SMDS measurements and modeling to predict performance

The authors describe a performance study of a trial switched multimegabit data service (SMDS) link (intended for inter-LAN connection) from the perspective of customers evaluating the feasibility of the link for some target applications. The goals were to take all measurements on the customer premises and to develop a methodology general enough to be used by customers to evaluate the link. The authors measured a lightly loaded system and developed a model of the SMDS connection suitable for evaluating applications via analysis or simulation. They document their methodology and present the SMDS connection delay values as well as a likely breakdown of the constituents of that delay. They used these data to create a simulation model and to simulate a simple application. In the trial configuration, where geographical distances were small, SMDS network delay was one of the notable components of end-to-end delay in the SMDS connection. However, for most packets, throughput is limited by the T1 capacity for transmitting SMDS cells, not by the SMDS network capacity

Effervescent Breakup and Combustion of Liquid Fuels: Experiment and Modelling

Tato práce se zaměřuje na oblast effervescentních sprejů a jejich aplikace na kapalné spalování s důrazem na průmyslové spalovací komory. Oba aspekty – modelování a experiment – jsou řešeny. Práce obsahuje obecný úvod, ve kterém jsou vysvětleny základní jevy rozpadu kapaliny a vířivého spalování a dále je představena effervescentní atomizace. Poté jsou popsány použité experimentální postupy jak pro měření spreje, tak pro měření tepelných toků do stěn při spalování. V následující kapitole jsou popsány numerické modely a jejich podstata je vysvětlena. Jsou zde uvedeny modely pro rozpad spreje, turbulenci a spalování použité během výzkumu. Vlastní výsledky práce jsou uvedeny formou samostatných článků (vydaných nebo přijatých) s dodatečnou částí věnovanou nepublikovaným relevantním výsledkům. Bylo zjištěno, že standardní modely sprejů jsou do jisté míry schopny popsat effervescentní spreje. Nicméně aby bylo možné predikovat plamen kapalného spreje, jsou zapotřebí detailnější modely sprejů, které dokáží přesně zachytit změnu průměrů kapek v radiálním a axiálním směru. Experimentální měření effervescentních sprejů bylo provedeno pomocí navrhnuté metodiky. Výsledky měření byly analyzovány s důrazem na radiální a axiální vývoj průměrů kapek a některé nové jevy byly popsány. Nepřímá úměrnost mezi gas-liquid-ratio a středním průměrem kapek byla potvrzena. Dále by popsán jev, kdy pro různé axiální vzdálenosti které dojde k úplnému převrácení závislosti středního průměru na axiální vzdálenosti. V závěru je uvedeno shrnutí, které rekapituluje hlavní výsledků a závěry. V závěrečných poznámkách je nastíněn možný budoucí postup. Experimentální data pro ověřování budoucích effervescentních modelů jsou poskytnuta.This thesis presents an investigation of effervescent sprays and their application to spray combustion with emphasis on large-scale combustors. Both aspects – modelling and experiment – are addressed. The thesis contains a general introductory part, where underlying phenomena of spray forming and turbulent combustion are explained and effervescent atomization is presented. Then, adopted experimental approaches are described both for the spray measurement and for the measurement of wall heat fluxes during combustion experiments. In the following chapter numerical models and their philosophy is discussed. Models for spray formation, turbulence and combustion adopted during the research are introduced and explained. The actual results of the thesis are presented in form of separate papers (published or accepted for publication) with an additional section devoted to unpublished relevant results. It is found that standard spray models can to some extent represent effervescent sprays. However, in order to predict a spray flame more detailed spray models are needed in order to describe accurately radial and axial variations of drop sizes. Numerous experimental measurements of effervescent sprays are performed using a proposed methodology. Drop size data are analysed with emphasis on radial and axial drop size evolutions and some new phenomena are described. The inverse relationship between gas-liquid-ratio and mean diameter has been confirmed. Moreover a complete reversal in radial mean diameter trends for various axial locations has been described. Finally, a result summary is put forward that recapitulates the main accomplishments and conclusions. In the closing remarks possible future research is outlined. Experimental data for future effervescent model validations are disclosed.

Role of physical and chemical properties of single and multicomponent liquid fuels on spray processes, flame stability, and emissions, The

2019 Fall.Includes bibliographical references.Ensuring reliable and clean combustion performance of IC engines, such as liquid-fueled gas turbines, is associated to our understanding of the impact of fuel composition and properties, as well as the processes that the liquid fuel experiences, e.g., atomization, vaporization, turbulent mixing, and chemical kinetics, on the combustion efficiency, stability, and emissions. This understanding is a key prerequisite to the development of fuel surrogates and the deployment of alternative jet fuels. Most of the surrogate formulation activities, especially with regard to aviation fuels, have targeted only the gas-phase behavior of the real fuels, often neglecting properties responsible for atomization, vaporization, and fuel/air mixing (i.e., physical properties). In addition, much research has been done to understand the flame stability (e.g., lean blowout limit and flame liftoff height) of gaseous and pre-vaporized fuels. Thus, the optimization of the fuels and the liquid fueled combustion devices, e.g., gas turbines, requires the consideration of the two-phase process and the coupling between the complex physical and chemical processes. This will improve the understanding of the mechanisms that controls flame lean blowout limit and liftoff height of liquid fuels. Therefore, an appropriate surrogates will be formulated and a faster processes to certify the alternative fuels will be achieved. In this work, the flame stability in spray burner, quantified by flame lean blowout liftoff height, for different single, binary, alternative, and conventional fuels were experimentally measured. The flame behavior from the spray burner was compared to the results which was done using gaseous flame platform, e.g., counterflow flame burner, to clearly demonstrate the significant importance of two-phase spray processes (i.e., atomization, vaporization, and turbulent mixing) on flame stability. It was found that the atomization process, which can lead to the variation of the droplet size and distribution, has significant impact on flame stability. This is because any change in the droplet size can enhance/diminish the vaporization and mixing processes, and therefore influence the clean and efficient energy conversion process. In addition, the sensitivity of the fuels properties on flame stability was evaluated to provide an explanation for why certain fuel properties govern flame stability, such as lean blowout and liftoff height. Thus, flame stability mechanisms can be developed. A number of approaches were used in this work to address these issues, such as multiple linear regression analysis, and previously developed correlations. The results indicate the importance of the atomization process (i.e. droplet size) on the vaporization rate and suggest that the liquid fuel fraction entering the flame plays a dominant role in controlling lean blowout limits. Thus, the large droplet and less volatile fuel was the most resistance fuel to flame blowout. The differences in liftoff height was shown to be a result of two-phase flame speed, which accounts for both pre-vaporized fuel reactivity defined by laminar flame speed (SL) and time scales associated with droplet evaporation. The influence of the physical and chemical properties of different jet fuels on spray process and thus on emissions is also investigated. This is done by measuring soot formation using Laser-Induced Incandescence (LII). The trends in spray flame soot formation are compared to the gas-phase Yield Sooting Index (YSI). Results indicate differences in planar soot distributions amongst the fuels and suggest a significant influence of the atomization and the vaporization processes on mixing and the soot formation

An energy-aware scheduling approach for resource-intensive jobs using smart mobile devices as resource providers

The ever-growing adoption of smart mobile devices is a worldwide phenomenon that positions smart-phones and tablets as primary devices for communication and Internet access. In addition to this, the computing capabilities of such devices, often underutilized by their owners, are in continuous improvement. Today, smart mobile devices have multi-core CPUs, several gigabytes of RAM, and ability to communicate through several wireless networking technologies. These facts caught the attention of researchers who have proposed to leverage smart mobile devices aggregated computing capabilities for running resource intensive software. However, such idea is conditioned by key features, named singularities in the context of this thesis, that characterize resource provision with smart mobile devices.These are the ability of devices to change location (user mobility), the shared or non-dedicated nature of resources provided (lack of ownership) and the limited operation time given by the finite energy source (exhaustible resources).Existing proposals materializing this idea differ in the singularities combinations they target and the way they address each singularity, which make them suitable for distinct goals and resource exploitation opportunities. The latter are represented by real life situations where resources provided by groups of smart mobile devices can be exploited, which in turn are characterized by a social context and a networking support used to link and coordinate devices. The behavior of people in a given social context configure a special availability level of resources, while the underlying networking support imposes restrictionson how information flows, computational tasks are distributed and results are collected. The latter constitutes one fundamental difference of proposals mainly because each networking support ?i.e., ad-hoc and infrastructure based? has its own application scenarios. Aside from the singularities addressed and the networking support utilized, the weakest point of most of the proposals is their practical applicability. The performance achieved heavily relies on the accuracy with which task information, including execution time and/or energy required for execution, is provided to feed the resource allocator.The expanded usage of wireless communication infrastructure in public and private buildings, e.g., shoppings, work offices, university campuses and so on, constitutes a networking support that can be naturally re-utilized for leveraging smart mobile devices computational capabilities. In this context, this thesisproposal aims to contribute with an easy-to-implement  scheduling approach for running CPU-bound applications on a cluster of smart mobile devices. The approach is aware of the finite nature of smart mobile devices energy, and it does not depend on tasks information to operate. By contrast, it allocatescomputational resources to incoming tasks using a node ranking-based strategy. The ranking weights nodes combining static and dynamic parameters, including benchmark results, battery level, number of queued tasks, among others. This node ranking-based task assignment, or first allocation phase, is complemented with a re-balancing phase using job stealing techniques. The second allocation phase is an aid to the unbalanced load provoked as consequence of the non-dedicated nature of smart mobile devices CPU usage, i.e., the effect of the owner interaction, tasks heterogeneity, and lack of up-to-dateand accurate information of remaining energy estimations. The evaluation of the scheduling approach is through an in-vitro simulation. A novel simulator which exploits energy consumption profiles of real smart mobile devices, as well as, fluctuating CPU usage built upon empirical models, derived from real users interaction data, is another major contribution. Tests that validate the simulation tool are provided and the approach is evaluated in scenarios varying the composition of nodes, tasks and nodes characteristics including different tasks arrival rates, tasks requirements and different levels of nodes resource utilization.Fil: Hirsch Jofré, Matías Eberardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto Superior de Ingeniería del Software. Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto Superior de Ingeniería del Software; Argentin

AAPS Workshop Report: Strategies to Address Therapeutic Protein–Drug Interactions during Clinical Development

Therapeutic proteins (TPs) are increasingly combined with small molecules and/or with other TPs. However preclinical tools and in vitro test systems for assessing drug interaction potential of TPs such as monoclonal antibodies, cytokines and cytokine modulators are limited. Published data suggests that clinically relevant TP-drug interactions (TP-DI) are likely from overlap in mechanisms of action, alteration in target and/or drug-disease interaction. Clinical drug interaction studies are not routinely conducted for TPs because of the logistical constraints in study design to address pharmacokinetic (PK)- and pharmacodynamic (PD)-based interactions. Different pharmaceutical companies have developed their respective question- and/or risk-based approaches for TP-DI based on the TP mechanism of action as well as patient population. During the workshop both company strategies and regulatory perspectives were discussed in depth using case studies; knowledge gaps and best practices were subsequently identified and discussed. Understanding the functional role of target, target expression and their downstream consequences were identified as important for assessing the potential for a TP-DI. Therefore, a question-and/or risk-based approach based upon the mechanism of action and patient population was proposed as a reasonable TP-DI strategy. This field continues to evolve as companies generate additional preclinical and clinical data to improve their understanding of possible mechanisms for drug interactions. Regulatory agencies are in the process of updating their recommendations to sponsors regarding the conduct of in vitro and in vivo interaction studies for new drug applications (NDAs) and biologics license applications (BLAs)

A Phenomenological Investigation of Ignition and Combustion in Alternative-Fueled Engines

Current diesel technologies involve a broad spectrum of combustion regimes. Previous diesel combustion models either lack the universality across various combustion regimes or suffer computational cost. This dissertation discusses the development of a phenomenological framework to identify and understand key in-cylinder processes that influence the overall performance of a compression ignition engine. The first part of this research is focused on understanding the ignition delay (ID) of diesel fuel in a pilot-ignited partially premixed, low temperature natural gas (NG) combustion engine. Lean premixed low temperature NG combustion is achieved by using small pilot diesel sprays (2-3% of total fuel energy) injected during early compression stroke (about 60° BTDC). Modeling ignition delay at advanced pilot injection timings (50°-60°BTDC) presents unique challenges. In this study, single component droplet evaporation model in conjunction with the Shell hydrocarbon autoignition (SAI) model is used to obtain ignition delay predictions of pilot diesel over a wide range of injection timings (20°-60° BTDC). Detailed sensitivity analysis of several SAI model parameters revealed that the model parameter Aq, which influences chain initiation reactions, was most important to predict ignition delays at very lean equivalence ratios. Additional studies performed to ascertain critical model parameters revealed that ignition delay was particularly sensitive to intake manifold temperature over the range of injection timings investigated. Finally, the validated SAI model was used to predict ignition delays of pilot diesel fuel at various exhaust gas recirculation (EGR) substitutions, intake manifold temperatures and engine loads (bmep = 6 bar and 3 bar, respectively). The second part of this research involved the development of a phenomenological simulation of diesel/biodiesel combustion, which included sub-models for diesel spray entrainment, evaporation, ignition and premixed and mixing-controlled combustion. In the simulation, the cylinder contents consisted of an unburned zone, packet zones, and a burned zone. The simulation, after appropriate calibration, was capable of predicting cylinder pressure and heat release rates at different engine load conditions over the injection timing range of 0°BTDC to 10°BTDC. The total number of packets, droplet evaporation rates, air entrainment rates; ignition delay and premixed/mixing-controlled reaction rate parameters had a profound influence on combustion predictions

Improving Methods for Propensity Score Analysis with Mis-Measured Variables by Incorporating Background Variables with Moderated Nonlinear Factor Analysis

There has been some research in the use of propensity scores in the context of measurement error in the confounding variables; one recommended method is to generate estimates of the mis-measured covariate using a latent variable model, and to use those estimates (i.e., factor scores) in place of the covariate. I describe a simulation study designed to examine the performance of this method in the context of differential measurement error and propose a method based on moderated nonlinear factor analysis (MNLFA) to try to address known problems with standard methods. Although MNLFA improves effect estimation somewhat in the presence of differential measurement error relative to standard factor analysis methods, the greatest gains come from the nonstandard practice of including the treatment variable as an indicator in the scoring models. More research is required on the effects of model misspecification on the performance of these methods for causal inference applications.Master of Art

Doctor of Philosophy

dissertationAtomization is chaos. The breakup of liquid structures by a gas encompasses such a wide range of possible configurations that a definitive mechanism describing breakup in any and all situations is an impossibility. However, when focus is applied, trends can be teased out of experimental data that seem to appropriately describe the action undertaken. These studies sought to better understand atomization, specifically coaxial, two-stream, airblast (or air-assist) atomization in which a central liquid jet is broken up by an annular, high-velocity gas stream. The studies enclosed focused on identifying the effect of changing the atomizer's scale on atomization. While most (but not all) atomization studies only focus on the resulting far-field drop diameters, these studies placed the focus largely on the intermediate structures, in the form of the intact liquid jet (ILJ), while also quantifying the resulting drop diameters. The location and shape of the ILJ constantly change, and on its surface, wavelengths were seen to form and grow, which have been correlated to the resulting drop diameters in previous studies. The studies enclosed herein are unique in that they attempt to apply and explain exiting mechanism-based breakup mechanisms to regimes, fluids, and geometry changes not yet evaluated in the literature. Existing correlations were compared to the experimental data for a range of atomizer geometries, and when they were found lacking, Buckingham-$\Pi$ theorem was used to develop new correlations for predicting behavior. Additionally, the method developed for the calculation of these parameters for other image sets is included, allowing for easy comparison and value verification. A small-scale, coaxial atomization system was used to atomize water and two silicone oils with air. The atomizers used in these studies had the same general geometry type, but had varying sizes, allowing for the effect of both scale and geometry to be evaluated. These studies quantified instability development and growth along with the resulting spray characteristics, allowing for correlations to be made between the two data sets as the more recent mechanism-based atomization models do. Existing mechanism-based models from the literature are compared to the experimental results, as these existing models have not been evaluated significantly with changing atomizer geometry, high-viscosity fluids, and high flow regimes as was done here. Additionally, two experimental campaigns were undertaken with atomizers used to operate the University of Utah's PDU-scale (process development unit) entrained flow gasifier. The first campaign showed the effect of gas velocity, atomizer load (total flow), and gas-liquid impingement angle on the qualitative cold-flow atomizer performance. These trends are then tied to behavior of the entrained flow gasifier, showing the existence of a minimum required degree of atomization to avoid substantial losses in fuel conversion and efficiency in a gasifier. The second campaign showed the effect of gas flow, liquid flow, and fluid on the quantitative cold-flow atomizer performance. While in the literature, changing fluid properties of Newtonian fluids are shown to have a relatively linear response on atomizer performance, the behavior of non-Newtonian fluids was shown to be much more complex and difficult to predict. The correlations developed for the small-scale atomizers are applied to the micro-hole atomizers and found to be erroneous for the change in atomizer geometry. Buckingham-$\Pi$ theorem is then used to develop correlations to predict the spray Sauter mean diameter for the micro-hole atomizers. Slurry-fed combustion and gasification systems are but one industrial implementation of atomization. Atomization plays important roles in numerous other industries, and despite decades of study, it is not well understood. This document serves to shed some light on a few small, specific subsets of the topic

Development and education of a liquid jet atomization and spray evolution simulation

A new computer model for liquid atomization and breakup has been developed. The new code, LISAM, was written specifically to model non-reacting liquid sprays injected into simple chamber geometries. Momentum and continuity equations are solved to model the gas flow, and gas/droplet interaction is included through a gas momentum source term. Parametric studies and comparisons with experimental data were performed. Parametric studies yielded conclusions about drop size distributions and spray penetration behavior. Turbulence modeling is not currently included in LISAM, however the results of parametric simulations with viscosity levels set at higher levels suggest that turbulence effects may be important for both drop sizes and spray dispersal. Parcel injection rates must be large enough to ensure statistically significant results. Trade-offs in parcel injection rate and grid density must be made to find a level that provides accurate predictions without resulting in unreasonably high run times. Comparisons with NASA water/air experiments underscored the need for more complete experimental information. Experimental researchers need to provide as much detailed information on experimental setup and data acquisition as possible. Simple test configurations that provide drop size and velocity distributions as well as spray penetration rates and even gas field visualization would be useful for detailed evaluation of code models