Academic literature on the topic 'SiOx Matrix'
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Journal articles on the topic "SiOx Matrix"
1
Sarikov, Andrey. "Thermodynamic Theory of Phase Separation in Nonstoichiometric Si Oxide Films Induced by High-Temperature Anneals." Nanomanufacturing 3, no. 3 (2023): 293–314. http://dx.doi.org/10.3390/nanomanufacturing3030019.
Full textAbstract:
High-temperature anneals of nonstoichiometric Si oxide (SiOx, x < 2) films induce phase separation in them, with the formation of composite structures containing amorphous or crystalline Si nanoinclusions embedded in the Si oxide matrix. In this paper, a thermodynamic theory of the phase separation process in SiOx films is proposed. The theory is based on the thermodynamic models addressing various aspects of this process which we previously developed. A review of these models is provided, including: (i) the derivation of the expressions for the Gibbs free energy of Si oxides and Si/Si oxide systems, (ii) the identification of the phase separation driving forces and counteracting mechanisms, and (iii) the crystallization behavior of amorphous Si nanoinclusions in the Si oxide matrix. A general description of the phase separation process is presented. A number of characteristic features of the nano-Si/Si oxide composites formed by SiOx decomposition, such as the local separation of Si nanoinclusions surrounded by the Si oxide matrix; the dependence of the amount of separated Si and the equilibrium matrix composition on the initial Si oxide stoichiometry and annealing temperature; and the correlation of the presence of amorphous and crystalline Si nanoinclusions with the presence of SiOx (x < 2) and SiO2 phase, respectively, in the Si oxide matrix, are explained.
2
Delimitis, A., S. D. Pappas, S. Grammatikopoulos, et al. "Microstructural Investigation of SiOx Thin Films Grown by Reactive Sputtering on (001) Si Substrates." Journal of Nano Research 17 (February 2012): 147–56. http://dx.doi.org/10.4028/www.scientific.net/jnanor.17.147.
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In the Current Study, the Structural Characteristics of Siox Thin Films Grown by Magnetron Sputtering on Si Substrates Are Reported. High Resolution Transmission Electron Microscopy Revealed the Formation of Amorphous Siox Films for the as-Deposited Samples, as Well as the Ones Annealed in Ambient Air for 30 Min at 950oC and of Si Nanocrystals, Embedded in Amorphous Siox, after Ar Annealing for 1-4 Hours at 1000oC. the Nanocrystals, with Sizes up to 6 Nm, Predominately Exhibit {111} Lattice Planes. Energy-Dispersive X-Ray Analysis Showed that the Si/O Ratio Is between 0.5-1, I.e. the Amorphous Films Comprise of a Mixture of Sio2 and Sio. Phase Images and Corresponding Strain Maps Created Using Fourier Filtering Revealed a Uniform Contrast in the Nanocrystals, which Shows that the Si Lattice Constant Does Not Vary Significantly. the Residual Strain Variations, around 4%, May Account for the Possible Existence of a Small Percentage of Highly Disordered Si or Siox Residual Clusters inside the Regular Si Matrix, in Full Agreement with Photoluminescence Measurements Performed on the same Materials.
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Kizjak, Anatoliy, Anatoliy Evtukh, Olga Steblova, and Yuriy Pedchenko. "Electron Transport through Thin SiO2 Films Containing Si Nanoclusters." Journal of Nano Research 39 (February 2016): 169–77. http://dx.doi.org/10.4028/www.scientific.net/jnanor.39.169.
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The electron transport mechanisms through nanocomposite SiO2(Si) films containing Si nanoclusters into dielectric SiO2 matrix have been investigated. SiO2(Si) films were obtained by oxide assisted growth. At the first stage the SiOx films with different content of excess Si were deposited by LP CVD method. Second stage includes high temperature (T=1100 C) annealing of SiOx films that promotes formation of Si nanocrystals. Current transport through SiO2(Si) films were studied in temperature range 100-350 K. As it was observed the dominant mechanism of electron transport depends as on voltage and temperature. The Mott’s conductivity caused by traps near Fermi level was revealed in low-voltage range for all temperatures. At increasing the voltage the SCLC conductivity is observed for films with higher content of excess silicon while in case low content of Si the Pool-Frenkel mechanism dominates. The further increase in voltage results in a double carrier injection.
4
Nikolenko, A. S. "Laser heating effect on Raman spectra of Si nanocrystals embedded into SiOx matrix." Semiconductor Physics Quantum Electronics and Optoelectronics 16, no. 1 (2013): 86–90. http://dx.doi.org/10.15407/spqeo16.01.086.
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Milutinović, A., Z. Dohčević-Mitrović, Diana Nesheva, M. Šćepanović, M. Grujić-Brojčin, and Zoran V. Popović. "Infrared and Photoluminescence Study of Rapidly Thermally Annealed SiOx Thin Films." Materials Science Forum 555 (September 2007): 309–14. http://dx.doi.org/10.4028/www.scientific.net/msf.555.309.
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Silicon suboxide, SiOx thin films with different oxygen contents (1.15≤x≤1.70) were prepared by thermal evaporation of silicon monoxide at a residual oxygen pressure of 1·10-3 Pa and deposition rates of 0.2, 1.0, 3.0 and 6.0 nm/s. Rapid thermal annealing (RTA) of films was carried out at 1100°C in vacuum for 15 and 30 s and the films were analyzed by infrared (FTIR) and photoluminescence (PL) spectroscopy. In the FTIR spectra of SiOx annealed samples, a blue-shift of the stretching band with initial oxygen content, x, is observed. This band is shifted to a much lower frequency with prolonged RTA time. This behavior can be interpreted in terms of the partial decrease of oxygen content and film density upon annealing in vacuum. With annealing time increase a new band at 1106 cm-1 appears. Therefore, infrared spectra of SiOx films are significantly affected by the oxygen content. PL spectra of these films also change drastically with increasing annealing time. In the PL spectra of films annealed for 15 s two bands are easily visible: broad redorange band at 2.2 eV and a green band at 2.4 eV, while for 30 s annealing only low-energy band exists. Green band is connected with the defects in the SiOx matrix while red-orange band can be deconvoluted into several bands at 2.0, 2.3 and 2.5 eV. Two types of defects can be responsible for the PL band at about 2 eV: defects in a-Si (amorphous silicon) nanoparticles separated during RTA, and nonbridging oxygen hole recombination centers (NBOHC) formed by loosing of oxygen during RTA. The PL band at 2.3 eV is associated with the defects formed at a-Si/SiOx interfaces while a hardly visible band at 2.5 eV is related to the defects connected with the oxygen deficiency formed in the SiOx matrix during RTA.
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Curiel, Mario, Ivan Petrov, Nicola Nedev, et al. "Formation of Si Nanocrystals in Thin SiO2 Films for Memory Device Applications." Materials Science Forum 644 (March 2010): 101–4. http://dx.doi.org/10.4028/www.scientific.net/msf.644.101.
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X-ray Diffraction and Reflectivity, Transmission Electron Microscopy and Atomic Force Microscopy were applied to study the effect of thermal annealing on the properties of thin SiOx films (~ 15 nm) prepared by thermal evaporation of SiO in vacuum. It has been shown that furnace annealing at 1000 oC causes phase separation and formation of uniformly distributed Si nanocrystals into a SiO2 matrix. Clockwise hysteresis has been observed in the C-V curves measured and explained by assuming charging and discharging of the NCs with carriers, which tunnel from the Si substrate.
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Prikryl, Radek, Pavel Otrisal, Vladimir Obsel, Lubomír Svorc, Radovan Karkalic, and Jan Buk. "Protective Properties of a Microstructure Composed of Barrier Nanostructured Organics and SiOx Layers Deposited on a Polymer Matrix." Nanomaterials 8, no. 9 (2018): 679. http://dx.doi.org/10.3390/nano8090679.
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The SiOx barrier nanocoatings have been prepared on selected polymer matrices to increase their resistance against permeation of toxic substances. The aim has been to find out whether the method of vacuum plasma deposition of SiOx barrier nanocoatings on a polyethylene terephthalate (PET) foil used by Aluminium Company of Canada (ALCAN) company (ALCAN Packaging Kreuzlingen AG (SA/Ltd., Kreuzlingen, Switzerland) within the production of CERAMIS® packaging materials with barrier properties can also be used to increase the resistance of foils from other polymers against the permeation of organic solvents and other toxic liquids. The scanning electron microscopy (SEM) microstructure of SiOx nanocoatings prepared by thermal deposition from SiO in vacuum by the Plasma Assisted Physical Vapour Deposition (PA-PVD) method or vacuum deposition of hexamethyldisiloxane (HMDSO) by the Plasma-enhanced chemical vapour deposition (PECVD) method have been studied. The microstructure and behavior of samples when exposed to a liquid test substance in relation to the barrier properties is described.
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Luna-López, José Alberto, G. Garcia-Salgado, J. Carrillo-López, et al. "Si Nanocrystals Deposited by HFCVD." Solid State Phenomena 194 (November 2012): 204–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.194.204.
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The structural and optical properties of Si nanocrystal (Si-nc) embedded in a matrix of off-stoichiometric silicon oxide (SiOx, x<2) films prepared by hot filament chemical vapor deposition technique were studied. The films emit a wide photoluminescent spectra and the maximum peak emission shows a blue-shift as the substrate temperature (Ts) decreases. Also, a wavelength-shift of the absorption edge in transmittance spectra is observed, indicating an increase in the energy band gap. The Si-nc’s size decreased from 6.5 to 2.5 nm as Ts was reduced from 1150 to 900 °C, as measured through High Resolution Transmission Electron Microscopy analysis. A combination of mechanisms is proposed to explain the photoluminescence in the SiOx films, which involve SiOx defects and quantum confinement effects.
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Han, Li Hao, Jing Wang, and Ren Rong Liang. "Germanium-Silicon Quantum Dots Produced by Pulsed Laser Deposition for Photovoltaic Applications." Advanced Materials Research 383-390 (November 2011): 6270–76. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.6270.
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Quantum dots applied in solar cells will be of great importance to enhance the quantum tunneling efficiency and improve the photogenerated current transport. In this study, a new easy-to-operate technology was developed to fabricate germanium-silicon quantum dots in a SiOx matrix. The quantum dots were formed by first deposited germanium-rich SiO on quartz substrate using pulsed laser deposition technique and then annealed under a comparatively high temperature. We have demonstrated a stable and low-cost fabrication process which is much cheaper than the epitaxy method to provide for the fabrication of high density germanium-silicon quantum dots. Quantum dots with diameters of 3~4 nm embedded in the amorphous SiOx layer were clearly observed. The morphological features of the thin film were characterized. The optical properties were performed by Raman spectroscopy, photoluminescence spectrum and XRD test respectively to verify the crystallization of quantum dots in the SiOx matrix. Reflectance spectrum displayed a high light absorption rate in a spectra region from 300 nm to 1200 nm, evidencing that germanium-silicon quantum dots have promising features to be used as absorber for photovoltaic application.
10
Feng, Xuejiao, Hongmin Cui, Zhenming Li, Rongrong Miao, and Nanfu Yan. "Scalable Synthesis of Dual-Carbon Enhanced Silicon-Suboxide/Silicon Composite as Anode for Lithium Ion Batteries." Nano 12, no. 07 (2017): 1750084. http://dx.doi.org/10.1142/s1793292017500849.
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The SiOx/Si composite enhanced by dual-carbon (i.e., multiwall carbon nanotubes and carbon) was fabricated from the micro silicon monoxide (SiO) by the combination of high-energy mechanical milling, spray drying and pyrolysis. The obtained SiOx/Si particles were composed of Si-suboxide and embedded nano-sized Si crystallites. As one of dual-carbons, the multi-walled carbon nanotubes were directly scaffolded of anchoring the SiOx/Si composite particles through spray drying. Another carbon source was directly deposited on the surface of the SiOx/Si by means of the carbonization of phenol–formaldehyde resin. Nano-sized silicon embedded in the Si-suboxide matrix and dual-carbon provided a compromise between the reversible capacity and cycle stability related to the volume change. The obtained SiOx/Si/MWCNT/PC-1 electrode delivered an initial capacity of 936.5[Formula: see text]mAh g[Formula: see text] and the reversible capacity was maintained at 825.9[Formula: see text]mAh g[Formula: see text] with excellent capacity retention of 87.5% on the 200th cycle versus the 6th one (compared with the same current rate). In contrast, although the SiOx/Si presented the higher initial capacity of 1271.4[Formula: see text]mAh g[Formula: see text], its capacity dropped quickly after several cycles and capacity retention was only 25.6% versus the 6th cycle after 100 cycles.
Dissertations / Theses on the topic "SiOx Matrix"
1
Seyhan, Ayse. "Photoluminescence Properties Of Si Nanocrystals Embedded In Sio2 Matrix." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611750/index.pdf.
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This thesis examines the luminescence properties of nanoscale silicon (Si) by
using spectroscopic techniques. Since the development of new optical devices
requires understanding light emission mechanism optical spectroscopy has
become more important tool in the analysis of these structures. In this thesis, Si
nanocrystals embedded in SiO2 matrix will be studied.
Photoluminescence (PL) and Time-resolved photoluminescence spectroscopy
(TRPL) have been used to detect the light emission in UV-Vis-NIR range.
Experiments have been performed in the temperature range 10-300 K. PL is
sensitive to impurities and defects that affect materials quality and device
performance. In this context, the role of defects in limiting the luminescence of Si
nanocrystals and the removal of these defects by hydrogen passivation has been
investigated.
v
TRPL was employed to determine the time evolution of photoluminescence as
function of temperature. The decay time of the PL spectra was determined by a
stretched exponential function and perfectly fitted to an expression based on three
excitonic levels. Carrier lifetimes associated with these three levels were
determined and compared with literature.
Additionally, temporal variation of PL from free-standing Si nanoparticles is
studied under a strong laser illumination. The observed bleaching behavior (time
dependent emission intensity), which is reversible, have discussed in terms of
exciton trapping at the interface between nanocrystal and the surrounding oxide
layer.
The results of this thesis will provide new insight on the understanding of light
emission mechanism of Si nanocrytals.
2
Dolores, Gonzalo Mármol de los. "Low-alkalinity matrix composites based on magnesium oxide cement reinforced with cellulose fibres." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/74/74133/tde-17082017-113846/.
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A lower-alkalinity cement based on MgO and SiO2 blends is analysed to develop clinker-free Fibre Reinforced Cementitious Composites (FRCC) with cellulosic fibres in order to solve the durability problems of this type of fibres when used in FRCC with Portland cement. Hydration evolution from 7 to 28 days of different MgO-SiO2 formulations is assessed. The main hydration products are Mg(OH)2 and M-S-H gels for all the formulations studied regardless of age. Hardened pastes are obtained with pH values < 11 and good mechanical properties compared to conventional Portland cement. 60% MgO-40% SiO2 system is chosen as optimal for the development FRCC since is the most mechanical resistant and is less alkaline compared with 70% MgO-30% SiO2. FRCC based on magnesium oxide and silica (MgO-SiO2) cement with cellulose fibres are produced to study the durability of lignocellulosic fibres in a lower pH environment than the ordinary Portland cement (PC). Flexural performance and physical tests (apparent porosity, bulk density and water absorption) of samples at 28 days and after 200 accelerated ageing cycles (aac) are compared. Two types of vegetable fibres are utilised: eucalyptus and pine pulps. MgO-SiO2 cement preserves cellulosic fibres integrity after ageing, so composites made out of MgO-SiO2 exhibit significant higher performance after 200 cycles of accelerated ageing than Portland cement composites. High CO2 concentration environment is evaluated as a curing treatment in order to optimise MgO- SiO2 matrices in FRCC. Samples are cured under two different conditions: 1) steam water curing at 55°C and 2) a complementary high CO2 concentration (20% by volume). In carbonated samples, Mg(OH)2 content is clearly lowered while new crystals of hydromagnesite [Mg5 (CO3)4⋅(OH) 2⋅4H2O] are produced. After carbonation, M-S-H gel content is also reduced, suggesting that this phase is also carbonated. Carbonation affects positively to the composite mechanical strength and physical properties with no deleterious effects after ageing since it increases matrix rigidity. The addition of sepiolite in FRCC is studied as a possible additive constituent of the binding matrix. Small cement replacement (1 and 2% wt.) by sepiolite is introduced and studied in hardened cement pastes and, later, in FRCC systems. When used only in cement pastes, it improves Dynamic Modulus of Elasticity over time. Bending tests prove the outcome of this additive on the mechanical performance of the composite: it improves composite homogeneity. Ageing effects are reported after embedding sisal fibres in MgO-SiO2 and PC systems and submitting them to different ageing conditions. This comparative study of fibre degradation applied in different cementitious matrices reveals the real compatibility of lignocellulosic fibres and Mg-based cements. Sisal fibres, even after accelerated ageing, do neither suffer a significant reduction in cellulose content nor in cellulose crystallinity and crystallite size, when exposed to MgO-SiO2 cement. Fibre integrity is preserved and no deposition of cement phases is produced in MgO-SiO2 environment.<br>Um cimento de baixa alcalinidade à base de blendas de MgO e SiO2 é analisado para o desenvolvimento de Compósitos Cimentícios Reforçados com Fibras (CCRF) celulósicas sem clínquer para resolver os problemas de durabilidade de este tipo de fibras quando são usadas em CCRF com cimento Portland. A evolução da hidratação, desde 7 aos 28 dias, das diferentes formulações é avaliada. Os principais produtos hidratados são o Mg(OH)2 e o gel M-S-H para todas as formulações independentemente da idade estudada. As pastas endurecidas apresentam valores de pH < 11 e bom desempenho mecânico comparado com o cimento Portland convencional. O sistema 60% MgO-40% SiO2 é escolhido como a formulação ótima para o desenvolvimento de CCRF já que é a mais resistente e menos alcalina comparada com 70% MgO-30% SiO2. CCRF com cimento à base de óxido de magnésio e sílica (MgO-SiO2) e fibras celulósicas são produzidos para a análise da durabilidade das fibras lignocelulósicas em ambientes com valores de pH mais baixos comparados com o cimento Portland (PC). O desempenho mecânico a flexão e os ensaios físicos (porosidade aparente, densidade aparente e absorção de água) são comparados aos 28 dias e após de 200 ciclos de envelhecimento acelerado. O cimento à base de MgO-SiO2 preserva a integridade das fibras após o envelhecimento. Os compósitos produzidos com este cimento exibem melhores propriedades após 200 ciclos de envelhecimento acelerado que os compósitos produzidos com cimento Portland. Ambientes com alta concentração de CO2 são avaliados como tratamento de cura para otimizar as matrizes MgO- SiO2 nos CCRF. As amostras são curadas sob 2 condições diferençadas: 1) cura com vapor de água a 55oC e 2) cura com alta concentração de CO2 (20% do volume). As amostras carbonatadas apresentam teores reduzidos de Mg(OH)2 enquanto é produzida uma nova fase cristalina: hidromagnesita [Mg5 (CO3)4⋅(OH) 2⋅4H2O]. Após a carbonatação, o conteúdo de gel M-S-H é reduzido também, indicando uma carbonatação desta fase. A carbonatação aumenta a rigidez da matriz o que influi positivamente no desempenho mecânico e as propriedades físicas dos compósitos sem efeitos prejudiciais ao longo prazo. A adição de sepiolita em CCRF é estudada como possível adição na composição da matriz aglomerante. Baixos teores (1 e 2% em massa) de cimento são substituídos por sepiolita para o estudo das pastas de cimento hidratado e, posteriormente, dos compósitos. O Módulo Elástico Dinâmico das pastas é incrementado com o tempo pela adição de sepiolita. Os ensaios a flexão demostram que a adição de sepiolita melhora a homogeneidade dos compósitos. Reportam-se os efeitos das fibras de sisal após da exposição a sistemas MgO-SiO2 e PC e submetidas a diferentes condições de envelhecimento. Este estudo comparativo da degradação das fibras expostas a diferentes matrizes cimentícias mostra a compatibilidade das fibras lignocelulósicas com os cimentos à base de Mg. As fibras de sisal, inclusive após o envelhecimento acelerado, não apresentam nem redução significativa no conteúdo de celulose nem na cristalinidade da celulose assim como do tamanho de cristalito, quando expostas a cimentos MgO-SiO2.
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Esteves, Ana Catarina de Carvalho. "Nanocompósitos de matriz polimérica do tipo SIO2/ polímero e Cds/ Polímero." Master's thesis, Universidade de Aveiro, 2002. http://hdl.handle.net/10773/21907.
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Mestrado em Ciência e Engenharia de Materiais<br>O principal objectivo desta dissertação foi estudar novas perspectivas na
preparação de nanocompósitos de matriz polimérica, através da síntese e
caracterização de nanomateriais do tipo SiO2/ polímero e CdS/ polímero.
O primeiro capítulo consiste numa revisão bibliográfica, com destaque para os
principais tópicos discutidos ao longo da tese. São efectuadas algumas
considerações sobre a utilização de nanopartículas inorgânicas como cargas,
e sobre os aspectos mais relevantes da aplicação de polímeros como
matrizes. São ainda descritas, algumas estratégias utilizadas para
compatibilizar estes componentes. A revisão é concluída com uma breve
descrição das metodologias aplicadas na preparação de nanocompósitos de
matriz polimérica.
No segundo capítulo apresenta-se a síntese e caracterização das cargas
inorgânicas. Seguindo métodos descritos na literatura, foram preparadas
nanopartículas de SiO2, esféricas e sob a forma de fibras ocas, nanocristais de
CdS e compósitos inorgânicos do tipo SiO2@CdS. Estes últimos, foram
sujeitos a um tratamento superficial orgânico com TOPO e ainda com SiO2.
Para os materiais tratados com TOPO verificou-se uma melhoria das suas
propriedades ópticas, nomeadamente ao nível da fotoluminescência à
temperatura ambiente.
No terceiro e quarto capítulos, são apresentados os nanocompósitos do tipo
SiO2/ polímero, que foram sintetizados por polimerização in situ de matrizes
semicristalinas (poliamidas e poliuretanos), e amorfas (poli(estireno)). A sua
caracterização foi efectuada por espectroscopia de IV, SEM, TEM, TGA e
DSC.
Os nanocompósitos de matriz semicristalina foram preparados por
polimerização por etapas. No caso das poliamidas, foi investigada a influência
das cargas de SiO2 com diferentes morfologias e tratamentos de superfície, no
processos de fusão e cristalização da matriz. Os materiais de matriz amorfa
foram preparados por polimerização radicalar em emulsão e dispersão. Neste
caso o estudo incidiu sobre a morfologia das partículas dos nanocompósitos,
nas possíveis condições experimentais que a determinam e na influência
destas sobre as propriedades térmicas do nanocompósito.
Por fim descreve-se no quinto capítulo a síntese e caracterização dos
nanocompósitos do tipo CdS/ polímero. Estes materiais foram preparados por
polimerização radicalar em solução, na presença de nanocristais de CdS, e
compósitos inorgânicos do tipo SiO2@CdS. A inserção das cargas na matriz
promoveu as suas propriedades de fotoluminescência à temperatura ambiente.
Foram ainda avaliadas as propriedades térmicas de algumas amostras
representativas.
Neste trabalho foram preparados uma série de novos nanocompósitos de
matriz polimérica, que fazem antever futuras aplicações tecnológicas. Foram
ainda estabelecidos novos caminhos para a compreensão dos mecanismos de
formação de materiais híbridos, e das interacções que ocorrem ao nível das
interfaces de natureza orgânica/ inorgânica.<br>The aim of this thesis was to study new methods for the preparation of polymer
based nanocomposites, through the synthesis and characterisation of
SiO2/polymer and CdS/ polymer nanomaterials.
The first chapter consists in an introduction to the aim topics that are discussed
in the thesis as well as a literature review. Some considerations are made
regarding the use of inorganic nanoparticles as fillers, and to the methods used
to modify the inorganic materials surface in order to make them more
compatible with the organic nature of polymeric matrices. In this introduction
some relevant aspects of the use of polymers as matrices are reported, and a
brief review of the polymerisation methods to be used in the nanocomposites
preparation is given.
The second chapter is devoted to the preparation and characterisation of the
fillers. Following methods previously described on the literature, SiO2
nanoparticles with spherical and hollow fibres morphologies, CdS
nanocristalites and SiO2@CdS inorganic composites were prepared. The last
were organically treated with TOPO and also with SiO2. It was concluded that
the TOPO capping results in improved room temperature photoluminescence
properties.
In the third and fourth chapters, the synthesis and characterisation of SiO2/
polymer nanocomposites is discussed. Using several in situ polymerisation
techniques semi-crystalline (polyurethanes and polyamides) and amorphous
(poly(styrene)) matrices were prepared. The materials were characterised by
FTIR spectroscopy, TEM and SEM, TGA and DSC analysis. The semicrystalline
polymeric matrix nanocomposites were prepared by steppolymerisation.
In the case of the polyamide based nanocomposites the
influence of the SIO2 nanoparticles on the melting and crystallization behaviour
of the matrices is discussed. As regards the amorphous matrix nanocomposites
these were prepared by radical emulsion and dispersion polymerisation. The
morphology of the nanocomposite particles is discussed in light of changes in
experimental conditions, and its possible influence on thermal properties.
Finally, the chapter five is concerned with CdS/ polymer nanocomposites
prepared by in situ polymerisation in the presence of CdS nanocrystals, and
SiO2@CdS inorganic composites. TOPO capping results in higher affinity of the
fillers to the matrix, and its insertion on the matrices promotes their optical
properties, namely room temperature photoluminescence. The thermal
properties of some representative samples were also studied.
In this work a wide range of novel polymer based nanocomposites were
prepared. This study showed that nanomaterials have unique properties that
can anticipate potential technologic applications. Furthermore, new routes have
been opened to the understanding of the mechanisms of nanocomposites
formation, as well as the nature of interactions between organic/ inorganic
interfaces.
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Costa, Maria Helena Carvalho da. "Coercividade de nanopartículas de CoFe2O4 dispersas em uma matriz de SiO2." Universidade Federal de Sergipe, 2015. https://ri.ufs.br/handle/riufs/5312.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>In this work, we study the magnetic properties of CoFe2O4 nanoparticles dispersed in silica (SiO2) matrix. Samples were produced by the sol-gel method and synthesized at different temperatures. The average distance between the particles and thus the nature of inter-particle interactions were controlled for using different concentrations of iron and cobalt salts and the starting material tetraethylorthosilicate (TEOS). The samples were characterized by thermogravimetry (TG), X-ray fluorescence (XRF), X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetization as a function of magnetic field and temperature. Thermogravimetric analysis showed that the weight loss increases with increasing concentration of salts in the starting solution. The results of X-ray diffraction combined with the transmission electron microscope images confirmed the presence of CoFe2O4 nanoparticles dispersed into the SiO2 matrix. Magnetization measurements showed a typical behavior generally showed by a magnetic nanoparticles system, that is, the observation of a peak in the curve FC-ZFC with a thermal hysteresis in the low temperature region. In particular, we observed a dependence of the coercive field with temperature of CoFe2O4 nanoparticles that did not follow the predictions of the model Bean-Livingston. We believe that this fact is linked more to the effect of size distribution than the possible effects of interaction between the nanoparticles. In this regard, a model considering a particle size distribution in the coercivity of nanoparticles was used. The model was able to fit the experimental data to wide temperature range.<br>Neste trabalho, nós estudamos as propriedades magnéticas de nanopartículas de CoFe2O4 dispersas em uma matriz de sílica (SiO2). As amostras foram produzidas através do método sol-gel para diferentes temperaturas de síntese. A distância média entre as partículas e, deste modo, a natureza das interações inter-partículas foram controladas utilizando diferentes concentrações dos sais de ferro e cobalto e do reagente de partida tetraetilortossilicato (TEOS). As amostras foram caracterizadas através de medidas de termogravimetria (TG), fluorescência de raios X (FRX), difração de raios X (DRX), microscopia eletrônica de transmissão (MET) e magnetização em função do campo magnético e da temperatura. As análises termogravimétricas mostraram que a perda de massa aumenta com o aumento da concentração dos sais de partida na solução. Os resultados de difração de raios X combinados com as imagens de microscopia eletrônica de transmissão confirmaram a presença das nanopartículas de CoFe2O4 dispersas dentro da matriz de SiO2. As medidas de magnetização mostraram um comportamento típico de um sistema de nanopartículas magnéticas, ou seja, o aparecimento de um pico na curva de ZFC-FC com uma histerese térmica na região de baixas temperaturas. Em particular, nós observamos uma dependência do campo coercivo com a temperatura das nanopartículas de CoFe2O4 que não seguiu as previsões do modelo de Bean Livingston. Nós acreditamos que esse fato está ligado muito mais ao efeito da distribuição de tamanhos do que aos possíveis efeitos de interação entre as nanopartículas. Neste sentido, um modelo que considera a distribuição de tamanhos de partículas na coercividade das nanopartículas foi utilizado. O modelo foi capaz de ajustar os dados experimentais para amplo intervalo de temperatura.
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Canevari, Thiago da Cruz 1980. "Construção de sensores eletroquímicos utilizando como matriz materiais cerâmicos SI 'O IND. 2'/ 'M IND. X' 'O IND. Y', e materiais cerâmicos eletricamento condutores SI 'O IND. 2'/ C/'M IND. X' 'O IND. Y', preparados pelo processo sol-gel." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249700.
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Orientador: Yoshitaka Gushikem<br>Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química<br>Made available in DSpace on 2018-08-20T16:56:50Z (GMT). No. of bitstreams: 1
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Previous issue date: 2012<br>Resumo: Este trabalho tem como objetivo sintetizar e caracterizar três materiais diferentes obtidos pelo processo sol-gel: SiO2/SnO2, SiO2/SnO2/Sb2O5 e o filme de Nb2O5 formado sobre a superfície do material cerâmico SiO2/C e utilizá-los como matriz no desenvolvimento de sensores eletroquímicos. O óxido misto, SiO2/SnO2, foi sintetizado utilizando como fonte de SnO2, SnCl4.5H2O, utilizando diferentes catalisadores ácidos HCl e HF (F-). As diferenças estruturais e morfológicas apresentadas pelos óxidos mistos, SiO2/SnO2, em virtude do uso de diferentes catalisadores ácidos, foram investigadas por meio das isotermas de adsorção/dessorção de N2, espectroscopia de fluorescência de raios X, difração de raios X, espectroscopia na região do infravermelho, microscopia eletrônica de transmissão, espectroscopia fotoeletrônica de raios X (XPS), medidas de condutividade elétrica e medidas eletroquímicas visando a utilização destes óxidos mistos como matriz suporte para desenvolvimento de sensores eletroquímicos. O material, SiO2/SnO2/Sb2O5, foi obtido por meio da incorporação do Sb2O5 sobre a superfície do óxido misto, SiO2/SnO2, previamente sintetizado utilizando como fonte de SnO2, o dibutildiacetato de estanho. Este recobrimento foi realizado utilizando, CH2Cl2 seco, em atmosfera inerte, pela técnica de "Enxerto¿. O material, SiO2/SnO2/Sb2O5, foi caracterizado por meio da isoterma de adsorção/dessorção de N2, espectroscopia de fluorescência de raios X, microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e espectroscopia fotoeletrônica de raios X (XPS). Sobre este material foi imobilizado o corante catiônico, azul de meldola, no qual foi preparado um eletrodo de disco rígido com objetivo de estudar a eletrooxidação do cofator NADH utilizando as técnicas de voltametria cíclica e cronoamperometria visando o desenvolvimento de um biossensor eletroquímico. A formação do filme de Nb2O5 sobre a superfície do material carbono cerâmico SiO2/C, utilizando a técnica de spin-coating, foi realizado após o material SiO2/C ser sintetizado utilizando o processo sol-gel. O filme de Nb2O5 preparado foi caracterizado utilizando a técnica de microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e espectroscopia fotoeletrônica de raios X (XPS). Com este material foi preparado um eletrodo de disco rígido com objetivo de estudar a eletrooxidação dos isômeros fenólicos, hidroquinona e catecol na presença de resorcinol utilizando a técnica de voltametria de pulso diferencial<br>Abstract: This work describes the synthesis and characterization of three different materials: SiO2/SnO2, SiO2/SnO2/Sb2O5 and the film of Nb2O5 formed on the surface of the ceramic material SiO2/C obtained by sol-gel process and to use them as matrix in the development of electrochemical sensors. The mixed oxides, SiO2/SnO2, were synthesized using as source of SnO2, SnCl4.5H2O, using different acid catalysts HCl and HF (F). The structural and morphological differences provided by mixed oxides, SiO2/SnO2, due to the use of different catalysts were evaluated by using several like area superficial BET technique, ray X fluorescence spectroscopic, ray X diffraction, IV spectroscopic, transmission electron microscopic (TEM), ray X spectroscopic photoelectron excited (XPS) and electrical conductivity and electrochemical measurements in order to use these mixed oxides as matrix support for development of electrochemical sensors. The material SiO2/SnO2/Sb2O5 was obtained by incorporation of Sb2O5 on the surface of the mixed oxide SiO2/SnO2, previously synthesized using as source of SnO2, dibutildiacetate of tin. This coating was performed using, CH2Cl2 dry, in inert atmosphere, using the technique of "Grafting." The SiO2/SnO2/Sb2O5 material was characterized using area superficial BET technique, ray X fluorescence spectroscopic, scanning electron microscopic (SEM), energy dispersive spectroscopic (EDS) and ray X spectroscopic photoelectron excited (XPS). On this material was immobilized on the cationic dye Meldola Blue, which was prepared in a rigid disk electrode to study the electrooxidation of the cofactor NADH using cyclic voltammetry and chronoamperometry technique for the development of an electrochemical biosensor. The formation of Nb2O5 film on the surface carbon ceramic material SiO2/C, using the technique of spin-coating was carried out after material for SiO2/C is synthesized using the sol-gel process. Nb2O5 film prepared was characterized using scanning electron microscopic (SEM), energy dispersive spectroscopic (EDS) and ray X spectroscopic photoelectron excited (XPS). With this material was prepared a disc rigid electrode in order to study the electrooxidation of phenolic isomers, hydroquinone and catechol in the presence of resorcinol using differential pulse voltammetry technique<br>Doutorado<br>Quimica Inorganica<br>Doutor em Ciências
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Karakuscu, Aylin. "Synthesis and Characterization of Luminescent Nanostructured SiOC Thin Films." Doctoral thesis, Università degli studi di Trento, 2010. https://hdl.handle.net/11572/368279.
Full textAbstract:
A new approach to obtain visible luminescence from sol-gel derived SiOC films is proposed. This novel method is based on a simple processing route to produce nanostructured multicomponent ceramics. According to this route, hybrid sol-gel derived precursors are converted to ceramic materials by a pyrolysis process in controlled atmosphere at 800-1000°C. Higher temperatures lead to formation of Si-rich SiOC, C-rich SiOC or stoichiometric SiOC according to the starting composition. The final composition, which is relevant to line emission, can be easily controlled through a number of processing parameters like the composition of the preceramic gel and the heat treatment conditions. Thus, this new processing method seems very well suited for the production of white emitting materials since the Si- and C-based emission can be tuned across the visible spectral range from UV-blue to red by controlling film composition. A further advantage of this method is that the thin films can be formed on Si or quartz wafers and this can serve as starting material to process more complex photonic devices such as waveguides or LEDs.
In the amorphous state (800-100°C), all SiOC films showed UV-blue luminescence peaking at about 410 nm, which is attributed to defect states present in the matrix such as dangling bonds. The increase of the pyrolysis temperature (≥1100°C) led to the partition of SiOC and formation of SiC, C and Si phases. The intense green-yellow luminescence observed in stoichiometric SiOC films caused by the presence of SiC and very low amount of free C. On the other hand, Si rich SiOC film showed a very broad and extremely intense white luminescence peak centred at 620 nm covering almost all visible range (430 nm-900 nm) at 1200 °C. This behaviour is explained by the simultaneous presence of SiC, C and Si in the film. External quantum efficiency measurements yielded 11.5% and 5% efficiencies in Si rich SiOC and stoichiometric SiOC films, respectively, pyrolysed at 1200°C. On the other hand, C rich SiOC films did not show any noticeable improvement in PL, indicating that C excess in the SiOC system is detrimental for the luminescence behaviour.
Solutions which used in thin film production have been characterized extensively by means of several characterization properties. Moreover, the related powders and bulks have been characterized for the sake of coherency and widen the study. In addition, a study on volumetric shrinkage of films and powders has been done. The results showed that the shrinkage in films happens almost 200°C earlier than powder and higher amount of siloxane release due to the low dimension, the shrinkage is higher than powders.
The last part of the study dedicated to two different systems, SiBOCs and SiOCNs, in order to understand the effect of the boron addition on SiOC system and study the optical properties of the SiOCN. Tunable (color emission change) SiOC films is obtained with high quantum efficiency by adding very few amount of boron in SiOC. Moreover, the processing temperature is decreased and very broad emission is obtained. Finally, results showed that SiOCN PDC gives very high emission in UV range and they are promising materials for UV-LEDs.
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Karakuscu, Aylin. "Synthesis and Characterization of Luminescent Nanostructured SiOC Thin Films." Doctoral thesis, University of Trento, 2010. http://eprints-phd.biblio.unitn.it/317/1/PhD_Dissertation_Aylin_Karakuscu.pdf.
Full textAbstract:
A new approach to obtain visible luminescence from sol-gel derived SiOC films is proposed. This novel method is based on a simple processing route to produce nanostructured multicomponent ceramics. According to this route, hybrid sol-gel derived precursors are converted to ceramic materials by a pyrolysis process in controlled atmosphere at 800-1000°C. Higher temperatures lead to formation of Si-rich SiOC, C-rich SiOC or stoichiometric SiOC according to the starting composition. The final composition, which is relevant to line emission, can be easily controlled through a number of processing parameters like the composition of the preceramic gel and the heat treatment conditions. Thus, this new processing method seems very well suited for the production of white emitting materials since the Si- and C-based emission can be tuned across the visible spectral range from UV-blue to red by controlling film composition. A further advantage of this method is that the thin films can be formed on Si or quartz wafers and this can serve as starting material to process more complex photonic devices such as waveguides or LEDs.
In the amorphous state (800-100°C), all SiOC films showed UV-blue luminescence peaking at about 410 nm, which is attributed to defect states present in the matrix such as dangling bonds. The increase of the pyrolysis temperature (≥1100°C) led to the partition of SiOC and formation of SiC, C and Si phases. The intense green-yellow luminescence observed in stoichiometric SiOC films caused by the presence of SiC and very low amount of free C. On the other hand, Si rich SiOC film showed a very broad and extremely intense white luminescence peak centred at 620 nm covering almost all visible range (430 nm-900 nm) at 1200 °C. This behaviour is explained by the simultaneous presence of SiC, C and Si in the film. External quantum efficiency measurements yielded 11.5% and 5% efficiencies in Si rich SiOC and stoichiometric SiOC films, respectively, pyrolysed at 1200°C. On the other hand, C rich SiOC films did not show any noticeable improvement in PL, indicating that C excess in the SiOC system is detrimental for the luminescence behaviour.
Solutions which used in thin film production have been characterized extensively by means of several characterization properties. Moreover, the related powders and bulks have been characterized for the sake of coherency and widen the study. In addition, a study on volumetric shrinkage of films and powders has been done. The results showed that the shrinkage in films happens almost 200°C earlier than powder and higher amount of siloxane release due to the low dimension, the shrinkage is higher than powders.
The last part of the study dedicated to two different systems, SiBOCs and SiOCNs, in order to understand the effect of the boron addition on SiOC system and study the optical properties of the SiOCN. Tunable (color emission change) SiOC films is obtained with high quantum efficiency by adding very few amount of boron in SiOC. Moreover, the processing temperature is decreased and very broad emission is obtained. Finally, results showed that SiOCN PDC gives very high emission in UV range and they are promising materials for UV-LEDs.
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Falkenstrand, Johanna, and Camilla Lemos. "Fostering Proactiveness in Data-Driven Matrix Organizations : A Study of Alfa Laval's Distribution Center in Tumba." Thesis, KTH, Industriell produktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254341.
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Globalization has increased the complexity of the business world, as it adds new dimensions to companies’ operations, such as global suppliers and customers, and competition from global actors. To handle the complexity, companies are pressured to become more data-driven to be able to measure and align their operations, and create possibilities for efficiency and competitiveness [Skjott-Larsen etal., 2007; Long, 2018]. In order to enable the change towards becoming more data-driven, companies need to rethink the structure of their organization. Matrix structures have gained popularity, since it allows companies to focus on more than one dimension by creating functional teams focused on specific tasks [Sy et al., 2005]. However, it is not uncommon that the functional groups becomes functional silos, with an inward focus on the own groups’ performance, leading to decreased understanding of other groups and poor communication between groups. A lack of understanding of other groups can lead to a reactive, rather than proactive, way of handling problems [Motiwalla and Pearson, 2009]. The purpose of this project is to create a process that can be used to facilitate proactive work in adata-driven matrix organization struggling with a reactive way of handling problems. The process can be used as a way to decide between possible solutions in decision-making processes, while making sure that any affected department is involved at an early stage in the decision-making process. At Alfa Laval’s distribution center (DC) in Tumba, they are facing the challenges of functional silos and reactive work. The organization is data-driven, why a lot of decisions are based on data. However, the best decision according to the data is not always feasible, which has lead to decisions being made that affects other departments negatively. Based on data from and observations made at the DC, a processwas created. The process was iterated and improved through application to real-life problems and point of improvements identified at DC Tumba. While it is based on the operations at Alfa Laval, it canbe applied to any organization facing similar challenges. The final version of the process proved to deliver good solutions to problems by involving stakeholders early on in the process, making it possible for them to influence how the solutions should be adjusted in order to avoid the changes affecting their daily work negatively. The most important conclusion is that important stakeholder departments should be involved earlyin decision-making processes. That way, their valuable competence and knowledge can be utilized when identifying possible solution, and any negative effects of a solution on another departments can be discovered before implementation. In addition, by taking the time to thoroughly analyze the root cause and effects to a problem, the understanding of the chain can increase.<br>Globalisering har ökat komplexiteten av affärsvärlden, då ytterligare dimensioner måste tas hänsyn till i företags verksamheter, så som globala leverantörer och kunder, och ökad konkurrens från globala aktörer. För att hantera komplexiteten blir företag mer datadrivna, för att kunna mäta och samordna sin verksamhet och skapa möjligheter för effektivitet och konkurrenskraftighet [Skjott-Larsen et al.,2007; Long, 2018]. För att möljiggöra ett skifte mot att bli mer datadriven, måste företag se över sin organisationsstruktur. Matrisstrukturer har ökat i popularitet då de möjliggör att företag kan fokusera på fler än en dimensioner samtidigt genom att skapa funktionella grupper fokuserade på specifikauppgifter [Sy et al., 2005]. Dock är det inte ovanligt att funktionella grupper förvandlas till funktionella silos, med ett inåtriktat fokus på den egna gruppens prestationer, vilket leder till minskad förtåelse och bristfällig kommunikation grupper emellan. Bristande förståelse för andra grupper kan leda till ett klimat där problem hanteras reaktivt snarare än proaktivt [Motiwalla and Pearson, 2009]. Syftet med detta projekt är att skapa en process som kan användas för att underlätta proaktivt arbetet i en datadriven organisation där problem hanteras reaktivt. Processen kan användas som ett hjälpmedel för att välja den bästa av flera möjliga lösningar, samtidigt som påverkade avdelningar involveras i ett tidigt stadium av beslutsprocessen. På Alfa Lavals distributionscenter (DC) i Tumba, finns utmaningar med funktionella silos och reaktivt arbete. Organisationen är datadriven, och beslut fattas baserat på data. Dock är inte alltid beslut som baserats på data rimliga, vilket har lett till att beslut tas som påverkar andra avdelningar negativt. Baserat på data från och observationer på DCt, skapades en preliminär process. Processen itererades och förbättrades sedan genom att appliceras på verkliga problem och förbättringsområden som identifierades på DC Tumba. Även om processen togs fram och baserades på Alfa Lavals verksamhet, kan den appliceras på andra organisationer som står inför samma utmaningar. Den slutgiltiga versionen av processen visade sig generera bra lösningar till problemen genom att involvera intressenter tidigt i processen, vilket gav dem möjligheten att påverka hur den rekommenderade lösningen skulle justeras för att undvika att dereas dagliga arbete skulle påverkas negativt. Den viktigaste slutsatsen är att det är viktigt att involvera intressentavdelningar i ett tidigt skede i beslutsfattandeprocesser. På så sätt kan deras värdefulla kompetens och kunskaper nyttjas när potentiella lösningar till ett problem genereras, och negativa effekter från lösningen på andra avdelningar kan upptäckas innan implementering. Att dessutom noggrant analysera roten till problemet och dess effekter kan leda till att förståelsen för hela kedjan ökar.
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Ferioli, Elena. "The hybrid model matrix in industrial application: il caso Meta System S.p.A." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25086/.
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Negli ultimi decenni, nell’ambiente aziendale sta prendendo sempre più piede l’utilizzo di modelli specifici per l’approccio all’innovazione.
Dei più comuni e utilizzati in letteratura, quelli analizzati in questo studio, sono lo Stage and Gate per lo sviluppo di nuovi prodotti, il Lean six-sigma per progetti di miglioramento, l’Agile per ottimizzare e velocizzare i processi, la Lean per ridurre gli sprechi e il Design Thinking per comprendere meglio i bisogni del cliente.
Per sfruttare al meglio ogni modello è bene che le aziende abbiano una linea guida che illustri quando utilizzare e in che modo ogni metodologia. In questa identificazione, oltre all’utilizzo lineare e puro degli approcci all’innovazione, possono emergere delle situazioni in cui risulti necessario utilizzare contemporaneamente più modelli così da usufruire di una metodologia ibrida che colga i benefici rispettivi di ogni modello integrato.
Con questa ambizione, lo scopo di questa tesi è stato quello di realizzare una matrice dei modelli ibridi che identificasse per ogni area, rappresentante le possibili situazioni, il modello, puro o ibrido, più idoneo da applicare.
Esaminando le pratiche dell’azienda di riferimento, si sono individuate le variabili tipiche che identificano e caratterizzano i contesti in cui si realizzano i progetti di innovazione.
In base a queste variabili si è costruita la struttura della matrice in cui clusterizzare i vari progetti.
Analizzando poi i modelli già in uso in azienda e confrontandosi con la letteratura, si sono individuati i modelli puri e ibridi rispettivi per ogni quadrante.
Al termine di queste fasi, è stato possibile studiare ed elaborare la realizzazione di una matrice dei modelli ibridi in grado di fornire l’approccio più corretto da utilizzare in ogni contesto e aiutare l’azienda a raggiungere più velocemente i risultati evitando l’insorgenza di problematiche.
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Baganha, César Chiesorin. "Considerações sobre a origem da emissão luminosa de Nanocristais de Si em Matriz de SiO2." reponame:Repositório Institucional da UFPR, 2010. http://hdl.handle.net/1884/23720.
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Resumo: Sistemas nanoestruturados de Si tem sido alvo de intensos estudos e discussões no meio científico devido às suas propriedades eletrônicas e ópticas, as quais produzem luminescência no visível, iferentes das apresentadas pelo Si bulk. O presente trabalho traz considerações a respeito de tal luminescência e visa contribuir com as discussões a respeito de sua origem apresentando um estudo detalhado da emissão luminosa de nanocristais Si obtidos pela técnica de implantação iônica de íons de silício (Si+) em matriz de dióxido de silício (SiO2). Utilizando diferentes técnicas ópticas (fotoluminescência em função da temperatura, fotoluminescência resolvida no tempo e excitação de fotoluminescência), um modelo de confinamento esférico e um modelo semi-empírico proposto por Varshni em 1967 para a variação de gap do Si bulk, comparamos os aspectos observados experimentalmente para as emissões envolvidas na luminescência com o comportamento esperado para recombinações banda-a-banda (estados sob confinamento) do nosso sistema. Para nanocristais de diâmetro iguais de 3 nm (diâmetro obtido por microscopia de transmissão de elétrons para nossa amostra) os modelos teóricos descrevem com razoável precisão a energia de
luminescência em função da temperatura observada para a emissão mais intensa em maiores energias do espectro de fotoluminescência a baixas temperaturas e as energias dos estados excitados identificados pela técnica de excitação de luminescência. No entanto para altas temperaturas, a dependência da luminescência com a temperatura parece indicar a presença simultânea de estados de superfície emitindo nessa mesma região do espectro. As demais emissões presentes no espectro de fotoluminescência (emissões com energias menores) parecem seguir o padrão de confinamento quanto à evolução do gap com o tamanho de nanopartícula, porém seus comportamentos com a temperatura não nos levam a uma comprovação de emissão via estados confinados, tampouco via estados de superfície, até o momento. Com isso as emissões nessa região do espectro ainda precisam de uma análise mais profunda e cuidadosa para a comprovação dos mecanismos envolvidos em suas bandas. Os resultados aqui apresentados nos permitem sugerir um modelo de emissão luminosa que é dominado pelos efeitos de confinamento quântico a baixas temperaturas, mas que aponta para um eventual domínio de recombinações através de estados ocalizados para temperaturas altas, próximas e superiores à ambiente. Nossa hipótese é que, para estas nanopartículas obtidas através de implantação iônica, os mecanismos de recombinação por estados onfinados e por estados de superfície coexistem, sendo que a importância de cada um depende crucialmente da temperatura.
Books on the topic "SiOx Matrix"
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Circuit simulation and optimization using matrix analysis. Addison-Wesley Pub. Co., 1993.
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Driscoll, Tobin A. Matrix iterations: The six gaps between potential theory and convergence. Cornell Theory Center, Cornell University, 1996.
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Burger, Jeff. Oberheim Matrix-Six: Getting the Most Out of Yours. Alexander Books, 1987.
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Chekhov, Leonid. Two-dimensional quantum gravity. Edited by Gernot Akemann, Jinho Baik, and Philippe Di Francesco. Oxford University Press, 2018. http://dx.doi.org/10.1093/oxfordhb/9780198744191.013.30.
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This article discusses the connection between large N matrix models and critical phenomena on lattices with fluctuating geometry, with particular emphasis on the solvable models of 2D lattice quantum gravity and how they are related to matrix models. It first provides an overview of the continuum world sheet theory and the Liouville gravity before deriving the Knizhnik-Polyakov-Zamolodchikov scaling relation. It then describes the simplest model of 2D gravity and the corresponding matrix model, along with the vertex/height integrable models on planar graphs and their mapping to matrix models. It also considers the discretization of the path integral over metrics, the solution of pure lattice gravity using the one-matrix model, the construction of the Ising model coupled to 2D gravity discretized on planar graphs, the O(n) loop model, the six-vertex model, the q-state Potts model, and solid-on-solid and ADE matrix models.
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The Hidden Matrix: Women’s Position and Gender Relation in six Indigenous Communities of Bangladesh. Pathok Somabesh, 2009.
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O'Meara, Simon. The Ka'ba Orientations. Edinburgh University Press, 2020. http://dx.doi.org/10.3366/edinburgh/9780748699308.001.0001.
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This book is about the most sacred site of Islam, the cuboid, black-robed Kaʿba of Mecca, a building the Qur’an calls the ‘ancient house.’ It explains how the building has been used, conceptualised and represented by Muslims from the earliest period of Islam onwards, and reveals the strata in the Kaʿba’s many meaning and the profundity of its importance for the Islamic world. It does this by investigating six of the building’s spatial effects: as the qibla (the direction faced in prayer); as the axis and matrix mundi of the Islamic world; as an architectural principle in the bedrock of this world; as a circumambulated goal of pilgrimage and a site of spiritual union for mystics and Sufis; and as a dwelling that is imagined to shelter temporarily an animating force; but which otherwise, as a house, holds a void.
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Steel, Duncan G. Introduction to Quantum Nanotechnology. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192895073.001.0001.
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Quantum physics is rapidly emerging as a transformative approach to expand the frontiers of technology in areas including communications, information processing, metrology, and sensing. Indeed, the end of Moore’s Law looms in the near future and quantum effects in modern electronics such as quantum tunneling are a limiting factor. In contrast, in new technology based on quantum behavior, the quantum properties represent a new dimension of opportunity. This shift is already creating a growing need for engineers and physical scientists who have specialized knowledge in this area, in order to contribute to the growing effort. There are numerous outstanding textbooks available for a general approach to the field of quantum physics. There is much to be gained by taking the traditional learning approach, but it can take two or three years before students encounter many of the exciting ideas and tools for this area. This book takes an application-motivated approach to enable students to build a quantum toolbox. The first six chapters describe the quantum states of various systems of interest, while the remaining chapters focus mainly on dynamics. Important concepts like the quantum flip-flop, based using Rabi oscillations, and engineering the quantum vacuum are presented. Powerful tools including the atomic operator approach and density matrix operator are introduced with examples of applications. This book is aimed at upper level undergraduates and some first year graduate students. The book is arranged to fulfil the needs for a one-semester or two-semester sequence. For a one-semester sequence, the preface describes several paths that emphasize different aspects of quantum behavior.
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Sobczyk, Eugeniusz Jacek. Uciążliwość eksploatacji złóż węgla kamiennego wynikająca z warunków geologicznych i górniczych. Instytut Gospodarki Surowcami Mineralnymi i Energią PAN, 2022. http://dx.doi.org/10.33223/onermin/0222.
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Hard coal mining is characterised by features that pose numerous challenges to its current operations and cause strategic and operational problems in planning its development. The most important of these include the high capital intensity of mining investment projects and the dynamically changing environment in which the sector operates, while the long-term role of the sector is dependent on factors originating at both national and international level. At the same time, the conditions for coal mining are deteriorating, the resources more readily available in active mines are being exhausted, mining depths are increasing, temperature levels in pits are rising, transport routes for staff and materials are getting longer, effective working time is decreasing, natural hazards are increasing, and seams with an increasing content of waste rock are being mined. The mining industry is currently in a very difficult situation, both in technical (mining) and economic terms. It cannot be ignored, however, that the difficult financial situation of Polish mining companies is largely exacerbated by their high operating costs. The cost of obtaining coal and its price are two key elements that determine the level of efficiency of Polish mines. This situation could be improved by streamlining the planning processes. This would involve striving for production planning that is as predictable as possible and, on the other hand, economically efficient. In this respect, it is helpful to plan the production from operating longwalls with full awareness of the complexity of geological and mining conditions and the resulting economic consequences. The constraints on increasing the efficiency of the mining process are due to the technical potential of the mining process, organisational factors and, above all, geological and mining conditions. The main objective of the monograph is to identify relations between geological and mining parameters and the level of longwall mining costs, and their daily output. In view of the above, it was assumed that it was possible to present the relationship between the costs of longwall mining and the daily coal output from a longwall as a function of onerous geological and mining factors. The monograph presents two models of onerous geological and mining conditions, including natural hazards, deposit (seam) parameters, mining (technical) parameters and environmental factors. The models were used to calculate two onerousness indicators, Wue and WUt, which synthetically define the level of impact of onerous geological and mining conditions on the mining process in relation to: —— operating costs at longwall faces – indicator WUe, —— daily longwall mining output – indicator WUt. In the next research step, the analysis of direct relationships of selected geological and mining factors with longwall costs and the mining output level was conducted. For this purpose, two statistical models were built for the following dependent variables: unit operating cost (Model 1) and daily longwall mining output (Model 2). The models served two additional sub-objectives: interpretation of the influence of independent variables on dependent variables and point forecasting. The models were also used for forecasting purposes. Statistical models were built on the basis of historical production results of selected seven Polish mines. On the basis of variability of geological and mining conditions at 120 longwalls, the influence of individual parameters on longwall mining between 2010 and 2019 was determined. The identified relationships made it possible to formulate numerical forecast of unit production cost and daily longwall mining output in relation to the level of expected onerousness. The projection period was assumed to be 2020–2030. On this basis, an opinion was formulated on the forecast of the expected unit production costs and the output of the 259 longwalls planned to be mined at these mines. A procedure scheme was developed using the following methods: 1) Analytic Hierarchy Process (AHP) – mathematical multi-criteria decision-making method, 2) comparative multivariate analysis, 3) regression analysis, 4) Monte Carlo simulation. The utilitarian purpose of the monograph is to provide the research community with the concept of building models that can be used to solve real decision-making problems during longwall planning in hard coal mines. The layout of the monograph, consisting of an introduction, eight main sections and a conclusion, follows the objectives set out above. Section One presents the methodology used to assess the impact of onerous geological and mining conditions on the mining process. Multi-Criteria Decision Analysis (MCDA) is reviewed and basic definitions used in the following part of the paper are introduced. The section includes a description of AHP which was used in the presented analysis. Individual factors resulting from natural hazards, from the geological structure of the deposit (seam), from limitations caused by technical requirements, from the impact of mining on the environment, which affect the mining process, are described exhaustively in Section Two. Sections Three and Four present the construction of two hierarchical models of geological and mining conditions onerousness: the first in the context of extraction costs and the second in relation to daily longwall mining. The procedure for valuing the importance of their components by a group of experts (pairwise comparison of criteria and sub-criteria on the basis of Saaty’s 9-point comparison scale) is presented. The AHP method is very sensitive to even small changes in the value of the comparison matrix. In order to determine the stability of the valuation of both onerousness models, a sensitivity analysis was carried out, which is described in detail in Section Five. Section Six is devoted to the issue of constructing aggregate indices, WUe and WUt, which synthetically measure the impact of onerous geological and mining conditions on the mining process in individual longwalls and allow for a linear ordering of longwalls according to increasing levels of onerousness. Section Seven opens the research part of the work, which analyses the results of the developed models and indicators in individual mines. A detailed analysis is presented of the assessment of the impact of onerous mining conditions on mining costs in selected seams of the analysed mines, and in the case of the impact of onerous mining on daily longwall mining output, the variability of this process in individual fields (lots) of the mines is characterised. Section Eight presents the regression equations for the dependence of the costs and level of extraction on the aggregated onerousness indicators, WUe and WUt. The regression models f(KJC_N) and f(W) developed in this way are used to forecast the unit mining costs and daily output of the designed longwalls in the context of diversified geological and mining conditions. The use of regression models is of great practical importance. It makes it possible to approximate unit costs and daily output for newly designed longwall workings. The use of this knowledge may significantly improve the quality of planning processes and the effectiveness of the mining process.
Book chapters on the topic "SiOx Matrix"
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Tashiro, Chuichi, and Hiroshi Nishioka. "The Influences of Al2O3 and CaSO4·2H2O on Hydrothermal Synthesis and Characterization of Compounds in System Cao-SiO2-H2O." In Brittle Matrix Composites 2. Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-2544-1_9.
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Schetanov, B. V., E. N. Kablov, and T. M. Scheglova. "The Formation Mechanism of the Stabilized Microstructure in the Fibers of Al2O3-SiO2 System." In High Temperature Ceramic Matrix Composites. Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527605622.ch3.
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Kirk, Matthew John. "Dimension-Six Matrix Elements from Sum Rules." In Charming New Physics in Beautiful Processes? Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-19197-9_6.
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Samoilovich, M. I., L. I. Ivleva, M. Yu Tsvetkov, S. M. Kleshcheva, and A. V. Gur’yanov. "Single Crystal SBN:Yb / Opal Matrix (SiO2):Er Composite as a Nanophotonic Structure." In Nanostructured Thin Films and Nanodispersion Strengthened Coatings. Springer Netherlands, 2004. http://dx.doi.org/10.1007/1-4020-2222-0_28.
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Diaz, Ismael, Mercedes Sanchez Moreno, Ma Cruz Alonso, Rodrigo González, and Antonio Zaldivar. "Colloidal Nano-SiO2 Migration in Hardened Mortars and Its Chemical Interaction with Cementitious Matrix." In Nanotechnology in Construction. Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-17088-6_21.
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Alkindy, Maryam B., Munirasu Selvaraj, Fawzi Banat, and Shadi Wajih Hasan. "Preparation of PES/GO/APTES-SiO2 Mixed Matrix Membrane for the Treatment of Oily Wastewater." In Frontiers in Water-Energy-Nexus—Nature-Based Solutions, Advanced Technologies and Best Practices for Environmental Sustainability. Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13068-8_112.
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Amarendra, Ch, and K. Harinadha Reddy. "PSO Algorithm Support Switching Pulse Sequence ISVM for Six-Phase Matrix Converter-Fed Drives." In Smart Intelligent Computing and Applications. Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-1921-1_55.
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Ştefănscu, Dan Mihai. "FEM Calculation of the Influence Matrix of a Six-Component Force Transducer for Robotics." In Toward the Factory of the Future. Springer Berlin Heidelberg, 1985. http://dx.doi.org/10.1007/978-3-642-82580-4_6.
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Minty, Michiko G., and Frank Zimmermann. "Transverse Beam Emittance Measurement and Control." In Particle Acceleration and Detection. Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-662-08581-3_4.
Full textAbstract:
AbstractThe beam emittance ∈xyz represents the volume of the beam occupied in the six dimensional phase space (x, x′, y, y′, φ, δ), where x and y are the transverse positions, x′ and y′ are the transverse angles, φ is the time-like variable representing the relative phase of the beam, and δ is the relative beam momentum error. Using the notation of the beam matrix Σbeam introduced in Chap. 1, the 6-dimensional emittance is $${\varepsilon _{xyz}} = \det \Sigma _{beam}^{xyz}.$$ Considering now only the horizontal plane, the corresponding 2-dimensional horizontal emittance is obtained from $${\varepsilon _x} = \sqrt {\left\langle {{x^2}} \right\rangle \left\langle {{{x'}^2}} \right\rangle- {{\left\langle {xx'} \right\rangle }^2}} ,$$ where the first moments have been subtracted, and the average (〈…〉) is taken over the distribution function of the beam; recall also (1.27–1.29). An analoguous expression holds for the vertical plane. For a coupled system, the general form of (4.1) must be taken.
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Xu, Yuemei, Zuwei Fan, and Han Cao. "A Multi-task Text Classification Model Based on Label Embedding Learning." In Communications in Computer and Information Science. Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-9229-1_13.
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AbstractDifferent text classification tasks have specific task features and the performance of text classification algorithm is highly affected by these task-specific features. It is crucial for text classification algorithms to extract task-specific features and thus improve the performance of text classification in different text classification tasks. The existing text classification algorithms use the attention-based neural network models to capture contextualized semantic features while ignores the task-specific features. In this paper, a text classification algorithm based on label-improved attention mechanism is proposed by integrating both contextualized semantic and task-specific features. Through label embedding to learn both word vector and modified-TF-IDF matrix, the task-specific features can be extracted and then attention weights are assigned to different words according to the extracted features, so as to improve the effectiveness of the attention-based neural network models on text classification. Experiments are carried on three text classification task data sets to verify the performance of the proposed method, including a six-category question classification data set, a two-category user comment data set, and a five-category sentiment data set. Results show that the proposed method has an average increase of 3.02% and 5.85% in F1 value compared with the existing LSTMAtt and SelfAtt models.
Conference papers on the topic "SiOx Matrix"
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Yoshioka, Naoki, Akira Heya, Naoto Matuo, et al. "Formation of nc-Si in SiOx by flash lamp anneling." In 2016 23rd International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD). IEEE, 2016. http://dx.doi.org/10.1109/am-fpd.2016.7543661.
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Heya, Akira. "Reduction and Etching of Si-Rich SiOx Film by Atomic Hydrogen Annealing." In 2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD). IEEE, 2019. http://dx.doi.org/10.23919/am-fpd.2019.8830571.
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Kim, Sehyeon, Kumar Mallem, Sooyoung Park, et al. "Field effect passivation of plasma oxidized SiOx layer on boron emitter surface by PECVD." In 2019 26th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD). IEEE, 2019. http://dx.doi.org/10.23919/am-fpd.2019.8830592.
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Zhou, Weiqi, and Susumu Horita. "Mechanism Study on Deposition of SiOx Films Produced by Silicone Oil and Ozone Gas." In 2020 27th International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD). IEEE, 2020. http://dx.doi.org/10.23919/am-fpd49417.2020.9224470.
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Matsuda, Tokiyoshi, Mamoru Furuta, Takahiro Hiramatsu, Hiroshi Furuta, Mutsumi Kimura, and Takashi Hirao. "Low temperature ZnO TFT fabricated on SiOx gate insulator deposited by facing electrodes chemical vapor deposition." In 2014 21st International Workshop on Active-Matrix Flatpanel Displays and Devices (AM-FPD). IEEE, 2014. http://dx.doi.org/10.1109/am-fpd.2014.6867191.
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Kolodziej, Andrzej, Tomasz Kolodziej, and Michal Kolodziej. "Low temperature manufacturing of Si nanocrystallites in the SiOx matrix applicable in solar cells." In 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC). IEEE, 2013. http://dx.doi.org/10.1109/pvsc.2013.6744218.
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Kar, Debjit, and Debajyoti Das. "One-step synthesis of silicon nanocrystals in a−SiOx matrix at low-temperature by RF magnetron sputtering." In SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4872779.
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Puglia, D., G. Sombrio, R. dos Reis, and H. Boudinov. "Photoluminescence from doped silicon nanocrystals in SiO2 matrix." In 2013 Symposium on Microelectronics Technology and Devices (SBMicro). IEEE, 2013. http://dx.doi.org/10.1109/sbmicro.2013.6676145.
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Moscoso-Martir, A., M. Avila-Ruiz, E. Duran-Valdeiglesias, et al. "Butler matrix based six-port passive junction." In 2014 IEEE Topical Conference on Wireless Sensors and Sensor Networks (WiSNet). IEEE, 2014. http://dx.doi.org/10.1109/wisnet.2014.6825495.
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Omrani, Khaled, Mohamed Ali Dami, and Mohamed Jemli. "Three to six-phase direct matrix converters." In 2016 7th International Renewable Energy Congress (IREC). IEEE, 2016. http://dx.doi.org/10.1109/irec.2016.7478863.
Full textReports on the topic "SiOx Matrix"
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Aharony, O., M. Berkooz, S. Kachru, and E. Silverstein. Matrix description of (1,0) theories in six dimensions. Office of Scientific and Technical Information (OSTI), 1997. http://dx.doi.org/10.2172/666066.
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Patricia M. Dove. Quantifying Silica Reactivity in Subsurface Environments: Reaction Affinity and Solute Matrix Controls on Quartz and SiO2 Glass Dissolution Kinetics. Office of Scientific and Technical Information (OSTI), 2000. http://dx.doi.org/10.2172/791682.
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Dove, Patricia M. Quantifying Silica Reactivity in Subsurface Environments: Reaction Affinity and Solute Matrix Controls on Quartz and SiO2 Glass Dissolution Kinetics. Office of Scientific and Technical Information (OSTI), 1999. http://dx.doi.org/10.2172/827365.
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Dove, P. M. Quantifying silica reactivity in subsurface environments: Reaction affinity and solute matrix controls on quartz and SiO{sub 2} glass. 1997 annual progress report. Office of Scientific and Technical Information (OSTI), 1997. http://dx.doi.org/10.2172/13538.
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Goeckeritz, Joel, Nathan Schank, Ryan L Wood, Beverly L Roeder, and Alonzo D Cook. Use of Urinary Bladder Matrix Conduits in a Rat Model of Sciatic Nerve Regeneration after Nerve Transection Injury. Science Repository, 2022. http://dx.doi.org/10.31487/j.rgm.2022.03.01.
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Previous research has demonstrated the use of single-channel porcine-derived urinary bladder matrix (UBM) conduits in segmental-loss, peripheral nerve repairs as comparable to criterion-standard nerve autografts. This study aimed to replicate and expand upon this research with additional novel UBM conduits and coupled therapies. Fifty-four Wistar Albino rats were divided into 6 groups, and each underwent a surgical neurectomy to remove a 7-millimeter section of the sciatic nerve. Bridging of this nerve gap and treatment for each group was as follows: i) reverse autograft—the segmented nerve was reversed 180 degrees and used to reconnect the proximal and distal nerve stumps; ii) the nerve gap was bridged via a silicone conduit; iii) a single-channel UBM conduit; iv) a multi-channel UBM conduit; v) a single-channel UBM conduit identical to group 3 coupled with fortnightly transcutaneous electrical nerve stimulation (TENS); vi) or, a multi-channel UBM conduit identical to group 4 coupled with fortnightly TENS. The extent of nerve recovery was assessed by behavioural parameters: foot fault asymmetry scoring measured weekly for six weeks; electrophysiological parameters: compound muscle action potential (CMAP) amplitudes, measured at weeks 0 and 6; and morphological parameters: total fascicle areas, myelinated fiber counts, fiber densities, and fiber sizes measured at week 6. All the above parameters demonstrated recovery of the test groups (3-6) as being either comparable or less than that of reverse autograft, but none were shown to outperform reverse autograft. As such, UBM conduits may yet prove to be an effective treatment to repair relatively short segmental peripheral nerve injuries, but further research is required to demonstrate greater efficacy over nerve autografts.
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Goeckeritz, Joel, Nathan Schank, Ryan L Wood, Beverly L Roeder, and Alonzo D Cook. Use of Urinary Bladder Matrix Conduits in a Rat Model of Sciatic Nerve Regeneration after Nerve Transection Injury. Science Repository, 2022. http://dx.doi.org/10.31487/j.rgm.2022.03.01.sup.
Full textAbstract:
Previous research has demonstrated the use of single-channel porcine-derived urinary bladder matrix (UBM) conduits in segmental-loss, peripheral nerve repairs as comparable to criterion-standard nerve autografts. This study aimed to replicate and expand upon this research with additional novel UBM conduits and coupled therapies. Fifty-four Wistar Albino rats were divided into 6 groups, and each underwent a surgical neurectomy to remove a 7-millimeter section of the sciatic nerve. Bridging of this nerve gap and treatment for each group was as follows: i) reverse autograft—the segmented nerve was reversed 180 degrees and used to reconnect the proximal and distal nerve stumps; ii) the nerve gap was bridged via a silicone conduit; iii) a single-channel UBM conduit; iv) a multi-channel UBM conduit; v) a single-channel UBM conduit identical to group 3 coupled with fortnightly transcutaneous electrical nerve stimulation (TENS); vi) or, a multi-channel UBM conduit identical to group 4 coupled with fortnightly TENS. The extent of nerve recovery was assessed by behavioural parameters: foot fault asymmetry scoring measured weekly for six weeks; electrophysiological parameters: compound muscle action potential (CMAP) amplitudes, measured at weeks 0 and 6; and morphological parameters: total fascicle areas, myelinated fiber counts, fiber densities, and fiber sizes measured at week 6. All the above parameters demonstrated recovery of the test groups (3-6) as being either comparable or less than that of reverse autograft, but none were shown to outperform reverse autograft. As such, UBM conduits may yet prove to be an effective treatment to repair relatively short segmental peripheral nerve injuries, but further research is required to demonstrate greater efficacy over nerve autografts.
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Olson, L. C., R. D. Knight, H L Crow, and H. A. J. Russell. Chemostratigraphic logging of the Lower Ordovician and Precambrian, Bells Corners borehole calibration facility, Ottawa, Ontario. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330519.
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Geochemical data were collected from a 120-meter-deep borehole (BC81-2) located at the Geological Survey of Canada's Bells Corners Borehole Calibration Facility in Ottawa, Ontario. This report documents geochemical data collected for the most frequently logged of the six boreholes located at the facility. The geochemical data were collected using a portable X-ray fluorescence (pXRF) spectrometer with a subset of samples collected for modern laboratory based fusion and multi-acid methods to calibrate the pXRF data for improved accuracy. Borehole geochemistry provides a characterization of Precambrian and overlying Ordovician rocks in the Ottawa area that augments the understanding of geophysical properties obtained from the calibration borehole. The combined geochemical and geophysical datasets further define rock characteristics, formational boundaries, as well as alteration zones. The results demonstrate the usefulness of pXRF derived geochemical data and chemostratigraphy of rock cores. The chemostratigraphic data augment data collected with spectral gamma logging tools and support an enhanced interpretation of geological contacts across transitional boundaries and the nature of the matrix mineralogy.
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Al-Qadi, Imad, Jaime Hernandez, Angeli Jayme, et al. The Impact of Wide-Base Tires on Pavement—A National Study. Illinois Center for Transportation, 2021. http://dx.doi.org/10.36501/0197-9191/21-035.
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Researchers have been studying wide-base tires for over two decades, but no evidence has been provided regarding the net benefit of this tire technology. In this study, a comprehensive approach is used to compare new-generation wide-base tires (NG-WBT) with the dual-tire assembly (DTA). Numerical modeling, prediction methods, experimental measurements, and environmental impact assessment were combined to provide recommendations about the use of NG-WBT. A finite element approach, considering variables usually omitted in the conventional analysis of flexible pavement was utilized for modeling. Five hundred seventy-six cases combining layer thickness, material properties, tire load, tire inflation pressure, and pavement type (thick and thin) were analyzed to obtained critical pavement responses. A prediction tool, known as ICT-Wide, was developed based on artificial neural networks to obtain critical pavement responses in cases outside the finite element analysis matrix. The environmental impacts were determined using life cycle assessment. Based on the bottom-up fatigue cracking, permanent deformation, and international roughness index, the life cycle energy consumption, cost, and green-house gas (GHG) emissions were estimated. To make the outcome of this research effort useful for state departments of transportation and practitioners, a modification to AASHTOWare is proposed to account for NG-WBT. The revision is based on two adjustment factors, one accounting for the discrepancy between the AASHTOware approach and the finite element model of this study, and the other addressing the impact of NG-WBT.
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Warrick, Arthur, Uri Shani, Dani Or, and Muluneh Yitayew. In situ Evaluation of Unsaturated Hydraulic Properties Using Subsurface Points. United States Department of Agriculture, 1999. http://dx.doi.org/10.32747/1999.7570566.bard.
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The primary information for accurately predicting water and solute movement and their impact on water quality is the characterization of soil hydraulic properties. This project was designed to develop methods for rapid and reliable estimates of unsaturated hydraulic properties of the soil. Particularly, in situ methodology is put forth, based on subsurface point sources. Devices were designed to allow introduction of water in subsurface settings at constant negative heads. The ability to operate at a negative head allows a direct method of finding unsaturated soil properties and a mechanism for eliminating extremely rapid preferential flow from the slow matrix flow. The project included field, laboratory and modeling components. By coupling the measurements and the modeling together, a wider range of designs can be examined, while at the same time realistic performance is assured. The developed methodology greatly expands the possibilities for evaluating hydraulic properties in place, especially for measurements in undisturbed soil within plant rooting zones. The objectives of the project were (i) To develop methods for obtaining rapid and reliable estimates of unsaturated hydraulic properties in situ, based on water distribution from subsurface point sources. These can be operated with a constant flow or at a constant head; (ii) To develop methods for distinguishing between matrix and preferential flow using cavities/permeameters under tension; (iii) To evaluate auxiliary measurements such as soil water content or tensions near the operating cavities to improve reliability of results; and (iv: To develop numerical and analytical models for obtaining soil hydraulic properties based on measurements from buried-cavity sources and the auxiliary measurements. The project began in July 1995 and was terminated in November 1998. All of the objectives were pursued. Three new subsurface point sources were designed and tested and two old types were also used. Two of the three new designs used a nylon cloth membrane (30 mm) arranged in a cylindrical geometry and operating at a negative water pressure (tension). A separate bladder arrangement allowed inflation under a positive pressure to maintain contact between the membrane and the soil cavity. The third new design used porous stainless steel (0.5 and 5 mm) arranged in six segments, each with its own water inlet, assembled to form a cylindrical supply surface when inflated in a borehole. The "old" types included an "off-the-shelf" porous cup as well as measurements from a subsurface drip emitter in a small subsurface cavity. Reasonable measurements were made with all systems. Sustained use of the cloth membrane devices were difficult because of leaks and plugging problems. All of the devices require careful consideration to assure contact with the soil system. Steady flow was established which simplified the analysis (except for the drip emitter which used a transient analysis).
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Pstuty, Norbert, Mark Duffy, Dennis Skidds, et al. Northeast Coastal and Barrier Network Geomorphological Monitoring Protocol: Part I—Ocean Shoreline Position, Version 2. National Park Service, 2022. http://dx.doi.org/10.36967/2293713.
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Following a review of Vital Signs – indicators of ecosystem health – in the coastal parks of the Northeast Coastal and Barrier Network (NCBN), knowledge of shoreline change was ranked as the top variable for monitoring. Shoreline change is a basic element in the management of any coastal system because it contributes to the understanding of the functioning of the natural resources and to the administration of the cultural resources within the parks. Collection of information on the vectors of change relies on the establishment of a rigorous system of protocols to monitor elements of the coastal geomorphology that are guided by three basic principles: 1) all of the elements in the protocols are to be based on scientific principles; 2) the products of the monitoring must relate to issues of importance to park management; and 3) the application of the protocols must be capable of implementation at the local level within the NCBN. Changes in ocean shoreline position are recognized as interacting with many other elements of the Ocean Beach-Dune Ecosystem and are thus both driving and responding to the variety of natural and cultural factors active at the coast at a variety of temporal and spatial scales. The direction and magnitude of shoreline change can be monitored through the application of a protocol that tracks the spatial position of the neap-tide, high tide swash line under well-defined conditions of temporal sampling. Spring and fall surveys conducted in accordance with standard operating procedures will generate consistent and comparable shoreline position data sets that can be incorporated within a data matrix and subsequently analyzed for temporal and spatial variations. The Ocean Shoreline Position Monitoring Protocol will be applied to six parks in the NCBN: Assateague Island National Seashore, Cape Cod National Seashore, Fire Island National Seashore, Gateway National Recreation Area, George Washington Birthplace National Monument, and Sagamore Hill National Historic Site. Monitoring will be accomplished with a Global Positioning System (GPS )/ Global Navigation Satellite System (GNSS) unit capable of sub-meter horizontal accuracy that is usually mounted on an off-road vehicle and driven along the swash line. Under the guidance of a set of Standard Operating Procedures (SOPs) (Psuty et al., 2022), the monitoring will generate comparable data sets. The protocol will produce shoreline change metrics following the methodology of the Digital Shoreline Analysis System developed by the United States Geological Survey. Annual Data Summaries and Trend Reports will present and analyze the collected data sets. All collected data will undergo rigorous quality-assurance and quality-control procedures and will be archived at the offices of the NCBN. All monitoring products will be made available via the National Park Service’s Integrated Resource Management Applications Portal.