Controlling ignition timing and flame stabilization is one of the most outstanding challenges limiting the development of modern, efficient and low-emission compression ignition engines (CIEs). In this study, the role of turbulence on two-stage ignition dynamics and subsequent flame stabilization at diesel engine conditions is assessed by performing direct numerical simulations in a simplified inflow-outflow premixed configuration. The thermochemical conditions are chosen to match those of the most reactive mixture in the Engine Combustion Network’s n-dodecane Spray A flame (temperature of 813 K, pressure of 60 atm, equivalence ratio of 1.3, and with 15% vol. O2 in the ambient gas). Inflow velocities 4 to 16 times larger than the laminar flame speed are considered. As a result, in the absence of turbulence, ignition and flame stabilization are controlled by advection and chemistry, diffusion being negligible. Ignition delays match those of the homogeneous reactor and both the cool flame, due to low-temperature chemistry (LTC), and the hot flame, due to high-temperature chemistry (HTC), are spontaneous ignition fronts. Turbulence alters this picture in two ways. First, the second-stage (HTC) ignition delay is increased considerably, in contrast with the first-stage (LTC) ignition delay, which remains virtually unaffected. Second, a sufficiently high turbulence intensity makes the cool spontaneous ignition front transition to a cool deflagration which moves upstream to the inlet, while the hot flame is pushed downstream, still stabilized by spontaneous ignition. The latter phenomenon is caused by the reduced reactivity of LTC products as the cool flame transitions from spontaneous ignition to deflagration. Further increasing the turbulence intensity leads to both cool and hot flames transitioning to deflagrations. For the hot flame, the mechanism governing this transition is the increase in magnitude of progress variable gradient under increased turbulence or reduced inflow velocity, while in cool flames it is mainly due to the reduction in chemical source terms. In addition to turbulence intensity, the role of inflow velocity, integral length scale, and oxygen concentration level on this transition is assessed and modeling challenges are discussed. Finally, a chemical explosive mode analysis is provided to further characterise the ignition and transition phenomena. The present results highlight important fundamental roles of turbulence expected to modulate CIE combustion dynamics.

The semestral thesis describes ECG signal compression methods designed to modify the data for transmission via communication channels. The thesis contains an introduction to Ethernet and explanation of communication in the network. The transport protocols TCP and UDP are discussed in more detail. In the practical part of the thesis was created two separate applications. The first application in the sender's computer opens a text file with the ECG signal. Loaded ECG signal is filtered by cascade of filters to eliminate interference. The resulting signal is displayed. A part of the application is the R wave detection, calculating the length of RR interval and heart rate. The application also allows to compress an ECG signal. ECG signal is sent via Ethernet network via UDP protocol for individual samples. Applications in the recipient's computer receives signal samples from the network. Recieved compressed data is reconstructed. The resulting ECG signal is displayed and there are again detected R waves, the length of RR intervals and sampling frequency are calculated.

The aim of this thesis was introducing the options of conversion between OTDM and WDM technologies. Since this issue is rather extensive, first of all the principle of optical transmission system is described. One chapter presents the effects influencing the optical transmissions. Material absorption, linear and nonlinear scattering and bending losses are mentioned in terms of fiber losses, followed by description of waveguide, chromatic and polarization-mode dispersion of optical fibers. Last part of the chapter presents nonlinear effects, including self-phase modulation, cross-phase modulation and four-wave mixing. The practical part of the thesis deals with multichannel systems. The principles of frequency, space a hybrid multiplexing are explained. Multichannel systems with optical time domain multiplexing and waveguide multiplexing are described in detail and compared. The elements of the transmission chain of multiplex, such as different types of lasers, detectors, modulators, optical amplifiers, splitters, couplers, MUX and DEMUX are discussed. The next part of the thesis was aimed at suggesting the model of mutual conversion between OTDM and WDM systems. First of all, the previously performed experiments concerning the conversion between OTDM and WTM were evaluated. Then the model of OTDM/WDM/OTDM conversion was designed, with explanation of its parts and their function. The general recommendations for practical implementation were are also included. Due to the limited amount of time reserved for access to the simulation program Optsim, the simulations were performed only for certain parts of the proposed conversion model. At the end of the thesis, the proposed model is evaluated.

<p>Dynamic modeling of Vapor Compression Cycles (VCC) is particularly important for designing and evaluating controls and fault detection and diagnosis (FDD) algorithms. As a result, transient modeling of VCCs has become an active area of research over the past two decades. Although a number of tools have been developed, the computational requirements for dynamic VCC simulations are still significant. A computationally efficient but accurate modeling approach is critically important to accelerate the design and assessment of control and FDD algorithms where a number of iterations with a variety of test input signals are required. Typically, the dynamics of compressors and expansion devices evolve on an order of magnitude faster than those of heat exchangers (HX) within VCC systems. As a result, most dynamic modeling efforts have focused on heat exchanger models. The switched moving boundary (SMB) method, which segments a heat exchanger depending on thermodynamic phase of the refrigerant, i.e. subcooled liquid, two-phase and superheated vapor, and moves control volumes as the length of each phase changes, can reduce the computation time compared with the finite volume (FV) method by solving fewer equations due to a smaller set of control volumes. Despite the computational benefit of the SMB, there is a well-known numerical issue associated with switching the model representations when a phase zone disappears or reappears inside of a heat exchanger. More importantly, the computational load is still challenging for many practical VCC systems. This thesis proposes an approach applying nonlinear model order reduction (MOR) methods to dynamic heat exchanger models to generate reduced order HX models, and then to couple them to quasi-static models of other VCC components to complete a reduced order VCC model. To enable the use of nonlinear model reduction techniques, a reformulated FV model is developed for matching the baseline MOR model structure, by using different pairs of thermodynamic states with some appropriate assumptions. Then a rigorous nonlinear model order reduction framework based on Proper Orthogonal Decomposition (POD) and the Discrete Empirical Interpolation Method (DEIM) is developed to generate reduced order HX models. </p><p> </p><p> The proposed reduced order modeling approach is implemented within a complete VCC model. Reduced order HX models are constructed for a centrifugal chiller test-stand at Herrick Labs, Purdue University, and are integrated with quasi-static models of compressor and expansion valve to form the complete cycle. The reduced cycle model is simulated in the Modelica-based platform to predict load-change transients, and is compared with measurements. The validation results indicate that the reduced order model executes 200 times faster than real time with negligible prediction errors.</p><br>

High-Performance Computing (HPC) necessarily requires computing with a large number of nodes. As computing technology progresses, internode communication becomes an ever more critical performance blocker. The execution time of software communication support is generally critical, often accounting for hundreds of times the latency of actual time-of-flight. This software support comes in two types. The first is support for core functions as defined in middleware such as the ubiquitous Message Passing Interface (MPI). Over the last decades this software overhead has been addressed through a number of advances such as eliminating data copies, improving drivers, and bypassing the operating system. However an essential core still remains, including message matching, data marshaling, and handling collective operations. The second type of communication support is for new services not inherently part of the middleware. The most prominent of these is compression; it brings huge savings in transmission time, but much of this benefit is offset by a new level of software overhead. In this dissertation, we address the software overhead in internode communication with elements of the emerging node architectures, which include FPGAs in multiple configurations, including closely coupled hardware support, programmable Network Interface Cards (NICs), and routers with programmable accelerators. While there has been substantial work in offloading communication software into hardware, we advance the state-of-the-art in three ways. The first is to use an emerging hardware model that is, for the first time, both realistic and supportive of very high performance gains. Previous studies (and some products) have relied on hardware models that are either of limited benefit (a NIC processor) or not sustainable (NIC augmented with ASICs). Our hardware model is based on the various emerging CPU-FPGA computing architectures. The second is to improve on previous work. We have found this to be possible through a number of means: taking advantage of configurable hardware, taking advantage of close coupling, and coming up with novel improvements. The third is looking at problems that have been, so far, nearly completely unexplored. One of these is hardware acceleration of application-aware, in-line, lossy compression. In this dissertation, we propose offload approaches and hardware designs for integrated FPGAs to bring down communication latency to ultra-low levels unachievable by today's software/hardware. We focus on improving performance from three aspects: 1) Accelerating middleware semantics within communication routines such as message matching and derived datatypes; 2) Optimizing complex communication routines, namely, collective operations; 3) Accelerating operations vital in new communication services independent of the middleware, such as data compression. % The last aspect is somewhat broader than the others. It is applicable both to HPC communication, but also is vital to broader system functions such as I/O.

This work presents a novel technique for data compression based on multi-residue number systems. The basic theorem is that an under-determined system of congruences could be solved to accomplish data compression for a signal satisfying continuity of its information content and bounded in peak-to -peak amplitude by the product of relatively prime moduli,. This thesis investigates this property and presents quantitative results along with MATLAB codes. Chapter 1 is introductory in nature and Chapter 2 deals in more detail with the basic theorem. Chapter 3 explicitly mentions the assumptions made and chapter 4 shows alternative solutions to the Chinese remainder theorem. Chapter 5 explains the experiments in detail whose results are mentioned in chapter 6. Chapter 7 concludes with a summary and suggestions for future work.

La presente investigación corresponde a la evaluación de las propiedades mecánicas de la madera contralaminada (CLT) elaborados con una especie de mediana densidad mediante ensayos de resistencia para mejorar su comportamiento como muros estructurales en edificaciones. La aplicación de la madera laminada cruzada denominada también CLT (Cross Laminated Timber) como material estructural en la construcción de edificaciones permitiría un mejor aprovechamiento del potencial forestal de muchos países, haciendo que este sector sea más sostenible. Esta aplicación es factible siempre en cuando el material a emplear cumpla con las solicitaciones de resistencia que demanda su uso estructural y su proceso industrial sea compatible con las condiciones y la oferta existente en el entorno. Para lograr este propósito, se elaboraron prototipos de paneles CLT con madera Cachimbo, especie de mediana densidad denominado científicamente como Cariniana doméstica perteneciente a la familia Lecythidaceae. Se realizaron ensayos para determinar las propiedades mecánicas de resistencia a esfuerzos de compresión perpendicular y paralela a las fibras de las capas exteriores, esfuerzo de flexión y resistencia al corte. Los procedimientos fueron realizados siguiendo normativas de madera contralaminada como la española EN16351, el EC5 y la E.010 de madera. Los resultados obtenidos dan cuenta que los paneles CLT elaborados con Cachimbo son capaces de resistir los requerimientos de carga que podría demandar una edificación de mediana altura y cumple con los requisitos básicos especificados en las normativas. Las resistencias alcanzadas son similares a las obtenidas con maderas de tipo coníferas en estudios realizados en otros países, siguiendo los mismos criterios y normatividad. / The present investigation corresponds to the evaluation of the mechanical properties of the Cross Laminated Timber (CLT) made with medium density species by means of resistance tests to improve its behavior as structural walls in buildings. The application of the cross laminated wood also called CLT (Cross Laminated Timber) as structural material in the construction of buildings would allow a better use of the existing forest potential in many countries, making this sector more sustainable. This application is feasible as long as the material to be used complies with the stresses of resistance that its structural use demands, and its industrial process is compatible with the conditions and the existing offer in the environment. To achieve this purpose, prototypes of CLT panels were made with Cachimbo wood, a medium-density species scientifically called Carinianadomestic belonging to the Lecythidaceae family. Tests were carried out to determine the mechanical properties of resistance to perpendicular and parallel compression stresses to the fibers of the outer layers, bending stress and shear strength. The procedures were carried out following norms of contra-laminated wood such as the Spanish EN16351, the EC5 and the Peruvian E.010 wood regulations. The results obtained show that the CLT panels made with Cachimbo can withstand the load requirements that a medium-height building could demand and meets the basic requirements specified in the regulations. The strengths achieved are similar to obtained with coniferous woods in studies carried out in other countries, following the same criteria and regulations. / Trabajo de investigación

This work investigates the optimal measurement matrices that can be used in compressive sensing (CS) image sensors. It also optimizes CMOS current-model pixel cell circuits for CS image sensors. Based on the outcomes from these optimization studies, three CS image senor circuits with compression ratios of 4, 6, and 8 are designed with using a 130 nm CMOS technology. The pixel arrays used in the image sensors has a size of 256X256. Circuit simulations with benchmark image Lenna show that the three images sensors can achieve peak signal to noise ratio (PSNR) values of 37.64, 33.29, and 32.44 dB respectively.

With the increasing popularity of interest rate swaps the need to understandswaptions, an option of an interest rate swap, is of great importance. A swap-tion can be used in both speculative purposes and to hedge against changesin interest rates. The most important thing to understand is the pricing for-mula. By starting at the basic rate instrument, bonds, we will work our waytowards the pricing formula for a swaption, the Black76 model. The Black76model is a variant of the Nobel prize winning formula Black-Scholes-Merton.With the pricing model we can start looking at the main scope of this thesis,a hedging strategy against swaptions from a clearinghouse perspective.Clearinghouses are central to the modern financial market. They act asa middleman in order to clear trades from clearing members and have anoversight of the financial market. In case a clearing member defaults, theclearinghouse will gain control over the defaulted portfolio. The clearing-house will host an auction of the portfolio which they strive to hold after5 to 15 days. When they hold the portfolio, they are exposed to the risksand therefore it’s of great importance to be able to hedge the assets in theportfolio. In this thesis a strategy and algorithm have been developed todelta-hedge swaptions in order to be delta-neutral under stable market con-ditions.In the thesis we will consider two cases. The first case is when the clear-inghouse receives the portfolio long before the swaptions maturity. In thiscase forward swaps are used to hedge and in order to reduce the number offorward swaps obtained, compression is used. The second case is when theswaption maturity will be reached within the period the clearinghouse holdsthe portfolio. For the days before maturity is reached, forward swaps andcompression is used. After maturity is reached interest rate swaps is used tohedge.For both cases the result is very close to achieving delta-neutrality. Withnormalized deltas with respect to the notional amount the mean delta ex-posure is of the magnitude 10−4 for the first case and 10−6 for the second.However, one thing to keep in mind is that everything is based on simu-lated values under some simplifying assumptions. This thesis should be asolid ground for future studies where more extreme scenarios are considered.With more extreme scenarios one could investigate the possibility to hedgewith Gamma or another Greek such as Vega. / Med den ökande användningen av ränteswappar är det av stor vikt att förståswaptioner, vilket är en option på en ränteswapp. En swaption kan användasbåde för spekulativa syften och för att hedgea mot risker i ränteförändringar.Det viktigaste att förstå är hur man prissätter en swaption. Eftersom swap-tioner baseras på underliggande tillgångar så kommer vi börja med det mestgrundläggande, obligationer, och arbeta oss fram till modellen vi kommer an-vända, Black76. Black76-modellen är en variant av den nobelprisvinnandemodellen Black-Scholes-Merton. Med denna modell kan vi börja undersökadet huvudsakliga syftet med avhandlingen, en hedgningsstrategi för swap-tioner från perspektivet av ett clearingshus.Clearinghus är en central del av den moderna finansmarknaden. De agerarsom en mellanhand för att hantera affärer mellan clearingmedlemmar ochhar en översikt över marknaden. Ifall en clearingmedlem går i konkurs,kommer clearinghuset att ta över portföljen med tillgångar. Clearinghusetkommer att hålla en auktion för att sälja av portföljen. De strävar efteratt hålla auktionen så snabbt som möjligt och det sker generellt efter 5 till15 dagar. Medan de har portföljen så är de exponerade mot riskerna i till-gångarna och därför är det av största vikt att kunna hedga tillgångarna. Iden här avhandlingen har en strategi och en algorithm tagits fram för attanvända delta-hedging för att uppnå delta-neutralitet under normala mark-nadsrörelser.Vi kommer att undersöka två olika fall. Det första fallet är när portföljen tasöver när det är lång tid kvar till swaptionens förfallodatum. Då kommer viatt använda forward swaps för att hedgea och för att minska antalet swapparkommer vi att använda kompression. Det andra fallet är när förfallodatumetuppnås under tiden som clearinghuset håller i portföljen. Dagarna innan för-fallodatumet kommer vi hedgea med forward swaps med kompression. Närdatumet är nått så kommer vi istället att använda ränteswappar.I båda fallen är resultaten nära att uppnå delta-neutralitet. Med normalis-erade deltan med avsenende på det nominella beloppet är medelvärdet avdelta-exponeringen av magnituden 10−4 för det första fallet och 10−6 för detandra. Men, det är värt att komma ihåg att allting är baserat på simuler-ade värden under förenklade antaganden. Denna avhandling bör utgöra enbra grund för vidare studier där man kan undersöka mer extrema mark-nadsrörelser. Med extremare rörelser skulle man kunna undersöka hedgn-ingsstrategier med andra Greker som till exempel Gamma och Vega.

Internal combustion engines has been used for more than 100 years. The use of the abundant energy supply stored as hydrocarbon fueled unprecedented economic growth. The use of hydrocarbons increased the work output of human labor significantly, thus increasing the economy and prosperity. However, during the latter part of the twentieth century negative consequences of the internal combustion engine has been noticed. Initially the being emissions of local pollutants such as carbon monoxide, nitrogen oxides and unburnt hydrocarbons. These pollutants have to this day in the western world been reduced significantly and further reductions are under way. Thereafter, has the focus been shifted somewhat to global emissions such as carbon dioxide due to the effect on the climate. However, as the most accessible oil resources have been exhausted the price of oil has five folded since the turn of the century, straining the exponential economic growth enjoyed for two centuries. Heavy duty diesel engine efficiency is still below 50\%, there is thus a need and a possibility to further increase engine efficiency. In this thesis, work has been done to increase the understanding of the flow prior to combustion. A better knowledge of pre-combustion in-cylinder flow would increase the possibility to reduce engine emissions and fuel consumption, through better mixing and lower heat transfer. The work presented is ordered in such a way that the flow structures created during the intake is presented first. Thereafter, the effect of compression is investigated. Intake flow structures are studied using Large-Eddy Simulations (LES) and experiments on a steady swirl test rig. The effects of compression are studied using simulations of predefined flow structures undergoing compression. It is found that the flow structures created during intake is qualitatively different depending of intake valve lift. And that a single Swirl Number (SN) is an insufficient quantity to characterize the flow created at low valve lifts, due to high fluctuations. During compression it is found that a high swirl number suppress small scale turbulence while the compression has an increasing effect of axial fluctuations due to vorticity-dilation interaction. Additionally, it is shown that turbulent kinetic energy is introduced in the flow field by the piston in the absence of tumble breakdown. / <p>QC 20130704</p>