825 research outputs found
Senator Edmund S. Muskie Interviewed by Paul Duke for NBC Nightly News
Senator Edmund S. Muskie interviewed by Paul Duke, discuss letter from Captain Daniel and Calley Case
Exploring model-based development for the verification of real-time Java code
Many safety- and security-critical systems are real-time systems and, as a result, tools and techniques for verifying real-time systems are extremely important. Simulation and testing such systems can be exceedingly time-consuming and these techniques provide only probabilistic measures of correctness. There are a number of model-checking tools for real-time systems. However, they provide formal verification for models, not programs. To increase the confidence in real-time programs written in real-time Java, this paper takes a modelling approach to the design of such programs. First, models can be mechanically verified, to check whether they satisfy particular properties, by using current real-time model-checking tools. Then, programs are derived from the model by following a systematic approach. To illustrate the approach we use a nontrivial example: a gear controller
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Development and Flight Results from the C3D2 Imager Payload on AlSat Nano
An experimental CubeSat camera system using 3 separate CMOS imagers was flown in 2014 on UKube-1. In response to an announcement opportunity in December 2014, we proposed an upgrade to our C3D imager payload, which was accepted to fly on AlSat Nano. Launched in September 2016 the system has been operational for over 1 year and has returned both images and housekeeping data, including detailed temperature and radiation dosimetry measurements. Through these in-orbit demonstrations on CubeSans, the image sensors and payload have attained TRL9, and these are now being used in other flight opportunities. In this paper we describe the C3D imager payload, which comprises 3 independent CMOS image sensors used in different camera systems; two wide field cameras are specifically optimised with one to observe the Earth from the 650 km orbit, and the other with its focus set to 40 cm to observe a deployable boom from the CubeSat. The experiment controller also contained thermometry and two RADFET dosimeters, one located on the payload, with the other deployed at a different point on the spacecraft.
In this paper we will describe the experiment design and operational performance, and review the in-orbit data obtained during the operations covering over 17 months in-orbit, in addition to discussing lessons learned from the flight experience. We also discuss further developments of the payload concept which we are currently working on toward future flight opportunities
Estimated Prevalence of Monocular Blindness and Monocular Severe Visual Impairment in Children of Cross Rivers State, Nigeria
Aim: The aim was to report on the prevalence of monocular blindness/monocular severe visual impairment (MB/MSVI) in children found in Cross River State Nigeria, using the key informant method (KIM). Settings and Design: A cross‑sectional study using the KIM. Patients and Methodology: Key informants were trained to identify children with vision problems through recognition of pictures of disease conditions, observation of behavior of the child and discussion with villagers during house to house visits, school visits, church visits, or market visits. They were instructed to bring the children to a predetermined health center for examination by a pediatric ophthalmologist led team. The children were examined, and findings recorded on the World Health Organization/prevention of blindness and low vision recording form for children. Statistical Analysis Used: Data were entered into MS Excel, transferred and analyzed with STATA 11. Results: Among 994 children with suspected visual impairment, 21.5% were diagnosed as MB/MSVI, with a population prevalence of 0.18/1000 children in the state. Males accounted for 61%. The leading anatomical causes were the cornea in 41%, the whole globe in 20%, and lens‑related in 19%. Boys were 2.6 times (95% confidence interval: 1.4–4.7, P = 0.002) more likely to have trauma as an etiology compared with girls. Conclusions: Monocular blindness/monocular severe visual impairment children are essentially “one‑eyed” children at risk of becoming blind individuals. The prevalence of MB/MSVI is 2.25 times that of bilateral blindness and severe visual impairment in children in this population. The main anatomical causes, as well as ocular trauma, are largely avoidable. Trauma that is avoidable was a significant etiology in boys compared with girls. MB/MSVI adds to the burden for child eye care services.Keywords: Child eye care services, monocular blindness, monocular severe visual impairment, Nigeria, ocular traum
Manned Mars missions: A working group report
The discussions of the Working Group (based in large part on working papers, which will shortly be published separately) are summarized. These papers cover a broad range of subjects which need to be addressed in the formulation of such a formidable enterprise as a manned Mars program. Science objective and operations; Mars surface infrastructure and activities; mission and system concepts and configurations; life sciences; impacts on the space infrastructure; and costs, schedules, and organizations are addressed
Manned Mars Mission. Working group papers, volume 2, section 5 - appendix
Topics discussed include: science investigations and issues; life science/medical issues; subsystems and technology development requirements; political issues; and impacts on other programs
The SO(32) Heterotic String on a K3 Surface
The SO(32) heterotic string on a K3 surface is analyzed in terms of the dual
theory of a type II string (or F-theory) on an elliptically fibred Calabi-Yau
manifold. The results are in beautiful agreement with earlier work by Witten
using very different methods. In particular, we find gauge groups of SO(32) x
Sp(k) appearing at points in the moduli space identified with point-like
instantons and see hypermultiplets in the (32,2k) representation becoming
massless at the same time. We also discuss some aspects of the E8 x E8 case.Comment: 12 pages, LaTeX, 1 figure, refs modifie
Key informant perceptions of vision loss in children and implications for their training
Background: The role of key informants (KIs) in identifying children with vision loss is expanding, yet there is a minimal understanding of KI perceptions of vision loss in children. The aim of the study was to understand the KI’s perception of childhood vision loss in order to design more effective training programmes.Materials and Methods: A population-based study on the prevalence and causes of childhood blindness and severe visual impairment was conducted using the KI method. KIs were selected by their communities and trained in advocacy, identifi cation and referral of children with visual impairment. Prior to the KI training, a pre-test was conducted, asking, “what is your perception of vision loss in children and how will you identify these children in your community?”.Result: The 742 KI provided 1,650 responses. There were three main methods suggested to identify children; observation of a child, vision assessment of a child, and recognition of isolation of a child.Conclusion: KI have a good understanding of the impact of vision loss on children. Training programmes should use existing knowledge of KI. Furthermore, training programmes should include the social impact of severe vision loss to help identify children needing the assessment.Keywords: Childhood blindness, key informant, Nigeria, perception, visio
Reducing the Visual Signature of the M4A1 Rifle
The Maneuver Center of Excellence (MCoE) presented a directive to reduce the visual signature for small arms weapons by altering the color of the M4A1 rifle from its traditional black color. This research utilizes the Systems Decision Process (SDP) to develop and analyze alternatives to create a feasible and permanent solution to reduce the weapon’s visual signature. The research consisted of an extensive stakeholder and functional analysis to develop a value model and framework that provides a values-based recommendation. The model establishes an optimal color change process that accounts for the design and performance characteristics of the weapon system and the stakeholder’s values. The research also analyzes the potential integration of short wave infrared (SWIR) mitigation into the new color of the weapon. This analysis will establish a baseline methodology for weapon color change for all Army small arms weapons
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