Nine 1B/1R translocated soft red winter wheat (SRWW) varieties and six non-1B/1R varieties from two crop years (1995-1996 and 1996-1997), grown in two Virginia locations (Warsaw and Blacksburg), were studied to evaluate the effects of the 1R rye chromosome on soft wheat flour quality and baking performance. The presence of the 1B/1R chromosomal translocation in wheat has been reported to provide disease resistance, but produce sticky doughs. The 1995-1996 and 1996-1997 SRWW flours were subjected to farinograph analysis and dough stickiness testing. Dough stickiness was determined by the Schwarzlaff-Shepherd Dough Stripping Method. Wheat samples from 1995-1996 were also analyzed for protein, ash, and moisture content, alkaline water retention capacity (AWRC), cookie diameter, tensile stress and strain, and by ¹³C nuclear magnetic resonance (¹³C-NMR) spectroscopy techniques. Significant (p = 0.0001) negative correlations were found between AWRC and cookie diameter of SRWWs grown in Warsaw and Blacksburg. Location was found to exert a significant effect on AWRC, cookie diameter and stickiness (p < 0.05). Farinograph data revealed that mixing characteristics of SRWW were affected significantly by variety, crop year and location (p < 0.05). In some cases the 1B/1R varieties had lower breakdown rates, longer departure times (DT) and lower mixing tolerance index (MTI), than their non-1B/1R counterparts. There was a significant difference (p = 0.0133) in the stickiness of 1B/1R and non-1B/1R samples from Blacksburg. However no such difference was found in the corresponding Warsaw samples (p = 0.9826), indicating that location exerted a significant effect on stickiness. Two flour samples exhibiting stickiness (one with and one without 1B/1R) and two non-sticky samples (one with and one without the 1B/1R) were fractionated into gluten, starch and water-solubles (WS) in order to determine if the sticky dough factor resided in the 1B/1R and / or non-1B/1R WS. The peel time of the interchanged samples, as in the case of 'Massey' flour combined with the WS from VA52-22, increased to 79 seconds from the 30 seconds originally observed in the Massey flour. However when gluten and starch fractions from a non-sticky, non-1B/1R sample,VA54-21, were mixed with WS from VA54-211 (sticky, 1B/1R), the peel time went from 18 in the original flour to 8 seconds. Tensile measurements showed dough stress was not significantly affected by the presence or absence of 1B/1R (p = 0.7057). However, dough strain was lower in 1B/1R translocated SRWWs (p = 0.0048). A ¹³C-NMR spectra failed to show differences amongst selected 1B/1R and non-1B/1R dough samples. Proton relaxation time (T1-rho-[H]) - a ¹³C-NMR technique, indicated that water did not exert a significant influence on the molecular dynamics within the dough samples of Massey (non-1B/1R), VA54-211 (1B/1R) and VA52-22 (1B/1R). However, the non-sticky, non-1B/1R sample (VA54-21) had a higher proton relaxation time at 62 ppm which may indicate the size of starch-protein particles in VA54-21 doughs were larger and less flexible than in the other three doughs. / Ph. D.

Made available in DSpace on 2016-12-12T20:15:52Z (GMT). No. of bitstreams: 1 Rafael Marques.pdf: 14630401 bytes, checksum: 352c48d8c01e0db8ba6b41f5e8317ec8 (MD5) Previous issue date: 2015-03-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The main subject developed in this dissertation is the characterization of the dynamics of high-dimensional conservative systems using different statistical approaches. Looking at the conservative system phase-space, we can find chaotic and regular regions that are characterized by a random distribution of points and periodic structures formed by closed orbits, respectively. The nonlinearity parameter has a fundamental hole to the occurrence of chaotic trajectories that can get stuck for a finite time on the vicinity of regular regions. This phenomenon is known as stickiness effect and can be identified using different tools as the spectrum of finite time Lyapunov exponents or the recurrence time statistics (RTS), e.g. Throughout this dissertation, we propose to characterize this effect using such approaches and also apply a new methodology which uses the time series of the spectrum of finite time Lyapunov exponents to separate the dynamics in different regimes of motion. For this purpose, we study two conservative systems that are derived from standard map, a symplectic map extensively used to investigate the transition from regular to chaotic dynamic. The first system consists in a chain of coupled standard maps that originates a 2N-dimensional system, where N is the number of coupled maps. Using this system, from the definition of regimes of motion, we obtained the cumulative distribution of the consecutive time that the trajectory spends in a particular regime, which reproduces with a good precision the results obtained when using the RTS. The second system studied was the Modified Standard Map, which is obtained adding an action variable to the standard map. The coupling with an extra dimension allows the penetration of the regular structures by the trajectories, what was forbidden for the two-dimensional case. The application of the method of separation of regimes in this system enables a more detailed analysis of the stickiness effect, showing that only the trajectories located near the regular structures have Local Lyapunov exponents about zero. Thus, the development of this research contributes to a better understanding of the stickiness effect in high-dimensional conservative systems. / O tema principal desenvolvido nesta dissertação de Mestrado está relacionado com o estudo da dinâmica de sistemas conservativos, utilizando diferentes abordagens estatísticas. Ao analisarmos o espaço de fases de um sistema dinâmico pertencente a esta classe, podemos encontrar regiões caóticas e regulares que são caracterizadas pela distribuição aleatória de pontos e por estruturas periódicas formadas por órbitas fechadas, respectivamente. O parâmetro de não-linearidade tem um papel fundamental na existência de trajetórias caóticas que podem ser aprisionadas por um tempo finito nas proximidades das regiões regulares. Este fenômeno é conhecido como efeito stickiness, e pode ser identificado através da utilização de diferentes abordagens como, por exemplo, o espectro de Lyapunov calculado a tempo finito ou a estatística dos tempos de recorrência de Poincaré (ETR). No decorrer desta dissertação, propomos caracterizar o efeito stickiness utilizando tais abordagens, além de aplicar uma nova metodologia que consiste em analisar séries temporais do espectro de expoentes de Lyapunov afim de definir diferentes regimes de movimento. Para isso, estudamos dois sistemas conservativos multidimensionais derivados do mapa padrão, um mapa simplético muito utilizado para a investigação da transição da dinâmica regular para caótica. O primeiro deles consiste em uma rede de mapas padrão acoplados que dá origem a um sistema de 2N-dimensões, sendo N o número de mapas acoplados. Utilizando este sistema, a partir da definição de regimes de movimento, foi possível determinar a distribuição cumulativa do tempo consecutivo que a trajetória permanece em um determinado regime, sendo que os resultados obtidos por meio da análise desta quantidade podem reproduzir de forma satisfatória aqueles obtidos quando utilizamos a ETR. O segundo sistema estudado foi o Mapa Padrão Modificado (MPM), resultante do acoplamento entre uma variável ação extra e o mapa padrão tradicional. O acoplamento com uma dimensão extra permite que trajetórias penetrem nas regiões de regularidade, o que antes era proibido para o caso bidimensional. A aplicação da técnica de separação de regimes neste sistema permite uma análise mais detalhada do efeito stickiness, mostrando que apenas trajetórias que se encontram em torno das estruturas de regularidade possuem expoentes de Lyapunov Locais com valores próximos a zero. Desta forma, o desenvolvimento desta pesquisa contribui para o melhor entendimento do efeito stickiness em sistemas conservativos de alta dimensionalidade.

Detta examensarbete gjordes i samarbete med det svenska eye tracking företaget Tobii AB, på avdelningen Tobii Tech. Syftet med arbetet var att utforska termen mänsklig teknologi och undersöka hur deras produkt EyeX i högre grad kan skapa naturligare och intuitivare interaktioner med datorn. För att åstadkomma detta har ett explorativt tillvägagångssätt, uppdelat i en teoretisk och praktisk del med sekundära, godtagbara källor och kvalitativ datainsamling. Examensarbetet initierades med den teoretiska delen i syfte att erhålla generell kunskap om eye tracking och dess nuvarande tillämpningsområden. Idag används eye tracking främst i forskningssyften och som kommunikations- och interaktionsverktyg för funktionshindrande. Tvärtemot dess nuvarande användningsområden, är målet med EyeX är att nå ut till konsumentoch spelmarknaden och därmed har examensarbete begränsats till icke funktionshindrande. Den teoretiska delen fortsattes med: mänskliga faktorer och mänskligare människa-dator interaktioner. Detta utgjorde en bas för att skapa en förståelse för hur mänskliga relationer skapas och hur mänskliga emotionella faktorer skulle kunna kopplas till datorinteraktion. Vidare i arbetet gjordes den praktiska delen: tre workshops, för att utreda relevansen av resultatet från litteraturstudien och en kvalitativ datainsamling i form av intervjuer och observationer av EyeX användare. Användarstudien visade att emotionella faktorer är viktiga vid design utav gränssnitt och därmed bör användas vid utveckling av människa–datorinteraktioner. Slutligen, för att undersöka till vilken grad mänskliga aspekter skulle kunna användas, gjordes ytterligare en workshop, där fakta från litteraturstudien användes för att koppla till praktiska tillämpningar av eye tracking och datorinteraktioner. Slutsatserna av arbetet resulterade  iutvecklingen av två utvärderingsmetoder för att analysera mänsklig teknologi: en designguide uppbyggd på frågor för att utveckla mänskligare datorinteraktioner. / This thesis has been done in collaboration with the Swedish eye tracking company Tobii AB, at the department Tobii Tech. The purpose has been to investigate what humanized technology means and how Tobii’s product EyeX can enhance a more natural and humanized interaction with the computer. This work has been conducted throughout an explorative approach; using secondary sources from relevant literature and qualitative studies; divided in a theoretical and practical part. Firstly, a theoretical part was conducted to gain general knowledge about the eye tracking and its different areas of implementation. Currently, eye tracking can be found in various fields of research and communication tools for people with neurological disabilities. Contrary to those application areas of eye tracking, EyeX is aimed for the consumer and gaming market and therefore the work is limited to able-bodied users. This was continued by research concerning: human interactions and humanization in human-computer interaction. The theoretical part of this project created a foundation for how relationships are created and how emotional aspects of human characteristics could possibly be related to computer interaction. It also described how a meaningful and lasting relationship could be created with computers and their various features by the means of habits. Furthermore, the work continued with the practical part: three workshops, performed to further understand the relevance of the results from the related work and qualitative data collection through interviews and observations with EyeX users. By the end of the user study it could be assumed that emotional aspects of human characteristics was essential for the development of interfaces and therefore should be implemented in human-computer interactions. Finally, a supplementary workshop was conducted to clarify how emotional and abstract factors could easier be related to practical eye tracking and computer features. Also, two evaluation methods were created for evaluating humanization and emotional aspects in features/products.

Submitted by silvia matos (silvia.matos@fgv.br) on 2011-05-11T12:11:33Z No. of bitstreams: 1 Tese_SilviaMatos.pdf: 612943 bytes, checksum: afbbe0d255820e85eb4639ae4f0ef00e (MD5) / Approved for entry into archive by Andrea Virginio Machado(andrea.machado@fgv.br) on 2011-05-11T12:35:35Z (GMT) No. of bitstreams: 1 Tese_SilviaMatos.pdf: 612943 bytes, checksum: afbbe0d255820e85eb4639ae4f0ef00e (MD5) / Made available in DSpace on 2011-05-11T18:12:35Z (GMT). No. of bitstreams: 1 Tese_SilviaMatos.pdf: 612943 bytes, checksum: afbbe0d255820e85eb4639ae4f0ef00e (MD5) Previous issue date: 2010-11-08 / The purpose of this thesis is to investigate the price-setting behavior in Brazil and, in particular, the effects on inflation and good-level real exchange rate persistence. This thesis is composed by three Chapters. In the first Chapter, we present the main stylized facts about the behavior of retail prices in Brazil using micro data from the CPI index computed by the Fundação Getulio Vargas. Moreover we construct time series of price-setting statistics and relate them to macroeconomic variables using regression analyses. In Chapter 2, we investigated the relevance of heterogeneity in countries price stickiness on good-level real exchange rate persistence, considering a newly constructed panel data set of relative prices of 115 common products between the U.S. and Brazil. Chapter 3 is devoted to the relation between sectoral price stickiness and inflation persistence. / O objetivo desta tese é investigar as estratégias de precificação no Brasil, enfatizando os efeitos sobre a persistência da inflação e da taxa de câmbio real setorial. Esta tese é composta por três capítulos. No primeiro capítulo, nós apresentamos as principais características do comportamento dos preços no Brasil, utilizando os microdados do Índice de Preços ao Consumidor, computado pela Fundação Getúlio Vargas. Adicionalmente, nós construímos as séries de tempo das estatísticas de price-setting e as relacionamos com as variáveis macroeconômicas utilizando análise de regressão. No capítulo 2, nós investigamos o efeito da heterogeneidade da rigidez de preços entre países sobre a persistência da taxa de câmbio real setorial, considerando um painel de preços relativos de 115 produtos comuns entre Brasil e EUA. Por fim, o capítulo 3 explora a relação entre rigidez de preço setorial e persistência inflacionária.

Studien har undersökt millenniers köpbeteende på kommersiella hemsidor online med syfte att få en djupare förståelse för dessa beteenden. Detta har undersökts med hjälp av följande två forskningsfrågor: ”Vilka faktorer påverkar millenniers val av kommersiella hemsidor?” samt ”Vilka faktorer påverkar millennier att stanna kvar på en hemsida och spendera pengar?”. Studien har grundats i teorier om influencer marketing och online stickiness. Empirin samlades in via en kvalitativ studie och djupintervjuer med sex stycken millennier genomfördes. Resultatet visade att influencer marketing har en signifikant påverkan på millenniers val av hemsidor. Vidare är hemsidans design och utseendet de främsta faktorerna som påverkar millennier att vilja stanna kvar på en hemsida. Viljan att stanna på en hemsida och spendera pengar påverkas främst av tilliten till hemsidan. / The purpose of this thesis has been to describe and explore millennials’ buying behavior on commercial websites. In order to reach this purpose, two research questions have been posed: “What factors influence millennials’ choice of a website?”; and “What factors influence millennials to stick around and spend money?”. Based on this overall purpose and research questions, a literature review was conducted in order to arrive at a frame of reference, used to guide the study’s data collection. Methodologically, a qualitative approach was used, using six, in-depth interviews with millennial students from Sweden. The findings indicate that influencer marketing has a significant effect on millennial’s choice of a commercial website. However, the design and appearance of such a website are the main factors that influence and persuade them to stick around. On the other hand, in order to get millennials to spend their money on a commercial website, the biggest factor is if they trust that site.

No description available.

This thesis examines both conventional and unconventional monetary policies in a DSGE model with an interbank market friction. The recent crisis during 2007-2009 affected economies worldwide and forced central banks to implement not just conventional monetary policies, but also direct interventions in financial markets. We investigate a DSGE model with financial frictions, to test conventional and unconventional monetary policies. The thesis starts by using the Gertler and Kiyotaki (2010)'s modelling framework, to examine eight different shocks under imperfect interbank market conditions. Unlike Gertler and Kiyotaki (2010) who consider the two extreme cases for the banking system, I firstly extend the analysis to a case in between the two extreme cases that they examined. The shocks considered include supply and demand shocks and also two shocks from the financial system itself (an interbank market shock and a shock to the deposit market). It is found that a negative shock to the interbank market has only a moderate impact to the banking system. However, a shock to the deposit market has a much stronger impact. Even though the impacts of these shocks are not large it is shown that thefinancial frictions magnify the effects of other shocks. The model is extended to include price stickiness. A modified Taylor rule is analysed to test how conventional monetary policy should respond to the shocks in the presence of financial frictions. Specifically the credit spread is added as a third term in the monetary policy rule. The stabilising properties of the policy rule are analysed and a welfare analysis is conducted. The model is further developed to include unconventional monetary policy in the form of direct lending to private sector firms from the central bank. A policy rule for unconventional policy is tested and its stabilising and welfare properties are analysed.

Using social media and norm-breaking material as an empirical touchstone this thesis elaborates, investigates and explores the entangled relationships between humans and technology in social media settings. Guided by uncomfortable, emotional and bodily online sharing the thesis gives voice to stories that are seldom heard, by people whose lives are rarely spoken of. By exploring the performative entanglements of/with/through technology, design and human intent the overall aim is to offer a critical and new understanding of our online togetherness and posthuman becoming. The conceptual framework throughout the thesis is based on posthuman theory and feminist technoscience, two closely connected theories providing a new onto-epistemological way of understanding the world’s becoming. The thesis should be seen as the product of an empirical practice of making theory about digital things, culture, humans and non-humans. By exploring diffraction and touch as not only theoretical standpoints but also hands-on methodology the thesis contributes to the development of new ways of doing research. Important findings arising from the practice of diffraction and touch are Technoemotions – conceptually agents built on a posthuman understanding of how emotions are entangled between and within the phenomenon, becoming important agents in the apparatus creating the phenomenon. Four Technoemotions seem particularly prominent in the material: Trust, Truth, Time and Embodiment. The thesis concludes by providing a discussion on critical alternatives for ethics, politics and power in relation to social media and the norms and norm-breaking practices most of us participate in. The responsibility and ability to respond are addressed, as well as social justice and hope for the future to come. / Sociala medier har för många människor blivit en naturlig del av vardagen där den digitala gemenskapen är lika viktig som den analoga. På platser så som Facebook, Twitter, bloggar och Instagram kommunicerar vi genom att dela med oss av tankar, händelse och åsikter i vår vardag. Vi varvar bilder från vår semester med politiska artiklar, delar vidare kloka citat eller resultatet från ett test av något slag, skryter på våra barn, filmar våra husdjur, delar med oss av sjukdomstillstånd och barnafödande och allt annat som en vardag kan vara fylld av. Just själva delandet är ett viktigt fundament i sociala mediers blivande och dess design är ofta optimerad för att kunna dela samma inlägg till flera olika sociala plattformar med ett enkelt klick. Denna avhandling handlar om hur vi genom sociala medier blir tillsammans på nätet, hur vi formar varandra men även hur vi formas av de tekniska scripts och den design som sociala medier är uppbyggt av. I avhandlingen får läsaren ta del av ett stort normbrytande empiriskt material. Med avstamp i detta normbrytande undersöker sedan författaren hur feministisk teknovetenskap och posthumanistisk teori kan användas som konkret metod för analys. Genom att applicera både närhet och diffraktion till det normbrytande empiriska materialet finner författaren det hon valt att kalla Teknoemotioner – konceptuella agenter som har sitt ursprung i sammanflätningar av digitala, sociala, mänskliga och icke-mänskliga material och kompositioner. Fyra teknoemotioner är särskilt framträdande, dessa är: förtroende, sanning, tid och förkroppsligande men författaren nämner också friktion och frusna berättelser som viktiga för att förstå fenomenet normbrytande delningar i sociala medier. Förtroende, sanning, tid och förkroppsligande är teknoemotioner som befinner sig i mellanrummet mellan skilda delningspraktiker i sociala medier. Dessas teknoemotioner skapar förutsättningar och påverkar upplevelser, ger indikationer om möjliga skillnader och likheter som är av betydelse för hur vi blir tillsammans med digitala material genom sociala medier. Författaren ger exempel på att det visserligen ofta är först i sin frånvaro som teknoemotioner blir uppenbara och får agens. Därmed konstaterar författaren att teknoemotioner också ofta är sin motsats. Analysen visar vidare att användare ofta uppfattar teknoemotionerna som valbara, exempelvis sanning. I sociala medier är sanning ofta en komplex agent, som ifrågasätts eller behandlat som något var och en får/kan avgöra på egen hand. Förtroende likaså. Med teknoemotionen, förkroppsligande, framgår också en tvetydighet, där kroppen (den fysiska) saknas i det virtuella rummet även om digitala kroppar är högst närvarande. Kan det vara så att känslan av anonymitet växer sig starkare om jag kan välja att vara i eller utanför min kropp?  Slutligen, tid. Tid är inte detsamma på internet som vi är vana. Där är tid ett högt arbiträrt begrepp och vi befinner oss i vår historia, samtid och till viss del även får framtid simultant. Avhandlingen avslutas med en metareflektion över hur det är möjligt att skapa kunskap om komplexa posthumanistiska fenomen där mänsklig handlingsförmåga vävs samman med digitala material och dess skilda rationaliteter. Genom att efterfråga alternativa ideal för kunskapsutveckling och design där etik, politik och makt är viktiga inslag hoppas författaren på en kritisk och alternativ förståelse av den verklighetsproduktion som sociala medier (och andra posthumana fenomen) bidrar till.

[pt] Nesse trabalho usamos um modelo DSGE de preços rígidos para estudar os efeitos de uma regra monetária que reage a mudanças no núcleo de inflação ao invés da inflação cheia. Começamos discutindo as dificuldades de inclusão das medidas de núcleo em nosso modelo DSGE e apresentamos uma solução viável. Com base em uma versão estilizada do modelo, mostramos que as volatilidades do núcleo e inflação cheia podem variar bastante dependendo da regra monetária adotada. Os resultados são interpretados em função da contribuição de choques agregados e setoriais na variância do núcleo e inflação cheia. A seguir conduzimos um exercício quantitativo com foco na Austrália. O interesse no último deriva da nossa percepção de que a autoridade monetária australiana começou a responder aos movimentos do núcleo de inflação por volta de 2007. Entretanto, nosso modelo calibrado não é capaz de reproduzir o comportamentos das medidas de inflação depois de 2007. / [en] We use a multi-sector sticky-price DSGE model to study the effects of a monetary rule that responds to changes in the underlying measure of inflation as opposed to headline inflation. We discuss the difficulties of including the underlying measure in our DSGE model and present a feasible solution. Using a stylized version of the model, we show that headline/underlying volatilities can experience significant changes under a policy rule that reacts to the underlying measure. The results are interpreted on the basis of the relevance of aggregate and sectoral shocks to headline and underlying inflation. We then conduct a quantitative exercise focused on Australia. The interest in the latter comes from our belief that monetary authority actually started to react to underlying inflation around 2007. We find that the calibrated model is not able to reproduce the behavior of headline/underlying inflation after 2007.

Spray drying is a widely used unit operation for producing particulate products directly from a liquid feed. Important processes that occur inside the spray dryer are droplet formation, droplet drying and interactions between droplets and recycled fines. Various studies have looked at the first two processes, but the latter phenomenon has received less attention. Literature on droplet-particle interaction which aims at quantitatively describing agglomeration in spray drying is scarce and mainly qualitative. For product quality the formation of agglomerates is often desirable. This thesis models and investigates the collisions of individual particles with single droplets. The surface tack of drying droplets has been identified as an important variable for the formation of agglomerates. In this thesis a novel method for measuring tack from the liquid phase has been further improved. The improvements are a more accurate load measurement, an automated control of the tack probe and an improved layout of the sample holder and probe. The key feature of the device is its ability to measure tack of drying droplets, whereas other devices measure tack by wetting a powder. Using our method the tack of a commonly spray dried product, yeast extract, has been measured. From these experiments it was found that with decreasing average moisture content the surface tack increases to a maximum. Below a critical average moisture content the surface of the droplet is dry and the tack rapidly decreases upon further drying. Another important parameter in determining the degree of agglomeration is the degree of penetration. If the particle penetrates the droplet too deeply, the agglomerate structure becomes too dense. To predict the penetration depth, a non-dimensional model has been developed. It describes the penetration of a particle into a liquid droplet during a head-on collision. It is based on a force balance and incorporates surface tension force, viscous force and capillary pressure force. The important parameters determining the collision outcome are the contact angle, the size of the droplet relative to the particle, the Reynolds and Weber numbers. For each contact angle an equilibrium penetration position exists, at this point the surface tension force vector is perpendicular to the penetration direction. Five different penetrations regimes are identified. At low Reynolds numbers, viscous forces dominate and the particle asymptotically travels towards the equilibrium position. Reducing the viscous drag force by increasing the Reynolds number results in initially overshooting the equilibrium position, but the surface tension force pulls the particle back, to attain the equilibrium in an oscillating motion. At even higher Reynolds numbers the particle fully penetrates the droplet, and reaches the centre of the droplet for even higher values for the Reynolds number. The ejection regime is found at high Reynolds number and low Weber numbers and the liquid should be non-wetting. Using the regime maps one is able to identify in which region a spray dryer is operating. Although the full penetration regimes are useful for capturing fines, it should be avoided when agglomeration is desired. The ejection regime should be avoided as well. To validate the model, impact experiments were carried out by dropping glass spheres on the surface of different liquids. These validation experiments were the first attempt to experimentally validate the collision of a single particle with a liquid surface. Besides yeast extract, which has non-Newtonian rheological properties, silicone oils with constant viscosities of 100 mPa•s and 1 Pa•s have been tested. The penetration over time for different impact velocities was determined by analysing high speed camera recordings. The typical penetration times ranged from 0.2 s to 2 s. To obtain accurate location data was recorded at frame rates up to 38 000 frames per second. Glass spheres, with a size of 2 mm were used to allow the visual tracking. Modelling the impacts showed that the model consistently predicted faster penetration times than were observed experimentally. The relative difference increased with increasing viscosity. A parameter fitting exercise showed that better agreement could be obtained by using a higher viscosity and a higher contact angle in the model. With this knowledge the most likely factor influencing the model-experiment mismatch was identified as being the dynamics of wetting of the particle surface. It was also found that using the dynamic contact angle in the model would improve its results. The non-Newtonian characteristics of the yeast extract resulted in the particle rebound and the formation of an air cavity upon impact. The tack measurement technique and penetration model presented in this thesis will be useful tools for the design of spray dryers. Recommendations are made for further model improvement. The experimental validation is the first attempt to validate the presented model. Future improvements are recommended and suggestions are presented.