This research is based on Gordon-Schaefer model, using the statistic data from the FAO between 1983 to 2007 to conduct an assessment on Argentine shortfin squid, Illex argentinus. First of all, calculate and compare the equilibrium levels of open access fishery and present value maximization fishery, then evaluate the stock size of Illex argentinus and compare the equilibrium levels of two models with the statistic readings, the result shows that Illex argentinus has no sign of depletion, but it has not yet reached the best status for development. By using sensitivity analysis,we understand the changes on the effort and stock effected by varying different parameters. Finally, by simulating the stock size of open access fishery and present value maximization fishery, we find that unrestricted developing can end up the resources, but Illex argentinus will receive sustainable development, if it can be effectively managed.

In industrial wastewater, there are usually many kinds of organics and heavy metals and can cause damage on human health and environment without well treatment. Printed Circuit Board (PCB) industrial wastewater is a typical example due to the complicated manufacture processes and the use of specific chemicals. In this study, the PCB industrial wastewater is collected and then treated by the combination of Fenton method and Ferrite Process (or called Fenton-Ferrite Process, FFP). Moreover, the recycling possibility of sludge generated from FFP is also studied. Through this study, the treatment procedure of wastewater containing organics heavy metals is established and the direction of sludge reuse is also provided. To realize the characteristic of PCB industrial wastewater, the wastewater from some PCB factory in southern Taiwan was firstly collected and analyzed to identify the pollution concentrations and then treated by FFP. The experimental results showed that the optimum parameters of Fenton method in FFP were pH = 2, [Fe2+]= 500 mg/L, [H2O2]= 3000 mg/L, reaction time= 60 min and batch dosing, and the residual COD and TOC were 84.9 mg/L and 58.3 mg/L under the COD regulation standard 120 mg/L. Meanwhile, the proper conditions of Ferrite Process in FFP were pH= 10, reaction temperature= 80¢J, reaction time= 40 min, aeration rate= 3 L/min/L wastewater, Fe/Cu molar ratio= 10 and three-stage reaction. Under that circumstance, the residual [Cu2+] in wastewater was 0.18 mg/L and the Toxicity Characteristic Leaching Procedure (TCLP) test of sludge from FFP was 4.58 far below the effluent standard 3 mg/L and TCLP standard 15 mg/L. The properties of sludge were further investigated by X-Ray Diffractometer (XRD), Scanning Electron Microscope (SEM) and Superconducting Quantum Interference Device (SQUID). The pattern of XRD indicated that the major structures were Fe3O4 and CuFe2O4; the figure of SEM showed that the surface of sludge was composed of many round particles and the distribution of particle size was from 50 nm-100 nm; the magnetic property analyzed by SQUID showed that the saturation moment was 62.85 emu/g. In the research of sludge applied in catalytic incineration, the o-xylene conversion was 97 % by sludge but only 31 % by quartz sand at 400 ¢J. Moreover, in the 72 hr-decay test of catalyst, the results clearly indicated that the performance did not obviously decline and there were no any byproducts but CO2. Therefore, the investigation revealed that the sludge had great potential in catalytic reaction. The catalytic performance of various ferrospinels generated from different manufactured conditions was also studied. Through the screening of catalysts, the order of various ferrospinels activity was Cu-ferrite > Mn-ferrite > ferrite ¡Ü Zn-ferrite and the most effective Cu-ferrite was manufactured at pH= 9 and T= 90 ¢J. After 72 hr test, the decay of catalyst was not also found. In the examination of Cu-ferrite physical property, the XRD pattern showed that the structure was CuFe2O4; the figure of SEM illustrated that there was no difference between the surface of fresh and used catalyst; the magnetic property measured by SQUID showed that the saturation moment was 30.89 emu/g.

Le sujet de thèse concerne l'étude de réseaux réguliers de nanofils magnétiques auto-organisés. Deux approches ont été utilisées pour la fabrication : 1) Préparation de réseaux planaires de nanofils alternés (Fe,Ag) sur Mo(110). Ce mode de croissance est attribué au caractère non miscible des deux métaux et à un mécanisme modulé de relaxation des contraintes d'épitaxie. 2) Préparation de nanofils de Fer sur une surface déjà structurée en tranchées périodiques. Ces tranchées se forment spontanément lors de la croissance homoépitaxiale d'un métal cc de W(110) (ou Mo) à température modérée. La période de la structuration unidimensionnelle est contrôlable par la température de dépôt. La deuxième étape consiste à déposer le Fer sur ce gabarit. Pour une température définie, Fe croît au fond des tranchées pour former des fils régulièrement espacés. Des réseaux de fils en trois dimensions ont aussi été fabriqués. Du point de vue magnétique, les deux systèmes présentent une forte anisotropie uniaxiale avec l'axe de facile aimantation planaire, le long des fils. A température ambiante les systèmes sont superparamagnétiques. L'évolution de la coercitivité en fonction de la température s'interprète selon un processus de renversement d'aimantation thermiquement activé par nucléation/propagation. Le renversement met en jeu plusieurs fils couplés pour le premier système et s'effectue au sein des fils individuels dans le deuxième.

Ce travail porte sur l'étude de l'anisotropie d'échange dans des agrégats de cobalt nanométriques (1-6 nm de diamètre) fabriqués par une source à pulvérisation magnétron et condensation en phase vapeur. Des mesures de microscopie électronique en transmission à haute résolution et de diffraction de rayons X montrent que les agrégats sont icosaédriques. Cette structure, confirmée par des calculs utilisant un modèle atomistique, est déformée de façon non homogène. L'anisotropie magnétique de ces nano-objets, calculée à l'aide du modèle de paires de Néel, oscille en fonction du remplissage des couches successives de l'icosaèdre. <br />Le couplage d'échange F/AF est d'abord étudiée sur une assemblée d'agrégats de cobalt de différentes densités, couplés à un matériau AF (CoO ou NiO) sous forme de couche mince ou de coquille. L'effet maximum est obtenu lorsque la couche AF est continue, soit par contact direct entre agrégats oxydés, soit via une couche mince AF.<br />Enfin, des mesures utilisant la technique micro-SQUID ont pour la première fois permis de mettre en évidence le phénomène de couplage d'échange sur un agrégat de cobalt unique couplé à un AF. Les agrégats de cobalt oxydés ou non sont déposés sur une couche mince de CoO puis recouverts d'une couche de niobium supraconducteur dans laquelle sont gravées les boucles micro-SQUIDs. Ces mesures montrent que le couplage d'échange est présent même si le système F/AF n'est pas refroidi sous un champ magnétique. Elles mettent aussi en évidence que chaque agrégat possède sa propre anisotropie d'échange, dont la direction et le sens sont fixés par l'anisotropie locale de l'AF.

Magnetic force microscopy studies in varying temperature and applied external magnetic field of magnetic thin films of LaCoO₃ under strain and single crystal UMn₂Ge₂ have been performed. In the case of LaCoO₃ thin films the aim is an understanding of the response of the magnetic microstructure to different signs and degrees of strain and a further attempt to distinguish the effect of defects from strain-induced effects. In UMn₂Ge₂ the magnetic microstructure is imaged for the first time and signatures of a possible phase transition at 150 K and crystalline anisotropy are explored. The first portion of this dissertation focuses on the synthesis methods used to produce the samples investigated and the critical role of synthesis in producing high-quality samples. This is followed by a discussion of characterization techniques used to obtain local and global magnetic and structural characteristics, with particular emphasis on magnetic force microscopy including noise characteristics and a discussion of achieving a high force gradient sensitivity by optimizing the fiber-optic interferometer used for cantilever deflection detection. Design elements and features of the multi-mode variable-temperature atomic force microscope used to obtain magnetic force microscopy images are presented and results for LaCoO₃ and UMn₂Ge₂ are discussed. / text

The magnetic properties of transition metal compounds have been studied using SQUID-magnetometry, magnetic force microscopy and Lorentz transmission electron microscopy. New magnetic materials have been found and their magnetic properties have been determined. How the magnetic properties of a material can be changed through e.g. chemical substitution of magnetic and nonmagnetic atoms and shape and size effects have also been studied. Three different sets of samples have been investigated: three new Mn-compounds, two substitution series of layered magnetic structures and ferromagnetic micronsized thin film elements. The three Mn-compounds, Mn3IrSi, IrMnSi and Mn8Pd15Si7, show different magnetic ordering. Mn3IrSi orders 'antiferromagnetically' at 210 K. IrMnSi forms a double cycloidal spin spiral below 460 K. Mn8Pd15Si7 only shows short-range magnetic ordering. Substituting Se with S in TlCo2Se2-xSx changes the magnetic order from a spin spiral to a colinear ferromagnet for a composition of x=1.75. An intermediate region exists where the compound is neither a pure ferromagnet, nor purely a spin spiral, as evidenced by the magnetization versus field measurements for the x=1.3 and 1.5 samples. This is also seen in the temperature dependent susceptibility measurements. For the TlCu2-xFexSe2 compounds it was found that the ordering temperature and saturation magnetic moment per Fe-atom changed with composition x. Ferromagnetic micronsized thin film elements in permalloy, Fe20Ni80, and epitaxial Fe/Co multilayers were studied. For the Fe/Co multilayer thin film elements it was found that it is possible to change the magnetization reversal process, by aligning the easy shape anisotropy axis with either the easy or the hard magnetocrystalline anisotropy axis. In the permalloy elements the effect of inter-elemental distance was found to determine the interval of fields where multidomain states were stable, so that for shorter inter-elemental distances multidomain states were stable for a shorter interval of fields. The domain structure of permalloy elements in rotating magnetic fields was also studied. Higher applied fields led to a broader interval of angles in which saturated states were stable.

This thesis will present research that studies the role of disorder, geometric frustration and the long range dipolar interaction on the collective behaviour of several insulating, rare earth magnets. Experiments were performed at low temperatures to measure the specific heat and magnetic susceptibility of several materials. Susceptibility was measured with a SQUID magnetometer that has been designed and constructed primarily for the study of slow dynamics in glassy systems. Specifically, this thesis will discuss three distinct topics. The first is the series of materials LiHo(x)Y(1-x)F(4), which are manifestations of the dilute, dipolar coupled Ising model. The low-x portion of the phase diagram has become a rather contentious issue in recent years with both theoretical and experimental groups disagreeing on the existence of a spin glass freezing transition and one experimental group arguing for the existence of an exotic "antiglass'' or spin liquid state resulting from quantum entanglement at x=0.045. We present specific heat and dynamical susceptibility measurements on four stoichiometries in this series: x = 0.018, 0.045, 0.080 and 0.012. No evidence of an unusual antiglass state is observed. Instead, our results show evidence, at all dilution levels studied, of a spin glass freezing transition. Interpretation of experimental data is found to be complicated by the anomalously slow dynamics in these materials. The relaxation time scales are found to increase as the concentration of Ho(3+) ions is reduced, an effect which can be attributed to single-ion physics and the importance of the nuclear hyperfine coupling in this system. A second set of materials studied here is a series of several Gd garnet materials, the most famous of which is Gd(3)Ga(5)O(12) (GGG), a material previously argued to be a disorder-free spin glass. Our specific heat experiments reproduce previous experiments on GGG and show that the homologous Gd garnets Gd(3)Te(2)Li(3)O(12) and Ga(3)Al(5)O(12) do not share the same glassy physics but exhibit sharp ordering features. By experimenting with the introduction of random site dilution, it is concluded that a 1-2% off-stoichiometry inherent in GGG is likely a special kind of disorder that is particularly effective in inducing random frustration and the formation of a spin glass. Finally, specific heat measurements on the pyrochlore antiferromagnet Gd(2)Sn(2)O(7) (GSO) are presented. While GSO has generally been found to be a well behaved and well understood model magnet, with long range order developing at around 1 K, like many other geometrically frustrated magnets, it has been discovered to possess persistent spin dynamics down to very low temperatures as measured by μSR and Mössbauer spectroscopy. Measurement of the low temperature limit of the specific heat when compared with linear spin-wave theory, however, presents a consistent picture of gapped magnon excitations that freeze out at low temperatures and make the existence of the proposed dynamic ground state unlikely.

Pendant la première année le microscope à microSQUID était mis en fonctionnement. On a avancé sur le plan cryogenique (dilution) et électronique (programmation de boucles de régulation et d'une détection synchrone). Les composants étaient testés à température ambiante et on est en train de tout tester à basse température. Une méthode était conçu pour déterminer la longueur de pénétration du champ magnétique dans un supraconducteur avec les données qui pourront être fait avec notre microscope. Ceci va être utilisé pour l'échantillon PrOs4Sb12. Il s'agit de trancher le débat sur la nature multibande de la supraconductivité dans ce composé. En deuxième année le developpement a continué, en particulière le microscope était mis à froid. Des différents problèmes due aux basses températures (mouvement de moteur, thermalisation, câblage) ont été resolues. Ensuite on a avancé sur le plan informatique, notamment le contrôle de differents composants. Pendant le deuxième année quelques images magnétique ont été faites, validant le concept. En troisième année on a commence a mésurer des domaines magnetiques d'un supraconducteur ferromagnetique (UCoGe) en Avril - Aout. On a obtenu des resultats tres interessants. Le même dispositif sera ainsi opérationnel pour l'imagerie de domaines dans des bolomètres supraconducteurs.

Cette thèse étudie l'application de le microscopie de champs magnétiques à l'analyse de défaillance des composants électroniques.

Fabrication of nanoscale Josephson junctions and Superconducting Quantum Interference Devices (SQUID) is very promising but challenging topic in the superconducting electronics and device technology. In order to achieve best sensitivity of SQUIDs and to reproduce them easily with a straightforward method, new fabrication techniques for realization of nanoSQUIDs needs to be investigated. This study concentrates on investigation of new fabrication methodology for manufacturing nanoSQUIDs with High Temperature Bi-Crystal Grain Boundary Josephson Junctions fabricated onto SrTiO3 bi-crystal substrates using YBa2Cu3O7-δ (YBCO) thin-films. In this process nanoscale patterning of YBCO was realized by using electron beam patterning and physical dry etching of YBCO thin films on STO substrates. YBCO thin films were deposited using RF magnetron sputtering technique in the mixture of Ar and O2 gases and followed by annealing at high temperatures in O2 atmosphere. Structural characterization of YBCO thin films was done by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Superconducting properties of thin films was characterized by AC magnetic susceptibility measurements. Nanoscale structures on YBCO thin films were fabricated by one E-Beam Lithography (EBL) step followed by Reactive Ion Etching (RIE) and physical dry etching. First SiO2 thin film were deposited on YBCO by RF magnetron sputtering and it was patterned by EBL using Polystyrene (PS) as resist material and RIE. Then SiO2 was used as an etch mask for physical dry etching of YBCO and nanoscale structures on YBCO were formed.