1,815 research outputs found
Large Amplitude Longitudinal Oscillations in a Solar Filament
We have developed the first self-consistent model for the observed
large-amplitude oscillations along filament axes that explains the restoring
force and damping mechanism. We have investigated the oscillations of multiple
threads formed in long, dipped flux tubes through the thermal nonequilibrium
process, and found that the oscillation properties predicted by our simulations
agree with the observed behavior. We then constructed a model for the
large-amplitude longitudinal oscillations that demonstrates that the restoring
force is the projected gravity in the tube where the threads oscillate.
Although the period is independent of the tube length and the constantly
growing mass, the motions are strongly damped by the steady accretion of mass
onto the threads by thermal nonequilibrium. The observations and our model
suggest that a nearby impulsive event drives the existing prominence threads
along their supporting tubes, away from the heating deposition site, without
destroying them. The subsequent oscillations occur because the displaced
threads reside in magnetic concavities with large radii of curvature. Our model
yields a powerful seismological method for constraining the coronal magnetic
field and radius of curvature of dips. Furthermore, these results indicate that
the magnetic structure is most consistent with the sheared-arcade model for
filament channels.Comment: ApJ in pres
Competition versus cooperation: German federalism in need of constitutional amendments
Article by Professor Dr Jur Ulrich Karpen (Hamburg) published in Amicus Curiae - Journal of the Society for Advanced Legal Studies. The Journal is produced by the Society for Advanced Legal Studies at the Institute of Advanced Legal Studies, University of London
Formation of Solar Filaments by Steady and Nonsteady Chromospheric Heating
It has been established that cold plasma condensations can form in a magnetic
loop subject to localized heating of the footpoints. In this paper, we use
grid-adaptive numerical simulations of the radiative hydrodynamic equations to
parametrically investigate the filament formation process in a pre-shaped loop
with both steady and finite-time chromospheric heating. Compared to previous
works, we consider low-lying loops with shallow dips, and use a more realistic
description for the radiative losses. We demonstrate for the first time that
the onset of thermal instability satisfies the linear instability criterion.
The onset time of the condensation is roughly \sim 2 hr or more after the
localized heating at the footpoint is effective, and the growth rate of the
thread length varies from 800 km hr-1 to 4000 km hr-1, depending on the
amplitude and the decay length scale characterizing this localized
chromospheric heating. We show how single or multiple condensation segments may
form in the coronal portion. In the asymmetric heating case, when two segments
form, they approach and coalesce, and the coalesced condensation later drains
down into the chromosphere. With a steady heating, this process repeats with a
periodicity of several hours. While our parametric survey confirms and augments
earlier findings, we also point out that steady heating is not necessary to
sustain the condensation. Once the condensation is formed, it can keep growing
also when the localized heating ceases. Finally, we show that the condensation
can survive continuous buffeting by perturbations resulting from the
photospheric p-mode waves.Comment: 43 pages, 18 figure
The Role of Helicity in Magnetic Reconnection: 3D Numerical Simulations
We demonstrate that conservation of global helicity plays only a minor role
in determining the nature and consequences of magnetic reconnection in the
solar atmosphere. First, we show that observations of the solar coronal
magnetic field are in direct conflict with Taylor's theory. Next, we present
results from three-dimensional MHD simulations of the shearing of bipolar and
multi-polar coronal magnetic fields by photospheric footpoint motions, and
discuss the implications of these results for Taylor's theory and for models of
solar activity. The key conclusion of this work is that significant magnetic
reconnection occurs only at very specific locations and, hence, the Sun's
magnetic field cannot relax completely down to the minimum energy state
predicted by conservation of global helicity.Comment: AGU LaTeX manuscript, 17 pages, 2 b-w figures, 4 color plate
Diagnosa Penyakit Kulit Wajah Menggunakan Metode Decession Tree Dan Algoritma C4.5
Today's face is something that is very much considered by both women and men. Women and men do facial treatments so often because the face is the first thing to see when meeting someone. However, there are those that often interfere with the face, one of which is a skin disease that is very diverse ranging from acne, dullness, blackheads to cancer. In fact, to overcome this, many people always consult with doctors, especially face problems. One thing that can be done is to diagnose facial skin diseases using the decession tree method and the c 4.5 algorithm. The existence of this system is expected to be a solution in conducting consultations for women and men for facial problems. By using the decession tree method and the c 4.5 algorithm and by using a number of data mining, it will give results that can be used as guidelines in treating facial skin diseases. In addition, the existence of this system will also be very helpful in the field of services to consumers, both women and men, especially for facial care to avoid facial skin diseases, which has been a problem so far
IMPLEMENTASI METODE CUSTOMER SATISFACTION INDEX (CSI) UNTUK MENGANALISA KEPUASAN PELANGGAN PADA FAMILY SWALAYAN
Family Swalayan merupakan salah satu tempat berbelanja yang cukup diminati oleh konsumen dan mempunyai lokasi yang strategis di Kota Dumai. Adanya persaingan yang terjadi antara para penjual produk atau ritel, menimbulkan sebuah kompetisi strategi yang tepat untuk meraih pangsa pasar terbesar. Pihak manajemen family swalayanharus memperhatikan hal-hal yang dapat mempengaruhi minat beli konsumen. Hal ini patut diperhatikan karena konsumen tidak hanya berpedoman pada harga yang murah saja, tetapi juga pada kualitas pelayanan, lokasi usaha, kualitas produk yang ditawarkan, serta kerapian tata letak produk yang. Faktor-faktor inilah yang dapat menyebabkan konsumen dapat beralih ke tempat-tempat perbelanjaan lain yang mempunyai daya tarik lebih dibandingkan. Tujuan penelitian untuk mengetahui kepuasan pelanggan family swalayan menggunakan metode customer satisfaction index (CSI) berdasarkan kualitas pelayanan, fasilitas, dan harga produk. Metode CSI digunakan untuk mengetahui tingkat kepuasan konsumen secara menyeluruh dengan melihat tingkat kepentingan atribut – atribut produk / jasa. Berdasarkan penelitian yang dilakukan, diperoleh hasil pencarian CSI untuk kepuasan pelanggan berada pada tingkat Puas sebesar 0.7
IMPLEMENTASI METODE CUSTOMER SATISFACTION INDEX (CSI) UNTUK MENGANALISA KEPUASAN PELANGGAN PADA FAMILY SWALAYAN
Family Swalayan merupakan salah satu tempat berbelanja yang cukup diminati oleh konsumen dan mempunyai lokasi yang strategis di Kota Dumai. Adanya persaingan yang terjadi antara para penjual produk atau ritel, menimbulkan sebuah kompetisi strategi yang tepat untuk meraih pangsa pasar terbesar. Pihak manajemen family swalayanharus memperhatikan hal-hal yang dapat mempengaruhi minat beli konsumen. Hal ini patut diperhatikan karena konsumen tidak hanya berpedoman pada harga yang murah saja, tetapi juga pada kualitas pelayanan, lokasi usaha, kualitas produk yang ditawarkan, serta kerapian tata letak produk yang. Faktor-faktor inilah yang dapat menyebabkan konsumen dapat beralih ke tempat-tempat perbelanjaan lain yang mempunyai daya tarik lebih dibandingkan. Tujuan penelitian untuk mengetahui kepuasan pelanggan family swalayan menggunakan metode customer satisfaction index (CSI) berdasarkan kualitas pelayanan, fasilitas, dan harga produk. Metode CSI digunakan untuk mengetahui tingkat kepuasan konsumen secara menyeluruh dengan melihat tingkat kepentingan atribut – atribut produk / jasa. Berdasarkan penelitian yang dilakukan, diperoleh hasil pencarian CSI untuk kepuasan pelanggan berada pada tingkat Puas sebesar 0.7
Signatures of impulsive localized heating in the temperature distribution of multi-stranded coronal loops
We study the signatures of different coronal heating regimes on the
differential emission measure (DEM) of multi-stranded coronal loops by means of
hydrodynamic simulations. We consider heating either uniformly distributed
along the loops or localized close to the chromospheric footpoints, in both
steady and impulsive conditions. Our simulations show that condensation at the
top of the loop forms when the localized heating is impulsive with a pulse
cadence time shorter than the plasma cooling time, and the pulse energy is
below a certain threshold. A condensation does not produce observable
signatures in the global DEM structure. Conversely, the DEM coronal peak is
found sensitive to the pulse cadence time. Our simulations can also give an
explanation of the warm overdense and hot underdense loops observed by TRACE,
SOHO and Yohkoh. However, they are unable to reproduce both the transition
region and the coronal DEM structure with a unique set of parameters, which
outlines the need for a more realistic description of the transition region.Comment: 31 pages, 7 figure
Can Thermal Nonequilibrium Explain Coronal Loops?
Any successful model of coronal loops must explain a number of observed
properties. For warm (~ 1 MK) loops, these include: 1. excess density, 2. flat
temperature profile, 3. super-hydrostatic scale height, 4. unstructured
intensity profile, and 5. 1000--5000 s lifetime. We examine whether thermal
nonequilibrium can reproduce the observations by performing hydrodynamic
simulations based on steady coronal heating that decreases exponentially with
height. We consider both monolithic and multi-stranded loops. The simulations
successfully reproduce certain aspects of the observations, including the
excess density, but each of them fails in at least one critical way. Monolithic
models have far too much intensity structure, while multi-strand models are
either too structured or too long-lived. Our results appear to rule out the
widespread existence of heating that is both highly concentrated low in the
corona and steady or quasi-steady (slowly varying or impulsive with a rapid
cadence). Active regions would have a very different appearance if the dominant
heating mechanism had these properties. Thermal nonequilibrium may nonetheless
play an important role in prominences and catastrophic cooling events (e.g.,
coronal rain) that occupy a small fraction of the coronal volume. However,
apparent inconsistencies between the models and observations of cooling events
have yet to be understood.Comment: 40 pages, 10 figures, accepted by the Astrophysical Journal (vol.
714
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