7,963 research outputs found
Reversible implementation of a disrete linear transformation
Discrete linear transformations form important steps in processing information. Many such transformations are injective and therefore are prime candidates for a physically reversible implementation into hardware. We present here the first steps towards a reversible digital implementation of two different integer transformations on four inputs: The Haar wavelet and the H.264 transform
Seasonal occurrence of Loricate Choanoflagellates in Danish inner waters
It is a trend in loricate choanoflagellate research that our knowledge of species diversity is insufficient in terms of understanding annual successional changes at any specific locality, whereas there is a fairly decent coverage worldwide - at least in more coastal realms - in terms of biodiversity within more narrowly defined time windows. To help address this knowledge gap, we have compiled all available loricate choanoflagellate occurrence data from Danish sampling sites covering an overall time span of close to four decades. The close to 100 samples analysed have a good annual coverage and they encompass in total more than 50 species. We demonstrate clear successional trends among well-defined clusters of species. A large contingent of 'non-native' species, which are in a global context largely considered part of the loricate choanoflagellate warm water community, occurred in September 2014 samples from the Baltic Sea entrance, i.e. the Sound between Denmark and Sweden. While the occurrence of these species is likely due to a large inflow of southern Atlantic water, we also discuss whether the findings may instead reflect recent and more permanent climate change-induced alterations to choanoflagellate biodiversity in inner Danish waters. (C) 2016 Elsevier GmbH. All rights reserved
CoMPflex: CoMP for In-Band Wireless Full Duplex
In this letter we consider emulation of a Full Duplex (FD) cellular base
station (BS) by using two spatially separated and coordinated half duplex (HD)
BSs. The proposed system is termed CoMPflex (CoMP for In-Band Wireless Full
Duplex) and at a given instant it serves two HD mobile stations (MSs), one in
the uplink and one in the downlink, respectively. We evaluate the performance
of our scheme by using a geometric extension of the one-dimensional Wyner
model, which takes into account the distances between the devices. The results
show that CoMPflex leads to gains in terms of sum-rate and energy efficiency
with respect to the ordinary FD, as well as with respect to a baseline scheme
based on unidirectional traffic.Comment: 4 pages, 4 figure
Effects of Ocean Acidification on the Ballast of Surface Aggregates Sinking through the Twilight Zone
The dissolution of CaCO3 is one of the ways ocean acidification can, potentially, greatly affect the ballast of aggregates. A diminution of the ballast could reduce the settling speed of aggregates, resulting in a change in the carbon flux to the deep sea. This would mean lower amounts of more refractory organic matter reaching the ocean floor. This work aimed to determine the effect of ocean acidification on the ballast of sinking surface aggregates. Our hypothesis was that the decrease of pH will increase the dissolution of particulate inorganic carbon ballasting the aggregates, consequently reducing their settling velocity and increasing their residence time in the upper twilight zone. Using a new methodology for simulation of aggregate settling, our results suggest that future pCO2 conditions can significantly change the ballast composition of sinking aggregates. The change in aggregate composition had an effect on the size distribution of the aggregates, with a shift to smaller aggregates. A change also occurred in the settling velocity of the particles, which would lead to a higher residence time in the water column, where they could be continuously degraded. In the environment, such an effect would result in a reduction of the carbon flux to the deep-sea. This reduction would impact those benthic communities, which rely on the vertical flow of carbon as primary source of energy
5 year-long monitoring of Barkley Canyon cold-seeps with the internet operated deep-sea crawler "Wally"
Despite the technological advances of the last decades (e.g. ROVs, AUVs, cabled
observatories), our knowledge of most deep-sea environments is still strongly
limited by spatio-temporal sampling and observational capabilities. The novel
Internet Operated Deep-Sea Crawler technology can provide high-frequency,
multi-sensor data, during long-term deployments, 24/7 communication with
researchers and broader spatial coverage (i.e. mobile platform) than fixed
instrument installations. The crawler “Wally” is deployed at the Barkley Canyon
methane hydrates site (NE Pacific, Canada; ~890 m depth) and connected to the
Ocean Networks Canada NEPTUNE cabled observatory network (ONC; www.
oceannetworks.ca). Here we present the environmental and biological datasets
obtained from Wally instruments and cameras, during the first deployment phase
(September 2010 to January 2015), as well as new features and preliminary
results obtained since it was re-deployed (May 2016 – present). In addition to data
provided by the standard payload of the crawler (i.e. ADCP, CTD, methane sensor,
turbidity sensor and fluorometer), the hydrates community was video-monitored at
different frequencies and timespans. Photomosaics were generated at two distinct
locations, in order to map chemosynthetic bacterial mats and vesicomyid clam
colonies covering the ~2-3 m high hydrate mounds, and document their temporal
dynamics. The crawler followed the development of a deep-sea shell taphonomic
experiment aiming to quantify biogenic carbon fluxes at the hydrates environment.
The composition and diel activity patterns of the hydrates megafaunal community
were studied with the use of linear video-transects conducted from February 2013 to
April 2014. Since the summer of 2016, video-frames recorded at different locations
of the site are analyzed for a biodiversity study and photomosaicing of the hydrate
mounds continues, with 3D modelling of the mound structures also available as a
new feature of the crawler deployed in May 2016. All data are archived in real-time
and can be accessed online on the Ocean Networks Canada database. As deep-sea
crawler technology and similar mobile, benthic platform technologies progress
towards full operational autonomy, they will provide an even greater capacity for
future monitoring and understanding of dynamic, extreme environments such as
methane hydrate fields.Peer Reviewe
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