28,771 research outputs found
Faddeev-Skyrme Model and Rational Maps
The Faddeev-Skyrme model, a modified O(3) nonlinear sigma model in three
space dimensions, is known to admit topological solitons that are stabilized by
the Hopf charge. The Faddeev-Skyrme model is also related to the low-energy
limits of SU(2) Yang-Mills theory. Here, the model is reformulated into its
gauge-equivalent expression, which turns out to be Skyrme-like. The solitonic
solutions of this Skyrme-like model are analyzed by the rational map ansatz.
The energy function and the Bogomolny-type lower bound of the energy are
established. The generalized Faddeev-Skyrme model that originates from the
infrared limits of SU(N) Yang-Mills theory is presented.Comment: 12 pages, LaTex, minor typo correcte
SWiM: A Simple Window Mover
As computers become more ubiquitous, traditional two-dimensional interfaces
must be replaced with interfaces based on a three-dimensional metaphor.
However, these interfaces must still be as simple and functional as their
two-dimensional predecessors. This paper introduces SWiM, a new interface for
moving application windows between various screens, such as wall displays,
laptop monitors, and desktop displays, in a three-dimensional physical
environment. SWiM was designed based on the results of initial "paper and
pencil" user tests of three possible interfaces. The results of these tests led
to a map-like interface where users select the destination display for their
application from various icons. If the destination is a mobile display it is
not displayed on the map. Instead users can select the screen's name from a
list of all possible destination displays. User testing of SWiM was conducted
to discover whether it is easy to learn and use. Users that were asked to use
SWiM without any instructions found the interface as intuitive to use as users
who were given a demonstration. The results show that SWiM combines simplicity
and functionality to create an interface that is easy to learn and easy to use.Comment: 7 pages, 4 figure
A Workload-Specific Memory Capacity Configuration Approach for In-Memory Data Analytic Platforms
We propose WSMC, a workload-specific memory capacity configuration approach
for the Spark workloads, which guides users on the memory capacity
configuration with the accurate prediction of the workload's memory requirement
under various input data size and parameter settings.First, WSMC classifies the
in-memory computing workloads into four categories according to the workloads'
Data Expansion Ratio. Second, WSMC establishes a memory requirement prediction
model with the consideration of the input data size, the shuffle data size, the
parallelism of the workloads and the data block size. Finally, for each
workload category, WSMC calculates the shuffle data size in the prediction
model in a workload-specific way. For the ad-hoc workload, WSMC can profile its
Data Expansion Ratio with small-sized input data and decide the category that
the workload falls into. Users can then determine the accurate configuration in
accordance with the corresponding memory requirement prediction.Through the
comprehensive evaluations with SparkBench workloads, we found that, contrasting
with the default configuration, configuration with the guide of WSMC can save
over 40% memory capacity with the workload performance slight degradation (only
5%), and compared to the proper configuration found out manually, the
configuration with the guide of WSMC leads to only 7% increase in the memory
waste with the workload's performance slight improvement (about 1%
Are Real Exchange Rates Nonlinear with a Unit Root? Evidence on Purchasing Power Parity for China: A Note
This article applies the threshold autoregressive model proposed by Caner and Hansen (2001) to examine both linearity and stationarity of China's real exchange rate vis-Ã -vis her 9 trading partner countries over the period of January 1986 to October 2009. Two main conclusions are drawn. Firstly, the empirical results indicate that China's real exchange is a nonlinear process. Secondly, a unit root in real exchange rate was found for most of the cases under study. This result provides no support for purchasing power parity for China relative to their major trading partner countries.Threshold Autoregressive Model; Linearity and Stationarity, Purchasing Power Parity; Threshold Unit Root Test
Grammatical errors in spoken english of University students in oral communication course
The present study examines the grammatical errors in spoken English of university
students who are less proficient in English. The specific objectives of the study are to
determine the types of errors and the changes in grammatical accuracy during the
duration of the English for Social Purposes course focussing on oral communication. The
language data were obtained from the simulated oral interactions of 42 students
participating in five role play situations during the 14-week semester. Error analysis of
126 oral interactions showed that the five common grammar errors made by the learners
are preposition, question, article, plural form of nouns, subject-verb agreement and tense.
Based on Dulay, Burt and Krashen’s (1982) surface structure taxonomy, the main ways
by which students modify the target forms are misinformation and omission, with
addition of elements or misordering being less frequent. The results also showed an
increase in grammatical accuracy in the students’ spoken English towards the end of the
course
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