Digital Dead Time Logic and Protection Circuitry for PWM Voltage Source Converters

Power semiconductor devices have finite turn on and turn off delays that may not be perfectly matched. In a leg of a voltage source converter, the simultaneous turn on of one device and the turn off of the complementary device will cause a DC bus shoot through, if the turn off delay is larger than the turn on delay time. To avoid this situation it is common practice to blank the two complementary devices in a leg for a small duration of time while switching, which is called dead time. This paper proposes a logic circuit for digital implementation required to control the complementary devices of a leg independently and at the same time preventing cross conduction of devices in a leg, and while providing accurate and stable dead time. This implementation is based on the concept of finite state machines. This circuit can also block improper PWM pulses to semiconductor switches and filters small pulses notches below a threshold time width as the narrow pulses do not provide any significant contribution to average pole voltage, but leads to increased switching loss. This proposed dead time logic has been implemented in a CPLD and is implemented in a protection and delay card for 3- power converters.

Fuzzy logic based TCSC supplementary controller for damping of inter area oscillations in power system

This paper describes an application of a FACTS supplementary controller for damping of inter area oscillations in power systems. A fuzzy logic controller is designed to regulate a thyristor controlled series capacitor (TCSC) in a multimachine environment to produce additional damping in the system. Simultaneous application of the excitation controller and proposed controller is also investigated. Simulation studies have been done with different types of disturbances and the results are shown to be consistent with the expected performance of the supplementary controller.

An Optimal Fuzzy Logic Controller tuned with Artificial Immune System

In this paper, a method for the tuning the membership functions of a Mamdani type Fuzzy Logic Controller (FLC) using the Clonal Selection Algorithm(CSA) a model of the Artificial Immune System(AIS) paradigm is examined. FLC's are designed for two problems, firstly the linear cart centering problem and secondly the highly nonlinear inverted pendulum problem. The FLC tuned by AIS is compared with FLC tuned by GA. In order to check the robustness of the designed PLC's white noise was added to the system, further, the masses of the cart and the length and mass of the pendulum are changed. The PLC's were also tested in the presence of faulty rules. Finally, Kruskal Wallis test was performed to compare the performance of the GA and AIS. An insight into the algorithms are also given by studying the effect of the important parameters of GA and AIS.

Dual enzyme responsive microcapsules simulating an ``OR'' logic gate for biologically triggered drug delivery applications

Hollow microcapsules capable of disintegrating in response to dual biological stimuli have been synthesized from two FDA approved drug molecules. The capsules fabricated from protamine and chondroitin sulphate disintegrate in the presence of either trypsin or hyaluronidase enzymes, which are documented to be simultaneously over-expressed under some pathological conditions.

Gene expression programming-fuzzy logic method for crop type classification

Crop type classification using remote sensing data plays a vital role in planning cultivation activities and for optimal usage of the available fertile land. Thus a reliable and precise classification of agricultural crops can help improve agricultural productivity. Hence in this paper a gene expression programming based fuzzy logic approach for multiclass crop classification using Multispectral satellite image is proposed. The purpose of this work is to utilize the optimization capabilities of GEP for tuning the fuzzy membership functions. The capabilities of GEP as a classifier is also studied. The proposed method is compared to Bayesian and Maximum likelihood classifier in terms of performance evaluation. From the results we can conclude that the proposed method is effective for classification.

Delineation of seismic source zones based on seismicity parameters and probabilistic evaluation of seismic hazard using logic tree approach

The delineation of seismic source zones plays an important role in the evaluation of seismic hazard. In most of the studies the seismic source delineation is done based on geological features. In the present study, an attempt has been made to delineate seismic source zones in the study area (south India) based on the seismicity parameters. Seismicity parameters and the maximum probable earthquake for these source zones were evaluated and were used in the hazard evaluation. The probabilistic evaluation of seismic hazard for south India was carried out using a logic tree approach. Two different types of seismic sources, linear and areal, were considered in the present study to model the seismic sources in the region more precisely. In order to properly account for the attenuation characteristics of the region, three different attenuation relations were used with different weightage factors. Seismic hazard evaluation was done for the probability of exceedance (PE) of 10% and 2% in 50 years. The spatial variation of rock level peak horizontal acceleration (PHA) and spectral acceleration (Sa) values corresponding to return periods of 475 and 2500 years for the entire study area are presented in this work. The peak ground acceleration (PGA) values at ground surface level were estimated based on different NEHRP site classes by considering local site effects.

Active yaw control of a vehicle using a Fuzzy logic algorithm

Yaw rate of a vehicle is highly influenced by the lateral forces generated at the tire contact patch to attain the desired lateral acceleration, and/or by external disturbances resulting from factors such as crosswinds, flat tire or, split-μ braking. The presence of the latter and the insufficiency of the former may lead to undesired yaw motion of a vehicle. This paper proposes a steer-by-wire system based on fuzzy logic as yaw-stability controller for a four-wheeled road vehicle with active front steering. The dynamics governing the yaw behavior of the vehicle has been modeled in MATLAB/Simulink. The fuzzy controller receives the yaw rate error of the vehicle and the steering signal given by the driver as inputs and generates an additional steering angle as output which provides the corrective yaw moment. The results of simulations with various drive input signals show that the yaw stability controller using fuzzy logic proposed in the current study has a good performance in situations involving unexpected yaw motion. The yaw rate errors of a vehicle having the proposed controller are notably smaller than an uncontrolled vehicle's, and the vehicle having the yaw stability controller recovers lateral distance and desired yaw rate more quickly than the uncontrolled vehicle.

How Does Effectual Logic Impact Survival of High-tech Startups in an Emerging Economy? - Evidence from 99tests.com Case Study

During the early stages of operation, high-tech startups need to overcome the liability of newness and manage high degree of uncertainty. Several high-tech startups fail due to inability to deal with skeptical customers, underdeveloped markets and limited resources in selling an offering that has no precedent. This paper leverages the principles of effectuation (a logic of entrepreneurial decision making under uncertainty) to explain the journey from creation to survival of high-tech startups in an emerging economy. Based on the 99tests.com case study, this paper suggests that early stage high-tech startups in emerging economies can increase their probability of survival by adopting the principles of effectuation.

Medieval pulse of great earthquakes in the central Himalaya: Viewing past activities on the frontal thrust

The Himalaya has experienced three great earthquakes during the last century1934 Nepal-Bihar, 1950 Upper Assam, and arguably the 1905 Kangra. Focus here is on the central Himalayan segment between the 1905 and the 1934 ruptures, where previous studies have identified a great earthquake between thirteenth and sixteenth centuries. Historical data suggest damaging earthquakes in A.D. 1255, 1344, 1505, 1803, and 1833, although their sources and magnitudes remain debated. We present new evidence for a great earthquake from a trench across the base of a 13m high scarp near Ramnagar at the Himalayan Frontal Thrust. The section exposed four south verging fault strands and a backthrust offsetting a broad spectrum of lithounits, including colluvial deposits. Age data suggest that the last great earthquake in the central Himalaya most likely occurred between A.D. 1259 and 1433. While evidence for this rupture is unmistakable, the stratigraphic clues imply an earlier event, which can most tentatively be placed between A.D. 1050 and 1250. The postulated existence of this earlier event, however, requires further validation. If the two-earthquake scenario is realistic, then the successive ruptures may have occurred in close intervals and were sourced on adjacent segments that overlapped at the trench site. Rupture(s) identified in the trench closely correlate with two damaging earthquakes of 1255 and 1344 reported from Nepal. The present study suggests that the frontal thrust in central Himalaya may have remained seismically inactive during the last similar to 700years. Considering this long elapsed time, a great earthquake may be due in the region.

Saber y poder, prodigios ambiguos e interpretación medieval en el Libro de Alexandre y el Poema de Fernán Gonçález

Resumen: Tanto en el Libro de Alexandre como en el Poema de Fernán Gonçález se presentan prodigios de signifi cación ambigua: el eclipse en el LA, el caballero tragado por la tierra y la serpiente voladora en el PFG. Los episodios en que aparecen insertos estos elementos extraordinarios o sobrenaturales ofrecen una serie de similitudes: el temor de los ejércitos y la habilidad retórica que se despliega para reinterpretar el signo, volverlo a favor del héroe y enardecer así a sus hombres. El objetivo de este trabajo es examinar estos episodios y su signifi cación en el marco de cada uno de los poemas, centrándonos en los problemas de la interpretación y la asignación de sentido, y la relación entre saber y poder que se postula.

La maurofilia en la poesía épica medieval

Resumen: El hispanista francés Georges Cirot fue el primero en emplear el término “maurofilia literaria” (maurophilie littéraire) en 1938 para referirse a la representación del valor y la nobleza de los moros en la literatura española del siglo XVI. Pero como señaló Ramón Menéndez Pidal (1957, 202), ya en los siglos XIV y XV los castellanos se habían sentido atraídos por los musulmanes de Granada, por su exótica civilización, su lujo en el vestir, la espléndida ornamentación de sus edificios y su modo de cabalgar, armarse y combatir. Francisco Márquez Villanueva (1984, 117-118) indicó que aunque la literatura maurófila del siglo XVI fue elaborada bajo el signo avanzado del humanismo cristiano, cuyas características fueron “el inconformismo y la sensibilidad para toda suerte de realidades en divergencia del mundo oficial”, las raíces de la maurofilia literaria se encuentran en el viejo romancero fronterizo y morisco elaborado en el siglo XV. En su opinión, el Romancero fue la patria de la “maurofilia pura” y es donde encontramos un cuadro de referencias temáticas “hecho de toponimia y onomástica, armas, indumentaria, policromía y cabalgadas” tendiente a caracterizar al moro como un ser refinado y superior. Para María Rosa Lida (1960, 355), en cambio, la imagen caballeresca del moro se remonta a don Juan Manuel, pues en sus obras aparecen las cortes musulmanas como “centros de molicie refinada y suntuosa”. En efecto, en el Libro de los estados se afirma el valor del moro como guerrero y en el Conde Lucanor aparecen una serie de reyes moros magnánimos y discretos. Sin embargo, el árabe como personaje sabio o “ejemplar” figura ya en una de las fuentes del Conde Lucanor, la Disciplina clericalis, obra compuesta a principios del siglo XII por el judío converso Pedro Alfonso. Por otra parte, el análisis de la representación de los moros en textos épicos, Avengalvón en el Poema de mio Cid y Almanzor en la Los siete infantes de Lara, nos permite descubrir un importante e insoslayable antecedente de la maurofilia de los últimos siglos de la Edad Media

El concepto de “texto medieval��� en el trabajo ecdótico : un ejemplo surgido de los avatares en la tradición manuscrita de la “Crónica de Sancho IV”

Resumen: La realidad manuscrita del texto medieval implica asumir la problemática en torno al concepto de texto con el que habrá de trabajar el editor al pretender establecer el texto crítico de una obra determinada. Las diferentes concepciones en torno a dicha ontología textual influyen en el tipo particular de trabajo ecdótico que se pretenda realizar. El artículo pretende, a partir del caso de la edición de la Crónica de Sancho IV, proponer un modelo de edición que contemple las variantes que la obra fue manifestando a lo largo de su tradición con el objetivo de dar cuenta de la naturaleza mutable del texto medieval en función de su intencionalidad política.