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  • 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.
81

Synthesis, Characterization and Modeling of Porous Copolymer Particles

Fang, Dongyu January 2007 (has links)
Hydrogels are polymeric materials that have three-dimensional polymeric networks, which are able to absorb and retain a large amount of water within their structures without being dissolved. Among the synthetic hydrogel, poly(2-hydroxylethyl methacrylate) (poly(HEMA)) has been of great interest because of its excellent biocompatibility with the three-dimensional networks. Therefore, poly(HEMA) hydrogels have been widely used in many areas, especially in biomedical and pharmaceutical areas, for such applications as packing materials in chromatography, sorbents in controlled release and drug delivery, implanting materials in tissue engineering. However, the applications of poly(HEMA) are still limited because of its weak mechanical strength and network properties. Therefore, in recent decades, the challenge of how to modify and control the polymer properties and how to build highly porous structures in it has received considerable attention because these modifications could significantly improve the performance of poly(HEMA) hydrogels for more favorable applications. Although HEMA and its polymers have been studied for more than 40 years, few reports about the preparation of micro-/nano-porous poly(HEMA) hydrogel particles and the requirements of their applications have risen. Furthermore, how to control the porous structures and the properties of HEMA copolymers have not been well understood. Accordingly, the objectives of this research were to investigate the synthesis of the porous copolymeric particles of HEMA with various comonomers (MMA, St and NVP), to characterize the porous structures and particle morphology, to simulate the synthesis process and porous characteristics, to explore the effects of the polymer compositions and the porous structures on the swelling properties, and to apply the resultant polymeric particles in the controlled release of the hydrophilic model drug. In the present studies, HEMA was copolymerized with three different comonomers, methyl methacrylate (MMA), styrene (St) and N-vinyl-2-pyrrolidone (NVP), respectively, to prepare highly porous particles crosslinked using ethylene glycol dimethacrylate (EGDMA) in the presence of 1-octanol used as a porogen by means of suspension copolymerization in an aqueous phase initiated by 2,2-azobisisobutyronitrile (AIBN). Nano-pores were observed in the present studies. The pore size and the swelling properties of these particles can be successfully controlled by changing comonomers or adjusting the crosslinker and porogen concentration. The results indicate that lower crosslinker or porogen concentration favors generating smaller pores, whereas a higher concentration of a hydrophilic comonomer, higher crosslinker concentration and higher porogen volume ratio promote the generation of larger pores. In addition, the effects of the porous structures and the network properties on the swelling properties were explored. The swelling capacity of the porous particles is reduced with an increase in the EGDMA molar concentration. However, higher porosity in the particles and higher amount of hydrophilic comonomer result in a higher swelling capacity of the particles. The gel formation and the porous characteristics of HEMA/comonomer/EGDMA systems were simulated using the mathematical models combining the reaction kinetics and the thermodynamics. It was found that the model over-predicted the experimental results of the porosity because the pores and the networks are shrunk or collapsed during the porogen removal. Therefore, the model predicts the maximum porosity that the polymeric particles can reach. If the hydrophobic contents are higher, the model gives better prediction of the porosity. It is concluded that the microporous structures of HEMA related hydrogels could be controlled by a properly designed process based on the knowledge gained via this research. The output of this research helps with a better understanding for industrial production of micro-porous hydrogels and their applications.
82

Synthesis, Characterization and Modeling of Porous Copolymer Particles

Fang, Dongyu January 2007 (has links)
Hydrogels are polymeric materials that have three-dimensional polymeric networks, which are able to absorb and retain a large amount of water within their structures without being dissolved. Among the synthetic hydrogel, poly(2-hydroxylethyl methacrylate) (poly(HEMA)) has been of great interest because of its excellent biocompatibility with the three-dimensional networks. Therefore, poly(HEMA) hydrogels have been widely used in many areas, especially in biomedical and pharmaceutical areas, for such applications as packing materials in chromatography, sorbents in controlled release and drug delivery, implanting materials in tissue engineering. However, the applications of poly(HEMA) are still limited because of its weak mechanical strength and network properties. Therefore, in recent decades, the challenge of how to modify and control the polymer properties and how to build highly porous structures in it has received considerable attention because these modifications could significantly improve the performance of poly(HEMA) hydrogels for more favorable applications. Although HEMA and its polymers have been studied for more than 40 years, few reports about the preparation of micro-/nano-porous poly(HEMA) hydrogel particles and the requirements of their applications have risen. Furthermore, how to control the porous structures and the properties of HEMA copolymers have not been well understood. Accordingly, the objectives of this research were to investigate the synthesis of the porous copolymeric particles of HEMA with various comonomers (MMA, St and NVP), to characterize the porous structures and particle morphology, to simulate the synthesis process and porous characteristics, to explore the effects of the polymer compositions and the porous structures on the swelling properties, and to apply the resultant polymeric particles in the controlled release of the hydrophilic model drug. In the present studies, HEMA was copolymerized with three different comonomers, methyl methacrylate (MMA), styrene (St) and N-vinyl-2-pyrrolidone (NVP), respectively, to prepare highly porous particles crosslinked using ethylene glycol dimethacrylate (EGDMA) in the presence of 1-octanol used as a porogen by means of suspension copolymerization in an aqueous phase initiated by 2,2-azobisisobutyronitrile (AIBN). Nano-pores were observed in the present studies. The pore size and the swelling properties of these particles can be successfully controlled by changing comonomers or adjusting the crosslinker and porogen concentration. The results indicate that lower crosslinker or porogen concentration favors generating smaller pores, whereas a higher concentration of a hydrophilic comonomer, higher crosslinker concentration and higher porogen volume ratio promote the generation of larger pores. In addition, the effects of the porous structures and the network properties on the swelling properties were explored. The swelling capacity of the porous particles is reduced with an increase in the EGDMA molar concentration. However, higher porosity in the particles and higher amount of hydrophilic comonomer result in a higher swelling capacity of the particles. The gel formation and the porous characteristics of HEMA/comonomer/EGDMA systems were simulated using the mathematical models combining the reaction kinetics and the thermodynamics. It was found that the model over-predicted the experimental results of the porosity because the pores and the networks are shrunk or collapsed during the porogen removal. Therefore, the model predicts the maximum porosity that the polymeric particles can reach. If the hydrophobic contents are higher, the model gives better prediction of the porosity. It is concluded that the microporous structures of HEMA related hydrogels could be controlled by a properly designed process based on the knowledge gained via this research. The output of this research helps with a better understanding for industrial production of micro-porous hydrogels and their applications.
83

Det här är Mixed Martial Arts! : En kvantitativ innehållsanalys om hur svensk dagspress framställer MMA / This is Mixed Martial Arts! : A quantitative study of the framing of Mixed Martial Arts in Swedish daily newspapers

Wångdahl, Max, Östling, Martin January 2012 (has links)
Purpose/aim: This study was performed in order to describe how Mixed Martial Arts (MMA) is reported in Swedish daily newspapers during a five-year period. MMA is a relative new sport in Sweden and it is important that the description by the Swedish daily newspapers is accurate and balanced. Then this sport will have the same opportunities to grow as already well-established sports in Sweden.  Material/Method: The material consists of 159 articles from six different daily newspapers gathered from 2006-12-07 to 2011-12-07. Quantitative content analysis is used to investigate how the newspapers describe MMA. The result from this quantitative analysis are then compiled, analysed and discussed by applying theories of agenda setting, framing and moral panic.  Main results: The result shows that the Swedish daily newspapers give a relative neutral and balanced picture in their coverage of MMA but they are affected to a certain degree of moral panic. A neutral framing of MMA was common in the majority of the newspapers. Swedish newspapers have fulfilled the requirements that you should have on balanced journalism. A majority of the articles described MMA with more or less deviancy and therefore made MMA “Folk Devils”. Further there was a consensus among politicians and other right-thinking people that MMA is a threat to and is dangerous to society. The negative reporting of MMA in the daily newspapers is volatile with one-year cycles with start in late 2009. With one quarter of the articles describing MMA as a problem, there is preconception that MMA is likely to have a negative impact on society. There is a disproportion in the reporting of MMA as a threat as “Swedish Sports” have approved MMA as a sport, but still report it as a problem. Therefore there is some kind of moral panic about MMA in Swedish daily newspaper.
84

Sportfans, sociala medier & UFC : En studie om sociala mediers inverkan på fandom

Mai, Lam, Hällström, Fabian January 2011 (has links)
We aim to develop knowledge of how new technology, in this case social media, can contribute to how sports fans interact with their idols. Therefore our framing of a question is to present how fans experience their contact with mixed martial arts (MMA) & ultimate fighting championship (UFC) through social media platforms. To specify our study, we also have a supplement question with in which way sports fans uses social media.We have chosen to conduct a qualitative study consisting of interviews and data observations of websites, related to the organization UFC, to approach our main question. We have interviewed nine randomly selected people with one common interest - MMA/UFC. With an implant of theories, consisting of social media, fandom and lurking, on the result of the interview and website data, we try to come closer to a conclusion for our intention with this thesis.Our conclusion is that the interviewed fans express that through the usage of social media, they feel like they have come closer to UFC. They have developed a deeper knowledge about the sport, the members and other fans that shares the same interest. Most of our respondents have a lurking attitude towards the social media usage, which means that they are more like observers and soak in the information and media material. They are active in the searching of material related to UFC, but they are not active in the way of contributing with comments, discussions or material.
85

A Route Optimization Method Using MMA (Middle Mobility Agent) for Mobile IP

Wu, Chen-Chi 11 August 2003 (has links)
Nowadays in mobile and wireless networks environment, Mobile IP is the preferred standard in supporting IP mobility among several standards. However, several problems still need to be solved. One of them is the triangle routing problem. Although drafts have been proposed by the IETF (Internet Engineering Task Force) for solving this problem, the proposed solution can not be achieved unless the draft of the Mobile IP route optimization method becomes a typical standard of the Mobile IP. In this paper, we present an extended routing agent architecture to solve this problem. The Middle Mobility Agent (MMA) in the proposed architecture can intercept datagrams earlier and determine to tunnel the incoming packet or not than the MH¡¦s original home agent. This architecture can solve the triangle routing problem by reducing packet¡¦s routing length. An analytical model and a simulation environment were set up to evaluate and measure the packet¡¦s routing length and delay time of proposed architecture. The evaluation and simulation results demonstrate that the proposed method can reduce the routing length, delay time and solve the triangle routing problem.
86

Methyl arsenic adsorption and desorption behavior on iron oxides

Lafferty, Brandon James 29 August 2005 (has links)
Arsenic is a toxic element that is widely distributed throughout the earth??s crust as a result of both natural geologic processes and anthropogenic activities. In virtually all environments, methylated forms of arsenic can be found. Because of the widespread distribution and toxicity of arsenic and methyl-arsenic, their adsorption behavior on soil minerals is of great interest. Although considerable attention has been given to the behavior of inorganic arsenic on mineral surfaces, little research has been conducted regarding interactions of the methyl-arsenic forms. The objective of this study was to compare the adsorption and desorption behavior of methylarsonate (MMAsV), methylarsonous acid (MMAsIII), dimethylarsinate (DMAsV), dimethylarsinous acid (DMAsIII), arsenate (iAsV), and arsenite (iAsIII) on iron oxide minerals (goethite and ferrihydrite) by means of adsorption isotherms and adsorption envelopes. Additionally, desorption envelopes were obtained using sulfate and phosphate as competitive ligands. Arsenic was measured by FI-HG-AAS. MMAsV and iAsV were adsorbed in higher amounts than DMAsV on goethite and ferrihydrite at all pH values studied. Although MMAsV and iAsV were adsorbed quantitatively at lower concentrations on goethite and ferrihydrite, as arsenic concentration was increased MMAsV was adsorbed in slightly lower quantities than iAsV. DMAsV was not quantitatively adsorbed at any concentration on goethite or ferrihydrite. MMAsV and iAsV exhibited high adsorption affinities on both goethite and ferrihydrite at pH values below 9 and showed decreasing adsorption above this point (more rapidly for MMAsV). DMAsV was adsorbed only at pH values below 8 on ferrihydrite and below 7 on goethite. MMAsV, iAsV, and DMAsV each exhibited adsorption characteristics suggesting specific adsorption on both goethite and ferrihydrite. Increased methyl substitution resulted in increased ease of arsenic release from the iron oxide surface. MMAsIII and DMAsIII exhibited no evidence for any type of specific adsorption under the conditions studied. Phosphate was a more effective desorbing ion than sulfate, but neither desorbed all arsenic species quantitatively.
87

Monitoramento em linha e em tempo real do diâmetro médio das partículas e dos teores de não voláteis e monômero durante a polimerização em emulsão usando espectroscopia NIR. / In-line real-time monitoring of average particle size and solids monomer contents during emulsion polymerization using NIR spectroscopy.

Wandeklébio Kennedy da Silva 02 April 2009 (has links)
A técnica de polimerização em emulsão tem sido usada cada vez mais na indústria de tintas, resinas, plásticos, entre outros. Esse crescimento se deve as razões ambientais (uma vez que se utiliza água como fase contínua desta reação), também a versatilidade e a capacidade de produzir látex com diferentes propriedades para diferentes aplicações. Polímeros em emulsão são produtos por processo, isto é, suas propriedades são definidas durante a polimerização. Por isso, é importante o adequado monitoramento da reação de modo a permitir o controle das propriedades desejadas. A técnica de espectroscopia na região do infravermelho próximo (NIR), combinada com o uso de fibras óticas, é muito promissora para o monitoramento multivariável, em linha e em tempo real do processo de polimerização. O objetivo deste trabalho foi o de estudar o uso de espectroscopia NIR para o monitoramento em linha e em tempo real das concentrações de monômero e de não- voláteis (conhecido também como teor de sólidos) e da evolução do tamanho médio das partículas de látex (Dp) durante a reação de polimerização em emulsão de metacrilato de metila (MMA), em escala de laboratório e processo semi-batelada. Os modelos de calibração para estas variáveis foram obtidos experimentalmente empregando o método de regressão por mínimos quadrados parciais, PLS. Os resultados obtidos confirmaram algumas regiões espectrais do NIR indicadas em literatura como sendo adequadas na predição de monômero e Dp e revelaram -1 comportamentos espectrais ainda não explicados na região entre 10.475 e 13.000 cm , relacionados às variações no tamanho das partículas. Os resultados mostram também que é possível monitorar em linha e em tempo real a evolução do Dp e dos teores de monômero (MMA) e de não voláteis, simultaneamente em um único instrumento, utilizando modelos de calibração com bandas espectrais e pré-tratamentos distintos. / Emulsion polymerization is a largely and increasingly used technique in industrial production of paints, resins, plastics among others. This increase is due to environmental reasons (since water, rather than organic solvents is used as dispersing medium), as well as to the versatility and capacity of producing products with different properties for different applications. Emulsion polymers are products by process, i.e., the properties are mainly defined during the polymerization process. Thus, the adequate process monitoring is important for achieving the target properties. The NIR spectroscopy combined with optical fibers is a promising technique for the task of multivariable, real-time, in-line monitoring of polymerization processes. The aim of this work is the study of use of NIR spectroscopy for in-line, real time monitoring of the monomer and solids content, as well as the evolution of average size of the polymer particles (Dp), during semi-batch emulsion polymerization of methyl methacrylate in laboratory reactor. The calibration models for each of the monitored variables were obtained by applying the partial least squares regression method (PLS). The results confirmed that some NIR spectral ranges recommended in the literature are appropriate for the prediction of monomer content and Dp, and that there are spectral -1 . The results behaviors not yet explained in the region between 10475 and 13000cm also show that the in-line, the changes in Dp, monomer and polymer content can be simultaneously monitored in-line and in real time by NIR spectroscopy by using calibration models based on adequate spectral regions and distinct data pretreatments.
88

MMA, den förbjudna frukten – En kvantitativ studie om hur svensk nyhetsmedia gestaltar MMA

Bringsén, Filip January 2020 (has links)
Syftet med studien är att undersöka hur MMA framställs i svensk nyhetsmedia eftersom det historiskt sätt har varit en väldigt omtalad sport och nyhetsmedier tenderar att framställa den väldigt våldsamt, vilket tidigare forskning visar. Studien applicerar två teoretiska perspektiv för att undersöka detta, gestaltningsteorin och moralpanik. Genom en kvantitativ innehållsanalys kombinerat med gestaltningsanalys analyseras ett urval artiklar i från några av de största nyhetsmedierna i Sverige, Aftonbladet, Expressen och SVT Nyheter samt två MMA inriktade nyhetsmedier, Kimura och MMANytt. Detta görs för att undersöka hur olika sorters nyhetsmedier skildrar MMA och på så vis se skillnader ochlikheter för att skapa en helhetsbild av problemet. Resultatet visar att sporten har växt ochblivit mer legitim de senaste åren jämfört med tidigare studier. Trots detta förmedlas ändåen grad av moralpanik i sättet artiklarna ramar in både sporten och sportens utövare på. / The purpose of this study is to examine how MMA is portrayed in Swedish news mediasince historically speaking there has been a stigma about the sport and news media tends to depict it in a very violent manner, which previous studies also shows. The study appliestwo theoretical perspectives, framing theory and moral panic. Through a quantitativecontent analysis combined with a framing analysis a selection of articles are analyzed from some of the biggest sources of news media in Sweden, Aftonbladet, Expressen and SVT Nyheter as well as two MMA focused ones, Kimura and MMANytt. This is done toexamine how different types of news media depicts MMA and, in that way, see differencesand similarities to create a comprehensive understanding of the problem. The results show that the sport has grown and become more legitimate the last few years when compared to previous studies. Despite this a level of moral panic is being mediated in the way articles frame both the sport and its practitioners.
89

Technologie přípravy aprotických gelových polymerních elektrolytů na bázi PMMA / Aprotic gel polymer electrolytes based on PMMA prepared by various methodes

Kratochvíl, Martin January 2008 (has links)
This work deals with the preparation and measurement of an ionic conductivity of the gel polymer electrolytes prepared by various methods. In the theoretical part of the work, the types of conducting membranes, the development and the state of the art of the gel polymer electrolytes are summarized. The preparation and the results on ionic conductivity of the gels based on MMA, EMA and EOEMA are discussed in the experimental part.
90

Výroba separačního rámu pro válcovací stolici. / Manufacturing of separation subrack for rolling stand.

Trčka, Libor January 2010 (has links)
The project elaborated in terms of engineering studies concern with project of a manufactural process of separator weldment and of an economical analysis of a production calculated for one item of a weldment and one item of a casting. During elaboration this project there were used all obtainable norms and technical bibliography. In literery studies there are summarized important knowledges related to welding constructions, welding technology, heat treatment and checking fusion splices. There was choosed box construction for this separator weldment. That is designed of two types of material. First of materials S355J2G3, EN 10025 is used for structural parts and the second material S235JR, EN 10025 is used for stiffering pars. The propriety checking of this construction and used materials was performed by Finite Element Method. After calculating costs of production of both variants we can say, that the costs of production of one piece seperator weldment are considerably lower, than costs of production of one piece of casting.

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