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Couleur et nuancier, territoires et fonctions : analyse poïétique de l'échantillonnage de la couleur par les manufactures, l'industrie et le commerce / Colour and color chart, territories and functions : poïetical analysis of the sampling mode by manufacters, industry and commerceVarichon, Anne 03 December 2011 (has links)
La couleur est omniprésente dans nos quotidiens, mais sa représentation par le marketing fait apparaître aujourd’hui un double paradoxe : d’une part le recours à une rhétorique publicitaire invoquant des caractéristiques de la couleur qui sont précisément niées par sa fabrication industrielle, et d’autre part, la multiplication de l’image du nuancier dans des conditions d’impression qui s’opposent aux fonctions d’exemplification qu’il est sensé assumer. Cette thèse se propose de mettre en évidence, grâce aux outils de la poïétique, les mutations qu’a connu la construction de la pensée de la couleur par les manufactures, l’industrie et le commerce depuis le milieu du XIXème siècle en interrogeant ses divers modes d’échantillonnage, le nuancier notamment, tels qu’ils ont été instaurés par ses producteurs. Mais l’échantillonnage de la couleur est ici envisagé comme une interface d’expression maximum entre les producteurs et commerçants de couleur et ceux auxquels il est destiné : il relève de conduites créatrices spécifiques, il en génère aussi.L’objectif de ce travail est de parvenir à mesurer l’évolution respective des divers types d’information apportés, et donc communiqués, par le nuancier. La recherche s’ancre dans un corpus de documents sur lequel est appliqué une grilled’analyse permettant dans un premier temps de mettre en évidence les cinq territoires d’information qui ont été identifiés dans l’échantillonnage de la couleur, puis d’en explorer les caractéristiques quantitatives et qualitatives. Des concepts opératoires ont ainsi pu être élaborés pour cerner précisément deux conduites créatives distinctes : celle générant le nuancier et celle générant le recueil d’échantillons. L’amplitude chronologique de cette recherche ainsi que le parti-pris de laisser au terrain la possibilité de déployer toute sa richesse a imposé ses limites à l’entreprise. Celle-ci devait poser le cadre et les principaux repères d’un sujet encore peu exploré et élaborer des outils conceptuels aptes à être réutilisés. Une évaluation de la pertinence de la méthode, des outils et des concepts mis en oeuvre a été effectuée. Ses résultats sont encourageants puisqu’ils montrent que la recherche entreprise est féconde pour déceler les enjeux dont le nuancier, entre industrie et individu, est partie prenante. Elle a mis en évidence que l’analyse du nuancier, entité riche de ce dont elle résulte et de ce qu’elle induit, peut être employée pour contribuer à décrypter la société contemporaine. Il s’agira de prolonger cette première étape par de nouvelles investigations sur l’échantillonnage de la couleur. / Colour is omnipresent in our daily lives, but its representation in today’s marketing shows a double paradox: on the one hand, the use of advertising rhetoric, invoking characteristics of color – the same being manifestly denied by the manufacturing industry, and on the other hand, the multiplication of the image of color chart – but under printing-conditions that are opposed to the functions of exemplification it is supposed to fulfill. Using tools from poietic, this thesis intends to demonstrate what kind of changes manufacturers, industry and commerce has gone through in terms of construction of theidea of colour since the mid-nineteenth Century by questioning its various sampling modes, in particular how the color chart was introduced by manufacturers. Sampling of colour is here considered as an interface of maximum expression betweencolour producers and traders and those for whom it is intended: it originates from specific creative conducts - which it also generates. The purpose of this work is to measure the evolution of each type of provided - and obviously communicated - information through the color chart. The research is anchored to a body of documentation, upon which an analytical grid isapplied, first of all in order to define the five fields of information the colour sampling has allowed for. It also enables one to explore their quantitative and qualitative characteristics. Thus it has been possible to develop operational concepts in order to define precisely two distinct creative lines: one generating the color chart and the other generating the sample collection. The chronological amplitude of this research and the prejudice to let the field maintain its ability to display all its treasures, has imposed its own limitations to this research. It has defined the framework and the main landmarks of a - until now - poorly explored subject and developed the conceptual tools capable of being re-used. An evaluation has been performed on the adequacy of the methodology, the tools and on implemented concepts. The results are encouraging as they show that the undertaken research has successfully identified the issues the color chart, the rich entity of where it comes from and what it leads to can contribute to deciphering contemporary society. The purpose is to extend this first step by carrying out new investigations on the sampling of color.
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Calibrating the photographic reproduction of colour digital imagesHeiss, Detlef Guntram January 1985 (has links)
Colour images can be formed by the combination of stimuli in three primary colours. As a result, digital colour images are typically represented as a triplet of values, each value corresponding to the stimulus of a primary colour. The precise stimulus that the eye receives as a result of any particular triplet of values depends on the display device or medium used. Photographic film is one such medium for the display of colour images.
This work implements a software system to calibrate the response given to a triplet of values by an arbitrary combination of film recorder and film, in terms of a measurable film property. The implemented system determines the inverse of the film process numerically. It is applied to calibrate the Optronics C-4500 colour film writer of the UBC Laboratory for Computational Vision. Experimental results are described and compared in order to estimate the expected accuracy that can be obtained with this device using commercially available film processing. / Science, Faculty of / Computer Science, Department of / Graduate
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Chemical composition and color attributes of Foch and deChaunac wines at various agesScaman, Christine H. January 1987 (has links)
Phenolic and color parameters of Marechal Foch and deChaunac wines of 1980 through 1983 vintages were analysed to determine variety and aging effects. Centroid Mapping Optimization together with the Simultaneous Factor Shift algorithm were used to determine the HPLC operating conditions which resolved the maximum number of phenolic components of whole red wine. A ternary gradient system using 1 % acetic acid : methanol : acetonitrile was changed from 100:0:0 to 4.8:82.8:12.4 in 130.6 minutes. A flow rate of 1.1 mL/min and a temperature of 32.9 °C were used. The HPLC system was used to separate at least 50 components from each injection of wine and of an ethyl acetate extract of wine. Foch wines were found to have more catechin and epicatechin than deChaunac wines. Peak areas for the ethyl acetate extracts common to all wines, and areas of peaks in the chromatograms of the whole wine, not present in the neutral extract, were used to form a data set for multivariate analyses.
Strong linear correlations were found between tristimulus and spectrophotometry measurements for each wine. The color of Foch wines was more stable and contained more brown and yellow hues than deChaunac wines, as determined by tristimulus measurements.
Total pigment levels of each wine and various fractions of the total, including ionized, un-ionized, polymeric and sulfur dioxide-bound anthocyanins, were determined spectro-photometrically. Total anthocyanin levels (un-ionized and ionized) in deChaunac wines decreased significantly with increasing age but remained constant in Foch wines. Tannin levels as determined by absorbance readings at 280 nm and by the Folin-Coicalteu reagent method were highly correlated. Foch had more flavonoid and less nonflavonoids than deChaunac wines.
The different color parameters, pigment and tannin fractions, as well as titratable acidity, pH and individual organic acids were used as a second data set of analytical parameters for multivariate analyses. A third data set composed of the combination of the analytical data and the HPLC peak areas was also used. Differences between the four vintages of wines, the two varieties, and between old and young wines within varieties were found using stepwise discriminant analysis (SDA). Discrimination of variety differences was more successful (100% correct classification by the jackknife procedure) and required fewer variables than classification by age. Cluster analyses, performed with variables chosen by SDA, gave similar results to the SDA. / Land and Food Systems, Faculty of / Graduate
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Computer graphics applications in offshore hydrodynamicsHodgkinson, Derek Anthony Martin January 1987 (has links)
The results of hydrodynamic analyses of two problems involving offshore structures are displayed graphically. This form of presentation of the results and the liberal use of colour have been found to significantly help the ease in which the results are interpreted.
For the transformation of waves around an artificial island, a time history of the evolution of the regular, unidirectional wave field around an artificial island is obtained. Through the use of colour, regions in which wave breaking occurs have been clearly defined. The numerical technique used is based on the finite element method using eight noded isoparametric elements. The determination of the transformed wave field takes wave breaking, wave refraction, diffraction, reflection and shoaling into account. The graphical display is achieved by using a plotting program developed for the output of finite element analyses.
The motions of a semi-submersible rig are computed from the RAO curves of the rig, used to obtain its' small response in a random sea. The numerical technique used in the analysis assumes that the vertical members are slender and may be analysed using the Morison equation whereas the hulls are treated as large members which are discretised and analysed using diffraction theory. The discretisation of the cylinders and hulls together with the time history of the rig's motions are displayed graphically. Once again, the graphical display is plotted using a program developed for the output of finite element analyses for four noded elements. In this case, a finite element technique has not been employed but the results were ordered to act as though this is the case. The slender members (cylinders) and large members (hulls) are clearly distinguishable by using different colours. The elements used in the analysis are also clearly shown.
The VAX 11/730 system was used to obtain the results shown. A video tape, using the results of a time stepping procedure, was made by successively recording the hardcopies produced by the VAX printer. The time stepping could also be seen, in real time, on the IRIS. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate
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Invloed van kleur in die televisie-advertensie op die begrip en geheue van die kindPretorius, Lina Pamela 17 February 2014 (has links)
M.A. (Psychology) / Please refer to full text to view abstract
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Client's Perception of Seeking Counseling as a Function of Counselor Ethnicity, Counselor Acculturation, Counselor Gender, and Client GenderLiu, Huan-Chung Scott 08 1900 (has links)
Due to demographic shifts and efforts to recruit culturally diverse professionals, it is plausible that more Caucasians will encounter ethnic minority counselors in the future. Yet, the majority of multicultural literature has only emphasized Caucasian counselors' multicultural counseling competence. Research has rarely discussed how ethic minority counselors influence the perceptions of Caucasian clients. The research purpose was to explore how acculturation and gender of Asian and Caucasian counselors influence Caucasians' perceptions of the counselors and counseling services.
With an analog research design, 562 Caucasian college students read 1 of 8 randomly assigned counselor descriptions, which were varied by counselor characteristics, and reported their perceptions on dependent measures: Counselor Rating Form - Short Version (CRF-S), Working Alliance Inventory - Short (WAI-S) and 4 Willingness items. With the Attitudes Toward Seeking Professional Psychological Help - Shortened Form as a covariate, 15 hypotheses were expected that Caucasians would prefer high-acculturated, same sex, and same ethnic counselors tested by simple contrast, while an exploratory question, investigating main and interaction effects among independent variables (counselor ethnicity, acculturation and gender, and participant gender) on dependent measures, was examined by MANCOVA and ANCOVA.
Although only 2 of 15 hypotheses showed significance, the exploratory investigation revealed: Caucasian participants had a preference of high-acculturated counselors on CRF-S attractiveness, WAI-S and willingness to seek help. However, present data did not replicate the impression of similar ethnic matching in counseling dyads. On CRF-S expertness, Caucasian participants reported that Asian male counselors were perceived as more expert than Caucasian male counselors. For gender differences, the current finding showed that female participants were more willing to seek help for academic/career concerns, whereas male participants were more willing to discuss their somatic concerns.
For the research implications, with appropriate trainings in multicultural counseling competence, both Caucasian and non-Caucasian counselors could become effective therapists. Counseling agencies may need to keep counselors' background information minimum so it would not impede counseling relationships. With the limitation of analog study, the generalization of the current findings to actual clinical settings needs to be cautious. The qualitative research approach could expand our understandings concerning the current research direction in depth.
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Cor e infográfico : o design da informação na imprensa e no livro didático / Color and infographic : the information design in the print press and schoolbookQuattrer, Milena, 1986- 12 December 2013 (has links)
Orientador: Anna Paula Silva Gouveia / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Artes / Made available in DSpace on 2018-08-24T05:36:06Z (GMT). No. of bitstreams: 1
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Previous issue date: 2013 / esumo: A presente dissertação de Mestrado tem como objetivo compreender o quanto a relação entre a cor e os outros elementos do infográfico interfere no processo de transmissão da informação e como os infográficos, publicados em jornais e revistas, contribuem para o aprimoramento daqueles destinados aos livros didáticos. Para tanto, realizei: o levantamento dos infográficos impressos, publicados em jornais e revistas, premiados nas edições 18, 19 e 20 dos 'Premios Internacionales Malofiej de Infografía¿, e dos infográficos impressos, publicados nos livros didáticos adotados através do 'Programa Nacional do Livro Didático¿ - 2011, nas disciplinas de Geografia, História e Ciências do ensino fundamental da EMEF CAIC 'Prof. Zeferino Vaz¿, localizada no município de Campinas/SP; entrevistas com os docentes responsáveis por essas disciplinas na unidade escolar e com membro do júri dos 'Premios Internacionales Malofiej de Infografía¿. Ademais, apresento, nesta dissertação, duas iniciativas de projeto, realizadas sob minha orientação, com alunos da EMEF CAIC 'Prof. Zeferino Vaz¿, sendo que uma delas, em especial, objetivou discutir a importância da informação, as formas de organizá-la e transmiti-la no contexto escolar e na sociedade, através do estímulo à pesquisa e à elaboração de infográficos. As reflexões geradas a partir das iniciativas de projetos realizados com os alunos, das análises dos infográficos e das entrevistas forneceram apontamentos importantes sobre o que pode ser aproveitado dos infográficos premiados para o aprimoramento dos que são destinados aos livros didáticos, em especial no uso da cor, e demonstraram como é importante proporcionar situações de ensino-aprendizagem, nas quais o aluno tenha a oportunidade de se apropriar dos códigos visuais e, consequentemente, ampliar sua cultura visual / Abstract: This research aims to understand how the relationship between color and other elements of the infographics interfere with the process of information transmission, and how infographics published in newspapers and magazines can contribute to improve the ones used in Schoolbooks. To achieve these goals, a survey of infographics printed in newspapers and magazines, which have won the 'Malofiej International Infographics Awards' in the 18th, 19th and 20th editions, and of infographics printed in Schoolbooks used in the EMEF CAIC ' Prof. Zeferino Vaz (Cam-pinas/SP/Brazil) elementary School for Geography, History and Science (these books were se-lected by a Federal Government Program "Programa Nacional do Livro Didático ¿ 2011¿) was made. Interviews with teachers responsible for the above-mentioned subjects and with the jury members of the 'Malofiej International Infographics Awards' were also performed. Furthermore, two projects under, my supervision, with the students of the above mentioned elementary school were also performed. The main goal of one of these projects was to discuss the importance of information and the ways to organize it and communicate it either in the school or in the society, encouraging the research and the development of infographics. The reflections generated after the projects undertaken with the elementary school students, analysis of infographics and interviews, provided important notes about what can be availed from the awarded infographics in order to improve the infographics made for the schoolbooks, especially in regards of the use of color. Finally, the present research demonstrated how important it is to provide teaching-learning situations in which the students have the opportunity to appropriate the visual codes and hence their visual culture / Mestrado / Artes Visuais / Mestra em Artes Visuais
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Influência da utilização de nanopartículas de dióxido de silício ou polissiloxano acrilado nas propriedades físicas de materiais resinosos = Influence of silicon dioxide or acrylated polisiloxane on resin-based materials physical properties / Influence of silicon dioxide or acrylated polisiloxane on resin-based materials physical propertiesYanikian, Cristiane Rumi Fujiwara, 1982- 26 August 2018 (has links)
Orientador: Luis Roberto Marcondes Martins / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-26T19:03:50Z (GMT). No. of bitstreams: 1
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Previous issue date: 2015 / Resumo: A utilização de resinas compostas restauradoras cresceu consideravelmente nos últimos anos, porém, a alteração de cor associado à degradação da resina composta ainda é um importante fator para sua substituição. Portanto, o objetivo dos estudos foram de avaliar in vitro as propriedades físicas de diferentes selantes experimentais e os seus efeitos sobre a superfície de resinas compostas. No primeiro capítulo foram abordados os efeitos da utilização de cobertura de nanopartículas de dióxido de silício (SiO2) sobre diferentes resinas compostas. Os grupos experimentais foram divididos de acordo com os fatores resina composta (Filtek Z250XT, Filtek Z350XT e IPS Empress Direct) e a aplicação ou não de cobertura de SiO2 (n=8). Foram avaliados rugosidade superficial (Ra), energia livre de superfície (mJ/cm2), ângulo de contato formado pela água (?o) e alteração de cor (?E) após 24h de armazenamento em água destilada e após 15, 90 e 180 dias de armazenamento em vinho tinto. Os dados obtidos foram analisados por meio de Análise de Variância de Medidas Repetidas e teste de Tukey (?=0.05). O tempo de exposição ao vinho tinto influenciou negativamente em todas as variáveis, a aplicação da cobertura de SiO2 reduziu a energia livre de superfície, tornando as resinas mais hidrófobas. O aumento na rugosidade superficial foi observada a partir de 90 dias para todas as resinas compostas, independente do tratamento. Quanto a alteração de cor, a Filtek Z250XT e a IPS Empress Direct apresentaram menores valores de ?E quando comparadas à Filtek Z350XT. No segundo capítulo, os grupos estudados foram: PER - selante resinoso comercial (PermaSeal); STD - resina padrão manipulada (matriz monomérica Bis-EMA+TEGDMA carregada com 10% de partículas inorgânicas); SIL-resina padrão modificada por nanopartículas de SiO2 e; APS-resina padrão modificada por polissiloxano acrilado (n=10). Foram avaliados grau de conversão (%), sorção de água e solubilidade (µg/mm3) e módulo de elasticidade (GPa) em corpos de prova maciços confeccionados a partir dos selantes resinosos. Para os ensaios de ângulo de contato com a água (?o) e alteração de cor (?E), os selantes resinosos foram aplicados sobre a superfície de discos de resina composta (Filtek Z250XT) para então realizar a avaliação das amostras, um grupocontrole sem tratamento foi incluído nestes ensaios. O ?E foi calculado a partir de medidas obtidas antes e depois de 15 dias de imersão das amostras em vinho tinto. Os resultados foram analisados por meio de Análise de Variância de 1 critério e posterior teste de Tukey (?=0.05). A adição de nanopartículas de SiO2 promoveu menor solubilidade, adequado módulo de elasticidade e menor grau de alteração de cor e; a incorporação de polissiloxano acrilado promoveu melhor grau de conversão, menor sorção de água, apresentou maior hidrofobicidade e causou menor grau de alteração de cor quando comparadas aos controles. Portanto, a incorporação de aditivos hidrófobos não interferiu negativamente nas propriedades físicas dos selantes experimentais e foram efetivos para tornar resinas compostas mais hidrófobas e reduzir a sua alteração de cor / Abstract: The use of restorative composites has been increased in dental practice, however, the color change associated to composite surface degradation is still important issue for composite restorations replacement. Therefore, the aim of these studies were to in vitro evaluate physical properties of different experimental surface sealants and its effects on composite resins surfaces. In the first chapter, it has been evaluated the effects of the silicon dioxide nanoparticles (SiO2) coating on different composites. The experimental groups were divided according to the resin composite type (Filtek Z250XT, Filtek Z350XT and IPS Empress Direct) and application or not of SiO2 coating (n=8). Surface roughness (Ra), surface free energy (mJ/cm2), water contact angle (?o) and color change (?E) were evaluated after 24h deionized water storage and after 15, 90 and 180 days of red wine storage. Data were analyzed using Repeated Measures ANOVA and Tukey test (? = 0.05). The red wine storage time negatively influenced all variables, irrespective of treatment or resin composite. The SiO2 coating application decreased the surface free energy, making the composite more hydrophobic. The increase in surface roughness was observed from 90 days for all composites, regardless of treatment. Significant less color change was observed in the Filtek Z250XT and the IPS Empress Direct compared to Filtek Z350XT. In the second chapter, the groups were: PER-commercial resin-based coating (PermaSeal); STD-standard manipulated resin (Bis-EMA+TEGDMA-based monomer matrix loaded with 10% of inorganic filler); SIL-standard resin modified by SiO2 nanoparticles adding; APS-standard resin modified by acrylated polysiloxane adding (n = 10). The degree of resin conversion (%) Water sorption and solubility (mg/mm3) and elasticity modulus (GPa) were evaluated in massive specimens prepared from the resin-based coatings. These resin-based coatings were applied on the composite resin discs surfaces (Filtek Z250XT) to water contact angle (?o) and color change (?E) tests. A control group without surface treatment was included in these trials. The ?E was calculated from measurements taken before and after 15 days of red wine storage. The results were analyzed using one - way ANOVA and Tukey test (? = 0.05). The addition of SiO2 promoted lower solubility, appropriate elasticity modulus and lower degree of color change, and; the incorporation of acrylated polysiloxane provided better degree of conversion, reduced water sorption, the highest hydrophobicity and cause less color change compared to that of controls. Therefore, the incorporation of hydrophobic additives did not negatively affect the physical properties of the resin-based coatings and were effective to make the composite more hydrophobic and less stain susceptible / Mestrado / Dentística / Mestra em Clínica Odontológica
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Corpo cor: entre o visual e o tátil / Body Color: between the visual and the tactileFabíola de Almeida Salles Mariano 02 October 2012 (has links)
A presente dissertação trata de três ciclos de trabalhos poéticos realizados entre 2009-2012 (vermelho, verde e cinza-cor-de-pele). A vivência do corpo com a cor nos três ciclos fez emergir, a partir de tonalidades e de balizas estipuladas a priori, processos de sensibilização do corpo no cotidiano, que foram entendidos em si como poética, bem como geraram desdobramentos: pinturas, objetos, ações... Nos ciclos, importaram as transformações que aconteceram no corpo, nas obras e num certo entre. Onde o dentro e o fora se encontram? O que separa um corpo do outro? No embate direto com a matéria, com o pigmento, a percepção tátil-visual foi ativada e, neste texto, entendida como chave conceitual para uma abordagem do corpo do artista nas artes visuais. Tal estudo deu-se principalmente a partir da Fenomenologia da Percepção de Maurice Merleau-Ponty, da Doutrina das Cores de Joahnn Wolfgang Goethe, do infra-mince descoberto por Marcel Duchamp e do Corpo do Artesão descrito por Pamela H. Smith. Além do estudo teórico, foram analisadas obras e manifestações culturais como auxílio reflexivo para toda a pesquisa: a pintura corporal do rito de passagem dos meninos da nação Kadiwéu, as Antropometrias da Fase Azul de Yves Klein e a performance e instalação Roda dos Prazeres de Lygia Pape. Ainda, fazem parte desta dissertação duas entrevistas com artistas que têm a cor e a atitude corporal diante do fazer artístico como foco de seus trabalhos. / This essay analyzes three cycles of poetic works made between 2009-2012 (red, green and skin-gray color). The interaction of color and body in the three cycles emerged from hues and goals stipulated a priori, affecting the behavior of the body, what was perceived as poetry, in that they stimulated paintings, actions, objects... The main focuses of attention in each cycle were the transformations that took place in the body, in the pieces and somewhere inbetween. Where the inside and the outside toutch each other? What separates one body from the other? In direct confrontation with materials, with pigments, the visual-tactile perception was activated and, in this text, understood as a conceptual key of the artist\'s body in the visual-art\'s field. The conceptual approach was mainly driven by the Phenomenology of Perception by Maurice Merleau-Ponty, the Theo-ry of Colors by Joahnn Wolfgang Goethe, the infra-mince discovered by Marcel Duchamp and the Body of the Artisan described by Pamela H. Smith. Besides the theoretical study, were analyzed some works and cultural manifestations: body painting of the rite of passage for boys in the nation Kadiwéu, the Antropometries of the Blue Períod by Yves Klein and the performance and installation Roda dos Prazeres of Lygia Pape. Still part of this dissertation, two interviews with artists that have the color and human attitude as artistic focus.
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IMPEDANCIA BIO-ELÉCTRICA COMO TÉCNICA NO-DESTRUCTIVA PARA MEDIR LA FIRMEZA DE LA FRESA (Fragaria x ananassa Duch) Y SU RELACIÓN CON TÉCNICAS CONVENCIONALESGonzález Araiza, José Raymundo 16 May 2014 (has links)
La técnica de impedancia bio-eléctrica permite la caracterización de sistemas biológicos
mediante la aplicación de una corriente eléctrica en un rango de frecuencias determinado,
logrando así la observación del comportamiento de las propiedades eléctricas, parámetros que
están relacionados con la estructura y composición del material. Asimismo, el análisis de la
impedancia bio-eléctrica, aplicada a los materiales biológicos, proporciona información acerca
de los cambios fisiológicos dentro y fuera de la célula, así como de las membranas y los tejidos.
Esta técnica tiene la ventaja de ser simple y no destructiva. Algunos estudios relacionados con
esta propiedad se han llevado a cabo en frutos como la nectarina, manzana, pepino, kiwi,
caqui y fresa.
El objetivo del presente trabajo fue desarrollar un procedimiento para medir de manera no
destructiva la impedancia bio-eléctrica de tres variedades de fresa (Fragaria x ananassa Duch)
(`Sweet charly¿, `Festival¿ y `Camino real¿) con el propósito de conocer si existe una relación
entre las variables de impedancia con la firmeza y el ¿grado de madurez¿ de las variedades en
mención. La selección del fruto de la fresa se debió a que es un cultivo importante en el estado
de Guanajuato.
Seis grupos por variedad fueron definidos utilizando como criterio de clasificación tres ¿grados
de madurez¿ y dos tipos de tamaño según el diámetro ecuatorial, ambos indicados en la
Norma mexicana NMX-FF-9-1982. La clasificación utilizando el primer criterio se llevó a cabo
de manera subjetiva ya que se utilizó la tabla de los ¿grados de maduración¿ de la fresa a
través de los colores y el segundo de manera objetiva utilizando un calibrador tipo Vernier.
Para lograr el objetivo se diseñó, construyó y probó un prototipo que permitió llevar a cabo los
ensayos para medir la impedancia en el fruto de la fresa. Las mediciones se llevaron a cabo
conectando el prototipo a un analizador de impedancia. Con los datos obtenidos se generaron
los espectros de impedancia de los cuales a partir de un modelo de circuito predefinido se
obtuvieron los elementos eléctricos Rs (resistor en serie), CPE (elemento de fase constante:
magnitud CPE-T y fase CPE-P) y Rp (resistor en paralelo).
Así mismo y con el uso de un espectrofotómetro, se midió el color superficial de las fresas
obteniendo los valores de la luminosidad L*, y las coordenadas cromáticas a* y b*, los cuales
también fueron utilizados para analizar su relación con los valores de la firmeza y el ¿grado de
madurez¿. Los valores obtenidos de las variables de color L*, a* y b*, para cada uno de los tres ¿grados de
madurez¿, fueron analizados utilizando la prueba estadística ANOVA, con el propósito de
determinar si entre ellos existía una diferencia estadísticamente significativa. Los resultados
mostraron en general para las tres variedades de fresas que los valores de L* entre los
diferentes grupos clasificados según su ¿grado de madurez¿, son estadísticamente diferentes.
Los valores de esta variable, en todos los casos, muestran una tendencia descendente
conforme va madurando el fruto.
Para evaluar la diferencia de color medido con el colorímetro entre los frutos pertenecientes a
cada grupo clasificados según su ¿grado de madurez¿, se utilizó el índice de grado de diferencia
de color ¿E*ab. En general los resultados mostraron diferencias significativas en ¿E*ab entre los
diferentes grupos preestablecidos según su ¿grado de madurez¿.
Con la finalidad de clasificar los ¿grados de madurez¿ preestablecidos según las variables de
color L*, a* y b*, se utilizó la prueba estadística de análisis discriminante, obteniendo para las
variedades `Festival¿ y `Camino real¿ un procentaje alto de casos correctamente clasificados. En
promedio se obtuvieron valores de 94 % y 93 %, respectivamente.
En el caso de los resultados obtenidos de las mediciones de impedancia la prueba estadística
ANOVA se utilizó con el objetivo de conocer si existian diferencias estadisticamente
significativas en los valores de las variables de impedancia para los distintos niveles de ¿grados
de madurez¿. Los resultados no fueron los esperados, ya que no se observó una tendencia en
los resultados obtenidos. Sin embargo, la prueba de análisis discriminante de los ¿grados de
madurez¿ en función de las variables de impedancia mostró porcentajes de casos
correctamente clasificados muy alentadores, ya que en el caso de los grupos tamaños B y C, de
las fresas de la variedad `Camino real¿, se obtuvieron porcentajes de 84 % y 82 %,
respectivamente, según las variables de impedancia Rs, CPE-P, CPE-T y Rp.
Los resultados de las pruebas de análisis discriminante de los grupos de las variedades 'Sweet
charly' mostraron que las variables que mejor discriminan para los grupos clasificados según su
¿grado de madurez¿ son para color, L* y para impedancia, CPE-P; para 'Festival' fueron la
variables de color, a* y de impedancia, Rs; y finalmente, para 'Camino real' fueron las variables
de color L* y a* y las variables de impedancia CPE-P y Rs.
En relación a los resultados de las mediciones destructivas de firmeza en general mostraron
que las fresas más pequeñas son más resistentes. La variedad que mostró los valores más altos
de firmeza fue `Festival¿ seguida de las fresas de la variedad `Camino real¿ y `Sweet charly¿.
Finalmente, se utilizó la prueba estadística de regresión lineal múltiple con el objetivo de
explicar el comportamiento de la variable firmeza a partir de las variables explicativas de
impedancia bio-eléctrica (Rs y CPE-P) y color (L*, a* y b*).
Los modelos obtenidos a partir de las variables explicativas de color L*, a* y b* mostraron para
las variedades 'Sweet charly' y 'Festival' , valores del coeficiente de determinación R2
mayores
a los modelos que incluyen las variables explicativas de impedancia Rs y CPE-P. Los modelos
que muestran la relación entre la variable firmeza con las variables explicativas Rs y CPE-P
para la variedad 'Camino real' presentaron los valores mas altos del coeficiente de
determinación / González Araiza, JR. (2014). IMPEDANCIA BIO-ELÉCTRICA COMO TÉCNICA NO-DESTRUCTIVA PARA MEDIR LA FIRMEZA DE LA FRESA (Fragaria x ananassa Duch) Y SU RELACIÓN CON TÉCNICAS CONVENCIONALES [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/37513 / TESIS
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