759 research outputs found
Kesan teknik pengaktifan bermangkin berbeza terhadap prestasi terma penyebar haba cip balikan(Effects of different catalytic activation techniques on the thermal performance of flip chip heat spreader)
Kertas ini membentangkan kesan dua teknik pengaktifan bermangkin yang berbeza terhadap prestasi terma bagi penyebar haba cip balikan. Penyaduran nikel tanpa elektrik digunakan sebagai salah satu teknik saduran kerana ia boleh membentuk satu lapisan nikel yang ketebalannya seragam ke atas substrat kuprum. Proses pengaktifan bermangkin perlu dilakukan dahulu untuk mengenapkan sesetengah atom nikel ke atas substrat kuprum, supaya enapan nikel mampu untuk memangkinkan proses penurunan yang seterusnya. Dua jenis teknik pengakitfan telah dikaji, iaitu pemulaan galvani dan penyaduran nipis nikel-kuprum. Ujian simpanan suhu tinggi telah dijalankan untuk mengkaji takat resapan antara logam bagi lapisan nikel and kuprum. Kemeresapan terma bagi penyebar haba telah dikaji dengan menggunakan peralatan Nano-flash. Keputusan yang diperolehi menunjukkan bahawa penyebar haba yang diproses dengan penyaduran nipis nikel-kuprum mempunyai nilai kemeresapan terma (35-65 mm2 s-1) yang lebih rendah berbanding dengan penyebar haba yang diproses dengan teknik pemulaan galvani (60-85 mm2 s-1). Selain daripada itu, kajian ini juga menemui ketebalan lapisan antara logam nikel-kuprum dalam penyebar haba ini bertambah daripada 0.2 μm pada keadaan asal kepada 0.55 μm selepas 168 jam simpanan suhu tinggi. Lapisan antara logam nikel-kuprum mempunyai kekonduksian terma yang lebih rendah berbanding dengan kuprum tulen, ini telah merendahkan kemeresapan terma bagi penyebar haba. Kesimpulannya, teknik pemulaan galvani meyediakan prestasi terma yang lebih baik untuk penyebar haba yang digunakan dalam pembungkusan semikonduktor
Are deviation from bi-maximal mixing and none-zero U_{e3} related to non-degeneracy of heavy Majorana neutrinos?
We propose a scenario that the mass splitting between the first generation of
the heavy Majorana neutrino and the other two generations of degenerate heavy
neutrinos in the seesaw framework is responsible for the deviation of the solar
mixing angle from the maximal mixing, while keeping the maximal mixing between
the tau and muon neutrinos as it is. On top of the scenario, we show that the
tiny breaking of the degeneracy of the two heavy Majorana neutrinos leads to
the non-zero small mixing angle in the PMNS matrix and the little
deviation of the atmospheric neutrino mixing angle from the maximal mixing.Comment: 12 pages, model claified, references added and correcte
Large Mixing Induced by the Strong Coupling with a Single Bulk Neutrinos
Neutrino is a good probe of extra dimensions. Large mixing and the apparent
lack of very complicated oscillation patterns may be an indication of large
couplings between the brane and a single bulk neutrino. A simple and realistic
five-dimensional model of this kind is discussed. It requires a sterile in
addition to three active neutrinos on the brane, all coupled strongly to one
common bulk neutrino, but not directly among themselves. Mindful that sterile
neutrinos are disfavored in the atmospheric and solar data, we demand induced
mixing to occur among the active neutrinos, but not between the active and the
sterile. The size of the extra dimension is arbitrary in this model,
otherwise it contains six parameters which can be used to fit the three
neutrino masses and the three mixing angles. However, in the model those six
parameters must be suitably ordered, so a successful fit is not guaranteed. It
turns out that not only the data can be fitted, but as a result of the
ordering, a natural connection between the smallness of the reactor angle
and the smallness of the mass-gap ratio can be derived.Comment: Misprints above eq. (22) corrected. To appear in PR
The second and third Sonine coefficients of a freely cooling granular gas revisited
In its simplest statistical-mechanical description, a granular fluid can be
modeled as composed of smooth inelastic hard spheres (with a constant
coefficient of normal restitution ) whose velocity distribution
function obeys the Enskog-Boltzmann equation. The basic state of a granular
fluid is the homogeneous cooling state, characterized by a homogeneous,
isotropic, and stationary distribution of scaled velocities, .
The behavior of in the domain of thermal velocities ()
can be characterized by the two first non-trivial coefficients ( and
) of an expansion in Sonine polynomials. The main goals of this paper are
to review some of the previous efforts made to estimate (and measure in
computer simulations) the -dependence of and , to report new
computer simulations results of and for two-dimensional systems,
and to investigate the possibility of proposing theoretical estimates of
and with an optimal compromise between simplicity and accuracy.Comment: 12 pages, 5 figures; v2: minor change
Mode of presentation and mortality amongst patients hospitalized with heart failure? A report from The First Euro Heart Failure Survey
Background:
Heart failure is heterogeneous in aetiology, pathophysiology, and presentation. Despite this diversity, clinical trials of patients hospitalized for HF deal with this problem as a single entity, which may be one reason for repeated failures.
Methods:
The first EuroHeart Failure Survey screened consecutive deaths and discharges of patients with suspected heart failure during 2000–2001. Patients were sorted into seven mutually exclusive hierarchical presentations: (1) with cardiac arrest/ventricular arrhythmia; (2) with acute coronary syndrome; (3) with rapid atrial fibrillation; (4) with acute breathlessness; (5) with other symptoms/signs such as peripheral oedema; (6) with stable symptoms; and (7) others in whom the contribution of HF to admission was not clear.
Results:
The 10,701 patients enrolled were classified into the above seven presentations as follows: 260 (2%), 560 (5%), 799 (8%), 2479 (24%), 1040 (10%), 703 (7%), and 4691 (45%) for which index-admission mortality was 26%, 20%, 10%, 8%, 6%, 6%, and 4%, respectively. Compared to those in group 7, the hazard ratios for death during the index admission were 4.9 (p ≤ 0.001), 4.0 (p < 0.001), 2.2 (p < 0.001), 2.1 (p < 0.001), 1.4 (p < 0.04) and 1.4 (p = 0.04), respectively. These differences were no longer statistically significant by 12 weeks.
Conclusion:
There is great diversity in the presentation of heart failure that is associated with very different short-term outcomes. Only a minority of hospitalizations associated with suspected heart failure are associated with acute breathlessness. This should be taken into account in the design of future clinical trials
Manifestations of Extra Dimensions in a Neutrino Telescope
Theories with large extra dimensions provide the possibility that a flavor
neutrino, localized in a 3+1 brane, can mix with a singlet neutrino living in
the bulk. This mixing leads to unconventional patterns of neutrino matter
oscillations and we examine in details how these oscillations depend upon two
parameters: the brane-bulk coupling and the effective mass of the
flavor neutrino inside matter. We find that high energy GeV)
neutrinos, to be detected by neutrino telescopes, can give signals of
extra dimensions. With a 1 k neutrino telescope extra dimensions with
radius down to can be tested directly, while for smaller radius an
indirect evidence can be established.Comment: 14 pages, 5 figures, added conclusion
Calculation of parity and time invariance violation in the radium atom
Parity (P) and time (T) invariance violating effects in the Ra atom are
strongly enhanced due to close states of opposite parity, the large nuclear
charge Z and the collective nature of P,T-odd nuclear moments. We have
performed calculations of the atomic electric dipole moments (EDM) produced by
the electron EDM and the nuclear magnetic quadrupole and Schiff moments. We
have also calculated the effects of parity non-conservation produced by the
nuclear anapole moment and the weak charge. Our results show that as a rule the
values of these effects are much larger than those considered so far in other
atoms (enhancement is up to 10^5 times).Comment: 18 pages; LaTeX; Submitted to Phys. Rev.
- …