19,007 research outputs found
Asymmetries Between Strange and Antistrange Particle Production in Pion-Proton Interactions
Recent measurements of the asymmetries between Feynman distributions of
strange and antistrange hadrons in interactions show a strong effect
as a function of . We calculate strange hadron production in the context
of the intrinsic model and make predictions for particle/antiparticle
asymmetries in these interactions.Comment: version to be published in Nucl. Phys. A, 46 pages LaTeX, 15 .eps
figure
Quantum-enhanced gyroscopy with rotating anisotropic Bose–Einstein condensates
High-precision gyroscopes are a key component of inertial navigation systems. By considering matter wave gyroscopes that make use of entanglement it should be possible to gain some advantages in terms of sensitivity, size, and resources used over unentangled optical systems. In this paper we consider the details of such a quantum-enhanced atom interferometry scheme based on atoms trapped in a carefully-chosen rotating trap. We consider all the steps: entanglement generation, phase imprinting, and read-out of the signal and show that quantum enhancement should be possible in principle. While the improvement in performance over equivalent unentangled schemes is small, our feasibility study opens the door to further developments and improvements
Relative sea-level rise and the development of channel-fill and shallow-water sequences on Cape Cod, Massachusetts
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution January 1999Channel-fill sediments located in shallow-water off the south shore of Cape Cod,
Massachusetts, provide a record of the late-Pleistocene and Holocene geological evolution
in a post-glacial setting. Though conventionally difficult to sample adequately and
anticipated to have low preservation potential, channel-fill sequences record in some detail
differing relative sea-level and sedimentation processes. Two distinct channel-fill
sequences record differing sequence stratigraphies, and hence different origins and post
glacial histories. These sequences have accumulated in channels eroded into two different
late-Pleistocene glacial units. The first fill-type was encountered in channels on the upper
portions of the channel network in northern half of the study site. Channels in this portion
of the channel system were incised into the late-Pleistocene glacial outwash substrate by
spring sapping Uchupi and Oldale, 1994. The channel-fill sequences are comprised of a
transgressive systems tract composed of a consistent sequence of coastal embayment and
shoreline facies that have succeeded one another in response to Holocene relative sea-level
rise. As relative sea-level flooded these paleo-channels, marsh environments were
established in response to rising relative sea-level. With continued sea-level rise, the marsh
environments migrated farther up channel. The exposed paleo-channels continued to flood,
accommodating quiet water coastal embayments, likely protected from wave action by
barrier beaches located more seaward. As relative sea-level rise continued, the coastline
was driven landward over regions within the paleo-channels that formerly accommodated
marsh and embayment sedimentation. The landward migration of the coastline was
indicated by beach and barrier facies that covered the fine grained coastal embayment
sediments. With further relative sea-level rise, beach and barrier settings were eroded as
the shoreface migrated farther landward and nearshore marine deposition by wave and tidal
flows ensued. Sedimentary environments similar to those recorded in the channels are
found in modern coastal embayments on the south shore of Cape Cod.
The second channel-fill type, which forms part of the southern and western portion
of the channel network is more difficult to relate to the previously described sequence. The
channels that contain fill were not adequately defined in this survey but were probably
incised during the late-Pleistocene in response to ice melting and retreat. The sediments
that make up this channel-fill are composed mainly of late-Pleistocene glaciolacustrine silts
and clays. Sediments that make up the Holocene transgressive systems tract are limited to
the upper meter of this channel sequence. They are composed of two sand units that reflect
Holocene beach and nearshore sedimentation. The absence of coastal embayment and other
paralic facies from the systems tract suggests that these channels did not accommodate
protected embayments or that these sediments were not well preserved during the submergence of this region. Changes in the channel orientation or in the rate of relative
sea-level rise may have contributed to this difference in sediment fill.While conducting this research the author was partially supported as a National
Science Foundation Coastal Trainee WHOI # 85412900. Funding from the Andrew W.
Mellon Foundation WHOI # 25903900 and the Woods Hole Oceanographic Institution
Education Office WHOI # 45050 also supported this work
Bethe-Salpeter bound-state structure in Minkowski space
The quantitative investigation of the scalar Bethe-Salpeter equation in
Minkowski space, within the ladder-approximation framework, is extended to
include the excited states. This study has been carried out for an interacting
system composed by two massive bosons exchanging a massive scalar, by adopting
(i) the Nakanishi integral representation of the Bethe-Salpeter amplitude, and
(ii) the formally exact projection onto the null plane. Our analysis, on one
hand, confirms the reliability of the method already applied to the ground
state and, on the other one, extends the investigation from the valence
distribution in momentum space to the corresponding quantity in the
impact-parameter space, pointing out some relevant features, like (i) the
equivalence between Minkowski and Euclidean transverse-momentum amplitudes, and
(ii) the leading exponential fall-off of the valence wave function in the
impact-parameter space.Comment: 15 pages, 7 figure
Experimental Study of the Role of Atomic Interactions on Quantum Transport
We report an experimental study of quantum transport for atoms confined in a
periodic potential and compare between thermal and BEC initial conditions. We
observe ballistic transport for all values of well depth and initial
conditions, and the measured expansion velocity for thermal atoms is in
excellent agreement with a single-particle model. For weak wells, the expansion
of the BEC is also in excellent agreement with single-particle theory, using an
effective temperature. We observe a crossover to a new regime for the BEC case
as the well depth is increased, indicating the importance of interactions on
quantum transport.Comment: 4 pages, 3 figure
In-situ steel solidification imaging in continuous casting using magnetic induction tomography
: Solidification process in continuous casting is a critical part of steel production. The speed and quality of the solidification process determines the quality of final product. Computational fluid dynamics (CFD) simulations are often used to describe the process and design of its control system, but so far, there is no any tool that provides an on-line measurement of the solidification front of hot steel during the continuous casting process. This paper presents a new tool based on magnetic induction tomography (MIT) for real time monitoring of this process. The new MIT system was installed at the end of the secondary cooling chamber of a casting unit and tested during several days in a real production process. MIT is able to create an internal map of electrical conductivity of hot steel deep inside the billet. The image of electrical conductivity is then converted to temperature profile that allows the measurement of the solid, mushy and liquid layers. In this study, such a conversion is done by synchronizing in one time step the MIT measurement and the thermal map generated with the actual process parameters available at that time. The MIT results were then compared with the results obtained of the CFD and thermal modelling of the industrial process. This is the first in-situ monitoring of the interior structure during a real continuous casting.The SHELL-THICK project has received funding from EU Research Fund for Coal and Steel under grant number 709830. This study reflects only the author's views and the European Commission is not responsible for any use that may be made of the information contained therein
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