844 research outputs found
Nucleon magnetic moments in an extended chiral constituent quark model
We present results for the nucleon magnetic moments in the context of an
extended chiral constituent quark model based on the mechanism of the Goldstone
boson exchange, as suggested by the spontaneous breaking of chiral symmetry in
QCD. The electromagnetic charge-current operator is consistently deduced from
the model Hamiltonian, which includes all force components for the
pseudoscalar, vector and scalar meson exchanges. Thus, the continuity equation
is satisfied for each piece of the interaction, avoiding the introduction of
any further parameter. A good agreement with experimental values is found. The
role of isoscalar two-body operators, not constrained by the continuity
equation, is also investigated.Comment: 7 pages, 1 table, submitted for publication to Phys. Lett. B,
elsart.sty/elsart12.sty include
Charge-Exchange and multi-scattering effects in (e,e'n) knockout
Final-state interactions in (e,e'n) knockout reactions in the quasi-free
region are studied by considering the multistep direct scattering of the
ejectile nucleon. Primary and multiple particle emission are included within
the same model and are found to become important with increasing excitation
energy. Charge-exchange effects taken into account through the two-step
(e,e'p)(p,n) and three-step (e,e'p)(p,N)(N,n) processes are also found to
increase with energy. A comparison with the results obtained with an
isospin-dependent optical potential at small excitation energies is presented.Comment: 12 pages, 4 Postscript figures. A new section on multiple particle
emission added together with 2 new figures including primary and multiple
emission cross section
Is query translation a distinct task from search?
INTRODUCTION
The University of Sheffield participated in iCLEF 2002 using, as a test-bed, the prototype under
development in the Clarity project. Clarity is an EU funded project aimed at developing a system for
cross-language information retrieval for so-called low density languages, those with few translation
resources. Currently translation between English and Finnish is supported; soon Swedish will be added
and in the near future Latvian and Lithuanian.
Clarity is being developed in a user-centred way with user involvement from the beginning. The design
of the first user interface was based on current best practise, particular attention was paid to empirical
evidence for a specific design choice. Six paper-based interface mock-ups representing important
points in the cross-language search task were generated and presented for user assessment as a part of
an extensive user study. The study (reported in Petrelli et al. 2002) was conducted to understand users
and uses of cross-language information retrieval systems. Many different techniques were applied:
contextual enquiry, interviews, questionnaires, informal evaluation of existing cross-language
technology, and participatory design sessions with the interface mock-ups mentioned above. As a
result, a user class profile was sketched and a long list of user requirements was compiled. As a followup,
a redesign session took place and the new system was designed for users whoknow the language(s) they are searching (polyglots);
• search for writing (journalists, translators business analysts);
• have limited searching skills;
• know the topic in advance or will learn/read on it while searching;
• use many languages in the same search session and often swap between them.
New system features were listed as important and the user interface was redesigned. Considering the
result of the study the new interface allowed the user to dynamically change the language setting from
query to query, hid the query translation and showed the retrieved set as ranked list primary.
Despite the fact that this new design was considered to be more effective, a comparison between the
first layout based on the relevant literature and the new one based on the user study was considered an
important research question. In particular, the choice of hiding the query translation was considered an
important design decision, against the common agreement to allow and support the user in controlling
the system actions. Thus the participation of Sheffield in iCLEF was organized around the idea of
checking if the user should validate the query translation before the search is run or instead if the
system should perform the translation and search in a single step without any user’s supervision
Stochastic Metallic-Glass Cellular Structures Exhibiting Benchmark Strength
By identifying the key characteristic “structural scales” that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date
Compression-compression fatigue of Pd_(43)Ni_(10)Cu_(27)P_(20) metallic glass foam
Compression-compression fatigue testing of metallic-glass foam is performed. A stress-life curve is constructed, which reveals an endurance limit at a fatigue ratio of about 0.1. The origin of fatigue resistance of this foam is identified to be the tendency of intracellular struts to undergo elastic and reversible buckling, while the fatigue process is understood to advance by anelastic strut buckling leading to localized plasticity (shear banding) and ultimate strut fracture. Curves of peak and valley strain versus number of cycles coupled with plots of hysteresis loops and estimates of energy dissipation at various loading cycles confirm the four stages of foam-fatigue
Cluster Model for Near-barrier Fusion Induced by Weakly Bound and Halo Nuclei
The influence on the fusion process of coupling transfer/breakup channels is
investigated for the medium weight Li+Co systems in the vicinity
of the Coulomb barrier. Coupling effects are discussed within a comparison of
predictions of the Continuum Discretized Coupled-Channels model. Applications
to He+Co induced by the borromean halo nucleus He are also
proposed.Comment: 5 pages, 3 figures, FINUSTAR2 Conference, Aghios Nikolaus, Crete,
Greece. 10-14 September 200
Premitotic Labeling and Inflammation in the Gingiva of Rhesus Monkeys
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141674/1/jper0606.pd
Effect of strain rate on the yielding mechanism of amorphous metal foam
Stochastic amorphous Pd_(43)Ni_(10)Cu_(27)P_(20) foams were tested in quasistatic and dynamic loading. The strength/porosity relations show distinct slopes for the two loading conditions, suggesting a strain-rate-induced change in the foam yielding mechanism. The strength/porosity correlation of the dynamic test data along with microscopy assessments support that dynamic foam yielding is dominated by plasticity rather than elastic buckling, the mechanism previously identified to control quasistatic yielding. The strain-rate-induced shift in the foam yielding mechanism is attributed to the rate of loading approaching the rate of sound wave propagation across intracellular membranes, thereby suppressing elastic buckling and promoting plastic yielding
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