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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.
221

Effects of plasticizing and crosslinking on the mechanical and barrier properties of coatings based on blends of starch and poly(vinyl alcohol)

Javed, Asif January 2015 (has links)
In the last decades, intensive research has been carried out in order to replace oil-based polymers with bio-based polymers due to growing environmental concerns. So far, most of the barrier materials used in food packaging are petroleum-based materials. The purpose of the barrier is to protect the packaged food from oxygen, water vapour, water and fat. The mechanical and barrier properties of coatings based on starch-plasticizer and starch-poly(vinyl alcohol) (PVOH)-plasticizer blends have been studied in the work described in this thesis. The plasticizers used were glycerol, polyethylene glycol and citric acid. In a second step, polyethylene coatings were extruded onto paperboard pre-coated with a starch-PVOH-plasticizer blend. The addition of PVOH to the starch increased the flexibility of the film. Curing of the film led to a decrease in flexibility and an increase in tensile strength. The flexibility of the starch-PVOH films was increased more when glycerol or polyethylene glycol was added than citric acid. The storage modulus of the starch-PVOH films containing citric acid increased substantially at high temperature. It was seen that the addition of polyethylene glycol or citric acid to the starch-PVOH blend resulted in an enrichment of PVOH at the surface of the films. Tensile tests on the films indicated that citric acid acted as a compatibilizer and increased the compatibility of the starch and PVOH in the blend. The addition of citric acid to the coating recipe substantially decreased the water vapour transmission rate through the starch-PVOH coated paperboard, which indicated that citric acid acts as a cross-linker for starch and/or PVOH. The starch-PVOH coatings containing citric acid showed oxygen-barrier properties similar to those of pure PVOH or of a starch-PVOH blend without plasticizer when four coating layers were applied on a paperboard. The oxygen-barrier properties of coatings based on a starch-PVOH blend containing citric acid indicated a cross-linking and increase in compatibility of the starch-PVOH blends. Polyethylene extrusion coating on a pre-coated paperboard resulted in a clear reduction in the oxygen transmission rate for all the pre-coating formulations containing plasticizers. The addition of a plasticizer to the pre-coating reduced the adhesion of polyethylene to pre-coated board. Polyethylene extrusion coating gave a board with a lower oxygen transmission rate when the paperboard was pre-coated with a polyethylene-glycol-containing formulation than with a citric-acid-containing formulation. The addition of polyethylene glycol to pre-coatings indicated an increase in wetting of the pre-coated paperboard by the polyethylene melt, and this may have sealed the small defects in the pre-coating leading to low oxygen transmission rate. The increase in brittleness of starch-PVOH films containing citric acid at a high temperature seemed to have a dominating effect on the barrier properties developed by the extrusion coating process. / Over the last few decades, industry and academia have made joint efforts to generate knowledge about renewable barrier materials in order to replace the oil-based barrier materials currently used in food packaging. This work has focused on the possibility of producing a material with high oxygen barrier properties including polyethylene as a moisture protection. The flexibility of starch films was increased by adding poly(vinyl alcohol) (PVOH) to the starch and the addition of a plasticizer to the starch-PVOH blend films further increase the flexibility of the films. The plasticizers used were glycerol, polyethylene glycol and citric acid. Curing of the films reduce their flexibility. The addition of citric acid to a starch-PVOH blend increased the compatibility of the starch-PVOH blend and affected the barrier properties of the coating layers containing citric acid. When a sufficient number of coating layers was applied, the starch-PVOH-citric-acid coatings showed oxygen-transmission-rate-values similar to those of the pure PVOH and of the starch-PVOH blend without plasticizers. Polyethylene extrusion coating on pre-coated paperboard resulted in a clear reduction in the oxygen transmission rate of all the pre-coating recipes based on starch-PVOH blends. The polyethylene extrusion coating showed a higher oxygen transmission rate for a board pre-coated with citric-acid-containing recipes than for a board pre-coated with polyethylene-glycol-containing recipes.
222

Linking spatial patterns of land-use to agents of deforestation in the Brazilian Amazon

Borrego Lorena, Rodrigo 09 April 2008 (has links)
Changes in land use and land cover are associated with many environmental issues observed on the earth’s surface. In the last decades, these changes were unprece-dented, mainly in tropical forest areas. The Brazilian Amazon, the world’s largest tropical forest, lost around 200.000 km² of primary forest in the last ten years (INPE, 2005). Considering this, and the consequences caused by this deforestation, it is important to know and define correctly the responsible agents, aiming at better pub-lic policies that can help preserve the forest. Searching for indicators that could help to identify the deforestation agents, some studies, such as Mertens and Lambin (1997), suggest that every deforestation process shapes the forest land in a specific way, producing a spatial pattern that can be interpreted as indicative of the agents with specific economic activities. Based on this hypothesis, the objective of this study was to contribute to a better understanding of land change processes in the Amazon forest, investigating the linkages between spatial patterns of deforestation, as visualized in satellite images, and different agents and their specific economic activities. To reach this objective, our methodological approach was based on socio-economic data acquired at a household level combined with data from satellite im-ages. First, different spatial patterns of deforestation were identified on the satellite images, based on the typologies proposed by Husson et al. (1995). Then, some of the identified spatial patterns were isolated and analyzed for specific aspects, such as, the deforestation rate calculated through satellite images. socio-economic character-istics based on household survey data and evolution of land use and land cover based on thematic maps derived from satellite images. In addition, cluster analysis was applied using the socio-economic data (household survey) and land use and land cover data (satellite images) in a search for homogeneous groups related to the spa-tial pattern. In the end, an Analysis of Variance (ANOVA) was applied to confirm the differences between spatial patterns. The results suggested that the different spatial patterns of deforestation found in the study area can be related to specific economic activities. Nevertheless, the re-sults have indicated that the spatial configuration is not a consequence of its main economic activity. They suggest that the spatial configuration is linked to the settle-ment project, and the main economic activity in the spatial patterns is a consequence of a set of factors such as: size of property, location and disposition of the property, presence or absence of infrastructure (road, market, transportation, economic and technical).
223

Characterization of the Structure, Function and Assembly of the DrrAB Antibiotic Efflux Pump in Streptomyces Peucetius

Rao, Divya Kishore 30 November 2008 (has links)
ATP binding cassette (ABC) transporters constitute one of the largest families of transport proteins. The occurrence of multidrug resistance (MDR) in human cancer cells has been correlated with the over expression of human ABC, P-glycoprotein (Pgp). Streptomyces peucetius produces two anticancer agents, doxorubicin and daunorubicin, that belong to the anthracycline family of antibiotics. The organism is self-resistant to the potent effects of the antibiotics it produces due to the action of an efflux pump, DrrAB. Both Pgp and DrrAB carry out similar functions, but in two different cell types. An understanding of the bacterial drug transporter DrrAB is thus expected to help in obtaining a better understanding of the function and evolution of the multidrug transporter P-glycoprotein. In DrrAB, the catalytic and membrane domains are present on separate subunits, DrrA and DrrB respectively. How the catalytic ATP-binding domains and the membrane domains in transporters interact with each other, or how energy is transduced between them, is not well understood. We introduced several single cysteine substitutions in DrrB and then by using a cysteine to amine hetero-bifunctional cross-linker showed that DrrA interacts predominantly with the N-terminal cytoplasmic tail of DrrB. Within this region of DrrB, we also identified a sequence with similarities to the EAA motif found in importers of the ABC family of proteins, thus leading to the proposal that the EAA or the EAA-like motif may be involved in forming a generalized interface between the ABC and the TMD of both uptake and export systems. By using a combination of approaches, including point mutations and disulfide cross-linking analysis, we show here that the Q-loop region of DrrA plays an important role in dimerization of DrrA as well as in interactions with DrrB. Furthermore, we also show that the interaction of the Q-loop with the N-terminus of DrrB is involved in transmitting conformational changes between DrrA and DrrB. The scope of the present study further extends into identifying the factors involved in the biogenesis of the DrrAB pump. We have identified two accessory proteins namely, FtsH and GroEL that may be involved in proper folding and assembly of the transporter.
224

Paperspace : a novel approach to document management by combining paper and digital documents

Sallam, Samer 20 November 2006
Personal document management systems provide good support for storing and organizing digital documents. However, there are no computer tools that support organization of paper documents on our desks. We ran a study of people's organization of their office desk space with respect to their digital workspace. This study resulted in a set of requirements for a media bridging tool. Based on these requirements, we built a prototype media bridging tool called PaperSpace that uses computer vision to link paper and digital documents. The system also tracks piles of paper documents on the real desktop, and links those papers to digital documents stored in the computer. Digital documents can be sorted and grouped according to the physical layout of the corresponding papers on the desk. The system automatically creates digital piles of documents in a simulated desktop that reflect the paper piles on the real desktop. The user can access valuable information through the system, such as printing statistics, location of a printed document on the desk, and past projects and their documents. A two week user evaluation of the system showed interesting usage scenarios and future trends for improving user interaction.
225

Paperspace : a novel approach to document management by combining paper and digital documents

Sallam, Samer 20 November 2006 (has links)
Personal document management systems provide good support for storing and organizing digital documents. However, there are no computer tools that support organization of paper documents on our desks. We ran a study of people's organization of their office desk space with respect to their digital workspace. This study resulted in a set of requirements for a media bridging tool. Based on these requirements, we built a prototype media bridging tool called PaperSpace that uses computer vision to link paper and digital documents. The system also tracks piles of paper documents on the real desktop, and links those papers to digital documents stored in the computer. Digital documents can be sorted and grouped according to the physical layout of the corresponding papers on the desk. The system automatically creates digital piles of documents in a simulated desktop that reflect the paper piles on the real desktop. The user can access valuable information through the system, such as printing statistics, location of a printed document on the desk, and past projects and their documents. A two week user evaluation of the system showed interesting usage scenarios and future trends for improving user interaction.
226

Foamed Eva-bitumen Blends And Composites

Cankaya, Burhan Fuat 01 January 2009 (has links) (PDF)
The thermal conductivities of foamed polymer based materials are much lower thermal conductivity values than unfoamed polymeric materials. Especially, thermal conductivity values of foamed polymers with closed-cell structure decreases to 0.03 W/m.K. The reinforcement of foamed polymeric materials by mixing with bitumen lowers the raw material cost. The main objective of this study is to make a new thermal insulation material with low thermal conductance. In this study, the effects of concentration of calcium carbonate as inorganic filler and the effects of cross-linking on the properties foamed and unfoamed ethylene-vinyl acetate (EVA) copolymer based bituminous blends and composites were investigated. Applications such as thermal, mechanical characteristics of foamed and unfoamed EVA based bituminous composites were investigated. Foamed EVA based bituminous composites were prepared by using Brabender Plastic Coder, PLV 151. Mixing was made at 120 &ordm / C at 60 rpm for 15 minutes. The prepared blends were molded by a technique called Hand Lay-up Self-expanding Batch Molding (HLUSEBM) which was firstly applied by our group. The molding temperature was 170 &ordm / C at which chemical blowing agent and cross-linking agent decomposes. According to test results, at moderate chemical blowing agent and EVA content, the best closed-cell structure with high porosity and low thermal conductivity values were obtained. The compressive properties of foamed polymer based bituminous composites (FPBBCs) increase with increasing CBA and EVA content. With increasing calcium carbonate and EVA concentration, the porosity of FPBBCs increases but thermal conductivity of them decreases. On the other hand, with increasing filler content but with decreasing EVA concentration elastic modulus of FPBBCs increases but elastic recovery decreases.
227

Grammar And Information: A Study Of Turkish Indefinites

Ozge, Umut 01 September 2010 (has links) (PDF)
Turkish, along with many other languages, marks its direct objects in two distinct ways: overt accusative marking (Acc) versus no marking (&empty / ). The research on the grammar and interpretation of Turkish inde
228

Aortic valve analysis and area prediction using bayesian modeling

Ghotikar, Miheer S 01 June 2005 (has links)
Aortic Valve Analysis and Area Prediction using Bayesian Modeling Miheer S. Ghotikar ABSTRACT Aortic valve stenosis affects approximately 5 out of every 10,000 people in the United States. [3] This disorder causes decrease in the aortic valve opening area increasing resistance to blood flow. Detection of early stages of valve malfunction is an important area of research to enable new treatments and develop strategies in order to delay degenerative progression. Analysis of relationship between valve properties and hemodynamic factors is critical to develop and validate these strategies. Porcine aortic valves are anatomically analogous to human aortic valves. Fixation agents modify the valves in such a manner to mimic increased leaflet stiffness due to early degeneration. In this study, porcine valves treated with glutaraldehyde, a cross-linking agent and ethanol, a dehydrating agent were used to alter leaflet material properties. The hydraulic performance of ethanol and glutaraldehyde treated valves was compared to fresh valves using a programmable pulse duplicator that could simulate physiological conditions. Hydraulic conditions in the pulse duplicator were modified by varying mean flow rate and mean arterial pressure. Pressure drops across the aortic valve, flow rate and back pressure (mean arterial pressure) values were recorded at successive instants of time. Corresponding values of pressure gradient were measured, while aortic valve opening area was obtained from photographic data. Effects of glutaradehyde cross-linking and ethanol dehydration on the aortic valve area for different hydraulic conditions that emulated hemodynamic physiological conditions were analyzed and it was observed that glutaradehyde and ethanol fixation causes changes in aortic valve opening and closing patterns. Next, relations between material properties, experimental conditions, and hydraulic measures of valve performance were studied using a Bayesian model approach. The primary hypothesis tested in this study was that a Bayesian network could be used to predict dynamic changes in the aortic valve area given the hemodynamic conditions. A Bayesian network encodes probabilistic relationships among variables of interest, also representing causal relationships between temporal antecedents and outcomes. A Learning Bayesian Network was constructed; direct acyclic graphs were drawn in GeNIe 2.0ʾ using an information theory dependency algorithm. Mutual Information was calculated between every set of parameters. Conditional probability tables and cut-sets were obtained from the data with the use of Matlabʾ. A Bayesian model was built for predicting dynamic values of opening and closing area for fresh, ethanol fixed and glutaradehyde fixed aortic valves for a set of hemodynamic conditions. Separate models were made for opening and closing cycles. The models predicted aortic valve area for fresh, ethanol fixed and glutaraldehyde fixed valves. As per the results obtained from the model, it can be concluded that the Bayesian network works successfully with the performance of porcine valves in a pulse duplicator. Further work would include building the Bayesian network with additional parameters and patient data for predicting aortic valve area of patients with progressive stenosis. The important feature would be to predict valve degenration based on valve opening or closing pattern.
229

Investigation and Synthesis of Novel Graphene-Based Nanocomposites for Hydrogen Storage

D'angelo, Anthony Joseph 01 January 2012 (has links)
It is of great interest to develop and utilize a high surface area material with optimized hydrogen sorption properties. The need for a renewable energy source to replace automobile gasoline has become more critical in the past decade. Hydrogen is a viable fuel source for automobile usage; however, the question of how hydrogen will be safely and efficiently stored still remains. Critical factors for optimum hydrogen storage include ambient conditions and low activation temperature for adsorption and desorption phenomena. In order for optimum hydrogen adsorption to be achieved, the properties of (1) high surface area, (2) optimum hydrogen adsorption energy, and (3) Kubas interactions between metals and hydrogen molecules need to be considered. Fullerenes have recently become more popular with the discovery and mass production of graphene sheets derived from graphite. Graphene is a modified form of graphite that takes the form of sheets with less agglomeration than its respective graphitic form. This form has the potential for high surface area and storage capabilities. Storage of hydrogen at room temperature must be optimized by increasing the surface area and having an adsorption enthalpy between 15 - 20 KJ/mol. Graphene (G) sheets and graphene oxide (GO) sheets have been utilized as a matrix for hydrogen storage. These materials can also be cross-linked with organic spacers in order to form a porous framework of higher surface area. Metal decorating by calcium and platinum of the G/GO matrix has been used to enhance Kubas interactions, adsorption enthalpies, and spillover phenomenon. The use of a polymer matrix has also been implemented. Polyaniline is a novel superconducting polymer with unique electronic properties. Complexes of Polyaniline with graphene and graphene oxide have been investigated for hydrogen storage properties. Graphene and graphene oxide surface modification via metal decoration have been investigated in order to determine the most efficient synthesis and particle size on the G/GO matrix. Characterization by XRD, BET, adsorption enthalpy, PCT, TGA, FT-IR, and TEM/SEM (when applicable) were employed to optimize and compare the materials in the effort to develop a suitable storage material.
230

碳交易市場之法律研究 / A Critical Legal Study on Linking Emission Trading Systems

陳韻竹, Chen, Yun Chu Unknown Date (has links)
氣候變遷已然成為國際間急需面對的課題。為了減輕溫室氣體排放量所採取之環境政策工具,不僅需要內國及國際環境法制加以處理,也需要輔以經濟誘因來推動溫室氣體減量工作。開發中國家因經濟成長使排放量急劇增加,包括亞洲主要國家的中國大陸、南韓、日本與台灣等,也開始積極推動碳交易機制。 碳交易機制連結是一種將各國的碳交易機制有組織性地連結而成全球碳交易市場的方式,在目前全球氣候變遷制度談判僵局之下,亞洲國家積極建立推動各國碳交易機制及其法規,亞洲碳交易市場連結發展之可能性成為氣候變遷焦點之一。本文採取文獻回顧法及歸納法,透過檢視分析學者文獻、歐盟、加州與魁北克碳交易機制的連結法規制度,探討連結碳交易機制所需要的法規要素,藉由分析成功的連結經驗,以探討亞洲國家複製歐盟、加州與魁北克碳交易機制連結模式之可行性。 以亞洲國家現今關於碳交易制度的立法規劃來看,目前只有韓國法規具有明確立法連結之相關規定,因此,進而比對韓國連結法規是否已具備足以對外連結之規範及要素,檢視韓國在運行了韓國碳交易機制之後,是否會有對外連結的可能性。台灣雖然已經於2015年通過溫室氣體減量及管理法,並於同年7月生效之,在該法規中有連結之基本概念,但是對於其他如減量階段時程、抵銷詳細規範等,在法規中或其他相關法規中未有具體擘劃。 在面臨亞洲地區一個大型的區域性碳交易市場即將崛起之際,亞洲地區的國家若要發展下一步的連結碳交易機制,在法規制度內須對於對外連結有明確的法律授權,其碳交易機制才有望可發展後續的對外連結。 / In order to reduce greenhouse gas emissions, every country should not only construct the international environmental law and country law, but also use economic strategies as assistant. The emission increases sharply because of rapid economic growth in developing countries in Asia. Therefore, major Asian countries including China, South Korea, Japan and Taiwan, promote the emission trading system. The emissions trading system is a key tool for reducing greenhouse gas emissions. Linking the emission trading systems is an organized way to create a global carbon market. When the global climate change negotiation is deadlocked, a growing number of countries in Asia are integrating cap-and-trade systems into their national climate policies, so that the probability of developing the carbon market in Asia becomes the main issue. This study summarizes and refers to the scholars’ reference materials, the law and regulation of the EU, California and Quebec emission trading systems. The aim of the study is to: (1) generalize the legal and institutional requirements for linking emissions trading systems by analyzing the experiences from the EU, California and Quebec; (2) discuss whether emission trading systems in Asia could be linked. The study concludes that only South Korea has the relevant legislation that authorizes linking with other emissions trading systems in Asia. It is more likely that South Korea emission trading system will establish link to other countries. By viewing and comparing the legal requirements for linking emissions trading system in this study, however, it seems like that there are still some legal challenges for South Korea to be fully prepared for linking with other emissions trading systems in the short term.

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