Complexity Reduction In A Telephone Switching-System

This paper review the some of the recent developments in Complexity theory as applied to telephone-switching. Some of these techniques are suitable for practical implementation in India.

Autonomous Line Scanning for SPC Telephone Switching Systems

An Autonomous Line Scanning Unit (ALSU) for completely autonomous detection of call originations in the SPC Telephone Switching System is described. Through its own memories, ALSU maintains an up-to-date record of subscribers' statuses, detects call originations, performs 'hit timing check' and informs the Switching System of the identity of calling subscribers. The ALSU needs minimum interaction with the Central Processor, resulting in increased call handling capacity

Sensitivity to switching rates in stochastically switched ODEs

We consider a stochastic process driven by a linear ordinary differential equation whose right-hand side switches at exponential times between a collection of different matrices. We construct planar examples that switch between two matrices where the individual matrices and the average of the two matrices are all Hurwitz (all eigenvalues have strictly negative real part), but nonetheless the process goes to infinity at large time for certain values of the switching rate. We further construct examples in higher dimensions where again the two individual matrices and their averages are all Hurwitz, but the process has arbitrarily many transitions between going to zero and going to infinity at large time as the switching rate varies. In order to construct these examples, we first prove in general that if each of the individual matrices is Hurwitz, then the process goes to zero at large time for sufficiently slow switching rate and if the average matrix is Hurwitz, then the process goes to zero at large time for sufficiently fast switching rate. We also give simple conditions that ensure the process goes to zero at large time for all switching rates. © 2014 International Press.

Global analysis of dynamical decision-making models through local computation around the hidden saddle

Bistable dynamical switches are frequently encountered in mathematical modeling of biological systems because binary decisions are at the core of many cellular processes. Bistable switches present two stable steady-states, each of them corresponding to a distinct decision. In response to a transient signal, the system can flip back and forth between these two stable steady-states, switching between both decisions. Understanding which parameters and states affect this switch between stable states may shed light on the mechanisms underlying the decision-making process. Yet, answering such a question involves analyzing the global dynamical (i.e., transient) behavior of a nonlinear, possibly high dimensional model. In this paper, we show how a local analysis at a particular equilibrium point of bistable systems is highly relevant to understand the global properties of the switching system. The local analysis is performed at the saddle point, an often disregarded equilibrium point of bistable models but which is shown to be a key ruler of the decision-making process. Results are illustrated on three previously published models of biological switches: two models of apoptosis, the programmed cell death and one model of long-term potentiation, a phenomenon underlying synaptic plasticity. © 2012 Trotta et al.

Studies on underwater propagation development of programmable arrays

The thesis presented here includes the designing of underwater transducer arrays, taking into account the ‘interaction effects’ [30] among the closely packed radiators. Methods of minimizing the ‘interaction effects‘ by modifying the radiating aperture, are investigated. The need for this study arises as it is one of the important peculiar limitations that stands in the way of achieving maximum range of transmission of acoustic signals. Application of the modified array format for the generation of narrow beam low frequency sound waves, through nonlinear interactions, is discussed. Other techniques that can be advantageously exploited in array synthesis are also investigated

Conversor inversor integrado três estados buck-boost para geração distribuída, com operação conectada ou ilhada

Pós-graduação em Engenharia Elétrica - FEIS

A dual resonance, image -guided, volume localization technique for magnetic resonance spectroscopy

An interleaved, dual resonance, volume localization technique for $\sp1$H/$\sp{31}$P magnetic resonance spectroscopy has been designed, implemented on a 2 T imager/spectrometer, and verified with phantom studies.^ Localization techniques, including several single voxel techniques and spectroscopic imaging, were implemented, and studies were performed to compare the efficiency of each sequence of $\sp1$H/$\sp{31}$P spectral acquisitions. The sequence chosen was a hybrid of the stimulated echo single voxel technique and the spectroscopic imaging technique.^ Water suppression during the $\sp1$H spectral acquisitions was accomplished by the use of three narrow bandwidth RF saturation pulses in combination with three spoiler gradients. The spoiler gradient amplitudes were selected on the basis of a numerical solution of the Bloch equations. A post-acquisition water suppression algorithm was used to minimize any residual water signal.^ For interleaved $\sp1$H/$\sp{31}$P acquisitions, a dual resonance RF coil was constructed and interfaced to the existing RF detection system via a custom-designed dual resonance transcoupler and switching system. Programmable attenuators were incorporated to allow for changes in receiver and transmitter attenuation "on the fly".^ To provide the rapidly switched gradient fields required for the $\sp1$H/$\sp{31}$P acquisitions, an actively screened gradient coil system was designed and implemented. With this system, gradient field rise times on the order of 100 $\mu$s were obtained. These rapid switching times were necessary for minimizing intrasequence delays and for improving localization quality and water suppression efficiency.^ The interleaved $\sp1$H/$\sp{31}$P volume localization technique was tested using a two-compartment phantom. Analysis of the data showed that the spectral contamination was less than three percent. One-to-one spatial correspondence of the $\sp1$H and $\sp{31}$P spectra was verified and allowed for direct correlation of the spectral data with a standard magnetic resonance image. ^

Plataformas experimentales para la formación en el área de la electrónica en entornos de e-learning

El campo de estudio relacionado con los laboratorios remotos en el ámbito educativo de las ciencias y la ingeniería está sufriendo una notable expansión ante la necesidad de adaptar los procesos de aprendizaje en dichas áreas a las características y posibilidades de la formación online. Muchos de los recursos educativos basados en esta tecnología, existentes en la actualidad, presentan ciertas limitaciones que impiden alcanzar las competencias que se deben adquirir en los laboratorios de ingeniería. Estas limitaciones están relacionadas con diferentes aspectos de carácter técnico y formativo. A nivel técnico las limitaciones principales se centran en el grado de versatilidad que son capaces de proporcionar comparado con el que se dispone en un laboratorio tradicional y en el modo de interacción del usuario, que provoca que el estudiante no distinga claramente si está realizando acciones sobre sistemas reales o simulaciones. A nivel formativo las limitaciones detectadas son relevantes para poder alcanzar un aprendizaje significativo. En concreto están relacionadas principalmente con un escaso sentimiento de inmersión, una reducida sensación de realismo respecto a las operaciones que se realizan o la limitada posibilidad de realizar actividades de forma colaborativa. La aparición de nuevas tecnologías basadas en entornos inmersivos, unida a los avances producidos relacionados con el aumento de la capacidad gráfica de los ordenadores y del ancho de banda de acceso a Internet, han hecho factible que las limitaciones comentadas anteriormente puedan ser superadas gracias al desarrollo de nuevos recursos de aprendizaje surgidos de la fusión de laboratorios remotos y mundos virtuales 3D. Esta tesis doctoral aborda un trabajo de investigación centrado en proponer un modelo de plataformas experimentales, basado en la fusión de las dos tecnologías mencionadas, que permita generar recursos educativos online que faciliten la adquisición de competencias prácticas similares a las que se consiguen en un laboratorio tradicional vinculado a la enseñanza de la electrónica. El campo de aplicación en el que se ha focalizado el trabajo realizado se ha centrado en el área de la electrónica aunque los resultados de la investigación realizada se podrían adaptar fácilmente a otras disciplinas de la ingeniería. Fruto del trabajo realizado en esta tesis es el desarrollo de la plataforma eLab3D, basada en el modelo de plataformas experimentales propuesto, y la realización de dos estudios empíricos llevados a cabo con estudiantes de grado en ingeniería, muy demandados por la comunidad investigadora. Por un lado, la plataforma eLab3D, que permite llevar a cabo de forma remota actividades prácticas relacionadas con el diseño, montaje y prueba de circuitos electrónicos analógicos, aporta como novedad un dispositivo hardware basado en un sistema de conmutación distribuido. Dicho sistema proporciona un nivel de versatilidad muy elevado, a nivel de configuración de circuitos y selección de puntos de medida, que hace posible la realización de acciones similares a las que se llevan a cabo en los laboratorios presenciales. Por otra parte, los estudios empíricos realizados, que comparaban la eficacia educativa de una metodología de aprendizaje online, basada en el uso de la plataforma eLab3D, con la conseguida siguiendo una metodología clásica en los laboratorios tradicionales, mostraron que no se detectaron diferencias significativas en el grado de adquisición de los resultados de aprendizaje entre los estudiantes que utilizaron la plataforma eLab3D y los que asistieron a los laboratorios presenciales. Por último, hay que destacar dos aspectos relevantes relacionados directamente con esta tesis. En primer lugar, los resultados obtenidos en las experiencias educativas llevadas a cabo junto a valoraciones obtenidas por el profesorado que ha colaborado en las mismas han sido decisivos para que la plataforma eLab3D se haya integrado como recurso complementario de aprendizaje en titulaciones de grado de ingeniería de la Universidad Politécnica de Madrid. En segundo lugar, el modelo de plataformas experimentales que se ha propuesto en esta tesis, analizado por investigadores vinculados a proyectos en el ámbito de la fusión nuclear, ha sido tomado como referencia para generar nuevas herramientas de formación en dicho campo. ABSTRACT The field of study of remote laboratories in sciences and engineering educational disciplines is undergoing a remarkable expansion given the need to adapt the learning processes in the aforementioned areas to the characteristics and possibilities of online education. Several of the current educational resources based on this technology have certain limitations that prevent from reaching the required competencies in engineering laboratories. These limitations are related to different aspects of technical and educational nature. At the technical level, they are centered on the degree of versatility they are able to provide compared to a traditional laboratory and in the way the user interacts with them, which causes the student to not clearly distinguish if actions are being performed over real systems or over simulations. At the educational level, the detected limitations are relevant in order to reach a meaningful learning. In particular, they are mainly related to a scarce immersion feeling, a reduced realism sense regarding the operations performed or the limited possibility to carry out activities in a collaborative way. The appearance of new technologies based on immersive environments, together with the advances in graphical computer capabilities and Internet bandwidth access, have made the previous limitations feasible to be overcome thanks to the development of new learning resources that arise from merging remote laboratories and 3D virtual worlds. This PhD thesis tackles a research work focused on the proposal of an experimental platform model, based on the fusion of both mentioned technologies, which allows for generating online educational resources that facilitate the acquisition of practical competencies similar to those obtained in a traditional electronics laboratory. The application field, in which this work is focused, is electronics, although the research results could be easily adapted to other engineering disciplines. A result of this work is the development of eLab3D platform, based on the experimental platform model proposed, and the realization of two empirical studies with undergraduate students, highly demanded by research community. On one side, eLab3D platform, which allows to accomplish remote practical activities related to the design, assembling and test of analog electronic circuits, provides, as an original contribution, a hardware device based on a distributed switching system. This system offers a high level of versatility, both at the circuit configuration level and at the selection of measurement points, which allows for doing similar actions to those conducted in hands-on laboratories. On the other side, the empirical studies carried out, which compare the educational efficiency of an online learning methodology based on the use of eLab3D platform with that obtained following a classical methodology in traditional laboratories, shows that no significant differences in the acquired degree of learning outcomes among the students that used eLab3D platform and those that attended hands-on laboratories were detected. Finally, it is important to highlight two relevant aspects directly related with this thesis work. First of all, the results obtained in the educational experiences conducted, along with the assessment from the faculty that has collaborated in them, have been decisive to integrate eLab3D platform as a supplementary learning resource in engineering degrees at Universidad Politecnica de Madrid. Secondly, the experimental platform model originally proposed in this thesis, which has been analysed by nuclear fusion researchers, has been taken as a reference to generate new educational tools in that field.

Sistema de conmutación y control de llamadas basado en OpenBTS y Asterisk

El presente trabajo empleó herramientas de hardware y software de licencia libre para el establecimiento de una estación base celular (BTS) de bajo costo y fácil implementación. Partiendo de conceptos técnicos que facilitan la instalación del sistema OpenBTS y empleando el hardware USRP N210 (Universal Software Radio Peripheral) permitieron desplegar una red análoga al estándar de telefonía móvil (GSM). Usando los teléfonos móviles como extensiones SIP (Session Initiation Protocol) desde Asterisk, logrando ejecutar llamadas entre los terminales, mensajes de texto (SMS), llamadas desde un terminal OpenBTS hacia otra operadora móvil, entre otros servicios.

Thermal and electrical switching studies on Ge20Se80-xBix (1 <= x <= 13) ternary chalcogenide glassy system

Alternating Differential Scanning Calorimetric (ADSC) and electrical switching studies have been undertaken on Ge20Se80-xBix glasses (1 <= x <= 13), to understand the effect of topological thresholds on thermal properties and electrical switching behavior. It is found that the compositional dependence of glass transition temperature (Tg), crystallization temperature (T-c1) and thermal stability (AT) of Ge20Se80-xBix glasses show anomalies at a composition x= 5, the rigidity percolation/stiffness threshold of the system. Further, unusual variations are also observed in different thermal properties, such as T-g, T-c1, Delta T, Delta C-p and Delta H-NR, at the composition x= 10, which indicates the occurrence of chemical threshold in these glasses at this composition. Electrical switching studies indicate that Ge20Se8o_RBig glasses with 5 11 exhibit threshold switching behavior and those with x = 12 and 13 show memory switching. A sharp decrease has been noticed in the switching voltages with bismuth concentration, which is due to the more metallic nature of bismuth and the presence of Bi+ ions. Further, a saturation is seen in the decrease in V-T around x = 6, which is related to bismuth phase percolation at higher concentrations of Bi. (C) 2010 Elsevier B.V. All rights reserved.

Surface electrode switching of a 16-electrode wireless EIT system using RF-based digital data transmission scheme with 8 channel encoder/decoder ICs

A Radio Frequency (RF) based digital data transmission scheme with 8 channel encoder/decoder ICs is proposed for surface electrode switching of a 16-electrode wireless Electrical Impedance Tomography (EIT) system. A RF based wireless digital data transmission module (WDDTM) is developed and the electrode switching of a EIT system is studied by analyzing the boundary data collected and the resistivity images of practical phantoms. An analog multiplexers based electrode switching module (ESM) is developed with analog multiplexers and switched with parallel digital data transmitted by a wireless transmitter/receiver (T-x/R-x) module working with radio frequency technology. Parallel digital bits are generated using NI USB 6251 card working in LabVIEW platform and sent to transmission module to transmit the digital data to the receiver end. The transmitter/receiver module developed is properly interfaced with the personal computer (PC) and practical phantoms through the ESM and USB based DAQ system respectively. It is observed that the digital bits required for multiplexer operation are sequentially generated by the digital output (D/O) ports of the DAQ card. Parallel to serial and serial to parallel conversion of digital data are suitably done by encoder and decoder ICs. Wireless digital data transmission module successfully transmitted and received the parallel data required for switching the current and voltage electrodes wirelessly. 1 mA, 50 kHz sinusoidal constant current is injected at the phantom boundary using common ground current injection protocol and the boundary potentials developed at the voltage electrodes are measured. Resistivity images of the practical phantoms are reconstructed from boundary data using EIDORS. Boundary data and the resistivity images reconstructed from the surface potentials are studied to assess the wireless digital data transmission system. Boundary data profiles of the practical phantom with different configurations show that the multiplexers are operating in the required sequence for common ground current injection protocol. The voltage peaks obtained at the proper positions in the boundary data profiles proved the sequential operation of multiplexers and successful wireless transmission of digital bits. Reconstructed images and their image parameters proved that the boundary data are successfully acquired by the DAQ system which in turn again indicates a sequential and proper operation of multiplexers as well as the successful wireless transmission of digital bits. Hence the developed RF based wireless digital data transmission module (WDDTM) is found suitable for transmitting digital bits required for electrode switching in wireless EIT data acquisition system. (C) 2011 Elsevier Ltd. All rights reserved.

Switching of a Sixteen Electrode Array for Wireless EIT System Using a RF-Based 8-Bit Digital Data Transmission Technique

Surface electrode switching of 16-electrode wireless EIT is studied using a Radio Frequency (RF) based digital data transmission technique operating with 8 channel encoder/decoder ICs. An electrode switching module is developed the analog multiplexers and switched with 8-bit parallel digital data transferred by transmitter/receiver module developed with radio frequency technology. 8-bit parallel digital data collected from the receiver module are converted to 16-bit digital data by using binary adder circuits and then used for switching the electrodes in opposite current injection protocol. 8-bit parallel digital data are generated using NI USB 6251 DAQ card in LabVIEW software and sent to the transmission module which transmits the digital data bits to the receiver end. Receiver module supplies the parallel digital bits to the binary adder circuits and adder circuit outputs are fed to the multiplexers of the electrode switching module for surface electrode switching. 1 mA, 50 kHz sinusoidal constant current is injected at the phantom boundary using opposite current injection protocol. The boundary potentials developed at the voltage electrodes are measured and studied to assess the wireless data transmission.

Phase control of switching from positive to negative index material in a four-level atomic system

Electric and magnetic responses of the medium to the probe field are analysed in a four-level loop atomic system by taking into account the relative phase of the applied fields. An interesting phenomenon is found: under suitable conditions, a change of the refractive index from positive to negative can occur by modulating the relative phase of the applied fields. Then the medium can be switched from a positive index material to a negative index material in our scheme. In addition, a negative index material can be realized in different frequency regions by adjusting the relative phase. It may give us a convenient way to obtain the desired material with positive or negative index.

Fluoxetine and norfluoxetine analysis by direct injection of human plasma in a column switching liquid chromatographic system

A column switching LC method is presented for the analysis of fluoxetine (FLU) and norfluoxetine (NFLU) by direct injection of human plasma using a lab-made restricted access media (RAM) column. A RAM-BSA-octadecyl silica (C-18) column (40 min x 4.6 mm, 10 mu m) is evaluated in both backflush and foreflush elution modes and coupled with a C-18 lab-made (50 mm x 4.6 mm, 3 pm) analytical column in order to perform online sample preparation. Direct injection of 100 mu L, of plasma samples is possible with the developed approach. In addition, reduction of sample handling is obtained when compared with traditional liquid-liquid extraction (LLE) and SPE. The total analysis time is around 20 min. A LOQ of 15 ng/mL is achieved in a concentration range of 15-500 ng/mL, allowing the therapeutic drug monitoring of clinical samples. The precision values achieved are lower than 15% for all the evaluated points with adequate recovery and accuracy. Furthermore, no matrix interferences are found in the analysis and the proposed method shows to be an adequate alternative for analysis of FLU in plasma.