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Studies of PF Resole / Isocyanate Hybrid AdhesivesZheng, Jun 09 January 2003 (has links)
Phenol-formaldehyde (PF) resole and polymeric diphenylmethane diisocyanate (PMDI) are two commonly used exterior thermosetting adhesives in the wood-based composites industry. There is an interest in combining these two adhesives in order to benefit from their positive attributes while also neutralizing some of the negative ones. Although this novel adhesive system has been reportedly utilized in some limited cases, a fundamental understanding is lacking. This research serves this purpose by investigating some of the important aspects of this novel adhesive system.
The adhesive rheological and viscometric properties were investigated with an advanced rheometer. The resole/PMDI blends exhibited non-Newtonian flow behavior. The blend viscosity and stability were dependent on the blend ratio, mixing rate and time. The adhesive penetration into wood was found to be dependent on the blend ratio and correlated with the blend viscosity. By using dynamic mechanical analysis, the blend cure speed was found to increase with the PMDI content. Mode I fracture testing of resole/PMDI hybrid adhesive bonded wood specimens indicated the dependence of bondline fracture energy on the blend ratio. The 75/25 PF/PMDI blend exhibited a high fracture energy with a fast cure speed and processable viscosity. Exposure to water-boil weathering severely deteriorated the fracture energies of the hybrid adhesive bondlines.
More detailed chemistry and morphological studies were performed with cross-polarization nuclear magnetic resonance and 13C, 15N-doubly labeled PMDI. A spectral decomposition method was used to obtain information regarding chemical species concentration and relaxation behavior of the contributing components within the major nitrogen resonance. Different urethane concentrations were present in the cured blend bondlines. Water-boil weathering and thermal treatment at elevated temperatures (e.g. > 200°C) caused reduced urethane concentrations in the bondline. Solid-state relaxation parameters revealed a heterogeneous structure in the non-weathered blends. Water boil weathering caused a more uniform relaxation behavior in the blend bondline.
By conducting this research, more fundamental information regarding the PF/PMDI hybrid adhesives will become available. This information will aid in the evaluation of, and improve the potential use of PF/PMDI hybrid adhesives for wood-based composites. / Ph. D.
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Modified Phenol-Formaldehyde Resins for C-Fiber Reinforced Composites: Chemical Characteristics of Resins, Microstructure and Mechanical Properties of their CompositesKim, Young Eun 06 January 2011 (has links) (PDF)
This work correlates the chemistry of phenol-formaldehyde (PF) resins, its functionalities with their microstructural and mechanical properties in composite materials. The main focus is put on the development of the pores in dependence on the chemical composition of the resins and their influence on the structure of the material.
Chemical characteristics of the synthesized resins are analyzed and physical/mechanical properties of the matrices based on PF resins are determined. Differences in the chemical properties are detected e.g. by FT-IR and NMR spectroscopy. They indicate the existence of similar molecular basic structure units, but different network conditions of the resins. DSC investigations point on different reaction mechanisms and temperatures; they reveal also their changed thermal behavior. The bulk matrix behavior differs from that of the composite based on the same resin due to the three dimensional stress and strain fields in the composites. The structure of the CFRP composites is strongly depended on the fiber/matrix interaction. The fiber matrix bonding (FMB) strength controls the load transfer via shear forces and therefore the segmentation of the fiber bundles.
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Vliv dusíkaté zátěže mokřadních luk na obsah volných aminokyselin v půdě. / Effect of N eutrofication of wetland soils on organic N content and qualityŠEDA, Martin January 2009 (has links)
This study deals with an effect of fertilization on amount and quality of free amino acids in soil from wet meadows affected by nutrient loading. Free amino acids were analysed in the soil from the field experiment situated at wet meadows, where an increased nutrient input is simulated (fertilizer NPK). The experiment was established on two sites with different types of soil {--} Záblatí with organic soil and Hamr with mineral soil, both areas in the South Bohemia region. The soil was repeatedly sampled for more than two years and year. One part of this study is focused on testing of ninhydrine-method and HPLC-method for measuring free amino acids and efficiency of different extractants.
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Modified Phenol-Formaldehyde Resins for C-Fiber Reinforced Composites: Chemical Characteristics of Resins, Microstructure and Mechanical Properties of their CompositesKim, Young Eun 06 January 2011 (has links)
This work correlates the chemistry of phenol-formaldehyde (PF) resins, its functionalities with their microstructural and mechanical properties in composite materials. The main focus is put on the development of the pores in dependence on the chemical composition of the resins and their influence on the structure of the material.
Chemical characteristics of the synthesized resins are analyzed and physical/mechanical properties of the matrices based on PF resins are determined. Differences in the chemical properties are detected e.g. by FT-IR and NMR spectroscopy. They indicate the existence of similar molecular basic structure units, but different network conditions of the resins. DSC investigations point on different reaction mechanisms and temperatures; they reveal also their changed thermal behavior. The bulk matrix behavior differs from that of the composite based on the same resin due to the three dimensional stress and strain fields in the composites. The structure of the CFRP composites is strongly depended on the fiber/matrix interaction. The fiber matrix bonding (FMB) strength controls the load transfer via shear forces and therefore the segmentation of the fiber bundles.:1 Introduction
2 Theoretical Overview
2.1 Phenol-Formaldehyde Resins
2.1.1 Overview
2.1.2 Reactions of phenol-formaldehyde resin
2.1.2.1 Addition reaction
2.1.2.2 Condensation reaction
2.1.2.3 Curing
2.1.3 Application of phenol-formaldehyde resin
2.2 Carbon-Fiber
2.2.1 PAN type carbon fiber
2.2.2 Pitch type carbon fiber
2.2.3 Application of carbon fiber
2.3 Composites
2.3.1 Carbon fiber composites
2.3.2 Matrix
2.3.3. Interfaces
2.3.3.1 Carbon fiber side interface between carbon fiber and matrix 2.3.3.2 Matrix side interface between carbon fiber and matrix
2.3.3.3 Toughening of fiber-reinforced polymer
3 Goal and Works
3.1 Problem and Motivation
3.2 Objective and Works plan
4 Experiments and Methods
4.1 Materials
4.1.1 Chemical reagents
4.1.2 Carbon fiber weave
4.2 Synthesis of Resin
4.3 Fabrication of Matrix
4.4. Measurement methods and Experimental approach
4.4.1 Chemical analysis
4.4.2 Microstructure characterization
4.4.3 Mechanical test
5 Chemical characterization of modified phenol-formaldehyde resin
5.1 Fourier Transformed Infrared spectroscopy (FT-IR)
5.1.1 Introduction
5.1.2 Preparation and Measurement
5.1.3 Results and Discussion
5.2 Nuclear Magnetic Resonance spectroscopy (NMR)
5.2.1 Liquid 13C Nuclear Magnetic Resonance spectroscopy
5.2.1.1 Introduction
5.2.1.2 Preparation and Measurement
5.2.1.3 Results and Discussion
5.2.2 Solid 13C CP-MAS Nuclear Magnetic Resonance spectroscopy
5.2.2.1 Introduction
5.2.2.2 Preparation and Measurement
5.2.2.3 Results and Discussion
5.3 Simultaneous Thermal Analysis (STA)
5.3.1 Introduction
5.3.2 Preparation and Measurement
5.3.3 Results and Discussion
5.3.3.1 Simultaneous Thermal Analysis
5.3.3.2 Different Scanning Calorimetry
5.4 Conclusion
6 Microstructural Characterization
6.1 Porosity
6.1.1 Introduction
6.1.2 Preparation and Measurement
6.1.3 Results and Discussion
6.1.3.1 Density
6.1.3.2 Porosity
6.2 Morphology
6.2.1 Introduction
6.2.2 Preparation and Measurement
6.2.3 Results and Discussion
6.2.3.1 Optical Microscopy
6.3.3.2 Scanning Electron Microscopy
6.3.3.2.1 Observation of the bulk matrix
6.2.3.2.2 Structural observation of the composite
6.3 Conclusion
7 Mechanical Properties
7.1 Hardness test
7.1.1 Introduction
7.1.2 Preparation and Measurement
7.1.3 Results and Discussion
7.2 Micro-bending test
7.2.1 Introduction
7.2.2 Preparation and Measurement
7.2.3 Results and Discussion
7.3 Conclusion
8 Summary and Conclusion
8.1 Summary
8.2 Conclusion
9 References
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Equal Pay in der ArbeitnehmerüberlassungLi, Bite 24 June 2022 (has links)
Diese Arbeit setzt sich hauptsächlich mit der Frage auseinander, inwieweit das chinesische Gesetzesrecht einerseits und das deutsche Gesetzesrecht andererseits in der Lage sind, dem in beiden Rechtsordnungen verankerten Anspruch des Leiharbeitnehmers auf Equal Pay Geltung zu verschaffen. Die Entwicklung der chinesischen Gesetzgebung über die Arbeitnehmerüberlassung zeigt, dass der Gesetzgeber in der Praxis weitverbreiteten Diskriminierung von Leiharbeitnehmern im Vergleich zu Festangestellten entschieden entgegentreten will. In Deutschland ist das genaue Gegenteil zu beobachten. War der Schutz des Leiharbeitnehmers bei Erlass des Arbeitnehmerüberlassungsgesetzes im Jahre 1972 noch das maßgebliche Motiv, wurde mit dem Reformgesetz vom 23.12.2002 damit begonnen, die Arbeitnehmerüberlassung mehr und mehr als Instrument der Beschäftigungspolitik zu sehen und die Arbeitnehmerüberlassungsvorschriften zu "liberalisieren". Anders als die chinesische Gesetzgebung zeigt die Rechtsprechung in China ein anderes Bild: Von den in der vorliegenden Arbeit untersuchten 25 Gerichtsfällen wurde nur in 4 Fällen zugunsten des Leiharbeitnehmers entschieden. Eine Analyse der ablehnenden Entscheidungen macht jedoch klar, dass die Gerichte für ihre Entscheidungen Begründungen heranzogen, die im Gesetz keine Stütze finden. Die Forschungsergebnisse zeigen: Das Problem eines unzureichenden Leiharbeitnehmerschutzes des chinesischen Rechts liegt darin, dass die Rechtsprechung das ihr zur Verfügung stehende gesetzliche Instrumentarium nicht hinreichend nutzt. In Deutschland ergibt sich dieses Problem vielmehr aus der bewussten und klaren Entscheidung des Gesetzgebers, der Vorgabe des Europäischen Gesetzgebers – tarifvertragliche Abweichung vom Equal Pay ausschließlich unter Berücksichtigung des Gesamtschutzes des Leiharbeitnehmers – nicht zu folgen. / This dissertation mainly deals with the question: To what extent the Chinese law and the German law can guarantee the validity of the right of temporary agency workers to equal pay, which is anchored in both legal systems. The development of Chinese legislation on temporary agency work shows that in practice, the legislator undoubtedly wants to decisively counteract widespread discrimination against temporary agency workers. In Germany, the exact opposite situation can be observed. While the protection of temporary agency worker remained the decisive motive when the Act on Temporary Agency Work was enacted in 1972, the reform law of December 23, 2002 began to view temporary agency work more and more as an instrument of employment policy and to "liberalize" the regulations on temporary agency work. In contrast to Chinese legislation, the judgement in China shows a different picture: Among the 25 cases researched in this dissertation, there are only 4 cases that were judged in favor of the temporary agency worker. This could lead to the assumption that in China, the law also attaches only secondary importance to the temporary agency worker's claim to equal pay. However, an analysis of the judgements clarifies that the courts used justifications for their decisions which could not find support in the law. According to the research of this dissertation, the problem of inadequate protection to temporary agency worker under Chinese law lies in the fact that the courts fail to make sufficient use of the legal instruments at their disposal. In Germany, this problem is resulted rather from the deliberate and clear decision of the legislator, namely failure to follow the specification of the European legislator - deviation from equal pay by collective agreement exclusively under consideration of the overall protection of the temporary agency worker.
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Development and Evaluation of an Active Radio Frequency Seeker Model for a Missile with Data-Link Capability / Utveckling och utvärdering av en radarbaserad robotmålsökarmodell med datalänkfunktionHendeby, Gustaf January 2002 (has links)
To develop and maintain a modern combat aircraft it is important to have simple, yet accurate, threat models to support early stages of functional development. Therefore this thesis develops and evaluates a model of an active radio frequency (RF) seeker for a missile with data-link capability. The highly parametrized MATLAB-model consists of a pulse level radar model, a tracker using either interacting multiple models (IMM) or particle filters, and a guidance law. Monte Carlo simulations with the missile model indicate that, under the given conditions, the missile performs well (hit rate>99%) with both filter types, and the model is relatively insensitive to lost data-link transmissions. It is therefore under normal conditions not worthwhile to use the more computer intense particle filter today, however when the data-link degrades the particle filter performs considerably better than the IMM filter. Analysis also indicate that the measurements generated by the radar model are neither independent, white nor Gaussian. This contradicts the assumptions made in this, and many other radar applications. However, the performance of the model suggests that the assumptions are acceptable approximations of actual conditions, but further studies within this are recommended to verify this.
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Citation of Psalm 68(67).19 in Ephesians 4.8 within the context of early Christian uses of the PsalmsEhorn, Seth January 2015 (has links)
This thesis examines the citation of Ps 68(67).19 in Eph 4.8. Following an introduction that introduces the problem of the altered wording in the citation in Eph 4.8, chapter 2 comprises a History of Research that is organised around the possible sources for the author’s citation in Eph 4.8. One of several conclusions made is that the proclivity of NT scholars to attribute the source text to particular Jewish traditions has contributed to overlooking the import of Ps 68(67).19 within a normal pattern of christological reading of the Psalms in early Christianity. Following these opening chapters, the thesis is divided broadly into Part One and Part Two. The first is deconstructive in nature; the second is constructive. Part One examines textual traditions of Ps 68(67).19 within Justin Martyr, the Peshitta Psalter, and Targum Psalms. Each of these sources share the reading ‘give’ rather than ‘receive’, raising the question of the relationship between these traditions and Eph 4.8. Chapter 3 examines Justin’s Dialogue with Trypho, which contains two citations of Ps 68(67).19 that strongly resemble Ephesians. Nevertheless, as nearly all interpreters acknowledge, Justin never refers directly to ‘Paul’ or ‘Pauline’ letters in any of his writings. Is the parallel wording of Justin’s citations evidence for an early Christian tradition that was also available to Ephesians? I argue that although unmentioned by name, a reasonable case can be made that Justin is familiar with the Pauline corpus, including Eph 4.8. Chapter 4 considers the evidence of Peshitta Psalms, which agrees with the reading of Eph 4.8 in a strand of its copyist tradition. After examining scholarly construals of the Peshitta MS tradition, I consider direct evidence for the influence of Eph 4.8 upon some Peshitta MSS as intimated by Theodore of Mopsuestia. Chapter 5 examines Targum Psalms, focusing on translation techniques and the targumist’s tendency to add, alter, or modify his source in various ways. I argue that when the targumist’s techniques and tendencies are taken into consideration, the targum’s reading ‘give’ is better understood as a typical targumic insertion. The proclivity of many scholars to link Targum Psalms to Eph 4.8 is a classic example of ‘parallelomania’. Part Two turns to make a constructive case for the citation found in Eph 4.8. Chapter 6 is a close examination of the author of Ephesians’ approach to literary borrowing. I consider both his citations from the Jewish scriptures and his use of Colossians as evidence. Chapter 7 examines how early Christians read the biblical Psalms as prophecies. Following a survey of Jewish readings of the Psalms, this chapter surveys how early Christians read the Psalms in light of the death and resurrection- exaltation of Christ. Drawing insights from this, chapter 8 turns to consider the phrases ‘he ascended . . . he gave gifts’ in Eph 4.8. I argue that an ambiguity of the addressee in the text of Ps 68(67).19 allowed for the application of this text to Christ. Moreover, the ‘ascent’ language could easily be applied to the resurrection- exaltation and this association naturally led to the language of gift-giving in Eph 4.8. Chapter 9 considers how the citation of Ps 68(67).19 fits into the context of Ephesians 4, focusing on several important factors such as the language of descent in Eph 4.9–10. Part One and Part Two are followed by a short conclusion that summarises the thesis and draws out several conclusions and implications based upon this study.
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Diuretic, natriuretic, and vasodepressor activity of a lipid fraction enhanced in medium of cultured mouse medullary interstitial cells by a selective FAAH inhibitorDaneva, Zdravka P 01 January 2019 (has links)
The relationship between the endocannabinoid system in the renal medulla and the long-term regulation of blood pressure is not well understood. To investigate the possible role of the endocannabinoid system in renomedullary interstitial cells, mouse medullary interstitial cells (MMICs) were obtained, cultured and characterized for their responses to treatment with a selective inhibitor of fatty acid amide hydrolase (FAAH), PF-3845. Treatment of MMICs with PF-3845 increased cytoplasmic lipid granules detected by Sudan Black B staining and multilamellar bodies identified by transmission electron microscopy. HPLC analyses of lipid extracts of MMIC culture medium revealed a 205nm-absorbing peak that showed responsiveness to PF-3845 treatment. The biologic activities of the PF-3845-induced product (PIP) isolated by HPLC were investigated in anesthetized, normotensive surgically-instrumented mice. Intramedullary and intravenous infusion of PIP at low dose rates (0.5-1 AU/10 min) stimulated diuresis and natriuresis, whereas at higher doses, these parameters returned toward baseline but mean arterial pressure (MAP) was lowered. Whereas intravenous bolus doses of PIP stimulated diuresis, GFR and medullary blood flow (MBF) and reduced or had no effect on MAP, an intraperitoneal bolus injection of PIP reduced MAP, increased MBF, and had no effect on urinary parameters. Genetic or pharmacological ablation of the cannabinoid type 1 receptors in mice completely abolished the diuretic and vasodepressor properties of intramedullary infused PIP, suggesting that the PF-3845-induced product requires the presence of CB1 receptors in order to elicit its renal effects. In a radioactive competition binding assay, using Chinese hamster ovary cells expressing CB1 receptors, PIP successfully displaced the CB1 selective inverse agonist [3H] SR141716A, revealing that the lipid extract was able to compete for binding to CB1 receptors. Finally, we investigated the tubular location of diuretic activity that the PF-3845-induced lipid fraction exhibits. In a renal function in vivo experiment, we pre-treated anesthetized mice with an intramedullary infusion of one of four well-known diuretics. This procedure was followed by an intramedullary infusion of PIP (1AU). Only inhibition of the proximal tubule sodium reabsorption diminished the diuretic activity of the PF-3845-induced product, suggesting that the lipid fraction requires a physiologically intact proximal tubular reabsorption mechanism for it to produce diuresis. These data support a model whereby PF-3845 treatment of MMICs results in increased secretion of a neutral lipid which acts directly to promote diuresis and natriuresis and indirectly through metabolites to produce vasodepression. Efforts to identify the structure of the PF-3845-induced lipid and its relationship to the previously proposed renomedullary antihypertensive lipids are ongoing.
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Development and Evaluation of an Active Radio Frequency Seeker Model for a Missile with Data-Link Capability / Utveckling och utvärdering av en radarbaserad robotmålsökarmodell med datalänkfunktionHendeby, Gustaf January 2002 (has links)
<p>To develop and maintain a modern combat aircraft it is important to have simple, yet accurate, threat models to support early stages of functional development. Therefore this thesis develops and evaluates a model of an active radio frequency (RF) seeker for a missile with data-link capability. The highly parametrized MATLAB-model consists of a pulse level radar model, a tracker using either interacting multiple models (IMM) or particle filters, and a guidance law. </p><p>Monte Carlo simulations with the missile model indicate that, under the given conditions, the missile performs well (hit rate>99%) with both filter types, and the model is relatively insensitive to lost data-link transmissions. It is therefore under normal conditions not worthwhile to use the more computer intense particle filter today, however when the data-link degrades the particle filter performs considerably better than the IMM filter. Analysis also indicate that the measurements generated by the radar model are neither independent, white nor Gaussian. This contradicts the assumptions made in this, and many other radar applications. However, the performance of the model suggests that the assumptions are acceptable approximations of actual conditions, but further studies within this are recommended to verify this.</p>
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Through the Prisms of Gender and Power: Agency in International Courtship between Colombian Women and American MenCogua-Lopez, Jasney E. 23 March 2010 (has links)
Since 1999 Colombia has experienced dramatic increases in emigration, particularly the emigration of women towards the U.S. as fiancées of U.S. citizens or residents. Parallel to this trend is the increased number of websites facilitating these Colombian-American matches. This dissertation investigates the agency of Colombian women and American men who pursue romantic courtship through the services of International Marriage Brokers (IMBs) from the “Gendered Geographies of Power” (GGP) framework of analysis. It examines how both groups’ social locations, their positioning in multiple axes of differentiation including gender, nationality and social class, affects how and why they exert their agency across and within different geographic scales. Most importantly, it investigates the role the imagination plays (imagination work) in both men and women’s agency, an aspect of the GGP framework that has been under-researched and theorized to date. The research also finds that this imagination work is promoted and cultivated in deeply gendered ways by IMBs seeking to profit off this transnational courtship. Employing data collected via interviews and content analysis of IMBs’ websites, the dissertation analyzes comparatively the expectations each group (women, men and IMBs) bring to their imagination work and experiences of the courtship marketplace. A central question posed and answered in the dissertation is “What do women and men courting each other in cyberspace seek and do they find it?” The dissertation finds that the men seek “traditional” women and the women seek “liberated” less “macho” men. Ironically, the men find Colombian women who are among the most “liberated” women in their homeland but who downplay this aspect of themselves in order to strategically find a more modern man and migrate abroad where they expect to find greater personal and professional opportunities.
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