Rozprawy doktorskie na temat „Z-pin”

Fibrous composites, having excellent mechanical properties in the direction of the fibres, have lower mechanical properties in the through thickness direction, controlled by resin. Z-pinning improves the delamination toughness (up to 500%) with a relatively modest reduction to the in-plane mechanical properties (typically 5-15%). This experimental study investigates the mechanical performance of Z-Pins bridging an existing delamination in fibre reinforced resin composites under pull-out (Mode I), shear-out (Mode II) and mixed mode loading conditions using a specially designed testing rig. In Mode II the opening displacement was restricted and measured by springs of three different stiffnesses. A new technique of needle assisted Z-Pin insertion was developed, in which prepreg panels were perforated with a steel needle in order to insert Z-Pins. This technique ensured the desired orientation of Z-Pins, improved pinning quality and removed the necessity of costly preforms used in the traditional UAZ method. Test specimens were blocks (15 mm x 15 mm x 6mm thick) of carbon-epoxy IM7/8552 composite in unidirectional (UD) and quasi-isotropic (QI) stacking sequences, with PTFE delamination film in the mid-plane recreating an existing crack, bridged with a single T300/9310 Z-Pin or a group of four pins of either 0.28 mm or 0.51 mm diameter. Three phases of pull-out were identified: Linear Phase (linear force-displacement curve), Crack Formation (unstable crack propagation phase) and Frictional Sliding (friction-controlled pull-out). Two phases of shear-out were identified: Linear Phase (with no energy loss) and Breaking Phase (where the fibrous structure of the Z-Pins is fractured, ending with Z-Pin breakage). In mixed mode specimens behaved similarly to pull-out for the pin angles up to 45°. For higher angles the behaviour was more similar to pure shear-out. The influence of the Z-Pin diameter, z-pinning depth, distance between adjacent Z-Pins, composite stacking sequence and pull-out speed on the Z-Pins behaviour were investigated. The results will be useful in the formulation of improved Z-Pin bridging laws for use in finite element models.

Z-pinning is a through-thickness reinforcement technology for polymer composite materials that has been developed and commercialised over the past fifteen years. The through-thickness reinforcement of composites with thin metallic or fibrous pins aids in suppressing delamination, improving impact damage tolerance and increasing joint strength. Z-pins are applied to the composite part during its manufacture. Pins are embedded within sheets of foam and placed over the unconsolidated part. Subsequently, the foam is compacted and the pins transferred into the part, which is usually an uncured prepreg. In this manner, large numbers of pins can be inserted quickly and easily. The pinned composite is then cured using conventional processes. The use of z-pins is currently limited to several high performance composite structures, most notably Formula One racing cars and F/A-18 E/F (Superhornet) fighter aircraft, although the technology has potential applications in a d iverse variety of aerospace and non-aerospace composite structures. A limited understanding of the mechanical performance of z-pinned parts under high load and fatigue loading conditions currently hinders the application of z-pinned composites. The aim of this PhD project is to investigate the mechanical properties, strengthening mechanics and failure mechanisms of z-pinned carbon/epoxy laminates and joints. The effect of z-pin reinforcement on the tensile and flexural properties of laminates under monotonic and fatigue loading is studied. The sensitivity of these properties to the volume content and diameter of the z-pins is systematically studied by experimentation and analytical modelling. This PhD also evaluates the efficacy of z-pins in improving the load-bearing properties of carbon/epoxy lap joints. Improvements to the room temperature and elevated temperature properties of z-pinned lap joints under monotonic and fatigue tensile loading were determined. The effect of strain rate on the load-bearing properties of z-pinned lap joints was also evaluated. A further aim of the PhD project was to assess the z-pin manufacturing process and the microstructural damage caused by that process. The outcome of this study augments the analysis of the me chanical properties of z-pinned laminates and joints.

Effective treatment of carbon fiber components to improve delamination resistance is vital to the application of such materials since delamination is one of the biggest concerns regarding the use of composites in the aerospace sector. Due to the significant application benefit gained from increased stiffness to density ratio with composite materials, innovative developments resulting in improved through-thickness strength have been on the rise. The inherent anisotropy of composite materials results in an added difficulty in designing structural elements that make use of such materials. Proposed techniques to improve the through-thickness strength of laminar composites are many and varied; however all share the common goal of improving inter-laminar bond strength. This research makes use of novel materials in the field of wet flocking and Z-pinning. Cellulose nanofibers (CNFs) have already demonstrated excellent mechanical properties in terms of stiffness and strength, originating at the nano-scale. These materials were introduced into the laminate while in a sol-gel suspension in an effort to improve load transfer between laminate layers. The effect of CNFs as lightweight renewable reinforcement for CFRPs will be investigated. Carbon nanotube (CNT) additives were also considered for their beneficial structural properties.
Master of Science

This thesis describes specific new applications of Z-Fibre ® pinning and focuses the attention onto the failure modes of locally reinforced (z-pinned) structures. Design implications of the use of localised reinforcement on structures, rather than laboratory coupons, are considered. Z-pinning reinforcement is applied to cylindrical crash tubes and I-section patch joints manufactured from woven carbon / epoxy pre-pregs. Z-pinning is shown to improve the Specific Energy Absorption (SEA) of the crash tubes by up to 76 %, the exact amount depending on the tube geometry. For the I-section patch joints, an initial increase in ultimate load carrying capability due to z-pin use is observed and, as the quantity of z- pins increases, a change in failure mode is induced. Z-pinning is also shown to enhance the damage tolerance of these. The ability to predict major changes to the structural response due to use of z-pins, and design for them accordingly, is the next step in the understanding of the technology. The design element of this study is contained in the development of a new Finite Element model using cohesive interface elements. The provision of mode II input data for this model comes from End Loaded Split (ELS) testing of the woven laminates and continued development of the Z-shear test. A new analysis for quantifying the crack sliding displacement, based on the ELS test, is developed. Z-shear testing has shown that the z-pin ‘mode II’ fracture energy is strongly affected by the amount of mode I opening of the shear surfaces. Here, new data are obtained for a fully constrained, pure mode II case. Using this modelling tool, changes in failure mode due to z-pin use can be predicted. Verification is provided by a new simulation of the I-section patch joint geometry.

Ce memoire presente une mesure de la production inclusive de pio dans les desintegrations hadroniques du z#o avec l'experience aleph au lep. Cette mesure s'inscrit dans le cadre de l'etude de la production des hadrons issus de la fragmentation des quarks et des gluons, decrite pour la partie perturbative par la chromodynamique quantique et pour la partie non perturbative par des modeles phenomenologiques. Nous commencons par une breve revue de l'etat actuel des connaissances sur ces deux aspects de la fragmentation. L'analyse presentee ensuite utilise deux millions d'evenements, selectionnes parmi les donnees prises par aleph pendant les annees 1992, 93 et 94. Les pio sont reconstruits a partir de leur desintegration en deux photons. Ces photons sont identifies soit par leur depot d'energie dans le calorimetre electromagnetique, soit a partir de leur conversion en une paire electron-positron, detectee dans les chambres a traces. Au cours des differentes etapes de la selection des photons, les efficacites calculees avec le monte-carlo sont controlees a l'aide des donnees elles-memes. Le signal des pio est alors extrait par un ajustement des distributions de masse invariante photon/photon. Les trois combinaisons de photons (converti/calorimetrique, calorimetrique/calorimetrique et converti/converti) sont utilisees. Les sections efficaces differentielles en energie, impulsion transverse et rapidite sont mesurees. Le nombre de pio mesures par evenement pour e#p#i#o superieure a 1. 14 gev est: n(pio) = 5. 24 0. 02 (stat. ) 0. 29 (syst. ) ces resultats sont compares a ceux obtenus par d'autres experiences lep, aux resultats obtenus par aleph sur les pions charges, ainsi qu'aux predictions de differents generateurs d'evenements. Un accord raisonnable est observe, meme si nous mesurons une section efficace legerement superieure, l'ecart atteignant deux deviations standard a basse energie. Pour terminer, une breve etude topologique est presentee, utilisant les variables globales d'evenement

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-04-25T11:14:43Z No. of bitstreams: 1 2012 - Liane Caroline S Nascimento.pdf: 1534381 bytes, checksum: a4191d92ac386756692de94030e95ef7 (MD5)
Made available in DSpace on 2017-04-25T11:14:43Z (GMT). No. of bitstreams: 1 2012 - Liane Caroline S Nascimento.pdf: 1534381 bytes, checksum: a4191d92ac386756692de94030e95ef7 (MD5) Previous issue date: 2012-06-25
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
This paper describes the investigation of the centesimal composition, chemical and antioxidant activity of Morinda citrifolia L. (Rubiaceae), native of Southeast Asia, popularly known as noni, which has emerged in Brazil as a plant with great healing potential. The empirical knowledge of the population has meant that the fruit is constantly present in the diet of Maranh?o. Early in the second half of 2010 seedlings of the species were planted in two experimental areas of the Federal Institute of Maranh?o (IFMA), Campus of Z? Doca-MA, broken down by planting time. After three months of the planting in the first area the fruiting process was initiated, and it was possible to perform bromatologic analyzes. For the centesimal composition was found in pulp, seed and mixtures of both, respectively: the ash content (0,82%?0,01; 0,60%?0,01 e 0,79%?0,03), moisture (90%?0,01; 28,34%?0,01; 80,64%?0,05), proteins (4,2%?0,01; 7,47%?0,06; 4,70%?0,02), total lipids (0,34%?0,04; 0,79%?0,03; 0,63%?0,07), carbohydrates (2,68%?0,01; 25,83%?0,02; 13,24%?0,01) and calorific value (30,58kcal/100g?0,02; 140,31 kcal/100g?0,03; 77,43 kcal/100g?0,03). It was found in the pulp and seed values soluble dietary fiber (0,51?0,04; 0,93%?0,03) and insoluble (1,44?0,05; 36,04%?0,38). For the chemical characterization it was found in the pulp, seed and mixtures of both: ? Brix (8,17?0,05;-), the total acidity (0,54?0,02; 0,28?0,01; 0,62?0,02%) and pH (3,95?0,07; 4,5?0,04; 4,1?0,05), the relationship TA / SS pulp was 14.97?0,07. The content of ascorbic acid was calculated by the method Tilmans, pulp and seed fractions (117,33?0,01; 24,33?0,03), expressed in mg/100 g sample. The antioxidant capacity analyzes were performed in three different parts: the pulp, peel and seed using alcoholic extracts (11,63?0,07; 10,03?0,04; 11,19?0,01) and aqueous extract (7,20?0,07; 6,98?0,07; 7,60?0,01) through the sequestration of free radical DPPH, expressed in mM of Trolox / g sample. It was further evaluated the antioxidant capacity of different extracts of the three parts of the fruit and alcoholic extract (98.78% in pulp, 84.76% in peel and 94.96% in the seed) showed much higher antioxidant capacity than the aqueous extract ( 8.08% in the pulp, 5.22% in peel and 22.66% in the seed) and the prominence given to the pulp, followed by seed and peel, respectively. It was demonstrated that the noni fruit grown in the municipality of Z? Doca presented a rich source of nutrition important fact that justifies its inclusion in the diet. It should be noted that the pulp showed a high content of vitamin C and antioxidant activity, and seed a significant amount of insoluble fiber, suggesting that this product can be inserted in the consumer market for being a nutritious food with great herbal medicine potential
Este trabalho descreve a investiga??o da composi??o centesimal, qu?mica e atividade antioxidante de Morinda citrifolia L. (Rubiaceae), origin?rio do sudoeste da ?sia, popularmente conhecida como noni, que vem se configurando no territ?rio brasileiro como um vegetal com grande potencial fitoter?pico. O conhecimento popular tem feito com que o fruto esteja presente constantemente na dieta alimentar maranhense. No in?cio do segundo semestre de 2010 foram plantadas mudas da esp?cie em duas ?reas experimentais do Instituto Federal do Maranh?o (IFMA), Campus Z? Doca-MA, divididas por ?poca de plantio. Ap?s tr?s meses do plantio na primeira ?rea o processo de frutifica??o foi iniciado, sendo poss?vel realizar as an?lises bromatol?gicas. Para composi??o centesimal verificou-se na polpa, semente e mistura de ambos, respectivamente: o teor de cinzas (0,82%?0,01; 0,60%?0,01 e 0,79%?0,03); a umidade (90%?0,01; 28,34%?0,01; 80,64%?0,05); prote?nas (4,2%?0,01; 7,47%?0,06; 4,70%?0,02); lip?deos totais (0,34%?0,04; 0,79%?0,03; 0,63%?0,07); carboidratos (2,68%?0,01; 25,83%?0,02; 13,24%?0,01) e valor cal?rico (30,58 kcal/100g?0,02; 140,31 kcal/100g?0,03; 77,43 kcal/100g?0,03). Verificou-se na polpa e semente os valores de fibras alimentares sol?veis (0,51?0,04; 0,93%?0,03) e insol?veis (1,44?0,05; 36,04%?0,38). Para caracteriza??o qu?mica verificou-se na polpa, semente e mistura de ambos: o ?Brix (8,17?0,05;-), a acidez total (0,54?0,02; 0,28?0,01; 0,62?0,02%) e o pH (3,95?0,07; 4,5?0,04; 4,1?0,05), a rela??o ATT/SS na polpa foi de 14,97?0,07. O Teor de ?cido asc?rbico foi calculado pelo m?todo Tilmans, nas fra??es polpa e semente (117,33?0,01; 24,33?0,03), expressos em mg/100g amostra. As an?lises da capacidade antioxidante foram realizadas em tr?s partes diferentes: polpa, casca e semente utilizando extrato alco?lico (11,63?0,07; 10,03?0,04; 11,19?0,01) e extrato aquoso (7,20?0,07; 6,98?0,07; 7,60?0,01), atrav?s do sequestro do radical livre DPPH, expressos em ?M de Trolox/g amostra. Foi ainda avaliada a capacidade antioxidante dos diferentes extratos, das tr?s partes do fruto e o extrato alco?lico (98,78% na polpa; 84,76% na casca e 94,96% na semente) apresentou capacidade antioxidante bem maior que o extrato aquoso (8,08% na polpa, 5,22% na casca e 22,66% na semente) sendo o destaque dado ? polpa, seguido da semente e da casca, respectivamente. Demonstrou-se que os frutos do noni cultivados no munic?pio de Z? Doca apresentaram uma rica fonte nutricional importante fato que justifica sua inser??o na dieta alimentar. Cabe destacar que a polpa apresentou um elevado teor de vitamina C, e atividade antioxidante, e a semente um relevante teor de fibras insol?veis, sugerindo que esse produto pode ser inserido no mercado consumidor por ser um alimento nutritivo e com grande potencial fitoter?pico.

Il numero di casi riguardanti patologie neurodegenerative che colpiscono il sistema nervoso centrale sotto forma di demenza aumenta di anno in anno. Si ha quindi la necessità di individuare la presenza della malattia non solo a livello qualitativo, ovvero tramite la sola diagnosi del medico, ma anche a livello quantitativo, cercando di elaborare un metodo di analisi che tenga conto della variabilità tra individuo e individuo, ma che rimanga applicabile per la maggior parte della popolazione. In questo lavoro di tesi sono stati utilizzati due metodi di analisi statistica di immagini PET cerebrali, denominati SPM e SSP Z-score, al fine di individuare mappe statistiche 3D che evidenzino, con probabilità fissata, le aree del cervello colpite. Entrambe le analisi statistiche si basano su un confronto del paziente con un gruppo di soggetti sani. Le immagini elaborate in questo lavoro di tesi provengono dal database dell'Ospedale di Parma, registrate dallo stesso scanner PET-CT, con l'utilizzo di traccianti diversi, denominati FDG e PiB marcato Fluoro. I due traccianti rilevano uno stato cerebrale anomalo, ma attraverso due indicatori diversi: FDG rende visibile l'afflusso sanguigno all'interno del cervello, legato al metabolismo; il PiB invece è in grado di rilevare i depositi di beta-amiloide, una proteina che, legandosi ai tessuti cerebrali, forma delle placche in grado di bloccare la connessioni tra neuroni. I traccianti sono legati al radionuclide 18F. Le analisi sono state effettuate principalmente su pazienti con morbo di Alzheimer utilizzando i due metodi di analisi precedentemente introdotti. Sono anche stati confrontati attraverso SPM due gruppi di pazienti con iniziale demenza lieve, che nel tempo si è evoluta in morbo di Alzheimer in alcuni casi, mentre in altri non sono state riscontrate variazioni. Infine, tramite un approccio SPM, sono stati valutati due template diversi per determinare quale potesse essere considerato migliore per l'analisi quantitativa.

L'etude de la desintegration du z en une paire de leptons tau est faite au lep, grand collisionneur electron-positron du cern, avec le detecteur aleph. L'amplitude du processus etudie (l'annihilation d'une paire electron-positron en un z qui se desintegre en une paire de leptons tau) est fonction des constantes des couplages vectoriel et vectoriel-axial, dont le rapport depend quadratiquement de la masse du top. La polarisation des leptons produits est l'observable la plus sensible a ce rapport, et n'est mesurable que dans le cas des tau, a l'aide de l'analyse des spectres en impulsion des pions d'une part et des muons d'autre part produits dans la desintegration des tau. Apres une description des methodes employees pour la selection de ces pions et ces muons, fondees essentiellement sur la chambre a projection temporelle et les calorimetres electromagnetique et hadronique d'aleph, on donne une estimation de la polarisation et on en deduit une valeur de l'angle de weinberg avec les statistiques actuelles; les methodes exposees ici permettront par la suite une estimation de la masse du top

In this study, two symbiotic fungi of Southern Pine Beetle (SPB), Entomocorticium peryii and Entomocorticium sp.A were evaluated in terms of polyphenol oxidase (PPO) production. The effect of different inhibitors, inducers and assay parameters such as temperature and pH on enzyme activity were investigated and maximum PPO activity was observed at 30°
C, pH 8.0 and when tannic acid was used as an inducer. Copper-chelator salicyl hydroxamic acid (SHAM) and pcoumaric acid, both indicated as inhibitors of tyrosinase and catechol oxidase significantly reduced the activity. For biochemical characterization studies, the enzyme was concentrated by ultrafiltration. To determine type of the enzyme, activity staining after Native-PAGE was carried out. Type of polyphenol oxidase produced by E. peryii and E. sp.A was determined as catechol oxidase by activity staining. However higher activity was observed on hydroquinone (p-diphenol) rather than catechol (o-diphenol). The enzyme obeys Michealis-Menten kinetics with Km and Vmaxvalues being 10.72 mM hydroquinone and 59.44 U/ml for E. peryii and 8.55 mM hydroquinone and 73.72 U/ml for E. sp.A respectively..

Táto diplomová práca sa zaoberá implementáciou bezpečnostnej funkcie pre elektrický aktuátor, ktorá spočíva v riadení BLDC motora, po výpadku napájacieho napätia, keď je aktuátor poháňaný vstavanou pružinou.. Celé riadenie motora je navrhnuté v prostredí Matlab-Simulink technikou nazývanou návrh systému z modelu. Následne pomocou automatického generovania kódu bol získaný zdrojový kód, ktorý bol použitý v reálnom aktuátore a odtestovaný v reálnych podmienkach. Cieľom týchto testov bolo overiť reálnu možnosť nasadenia vyvinutých algoritmov v reálnych, komerčne dostupných produktoch.

Tato diplomová práce se zabývá netradičními druhy biomasy využitelnými v České republice a Španělsku a jejich srovnáním. V prvních kapitolách jsou popsány netradiční druhy biomasy, mezinárodní projekty, smlouvy a legislativa. V následujích kapitolách je rozbor netradičních druhů biomasy zejména vznikajících z potravinářského průmyslu každé země s detailním rozborem a srovnáním zbytků z průmyslového zpracování slunečnice a oliv. V závěru je uděláno celkové srovnání těchto druhů biomasy České republiky a Španělska z aspektů výkupních cen, výhřevností, vlhkosti a množství popelovin.

The bearing behavior of bolted composite joints is significantly poorer than that of their metallic counterparts. The objective of the present study was to examine ways of improving the bearing performance of bolted joints in carbon fibre reinforced epoxy laminates. Two strategies were examined, namely stiffening of the matrix using nanofillers and through- thickness reinforcement of the laminates using z- pins. The development of a nanoparticle reinforced matrix resin, and its performance in a composite loaded in bearing, was the focus of the first part of the study. A commercial nanoclay, I30E from Nanocor, was chosen as the reinforcement since the nanoclay particles are modified with long alkyl chain amines which improves dispersion in the epoxy resin. The c onditions for preparing nanocomposites based on the nanoclay were examined for two epoxy resin systems , DGEBA and TGDDM. Significant improvements in the elastic modulus were obtained , with a 20% increase being recorded w ith 8.4 phr nanoclay content in the DGEBA resin and a 50% increase with 20 phr nanoclay content in the TGDDM system. Carbon fibre reinforced laminates w ere prepared from nanoclay reinforced TGGDM matrix resin, using a vacuum assisted prepregging process. The bearing strength and stiffness of the laminated composites was improved by 7% and 15% respectively but the strain to failure was reduced. The addition of nanoclay to the matrix resin was found to change the failure mode. Enhancement of the bearing performance of laminates by through-thickness reinforcement (z-pins) was examined as the second strategy trialed in this thesis. The bearing strength, stiffness and energy to failure of carbon fibre laminates was found to increase progressively with increasing volume content of z-pins , with increases of 10%, 10% and 16%, respectively , being achieved at a z-pin volume content of 4%. No significant change in strength, stiffness or failure energy was observed when the z-pin diameter was changed from 0.28 to 0.51 mm at the same volume content.

碩士
聖約翰科技大學
自動化及機電整合研究所
102
Since the inverted pendulum is a non-linear, single input multi-output system with the characteristics of non-minimum phase and instability, it is widely used by scholars and researchers for verifying the performance of various controllers.This paper proposes the use of PID controller is applied to single-axis inverted pendulum control system balance and add parameters to adjust the Ziegler-Nichols method and genetic algorithm to compute approximate solutions of optimal PID parameters to avoid ever by an expert system design, time-consuming trial and error or subjective experience method to design the controller parameters to achieve the goal of intelligent search optimization parameters and time-saving controller design.In the simulation and experiment, proposed a simple PID controller architecture and applied Ziegler-Nichols method and genetic algorithm parameter tuning PID controller to adjust the search parameters, to design a perfect system PID controller, succeeded in getting the formula down uniaxial pendulum stability control system vertically upwards.Moreover, after a comparison and analysis on the control performance of each controller, found that the above two methods designed to control the performance of the controller is relatively good genetic algorithm PID controller. Finally, through a single-axis platform inverted pendulum experiment proves the genetic algorithm PID controller in inverted pendulum control system is feasible.