26,113 research outputs found
Data management for community research projects: A JGOFS case study
Since the mid 1980s, much of the marine science research effort in the United Kingdom has been focused into large scale collaborative projects involving public sector laboratories and university departments, termed Community Research Projects. Two of these, the Biogeochemical Ocean Flux Study (BOFS) and the North Sea Project incorporated large scale data collection to underpin multidisciplinary modeling efforts. The challenge of providing project data sets to support the science was met by a small team within the British Oceanographic Data Centre (BODC) operating as a topical data center. The role of the data center was to both work up the data from the ship's sensors and to combine these data with sample measurements into online databases. The working up of the data was achieved by a unique symbiosis between data center staff and project scientists. The project management, programming and data processing skills of the data center were combined with the oceanographic experience of the project communities to develop a system which has produced quality controlled, calibrated data sets from 49 research cruises in 3.5 years of operation. The data center resources required to achieve this were modest and far outweighed by the time liberated in the scientific community by the removal of the data processing burden. Two online project databases have been assembled containing a very high proportion of the data collected. As these are under the control of BODC their long term availability as part of the UK national data archive is assured. The success of the topical data center model for UK Community Research Project data management has been founded upon the strong working relationships forged between the data center and project scientists. These can only be established by frequent personal contact and hence the relatively small size of the UK has been a critical factor. However, projects covering a larger, even international scale could be successfully supported by a network of topical data centers managing online databases which are interconnected by object oriented distributed data management systems over wide area networks
The nucleus of 103P/Hartley 2, target of the EPOXI mission
103P/Hartley 2 was selected as the target comet for the Deep Impact extended
mission, EPOXI, in October 2007. There have been no direct optical observations
of the nucleus of this comet, as it has always been highly active when
previously observed. We aimed to recover the comet near to aphelion, to a)
confirm that it had not broken up and was in the predicted position, b) to
provide astrometry and brightness information for mission planning, and c) to
continue the characterisation of the nucleus. We observed the comet at
heliocentric distances between 5.7 and 5.5 AU, using FORS2 at the VLT, at 4
epochs between May and July 2008. We performed VRI photometry on deep stacked
images to look for activity and measure the absolute magnitude and therefore
estimate the size of the nucleus. We recovered the comet near the expected
position, with a magnitude of m_R = 23.74 \pm 0.06 at the first epoch. The
comet had no visible coma, although comparison of the profile with a stellar
one showed that there was faint activity, or possibly a contribution to the
flux from the dust trail from previous activity. This activity appears to fade
at further epochs, implying that this is a continuation of activity past
aphelion from the previous apparition rather than an early start to activity
before the next perihelion. Our data imply a nucleus radius of \le 1 km for an
assumed 4% albedo; we estimate a ~6% albedo. We measure a colour of (V-R) = 0.
26 \pm 0.09.Comment: 5 pages, 4 figures, accepted for publication in A&
Lubricant Selection Manual, Phase 3
Future spacecraft must be designated to operate for very long time periods in space. For example, a target goal for the Space Station is 30 years of operation. Although the actual life may be significantly less than this optimistic goal, the life will certainly be a critical issue in design. The bearings on primary components such as the alpha and beta joints must obviously be designed and lubricated with the objective of optimum performance life. In addition to these joints, there will be numerous other tribological (rubbing or rolling) interfaced that will be required to function for the life of the spacecraft. A major key to adequate performance of tribological interface is proper lubrication. Lubricants can be divided into two basic classes: solid films and liquids. Both types have been used extensively in space applications. Both have advantages and disadvantages that must be carefully considered in their selection. The purpose here is to summarize selection criteria for liquid and solid lubricants applied to long-life spacecraft
Frozen to death? -- Detection of comet Hale-Bopp at 30.7 AU
Comet Hale--Bopp (C/1995 O1) has been the single most significant comet
encountered by modern astronomy, still having displayed significant activity at
25.7 AU solar distance in late 2007. It is a puzzling question when and where
this activity will finally cease. Here we present new observations with the ESO
2.2m telescope at La Silla to check the activity of Hale--Bopp at 30.7 AU solar
distance. On 2010-12-04, 26 CCD images were taken with 180 s exposure times for
photometry and morphology. The comet was detected in R and had a total
brightness of 23.3+-0.2 mag, referring to an absolute brightness of
R(1,1,0)=8.3. The profile of the coma was star-like at a seeing of 1.9",
without any evidence of a coma or tail extending farther than 2.5" (=55,000 km
in projection) and exceeding 26.5 mag/arcs^2 surface brightness. The measured
total brightness corresponds to a relative total reflecting surface, a_RC, of
485 km^2, nine times less than three years before. The calculated a_RC value
would imply a nucleus with 60--65 km radius assuming 4% albedo. This size
estimate is in significant contradiction with the previous results scattering
around 35 km. Therefore we suggest that the comet may still be in a low-level
activity, despite the lack of a prominent coma. Alternatively, if the nucleus
is already dormant, the albedo should be as high as 13%, assuming a radius of
35 km. With this observation, Hale--Bopp has been the most distant comet ever
observed, far beyond the orbit of Neptune.Comment: 4 pages, accepted by A&
Property Rights in Virtual Reality: All’s Fair in Life and Warcraft?
To explore these issues, this Comment will first give some background on the rise and explosive growth of virtual worlds. The focus of the first section will be on the development-and especially the economics-of massively multiplayer online role-playing games (MMORPGs), in which millions of subscribers interact with each other via the Internet to accomplish tasks or to engage in commerce or other activities. After a general tour of MMORPGs, the Comment will concentrate on the world of Second Life. Second Life is unusual among MMORPGs in that it is totally free-form, with no goals or quests or prizes to win. It is a world created by its residents. But the feature of Second Life attracting most attention is that Second Life is the first virtual world that allows its residents to retain intellectual property rights to their in-world creations. The Comment will then review litigation related to in-world activities and the ability of the real-world legal system to resolve in-world disputes. What rights do avatars have in the real world? Does Kevin Alderman, the real-world head of Eros, LLC have a cause of action against Robert Leatherwood, the real-world name of the avatar Volkov Catteneo, for theft of intellectual property created in Second Life by Alderman\u27s avatar Stroker Serpentine ? Section III will use Bragg v. Linden Research, Inc. and Eros, LLC v. Doe to focus on issues related to both virtual real property and virtual intellectual property. Section IV will describe the current intellectual property regimecopyright, trademark, and patent law-as it relates to virtual property. Among the issues discussed in this section will be the failure of the Digital Millennium Copyright Act (DMCA) to protect the copyrights represented in the Catteneo and Simon lawsuits. This Comment concludes, first, that real-world courts are an appropriate forum for virtual-world property disputes. A second conclusion is that, rather than applying the contract law embodied in End User License Agreements (EULA) to every dispute involving a virtual world, the law applied should depend on the nature of the dispute. Finally, this Comment concludes that copyright, trademark, and patent laws need revision to deal with virtual intellectual property, and they are ill-suited to other types of virtual property
Space Station long term lubrication analysis. Phase 1 preliminary tribological survey
Increases in the size, complexity, and life requirements of satellites and space vehicles have put increasing demands on the lubrication requirements for trouble-free service. Since the development costs of large systems are high, long lives with minimum maintenance are dictated. The Space Station represents the latest level of size and complexity in satellite development; it will be nearly 100 meters in major dimensions and will have a life requirement of thirty years. It will have numerous mechanisms critical to its success, some of which will be exposed to the space environment. Designing long-life lubrication systems and choosing appropriate lubricants for these systems will be necessary for their meeting the requirements and for avoiding failures with associated dependent mechanisms. The purpose of this program was to identify the various critical mechanisms and review their designs during the overall design and development stage so that problem areas could be avoided or minimized prior to the fabrication of hardware. The specific objectives were fourfold: (1) to perform a tribology survey of the Space Station for the purpose of documenting each wear point as to materials involved, environmental conditions, and operating characteristics; (2) to review each wear point (point of relative motion) as to the lubrication used and substrate materials selected in the context of its operating characteristics and the environmental conditions imposed; (3) to make recommendations for improvement in areas where the lubricant chosen and/or where the substrate (materials of the wear couple) are not considered optimum for the application; and (4) to make or recommend simulated or full scale tests in tribological areas where the state-of-the-art is being advanced, in areas where new designs are obviously being employed and a critical review would indicate that problems are a strong possibility, and/or where excessive wear, a malfunction, or excessive leakage would create fluid systems problems or contamination of exposed optical equipment
ANALYSIS OF THE 2021 OFFICE OF FEDERAL PROCUREMENT POLICY DEFINITION OF PROCUREMENT ACQUISITION LEAD TIME
In January 2021, the Office of Federal Procurement Policy (OFPP) issued a memorandum defining procurement acquisition lead time (PALT) as “the time between the date on which a federal department or agency issues an initial solicitation for a contract or order and the date of the award of the contract or order.” While this definition supports identifying and addressing causes of procurement delays and meets the intent of the direction in Section 886 of the 2018 National Defense Authorization Act (NDAA), the extent of alignment between this definition and Air Force contracting execution is unclear. This research explores the alignment between the January 2021 PALT definition and Air Force contracting execution from October 1, 2015, to December 31, 2021. By applying qualitative content, policy, and Air Force internal metrics analyses, the findings indicate that the current Office of Federal Procurement Policy’s (OFPP) definition of PALT does not measure the majority of policies issued to reduce lead times and that the current metrics tracked by the Air Force do not cover the impact of those policies. This research recommends using a metric that captures pre-solicitation lead time to give the Air Force valuable insight into procurement delays and achieved efficiencies and include more process-based metrics to understand and identify procurement delays.Civilian, Department of the Air ForceCivilian, Department of the Air ForceApproved for public release. Distribution is unlimited
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