241 research outputs found
Functional design of mechanical products based on behavior-driven function-environment-structure modeling framework
The relative significance of upstream design activity to downstream design activity is widely recognized, due to its critical role in determining the final product’s functionality. Although there are now some general methodologies dealing with functions or reasoning about functions, virtually no commercial CAD system can support functional design. In functional modeling, a design problem is represented in a hierarchy of functions and the behaviors that realize the functions. This paper presents a functional design methodology based on a behavior-driven function-environment-structure (B-FES) modeling framework to guide functional design through functional reasoning steps including causal behavioral reasoning (CBR) and functional decomposition. The proposed functional design starts from a set of design specifications including functional requirements and design constraints, and results in diverse behavioral schema corresponding to a set of design alternatives. A design example for functional design of a terminal cut-off unit in an automatic assembly system is used to provide a demonstration of the proposed functional design methodology.Singapore-MIT Alliance (SMA
A Statistical Study on Photospheric Magnetic Nonpotentiality of Active Regions and Its Relationship with Flares during Solar Cycles 22-23
A statistical study is carried out on the photospheric magnetic
nonpotentiality in solar active regions and its relationship with associated
flares. We select 2173 photospheric vector magnetograms from 1106 active
regions observed by the Solar Magnetic Field Telescope at Huairou Solar
Observing Station, National Astronomical Observatories of China, in the period
of 1988-2008, which covers most of the 22nd and 23rd solar cycles. We have
computed the mean planar magnetic shear angle (\bar{\Delta\phi}), mean shear
angle of the vector magnetic field (\bar{\Delta\psi}), mean absolute vertical
current density (\bar{|J_{z}|}), mean absolute current helicity density
(\bar{|h_{c}|}), absolute twist parameter (|\alpha_{av}|), mean free magnetic
energy density (\bar{\rho_{free}}), effective distance of the longitudinal
magnetic field (d_{E}), and modified effective distance (d_{Em}) of each
photospheric vector magnetogram. Parameters \bar{|h_{c}|}, \bar{\rho_{free}},
and d_{Em} show higher correlation with the evolution of the solar cycle. The
Pearson linear correlation coefficients between these three parameters and the
yearly mean sunspot number are all larger than 0.59. Parameters
\bar{\Delta\phi}, \bar{\Delta\psi}, \bar{|J_{z}|}, |\alpha_{av}|, and d_{E}
show only weak correlations with the solar cycle, though the nonpotentiality
and the complexity of active regions are greater in the activity maximum
periods than in the minimum periods. All of the eight parameters show positive
correlations with the flare productivity of active regions, and the combination
of different nonpotentiality parameters may be effective in predicting the
flaring probability of active regions.Comment: 20 pages, 5 figures, 4 tables, accepted for publication in Solar
Physic
Photospheric Magnetic Field: Relationship Between North-South Asymmetry and Flux Imbalance
Photospheric magnetic fields were studied using the Kitt Peak synoptic maps
for 1976-2003. Only strong magnetic fields (B>100 G) of the equatorial region
were taken into account. The north-south asymmetry of the magnetic fluxes was
considered as well as the imbalance between positive and negative fluxes. The
north-south asymmetry displays a regular alternation of the dominant hemisphere
during the solar cycle: the northern hemisphere dominated in the ascending
phase, the southern one in the descending phase during Solar Cycles 21-23. The
sign of the imbalance did not change during the 11 years from one polar-field
reversal to the next and always coincided with the sign of the Sun's polar
magnetic field in the northern hemisphere. The dominant sign of leading
sunspots in one of the hemispheres determines the sign of the magnetic-flux
imbalance. The sign of the north-south asymmetry of the magnetic fluxes and the
sign of the imbalance of the positive and the negative fluxes are related to
the quarter of the 22-year magnetic cycle where the magnetic configuration of
the Sun remains constant (from the minimum where the sunspot sign changes
according to Hale's law to the magnetic-field reversal and from the reversal to
the minimum). The sign of the north-south asymmetry for the time interval
considered was determined by the phase of the 11-year cycle (before or after
the reversal); the sign of the imbalance of the positive and the negative
fluxes depends on both the phase of the 11-year cycle and on the parity of the
solar cycle. The results obtained demonstrate the connection of the magnetic
fields in active regions with the Sun's polar magnetic field in the northern
hemisphere.Comment: 24 pages, 12 figures, 2 table
Physics of Solar Prominences: I - Spectral Diagnostics and Non-LTE Modelling
This review paper outlines background information and covers recent advances
made via the analysis of spectra and images of prominence plasma and the
increased sophistication of non-LTE (ie when there is a departure from Local
Thermodynamic Equilibrium) radiative transfer models. We first describe the
spectral inversion techniques that have been used to infer the plasma
parameters important for the general properties of the prominence plasma in
both its cool core and the hotter prominence-corona transition region. We also
review studies devoted to the observation of bulk motions of the prominence
plasma and to the determination of prominence mass. However, a simple inversion
of spectroscopic data usually fails when the lines become optically thick at
certain wavelengths. Therefore, complex non-LTE models become necessary. We
thus present the basics of non-LTE radiative transfer theory and the associated
multi-level radiative transfer problems. The main results of one- and
two-dimensional models of the prominences and their fine-structures are
presented. We then discuss the energy balance in various prominence models.
Finally, we outline the outstanding observational and theoretical questions,
and the directions for future progress in our understanding of solar
prominences.Comment: 96 pages, 37 figures, Space Science Reviews. Some figures may have a
better resolution in the published version. New version reflects minor
changes brought after proof editin
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
BESII Detector Simulation
A Monte Carlo program based on Geant3 has been developed for BESII detector
simulation. The organization of the program is outlined, and the digitization
procedure for simulating the response of various sub-detectors is described.
Comparisons with data show that the performance of the program is generally
satisfactory.Comment: 17 pages, 14 figures, uses elsart.cls, to be submitted to NIM
Measurement of branching fractions for the inclusive Cabibbo-favored ~K*0(892) and Cabibbo-suppressed K*0(892) decays of neutral and charged D mesons
The branching fractions for the inclusive Cabibbo-favored ~K*0 and
Cabibbo-suppressed K*0 decays of D mesons are measured based on a data sample
of 33 pb-1 collected at and around the center-of-mass energy of 3.773 GeV with
the BES-II detector at the BEPC collider. The branching fractions for the
decays D+(0) -> ~K*0(892)X and D0 -> K*0(892)X are determined to be BF(D0 ->
\~K*0X) = (8.7 +/- 4.0 +/- 1.2)%, BF(D+ -> ~K*0X) = (23.2 +/- 4.5 +/- 3.0)% and
BF(D0 -> K*0X) = (2.8 +/- 1.2 +/- 0.4)%. An upper limit on the branching
fraction at 90% C.L. for the decay D+ -> K*0(892)X is set to be BF(D+ -> K*0X)
< 6.6%
The pole in
Using a sample of 58 million events recorded in the BESII detector,
the decay is studied. There are conspicuous
and signals. At low mass, a large
broad peak due to the is observed, and its pole position is determined
to be - MeV from the mean of six analyses.
The errors are dominated by the systematic errors.Comment: 15 pages, 6 figures, submitted to PL
Study of
New data are presented on from a sample of 58M
events in the upgraded BES II detector at the BEPC. There is a
conspicuous signal for and a peak at higher mass which
may be fitted with . From a combined analysis with
data, the branching ratio
is at the 95%
confidence level.Comment: 11 pages, 5 figures. Submitted to Phys. Lett.
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