40,290 research outputs found
Solar transition region in the quiet Sun and active regions
The solar transition region (TR), in which above the photosphere the tempera-
ture increases rapidly and the density drops dramatically, is believed to play
an important role in coronal heating and solar wind acceleration. Long-lasting
up-flows are present in the upper TR and interpreted as signatures of mass
supply to large coronal loops in the quiet Sun. Coronal bright points (BPs) are
local heating phenomena and we found a different Doppler-shift pattern at TR
and coronal temperatures in one BP, which might be related to the twisted loop
system. The dominant energy loss in the lower TR is the Ly-alpha emission. It
has been found that most Ly-alpha radiance profiles are stronger in the blue
peak, an asymmetry opposite to higher order Lyman lines. This asymmetry is
stronger when the downflow in the middle TR is stronger, indicating that the TR
flows play an important role in the line formation process. The peak separation
of Ly-alpha is found to be larger in coronal holes than in the quiet Sun,
reflecting the different magnetic structures and radiation fields between the
two regions. The Lyman line profiles are found to be not reversed in sunspot
plume and umbra regions, while they are obviously reversed in the surrounding
plage region. At TR temperatures, the densities of the sunspot plume and umbra
are a factor of 10 lower than of the plage, indicating that the sunspot plasma
emitting at TR temperatures is higher and possibly more extended above sunspots
than above the plage region.Comment: This paper has been withdrawn by the author because it's not a
referred pape
One Hour of Chemical Demonstrations
This article describes a diverse set of chemistry demonstrations especially selected to encourage student interaction and to be easily transported. The demonstrations may be presented at a level that can be tailored to any audienceâ from very young children to high school students planning careers in science. An ideal environment is a small classroom with 20-30 students where everyone can take part in the discussion. Once the chemicals are prepared, the collection of demonstrations takes about ten minutes to set-up, and one hour (or less) to perform. Very little is needed at the visiting site, no more than a table and a pitcher of water. A single electrical outlet is useful, but not essential. In Table 2 th
Improved thermal performance of a large laminated lithium-ion power battery by reciprocating air flow
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Thermal safety issues are increasingly critical for large-size laminated Lithium-Ion Batteries (LIBs). Despite a number of investigations conducted on the Battery Thermal Management System (BTMS) with reciprocating air-flow cooling, large laminated power LIBs are still not sufficiently investigated, particularly in the view of battery thermal characteristics. The present study investigates the thermal behaviors of an air-cooled NCM-type LIB (LiNi1âxâyCoxMnyO2 as cathode) from an experimental and systematic approach. The temperature distribution was acquired from different Depth of Discharge (DOD) by the infrared imaging (IR) technology. A reciprocating air-flow cooling method was proposed to restrict the temperature fluctuation and homogenize temperature distribution. Results showed that there was a remarkable temperature distribution phenomenon during the discharge process, the temperature distribution was affected by direction of air-flow. Forward air-flow (from current collector side to lower part of battery) was always recommended at the beginning of the discharge due to the thermal characteristics of the battery. After comprehensive consideration on battery temperature limit and cooling effect, the desired initial reversing timing was about 50% DOD at 3 C discharge rate. Different reversing strategies were investigated including isochronous cycles and aperiodic cycles. It was found that the temperature non-uniformity caused by heat accumulation and concentration was mitigated by reciprocating air-flow with optimized reversing strategy
Infrared imaging investigation of temperature fluctuation and spatial distribution for a large laminated lithium ion power battery
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The present study investigates the thermal behaviors of a naturally cooled NCM-type LIB (LiNi1âxâyCoxMnyO2 as cathode) from an experimental and systematic approach. The temperature distribution was acquired for different discharge rates and Depth of Discharge (DOD) by the infrared imaging (IR) technology. Two new factors, the temperature variance ( ) and local overheating index (LOH index), were proposed to assess the temperature fluctuation and distribution. Results showed that the heat generation rate was higher on the cathode side than that on the anode side due to the different resistivity of current collectors. For a low-power discharge, the eventual stable high-temperature zone occurred in the center of the battery, while with a high-power discharge, the upper part of the battery was the high temperature region from the very beginning of discharge. It was found that the temperature variance ( ) and local overheating index (LOH index) were capable of holistically exhibiting the temperature non-uniformity both on numerical fluctuation and spatial distribution with varying discharge rates and DOD. With increasing the discharge rate and DOD, temperature distribution showed an increasingly non-uniform trend, especially at the initial and final stage of high-power discharge, the heat accumulation and concentration area increased rapidly
Radiance and Doppler shift distributions across the network of the quiet Sun
The radiance and Doppler-shift distributions across the solar network provide
observational constraints of two-dimensional modeling of transition-region
emission and flows in coronal funnels. Two different methods, dispersion plots
and average-profile studies, were applied to investigate these distributions.
In the dispersion plots, we divided the entire scanned region into a bright and
a dark part according to an image of Fe xii; we plotted intensities and Doppler
shifts in each bin as determined according to a filtered intensity of Si ii. We
also studied the difference in height variations of the magnetic field as
extrapolated from the MDI magnetogram, in and outside network. For the
average-profile study, we selected 74 individual cases and derived the average
profiles of intensities and Doppler shifts across the network. The dispersion
plots reveal that the intensities of Si ii and C iv increase from network
boundary to network center in both parts. However, the intensity of Ne viii
shows different trends, namely increasing in the bright part and decreasing in
the dark part. In both parts, the Doppler shift of C iv increases steadily from
internetwork to network center. The average-profile study reveals that the
intensities of the three lines all decline from the network center to
internetwork region. The binned intensities of Si ii and Ne viii have a good
correlation. We also find that the large blue shift of Ne viii does not
coincide with large red shift of C iv. Our results suggest that the network
structure is still prominent at the layer where Ne viii is formed in the quiet
Sun, and that the magnetic structures expand more strongly in the dark part
than in the bright part of this quiet Sun region.Comment: 10 pages,9 figure
Numerical Study on Indoor Wideband Channel Characteristics with Different Internal Wall
Effects of material and configuration of the internal wall on the performance of wideband channel are investigated by using the Finite Difference Time-Domain (FDTD) method. The indoor wideband channel characteristics, such as the path-loss, Root-Mean-Square (RMS) delay spread and number of the multipath components (MPCs), are presented. The simulated results demonstrate that the path-loss and MPCs are affected by the permittivity, dielectric loss tangent and thickness of the internal wall, while the RMS delay spread is almost not relevant with the dielectric permittivity. Furthermore, the comparison of simulated result with the measured one in a simple scenario has validated the simulation study
Any l-state solutions of the Woods-Saxon potential in arbitrary dimensions within the new improved quantization rule
The approximated energy eigenvalues and the corresponding eigenfunctions of
the spherical Woods-Saxon effective potential in dimensions are obtained
within the new improved quantization rule for all -states. The Pekeris
approximation is used to deal with the centrifugal term in the effective
Woods-Saxon potential. The inter-dimensional degeneracies for various orbital
quantum number and dimensional space are studied. The solutions for the
Hulth\'{e}n potential, the three-dimensional (D=3), the -wave () and
the cases are briefly discussed.Comment: 15 page
Parasitic Effects Reduction for Wafer-Level Packaging of RF-Mems
In RF-MEMS packaging, next to the protection of movable structures,
optimization of package electrical performance plays a very important role. In
this work, a wafer-level packaging process has been investigated and optimized
in order to minimize electrical parasitic effects. The RF-MEMS package concept
used is based on a wafer-level bonding of a capping silicon substrate to an
RF-MEMS wafer. The capping silicon substrate resistivity, substrate thickness
and the geometry of through-substrate electrical interconnect vias have been
optimized using finite-element electromagnetic simulations (Ansoft HFSS). Test
structures for electrical characterization have been designed and after their
fabrication, measurement results will be compared with simulations.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Constrained structure of ancient Chinese poetry facilitates speech content grouping
Ancient Chinese poetry is constituted by structured language that deviates from ordinary language usage [1, 2]; its poetic genres impose unique combinatory constraints on linguistic elements [3]. How does the constrained poetic structure facilitate speech segmentation when common linguistic [4, 5, 6, 7, 8] and statistical cues [5, 9] are unreliable to listeners in poems? We generated artificial Jueju, which arguably has the most constrained structure in ancient Chinese poetry, and presented each poem twice as an isochronous sequence of syllables to native Mandarin speakers while conducting magnetoencephalography (MEG) recording. We found that listeners deployed their prior knowledge of Jueju to build the line structure and to establish the conceptual flow of Jueju. Unprecedentedly, we found a phase precession phenomenon indicating predictive processes of speech segmentationâthe neural phase advanced faster after listeners acquired knowledge of incoming speech. The statistical co-occurrence of monosyllabic words in Jueju negatively correlated with speech segmentation, which provides an alternative perspective on how statistical cues facilitate speech segmentation. Our findings suggest that constrained poetic structures serve as a temporal map for listeners to group speech contents and to predict incoming speech signals. Listeners can parse speech streams by using not only grammatical and statistical cues but also their prior knowledge of the form of language
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