272 research outputs found
Poland read by a Haitian, or Haiti read by a Pole? : romantic spirituality in the film "The art of disappearing" by Piotr Rosołowski and Bartek Konopka
No full textThe main objective of this paper is to analyze the 2013 documentary The Art of Disappearing, directed by Bartek Konopka and Piotr Rosołowski, using the category of spirituality. Although the film attempts to show everyday life in the Polish People's Republic from the perspective of a stranger, a Haitian voodoo practitioner, looking closer at the type of spirituality presented in the movie, makes the article's author lean towards an opposite idea: The Art of Disappearing permeated by the romantic spirituality makes its protagonist, Amon Frémon a convenient vessel for the worldview and ideas shaped by polish Romanticism
Altimeter ball: From a concept demonstrator towards a production prototype
No full textIn deze thesis is het ontwerpproces van de ’Altimeter bal’ beschreven. Deze bal is bedoeld als speelgoed voor kinderen en behoort na een worp de maximale hoogte van die worp weer te geven. Onderzoek is gedaan naar de manier van hoogtebepaling, het materiaal waarvan de bal gemaakt is en de manier waarop de Altimeter bal met de gebruiker communiceert. Het resultaat van het proces is een ontwerp en exemplaar van een prototype. Metingen met het prototype waren echter niet mogelijk.Electrical EngineeringElektronische componenten, technologie en materialenElectrical Engineering, Mathematics and Computer Scienc
Hybrid Wafer-Level Packaging for RF-MEMS and Optoelectronic Applications
No full textThe current trend in electronic packaging research is to integrate more functions into one package, reduce electrical path parasitic, and increase the heat conduction in order to make the final packaged system smaller, more reliable, more functional and more complete, while keeping the packaging cost low. In this trend, unconventional devices (such as MEMS and optoelectronic devices) and various substrate materials (e.g., InP, GaAs, etc.) are integrated into a single package together with conventional silicon-based ICs. The resulting novel packages are produced by both wafer-level batch processes as well as many multichip 2D/3D serial assembly processes. Therefore a complete functional unit can be built in a single package. This feature is particularly valuable in space-constrained environments such as mobile phones, as it increases the packaging efficiency while decreasing complexity of the PCB and overall design. In this thesis, the development of wafer-level fabrication processes and supplemental techniques for applications in hybrid wafer-level packaging for MEMS and optoelectronic devices is presented. Hybrid wafer-level packaging makes it possible to integrate a variety of dies (i.e., silicon IC, MEMS, optoelectronic) into one final package, while using potentially economical wafer-level batch processing. Chapter 1 introduces the concept of hybrid wafer-level packaging and the research trends in relation to MEMS and optoelectronic packaging. The scope and outline of this thesis work is also outlined. In Chapter 2, the development of the through-silicon via (TSV) fabrication process using deep reactive ion etching process is presented. First, the Bosch process is characterized with emphasis on overcoming the non-uniform etching effects, such as ARDE, to fabricate simultaneously through-silicon features with a large aspect ratio difference. Via-first and via-last fabrication methods were developed. The via-first approach involves wafer backside lapping and ultrasonic break off, while in the via-last approach an Al etch stop layer is used. Both methods are demonstrated by forming 50-?m diameter through-silicon vias and 2 x 5 mm2 cavities. The cavities can be used for the alignment and insertion of additional IC dies. Chapter 3 presents the development of copper electroplating for TSV filling and gold and tin plating for fabricating solder bumps. The TSV filling with copper forms a low-resistivity through-silicon interconnect which enables hybrid (RF-)MEMS wafer-level packaging. Cu-filled TSVs with a diameter of less than 50 µm and an aspect ratio of more than 5 : 1 are successfully demonstrated. The developed processing module is based on Cu electroplating in two steps in combination with a chemical-mechanical polishing (CMP). In the first electroplating step, which is performed on the wafer front side, a copper plug in the via and front-side copper structures in a photo resist mold are formed. In the second step, the wafer is turned back side up and the TSVs are filled in a bottom-up approach. The overplating features that only occur on the wafer back side are then removed in a CMP step. In the Au and Sn electroplating, the aiming application is bump fabrication. Sequential Au/Sn plating in a resist mold on an Au/Cr seed/adhesion layer was successfully used for Au80Sn20 solder-bump formation. Using reflow at 300 °C, the AuSn bumps were bonded to another substrate. An electrical resistivity of 189 ???cm, and a bonding tensile strength of 36.4 MPa were measured. Chapter 4 presents adhesive wafer-level bonding for packaging applications with a focus on electrically conductive adhesives (ECA). An ECA is basically an epoxy filled with metal flakes, such as Ag. Depending on the metal flake concentration, an ECA can further classified as an ACA (anisotropic conductive adhesive, low metal flake concentration), and an ICA (isotropic conductive adhesive, high metal flake concentration). In this chapter, the electrical resistivity of the ECA (CE3103 WLV) with respect to the curing temperature and bonding pressure is studied. Chapter 5 describes a novel hybrid wafer-level packaging solution that is applicable to RF-MEMS devices and is based on the fabrication techniques described in the previous chapters of this thesis. In this packaging concept, a capping HRS substrate with copper-filled through-silicon vias and pre-etched cavities is wafer-level bonded to an RF-MEMS device wafer using an electrically conducted adhesive. This RF-MEMS packaging solution minimizes the packaging design effort in the RF-MEMS device design and fabrication while keeping the packaging cost low. An important aspect of this package is the possibility to include through-substrate cavities for aligned insertion of control ICs on the die-to-wafer level making it a hybrid WLP solution. Furthermore, the applied adhesive wafer-level bonding provides a low thermal budget and fewer stringent requirements on the surface quality, which might be attractive in many applications. Next to the fabrication process development, this chapter also focuses on design optimization and RF characterization. The Ansoft HFSS full 3D EM simulation tool was used to predict and optimize the RF behavior of a packaged system. The electrical measurement data obtained from packaged CPWs are promising (i.e., insertion loss of 0.11 dB at 10 GHz). Chapter 6 presents the initial study on thermal and thermo-mechanical aspects of a SiP-based optoelectronic package to be used in an optical network unit. A finite-element model representing the relevant parts of the package structure was built and extensive thermal and thermo-mechanical simulations were carried out. The gold bumps (i.e., their geometry and count) used to flip-chip the InP optical transceiver chip to the silicon platform represent the main optimizing parameter. The simulation results show that by increasing the bump count and decreasing the height, a sufficiently low thermal resistance between the SOA active region and the heat sink can be realized. The FEM thermal simulation results were validated by designing, fabricating and measuring flip-chip bonded micro-hotplate and resistive temperature sensor (phosphorus-doped polysilicon) arrays.DIMESElectrical Engineering, Mathematics and Computer Scienc
Substrate Crosstalk Suppression Using Wafer-Level Packaging: Metalized Through-Substrate Trench Approach
No full textThe demand for miniaturization technology has been increasing over the last decades. Consumer electronics end-users often, if not always, go for more functionality and practicality. This is translated into systems that are more complex and yet smaller in size such as smart cellular phones and portable audio/video systems. System on Chip (SoC) is still a solution preferred by many. The SoC comprises of many different circuit blocks that fall into two categories namely analog/RF and digital. The integration of the analog/RF circuitry and digital circuitry on the same silicon substrate has yet another challenge to cope with. The noise generated from the switching activity of the digital circuitry is injected into the silicon substrate, which then can propagate to the sensitive analog/RF circuitry. Such substrate noise can significantly degrade the functionality of the analog/RF circuitry, thus deteriorating the performance of the entire electronic system. In this thesis, a method to isolate the noise generating circuit block from the noise sensitive circuit block is proposed and demonstrated. The proposed method is based on through-substrate trench isolation scheme to suppress the substrate noise. The idea behind this isolation scheme is to create a full through-substrate trench that physically separates the noise agressor from the victim. This idea is very simple and effective. The through-substrate trench is achieved by means of wafer-level packaging (WLP) technology and consists of only a few additional fabrication steps that can readily be incorporated in the WLP processing flow. In a few words, it can be described as follows: the silicon substrate is first bonded to a spacer substrate, e.g. AF-45 glass or High-Resistivity Polycrystalline Silicon (HRPS). Then, the bonded wafer stack is turned upside down before being thinned down. The next step is to create the through-substrate trench by means of KOH etching. At this stage, we now have an air-filled through-substrate trench. This isolation scheme can be further improved by metalizing the trench resulting in a backside metal plane. The backside metal can then be connected to ground to drain the substrate noise. This is called grounded-metalized through-substrate trench. In this work, we have successfully fabricated and measured several devices, i.e. control device (without isolation), air-filled trench device, and metalized trench device. At 50 MHz air-filled trench provides around 55 dB isolation with respect to control device, whereas the metalized-trench provides additional isolation of 7 dB. At 10 GHz air-filled trench provides around 10 dB isolation with respect to control device, whereas the metalized-trench provides additional isolation of 23 dB. At 40 GHz air-filled trench provides around 2 dB isolation with respect to control device, whereas the metalized-trench provides additional isolation of 20 dB.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Selective Epitaxial Growth for Smart Silicon Sensor Applications
No full textElectrical Engineering, Mathematics and Computer Scienc
Hospodaření se srážkovou vodou v urbanizovaném prostředí
No full textThe bachelor‘s thesis focuses on rainwater management in an urbanized environment. The author divided thesis into three parts: theoretical, analytical and projection. In the first (theoretical) part, the author describes the causes and impacts of current climate change. Also in this section, the author explores the possibilities of adapting the current urban environment to climate change. He applies theoretical knowledge in the evaluation of urban spaces in Brno, which he personally visited, he also gives examples from abroad. In the second (analytical) part, the author is engaged in a particular urban space. This is the pre-space of the Cultural House and the area around the small shopping mall in Frýdek-Místek. The area around Cultural House and shopping mall was analysed in detail for the projection part. In the third (projection) part, the author conducted an architectural study of a given space aimed at using elements of blue-green infrastructure to use rainwater more efficiently
Similarity metrics for binary cell clustering: How close can we get to state-of-the-art ?
No full textAnalysing single-cell RNA sequencing data is becoming an increasingly tedious task as the size of data sets grows. As a proposed solution, recent discoveries suggest that these data sets can be binarized without losing much information. This in turn should allow for memory and time efficient methods of storage and computation. Numerous analyses techniques require cell clustering as a preliminary procedure, which suggests the need to evaluate binary representation performance under that context. In this work we present a comparison between binary clustering results and the state-of-the-art, with a focus on similarity metric choice and the impact on intermediate steps of the procedure (i.e. similarity matrices and kNN graphs). The method was evaluated on single-cell transcriptomic data sets, utilizing a combination of R and C++ as an evaluation framework. Through these means we found that some of the similarity metrics operating on continuous input can possibly be reproduced with similarity metrics operating on binary input.CSE3000 Research ProjectComputer Science and Engineerin
Performance modelling of a multiple threshold RED mechanism for bursty and correlated Internet traffic with MMPP arrival process
No full textYesAccess to the large web content hosted all over the world by users of the Internet engage
many hosts, routers/switches and faster links. They challenge the internet backbone to operate at
its capacity to assure e±cient content access. This may result in congestion and raises concerns over
various Quality of Service (QoS) issues like high delays, high packet loss and low throughput of the
system for various Internet applications. Thus, there is a need to develop effective congestion control
mechanisms in order to meet various Quality of Service (QoS) related performance parameters. In this
paper, our emphasis is on the Active Queue Management (AQM) mechanisms, particularly Random
Early Detection (RED). We propose a threshold based novel analytical model based on standard RED
mechanism. Various numerical examples are presented for Internet traffic scenarios containing both the
burstiness and correlation properties of the network traffic
Mathematical Modeling, Laboratory Experiments, and Sensitivity Analysis of Bioplug Technology at Darcy Scale
No full textIn this paper, we study a Darcy-scale mathematical model for biofilm formation in porous media. The pores in the core are divided into three phases: water, oil, and biofilm. The water and oil flow are modeled by a generalized version of Darcy's law, and the substrate is transported by mechanical dispersion, diffusion, and convection in the water phase. Initially, there is biofilm on the pore walls. The bio-film consumes substrate for production of biomass and modifies the pore space, which changes the rock permeability. The model includes detachment of biomass caused by water flux and death of bacteria, and it is implemented in the MATLAB Reservoir Simulation Toolbox (MRST). We discuss the capability of the numerical simulator to capture results from laboratory experiments. We perform a novel sensitivity analysis based on sparse-grid interpolation and multiwavelet expansion to identify the critical model parameters. Numerical experiments using diverse injection strategies are performed to study the impact of different porosity/permeability relationships in a core saturated with water and oil. Introduction After primary and secondary production, up to 85% of the oil remains in the reservoir (Patel et al. 2015). Microbial improved and enhanced oil recovery (MIEOR) is one of the secondary and tertiary methods to increase the oil production using microorganisms (Wood 2019). Bioplug technology is an MIEOR strategy that comprises plugging the most permeable zones in the reservoir, which provokes water to flow through new paths, and recovering the oil in these new zones. However, microorganisms could also form biofilms in undesirable zones in the reservoir, leading to negative effects such as a decrease in water injectivity. Therefore, understanding the mechanisms involved in the development of biofilms is important to control their formation. The bioplug technology is intended for use on the field scale but to perform field-scale experiments is both time consuming and economically infeasible. Experiments in microsystems allow us to observe processes in greater detail, which leads to improvement of the experimental methods in core-scale experiments before field applications. For example, in Liu et al. (2019), the effects of flow velocity and substrate (also referred to as nutrients/food) concentration on biofilm in a microchannel was studied, finding values of substrate concentration and flow velocity for a strong plugging effect. Core samples from reservoirs can be used to study changes in permeability because of biofilm formation; for example, in Suthar et al. (2009), two-phase flow experiments were performed to study the selective plugging strategy for MIEOR. In that study, the MIEOR effects increased the oil recovery by approximately 25%. Mathematical models of bioplug technology are important because they help to predict the applicability of this MIEOR strategy and to optimize its benefits. In Kim (2006), a mathematical model for single-phase flow was proposed that includes changes of rock porosity and permeability as a result of biofilm growth. The author calibrated the model using data from experiments in silica sand columns and performed a simple sensitivity analysis (one-at-a-time technique) of a few model parameters. Li et al. (2011) built a mathematical model for two-phase flow including the effects of bio-surfactants and biomass on improving oil recovery. The authors also performed a simple sensitivity analysis of a few model parameters and compared the numerical results for two different porosity/permeability relationships. They concluded that MIEOR could enhance the oil recovery substantially if a larger capillary number is achievable. Nielsen et al. (2016) built a two-phase-flow mathematical model for MIEOR that included a decrease in oil/water interfacial tension by produced surfactants and selective plugging by microbes and metabolic products. The authors studied the oil recovery for diverse injection strategies, changing the pore volumes injected and substrate concentration at a fixed-flow rate. In Dzianach et al. (2019), the authors present a recent review of mathematical models of biofilms for diverse purposes. They concluded that cooperation between various disciplines is required to develop novel models. In this work, we present a two-phase core-scale model of bioplug technology. To our knowledge, this is the first mathematical model for two-phase flow and permeable biofilm. This mathematical model is the result of a research project where microbiologists, physicists, chemists, and mathematicians were involved. A detailed description of this project and previous publications can be found in Landa-Marbán (2019). In contrast to Li et al. (2011), in this work, we perform simulations to find at which part (low, medium, or high porosity) of five porosity/permeability relationships the oil recovery is more sensitive. Unlike Nielsen et al. (2016), we study the oil recovery for several injection strategies by changing the substrate concentration, flow rate, and injection direction. Sensitivity studies of mathematical models are of great interest because they provide estimates of the influence of the inputs (e.g., physical parameters) on a quantity of interest (e.g., biofilm formation). In Brockmann et al. (2006), a regional steady-state sensitivity analysis was performed to identify parameters with the largest impact on a mathematical model for deammonification in biofilm systems. Sensitivity analysis by means of Sobol decomposition provides rigorous estimates of parameter dependencies but are prohibitively expensive to compute if the number of parameters is large. This is remedied for smooth problems by first computing spectral (generalized polynomial chaos) expansions in the parameters, which then leads to efficient evaluation of the sensitivity indices via post-processing of spectral coefficients (Sudret 2008). The latter method was used in Landa-Marbán et al. (2019), where a global sensitivity analysis was performed using Sobol indices to identify the critical parameters of a pore-scale model for permeable biofilm. In this paper, we introduce a different approach that can also be used for nonsmooth mathematical models in the dependent parameters, where spectral expansions with global smooth-basis functions are not a robust choice. We propose a two-stage method where we first useThe work of DLM, GB, BFV, KK, PP, and FAR was partially supported by the Research Council of Norway through Projects IMMENS 255426, MICAP 268390, and CHI 255510. ISP was supported by the Research Foundation-Flanders Belgium, through the Odysseus program (Project G0G1316N) and an Akademia grant from Equinor ASA. The authors also appreciate the support from Equinor ASA related to the experimental work reported herein
Optimisation of a protocrystalline hydrogenated amorphous silicon top solar cell for highest stabilised efficiency
No full textIn recent decades, the public awareness of the need for renewable energy sources has increased greatly. Considering the current climate changes, it is clear that today’s energy systems have to be radically transformed onto a more sustainable basis to avoid the otherwise very likely adverse effects of global warming on tomorrow’s society and economy. In this framework, solar cells offer an interesting alternative for large-scale electricity generation. The first-generation crystalline silicon (c-Si) solar cells, which still dominate the photovoltaic market, will likely not be used for such large-scale applications, because of the relatively large amounts of material that would be required for the fabrication. Thinfilm solar cells, such as hydrogenated amorphous silicon (a-Si:H) solar cells, have a great potential with respect to the costs, because much smaller amounts of material are needed in the fabrication process in comparison to c-Si solar cells. However, the typical conversion efficiency of an a-Si:H silicon solar cell is much lower than the typical conversion efficiency of a c-Si solar cell. Further, the performance of an a-Si:H solar cell degrades over time when the solar cell is exposed to light, which is not the case for c-Si solar cells. In an attempt to increase the conversion efficiency of thin-film solar cells, research interest moved towards multiple-junction solar cells, as opposed to the conventional single-junction solar cells, so a wider range of the solar spectrum could be absorbed. One particularly interesting multiple-junction solar cell is the so-called micromorph tandem solar cell, which consists of an a-Si:H top solar cell and a hydrogenated microcrystalline silicon (?c-Si:H) bottom solar cell. The interesting aspect of this particular multiple-junction solar cell is that both the bottom and the top solar cell can be produced from the same cheap base material: silicon. Both solar cells can be deposited by means of plasma-enhanced chemical vapour deposition (PECVD) from silane gas. To obtain a highly efficient a-Si:H solar cell for possible later use in a micromorph tandem solar cell, it will be attempted in this thesis to optimise the heart of the a-Si:H solar cell: the absorber layer. To obtain a stable material, a hydrogen-to-silane dilution ratio of 20 is used during the PECVD deposition of a-Si:H. The influence of various deposition parameters, such as the pressure, the rf-power, the silane flow, and the substrate temperature on the quality of films and absorber layers is investigated. Fourier Transform Photocurrent Spectroscopy is used to evaluate the quality of Si:H films and solar cell absorber layers, since from the obtained sub-band gap absorption coefficient spectrum the defect concentration can be estimated. It is found that the highest material quality of films and absorber layers is achieved for a high deposition pressure, a low rf-power, and a low substrate temperature. The silane flow does not have a significant influence of the quality of the deposited material. None of these deposition parameters has an influence on the degradation rate in films and absorber layers. An increased stability against light soaking is observed for the films and absorber layers deposited at a hydrogen-to-silane dilution ratio of 20 in comparison to a film and an absorber layer deposited from undiluted silane.Solar Cell GroupElectronic Components, Technology and MaterialsElectrical Engineering, Mathematics and Computer Scienc
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