Dissertations / Theses on the topic 'Aggregace'

This research demonstrates that rubber particle size affects concrete workability and water permeability to a greater extent than fresh density and strength. Concrete with rubber particles of larger size tends to have a higher workability and fresh density than that with smaller particle sizes. However, rubber aggregates with smaller or continuously graded particle sizes are shown to have higher strengths and water permeability resistance. Influence of recycled aggregate and rubber aggregate as part substitutions for natural aggregates on concrete compressive strength was investigated and four equations were proposed to predict compressive strength of the designed concrete. Besides, it is experimentally shown that silane coupling agent (SCA) has a positive effect on reducing the loss of strength of rubber concrete, especially when concrete is weak. This effect becomes more significant with the increase of mass fraction of SCA solution. Experiment results also show a better performance of concrete with SCA-treated rubber than with as-received or sodium hydroxide solution (NaOH)-treated rubber. A brief cost analysis suggests that this approach of surface modification is economically viable. Referring to a provided fatigue load spectrum and fatigue failure mechanism, this method is potentially to be used for rubber concrete in high-cycle fatigue condition.

Master of Science
Department of Civil Engineering
Kyle Riding
Concrete is most widely used material in construction industry, which is made up of cement, water and aggregates as its major ingredients. Aggregates contribute to 60 to 75 % of the total volume of concrete. The aggregates play a key role in the concrete durability. The U.S Midwest has many aggregates that can show distress in the field under freezing and thawing conditions. The objective of this research was to determine if the Test Method for the Resistance of Unconfined Coarse Aggregate to Freezing and Thawing, method CSA A23.2-24A, could be used to differentiate good from poor performing aggregates in concrete. In this study fifty one KDOT aggregates (including twelve ledge and thirty nine production samples) were tested for freeze thaw resistance using CSA A23.2-24A test method and were compared to the results of the standard KDOT aggregate qualification tests. In addition to performing the CSA test method using a 3% sodium chloride solution, a subset of the aggregates were tested using either a 3% magnesium chloride or calcium chloride solution to determine the effects of the salt type on the aggregate performance. No correlation was found between the CSA A23.2-24A test method results and the standard KDOT aggregate qualification tests. The results also indicated that the mass loss in the CSA A23.2-24A was similar for the aggregate sizes tested. The use of alternate salt solutions like MgCl2 and CaCl2 resulted in increased freeze thaw mass loss in limestone aggregates.

I investigate the information in aggregated US equity analysts' earnings forecasts. Despite a voluminous body of research evaluating the information in, and characteristics of, equity analysts' forecasts, relatively little is known regarding aggregated forecasts. However, Kothari, Lewellen and Warner (2006) demonstrate how estimated relationships between, for example, earnings and returns may differ markedly at the aggregate level compared with the individual stock level. I generate time series of aggregated forecast earnings, aggregated forecast revisions and aggregated realized earnings for the period extending from the first quarter of 1979 through to the last quarter of 2009. These variables are employed in three examinations of aggregated earnings expectations. Firstly, prior research indicates significant information in analysts' forecasts for future realized earnings, and strong positive correlation between realized earnings and indicators of macroeconomic activity. I therefore hypothesize significant information in aggregated analysts' forecasts for future realized economic activity. Secondly, I investigate the informational efficiency of analysts' forecasts with respect to realized macroeconomic variables, and implications of earnings revision predictability for return predictability. Thirdly, I employ aggregated earnings revisions as proxies for market earnings surprise in tests of cash flow and discount rate effects in market returns. I find evidence of statistically significant information for future US industrial production growth in aggregated analysts' forecasts, the magnitude of which is a partial function of earnings smoothing by management, firm size and earnings cyclicality. I also find evidence of systematic underreaction by analysts to realized macroeconomic factors, resulting in revision predictability which in turn is able to explain significant systematic variation in future industry returns. In addition, my results suggest that the negative relationship between aggregated earnings surprise and contemporaneous returns identified by Kothari et al. (2006) is at least partially a product of the period they evaluate. In robustness tests employing both aggregated realized earnings and aggregated forecast revisions, I find evidence of positive (albeit insignificant) relationships between these proxies for earnings surprise and contemporaneous market returns. My results do not support the notion of a discount rate effect dominating a cash flow effect at the aggregate level.
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A 1H, 13C, and 6Li NMR study of 2-ethylhexyllithium showed that 2- ethylhexyllithium exists solely as a hexamer in cyclopentane solution over the temperature range from 25 to -65 °C. Furthermore, 2-ethylhexyllithium and lithium 2- ethyl-1-hexoxide were shown to form mixed aggregates when the alkoxide was formed in situ by reacting 2-ethylhexyllithium with 2-ethyl-1-hexanol. A multinuclear, variable temperature NMR study of a sample with an O:Li ratio of 0.2 led to the identification of at least four such aggregates, one of which was found to be a hexamer with the composition R5(RO)Li6. Studies of samples with higher O:Li ratios, up to 0.8, showed additional mixed aggregates present. All solutions containing mixed aggregates were also shown to contain hydrocarbon soluble lithium hydride. A study of lithium 2-ethyl-1- hexoxide indicated that it aggregates in solution as well.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第19025号
農博第2103号
新制||農||1030(附属図書館)
学位論文||H27||N4907(農学部図書室)
31976
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 加納 健司, 教授 植田 和光, 教授 植田 充美
学位規則第4条第1項該当

The Wisconsin Department of Transportation (WisDOT) uses approximately 11,000,000 tons of aggregate per year for transportation projects. Being able to select durable aggregates for use in transportation projects is of considerable importance, if the aggregate deteriorates then the constructed facility requires premature repair, rehabilitation or replacement. Realizing the importance and also that deficiencies in the current WisDOT testing protocol may exist, it has been concluded that the durability-testing program for Wisconsin aggregates needs to be updated. For example, WisDOT is currently using the Sodium Sulfate Soundness Test (ASTM C 88) to measure durability, a test that was put in place in 1960. The ability of this test to predict durability performance and simulate field conditions is questionable and it has also been criticized for its lack of precision. It should also be noted that the use of recycled and reclaimed aggregates has increased in recent years and not all typical durability tests can be used for testing these aggregates. The Sulfate Test in particular cannot be used for testing Recycled Concrete Aggregates (RCA) because the chemical reaction produces erroneous and misleading results. This project has identified recent advances in the understanding and testing of aggregate durability. An in depth literature review has been conducted and from the compiled information a laboratory testing program was developed. Selection of the tests was based upon the tests' precision, efficiency, and predictive capabilities. In the laboratory-testing phase of this project the proposed durability tests along with current WisDOT durability tests were used to evaluate the full range of Wisconsin aggregates. From the test results it was found that the WisDOT aggregate testing protocol could be reduced substantially by eliminating many of the testing requirements for aggregates that have a vacuum saturated absorption of less than 2%. Also, the addition of several tests was ruled out due to their lack of correlation with field performance records. The Micro-Deval abrasion test is recommended for inclusion in WisDOT testing protocol as a test to measure the abrasion resistance of aggregate while the L.A. Abrasion test is better suited as a measure of aggregate strength. Additional conclusions were made based on the durability testing conducted and an overall testing protocol has been developed and is recommended for implementation by WisDOT.
Master of Science

The current usage of both classical and fluid combustion ashes is not sufficient and they are deposited in large quantities. The focus of this master´s thesis is to determine and verify some possibilities of their suitable applications in construction industry, specifically as the alternative aggregates for concrete. After the performed analysis several systems based on both classical and fluid combustion ashes have been proposed. Portland cement and hydrated lime were used as admixtures and binding properties of fluid combustion ashes were also tested. The most important properties were compressive strength and bulk density. The aim was to appropriate an optimal ratio between the addition of modifying substance and resulting strength of prepared aggregate in order to correspond to standards for aggregates for concrete.

Aquesta tesis tracta sobre les diferències en la productivitat agregada del treball entre diferents economies. Gran part de la diversitat en rendes que observem entre països té a veure amb les diferències en productivitat. Per tant, sembla clar que part del patiment humà podria ser alleugerit augmentant l'eficiència en la producció. Aquest objectiu requereix tenir una idea qualitativa i quantitativa de les barreres que ens separen del seu assoliment. Evidentment, la productivitat ha sigut quelcom estudiat pels economistes d'ençà l'Economia inicià el seus passos. No obstant, malgrat la seva importància, o potser precisament per a la seva importància, aquesta àrea de recerca encara ofereix un gran marge d'exploració. En els següents capítols tractaré aquest tema des de diversos angles i utilitzant diferents tècniques però sempre amb el mateix objectiu. El primer capítol, titulat Comptabilitat en el Desenvolupament i Béns Intermedis, gira entorn a la pregunta de si els béns intermedis són part important en explicar les diferències, relatives i agregades, en la productivitat entre països. Tres observacions suggereixen que així és: (i) els béns intermedis són relativament més cars en els països pobres; (ii) les indústries productores de béns demanden béns intermedis amb més intensitat que aquelles que produeixen serveis; (iii) les indústries productores de béns són més prominents com a oferents de béns intermedis en els països pobres. Construeixo un model de creixement multisectorial estàndard que té en compte els tres fets anomenats anteriorment per mostrar que la producció ineficient de béns intermedis afecta negativament la productivitat agregada i augmenta la ràtio de preus entre béns i serveis. Aplicant el model a les dades dels països de renda mitjana i alta, trobo que aquells països més pobres tan sols són una mica més ineficients produint béns que serveis però, en canvi, són molt ineficients produint béns intermedis respecte béns finals i serveis. Si tots els països tinguessin la mateixa eficiència produint béns intermedis que té l'economia d'EE.UU., el model prediu que la diferencia de productivitat entre entre els països de renda més baixa i els de renda més alta, de la mostra, es reduiria en gairebé dos terços mentre les diferencies en el ràtio de preus finals entre països pràcticament desapareixeria. El segon capítol, titulat Delegació de Gestió i Productivitat Agregada, proposa un nou mecanisme per explicar perquè les empreses dels països de renda baixa estan mal gestionades, i quantifica la pèrdua de productivitat resultant. Primer, presento evidència empírica sobre la significativa correlació entre la proporció de treballadors dedicats a la gestió i les garanties de compliment de contractes entre països. En segon lloc, construeixo un model tractable que captura els avantatges de delegar tasques en grans organitzacions. En el model també té lloc un problema de risc moral entre el propietari de la companyia i els gestors de la mateixa. Quan les garanties contractuals no son efectives, és a dir, quan els gestors poden apoderar-se de rendes empresarials, això limita la capacitat de la companyia per créixer i arribar al nivell òptim de gestors. En tercer lloc, utilitzo una versió calibrada del model per a mesurar l'efecte de reduir les garanties per al compliment de contractes. Comparat amb la referència en el nivell de garanties contractuals d'EE.UU., cap tipus de garantia redueix la proporció agregada de gestors en 10 punts percentuals, caracteristic de països amb un nivell de renda d'un desè respecte EE.UU. La pèrdua associada en productivitat es, aproximadament, de 18 punts percentuals. Estadístics addicionals sobre la mida mitjana de les empreses, l'autoocupació i la dispersió de la productivitat ofereixen validació addicional dels resultats. El tercer capítol, titulat Imposició Progresiva i Productivitat Agregada i escrit conjuntament amb en Tomaz Cajner, ofereix una teoria sobre com la imposició progressiva del treball pot afectar la decisió individual d'esdevenir emprenedors o ser treballadors assalariats. Els emprenedors viuen en un entorn amb friccions per a la recerca d'empreses. Un cop fet l'emparellament, s'assumeix una negociació sobre els beneficis del mateix. Quan els impostos són més progressius, aquells projectes més arriscats esdevenen menys lucratius i, per tant, la cua dreta de la distribució dels ingressos es redueix. S'utilitza el model per entrellaçar tres fenòmens macroeconomics importants que han tingut lloc les ultimes dues o tres dècades en els països desenvolupats: el descens de la imposició marginal del treball per les rendes més altes, l'augment de la desigualtat i la reobertura de l'escletxa de productivitat entre EE.UU. i Europa. Una versió parametritzada del model és capaç de generar els dos últims fets com a resultat d'un descens de la imposició sobre el treball de les rendes més altes. No obstant, els resultats quantitatius del model no estan d'acord amb les dades observades.
This thesis is concerned with differences in aggregate labor productivity across economies. Much of the income disparities that we observe across countries today are related to productivity differences. It follows that much human suffering could be alleviated by raising the efficiency of production. This requires an idea of the qualitative and quantitative significance of potential barriers. Unsurprisingly, productivity has been studied by economists for as long as economics has been around but despite its importance - or perhaps rather because of it - this research area applied to the aggregate economy still offers a huge field open to exploration. In the following chapters I tackle the issue at hand from several distinct angles and using a variety of techniques, but always with the same aim. The first chapter, entitled Development Accounting with Intermediate Goods, asks whether intermediate goods help explain relative and aggregate productivity differences across countries. Three observations suggest they do: (i) intermediates are relatively expensive in poor countries; (ii) goods industries demand intermediates more intensively than service industries; (iii) goods industries are more prominent intermediate suppliers in poor countries. I build a standard multisector growth model accommodating these features to show that inefficient intermediate production strongly depresses aggregate productivity and increases the price ratio of final goods to services. Applying the model to data for middle and high income countries, I find that poorer countries are only modestly less efficient at producing goods than services, but substantially less efficient at producing intermediate relative to final goods and services. If all countries had the intermediate production efficiency of the US, the aggregate productivity gap between the lowest and highest income countries in the sample is predicted to shrink by roughly two thirds while cross-country differences in the final price ratio would virtually vanish. The second chapter, entitled Managerial Delegation and Aggregate Productivity, proposes a novel mechanism to answer why firms in low income countries are badly managed, and quantifies the resulting productivity loss. First, I present empirical evidence on a significant positive correlation between the share of managerial workers and contract enforcement across countries. Second, I construct a tractable model that captures benefits to managerial delegation in large organizations. The model also features an agency problem between the owner of a firm and its middle management. Ineffective contract enforcement, allowing middle managers to steal from the firm, constrains firm size by limiting the efficient delegation of managerial authority. Third, I use a calibrated version of the model to measure the effect of lowering contract enforcement. Compared to the benchmark of US contract enforcement, no enforcement decreases the aggregate share of managerial workers by about 10 percentage points, typical of countries with income levels of about one-tenth of the US. The associated loss in aggregate labor productivity is roughly 18 percentage points. Auxiliary statistics on the mean firm size, self-employment and productivity dispersion offer additional empirical validation of these results. The third chapter, entitled Progressive Income Taxation and Aggregate Productivity and co-authored with Tomaz Cajner, offers a theory on how the progressivity of the labor tax may affect individuals’ decision to manage firms or work as production workers. Managers must be matched to firms in an environment featuring search frictions and the pair bargain over the surplus from the match. A higher tax progressivity makes it less lucrative to create and improve risky projects as it compresses the right tail of outcomes. The model is used to link three prominent macroeconomic phenomena occurring over the last two to three decades in the developed world: the lowering of the top marginal labor taxes, the rise in inequality and the renewed opening of the aggregate labor productivity gap between Europe and the US. A parameterized version of the model is capable of delivering the concomitant occurrence of the latter two phenomena as a result of the lowering of top labor income taxes. The quantitative effects predicted by the model, however, cannot match the data.

Approved for public release, distribution unlimited
CIVINS
Modern naval warships rely on vast arrays of sensor networks to evaluate the performance of mission critical systems. Although these sensor networks enable increased levels of automation, they are costly to install and to maintain. The power distribution network offers an alternative solution for tracking the performance of mission critical systems. Research conducted at Massachusetts Institute of Technology's Laboratory for Electromagnetic and Electronic Systems (LEES) has proven that the power distribution network contains vital information that can provide performance monitoring and automatic diagnostic functions. This thesis will address the issue of sensor-count reduction through the application of Non-Intrusive Load Monitoring (NILM) technology. Theoretical studies and field experiments will be presented in order to demonstrate the NILM's ability to correlate load activity with power measured from an aggregate level in the distribution system. Additionally, a critical evaluation is conducted on the current NILM configuration's ability to perform automated classification. Findings will be supported using data collected from NILMs monitoring power flow on board the U.S. Coast Guard Cutter ESCANABA (WMEC-907).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.
Includes bibliographical references (leaves 91-95). Also available in electronic version. Access restricted to campus users.

Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.
Includes bibliographical references (p. 96-100).
Modem naval warships rely on vast arrays of sensor networks to evaluate the performance of mission critical systems. Although these sensor networks enable increased levels of automation, they are costly to install and to maintain. The power distribution network offers an alternative solution for tracking the performance of mission critical systems. Research conducted at Massachusetts Institute of Technology's Laboratory for Electromagnetic and Electronic Systems (LEES) has proven that the power distribution network contains vital information that can provide performance monitoring and automatic diagnostic functions. This thesis will address the issue of sensor-count reduction through the application of Non-Intrusive Load Monitoring (NILM) technology. Theoretical studies and field experiments will be presented in order to demonstrate the NILM's ability to correlate load activity with power measured from an aggregate level in the distribution system. Additionally, a critical evaluation is conducted on the current NILM configuration's ability to perform automated classification. Findings will be supported using data collected from NILMs monitoring power flow on board the U.S. Coast Guard Cutter ESCANABA (WMEC-907).
by Keith P. Douglas.
Nav.E.and S.M.

In the usual version of the neoclassical growth model used to identify neutral (N-Shock) and investment shocks (I-Shock), a linear transformation frontier between consumption and investment goods is assumed. This paper extends the original framework, allowing for curvature in the transformation frontier, and studies how this affects the relative price of investment goods and hence the identification of investment shocks. A concave frontier allows a substantial improvement in the prediction of the saving rate. Furthermore, a concave frontier induces short-run aggregate effects of relative demand shifts, thereby fostering the propagation of the shocks under consideration, which overall account for 86% of the aggregate fluctuations. When I identify shocks with curvature, the N-shock appears to be stationary while the I-shock is a unit root. This leads the N-shock to play a major role: 91% of the fluctuations explained are due to the N- shock

Alkali Aggregate Reaction (AAR) is a deterioration mechanism which affects concrete structures all over the world. Different parts of the world employ various mitigation and control measures for AAR damage. Different tests are also performed worldwide to assess AAR. With the variety of AAR avoidance measures and AAR tests performed worldwide, it is necessary to have a thorough compilation and critical assessment of these AAR avoidance measures and AAR tests, which may be of assistance to engineers and other professionals who are involved in structural and material design of concrete structures or in the construction, quality control and condition monitoring and assessment of concrete structures. This dissertation aims to outline the types of AAR and the mechanisms associated with them, and to highlight case studies of AAR incidences around the world. This dissertation further aims to provide a comprehensive compilation and analysis of various AAR avoidance measures as well as AAR tests that are performed worldwide. Commonalities and differences will be highlighted between the different case studies, and critical analyses will be done on the AAR avoidance measures and AAR tests that will be discussed. There are three main types of AAR, distinguishable by the aggregate source. These are: AlkaliSilica Reaction (ASR), Alkali-Silicate Reaction and Alkali-Carbonate Rock Reaction (ACR). Since AAR is a type of internal chemical damage to concrete, it can be avoided by engineering design and by carefully selecting the concrete construction materials. In order for damaging AAR to occur in concrete, the following conditions need to be met: • Reactive silica in the aggregates should be present • Alkali, which is primarily from Portland cement, should be of a sufficient concentration • There should be sufficient moisture in the concrete • Portlandite should be in a sufficient concentration (this is specifically for ACR) To prevent the occurrence of AAR in concrete, one or more of the conditions above should be eliminated, except for the case of ASR in which one or more of the first three conditions should be eliminated. Since this dissertation mainly focuses on ASR, only the first three conditions will be considered as these are the only conditions for the occurrence of ASR. Various testing methods are employed all over the world to assess AAR. These tests include tests performed to assess whether certain aggregates are susceptible to AAR; tests to assess the performance of specific concrete mixes and thus determine if they are susceptible to AAR, and also tests performed to assess the occurrence and extent of AAR in existing concrete structures.

I tradizionali materiali da costruzione provengono da un processo di estrazione di risorse naturali e dal loro trattamento secondo tecniche energivore. Allo stesso tempo, vi è una crescita di sottoprodotti industriali di scarto causante problemi di smaltimento. Il futuro nel settore delle costruzioni si dovrà ricercare in risorse di nuova generazione, basate su processi sostenibili e rispettosi dell'ambiente. La riqualificazione dei rifiuti attraverso il processo di alcali-attivazione (AA) consente lo sviluppo di materiali ad alte prestazioni e basso impatto. Lo scopo di questa tesi riguarda lo sviluppo e la sperimentazione di materiali innovativi AA alleggeriti da utilizzare in applicazioni ingegneristiche. I precursori sono due polveri ricche in alluminio e silicio, scarto di processi industriali: bentonite esausta (BE) e polvere di basalto (B). Gli attivanti sono miscele costituite da idrossido e silicato di sodio. Una percentuale ottimizzata di perossido di idrogeno è aggiunta come agente espandente. Questi materiali sono combinati con metacaolino e sottoposti ad AA per dare luogo a due materiali alleggeriti. La sperimentazione prosegue con la produzione di aggregati alleggeriti il cui processo produttivo comprende: dosaggio dei componenti, preparazione della miscela, produzione a mano dei campioni e infine la maturazione tra i 60 e 80°C in un forno ventilato. Ne risultano particelle sferiche ad elevata porosità. Successivamente si provvede alla caratterizzazione fisica e meccanica degli aggregati: i BE presentano una porosità composta da pori grandi, al contrario i B mostrano una porosità più fine. Questo ne influenza la densità e le proprietà meccaniche. B presenta buona resistenza alla frantumazione, superando chiaramente BE. È infine valutata la loro idoneità ad applicazioni stradali: una tipica miscela bituminosa per strato di usura è fatta con il 12% di aggregato alleggerito B. Le prestazioni fisiche e meccaniche rivelano risultati positivi.

Utilizzare i singoli dispositivi come astrazione di base nei moderni algoritmi di programmazione pone dei limiti progettuali. La complessità nel gestire le interazioni ed i comportamenti può portare ad errori di progettazione, oltre che aumentare notevolmente il tempo di sviluppo. L'aggregate computing è un paradigma che cerca di risolvere queste problematiche. Mette a disposizione funzioni basate sul field calculus, per orchestrare dispositivi mobili situati nello spazio fisico, definiti in letteratura come campi computazionali. Gli attuali algoritmi di programmazione aggregata non tengono conto della possibilità che alcuni dispositivi possano comportarsi in modo scorretto o opportunistico. Essendo questi algoritmi spesso utilizzati in sistemi critici è essenziale affrontare il problema. In questa trattazione si andranno a sviluppare soluzioni e proporre idee per nuovi approcci ibridi che utilizzano i sistemi di trust.

This document reports on a research project aimed at developing a concrete acoustic barrier made from Recycled Aggregate (RA) Concrete. The research project was undertaken in response to the needs expressed by the Victorian concrete recycling industry. The industry, the scientific community conducting research into relevant disciplines, and the community at large, represented by Victorian government agencies, are of the opinion that there is a need to devise a higher value utilisation application for selected concrete recycling products. This document outlines the rationale and objectives of the research project which involves the examination of Recycled Concrete (RC) Aggregate, the design and examination of RA Concrete, and finally the development of an acoustic barrier made from RA Concrete. The literature review presented in this report examines aspects of concrete recycling and concrete technology pertaining to traditional and alternative constituent materials for concrete production. Firstly, the importance and influence of fine and coarse aggregate on basic properties of concrete is introduced. Secondly, an account on the use of alternative materials in concrete technology, especially of coarse recycled aggregates and supplementary cementitious materials (SCM) is described. Thirdly, some of the physical and mechanical properties and how the use of RC Aggregate and SCM changes these properties are discussed. Fourthly, a number of commonly used techniques and neutron scattering techniques to investigate aggregate and concrete properties are introduced and discussed. Fifthly, the porosity of aggregate and concrete including durability are specifically discussed and testing methods are reasoned. The literature review also discusses the use of no-fines concrete; its physical, mechanical and acoustic properties. Finally it presents an account of the use of concrete in transportation traffic noise attenuation devices. This document continues with an outline of a methodology that was adopted in this research project. It outlines experimental work aimed at examining the properties of RC Aggregate which amongst other properties includes porosity, particle size distribution, water absorption, shape and density. It continues examining RA Concrete properties and includes, among other properties, compressive strength, porosity and durability as well as sound absorption of acoustic barrier. The methodology introduces standard and purposely modified test procedures used in the examination of aggregates, concrete and acoustic barrier. An account of various research techniques is presented, spanning from simple visual observations to more sophisticated neutron scattering techniques. The summary of test procedures follows a description of test specimen composition and their sizes, and a suite of tested specimens. It also introduces statistical methods used to analyse test results. After a detailed description of the aggregate, concrete and RA Concrete acoustic barrier, the document outlines a summary of data generated through the experimental program of this research project. The data on fine aggregate, on selected 14/10mm coarse RC Aggregate, on concrete made from natural and recycled aggregate and on acoustic barrier are presented and discussed. Test results of various physical, mechanical and acoustic properties of aggregate, concrete and barrier are reported, analysed and discussed. The data from observations, visual assessment and scientific experimentation of specific properties are then crossed analysed in a search for relationships between properties of fine and coarse aggregates and properties of concrete made from such aggregates. A cross analysis of data on ?less-fines? RA Concrete and on the acoustic performance of barrier is examined, and the relationship between the volume of interconnected voids in a porous part of ?less-fines? concrete, and the sound absorption of acoustic barrier is discussed and reported. The document then presents a synthesis of the literature review results, project aims adopted within the experimental program and test results in the three main areas of this research project. These areas include recycled concrete aggregate, recycled aggregate concrete and acoustic barrier made from RA Concrete. Finally, conclusions reached through the course of this investigation are summarised and recommendations are proposed in relation to the RA Concrete acoustic barrier. The main conclusion is that selected RC Aggregate can be used in the production of concrete of a compressive strength of 25MPa, if the moisture content and water absorption in the aggregate are closely monitored, and the foreign material content is kept below 1.5%. The author concludes that acoustic barrier made from selected RC Aggregate has unique sound absorption characteristics that can easily be tunable by a selection of appropriate aggregate and by specific concrete mix designs. Recommendations for further research are also proposed.

Thesis (PhD) - Swinburne University of Technology, 2006.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering, Swinburne University of Technology - 2006. Typescript. Includes bibliographical references.

This thesis explores links between aggregate investment and asset prices. Many popular theories that link investment and asset prices - such as rational bubbles and Tobin's q - do a poor job of describing the empirical reality. Examples include asset price booms that, in hindsight, may be described as bubbles leading to higher investment, contradicting the predictions from rational bubble models. Another example is the very low sensitivity of investment to Tobin's q in almost all empirical applications and evidence suggesting that q is not a sufficient statistic for investment. One relatively undeveloped area ofthe investment is that which considers a role for information asymmetries and social learning. Chapter II develops a partial equilibrium model based on Caplin and Leahy (1994) in which firms make investment decisions regarding a risky project each period after learning new infonnation about likely returns. This information is from private sources and the asset market. The key results of this model are that: asset prices affect the length and amplitude ofthe investment cycle; a small number of noisy market signals may dominate a very large number of accurate firm signals, due to frict~onal costs faced by the fum; there exist feedback channels from investment back to asset prices; and informational asymmetries impose ex-ante welfare costs on the economy. Chapter III extends this model by describing in detail the process of asset price formation. Chapter IV empirically tests some hypotheses from these theoretical models using aggregate U.S. data and a V AR model. The key result is that q is not a sufficient statistic for aggregate investment; indeed, investment Granger causes some important components of q. This suggests that market prices are not infonnationally efficient; fums hoard information which is then released through their publicly observable actions.

Isolierte Molekülcluster können durch Fourier-Transformations-Infrarotspektroskopie von Überschallexpansionen untersucht werden. Es wird gezeigt, wie Multischlitzdüsen verschiedener Geometrien sowohl zur Aufklärung des Strukturverhaltens von Wasseraggregaten bei thermischer Anregung als auch zur Erzeugung von Mischclustern bei gleichzeitiger Unterdrückung von Isotopenaustauschreaktionen eingesetzt werden können. Zusätzlich wurde ein Aufbau zur chemischen Bildgebung von Expansionen entwickelt und zur ortsaufgelösten Visualisierung von Aggregationsprozessen sowie Dichte- und Temperaturentwicklungen verwendet.

Sustainable development is gaining popularity around the globe nowadays. Governments are under pressure, on many fronts, to embed sustainable development in policies, practice, and operations to secure the planet's future. Adding to this, increased populations, and the need for more infrastructures, have unfortunately led to the unacceptable depletion of raw materials, increasing amounts of construction and demolition waste (C&DW) and accelerated deterioration of the natural environment in many places worldwide. For the conservation of natural resources, reuse and recycling of C&DW is the most obvious way to achieve sustainability in the construction sector. Currently, recycled aggregate (RA) is produced from C&DW in modern recycling facilities, under good quality control provisions which could lead to improve its performance compared with the earlier days of recycling. In addition to C&DW, large amounts of industrial and mining by-products such as fly ash, slag, limestone powders, aggregate dust, etc. are dumped in landfills. Fly ash has been used successfully in concrete for a long time due to its numerous advantages across a wide range of properties, including aspects of durability. A concrete produced with the combination of PFA and RA i.e. recycled aggregate concrete (RAC) is obviously more sustainable and economical than conventional natural aggregate concrete (NAC). To date, statistics show that a considerable proportion of the world's RA is used for low-utility applications due to perceived risks and uncertainty over their performance formed as a result of previous history of use when RA was produced manually and low strength cement and higher water to cement ratios were used. Despite the advances in recycling, materials and concreting technologies, this impression prevails. However, to increase the use of RA, it is believed that the quality of RAC should be improved by chemical and mineral additives. For cost effectiveness, quality-improving additives should be abundant, safe, and inexpensive; PFA and new generation polymer-based superplasticizer (SP) are deemed to be a good option. The aims of this study are to investigate the possibility of producing good quality RAC that could be used as a substitute for NAC in normal strength concrete members, and to study its fundamental properties. An attempt has been made to create superplasticized RAC concretes, in which new generation polymer-based SP and PFA produced to the latest European standards were used. PFA was used to partially replace fine aggregate and cement in ordinary and self-compacting concretes. The thesis also includes an investigation into the potential of utilising an aggregate by-product (red granite dust (RGD) in producing environmentally beneficial RAC. The findings show that good performance RAC can be produced with the help of SP and PFA. The study also revealed that it is possible to utilise RGD to substitute up to 30% of cement without substantially influencing the performance of concrete, while also providing cost savings. Strengths and stifnesses of the ensuing RAC either with SP, PFA, or RGD were comparable, or better than, a wide range of counterpart NACs. The author's produced RAC concretes can replace NAC concrete used unnecessarily for many applications including structural concrete.

The paper investigates how including the distribution of wealth changes the demand effects of redistributing functional income. It develops a model with an endogenous wealth distribution and shows that the endogenous rise in wealth inequality resulting from a redistribution towards profits weakens the growth effects of this redistribution. Consequently, a wage-led regime becomes more strongly wage-led. A profit-led regime on the other hand becomes less profit-led and there may even be a regime switch - in this case the short-run profit-led economy becomes wage-led in the long run due to the endogenous effects of wealth inequality. The paper thereby provides a possible explanation for the instability of demand regimes over time.
Series: Ecological Economic Papers

This dissertation explores the effects of factors such as industrial policy and listing on the stock market on manufacturing firms’ profitability and productivity. The second chapter investigates the effect of industrial policies on misallocation using a rich data-set of Chinese firms. Using a difference-in-difference approach, I provide evidence that government policies (i.e. the 10th Five Year Plan) favoring particular industries lead to increased misallocation (i.e., an increase in the dispersion of revenue productivity across firms in four-digit industries). Moreover, the differential changes between industries supported and not supported by the 10th Five Year Plan are quantitatively large and indicative of a substantial negative impact on aggregate TFP. Using a changes-in-changes model, I find evidence that the Five Year Plan had a positive and significant effect for most of the TFPR distribution while the effect was negative for the lowest quintile of TFPQ and positive for the highest TFPQ quintile. The results suggest increased misallocation is related to the way in which the Chinese government doled out support through the increase of subsidies and the improvement of credit conditions for a subset of firms. In the third chapter, I study the heterogeneous effects of an industrial policy -the 10th Five Year Plan on misallocation, profitability and real technology in Chinese provinces with different mix of supported intensities. I find that the 10th Five Year Plan increased misallocation, profitability and technology of supported industries in provinces with higher supporting intensities. After controlling the effects of China’s state-owned enterprise (SOE) reforms and joining into World Trade Organization (WTO), the results are still robust and consistent. In the fourth chapter, I investigate the effects of listing on the stock market on firm’s profitability and technology. Using Chinese firm level data, I identify listing firms, and compute revenue productivity and physical productivity to measure profitability and technology, respectively. To deal with the endogenous problem of listing, I use the number of investment banks as instrument variable. With a difference-in-difference model, I find that listing increases firm’s profitability and technology. Empirical findings also reveal that listing changes characteristics of firms, such as asset, liability and capital structure.

Most systems in HPC make use of hierarchical designs that allow multiple levels of parallelism to be exploited by programmers. The use of multiple multi-core/multi-processor computers to form a computer cluster supports both fine-grain and large-grain parallel computation. Aggregate function communications provide an easy to use and efficient set of mechanisms for communicating and coordinating between processing elements, but the model originally targeted only fine grain parallel hardware. This work shows that a hierarchical implementation of aggregate functions is a viable alternative to MPI (the standard Message Passing Interface library) for programming clusters that provide both fine grain and large grain execution. Performance of a prototype implementation is evaluated and compared to that of MPI.

This thesis concerns design of two pieces of suspension dewatering equipment (i.e. transient batch settlers and steady state continuous gravity thickeners). In a transient batch settler, very slow densification of aggregates within the suspension is considered whilst the drag on the solids in the suspension is assumed to be negligible. The interface of the suspension is then determined by a balance between gravity and the gradient of the compressive yield stress of the gelled suspension. The compressive yield stress functional form in general could be either a weakly gelled formula, or a strongly gelled formula. These formulae differ in the way they behave for solids concentrations in the neighbourhood of the suspension gel point. The effects of the above two gel formulae, the evolution of the compressive yield stress functional form over time during aggregate densification, different initial suspension heights, and different initial feed solids volume fractions upon the predictions of consolidated bed structures and solids volume fractions obtained at the bottom of a batch settler, and upon the evolution of the heights of the suspension and the consolidated bed have been explored. A sufficiently tall initial suspension height might lead to insignificant increases in the solids volume fractions obtained at the bottom of batch settlers after time-dependent aggregate densification. The interfaces of the suspension and the consolidation zone coincide after aggregate densification if the gel point, which increases with time, is larger than the initial feed solids volume fractions. Moreover, the maximum permitted underflow solids fluxes predicted from steady state thickeners have been investigated and compared. Pre-shearing of aggregates which densifies aggregates to have smaller diameters upon entering the thickener is necessary if large underflow solids fluxes and small underflow solids volume fractions are specified. The solids volume fraction at the top of the consolidated bed which is the densified gel point is influenced by the extent of pre-shearing of aggregates. An algorithm for determining this densified gel point has also been developed. In reality, thickeners contain not just a consolidating bed, but also a hindered settling region above it. When the hindered settling region is considered in a thickener, the effects of the extent of aggregate densification that has occurred in the hindered settling region and how that impacts upon thickener performance and sludge rheological properties have been explored in this thesis. A new algorithm for predicting the densified gel point obtained at the top of the consolidated bed has been developed when the hindered settling region is present. The effects of underflow solids volume fractions, aggregate densification rate parameters and pre-shearing of aggregates upon the predictions of maximum permitted underflow solids fluxes, sludge rheological properties, and thickener performance have been explored. The predictions of thickener performance using both the weakly and strongly gelled formulae have also been achieved. In cases where it is possible to neglect the hindered settling region, substantial increases in the maximum permitted underflow solids fluxes, and substantial decreases in the consolidated bed heights and the total solids residence times have been achieved after aggregate densification for a comparatively small underflow solids volume fraction. The benefits arising from aggregate densification are more modest if the underflow solids volume fraction is larger. On the other hand, when the hindered settling region is included, more densification of aggregates occurring in the hindered settling region might lead to taller consolidated bed heights for a specified suspension flux and a specified aggregate densification rate parameter due to higher underflow solids volume fractions.

This thesis is inspired by the ESRC-Cambridge project "Structural Modelling of the UK Economy within a VAR Framework using Quarterly and Monthly Data" and, in particular, the studies by Garratt et al (1998, 2001). The primary aim is to apply the Long-Run Structural Cointegrating VAR approach, developed within the ESRC-Cambridge project, in order to empirically investigate UK Aggregate Demand and Supply. The empirical analysis is intended to complement the recently developed macro-econometric model of the UK in Garratt et al (1998, 2001) by (i) addressing the issue of structural change and (ii) providing an explicit model of the supply-side of the economy. The recently developed techniques in Johansen and Nielsen (1994), Hansen (2000) and Johansen, Mosconi and Nielsen (2000) are utilised in order to control for and assess the possible long-run effects of different exchange rate regimes. In the light of the well documented finite-sample bias, statistical inference relies in large part on simulation methods along the lines of, inter alia, van Giersbergen (1996), Li and Maddala 1997 Harris , and Judge (1998), Mantalos and Shukur (1998), Gredenhoff and Jacobson (1998), Fachin (2000), Jacobson et al (2001) and Greenslade et al (2002). A practical problem concerning the use of these methods for inference on the cointegrating parameters is identified and a solution is proposed. The Generalised Impulse Responses developed in Koop et al (1996) and Pesaran and Shin (1998) and the Persistence Profiles proposed by Lee et al (1992) and Lee and Pesaran (1993a) are used in order to illustrate the dynamic properties of the estimated systems and provide an informal comparison with the Garratt et al (1998, 2001) models.

Le smartcam sono telecamere capaci di rilevare entità di interesse, e sono generalmente impiegate nella sorveglianza. Con l'avanzamento della tecnologia si è creata la possibilità di renderle mobili e dotarle di mezzi trasmissivi. Questo ha aperto grandi opportunità per la coordinazione di reti di smartcam con lo scopo di aumentarne l'efficienza. Lo sviluppo di tali sistemi può beneficiare dall'impiego di specifici strumenti per la simulazione e programmazione in modo da facilitarne l'implementazione e la valutazione. Nell'ambito di questa tesi viene adottato Alchemist, uno degli ambienti che consentono simulazioni di Collective Adaptive System. Vengono quindi illustrate e discusse la fasi di sviluppo di un nuovo modulo software volto ad estendere Alchemist con il supporto alle smartcam. Inoltre vengono riprodotti alcuni algoritmi presenti in letteratura ed implementati di nuovi con l'ausilio dell'Aggregate Programming, un paradigma per la programmazione di sistemi distribuiti. Questi algoritmi hanno lo scopo di creare un sistema adattativo di smartcam che comunicano fra di esse per coordinarsi nei movimenti, e nella decisione degli obiettivi da raggiungere. L'obiettivo è l'incremento del livello di copertura della zona alla quale sono preassegnate, ed il raggiungimento di un certo livello di ridondanza nell'osservazione di eventuali entità di interesse. Infine viene effettuata una validazione empirica degli algoritmi attraverso la simulazione di alcuni scenari.

Work done by several researchers reveals that unbound aggregate materials show nonlinear cross-anisotropic behavior. The incorporation of cross-anisotropic properties significantly improves the predictions of stress distribution by reducing tensile stresses computed within granular layers. Existing pavement analysis and design approaches, however, generally assume the pavement structure to be linear isotropic layered system. This assumption is motivated by the difficulties in determining cross-anisotropic resilient material properties from laboratory experiments and lack of pavement anisotropic analysis programs. Recently, the International Center for Aggregates Research (ICAR) developed a methodology to characterize unbound aggregate layers by considering stress-sensitivity and nonlinear cross-anisotropy. The ICAR model requires nine coefficients to account for stress-sensitivity and anisotropy of vertical, horizontal, and shear moduli. Unfortunately, ICAR testing protocol is time-consuming and expensive to perform and certainly do not lend themselves to routine testing. Since it is important to be able to consider the stress-sensitive and anisotropic nature of unbound granular materials, a simple procedure was proposed by accounting for the effects of aggregate gradation and shape properties in predicting the cross-anisotropic modular ratio of unbound granular materials. Variable confining pressure type repeated load triaxial tests were performed on six aggregate sources with three different gradations and three different moisture contents. The experimental results were analyzed within the framework of nonlinear cross-anisotropic elastic model in order to determine the model coefficients. Image analysis techniques were utilized to measure aggregate shape properties. The gradation and shape properties were fitted using a cumulative distribution function and nonlinear regression analysis, which is capable of capturing the complete distribution of these properties. The experimental and analytical results indicate that the vertical resilient modulus is greater than the horizontal resilient modulus and that aggregate physical properties significantly affect the anisotropic resilient behavior. Based on finite element analysis, the anisotropic resilient behavior has substantial effect on the critical pavement responses. Thus, it is extremely valuable to approximate the degree of cross-anisotropy in unbound aggregates and to use it as input in the pavement analysis programs to adequately model unbound aggregate bases for pavement design and analysis.

Alkali-Aggregate Reactions (AAR) is a deterioration mechanism in concrete that affects numerous structures worldwide. The most widespread type of AAR is the Alkali-Silica Reactions (ASR), a chemical reaction between silica sensu lato in the aggregates and the alkali hydroxides in the pore solution of concrete. Test methods to assess the potential alkali-reactivity of the aggregates have been under development for decades. The petrographic method shall always be the first step, followed by expansion tests (mortar bars and/or concrete prisms). The petrographic method has proven to be very effective, reliable, and time efficient when performed by experienced petrographers. However, some challenges in its application have been reported on a global scale for specific rock types. This thesis provides suggestions of test methods to be used as supplement to the petrographic method (RILEM-AAR-1, 2003) in order to overcome some of those challenges. The mineral content of a variety of European aggregate samples was studied applying geology knowledge and techniques. Special focus was given to the characterization of the silica minerals within the aggregates. These results were critically reviewed against expansion results and experience in structures to ascertain the aggregate potential alkali-reactivity. As a result, a better understanding of some characteristics of the silica minerals that influence the potential alkali-reactivity of the aggregates was achieved. These finding were then used to develop methods able to quantify specific properties of the silica minerals that influence the aggregates reactivity under ASR environment. The developed methods are adapted to the characteristics of the aggregates: normally reactive or slowly reactive. The proposed methods are intended to overcome some of the limitations of the traditional petrographic method that have been reported in the literature with specific rock types. Therefore, their utilization may strengthen the petrographic method and improve its value as a tool to assess the potential reactivity of aggregates for concrete. For slowly reactive aggregates, an image analysis petrographic method for quartz grain size and grain shape characterization was proposed. This method has proven to be more time efficient than the traditional point-counting method, while the results can be more accurate and precise. Not only a much larger number of points can be analysed, typical stereological problems such as the overestimation of the small grains produced by a two-dimensional representation of a rock (thin-section) can be easily and efficiently overcome. The correlation trends found between the grain size descriptors of quartz and expansion results confirm that the reactivity of slowly reactive aggregates is related to the total grain boundary area of quartz, which is strongly influenced by sub-granulation. This method has also great potential to be used in thin-section from concrete structures in the assessment of the structure deterioration. Some inconsistencies between grain size descriptors and expansion data were found for samples with high degree of strain. Electron backscatter diffraction (EBSD) analysis was applied to characterize the grain boundaries of quartz and investigate its influence on the reactivity of the slowly reactive aggregates for concrete. The initial results suggest that high angle boundaries increase quartz solubility, whereas low angle boundaries seem to have a lesser effect. This method bears a great potential to improve the understanding of the influence of strain in the potential alkali-reactivity of aggregates for concrete, especially when it comes to determining the role of different geometry and origin. The findings in this field can help to overcome the limitation found in the image analysis petrography method discussed above. For normally reactive aggregates, the use of polished sections instead of the traditional powdered specimens to perform quantitative modal analysis by x-ray diffraction (XRD) was proposed. For fine-grained rock types without preferential orientation this alternative sample preparation has proven to be as accurate and precise as the traditional powdered specimens, while it offers several advantages in concrete petrography. By using polished section to investigate the mineral content by XRD in a number of normally reactive aggregates, it was possible to show that different polymorphs and species of silica have different impacts in the reactivity of normally reactive aggregates.

Artificial reefs have been constructed of many different materials including concrete, tires and limestone quarry rock. Few studies have compared the suitability of different construction materials in terms of their efficacy in acquiring diverse faunal assemblages. This study compares the fishes and macroinvertebrates associated with twelve collocated reefs constructed of gravel-concrete aggregate, tire-concrete aggregate, and limestone quarry boulders (four of each treatment) in 7m of water, 200m offshore Miami Beach, FL. All twelve reefs were deployed the same day in two lines of six, 100m apart. The four quarry stone reefs consist of a pile of 50 boulders. Four reefs were constructed of concrete with gravel aggregate and four of concrete with tire aggregate. These eight reefs, produced by CSR Rinker under license agreement with Stability Reefs Inc., contain 25, 1.5 m edge and 25, 1.2 m edge modules. Fish species, abundance, size (TL) and macroinvertebrate presence/absence from all reefs were recorded every two months by SCUBA divers. Data were analyzed with non-parametric two-way analysis of variance using Statistical Analysis Systems (SAS) software. After 18 months, fish abundance and species richness on each treatment exhibited a significant (p0.05). Species richness on the quarry stone reefs was significantly greater than on gravel-concrete aggregate and tire-concrete aggregate tetrahedron reefs (which did not differ). However, further statistical tests on species richness showed no difference between substrate types. Examination of the invertebrate data indicated no obvious differences in invertebrate reef preferences, excepting hard corals, which were more abundant on the quarry stone reefs.

L'elevata diffusione di entità computazionali ha contribuito alla costruzione di sistemi distribuiti fortemente eterogenei. L'ingegnerizzazione di sistemi auto-organizzanti, incentrata sull'interazione tra singoli dispositivi, è intrinsecamente complessa, poiché i dettagli di basso livello, come la comunicazione e l’efficienza, condizionano il design del sistema. Una pletora di nuovi linguaggi e tecnologie consente di progettare e di coordinare il comportamento collettivo di tali sistemi, astraendone i singoli componenti. In tale gruppo rientra il field calculus, il quale modella i sistemi distribuiti in termini di composizione e manipolazione di field, "mappe" dispositivo-valore variabili nel tempo, attraverso quattro operatori sufficientemente generici e semplici al fine di rendere universale il modello e di consentire la verifica di proprietà formali, come la stabilizzazione di sistemi auto-organizzanti. L'aggregate programming, ponendo le sue fondamenta nel field calculus, utilizza field computazionali per garantire elasticità, scalabilità e composizione di servizi distribuiti tramite, ad esempio, il linguaggio Protelis. Questa tesi contribuisce alla creazione di una libreria Protelis per l'aggregate programming, attraverso la creazione di interfacce di programmazione (API) adatte all'ingegnerizzazione di sistemi auto-organizzanti con crescente complessità. La libreria raccoglie, all’interno di un unico framework, algoritmi tra loro eterogenei e meta-pattern per la coordinazione di entità computazionali. Lo sviluppo della libreria richiede la progettazione di un ambiente minimale di testing e pone nuove sfide nella definizione di unit e regression testing in ambienti auto-organizzanti. L'efficienza e l'espressività del lavoro proposto sono testate e valutate empiricamente attraverso la simulazione di scenari pervasive computing a larga scala.

Thesis (M.S. in Operations Research)--Naval Postgraduate School, June 2006.
Thesis Advisor(s): Samuel E. Buttrey. "June 2006." Includes bibliographical references (p. 49-50). Also available in print.

Diese Dissertation umfasst drei voneinander unabhängige Artikel. In diesen werden neue Prozess-modelle vorgestellt, die von der entscheidungspsychologischen Forschung inspiriert wurden. Im ersten Artikel werden Entscheidungsprozesse mit mehreren Entscheidungsmerkmalen als gesteuerte Suchprozesse modelliert. Zunächst wird ein theoretischer Rahmen vorgestellt, in dem ökonomische Modelle Entscheidungen mit Suche mit Modellen des subjektiven Nutzens aus dem Bereich der psychologischen Forschung integriert wird. In den so modellierten Entscheidungsprozessen wird angenommen, dass Individuen ihre Entscheidungsalternativen nach deren abnehmenden Nutzen ordnen und dann so lange durchsuchen, bis die erwarteten Suchkosten höher als die entsprechenden Gewinne sind. Anschliessend wird die Güte dreier Entscheidungsmodelle an zwölf realen Datensätzen überprüft. Im zweiten Artikel werden die Ergebnisse zweier Experimente vorgestellt, in denen untersucht wurde, wie Personen ihre Urteile verändern, wenn sie den Urteilen und dem der Konfidenzniveau anderer Personen ausgesetzt sind. Ein Baummodell wird eingeführt, welches abbildet, wie Urteile aufgrund solcher Informationen revidiert werden. Dieses Modell basiert auf den Ergebnissen der beiden Experimente: Indem soziale Informationen berücksichtigt werden, kann es zeigen, wie Urteile in einer Gruppe interagierender Personen zusammenlaufen oder polarisieren. Im dritten Artikel wird kollektives Verhalten in Märkten für kulturelle Produkte untersucht. Personen ordnen die Optionen entsprechend ihrer Popularität an und entscheiden sich dann für diejenige, die einen Nutzen hat, der über einer bestimmten ausreichend guten Schwelle liegt. Nach jeder individuellen Entscheidung wird die Rangfolge revidiert. Innerhalb dieses einfachen Rahmens wird demonstriert, dass solche Märkte durch eine sogenannte rich get richer-Dynamik charakterisiert sind. Diese führt zu Ungleichheiten in den Marktanteilen und ungewissen finanziellen Erlösen.
This dissertation comprises of three independent essays which introduce novel psychologically inspired process models and examine their implications for individual, collective or market behavior. The first essay studies multi-attribute choice as a guided process of search. It puts forward a theoretical framework which integrates work on search and stopping with partial information from economics with psychological subjective utility models from the field of judgment and decision making. The alternatives are searched in order of decreasing estimated utility, until the expected cost of search exceeds the relevant benefits; The essay presents the results of a performance comparison of three well-studied multi-attribute choice models.The second essay reports the results of two experiments designed to understand how people revise their judgments of factual questions after being exposed to the opinion and confidence levels of others. It introduces a tree model of judgment revision which is directly derived from the empirical observations. The model demonstrates how opinions in a group of interacting people can converge or polarize over repeated interactions. The third essay, studies collective behavior in markets for search products. The decision makers consider the alternatives in order of decreasing popularity and choose the first alternative with utility higher than a certain satisficing threshold. The popularity order is updated after each individual choice. The presented framework illustrates that such markets are characterized by rich-get-richer dynamics which lead to inequality in the market-share distribution and unpredictability in regard to the final outcome.

Les nanocomposites polymères ont fait l'objet de recherches académiques et industrielles au cours des dernières décennies, du fait de leurs remarquables propriétés mécaniques et rhéologiques comparés aux polymères purs. En particulier, ils présentent du renforcement pour des fractions volumiques modérées, et des effets non linéaires pour des déformations relativement faibles. Malgré des décennies de recherche, la relation entre la rhéologie et la structure des nanocomposites est loin d'être comprise. Les simulations atomistiques peuvent donner une vision détaillée de l'interaction entre la dynamique des chaînes polymères et les charges renforçantes à une échelle locale. Cependant, il est difficile d'aborder les propriétés émergentes à une échelle mésoscopique, par exemple, simuler un grand nombre d'agrégats dans une matrice polymère enchevêtrée reste toujours hors de portée. Dans ce travail, nous proposons un modèle mésoscopique pour simuler la rhéologie des nanocomposites avec un fluide simple ou une matrice polymère enchevetrée, en utilisant la dynamique brownienne et la dynamique généralisée de Langevin, respectivement. Dans les deux dynamiques, le mouvement des chaines de polymère n'est pas décrit de façon explicite et son effet sur la dynamique de la charge est «moyenné». En utilisant ce modèle, nous étudions l'influence du type de charge, de leur taille, morphologie, et fraction volumique sur la rhéologie du composite modèle, ainsi que la morphologie des charges dans les simulations. Un cas particulièrement intéressant est celui d'agrégats quasi-fractals, qui peuvent être flexibles ou bien rigides. Nous démontrons que les systèmes avec agrégats présentent un renforcement significatif, qui augmente avec la taille des agrégats, leur rigidité, leur fraction volumique et leur polydispersité en taille. Une relaxation lente est également mise en évidence, et nous montrons qu'elle est liée à la rotation lente des agrégats. L'effet Payne, associé à la réponse non linéaire des modules dynamiques avec l'amplitude de déformation de cisaillement, est également observé pour nos modèles de composites. Nous faisons le lien entre l'arrangement microscopique des charges sous cisaillement et les propriétés macroscopiques du composite
Polymer nanocomposites have drawn a lot of attention both from the academic and industrial research in the last decades, thanks to their remarkable mechanical and rheological properties as compared to pure polymers. In particular, they may display reinforcement for moderate volume fractions, and several non linear effects that appear for small deformation amplitudes. In spite of decades of research, the relation between nanocomposites structure and rheology is far from being understood. Atomistic simulations can give a detailed view of the interplay between polymer chains dynamics and fillers at a local scale. However, it is much more difficult to address the properties emerging at a mesoscopic scale, for instance, to simulate a large number of aggregates in an entangled polymeric matrix remains out of reach. In this work, we build a mesoscopic model to simulate the rheology of polymer nanocomposites with a simple fluid and an entangled polymer matrix, by using the Brownian dynamics and the generalized Langevin dynamics, respectively. In both cases, the motion of the polymer chains is not explicitly described and its effect on the filler dynamics is "averaged out". Using this model, we quantitatively determine the influences of the filler type, the filler volume fraction, size and morphology on the rheology of the model composite. Of particular interest is the case of fractal-like aggregates, which may be flexible or rigid. We demonstrate that model aggregates display significant reinforcement, which increases with the aggregate size, aggregate rigidity, filler volume fraction and polydispersity. Long relaxation times are also evidenced, which are related to the slow rotation of the aggregates. The well-known Payne effect, associated to the nonlinear response of the dynamic moduli with the shear deformation amplitude, is also seen in our model composites. We relate the behavior of microscopic filler to the macroscopic properties of the composite