We transport the standard time signal by using the single-mode fiber (SMF) media through the synchronous optical network (SONET)/ synchronous digital hierarchy (SDH) data signal, in which the time signal generated from the atomic clock was inserted into the unused bytes in the overhead of the SONET/SDH OC-3 155 Mb/s frame. Based on the NIST MODEM architecture, which was developed by the National Institute of Standard and Technology in the States, the time transfer system is composed of the control unit of the OC-3 transceiver module and the time-signal transmiting/receiving unit. We design and fabricate the required time-signal transmitting/receiving circuits and the control and monitoring circuits. The personal computer (PC) can read/write and monitor the operation status of the optical transceiver module through the control circuit, and the 1-PPS (pulse per second) time signal can therefore be read/written from/into the transceiver module. The frequency stability of about 2.6E-16 within one day can be achieved for this 1310-nm optical-fiber-based time transfer system over a 35-km SMF link without using electronic regererator. Such stability performance is comparable with that of today¡¦s GPS-based time transfer system.

<p> This thesis reports a systematic study of geometrically frustrated f.c.c. double perovskites with both monoclinic (P2₁/n) La₂LiMO₆ and cubic (Fm3m) Ba₂YMO₆ symmetries, where M=Mo (S=1/2), Re (S=1) and Ru (S=3/2). The roles of both the spin quantum number, i.e. quantum spin fluctuations, and the local site symmetry, i.e. orbital ordering, on the determination of the ground magnetic state were studied. All the compounds were prepared by solid state reaction and the structural information and magnetic properties of the compounds were collected using diffraction techniques (X-ray and neutron), de susceptibility, heat capacity, muon spin relaxation (μSR) and solid state NMR. </p> <p> The S=3/2 materials, La₂LiRuO₆ and Ba₂YRuO₆, while highly frustrated with frustration indices f ~ 16 and 8, respectively, both show antiferromagnetic (AF) long range ordering at 24K and 37K, respectively. The Neel temperature of the latter compound was determined for the first time by the heat capacity and neutron diffraction. This compound shows an unusual AF transition as two broader peaks were observed in the susceptibility while La₂LiRuO₆ shows a typical AF behavior. There is about 1 % of Y/Ru site mixing observed by 89Y MAS NMR in Ba₂YRuO₆. </p> <p> For the S=1 materials, monoclinic La₂LiReO₆ shows collective singlet like behavior as zero magnetization was observed in the ZFC susceptibility and a static and diluted spin system was indicated by μSR. On the other hand, the cubic phase, Ba₂YReO₆ surprisingly shows a spin glass behavior confirmed by μSR while no Y/Re site mixing was observed by MAS NMR. It is also a surprising observation that this compound retains cubic symmetry down to 3K where it would have a structure transition subject to the Jahn-Teller theorem. </p> <p> Finally, the S=1/2 compounds, La₂LiMoO₆ and Ba₂YMoO₆, show quite different magnetic behavior. Monoclinic La₂LiMoO₆ shows the presence of at least short range order achieved at 18K according to the heat capacity and μSR measurements. Ba₂YMoO₆ retains cubic symmetry down to 3K and no Jahn-Teller distortion was observed at the limit of the resolution of neutron diffraction. This compound surprisingly appears to remain paramagnetic down to 2K, yet evidence for a collective singlet state was observed by a paramagnetic Knight shift measurement in NMR. This is consistent with an existing theoretical prediction. </p> <p> An extended study on other S=1/2 Mo analogues, Ba₂LuMoO₆ and Ba₂ScMoO₆ is also presented. Both compounds show cubic structure confirmed by X-ray diffraction and paramagnetic behavior down to 2K in the susceptibility. </p> / Thesis / Doctor of Philosophy (PhD)

El presente documento presenta un estudio basado en el análisis del comportamiento de las propiedades mecánicas de un suelo limo arcilloso con la incorporación de fibras de PET triturado. Para conocer el comportamiento de un suelo, es necesario conocer primero su génesis. Las muestras analizadas provienen de la capa de subrasante de una carretera que une las ciudades de Munichis y Yurimaguas, en el departamento de Loreto, Perú. El tipo de suelo en las zonas de selva baja suele tener características como bajo índice de soporte, media a elevada plasticidad, y demás características que lo hacen considerar como un suelo problemático, esto debido a factores como el clima, humedad, y ubicación geográfica. Para realizar un análisis preciso del comportamiento de este suelo en combinación con el PET, se llevó a cabo ensayos como la prueba del hidrómetro, Proctor modificado y CBR con porcentajes variables de PET respecto a la masa de la muestra de suelo. Cada uno de ellos, principalmente, para conocer bien el tipo de muestra, y el índice de soporte con cada porcentaje incorporado. Los resultados son evidencia que mientras mayor sea el porcentaje de PET, el suelo pierde características resistentes, por lo que su índice de soporte disminuye; por el contrario, mientras menor es el porcentaje de PET incorporado, el índice de soporte se incrementa. En suma, para poder conocer el comportamiento esperado, es necesario realizar distintas pruebas, y haciendo uso de distintos tipos de suelos. / This study is based on the analysis of the behavior of the mechanical properties of a silty clay soil with crushed PET fibers incorporated. To understand the behavior of a soil, it is necessary to know its origin. The analyzed samples come from the subgrade layer of a highway that connects the cities of Munichis and Yurimaguas, in the region of Loreto, Peru. The material in this area usually has characteristics such as low support index, medium to high plasticity, and other characteristics that make it considered a problematic soil, this due to factors such as climate, humidity, and geographical location. To perform a precise analysis of the behavior of this soil in combination with PET, tests such as the hydrometer test, Modified Proctor and CBR with different percentages of PET, were carried out. to the mass of the sample. Each of them mainly to know well the type of sample, and the support index with each percentage incorporated. The results show that as higher the percentage of PET, the soil loses resistant characteristics, so its support index decrease, on the other hand, the lower percentage of PET used, the support index increases. In summary, to know the expected behavior, it is necessary to carry out different tests, and make use of different types of soil. / Trabajo de investigación

In this dissertation the effects of variations in stimulus properties and CTOA, in auditory attention tasks were explored using recently developed approaches to EEG analysis including LIMO. The last experiment was structured using information theory, designing an effective experiment. Four studies were carried out using a number parity decision task, that employed different combinations of cueing Tone (T), Novel (N) and the Goal (G) stimuli. In the first EEG study, contrary to previous findings (Polich 2002, 2007) in control participants, no correlation between the time of a novel condition to the next novel condition and P300 amplitude was found. Therefore single trial across-subject averaging of participants’ data revealed significant correlations (r > .3) of stimulus properties (such as probability, frequency, amplitude and duration) on P300, and even r > .5 was found when N was an environmental sound in schizophrenic patients. In the second EEG study, simultaneously with fMRI recordings, the participants that showed significant behavioural distraction evoked brain activations and differences in both hemispheres (similar to Corbetta, 2002, 2008) while the participants, as a whole, produced significant activations mainly in left cortical and subcortical regions. A context analysis was run in distracted participants contrasting the trials immediately prior to the G trials, resulting in different prefrontal activations, which was consistent with studies of prefrontal control of visual attention (Koechlin 2003, 2007). In the third EEG study, the distractor noise type was manipulated (white vs environmental sounds) as well as presence or absence of scanner background noise in a blocked design. Results showed consistent P300, MMN and RON due to environmental noise. In addition, using time constants found in MEG results (Lu, Williamson & Kaufman, 1992) and adding the CTOA to the analysis, an information theory framework was calculated. After the simulation of the information of the experiment, a saddle indentation in the curve of the information measure based on the states of the incoming signal at around 300 ms CTOA was found. This saddle indentation was evident in more than 60 novel trials. In the fourth study, the CTOA and stimulus properties were manipulated in a parametric experiment. Based on the three studies, reducing complexity if the task (first study), using more than 60 stimuli in the novel conditions (third study). The CTOA randomly varying between 250 ms or 500 ms. Thirty-eight ANCOVA with 2 categorical and 1 continuous regressors were conducted and determined which time and channels elicited reliably signatures (p <.05) in the whole participants at short CTOA. Results revealed differences for the waveforms of current condition by depending on which condition appeared previously as well in terms of frequency and duration in scalp frontal electrodes (such as the second study). These results were interpreted as a consequence of switching between modes of attention and alerting states which resulted in the activation of frontal areas. Moreover, contextual analyses showed that systematic manipulation of stimulus properties allowed the visualization of the relationships between CTOA, executive function and orienting of attention.