An alternate method for achieving temperature control in the -130 C to 75 C range

Thermal vacuum testing often requires temperature control of chamber shrouds and heat exchangers within the -130 C to 75 C range. There are two conventional methods which are normally employed to achieve control through this intermediate temperature range: (1) single-pass flow where control is achieved by alternately pulsing hot gaseous nitrogen (GN2) and cold LN2 into the feed line to yield the setpoint temperature; and (2) closed-loop circulation where control is achieved by either electrically heating or LN2 cooling the circulating GN2 to yield the setpoint temperature. A third method, using a mass flow ratio controller along with modulating control valves on GN2 and LN2 lines, provides excellent control but equipment for this method is expensive and cost-prohibitive for all but long-term continuous processes. The single-pass method provides marginal control and can result in unexpected overcooling of the test article from even a short pulse of LN2. The closed-loop circulation method provides excellent control but requires an expensive blower capable of operating at elevated pressures and cryogenic temperatures. Where precise control is needed (plus or minus 2 C), single-pass flow systems typically have not provided the precision required, primarily because of overcooling temperature excursions. Where several individual circuits are to be controlled at different temperatures, the use of expensive cryogenic blowers for each circuit is also cost-prohibitive, especially for short duration of one-of-a-kind tests. At JPL, a variant of the single-pass method was developed that was shown to provide precise temperature control in the -130 C to 75 C range while exhibiting minimal setpoint overshoot during temperature transitions. This alternate method uses a commercially available temperature controller along with a GN2/LN2 mixer to dampen the amplitude of cold temperature spikes caused by LN2 pulsing. The design of the GN2/LN2 mixer, the overall control system configuration, the operational procedure, and the prototype system test results are described

A new approach for performing contamination control bakeouts in JPL thermal vacuum test chambers

Contamination control requirements for the Wide Field/Planetary Camera II (WF/PC II) are necessarily stringent to protect against post-launch contamination of the sensitive optical surfaces, particularly the cold charge coupled device (CCD) imaging surfaces. Typically, thermal vacuum test chambers have employed a liquid nitrogen (LN2) cold trap to collect outgassed contaminants. This approach has the disadvantage of risking recontamination of the test article from shroud offgassing during post-test warmup of the chamber or from any shroud warming of even a few degrees during the bakeout process. By using an enclave, essentially a chamber within a chamber, configured concentrically and internally within an LN2 shroud, a method was developed, based on a design concept by Taylor, for preventing recontamination of test articles during bakeouts and subsequent post-test warmup of the vacuum chamber. Enclaves for testing WF/PC II components were designed and fabricated, then installed in three of JPL's Environmental Test Lab chambers. The design concepts, operating procedures, and test results of this development are discussed

Manual de árvore hiperbólica.

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Motion Consistency Loss for Monocular Visual Odometry with Attention-Based Deep Learning

Deep learning algorithms have driven expressive progress in many complex tasks. The loss function is a core component of deep learning techniques, guiding the learning process of neural networks. This paper contributes by introducing a consistency loss for visual odometry with deep learning-based approaches. The motion consistency loss explores repeated motions that appear in consecutive overlapped video clips. Experimental results show that our approach increased the performance of a model on the KITTI odometry benchmark

El Estado de Salud de los Jóvenes Uruguayos

This work studies the health status of young Uruguayan population based on the Survey on Health and Social Networks, carried by Department of Economics of the Faculty of Social Sciences of the UdelaR, during the year 2004. Through an ordered probit model,Health status, young people, risky behaviour, Uruguay

Dense Prediction Transformer for Scale Estimation in Monocular Visual Odometry

Monocular visual odometry consists of the estimation of the position of an agent through images of a single camera, and it is applied in autonomous vehicles, medical robots, and augmented reality. However, monocular systems suffer from the scale ambiguity problem due to the lack of depth information in 2D frames. This paper contributes by showing an application of the dense prediction transformer model for scale estimation in monocular visual odometry systems. Experimental results show that the scale drift problem of monocular systems can be reduced through the accurate estimation of the depth map by this model, achieving competitive state-of-the-art performance on a visual odometry benchmark

Aprendizagem e disseminação de conhecimento nos colaboratórios das redes de pesquisa da Embrapa.

O objetivo deste artigo é apresentar e discutir uma proposta de modelo conceitual para a criação de Colaboratórios para as redes de pesquisa da Embrapa. Os Colaboratórios são espaços virtuais de aprendizagem que, estruturados sob uma lógica sócio-interacionista e com ferramentas da web 2.0, tendem a potencializar a construção de novos conhecimentos e aprendizagens entre os cientistas das redes de pesquisa, fomentando também a aprendizagem organizacional.SBIE 2012

Autonomous Agent for Beyond Visual Range Air Combat: A Deep Reinforcement Learning Approach

This work contributes to developing an agent based on deep reinforcement learning capable of acting in a beyond visual range (BVR) air combat simulation environment. The paper presents an overview of building an agent representing a high-performance fighter aircraft that can learn and improve its role in BVR combat over time based on rewards calculated using operational metrics. Also, through self-play experiments, it expects to generate new air combat tactics never seen before. Finally, we hope to examine a real pilot's ability, using virtual simulation, to interact in the same environment with the trained agent and compare their performances. This research will contribute to the air combat training context by developing agents that can interact with real pilots to improve their performances in air defense missions

Uso de regras de associação para enriquecer o suporte do planejamento agrícola municipal: estudo de caso.

As técnicas de mineração de dados são úteis para explorar padrões em grandes banco de dados, subsidiando novos conhecimentos. Essas técnicas tem sido usadas com sucesso em diversas áreas, da comercial a científica. O objetivo deste trabalho é apresentar um estudo de caso em Taquarituba-SP, onde os dados das propriedades rurais foram coletados e submetidos à regras de associação, uma das tarefa da mineração de dados . A eficiência desta tarefa evidenciará novas informações para os municípios, destacando pontos fortes e fracos e enriquecerá os subsídios para o planejamento rural municipal.SBIAgro 2009