Periodic polymer photonic bandgap structures for on-chip optical cavities

Integrated on-chip optical platforms enable high performance in applications of high-speed all-optical or electro-optical switching, wide-range multi-wavelength on-chip lasing for communication, and lab-on-chip optical sensing. Integrated optical resonators with high quality factor are a fundamental component in these applications. Periodic photonic structures (photonic crystals) exhibit a photonic band gap, which can be used to manipulate photons in a way similar to the control of electrons in semiconductor circuits. This makes it possible to create structures with radically improved optical properties. Compared to silicon, polymers offer a potentially inexpensive material platform with ease of fabrication at low temperatures and a wide range of material properties when doped with nanocrystals and other molecules. In this research work, several polymer periodic photonic structures are proposed and investigated to improve optical confinement and optical sensing. We developed a fast numerical method for calculating the quality factor of a photonic crystal slab (PhCS) cavity. The calculation is implemented via a 2D-FDTD method followed by a post-process for cavity surface energy radiation loss. Computational time is saved and good accuracy is demonstrated compared to other published methods. Also, we proposed a novel concept of slot-PhCS which enhanced the energy density 20 times compared to traditional PhCS. It combines both advantages of the slot waveguide and photonic crystal to localize the high energy density in the low index material. This property could increase the interaction between light and material embedded with nanoparticles like quantum dots for active device development. We also demonstrated a wide range bandgap based on a one dimensional waveguide distributed Bragg reflector with high coupling to optical waveguides enabling it to be easily integrated with other optical components on the chip. A flexible polymer (SU8) grating waveguide is proposed as a force sensor. The proposed sensor can monitor nN range forces through its spectral shift. Finally, quantum dot - doped SU8 polymer structures are demonstrated by optimizing spin coating and UV exposure. Clear patterns with high emission spectra proved the compatibility of the fabrication process for applications in optical amplification and lasing.

Lateral load distribution for curved steel I -girder bridges

Lateral load distribution factor is a key factor for designing and analyzing curved steel I-girder bridges. In this dissertation, the effects of various parameters on moment and shear distribution for curved steel I-girder bridges were studied using the Finite Element Method (FEM). The parameters considered in the study were: radius of curvature, girder spacing, overhang, span length, number of girders, ratio of girder stiffness to overall bridge stiffness, slab thickness, girder longitudinal stiffness, cross frame spacing, and girder torsional inertia. The variations of these parameters were based on the statistical analysis of the real bridge database, which was created by extracting data from existing or newly designed curved steel I-girder bridge plans collected all over the nation. A hypothetical bridge superstructure model that was made of all the mean values of the data was created and used for the parameter study. ^ The study showed that cross frame spacing and girder torsional inertia had negligible effects. Other parameters had been identified as key parameters. Regression analysis was conducted based on the FEM analysis results and simplified formulas for predicting positive moment, negative moment, and shear distribution factors were developed. Thirty-three real bridges were analyzed using FEM to verify the formulas. The ratio of the distribution factor obtained from the formula to the one obtained from the FEM analysis, which was referred to as the g-ratio, was examined. The results showed that the standard deviation of the g-ratios was within 0.04 to 0.06 and the mean value of the g-ratios was greater than unity by one standard deviation. This indicates that the formulas are conservative in most cases but not overly conservative. The final formulas are similar in format to the current American Association of State Highway and Transportation Officials (AASHTO) Load Resistance and Factor Design (LRFD) specifications. ^ The developed formulas were compared with other simplified methods. The outcomes showed that the proposed formulas had the most accurate results among all methods. ^ The formulas developed in this study will assist bridge engineers and researchers in predicting the actual live load distribution in horizontally curved steel I-girder bridges. ^

Modelagem numérica de uma estrutura de contenção de estacas espaçadas atirantadas em areia

Retaining walls design involves factors such as plastification, loading and unloading, pre-stressing, excessive displacements and earth and water thrust. Furthermore, the interaction between the retained soil and the structure is rather complex and hard to predict. Despite the advances in numerical simulation techniques and monitoring of forces and displacements with field instrumentation, design projects are still based on classical methods, whose simplifying assumptions may overestimate structural elements of the retaining wall. This dissertation involves a three-dimensional numerical study on the behavior of a retaining wall using the finite element method (FEM). The retaining wall structure is a contiguous bored pile wall with tie-back anchors. The numerical results were compared to data obtained from field instrumentation. The influence of the position of one or two layers of anchors and the effects of the construction of a slab bounded at the top of the retaining wall was evaluated. Furthermore, this study aimed at investigating the phenomenon of arching in the soil behind the wall. Arching was evaluated by analyzing the effects of pile spacing on horizontal stresses and displacements. Parametric analysis with one layers of anchors showed that the smallest horizontal displacements of the structure were achieved for between 0.3 and 0.5 times the excavation depth. Parametric analyses with two anchor layers showed that the smallest horizontal displacements were achieve for anchors positioned in depths of 0.4H and 0.7H. The construction of a slab at the top of the retaining wall decreased the horizontal displacements by 0.14% times the excavation depth as compared to analyses without the slab. With regard to the arching , analyzes showed an optimal range of spacing between the faces of the piles between 0.4 and 0.6 times the diameter of the pile

Origine dell'associazione peridotiti-migmatiti-gneiss nel basamento Varisico della Zona d'Ultimo, Austroalpino superiore

Per investigare il ruolo del contrasto di densità fra rocce crostali e mantelliche, nell’origine dell’associazione peridotiti-migmatiti-gneiss della Zona d’Ultimo (Austroalpino superiore, Italia), durante l’orogenesi Varisica, sono stati studiati tre diversi litotipi provenienti dall’area in esame. Mediante l’utilizzo del software Perple_X, sono state modellizzate le condizioni P-T di equilibrio di: un paragneiss a granato e staurolite di grado metamorfico medio, un fels a granato prodotto per fusione parziale ed estrazione del fuso dalla roccia sorgente (restite), e una peridotite ad anfibolo rappresentativa del cuneo di mantello. A partire dalle peridotiti, sono state calcolate condizioni metamorfiche di picco per la Zona d’Ultimo di 900 °C e 13 kbar, in facies granulitica, confrontabili con profondità di circa 40-50 km. In queste condizioni, le peridotiti ad anfibolo presentano una densità di 3230 kg/m3, nettamente inferiore rispetto a quanto calcolato per il campione di restite, cioè 3730 kg/m3. In particolare, è stato calcolato che è necessario estrarre dalla roccia sorgente una quantità di fuso pari al 10-12 wt.%, per generare un residuo refrattario di densità equivalente alle peridotiti idrate. La differenziazione fra neosoma e paleosoma, prodotta dalla fusione parziale, può generare quindi una situazione di instabilità fra crosta e mantello, a causa del contrasto di densità fra le rocce poste a contatto. Per effetto di questa instabilità, possono verificarsi meccanismi duttili di trasferimento di massa, con inclusione di lenti di peridotiti all’interno della crosta, all’interfaccia fra lo slab continentale in subduzione ed il cuneo di mantello, ma anche, in caso di crosta inspessita, in corrispondenza della transizione crosta profonda-mantello litosferico (Moho) nella upper plate.

Modelagem molecular voltada para a construção de um nanobiossensor para detecção do herbicida Imazaquin

In this study, our goal was develop and describe a molecular model of the enzyme-inhibiting interaction which can be used for an optimized projection of a Microscope Force Atomic nanobiosensor to detect pesticides molecules, used in agriculture, to evaluate its accordance with limit levels stipulated in valid legislation for its use. The studied herbicide (imazaquin) is a typical member of imidazolinone family and is an inhibitor of the enzymatic activity of Acetohydroxiacid Synthase (AHAS) enzyme that is responsible for the first step of pathway for the synthesis of side-chains in amino acids. The analysis of this enzyme property in the presence of its cofactors was made to obtain structural information and charge distribution of the molecular surface to evaluate its capacity of became immobilized on the Microscopy Atomic Force tip. The computational simulation of the system, using Molecular Dynamics, was possible with the force-field parameters for the cofactor and the herbicides obtained by the online tool SwissParam and it was implemented in force-field CHARMM27, used by software GROMACS; then appropriated simulations were made to validate the new parameters. The molecular orientation of the AHAS was defined based on electrostatic map and the availability of the herbicide in the active site. Steered Molecular Dynamics (SMD) Simulations, followed by quantum mechanics calculations for more representative frames, according to the sequential QM/MM methodology, in a specific direction of extraction of the herbicide from the active site. Therefore, external harmonic forces were applied with similar force constants of AFM cantilever for to simulate herbicide detection experiments by the proposed nanobiosensor. Force value of 1391 pN and binding energy of -14048.52 kJ mol-1 were calculated.

Chlorine concentrations and stable isotope ratios in Izu Bonin tephra

d37Cl values were determined for Izu Bonin arc magmas erupted 0-44 Ma in order to better understand the time-dependent processing of volatiles in subduction zones. Pristine ash-sized particles (glass, pumice, scoria, and rock fragments) were handpicked from tephra drilled at ODP Site 782. d37Cl values for these particles span a large range from -2.1 to +1.7 per mil (error = ± 0.3 per mil) vs. SMOC (Standard Mean Ocean Chloride, defined as 0 per mil). The temporal data extend the previously reported range of d37Cl values of -2.6 to 0.4 per mil (bulk ash) and -5.4 to -0.1 per mil (volcanic gases) from the Quaternary Izu Bonin-Mariana volcanic front to more positive values. Overall, the temporal data indicate a time-progressive evolution, from isotopically negative Eocene and Oligocene magmas (-0.7 ± 1.1 per mil, n = 10) to Neogene magmas that have higher ?37Cl values on average (+0.3 ± 1.1 per mil; n = 13). The increase is due to the emergence of positive d37Cl values in the Neogene, while minimum d37Cl values are similar through time. The range in d37Cl values cannot be attributed to fractionation during melt formation and differentiation, and must reflect the diversity of Cl present in the arc magma sources. Cl clearly derives from the slab (> 96% Cl in arc magmas), but d37Cl values do not correlate with isotope tracers (e.g. 207Pb/204Pb and 87Sr/86Sr) that are indicative of the flux from subducting sedimentary and igneous crust. Given the steady, high Cl flux since at least 42 Ma, the temporal variability of d37Cl values is best explained by a flux from subducting isotopically positive and negative serpentinite formed in the ocean basins that mingles with and possibly overprints the isotopically negative flux from sediment and igneous crust at arc front depths. The change in the d37Cl values before and after backarc spreading may reflect either a tectonically induced change in the mechanism of serpentinite formation on the oceanic plate, or possibly the integration of isotopically positive wedge serpentinite as arc fluid source during the Neogene. Our study suggests that serpentinites are important fluid sources at arc front depth, and implies the return of isotopically positive and negative Cl from the Earth surface to the mantle.

Noble gas concentrations of oceanic crust and sediments from the Ninety East Ridge in the Indian Ocean

We have determined the concentrations and isotopic composition of noble gases in old oceanic crust and oceanic sediments and the isotopic composition of noble gases in emanations from subduction volcanoes. Comparison with the noble gas signature of the upper mantle and a simple model allow us to conclude that at least 98% of the noble gases and water in the subducted slab returns back into the atmosphere through subduction volcanism before they can be admixed into the earth's mantle. It seems that the upper mantle is inaccessible to atmospheric noble gases due to an efficient subduction barrier for volatiles.

(Table 2) Chlorine geochemistry and mineralogy of altered oceanic crust samples

Bulk chlorine concentrations and chlorine stable isotope compositions were determined for hydrothermally altered basalt (extrusive lavas and sheeted dikes) and gabbro samples (n = 50) from seven DSDP/ODP/IODP drill sites. These altered oceanic crust (AOC) samples span a range of crustal ages, tectonic settings, alteration type, and crustal depth. Bulk chlorine concentrations range from < 0.01 wt.% to 0.09 wt.%. In general, higher chlorine concentrations coincide with an increase in temperature of alteration and amphibole content. d37Cl values of whole rock AOC samples range from -1.4 to +1.8 per mil. High d37Cl values (>=~0.5 per mil) are associated with areas of higher amphibole content. This observation is consistent with theoretical calculations that estimate amphibole should be enriched in 37Cl compared to co-existing fluid. Negative to near zero d37Cl values are found in areas dominated by clay minerals. Chlorine geochemistry is a rough indicator of metamorphic grade and mineralogy. AOC is a major Cl host in the subducting oceanic lithospheric slab. Here we show that bulk chlorine concentrations are ~3 times higher than previous estimates resulting in a greater contribution of Cl to the mantle.

Fiber-optic vibration sensing of cantilevers immersed in fluids

An all fiber-optical method to monitor densities and viscosities of liquids utilizing a steel cantilever (4 x 0.3 x 0.08 cm3) is presented. The actuation is performed by photothermally heating the cantilever at its base with an intensity-modulated 808 nm diode laser. The cantilever vibrations are picked up by an in-fiber Fabry Perot cavity sensor attached along the length of the cantilever. The fluid properties can be related to the resonance characteristics of the cantilever, e.g. a shift in the resonance frequency corresponds to a change in fluid density, and the width of the resonance peak gives information on the dynamic viscosity after calibration of the system. Aqueous glycerol, sucrose and ethanol samples in the range of 0.79–1.32 gcm−3 (density) and 0.89–702 mPas (viscosity) were used to investigate the limits of the sensor. A good agreement with literature values could be found with an average deviation of around 10 % for the dynamic viscosities, and 5–16 % for the mass densities. A variety of clear and opaque commercial spirits and an unknown viscous sample, e.g. home-made maple syrup, were analyzed and compared to literature values. The unique detection mechanism allows for the characterization of opaque samples and is superior to conventional microcantilever sensors. The method is expected to be beneficial in various industrial sectors such as quality control of food samples.

The role of material characterisation in the crush modelling of thermoplastic composite structures

The predictive capability of high fidelity finite element modelling, to accurately capture damage and crush behaviour of composite structures, relies on the acquisition of accurate material properties, some of which have necessitated the development of novel approaches. This paper details the measurement of interlaminar and intralaminar fracture toughness, the non-linear shear behaviour of carbon fibre (AS4)/thermoplastic Polyetherketoneketone (PEKK) composite laminates and the utilisation of these properties for the accurate computational modelling of crush. Double-cantilever-beam (DCB), four-point end-notched flexure (4ENF) and Mixed-mode bending (MMB) test configurations were used to determine the initiation and propagation fracture toughness in mode I, mode II and mixed-mode loading, respectively. Compact Tension (CT) and Compact Compression (CC) test samples were employed to determine the intralaminar longitudinal tensile and compressive fracture toughness. V-notched rail shear tests were used to measure the highly non-linear shear behaviour, associated with thermoplastic composites, and fracture toughness. Corresponding numerical models of these tests were developed for verification and yielded good correlation with the experimental response. This also confirmed the accuracy of the measured values which were then employed as input material parameters for modelling the crush behaviour of a corrugated test specimen.

Basalt Fibre Reinforced Polymer Strengthening of Normal Strength Reinforced Concrete Floor Slabs Subject to Arching Effects

With ever increasing demands to strengthen existing reinforced concrete structures to facilitate higher loading due to change of use and to extend service lifetime, the use of fibre reinforced polymers (FRPs) in structural retrofitting offers an opportunity to achieve these aims. To date, most research in this area has focussed on the use of glass fibre reinforced polymer (GFRP) and carbon fibre reinforced polymer (CFRP), with relatively little on the use of basalt fibre reinforced polymer (BFRP) as a suitable strengthening material. In addition, most previous research has been carried out using simply supported elements, which have not considered the beneficial influence of in-plane lateral restraint, as experienced within a framed building structure. Furthermore, by installing FRPs using the near surface mounted (NSM) technique, disturbance to the existing structure can be minimised.
This paper outlines BFRP NSM strengthening of one third scale laterally restrained floor slabs which reflect the inherent insitu compressive membrane action (CMA) in such slabs. The span-to-depth ratios of the test slabs were 20 and 15 and all were constructed with normal strength concrete (~40N/mm2) and 0.15% steel reinforcement. 0.10% BFRP was used in the retrofitted samples, which were compared with unretrofitted control samples. In addition, the bond strength of BFRP bars bonded into concrete was investigated over a range of bond lengths with two different adhesive thicknesses. This involved using an articulated beam arrangement in order to establish optimum bond characteristics for use in strengthening slab samples.