A Comparison of Education in Post-Revolutionary Mexico and Post-Independence India

Comparison, Education, History, India, Mexic

Simple Mechanically Reconfigurable Patch Antennas

Reconfigurable antennas form an active subdivision of antenna and communications research primarily targeted at achieving reconfigurability in the RF, microwave, and millimeter-wave frequency regimes. Mechanical, all-electronic, material based, and optical methods are the most common approaches to achieve reconfigurability. Each method can overlap to create new and innovative approaches to enable device tunability. The sub-class of reconfigurable antennas are antennas that dynamically achieve an adaptable transformation of their frequency, radiation-pattern, polarization, and/or bandwidth characteristics to enable multiple dynamic functionalities. In this thesis, we designed new rectangular and triangular microstrip patch array antennas operating in the 5G midband at 5GHz. These patch antennas were designed and inspired by the Yagi-Uda antenna, where the driven and passive director or parasitic patches are the main elements. It was found that by increasing the number of parasitic elements, the antenna’s gain can be improved, despite some impedance mismatch. The triangular patch array with the best result was then selected to further investigate its reconfigurability capability using two simple mechanically reconfigurable approaches, i.e., 1) single-plane and 2) double-plane patch arrays, focusing on the radiation pattern, gain, and operating frequency, and other antenna performances. The single-side and double-side folded structures were examined in both approaches, while the folded feeding line and curvature folded substrate were also studied in the single-plane patch array. The results provided clear evidence that by folding the substrate at varying angles one can effectively manipulate the antenna\u27s radiation pattern, gain, and center operating frequency location. The impact varies with the degree of folding, signifying a direct relationship between the folding angle and the returning loss or S11 value. Three proposed microstrip array antennas, i.e., the single-plane patch antenna array, the triangle microstrip array, and the microstrip Yagi-Uda antenna array, were fabricated and tested. The simulation and measurement results are in good agreement

One-Shot Learning for Periocular Recognition: Exploring the Effect of Domain Adaptation and Data Bias on Deep Representations

One weakness of machine-learning algorithms is the need to train the models for a new task. This presents a specific challenge for biometric recognition due to the dynamic nature of databases and, in some instances, the reliance on subject collaboration for data collection. In this paper, we investigate the behavior of deep representations in widely used CNN models under extreme data scarcity for One-Shot periocular recognition, a biometric recognition task. We analyze the outputs of CNN layers as identity-representing feature vectors. We examine the impact of Domain Adaptation on the network layers' output for unseen data and evaluate the method's robustness concerning data normalization and generalization of the best-performing layer. We improved state-of-the-art results that made use of networks trained with biometric datasets with millions of images and fine-tuned for the target periocular dataset by utilizing out-of-the-box CNNs trained for the ImageNet Recognition Challenge and standard computer vision algorithms. For example, for the Cross-Eyed dataset, we could reduce the EER by 67% and 79% (from 1.70% and 3.41% to 0.56% and 0.71%) in the Close-World and Open-World protocols, respectively, for the periocular case. We also demonstrate that traditional algorithms like SIFT can outperform CNNs in situations with limited data or scenarios where the network has not been trained with the test classes like the Open-World mode. SIFT alone was able to reduce the EER by 64% and 71.6% (from 1.7% and 3.41% to 0.6% and 0.97%) for Cross-Eyed in the Close-World and Open-World protocols, respectively, and a reduction of 4.6% (from 3.94% to 3.76%) in the PolyU database for the Open-World and single biometric case.Comment: Submitted preprint to IEE Acces

Cross-Spectral Periocular Recognition with Conditional Adversarial Networks

This work addresses the challenge of comparing periocular images captured in different spectra, which is known to produce significant drops in performance in comparison to operating in the same spectrum. We propose the use of Conditional Generative Adversarial Networks, trained to con-vert periocular images between visible and near-infrared spectra, so that biometric verification is carried out in the same spectrum. The proposed setup allows the use of existing feature methods typically optimized to operate in a single spectrum. Recognition experiments are done using a number of off-the-shelf periocular comparators based both on hand-crafted features and CNN descriptors. Using the Hong Kong Polytechnic University Cross-Spectral Iris Images Database (PolyU) as benchmark dataset, our experiments show that cross-spectral performance is substantially improved if both images are converted to the same spectrum, in comparison to matching features extracted from images in different spectra. In addition to this, we fine-tune a CNN based on the ResNet50 architecture, obtaining a cross-spectral periocular performance of EER=1%, and GAR>99% @ FAR=1%, which is comparable to the state-of-the-art with the PolyU database.Comment: Accepted for publication at 2020 International Joint Conference on Biometrics (IJCB 2020

Diseño e implementación de combinadores de potencia para amplificador LINC @ 868MHz

The ISM is a free band generally used in the environmental scientific and medical study. The regulation depends on the government of each country. This study is focused on the European¡¯s level frequency of 868 MHz, this frequency does not require standards or permissions, as long as they do not exceed the regulations. The project was based on the realization of a LINC transmitter with class E amplifiers made of passive matching networks. Also, the design and production of three combiners: Hybrid 90¨¬, Wilkinson and Chireix. In this project we have seen the different existing types of amplifiers (Class A, Class B ...) and the two main transistors that we can find in the market (BJT and FET). The amplifier¡¯s design was done using the ADS program from Agilent, and to characterize matching networks we have used the Smith Chart and ADS LineCalc. The first thing was find the polarization voltages, to characterize the S parameters of the transistor. The stability calculations have been made as theoretical as graphically (ADS). Matching networks are realized with passive elements such as coils and capacitors, that has been the difference of previous studies. At this point of the project the tunning tool was used to refine the results. The Bias Network were designed with shock coils and decoupling capacitors. The last step was the design of the layout with ADS software and then assembled. The other branch of the study has been the design and implementation of three combiners, for the simulation of both the ADS program was also used and finally took the design to a board. The results obtained for the amplifier with matching networks made of passive elements were good only for one channel. For this reason we have had to continue the combiners study with a project implemented earlier by another student, made with ¥ë / 4 lines. As we have seen in the laboratory, the Chireix combiner is positioned as the most efficient and which allows the maximum gain. Future studies may try to improve the performance of a class E type LINC amplifier with stable matching networks made of passive elements, as well as, improve the efficiency of the Chireix combiner and open new ways of study.La banda ISM es una banda libre que generalmente se usa en el estudio medioambiental, científico y médico. La normativa depende del gobierno de cada territorio. Este estudio se ha centrado en el ámbito europeo a la frecuencia de 868 MHz. Esta frecuencia no requiere de estándares ni permisos siempre que no supere la normativa