Deployable reflector antenna performance optimization using automated surface correction and array-feed compensation

Methods for increasing the electromagnetic (EM) performance of reflectors with rough surfaces were tested and evaluated. First, one quadrant of the 15-meter hoop-column antenna was retrofitted with computer-driven and controlled motors to allow automated adjustment of the reflector surface. The surface errors, measured with metric photogrammetry, were used in a previously verified computer code to calculate control motor adjustments. With this system, a rough antenna surface (rms of approximately 0.180 inch) was corrected in two iterations to approximately the structural surface smoothness limit of 0.060 inch rms. The antenna pattern and gain improved significantly as a result of these surface adjustments. The EM performance was evaluated with a computer program for distorted reflector antennas which had been previously verified with experimental data. Next, the effects of the surface distortions were compensated for in computer simulations by superimposing excitation from an array feed to maximize antenna performance relative to an undistorted reflector. Results showed that a 61-element array could produce EM performance improvements equal to surface adjustments. When both mechanical surface adjustment and feed compensation techniques were applied, the equivalent operating frequency increased from approximately 6 to 18 GHz

Privacy-Preserving Shortest Path Computation

Navigation is one of the most popular cloud computing services. But in virtually all cloud-based navigation systems, the client must reveal her location and destination to the cloud service provider in order to learn the fastest route. In this work, we present a cryptographic protocol for navigation on city streets that provides privacy for both the client's location and the service provider's routing data. Our key ingredient is a novel method for compressing the next-hop routing matrices in networks such as city street maps. Applying our compression method to the map of Los Angeles, for example, we achieve over tenfold reduction in the representation size. In conjunction with other cryptographic techniques, this compressed representation results in an efficient protocol suitable for fully-private real-time navigation on city streets. We demonstrate the practicality of our protocol by benchmarking it on real street map data for major cities such as San Francisco and Washington, D.C.Comment: Extended version of NDSS 2016 pape

IMPLEMENTING TARIFF RATE QUOTAS IN CGE MODELS: AN APPLICATION TO SUGAR TRADE POLICIES IN OECD COUNTRIES

We use Mixed-Complementarity-Problem programming to implement tariff rate quotas (TRQ) in the global CGE LINKAGE model. We apply the approach to tariff rate quotas in sugar markets in OECD countries. We calibrate the model on 2000 policy levels for OECD countries to reflect the full implementation of their World Trade Organization commitments. We look at reforms of TRQ and TRQ-like schemes in the EU, the United States, and Japan, as well as multilateral trade liberalization. We derive the impact of reforms on welfare, bilateral trade flows, and terms of trade. A 33-percent multilateral decrease of ad-valorem tariffs, combined with a 33-percent increase in imports under TRQ-like schemes in the EU, the United States, and Japan, induces a global welfare gain of about 889 million dollars. These three countries' trade policies create substantial trade diversion, which excludes many low-cost producers from trading opportunities. An expansion of their import quotas alone, without multilateral trade liberalization, induces welfare gains but preserves most of the trade diversion patterns. The latter diversion benefits some Least Developed Countries' producers because of granted bilateral TRQ allocations. In the context of greater market access, reductions in tariffs in the EU and the United States, and in border "surcharges" in Japan will have to be dramatic before they can significantly affect trade flows as compared to TRQ expansion. Full multilateral trade liberalization induces global welfare gains of about $3 billion.International Relations/Trade,

Ground Systems Development Environment (GSDE) interface requirements and prototyping plan

This report describes the data collection and requirements analysis effort of the Ground System Development Environment (GSDE) Interface Requirements study. It identifies potential problems in the interfaces among applications and processors in the heterogeneous systems that comprises the GSDE. It describes possible strategies for addressing those problems. It also identifies areas for further research and prototyping to demonstrate the capabilities and feasibility of those strategies and defines a plan for building the necessary software prototypes

Weighted feature selection criteria for visual servoing of a telerobot

Because of the continually changing environment of a space station, visual feedback is a vital element of a telerobotic system. A real time visual servoing system would allow a telerobot to track and manipulate randomly moving objects. Methodologies for the automatic selection of image features to be used to visually control the relative position between an eye-in-hand telerobot and a known object are devised. A weighted criteria function with both image recognition and control components is used to select the combination of image features which provides the best control. Simulation and experimental results of a PUMA robot arm visually tracking a randomly moving carburetor gasket with a visual update time of 70 milliseconds are discussed