Naval Postgraduate School

About: Naval Postgraduate School is a education organization based out in Monterey, California, United States. It is known for research contribution in the topics: Tropical cyclone & Nonlinear system. The organization has 5246 authors who have published 11614 publications receiving 298300 citations. The organization is also known as: NPS & U.S. Naval Postgraduate School.

Getting to "we"

Abstract: Solidarity, not software, generates collaboration.

Mineral Mapping Using Simulated Worldview-3 Short-Wave-Infrared Imagery

Abstract: WorldView commercial imaging satellites comprise a constellation developed by DigitalGlobe Inc. (Longmont, CO, USA). Worldview-3 (WV-3), currently planned for launch in 2014, will have 8 spectral bands in the Visible and Near-Infrared (VNIR), and an additional 8 bands in the Short-Wave-Infrared (SWIR); the approximately 1.0–2.5 μm spectral range. WV-3 will be the first commercial system with both high spatial resolution and multispectral SWIR capability. Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data collected at 3 m spatial resolution with 86 SWIR bands having 10 nm spectral resolution were used to simulate the new WV-3 SWIR data. AVIRIS data were converted to reflectance, geographically registered, and resized to the proposed 3.7 and 7.5 m spatial resolutions. WV-3 SWIR band pass functions were used to spectrally resample the data to the proposed 8 SWIR bands. Characteristic reflectance signatures extracted from the data for known mineral locations (endmembers) were used to map spatial locations of specific minerals. The WV-3 results, when compared to spectral mapping using the full AVIRIS SWIR dataset, illustrate that the WV-3 spectral bands should permit identification and mapping of some key minerals, however, minerals with similar spectral features may be confused and will not be mapped with the same detail as using hyperspectral systems. The high spatial resolution should provide detailed mapping of complex alteration mineral patterns not achievable by current multispectral systems. The WV-3 simulation results are promising and indicate that this sensor will be a significant tool for geologic remote sensing.

Recrystallization and superplasticity at 300 C in an aluminum-magnesium alloy

Abstract: Variations in thermomechanical processing (TMP) which regulate the microstructural characteristics and superplastic response of an Al-lOMg-0.1Zr alloy at 300 °C were evaluated. Mechanical property data revealed that the superplastic ductility can be enhanced by simultaneously increasing the total rolling strain, the reduction per pass, and the duration of reheating intervals between passes during isothermal rolling. Texture and microscopy data were consistent with the development of a refined microstructure by recovery-dominated processes, i.e., continuous recrystallization, during the processing. The mechanisms by which a refined substructure can be progressively converted into a fine-grained structure during repeated cycles of deformation and annealing are addressed. A qualitative description of the complex sequence of developments leading to a microstructure better suited to support superplastic response is presented.

A wall-following method for escaping local minima in potential field based motion planning

Abstract: A wall-following method for escaping local minima encountered by the potential field based motion planning method used in real-time obstacle avoidance is presented. The new algorithm switches to a wall-following control mode when the robot falls into a local minimum. A switches back to the potential field guided control mode when a certain condition is met. A simple switch condition derived from monitoring the distance from the robot's position to the goal position is shown to be effective in escaping local minima in typical laboratory environments. A provision is built into the algorithm, allowing the robot to follow a wall in a different direction if the first attempt fails. The new algorithm is implemented on a Nomad 200 mobile robot. Simulation and experimental results are presented to demonstrate the usefulness of the method.

Safe Update of Hybrid SDN Networks

Abstract: The support for safe network updates, i.e., live modification of device behavior without service disruption, is a critical primitive for current and future networks. Several techniques have been proposed by previous works to implement such a primitive. Unfortunately, existing techniques are not generally applicable to any network architecture, and typically require high overhead (e.g., additional memory) to guarantee strong consistency (i.e., traversal of either initial or final paths, but never a mix of them) during the update. In this paper, we deeply study the problem of computing operational sequences to safely and quickly update arbitrary networks. We characterize cases, for which this computation is easy, and revisit previous algorithmic contributions in the new light of our theoretical findings. We also propose and thoroughly evaluate a generic sequence-computation approach, based on two new algorithms that we combine to overcome limitations of prior proposals. Our approach always finds an operational sequence that provably guarantees strong consistency throughout the update, with very limited overhead. Moreover, it can be applied to update networks running any combination of centralized and distributed control-planes, including different families of IGPs, OpenFlow or other SDN protocols, and hybrid SDN networks. Our approach therefore supports a large set of use cases, ranging from traffic engineering in IGP-only or SDN-only networks to incremental SDN roll-out and advanced requirements (e.g., per-flow path selection or dynamic network function virtualization) in partial SDN deployments.