Dissertations / Theses on the topic 'Complexing agents'

Various chelating ligands have been designed and synthesised; these include amino-amide ligands, tetraacetic acid systems and sulfur-containing amide ligands. Difficulties in the synthesis and purification of the amino-amide ligands were largely overcome, permitting the mono acylation of ethylenediamine and the synthesis of bis(2-aminoethyl)-2-benzylpropanediamide. Novel tetraacetic acid ligands, based on the propanediamide backbone and targeted as EDTA analogues, were obtained from their methyl and benzyl esters; but the instability of the tetraacids prevented their full characterisation. Bidentate, tridentate and tetradentate sulfur-containing monoamide ligands, based on the ortho-thio acetanilide moiety, were designed to specifically chelate platinum and palladium in the presence of base metals. In their synthesis, thiocyanation was used to introduce the orth-thio group on para-substituted anilines, and further functionalisation was achieved via appropriate protection of nucleophilic sulfur moieties. A range of tetradentate, sulfur-containing diamide ligands was also synthesised by reacting substituted 2-mercaptoacetanilides with 1,2- dibromoethane. Novel ligands were characterised by spectroscopic (¹H and ¹³C NMR; IR and M S) techniques and elemental (combustion and high resolution MS) analysis. Computer modelling and ¹H NMR chemical shift data have been used to explore the conformational preferences of the sulfur-containing acetanilide ligands. The macrocyclic ligands and systems with ortho-methylthio substituents appear to exhibit the greatest degree of coplanarity of the aromatic and amide functions. Solvent extraction studies revealed that the sulfur-containing amide ligands selectively extracted palladium(II) from platinum(II), copper(II}, nickel(II} and cobalt(II}. Even though the palladium(II} was extracted from an acidic medium, certain monoamide ligands were able to complex palladium(II) through their sulfur and deprotonated amide nitrogen donors, a trithia monoamide ligand being observed to displace all the chloride ligands on palladium to form a monomeric tetracoordinate complex. The diamide ligands, however, appeared to favour extraction of palladium(II) by coordination through their sulfur donors, forming 5-membered sulfur-sulfur chelates. In basic media (pH 8-9), selected sulfur-containing monoamide and diamide ligands have been shown to complex platinum(II) and palladium(II) through their sulfur and deprotonated amide nitrogen donors. At neutral pH, a dimercapto monoamide ligand has been shown to complex platinum from cisplatin with partial expulsion of the ammine ligands, while a macrocyclic trithia monoamide ligand has been observed to complex platinum from tetrachloroplatinate with concomitant deprotonation of the amide nitrogen. Where possible, the complexes were characterised by infrared and ¹H NMR spectroscopy and have also been studied using the computer modelling soft-ware programmes, Momec® and Hyperchem®.

Characterising the geochemistry and speciation of major contaminant radionuclides is crucial in order to understand their behaviour and migration in complex environmental systems. Organic complexing agents used in nuclear decontamination have been found to enhance migration of radionuclides at contaminated sites; however, the mechanisms of the interactions in complex environments are poorly understood. In this work, radionuclide speciation and sorption behaviour were investigated in order to identify interactions between four key radionuclides with different oxidation states (Cs(I) and Sr(II) as important fission products; Th(IV) and U(VI) as representative actinides), three anthropogenic organic complexing agents with different denticities (EDTA, NTA and picolinic acid as common co-contaminants), and natural sand (as simple environmental solid phase). A UV spectrophotometric and an IC method were developed to monitor the behaviour of EDTA, NTA and picolinic acid in the later experiments. The optimised methods were simple, applied widely-available instrumentation and achieved the necessary analytical figures of merit to allow a compound specific determination over variable background levels of DOC and in the presence of natural cations, anions and radionuclides. The effect of the ligands on the solubility of the radionuclides was studied using a natural sand matrix and pure silica for comparison of anions, cations and organic carbon. In the silica system, the presence of EDTA, NTA and, to a lesser extent, picolinic acid, showed a clear net effect of increasing Th and U solubility. Conversely, in the sand system, the sorption of Th and U was kinetically controlled and radionuclide complexation by the ligands enhanced the rate of sorption, by a mechanism identified as metal exchange with matrix metals. Experiments in which excess EDTA, NTA and picolinic acid (40 – 100 fold excess) were pre-equilibrated with Th and U prior to contact with the sand, to allow a greater degree of radionuclide complex formation, resulted in enhanced rates of sorption. This confirmed that the radionuclide complexes interacted with the sand surface more readily than uncomplexed Th or U. Overall this shows that Th and U mobility would be lowered in this natural sand by the presence of organic co-contaminants. In contrast, the complexation of Sr with the complexing agents was rapid and the effect of the ligands was observed as a net increase on Sr solubility (EDTA, picolinic acid) or sorption (NTA). As expected, Cs did not interact with the ligands, and showed rapid sorption kinetics. Finally, ESI-MS was used to study competitive interactions in the aqueous Th-Mn-ligand ternary system. Quantification presented a challenge, however, the careful approach taken to determine the signal correction allowed the competitive interactions between Mn and Th for EDTA to be studied semi-quantitatively. In an EDTA limited system, Th displaced Mn from the EDTA complex, even in the presence of a higher Mn concentration, which was consistent with the higher stability constant of the Th-EDTA complex.

X-ray crystallographic analyses of a group of salicylaldoxime ligands, and their copper(II) complexes were carried out. The three of the copper(II) complexes studied, bis-(2-hydroxy-5-methylbenzaldehydeoximato)copper(II), [(L1)2Cu]n, bis-(2-hydroxy-5-methylbenzophenoneoximato)copper(II), [(L5 )2Cu] and bis-(2-hydroxy-3-t-butyl-methylbenzaldehydeoximato)copper(II), [(L7 )2Cu], existed as centrosymmetric molecules, with the copper atom at crystallographic inversion centre. Two bidentate ligands produce a planar arrangement of donor atoms around the copper. The molecules reassemble macrocyclic systems, due to effective intramolecular hydrogen bonding linking the two ligands. To correlate chelating properties with intramolecular H-bond strengths an X-ray structural analysis was carried out on one ligand supplied by ICI, and thought to be 3,5-dimethyl-2-hydroxy acetophenone methoxyimine. Unexpectedly the molecule was found to be 3,5-dimethyl-4-hydroxy acetophenone methoxyimine. This was successful in explaining the anomolously low efficiency of extraction for copper(ll), shown by the related n-nonyl oxime ligand. It is thought that the presence of syn and anti isomers in 2-hydroxybenzophenone oximes accounts for the low efficiency of copper extraction shown by reagents which contain this chelating unit. The syn and anti forms, of 2-hydroxy-5-methylbenzophenone oxime (L5H) were prepared separately. Significantly both forms appear to yield [L5]2CH] when treated with Cu(CH3CO2)2.H20 in a homogeneous solution, although there are indications that formation of the complex from the syn-form is slower. Selectivity of complexation of metal ions by macrocyclic ligands were investigated. The stability constant data of zinc(II) and cadmium(II) complexes of a series of cyclic quadridentate ligands were compared. For the 15-membered N4 macrocyle L15, the propyl (L15p) and butyl (L15b) C-alkylated derivatives were synthesised for the first time, and the cadmium(II) complex of (L15b) was prepared. X-ray analysis were performed on the free ligand L15b, and the three metal complexes [Zn(L15)(NO3)(H2O)]NO3, [Cd(15)(NO3)NO3, and [Cd(L15b)(NO3)NO3. These results were then correlated with the results of stability constant measurements in discussing the probable behaviour of the ligands in the solution environment and hence to provide some insight into the effect of alkylation on the discrimination for zinc(II) over cadmium(II). The discrimation for zinc over cadmium is decreased on alkylation and the reason for this is discussed.

Bibliography: leaves 137-146.
This study examines the role complexing agents play in pentlandite-pyroxene flotation and focuses on the surface chemistry and interaction between valuable and gangue minerals as well as the interaction of complexing agents and reagents (xanthate, copper sulphate) in the system at pH 9. Microflotation, zeta potential measurements, ToF-SIMS analyses (time of flight secondary ion mass spectrometry) and X-ray photoelectron spectroscopy (XPS) were used as tools in determining the extent of surface alteration.

The semiconductor industry has been growing at a fast pace in the last several decades and this growth is expected to continue in the future. One process that is repeated several times in a microchip fabrication is the Chemical Mechanical Planarization (CMP). CMP is a critical process that must be employed after the metal deposition step to eliminate any topography over which the next layer must be processed. Today, copper interconnect is widely used. In addition to possess a high resistance to electro migration effects and low electrical resistivity, copper techniques require fewer (approximately 25%) processing steps. CMP and post-CMP cleaning processes are projected to account for 50 percent of the water consumed by fabrication's ultra pure water. While there are a variety of treatment schemes currently available for the removal of heavy metals from CMP wastewater streams, many introduce additional chemicals to the process, have large space requirement, or are not effective. Polyethyleneimine (PEI) is well known to use in the ion metal affinity chromatography (IMAC) due to the great metal ion binding abilities. While work has been conducted on the use of PEI on membrane filtration for binding metals from industrial wastewaters, the experiments performed in this research are novel with respect to the waste (Cu CMP) treated as well as the method of packed bed column treatment. This research focused primarily on the study of an alternative technique to remove both metal ions and metal-chelated complexes from Cu CMP wastewater streams. Not only copper, wastewater often contains chelating agents, surfactant, organic compounds, and inhibitors. Thus, most of the time copper ions form complexes with chelating agents, which made typical ion exchange resins ineffective. The work, then, explored the effect of components typically found in Cu CMP waste streams on the binding of copper ions to PEI. The competitive binding of copper between PEI and other complexing agents were also investigated. A secondary focus of this study was to fully develop and characterize the column performance and behavior. This includes the understanding of the chemistry of CMP waste characterization. This treatment technique using a PEI packed bed column showed great copper binding capacity. The column is capable of removing Cu CMP waste streams, which contain both copper ions and copper complexes, due to the unique ability of PEI that can play both cation and anion exchanger roles. This waste treatment technique is feasible for the semiconductor industry as large volumes of copper contaminated solutions from actual waste can be concentrated twelve-fold for metal recovery using hydrochloric acid. The adsorbent can be regenerated more than hundred of times with changing in the performance and the reproducibility.

The Vanadium bromide (V/Br) flow cell employs the Br3-/Br- couple in the positive and the V(II)/V(III) couple in the negative half cell. One major issue of this flow cell is bromine gas formation in the positive half cell during charging which results from the low solubility of bromine in aqueous solutions. Bromine complexing agents previously used in the zinc-bromine fuel cell were evaluated for their applicability in V/Br flow cell electrolytes. Three quaternary ammonium bromides: N-ethyl-N-methyl-morpholinium bromide (MEM), N-ethyl-N-methyl-pyrrolidinium bromide (MEP) and Tetra-butyl ammonium bromide (TBA) were studied. It is known that aqueous bromine reacts with quaternary ammonium bromides to form an immiscible organic phase. Depending on the number of quaternary ammonium bromides used and the environmental temperature, the second phase formed will either be solid or liquid. As any solid formation would interrupt the flow cell operation, potential formation of such kind has to be eliminated. Stability tests of simulated V/Br electrolyte with added quaternary ammonium bromides were carried out at 11, 25 and 40 oC. In the absence of bromine, the addition of MEM, MEP and TBA were found to be stable in V/Br electrolytes. However, in the presence of bromine, solid formation was observed in the bromine rich organic phase when the V/Br electrolyte contained a single quaternary ammonium bromide (QBr) compound. For V/Br electrolytes with binary or ternary QBr mixtures containing TBA, the presence of bromine caused a viscous polybromide phase to form at room temperature and the release of bromine gas at higher temperature. Only a binary mixture of MEM and MEP formed a stable liquid organic phase between 11 ?? 40 oC. In this study it was found that V/Br electrolytes containing a binary QBr mixture (0.75M) of MEM and MEP gave the best combination that formed an orange oily layer in the presence of bromine without solidification between 11 ?? 40oC. Furthermore, it was found that samples of V/Br electrolytes containing a ternary QBr mixture, are less effective in bromine capturing if the total QBr concentration was less than 1 M at 40oC, where bromine gas evolution was observed. From electrochemical studies of V3+/V2+, it was found that the addition of MEM and MEP had a minimal effect on the formal potential of the V3+/V2+ couple, the V2+/V3+ transfer coefficient and the diffusion coefficient of V3+. Therefore, MEM and MEP can be added to the negative half-cell of a V/Br flow cell without major interference From linear sweep voltammetry, the kinetics of the Br-/Br3- redox couple was found to be mass transfer controlled. After the addition of MEM and MEP mixture, the exchange current density was found to decrease from 0.013 Acm-2 to 0.01 Acm-2. On the other hand the transfer coefficient before and after MEM and MEP addition was found to be 0.5 and 0.44 respectively. Since the kinetic parameters were not significantly affected by the addition of MEM and MEP mixture, they can be added to the positive half-cell of the V/Br flow cell as bromine complexing agents. The electrochemical studies of both V3+/V2+ and Br-/Br3- showed the addition of MEM and MEP has minimal interference with the redox reactions of the vanadium bromide flow cell. This thesis also investigated the effect of MEM and MEP addition on the cell performance of a lab scale V/Br flow cell using two different membranes (ChiNaf and VF11). Flow cell performance for 2 M V3.7+ + 0.19 M MEM + 0.56 M MEP electrolytes utilising ChiNaf membrane at 10 mAcm-2 produced an energy efficiency of 59%, and this decreased to 43% after 15 cycles. For the static cell utilising VF11 membrane, the addition of MEM and MEP reduced the energy efficiency from 59.7% to 43.4%. It is believed that this is caused by the mass transfer controlled Br-/Br3- couple in the complexed positive half-cell solution. Therefore, uniformity between the organic and aqueous phase is important for flow cells utilising electrolytes with MEM and MEP. Finally, the polarization resistance of a lab scale V/Br flow cell utilising ChiNaf membrane and 2 M V3.7+ electrolytes was found to be slightly higher during cell charging (3.9 cm2) than during the discharge process (3.6 cm2), which is opposed to that in the all-vanadium redox cell.

The effects of a range of complexing agents on the radiation damage routes in frozen aqueous DNA have been analyzed by ESR techniques in a semi-quantitative way. Establishment of additive-free DNA standards for this study revealed an ESR pattern different from the four elementary shapes which contributed ∼ 13X of the total spin seen after annealing to 210 K. It is proposed that this represents a population of sugar radicals; hitherto unseen intermediates in additive-free systems between secondary base radicals and strand breaks. The intercalating aminoanthraquinones, mitoxantrone and ametantrone, were found to compete very efficiently with thymine for electron capture, and behaved as protecting agents. Concomitant strand break studies did not support this, and more extensive ESR studies suggested that the intercalator radical centre could also lead to strand breaks. It is therefore proposed that the mode of action of these drugs does not involve free radical processes in DNA. Use of these agents provided evidence that electron migra tion in DNA is much more extensive than previously thought. Copper ions were found to reduce the amounts of T/TH detected, with no effect on G . During this evaluation, evidence appeared for the existence of a site on DNA that could bind two Cu(II) ions so close together that they became ESR silent. Of special interest was the finding that this binding was preferred over that of single Cu(II) ions, and it is proposed that this might have a physiological significance. The dominance of thymine over cytosine as the site of electron capture is reinforced by the above studies, but it is suggested that it is the nature of the system under study that determines the ratio of T to C.

Macrocyclic complexing agents have been synthesised for the binding of indiumdil(III), gallium(III), yttrium(III), gold(I), silver(I) and rhenium(V) and a comparative study has been made between the macrocyclic complexing agents, 18N(_4)S(_2), 18N(_4)S(_2)Me(_4), 18N(_4)O(_2) and 18N(_4)0(_2)Me(_4) and their ability to bind silver (I). The gallium(III) and indium(III) complexes of 9N(_3)C(_3)Me(_3) and 9N(_3)C(_3)Ph(_3) have been investigated extensively both in vitro and in vivo. The stability of the complexes have been characterised using 71Ga NMR, 1H NMR, U.V. spectral analysis, ligand protonation constants, and complex binding constants. A full X-ray crystallographic structural determination has been obtained for the indium-9N(_3)C(_3)Me(_3) complex. Following confirmation of the excellent binding characteristics of the 9N(_3)C(_3)Me(_3) and 9N(_3)C(_3)Ph(_3) complexing agents, the in vivo kinetic stability of the indium and gallium complexes has been investigated. The 9N(_3)C(_3)Me(_3) complexes were exceptionally stable and cleared rapidly (99% within 24 hrs) via the renal excretion pathway. The complexes of the 9N(_3)C(_3)Ph(_3) were less stable and also showed a preference for clearance via the kidneys. Further to this, the tumour localising properties in a human melanotic melanoma has been investigated for the 67Ga- 9N(_3)C(_3)Ph(_3) complex. The complex has shown a preference for. tumour localisation, although a low tumour: blood ratio (1:1) may prohibit its application for tumour targeting. The stability constants of the silver(I) complexes of 18N(_4)S(_2), 18N(_4)S(_2)Me(_4), 18N(_4)O(_2) and 18N(_4)0(_2)Me(_4) have been measured both in methanolic and aqueous media. The [Ag-18N(_4)S(_2)Me(_4)]+ complex stability (log KmL= 14.6) is the highest stability constant recorded in methanol. In aqueous media, of the four complexes, the [Ag-18N(_4)S(_2)]+ is the most stable (log KmL=10-4) a reversal of the observed order of complex stability in methanol. The stability of the new yttrium(III) complexing agent has been ascertained using 1H NMR and HPLC radiometry and proved to be insufficiently stable for in vivo use, and was easily displaced by DTPA in a trial experiment.

Motor car exhaust catalysts are some of the most important users of platinum, and much attention is given to the recycling of scrap platinum from spent exhaust systems. The dissolution of platinum from waste exhausts was previously only possible by pyrometallurgical processes or by the use of aggressive chemicals, such as aqua regia and cyanide, all of which, however, cause pollution problems. Recently the potential for the development of hydrometallurgical processes was identified. These processes are more efficient and more environmentally friendly than traditional processes. It was the aim of this study to investigate the oxidation of platinum with ozone as oxidizing agent in the presence of chloride as complexing agent. The influence of various factors, such as chloride ion concentration, pH and temperature were studied thermodynamically and electrochemically in order to achieve efficient leaching. The thermodynamic investigation, leading to the construction of Pourbaix diagrams of platinum in the presence of chloride, confirmed the possibility of the formation of stable aqueous complexes, as well as platinum oxides. From the electrochemical results obtained it can be concluded that ozone may be useful as an oxidizing agent, but according to the leaching results obtained, ozone holds few benefits compared to aqua regia and cyanide, although they still present some environmental challenges. The relatively low percentages of recovery obtained with leaching may be attributed to the rapid decomposition of ozone, which is affected by several factors, such as temperature, pH, initial concentration of ozone, ionic strength and stirring rate. Further optimisation of these factors can possibly prove ozone to be a useful oxidizing agent for the recovery of platinum.
Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2013.

Le combustible nucléaire usé, après avoir été débarrassé de l'uranium, du plutonium et potentiellement du neptunium par le procédé PUREX, est encore constitué d'environ la moitié des éléments du tableau périodique. Au sein de ceux-ci, l'américium est majoritairement responsable des émissions thermiques à long terme des colis de déchets. En le recyclant, la compacité des sites de stockage pourrait être significativement améliorée. Le procédé d'extraction liquide-liquide EXAm, dont l'étape clé est la séparation Am/Cm, a donc été développé afin de séparer l'Am seul. Pour ce faire, un mélange d'extractants est utilisé conjointement au TEDGA (N,N',N,N'-tétraéthyl-diglycolamide), un complexant aqueux. Ce dernier permet en effet d'améliorer la séparation Am/Cm en maintenant préférentiellement le curium en phase aqueuse, mais sa relation structure sélectivité est encore mal comprise. Ces travaux de thèse concernent donc la synthèse et l'évaluation d'analogues structuraux du TEDGA afin de mieux comprendre l'influence de sa structure sur la sélectivité Am/Cm dans le procédé EXAm. Durant cette étude, 14 analogues du TEDGA ont été synthétisés et 17 molécules ont été évaluées en extraction liquide-liquide. Plusieurs modifications structurales ont été étudiées : la longueur et l'encombrement stérique des chaines alkyle portées par les azotes, la taille de l'espaceur, ainsi que l'utilisation d'amides secondaires. Ainsi, ces travaux ont montré qu'à partir des chaines tétrabutyle, il n'est plus possible de maintenir les molécules en phase aqueuse et que l'ajout d'encombrement stérique sur les chaines alkyles ou la modification de la balance hydrophilie/lipophilie diminue systématiquement la sélectivité des ligands. L'introduction d'amides secondaires (-CONHR) donne des ligands extractibles par le solvant (formation de liaison hydrogène avec les extractants) ce qui les rend inutilisables dans le procédé EXAm. Quant à l'espaceur, il joue un rôle prépondérant sur la sélectivité : le raccourcir (malonamides) entraine la disparition du caractère complexant de la molécule à forte acidité, et l'allonger entraine une préférence du ligand pour l'Am au lieu du Cm (inversion de sélectivité). L'ensemble de l'étude met en lumière la particularité de la sélectivité apportée par le TEDGA face aux autres diglycolamides ainsi que la difficulté d'améliorer le procédé en utilisant cette famille de molécules. Néanmoins la meilleure compréhension de sa chimie a permis d'affiner sa modélisation dans le procédé et l'étude de sa relation structure sélectivité montre qu'une amélioration de la sélectivité des ligands pourrait encore être envisagée en rigidifiant l'espaceur
After the reprocessing of uranium, plutonium and eventually neptunium by the PUREX process, the spent fuel is still composed of half of the periodic table. Among these elements, the main responsible for the heat of the wastes is americium. Its reprocessing could allow improving the compactness of deep geological storage of the wastes. Thus the liquid-liquid extraction process called EXAm was developed in order to recover the americium alone. The key step of the process is the Am/Cm separation. An extractant mixture is used with an aqueous complexing agent: TEDGA (N,N',N,N'-tetraethyl-diglycolamide). It allows to enhance the Am/Cm separation by keeping preferentially curium in the aqueous phase, but its structure selectivity relationship is not well known yet. Therefore, the purpose of this thesis is to synthesize and evaluate some structural analogues of TEDGA, in order to better understand the impact of its structure on the Am/Cm selectivity in the EXAm process.During this study, 14 analogues of TEDGA were synthesized and 17 molecules were evaluated in liquid-liquid extraction. Several structural modifications were studied: length and steric hindrance of the N-alkyl chains, size of the spacer, and the introduction of secondary amide functions. This work shows that it is not possible to maintain the ligand in the aqueous phase from tetrabutyl derivatives, and the addition of steric hindrance, or modification of hydrophilicity/lipophilicity balance, systematically decreases the selectivity of ligands. The addition of secondary amide functions (-CONHR) makes the molecules extractible by the solvent (formation of hydrogen bonds with the extractants), therefore they are unsuitable to be used in the EXAm process. The spacer has the main impact on the selectivity: the complexation capacity in high acid medium disappears when it is shortened (malonamide), whereas the ligand has a preference for Am instead of Cm (inversion of selectivity) when it is lengthen (TEDOODA and TETOUDA derivatives).This whole study shows the peculiar selectivity given by the TEDGA in comparison with other diglycolamides, and the difficulties to enhance the process using this family of ligands. Nevertheless, a better understanding of its chemistry has allowed to define more clearly its modeling in the process and the studying of its structure/selectivity relationship has shown that the enhancing of the ligands selectivity probably requires spacer preorganization

The concentration of tin and palladium in catalysts used in electroless copper plating have been determined by Rutherford backscattering spectrometry with high energy (2-5) MeV ⁴He⁺. The tin:palladium ratio in the catalyst decreases when exposed to an alkaline solution. X-ray photoelectron spectroscopy has confirmed this result and has shown the palladium in the catalyst is present as palladium metal and the tin is present, probably as an oxidized species, to a depth of about 30 Å. Catalysts for the electroless plating of copper are obtained by the reaction of Pd(II) and Sn(II). The extent of the reaction and the concentrations of the reaction products depend on the solution conditions. Conflicting results obtained in previous investigations of tin-palladium catalysts can be explained on this basis. Single crystals of gallium arsenide (GaAs(100)) were found to dissolve in synthetic lung fluid (Gamble solution). The concentrations of arsenic and gallium in the Gamble solution as well as the arsenic:gallium ratio on the GaAs surface increased continuously as the time of exposure to the Gamble solution increased. X-ray photoelectron spectroscopic studies of the gallium arsenide surface showed that arsenic migrated to the surface and it was oxidized to a species resembling As₂O₃ and finally solubilized by the Gamble solution. The solubility of gallium was governed primarily by the formation of stable complexes with the citrate and phosphate ions in the Gamble solution. Zinc that was present in the single crystals of gallium arsenide also migrated to the surface.

[EN] The increase in energy needs, particularly in terms of environmental protection, has greatly stimulated research in the field of photovoltaic conversion in recent years. Solar radiation provides an excellent resource for producing clean and sustainable electricity without toxic pollution or global warming, but in terms of high demand for energy for electricity production as well as the toxicity or scarcity of components constitute the solar cells, this solar transformation technology is still somewhat limited. Because these parameters constitute the main environmental concerns surrounding the photovoltaic industry. The compound Cu2ZnSnS4 (CZTS) can be considered as one of the most promising absorbent layer materials for low cost thin film solar cells. The abundance and non-toxicity of the constituent elements this promising material is the subject of this work. Obviously, this leads us to think about optimizing the other parameters influencing the formation of thin layers by the electrodeposition method. An electrochemical deposition technique which offers an advantageous alternative from an economic point of view and especially from the possibility of using large surface substrates. The initial focus was on determining the optimal parameters for the CZTS quaternary thin film development process. The electrodeposition is implemented by the technique of polarization of a potentiostatic electrode. Because this technique is based on the deposition potential of each substance constituting the electrolytic bath, a study has been conducted on the effect of the factors of complexity in order to assimilate these reduction potentials. Then, the annealing process which is a necessary step in the formation of absorbent layers in CZTS was mastered, under the influence of the complexity factor so as to reduce the annealing temperature while preserving the properties of the material. High quality kesterite films with a compact morphology and a well-defined crystal structure at low temperatures were synthesized using Na2SO4 as the complexing agent. Subsequently, the CZTS kesterite films were prepared on different conductive substrates (ITO, FTO and Mo / glass) due to specifying the effect of back contact. The best behavior is a specific combination of the parameters studied. This work made it possible in particular to master the composition of the films deposited, the annealing process as well as the necessary characterization techniques. Finally, our strategy implements a digital simulation of the CZTS solar cell using the SCAPS-1D software. After the experimental visualization of the thin layers of CZTS on different conductive substrates, modeling by the SCAPS-1D software of the CZTS solar cell device showed that the back-contact Mo mounts the best performances.
[ES] El aumento de las necesidades energéticas, particularmente en términos de protección del medio ambiente, ha estimulado en gran medida la investigación en el campo de la conversión fotovoltaica en los últimos años. La radiación solar proporciona un recurso excelente para producir electricidad limpia y sostenible sin contaminación tóxica o calentamiento global, pero en términos de alta demanda de energía eléctrica, así como la toxicidad o escasez de componentes que constituyen las células solares, esta tecnología de transformación solar todavía es algo limitada. En consecuencia estos parámetros constituyen las principales preocupaciones ambientales que rodean a la industria fotovoltaica. El compuesto Cu2ZnSnS4 (CZTS) puede considerarse como uno de los materiales absorbentes más prometedores para las células solares de película delgada de bajo costo. La abundancia y la no toxicidad de los elementos constitutivos de este prometedor material es el tema de este trabajo. Este objetivo nos ha llevado a pensar en optimizar los parámetros que influyen en la formación de capas delgadas por métodos electroquímicos. La técnica de deposición electroquímica o electrodeposición catódica ofrece una alternativa ventajosa desde un punto de vista económico y especialmente ofrece la posibilidad de utilizar sustratos de gran superficie. El enfoque inicial fue determinar los parámetros óptimos para el proceso de desarrollo de película delgada cuaternaria de CZTS. La electrodeposición se implementó mediante la técnica de polarización de un electrodo por el método potenciostático, o sea a potencial constante. Debido a que esta técnica se basa en el potencial de deposición de cada sustancia que constituye el baño electrolítico, se ha llevado a cabo un estudio sobre el efecto de los factores de complejidad para acercar estos potenciales de reducción. Una vez fueron depositadas las capas, se continuó con el estudio del proceso de recocido, que es un paso necesario en la formación de capas absorbentes de CZTS bajo la influencia del factor de complejidad, debido a que conviene reducir la temperatura de recocido mientras se intenta conservan las propiedades del material. Se sintetizaron películas de kesterita de alta calidad con una morfología compacta y una estructura cristalina bien definida a bajas temperaturas usando Na2SO4 como agente acomplejante. Posteriormente, las películas de kesterita CZTS se prepararon en diferentes sustratos conductores (ITO, FTO y Mo / vidrio) para estudiar el efecto del contacto posterior. Comprobamos que el mejor comportamiento se produce para una combinación específica de los parámetros estudiados. En particular este trabajo nos ha permitido controlar la composición de las películas depositadas, dominar el proceso de recocido y usar las técnicas de caracterización necesarias para evaluar la composicion, calidad y propiedades optoelectrónicas de las capas de CZTS sintetizadas. Finalmente, nuestra estrategia implementa una simulación digital de la célula solar CZTS utilizando el software SCAPS-1D. Después de la visualización experimental de las capas delgadas de CZTS en diferentes sustratos conductores, el modelado por el software SCAPS1D del dispositivo de células solares CZTS demostró que el contacto trasero Mo ofrece los mejores rendimientos.
[FR] L'augmentation des besoins énergétiques, notamment en matière de protection de l'environnement, a fortement stimulé la recherche dans le domaine de la conversion photovoltaïque ces dernières années. Le rayonnement solaire fournit une excellente ressource pour produire de l'électricité propre et durable sans pollution toxique ni réchauffement climatique, mais en termes de forte demande d'énergie pour la production de l’électricité ainsi que la toxicité ou la rareté des composants constituent les cellules solaires, cette technologie de transformation solaire est encore un peu limitée. En raison que ces paramètres constituent les principales préoccupations environnementales entourant l'industrie photovoltaïque. Le composé C2ZnSnS4 (CZTS) peut être considéré comme l'un des matériaux de couche absorbante les plus prometteurs pour les cellules solaires en couches minces à faible coût. L’abondance et la non-toxicité des éléments constitutifs ce matériau prometteur fait l'objet de ce travail. De toute évidence, cela nous amène à réfléchir pour optimiser les autres paramètres influençant la formation de couches minces par la méthode d'électrodéposition. Une technique de dépôt par voie électrochimique qui offre une alternative avantageuse du point de vue économique et surtout de la possibilité d’utiliser des substrats de grande surface. Initialement, l'accent était mis sur la détermination des paramètres optimaux pour le processus d’élaboration de couches minces du quaternaire CZTS. L'électrodéposition est mise en œuvre par la technique de polarisation d'une électrode potentiostatique. En raison, que cette technique reposant sur le potentiel de dépôt de chaque substance constituant le bain électrolytique, une étude a été menée sur l'effet des facteurs de complexité afin de rapprocher ces potentiels de réduction. Ensuite, Le processus de recuit qui est une étape nécessaire dans la formation de couches absorbantes en CZTS a été maîtriser, sous l'influence du facteur de complexité en raison de réduire la température de recuit tout en conservant les propriétés du matériau. Des films de kësterite de haute qualité avec une morphologie compacte et une structure cristalline bien définie à basse température ont été synthétisés en utilisant Na2SO4 comme agent complexant. Par la suite, les films de kestérite CZTS ont été préparés sur différents substrats conducteurs (ITO, FTO et Mo / verre) en raison de spécifier l'effet du contact arrière. Le meilleur comportement est une combinaison spécifique des paramètres étudiés. Ces travaux ont permis notamment de maîtriser la composition des films déposés, le processus de recuit ainsi que les techniques de caractérisation nécessaire. Finalement, notre stratégie met en œuvre une simulation numérique de la cellule solaire CZTS à l'aide du logiciel SCAPS − 1D. Après la visualisation expérimentale des couches minces de Czts sur différent substrats conducteur, une modélisation par le logiciel SCAPS-1D du dispositif CZTS cellules solaires a montré que le Mo contact arrière monte les meilleures performances.
[CA] L'augment de les necessitats energètiques, particularment en termes de protecció de l'entorn, ha estimulat en gran mesura la investigació en el camp de la conversió fotovoltaica en els últims anys. La radiació solar proporciona un recurs excel·lent per produir electricitat neta i sostenible sense contaminació tòxica ni escalfament global, però en termes de l'alta demanda d'energia elèctrica, així com la toxicitat o escassetat de components que constitueixen les cèl·lules solars, aquesta tecnologia de transformació solar encara trova barreres limitadores. En conseqüència aquests paràmetres constitueixen les principals preocupacions ambientals que envolten a la indústria fotovoltaica. El compost Cu2ZnSnS4 (CZTS) pot considerar-se com un dels materials absorbents més prometedors per a les cèl·lules solars de pel·lícula prima i de baix cost. L'abundància i la no toxicitat dels elements constitutius d'aquest prometedor material és el tema d'aquest treball. Aquest objectiu ens ha portat a treballar en l’optimització dels paràmetres que influeixen en la formació de capes primes de CZTS per mètodes electroquímics. La tècnica de deposició electroquímica o electrodeposició catòdica ofereix una alternativa avantatjosa des d'un punt de vista econòmic i especialment ofereix la possibilitat d'utilitzar substrats de gran superfície. L'enfocament inicial va ser determinar els paràmetres òptims per al procés de desenvolupament d’una pel·lícula prima quaternària de CZTS. La electrodeposició es va implementar mitjançant la tècnica de polarització d'un elèctrode pel mètode potenciostàtic, o siga a potencial constant. Aquesta tècnica es basa en el potencial de deposició de cada substància que constitueix el bany electrolític es diferent i per tant s'ha dut a terme un estudi sobre l'efecte dels factors de complexitat per tal apropar aquests potencials de reducció de tots els components involucrats. Un cop van ser dipositades les capes, es va continuar amb l’estudi del procés de recuit, que és un pas necessari en la formació de capes absorbents de CZTS sota la influència del factor de complexitat, a causa de la reducció de la temperatura de recuit mentre es conserven les propietats de l'material. Es van sintetitzar pel·lícules de kesterita d'alta qualitat amb una morfologia compacta i una estructura cristal·lina ben definida a baixes temperatures usant Na2SO4 com a agent acomplexant. Posteriorment, les pel·lícules de kesterita CZTS es van preparar en diferents substrats conductors (ITO, FTO i Mo / vidre) per estudiar l'efecte del contacte posterior sobre les capes fines. Obtinguerem que el millor comportament és una combinació específica dels paràmetres estudiats. En particular aquest treball ens ha permès controlar la composició de les pel·lícules dipositades, controlar el procés de recuit i usar les tècniques de caracterització necessàries per avaluar la composició, qualitat i propietats optoelectròniques de les capes de CZTS depositades. Finalment, en la nostra estratègia es va implementar una simulació numérica d’una cèl·lula solar de CZTS utilitzant el programari SCAPS-1D. Després de la visualització experimental de les capes primes de CZTS en diferents substrats conductors, el modelatge pel programari SCAPS-1D del dispositiu fotovoltaic de CZTS va demostrar que el contacte posterior de Mo és el que ofereix el millor rendiment.
I would like to thank the Moroccan Center for Scientific and Technical Research and the Doctoral school of the Polytechnic University of Valencia for the financial assistance they have allocated. I also extend my sincere thanks to the UPV Electron Microscopy Service and to Mr Ángel Sans Tresserras for their help to learn how to work with characterization techniques.
Toura, H. (2020). Elaboration and characterization by electrochemical technique CZTS thin layers for photovoltaic application [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/154334
TESIS

Cette thèse traite l’utilisation des agents mobiles dans le domaine des algo- rithmes distribués en les déplaçant de manière aléatoire dans le réseau. Initialement k agents mobiles ayant les identités uniques sont placés dans le réseau. On décrit un algorithme distribué pour calculer un arbre couvrant dans les réseaux dynamiques en utilisant les agents mobiles. Les agents marquent les noeuds sur les quelles ils arrivent. Ils utilisent deux techniques di?érentes : le clonage dans lequel un agent crée son propre clone pour faire quelques tâches et le marquage sur la tableau de bord (un espace mémoire sur les noeuds). Ces techniques sont utilisés dans les applications comme l’arbre couvrant, le rassemblement et la collecte d’information. Chacun des agents détient une information partielle. Quand deux ou plusieurs agents se rencontrent sur un noeud, ils fusionnent en un seul agent. On s’intéresse alors au temps nécessaire ou tous les k agents fusionnent en un seul et unique agent. On présent une chaîne de Markov pour le comportement des agents, et on montre comment on peut utiliser cette technique pour calculer la bourne supérieur. On étudie le même problème quand les agents mobile commencent la marche aléatoire sous un régime stationnaire. On a aussi étudié le problème de Handshake et on l’a analysé en utilisant les agents mobiles
This thesis deals with the use of mobile agents in distributed algorithms by performing random walks in the network. k mobile agents having unique identities are placed initially in a network. We describe a distributed algorithm for computing spanning trees in dynamic networks by using mobile agents. The agents mark the nodes on which they arrive. They use two di?erent techniques. In one problem they use the cloning in which an agent creates its own clone to do some task assigned. In the second, the mobile agents mark on the whiteboard (a memory location on the nodes). These techniques are used in applications such as spanning tree, gathering and collecting information. The mobile agents have limited knowledge and hence, they are not intelligent and do not have computational capabilities. When two or more agents meet at a node of the underlying graph, they merge into a single agent. The parameter of interest is the expected time for all the agents to merge into a single agent. We present a Markov chain, modelling the agents behavior, and show how this can be used to upper bound the expected time for all the k agents to merge into a single agent. We study the same problem when the mobile agents start their walk directly under stationary regime. Handshake problem is also studied and analyzed using mobile agents

Nous considérons dans ce travail, des problèmes d’optimisation dans des graphes de flot multi-agent. Trois types d’agents sont considérés : les agents producteurs, transporteurs et usagers et différentes variétés de topologies de réseaux sont abordées. Chaque agent transporteur contrôle la capacité d’un ensemble de routes élémentaires (arcs), ayant chacun une capacité qui peut être augmenté jusqu’à une valeur maximale moyennant un coût fixe. Les autres agents (i.e., usagers/producteurs) sont intéressés par la maximisation du flot qu’ils reçoivent. Dans ce but, ces derniers offrent une récompense aux agents transporteurs, cette récompense est proportionnelle à la valeur du flot reçu. Ce contexte multi-agent particulier est appelé jeu expansion de réseau multi-agent. La stratégie d’un agent transporteur consiste à décider de la capacité de ses arcs sachant qu’un coût supplémentaire est encouru pour toute expansion unitaire de capacité. Il reçoit en contrepartie une part de la récompense. Il est intéressé par la maximisation de son profit et se comporte en conséquence. En outre, la stratégie d’un agent producteur/usager consiste à décider de la politique de partage de sa récompense afin de maximiser le flot qu’il reçoit. Le flot total réalisé dépend finalement des stratégies de tous les agents. Dans ces jeux d’expansion de réseau multi-agent, nous nous intéressons à caractériser des stratégies stables (i.e., Equilibre de Nash) selon diverses hypothèses. En se basant sur cette caractérisation, différents cas sont définis et étudiés. L’analyse de la complexité de quelques problèmes de décision est présentée dans ce manuscrit. Nous nous intéressons particulièrement au problème de recherche d’un équilibre de Nash qui maximise la valeur du flot total circulant dans le réseau. Nous montrons que ce problème est NP-difficile au sens fort et nous montrons comment une telle stratégie peut être caractérisée par des chemins spécifiques dans des graphes résiduels. Nous proposons également un programme linéaire à variables mixtes (PLM) qui résout le problème dans le cas d’un seul agent producteur/usager et un ensemble d’agents transporteurs. Des résultats expérimentaux sont fournis pour prouver l’efficacité de notre approche
In this work, multi-agent network flow problems are addressed. Three types of agentsare considered, namely the producer, transportation and customer agents and various network topologies are tackled. Every transportation agent controls the capacities of a set of elementary routes (arcs), each one having a capacity that can be increased up to a certain point at a given cost. The other agents (i.e., customers/producers) are interesting in maximizing their flow of products. For that aim, we assume that they offer to the transportation agents a reward that is proportional to the realized flow value. This particular multi-agent framework is referred to as a multi-agent network expansion game. The transportation agent’s strategy consists in deciding upon the capacity of its arcs, an extra-cost being incurred for any capacity expansion. It receives in return a part of the total reward. It is interested in the maximization of its profit and behaves accordingly. Beside that, the producers/customers’ strategies consist in deciding the sharing policy for their reward for maximizing their own flow of products. The total network flow value eventually depends on all agents’ strategies. We take interest in characterizing and finding particular stable strategies (i.e., Nash Equilibria) that are of interest for this game under various assumptions. Based on this characterization, several cases are defined and studied. The analysis of the complexity of some decision problems is made. We particularly focus on the problem of finding a Nash Equilibrium that maximizes the value of the total flow. We prove that this problem is NP-hard in the strong sense and show how such a strategy can be characterized considering paths in specific reduced agent-networks. We also provide a mixed integer linear programming (MILP) formulation that solves the problem in the case of a single producer/customer agent and a set of transportation agents. Computational experiments are provided to prove the effectiveness of our approach

Cette thèse porte sur l’étude de la complexité de l’exploration de graphes dynamiquespar agent mobile. Une entité mobile (appelée agent) se déplaçant dans un graphe dynamiquedoit traverser/visiter au moins une fois chacun de ses sommets. (Le tempsde traversée d’une arête est unitaire.) Ce problème fondamental en algorithmique paragents mobiles a été très étudié dans les graphes statiques depuis l’article originel deClaude Shannon. Concernant les graphes dynamiques, seul le cas des graphes dynamiquespériodiques a été étudié. Nous étudions ce problème dans deux familles degraphes dynamiques, les graphes dynamiques périodiquement variables (PV-graphes)et les graphes dynamiques T-intervalle-connexes. Les résultats obtenus dans cette thèseaméliorent des résultats existants et donnent des bornes optimales sur le problèmeétudié
In this thesis, we study the complexity of the problem of exploration by a mobileagent in dynamic graphs. A mobile entity (called agent) moving in a dynamic graph hasto traverse/visit each of its vertices at least once. This fundamental problem in computatingby mobile agents has been well-studied in static graphs since the original paper ofClaude Shannon. However, for highly dynamic graphs, only the case of periodic dynamicgraphs has been studied. We study this problem in two families of dynamic graphs,periodically-varying graphs (PV-graphs) and T-interval-connected dynamic graphs. Theobtained results improve the existing results and give optimal bounds on the studiedproblems

This thesis is concerned with the analysis of economic network formation. There are three novel sections to this thesis (Chapters 5, 6 and 8). In the first, the non-cooperative communication network formation model of Bala and Goyal (2000) (BG) is re-assessed under conditions of no inertia. It is found that the Strict Nash circle (or wheel) structure is still the equilibrium outcome for n = 3 under no inertia. However, a counter-example for n = 4 shows that with no inertia infinite cycles are possible, and hence the system does not converge. In fact, cycles are found to quickly dominate outcomes for n > 4 and further numerical simulations of conditions approximating no inertia (probability of updating > 0.8 to 1) indicate that cycles account for a dramatic slowing of convergence times. These results, together with the experimental evidence of Falk and Kosfeld (2003) (FK) motivate the second contribution of this thesis. A novel artificial agent model is constructed that allows for a vast strategy space (including the Best Response) and permits agents to learn from each other as was indicated by the FK results. After calibration, this model replicates many of the FK experimental results and finds that an externality exploiting ratio of benefits and costs (rather than the difference) combined with a simple altruism score is a good proxy for the human objective function. Furthermore, the inequity aversion results of FK are found to arise as an emergent property of the system. The third novel section of this thesis turns to the nature of network formation in a trust-based context. A modified Iterated Prisoners' Dilemma (IPD) model is developed which enables agents to play an additional and costly network forming action. Initially, canonical analytical results are obtained despite this modification under uniform (non-local) interactions. However, as agent network decisions are 'turned on' persistent cooperation is observed. Furthermore, in contrast to the vast majority of non-local, or static network models in the literature, it is found that a-periodic, complex dynamics result for the system in the long-run. Subsequent analysis of this regime indicates that the network dynamics have fingerprints of self-organized criticality (SOC). Whilst evidence for SOC is found in many physical systems, such dynamics have been seldom, if ever, reported in the strategic interaction literature.

‘This BDI-model (beliefs, desires and intents) is a very commonly used method for modeling intelligent agents. Th‘e model is very commonly extended with new features and att‹ributes. Th‘is thesis presents a new such extension of the BDI-model with added social awareness. Multi-agent system can be very computationally complex so in order to €find out how well this architecture would work, a complexity analysis was made. Th‘e results of this analysis shows that the agent always will select a goal that appears to be desirable by other agents in the environment. It does however come with a computational cost where the amount of di‚fferent options the agent has to choose from plays a big part in the speed of the algorithm.

Ce projet utilise l’analyse de réseaux et la modélisation à base d’agents pour examiner des sujets classiquement traités mais qui peuvent maintenant être abordés, grâce aux riches données rencontrées dans le sud-ouest du Colorado et en France méridionale : comment les Gaules et les marchands méditerranéens établissaient leurs partenariats économiques, comment la violence a pu façonner le développement de niveaux divers de leadership, et comment les premiers agriculteurs interagissaient avec leur environnement. Pour écrire cette thèse composée de trois études de cas différents, deux dans le Sud-Ouest des États-Unis et un en France méridionale, nous utilisons des outils élaborés par les sciences de la complexité pour mieux aborder comment les individus de la préhistoire surmontaient les défis liés à l’acquisition de ressources. La modélisation à base d’agents et l’analyse de réseaux (sociaux et trophiques) nous permettront de décrire les processus décisionnels et d’analyser comment le partage de stratégies au sein du groupe peut entraîner une plus grande aptitude des individus à agir au sein du groupe
This project utilizes network analysis and agent-based modeling to examine long-standing questions that can only now be asked with the rich data provided in southwestern Coloradoand southern France: how Gauls and colonists established economic partnerships, how violence may have shaped the development of multiple levels of leadership, and how earlyf armers interacted with their environments. Writing a dissertation composed of three distinct case studies, two from the U.S. Southwest and one from the south of France, I use tools developed in complexity science to better address how people in the past dealt with challenges related to resource acquisition. Agent-based modeling and network analysis (both social network analysis and trophic network analysis) will allow me to characterize human decision making processes and discuss how sharing of strategies within a group can lead to greater fitness of those in the in-group

We study the computational complexity of collecting items inside a grid map with obstacles, using an agent that always slides to the maximal extend, until it is stopped by an obstacle. An agent could be, for example, a robot or a vehicle, while obstacles could be walls or other immovable objects, and items could be packages that need to be picked up. This problem has very natural applications in robotics. The restricted type of motion of the agent naturally models movement on a frictionless surface, and movement of a robot with limited sensing capabilities and thus limited localization. For example, if a robot cannot determine the distance traveled once it starts moving, then it makes sense to keep moving until an obstacle is reached, even if the robot has a map of the environment. With today’s technology it is possible to create sophisticated robots but, since the complexity and the costs of such robots are high, it is sometimes better to use simple inexpensive robots that can still solve relatively complex tasks. In fact, simple robots are quite common and usually built using simple sensors that have limited capabilities, but that are easy to use and are considerably cheaper than more sophisticated ones. The computational complexity of numerous problems with movable objects has been extensively studied before. However, only a few of them have maximal sliding agents, and they usually do not have the goal of collecting items. We show that the problem of deciding if all the items can be collected by a maximal sliding agent can be solved efficiently when the agent is the only moving object in the map. However, we show that optimization problems such as determining the minimum number of moves required to collect all the items, and also variants in more complex environments are computationally intractable. Hence, for those problems it is better to focus on using heuristics than on finding optimal solutions.

The Hohokam Water Management Simulation (HWM) is a computer simulation for exploring the operation of the Hohokam irrigation systems in southern Arizona. The simulation takes a middle road between two common kinds of archaeological simulation: large-scale, detailed landscape and environmental reconstructions and highly abstract hypothesis-testing simulations. Given the apparent absence in the Hohokam context of a central authority, the specific aim of the HWM is approaching the Hohokam as a complex system, using principles such as resilience, robustness, and self-organization. The Hohokam case is reviewed, and general questions concerning how the irrigation systems operated are shown to subsume multiple crosscutting and unresolved issues. Existing proposals about the relevant aspects of Hohokam society and of its larger long-term trajectory are based on widely varying short- and long-term processes that invoke different elements, draw different boundaries, and operate at different spatial and temporal scales, and many rely on information that is only incompletely available. A framework for pproaching problems of this kind is put forward. A definition of modeling is offered that specifies its epistemological foundations, permissible patterns of inference, and its role in our larger scientific process. Invoking Logical Positivism, a syntactic rather than semantic view of modeling is proposed: modeling is the construction of sets of assertions about the world and deductions that can be drawn from them. This permits a general model structure to be offered that admits hypothetical or provisional assertions and the flexible interchange of model components of varying scope and resolution. Novel goals for archaeological inquiry fall from this flexible approach; these move from specific reconstruction to a search for more universal and general dynamics. A software toolkit that embodies these principles is introduced: the Assertion-Based Computer Modeling toolkit (ABCM), which integrates simulation with the logical architecture of a relational database, and further provides an easy means for linking models of natural and social processes (including agent-based modeling). The application of this to the Hohokam context is described, and an extended example is presented that demonstrates the flexibility, utility and challenges of the approach. An attached file provides sample output.

The aim of this thesis is to examine a radical relational agency, applied to contemporary environmental resistances, that incorporates both the thought of Michel Foucault and complexity theory. While Foucault’s thought, following from his argument that power is a relation, implies a relational agency, it does not, however, account for the agency of nonhumans and environments. Because power is a relation and not a possession, it can no longer be viewed as an attribute of individual subjects. Similarly, a relational agency is defined as an aspect of power relations. Complexity theory, on the other hand, acknowledges that humans interact with nonhumans and environments, but does not acknowledge that all relations are relations of power. In addition to Foucault’s explanation of power relations, complexity theory explicitly describes the processes of self-organization through which individual and diverse agents interact and change can emerge. Thus, a radical relational agency is defined as an aspect of the power relationships between many diverse agents. Change, according to both Foucault and complexity theory, happens nonlinearly. As a result, it often occurs unpredictably. However, change within complex systems is also limited by previous historical emergences. In this sense, both possibility and risk are inherent in the relationships between humans, nonhumans and environments. Indeed, I argue that a radical relational agency occurs because there are both possibilities and risks generated within ecological relations and relations of power. Therefore, I argue that any environmental action must account for the unpredictability inherent to the complex interactions between humans, nonhumans and environments.

Nosso estudo foi elaborado a partir de uma analogia do modelo de Ising em duas dimensões para analisar a influência que a rede de contatos e as forças externas podem exercer no indivíduo para que ele tenha ou não a intenção de agir licitamente. Esse estudo teve como inspiração o modelo proposto no artigo Analysing Tax Evasion Dynamics Via The Ising Model (ZAKLAN; WESTERHOFF; STAUFFER, 2009), porém, com ênfase à intenção dos agentes, que precede a conduta delituosa, e não ao cometimento do crime em si, quando já ocorreu o dano à sociedade. A analogia e inclusão de algumas variáveis ao referido modelo nos possibilitou estudar, de acordo com cada cenário, formas de manter ou reduzir os índices criminais, prever possíveis situações de histerese, suas consequências e possíveis custos para a sociedade e para o governo.
Our study was drawn from an analogy of the Ising model in two dimensions to analyze the influence that the network and the external forces can exert on the individual so that whether or not he intends to act lawfully. This study was inspired by that proposed in the article \"Analysing Tax Evasion Dynamics Via The Ising Model\" (ZAKLAN; WESTERHOFF; STAUFFER, 2009) model, but with emphasis on the intention of the agents, which precedes the criminal conduct, not to the commission of the crime itself, when the damage has already occurred to society. The analogy is the inclusion of some variables that model allowed us to study, according to each scenario, ways to maintain or reduce crime rates, predict possible situations hysteresis, their consequences and potential costs to society and the government.

Nous étudions la complexité théorique de tâches de raisonnement mettant en jeu la connaissance des agents dans les systèmes multi-agents. Nous considérons la logique épistémique dynamique (DEL) comme une façon naturelle d'exprimer la connaissance, qui permet d'exprimer la connaissance d'ordre supérieur des agents et des actions dynamiques partiellement observées. Nous montrons des résultats de complexité algorithmique pour la vérification de modèles et la satisfiabilité de formules de DEL, et définissons une approche symbolique pour ces mêmes problèmes. Nous étudions également la planification basée sur DEL ainsi que des quantifications sur certaines actions : les annonces publiques
We study the theoretical complexity of reasoning tasks involving knowledge in multi-agent systems. We consider dynamic epistemic logic (DEL) as a natural way of expressing knowledge, which allows to express nested knowledge of agents and partially observed dynamic actions. We show complexity results for model checking and satisfiability of DEL formulas, and define a symbolic approach for these problems. We also study DEL-based planning and quantification over specific actions: public announcements

In recent decades, millions of articles, books and journals have been written and thousandsseminars and conferences have been held to present increasing importance of supply chainmanagement both in practice and theory. Undoubtedly, nowadays, success is not tied-upjust in processes of a focal company but in processes of all its value chain and network. Inorder to survive in highly competitive markets, it sounds essential that all processes andentities of the supply and demand network be analyzed and value-adding ones be separatedfrom those which are not.One of the origins of non-value adding processes is non-value adding complexity. So, asystematic study and analysis of supply chain complexity and rendering remedies forsimplicity are essential.In this thesis, at first, some definitions as well as causes of supply chain complexity basedon its complication and complexity are mentioned. In the next step, embodiments of somethemes of complexity science in discipline of supply chains are explained. Later, a recipefor studying complexity is offered. Ingredients of this recipe are identification,classification, measurement, modeling, and simplification. Finally, implementation ofintelligent agents as assured tools for simplification of supply chains complexity isdescribed.
Uppsatsnivå: D

Les systèmes multi-agents sont caractérisés par le travail coopératif d'un ensemble d'agents autonomes, fonctionnant de manière décentralisée en vue de la réalisation d'un objectif global. Au sein de ces systèmes se produisent des phénomènes dits d'émergence, ou d'auto-organisation, par lesquels des structures ou des organisations particulières peuvent apparaître au niveau collectif qui n'étaient pas décrites de manière explicite au niveau individuel. Ainsi des fourmis qui s'organisent en files d'individus sans qu'aucune n'ait de représentation correspondant à la notion de "file". De par leurs interactions au niveau local, les agents produisent et maintiennent dynamiquement des structures au niveau global qui contraignent en retour l'activité de chacun des individus. Ces phénomènes sont fondamentaux dans l'étude des systèmes biologiques complexes mais sont pourtant très difficiles à formaliser car liés généralement à une interprétation en partie subjective d'un observateur extérieur au système. Le sujet proposé vise à aborder le problème du passage d'un niveau d'abstraction à un autre, ainsi que l'interaction, au sein d'un système, entre agents de différents niveaux, en combinant plusieurs approches complémentaires: une première approche concerne l'étude de formalismes adaptés à la représentation de phénomènes émergents. Cela passe notamment par la prise en compte de relations entre entités de différents niveaux d'abstraction, et par la prise en compte de comportements qui s'expriment différemment en fonction du niveau d'abstraction auquel l'entité est considérée. une deuxième approche qui s'appuiera sur la précédente concerne la détection automatique de phénomènes émergents. Pour ce faire, il sera nécessaire de développer des mécanismes permettant aux entités qui participent au système de détecter l'apparition de structures particulières (spatiales et/ou temporelles, statiques ou dynamiques) et de caractériser le passage d'un niveau d'abstraction donné au niveau supérieur. du fait de la très grande difficulté d'aborder le problème précédent dans toute sa généralité, nous prévoyons de développer une approche semi-interactive dans laquelle un observateur humain pourra avoir un rôle pour orienter le système vers la détection de structures particulières et leur caractérisation d'une manière particulière. Outre l'aide apportée au système, il s'agit d'orienter ce dernier vers la prise en compte d'abstractions a priori utiles et intéressantes. Cela passe notamment par la conception de modalités de visualisation et d'interaction adaptées à ce problème. ces différentes problématiques seront étudiées dans le cadre de plusieurs problèmes de simulation multi-agent pour la biologie
Multi-agent systems are characterized by the cooperative work of a set of autonomous agents, operating in a decentralized manner with a view to achieving a goal. Within these systems produce phenomena known as emergence, or self-organization, in which structures or organizations may appear on a collective level that were not explicitly described at the individual level. Thus ants that are organized into files of individuals without having representation corresponding to the "file". Through their interactions at the local level, the agents produce and maintain structural dynamics at the global level which in turn constrain the activities of each individual. These phenomena are fundamental in the study of complex biological systems but are very difficult to formalize because usually related to a subjective interpretation of an observer outside the system. The subject is intended to address the problem of transition from one level of abstraction to another, and the interaction, within a system between officers of different levels, combining several complementary approaches: a first approach concerns study formalisms adapted to the representation of emergent phenomena. This includes taking account of relationships between entities of different levels of abstraction, and by taking behaviors that are expressed differently depending on the level of abstraction to which the entity is considered. a second approach which builds on the previous concerns the automatic detection of emergent phenomena. To do this, it will be necessary to develop mechanisms that allow entities that participate in the system to detect the emergence of structures (spatial and / or temporal, static or dynamic) and characterize the passage of a given level of abstraction to the next level. because of the great difficulty of dealing with the previous problem in all its generality, we plan to develop a semi-interactive approach in which a human observer may have a role to guide the system to detect structures and their characterization of a particular way. In addition to assisting the system, it is the guide to take into account a priori abstractions useful and interesting. This includes the design of procedures for display and interaction adapted to this problem. these issues will be explored in several issues of multi-agent simulation in biology

This case study explored how specific behaviors shape the connections between people within an inter-sector health collaborative as an important antecedent to achieving collaborative outcomes. The primary research question guiding this study was, “How do individual complexity leader behaviors—a subset of complexity leadership behaviors—shape the connectivity of agents within a complex adaptive system made up of elected, unpaid volunteers immediately following their annual strategic planning retreat?” Methods included observations, interviews, and document review. Individual complexity leader behaviors (CLBs) were found to shape the connectivity of agents within this complex adaptive system in a variety of ways that depended on the extant level of connectivity between agents. Specifically, when experiencing low-negative connectivity, the utility of CLBs shaped the extant connectivity in a negative manner. When experiencing low-neutral connectivity, the utility of CLBs shaped the extant connectivity in either a negative or a positive manner, or in a manner that reinforced the status quo. When experiencing moderate connectivity, the utility of CLBs shaped the extant connectivity in a manner that reinforced the status quo or the behavior made no impact on the extant connectivity. Lastly, when experiencing high/deep connectivity, the utility of CLBs shaped the extant connectivity in a positive manner, in a manner that reinforced the status quo, or the behavior made no impact on the extant connectivity. There were also a number of additional findings related to the nature of both CLBs and the indices of connectivity. These findings are critical given that the relative connectivity of agents within a complex adaptive system is predictive of that system’s capacity to achieve outcomes. This study empirically supports and extends several core assumptions of complexity leadership theory; it also demonstrates that individual CLBs are identifiable and influential; that anybody can utilize CLBs; and that CLBs should be intentionally and mindfully utilized. Moreover, this study empirically supports the existence of non-linearity and (inter)connectivity in complex adaptive systems; it also demonstrates the versatility of connectivity and its indices. The results of this study have practical implications for inter-sector collaboratives—particularly related to how they utilize complexity leadership behaviors and achieve outcomes—and for capacity-building practitioners—specifically related to re-framing their conceptualization of leadership for their students.

Les travaux de cette thèse s’articulent autour des « problèmes d’ordonnancement multiagent avec une fonction objectif globale ». Ces modèles considèrent différents agents associés à des sous-ensembles de travaux disjoints, chacun d’eux vise à minimiser un objectif qui ne dépend que de ses propres travaux. Un critère global est aussi considéré, qui est appliqué à la totalité des travaux. La résolution de ces problèmes revient à trouver les meilleurs compromis entre les critères des agents et le critère global. Ces problèmes sont une classe particulière des problèmes d’ordonnancement « multi-agents » qui ont connu une grande expansion, reflétant leurs intérêts dans le domaine de l’ordonnancement
This thesis addresses the multi-agent scheduling problems with a global objective function. We consider the problems featured by various agents, each of which is associated with a distinct subset of jobs. Each agent aims at minimizing a certain objective function, which only operates on its assigned jobs. A global criterion associated with a global agent is applied on the whole set of the jobs. Solving these problems involves finding the best compromises between the requirements of agents and that of the global agent. These problems belong to a particular class of multi-criteria scheduling problems. Such a class has drawn a significant interest to researchers in the area of scheduling and operational research

The decentralized Markov decision process (Dec-POMDP) is a powerful formal model for studying multiagent problems where cooperative, coordinated action is optimal, but each agent acts based on local data alone. Unfortunately, it is known that Dec-POMDPs are fundamentally intractable: they are NEXP-complete in the worst case, and have been empirically observed to be beyond feasible optimal solution.To get around these obstacles, researchers have focused on special classes of the general Dec-POMDP problem, restricting the degree to which agent actions can interact with one another. In some cases, it has been proven that these sorts of structured forms of interaction can in fact reduce worst-case complexity. Where formal proofs have been lacking, empirical observations suggest that this may also be true for other cases, although less is known precisely.This thesis unifies a range of this existing work, extending analysis to establish novel complexity results for some popular restricted-interaction models. We also establish some new results concerning cases for which reduced complexity has been proven, showing correspondences between basic structural features and the potential for dimensionality reduction when employing mathematical programming techniques.As our new complexity results establish that worst-case intractability is more widespread than previously known, we look to new ways of analyzing the potential average-case difficulty of Dec-POMDP instances. As this would be extremely difficult using the tools of traditional complexity theory, we take a more empirical approach. In so doing, we identify new analytical measures that apply to all Dec-POMDPs, whatever their structure. These measures allow us to identify problems that are potentially easier to solve on average, and validate this claim empirically. As we show, the performance of well-known optimal dynamic programming methods correlates with our new measure of difficulty. Finally, we explore the approximate case, showing that our measure works well as a predictor of difficulty there, too, and provides a means of setting algorithm parameters to achieve far more efficient performance.

We use an agent-based model to investigate the interdependent dynamics between individual agency and emergent socioeconomic structure, leading to institutional change in a generic way. Our model simulates the emergence and exit of institutional units, understood as generic governed social structures. We show how endogenized trust and exogenously given leader authority influences institutional change, i.e., diversity in institutional life-cycles. It turns out that these governed institutions (de)structure in cyclical patterns dependent on the overall evolution of trust in the artificial society, while at the same time, influencing this evolution by supporting social learning. Simulation results indicate three scenarios of institutional life-cycles. Institutions may, (1) build up very fast and freeze the artificial society in a stable but fearful pattern (ordered system); (2) exist only for a short time, leading to a very trusty society (highly fluctuating system); and (3) structure in cyclical patterns over time and support social learning due to cumulative causation of societal trust (complex system).

Cette thèse a pour objectif principal de développer un simulateur multi-agents pour concevoir un système d'aide à la maitrise des risques des activités de maintenance. Le but est d'explorer la complexité de la maintenance et de spécifier les interactions entre la fonction maintenance, l'analyse et l'évaluation des risques. Nous nous intéressons d’une part, à concevoir un modèle systémique permettant d’identifier et de modéliser un système industriel, à montrer les différentes interactions entre ses éléments, à analyser et évaluer les risques des activités de maintenance. Nous proposons la méthode MOSAR et le langage UML pour concevoir un modèle cognitif de référence. Ce modèle a servi de point de départ pour la conception d’une base de données à l’aide du langage SQL, qui est exploitée par le modèle Multi-Agents afin d’acquérir les informations nécessaires à son fonctionnement.D’autre part, nous développons une architecture d’un Système Multi-Agents qui a pour vocation d’anticiper les situations de défaillances et la prise de décisions à l’aide de la simulation du comportement du système étudié. Une comparaison entre les plateformes existantes dédiées aux Systèmes Multi-Agents est effectuée pour choisir la plateforme adéquate à notre problématique pour la réalisation de la simulation.Finalement, les modèles développés sont appliqués dans le cadre d’une chaîne logistique pour le chargement et le déchargement de GPL (Gaz de Pétrole Liquéfié). Un simulateur a été développé à l’aide de la plateforme AnyLogic dans le but d’étudier le comportement du système et de simuler les scénarios de défaillances choisis par l’industriel pour le calcul de la criticité à partir de trois paramètres (fréquence, gravité, détectabilité) et l’obtention d’un Tableau de Bord contenant un ensemble d’indicateurs de performance de la maintenance. Les modèles de simulation proposés permettent d’orienter les industries vers les bonnes décisions pour éviter les situations à risques pouvant déclencher des événements perturbateurs dommageables
The main objective of this thesis is to develop a multi-agent approach to designing a model to overcome risks of maintenance activities. The aim is to explore the maintenance complexity and to indicate the interactions between the maintenance function and the risk assessment.Firstly, we are interested in designing a systemic model to identify and model the industrial system, to show the different interactions between its elements, to analyze and to evaluate risks of maintenance activities. We propose the MOSAR method and the UML language to design a cognitive reference model. This model served as a starting point for designing a database using the SQL language, which is operated by Multi-Agent model to acquire the necessary information for its operation.On the other hand, we develop a framework of a multi-agent system that aims to anticipate failures scenarios and the decision-making by simulating the studied system behaviour. A comparison between the existing platforms dedicated to Multi-Agent Systems is performed to choose the appropriate platform for the simulation.Finally, the developed models are applied in the LPG supply chain (Liquefied Petroleum Gas). A simulator was developed using the AnyLogic platform in order to study the system behaviour and to simulate the failure scenarios chosen by the industry, for the calculation of the criticality from three parameters (Frequency, severity, detectability), and for obtaining a Dashboard containing a set of maintenance performance indicators. The proposed simulation models help to guide the industries toward good decisions to avoid risky situations that may trigger disruptive events damaging

Nous décrivons dans ce travail l'élaboration de latex nanocomposites à base d'oxyde de cérium en vue d'applications dans le domaine des revêtements. Deux procédés originaux ont été développés afin de contrôler la morphologie des particules. Dans un premier temps, nous avons tiré parti de la forte densité de charges des nanoparticules d'oxyde de cérium pour stabiliser des particules de latex obtenues par polymérisation en émulsion ou en miniémulsion " de Pickering ". Dans les deux cas, la réaction est conduite en présence des particules inorganiques et d'un agent complexant à caractère acide, l'acide méthacrylique, en l'absence de tout tensioactif. Des particules de latex, décorées en surface par les nanoparticules d'oxyde de cérium ont été ainsi synthétisées. Par la suite, une stratégie qui consiste à utiliser des chaînes de polymères hydrophiles, réactivables (macro-agent RAFT) et préalablement adsorbées à la surface des nanoparticules d'oxyde de cérium a été envisagée. Ces chaînes polymères comportant à la fois des fonctions carboxyliques et un groupe trithiocarbonate terminal sont capables de stabiliser la suspension colloïdale des nanoparticules et de réamorcer la polymérisation en mode semi-continu permettant ainsi l'encapsulation de l'oxyde de cérium. Une optimisation visant à utiliser un procédé batch a également été évaluée. Quelle que soit la stratégie employée, une attention toute particulière a été portée à la stabilité colloïdale du milieu ainsi qu'à la cinétique de la réaction. La morphologie des particules composites a été caractérisée par MET et cryo-MET et reliée aux conditions de modification de surface et de polymérisation

La photodégradation du bêta-estradiol (E2), un perturbateur chimique endocrinien, est réalisée en présence d'un complexe de fer, d'argiles et d'un oxyde de fer. L'impact d'un agent complexant du fer l'acide éthylénediamine-N,N'-disuccinique (EDDS) est aussi étudié. Après la détermination des propriétés physico-chimiques du complexe Fe(III)-EDDS, les rendements quantiques de formation des °OH et de dégradation de E2 ont été évalués en fonction de différents (pH, [O2], [Fe(III)-EDDS], [Fe(III)]. Pour la première fois, les rendements quantiques de production d'°OH ont été mesurés via la photolyse du complexe Fe(III)-EDDS en utlilisant l'acide téréphtalique comme sonde. Dans une seconde partie, les processus d'adsorption et de dégradation photocatalytique de E2 dans des suspensions de Montmorillonite KSF, de Montmorillonite naturel et de Goethite sont étudiés. L'adsorption de E2 sur les minéraux est rapide et faible. La vitesse de photodégradation de E2 est influencée par la concentration en minéraux et le pH. Le processus de dégradation photocatalytique de E2 dans ces systèmes a par la suite été étudié en présence d'EDDS. Dans les trois suspensions et en présence d'EDDS, la photodégradation de E2 augmente significativement dans la zone de pH neutre et basique (de 5,0 à 9,0). Au contraire, sans EDDS le pH optimal est limité aux pHs acides ( entre 3,0 et 4,0). Les cinétiques de dégradation de E2 suivent une loi de vitesse du modèle Langmuir-Hinshelwood pour les trois systèmes. Sur la base de nos résultats, il est possible de conclure que les systèmes EDDS-Fe(III)/minéraux sont photocatalytiquement efficaces pour l'élimination de polluants dans l'eau

Engineering complex systems and New Product Development (NPD) are major challenges for contemporary engineering design and must be studied at three levels of: Products, Processes and Organizations (PPO). The science of complexity indicates that complex systems share a common characteristic: they are robust yet fragile. Complex and large scale systems are robust in the face of many uncertainties and variations; however, they can collapse, when facing certain conditions. This is so since complex systems embody many subtle, intricate and nonlinear interactions. If formal modelling exercises with available computational approaches are not able to assist designers to arrive at accurate predictions, then how can we immunize our large scale and complex systems against sudden catastrophic collapse? This thesis is an investigation into complex product design. We tackle the issue first by introducing a template and/or design methodology for complex product design. This template is an integrated product design scheme which embodies and combines elements of both design theory and organization theory; in particular distributed (spatial and temporal) problem solving and adaptive team formation are brought together. This design methodology harnesses emergence and innovation through the incorporation of massive amount of numerical simulations which determines the problem structure as well as the solution space characteristics. Within the context of this design methodology three design methods based on measures of complexity are presented. Complexity measures generally reflect holistic structural characteristics of systems. At the levels of PPO, correspondingly, the Immunity Index (global modal robustness) as an objective function for solutions, the real complexity of decompositions, and the cognitive complexity of a design system are introduced These three measures are helpful in immunizing the complex PPO from chaos and catastrophic failure. In the end, a conceptual decision support system (DSS) for complex NPD based on the presented design template and the complexity measures is introduced. This support system (IMMUNE) is represented by a Multi Agent Blackboard System, and has the dual characteristic of the distributed problem solving environments and yet reflecting the centralized viewpoint to process monitoring. In other words IMMUNE advocates autonomous problem solving (design) agents that is the necessary attribute of innovative design organizations and/or innovation networks; and at the same time it promotes coherence in the design system that is usually seen in centralized systems.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Commercial fig production with popular European cultivars, Bourjasotte Noire, Col de Damme Noire and Noire de Caromb, is new to the Western Cape. Little research on fig production has been conducted in South Africa and producers are struggling to implement effective commercial practices. In order to establish practices that will maximise yield of quality fruit, the most productive one-year-old shoot lengths were identified in a phenological study. All shoot length categories evaluated in ‘Bourjasotte Noire’ (10 – 15 cm, 25 – 40 cm, 50 – 65 cm, 75+ cm) yielded fruit and will probably yield well the following season. In ‘Col de Damme Noire’, shoots longer than 60 cm seem to be suited to reproduction, yet they might produce a poor yield the following season. Shoots 10 – 20 cm long in ‘Noire de Caromb’ are productive relative to their length, while shoots 30 – 50 cm and 60 – 80 cm long are also fairly productive. Shoots longer than 100 cm produced suitable shoot lengths for yield the following season. Two experiments were conducted on ‘Bourjasotte Noire’ and ‘Col de Damme Noire’ to establish the type (Experiment 1, different intensity heading cuts) and timing (Experiment 2) of pruning cuts required to stimulate the growth of shoots of the same length as the shoots selected to be optimal for yield in the phenology study, and to reduce the expression of distal branching. In ‘Bourjasotte Noire’, removing one third of the total length of one-year-old shoots on 21 July by heading stimulated the development of more growth and longer current season shoots compared to other treatments, while reducing yield slightly. Heading back to three nodes in ‘Col de Damme Noire’ stimulated the growth of current season shoots of the optimal length established in the phenology study, while heading cuts on 30 June produced the longest average current season shoot length in ‘Col de Damme Noire’. To further address the effects of distal branching (acrotony), an experiment was conducted to establish whether rest breaking agents (RBA’s) in combination with tip-pruning can increase tree complexity by improving bud break, and whether increased complexity would increase yield in all three cultivars. A second experiment was conducted to evaluate the effects of timing RBA applications on bud break and harvest scheduling. Lift® increased the number of buds breaking in ‘Bourjasotte Noire’, while in ‘Noire de Caromb’ Dormex® and oil increased bud break. Tip-pruning increased the average shoot length in ‘Bourjasotte Noire’ and ‘Col de Damme Noire’, while causing a reduction in the amount of new growth in ‘Noire de Caromb’. Lift® applied 3 August and Dormex® applied 30 June shortened the number of days to 50% bud break in ‘Bourjasotte Noire’ and ‘Col de Damme Noire’. Both Lift® and Dormex® applied on 30 June decreased the number of days to 50% bud break and 50% harvest of the breba crop in ‘Noire de Caromb’. These treatments increased the number of fruit in both the breba and main crop of ‘Noire de Caromb’, but reduced fruit size. In conclusion, different approaches with regards to pruning needs to be followed for each cultivar to establish or maintain the optimal shoots for reproduction, while RBA’s can be used to force earlier, increased- bud break and harvest of breba fruit.
AFRIKAANSE OPSOMMING: Kommersiele verbouing van drie Europese vykultivars, Bourjasotte Noire, Col de Damme Noire en Noire de Caromb is nuut tot die Wes-Kaap. Baie min navorsing oor die verbouing van vye is al in Suid-Afrika gedoen, met die gevolg dat produsente sukkel om effektiewe kommersiële verbouingspraktyke te implementeer. ‘n Fenologiese studie van die drie kultivars is uitgevoer om vas te stel wat die mees produktiewe een-jaar-oue lootlengte is, met die doel om die opbrengs van kwaliteit vrugte te maksimeer. Al vier kategorieë wat ge-evalueer is in ‘Bourjasotte Noire’ (10 – 15 cm, 25 – 40 cm, 50 – 65 cm, 75+ cm) is gevind om geskik te wees vir huidige en volgende seisoen opbrengs. Lote langer as 60 cm is geskik vir opbrengs in ‘Col de Damme Noire’ in die huidige seisoen, maar mag in die volgende seisoen swak presteer a.g.v. die gebrekkige lengte van nuwe lote wat daarop ontwikkel. In ‘Noire de Caromb’ is gevind dat lote 10 – 20 cm lank baie produktief is relatief tot hul lengte en dat lote 20 – 50 cm en 60 – 80 cm lank ook relatief produktief is. Lote langer as 100 cm was minder produktief, maar het nuwe lote gelewer wat geskik is vir opbrengs die volgende seisoen. Twee snoei eskperimente is uitgevoer op ‘Bourjasotte Noire’ en ‘Col de Damme Noire’ om vas te stel wat die mees geskikte tipe snoeisnit (Eksperiment 1, verskillende dieptes van topsnitte) en tydstip om te snoei (Eksperiment 2) is met die doel om lote te produseer soortgelyk in lengte aan die wat in die fenologie studie uitgewys is as die produktiefste, en om moontlik die voorkoms van “kaalnekke” te verminder. In ‘Bourjasotte Noire’ is gevind dat die wegsnoei van ‘n derde van die loot op 21 Julie aanleiding gee tot meer groei, langer een-jaar-oue lote en ‘n effense afname in opbrengs. Geskikte lote langer as 60 cm kan in ‘Col de Damme Noire’ verkry word deur lote te top sodat net drie nodes oorbly. Die uitvoer van topsnitte op 30 Junie het langer gemiddelde lootlengtes tot gevolg gehad. Om die probleem van “kaalnekke” (apikale dominansie) verder aan te spreek, is ‘n eksperiment uitgevoer om vas te stel of rusbreekmiddels gekombineerd met tip-snoei gebruik kan word om kompleksiteit te vermeerder deur knopbreek te verhoog, en indien wel, of dit sal aanleiding gee tot verhoogde opbrengs in al drie kultivars. ‘n Tweede eksperiment met verskillende toedieningstye van rusbreekmiddels is uitgevoer om vas te stel of oeste geskeduleer kan word. Lift® het knopbreek verhoog in ‘Bourjasotte Noire’, terwyl Dormex® en olie knopbreek verhoog het in ‘Noire de Caromb’. Tip-snoei het die gemiddelde lootlengtes verhoog in ‘Bourjasotte Noire’ en ‘Col de Damme Noire’, terwyl dit groei verminder het in ‘Noire de Caromb’. Lift® toediening op 3 Augustus en Dormex® toediening op 30 Junie het die aanvang van 50% knopbreek vervroeg in ‘Boujasotte Noire’ en ‘Col de Damme Noire’. Beide Lift® en Dormex® toediening op 30 Junie het die bereiking van 50% knopbreek- en 50% oes vervroeg in ‘Noire de Caromb’. Hierdie behandeling het ook die aantal vrugte van die breba- en hoofoes vermeerder, maar vruggrootte verminder. Verskillende snoeibenaderings behoort dus gevolg te word om vir elke kultivar die regte lootlengtes te genereer of te onderhou, terwyl rusbreekmiddels gebruik kan word om knopbreek te vervroeg en verhoog, en om die breba oes te vervroeg.

Navigating complexity for change toward sustainability in large companies is best done using a systems perspective, a principled vision of success and a step-wise planning process, as espoused for instance by the Framework for Strategic Sustainable Development. Many large companies have a significant contribution to un-sustainability and stand to benefit from such a transition. However, the human factor of the undertaking is as of yet underdeveloped in extant literature. Seeking insights into experiences of sustainability change-agents in large companies, the authors conducted 20 semi-structured interviews with sustainability change- agents in large companies. Using a relational view as an analytical lens, they examined the dynamics of social interactions involving these change-agents and thereby gained a greater understanding of the place held by these individuals in the broader company system. The 11 relational categories that emerged permitted to draw links between structural, behavioural and personal facets of advancing sustainability in large companies and highlighted the human aspect of strategic planning as well as the strategic nature of building relationships, teams and coalitions. Overall, the authors believe that consideration by the change-agents of relational aspects may help foster commitment and collaboration in the transition toward sustainability

Nous étudions dans cette thèse les effets des institutions du marché du travail et notamment des allocations chômage, du salaire minimum et de l’impôt négatif dans une économie où les inégalités inter et intra-catégorielles sont dues à un biais technologique. Dans une première partie, nous considérons que ce biais qui prend la forme d'un accroissement de la complexité des emplois comme une variable endogène résultant du choix des entreprises et nous utilisons un modèle d'appariement dans lequel les travailleurs sont différenciés verticalement par leur niveau de qualification
We study in this thesis the effects of the institutions of the labour market in an economy where the inequalities within and between skills are due to a technological bias. In a first part, we consider that this bias which takes the form of an increase in the complexity of jobs as an endogenous variable resulting from the choice of the firms and we use a matching model in which the workers are differentiated vertically by their level of qualification. In the second part, we re-study the interactions between the public policies and the technological choices of the firms within a different framework. Indeed, contrary to the first part, endogenous technological bias is considered here as an increased specialization of jobs in a matching model with an horizontal differentiation of the agents

A moeda fiduciária permitiu o surgimento da política monetária e esta vêm ganhando cada vez mais destaque entre as ferramentas e políticas econômicas. Porém, não existe consenso no meio acadêmico sobre a influência da política monetária à economia, alguns acreditam que ela apenas resulta em variações nominais e outros que ela pode afetar fatores reais da economia. Diversas pesquisas feitas comprovam, ao menos no curto prazo, a existência do chamado ajuste nominal incompleto, onde choques monetários afetam os valores reais dos agregados econômicos. Porém, quais são os custos e externalidades que advem desta rigidez de preços? Tentando oferecer novas respostas a esta questão, remontamos o reconhecido modelo de Ball e Romer (1989) sob a perspectiva da complexidade e dos modelos computacionais baseados em agentes. Os resultados encontrados nesta nova perspectiva foram muito diferentes dos resultados encontrados no modelo original, com a possibilidades de vantagens e externalidades positivas da rigidez, inserção de problemas distribuitivos, valores mais significativos de custos privados e sociais vinculados à rigidez, tudo isso devido à heterogeneidade presente no modelo computacional.
The fiduciary money allowed the emergence of monetary policy, that are gaining more prominence among the economic tools and policies. However, there is no consensus in the academy about the influence of the monetary policy in the economy, some believe it results in only nominal changes, others that it can affect real factors of the economy. Several researches show, at least in the short term, the existence of so-called incomplete nominal adjustment, where monetary shocks affect the real values of economic aggregates. But which are the costs and externalities that come from this price rigidity? Trying to provide new answers to this question, we reassembled the recognized model of Ball and Romer (1989) from the perspective of complexity and computational agent-based models. The new results are very different from the findings of the original model, with the potential benefits and positive externalities from rigidity, insertion of distributive problems, more significant amounts of private and social costs related to rigidity, all because of the heterogeneity inserted by the computational model.

The aim of this study is to test the audit fee determinants for companies listed on Nasdaq OMX Stockholm Stock Exchange and to examine whether the audit fee determinants diverge for ownership structures. By testing the audit fee determinants in a Swedish setting the study contributes to the research body in two ways; by testing a previously sparsely researched setting and examining the monitoring need for different ownership structures. The results indicate that audit fees are explained to a large extent by accounting complexities, business complexities and assurance.  The results also suggest that ownership structure does not have a large effect on the monitoring need.  Altogether the results provide further evidence on audit fee determinants whilst adding initial insight into the area of audit fee determinants for ownership structures.