pwc-archive/papers-with-abstracts huggingface dataset:
Dynamically evolved community size and stability of random Lotka-Volterra ecosystems
Date: 2018-08-20 00:00:00

We use dynamical generating functionals to study the stability and size of
communities evolving in Lotka-Volterra systems with random interaction
coefficients. The size of the eco-system is not set from the beginning.
Instead, we start from a set of possible species, which may undergo extinction.
How many species survive depends on the properties of the interaction matrix;
the size of the resulting food web at stationarity is a property of the system
itself in our model, and not a control parameter as in most studies based on
random matrix theory. We find that prey-predator relations enhance stability,
and that variability of species interactions promotes instability. Complexity
of inter-species couplings leads to reduced sizes of ecological communities.
Dynamically evolved community size and stability are hence positively
correlated.
An Isolated Power Factor Corrected Power Supply Utilizing the Transformer Leakage Inductance
Date: 2018-08-20 00:00:00

The widespread use of electronic devices increases the need for compact power
factor corrected power supplies. This paper describes an isolated power factor
corrected power supply that utilizes the leakage inductance of the isolation
transformer to provide boost inductor functionality. The bulk capacitor is in
the isolated part of the power supply allowing for controlled startup without
dedicated surge limiting components. A control method based on switch timing
and input/output voltage measurements is developed to jointly achieve voltage
regulation and input power factor control. A prototype design is implemented
with detailed measurements and waveforms shown to confirm the desired
functionality.
The strategy of conflict and cooperation
Authors: Mehmet S. Ismail
Date: 2018-08-21 00:00:00

This paper introduces a unified framework called cooperative extensive form games, which (i) generalizes standard non-cooperative games, and (ii) allows for more complex coalition formation dynamics than previous concepts like coalition-proof Nash equilibrium. Central to this framework is a novel solution concept called cooperative equilibrium system (CES). CES differs from Nash equilibrium in two important respects. First, a CES is immune to both unilateral and multilateral `credible' deviations. Second, unlike Nash equilibrium, whose stability relies on the assumption that the strategies of non-deviating players are held fixed, CES allows for the possibility that players may regroup and adjust their strategies in response to a deviation. The main result establishes that every cooperative extensive form game, possibly with imperfect information, possesses a CES. For games with perfect information, the proof is constructive. This framework is broadly applicable in contexts such as oligopolistic markets and dynamic political bargaining.
Energy Efficient Event Localization and Classification for Nano IoT
Date: 2018-08-21 00:00:00
Tasks: Classification

Advancements in nanotechnology promises new capabilities for Internet of
Things (IoT) to monitor extremely fine-grained events by deploying sensors as
small as a few hundred nanometers. Researchers predict that such tiny sensors
can transmit wireless data using graphene-based nano-antenna radiating in the
terahertz band (0.1-10 THz). Powering such wireless communications with
nanoscale energy supply, however, is a major challenge to overcome. In this
paper, we propose an energy efficient event monitoring framework for nano IoT
that enables nanosensors to update a remote base station about the location and
type of the detected event using only a single short pulse. Nanosensors encode
different events using different center frequencies with non overlapping half
power bandwidth over the entire terahertz band. Using uniform linear array
(ULA) antenna, the base station localizes the events by estimating the
direction of arrival of the pulse and classifies them from the center frequency
estimated by spectral centroid of the received signal. Simulation results
confirm that, from a distance of 1 meter, a 6th derivative Gaussian pulse
consuming only 1 atto Joule can achieve localization and classification
accuracies of 1.58 degree and 98.8%, respectively.
Direction of Arrival and Center Frequency Estimation for Impulse Radio Millimeter Wave Communications
Date: 2018-08-21 00:00:00

The 30-300GHz millimeter wave (mmWave) band is currently being pursued to
combat the rising capacity demands in 5G, WiFi, and IoT networks. Due to the
high frequency, impulse radio (IR) in this band is better suited for
positioning than other existing low-frequency bands. Besides precision
positioning, the exceptionally wide bandwidth also enables concurrent use of
multiple center frequencies in the same application, which opens up additional
avenues of information encoding in IR mmWave networks. In this paper, we
propose a new mmWave IR framework that can simultaneously detect direction of
arrival (DOA) as well as the center frequency of the transmitted pulse. Based
on the emerging graphene-based transceivers, we evaluate the performance of the
proposed framework in the higher frequency region of mmWave band (100-300GHz).
Numerical experiments demonstrate that the proposed framework can detect the
DOA of a 0.1 $\mu$Watt mmWave pulse within 1 degree of precision at 20 meters,
and classify three different center frequencies with 100% accuracy from a
distance of 10 meters. These performances could be further improved by trading
off the pulse rate of the system.
Modeling of reaction-diffusion transport into a core-shell geometry
Date: 2018-08-21 00:00:00
Tasks: Cultural Vocal Bursts Intensity Prediction

Fickian diffusion into a core-shell geometry is modeled. The interior core
mimics pancreatic Langerhan islets and the exterior shell acts as inert
protection. The consumption of oxygen diffusing into the cells is approximated
using Michaelis-Menten kinetics. The problem is transformed to dimensionless
units and solved numerically. Two regimes are identified, one that is diffusion
limited and the other consumption limited. A regression is fit that describes
the concentration at the center of the cells as a function of the relevant
physical parameters. It is determined that, in a cell culture environment, the
cells will remain viable as long as the islet has a radius of around $142 \mu
m$ or less and the encapsulating shell has a radius of less than approximately
$283 \mu m$. When the islet is on the order of $100 \mu m$ it is possible for
the cells to remain viable in environments with as little as $4.6\times10^{-2}
mol/m^{-3}$ $O_2$. These results indicate such an encapsulation scheme may be
used to prepare artificial pancreas to treat diabetes.
Making a Dynamic Interaction Between Two Power System Analysis Software
Date: 2018-08-21 00:00:00
Tasks: Vocal Bursts Valence Prediction

This paper presents a distributed simulation based method for harmonic
resonance assessment (HRA) in multi-area large-scale power systems. Further
consideration is devoted to the early harmonic frequency-scan formulation to
shape them into a Bordered Blocked Diagonal Form (BBDF), which is suitable for
parallel processing. The proposed algorithm (BBDF) allows operator of each area
of an interconnected system to independently conduct the HRA. A large-change
sensitivity based approach is then handled in a secure platform to apply the
effects of whole network to each single area. The introduced decentralized HRA
is capable to find the exact values as those of the interconnected system
through TCP/IP communication media. The developed method is successfully
implemented in an existing software package and applied to IEEE 14-bus harmonic
test system, followed by a discussion on results.
The Role of the Task Topic in Web Search of Different Task Types
Authors: Hienert Daniel, Mitsui Matthew, Mayr Philipp, Shah Chirag, Belkin Nicholas J.
Date: 2018-08-21 00:00:00

When users are looking for information on the Web, they show different
behavior for different task types, e.g., for fact finding vs. information
gathering tasks. For example, related work in this area has investigated how
this behavior can be measured and applied to distinguish between easy and
difficult tasks. In this work, we look at the searcher's behavior in the domain
of journalism for four different task types, and additionally, for two
different topics in each task type. Search behavior is measured with a number
of session variables and correlated to subjective measures such as task
difficulty, task success and the usefulness of documents. We acknowledge prior
results in this area that task difficulty is correlated to user effort and that
easy and difficult tasks are distinguishable by session variables. However, in
this work, we emphasize the role of the task topic - in and of itself - over
parameters such as the search results and read content pages, dwell times,
session variables and subjective measures such as task difficulty or task
success. With this knowledge researchers should give more attention to the task
topic as an important influence factor for user behavior.
A Usefulness-based Approach for Measuring the Local and Global Effect of IIR Services
Authors: Hienert Daniel, Mutschke Peter
Date: 2018-08-21 00:00:00
Tasks: Information Retrieval, Retrieval

In Interactive Information Retrieval (IIR) different services such as search
term suggestion can support users in their search process. The applicability
and performance of such services is either measured with different
user-centered studies (like usability tests or laboratory experiments) or, in
the context of IR, with their contribution to measures like precision and
recall. However, each evaluation methodology has its certain disadvantages. For
example, user-centered experiments are often costly and small-scaled; IR
experiments rely on relevance assessments and measure only relevance of
documents. In this work we operationalize the usefulness model of Cole et al.
(2009) on the level of system support to measure not only the local effect of
an IR service, but the impact it has on the whole search process. We therefore
use a log-based evaluation approach which models user interactions within
sessions with positive signals and apply it for the case of a search term
suggestion service. We found that the usage of the service significantly often
implicates the occurrence of positive signals during the following session
steps.
Microwave Hilbert Transformer and its Applications in Real-time Analog Processing (RAP)
Date: 2018-08-21 00:00:00
Tasks: Edge Detection

A microwave Hilbert transformer is introduced as a new component for
Real-time Analog Processing (RAP). In contrast to its optical counterpart, that
resort to optical fiber gratings, this Hilbert transformer is based on the
combination of a branch-line coupler and a loop resonator. The transfer
function of the transformer is derived using signal flow graphs, and two
figures of merits are introduced to effectively characterize the device: the
rotated phase and the transition bandwidth. Moreover, a detailed physical
explanation of its physical operation is given, using both a steady-state
regime perspective and a transient regime perspective. The microwave RAP
Hilbert transformer is demonstrated experimentally, and demonstrated in three
applications: edge detection, peak suppression and single sideband modulation.
Emergence of Fractional Kinetics in Spiny Dendrites
Date: 2018-08-13 00:00:00

Fractional extensions of the cable equation have been proposed in the
literature to describe transmembrane potential in spiny dendrites. The
anomalous behavior has been related in the literature to the geometrical
properties of the system, in particular, the density of spines, by experiments,
computer simulations, and in comb-like models.~The same PDE can be related to
more than one stochastic process leading to anomalous diffusion behavior. The
time-fractional diffusion equation can be associated to a continuous time
random walk (CTRW) with power-law waiting time probability or to a special case
of the Erd\'ely-Kober fractional diffusion, described by the ggBm. In this
work, we show that time fractional generalization of the cable equation arises
naturally in the CTRW by considering a superposition of Markovian processes and
in a {\it ggBm-like} construction of the random variable.
Who is Really Affected by Fraudulent Reviews? An analysis of shilling attacks on recommender systems in real-world scenarios
Authors: Shrestha Anu, Spezzano Francesca, Pera Maria Soledad
Date: 2018-08-21 00:00:00
Tasks: Recommendation Systems

We present the results of an initial analysis conducted on a real-life
setting to quantify the effect of shilling attacks on recommender systems. We
focus on both algorithm performance as well as the types of users who are most
affected by these attacks.
URLLC Services in 5G - Low Latency Enhancements for LTE
Date: 2018-08-22 00:00:00

5G is envisioned to support three broad categories of services: eMBB, URLLC,
and mMTC. URLLC services refer to future applications which require reliable
data communications from one end to another, while fulfilling ultra-low latency
constraints. In this paper, we highlight the requirements and mechanisms that
are necessary for URLLC in LTE. Design challenges faced when reducing the
latency in LTE are shown. The performance of short processing time and frame
structure enhancements are analyzed. Our proposed DCI Duplication method to
increase LTE control channel reliability is presented and evaluated. The
feasibility of achieving low latency and high reliability for the IMT-2020
submission of LTE is shown. We further anticipate the opportunities and
technical design challenges when evolving 3GPP's LTE and designing the new 5G
NR standard to meet the requirements of novel URLLC services.
On the uniqueness of the maximum parsimony tree for data with up to two substitutions: an extension of the classic Buneman theorem in phylogenetics
Date: 2019-03-21 00:00:00

One of the main aims of phylogenetics is the reconstruction of the correct
evolutionary tree when data concerning the underlying species set are given.
These data typically come in the form of DNA, RNA or protein alignments, which
consist of various characters (also often referred to as sites). Often,
however, tree reconstruction methods based on criteria like maximum parsimony
may fail to provide a unique tree for a given dataset, or, even worse,
reconstruct the `wrong' tree (i.e. a tree that differs from the one that
generated the data). On the other hand it has long been known that if the
alignment consists of all the characters that correspond to edges of a
particular tree, i.e. they all require exactly $k=1$ substitution to be
realized on that tree, then this tree will be recovered by maximum parsimony
methods. This is based on Buneman's theorem in mathematical phylogenetics. It
is the goal of the present manuscript to extend this classic result as follows:
We prove that if an alignment consists of all characters that require exactly
$k=2$ substitutions on a particular tree, this tree will always be the unique
maximum parsimony tree (and we also show that this can be generalized to
characters which require at most $k=2$ substitutions). In particular, this also
proves a conjecture based on a recently published observation by Goloboff et
al. affirmatively for the special case of $k=2$.
Satellite Positioning with Large Constellations
Date: 2018-08-21 00:00:00

Modern global navigation satellite system receivers can access signals from
several satellite constellations (including GPS, GLONASS, Galileo, BeiDou).
Once these constellations are all fully operational, a typical receiver can
expect to have on the order of 40-50 satellites in view. Motivated by that
observation, this paper presents an asymptotic analysis of positioning
algorithms in the large-constellation regime. We determine the exact asymptotic
behavior for both pseudo-range and carrier-phase positioning. One interesting
insight from our analysis is that the standard carrier-phase positioning
approach based on resolving the carrier-phase integer ambiguities fails for
large satellite constellations. Instead, we adopt a Bayesian approach, in which
the ambiguities are treated as noise terms and not explicitly estimated.
Fixation Probabilities in Weakly Compressible Fluid Flows
Date: 2019-01-23 00:00:00

Competition between biological species in marine environments is affected by
the motion of the surrounding fluid. An effective 2D compressibility can arise,
for example, from the convergence and divergence of water masses at the depth
at which passively traveling photosynthetic organisms are restricted to live.
In this report, we seek to quantitatively study genetics under flow. To this
end, we couple an off-lattice agent-based simulation of two populations in 1D
to a weakly compressible velocity field--first a sine wave and then a shell
model of turbulence. We find for both cases that even in a regime where the
overall population structure is approximately unaltered, the flow can
significantly diminish the effect of a selective advantage on fixation
probabilities. We understand this effect in terms of the enhanced survival of
organisms born at sources in the flow and the influence of Fisher genetic
waves.
Mathematical modelling indicates that lower activity of the haemostatic system in neonates is primarily due to lower prothrombin concentration
Date: 2018-08-21 00:00:00

Haemostasis is governed by a highly complex system of interacting proteins.
Due to the central role of thrombin, thrombin generation and specifically the
thrombin generation curve (TGC) is commonly used as an indicator of haemostatic
activity. Functional characteristics of the haemostatic system in neonates and
children are significantly different compared with adults; at the same time
plasma levels of haemostatic proteins vary considerably with age. However,
relating one to the other has been difficult, both due to significant
inter-individual differences for individuals of similar age and the complexity
of the biochemical reactions underlying haemostasis. Mathematical modelling has
been very successful at representing the biochemistry of blood clotting. In
this study we address the challenge of large inter-individual variability by
parameterising the Hockin-Mann model with data from individual patients, across
different age groups from neonates to adults. Calculating TGCs for each patient
of a specific age group provides us with insight into the variability of
haemostatic activity across that age group. From our model we observe that two
commonly used metrics for haemostatic activity are significantly lower in
neonates than in older patients. Because both metrics are strongly determined
by prothrombin and prothrombin levels are considerably lower in neonates we
conclude that decreased haemostatic activity in neonates is due to lower
prothrombin availability.
Revealing evolutionary constraints on proteins through sequence analysis
Date: 2019-03-11 00:00:00

Statistical analysis of alignments of large numbers of protein sequences has
revealed "sectors" of collectively coevolving amino acids in several protein
families. Here, we show that selection acting on any functional property of a
protein, represented by an additive trait, can give rise to such a sector. As
an illustration of a selected trait, we consider the elastic energy of an
important conformational change within an elastic network model, and we show
that selection acting on this energy leads to correlations among residues. For
this concrete example and more generally, we demonstrate that the main
signature of functional sectors lies in the small-eigenvalue modes of the
covariance matrix of the selected sequences. However, secondary signatures of
these functional sectors also exist in the extensively-studied large-eigenvalue
modes. Our simple, general model leads us to propose a principled method to
identify functional sectors, along with the magnitudes of mutational effects,
from sequence data. We further demonstrate the robustness of these functional
sectors to various forms of selection, and the robustness of our approach to
the identification of multiple selected traits.
Assessing sources of uncertainty in length-based estimates of body growth in populations of fishes and macroinvertebrates with bootstrapped ELEFAN
Date: 2018-08-21 00:00:00

The determination of rates of body growth is the first step in many aquatic
population studies and fisheries stock assessments. ELEFAN (Electronic LEngth
Frequency ANalysis) is a widely used method to fit a growth curve to
length-frequency distribution (LFD) data. However, up to now, it was not
possible to assess its accuracy or the uncertainty inherent of this method, or
to obtain confidence intervals for growth parameters within an unconstrained
search space. In this study, experiments were conducted to assess the precision
and accuracy of bootstrapped and single-fit ELEFAN-based curve fitting methods,
using synthetic LFDs with known input parameters and a real data set of Abra
alba shell lengths. The comparison of several types of bootstrap experiments
and their outputs (95% confidence intervals and confidence contour plots)
provided a first glimpse into the accuracy of modern ELEFAN-based fit methods.
The main components of uncertainty (precision and reproducibility of fit
algorithms, seed effects, sample size and matrix information content) could be
assessed from partial bootstraps. Uncertainty was mainly determined by LFD
matrix size, total number of non-zero bins and the sampling of large-sized
individuals. A new pseudo-Rsquared index for the goodness-of-fit of VBGF models
to LFD data is proposed. For a large, perfect synthetic data set,
pseudo-RsquaredPhi was very high (88 to 100%), indicating an excellent fit of
the VBGF model. The small Abra alba data set showed a low pseudo-RsquaredPhi,
from to 54% to 68%, indicating the need for more samples and a larger LFD data
matrix. New, robust, bootstrap-based methods for curve fitting are presented
and discussed. This study demonstrates a promising new path for length-based
analyses of growth and mortality in natural populations, which are the basis
for a new suite of methods that are included in the new fishboot package.
Recovering Hidden Components in Multimodal Data with Composite Diffusion Operators
Date: 2018-08-22 00:00:00

Finding appropriate low dimensional representations of high-dimensional
multi-modal data can be challenging, since each modality embodies unique
deformations and interferences. In this paper, we address the problem using
manifold learning, where the data from each modality is assumed to lie on some
manifold. In this context, the goal is to characterize the relations between
the different modalities by studying their underlying manifolds. We propose two
new diffusion operators that allow to isolate, enhance and attenuate the hidden
components of multi-modal data in a data-driven manner. Based on these new
operators, efficient low-dimensional representations can be constructed for
such data, which characterize the common structures and the differences between
the manifolds underlying the different modalities. The capabilities of the
proposed operators are demonstrated on 3D shapes and on a fetal heart rate
monitoring application.