149 research outputs found
Low-Temperature Vaterite-Type LuBO<sub>3</sub>, a Vacancy-Stabilized Phase Synthesized at High Temperature
No full textLow-temperature
vaterite-type LuBO<sub>3</sub> (π-LBO) was prepared by a solid-state
reaction method at high temperature. The reasoning of the existence
of vacancy-stabilized π-LBO was investigated for the first time
using neutron diffraction patterns, Fourier transform infrared (FT-IR)
spectra, and high-resolution transmission electron microscopy. The
results clearly demonstrated that the B and O vacancies in π-LBO
came into being during the heating process. The existence of an open
B<sub>3</sub>O<sub>9</sub> ring consisting of BO<sub>3</sub> and BO<sub>4</sub> units in π-LBO due to the B and O vacancies was demonstrated
by FT-IR. The vacuum ultraviolet–ultraviolet spectroscopic
properties of π-LBO were studied in detail. In addition, the
luminescence mechanism of Ce<sup>3+</sup> in π-LBO was put forward
and discussed with that of calcite-type LuBO<sub>3</sub> (β-LBO)
High T-g, melt processable copolyimides based on isomeric 3,3' and 4,4'-hydroquinone diphthalic anhydride (HQDPA)
No full textTo extend the upper operating temperature range of melt processable PIs, two series of end-capped copolyimides based on hydroquinone diphthalic anhydride (HQDPA) isomers were designed by varying the contents of appropriate diamines. Thus, copolyimides PI-(0a similar to 20a) based on 3,3'-HQDPA were prepared by varying the ratio of rigid 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) and flexible 4,4'-oxydianiline (ODA). The resulting copolyimides demonstrated good properties, such as excellent solubility, high T-g ranging from 328 to 354 degrees C as determined by dynamic mechanical analyzer (DMA), besides, exhibited good thermal stability based on 5% weight loss temperature (T-5%) of 502-514 degrees C and low melt viscosity in the range of 291-935 Pa.s. Most importantly, PI-20a showed a good combination of low melt viscosity simultaneously with significantly high T-g (328 degrees C). Furthermore, this system was modified by copolymerization with different feed ratio of 4,4'-HQDPA isomer and produced another series PI-(20a similar to 20e), that exhibited high T-g in the range of 315-330 degrees C with T-5% of 502-543 degrees C and minimum complex viscosity in the range of 291-479 Pa.s. All PIs form tough and flexible films that have remarkable tensile strength and moduli in the range of 93-116 MPa and 3.7-4.7 GPa, respectively. (C) 2017 Elsevier Ltd. All rights reserved
Experimental Study of Anisotropically Mechanical Features of Phyllite and Its Engineering Effect
No full text
Arrangement of oil wells in the electrical system of caño limon field: fitting proposal
No full textEl sistema interconectado del campo Caño limón esta conformado por una red de líneas de distribución que transportan la energía requerida por el sistema de levantamiento artificial de los pozos. Debido a que la adición de un nuevo pozo al sistema interconectado depende exclusivamente de su posición geográfica, es inevitable que en ocasiones se formen concentraciones de carga según las tendencias de crecimiento propias del campo, haciendo que la energía necesaria para el proceso de extracción se distribuya de manera irregular en la red de distribución. Con el desarrollo de este trabajo de grado se busca proponer una solución al irregular suministro eléctrico de los pozos del campo Caño Limón, con el fin de solucionar la sobrecarga de algunas de sus líneas de distribución, y facilitar la adición de nuevos pozos al sistema interconectado de la empresa Occidental de Colombia, Inc. Se atacó el problema realizando un estudio de la distribución de los pozos actuales y pozos nuevos, y de la cargabilidad de las líneas del campo. A su vez se analizó la topología de la red, permitiendo plantear un nuevo esquema del suministro eléctrico de los pozos dentro del sistema interconectado de la empresa, que asegure una operación de las líneas de distribución dentro de los parámetros establecidos por la empresa, y que cumpla con la normatividad establecida para el diseño de líneas eléctricas.PregradoIngeniero ElectricistaInterconnected system of Caño Limon field set up is a distribution lines net used for transporting the required energy to oil well artificial lifting system. Because addition of a new well to the interconnected system depends exclusively of its geographical position, it is unavoidable in some cases the formation of load concentrations according to the own tendency of growing for an specific field, and that event causes that necessary energy for the extraction process can be delivered in an irregular way in the distribution net. With the development of this graduation project the author looks for propose a solution to the irregular electrical supply to Wells of Caño Limón field, in order to avoid the extra load in some of its distribution lines and facilitate addition of new wells to the interconnected system for the enterprise Occidental de Colombia, Inc. The specific problem was attacked carrying out a survey taking account the distribution of actual and new Wells, and the load capacity of the lines in the field. At the same time the topology of the net was analyzed, allowing establishing a new scheme of electrical supply to the Wells inside interconnected system of the enterprise, that guarantee the operation of the distribution lines within enterprise established parameters, and fulfill the established norms used to design electrical lines
Instantaneous Frequency Estimation Based on the Wigner‐Ville Distribution Associated with Linear Canonical Transform (WDL)
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