3,484 research outputs found
Linear cryptanalysis of pseudorandom functions
Relatório de projeto de pesquisa.In this paper, we study linear relations propagating across block ciphers from the key input to the ciphertext (for a fixed plaintext block). This is a usual setting of a one-way function, used for instance in modes of operation such as KFB (key feedback). We instantiate the block cipher with the full 16-round DES and -DES, 10-round LOKI91 and 24-round Khufu, for which linear relations with high bias are well known. Other interesting targets include the full 8.5-round IDEA and PES ciphers for which high bias linear relations exist under the assumption of weak keys. Consequences of these findings impact the security of modes of operation such as KFB and of pseudorandom number/bit generators. These analyses were possible due to the linear structure and the poor diffusion of the key schedule algorithms. These findings shall motivate carefull (re)design of current and future key schedule algorithms
Computer science: Key to a space program renaissance. The 1981 NASA/ASEE summer study on the use of computer science and technology in NASA. Volume 2: Appendices
Adoption of an aggressive computer science research and technology program within NASA will: (1) enable new mission capabilities such as autonomous spacecraft, reliability and self-repair, and low-bandwidth intelligent Earth sensing; (2) lower manpower requirements, especially in the areas of Space Shuttle operations, by making fuller use of control center automation, technical support, and internal utilization of state-of-the-art computer techniques; (3) reduce project costs via improved software verification, software engineering, enhanced scientist/engineer productivity, and increased managerial effectiveness; and (4) significantly improve internal operations within NASA with electronic mail, managerial computer aids, an automated bureaucracy and uniform program operating plans
Advanced Automation for Space Missions
The feasibility of using machine intelligence, including automation and robotics, in future space missions was studied
Exposure of tropical ecosystems to artificial light at night: Brazil as a case study
Artificial nighttime lighting from streetlights and other sources has a broad range of biological effects.
Understanding the spatial and temporal levels and patterns of this lighting is a key step in determining
the severity of adverse effects on different ecosystems, vegetation, and habitat types. Few such
analyses have been conducted, particularly for regions with high biodiversity, including the tropics.
We used an intercalibrated version of the Defense Meteorological Satellite Program’s Operational
Linescan System (DMSP/OLS) images of stable nighttime lights to determine what proportion of
original and current Brazilian vegetation types are experiencing measurable levels of artificial light
and how this has changed in recent years. The percentage area affected by both detectable light and
increases in brightness ranged between 0 and 35% for native vegetation types, and between 0 and
25% for current vegetation (i.e. including agriculture). The most heavily affected areas encompassed
terrestrial coastal vegetation types (restingas and mangroves), Semideciduous Seasonal Forest, and
Mixed Ombrophilous Forest. The existing small remnants of Lowland Deciduous and Semideciduous
Seasonal Forests and of Campinarana had the lowest exposure levels to artificial light. Light pollution
has not often been investigated in developing countries but our data show that it is an environmental
concern
I Congresso Brasileiro da Indústria: momento de consolidação das ideias de Roberto Simonsen como parte da ideologia da burguesia industrial brasileira
O presente trabalho tem o objetivo de debater a hipótese de que as ideias defendidas pelo intelectual e empresário Roberto Simonsen foram assimiladas pelo grupo industrialista e tornaram-se parte da dinâmica de construção de um pensamento dos industriais brasileiros da época, sendo o momento desta convergência a realização do I Congresso Brasileiro da Indústria, em 1948. Para tanto, partimos da análise dos Anais do I Congresso Brasileiro da Indústria, analisamos as propostas aprovadas e os discursos apresentados pelas autoridades presentes, bem como apresentamos em parte as obras e ideias de Simonsen, demonstrando como tais questões deixaram de ser parte de seu leque de pensamentos para integrar a base ideológica da então classe industrial brasileira
Multivariable control strategy for a bucket wheel reclaimer / Estratégia de controle multivariável de retomadora de roda de alcatruzes
Mining operations are generally done by large machines working in very harsh environments and historically having shy embedded technology. The use of control strategies, in many cases, dramatically increases the operating efficiency without large financial investments. In this context, this paper presents the method of choice and practical application of a multivariable control strategy for a bucket wheel ore reclaimer. This strategy adopts PI and PID controllers following a type override strategy acting on the manipulated variable: the slewing angular velocity. This manipulated variable was chosen because its actions affect the controlled variable very fast, so, allowing correcting disturbances in an adequate time. In addition, a fuzzy type controller was implemented to act on a second manipulated variable: the translation step. The second manipulated variable aims at taking the first one (angular speed) out of saturation states. When working together, these controllers seek to increase the equipment and process performance, taking into account, however, their operating limitations. Finally, a statistical analysis of results was performed in order to validate the feasibility of the implanted strategy when compared with the method previously in operation
Efficient Battery Usage in Wireless-Powered Cell-Free Systems with Self-Energy Recycling
This paper investigates wireless-powered cell-free systems, in which the
users send their uplink data signal while simultaneously harvesting energy from
network nodes and user terminals - including the transmitting user terminal
itself - by performing self-energy recycling. In this rather general setting, a
closed-form lower bound of the amount of harvested energy and the achieved
signal-to-interference-plus-noise ratio expressions are derived. Then, to
improve the energy efficiency, we formulate the problem of minimizing the
users' battery energy usage while satisfying minimum data rate requirements.
Due to the non-convexity of the problem, a novel alternating optimization
algorithm is proposed, and its proof of convergence is provided. Finally,
numerical results show that the proposed method is more efficient than a
state-of-art algorithm in terms of battery energy usage and outage rate.Comment: Accepted as a correspondance at IEEE TV
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