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1
Popara, Nikola. „Využití umělé inteligence k monitorování stavu obráběcího stroje“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-444960.
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This thesis is focus on monitoring state of machine parts that are under the most stress. Type of artificial intelligence used in this work is recurrent neural network and its modifications. Chosen type of neural network was used because of the sequential character of used data. This thesis is solving three problems. In first problem algorithm is trying to determine state of mill tool wear using recurrent neural network. Used method for monitoring state is indirect. Second Problem was focused on detecting fault of a bearing and classifying it to specific category. In third problem RNN is used to predict RUL of monitored bearing.
2
Solano, Alvarez Wilberth. „Microstructural degradation of bearing steels“. Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/249201.
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The aim of the work presented in this thesis is to clarify one of the most fundamental aspects of fatigue damage in bearings steels through critical experiments, in particular whether damage in the form of cracks precedes hard “white-etching matter" formation, which is carbon supersaturated nanoscaled ferrite. Heat treatments have been designed to create four different crack types and distributions: scarce martensite plate cracks, fine grain boundary cracks, abundant martensite plate cracks, and surface cracks. Subsequent rolling contact fatigue experiments showed that the amount of hard white-etching matter is higher in pre-cracked samples compared to those without prior damage and that its formation mechanism is the frictional contact of disconnected surfaces within the bulk that elevate the temperature and localise deformation. These key experiments indicate that hard white-etching matter is the consequence, not the cause, of damage. Therefore, one way to avoid white-etching matter is by increasing the toughness of the material. The macroscopically homogenous distribution of microcracks proved also to be a useful rolling contact fatigue life enhancer due to damage deflection via crack branching and a powerful trap for diffusible hydrogen. Successful trapping was corroborated by the inability of hydrogen to cause crack propagation via embrittlement or accelerate white-etching matter generation during rolling contact fatigue. By also studying the behaviour of a nanostructured bainitic steel under rolling contact fatigue, it was found that its degradation mechanism is ductile void formation at bainitic ferrite/stress-induced martensite interfaces, followed by growth and coalescence into larger voids that lead to fracture along the direction of the softer phase as opposed to the conventional damage mechanism in 52100 steel of crack initiation at inclusions and propagation. Given the relevance of phase quantification in nanobainite and the possible surface artefacts introduced by preparation, alternative methods to X-ray diffraction such as magnetic measurements were also investigated. The lack of hard white-etching matter obtained in the carbide-free nanostructured bainite led to conclude that an alternative route to mitigate hard white-etching matter could be by eliminating pre-eutectoid carbides from the microstructure, therefore restricting their dissolution and ultimate carbon supersaturation of the mechanically deformed and homogenised nanoferrite.
3
Patel, Prakash Shashikant. „Diffusion problems and degradation of bearing overlays“. Thesis, London Metropolitan University, 1989. http://repository.londonmet.ac.uk/3192/.
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The corrosion and degradation of Pb-Sn bearing overlays Is a bilateral process . During service, the lubricant becomes corrosive due to the breakdown of inhibitors with subsequent oxidation occurring at operating temperatures (120-170[degrees]). ...
4
Swan, Iain Peter. „The efffect of elastomeric bearing degradation on bridge dynamic response“. Thesis, Edinburgh Napier University, 2006. http://researchrepository.napier.ac.uk/Output/3800.
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The dynamic response of highway bridges is a topic that has been thoroughly researched over many years. However, understanding of how the dynamic response of bridges is affected by the performance of their bearings over an extended period of time is, at present, not clearly defined. Although health monitoring of bridge structures is relatively advanced, the scope for further research is wide. The study presented in this thesis contains research on plate structures; ranging from a simple Euler-Bernoulli method to determine natural frequencies; modal analysis of a plate structure in the laboratory; FEA of the plate structure; modal analysis on a full-scale structure subjected to vehicle loading; and FEA of a simplified model representing the full-scale structure. A combination of these methods has allowed the conclusions presented herein to be drawn with respect to the effects of support degradation, and the consequent effect on structural performance. In the laboratory, modal analysis of a small-scale, thin rectangular plate of Perspex' has been completed. A series of boundary conditions have been investigated through altering the support offered to the plate by a series of springs, each with a different stiffness, to simulate bearings with different stiffnesses. Vibrations of varying frequency have also been forced upon the plate, and its response recorded. Displacement values provided the clearest indication of the effect of bearing stiffness, with the least stiff spring resulting in the largest displacement. Alteration of support stiffness in the model can have a marked effect on the resonant frequency of the plate (approx. 23 % frequency change between spring 1 (1.22 Nmm 1) and 5 (15.62 Nmm 1)). Full-scale testing on a highway bridge at Berwick-upon-Tweed on the Al, over the River Tweed, was completed in May 2005. These data form the baseline for future dynamic testing and condition monitoring of the structure. To describe the dynamic properties of the structure, the force generated by each type of vehicle traversing the structure was determined using instrumentation already in place on the bridge. Statistics drawn from the data are presented, which indicate that the bearings are functioning as expected, but are subjected to forces of a much larger magnitude due to overloaded HGVs than in current design specifications. Larger HGVs made up a small percentage of overall vehicles recorded, but contribute a much higher proportion of damage caused to the bridge. Displacement and frequency were both valid measures of bearing performance and therefore state of degradation. The method is offered as a condition monitoring test for bridges and their bearings.
5
Alshimmeri, Fiasael. „Diagnosis of low-speed bearing degradation using acoustic emission techniques“. Thesis, Cranfield University, 2017. http://dspace.lib.cranfield.ac.uk/handle/1826/12324.
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It is widely acknowledged that bearing failures are the primary reason for
breakdowns in rotating machinery. These failures are extremely costly,
particularly in terms of lost production. Roller bearings are widely used in
industrial machinery and need to be maintained in good condition to ensure the
continuing efficiency, effectiveness, and profitability of the production process.
The research presented here is an investigation of the use of acoustic emission
(AE) to monitor bearing conditions at low speeds.
Many machines, particularly large, expensive machines operate at speeds below
100 rpm, and such machines are important to the industry. However, the
overwhelming proportion of studies have investigated the use of AE techniques
for condition monitoring of higher-speed machines (typically several hundred
rpm, or even higher). Few researchers have investigated the application of these
techniques to low-speed machines (<100 rpm), This PhD addressed this
omission and has established which, of the available, AE techniques are suitable
for the detection of incipient faults and measurement of fault growth in low-speed
bearings.
The first objective of this research program was to assess the applicability of AE
techniques to monitor low-speed bearings. It was found that the measured
statistical parameters successfully monitored bearing conditions at low speeds
(10-100 rpm).
The second objective was to identify which commonly used statistical parameters
derived from the AE signal (RMS, kurtosis, amplitude and counts) could identify
the onset of a fault in either race. It was found that the change in AE amplitude
and AE RMS could identify the presence of a small fault seeded into either the
inner or the outer races. However, the severe attenuation of the signal from the
inner race meant that, while AE amplitude and RMS could readily identify the
incipient fault, kurtosis and the AE counts could not. Thus, more attention needs
to be given to analysing the signal from the inner race. The third objective was to identify a measure that would assess the degree of
severity of the fault. However, once the defect was established, it was found that
of the parameters used only AE RMS was sensitive to defect size.
The fourth objective was to assess whether the AE signal is able to detect defects
located at either the centre or edge of the outer race of a bearing rotating at low
speeds. It is found that all the measured AE parameters had higher values when
the defect was seeded in the middle of the outer race, possibly due to the shorter
path traversed by the signal between source and sensor which gave a lower
attenuation than when the defect was on the edge of the outer race. Moreover,
AE can detect the defect at both locations, which confirmed the applicability of
the AE to monitor the defects at any location on the outer race.
6
Elliott, David. „Corrosion inhibitors for load-bearing steels“. Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303645.
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7
Zambre, Nirupama. „Degradation Rate Modeling of Ohio State Bridges“. University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1205935821.
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8
Shields, Andrew James. „Discharge degradation of mica“. Thesis, Glasgow Caledonian University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370768.
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9
Prescott, Robert. „The corrosion of alloys and metals in high-temperature chlorine-bearing gases“. Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236260.
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10
Boudghene, Stambouli Amine. „Degradation mechanism in zinc sulphide/manganese electroluminescent displays“. Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328389.
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11
Lawrence, Bryce T. „Recreation related degradation in Kansas state parks : applying GIS models“. Thesis, Manhattan, Kan. : Kansas State University, 2005. http://hdl.handle.net/2097/74.
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12
Arnott, Stephanie Helena Louise. „Ultrasonic evaluation of the degradation state of marine archaeological wood“. Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406037.
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13
Al-Masri, Y. S. „Adaptive state estimation compared with proportional navigation for bearing-only missile guidance“. Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373969.
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14
Powell, David C. „Characterization of Iron-Bearing Solids Used by Naturally-Occurring Microbes in the Anaerobic Degradation of Hydrocarbons“. W&M ScholarWorks, 2000. https://scholarworks.wm.edu/etd/1539617754.
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15
Cornelius, Karl. „Radiolytic degradation of organic pesticides : a pulse radiolysis and steady state study“. Title page, abstract and contents only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phc814.pdf.
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16
Dick, Caroline Macleod. „A solid state NMR investigation of char forming processes in polymer degradation“. Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249132.
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17
Tinmanee, Radaduen. „The role of pharmaceutical excipients in the solid-state degradation of Gabapentin“. Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1919.
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Drug instability in solid dosage forms includes chemical or physical processes involving covalent or polymorphic transformations wherein different polymorphs possess crystal structure differences. Gabapentin chemically degrades by intramolecular cyclization to gabapentin-lactam (lactam) in the solid-state. Additionally, gabapentin undergoes polymorphic solid-state transformations. A kinetic model was developed to describe the environmental and excipient effects on chemical and physical instability associated with milling induced stress and subsequent storage under controlled temperature and humidity conditions.
Reaction mixtures were generated by co-milling gabapentin Form II with various excipients. The effects of environmental conditions were studied by storing reaction mixtures at 40-60 ºC and 5-50 %RH. The chemical and polymorphic compositions of the reaction mixtures were measured as a function of time using a combination of chromatographic method, 13C ssNMR and XRPD. Degradation models that describe the relationship between polymorphs and degradation product in a series of sequential or parallel steps were devised based on analysis of the resultant concentration time profiles. Model parameters were estimated using non-linear regression and Bayesian methods and evaluated in terms of their quantitative relationship to compositional and conditional variations.
In reaction mixtures composed of co-milled gabapentin and excipients, gabapentin was found to exist in three forms: anhydrous polymorph II and III and gabapentin-lactam. A fourth form (II*) was observed based on initial degradation kinetics and was hypothesized to be a crystal-disordered form generated by mechanical stress. The effect of environment moisture was to decrease the net rate of lactam formation by facilitating polymorphic transformation kinetics and crystal annealing. However, excipient blocked the catalytic moisture effect on polymorphic transformations. The key features of our model are first-order physical state transitions of II* and III to II, first-order degradation of II* to lactam and autocatalytic lactamization of II and III. For chemical transitions, no humidity effect was present but the catalytic effects of excipients on the conversion of II and III → lactam were observed. For physical transitions, excipient primarily influenced the physical state transitions of II*and III → II through its ability to interact with humidity and the degree of contact between excipient and substrate.
18
Kuznetov, Alexandru Marius. „An investigation of the steady-state performance of a pressurized air wave journal bearing“. Toledo, Ohio : University of Toledo, 2010. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1262985839.
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Thesis (M.S.)--University of Toledo, 2010.Typescript. "Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science degree in Mechanical Engineering." "A thesis entitled"--at head of title. Title from title page of PDF document. Bibliography: p. 51-56.
19
Prudent-Phillip, Marie Patricia. „Low-income housing, the environment and the state : the case of St. Lucia“. Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325235.
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The convening of the Earth Summit in Rio de Janeiro in June 1992 represented a major milestone in the global debate on environment and development. This thesis, however, is not concerned about the broad views and perspectives advanced by developed and developing countries. Rather, the focus is at a much more micro level. The thesis examines the relationship between the environment and one aspect of development, namely, housing. The discussion centres on environmental conditions in low-income communities in a developing country: St. Lucia. This is really the reality of the debate within the boundaries of Small-Island Developing States (SIOS). As Dr. Mahathir Mohamad, Prime Minister of Malaysia states " ... peasants are likely to be far less concerned about holes in the ozone layer than about holes in their rooft" (in Main, 1994:3). It is within this context that the thesis is set. Brown agenda issues are becoming increasingly more evident in the cities of the developing world. In St. Lucia this is most visible in low-income housing communities. This thesis examines the underlying reasons for the neglect of low-income community environments and assesses whether there is a direct correlation between the level of government intervention in the establishment of these communities and the state of their household and neighbourhood environments. It also provides a comprehensive understanding of the operations of the formal and informal housing sectors in respect of low-income housing. The thesis argues that the State has failed in its attempts to provide lowincome housing and that low-income households have taken the provision of their shelter needs literally into their own hands. However, construction within the informal sector has resulted in serious environmental degradation. While households themselves are making some effort to address their environmental conditions, their actions tend to be reactive and ad-hoc, with little improvements being realized. These households have however acknowledged that they are unable by themselves to ameliorate their environmental conditions to any significant extent. They emphasize that the State must playa facilitating role in the process. This thesis is therefore concerned about the ways in which these stakeholders can work together to ensure the delivery of low-income housing within an environmentally sustainable framework. The argument put forward is that this can be achieved through an aided self-help approach, which will signal a new orientation towards the provision of low-income housing in St. Lucia and implicitly, a new environmental agenda for low-income communities.
20
Juhlin, Olof. „Modeling of Battery Degradation in Electrified Vehicles“. Thesis, Linköpings universitet, Fordonssystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-134114.
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This thesis provides an insight into battery modeling in electric vehicles which includes degradation mechanisms as in automotive operation in electric vehicles. As electric vehicles with lithium ion batteries increase in popularity there is an increased need to study and model the capacity losses in such batteries. If there is a good understanding of the phenomena involved and an ability to predict these losses there is also a foundation to take measures to minimize these losses. In this thesis a battery model for lithium ion batteries which includes heat dissipation is used as groundwork. This model is expanded with the addition of capacity losses due to usage as well as storage. By combining this with a simple vehicle model one can use these models to achieve an understanding as to how a battery or pack of several batteries would behave in a specific driving scenario. Much of the focus in the thesis is put into comparing the different factors of degradation to highlight what the major contributors are. The conclusion is drawn that heat is the main cause for degradation for batteries in electric vehicles. This applies for driving usage as well as during storage. As heat is generated when a battery is used, the level of current is also a factor, as well as in which state of charge region the battery is used.
21
Al-Achkar, Mohamed. „Efficiency enhancement and degradation processes in Cuâ†xS/CdS thin film solar cells“. Thesis, University of Hull, 1990. http://hydra.hull.ac.uk/resources/hull:3703.
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An investigation has been made into the structure and properties of polycrystalline CuxS-CdS solar cells in order to develop an improved understanding of some of the processes which lead to unsatisfactory reproducibility and long term stability of the characteristics of these devices. The cells studied during this project were fabricated using vacuum evaporation for production of the CdS base layer and the well known chemical exchange process in a CuCl solution for formation of the CuxS layer. In view of the non-uniform thickness of the CuxS layer and non-planar structure of the Cu, S-CdS interface, it was found to be necessary to employ a variety of different characterisation techniques to monitor changes in the structure and properties of the devices. These techniques included I/V, C-V, spectral response and sheet resistance measurements, electrochemical analysis, cathodoluminescence spectroscopy and Rutherford backscattering. Detailed consideration was given to the influence of the conditions of formation on the properties of each cell component, in order to establish procedures necessary for the production of reproducible structures. particular attention was paid to the rate of growth of the CuxS layer and a theoretical analysis was developed to account for the time dependence of the growth in mean thickness of the CuxS layer in terms of the contributions associated with growth at the surface of the CdS layer and in the CdS grain boundary regions. The grain boundary contribution was found to be very sensitive to the CdS grain structure and to the previous treatment given to the CdS layer. Pre-annealing in air at 2000C enhanced the grain boundary penetration while the effect of ion implantation (with either Cu or Zn ions) was found to depend on the initial structure and the implantation conditions, but substantial improvements in the photovoltaic conversion efficiency were shown to be possible as a result of such treatment.The rate of degradation of cells exposed to air was also found to be dependent on the previous history of the cell. An increased concentration of Cd in the CuxS film (due to diffusion from the CdS layer) appeared to reduce the rate of qegradation while use of the standard stabilizing treatment (deposition of Cu overlayer followed by annealing in air) was shown to reduce interfacial diffusion as well as protecting the front surface of the CuxS layer against oxidation.
22
Shrestha, Prakash. „Study of the dielectric degradation of XLPE and EPR power cables by switching impulses“. Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-08212008-151448.
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23
Vahdat, Laleh. „Factors influencing the rate of degradation of Amoxycillin sodium and potassium clavulanate in the liquid and frozen states“. Curtin University of Technology, School of Pharmacy, 2000. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=9984.
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Kinetics of the reactions of amoxycillin sodium and potassium clavulanate alone and in combination were investigated in the liquid and frozen states at selected pH values of 2.0, 4.6 and 7.0. A stability indicating HPLC assay was developed to perform simultaneous quantification of these compounds validated under stressed conditions.Amoxycillin and clavulanate degradation obeyed first-order kinetics under all conditions of this study. The effect of temperature, buffer, concentrations and complexation were investigated. Both compounds showed acceleration in rates due to general acid catalysis from buffer species. The buffer catalysis rate constants due to total phosphate and total acetate at 55 degrees celsius were 5.84x10(subscript)-1 (mol dm(subscript)-3)(subscript)-1 h(subscript)-1 and 1.53 X10(subscript)-1 (mol dm(subscript)-3)(subscript)-1 h(subscript)-1 for amoxycillin, 2.33 (mol dm(subscript)-3)(subscript)-1 h(subscript)-1 and 4.4x10(subscript)-1 mol dm(subscript)-3)(subscript)-1 h(subscript)-1 for clavulanate respectively. The buffer independent rate constant values were obtained and interpreted according to the available literature data. Increase in the initial concentration of amoxycillin or clavulanate did not change the first-order rate constant values of these antibiotics significantly at liquid state temperatures. However in the buffer systems, the rate of hydrolysis of amoxycillin in the combination was significantly subject to clavulanate catalysis. This novel finding was influenced by phosphate buffer concentration. A kinetic model was proposed and the second-order catalytic rate constant values at pH 7.0 and 55 degrees celsius were estimated for clavulanate catalysis of amoxycillin (k(subscript)cvc) to be k(subscript)cvc = 1.75 X10(subscript)2 (mol dm(subscript)-3)(subscript)-1 h(subscript)-1 and for phosphate catalyzed of clavulanate catalysis of ++amoxycillin (k(subscript)phccv) as k(subscript)phccv = 2.87 (mol dm(subscript)-3)(subscript)-1 h(subscript)-1.The temperature dependence of the rate of amoxycillin sodium degradation over the pH range evaluated did not change significantly. However the E(subscript)a values of potassium clavulanate decreased slightly with increase in pH. Both the compounds showed similar E(subscript)a values at pH 4.6 in acetate system. Hence 71.2 kJ mol(subscript)-1 for amoxycillin and 75.1 kJ mol(subscript)-1 for clavulanate.The investigation on complexation effects by HPbetaCD on the rate of hydrolysis of amoxycillin and clavulanate indicated no significant change in the rate of reaction of amoxycillin in the acetate buffer system. But the rate of clavulanate hydrolysis in combination was decreased by approximately 10%. The rate constant within the cyclodextrin complex and the stability constant of the complex obtained for clavulanate at pH 4.6 and 55 degrees celsius were k(subscript)c = 1.54x 10(subscript)-1 h(subscript)-1 and K(subscript)c = 74.2 (mol dm(subscript)-3)(subscript)-1.Extrapolation of the rate constant values to the frozen state from the liquid state data indicated marked acceleration of the rate of amoxycillin and clavulanate in all the pH values investigated. The highest acceleration in rate recorded was 15.0 fold for clavulanate in the hydrochloric acid system and the lowest value was 4.4 fold for amoxycillin at -7.3 degrees celsius. The rate constant values obtained were interpreted in terms of the concentration model (Pincock and Kiovsky 1966), phase-temperature relationship of the solutes, buffer catalysis, pH change and polymerization reactions.In the hydrochloric acid system a kinetic model was deduced providing adequate explanation of the experimental results. The stabilizing effect of sodium chloride used for maintaining constant ionic strength (mu=0.5) was ++
enormous in this system. The shelf-life of amoxycillin was increased from 2.2 h to 58.3 h at -7.3 degrees celsius when sodium chloride was included in the system. It also stabilized the rates of the reactions significantly in the buffer systems.The buffer systems used in this study stabilized the rates of the reaction of both the drug compounds considerably. The shelf-life of amoxycillin in phosphate buffer was 621.3 h at -13.5 degrees celsius and in acetate buffer the shelf-life of clavulanate was 71.9 h at the same temperature. These are the highest shelf-life values recorded so far in the literature for amoxycillin and clavulanate at this frozen temperature.
24
Oyedeji, Ayodele A. „Impacts of selected leguminous tree species and kaolinite pre-amendment on oil-contaminated soil for bioremediation in the oil-bearing region of Nigeria“. Thesis, University of Wolverhampton, 2016. http://hdl.handle.net/2436/609041.
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This study investigates the impacts of selected Leguminous Tree Species (LTS) and kaolinite pre-amendment on oil-contaminated soil. It covered assessment of different levels of contamination (0, 25, 50, 75 and 100 ml in 4000 g soil; which represents the degree of light crude oil spillage concentration as 0.0, 0.63, 1.25, 1.88 and 2.5 %v/w) on the growth performance of Albizia adianthifolia, Albizia odoratissima, Bauhinia monandra, Delonix regia, Peltophorum pterocarpum and Tetrapleura tetraptera LTS investigated. Percentage germination, seedling height, seedling girth, number of leaves and number of nodules decreased as the concentrations of crude oil in soil samples increased. LTS affected soil physicochemical properties. Soil acidity decreased; soil organic matter, carbon content and exchangeable ions increased. N, P and K were altered in the LTS planted soil as compared to controls, but there were no significant (P > 0.05) differences. There were increased microbial counts in the crude oil-contaminated soil planted with LTS as compared with non-LTS planted soils. Hydrocarbon removal was significantly higher (P < 0.05, n = 3) in LTS planted soil than in non-planted soil. D. regia planted soils had most hydrocarbon removal and had significantly more growth in terms of plant height, girth and leaf production in the field. Kaolinite (10 and 20 g samples) applications were suitable and effective sorbent agents for oil-contamination at the different oil concentrations. The sorption potential of kaolinite increased with the increase in kaolinite to 20 g. The potential re-usability of kaolinite after the initial use for oil sorption was analysed and 10 g of burnt kaolinite sorbed 43.62%, while 20 g sorbed 58.90%. The rate of oil sorption by fresh kaolinite was significantly higher than burnt kaolinite. Results show the considerable potential of phytoremediation protocols with LTS and kaolinite as combined remediating agents for oil spill remediation in the humid tropics.
25
Sawangchan, Phawanan. „The effect of aggregation state on the degradation kinetics of Amphotericin B in aqueous solution“. Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5992.
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Amphotericin B (AmB) is an amphiphile antifungal agent composed of lipophilic and hydrophilic structures and is known to aggregate in aqueous solution. The effect of substrate aggregation on the degradation kinetics of aqueous AmB was studied.
Aggregation state of AmB (0.0108 mM) in 10.0%v/v methanol aqueous solutions were pH dependent. The dissociation equilibrium constant (Kd) values suggested that monomeric form was predominant in acidic and alkaline condition and aggregated form appeared predominantly in neutral condition. At methanol concentration above 35.0%v/v, 0.0108 mM AmB in reaction mixtures presented in a monomeric form regardless of pH.
The degradation pathways of AmB were found to be pH-dependent. The effect of oxidants, antioxidants, oxidation initiators and chelators suggested that AmB was susceptible to oxidation in acidic and neutral pH regions which led spectral changes associated with the heptaene moiety. In basic conditions (pH > 9), AmB underwent hydroxide-catalyzed ring-opening lactone hydrolysis.
A degradation model describing substrate loss was constructed based on the kinetics of substrate loss. The pH-rate profile displayed three regions: specific acid-catalyzed degradation at pH below 4, a specific basic-catalyzed hydrolysis at pH above 9 and a pH-independent degradation in the neutral pH range 4 – 9. The effect of methanol on degradation kinetics in the neutral pH region indicated that aggregated AmB was more susceptible to oxidative degradation than monomeric AmB.
26
Jackson, Lauren W., und Barry M. Pryor. „Degradation of aflatoxin B1 from naturally contaminated maize using the edible fungus Pleurotus ostreatus“. BIOMED CENTRAL LTD, 2017. http://hdl.handle.net/10150/625197.
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Aflatoxins are highly carcinogenic secondary metabolites that can contaminate approximately 25% of crops and that cause or exacerbate multiple adverse health conditions, especially in Sub-Saharan Africa and South and Southeast Asia. Regulation and decontamination of aflatoxins in high exposure areas is lacking. Biological detoxification methods are promising because they are assumed to be cheaper and more environmentally friendly compared to chemical alternatives. White-rot fungi produce non-specific enzymes that are known to degrade aflatoxin in in situ and ex situ experiments. The aims of this study were to (1) decontaminate aflatoxin-B-1-(AFB(1)) in naturally contaminated maize with the edible, white-rot fungus Pleurotus ostreatus (oyster mushroom) using a solid-state fermentation system that followed standard cultivation techniques, and to (2) and to assess the risk of mutagenicity in the resulting breakdown products and mushrooms. Vegetative growth and yield characteristics of P. ostreatus were not inhibited by the presence of-AFB(1).-AFB(1) was degraded by up to 94% by the Blue strain. No aflatoxin could be detected in P. ostreatus mushrooms produced from-AFB(1)-contaminated maize. Moreover, the mutagenicity of breakdown products from the maize substrate, and reversion of breakdown products to the parent compound, were minimal. These results suggest that P. ostreatus significantly degrades-AFB(1) in naturally contaminated maize under standard cultivation techniques to levels that are acceptable for some livestock fodder, and that using P. ostreatus to bioconvert crops into mushrooms can reduce-AFB(1)-related losses.
27
Axtell, Jonathan Clayton. „Synthesis and reactivity of high oxidation state tungsten and molybdenum olefin metathesis catalysts bearing new imido ligands“. Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98598.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references.
Chapter 1 details the synthesis of tungsten imidoalkylidene compounds bearing strongly electron-withdrawing imido ligands. An alternative synthesis involving the treatment of WCl6 with 4 equivalents of N-trimethylsilyl-substituted anilines and subsequent workup with 1,2-dimethoxyethane (DME) has been employed to form complexes of the type W(NAr)2C12(dme); syntheses employing WO2C 2(dme) as the tungsten precursor were unsuccessful. Alkylation with neopentylmagnesium chloride (ClMgNp) and subsequent treatment with trifluoromethanesulfonic acid (HOTf) affords imidoalkylidene species W(NAr)(CHCMe 3)(OTf)2(dme) (OTf = trifluoromethanesulfonate); analogous neophylidene ([W]CHCMe 2Ph) species could not be made under these conditions. Treatment of these compounds with two equivalents of LiO(2,6-(CHCPh 2)C6H3)-Et2O affords the bisaryloxide complexes of the type W(NAr)(CHCMe3)(OR)2. Ring-Opening Metathesis Polymerization (ROMP) studies using a series of these bisaryloxides show that rates of ROMP increase as the electron-withdrawing power of the substituents on the imido ligand increase if steric bulk about the metal center is held constant. A similar trend between two bisaryloxides is observed for anti-to-syn alkylidene rotation rates at 50*C in toluene-d8 . Difficulties synthesizing bis-pyrrolide complexes of the type W(NAr)(CHCMe3)(pyr)2 precluded their use as catalyst precursors; some MAP species containing the more sterically encumbering 2,5-dimethylpyrrolide ligand are presented and the metathesis activity of MAP species bearing the 2,5-dimethylpyrrolide ligand is discussed. Chapter 2 introduces Mo and W complexes bearing the current extreme in sterically bulky imido ligands, the NHIPT (HIPT = 2,6-(2,4,6-iPr 3CH2)CH3) ligand, in an effort to generate all anti alkylidene species. A non-traditional synthetic route is employed in order to install this ligand first as an anilide, and after subsequent proton transfer, as an imido ligand to form a mixed imido species of the type M(NHIPT)(N'Bu)(NH'Bu)Cl. Addition of one equivalent of 2,6-lutidinium chloride, followed by alkylation affords dialkyl species M(NHIPT)(N'Bu)Np 2, and treatment with three equivalents of pyridinium chloride yields all anti imidoalkylidene dichloride species as mono-pyridine adducts, M(NHIPT)(CHCMe 3)C 2(py) (M = Mo, W). General reactivity, including strategies for removal of the pyridine adduct as well as substitution and metathesis chemistry, are discussed. ROMP of MPCP (MPCP = 3-methyl-3-phenylcyclopropene) by a Mo-based MAP species bearing the NHIPT ligand yields predominantly cis,syndiotactic poly(MPCP) and in the homo-metathesis of 1 -octene yields ~81% cis-7-tetradecene. The possible source of trans olefinic product is addressed. Chapter 3 presents the synthesis of the first (1-adamantyl)imido species of tungsten. The functional equivalent of common bisimido precursors for other Mo/W alkylidene species, [W(NAd) 2C 2(AdNH2)1 2, is shown to be a dimer stabilized by hydrogen-bonding interactions between adamantylamine protons and adjacent chlorides bound to the second metal of the dimer. Subsequent alkylation with ClMgNp affords the expected dialkyl species, and treatment with three equivalents of 3,5-lutidinium chloride affords imidoalkylidene complex W(NAd)(CHCMe 3)(C) 2(lut)2 (lut = 3,5-dimethylpyridine). The most desirable synthetic route toward monoalkoxide pyrrolide (MAP) species proceeds through a monoaryloxide monochloride intermediate W(NAd)(CHCMe 3)(Cl)(OAr)(lut) (Ar = 2,6-(2,4,6-Me 3)C6H3, 2,6-(2,4,6-'Pr 3)C6H3). Removal of lutidine with B(C6 F5 )3 and subsequent treatment with lithium pyrrolide affords W(NAd)(CHCMe3)(pyr)(OAr) (pyr = pyrrolide); 2,5-dimethylpyrrolide analogues (W(NAd)(CHCMe3)(Me2pyr)(OAr) can be accessed via protonolysis by HOAr from W(NAd)(CHCMe3)(Me2pyr)2(lut).
by Jonathan Clayton Axtell.
Ph. D.
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Kothottil, Dinek. „Markov-based Predictive Models For Estimation of Degradation Rates of Bridges in the State of Ohio“. University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282569111.
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Endicott, Roger A. „Immunoregulation of T-lymphocyte proliferative activity by alveolar macrophages from mice bearing Lewis lung carcinoma tumors“. Virtual Press, 1986. http://liblink.bsu.edu/uhtbin/catkey/458971.
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The immune regulatory abilities of alveolar macrophages from C57B1/6 mice bearing a metastatic variant of Lewis lung carcinoma were determined. During early stages of tumor development, or before tumors metastasized to the lungs, alveolar macrophages did not affect or slightly enhanced T-lymphocyte proliferation; as tumor growth progressed, or following tumor metastasis, alveolar macrophages suppressed the T-cell response. Macrophage suppressor activity was probably not mediated by their production of PGE, since macrophages of tumor-bearing mice secreted less 2 PGE than did macrophages of normal mice. Normal alveolar 2 macrophages or macrophages preincubated in tumor cell supernatant for a short period stimulated T-cell blastogenesis and secreted PGE during in vitro culture. However, with 2 longer exposure to tumor cell supernatant, alveolar macrophages lost the capacity to augment T-cell proliferation and secreted less PGE 2.Ball State UniversityMuncie, IN 47306
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Elgubshawi, Abdelmoneim A. I. „Soil degradation: Its aspects and modelling: a case study of Northeast Nuba Mountain South Kordofan State, Sudan“. Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23615.
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The study was carried out at Abujubeha area (10? 52 48.17 ‐11? 23 08.79 N and 30? 00 05.99 ‐ 31? 28 04.91’ E) in Northeast Nuba Mountain, South Kordofan region, Sudan. In order to investigate the soil degradation aspects in the study area, its causal, rate per time and mapping; the remote sensing and GIS technologies were used beside the routine soil survey and laboratory analyses. Quantitative information on soils degradation and vegetation cover changes was acquired. Using multi‐spectral satellite imagery the most dynamic land cover types have been able to be mapped with 64% accuracy (Dense Forest, Moderate Forest, Light Forest, Fallow and Bare soils). The result showed that 38% of the forested areas were lost in the last two decades at annual rate of 1.8%. Forest clearance in the last 5 (199‐2005) years equal two times the clearance happened in the previous 15 years (1986‐1999). The geostatistical characterization of soil variability showed that soil properties are highly spatially dependent, with significant sensitivity to soil‐forming factors. Soils dynamic are affected by land use system as well as with soil physiographic position. The Red soils (Gardud) are more dynamic than the Dark clayey soils. The Universal Soil Loss Equation (USLE) was used; the result revealed that the study area is potentially susceptible to be eroded by water. The Erosion rate was measured in term of erosion Risk Assessment. The model indicated that the overall average of soil loss is 1.32 t/ha /y.
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Oktem, Gozde. „Syntheses Of Benzotriazole Bearing Donor Acceptor Type Random Copolymers For Full Visible Light Absorption“. Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613535/index.pdf.
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The synthesis and preliminary optoelectronic properties of a series of donor-acceptor (DA) type polymers differing by the acceptor units in the polymer backbone were investigated. Polymers CoP1, CoP2 and CoP3 were designed to yield alternating DA segments with randomly distributed different acceptor units along polymer backbone. The combination of neutral state red colored and neutral state green colored materials resulted in different neutral state colors with respect to their additional acceptor unit. 5,8-Dibromo-2,3-bis(4-tert-butylphenyl) quinoxaline, 5,8-dibromo-2,3-di(thiophen-2-yl)quinoxaline and 4,7-dibromobenzo[c][1,2,5]selenadiazole units were perceived as additional acceptor units and these constituents were combined with the 4,7-dibromo-2-dodecyl-2H-benzo[d][1,2,3]triazole unit and the 2,5-bis(tributylstannyl)thiophene moiety via Stille coupling. The resultant donor acceptor type random copolymers indicated that possessing 5,8-dibromo-2,3-di(thiophen-2-yl)quinoxaline as an extra electron deficient with 4,7-dibromo-2-dodecyl-2H-benzo[d][1,2,3]triazole unit on the same polymer backbone originated a neutral state black colored copolymer along with spanning the entire visible spectrum.
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Mitroka, Susan M. „Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene“. Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77137.
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Oxidative processes are linked to a number of major disease states as well as the breakdown of many materials. Of particular importance are reactive oxygen species (ROS), as they are known to be endogenously produced in biological systems as well as exogenously produced through a variety of different means. In hopes of better understanding what controls the behavior of ROS, researchers have studied radical chemistry on a fundamental level. Fundamental knowledge of what contributes to oxidative processes can be extrapolated to more complex biological or macromolecular systems.
Fundamental concepts and applied data (i.e. interaction of ROS with polymers, biomolecules, etc.) are critical to understanding the reactivity of ROS. A detailed review of the literature, focusing primarily on the hydroxyl radical (HO•) and hydrogen atom (H•) abstraction reactions, is presented in Chapter 1. Also reviewed herein is the literature concerning high density polyethylene (HDPE) degradation. Exposure to treated water systems is known to greatly reduce the lifetime of HDPE pipe. While there is no consensus on what leads to HDPE breakdown, evidence suggests oxidative processes are at play.
The research which follows in Chapter 2 focuses on the reactivity of the hydroxyl radical and how it is controlled by its environment. The HO• has been thought to react instantaneously, approaching the diffusion controlled rate and showing little to no selectivity. Both experimental and calculational evidence suggest that some of the previous assumptions regarding hydroxyl radical reactivity are wrong and that it is decidedly less reactive in an aprotic polar solvent than in aqueous solution. These findings are explained on the basis of a polarized transition state that can be stabilized via the hydrogen bonding afforded by water. Experimental and calculational evidence also suggest that the degree of polarization in the transition state will determine the magnitude of this solvent effect.
Chapter 3 discusses the results of HDPE degradation studies. While HDPE is an extremely stable polymer, exposure to chlorinated aqueous conditions severely reduces the lifetime of HDPE pipes. While much research exists detailing the mechanical breakdown and failure of these pipes under said conditions, a gap still exists in defining the species responsible or mechanism for this degradation. Experimental evidence put forth in this dissertation suggests that this is due to an auto-oxidative process initiated by free radicals in the chlorinated aqueous solution and propagated through singlet oxygen from the environment. A mechanism for HDPE degradation is proposed and discussed. Additionally two small molecules, 2,3-dichloro-2-methylbutane and 3-chloro-1,1-di-methylpropanol, have been suggested as HDPE byproducts. While the mechanism of formation for these products is still elusive, evidence concerning their identification and production in HDPE and PE oligomers is discussed.
Finally, Chapter 4 deals with concluding remarks of the aforementioned work. Future work needed to enhance and further the results published herein is also addressed.Ph. D.
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Amiraux, Rémi. „Ice biota degradation in the Arctic environment : impact of bacterial stress state on this material's preservation and burial“. Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0189/document.
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L’océan Arctique, particulièrement sensible au changement climatique, a vu lors des dernières décennies une augmentation de sa température deux fois supérieure à la moyenne mondiale. Certains scientifiques prévoient la disparition complète de la banquise pour 2050. Du fait de la future disparition des algues de glace et de l’augmentation de la fonte du pergélisol, une réévaluation de leurs contributions respectives au stockage de CO2 est nécessaire. Dans cette étude, nous avons ainsi montré que les algues de glace possèdent une forte capacité de préservation dans les sédiments (et donc de stockage du CO2) due à l’incapacité de leurs bactéries à les reminéraliser. A l’inverse, les quantités grandissantes de pergélisol rejetées en mer sont fortement reminéralisables. L’effet conjoint de l’augmentation du rejet de CO2 lors de la dégradation du pergélisol et de la diminution de son stockage par les algues de glace devrait donc contribuer à une amplification du réchauffement climatiqueWith a rise in Arctic temperatures almost twice as large as the global average in recent decades, it is at high latitude that the effects of global warming are the most evident. Thus, some scientists have already predicted the complete disappearance of sea ice for 2050. Due to the future disappearance of ice algae and the increase of permafrost thawing, a reassessment of their respective contributions to CO2 storage was required. We have shown that unlike permafrost, ice algae are highly preserved in sediments (allowing CO2 storage) due to the inability of their bacteria to remineralize them. The combined effect of increasing discharge of permafrost by Arctic rivers and decreasing storage of ice algae due to the disappearance of sea ice should thus contribute to increase the global warming
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Zong, Zhixin. „Studies on the mechanisms of solid state and solution instability of drugs“. Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2795.
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The overarching objective of this thesis is to demonstrate a systematic approach for addressing the instability issues associated with low limit degradants by developing quantitative degradation models that incorporate key instability determinants into predictive equations. Chlorhexidine was used as model compound in aqueous solution to demonstrate the application of the predictive models to issues of formulation design and manufacturing. Chorhexidine degrades to p-chloroaniline, a well-established toxicant, by various pH-dependent pathways. In acidic conditions, the direct formation of p-chloroaniline from chlorhexidine is the major pathway whereas the indirect formation of p-chloroaniline via p-chlorophenylurea is the main alkaline pathway. Rate laws and mechanisms for each pathway were presented. Shelf life predictions equations for chlorhexidine formulations were derived based on the kinetics of p-chloroaniline appearance as a function of formulation strength, solution pH, bulk chlorhexidine purity and storage temperature. The pH range for optimal shelf-life was 5.0 to 5.5. Simple extraction procedures used during formulation preparation were identified to improve bulk chlorhexidine purity and thereby extend product shelf-life. Gabapentin degrades directly to gabapentin-lactam in the solid-state. The established limit on gabapentin-lactam in gabapentin pharmaceutical formulations is <0.5% w/w thus gabapentin instability was studied as a model compound for solid state formulation applications. Mechanical stress associated with drug product manufacturing in unit operations such as milling increased the subsequent lactamization rate upon storage due to increased gabapentin crystal disorder. The effect of environment moisture was to decrease the rate of gabapentin-lactam formation due to competitive recovery of gabapentin crystallinity which was accelerated by humidity. A degradation model that combined both physical and chemical instability pathways including autocatalytic branching, spontaneous intra-molecular cyclization and moisture-induced physical transformation steps was shown to be consistent with lactamization kinetics as a function of both environmental (temperature and humidity) and manufacturing-related effects. This kinetic model was used to predict the shelf-life of gabapentin tablets prepared under various exemplary manufacturing conditions thereby demonstrating the ability of the model to link manufacturing variation and shelf-life stability in for solid-state drug formulations.
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Closas, Farriol Alvar Eduardo. „Burning water : the state, irrigation technology and the production of scarcity in Spain“. Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:afbffe73-fd96-4a9f-9874-ba4fcb4acba5.
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Through studying the adoption of groundwater abstraction technology in the twentieth century in La Mancha, this research investigates the historical role of the state in the development of modern groundwater-fed irrigation in Spain between the 1940s and 1985. By focusing on the Mancha Occidental aquifer and the Las Tablas de Daimiel wetland, this study also scrutinizes how the adoption of groundwater abstraction technology led by the state fed back into the environment through ecosystem degradation and groundwater scarcity at the local and regional level. By examining the historical links between technology adoption, statecraft and ecological change, this study explores the different ways through which the state has taken a prominent role in producing groundwater-fed irrigation socio-ecologies. Additionally, it traces the socio-political mechanisms involved in the progressive desiccation of the Las Tablas de Daimiel wetland and its transformation into a burning dryland.
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Junzuo, Zhang. „Villagers and the Chinese State in tree planting campaigns of the 1990s : a case study of a reforestation programme from the subtropical hilly region“. Thesis, SOAS, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343566.
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Chu, Thi Thu Ha. „State of the environment and natural resources in Vietnam“. Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-176875.
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Vietnam is considered as one of the countries having rich resources from forest and sea, with a high average annual rainfall. However, in view of IWRA, water volume per capita annually in Vietnam is lower than the standard for nations having water resources at average level. Vietnam was recognized by the World Wildlife Fund (WWF) as having three out of more than 200 biological zones of the world. Flora and fauna in Vietnam are very rich and abundant, but due to indiscriminate exploitation, along with weak management, biodiversity levels are significantly reduced. This is also one of the causes of environmental pollution and degradation in Vietnam, besides the impacts from production activities, population migration from rural areas to urban areas, rapid urbanization, climate change and sea level rise, etcTảo đóng vai trò quan trọng trong mạng lưới thức ăn và chu trình sinh địa hóa của thủy vực và chúng chịu sự chi phối của nhiều yếu tố môi trường như ánh sáng, pH, nhiệt độ và dinh dưỡng. Nghiên cứu này trình bày đa dạng thành phần loài và biến động sinh khối thực vật phù du tại hồchứa Hòa Bình từ tháng 3 đến tháng 12 năm 2011. Các mẫu thực vật nổi được thu thập hàng tháng tại 4 điểm. Kết quả đã xác định được 6 lớp tảo chính bao gồm: Vi khuẩn lam, tảo lục, tảo silic, tảo mắt, tảo giáp và tảo lông roi hai rãnh. Nhóm tảo silic và Vi khuẩn lam chiếm ưu thế với độ phong phú tương đối là 61% và 32% tương ứng trong quần xã thực vật nổi. Vi khuẩn lam dạng tập đoàn và dạng sợi (Microcystis aeruginosa, M. wesenberg, Oscillatoria sp. tương ứng) chiếm ưu thế trong quần xã thực vật nổi vào các thời điểm đầu hè và mùa thu (tháng 4 và tháng 9). Tổng mật độ tế bào thực vật nổi dao động từ 84210 đến 100 x106 cell/L. Mật độ thực vật nổi biển động theo mùa với sinh khối tê bào cao vào đầu hè và mùa đông (tháng 4 và tháng 12) và sinh khối tếbào thấp vào các mùa hè và thu (tháng 6 đến tháng 10)
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Chu, Thi Thu Ha. „State of the environment and natural resources in Vietnam“. Technische Universität Dresden, 2014. https://tud.qucosa.de/id/qucosa%3A28879.
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Vietnam is considered as one of the countries having rich resources from forest and sea, with a high average annual rainfall. However, in view of IWRA, water volume per capita annually in Vietnam is lower than the standard for nations having water resources at average level. Vietnam was recognized by the World Wildlife Fund (WWF) as having three out of more than 200 biological zones of the world. Flora and fauna in Vietnam are very rich and abundant, but due to indiscriminate exploitation, along with weak management, biodiversity levels are significantly reduced. This is also one of the causes of environmental pollution and degradation in Vietnam, besides the impacts from production activities, population migration from rural areas to urban areas, rapid urbanization, climate change and sea level rise, etc.Tảo đóng vai trò quan trọng trong mạng lưới thức ăn và chu trình sinh địa hóa của thủy vực và chúng chịu sự chi phối của nhiều yếu tố môi trường như ánh sáng, pH, nhiệt độ và dinh dưỡng. Nghiên cứu này trình bày đa dạng thành phần loài và biến động sinh khối thực vật phù du tại hồchứa Hòa Bình từ tháng 3 đến tháng 12 năm 2011. Các mẫu thực vật nổi được thu thập hàng tháng tại 4 điểm. Kết quả đã xác định được 6 lớp tảo chính bao gồm: Vi khuẩn lam, tảo lục, tảo silic, tảo mắt, tảo giáp và tảo lông roi hai rãnh. Nhóm tảo silic và Vi khuẩn lam chiếm ưu thế với độ phong phú tương đối là 61% và 32% tương ứng trong quần xã thực vật nổi. Vi khuẩn lam dạng tập đoàn và dạng sợi (Microcystis aeruginosa, M. wesenberg, Oscillatoria sp. tương ứng) chiếm ưu thế trong quần xã thực vật nổi vào các thời điểm đầu hè và mùa thu (tháng 4 và tháng 9). Tổng mật độ tế bào thực vật nổi dao động từ 84210 đến 100 x106 cell/L. Mật độ thực vật nổi biển động theo mùa với sinh khối tê bào cao vào đầu hè và mùa đông (tháng 4 và tháng 12) và sinh khối tếbào thấp vào các mùa hè và thu (tháng 6 đến tháng 10).
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Ramani, Sathyanarayana. „A Markov-based Analysis of the State of Ohio's Bridge Inventory and Novel Approaches to the Estimation of Bridge Degradation Rates“. University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1271707686.
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Zhang, Qian. „Pastoralists and the Environmental State : A study of ecological resettlement in Inner Mongolia, China“. Doctoral thesis, Stockholms universitet, Kulturgeografiska institutionen, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-115316.
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China's quest for sustainable development has given birth to a set of contested ‘ecological construction’ programmes. Focusing on ‘ecological resettlement’, a type of policy measure in a programme for restoring degraded grasslands, this thesis sets out a critical analysis in opposition to the dominant technical and managerial approaches to understanding environmentalisation. The aim is to draw out the politics of the formulation, implementation and effects of ecological resettlement at and across different scales. The study combines fieldwork, interviews, analysis of policy documents, and statistical analysis while theoretically, in addition to political ecology, it incorporates concepts and models from environmental governance, migration, and pastoralism studies. Environmentalisation is examined through three types of analysis: environmentalisation of the state, reshaping of state-society relations, and (re)territorialisation. A central theme is how local processes are linked to national considerations and how the local state acts as an intermediary between the central state and the pastoralists. The analysis exposes the practices that enabled the central state to define the problem of grasslands and devise interventions, illustrating the environmentalisation of the state. However, at the local level, incentives and interests defined by the political structure drove the developmental local state to pursue short-term-effective rather than sustainable practices. On the other hand, while the pastoral households responded to the projects with different strategies, their migration decisions suggested that social, economic and cultural considerations played a more important role than environmental concerns. Moreover, ecological resettlement has led to a significant change of Mongolian pastoralism. Land-tenure-based management further fragmented rangelands while the emergence of new social arrangements enabled migrant households to remain involved with pastoralism.
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Wu, Xinying. „Reliability Assessment of a Continuous-state Fuel Cell Stack System with Multiple Degrading Components“. Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1556794664723115.
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Inamoto, Jun-ichi, und Junichi Inamoto. „Electrochemical Characterization of Surface-State of Positive Thin-Film Electrodes in Lithium-Ion Batteries“. Kyoto University, 2017. http://hdl.handle.net/2433/226784.
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Ibrahim, Ali Hano Abdelnasir. „Assessment of Impacts of Changes in Land Use Patterns on Land Degradation/Desertification in the Semi- arid Zone of White Nile State, Sudan, by Means of Remote Sensing and GIS“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-157627.
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In Sudan, land degradation/desertification (LDD) has devastated large areas and consequently, it includes social, economic, and environmental aspects. LDD results from various factors, including climatic variation and human activities. Probably the LU practices and their changes have contributed to an increase of LDD in that area. Remote sensing technology has become unique and developed tool for providing temporal and spatial information for the LDD research and other environmental aspects. Determination of LDD and its relationship to land use pattern change (LUC) at spatiotemporal scale is rare, critical issue, and is one of the recommended research in semi-arid regions of Sudan. The study was carried out to derive accurate and improved spatiotemporal information: to assess the status of land LDD of vegetation and soil, to assess and model influences of the LUC on LDD, and moreover to analyse the synergistic factors that have caused the land use change and/or LDD in semi- arid zone of Elgeteina Locality in While Nile State, Sudan during the last 36 years, using appropriate remote sensing (RS) and GIS technology. The study used four-cloud free images of different sensors (MSS 1973, TM 1986, ASTER 2009 and TM 2010). The imageries were Geo-referenced and radiometrically corrected by using ENVI-FLAASH software. Then subsets of the study area were taken, ranging from 1600-2000 Km2. The study applied the new approach of integration between vegetation and soil indices and in situ data to assess the LDD. Comparison between pixel based image analysis (PBIA) and latterly approach of object based image analysis (OBIA) was done by selecting the best one for mapping LUC and LDD accurately. The change detection - matrix was applied to estimate the spatiotemporal of changes in land use and land degradation. Moreover, correlation and model approach was employed for fusing the climatic, socioeconomic and remote sensing data to determine the relationships between the different factors and to analyse the reasons for the LUC and LDD as well as for modelling LU effects on LDD. The study revealed that: The changes in land use patterns (RA, FWL and FML) took place in 1973 – 86 – 2009, and affecting thoroughly different patterns of the vegetation cover. Likewise the LUC affected soil degradation which led to the movement of sand dunes in 1973 – 2009. The agricultural activity is the dominant and has more effect on LDD particularly on the vegetation cover degradation. The population growth and the socioeconomic status of local people are the main indirect human inducing factors responsible for LUC and/or LDD. SARVI is slightly more efficient than NDVI, SAVI, ND4-25 and ND42-57, for detecting the vegetation status in semi-arid area, therefore the study selected it for the assessment. GSI proved highly efficient in determining the different types of soil degradation, and in producing the map of top soil grain size, which assisted in the assessment of land degradation and desertification. OBIA-fuzzy logic classification performed better than the PBIA- hybrid classification for assessing LU patterns impact on LDD. The study recommends to: replication of this study by using different imagery with high resolutions and sophisticated software, such as eCognition and Feature Analyst (FA) for increasing the validity and accuracy of the assessment and modelling of LU patterns and LDD status in dry land is important in the SudanIm Sudan hat Land Degradation/ Desertifikation (LDD) weite Gegenden verwüstet, wobei hierbei soziale, wirtschaftliche und Umweltaspekte eine Rolle spielen. LDD wird von verschiedenen Faktoren ausgelöst, darunter Klimavariationen und menschliche Aktivitäten. Wahrscheinlich haben Landnutzungspraktiken und ihre Änderungen zu erhöhter LDD in der untersuchten Gegend beigetragen. Fernerkundungstechnologien sind sehr gute und weit entwickelte Werkzeuge um zeitliche und räumliche Informationen zur Erforschung von LDD und anderen Umweltaspekten zu ermitteln. Die Bestimmung von LDD und ihre Beziehung zur Änderung von Landnutzungsmustern (LUC) im raum-zeitlichen Maßstab ist bislang noch selten erforscht und ist ein Forschungsbereich, der für die semi-ariden Regionen des Sudan empfohlen wird. Die Studie wurde durchgeführt, um genaue und verbesserte raum-zeitliche Informationen zu gewinnen: um den Status der LDD von Vegetation und Boden zu bewerten, um den Einfluss des Landnutzungswandels auf LDD zu beurteilen und zu analysieren, und außerdem um die synergetischen Faktoren die den Landnutzungswandel und/oder LDD verursacht haben zu analysieren. Dabei wurde die semi-ariden Zone des Elgeteina Gebietes im Staat Weisser Nil (Sudan) während der vergangenen 36 Jahren unter Verwendung von geeigneter Fernerkundungs- und GIS-Technologie untersucht. Für die Studie wurden vier wolkenfreie Bilder von verschiedenen Sensoren (MSS 1973, TM 1986, ASTER 2009 and TM 2010) verwendet. Die Bilder wurden georeferenziert und radiometrische korrigiert, wobei die ENVI-FLAASH Software verwendet wurde. Anschließend wurden Teilgebiete des Untersuchungsgebietes mit einer Größe zwischen 1.600 und 2.000 Km2 ausgewählt. In der Studie fand der neue Ansatz der Integration von Vegetation und Boden Indizes und in-situ Daten Verwendung, um LDD zu bewerten. Ein Vergleich von pixel-basierter Bildanalyse (PBIA) und einem Ansatz von objekt-basierter Bildanalyse (OBIA) wurde durchgeführt, um die beste Methode der Kartierung von LUC und LDD ermitteln. Veränderungsmatrizen wurden eingesetzt, um räumlich-zeitlichen Änderungen der Landnutzung und Land Degradation abzuschätzen. Außerdem wurde ein Korrelation- und Modellierungs-Ansatz eingesetzt, um die klimatischen, sozioökonomischen und Fernerkundungsdaten zu verschmelzen und das Verhältnis zwischen den unterschiedlichen Faktoren zu bestimmen und um die Gründe für LUC und LDD zu analysieren aber auch um die Auswirkungen der Landnutzung auf LDD zu modellieren. Die Studie hat folgendes gezeigt: Die Änderungen der Landnutzungsmuster (RA, FWL and FML) fand in 1973 – 86 – 2009 statt und betraf sehr unterschiedliche Vegetationsmuster. Ebenso hatte die LUC Auswirkungen auf die Bodendegradation, was zu einer Verschiebung von Sanddünen im Zeitraum 1973-2009 führte. Landwirtschaft dominiert und hat starke Auswirkungen auf LDD, insbesondere auf die Degradation der Vegetationsbedeckung. Die Bevölkerungszunahme und der sozioökonomische Status der lokalen Bevölkerung sind die wesentlichen indirekten menschlichen Faktoren die verantwortlich für LUC und/oder LDD sind. SARVI ist etwas effizienter als NDVI, SAVI, ND4-25 und ND42-57, um den Zustand der Vegetation in semi-ariden Gebieten zu bestimmen, deshalb wurde dieser für die Studie ausgewählt. Es stellte sich heraus, dass der GSI hoch-effizient war, sowohl bei der Bestimmung der unterschiedlichen Typen von Bodendegradation als auch bei der Erstellung von Karten der obersten Bodenkorngröße, die bei der Bewertung der Landdegradation und Desertifikation half. OBIA-Fuzzy Logic Classification arbeitete dabei etwas genauer und effizienter als die PBIA-Hybrid Classification, um die Auswirkungen der Landnutzungsmuster auf LDD zu beurteilen. Als Fortsetzung der durchgeführten Arbeiten empfiehlt sich eine nochmalige Durchführung der Studie wobei anderes, hochaufgelöstes Bildmaterial und anspruchsvolle Software, wie eCognition und Feature Analyst (FA) verwendet werden sollten, um die Gültigkeit und Genauigkeit der Bewertungen und Modellierung des LU und LDD Status von Trockenland im Sudan zu beurteilen
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Göring, M., A. Seifert, K. Schreiter, P. Müller und S. Spange. „A non-aqueous procedure to synthesize amino group bearing nanostructured organic–inorganic hybrid materials“. Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-152006.
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Amino-functionalized organic–inorganic hybrid materials with a narrow distributed nanostructure of 2–4 nm in size were obtained by means of a template-free and non-aqueous procedure. Simultaneous twin polymerization of novel amino group containing twin monomers with 2,2′-spirobi[4H-1,3,2-benzodioxasiline] has been applied for this purpose. The amino groups of the organic–inorganic hybrid material are useful for post derivatizationDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Epshteyn, Albert. „Synthesis, stability, and reactivity of high-oxidation-state pentamethylcyclopentadienyl acetamidinate [beta]-Hydride- or [beta]-Methide-bearing alkyl complexes of zirconium, titanium, and tantalum“. College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4249.
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Thesis (Ph. D.)--University of Maryland, College Park, 2006.Thesis research directed by: Chemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Shen, Wenting. „Supramolecular assembly of π-systems using bimetallic CuI-clip bearing organophosporous ligands : control of the sold state organization in crystals and on surfaces“. Rennes 1, 2010. http://www.theses.fr/2010REN1S078.
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La polyvalence d’un clip de (CuI)2 basé sur des ligands phosphorés et utilisé afin de contrôler l’organisation à l’état solide d’assemblages supramoléculaires variés des systèmes-π a été étudiée dans ce travail. Le chapitre I présente les résultats obtenus afin de construire des analogues supramoléculaires variés de [2,2]paracyclophanes en interaction πà partir de connecteurs totalement π-conjugués ayant différentes natures et topologies. Dans les chapitres II et III, nous avons étudié les effets de variations structurales centrées sur les systèmes-π. Nous avons ainsi introduit des chaînes aliphatiques flexibles dans le squelette des connecteurs π-conjugués afin d’examiner le rôle joué par les fragments π-conjugués lors de la construction d’édifices étendus en interaction π et utilisé des systèmes π monotopiques. Le dernier chapitre présente les études AFM préliminaires de l’organisation sur surface de certains des assemblages en interaction décrits dans ce travailThe versatility of (CuI)2-clip bearing organophosphorous ligands in order to control the solid state organization of a variety of π-stacked supramolecular assemblies with cyano-capped π-systems has been investigated in this work. The Chapter I presents the results we had in order to build various π-stacked supramolecular analogues of [2,2]paracyclophanes based on fully π-conjugated linkers having different nature and topology. In the Chapter II and Chapter III, we present investigations we made focused on structural variation of the π-systems. We introduce “flexible” aliphatic chains in the core of the π-conjugated linkers to investigate the role of the π-systems to obtain long range π-stacked organization (Chapter II) and use monotopic π-conjugated systems (Chapter III). The last chapter presents the preliminary AFM studies of organization on surfaces of some of the π-stacked assemblies described in this work
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Ige, Mayowa. „Whoever Controls Access to the Tap Collects Rent On It: How Nigeria’s Function as a Gatekeeper State Fostered Environmental Degradation by Transnational Corporations“. Scholarship @ Claremont, 2016. http://scholarship.claremont.edu/pomona_theses/143.
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Every year, for the past 50 years, Nigeria’s oil-rich Niger Delta has suffered the same magnitude of oil spill in its rivers and swamps than was spilled in the 2010 Gulf Oil Spill. The damage has devastated the way of life of the Ogoni people who live in the area. They have consistently suffered environmental injustice as a result of Shell’s oil exploration, and the Nigerian government has ignored their cries for help and restitution. In fact, movements to garner support for environmental justice and fare share of oil profits and ownership from Shell and the state have been brutally shut down by the Nigerian government.
Could it be that the reason that the state is willing to allow such a grave level of environmental degradation to persist is not only because it is corrupt, but also because the Nigerian government functions as a gatekeeper state guarding its precious oil resources? Following independence, many oil-producing countries turned to spigot economies that allowed whoever controlled access to the tap to collect rent on it. Thus, as a gatekeeper state, it is not in the best interest of the Nigerian government to give up its rent-seeking behaviors with Shell to appease its citizens because it may disrupt its relationship with the outside corporations. As a result, many of the cries for environmental justice by the Ogoni people have been met with resistance from the state since their function has evolved to collect taxes on exports and imports—not to maintain the trust of its citizens.
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Ovejas, Benedicto Victòria Júlia. „Determination of the state of health of Li-ion batteries : the irreversible entropy production approach“. Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461681.
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In recent years, portable applications have experienced an exponential growth and consequently, the demand of batteries has increased accordingly. It is widely known, though, that the performance of batteries decreases with time and use. This loss of performance is easured by the State-of-Health (SoH) of the cells. However, there is no consensus in defining this parameter. Experimental, theoretical or even heuristic approaches can be found in literature and commercial systems, but usually, they only work for particular conditions and they are not linked to the degradation suffered by the cells themselves.
The aim of this study is to find a parameter directly related to this degradation. For this purpose, we investigate the irreversible entropy production in Li-ion cells because irreversible entropy is related to energy dissipation and thus, to irrversibilities due to system or energy degradation.
In order to evaluate the degradation of the cells and its correspondence to irreversible entropy generation, we studied different Li-ion chemistries (NMC, LFP and LCO). Batteries were cycled at different discharge rates (close to and far from equilibrium) and evaluated at different SoHs. Therefore, capacity fade and impedance rise (the most commonly used techniques in SoH determination) were characterized and related to irreversible entropy generation. In addition, post-mortem analysis was carried out to achieve a deeper knowledge of the causes and effects of degradation.
As a result of this study, we introduced a new parameter for system degradation characterization, the Relative-Entropy-Production (REP), defined as the irreversible entropy generation ratio at actual state and the initial state. In particular, we found irreversible entropy production evaluated at low discharge rates was higher as more degraded were the NMC cells. In the case of LFP cells, irreversible entropy production decreased during initial cycles but then increased towards the EoL. This behavior coincided with a capacity increase during initial cycles. In addition, we found a relationship between irreversible entropy generation and the phase transformations taking place during the discharge processes in all the evaluated cells because the materials undergoing phase transformations expand and contract yielding to cracks and other structural.
Irreversible entropy production is found to be a promising magnitude to characterize battery aging. Even though much research has still to be carried out, the idea is to define, in the future, a threshold in irreversible entropy production that the cells can stand before considering their EoL is reached.En els darrers anys, la demanda de bateries ha augmentat considerablement gràcies a la creixent proliferació de dispositius portàtils. Tot i això, és ben sabut que el funcionament de les bateries empitjora amb el temps i l'ús. Aquesta pèrdua de rendiment es mesura amb un paràmetre anomenat State-oh-Health (SoH) encara que, avui dia, no s'ha arribat a un consens per a definir-lo. A la literatura o als mateixos sistemes comercials s'hi poden trobar aproximacions experimentals, teòriques o heurístiques, que generalment funcionen en situacions particulars i que, moltes sovint, no estan directament relacionades amb la degradació que pateixen les cel·les. L'objectiu d'aquest estudi és trobar un paràmetre que estigui directament relacionat amb la degradació patida per les cel·les. Per aquest motiu, ens hem centrat en la producció d'entropia irreversible perquè aquesta està relacionada amb la dissipació d'energia i, per tant, amb les irreversibilitats degudes a la degradació del sistema o de l'energia. Es va treballar amb vàries químiques de bateries d'ions de liti (NMC, LFP i LCO) per tal d’avaluar la degradació patida per aquestes i la correspondència amb la generació d'entropia irreversible. Aquestes cel·les van ser avaluades a taxes baixes i elevades a diferents nivells de SoH. En particular, la disminució de capacitat i l’augment d’impedància, que són les tècniques més utilitzades per a determinar el SoH, van ser determinades i posteriorment relacionades amb la generació d’entropia irreversible. A més a més, l’anàlisi post-mortem de les cel·les ens va permetre obtenir un coneixement major de les causes i els efectes de la degradació. Com a resultat d’aquest estudi, hem introduït un nou paràmetre per a la caracterització de la degradació d’un sistema. Aquest paràmetre l’hem anomenat Relative-Entropy-Production (REP) i l’hem definit com la relació entre la generació d’entropia irreversible en el moment actual i l’estat inicial. En particular, hem trobat que la producció d’entropia irreversible a taxes baixes de descàrrega és més gran com més degradades estan les cel·les de NMC. En canvi, en el cas de les cel·les de LFP, hem trobat que la generació d’entropia irreversible disminueix durant els primers cicles per després augmentar fins al final de la seva vida útil. S’ha vist que aquesta disminució coincideix amb un increment de la capacitat. A més a més, a totes les cel·les amb les que hem treballat, hem trobat una relació entre la producció d’entropia irreversible i les transformacions de fase que tenen lloc als elèctrodes durant la descàrrega. Aquesta relació ha sigut associada al fet de que els materials que pateixen una canvi de fase s’expandeixen i es contrauen el que fa que es produeixin fractures o esquerdes o altres modificacions estructurals. Totes elles produeixen degradació i, per tant, generen entropia irreversible. S’ha trobat que REP i la generació d’entropia irreversible són magnituds prometedores per a caracteritzar l’envelliment de bateries. Encara que queda molta feina per fer, la idea és, en un futur, poder definir un llindar de REP o de generació d’entropia irreversible que les cel·les siguin capaces de suportar abans no es consideri que han assolit el final de les seves vides útils.
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Kelly, Lori Lee. „THE ECONOMIC AND ENVIRONMENTAL IMPACTS THE U.S. FARM BILLS HAVE ON THE STATE OF OHIO“. Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1375792739.
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Turek, Milan. „Inteligentní řídící člen aktivního magnetického ložiska“. Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-233984.
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The PhD thesis describes control design of active magnetic bearing. Active magnetic bearing is nonlinear unstable system. This means it is not possible to use classic methods of control design for linear time invariant systems. Also methods of nonlinear control design are not universal and theirs application is not easy task. The thesis describes usage of simple nonlinear compensation which linearizes response of active magnetic bearing and allows usage of classic methods of control design for linear time invariant systems. It is shown that CARLA method can significantly improve parameters of designed controller. First part of thesis describes derivation of model of controlled active magnetic bearing and nonlinear compensation which linearizes response of controlled active magnetic bearing on input signal. Following part contains description of methods of state control design methods, selected methods of robust control design and most common methods of artificial intelligence used for control design and implementation. Next part describes hardware of used experimental device and its parameters. It also contains experimental derivation of model of electromagnetic force because the parameters are not available from manufacturer. Last part describes control design of active magnetic bearing. Several different approaches are described here. The approaches vary from completely experimental approach, through using Ziegler-Nichols method, state control design to methods for robust control design. During design is heavily used CARLA method which is very suitable for usage for online learning in real controller due its principle.