28,402 research outputs found
RV Knorr Cruise KN200-4, 13 Apr-03 May 2011. RAPID Mooring Cruise
This report describes the mooring operations conducted during RV Knorr cruise KN200-4 between 13 April and 3 May 2011.
These mooring operations were completed as part of the United Kingdom Natural Environment Research Council (NERC) funded RAPID-WATCH Programme to monitor the Atlantic Meridional Overturning Circulation (MOC) at 26.5°N. The primary purpose on this cruise for the UK team was to service the RAPID Western Boundary moorings while the US teams worked on the Western Boundary Time Series project and the RAPID-MOCHA Western Boundary moorings.
Cruise KN200-4 was from Port Everglades, Florida to Port Everglades, Florida and covered the Western Boundary moorings deployed on RB0901 and OC459. This cruise was the ninth annual refurbishment of the Western Boundary section of an array of moorings deployed across the Atlantic in order to continuously observe the MOC. This array will be further refined and refurbished during subsequent years.
The instruments deployed on the array consist of a variety of current meters, bottom pressure recorders, and CTD loggers, which, combined with time series measurements of the Florida Straits Current and wind stress estimates, will be used to determine the strength and structure of the MOC at 26.5°N.
(http://www.noc.soton.ac.uk/rapid
Ultracold atoms in an optical lattice with dynamically variable periodicity
The use of a dynamic "accordion" lattice with ultracold atoms is
demonstrated. Ultracold atoms of Rb are trapped in a two-dimensional
optical lattice, and the spacing of the lattice is then increased in both
directions from 2.2 to 5.5 microns. Atoms remain bound for expansion times as
short as a few milliseconds, and the experimentally measured minimum ramp time
is found to agree well with numerical calculations. This technique allows an
experiment such as quantum simulations to be performed with a lattice spacing
smaller than the resolution limit of the imaging system, while allowing imaging
of the atoms at individual lattice sites by subsequent expansion of the optical
lattice.Comment: 4 pages, 3 figures. Minor changes made and references update
Observation of vortex nucleation in a rotating two-dimensional lattice of Bose-Einstein condensates
We report the observation of vortex nucleation in a rotating optical lattice.
A 87Rb Bose-Einstein condensate was loaded into a static two-dimensional
lattice and the rotation frequency of the lattice was then increased from zero.
We studied how vortex nucleation depended on optical lattice depth and rotation
frequency. For deep lattices above the chemical potential of the condensate we
observed a linear dependence of the number of vortices created with the
rotation frequency,even below the thermodynamic critical frequency required for
vortex nucleation. At these lattice depths the system formed an array of
Josephson-coupled condensates. The effective magnetic field produced by
rotation introduced characteristic relative phases between neighbouring
condensates, such that vortices were observed upon ramping down the lattice
depth and recombining the condensates.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Let
A review of data visualization: opportunities in manufacturing sequence management.
Data visualization now benefits from developments in technologies that offer innovative ways of presenting complex data. Potentially these have widespread application in communicating the complex information domains typical of manufacturing sequence management environments for global enterprises. In this paper the authors review the visualization functionalities, techniques and applications reported in literature, map these to manufacturing sequence information presentation requirements and identify the opportunities available and likely development paths. Current leading-edge practice in dynamic updating and communication with suppliers is not being exploited in manufacturing sequence management; it could provide significant benefits to manufacturing business. In the context of global manufacturing operations and broad-based user communities with differing needs served by common data sets, tool functionality is generally ahead of user application
Resilient Sliding Mode Control via Direct Pole Placement Technique for Large Scale Systems
This paper introduces an innovative method for determining the switching surface within an equivalent pole placement control framework designed specifically for multivariable systems. Moreover, it showcases adaptability across both minimum phase and non-minimum phase systems. The sliding mode control system offers significant flexibility in shaping the closed-loop eigenvalues, providing considerable freedom in customizing the system's characteristics. The formulation of the sliding surface plays a crucial role in defining the performance features of the control system, as the representative point of the system is constrained to follow a predetermined switching surface. Researchers are actively addressing the pole assignment problem within sliding mode control, presenting a unique geometric approach for designing sliding surfaces. This contribution introduces a fresh perspective to the domain of control system design, and the inclusion of numerical examples serves to highlight the simplicity and effectiveness of the proposed method
RV Walton Smith Cruise WS16336, 01 - 07 Dec 2016, Miami to Miami, USA. MerMEED microstructure cruise report
The MerMEED (Mechanisms responsible for Mesoscale Eddy Energy Dissipation) project is a NERC funded project (NE/N001745/1, 2015-2018) to investigate the levels of dissipation associated with eddies at a western boundary, in order to identify the mechanisms responsible. Mesoscale eddies are ubiquitous in the worlds oceans, and can be found in the subtropical Atlantic travelling slowly westward (at 4-5 cm/s), with a radius of about 100 km. These eddies are formed through baroclinic instability or wind forcing across the Atlantic, but when they reach the western boundary (east coast of the USA), they disappear from the satellite altimetry record. This disappearance of eddies occurs throughout the worldsà oceans at western boundaries, but from altimetry alone, it is not known whether they disappear because energy is transferred to other wave modes or the mean flow, or whether it is locally dissipated through eddy-topography interactions.
The purpose of this cruise was to make microstructure temperature and shear measurements in order to measure dissipation at the intersection of an anticyclonic eddy and the steep topography to the east of Abaco, Bahamas. During the 7 day cruise, 70 profiles of microstructure data were collected using a tethered microstructure profiler, and a shipboard 75 kHz ADCP collected concurrent measurements of ocean currents. This cruise is the first of several planned cruises for the MerMEED project, and the data collected are intended to complement additional field operations, including moored instruments added to the RAPID array (thermistors and ADCPs on the WB1 mooring) and glider deployments planned for the 2017/18 year
Steam reforming of biomass tar over tyre char for hydrogen production
Carbonaceous materials have been proven to have a high activity for tar removal. The simultaneous gasification of pyrolysis gases and char has a significant role in increasing the gas yield and decreasing the tar in the product syngas. This study investigates the use of tyre char as a catalyst for hydrogen production and tar reduction during the pyrolysis/reforming of biomass using a two stage fixed bed reactor. The biomass sample was pyrolysed under nitrogen at a pyrolysis temperature of 500 deg;C. The evolved pyrolysis volatiles were passed to a second stage with steam and the gases were reformed at a temperature of 900 deg;C with the presence of tyre char as catalyst. The influence of catalyst bed temperature, steam flow rate, reaction time and addition of metals were investigated. Char was characterized using BET surface analysis and scanning electron microscopy (SEM). Raising the steam injection rate and reforming temperature resulted in an increase in hydrogen production as steam reforming and gasification of char increased. Over the ranges of operating conditions examined, the maximum hydrogen content reached 52% and the ratio of H 2 /CO varied between 1.3 to 2. The presence of steam promotes the char conversion, however, increasing the amount of steam from 6.64 g/h to 8.64 g/h doesn't contribute to decrease the char yield and the obtained hydrogen yield was almost the same at about 51 vol. %. The results indicate that the char bed exhibited a higher tar reduction than the thermal cracking conditions
Credibility-based social network recommendation: Follow the leader
In Web-based social networks (WBSN), social trust relationships between users indicate the similarity of their needs and opinions. Trust can be used to make recommendations on the web because trust information enables the clustering of users based on their credibility which is an aggregation of expertise and trustworthiness. In this paper, we propose a new approach to making recommendations based on leaders' credibility in the "Follow the Leader" model as Top-N recommenders by incorporating social network information into user-based collaborative filtering. To demonstrate the feasibility and effectiveness of "Follow the Leader" as a new approach to making recommendations, first we develop a new analytical tool, Social Network Analysis Studio (SNAS), that captures real data and used it to verify the proposed model using the Epinions dataset. The empirical results demonstrate that our approach is a significantly innovative approach to making effective collaborative filtering based recommendations especially for cold start users. © 2010 Al-Sharawneh & Williams
An evaluation on the effectiveness of Web 2.0 Startpages (Netvibes & Pageflakes) within NHS libraries.
Carol McCormick was Learning Resources Advisor in the library at James Cook University Hospital, South Teesside when she completed her BSc (Hons) Librarianship (Work Based Learning) degree at Northumbria University. She gained a 1st Class Honours and is now Learning Resources Librarian. Carol’s dissertation formed part of a wider action research project into the provision of current awareness services at James Cook University Hospital. This article reports on the evaluation which was conducted after a Web 2.0 Startpage, or portal, had been introduced to improve access to current awareness information for all staff within the Trust. It is the second article in the Dissertations into practice series to examine the use of web-based tools to improve access to information for NHS staff
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