli to promote cellular organization, growth and differentiation to create a tissue with adequate functional and morphological characteristic. Scaffolds are therefore characterized by peculiar features (e.g. porosity, mechanical properties) determined by the material and by the manufacture process. Nowadays, the additive Rapid Prototyping (RP) techniques are the best approach to realize complex structures, because overcome all the problem of conventional (subtractive) techniques. Despite the high potential, RP techniques are not always compatible with all materials. In particular, hydrogels, an elective class of biomaterial for scaffolds realization because the lot of features in common with the extracellular matrix, results very difficult to be processed. To overcome these limitations and take advantage of all benefits of rapid prototyping, indirect rapid prototyping (iRP) was developed, that is the realization of scaffold or other structures starting from sacrificial molds realized by RP. The iRP offers the benefits to fabricate composite scaffold realized with different materials, with less waste and high fidelity in the realization of the designed structure. One of the critical aspect of this class of realization process is the extraction of the final object from the mold. A possible solution, proposed in this research, is to realize the mold with low melting point materials, dissolving the mold at the end of the process without damaging the scaffold. Moving in this direction, the attention of this research is focused on two classes of materials, low melting point waxes and agarose. Two alternative RP techniques have been evaluated: new modules of the PAM^2, a continuous flow system, and a inkjet-based device have been designed and realized to test the feasibility of this approach. In addiction, an alternative approach to fabricate agarose microstructure, by exploiting the different agarose gelling ability in DMSO and water, has been proposed. In a future perspective, casting of the desired material, which may include also cells, should be performed directly in the surgery room using an anatomical shaped mold designed on the patient needs. Following this approach, two plugins for bioimages de-noising and segmentation, based on the ITK library, have been implemented for the OsiriX software. To further test the versatility of the two microfabrication devices, other applications have been explored, such as the realization of microfluidic circuits using PAM^2 or printing carbon nanotubes suspension for polymeric actuators