3,027 research outputs found
Multibeam systems for the detection of gas flares in the water column
Wärtsilä ELAC Nautik is one major global player in the multibeam business.
The multibeam systems are marketed under the well-known brand name
SeaBeam, including systems for medium water depth and deep-water areas.
The ELAC SeaBeam 3012/3020 deep-water systems operate in the 12 kHz and
20 kHz frequency bands, whereas the ELAC SeaBeam 3030/3050 medium-depth
systems operate in the 30 kHz and 50 kHz frequency bands. While formerly
only continuous wave (CW) pulses were applied, the new Mk II series of the
ELAC SeaBeam 3030/3050 multibeam systems offer the possibility to apply
frequencymodulated (FM) pulses for increased measurement ranges, improved
range resolution and better data quality. FM pulses require a correlation of the
beamformed data of all beam directions with pulse replica in order to obtain
pulse compression. Additionally, Doppler shifts of the operating frequencies
induced by the ship’s movement have to be compensated. In order to obtain
unrivalled data quality, the ELAC SeaBeam 3030 / 3050 multibeam ystems apply
Doppler compensation not only on the bathymetric depth data, but also on
the water column imaging (WCI) data. In order to provide high data density,
all ELAC SeaBeam MBES can transmit two quasisimultaneous swaths per ping
cycle, which are frequency-separated. Compared to the singleping mode, the
data density is doubled. The ELAC SeaBeam 3030/3050 multibeam systems
include a functionality for to automatic cyclical steering of the transmitted
swaths in the along-ship direction. Via this functionality, which is called
“Advanced Transmission Beam Steering”, an entire volume below the vessel can
be insonified without requiring any movement of the vessel. The operator can
specify an angle range and an angle increment, resulting in a periodic oscillation
of the transmitted swaths from bow to aft and vice versa. This functionality is
very helpful for the detection and analysis of gas flares, leakages or other objects
in the water column during stationary vessel operation or on fixed platforms.
Wärtsilä ELAC Nautik GmbH Page 2 of 3 31. May 2016
On order to provide highest operational flexibility, the ELAC SeaBeam 3050
and ELAC SeaBeam 3030 are available as mobile systems, providing the sonar
electronics in flight cases and utilizing mobile transducer brackets for spatial
resolutions of 1.5° x 2° for ELAC SeaBeam 3050 and 3° x 2° for ELAC SeaBeam 3030.
Wärtsilä ELAC Nautik is the only supplier, offering a mobile 30 kHz multibeam
of the sea water profile and sea water surface will be designed, studied,
developed and applied to a real situation. A thermometer, based on distributed
temperature sensor, will be designed, paying special attention to the involved
materials, in order to avoid the damages of such corrosive environment.
Nowadays, this techique is used in many infraestructures as bridge or airports
by never has been used in sea, where the sea currents and biofouling are
problems that will are wtudied at the project. However the optical fibers must
been calibrated to know the uncertainty in temperature measure, and it is the
purpose of the paper.
system with a depth performance of more than 6,000 meters. Wärtsilä ELAC
Nautik is a main industrial partner within the German „Lighthouse“ Research
Project SUGAR (Submarine Gas Hydrate Reservoirs) and cooperates with the
GEOMAR Helmholtz Centre for Ocean Research Kiel. Wärtsilä ELAC Nautik
participates in a SUGAR subproject, which is related to gas flare detection.
Gas flares at the seabed are indicators for potential gas hydrate reservoirs and
potential leakages of gas deposits. Therefore, gas flare detection is important for
the exploration of submarine gas hydrates and for environmental monitoring.
Driven by the SUGAR project, the ELAC SeaBeam multibeam systems store
WCI data with very high resolution. For the online and offline visualization of
high-resolution WCI data, the ELAC WCI Viewer is utilized, providing different
window types for data visualization, different scaling and range options,
forward and backward data playback as movies or single pictures, object and
event functionalities and the display of external sensor data. These capabilities
help to identify and analyze any kinds of objects in the water column or on the
bottom (e.g. gas seeps).
Despite helpful aids for the online visualization of high-resolution WCI data,
there is a need for an automatic processing of WCI data with respect to object
detection. Such automatic processing will reduce the workload of survey
operators significantly. Therefore, Wärtsilä ELAC Nautik has developed an
automatic object detector (ELAC AOD) which is dedicated to gas flares in the
water column. Due to the huge data volumes of high-resolution WCI data, the
development of the ELAC AOD was ambitious and challenging. The ELAC AOD
was implemented within the MATLAB development environment. The ELAC AOD
is dedicated to WCI data from ELAC SeaBeam 3030 and 3050 medium-depth
multibeam systems and stores all relevant information of detected objects in
so-called object log files. It is possible to import such object log files into the
ELAC WCI Viewer for visualization purposes. Due to the above-mentioned
characteristics, multibeam systems from Wärtsilä ELAC Nautik are excellently
applicable in order to detect and analyze gas flares in the water column. The
presentation will provide detailed system information and important data
examples.Peer Reviewe
Phase-space geometry of the generalized Langevin equation
The generalized Langevin equation is widely used to model the influence of a
heat bath upon a reactive system. This equation will here be studied from a
geometric point of view. A dynamical phase space that represents all possible
states of the system will be constructed, the generalized Langevin equation
will be formally rewritten as a pair of coupled ordinary differential
equations, and the fundamental geometric structures in phase space will be
described. It will be shown that the phase space itself and its geometric
structure depend critically on the preparation of the system: A system that is
assumed to have been in existence for ever has a larger phase space with a
simpler structure than a system that is prepared at a finite time. These
differences persist even in the long-time limit, where one might expect the
details of preparation to become irrelevant
Counting rule for Nambu-Goldstone modes in nonrelativistic systems
The counting rule for Nambu-Goldstone modes is discussed using Mori's
projection operator method in nonrelativistic systems at zero and finite
temperatures. We show that the number of Nambu-Goldstone modes is equal to the
number of broken charges, Q_a, minus half the rank of the expectation value of
[Q_a,Q_b].Comment: 5 pages, no figures; typos corrected; some discussion added and
clarifie
Anisotropy and Order of Epitaxial Self-Assembled Quantum Dots
Epitaxial self-assembled quantum dots (SAQDs) represent an important step in
the advancement of semiconductor fabrication at the nanoscale that will allow
breakthroughs in electronics and optoelectronics. In these applications, order
is a key factor. Here, the role of crystal anisotropy in promoting order during
early stages of SAQD formation is studied through a linear analysis of a
commonly used surface evolution model. Elastic anisotropy is used a specific
example. It is found that there are two relevant and predictable correlation
lengths. One of them is related to crystal anisotropy and is crucial for
determining SAQD order. Furthermore, if a wetting potential is included in the
model, it is found that SAQD order is enhanced when the deposited film is
allowed to evolve at heights near the critical surface height for
three-dimensional film growth.Comment: 11 pages, 1 figur
A non-equilibrium dynamic mechanism for the allosteric effect
Allosteric regulation is often viewed as thermodynamic in nature. However
protein internal motions during an enzymatic reaction cycle can be slow hopping
processes over numerous potential barriers. We propose that regulating
molecules may function by modifying the nonequilibrium protein dynamics. The
theory predicts that an enzyme under the new mechanism has different
temperature dependence, waiting time distribution of the turnover cycle, and
dynamic fluctuation patterns with and without effector. Experimental tests of
the theory are proposed.Comment: accepted by Phys. Rev. Lett. Major revisions were made to fit the
style. 4 pages, 2 figure
Memory Effects In Nonequilibrium Quantum Impurity Models
Memory effects play a key role in the dynamics of strongly correlated systems
driven out of equilibrium. In the present study, we explore the nature of
memory in the nonequilibrium Anderson impurity model. The
Nakajima--Zwanzig--Mori formalism is used to derive an exact generalized
quantum master equation for the reduced density matrix of the interacting
quantum dot, which includes a non-Markovian memory kernel. A real-time path
integral formulation is developed, in which all diagrams are stochastically
sampled in order to numerically evaluate the memory kernel. We explore the
effects of temperature down to the Kondo regime, as well as the role of
source--drain bias voltage and band width on the memory. Typically, the memory
decays on timescales significantly shorter than the dynamics of the reduced
density matrix itself, yet under certain conditions it develops a smaller long
tail. In addition we address the conditions required for the existence,
uniqueness and stability of a steady-state.Comment: 4 pages, 3 figure
Geometric and projection effects in Kramers-Moyal analysis
Kramers-Moyal coefficients provide a simple and easily visualized method with
which to analyze stochastic time series, particularly nonlinear ones. One
mechanism that can affect the estimation of the coefficients is geometric
projection effects. For some biologically-inspired examples, these effects are
predicted and explored with a non-stochastic projection operator method, and
compared with direct numerical simulation of the systems' Langevin equations.
General features and characteristics are identified, and the utility of the
Kramers-Moyal method discussed. Projections of a system are in general
non-Markovian, but here the Kramers-Moyal method remains useful, and in any
case the primary examples considered are found to be close to Markovian.Comment: Submitted to Phys. Rev.
Enhanced diffusion and ordering of self-propelled rods
Starting from a minimal physical model of self propelled hard rods on a
substrate in two dimensions, we derive a modified Smoluchowski equation for the
system. Self -propulsion enhances longitudinal diffusion and modifies the mean
field excluded volume interaction. From the Smoluchowski equation we obtain
hydrodynamic equations for rod concentration, polarization and nematic order
parameter. New results at large scales are a lowering of the density of the
isotropic-nematic transition and a strong enhancement of boundary effects in
confined self-propelled systems.Comment: 4 pages, 2 figure
Improved Calculation of Vibrational Mode Lifetimes in Anharmonic Solids - Part I: Theory
We propose here a formal foundation for practical calculations of vibrational
mode lifetimes in solids. The approach is based on a recursion method analysis
of the Liouvillian. From this we derive the lifetime of a vibrational mode in
terms of moments of the power spectrum of the Liouvillian as projected onto the
relevant subspace of phase space. In practical terms, the moments are evaluated
as ensemble averages of well-defined operators, meaning that the entire
calculation is to be done with Monte Carlo. These insights should lead to
significantly shorter calculations compared to current methods. A companion
piece presents numerical results.Comment: 18 pages, 3 figure
- …