Hydromechanical Stress and Internal Erosion under Earthen Structures

Dam failures by seepage and internal erosion have reportedly been attributed to up to 40% of all dam failures in the United States. Backwards piping erosion either through the embankment or foundation soils has been reported to be the major contributing method to seepage and internal erosion dam failures. This proposed research is motivated by the lack of understanding of the complex stress regimes associated with internal erosion in cohesionless soils under earthen structures. The overall goal of this research is to provide a fundamental understanding of internal erosion and the hydromechanical stress conditions necessary for the initiation and continuation of internal erosion in cohesionless soils under earthen structures. This research project consisted of three experimental tasks to evaluate internal erosion in cohesionless soils. Task 1 consisted of laboratory soil characterization of regional geo-materials representative of typical Missouri earthen dam foundation materials. Task 2 consisted of a conventional finite element method numerical analysis of a typical Missouri embankment dam geometry to determine foundation stresses/strains and hydraulic flow conditions. Task 3 consisted of the bench-scale design, construction, and testing of an Internal Erosion Plane-Stain Direct Simple Shear (PSDSS) device to evaluate internal erosion. The results indicated that within internally unstable soils internal erosion typically initiates and then may terminate or continue depending upon the hydromechanical conditions. Any changes in the hydromechanical conditions can cause the re-initiation and continuation of internal erosion. Internally stable soils did not exhibit the potential for internal erosion when tested under changing hydromechanical conditions --Abstract, p. ii

Engineered morphologic material structures: physical/chemical properties and applications

Morphologies include the study of shape, size and structure for materials from atomic scale to macroscales. Properties/functions of material structures in general are dependent on morphologies, and tunable properties in chemical and physical can be realized through changing morphologies on surfaces and in bulk systems of materials. For low-dimensional materials, atomic modifications and changes in lattice morphologies can introduce varieties of fascinating phenomena and unconventional intrinsic properties in electric, mechanics chemistry and etc. The reason behind such controllability is that morphological undulation usually is consistent with the mapping of strain, which is related to atomic structures of materials. For micro/macro scale materials, interactions of surface tension, mechanical deformation, etc. dominate the morphological evolution. Structural designs and morphological control can achieve desirable functionalities, for example mechanical flexibility and liquid wettability for practical applications. Herein, strain-engineering strategies including mechanical loading and atomic displacement were applied to modify and control morphologies in materials with different length scales. We firstly investigated the fundamental mechanism of morphological evolution through various load strategies, and relationship between morphologies and the properties of material structures across from nanoscale, microscale to macroscale, including graphene, phosphorene, core-shell microparticles and soft materials/bilayers, etc. Furthermore, we demonstrated to two applications of utilizing designed morphologies, which targeted to figures out challenges in the field of energy conversion and storage to close energy loop. Therefore, we mainly focus on the relation of engineered strategy-morphology-mechanism/property-functional devices in this thesis. Firstly, engineered morphologies in nanomaterials of graphene and phosphorene were investigated through strain-localization, gradient strain, bending/pressing. The effects of surface morphologies on fundamental properties including thermal conductivities, mechanics, electrics, surface energy and chemical reactivities were studied through molecular dynamics (MD) simulations and first-principle calculations combined with experimental verifications: Increased applications of nanoporous graphene in nanoelectronics and membrane separations require ordered and precise perforation of graphene, whose scalablility and time/cost effectiveness represent a significant challenge in existing nanoperforation methods, such as catalytical etching and lithography. We reported a strain-guided perforation of graphene through oxidative etching, where nanopores nucleate selectively at the bulges induced by the pre-patterned nano-protrusions underneath. Using reactive molecular dynamics and theoretical models, we uncover the perforation mechanisms through the relationship between bulge-induced strain and enhanced etching reactivity. Parallel experiments of CVD graphene on SiO2 NPs/ SiO2 substrate verify the feasibility of such strain-guided perforation and evolution of pore size by exposure durations to oxygen plasma. When a nanodroplet is placed on a lattice surface, an inhomogeneous surface strain field perturbs the balance of van der Waals force between the nanodroplet and surface, thus providing a net driving force for nanodroplet motion. Using molecular dynamics and theoretical analysis, we studied the effect of strain gradient on modulating the movement of a nanodroplet. Both modeling and simulation showed that the driving force is opposite to the direction of strain gradient, with a magnitude that is proportional to the strain gradient as well as nanodroplet size. Two representative surfaces, graphene and copper (111) plane, were exemplified to demonstrate the controllable motion of nanodroplet. When the substrate underwent various types of reversible deformations, multiple motion modes of nanodroplets could be feasibly achieved, including acceleration, deceleration and turning, becoming a facile strategy to manipulate nanodroplets along a designed 2D pathway. Using molecular dynamics (MD) simulations, we explored the structural stability and mechanical integrity of phosphorene nanotubes (PNTs), where the intrinsic strain in the tubular PNT structure plays an important role. It was proposed that the atomic structure of larger-diameter armchair PNTs (armPNTs) could remain stable at higher temperature, but the high intrinsic strain in the hoop direction renders zigzag PNTs (zigPNTs) less favorable. The mechanical properties of PNTs, including the Young’s modulus and fracture strength, are sensitive to the diameter, showing a size dependence. A simple model is proposed to express the Young’s modulus as a function of the intrinsic axial strain which in turns depends on the diameter of PNTs. A new phosphorous allotrope, closed-edged bilayer phosphorene nanoribbon, was proposed via radially deforming armchair phosphorene nanotubes. Using molecular dynamics simulations, the transformation pathway from round phosphorene nanotubes falls into two types of collapsed structures: arc-like and sigmoidal bilayer nanoribbons, dependent on the number of phosphorene unit cells. The fabricated nanoribbions are energetically more stable than their parent nanotubes. It was also found via ab initio calculations that the band structure along tube axis substantially changes with the structural transformation. The direct-to-indirect transition of band gap was highlighted when collapsing into the arc-like nanoribbons but not the sigmoidal ones. Furthermore, the band gaps of these two types of nanoribbons showed significant size-dependence of the nanoribbon width, indicative of wider tunability of their electrical properties. Secondly, we studied fundamental mechanisms of generating fascinating surface morphologies on the micro materials/structures of core/shell microsphere driven by surface instability, which is not different those in nanoscale. The island-like dot pattern on spherical substrate were investigated: Through strain-induced morphological instability, protruding patterns of roughly commensurate nanostructures are self-assembled on the surface of spherical core/shell systems. A three-dimensional (3D) phase field model was established for closed substrate. We investigated both numerically and analytically the kinetics of the morphological evolution, from grooves to separated islands which are sensitive to substrate curvature, misfit strain and modulus ratio between core and shell. The faster growth rate of surface undulation was associated with the core/shell system of harder substrate, larger radius or misfit strain. Based on a Ag core/SiO2 shell system, the self-assemblies of SiO2 nano-islands were explored experimentally. The numerical and experimental studies herein could guide the fabrication of ordered quantum structures via surface instability on closed and curved substrates. Up to macroscale material structures, the variety and controllability surface morphologies on soft materials and bilayer films were realized through pre-pattern defects of cavities and in-plane compression. The checkboard and wrinkling surface patterns were observed in different systems through both finite element simulations and 3D printing technique: A rich diversity of surface topologies is controllably engineered by patterning cavities embedded beneath the surface of soft materials. Upon external compression, the surface undergoes the reversible transformation from the flat surface to various surface topographies, including the periodic checkerboard pattern with alternatively convex and concave features. To design the surface features, both 2D and 3D finite element based-simulations were performed. It was demonstrated that the periodic surface features with controllable morphology, such as 1D waves, checkerboard pattern and mutually perpendicular apexes, etc. can be realized through varying cavity geometries (e.g., relative inter-cavity distance, shapes and biaxial/uniaxial load). Based on 3D printed prototypes, we further conducted experiments to validate the simulation results of 2D morphologies. The patterned cavities in soft materials made designing a variety of reversible surface features possible, offering an effective fabrication approach for wide application across multiple scales. Wrinkle formation followed by sharp strain localization is commonly observed in compressed stiff film/soft substrate systems. However, cavities or defects beneath the film may directly trigger the formation of local ridges and then folding configurations at a relatively small compressive strain, and a mixture of wrinkles and folds upon further compression. The morphological transition is different than those of defect-free substrates. Numerical simulations of continuously compressed bilayer with pre-patterned cavities were carried out to elucidate the transition mechanism of surface patterns. Parallel experiments of cavities-patterned bilayer prototypes by 3D-printing were also performed to validate the findings in simulations. A rich diversity of periodic surface topologies, including overall spreading waves, localizations, saw-like and co-existing features of folds and wrinkles can be obtained by varying the diameter, depth and spacing of cavities, which provides a potential approach to engineer various surface patterns for applications. Since these discussed material structures are promising candidates for energy/environmental applications, two device-level functional systems/products here utilize intriguing morphologies in both nanoscale and macroscale. To close energy loop, the energy conversion reactor (chemical loop reduction of CO2) and the energy storage device (flexible lithium ion battery) were demonstrated: We reported an effective reduction method for splitting air-containing CO2 into CO for high-value chemicals, through a chemical looping redox scheme with Cu-doped LaFeO3 perovskites as efficient oxygen carriers for splitting CO2 with a high-concentration of O2 (e.g. 1:5 O2/CO2 molar ratio, mimicking 1:1 CO2/air mixture). Up to 2.28 mol/kg CO yield was achieved with good stability in the CO2 splitter, five times higher than that with the conventional pristine LaFeO3 perovskite. Through ab initio calculations, we uncovered that the exsolution of metallic Cu on the surface of reduced perovskite is capable of mitigating the competition between CO2 and O2 for the re-oxidation step. This air-stable and scalable scheme can economically integrate with upstream DAC and downstream gas-to-liquids plants, exhibiting up to 94.5% and 42.8% reduction in net CO2 emission for valuable chemicals production (methanol and acetic acid) when compared with the coal gasifier-based route and this redox scheme using pure CO2, respectively. Flexible batteries, seamlessly compatible with flexible and wearable electronics, attract a great deal of research attention. Current designs of flexible batteries are unable to meet one of the most extreme yet common deformation scenarios in practice, folding, while retaining high energy density. Inspired by origami folding, we proposed a novel strategy to fabricate zigzag-like lithium ion batteries with superior foldability. The battery structure could approach zero-gap between two adjacent energy storage segments, achieving an energy density that is 96.4% of that in a conventional stacking cell. A foldable battery thus fabricated demonstrated an energy density of 275 Wh L-1 and was resilient to fatigue over 45,000 dynamic cycles with a folding angle of 130°, while retaining stable electrochemical performance. Additionally, the power stability and resilience to nail shorting of the foldable battery were also examined

ResFrac Technical Writeup

ResFrac is a combined hydraulic fracturing, reservoir, and hydraulic fracturing simulator. It describes multiphase fluid flow (black oil or compositional), proppant transport, transport of non-Newtonian fluid additives, and thermal transport. It also includes stress shadowing from fracture propagation and porothermoelastic responses from pressure change in the matrix. It uses constitutive equations that smoothly transition between equations for flow through an open crack to flow through a closed crack (with or without proppant). This document provides a detailed technical description of the code, along with validation simulations to confirm numerical accuracy

Electrical Discharge in Water Treatment Technology for Micropollutant Decomposition

Hazardous micropollutants are increasingly detected worldwide in wastewater treatment plant effluent. As this indicates, their removal is insufficient by means of conventional modern water treatment techniques. In the search for a cost-effective solution, advanced oxidation processes have recently gained more attention since they are the most effective available techniques to decompose biorecalcitrant organics. As a main drawback, however, their energy costs are high up to now, preventing their implementation on large scale. For the specific case of water treatment by means of electrical discharge, further optimization is a complex task due to the wide variety in reactor design and materials, discharge types, and operational parameters. In this chapter, an extended overview is given on plasma reactor types, based on their design and materials. Influence of design and materials on energy efficiency is investigated, as well as the influence of operational parameters. The collected data can be used for the optimization of existing reactor types and for development of novel reactors

Large Scale Synthesis of Nanostructured Carbon Ti4O7 Hollow Particles as Efficient Sulfur Host Materials for Multilayer Lithium Sulfur Pouch Cells

Applications of advanced cathode materials with well designed chemical components and or optimized nanostructures promoting the sulfur redox kinetics and suppressing the shuttle effect of polysulfides are highly valued. However, in the case of actual lithium sulfur Li amp; 8722;S batteries under practical working conditions, one long term obstacle still exists, which is mainly due to the difficulties in massive synthesis of such nanomaterials with low cost and ease of control on the nanostructure. Herein, we develop a facile synthesis of carbon coated Ti4O7 hollow nanoparticles C amp; 8722;Ti4O7 using spherical polymer electrolyte brush as soft template, which is scalable via utilizing a minipilot reactor. The C amp; 8722;Ti4O7 hollow nanoparticles provide strong chemical adsorption to polysulfides through the large polar surface and additional physical confinement by rich micro amp; mesopores and have successfully been employed as an efficient sulfur host for multilayer pouch cells. Besides, the sluggish kinetics of the sulfur and lithium sulfide redox mechanism can be improved by the highly conductive Ti4O7 via catalyzation of the conversion of polysulfides. Consequently, the C amp; 8722;Ti4O7 based pouch cell endows a high discharge capacity of 1003 amp; 8197;mAh amp; 8201;g amp; 8722;1 at 0.05 amp; 8197;C, a high capacity retention of 83.7 amp; 8201; after 100 amp; 8197;cycles at 0.1 amp; 8197;C, and a high Coulombic efficiency of 97.5 amp; 8201; at the 100th cycle. This work proposes an effective approach to transfer the synthesis of hollow Ti4O7 nanoparticles from lab to large scale production, paving the way to explore a wide range of advanced nanomaterials for multilayer Li amp; 8722;S pouch cell

Cell adhesion promotion strategies for signal transduction enhancement in microelectrode array in vitro electrophysiology: An introductory overview and critical discussion

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Development of Nanoporous Anodic Alumina Technologies for Drug Delivery

L'alliberament de fàrmacs és un procediment en què un compost o un dispositiu allibera una molècula de manera controlada. D’aquesta manera, el medicament podrà ser sotmès a absorció, distribució, metabolisme i excreció. Els semiconductors nanoporosos com l'alúmina o el silici s'utilitzen per a la fabricació de vehicles de fàrmacs a causa de les seves característiques distintives, com ara: fabricació de baix cost, estructura de porus/ mida controlable dels nanotubs, química superficial adaptable, gran àrea superficial, capacitat d'alta càrrega, resistivitat química i rigidesa mecànica. Aquesta materials poden tenir un paper especial en la tecnologia d’alliberament de fàrmacs. Tot i que s'ha estudiat l'alliberament de medicaments a partir de materials nanoporosos i mesoporosos, hi ha una manca de comprensió de les cinètiques d'alliberament d'aquestes plataformes i la dinàmica que les regula. Per aquest motiu, el nostre objectiu és explicar la cinètica d'alliberament des de les superfícies nanoporoses i mesoporoses i modelar-les. Aquest model serà dilucidat mitjançant un estudi sistemàtic dels perfils d'alliberament. En conjunt, la tecnologia, la caracterització i les aplicacions presentades en aquesta tesi són força alentadores i proporcionen un punt de partida per desenvolupar estructures intel·ligents innovadores que trobaran aplicacions en sistemes de lliurament de medicaments.La liberación de fármaco es un procedimiento en el que un compuesto o un dispositivo libera una molécula de una manera controlada. Posteriormente, este fármaco podrà someterse a absorción, distribución, metabolismo y excreción. Se utilizan semiconductores nanoporosos como la alúmina o el silicio para fabricar vehículos de fármacos debido a sus características distintivas tales como: fabricación de bajo costo, estructura de poros/tamaño controlable de los nanotubos, química de superficie adaptable, área superficial grande, alta capacidad de carga, resistividad química y rigidez mecánica. Estos materiales pueden tener papel especial en la tecnología de liberación controlada de fármacos. Aunque se ha estudiado la liberación de fármacos a partir de materiales nanoporosos y mesoporosos, existe una falta de comprensión de la cinética de liberación de estas plataformas y de la dinámica que las gobierna. En este sentido, nuestro objetivo es explicar la cinética de liberación de superficies nanoporosas y mesoporosas y modelarlas. Este modelo será elucidado mediante un estudio sistemático de los perfiles de liberación. En conjunto, la tecnología, la caracterización y las aplicaciones presentadas en esta tesis son bastante alentadoras y proporcionan un punto de partida para el desarrollo de estructuras inteligentes e innovadoras que encontrarán aplicaciones en los sistemas de administración de fármacos.Drug release is a procedure in which a composite or a device releases a molecule in a controlled way. Subsequently the drug would be subjected to absorption, distribution, metabolism and excretion. Nanoporous semiconductors like alumina or silicon are used to fabricate carriers because of their distinctive features such as: low-cost fabrication, controllable pore/nanotube structure, tailored surface chemistry, high surface area, high loading capability, chemical resistivity and mechanical rigidity, have affianced a special role in drug delivery technology. Although drug release from nanoporous and mesoporous materials has been studied, there is a lack of understanding of the release kinetics from these platforms and the dynamics governing them. For this reason, our aim is to explain the release kinetics from nanoporous and mesoporous surfaces and model them. This model will be elucidated by means of a systematic study of release profiles. Altogether, technology, characterization and applications presented in this thesis are rather encouraging and are providing a starting point for developing innovative smart structures that will find applications in drug delivery systems

Structural and chemical modifications of porous silicon for biomedical applications

The versatility in properties of porous silicon (PSi) has enabled a broad spectrum of applications, ranging from microelectronics and various types of sensors to its use as a biocompatible material in drug delivery. Structural properties of PSi were shown in this work to be adaptable post-fabrication using thermal annealing. Control over the average pore size of the material proved to be beneficial, when adjustments were necessary to accommodate larger biomolecules within the pores of the PSi. Furthermore, a facile method of fabricating PSi nanoparticles was introduced using a multilayer approach with a stepwise electrochemical etching process, where the comminution of the material was guided with formation of fragile, high porosity perforation layers at specific intervals. This method has been proven successful, being utilized in over 70 publications so far. For extended control over biocompatibility and biodistribution of PSi micro- and nanoparticles, two new surface modifications based on hydrolytically stabilized PSi were introduced. Amine-terminated thermally carbonized PSi, capable of carbodiimide crosslinking for further functionalization with biomolecules, and an alkyne-terminated hydrocarbonized PSi, enabling the use of click chemistry -based addition reaction for secondary functionalization. Solid-state properties of confined drug molecules adsorbed into PSi microparticles were also studied. As PSi is known to enhance aqueous dissolution and cellular permeability of poorly soluble drugs, more accurate information was sought on the effects of the mesoscale confinement. Small molecule drugs were observed to partially have a liquid-like behavior according to solid-state NMR analysis and participate in interactions with the pore walls, according the availability of specific functional groups. Slight disruption in short-range order of the adsorbed drugs was also found, as the confinement appeared to reduce the true density of the drug molecules below that of a bulk amorphous state. Study over the conditions for efficient drug adsorption into the pores showed the importance of solvent and drug solution concentration selection. Optimal choices enabled high drug payload within the PSi, without precipitation of crystalline drug on the external surface of the PSi microparticles.Huokoisen piin (porous silicon, PSi) monipuoliset ominaisuudet ovat mahdollistaneet runsaasti erilaisia sovelluksia, lähtien mikroelektroniikasta ja ilmaisimista aina tämän käyttöön bioyhteensopivana materiaalina lääkeannostelussa. Tässä työssä osoitettiin huokoisen piin rakenteen olevan jälkikäteen muokattavissa hallitusti lämpökäsittelyn avulla. Huokoskokoa kasvattamalla mahdollistettiin tarpeen vaatiessa suurempien biomolekyylien pääsy huokosiin. Tämän lisäksi esiteltiin menetelmä huokoisen piin nanopartikkelien valmistamiseksi syövyttämällä sähkökemiallisesti huokoinen monikerrosrakenne, missä tasaisin välimatkoin sijaitsevat hauraat korkean huokoisuuden kerrokset toimivat murtumista edistävinä kohtina. Menetelmää on sittemmin hyödynnetty tähän mennessä yli 70:ssä tieteellisessä julkaisussa. Huokoisen piin mikro- ja nanopartikkelien bioyhteensopivuuden ja kulkeutumisen hallintaan työssä kehitettiin kaksi uutta pintakemiallista muunnosta huokoiselle piille, mikä oli esikäsitelty heikosti veteen liukenevaksi. Muunnokset perustuivat vapaiden amiiniryhmien ja alkyynien saatavuuteen huokoisen piin pinnoilla. Näistä edellinen mahdollisti biologisen funktionalisoinnin karbodi-imidisilloituksen kautta, jälkimmäisen puolestaan mahdollistaen monipuolinen funktionalisointi kupariavusteisen sykloadditioreaktion kautta. Lääkemolekyylien fysikaalista olotilaa nanokokoluokan huokosissa tutkittiin huokoisen piin mikropartikkelien avulla. Huokosiin adsorboitujen niukkaliukoisten lääkeaineiden tiedetään liukenevan tehokkaasti veteen, mutta syitä tälle voi olla useita. Pienmolekyylilääkkeiden havaittiin olevan osittain nestemäisessä muodossa huokosten sisällä NMR-tutkimusten mukaan. Molekyylien lähijärjestys vaikutti myös osittain muuttuneen, huokosiin adsorboituneen lääkeaineen tiheyden ollessa tavallista amorfista tilaa alhaisempi. Lääkeaineen adsorptiota huokosiin pyrittiin myös tehostamaan seuraamalla liuottimen ja lääkeaineliuoksen konsentraation vaikutusta. Sopivin parametrein saavutettiin korkea lääkkeen hyötykuorma, ilman lääkemolekyylien kiteytymistä huokoisen piin mikropartikkelien ulkopinnoille