Sustainable and cost-effective long-term storage remains an unsolved problem. The most widely used storage technologies today are magnetic (hard disk drives and tape). They use media that degrades over time and has a limited lifetime, which leads to inefficient, wasteful, and costly solutions for long-lived data. This article presents Silica: the first cloud storage system for archival data underpinned by quartz glass, an extremely resilient media that allows data to be left in situ indefinitely. The hardware and software of Silica have been co-designed and co-optimized from the media up to the service level with sustainability as a primary objective. The design follows a cloud-first, data-driven methodology underpinned by principles derived from analyzing the archival workload of a large public cloud service. Silica can support a wide range of archival storage workloads and ushers in a new era of sustainable, cost-effective storage.

Sustainable and cost-effective long-term storage remains an unsolved problem. The most widely used storage technologies today are magnetic (hard disk drives and tape). They use media that degrades over time and has a limited lifetime, which leads to inefficient, wasteful, and costly solutions for long-lived data. This paper presents Silica: the first cloud storage system for archival data underpinned by quartz glass, an extremely resilient media that allows data to be left in situ indefinitely. The hardware and software of Silica have been co-designed and co-optimized from the media up to the service level with sustainability as a primary objective. The design follows a cloud-first, data-driven methodology underpinned by principles derived from analyzing the archival workload of a large public cloud service. Silica can support a wide range of archival storage workloads and ushers in a new era of sustainable, cost-effective storage.

We present a vision-based navigation system that uses a visual memory to navigate. Such memory corresponds to a topological map of key images created from moving a virtual camera over a model of the real scene. The advantage of our approach is that it provides a useful insight into the navigability of a visual path without relying on a traditional learning stage. During the navigation stage, the robot is controlled by sequentially comparing the images stored in the memory with the images acquired by the onboard camera.The evaluation is conducted on a robotic arm equipped with a camera and the model of the environment corresponds to a top view image of an urban scene.

This paper is about the collaborative use of a far-infrared spectrum human detector and a visible spectrum human detector; the idea is to make collaborate these two detectors of different nature to automatically adapt the human detection whatever the luminosity changes and whatever the infrared emission changes of the scene. Our collaborative approach of detection handles: 1) gradual luminosity changes due, for instance, to the passage from night to day (and vice-versa), 2) sudden luminosity changes due, for instance, to navigation in a forest (when going through a glade in a forest), 3) infrared emission saturation when the global temperature of the scene is very high and does not permit to distinguish human people in infrared. Our approach of detection permits to detect people 24 hours a day and regardless the weather conditions. Furthermore, the proposed approach is relatively fast: it is practically as fast as using one detector alone whereas two are used in the same time.

A major limitation of existing battery-powered quadrotor UAVs is their reduced flight endurance. To address this issue, by leveraging the electrical model of a brushless DC motor, we explicitly determine minimum-energy paths between a predefined initial and final configuration of a quadrotor by solving an optimal control problem with respect to the angular accelerations of the four propellers. As a variation on this problem, if the total energy consumption between two boundary states is fixed, minimum-time and/or minimum-control-effort trajectories are computed for the aerial vehicle. The theory is illustrated for the DJI Phantom 2 quadrotor in three realistic scenarios.

In this paper, the modeling and control design of a vertical flight attitude control for a mini tail-sitter with variable pitch propeller is discussed. Tail-sitters VTOL-UAVs have operational flexibility of typical helicopters while having the cruise performance of fixed wing airplanes. The configuration proposed in this work is highly unstable in its natural flight state in vertical mode. A dynamic model is developed and a linear control strategy has been developed to stabilize the platform. The results are supported by experimental tests.