Friction continues to be one of the main causes of energy loss in mechanical systems despite the advances in technology. As a result, this not only involves energy overuse but also maintains high levels of CO2 emissions that cannot be assumed if society wishes to shift towards a more sustainable industry. In this regard, textured surfaces have proven to be a useful feature to decrease or increase friction between two surfaces in contact. Through several pin-on-disk tribotests, this thesis aims to study the influence of three different textures on the friction coefficient: crosspatched, circumferential smooth, and circumferential rough. Height and functional parameters were extracted from the surfaces by measuring them with an optical profiler to study their influence on the tribological properties of the disks. The wear volume and film parameter were also calculated from the measured data. The crosspatched texture yielded the lowest coefficient of friction, followed by circumferential smooth and circumferential rough. The highest values of the film parameter and lowest values of wear volume were achieved by the circumferential smooth texture. Three significant correlations were found: The Sdr parameter and the Svk/Spk ratio are statistically related to the film parameter. The interaction between Sdr and Sk is correlated with the friction coefficient, although their relation does not have a practical use. Future possibilities for research can be centred around studying the validity of these correlations and the phenomena behind them, as well as expanding the study of crosspatched textures to further optimize friction. / Friktion fortsätter att vara en av de främsta orsakerna till energiförluster i mekaniska system trots teknikens framsteg. Som ett resultat av detta, innebär det inte bara överanvändning av energi utan även höga nivåer av CO2-utsläpp upprätthålls vilket inte kan antas om samhället vill ställa om mot en mer hållbar industri. I detta avseende har texturerade ytor visat sig vara en användbar egenskap för att minska eller öka friktionen mellan två ytor i kontakt. Genom flera pin-on-disk-tribotester, syftar denna avhandling till att studera inverkan av tre olika texturer på friktionskoefficienten: korspatchad, periferiell slät, och periferiell grov. Höjd- och funktionsparametrar extraherades från ytorna genom att mäta dem med en optisk profilerare för att studera deras inverkan på skivornas tribologiska egenskaper. Slitvolymen och filmparametern beräknades också från den uppmätta data. Den korspatchade texturen gav den lägsta friktionskoefficienten, följt av periferiell slät och periferiell grov. De högsta värdena för filmparametern och de lägsta värdena för slitagevolymen uppnåddes genom den periferiella släta texturen. Tre signifikanta korrelationer hittades: Sdr-parametern och Svk/Spk förhållandet är statistiskt relaterade till filmparametern. Interaktionen mellan Sdr och Sk är korrelerad med friktionskoefficienten, även om deras relation inte har någon praktisk användning. Framtida möjligheter för forskning kan centreras kring att studera giltigheten av dessa korrelationer och fenomenen bakom dem, samt att utöka studiet av korspatchade texturer för att ytterligare optimera friktionen.

Bolts and nuts are one of most common joining methods since they are simple and low-cost to connect parts. Appropriate clamp force from bolted joint remains resultant joints secured, but higher/lower preload on bolted joint increases risk of the failure of mechanism. Therefore, achieving accurate clamp force in bolted joint is always the aim of tightening process. Torque control tightening tool are the most common tightening tool present in the market. The clamp force obtained from torque control tightening is highly dependent upon friction. Only small part of applied torque is transferred into the effective torque that turns in to clamp forces because most of applied torque is consumed by friction forces under bolt /nut head and in a thread interface. However, friction coefficient does not remain constant during tightening process and it relates to many factors such as tightening speed, speed profile, tightening time, joint’s material, etc. Hence, it changes the distribution ratio and leads to an error in estimation of clamp force between the components. This project aims to develop a tribometer which is capable of operating in different speeds and load conditions corresponding to different tightening process. A new concept of pin-on-disc tribometer is proposed and the speed and load profile are achieved by using closed loop control in the linear actuator and the motor. The test rig was built up and the several validation tests were done. / Skruv och mutter tillhör bland de vanligaste medlen att binda ihop två ytor med varandra då det är ett billigt och enkelt sätt att uppnå det önskade resultatet. Det är viktigt att rätt klämkraft uppnås i skruvförbandet, vid för låg/hög klämkraft är risken för haveri i konstruktionen stor. Därför är att uppnå korrekt klämkraft i ett skruvförband alltid målet i en åtdragningsprocess. Skruvdragare som drar åt med ett förinställt moment (torque control) är för tillfället det vanligaste verktyget på marknaden för att uppnå rätt klämkraft. Klämkraften som uppstår vid åtdragning av ett skruvförband med ett sådant verktyg är i största del beroende på friktionskraften i skruvförbandet för korrekt moment. Endast en liten del av momentet som påverkar skruven övergår till effektivt fasthållande moment i skruvförbandet, det mesta momentet går åt för att övervinna friktionen mellan skruv och mutter. Friktionskoefficitenten håller sig inte konstant vid ett åtdragande moment utan beror på flera faktorer såsom åtdragningshastighet, profilhastighet, åtdragningstid och vilket material skruvförbandet är gjort av bland annat. Eftersom friktionskoeffiecienten ständigt ändrar sig leder detta till ett fel då man ska uppskatta klämkraften mellan två ytor. Detta examensarbete ämnar till att bygga en tribometer som är kapabel till att fungera vid olika hastigheter och kraftförhållanden som korresponderar till olika åtdragningsprocesser. Ett koncept på en ny pin-on-disc tribometer föreslås och hastighets samt kraftprofiler skapas genom ett closed-loop reglertekniksystem i ett linjärt ställdon och motorn. Testriggen konstruerades och flertalet utvärderingstester utfördes.

Ce mémoire présente les résultats d’une étude ayant pour but de modéliser la remontée de la cime du pin gris en vue de son utilisation par le modèle de croissance forestière CROBAS. Pour ce faire, des peuplements de pin gris présentant des différences en termes d’âge, de densité et de qualité de station ont été échantillonnés. Différents modèles de hauteur de la base de la cime vivante ont été calibrés, certains provenant d’adaptations de modèles présents dans la littérature scientifique, d’autres provenant d’une sélection pas-à-pas de variables. Les équations des modèles de hauteur de la base de la cime vivante ont été dérivées par rapport au temps afin de les transformer en modèles de remontée de cime. Les valeurs prédites par les équations ont ensuite été comparées à des taux de remontée de cime calculés à l’aide de la datation de la mort des branches situées sous la base de la cime vivante. La dérivée, par rapport au temps des équations de la hauteur de la base de cime vivante, a permis de modéliser avec succès la remontée de la cime vivante. La croissance en hauteur du pin gris, de même que l’intensité de la compétition latérale expérimentée par l’arbre, semblent être les deux principaux facteurs qui déterminent le taux de remontée de la base de la cime vivante. Les modèles expliquent une quantité significative de la variation de la remontée de la cime calculée à l’aide de l’analyse rétrospective des branches mortes. / Jack pine crown recession was studied using data from stands varying in age, density and site index. The resulting model should be included in the CROBAS forest growth model. As a first step, several crown height equations were derived from previously published results and from a stepwise selection. These equations were then derived with respect to age to estimate crown recession rates. Predicted crown recession rates were then compared to a data set of crown recession values calculated from dated branch mortality. The proposed method of using the time was able to explain a significant amount of the observed crown recession rate. Height growth and stand competition seem to be the main factors that influence crown recession rate.

Este trabalho descreve um ataque que detecta as teclas pressionadas em teclados mecânicos pela análise das vibrações geradas quando as mesmas são pressionadas. Dois equipamentos foram experimentados no ataque: um teclado genérico de automação comercial e um terminal de ponto de venda (POS / PIN-pad). Acelerômetros são utilizados como sensores de vibração. Propositalmente, o equipamento necessário para a execução do ataque é de baixíssimo custo, de modo a ressaltar o risco das vulnerabilidades encontradas. Obtivemos taxas de sucesso médio de 69% no reconhecimento das teclas pressionadas para o terminal PIN-pad em repouso e 75% para o mesmo sendo segurado na mão. No caso de teclado de automação comercial, as taxas médias de acerto ficaram em torno de 99%. / This work describes an attack that identifies the sequence of keystrokes analyzing mechanical vibrations generated by the act of pressing keys. We use accelerometers as vibration sensors. The apparatus necessary for this attack is inexpensive and can be unobtrusively embedded within the target equipment. We tested the proposed attack on an ATM keypad and a PIN-pad. We achieved the key recognition rates of 99% in ATM keypad, 69% in PIN-pad resting on a hard surface and 75% in PIN-pad hold in hand.

Este trabalho descreve um ataque que detecta as teclas pressionadas em teclados mecânicos pela análise das vibrações geradas quando as mesmas são pressionadas. Dois equipamentos foram experimentados no ataque: um teclado genérico de automação comercial e um terminal de ponto de venda (POS / PIN-pad). Acelerômetros são utilizados como sensores de vibração. Propositalmente, o equipamento necessário para a execução do ataque é de baixíssimo custo, de modo a ressaltar o risco das vulnerabilidades encontradas. Obtivemos taxas de sucesso médio de 69% no reconhecimento das teclas pressionadas para o terminal PIN-pad em repouso e 75% para o mesmo sendo segurado na mão. No caso de teclado de automação comercial, as taxas médias de acerto ficaram em torno de 99%. / This work describes an attack that identifies the sequence of keystrokes analyzing mechanical vibrations generated by the act of pressing keys. We use accelerometers as vibration sensors. The apparatus necessary for this attack is inexpensive and can be unobtrusively embedded within the target equipment. We tested the proposed attack on an ATM keypad and a PIN-pad. We achieved the key recognition rates of 99% in ATM keypad, 69% in PIN-pad resting on a hard surface and 75% in PIN-pad hold in hand.

La recherche de cette thèse s’articule autour de mon travail plastique de la série « Raw Meat » où je me sers exclusivement de l’image publicitaire de viande crue que je détourne pour construire des corps féminins. Elle répond à la question suivante : Pourquoi sommes-nous affectés par la vue, par l’aspect de la matière de la viande crue ; et pourquoi sommes-nous davantage affectés lorsque la viande crue forme – ou fusionne avec – le corps de la femme ? L’origine de la force de cette image est ciblée comme issue de notre passé primitif ; la recherche soulève nos liens les plus profonds avec la chair animale et ses pratiques liées aux sociétés primitives, et démontre comment les mythes, les rites, et les interdits autour du corps animal/humain sont toujours à l’œuvre. Nous soutenons les hypothèses d’une image comestible, de l’œil cannibale, de la pulsion scopique au sein d’une œuvre, du regard pulsionnel, voire criminel de l’artiste, de la cruauté de l’être, du dévoilement, de l’image violente (de la femme) et de sa sublimation. Nous regardons comment les différents mécanismes à l’œuvre dans l’image de la femme, à l’instar de la série « Raw Meat », permettent une multitude d’interprétations de la chair, dont les sens vont de notre passé primitif à notre contemporanéité. Notre plaidoyer pour cette polysémie est celle de la nécessité de cette image « vraie » de femme, à l’image de son émancipation. / The research of this thesis focuses upon a series of my artwork in which I utilizeadvertisement photographs taken from local supermarket flyers that depict raw meat. I use these to construct female figures. The research responds to the inquiry: Why are we affected by the image of raw meat; and why are we even more so affected when the images of raw meat compose – or fuse with – the female figure? The origin of the effect this image has on the spectator is targeted as being found within our primitive past; stemming from our relationship with the animal flesh, and thus with the animal itself. We illustrate our profound ties to the animal, including surrounding acts which were an integral part of daily lives in primitive societies. We show how the myths, rites, and taboos, associated with the animal/human body are still at work today. The research supports different hypotheses: the edible image, the cannibal’s eye, the “scopique” impulse within an artwork (relative to the eye), and the criminality of the artist, a being’s cruelty, the unveiling of the body, violent images (of women) and their sublimation. We plead the necessity of this never-been-seen-before, polysemous, “true” image of the female figure whose significance spans from our primitive past to contemporary societies; as one of her emancipation.

Aukštųjų energijų fizikos eksperimentuose plačiai taikomi puslaidininkiniai pin struktūros dalelių detektoriai jonizuojančiosioms dalelėms registruoti. Radiacinė spinduliuotė sukuria defektus medžiagoje ir neigiamai įtakoja detektorių parametrus, todėl būtina charakterizuoti apšvitintus detektorius ieškant būdų, kaip juos patobulinti. Apšvitintų detektorių charakterizavimui taikomi volt-amperinių, volt-faradinių būdingųjų dydžių matavimai ir analizė, giliųjų lygmenų talpinė bei šiluma skatinamų srovių spektroskopija. Tačiau stipriai apšvitintuose detektoriuose, kai defektų koncentracija viršija legirantų koncentraciją bei išauga nuotėkio srovė, šie metodai negali būti taikomi siekiant korektiškai įvertinti radiacinių defektų parametrus. Šiame darbe buvo sukurti modeliai, apibūdinantys slinkties sroves, tekančias detektoriuje dėl elektrinio lauko persiskirstymo keičiantis išorinei įtampai arba elektriniame lauke judant injektuotam krūviui. Šie modeliai buvo pritaikyti naujų metodikų sukūrimui, kurios įgalina įvertinti krūvio pernašos, pagavimo, rekombinacijos/generacijos parametrus stipriai apšvitintuose detektoriuose po apšvitos. Sukurti metodai buvo pritaikyti defektų spektroskopijai ir skersinei žvalgai sluoksninėse struktūrose bei defektų evoliucijos tyrimams apšvitos metu. Disertacijoje pateikti ir aptarti apšvitintų detektorių ir apšvitos metu pasireiškiančios parametrų kaitos rezultatai. Elektronikos grandynuose plačiai naudojami galios pin struktūros diodai, kurie... [toliau žr. visą tekstą] / In high energy physics experiments the semiconductor particle detectors of pin structure are commonly employed for tracking of the ionising particles. However, ionising radiation creates defects and consequently affects the parameters of particle detectors. Therefore, it is necessary to characterize irradiated detectors and search for the new approaches on how to suppress or control the degradation process. Measurements of current-voltage, capacitance-voltage characteristics as well as deep level transient spectroscopy, thermally stimulated currents spectroscopy are employed for the characterization of irradiated particle detectors. At high irradiation fluences when defects concentration exceeds that of dopants, a generation current increases and, thus, the above mentioned techniques can not be applied for the correct evaluation of defect parameters. In this work, models describing displacement currents in detectors due to redistribution of electric field determined by variations of external voltage or a moving charge in electric field are discussed. These models were applied for creation of the advanced techniques which allow evaluating of charge transport, trapping and recombination/generation parameters in heavily irradiated detectors after irradiation. These techniques were applied for the spectroscopy of deep levels associated with defects, for cross-sectional scans within layered junction structures as well as for examination of defects evolution during irradiation. In... [to full text]

In high energy physics experiments the semiconductor particle detectors of pin structure are commonly employed for tracking of the ionising particles. However, ionising radiation creates defects and consequently affects the parameters of particle detectors. Therefore, it is necessary to characterize irradiated detectors and search for the new approaches on how to suppress or control the degradation process. Measurements of current-voltage, capacitance-voltage characteristics as well as deep level transient spectroscopy, thermally stimulated currents spectroscopy are employed for the characterization of irradiated particle detectors. At high irradiation fluences when defects concentration exceeds that of dopants, a generation current increases and, thus, the above mentioned techniques can not be applied for the correct evaluation of defect parameters. In this work, models describing displacement currents in detectors due to redistribution of electric field determined by variations of external voltage or a moving charge in electric field are discussed. These models were applied for creation of the advanced techniques which allow evaluating of charge transport, trapping and recombination/generation parameters in heavily irradiated detectors after irradiation. These techniques were applied for the spectroscopy of deep levels associated with defects, for cross-sectional scans within layered junction structures as well as for examination of defects evolution during irradiation. In... [to full text] / Aukštųjų energijų fizikos eksperimentuose plačiai taikomi puslaidininkiniai pin struktūros dalelių detektoriai jonizuojančiosioms dalelėms registruoti. Radiacinė spinduliuotė sukuria defektus medžiagoje ir neigiamai įtakoja detektorių parametrus, todėl būtina charakterizuoti apšvitintus detektorius ieškant būdų, kaip juos patobulinti. Apšvitintų detektorių charakterizavimui taikomi volt-amperinių, volt-faradinių būdingųjų dydžių matavimai ir analizė, giliųjų lygmenų talpinė bei šiluma skatinamų srovių spektroskopija. Tačiau stipriai apšvitintuose detektoriuose, kai defektų koncentracija viršija legirantų koncentraciją bei išauga nuotėkio srovė, šie metodai negali būti taikomi siekiant korektiškai įvertinti radiacinių defektų parametrus. Šiame darbe buvo sukurti modeliai, apibūdinantys slinkties sroves, tekančias detektoriuje dėl elektrinio lauko persiskirstymo keičiantis išorinei įtampai arba elektriniame lauke judant injektuotam krūviui. Šie modeliai buvo pritaikyti naujų metodikų sukūrimui, kurios įgalina įvertinti krūvio pernašos, pagavimo, rekombinacijos/generacijos parametrus stipriai apšvitintuose detektoriuose po apšvitos. Sukurti metodai buvo pritaikyti defektų spektroskopijai ir skersinei žvalgai sluoksninėse struktūrose bei defektų evoliucijos tyrimams apšvitos metu. Disertacijoje pateikti ir aptarti apšvitintų detektorių ir apšvitos metu pasireiškiančios parametrų kaitos rezultatai. Elektronikos grandynuose plačiai naudojami galios pin struktūros diodai, kurie... [toliau žr. visą tekstą]

L'objectif de cette thèse est de réaliser un système radio-sur-fibre bidirectionnel fonctionnant dans la bande des fréquences millimétriques autour de 60 GHz. La solution proposée est basée sur l'utilisation d'une photodiode PIN en tant que mélangeur optoélectronique. Une étude théorique associée à une caractérisation non-linéaire et large bande de la photodiode a permis de modéliser le comportement mélangeur de la photodiode. Le modèle de photodiode obtenu a ensuite été utilisé pour optimiser les performances du mélangeur optoélectronique puis du système radio-sur-fibre complet. Des mesures expérimentales ont permis de vérifier la compatibilité du système proposé avec les spécifications du standard ECMA 387 proposé pour régir la création de réseaux locaux aux fréquences de 60 GHz, pour au moins les deux premiers débits proposés (394 Mb/s et 794 Mb/s). / The aim of this thesis is to develop a bidirectional millimeter-wave radio-over-fiber system. The proposed system is based on the use of a p-i-n photodiode as an optoelectronic mixer. A theoretical study coupled with a non-linear and wideband photodiode characterization allows modeling of the photodiode mixing process. Then, the developed photodiode model was used to optimize the optoelectronic mixer efficiency and finally, to optimize the complete radio-over-fiber system efficiency. Experimental measurement has been made to check the compliance of the developed system with the specifications of the ECMA 387 standard that is proposed for the use of the 60 GHz frequency band. Measurement complies with the standard for at least the first data rates (394 Mb/s and 794 Mb/s).

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-06-08T11:53:57Z No. of bitstreams: 1 jovianafernandesmarques.pdf: 23501506 bytes, checksum: f13147f1997cc6dfee331cfe55423786 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-13T13:26:14Z (GMT) No. of bitstreams: 1 jovianafernandesmarques.pdf: 23501506 bytes, checksum: f13147f1997cc6dfee331cfe55423786 (MD5) / Made available in DSpace on 2016-07-13T13:26:14Z (GMT). No. of bitstreams: 1 jovianafernandesmarques.pdf: 23501506 bytes, checksum: f13147f1997cc6dfee331cfe55423786 (MD5) Previous issue date: 2016-04-05 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A presente pesquisa busca traçar um panorama sucinto das transformações observadas na ilustração americana, tendo por base um recorte temporal definido que abrange as décadas de 1890 a 1945. Para tanto, selecionamos um número limitado de artistas que tornam seus trabalhos símbolos de tais representações, analisando-os e comparando-os afim de nos aproximarmos de seu papel social, político e cultural, visando compreender as mutações sofridas em modelos ilustrados ao longo do anos. Assim procedemos também no capítulo último, ao elegermos para análise o ilustrador brasileiro Alceu Penna, no intuito de traçar os diálogos da ilustração americana com a ilustração nacional. Palco de grande produtividade gráfica, o recorte temporal proposto se inicia no fim da década de 1890 nos Estados Unidos, período que viu o nascimento do modelo da new woman personificado nos traços das famosas Gibson Girls. Percorremos a década de 1920, onde a euforia dos “anos loucos” deu a luz à mulheres de tornozelos a mostra e madeixas curtíssimas: a Era flapper. Com a Grande Depressão de 1929 bem como a Segunda Guerra Mundial, outro modelo emerge, as pin ups, transformando a euforia anterior em uma atmosfera regada ao patriotismo e sensualidade. Sua influência chega até o território nacional, influenciando a produção de ilustradores diversos, como o mineiro Alceu Penna. Para construir e compreender as transformações sofridas e suas influências, nos valemos de fontes primárias, como as ilustrações encontradas em acervos digitais e pessoais de colaboradores, e secundárias, como livros diversos, artigos e ensaios. Buscamos traçar diálogos que enriqueçam o debate em torno das representações ilustrativas de ambos países, esperando expandir os olhares a respeito dos caminhos que a ilustração é capaz de revelar. Ao analisarmos representações do feminino em Alceu Penna por paralelos e conversas com modelos norte-americanos, esperamos auxiliar nas visualizações de similaridades e diferenças entre as duas produções, contribuindo com novos pensamentos sobre o material gráfico de tais culturas, suas potencialidades e aproximações. / This research seeks to draw a brief overview of the changes observed in american illustration, based on a defined time frame spanning the decades from 1890 to 1945. To this end, we selected a limited number of artists who make their work popular symbols of such representations, analyzing and comparing them in order to get closer to its social, political and cultural role, to understand the changing in models shown throughout the years. Likewise we proceeded in the last chapter. We elect to analyze the brazilian illustrator Alceu Penna in order to map out the dialogues of american illustration with national illustration. A stage for large graphical productivity, the proposed time frame begins at the end of the 1890s in the United States, a period that we saw the birth of the new model of woman personified in the features of the famous Gibson Girl. Go through to the 1920s, where the euphoria of the "crazy years" gave birth to women's ankles show and very short strands: the Age of the flapper. With the Great Depression of 1929 and World War II, another model emerges, the pin ups, making the previous euphoria in an atmosphere watered with patriotism and sensuality. Its influence reaches the country, influencing the production of various illustrators, like Alceu Penna. To build and understand the transformations suffered and their influences, we make use of primary sources, such as the illustrations found in digital museum collections and personal archives, and secondary sources, as several books, articles and essays. We seek to trace dialogues to enrich the debate about the illustrative representations of both countries, hoping to expand looks about the ways that the illustration is able to reveal. Analyzing female representations in Penna by parallels and conversations with north american models, we hope to assist in views of similarities and differences between the two productions, contributing with new thoughts on the graphic material of such cultures, their approaches and potential.