660 research outputs found
THE WAIT-AND-SEE OPTION IN ASCENDING PRICE AUCTIONS
Cake-cutting protocols aim at dividing a ``cake'' (i.e., a divisible
resource) and assigning the resulting portions to several players in a way that
each of the players feels to have received a ``fair'' amount of the cake. An
important notion of fairness is envy-freeness: No player wishes to switch the
portion of the cake received with another player's portion. Despite intense
efforts in the past, it is still an open question whether there is a
\emph{finite bounded} envy-free cake-cutting protocol for an arbitrary number
of players, and even for four players. We introduce the notion of degree of
guaranteed envy-freeness (DGEF) as a measure of how good a cake-cutting
protocol can approximate the ideal of envy-freeness while keeping the protocol
finite bounded (trading being disregarded). We propose a new finite bounded
proportional protocol for any number n \geq 3 of players, and show that this
protocol has a DGEF of 1 + \lceil (n^2)/2 \rceil. This is the currently best
DGEF among known finite bounded cake-cutting protocols for an arbitrary number
of players. We will make the case that improving the DGEF even further is a
tough challenge, and determine, for comparison, the DGEF of selected known
finite bounded cake-cutting protocols.Comment: 37 pages, 4 figure
E-85 vs. regular gasoline: effects on engine performance, fuel efficiency, and exhaust emissions
This study compared the performance, fuel efficiency, and exhaust emissions of a 2.61 kW engine fueled with regular unleaded gasoline (87 octane) and an 85% ethanol blend (E85) under two load conditions. Four 1-h tests were conducted with each fuel at both governor’s maximum (3400 rpm) and peak torque (2800 rpm) conditions for a total of 16 tests. At governor’s maximum engine speed, there were no significant differences (p\u3e0.05) between fuels for engine torque, power, specific carbon dioxide (sCO2 ), specific carbon monoxide (sCO), specific hydrocarbons (sHC), or specific oxides of nitrogen (sNOX) emissions. However, there was a significant difference in specific fuel consumption and specific dioxide (sO2 ) emissions with E85 requiring the consumption of more fuel and emitting fewer oxide gases. Under peak-torque test conditions, there were significant differences by fuel for power, torque, and specific fuel consumption, as ethanol required more fuel while developing less power and torque when compared to gasoline. There were no significant differences by fuel type in sCO2 , sCO, sHC, sO2 , or sNOX emissions. The results indicate that performance was similar when the engine was fueled by regular unleaded gasoline or E85 under rated engine-speed conditions; however, the ethanol-fueled engine produced significantly less power and torque under peak torque testing conditions. In both testing conditions, specific fuel consumption was significantly higher with E85
A Discrete and Bounded Envy-free Cake Cutting Protocol for Four Agents
We consider the well-studied cake cutting problem in which the goal is to
identify a fair allocation based on a minimal number of queries from the
agents. The problem has attracted considerable attention within various
branches of computer science, mathematics, and economics. Although, the elegant
Selfridge-Conway envy-free protocol for three agents has been known since 1960,
it has been a major open problem for the last fifty years to obtain a bounded
envy-free protocol for more than three agents. We propose a discrete and
bounded envy-free protocol for four agents
Ignition Performance of New and Used Motor Vehicle Upholstery Fabrics
This paper examines the standards for fire safety in transport systems and in particular the test method for the flammability of materials within passenger compartments of motor vehicles. The paper compares data from ignition tests conducted in the Cone Calorimeter and the FIST apparatus with tests conducted using the FMVSS 302 horizontal flame spread apparatus. Ten materials were selected as representative of those used as seat coverings of private and commercial passenger vehicles. The time to ignition of new and used materials subject to exposure heat fluxes between 20 kW/m2 and 40 kW/m2 was measured. The results from the ignition tests were analyzed using thermally thick and thermally thin theoretical models.
The critical heat flux for sustained piloted ignition was determined from the time to ignition data using the thermally thin approach. Derived ignition temperatures from both the thermally thick and thermally thin methods were compared with measurements using a thermocouple attached to the back surface of materials in selected tests. The flame spread rates in the FMVSS 302 apparatus were determined and a comparison was made between the performance of the materials in the flame spread apparatus, the Cone Calorimeter and the FIST. The results suggests that a critical heat flux criterion could be used to provide an equivalent pass/fail performance requirement to that specified by the horizontal flame spread test although further testing is needed to support this
The Role of Pressure in Inverse Design for Assembly
Isotropic pairwise interactions that promote the self assembly of complex
particle morphologies have been discovered by inverse design strategies derived
from the molecular coarse-graining literature. While such approaches provide an
avenue to reproduce structural correlations, thermodynamic quantities such as
the pressure have typically not been considered in self-assembly applications.
In this work, we demonstrate that relative entropy optimization can be used to
discover potentials that self-assemble into targeted cluster morphologies with
a prescribed pressure when the iterative simulations are performed in the
isothermal-isobaric ensemble. By tuning the pressure in the optimization, we
generate a family of simple pair potentials that all self-assemble the same
structure. Selecting an appropriate simulation ensemble to control the
thermodynamic properties of interest is a general design strategy that could
also be used to discover interaction potentials that self-assemble structures
having, for example, a specified chemical potential.Comment: 29 pages, 8 figure
Data Mining and Machine Learning in Astronomy
We review the current state of data mining and machine learning in astronomy.
'Data Mining' can have a somewhat mixed connotation from the point of view of a
researcher in this field. If used correctly, it can be a powerful approach,
holding the potential to fully exploit the exponentially increasing amount of
available data, promising great scientific advance. However, if misused, it can
be little more than the black-box application of complex computing algorithms
that may give little physical insight, and provide questionable results. Here,
we give an overview of the entire data mining process, from data collection
through to the interpretation of results. We cover common machine learning
algorithms, such as artificial neural networks and support vector machines,
applications from a broad range of astronomy, emphasizing those where data
mining techniques directly resulted in improved science, and important current
and future directions, including probability density functions, parallel
algorithms, petascale computing, and the time domain. We conclude that, so long
as one carefully selects an appropriate algorithm, and is guided by the
astronomical problem at hand, data mining can be very much the powerful tool,
and not the questionable black box.Comment: Published in IJMPD. 61 pages, uses ws-ijmpd.cls. Several extra
figures, some minor additions to the tex
Detection of Ventricular Tachycardia Using Scanning Correlation Analysis
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72896/1/j.1540-8159.1990.tb06919.x.pd
Truthful Allocation Mechanisms Without Payments: Characterization and Implications on Fairness
We study the mechanism design problem of allocating a set of indivisible
items without monetary transfers. Despite the vast literature on this very
standard model, it still remains unclear how do truthful mechanisms look like.
We focus on the case of two players with additive valuation functions and our
purpose is twofold. First, our main result provides a complete characterization
of truthful mechanisms that allocate all the items to the players. Our
characterization reveals an interesting structure underlying all truthful
mechanisms, showing that they can be decomposed into two components: a
selection part where players pick their best subset among prespecified choices
determined by the mechanism, and an exchange part where players are offered the
chance to exchange certain subsets if it is favorable to do so. In the
remaining paper, we apply our main result and derive several consequences on
the design of mechanisms with fairness guarantees. We consider various notions
of fairness, (indicatively, maximin share guarantees and envy-freeness up to
one item) and provide tight bounds for their approximability. Our work settles
some of the open problems in this agenda, and we conclude by discussing
possible extensions to more players.Comment: To appear in the 18th ACM Conference on Economics and Computation
(ACM EC '17
From the discrete to the continuous - towards a cylindrically consistent dynamics
Discrete models usually represent approximations to continuum physics.
Cylindrical consistency provides a framework in which discretizations mirror
exactly the continuum limit. Being a standard tool for the kinematics of loop
quantum gravity we propose a coarse graining procedure that aims at
constructing a cylindrically consistent dynamics in the form of transition
amplitudes and Hamilton's principal functions. The coarse graining procedure,
which is motivated by tensor network renormalization methods, provides a
systematic approximation scheme towards this end. A crucial role in this coarse
graining scheme is played by embedding maps that allow the interpretation of
discrete boundary data as continuum configurations. These embedding maps should
be selected according to the dynamics of the system, as a choice of embedding
maps will determine a truncation of the renormalization flow.Comment: 22 page
- …