<div>Self-sensing materials are engineered to transduce mechanical effects like deformations and damages into detectable electrical changes. As such, they have received immense research attention in areas including aerospace, civil infrastructure, robotic skin, and biomedical devices. In structural health monitoring (SHM) and nondestructive evaluation (NDE) applications, damages in the material cause breakage in the conductive filler networks, resulting in changes in the material's conductivity. Most SHM and NDE applications of self-sensing materials have used direct current (DC) measurements. DC-based methods have shown advantages with regard to sensitivity to microscale damages compared to other SHM methods. Comparatively, alternating current (AC) measurement techniques have shown potential for improvement over existent DC methods. For example, using AC in conjunction with self-sensing materials has potential for benefits such as greater data density, higher sensitivity through electrodynamics effects (e.g., coupling the material with resonant circuitry), and lower power requirements. Despite these potential advantages, AC techniques have been vastly understudied compared to DC techniques. </div><div><br></div><div>To overcome this gap in the state of the art, this thesis presents two contributions: First, an experimental study is conducted to elucidate the effect of different damage types, numbers, and sizes on AC transport in a representative self-sensing composite. And second, experimental data is used to inform a computational study on using AC methods to improve damage detection via electrical impedance tomography (EIT) – a conductivity imaging modality commonly paired with self-sensing materials for damage localization. For the first contribution, uniaxial glass fiber specimens containing 0.75 wt.% of carbon nanofiber (CNF) are induced with five types of damage (varying the number of holes, size of holes, number of notches, size of notches, and number of impacts). Impedance magnitude and phase angle were measured after each permutation of damage to study the effect of the new damage on AC transport. It was observed that permutations of hole and notch damages show clear trends of increasing impedance magnitude with the increasing damage, particularly at low frequencies. These damages had little-to-no effect on phase angle, however. Increasing numbers of impacts on the specimens did not show any discernable trend in either impedance magnitude or phase angle, except at high frequencies. This shows that different AC frequencies can be more or less useful for finding particular damage types.</div><div><br></div><div>Regarding the second contribution, AC methods were also explored to improve damage detection in self-sensing materials via EIT. More specifically, the EIT technique could benefit from developing a baseline-free (i.e., not requiring a ‘healthy’ reference) formulations enabled by frequency-difference (fd) imaging. For this, AC conductivity measurements ranging from 100 Hz to 10 MHz were collected from various weight fractions of CNF-modified glass fiber/epoxy laminates. This experimental data was used to inform fdEIT simulations. In the fdEIT simulations, damage was simulated as a simple through-hole. Simulations used 16 electrodes with four equally spaced electrodes on each side of the domain. The EIT forward problem was used to predict voltage-current response on the damaged mesh, and a fdEIT inverse problem was formulated to reconstructs the damage state on an undamaged mesh. The reconstruction images showed the simulated damage clearly. Based on this preliminary study, this research shows that fdEIT does have potential to eliminate the need for a healthy baseline in NDE applications, which can potentially help proliferate the use of this technique in practice.</div>

Cellulose nanofibrils (CNF) is a renewable material with unique strength properties. A difficulty in CNF production is that CNF suspensions contain large amounts of water. If CNF suspension volume can be decreased by dewatering facilitated by centrifugation, then transportation costs and storage costs can be reduced. The aim of this thesis is to investigate the impact various parameters have on CNF centrifugation dewatering and identify optimal conditions for maximal water removal. A laboratory study was conducted using four materials; 2.0 w% enzymatically treated CNF (CNF1), 1.9 w% carboxymethylated CNF (CNF2) and two commercial samples (1.9 w% CNFA and 1.8 w% CNFB). The main method was analytical centrifugation up to 2330 g. Parameters tested were initial concentration before centrifugation, temperature, NaCl addition, pH, and applied solid compressive pressure (g-force and surface weight). In addition to centrifugation experiments the four materials were characterized with laser diffraction, UV-vis absorption, Dynamic light scattering, and dry weight measurements. Analysis of the experimental data collected show that increase in initial concentration give a higher final concentration, but less water is removed. Furthermore, temperature changes have no effect on separation of CNF and water. At an applied solid compressive pressure of 3 kPa and initial concentration at 1.5 w% the concentrations 5.5 w%, 1.5 w%, 4.0 w%, and 4.3 w% can be reach for CNF1, CNF2, CNFA, and CNFB respectively. After extrapolation of polynomial functions fitted to experimental data an applied solid compressive pressure of 22 kPa and initial concentration at 1:5 w%, the concentrations 9.1 w%, 1.5 w%, 6.9 w%, and 7.9 w% are predicted for CNF1, CNF2, CNFA, and CNFB respectively. The thickening of CNF suspensions achieved and predicted in this thesis implies possibilities for large amounts of water removal, e.g. the water content in a CNF1 suspension is reduced from 65.7 litres/kg CNF to 10.0 litres/kg CNF at the solid compressive pressure 22 kPa. The concentrations at 22 kPa are determined by extrapolation from experimental data &lt;3 kPa solid compressive pressure. The carboxymethylated CNF2 can not be dewatered unless it is diluted or if salt or pH is adjusted. This is directly correlated to the electrostatic forces in the suspension and the Debye length. Addition of salt or lowered pH also eliminate any concentration gradients in diluted and centrifuged CNF2 suspensions. / Cellulosa nanofibriller (CNF) är ett förnybart material med unika styrkeegenskaper. En svårighet med produktion av CNF är att CNF suspensioner innehåller stora mängder vatten. Om volymerna av CNF suspensioner kan minskas med avvattning genom centrifugering, då kan transport- och lagerkostnader sänkas. Målet med det här examensarbetet är att undersöka vilken inverkan olika parametrar har på CNF-avvattning genom centrifugering och identifiera optimala förhållanden för maximalt avlägsnande av vatten. En laboratoriestudie utfördes på fyra olika material. De fyra materialen är 2 w% enzymatiskt behandlad CNF (CNF1), 1.9 w% karboxymetylerad CNF (CNF2) och två kommersiella prover (1.9 w% CNFA och 1.8 w% CNFB). Den huvudsakliga metoden var analytisk centrifugering upp till maximalt 2330 g. De testade parametrarna var initial koncentration innan centrifugering, temperatur, NaCl tillsats, pH, och applicerat fast kompressionstryck (g-kraft och ytvikt). Förutom centrifugeringsexperimenten så karaktäriserades the fyra mmaterialen med laser diffraktion, UV-vis absorption, dynamisk ljusspridning och vägningar av torrhalt. Analys av den experimentella data som insamlats visar att en ökad initial koncentration ger en högre slutkoncnentration, men mindre vatten kan bortföras. Temperaturförändringar har ingen effekt på separation av CNF och vatten. Vid ett applicerat fast kompressibelt tryck på 3 kPa och en initial koncentration 1.5 w% kan koncentrationerna 5.5 w%, 1.5 w%, 4.0 w%, och 4.3 w% nås för CNF1, CNF2, CNFA, och CNFB. Efter extrapolering av polynoma funktioner passad till experimentell data förutspås att koncentrationerna 9.1 w%, 1.5 w%, 6.9 w%, och 7.9 w% kan nås för CNF1, CNF2, CNFA, and CNFB vid 22 kPa och en initial koncentration på 1.5 w%. Förtjockningen av CNF suspensioner som kan, eller förutspås kunna nås genom centrifugering i det här examensarbetet innebär att det är möjligt att avlägsna stora mängder vatten, till exempel kan vatteninnehållet i CNF1 minskas från 65.7 liter/kg CNF till 10.0 liter/kg CNF vid 22 kPa fast kompressionstryck. Koncentrationerna vid 22 kPa fast kompressionstryck är extrapolerade från exprimentell data &lt;3 kPa fast kompressionstryck. Den karboy- metylerade CNF2 kan inte avvattnas om den inte späds ut eller om salt eller pH justeras. Detta är direkt kopplat till de elektrostatiska krafterna i suspensionen och Debye längden. Tillsats av salt eller sänkt pH eliminerar också de koncentrationsgradienter som kan förekomma i utspädda centrifugerade CNF2 suspensioner.

This work describes three alternative processes for producing microfibrillated cellulose (MFC; also referred to as cellulose nanofibrils, CNF) in which bleached pulp fibres are first pretreated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated by a combined enzymatic and mechanical pretreatment. In the two other processes, cell wall delamination was facilitated by pretreatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethylcellulose (CMC) to the fibres. All three processes are industrially feasible and enable energy-efficient production of MFC. Using these processes, MFC can be produced with an energy consumption of 500–2300 kWh/tonne. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long. The MFCs were also evaluated in a number of applications in paper. The carboxymethylated MFC was used to prepare strong free-standing barrier films and to coat wood-containing papers to improve the surface strength and reduce the linting propensity of the papers. MFC, produced with an enzymatic pretreatment, was also produced at pilot scale and was studied in a pilot-scale paper making trial as a strength agent added at the wet-end for highly filled papers. / <p>QC 20150126</p>

This work focuses on proposition of transfer of the expressions entered in the C pro­gramming language into DIMACS format and creation of program in programming language C++ making this transfer. This work contains a description of the C pro­gramming language and its operators. It also con­tains a description of the conjunctive normal form and a descri­ption of the DIMACS format. Following is a proposal for a program for the transfer of expression in the C programming language to the DIMACS format and description of reali­zation of program performing this transfer.

The growing need for computer software in different sectors of activity, (health, agriculture, industries, education, aeronautic, science and telecommunication) together with the increasing reliance of the society as a whole on information technology, is placing a heavy and fast growing demand on complex and high quality software systems. In this regard, the anticipation has been on non-functional requirements (NFRs) engineering and formal methods. Despite their common objective, these techniques have in most cases evolved separately. NFRs engineering proceeds firstly, by deriving measures to evaluate the quality of the constructed software (product-oriented approach), and secondarily by improving the engineering process (process-oriented approach). With the ability to combine the analysis of both functional and non-functional requirements, Goal-Oriented Requirements Engineering (GORE) approaches have become de facto leading requirements engineering methods. They propose through refinement/operationalisation, means to satisfy NFRs encoded in softgoals at an early phase of software development. On the other side, formal methods have kept, so far, their promise to eliminate errors in software artefacts to produce high quality software products and are therefore particularly solicited for safety and mission critical systems for which a single error may cause great loss including human life. This thesis introduces the concept of Complementary Non-functional action (CNF-action) to extend the analysis and development of NFRs beyond the traditional goals/softgoals analysis, based on refinement/operationalisation, and to propagate the influence of NFRs to other software construction phases. Mechanisms are also developed to integrate the formal technique Z/Object-Z into the standardised User Requirements Notation (URN) to formalise GRL models describing functional and non-functional requirements, to propagate CNF-actions of the formalised NFRs to UCMs maps, to facilitate URN construction process and the quality of URN models. / School of Computing / D. Phil (Computer Science)

It was found that a significant improvement of mechanical properties of CFRPs can be achieved by the adjustment of the matrix properties such as toughness and CF/matrix adhesion via the chemical modification, as well as the physical modification by a small amount of cheap and environment-friendly nano fibers. Based on investigation of fracture mechanisms at macro/micro scale, the effects of matrix properties and nano fiber on the mechanical properties of CFRP have been discussed. Subsequently, the relationship has been characterized by a numerical model to show how to modulate the parameters of the matrix properties to achieve excellent fatigue properties of CFRP. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

Dans cette thèse, des particules de polymère fonctionnalisées en surface avec des groupes poly (éthylène glycol) (PEG) ont été synthétisées pour favoriser leur interaction avec les dérivés cellulosique via liaisons hydrogène intermoléculaires. Deux voies de synthèse ont été proposées pour obtenir ses composites cellulose/latex.La première voie est basée sur l'auto-assemblage induit par polymérisation (PISA) pour former des nanoparticules fonctionnalisées avant leur adsorption sur un substrat cellulosique. La PISA tire profit de la formation de copolymères blocs amphiphiles dans l'eau en combinant la polymérisation en émulsion avec les techniques de polymérisation radicalaire contrôlées (RDRP). Ces dernières sont utilisées pour synthétiser des polymères hydrophiles agissant à la fois comme précurseur pour la polymerization en émulsion d'un monomère hydrophobe, et comme stabilisant des particules de latex obtenues. Deux techniques de RDRP ont été étudiées : les polymérisations RAFT et SET-LRP. Des polymères hydrophiles à base de PEG de faible masse molaire ont été synthétisés en utilisant ses deux techniques qui sont ensuite utilisés pour la polymérisation d'un bloc hydrophobe dans l'eau. Le transfert de l'agent de contrôle au site de la polymérisation était difficile en utilisant la SET-LRP en émulsion, conduisant à la formation de larges particules. En utilisant la RAFT en émulsion, des particules nanométriques ont été obtenues, avec un changement morphologique observé en fonction de la taille du segment hydrophobe, puis adsorbées sur des nanofibrilles de cellulose (CNF).La seconde voie utilise la polymérisation en émulsion classique réalisée en présence de nanocristaux de cellulose (CNC) conduisant à une stabilisation Pickering des particules de polymère. L'interaction cellulose/particule est assurée grâce à l'ajout d’un comonomère à type PEG. Une organisation a été visualisé dans laquelle plusieurs particules de polymère recouvrent chaque CNC / In this thesis, polymer particles surface-functionalized with poly(ethylene glycol) (PEG) groups were synthesized to promote their interaction with cellulose derivatives via intermolecular hydrogen bond. Two synthetic routes were proposed to obtain such cellulose/latex composites.The first route was based on the polymerization-induced self-assembly (PISA) to form functionalized polymer nanoparticles prior to adsorption onto cellulosic substrate. PISA takes advantage of the formation of amphiphilic block copolymers in water by combining emulsion polymerization with reversible-deactivation radical polymerization (RDRP) techniques. The latter were used to synthesize well-controlled hydrophilic polymer chains, acting as both precursor for the emulsion polymerization of a hydrophobic monomer, and stabilizer of the final latex particles. Two RDRP techniques were investigated: reversible addition-fragmentation chain transfer (RAFT), and single electron transfer-living radical polymerization (SET-LRP). Low molar mass PEG-based hydrophilic polymers have been synthesized using both techniques, used for the polymerization of a hydrophobic block in water. The transfer of controlling agent at the locus of the polymerization was challenging for SET-LRP in emulsion conditions leading to surfactant-free large particles. Nanometric latex particles were obtained via RAFT-mediated emulsion polymerization, with morphology change from sphere to fibers observed depending on the size of the hydrophobic segment, which were then able to be adsorbed onto cellulose nanofibrils (CNFs).The second route used conventional emulsion polymerization performed directly in presence of cellulose nanocrystals (CNCs) leading to Pickering-type stabilization of the polymer particles. Cellulose/particle interaction was provided thanks to the addition of PEG-based comonomer. Original organization emerged where CNCs were covered by several polymer particles