Crosstalk aware light-path selection in optical wdm/dwdm networks

Physical layer impairments are the major limitation for the high speed optical WDM/DWDM networks. They significantly affect the signal quality resulting poor quality of transmission which is normally expressed in terms of bit-error rate. To cope of with the future demand, increase in the no of channels and data speed further enhances these impairments. Hence new techniques are needed, which mitigate these impairments and ensure a better quality of transmission. Among the physical layer impairments we have studied the impact of in-band crosstalk on transmission performance of a transparent WDM/DWDM network. Error probabilities and power penalties produced by crosstalk are also investigated. As traditional RWA scheme pays a little regard to the physical layer impairments and cannot provide optimized network performance in practical networks, we have proposed a novel BER constrained, FWM aware RWA algorithm. The performance of the proposed algorithm is demonstrated through simulation and the results show that our algorithm not only gives a guaranteed quality of transmission but also improves the network performance in terms of blocking probability

Space programs summary no. 37-51, volume 3 for the period April 1 to May 31, 1968. Supporting research and advanced development

Space Programs Summary - supporting research and advanced developmen

Quality of service estimation techniques for an optical virtual private network over wdm/dwdm network

Quality of Service (QoS) in optical virtual private network (OVPN) is a demanding factor for communication network application. To provide desired QoS, the control plane in an all optical network (AON) has to be designed to maximize the quality of an OVPN connections (OVPNC). The AON is generally characterized by various network and physical layer parameters, which are used by the OVPN control manager (OVPNCM) for the estimation of quality factor (Q-Factor) for a set of possible OVPNC. It is observed that, not only the network layer parameters, but also the physical layer parameters called as physical layer impairments (PLIs) have impact on connection quality. In optical networks, the PLIs are incurred by non-ideal optical transmission media and accumulate along the optical connection. The overall effect of PLIs can be analyzed to determine the feasibility of quality based OVPNC. It is important to understand the process and provide the network as well as the PLI information to the OVPNCM and use this information efficiently to compute feasible connections along with Q-Factor values. Based on these, four different QoS estimation techniques have been proposed here

Publications of the Jet Propulsion Laboratory, July 1968 through June 1969

Annotated bibliography on space exploration, materials, and physical science

Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial cellular communications services. While the first and second International Mobile Satellite Conferences (IMSC) mostly concentrated on technical advances, this Third IMSC also focuses on the increasing worldwide commercial activities in Mobile Satellite Services. Because of the large service areas provided by such systems, it is important to consider political and regulatory issues in addition to technical and user requirements issues. Topics covered include: the direct broadcast of audio programming from satellites; spacecraft technology; regulatory and policy considerations; advanced system concepts and analysis; propagation; and user requirements and applications

Novel method and instruments for the optimal techno-economic sizing of borehole heat exchangers

El test de respuesta térmica (TRT) es ampliamente utilizado como método estándar para caracterizar las propiedades térmicas del terreno adyacente a un intercambiador de calor enterrado (BHE). Los métodos tradicionales para interpretar los resultados aplican soluciones analíticas o numéricas asumiendo que el terreno es infinito, homogéneo e isotrópico. Sin embargo, en realidad el subsuelo presenta generalmente una estructura estratificada y heterogénea, y por lo tanto las propiedades térmicas pueden variar sustancialmente con la profundidad. En este sentido y con la intención de resolver las limitaciones del TRT estándar, la presente tesis doctoral se centra en el desarrollo de métodos e instrumentos para cuantificar las propiedades de transferencia de calor de las capas geológicas alrededor de un BHE. Información que resulta imprescindible para alcanzar la máxima eficiencia energética y el dimensionado técnico-económico óptimo de un BHE. En particular, se propone un nuevo método de TRT, llamado observer pipe TRT (OP-TRT), basado en una medición de temperatura adicional a lo largo de una tubería auxiliar. En las últimas décadas, varios investigadores han desarrollado TRT distribuidos (DTRT) en los cuales se realizan mediciones de temperatura a lo largo del tubo-U en el que se inyecta calor. No obstante, a partir de las investigaciones llevadas a cabo en esta tesis, el tubo observador ha demostrado amplificar los efectos térmicos producidos debido a capas geológicas con propiedades termo-físicas diferentes, requiriéndose así sensores menos precisos para obtener resultados más detallados. En base a este logro, se ha desarrollado un modelo numérico de simulación inversa para parametrizar la conductividad térmica de las capas geológicas a partir de las mediciones a lo largo del tubo observador. Básicamente, el modelo ajusta la conductividad térmica de las capas geológicas hasta que los resultados de la simulación coinciden con el perfil de temperatura experimental a lo largo del tubo observador. El modelo ha sido desarrollado con un algoritmo de estimación de parámetros para un ajuste automático y obtención de resultados más precisos. Otra ventaja es que este método solo requiere dos perfiles de temperatura: (1) subsuelo en reposo (antes del TRT) y (2) al final del TRT (antes de detener la inyección de calor). Con la intención de continuar investigando el método propuesto a partir de datos de mayor calidad, se ha desarrollado un instrumento específico (Geowire) para medir de forma automática y con mayor precisión los perfiles de profundidad-temperatura requeridos. El diseño del Geowire también ha sido orientado para cubrir otros requisitos, como compatibilidad con equipos de TRT y operación intuitiva. Además, se ha desarrollado una versión mejorada de una sonda de temperatura (Geoball) que es arrastrada por el fluido que circula en las tuberías a la vez que calcula su posición, con la ventaja de que puede ser utilizada en tuberías con disposición vertical y horizontal. Después de las pruebas de validación en el laboratorio, las características fundamentales de ambos instrumentos han sido evaluadas en comparación con otros instrumentos novedosos y estándar para mediciones de temperatura distribuidas durante un experimento en un BHE de pruebas. La ventaja principal de los instrumentos propuestos sobre la popular fibra óptica es que miden la temperatura instantáneamente (para intervalos temporales precisos). Asimismo, no necesitan de una calibración dinámica para obtener resultados precisos mientras que proporcionan una mayor resolución espacial y de temperatura: Geowire (0.5 mm, 0.06 K) y Geoball (10 mm, 0.05 K). Además, son más fáciles de integrar en pozos existentes y son una solución potencialmente más rentable para medir la temperatura distribuida. Finalmente, se demuestran los beneficios del método e instrumentos propuestos durante un DTRT en comparación con la fibra óptica y con un programa basado en el modelo de línea infinita para estimar la conductividad térmica distribuida. Los resultados del modelo propuesto revelaron una zona altamente conductiva al usar los datos del Geowire, mientras que esta zona no fue detectada al procesar los datos de fibra óptica.The thermal response test (TRT) is widely used as a standard test to characterize the thermal properties of the ground near a borehole heat exchanger (BHE). Typical methods to interpret the results apply analytical or numerical solutions which assume that the ground is infinite, homogeneous and isotropic. However, in reality the underground is commonly stratified and heterogeneous, and therefore thermal properties may significantly vary with depth. In this sense and with the intention to overcome standard TRT limitations, this Ph.D. study is focused on developing methods and instruments for the evaluation of the heat transfer behavior of the geological layers surrounding a BHE. This information is key for the optimal energy efficiency and techno-economic sizing of BHE. In particular, a novel TRT method, called observer pipe TRT (OP-TRT), is proposed based on an additional temperature measurement along an auxiliary pipe. In the last decades, some researchers developed the so-called distributed TRT (DTRT) by measuring the temperature along the length of the heated U-pipe. However, from the studies carried out in this Ph.D. work, the observer pipe demonstrated to amplify the thermal effects produced due to geological layers with different thermo-physical properties, hence requiring less accurate sensors for obtaining more detailed results. Based on this achievement, an inverse numerical solution was developed to parametrize thermal conductivity of geological layers from the measurements along the observer pipe. Basically, the model adjusts thermal conductivity of the geological layers until simulation results fit experimental temperature profile along the observer pipe. The model was developed with a parameter estimation solver for an automatic fitting and more accurate results. Another advantage is that this method only requires two temperature profiles: (1) undisturbed ground (before the TRT) and (2) at the end of the TRT (before stopping the heat injection). In order to further investigate the proposed method by using higher quality data, a specific instrument (Geowire) was developed to automatically measure the required depth-temperature profiles with high accuracy. The design of the Geowire also coveredother features, such as compatibility with TRT equipment and intuitive operation. In addition, an enhanced version of a flowing probe (Geoball) was developed, suitable for both vertical and horizontal pipe arrangements. After laboratory validation tests, the key features of both instruments were evaluated in comparison with new and standard in-borehole instruments for temperature measurements in a test BHE. The main advantage of the proposed instruments over the widespread fiber optics is that they measure the temperature instantaneously (for precise time instants). Moreover, they do not require a dynamic calibration for accurate results while providing higher spatial and temperature resolutions: Geowire (0.5 mm, 0.06 K) and Geoball (10 mm, 0.05 K). Also, they are easier to integrate in existing boreholes and are a potentially more cost-effective solution to measure the distribute temperature. Finally, the benefits of the proposed method and instruments are demonstrated throughout a DTRT in comparison with fiber optics and with a computer program based on the infinite line source model to estimate the distributed thermal conductivity. The results from the proposed model revealed a highly conductive zone when using data from the Geowire, whereas this was not the case when data from fiber optics were processed

Analysis of systems hardware flown on LDEF. Results of the systems special investigation group

The Long Duration Exposure Facility (LDEF) was retrieved after spending 69 months in low Earth orbit (LEO). LDEF carried a remarkable variety of mechanical, electrical, thermal, and optical systems, subsystems, and components. The Systems Special Investigation Group (Systems SIG) was formed to investigate the effects of the long duration exposure to LEO on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. Discussed here is the status of the LDEF Systems SIG investigation through the end of 1991