82,569 research outputs found
Wear and Friction Modeling on Lifeboat Launch Systems
The RNLI provides search and rescue cover along the UK and RoI coast using a variety of lifeboats
and launch techniques. In locations where there is no natural harbour it is necessary to use a slipway
to launch the lifeboat into the sea. Lifeboat slipway stations consist of an initial section where the
boat is held on rollers followed by an inclined keelway lined with low friction composite materials,
the lifeboat is released from the top of the slipway and proceeds under its own weight into the water.
The lifeboat is later recovered using a winch line. It is common to manually apply grease to the
composite slipway lining before each launch and recovery in order to ensure sufficiently low friction
for successful operation. With the introduction of the Tamar class lifeboat it is necessary to upgrade
existing boathouses and standardise slipway operational procedures to ensure consistent operation.
The higher contact pressures associated with the new lifeboat have led to issues of high friction and
wear on the composite slipway linings and the manual application of grease to reduce friction is to be
restricted due to environmental impact and cost factors. This paper presents a multidisciplinary
approach to modelling slipway panel wear and friction using tribometer testing in conjunction with
finite element analysis and slipway condition surveys to incorporate common real-world effects such
as panel misalignments. Finally, it is shown that a freshwater lubrication system is effective,
reducing cost and environmental impacts while maintaining good friction and wear performance
Monodisperse Dry Granular Flows on Inclined Planes : Role of Roughness
Recent studies have pointed out the importance of the basal friction on the
dynamics of granular flows. We present experimental results on the influence of
the roughness of the inclined plane on the dynamics of a monodisperse dry
granular flow. We found experimentally that it exists a maximum of the friction
for a given relative roughness. This maximum is shown to be independent of the
angle of the slope. This behavior is observed for four planes with different
bump sizes (given by the size of the beads glued on the plane) from 200 microns
to 2 mm. The relative roughness corresponding to the maximum of the friction
can be predicted with a geometrical model of stability of one single bead on
the plane. The main parameters are the size of the bumps and the size of the
flowing beads. In order to obtain a higher precision, the model also takes into
account of the spacing between the bumps of the rough plane. Experimental
results and model are in good agreement for all the planes we studied. Other
parameters, like the sphericity of the beads, or irregularities in the
thickness of the layer of glued particles, are shown to be of influence on the
friction.Comment: 17 pages, 15 figures, submitted to EPJ
Mariner 9 data storage subsystem flight performance summary
The performance is summarized of the Mariner 9 Data Storage Subsystem (DSS) throughout the primary and extended missions. Information presented is limited to reporting of anomalies which occurred during the playback sequences. Tables and figures describe the anomalies (dropouts, missing and added bits, in the imaging data) as a function of time (accumulated tape passes). The data results indicate that the performance of the DSS was satisfactory and within specification throughout the mission. The data presented is taken from the Spacecraft Team Incident/Surprise Anomaly Log recorded during the mission. Pertinent statistics concerning the tape transport performance are given. Also presented is a brief description of DSS operation, particularly that related to the recorded anomalies. This covers the video data encoding and how it is interpreted/decoded by ground data processing and the functional operation of the DSS in abnormal conditions such as loss of lock to the playback signal
Minimal Pati-Salam Model from String Theory Unification
We provide what we believe is the minimal three family SUSY
and conformal Pati-Salam Model from type IIB superstring theory. This
orbifolded AdS model has long lived protons and has potential
phenomenological consequences for LHC.Comment: 8 page
A time dependent relation between EUV solar flare light-curves from lines with differing formation temperatures
Extreme ultraviolet (EUV) solar flare emissions evolve in time as the
emitting plasma heats and then cools. Although accurately modeling this
evolution has been historically difficult, especially for empirical
relationships, it is important for understanding processes at the Sun, as well
as for their influence on planetary atmospheres. With a goal to improve
empirical flare models, a new simple empirical expression is derived to predict
how cool emissions will evolve based on the evolution of a hotter emission.
This technique is initially developed by studying 12 flares in detail observed
by the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory
(SDO). Then, over 1100 flares observed by EVE are analyzed to validate these
relationships. The Cargill and Enthalpy Based Thermal Evolution of Loops
(EBTEL) flare cooling models are used to show that this empirical relationship
implies the energy radiated by a population of hotter formed ions is
approximately proportional to the energy exciting a population of cooler formed
ions emitting when the peak formation temperatures of the two lines are up to
72% of each other and above 2 MK. These results have practical implications for
improving flare irradiance empirical modeling and for identifying key emission
lines for future monitoring of flares for space weather operations; and also
provide insight into the cooling processes of flare plasma.Comment: Final version accepted for publication by the Journal of Space
Weather and Space Climate on 23 November 201
Positional changes of pericentromeric heterochromatin and nucleoli in postmitotic Purkinje cells during murine cerebellum development
Previous studies revealed changes of pericentromeric heterochromatin arrangements in postmitotic Purkinje cells (PCs) during postnatal development in the mouse cerebellum (Manuelidis, 1985; Martou and De Boni, 2000). Here, we performed vibratome sections of mouse cerebellum (vermis) at P0 (day of birth), at various stages of the postnatal development (P2-P21), as well as in very young (P28) and 17-months-old adults. FISH was carried out on these sections with major mouse satellite DNA in combination with immunostaining of the nucleolar protein B23 (nucleophosmin). Laser confocal microscopy, 3D reconstructions and quantitative image analysis were employed to describe changes in the number and topology of chromocenters and nucleoli. At all stages of postnatal PC development heterochromatin clusters were typically associated either with nucleoli or with the nuclear periphery, while non-associated clusters were rare (<1% at P0 to P21 and about 3% in adult stages). At P0, about 2-4 nucleoli and 7-8 pericentromeric heterochromatin clusters were variably located within PC nuclei. The relative volume of heterochromatin clusters associated with the nucleoli (about 50%) was roughly equal to the volume of clusters associated with the nuclear periphery. Positional changes of both nucleoli and centromeres towards the nuclear center occurred between P0 and P6. At P6 the average number of chromocenters per PC nucleus had decreased to about five. In agreement with previous studies, one or occasionally two nucleoli were noted at the nuclear center surrounded by major perinucleolar heterochromatin clusters. The relative volume of these perinucleolar clusters increased to about 84%, while the volume of clusters in the nuclear periphery decreased to about 15%. At subsequent postnatal stages, the arrangement of most pericentromeric heterochromatin around a central nucleolus was maintained. In adult animals, however, we observed a partial redistribution of heterochromatin towards the nuclear periphery. The average total number of pericentromeric heterochromatin signals increased again to about ten. The volume of heterochromatin associated with the nuclear periphery roughly doubled (30%), while the volume of the perinucleolar heterochromatin decreased correspondingly. Copyright (C) 2004 S. Karger AG, Basel
Meson decay in an independent quark model
Leptonic decay widths and leptonic decay constants of light vector mesons and
weak leptonic decay widths and weak decay constants of light and heavy
pseudoscalar mesons have been studied in a field- theoretic framework based on
the independent quark model with a scalar- vector power-law potential. The
results are in very good agreement with the experimental data.Comment: 13 page
Transparency and the Marketplace for Student Data
Student lists are commercially available for purchase on the basis of ethnicity, affluence, religion, lifestyle, awkwardness, and even a perceived or predicted need for family planning services. This study seeks to provide an understanding of the commercial marketplace for student data and the interaction with privacy law. Over several years, Fordham CLIP reviewed publicly-available sources, made public records requests to educational institutions, and collected marketing materials received by high school students. The study uncovered and documents an overall lack of transparency in the student information commercial marketplace and an absence of law to protect student information.https://ir.lawnet.fordham.edu/clip/1003/thumbnail.jp
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