1,047 research outputs found
On the stabilization of ion sputtered surfaces
The classical theory of ion beam sputtering predicts the instability of a
flat surface to uniform ion irradiation at any incidence angle. We relax the
assumption of the classical theory that the average surface erosion rate is
determined by a Gaussian response function representing the effect of the
collision cascade and consider the surface dynamics for other
physically-motivated response functions. We show that although instability of
flat surfaces at any beam angle results from all Gaussian and a wide class of
non-Gaussian erosive response functions, there exist classes of modifications
to the response that can have a dramatic effect. In contrast to the classical
theory, these types of response render the flat surface linearly stable, while
imperceptibly modifying the predicted sputter yield vs. incidence angle. We
discuss the possibility that such corrections underlie recent reports of a
``window of stability'' of ion-bombarded surfaces at a range of beam angles for
certain ion and surface types, and describe some characteristic aspects of
pattern evolution near the transition from unstable to stable dynamics. We
point out that careful analysis of the transition regime may provide valuable
tests for the consistency of any theory of pattern formation on ion sputtered
surfaces
Indentation of ultrathin elastic films and the emergence of asymptotic isometry
We study the indentation of a thin elastic film floating at the surface of a
liquid. We focus on the onset of radial wrinkles at a threshold indentation
depth and the evolution of the wrinkle pattern as indentation progresses far
beyond this threshold. Comparison between experiments on thin polymer films and
theoretical calculations shows that the system very quickly reaches the Far
from Threshold (FT) regime, in which wrinkles lead to the relaxation of
azimuthal compression. Furthermore, when the indentation depth is sufficiently
large that the wrinkles cover most of the film, we recognize a novel mechanical
response in which the work of indentation is transmitted almost solely to the
liquid, rather than to the floating film. We attribute this unique response to
a nontrivial isometry attained by the deformed film, and discuss the scaling
laws and the relevance of similar isometries to other systems in which a
confined sheet is subjected to weak tensile loads.Comment: 5 pages, close to published versio
Polarization memory in single Quantum Dots
We measured the polarization memory of excitonic and biexcitonic optical
transitions from single quantum dots at either positive, negative or neutral
charge states. Positive, negative and no circular or linear polarization memory
was observed for various spectral lines, under the same quasi-resonant
excitation below the wetting layer band-gap. We developed a model which
explains both qualitatively and quantitatively the experimentally measured
polarization spectrum for all these optical transitions. We consider quite
generally the loss of spin orientation of the photogenerated electron-hole pair
during their relaxation towards the many-carrier ground states. Our analysis
unambiguously demonstrates that while electrons maintain their initial spin
polarization to a large degree, holes completely dephase.Comment: 6 pages, 4 figure
Small Volume Resuscitation in Hemorrhagic Shock: Historical and Scientific Background
Exsanguination is the primary cause of death in trauma. The mortality can be prevented if bleeding can be stopped and blood loss can be replaced with fluid. Fluid resuscitation has been proven to improve tissue perfusion and reverse the cellular injury and swelling in state of hemorrhage. Fluid resuscitation can also depress the cytokines that could lead to multiple organ failure in hemorrhagic shock. The method of fluid resuscitation widely used nowadays refers to guideline by American College of Surgeon. Despite its wide application, some studies reported the guideline may be harmful and addressed the lack of its scientific basis. These studies introduced another strategy called small volume fluid resuscitation. Although studies were limited to animal model and some small clinical trials, they showed promising result for small volume fluid resuscitation. Small volume fluid resuscitation could reduce the additional blood loss due to continued bleeding or re-bleeding and lower mortality rate. Small volume fluid is an appropriate option in resuscitating patients especially those with uncontrolled hemorrhage
Analisis Kelayakan Ekonomis Cloud Computing Pada Lembaga Keuangan Mikro Di Indonesia Dengan Metode Ranti's Generic Is/it Business Value Dan Economic Value Added: Studi Kasus Pada Bank Perkreditan Rakyat Di Jakarta
Bank Perkreditan Rakyat (BPR) sebagai salah satu pemain terbesar dalam bisnis keuangan mikro di Indonesia telah meningkatkan penggunaan Sistem Informasi/Teknologi Informasi (SI/TI) untuk mendukung bisnis mereka. Namun, hanya sedikit dari mereka yang menyadari isu-isu seputar investasi TI. Ada kekhawatiran tentang tidak tersedianya sumber daya yang cukup untuk membeli, memelihara, dan mengamankan SI/TI mereka sendiri. Di sisi lain, investasi yang besar diperlukan dan akhirnya menjadi momok bagi BPR yang paling menerapkan SI/TI untuk mendukung pengembangan bisnis mereka. Penelitian ini menganalisis nilai ekonomi dari penerapan komputasi awan di BPR. Analisis dilakukan, pertama dengan mengidentifikasi dan mengukur relevansi manfaat SI/TI menggunakan Ranti's IS/IT Generic Business Values dan kedua dengan menempatkan nilai-nilai yang diukur atau manfaat pada metode Economic Value Added (EVA), untuk melakukan analisis keuangan. Komputasi awan mampu memberikan solusi bagi masalah yang dihadapi oleh BPR seperti dapat dilihat dari nilai EVA positif. Oleh karena itu, komputasi awan merupakan pendekatan yang berharga bagi BPR untuk bergerak maju. Resiko investasi SI/TI dapat ditransfer ke penyedia komputasi awan, dengan kata lain, tidak ada waktu untuk berpikir tentang teknologi USAng sebelum Return of Investment (ROI) tercapai.
Bank Perkreditan Rakyat (BPR) as one of the biggest players in Indonesia's microfinance business has increased their use of Information Systems/Information Technology (IS/IT) to support their business. However, only few of them are aware of issues around IT investment. There are concerns about the unavailability of sufficient resource to purchase, maintain, and secure their own IS/IT. On the other hand, a large investment is needed and it eventually becomes the scourge for most rural banks to apply IS/IT to support their business development. This research analyzes the economic value of implementing cloud computing in BPR. Analysis is done, firstly by identifying and quantifying the relevant IS/IT benefits using Ranti's IS/IT Generic Business Values and, secondly by putting the quantified values or benefits into Economic Value Added (EVA) method to do the financial analysis. Cloud computing is able to provide solutions for problems faced by BPR as can be seen from the positive EVA value. Hence, the cloud computing is a valuable approach for BPR to move forward. IS/IT investment risk can be transferred to cloud computing providers, in other words, there is no time to think about outdated technology before Return of Investment (ROI) is achieved
Effect of strain rate on the yielding mechanism of amorphous metal foam
Stochastic amorphous Pd_(43)Ni_(10)Cu_(27)P_(20) foams were tested in quasistatic and dynamic loading. The strength/porosity relations show distinct slopes for the two loading conditions, suggesting a strain-rate-induced change in the foam yielding mechanism. The strength/porosity correlation of the dynamic test data along with microscopy assessments support that dynamic foam yielding is dominated by plasticity rather than elastic buckling, the mechanism previously identified to control quasistatic yielding. The strain-rate-induced shift in the foam yielding mechanism is attributed to the rate of loading approaching the rate of sound wave propagation across intracellular membranes, thereby suppressing elastic buckling and promoting plastic yielding
Moving boundary approximation for curved streamer ionization fronts: Solvability analysis
The minimal density model for negative streamer ionization fronts is
investigated. An earlier moving boundary approximation for this model consisted
of a "kinetic undercooling" type boundary condition in a Laplacian growth
problem of Hele-Shaw type. Here we derive a curvature correction to the moving
boundary approximation that resembles surface tension. The calculation is based
on solvability analysis with unconventional features, namely, there are three
relevant zero modes of the adjoint operator, one of them diverging;
furthermore, the inner/outer matching ahead of the front has to be performed on
a line rather than on an extended region; and the whole calculation can be
performed analytically. The analysis reveals a relation between the fields
ahead and behind a slowly evolving curved front, the curvature and the
generated conductivity. This relation forces us to give up the ideal
conductivity approximation, and we suggest to replace it by a constant
conductivity approximation. This implies that the electric potential in the
streamer interior is no longer constant but solves a Laplace equation; this
leads to a Muskat-type problem.Comment: 22 pages, 6 figure
Complete control of a matter qubit using a single picosecond laser pulse
We demonstrate for the first time that a matter physical two level system, a
qubit, can be fully controlled using one ultrafast step. We show that the spin
state of an optically excited electron, an exciton, confined in a quantum dot,
can be rotated by any desired angle, about any desired axis, during such a
step. For this we use a single, resonantly tuned, picosecond long, polarized
optical pulse. The polarization of the pulse defines the rotation axis, while
the pulse detuning from a non-degenerate absorption resonance, defines the
magnitude of the rotation angle. We thereby achieve a high fidelity, universal
gate operation, applicable to other spin systems, using only one short optical
pulse. The operation duration equals the pulse temporal width, orders of
magnitude shorter than the qubit evolution life and coherence times.Comment: main text: 4 pages, 3 figures Supplemental material: 3 pages, 1
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