5,070 research outputs found
Fast, uniform, and compact scalar multiplication for elliptic curves and genus 2 Jacobians with applications to signature schemes
We give a general framework for uniform, constant-time one-and
two-dimensional scalar multiplication algorithms for elliptic curves and
Jacobians of genus 2 curves that operate by projecting to the x-line or Kummer
surface, where we can exploit faster and more uniform pseudomultiplication,
before recovering the proper "signed" output back on the curve or Jacobian.
This extends the work of L{\'o}pez and Dahab, Okeya and Sakurai, and Brier and
Joye to genus 2, and also to two-dimensional scalar multiplication. Our results
show that many existing fast pseudomultiplication implementations (hitherto
limited to applications in Diffie--Hellman key exchange) can be wrapped with
simple and efficient pre-and post-computations to yield competitive full scalar
multiplication algorithms, ready for use in more general discrete
logarithm-based cryptosystems, including signature schemes. This is especially
interesting for genus 2, where Kummer surfaces can outperform comparable
elliptic curve systems. As an example, we construct an instance of the Schnorr
signature scheme driven by Kummer surface arithmetic
A Type System for Julia
The Julia programming language was designed to fill the needs of scientific
computing by combining the benefits of productivity and performance languages.
Julia allows users to write untyped scripts easily without needing to worry
about many implementation details, as do other productivity languages. If one
just wants to get the work done-regardless of how efficient or general the
program might be, such a paradigm is ideal. Simultaneously, Julia also allows
library developers to write efficient generic code that can run as fast as
implementations in performance languages such as C or Fortran. This combination
of user-facing ease and library developer-facing performance has proven quite
attractive, and the language has increasing adoption.
With adoption comes combinatorial challenges to correctness. Multiple
dispatch -- Julia's key mechanism for abstraction -- allows many libraries to
compose "out of the box." However, it creates bugs where one library's
requirements do not match what another provides. Typing could address this at
the cost of Julia's flexibility for scripting.
I developed a "best of both worlds" solution: gradual typing for Julia. My
system forms the core of a gradual type system for Julia, laying the foundation
for improving the correctness of Julia programs while not getting in the way of
script writers. My framework allows methods to be individually typed or
untyped, allowing users to write untyped code that interacts with typed library
code and vice versa. Typed methods then get a soundness guarantee that is
robust in the presence of both dynamically typed code and dynamically generated
definitions. I additionally describe protocols, a mechanism for typing
abstraction over concrete implementation that accommodates one common pattern
in Julia libraries, and describe its implementation into my typed Julia
framework.Comment: PhD thesi
A New Look at Optimum Design for Convecting-Radiating Annular Fins of Trapezoidal Profile
This paper deals with a controversial problem in answering the question “Does the optimum fin design always exist? If not, what are the optimization ranges and limitations?” These authors employ a general example of convecting-radiating trapezoidal annular fin with heat transfer at the tip and wall resistance at the interface. The present results indicate that the answer to the above first question is negative. The ranges of fin optimum design under different thermal and physical conditions are proposed. The effects of Biot number, radiation number, the heat loss at the tip, fin profile and overall wall resistance on fin optimization range are further investigated and discussed.
http://dx.doi.org/10.2174/1874396X0110501009
Design Charts for Circular Fins of Arbitrary Profile Subject to Radiation and Convection with Wall Resistances
In this work, the optimization for a radiative-convective annular fin of arbitrary profile with base wall thermal resistances is considered. A fourth order Runge-Kutta method is used to solve the associated non-linear governing equa-tions. Further differentiations yield the optimum heat transfer and the optimum fin dimensions. To facilitate the thermal design, design charts for optimum dimensions are proposed. Furthermore, the fin effectiveness for the optimal annular ra-diative-convective fins is presented to check the practicality of the design.
http://dx.doi.org/10.2174/1874396X0120601001
Recoiling Supermassive Black Hole Escape Velocities from Dark Matter Halos
We simulate recoiling black hole trajectories from to in dark
matter halos, quantifying how parameter choices affect escape velocities. These
choices include the strength of dynamical friction, the presence of stars and
gas, the accelerating expansion of the universe (Hubble acceleration), host
halo accretion and motion, and seed black hole mass. CDM halo
accretion increases escape velocities by up to 0.6 dex and significantly
shortens return timescales compared to non-accreting cases. Other parameters
change orbit damping rates but have subdominant effects on escape velocities;
dynamical friction is weak at halo escape velocities, even for extreme
parameter values. We present formulae for black hole escape velocities as a
function of host halo mass and redshift. Finally, we discuss how these findings
affect black hole mass assembly as well as minimum stellar and halo masses
necessary to retain supermassive black holes.Comment: 10 pages, 17 figures. Updated to correct a typo (sign error) in fit
to escape velocity, for return by z=0 (eq. 19
Adoption of robotic assisted partial nephrectomies: a population-based analysis of U.S. surgeons from 2004-2013
The advent of minimally invasive and robotic techniques has resulted in the rapid adoption of this novel technology, with the field of urology at the forefront. Since the first Robotic‐Assisted Laparoscopic Radical Prostatectomy (RALP) was performed in 2000 using the da Vinci Surgical System (Intuitive Surgical, Inc., Sunnyvale, CA, USA), surgeons have rapidly incorporated robotic technology for the use of radical prostatectomies for prostatic carcinoma. Prior to 2005, only a minority of surgeons‐‐fewer than 2.5%‐‐performing radical prostatectomies utilized robotic assistance. However, robotic assistance has become the predominant approach for radical prostatectomies, increasing from 22% to 85% between the years 2002 to 2013, representing a nearly five‐fold increase in utilization
Laparoscopic Radical Nephrectomy in a Pelvic Ectopic Kidney: Keys to Success
Preoperative imaging to delineate anomalous vascular anatomy is mandatory to perform laparoscopic radical nephrectomy for a pelvic ectopic kidney
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