Optimal Code Set Selection and Security Issues in Spectral Phase-Encoded Time Spreading (SPECTS) OCDMA Systems

In this paper, we perform a thorough analysis of a spectral phase-encoded time spreading optical code division multiple access (SPECTS-OCDMA) system based on Walsh-Hadamard (W-H) codes aiming not only at finding optimal code-set selections but also at assessing its loss of security due to crosstalk. We prove that an inadequate choice of codes can make the crosstalk between active users to become large enough so as to cause the data from the user of interest to be detected by other user. The proposed algorithm for code optimization targets code sets that produce minimum bit error rate (BER) among all codes for a specific number of simultaneous users. This methodology allows us to find optimal code sets for any OCDMA system, regardless the code family used and the number of active users. This procedure is crucial for circumventing the unexpected lack of security due to crosstalk. We also show that a SPECTS-OCDMA system based on W-H 32(64) fundamentally limits the number of simultaneous users to 4(8) with no security violation due to crosstalk. More importantly, we prove that only a small fraction of the available code sets is actually immune to crosstalk with acceptable BER (<10(-9)) i.e., approximately 0.5% for W-H 32 with four simultaneous users, and about 1 x 10(-4)% for W-H 64 with eight simultaneous users.

Approach to Food and Nutrition issues in Teaching Materials in Elementary School: interface with food and nutritional security and national curriculum parameters

Food and Nutrition Security (FNS) must be ensured to everybody. The school environment is favorable to the formation of healthy habits and citizenship. The National Curriculum Parameters (PCNs) guide the promotion of health concepts in a transversal way in the school curriculum. This study aimed to identify and analyze the approach used for food and nutrition themes in Fundamental Education's teaching material and its interface with the concept of FNS and the PCNs. Documental research was conducted on the teaching material from 5th to 8th grades of Fundamental Education in Public School of the state of Sao Paulo. The diffuse presence of food and nutrition themes was found in most disciplines in all bimesters in the four series, which shows the interdisciplinarity in health. It was found that the PCNs are related to the concept of SAN in its various aspects and that most subjects include topics that approach this relationship. In the correlation between themes, there is emphasis to health promotion and food production. The methodology used in the teaching material presents the theme, but not the correspondent content, what made the analysis of its suitability impossible. We conclude that there is the approach of the issues related to food and nutrition in the teaching material, some of them in an inconsistent way; it is the educators' task to select the contents and the appropriate strategy, doing an effort of constant update. This isbeing proposed by the State, however it is not accessible to all professionals and therefore still depends on the initiative of each teacher.