2,095 research outputs found
Search for IR Emission from Intracluster Dust in A2029
We have searched for IR emission from the intracluster dust (ICD) in the
galaxy cluster A2029. Weak signals of enhanced extended emission in the cluster
are detected at both 24 and 70 micron. However, the signals are
indistinguishable from the foreground fluctuations. The 24 versus 70 micron
color map does not discriminate the dust emission in the cluster from the
cirrus emission. After excluding the contamination from the point sources, we
obtain upper limits for the extended ICD emission in A2029, 5 x 10^3 Jy/sr at
24 micron and 5 x 10^4 Jy/sr at 70 micron. The upper limits are generally
consistent with the expectation from theoretical calculations and support a
dust deficiency in the cluster compared to the ISM in our galaxy. Our results
suggest that even with the much improved sensitivity of current IR telescopes,
a clear detection of the IR emission from ICD may be difficult due to cirrus
noise.Comment: 5 pages, 4 figures, accepted by ApJ
Department of Anatomy and Cell Biology: 1983-2007
This departmental history was written on the occasion of the UND Quasquicentennial in 2008.https://commons.und.edu/departmental-histories/1061/thumbnail.jp
Analisis Strategi Bersaing pada Distributor Gula di Indonesia
Penelitian ini dilakukan dengan tujuan untuk mengetahui strategi bersaing yang dapat digunakan dalam menghadapi persaingan di sektor perdagangan industri distributor gula. Seperti yang kita ketahui bahwa produksi gula di Indonesia, sampai saat ini masih belum dapat memenuhi permintaan masyarakat Indonesia. Oleh karena itu pemerintah tidak punya pilihan lain selain mengimport gula dari luar negeri untuk dapat memenuhi permintaan gula di pasar. Hal ini menyebabkan banyak pembisnis yang berkecimpung dalam bisnis ini, hal ini menjadi sangat menarik untuk diteliti bagi penulis mengenai bagaimana strategi yang dapat digunakan Perusahaan distributor gula untuk dapat bersaing dengan Perusahaan pesaing yang ada. Pengumpulan data dilakukan oleh penulis dengan cara wawancara dan observasi secara langsung di lapangan. Setelah mendapatkan data, penulis memastikan keabsahan data dengan metode Trianggulasi. Cara yang dilakukan dalam penelitian ini adalah dengan membadingkan data hasil pengamatan dengan data hasil wawancara, dan membandingkannya kembali dengan data – data tertulis yang dimiliki oleh Perusahaan . Hasil penelitian ini menunjukan, bahwa strategi yang digunakan oleh Perusahaan adalah pengembangan pasar, dan strategi ini masih relevan untuk digunakan. Perusahaan hanya perlu menambahkan strategi baru yaitu penetrasi pasar untuk dapat memaksimalkan omset penjualan
The Decay of Debris Disks around Solar-Type Stars
We present a Spitzer MIPS study of the decay of debris disk excesses at 24
and 70 m for 255 stars of types F4 - K2. We have used multiple tests,
including consistency between chromospheric and X-ray activity and placement on
the HR diagram, to assign accurate stellar ages. Within this spectral type
range, at 24 m, of the stars younger than 5 Gyr have
excesses at the 3 level or more, while none of the older stars do,
confirming previous work. At 70 m, of the younger stars
have excesses at 3 significance, while only
% of the older stars do. To characterize the far infrared
behavior of debris disks more robustly, we double the sample by including stars
from the DEBRIS and DUNES surveys. For the F4 - K4 stars in this combined
sample, there is only a weak (statistically not significant) trend in the
incidence of far infrared excess with spectral type (detected fractions of
21.9, late F; 16.5, G; and
16.9, early K). Taking this spectral type range together,
there is a significant decline between 3 and 4.5 Gyr in the incidence of
excesses with fractional luminosities just under . There is an
indication that the timescale for decay of infrared excesses varies roughly
inversely with the fractional luminosity. This behavior is consistent with
theoretical expectations for passive evolution. However, more excesses are
detected around the oldest stars than is expected from passive evolution,
suggesting that there is late-phase dynamical activity around these stars.Comment: 46 pages. 7 figures. Accepted to Ap
Common Warm Dust Temperatures Around Main-sequence Stars
We compare the properties of warm dust emission from a sample of main-sequence A-type stars (B8-A7) to those of dust around solar-type stars (F5-K0) with similar Spitzer Space Telescope Infrared Spectrograph/MIPS data and similar ages. Both samples include stars with sources with infrared spectral energy distributions that show evidence of multiple components. Over the range of stellar types considered, we obtain nearly the same characteristic dust temperatures (~190 K and ~60 K for the inner and outer dust components, respectively)—slightly above the ice evaporation temperature for the inner belts. The warm inner dust temperature is readily explained if populations of small grains are being released by sublimation of ice from icy planetesimals. Evaporation of low-eccentricity icy bodies at ~150 K can deposit particles into an inner/warm belt, where the small grains are heated to T_(dust)~ 190 K. Alternatively, enhanced collisional processing of an asteroid belt-like system of parent planetesimals just interior to the snow line may account for the observed uniformity in dust temperature. The similarity in temperature of the warmer dust across our B8-K0 stellar sample strongly suggests that dust-producing planetesimals are not found at similar radial locations around all stars, but that dust production is favored at a characteristic temperature horizon
Analysis and design significance of the B-3, single seal, high pressure, isothermal test data
This report analyzes the available B-3, single seal, high pressure, isothermal test data in compliance with the NRX-A1 Cold Flow Test pre-requisite requirements
The Ising Model for Neural Data: Model Quality and Approximate Methods for Extracting Functional Connectivity
We study pairwise Ising models for describing the statistics of multi-neuron
spike trains, using data from a simulated cortical network. We explore
efficient ways of finding the optimal couplings in these models and examine
their statistical properties. To do this, we extract the optimal couplings for
subsets of size up to 200 neurons, essentially exactly, using Boltzmann
learning. We then study the quality of several approximate methods for finding
the couplings by comparing their results with those found from Boltzmann
learning. Two of these methods- inversion of the TAP equations and an
approximation proposed by Sessak and Monasson- are remarkably accurate. Using
these approximations for larger subsets of neurons, we find that extracting
couplings using data from a subset smaller than the full network tends
systematically to overestimate their magnitude. This effect is described
qualitatively by infinite-range spin glass theory for the normal phase. We also
show that a globally-correlated input to the neurons in the network lead to a
small increase in the average coupling. However, the pair-to-pair variation of
the couplings is much larger than this and reflects intrinsic properties of the
network. Finally, we study the quality of these models by comparing their
entropies with that of the data. We find that they perform well for small
subsets of the neurons in the network, but the fit quality starts to
deteriorate as the subset size grows, signalling the need to include higher
order correlations to describe the statistics of large networks.Comment: 12 pages, 10 figure
Spitzer Observations of Low Luminosity Isolated and Low Surface Brightness Galaxies
We examine the infrared properties of five low surface brightness galaxies
(LSBGs) and compare them with related but higher surface brightness galaxies,
using Spitzer Space Telescope images and spectra. All the LSBGs are detected in
the 3.6 and 4.5um bands, representing the stellar population. All but one are
detected at 5.8 and 8.0um, revealing emission from hot dust and aromatic
molecules, though many are faint or point-like at these wavelengths. Detections
of LSBGs at the far-infrared wavelengths, 24, 70, and 160um, are varied in
morphology and brightness, with only two detections at 160um, resulting in
highly varied spectral energy distributions. Consistent with previous
expectations for these galaxies, we find that detectable dust components exist
for only some LSBGs, with the strength of dust emission dependent on the
existence of bright star forming regions. However, the far-infrared emission
may be relatively weak compared with normal star-forming galaxies.Comment: 20 pages, 8 figures, accepted to Ap
Advanced ceramic coating development for industrial/utility gas turbine applications
The effects of ceramic coatings on the lifetimes of metal turbine components and on the performance of a utility turbine, as well as of the turbine operational cycle on the ceramic coatings were determined. When operating the turbine under conditions of constant cooling flow, the first row blades run 55K cooler, and as a result, have 10 times the creep rupture life, 10 times the low cycle fatigue life and twice the corrosion life with only slight decreases in both specific power and efficiency. When operating the turbine at constant metal temperature and reduced cooling flow, both specific power and efficiency increases, with no change in component lifetime. The most severe thermal transient of the turbine causes the coating bond stresses to approach 60% of the bond strengths. Ceramic coating failures was studied. Analytic models based on fracture mechanics theories, combined with measured properties quantitatively assessed both single and multiple thermal cycle failures which allowed the prediction of coating lifetime. Qualitative models for corrosion failures are also presented
- …