• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 9
  • 7
  • 5
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 30
  • 10
  • 5
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Podávací válce kruhových tyčí pro kosoúhlou rovnačku / Feeding roller for bar straightener

Hasík, Dávid January 2021 (has links)
The diploma thesis consists of two main parts. First part contains analysis of general knowledge of bar feeding machines in the straightening industry. Second part of the thesis follows with three designs of feeding roller devices. One of the designs is chosen and deeply described with drawings included.
12

Finite element modeling of straightening of thin-walled seamless tubes of austenitic stainless steel

Johansson, Robert January 2016 (has links)
During this thesis work a coupled thermo-mechanical finite element model (FEM) was builtto simulate hot rolling in the blooming mill at Sandvik Materials Technology (SMT) inSandviken. The blooming mill is the first in a long line of processes that continuously or ingotcast ingots are subjected to before becoming finished products. The aim of this thesis work was twofold. The first was to create a parameterized finiteelement (FE) model of the blooming mill. The commercial FE software package MSCMarc/Mentat was used to create this model and the programing language Python was used toparameterize it. Second, two different pass schedules (A and B) were studied and comparedusing the model. The two pass series were evaluated with focus on their ability to healcentreline porosity, i.e. to close voids in the centre of the ingot. This evaluation was made by studying the hydrostatic stress (σm), the von Mises stress (σeq)and the plastic strain (εp) in the centre of the ingot. From these parameters the stress triaxiality(Tx) and the hydrostatic integration parameter (Gm) were calculated for each pass in bothseries using two different transportation times (30 and 150 s) from the furnace. The relationbetween Gm and an analytical parameter (Δ) was also studied. This parameter is the ratiobetween the mean height of the ingot and the contact length between the rolls and the ingot,which is useful as a rule of thumb to determine the homogeneity or penetration of strain for aspecific pass. The pass series designed with fewer passes (B), many with greater reduction, was shown toachieve better void closure theoretically. It was also shown that a temperature gradient, whichis the result of a longer holding time between the furnace and the blooming mill leads toimproved void closure.
13

Avaliação das propriedades das fibras capilares tratadas com alisante ácido com diferentes valores de pH / Evaluation of hair fibers properties treated with acid straightener at different pH values

Goshiyama, Alessandra Mari 11 April 2019 (has links)
Os produtos para alisamento das fibras capilares são amplamente utilizados no Brasil principalmente, pelo público feminino. Porém, estes procedimentos podem causar danos ao cabelo do usuário e, também, para o profissional que está atuando. Os alisantes químicos podem ser divididos em dois grupos: alcalinos e ácidos. Os primeiros (tioglicolato de amônio e os hidróxidos de sódio ou guanidina) apresentam valor de pH elevado (superior a 9,0) e alisam por meio da quebra e reorganização das pontes de dissulfeto (S-S) presentes na queratina, proteína estrutural da fibra capilar. Os alisantes ácidos como o formaldeído, ácido glioxílico e seus associados, possuem pH baixo (≥ 2,0) e causam uma reorganização no interior da fibra e geralmente leva a formação de um filme na superfície do fio. O ácido glioxílico associado à carbocisteína e aminoácidos (nomenclatura INCI -International Nomenclature of Cosmetic Ingredient apresentada entre parênteses) (Glyoxyloyl Carbocysteine (and) Glyoxyloyl Keratin Aminoacids (and) Water) é o único ingrediente permitido ao uso como alisante ácido até o momento. O objetivo deste trabalho foi estudar o efeito deste alisante ácido incorporado em uma emulsão óleo e água (O/A) com valores de pH 1,0 e 2,0 (com reaplicações); e o impacto que podem causar nas propriedades mecânicas e químicas da fibra capilar, como força de ruptura, coloração, elasticidade e teor de triptofano da fibra capilar. E também o efeito da radiação ultravioleta nos fios alisados. Nos testes realizados observou-se que as mechas tratadas com a emulsão a pH 1,0 obtiveram melhor resultado de alinhamento das cutículas e capacidade alisante da fibra, com penteabilidade superior ao cabelo virgem (59,4 %), enquanto as mechas com a formulação pH 2,0 foi apenas 33,0%. Entretanto, a força de tração para a ruptura do fio foi inferior, diminuindo em 16,0% (pH 1,0) e 9,0 % (pH 2,0). Quanto a variação da coloração, a variação do tom de cor foi mais exacerbada para as mechas tratadas com a formulação em pH 1,0. O teor de triptofano foi inferior nas mechas alisadas com a formulação pH 1,0. Para o teste de DSC e Raman, ambas as mechas tratadas apresentaram modificações nas suas estruturas. As fibras alisadas e expostas à radiação UV apresentaram danos maiores nas cutículas, e certa proteção na degradação de proteínas em relação aquelas sem tratamento e irradiadas ao UV. Considerando as reaplicações do produto alisante ácido, quanto maior o número de aplicações, mais alinhadas e seladas tornaram se as fibras, mas mais rígida e suscetível à quebra ficaram. Devemos considerar a importância do valor do pH da formulação no impacto do alisamento e dano da fibra capilar. / Hair straightening products are widely used in Brazil by the female public. However, these procedures can cause damage to the hair shaft and to professional´s and client´s health. Chemical straighteners can be divided into two groups: alkaline and acid. Alkaline straighteners has a very high pH value (> 9.0) and the straightening process is due to the break followed by reorganization of the disulfide bridges (S-S) present in the keratin, a structural protein of the hair shaft. Some examples of alkaline straighteners are ammonium thioglycolate and sodium or guanidine hydroxides. On the other hand, acid straighteners like formaldehyde, glyoxylic acid, and their associated, present a low pH value (≥ 2.0), which causes a rearranging within the fiber, and sometimes creates a film on the surface of the hair. Nowadays, the glyoxylic acid associated with carbocysteine and amino acids (INCI - International Nomenclature of Cosmetic Ingredient nomenclature presented in parentheses) (Glyoxyloyl Carbocysteine (and) Glyoxyloyl Keratin Aminoacids (and) Water) is the only acid straightener permitted. Therefore, the objective of this work is to study the effect of this acid straightener, incorporated into oil in water (o/w) base emulsions at two different pH values 1.0 and 2.0 ( with reapplication) on the mechanical and physicochemical properties of the hair shaft. Also, the impact of UV radiation in straightened tresses. In the experiments conducted, it was possible to observe that tresses treated with the emulsion at pH 1.0 had a better result on the alignment and the straightening capacity, improving the combing test (59.4%/), while the tresses with the formulation at pH 2.0, 33.0%. However, the tensile strength, to pH 1.0 decreased by 16.0% and to pH 2.0 only 9.0%. As for color, the difference when compared with virgin hair it was major at pH 1.0. The tryptophan content also was lower in tresses treated at pH 1, 0. For the DSC and Raman analyzes all the treated tresses presented modifications in their structure. Straightened strands exposed to radiation had major damage in the cuticles, and some protection in proteins degradation compared to untreated tresses exposed to radiation. Considering the reapplications of the straightening product, as higher the number of applications more aligned and sealed it becomes, however the hair fiber becomes stiffer and susceptible to breakage. Thats why we should consider the importance of the pH value in the product, and the impact of straightening and damage of the hai fiber.
14

Contribution à l’amélioration de la rectitude dans l’obtention de produits longs : application aux abouts de rails / Contribution to improving straightness in long product manufacturing : application to rail ends

Belhadj Ahmed, Abdelwahed 18 December 2013 (has links)
Les produits longs se distinguent par une dimension, généralement la longueur plus importante que la hauteur et la largeur, à titre d'exemple les rails de chemin de fer. Ces produits sont obtenus par déformation plastique à chaud puis refroidissement. Au cours du processus de fabrication, l'hétérogénéité du refroidissement et de la déformation plastique induisent un défaut géométrique de rectitude. Pour parachever la rectitude du produit, un redressage à froid est alors nécessaire. Souvent des dresseuses à galets sont utilisées pour corriger la rectitude du centre de produit, cependant, il reste les abouts. Ces derniers sont redressés au moyen d'une presse à partir de l'image de leurs profils obtenus par mesurage optique. La procédure de mesure/redressage est répétée jusqu'à la conformité du produit. Le temps de réalisation est variable, il dépend de l'apprentissage des paramètres clés liés à la géométrie et au matériau du produit à redresser. Compte tenu des exigences de plus en plus sévères sur la rectitude des produits longs d'une part et une volonté d'augmenter la productivité d'autre part, l'objet de ce travail de recherche consiste à optimiser le procédé de redressage des abouts de produits longs. Dans un premier temps, les déformations élastiques générées au cours du mesurage d'un produit long ont été filtrées. Ensuite, les erreurs des moyens de mesure ont été séparées de la mesure du produit au moyen d'une analyse couplée ce qui a permis une meilleure évaluation de la rectitude du produit. Par ailleurs, en se basant sur l'image du profil du produit, une méthodologie de redressage semi-automatique a été mise en place. Cette dernière est essentiellement basée sur une interaction entre la métrologie et la mécanique et représente une contribution à l'automatisation du procédé de redressage des abouts des produits longs. / Long workpieces are characterized by one dimension, usually length is larger than the height and width, for example, railway rails. These products are obtained by hot rolling and then cooling. During manufacturing process, heterogeneity of cooling and plastic deformation induced straightness error. In order to correct this geometrical error, cold straightening process is necessary. Usually, straightening machines are used to correct the straightness of the workpiece center however; the ends' sides were still not straightened. Based on the optical measurement profile, these ends are straightened by mechanical press. The measuring/straightening closed loop is repeated until the straightness of the product is conformed. The process time depends on the knowledge of key parameters related to geometry and material of workpiece. The objective of this research work is to optimize straightening process of the ends of long workpieces. As a first step, the elastic deformation generated during the measurement of long workpiece has been filtered. Then, a coupled analysis of measurement was used to separate error of machine measurement from workpiece measurement, which allowed a better assessment of workpiece straightness profile. Furthermore, based on straightness profile, a semi-automatic straightening methodology has been developed. It is essentially based on an interaction between metrology and mechanics and it is a contribution to the automation of straightening process for ends parts of long workpieces.
15

Vliv modelu zpevnění na výsledky simulace kosoúhlého rovnání / Influence of hardening model on the results of cros-roll straightening simulation

Meňhert, Samuel January 2019 (has links)
This diploma thesis deals with simulation of cross-roll straightening using computational modeling with finite element method in software ANSYS. The main goal of this thesis is to quantify the influence of inaccurate knowledge of mechanical properties on the straightening process and correct setting of machine. It also aims for comparison of hardening models and their influence on the final curvature and residual stresses in the cross section of the bar.
16

Konstrukční návrh manipulátoru obrobků / Design of manipulator for workpiece

Pruša, Lubomír January 2012 (has links)
This master’s thesis deals with design of manipulator which manipulate the types of shift forks 1/5, 2/4, 3/7 and 6/R. The machine takes parts from the belt, which transports them from mark station. Parts are moved to the straightening machine by manipulator. Straightened parts are transported on the storage place, from which are sorted into the boxes and palletized by robot. As a part of work is the proposal of alternativ solutions, selecting the best solution, the design of the chosen variant and technical calculations of the main parts of the manipulator. The work includes the accompanying drawings, assembly drawings and 3D model.
17

Výpočtová simulace rovnání tyčí nekruhového průřezu / Computational simulation of leveling of long profiles

Čupr, Pavel January 2015 (has links)
The purpose of this study is to compare two possible methods of computational modeling of straightening long profiles. The study presents fundamentals of the straightening process, basic principles of the finite element method and the principle of fast algorithm based on Eulerian description of motion of continuum. The study investigates how the two methods are computationally demanding and precise. Finally, the acquired results are summarised and the effectiveness of both algorithms is assessed.
18

“Dark Shades Don’t Sell”: Race, Gender, and Cosmetic Advertisements in the Mid-Twentieth Century United States

Collins, Shawna January 2018 (has links)
In this study I examine the two major cosmetic categories - products for skin and products for hair - aimed at frican American women and advertised within the black press between 1920 and 1960. Specifically, I examine the Chicago Defender, Afro-American, Plaindealer, and Ebony. My project analyzes the images and conceptions of blackness and beauty sold to women of colour by white-owned and black-owned cosmetics companies.  I explore the larger racial and social hierarchies these advertising images and messages maintained or destabilized. A central theme of this project has been tracing the differences in advertising messages and conceptions of beauty communicated by black-owned and white-owned companies. Many of the images and much of the advertising copy produced by black-owned cosmetic companies challenged hegemonic beauty ideals that venerated white beauty and sold white idealization as a norm. The black cosmetic industry, however, was dominated by white-owned companies. The dominant position of white-owned companies was linked to the advantages associated with whiteness, which allowed these companies to advertise with greater frequency throughout the forty-year period. White-owned and black-owned companies often pursued diverging advertising strategies and messaging about black beauty. An important finding of the project is that white-owned companies were more likely to use degrading language and stereotypes to describe black beauty in their advertisements. However, a company’s racial identity did not always determine advertising strategies or messaging about black beauty. An important concept that permeated the 1920s and 1930s was the strategy of racial uplift, which was promoted by several black-owned companies. This strategy tapered out by the1940s as new technologies like photography regularly depicted black women with dignity and accuracy. The 1940s and 1950s witnessed new advertising strategies including the appeal to glamour. This period also saw the introduction of Ebony magazine, which fundamentally altered advertising messages through their appeal to middle class sensibilities. / Thesis / Master of Arts (MA) / My project analyzes skin bleaching and hair straightening advertisements appearing in four black-owned periodicals between 1920-1960: Chicago Defender, Afro-American, Plaindealer, and Ebony. The main goal has been to document the advertising messages about blackness and beauty communicated to black women through the advertisements of black-owned and white-owned cosmetic companies. I explore the larger racial and social hierarchies these advertising images and messages maintained or destabilized. A major finding of this project has been that advertising messages usually, but not always, diverged along racial lines. White-owned companies were more likely to use denigrating language to describe black hair and skin, and more likely to measure the beauty of black women based on how closely they approximated whiteness. Black-owned companies tended to challenge this ideology. They used messages about racial uplift as part of this challenge.
19

Desenvolvimento de formulações cosméticas contendo óleos vegetais para proteção e reparação capilar / Development of cosmetic formulations with vegetable oils for hair care

Araújo, Lidiane Advíncula de 23 April 2015 (has links)
A fibra capilar está exposta a danos diários, como radiação solar, poluição, ato de pentear, higienização e fatores endógenos, além de tratamentos químicos, com o alisamento capilar. Assim, os produtos cosméticos possuem grande importância, uma vez que são desenvolvidos de forma a restaurar a fibra capilar danificada, que é mais porosa e hidrofílica, e proteger os cabelos de danos futuros. Os óleos vegetais destacam-se como importantes constituintes de produtos cosméticos, seguindo uma tendência mundial de incorporar ingredientes naturais em formulações para cuidados da pele e cabelos. Nesse contexto, o objetivo do presente trabalho foi desenvolver formulações cosméticas contendo óleos vegetais para a proteção e reparação capilar. Para tal, foram selecionados os óleos vegetais de abacate, argan e moringa, e desenvolvidas formulações contendo os óleos isolados ou associados, para aplicação em cabelos submetidos ao alisamento químico. Além disso, na etapa de pré-tratamento, foi incorporado um filtro solar às formulações. Em seguida, foi feito um direcionamento racional da escolha da formulação com maior potencial para ser utilizada nas etapas posteriores, usando a análise sensorial em mechas de cabelo e avaliação das propriedades mecânicas do fio. A formulação contendo a associação dos 3 óleos vegetais foi selecionada e, então, submetida aos estudos de estabilidade e reologia. Ao final das análises, as formulações mais adequadas à proposta do estudo foram selecionadas e aplicadas em mechas de cabelo submetidas a radiação solar, em duas etapas: pré e pós-tratamento, em relação à indução do dano. Com isso, o objetivo foi verificar se os cosméticos desenvolvidos teriam efeitos na prevenção ou recuperação dos danos causados pela radiação solar. Assim, foram avaliadas imagens obtidas por meio de Microscopia Eletrônica de Varredura, além da resistência mecânica do fio, dosagem da perda de triptofano por avaliação da intensidade de fluorescência e medidas da variação da cor da fibra capilar. Observou-se que os melhores resultados obtidos com os óleos vegetais foi na avaliação da resistência capilar, enquanto a adição do filtro solar teve impacto positivo também na redução da degradação do triptofano. Além disso, de maneira geral, os resultados indicam que o pré-tratamento foi mais eficaz em proteger a fibra capilar, quando comparado à capacidade de recuperar os danos por meio do pós-tratamento. Entretanto, o pós-tratamento foi importante para melhoria das propriedades sensoriais e para proteção de danos futuros. Com isso, dentre as formulações desenvolvidas, a que continha a associação dos óleos vegetais e do filtro solar, utilizada na etapa de prétratamento, foi a que levou aos melhores resultados, quando aplicada em mechas de cabelo. / Hair is a very important and distinctive feature that plays a major role in self perception and is part of the individual\'s identity. The hair fiber is exposed to daily damage, such as solar radiation, pollution and grooming, and endogenous factors, besides chemical treatments such as hair straightening. Therefore, cosmetic products are of great importance, since they are developed to restore the damaged hair fiber and to protect the hair from further damage. Vegetable oils stand out as important cosmetic ingredients, following a global trend to add natural ingredients in formulations for skin and hair care. In this context, the aim of this study was to develop cosmetic formulations containing vegetable oils for hair protection and repairing . For this purpose, three vegetable oils (avocado, argan and moringa oil) were selected for the development of cosmetic formulations for use in straightened hair. After that, the most suitable formulation was selected based on the results of sensory analysis and mechanical properties evaluation on hair tresses. The formulation containing the combination of 3 vegetable oils was selected and then evaluated in terms of stability studies and rheological behaviour. This way, the most appropriate formulations were selected and applied to strands of hair exposed to solar radiation in two different stages: pre and post-treatment in relation to the induction of the damage. Thus, the objective was to verify if the developed formulations would have effects in the prevention or repairing of solar damage hair. For this purpose, observations in Scanning Electron Microscopy, tensile properties evaluation, tryptophan degradation, and color measurements of the hair fiber were performed. Regarding the vegetable oils, the best results were found in the the tensile properties evaluation, whereas the addition of sunscreen had a positive impact on the assessment of the tensile properties evaluation and in the tryptophan degradation analysis, as well. Moreover, the results indicate that the pre-treatment was most effective than the post-treatment. Nevertheless, the posttreatment was important to improve the sensory properties. Thus, among the developed formulations, the one containing the combination of vegetable oils and the sunscreen, used in the pre-treatment, led to the best results when applied to hair tresses.
20

Caracterização dos cabelos submetidos ao alisamento/relaxamento e posterior tingimento / Characterization of straightened and dyed hair

França, Simone Aparecida da 17 February 2014 (has links)
O uso de cosméticos com a finalidade de alterar a cor e o formato dos cabelos, como tintura ou alisantes químicos, ocorre com elevada frequência, principalmente entre o público feminino. Porém, esses tratamentos, devido aos seus mecanismos de ação, podem causar danos a estrutura da fibra capilar. Assim, este trabalho teve como objetivo avaliar a extensão dos danos provocados pelo tratamento com tintura capilar oxidativa associado ou não ao uso de alisantes químicos a base de tioglicolato de amônio, hidróxido de sódio ou hidróxido de guanidina. Foram desenvolvidas formulações de tintura capilar oxidativa na cor castanho natural nas formas de emulsão, gel e solução, que foram aplicadas a mechas de cabelo virgens. Após nove procedimentos de lavagem, verificou-se qual formulação apresentava maior poder de cobertura e manutenção de cor e brilho. A formulação escolhida (emulsão) foi aplicada a mechas de cabelo virgens associado ou não aos alisantes químicos. As mechas foram avaliadas quanto a alterações de características como diâmetro, resistência à tensão/deformação, perfil térmico de degradação e perda proteica pelo método BCA, validado conforme os parâmetros linearidade, precisão, exatidão, limite de detecção e de quantificação, e especificidade. Observou-se redução do diâmetro do fio (14%) após a aplicação da tintura. Os alisamentos com o hidróxido de guanidina e tioglicolato de amônio promoveram aumento de diâmetro do fio (124,2 e 25,7%, respectivamente), sendo que após aplicação da tintura houve redução (10,7 e 18,8%, respectivamente). O hidróxido de sódio também provocou aumento inicial no diâmetro (106,1%), mas com posterior aumento após aplicação da tintura (8,8%). Quanto aos ensaios de resistência, observou-se elevação de resistência mecânica nas mechas tingidas, em comparação às virgens, o que pode sugerir aumento na massa interna da córtex, devido à deposição dos polímeros coloridos no interior do fio do cabelo. Nas mechas tratadas com os alisantes, houve redução desse parâmetro. Na análise térmica por TG/DTG foram observados quatro picos, sendo que em mechas tingidas houve deslocamento do pico do quarto evento, provavelmente devido à presença do polímero sintético formado no interior do fio de cabelo. O perfil da curva DTA de todos as mechas tratadas com alisante químico foi semelhante e observou-se que para as mechas submetidas à tintura capilar, foi necessária maior energia para ocorrer o último evento exotérmico próximo a 600ºC. A aplicação da tintura teve grande influência sobre a perda proteica na mecha virgem, aumentando este parâmetro em 48%. Entre os produtos de alisamento testados, hidróxido de sódio promoveu maior perda de proteína, cerca de 276% maior do que o cabelo virgem e 207% maior do que o cabelo tingido. Estes resultados podem indicar que, quando se desejar aplicar os dois tipos de produto (alisante e tintura), o tioglicolato de amônio ou hidróxido de guanidina podem ser opções mais interessantes / The use of cosmetics in order to change the color and shape of the hair, such as dye or chemical straighteners, occurs with high frequency , especially among women. However, these treatments, due to their mechanisms of action, can damage the structure of the hair fiber. This study aimed to evaluate the extent of damage caused by treatment with oxidative hair dye with or without the use of chemical straighteners based on ammonium thioglycolate, sodium hydroxide or guanidine hydroxide. Oxidative hair dye formulations in natural brown color were developed in emulsion, gel and solution and were applied to virgin hair tresses. After nine washing procedures, tresses were analyzed in relation to brightness and color maintenance. The chosen formulation (emulsion) was applied to virgin hair tresses associated or not to chemical straighteners. They were evaluated for characteristics such as diameter, tensile stress/strain, thermal degradation profile and protein loss by the BCA method, validated according to the parameters linearity, precision, accuracy , limit of detection and quantification, and specificity. It was observed reduction of the diameter (14%) after application of the dye hair. The straightening with guanidine hydroxide and ammonium thioglycolate caused an increase in diameter of the fiber (124.2 and 25.7%, respectively), while both treatments reduced this parameter (10.7 and 18.8%, respectively). The sodium hydroxide also caused an initial increase in diameter (106.1%), but with further increase after application of the dye (8.8%). In relation to mechanical properties, it was observed increase of resistance in comparison to virgin, which might suggest an increase in mass of the inner cortex due to the deposition of the pigment. In tresses treated with the straighteners, it was observed a reduction of this parameter. In the thermal analysis by TG/DTG four peaks were observed, including a peak shift of the fourth event in dyed tresses probably due to the presence of the synthetic polymer formed within the hair. The profile of the DTA curve of all tresses was similar, except for dyed hair because more energy was required for the last exothermic event at 600°C. The application of the dye had great influence on protein loss in the virgin tresses, increasing this parameter by 48%. Among the straightening products tested, sodium hydroxide promoted greater loss of protein, about 276% greater than the virgin hair, and 207% greater than the dyed hair. These results may indicate that when it is desired to apply both types of product (straightening and dye), ammonium thioglycolate or guanidine hydroxide can be most interesting options.

Page generated in 0.0845 seconds