3,694 research outputs found
Wigner's Spins, Feynman's Partons, and Their Common Ground
The connection between spin and symmetry was established by Wigner in his
1939 paper on the Poincar\'e group. For a massive particle at rest, the little
group is O(3) from which the concept of spin emerges. The little group for a
massless particle is isomorphic to the two-dimensional Euclidean group with one
rotational and two translational degrees of freedom. The rotational degree
corresponds to the helicity, and the translational degrees to the gauge degree
of freedom. The question then is whether these two different symmetries can be
united. Another hard-pressing problem is Feynman's parton picture which is
valid only for hadrons moving with speed close to that of light. While the
hadron at rest is believed to be a bound state of quarks, the question arises
whether the parton picture is a Lorentz-boosted bound state of quarks. We study
these problems within Einstein's framework in which the energy-momentum
relations for slow particles and fast particles are two different
manifestations one covariant entity.Comment: LaTex 12 pages, 3 figs, based on the lectures delivered at the
Advanced Study Institute on Symmetries and Spin (Prague, Czech Republic, July
2001
Optical Activities as Computing Resources for Space-time Symmetries
It is known that optical activities can perform rotations. It is shown that
the rotation, if modulated by attenuations, can perform symmetry operations of
Wigner's little group which dictates the internal space-time symmetries of
elementary particles.Comment: 13 pages, to be published in J. Mod. Optic
On the Existence of Positive Solutions of Quasilinear Elliptic Boundary Value Problems
AbstractWe establish the existence of positive solutions to a class of quasilinear anisotropic problems which have either sublinear or superlinear nonlinearity. With a, b nonnegative constants and α, ÎČ positive constants, one example is If bâa<1 (sublinear case), then for each λâ[0,â), (1) has a solution. On the other hand, if bâa>1 (superlinear case), then there exists a λ*>0 such that for 0⩜λ<λ*, (1) has at least one solution, and for λ>λ* no solution exists
POST-IRRADIATION ANALYSES OF U-MO DISPERSION FUEL RODS OF KOMO TESTS AT HANARO
Since 2001, a series of five irradiation test campaigns for atomized U-Mo dispersion fuel rods, KOMO-1, -2, -3, -4, and -5, has been conducted at HANARO (Korea) in order to develop high performance low enriched uranium dispersion fuel for research reactors. The KOMO irradiation tests provided valuable information on the irradiation behavior of U-Mo fuel that results from the distinct fuel design and irradiation conditions of the rod fuel for HANARO. Full size U-Mo dispersion fuel rods of 4â5 g-U/cm3 were irradiated at a maximum linear power of approximately 105 kW/m up to 85% of the initial U-235 depletion burnup without breakaway swelling or fuel cladding failure. Electron probe microanalyses of the irradiated samples showed localized distribution of the silicon that was added in the matrix during fuel fabrication and confirmed its beneficial effect on interaction layer growth during irradiation. The modifications of U-Mo fuel particles by the addition of a ternary alloying element (Ti or Zr), additional protective coatings (silicide or nitride), and the use of larger fuel particles resulted in significantly reduced interaction layers between fuel particles and Al
Standing waves in the Lorentz-covariant world
When Einstein formulated his special relativity, he developed his dynamics
for point particles. Of course, many valiant efforts have been made to extend
his relativity to rigid bodies, but this subject is forgotten in history. This
is largely because of the emergence of quantum mechanics with wave-particle
duality. Instead of Lorentz-boosting rigid bodies, we now boost waves and have
to deal with Lorentz transformations of waves. We now have some understanding
of plane waves or running waves in the covariant picture, but we do not yet
have a clear picture of standing waves. In this report, we show that there is
one set of standing waves which can be Lorentz-transformed while being
consistent with all physical principle of quantum mechanics and relativity. It
is possible to construct a representation of the Poincar\'e group using
harmonic oscillator wave functions satisfying space-time boundary conditions.
This set of wave functions is capable of explaining the quantum bound state for
both slow and fast hadrons. In particular it can explain the quark model for
hadrons at rest, and Feynman's parton model hadrons moving with a speed close
to that of light.Comment: LaTex 20 pages, presented at the 2004 meeting of the International
Association of Relativistic Dynamincs, to be published in the proceeding
Nonpropagation of tachyon on the BTZ black hole in type 0B string theory
We obtain the BTZ black hole (AdSS) as a non-dilatonic
solution from type 0B string theory. Analyzing the perturbation around this
black hole background, we show that the tachyon is not a propagating mode.Comment: some detailed explanations are added, modified version will be
appeared in Physics Letters B, 11 pages in RevTeX, no figure
Slowly rotating black holes in the Horava-Lifshitz gravity
We investigate slowly rotating black holes in the Ho\v{r}ava-Lifshitz (HL)
gravity. For and , we find a slowly rotating black
hole of the Kehagias-Sfetsos solution in asymptotically flat spacetimes. We
discuss their thermodynamic properties by computing mass, temperature, angular
momentum, and angular velocity on the horizon.Comment: 12 pages, no figures, version to appear in EPJ
Big data analysis of public library operations and services by using the Chernoff face method
Purpose â The purpose of this paper is to conduct a big data analysis of public library
operations and services of two cities in two countries by using the Chernoff face method.
Design/methodology/approach â The study is designed to evaluate library services by
analysing the Chernoff face. Big data on public libraries in London and Seoul were
collected respectively from CIPFA and the Korean governmentâs website for drawing a
Chernoff face. The association of variables and human facial features was decided by
survey. Although limited in its capacity to handle a large number of variables (eight were
analysed in this study) the Chernoff face method does readily allow for the comparison
of a large number of instances of analysis. 58 Chernoff faces were drawn from the
formatted data by using the R programming language.
Findings â The study reveals that most of the local governments in London perform
better than those of Seoul. This consequence is due to the fact that local governments in
London operate more libraries, invest more budgets, allocate more staff and hold more
collections than local governments in Seoul. This administration resulted in more use of
libraries in London than Seoul. The study validates the benefit of using the Chernoff
face method for big data analysis of library services.
Practical implications â Chernoff face method for big data analysis offers a new
evaluation technique for library services and provides insights that may not be as readily
apparent and discernible using more traditional analytical methods.
Originality/value â This study is the first to use the Chernoff face method for big data
analysis of library services in library and information research
Comparison of computed tomographic findings in pulmonary mucormycosis and invasive pulmonary aspergillosis
AbstractBecause there are no available molecular markers for pulmonary mucormycosis (PM), which has low culture sensitivity, early diagnosis and treatment rely heavily on imaging modes such as computed tomography (CT). However, there are limited data comparing CT findings for PM with those for invasive pulmonary aspergillosis (IPA). Adult patients who met the modified criteria for proven and probable PM (over an 11-year period) and IPA (over a 6-year period, owing to the availability of the galactomannan assay) according to the modified European Organization for Research and Treatment of Cancer/Mycosis Study Group definitions were retrospectively enrolled. IPA cases were selected at a 1 : 4 (PM/IPA) ratio. Thoracic CT scans were reviewed by two experienced radiologists blinded to the patients' demographics and clinical outcomes. A total of 24 patients with PM, including 20 (83%) with proven PM and four (17%) with probable PM, and 96 patients with IPA, including 12 (13%) with proven IPA and 84 (87%) with probable IPA, were eventually analysed. The reverse halo sign was more common in patients with PM (54%) than in those with IPA (6%, p < 0.001), whereas some airway-invasive features, such as clusters of centrilobular nodules, peribronchial consolidations, and bronchial wall thickening, were more common in patients with IPA (IPA 52% vs. PM 29%, p 0.04; IPA 49% vs. PM 21%, p 0.01; IPA 34% vs. PM 4%, p 0.003, respectively). The reverse halo sign was more common, and airway-invasive features were less common, in patients with PM than in those with IPA. These findings may help physicians to initiate Zygomycetes-active antifungal treatment earlier
An acoustic, aerodynamic and perceptual investigation of word-initial denasalization in Korean
Korean nasals /m/ and /n/ are generally considered by Korean phoneticians to be hardly different from the corresponding English sounds, but those in word-initial position are often perceived as plosives by native speakers of English. This had been noted by only a few previous observers, and investigated on a very limited scale.
In this study, various experimental methods were employed in systematic analyses of the production and acoustic form of word-initial /m/ and /n/ from fluent connected speech collected from a relatively large number of informants, and corresponding perception tests were conducted with groups of Korean and English listeners.
Auditory and spectrographic analyses confirmed that the segments were commonly âdenasalizedâ. They display characteristics widely different from those of sonorant nasals, lacking the nasal formants commonly seen in spectrograms; in most cases they were more similar to voiced plosives, many tokens even showing plosive-like release bursts. Spectral analyses confirmed that denasalized nasals are significantly different from sonorant nasals throughout the whole frequency range but remain somewhat different from voiced plosives in the low and high frequency regions. Aerodynamic and accelerometer studies, which examined the consonants in CV combinations, indicated that the denasalized sounds are evidently produced with a pattern of velopharyngeal control which is different from those of sonorant nasals or of plosives. Perception tests showed overwhelmingly that the word-initial denasalized sounds are categorized as nasals by Korean listeners but as plosives by English listeners. When real voiced plosive tokens from another context are artificially moved to word-initial position, Koreans perceive these too as nasals, while English listenersâ responses are not sensitive to the context.
The study shows that denasalization needs to be acknowledged as a major regular feature of spoken Korean, even though it has been largely ignored up to now. Directions for further research are outlined
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