No description available.

As typically designed, the beam-column-brace connections of buckling-restrained braced steel frames have undesirable failure modes that compromise the integrity and performance of the frames and are costly to repair. To decrease the time and resources needed to repair the frames following an earthquake, a new connection design was developed that attempts to confine yielding to replaceable frame components. The design incorporates a gap in the beam beyond the edge of the beam-gusset weld that acts as a hinge and reduces moment forces transferred to the connection; it is bridged by splice plates that are bolted to the beam top flanges. The splice plates and buckling-restrained braces are the only frame components that are expected to yield. To investigate the performance of the proposed connection design, a prototype bay was designed and two test specimens were fabricated and tested. Each specimen represented a corner of the prototype braced bay and consisted of a beam, column, gusset plate, brace core extension assembly, splice plates, and lateral bracing angles. Both standard design procedures and newly developed criteria were used to design the connection. In preparation for testing, a method was developed for estimating the hysteretic response of a buckling-restrained brace. By using this method to program an actuator, the specimens could be tested without using actual braces, resulting in a significant reduction in testing cost. Testing was conducted using two 600 kip actuators; the first followed a static loading protocol with a maximum design drift of 6.5%, and the second replicated the prototype BRB's response. The tests yielded promising results: both specimens withstood the maximum displacements and avoided yielding in the beams, columns, and gusset plates; yielding did occur in the splice plates and BRB core extension assembly, as anticipated. Possible limitations in the design may arise under the presence of increased shear loads, concrete floor slabs, or out-of-plane loading. Additional testing is recommended.

No description available.

Low power consumption is a critical requirement for all liquid crystal display (LCD) devices. A field sequential color (FSC) LCD was proposed by using red (R), green (G) and blue (B) LEDs and removing the lossy component of color filters which only transmits ~30% of the incoming white light. Without color filters, FSC LCDs exhibit a ~3X higher optical efficiency and 3X higher resolution density as compared to the conventional color filters-based LCDs. However, color breakup (CBU) is a most disturbing defect that degrades the image quality in FSC displays. CBU can be observed in stationary or moving images. It manifests in FSC LCDs when there is a relative speed between the images and observers’ eyes, and the observer will see the color splitting patterns or rainbow effect at the boundary between two different colors. In Chapter 2, we introduce a five-primary display by adding additional yellow(Y) and cyan(C) colors. From the analysis and simulations, five primaries can provide wide color gamut and meanwhile the white brightness is increased, as compared to the three-primary. Based on the five-primary theorem, we propose a method to reduce CBU of FSC LCDs by using RGBYC LEDs instead of RGB LEDs in the second section. Without increasing the sub-frame rate as three-primary LCDs, we can reduce the CBU by utilizing proper color sequence and weighting ratios. In addition, the color gamut achieves 140% NTSC and the white brightness increases by more than 13%, as compared to the three-primary FSC LCDs. Another strategy to suppress CBU is using higher field frequency, such as 540 Hz or even up to 1000 Hz. However, this approach needs liquid crystals with a very fast response time (

n recent years, there has been a surge in interest and research into the utilisation of soft actuators within the field of robotics, driven by the novel capabilities of their inherently compliant material. One such actuator is the Pneumatic Artificial Muscle (PAM) which offers a high power-to-mass ratio, compliance, safety, and biological mimicry when compared to their traditional counterparts. However, because of their flexible and complex physical structure and the compressibility of air inside the PAM, they exhibit nonlinear dynamic behaviour, largely due to the influence of the hysteresis phenomenon. In order to implement strategies to counteract this effect, it first needs to be modelled. As such, this thesis investigates two approaches, namely the Maxwell-Slip (MS) and generalised Bouc-Wen (BW) models. Firstly, the test muscle's initial braid angle, maximum displacement, and maximum force are determined to establish the static force using a modified model. Data is then collected on the PAM's force-displacement hysteresis for 2-6 bar of pressure. Using the results from these experiments, the MS and BW model parameters are identified through optimisation. With the static and hysteresis force components characterised, two complete dynamic models are created. The findings show that, when compared to the collected force-displacement data, the BW model has greater accuracy for all pressures except at 4 bar, although both approaches demonstrate results within a satisfactory margin. Lastly, a model validation is conducted to compare the models using a new dataset, separate from the one on which they were trained. Data for this test is recorded at a pressure of 4 bar with a more complex reference that covers four different regions of the muscle's displacement range. Thereafter, both dynamic models are applied to assess their performance. It is evident from the results that the BW model produces a better outcome than the MS, achieving a normalised error of 5.3746% as compared to the latter's 12.835%. The higher accuracy of the generalised BoucWen method is likely due to it having a more complex structure, specialised parameters, and the ability to model asymmetric hysteresis. The Maxwell-Slip model may however still be preferable in some applications due to its relative simplicity and faster optimisation. / Under de senaste åren har intresset och forskningen ökat kring användningen av mjuka ställdon inom robotik, drivet av den innovativa potentialen som erbjuds av egenskaperna hos deras naturligt flexibla material. Ett sådant ställdon är den Pneumatiska Artificiella Muskeln (PAM) som erbjuder hög kraft i förhållande till vikten, elasticitet, säkerhet och biologisk imitation jämfört med dess traditionella motsvarigheter. Trots dessa fördelar så uppvisar PAM:s ett icke-önskvärt olinjärt dynamiskt beteende, till stor del på grund av deras flexibla och komplexa fysiska struktur samt kompressibiliteten av luft inuti PAM:en. Dessa olinjäriteter orsakar hysteresfenomenet i muskeln. För att implementera strategier för att kunna motverka denna effekt så måste den först modelleras. Till följd därav så undersöker denna avhandling två tillvägagångssätt, nämligen Maxwell-Slip (MS) och den generaliserade Bouc-Wen (BW) modellen. Inledningsvis identifieras testmuskelns initiala flätvinkel, maximala förskjutning och maximala kraft för att fastställa den statiska kraften med hjälp av en modifierad modell. Data samlas sedan in på PAM:ens kraft-förskjutningshysteres för 2-6 bar av tryck. Med hjälp av resultaten från dessa experiment identifieras MS- och BW-modellparametrarna genom optimering. Med de statiska och hystereskraftskomponenterna karakteriserade kan två kompletta dynamiska modeller framkallas. Resultaten visar att jämfört med den insamlade kraft-förskjutningsdatan har BW-modellen en större noggrannhet för alla tryck förutom vid 4 bar, men båda metoderna uppvisar resultat som är inom en godtagbar marginal. Slutligen genomförs en modellvalidering för att jämföra modellerna med hjälp av ett nytt dataset, annorlunda från den som de tränades på. Datan för detta test mäts vid ett tryck på 4 bar med en mer komplex referens som täcker fyra olika regioner av muskelns förskjutningsområde. Därefter tillämpas båda dynamiska modellerna för att bedöma deras prestanda. Det är uppenbart från resultaten att BW-modellen ger ett bättre resultat än MS-modellen, och uppnår ett normaliserat fel på 5,3746% jämfört med den sistnämndas 12,835%. Den högre noggrannheten hos den generaliserade Bouc-Wen-metoden beror sannolikt på att den har en mer komplex struktur, specialiserade parametrar och förmågan att modellera asymmetrisk hysteres. Maxwell-Slipmodellen kan däremot ändå vara att föredra i vissa sammanhang på grund av dess relativa simplicitet och snabbare optimering

Dichtungen spielen für die Funktion von Maschinen eine zentrale Rolle. Sie verhindern den Austritt von Schmierstoff aus dem Innenraum in die Umgebung und das Eindringen von Schmutz von Außen. Neben einer möglichst guten Abdichtung ist jedoch auch die durch die Dichtung auftretende Reibung von immer größerer Bedeutung für die Funktionalität von Maschinen und Anlagen. Aus diesem Grund wird in der vorliegenden Arbeit untersucht, welche wesentlichen Einflussfaktoren das Reibmoment, bzw. den Reibwert von Radialwellendichtungen, beeinflussen. Experimentelle Untersuchungen erfolgen dafür an einem speziell entwickelten Versuchstand. Dabei wird ersichtlich, dass die Umfangsgeschwindigkeit, die Schmierstoffviskosität und die Temperatur im Dichtkontakt die wesentlichsten Einflussfaktoren bei einer festen Kombination aus Dichtung und Gegenlaufläche darstellen. Im Vergleich zwischen verschiedenen Dichtungen spielt zudem die Radialkraft der Dichtung eine entscheidende Rolle. Des weiteren wird ein komplexes Modell entwickelt, welches die Effekte im tribologischen Kontakt beschreibt und so das Reibmoment der Dichtung berechenbar macht. Berücksichtigt werden dabei sowohl die durch Oberflächenstrukturen beeinflusste Fluidreibung im Schmierspalt, als auch die Hysteresereibung im Dichtungsmaterial und die Temperatur im Dichtkontakt. Durch die Kopplung der Einzelmodelle wird zudem die gegenseitige Beeinflussung berücksichtigt. Die Simulationsergebnisse ermöglichen einen tiefen Einblick in das Zusammenwirken der Phänomene im Dichtkontakt. Das Modell erlaubt die Berechnung des Reibwertes der Dichtung anhand der Betriebsbedingungen. Der Vergleich zwischen numerischen und experimentellen Ergebnissen zeigt eine sehr gute Übereinstimmung. Ein weiteres, vereinfachtes Modell auf Basis der Gümbelzahl ermöglicht die direkte und extrem schnelle Berechnung des Reibwertes der Dichtung. Das reduzierte Modell kann hierbei sowohl von experimentellen als auch numerischen Ergebnissen parametriert werden.:1 Einleitung und Ziel der Arbeit 1 2 Stand des Wissens 3 2.1 Dynamische Dichtungen 3 2.2 Tribologie des Dichtkontaktes 4 2.2.1 Mechanismen im tribologischen Kontakt 5 2.2.2 Einflüsse auf die Dichtwirkung 6 2.2.3 Schmierfilmhypothesen 7 2.2.4 Stribeck-Kurve und Gümbelzahl 8 2.3 Materialeigenschaften von Elastomeren 9 2.4 Schmierstoffeigenschaften 11 2.5 Modelle zur Beschreibung von Dichtungsreibung 13 2.5.1 Modellierung der Hysteresereibung 14 2.5.2 Modellierung der Fluidreibung 16 2.5.3 Modellierung des Dichtungskontaktes 19 2.5.4 Modellierung der Temperatur im Dichtkontakt 20 3 Experimentelle Untersuchungen 21 3.1 Radialkraft 21 3.2 Kontaktbreite 23 3.3 Reibwertkennlinien 24 3.3.1 Radial-Dichtungsprüfstand 24 3.3.2 Ermittlung von Reibwertkennlinien unter stationären Randbedingungen 25 3.3.3 Ermittlung von Reibwertkennlinien unter instationären Randbedingungen 31 3.4 Elastomereigenschaften 34 3.4.1 Zugversuch 34 3.4.2 Dynamisch-Mechanisch-Thermische Analyse 34 4 Simulationen 37 4.1 FE-Modelle und Parametrierung 37 4.2 Modell zur Simulation des Dichtungsreibmomentes 39 4.2.1 Modellierung der Fluidreibung 40 4.2.2 Modellierung der Hysteresereibung 51 4.2.3 Approximation der Temperatur im Dichtkontakt 60 4.2.4 Kopplung/Abhängigkeiten 60 4.2.5 Berechnung der wahren Kontaktfläche 62 4.2.6 Ankopplung der Hysteresereibung 64 4.3 Ergebnisse zur Simulation des Dichtungsreibwertes 64 4.3.1 Fluidreibung 64 4.3.2 Hysteresereibung 69 4.3.3 Fluid- und Hysteresereibung 74 4.3.4 Einfluss der Umgebungstemperatur 77 4.3.5 Instationäre Randbedingungen 79 5 Zusammenfassung 83 A Einfluss der Maxwell-Äste auf das Ergebniss der Hysteresereibung 87 B Koeffizienten für die Flussfaktorenberechnung 89 Literaturverzeichnis 91 / Seals are very important for the proper function of machines. They prevent lubricant from escaping from the interior into the environment and the ingress of dust from outside. Yet not only the sealing properties are relevant, also the friction is getting more and more in focus. Therefore, in this thesis, the relevant influences on the friction moment, and on the friction coefficient are investigated. A special test rig has been developed for the experimental investigations. It has been found that the circumferential velocity and the lubricants viscosity in conjunction with the temperature at the seals contact are the main influence factors of a defined combination of seal and surface. For the comparison of different seals, the radial contact force has an important influence, too. Beside these experimental investigations a complex simulation model has been developed. It describes the effects inside the tribological contact and allows the calculation of the seals friction moment. The model uses calculation routines for the fluid friction due to the fluid film inside the seals contact with respect to the surface structures, as well as the hysteresis friction inside the seals lip. Furthermore, the seals contact temperature is calculated. All these models relate and respect the influence between each other. The simulation results allow a deep view on the phenomena inside the seals contact and their interaction with each other. The model allows the calculation of the friction coeficient. A good agreement between experimental and numeric results could be achieved. An additional, reduced model on basis of the Gümbel number allows a direct and extreme fast calculation of the friction coeficient. The reduced model could be parameterized both on experimental and simulation results.:1 Einleitung und Ziel der Arbeit 1 2 Stand des Wissens 3 2.1 Dynamische Dichtungen 3 2.2 Tribologie des Dichtkontaktes 4 2.2.1 Mechanismen im tribologischen Kontakt 5 2.2.2 Einflüsse auf die Dichtwirkung 6 2.2.3 Schmierfilmhypothesen 7 2.2.4 Stribeck-Kurve und Gümbelzahl 8 2.3 Materialeigenschaften von Elastomeren 9 2.4 Schmierstoffeigenschaften 11 2.5 Modelle zur Beschreibung von Dichtungsreibung 13 2.5.1 Modellierung der Hysteresereibung 14 2.5.2 Modellierung der Fluidreibung 16 2.5.3 Modellierung des Dichtungskontaktes 19 2.5.4 Modellierung der Temperatur im Dichtkontakt 20 3 Experimentelle Untersuchungen 21 3.1 Radialkraft 21 3.2 Kontaktbreite 23 3.3 Reibwertkennlinien 24 3.3.1 Radial-Dichtungsprüfstand 24 3.3.2 Ermittlung von Reibwertkennlinien unter stationären Randbedingungen 25 3.3.3 Ermittlung von Reibwertkennlinien unter instationären Randbedingungen 31 3.4 Elastomereigenschaften 34 3.4.1 Zugversuch 34 3.4.2 Dynamisch-Mechanisch-Thermische Analyse 34 4 Simulationen 37 4.1 FE-Modelle und Parametrierung 37 4.2 Modell zur Simulation des Dichtungsreibmomentes 39 4.2.1 Modellierung der Fluidreibung 40 4.2.2 Modellierung der Hysteresereibung 51 4.2.3 Approximation der Temperatur im Dichtkontakt 60 4.2.4 Kopplung/Abhängigkeiten 60 4.2.5 Berechnung der wahren Kontaktfläche 62 4.2.6 Ankopplung der Hysteresereibung 64 4.3 Ergebnisse zur Simulation des Dichtungsreibwertes 64 4.3.1 Fluidreibung 64 4.3.2 Hysteresereibung 69 4.3.3 Fluid- und Hysteresereibung 74 4.3.4 Einfluss der Umgebungstemperatur 77 4.3.5 Instationäre Randbedingungen 79 5 Zusammenfassung 83 A Einfluss der Maxwell-Äste auf das Ergebniss der Hysteresereibung 87 B Koeffizienten für die Flussfaktorenberechnung 89 Literaturverzeichnis 91

No description available.

<p>  </p> <p>Architectured materials offer engineers more options for choosing materials with their desired properties. Segmenting materials to create topological interlocking materials (TIMs) creates materials, which can deform in greater amounts without failure and absorb more strain energy. Previous research on TIMs has shown that the stiffness and reaction force of these materials can be directly controlled by controlling the boundary forces offered by the frame which constrains these materials.</p> <p>The research presented in this paper investigated a TIM made into a 1-Dimension beam like structure called a lintel. This research investigated not only the mechanics of this structure, but also developed a method of directly controlling the reaction force at a given displacement using shape memory alloy (SMA) wires. These wires would actuate the boundary pieces used to constrain the system. These actuation wires coupled with force sensors imbedded into the lintel allowed a feedback control loop to be established, which would control the reaction force. The reaction force was then controlled to create a smart structure which could optimize the strain energy absorption under the constraint of a maximum allowable load, similar to cellular solids used in packaging and padding materials.</p> <p>To develop this smart structure, four separate investigations occurred. The first was finite element analysis (FEA) performed to model the loading response of the lintel. This experiment demonstrated that the Mises Truss Model was effective at modelling the lintel. The second was an experimental validation of the FEA model performed in the first investigation. This experiment validated the Mises Truss Model for the lintel. The third investigation simulated the active lintel using computational software and the model of the lintel established in the first two investigations. This experiment demonstrated computationally the ability of SMA wires to control the reaction force as desired in an idealized case. The fourth and final investigation experimentally validated the ability to create and active lintel and created a functioning prototype. This demonstrated experimentally the ability of the active lintel to control reaction force as desired.</p> <p>This project has demonstrated the viability to create smart structures using segmented materials, which in the future may be used in a variety of applications including robotics and adaptive structures in harsh environments. </p>

A hydraulic damper plays an important role in tuning the handling and comfort characteristicsof a vehicle. Tuning and selecting a damper based on subjective evaluation, by considering theopinions of various users, would be an inefficient method since the comfort requirements of usersvary a lot. Instead, mathematical models of damper and simulation of these models in variousoperating conditions are preferred to standardize the tuning procedure, quantify the comfortlevels and reduce cost of testing. This would require a model, which is good enough to capture thebehaviour of damper in various operating and extreme conditions.The Force-Velocity (FV) curve is one of the most widely used model of a damper. This curve isimplemented either as an equation or as a look-up table. It is a plot between the maximum forceat each peak velocity point. There are certain dynamic phenomena like hysteresis and dependencyon the displacement of damper, which cannot be captured with a FV curve model, but are requiredfor better understanding of the vehicle behaviour.This thesis was conducted in cooperation with Volvo Cars with an aim to improve the existingdamper model which is a Force-Velocity curve. This work focuses on developing a damper model,which is complex enough to capture the phenomena discussed above and simple enough to beimplemented in real time simulations. Also, the thesis aims to establish a standard method toparameterise the damper model and generate the Force-Velocity curve from the tests performedon the damper test rig. A test matrix which includes the standard tests for parameterising andthe extreme test cases for the validation of the developed model will be developed. The final focusis to implement the damper model in a multi body simulation (MBS) software.The master thesis starts with an introduction, where the background for the project is described and then the thesis goals are set. It is followed by a literature review in which fewadvanced damper models are discussed in brief. Then, a step-by-step process of developing thedamper model is discussed along with few more possible options. Later, the construction of a testmatrix is discussed in detail followed by the parameter identification process. Next, the validationof the developed damper model is discussed using the test data from Volvo Hällered ProvingGround (HPG). After validation, implementation of the model in VI CarRealTime and Adams Caralong with the results are presented. Finally the thesis is concluded and the recommendations forfuture work are made on further improving the model. / En hydraulisk stötdämpare spelar en viktig roll för att fordonets hantering och komfort. Attjustera och välja en stötdämpare baserat på subjektiv utvärdering, genom att beakta olika användares åsikter, skulle vara en ineffektiv metod eftersom användarnas komfortkrav varierarmycket. Istället föredras matematiska modeller av stötdämpare och simulering av dessa modellerunder olika driftsförhållanden för att standardisera inställningsförfarandet, kvantifiera komfortnivåerna och minska testkostnaden. Detta skulle kräva en modell som är tillräckligt bra för attfånga upp stötdämparens beteende under olika drifts- och extrema förhållanden.Force-Velocity (FV) -kurvan är en av de mest använda stötdämparmodellerna. Denna kurvaimplementeras antingen som en ekvation eller som en uppslagstabell. Det är ett diagram somredovisar den maximala kraften vid varje maxhastighetspunkt. Det finns vissa dynamiskafenomen som hysteres och beroende av stötdämparens förskjutning, som inte kan fångas med enFV-kurvmodell, men som krävs för att bättre förstå fordonets beteende.Denna avhandling genomfördes i samarbete med Volvo Cars i syfte att förbättra den befintligastötdämparmodellen som är en Force-Velocity-kurva. Detta arbete fokuserar på att utveckla enstötdämparmodell, som är tillräckligt komplex för att fånga upp de fenomen som diskuteratsovan och tillräckligt enkel för att implementeras i realtidssimuleringar. Avhandlingen syftarockså till att upprätta en standardmetod för att parametrisera spjällmodellen och generera ForceVelocity-kurvan från de test som utförts på stötdämpartestriggen. En testmatris som innehållerstandardtest för parametrisering och extrema testfall för validering av den utvecklade modellenkommer att utvecklas. Det sista fokuset är att implementera stötdämparmodellen i en multi-bodysimulation (MBS) programvara.Examensarbetet inleds med en introduktion, där bakgrunden för projektet beskrivs ochdärefter definieras målen med arbetet. Det följs av en litteraturöversikt där några avanceradestötdämparmodeller diskuteras i korthet. Därefter diskuteras en steg-för-steg-process för attutveckla stötdämparmodeller tillsammans med några fler möjliga alternativ. Senare diskuteraskonstruktionen av en testmatris i detalj följt av parameteridentifieringsprocessen. Därefterdiskuteras valideringen av den utvecklade stötdämparmodellen med hjälp av testdata från VolvoHällered Proving Ground (HPG). Efter validering presenteras implementeringen av modellen iVI CarRealTime och Adams Car tillsammans med resultaten. Slutligen avslutas rapporten medslutsatser från arbetet och rekommendationer för framtida arbete görs för att ytterligare förbättramodellen.

<p dir="ltr">Metal speciation and structure can be influenced by the deposition method used during synthesis, interactions with the support, and by post-deposition treatments and reaction conditions experienced during its lifetime of carrying out a catalytic reaction. Supported metal particles of different size contain different surface structures and coordination environments, which may not only influence reaction rates but also the interconversion between agglomerated metallic domains and dispersed metal atom or ion sites. Here, we address the influence of post-deposition treatments and support properties on the structural interconversion of Pd and Cu on aluminosilicate chabazite (CHA) zeolites, Pt on gamma-alumina (γ-Al2O3), and Pd on amorphous oxides (γ-Al2O3, La-doped Al2O3, ΘΔ-Al2O3). The fundamental insights from these studies can be used to design catalysts used widely in automotive exhaust aftertreatment systems, including Pd-exchanged zeolites for passive NOx (x = 1,2) adsorbers (PNA), Cu-exchanged zeolites for NOx (x = 1,2) selective catalytic reduction (SCR), Pt/Al2O3 for NH3 oxidation, and Pd/oxides for three-way catalysts (TWC). Incipient wetness impregnation (IWI) and colloidal methods were used to prepare Pd nanoparticles deposited on CHA zeolites with distinct Pd nanoparticle sizes and distributions. These Pd-CHA samples were used to investigate the effects of Pd particle size distribution on structural interconversion between ion-exchanged Pd and agglomerated Pd domains under realistic operating conditions. Smaller Pd nanoparticles had larger fractions of agglomerated Pd that converted to ion-exchanged Pd2+ sites at fixed air treatment temperatures (598–973 K) and H2O pressures (2–6 kPa H2O), consistent with thermodynamic predictions from DFT calculations. Furthermore, the addition of H2O during air treatment of different Pd nanoparticles (2–14 nm) inhibited the formation of ion-exchanged Pd2+ (thermodynamics), but not the rate of redispersion (kinetics). This demonstrates that, regardless of Pd nanoparticle size, water vapor in automotive exhaust streams facilitate metal sintering in PNA applications. Aqueous-phase exchange of Cu on CHA zeolites with varying support properties (i.e., number of paired Al sites in the 6 membered ring) were used to prepare materials with distinct types and numbers of extraframework Cu species (Cu2+, CuOH+). These Cu-CHA materials were used to analyze Cu structural changes before and after exposure to hydrothermal aging conditions. In the absence of H2O, some Cu2+ sites condense to form binuclear Ox-bridged Cu species that can be reduced with H2 to form Cu-hydride sites and reject H2O, leading to a sub-stoichiometric H2 consumption (H2/Cu < 0.5). In the presence of H2O, all nominally isolated Cu2+ species convert to [CuOH]+ structures, which can subsequently be reduced by H2 to form a Cu-hydride and reject H2O, leading to stoichiometric H2 consumption (H2/Cu ~ 0.5). Furthermore, the presence of H2O led to reduction features in H2 temperature programmed reduction (TPR) profiles that were similar among Cu-CHA materials, regardless of the initial Cu2+ speciation, further supporting the proposal that all nominally isolated Cu2+ sites convert to a similar [CuOH]+ motif. This demonstrates how water influences Cu speciation on CHA materials of varying origin or treatment history, aiding in quantifying SCR-active isolated Cu ions and SCR-inactive Cu species (e.g., CuO, CuAl2O4). Pt supported on γ-Al2O3 were prepared with different average Pt particle sizes (2–13 nm) by increasing the temperature of post-deposition air treatment (523–873 K). This suite of materials was interrogated to isolate the effects of Pt particle size on NH3 oxidation rates and selectivities during conditions relevant to NH3 slip applications in diesel exhaust aftertreatment. For all Pt particle sizes, NH3 oxidation rates displayed a hysteresis with temperature, with high rates measured during temperature decreases than during temperature increases. Smaller Pt particles (2 nm) had lower rates (per surface Pt, quantified by CO chemisorption) than larger Pt particles (13 nm), signifying that NH3 oxidation is a structure-sensitive reaction. Furthermore, surfaces of Pt particles restructure under NH3 oxidation reaction conditions, influencing effective Pt oxidation states, surface structures (numbers and types of exposed Pt sites), and surface coverages of intermediates leading to the observed hysteresis in rate. These findings demonstrate that Pt particles undergo dynamic structural changes during reaction, influencing their ability to convert NH3 to environmentally benign products in NH3 slip applications. The influence of treatment conditions, support properties, and initial Pd particle size and distribution on the kinetics of nanoparticle sintering were investigated to identify which material properties allow maintaining high dispersion to maximize metal utilization for three way catalysts (TWC) during the conversion of regulated pollutants (CO, hydrocarbons, NOx). Pd was deposited by IWI methods to generate polydiserse particle size distributions, and using colloidal Pd nanoparticle solutions to generate monodisperse size distributions, onto various supports (γ-Al2O3, La-doped Al2O3, ΘΔ-Al2O3) and subjected to aging under oxidative and reductive conditions relevant for TWC operation. The average Pd particle size for all materials increased with treatment time under both reductive and oxidative environments. For samples prepared with IWI (i.e., log normal distribution of Pd particle sizes), reductive aging treatments led to higher sintering rates than oxidative treatments. In contrast, for samples prepared using colloidal Pd solutions (i.e., normal distribution of Pd particle sizes), oxidative aging treatments led to higher sintering rates than reduction treatments. Furthermore, after the same treatment condition and time, samples prepared with IWI resulted in higher average Pd particle sizes. These results indicate that more monodisperse initial Pd particle size distributions lead to lower sintering rates, providing guidance to design of supported metal TWCs with improved metal utilization during their lifetimes. Here, the combination of synthesis approaches to prepare a suite of model (e.g., powder) supported metal catalysts of varying structure and composition, interrogated using site and structural characterizations and steady-state and transient kinetic measurements, along with predictions from theoretical calculations, enabled unraveling the influence of material properties and gas environments that affect metal speciation, structure, and oxidation state in real-world aftertreatment systems that use more complex catalytic architectures (e.g., layered washcoats) and reactor designs (e.g., monoliths). This approach provides insights into the fundamental thermodynamic and kinetic factors influencing metal restructuring and interconversion under realistic conditions encountered in automotive exhaust aftertreatment applications, and the kinetic and mechanistic factors that underlie complex phenomena (e.g., reaction rate hysteresis) from data measured in the absence of hydrodynamic artifacts. The overall approach used in this work enabled development of synthesis-structure-function relationships on various metal supported catalysts for automotive exhaust aftertreatment applications, which can provide guidance for material design and treatment strategies to form and retain desired metal structures throughout the material lifetime, including synthesis, reaction, and regeneration treatments.</p>