Formation of elliptically polarized beam from h-plane sectoral horns using corrugated flanges

The flange technique, suggested by Reynolds72 is simple technique to improve antenna characteristics. Using flange technique we can trim the antenna characteristic by suitably adjusting the flange parameters75. Later corrugated flanges87 are used for beam shaping. The important parameters of the corrugated flanges are (a) flange angle, (b) flange width, (c) flange position, (d) conductivity of the flange, (e) amplitude excitation of the flange elements, (f) period of corrugation etc. Compared to a compound horn the flange technique offers great convenience in trimming antenna characteristics. Horns are commonly used as a feed in radar and satellite communications. A large number of work had been done to improve the characteristics of horn antennas. It is an established fact that grooved walls on the inner surface of a horn can improve the antenna characteristics44. Corrugated comb surface can be used for the circular polarization98, tilt of polarization99 etc. This suggests the possibility to combine these two phenomena and to obtain a resultant beam. This thesis presents the result of an investigation to study the possibility of controlling different antenna characteristics like polarization, beam shaping, matching etc, using corrugated flange techniques.

Investigations on the radiation characteristics of flanged sectoral horn antennas and corner reflector systems

Antennas play an important role in determining the characteristics of any electronic system which depends on free space as the propagation medium. Basically, an antenna can be considered as the connecting link between free space and the transmitter or receiver. For radar and navigational purposes the directional properties of an antenna is its most basic requirement as it determines the distribution of radiated energy. Hence the study of directional properties of antennas has got special significance and several useful applications.

Variation in radio refractivity index associated with formation of low - pressure systems

Numerous low - pressure systems form in the Arabian Sea and Bay of Bengal. These low-pressure systems are highly useful in bringing the rainfall over the Indian sub continent. The developments of these systems are accompanied by the reduction in air temperature and an increase in atmospheric humidity. The radio refractivity, which is a function of the atmospheric pressure, temperature and humidity, also changes following the development of these systems. Variation of radio refractive index and its vertical gradient are analysed for many low pressure systems formed over the Arabian Sea and Bay of Bengal. It is found that the atmosphere becomes super refractive associated with the formation of these systems, caused by the increase in humidity and decrease in temperature. The maximum gradient is observed near the surface layers, especially in the lowest 1 km. Super refraction leads to increased radar detection range and extension of radio horizon

Diurnal Structure of Monsoon Boundary Layer

The characteristics of the monsoon boundary layer are imperative to understand in the perception of the tropical regions. The southwest monsoon is associated with a strong wind in the lower troposphere near 1.5 km and is referred to as Low Level Jet stream (LLJ). The boundary layer structure associated with the LLJ during monsoon can be studied using L-band Ultra High Frequency (UHF) radar. This L-band wind profiler-commonly referred as lower atmospheric wind profiler (LAWP), was installed at NARL, Gadanki. Zonal, meridional and vertical wind components are used to understand the diurnal variation of the wind in the Atmospheric Boundary Layer (ABL) and associated features. From the analysis during non rainy days of the southwest monsoon, it is found that the LLJ has maximum strength during the early morning hours at lower level and the height increases as day progresses. The vertical wind shows the transfer of momentum from the LLJ towards the surface, indicating the sinking motion during the daytime. Vertical gradient of the wind shear shows the intensity of clear air turbulence is moderate and no severe clear air turbulence is noticed during the monsoon period

The diagnosis of severe thunderstorms with high-resolution WRF model

Thunderstorm, resulting from vigorous convective activity, is one of the most spectacular weather phenomena in the atmosphere. A common feature of the weather during the pre-monsoon season over the Indo-Gangetic Plain and northeast India is the outburst of severe local convective storms, commonly known as ‘Nor’westers’(as they move from northwest to southeast). The severe thunderstorms associated with thunder, squall lines, lightning and hail cause extensive losses in agricultural, damage to structure and also loss of life. In this paper, sensitivity experiments have been conducted with the Non-hydrostatic Mesoscale Model (NMM) to test the impact of three microphysical schemes in capturing the severe thunderstorm event occurred over Kolkata on 15 May 2009. The results show that the WRF-NMM model with Ferrier microphysical scheme appears to reproduce the cloud and precipitation processes more realistically than other schemes. Also, we have made an attempt to diagnose four severe thunderstorms that occurred during pre-monsoon seasons of 2006, 2007 and 2008 through the simulated radar reflectivity fields from NMM model with Ferrier microphysics scheme and validated the model results with Kolkata Doppler Weather Radar (DWR) observations. Composite radar reflectivity simulated by WRF-NMM model clearly shows the severe thunderstorm movement as observed by DWR imageries, but failed to capture the intensity as in observations. The results of these analyses demonstrated the capability of high resolution WRF-NMM model in the simulation of severe thunderstorm events and determined that the 3 km model improve upon current abilities when it comes to simulating severe thunderstorms over east Indian region

Predicted impact of the sea-level rise at VellareColeroon estuarine region of Tamil Nadu coast in India: Mainstreaming adaptation as a coastal zone management option

Low-lying coastal areas are more vulnerable to the impacts of climate change as they are highly prone for inundation to SLR (Sea-Level Rise). This study presents an appraisal of the impacts of SLR on the coastal natural resources and its dependent social communities in the low-lying area of VellareColeroon estuarine region of the Tamil Nadu coast, India. Digital Elevation Model (DEM) derived from SRTM 90M (Shuttle Radar Topographic Mission) data, along with GIS (Geographic Information System) techniques are used to identify an area of inundation in the study site. The vulnerability of coastal areas in Vellar-Coleroon estuarine region of Tamil Nadu coast to inundation was calculated based on the projected SLR scenarios of 0.5 m and 1 m. The results demonstrated that about 1570 ha of the LULC (Land use and Land cover) of the study area would be permanently inundated to 0.5 m and 2407 ha for 1 m SLR and has also resulted in the loss of three major coastal natural resources like coastal agriculture, mangroves and aquaculture. It has been identified that six hamlets of the social communities who depend on these resources are at high-risk and vulnerable to 0.5 m SLR and 12 hamlets for 1 m SLR. From the study, it has been emphasized that mainstreaming adaptation options to SLR should be embedded within a coastal zone management and planning effort, which includes all coastal natural resources (ecosystem-based adaptation), and its dependent social communities (community-based adaptation) involved through capacity building

APSYM 2014

14th Biennial International Symposium on Antennas and propagation Department of Electronics, Cochin University of Science & Technology, Cochin 682022, INDIA

Design and Development of Compact Chipless RFID Tags with High Data Encoding Capacity

The main objective of this thesis is to develop a compact chipless RFID tag with high data encoding capacity. The design and development of chipless RFID tag based on multiresonator and multiscatterer methods are presented first. An RFID tag using using SIR capable of 79bits is proposed. The thesis also deals with some of the properties of SIR like harmonic separation, independent control on resonant modes and the capability to change the electrical length. A chipless RFID reader working in a frequency band of 2.36GHz to 2.54GHz has been designed to show the feasibility of the RFID system. For a practical system, a new approach based on UWB Impulse Radar (UWB IR) technology is employed and the decoding methods from noisy backscattered signal are successfully demonstrated. The thesis also proposes a simple calibration procedure, which is able to decode the backscattered signal up to a distance of 80cm with 1mW output power.

Assessment of land use and land cover changes during the last 50 years in oases and surrounding rangelands of Xinjiang, NW China

An analysis of historical Corona images, Landsat images, recent radar and Google Earth® images was conducted to determine land use and land cover changes of oases settlements and surrounding rangelands at the fringe of the Altay Mountains from 1964 to 2008. For the Landsat datasets supervised classification methods were used to test the suitability of the Maximum Likelihood Classifier with subsequent smoothing and the Sequential Maximum A Posteriori Classifier (SMAPC). The results show a trend typical for the steppe and desert regions of northern China. From 1964 to 2008 farmland strongly increased (+ 61%), while the area of grassland and forest in the floodplains decreased (- 43%). The urban areas increased threefold and 400 ha of former agricultural land were abandoned. Farmland apparently affected by soil salinity decreased in size from 1990 (1180 ha) to 2008 (630 ha). The vegetated areas of the surrounding rangelands decreased, mainly as a result of overgrazing and drought events.The SMAPC with subsequent post processing revealed the highest classification accuracy. However, the specific landscape characteristics of mountain oasis systems required labour intensive post processing. Further research is needed to test the use of ancillary information for an automated classification of the examined landscape features.

An Analysis of the Effect of Gaussian Error in Object Recognition

Object recognition is complicated by clutter, occlusion, and sensor error. Since pose hypotheses are based on image feature locations, these effects can lead to false negatives and positives. In a typical recognition algorithm, pose hypotheses are tested against the image, and a score is assigned to each hypothesis. We use a statistical model to determine the score distribution associated with correct and incorrect pose hypotheses, and use binary hypothesis testing techniques to distinguish between them. Using this approach we can compare algorithms and noise models, and automatically choose values for internal system thresholds to minimize the probability of making a mistake.

Alignment by Maximization of Mutual Information

A new information-theoretic approach is presented for finding the pose of an object in an image. The technique does not require information about the surface properties of the object, besides its shape, and is robust with respect to variations of illumination. In our derivation, few assumptions are made about the nature of the imaging process. As a result the algorithms are quite general and can foreseeably be used in a wide variety of imaging situations. Experiments are presented that demonstrate the approach registering magnetic resonance (MR) images with computed tomography (CT) images, aligning a complex 3D object model to real scenes including clutter and occlusion, tracking a human head in a video sequence and aligning a view-based 2D object model to real images. The method is based on a formulation of the mutual information between the model and the image called EMMA. As applied here the technique is intensity-based, rather than feature-based. It works well in domains where edge or gradient-magnitude based methods have difficulty, yet it is more robust than traditional correlation. Additionally, it has an efficient implementation that is based on stochastic approximation. Finally, we will describe a number of additional real-world applications that can be solved efficiently and reliably using EMMA. EMMA can be used in machine learning to find maximally informative projections of high-dimensional data. EMMA can also be used to detect and correct corruption in magnetic resonance images (MRI).

Liderazgo e innovación dentro del sistema de negocio. Estudio de caso de la campaña AmeriTel en Teleperformance Colombia

Uno de los retos más complejos que enfrentan los líderes de las empresas es obtener resultados que las hagan perdurables a lo largo del tiempo. Usualmente, la innovación es vista como una estrategia para mejorar los resultados a corto plazo y el liderazgo como habilitador de su implementación. Sin embargo, la innovación también puede ser vista como parte central del sistema de negocio, y las prácticas del liderazgo como facilitadores que permitan mejorar los resultados no sólo a corto, sino también a mediano y largo plazo. Con base en lo anterior, se realizó un estudio de caso en la campaña de AmeriTel en Teleperformance Colombia para analizar la asociación que tiene el liderazgo y la innovación con sus resultados, y cómo esta relación se refleja en la perdurabilidad de la campaña. De acuerdo a los hallazgos de la investigación, se puede observar el desempeño de una campaña que está enfocada en resultados, en cómo cambia la perspectiva y efectividad de todo el personal, pasando de la innovación de un nuevo modelo de gestión visto como estrategia, al mismo modelo visto como innovación dentro del modelo de negocio, el círculo del cambio y la aplicación de un liderazgo efectivo.

Caracterización de la utilización de innovación en el sector bancario: Una aproximación hacia la adquisición de ventajas competitivas

Investigación exploratoria mixta siguiendo un método deductivo con la que se logró caracterizar el grado de utilización de innovación en el sector bancario y su utilidad en la adquisición de ventajas competitivas con la ayuda de del modelo del Radar de Innovación.

Plan de negocios para la exportación de tarjetas de felicitación e internacionalización de la empresa alternativas expresión

Este trabajo muestra el plan de internacionalización de la empresa Alternativas Expresión, la cual está dedicada a la fabricación y comercialización de productos de expresión social como tarjetas, chocolates y empaques. De esta forma, el estudio se enfocó principalmente en la exportación de Tarjetas de Felicitación, se desarrollaron varias metodologías como el análisis del potencial exportador de la empresa y el estudio de la competencia nacional e internacional. Posteriormente se evaluaron variables macro económicas, comercio internacional y de selección, en once países del norte, centro y sur de América, de los cuales se seleccionaron tres mercados Estados Unidos, Chile y Panamá. Después de la fase de selección de mercados, se elaboró una descripción detallada de cada país seleccionado y se procedió a realizar el trabajo de campo para el país potencial, Estados Unidos. En donde se consideraron diferentes factores como demanda, producto, precio, canales de distribución, competencia, y distribución física internacional. Finalmente, se propuso un plan de mejoramiento para la empresa Alternativas Expresión, con el propósito de minimizar las debilidades que se identificaron en el estudio del potencial exportador y maximizar las oportunidades detalladas en el análisis de la competencia y el trabajo de campo en Estados Unidos.

La conciliación administrativa en Colombia

Descripción histórica de la conciliación desde sus inicios hasta llegar a nuestros días y en forma especial al tratamiento que el ordenamiento jurídico colombiano realiza. Se crea una definición de la misma, se clasifica