Experimental and Numerical Characterization of Scalable Cellulose Nano-fiber Composite

Fiber-reinforced polymer composites have been used in recent years as an alternative to the conventional materials because of their low weight, high mechanical properties and low processing temperatures. Most polymer composites are traditionally made using reinforcing fibers such as carbon or glass fibers. However, there has been recent interest in making these reinforcing fibers from natural resources. The plant-derived cellulose nano-fibers (CNF) are a material with remarkable mechanical properties at the nano-scale that are much superior to the mechanical properties of the traditional natural fibers (such as jute, hemp, kenaf, etc) used in the natural-fiber based polymer composites. Because CNF is bio-based and biodegradable, it is an attractive ‘green’ alternative for use in automotive, aerospace, and other engineering applications. However, efforts to produce CNF based nano-composites, with successful scaling-up of the remarkable nanoscale properties of CNF, have not met with much success and form an active area of research. The main goals of this research are to characterize the scalable CNF based nano composites using experimental methods and to develop effective models for flow of polymeric resin in the CNF-based porous media used during the proposed manufacture of CNF nano-composites. In the CNF composite characterization section, scalable isotropic and anisotropic CNF composites were made from a porous CNF preforms created using a freeze drying process. Formation of the fibers during freeze-drying process can change the micro skeleton of the final preform structure as non-aligned or isotropic and aligned or anisotropic CNF. Liquid Composite Molding (LCM) processes form a set of liquid molding technologies that are used quite commonly for making the conventional polymer composites. An improvised vacuum-driven LCM process was used to make the CNF-based nanocomposites from CNF preforms using a ‘green’ epoxy resin with high bio-content. Under the topic of isotropic CNF, formation of the freeze-dried CNF preforms’ porous network strongly affects the mechanical, microstructural and tribological properties of the composite, therefore experimental testing was performed to characterize the effects of pore structure on global properties of isotropic CNF composites. Level of curing was investigated by experimental methods such as DSC in order to analyze its effects on the mechanical properties. The causes of failure in the composites were discussed by analyzing the SEM micrographs of fractured surfaces. The investigations revealed that the silane treated samples show superior mechanical behavior and higher storage modulus compared to the untreated (no silane) samples. The DMA and DSC results indicated a reduction in the glass transition temperature for the CNF composites compared to the pure resin samples. The tensile results showed higher elastic moduli in composites made from silane treated CNF preforms compared to those made from non silane-treated preforms. The tribological behavior of the silylated CNFs composites showed lower coefficient of friction and wear volumes than the neat bio-epoxy due to the formation of a transfer film on the mating surfaces, which led to a decrease in the ‘direct contact’ of the composite with the asperities of the hard metallic counterface. Under the topic of anisotropic CNF nanocomposites, a recently-discovered new type of CNF preform with more-aligned pore structure was used in our improvised LCM process to make the CNF-based anisotropic nanocomposite. The effect of such aligned pore structure on the mechanical and microstructural properties of CNF-based nanocomposites was investigated. As before, we used the tensile test, DMA and SEM to characterize this new material. Our investigation revealed that anisotropic CNF preform improved the overall mechanical properties of CNF composites due to better interfacing between the CNF and resin inside aligned pore structure of anisotropic CNF. Also, DMA results showed an improvement in the glass transition temperature of the anisotropic samples compared to the isotropic ones. For flow modeling in the CNF-based porous medium, the closure formulation, developed as a part of the derivation of Darcy’s law developed by Whitaker [1], was used to develop novel numerical and experimental methods for estimating the permeability and absorption characteristics of a porous medium with a given pore-level microstructure. The permeability of such a porous medium was estimated numerically while the absorption characteristics were analyzed through experiments. In order to use real micrograph in permeability simulations, 2D SEM pictures of the CNF-based porous media were considered. The falling head permeameter was used for measuring the experimental permeability in order to test the accuracy of the permeability tensor obtained by the proposed numerical simulation. The permeability values were also compared with the theoretical models of Kozeny-Carman. A good agreement between the numerical, experimental and analytical methods demonstrated the accuracy of the closure formulation and the resulting simulation. These results also present the closure formulation based method as a viable method to estimate the permeability of porous media using 2D SEM micrographs; such a method harnesses the micro-macro coupling and is marked with absence of any constitutive-relation based assumption for such upscaling. Such a method is also faster, less expensive and less problematic than the corresponding 3D micro-CT scan based method because of much smaller degrees-of-freedom, memory and storage requirements. Under the absorption characteristics study, absorption characteristics of paper-like CNF porous medium was modeled using theoretical derivation of governing equation for single-phase flow and swelling behavior and absorption coefficient were investigated through experiments. In derivation part, unique form of mass conservation was developed using volume averaging theorem in the swelling, liquid-absorbing CNF-based preform. The case of the absorption coefficient, b being unity, which corresponds to the liquid absorption rate into fibers being equal to the fiber expansion rate, results in the classical form of the continuity equation that is originally derived for a rigid, non-deforming porous medium. The value of b was determined using a novel dipping experiment conducted with the help of a microbalance and was found to be unity for flow models in swelling porous media made of the CNF

Asset markets, stochastic policy and international trade

The present study examines the role of financial markets for trade policy under conditions of uncertainty. It builds upon and extends an earlier work by Stockman and Dellas. Using a two country, two good stochastic general equilibrium model where both countries impose a combination of export and import tariffs and the agents trade in financial contracts to insure against policy risk, with the provision of spot trading in consumption goods, it is shown that: (i) the structure of commercial policy (i.e. import or export tariffs) matters, so that Lerner\u27s symmetry theorem does not extend to a stochastic framework with asset markets; (ii) the Stockman-Dellas conclusions are sensitive to the choice of tariffs; (iii) in general, it is optimal to use both export and import tariffs in such a framework;The assumption of exogenous tariffs is relaxed next by making endowments random and by assuming tariffs are chosen optimally. The values of optimal policies are compared across states within any regime as well as across alternative policy regimes. The simulation results indicate that the expected welfare when both export and import tariffs are used is at least as high as that when only import tariffs are used. However, if commercial policy is restricted to import tariffs, the introduction of asset markets can be welfare-deteriorating, even though there remains potential gains from engaging in inter-state trade. Finally, the potential time consistency issues inherent in such a framework are addressed. The financial structure is found to play a crucial role in determining the time consistent policy ex post

Combustion Kinetics of Advanced Biofuels

Use of biofuels, especially in automotive applications, is a growing trend due to their potential to lower greenhouse gas emissions from combustion. Ketones are a class of biofuel candidates which are produced from cellulose. However, ketones received rather scarce attention from the combustion community compared to other classes such as, alcohols, esters, and ethers. There is little knowledge on their combustion performance and pollutant generation. Hence their combustion chemistry needs to be investigated in detail. Diisopropyl ketone (DIPK) is a promising biofuel candidate, which is produced using endophytic fungal conversion. A detailed understanding of the combustion kinetics of the oxidation of DIPK in advanced engines such as, the homogeneous charge compression ignition (HCCI) engine is warranted. This dissertation concentrates on the combustion kinetics of DIPK over a wide range of temperature and pressure with a focus on HCCI engine application. An existing DIPK kinetic mechanism has been reviewed and a single zone HCCI engine model has been modeled and validated against recent experimental data from Sandia National Lab. Therefore different HCCI modeling assumptions were tested and the DIPK reaction mechanism was modified with missing reactions and the required thermochemical data. As a result, the HCCI pressure trace, heat release rate and reactivity have been improved. In order to improve the ignition delay time simulation results, the low temperature oxidation of DIPK was studied as the fuel chemistry effects on the autoignition behavior becomes important in low temperature. Therefore DIPK low temperature oxidation experimental data was obtained from the synchrotron photoionization experiments conducted at the Advanced Light Source (ALS) so that the primary products as well as the dominant oxidation pathways are identified. Furthermore, the aldehydes oxidation, as a result of partial or incomplete combustion and as the primary stable intermediate products in oxidation and pyrolysis of biofuel were studied at low temperature in ALS. A high temperature reaction mechanism was created using the reaction class approach. The reaction mechanism for DIPK was improved using the experimental data along with quantum chemical calculation of activation energies and barriers as well as vibrational modes for the important reactions identified in ALS experiment. The rate constants for important reactions were calculated based on modified Arrhenius equation. DIPK oxidation and pyrolysis were studied at high temperature and pressure using UCF shock tube. The ignition delay times as well as the product (methane) time histories were investigated and used as validation targets for the new model

CEE Banking Sector Co-Movement: Contagion or Interdependence?

We study the evolution of global equity market integration using US dollar denominated iShares. Designed to mimic the movements of MSCI indices, these securities provide an easy pool of international diversification products for the investor. As such they allow us to conduct an analysis of the largest equity markets comovements devoid of problems associated with trading restrictions, exchange rates fluctuations and non-synchronous trading. In contrast to most of the previous studies, we apply time varying methodology for the analysis of both short-term and long-term comovements that provide detailed evidence on the pattern and dynamics of the equity market linkages. We find evidence in favour of increasing conditional correlations for all of the markets since 2001. Time-varying and recursive cointegration tests provide somewhat weak evidence in favour of the presence of bivariate cointegration relationships, but stronger evidence in the multivariate case, suggesting limited diversification opportunities for the U.S. based investor in the long run.Stock Market Integration, G7 Stock markets, Cointegration, GARCH

Domestic politics in Israeli peace-making, 1988-1994.

Available from British Library Document Supply Centre-DSC:DXN048330 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Effect of operation procedures in sediment transport in a transbasin canal system

Presented at the 2001 USCID water management conference, Transbasin water transfers on June 27-30, 2001 in Denver, Colorado.Includes bibliographical references.The purpose of this paper is to discuss problems associated with performance of earth canals, designed for non-scouring and non-silting flow, and suggest operational procedures to minimize the sedimentation problem for transbasin projects, where adequate facilities for removal of suspended solids may not be available at the headworks. Remarks are based on observations of site characteristics, and analysis of field data for the Moghan Irrigation Project, as a part of the Mill and Moghan Project constructed jointly between Iran and the Republic of Azerbaijan (a former Soviet Union republic)

Proizvodnja biodizela heterogeno kataliziranom transesterifikacijom loja

Biodiesel is an eco-friendly alternative diesel fuel prepared from domestic renewable resources i.e. vegetable oils and animal fats. In this process, biodiesel is produced by transesterification of triglycerides present in animal fat or vegetable oils, by displacing glycerine with a low molar mass alcohol using homogeneous or heterogeneous catalysis. The resulting ester, after mixing with diesel fuels, has physicochemical properties similar to those of conventional fuels. In this work, the batch process of biodiesel production has been studied using tallow fat as raw material with methanol and a heterogeneous catalyst. The quality of the produced biodiesel was evaluated by the determination of important properties, such as viscosity, flash point, cetane number, oxidation stability, glycerine content, acid value, etc. The produced biodiesel was found to demonstrate fuel properties within the ranges recommended by the ASTM D6751. This work is licensed under a Creative Commons Attribution 4.0 International License.Biodizel je ekološki prihvatljiva alternativa dizelskom gorivu, pripremljena iz domaćih obnovljivih izvora kao što su biljno ulje i životinjske masnoće. U tim procesima biodizel se proizvodi transesterifikacijom triglicerida prisutnim u životinjskoj masnoći ili u biljnim uljima zamjenom glicerina s alkoholima male molekulske mase koristeći se homogenom ili heterogenom katalizom. Ester nakon miješanja s dizelskim gorivima ima fizičko-kemijska svojstva slična konvencionalnim gorivima. Ovdje je istražena šaržna proizvodnja biodizela iz loja i metanola uz heterogeni katalizator. Kvaliteta biodizela ocjenjena je prema važnim svojstvima kao što su viskoznost, plamište, cetanski broj, oksidacijska stabilnost, sadržaj glicerina, kiselinski broj itd. Svojstva proizvedenog biodizela u skladu su sa standardima ASTM D6751. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna

Mediating Role of Teachers Self-Efficacy in the Relationship between Primary Teachers Emotional Intelligence and Job Burnout in Babol City

The purpose of this study was to investigate the relationship between emotional intelligence and self-efficacy with job burnout among primary school teachers in Babol (Mazandaran, Iran). This is a descriptive correlational study clearly based on structural equation modeling (SEM). The participants of this study were 225 of public primary school teachers in Babol in academic year 2013-14 that were selected via cluster random sampling method. Participants completed Maslach and Jackson's Job Burnout Inventory (MBI) (1996), Teacher Self-Efficacy Questionnaire (by Tschannen-Moran, Woolfolk, 2001) and Emotional Intelligence Questionnaire (by Schutte, 1998) and reliability and validity of these questionnaires were obtained. Results of Pearson correlation showed that all emotional intelligence, job burnout and self-efficacy components are mutually correlated with each other (p <0.01(. Implementing structural equation modeling (SEM) for casual relationship between emotional intelligence and job burnout through mediator variable self-efficacy, we found that the proposed model has a good fit and burnout is well explained by emotional intelligence and self-efficacy. Also all of the model path coefficients were significant

Vertical capacity of bucket foundations in undrained soil

Offshore wind turbine structures are traditionally founded on gravity concrete foundations or mono-piles. Bucket foundations were developed for the offshore oil and gas industry and are now being used in wind turbine construction. The loading in this application is characterized by a vertical load due to the slender construction combined with horizontal forces inducing a large overturning moment. Field tests on bucket foundations were performed to gain insight into the vertical load response of bucket foundations in clay soils. The field tests were accompanied by finite element numerical simulations in order to provide a better understanding of the parameters influencing bucket foundation behaviour