Experimental Evaluation of Steady-State Control Properties of an Electron-Bombardment Ion Thrustor

Examined in this report are the experimental steady-state gains, or changes, in beam-current output with changes in thrustor inputs for a 10-centimeter-diameter electron-bombardment ion thrustor. A general leveling off of beam current as a function of an input variable was found at the upper range of each variable, At the design operating point, the filament-heating current exhibited the greatest sensitivity, or percentage beam-current output change for a percentage change in the input (2 to 4). Accelerator voltage showed the least effect (0.04) while discharge voltage, magnetic field, and neutral propellant flow exhibited about the same sensitivity (0.4 to 0.5). Some effects of nonlinearity are shown that may require consideration in the design of a closed-loop control system

Modeling Human-Agent Interaction with Active Ontologies

As computer systems continue to grow in power and access more networked content and services, we believe there will be an increasing need to provide more user-centric systems that act as intelligent assistants, able to interact naturally with human users and with the information environment. Building such systems is a difficult task that requires expertise in many AI fields, ranging from reasoning, planning, scheduling, natural language and multimodal user interfaces. In contrast to many approaches to building agent assistants where diverse AI components are stitched together at a surface level, we propose an approach, called ”Active Ontologies”, and a toolset, called ”Active”, where a developer can model all aspects of an intelligent assistant: ontology-based knowledge structures, servicebased primitive actions, composite processes and procedures, and natural language and dialog structures. We demonstrate this approach through an example prototype of an intelligent meeting scheduling assistant that communicates using instant messages and emails

ACTIVE, A PLATFORM FOR BUILDING INTELLIGENT OPERATING ROOMS

Today computers are part of the standard equipment of modern surgery rooms. They assist surgeons in performing complex procedures that would not be possible otherwise. However, despite the availability of more powerful and complex computer systems, their user interfaces have not been adapted to fully leverage their potential. A new type of software, behaving as an independent intelligent assistant, is needed to better assist surgeons and their staff. Building an intelligent assistant is a difficult task that requires expertise in many fields ranging from artificial intelligence to core software and hardware engineering. We believe that providing a unified tool and methodology to create intelligent software will bring many benefits to this area of research. Our solution, the Active framework, introduces the original concept of Active Ontologies to model and implement intelligent applications. Based on suggestions and constant evaluations from surgeons, an Active based assistant for endoscopic neurosurgery is under development. Using natural modalities such as speech recognition and hand gestures, it enables surgeons to interact with computer based equipments of the operating room as if they were full active members of the team. In a broader context, Active aims to ease the development of intelligent software by making required technologies more accessible. It will help foster research innovation, easier development cycle and deployment of this new type of applications

Force sensitive hook for epiretinal membrane peeling in eye surgery

This project addresses the design, construction and evaluation of a peeling hook with force measurement capability for in-vivo intra-ocular vitreoretinal surgery. The force sensor consists of a miniature multi-degree-offreedom flexure where deformations induced by contact forces are measured using optical fiber white light interferometry. This instrument will be used for epiretinal membrane peeling procedures and should then lead to the creation of a new generation of force sensitive surgical tools

Design and clinical evaluation of an image-guided surgical microscope with an integrated tracking system

A new image-guided microscope system using augmented reality image overlays has been developed. With this system, CT cut-views and segmented objects such as tumors that have been previously extracted from preoperative tomographic images can be directly displayed as augmented reality overlays on the microscope image. The novelty of this design stems from the inclusion of a precise mini-tracker directly on the microscope. This device, which is rigidly mounted to the microscope, is used to track the movements of surgical tools and the patient. In addition to an accuracy gain, this setup offers improved ergonomics since it is much easier for the surgeon to keep an unobstructed line of sight to tracked objects. We describe the components of the system: microscope calibration, image registration, tracker assembly and registration, tool tracking, and augmented reality display. The accuracy of the system has been measured by validation on plastic skulls and cadaver heads, obtaining an overlay error of 0.7mm. In addition, a numerical simulation of the system has been done in order to complement the accuracy study, showing that the integration of the tracker onto the microscope could lead to an improvement of the accuracy to the order of 0.5mm. Finally, we describe our clinical experience using the system in the operation room, where three operations have been performed to dat

The value of Statistical Shape Models to Spine Surgery

The increased use of 3D models of organs or bones by the surgeon has lead to rapid development of new methods to automaKze model generaKon

Solar Wind Neon from Genesis: Implications for the Lunar Noble Gas Record

Lunar soils have been thought to contain two solar noble gas components with distinct isotopic composition. One has been identified as implanted solar wind, the other as higher-energy solar particles. The latter was puzzling because its relative amounts were much too large compared with present-day fluxes, suggesting periodic, very high solar activity in the past. Here we show that the depth-dependent isotopic composition of neon in a metallic glass exposed on NASA's Genesis mission agrees with the expected depth profile for solar wind neon with uniform isotopic composition. Our results strongly indicate that no extra high-energy component is required and that the solar neon isotope composition of lunar samples can be explained as implantation-fractionated solar wind

Optimal vs naïve diversification in cryptocurrencies

This paper contributes to the literature on cryptocurrencies by examining the performance of naïve (1/N) and optimal (Markowitz) diversification in a portfolio of four popular cryptocurrencies. We employ weekly data with weekly rebalancing and show there is very little to select between naïve diversification and optimal diversification. Our results hold for different levels of risk-aversion and an alternative estimation window

Data coding tools for color-coded vector nanolithography

We propose and demonstrate the ability and efficiency of using a universal file format for a nanolithography pattern. A problem faced by the physicists working in the field of nanolithography is a lack of a flexible pattern design software (possibly open–source) that could be applied in combination with a broad range of commercial scanning probe microscope (SPM) systems. The current nanolithography software packages are device–specific and not portable. Therefore, it is impossible to make a lithography pattern and share it with fellow physicists working on a networked sub-system. In this paper we describe the software designed to read and interpret a nanolithography pattern stored in a Windows Metafile (WMF) standard graphic format and next to draw it on a substrate using an SPM tip. The nanolithography parameters like height, velocity, feedback force, etc. are coded in the color of the WMF onto the RGB channels of the image establishing a distinct relation between a graphical feature (color) and the used nanolithography scheme (voltage, height, etc.). The concept enables preparation of complex patterns using any standard graphic software and aids an intuitive recognition of the mode and parameters set for a pattern. The advantages of using a WMF over other approaches and the universal scope of the software are discussed