The high magnetoresistance is one of the most important properties that led the colossal magnetoresistance (CMR) materials been kept attention, however, because of the low phase transition temperature (Tp) and Curie temperature (TC) limits the application of the materials. The Tp could be influenced by many factors, as for the R1-xAxMnO3(R=rare earth element, A=alkaline metal, 0¡Õx¡Õ1) CMR materials, the selections of elements on R, A, and the ratio of x would make the difference. Besides these factors, when the film was grown on a substrate, the strain effect initiated at the substrate/film interface plays an essential role on the change of Tp and other physic properties. In other hand, the Sr element, existed in the SrTiO3(100) substrate, may also diffuse into the thin films during growth and alter the composition of the film and change its physic properties. In this thesis, we mainly focused on the modifying of the surface of substrates to prevent the diffusion problems. A wet chemical method was applied to modify the top layer of substrates such that the surface layer of the substrate is consisted of Ti-O layer only. By varying the high temperature annealing and etching processes, an optima processing condition was established.

La synthèse de fréquences est une fonction largement utilisée dans les émetteur-récepteurs radios. En général, la fonction synthèse de fréquence est réalisée à l’aide d’une boucle à verrouillage de phase utilisant des diviseurs de fréquence numériques. Cette thèse présente un nouveau type de diviseur de fréquence faisant appel à des mémoires D et son application à la synthèse de fréquences. Ce nouveau diviseur permet de repousser les limites des diviseurs numériques classiques à bascules D, en matière de fréquence maximale de fonctionnement et de consommation, tout en conservant leur souplesse d’utilisation. La première partie de cette thèse présente les techniques usuelles de réalisation des synthèses de fréquence et des diviseurs de fréquences, ainsi que le nouveau diviseur SRO à base de mémoires D, sujet de ces travaux. Une étude détaillée de ce diviseur est réalisée avec un premier modèle utilisant une approche numérique, puis un second plus réaliste faisant appel à une modélisation de type analogique. Cette étude démontre que ce nouveau diviseur SRO est capable de fonctionner à une fréquence plus élevée ou avec une consommation moindre, tout en réalisant les mêmes facteurs de division, que les diviseurs classiques à bascules D. La dernière partie de cette thèse présente plusieurs implémentations en technologies CMOS et BiCMOS de ST Microelectronics du diviseur SRO. En particulier son implémentation dans deux synthétiseurs de fréquences fractionnaires à 24 GHz montre son intérêt de part la réduction significative de consommation obtenue, tout en conservant une structure simple utilisant une surface de silicium réduite / Frequency synthesis is almost used in all RF transceivers, where this function is usually achieved by using phase-locked-loop circuits. Most often, the phase-locked-loop includes digital frequency dividers in the feedback that present high power dissipation and low maximum frequency at gigahertz frequencies. This thesis presents a versatile new D latch-based divider that improves these issues and its application to frequency synthesis. The first part presents several frequency synthesis techniques and theirs main characteristics. Then is described various classical frequency dividers and the proposed new D latch-based SRO divider. A detailed study of the SRO divider is presented with two approaches, the digital one and the analogue one. This study demonstrates the benefit of the SRO divider in terms of power dissipation and speed compared with the widely used D flip-flop based dividers. The last part presents several implementations of the SRO divider in CMOS and BiCMOS processes of ST Microelectronics. Particularly, the SRO divider was implemented in two 24 GHz fractional synthesizers, where it demonstrates its interest for reduction of power dissipation while using small silicon area.

Neste trabalho estudou-se a influência da adição do SrO no comportamento varistor do TiO2. As concentrações utilizadas de SrO foram: 0,50, 1,00, 1,50 e 2,00 mol %. O processamento empregado foi o método convencional de mistura de óxidos, onde os reagentes foram submetidos ao moinho de bolas para homogeneização, utilizando PVA como agente plastificante. A sinterização, em forno convencional ocorreu nas temperaturas de 1200, 1300 e 1400oC durante 1 h com taxa de aquecimento e resfriamento de 5oC=min. Pelas imagens de MEV foi possível observar a evolução microestrutural das amostras com o aumento da temperatura de sinterização. Relacionando análises de MEV, densidade e dilatometria, foi possível se chegar a uma temperatura de sinterização considerada ideal para aplicação em sistemas varistores de 1400oC. Nas micrografias das amostras sinterizadas a 1400oC foi possível observar uma microestrutura com características morfológicas adequadas para varistores. Juntamente com a análise de EDS, acoplada ao MEV e mapeamento de raios X, identificou-se a presença de Sr na região do contorno de grão das amostras contendo 0,50 e 1,00 mol %, sendo que com a concentração de 1,00 mol % o Sr mostrou-se distribuído de maneira mais uniforme na região do contorno de grão. Para concentrações superiores a 1,00 mol %, ocorre a precipitação do Sr além do contorno de grão, a análise de EDS e mapeamento de raios X aponta além do Sr o O, indicando a formação de SrTiO3. As medidas elétricas em corrente contínua realizadas em temperatura ambiente apontam um melhor coeficiente não linear de 5,50 para composição contendo 1,00 mol % de SrO. Para o modelamento da barreira de potencial tipo Schottky foram realizadas medidas em CC (25 - 200oC), onde encontrou-se uma melhor relação altura/largura de barreira para a composição contendo 1,00 mol % de SrO, sendo proposto um modelo de barreira de potencial. Com as medidas em corrente alternada, foi possível identificar e mensurar a contribuição do grão e do contorno de grão. Também foi realizado tratamento em atmosfera oxidante, onde foi possível obter uma considerável melhora nas propriedades varistoras, a = 8,54, com a adsorção de O2 no contorno de grão. / In this work the influence of SrO in Varistor behavior of TiO2 is assessed. The used concentrations were SrO: 0.50, 1.00, 1.50 and 2.00 mol %. The applied process used conventional method of mixing oxides, where the reactants were subjected to a ball mill for homogenization using PVA as a plasticizer. The sintering was performed in conventional oven temperatures at the temperatures of 1200, 1300 and 1400oC for 1 h with heating and cooling rate of 5oC=min. From the SEM images, it is possible to identify the microstructural evolution of samples while the sintering temperature increases. Using SEM analysis, density and dilatometry, it is possible to obtain the optimal sintering temperature applied for varistors of 1400oC. In micrographs of the sintered samples at 1400oC it is identified a microstructure with suitable morphological characteristics for varistors. By the EDS analysis coupled to SEM X-ray mapping, is identified the presence of Sr in the grain boundary region samples containing 0.50 and 1.00 mol %, and the concentration of 1.00 mol % Sr appears to be more evenly distributed in the grain boundary region For concentrations higher than 1.00 mol %, the precipitation of Sr occurs beyond the grain boundaries, and the analysis of EDS X-ray mapping show points beyond Sr and O, indicating the formation of SrTiO3. The electrical measurements in DC held at room temperature showed an optical non linear coefficient of 5.50 for the composition containing 1.00 mol % of SrO. For the potential barrier modeling type Schottky, measures were carried out in DC (25 - 200oC) where a better height/width barrier was found with the composition containing 1.00 mol % of SrO, being proposed a potential barrier model. In alternating current measurements, it was possible to identify and evaluate the grain and grain boundary contribution. It was also performed treatment in an oxidizing atmosphere, where it was possible to obtain a considerable improvement in the varistor properties, a = 8.54, with adsorption of O2 in the grain boundary.

According to the National Association of School Resource Officers (2009), every state in the nation employs school resource officers. The trend, which began in 1991, was initially funded by federal monies. Since that time, school resource officers have remained in schools, gaining popularity as a proactive strategy in fighting against school violence. The purpose of the study was to examine students' and teachers' perceptions regarding school resource officers' performance related to the 3 dimensions of their responsibilities: maintaining a safe environment, enforcing the law, and teaching. Data were gathered from 104 teachers and 272 students from a middle school and a high school, totaling 376 participants. An analysis of data was based on 6 research questions and information gathered from participant surveys. A t test for independent samples was then conducted to evaluate the mean differences for the 3 dimensions measured in the survey. The following grouping variables were used in the comparisons for each dimension: students and teachers, male and female students, male and female teachers, teachers with varied years of experience, middle and high school students, and middle and high school teachers. A significance difference was found between middle school students and high school students regarding each dimension, suggesting that middle school students observed school resource officers actively performing each role to a higher degree than did high school students. There was also a significant difference between teachers and students regarding the role of maintaining a safe environment and enforcing the law, suggesting that teachers observed school resource officers more active in these roles than in the role of counseling. A significant difference was also found between high school teachers and middle school teachers regarding the role of enforcing the law. High school teachers observed enforcement of law more than middle school teachers. This study suggests that school resource officers' roles need to be clearly defined for teachers and students. Students need to know they can report crime, have knowledge that they are being monitored, and know they have resources available other than administrators and teachers.

Neste trabalho estudou-se a influência da adição do SrO no comportamento varistor do TiO2. As concentrações utilizadas de SrO foram: 0,50, 1,00, 1,50 e 2,00 mol %. O processamento empregado foi o método convencional de mistura de óxidos, onde os reagentes foram submetidos ao moinho de bolas para homogeneização, utilizando PVA como agente plastificante. A sinterização, em forno convencional ocorreu nas temperaturas de 1200, 1300 e 1400oC durante 1 h com taxa de aquecimento e resfriamento de 5oC=min. Pelas imagens de MEV foi possível observar a evolução microestrutural das amostras com o aumento da temperatura de sinterização. Relacionando análises de MEV, densidade e dilatometria, foi possível se chegar a uma temperatura de sinterização considerada ideal para aplicação em sistemas varistores de 1400oC. Nas micrografias das amostras sinterizadas a 1400oC foi possível observar uma microestrutura com características morfológicas adequadas para varistores. Juntamente com a análise de EDS, acoplada ao MEV e mapeamento de raios X, identificou-se a presença de Sr na região do contorno de grão das amostras contendo 0,50 e 1,00 mol %, sendo que com a concentração de 1,00 mol % o Sr mostrou-se distribuído de maneira mais uniforme na região do contorno de grão. Para concentrações superiores a 1,00 mol %, ocorre a precipitação do Sr além do contorno de grão, a análise de EDS e mapeamento de raios X aponta além do Sr o O, indicando a formação de SrTiO3. As medidas elétricas em corrente contínua realizadas em temperatura ambiente apontam um melhor coeficiente não linear de 5,50 para composição contendo 1,00 mol % de SrO. Para o modelamento da barreira de potencial tipo Schottky foram realizadas medidas em CC (25 - 200oC), onde encontrou-se uma melhor relação altura/largura de barreira para a composição contendo 1,00 mol % de SrO, sendo proposto um modelo de barreira de potencial. Com as medidas em corrente alternada, foi possível identificar e mensurar a contribuição do grão e do contorno de grão. Também foi realizado tratamento em atmosfera oxidante, onde foi possível obter uma considerável melhora nas propriedades varistoras, a = 8,54, com a adsorção de O2 no contorno de grão. / In this work the influence of SrO in Varistor behavior of TiO2 is assessed. The used concentrations were SrO: 0.50, 1.00, 1.50 and 2.00 mol %. The applied process used conventional method of mixing oxides, where the reactants were subjected to a ball mill for homogenization using PVA as a plasticizer. The sintering was performed in conventional oven temperatures at the temperatures of 1200, 1300 and 1400oC for 1 h with heating and cooling rate of 5oC=min. From the SEM images, it is possible to identify the microstructural evolution of samples while the sintering temperature increases. Using SEM analysis, density and dilatometry, it is possible to obtain the optimal sintering temperature applied for varistors of 1400oC. In micrographs of the sintered samples at 1400oC it is identified a microstructure with suitable morphological characteristics for varistors. By the EDS analysis coupled to SEM X-ray mapping, is identified the presence of Sr in the grain boundary region samples containing 0.50 and 1.00 mol %, and the concentration of 1.00 mol % Sr appears to be more evenly distributed in the grain boundary region For concentrations higher than 1.00 mol %, the precipitation of Sr occurs beyond the grain boundaries, and the analysis of EDS X-ray mapping show points beyond Sr and O, indicating the formation of SrTiO3. The electrical measurements in DC held at room temperature showed an optical non linear coefficient of 5.50 for the composition containing 1.00 mol % of SrO. For the potential barrier modeling type Schottky, measures were carried out in DC (25 - 200oC) where a better height/width barrier was found with the composition containing 1.00 mol % of SrO, being proposed a potential barrier model. In alternating current measurements, it was possible to identify and evaluate the grain and grain boundary contribution. It was also performed treatment in an oxidizing atmosphere, where it was possible to obtain a considerable improvement in the varistor properties, a = 8.54, with adsorption of O2 in the grain boundary.

Neste trabalho estudou-se a influência da adição do SrO no comportamento varistor do TiO2. As concentrações utilizadas de SrO foram: 0,50, 1,00, 1,50 e 2,00 mol %. O processamento empregado foi o método convencional de mistura de óxidos, onde os reagentes foram submetidos ao moinho de bolas para homogeneização, utilizando PVA como agente plastificante. A sinterização, em forno convencional ocorreu nas temperaturas de 1200, 1300 e 1400oC durante 1 h com taxa de aquecimento e resfriamento de 5oC=min. Pelas imagens de MEV foi possível observar a evolução microestrutural das amostras com o aumento da temperatura de sinterização. Relacionando análises de MEV, densidade e dilatometria, foi possível se chegar a uma temperatura de sinterização considerada ideal para aplicação em sistemas varistores de 1400oC. Nas micrografias das amostras sinterizadas a 1400oC foi possível observar uma microestrutura com características morfológicas adequadas para varistores. Juntamente com a análise de EDS, acoplada ao MEV e mapeamento de raios X, identificou-se a presença de Sr na região do contorno de grão das amostras contendo 0,50 e 1,00 mol %, sendo que com a concentração de 1,00 mol % o Sr mostrou-se distribuído de maneira mais uniforme na região do contorno de grão. Para concentrações superiores a 1,00 mol %, ocorre a precipitação do Sr além do contorno de grão, a análise de EDS e mapeamento de raios X aponta além do Sr o O, indicando a formação de SrTiO3. As medidas elétricas em corrente contínua realizadas em temperatura ambiente apontam um melhor coeficiente não linear de 5,50 para composição contendo 1,00 mol % de SrO. Para o modelamento da barreira de potencial tipo Schottky foram realizadas medidas em CC (25 - 200oC), onde encontrou-se uma melhor relação altura/largura de barreira para a composição contendo 1,00 mol % de SrO, sendo proposto um modelo de barreira de potencial. Com as medidas em corrente alternada, foi possível identificar e mensurar a contribuição do grão e do contorno de grão. Também foi realizado tratamento em atmosfera oxidante, onde foi possível obter uma considerável melhora nas propriedades varistoras, a = 8,54, com a adsorção de O2 no contorno de grão. / In this work the influence of SrO in Varistor behavior of TiO2 is assessed. The used concentrations were SrO: 0.50, 1.00, 1.50 and 2.00 mol %. The applied process used conventional method of mixing oxides, where the reactants were subjected to a ball mill for homogenization using PVA as a plasticizer. The sintering was performed in conventional oven temperatures at the temperatures of 1200, 1300 and 1400oC for 1 h with heating and cooling rate of 5oC=min. From the SEM images, it is possible to identify the microstructural evolution of samples while the sintering temperature increases. Using SEM analysis, density and dilatometry, it is possible to obtain the optimal sintering temperature applied for varistors of 1400oC. In micrographs of the sintered samples at 1400oC it is identified a microstructure with suitable morphological characteristics for varistors. By the EDS analysis coupled to SEM X-ray mapping, is identified the presence of Sr in the grain boundary region samples containing 0.50 and 1.00 mol %, and the concentration of 1.00 mol % Sr appears to be more evenly distributed in the grain boundary region For concentrations higher than 1.00 mol %, the precipitation of Sr occurs beyond the grain boundaries, and the analysis of EDS X-ray mapping show points beyond Sr and O, indicating the formation of SrTiO3. The electrical measurements in DC held at room temperature showed an optical non linear coefficient of 5.50 for the composition containing 1.00 mol % of SrO. For the potential barrier modeling type Schottky, measures were carried out in DC (25 - 200oC) where a better height/width barrier was found with the composition containing 1.00 mol % of SrO, being proposed a potential barrier model. In alternating current measurements, it was possible to identify and evaluate the grain and grain boundary contribution. It was also performed treatment in an oxidizing atmosphere, where it was possible to obtain a considerable improvement in the varistor properties, a = 8.54, with adsorption of O2 in the grain boundary.

No description available.

We imitated the sandwich structure of TMR(Tunneling Magnetoresistance) to apply to CMR(Colossal Magnetoresistance) material . We choose one of the Colossal Magnetoresistance material La0.67Sr0.33MnO3(113) to be the Ferromagnetic(FM) layers as top and bottom layer in sandwich structure and use La0.67Sr0.33MnO3 ¡P SrO(214) to be middle layer which have Antiferromagnetic(AFM) property to form FM-AFM-FM structure. The FM and AFM layer can match their lattice in interface joint. What its purpose is to use this structure to enhance SPT (Spin Polarization Tunneling) effect and let spintronics can periodical spin-flip in supper lattice structure of antiferromagnetic. Upon this compose we try to show increase the LFMR (Low Field Magnetoresistance) by use CMR. The experiment result shows maybe the film structure damage occurred in our made TMR tunneling device process (ex. Ion etching process), so we should improvement the process to get the exactly experiment data. Additional, due to the alignment of the moment of La0.67Sr0.33MnO3 is unstable, the back and forth hysteresis loop can¡¦t overlap, So that afterwards we can use the more stable material La0.67Ca0.33MnO3 which have more stable moment.

Background: Disabling hearing loss is a global burden. This burden is worsened by the emergence of multi-drug resistant tuberculosis (MDR-TB). Some of the medications used to treat MDR-TB are damaging to the cochlea and auditory nerve (ototoxic) and can lead to permanent hearing loss and/or balance disorders. Ototoxicity monitoring aims to reduce this burden by preventing or minimising the damage caused by ototoxic treatment as it can progress and worsen speech perception difficulties. However, the proposed test battery for ototoxicity monitoring is lengthy and demands active participation which is not ideal for ill patients (such as those on MDR-TB treatment). The Sensitive Range of Ototoxicity (SRO) technique is recommended to shorten the test time. The SRO consists of seven consecutive relatively high frequencies determined from the highest frequency the participant responded to. The SRO technique is time efficient. Although the SRO technique provides the prospect of a shortened test battery, there is still a global lack of audiologists. Automated audiometry is a vital application for testing especially when audiologists are not available to physically do the test. Automated audiometry has been previously validated. Clinically, automated audiometry is objective and allows for standardisation. Even though automated audiometry helps improve access to monitoring more patients, patient preference is an important factor when using automated audiometry to ensure patient-centred care is not compromised. Aims and Objectives: This study aimed to investigate the specificity and sensitivity of the SRO technique with automated audiometry compared to the gold standard (manual audiometry). This comparison was made by firstly, determining the testing time efficiency and the correlation of thresholds obtained with the different test methods and, secondly, testing the diagnostic value of automated audiometry using the SRO technique. The incidence of an ototoxicity-induced hearing loss was described by determining the time interval between starting ototoxic MDR-TB treatment and the onset of a significant threshold shift (STS) according to ASHA's criteria. Lastly, the test method preference of the participants with MDR-TB was described and compared using a short exit survey. Study Design: A prospective repeated-measures study design was used. Participants were chosen based on a risk factor (i.e. exposure to ototoxic medication) for an outcome of interest (i.e. the presence or absence of an STS). With a repeated measures study, multiple tests using different test methods can be compared with the same sample. Participants: Twenty-seven in-patients at Brooklyn Chest Hospital and DP Marais TB Hospital with normal hearing and on MDR-TB medication were included in the study. Their age range was from 19 to 51 years old with an average age of 33 years old. Non-probability convenience sampling was used as it was cost-effective, reduced data collection time and was relatively easy to execute. Data collection materials and procedures: The procedure for data collection included weekly follow-up testing for a maximum of four weeks. The test battery was as follows: an auditory symptom questionnaire, otoscopy examination, and manual and automated audiometry using the SRO technique with a fifteen-minute break in between. Participants were tested with the KUDUwave ™ in a non-sound treated room. The frequency range was determined with the SRO technique. If an STS was obtained, the patient was discharged from the study after completing an exit survey. Statistics: Analysis included descriptive statistics and inferential statistics. A Bonferroni corrected p-value (initially p ≤ 0.05) was used. Manual and automated audiometry thresholds were compared using the Pearson's Correlation Coefficient test. Manual and automated audiometry testing time and threshold means were compared using paired sample's t-tests. The diagnostic value of automated audiometry with the SRO technique was assessed with Receiver Operating Characteristics (ROC) Curves. Results: Manual audiometry was statistically more time-efficient compared to automated audiometry by an average of one minute and ten seconds (t (94) = -5.44; p< 0.003). There was a strong positive correlation for both left and right ears between the thresholds' obtained from manual and automated audiometry at 8kHz to 16 kHz (df> 28 = r > 0.70, p< 0.003). Automated audiometry was found to be a fair diagnostic test (area under the curve was 0.75; p= 0.002). Also, the ROC curve revealed that automated audiometry had a sensitivity of 61% and specificity of 90% when compared to manual audiometry (gold standard). Only participants that started data collection within 31 days after starting their MDR-TB treatment were included in the analysis of determining the incidence of an ototoxicity-induced hearing loss (n= 24 ears). This study found that 41.67% of ears (n= 10) had an ototoxicity-induced hearing loss. A box and whisker plot revealed that data was skewed to the right (i.e. more variation in data between the median and the maximum values) and that the median number of days for an ototoxicity-induced hearing loss to appear was 33 days. Secondly, 55.55% of participants (n=15 out of 27) reported auditory symptoms before data collection commencement. Aural fullness was the most reported symptom (n= eight out of 15). Ten out of 15 (66.66%) participants that reported auditory symptoms obtained an ototoxicity-induced hearing loss. Lastly, most participants (i.e. 13 out of 19; 68.42%) that completed the exit survey had no preference between manual or automated audiometry. The common rationale among these participants was “No difference noted.” Conclusion: This research study has revealed that manual audiometry was more time-efficient compared to automated audiometry in patients with MDR-TB. Also, automated audiometry was a fair diagnostic test. It may aid in reducing the disproportionate audiologist to patient ratio, especially in a developing country. However, manual audiometry (with the SRO technique) is more clinically appropriate in patients that are difficult-to-test. Secondly, audiometric settings can be changed to accommodate testing frequencies in 1/6 octaves so that the SRO technique can be clinically adopted. An ototoxicity-induced hearing loss seems to appear 33 days after ototoxic MDR-TB treatment commencement. Aural fullness was a commonly reported symptom among participants with MDRTB. Aural fullness is omnipresent in peripheral auditory pathologies. Therefore, auditory symptoms reported by patients' needs a comprehensive audiological investigation. Lastly, more research is needed on how patients (and clinicians) experience the advances in technology innovation especially in audiology where technology innovation is continuously evolving.

Widespread use of solid oxide fuel cells is hindered by a lack of long-term durability of seals between metallic and ceramic components caused by thermal expansion mismatch induced cracking. A novel gas seal design incorporating an engineered thermal expansion gradient in a SrO-La₂O₃-A₂O₃-B₂O₃-SiO₂ glass matrix with a TiNiHf shape memory alloy mesh for active stress relief and crack healing is being developed. Coefficient of thermal expansion (CTE) measurements of the seal and fuel cell components shows the possibility for a thermal expansion gradient. Differential scanning calorimetry and microscopy have shown that the TiNiHf alloy has a shape memory transition in the desired range of 200-250ºC. The oxide glass partially crystallizes during thermal cycling which has been observed through X-ray diffraction and dilatometry. The CTE decreases from 9.3Ã 10-6/°C to 6.6Ã 10-6/°C after thermal cycling. Neutron diffraction data from TiNiHf /glass composite samples reveals that the TiNiHf alloy has the ability of absorbing residual stresses from a glass matrix during martensitic phase transition. There is evidence from microscopy that the glass composition is important in determining if reaction will occur with the TiNiHf alloy. The TiNiHf alloy mesh structures can be created using the 3D printing process. This process has been adapted to allow for printing of very thin wire mesh structures of Ni and NiTi powders with a more suitable binder solution. A bi-layer test fixture has been developed which will be useful for assessing leak rate through seal materials. / Master of Science